JP2008032058A - Brake pad, disk rotor, and disc brake mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the lowering of a braking force when a parking brake is operated caused when a temperature is lowered while suppressing an increase in a wire operation amount when the parking brake is operated in a disk brake device utilized as a parking brake. <P>SOLUTION: This brake pad 14 is installed in the disk brake mechanism 100A utilized as a parking brake. A first friction member 20a is pressed against the frictional sliding surface 18a of the disk rotor 18. A second friction member 20b is pressed against the frictional sliding surface 18a of the disk rotor 18. The second friction member 20b is installed on the disk rotor radial outer side from the first friction member 20a. The first friction member 20a is higher in the coefficient of thermal expansion than the second friction member 20b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a disc brake mechanism, a brake pad and a disc rotor provided in the disc brake mechanism, and more particularly, a disc brake mechanism used as a parking brake, and a brake pad and disc provided in a disc brake mechanism used as a parking brake. Regarding the rotor.

  Conventionally, for example, as described in Patent Document 1, a friction member having a low coefficient of thermal expansion and a large coefficient of friction as compared to a disk rotor body has been provided in a holding hole that opens on the friction surface of the disk rotor body. Disc brake disc rotors to be held are known. Further, as described in Patent Document 2, for example, a railway vehicle in which the thickness of the annular sliding plate is changed in the radial direction so that the thermal stress generated during braking is reduced to the same extent as the outer peripheral side on the inner peripheral side. Disc brake devices are known. The technology described in these patent documents aims to solve problems such as disk brake noise and disk rotor thermal fatigue when the disk brake is used as a service brake.

On the other hand, when a disc brake device used as a parking brake is provided in a vehicle or the like, if the parking brake is kept in an operating state for a long time, the wheel braking force is reduced due to contraction of the brake pad accompanying a decrease in the temperature of the brake pad. It is necessary to consider. For this reason, for example, Patent Document 3 proposes an electric parking brake in which an elastic biasing means is provided in a force transmission path between the electric motor and the friction element.
JP-A-11-125283 JP 2000-130481 A JP 2000-297833 A

  However, in the technique described in Patent Document 3, in order to sufficiently elastically deform the elastic biasing means, it is necessary to largely operate a wire for operating the parking brake as compared with the case without the elastic biasing means. The For this reason, when the electric parking brake mechanism is adopted, it may lead to an increase in the time until the parking brake is operated or released. When the manual parking brake mechanism is adopted, the parking brake of the driver is It can affect the operability.

  Therefore, the present invention provides a disc brake device used as a parking brake, which suppresses a decrease in braking force when the parking brake is activated due to a decrease in temperature while suppressing an increase in the amount of wire operation when the parking brake is activated. Objective.

  In order to solve the above-described problems, a brake pad according to an aspect of the present invention is a brake pad provided in a disc brake mechanism used as a parking brake, and is a first that is pressed against a friction sliding surface of a disc rotor. A friction material; and a second friction material that is provided on the outer side in the radial direction of the disk rotor than the first friction material and is pressed against the friction sliding surface of the disk rotor. The first friction material has a higher coefficient of thermal expansion than the second friction material.

  According to this aspect, for example, when the brake pad becomes hot by operating the disc brake mechanism as a service brake while the vehicle is running, the first friction material has a higher coefficient of thermal expansion than the second friction material. Larger expansion toward the disc rotor than the material. For this reason, when the vehicle is parked with the brake pads at a high temperature and this time the disc brake mechanism is operated as a parking brake, the first friction material is frictionally slid by the disc rotor with a stronger force than the second friction material. Pressed against the surface. When the temperature of the brake pad gradually decreases from this state, the difference between the force with which the first friction material presses against the disc rotor and the force with which the second friction material presses against the disc rotor gradually decreases.

  Here, the pressing force for pressing the brake pad against the disc rotor is F, the friction coefficient between the friction sliding surface of the disc rotor and the brake pad is μ, and the brake pad is on the friction sliding surface of the disc rotor. The braking torque that acts on the disk rotor when it is pressed against is T, and R when the braking torque T is represented by T = μFR is the virtual effective diameter.

  When the brake pad is hot, the virtual effective system R is small because the first friction material is pressed against the disc rotor with a stronger force than the second friction material on the radially outer side. When the temperature of the brake pad gradually decreases, the difference in the pressing force between the first friction material and the second friction material against the disk rotor gradually decreases, so that the virtual effective system R increases. For this reason, even when the pressing force F is reduced due to the contraction of the first friction material and the second friction material, the virtual effective diameter R is increased, so that the reduction of the braking torque T at T = μFR is suppressed.

