Engaging a parking lock on an incline at the end of an automatic parking maneuver

Abstract

Method for automatically engaging a parking lock (PS) on an incline at the end of an automatic parking maneuver of a motor vehicle comprising a parking assist system (PMA) with automatic longitudinal and lateral guidance for parking the motor vehicle to a predetermined parking end position, an automatic transmission with parking lock (PS), a service brake (BB) and an electric parking brake (EMF), comprising the steps: - before reaching the parking end position, automatic application (100) of the service brake (BB) of the motor vehicle; - Determine that the parking end position has been reached; - in response to the detection of reaching the park end position, initiating the application of the electric parking brake (EMF) and initiating the application of the parking lock (PS); and - Terminating (150) the operation of the service brake (BB) after the parking brake (EMF) has been engaged or at least the engagement of the parking brake (EMF) has been initiated.

Description

[0001] The invention relates to the insertion of a parking lock on an incline at the end of an automatic parking process with automatic lateral and longitudinal guidance.

[0002] With parking assistance systems featuring automatic lateral guidance, the system controls the vehicle's steering during the parking maneuver. The driver is responsible for longitudinal control through appropriate acceleration and braking. In parking assistance systems with automatic lateral and longitudinal guidance, the system also takes over longitudinal control (acceleration and braking). This includes automatic gear changes during the parking maneuver and engagement of the parking lock at the end of the parking process. This is also known as fully automatic parking. With such parking assistance systems featuring automatic lateral and longitudinal guidance, the driver generally has the option of manually parking the vehicle and, optionally, exiting it by using a control in the vehicle's cockpit.

[0003] An exemplary parking assistance system with automated lateral and longitudinal guidance is described in the publication "Parking Assistance with Longitudinal and Lateral Guidance," Dirk Ahrens, 5th Conference on Driver Assistance at the Technical University of Munich, Munich, 2012. When a vehicle manually drives past parked vehicles, a suitable parallel parking space is located using lateral sensors and visually displayed to the driver on an in-vehicle display. The driver then confirms the identified parking space. If the driver is within a valid starting corridor next to the front boundary object, from which there is a possible driving trajectory to a valid parking position, the parking maneuver is activated by pressing and holding a parking button and then releasing the service brake.After activation of the parking maneuver, the vehicle reverses into the parallel parking space in one or more maneuvers along a calculated parking trajectory, automatically controlling the steering and longitudinal movement, and comes to a stop in the final parking position.

[0004] When fully automatic parking, if the transmission selector P (P for Park) is automatically engaged at the end of the parking process and the parking lock is engaged in connection with this, the driver may experience an unpleasant jolt on an incline (uphill or downhill).

[0005] A parking lock is typically implemented by locking the output shaft of the automatic transmission with a parking pawl after the parking lock is activated. The parking pawl engages positively with a parking wheel on the output shaft. Since the output shaft can then no longer rotate, the vehicle is held stationary and secured against rolling away.

[0006] Since the parking pawl does not immediately engage positively with the parking pawl wheel after it is released, it can happen on an incline that the vehicle is accelerated by gravity before finally being abruptly decelerated when the parking pawl engages positively with the parking pawl wheel. Depending on the incline, this abrupt deceleration is felt by the driver as a jolt, to a greater or lesser degree.

[0007] To prevent a jolt when engaging a parking lock during a manual parking maneuver on an incline, US Patent 2012 / 0191311 A1 discloses that the system must detect when the driver has moved the gear selector to the Park (P) position. The braking force of the service brake is then automatically reduced until the vehicle begins to move. When the vehicle stops, the braking force is gradually reduced further until the vehicle reaches its final position.

[0008] In this publication DE 10 2004 047 100 B3 and in the publication US 2012 / 0 191 311 A1 it is described that a parking brake can be activated before a parking lock is activated.

