Power steering pump, diesel engine
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Power steering pump, diesel engine
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The power steering pump is driven by a multigroove V-belt from the crankshaft pulley.
Besides the pump elements, the pump comprises a control valve for regulating the flow and an overflow valve.
Warning
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To avoid damage to the pump, the following points should be observed:
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Never forcibly hold the steering wheel at full lock for any length of time with the engine running as the pump may then overheat and be damaged.
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Take care to prevent any particles of dirt from entering the hydraulic system when checking the fluid level or topping up with fluid.
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Never let the pump run without fluid in the hydraulic system.
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The pump element comprises a rotor with a number of slots, a vane for each slot, a pump ring and two end plates with inlet and outlet ports for the hydraulic fluid.
The oval shape of the pump ring causes an increase and decrease in the volume between the pump ring and the rotor. Inlet ports lead to the areas where the volume increases and outlet ports from the areas where the volume decreases, producing a pump effect.
There are ten pump cells between the ten vanes. The volume decreases and increases twice per revolution. Besides being forced outwards by centrifugal force, the vanes are also pressed outwards towards the pump ring by the pressurized hydraulic fluid entering the slots inside the vanes.
The adapted combination of the restrictor (13) and the flow control valve (12) makes it possible to obtain a constant flow from the pump, irrespective of the engine/pump speed. The overflow valve (11) protects the pump from harmfully high pressure, e.g. steering wheel at full lock.
A certain amount of hydraulic fluid must pass through the valve for the control valve to be able to operate, but not when the steering wheel is at full lock. Continuous fluid circulation also helps to cool the pump.
The pump delivers a maximum pressure of approximately 10 MPa (100 bar) and a maximum flow of approximately 6 litres per minute.
