Method for identifying temperature changes, caused by a defect, at wheel ends of a vehicle, evaluation unit and vehicle

Abstract

The invention relates to a method for identifying temperature changes, caused by a defect, at wheel ends (11) of a vehicle (1), wherein at least two of the wheel ends (11) have a wheel speed sensor (5) which has a temperature sensor (4) designed to measure, around its position (P), a sensor temperature (T) in a sensing area (4S), having at least the following steps: - reading a first sensor temperature which is measured by a first temperature sensor (4a) at a first wheel end (11a), and - reading a second sensor temperature which is measured by a second temperature sensor (4b) at a second wheel end (11b), - determining a temperature deviation depending on the first sensor temperature and the second sensor temperature, - comparing the temperature deviation with a deviation threshold, and - outputting a message (H) if the deviation threshold is exceeded, wherein the message (H) contains the information that a temperature change caused by a defect has been detected at at least one of the wheel ends (11; 11a, 11b) which have a wheel speed sensor (5) having a temperature sensor (4).

Description

[0001] Method for detecting temperature changes at wheel ends of a vehicle caused by defects, evaluation unit and vehicle

[0002] The present invention relates to a method for detecting temperature changes at wheel ends of a vehicle, as well as an evaluation unit and a vehicle for carrying out the method.

[0003] So-called wheel ends or wheel end assemblies of a vehicle have a multitude of safety-relevant components, for example components of a braking system, in particular a brake caliper, a mounting flange for mounting a vehicle wheel, bearings, sensors or the like. The temperature prevailing at a wheel end thus represents a relevant input variable for a self-diagnosis of the vehicle. For example, an elevated temperature can indicate excessive stress on the brake. For this purpose, a method is known from the prior art, for example from EP 1 564 431 A1, in which a temperature sensor is arranged on a non-rotating braking component, for example a brake pad, in order to obtain temperature information about the temperature of a brake disc.

[0004] Separate temperature sensors are also described in DE 10 2019 004 963 A1 and GB 2 557 195 A. US 7 883 159 B2 further describes estimating the temperature or temperature change based on the energy generated by friction during braking, using rotational speeds from a wheel speed sensor at the wheel end.

[0005] The object of the present invention is to provide an alternative method for detecting defect-induced temperature changes at the wheel ends of a vehicle, as well as an evaluation unit and a vehicle configured to implement said method. This object is achieved according to the invention by a method, an evaluation unit, and a vehicle according to the independent claims, wherein the subclaims describe preferred developments and embodiments.

[0006] According to the invention, there is therefore provided a method for detecting temperature changes caused by defects (i.e. caused by a defect), in particular temperature increases caused by defects, at wheel ends (wheel end arrangements) of a vehicle, preferably a commercial vehicle, wherein a wheel is rotatably mounted on each wheel end and at least two of the wheel ends further each have a wheel speed sensor for measuring a wheel speed of the respectively assigned wheel, preferably an actively operated wheel speed sensor, wherein the respective wheel speed sensor has a temperature sensor, i.e. as an integral part of the wheel speed sensor, wherein the temperature sensor is designed to measure and output a sensor temperature in a sensing range comprising at least the respective wheel speed sensor.

[0007] A wheelend or wheel-end assembly of a vehicle is preferably formed by the stationary, i.e., non-rotating, outer end of a vehicle axle. The vehicle axle, as in the case of independent wheel suspension, may also be merely virtual. A wheelend thus represents the area to which the rotating wheel mounted on the wheelend adjoins in the outer direction. Accordingly, a two-axle vehicle has four wheelends.

[0008] The aforementioned wheel speed sensor is to be arranged at the wheel end in such a way that it can interact with the rotating wheel. Preferably, a magnet wheel attached to the rotating wheel generates an alternating magnetic field in the respective wheel speed sensor, which is evaluated by the wheel speed sensor to determine the wheel speed. The wheel speed sensor includes a temperature sensor, for example, to adjust the sensitivity of the alternating magnetic field generated by the magnet wheel, since this is temperature-dependent.

[0009] According to the invention, it was recognized that due to the arrangement of the wheel speed sensor in the wheel end area, it is possible to indirectly record information about the temperature or temperature changes in the area of ​​the respective wheel end via the temperature sensor integrated in the wheel speed sensor. This allows conclusions to be drawn about a defect in the wheel end area with appropriate analysis if the defect is a friction-causing defect that leads to an increase in temperature in the surrounding area, which also occurs in the sensing area of ​​the respective temperature sensor and can thus be detected.

