Over-speed control system and method

摘要

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.

主权项

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; and a 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.