U.S. patent application number 09/738322 was filed with the patent office on 2001-08-09 for clutch control apparatus.
Invention is credited to Kohno, Tetsuya, Maki, Naoyuki, Naito, Takao, Terakawa, Tomomitsu.
Application Number | 20010011625 09/738322 |
Document ID | / |
Family ID | 18488340 |
Filed Date | 2001-08-09 |
United States Patent
Application |
20010011625 |
Kind Code |
A1 |
Naito, Takao ; et
al. |
August 9, 2001 |
Clutch control apparatus
Abstract
A clutch control apparatus includes a clutch disk, which is
engaged with a flywheel, by means of a diaphragm spring; a release
mechanism (including a rod and an electric motor) for pressing a
central portion of the diaphragm spring; and a clutch control
circuit. The flywheel and an outer circumferential portion of the
diaphragm spring abut each other via taper portions of a pressure
plate and an adjust wedge member. The clutch control circuit
calculates an ideal clutch load and an output torque of the
electric motor for a detected stroke of the rod. On the basis of
these values, the clutch control circuit obtains the acceleration
of the rod. The clutch control circuit estimates a stroke of the
rod from the obtained acceleration and causes the adjust wedge
member to rotate such that a detected actual stroke and the
estimated stroke become equal, thereby modifying the attitude of
the diaphragm spring accordingly.
Inventors: |
Naito, Takao; (Nagoya-shi,
JP) ; Maki, Naoyuki; (Kariya-shi, JP) ;
Terakawa, Tomomitsu; (Anjyo-shi, JP) ; Kohno,
Tetsuya; (Okazaki-shi, JP) |
Correspondence
Address: |
Oliff & Berridge PLC
P.O. Box 19928
Alexandria
VA
22320
US
|
Family ID: |
18488340 |
Appl. No.: |
09/738322 |
Filed: |
December 18, 2000 |
Current U.S.
Class: |
192/70.252 ;
192/110R; 192/70.27; 192/84.6 |
Current CPC
Class: |
F16D 2500/10412
20130101; F16D 2500/3067 20130101; F16D 2500/31466 20130101; F16D
48/06 20130101; F16D 2500/70404 20130101; F16D 2500/3111 20130101;
F16D 2500/70408 20130101; F16D 2500/70264 20130101; F16D 2500/7041
20130101; B60W 2710/022 20130101; F16D 2500/3026 20130101; F16D
2500/30806 20130101; F16D 2500/1023 20130101; F16D 2500/30401
20130101; F16D 2500/30816 20130101 |
Class at
Publication: |
192/70.25 ;
192/70.27; 192/84.6; 192/110.00R |
International
Class: |
F16D 013/75; F16D
027/14 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 24, 1999 |
JP |
11-367050 |
Claims
What is claimed is:
1. A clutch control apparatus for a vehicle, comprising: a clutch
disk disposed opposite a flywheel which rotates unitarily with an
output shaft of a drive unit; a pressure plate for applying a
press-contact load to said clutch disk so as to press said clutch
disk toward said flywheel to thereby engage said clutch disk with
said flywheel; a diaphragm spring for causing said pressure plate
to generate the press-contact load; an actuator for generating and
applying a force to a predetermined portion of said diaphragm
spring by moving a member to deform said diaphragm spring for
disengaging said clutch disk from said flywheel according to
driving conditions of the vehicle; said clutch control apparatus
further comprising press-contact load adjustment means for
modifying the press-contact load by modifying a posture of said
diaphragm spring as observed when said clutch disk is engaged with
said flywheel, according to an instruction; stroke estimation means
for estimating a stroke of said member on the basis of an
calculated ideal reaction force to be imposed on said member
through said diaphragm spring and an estimated force generated by
said actuator; stroke detection means for detecting an actual
stroke of said member; and adjustment instruction means for
providing said press-contact load adjustment means with said
instruction such that the detected stroke becomes equal to the
estimated stroke to thereby make adjustment.
2. A clutch control apparatus according to claim 1, wherein said
stroke estimation means further comprising: ideal reaction-force
calculation means for calculating said ideal reaction force to be
imposed on said member on the basis of a stroke of said member
which has been estimated a predetermined time beforehand; and
actuator force estimation means for estimating said estimated force
to be generated by said actuator on the basis of a drive signal
issued to said actuator.
3. A clutch control apparatus according to claim 2, wherein said
stroke estimation means estimates said stroke by integrating stroke
speed of said member, the stroke speed being calculated by
integrating stroke acceleration of said member which is calculated
on the basis of said ideal reaction-force and said estimated
force.
4. A clutch control apparatus according to claim 1, wherein said
adjustment instruction means provides said instruction only when a
difference between the detected stroke and the estimated stroke
becomes larger than a predetermined amount.
5. A clutch control apparatus according to claim 1, wherein said
adjustment instruction means does not provide said instruction when
said clutch disk engages with said flywheel according to driving
conditions of the vehicle.
6. A clutch control apparatus according to claim 1, wherein said
adjustment instruction means does not provide said instruction when
the vehicle is parked with clutch disk being engaged.
7. A clutch control apparatus according to claim 1, wherein said
adjustment instruction means does not provide said instruction when
the rotational seed of the drive unit of the vehicle is lower than
a predetermined speed.
8. A clutch control apparatus according to claim 1, wherein said
adjustment instruction means does not provide said instruction when
resonance of the clutch occurs due to vibration of the drive
unit.
9. A clutch control apparatus according to claim 1, wherein said
adjustment instruction means does not provide said instruction when
the rotational seed of a drive unit of the vehicle is higher than a
predetermined speed.
10. A clutch control apparatus according to claim 1, wherein said
adjustment instruction means does not provide said instruction when
the seed of an the vehicle is not zero.
11. A clutch control apparatus according to claim 1, further
comprising: a release bearing which comes into contact with said
diaphragm spring; a release fork for moving said release bearing
through application of pressure; a rod as said member of said
actuator for deflecting said release fork in order to move said
release bearing through application of pressure.
12. A clutch control apparatus according to claim 1, wherein said
press-contact load adjustment means includes a mechanism to modify
a distance between an outer circumferential portion of said
diaphragm spring and said pressure plate.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a clutch control apparatus
of a vehicle for automatically controlling a frictional clutch for
transmission of torque between a power source, such as an internal
combustion engine, and a transmission, according to the state of
operation of the vehicle. More particularly, the invention relates
to a clutch control apparatus capable of absorbing characteristic
errors in manufacture (variations among products) of a clutch disk
and an actuator, which may be an electric motor.
[0003] 2. Description of the Related Art
[0004] Conventionally, there has been known a clutch control
apparatus for automatically engaging/disengaging a clutch through
operation of an electrically controlled actuator, according to, for
example, confirmation of a driver's intention to change gears.
Generally, in such a clutch control apparatus, a force generated by
a diaphragm spring is transmitted to a clutch disk via a pressure
plate to thereby engage the clutch disk with a flywheel under a
predetermined press-contact load. In order to disengage the clutch
disk from the flywheel, a force generated by the actuator is
applied to the diaphragm spring so as to deform the same, to
thereby reduce the press-contact load.
[0005] However, in the above-mentioned conventional clutch control
apparatus, operating characteristics of a clutch in
engagement/disengagement of the clutch (particularly, elapsed time
in transfer of the clutch disk from the engaged state to the
disengaged state or vice versa) vary among products, because of
errors in manufacture and installation of the diaphragm spring or
errors in manufacture of the actuator.
SUMMARY OF THE INVENTION
[0006] An object of the present invention is to provide a clutch
control apparatus capable of compensating for the above-mentioned
variation among products.
