Gearbox reduction gear control system

The Electrohydraulic System incorporates a control panel (1) located in the tractor cab to the right of the operator, lever (3) for shifting gears and selecting the gearbox reduction gear stages, gearbox neutral position sensor (5), transducers (7) and (8) installed on the reduction gearshift hydraulic cylinder, electrohydraulic distributor (6) mounted on top of the gearbox cover and connecting cables (4) with terminal blocks (9).
The system is energized from the on-board electric circuit through a safety fuse box (2). The electrical power is supplied to the system before starting the engine (after turning the starter and instrumentation switch to the “Instrumentation Supply” position).
The buttons (10, 11) and annunciators (13, 12) for engaging the lower and higher stages of the gearbox reduction gear are fitted on the handle of the lever (3), respectively.

The warning lights (15 and 14) of engagement of the lower and higher stages of the reduction gear and the reduction gear control relay are located on the panel (1).
This system allows the gearbox reduction gear stages to be selected only provided the lever (3) is in neutral position (i.e. the sensor (5) contacts of the gearbox neutral are closed). The gearbox reduction gear stages shall be switched over on the stopped tractor.

1 – control panel; 2 – safety fuse box; 3 – lever for shifting gears and selecting the reduction gear stages; 4 – connecting cables; 5 – gearbox neutral sensor; 6 – electrohydraulic distributor of the reduction gear; 7 – higher stage pressure transducer; 8 – lower stage pressure transducer; 9 – terminal blocks; 10 – lower stage selection button; 11 – higher stage selection button; 12 – light-emitting diode of the higher stage; 13 - light-emitting diode of the lower stage; 14, 15 – warning lamps. The signals are sent to the annunciators (13, 12) and warning lights (15, 14) from the respective pressure transducers (8 and 7).

After starting the engine, the gearbox reduction gear lower stage is initially engaged. When it will be done, the annunciator (13) and the warning light (15) shall light up.

Upshifting to the gearbox reduction gear higher stage is achieved by pressing the button (11). At the same time, the lights (13 and 15) shall go out and the annunciator (12) and the warning light (14) shall light up.
Downshifting from the higher to lower stage is done by pressing button (10).