[0009] German patent application DE 10 2005 005 669 A1 describes a method for engaging and disengaging a shift-by-wire parking lock. Particularly on slopes / declines, the drivetrain can be additionally locked steplessly at the vehicle wheels with a friction-lock parking brake to prevent drivetrain tension on slopes / declines.

[0010] In this process, the vehicle is held by the service brake until feedback is received from the parking brake control unit (and the service brake is then released). Only then is the parking brake engaged.

[0011] Furthermore, reference is made to the publications DE 102 13 346 A1, DE 10 2009 037 949 A1 and KR 10 1 371 478 B1 as further prior art.

[0012] The object of the invention is to prevent or at least reduce a noticeable jerk at the end of a fully automatic parking process in connection with the engagement of the parking lock.

[0013] The problem is solved by the features of the independent claims. Advantageous embodiments are described in the dependent claims. It should be noted that additional features of a claim dependent on an independent claim, without the features of the independent claim or only in combination with a subset of the features of the independent claim, can constitute a separate invention independent of the combination of all features of the independent claim, which can be made the subject of an independent claim or a divisional application.

[0014] A first aspect of the invention relates to a method for automatically engaging a parking lock on an incline at the end of an automatic parking maneuver of a motor vehicle. The motor vehicle comprises a parking assistance system with automatic longitudinal and lateral guidance for fully automatic parking of the motor vehicle along a parking trajectory to a predetermined parking position in a parking space (in particular a parallel parking space). Furthermore, the vehicle comprises an automatic transmission with a parking lock and an electric parking brake. According to the method, it is first determined that the desired parking position has been reached. In response, the engagement of the electric parking brake is automatically initiated. Additionally, in response to the determination that the parking position has been reached, the parking lock is engaged.

[0015] By activating the electric parking brake, a jerk when engaging the parking pawl can be prevented or at least reduced, as the vehicle is held by the parking brake or at least its rolling motion is slowed down by the parking brake.

[0016] An electric parking brake is electrically operated. For example, it could be an electric caliper parking brake with a flanged electric motor. Alternatively, an electrically operated parking brake with an electromechanical actuator can be used.

[0017] It may be possible for the electric parking brake to be initiated by a control unit before the parking lock is engaged. For example, the parking lock may only be engaged once the parking brake is already engaged.

[0018] Preferably, the engagement of the electric parking brake is triggered at least no later than the engagement of the parking lock. The engagement of the electric parking brake and the engagement of the parking lock can be triggered essentially simultaneously by a single control unit, thus preventing any additional delay in the engagement of the parking lock.

[0019] Depending on the time required for the parking brake to reach its full braking force, it may not have reached its full braking force when the parking lock is engaged. However, this reduced braking force already means that at least the acceleration of the vehicle along the slope is reduced compared to the situation without the parking brake, thus reducing the jerk, if not preventing it entirely (for example, if the braking force is sufficient to hold the vehicle).

[0020] It would be conceivable to automatically engage the electric parking brake in every situation after reaching the parking position. However, on level ground, automatic engagement of the parking brake is unnecessary to avoid a jolt and creates unnecessary noise when engaging the brake. Furthermore, the driver might not want to park the vehicle with the parking brake engaged on level ground, meaning that automatic engagement of the parking brake on level ground would not meet the driver's needs.

[0021] Therefore, it is advantageous if the electric parking brake is only automatically engaged when a gradient criterion is met, i.e., when there is a sufficiently steep incline uphill or downhill. For example, the gradient criterion checks whether the magnitude of the gradient angle is greater than or equal to a threshold value. This threshold value is preferably in the range of 1 to 10% and corresponds, for example, to approximately 3%.

[0022] It is advantageous if the service brake is automatically applied before the vehicle reaches the parking position to bring it to a standstill. However, the automatic application of the service brake should continue even after the vehicle reaches the parking position. Preferably, the service brake application is only terminated after the parking lock has been engaged. For this purpose, a sensor is preferably used to first detect that the parking lock is engaged, and the service brake application is terminated as soon as this is confirmed. Only after the service brake application is terminated should the driver preferably switch off the vehicle's drive motor.