[0010] If there is sufficient heat transfer from the surroundings of the wheel end to the temperature sensor integrated in the wheel speed sensor, for example via the air or through heat transfer to components of the wheel end, such friction-causing defects can be detected without additional sensors, whereby this is achieved according to the invention with at least the following steps:

[0011] Reading a first sensor temperature measured by a first temperature sensor of a first wheel speed sensor at a first wheel end, and

[0012] Reading a second sensor temperature measured by a second temperature sensor of a second wheel speed sensor at a second wheel end,

[0013] Determining a temperature deviation depending on the first sensor temperature and the second sensor temperature, for example by subtraction or by forming a ratio,

[0014] Comparing the temperature deviation with a deviation limit value, and issuing a notification when the deviation limit value is exceeded or when the two sensor temperatures differ too greatly from one another, wherein the notification includes that a temperature change, in particular a temperature increase, caused by a defect, in particular caused by a friction-causing defect, was detected on at least one of the wheel ends that have a wheel speed sensor with a temperature sensor, ie on the first wheel end with the first wheel or on the at least second wheel end with the second wheel.

[0015] According to the invention, an evaluation unit and a vehicle are also provided for carrying out the method. Thus, relative temperature differences between two wheel ends are evaluated, which do not normally occur, and this is taken into account by the deviation limit. The deviation limit is therefore selected such that the warning is only issued in the event of an unexpected temperature change at each wheel, for example due to a defect such as a bearing failure or an overheating or overheated service brake. Since the temperature change triggered by such a defect at the temperature sensor depends on the type of defect and also on the position of the respective wheel speed sensor or the temperature sensor integrated therein at the wheel end, the deviation limit should preferably also be adapted depending on the position of the temperature sensor and also be set depending on the defect.

[0016] This would allow, for example, the temperature change to be determined at the integrated temperature sensor, e.g., at the mounted wheelend, if the defect were to occur during ferry operation at a specific ambient temperature. This can be determined through appropriate tests or simulations, which would then determine the temperature change and thus the deviation limit at which an alert would be appropriate. For example, if a service brake on a mounted wheelend, which overheated (or overheated) in previous tests due to deliberate braking, causes a temperature change of between 80°C and 100°C at the respective temperature sensor, the deviation limit can be set to, for example, 60°C (at an ambient temperature of 20°C).

[0017] This temperature value can be assumed because the temperature behavior during such a test braking is comparable to that of a brake that is running hot or has overheated. If intrinsic differences in the temperature measurement between two temperature sensors arise during subsequent ferry operation (without any indication of such a hot brake), the deviation limit can be adaptively adjusted accordingly using a learning algorithm.

[0018] This can be done in a similar way for a bearing failure, which can be simulated, for example, to determine the temperature change at the respective temperature sensor and thus the deviation limit value for the respective position of the temperature sensor and this defect.

[0019] In order to exclude wheel-specific temperature changes that are not due to a defect, it can be provided that the method is only carried out and / or the notification is only issued if, within a predetermined period of time before the first sensor temperature and the second sensor temperature are read out, there is no (manual or automated) braking request due to which the respective service brake was actuated at the respective wheel end at which the respective sensor temperature was measured.

[0020] If, for example, a braking request results in different brake applications on each side, e.g., under p-split conditions or during steering braking, or similar situations, the service brakes may also heat up differently on each side. This is then measured by the respective temperature sensor in the wheel speed sensor and could lead to a warning in the evaluation. To avoid incorrectly concluding a defect in this case, the evaluation according to the invention (or the output of the warning) only takes place when the specified period has elapsed after a (manual or automated) braking request.

[0021] The time period should therefore be selected such that temperature effects of a braking request do not distort the method according to the invention. This time period cannot be specified in a general way, since the temperature increase at the service brakes caused during a braking request continues to affect the temperature sensor after the braking request has ceased, depending on a number of influencing parameters. Influencing parameters include, for example, the duration of the previous braking request, the strength of the previous braking request, the design of the service brake and the associated cooling of the brake disc, the positioning of the respective wheel speed sensor or the temperature sensor integrated therein at the wheel end, the ambient temperature, the vehicle speed (airstream), etc.Therefore, when determining the cooling period, it's important to consider not only how quickly the brake disc cools down, but also how "quickly" this can be detected by the temperature sensor. The cooling period can initially be preset based on design parameters after the wheel end has been installed and then adjusted during the ride depending on the current braking requirements, such as their length and intensity. Furthermore, the preset cooling period can be adaptively adjusted during the ride using a learning algorithm.

