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A method of controlling a power transmission device between a driving engine and a drive axle comprising a torque converter and an automatic step gearbox, and a power transmission device for carrying out the method. In the gearbox, an electric control device with a microcomputer permits the operator

A method of controlling a power transmission device between a driving engine and a drive axle comprising a torque converter and an automatic step gearbox, and a power transmission device for carrying out the method. In the gearbox, an electric control device with a microcomputer permits the operator to select, by means of a direction selector, the desired driving direction of the vehicle even when moving opposite to the desired direction. When such a directional command signal is sent to the control device, the reversing gear control reverses the working direction of the gearbox to make it work in the opposite direction to the driving direction. This signal is also sent to the drive gear control in the control device which during retardation maintains the engaged gear in engagement. If the highest gear is engaged when the command signal is changed, however, downshifting to the next higher gear immediately takes place which gear is then maintained during retardation. The reversing gear control is prevented from reversing the working direction of the gearbox if the vehicle speed exceeds a predetermined maximum value. The beginning of the retardation is then carried out with the working direction of the gearbox unchanged until the speed has dropped below that maximum, and then the working direction is reversed.

대표청구항 ▼

In a method of controlling a power transmission device arranged between a driving engine and a drive axle and comprising a torque converter and a mechanical step gearbox, especially for vehicles such as wheeled loaders, comprising controlling the gearbox both automatically in response to engine para

In a method of controlling a power transmission device arranged between a driving engine and a drive axle and comprising a torque converter and a mechanical step gearbox, especially for vehicles such as wheeled loaders, comprising controlling the gearbox both automatically in response to engine parameters such as rotational speed and torque, and in response to a directional signal from a manually actuated direction selector control, emitting a command value for the rotational direction of the drive axle, delaying the reversal of the working direction of the gearbox until the speed is less than a predetermined limiting speed value if the speed of the vehicle or the rotational speed of the drive axle exceeds said value, and reversing the direction of the gearbox when the directional command value signal is changed to indicate the opposite rotational direction to the prevailing rotational direction of the drive axle so that during the subsequent retardation it works against the prevailing drive axle direction; the improvement comprising maintaining during the entire retardation that gear in engagement which is in engagement at the beginning of the retardation, downshifting immediately to the next-to-the-highest gear if the highest gear is engaged when the directional command signal is changed, and when the retardation has been completed and the speed of the axle and vehicle is zero, engaging the next-to-the-lowest gear of the gearbox for the subsequent acceleration.