WO2018092900A1

WO2018092900A1 - Wheel cylinder for drum brake and drum brake for vehicle

Info

Publication number: WO2018092900A1
Application number: PCT/JP2017/041610
Authority: WO
Inventors: 智之馬杉; 真吾岩崎; 岩井　俊介
Original assignee: 株式会社アドヴィックス
Priority date: 2016-11-18
Filing date: 2017-11-20
Publication date: 2018-05-24
Also published as: JP2018080822A

Abstract

In the present invention a vehicle brake is, for example, equipped with: a movable component that includes a first piston for pressing a first brake shoe and a second piston for pressing a second brake shoe, and that is interposed between the first brake shoe and the second brake shoe so as to be able to move integrally inside a cylinder hole in a state in which a pressure chamber is in a non-pressurized state; a ratchet mechanism that rotationally displaces the first piston or the second piston such that the angle of rotation around an axis with respect to a housing increases as the stroke between the non-pressurized state and the pressurized state increases; and multiple extension mechanisms that increase the length of the movable component in the axial direction as the angle of rotation increases. One of the extension mechanisms is arranged between the one piston that is rotationally displaced by the ratchet mechanism and the brake shoe pressed by that piston, and the other extension mechanism is arranged between the first piston and the second piston.

Description

Drum brake wheel cylinder and vehicle drum brake

The present invention relates to a drum brake wheel cylinder and a vehicle drum brake.

Conventionally, a vehicular drum brake having a strut with an adjuster for automatically adjusting the shoe clearance of the brake shoe is known (for example, Patent Document 1).

JP 11-351295 A

¡Struts with adjusters of this type are easily affected by rattling of component parts and set position, and stable clearance adjustment may be difficult.

Also, it would be beneficial if the drum brake could be made smaller.

Therefore, one of the problems of the present invention is to obtain a drum brake wheel cylinder and a vehicle drum brake that can eliminate, for example, a strut with an adjuster.

A drum brake wheel cylinder according to the present disclosure includes, for example, a housing provided with a cylinder hole and a first brake shoe that is accommodated in the cylinder hole so as to be movable in an axial direction in a pressurized state of a pressure chamber in the cylinder hole. A first piston that presses in one of the axial directions, and a second piston that is accommodated in the cylinder hole so as to be movable in the axial direction and presses the second brake shoe in the axial direction in the axial direction. A movable part interposed between the first brake shoe and the second brake shoe so as to be integrally movable in the axial direction within the cylinder hole in a pressure-removed state of the pressure chamber, and the first piston or As the stroke between the pressure-removed state and the pressure-applied state of the second piston increases, the rotation angle about the axis with respect to the housing increases. A ratchet mechanism that rotationally displaces one of the second piston and the second piston, and a plurality of extension mechanisms that increase the axial length of the movable part as the rotation angle increases. The one piston that is rotationally displaced by the ratchet mechanism and the brake shoe that is pressed by the piston are disposed between the first piston and the second piston. Arranged.

According to such a drum brake wheel cylinder, one piston is rotationally displaced by the ratchet mechanism, so that the axial distance between the first piston and the second piston, and each piston and each brake shoe corresponding thereto. Can be adjusted appropriately according to the stroke. In other words, a single wheel cylinder can have a shoe clearance adjustment function for two brake shoes with a simple configuration, for example, because the movable parts of the wheel cylinder can function as a strut with an adjuster. A strut with an adjuster provided separately from the wheel cylinder is not required. Therefore, for example, the vehicle drum brake can be configured more compactly. Further, for example, the labor and cost required for manufacturing the vehicle drum brake can be reduced by reducing the number of parts. Contributes to improved workability when replacing brake shoes (lining).

Further, in the drum brake wheel cylinder, for example, the ratio of the increase amount of the length of the movable part to the increase amount of the stroke of one of the plurality of extension mechanisms is different from the ratio of the other extension mechanism. Different.

