Note: Descriptions are shown in the official language in which they were submitted.
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Field of the Invention
This invention is related to automatic and remote
electronic control systems particularly adapted for use with the
mechanical and hydromechanical transmissions of motor vehicles
such as trucks, busses, oil tankers, earthmoving machines as well
as transmissions for railway ancl military applications.
Background of the Invention
Fully automatic systems which comprise combinations of
hydraulic torque converter transmissions and complementary gears
are well known in the art and common on the market. Althouyh many
of these systems have hydromechanical control systems, the in-
creased demands for a system which is capable of varying the shift
conditions in relation to a wide variety of factors, as well as
the increased demand for inclusion of safety functions in the basic
automatic systems, has resulted in the development of electronic
control systems for this purpose. An example of a system incor-
porating such electronic controls is that disclosed in commonly
assigned U.S. Patent No. 4,033,202.
While thes~ systems, and similar systems, make it poss-
ible to tailor the operation to most conventional demands, such
systems become large and quite complicated as the demands thereon
increase. Further, such systems do not permit variations in the basl,
operati~g mode without a complete redesign and reconstruction of the
system. Thus, the electronic autopilots or control systems of the
type in question are not able to serve transmission units and assem-
blies which are of various forms and types, and which incorporate
various accessories. Further, due to the complexity involved,
such systems a.re normally limited to determining.the drive connection
in dependence upon primary speeds, secondary speeds and speed
ratios only.
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Summary of the Invention
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In accordance with the invention, a vehicle transmission
control system is provided which affords substantial advantages
in capacity and versatility as compared with prior art systems.
The vehicle transmission control system of the invention comprises
an electronic control system which is capable of taking in to
account, practically speaking, a virtually unlimited number of
input signals relating to the actual operating conditions of the
vehicle transmission and the settings of the controls therefor.
The electronic control system senses the operating conditions,
control settings, and/or other inputs to develop demand signals
for automatically controlling the operation of the transmission
in accordance with the input signals and the relationship there-
between. In addition, the system is capable of handling a wide
range of demand signals including acceleration and/or deceleration
signals. Moreoverr the system is applicable to a wide variety
of mechanical and hydromechanical motor vehicle transmissions,
even including hy~rostatic and hydrodynamic torque converters and
provides automatic gear operation for both driving and braking.
The system of the invention can provide for different modes Oe
operation and adapt to different conditions and usages with minor,
readily effected changes in the operating program. A further
important advantage of the electronic control system of the inven-
tion is the substantial reduction in cost as compared with prior
art autopilots. In addition to the obvious advantages thereof,
this cost reduction permits the use of a standard control system
with relative:Ly small transmissions, i.e., auto transmissions,
while still enabling the use of the same standard or basic control
system with relatively large, complex transmissions such as those
of high power military vehicles, locomotives and railcars. However,
in general, the vehicle transmission control system is perhaps
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best adapted for use as part of the automatic transmissions of
busses, trucks and the like, for both on-the-road and off-the~
road applications.
In accordance with a preferred embodiment thereof,
the vehicle transmission control system of the invention basically
comprises an electronic control system for controlling the ve-
hicle transmission by converting input signals thereto related
to operating conditions of the transmission into output control
signals for the transmission in accordance with a predetermined
set of criteria. The electronic control system comprises means
for sensing a plurality of transmission operating conditions and
producing input signals, comprising pulses, in accordance therewith,
microprocessor means for monitoring the states of the input signals,
programmable read-only memory means connected to the microprocessor
means, timing means connected to the microprocessor means for
directly delivering clock pulses to the` microprocessor meansl
output means, connected to the microprocessor and including latch
means, for producing output control signals under the control of
the microprocessor means, and addressing means for synchronizing
the operation of the programmable read-only memory means and the
latch means under the control of the microprocessor means. The
electronic control system further comprises electro-mechanical
operators, e.g., solenoid valves and/or relays, which arP respon-
sive to the output signals and which control the operation of~ the
vehicle transmission accordingly.
Preferably, the electronic control system also includes;
random access memory means connected to the microprocessor means
for storing the states of signals being monitored and enabling
arithmetical operations~o be performed on the stored signals states.
The output means also include eIectrical switching means continu-
ously control~ed by the latch means, these electrical swi~ching
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means advantageously comprising power transistors of a type
having current limiting, power limiting, and thermal overload
protection.
Preferably, a voltage/frequency converter is provided
for converting at least one voltage input signal in a pre-
determined manne~ into a series of pulses to be fed directly
to the microprocessor means. Advantageously, this voltage signal
is controlled by a potentiometer. In addition, a multiplexer
means is connected to the microprocessor means for providing
an increased number of input signals which are directly fed to
the microprocessor means. Advantageously, at least one delay
circuit means, comprising one resistor, one capacitor, and one
rectifier, is provided for delaying the change in at least one
input signal and for limiting thelevelof that at least one signal.
Further, at least one resistor-zener diode arrangement is pre-
ferably provided for limiting the current and voltage of at least
one signal to be directly fed to the microprocessor means. A
circuit arrangement, comprising one resistor, one capacitor, one
rectifier, and one gate means, is also utilized to provide dis-
tinct starting signals to said micropxocessor means. In addition,
a switch is employed for controllingthe input signal to the at
least one delay circuit means.
In a preferred embodiment, a motion sensing means is
used to produce at least one of the input signals to control system.
The range of frequencies of the pulses produced by the motlon
sensing means preferably has the lower limit of zero Hz.The motion
sensing means includes a magnetoresistive sensing arrangement and
amplifying means, incIuding at least one operational amplifier,
for providing - approprlate control signals. Advantageously,
this magnetoresistive sensing arrangement is operated with a
potential difference of no more than 3 volts and this potential
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difference is maintained by a separate voltage regulator. The
magnetoresistive sensing arrangement preferably comprises a
magnetoresistor connected in a bridge circuit together with a pair
of fixed resistors such that a signal voltage is obtained across
a connection between the two fixed resistors and a central terminal
of said magnetoresistor. Where remote sensing is employed, the
magnetoresistor and the amplify~ing means are connected together
by a twisted-pair cable.
In an embodiment utilizing a motion or movement sensing
means, the periodicity of processing the input signals by the
microprocessor means to produce the output signals is primarily
dependent upon the rate of acquisition of a predetermined number
of digital input signals produced by the movement sensing means.
This movement sensing means preferably comprising means for pro-
ducing signals indicative of the transmission input and output
shaft speedswherein the time necessary for determination of the
input and output shaft speeds is solely dependent upon the input
shaft speed. Further, the output shaft speed is determined by
performing arithmetical operations upon values solely relating
to the input shaft speed and the ratio of output shaft speed to
input shaft speed. Advantageously, the output shaft speed is
determined by dividing a value, which is directly proportional
to the speed ratio, by a value which is inversly proportional
to the input shaft speed. As a result of the invention, the
accuracy of determination of the output shaft speed is independent
of the output shaft speed over the entire range of obtainable
values.
In the preferred embodiment referred to, the mioro-
processor means controls the transmission in accordance with a
predetermined program in relation to driving conditions of the ;
transmission, and the input and output speeds, as well as signals
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related to the settin~ of a prime mover, are sensed and directly
supplied to the microprocessor means. The system further includes
buffer means connected to said microprocessor for receiving signals
related to setting of the prime mover for the transmission as
well as additional input signals. The electro-mechanical means
preferably comprises solenoid valves for controlling the setting
of the transmission, the input signals being processed in accordance
with a predetermined program to produce output signals which are
fed to said solenoid valves. Input signals related to the setting
of the prime mover for said transmission can also be processed
according to the program to control the operating conditions of
the transmission. The prime mover preferably comprises an engine
whose setting is utili~ed to influence, in a predetermined manner,
a part of the program for controlling the operationof the micro-
processor means so as to determine the shift points of the trans- -
mission. The movement sensing means in this embodiment comprises
means for sensing output speed signals of the transmission, the
microprocessor means processing the speed signals to obtain an
acceleration factor and employing this factor in relation to the
setting of the prime mover and the speed of prime mover in deter-
mining the transmission shift points.
