Friction member sensor system

Abstract

To provide a friction member sensor system capable of detecting the thickness of a friction material continuously before a friction state in which the friction member needs to be replaced is reached.SOLUTION: A friction member sensor system comprises: a friction member 10 which comprises a friction material 12 coming into contact with a disk rotor 20 as an opposite member rotating integrally with a wheel of a vehicle; a vibration sensor 30 which detects vibrations of the friction member 10 generated as the friction member 10 is pressed against the disk rotor 20; and a friction detection part 40 which detects the thickness of the friction material 12 from a detection signal output from the vibration sensor 30 and varying with the thickness of the friction material 12.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a friction member sensor system used in brake devices for automobiles, railways, industrial machines, and the like. [Background technology]

[0002] 2. Description of the Related Art Conventionally, disc brake devices and drum brake devices have been used as brake devices for automobiles, railways, industrial machines, and the like.

[0003] A disc brake device is a brake device that has brake pads with friction material attached to a back plate as the friction member and a disc rotor as the mating member, and brakes the wheels, etc. by pressing a pair of brake pads, which are provided on both sides of the disc rotor that rotates integrally with the wheels, etc., against the disc rotor.

[0004] Such friction members may be fitted with friction member sensors that detect the wear state of the friction material, and audible and electrical friction member sensors are known. An audible friction member sensor is configured to detect wear of the friction material by a metal fitting attached to the friction member coming into contact with a mating member and generating a sound when the friction material wears and becomes thinner (e.g., Patent Document 1). An electrical friction member sensor is configured to detect wear of the friction material by an electric wire embedded in the friction material becoming exposed and broken when the friction material wears and becomes thinner. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP2019-39511A Summary of the Invention [Problem to be solved by the invention]

[0006] In this way, conventional friction material sensors are configured to detect the wear state of the friction material that has become thin enough to require replacement by the sound generated by the metal fittings coming into contact with the counter member or by the cutting of the electric wire embedded in the friction material. Even with this detection method, for example, if the driver who owns the vehicle is able to grasp the running condition of the vehicle, he or she can also grasp that the friction material has worn to a certain extent, so there is no particular problem as long as it is detected that the friction material has reached a predetermined thickness. However, in a form of vehicle usage such as car sharing, it becomes difficult for the vehicle manager to grasp the running condition of the vehicle, so there is an increasing demand for a system that can detect the actual wear state of the friction material before it reaches a predetermined thickness.

[0007] Therefore, an object of the present invention is to provide a friction member sensor system that can continuously detect the thickness of a friction material before the friction material reaches a wear state that requires replacement. [Means for solving the problem]

[0008] The friction member sensor system of the present invention is configured to include a friction member having a friction material that contacts a counter member that rotates integrally with a vehicle wheel, a vibration sensor that detects vibrations of the friction member generated when the friction member is pressed against the counter member, and a wear detection unit that calculates the thickness of the friction material from a detection signal output from the vibration sensor that changes depending on the thickness of the friction material. Effect of the Invention

[0009] According to the friction member sensor system of the present invention, the thickness of the friction material can be continuously detected before it reaches a thickness that requires replacement of the friction member. [Brief description of the drawings]

