Note: Descriptions are shown in the official language in which they were submitted.
CA 02240229 1998-06-10
[DETAILED DESCRIPTION OF THE INVENTION]
[Field of the Invention]
In general, the present invention relates to a
shift control method to be adopted in an electric-power-
assist-type transmission. In particular, the present
invention relates to a shift control method to be adopted
in an electric-power-assist-type transmission wherein a
gear shift as well as the operations to put the clutch in
an engaged or disengaged state are carried out
electrically. To put it even more concretely, the present
invention relates to a shift control method to be adopted
in an electric-power-assist-type transmission whereby the
clutch is put back in an engaged state after being released
from an engaged state by rotation of the shift spindle from
a first rotational position to a second rotational position
with a rotational speed of the shift spindle changed from a
first speed to a second speed lower than the first speed
with predetermined timing.
[Description of the Prior Art)
In the conventional transmission, a gear shift is
carried out by operating both a clutch pedal (or a clutch
lever) and a shift-change lever. On the other hand, in an
electric-power-assist-type transmission disclosed in
Japanese Patent Laid-open No. Hei S-39865, a gear shift is
carried out electrically by a motor. In the conventional
technologies described above, a shift drum is
CA 02240229 1998-06-10
intermittently rotated in both directions by a driving
motor so as to actuate a desired shift fork in a gear-
shift-change operation. On the other hand, it is possible
to put the clutch in an engaged or disengaged state also by
using a motor as well.
[Problems to be Solved by the Invention]
In such a case, when thinking of the conventional
manual transmission, only by repeating the shift-change
operation can the shift change be eventually completed even
if the gear is not shifted smoothly. In addition, whether
or not the clutch can be put in an engaged state smoothly
after the shift change much depends on the operation of the
clutch carried out by the driver.
As described above, in the conventional manual
trans-mission, most of poor operatability as evidenced by
whether or not a shift change can be completed without
repeating the shift-change operation or whether or not the
clutch can be put in an engaged state smoothly much depends
on how the operation is carried out by the driver. In
other words, the driver's learning effects allow good
operatability to be obtained.
By driving both the clutch and the shift-change
lever by means a motor, on the other hand, elements
dependent on the operation carried out by the driver do not
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CA 02240229 1998-06-10
exist any more. Thus, in a state where a gear shift is
impossible, if the clutch is not put in an engaged state
smoothly or not in accordance with the driver's intention,
it is quite within the bounds of possibility that the
driver feels a sense of incompatibility.
When putting back the clutch in an engaged state
after being released from an engaged state, for example, it
is desirable to put the clutch in an engaged state slowly
in order to reduce the magnitude of a generated shift
shock. On the other hand, the speed of a shift change is
dependent on the engagement speed of the clutch. It is
thus necessary to put the clutch in an engaged state
quickly in order to implement a fast shift change.
It is thus an object of the present invention to
solve the problems described above by providing a shift
control method to be adopted in an electric-power-assist-
type transmission offering good operatability wherein the
time it takes to put the clutch in an engaged state can be
shortened and the magnitude of a generated shift shock can
also be decreased as well.
[Means for Solving the Problems)
In order to achieve the object described above, the
present invention provides a shift control method to be
adopted in an electric-power-assist-type transmission
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wherein a clutch is put in an engaged or disengaged state
in a manner interlocked with the rotation of a shift
spindle rotated by a driving motor. The shift control
method is characterized in that the clutch is put back in
an engaged state after being released from an engaged state
by rotation of the shift spindle with a rotational speed
thereof changed from a high speed to a low speed with
predetermined timing.
According to the configuration described above, in
an operating zone having nothing to do with a shift shock,
the clutch is driven at a high speed but, in an operating
zone where the clutch is about to be put in an engaged
state, the clutch is driven at a low speed. As a result,
the time it takes to put the clutch in an engaged state can
be shortened and, at the same time, the magnitude of a
generated shift shock can also be decreased as well.
[Detailed Description of the Preferred Embodiment]
The present invention will become more apparent
from a careful study of the following detailed description
of a preferred embodiment with reference to accompanying
diagrams showing the embodiment. Fig. 1 is a plane diagram
showing an operation unit of a vehicle on which the
electric-power-assist-type transmission provided by the
present invention is mounted.
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As shown in the figure, the operation unit
comprises a shift-up switch 51 for the electric-power-
assist-type transmission and a shift-down switch 52 also
for the electric-power-assist-type transmission, a dimmer
switch 53 for changing the direction of a front light, a
lighting switch 54 for turning on and off the front light,
a start switch 55 for starting the engine and a stop switch
56 for stopping the engine. In the present embodiment,
pressing the shift-up switch 51 once will raise the shift
position by one stage. On the other hand, pressing the
shift-down switch 52 once will lower the shift position by
one stage.
Fig. 2 is a diagram showing a partial cross section
of the configuration of major components employed in a
driving system of the electric-power-assist-type
transmission provided by an embodiment of the present
invention.
In the configuration shown in the figure, a driving
motor 1 which serves as an electric actuator rotates a
shift spindle 3 in a normal or reversed direction through a
deceleration gear mechanism 2. The rotational position~(or
the angle) of the shift spindle 3 is sensed by an angle
sensor 28 which is installed at one end of the shift
spindle 3. A clutch arm 6 extends perpendicularly to the
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shift spindle 3. At one end of the clutch arm 6, there is
provided a gear mechanism 8 for converting the rotational
movement of the shift spindle 3 into a rectilinear
propagation. When the shift spindle 3 is rotated away from
a neutral position by the driving motor l, the gear
mechanism 8 releases the engaged state of a gear clutch 5
without regard to the direction of the rotation in the
course of the rotation. when the shift spindle 3 is
rotated back to reach the neutral position in the opposite
direction, on the other hand, the engaged state of the gear
clutch 5 is restored in the course of the rotation in the
reversed direction. The clutch arm 6 and the gear
mechanism 8 are configured so that the engaged state of the
gear clutch 5 is released at a point of time the shift
spindle 3 is rotated by a predetermined angle of typically
+/-6 degrees.
