DE102006033473B4 - Method for operating a brake with an emergency release device and corresponding brake - Google Patents

Abstract

Method for operating a brake (18) with an emergency release device (12) for emergency opening of the brake (18), in which the emergency release device (12) changes from a service brake position (II) to an emergency release position (III), characterized by a position control of the emergency release device (12) 12) in the service brake position (II), wherein parameters for the position control based on a clamping force (FZ) are adjusted.

Description

The present invention relates to a method for operating a brake with an emergency release device and a corresponding brake according to the preambles of the independent claims. The present invention further relates to a corresponding computing unit, a computer program and a computer program product.

State of the art

Although reference will be made hereafter essentially to self-energizing electromechanical brakes, the invention is not limited thereto. It applies equally to all (electric) brakes with an emergency release device for emergency opening of the brake in the event of a fault or in the event of a blockage, for example in the case of a spindle break.

Self-energizing electromechanical brakes usually include an electrically actuated actuator (brake actuator), usually an electric motor having a first brake element or friction member with a friction lining against a second element to be braked, such. B. a brake disc, presses or dissolves. In a brake operation, the friction member is entrained by the kinetic energy of the element to be braked and amplifies the braking effect automatically (self-energizing).

Self-energizing electromechanical brakes are typically implemented as wedge brakes. Such a wedge brake is z. B. in the DE 198 19 564 C2 described and sufficiently known from many other documents. As a rule, the wedge element is dimensioned so that the tangent of the wedge angle α corresponds approximately to an expected coefficient of friction μ between the friction member and the element to be braked.

In this ideal case, the wedge element is neither drawn into nor pressed out of the gap, so that the force to be applied by the actuator is zero. In case of unfavorable, d. H. high, coefficients of friction between the friction member and abzubremsendem element, however, are relatively high tensile forces applied by the actuator to hold the friction member and prevent it from slipping. If the actuator fails in this state, the friction member is taken unhindered and the brake can block suddenly. In the case of a motor vehicle wheel brake this must be prevented in any case.

In order to prevent the brake from locking, various emergency release devices are known from the prior art. Such emergency release device is intended to be used in a serious misconduct, such. As a power failure or a mechanical Aktuatordefekt to fully reduce the clamping force of the brake. For this purpose, the emergency release device usually maintains a specific operating position by means of a further actuator provided (emergency release actuator) or electric motor. In the event of a fault, it automatically moves, for example, under the action of force, for example the application force or a spring force, into a release position in which the brake fully opens. Thereafter, the brake is no longer usable until the emergency release device by the driver or user manually or in a workshop is returned to the operating position. Unintentional triggering should therefore be avoided.

The force which the emergency release actuator must expend to keep the emergency release device in the operating position is usually dependent on the frictional force of the brake. The actuator must also comply with the operating position exactly when the braking torque varies rapidly. If the associated regulation can no longer compensate for a rapid variation, an undesired transition of the emergency release device into the release position may occur. As a result, the brake can no longer provide braking power, which can lead to critical vehicle conditions or even accidents. In the prior art, no approaches are known to solve this problem, since such brakes are a relatively new technology.

The present invention is therefore based on the object to provide a solution with which the described problems are overcome and the operation of a brake with an emergency release device is improved.

This object is achieved by a method for operating a brake with an emergency release device and a corresponding brake with the features of the independent claims. Advantageous embodiments are the subject of the dependent claims and the following description.

According to the invention, a position control of the emergency release device in the service brake position is provided in a brake with an emergency release device with a service brake position and an emergency release position, wherein control parameters for the position control based on, d. H. depending on, a clamping force to be adjusted, in particular based on, or as a function of a temporal development of the clamping force. A suitable motor vehicle brake has in particular a first brake element, a second brake element and an actuator for pressing the first to the second brake element and for releasing thereof.

It is preferably a self-energizing brake.

It is preferably a brake for a motor vehicle.