Other features and advantages of the invention will
be set forth in, or apparent from, the detailed description of
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a preferred embodiment of the invention found hereinbelow.
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- Brief Description of the Drawings
F.igure 1 is a longitudinal cross section o~ a trans-
mission in which, in a preferred em~odiment, the electronic
control s~vstem of the invention is i.ncorporated;
Figure 2 is a schematic diagram of the essential com-
ponents of the transmission of Figure 1 to~ether with the -~
mechanical and electronic controls thereof;
Figure 3 is a block diagram of the basic units of
the transmission control system of the invention;
Figure 4 and Figures 5(a) and 5 (b) are diagrams of
selected operating characteristics of a transmission incorporat-
ing the electronic control system of the invention, wherein
Figure 4 shows operating conditions of the transmission when the
engine is applying tractive effort, and Figures 5(a) and 5(b)
show op~rating conditions of the transmission under hydraulic
braking conditions;
Figures 6(a), 6(b) and 6(c) are consecutive p~rts
of a chart setting forth the sensed and controlled parameters
or conditions which interface with the microcomputer of the
electronic control system of the invention;
Figure 7 is a schematic circuit diagram of the central
processing unit of the microcomputer of the invention;
Figures 8a to Bd show input and output circuitry
utilized with the central processing unit of Figure 7;
Figure 9 is a generalized flow diagram setting forth
the basic operations of the microcomputer of the invention; and ~
Figure 10 is a schematic circuit diagram of a motion ~ ~ -
sensing arrangement in accordance with a preferred embodiment
of the invention.
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Detailed Description Of The Preferred Embodiments
Referring now to the drawings, like elements are repre-
sented by like numerals throughout the several views.
Figure 1 illustrates a hydromechanical transmission
with which the electronic control system of the present invention
can be used. At the left end of Figure 1 there is shown a torque
converter TCincluding arotating casing2 adapted to be driven by
a vehicle engine or the like via abutment means 2a. Internally,
the illustrated torque converter comprises a pump member 3 having
a ring of pump blades 4 mounted thereon. The torque converter
further comprises a turbine member 5 having a ring of turbine
blades 6 mounted thereon and a guide vane 7 having a ring of
guide blades 8 thereon, wherein said guide blades ma~ be used as
a turbine. Connected to the turbine member 5 is a hub 14 to the
outer periphery of which is attached a friction disc 12. The
rotating casing 2 includes an inward extension 2b located between
the disc 12 and the pump member 3 and a servo piston 10 on the
outer side of disc 12. The torque converter shown herein is of the
releasable pump member type which is shown and described in detail
in prior U.S. Patent No. 3,893,551, issued July 8, 1975. In
accordance therewith, the pump member 3 is movable to the left
to engage the pump member 3 with the rotating casing at conical
friction coupling 9 for hydraulic drive. In another mode of
operation, pump member 3 is moved to the right, releasing coupling
9, and the servo piston 10 is actuated to urge disc 12 into
frictional engagement with extension 2b for direct drive between
the rotating casing 2 and the turblne member 5. The turbine
member 5 and the hub 14 are drivingly engaged with the turbine
shaft 16. The guide member 7 is mounted on a guide member shaft 18
which rotate relative to turbine shatt 16 and which is mount-d to
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the stationar~ portion o.~ the casing at bearings 20. Shaft 18
is connected via a hub and friction discs to a brake 26 oper-
able by servo piston 23 for holdrng the guide member 7 station-
ary for "single rotation". Shaft 18 is further connected to a
planetary gear 22, the carrier of which is connected to fric-
tion discs forming a part of brake ~4 which is operated by servo
piston 25, whereby the guide member rotates oppositely from
the turbine member for "double rotation". Arrangements for
braking the guide member for single or double rotation are well
known, one example being shown in the prior U.S. Patent No.
4,010,660, issued March 8, 1977. In hydraulic drive, torque
multiplication is provided via the guide member blades, and the
output of increased torque via the turbine member to the tur-
bine shaft 16. Double rotation with brake 24 actuated allows
a much higher multiplication of torque, but over a smaller range
of speed ratios, than does single rotation (engagement of brake
23) wherein speed ratio is defined as the ratio of turbine
shaft speed to rotating casing speed. Torque multiplication
decreases with increasing speed until it becomes advantageous
to disconnect hydraulic drive, i.e. disconnect the conical
coupling 9, and to actuate servo piston 10 to drive the turbine
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shaft 16 directly from the rotating casing 2 via elements 12 ;
and 14.
The torque converter includes a heat exchanger 68
through which fluid is pumped by means of a gear 70 via an in-
termediate gear 72. A system including, in a torque converter,
a heat exchanger of this type, together with a pump and the`
appropriate fluid lines, is shown in greater detail in prior
U.S. Patents 4,056,019 and 4,Q58,980, issued respectively on
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Nov. 1, 1977 and Nov. 22, 1977.
There is provided downstream from the torque conver-
ter a mechanical ~ear transmission comprising a first portion P
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having ~our ~orward gear ratios and a reverse gear, and a sec-
ond portion, R re~erred to as a "range gear" having either a
1:1 drive or a further gear reduction. A transmission having
such a first portion P followed by a second "range" portion R
is shown in greater detail in co-pending Canadian Application
Serial No. 318,971, filed on even date herewith, in the name of
Xarl G. Ahlen, one of the inventors herein. This downstream
mechanical gear is normally used during acceleration and also
during braking for overspeeding the turbine.
The turbine shaft 16 is connected to a ring gear 30.
The secondary or output shaft of this first portion is designat-
ed as 32. Ring gear 30 drives a planetary gear 34 having a
plurality of sections including a large diameter section 31
splined onto an intermediate diameter section 33 with a smaller
diameter section 35 to the right. Intermediate between sections
33 and 35 is a bearing means for mounting this planetary gear
34. Sections 31, 33 and 35 are respectively drivingly engaged
wi.h splines of sun gears 36, 38 and 40. Section 35 is further
engaged with a ring gear 50 operating as a reverse gear. Sun
gears 36, 38 and 40 are either released for free rotation or
connected to the stationary portion of the casing via friction
brakes 46, 44 and 42, respectively, which friction brakes are
actuated by servo pistons 47, 45 and 43, respectively. Reverse
gear 50 is selectively engaged with the casing via friction
brake 52 which is actuated via servo piston 53.
Alternatively, the ring gear 30 can be connected ~i-
rectly to the carrier of planetary gear 34 and hence directly
to secondary shaft 32 by engagement of friction clutch 48, the
latter caused by actuation of servo piston 49, this in turn ~;
urging member 51a to the left to turn lever 51b such that its
upper portion moves to the right to engage clutch 48.
Shaft 32 extends toward the right in Figure 1 into
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~ the second portion or "range ge~r" whereat it is drivingly en-
- gaged with an elongated spl~ned member 54 which is drivin~ly
engaged with both a hub 56 and planetary ~ears 64. The holder
60 of planetary gear 64 is drivingl~ enga~ed with a secondary
gear 58 which is the output shaft of the entire transmission.
Planetary gear 64 is engaged with a ring gear 66 which can be
braked relative to the stationary portion of the housing by
means of a friction brake 67 which is actuated by servo piston
69. This would permit a speed reduction between shafts 32 and
58. Alternatively, shafts 32 and 58 may be operatively engaged
to each other via hub 5Ç and friction clutch 62, the latter
frictionally engaging hub 56 with the planetary gear holder 60.
Friction clutch 62 is actuated via a servo piston 63 which acts
via a lever system 65.