One end of a master arm 7 fixed on the shift
spindle 3 is engaged with a clutch mechanism 9 which is
installed on a shift-drum mechanism 800. When the shift
spindle 3 is rotated by the driving motor 1, a shift drum
is rotated in a direction determined by the rotational
direction of the shift spindle 3. The master arm 7 and the
clutch mechanism 9 form such a clutch mechanism that, when
the shift spindle 3 is rotated away from the neutral
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position in either direction, the master arm 7 and the
clutch mechanism 9 get engaged with the shift spindle 3,
rotating the shift drum 10 and, when the shift spindle 3 is
rotated back to the neutral position, the engaged state of
the master arm 7 and the clutch mechanism 9 with the shift
spindle 3 is released, leaving the shift drum 10 at a
position where the engaged state is released.
The edge of each shift fork 11 is engaged with an
external circumference groove 31 of one of sleeves 30 to be
described later by referring to Fig. 4. When the shift
drum 10 is rotated, the shift forks 11 are moved by the
rotation of the shift drum 10 in a direction parallel to
the axial direction of the rotation, moving one of the
sleeves 30 determined by the rotational direction and the
rotational angle of the shift drum 10 in a direction
parallel to a main shaft 4.
Fig. 4 is a diagram showing a squint view of the
sleeve 30 inserted in a state slideable in the axial
direction of the main shaft which is not shown in the
figure. On the circumference side surface of the sleeve
30, a groove 31 is provided in the circumrefential
direction. The edge of a shift fork 11 cited earlier is
engaged with the groove 31. A plurality of protruding-side
dowels 32 are provided on a ring-shaped flange 33 to form a
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single body on the circumference of the shaft hole of the
sleeve 30. The protruding-side dowels 32 are engaged with
denting-side dowels 42 of a gear 40 to be described by
referring to Fig. 5.
Fig. 5 is a diagram showing a squint view of the
gear 40 supported rotatably at a predetermined position on
the main shaft which is not shown in the figure. A
plurality of aforementioned denting-side dowels 42 are
provided on a ring-shaped flange 43 to form a single body
on the circumference of the shaft hole of the gear 40. As
described above, the denting-side dowels 42 are engaged
with protruding-side dowels 32 of the sleeve 30. Fig. 3 is
a conceptual diagram showing a state in which the
protruding-side dowels 32 of the sleeve 30 and the denting-
side dowels 42 of the gear 40 are engaged with each other.
On the other hand, Fig. 9 is a diagram showing a
squint view of the conventional sleeve 38 and Fig. 10 is a
diagram showing a squint view of the conventional gear 48.
As shown in Fig. 9, a plurality of stand-alone protruding-
side dowels 39 are provided on the sleeve 38 concentrically
with respect to the shaft hole of the gear 48. In order to
assure the strength of each of the stand-alone protruding-
side dowels 39, however, the area of the bottom surface of
each of the stand-alone protruding-side dowels 39 must be
8
CA 02240229 1998-06-10
made relatively large. As a result, with the conventional
technology, the ratio of the width of each of the
protruding dowels 39 to the length of the circumference on
which the protruding-side dowels 39 are provided increases,
allowing only four protruding-side dowels 39 to be created
thereon as shown in Fig. 9. This holds true of slits 49
bored on the gear 48 shown in Fig. 10.
Fig. 12 is a diagram showing a model of relative
positions of a protruding-side dowel 39 on the conventional
sleeve 38 and a slit 49 on the conventional gear 48. As
shown in the figure, the width D2 of the slit 49 in the
rotational direction is about twice the width Dl of the
protruding-side dowel 39. As a result, a period Ta during
which the protruding-side dowel 39 can not be engaged with
the slit 49 is long in comparison with a period Tb allowing
the protruding-side dowel 39 to be put in an engaged state
with the slit 49. The state of engagement of the
protruding-side dowel 39 with the slit 38 is referred to
hereafter as a dowel-in state.
In the case of the present embodiment, on the other
hand, the protruding-side dowels 32 are provided on a ring-
shaped flange 33 to form a single body. Thus, the width D3
of the protruding-side dowel 32 and the width D4 of the
denting-side dowel 42 in the rotational direction can be
9
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made sufficiently small with yet adequately enough strength
kept as shown in Fig. 13, a diagram showing a model of
engagement timing of relative positions of a protruding-
side dowel 32 on the sleeve 30 provided by the present
embodiment and a denting-side dowel 42 on the gear 40
provided by the present invention. As a result, the period
Ta during which the dowel-in state is impossible is short
in comparison with the period Tb making a dowel-in state
possible, increasing the probability of the dowel-in state.
In this case, the dowel-in state is a state of engagement
of the protruding-side dowel 32 with a slit 46 on the gear
40.
In addition, in the present embodiment, the
difference between the width DS in the rotational direction
of the slit 46 and the width D3 in the rotational direction
of the protruding-side dowel 32 can be made small, allowing
the play after the engagement of the protruding-side dowel
32 with the slit 46 to be reduced. As a result, the
magnitude of a shift shock and the amount of noise
generated in the engagement can also be decreased.
On the top of that, in the present embodiment, the
taper of the protruding-side dowel 32 is bent to form a
convex shape as shown in Fig. 6 while the taper of the
denting-side dowel 42 has a straight-line shape as shown in
CA 02240229 1998-06-10
Fig. 7. Thus, the dowels 32 and 42 can be brought into
line contact with each other in the axial direction as
shown in Fig. 8, allowing concentration of stress to be
avoided. As a result, the dowel strength can be increased
substantially and, at the same time, the durability and the
resistance against abrasion can also be improved as well.
In the configuration described above, the sleeves
30 are moved in parallel by the shift forks 11 to a
predetermined position, causing the protruding-side dowels
32 on one of the sleeves 30 to be put in an engaged state
with the slits 46 of the gear 40. In this dowel-in state,
the gear 40 which has been supported in an idle state so
far with respect to the main shaft 4 is engaged with the
main shaft 4 by the sleeve 30, being rotated synchronously
with the main shaft 4 as is generally known. As a result,
a rotating force transferred from a clutch shaft to a
counter shaft is propagated to the main shaft 4 by way of
the gear. It should be noted that both the clutch and
counter shafts are not shown in the figure.
