JPH10318294A - Disc brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the structure, lower the cost, and prevent the irregular abrasion of a brake pad without increasing dimension of a device by setting a sliding resistance between a cylinder and a piston of each cylinder-piston mechanism larger, as the piston-cylinder mechanism is positioned closer to a turn-in side of a disc rotor. SOLUTION: Since a necessity of offsetting a cylinder is eliminated by adjusting seal width and a seal tightening margin and changing seal raw material so as to change the sliding resistance, a necessity of changing dimension of a piston, a necessity of adjusting oil pressure to be applied to each piston, and a necessity of adding other device are eliminated, and cost is not raised. Since sliding resistance of each cylinder is set larger, as a device is positioned closer to a turn-in side of a disc rotor, pushing force of a brake pad of a turn-in side (a second) piston is restricted, and the pushing force of the brake pad to the disc rotor can be easily evened so as to prevent the irregular abrasion of the brake pad.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc brake device which presses a disc rotor, which rotates together with wheels, with a brake pad made of a friction material to brake the disc rotor.

[0002]

2. Description of the Related Art Conventionally, a disc brake device is formed in a caliper cylinder (hereinafter simply referred to as a "cylinder") supported on a vehicle body when braking is applied during vehicle running to reduce the rotation of wheels. The brake pad is pressed against a disk rotor that rotates together with the wheels by a pressing force of a piston (cylinder-piston mechanism) to perform braking.

[0003] As such a disk brake device,
It is known that a plurality of cylinders for pressing a brake pad are provided in a disk rotor rotation direction.

For example, Japanese Patent Application Laid-Open No. 63-135623 discloses a so-called opposed four-pot type disk brake device having two sets of cylinders opposed to each other with a disk rotor interposed therebetween.

[0005]

In such a conventional disc brake device, a frictional force is applied between the disc rotor and the brake pad in a rotational tangential direction by pressing the brake pad against the rotating disc rotor during braking. Occurs. Since the brake pad has a thickness, momentum is generated due to the frictional force, and the center of the pressing force, which is the center of the reaction force received by the brake pad from the disk rotor, is moved to the center of the brake pad in the drawing (hereinafter referred to as centroid). ). As a result, a couple that rotates the brake pad is generated in a plane parallel to a tangential direction in which the disk rotor contacts the brake pad and perpendicular to the plane of the disk rotor. Due to this couple, the entry end of the brake pad pushes the disc rotor more strongly than the exit end,
There is a problem that uneven wear of the brake pad occurs.

Accordingly, in a disk brake device of a type in which a plurality of cylinders (for example, two cylinders) are provided in the disk rotor rotation direction, the centroid between the brake cylinder pads and the pistons of the two cylinders is determined by the disk rotor rotation. By offsetting to the side, the center of the pressing is aligned with the centroid of the brake pad, the actual pressing force (surface pressure) of the brake pad acting on the disk rotor during braking is made uniform, and uneven wear of the brake pad is reduced. It is possible to prevent it.

However, offsetting the piston (cylinder) is limited by space in relation to the shape of the brake pad and the arrangement of the two pistons. By offsetting, the brake pad and the caliper holding the brake pad are offset. There is a problem that the body becomes large and the disc brake device itself becomes large. In addition, there is also a problem that when the offset is performed, the rigidity (deformation) of the cylinder is not symmetrical with respect to the pad.

For example, in the case of the opposed four-pot type, if the same device configuration is adopted for the outer and inner pistons opposed to each other with the disk rotor interposed therebetween, the outer and inner pistons are offset in opposite directions. In addition, there is a problem that the arrangement is asymmetric and the processing steps are complicated.

On the other hand, it is conceivable to change the size of the piston in order to equalize the actual pressing force. However, there is a problem that the number of types of parts is increased, the machining process is also complicated, and the cost is increased. Also, the method of adjusting the hydraulic pressure applied to each piston to change the pressing force of each piston causes a change and complication of the hydraulic circuit.

The present invention has been made in view of the above-mentioned conventional problems, and does not increase the size of the device, does not complicate the working process or the hydraulic circuit, and is simple and inexpensive. It is an object of the present invention to provide a disc brake device capable of preventing uneven wear of a disc.

