DE102018106939A1 - Method for determining a state of a parking brake of a vehicle - Google Patents

Abstract

The invention relates to a method for determining a state of a parking brake of a vehicle, in which a parking pawl (8) by an actuator (6) automatically in a parking lock gear (2) is positively latched. In a method in which the actual state of the parking brake can be reliably detected, it is determined in dependence on a load-dependent actuator current, whether the parking brake (1) is securely engaged or a tooth of Parkklinke (8) on a tooth (5) of the parking lock gear (1) stands.

Description

The invention relates to a method for determining a state of a parking brake of a vehicle, in which a parking pawl is automatically latched in a form-locking manner by an actuator in a parking lock gear.

In automated powertrains of vehicles parking locks are used to prevent the movement of the vehicle in the parking mode, in particular at road slopes. The parking lock usually has a parking link and a parking lock gear. By engaging the parking pawl in a tooth gap of the parking lock gear a positive connection between a drive train and a transmission housing is made. Thus, the vehicle is secured. By laying out the parking pawl from the tooth gap of the parking lock gear, the drive train and thus the vehicle is unlocked.

From the DE 10 2008 000 177 A1 a parking lock is known in which the parking brake is actuated by an actuator. The position of the parking pawl is not detected by a sensor, but it is the position of the actuating actuator determined. The disadvantage here is that between the states of the parking brake "safely inserted" and "tooth on tooth" can not be distinguished. Under the condition "tooth on tooth" is to be understood hereinafter a state in which a tooth of the parking pawl is located on a tooth of the parking lock gear. In the condition "tooth on tooth" a reliable gripping the parking brake is not guaranteed. Since the parking brake is a safety mechanism, it is very important to safely detect the state of the parking brake.

The invention has for its object to provide a method for determining a state of a parking brake of a vehicle, in which the state of the parking brake can be reliably detected.

According to the invention the object is achieved in that it is determined in dependence on a load-dependent actuator current, whether the parking brake is securely engaged or a tooth of the parking pawl is on a tooth of the parking lock gear. This has the advantage that the current state of the parking brake can be reliably determined without the use of sensors on the mechanical components of the parking brake and thus without additional effort. Thus, between the two states of the parking brake "safely inserted" or "tooth on tooth" can be distinguished.

Advantageously, the measured load-dependent actuator current is compared with a current limit and closed when exceeding the current limit by the measured load-dependent actuator current to a safe engagement of the parking brake or falls below the current limit by the measured load-dependent actuator current to a standing tooth of the parking pawl on a tooth of the parking lock gear , Since the actuator current increases with the load of the actuator, it is possible to reliably identify the parking lock state from the actuator current.

In one embodiment, according to the method of the actuator in a position that is required for engaging the parking brake, the actuator is returned to a predefined way and measured the current load-dependent actuator current, which is compared with the current limit. Due to this reduction by the predefined path, the state of the parking lock can be easily determined by measuring the load-dependent actuator current. This is possible because the load on the actuator is at least as high as the force on a biasing spring of the parking pawl when the parking pawl is inserted in a tooth space of the parking ratchet wheel. But if the tooth of the parking pawl on a tooth of the parking lock gear, no load is transferred from the parking mechanism to the actuator, since both are decoupled from each other. Thus, only a relatively low load-dependent actuator current is measured.

In one variant, the current load-dependent actuator current is measured in an actuator travel window of the predefined path of the actuator, in which no movement of the actuator takes place. This ensures that the Aktorstromspitzen occurring during the acceleration of the actuator is not included in the measurement and the Aktorstrom is evaluated by the method of the actuator to the predefined path in a rest position of the actuator.

In one variant, the predefined distance, by which the actuator is returned, is a maximum of 1 to 2 mm. This predefined path is determined as a function of the respective parking lock system and must be chosen such that this predefined route does not lead to the laying out of the parking lock.