[0010] [Figure 1] 1 is an explanatory diagram of a friction member sensor system according to an embodiment of the present invention; [Diagram 2]2 is an explanatory diagram of an example of a detection result of vibration of a friction member by the friction member sensor system of FIG. 1. [Diagram 3] FIG. 2 is a diagram showing an example of the detection result of vibration in the sliding direction of a friction member by the friction member sensor system of FIG. 1, showing the inertance for each frequency when the brake fluid pressure is 0.5 MPa. [Figure 4] FIG. 2 is a diagram showing an example of the detection result of vibration in the sliding direction of a friction member by the friction member sensor system of FIG. 1, showing the inertance for each frequency when the brake fluid pressure is 2.0 MPa. [Diagram 5] FIG. 2 is a diagram showing an example of the detection results of vibration in the axle direction of a friction member by the friction member sensor system of FIG. 1, showing the inertance for each frequency when the brake fluid pressure is 0.5 MPa. [Figure 6] FIG. 2 is a diagram showing an example of the detection results of vibration in the axle direction of a friction member by the friction member sensor system of FIG. 1, showing the inertance for each frequency when the brake fluid pressure is 2.0 MPa. [Figure 7] 2 is a diagram illustrating an example of a wear detection unit in the friction member sensor system of FIG. 1. [Figure 8] 8 is a graph showing the relationship between the thickness of the friction material and the vibration index using the friction member sensor system of FIG. 7, and shows the case where vibration with a frequency of 7 kHz in the sliding direction is extracted. [Figure 9] 8 is a graph showing the relationship between the thickness of the friction material and the vibration index as measured by the friction member sensor system of FIG. 7, and shows the case where vibration in the sliding direction with a frequency of 10 kHz is extracted. [Figure 10] 8 is a graph showing the relationship between the thickness of the friction material and the vibration index using the friction member sensor system of FIG. 7, and shows the case where vibration with a frequency of 14 kHz in the sliding direction is extracted. [Figure 11] 8 is a graph showing the relationship between the thickness of the friction material and the vibration index as measured by the friction member sensor system of FIG. 7, and shows the case where vibration in the axle direction with a frequency of 5 kHz is extracted. [Figure 12]8 is a graph showing the relationship between the thickness of the friction material and the vibration index as measured by the friction material sensor system of FIG. 7, and shows the case where vibration in the axle direction with a frequency of 8 kHz is extracted. [Figure 13] 8 is a graph showing the relationship between the thickness of the friction material and the vibration index as measured by the friction member sensor system of FIG. 7, in which the arrangement of the vibration sensor is changed to extract vibrations with a frequency of 7 kHz in the sliding direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The friction member sensor system of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments, and the members, materials, etc. described below can be modified in various ways within the scope of the present invention. In the drawings, the same reference numerals indicate the same or equivalent parts, and the size and positional relationship between the components are for convenience and may not strictly reflect the actual situation.

[0012] A friction member sensor system according to one embodiment of the present invention will now be described. Fig. 1 is an explanatory diagram of the friction member sensor system according to this embodiment, showing an example in which it is applied to a disc brake device.

[0013] As shown in FIG. 1, similar to a general disc brake device, friction members 10 are arranged on both sides of a disc rotor 20 (corresponding to a mating member) that rotates together with a wheel or the like, and braking is performed by pressing against the disc rotor 20 from both sides. The friction member 10 is configured such that a friction material 12 is attached to a back plate 11 by an adhesive member, and the friction material 12 comes into contact with the disc rotor 20, causing the disc rotor 20 to slide. This sliding generates vibration (friction vibration) in the friction member 10. The friction member sensor system of this embodiment is configured to include a vibration sensor 30 that detects the vibration of the friction member 10 in order to detect the thickness of the friction material 12, and a wear detection unit 40 that calculates the thickness of the friction material 12 from the detection result of the vibration sensor 30, and outputs a wear detection signal. The friction member sensor system of this embodiment will be described in detail below.

[0014] The back plate 11 constituting the friction member 10 constitutes a part of the support member of the friction member 10 and is made of, for example, hot-rolled steel plate for automobile structures such as SAPH440 or hot-rolled high-tensile steel plate for automobiles such as SPFH590.

[0015] The friction material 12 constituting the friction member 10 is made of a common material. Specifically, it is made of a composite material including, for example, a binder such as phenolic resin, a fiber base material such as aramid pulp, a lubricant such as graphite or molybdenum disulfide, an inorganic friction modifier such as zirconium oxide or zirconium silicate, an organic friction modifier such as cashew dust, a filler such as barium sulfate, etc. When the friction material 12 comes into contact with the disc rotor 20, the surface of the friction material 12 gradually wears and becomes thinner.