Referring now to Figure 2, there is shown an electro-
hydraulic-electronic control system in accordance with the pre-
sent invention. In Figure 2, mechanical connections are indi-
cated in solid lines and electrical connections in dashed lines.
For convenience, the hydraulic systems contained
within Figure 2 will be described first. A pump system 300 in- -~
cludes a high pressure gear pump GPH and a pair of low pressure
gear pumps GPL-l and GPL-2 the pressure of which is controlled
by a solenoid valve CBV. There is also included a heat exchang-
er HE as described in the previously mentioned U.S. Patent No.
4,058,980. These pumps provide the pressurized oil to operate
the valves of the system and the pressurized oil which flows
through the valves to the various servo pistons and to the ~ ;
torque converter chamber. The system comprises a first valve
302 which controls the Elow of fluid to the torque converter,
a second valve 304 which controls the flow of fluid to single
and dou~le rotation servo piston 23 and 25, a third valve 306,
which together with secondary valves 306A and 306B, controls the
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-~ flow of fluid to the ~irst portion of the mechanical transmis-
sion and lastly a valve 308 which controls the flow of fluid to
the servo pistons 63 and 69 of the xange gear. Oil under pres-
sure is delivered from pump GPL~l to the valve 302 for delivery
to the torque converter, to all of the electric solenoid valves
for delivery to the ends of all of said valves for moving same
axially, and tc the valve 304 for delivery to single and double
rotation servo pistons 23 and 25. Oil under pressure is also
delive~ed from pump 300 to the valve 306 and its secondary
valves 306A and 306B for delivery to the servo pistons of the
rirst portion P of the mechanical transmission.
Referring again to Figure 2, and specifically to valve
302, it will be seen that the pressurized oil enters the valve
at lir.e 70'. With the spool of valve 302 in its neutral posi-
tion, the torque converter is in its neutral position with
neither the coupling 9 nor the disc 12 engaged with extension 2b
of the rotating casing 2. Movement of valve 302 in one direc-
tion will then connect the pressurized fluid from line 70' to
line H for hydraulic drive and movement of this valve in the
other direction will connect such pressurized fluid with line D -~
for actuation of servo piston 10 and hence direct drive. It
is obvious, therefore, that one cannot place both lines H and
D under pressure at the same time.
Turning to valve 304, pressurized fluid through line
71 will flow through either a first line SR or a second line DR,
depending on the direction of movement of valve 304, to actuate
either single rotation piston 23 or double rotation piston 25.
At valve 306, pressurized oil entering at line 74 is
delivered either throu~h line R to servo piston 53 or through
line S to the two ~urther valves 306~ and 306B. Valve 306A has
three pos~tions includin~ two end positions whereat the enter-
ing pressurized fluid is delivered to either servo piston 45
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or servo piston 43. The third position is a neutral position
whereat the fluid passes throu~h valve 306A to valve 306B. The
latter, in turn, has two positions, a first end position where-
at this pressurized fluid passes through a line to servo piston
47 and a second position whereat this fluid passes through an-
other line to servo piston 49.
Finally, valve 308 receives pressurized fluid from
line 76. As this valve 308 is moved to its end positions this
pressurized fluid is delivered to either servo piston 63 which
operates friction clutch 62 or servo piston 69 which operates
brake 67.
Thus, in summary, the hydraulic control valve system,
including valves 302, 304, 306, 306A, 306B and 308, controls
the flow of oil to the servo-pistons which directly engages the
various brakes and clutches in the transmission of Figure 1 as
described above, with pressurized oil being obtained from the
feeder pump system which is driven by the primary side of the
transmission. The hydraulic valve system is, in turn, control-
led by means of solenoid valves which are described below and
which, through electrical signals, control the flow of oil actu
ating the various servo-pistons in the hydraulic valve system.
The system of Figure 2 further includes an engine
brake cylinder CEB, a fuel injection cylinder CFI and a fuel
cut-off cylinder CFC which are controlled by solenoids EBV, FIV,
FCV. These operators and their functions are conventional.
As mentioned hereinabove and shown in Figure 2, the
setting of the transmission is determined by a plurality of
solenoid-type valves. These valves are indicated in Figure 2
at DV, HV, SRV, DRV, FV, RV, and EHVl to EHV6. These valves
control, via the hydraulic valve system including valves 302,
304, 306, 306A 306B and 308, the flow of oil for (1) connection~
of direct drive or hydraulic drive (2) single rotation drive vr
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double rotation drive, (3) forward or reverse drive (4) a firstgroup of mechanical c~ears P, (5) a second group of mechanical
gears P, (6) the range gear R, respectively. The solenoid
valve CBV controls the Bypass around low pressure pump GBL-2
and thereby controls the contribution of the output of that pump
to the overall output of the pump system 300.
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In particular, solenoid valves DV and HV control valve 302, solenoidvalves SRV and DRV control valve 304, solenoid valves F and R control
valve 306, solenoid valves EHVl to E~V6 control valves 306A, 306B
and 308, while, as mentioned previously, solenoid valve CBV controls
1~ c p~ ~ fIV
L~ pump/~. In addition, the further solenoid valves ~ , FCV, and
EBV control the engine-influencing devices for fuel injection, fuel
cut-off, and engine braking, respectivelyl as mentioned hereinabove.
It should be noted that the arrangement of the solenoid valves illus-
trated in Figure 2 is obviously not the only arrangement that can
be used and, moreover, it is not necessary for the output signals
derived from the system to control solenoid valves in that such
signals can equally well be used in thecontrol of signal lamps,
relays, or other electrical devices. The solenoid valves are suPplied
frcm a microcomputer described herebelow by a common +24V line con-
nected to the vehicle battery s. Generally speaking, an individual
solenoid valve is actuated by completing, through a power transistor
in the microcomputer-,-a connection from that solenoid valve to ground.
The valve system of the transmission is arranged so that a complete
neutral setting is obtained (no clutches connected) when no solenoid
valve is acti~ated (the condition where, for instance, the vehicle
ignition is off).
Before discussing the input signals to the electronic
control system and their origins, it may be helpful to briefly con-
sider the overall electronically controlled transmission. Thus,
referring to Figure 3, the basic units of the overall system of the
invention are illustrated. The heart of the electronic control
system is a microcomputer 200, which, as shown, receives input si~nals
from (i) shaft speed pickups, individually denoted Gl, G2, G3 and
collectively de:noted 210; (ii) the selector lever position sensor 212;
(iii) the brake pedal and brake lever position sensors 214; (iv) the
oil temperature, pressure and level switches 216; and (v) the throttl~
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position sensor 218. ~s noted, these inputs are described in
more detail below. The output of microcomputer 200 controls
the pluralit~ of solenoid valves which were discussed herein-
above and which are collectively denoted 22~. 5Olenoid valves
220, in turn, control the operation of the transmission 222
and the engine 224 as discussed hereinafter. As in Figure 2,
the dashed lines indicate electrical connections and, as shown,
the speed signals are fed ~ack from the engine and transmission
so as to form inputs to~microcomputer 200.
Turning again to Figure 2, the input signals referred
to above comprise shaft speed signals Gl, G2 and G3 (see block
212 of Figure 3) which appear on lines 309, 310 and 311, throt-
tle position signals (block 218 of Figure 3) which appear on
lines 312, 313 and 314, brake pedal and handbrake signals (block
214 of Figure 3) which appear on lines 315 and 316 respectively,
oil level and temperature safety signals (block 216 of Figure 3)
which appear on lines 317 and 318, respectively; selector lever
position signals (block 212 of Figure 3) which appear on lines -
319, 320, 321, 322, 323 and 324; and brake lever position sig-
nals (also block 214 of Figure 3) which appear on lines 325,
325 and 327.