In a further embodiment, after comparing the current load-dependent actuator current with the current limit value, the actuator is moved back into the position required for engaging the parking brake. Thus, the measuring phase for determining the state of the parking brake is completed.

Advantageously, the vehicle is secured during the measurement of the current load-dependent actuator current by an on-board brake. This has the advantage that, if the parking brake is not loaded reliably, a rolling away of Vehicle, especially on the mountain, is reliably prevented.

The invention allows numerous embodiments. One of them will be explained in more detail with reference to the figures shown in the drawing.

• 1 ein Ausführungsbeispiel einer Parksperre zur Durchführung des erfindungsgemäßen Verfahrens,
• 2 ein Ausführungsbeispiel der Parksperre im Zustand „Parksperre ausgelegt“,
• 3 ein Ausführungsbeispiel der Parksperre im Zustand „Parksperre eingelegt“,
• 4 ein Ausführungsbeispiel der Parksperre im Zustand „Zahn auf Zahn“,
• 5 ein Ausführungsbeispiel des erfindungsgemäßen Verfahrens.

Show it:

• 1 An embodiment of a parking brake for performing the method according to the invention,
• 2 an embodiment of the parking brake in the state "parking brake designed",
• 3 an embodiment of the parking brake in the state "parking brake engaged",
• 4 an embodiment of the parking brake in the state "tooth on tooth",
• 5 an embodiment of the method according to the invention.

In 1 is an embodiment of a parking brake 1 shown. Such parking locks are advantageously arranged in a transmission. The parking lock 1 includes a parking lock gear rotatable about a rotation axis 2 , wherein the axis of rotation by an intermediate shaft 3 is formed, with which the parking lock wheel 2 is directly connected to the drive wheels of the vehicle. The parking lock wheel 2 has several teeth on its circumference 4 on that through a tooth gap 5 are separated. To operate the parking brake 2 is an actor 6 provided, which is actuated by an electric motor, not shown. The electric motor drives a spindle 7 on, which has a screw drive. A parking pawl 8th is on a cabinet frame 9 attached to a transmission, wherein a return spring 10 at a fixed end of the parking pawl 8th attacks. A locking wedge 11 is over a biasing spring 12 with the case frame 9 connected and can with the park pawl 8th as well as with the spindle 7 of the actor 6 enter into an operative connection. The path position of the spindle becomes 7 via a position sensor 13 measured, with the actuator 6 the spindle 7 starting from right to left to actuate the parking brake 1 moved (arrow P1 ). Within the actor 6 is a current sensor 14 arranged, with which a change of the actuator current in response to a changing load on the actuator 6 is detected. As the actuator current increases with the load, it is possible to identify the park lock state from the actuator current.

In 2 is the parking lock 1 shown in the state "designed". Here is the parking pawl 8th from the tooth gap 5 of the parking lock wheel 2 triggered, the spindle 7 of the actor 6 on the locking wedge 11 is applied.

The state "engaged" the parking brake 1 is in 3 shown in which by the locking wedge 11 the parking pawl 8th with resetting spindle 7 in a tooth gap 5 of the parking lock wheel 2 is pressed. Thus, a reliable locking of the parking brake 1 allows.

In 4 is the condition "tooth on tooth" of the parking brake 1 shown. Here are the spindle 7 of the actor 6 and the locking wedge 11 decoupled from each other, although the locking wedge 11 the parking pawl 8th against a tooth 4 of the parking lock wheel 1 suppressed.

To now the parking lock 1 with respect to the state "safely inserted" or the state "tooth on tooth" to distinguish, the actuator 6 first drove to a position to insert the parking brake 1 is needed. This is done by the spindle 7 of the actor 6 travels a path through the position sensor 13 is detected. After the actor 6 has reached this position, this drives a predefined small path of about 1 mm in the direction of parking brake 1 interpret back. This is in 5 shown in the diagrams a and b. Thereafter, the actuator current is measured.

