Toro 4100-D service manual Steering Circuit, Left Turn, Right Turn

Steering Circuit

A four section gear pump is coupled to the piston (trac- tion) pump. The third gear pump section supplies hy- draulic flow to the steering control valve and the lift/lower control valve. Pump hydraulic flow is delivered to the two circuits through a proportional flow divider located in the fan drive manifold. The gear pump takes its suction from the hydraulic reservoir. Steering circuit pressure is limit- ed to 1350 PSI (93 bar) by a relief valve located in the steering control.

With the steering wheel in the neutral position and the engine running, flow enters the steering control valve at the P port and goes through the steering control spool valve, by--passing the rotary meter (V1) and steering cylinder. Flow leaves the control valve through the PB port to the oil filter and traction charge circuit.

Left Turn

When a left turn is made with the engine running, the turning of the steering wheel positions the spool valve so that flow goes through the top of the spool. Flow entering the steering control valve at the P port goes through the spool and is routed to two places. First, most of the flow through the valve is by--passed out the PB port back to the oil filter and traction charge circuit. Second, the re- mainder of the flow is drawn through the rotary meter (V1) and out the L port. Pressure contracts the steering cylinder piston for a left turn. The rotary meter ensures

that the oil flow to the cylinder is proportional to the amount of the turning on the steering wheel. Fluid leav- ing the cylinder flows back through the spool valve then through the T port and to the hydraulic reservoir.

The steering control valve returns to the neutral position when turning is completed.

Right Turn

When a right turn is made with the engine running, the turning of the steering wheel positions the spool valve so that flow goes through the bottom of the spool. Flow en- tering the steering control valve at the P port goes through the spool and is routed to two places. As in a left turn, most of the flow through the valve is by--passed out the PB port back to the oil filter and traction charge cir- cuit. Also like a left turn, the remainder of the flow is drawn through rotary meter (V1) but goes out port R. Pressure extends the steering cylinder piston for a right turn. The rotary meter ensures that the oil flow to the cyl- inder is proportional to the amount of the turning on the steering wheel. Fluid leaving the cylinder flows back through the spool valve then through the T port and to the hydraulic reservoir.

The steering control valve returns to the neutral position when turning is completed.

Hydraulic System

STEERING CYLINDER				STEERING CYLINDER				STEERING CYLINDER
NO PISTON MOVEMENT				PISTON MOVEMENT				PISTON MOVEMENT
	R		L		R	L			R		L
		1350				1350				1350
		PSI				PSI				PSI
T	PB	P	STEERING	T	PB	P	STEERING	T	PB	P	STEERING
			CONTROL				CONTROL				CONTROL
NEUTRAL POSITION				LEFT TURN				RIGHT TURN

Figure 13

Groundsmaster 4100--D Page 4 -- 23 Hydraulic System