The shaft speed signals are square wave, TTL pulses -
consisting of two levels, viz., OV and ~5V. The pulses are ob-
tained from the sensor/amplifier units Gl, G2 and G3 disposed
adjacent to gear teeth rotating with the engine shaft ES, con-
verter turbine shaft CTS, and transmission output shaft TOS,
respectively, as illustrated.
Considering the other input signals in more detail, ~.
the throttle position signals appearing on lines 312 to 314 are -
related to the pasition of the throttle lever indicated at 330
and these signals include a variable voltage between 0 and 5V
which is, proportional to the throttle position and which is
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provided b~ a potentiometer (not shown~, the tap of which is
attached to the throttle
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lever 330. Two further signals, indicating the terminal posi-tions
"throttle released" (or N) and "kickdown" (or KD), respectively,
are obtained by use of contactors 332 and 334 which open or close
connections to ground.~ When the contactors 332, 334 are in the
open positions, the~microcomputer holds the signal line at +5V.
The brake pedal (Br) and handbrake (HP) signals on
lines 315 and 316 are obtained in a same manner, i.e., through the
use of contactors, indicated generally at 335 and 338, respectively,
which provide openings or closing of a connection to ground.
The oil level (OL) and temperature safety (TS) switch
signals appearing on lines 317 and 318 are provided by switches,
indicated generally at 340 and 342, and are held at ~24V (the battery
voltage) during normal operation. Excessively low oil level or high
oil temperature cause the respective switch 340 or 342 to close a
connection to ground, thus lighting a warning lamp WL on the instru-
ment panel and simultaneously activating a delay circuit in the
microcomputer. This delay circuit allows time for the driver to take
some independent action before the microcomputer releases the trans-
mission so as to prevent damage.
The selector lever and the brake lever are intended to
be directly controlled by the driver through the autopiloth~. The
signals are produced, as shown, by a number of switch contactors
which control the completion of connections to ground, thereby pro-
viding for a combination of signals. The microcomputer 200 holds
the signal lines at +5V for an open connection. The selector lever
is indicated in Figure 2 in dashed lines at 344 and the contact
plate at 346,)while the six output lines 319 to 323 are respectively
dedicated to the following driving settings: reverse (R), reverse ~
neutral (RN), neutral (N), forward neutral (FN), forward (F), low (L),
and extra low (EL). In the neutral (N) position, the transmission
brakes are rel~ased and the turbine pump is released. In the forward
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neutral (FN) position, the DR brake (or possibly the SR brake) is
applied. The turbine pump is released, so that free wheeling is
provided and instantaneous vehicle stopping can be provided. In
the forward (F~ position, the turbine pump is engaged and this is
the normal driving position. The other positions are self-explana-
tory. It will, of course, be understood that more and different
settings can be provided as desired.
The brake lever, which is indicated at 348, uses lines
325 to 327 to indicate eight different braking levels by virtue
of the pattern of switch contactors 348a illustrated. These brake
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lever input lines like those from the selector lever are connected
~,, ~ r~ ~o ,~ c r
~ to the/microproccs30~ 200.
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Again, it will be understood that the forgoing listing
is not exhaustive, and the microcomputer 200 has a capacity to
process many more of each of the`dirferent types of signals discussed.
The system is powered by the vehicle battery B which
provides +24V and the system ground. The battery B is connected to
a voltage regulator 352 which provides a stabilized +5V supply,
the voltage regulator being located in the selector lever box or
hou~ing with an ignition switch 350 and serving to supply the micro-
computer, the shaft speed signal amplifiers, and the throttle posi-
tion potentiometer mentioned above. All connections to ground in
the system are made through a common ground line, connected to the
minus pole of battery B via the microcomputer 200.
Before discussing the details of the microcomputer 200
the operating characteristics of the overall system will be briefly
considered. The full throttle performance characteristics of an
engine-transmis~;ion unit as described above are shown in Figure 4,
including the characteristics for double rotation drive, single ro-
tation drive, and direct drive together with the eighc-speed goar.
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For the sake of simplicity, the h~draulic drive characteristics
are shown for tfie first four mechanical gear ratios only; how-
ever, all combinations are, of course, possible and the deter-
mination and control of these combinatIons (for all throttle
positions) necessitates the use of the electronic control sys-
tem according to the invention. In addition, the determination
and control of transmission settings (including the influence
; of engine) during ~raking by overspeeding the turbine or varia-
tions thereof require such a control system. Braking by means
Of overspeeding the turbine is obtained for the transmission of
Figure 1 by releasing the direct clutch friction disc 12, and
connecting the releasable pump 3 as well as the single rotation
brake 26 when the speed ratio as defined above is greater than
unity. This condition is achieved by providing for a gear ratio
in the mechanical gear which is lower than what would normally
be provided. Reference is made to co-pending, common assigned
Canadian Application Serial No. 318,971, filed on even date
herewith, entitled "Braking Method for Vehicle Transmission"
for a further description of this braking technique. In any
event, the direction of the flow of power in the transmission
is thus reversed, thereby producing a retarding effect. The
` characteristics of the retarding function are shown in Figures ;~
5(a) and 5(b), where modulation of the amount of braking is -~
achieved in part by influencing the engine, by means of pres-
` surized air aevices, vacuum devices, electro-magnet devices,
or other electrical devices, which devices are energized by
` means of electricàl signals. Figure 5(b) shows other varia-
tions of hydraulic braking, where either the pump member 3 or ;
the single rotation brake 26 is released, that is, free to ro-
tate. These yariation~ also produce a retarding ef~ect which
is modulated b~ ~nfluencin~ or controllin~ the engine aS des- -
cribed above.
- 1 g
~: ~
Referring to Figure 6, a diagram is provided which
indicates the driving conditions, remote control settings, auto-
matic contactors related to manual settings, shaft speed sig-
nals, values calculated in microcomputer, output signals, and
so on. This diagram is included as an aid in understanding of
the operation of the system of the invention in connection with
the description of the autopilot or microcomputer 200. ~owever,
it should be noted that Figure 6 is not suitable for showing
shift points between different driving conditions in that the
10 relationships between primary conditions and secondarv condi-
tions are normally variables. Figure 6 shows the level of co~.-
plexity of the problem to be solved, especially for a high per-
formance transmission. In this regard, Figure 6 is not intend-
ed to describe in detail the programming of the autopilot of
the invention for the special applications in question, but
rather to show that the autopilot is capable of solving the
problem of converting input signals to suitable output signals
for the type of transmission in question.
Considering Figure 6 in more detail, and referring
20 to driving conditions set forth at the left side of Figure 6, -
condition No. 1 is the setting for forward drive wherein the
guide member 7 of the torque converter TC is connected for
single or double rotation drive and the turbine shaft 16 is
connected via mechanical gear transmissions P and R to the out-
put shaft 58. For this particular transmission the guide mem- ;
ber 7 would be connected for single rotatioh drive via plane-
tary gear 22 to the turbine shaft 16 and the turbine shaft 16
would then be connected over mechanical gear transmissions P
and R to the output shaft 58 for driving the vehicle. Obvious-
30 ly for purposes of norm~1 st~rting, the lower gears of trans-
missions P and R would ~e connected, For this specific trans- ;
mission, the pump member 3 of the torque converter TC would not
- 20 -
. ~
.
~ .: . : . :
3~
~ yet be connected. This is to avoid drag torque and to prevent
load on the engine when the vehicle is stopped. The pump mem-
ber 3 is then connected to the rotating casing 2 via coupling
9 at the moment when the throttle is set to increase engine
speed, and at this time the transm:ission passes from condition
No. l to condition No. 2. The reason why the pump member 3 is
the last connection in the row-of transmission connections to
be actually engaged is that, with the transmission described
herein, this arrangement will avoid connection shocks by avoid-
ing circulation of fluid in the torque converter chamber. Uponconnection of the pump member 3 such fluid circulation then
commences, whereby torque multiplication builds up. Hence, con-
nection of the pump member 3 constitutes the transition between
driving conditions No. l and 2.
