DE102007035541A1 - Electromechanically operated parking brake for a vehicle comprises devices for changing the current consumption of an electromechanical actuator so that certain values of the locking force are determined beforehand - Google Patents

Abstract

Electromechanically operated parking brake comprises devices (9) for changing the current consumption of an electromechanical actuator (15) so that certain values of the locking force are determined beforehand. An independent claim is also included for a method for operating an electromechanically operated parking brake. Preferred Features: The devices for changing the current consumption of an electromechanical actuator are formed in such a way that they effect a significant change of the current consumption during tightening or loosening of the parking brake.

Description

The The present invention relates to an electromechanically operable one Parking brake for Motor vehicles with at least one electromechanical actuator, the rotational movement of which is converted by an actuating unit in a translational movement is and at least one brake member shifts so that at least a brake pad connected to the brake member with a locking force pressed against a fixedly connected to a motor vehicle rotor is, wherein during the application and / or release of the parking brake, the current consumption of the electromechanical actuator can be determined. It also concerns the invention a method for operating the electromechanically actuated Parking brake.

A general task of prior art method of electromechanical actuated Parking brake is it, as far as possible a sufficient locking force to adjust exactly. For a sufficient locking force is usually at least one Force level required, which is sufficient, the motor vehicle permissible Total weight on a slope with 30% slope safe and durable to keep. For this purpose, the measured variable "current" with which the electromechanical actuator stands operated as stream / time history available. Stand other measures such as for example, a rotary encoder value from the electromechanical actuator or the traveled Travel available, so can this information to increase the positioning accuracy can be used. This additional information is available however often not available, because this additional information due to the other sensors, the for this additional measured variables necessary are, additional Cause costs.

From the DE 10 2004 60 454 A1 is a method and apparatus for actuating a parking brake system for vehicles. The parking brake system has an electromotive actuatable actuating unit for detecting or releasing the parking brake system. To determine a defined locking force is specified and saved non-volatile. When the parking brake system is actuated, a current sensor emits a signal when a defined current intensity is reached. This signal is used to control the parking brake system, so for example to shut down the motor drive when a predetermined current value is reached, which corresponds to a certain value of the locking force. The problem with such a current control is that absolute current values are determined. However, the absolute current value, which corresponds to a certain value of the locking force is strongly dependent on the ambient temperature, ie a current value that corresponds to an adequate locking force at an ambient temperature of 20 ° C, ent speaks at -10 ° C by no means a sufficient locking force.

It is therefore an object of the present invention, a parking brake system of the type mentioned and a method for their operation to the effect to improve that independently from the ambient temperature safe operation and reliable setting the locking force only on the basis of the determined current consumption of the electromechanical actuator is enabled.

These Task is inventively characterized solved, that means are provided which reduce the current consumption of the electromechanical Change the actuator in such a way that certain values of the locking force can be determined beforehand. The funds are designed such that they have a significant change the current consumption of the electromechanical actuator during application or when loosening effect the parking brake to a predetermined value Close the locking force leaves.

at an advantageous development, the funds are at least a prestressed spring element is formed, which reduces the rigidity of the Parking brake influenced. The at least one spring element is at a preferred embodiment as a biased plate spring package in the power flow of the parking brake or as a preloaded torsion spring formed in the torque flux of the parking brake.

alternative the means are formed by at least one slip clutch.

The Object of the present invention is according to the method thereby solved, that the current consumption of the electromechanical actuator when tightening and / or solving the parking brake is evaluated so that previously determined values the locking force can be determined.

there is provided that the determination of the predetermined values by Determination of inflection points in the signal curve of the current consumption of the electromechanical actuator, which is based on a determination of set locking force and / or to a position determination be evaluated out of the brake member.

at a preferred embodiment the method according to the invention the slope of the waveform is the current consumption of the electromechanical Actuators are determined and based on a determination of the set Locking force and / or to a position determination of the brake member be evaluated.

In an advantageous development of the method according to the invention, it is provided that the absolute current value of the current consumption of the electromechanical actuator is determined and is used for plausibility of the determined Feststellkraftwertes.

