5. Ground drive hydraulics 5.1.3
JAGUAR
TIC
Function of ground drive
Linde HPV - HMV ground drive, variable, with maximum propulsive force control Motor started, ground speed control lever in neutral position
- The ground drive feed pump (209) takes in cooled oil and pumps it to the pressure filter (102). - In case of cold oil, the ground drive feed circuit cold weather starting valve (718) prevents pressure build-up > 28 bar. - Oil flows through pressure filter (102). When the filter resistance exceeds a ∆p = 2 bar, the ground drive filter bypass valve (710) is opened and lets the oil continue to flow without filtering. - The ground drive feed pressure relief valve (716) controls the cooled and filtered oil to a pressure of 22.5 bar which is available as feed pressure at the following points: • Via orifice plate (401) Ø 1.8 mm to the low-pressure hydraulics • to feed the ground drive multi-function valves (713) (714). • on both sides of the ground drive pump servo control (313) • at the ground drive control pressure speed control valve (616). The oil pressure controlled to 21 bar by the low-pressure hydraulics pressure relief valve (729) is applied as control pressure to the ground drive motor servo control cylinder (355) via the ground drive servo control motor speed valve (737). The motor swivels to maximum input volume (= low speed and high propulsive force). The ground drive servo control direction pump valve (738) is springcentred and in its neutral position. Both cylinder spaces are connected with the tank via the ground drive control pressure direction valve (615).
Motor started, ground speed control lever moved to forward travel
Pump: When moving the ground speed control lever, the ground drive control pressure direction valve (615) and the ground drive control pressure speed control valve (616) are actuated. This pre-selects the forward direction of travel and a control pressure proportional to the lever movement is built up for the servo control. At a control pressure of 4 bar and higher, the spring force at the ground drive servo control direction pump valve (738) is overcome. The ground drive servo control direction pump valve (738) now actuates the ground drive pump servo control cylinder (313). The HPV pump swivels proportionally to the position of the ground speed control lever. At a control pressure of 9 bar, the pump has reached its maximum position = max. volumetric displacement. Motor: The control pressure generated by actuating the ground speed control lever is also applied at the servo control motor speed valve (737). When the ground speed control lever is moved so far that a control pressure of > 9 bar is built up, the spring force of this valve is overcome and the ground drive motor servo control cylinder (355) is adjusted proportionally to the position of the ground speed control lever towards low input volume = max. ground speed. Maximum ground speed is reached: • with motor HMV 105 at 10.5 bar and • with motor HMV 135 at 12 bar control pressure. The Bowden cable on the pump is mounted in the inner bore of the adjusting lever on ground drives with HMV 135 and in the outer bore with the HMV 105. The pivot position of the Bowden cable must not be modified.
5-8
Jag-h-Kap05
11/04
