JP2009168210A - Brake pad wear detector, lining wear detector - Google Patents

Abstract

[PROBLEMS] To reduce the possibility of erroneous determination of brake pad wear.
A braking brake pad 14 contacts a disk rotor 18 to generate a braking force on a wheel. The vibration generating brake pad 16 is disposed adjacent to the braking brake pad 14 in the wheel radial direction, and has a thickness substantially equal to the wear limit thickness of the braking brake pad 14. The disk rotor 18 has a circumferential undulation formed in a portion facing the vibration generating brake pad 16. The microphone 28 collects a contact sound between the vibration generating brake pad 16 and the disk rotor 18. The wear determination unit 34 estimates the frequency of the contact sound generated when the vibration generating brake pad 16 and the disk rotor 18 come into contact based on the rotational frequency of the wheel and the number of undulation peaks of the disk rotor 18. It is determined whether or not a sound having a frequency has a sound pressure equal to or higher than a predetermined threshold value.
[Selection] Figure 1

Description

  The present invention relates to an automobile brake device, and more particularly to an apparatus for detecting wear of a brake pad.

  Generally, in a disc brake device of a vehicle, pads attached to a steel plate back metal are arranged on both sides of the disc rotor, and braking force is exerted by pressing the brake pads against both sides of the disc rotor during braking. . The brake pads are worn every time the vehicle is braked. In order to ensure an appropriate braking force of the vehicle, it is necessary to promptly replace a brake pad that has been worn to the wear limit.

  Two types of techniques are known mainly for detecting worn brake pads. First, a leaf spring whose tip protrudes to the wear limit thickness surface of the pad is fixed to the back pad of the brake pad, and when the pad reaches the wear limit, the tip of the leaf spring contacts the disc rotor. It is an audio type that generates an audible sound. When the brake pad is worn, sound is generated by contact between the leaf spring and the rotor, so that the driver can detect the wear of the pad. The other is to provide a sensor through the harness on the back metal. When the pad reaches the wear limit, the disk rotor contacts the harness and cuts the harness. It is an electric type that detects this disconnection and turns on a warning light in the passenger compartment.

  All the above methods have drawbacks. In the case of the voice type, the driver may not be able to detect sound when the vehicle window is closed or the air conditioner or audio is activated. Furthermore, it is difficult to distinguish from the brake squeal. Although there is no such problem in the electric system, it is necessary to wire the brake part of each wheel, which increases the cost.

In Patent Document 1, as a solution to the drawbacks of the voice type, the sound picked up by the microphone fixed to the inner surface of the tire house is passed through a band-pass filter that allows only the vibration sound of the leaf springs to pass through the amplifier. A lining wear warning device is disclosed in which a warning device is activated to inform the driver of the time for pad replacement.
JP 59-40028

  However, in Patent Document 1, when noise substantially equal to the vibration sound of the leaf spring is generated from the traveling vehicle, there is a possibility that the wear of the pad may be erroneously determined even if the bandpass filter is passed. .

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a brake pad wear detection device that is less likely to make an erroneous determination of wear.

  One embodiment of the present invention is a brake pad wear detection device for a disc brake. This device is disposed adjacent to the brake pad for braking to generate a braking force on the wheel in contact with the disc rotor, and to the brake brake pad in the radial direction of the wheel. A vibration generating brake pad having an equal thickness, a disk rotor having a circumferential undulation formed in a portion facing the vibration generating brake pad, and a contact sound between the vibration generating brake pad and the disk rotor Based on a microphone that collects sound, a sound analysis unit that performs frequency analysis on the sound collected by the microphone, and the rotational frequency of the wheel and the number of undulation peaks of the disk rotor. Estimating the frequency of the contact sound that occurs when the brake pad and the disc rotor come into contact, and the sound pressure with the frequency is equal to or higher than a predetermined threshold And whether the determined wear judgment unit there, when the determination is affirmative, and an alarm unit for informing the wear of the brake brake pads.

  According to this aspect, when the brake pads for wear are worn, vibration sounds having different frequencies are generated according to the vehicle speed, and wear is determined on the sound collection side for the frequency according to the vehicle speed. The possibility of erroneous determination due to other noise can be reduced.