[0007] To achieve the above object, the present invention provides
a clutch control apparatus for a vehicle, comprising: a clutch disk
disposed opposite a flywheel, which rotates unitarily with an
output shaft of a drive unit; a pressure plate for applying a
press-contact load to said clutch disk so as to press said clutch
disk toward said flywheel to thereby engage said clutch disk with
said flywheel; a diaphragm spring for causing said pressure plate
to generate the press-contact load; an actuator for generating and
applying a force to a predetermined portion of said diaphragm
spring by moving a member to deform said diaphragm spring for
disengaging said clutch disk from said flywheel according to
driving conditions of the vehicle; said clutch control apparatus
further comprising: press-contact load adjustment means for
modifying the press-contact load by modifying a posture of said
diaphragm spring as observed when said clutch disk is engaged with
said flywheel, according to an instruction; stroke estimation means
for estimating a stroke of said member on the basis of an
calculated ideal reaction force to be imposed on said member
through said diaphragm spring and an estimated force generated by
said actuator and; stroke detection means for detecting an actual
stroke of said member; and adjustment instruction means for
providing said press-contact load adjustment means with said
instruction such that the detected stroke becomes equal to the
estimated stroke to thereby make adjustment.
[0008] According to the present invention, stroke estimation means
estimates a stroke of said member (e.g. a rod of the actuator) on
the basis of an calculated ideal reaction force to be imposed on
said member through said diaphragm spring and an estimated force
generated by said actuator. That is, the stroke of the member is
estimated on the assumption that a clutch operation system has
designed characteristics (ideal characteristics). Simultaneously,
stroke detection means detects an actual stroke of the member. The
thus-detected stroke of the rod reflects all characteristic errors
(for example, variations among products and installation errors)
arising in manufacture of the clutch operation system. Accordingly,
when press-contact load adjustment means modifies the press-contact
load by modifying a posture of said diaphragm according to the
instruction provided by the adjustment instruction means to make
the detected stroke equal to the estimated stroke, characteristic
errors which have arisen in the course of manufacture are
compensated. Thus, substantially no variations are observed in
clutching characteristics among products.
[0009] It is another object of the present invention to provide a
clutch control apparatus which can compensate for the
characteristic errors automatically without causing disadvantage to
the normal driving of the vehicle by limiting the adjustment timing
to a certain timing.
[0010] It is another object of the present invention to provide a
clutch control apparatus that can compensate for the characteristic
errors accurately by limiting the adjustment timing to a certain
timing.
[0011] Other features and advantages of the invention will be
apparent from the following description taken in connection with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a schematic diagram showing a clutch control
apparatus according to a first embodiment of the present
invention;
[0013] FIG. 2 is a schematic sectional view of a clutch shown in
FIG. 1;
[0014] FIG. 3 is a front view of the clutch shown in FIG. 1;
[0015] FIGS. 4A to 4C are views for explaining action of the clutch
shown in FIG. 1;
[0016] FIG. 5 is a view for explaining action of the clutch
(adjustment member) shown in FIG. 1;
[0017] FIG. 6 is a diagram showing the relationship between the
stroke of a rod shown in FIG. 1 and a release load;
[0018] FIG. 7 is a diagram showing the relationship among the
stroke of the rod shown in FIG. 1, a release load, and a diaphragm
spring force;
[0019] FIG. 8 is a diagram showing variation of a press-contact
load with the attitude of a diaphragm spring;
[0020] FIG. 9 is a flowchart showing a program to be executed by a
CPU shown in FIG. 1;
[0021] FIG. 10 is a flowchart showing a program to be executed by
the CPU shown in FIG. 1;
[0022] FIG. 11 is a flowchart showing a program to be executed by
the CPU shown in FIG. 1;
[0023] FIG. 12 is a schematic sectional view showing a clutch
according to a second embodiment of the present invention;
[0024] FIG. 13 is a front view of the clutch shown in FIG. 12;
[0025] FIG. 14 is a side view of an adjustment member of the clutch
shown in FIG. 12;
[0026] FIG. 15 is a perspective view showing a pressure plate and
the adjustment member of the clutch shown in FIG. 12;
[0027] FIG. 16 is an enlarged view showing the adjustment member
and its peripheral members of the clutch shown in FIG. 12;
[0028] FIG. 17 is an exploded perspective view showing the pressure
plate and the adjustment member of the clutch shown in FIG. 12;
[0029] FIG. 18 is a flowchart showing a program to be executed by a
CPU of a clutch control apparatus according to the second
embodiment; and
[0030] FIGS. 19A to 19D are views for explaining action of the
clutch shown in FIG. 12.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] Embodiments of the present invention will next be described
in detail with reference to the drawings.
[0032] A clutch control apparatus according to a first embodiment
of the present invention will next be described with reference to
FIGS. 1 to 11. As schematically shown in FIG. 1, the clutch control
apparatus includes a frictional clutch 20 disposed between an
engine 10, serving as a drive unit (a power source), and a
transmission 11; an actuator 30 for operating the clutch 20; and a
clutch control circuit 40 for outputting a drive instruction signal
(drive signal) to the actuator 30.
[0033] FIG. 2 shows the details of the frictional clutch 20. As
shown in FIG. 2, main components of the frictional clutch 20 are a
flywheel 21, a clutch cover 22, a clutch disk 23, a pressure plate
24, a diaphragm spring 25, a release bearing 26, a release fork 27,
a pivot support member 28 fixedly attached to a transmission casing
11a, and an adjust wedge member 29. Clutch components attached
unitarily to the clutch cover 22, such as the pressure plate 24,
the diaphragm spring 25, and the adjust wedge member 29, may be
called a clutch cover assembly.
[0034] The flywheel 21 is a disk of cast iron and is fixedly
attached to a crank-shaft (output shaft of a drive unit) 10a of the
engine 10 by means of bolts for unitary rotation with the
crank-shaft 10a.
[0035] The clutch cover 22 has a substantially cylindrical shape
and includes a cylindrical portion 22a; a flange portion 22b
extending radially inward from the cylindrical portion 22a; a
plurality of holder portions 22c formed at the inner
circumferential edge of the cylindrical portion 22a while been
arranged equally spaced in a circumferential direction; and
pressure plate stopper portions 22d, which is bent radially inward
from the cylindrical portion 22a. A portion extending radially
outward from the cylindrical portion 22a is fixedly attached to the
flywheel 21 by means of bolts, so that the clutch cover 22 rotates
unitarily with the flywheel 21.
[0036] The clutch disk 23 is a frictional disk for transmitting the
power of the engine 10 to the transmission 11 and is disposed
between the flywheel 21 and the pressure plate 24. A central
portion of the clutch disk 23 is spline connected with an input
shaft of the transmission 11 so that the clutch disk moves axially.
Clutch facings 23a and 23b are fixedly attached to the opposite
sides of an outer circumferential portion of the clutch disk 23 by
means of rivets. The clutch facings 23a and 23b are formed of a
friction material.
[0037] The pressure plate 24 can move in a reciprocating manner
along the axial direction of the input shaft of the transmission
11. The pressure plate 24 presses the clutch disk 23 toward the
flywheel 21 such that the clutch disk 23 is gripped between the
pressure plate 24 and the flywheel 21 to thereby be engaged with
the flywheel 21 for unitary rotation therewith. The pressure plate
24 is connected to the clutch cover 22 by means of straps 24a so as
to rotate with the clutch cover 22.
[0038] The strap 24a assumes the form of a laminate of a plurality
of thin leaves for spring use. As shown in FIG. 3, one end of the
strap 24a is fixedly attached to an outer circumferential portion
of the clutch cover 22 by means of a rivet R1, whereas the other
end is fixedly attached to a portion of the pressure plate 24 which
projects from an outer circumferential portion of the pressure
plate 24 by means of a rivet R2. The thus-attached straps 24a apply
a force to the pressure plate 24 in an axial direction urging the
pressure plate 24 to move away from the flywheel 21.
[0039] As shown in FIGS. 2 and 4, a contact portion 24b is formed
on the outermost circumferential portion of the pressure plate 24.
When the pressure plate 24 moves by a predetermined amount toward
the diaphragm spring 25, the contact portion 24b abuts the pressure
plate stopper portion 22d of the clutch cover 22. A guide portion
24c is formed on the pressure plate 24 on the radially inward side
of the contact portion 24b in a condition standing toward the
diaphragm spring 25. As shown in FIG. 5, a plurality of sawtoothed
taper portions 24d are formed on the pressure plate 24 on the
radially inward side of the guide portion 24c in a condition
standing toward the diaphragm spring 25.