[0023] By applying the service brake at least until the parking lock is engaged, a jerk during this period can be prevented, as the vehicle is held by the service brake, thus preventing the parking lock pawl from falling into the parking lock wheel. Even if, for example, the parking lock is engaged so quickly that the parking brake does not yet provide sufficient braking force when the parking lock is engaged, a jerk will still be prevented by the service brake. Once the parking brake has provided sufficient braking force to hold the vehicle, the service brake is no longer needed to hold it.

[0024] The service brake can also be released after the parking brake has been engaged or at least after the parking brake engagement has been initiated. For example, before the service brake is released at the end of the parking maneuver, the electric parking brake is engaged, and only then is the service brake released.

[0025] It could be provided, in particular, that the service brake operation is only terminated when it is determined that the electric parking brake is (fully) engaged (i.e., applied).

[0026] For example, the release of the parking brake could only be triggered when both a first condition, that it has been determined that the parking lock has been engaged, and a cumulative second condition, that it has been determined that the parking brake has been (fully) engaged, are met.

[0027] To prevent a sudden jerk when pulling out of the parking space due to the vehicle engaging the parking brake, it is recommended that the service brake be applied before the electric parking brake disengages and remain applied at least until the parking brake disengages. The service brake can be applied manually by the driver using the brake pedal. Alternatively, the service brake can be applied automatically before the electric parking brake disengages, at least until the parking brake disengages.

[0028] It would also be conceivable that the electric parking brake remains engaged at least until the parking lock is released again, in order to prevent a jolt caused by falling into the parking lock.

[0029] The release of the electric parking brake and the release of the parking lock after the automatic application of the service brake can also be initiated automatically. In this case, the automatic release of the parking lock could occur after the automatic release of the electric parking brake.

[0030] The parking maneuver is then preferably carried out automatically by means of the parking assistance system with automatic longitudinal and lateral guidance, whereby the application of the service brake, the deployment of the parking lock and the deployment of the electric parking brake are automatically controlled by the parking assistance system.

[0031] A second aspect of the invention relates to a parking assistance system with automatic longitudinal and lateral guidance for parking a motor vehicle along a predetermined parking trajectory to a predetermined parking end position for a motor vehicle with an automatic transmission including a parking lock and an electric parking brake. The parking assistance system is designed to detect, on an incline, that the predetermined parking end position has been reached. Once the parking end position has been reached, the parking assistance system automatically initiates the engagement of the electric parking brake and the parking lock.

[0032] The foregoing descriptions of the method according to the first aspect of the invention also apply accordingly to the parking assistance system according to the second aspect of the invention. Advantageous embodiments of the parking assistance system according to the invention not explicitly described here or in the claims correspond to the advantageous embodiments of the method according to the invention described above or in the claims.

[0033] The invention is described below with reference to the accompanying drawings and an exemplary embodiment. These show: Fig. 1 an exemplary parking assistance system PMA; Fig. 2. An exemplary procedure for engaging the parking lock PS; and Fig. 3 exemplary timelines.

[0034] The in Fig. The exemplary parking assistance system PMA shown in Figure 1 comprises a lateral guidance unit QF, which is responsible for the lateral guidance of the vehicle during the parking maneuver, and a longitudinal guidance unit LF, which is responsible for the longitudinal guidance of the vehicle during the parking maneuver. The lateral guidance unit QF is preferably arranged on a different control unit than the longitudinal guidance unit LF. The lateral guidance unit QF controls the EPS control unit of an electromechanical power steering system, for example, via a wheel steering angle interface. Furthermore, the lateral guidance unit QF also serves to track the vehicle's position along the trajectory and is connected to an ultrasonic sensor system. The longitudinal guidance unit LF controls the DME engine control unit of the vehicle's drive system, the EGS transmission control unit of the automatic transmission, and the DSC brake control unit. The DSC brake control unit, in turn, controls the service brake BB and the electric parking brake EMF.The transmission control unit EGS controls the engagement and disengagement of the parking lock (PS). A sensor is provided on the parking lock (PS) that indicates to the transmission control unit EGS when the parking lock (PS) is mechanically engaged.

