A powershift transmission for a work vehicle is disclosed having two modes of applying power: a direct connection through a series of gears, and a connection through a torque converter integral with the transmission. The two paths branch at the input shaft, on which is mounted and which drives a torque converter that has a gear coupled to its output. Another gear on the input shaft is connected to that shaft by a hydraulic clutch. When the clutch is engaged, the transmission provides several high-range forward gear ratios through a direct gear drive. When that clutch is disconnected, the torque converter supplies power to the transmission to low forward and low reverse ranges of gear ratios. The transmission includes a first countershaft, on which are mounted a reverse master clutch engaged in all reverse gear ratios) and a forward low range clutch, which is engaged in the low range of forward gear ratios. The reverse master clutch couples the countershaft directly to the output shaft. The forward low-range clutch connects the countershaft to a second countershaft. The second countershaft and the output shaft each has two speed clutches. Only one of these speed clutches is engaged in any individual gear ratio. The output shaft is also engaged to a mechanical front wheel drive output shaft via a clutch. This output shaft is engaged via that clutch and counter-rotates with the output shaft to drive the front wheels or tracks of the vehicle.

A planet carrier for a compound planetary gear arrangement has four side plates supporting six pinion gears. One pair of side plates, supporting three of the pinion gears, have one of the other pair of side plates disposed axially between them. This allows the pinions to be in meshing relation between adjacent side plates which are each supporting three pinions, respectively. To complete the planetary arrangement, the outer side plates are sized to permit central access at respective sun gears and outer axial access at respective ring gears. The ring gears and sun gears do not encroach upon the meshing location of the pinion gears. With the judicious use of friction clutches and brakes and two input gear sets providing ratios, the compound planetary arrangement can be controlled to provide powertrains having from five forward speeds (the four friction devices) to seven forward speeds and two reverse speeds (with eight friction devices). Thus, the planetary arrangement can be utilized to provide a plurality of speed ratios, wherein the number of friction devices is one less than the total number of speed ratios.

This invention relates to a power transmission apparatus for flexibly coupling a power source to its intended torque load. This apparatus is addressed to producing an infinitely flexible ratio of gear reduction while continuously maintaining economical, solid contact gear meshings. The simultaneous selection of division ratios, and of optional torque transfer channels, while splitting the input torque provides the two torque components needed for composing the optimum output torque ratio. A plurality of dual journallings permit an annularly torqued rotation to progressively supplement and then replace, the torque from the epicyclic gear reduction rotations. Multiple progressions of infinitely variable reduction ratios selectively activate the amount of input torque energy deflected from the gear reduction apparatus, into a direct torquing of the output shaft. The continuous infinite selectivity of a controlling impedance within the meshings of the gear reduction apparatus, as it responds to external control sensors or to manual selection, determines the gear reduction ratio of the two torque supplements recombined. The ratio of gear reduction is, therefore, continuously responsive to a changing torque load.

A controller including a microprocessor for automatically shifting a transmission and selectively locking and unlocking a torque converter connecting the engine with the transmission. The controller has both manual and automatic modes of operation. In the automatic mode, one of three different shift patterns is automatically selected depending on the condition of a transport/loading mode switch and a throttle position switch. Transmission output speed is monitored and downshifts are prevented when the output is accelerating. Solenoid valves which are selectively activated to shift the transmission are monitored for open- or short-circuits. When a faulty solenoid is detected, the controller prevents shifting to a gear ratio which utilizes that solenoid and a display flashes diagnostic information including the gear ratios still available. The solenoids are pulsed at one of two duty cycles depending on the voltage level of the power supply.

An electronic transmission control system for a self-propelled off-road vehicle having an internal combustion engine and multiple gear powershift transmission. The control system controls the powershift transmission and provides at least one control signal to the engine for selecting the speed at which the engine is to operate. The system includes a first electronic controller that provides transmission control signals required to command the powershift transmission to shift to and operate in any particular one of its forward gears, and second electronic controller that provides at least one engine control signal required to command the engine to operate at one of a number of different desired engine speeds and to monitor the actual engine speed. By use of gear ranges which overlap slightly, and a throttle that is infinitely adjustable within a range of engine speeds, any given ground speed within the range of possible vehicle speeds can be achieved and maintained, as long as engine is operating within its overall power envelope. Once the desired ground speed is specified by the operator, the control system automatically selects the specific transmission gear and engine speed required to achieve the desired ground speed. The control system also performs automatic upshifts or downshifts, as required, to achieve the desired ground speed. The system has a comfort mode, fuel economy mode, and a maximum horsepower mode, all selectable by the operator. The system also supports a pseudo-gear mode where the operator interface indicates there are more gears in the transmission than actually exist.