[0040] The diaphragm spring 25 is composed of 12 resilient plate
members 25a (hereinafter called "lever members 25a") arranged
radially along the inner circumferential wall of the cylindrical
portion 22a of the clutch cover 22 (see FIG. 3). As shown in FIG.
2, each of the lever members 25a is held by the holder portions 22c
of the clutch cover 22 via a pair of annular fulcrum members (ring
members) 25b and 25c. Thus, the lever members 25a can pivot on the
ring members 25b and 25c with respect to the clutch cover 22.
[0041] An adjust wedge member 29, which serves as a portion of an
adjustment member (press-contact load adjustment means), is
disposed between the taper portions 24d of the pressure plate 24
and an outer circumferential portion of the diaphragm spring 25.
The adjust wedge member 29 is an annular member. As shown in FIG.
5, the adjust wedge member 29 includes a plurality of taper
portions 29a, which assume the same shape as that of the taper
portions 24d of the pressure plate 24. The taper portions 29a of
the adjust wedge member 29 and the corresponding taper portions 24d
of the pressure plate 24 abut each other at the corresponding taper
planes TP. An end face of the adjust wedge member 29 which faces
the diaphragm spring 25 (upper end face in FIG. 5) is flat. The
adjust wedge member 29 forms a transmission path for transmitting a
force between the pressure plate 24 and the diaphragm spring 25.
The adjust wedge member 29 transmits to the pressure plate 24 a
force applied to the diaphragm spring 25 and a force generated by
the diaphragm spring 25.
[0042] Cuts 29b are formed at appropriate positions on the end face
of the adjust wedge member 29 which faces the diaphragm spring 25.
Through-holes 24e are formed at appropriate positions on the taper
portions 24d of the pressure plate 24. End portions of a stretched
coil spring CS are caught by the corresponding cut 29b and
through-hole 24e. The thus-installed coil springs CS apply a force
to the pressure plate 24 and the adjust wedge member 29 in such a
manner as to rotate the pressure plate 24 and the adjust wedge
member 29 in mutually opposite directions such that the tooth-crest
of each of the taper portions 24d of the pressure plate 24 and the
corresponding tooth-crest of each of the taper portions 29a of the
adjust wedge member 29 mutually approach.
[0043] The release bearing 26 is slidably supported on a support
sleeve 11b, which is supported by the transmission casing 11a in
such a manner as to surround the input shaft of the transmission
11. The release bearing 26 forms a force-application portion 26a
for moving inner-end portions of the lever members 25a (central
portion of the diaphragm spring 25) toward the flywheel 21 through
application of pressure.
[0044] The release fork 27 (fork member) is adapted to axially
slide the release bearing 26 according to the operation of the
actuator 30. One end of the release fork 27 abuts the release
bearing 26, whereas a contact portion 27a located at the other end
abuts an end of a rod 31 of the actuator 30. The release fork 27 is
attached to the pivot support member 28 by means of a spring 27c
fixedly attached to the transmission casing 11a. A substantially
central portion 27b of the release fork 27 is supported on the
pivot support member 28 such that the release fork 27 swings on the
pivot support member 28.
[0045] The actuator 30 is adapted to move the rod 31 in a
reciprocating manner. The actuator 30 includes an electric (DC)
motor 32 and a housing 33, which supports the electric motor 32 and
is fixed in an appropriate place within a vehicle. The housing 33
accommodates a rotating shaft 34, which is rotated by the electric
motor 32; a sector gear (a worm wheel) 35, which assumes the form
of a fan in a side view and is swingably supported by the housing
33; and an assist spring 36.
[0046] The rotating shaft 34 is a worm and is engaged with an arc
portion of the sector gear 35. A root end portion of the rod 31 (an
end portion opposite that in contact with the release fork 27) is
pivotably supported by the sector gear 35. As the electric motor 32
rotates, the sector gear 35 rotates, thereby causing the rod 31 to
move in a reciprocating manner with respect to the housing 33.
[0047] The assist spring 36 is compressed while the sector gear 35
swings within a predetermined range. One end of the assist spring
36 is caught at a rear-end portion of the housing 33, whereas the
other end is caught by the sector gear 35. Thus, the assist spring
36 applies a force to the sector gear 35 in a direction urging the
sector gear 35 to rotate clockwise to thereby urge the rod 31 to
move rightward in FIG. 2, thereby assisting the electric motor 32
to move the rod 31 rightward.
[0048] Referring again to FIG. 1, the clutch control circuit 40
includes a microcomputer (CPU) 41, interfaces 42 to 44, an EEPROM
45, a power circuit 46, and a drive circuit 47. The CPU 41 contains
a ROM in which a program and a map (look-up table), which will be
described later, are stored, and a RAM.
[0049] The interface 42 is connected to the CPU 41 via a bus as
well as to a shift lever load sensor 51 for detecting a load which
is generated when the shift lever of transmission is operated
(shift lever load); a vehicle speed sensor 52 for detecting a
vehicle speed V; a gear position sensor 53 for detecting an actual
transmission gear position; a transmission input shaft
revolving-speed sensor 54; and a stroke sensor 37 fixedly attached
to the actuator 30 and adapted to detect a stroke ST of the rod 31
through detection of the swing angle of the sector gear 35. The
interface 42 supplies the CPU 41 with detection signals received
from these sensors.
[0050] The interface 43 is connected to the CPU 41 via a bus as
well as to an engine control unit 60 in a bidirectionally
communicating manner. Thus, the CPU 41 of the clutch control
circuit 40 can obtain information collected by a throttle opening
angle sensor 55 and an engine speed sensor 56 through the engine
control unit 60.
[0051] The interface 44 is connected to the CPU 41 via a bus as
well as to the drive circuit 47 and one input terminal of an OR
circuit 46a of the power circuit 46 so as to send an appropriate
signal to the drive circuit 47 and the OR circuit 46a according to
an instruction from the CPU 41.
[0052] The EEPROM 45 is a nonvolatile memory capable of retaining
data even when no power is supplied thereto. The EEPROM 45 is
connected to the CPU 41 via a bus and adapted to store data
received from the CPU 41 and to supply stored data to the CPU 41,
while powered.
[0053] The power circuit 46 includes the OR circuit 46a; a power
transistor Tr whose base is connected to an output terminal of the
OR circuit 46a; and a constant-voltage circuit 46b. The collector
of the power transistor Tr is connected to the plus terminal of a
battery 70 mounted on the vehicle, whereas the emitter of the power
transistor Tr is connected to the constant-voltage circuit 46b and
the drive circuit 47. Thus, when the power transistor Tr is turned
on, power is supplied to the constant-voltage circuit 46b and the
drive circuit 47. The constant-voltage circuit 46b is adapted to
convert the battery voltage to a predetermined constant voltage (5
V) and connected to the CPU 41, the interfaces 42 to 44, and the
EEPROM 45 so as to supply power thereto. One terminal of an
ignition switch 71, which is turned on or off by a driver, is
connected to the other input terminal of the OR circuit 46a. The
other terminal of the ignition switch 71 is connected to the plus
terminal of the battery 70. The terminal of the ignition switch 71
connected to the OR circuit 46a is also connected to the interface
42, so that the CPU 41 can detect the on/off state of the ignition
switch 71.
[0054] The drive circuit 47 contains four switching elements (not
shown) which go on or off in response to an instruction signal
received via the interface 44. These switching elements constitute
a known bridge circuit and are selectively turned on with their ON
periods being controlled. Thus, the drive circuit 47 supplies power
to the electric motor 32 such that a current of a certain intensity
flows to the electric motor 32 in a predetermined direction or in a
direction opposite the predetermined direction.
