Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
ELECTRIC-POWER-ASSIST-TYPE TRANSMISSION AND ITS
CONTROL METHOD
Field of the Invention
In general, the present invention relates to an electric-power-
assist-type transmission and its shift control method. In particular,
the present invention relates to an electric-power-assist-type
transmission wherein a gear shift as well as the operation to put
1o the clutch in an engaged or disengaged state are carried out
electrically and relates to its shift control method, with the
transmission and the method characterized in that, in a situation
with a small shift shock expected in a shift, switching from shift
control for reducing the magnitude of a shift shock carried out at
normal times to fast shift control is carried out. To put it even
more concretely, the present invention relates to an electric-power-
assist-type transmission wherein, with the clutch put in a
disengaged state in a shift process, if the rotational speed of the
engine exhibits a predicted change, control of a motor for driving
2o the clutch is carried out in a way different from control at normal
times and relates to its shift control method.
Furthermore, the present invention relates to a shift control
method to be adopted in an electric-power-assist-type transmission
z5 whereby, if a shift-change operation is carried out with the vehicle
put in an all but halted state, the clutch is released from an engaged
state and a gear change is made before putting back the clutch in an
engaged state quickly.
30 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. HeiS-
35 39865, a gear shift is carried out electrically by a motor. In the
conventional technologies described above, a shift drum is
intermittently rotated in both directions by a driving motor so as to
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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.
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
transmission, 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.
2o 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 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
z5 intention, it is quite within the bounds of possibility that the driver
feels a sense of incompatibility. While control is executed to
engage the clutch smoothly and slowly in an ordinary shift so that
no shift shock is resulted in, particularly, for a situation like one
described below, there are cases in which the clutch had better be
3o put in an engaged state quickly.
For example, in an ordinary shift-up operation, the driver
normally turns on a shift-up switch after restoring the acceleration
pedal. Then, after the shift-change operation has been completed
35 and the clutch has been put back in an engaged state, the driver
carries out an operation to open the accelerator. It is also quite
within the bounds of possibility, however, that the driver turns on
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the shift-up switch without restoring the accelerator pedal or opens
the accelerator before the clutch is put back in an engaged state.
Likewise, in a shift-down operation, the driver normally turns
on a shift-down switch after restoring the acceleration pedal. Then,
after the shift-change operation has been completed and the clutch
has been put back in an engaged state, the driver operates the
accelerator pedal. It is also quite within the bounds of possibility,
however, that in a shift-down operation, the driver does empty
to puffing of the engine in order to adjust the rotational speed of the
engine to a rotational speed after the shift down. In this way, since
the operation of the acceleration pedal in a shift change may vary
from driver to driver, various kinds of control adjusted to the
operation are required.
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 the engaged state slowly in order to reduce the
magnitude of a generated shift shock while the vehicle is running.
2o With the vehicle put in a halted state, however, it is desirable to
put the clutch in the engaged state quickly because no shift shock is
generated anyway.
The present invention uses an electric-power-assist-type
transmission and a shift control method to provide good
operatability. The electric-power-assist-type transmission and a
shift control method are characterized in that fast clutch
engagement control different from the normal clutch engagement
control is executed particularly for a situation in which the
3o magnitude of shift shock is expected to be small.
The present invention provides an electric-power-assist-type
transmission and a shift control method wherein the clutch is put
in an engaged or disengaged state in a manner inter- locked with
the rotation of a shift spindle and, at normal times, the rotational
direction and the rotational speed of the shift spindle rotated by a
driving motor are controlled in accordance with a first control
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procedure but, with the clutch put in a disengaged state, as the
rotational speed of the engine exhibits a predicted change, the
rotational direction and the rotational speed of the shift spindle are
controlled in accordance with a second control procedure which is
different from the first control procedure.
Furthermore, the shift control method is characterized in that,
if a shift-change operation is carried out with the vehicle put in an
all but halted state, the clutch is released from an engaged state and
io a gear change is made before putting back the clutch in an engaged
state quickly.
