초록 ▼

A hydraulic power control system includes an engine driving a variable displacement pump. The variable displacement pump is fluidly connected to a first passageway and a second passageway, and has a selectively variable displacement that is adjustable in response to a pump displacement command signa

A hydraulic power control system includes an engine driving a variable displacement pump. The variable displacement pump is fluidly connected to a first passageway and a second passageway, and has a selectively variable displacement that is adjustable in response to a pump displacement command signal. A hydraulic motor fluidly connected to the first and second passageways operates by a flow of hydraulic fluid originating from the pump. A controller receives an engine speed signal and adjusts pump displacement based on the engine speed signal to reduce the rotation speed of the pump when an overrun condition is present.

대표청구항 ▼

1. A hydraulic power control system, comprising: an engine operating at an engine speed, the engine speed sensed by an engine speed sensor providing an engine speed signal;a variable displacement pump connected to and operated by the engine, the variable displacement pump fluidly connected to a firs

1. A hydraulic power control system, comprising: an engine operating at an engine speed, the engine speed sensed by an engine speed sensor providing an engine speed signal;a variable displacement pump connected to and operated by the engine, the variable displacement pump fluidly connected to a first passageway and a second passage way, the variable displacement pump having a selectively variable displacement that is adjusted in response to a pump displacement command signal;a variable displacement hydraulic motor fluidly connected to the first and second passageways in a closed hydraulic loop with the variable displacement pump, the variable displacement hydraulic motor operating by a flow of hydraulic fluid originating from the variable displacement pump and passing through the first and second passageways, the variable displacement hydraulic motor having a selectively variable displacement that is controlled in response to a motor control signal, the motor operating at a motor speed, the motor speed is sensed by a motor speed sensor providing a motor speed signal;a waste flow valve fluidly interconnecting the first and second passageways; anda controller associated with the engine, the variable displacement pump and the variable displacement hydraulic motor, the controller disposed to: receive the engine speed signal and the motor speed signal;calculate a speed ratio of engine speed to motor speed based on the engine and motor speed signals;estimate a waste flow of hydraulic fluid from the pump that bypasses the motor as the flow of hydraulic fluid passes through the waste flow valve based on the speed ratio; andwhen an overrun condition of the engine is indicated by the engine speed signal, adjust the pump displacement command signal based on the engine speed signal and the estimated waste flow of fluid to reduce a rotation speed of the pump and avoid an over-speed condition of the pump, and adjust the motor displacement signal to effectively retard rotation of the variable displacement hydraulic motor. 2. The hydraulic power control system of claim 1, wherein the controller is further disposed to calculate a speed ratio error based on the speed ratio and a commanded speed ratio, and wherein the displacement of the motor is selectively adjusted based on a motor scaling factor that is determined based on the engine speed signal and the speed ratio error. 3. The hydraulic power control system of claim 2, further comprising selectively adjusting the displacement of the pump in the controller by adjusting the pump displacement command based on a pump scaling factor that is determined based on the engine speed signal and the speed ratio error. 4. A machine, comprising: an engine operating at an engine speed, the engine speed sensed by an engine speed sensor providing an engine speed signal;a variable displacement pump connected to and operated by the engine, the variable displacement pump fluidly connected to a first passageway and a second passage way, the variable displacement pump having a selectively variable displacement that is adjusted in response to a pump displacement command signal;a hydraulic motor fluidly connected to the first and second passageways in a closed hydraulic loop with the variable displacement pump, the hydraulic motor operating by a flow of hydraulic fluid originating from the variable displacement pump and passing through the first and second passageways, the hydraulic motor operating to power an implement of the machine; anda controller associated with the engine and the variable displacement pump, the controller disposed to receive the engine speed signal and to adjust the pump displacement command signal based on the engine speed signal to reduce a rotation speed of the pump and avoid an over-speed condition of the pump when an overrun condition of the engine is indicated by the engine speed signal,wherein the hydraulic motor is a variable displacement hydraulic motor having a selectively variable displacement that is controlled in response to a motor control signal, and the motor operates at a motor speed, which motor speed is sensed by a motor speed sensor and is provided to the controller as a motor speed signal, andwherein when the overrun condition is present the controller is disposed to calculate a speed ratio of engine speed to motor speed based on the engine and motor speed signals, and to regulate the displacement of at least one of the hydraulic pump and the hydraulic motor. 5. The machine of claim 4, wherein the machine is a track-type tractor and the implement is a track that engages the ground to propel the machine. 6. The machine of claim 4, wherein the machine is a compactor and the implement is a vibratory device that includes a rotating weight. 7. The machine of claim 4, further comprising a waste flow valve fluidly interconnecting the first and second passageways, wherein the controller is further disposed to estimate a waste flow of hydraulic fluid from the pump that bypasses the motor as the flow of hydraulic fluid passes through the waste flow valve, wherein the controller is further disposed to selectively adjust the pump control signal based on the estimated waste flow of fluid. 8. The machine of claim 7, wherein estimation in the controller of the waste flow of fluid is based on the speed ratio. 9. The machine of claim 8, wherein the controller is further disposed to calculate a speed ratio error based on the speed ratio and a commanded speed ratio, and wherein the displacement of the motor is selectively adjusted based on a motor scaling factor that is determined based on the engine speed signal and the speed ratio error. 10. The machine of claim 9, further comprising selectively adjusting the displacement of the pump in the controller by adjusting the pump displacement command based on a pump scaling factor that is determined based on the engine speed signal and the speed ratio error. 11. A method for operating a hydraulic system, comprising: monitoring various operating parameters of the hydraulic system, including a motor speed of a motor operated by a circulating of hydraulic fluid by a hydraulic pump, and an engine speed of an engine driving the hydraulic pump;determining, based on the operating parameters, whether an engine over-speed condition is present;when the engine over-speed is determined to be present, activating a retarding and over-speed protection function, said function:calculating an actual speed ratio based on the motor speed to the engine speed; andoperating to selectively adjust a pump displacement of the hydraulic pump based on the actual speed ratio such that a pump over-speed condition is avoided. 12. The method of claim 11, further comprising determining a waste flow of the system as a difference between the actual speed ratio and a desired speed ratio, wherein selectively adjusting a pump displacement is accomplished in part based on the waste flow of the system. 13. The method of claim 12, further comprising selectively adjusting a displacement of the motor based, at least in part, on the waste flow of the system and engine speed. 14. The method of claim 11, wherein selectively adjusting the pump displacement is accomplished in part by determining a pump setting scaling factor that is applied to modify a pump command signal, said pump setting scaling factor being determined based at least in part on engine speed. 15. The method of claim 11, further comprising selectively adjusting a motor displacement by applying a motor setting scaling factor to modify a motor command signal, said motor setting scaling factor being determined based at least in part on engine speed and operating slow rotation of the motor in a retard mode of operation when the over-speed condition is present.