  Another aspect of the present invention is also a brake pad. This brake pad is a brake pad provided in a disc brake mechanism used as a parking brake, and a friction material formed so that the thickness in the disc rotor axial direction increases as the disc rotor diameter progresses inward. Prepare.

  According to this aspect, when the brake pad reaches a high temperature, the friction material swells greatly toward the disk rotor as it advances in the disk rotor diameter inward direction. For this reason, when the vehicle is parked with the brake pads at a high temperature and the disc brake mechanism is operated as a parking brake, the friction material is pressed against the disc rotor with a strong force as it advances inward in the disc rotor diameter. When the temperature of the brake pad gradually decreases from this state, the difference in the pressing force in the disk rotor radial direction gradually decreases.

  Therefore, also in this aspect, the virtual effective system R becomes smaller when the brake pad is hot, and the virtual effective system R becomes larger as the temperature of the brake pad gradually decreases. For this reason, even when the pressing force F is reduced due to the contraction of the friction material, the virtual effective diameter R is increased, so that the reduction of the braking torque T at T = μFR is suppressed.

  Yet another embodiment of the present invention is a disk rotor. This disc rotor is a disc rotor provided in a disc brake mechanism used as a parking brake, and is formed such that its axial thickness increases as it progresses in the radially inward direction.

  According to this aspect, when the disk rotor reaches a high temperature, the disk rotor swells greatly toward the brake pad as it advances in the radially inward direction. For this reason, when the vehicle is parked while the disc rotor is at a high temperature and the disc brake mechanism is operated as a parking brake, the friction material is pressed against the disc rotor with a strong force as it advances in the disc rotor diameter inward direction. When the temperature of the brake pad gradually decreases from this state, the difference in the pressing force in the disk rotor radial direction gradually decreases.

  Therefore, also in this aspect, the virtual effective system R becomes smaller when the brake pad is hot, and the virtual effective system R becomes larger as the temperature of the brake pad gradually decreases. For this reason, even when the pressing force F is reduced due to the contraction of the friction material, the virtual effective diameter R is increased, so that the reduction of the braking torque T at T = μFR is suppressed.

  Yet another embodiment of the present invention is a disc brake mechanism. This disc brake mechanism is a disc brake mechanism used as a parking brake, and includes a disc rotor and a brake pad pressed against the frictional sliding surface of the disc rotor. The pressing force for pressing the brake pad against the disk rotor is F, the friction coefficient between the friction sliding surface of the disk rotor and the brake pad is μ, and the brake pad is pressed against the friction sliding surface of the disk rotor. When the braking torque acting on the disc rotor is T and R is a virtual effective diameter when the braking torque T is expressed by T = μFR, the parking brake in which the brake pad is pressed against the disc rotor In some cases, the virtual effective diameter R increases as the temperature decreases. According to this aspect, even when the pressing force F is reduced due to the contraction of the friction material, the virtual effective diameter R is increased, so that the reduction of the braking torque T is suppressed.

  According to the present invention, in a disc brake device used as a parking brake, it is possible to suppress a decrease in braking force when the parking brake is activated due to a decrease in temperature while suppressing an increase in the amount of wire operation when the parking brake is activated. it can.

  Hereinafter, embodiments of the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram schematically illustrating a main part of a disc brake mechanism 100A according to the first embodiment. The disc brake mechanism 100A is provided on the left and right rear wheels of the vehicle. Of course, the disc brake mechanism 100A may also be provided on the left and right front wheels.

  FIG. 1 shows a state where a disc brake mechanism 100A provided on the left rear wheel is viewed from the front of the vehicle. Therefore, in FIG. 1, the right direction is the vehicle outer direction, and the left direction is the vehicle inner direction.

  The disc brake mechanism 100A includes a caliper unit 10, a disc rotor 18, and a brake pad 14. In order to facilitate understanding, in FIG. 1, the disk rotor 18 and the brake pad 14 are shown by a cross section by a plane including the rotation center of the disk rotor 18.

  The disk rotor 18 is formed in a disk shape. Friction sliding surfaces 18 a are provided on both side surfaces of the disc rotor 18 in a predetermined length range from the vicinity of the outer periphery of the disc rotor 18 to the radially inward direction.

  The disc brake mechanism 100A according to the first embodiment employs a so-called built-in caliper that has not only a function of operating a service brake but also a function of operating a parking brake. For this reason, the caliper unit 10 includes not only the caliper 16 and the piston 26 but also the parking brake unit 30, the push rod 32, and the parking brake drive lever 34 that contribute to the operation of the parking brake.

  The caliper 16 has a cylinder housing 16a and a claw portion 16b. The cylinder housing 16a and the claw portion 16b are opposed to each other and are partially coupled to each other. As a result, the caliper 16 is formed in a U shape.