It is worth noting that, while not shown explicitly
in the figure, the engine of the vehicle employing the
electric-power-assist-type transmission adopting the shift
control method provided by the present invention is a four-
cycle engine. In a power transmission system for
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CA 02240229 1998-06-10
propagating power from the crank shaft to the main shaft, a
power output by the engine is propagated through a
centrifugal clutch on the crank shaft and a clutch on the
main shaft. Thus, for an engine rotational speed lower
than a predetermined value, the centrifugal clutch on the
crank shaft cuts the propagation of power to the clutch on
the main shaft. As a result, the gear can be shifted to
any speed if the vehicle is put in a halted state.
Fig. 14 is a block diagram showing the
configuration of major components employed in a control
system of the electric-power-assist-type transmission
provided by the embodiment of the present invention and
Fig. 15 is a block diagram showing a typical configuration
of an ECU 100 employed in the control system shown in Fig.
14.
As shown in Fig. 14, the driving motor 1 described
earlier is connected between motor+ and motor- pins of the
ECU 100. Sensor-signal pins S1, S2 and S3 are connected
respectively to a vehicle-speed sensor 26 for sensing the
speed of the vehicle, an Ne sensor 27 for sensing the
rotational speed Ne of the engine and the angle sensor 28
described earlier for sensing the rotational angle of the
shift spindle 3. Shift-instruction pins G1 and G2 are
connected to the shift-up and shift down switches 51 and 52
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described earlier respectively.
A battery 21 is connected to a main pin of the ECU
100 through a main fuse 22, a main switch 23 and a fuse box
24. The battery 21 is also connected to a VB pin through
a fail-safe (F/S) relay 25 and the fuse box 24. An
excitation coil 25a of the fail-safe relay 25 is connected
to a relay pin.
As shown in Fig. 15, the main and relay pins of the
ECU 100 are connected internally to a power-supply circuit
106 which is connected to a CPU 101. The sensor-signal
pins Sl, S2 and S3 are connected to input pins of the CPU
101 through an interface circuit 102. On the other hand,
the shift-instruction pins Gl and G2 are connected to input
pins of the CPU 101 through an interface circuit 103.
A switching circuit 105 comprises a FET (1) and a
FET (2) connected in series and a FET (3) and a FET (4)
also connected in series. The series circuit of the FET
(1) and the FET (2) and the series circuit of the FET (3)
and the FET (4) are connected to each other to form a
parallel circuit. One terminal of the parallel circuit is
connected to the VB pin while the other terminal is
connected to a GND pin. The junction point between the FET
(1) and the FET (2) is connected to the motor- pin while
the junction point between the FET (3) and the FET (4) is
13
CA 02240229 1998-06-10
connected to the motor+ pin. The FETs (1) to (4) are
selectively controlled by PWM by the CPU 101 through a pre-
driver 104. The control of the FETs (1) to (4) carried out
by the CPU 101 is based on a control algorithm stored in a
memory unit 107.
Next, the shift control method implemented by the
electric-motor-assist-type transmission provided by the
present invention is explained by referring to flowcharts
shown in Figs. 16 to 21 and operational timing charts shown
in Fig. 22.
The flowchart shown in Fig. 16 begins with a step
S10 to form a judgment as to whether or not either the
shift-up or shift-down switch 51 or 52 has been operated.
If one of the switches is found turned on, the flow of
control goes on to a step S11 to form a judgment as to
whether it is the shift-up switch 51 or the shift-down
switch 52 that has been turned on. If it is the shift-up
switch 51 that has been turned on, the flow of control
proceeds to a step S13. If it is the shift-down switch 52
that has been turned on, on the other hand, the flow of
control proceeds to a step S12 at which the rotational
speed Ne of the engine is stored in a variable Nel. The
flow of control then continues to the step S13.
At the step 513, the FETs employed in the switching
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circuit 105 of the ECU 100 are selectively controlled by
PWM in dependence on whether it is the shift-up switch 51
or the shift-down switch 52 that has been turned on
starting from a point of time tl of the time chart shown in
Fig. 22. To be more specific, if it is the shift-up switch
51 that has been turned on, the FETs (2) and (4) are
controlled by PWM at a duty ratio of 1000 with the FETs (1)
and (3) turned off. As a result, the driving motor 1
starts to rotate in a shift-up direction, driving the shift
spindle 3 also to rotate in the shift-up direction as well
in a manner interlocked with the driving motor 1.
If it is the shift-down switch 52 that has been
turned on, on the other hand, the FETs (1) and (3) are
controlled by PWM at a duty ratio of 100% with the FETs (2)
and (4) turned off. As a result, the driving motor 1
starts to rotate in a shift-down direction, a direction
opposite to the shift-up direction, driving the shift
spindle 3 also to rotate in the shift-down direction as
well in a manner interlocked with the driving motor 1.
By setting the duty ratio at 100a in this way, the
speed of the shift can be increased, allowing the duration
of the shift to be shortened. As a result, the clutch can
be put in a disengaged state in a short period of time. It
should be noted that the present embodiment is designed so
CA 02240229 1998-06-10
that, by rotating the shift spindle by merely five to six
degrees, the clutch can be put in a disengaged state.
The flow of control then goes on to a step S14 at
which a first timer not shown in the figure is started to
measure time. Then, the flow of control proceeds to a step
S15 at which a rotational angle THETAO of the shift spindle
3 detected by means of the angle sensor 28 is read in.
Subsequently, the flow of control goes on to a step S16 to
compare the detected rotational angle THETAO with a first
reference angle THETAref which is set at +/- 14 degrees in
the case of the present embodiment. To be more specific,
the flow of control proceeds to the step S16 to form a
judgment as to whether or not the rotational angle THETAO
exceeds the reference angle THETAref. To put it in more
detail, the judgment formed at the step S16 is a judgment
as to whether or not the rotational angle THETAO is equal
to or greater than 14 degrees, or the rotational angle
THETAO is equal to or smaller than -14 degrees. It should
be noted that, in the following description, the phrase
stating "a quantity goes beyond a +/- value" is used to
imply that either the quantity is equal to or greater than
the + value, or the quantity is equal to or smaller than
the - value for the sake of expression simplicity.