[0022] Preferably, it is further provided that, when the deviation limit is exceeded or when the two sensor temperatures differ too greatly from one another, the indication includes that a first service brake arranged at the first wheel end or a second service brake assigned to the second wheel end, depending on which assigned sensor temperature is higher, is running hot or has run hot due to a defect (hot runner), preferably because the brake pad at the respective wheel end is pressed against the brake disc even without a braking request. In this way, defects caused, for example, by residual pressure in the brake line or incorrect adjustment of the service brake can be detected if the deviation limit is selected accordingly, as described above.Even without a braking request, these cause the brake pad to press against the brake disc, resulting in increased friction and thus a rise in temperature, which can also be detected via the wheel speed sensor's temperature sensor. Since such a defect usually occurs on a wheel-by-wheel basis, it can be detected by determining the relative temperature difference or temperature deviation.

[0023] To enable this, it is preferably provided that the respective wheel speed sensor is arranged at the wheel end in such a way that heating caused by a defect on the brake pad and / or on the brake disc results in a change in the sensor temperature of the respective temperature sensor of the respective wheel speed sensor. This means that a temperature increase on the brake disc and / or the brake pad can be detected at least indirectly by a temperature increase at the wheel speed sensor if the temperature sensor is not located directly on the brake disc or on the brake pad, as is the case here. Heating of these can nevertheless also be detected in the remote sensing area of ​​the temperature sensor of the wheel speed sensor. Depending on the distance or positioning, the deviation limit can be adjusted accordingly in order to make the measurement more sensitive.

[0024] Preferably, it is further provided that the wheel end has a bearing, wherein an axle shaft connected to the respective wheel is rotatably mounted on the wheel end via the bearing, wherein the respective wheel speed sensor is arranged on the wheel end in such a way that heating caused by a defect occurring on the bearing of the respective wheel end results in a change in the sensor temperature of the respective temperature sensor of the respective wheel speed sensor. This means that a temperature increase on the bearing can be detected at least indirectly by a temperature increase on the wheel speed sensor, even if the temperature sensor is not located directly on the bearing. Excessive heating of the bearing, for example in the event of bearing damage, can nevertheless also be detected in the remote sensing range of the temperature sensor of the wheel speed sensor if the deviation limit value is selected accordingly, as described above.Depending on the distance or positioning, the deviation limit can be adjusted accordingly to make the measurement more sensitive.

[0025] Preferably, in this case, it can be provided that the indication, if the deviation limit is exceeded or if the two sensor temperatures differ too greatly from each other, includes the fact that the bearing at the wheel end for which a higher sensor temperature was determined is overheating due to a defect or has overheated. For the reasons stated above, this can also preferably be combined with the fact that within a predetermined period of time, before the first sensor temperature and the second sensor temperature are read out, there is no (manual or automated) braking request that would have caused the respective service brake to be applied at the respective wheel end at which the respective sensor temperature was measured.

[0026] In this way, for example, a bearing damaged during operation can be detected, resulting in increased friction and thus a rise in temperature, which can also be detected via the wheel speed sensor's temperature sensor. Since such a defect usually occurs on a wheel-by-wheel basis, it can be detected by determining the relative temperature difference or temperature deviation.

[0027] In order to be able to determine a corresponding temperature deviation where one of the described defects does not affect the temperature measurement of both temperature sensors simultaneously, it is preferably provided that the first wheelend and the second wheelend under consideration are arranged on different sides of the vehicle, for example on the same vehicle axle. In this variant, the load on the wheelends is approximately identical during normal ferry operation, so that the two sensor temperatures can be compared most easily. However, it is also possible for the first wheelend and the second wheelend under consideration to be arranged on the same side of the vehicle on different vehicle axles, thus allowing sensor temperatures from different vehicle axles to be compared with each other.In order to take into account axle-specific influences, for example from the environment or load or the like, the deviation limit can be set differently accordingly, whereby these different influences can also be learned or adaptively adjusted during the journey by a learning algorithm based on observations.