With the control scheme described above, when the driver
operates the accelerator pedal during shift control, the second
control procedure is executed in accordance with the operation of
the accelerator pedal carried out by the driver, allowing good shift
control to be performed in accordance with the operation of the
accelerator pedal carried out by the driver. In addition, it is possible
to prevent a shift shock from being generated while the vehicle is
2o running and, at the same time, the clutch can be put in an engaged
state quickly with the vehicle put in a halted state.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are sown in the drawings
wherein:
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 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 is a conceptual diagram showing a state in which the
sleeve and the gear are engaged with each other;
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Fig. 4 is a diagram showing a perspective view of the sleeve
provided by the present invention;
5 Fig. 5 is a diagram showing a perspective view of the gear
provided by the presentinvention;
Fig. 6 is a diagram showing an enlarged portion of a
protruding-side dowel 32 of the sleeve;
Fig. 7 is a diagram showing an enlarged portion of a denting-
side dowel 42 of the gear;
Fig. 8 is a diagram showing a state in which the protruding
i5 side dowel 32 of the sleeve and the denting-side dowel 42 of the
gear are engaged with each other;
Fig. 9 is a diagram showing a perspective view of the
conventional sleeve;
Fig. 10 is a diagram showing a perspective view of the
conventional gear;
Fig. 11 is a functional block diagram showing a shift disabling
system;
Fig. 12 is a diagram showing a model of engagement timing of
the conventional sleeve and the conventional gear;
Fig. 13 is a diagram showing a model of engagement timing of
the sleeve and the gear provided by the present invention;
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;
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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 is a diagram showing Part I of a flowchart provided by
the embodiment of the present invention;
Fig. 17 is a diagram showing Part II of a flowchart provided by
the embodiment of the present invention;
to Fig. 18 is a diagram showing Part III of a flowchart provided by
the embodiment of the present invention;
Fig. 19 is a diagram showing Part IV of a flowchart provided by
the embodiment of the present invention;
Fig. 20 is a diagram showing Part V of a flowchart provided by
the embodiment of the present invention;
Fig. 21A and Fig.2lB is a diagram showing Part VI of a
2o flowchart provided by the embodiment of the present invention;
Fig. 22 is a diagram showing operational timing charts of the
rotational angle of a shift spindle provided by the present
invention;
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 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-down
operation;
Fig. 25 is a diagram showing a relation between a PID
(Proportional, Integral and Differential) sum value and a duty
ratio;
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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.
1o 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.
zo
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
3o 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 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 1, the gear mechanism 8 releases the engaged
state of a gear clutch 5 without regard to the direction of the
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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.
1o 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 axis 8. When the shift spindle 3 is rotated by the driving
motor 1, a shift drum 10 is rotated in a direction determined by the
rotational direction of the shift spindle 3. The master arm 7 and
i5 the clutch mechanism 9 form such a clutch mechanism that, when
the shift spindle 3 is rotated away from the neutral 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
2o 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
z5 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
3o rotational angle of the shift drum 10 in a direction parallel to a
main shaft 4.
Fig. 4 is a diagram showing a perspective view of the sleeve 30
inserted in a state slideable in the axial direction of the main shaft
35 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
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engaged with the groove 31. A plurality of protruding-side dowels
32 are provided on a ring-shaped flange 33 to form a 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 perspective 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
1o 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 perspective
view of the conventional sleeve 38 and Fig. 10 is a diagram
2o showing a perspective 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
z5 bottom surface of each of the stand-alone protruding-side dowels 39
must be 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-
3o 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
35 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
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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
5 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
io dowel 32 and the width D4 of the denting-side dowel 42 in the
rotational direction can be 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
z0 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 D5 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
3o 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 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
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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
1o 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
zo provided by the present invention is a four-cycle engine. In a
power transmission system for 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.
3o 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
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connected between motor+ and motor- pins of the ECU 100.
Sensor-signal pins Sl, 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 described earlier
respectively.
1o 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 G1 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
3o 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 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.
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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 21A and
21B 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
to 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
i5 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 S13, the FETs employed in the switching circuit 105
of the ECU 100 are selectively controlled by PWM in dependence
20 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 t1 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 100% with the FETs (1) and (3)
25 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.
3o 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
35 spindle 3 also to rotate in the shift-down direction as well in a
manner interlocked with the driving motor 1.
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By setting the duty ratio at 100% 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 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
i0 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 B o of the shift spindle 3 detected by means of the angle
sensor 2S is read in. Subsequently, the flow of control goes on to a
step S16 to compare the detected rotational angle B p with a first
reference angle B REF 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 B o exceeds the reference angle B REF. To put it
in more detail, the judgment formed at the step S16 is a judgment
2o as to whether or not the rotational angle B p is equal to or greater
than 14 degrees, or the rotational angle B p 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 Slb indicating
that the rotational angle B o goes beyond t 14 degrees means that it
3o 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 S17. On the other hand, an outcome of the judgment formed
at the step S16 indicating that the rotational angle B p 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
CA 02246884 1998-09-10
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
5 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 B 0 with the reference rotational angle B REF. the
flow of control proceeds to the step S17 at which the first timer is
reset. The flow of control then conrinues to a step S18 at which the
10 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.
15 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 rario of 100% with
2o 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. 17
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 step S21 to execute control of the rotational speed Ne of the
engine to be described later. The pieces of processing at the steps
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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
1o 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 70% 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 70%
i5 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 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
3o 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
CA 02246884 1998-09-10
17
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 is light,
being favorable to the strength of the dowel.
