DE102012223104A1 - Brake holder for use in device for determining measure for braking force acting on disk brake of motor vehicle, has sensor device, by which displacement of brake holder induced by action of braking force is measured in direction - Google Patents

Abstract

The brake holder (1) has two lining guide rails (5a,5c) overlapping a brake disk, on which friction linings arranged on both sides of the brake disk are displaceably guided in the axial direction of the brake disk in a limited manner. A sensor device is provided, by which a displacement of the brake holder induced by the action of braking force is measured in a direction different from the displacement direction that is perpendicular to the axial direction of the brake disk. Independent claims are included for the following: (1) a device with a controlling- and regulating unit for determining a measure for braking force acting on a disk brake of a motor vehicle; and (2) a method for determining a measure for braking force acting on a disk brake of a motor vehicle.

Description

The invention relates to a brake holder for determining a measure of an effective braking force on a disc brake of a motor vehicle, which is fastened to the motor vehicle, the brake holder at least two brake disc cross-deck guide rails on which both sides of the brake disc arranged friction linings in the axial direction of the brake disc limited guidable, and comprises a sensor device, by means of which a caused by a braking force displacement of at least a portion of the brake holder, in particular a pad guide rail is measured in a first direction perpendicular to the axial direction of the brake disc, the sensor device a first and at least one further Sensor element whose relative movement is measured. It further relates to a corresponding device and a corresponding method.

Disc brakes for motor vehicles usually have a running on the hub of a wheel to be braked brake disc to which both sides friction linings are pressed during a braking operation. The friction linings are arranged in a caliper which spans the brake disk. Floating caliper brakes are preferably used in motor vehicles in which the actuator is arranged only on one side of the brake disc, but due to the floating saddle during a braking operation, the friction lining arranged on the other side of the brake disc is also pressed against the brake disc. The actuator can be operated hydraulically or - in the case of electromechanical brakes - by means of an electric motor.

For automatic brake control operations, in which active by a control and regulation unit and not (alone) by the driver brake pressure to be built in a brake, it is desirable to detect a currently operating braking force as accurate as possible so that the brake on the one hand as precisely as possible can be controlled and on the other hand, the expressed by the driver braking requests can be accurately implemented.

Technical proposals for detecting brake forces are already widely known from the prior art.

So will in the DE 10 2006 029 978 B3 a method for measuring the elastic expansion of a caliper by means of stretch marks as a measure of the clamping force or normal force described.

The DE 10 2005 013 142 A1 discloses a technical solution in which the measurement of the braking force or circumferential force on frame saddles by the displacement measurement of two mutually movable machine parts is performed.

From the DE 10 2008 042 298 A1 It is known to determine the expansion of the caliper by means of a arranged in a cavity of a yoke of the caliper rod-shaped, cantilever retainer for determining the clamping force of a disc brake by the movement of the free end of the holder is measured with a magnetic sensor.

In the WO 2012/059313 A1 a brake holder is described in which a partial displacement of the brake holder by means of a sensor device is measured to determine the circumferential force, wherein the sensor device comprises two sensor elements whose relative movement is detected to each other. For this purpose, the one arm of the brake holder of a floating caliper brake, which is loaded by the traction of the circumferential force between the outer brake pad and brake disc on the pad guide rail, used as a beam spring, the radian measure of the occurring under braking load bending angle of this beam spring measured and effective as a measure of the disc Cusp force is evaluated. For this purpose, the holding arm is designed with a tubular cavity, in which a rigid rod protrudes, which is anchored with one end mechanically fixed in this cavity and the free end shifts in bending of the support arm relative to the center of the opposite side of the cavity. The displacement is evaluated as a measure of the braking force on the disc and measured by two sensory partial components, namely the two above-mentioned sensor elements.

The invention has for its object to improve such a brake holder to the effect that additional measures of forces acting in the brake holder forces can be determined. Furthermore, a corresponding device and a corresponding method are to be specified.

With regard to the brake holder, this object is achieved in that by means of the sensor device in at least one other, different direction from the first direction a caused by the braking force displacement is measured.

Advantageous embodiments of the invention are the subject of the dependent claims.