[0028] Furthermore, in this case it can also be provided that the temperature deviation between a first mean value, which is dependent on the first sensor temperature, and a second mean value, which is dependent on the second sensor temperature.is formed, wherein the first mean value is formed from the first sensor temperature, which is measured on a first vehicle axle at the first wheel speed sensor by the first temperature sensor at the first wheel end, and a further sensor temperature, which is also measured on the first vehicle axle at a further wheel speed sensor by its temperature sensor at a further wheel end, and the second mean value is formed from the second sensor temperature, which is measured on a second vehicle axle at the second wheel speed sensor by the second temperature sensor at the second wheel end, and a further sensor temperature, which is also measured on the second vehicle axle at a further wheel speed sensor by its temperature sensor at a further wheel end. By forming the mean value in this way, more robust results can be delivered when considering multiple axles.

[0029] Depending on the driving situation and the load on the wheels, different observations (by wheel or by axle) may be advantageous in order to determine a meaningful temperature deviation.

[0030] In all of the above-mentioned embodiments, plausibility can generally be checked by taking into account additional sensor data or diagnostic states of the vehicle that are also influenced by a defect.

[0031] For the evaluation in the evaluation unit, it can be provided that it is part of a brake control unit of a vehicle's braking system. This allows a defect detected by the method to be taken into account directly by the brake control unit. Furthermore, the brake control unit is normally connected to the wheel speed sensors via a signal-conducting connection, and the corresponding measured temperature values ​​are available there. However, a corresponding connection can also be provided between the evaluation unit and the brake control unit or directly to the individual wheel speed sensors.

[0032] The invention is explained in more detail below with reference to the accompanying drawings. They show:

[0033] Fig. 1 schematic overview of a vehicle equipped to carry out the method according to the invention;

[0034] Fig.2 Detailed view of a section of Figure 1 ; and

[0035] Fig. 3 is a flowchart of the method according to the invention. Figure 1 shows a vehicle 1 with two vehicle axles FA; FA1, FA2 and a pneumatic or electropneumatic braking system 2, which can be electrically controlled by means of a brake control unit 10. For this purpose, the braking system 2 has service brakes 7, in particular disc brakes with brake discs 6, on the individual wheels 3 of the vehicle 1, which can be actuated with a certain braking pressure pB in order to brake the vehicle 1. The braking pressure pB is generated pneumatically or electropneumatically (as shown in Fig. 1 via an axle modulator 15) depending on a manually or automatically specified braking request B.

[0036] The vehicle 1 further has wheel ends 11 or wheel end arrangements, with each wheel 3 being assigned such a wheel end 11. As shown in Fig. 2, a wheel 3 is fastened, for example screwed, to the respective wheel end 11 via a receiving flange 16. The receiving flange 16 is connected, as shown highly schematically in Fig. 2, to an axle shaft 17, which in turn is rotatably mounted on a housing of the wheel end 11 via a bearing 13, so that the axle shaft 17, together with the wheel 3 fastened thereto, can rotate about a wheel axis A3. Also part of the wheel end 11 is a brake caliper (not shown in detail), which is also fastened to the housing of the wheel end 11 and which has a brake pad 8 that presses against the brake discs 6 during braking.

[0037] Without a braking request B, the service brakes 7 are normally not applied or not actuated, i.e. the brake pad 8 of the service brake 7 is not pressed against the brake disc 6 connected to the respective wheel 3 by the brake pressure pB (approx. ambient pressure pU) then acting in the brake pressure lines. However, if the service brakes 7 are incorrectly adjusted and / or if there is a residual pressure pR in the brake pressure lines that is higher than the ambient pressure pU, i.e. pB = pR > pU, it can happen that the brake pad 8 is pressed against the brake disc 6 even without a braking request B being present. As a result, the respective service brake 7 overheats during operation of the vehicle 1 because there is constant frictional contact between the brake pad 7a and the brake disc 6. Furthermore, wheel speed sensors 5 are assigned to each wheel 3 of the vehicle 1, via which wheel speed sensors 5 a wheel speed N3 of the respective wheel 3 can be determined by sensors.The wheel speed sensor 5 is also a component of the wheel end 11 and is attached to the housing of the wheel end 11 via a corresponding bracket. The wheel speed sensors 5 are actively operated, meaning they only output or generate a signal encoding the wheel speed N3 when a supply voltage is applied.

[0038] Such wheel speed sensors 5 also have a temperature sensor 4, via which a sensor temperature T within the wheel speed sensor 5 or within a certain sensing range 4S around the position P of the temperature sensor 4 can be measured, for example, to adjust the sensitivity of the wheel speed sensor 5 for operation. During an incremental magnetic measurement of the wheel speeds N3, a magnetic field is induced by a pole wheel 14, whereby temperature-dependent effects can arise during this measurement.