[0011]

According to the present invention, there is provided a disk rotor which rotates together with wheels, a brake pad supported on a vehicle body side, and a plurality of cylinder-piston mechanisms arranged in the rotation direction of the disk rotor. In a disc brake device for performing braking by pressing the brake pad against the disc rotor by a pressing force of a cylinder-piston mechanism, the plurality of cylinder-piston mechanisms are formed to have the same size, and each cylinder-piston mechanism is formed. The above-mentioned problem has been solved by setting the sliding resistance between the cylinder and the piston to be higher at the position closer to the rotation entrance side of the disk rotor.

According to the present invention, since the sliding resistance between the cylinder and the piston is set to be larger as the cylinder-piston mechanism is positioned closer to the rotation entrance side of the disk rotor, the pressing force of the rotation entrance side pressing the brake pad is suppressed. Is done. As a result, the pressing force of the brake pad against the disk rotor on the rotation entry side is suppressed, and the actual pressing force of the brake pad acting on the disk rotor during the braking operation is made uniform, thereby preventing uneven wear of the brake pad. be able to.

In the present invention, since the cylinder-piston mechanism is not offset with respect to the center of the brake pad, the size of the disc brake device does not increase.

Further, according to the present invention, since the size and hydraulic pressure of each cylinder are the same, it is possible to prevent uneven wear of the brake pad simply and at low cost without complicating the working process and the hydraulic circuit. it can.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a schematic configuration of a disc brake device to which the present invention is applied.

In FIG. 1, the caliper 10 supported on the vehicle body side has a first cylinder 14 and a second cylinder 16. These two cylinders 14 and 16 are arranged along the rotation direction (indicated by an arrow R in the figure) of the disk rotor 12 that rotates with the rotation of a wheel (not shown). The first and second cylinders 14, 16 are respectively provided with first and second cylinder bores 18, each having a cylindrical shape formed therein,
20, in which a cylindrical first piston 22 and a second piston 24 are respectively slidably fitted (cylinder-piston mechanism).

First piston 22 and first cylinder bore 18
, A first piston seal 26 is provided,
Between the piston 24 and the second cylinder bore 20, a second
A piston seal 28 is provided. The first piston seal 26 and the second piston seal 28 maintain the liquid tightness of the first piston 22 and the second piston 24, respectively, and impart a certain sliding resistance to each piston 22, 24.
In the present embodiment, the sliding resistance f2 between the second piston 24 and the second piston seal 28 is larger than the sliding resistance f1 between the first piston 22 and the first piston seal 26.

A brake pad 30 is provided between the first and second pistons 22, 24 and the disk rotor 12. The brake pad 30 includes a pad (friction material) 32
And pad back metal 34. First and second pistons 2
The pads 32 are pressed against the disk rotor 12 by pressing the pad back metal 34 by the pads 2 and 24.

The both ends of the caliper 10 in the direction of rotation of the disk rotor form claw portions 36, which receive the pad back metal 34 when the brake pad 30 is dragged in the direction of rotation by the frictional force with the disk rotor 12.

In this embodiment, the sliding resistance f1 between the first piston 22 and the first piston seal 26 is changed by changing the width of the first piston seal 26 or the interference at the time of attaching the seal. Further, the sliding resistance f2 between the second piston 24 and the second piston seal 28 is changed by changing the width of the second piston seal 28 or the interference at the time of attaching the seal (described later in detail).

Hereinafter, the operation of the present embodiment will be described.

When a brake pedal (not shown) is depressed while the vehicle is traveling, the same hydraulic pressure is supplied to the first and second cylinder bores 18 and 20 (by a known hydraulic circuit).
As a result, basically the same hydraulic pressure is applied to the first and second pistons 22 and 24, and the first and second pistons 22 and 24 receive the hydraulic pressure.
When the pistons 22 and 24 move downward in the figure, the brake pads 30 are pressed against the disk rotor 12 and braking is performed.

At this time, the brake pad 30 is dragged to the rotation exit side by the frictional force of the disk rotor 12 in the tangential direction. As a result, the brake pad 30 moves to the left side in the drawing, and the pad back metal 34 of the brake pad 30 contacts the claw 36 on the left side of the caliper 10.