  Inside the cylinder housing 16a, a cylinder portion 16c, which is a cylindrical space portion that opens toward the claw portion 16b, is provided. The piston 26 is formed in a cylindrical shape having an outer diameter substantially the same as the inner diameter of the cylinder portion 16c, and is fitted into the cylinder portion 16c.

  The caliper 16 according to the first embodiment is a floating type. The caliper 16 is supported by the mounting by a known slide pin mechanism or the like so as to be movable in a predetermined range in the left-right direction of the vehicle. At this time, the caliper 16 is supported by the mounting so that the cylinder housing 16a is located in the vehicle interior direction, the claw portion 16b is located in the vehicle outer direction, and the central axis of the cylinder portion 16c is directed in the vehicle left-right direction. Further, the caliper 16 is disposed such that the friction sliding surface 18a of the disk rotor 18 is located between the claw portion 16b and the cylinder portion 16c.

  The brake pad 14 includes a friction material 20 including a first friction material 20 a, a second friction material 20 b, and a pad back metal 22. The pad back metal 22 is formed in a plate shape having a substantially rectangular outer shape. The first friction material 20 a is formed in a plate shape having a rectangular outer shape having a long side slightly smaller than the long side of the pad back metal 22 and a short side slightly smaller than half the short side of the pad back metal 22. Is done. The second friction material 20b is also formed in a plate shape having a rectangular outer shape substantially the same as the first friction material 20a. Further, the first friction material 20a and the second friction material 20b have a uniform and the same thickness at room temperature. The first friction material 20a and the second friction material 20b are made of a non-metallic material, a low metallic material, a carbon metallic material, or the like. The pad back metal 22 is formed of an iron-based metal material or the like.

  The friction material 20 is configured such that the first friction material 20a and the second friction material 20b are fixed to each other by bonding at a portion corresponding to the long side of each rectangle. The friction material 20 and the pad back metal 22 are fixed to each other by bonding the side surfaces thereof.

  One brake pad 14 is disposed between the friction sliding surface 18a on the vehicle inner side and the piston 26, and between the friction sliding surface 18a on the vehicle outer side and the claw portion 16b. The brake pad 14 (hereinafter referred to as “the brake pad 14 on the vehicle interior side”) disposed between the friction sliding surface 18a on the vehicle interior side and the piston 26 includes the first friction material 20a and the second friction material 20b. The second friction material 20b is arranged so as to face one friction sliding surface 18a and to be located on the outer side in the disk rotor radial direction than the first friction material 20a. In other words, the first friction material 20a is disposed so as to be positioned closer to the U-shaped opening side of the caliper 16 than the second friction material 20b.

  The brake pad 14 (hereinafter referred to as “the brake pad 14 on the vehicle exterior side”) disposed between the friction sliding surface 18a on the vehicle exterior side and the claw portion 16b is a first friction material 20a and a second friction material 20b. And the other friction sliding surface 18a are opposed to each other, and the second friction material 20b is disposed outside the first friction material 20a in the disc rotor radial direction. In other words, the first friction material 20a is disposed so as to be positioned closer to the U-shaped opening side of the caliper 16 than the second friction material 20b.

  The brake pad 14 is restricted from moving in the disk rotor radial direction and circumferential direction by mounting. However, the brake pad 14 on the vehicle inner side is between the friction sliding surface 18a on the vehicle inner side and the opening of the cylinder portion 16c, and the brake pad 14 on the vehicle outer side is the friction sliding surface 18a on the vehicle outer side and the claw portion. 16b is movable in the disk rotor axial direction.

  The cylinder portion 16 c communicates with a master cylinder (not shown), or a pressure increasing valve or a pressure reducing valve through the hydraulic pressure pipe 28. When the driver depresses the brake pedal (not shown), the master cylinder pressure, which is the hydraulic pressure in the master cylinder, increases, or the pressure increase valve opens according to the amount of brake pedal operation and the master cylinder pressure. The hydraulic fluid is supplied to the cylinder portion 16c, and the hydraulic fluid pressure in the cylinder portion 16c is increased. As a result, the piston 26 is propelled toward the brake pad 14 on the vehicle interior side.

  Before the piston 26 is propelled, each of the brake pads 14 is located at an initial position where the first friction material 20 a and the second friction material 20 b are separated from the disk rotor 18. When the piston 26 is propelled toward the brake pad 14 on the vehicle inner side, the brake pad 14 on the vehicle inner side is pushed by the piston 26, and the first friction material 20a and the second friction material 20b are frictioned on the vehicle inner side. It is pressed against the sliding surface 18a. The reaction force causes the entire caliper 16 to slide in the vehicle interior direction, the brake pad 14 on the vehicle exterior side is pushed by the claw portion 16b, and the first friction material 20a and the second friction material 20b are disposed on the vehicle exterior side. It is pressed against the friction sliding surface 18a. As described above, the disc brake mechanism 100A causes the first friction material 20a and the second friction material 20b of the brake pad 14 to be applied to the friction sliding surface 18a of the disc rotor 18 with a force corresponding to the amount of operation of the brake pedal of the driver. The pressing force is applied to the disc rotor 18 and the wheels.