In the control, the actual position value is expediently detected as a controlled variable and adjusted to the position setpoint as a reference variable. As usual, the control can be adjusted via control parameters. Suitable parameters are, for example, the proportional component (P), the integral component (I) and the damping component (D). According to the invention, the control parameters are adjusted based on the application force and in particular their time evolution. In conventional regulations, the actual value always follows the target value when the control environment changes, since a certain computing and positioning time is necessary. This can mean that certain requirements can not be responded to in a timely manner. In the method according to the invention, the control parameters are adapted by a prediction strategy for the engine torque or the holding force of another holding member. As a result, the control with its parameters substantially without dead times, which are usually generated by sensors and software loops, are adapted to the application and / or friction force. As a result, with less computational effort a more accurate and faster result of the position control and a saving of system resources can be achieved.

Advantageously, the parameters for the position control of the emergency release device are adjusted based on a linear extrapolation of the application force over time. It is an easy-to-do, yet effective way of adapting.

It is also expedient if the parameters for the position control of the emergency release device are adapted over time based on a polynomial extrapolation of the application force. In a polynomial sentence, the result can be improved with a certain increase of the computational effort.

It is particularly advantageous if the parameters for the position control of the emergency release device are adjusted based on a application force request of a central brake control device. As a central brake control device, in particular a control device with integrated slip control (antilock braking system, ABS) or vehicle stability algorithms can be used. This allows the position control in a particularly simple manner to take into account that the clamping dynamics of a brake abruptly changes when reaching the desired application force. In the case of an ABS control, this approach is particularly advantageous for the position control of the emergency release device to use, because on the one hand, the application force request to the brake actuator stochastically changes, whereas the brake actuator on the other hand, a changed specification of the application force will follow only with a certain delay. The position control thus obtains the possibility of determining the application force dynamics substantially in a forward-looking manner.

Advantageously, the parameters for the position control of the emergency release device are adjusted based on a relationship between the application force and an associated drive torque of the actuator. The moment / force ratio (Nm / kN) between the necessary engine torque and the application force can be determined regularly, especially at low application forces, and introduced into the control parameters. This has a particularly favorable effect on the control since the said ratio can vary within a wide range up to a factor of 4.

A brake according to the invention has an emergency release device, a position control device for a position control of the emergency release device in the service brake position and calculation and adjustment means for adjusting parameters for the position control based on a calculation taking into account a clamping force. Advantageously, it also has means to perform an embodiment of the method according to the invention.

A computing unit according to the invention has calculation and adaptation means for adapting parameters for position control based on a calculation taking into account a clamping force. Advantageously, the calculation and adaptation means can be designed to carry out other embodiments of the method according to the invention.

Preferably, the arithmetic unit is a position control device.

A computer or microprocessor program according to the invention contains program code means for carrying out a method according to the invention when the computer program is executed on a computer or a corresponding computing unit, in particular a computer unit according to the invention, in particular a control unit in a motor vehicle.

A computer or microprocessor program product according to the invention contains program code means which are stored on a machine or computer-readable data carrier in order to carry out a method according to the invention, if the program product is executed on a computer, a microprocessor or on a corresponding computing unit, in particular a computer unit according to the invention, in particular a control unit in a motor vehicle. Suitable data carriers are in particular floppy disks, hard disks, ROM, flash memory, EEPROMs, CD-ROMs, etc. Also a download of a program via computer networks (Internet, Intranet, etc.) and vehicle networks (body bus, infotainment bus, etc.) or air interfaces (Mobile) is possible.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention is illustrated schematically with reference to an embodiment in the drawing and will be described below in detail with reference to the drawings.

figure description

1 shows a schematic side view of a self-energizing brake with a emergency release with position control according to an embodiment of the invention;

2 shows the curve of a cam 1 ;

3a shows a schematic representation of an emergency release position of the emergency release device 1 ;

3b shows a side view of the emergency release device 1 in the emergency release position;

4a shows a schematic representation of a service brake position of the emergency release device 1 ;

4b shows a side view of the emergency release device 1 in the service brake position;

5a shows a schematic representation of a parking brake position of the emergency release device 1 ;

5b shows a side view of the emergency release device 1 in the park brake position;

6 shows a graphical plot of a clamping force over time with a linear extrapolation;

7 shows a graphical application of a clamping force over time in an ABS braking;

8a shows a section 7 with a prediction based on a linear extrapolation; and

8b shows a section 7 with a prediction based on a clamping force request of a brake control device.