[0055] The engine control unit 60 is mainly composed of an
unillustrated microcomputer and adapted to control, for example,
the amount of fuel to be injected and ignition timing. As mentioned
previously, the engine control unit 60 is connected to the throttle
opening angle sensor 55 for detecting a throttle opening angle TA
of the engine 10 and the engine speed sensor 56 for detecting a
rotational speed NE of the engine 10 so as to receive signals from
the sensors 55 and 56 and so as to process the received
signals.
[0056] Next, the operation of the thus-configured clutch apparatus
will be described. In contrast to conventional driver-effected
clutch pedal operation, in this clutch apparatus, the actuator 30
automatically performs a clutch engagement/disengagement operation.
Specifically, the clutch engagement/disengagement operation is
performed when the CPU 41 detects, for example, any one of the
following conditions: (1) a vehicle is shifting from a traveling
state to a stopping state (the rotational speed of the input shaft
of the transmission has dropped to or below a predetermined value);
(2) a load detected by the shift lever load sensor 51 has increased
to or above a predetermined value (the driver's intention to shift
gears has been confirmed); and (3) an accelerator pedal is stepped
on when the vehicle is halted.
[0057] There will be described an operation while the clutch is
engaged so as to transmit the power of the engine 10 to the
transmission 11. First, in response to an instruction signal from
the clutch control circuit 40, the drive circuit 47 applies a
predetermined current to the electric motor 32 to thereby rotate
the electric motor 32. As a result, the sector gear 35 rotates
counterclockwise in FIG. 2, causing the rod 31 to move
leftward.
[0058] Meanwhile, the release bearing 26 receives a force which the
diaphragm spring 25 applies thereto in a direction urging the
release bearing 26 to move away from the flywheel 21 (rightward in
FIG. 2). This force is transmitted to the release fork 27 via the
release bearing 26 and urges the release fork 27 to rotate
counterclockwise in FIG. 2 on the pivot support member 28.
Accordingly, when the rod 31 moves leftward in FIG. 2, the release
fork 27 rotates counterclockwise, and a central portion of the
diaphragm spring 25 moves away from the flywheel 21.
[0059] At this time, the diaphragm spring 25 swings (i.e., deforms
and undergoes change in posture (attitude)) about the ring members
25b and 25c, thereby moving the adjust wedge member 29, which abuts
an outer circumferential portion of the diaphragm spring 25, toward
the flywheel 21 through application of pressure. As a result, the
pressure plate 24 receives a force which urges the pressure plate
24 toward the flywheel 21 via the taper portion 24d, thereby
gripping the clutch disk 23 in cooperation with the flywheel 21.
Thus, the clutch disk 23 is engaged with the flywheel 21 to thereby
rotate unitarily with the flywheel 21, thereby transmitting the
power of the engine 10 to the transmission 11.
[0060] Next will be described an operation to disengage the clutch
so as not to transmit the power of the engine 10 to the
transmission 11. First, the electric motor 32 is rotated so as to
rotate the sector gear 35 clockwise in FIG. 2. The rod 31 moves
rightward in FIG. 2 and applies a rightward force to the contact
portion 27a of the release fork 27. The release fork 27 rotates
clockwise in FIG. 2 on the pivot support member 28, thereby moving
the release bearing 26 toward the flywheel 21 through application
of pressure.
[0061] Thus, the diaphragm spring 25 receives a force directed
towards the flywheel at the central portion of the diaphragm spring
25, i.e. , at the force application portion 26a. As a result, the
diaphragm spring 25 swings (i.e., deforms and undergoes change in
attitude) about the ring members 25b and 25c, thereby causing the
outer circumferential portion of the diaphragm spring 25 to move
away from the flywheel 21. Accordingly, there is reduced the force
which presses the pressure plate 24 toward the flywheel 21 via the
adjust wedge member 29. Since the pressure plate 24 is connected to
the clutch cover 22 by means of the straps 24a in such a manner as
to be always subjected to a force which urges the pressure plate 24
to move away from the flywheel 21, this force causes the pressure
plate 24 to move slightly away from the clutch disk 23. As a
result, the clutch disk 23 becomes free, thereby establishing a
state in which the power of the engine 10 is not transmitted to the
transmission 11.
[0062] When the clutch is to be disengaged during regular vehicle
operation, the stroke of the rod 31 is controlled to a value ST0 so
as to maintain a predetermined distance Y between the contact
portion 24b of the pressure plate 24 and the pressure plate stopper
portion 22d of the clutch cover 22 as shown in FIG. 4A.
[0063] Generally, it is inevitable that manufacture of components
of the clutch apparatus involves characteristic errors (variations
among products). Particularly, characteristic errors arising in
manufacture of the diaphragm spring 25 have a great effect on a
load exerted for complete engagement (press contact) of the clutch
disk 23 and the flywheel 21; i.e., a press-contact load. Also, the
work of assembling components of the clutch apparatus involve
errors which influence the press-contact load. Thus, as shown in
FIG. 6, a reaction force which is applied to the rod 31 relative to
the stroke of the rod 31 (position of the rod 31), or a release
load, falls within the range defined with respect to a solid line
L1, which represents design (ideal) values; i.e., within the range
defined by a dashed line L2 and a dashed line L3. The release load
varies among products. Accordingly, unless such characteristic
errors are compensated, products vary in operating characteristics
of a clutch; particularly, in time required for shift from
disengagement to engagement or from engagement to disengagement
(hereinafter called the "clutch response time"; clutch performance
represented in terms of clutch response time is called the "clutch
response characteristic").
[0064] A method for preventing the occurrence of an excessively
long clutch response time associated with the occurrence of
characteristic errors in the course of manufacture is to select an
appropriate spring constant for the assist spring 36 of the
actuator 30 (electric motor 32). Specifically, characteristics (for
example, spring constant, length, and arrangement) of the assist
spring 36 are determined such that the maximum difference between
the maximum potential release load represented by a line L2 in FIG.
7 and the assist-spring force represented by a line L4 in FIG. 7
(the maximum required output of the electric motor 32; represented
by "MAXIMUM OPERATING FORCE" in FIG. 7) becomes not greater than a
predetermined value, thereby keeping a clutch response time within
a predetermined range.
[0065] However, in order to increase the spring constant, the
spring diameter must be increased. An increase in spring diameter
results in an increase in the size of the actuator 30. Also, in the
case of the minimum potential release load represented by a line L3
in FIG. 7, the operating force becomes excessively small
(represented by "MINIMUM OPERATING FORCE" in FIG. 7), resulting in
an excessively short clutch response time.
[0066] In order to avoid the above problems and automatically
compensate characteristic variations derived from errors which have
arisen in the course of manufacture, the present clutch control
apparatus performs control (automatic adjustment) such that the
press-contact load is modified so as to attain desired clutch
characteristics (operating characteristics of clutch). As shown in
FIG. 8, the press-contact load changes (varies) with the attitude
of the diaphragm spring 25 as observed when the clutch disk 23 is
completely engaged with the flywheel 21. Therefore, the clutch
control apparatus modifies the press-contact load through
modification of the attitude of the diaphragm spring 25 as observed
when the clutch is completely engaged. In FIG. 8, an increase in
the attitude of the diaphragm spring 25 (rightward movement along
the x-axis in FIG. 8) means that the diaphragm spring 25 becomes
flatter (in FIG. 2, the angle between the diaphragm spring 25 and
the input shaft of the transmission approaches 90 degrees). In FIG.
8, the modification of the attitude of the diaphragm spring 25 as
represented by an arrow means a reduction in the load of the
diaphragm spring 25.
[0067] A specific example of a compensation operation (adjustment)
to be performed for variations among products according to the
present invention will next be described with reference to the
routines shown in FIGS. 9 to 11. A routine shown in FIG. 9
determines the necessity for performing the above-described
adjustment. The CPU 41 executes this routine repeatedly at
predetermined intervals. When predetermined timing is reached, the
CPU 41 starts executing the routine from step 900. In step 905, the
CPU 41 determines whether or not the clutch 20 (clutch disk 23) has
been completely engaged. Specifically, when the stroke ST is equal
to a predetermined stroke STKIGO, the CPU 41 determines that the
clutch 20 is engaged completely. When the stroke ST is greater than
the stroke STKIGO, the CPU 41 determines the clutch 20 is not
engaged completely.
