Excavator Hydraulic Pump Working Principle: How It Works

A hydraulic pump is an excavator component that takes power from the engine, converts it into hydraulic pressure, and delivers pressurized fluid through hoses which then work to move parts of the machine by transferring energy. The hydraulic pump is the heart of an excavator.

Excavator hydraulic pump is a device that enables the operator to use the excavator more effectively. It is a mechanical part of the excavator, which helps you drive and steer the machine depending on your requirement.

Using a hydraulic excavator pump, the operator has more control over the hydraulic system and can run multiple attachments without overheating or speed control problems.

With an excavator hydraulic pump, you can drive an excavator boom, excavator arm, and attachments like an excavator bucket, excavator hydraulic hammer, etc. Without the excavator hydraulic pump, you will be unable to operate your excavator.

Main Components of Excavator Hydraulic Pump and Their Functions

Before understanding the working principle of the excavator hydraulic pump, it is necessary to understand the components it is made of. The main features of an excavator hydraulic pump are as follows:

Sr. No. Pump Components Sr. No. Pump Components
1 Valve Plate 8 Support
2 Cylinder Block 9 Drive Shaft Front
3 Ball Guide 10 Drive Shaft Rear
4 Retainer Plate 11 Servo Block
5 Piston Shoe 12 Charge Pump 2/4 holes
6 Thrust Plate 13 Pilot Valve
7 Swash Plate 14 Flow Regulator


1.   Valve Plate

A valve plate is installed in the hydraulic pump to control the direction of oil flow. Valve plates can transmit the flow of oil through the valves, and they also play a protective role.

Valve plates are usually made of wear-resistant materials, such as low-alloy steel, cast iron, or forged steel. It works utilizing a hydraulic pressure differential between two sides of the plate. Using this method to move fluid through the pump, you can increase its output.

The valve plate is installed between the pump casing and the inner lining, made of steel or cast-iron materials. Its purpose is to ensure that the liquid that flows through it can move smoothly to ensure regular operation.

2.   Cylinder Block

Cylinder Block is a vital part of the excavator hydraulic pump, closing the hydraulic circuits. Its main job is to reduce the fluctuations in oil pressure, which is also called oil damping.

It also prevents slippage between pistons and liners due to motion and vibration. (the structure material is cast iron, forged iron, alloy steel, etc.).

This can get high-pressure oil flow into the working chamber to meet the requirements of the high-pressure operating system. The cylinder block is situated between the swash plate and valve plate in the excavator hydraulic pump.

3.   Ball Guide

Ball Guide is a part of the excavator hydraulic pump. The ball guide sets the direction and speed of the rotating shaft. It affects the stability, reliability, and efficiency of the whole pump.

As a support device, the ball guide protects the bearing from overload and external damage; as a sealing device, it prevents fluid leakage from one end to another by using O rings.

Ball Guide is the round seat with a ball surface. It allows the passage of the body without affecting its direction of motion and relieves strain due to changing pressures such as bumping.

4.   Retainer Plate

The retainer plate is a piece of metal that prevents the hydraulic pump components from changing place, especially when there is high pressure in the system.

The retainer plate is a metal disc with a channel or groove on the inner surface to accommodate the rotor pin.

A retainer plate can significantly reduce the bearing load of the motor shaft to alleviate bearing wear and prolong its life. In addition, this part can also extend the service life of other components by preventing them from being damaged.

It has two main functions. The first one is to prevent dust, foreign objects, and oil leakage from the pump’s interior. The second one is to make sure its operation can run smoothly by absorbing vibration.

5.   Piston Shoe

The piston shoe is located between the cylinder and pump bodies and maintains the rod seal stable.

This means that the piston can move freely within its ring groove while preventing any slippage of the piston itself based on vibrations imposed on it by pump operation. It is used to avoid excessive wear when the piston passes through its corresponding bore.

6.   Thrust Plate

The thrust Plate is one of the most critical components of the excavator hydraulic pump. The thrust plate is a metal plate fitted on top of the piston rod end that helps transfer some load pressure to the cylinder head.

The use of a thrust plate enables the service life of the excavator hydraulic pump to be prolonged without adding a high cost to it.

7.   Swash Plate

A Swashplate is a movable plate used in most hydraulic pumps, especially those with a swash plate design. You can change its angle.

