Denso Corporation

Nippondenso Co., Ltd.

Kazushi Nakatani

Akira Takagi

Shinya Sakaguchi

Hajime Yokoyama

A hydraulic pressure control system for an automatic transmission is capable of reducing the size and simplifying the structure of a lockup controlling hydraulic circuit. An oil pressure output from a solenoid valve acts on an oil pressure chamber. The internal pressure of another oil pressure chamber becomes high only in a forward low-speed range and becomes low in all of the other gear shift ranges. The internal pressure of another oil pressure chamber becomes high only in forward ranges and becomes low in neutral and reverse ranges. The valve member moves in accordance with oil pressures applied to the oil pressure chambers to change over oil paths connected to a clutch control oil chamber and a torque converter oil chamber, whereby a lockup clutch assumes one of engaged, slip, and released states. Since an oil pressure signal according to a gear shift range and a vehicular running range is fed to the changeover valve and on the basis of this signal the changeover valve determines whether the engagement of the lockup clutch is to be permitted or inhibited, the circuit of a lockup control unit can be reduced in size and simplified.

Hydraulic pressure control system

To provide a hydraulic controller for automatic transmission use which commonalizes a lockup control valve and a friction engagement element control valve, thereby simplifying a hydraulic circuit, reducing the number of parts, and achieving low cost, a lockup solenoid to control engagement or release of a lockup clutch, a first friction engagement element to engage an friction engagement element only in a portion or entirety of a shifting stage to prohibit lockup, and a manual shift lever to determine whether a vehicle exists in a lockup prohibition condition are provided. A switching valve selectively switches the lockup solenoid to either communicate with the lockup clutch or communicate with the foregoing first friction engagement element. The manual shift valve is disposed in a path extending from the switching valve to the first friction engagement element.

Hydraulic controller for automatic transmission use

A lockup control system for an automatic transmission is provided with an electromagnetic valve 11 and a spool valve 13. When the electromagnetic valve 11 is inactive, the spool valve 13 is set so that a pressure at an OFF port 171 of a torque converter 12 is higher than that of an ON port 172, thereby opening a lockup clutch mechanism 19. When the electromagnetic valve 11 is activated, its control pressure Pc becomes lower than a secondary pressure PL2and the spool valve 13 is actuated so that the control pressure Pc is supplied to a clutch control chamber 18. As a result, the lockup clutch mechanism 19 is closed, thereby setting the lockup state. At this time, the control pressure Pc acts directly on the clutch control oil chamber 18, so that the lockup clutch mechanism 19 is controlled with high precision.

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Obu, Japan

Kazushi Nakatani