Hydrostatic auxiliary drive system

A vehicle comprising;

• a frame;
• an engine mounted to the frame;
• a main clutch drivingly coupled to the engine;
• a main transmission drivingly coupled to the main clutch, wherein the main clutch modulates the speed of the main transmission and the engine;
• a clutch activation switch is actuated when the main clutch is engaged and disengaged;
• a clutch mode selector switch having a first position defining a first mode of operation and a second position defining a second mode of operation;
• left and right main drive wheels are mounted to the frame and are drivingly coupled to the transmission for propelling the work vehicle;
• left and right auxiliary drive wheels are mounted to the frame, the left and right auxiliary drive wheels are drivingly coupled to at least one hydraulic motor which is driven by at least one hydraulic pump, the at least one hydraulic pump having an output;
• an auxiliary drive controller for controlling the output of the at least one hydraulic pump for driving the left and right auxiliary wheels, the auxiliary drive controller being in communication with the clutch activation switch and the clutch mode selector switch, when the clutch mode selector switch is in its first position the auxiliary drive controller reduces the output of the at least one hydraulic pump when the main clutch is engaged as indicated by the clutch activation switch, when the clutch mode selector switch is in its second position the auxiliary drive controller attempts to mirror the operation of the main clutch in controlling the output of the at least one hydraulic pump.

An auxiliary drive system for a vehicle having an engine, a main transmission driven by the engine and main drive wheels driven by the main transmission;

• the auxiliary drive system comprising;
• left and right auxiliary drive wheels each of which are driven by an independent hydraulic motor located in a separate hydraulic circuit, each of the independent hydraulic motors have separate hydraulically actuated clutches, the separate hydraulic circuits each having a variable displacement pump;
• a main speed sensor providing a main speed signal indicating the speed of the main drive wheels;
• auxiliary wheel speed sensors providing auxiliary wheel speed signals indicating the speeds of the left and right auxiliary drive wheels;
• clutch pressure sensors providing clutch pressure signals indicating the hydraulic pressure being applied to the hydraulically actuated clutches;
• an auxiliary drive controller controllably connected to the variable displacement hydraulic pumps, the auxiliary drive controller being in communication with the main speed sensor for receiving the main speed signal, the auxiliary drive controller being in communication with the auxiliary wheel speed sensors for receiving the auxiliary wheel speed signals, the auxiliary drive controller being in communication with the clutch pressure sensors for receiving the clutch pressure signals, the auxiliary drive controller independently controlling the output of the variable displacement hydraulic pumps in response to the main speed signal and the auxiliary wheel speed signals so that the auxiliary drive wheels are driven at a speed proportional to the main drive wheels, a hydraulic pressure boundary is stored in the auxiliary drive controller, the auxiliary drive controller independently reduces the output of the variable displacement hydraulic pumps when the clutch hydraulic pressure signals exceed the hydraulic pressure boundary.

An auxiliary drive system for a vehicle having an engine, a main transmission driven by the engine and main drive wheels driven by the main transmission;

• the auxiliary drive system comprising;
• left and right auxiliary drive wheels each of which are driven by an independent hydraulic motor located in a separate hydraulic circuit, the separate hydraulic circuits each having a variable displacement pump generating a hydraulic pressure;
• a main speed sensor providing a main speed signal indicating the speed of the main drive wheels;
• auxiliary wheel speed sensors providing auxiliary wheel speed signals indicating the speeds of the left and right auxiliary drive wheels;
• an auxiliary drive controller controllably connected to the variable displacement hydraulic pumps, the auxiliary drive controller being in communication with the main speed sensor for receiving the main speed signal, the auxiliary drive controller being in communication with the auxiliary wheel speed sensors for receiving the auxiliary wheel speed signals, the auxiliary drive controller independently controlling the output of the variable displacement hydraulic pumps in response to the main speed signal and the auxiliary wheel speed signals so that the auxiliary drive wheels are driven at a speed proportional to the main drive wheels, a motor speed boundary is stored in the auxiliary drive controller, the auxiliary drive controller independently reduces the output of the variable displacement hydraulic pumps when the auxiliary wheel speed signals exceed the motor speed boundary.

An auxiliary drive system for a vehicle having an engine, a main transmission driven by the engine and main drive wheels driven by the main transmission;

• the auxiliary drive system comprising;
• left and right auxiliary drive wheels each of which are driven by an independent hydraulic motor located in a separate hydraulic circuit, the separate hydraulic circuits each having a variable displacement pump;
• a main speed sensor providing a main speed signal indicating the speed of the main drive wheels;
• auxiliary wheel speed sensors providing auxiliary wheel speed signals indicating the speeds of the left and right auxiliary drive wheels;
• an auxiliary drive controller controllably connected to the variable displacement hydraulic pumps, the auxiliary drive controller being in communication with the main speed sensor for receiving the main speed signal, the auxiliary drive controller being in communication with the auxiliary wheel speed sensors for receiving the auxiliary wheel speed signals, the auxiliary drive controller independently controlling the output of the variable displacement hydraulic pumps in response to the main speed signal and the auxiliary wheel speed signals so that the auxiliary drive wheels are driven at a speed proportional to the main drive wheels, wherein a power limit boundary is stored in the auxiliary drive controller, the power limit boundary is proportion to maximum engine output of the engine, the auxiliary drive controller independently reduces the output of the variable displacement hydraulic pumps when the clutch hydraulic pressure signals combined with the auxiliary wheel speed signals exceed the power limit boundary.

An auxiliary drive system for a vehicle having an engine, a main transmission driven by the engine and main drive wheels driven by the main transmission;

• the auxiliary drive system comprising;
• left and right auxiliary drive wheels each of which are driven by an independent hydraulic motor located in a separate hydraulic circuit, the separate hydraulic circuits each having a variable displacement pump;
• a main speed sensor providing a main speed signal indicating the speed of the main drive wheels;
• auxiliary wheel speed sensors providing auxiliary wheel speed signals indicating the speeds of the left and right auxiliary drive wheels;
• an auxiliary drive controller controllably connected to the variable displacement hydraulic pumps, the auxiliary drive controller being in communication with the main speed sensor for receiving the main speed signal, the auxiliary drive controller being in communication with the auxiliary wheel speed sensors for receiving the auxiliary wheel speed signals, the auxiliary drive controller independently controlling the output of the variable displacement hydraulic pumps in response to the main speed signal and the auxiliary wheel speed signals so that the auxiliary drive wheels are driven at a speed proportional to the main drive wheels, wherein a minimum engine speed boundary is stored in the auxiliary drive controller, the auxiliary drive controller receives an engine speed signal from an engine speed sensor indicating the speed of the engine, the auxiliary drive controller reduces the output of the left and right variable displacement hydraulic pumps if the engine speed signal falls below the minimum engine speed boundary.