Variator pressure-set torque control
AssigneeCaterpillar Inc.
InventorsFrank A. DeMarco, Michael G. Cronin
Life of this patent
Estimating the term…
Abstract
A method and system for configuring a hydromechanical transmission having a hydraulic pump and a hydraulic motor driven by the hydraulic pump and a pressure-driven actuator employs a particular torque-pressure curve configuration to maximize torque resolution with respect to actuator pressure changes while ensuring that the curve is substantially monotonic in each dimension and at any available motor speed within a predetermined motor speed limit and any available actuator pressure within predetermined actuator pressure limits. The resultant four-dimensional association between actuator pressure, motor speed, primary power source speed and motor torque allows selection of an actuator pressure to provide a desired torque.
Claims20
A method of configuring a transmission having an engine input for receiving power from a primary power source and a motor input linked to a hydraulic variator comprising a hydraulic pump and a hydraulic motor driven by the hydraulic pump, the variator further including a pressure-driven actuator for controlling a displacement of the hydraulic pump, the method comprising:
- establishing a torque-pressure curve of the transmission, wherein the torque-pressure curve relates motor output torque to motor speed, actuator pressure, and pump speed to maximize output torque resolution of the variator with respect to actuator pressure changes while maintaining the curve substantially monotonic in each dimension at any available motor speed, without exceeding a predetermined motor speed limit and without exceeding available actuator pressure limits;
- and
- configuring the transmission to output a torque by determining an actuator pressure to be applied based on the established torque-pressure curve, the desired torque, a current motor speed, and a current pump speed.
An improved hydraulic transmission comprising:
- a primary input for receiving power from a primary power source;
- a motor input linked to a hydraulic variator comprising a hydraulic pump and a hydraulic motor driven by the hydraulic pump, the variator further including a pressure-driven actuator for controlling a displacement of the hydraulic pump;
- and
- a controller for receiving an indication of desired torque and for controlling the transmission to supply the desired torque by applying a predetermined mapping to identify an actuator pressure to apply to create the desired output torque, wherein the predetermined mapping relates motor output torque to motor speed, actuator pressure, and pump speed, and wherein the resolution of output torque as a function of actuator pressure is substantially maximized while maintaining the map substantially monotonic in each dimension without exceeding a predetermined motor speed limit and without exceeding available actuator pressure limits.
A method of generating a torque-pressure curve for a hydraulic transmission including a hydraulic pump and a hydraulic motor driven by the hydraulic pump via a pump port plate having a port plate angle, the variator further including a pressure-driven actuator for controlling a displacement of the hydraulic pump, the actuator having one or more springs biased to center the actuator, the method comprising:
- selecting a port plate angle for the pump port plate and selecting one or more respective spring rates for the one or more actuator springs so as to maximize output torque resolution of the hydraulic motor with respect to actuator pressure changes while allowing the motor to reach maximum available torque without the transmission exceeding a predetermined motor speed limit and actuator pressure limits;
- and
- applying a plurality of actuator pressures at a plurality of motor speeds and pump speeds to generate a respective plurality of motor torques, and recording the respective plurality of motor torques in association with the applied actuator pressures, motor speeds and pump speeds to create a torque-pressure curve for the transmission.
Dependencies are inferred from the claim text.