US 11,746,901 B2
Device for operating a parking lock of a motor vehicle transmission
Tobias Rolser, Ravensburg (DE); Christian Popp, Kressbronn (DE); Thilo Schmidt, Meckenbeuren (DE); and Armin Gierling, Langenargen (DE)
Assigned to ZF FRIEDRICHSHAFEN AG, Friedrichshafen (DE)
Filed by ZF Friedrichshafen AG, Friedrichshafen (DE)
Filed on Jan. 27, 2022, as Appl. No. 17/586,094.
Claims priority of application No. 10 2021 200 774.0 (DE), filed on Jan. 28, 2021.
Prior Publication US 2022/0235862 A1, Jul. 28, 2022
Int. Cl. F16H 63/34 (2006.01); F16H 63/36 (2006.01)
CPC F16H 63/3483 (2013.01) [F16H 63/36 (2013.01)] 17 Claims
OG exemplary drawing
 
1. A device for operating a parking lock (34) of a transmission (3) in a motor vehicle (1), comprising:
an engagement spring (345) configured for engaging the parking lock (34);
an actuator (340) hydraulically actuatable to disengage the parking lock (34), the actuator (340) comprising a hydraulic piston (341) operatively connected to the parking lock (34) and axially displaceably mounted in a housing of the actuator (340), the hydraulic piston (341) and the housing forming a pressure chamber (346);
an electrohydraulic control unit (35) configured to hydraulically actuate gear-forming shift elements (33) of the transmission (3) as well as the actuator (340) with pressure provided by a pump (37) of the transmission (3);
an electronic control unit (36) configured to electrically actuate electromagnetically actuatable hydraulic valves (350, 351) of the electrohydraulic control unit (35) in order to implement shift positions (P, R, N, D) and gears in the transmission (3), the electrohydraulic control unit (35) is configured to generate, by one of the electromagnetically actuatable hydraulic valves (351), a system pressure (P_sys) predefined by the electronic control unit (36) to provide a pressure supply for the gear-forming shift elements (33) and of the actuator (340), the pressure chamber (346) of the actuator (340) acted upon by the system pressure (P_sys) via a pressure line (347) when the parking lock (34) is disengaged and emptied via the pressure line (347) when the parking lock (34) is engaged;
an interlocking device (342) operable to mechanically interlock the hydraulic piston (341), the interlocking device (342) actuatable by the electronic control unit (36) in a piston position (E) associated with an engaged condition of the parking lock (34) as well as in a piston position (A) associated with a disengaged condition of the parking lock (34);
a choke unit (352) comprising an orifice (353) and a non-return valve (354), the choke unit (352) installed in the pressure line (347) between the one of the electromagnetically actuatable hydraulic valves (351) that generates the system pressure (P_sys) and the pressure chamber (346);
a hydraulic damper (356) fluidically connected to the pressure line (347) between the choke unit (356) and the pressure chamber (346); and
a pressure limiting valve (355) fluidically connected to the pressure line (347) between the choke unit (352) and the pressure chamber (346), wherein the pressure limiting valve (355) is integrated in the hydraulic damper (356),
wherein the orifice (353) is configured to limit flow in a feed direction to the pressure chamber (346) as well as in a return direction from the pressure chamber (346), and
wherein the non-return valve (354) is configured to close in the feed direction to the pressure chamber (346) and to open in the return direction from the pressure chamber (346).