Deere & Company

David E Brandon

Dennis Lee Jeffries

Peter Leslie Falck

Kevin D McKee

Brian A Ahlschwede

Dean H Symonds

A system and method for controlling the clutches in a vehicle powershift transmission. The control system includes a microprocessor which periodically executes an algorithm and which has a memory in which is stored a sequential set of time reference values and a sequential set of pressure values. The control system applies to each oncoming element a fill pressure pulse for fill periods which are unique for each element. The control system determines shift time values, subsequent to filling of the control elements, as a function of the fill period. The control system applies pressure signals to the control elements at times represented by the shift time values which are unique for each element. The control system determines, subsequent to a realignment time, realignment shift time values which are the same for all of the control elements. The control system also applies pressure signals to the control elements subsequent to the realignment time, at times determined as a function of the realignment shift time values.

Method for controlling transmission control clutches

The hydraulically operated brake and clutch elements (controlled by proportional control valves) of a vehicle powershift transmission have fill pressures which are calibrated by a method wherein the output shaft of the transmission is disconnected from the vehicle drive shaft so that the transmission output shaft is free to rotate and certain ones of the plurality of the control elements other than the control element being calibrated are fully pressurized in order to prevent rotation of a part of the control element being calibrated. The engine is run at a predetermined speed and the pressure applied to the control element being calibrated is gradually increased while engine speed is monitored. When the monitored engine speed changes by predetermined amount, a value is saved corresponding to the calibration pressure. The transmission is automatically shifted to neutral if vehicle motion is sensed. The volume of hydraulic fluid required to initially engage the control element may be calibrated in a similar manner.

Calibration method for transmission control clutches

A vehicle control system automatically controls both the engine and transmission of the vehicle in response to operator inputs and in response to sensed parameters. The control system has separate selectable operational modes--a constant ground speed mode and a constant engine speed mode.

Automatic engine/transmission control system

An inductive displacement transducer includes a primary and at least two secondary coils with a movable coupling member for varying the amount of mutual coupling therebetween as a function of the displacement of a movable member. The secondary coils are wrapped around magnetic cores which are embedded in a disc-shaped core structure. The coupling member comprises a pair of magnetic conductive arms disposed on either side of the core structure and attached to a shaft rotatably received by a central axial bore in the core structure. An end of the shaft may be attached to the movable member. A control circuit excites the primary coil with an excitation signal with abrupt repetitive transients so that voltage spikes appear in the secondary coils with an amplitude related to the amount of mutual coupling. The voltage spikes are integrated into a D. C. voltage with an amplitude of the voltage spikes and thus, indicative of the displacement of the movable member.

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Waterloo, IA, United States of America

David E Brandon