What is the reason why the steering wheel of small mixer truck is too heavy to move?

使用液压转向系统的小型搅拌车由于方向沉重，跑偏，发抖等故障较为常见且十分复杂。修理工在排除起来难度也比较大，往往是吃不准故障原因，便采用换件试验的办法。这样一来方向机助力泵就不可避免地成为试验品或无辜的牺牲品。这在三包服务中尤为明显，退货率居高不下，给经销商和制造商带来了极大的损失。因此，本文将汽车液压转向系统的性能，工作原理以及常见故障的排除方法介绍给广大用户。

The small mixer with hydraulic steering system has common and complex faults due to heavy direction, deviation, shaking and so on. The repairman is also difficult to eliminate. He is often uncertain about the cause of the fault, so he adopts the method of replacement test. In this way, the steering engine booster pump will inevitably become a test object or innocent victim. This is particularly evident in the Three Guarantees service. The return rate remains high, which has brought great losses to dealers and manufacturers. Therefore, this paper introduces the performance, working principle and troubleshooting methods of automobile hydraulic steering system to the majority of users.

小型搅拌车转向助力泵，我们通常把它叫做方向机助力泵，它是清障车转向助力系统的动力源，也是转向系统的心脏部分。对于重型清障车来说，由于机械式方向机，驾驶员操作劳动强度大，所以液压转向系统就更为重要。

The steering power pump of small-scale mixer is usually called steering engine power pump. It is not only the power source of the steering power system of obstacle removal vehicle, but also the heart of the steering system. For heavy-duty obstacle removal vehicles, the hydraulic steering system is more important because of the mechanical steering machine and the high labor intensity of the driver.

小型搅拌车常用的方向机助力泵，分叶片式和齿轮式两种。

The steering machine booster pump commonly used in small mixer truck is divided into blade type and gear type.

这里将着重介绍叶片式方向机助力泵。

Here will focus on the vane steering engine booster pump.

一般的叶片泵是由一个内腔双圆弧曲线的泵体带槽转子.叶片等零件组成。有的安装在发动机后端的飞轮壳上，也是靠正时齿轮驱动。当发动机运转时，带动助力泵转子转动，叶片在离心力的作用下，沿叶片槽向外移动，紧靠泵体的内壁，在转子转动过程中，由于叶片间封闭的容积不断的增加和减小实现了吸油和压油的过程。转子每转一周，完成吸油和压油二次。在泵体内还有阀以限制压力。当转向系外部负荷增加，导致油压升高到一定数值时，阀开启卸掉负荷。泵体内还安装有节流阀和流量控制阀，以保证助力泵的排量基本上处于稳定性。

The general vane pump consists of a grooved rotor with double circular arc curve in the inner cavity Composed of blades and other parts. Some are installed on the flywheel housing at the rear end of the engine and are also driven by timing gears. When the engine is running, it drives the rotor of the booster pump to rotate. Under the action of centrifugal force, the blade moves outward along the blade groove and close to the inner wall of the pump body. In the process of rotor rotation, due to the continuous increase and decrease of the closed volume between the blades, the process of oil absorption and oil pressure is realized. The rotor completes oil suction and oil pressure twice every revolution. There is also a safety valve in the pump body to limit the maximum pressure. When the external load of the steering system increases, causing the oil pressure to rise to a certain value, the safety valve opens to unload the load. A throttle valve and a flow control valve are also installed in the pump body to ensure that the displacement of the booster pump is basically stable.

方向机助力泵的使用与维护尤为重要，因此，必须做到以下几点：

The use and maintenance of steering engine booster pump is particularly important. Therefore, the following points must be achieved:

一. 正确选择液压油是保证助力泵率，延长寿命的关键。

I Correct selection of hydraulic oil is the key to ensure high efficiency and prolong service life of booster pump.

二. 定期检查储油罐的油平面，不足应及时补充清洁的液压油，储油罐内的滤芯应在保养时用酒精清洗干净。

II Regularly check the oil level of the oil storage tank. If it is insufficient, add clean hydraulic oil in time. The filter element in the oil storage tank should be cleaned with alcohol during maintenance.

三. 在使用中如发现方向机助力泵渗漏，冲击或有异常的噪音，应及时检查排除。

III In case of leakage, impact or abnormal noise of steering engine booster pump during use, it shall be checked and eliminated in time.

四.小型搅拌车运行一段时间后，应及时更换液压油几滤芯，尤其是新泵装车后使用2500-3000应更换液压油。

IV After the small mixer truck has been running for a period of time, the filter elements of the hydraulic oil should be replaced in time, especially after the new pump is loaded and used for 2500-3000 kilometers, the hydraulic oil should be replaced.

换油方法如下：

The oil change method is as follows:

1. 支起前桥，使车轮离地。

1. Support the front axle and keep the wheels off the ground.

2. 拆下储油罐盖，拆下回油管及方向机放油螺塞。

2. Remove the oil storage tank cover, remove the oil return pipe and the oil drain plug of the steering gear.

3. 启动发动机高速运转10分钟左右，使储油罐，方向机助力泵，方向机内的液压油排出。

3. Start the engine and run it at high speed for about 10 minutes to drain the hydraulic oil in the oil storage tank, steering engine booster pump and steering engine.

4. 发动机熄火，左右转动方向盘极限位置，把残余的液压油全部排出。

4. Stop the engine, turn the steering wheel left and right to the limit position, and drain all the residual hydraulic oil.

5. 更换滤芯，加液压油规定的高度，排净液压系统的空气。

5. Replace the filter element, add hydraulic oil to the specified height, and exhaust the air of the hydraulic system.