[0016] The friction member 10 vibrates together with the vehicle body while the vehicle is running. When braking, the friction member 10 is pressed against the disc rotor 20, the friction material 12 comes into contact with the rotating disc rotor 20, and the disc rotor 20 slides, causing the friction member 10 to vibrate. The frequency characteristics of the vibration of the friction member 10 caused by this sliding become the frequency characteristics specific to the vehicle when the friction member 10 is incorporated into the vehicle body as a disc brake device. The magnitude of the vibration changes depending on the speed of the vehicle (the rotation speed of the disc rotor 20) and the pressure with which the friction member 10 is pressed against the disc rotor 20. Furthermore, if the thickness of the friction material 12 is different, the vibration changes depending on the thickness. Therefore, the vibration of the friction member 10 is detected by the vibration sensor 30, and the thickness of the friction material 12 is calculated from the detection signal related to the vibration that changes depending on the thickness of the friction material 12.

[0017] First, the vibration of the friction member 10 detected by the vibration sensor 30 will be described. FIG. 2 is an explanatory diagram of an example of the detection result of the vibration of the friction member 10 by the vibration sensor 30 of the friction member sensor system of the present embodiment shown in FIG. 1. FIG. 2 shows the detection signal of the vibration of the friction member 10 output from the vibration sensor 30 (upper diagram), and the measurement results of the vehicle speed (vehicle speed) (middle diagram) and brake fluid pressure (lower diagram) when this detection signal is obtained. Note that the brake fluid pressure is the pressure applied to the friction member 10, that is, the pressure with which the friction member 10 presses the disc rotor 20, and is pressure data that can be easily obtained in a general vehicle. As shown in FIG. 2, a vibration detection signal is obtained during driving (when the brake fluid pressure is zero), but when braking is started (when the brake fluid pressure starts to increase and the vehicle speed starts to decrease), a vibration detection signal larger than that during driving is obtained. When a specified brake fluid pressure continues to be applied, the vehicle speed decreases and the vibration detection signal gradually becomes smaller, and vibration is detected until the vehicle stops (vehicle speed becomes zero), at which point the vibration is no longer detected.

[0018] The magnitude of such a vibration detection signal changes depending on the vehicle speed and brake fluid pressure when the friction member 10 contacts the disc rotor 20. Specifically, the faster the vehicle speed is and the greater the brake fluid pressure is, the larger the detection signal becomes. The magnitude of the vibration detection signal also changes depending on the thickness of the friction material 12, but this change is relatively small and difficult to detect directly from the large vibration of the friction member 10. Therefore, in this embodiment, in order to make it easier to detect the change even when the detection signal that changes depending on the thickness of the friction material 12 is small, the thickness of the friction material 12 is not calculated from all detection signals of the vibration detected by the vibration sensor 30, but a detection signal during the period from when the vehicle speed slows down to a predetermined speed to when it stops (the period when the vibration of the friction member 10 is small) and when the magnitude of the brake fluid pressure is within a predetermined range is extracted as a detection signal that changes depending on the thickness of the friction material 12. Specifically, as an example, when the vehicle speed is in the range of 2 to 20 km / h and the brake fluid pressure is 0.5 MPa or higher (the "detection signal extraction period" shown in Figure 2), good results were obtained by extracting the detection signal of the vibration detected by the vibration sensor 30 as a detection signal that changes depending on the thickness of the friction material 12, as will be described later.

[0019] Here, the frequency characteristics and direction of vibration will be described. The vibration of the friction member 10, except for the vibration generated by the running of the vehicle, is generated when the friction material 12 of the friction member 10 contacts the disc rotor 20 and the disc rotor 20 slides. Specifically, vibration occurs substantially parallel to the contact surface between the friction material 12 and the disc rotor 20 in the rotation direction of the disc rotor 20 and in the opposite direction (this direction is called the "sliding direction"). Vibration also occurs in a direction substantially perpendicular to the contact surface between the friction material 12 and the disc rotor 20 (this direction is called the "axial direction"). Figures 3 and 4 are diagrams showing an example of the results of detecting vibration in the sliding direction of the friction member 10 by the friction member sensor system of this embodiment shown in Figure 1 using an acceleration sensor as the vibration sensor 30. Figure 3 shows the inertance for each frequency when the brake fluid pressure is 0.5 MPa, and Figure 4 shows the inertance for each frequency when the brake fluid pressure is 2.0 MPa. Here, a brake fluid pressure of 0.5 MPa is the pressure when the brake is lightly applied, and a brake fluid pressure of 2.0 MPa is the pressure when the brake is applied somewhat strongly; these are the brake fluid pressures used for braking during normal driving.