[0039] In the embodiment shown in Figure 1, it is thus possible to detect even unintentional temperature changes at the individual wheel ends 11 as a whole. This is done by a combined or comparative observation of the sensor temperature T at different wheel ends 11, in Figure 1 in particular at a first wheel end 11a and at a second wheel end 11b, which are assigned to a first wheel 3a and a second wheel 3b of the front axle as the first vehicle axle FA1 and which have the required first and second wheel speed sensors 5a, 5b, each with a temperature sensor 4. In principle, the other wheel ends 11 on the rear axle as the second vehicle axle FA2 in Figure 1 can also have the wheel speed sensors 5 required to carry out the method according to the invention.

[0040] According to the invention, it was recognized that the sensing area 4S of the temperature sensors 4 in the respective wheel speed sensors 5 is designed in such a way that temperature changes can also be specifically detected that occur due to undesired defects D in the area of ​​the respective wheel end 11, for example due to an overheated service brake 7 or a defective bearing 13. In the case of such defects D, a local increase in the ambient temperature in the area of ​​the wheel end 11 occurs, particularly due to increased friction, which can be identified by a suitable wheel-specific temperature evaluation of the sensor temperature T in an evaluation unit 12 (as a component of the brake control unit 10 as shown or as an external unit (not shown) that can communicate with the wheel speed sensors 5 via corresponding lines in order to read the sensor temperature T) as follows (see Fig. 3):

[0041] First, in a first step ST1, a first sensor temperature Ta is determined or read out, which is measured by a first temperature sensor 4a of a first wheel speed sensor 5a at a first wheel end 11a. Subsequently, in a second step ST2, a second sensor temperature Tb is determined or read out, which is measured by a second temperature sensor 4b of a second wheel speed sensor 5b at a second wheel end 11b. The two wheel ends 11a, 11b do not necessarily have to be on the same vehicle axle FA (front axle (first vehicle axle FA1) or rear axle (second vehicle axle FA2)) or on the same side of the vehicle, since only a temperature deviation dT depending on the first sensor temperature Ta and the second sensor temperature Tb at remote positions in the vehicle 1 is relevant, which is determined in a third step ST3.A local temperature increase due to a wheel-specific defect D should not affect both temperature measurements in the first and second steps ST1, ST2 simultaneously.

[0042] However, it is advantageous if the two wheel ends 11a, 11b to be compared are located on the same vehicle axle FA, as this results in comparable loads on the vehicle body and also comparable other influences on the wheel ends 11a, 11b under consideration. If an inter-axle analysis is nevertheless planned, the temperature deviation dT can be obtained by averaging as follows:

[0043] In this case, a first mean value MW1 is formed from the first sensor temperature Ta, which in this case is measured on the first vehicle axle FA1 (e.g. front axle) at the first wheel speed sensor 5a by the first temperature sensor 4a at the first wheel end 11a, and a further sensor temperature T, which is also measured on the same first vehicle axle FA1 (e.g. front axle) at a further wheel speed sensor 5 (on the other vehicle side) by its temperature sensor 4 at a further wheel end 11. The second mean value MW2 is formed in a similar way from the read-out second sensor temperature Tb, which in this case, however, contrary to the illustration in Fig. 1, is measured on the second vehicle axle FA2 (e.g.Rear axle) arranged second wheel speed sensor 5b by the second temperature sensor 4b at the second wheel end 11b, and a further sensor temperature T, which is also measured on the second vehicle axle FA2 at a further wheel speed sensor 5 (on the other vehicle side) by its temperature sensor 4 at a further wheel end 11.

[0044] Subsequently, in a fourth step ST4, the temperature deviation dT is compared with a deviation limit value GW, whereby the deviation limit value GW can be determined depending on the type of defect D (hot box, positional damage) and the position P of the respective temperature sensor 4 at the respective wheel end 11a, 11b. This also takes into account the extent to which a specific defect D affects the sensing range 4S of the respective temperature sensor 4, taking into account the normally expected temperature fluctuations between the individual wheel ends 11; 11a, 11b. Furthermore, changes in the deviation limit value GW can occur over a longer period of time during ferry operation, which can be adaptively adjusted, for example, using a learning algorithm.

[0045] If it is determined that the deviation limit GW has been exceeded, i.e., the sensor temperatures Ta, Tb deviate too greatly from one another, a message H is output in a fifth step ST5. This then indicates, for example, that an unexpected temperature increase has occurred at the wheel end 11; 11a, 11b with the higher of the two determined sensor temperatures T; Ta, Tb. It is assumed that if the temperature deviation dT is too high, it is not the lower of the two sensor temperatures T; Ta, Tb that is critical, but rather the higher sensor temperature T; Ta, Tb.