[0068] When the clutch 20 is engaged completely, the CPU 41 makes a
"Yes" determination in step 905 and proceeds to step 910. In step
910, the CPU 41 sets the value of an estimation calculation
enabling flag FEK to "1." The estimation calculation enabling flag
FEK is used to determine whether to permit execution of a
calculation in step 940 described later to estimate a clutch
stroke. Next, the CPU 41 proceeds to step 915. In step 915, the CPU
41 sets the value of an estimated clutch stroke SIST to a present
stroke ST (a value detected by the stroke sensor 37) to thereby
initialize the estimated clutch stroke SIST. Subsequently, the CPU
41 proceeds to step 920. In step 920, the CPU 41 sets the value of
an estimated clutch stroke speed SIV to "0" to thereby initialize
the estimated clutch stroke speed SIV. Then, the CPU 41 proceeds to
step 925. Notably, in step 905, when the CPU 41 determines that the
clutch 20 is not engaged completely, the CPU 41 jumps to step
925.
[0069] In step 925, when the CPU 41 determines whether or not the
clutch 20 is disengaged. Specifically, when the stroke ST is
greater than a predetermined stroke STHIKG, which is greater than
the predetermined stroke STKIGO, the CPU 41 determines that the
clutch 20 is disengaged, but otherwise the CPU 41 determines that
the clutch 20 is not disengaged. When the clutch 20 is disengaged,
the CPU 41 makes a "Yes" determination in step 925 and proceeds to
step 930. In step 930, the CPU 41 sets the value of the estimation
calculation enabling flag FEK to "0."
[0070] Next, the CPU 41 proceeds to step 935. In step 935, the CPU
41 determines whether or not the value of the estimation
calculation enabling flag FEK is "1." When the value is "1," the
CPU 41 proceeds to step 940. In step 940, the CPU 41 executes the
subroutine shown in FIG. 10 in order to estimate a clutch
stroke.
[0071] The estimated clutch stroke calculation will next be
described with reference to FIG. 10. First, the CPU 41 proceeds
from step 1000 to step 1005. In step 1005, the CPU 41 calculates a
new estimated motor current SIIM according to the calculation
expression shown in step 1005 by use of the last calculated
estimated motor current SIIM (initial value: "0") and a current IM
which the clutch control circuit 40 instructs at present to apply
to the electric motor 32 (i.e., motor current at present). In the
expression shown in step 1005, Kn is a predetermined constant of 0
to 1. Through this calculation, a time delay (time-lag of the first
order) is imparted to the estimated motor current SIIM with respect
to the motor current IM at present. That is, the calculation
considers a current delay caused by a motor inductance, thereby
obtaining a current flowing to the electric motor 32 at higher
accuracy. Alternatively, the motor current may be calculated in the
following manner. A shunt resistor is inserted in series in a power
circuit of the electric motor 32. An actual current flowing to the
electric motor 32 is obtained (determined) on the basis of a
voltage drop across the shunt resistor and the resistance (known)
of the electric motor 32.
[0072] Next, the CPU 41 proceeds to step 1010. In step 1010, the
CPU 41 determines a clutch load CL on the basis of the clutch load
map shown in step 1010 and the estimated clutch stroke SIST which
is available at present (the last estimated clutch stroke SIST).
Notably, the estimated clutch stroke SIST to be used in step 1010
is updated in step 1025, which will be described later. When step
1020 is executed for the first time after the value of the
estimation calculation enabling flag FEK is changed from "0" to
"1," the estimated clutch stroke SIST is equal to the actual stroke
ST because of initialization in step 915 described previously. The
clutch load CL is an ideal reaction force to be imposed on the rod
31 via the release bearing 26 and the release fork 27 at a certain
stroke ST. In other words, the clutch load CL is an ideal load
which acts on the electric motor 32 (actuator 30) when components
for operating the clutch 20 are manufactured such that their design
parameters assume the corresponding center values of design
ranges.
[0073] After determining the clutch load CL in step 1010, the CPU
41 proceeds to step 1015. In step 1015, the CPU 41 calculates an
estimated clutch stroke acceleration SIACC. Specifically, the CPU
41 employs as a new estimated clutch stroke acceleration SIACC a
value obtained through subtraction of the clutch load CL from the
product of the estimated motor current SIIM and a predetermined
constant KT. Since the output torque of the electric motor 32 is
proportional to a current flowing to the electric motor 32, the
product of the estimated motor current SIIM and a predetermined
constant KT represents a force by which the electric motor 32 moves
the rod 31 in a reciprocating manner. Accordingly, the value
obtained through subtraction of the clutch load CL from the
product; i.e., the estimated clutch stroke acceleration SIACC to be
obtained in step 1015 is proportional to a force applied to the rod
31. Thus, the value obtained in step 1015 is an estimated
acceleration of the clutch stroke ST.
[0074] Next, the CPU 41 proceeds to step 1020. In step 1020, the
CPU 41 affinely integrates the estimated clutch stroke acceleration
SIACC to thereby obtain the estimated clutch stroke speed SIV.
Specifically, the CPU 41 adds the product of the above-obtained
estimated clutch stroke acceleration SIACC and an execution cycle t
of the present routine (t.cndot.SIACC) to the last obtained
estimated clutch stroke speed SIV. The CPU 41 employs the resulting
value as a new estimated clutch stroke speed SIV.
[0075] Then, the CPU 41 proceeds to step 1025. In step 1025, the
CPU 41 affinely integrates the estimated clutch stroke speed SIV to
thereby obtain the estimated clutch stroke SIST. Specifically, the
CPU 41 adds the product of the above-obtained estimated clutch
stroke speed SIV and the execution cycle t of the present routine
(t.cndot.SIV) to the last obtained estimated clutch stroke SIST.
The CPU 41 employs the resulting value as a new estimated clutch
stroke SIST. Subsequently, the CPU 41 proceeds to step 1095 to
thereby terminate the present routine. In this manner, on the basis
of the current IM of the electric motor 32, an ideal (target)
clutch stroke (estimated clutch stroke SIST) is determined.
[0076] After calculating the estimated clutch stroke SIST, the CPU
41 proceeds to step 945 in FIG. 9. In step 945, the CPU 41
determines whether or not the difference between the estimated
clutch stroke SIST and the actual clutch stroke ST is equal to or
greater than a predetermined threshold value .DELTA.S. The "Yes"
determination in step 945 means that characteristic variations
derived from errors which have arisen in the course of manufacture
are of a great degree, resulting in a big difference between an
ideal stroke and an actual stroke at the time when a predetermined
current flows to the motor 32. In this case, adjustment must be
performed; thus, the CPU 41 proceeds to step 950. In step 950, the
CPU 41 sets the value of an adjustment request flag FADJ to "1."
Then, the CPU 41 proceeds to step 995 and terminates the present
routine.
[0077] The "No" determination in step 945 means that characteristic
variations derived from errors which have arisen in the course of
manufacture are of a small degree, so that execution of adjustment
is not necessary. In this case, The CPU 41 jumps to step 995 and
terminates the present routine. As described above, the CPU 41
determines whether or not execution of adjustment is necessary, and
sets the adjustment request flag FADJ accordingly.
[0078] Next, actions associated with execution of adjustment will
be described with reference to the routine shown in FIG. 11. The
CPU 41 executes the routine shown in FIG. 11 repeatedly at
predetermined intervals. When predetermined timing is reached, the
CPU 41 starts executing the routine from step 1100 and proceeds to
step 1105 and subsequent steps. In steps 1105 to 1120, the CPU 41
determines whether or not the conditions for execution of
adjustment are established.
[0079] Description will be continued on the assumption that the
conditions for execution of adjustment (steps 1105 to 1120) are all
established. In step 1105, the CPU 41 determines whether or not the
value of the adjustment request flag FADJ is "1." Step 1105 is
provided to perform adjustment only when a request to perform
adjustment is present.
