3.3 POWER LIFT CONTROL UNIT 3. INTRODUCTION TO THE ELECTRONIC SYSTEM OF THE TRACTOR 3.3 POWER LIFT CONTROL UNIT The function of the lift control unit is to supervise the correct operation of the hydraulic lift and the ASM system. 3.3.1 HYDRAULIC LIFT SYSTEM The electronic system controls the movements of the lift according to the commands and the operating mode selected by the operator using the control panel on the side console. The operator can select six types of control: - position control; - draft control; - depth control; - wheelslip control; - draft, wheelslip and depth control; - transport lock.
Another function provided by the system is that of automatically activating pitch control when travelling on the highway at speeds higher than 8 km/h with the lift control lever in the transport lock position. This operating mode reduces the pitching motion of the tractor when running over uneven surfaces by allowing small compensating movements of the lift, using the mounted implement as a “ballast weight”.
The transport lock can be engaged by the operator, but for reasons of safety it will be engaged automatically by the control unit whenever the lift control is in the stop position and three minutes are allowed to elapse since the tractor was last in mo- tion at less than 20 km/h, or whenever the ground speed of the tractor exceeds 20 km/h. The control unit compares the command given by the operator with the signals received from the lift position sensor, the draft sensors, the wheel speed sensor and the radar, and responds by operating a directional control valve equipped with two proportional solenoid valves.
The control valve directs oil at high pressure to two hydraulic cylinders that raise or lower the implement mounted to the three-point linkage. The signals from the control console are transmitted to the lift control, and the signals from the sensors essential to the op- eration of the system and the lift control pushbuttons on the rear fenders are connected directly to the control unit.
JX1 JX2 JX1 JX2 1 X18 1 - Diagnostics connector 2 - Rear lift Up pushbutton 3 - Rear lift Down pushbutton 4 - Lift and hand throttle console 5 - Lift control panel 6 - 4WD switch 7 - Differential lock switch 8 - Lift Up solenoid valve 9 - Lift Down solenoid valve 2 1 2 7.5A F34 UPDX +15 2 1 DWDX 3 1 2 3 4 2 1 2 EV DW X14 EHR 5 7 8 9 6 D0017260 20-16 1 2 3 21 15 23 10 17 1422 8 18 13 7 19 169 4 20 11 3 9 7 9 10