[0035] In Fig. 2 is an example procedure for engaging the parking lock PS by the in Fig. 1. The PMA parking assistance system is shown.

[0036] In step 100, the service brake BB is applied to bring the vehicle to a stop in the parked position. The service brake BB remains applied until the parking lock PS is engaged. To apply the service brake BB, the longitudinal control unit LF sends a brake torque signal to the brake control unit DSC, which specifies the desired brake torque at any given time. Fig. 3 above is the resulting brake pressure p BB The service brake BB over time t is shown schematically.

[0037] In step 110, the parking end position is reached. The lateral guidance unit QF detects that the parking end position has been reached and communicates this to the longitudinal guidance unit LF. The time t PEP of reaching the parking end position is in Fig. 1 marked.

[0038] After reaching the parking end position, step 115 checks whether the magnitude of the slope s is greater than a threshold value s. TH is (e.g. s TH = 3%), i.e., abs(s) > 3%. If this is the case, the application of the electric parking brake EMF is triggered in step 120; otherwise, the application of the electric parking brake EMF is omitted. To apply the electric parking brake, the longitudinal control unit LF sends a corresponding command to the brake control unit DSC to apply the electric parking brake EMF. In the middle diagram in Fig. Figure 3 is an example of the force F curve. EMFThe electric parking brake EMF is shown, with the force F being applied after reaching the parking end position. EMF The electric parking brake EMF increases from zero to a target value.

[0039] After reaching the park end position, the parking lock (PS) is engaged in step 130. For this, the transmission selector stage P (P for Park) is selected, thus triggering the engagement of the parking lock. A corresponding command to engage transmission selector stage P is sent from the longitudinal control unit (LF) to the transmission control unit (EGS). (See the bottom diagram in...) Fig. 3 is position pos PS the parking lock latch is shown; the process of engaging the parking lock latch is described in Fig. 3 by increasing the position pos PS illustrated by the parking lock latch.

[0040] In step 140, the system checks whether the parking lock (PS) is engaged. For this purpose, the longitudinal control unit (LF) checks whether it has received a signal from the transmission control unit (EGS) indicating that the parking lock (PS) is engaged. The parking lock (PS) has a sensor connected to the transmission control unit (EGS), which allows the EGS to detect an engaged parking lock (PS) and communicate this to the longitudinal control unit (LF).

[0041] When the parking lock PS is engaged, the application of the service brake BB is terminated in step 150. The point in time at which the parking lock PS is engaged is in Fig. 3 with t PS This is referred to as... For this purpose, it is determined after time t. PSThe value of the braking torque requested by the longitudinal control unit LF, which is communicated to the brake control unit DSC via the braking torque signal, is reduced in a ramp-like manner. Preferably, the desired braking torque is reduced by the maximum possible amount of the ramp.

[0042] In connection with the subsequent exiting from the parking space, at time t AP1 The brake pressure of the service brake BB is automatically increased again. After reaching sufficient brake pressure P BB The service brake is engaged at time t AP2 They will begin installing the electric parking brake (EMF). They will also begin installing the parking lock (PS).