[0046] Thus, in the event that the brake disc 6 of a service brake 7 assigned to the respective wheel 3 is overheated, a corresponding temperature deviation dT can be detected if the temperature increase caused by friction can also be detected at least partially in the sensing range 4S of the temperature sensor 4 on this wheel 3. It must be taken into account that within a predetermined period of time Z there was no braking request B that would have led to the deliberate application of the service brake 7 and thus automatically to the generation of heat. In the case of wheel-specific braking, this would otherwise also lead to a temperature deviation dT, which is then desired and not attributable to a defect.

[0047] The period of time Z cannot be specified as a general rule, since the temperature increase at the service brakes 7 caused during a braking request B continues to have an effect on the temperature sensor 4 after the braking request B has ceased, depending on a series of influencing parameters. Influencing parameters include, for example, the duration of the previous braking request DB, the strength of the previous braking request DB, the design K of the service brake 7 and the associated cooling of the brake disc 6, the position P of the respective wheel speed sensor 5 or the temperature sensor 4 integrated therein at the respective wheel end 11, the ambient temperature TU, the vehicle speed v1 (headwind), etc. The period of time must therefore be adapted to the driving situation, whereby adaptive adjustment by a learning algorithm is also possible in the event of temporal changes.

[0048] If such a braking request B was not present in the previous period Z and is not present at the current time, and an excessive temperature deviation dT was or is nevertheless determined, this may be due, among other things, to a heated brake disc 6 due to incorrect adjustment of the service brake 7 and / or due to an increased residual pressure pR. In this way, it can be indirectly concluded via the temperature sensor 4 that the service brake 7 at the wheel end 11 may have overheated, with the respective higher determined sensor temperature T.

[0049] A further cause for an excessively high temperature deviation dT, preferably without the previous and current presence of a braking request B, can be a defect in the bearing 13 in the respective wheel end 11, because even then the temperature increase caused by the friction can be directly detected, at least in part, in the sensing area 4S of the temperature sensor 4 on this wheel 3.

[0050] In order to differentiate between the respective causes, the deviation limit values ​​GW can be defined according to the defect D, for example in previous tests or simulations.

[0051] Reference symbol (part of the description)

[0052] 1 vehicle

[0053] 2 braking system

[0054] 3 wheels of the vehicle 1

[0055] 3a first wheel

[0056] 3b second wheel

[0057] 4 Temperature sensor

[0058] 4a first temperature sensor

[0059] 4b second temperature sensor

[0060] 4S sensing range

[0061] 5 Wheel speed sensor

[0062] 5a first wheel speed sensor

[0063] 5b second wheel speed sensor

[0064] 6 brake disc

[0065] 7 Service brake

[0066] 7a first service brake

[0067] 7b second service brake

[0068] 8 brake pad

[0069] 10 Brake control unit

[0070] 11 Wheelend

[0071] 11a first wheel end

[0072] 11 b second wheelend

[0073] 12 Evaluation unit

[0074] 13 camps

[0075] 14 Flywheel

[0076] 15 Axis modulator

[0077] 16 Mounting flange

[0078] 17 axle shaft

[0079] A3 wheel axle

[0080] B Brake request

[0081] D Defect

[0082] DB Duration of braking request B dT Temperature deviation FA Vehicle axle

[0083] FA1 first vehicle axle

[0084] FA2 second vehicle axle

[0085] GW deviation limit

[0086] H Note

[0087] K Design of the service brake 7

[0088] MW1 first mean

[0089] MW2 second mean

[0090] N3 wheel speed

[0091] P Position of temperature sensor 4 p3 Tire pressure value pB Brake pressure pR Residual pressure pU Ambient pressure

