| 摘要 |
PROBLEM TO BE SOLVED: To improve shift feel without causing large hydraulic vibration even when an oil temperature is in a low temperature zone in a hydraulic pressure control device for an automatic transmission. SOLUTION: This hydraulic pressure control device for the automatic transmission comprises a hydraulic servo 11 controlling engagement and disengagement of a frictional engagement element, a control valve 13 inputting hydraulic pressure supplied form a hydraulic pressure source and outputting the fed-back hydraulic pressure to the hydraulic servo, and a damper 14 connected with an oil passage connecting the control valve 13 and the hydraulic servo 11 through a branch oil passage to reduce vibration of hydraulic pressure. The damper 14 is defined by a piston 14a sliding inside, has a hydraulic chamber 14c communicated with the branch oil passage, and further has a coil spring 14d for energizing the piston 14a in the direction to reduce a volume of the hydraulic chamber 14c. The coil spring 14d is composed of shape memory alloy contracted and deformed, and free from energizing force in the low temperature zone, and recovering the shape before deformation, and also recovering its energizing force, when a temperature is over the low temperature zone. COPYRIGHT: (C)2007,JPO&INPIT
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