Swash Plate is a cylinder-like disc that rubs against the teeth of the piston rod, which is directly connected to the hydraulic pump drive. An excavator hydraulic pump transmits the power generated by pistons rotating in their bores to move the pump fluid to and from end ports. A swash plate is used when varying speeds and pressure levels are desired.

8.   Support

The excavator hydraulic pump supports the housing, holds the internal components, and stays in place while moving up and down to create pressure.

The Support provides a sturdy foundation for the pump, preventing damage from pulsation. The Support is an essential component of a hydraulic excavator pump located at the bottom of the pump.

9.   Drive Shaft Front/Rear

The drive shaft front and rear are standard components of the excavator hydraulic pump. It is also known as the transmission shaft or motor shaft. It transmits power from the motor to move the pump for apparent reasons.

All the components, including Support, swash plate, retainer plate, thrust plate, and other features, are placed throughout this shaft.

10.  Servo Block

A servo block is a device used to precisely control fluid flow into and out of a pump or cylinder. It is also used as digital level control in many types of machinery. The principle behind this technology is based on the idea that as pressure increases, so does the force on the piston inside. This allows for consistent pumping for all jobs.

11.  Charge Pump 2 holes/ 4 holes

When it comes to charge pumps, there are two basic configurations. One has two holes for alternate connection of suction and discharge ports, which helps increase power on one side due to its low pressure. In contrast, another 4-hole configuration produces high pressure by simultaneously supplying oil from both sides.

The primary function of the charge pump is to supply the pressure fluid required by the machine. It also overcomes the fluid loss due to the inefficiency of the pump or motor.

12.  Pilot Valve

The pilot valve controls oil flow and is a part of the oil circuit. It is opened by a pilot pressure, which is higher than the prime line pressure.

The primary function of the pilot valve is to send oil flow, but when it comes to position control devices, it will significantly affect the degree of adaptation. If you don’t have a sound pilot valve control system, your machine won’t work correctly, even with high-end pumps and motors. So, you must have a suitable quality pilot valve.

13.  Flow Regulator

Flow Regulator is a self-contained assembly that allows pressure regulation through a change in flow rate. Flow Regulators have been explicitly designed to meet or exceed the requirements of the most demanding applications.

Flow Regulator in excavator hydraulic pump provides uniform flow to the machine. It is also used as a safety device and protects the engine from over-pumping damage. Flow Regulators help determine the correct amount of fluid that should be used while performing a specific task. This can save both time and money over time.

Excavator Hydraulic Pump Working Principle

The variable plunger pump is the driving force for the motor and other actuators, highlighting pressurizing and delivering hydraulic oil from the tank.

The pump comprises a casing, shaft, cylinder block, plunger swash plate, valve plate, etc.

The plunger strokes and the swash plate as the shaft rotates, sucking and delivering hydraulic oil. The delivery flow can be adjusted by altering the inclination of the swashplate.

The regulator controls the delivery flow. The regulator controls the pump output to correspond with the engine output by adjusting the delivery flow.

Next, we will explain how the regulator decreases the flow rate. When the delivery pressure of the pump P one or a companion pump P two increases. The force moves the compensating piston pushing it against the compensating rod.

The lever rotates as the compensating rod is pushed, moving the feedback lever, which carries the spool. Also, the delivery pressure of P one passes through the spool and goes against the larger side of the servo piston.

As the servo piston moves, the inclination of the swashplate decreases, reducing the delivery flow.

Next, we will explain how the regulator increases the flow rate.

When the delivery pressure of the pump P one or a companion pump P two decreases or when the pilot pressure is released by the power increasing control system.

The compensation rod and piston are pushed back by their springs.

The lever rotates as the compensating rod moves, moving the feedback lever, which carries the spool.

As a result, the pressure within the larger side of the servo piston is released through the tank port, which then moves the servo piston.

As the servo piston moves, the inclination of the swash plate increases, increasing the delivery flow.

Final Words: Excavator Hydraulic Pump Working Principle

The hydraulic pump is the primary power device in excavators, and it can improve the working efficiency of the excavator to a great extent.

It does not work independently, only combined with other components to form a satisfactory machinery arrangement.

Hydraulic pumps are essential in hydraulic excavators, as they provide hydraulic fluid to the hydraulic motors and hydraulic cylinder, which are used to perform the digging work.

Therefore, understanding the working principle of the excavator hydraulic pump is very important for operators and maintenance personnel.

Once an operator is entirely familiar with the working of different components within the excavator hydraulic pump, he will be able to point out the fault immediately and cope with the emergencies.

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