CLAAS ACADEMY LEXION II Steering hydraulics Key to diagram 118 - Restrictor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 mm 503 - Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.7 l / 80 bar 604 - Pressure relief bolt 732 - One-way valve (delivery valve) 734 - One-way valve (lock-up valve unit) B5 - Oil pressure switch, NC contact . . . . . . . . . . . . 135/160±5 bar Z4 - Oil pressure switch, NC contact . . . . . . . . . . . .
135/160±5 bar Y9 - Solenoid valve (coil core with spring) Y10 - Solenoid valve (coil core with spring) T -Working hydraulics returns connection P1 -Working hydraulics pump connection over returns valve A -Steering ram connection B -Steering ram connection Caution: When disassembling items 503, 732, B5/Z4, Y9 or Y10 the pressure in the accumulator must be released using the pressure relief screw (604). Description of operation Should the pressure in the accumulator drop below 135 ± 5 bar when the engine is running, then the oil pressure switch (B5/Z4) on the returns valve is operated. This causes the system pressure to be switched to the accumulator (503) via the one way valve (732).
When the system pressure is present, and the accumulator has been charged to 160 ± 5 bar, the oil pressure switch (B5/Z4) opens and the returns valve switches back into the neutral position. The one way valve (732) separates the stored energy and the systems working hydraulics. The stored pressure is held in the closed system and lies on the balls of the two solenoid valves (Y9/Y10). The module for the autopilot system will switch one of the solenoid valves (Y9/Y10), depending on steering direction required. The valve pin then presses down on the ball within the valve cartridge and shuts off the return line to the tank.
The pressure then pushes against the ram and opens the one-way valve at A or B. The return oil from the ram is then switched via the non-operated solenoid valve (Y9/Y10) back to the tank. The pressure increasing further now opens the opposite one-way valve and the steering cylinder is retracted or extended. When the required angle for the steering has been achieved, then the Autopilot module switches off the solenoid valve (Y9/Y10). Should the pressure in the accumulator (503) fall below the 135 ± 5 bar due to steering demands, then the pressure switch (B5/Z4) will operate, the returns valve will be switched and pressure will be reinstated to the accumulator (503). Note:
More information on the valve parts and the returns valve can be found in the working hydraulics chapter. 02/2001 2-15