Patent Application
20240167525
The disclosure relates to a method for determining the braking force on vehicles with wheel brakes. In addition, the disclosure relates to an axle with wheel brakes and a vehicle with at least one corresponding axle.
Wheel brakes on vehicles, especially motor vehicles or commercial vehicles, do not have a permanent uniform effect. For example, the braking effect can deteriorate due to so-called fading of brake pads as a result of insufficient temperature introduction in vehicles with wear-free continuous brakes or recuperation devices. Conversely, mechanical defects, so-called hanging of the brake, can cause a higher braking force than intended. In practice, such defects can hardly be or may not be detected by the driver. Insufficient braking force is usually only detected in the course of legal inspections, a dragging or hanging brake only by strong temperature generation, which has then already caused consequential damage to the brake disc, wheel bearing or other parts. This results in a potential danger to other road users.
In order to determine that the brakes are in perfect condition, extensive checks on a roller dynamometer are necessary. For the measurement on the roller dynamometer, the vehicle must be driven over the roller dynamometer by a workshop employee with a defined minimum axle load. This requires time and, under certain circumstances, travel distances, as not every vehicle operator has a brake test bench. In addition, the measurement is only a snapshot.
It is an object of the disclosure is to provide a method for determining the braking force on vehicles with wheel brakes during braking.
This object is, for example, achieved via a method for determining a braking force on vehicles with wheel brakes. The method includes determining, at least indirectly, a reaction force occurring on the vehicle during braking.
In this context, braking force is understood to mean a force acting between the wheel and the road in the longitudinal direction of the vehicle in the opposite direction to the driving speed when the vehicle brakes. As soon as braking is applied, reaction forces occur on the vehicle, which can be measured in different ways and which are representative of the braking force.
According to another aspect of the disclosure, the reaction force can be determined separately for each wheel brake. This is preferably possible by determining the reaction forces in close proximity to each wheel brake. In this way, the braking force can be determined individually for each wheel brake. The measured reaction forces can be recorded and used for the control of the wheel brakes and/or as a database for maintenance work.
According to a further aspect of the disclosure, for the determination of the reaction force at least
According to a further aspect of the disclosure, for the determination of the reaction force at least
According to another aspect of the disclosure, strain gauges or force measurement bolts can be used as sensors for measuring a mechanical deformation. Strain gauges are low-cost sensors that can be used to measure very small changes in length in a simple way. Force measurement bolts are also known as load measurement bolts and are also inexpensive standard components. These measure the change in an electrical resistance or a change in a magnetic field that occurs during mechanical deformation.
According to another aspect of the disclosure, the reaction force on a component between wheel brakes inclusively and the chassis frame inclusively can be determined. Preferably, the deformation of the component is measured during braking. The component itself can also be part of the wheel brake or the chassis frame or belong to a component that is held between the wheel brake and the chassis frame.
According to another aspect of the disclosure, the reaction force can be determined at a transition between two components between wheel brakes inclusively and the chassis frame inclusively. For example, the reaction force can measurably change distances between two components.
According to another aspect of the disclosure, the reaction force can be determined by a torsion measurement on an axle tube. Trailers in particular have axles with axle tubes. The axle tube is mounted non-rotatably in axle brackets on the chassis frame and itself holds a wheel with a wheel bearing and a wheel brake at each free end. The wheel brake is supported by the axle tube in the circumferential direction, so that every braking operation leads to a torsion of the axle tube. This torsion can be measured by appropriately adapted sensors and is also a measure of the braking force that occurs during braking. Typically, the axle tube is a high-precision component, so a sensor intended for the axle tube does not need to be calibrated individually for each axle tube. The torsion measurement is carried out on the axle tube, in particular between the wheel brake and the axle bracket.
According to another aspect of the disclosure, the reaction force can be determined by a bending measurement on a brake pad carrier. During braking, the brake pad carrier undergoes very small deformations, which can be measured with appropriately adapted sensors.
According to another aspect of the disclosure, the reaction force can be determined by a bending measurement on a brake caliper mount. The brake caliper mount undergoes very small deformations during braking, which can be measured with appropriately adapted sensors.
According to another aspect of the disclosure, the reaction force can be determined by a bending measurement on a bolt between a trailing arm for an axle and a retaining bracket for the trailing arm. The axle or axle tube can be held on the vehicle frame by trailing arms. For this purpose, the chassis frame can have suitable retaining brackets (also known as bearing blocks or spring shoes). The trailing arm is held in the retaining bracket by a bolt and the bolt undergoes a slight deformation during braking, which can be measured with appropriately adapted sensors.