As described above, in the present embodiment, the second cylinder 16 (accurately, the second piston seal 28), which is a cylinder-piston mechanism on the rotation entrance side (right side in the drawing) of the disk rotor 12, and the second piston Sliding resistance f2 between
Is the sliding resistance f1 between the first cylinder 14 (more precisely, the first piston seal 26) on the rotation exit side and the first piston 22.
By making the pressure larger and making the pressing force of the second piston 24 on the rotation entrance side smaller, and making the actual pressing force of the brake pad 30 pressing the disk rotor 12 uniform during braking,
This is to prevent uneven wear of the brake pad 30.

Hereinafter, the relationship between the sliding resistances f1 and f2 will be described in detail.

In FIG. 1, when the first and second pistons 22 and 24 press the brake pad 30 during braking, the brake pad 30 receives a reaction force of the same magnitude from the disk rotor 12. The center of pressing, which is the center at which this reaction force acts on the brake pad 30, is represented by reference symbol C. Assuming that the pressing force of the first piston 22 is F1 and the pressing force of the second piston 24 is F2, the magnitude of the reaction force is F0 = F1 + F2.

If the pressing center C is deviated from the centroid B of the pad 32, a couple is generated to rotate the brake pad 30 in the plane of the drawing, and the brake pad 30 is rotated.
Brake pads 30 are attached to the disk rotor 12
The magnitude of the pressing force for pressing the brake pad differs, which causes uneven wear of the brake pad 30.

Therefore, in order to prevent the uneven wear, the pressing center C is brought closer to the centroid B of the pad 32 (so that the distance x between the two points BC in the drawing is approximately x = 0). The actual pressing force of the brake pad 30 pressing the disk rotor 12 during braking may be made uniform. For this purpose, the relationship between the pressing forces F1 and F2 of each piston is obtained.

The point at which the pad back metal 34 abuts the claw portion 36 on the left side of the figure is denoted by A. Disk rotor 12 and pad 32
Is the friction coefficient between the frictional force and the frictional force is (F1 + F
2) xμ, and a force of the same magnitude but in the opposite direction acts on the pad back metal 34 at the point A.

The distance between the center of the pad back metal 34 parallel to the disk rotor 12 and the disk rotor 12 is L, the point A
, The distance between the center of the first piston 22 and the center of the first piston 22 is b, the distance between the centers of the first and second pistons 22 and 24 is 2a, and the diameter of each piston is D.

Considering the moment around the point A, the following equation (1) is established.

F1 × b + F2 × (2a + b) + (F1 + F2) × μ × L = (F1 + F2) × (a + b + x) (1)

From this, when the distance x between the two points BC is obtained, the following equation (2) is obtained.

X = a × (F2−F1) / (F1 + F2) + μ × L (2)

Here, when the relationship between F1 and F2 where x = 0 is obtained, the following equation (3) is obtained.

F1 = F2 × (a + μ × L) / (a-μ × L) (3)

Thus, the pressing force F1 of the first piston 22
Is smaller than the pressing force F2 of the second piston 24 by (a + μ ×
L) / (a-μ × L) times so that the second piston 2
It can be seen that the sliding resistance f2 of No. 4 should be set.

For example, a = 30 mm, μ = 0.4, L =
Assuming that 7.5 mm (the pressing center C is equal to the pad centroid B at the time of pad half friction), the following equation (4) is obtained.

F1 = 1.22 × F2 (4)

Here, assuming that the hydraulic pressure is P, the pressing forces F1 and F2 of the pistons are expressed by the following equations (5) and (6).

F1 = P × (π / 4) × D ² −f1 (5) F2 = P × (π / 4) × D ² −f2 (6)

Substituting this into equation (4) gives the following (7)
An expression is obtained.

F1 = 1.22 × f2−0.22 × (π / 4) × D ² × P (7)

Therefore, the distribution of the sliding resistances f1 and f2 is determined by the actual average hydraulic pressure P when the brake is used.

For example, if P = 15 MPa, the following equation (8) is obtained by substituting the piston diameter D = 42 mm into equation (7).

F1 = 1.22 × f2-30 (8)

Therefore, for example, if f1 = 20 kgf,
From equation (8), the sliding resistance f2 of the second piston 24 is
f2 = (20 + 30) /1.22≒40 kgf.

Next, concretely, the sliding resistances f1, f2
The method for changing is described.