A particularly advantageous embodiment of the method according to the invention provides that the application and / or release of the parking brake in Phases is divided, the current consumption of the electromechanical Actuator is evaluated for phase detection.

there is the application of the parking brake in a start-up phase, a Freewheeling phase, a landing phase, an application phase and a safety phase divided while the release the parking brake in a start-up phase, a reset phase, a Lüftspielphase, divided a freewheeling phase and a stop phase.

The Phases are determined using a model, which is a learning process supplied to take account of aging and wear processes. In the model just mentioned, other influencing parameters such as Ambient temperature and the temperature of the rotor taken into account and their influences minimized.

The The invention will be described below with reference to two exemplary embodiments closer with the enclosed drawing explained. In the drawing show:

1 a schematic representation of an electromechanically actuated parking brake for motor vehicles,

2 a diagram showing the current consumption of the electromechanical actuator, the locking force and the position of the brake member over time when applying the parking brake;

3a , b, c representations of the phase division of the current consumption of the electromechanical actuator, the locking force and the speed of the electromechanical actuator when applying the parking brake and

4a , b, c a the 3a to c corresponding representation when releasing the parking brake.

The The present invention includes both electromechanically operable ones Parking brakes acting on a disc brake, as well as parking brakes, which act on a drum brake. The process according to the invention is corresponding applicable to these different parking brakes.

Based on 1 For example, an electromechanically actuated parking brake is described, which essentially consists of a per se known drum brake of the "duo-servo" type, as well as an electromechanical actuator 15 consists. The drum brake type "Duo-Servo" has a brake drum only partially shown 5 acting as a rotor 5 firmly connected to a motor vehicle wheel, one with brake pads 10 . 11 provided pair of brake shoes 3 . 4 , which act as a braking member, and an operating unit 2 on. The operating unit 2 is as an expansion lock 2 trained and sets the rotational movement of the electromechanical actuator 15 in a translational motion and can the brake pads 10 . 11 the brake shoes 3 . 4 with the inside of the brake drum 5 engage. Characteristic of the drum brake type "Duo-Servo" is a freely movable or floating support device 16 that the spreader lock 2 opposite and between the brake shoes 3 . 4 is arranged. The just mentioned Spreizschloss 2 is essentially a threaded nut spindle arrangement 8th and two plungers 13 . 14 formed, which is a pressure piece 13 with the spindle 7 and the other pressure piece 14 with the threaded nut 6 interacts. As in 1 Verdeut is light, the threaded nut spindle assembly 8th from a helical gear 1 This is actuated by the electromechanical actuator 15 with the interposition of a reduction gear shown only schematically 12 is driven. For this purpose, the threaded nut 6 on the outer surface of a toothing, which is parallel to the axis of the threaded nut 6 runs. With this straight toothing of the threaded nut 6 forms the just mentioned helical gear 1 a helical gear. Upon actuation of the helical gear 1 through the electromechanical actuator 15 becomes the threaded nut 6 put in a rotational movement. Due to this rotational movement of the threaded nut 6 completes the spindle 7 the nut-spindle arrangement 8th a translational movement and brings the two brake shoes 3 . 4 with the desired locking force with the brake drum 5 engaged.

To perform a parking brake operation, either the reduction gear 12 or the nut assembly 8th self-locking trained. By this measure, the brake shoes remain 3 . 4 in the de-energized state of the electromechanical actuator 15 with the brake drum 5 engaged.

If the motor vehicle is parked on a slope, after setting the desired application force, a slight movement of the motor vehicle in the direction of the slope force. This also turns the brake drum 5 by a certain angular amount until it is characteristic for a drum brake of the "duo servo" type a self-reinforcing effect is used. As a result, however, the desired clamping force is reduced. For this reason, it is envisaged that in the power flow between the threaded nut spindle assembly 8th and with the threaded nut 6 cooperating pressure piece 14 a spring element 9 is arranged, which compensates the just described reduction of the desired clamping force. In addition, it is possible that a release operation of the parking brake can not be performed when a cooling of the previously heated brake drum 5 entry. During this cooling, the brake drum completes 5 a slight shrinking process, after which the clamping force increases due to the high rigidity of the components located in the power flow. In this case it is possible that the electromechanical actuator 15 can not perform a release operation of the parking brake, since the clamping force is too large and the components located in the power flow have jammed. By the just mentioned, in 1 shown arrangement, this effect is also prevented. At the same time, the spring element serves to change the current consumption of the electromechanical actuator in such a way that certain values of the locking force can be determined beforehand, as described below with reference to FIG 2 will be explained in more detail.