Claims

[1] Method for automatically engaging a parking lock (PS) on an incline at the end of an automatic parking maneuver of a motor vehicle comprising a parking assist system (PMA) with automatic longitudinal and lateral guidance for parking the motor vehicle to a predetermined parking end position, an automatic transmission with parking lock (PS), a service brake (BB) and an electric parking brake (EMF), comprising the steps: - before reaching the parking end position, automatic application (100) of the service brake (BB) of the motor vehicle; - Determine that the parking end position has been reached; - in response to the detection of reaching the park end position, initiating the application of the electric parking brake (EMF) and initiating the application of the parking lock (PS); and - Terminating (150) the operation of the service brake (BB) after the parking brake (EMF) has been applied or at least the application of the parking brake (EMF) has been initiated. [2] Method for automatically engaging a parking lock (PS) on an incline at the end of an automatic parking maneuver of a motor vehicle comprising a parking assist system (PMA) with automatic longitudinal and lateral guidance for parking the motor vehicle to a predetermined parking end position, an automatic transmission with parking lock (PS), a service brake (BB) and an electric parking brake (EMF), comprising the steps: - before reaching the parking end position, automatic application (100) of the service brake (BB) of the motor vehicle; - Determine that the parking end position has been reached; - Check (115) whether a slope criterion is met, - provided that the parking end position has been reached and the gradient criterion has been met, the electric parking brake (EMF) and the parking lock (PS) are initiated; and - Terminating (150) the operation of the service brake (BB) after the parking brake (EMF) has been applied or at least the application of the parking brake (EMF) has been initiated. [3] Method according to claim 2, wherein the slope criterion is whether the magnitude of the slope angle is greater than or greater than or equal to a threshold value (s TH ) is. [4] Method according to one of the preceding claims, wherein the termination (150) of the operation of the service brake (BB) takes place after the parking lock (PS) has been engaged. [5] The method of claim 4, comprising the further step: - Determining that the parking lock (PS) is engaged, whereby, provided that the engagement of the parking lock (PS) has been determined, the operation of the service brake (BB) is terminated. [6] Method according to any of the preceding claims, comprising the further step: - Determining that the electric parking brake (EMF) is engaged, whereby, provided that the engagement of the electric parking brake (EMF) has been determined, the operation of the service brake (BB) is terminated. [7] Method according to any of the preceding claims, wherein the parking brake (EMF) is engaged faster than the parking lock (PS). [8] Method according to any of the preceding claims, comprising the further step in connection with exiting the parking space: - before the electric parking brake (EMF) is released, the service brake (BB) is automatically applied, with the automatic application of the service brake (BB) continuing at least until the parking lock (PS) is released again. [9] Method according to claim 8, wherein the deployment of the electric parking brake (EMF) and the deployment of the parking lock (PS) are initiated automatically. [10] Method according to one of claims 8 to 9, wherein the parking maneuver is carried out automatically by means of the parking assistance system (PMA) with automatic longitudinal and lateral guidance. [11] Parking Assistance System (PMA) with automatic longitudinal and lateral guidance for parking the motor vehicle along a predetermined parking trajectory to a predetermined parking end position for a motor vehicle with an automatic transmission including a parking lock (PS), a service brake (BB) and an electric parking brake (EMF), wherein the Parking Assistance System (PMA) is configured to operate on an incline - to automatically confirm the service brake (BB) of the motor vehicle before reaching the parking end position, - to determine that the parking end position has been reached, - in response to the detection that the parking end position has been reached, to initiate the application of the electric parking brake (EMF) and the engagement of the parking lock (PS), and - to end the operation of the service brake (BB) after the parking brake (EMF) has been engaged or at least the engagement of the parking brake (EMF) has been triggered. [12] Parking Assistance System (PMA) with automatic longitudinal and lateral guidance for parking the motor vehicle along a predetermined parking trajectory to a predetermined parking end position for a motor vehicle with an automatic transmission including a parking lock (PS), a service brake (BB) and an electric parking brake (EMF), wherein the Parking Assistance System (PMA) is configured to operate on an incline - to automatically confirm the service brake (BB) of the motor vehicle before reaching the parking end position, - to determine that the parking end position has been reached, - to check (115) whether a slope criterion relating to the gradient is met, - provided that the parking end position has been reached and the gradient criterion relating to the incline has been met, to initiate the engagement of the electric parking brake (EMF) and the engagement of the parking lock (PS), and - to end the operation of the service brake (BB) after the parking brake (EMF) has been engaged or at least the engagement of the parking brake (EMF) has been triggered.

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