[0080] Because of the aforementioned assumption, the value of the
adjustment request flag FADJ is "1." Thus, the CPU 41 makes the
"Yes" determination in step 1105 and proceeds to step 1110. In step
1110, the CPU 41 determines whether or not the clutch disk 23 is
disengaged. This is because when the clutch 20 is engaged in a
certain state of operation, adjustment cannot be performed.
[0081] Because of the aforementioned assumption, the clutch disk 23
is disengaged. Thus, the CPU 41 makes the "Yes" determination in
step 1110 and proceeds to step 1115. In step 1115, the CPU 41
determines whether or not the engine speed NE is greater than a
predetermined low rotational speed a (for example, a minimum
rotational speed of 400 rpm required for operation of the engine
10) and less than a predetermined high rotational speed .beta. (for
example, a rotational speed of 2000 rpm, at which vibration of the
engine 10 begins to increase).
[0082] Step 1115 is provided to perform adjustment only when
vibration of the engine 10 is small and therefore possibility of
resonance of the clutch 20 is small, in order to avoid erroneous
adjustment. The reason why the adjustment is enabled only when the
engine speed NE is greater than the rotational speed .alpha. is
that, at the time of "geared parking," in which a vehicle is parked
while a predetermined shift gear is engaged, execution of
adjustment, which involves disengagement of the clutch disk 23, is
not desirable. An engine speed NE greater than the predetermined
rotational speed .alpha. indicates that geared parking is not the
case.
[0083] Because of the aforementioned assumption, the engine speed
NE is greater than the low rotational speed .alpha. and less than
the high rotational speed .beta.. Thus, the CPU 41 makes the "Yes"
determination in step 1115 and proceeds to step 1120. In step 1120,
the CPU 41 determines whether or not the vehicle speed V is "0."
Step 1120 is provided to avoid erroneous adjustment which may be
caused by vibration of a traveling vehicle. Because of the
aforementioned assumption, the vehicle is halted, so that the
vehicle speed V is "0." Thus, the CPU 41 makes the "Yes"
determination in step 1120 and proceeds to step 1125.
[0084] In step 1125, the CPU 41 determines whether or not the
stroke ST is greater than the total of a stroke ST0 , a stroke SX,
and a stroke SY (ST0+SX+SY). As mentioned previously, the stroke
ST0 is a stroke ST as established when the clutch 20 is disengaged
during regular vehicle operation. The stroke SY is a stroke
corresponding to the distance Y between the contact portion 24b of
the pressure plate 24 and the pressure stopper portion 22d of the
clutch cover 22. The stroke SX is a stroke corresponding to an
adjustment amount X by which an outer circumferential portion of
the diaphragm spring 25 is moved away from an outer circumferential
portion of the pressure plate 24 through current adjustment.
[0085] At this stage, since the clutch 20 is in the regular
disengaged state, the stroke ST is equal to ST0. Accordingly the
CPU 41 makes the "No" determination in step 1125 and proceeds to
step 1130. In step 1130, the CPU 41 makes the current IM of the
electric motor 32 equal to an adjustment current IMADJ. As a
result, the stroke ST begins to gradually approach the criterion
value (ST0+SX+SY) shown in step 1125. Subsequently, the CPU 41
proceeds to step 1195 and terminates the present routine.
[0086] The CPU 41 executes the routine at predetermined intervals
and therefore continues to see, through steps 1105 to 1120, whether
or not the conditions for execution of adjustment are established
and to see in step 1125 whether or not the stroke ST becomes equal
to the criterion value (ST0+SX+SY).
[0087] Subsequently, the diaphragm spring 25 undergoes change in
attitude from the one shown in FIG. 4A to the one shown in FIG. 4B.
Specifically, the diaphragm spring 25 receives a force directed to
the flywheel 21 at the force-application portion 26a and thus
swings (undergoes change in attitude) about the ring members 25b
and 25c. As a result, the contact portion 24b of the pressure plate
24 abuts the pressure plate stopper portion 22d of the clutch cover
22.
[0088] At this point of time, since the stroke ST is smaller than
the criterion value (the stroke ST assumes the value (ST0+SY)), the
CPU 41 makes the "No" determination in step 1125 and executes step
1130. Thus, the current IMADJ continues flowing to the electric
motor 32; consequently, the attitude of the diaphragm spring 25
changes further. Since the contact portion 24b of the pressure
plate 24 is in contact with the pressure stopper portion 22d of the
clutch cover 22, further movement of the pressure plate 24 is
disabled. As a result, the distance between an outer
circumferential end portion of the diaphragm spring 25 and the
taper portion 24d of the pressure plate 24 increases. Consequently,
as shown in FIG. 5, the coil springs CS cause the adjust wedge
member 29 to rotate in the direction of the arrow such that each
taper portion 29a of the adjust wedge member 29 and the
corresponding taper portion 24d of the pressure plate 24 contact
each other at their higher portions. In this manner, a flat portion
of the adjust wedge member 29 follows the movement of the outer
circumferential end portion of the diaphragm spring 25.
[0089] When after the elapse of a predetermined time, the stroke ST
becomes equal to the criterion value (ST0+SX+SY), the CPU 41 makes
the "Yes" determination in step 1125 and proceeds to step 1135. In
step 1135, the CPU 41 sets the value of the adjustment request flag
FADJ to "0." Then, the CPU 41 proceeds to step 1195 and terminates
the present routine. Thus, the adjustment is completed.
Subsequently, a current corresponding to every state of operation
(driving condition of the vehicle) is applied to the electric motor
32, thereby performing appropriate clutch control.
[0090] The above adjustment causes the distance between the
diaphragm 25 and the pressure plate 24 to increase by the
adjustment amount X (see FIG. 4C). As a result, the attitude of the
diaphragm varies, causing modification of a press-contact load
imposed on the clutch disk 23 (accordingly, modification of a load
of operation of the clutch 20). Through modification of the
press-contact load, characteristic errors which have arisen in the
course of manufacture are compensated, thereby providing desirable
clutch characteristics (desirable operating characteristics of
clutch).
[0091] Next will be described the case where in execution of the
routine shown in FIG. 11, any one of the conditions for execution
of adjustment (steps 1105 to 1120) fails to be established. The CPU
41 makes the "No" determination in any one of steps 1105 to 1120
and proceeds to step 1195. In step 1195, the CPU 41 terminates the
present routine. Subsequently, a current corresponding to every
state of operation (driving condition of the vehicle) is applied to
the electric motor 32, thereby performing appropriate clutch
control.
[0092] According to the above-described first embodiment, when a
predetermined state of operation is established, the electric motor
32 is operated so as to move the rod 31 in a reciprocating manner.
The thus-moved rod 31 applies a force to a predetermined portion
(substantially central portion) of the diaphragm spring 25 via the
release fork 27 and the release bearing 26. The thus-applied force
causes the diaphragm spring 25 to deform (undergo change in
attitude on the ring members 25b and 25c), thereby disengaging the
clutch disk 23 and the flywheel 21.
[0093] The above-described clutch control apparatus for a vehicle
includes press-contact load adjustment means (actuator 30, release
fork 27, release bearing 26, and adjust wedge member 29, among
others) for modifying the posture of the diaphragm spring 25 as
observed when the clutch disk 23 is engaged with the flywheel 21,
according to an instruction (adjustment request flag FADJ, for
example), to thereby modify a press-contact load; means for
obtaining the current SIIM of the electric motor 32 (step 1005);
reaction-force calculation means for calculating an ideal reaction
force CL to be imposed on the rod 31 for the stroke SIST of the rod
31 which has been estimated a predetermined time before (step
1010); stroke estimation means for estimating the acceleration
SIACC of the rod 31 on the basis of the calculated ideal reaction
force and an output torque of the electric motor 32 (actuator 30)
estimated from the current SIIM of the electric motor 32 (i.e., a
drive signal issued to the actuator 30), and estimating a new
stroke SIST of the rod 31 on the basis of the estimated
acceleration SIACC (steps 1015 to 1025); stroke detection means
(stroke sensor 37) for detecting an actual stroke ST of the rod 31;
and adjustment instruction means for instructing the press-contact
load adjustment means to make adjustment such that the detected
stroke ST becomes equal to the estimated stroke SIST (steps 945,
590, 1125, and 1130).