As already mentioned at the beginning, The invention and the method according to the invention also relate on an electromechanically actuated Parking brake acting on a disc brake. This is the Brake member formed by a brake piston, which is designed as a threaded nut spindle unit operating unit is shifted, whereby a brake pad connected to the brake pad is pressed against the rotor acting as a brake disc.

In 2 is a characteristic course of the locking force F, the position S of the brake member or the Bremsba bridges 3 . 4 , the current consumption I and the voltage U when applying the parking brake. Of these measured quantities, only the current consumption I is available in the present method. One does not have to know unconditional values of the current consumption I - an approximate course is sufficient for the present method. In order to better explain the present method, the other mentioned measured variables, which are not available during operation of the electromechanically actuated parking brake, are plotted on the ordinate, while the time t is shown on the abscissa. The locking force F is shown in dashed lines, the position S of the brake shoes 3 . 4 is knotted and the current consumption I of the electromechanical actuator 15 is represented by a sequence of "+" symbols The voltage supply U is shown as a solid line.

At the beginning of in 2 shown time course is the parking brake in the released state, ie the position of the brake shoes 3 . 4 is "zero" and the locking force is also "zero", as in position 20 is shown at time t ₀ . position 21 shows that at the beginning of a Zuspannvorgangs a comparatively high starting current is necessary. At the time t ₁ ends this start-up phase and it closes until the time t _2, the so-called landing phase. At time t ₂ are the brake pads 10 . 11 for contact with the brake drum 5 come and accordingly increases when further move or spread the brake shoes 3 . 4 the locking force F, as is the case with position 23 is shown. The locking force F increases during the application phase until time t ₃ with a first slope. The current consumption I runs almost parallel. Then, at the instant t _3, the slope of the fixing force F bends and the course of the current consumption I describes at the position 23 a turning point. At this time t ₃ , the locking force is so great that the spring assembly 9 is compressed. Because the spring package 9 is biased, you know how large the locking force F at time t ₃ . If the spring assembly is preloaded, for example, to 2000 N, then the locking force F at the time t _{3 is} also 2000 N. The further spreading of the brake shoes 3 . 4 leads to a further compression of the spring assembly 9 , The locking force F does not increase as much between the times t ₃ and t ₄ as between the times t ₂ and t ₃ , since the locking force from the spring assembly 9 is absorbed. At time t ₄ is the spring package 9 completely compressed and pressed on block. The current consumption describes at time t ₄ a turning point and in turn follows almost parallel to the again sharply increasing locking force F.

At time t ₅ , the current consumption I reaches the maximum available current value I _max . At the same time there is no further displacement or spreading of the brake shoes 3 . 4 instead of and the position S of the brake shoes 3 . 4 does not change after time t ₅ . Because the brake shoes 3 . 4 are no longer spread apart, the locking force F after time t ₅ no longer increases.

It is crucial that through the spring package 9 the current consumption I of the electromechanical actuator 15 is changed so that in advance certain values of the locking force, namely the force on the spring package 9 is biased and the force value that is necessary to the spring assembly 9 to press on block, can be determined. These significant changes to the positions 23 and 24 can be determined in the current consumption of the electromechanical actuator.

The just described significant change in the current consumption of the electromechanical actuator 15 is in the described embodiment by the prestressed plate spring package 9 causes. This plate spring package 9 is located in the power flow of the parking brake and affects the stiffness of the entire parking brake. A preloaded torsion spring, which is arranged in the torque flow of the parking brake, is also suitable for the described change in the power consumption of the electromechanical actuator 15 to effect.