[0020] 3 and 4, it can be seen that there are several peak frequencies in the vibration in the sliding direction that are almost unchanged by the brake fluid pressure. It has also been confirmed that these peak frequencies are specific to each vehicle and are almost unchanged by the thickness of the friction material 12. In other words, at these peak frequencies, the friction member 10 is likely to vibrate regardless of the brake fluid pressure or the thickness of the friction material 12, and a large detection signal can be obtained.

[0021] 5 and 6 are diagrams showing an example of the results of detecting vibration in the axle direction of the friction member 10 by the friction member sensor system of the present embodiment shown in Fig. 1 using an acceleration sensor as the vibration sensor 30. Fig. 5 shows the inertance for each frequency when the brake fluid pressure is 0.5 MPa, and Fig. 6 shows the inertance for each frequency when the brake fluid pressure is 2.0 MPa.

[0022] As shown in Figures 5 and 6, it can be seen that there are peak frequencies for vibration in the axle direction that are almost unchanged by brake fluid pressure, similar to the vibration in the sliding direction shown in Figures 3 and 4. These peak frequencies are also specific to each vehicle, and it has been confirmed that they are almost unchanged by the thickness of the friction material 12.

[0023] For the friction member 10 having the vibration frequency characteristics shown in Figs. 3 to 6, extraction of a detection signal that changes according to the thickness of the friction material 12 is considered. In order to extract a predetermined vehicle speed and brake fluid pressure as well as vibration of a predetermined direction and frequency, a wear detection unit 40A is configured as shown in Fig. 7 as an example of the wear detection unit 40 of the friction member sensor system of the present embodiment shown in Fig. 1. In the example of the present embodiment shown in Fig. 7, the vibration sensor 30 is configured as an acceleration sensor. The wear detection unit 40A is configured to include a vibration extraction unit 41, a brake state determination unit 42, a vehicle speed determination unit 43, and a friction material thickness calculation unit 44. The vibration extraction unit 41 receives the detection result of the vibration sensor 30, the determination result of the brake state determination unit 42 to which, for example, the measurement result of the brake fluid pressure of the brake device is input, and the determination result of the vehicle speed determination unit 43 to which, for example, data related to the vehicle speed (vehicle speed) is input from a tachometer. Then, in the vibration extraction unit 41, the detection result of the predetermined brake fluid pressure and the predetermined vehicle speed range is extracted, and further, the detection result of the vibration at the peak frequency is extracted by filtering at the peak frequency. As described above, as an example, from the vibration detection results extracted when the vehicle speed was in the range of 2 to 20 km / h and the brake fluid pressure was in the range of 0.5 MPa or more, vibrations at frequencies of 7 kHz, 10 kHz, and 14 kHz, where peaks were observed, were extracted for vibrations in the sliding direction, and vibrations at frequencies of 5 kHz and 8 kHz, where peaks were observed, for vibrations in the axial direction.

[0024] Next, the vibration at each peak frequency obtained is converted into a vibration index. Here, the "vibration index" means the average vibration level per sampling, which is indicated by adding up the absolute values ​​of the vibration detection signals at the extracted predetermined frequencies during a predetermined vehicle speed, for example, 2 to 20 km / h, and a predetermined brake hydraulic pressure, for example, 0.5 MPa or more, and dividing the sum by the number of data. The detection signals are added up as absolute values ​​in order to process all detection signals where the vibration detection signals are output as positive and negative signals as shown in FIG. 2, and the average vibration level is indicated by dividing by the number of data in order to process the detection signals regardless of the braking time.