It will be understood that mechanical transmissions P
and R provide eight forward gear steps as shown schematically
and numerically on Figure 4. The first four gear steps are of
course the four forward gear ratios in mechanical transmission
P with the brake 67 of the mechanical range gear R connected to
the stationary casing, thereby providing a reduction gear ratio
through the mechanical transmission R. The next four gear
steps V through VIII again comprise the same four gear steps of
mechanical transmission P, but this time with the input to
mechanical range gear transmission R connected directly to the
output shaft 58 via engagement of brake 62.
Depending on how hard the throttle is pressed, one
will have different tractive efforts. If the throttle is press-
ed down to maximum, then one achieyes the tractive effort illus-
trated in ~igure 4 at curve PhI. However, normally, the vehicle
accelerates fastex than the engine in the low ~ears, and there-
fore this high tractive effort is not actually obtained except
when climbing extremely high grades. When, however, the veh1cle
- 21 -
7~3~31
has accelerated to a certain point in relation to the enginespeed, then the guide member 7 is d~sconnected from the turbine
and connected to the stationaxy casing, i.e. br~ke 24 is re-
leased and brake 26 is engaged, wh:~ch of course comprises nor-
mal single rotation drive. This then is driving condition No 3
of Figure 6. This condition remains until the point is reached
whereat direct drive is required, at which point coupling 9 is
disengaged, freelng the pump member 3 from the rotating casing
and piston 10 is then activated to engage the disc 12 against
the extension 2b of the rotating casing 2. This of course, is
driving condition No. 4. The point at which the transition
from condition 3 to condition 4 occurs is related to the throt-
tle-pedal position which will be at different speed ratios be-
tween the pump member and the turbine member after the vehicle
has accelerated sufficiently. In first gear the vehicle can
now accelerate up to about 12 km/hour and the tractive effort
is represented by the curve PlI in the case of maximum throttle.
Normally the first two or three gear steps of the mechanical
transmission P and R are used only for starting under severe
conditions or for driving fully loaded up very high grades.
Normally, therefore, the automatic control means may have al-
ready connected up to the fifth gear or possibly up to the
eighth gear before there arises the need for applying some type
of retardation.
Condition No. 5 of Figure 6 represents conventional -~
hydraulic braking wherein, at the torque converter, the direct
drive is connected and the guide member 7 is held fixed to the
stationary casing or at lower vehicle speeds the guide member
7 can be connected to the turbine at brake 24 (again, with di-
rect drive connected) thereby making the guide mcmber rotate
backwards.
While t~is conventional type o~ braking is satisfac-
- 22 -
~, '.
7?~3~
~ tory, it does not provide the ability to ~odulate the brakingexcept by connecting different gears. Therefore, in lieu of
this conventional brakin~, with the present system it is pos-
sible to provide a hydraulic braking by overspeeding the turbine,
havin~ disconnected the direct drive connection. According to
this
; ~
;:
~ .:
`~
- 22a -
'
, ~ ~
~7'~
arrangement, the automatic control means must connect a gear for
a certain overspeeding of the turbine as shown diagran~atically
in Figures 5(a) and 5(b). In Figure 5(a) the lines marked n
with the indices I-VIII indicate turbine speeds, and the areas
marked P with indices I-VII indicate the retardation force
obtainable, the lower limits of the obtained regardation force
being with a released guide member and wi~h the engine running
due to torque transmitted from the turbine member to the pump
member. These lower limits of Figure 5(a) are represented
in Figure 5(b) by the line Ph I-IIIc' for three different gear
ratios, and the upper lines in Figure Sa are represented in Figure
5(b) by the lines marked Ph I-IIIa'. There is a difference,
however, in Figure 5(b) wherein the lines relate to constant
braking torque on the engine by compression braking or the like
and the speeds of the engine in Figure 5(b) are in accordance
with the dot-dash lines marked n I-IIIa-c. Figure 5(b) is the -
more theoretical diagram while Figure 5(a) shows the limits of
retardation force obtainable by controlling the connection of gear
ratios in relation to speed and engine speed, also taking in~o
consideration the temperature of the transmission, etc.
Referring again to Figure 6, driving condition No. 6
shows how under acceleration or retardation, direct drive at the
torque converter can be released, for example, by pressing the
throttle pedal down to a lower position, meaning of course a return
to hydraulic drive, or possible a disconnection of the direct
drive simply to avoid the engine speed being reduced below idling.
('ondition No. 7 illustrates that it is possible~, when
coasting, to release both the torque converter direct drive and
the pump member 3 to diminish the retardation force otherwise
obtained when driving the engine.
.~
,
~3Ç~
The type of transmission described herein permits
such functions as described hereinabove becausethe ~?rovision of
a releasable driving member at the torque converter permits soft
reconnections which can be automatically obtained. Under these
conditions, freewheeling is not dangerous.
Finally, driving condition No. 8 merely represents
connecting the reverse gear for driving in reverse.
Reading across the top of Figure 6 there is set forth
types of signals and calculations which can be utilized in control
of the vehicle transmission. These include Group I "contactors"
i.e., solenoid switches, (columns 1-4), Group II "automatic
contactors relating to manual settings", i.e., switch contacts
~hich are completed responsive to a manual setting, (columns 5-9),
Group II~ "pick-up input signals and automatic signal", i.e.,
speed and safety signals and the like, (columns 12-16), Group IV,
"manuever signals" (columns 19-26) and finally a group entitled
"position and~or conn. signals M4+M2 or M4~U+M2" (columns 30-37)0
To obtain automatic control, it is first of all
necessary to have manually set contactors such as are represented
by Group I, wherein, for example, column 4 represents the connection
of reverse which obviously is the result of a manual setting. For
the exemplary transmission under consideration, reverse connection
of the mechanical transmission gears and connection of the guide
` member is represented by column 3, and the difference between
columns 3 and 4 is simply the movement of the throttle pedal.
Connection for forward drive is represented by columns l and 2.
It will be obvious that columns 1-4 of Group I are
related to driving conditions. For controlling the transmission,
there must a:Lso be a number of contactors (and thus signals pro-
duced in response to the closing of these contactors) which are
actuated automatically in response to throttl~e, hydraulic braking
; - 24 -
'
.
~7~4~
setting and hand brake setting, these being represented by columns
5-9. These signals also are related to the driving conditions
but are automatically set and utilized in the electronic control
system to prevent "erroneous" driving conditions or to influence
driving conditions. Group III, in columns 12-16 illustrates
digital signals necessary as a basis for deciding the setting of
the transmission such as signals related to input and output speeds
and to the condition of safety devices for controlling tempera-
ture and oil level (columns 15 and 16). As described elsewhere
these signals can be utilized automatically to disconnect the
transmission in the event of conditions such as too high a temp-
erature or too low an oil level.
Group IV represents items to be calculated in the com~
puter based on the input signals, for example, the ratios of speeds
n2 / nl or n3 / nl, or the acceleration corresponding to the speed
n2. In mode of operation, the acceleration is then compared with
the throttle position (column 7) and the primary speed (column 12)~
Obviously this description covers only a sampling of the innumer-
able values which can be determined. ~s a result of these cal~ :
culated values in relation to the manner by which the automatic
control means is programmed, different output signals according
to Group V, maneuver signals and gear connection signals, the
points on columns 19~26 and 30-37 can be obtained.
Turning now to a further consideration of the microcomput~
which controls the settings of the various solenoid valves on the
basis of the input signals described above, the details of the
microcomputer are illustrated in Figures 7 and 8(a) to 8(d). In
; an exemplary preferred embodiment, two circuit cards are used, a
CPU card (Figure 7) and an "Input/Output" card (Figures 8(a) to
8(d)). Briefly considering these cards, the CPU card contains the
microprocessor and timing circuitry, capacity for up to 4096
.