Another possibility, a significant change in the current consumption of the electromechanical actuator 15 To achieve, is the targeted influencing of the component stiffness course, for example by weakening of cross sections such that at a defined load height, an enlarged cross-section enters the power flow and thus increases the stiffness abruptly. Alternatively or additionally, the use of a slip clutch is conceivable, which specifies a maximum locking force before the slip clutch slips. A method for detecting the operation of a slip clutch is known from WO2006 / 024635 known.

The determination of the positions 23 and 24 in the current consumption, the previously determined values of the locking force or a specific position of the brake shoes 3 . 4 is determined by determining these inflection points 23 . 24 in the signal course. The different slope of the Signalver run between the times t ₂ and t ₃ , between t ₃ and t ₄ and t ₄ and t ₅ is also determined and used to determine the set locking force F. For plausibility, the absolute current value is measured and compared with previously determined values. In this context, a subdivision of the power consumption in phases makes sense, with subsequent phase detection is performed, as shown by the 3a to 3c is explained in more detail.

3a represents the basis of 2 described current consumption of the electromechanical actuator 15 while 3b represents the set locking force. 3c represents the number of revolutions of the electromechanical actuator. The application of the parking brake is in a start-up phase (phase 1), a freewheeling phase (phase 2), an application phase (phase 3), an application phase (phase 4) and a safety phase (phase 5) divided. During the start-up phase / phase 1 the electromechanical actuator runs 15 at. If less and less power is consumed in this phase, ie if there is a negative slope, but no constant current consumption, then there is still no locking force. The locking force is on the pressure pieces 13 . 14 equals zero. If the start-up phase / phase 1 is detected and a comparatively low current consumption remains constant for a certain time, then the free-running phase designated as phase 2 is detected. There is still no or only a small locking force.

Exceeds the current consumption of the electromechanical actuator 15 in the freewheeling phase / phase 2 a certain threshold and rises slightly, for example steadily with relatively low slope, then the landing phase is identified, which is characterized as phase 3. The application phase is designated phase 4 and is recognized when the current consumption in the application phase / phase 3 increases even more linearly. The spring element ensures in the application phase / phase 4 for differently stronger gradients with consideration of the break points. The current and force curve in the application phase / phase 4 are dependent on the design of the spring element used and can assume a different shape. Subsequently, the designated as phase 5 safety phase and the maximum set current consumption is achieved, which serves to secure the achieved in the application phase / phase 4 clamping force. The constant current profile in the safety phase 5 is due to a current limitation.

4a to c show according to a release operation of the electromechanically actuated parking brake. The release of the parking brake is divided into a start-up phase (phase 1), a reset phase (phase 2), a clearance phase (phase 3), a freewheeling phase (phase 4) and a stop phase (phase 5).

There are 5 phases to pass through during a Zuspann- and dissolution process. Phase 5, the stop phase, during a release operation is very important in order to clearly recognize that the parking brake has completely disengaged. The disadvantage of this is that the time required for tightening thereby becomes longer and also the durability of the electromechanical actuator 15 and other parts must be larger. Therefore, it is envisaged that the electromechanical actuator 15 after some time during phase 4, the freewheeling phase is switched off. The turn-off is dependent on many parameters, taking into account the Zeitin tervalle the phases of the last Zuspannvorgangs such as the overcoming time of the air gap in the last application process.

The phase 5 in a release operation should be set if a complete release of the brake is not unique, or for learning the air play time, for example, after a certain number of actuation. To shorten the clamping time despite phase 5 during a release operation, the electromechanical actuator 15 shortly after the end of phase 5, ie shortly in the opposite direction.

The electromechanical actuator 15 is not driven in a release operation without phase 5 to the stop and therefore the force of the electromechanical actuator is shortly before the end of phase 4 zero.

During a system development, in addition to the measurement of the current consumption of the electromechanical actuator 15 also the locking force according to the 3b and 4b and the speed of the electromechanical actuator 15 according to the 3c and 4c measured. Characteristics of the current consumption, the locking force and the speed are stored, which determine the set locking force and for determining the position of the brake shoes 3 . 4 serve. From the characteristics of the current consumption, the locking force and the speed of an overall model is created, which estimates the current applied locking force or the position of the brake member during a Zuspann- or release operation and the end of a process, that is, whether the parking brake is applied or released , clearly recognizes.

