METHOD FOR DETERMINING THE BRAKING FORCE ON VEHICLES

Abstract

A method is for determining the braking force of vehicles with wheel brakes. In the method, a reaction force occurring on the vehicle during braking is determined, at least indirectly. An axle assembly includes: an axle; a wheel brake mounted on the axle; and, at least one sensor configured to measure variables for determining reaction forces during braking.

Claims

1. A method for determining a braking force on vehicles with wheel brakes, the method comprising determining, at least indirectly, a reaction force occurring on the vehicle during braking.

2. The method of claim 1, wherein the reaction force for each wheel brake is determined separately.

3. The method of claim 1, wherein said determining the reaction force includes measuring at least one of a change in mechanical variables, a change in magnetic variables, and a change in electrical variables.

4. The method of claim 3, wherein said determining the reaction force includes measuring at least one of an elastic deformation, a mechanical force, a magnetic field change, a change in an electrical resistance, and a change in a magnetic resistance.

5. The method of claim 4, wherein strain gauges or force measurement bolts are used as sensors for measuring a mechanical deformation.

6. The method of claim 1, wherein the reaction force on a component is determined between wheel brakes inclusively and a chassis frame inclusively.

7. The method of claim 1, wherein the reaction force is determined at a junction between two components between wheel brakes inclusively and a chassis frame inclusively.

8. The method of claim 1, wherein the reaction force is determined by a torsion measurement on an axle tube.

9. The method of claim 1, wherein the reaction force is determined by a bending measurement on a brake pad carrier.

10. The method of claim 1, wherein the reaction force is determined by a bending measurement on a brake caliper mount.

11. The method of claim 1, wherein the reaction force is determined by a bending measurement on a bolt between a trailing arm for an axle and a retaining bracket for the trailing arm.

12. The method of claim 1, wherein the reaction force is determined by measuring a mechanical deformation on a retaining bracket for a trailing arm of an axle.

13. The method of claim 1 further comprising determining, at least indirectly, an axle load.

14. The method of claim 13, wherein said determining the axle load includes measuring a mechanical deformation via strain gauges or force measurement bolts.

15. An axle assembly comprising: an axle; a wheel brake mounted on said axle; and, at least one sensor configured to measure variables for determining reaction forces during braking.

16. The axle assembly of claim 15, wherein a plurality of wheel brakes are mounted on said axle; and, at least one of said at least one sensor is provided for each of said plurality of wheel brakes for measuring the variables for the determination of the reaction forces.

17. The axle assembly of claim 15, wherein said at least one sensor includes at least one of a strain gauge, a force measurement bolt, a piezoelectric sensor, a magnetoelastic sensor, and a magnetostrictive sensor.

18. The axle assembly of claim 15 further comprising an axle tube provided with at least one of said at least one sensor.

19. The axle assembly of claim 18, wherein said axle tube is provided with a sensor for torsion measurement.

20. The axle assembly of claim 19, wherein said sensor for torsion measurement is a strain gauge and said strain gauge is arranged at an angle, that is, at an angle to a circumferential direction of said axle tube.

21. The axle assembly of claim 15, wherein said at least one sensor includes a force measurement bolt which holds a trailing arm for said axle in a retaining bracket.

22. The axle assembly of claim 15, wherein said at least one sensor includes a strain gauge arranged on a brake pad carrier.

23. The axle assembly of claim 15, wherein said at least one sensor includes a strain gauge arranged on a brake caliper mount.

24. The axle assembly of claim 15, wherein said at least one sensor includes two sensors arranged for determining the reaction forces for said wheel brake; and, said two sensors are oriented differently, such that variables are measurable in different directions.

25. The axle assembly of claim 15, wherein said at least one sensor includes a sensor for measuring an axle load.

26. The axle assembly of claim 25, wherein said sensor for measuring the axle load is at least one strain gauge.

27. A vehicle comprising the axle assembly of claim 15.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0049] The invention will now be described with reference to the drawings wherein:

[0050] FIG. 1 shows a top view of a semi-trailer chassis with axles and disc brakes;

[0051] FIG. 2 shows a side view of a wheel suspension with a trailing arm on the axle tube;

[0052] FIG. 3 shows a half view of an axle tube with a holder, wheel and wheel brake;

[0053] FIG. 4 shows a top view of a chassis of a semi-trailer with axles and drum brakes; and,

[0054] FIG. 5 shows a view as in FIG. 3, but with further sensors or positions of the same.

DETAILED DESCRIPTION

[0055] A chassis 10 for a trailer vehicle can be seen in FIG. 1. In this case, the trailer vehicle is a semi-trailer with a king pin 11.

[0056] Three axles 15 are mounted under a chassis frame 12 with longitudinal members 13 and cross members 14. The axles 15 are held non-rotatably with axle brackets 29 on trailing arms 16, which are hinged on a bearing block 17 on one side and on the other side act on an air suspension bellows 18, see also FIG. 2.

[0057] Each axle 15 has a continuous axle tube 19, at the ends of which wheels 20 with wheel brakes 21 are mounted. During braking, a braking force B acts parallel to the longitudinal direction of the vehicle F, see FIG. 2. Depending on the braking force B, reaction forces occur on the chassis, the effects of which can be detected to determine the braking force B.

[0058] On the axle tubes 19, sensors 22 are arranged between the wheel brakes 21 and the axle mounts 29. The sensors 22 shown in FIG. 1 are preferably strain gauges, which measurably change their electrical resistance when their length changes. For this purpose, the strain gauges (sensors 22) with their measuring direction M are kept at an angle to the circumferential direction U of the respective axle tube 19, see FIG. 3. At the same time, this results in an angle relative to a longitudinal direction L of the respective axle 15. The angle of the measuring direction M relative to the circumferential direction U of the respective axle tube 19 is preferably 30 to 60 degrees. The orientation and angle depend on a reaction force that occurs in practice during braking, which depends on the braking force B, and on the resulting torsion of the axle tubes 19. This can be determined by experiments.

