| 摘要 |
<p>1460407 Hydrostatic transmission control CATERPILLAR TRACTOR CO 19 May 1975 [28 Aug 1974] 21209/75 Heading F2W In a hydrostatic drive system for a tracked vehicle wherein two hydrostatic transmissions 11, 12 each comprise a variable displacement swash-plate pump 13; 24 in closed circuit 17, 18; 33, 34 with a fixed displacement motor 14; 29, the motor speeds are maintained identical during low load straight travel by a pressure equalizing valve 38 which interconnects the high pressure lines of the transmissions when the pressures therein are below a predetermined value and blocks flow between the high pressure lines when the pressure in one of the lines exceeds the predetermined value. A spool 66 of the valve 38 is biased by a spring 72 to a position in which it provides a throttled connection between lines 44, 46 respectively connected through shuttle valves 39, 42 with the high pressure lines of the transmissions. The pressures in the transmission high pressure lines act through a line 90 and shuttle valve 91 on the end of the valve spool 66 which, when the pressure in one of the high pressure lines exceeds the predetermined value, is moved against the spring bias to block flow between the lines 44, 46. Thereafter the transmissions operate independently until the high pressures fall below the predetermined value and the valve 38 reopens. When the displacements of the pumps 13, 24 are adjusted differentially for steering purposes the flow through the valve 38 increases and produces a pressure differential between the lines 44, 46. The higher pressure in the line 44 or 46 acts through the line 90 and shuttle valve 91 on the end of the valve spool 66 to move the latter to a position in which it blocks flow between the lines 44, 46 and thus permits independent operation of the transmissions for steering purposes.</p> |
