초록 ▼

A hydraulic drive system includes a pair of hydraulic drive motors connected in series. Each motor includes a hydraulic circuit with a spring-biased directional control valve and a pair of check valves. The circuits are located in the end cover for each motor, and are in fluid communication with the

A hydraulic drive system includes a pair of hydraulic drive motors connected in series. Each motor includes a hydraulic circuit with a spring-biased directional control valve and a pair of check valves. The circuits are located in the end cover for each motor, and are in fluid communication with the respective motor and with each other. The circuits are responsive to the pressure differential across the motors, due to the load and direction of the vehicle, and direct flow to one wheel or the other. Flow is directed to the inside motor when accelerating and/or climbing, while the outside motor is allowed to turn freely to compensate for the different turning radius. This reverses when the vehicle is going downhill and/or decelerating, when the motors are braking. If the drive wheel loses traction, the flow and pressure shifts to the other wheel (or to both wheels), until traction is regained.

대표청구항 ▼

What is claimed is: 1. A hydraulic drive system for a vehicle, the vehicle having a pair of turning wheels for directing the vehicle, wherein the wheels having different rates of rotation when the vehicle is turning due to the turning radius of the vehicle, the drive system comprising: a pair of hy

What is claimed is: 1. A hydraulic drive system for a vehicle, the vehicle having a pair of turning wheels for directing the vehicle, wherein the wheels having different rates of rotation when the vehicle is turning due to the turning radius of the vehicle, the drive system comprising: a pair of hydraulic drive motors, each of which includes i) a hydraulic drive mechanism operatively connected to a drive shaft for driving a respective wheel for moving the vehicle, ii) an inlet port and an outlet port for directing fluid to and from the drive mechanism, and iii) a hydraulic circuit fluidly communicating with the hydraulic drive mechanism and with the hydraulic circuit of the other motor, and responsive to a pressure differential across the motors to provide increased flow to the motor of a wheel having a greater rate of rotation than the other, wherein the drive motors are connected in series, with the inlet port of one motor fluidly connected to receive fluid from a fluid source, the outlet port of the one motor fluidly connected to the inlet port of the other motor for directing fluid from the one motor into the other motor, and the outlet port of the other motor fluidly connected to direct fluid from the other motor to a reservoir, wherein each hydraulic circuit includes a control valve responsive to the pressure differential across the motors enclosed within an end cover assembly of the respective motor. 2. The hydraulic drive system as in claim 1, wherein each hydraulic circuit further includes a pair of one-way check valves, such check valves controlling the flow through the control valve of the hydraulic circuit depending on the pressure differentials across the motors and the direction of fluid flow through the hydraulic circuit. 3. The hydraulic drive system as in claim 1, wherein each hydraulic drive mechanism comprises a gerotor drive mechanism. 4. The hydraulic drive system as in claim 1, wherein each hydraulic circuit includes a control device responsive to the pressure differential across the motors for controlling fluid flow in each circuit, and having high and low pressure fluid zones, incorporated within an end cover attached to the respective motor. 5. The hydraulic drive system as in claim 1, wherein the fluid reservoir is one of; the fluid source or a tank. 6. A hydraulic drive system for a vehicle, the vehicle having a pair of turning wheels for directing the vehicle, wherein the wheels having different rates of rotation when the vehicle is turning due to the turning radius of the vehicle, the drive system comprising: a pair of hydraulic drive motors, each of which includes i), a hydraulic drive mechanism operatively connected to a drive shaft for driving a respective wheel for moving the vehicle, ii) an inlet port and an outlet port for directing fluid to and from the drive mechanism, and iii) a hydraulic circuit fluidly communicating with the hydraulic drive mechanism and with the hydraulic circuit of the other motor, and responsive to a pressure differential across the motors to provide increased flow to the motor of a wheel having a greater rate of rotation than the other, wherein the drive motors are connected in series, with the inlet port of one motor fluidly connected to receive fluid from a fluid source, the outlet port of the one motor fluidly connected to the inlet port of the other motor for directing fluid from the one motor into the other motor, and the outlet port of the other motor fluidly connected to direct fluid from the other motor to a reservoir, wherein each hydraulic circuit includes control means responsive to the pressure differential across the motors enclosed within an end cover assembly of the respective motor. 7. A hydraulic motor for a hydraulic drive system, the hydraulic motor comprising: a housing enclosing a drive mechanism, and a drive shaft operatively connected to the drive mechanism and projecting exteriorly of the housing, inlet and outlet ports in the housing providing inlet and outlet fluid flows to the drive mechanism, the drive mechanism providing high and low pressure fluid flows, and the housing having an end face defining high and low pressure fluid zones in communication with the high and low pressure fluid flows, respectively; and an end cover fixed to the housing, the end cover enclosing a hydraulic circuit, the hydraulic circuit including a control valve in fluid communication with the high and low pressure fluid zones and with the drive mechanism, the control valve responsive to pressure differentials between the fluid zones to control the flow of fluid to the drive is mechanism. 8. The hydraulic motor as in claim 7, wherein the end cover comprises a cylindrical body with a mounting face disposed in adjacent relation to the end face of the housing, and fasteners securely fixing the end cover to the housing. 9. The hydraulic motor as in claim 7, wherein a first signal line is provided from the inlet port to the control valve, and the end cover includes an additional port to enable fluid communication with another hydraulic circuit, and a second signal line is provided from the additional port to the control valve. 10. The hydraulic motor as in claim 9, wherein the hydraulic circuit further includes a pair of check valves, such check valves controlling the flow through the control a valve of the hydraulic circuit depending on the pressure differentials across the motors and the direction of fluid flow through the hydraulic circuit. 11. A hydraulic drive system for a vehicle, the vehicle having a pair of turning wheels for directing the vehicle, wherein the wheels having different rates of rotation when the vehicle is turning due to the turning radius of the vehicle, the drive system comprising: a pair of hydraulic drive motors, each of which includes i) a hydraulic drive mechanism operatively connected to a drive shaft for driving a respective wheel for moving the vehicle, ii) an inlet port and an outlet port for directing fluid to and from the drive mechanism, and iii) a hydraulic circuit fluidly communicating with the hydraulic drive mechanism and with the hydraulic circuit of the other motor, and responsive to a pressure differential across the motors to provide increased flow to the motor of a wheel having a greater rate of rotation than the other, wherein the drive motors are connected in series, with the inlet port of one motor fluidly connected to receive fluid from a fluid source, the outlet port of the one motor fluidly connected to the inlet port of the other motor for directing fluid from the one motor into the other motor, and the outlet port of the other motor fluidly connected to direct fluid from the other motor to a reservoir, and further including a housing enclosing the drive mechanism of each motor, the drive mechanism providing high and low pressure fluid flows in the respective motor, and the housing for each motor having an end face defining high and low pressure fluid zones in communication with the high and low pressure fluid flows, respectively; and an end cover fixed to the housing, the end cover enclosing the hydraulic circuit within the motor, the hydraulic circuit including a control valve in fluid communication with the high and low pressure fluid zones and with the drive mechanism, the control valve responsive to pressure differentials between the fluid zones to control the flow of fluid to the drive mechanism.