The hydrostatic power train is a dual path hydrostatic transmission with high pressure, closed drive loops. The dual path system allows the machine to perform a pivot turn and the dual path system allows the machine to counterrotate.
The drive loops consist of a piston pump with a rotating group for each track and of a separate piston motor for each track. The piston pump is an overcenter pump and the piston pump provide oil flow for forward travel and for reverse travel. Travel direction is determined by the direction of flow from the piston pump. The piston motors are infinitely variable and the piston motors provide a range of ground speeds. The piston pump also affects the ground speed of the machine. First, the pump upstroke to provide the desired speed. The motors will destroke if more speed is commanded.
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Location of power train components (1) Pedal control group (2) Transmission Lever (3) Hydrostatic pump (4) Hydraulic motors (5) Hydraulic oil filters | |
The electronic hystat control system controls the hydrostatic transmission functions. The hydrostatic transmission responds to inputs from the operator. Also, the hydrostatic transmission responds to inputs from the sensors. The electronic hystat control system controls the following items:
- The displacements of the hydrostatic drive pumps and motors
- The output for the backup alarm
- The state of the hydrostatic transmission override valve
- The state of the parking brake valve
The system also provides engine overspeed and underspeed protection. In an overspeed condition, the system automatically adjusts the current that is supplied to the hydrostatic transmission pumps and motors to slow the machine. Engine underspeed protection is provided by decreasing the control currents to the hydrostatic transmission pumps and to the motors. This action is in response to the low engine speeds and to the engine lug.
Operator Presence Determination
Machine operation will be enabled or machine operation will be disabled based on the operator presence status. The operator presence status will be set to "Operator Not Present" when the operator is not sensed in the seat and the brake pedal is not depressed.
In all other situations, the operator presence status will be set to "Operator Present".
If the operator presence status is "Operator Not Present", the transmission and implement controls will be inoperable.
If the operator presence status changes from "Operator Not Present" to "Operator Present", the parking brake switch must be toggled to allow the transmission and implements to be activated.
If the operator presence status changes from "Operator Present" to "Operator Not Present" while the machine is in motion, the machine will not stop.