According to such a drum brake wheel cylinder, for example, even when the length of the movable part increases with time, the change with time (displacement) of the relative position of the movable part with respect to the housing is set smaller. can do.

In the drum brake wheel cylinder, for example, the first brake shoe is a leading shoe for forward rotation of the wheel, and the second brake shoe is a trailing shoe for forward rotation of the wheel. Among the extension mechanisms, when the extension mechanism is disposed between the first piston and the first brake shoe, the ratio of the extension mechanism is equal to the ratio between the first piston and the first brake shoe. When the extension mechanism is not provided between the first and second pistons, the ratio of the extension mechanism provided between the first piston and the second piston is greater than the ratio of the other extension mechanism.

According to such a drum brake wheel cylinder, for example, when the wear speed of the brake shoe lining serving as the leading shoe against forward rotation is greater than the wear speed of the brake shoe lining serving as the trailing shoe, It becomes possible to set the change with time of the relative position of the movable part smaller.

In the drum brake wheel cylinder, for example, when a lever that is pivotably connected to one of the first brake shoe and the second brake shoe is braked, the movable component is And a strut between the first brake shoe and the second brake shoe.

Such a wheel cylinder eliminates, for example, a strut with an adjuster provided separately from the wheel cylinder in a vehicle drum brake having the lever (for example, a parking brake operating lever). Therefore, for example, the vehicle drum brake can be configured more compactly. Further, for example, the labor and cost required for manufacturing the vehicle drum brake can be reduced by reducing the number of parts.

FIG. 1 is an exemplary and schematic side view of the vehicle brake according to the embodiment from the outside in the vehicle width direction. FIG. 2 is an exemplary and schematic side view of the wheel cylinder of the vehicle brake according to the embodiment from the outside in the vehicle width direction. FIG. 3 is an exemplary and schematic top view of the wheel cylinder of the vehicle brake according to the embodiment from above the vehicle. FIG. 4 is an exemplary and schematic rear view of the wheel cylinder of the vehicle brake according to the embodiment from the front of the vehicle. FIG. 5 is a schematic and exemplary cross-sectional view showing the internal configuration of the wheel cylinder of the vehicle brake according to the embodiment, and is a cross-sectional view taken along the line VV of FIG. FIG. 6 is a schematic and exemplary cross-sectional view at the same position as FIG. 5 showing the internal configuration of the wheel cylinder of the vehicle brake according to the modification.

Hereinafter, exemplary embodiments of the present invention will be disclosed. The configuration of the embodiment shown below, and the operation and result (effect) brought about by the configuration are examples. The present invention can be realized by configurations other than those disclosed in the following embodiments. According to the present invention, it is possible to obtain at least one of various effects (including derivative effects) obtained by the configuration.

The following embodiments and modifications include similar components. Therefore, in the following, the same reference numerals are given to the same components, and redundant description may be omitted. Moreover, in this specification, the ordinal number is given for convenience in order to distinguish parts, parts, and the like, and does not indicate priority or order.

In each figure, for the sake of convenience, the rear side in the vehicle front-rear direction is indicated by an arrow X, the inner side in the vehicle width direction (axle direction) is indicated by an arrow Y, and the upper side in the vehicle vertical direction is indicated by an arrow Z.

Moreover, although the case where the brake device 1 which is an example of a vehicle brake is applied to the right rear wheel (non-driving wheel) will be exemplified below, the present invention can be similarly applied to other wheels. It is.