[0094] As a result, since characteristic variations among clutch
apparatus derived from errors which have arisen in the course of
manufacture are compensated, variations in clutch characteristics
(operating characteristics of clutch) among products can be
reduced; the size of the assist spring 36 can be reduced; and the
size of the actuator 30 can be reduced.
[0095] Next, a clutch control apparatus according to a second
embodiment of the present invention will be described with
reference to FIGS. 12 to 19. A clutch according to the second
embodiment differs from that according to the first embodiment in
an adjustment mechanism (press-contact load adjustment means or
adjustment member) disposed between an outer circumferential
portion of the pressure plate 24 and an outer circumferential
portion of the diaphragm spring 25. Same members as those of the
first embodiment are denoted by common reference numerals, and
repeated description thereof is omitted.
[0096] In the second embodiment, an annular taper member 81 is
fixedly attached to an outer circumferential portion of the
pressure plate 24 such that a plurality of taper portions 81a of
the taper member 81 is provided to face the diaphragm spring 25
(see FIG. 17). The taper portions 81a assume the form of sawteeth.
An adjust wedge member 82, which serves as a portion of the
press-contact load adjustment means, is disposed between the taper
portions 81a and an outer circumferential portion of the diaphragm
spring 25.
[0097] The adjust wedge member 82 assumes the form of a ring and is
held by the taper member 81 in such a manner as to be coaxially
rotatable with the taper member 81. The adjust wedge member 82
includes a plurality of taper portions 82a, each of which assumes
the same shape as that of the taper portion 81a. As shown in FIG.
15, the taper portions 82a of the adjust wedge member 82 and the
corresponding taper portions 81a of the taper member 81 abut each
other at the corresponding taper planes TP1. An end face of the
adjust wedge member 82 which faces the diaphragm spring 25 is
flat.
[0098] As shown in FIG. 15, cuts 82b are formed at appropriate
positions on the end face of the adjust wedge member 82 which faces
the diaphragm spring 25. Catch portions 81b are formed at
appropriate positions on the taper member 81, which is fixedly
attached to the pressure plate 24. End portions of a stretched coil
spring CS1 are caught by the corresponding cut 82b and catch
portion 81b. The thus-installed coil springs CS1 apply a force to
the pressure plate 24 (taper member 81) and the adjust wedge member
82 in such a manner as to rotate the pressure plate 24 and the
adjust wedge member 82 in mutually opposite directions such that
the tooth-crest of each of the taper portions 81a of the taper
member 81 and the corresponding tooth-crest of each of the taper
portions 82a of the adjust wedge member 82 mutually approach.
[0099] An adjust rack 83 is fixedly attached to the outer
circumferential surface of the adjust wedge member 82. The adjust
rack 83 includes first sawteeth 83a (or triangular teeth arranged
in an equally spaced manner) formed in a condition standing toward
the diaphragm spring 25 and arranged in a circumferential direction
of the adjust wedge member 82 and second sawteeth 83b formed
opposite the first sawteeth 83a and shifted by a half pitch with
respect to the first sawteeth 83a.
[0100] As shown in FIGS. 16, 17, and 19, a cylindrical member 84,
which is open at one end, is fixedly attached to the pressure plate
24 at an appropriate position while the open end faces upward. A
cylindrical adjust pinion 85, which is open at one end, is fitted
to the cylindrical member 84 in a slidably rotatable manner while
the open end faces downward. A coil spring 86 is disposed between
the cylindrical member 84 and the adjust pinion 85. A plurality of
teeth 85a formed on the side wall of the adjust pinion 85 are
arranged between a row of the first sawteeth 83a and a row of the
second sawteeth 83b, which are formed on the adjust rack 83, so as
to be selectively engaged with the first sawteeth 83a or the second
sawteeth 83b.
[0101] Next, the operation of the clutch apparatus according to the
second embodiment will be described. As in the case of the first
embodiment, during regular vehicle operation, when an unillustrated
actuator causes an unillustrated rod to retreat, a central portion
of the diaphragm spring 25 moves away from the flywheel 21. At this
time, the diaphragm spring 25 swings (i.e., deforms and undergoes
change in attitude) about the ring members 25b and 25c, thereby
moving the adjust wedge member 82 toward the flywheel 21 through
application of pressure. As a result, the pressure plate 24
receives a force which urges the pressure plate 24 toward the
flywheel 21 via the taper member 81, thereby gripping the clutch
disk 23 in cooperation with the flywheel 21. Thus, the clutch disk
23 is engaged with the flywheel 21 to thereby rotate unitarily with
the flywheel 21, thereby transmitting the power of the engine 10 to
the transmission 11.
[0102] In the above-mentioned clutch-engaged state during regular
vehicle operation, as shown in FIG. 16, an end face 85b of the
adjust pinion 85 is not in contact with the clutch cover 22. Thus,
as schematically shown in FIG. 19A, engagement of the teeth 85a of
the adjust pinion 85 with the second sawteeth 83b of the adjust
rack 83 is still maintained. As a result, the adjust wedge member
82 does not rotate with respect to the pressure plate 24.
[0103] Next will be described an operation to disengage the clutch
so as not to transmit the power of the engine 10 to the
transmission 11. An unillustrated electric motor is rotated so as
to advance the rod, thereby moving an unillustrated release bearing
toward the flywheel 21 through application of pressure.
[0104] Thus, the diaphram spring 25 receives a force directed
towards flywheel 21, at the force-application portion 26a, located
in the vicinity of a central portion of the diaphragm spring 25. As
a result, the diaphragm spring 25 swings (i.e., deforms and
undergoes change in attitude) about the ring members 25b and 25c,
thereby causing an outer circumferential portion of the diaphragm
spring 25 to move away from the flywheel 21. Accordingly, there is
reduced the force which presses the pressure plate 24 toward the
flywheel 21 via the adjust wedge member 82. Since the pressure
plate 24 is connected to the clutch cover 22 by means of the straps
24a in such a manner as to be always subjected to a force which
urges the pressure plate 24 to move away from the flywheel 21, this
force causes the pressure plate 24 to move slightly away from the
clutch disk 23. As a result, the clutch disk 23 becomes free,
thereby establishing a state in which the power of the engine 10 is
not transmitted to the transmission 11.
[0105] The stroke of the rod of the actuator is controlled such
that in the thus-established clutch-disengaged state during regular
vehicle operation, the end face 85b of the adjust pinion 85 abuts
the clutch cover 22 so as to slightly compress the spring 86.
Through employment of such control, as schematically shown in FIG.
19B, engagement of the teeth 85a of the adjust pinion 85 with the
second sawteeth 83b of the adjust rack 83 is maintained. As a
result, the adjust wedge member 82 does not rotate with respect to
the pressure plate 24. Notably, the stroke of the rod may be
controlled such that even in the clutch-disengaged state during
regular vehicle operation, as shown in FIG. 16, a slight clearance
Z is maintained between the end face 85b of the adjust pinion 85
and the clutch cover 22. In this case, a clutch-disengaging
operation during regular vehicle operation does not involve mutual
sliding between the adjust pinion 85 and the cylindrical member 84,
thereby reducing wear of the members which would otherwise increase
due to frequent mutual sliding between the members.
[0106] Next, adjustment for compensation for characteristic
variations among clutch apparatus derived from errors which have
arisen in the course of manufacture will be described with
reference to FIG. 18. The routine of FIG. 18 differs from that of
FIG. 11 only in that step 1825 replaces step 1125. Accordingly,
steps shown in FIG. 18 other than step 1825 are denoted by common
reference numerals with those of FIG. 11, and repeated description
thereof is omitted. Notably, also in the second embodiment, the
routines of FIGS. 9 and 10 are executed at predetermined intervals
to thereby set the adjustment request flag FADJ to "1" or "0."