In 5c and 5d the actuator current I occurring during the movement of the actuator is shown over the time t. This is measured in a Aktorwegfenster AWF and compared with a current limit GW, in which the actuator 6 Although in the direction of laying out the parking brake 1 has retreated, but is at a standstill. Exceeds the measured Aktorstrom the current limit GW, it is concluded that the parking brake 1 is safely inserted. This results from the process of the spindle 7 in the direction of "laying out" where the load is on the actuator 6 at least as high as the force in the biasing spring 10 of the locking wedge 11 when the parking pawl 8 in a tooth gap 5 of the parking lock wheel 2 intervenes. If the vehicle is on a slope, the resulting load on the actuator 6 even higher. Therefore, a relatively high actuator current is measured in the actuator path window AWF.

But now lies, as in 5d represented, the tooth of the park pawl 8th on a tooth 4 of the parking lock wheel 2 , no load from the parking mechanics 2 . 8th . 11 on the actor 6 transferred because of the locking wedge 11 and the spindle 7 are decoupled from each other ( 4 ). As a result, only a relatively low actuator current is measured in Aktorwegfenster AWF, which is below the current limit GW. If the condition "tooth on tooth" is detected, then the vehicle can briefly be put into oscillation, so that the parking pawl 8th in a tooth gap 5 of the parking lock wheel 2 slips.

When accelerating the actuator 6 the actuator current exceeds the limit value GW by a multiple, because a big load has to be overcome to get the actor 6 to set in motion. Therefore, the measurement of the load-dependent actuator current must take place within the Aktorwegfensters AWF, in which the acceleration phase of the actuator 6 has already ended safely and the actuator is at a standstill.

After the measurement of the Aktorstromes and the comparison with the current limit GW is the actuator 6 back to the predefined position for inserting the parking brake 1 scaled back. In order to prevent the vehicle from rolling away during the state determination phase, a service brake or a parking brake of the vehicle is engaged in this phase.

LIST OF REFERENCE NUMBERS

1

parking lock

2

parking gear

3

intermediate shaft

4

tooth

5

gap

6

actuator

7

spindle

8th

parking pawl

9

housing frame

10

return spring

11

locking wedge

12

biasing spring

13

position sensor

14

current sensor

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008000177 A1 [0003]

Claims (7)

Method for determining a state of a parking brake of a vehicle, in which a parking pawl (8) by an actuator (6) automatically in a parking lock gear (2) positively latched, characterized in that is determined in response to a load-dependent actuator current, whether the parking brake (1) is securely inserted or a tooth of the parking pawl (8) on a tooth (5) of the parking lock gear (1) is. Method according to Claim 1 , characterized in that the measured load-dependent actuator current is compared with a current limit (GW) and when exceeding the current limit (GW) by the measured load-dependent actuator current to a safe engagement of the parking brake (1) or falls below the current limit (GW) by the measured load-dependent actuator current to a standing of a tooth of the parking pawl (8) on a tooth (4) of the parking lock gear (2) is closed. Method according to Claim 1 or 2 , characterized in that after the process of the actuator (6) in a position that is required for engaging the parking brake (1), the actuator (6) traced back a predefined way and then the current load-dependent actuator current is measured, which is the current limit (GW) is compared. Method according to Claim 3 , characterized in that the current load-dependent actuator current in an Aktorwegfenster (AWF) of the predefined path of the actuator (6) is measured, in which no movement of the actuator (6). Method according to at least one of the preceding claims, characterized in that the predefined path, by which the actuator (6) is returned, is at most 1 to 2 mm. Method according to at least one of the preceding claims, characterized in that the actuator (6) after the comparison of the current load-dependent Aktorstromes with the current limit (GW) is moved back into the position that is required for inserting the parking brake (1). Method according to at least one of the preceding claims, characterized in that the vehicle is secured during the measurement of the current load-dependent actuator current by an on-board brake.

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