The concrete self loading mixer is composed of an automobile chassis and a special device for concrete mixing and transportation. The chassis of concrete mixer truck produced in China mostly adopts class II general chassis provided by vehicle manufacturers. The special mechanism for concrete mixer truck mainly includes power takeoff, front and rear supports of mixing drum, reducer, hydraulic system, mixing drum, control mechanism, cleaning system, etc.

动力换挡变速器离合器接合时，液压油的压力克服弹簧力压紧摩擦片。随着液压油压力的升高，摩擦片与金属盘接触并逐渐压紧，使混凝土搅拌车离合器将飞轮动力平稳地传递到变速器输人轴。每次换挡时，摩擦片都要与钢片发生摩擦，产生的热量由冷却液散发出去。

When the power shift transmission clutch is engaged, the pressure of the hydraulic oil presses the friction plate against the spring force. With the increase of hydraulic oil pressure, the friction plate contacts with the metal plate and gradually compresses, so that the clutch of the concrete mixer can smoothly transfer the flywheel power to the transmission input shaft. During each shift, the friction plate will rub with the steel plate, and the heat generated will be dissipated by the coolant.

当摩擦片及钢片变薄时，为了使它们充分接合就需要更多的液压油，发动机须进一步加速，摩擦片在钢片上的打滑时间也随之延长，由此产生的摩擦热量也会更多，促使液压油的温度增加，当达到足以改变变速器中密封件性能的温度时，变速器就会产生内泄。

When the friction plate and steel plate become thinner, more hydraulic oil is required to make them fully engaged. The engine must be further accelerated, and the sliding time of the friction plate on the steel plate will be prolonged, resulting in more friction heat, which will increase the temperature of the hydraulic oil. When the temperature sufficient to change the performance of the seals in the transmission is reached, the transmission will produce internal leakage.

而内泄又从两个方面继续引起热量的增加：高压油经损坏的密封处泄漏，使油温继续升高；由于漏油，液压泵势必要输送更多的油液来保障接合离合器时所需的压力，使混凝土搅拌车离合器充分地接合，这也要求发动机继续加速，使液压泵产生更大的流量。如此恶性循环，必将导致混凝土搅拌车离合器过热或烧损，直完全失效。

The internal leakage continues to cause the increase of heat from two aspects: the leakage of high-pressure oil through the damaged seal continues to increase the oil temperature; Due to oil leakage, it is necessary for the hydraulic pump to deliver more oil to ensure the pressure required to engage the clutch and make the clutch of the concrete mixer fully engage, which also requires the engine to continue to accelerate and make the hydraulic pump produce greater flow. Such a vicious cycle will inevitably lead to overheating or burning of the clutch of the concrete mixer until it is completely ineffective.