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| Illustration 1 | g00818365 |
Steering System
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| Illustration 2 | g00558059 |
Engine Compartment (1) Brake pilot pump (2) Steering pump | |
Steering pump (2) is mounted on the front of the engine with the brake pilot pump (1). Both pumps are driven by the engine. The steering pump is connected to the hydraulic oil tank. Supply oil flows from the pump to the steering valve.
The steering valve is supplied with oil by the steering pump. Turning the steering wheel actuates the steering valve which delivers oil through the swivel to the steering cylinder. Return oil goes from port (T) at the steering valve through the return oil manifold to the hydraulic tank.
The steering cylinder is integrated in the axle housing. Oil from the steering valve flows through two ports at the steering cylinder. The stroke of the piston in the steering cylinder causes steering movement at the wheels.
Steering Pump
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| Illustration 3 | g00558044 |
The brake pilot pump and the steering pump are external gear pumps. Both pumps turn at engine speed. The flow capacity of the steering pump is 19 L/min (5 US gpm).
The steering pump consists of gears in a housing. The housing is bolted with intermediate plates at the front end plate which is bolted to the rear of brake pilot pump. The drive shaft in the front end plate is sealed with a sealing ring.
The steering pump is driven by a shaft that is connected to the brake pilot pump. The shaft is attached to the drive gear. The two gears form a sealing area inside the walls of the pump housing. The hydraulic oil is trapped in the tooth chamber and propelled along the inside of the housing from the suction inlet to the outlet port. The seal between the intake area and the outlet area is a meshing gear.
A vacuum in the tooth chamber pulls in hydraulic oil. The vacuum is caused by the increase in volume which results when the gear goes out of mesh. In the pressure chamber, the teeth come into mesh again. This forces the oil through the outlet port. When the gear teeth come into mesh, oil is trapped between the teeth, which are actually in contact with each other. The trapped oil is pushed out during the rotation.
To prevent pressure peaks and noise, the bearing bushings are provided with relief slots. The sealing section between the gears and the bearing bushings is determined by the operating pressure that is applied at the rear of the bearing bushing. This reduces axial play and inner leakage.
Steering Flow Control Valve
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| Illustration 4 | g00558060 |
The steering flow control valve is installed in the rear end plate of the steering pump.
Hydraulic oil enters the steering pump through the suction line. The steering flow control spring keeps the valve against the seat which sends all pump flow to the steering valve through the outlet port. As the pump pressure at the inlet port increases, the flow control valve is moved in order to compress the spring. Now, the valve is shifted in order to allow flow to the oil cooler through the outlet port while a flow rate of 19 L/min (5 US gpm) is maintained to the steering valve.
When the pressure decreases, the flow control valve shifts back to the original position in order to block the connection to the oil cooler. In the regulating process, the flow control valve is positioned in order to establish a constant oil flow to the steering valve regardless of the engine speed.