1 shows a schematic side view of a self-energizing brake according to an embodiment of the invention. The actual brake mechanism is in total with the reference numeral 18 characterized. In the brake shown here 18 it is a known motor vehicle wheel brake with a movable wedge plate 2 that by an actuator 31 in the direction of the arrow A is movable to determine or release the brake.

The movable wedge plate 2 has at its front (bottom) a brake pad 1 on, against the friction surface of a brake disc 3 acts. At the back of the wedge plate 2 are several wedge surfaces 29 provided, which are located over intermediate rolling bearings 4 on an opposite wedge surface 5 support. The opposite wedge surface 5 is on a printing plate 6 arranged.

Upon actuation of the brake 18 the wedge plate moves 2 with the brake pad 1 along a through the wedge surfaces 5 . 29 predetermined movement path parallel and perpendicular to the brake disc 3 , The rolling bearings 4 serve in particular to reduce the sliding friction. The movable wedge plate 2 when approaching the brake disc 3 taken from this and thus pushes even stronger against the brake disc 3 (Self-reinforcement).

The illustrated wedge brake is equipped with a Nacheinstelleinrichtung and an emergency release device, here in each case as a whole with the reference numerals 7 respectively. 12 are designated. The adjusting device 7 serves to readjust the clearance, especially when brakes are worn. It may be used advantageously but not necessary in combination with the invention. The emergency release is used to quickly release the brake in case of failure, such. B. a power failure.

The adjusting device 7 essentially comprises a wedge 8th and a spindle 9 , The wedge 8th has an internal thread (not shown) and can be rotated by turning the spindle 9 parallel to the printing plate 6 in Direction of the arrow B are adjusted. A wedge surface 26 of the wedge 8th slides on a corresponding wedge surface 27 an abutment element 10 along, attached to a caliper 11 supported. In a wedge actuation, the pressure plate move 6 and all related elements ( 7 . 12 . 16 . 17 . 28 ) in the direction of arrow C on the brake disc 3 to or from this way. By turning the spindle 9 thus can the clearance between brake pad 1 and brake disc 3 can be adjusted as desired.

The wedge arrangement also serves to divert a portion of the application force F _Z transverse to the application force F _Z. The derived force F _Q is through the spindle 9 and the emergency release device 12 in a second abutment 17 directed, with the pressure plate 6 is firmly connected. The entire arrangement, consisting of the adjusting device 7 , the emergency release device 12 and a motor drive 16 , therefore moves in the direction of arrow C.

The emergency release device 12 has two cams 13 . 14 on, dealing with their curve surfaces 19 face. Between the two cams 13 . 14 are several rolling elements 15 arranged, which are held by a cage and together represent a rolling bearing. In the illustrated embodiment, axial cams are used. Optionally, but also radial cam could be used.

The in the 1 left cam 14 is non-rotatable with the spindle 9 connected. The other cam 13 is rotatable on the abutment 17 stored and powered by an electric motor 16 over a belt 28 driven. The two cams 13 . 14 Depending on the operating mode, they can be rotated either against each other or together, ie synchronously. When the two cams 13 . 14 rotate against each other, the distance between the discs changes. This change in length is via the spindle 9 , the wedge 8th and the pressure plate 6 on the wedge element 2 with the brake pad 1 transfer. If the two cams 13 . 14 on the other hand be turned simultaneously, the adjusting device 7 pressed and thus adjusted the clearance.