This Overall model considered the influencing parameters such as rotor temperature, outside temperature, load collective, Voltage supply, in the example, current-Feststellkraft-speed characteristics under different external conditions to be recorded.

1

screw gear

2

Actuator / expanding lock

3

Brake shoe / brake member

4

Brake shoe / brake member

5

Brake drum / rotor

6

threaded nut

7

spindle

8th

Threaded nut-spindle unit

9

spring element

10

brake lining

11

brake lining

12

Reduction gear

13

Pressure piece

14

Pressure piece

15

electromechanical actuator

16

Support device

Claims (12)

Electromechanically actuable parking brake for motor vehicles with at least one electromechanical actuator ( 15 ), whose rotational movement from an actuating unit ( 2 ) is converted into a translational movement and at least one brake member ( 3 . 4 ) such that at least one with the brake member ( 3 . 4 ) connected brake pad ( 10 . 11 ) with a locking force against a fixedly connected to a motor vehicle rotor ( 5 ) is pressed, wherein during the application and / or release of the parking brake, the current consumption of the electromechanical actuator ( 15 ), characterized in that means ( 9 ) are provided, the current consumption of the electromechanical actuator ( 15 ) in such a way that predetermined values of the locking force can be determined in advance. Electromechanically actuable parking brake according to claim 1, characterized in that the means ( 9 ) are designed such that they produce a significant change in the current consumption of the electromechanical actuator ( 15 ) when applying or releasing the parking brake, which suggests a predetermined value of the locking force. Electromechanically actuable parking brake according to claim 2, characterized in that the means ( 9 ) by at least one biased spring element ( 9 ), which affects the stiffness of the parking brake. Electromechanically actuated parking brake according to claim 3, characterized in that the at least one spring element ( 9 ) is designed as a prestressed plate spring package in the power flow of the parking brake or as a preloaded torsion spring in the torque flux of the parking brake. Electromechanically actuated parking brake according to Claim 2, characterized in that the means by at least a slip clutch are formed Method for operating an electromechanically actuatable parking brake for motor vehicles with at least one electromechanical actuator ( 15 ), whose rotational movement from an actuating unit ( 2 ) is converted into a translational movement and at least one brake member ( 3 . 4 ) such that at least one with the brake member ( 3 . 4 ) connected brake pad ( 10 . 11 ) with a locking force against a fixedly connected to a motor vehicle rotor ( 5 ) is pressed, wherein during the application and / or release of the parking brake, the current consumption of the electromechanical actuator ( 15 ), characterized in that the current consumption of the electromechanical actuator ( 15 ) is evaluated when applying and / or releasing the parking brake to the effect that predetermined values of the locking force are determined in advance. A method according to claim 6, characterized in that the determination of the predetermined values by determining inflection points ( 23 . 24 ) in the waveform of the current consumption of the electromechanical actuator ( 15 ), which is based on a Be mood of the set locking force and / or for determining the position of the brake member ( 3 . 4 ) be evaluated. A method according to claim 7, characterized in that the slope of the signal waveform of the current consumption of the electromechanical actuator ( 15 ) are determined and on a determination of the set locking force and / or on a position determination of the braking member ( 3 . 4 ) are evaluated. Method according to one of claims 6 to 7, characterized in that the absolute current value of the current consumption of the electromechanical actuator ( 15 ) is determined and is used for plausibility of the determined Feststellkraftwertes. Method according to one of claims 6 to 9, characterized in that the application and / or release of the parking brake is divided into phases, wherein the current consumption of the electromechanical actuator ( 15 ) is evaluated for phase detection. Method according to claim 10, characterized in that that the application of the parking brake in a start-up phase (phase 1), a freewheeling phase (phase 2), an application phase (phase 3), an application phase (Phase 4) and a security phase (Phase 5) is divided, while the Release the parking brake in a start-up phase (phase 1), a reset phase (phase 2), a Lüftspielphase (Phase 3), a freewheeling phase (Phase 4) and a stop phase (Phase 5) is divided. Method according to claim 11, characterized in that that the phases are determined with the help of a model, the one Learning method supplied to take account of aging and wear processes.