In the first method, as shown in FIG.
(Or second) This is a method of changing the width L1 of the piston seal 26 (28).

The sliding resistance f1 of the first piston 22 is
Assuming that the surface pressure exerted by the piston seal 26 on the first piston 22 is P1, the seal width is L1, and the friction coefficient between the first piston 22 and the first piston seal 26 is μ1, the following expression (9) is used. It is.

F1 = π × D × L1 × P1 × μ1 (9)

Therefore, for example, when the sliding resistance f1 of the first piston 22 is 20 kgf, and the sliding resistance f2 of the second piston 24 is doubled to 40 kgf, the seal tightening margin (the seal between the caliper and the cylinder is changed). The second piston seal 28 while maintaining the same amount of flexure due to compression when
May be doubled (2 × L1).

Actually, the width of the second piston seal 28 is set to 2L.
When the sliding resistance f2 of the second piston 24 is calculated as 1, the following equation (10) is obtained.

F2 = π × D × 2L1 × P1 × μ1 (10)

Therefore, f1: f2 = 1: 2, and the second
The sliding resistance f2 of the piston 24 is twice the sliding resistance f1 of the first piston 22.

As shown in FIG. 3, a second method of changing the sliding resistance is a first (or second) piston seal 26 (2).
This is a method of changing the interference y1 from the free shape (line Y in the drawing) before the assembly of 8).

For example, the sliding resistance f2 of the second piston 24
Is to be doubled in comparison with the sliding resistance f1 of the first piston 22, the interference y of the second piston seal 28 is required.
2 is twice (y2) the interference y1 of the first piston seal 26.
= 2y1). At this time, since the interference is doubled, the stress due to the compressive deformation of the second piston seal 28 is doubled, and the second piston seal 28 is
4 is also doubled. As a result, the second
The sliding resistance f2 of the piston 24 is also twice the sliding resistance f1 of the first piston 22.

The third method for changing the sliding resistance is the first and second methods.
The purpose is to change the material of the piston seals 26 and 28 and to change the values of the friction coefficients μ1 and μ2 with the first and second pistons 22 and 24, respectively. In the above example, 2μ1 = μ
By setting to 2, the same effect can be obtained.

As described above, if the sliding resistance is changed by adjusting the seal width and the seal allowance, or by changing the material of the seal, the cylinder does not need to be offset, which may lead to an increase in the size of the apparatus. In addition, there is no need to change the size of the piston, adjust the hydraulic pressure applied to each piston, or add another device, so that the cost does not increase. Further, since the sliding resistance of each piston is increased toward the rotation entrance side of the disk rotor, the pressing force of the brake pad of the (second) piston on the rotation entrance side is suppressed, and the pressing force of the brake pad against the disk rotor is easily made uniform. And uneven wear of the brake pad can be prevented.

[0061]

As described above, according to the present invention,
The pressing force of the brake pad against the disk rotor can be easily made uniform, and the brake pad can be prevented from uneven wear without increasing the size of the device.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a schematic configuration of a disc brake device to which the present invention is applied.

FIG. 2 is an enlarged sectional view near arrow II of FIG. 1 showing a method of changing the sliding resistance of the piston seal.

FIG. 3 is an enlarged sectional view similar to FIG. 2, showing another method of changing the sliding resistance of the piston seal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Caliper 12 ... Disk rotor 14 ... 1st cylinder 16 ... 2nd cylinder 18 ... 1st cylinder bore 20 ... 2nd cylinder bore 22 ... 1st piston 24 ... 2nd piston 26 ... 1st piston seal 28 ... 2nd piston seal 30 … Brake pad 32… pad 34… pad back metal 36… claw

Claims (1)

[Claims] 1. A disk rotor which rotates with wheels, a brake pad supported on a vehicle body side, and a plurality of cylinder-piston mechanisms arranged in a rotation direction of the disk rotor, wherein a pressing force of the cylinder-piston mechanism is provided. In a disk brake device for performing braking by pressing the brake pad against the disk rotor, the plurality of cylinder-piston mechanisms are formed to have the same size, and a slide between a cylinder and a piston of each cylinder-piston mechanism. A disk brake device wherein the dynamic resistance is set to be greater as the disk is positioned closer to the rotation of the disk rotor.