液压基础知识汇总x.pptVIP

Downhill Testing - - How-To: Test in “real” downhill conditions May need to challenge your OEM to find a safe downhill site for testing Apply at least max. vehicle weight (drawbar machines pulling loaded trailers, etc.) Monitor Motor Pump speeds Do sustained full speed driving down steep hill Also do deceleration down steep hill (check for engine pump O/S) Need safe test site - - Assume the vehicle will lose braking ability ~ Downhill Testing - - How-To: Worst case for “block tipping” is usually just after cresting a hill Near highest speed condition Both system pressures near charge Very little holddown force What to do? Select motor min. angle to avoid the “point of no return” Use microcontroller based over speed control Select ramp rates to avoid engine over speed during braking In extreme cases, OEM can add braking capabilitiy: Based on speed, microcontroller can: Actuate engine exhaust brakes (“Jake brake”) Add a hydraulic load (gear pump over orifice) Apply vehicle service (not parking!) brakes Theoretically - - not sure it’s been done before ~ 谢谢！ Fluid must have high enough viscosity to maintain oil film between sliding surfaces Fluid that is too thin will result in excessive leakage and adhesive wear Viscosity and temperature limits must be met simultaneously Viscosity depends on fluid selection Remember low temperature viscosity during selection * 粘度太大： 增强了油液内摩擦作用，增加了能量消耗 不能有效冷却 容易过热氧化 易起泡，分水性差（乳化），难以过滤，杂质不易分出。 * * 分流合流阀应设计为工作于分流工况以降低发热, ? Creates heat when 500 psid drops are not uncommon. Size of HX is influenced. ? Motor bearing life is reduced when both ports are pressurized. Combining mode should be used in least frequent travel direction. ? Available with lockout feature for operator controlled posi-traction which would minimize amount of time valve regulates flow. ? Anti cavitation check valves may be necessary to protect motor inlets. ? Thorough testing is necessary to check charge and motor inlet pressures at all operating conditions! Pres