Tham khảo tài liệu 'advanced vehicle technology 2 episode 15', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Fig. Multiplate friction type retarder and outer roller and ball bearing respectively. Interleaved with the driven plates are five cast iron stationary counter plates also of the annular form with four outer radial lugs. Four stator pins supported at their ends by the casing are pressed through holes in these lugs to prevent the counter plates rotating and therefore absorb the frictional reaction torque. Between the pump housing flange and the friction plate assembly is an annular stainless steel bellows. When oil under pressure is directed into the bellows it expands to compress and clamp the friction plate assembly to apply the retarder. The friction level achieved at the rubbing surfaces is a function of the special oil used and the film thickness as well as of the friction materials. The oil flow is generated by a lobe type positive displacement pump housed in the same inner housing that supports the stator pins. The inner member of the pump is concentric with the shaft to which it is keyed and drives the outer member. The pump draws oil from the pump pick-up and circulates it through a control valve. It then passes the oil through a relief valve and a filter both not shown and a heat exchanger before returning it to the inlet port. The heat exchanger dissipates its heat energy into the engine cooling system at the time when the waste heat from the engine is at a minimum. Output torque control Fig. When the spool control valve is in the off position part of the oil flow still circulates through the heat exchanger so that cooling continues but the main flow returns direct to the casing sump. The bellows are vented into the casing releasing all pressure on the friction surfaces. When the control valve is moved to the open position it directs some oil into the bellows at a pressure which is governed by the amount the spool valve shifts to one side. This pressure determines the clamping force on the friction assembly. The main oil flow is now passed .
