As a construction robot, the
Excavator is the equipment that we deal with every day, and it is also the main source of our income. Many users treat the excavator as their friend. However, the excavator is a machine composed of thousands of parts. It is inevitable that there will be some failures during use, especially for those old cars. The most common failures are car holding, walking weakness, and high engine water temperature. , move slowly and so on.
Excavator walking failure is a very vague concept. More specific failure phenomena may include these: unilateral walking is boring, the engine is blocked when walking, walking is stuck, walking speed is slow, and walking is frustrating. Today, Tiejia will analyze the excavator in detail. The reasons and solutions for these walking failures. If your excavator has the above symptoms, please don`t walk away. The exciting content is below, and you will definitely gain something after reading it!
To analyze the walking fault of the excavator, we can first understand the walking system of the excavator.
First of all, the engine of the excavator is used as the power source of the whole vehicle to drive the main hydraulic pump and the pilot pump. Generally, the main pump of the excavator is a variable swash plate type plunger pump, the pilot pump is a gear pump, and the main pump and the pilot pump are hydraulic pressure pumps. The oil reaches the main control valve through the hydraulic pipeline. At the same time, the pilot pressure oil is connected to the pilot control valve in the cab of the excavator. The driver controls the hydraulic circuit of the pilot system through the operating handle and walking pedal to realize the control of the spool of the main control valve. The hydraulic oil of each circuit output by the main control valve reaches different actuators (oil cylinders, hydraulic motors) to realize different actions of the excavator. The hydraulic pressure of the walking system is output through the main control valve and then reaches the left and right traveling motors of the excavator through the central rotary joint. Finally, the hydraulic oil returns to the hydraulic oil tank through the return line through the central rotary joint.
Excavator main pump (triple pump)
In the hydraulic circuit of the entire travel system of the excavator, there is also systematic control from the power element (main pump) to the actuator (travel hydraulic motor). The pump control system of the main pump can collect the outlet hydraulic oil of the main pump through the central controller After the pressure is analyzed and calculated, the electric signal is output, and the angle of the swash plate of the main pump is changed by the cooperation of the control valve, pressure reducing valve, adjustment cylinder and other components, so as to achieve the purpose of adjusting the displacement and output flow of the main pump.
Hydraulic schematic diagram of excavator pilot system
The pilot control valve of the excavator is a proportional control valve in essence, which are the arm rotation operation valve in the cab, the boom bucket operation valve and the left and right travel operation valve. The operation handles are located in different positions so that the corresponding operation valves output different values. The secondary pilot pressure oil controls the opening or position of the spool of the main control valve, which is reflected in the walking speed and direction switching of the excavator walking system.
Excavator pilot control valve
You may think that the walking system of an excavator is just a hydraulic motor. In fact, it is not the case. Taking the unilateral walking system as an example, the walking system of an excavator includes a walking balance 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 speed of the excavator is realized through the mutual cooperation of a series of control elements and executive elements.
Excavator travel motor reducer
After understanding the composition of the walking system of the excavator, the following iron armor will analyze the failure phenomena and causes of the walking system one by one.
Walking on one side is boring
The excavator`s boring walking may be the most common walking fault. It may be a unilateral fault or a fault on both sides. The reasons for this fault are generally as follows:
1. Internal leakage and oil leakage of the central rotary joint
The central rotary joint of the excavator is an important hub where the hydraulic circuit of the upper body is connected to the chassis, ensuring the smooth flow of the hydraulic circuit of the traveling system when the excavator is rotating. It is composed of an inner cylinder and an outer shell. Each oil passage has an opening to connect to the lower oil outlet. At the same time, the cylinder of the central rotary joint and the shell, and between each adjacent oil passage are sealed by sealing rubber rings to ensure that the central rotary joint The hydraulic oil in different circuits does not interfere with each other when the cylinder and the shell move relative to each other.
Excavator central swivel joint
When the sealing effect of the central rotary joint is poor, internal leakage or oil leakage will occur. The hydraulic oil driving the hydraulic motor cannot reach the hydraulic motor completely, and part of the hydraulic oil returns to the oil tank through other circuits, causing pressure loss in the hydraulic circuit, resulting in hydraulic failure. The motor is weak.
Central rotary joint shell (the inner blue rubber ring is the sealing rubber ring)
2. Internal leakage and failure of the travel motor
Tiejia mentioned before that the walking system is composed of walking balance valve, walking safety valve, walking speed switching valve, walking speed switching oil cylinder, walking brake oil cylinder, throttle valve and walking motor. It will cause pressure loss in the hydraulic circuit of the walking system, resulting in dull walking.
3. The pressure of the hydraulic pump is insufficient, and the pump control circuit is faulty
Insufficient pressure of the hydraulic main pump is also an important reason for the dullness of walking. The main reasons for the insufficient pressure of the hydraulic pump are internal leakage of the pump and failure of the pump control system, resulting in pressure loss.
