192 clutches and power-stop control – Clutches – Automatic
Reexamination Certificate
2002-07-02
2004-04-13
Lorence, Richard M. (Department: 3681)
192 clutches and power-stop control
Clutches
Automatic
C192S070120, C192S084910, C192S113340
Reexamination Certificate
active
06719110
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a wet type friction clutch and an electromagnetic clutch for use in a coupling device or a differential gear device of a vehicle.
Japanese Patent Provisional Publication No. 10-329562 discloses a torque transmitting device
301
which is exemplarily shown in FIG.
1
.
The torque transmitting device
301
is comprised of a rotary case
303
, an inner shaft
305
, a main clutch
307
, a ball cam
309
, a pressure plate
311
, a cam ring
313
, a pilot clutch
315
, an armature
317
and an electromagnet
319
.
The torque transmitting device
301
is disposed between separate rear propeller shaft components which are rendered to be separate from one another during a two wheel drive condition in a four wheel drive vehicle, with the rotary case
303
being connected to a front side propeller shaft component while the inner shaft
305
is connected to a rear side propeller shaft component.
The rotary case
303
is comprised of a cylindrical member
321
, to which the main clutch
307
is coupled, and a rotor
323
which forms a part of a magnetic flux path of the electromagnet
319
, with the cylindrical member
321
being made of stainless steel to preclude a magnetic flux from being leaked from the magnetic flux path.
The main clutch
307
includes a multi plate clutch disposed between the cylindrical member
321
and the inner shaft
305
, and the ball cam
309
is disposed between the pressure plate
311
, which is connected to the inner shaft
305
for free movement, and the cam ring
313
.
The pilot clutch
315
includes a multi plate clutch and is kept between the armature
317
and the rotor
323
.
The torque transmitting device
301
is arranged such that the magnetic flux path of the electromagnet
319
is defined as indicated by a magnetic flux path
325
with the clutch rotor
323
, the pilot clutch
315
and the armature
317
whereby, when the electromagnet
319
is energized, the armature
317
is attracted with the magnetic flux path
325
to cause the pilot clutch
315
to be pressured contact into a coupled condition.
Upon coupling of the pilot clutch
315
, a pilot torque is produced to allow a drive power output of an engine to be imparted to the ball cam
309
to create a cam thrust force by which the main clutch
307
is urged to cause the torque transmitting device
301
to be coupled to transfer the drive power output to the rear wheel side to render the vehicle to be operative in the four wheel drive condition.
Further, if the excitation of the electromagnet
319
is interrupted, the pilot clutch
315
is released to cause the ball cam
309
to lose the cam thrust force whereby the main clutch
307
is released to uncouple the torque transmitting device
301
for disconnecting the rear wheel side to render the vehicle operative in the two wheel drive condition.
The pilot clutch
315
including the multi plate clutch is comprised of a plurality of outer plates and a plurality of inner plates, which are alternately interleaved with respect to one another. Further, the outer plates are disposed in engagement with the cylindrical member
321
and, to this end, an outer periphery of each outer plate is formed with engaging protrusions circumferentially spaced in a given distance. The inner plates are disposed in engagement with the cam ring
313
and, to this end, an inner periphery of each inner plate is formed with engaging protrusions circumferentially spaced in a given distance.
The pilot clutch
315
is arranged to be coupled when the interleaved outer plates and the inner plates are brought into pressured contact with respect to one another to create a frictional force due to the magnetic flux path
325
of the electromagnet
319
to cause the armature
317
to be attracted. In contrast, during an uncoupled condition of the pilot clutch
315
, since the outer plates and the inner plates are operative for free sliding movements, there is a need for these components to be lubricated with oil and, for such a purpose, the rotary case
303
is filled with oil.
With the pilot clutch
315
, since the outer plates and the inner plates are sliding under interleaved conditions even during the two wheel drive condition where the electromagnet
319
is de-energized, there is a probability for a drag torque to be created between the adjacent clutch plates due to the viscosity of oil at a low operating temperature. As the drag torque exceeds a given level, the outer plates and the inner plates tend to operate just as they are coupled, inviting a risk for the pilot clutch
315
to produce the pilot torque which is transferred through the ball cam
309
to the main clutch
307
which is consequently exerted with an urging force to transfer the drive power output to the rear wheel side.
During a time interval in which the coupling of the clutch is not required, if the drive power output is transferred to the rear wheel side, the vehicle encounters a drive power loss with a resultant adverse affect in a running characteristic or fuel consumption of the vehicle.
Further, while the magnetic flux produced by the electromagnet
319
forms the magnetic flux path
325
through which the magnetic flux path is circulated via the clutch rotor
323
, the pilot clutch
315
and the armature
317
set forth above, the inner clutch plates of the pilot clutch
315
are arranged to be formed with through-bores to preclude a reduction in the magnetic flux density caused by the leakage of the magnetic flux from the circulated magnetic flux path
325
.
The above described inner clutch plate is formed with a plurality of the through-bores between which a bridge portion is intervened. Outer clutch plates, which are not shown, are formed with through-bores with a similar structure. With such a structure, an inner peripheral portion and an outer peripheral portion of each through-bore form magnetic flux path forming portions which serve as routes of the circulated magnetic flux path
325
.
However, even in a case where the clutch plate of such a state-of-the-art electromagnet clutch is formed with the circumferentially extending through-bores in an area between the inner peripheral, magnetic flux path forming portion and the outer peripheral, magnetic flux path forming portion, the clutch plate is inevitably formed with the above described bridge portions on a circumferential periphery at six locations thereof for interconnecting the inner peripheral portion and the outer peripheral portion, with associated opposing walls of the above described bridge portions of the mutually adjacent clutch plates bearing in contact with one another.
As a result, the associated opposing walls, held in contact with respect to one another, of the bridge portions become loopholes through which the magnetic flux circulating in the magnetic flux path forming portion escapes to an opposing magnetic flux path, resulting in a reduction in the magnetic flux density produced by the electromagnet
319
to decrease the attraction force to be exerted to the armature
317
for thereby causing the coupling force of the pilot clutch mechanism to be lessened.
In order for the amount of escape of the magnetic flux to be decreased, further, it is conceivable to reduce the number of the above described bridge portions, but the clutch plate undergoes a decreased strength with a deterioration in the durability.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a wet type friction clutch and an electromagnetic clutch which have an ability of eliminating a drag torque between clutch plates with no undesired coupling of the clutch plates whereby, when applied to a torque transmitting device (coupling device) of a vehicle, the vehicle has an improved fuel consumption with no adverse effect to a running characteristic.
It is another object of the present invention to provide a clutch plate for an electromagnetic clutch which includes a bridge portion with a reduced whole surface area, while ensuring a strength required for the bridge porti
Iizuka Kouji
Ishikawa Yasuhiko
Ishizuka Makoto
Karasawa Kenji
Kitsunezuka Yoshiaki
Lorence Richard M.
Morrison & Foerster / LLP
Tochigi Fuji Sangyo Kabushiki Kaisha
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