[0107] The CPU 41 executes the routine of FIG. 18 at predetermined
intervals and starts executing the routine from step 1800 at
predetermined timing. At this timing, when the conditions for
permitting adjustment (conditions for execution of adjustment) are
established, the CPU 41 makes the "Yes" determinations in all of
steps 1105 to 1120 and proceeds to step 1825. In step 1825, the CPU
41 determines whether or not the stroke ST of the rod is greater
than a predetermined threshold L0.
[0108] The threshold L0 is set sufficiently greater than a stroke
as established when the clutch is disengaged during regular vehicle
operation. Thus, when the CPU 41 proceeds to step 1825 upon first
establishment of the conditions of steps 1105 to 1120, the stroke
ST is less than the predetermined threshold L0. Therefore, the CPU
41 makes the "No" determination in step 1825 and proceeds to step
1130. In step 1130, the CPU 41 sets the current IM flowing to the
electric motor 32 to a sufficiently large predetermined current
IMADJ. Subsequently, the CPU 41 proceeds to step 1895 and
terminates the present routine. As a result, the rod starts to
move, and thus the central portion of the diaphragm spring 25
starts to deflect toward the flywheel 21.
[0109] Subsequently, the CPU 41 repeatedly performs steps 1105 to
1120 and 1825 at predetermined intervals to determine through steps
1105 to 1120 whether or not the conditions for execution of
adjustment are established and determines in step 1825 whether or
not the stroke ST is greater than the threshold L0. When any one of
the conditions for execution of adjustment fails to be established
before the stroke ST reaches the threshold L0, the CPU 41 makes the
"No" determination in the corresponding step of 1105 to 1120 and
proceeds to step 1895. In step 1895, the CPU 41 terminates the
present routine.
[0110] When the conditions for execution of adjustment are
maintained, the current of the electric motor 32 is held at the
current IMADJ. Accordingly, the attitude of the diaphragm spring 25
continues to change. When a predetermined time elapses, the end
face 85b of the adjust pinion 85 abuts the clutch cover 22. This
abutment prevents further movement of the adjust pinion 85.
However, since the pressure plate 24 receives a force which is
generated by the straps 24a extending between the pressure plate 24
and the clutch cover 22 and urges the pressure plate 24 to move
away from the flywheel 21, the pressure plate 24 moves further
against the force of the spring 86.
[0111] As a result, the relative position between the adjust rack
83 and the adjust pinion 85 begins to change. When a change in the
relative position becomes a predetermined amount or greater, as
shown in FIG. 19C, the teeth 85a of the adjust pinion 85 and the
second sawteeth 83b are disengaged. As a result, a force applied by
the coil springs CS1 causes the adjust wedge member 82 to rotate
with respect to the pressure plate 24 (taper member 81). In this
state, the teeth 85a of the adjust pinion 85 and the first sawteeth
83a are in such a position as to be able to mutually engage.
Accordingly, when the teeth 85a of the adjust pinion 85 engage the
first sawteeth 83b, further rotation of the adjust wedge member 82
is prevented. As a result of the above-described action, the
position of contact between the taper portion 81a of the taper
member 81 and the corresponding taper portion 82a of the adjust
wedge member 82 changes by half the pitch of the first sawteeth 83a
(second sawteeth 83b).
[0112] Subsequently, after the elapse of a predetermined time, the
stroke ST becomes greater than the threshold L0. The CPU 41 makes
the "Yes" determination in step 1825 and proceeds to step 1135. In
step 1135, the CPU 41 sets the value of the adjustment request flag
FADJ to "0" and proceeds to step 1895. In step 1895, the CPU 41
terminates the present routine.
[0113] Subsequently, when execution of unillustrated another
routine causes the clutch disk 23 to return to a regular
disengagement position, the relative position between the adjust
rack 83 and the adjust pinion 85 is restored to the regular state.
Accordingly, since the teeth 85a of the adjust pinion 85 and the
first sawteeth 83a are disengaged, a force applied by the coil
springs CS1 causes the adjust wedge member 82 to rotate again with
respect to the pressure plate 24 (taper member 81). When the teeth
85a of the adjust pinion 85 engage the second sawteeth 83a, further
rotation of the adjust wedge member 82 is prevented. The position
of contact between the taper portion 81a of the taper member 81 and
the corresponding taper portion 82a of the adjust wedge member 82
changes by another half the pitch of the first sawteeth 83a (second
sawteeth 83b). As a result of the above-described action, the
attitude of the diaphragm spring 25 during regular vehicle
operation is corrected so as to increase a press-contact load,
thereby compensating for characteristic variations among clutch
apparatus derived from errors which have arisen in the course of
manufacture.
[0114] As described above, according to the second embodiment, when
the clutch apparatus is in need of compensation for characteristic
variations derived from errors which have arisen in the course of
manufacture (when the value of the adjustment request flag FADJ is
"1"), a single execution of adjustment increases the distance
between an outer circumferential portion of the pressure plate 24
and an outer circumferential portion of the diaphragm spring 25 by
an amount corresponding to a single pitch of the second sawteeth
83b to thereby modify the attitude of the diaphragm spring 25 so as
to compensate for characteristic variations derived from errors
which have arisen in the course of manufacture.
[0115] Thus, variations in clutch characteristics (operating
characteristics of clutch) among products can be reduced. Also,
since there is no need for determining design parameters of the
assist spring 36 so as to cope with the maximum potential release
load, the size of the assist spring 36 is reduced, thereby enabling
a reduction in the size of the actuator 30.
[0116] According to the second embodiment, through engagement of
the teeth 85a and the first sawteeth 83a or the second sawteeth
83b, the rotation of the adjust wedge member 82 is prevented. Thus,
the amount of adjustment remains unchanged during subsequent
vehicle operation, thereby enabling clutch engagement/disengagement
in an appropriate condition all the time. Furthermore, according to
the second embodiment, the threshold L0 can be a sufficiently large
predetermined amount, thereby further facilitating adjustment as
compared with the first embodiment, in which the distance between
the pressure plate 24 and the diaphragm spring 25 must be increased
accurately by the adjustment amount X.
[0117] As described above, according to the clutch control
apparatus of the present invention, the attitude of the diaphragm
spring 25 is adjusted so as to absorb characteristic variations
among clutch apparatus derived from errors which have arisen in the
course of manufacture, thereby maintaining constant clutch
characteristics (operating characteristics of clutch) among
products. The clutch control apparatus is configured such that
adjustment is performed in a condition that the clutch cover, for
example, is less influenced by vehicle vibration, thereby reducing
the possibility of excessive modification of the attitude of the
diaphragm spring 25. A certain conventional clutch apparatus
employs a sensor diaphragm for automatically compensating for wear
of a clutch disk. Specifically, the sensor diaphragm reflects a
load associated with clutch engagement/disengagement and deforms
accordingly. The height of a fulcrum of a diaphragm spring is
mechanically adjusted according to the deformation of the sensor
diaphragm. However, when the conventional technique is employed,
manufacture-caused characteristic variations among sensor
diaphragms themselves affect the clutch characteristics, so that
the characteristic variations of the clutch due to errors which
have arisen in the course of manufacture cannot be compensated
accurately. By contrast, the clutch control apparatus of the
present invention can absorb all kinds of characteristic variations
which would otherwise influence a load of operation of the
clutch.
[0118] Notably, modifications and variations of the present
invention are possible. For example, the first and second
embodiments are described while mentioning the clutch control
circuit 40 and the actuator 30 which are employed in the form of
separate components. However, the components may be integrated into
a single unit. Also, in place of the actuator 30 which employs the
electric motor 32, there may be employed a hydraulic actuator
(hydraulic cylinder) for moving the rod 31 in a reciprocating
manner through application of a hydraulic pressure which is
controlled by use of, for example, a solenoid valve.
[0119] This invention can be practiced or embodied in still other
ways without departing from the spirit or essential character
thereof as described heretofore. Therefore, the preferred
embodiments described herein are illustrative and not restrictive,
the scope of the invention being indicated by the claims and all
variations which come within the meaning of the claims are intended
to be embraced therein.
* * * * *