| 摘要 |
<p>1535596 Power steering valves TRW Inc 17 May 1976 [4 June 1975] 20333/76 Heading B7H A valve assembly for supplying hydraulic power steering and implement circuits comprises a first valve having a neutral position in which it supplies the implement circuit and being movable to positions in which it supplies the steering circuit, supply to the implement circuit being progressively reduced, and a second valve for supplying the implement circuit when the first valve is cut off thereof. The valve assembly is arranged in a housing 30 and is connected to a gerotor metering pump 16. The first valve comprises a bore 51 in the housing having annular grooves P, M, X, R, Y, C1, P1, AUX and P2 and an axially slidable spool 15 having grooves 62, 68. An actuating shaft 14 connected to the steering wheel moves the spool through a ball 60 and helical groove connection and is connected by a torsion bar 75 to the shaft 72 connected at 73, 74 to the gerotor pump and spool. With spool 15 in the neutral position fluid entering inlet part 13 passes to groove P and through line 52 to grooves P1, P2 and thence via grooves 67, 68 and AUX to the implement port 22. As the spool moves to the left grooves P, 62 and M and line 53 supply fluid to the gerotor. valve 77 and fluid is returned from the gerotor pump to a central bore 79 of the spool. A radial bore 80 from the bore 79 passes fluid to groove 66 and via groove C1 to one side of a steering cylinder. Return fluid from the other side of the cylinder passes to groove C and via grooves 63, X, 64 and R to return part 21. Movement of the spool to the right allows fluid to flow from groove P via line 52 to groove P, and then via bore 80, the gerotor pump, line 52 and grooves M, 63, and C to the steering gear. Groove C1 connects with groove R for return fluid. Movement of the spool in either direction cuts off the connection between grooves P1, P2 and AUX but if sufficient pressure exists a valve 90 maintains supply to the implement circuit. The valve spool 91 of valve 90 has annular grooves 100, 101 to allow flow to return 21 and, whilst spool 15 is in the neutral position, flow to the auxiliary port 22, and is provided with an end projection 93 so as to form a chamber 94 with its wall 91a when urged to the right by spring 92 in chamber 92a. The chamber 94 connects with groove P2 so that as spool 15 moves to sever supply between P1, P2 and AUX pressure builds up in chamber 94. Fluid passing through a restriction 110 in the spool 91 to chamber 111 opens a relief valve 105 and fluid in chamber 92a is spilled to exhaust through line 115, chamber 111, valve 105, line 107 and port 21, thus allowing the spool 91 to move against spring 92. As the spool moves to the left a land 101a opens the implement port 22 to groove P2 and fluid is supplied to the implement. If the fluid pressure at inlet 13 is insufficient to operate both steering and implement circuits the former is given preference since the metering pump 16 draws fluid from groove P and P2.</p> |
