| 摘要 |
1,240,582. Vehicle power steering. MASSEYFERGUSON Inc. 22 May, 1969 [28 May, 1968], No. 26087/69. Heading B7H. In a power steering system, for providing two-wheel or four-wheel steering, comprising first and second double acting actuators 21, 23 for turning first and second wheels 1, 5, a pressure fluid source 37, a valve 31 for selectively directing pressure fluid to one side 53 of the first actuator 21 or to one side 63 of the actuator 23 for turning a vehicle in one or the opposite sense, a fluid transfer means 57, 59 whereby fluid forced out of the other side 54 of the first actuator 21 is conducted to the other side of the second actuator 23, follow-up linkage between the first actuator and the valve 31, and means 71 controlling flow of oil out of the side 63 of the second actuator to provide a high resistance to turning of the second wheel 5 and means 79 allowing free flow of fluid under pressure from the valve 31 to the side 63. In the vehicle shown a manually operated steering mode selector valve 55 is provided and in the two-wheel steering mode operation of the steering wheel 35 and hence of the valve 31 directs pressure fluid to one or other side of each of a pair of actuators 21, 22 in parallel, connected to the front wheels. In the four-wheel mode shown, when steering straight ahead deflection of the rear wheels due to road irregularities is controlled by two relief valves 71, 77 which operate at 1000 p.s.i. connected to respective sides of a pair of rams 23, 24 connected to the rear wheels. The valve 71 has a pilot line 81 operative, when the lines 49, 50 are pressurized for clockwise turning of the vehicle, to reduce the break-open pressure of the valve to 100 p.s.i. to permit steering of the rear wheels. For anticlockwise turning of the vehicle pressure fluid is directed through a check valve 79 in parallel with the pressure relief valve 71 between lines 51 and 65. If, when changing from the two-wheel to the four-wheel steering mode, the front and rear wheels are not symmetrically directed the valve 73 acts as a make-up valve or the valve 77 as a release valve. |