  When the driver releases the depression of the brake pedal, the master cylinder pressure is reduced, or the pressure reducing valve opens according to the amount of brake pedal operation and the master cylinder pressure, and the hydraulic fluid is discharged outside the cylinder portion 16c. Then, the hydraulic fluid pressure in the cylinder portion 16c is reduced. As a result, the piston 26 is propelled in a direction away from the claw portion 16b. Accordingly, each of the brake pads 14 is returned to the initial position, and the first friction material 20a and the second friction material 20b of each brake pad 14 are given to the disk rotor 18 and the wheels by being separated from the friction sliding surface 18a. The braking force that has been released is released.

  The parking brake unit 30 is provided inside the cylinder housing 16a and on the vehicle interior side of the cylinder portion 16c. The parking brake unit 30 includes a push rod 32, a parking brake drive lever 34, and a cam mechanism (not shown).

  The push rod 32 is coupled to one end of the piston 26 on the vehicle inner side so as to extend coaxially with the piston 26. The parking brake drive lever 34 is connected to the cam mechanism so as to be rotatable about the central axis of the push rod 32. The cam mechanism converts the rotational motion of the parking brake drive lever 34 into the linear motion of the push rod 32 in the axial direction.

  The parking brake drive lever 34 is connected to a parking brake lever provided around the driver's seat in the vehicle compartment via a wire (not shown). The parking brake lever is provided so that it can be rotated by the driver. Of course, a parking brake pedal that can be depressed by the driver may be used instead of the parking brake lever.

  When the driver operates the parking brake lever to operate the parking brake, the wire connecting the parking brake lever and the parking brake drive lever 34 is pulled, and the parking brake drive lever 34 is rotated. As a result, the push rod 32 is propelled toward the vehicle outer side, and the piston 26 is pushed toward the brake pad 14 on the vehicle inner side. In the same manner as when the brake pedal is depressed, the first friction material 20a and the second friction material 20b of the brake pad 14 are pressed against the friction sliding surface 18a, and braking force is applied to the disk rotor 18 and the wheels. Given. Hereinafter, the state where the parking brake is operated refers to a state where the first friction material 20a and the second friction material 20b of the brake pad 14 are pressed against the friction sliding surface 18a.

  When the driver rotates the parking brake lever in the reverse direction so as to release the parking brake, the wire connecting the parking brake lever and the parking brake drive lever 34 is loosened, and the parking brake is applied by the biasing force of the spring. The drive lever 34 is rotated in the reverse direction to the original initial position. As a result, the push rod 32 and the piston 26 are propelled toward the inside of the vehicle. As described above, each brake pad 14 is returned to the initial position as in the case where the depression operation of the brake pedal is released as described above, and the first friction material 20a and the second friction material 20b of each brake pad 14 are frictionally slid. By separating from the moving surface 18a, the braking force applied to the disc rotor 18 and the wheels is released.

  When the disc brake mechanism is operated as a service brake, the friction material of the brake pad is pressed against the rotating disc rotor, and the vehicle having a large mass is decelerated or stopped by the frictional force generated between the two. Therefore, the brake disc and the friction material become high temperature due to the frictional heat generated at this time. In particular, when the vehicle traveling at high speed is decelerated, the friction material has a very high temperature.

  The friction material has a linear expansion coefficient, and when the friction material reaches a high temperature, the friction material expands such that its thickness increases according to the linear expansion coefficient and the temperature of the friction material. When the disc brake is used as a service brake, even when the friction material expands or contracts due to a temperature change, the timing at which the friction material contacts the friction sliding surface of the disc rotor slightly deviates when the brake pedal is depressed. The brake pedal operability by the driver and the braking force applied to the wheels are hardly affected.

  On the other hand, as the temperature of the friction material decreases, the thickness of the friction material, which has been expanded and increased in thickness, gradually decreases to return to the original thickness. For this reason, when the parking brake is operated while the friction material is at a high temperature and the vehicle is parked for a long time, the pressing force of the friction material against the disc rotor gradually decreases, and the braking force applied to the disc rotor and wheels decreases. To do. When the vehicle is parked on a slope, the decrease in the braking force of the parking brake leads to the vehicle sliding down.

  For this reason, in the disc brake mechanism 100A according to the first embodiment, the first friction material 20a is formed of a material having a larger linear expansion coefficient than the second friction material 20b, that is, a high thermal expansion coefficient. This will be described in detail below with reference to FIG.