- 25 - . ~
3~ 3~
s b ~ ~e i
~ytes of programmable read only memory (PROM) and 32-by*e~ of
random access memory (RAM), all of the addressing circuitry for
the various components in the microcomputer and input buffers
allowing the sensing of the state of twelve different contactors
which either open or close a connection to ground. The "Input/
Output" card contains sixteen power transistors which directly
control the sixteen solenoid valves described below, two output
latches which hold the signals controlling the state of the power
transistors, a voltage/frequency converter which transforms
the voltage indicating throttle position into TTL pulses the
frequency of which is porportional to throttle position, a delay
Gircuit for the "safety" signals, and three circuits which
guard against overloading of the shaft speed signal lines de-
scribed above. It is noted that the arrangement of components
on the two cards has been chosen so that the CPU card will be
identical for all applications envisioned, whereas the "Input/
Output" card will contain only those components needed for a
specific application. There is, of course, nothing which would
prevent placing of all thè components on one card, or distri-
buting the various components on more than two cards.
~`'' '
,
26
.
3~`3
Considering the CPU circuitry in more detail and re-
ferring to Figure 7, the basic components of the central pro-
cessing unit are a microprocessor 40Q, a random access memory
(RAM) 402, one or two programmable memories (PROMs) 404 ttwo
being provided in the embodiment under considexation), a pair
of hex inverting buffers 4Q6, a multiplexer 408, a pair of
latches 410 which are used in the decoding process, and addres-
sing circuitry 411 and timing circuitry including decoder 412
and crystal 415. Similarly, the output circuitry for processing
the CPU output is illustrated in Figure 8a and basically com-
prises a pair of latches 420 and 422 and sixteen power transis-
tors collectively denoted 424.
Microprocessor 400 controls the flow of data on eight
input data lines, referred to collectively as a data bus and
denoted 414. This data flow is to and/or from the memories 402
and 404, input buffers 406 and output latches 420, 422. Micro-
processor 400 also directly senses the state of external signals
(such as the shaft speed pulses, safety signals, throttle posi-
tion pulses described above~, and internally performs arithme-
tical and logical operations on these data, specifically on thebasis of these data. This processing of the data by micropro-
cessor 400 is controlled by storing an ordered set of date,
i.e., a program, in the programmable read only memories 404
which program will be input, via the data bus 414. ~ ~
~0 . ' . :
.
- 27 -
, .
L7~3~
to the Microprocessor 400 in the course of the normal operation
thereof and will be understood by the microprocessor as being a
set of coded instructions. The microprocessor 400 understands 256
different codes (corresponding to the 256 different possible per-
mutations of the states of the eight lines in the data bus) and
takes a specific and unique action in response to each of these
instructional codes. It is noted that not all of the data input
on the data bus 414, and in the PROMs 404, is instructions, and the
data input may also include data intended to be processed according
to the "instructions", or data to be input or output to and/or from
the random access memory 402, input buffers 406, or output latches
420, 422. As will be readily apparent to those skilled in the art,
the program is thus a series of instructions and data bytes which
control the operation of the microprocessor 400, and thereby all
of the other microcomputer components. The program which provides
for controlling the engine-transmission unit on the basis of the
input signals referred to above is described in general terms here-
inafter.
Timing circuitry, including a 2.0 MHz clock 415, times
the operations of the microprocessor. Most of the instructions used
are executed in 8~s (the other instructions take 12~s to execute),
thus permitting about 1~5,000 instructions to be executed each
second. This arrangement also makes it possible to determine time
periods very accurately, a feature which is effectively exploited
in determining the fre~uency of, for instance, the shaft speed
pulses. The 32 bytes of random access memory (R~) provided by
memory 402 are used to store variable information which can be
retrieved to perform logical and arithmetical operations. RAM 402
is used partly as an extension of the internal variable storage
of microprocessor 400, although the basic use is as a complement
to the microprocessor 400, thereby allowing full~useage of the
.
- 28 ~
~''743~ ~
microprocessor instruction set. In the present embodi~ent,
this provides the capability of per~orming arithmetical opera-
tions (viz.~ multiplication and division) between variable
values. In many microprocessors, this capability is included
as a part of the microprocessor itsielf.
The two hex-inverting input ~uffers 406 are used to
sense the state of the various contactors which, as noted
above, either open or close a connection to ground. Resistors
416 connected between the input lines and the ~5V line hold the
input line at ~5V when a respective contactor is open. When
the contactor is grounded, the input lines is held at OV. Be-
cause the buf~`ers 406 are inverting buffers, a signal which
is grounded by the corresponding contactor will be presented at
the data bus 414 as +5V signal when input is demanded by the
microprocessor 400. Likewise, an open contactor will produce a
signal o~ OV on the data bus 414.
The output latches 420, 422 shown in Figure 8a store
the eight signal levels of the data bus 414 when each is addres-
sed by the microcomputer 400, and hold those signals until
again addressed. In the latter case, the contents of the data
bus will then be stored. These two level (0 or +5V) logic
signals are then used by output latch 420 or 422 to control the
state of the eight power transistors 424 connected to that out-
put latch. As noted above, these power transistors 424 are
located within microcomputer 200. Thus, a latch output of +5V
on an input line causes the respective power transistor 424 to
close or complete a connection between ground and the output
signal line wh~ch connected to a corresponding solenoid valve.
Similarly, a latch output of OV causes the power transistor
424 to open its connection. The ind~vidual connections between ~;
particular transistors and the solenoids controlled thereby are
indicated in ~igure 8a.
- 29 -
.
743~
The power transistors 424 referred to above and
shown in FIqure 8a are chosen to have short switching times as
well as
;:
.:
; ;. ~':' ~
~'
~' '.
- 29a - -
the additional features of internal current limitin~, power limiting,
and thermal limitinq protection making them virtually impossible
to damage from any type of overload. In addition, transistors 424
are mounted on the card in such a way as to facilitate their cooling
by means of externally mounted conduction/convection arrangements
(not shown).
The latching circuits 41n and the addressing
circuits 411 are used to decode the signals produced
on the address lines by the microprocessor 400, these signals indi-
~? o~n~ c ~ ~
cating the commponcnt to which the microprocessor 400 intends to senddata or from which it expects to receive data. The address, to-
gether with the appropriate read or w~ite signal from the micro-
processor 400, is decoded to produce a unique signal for activating
one and only one of the microcomputer components described above,
i.e., memories 402, 404, input buffers 406, or output latches 420,
422.
The multiplexer 408 is controlled directly by the
microprocessor 400 and enables the microprocessor to directly
monitor, on lines 419, the state of up to eight external signals
such as the shaft speed pulses, throttle position pulses, or delayed
safety signals. These external signals do not use the data bus,
but instead are connected directly to the microprocessor 400 via
four lines 417 for which special instructions are provided. The
switching of the input lines as provided by multiplexer 408 enables
monitoring of any number of such signals.
Before some of the signals on lines 417 are directly
inputted to the microprocessor 400, certain steps are taken to limit
and transform the signals prior to the arrival thereof at the micro-
~processor 400. As shown in Figure ~ , protection of the shaf-t
speed signals against overload is provided by means of ~ener diodes
421 which open at 4.7V. Series resis~ors 423 are also includedO
,~
~ 30 ~
~7~
Further, the safety signals referred to above are reduced from
+24V to +5V by the circuit shown in Figure-Q~b~ which comprises
resistor 425, capacitor 427 and cliode 429. Finally, the throttle
position voltage from the potentiometer (not shown) connected to
line 312 (see Figure 2) is converted by a voltage-to-frequency
converter 431, and the associatecl circuitry illustrated, into TTL
pulses having a frequency of bewteen 500 Hz and 1500 Hz, the precise
frequency being proportio~al to the actual throttle position.
