Caterpillar Inc.

Randy R Hayward

James Elmer Winzeler

Steven T Ufheil

Robert D Carlson

Laurence M Rubin

A method and apparatus for controllably engaging, or disengaging, or both engaging and disengaging, a neutralize mode associated with a transmission located on a machine is disclosed. The machine has a controller, a memory associated with the controller, and a braking system. A determined system brake pressure is compared with at least one of an established neutralize pressure value and in gear pressure value. The neutralize mode is engaged or disengaged in response to the comparison.

Method and apparatus for controlling a transmission associated with a neutralize mode

A gear dependent manual modulation transmission control strategy is provided in a machine having an inching control arrangement so that during inching control operation the pressure of the fluid being directed to the selected clutches verses the displacement of the inching pedal can be changed relative to the selected gear ratio. This is accomplished by disposing a solenoid actuated manual modulation valve between a source of pressurized fluid and certain ones of the fluid actuated clutches and a controller operating to change the pressure relationship by changing the magnitude of the signal to the solenoid actuated manual modulation valve upon receiving a signal from a shift lever indicating a different pre-selected gear ratio.

Gear dependent manual modulation transmission control strategy

A transmission warm-up control strategy is provided for an automatic transmission used in a machine that is started or operated in cold conditions. When the operating value of the oil in the transmission is below a predetermined level, as sensed by a temperature sensor or a viscosity sensor, a controller turns on an indicator lamp, de-energizes all of the solenoid to the solenoid actuated valves, and holds for a predetermined period of time. The respective solenoids are incrementally energized and held for a second period of time while continuously monitoring the operating condition of the oil in the transmission. Once the operating condition of the oil is above the predetermined operating value, the indicator lamp is turned off and the system is returned to normal operating conditions. If the shift lever is moved from the park position during warm-up, all solenoids are de-energized and the indicator lamp is set to flash. The condition is held for the first predetermined period of time then the solenoids for the neutral clutches are energized and if the shift lever is not in the neutral position, the controller require that the shift lever be returned to the neutral or park position.

Transmission warm-up control strategy

A shift control strategy is provided for an automatic transmission used in a machine that is started or operated with cold oil in the transmission. When the operating value of the oil in the transmission is below a predetermined level, as sensed by a temperature sensor or a viscosity sensor, a controller turns on an indicator lamp. When a shift lever is moved from the neutral position or moved to select a different direction of travel, the controller detects the amount of time the shift lever has been in the neutral position or out of the one direction of travel and compares the amount of time to a predetermined amount of time. If the amount of time is less than the predetermined amount of time, the controller flashes the indicator lamp, inhibits the engagement of the clutches for the desired gear ratio or new travel direction, and requires the shift lever be moved back to the neutral position.

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Mapleton, IL, United States of America

Randy R Hayward