METHOD FOR MONITORING THE WEAR CONDITION OF A VEHICLE BRAKE COMPONENT

Abstract

A method for monitoring the wear of a vehicle brake element, the brake element comprising a first piezoelectric sensor and a second piezoelectric sensor, the method comprising the following steps: - a generation step (E1) of a surface wave in the brake element by the first piezoelectric sensor, the surface wave comprising a Rayleigh wave; - a reception step (E2) of a signal by the second piezoelectric sensor, the surface wave being transmitted and / or reflected in the brake element; - a comparison step (E3) of the received signal to a predetermined reference signal, so as to monitor the wear of the brake element. Abstract figure: Fig. 2

Description

Title of the invention: METHOD FOR MONITORING THE WEAR STATE OF A BRAKE COMPONENT OF A VEHICLE

[0001] The invention relates to a method for monitoring the wear condition of a brake element of a vehicle, such as an automobile.

[0002] Patent application EP2986868 describes a vehicle brake element, the brake element having a surface extending along a longitudinal axis. The brake element comprises a first plurality of piezoelectric sensors and a second plurality of piezoelectric sensors. The first plurality of piezoelectric sensors is configured to detect a wave along a first predetermined polarization direction along a transverse axis, namely perpendicular to the longitudinal axis. Furthermore, the second plurality of piezoelectric sensors is configured to detect a wave along a second predetermined polarization direction parallel to the longitudinal axis. Generally, the wave originates from a mechanical stress exerted on the brake element, for example, by the pressure of brake discs on the brake element.Thus, the first plurality of piezoelectric sensors detects the wave in such a way as to determine the mechanical stress along the transverse axis, while the second plurality of piezoelectric sensors detects the wave in such a way as to determine the mechanical stress along the longitudinal axis.

[0003] However, due to their polarization, the first plurality of piezoelectric sensors exhibits limited sensitivity in any direction other than the first predetermined polarization direction. Similarly, the second plurality of piezoelectric sensors exhibits limited sensitivity in any direction other than the second predetermined polarization direction. Furthermore, increasing the number of piezoelectric sensors, in order to improve the accuracy of the determined mechanical stresses, increases the complexity of the received signal processing as well as the manufacturing, labor, and maintenance costs.

[0004] Furthermore, the waves, generated for example by pressure on the brake element, do not exhibit any particular distinction within their wave structure, thus limiting the ability of piezoelectric sensors to accurately identify the different modes of cracking and degradation of the brake element, reducing the effectiveness of the monitoring device in detecting certain types of defects in the brake element. In particular, in some cases, the brake element includes surface defects, often caused by corrosion or mechanical fatigue phenomena, manifesting as superficial cracks or areas of alteration in the material structure of the brake element, these defects develop and extend in response to the thermomechanical stress cycles imposed on the brake element during vehicle use. Due to their superficial nature, these defects require waves with specific sensitivity to capture small surface variations or microcracks that would otherwise go undetected using the aforementioned waves. Consequently, the waves described in the aforementioned patent application do not appear to be particularly well-suited for effectively detecting these superficial defects.

[0005] Moreover, in other cases, the brake element includes internal defects, such as internal cracks or delaminations between layers of the brake element material. In these cases, internal cracks, for example, are likely to form under the effect of mechanical fatigue imposed on the brake element, leading to a progressive degradation of the internal structure before a visible defect is perceptible on the surface. Delaminations, for their part, are partial or complete separations between the different layers of material in multilayer structures, as is often the case in certain brake pads, comprising, for example, composite or laminated materials.These types of internal defects alter the propagation of waves within the brake element, but their detection requires waves capable of passing through different layers with sufficient sensitivity to capture internal irregularities in the cohesion of the material.

[0006] The objective of the present invention is to remedy these drawbacks and to increase the reliability and lifespan of vehicle brakes.

[0007] To achieve this objective, the invention proposes a method for monitoring the wear condition of a vehicle brake element, the brake element comprising a first piezoelectric sensor and a second piezoelectric sensor, the method comprising the following steps: - a step of generating a surface wave in the brake element by the first piezoelectric sensor, the surface wave comprising a Rayleigh wave; - a stage of receiving a signal by the second piezoelectric sensor, the surface wave being transmitted and / or reflected in the brake element; - a step of comparing the received signal to a predetermined reference signal, in order to monitor the wear condition of the brake element.