[0092] SB Strength of braking request B

[0093] T Sensor temperature

[0094] Ta first sensor temperature

[0095] Tb second sensor temperature

[0096] TU Ambient temperature v1 Vehicle speed

[0097] Z period

[0098] ST1, ST2, ST3, ST4, ST5 steps of the procedure

Claims

Patent claims 1. A method for detecting temperature changes caused by defects at wheel ends (11) of a vehicle (1), preferably a commercial vehicle, wherein a wheel (3) is rotatably mounted on each wheel end (11) and at least two of the wheel ends (11) each further comprise a wheel speed sensor (5) for measuring a wheel speed (N3) of the respectively assigned wheel (3), wherein the respective wheel speed sensor (5) comprises a temperature sensor (4), wherein the temperature sensor (4) is designed to measure and output its position (P) and a sensor temperature (T) in a sensing range (4S) comprising at least the respective wheel speed sensor (5), wherein at least the following steps are carried out in the method: - reading out a first sensor temperature (Ta) measured by a first temperature sensor (4a) of a first wheel speed sensor (5a) at a first wheel end (11a) (ST1), and - reading out a second sensor temperature (Tb) measured by a second temperature sensor (4b) of a second wheel speed sensor (5b) at a second wheel end (11b) (ST2), - Determining a temperature deviation (dT) depending on the first sensor temperature (Ta) and the second sensor temperature (Tb) (ST3), - comparing the temperature deviation (dT) with a deviation limit value (GW) (ST4), and - Outputting an indication (H) when the deviation limit value (GW) is exceeded and / or when the two sensor temperatures (T; Ta, Tb) deviate too greatly from one another (ST5), wherein the indication (H) includes that a temperature change caused by a defect (D) was detected on at least one of the wheel ends (11; 11a, 11b) which have a wheel speed sensor (5) with a temperature sensor (4).

2. Method according to claim 1, characterized in that the indication (H) includes that a friction-causing defect (D) was detected at the wheel end (11) with the respective higher sensor temperature (T; Ta, Tb), which causes a temperature change in the sensing area (4S) of the respective temperature sensor (4).

3. Method according to one of the preceding claims, characterized in that a separate deviation limit value (GW) is defined for each defect (D).

4. Method according to one of the preceding claims, characterized in that the respective deviation limit value (GW) is determined as a function of the position (P) of the respective temperature sensor (4) at the respective wheel end (11) and / or within the respective wheel speed sensor (5).

5. Method according to one of the preceding claims, characterized in that the deviation limit value (GW) is adaptively adjusted during the journey.

6. Method according to one of the preceding claims, characterized in that a brake pad (8) of a service brake (7) is arranged on the wheel end (11), which can be pressed against a brake disc (6) connected to the respective wheel (3) in order to brake the respective wheel (3) when a braking request (B) is present.

7. The method according to claim 6, characterized in that the indication (H), when the deviation limit value (GW) is exceeded and / or when the two sensor temperatures (T; Ta, Tb) deviate too greatly from one another, includes that a first service brake (7a) arranged on the first wheel end (11a) or a second service brake (7b) assigned to the second wheel end (11b), depending on which assigned sensor temperature (T; Ta, Tb) is higher, is running hot or has run hot due to a defect (D), wherein the defect (D) preferably consists in the brake pad (8) on the respective wheel end (11; 11a, 11b) being pressed against the brake disc (6) even without the presence of a braking request (B).

8. Method according to claim 6 or 7, characterized in that the respective wheel speed sensor (5) is arranged on the wheel end (11) in such a way that a defect-induced heating occurring on the brake pad (8) and / or on the brake disc (6) results in a change in the sensor temperature (T) of the respective temperature sensor (4) of the respective wheel speed sensor (5).

9. Method according to one of claims 6 to 8, characterized in that the method is only carried out and / or the output of the indication (H) only occurs if, within a predetermined period of time (Z) before the reading of the first sensor temperature (Ta) and the second sensor temperature (Tb), there is no braking request (B) on the basis of which the respective service brake (7) at the respective wheel end (11) at which the respective sensor temperature (T) was measured was actuated.

10. The method according to claim 9, characterized in that the period (Z) is specified as a function of at least one influencing variable selected from the group consisting of: Duration (DB) of the previous braking request (B), strength (SB) of the previous braking request (B), design (K) of the respective service brake (7), position (P) of the respective temperature sensor (4) at the respective wheel end (11) and / or within the respective wheel speed sensor (5), ambient temperature (TU), vehicle speed (v1).

11. Method according to one of the preceding claims, characterized in that the wheel end (11) has a bearing (13), wherein an axle shaft (17) connected to the respective wheel (3) is rotatably mounted on the wheel end (11) via the bearing (13), wherein the respective wheel speed sensor (5) is arranged on the wheel end (11) in such a way that heating caused by a defect occurring on the bearing (13) of the respective wheel end (11) results in a change in the sensor temperature (T) of the respective temperature sensor (4) of the respective wheel speed sensor (5).