In addition, the time-up time of the third timer does not have
to 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 B o has not exceeded
the first reference angle B REF, on the other hand, the flow of
control goes on to the step S30 shown in Fig. 18 to form a judgment
2o 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
3o 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
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,
CA 02246884 1998-09-10
18
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
to 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
i5 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 processing of making a re
movement (re-inrush) attempt to once reduce the movement
torque before applying a predetermined torque again to the shift
2o 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 20%. To be more specific, the duty ratio of the FETs (2) and (4) or
25 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
3o 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
35 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
CA 02246884 1998-09-10
19
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 100%, 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
1o 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
i5 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 t1, the engagement of the clutch is released at a point
2o of time tZ2 and the rotation of the shift spindle is completed at the
point of time t3. Later 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.
25 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 other hand, the speed of a shift change is
dependent on the rotational speed of the shift spindle 3. It is thus
3o 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
35 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
CA 02246884 1998-09-10
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
5 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
l0 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 B 0 of the shift spindle in the
clutch-on control and the rotational speed of the engine in the Ne
i5 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 B p 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 51 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 that the driver has
CA 02246884 1998-09-10
21
turned on the shift-up switch 51 without restoring the accelerator
pedal. In this case, quick return control of the rotational angle B o
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 B p of the shift
spindle to put the clutch in an engaged state immediately is
to 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.
2o
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 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 experienced empty puffing. In this case, quick return control of
3o the rotational angle B p 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
CA 02246884 1998-09-10
22
the steps S21, 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 550.
Then, the flow of control proceeds to a step S52 to form a judgment
1o 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 continues to a step S56.
If the shift change is a shift down, on the other hand, the flow of
control continues to a step 553.
i5 At the step 556, 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.
z0
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
25 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
3o 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
35 the step S52 indicates that the shift change is a shift down, on the
other hand, the flow of control continues to the step 553. At the
step 553, the rotational speed Ne of the engine measured at the step
CA 02246884 1998-11-13
23
S50 is compared with the rotational speed Ne1 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 - Ne1) is equal to or greater than
300 rpm. If the difference between the two (Ne - Ne1) 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
i5 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. 21A and Fig. 21B is a diagram showing a flowchart
representing the method of the clutch-on control carried out at the
steps S28 and S36.
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 8 T of the shift spindle 3 is set at a neutral
position. The flow of control then proceeds to a step S73. 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 3
km/h, on the other hand, the flow of control goes on to a step S71
at which the target angle B T of the shift spindle is set at a second
CA 02246884 1998-09-10
24
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 angle is ~ 12 degrees. The flow of control then
continues to a step S73 at which the current rotational angle 8 0 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 (B p - B T) between the
current rotational angle B p detected at the step S73 and the target
rotational angle B T. 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
2o 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 be controlled by PWM. For
example, a duty ratio of +50% means that the FETs (2) and (4)
3o should be controlled by PWM at a duty ratio of 50%. On the other
hand, a duty ratio of -50% means that the FETs (1) and (3) should be
controlled by PWM at a duty ratio of 50%.
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
CA 02246884 1998-09-10
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
5 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 580.
As time goes by, the time measured by the fifth timer exceeds
10 10 ms at a point of time is 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 or
reset state. If the quick-return flag F is in a set state, the flow of
15 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
2o 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
z5 neutral angle, the flow of control returns to the step 573. 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 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
CA 02246884 1998-09-10
26
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
to 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 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
3o 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
CA 02246884 1998-09-10
27
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.
According to the electric-power-assist-type transmission and
the shift control method provided by the present invention, when
to the driver operates the acceleration pedal in the course of shift
control such as opening the accelerator prior to re-engagement of
the clutch after turning on the shift-up switch without restoring
the accelerator pedal or carrying out empty puffing of the engine in
a shift-down operation, the clutch is put in an engaged state in
accordance with the operation of the acceleration pedal carried out
by the driver, allowing a shift to be carried out in accordance with
the intention of the driver without providing a sense of
incompatibility to the driver.
Although various preferred embodiments of the present
invention have been described herein in detail, it will be
appreciated by those skilled in the art, that variations may be made
thereto without departing from the spirit of the invention or the
scope of the appended claims.
CA 02246884 1998-09-10
28
[List of Reference Numerals]
1 --- Driving motor
2 --- Deceleration gear mechanism
3 --- Shift spindle
5 --- Shift clutch
--- Shift drum
11 --- Shift fork
28 --- Angle sensor
10 30 --- Sleeve
40 --- Gear
51 --- Shift-up switch
52 --- Shift-down switch