4. Internal leakage of the main control valve
The main control valve is a multi-spool valve group. When the working time is long or the hydraulic oil contains impurities, the spool will wear out. When the spool in the hydraulic circuit of the control walking system is worn too much, internal leakage will occur, resulting in hydraulic pressure. Loop pressure loss, resulting in dull walking.
main control valve
5. The secondary pressure oil pressure of the pilot system is insufficient
The secondary pressure oil of the pilot system is output by the proportional control valve. When the travel operation valve of the excavator cab is internally leaked or stuck, the pressure of the secondary pressure oil of the pilot will be insufficient, and the spool of the main control valve cannot be pushed in place. The hydraulic circuit flow of the walking system is reduced.
6. The high and low speed conversion failure of the walking system
We know that the general excavator travel system has a rabbit gear and a tortoise gear. When switching to the rabbit gear, the hydraulic circuit flow of the travel system is large, the pressure is low, the hydraulic motor speed is fast, but the torque is low. When switching to the tortoise gear, the hydraulic circuit flow of the walking system is small, the pressure is high, and the hydraulic motor speed is slow, but the torque is high.
When the walking system cannot be switched to the tortoise gear, the walking system of the excavator will experience dull symptoms.
Engine stalls while walking
Engine blockage is also a common fault on
Excavators. Today, Tiejia will focus on understanding the reasons for blockage when walking.
1. Hydraulic motor reducer failure
The hydraulic motor is a motor with high speed and low torque, which cannot directly drive the excavator to walk. Generally, the excavator will use a planetary gear set to decelerate the hydraulic motor to increase the torque.
Hydraulic motor planetary gear reducer
When the reducer fails, the reducer's own resistance is too large, resulting in excessive load on the hydraulic motor, increasing the pressure of the hydraulic circuit, and causing the engine to stall.
2. The track is too tight
As we all know, the tightness of the track of the excavator is adjustable, and the stroke of the tension cylinder is adjusted. When the track is too tight, the resistance of the hydraulic motor is too large, which is easy to cause the car to hold back.
3. Tracks are frozen in winter
Excavator tracks are prone to freezing in snowy days
In winter, the temperature in some areas is extremely low. After the excavator worked the previous day, the track was stained with water and mud. When the water freezes when it is started the next day, the track will be frozen, causing the hydraulic motor to be overloaded and the pressure of the hydraulic circuit to rise. Causes the engine to stall.
Walking Card Issuance
1. The pilot valve stem is not in place
When the pilot valve stem is not in place, the pilot system cannot produce stable secondary pilot pressure oil, resulting in the unfixed position of the main control valve spool, resulting in a trip card.
2. Mechanical failure of the reducer
When there is a mechanical failure in the internal gear set of the reducer, it will cause the reducer to work abnormally, unable to output stable speed and torque, and cause the card to travel.
3. Walking system failure
Excavator travel hydraulic motor internal structure and valve group
When components such as walking balance valve, walking safety valve, walking speed switching valve, walking speed switching cylinder, walking brake cylinder, throttle valve and walking motor fail, it may cause the walking card to be issued.
Walking frustration
1. The main pump variable is unstable
The pump control system of the main pump of the excavator can collect the outlet hydraulic oil pressure of the main pump through the central controller, and output an electrical signal after analysis and calculation. , so as to achieve the purpose of adjusting the displacement and output flow of the main pump.
Hydraulic schematic diagram of excavator pump control system
When the pump control system fails, it is easy to cause the output flow of the main pump to be unstable, resulting in a sense of frustration when operating the excavator.
2. The main valve and secondary valve of the safety relief valve are faulty
Generally speaking, the maximum pressure of the excavator hydraulic system is determined by the relief valve. When the relief valve fails, such as the relief valve spring fatigue failure or the spool stuck, etc., it is easy to cause the relief valve to overflow. The pressure setting value changes, and the pressure in the hydraulic circuit is unstable, resulting in a sense of frustration when operating the excavator.
slow walking
1. The high and low speed conversion failure of the walking system
When the high-low speed conversion of the walking system of the excavator fails, it may not be able to switch to the rabbit gear, resulting in the excavator always walking in the tortoise gear, and the walking speed is slow.
2. The pump control system is abnormal and the flow is insufficient
The walking speed of the excavator is determined by the speed of the hydraulic motor. When the pump control system of the main pump is abnormal, the output flow of the main pump is unstable. When the swash plate angle of the main pump is too small, the output flow of the main pump is low, which will cause the excavator to walk slowly. .
3. The pilot system is abnormal
Pilot control valve structure
The secondary pressure oil of the pilot system is output by the proportional control valve. When the travel operation valve of the excavator cab is internally leaked or stuck, the pressure of the secondary pressure oil of the pilot will be insufficient, and the spool of the main control valve cannot be pushed in place. The hydraulic circuit flow of the walking system is reduced, resulting in a slow walking speed of the excavator.
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Crawler Excavator, Excavator, Hydraulic Excavator, Mini Rubber Excavator, Power Trowel, Road marking machine 