  The wear determination unit may perform the determination when the vehicle is braking. Since the wear determination is not performed on the sound generated except when the vehicle is braked, the possibility of erroneous determination is further reduced.

  There may be a plurality of undulation peaks of the disk rotor. The greater the number of undulation peaks, the more preferable it is because vibration is less likely to be detected by the driver.

  The number of undulation peaks of the disc rotor may be set so as to generate a contact sound having a frequency equal to or lower than a human audible range lower limit value. When the vehicle is running in a normal state, low-frequency sound outside the human audible range is not generated from the vehicle, so the sound generated by the contact between the brake pad for vibration generation and the disc rotor and the vehicle running It becomes easy to distinguish from other noises generated inside.

  The vibration generating brake pad may be made of a material softer than the material of the braking brake pad. By making the brake pad for braking harder than the brake pad for generating vibration, the brake pad for braking is more likely to come into contact with the rotating surface of the disc rotor even after the brake pad reaches the wear limit thickness. The required braking force can be secured.

  Another aspect of the present invention is a drum brake lining wear detection device. This device is disposed adjacent to the braking lining that contacts the inner peripheral surface of the brake drum to generate a braking force on the wheel, and the braking lining adjacent to the braking lining in the axial direction. A vibration generating lining having an equal thickness, a brake drum in which circumferential undulation is formed in a portion facing the vibration generating lining, and a contact sound between the vibration generating lining and the brake drum. And a sound analysis unit that performs frequency analysis on the sound collected by the microphone, the vibration generating lining, and the number of undulation peaks of the brake drum The frequency of the contact sound generated when the brake drum comes into contact is estimated, and it is determined whether or not the sound having the frequency is equal to or higher than a predetermined threshold. When a determination unit, the determination is affirmative, and an alarm unit for informing the wear of the brake lining.

  According to the present invention, there is provided a brake pad wear detection device that has a low possibility of erroneous wear determination.

  FIG. 1 shows a brake pad wear detection device 100 according to an embodiment of the present invention. A disc brake 10 installed on each wheel of a vehicle (not shown) is shown in a sectional view. The disc brake 10 includes a mounting (not shown) fixed to a non-rotating member of the vehicle and a caliper 22 that is slidably supported with respect to the mounting. A piston 20 is arranged inside the caliper 22. The caliper 22 is formed in a U-shape and is disposed with a disc rotor 18 that rotates coaxially with the wheel. On both sides of the disk rotor 18, braking brake pads 14 are arranged to face each other. The back metal 12 is attached to each side of the braking brake pad 14 that does not face the disc rotor 18. The back metal 12 is supported so as to be slidable in the axial direction of the disk rotor 18 by mounting.

  A piston 20 of the caliper 22 is disposed on the back of the back metal 12 on the left side in the drawing. When a driver depresses a brake pedal (not shown), the piston 20 is actuated to push the back metal 12 in the right direction in the figure, and the left brake pad 14 is pressed against the left side of the disc rotor 18. Further, the caliper 22 moves to the left side in the drawing in accordance with the operation of the piston 20, and the claw portion on the side opposite to the piston 20 of the caliper 22 moves to push the right back metal 12. Then, the brake brake pad 14 on the right side is pressed against the right side surface of the disc rotor 18. In this way, the disc rotor 18 is clamped from both sides by the left and right braking brake pads 14, and braking force is generated on the wheels.

  As will be described in detail later, in this embodiment, in addition to the brake pad 14 for braking, a brake pad 16 for vibration generation is provided on the left and right back metal. The vibration generating brake pad 16 is disposed adjacent to the braking brake pad 14 in the wheel radial direction, and has a thickness substantially equal to the wear limit thickness of the braking brake pad 14. When the brake pad 14 for braking is worn and reaches the wear limit thickness, the brake pad 16 for vibration generation comes into contact with the rotating surface of the disc rotor 18 and generates vibration sound having a specific frequency. The vibration sound is adjusted so as to have a frequency equal to or lower than the lower limit value of the human audible frequency range. Therefore, the sound generated by the contact between the vibration generating brake pad 16 and the disk rotor 18 cannot be heard by the driver or a person around the vehicle.

