Hydraulic servo device for a friction brake in a planetary transmission

摘要

An hydraulic servo device for a friction brake in a planetary transmission for motor vehicles contains a cylinder with stepped interior wall, a stationary dividing wall that has a hole and divides the interior of the cylinder into two regions, one piston in each of the two regions formed by the dividing wall, and a hollow piston rod that passes through the hole of the dividing wall and connects the two pistons. The wall of the cylinder has passages, through which a pressure medium enters or exits the cylinder, in each one of the regions formed by the dividing wall. The pistons in each of the regions of the cylinder divides each of the regions into an application-pressure chamber and a release-pressure chamber, forming four chambers in the order of an application-pressure chamber, a release-pressure chamber, an application-pressure chamber, and a release-pressure chamber. The hollow piston rod has openings which allow the pressure medium to enter or exit the piston rod and the application-pressure chambers. One of the ends of the piston rod is connected to the friction brake. The pressure caused by the inflow of the pressure medium moves the two pistons, which because of the rigid connecting rod, move with the same speed and direction, and the connecting rod, which engages or releases the friction brake, depending on the direction of the two pistons' motion.