The invention is based on the consideration that for control processes primarily a knowledge of the peripheral force is advantageous, since these are usually a represents a suitable measure of the size of the braking force. The sole knowledge of Zuspannkraft or normal force, ie the force with which the brake pads are pressed by the actuator against the brake disc, is only partially suitable because different friction between linings and disc leads to different levels of effective braking force.

Even more precise control of braking is possible when additional information about the forces acting in the brake is available. In particular, the friction coefficient for the friction acting between linings and brake disc is valuable information. In conjunction with the coefficient of friction between the wheel and the road surface, which can be determined by model calculations and / or slip measurements, braking processes can be regulated even more precisely, thereby shortening braking distances, which represents a decisive improvement in safety. This coefficient of friction results from the ratio of circumferential force and normal force.

As has now been recognized, additional measures of forces in the brake can be detected by making the sensor assembly capable of measuring partial displacements of the brake holder in a further direction different from the first direction. Different in this context means that two vectors, which are assigned to the two directions, are not colinear. The sensor arrangement thus measures directionally selective in two directions.

Preferably, the further direction is perpendicular to the axial direction of the brake disc. That is, the first direction and the further direction span a plane perpendicular to the axial direction of the brake disk. In this plane, both the circumferential force and the clamping force or normal force act and act as displacements of a portion of the support arms in this plane, so that by measuring directions in this plane, these forces can be precisely determined.

The first and the further direction are advantageously orthogonal to one another, so that in this way orthogonal components of the total force applied to the brake holder can be measured. The two measured components or directions can then be measured so that they also correspond to physically different forces, so that these forces can be determined independently of each other.

For detecting the acting forces, in particular the circumferential force and the clamping force, the further sensor element is advantageously designed as a direction-selective sensor, which detects a relative movement of the first and further sensor element in two spatial dimensions. This means that the signal produced by this sensor provides simultaneous information about shifts in both directions.

In a further preferred embodiment, two further sensor elements are provided, each of which measures the relative movement between itself and the first sensor element in each case in one direction. Accordingly, each signal of the two sensors separately provides information or data about the displacement in the measured direction. In this case, the two sensor elements are preferably aligned without an angle of rotation with respect to the measuring directions, so that the signals of the two sensor elements can be set directly in relation to the acting force. If a twist angle exists, trigonometric functions can be used. d. H. an effective rotation of the coordinate system that determine components of the forces.

The first and the further sensor element cooperate advantageously according to a magnetic measuring principle. This can be realized in particular by means of the anisotropic magnetoresistive (AMR) effect. In this case, for example, one of the sensor elements generates a, preferably rotationally symmetric, magnetic field, and the second or further sensor element reacts directionally or selectively to the magnetic field.

Alternatively, the first and the further sensor element can also interact according to an optical principle. In this case, the deflection of the first sensor element is preferably determined or measured optically by the further sensor element, in particular by registering light, for example by a laser beam. In this case, the first sensor element can be illuminated by a light source and the light on the other sensor element, which is preferably designed as a planar, photosensitive sensor, depending on the forces acting, distract.

The first sensor element preferably comprises an arrangement of a number of mirrors, in particular micromirrors, wherein the further sensor element is designed as a two-dimensional photosensitive sensor, in particular as a stationary surface array of photosensitive elements, wherein a laser is provided which is aligned with at least one mirror.

Advantageously, the first and further sensor elements are arranged on the brake holder. Thereby, the sensor device can be mounted easily and inexpensively. To achieve the highest possible resolution, this extends first sensor element preferably along a pad guide rail, so that when braking forces as large as possible displacement or deformation of the pad guide rail can be detected.

With regard to the device, the above-mentioned object is achieved according to the invention with a brake holder fastened to the motor vehicle and with a control and regulation unit, which is connected on the input side to the sensor device and performs a brake control based on at least one measurement signal of the sensor device. The control and regulation unit preferably comprises a processing logic for determining or determining a brake control variable and / or an acting brake force or an acting brake torque on the basis of at least one measurement signal of the sensor device.

With regard to the method, the above-mentioned object is achieved according to the invention by two displacements of at least one part of the brake holder caused by a braking force being measured by a sensor device having a first and at least one further sensor element, both of which are arranged on the brake holder.

