950G Series II Wheel Loader Caterpillar


Hydraulic Pump and Motor Introduction

Usage:

950G II AXR


Hydraulic Pumps and Motors

Pumps and motors are similar in construction, but are different in operational characteristics.

Hydraulic Pump




Illustration 1g01062087

The hydraulic pump transfers mechanical energy into hydraulic energy. The pump is a device that takes energy from one source (i.e. engine, electric motor, etc.) and transfers that energy into a hydraulic form. The pump takes oil from a storage container (i.e. tank) and then pushes the oil into a hydraulic system as flow.

All pumps produce oil flow in the same way. A vacuum is created at the pump inlet. The higher atmospheric pressure or tank pressure will push the oil through the inlet passage and into the pump inlet chambers. The pump gears carry the oil to the pump outlet chamber. The volume of the chamber decreases as the chamber approaches the outlet. This decrease in chamber size will push the oil out of the outlet.

Pumps produce only the flow (i.e. gallons per minute, liters per minute, cubic centimeters per revolution, etc.) used in the hydraulic system. Pumps DO NOT produce or cause pressure. Pressure is caused by the resistance to the flow. Resistance can be caused by flow through hoses, orifices, fittings, cylinders, motors, or anything in the system that slows down free flow to the tank.

Pumps can be classified into two types:

  • Non-positive displacement pump

  • Positive displacement pump

Hydraulic Motor




Illustration 2g01062092

The hydraulic motor transfers hydraulic energy into mechanical energy. It uses the oil flow being pushed into the hydraulic system by a pump and transfers it into a rotary motion to drive another device (i.e. final drives, differential, transmission, wheel, fan, another pump, etc.).

Pump ISO Symbols




Illustration 3g01062096

Pump ISO symbols are distinguished by a dark triangle in a circle with the point of the triangle pointing toward the edge of the circle. An arrow across the circle indicates a variable output per revolution.

Motor ISO Symbols




Illustration 4g01062099

Motor ISO symbols are distinguished by a dark triangle in a circle with the point of the triangle pointing toward the center of the circle. An arrow across the circle indicates a variable input per revolution.

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