| 摘要 |
The hydraulic control valve (30) of a hydraulic actuator (20) for generating steering assist force comprises a first valve member (31) and a second valve member (32) both of which are rotatable to each other in response to steering resistance. Throttling portions are formed of spaces between axially extending edges defined by slots of the first valve member and axially extending edges defined by slots of the second valve member. The first hydraulic oil outlet slot (51b) is located between a right turn slot (50a) and a left turn slot (50b), the second hydraulic oil outlet slot (51c) is located between communication slots (50c), hydraulic oil feed slots (51a) is located between a right turn slot (50a) and a communication slot (50c) and between a left turn slot (50b) and a communication slot (50c). Closing angle of at least one type of the throttling portions (A', B', C', D'), which belong to a second group divided into two types of throttling portions, is set larger than closing angle of each of the first group throttling portions (A, B, C, D). A variable throttle valve (60), capable of varying the flow area of its own throttling portion in response to driving conditions, is disposed between the second group throttling portions (A', B', C', D') and the tank (71). <IMAGE> <IMAGE> |