  FIG. 2 is an enlarged view of the disk rotor 18, the back metal 12, the braking brake pad 14, and the vibration generating brake pad 16 of FIG. 1. Non-contact portions A that do not come into contact with the brake pads 14 for braking are formed on both sides of the disc on the outer periphery of the disc rotor 18. A vibration generating brake pad 16 is disposed opposite to the non-contact portion A. As described above, the thickness of the vibration generating brake pad 16 is substantially equal to the wear limit thickness of the braking brake pad 14. Therefore, when the brake pad 14 for braking is worn to the wear limit thickness, the brake pad 16 for vibration generation and the non-contact portion A of the disk rotor 18 come into contact with each other. The non-contact portion A may be formed on the inner peripheral side of the disk rotor 18.

  Waviness in the circumferential direction is formed on the rotating surface of the non-contact portion A of the disk rotor 18. When this swell and the vibration generating brake pad 16 come into contact with each other, a low frequency vibration sound is generated.

  FIG. 3 is an example of a change in the thickness of the swell formed in the non-contact portion A of the disk rotor. In this example, five peaks are formed during one rotation of the disk rotor. The number of hills may be one during one rotation of the rotor, but the larger the number of hills, the more difficult it is to detect vibrations by the driver. However, when the number of peaks is increased, when the vehicle speed increases, the frequency of vibration sound caused by the contact between the disc rotor and the vibration generating brake pad enters the audible range. Therefore, it is preferable to determine the number of peaks so that the frequency of the vibration sound is equal to or lower than the audible range lower limit value even while the vehicle is traveling at the legal speed upper limit value.

  The change in thickness of the disc rotor 18 may be transmitted as pulsation to a brake pedal (not shown) via the piston 20 in the caliper 22 and the brake path. Therefore, the thickness change amount D of the disk rotor shown in FIG. 3 is preferably set to such a magnitude that the driver does not feel pedal pulsation. However, this does not apply when the brake is controlled by wire.

  The material of the vibration generating brake pad 16 preferably has a softer characteristic than the material of the braking brake pad 14. If only the brake pad 16 for vibration generation comes into contact with the disc rotor 18 after the brake pad 14 reaches the wear limit thickness, the braking force is insufficient. By making the brake pad 14 for braking more rigid than the brake pad 16 for generating vibration, the brake pad 14 for braking is the rotating surface of the disc rotor 18 even after the brake pad 14 reaches the wear limit thickness. The required braking force can be secured.

  Returning to FIG. 1, the sound generated by the contact between the disc rotor and the vibration-generating brake pad is collected by the microphone 28 installed on the vehicle body and input to the processing unit 30.

  The processing unit 30 includes a sound analysis unit 32, a wear determination unit 34, and a warning display unit 36. These functional blocks can be realized by hardware such as a CPU and a memory of a computer, and can be realized by a computer program or the like in terms of software. Those skilled in the art will understand that these functional blocks can be realized in various forms by a combination of hardware and software.

  The sound analysis unit 32 performs frequency analysis on the sound collected by the microphone 28 by a known method. The sound pressure level for each frequency obtained by frequency analysis is input to the wear determination unit 34.

  Normally, when the vehicle is running in a normal state, no low-frequency sound outside the human audible range is generated from the vehicle. Therefore, vibration is obtained by performing frequency analysis on the sound collected by the microphone 28. Sounds generated by the contact between the generating brake pads and the disk rotor can be clearly distinguished from other sounds generated while the vehicle is running.

The wear determination unit 34 receives the rotation frequency of the wheel from the wheel speed sensor 40 and the sound pressure level for each frequency from the sound analysis unit 32, and the sound pressure level of the frequency F that satisfies the following equation reaches a predetermined threshold T. It is determined whether or not.
C ・ R−d ≦ F ≦ C ・ R + d (1)
Where C is the number of swells per rotation formed in the disk rotor, R is the wheel rotation frequency detected by the wheel speed sensor [Hz], F is the frequency [Hz] output from the sound analysis unit, d is an allowable error. The threshold value T is, for example, a sound pressure level generated when the vibration-generating brake pad 16 and the disc rotor 18 come into contact while the vehicle is traveling at a normal speed (for example, 30 to 80 km / h). Is set to a value slightly smaller than the average value.

