Search

DE-102024132214-B4 - Method for controlling a parking barrier

DE102024132214B4DE 102024132214 B4DE102024132214 B4DE 102024132214B4DE-102024132214-B4

Abstract

The invention relates to a method for controlling a parking lock (20) for a motor vehicle, comprising a control unit which controls a slave cylinder (13) that moves the parking lock (20) from an engaged to a disengaged state and is pressurized by a pump (3) controlled by the control unit, and an electrically actuated holding device (18) controlled by the control unit, which positively engages the parking lock (20) in the disengaged state. To prevent the motor vehicle from unintentionally rolling away from a standstill or the parking lock from locking while driving in the event of a defective holding device (18), the function of the holding device (18) is checked before the parking lock (20) is disengaged, and disengagement of the parking lock (20) is prevented if the holding device (18) malfunctions.

Inventors

  • Kirill Prokhorov

Assignees

  • Schaeffler Technologies AG & Co. KG

Dates

Publication Date
20260513
Application Date
20241105

Claims (8)

  1. Method for controlling a parking lock (20) for a motor vehicle with a control unit which controls a slave cylinder (13) pressurized by a pump (3) controlled by the control unit, which moves the parking lock (20) from an engaged to a disengaged state, and an electrically actuated holding device (18) controlled by the control unit, which positively engages the parking lock (20) in the disengaged state, wherein the function of the holding device (18) is checked before the parking lock (20) is disengaged and disengagement of the parking lock (20) is prevented in the event of a malfunction of the holding device (18), characterized in that the control unit switches to an emergency operating mode in the event of a malfunction and wherein the motor vehicle is prevented from rolling away by actuating an electrically controlled parking brake and/or electrically controlled service brakes.
  2. Procedure according to Claim 1 , characterized in that the holding device (18) includes a locking element (19) which engages in a locking manner in a locking manner in a locking element (19) which engages the parking lock (20) along an actuation path (s) in an axially displacing slave cylinder piston (14) of the slave cylinder (13) or which engages the parking lock (20) in an actuating manner and which is controlled by means of a magnetic switch (22) controlled by the control unit, wherein electrical parameters of the holding device (18) are checked by the control unit before the parking lock (20) is deployed.
  3. Procedure according to Claim 2 , characterized in that electrical properties of a coil of the magnetic switch (22) are checked.
  4. Procedure according to Claim 3 , characterized in that an error is detected when an electrical resistance of the magnetic switch (22) lies outside a predetermined range.
  5. Procedure according to Claim 3 or 4 , characterized in that a fault is detected if the current consumption of the magnetic switch (22) under load is outside a predetermined range.
  6. Procedure according to one of the Claims 1 until 5 characterized in that a malfunction is detected in the event of one or more successive errors.
  7. Procedure according to Claim 6 , characterized in that, after at least one automated or driver-performed reset of the control unit, a continuing fault is detected as a malfunction.
  8. Procedure according to one of the Claims 1 until 7 , characterized in that a check of the holding device (18) is carried out when the motor vehicle is started.

Description

The invention relates to a method for controlling a parking lock for a motor vehicle with a control unit which controls a slave cylinder which moves the parking lock from an engaged to an extended state and which is pressurized by a pump controlled by the control unit and carries out system pressure, and an electrically actuated holding device controlled by the control unit which holds the parking lock positively in the extended state. DE 10 2013 213 964 A1 discloses a method for operating a parking lock system of a vehicle transmission and a control device for carrying out the method. From the printed text DE 10 2020 117 020 A1 A device for actuating a parking lock by means of a slave cylinder and a method for controlling the actuation by means of this device are known. In order to keep the parking lock in the open state, and thus actuated by the slave cylinder, regardless of the system pressure acting on the slave cylinder, a holding device with an auxiliary cylinder is provided, the locking pin of which engages positively when the parking lock is actuated. Furthermore, the DE 10 2023 103 469 A1 a device for actuating a parking lock, in which the parking lock is held in a form-fitting manner in both the actuated and open states by means of an electrically operated holding device. The object of the invention is to further develop a method for controlling a parking lock that is hydraulically actuated by means of a slave cylinder and positively locked in the actuated state by means of a holding device. In particular, the object of the invention is to propose a method for controlling such a parking lock that prevents the vehicle from rolling away unintentionally and/or the parking lock from closing unintentionally. The problem is solved by the subject matter of claim 1. The dependent claims describe advantageous embodiments of the subject matter of claim 1. The proposed method serves to control a parking lock for the powertrain of a motor vehicle, for example, a hybrid or purely electric vehicle. A control unit is provided to actuate the parking lock. This unit controls an electrically actuated pump, thereby regulating system pressure, and also controls a slave cylinder along the stroke of its piston. To actuate the parking lock, the slave cylinder is pressurized with system pressure, so that a movement of its piston actuates and thus opens the parking lock, whether it is engaged or disengaged. The parking lock is therefore closed when not actuated and open when actuated. To keep the parking lock open in the actuated state, regardless of the state of the slave cylinder, an electrically actuated holding device, controlled by the control unit, is provided. This device positively engages the parking lock in both the engaged and disengaged states. The proper functioning of the parking lock, and thus the safe operation of the vehicle, depends significantly on the function of the holding device. Therefore, it is necessary to check the function of the holding device before engaging or disengaging the parking lock and to prevent engagement if the holding device malfunctions. In the event of a malfunction, the primary measure is to prevent movement of the vehicle. Further steps to at least partially enable the vehicle to operate may be implemented as described below. A malfunction may occur, for example, if the holding device cannot be released when the parking lock is engaged. In this case, the parking lock cannot be returned to its locked position (i.e., the unengaged state in this configuration), for instance, by the slave cylinder being returned to its depressurized zero position by the force of a spring mechanism pre-tensioned when the parking lock is engaged. Consequently, the parking lock is ineffective, and the vehicle may roll unintentionally. Alternatively, if the parking lock is engaged and the holding device is malfunctioning, the parking lock can be at least partially engaged, for example, while driving, such as when the system pressure drops. Monitoring the holding device and, if necessary, intervening in the parking lock's operation prevents potentially hazardous situations in the event of a malfunctioning holding device. For example, the holding device can include a slave cylinder piston of the slave cylinder that moves axially and actuates the parking lock along an actuation path, or a locking element that engages positively with this component and is controlled by a magnetic switch controlled by the control unit, whereby electrical parameters are checked by the control unit before the parking lock is deployed. The proposed method can, for example, be implemented in a hydraulic system with a hydraulic actuator, which may include a pump that pumps a pressure medium into a pressure line, thereby generating system pressure. The pump can be driven by an electric motor, such as a contactless commutated electric motor, which drives the pump at a controlled speed, so that the pumping capacity is adjusted by