In a preferred version of the method, a friction coefficient characterizing the friction between the brake pads and the brake disc is determined from the ratio of the displacements and / or the ratio of circumferential force to clamping force determined by means of the displacements.

The advantages of the invention are in particular that by measuring a second, at least partial displacement of the brake holder measured variables can be obtained to further forces acting in the brake and the brake holder and used in braking control operations. An orthogonal to the circumferential force measured component is a measure of the force acting on the brake clamping force and thus for the introduced via the brake actuator normal force. The present arrangement or sensor device uses this basic principle in order to obtain a measure of the effective application force on the brake while dispensing with pressure sensors and thus in a cost-effective and robust manner.

By determining displacements or deflections of the first sensor element in two orthogonal directions with the aid of at least one further sensor element, the circumferential force and the normal force can be determined simultaneously, from which further variables characterizing the brake state, such as the friction coefficient, can be determined.

An embodiment of the invention will be explained in more detail with reference to a drawing. In it show in a highly schematic representation:

1 a brake holder in a preferred embodiment for a floating caliper brake in a rear view,

2 the brake holder off 1 in a plan view,

3 the left arm of the brake holder according to the 1 and 2 in a perspective view,

4 an enlarged section of the support arm from the back view 1 in force-free condition with a superimposed coordinate system and a bar magnet in the force-free state,

5 the clipping according to 4 with a midpoint shift of the bar magnet due to a clamping force,

6 the clipping according to the 4 and 5 with a midpoint shift due to an interaction of a circumferential force and a tensile force,

7 Results of a simulation for the expected deflections, each as a function of an effective braking force, and

8th a sensor arrangement for detecting the parameters for circumferential force and clamping force.

Identical parts are provided with the same reference numerals in all figures.

An in 1 in a back presentation and in 2 in a plan view shown brake holder 1 for a designed as a disc brake floating caliper brake is screwed 2 with a chassis 3 a motor vehicle mechanically bolted stationary. The brake holder 1 has on both sides in each case a holding arm 5 . 5b each with a pad guide rail 5a . 5c on, wherein in a braking operation of the left-hand holding arm 5 is loaded by train.

The brake holder 1 points in the holding arm 5 a hole 4 through its neutral fiber. With reference to 3 is at a mounting end 7 the bore 4 as the first sensor element 6a a sensor device 16 (see 8th ) acting bar 6 made of magnetically conductive steel. In the unattached or free end of the rod 6 is a bar magnet 8th introduced, which consists essentially of a material of Element group of rare earths and thus has a very high magnetic energy density. Alternatively, conventional materials such as iron, cobalt, nickel or ferrite may be used.

In a braking operation, in which by the brake holder 1 acting forces undergoes this at different locations differently large shifts, the bar magnet is 8th towards a stationary coordinate system 8a move. The x-axis 8b points to the right while the y-axis 8c points upwards. Displacements of the bar magnet 8th in the direction of the negative x-axis 8b are symbolized on the basis of an arrow 8d Peripheral force FU caused while shifts in the direction of the y-axis 8c on one with an arrow 8e symbolized acting clamping force F _S are based. The circumferential force F _U thus acts in the direction of the negative x-axis 8b that is a transverse direction 20 which corresponds essentially to a direction through two identical parts of the two retaining arms 5 . 5b equivalent. The clamping force F _S acts in the direction of the positive y-axis, which is perpendicular to the transverse direction 20 and x-axis 8b is.

In 4 is an enlarged section of the upper part of the support arm 5 out 1 shown in an off-state, with the midpoint 18 of the coordinate system 8a with the force-free or rest position of the bar magnet 8th was reconciled. For reasons of clarity, only the end-side pole of the bar magnet is in the coordinate center 8th without its embedding in the staff 6 shown. You can still see the hole 4 into the bar magnet 8th carrying rod 6 is introduced.

The 5 again shows the section of the holding arm according to 4 with the difference that now a clamping force F _S in the positive direction of the y-axis 8c acts. Due to the effective clamping force F _S have bore 4 and bar magnet 8th in the positive direction of the y-axis 8c moved, with the bar magnet 8th is shown only in the force-free position, and the shifted end-side bore end is shown in dashed lines. This results in a shift ΔY (S), ie, the displacement in the Y direction is a function of the magnitude of the clamping force F _S.