  When the sound pressure level of the frequency F that satisfies Equation (1) is equal to or greater than the threshold value T, the wear determination unit 34 is in contact with the vibration-generating brake pad 16 and the disc rotor 18, and therefore the brake It is determined that the pad 14 has been worn to the wear limit thickness.

  Note that the wear determination unit 34 may execute the above-described determination only while the driver is braking based on the output of the brake pedal sensor 42. In this case, since the wear determination is not performed for the sound generated except when the vehicle is braked, the possibility of erroneous determination is further reduced.

  When the wear determination unit 34 determines that the braking brake pad 14 has been worn to the wear limit thickness, the warning display unit 36 turns on a warning light 38 disposed in a meter unit or the like in the passenger compartment. In this way, the driver does not hear the contact sound between the vibration generating brake pad 16 and the disc rotor 18 but the wear determination result is displayed with the warning light, thereby preventing the driver from missing the sound. . Note that the warning display unit 36 may cause a warning message or the like to flow into the vehicle interior through a speaker (not shown) instead of the warning light.

  It is only necessary to provide one microphone 28 on the vehicle body. The place where the microphone is installed is not particularly limited, and may be installed in the passenger compartment or the engine room as long as the sound from the disk rotor can be picked up. However, one microphone may be installed at the front and rear of the vehicle, or one microphone may be installed near the wheel or tire house of each wheel.

FIG. 4 is a flowchart of processing executed by the wear determination unit 34.
First, the wear determination unit 34 determines whether or not the vehicle speed is within a predetermined upper and lower limit range based on the output of the wheel speed sensor 40 (S12). This determination is based on the fact that if the vehicle speed is too low, the generation time of vibration noise from the vibration generating brake pad is short and it is difficult to determine wear.If the vehicle speed is too high, the vibration sound from the vibration generating brake pad is within the audible range. This is executed to prevent erroneous determination by the wear determination unit because of the possibility of entering. However, the determination of S12 may not be performed.

  If the vehicle speed is outside the upper / lower limit value range (N in S12), this flow is terminated. When the vehicle speed is within the upper / lower limit value range (Y in S12), the wear determination unit 34 determines whether or not the driver is performing a braking operation based on the output of the brake pedal sensor 42 (S14). If the braking operation is not being performed (N in S14), this flow is terminated. When the braking operation is being performed (Y in S14), the result of the frequency analysis is received from the sound analysis unit 32 (S16), and the wear determination using the above equation (1) is performed (S18).

  As described above, according to the present embodiment, when the brake pads are worn, the sound generated by the contact between the brake pads for generating vibrations provided on the disc brakes of the respective wheels and the disc rotor is obtained by the microphone installed on the vehicle body. Since it is configured to pick up, there is no need to wire the brake part of each wheel. Further, the frequency of the vibration sound generated from the vibration generating brake pad is estimated based on the wheel rotation frequency detected by the wheel speed sensor, and the wear determination is performed based on the sound pressure level of the frequency. Thereby, it is possible to reduce the possibility that a sound generated from other than the vibration generating brake pad is erroneously determined as a contact sound. Further, since the wear of the pad is determined based on the result of the frequency analysis, the wear of the brake pad can be detected without depending on the driver's hearing. Furthermore, since the cost required for wiring is small, it becomes possible to mount the brake pad wear detection device on a relatively low-priced vehicle.

  FIG. 5 is a diagram for explaining pad wear detection of a drum brake according to another embodiment of the present invention. FIG. 5 shows a brake drum 60, a braking lining 64 that generates a braking force in contact with the inner peripheral surface of the brake drum, a rim 62 that presses the braking lining 64 against the inner peripheral surface of the brake drum, and a braking lining 64. A vibration generating lining 66 having a thickness substantially equal to the wear limit thickness is shown. Similarly to the example shown in FIG. 2, a non-contact portion B that does not contact the braking lining 64 is formed on a part of the inner peripheral surface of the brake drum. The vibration generating lining 66 is disposed to face the non-contact portion B. In the non-contact portion B, a swell having one or more peaks per one rotation of the drum is formed. When the braking lining 64 is worn down to the wear limit thickness, the vibration generating lining 66 and the non-contact portion B of the brake drum 60 come into contact with each other, and a vibration sound having a frequency equal to or lower than the lower limit value of the human audible range is generated. Other configurations such as wear by the wear determination unit are the same as the above-described example of the disc brake.