  FIG. 2A is a diagram showing a relationship between the disc rotor 18 and the brake pad 14 when the parking brake is operated in a state where the temperature of the first friction material 20a and the second friction material 20b is high. FIG. 2B is a diagram showing a relationship between the disc rotor 18 and the brake pad 14 when the temperature of the first friction material 20a and the second friction material 20b is lowered from the state of FIG. 2A. 2A and 2B show a cross section of a plane including the central axis of the disk rotor 18.

  For example, when the disc brake mechanism 100A is operated as a service brake while the vehicle is running, the first friction material 20a and the second friction material 20b of each brake pad 14 are connected to the disc rotor 18 that rotates. Therefore, the first friction material 20a and the second friction material 20b may become high temperature. At this time, since the first friction material 20a has a larger linear expansion coefficient than the second friction material 20b, the first friction material 20a is more frictional than the second friction material 20b in any brake pad 14. Swells slightly larger toward the moving surface 18a.

  When the vehicle is parked while the first friction material 20a and the second friction material 20b are at a high temperature, and this time the disc brake mechanism 100A is operated as a parking brake, the first friction material 20a is more than the second friction material 20b. Since the first friction material 20a is slightly larger than the friction sliding surface 18a, the first friction material 20a is second as shown by arrows in the first friction material 20a and the second friction material 20b in FIG. It is pressed against the friction sliding surface 18a with a force stronger than that of the friction material 20b.

  When the parking state of the vehicle continues for a long time, the temperature of the first friction material 20a and the second friction material 20b gradually decreases, and the first friction material 20a and the second friction material 20b are pressed against the friction sliding surface 18a. The difference in contact force gradually decreases. When the temperature of the first friction material 20a and the second friction material 20b is lowered to room temperature, the thickness of the first friction material 20a and the second friction material 20b is the same in an unloaded state. As shown in FIG. 1, the first friction material 20a and the second friction material 20b are pressed against the friction sliding surface 18a by the same pressure.

  The braking force applied to the disk rotor is generated when the side surface of the friction material is pressed against the friction sliding surface 18a of the disk rotor. The pressing force for pressing the brake pad against the disc rotor is F, the friction coefficient between the friction sliding surface of the disc rotor and the friction material of the brake pad is μ, and the friction material of the brake pad is pressed against the friction sliding surface of the disc rotor. When the braking torque acting on the disk rotor is T, the contact surface between the friction material and the disk rotor has a width in the disk rotor radial direction, so the position in the disk rotor radial direction where the pressing force F is applied. It is inherently difficult to express the braking torque T as T = μFR, where R is a predetermined value. However, since the braking torque T can be expressed in a simple manner, the braking torque T is often expressed as T = μFR. Let R at this time be a virtual effective diameter.

  As shown in FIG. 2A, the virtual effective diameter R when the parking brake is operated when the first friction material 20a and the second friction material 20b are high is defined as the virtual effective diameter Rh at high temperature. Further, as shown in FIG. 2 (b), the virtual effective diameter R when the first friction material 20a and the second friction material 20b become low temperature while the parking brake is operated is reduced to the virtual effective diameter Rc at low temperature. And

  As shown in FIG. 2A, when the first friction material 20a and the second friction material 20b are at a high temperature, the first friction material 20a is pressed against the disk rotor 18 with a stronger force than the second friction material 20b. Is done. Since the first friction material 20a is arranged on the inner side in the disk rotor radial direction than the second friction material 20b, the virtual effective diameter Rh at a high temperature is a small value.

  When the temperature of the first friction material 20a and the second friction material 20b gradually decreases, as shown in FIG. 2B, the force by which the first friction material 20a presses against the disk rotor 18 and the second friction material 20b is the disk. Since the difference between the pressing force against the rotor 18 is gradually reduced, the low temperature virtual effective diameter Rc is larger than the high temperature virtual effective diameter Rh.

  When the temperature of the first friction material 20a and the second friction material 20b is lowered while the parking brake is operated, the first friction material 20a and the second friction material 20b contract, so that the pressing force F is totally reduced. To drop. However, in the disc brake mechanism 100A according to the first embodiment, the virtual effective diameter R increases conversely as the temperature of the first friction material 20a and the second friction material 20b decreases. For this reason, although the pressing force F is reduced, the virtual effective diameter R is increased, so that the reduction of the braking torque T is suppressed in the equation T = μFR.

(Second Embodiment)
FIG. 3 is a diagram schematically showing a main part of the disc brake mechanism 100B according to the second embodiment. The disc brake mechanism 100B also employs a so-called built-in caliper that has not only a function of operating the service brake but also a function of operating the parking brake. In addition, the same code | symbol is attached | subjected about the location similar to the disc brake mechanism 100A which concerns on 1st Embodiment, and description is abbreviate | omitted.

