| 摘要 |
<p>1362118 Hydraulic transmissions; valves SUNSTRAND CORP 24 Aug 1972 [14 Sept 1971] 39470/72 Headings F2D and F2V A hydrostatic transmission in which a variable displacement axial piston pump 14 supplies fluid to a motor 16, shown as fixed displacement but optionally variable, through flow and return conduits 18, 20, has a by-pass valve 120, which acts as a starting valve to allow by-pass to occur on an initial rise in pressure in conduit 18 or 20 to limit acceleration and then closes on further pressure increase and also acts to limit and control hydrostatic braking. The valve, shown in Fig. 2, has identical axially movable spools 133 and 135, biased apart by a spring 139. Each spool has lands 144, 145, peripheral passages 142, 146 and a central bore with which a bore 150 communicates and which has a member 153 with a central passage 154 and a radial bore 155 and through which fluid can reach the end of the spool to move it towards an abutment 129, contact between which and the spool causes passages 142 to be closed off. In operation, with conduit 18 being the flow conduit, an initial pressure rise in the conduit is slowed by fluid passing through passages 142 in each spool to pass through the valve 120. Eventually the pressure rise, transmitted through the various passages to the back of spool 133, moves the spool to close off the valve. On sudden reduction to neutral of the pump 14 and the motor 16 acting as pump the pressure in conduit 122 drops and that in 124 rises to move spool 133 back to the illustrated position to provide by-pass and reduce braking, a check valve 159 opening to hasten this. This pressure eventually moves spool 135 to the right to give a controlled braking.</p> |
