Final Drives Fault

Updated: Sep 29, 2018

Excavator final drives system fault is a very vague concept. More specific fault phenomena may have these: unilateral walking, lack of strength, engine braking while walking, walking and issuing cards, slow walking speed, and walking sensation. Today we will analyze the excavator in detail. The causes and treatment of these aspects of walking failure, if your excavator has these symptoms, please

To analyze the walking fault of the excavator, we can first understand the travel motors system of the excavator.

First of all, the engine of the excavator acts as the power source of the whole car, driving the hydraulic main pump and the pilot pump. The general excavator uses the main pump as the variable swash plate type plunger pump, the pilot pump is the gear pump, the main pump and the pilot pump hydraulic pressure. The oil reaches the main control valve through the hydraulic line. At the same time, the pilot pressure oil is connected to the pilot control valve of the excavator cab. The driver controls the hydraulic circuit of the pilot system through the operating handle and the walking pedal to realize the control of the main control valve spool. The hydraulic oil of each circuit output by the main control valve reaches different actuators (cylinder, hydraulic motor) to realize different actions of the excavator. The hydraulic pressure of the traveling system passes through the main control valve and then reaches the excavator left and right travel motor through the central rotary joint. Finally, the hydraulic oil is returned to the hydraulic tank through the return line through the central swivel joint.

Excavator main pump (dual pump)

In the hydraulic circuit of the entire traveling system of the excavator, the power component (main pump) to the actuator (traveling hydraulic motor) also has system control, and the pump control system of the main pump can collect the outlet hydraulic oil of the main pump through the central controller. The pressure, after the analysis and calculation, outputs the electric signal, and the angle of the main pump swash plate is changed by the cooperation of the control valve, the pressure reducing valve, the adjusting cylinder and the like, thereby achieving the purpose of adjusting the displacement and output flow of the main pump.

The pilot control valve of the excavator is essentially a proportional control valve, which is an arm swing operation valve, a boom bucket operation valve and a left and right travel operation valve in the cab. The operation handles are located at different positions, so that the corresponding operation valve outputs are different. The secondary pilot pressure oil controls the opening or position of the main control valve spool, which is reflected in the speed of the walking speed of the excavator walking system and the direction of the walking.

Excavator pilot control valve

The excavator's walking system may be considered as a hydraulic motor. In fact, the unilateral walking system includes a walking balancing valve, a walking safety valve, a walking speed switching valve, and a walking speed switching cylinder. , travel brake cylinder, throttle valve and travel motor. The control of the walking direction and walking speed of the excavator is realized by the cooperation of the series of control elements and the executing elements.

Excavator travel motor reducer

Understand the composition of the excavator walking system, let's analyze the fault phenomenon of the walking system and its causes one by one.

Unilateral walking

The boring of the excavator may be the most common walking fault. It may be a single-sided fault or a fault on both sides. The cause of this fault is generally the following:

1. The central rotary joint leaks and leaks oil.

The central swivel joint of the excavator is an important hub for the hydraulic circuit of the upper body to connect the chassis. It ensures the smooth flow of the hydraulic circuit of the travel system when the excavator rotates. It consists of an inner cylinder and an outer casing. The inner cylinder is cast with annular groove oil. Each channel has an opening connected to the lower outlet, and at the same time, the cylinder of the central rotary joint is sealed with the casing and between each adjacent oil passage by a sealing rubber ring to ensure the central rotary joint. Different circuit hydraulic oils do not interfere with each other when the cylinder and the outer casing move relative to each other.

Excavator central swivel joint

When the central rotary joint seals poorly, it will cause internal leakage or oil leakage. The hydraulic oil driving the hydraulic motor cannot reach the hydraulic motor completely, and some hydraulic oil returns to the fuel tank through other circuits, causing pressure loss in the hydraulic circuit, resulting in hydraulic pressure. The motor is boring.

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