[0059] FIG. 2 shows two further possible installation locations for sensors 23, 24. Sensor 23 is also a strain gauge, arranged on the retaining bracket 17. During braking, a reaction force dependent on the braking force B acts on the retaining bracket 17, which causes a slight bending of the retaining bracket 17 and can be detected by the sensor 23.

[0060] The trailing arm 16 is hinged at one end with a bolt in the retaining bracket 17. The bolt can be a force measurement bolt and thus the sensor 24 at the same time. During braking, the force measurement bolt experiences a reaction force depending on the effective braking force B and consequently a slight deflection, which is detectable and can be evaluated to determine the braking force B.

[0061] FIG. 3 shows a half view of an axle 15 with a greatly simplified representation of the bearing of the axle tube 19. Only the air suspension bellows 18 and the longitudinal member 13 are shown. Three different possible positions of sensors 22, 25 and 26 can be seen. Sensor 22 is the strain gauge on the axle tube 19. Sensor 25 is a strain gauge on a brake pad carrier 27 of the wheel brake 21 provided here as a disc brake. During braking, a reaction force dependent on the braking force B acts on the brake pad carrier 27, which results in a slight deformation of the brake pad carrier 27. The deformation is detected with the sensor 25.

[0062] The brake pad carrier 27 is bolted to a brake caliper mount 28, which is non-rotatably mounted on the axle tube 19, for example by welding or screwing. During braking, the caliper mount 28 is also acted upon by a reaction force dependent on the braking force B, which leads to a slight deformation. The deformation can be detected with the sensor 26 in the form of a strain gauge. The sensor 26 can also be arranged across components, for example from the caliper mount 28 to the axle tube 19. A cross-component deformation is then detected.

[0063] For determining the braking forces in forward and reverse travel or for other reasons, an additional sensor may be provided on the axle tube 19 in addition to sensor 22, in particular on the rear surface of the axle tube 19, which is not visible in FIG. 3, and which is visually hidden by the axle tube 19 and the sensor 22.

[0064] FIG. 4 shows the chassis 10 with drum brakes as wheel brakes 21. Brake linings (not shown) in brake drums 30 are actuated by brake cylinders 31 via linkage adjusters 32. The brake cylinders 31 are mounted on the axle tubes 19 between the longitudinal members 13. Here, too, strain gauges are arranged as sensors 22 on the axle tubes 19, namely between brake drums 30 and axle brackets 29.

[0065] In all exemplary embodiments, at least one sensor 22 to 26 is assigned to each wheel 20. Sensors 22 to 26 can be provided on different components and in different positions. It is important to have an arrangement and an orientation such that an effect associated with the braking force of the respective wheel brake 21 can be measured.

[0066] The sensors 22 to 26 detect elastic deformations, a change in an electrical resistance or changes in magnetic fields directly or indirectly. Strain gauges detect a change in length indirectly via the electrical resistance. Force measurement bolts are provided with a strain gauge to detect deformation thereof or can detect a deformation due to changes in magnetic properties, as a magnetoelastic or magnetostrictive sensor. The use of sensors of a different kind is conceivable, as long as only the braking force that occurs can be determined indirectly.

[0067] The sensors 22 to 26 provide signals that can be evaluated by the braking system, which is not shown, for example for detecting dragging brakes and/or insufficient braking force in relation to a current brake pressure. The braking force can be individually determined and monitored for each wheel 20. The sensors require no moving parts and can be located outside the thermally highly loaded wheel brakes 21.

[0068] The sensors 22 can be arranged on the top, bottom, front and/or back of the axles 15 or axle tubes 19 for determining the torsion, as well as in an intermediate position. FIG. 5 shows sensors 33, 34 on and under the axle tube 19. Two or more sensors can also be arranged in combination, for example two sensors 22, 34 on the axle tube or two sensors 22, 33 under the axle tube.

[0069] In addition, sensors can be provided for axle load measurement. For example, sensors 33, 34 can be provided for determining the axle load by measuring the bending of the axle tube 19.

[0070] It is also possible to evaluate only one sensor for determining braking force and axle load, in particular for each wheel brake 21, see preferably sensors 33, 34.

[0071] It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.

LIST OF REFERENCE SIGNS AS PART OF THE DESCRIPTION

[0072] 10 Chassis [0073] 11 Kingpin [0074] 12 Chassis frame [0075] 13 Longitudinal member [0076] 14 Cross member [0077] 15 Axles [0078] 16 Trailing arm [0079] 17 Retaining brackets [0080] 18 Air suspension bellows [0081] 19 Axle tubes [0082] 20 Wheels [0083] 21 Wheel brakes [0084] 22 Sensor (on axle tube) [0085] 23 Sensor (on retaining bracket) [0086] 24 Sensor (force measurement bolt) [0087] 25 Sensor (on brake pad carrier) [0088] 26 Sensor (on the brake caliper mount) [0089] 27 Brake pad carrier [0090] 28 Brake caliper mount [0091] 29 Axle bracket [0092] 30 Brake drum [0093] 31 Brake cylinder [0094] 32 Linkage adjuster [0095] 33 Sensor (under the axle tube) [0096] 34 Sensor (on the axle tube) [0097] B Braking force [0098] F Longitudinal direction of the vehicle [0099] L Longitudinal Direction of the Axle [0100] M Measuring direction of the sensor [0101] U Circumferential direction of the axle tube