  The disc brake mechanism 100B is provided on the left and right rear wheels of the vehicle in the same manner as the disc brake mechanism 100A. Of course, the disc brake mechanism 100B may also be provided on the left and right front wheels. FIG. 3 shows a state where the disc brake mechanism 100B provided on the left rear wheel is viewed from the front of the vehicle.

  The disc brake mechanism 100B includes a caliper unit 60, a disc rotor 18, and a brake pad 50. The caliper unit 60 includes a caliper 66 and a piston 62, and other components are the same as those of the caliper unit 10 according to the first embodiment.

  The caliper 66 has a cylinder housing 66a and a claw portion 66b. The caliper 66 has a cylinder housing 66a and a claw portion 66b. The cylinder housing 66a and the claw portion 66b are opposed to each other, and are partially coupled together. As a result, the caliper 66 is formed in a U shape. At this time, the cylinder housing 66a and the claw portion 66b respectively have opposing inclined surfaces that gradually expand toward each other as they proceed toward the U-shaped opening side.

  Inside the cylinder housing 66a, a cylinder portion 66c, which is a cylindrical space that opens on an inclined surface, is provided. The piston 62 is formed in a cylindrical shape having an outer diameter substantially the same as the inner diameter of the cylinder portion 66c, and is fitted into the cylinder portion 66c. The piston 62 also has an inclined surface that faces the claw portion 66b and inclines substantially parallel to the inclined surface of the cylinder housing 66a.

  The caliper 66 is also of a floating type, and the position and direction of the caliper 66 when supported by the mounting are the same as those of the caliper 16 according to the first embodiment.

  The brake pad 50 has a pad back metal 54 and a friction material 52. The pad back metal 54 is formed in a plate shape having a substantially rectangular outer shape. The friction material 52 has a rectangular outer shape having a long side and a short side slightly smaller than the long side and the short side of the pad back metal 22. Further, the friction material 52 is formed so as to increase linearly as it proceeds in the short side direction. The friction material 52 is formed of a non-metallic material, a low metallic material, a carbon metallic material, or the like. The pad back metal 54 is formed of an iron-based metal material or the like. The side surfaces of the friction material 52 and the pad back metal 54 are bonded to each other and fixed to each other.

  One brake pad 50 is arranged between the friction sliding surface 18a on the vehicle inner side and the inclined surface of the piston 62, and between the friction sliding surface 18a on the outer side of the vehicle and the inclined surface of the claw portion 66b. Is done. At this time, each of the brake pads 50 is disposed such that the thickness of the friction material 52 in the disc rotor axial direction increases as it advances in the disc rotor diameter inward direction. As a result, at normal temperature, the inclination of the inclined surface of the piston 62 and the inclined surface of the claw portion 66b are offset, and the surface of the friction material 52 facing the friction sliding surface 18a is parallel to the friction sliding surface 18a.

  When the driver depresses the brake pedal so that the service brake is activated, or the parking brake lever is rotated by the driver so that the parking brake is activated, the friction of the disc rotor 18 is increased. The moving surface 18a is pressed against the friction material 52 of the brake pad 50, and the braking force is applied to the disk rotor 18 and the wheels by the frictional force generated between them, as in the first embodiment.

  As described above, in the brake pad 50 according to the second embodiment, the thickness of the friction material 52 in the disc rotor axial direction increases as the disc rotor diameter advances inward. Therefore, when the temperature of the friction material 52 becomes high, the friction material 52 swells greatly toward the friction sliding surface 18a as it advances in the disk rotor diameter inward direction without being pressed against the friction sliding surface 18a.

  For this reason, if the parking brake is operated when the friction material 52 is at a high temperature and the friction material 52 is pressed against the friction sliding surface 18a, the friction material 52 is pressed against the friction sliding surface 18a. The pressing force increases as the disk rotor progresses in the inward direction. However, when the parking state of the vehicle continues for a long time, the temperature of the friction material 52 gradually decreases, and the difference in the pressing force between the friction material 52 and the friction sliding surface 18a due to the difference in the position in the disk rotor radial direction is Gradually get smaller. When the friction material 52 reaches room temperature, the friction material 52 is pressed against the disk rotor 18 with the same pressure at any position in the disk rotor radial direction.