The specific components used on the two cards in a
specific embodimelnt are as follows:
,
CPU Card
Reference Model
Numeral No. Manuf. No. Description
400 1 RCA CDP 1802 Microprocessor
402 1 RCA CDP 1824 32-byte random access memory
(RAM)
4041 or 2 INTEL B 2716 2048-byte programmable read
only memory (PROM)
415 1 2,0 MHz clock crystal
410 2 Motorola MC1404sBCP Quad D Latch
411 1 -"- MC14555BCP Dual 1 of 4 decoder with
active high outputs
411, 4I2 1 -"- MC14556BCP Dual 1 of 4 decoder with
active low outputs (one half
each)
408 1 -"- MC14519BCP Quad two input multiplexer
406 2 -"- MC14502BCP Strobed hex inverter/buffers
Input/Output Card
420, 422 2 Motorola MC14508BCP Dual 4-bit Latch
424 16 National Semiconductor
LM395T Power transistors
431 1 Analog Devices
AD537JD Voltage/frequency converter
31 -
,
~, . - , ,,
7~
It will, of course, be understood that equivalent
compone~ts are available from several manufacturers, and in dif-
ferent variations, so that equivalent arrangements of components
are possible without departing from the principles of the micro-
computer of the invention.
In operation, the input signals applied via the input
buffers~ or the external signal input lines 419 are read in and
processed, and output signals are determined. These output signals
are.transmitted via the output latches 420, 422 and power transistors
424 under the direction of the program stored in one, or two, ex-
changeable PROMs 404 as described above. It might be noted at this
point that it is also possible to have two entirely different progra~
stored in two different PROMs, an arbitrary input`signal or combin-
ation of input signals determining which PROM is to be utilized and
thus which program is to be executed. As noted, the programs are
a series of coded instructions and sets of data representing~ for
example, shift criteria or output sequences, which.exactly deter-
mines the operation and coordination of the various components
in the auto-pilot (control system) of Figure 2.
The basic elements of the microcomputer program are
shown in Figure 9 and are largely self-explanatory. The program
is started when the engine is startedand, after-the necessary ini-
tiation instructions, goes into a cycle which is repeated until the
engine, and thus the autopilot is turned off. It is noted that the
proper start of the microprocessor 400, and thus the program, is
insured by means of a circuit arrangement connected to the "clear"
input of the microprocessor 400 and consisting of a resistor 430,
a capacitor 432, and a diode rectifier 434, together with timing
gate 412 of a dual decod~r.circuit, (see Figure 8). The gate circuit
412 delays the start of the microprocessor for about 1 millisecond,
allowing all other components to be i.nitialized, before energizing
the microprocessor with a distinct signal transmitted to the "clear"
32
' :
~74~
input thereof.
As indicated in Figure 9, a program cycle consists of
three phases: input, test and output. During the input phase,
the various input signals (shaft speeds, throttle position, selec-
tor lever position, etc.) are read in, evaluated, and stored for
later use. These input signals together with the present or
actual transmission setting are used, during the test phase,
to determine a new transmission setting. (Of course, the new
setting may be, and usually is, the same as the present setting).
When the setting is determined, the signals corresponding to
that setting are outputted during the output phase. In case of
a change in setting (i.e., a shift), the output signals may be
transmitted in a specified order and held for specified time
intervals which can be determined with an accuracy of 16 micro-
seconds. Thus, the transmission, and the engine, may be accurately
controlled by means of the solenoid valves thereby insuring, among
other things, gentle, smooth connections in the transmission.
Since an entire set of output signals is transmitted which will be
in effect during the whole of the next cycle and since the output
latches 420, 422 hold these signals until new signals are received
at the end of the next cycle, the power transistors 424 are held
in the proper states thereof under the control of continuous
signals which are periodically renewed. This gives an important
measure of slecurity against disturbances in the output circuits.
As discussed above, the electronic autopilot or micro-
computer of the invention can be programmed for utilization of a
wide variety of different input signals to control the torque
converter setting and/or a mechanical gear setting. For a rela-
tively simpl~e case, such as 1 1/2-stage torque converter alone,l
sufficient if even not good control can be provided with prlmary
~.'
- 33 -
.
~7~
speed and engine setting inputs. If a multi-step mechanical
gear is added, the secondary shaft speed signals or output shaft
speed signals then become necessary. For more advanced tor~ue
converters, such as those which provide selective release or
connection of the guide vanes and possible use as a turbine, with,
for example, a releaseable torque transmitting bladed part,
it becomes necessary, or at least highly preferable, to also
utilize inputs corresponding to a primary shaft speed and a
secondary shaft speed. This is also necessary when a mechanical
complementary ~ear is used, even if, for a mechanical gear alone,
the secondary shaft speed and engine setting may be sufficient.
It will be appreciated that immediately preceeding
discussion does not take into consideration the s~tting of the
feeder fluid gear pump, the maximum pressure values and temper-
~ es~ /th~sc
ature and oil level safety signalsland also can be red into the
mic'ocomputer as a basis for deciding when connections or dis-
connections are to be made.
The input signals can also be utilized in a variety of
different ways. For example, it is quite obvious that in the
examplary embodiment, a signal indicating an excessive temperature
can be used to energize a warning lamp and/or disconnection of
the pump, and a predetermined time delay can be provided between
the warning lamp and the release of the pump. The same can be
said for the oil level signals and possibly other "safety signals"
which might be desirable to incorporate.
In providing the basic control for the setting of a
transmission in different driving conditions or braking conditions
and assuming that the transmission is of the type described~above,
the input speed and output speed are normally measured, and under
some circumstances, an intermediate speed, i.e., the turbine speed,
as well as the engine setting, are also determined. For shifting
:
.
,
~7~3~
between single rotation and double rotation, i.e., between the
brakes 26 and 24, is the ratio between t~e primary speed and
the turbine speed, either as directly measured or calculated
from the speed of the output shaf~ TOS in relation to the
transmission setting. Thus, in a simple example of controlling
shifting between single rotation and double rotation, the micro-
processor 400 would be programmed to calculate the speed ratio
from signals corresponding to the speeds in question (as derived
from the speed sensors discussed a~ove) and then compare this
ratio with a predetermined value stored, e.g., in one of the
PROMs 404, to determine whether shifting is appropriate. A
typical reference value is about 0.4 for double rotation.
Such a speed ratio is also used to control the setting
of the 3-element pump arrangement 300 shown in Figure 2. Such
speed ratio is also utilized in connection of the direct drive
~with a reference ratio of 0.7 being typical) whereas disconnec-
tion o the direct drive is made related to speed. The setting
of the torque converter, and especially the connection of direct
drive, can suitably be controlled by a so-called kick-down func- ;~
tion resulting in a later connection of the direct drive and an
earlier disconnection. When the throttle pedal is released,
.
a signal indicating this condition is fed into the electronic
autopilot and compared with the engine speed or primary speed,
and may be used to disconnect the converter completely i.e., `~
both brakes 26 and 24 are then disconnected. Such disconnection,
however, is also related to the manual setting signals and the
disconnection of the pump member. Thus, in general, the syst~em
can be programmed to provide any desired operation of the $orqua
converteX as long as one has input information relating to input
speed, i.e., engine speed and turbine speed (as directly measur-
ed or calculated from the transmission output shaft speed) and
the
- 3~ -
~` .
~743~
throttle or fuel injection setting, including kick-down. This is
only to indicate that if throttle position input signals are
available, these can be used in a suitable manner to control
connection and disconnection points o~thedirect drive.
The control of hydraulic kraking, whlc~ according to
conventional systems, requires connection of direct drive and one
of the brakes simultaneously, will depend principally on the
output shaft speed or turbine shaft speed together with a manual
setting signal which provides for a higher or lower amount of
braking.