  The present invention has been described based on some embodiments. These embodiments are merely examples, and modifications such as arbitrary combinations of the embodiments, each component of the embodiments, and any combination of the processing processes are also within the scope of the present invention. It will be understood by those skilled in the art.

  The present invention is not limited to the above-described embodiments, and various modifications such as design changes can be added based on the knowledge of those skilled in the art. The configuration shown in each drawing is for explaining an example, and can be appropriately changed as long as the configuration can achieve the same function.

  In the embodiment, it has been described that the undulation is formed in the non-contact portion of the disk rotor. Instead of or in addition to this, the undulation is formed in the contact surface of the brake pad for vibration generation facing the non-contact portion. May be.

It is a figure which shows the brake pad wear detection apparatus which concerns on one Embodiment of this invention. FIG. 2 is an enlarged view of the disk rotor, backing metal, braking brake pad, and vibration generating brake pad of FIG. 1. It is a figure which shows an example of the thickness change of the wave | undulation formed in the non-contact part A of a disk rotor. It is a flowchart of the process performed in a wear determination part. It is a figure explaining the pad abrasion detection of the drum brake which concerns on another embodiment of this invention.

Explanation of symbols

  10 Disc brake, 12 Back metal, 14 Brake brake pad, 16 Brake pad for vibration generation, 18 Disc rotor, 20 Piston, 22 Caliper, 28 Microphone, 30 Processing unit, 32 Sound analysis unit, 34 Wear determination unit, 36 Warning display 38 warning light, 40 wheel speed sensor, 60 brake drum, 64 braking lining, 66 vibration generating lining.

Claims (6)

A brake pad for braking that generates braking force on the wheels in contact with the disk rotor;
A brake pad for vibration generation that is disposed adjacent to the brake brake pad in the radial direction of the wheel and has a thickness substantially equal to a wear limit thickness of the brake pad for braking;
A disk rotor in which a circumferential swell is formed in a portion facing the vibration generating brake pad;
A microphone that collects contact sound between the vibration-generating brake pad and the disk rotor;
A sound analysis unit that performs frequency analysis on the sound collected by the microphone;
Based on the rotational frequency of the wheel and the number of undulation peaks of the disk rotor, the frequency of the contact sound generated when the vibration-generating brake pad and the disk rotor contact each other is estimated, and the sound having the frequency is predetermined. A wear determination unit for determining whether or not the sound pressure is equal to or greater than a threshold value;
When the determination is affirmative, an alarm unit that informs wear of the brake pad for braking,
A brake pad wear detection device for a disc brake, comprising:   The brake pad wear detection device according to claim 1, wherein the wear determination unit performs the determination when the vehicle is braking.   The brake pad wear detection device according to claim 1 or 2, wherein the number of undulation peaks of the disk rotor is plural.   4. The brake according to claim 1, wherein the number of undulation peaks of the disc rotor is set so as to generate a contact sound having a frequency equal to or lower than a human audible range lower limit value. Pad wear detection device.   The brake pad wear detecting device according to any one of claims 1 to 4, wherein the vibration generating brake pad is formed of a material softer than a material of the braking brake pad. A braking lining that generates braking force on the wheels in contact with the inner peripheral surface of the brake drum;
A vibration generating lining disposed adjacent to the braking lining in the axle direction and having a thickness substantially equal to a wear limit thickness of the braking lining;
A brake drum in which a circumferential swell is formed in a portion facing the vibration generating lining;
A microphone for collecting a contact sound between the vibration generating lining and the brake drum;
A sound analysis unit that performs frequency analysis on the sound collected by the microphone;
Based on the rotational frequency of the wheel and the number of undulation peaks of the brake drum, the frequency of the contact sound generated when the vibration lining contacts the brake drum is estimated. A wear determination unit for determining whether the sound pressure is equal to or higher than a threshold;
When the determination is affirmative, an alarm unit that informs wear of the braking lining;
A drum brake lining wear detection device comprising:

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