[0025] Figures 8 to 10 are graphs showing the relationship between the thickness of the friction material 12 and the vibration index of the vibration in the sliding direction, as measured by the friction member sensor system shown in Figure 7. Figure 8 shows a plot of the vibration index at a frequency of 7 kHz, among the vibrations in the sliding direction, against the thickness of the friction material 12, in a friction member sensor system provided with a friction material 12 of a predetermined thickness, when the vehicle speed is 2 to 20 km / h and the brake fluid pressure is 0.5 MPa or more, and shows the results when the vibration sensor 30 is disposed on the outer pad. Similarly, Figures 9 and 10 show plots of the vibration indexes at frequencies of 10 kHz and 14 kHz, among the vibrations in the sliding direction, against the thickness of the friction material 12, respectively.

[0026] As shown in Figures 8 to 10, from the relationship between the thickness of the friction material 12 and the vibration index of the vibration in the sliding direction, it can be seen that the thinner the friction material 12, the larger the vibration index at any frequency. In particular, the smaller the frequency, the larger the change, which is preferable. This is thought to be because, as the friction material 12 becomes thinner, the amount of vibration damping decreases, and the vibration is more likely to change depending on the thickness of the friction material 12. Also, the amount of vibration damping decreases as the frequency decreases, which is thought to be due to the fact that the change depending on the thickness of the friction material 12 is more pronounced.

[0027] 11 and 12 are graphs showing the relationship between the thickness of the friction material 12 and the vibration index of the vibration in the axle direction, as measured by the friction member sensor system shown in FIG. 7. FIG. 11 plots the vibration index of the vibration in the axle direction at a frequency of 5 kHz against the thickness of the friction material 12 when the vehicle speed is 2 to 20 km / h and the brake fluid pressure is 0.5 MPa or more, in a friction member sensor system equipped with a friction material 12 of a predetermined thickness, and shows the results when the vibration sensor 30 is disposed on the outer pad. Similarly, FIG. 12 plots the vibration index of the vibration in the axle direction at a frequency of 8 kHz against the thickness of the friction material 12.

[0028] As shown in Figures 11 and 12, from the relationship between the thickness of the friction material 12 and the vibration index in the axle direction, it can be seen that although there is a tendency for the vibration index to increase as the thickness of the friction material 12 becomes thinner, detection becomes more difficult as the friction material becomes thinner.

[0029] As described above, from the results of Figs. 8 to 12, when detecting the thickness of the friction material 12 using the friction member sensor system shown in Fig. 7, it is preferable to use the vibration index of the vibration in the sliding direction when the vehicle speed is 2 to 20 km / h and the brake fluid pressure is 0.5 MPa or more, and it is more preferable to use the vibration index of the frequency of 7 kHz. Fig. 13 is a graph showing the relationship between the thickness of the friction material 12 and the vibration index of the vibration in the sliding direction by the friction member sensor system shown in Fig. 7. Fig. 13 shows the results when the vibration sensor 30 is arranged on the inner pad, plotting the vibration index of the frequency of 7 kHz among the vibrations in the sliding direction against the thickness of the friction material 12 when the vehicle speed is 2 to 20 km / h and the brake fluid pressure is 0.5 MPa or more in a friction member sensor system having a friction material 12 of a predetermined thickness. It can be seen that the vibration index increases as the thickness of the friction material 12 becomes thinner, similar to the results when the vibration sensor 30 is arranged on the outer pad shown in Fig. 8. Therefore, in this embodiment, a detection signal of a predetermined direction and frequency is extracted from the detection signal of vibration detected by the vibration sensor 30 as a detection signal that changes depending on the thickness of the friction material 12, and the thickness of the friction material 12 is calculated from this detection signal. Specifically, as an example, good results were obtained when the thickness of the friction material 12 was calculated from the vibration in the sliding direction extracted from the detection signal of vibration detected by the vibration sensor 30 and a detection signal with a frequency of 7 kHz.