[0008] Such a method allows continuous and precise monitoring of the wear condition of the brake element, thus ensuring the safety and reliability of the brake element.

[0009] Depending on the specific requirements of the brake element and the expected degradation mode, the second piezoelectric sensor produces a surface wave. Rayleigh waves propagate substantially on the surface of the brake element. This allows detect with greater accuracy superficial variations in the brake element and defects in the brake element.

[0010] In its general definition, the invention provides for a first piezoelectric sensor and a second piezoelectric sensor. However, it is also conceivable to provide for a first plurality of piezoelectric sensors and a second plurality of piezoelectric sensors, for example four, or even six piezoelectric sensors, in order to improve the detection of possible defects in the brake element without, however, excessively increasing the complexity of the signal processing.

[0011] Advantageously, Rayleigh Fonde has a frequency value between 10 MHz and 1000 MHz.

[0012] Advantageously, Surface Foundation includes a Love wave.

[0013] Moreover, due to their structure, Love waves propagate within The brake element, particularly through a thin plate or a layered structure, such as a brake pad or brake disc, is analyzed. This allows for the more precise detection of internal variations within the brake element, such as delamination, internal cracks, and density changes. Furthermore, Love waves enable the detection of brake element deformations, especially those caused by shear stresses.

[0014] Advantageously, Fonde de Love has a frequency value between 1 MHz and 10 MHz.

[0015] Advantageously, in the generation stage, the surface wave is generated by the first piezoelectric sensor according to a predetermined period.

[0016] The Rayleigh wave is generated according to a predetermined period chosen so as to avoid regular manual inspection, thereby reducing labor costs and vehicle service interruptions while ensuring that a possible defect is detected before causing a failure of the brake element.

[0017] Advantageously, at the generation stage, Surface background is generated by the first piezoelectric sensor when the vehicle starts.

[0018] Advantageously, the method further includes a step of issuing an alert when the comparison of the received signal to the predetermined reference signal indicates that the brake element is in a worn state.

[0019] By alerting the driver to brake wear that needs replacing, such a process ultimately reduces the vehicle's electrical consumption, thus contributing to the vehicle's range while ensuring thermal and auditory comfort for the driver.

[0020] The invention also relates to a computer program comprising program code instructions for executing the steps of the process of monitoring defined as above, when said program is running on a computer.

[0021] The invention further relates to an electronic control unit comprising an acquisition means, a processing means and a control means required for the implementation of a computer program defined as above.

[0022] The invention further relates to a vehicle comprising: - an electronic control unit defined as above; - a brake element comprising a first piezoelectric sensor and a second piezoelectric sensor electronically connected to the electronic control unit.

[0023] The invention will be further detailed by describing non-limiting embodiments, and based on the accompanying figures illustrating variants of the invention, in which: - [Fig.1] schematically illustrates a device for monitoring the wear condition of a brake element of a vehicle according to an embodiment of the present invention; - [Fig.2] illustrates a flowchart representing the steps of a process to monitor the wear state of the brake element according to a first embodiment of the present invention; - [Fig.3] illustrates a flowchart representing the steps of a process for monitoring the wear state of the brake element according to a second embodiment of the present invention; - [Fig.4] illustrates a flowchart representing the steps of a process for monitoring the wear state of the brake element according to a third embodiment of the present invention.

[0024] According to one embodiment of the present invention, a brake element 10 comprises a first piezoelectric sensor 11 and a second piezoelectric sensor 12, as illustrated in [Fig. 1]. The first piezoelectric sensor is configured to generate a surface wave.

[0025] The first piezoelectric sensor 11 and the second piezoelectric sensor 12 generally comprise materials such as quartz, ceramics such as lead zirconate titanate, or polymers such as polyvinylidene fluoride. These materials have the property of generating a wave when subjected to mechanical deformation. In practice, the first piezoelectric sensor 11 comprises a ceramic material, in particular lead zirconate, commonly used because of its wide operating temperature range, which is suitable for the thermal stresses of the brake element, for example, due to mechanical friction in use.