(Embodiment) (Configuration of Brake Device)
FIG. 1 is a side view of the brake device 1 from the outside in the vehicle width direction. The brake device 1 is accommodated inside a peripheral wall (not shown) of a cylindrical wheel. The brake device 1 is a so-called drum brake. As shown in FIG. 1, the brake device 1 includes two brake shoes 3 L and 3 T that are separated in the front-rear direction. The two

brake shoes

3L and 3T extend in an arc shape along the inner peripheral surface 2a of the cylindrical drum 2. The drum 2 rotates integrally with the wheel around a rotation center C along the vehicle width direction. The brake device 1 moves the two

brake shoes

3L and 3T so as to contact the inner peripheral surface 2a of the cylindrical drum 2, and brakes the drum 2 and thus the wheel by friction between the

brake shoes

3L and 3T and the drum 2. To do. When the wheel rotation direction Rw when the vehicle moves forward is the clockwise direction in FIG. 1, the right brake shoe 3L in FIG. 1 is an example of a leading shoe, and the left brake shoe 3T is a trailing shoe. It is an example. The

brake shoes

3L and 3T are examples of a braking member. The brake shoe 3L is an example of a first brake shoe, and the brake shoe 3T is an example of a second brake shoe. The brake device 1 is an example of a vehicle brake.

The brake device 1 includes a wheel cylinder 100 that operates by hydraulic pressure and a motor (not shown) that operates by energization as actuators that move the

brake shoes

3L and 3T. The wheel cylinder 100 and the motor can move the two

brake shoes

3L and 3T, respectively. The wheel cylinder 100 is used, for example, for braking during traveling, and the motor is used, for example, for braking during parking. That is, the brake device 1 is an example of an electric parking brake. The motor may be used for braking during traveling.

The brake device 1 includes a disk-shaped back plate 4. The back plate 4 is provided in a posture intersecting with the rotation center C. That is, the back plate 4 extends substantially along the direction intersecting with the rotation center C, specifically, substantially along the direction orthogonal to the rotation center C.

The back plate 4 directly or indirectly supports each component of the brake device 1. The back plate 4 supports components positioned outward in the vehicle width direction from the back plate 4 as shown in FIG. Further, the back plate 4 supports a component (not shown) positioned inward in the vehicle width direction with respect to the back plate 4. The components positioned inward in the vehicle width direction supported by the back plate 4 include, for example, a motor for an electric parking brake, and a motion conversion mechanism that converts the rotation of the motor into a linear movement of the cable 62 (or rod). (Not shown). The back plate 4 is an example of a support member. The cable 62 can also be referred to as an operating member.

Further, the back plate 4 is coupled to a connection member (not shown) with the vehicle body. The connection member is, for example, a part of the suspension (for example, an arm, a link, an attachment member, etc.). The opening 4a provided in the back plate 4 is used for coupling with the connection member. The brake device 1 of FIG. 1 can be used for both drive wheels and non-drive wheels. When the brake device 1 is used for a drive wheel, an axle shaft (not shown) passes through an opening 4b provided in the approximate center of the back plate 4.

(Brake shoe operation by wheel cylinder)
As shown in FIG. 1, the lower ends 3a of the

brake shoes

3L and 3T are supported by the back plate 4 so as to be rotatable around a rotation center C1. The rotation center C1 is substantially parallel to the rotation center C of the wheel. The rotation center C1 can also be referred to as a rotation support point.

The wheel cylinder 100 is supported on the upper part of the back plate 4. The wheel cylinder 100 has two pressing portions 110l and 110t that can project in the vehicle front-rear direction (left-right direction in FIG. 1). The wheel cylinder 100 projects the two pressing portions 110l and 110t in accordance with the pressurization of the internal pressure chamber.

The protruding two pressing portions 110l and 110t press the upper portions 3b of the

brake shoes

3L and 3T, respectively. Due to the protrusion of the two movable parts, the two

brake shoes

3L and 3T each rotate about the rotation center C1 and move so that the upper parts 3b are separated from each other in the vehicle front-rear direction. As a result, the two

brake shoes

3L and 3T move outward in the radial direction of the rotation center C of the wheel. A belt-like lining 3c along the cylindrical surface is provided on the outer periphery of each

brake shoe

3L, 3T. Therefore, the lining 3c and the inner peripheral surface 2a of the drum 2 come into contact with each other by the movement of the two

brake shoes

3L and 3T outward in the radial direction of the rotation center C. The friction between the lining 3c and the inner peripheral surface 2a brakes the drum 2 and thus the wheel. Note that the stroke between the non-braking position and the braking position of the

brake shoes

3L and 3T is very small, for example, 1 mm or less.