According to another aspect of the disclosure, the reaction force can be determined by measuring a mechanical deformation on a retaining bracket for a trailing arm of an axle. The retaining bracket itself can experience a measurable deformation during braking, especially bending.
According to another aspect of the disclosure, an axle load can also be determined, at least indirectly. The axle load can be determined by at least one additional sensor or, together with the reaction force occurring during braking, by a common sensor. Preferably, the sensor is located on the axle or on a component connected to the axle.
According to another aspect of the disclosure, the axle load can be determined by measuring a mechanical deformation via strain gauges or force measurement bolts. Mechanical deformation is, in particular, a bending or torsion of a component.
An axle assembly according to the disclosure 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. The sensor determines the reaction forces, at least indirectly. The braking forces can be inferred from the reaction forces. Preferably, these are rigid axles, non-driven axles or combinations thereof. However, axles of a different kind may also be formed according to the disclosure. In addition, the disclosure can be used in vehicles with independent suspension.
According to another aspect of the disclosure, sensors for measuring the variables for the determination of reaction forces can be provided for all wheel brakes. As a result, the braking force for each wheel brake can be determined individually from the reaction force that occurs.
According to a further aspect of the disclosure, at least one of the following sensors can be provided for the determination of the reaction forces:
According to another aspect of the disclosure, an axle tube can be provided with at least one sensor for the determination of the reaction forces. The axle tube is a rigid and easily accessible component on the axle, so that a sensor can be easily arranged there. Sensors can also be connected to the axle tube ex works.
According to another aspect of the disclosure, the axle tube can be provided with at least one sensor for torsion measurement. During braking, the axle tube twists slightly, which can be measured with an adapted sensor.
According to another aspect of the disclosure, the sensor for torsion measurement can be a strain gauge, wherein the strain gauge can be arranged at an angle, that is, at an angle to the circumferential direction of the axle tube. The aforementioned oblique arrangement is particularly good at detecting the torsion that occurs in the axle tube. The angle is preferably 30 to 60 degrees.
According to another aspect of the disclosure, the sensor can be a force measurement bolt, which holds a trailing arm for an axle in a retaining bracket. The retaining bracket is held on the vehicle frame and serves as a bearing for one end of the trailing arm. The connection between the trailing arm and the retaining bracket can be made via the force measurement bolt.
According to another aspect of the disclosure, the sensor can be a strain gauge arranged on a brake pad carrier. The brake pad carrier deforms slightly during braking depending on the braking force that occurs. This can be detected by the strain gauge.
According to another aspect of the disclosure, the sensor can be a strain gauge arranged on a brake caliper mount. The brake caliper mount also deforms depending on the braking force that occurs, which can be measured with the strain gauge.
According to another aspect of the disclosure, two sensors can be arranged to determine the reaction force for a wheel brake, wherein the sensors are oriented differently, in such a way that variables can be measured in different directions. For example, braking forces can be reliably determined when driving forward and reversing. Two strain gauges for torsion measurement on the axle tube can be arranged perpendicular to each other or as mirror images. For example, components subjected to bending can be provided with a strain gauge on a front surface and one on a rear surface. In addition, different measuring directions can already be realized in one sensor.
According to another aspect of the disclosure, at least one sensor for measuring an axle load can be provided on the axle. The sensor can be provided for measuring the reaction force during braking additionally or at the same time. Preferably, the sensor is located on a top surface and/or bottom surface of the axle.
According to another aspect of the disclosure, at least one strain gauge can be provided on the axle as a sensor for measuring the axle load. The strain gauges can be glued to the surface of the axle or joined to the axle in some other way.
A vehicle according to the disclosure includes an axle assembly according to the disclosure. The vehicle is preferably a trailer vehicle but can also be a motor vehicle.
The invention will now be described with reference to the drawings wherein:
A chassis 10 for a trailer vehicle can be seen in
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
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
On the axle tubes 19, sensors 22 are arranged between the wheel brakes 21 and the axle mounts 29. The sensors 22 shown in
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 120 185.3 | Aug 2021 | DE | national |
This application is a continuation application of international patent application PCT/EP2022/071163, filed Jul. 28, 2022, designating the United States and claiming priority from German application 10 2021 120 185.3, filed Aug. 3, 2021, and the entire content of both applications is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2022/071163 | Jul 2022 | US |
| Child | 18427425 | US |