[0026] The second piezoelectric sensor 12 typically comprises a piezoelectric element encapsulated between two electrodes. When a mechanical wave, such as a compression, shear, or tension wave, reaches the piezoelectric element, the latter deforms slightly. This deformation generates a potential difference between the two electrodes, thus producing an electrical signal proportional to the applied deformation. This signal can then be processed to measure various parameters, such as the frequency and amplitude of the mechanical waves, which are indicative of the mechanical stresses and the condition of the structure of the brake element 10.

[0027] The brake element 10 is preferably a brake pad. The brake pad comprises a friction material, often a composite resistant to heat and pressure during the use of the brake element, for example when the brake pad is pressed against the brake disc to generate a braking force.

[0028] Alternatively, the brake element 10 is a brake disc. Generally, the brake disc comprises a cast iron or ceramic composite material for its thermal resistance and durability during the use of the brake element.

[0029] Furthermore, the first piezoelectric sensor and the second piezoelectric sensor are fixed to the brake element 10 by means of fastening. The fastening means include crimping, gluing, screwing, hooking, welding or clipping.

[0030] The first piezoelectric sensor 11 and the second piezoelectric sensor 12 are connected to an electronic control unit 20. The electronic control unit 20 comprises an acquisition means 21, a processing means 22, and a control means 23. Preferably, the first piezoelectric sensor 11 is electronically connected to the control means 23, while the second piezoelectric sensor 12 is electronically connected to the acquisition means 21.

[0031] Generally, the control means 23 electronically transmits a first electrical signal to the first piezoelectric sensor 11. Thus, the first piezoelectric sensor 11 emits the surface wave from the first transmitted electrical signal. Furthermore, the second piezoelectric sensor 12 converts a wave transmitted and / or reflected in the brake element into a second electrical signal. The second electrical signal is transmitted electronically to the acquisition means 21.

[0032] The processing means 22 is advantageously electronically connected to the acquisition means 21 and the control means 22. The processing means 22 even more advantageously comprises a multiplexer. The multiplexer allows the signals from, for example, the input of the acquisition means 21 to be transmitted, at the output, to the control means 22 to be combined, simplifying the electronic circuit of the unit. electronic control 20 by pooling the communication channels between the acquisition means 21 and the control means 22.

[0033] The control means 23 comprises a low-frequency generator and a voltage amplifier, electronically connected to each other. The low-frequency generator allows for precise adjustment of the frequency of the first electrical signal. In this way, the difference between surface waves emitted at the same frequency value is reduced.

[0034] The voltage amplifier allows the amplitude of the second electrical signal to be adjusted. In this way, the surface wave propagates in the brake element, in particular between the first piezoelectric sensor 11 and the second piezoelectric sensor 12, without attenuation below a detection threshold of the second piezoelectric sensor 12.

[0035] The acquisition means 21 is advantageously electronically connected to the multiplexer. The multiplexer is advantageously electronically connected to the low-frequency generator and the voltage amplifier. The amplifier is advantageously electronically connected to the first piezoelectric sensor 11. The acquisition means 21 is advantageously electronically connected to the second piezoelectric sensor 12.

[0036] The surface wave includes a Rayleigh wave. To illustrate this, the Rayleigh wave propagates along a longitudinal axis, while the brake element material follows an elliptical motion, preferably retrograde, meaning that the elliptical motion occurs in the opposite direction to the propagation of the Rayleigh wave along the longitudinal axis. The Rayleigh wave generally remains confined to the surface of the brake element 10, typically at a depth of approximately one wavelength. Thus, the Rayleigh wave is sensitive to surface defects, such as cracks caused by fatigue or corrosion.

[0037] Preferably, the Rayleigh wave has a frequency value between 10 MHz and 1000 MHz.

[0038] The surface wave advantageously includes a Love wave. To illustrate this, the Love wave propagates along a longitudinal axis, the material of the brake element following a transverse movement, perpendicular to the longitudinal axis.

[0039] Preferably, the Love wave has a frequency value between 1 MHz and 10 MHz.

[0040] The surface wave also advantageously includes a Lamb wave. Preferably, the Lamb wave has a frequency value between 100 kHz and 1 MHz.

[0041] Figure 2 illustrates a flowchart of a method for monitoring the wear condition of the brake element 10 of a vehicle according to a first embodiment, with the vehicle in motion, steps of the method being described below.

[0042] In a generation step El, a surface wave is generated in the brake element 10 by the first piezoelectric sensor 11, the surface wave comprising a Rayleigh wave.

