Caterpillar Inc.

Frank A DeMarco

Brian Dean Kuras

Michael G Cronin

Michael John Barngrover

Thomas M Sopko

Brian Douglas Hoff

Hongliu Du

Adam Vaccari

Mustafa Guven

Alberto Martinez, Jr

Tyler Bowan

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.

Variator pressure-set torque control

A hydraulic motor system for improved frequency response includes a hydraulic variator having a pump and a motor, wherein the pump includes a variable angle swash plate, and the system further includes an electric actuator for controlling an angle or torque of the swash plate, thereby controlling the motor output characteristics. The electric actuator for controlling the variable angle swash plate may comprise a linear electric motor, ball screw drive or a rotary electric motor. In an example, the rotary electric motor tilts the swash plate by applying a torque to the swash plate at a point away from its tilt axis. In a further example, the rotary electric motor tilts the swash plate via a worm drive or ball screw drive.

Electric motor actuation of a hydrostatic pump

A variator torque control system adjusts a variator output so that the actual output torque of the variator closely matches an expected output torque. In an example, pressure values of an existing torque control map are supplemented in real time with calculated pressure supplement values based on the current operation of the variator. The pressure supplement value for each mapped pressure value may be derived based on a prior application of the same or another map value.

Open-loop torque control with closed-loop feedback

A variator torque control system and method utilize a hydraulic actuator to control the variator output via a torque control map, wherein the values of the torque control map are evaluated and modified during use of the map to improve map accuracy. In an example, errors in the map are evaluated to determine whether a system fault has occurred.

Feedback adjustment for open-loop torque control map

A method of adjusting the operation of an engine-driven machine to avoid engine under-speeding entails converting a received speed or torque command into a power command. When an engine under-speed condition is sensed, the system performs underspeed correction in the power domain before converting the underspeed processed power command back into the units of the original domain. The converted underspeed processed power command is issued to the transmission or other component to alleviate the engine under-speeding condition.

Power-based underspeed control

A system and method for controlling a variator operate to detect variator torques and/or internal pressures and generates a preliminary corrective command. The preliminary corrective command is transformed via a dynamic transform to account for system characteristics during transient operating conditions such as machine acceleration, such that the acceleration of the system during transient periods is not torque-limited by static torque-control map values. In an embodiment, the acceleration may be positive or negative, and in a further embodiment, braking is automatically applied in the case of negative requested power or desired machine retarding.

Feedback acceleration reduction for fluid supply valves

A method is provided for increasing a temperature of oil in a continuously variable transmission during engine start-up, the transmission including a fluid pump and motor, and a mechanical transmission. The method includes starting the engine, maintaining the fluid pump at substantially zero displacement, and heating the transmission oil by relative rotation of a first clutch disc and first clutch hub of a first clutch assembly and by relative rotation of a second clutch disc and second clutch hub of a second clutch assembly. The method further includes maintaining a substantially zero net torque from the transmission during the heating of the oil by the first and second clutch assemblies.

Oil warming strategy for transmission

A system and method for largely controlling transmission gear ratio oscillation is disclosed. When shifts are executed substantially at synchronous points rendering hysteretic anti-hunting schemes impractical, the disclosed techniques in any combination thereof may allow for oscillation control via an overridable lock-out timer. For oscillation control during incline navigation and other similar loading scenarios, the transmission may be selectively locked if certain operational criteria are met.

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East Peoria, IL, United States of America

Frank A DeMarco