Introduction to hydraulic principle of excavator walking system

1, walking conditions

The excavator is generally tracked and tire-type. The crawler type has large adhesion, the grounding pressure is small, and the bearing is heavy; the tire type is flexible, the buffer is good, and the noise is low. This article takes the crawler excavator as an example to introduce the excavator walking system.

The crawler type walking system generally consists of "four wheels and one belt" (drive wheel, guide wheel, roller, roller and track), tensioning device, buffer device and walking frame, etc., wherein the driving wheel can be driven by a motor planetary gear reducer or low speed. High torque final drive motors. The two crawlers are driven by a motor and can be operated independently, enabling forward, reverse, conventional steering, and in-situ steering.

Introduction to hydraulic principle of excavator walking system

2, walking hydraulic principle

The following is an example of a high-speed open drive scheme. The hydraulic principle is as follows, mainly including parking brake (1), travel motor (2), high and low speed switching main valve (3), buffer relief valve (4), check valve (5), balance valve (6), main valve (7), shuttle valve (8), relief valve (9), secondary boost solenoid valve (10), high and low speed first conductive magnetic valve (11) and so on.

Introduction to hydraulic principle of excavator walking system

P1 and P2 respectively control the left and right travel motors through the left and right travel main valves, and P3 is the pilot control oil passage. When the main valve starts to travel, the high pressure oil enters the motor side through the one-way valve, the motor return oil is cut off by the balance valve and the check valve, and the motor has no action; when the motor enters the oil to establish a certain pressure, the balance valve is opened, the parking is stopped. When the brake is turned on, the motor returns to the oil through the balancing valve and the motor starts to rotate.

3, the function of the walking system

3.1 anti-speeding / rolling

The anti-overspeed function is mainly realized by the balance valve, which prevents the motor from overspeeding due to gravity when the motor is going downhill, causing the motor to be sucked up, thereby causing cavitation and damaging the motor; when the excavator stops at the slope, the balance valve first cuts off the oil return passage, and the travel locks Then, turn off the parking brake, first establish a certain pressure and then open the balance valve when the slope starts to prevent the car from slipping.

Introduction to hydraulic principle of excavator walking system

3.2 buffer overflow

The buffer overflow function consists of a relief valve with a buffer piston. The relief valve defines the maximum drive pressure for forward and reverse. Since the buffer piston moves for a period of time, the relief valve pressure gradually rises to the rated value when the excavator starts and stops. Pressure, which reduces pressure shocks, protects the motor and system while improving driving comfort.

Introduction to hydraulic principle of excavator walking system

3.3 high and low speed switching

Excavators require low speeds to increase torque when climbing or loading, and high speeds to improve efficiency when leveling or no load. Therefore, the excavator is generally equipped with a high and low speed switching function, which consists of a high and low speed switching main valve and a first conductive magnetic valve. The main valve pressure P port pressure is taken from the high pressure side of the motor, and the pilot pressure is controlled by a high and low speed solenoid valve.

Introduction to hydraulic principle of excavator final drives

3.4 secondary boost

When the arbitrary running main valve is operated, the neutral control oil path Py is returned to the oil, the Py pressure is introduced into the overflow valve spring chamber, and the spring pre-compression force is used to jointly control the main relief valve pressure to increase the driving torque and adapt to the severe working condition. If the Py loses pressure, the relief valve is set to 320 bar, and when the Py is built, the relief valve is set to 350 bar. In addition, when it is necessary to increase the digging force, the relief valve pressure can also be controlled by the solenoid valve to increase the pressure.

3.5 straight driving

See the hydraulic principle of the linear travel valve of the excavator

3.6 multi-function motor

See the main part of the KYABA excavator travel motor for details (Part 1)

See the KYABA excavator travel motor control section for details (Part 2)

4, summary

The main functions that the excavator hydraulic walking system can realize are parking brake, two-way balance, two-way buffering, two-way overflow, high and low speed switching, secondary boosting, straight running, etc., to meet the different working conditions.

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