Electronic-hydraulic control device for motor vehicle automatic gearbox maintains pressure to forward change element if electronics switched off, selects neutral if speed at least close to zero

摘要

The device has hydraulically actuated gear change elements operated by an electronic controler. If a fault occurs leading to the gearbox electronics being switched off, a defined change element for forward travel remains subjected to pressure via a reversing valve, whereby the pressure set by the valve is speed dependent and if it corresponds at least approximately to zero speed a hydraulic change to neutral is triggered. The device has hydraulically actuated gear change elements (A-E) and an electronic controler (32) for operating the change elements depending on gearbox and drive motor parameters, gear selector position and a drive influence connected to the gearbox via an electrical interaction. If a fault occurs leading to the gearbox electronics being switched off, a defined change element for forward travel remains subjected to pressure via a reversing valve (7), whereby the pressure set by the valve is speed dependent and if it corresponds at least approximately to zero speed a hydraulic change to neutral is triggered.