The cams 13 . 14 have a characteristic curve with various curve segments that define different operating states of the emergency release device, namely in particular a service brake position, an emergency release position and a parking brake position. The individual curve segments are each used in the corresponding operating state of the emergency release device.

2 shows an example of a curve 19 one of the cams 13 respectively. 14 , As can be seen, the curve includes 19 several segments 20 - 25 in different modes of the brake 18 be used. This curve 19 Repeats several times periodically along the circumference of a cam 13 . 14 wherein each period is a rolling element 15 , preferably a ball, is assigned. (In the present example, however, there are several rolling elements 15 shown to the main operating positions of the cam discs 13 . 14 The essential positions are a parking brake position I , a service brake position II and an emergency release position III , In this case, the emergency release device is, for example, in the emergency release position III when the rolling elements 15 on both cams 13 . 14 in the segments 20 It is understood that the parking brake position is provided only as an option and the invention is generally applicable to emergency release devices with at least two positions.

In normal operation, the rolling elements or the rolling bearing 15 and the cams 13 . 14 in the service brake position II arranged. The rolling bearing 15 is on a segment 21 in the direction of the emergency release position III is inclined. The slope of this segment 21 is chosen so that at axial load on the cams 13 . 14 acting torque substantially less than a breakaway torque M _{L of} the spindle 9 is. This will prevent the spindle 9 during a braking operation rotates. The slope of the segment 21 may be for example about 1 °.

Around the cam 13 upon actuation of the brake 18 in the service brake position II to hold, a position control according to the invention is performed. This is the engine 16 from a position control device 30 controlled. The position control device 30 For example, data relating to the current clamping force F _{Z are} fed, which is indicated by an arrow 32 is pictured. The position control device 30 has calculation and adaptation means which are an adaptation of control parameters based on a temporal development of the application force F _z , in the present example due to a linear extrapolation according to 6 , make. This improves the position control.

To move from the service brake position II in the parking brake position I to get to, is the cam 13 from the engine 16 driven accordingly. The rolling bearing 15 runs over a curve segment 22 and the emergency release moves to the park brake position I , The movement increases the distance between the cams 13 . 14 , causing the brake 18 becomes increasingly tense. The segment 22 has a slightly larger slope than the segment 21 that z. B. can be 1.2 °. The slope of the transition segment 22 is relatively uncritical, but it should be ensured that the rolling elements 15 can get into the parking brake position in the course of the application movement. In the parking brake position I is the associated segment 23 the curve 19 designed such that substantially no torque on the cams 13 . 14 acts. The curve segment 23 has the form of an energetic minimum or a kind of catch mark, in which the rolling bearing 15 can rest. One to the segment 23 adjacent curve segment 25 on the other hand has such a high pitch that the breakaway torque M _{L of} the spindle 9 is clearly exceeded and the spindle 9 turns when the cam 14 from the engine 16 is driven. This allows the two discs 13 . 14 be turned together. The curve segment 25 forms a stop for the rolling elements 15 ,

On the service brake position II follows in the other direction an emergency release position III , The associated segment 20 has the form of an energetic minimum. In this state, the distance between the cam discs 13 . 14 minimal, leaving the wedge 8th (please refer 1 ) can move far to the right and the brake 18 completely releases. The contour of the segment 20 is preferably designed so that the brake 18 can not be stretched even at maximum actuation.

Emergency release of the brake 18 In essence, this happens as follows: in case of power failure, the engine can 16 the disc 13 no longer hold, so that the disc 13 opposite the cam 14 automatically in the emergency release position III twisted. The rolling bearing 15 rolls over the segment 24 in the emergency release position III , This can happen within a few milliseconds. The slope of the segment 24 is chosen so that the transition to the emergency release position III runs very fast. You can z. B. 25 °. In addition, biasing elements such. B. springs may be provided which bias the emergency release device in the direction of the emergency release position. To complicate a faulty release of the emergency release device or even prevent the position control according to the invention is performed.

