Oliff & Berridge
Hydraulic control device for 4WD torque distribution clutch providing stabilized pressure characteristics
 A hydraulically actuated clutch is included in a four wheel drive device included in a vehicle power train, and is utilized for torque distribution between the front vehicle wheels and the rear vehicle wheels. A hydraulic control device for this torque distribution clutch includes a device for producing a control hydraulic fluid pressure for this clutch according to an oscillatory method such as a duty factor method or a dither method, an output conduit for conducting this control hydraulic fluid pressure out from this device for producing it, and a device for smoothing hydraulic pressure fluctuations in this output conduit. Accordingly, when wobbling or relatively small fluctuations tend to be induced in this control hydraulic fluid pressure in this output conduit, as may typically be caused by the oscillatory nature of the process for producing this control hydraulic fluid pressure, these wobbles and fluctuations are smoothed out by the smoothing device, thus making for smoother control of the control pressure for the clutch. Thereby, the engagement pressure of the clutch and hence the torque transmission capacity thereof are properly stabilized, and the torque distribution between the front wheels of the vehicle and the rear wheels of the vehicle is prevented from fluctuating, accordingly enhancing the drivability and the operational feeling of the vehicle, as well as decreasing tire wear and increasing roadability. This device for smoothing hydraulic pressure fluctuations may be a hydraulic accumulator; and the device for producing a control hydraulic fluid pressure may be an electromagnetic valve. 
Toyota Jidosha Kabushiki Kaisha
F B F F F F F F F
F16D B60K F16D F16H F16D F16D F16D F16D F16D
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Tokuyuki Hiroshi Nobuyuki
Takahashi Itoh Kato