12. The method according to claim 11, characterized in that the indication (H) when the deviation limit value (GW) is exceeded and / or when the two sensor temperatures (T; Ta, Tb) deviate too greatly from one another includes that the bearing (13) on the wheel end (11), for which a higher sensor temperature (T; Ta, Tb) was determined, is running hot or has run hot due to a defect (D), the defect (D) preferably consisting in the fact that the bearing (13) is damaged.

13. Method according to one of the preceding claims, characterized in that the first wheel end (11a) and the second wheel end (11b) are arranged on the same vehicle axle (FA) of the vehicle (1) or on different vehicle axles (FA) of the vehicle (1).

14. The method according to claim 13, characterized in that the temperature deviation (dT) is formed between a first mean value (MW1) and a second mean value (MW2), wherein the first mean value (MW1) is formed from the first sensor temperature (Ta) measured on a first vehicle axle (FA1) at the first wheel speed sensor (5a) by the first temperature sensor (4a) at the first wheel end (11a), and a further sensor temperature (T) also measured on the first vehicle axle (FA1) at a further wheel speed sensor (5) by its temperature sensor (4) at a further wheel end (11), and the second mean value (MW2) is formed from the second sensor temperature (Tb) measured on a second vehicle axle (FA2) at the second wheel speed sensor (5b) by the second temperature sensor (4b) at the second wheel end (11b), and a further Sensor temperature (T),which is also measured on the second vehicle axle (FA2) at another wheel speed sensor (5) by its temperature sensor (4) at another wheel end (11).

15. Evaluation unit (12) for a vehicle (1), in particular a commercial vehicle, in particular for carrying out a method according to one of the preceding claims, wherein the evaluation unit (12) is designed to read in a sensor temperature (T) measured in a sensing area (4S) comprising at least the respective wheel speed sensor (5) from at least two wheel speed sensors (5), each of which is arranged at different wheel ends (11) of the vehicle (1) and each of which has a temperature sensor (4), and to carry out at least the following steps: - reading a first sensor temperature (Ta) output by a first temperature sensor (4a) of a first wheel speed sensor (5a) at a first wheel end (11a), and - Reading a second sensor temperature (Tb) which is measured by a second temperature sensor (4b) of a second wheel speed sensor (5b) at a second wheel end (11b), - Determining a temperature deviation (dT) depending on the first sensor temperature (Ta) and the second sensor temperature (Tb), - comparing the temperature deviation (dT) with a deviation limit value (GW), and - Outputting an indication (H) when the deviation limit value (GW) is exceeded and / or when the two sensor temperatures (T; Ta, Tb) deviate too greatly from one another, wherein the indication (H) includes that a temperature change caused by a defect (D) was detected on at least one of the wheel ends (11; 11a, 11b) which have a wheel speed sensor (5) with a temperature sensor (4).

16. Vehicle (1), preferably a commercial vehicle, with several wheelends (11), wherein a wheel (3) is rotatably mounted on each wheelend (11) and at least two of the wheelends (11) further each have a wheel speed sensor (5), which is preferably actively operated, for measuring a wheel speed (N3) of the respectively assigned wheel (3), wherein the respective wheel speed sensor (5) has a temperature sensor (4), wherein the temperature sensor (4) is designed to determine its position (P) a sensor temperature (T) in a sensor which at least determines the respective wheel speed sensor (5) comprising a sensing area (4S), wherein the vehicle (1) further comprises an evaluation unit (12), in particular an evaluation unit (12) according to claim 15, which is designed to read the output sensor temperature (T) and to carry out at least the following steps: - reading a first sensor temperature (Ta) output by a first temperature sensor (4a) of a first wheel speed sensor (5a) at a first wheel end (11a), and - reading a second sensor temperature (Tb) output by a second temperature sensor (4b) of a second wheel speed sensor (5b) at a second wheel end (11b), - Determining a temperature deviation (dT) depending on the first sensor temperature (Ta) and the second sensor temperature (Tb), - comparing the temperature deviation (dT) with a deviation limit value (GW), and - issuing an indication (H) when the deviation limit value (GW) is exceeded and / or when the two sensor temperatures (T; Ta, Tb) deviate too greatly from one another, wherein the indication (H) includes that a temperature change caused by a defect (D) was detected on at least one of the wheel ends (11; 11a, 11b) which have a wheel speed sensor (5) with a temperature sensor (4).

17. Vehicle (1) according to claim 16, characterized in that the evaluation unit (12) is a component of a brake control unit (10) of a brake system (2) of the vehicle (1).

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