A When there is a questionl~ providing a suitable setting
for a complementary gear, it is possible to obtain fairly good
shift points by monitoring the engine setting and output shaft
speed where the output shaft represents vehicle speed. But systems
used prior to the present invention do not take into consideration
- variation of the shift points such as would be desired in dependence
upon the weight of the vehicle and the grade of the hill to be
climbed. However, the input s gnals mentioned above can be used to
calculate the power delivered from the transmission and to compare
this with the vehicle acceleration to provide for a gear setting
which might be suitable from a fuel comsumption saving standpoint,
i.e., to provide higher gear ratios at lower vehicle speeds when the
vehicle is heavily loaded andJor climbing a hill. It is then
possible to use acceleration in xelation to the output power to
- provide a sliding or variable value of speed where a selected gear
setting is connected. The servo-cylinders CFI and CFC and the
corresponding electro-hydraulic or electro-pneumatic valves FIV
and F~V can be controlled to set engine fuel injection during a
shift between gears. It might be mentioned that when calculating
the acceleration of deceleration from the change of the output
shaft speed, it is possible to program the mi~roprocessor ln such
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a way that a certain deceleration is automatically set related
to a manual setting, within predetermined limits.
It will be appreciated that the actual programs used
in controlling the operation of the microprocessor will vary
widely depending on the vehicle transmission system which is to
be controlled and the nature and complexity of the control to be
provided. ~owever, it will be understood that the programs invol-
ved will be quite straightforward and that one of ordinary skill
in the art of programming will be able to readily provide suitable
programs. In this regard, it is noted that onl~ very simple
tasks are required of the microprocessor, i.e., the straightforward
mathematical evaluation and manipulation of predetermined input
signals to provide corresponding output control signals. In general
this merely involves very simple calculations and comparisons with
fixed or calculated values and such operations are, of course,
extremely commonplace in computer programming. As set forth above,
in one example, the ratio of signals corresponding to different
input speeds would be determined by simply dividing one by the
other and the resultant quotient then compared with a fixed constant
Where the quotient is less than the constant, one action (or no
action) is to be taken and where the quotient exceeds the constant
another action is to be taken (e.g., shift to double rotation).
More complex control operations merely involve further but similar,
manipulation of the input data with, for example, a large number
of comparisons being made to take into consideration a number of
factors before a given action is to be taken.
A number of further examples of the type of vehicle
transmissionoperationswhich can be controlled by the system of the
invention and the factors (including numerical examples provided
in the drawings) to be taken into consideration in effecting~various
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operations (i.e., shifting, etc.) a~e provid~d in commonly
assigned U.S. Patent No. 4,033,202 (~hlen et al) issued on
July 5, 1977 and the subject matter of that patent is hereby
incorporated by reference. A further patent of interest in this
general regard is U.S. Patent No. 3,005,359 (Ahlen) issued on
October 24, 1961.
An example of one of the sensor/amplifier arrangements
Gl, G2 and G3 (see Figure 2) is shown in Figure 10. The
sensor preferably comprises magneto-resistor 500 connected in
a bridge with two trimming resistors 502 as shown. The magneto-
resistor may be a Siemens FP212L100. A supply voltage is supplied
the sensor as illustrated. A gear tooth 504, which contains
iron and moves at cor,stant speed past the magneto-resistor 500
in the plane of the drawing,produ~es a signal voltage in the
form of a sine wave whose frequency correspon~s to the rate at
which the gear tooth rotates thereby. The gear tooth 504 is,
if course, part of a toothed wheel mounted for rotation on the
shaft whose speed is to be measured. The voltages across the
two fixed resistors 502 are detected as shown. The difference
between these two voltages is a stable sine wave voltage which
forms the input to the amplifier.
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The amplifier basically comprises a pair of operational
amplifiers 506 and Schmitt trigger circuit 508,`and produces
TTL pulses with a frequenc~ equal to that of the input sine
wave. The amplifier may be located in the vicinity of the
corresponding sensor as shown in Figure 2, or at a distanGe
from the sensor, in which case the amplifier and sensor are
connected by a twisted pair cable 510 to eliminate the effect of
outside disturbances. The sensor/amplifier arrangement described
above has a very high upper frequency limit (over lO KHz) and
the special advantage of having no lower frequency limit. This
means that all sensible shaft speeds, including very low speeds,
can be accurately determined. The possibility of measuring low
shaft speeds (and thus low vehicle velocities) is not available
with conventional speed pick-ups (where the signal voltage
from the pick-up is speed dependent), and is an important safety
feature in many applications such as control of door opening on
a bus.
~- Although the sensor may be aupplic~ directly by the
same voltage source as the amplifier (+5V), in the illustrated
embodiment the sensor is supplied with a potential difference
of less than 3V by means of the two transistor-rectifier pairs
~ ..
connected as illustrated. This arrangement permits lower
power dissipation in the magneto-resistors 500 and thus use with
a higher allowable ambient temperature, an important feature in many
applications, including applications`utilizing the transmission of
Fig. l. The voltage regulating arrangement may be located anywhere
in the system, but is included in the preferred embodiment as a part
of the amplifier since, in large scale production, the amplifying
circuits together with the voltage regulating circuits will be
integrated on a signal circuit chip or board to be located in the
vicinity of the sensor.
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43al `
The accurate determination of output shaft speed
over the entire operating range and within a time period that is
entirely dependent upon lnput shaft speed (i.e., independent
of outputshaft speed) is central to the effective operation
of the autopilot of the invention. This determination is
accomplished in the microcomputer by directlv determining a
value which is inversely proportional to the input shaft speed
and by counting the number of output shaft pulses received by
the microprocessor during the time that a predetermined number of
input shaft pulses are received by the microprocessor. In this
way a signal is produced having a value which is directly pro-
portional to the ratio of output shaft speed to input shaft speed~
This speed ratio can be accurately determined over the entire
operating range of the transmission because, as noted, the sensor/
amplifier arrangement of Figure 10 has no lower frequency limit
and a sufficiently high upper limit. The output shaft speed
is then calculated from the above-mentioned values by dividing
the value directly proportional to the` speed ratio by the value
inversely proportional to the input shaft speed. This operation
results in a value which is directly proportional to the output
shaft speed, which is obtained in a time which is independent of
that speed, and which has an accuracy that is also independent of
the output shaft speed. This overall process is controlled
directly by the program, making it possible to obtain any desired
accuracy in determining the shaft speed or speed ratio. This
method ~f calculation is, however, dependent upon the construction
of the microcomputer system as described above.
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~L7~
The operational reliability of the entire system is
dependent upon minimizing the time necessary to complete a cycle
resulting in an outputted set of signals, without sacrificing
accuracy in the various measurement and, in particular, the deter-
mination of the transmission output shaft speed. This is accom-
plished in the system described above by programming the micro-
compute~ in sùch a way as to make the cycle time almost entirely
dependent upon engine speed since the latter cannot fall below a
certain idling speed. This capability depends upon the construction
of the entire system as described above. Thus, the microprocessor
00 should have the capacity for directly monitoring pulse type
of
signals; further, the capability/performing arithmetical operations
must be present, the capacity for measuring very slow shaft speeds
musi be provided, and the output system must be constructed in the
manner described above. When the system of the invention is con-
structed in this way other additional advantages and features are
made available. Among these features is the ability to compute
vehicle acceleration on the basis of known speeds and successively
stored time differences and to relate this to the engine setting,
by means of a potentiometer-voltage/frequency converter arrangement
Q
- such as described above for producing pulses which are directly
monitored and measured by the microprocessor 400, in order to deter-
o~ mine the vehicle load and grade to be used in selecting a speclfic
set of predetermined shift criteria which are then used to determine
the transmission setting.
Although the invention has been described with respect
to an examplary embodiment thereof, it will be understood that
variations and modifications can be effected inthis embodiment
without departing from the scope or spiri-t of the invention.
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