In 6 is again the clipping according to the 4 and 5 shown, this time in the event that both a circumferential force F _U and a clamping force F _S act. Accordingly, have bar magnet 8th and bore 4 both in the y direction by the amount ΔY (S) and in the negative x direction by the amount Δ X (U), ie, the latter shift is a function of the magnitude of the attacking circumferential force F _U. This corresponds to these compared to the spatial dimensions of the brake holder 1 small displacements, the respective displacement about the radians to the bar magnet 8th is deflected.

The deflections or displacements ΔY (S) and ΔX (U) in micrometers to be expected during a specific braking operation as a function of an acting braking force F _U in the unit kN are in 7 represented and arise from a simulation calculation under the proviso of an assumed load distribution of 30% for the outer brake pad and 70% for the inner brake pad on the piston side. For both deflections, these values increase linearly with the braking force within a range of up to approx. 3 kN. The deflection .DELTA.X (U) then increases linearly even for larger braking forces up to about 12.5 kN, and then kinks with linear behavior, but less slope. The deflection ΔY (S) increases substantially quadratically as a function of the braking force due to the quadratic characteristic or spring characteristic of the brake caliper.

A section of the support arm 5 with a sensor device 16 for recording the measured quantities is in 8th shown. The sensor mechanics to which the bore 4 , the rod 6 and the bar magnet 8th which is the first sensor element 6a represents, ends in level AB. Between the levels AB and CD is a molded part 9 arranged of non-magnetic material and connected in a stationary manner with the sensor mechanism in the plane AB by gluing. Suitable non-magnetic materials for this purpose, for example, plastics, aluminum or mixtures thereof. Essential criteria for the selection of materials are strength and heat compatibility under the physical conditions prevailing in the brake caliper during a braking process.

The molding 9 on the one hand serves the precise guidance of a sensor head 10 and on the other the attachment of a sensor body 11 with a connected cable 12 or a connected electrical line at level CD via screw connections 13a . 13b , In the feeler head 10 is as another sensor element 14 embedded a single, directionally-selective partial component. This works together with the rotationally symmetric magnetic field of the bar magnet 8th which represents the second partial component. The further sensor element 14 Accordingly, a signal is provided which gives information about both displacements ΔX (U) and ΔY (S).

In an alternative embodiment, which is not shown here, are two separate, magnetosensory further sensor elements 14 provided, which are selective in two mutually orthogonal directions and separately measure the deflection ΔX (U) and ΔY (S). These act in parallel or simultaneously, but independently, with the rotationally symmetric field of the bar magnet 8th together. That is, each of the two other sensor elements 14 provides a separate signal, each a measure of the corresponding, from this sensor element 14 measured displacement is. The two directionally selective partial components or further sensor elements are preferably aligned without twisting angle on the measuring direction. That is, each of the two partial components measures only the deflection in either direction. Even with a twist angle, the arrangement is possible, but then, knowing this angle, they must be calculated from the respective measured signal, or the actual displacements can be determined with the aid of the angle. As magnetosensory sensor elements 14 or partial components are, for example, AMR angle sensors from Sensitec.

The representation of the holding arm in 8th corresponds to scaled-up preferred natural proportions. The diameter of the hole 4 is 5 mm, the diameter of the rod 6 is 3 mm. The bar magnet 8th is made of CoSm material and has a diameter of 1.5 mm and a length of 3 mm.

In a further preferred embodiment, not shown here, the bar magnet 8th replaced by an array of micromirrors. Furthermore, a miniature laser or a laser diode is provided, wherein in each state of the brake (force-free or with effective circumferential force and normal force) at least one micromirror is illuminated by the miniature laser. The laser is advantageously integrated stationary on or in the molded part. It is in this embodiment further a further sensor element 14 provided, which is designed as a two-dimensional photosensitive sensor, in particular as a fixedly installed surface array. For this purpose, for example, a CCD sensor is suitable. By a two-dimensional sensor, a determination of the two deflections .DELTA.X (U) and .DELTA.Y (S) in a comfortable manner possible in that the pixel or light element or the plurality of pixels or light elements is determined in the sensor, which is hit by the laser beam ,