  Here, as in the first embodiment, when the pressing force F, the friction coefficient μ, the braking torque T, the virtual effective diameter R, the high temperature virtual effective diameter Rh, and the low temperature virtual effective diameter Rc are defined, the friction material 52 When the temperature is high, the pressing force F increases as the disk rotor diameter progresses inward, so the virtual effective diameter Rh at a high temperature becomes a small value. When the temperature of the friction material 52 is lowered, the difference in the pressing force between the friction material 52 and the friction sliding surface 18a due to the difference in the position in the disk rotor radial direction is gradually reduced. The value is larger than the hourly virtual effective diameter Rh. Therefore, in the state where the parking brake is operated, the virtual effective diameter R increases with the decrease in the pressing force F due to the decrease in the temperature of the friction material 52. Therefore, the decrease in the braking torque T is suppressed in the equation T = μFR. The

(Third embodiment)
FIG. 4 is a diagram schematically showing a main part of a disc brake mechanism 100C according to the third embodiment. The disc brake mechanism 100C also employs a so-called built-in caliper that has not only a function of operating the service brake but also a function of operating the parking brake. In addition, the same code | symbol is attached | subjected about the location similar to the disc brake mechanism 100A which concerns on 1st Embodiment, and description is abbreviate | omitted.

  As with the disc brake mechanism 100A, the disc brake mechanism 100C is provided on the left and right rear wheels of the vehicle. Of course, the disc brake mechanism 100C may also be provided on the left and right front wheels. FIG. 4 shows a state in which the disc brake mechanism 100C provided on the left rear wheel is viewed from the front of the vehicle.

  The disc brake mechanism 100C includes a caliper unit 60, a disc rotor 68, and a brake pad 70. The disk rotor 68 is formed in a disk shape from an iron-based metal material. Friction sliding surfaces 68 a are provided on both side surfaces of the disk rotor 68 within a predetermined length range from the vicinity of the outer periphery of the disk rotor 68 to the radially inward direction. The disk rotor 68 is formed such that the axial thickness of the portion having the frictional sliding surface 68a as a side surface increases as it advances in the radially inward direction. Accordingly, the inclined surface of the piston 62 and the friction sliding surface 68a on the vehicle inner side are parallel to each other, and the inclined surface of the claw portion 66b and the friction sliding surface 68a on the vehicle outer side are parallel to each other.

  The brake pad 70 has a pad back metal 74 and a friction material 72. The pad back metal 74 is formed in a plate shape having a substantially rectangular outer shape. The friction material 72 has a rectangular outer shape having long sides and short sides slightly smaller than the long sides and short sides of the pad back metal 22, and is formed in a plate shape having a uniform thickness. The friction material 72 is formed of a non-metallic material, a low metallic material, a carbon metallic material, or the like. The pad back metal 74 is formed of an iron-based metal material or the like. The friction material 72 and the pad back metal 74 are fixed to each other by bonding the side surfaces thereof.

  The brake pad 70 is arranged between the friction sliding surface 68a on the vehicle inner side and the piston 62 and between the friction sliding surface 68a on the outer side of the vehicle and the claw so that each friction material 72 faces the friction sliding surface 68a. 66b, one each.

  The disk rotor 68 has a friction sliding surface 68a against which the friction material 72 of the brake pad 70 is pressed. When the driver depresses the brake pedal so that the service brake is activated, or when the parking brake lever is rotated so that the parking brake is activated, the friction of the disc rotor 68 is increased. The moving surface 68a is pressed by the friction material 72 of the brake pad 70, and the braking force is applied to the disc rotor 68 and the wheels by the frictional force generated between them, as in the first embodiment.

  As described above, the disk rotor 68 according to the third embodiment is formed such that the axial thickness of the portion having the friction sliding surface 68a as the side surface becomes thicker as it progresses in the radially inward direction. Therefore, when the disk rotor 68 reaches a high temperature, the disk rotor 68 swells greatly toward the friction material 72 as it proceeds in the radially inward direction in a no-load state where the disk rotor 68 is not pressed against the friction material 72.

  Therefore, when the parking brake is operated when the disk rotor 68 is at a high temperature and the friction material 72 is pressed against the friction sliding surface 68a, the friction material 52 is pressed against the friction sliding surface 68a. The contact force increases as the disk rotor diameter progresses inward. However, when the parking state of the vehicle continues for a long time, the temperature of the disc rotor 68 gradually decreases, and the difference in the pressing force between the friction material 72 and the friction sliding surface 68a due to the difference in the position in the disc rotor radial direction is Gradually get smaller. When the disk rotor 68 reaches room temperature, the disk rotor 68 is pressed by the friction material 72 at the same pressure at any radial position.

  Here, when the pressing force F, the friction coefficient μ, the braking torque T, the virtual effective diameter R, the high temperature virtual effective diameter Rh, and the low temperature virtual effective diameter Rc are defined as in the first embodiment, the disk rotor 68 is defined. When the temperature is high, the pressing force F increases as the disk rotor diameter progresses inward, so the virtual effective diameter Rh at a high temperature becomes a small value. When the temperature of the friction material 52 decreases, the difference in the pressing force between the friction material 72 and the friction sliding surface 68a due to the difference in the position in the radial direction of the disk rotor gradually decreases, so the virtual effective diameter Rc at low temperature is high. The value is larger than the hourly virtual effective diameter Rh.