The 3 to 5 show the position of the cams 13 . 14 in the individual positions I to III , It is in 3a first the emergency release position III shown. As can be seen, the rolling element is located 15 between opposing emergency release segments 20 the cams 13 . 14 , The minimum distance h1 of the cam discs 13 . 14 is preferably a few millimeters, for example about 6 mm, lower than in the service brake position II ( 4a ). 3b shows an associated side view of the cams 13 . 14 in which the cams in the emergency release position III are located.

4a shows the service brake position II the cams 13 . 14 in which are the rolling elements 15 on opposite segments 21 are located. The distance h is here designated by the value h0 and by a few millimeters larger than in the emergency release position of 3a , 4b shows an associated side view of the cams 13 . 14 in which the cams in the service brake position II are located.

5a finally shows the parking brake position III the cams 13 . 14 , The rolling elements 15 are located between opposite sections of the curve 23 , Compared to the representation of 4a has the distance h of the two cams 13 . 14 increased again and has a value h2, which is preferably something (up to a few millimeters, for example, 0.7 mm) greater than h0. 5b shows an associated side view of the cams 13 . 14 in which the cams in the parking brake position I are located.

In 6 is a diagram 60 in which values of the application force F _z are plotted against the time t. The application force F _z is on a Y-axis 62 against time t on an x-axis 61 applied. In the diagram 60 is the temporal evolution of Zuspannkraft F _z shown, starting with a first value 63 a set of values 63 to 67 is applied, which represent an increasing over time clamping force.

In the illustrated embodiment of the invention, a linear extrapolation is performed to determine the likely next value of the application force. This will be a linear fit 69 carried out as known in the art. On the basis of the linear extrapolation, an expected closest value results 68 the application force F _z . The number of values used for extrapolation depends in particular on the time difference between two values. The exact determination of the number of values, the associated time difference, the type of extrapolation, etc. is preferably adapted to the respective brake or emergency release device.

In 7 is a diagram 70 in which the application force F _{z of} a brake is plotted against the time t. The application force F _z is on a y-axis 72 against time t on an x-axis 71 applied. In the diagram 70 is the temporal evolution 73 the application force F _{z shown} during an ABS braking. The illustrated application force curve is composed of individual measured values (not shown), which were recorded in each case at a time interval of 2 ms.

It can be seen that the value of the application force F _z regularly rises to a high value and then drops relatively quickly to a low value. For example, such a stage of Zuspannkraftverlaufs up to a maximum value 74 shown in the ABS-controlled release of the brake to a value 75 drops. A section 76 of Zuspannkraftverlaufs is in the 8a and 8b shown enlarged.

In the 8a and 8b is each a diagram 80 pictured in which the neckline 76 the Zuspannkraftverlaufs 73 out 7 is shown enlarged. In 8a is a forecast history 81 dashed lines shown for the clamping force. The forecast history 81 the clamping force is based on a linear extrapolation of the measured curve 73 in which the application force requirement is determined at a time t _n by the linear extrapolation of the preceding values t _n-1 to t _n-3 . In the case of a sudden change in the application force requirement 73 or their temporal derivative results in this approach of linear extrapolation a significant error of the prediction process 81 , In 8b is a forecast history 82 dashed lines shown for the clamping force. The forecast history 82 the application force is based on a application force request of a central brake control device. It can be seen that the prediction process 82 the application force in about a time shift of the measured course 73 equivalent. In the adjustment of the parameters based on a Zuspannkraftanforderung a central brake control unit, the value of the application force is transmitted to a position control device of the brake control unit in the example shown, which is also transmitted as a request to the brakes. Therefore, the position control device has the expected delivery force value in advance and can adjust the emergency release device accordingly and adjust the control parameters.