Further, the brake device 1 includes a return member 5. When the pressure chamber in the wheel cylinder 100 is depressurized and the pressing of the two

brake shoes

3L and 3T by the pressing portions 110l and 110t is released, the return member 5 removes the two

brake shoes

3L and 3T from the drum 2 Is returned from a position in contact with the inner peripheral surface 2a (braking position) to a position not in contact with the inner peripheral surface 2a of the drum 2 (nonbraking position). The return member 5 is an elastic member such as a coil spring, for example, and forces the

brake shoes

3L and 3T to approach the

other brake shoes

3L and 3T, that is, a direction away from the inner peripheral surface 2a of the drum 2. Giving the power of. The return member 5 can also be called an urging member or an elastic member.

(Brake shoe operation by motor)
The brake device 1 includes a moving mechanism 6. Based on the operation of a drive mechanism (not shown) including a motor and a motion conversion mechanism, the moving mechanism 6 moves the two

brake shoes

3L and 3T from the non-braking position to the braking position.

The moving mechanism 6 is provided outside the back plate 4 in the vehicle width direction. The moving mechanism 6 includes a lever 61, a cable 62, and a wheel cylinder 100.

The lever 61 is provided between one of the two

brake shoes

3L and 3T, for example, the left brake shoe 3T in FIG. 1 and the back plate 4, and rotates around the rotation center C2 in the brake shoe 3T. Supported as possible. The rotation center C2 is located at the end of the brake shoe 3L opposite to the rotation center C1 (upper side in FIG. 1) and is substantially parallel to the rotation center C1. The cable 62 moves substantially along the back plate 4 and moves the lower end 61a of the lever 61 on the side far from the rotation center C2 on the other hand, for example, in a direction approaching the right brake shoe 3L in FIG. The operating position PL1 where the lever 61 is moved by the cable 62 is indicated by a two-dot chain line in FIG.

The lever 61 has a protrusion 61b that contacts the inner peripheral surface of the brake shoe 3T. By this protrusion 61b, an initial position PL0 in a state before being moved by the cable 62 of the lever 61 is determined. The protrusion 61b can also be referred to as an initial position setting unit.

In the present embodiment, the movable part 110 movably accommodated in the wheel cylinder 100 includes a lever 61 that is moved by the cable 62, a brake shoe 3L that is different from the brake shoe 3T connected to the lever 61, and It can be stretched by interposing between the two. Here, the connection position P 1 between the lever 61 and the movable part 110 is set between the rotation center C 2 and the connection position P 2 between the cable 62 and the lever 61.

In such a configuration, when the cable 62 is pulled by the operation of the motor and moves to the right in FIG. 1, the lever 61 moves from the initial position PL0 toward the brake shoe 3L (arrow a, operating position PL1). ), The lever 61 pushes the brake shoe 3L through the movable part 110 of the wheel cylinder 100 (arrow b). As a result, the brake shoe 3L rotates around the rotation center C1 from the non-braking position (arrow c) and moves to the braking position where it contacts the inner peripheral surface 2a of the drum 2. In this state, the connection position P2 between the cable 62 and the lever 61 corresponds to a force point, the rotation center C2 corresponds to a fulcrum, and the connection position P1 between the lever 61 and the movable part 110 corresponds to an action point. Furthermore, when the brake shoe 3L is in contact with the inner peripheral surface 2a and the lever 61 moves to the right in FIG. 1, that is, in the direction in which the movable part 110 pushes the brake shoe 3L (arrow b), the movable part 110 is moved. By stretching the lever 61, the lever 61 rotates in the direction opposite to the direction in which the lever 61 moves, that is, counterclockwise in FIG. 1 (arrow d), with the connection position P1 with the movable part 110 as a fulcrum. As a result, the brake shoe 3T rotates around the rotation center C1 from the non-braking position and moves to the braking position where it comes into contact with the inner peripheral surface 2a of the drum 2. Thus, the