An outcome of the judgment formed at the step S16
1~
CA 02240229 1998-06-10
indicating that the rotational angle THETAO goes beyond +/-
14 degrees means that it is quite within the bounds of
possibility that the sleeves moved in parallel by the shift
forks 11 have arrived at a normal engaged (dowel-in)
position. In this case, the flow of control goes on to a
step 517. On the other hand, an outcome of the judgment
formed at the step S16 indicating that the rotational angle
THETAO does not go beyond +/-14 degrees means that it is
quite within the bounds of .possibility that the sleeves
moved in parallel by the shift forks 11 have not arrived at
the normal engaged (dowel-in) position. In this case, the
flow of control goes on to a step S30 to be described
later.
When the fact that the sleeves moved in parallel by
the shift forks 11 have arrived at the normal engaged
(dowel-in) position is detected at a point of time t2 as a
result of the comparison of the rotational angle THETAO
with the reference rotational angle THETAref, the flow of
control proceeds to the step S17 at which the first timer
is reset. The flow of control then continues to a step S18
at which the FETs employed in the switching circuit lOS~of
the ECU 100 are selectively controlled by PWM in dependence
on whether it is the shift-up switch 51 or the shift-down
switch 52 that has been turned on.
17
CA 02240229 1998-06-10
To be more specific, if it is the shift-up switch
51 that has been turned on, the FETs (1) and (4) are
controlled by PWM at a duty ratio of 100% with the FETs (2)
and (3) turned off. If it is the shift-down switch 52 that
has been turned on, on the other hand, the FETs (2) and (4)
are controlled by PWM at a duty ratio of 1000 with the FETs
(1) and (3) turned off. As a result, the input pins of the
driving motor 1 are short-circuited, providing a rotational
load to the driving motor 1.. In this state, a braking
effect is applied to the driving force working in the
shift-up or shift-down direction of the shift spindle 3,
reducing the magnitude of an impact of the shift spindle 3
on a stopper. Such an impact is generated when the shift
spindle 3 is brought into contact with the stopper. It
should be noted that the rotational angle of the shift
spindle 3 at which the shift spindle 3 is brought into
contact with the stopper is 18 degrees.
The flow of control then goes on to a step S19
shown in Fig. l7 at which a second timer not shown in the
figure is started to measure time. Then, the flow of
control proceeds to a step S20 to form a judgment as to'
whether or not the time measured by the second timer has
exceeded 15 ms. If the time measured by the second timer
has not exceeded 15 ms, the flow of control continues to a
18
CA 02240229 1998-06-10
step S21 to execute control of the rotational speed Ne of
the engine to be described later. The pieces of processing
at the steps S20 and S21 are repeated till the time
measured by the second timer exceeds 15 ms. As the time
measured by the second timer exceeds 15 ms at a point of
time t3, the flow of control goes on to a step S22 at which
the second timer is reset.
Subsequently, the flow of control proceeds to a
step S23 at which the FETs employed in the switching
circuit 105 of the ECU 100 are selectively controlled by
PWM in dependence on whether it is the shift-up switch 51
or the shift-down switch 52 that has been turned on. To be
more specific, if it is the shift-up switch 51 that has
been turned on, the FETs (2) and (4) are controlled by PWM
at a duty ratio of 70o with the FETs (1) and (3) turned
off. If it is the shift-down switch 52 that has been
turned on, on the other hand, the FETs (1) and (3) are
controlled by PWM at a duty ratio of 70o with the FETs (2)
and (4) turned off. As a result, since the sleeves are
pushed against the gear by a relatively weak torque, the
load borne by each dowel is reduced till the engaged
(dowel-in) state is reached, allowing the dowel-in state to
be sustained with a high degree of reliability.
The flow of control then goes on to a step S24 at
19
CA 02240229 1998-06-10
which a third timer not shown in the figure is started to
measure time. Then, the flow of control proceeds to a step
S25 to form a judgment as to whether or not the time
measured by the third timer has exceeded 70 ms. If the
time measured by the third timer has not exceeded 70 ms,
the flow of control continues to a step S26 at which the
control of the rotational speed Ne of the engine is
executed. The pieces of processing at the steps S25 and
S26 are repeated till the time measured by the third timer
exceeds 70 ms. As the time measured by the third timer
exceeds 70 ms at a point of time t4, the flow of control
goes on to a step S27 at which the third timer is reset.
The flow of control then proceeds to a step S28 to start
clutch-on control to be described later.
It should be noted that the time-up time of the
third timer adopted in the present embodiment is determined
from the period Ta during which an engaged state can not be
established as described earlier by referring to Fig. 13.
To put it in detail, the time-up time of 70 ms is set so
that the control to push the sleeves against the gear is
executed at least till the period Ta is over. In the mean
time, the protruding-side dowels are brought into contact
with the denting-side dowels. Since the duty ratio has
been reduced to 70%, however, the load borne by each dowel
CA 02240229 1998-06-10
is light, being favorable to the strength of the dowel.
In addition, the time-up time of the third timer
does not have to be set at a fixed value. The time-up time
can be set at a variable value determined as a function of
gear setting. For example, the time-up time is set at 70
ms and 90 ms for the gear set at the range first to third
speeds and the range fourth to fifth speeds respectively.
If the outcome of the judgment formed at the step
S16 shown in Fig. 16 indicates that the rotational angle
THETAO has not exceeded the first reference angle THETAref,
on the other hand, the flow of control goes on to the step
S30 shown in Fig. 18 to form a judgment as to whether or
not the time measured by the first timer has exceeded 200
ms. Since the outcome of the judgment formed for the first
time indicates that the time measured by the first timer
has not exceeded 200 ms, the flow of control goes on to a
step S31 at which the Ne control is executed before
returning to the step S16 shown in Fig. 16.
As time goes by, the outcome of the judgment formed
at the step S30 indicates that the time measured by the
first timer has exceeded 200 ms, implying that the shift
change attempted this time ends in a failure. In this
case, the flow of control goes on to a step S32 at which
the first timer is reset. The flow of control then
21
CA 02240229 1998-06-10
proceeds to a step S33 at which the value of a re-inrush
flag to be described later is referenced. A reset state of
the re-inrush flag, that is, a value thereof of zero,
indicates that re-inrush control to be described later has
not been executed. In this case, the flow of control
continues to a step S34 at which the re-inrush control is
executed for the first time. The in-rush control is
executed because, in some cases, the driver feels a sense
of incompatibility if it takes a long time to accomplish a
shift change.
