Assembly for actuating double-acting shift cylinder of shift assembly of automatic transmission of motor vehicle

Abstract

The invention relates to an assembly (31) for actuating a double-acting shift cylinder (32) of a shift assembly (18) of an automatic transmission (19) of a motor vehicle, comprising a hydraulic fluid reservoir (33) having a motor-driven hydraulic pump (35) and two control valves (37, 38) that are each connected to a pressure supply line (36) of the hydraulic pump (35) and to a return line to the hydraulic fluid reservoir (33), wherein the shift cylinder (32) has two pressure chambers (40, 41) that are each connected to one control valve (37; 38), wherein the control valves (37, 38) each connect one pressure chamber (40; 41) of the shift cylinder (32) to the pressure supply line (36) of the hydraulic pump (35) or to the return line (39) to the hydraulic fluid reservoir (33), wherein the assembly (31) contains at least one pressure-limiting valve that connects the pressure supply line (36) to the return line (39) if a hydraulic over-pressure is present. According to the invention, in order to improve the assembly, the control valves (37, 38) are each designed as 3 / 2-directional valves (47, 48) having integrated pressure-limiting valves.

Description

technical field [0001] The invention relates to a device for actuating a double-acting shift cylinder of a shifting device of an automatic transmission of a motor vehicle having the features of the preamble of claim 1 . Background technique [0002] Automatic transmissions of motor vehicles, in particular commercial vehicles, usually have an arrangement of easily controllable structural units for actuating at least one double-acting shift cylinder of a shifting device of the automatic transmission of the motor vehicle. Such devices are known, for example, from DE 10 2005 015 481 A1 and DE 199 50 443 A1. The device has at least two shift valves, via which a double-acting shift cylinder can be acted upon with pneumatic or hydraulic pressure. The piston rod of the piston of the shifting cylinder is usually connected to a shifting dog, a shifting pin or similar actuating elements, by means of which the shifting gates of the transmission can be shifted if necessary. Alternate a...

AI Technical Summary

Problems solved by technology

However, since the corresponding pressure limiting valve has not been actuated under normal conditions for many years, this can lead to the fact that the pressure limiting valve can no longer function properly in extreme cases, which can cause the valve link to fail due to corrosion or other influences. no longer able to exercise

This can correspondingly lead to unacceptable damage to the system, which manifests itself, for example, in the form of burst hydraulic lines or actuation of the shift cylinder when there is a particularly high overpressure, whereby an unintentional engagement or withdrawal of a certain gear, which can result in serious damage to the transmission or vehicle.

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