It is understood that the brake and emergency release device shown should be understood as illustrative and not limiting. Likewise, differently designed brakes or emergency release devices with or without adjustment mechanism and with two or more positions, which may also be arranged directly in the power flow can be used.

LIST OF REFERENCE NUMBERS

1

brake lining

2

wedge plate

3

brake disc

4

roller bearing

5

wedge surface

6

printing plate

7

Nacheinstelleinrichtung

8th

wedge

9

spindle

10

Abutment element

11

caliper

12

emergency release

13, 14

cams

15

rolling elements

16

drive

17

abutment

18

brake

19

curved surfaces

20-25

segments

26

wedge surface

27

wedge surface

28

locking lugs

29

wedge surfaces

30

Position locking device

31

actuator

32

data feed

60

diagram

61

X axis

62

y-axis

63-67

readings

68

extrapolated value

69

linear adjustment

70

diagram

71

X axis

72

y-axis

73

Zuspannkraftverlauf

74

high value of the clamping force

75

low value of the clamping force

76

neckline

81

Prediction curve based on linear extrapolation

82

Prediction course based on a clamping force request of a brake control device

F _Q

derived force

F _Z

clamping force

t

Time

I

Parking brake position

II

Service brake position

III

Notlöseposition

Claims (15)

Method for operating a brake ( 18 ) with an emergency release device ( 12 ) for emergency opening of the brake ( 18 ), in which the emergency release device ( 12 ) of a service brake position ( II ) in an emergency release position ( III ), characterized by a position control of the emergency release device ( 12 ) in the service brake position ( II ), wherein parameters for the position control based on a clamping force (F _Z ) are adjusted. A method according to claim 1, characterized in that the parameters for the position control based on a temporal evolution of the application force (F _Z ) are adjusted. Method according to claim 2, characterized in that the parameters for the Position control based on a linear extrapolation of the clamping force (F _Z ) over time (t) are adjusted. A method according to claim 2 or 3, characterized in that the parameters for the position control based on a polynomial extrapolation of the application force (F _Z ) over time (t) are adjusted. Method according to one of the preceding claims, characterized in that the parameters for the position control are adjusted based on a clamping force request of a central brake control device. Method according to one of the preceding claims, characterized in that the parameters for the position control based on a ratio between the application force (F _Z ) and an associated drive torque of a brake actuator ( 31 ) to close the brake. Brake with an emergency release device ( 12 ) for emergency opening of the brake ( 18 ), in which the emergency release device ( 12 ) of a service brake position ( II ) in an emergency release position ( III ), characterized by a position control device ( 30 ) for a position control of the emergency release device ( 12 ) in the service brake position ( II ) and calculating and adjusting means for adjusting position control parameters based on a calculation taking into consideration a tightening force (F _z ). Brake according to claim 7, characterized in that the calculation and adaptation means comprise means for temporally developing the application force (F _Z ). Brake according to Claim 8, characterized in that the calculation and adjustment means comprise means for linearly extrapolating the application force (F _Z ) over time (t). Brake according to claim 8 or 9, characterized in that the calculation and adaptation means comprise means for polynomial extrapolation of the application force (F _Z ) over time (t). Brake according to one of claims 7 to 10, characterized in that the calculation and adjustment means for receiving a application force value are connected to a central brake control device. Brake according to one of claims 7 to 11, characterized in that the position control device ( 30 ) comprises the calculating means and / or the adjusting means. Arithmetic unit characterized by calculating and adapting means for adjusting parameters for a position control of an emergency release device ( 12 ) in a service brake position ( II ) based on a calculation taking into account a clamping force (F _Z ). Computer program with program code means for carrying out the steps of a method according to one of claims 1 to 6, when the computer program is executed on a computer or a corresponding computing unit. A computer program product comprising program code means stored on a computer-readable medium for carrying out the steps of a method according to any one of claims 1 to 6 when the computer program product is executed on a computer or on a corresponding computing unit.

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