On the other hand, a set state of the re-inrush
flag, that is, a value thereof of one, indicates that the
shift change was not successful in spite of the fact that
the re-inrush control was executed. In this case, the flow
of control continues to a step S35 at which the clutch is
put in an engaged state without making a shift change. At
the same time, the re-inrush flag is reset. The flow of
control then goes on to a step S36 at which the clutch-on
control to be described later is executed.
Next, a method adopted for the re-inrush control is
explained by referring to the flowchart shown in Fig. 19.
Carried out when the sleeves driven by the shift forks into
a parallel movement in the axial direction did not arrive
at the normal engagement position, the re-inrush control is
22
CA 02240229 1998-06-10
processing of making a re-movement (re-inrush) attempt to
once reduce the movement torque before applying a
predetermined torque again to the shift forks.
As shown in the figure, the flowchart begins with a
step S40 at which the duty ratio of the FETs under the PWM
control is reduced to 200. To be more specific, the duty
ratio of the FETs (2) and (4) or that of the FETs (1) and
(3) is reduced in a shift-up operation or in a shift-down
operation respectively. As a result, the driving torque
applied to the shift forks 11 is weakened.
The flow of control then goes on to a step S41 at
which a fourth timer not shown in the figure is started to
measure time. Then, the flow proceeds to a step S42 to
form a judgment as to whether or not the time measured by
the fourth timer has exceeded 20 ms. If the time measured
by the fourth timer has not exceeded 20 ms, the flow of
control continues to a step S43 at which the Ne control is
executed. If the time measured by the fourth timer has
exceeded 20 ms, on the other hand, the flow of control goes
on to a step S44 at which the fourth timer is reset. The
flow of control then goes on to a step S45 at which the~re-
inrush flag is set. Then, the flow of control returns to
the step S13 shown in Fig. 16 at which the driving motor 1
is again controlled by PWM at a duty ratio of 1000,
23
CA 02240229 1998-06-10
applying a large torque to the shift forks as usual.
As described above, in the present embodiment, if a
shift change is not made normally, the torque applied to
the shift forks is once weakened before being strengthened
again to push forth the sleeves. As a result, the
operation to re-inrush the sleeves can be carried out with
ease.
Next, essentials and general operations of the Ne
control and the clutch-on control cited above are explained
in a simple and plain manner by referring to Figs. 23 and
24 respectively prior to detailed description of the
operations thereof.
As described by referring to Fig. 22, in the
present embodiment, when the rotation of the shift spindle
is started at the point of time tl, the engagement of the
clutch is released at a point of time t22 and the rotation
of the shift spindle is completed at the point of time t3.
hater on, at the point of time t4, the control to push the
sleeves is executed before a transition to the clutch-on
control, control to put the clutch in an engaged state.
In the clutch-on control, the clutch is put in an
engaged state slowly in order to reduce the magnitude of a
generated shift shock. In other words, it is necessary to
lower the rotational speed of the shift spindle 3. On the
24
CA 02240229 1998-06-10
other hand, the speed of a shift change is dependent on the
rotational speed of the shift spindle 3. It is thus
necessary to increase the rotational speed of the shift
spindle 3 in order to implement a fast shift change.
In order to satisfy the two requirements described
above at the same time, according to the present invention,
in a period from the point of time t4 to the point of time
t5, the shift spindle 3 is rotated at a high rotational
speed till a zone in close.proximity to an angular range to
put the clutch in an engaged state is reached whereas,
after the point of time t5, that is, in the angular range
to put the clutch in an engaged state, the shift spindle 3
is rotated at a low rotational speed as shown in the time
chart of Fig. 22. By executing such two-stage return
control in the present embodiment, the magnitude of the
generated shift shock and the time it takes to make a shift
change can be both reduced simultaneously.
In addition, in the present embodiment, the timing
to put the clutch in an engaged state is controlled to
timing optimum for the operation of the accelerator pedal
carried out by the driver. Fig. 23 is a diagram showing
operational timing charts representing changes of the
rotational angle THETAO of the shift spindle in the clutch-
on control and the rotational speed of the engine in the Ne
CA 02240229 1998-06-10
control in a shift-up operation. On the other hand, Fig.
24 is a diagram showing operational timing charts
representing changes of the rotational angle THETAO of the
shift spindle in the clutch-on control and the rotational
speed of the engine in the Ne control in a shift-down
operation.
As shown in Fig. 23, as a general practice in a
shift-up operation, the control method comprises the steps
of restoring the accelerator pedal, turning on the shift-up
switch 51, letting a shift change take place, putting the
clutch back in an engaged state and opening the
accelerator. In the mean time, the rotational speed Ne of
the engine changes as shown by a solid line a. At that
time, the shift spindle is controlled as shown by solid
lines A and B.
It is also quite within the bounds of possibility,
however, that the driver turns on the shift-up switch S1
without restoring the accelerator pedal or opens the
accelerator before the clutch is put back in an engaged
state. In such a case, it is desirable to put the clutch
in an engaged state quickly since the driver usually
desires a fast shift change.
In the present embodiment, changes in engine
rotational speed Ne represented by a solid line b indicate
26
CA 02240229 1998-06-10
that the driver has turned on the shift-up switch 51
without restoring the accelerator pedal. In this case,
quick return control of the rotational angle THETAO of the
shift spindle to put the clutch in an engaged state
immediately is executed as shown by a solid line C. On the
other hand, changes in engine rotational speed Ne
represented by a solid line c indicate that the driver has
opened the accelerator with timing preceding timing to put
the clutch in a re-engaged .state. In this case, quick
return control of the rotational angle THETAO of the shift
spindle to put the clutch in an engaged state immediately
is executed as shown by a solid line D.
As a general practice in a shift-down operation, on
the other hand, as shown in Fig. 24, the control method
comprises the steps of restoring the accelerator pedal,
turning on the shift-down switch 52, letting a shift change
take place, putting the clutch back in an engaged state and
opening the accelerator. In the mean time, the rotational
speed Ne of the engine changes as shown by a solid line a.
At that time, the shift spindle is subject to two-stage
control as shown by solid lines A and B.
In a shift-down operation, however, the engine may
experience empty puffing. In such a case, it is desirable
to put the clutch in an engaged state quickly since quick
27
CA 02240229 1998-06-10
engagement of the clutch in such a state will generate a
shift shock having a small magnitude.