[0043] In a reception step E2, a signal is received by the second piezoelectric sensor 12, the surface wave being transmitted and / or reflected in the brake element 10.

[0044] In a comparison step E3, the received signal is compared to a predetermined reference signal, so as to monitor the wear condition of the brake element.

[0045] For example, the processing means measures the propagation speed and amplitude of the received signal. The received signal's propagation speed is then compared to a predetermined signal propagation speed. Similarly, the received signal's amplitude is compared to a predetermined signal amplitude. Thus, in this example, the comparison between the received signal and the predetermined signal indicates that the brake element is worn when the received signal's propagation speed is less than the predetermined signal propagation speed or when the received signal's amplitude is less than the predetermined signal amplitude.

[0046] Steps of a method for monitoring the wear condition of the vehicle's brake are described below according to a second embodiment illustrated in [Fig.3], with the vehicle stationary.

[0047] In a generation step E' 1, a surface wave is generated in the brake element 10 by the first piezoelectric sensor 11, the surface wave comprising a Rayleigh wave.

[0048] Advantageously, the surface wave is generated according to a predetermined period. Preferably, the predetermined period is equal to 15 days.

[0049] In a reception step E'2, a signal is received by the second piezoelectric sensor 12, the surface wave being transmitted and / or reflected in the brake element 10.

[0050] In a comparison step E'3, the received signal is compared to a predetermined reference signal, so as to monitor the wear condition of the brake element.

[0051] Steps of a method for monitoring the wear condition of the vehicle's brake are described below according to a third embodiment illustrated in [Fig.4], with the vehicle switched off.

[0052] In a generation step E” 1, a surface wave is generated in the brake element 10 by the first piezoelectric sensor 11, the surface wave comprising a Rayleigh wave.

[0053] Advantageously, the surface wave is generated according to a predetermined period. Preferably, the predetermined period is equal to 15 days.

[0054] In a reception step E”2, a signal is received by the second piezoelectric sensor 12, the surface wave being transmitted and / or reflected in the brake element 10.

[0055] In a comparison step E”3, the received signal is compared to a predetermined reference signal, so as to monitor the wear condition of the brake element.

[0056] The method advantageously includes a step of issuing an alert when the brake is worn. For example, the alert is visual or audible. This makes it possible to detect a possible failure before the vehicle is restarted. Even more advantageously, the alert is issued at the next time the vehicle is started.

Claims

Demands

1. A method for monitoring the wear status of a brake element (10) of a vehicle, the brake element (10) comprising a first piezoelectric sensor (11) and a second piezoelectric sensor (12), the method comprising the following steps: - a step of generating (E1) a surface wave in the brake element (10) by the first piezoelectric sensor (11), the surface wave comprising a Rayleigh wave; - a step of receiving (E2) a signal by the second piezoelectric sensor (12), the surface wave being transmitted and / or reflected in the brake element (10); - a step of comparing (E3) the received signal to a predetermined reference signal, so as to monitor the wear status of the brake element.

2. A method according to claim 1, characterized in that the Rayleigh wave has a frequency value between 10 MHz and 1000 MHz.

3. A method according to claim 1 or 2, characterized in that the surface wave comprises a Love wave.

4. A method according to claim 3, characterized in that the Love wave has a frequency value between 1 MHz and 10 MHz.

5. A method according to any one of claims 1 to 4, characterized in that at the generation step (El), the surface wave is generated by the first piezoelectric sensor (11) according to a predetermined period.

6. A method according to any one of claims 1 to 5, characterized in that at the generation step (El), the surface wave is generated by the first piezoelectric sensor (11) when the vehicle starts.

7. A method according to any one of claims 1 to 6, characterized in that the method further comprises a step of issuing an alert when the comparison of the received signal with the predetermined reference signal indicates that the brake element (10) is in a worn state.

8. Computer program comprising program code instructions for performing the steps of the monitoring process according to any one of claims 1 to 7, when said program is running on a computer.

9. Electronic control unit (20) comprising an acquisition means (21), a processing means (22) and a control means (23) required for the implementation of a computer program according to claim 8.

10. Vehicle comprising: - an electronic control unit (20) according to claim 9; - a brake element comprising a first piezoelectric sensor (11) and a second piezoelectric sensor (12) electronically connected to the electronic control unit (20).

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