对于小型搅拌车来说，出车前预热发动机是必须的。但是当搅拌车到达施工现场后，上装部分泵送系统还要进行预热，否则就无法正常施工。那么搅拌车预热前后期的主油泵保持什么？

It is necessary to preheat the engine before leaving the small mixer. However, when the mixer truck arrives at the construction site, the upper part of the pumping system must be preheated, otherwise the normal construction will not be possible. What does the main oil pump maintain before and after the mixer is preheated?

对搅拌车车身进行预热的通常做法是在发动机运转时开启车身以取电。当液压泵被动工作一段时间后，液压油温度上升到规定值，液压油粘度达到正常工作状态，车体预热完成。这种公认的预热操作方式看似简单，其实不然。如果搅拌车车体的预热操作在正确的状态下进行，可以有效降低车体液压系统的磨损和故障率。相反，不正确的预热行为将不可避免地增加设备的磨损。下面我们介绍一下搅拌车预热的正确操作方法。

The usual way to preheat the mixer truck body is to turn on the body to get power when the engine is running. When the hydraulic pump works passively for a period of time, the hydraulic oil temperature rises to the specified value, the hydraulic oil viscosity reaches the normal working state, and the car body preheating is completed. This accepted preheating operation seems simple, but it is not. If the preheating operation of the mixer car body is carried out in the correct state, the wear and failure rate of the car body hydraulic system can be effectively reduced. On the contrary, incorrect preheating behavior will inevitably increase equipment wear. Next, we will introduce the correct operation method of mixer preheating.

预热前期，主油泵必须保持干转

At the early stage of preheating, the main oil pump must keep running dry

安装在混凝土搅拌车上的液压系统中的液压泵一般有四种，分别是主油泵、平衡压泵、搅拌泵和臂架泵。从液压泵的工作原理上分，除搅拌泵属于齿轮泵外，其他三种泵都属于斜盘柱塞泵。相比较而言，斜盘柱塞泵的性能优于齿轮泵，而且精度更高，也更高，因此更应引起重视。

There are generally four types of hydraulic pumps in the hydraulic system installed on the concrete mixer, namely, the main oil pump, the balance pressure pump, the mixing pump and the boom pump. From the working principle of the hydraulic pump, except that the mixing pump belongs to the gear pump, the other three pumps belong to the swashplate piston pump. In comparison, the performance of the swashplate piston pump is better than that of the gear pump, with higher precision and higher price. Therefore, more attention should be paid to it.

对于不同工作原理的搅拌车，让主油泵干转的操作方法是不同的。在目前常见的混凝土泵送液压系统中，主要有两种——开式系统和闭式系统。对于这两个系统的原理、区别和特点，这里就不方便介绍了。我们只介绍根据原理保持主油泵斜盘不倾斜的操作方法。

For mixer trucks with different working principles, the operation method of dry running the main oil pump is different. At present, there are two kinds of common concrete pumping hydraulic systems - open system and closed system. It is not convenient to introduce the principles, differences and characteristics of the two systems here. We only introduce the operation method to keep the swashplate of the main oil pump from tilting according to the principle.

(1)对于开式系统的混凝土搅拌车，可在开启上装取力器时将泵送排量设置在“零”位置。根据搅拌车的企业和使用年限，设置方法可能会略有不同。

(1) For the concrete mixer with open system, the pumping displacement can be set at "zero" position when the upper power take-off is opened. The setting method may be slightly different according to the brand and service life of the mixer.

(2)对于封闭系统混凝土搅拌车，方法比较简单，即在开启车身取力器时，保持泵送停止状态。

(2) For the closed system concrete mixer, the method is relatively simple, that is, when the power take-off of the vehicle body is opened, the pumping stops.

预热后期，主油泵逐渐增大排量

At the later stage of preheating, the main oil pump gradually increases its displacement

小型搅拌车的液压泵在空转过程中，轴承、配油盘等部件由于运动 摩擦不可避免地会发热。这些热量逐渐传递给周围的液压油，使液压油的温度逐渐升高，粘度逐渐降低。一段时间后，可将液压泵的斜盘调整到较小的角度变化，使液压油流动，从而将温度较高的液压油送入液压回路。由于对流和传导，液压马达和管路中的油逐渐升温。直到整个泵送系统的液压油达到工作温度，预热工作才顺利完成。

During the idling process of the hydraulic pump of the small mixer truck, the bearing, oil distribution plate and other components will inevitably heat up due to motion friction. The heat is gradually transferred to the surrounding hydraulic oil, so that the temperature of the hydraulic oil gradually increases and the viscosity gradually decreases. After a period of time, the swashplate of the hydraulic pump can be adjusted to a small angle change to make the hydraulic oil flow, so as to send the hydraulic oil with higher temperature into the hydraulic circuit. Due to convection and conduction, the oil in the hydraulic motor and pipeline gradually heats up. The preheating will not be completed until the hydraulic oil of the whole pumping system reaches the operating temperature.

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