In the present embodiment, changes in engine
rotational speed Ne represented by a solid line b or c
indicate that the engine has experier_~ed empty puffing. In
this case, quick return control of the rotational angle
THETAO of the shift spindle to put the clutch in an engaged
state immediately is executed as shown by a solid line C or
D respectively.
Next, operations of the Ne control and the clutch-
on control for implementing the two-stage control and the
quick return control are explained in detail. Fig. 20 is a
diagram showing a flowchart representing the method of the
Ne control carried out at the steps 521, S26, S31 and 543.
As shown in the figure, the flowchart begins with a
step S50 at which the rotational speed Ne of the engine is
measured. The flow of control then goes on to a step S51
at which a peak-hold value Nep or a bottom-hold value Neb
of the rotational speed Ne of the engine measured so far is
updated in dependence on the value of the rotational speed
Ne of the engine measured at the step SSO. Then, the flow
of control proceeds to a step S52 to form a judgment as to
whether the shift change is a shift up or a shift down. If
the shift change is a shift up, the flow of control
28
CA 02240229 1998-06-10
continues to a step 556. If the shift change is a shift
down, on the other hand, the flow of control continues to a
step S53.
At the step S56, the rotational speed Ne of the
engine measured at the step S50 is compared with the
bottom-hold value Neb updated at the step S51 in order to
form a judgment as to whether or not the difference between
the two (Ne - Neb) is equal to or greater than 50 rpm.
This judgment is a .judgment as to whether or not
the accelerator is closed in a shift-up operation. A
difference (Ne - Neb) equal to or greater than 50 rpm
indicates that the driver has turned on the shift-up switch
51 without restoring the accelerator pedal or has opened
the accelerator with timing preceding timing to put the
clutch in a re-engaged state. In this case, the flow of
control goes on to a step S55 to set a quick-return flag F
to suggest that the clutch be immediately put in an engaged
state before finishing the processing. On the other hand,
a difference (Ne - Neb) smaller than 50 rpm indicates that
the normal control should be continued. In this case, the
control of the rotational speed of the engine is completed
without setting the quick-return flag F.
As described above, if the outcome of the judgment
formed at the step S52 indicates that the shift change is a
29
CA 02240229 1998-06-10
shift down, on the other hand, the flow of control
continues to the step S53. At the step S53, the rotational
speed Ne of the engine measured at the step S50 is compared
with the rotational speed Nel of the engine stored at the
step S12 in order to form a judgment as to whether or not
the difference between the two (Ne - Nel) is equal to or
greater than 300 rpm. If the difference between the two
(Ne - Nel) is equal to or greater than 300 rpm, the flow of
control continues to a step S54 at which the rotational
speed Ne of the engine measured at the step S50 is compared
with the peak-hold value Nep updated at the step S51 in
order to form a judgment as to whether or not the
difference between the two (Nep - Ne) is equal to or
greater than 50 rpm.
This judgment is a judgment as to whether or not
the driver has carried out empty puffing on the engine in
the shift-down operation. If the outcomes of the judgments
formed at both the steps S53 and S54 are an acknowledgment
(YES), the flow of control goes on to the step S55 to set a
quick-return flag F to suggest that the clutch be
immediately put in an engaged state before finishing the
processing.
Fig. 21 is a diagram showing a flowchart
representing the method of the clutch-on control carried
CA 02240229 1998-06-10
out at the steps S28 and 536.
As shown in the figure, the flowchart begins with a
step S70 to form a judgment as to whether or not the speed
of the vehicle is about zero. In the present embodiment,
speeds of a vehicle up to 3 km/h are regarded as a vehicle
speed of about zero. If the speed of the vehicle is about
zero, the flow of control goes on to a step S72 at which a
target angle THETAt of the shift spindle 3 is set at a
neutral position. The flow of control then proceeds to a
step 573. This flow of control is implemented to make a
shift at the time the vehicle is in an all but halted
state. In such a case, it is desirable to make a shift
change quickly since no shift shock will be generated
anyway.
If the outcome of the judgment formed at the step
S70 indicates that the speed of the vehicle is equal to or
greater than 30 km/h, on the other hand, the flow of
control goes on to a step S71 at which the target angle
THETAt of the shift spindle is set at a second reference
angle, an angle differing from an angle, at which the
rotation of the shift spindle 3 is halted by the stopper,
by 6 degrees. Since the angle, at which the rotation of
the shift spindle 3 is halted by the stopper, is +/-18
degrees in the present embodiment, the second reference
31
CA 02240229 1998-06-10
angle is +/-12 degrees. The flow of control then continues
to a step S73 at which the current rotational angle THETAO
of the shift spindle 3 detected by the angle sensor 28 is
input. Then, the flow of control goes on to a step S74 at
which the Ne control is executed.
Subsequently, the flow of control proceeds to a
step S75 at which a PID (Proportional, Integral and
Differential) sum value for PID control is found. To put
it in detail, a proportional (P) term, the integral (I)
term and the differential (D) term are found and then added
up. The P term is the difference (THETAO - THETAt) between
the current rotational angle THETAO detected at the step
S73 and the target rotational angle THETAt. The I and D
terms are the integrated and differentiated values of the P
term respectively. The flow of control then goes on to a
step S76 at which the PID sum value is used for computing
the duty ratio of the PWM control. Then, the flow of
control proceeds to a step S77 at which the PWM control is
executed.
Fig. 25 is a diagram showing a relation between a
PID sum value and a duty ratio. As shown in the figure', a
positive PID sum value gives a positive duty ratio while a
negative PID sum value provides a negative duty ratio. The
polarity of a duty ratio indicates a combination of FETs to
32
CA 02240229 1998-06-10
be controlled by PWM. For example, a duty ratio of +500
means that the FETs (2) and (4) should be controlled by PWM
at a duty ratio of 500. On the other hand, a duty ratio of
-50o means that the FETs (1) and (3) should be controlled
by PWM at a duty ratio of 500.