brake shoes

3L and 3T are both moved from the non-braking position to the braking position by the operation of the moving mechanism 6. In the state after the brake shoe 3L comes into contact with the inner peripheral surface 2a of the drum 2, the connection position P1 between the lever 61 and the movable part 110 serves as a fulcrum. At the same time as the brake shoe 3L returns to the non-braking position, the protrusion 61b of the lever 61 contacts the inner peripheral surface of the brake shoe 3T, and the lever 61 returns to the initial position. As described above, in this embodiment, the movable part 110 of the wheel cylinder 100 functions as a strut interposed between the

brake shoes

3L and 3T together with the lever 61 when the brake device 1 operates as an electric brake.

(Configuration of wheel cylinder)
2 is a side view of the wheel cylinder 100, FIG. 3 is a top view of the wheel cylinder 100, FIG. 4 is a rear view of the wheel cylinder 100, and FIG. 5 is a VV cross-sectional view of FIG. In the description of the wheel cylinder 100, the axial direction of the central axis Ax of the cylinder hole 10a is simply referred to as an axial direction, and the brake shoe 3L side (the right side in FIG. 5) is axially shifted in the axial direction. The side is referred to as the other axial direction (left side in FIG. 5).

As shown in FIG. 5, the wheel cylinder 100 includes a housing 10 provided with a cylinder hole 10a. The housing 10 is fixed to the back plate 4 (FIG. 1).

The first piston 20 and the second piston 30 are accommodated in the cylinder hole 10a so as to be movable along the axial direction of the central axis Ax of the cylinder hole 10a. In the present embodiment, the central axis Ax extends substantially along the vehicle front-rear direction as an example, but is not limited thereto.

The pressure chamber Rp is formed between the first piston 20 and the second piston 30 in the cylinder hole 10a. In the pressurized state of the pressure chamber Rp, the first piston 20 projects in one axial direction, and the second piston 30 projects in the other axial direction. That is, the first piston 20 can function as the pressing portion 110l, and the second piston 30 can function as the pressing portion 110t.

In the depressurized state of the pressure chamber Rp, the first piston 20 returns to the other side in the axial direction by receiving the force of the return member 5 or the like via the brake shoe 3L (FIG. 1), and the second piston 30 is moved to the brake shoe 3T (FIG. By returning to one side in the axial direction by receiving the force of the return member 5 or the like via 1).

And in the pressure-removed state of the pressure chamber Rp, the first piston 20 and the second piston 30 can move integrally along the axial direction of the cylinder hole 10a. That is, the first piston 20 and the second piston 30 can function as the movable part 110 (strut). In the present embodiment, only the first piston 20 and the second piston 30 function as the movable part 110. However, the present invention is not limited to this. For example, the first piston 20 and the second piston 30 There may be another component that moves integrally as the movable component 110.

(Extension mechanism)
As shown in FIG. 5, the first piston 20 has a linear motion part 21, a rotatable part 22, and a linear motion part 23. The second piston 30 has a linear motion part 31.

The linear motion part 21 is restricted from turning around the central axis Ax. The linear motion part 21 is provided with a connection part 21a with the brake shoe 3L. The connecting portion 21a allows relative movement in the vehicle vertical direction with respect to the brake shoe 3L, restricts relative movement in the vehicle width direction with respect to the brake shoe 3L, and around the central axis Ax with respect to the brake shoe 3L. The brake shoe 3L is connected in a state in which relative rotation is limited. That is, in the present embodiment, as an example, the rotation of the linear motion portion 21 around the central axis Ax is limited by the brake shoe 3L. The linear motion part 21 can also be referred to as a rotation restriction part or a non-rotation part. Note that the rotation of the linear motion portion 21 around the central axis Ax may be limited by a member other than the brake shoe 3L, such as the housing 10, for example.