[0030] 7, the vibration extraction unit 41 can extract a detection signal of a predetermined direction and frequency from the detection signal of vibration detected by the vibration sensor 30, and the friction material thickness calculation unit 44 calculates a vibration index from the detection signal output from the vibration extraction unit 41, calculates the thickness of the friction material 12 from a pre-stored relationship between the friction material thickness and the vibration index, and outputs it as a wear detection signal. In a preferred embodiment, as described above, the vibration extraction unit 41 also detects that the vehicle speed and brake fluid pressure are in predetermined cases, and extracts a detection signal that changes depending on the thickness of the friction material 12 from the detection signal of vibration detected by the vibration sensor 30.

[0031] Although the embodiment of the present invention has been described above, the friction member sensor system of the present invention is not limited to the extraction of the detection signal described in the present embodiment, as long as the thickness of the friction material can be calculated from the detection signal when extracting the detection signal output from the vibration sensor, which varies depending on the thickness of the friction member. For example, it is not essential to limit the extraction range based on the vehicle speed or the pressure with which the friction member presses the mating member. In addition, the vibration characteristics of the friction member incorporated in the brake device do not necessarily have the peak frequency described above. Therefore, it is sufficient to appropriately select a detection signal that varies depending on the thickness of the friction material, such as the direction of vibration or peak frequency, for each brake device, and for example, the thickness of the friction material may be calculated from the detection signal of the vibration in the axle direction.

[0032] The wear detection signal output from the friction member sensor system is not limited to indicating the thickness of the friction material 12, but may also output a signal to indicate the level of the thickness of the friction material 12, such as a state in which the friction material 12 is sufficiently thick, a state in which the friction material 12 is relatively thick and replacement of the friction members 10, etc. is not necessary but preparation for replacement is preferable, or a state in which the friction material 12 is thin and replacement of the friction members 10, etc. is necessary, or a signal to indicate the percentage (%) of the thickness compared to a state in which the friction material 12 is not worn.

[0033] (summary) (1) One embodiment of the friction member sensor system of the present invention is configured to include a friction member having a friction material that contacts a counter member that rotates integrally with a vehicle wheel, a vibration sensor that detects vibrations of the friction member generated when the friction member is pressed against the counter member, and a wear detection unit that calculates the thickness of the friction material from a detection signal output from the vibration sensor that changes depending on the thickness of the friction material.

[0034] (2) According to another embodiment, in the friction member sensor system of (1) above, the wear detection unit is configured to calculate the thickness of the friction material when the vehicle is traveling at a preset speed and the friction member is pressed against the mating member with a preset pressure, making it easy to detect the change in the detection signal that changes according to the thickness of the friction material even if the change is small.

[0035] (3) According to another embodiment, in the friction member sensor system of (1) or (2) above, the detection signal is an inertance at a peak frequency of the inertance for each frequency of vibration of the friction member, thereby making it possible to obtain a large detection signal.

[0036] (4) According to still another embodiment, in the friction member sensor system of (3) above, the vibration of the friction member is configured to be a vibration in the sliding direction, which makes it possible to obtain a large detection signal. [Explanation of symbols]

[0037] 10 Friction material 11 Backplate 12 Friction material 20 Disc rotor 30 Vibration Sensor 40, 40A Wear detection unit 41 Vibration extraction part 42 Brake state determination unit 43 Vehicle speed determination section 44 Friction material thickness calculation section

Claims

1. A friction member having a friction material that comes into contact with a mating member that rotates integrally with a wheel of a vehicle; a vibration sensor that detects vibration of the friction member caused when the friction member is pressed against the counter member; a wear detection unit that calculates the thickness of the friction material from a detection signal that is output from the vibration sensor and that changes depending on the thickness of the friction material; A friction member sensor system comprising:

2. the wear detection unit calculates a thickness of the friction material when the vehicle is traveling at a preset speed and the friction member is pressed against the counter member with a preset pressure. The friction member sensor system of claim 1 .

3. the detection signal is an inertance at a peak frequency of the inertance for each frequency of vibration of the friction member, 3. The friction member sensor system according to claim 1 or 2.

4. The vibration of the friction member is a vibration in a sliding direction.

4. The friction member sensor system of claim 3.

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