Subsequently, the flow of control goes on to a step
S78 to form a judgment as to whether or not the time
measured by a sixth timer has exceeded 100 ms. Since the
sixth timer has not been started yet to measure time
initially, the time should have not exceeded 100 ms,
causing the flow of control to proceed to a step S79 at
which a fifth timer is started to measure time. The flow
of control then proceeds to a step S80 to form a judgment
as to whether or not the time measured by a fifth timer has
exceeded 10 ms. Initially, the time measured by the fifth
timer should have not exceeded 10 ms, causing the flow of
control to return to the step S73 to repeat the pieces of
processing carried out at the steps S73 to S80.
As time goes by, the time measured by the fifth
timer exceeds 10 ms at a point of time t5 of the time chart
shown in Fig. 22. At that time, the flow of control goes
on to a step S81 at which the fifth timer is reset. The
flow of control then proceeds to a step S82 to form a
judgment as to whether the quick-return flag F is in a set
33
CA 02240229 1998-06-10
or reset state. If the quick-return flag F is in a set
state, the flow of control continues to a step s83 to
catalog a new target angle set at a value smaller than the
present target angle by two to four degrees for use in the
execution of quick-return control. If the quick-return
flag F is in a reset state, on the other hand, the flow of
control continues to a step S84 to catalog a new target
angle set at a value smaller than the present target angle
by 0.2 degrees.
The flow of control goes on from either the step
S83 or S84 to a step S85 to form a judgment as to whether
or not the target angle is close to a neutral angle. If
the target angle is not close to the neutral angle, the
flow of control returns to the step S73. The pieces of
processing carried out at the steps S73 to S85 are repeated
till the target angle becomes sufficiently close to the
neutral angle. Later on, as the target angle is found
sufficiently close to the neutral angle at the step S85,
the flow of processing proceeds to a step S86 at which the
neutral angle is cataloged as a target angle_ The flow of
control then continues to a step S87 at which the sixth
timer starts to measure time.
If the outcome of the judgment formed at the step
S78 indicates that the time measured by the sixth timer has
34
CA 02240229 1998-06-10
exceeded 100 ms, on the other hand, the flow of control
goes on to a step S90 at which the sixth timer is reset.
The flow of control then proceeds to a step S91 at which
the quick-return flag F is reset. Then, the flow of
control continues to a step S92 at which the PWM control of
the switching circuit 105 is terminated.
It should be noted that, if the gear is shifted
from a neutral state at a high engine rotational speed in
the course of a high-speed .cruise, a relatively large
engine brake works, imposing an excessively large load on
the engine. In order to solve this problem, in the present
embodiment, there is provided a shift disabling system for
preventing the control shown in Fig. 16 from being executed
at a vehicle speed equal to or higher than 10 km/h or an
engine rotational speed equal to or higher than 3,000 rpm
even if the shift-up switch 51 has been turned on.
Fig. 11 is a functional block diagram showing the
shift disabling system. As shown in the figure, the shift
disabling system employs a neutral-position detecting unit
81 for outputting an "H"-level signal to indicate that the
gear is placed at a neutral position. A vehicle-speed
judging unit 82 generates an "H"-level signal for a speed
of the vehicle equal to or higher than 10 km/h. On the
other hand, an engine-rotational-speed judging means 83
CA 02240229 1998-06-10
generates an "H"-level signal for a rotational speed of the
engine equal to or higher than 3,000 rpm.
An OR circuit 84 generates an "H"-level signal when
the vehicle-speed judging unit 82 generates an "H"-level
signal or the engine-rotational-speed judging means 83
generates an "H"-level signal. On the other hand, an AND
circuit 85 generates an "H"-level signal when the neutral-
position detecting unit 81 generates an "H"-level signal
and the OR circuit 84 generates an "H"-level signal. With
the AND circuit 85 outputting the "H"-level signal, the
shift disabling system prevents the control shown in Fig.
16 from being executed even if the shift-up switch 51 has
been turned on.
If a shift change is made to a neutral state by
mistake at a vehicle speed equal to or higher than 10 km/h
or an engine rotational speed equal to or higher than 3,000
rpm in the course of acceleration from the first speed,
however, it takes time to accomplish re-acceleration.
Thus, a system for disabling a shift to a neutral state in
the course of a vehicle cruise, for example, at a vehicle
speed equal to or higher than 3 km/h can be further added
besides the shift disabling system described above.
[Effects of the Invention)
According to the present invention, when putting
36
CA 02240229 1998-06-10
back a clutch in an engaged state after being released from
an engaged state, a shift spindle is rotated with a
rotational speed thereof changed from a high speed to a low
speed with predetermined timing. As a result, the time it
takes to put the clutch in an engaged state can be
shortened and, at the same time, the magnitude of a
generated shift shock can also be decreased as well.
[Brief Description of the Drawings]
[Fig. 1]
Fig. 1 is a plane diagram showing an operation unit
of a vehicle on which the electric-power-assist-type
transmission provided by the present invention is mounted.
[Fig. 2]
Fig. 2 is a diagram showing a partial cross section
of the configuration of major components employed in a
driving system of the electric-power-assist-type
transmission provided by an embodiment of the present
invention.
[Fig. 3]
Fig. 3 is a conceptual diagram showing a state in
which the sleeve and the gear are engaged with each other.
[Fig. 4]
Fig. 4 is a diagram showing a squint view of the
sleeve provided by the present invention.
3r
CA 02240229 1998-06-10
[Fig. 5]
Fig. 5 is a diagram showing a squint view of the
gear provided by the present invention.
[Fig. 6)
Fig. 6 is a diagram showing an enlarged portion of
a protruding-side dowel 32 of the sleeve.
[Fig. 7]
Fig. 7 is a diagram showing an enlarged portion of
a denting-side dowel 42 of .the gear.
[Fig. 8]
Fig. 8 is a diagram showing a state in which the
protruding-side dowel 32 of the sleeve and the denting-side
dowel 42 of the gear are engaged with each other.
[Fig. 9]
Fig. 9 is a diagram showing a squint view of the
conventional sleeve.
[Fig. 10]
Fig. 10 is a diagram showing a squint view of the
conventional gear.
[Fig. 11]
Fig. 11 is a functional block diagram showing a'
shift disabling system.
[Fig. 12]
Fig. 12 is a diagram showing a model of engagement
38
CA 02240229 1998-06-10
timing of the conventional sleeve and the conventional
gear.
