초록 ▼

In a powershift transmission having electro-hydraulic clutches for selectively connecting an input shaft in driving relationship with an output at any one of a plurality of output to input shaft speed ratios, creeper gear speeds, less than those obtained by selecting the lowest output to input shaft

In a powershift transmission having electro-hydraulic clutches for selectively connecting an input shaft in driving relationship with an output at any one of a plurality of output to input shaft speed ratios, creeper gear speeds, less than those obtained by selecting the lowest output to input shaft speed ratio, are obtained by placing the transmission in the lowest gear (forward or reverse) and controlling the output shaft speed by automatically controlling clutch slippage. Any one of a plurality of forward or reverse creeper gear speeds may be selected by operation of a gearshift lever. The speeds of the input and output shafts are sensed and a microprocessor responds to the sensed shaft speeds and the selected creeper gear speed to control slipping of the clutch. In one embodiment the output shaft speed is controlled to a specific speed value independent of the input shaft speed. In a second embodiment, the output shaft speed is controlled to obtain a specific ratio of output to input shaft speed.

대표청구항 ▼

In a transmission system having gears and a plurality of clutches for transmitting torque from an input member to an output member said clutches selectively connecting a rotatable input shaft to a rotatable output shaft at one of a plurality of output shaft to input shaft speed ratios including a lo

In a transmission system having gears and a plurality of clutches for transmitting torque from an input member to an output member said clutches selectively connecting a rotatable input shaft to a rotatable output shaft at one of a plurality of output shaft to input shaft speed ratios including a lowest speed ratio, a method of driving said output shaft at a desired creeper speed such that the ratio of output shaft speed to input shaft speed is less than said lowest speed ratio, said method comprising the steps of: a) establishing a value representing said desired creeper speed; b) actuating said clutches to select said lowest speed ratio; c) sensing the speed of said output shaft to develop an output shaft speed indication; d) comparing said value representing said desired creeper speed to said output shaft speed indication; and, e) in response to said comparison, controlling one of said clutches so that the torque transmitted by the clutch is reduced when said output shaft speed indication is greater than said value representing said desired creeper speed.