LIST OF REFERENCE NUMBERS

1

 brake support

2

 screw

3

 chassis

4

 drilling

5

 holding arm

5a

 Covering guide rail

5c

 Covering guide rail

6

 Rod

6a

 first sensor element

7

 attachment end

8th

 bar magnet

8a

 coordinate system

8b

 X axis

8c

 y-axis

8d

 arrow

8e

 arrow

9

 molding

10

 probe head

11

 probe body

12

 electric wire

13a

 screw

13b

 screw

14

 another sensor element

16

 sensor device

18

 Focus

20

 transversely

F _U

 peripheral force

F _S

 tension

μ

 coefficient of friction

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 102006029978 B3 [0005]
• DE 102005013142 A1 [0006]
• DE 102008042298 A1 [0007]
• WO 2012/059313 A1 [0008]

Claims (11)

Brake holder ( 1 ) for determining a measure of an effective braking force (F _U ) on a disc brake of a motor vehicle, which is attachable to the motor vehicle, wherein the brake holder ( 1 ) at least two brake disc overlapping pad guide rails ( 5a . 5c ), on which both sides of the brake disc arranged friction linings in the axial direction of the brake disc are limited displaceable feasible, and a sensor device ( 16 ) by means of which a by a braking force effect caused displacement (.DELTA.X (U)) of at least a portion of the brake holder ( 1 ), in particular a pad guide rail ( 5a ) is measured in a first direction perpendicular to the axial direction of the brake disk, wherein the sensor device ( 16 ) a first ( 6a ) and at least one further sensor element ( 14 ) whose relative movement is measured, characterized in that by means of the sensor device ( 16 ) is measured in at least one further, different from the first direction direction caused by the braking force displacement (ΔY (S)). Brake holder ( 1 ) according to claim 1, wherein the further direction is perpendicular to the axial direction of the brake disc. Brake holder ( 1 ) according to claim 1 or 2, wherein the first and the further direction are orthogonal to each other. Brake holder ( 1 ) according to one of claims 1 to 3, wherein the further sensor element ( 14 ) is designed as a direction-selective sensor, which a relative movement of the first ( 6a ) and further sensor element ( 14 ) in two spatial dimensions. Brake holder ( 1 ) according to one of claims 1 to 3, wherein two further sensor elements ( 14 ) are provided, each of which the relative movement between itself and the first sensor element ( 6a ) in one direction. Brake holder ( 1 ) according to one of claims 1 to 5, wherein the first ( 6a ) and the further sensor element ( 14 ) cooperate according to a magnetic measuring principle. Brake holder ( 1 ) according to one of claims 1 to 5, wherein the first ( 6a ) and the further sensor element ( 14 ) interact according to an optical principle. Brake holder ( 1 ) according to claim 7, wherein the first sensor element ( 6a ) comprises an arrangement of a number of mirrors, in particular micromirrors, and wherein the further sensor element ( 14 ) is designed as a two-dimensional photosensitive sensor, in particular as a stationary surface array of photosensitive elements, wherein a laser is provided, which is aligned with at least one mirror. Device for determining a measured variable for an acting braking force (F _U ) on a, in particular hydraulically actuated, disc brake of a motor vehicle, with a brake holder fastened to the motor vehicle ( 1 ) according to one of claims 1 to 8 and with a control and regulating unit, the input side with the sensor device ( 16 ) and a brake control based on at least one measurement signal of the sensor device ( 16 ). Method for determining a measured variable for an acting braking force (F _U ) on a, in particular hydraulically actuated, disc brake of a motor vehicle with a brake holder fastened to the motor vehicle ( 1 ), in particular according to one of claims 1 to 8, characterized in that two caused by a braking force shifts (.DELTA.X (U), .DELTA.Y (S)) at least a portion of the brake holder ( 1 ) by a sensor device ( 16 ) with a first ( 6a ) and at least one further sensor element ( 14 ), which are both arranged on the brake holder, are measured. Method according to Claim 10, wherein the ratio of the displacements (ΔX (U) and ΔY (S)) and / or the ratio of circumferential force (F _U ) to clamping force determined by means of the displacements (ΔX (U) and ΔY (S)) (F _S ) a frictional coefficient (μ) characterizing the friction between the brake linings and the brake disk is determined.

Images