(Fig. 13]
Fig. 13 is a diagram showing a model of engagement
timing of the sleeve and the gear provided by the present
invention.
[Fig. 14]
Fig. 14 is a block diagram showing the
configuration of major components employed in a control
system of the electric-power-assist-type transmission
provided by the embodiment of the present invention.
[Fig. 15]
Fig. 15 is a block diagram showing a typical
configuration of an ECU 100 employed in the control system
shown in Fig. 14.
[Fig. 16)
Fig. 16 is a diagram showing Part I of a flowchart
provided by the embodiment of the present invention.
[Fig. 17)
Fig. 17 is a diagram showing Part II of a flowchart
provided by the embodiment of the present invention.
[Fig. 18)
Fig. 18 is a diagram showing Part III of a
flowchart provided by the embodiment of the present
39
CA 02240229 1998-06-10
invention.
[Fig. 19]
Fig. 19 is a diagram showing Part IV of a
flowchart provided by the embodiment of the present
invention.
(Fig. 20]
Fig. 20 is a diagram showing Part V of a flowchart
provided by the embodiment of the present invention.
[Fig. 21]
Fig. 21 is a diagram showing Part VI of a flowchart
provided by the embodiment of the present invention.
[Fig. 22]
Fig. 22 is a diagram showing operational timing
charts of a shift spindle provided by the present
invention.
[Fig. 23]
Fig. 23 is a diagram showing operational timing
charts of the rotational angle of a shift spindle and the
rotational speed of the engine provided by the present
invention in a shift-up operation.
[Fig. 24]
Fig. 24 is a diagram showing operational timing
charts of the rotational angle of a shift spindle and the
rotational speed of the engine provided by the present
CA 02240229 1998-06-10
invention in a shift-down operation.
[Fig. 25]
Fig. 25 is a diagram showing a relation between a
PID (Proportional, Integral and Differential) sum value and
a duty ratio.
[List of Reference Numerals]
1 --- Driving motor
2 --- Deceleration gear mechanism
3 --- Shift spindle
--- Shift clutch
--- Shift drum
11 --- Shift fork
28 --- Angle sensor
30 --- Sleeve
40 --- Gear
51 --- Shift-up switch
52 --- Shift-down switch
41
CA 02240229 1998-06-10
Fig. 11
81 Neutral-position detecting unit
82 vehicle speed > 10 km/h
86 Shift disabling unit
Fig. 12
Conventional technology
Fig. 13
Present invention
Fig. 14
21 Battery
28 Angle sensor
26 vehicle-speed sensor
27 Ne sensor
Fig. 15
106 Power-supply circuit (Voltage monitoring)
107 Memory 104 Pre-driver
Fig. 16
Start
S10 Is the shift switch on?
44
CA 02240229 1998-06-10
S11 Is it a shift-up?
S13 Carry out PWM control
For a shift-up, control the FETs (2) and (4) by PWM at a
duty ratio of 1000
For a shift-down, control the FETs (1) and (3) by PWM at a
duty ratio of 1000
S14 Start the first timer
S15 Detect a rotational angle THETAO
S16 Is THETAO > reference value of 14 degrees?
S17 Reset the first timer S18 Carry out PWM control
For a shift-up, control the FETs (1) and (4) by PWM at a
duty ratio of 100a
For a shift-down, control the FETs (2) and (3) by PWM at a
duty ratio of 100%
Fig. 17
S19 Start the second timer
S20 Is the second timer > 15 ms?
S21 Carry out Ne control
S22 Reset the second timer S23 Carry out PWM control
For a shift-up, control the FETs (2) and (4) by PWM at ~a
duty ratio of 700
For a shift-down, control the FETs (1) and (3) by PWM at a
duty ratio of 700
CA 02240229 1998-06-10
S24 Start the third timer
S25 Is the third timer > 70 ms?
S26 Carry out Ne control
S27 Reset the third timer
S28 Carry out clutch-on control 1 Return
Fig. 18
S30 Is the first timer > 200 ms?
S31 Carry out Ne control
S32 Reset the first timer
S33 Is the re-inrush flag = 0?
S34 Carry out re-inrush control
S35 Reset the re-inrush flag
S36 Carry out clutch-on control 1 Return
Fig. 19
S34 Re-inrush Control
S40 Carry out PWM control
For a shift-up, control the FETs (2) and (4) by PWM at a
duty ratio of 20%
For a shift-down, control the FETs (1) and (3) by PWM at a
duty ratio of 200
S41 Start the fourth timer
S42 Is the fourth timer >_ 20 ms?
46
CA 02240229 1998-06-10
S43 Detect Ne
S44 Reset the fourth timer
S45 Set the re-inrush flag to a "1" END
Fig. 20
Ne Control
S50 Detect Ne
S51 Update the peak-hold value Nep or the bottom-hold value
Neb
S52 Is it a shift-up?
S55 Set the flag F to a "1"
1 To the next processing
Fig. 21
Clutch-on Control
S70 Is the vehicle speed < 3 km/h?
S72 Set the neutral angle as a target angle THETAt
S71 Set a second reference angle as a target angle THETAt
S73 Detect a rotational angle
S74 Carry out Ne control
S75 Compute the PID sum value
S76 Determine a duty ratio
S77 Carry out PWi~i control
S78 Is the sixth timer >_ 100 ms?
47
CA 02240229 1998-06-10
S79 Start the fifth timer
S90 Reset the sixth timer
S91 Reset the flag F
S92 Halt the PWM control
1 To the next processing
S80 Is the fifth timer > 10 ms?
S81 Reset the fifth timer
S82 Is the flag F = 1?
S84 set (target angle - 0.2 degrees) as a target angle
S83 Set (target angle - 2 to 4 degrees) as a target angle
S85 Is the target angle about equal to the neutral angle?
S86 Set the neutral angle as a target angle S87 Start the
sixth timer
Fig. 22
Shift spindle's rotational angle
Fig. 23
1 Spindle position THETAO
2 Time
3 Shift-up switch turned on
4 Shift completed
Fig. 24
48
CA 02240229 1998-06-10
1 Spindle position THETAO
2 Time
3 Shift-down switch turned on
4 Shift completed
Fig. 25
1 Duty ratio
2 PID sum value
3 Return direction
4 Braking zone
Anti-return direction
6 Negative
7 Positive
49