  Therefore, in the state where the parking brake is operated, the virtual effective diameter R increases with a decrease in the pressing force F due to a decrease in the temperature of the friction material 72. Therefore, a decrease in the braking torque T is suppressed in the equation T = μFR. The

  The present invention is not limited to the above-described embodiments, and an appropriate combination of the elements of each embodiment is also effective as an embodiment of the present invention. Various modifications such as design changes can be added to each embodiment based on the knowledge of those skilled in the art, and embodiments to which such modifications are added can also be included in the scope of the present invention. Here are some examples.

  In one variation, an electric parking brake system is provided instead of the parking brake lever or the parking brake pedal. The electric parking brake system includes a parking brake switch provided in a vehicle compartment, a motor that operates when the parking brake switch is turned on, and a wire that is connected to the parking brake drive lever 34 and is pulled when the motor is operated. Have. Thus, even when the electric parking brake system is provided, it is possible to suppress a decrease in the braking force of the disc brake mechanism due to a decrease in the temperature of the friction material.

  In another modification, the disc rotor has a first annular portion and a second annular portion. The first annular part has a friction sliding surface pressed by the friction material of the brake pad. The second annular portion has a friction sliding surface pressed by the friction material of the brake pad, and is provided on the outer side in the disk rotor radial direction than the first annular portion. The first annular part has a larger linear expansion coefficient than the second annular part. Therefore, when the disk rotor reaches a high temperature, the first annular portion swells more toward the friction material than the second annular portion in an unloaded state where the disk rotor is not pressed against by the friction material.

  For this reason, when the parking brake is operated when the disk rotor is at a high temperature and the friction material is pressed against the first annular portion and the second annular portion, the first annular portion becomes the second circle. It is strongly pressed by the friction material from the ring part. However, if the parking state of the vehicle continues for a long time, the temperature of the disc rotor gradually decreases, and the difference in the pressing force between the first and second annular portions gradually decreases. When the disk rotor reaches room temperature, the friction material is pressed against the first and second annular portions with the same pressing force. Therefore, in a state where the parking brake is operated, the virtual effective diameter increases with a decrease in the pressing force due to a decrease in the temperature of the friction material, so that a decrease in the braking torque in the disc brake mechanism is suppressed.

It is a figure which shows typically the principal part of the disc brake mechanism which concerns on 1st Embodiment. (A) is a figure which shows the relationship between a disc rotor and a brake pad when a parking brake is operated in the state where the temperature of a 1st friction material and a 2nd friction material is high, (b) is a figure of (a). It is a figure which shows the relationship between a disc rotor and a brake pad when the temperature of a 1st friction material and a 2nd friction material becomes low from the state. It is a figure which shows typically the principal part of the disc brake mechanism which concerns on 2nd Embodiment. It is a figure which shows typically the principal part of the disc brake mechanism which concerns on 3rd Embodiment.

Explanation of symbols

  10 caliper unit, 14 brake pad, 16 caliper, 18 disc rotor, 18a friction sliding surface, 20a first friction material, 20b second friction material, 100A to 100C disc brake mechanism.

Claims (4)

A brake pad provided in a disc brake mechanism used as a parking brake,
A first friction material pressed against the friction sliding surface of the disk rotor;
A second friction material provided on the outer side in the disk rotor radial direction than the first friction material, and pressed against the friction sliding surface of the disk rotor,
The brake pad, wherein the first friction material has a higher coefficient of thermal expansion than the second friction material. A brake pad provided in a disc brake mechanism used as a parking brake,
A brake pad comprising: a friction material formed so that a thickness in a disc rotor axial direction increases as the disc rotor diameter progresses in an inward direction. A disc rotor provided in a disc brake mechanism used as a parking brake,
A disk rotor, characterized in that an axial thickness is formed so as to increase in a radially inward direction. A disc brake mechanism used as a parking brake,
A disk rotor,
A brake pad pressed against the frictional sliding surface of the disk rotor,
The pressing force for pressing the brake pad against the disk rotor is F, the friction coefficient between the friction sliding surface of the disk rotor and the brake pad is μ, and the brake pad is pressed against the friction sliding surface of the disk rotor. When the braking torque acting on the disc rotor is T and R is a virtual effective diameter when the braking torque T is expressed by T = μFR, the parking brake in which the brake pad is pressed against the disc rotor In some cases, the virtual effective diameter R increases as the temperature decreases.

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