The rotatable part 22 has a slide part 22a and a protruding part 22b. The slide portion 22a is accommodated in the cylinder hole 10a so as to be slidable along the central axis Ax. An annular concave groove 22c is provided on the outer peripheral surface of the slide portion 22a. A seal member 24 is accommodated in the concave groove 22c. The seal member 24 seals a gap between the inner peripheral surface of the cylinder hole 10a and the outer peripheral surface of the slide portion 22a, and suppresses leakage of hydraulic oil from the gap. The seal member 24 slides in the axial direction together with the slide portion 22a.

The protruding portion 22b protrudes from the slide portion 22a in one axial direction with an outer diameter smaller than the outer diameter of the slide portion 22a.

The linear motion part 21 and the rotatable part 22 are connected via a screw mechanism. In this embodiment, as an example, the linear motion portion 21 is provided with a male screw portion 21b, and the rotatable portion 22 is provided with a female screw portion 22d that meshes with the male screw portion 21b. May be provided, and the rotatable part 22 may be provided with a male screw part.

In such a configuration, when the rotatable portion 22 rotates according to the operation of the rotation drive mechanism 50 described later, since the rotation of the linear motion portion 21 is restricted, the male screw portion 21b and the female screw portion 22d. , The total length of the sub-assembly of the linear motion portion 21 and the rotatable portion 22 changes. Here, in the present embodiment, the total length of the sub-assembly of the linear motion portion 21 and the rotatable portion 22 by the rotation of the rotatable portion 22 in the predetermined direction (direction Rs in FIG. 4) by the rotation drive mechanism 50. The direction of the spiral of the screw in the screw mechanism is set so that is longer. When the total length of the sub-assembly of the linear motion portion 21 and the rotatable portion 22 increases, the total length of the movable part 110 pushed from the

brake shoes

3L, 3T to both sides in the axial direction also increases in the pressure chamber Rp depressurization state. It will be. That is, the first extension mechanism 41 is configured by the male screw portion 21b and the female screw portion 22d. In the first extension mechanism 41, the amount of increase in the length of the sub-assembly of the linear motion part 21 and the rotatable part 22 per unit rotation angle of the rotatable part 22 is determined by the pitch of the screw part.

The rotation of the linear motion part 31 of the second piston 30 around the central axis Ax is restricted. The linear motion part 31 is provided with a connection part 31a with the brake shoe 3T. The connecting portion 31a allows relative movement in the vehicle vertical direction with respect to the brake shoe 3L, restricts relative movement in the vehicle width direction with respect to the brake shoe 3T, and around the central axis Ax with respect to the brake shoe 3T. The brake shoe 3T is connected in a state in which relative rotation is limited. That is, in the present embodiment, as an example, the rotation of the linear motion portion 31 around the central axis Ax is limited by the brake shoe 3T. The linear motion part 31 may also be referred to as a rotation restriction part or a non-rotation part. Note that the rotation of the linear motion portion 31 around the central axis Ax may be limited by a member other than the brake shoe 3T, such as the housing 10 or the like.

An annular groove 31 d is provided on the outer peripheral surface of the linear motion portion 31. The sealing member 33 is accommodated in the concave groove 31d. The seal member 33 seals a gap between the inner peripheral surface of the cylinder hole 10a and the outer peripheral surface of the linear motion portion 31, and suppresses leakage of hydraulic oil from the gap. The seal member 33 slides in the axial direction together with the linear motion portion 31.

Rotation around the central axis Ax is also restricted for the linear motion part 23 of the first piston 20. The linear motion part 23 is provided with a connection part 23 a, and the connection part 23 a meshes with a connection part 31 b provided on the linear motion part 31 of the second piston 30. The relative rotation about the central axis Ax between the linear motion part 23 and the linear motion part 31 is restricted by the meshing of the connection part 23a and the connection part 31b. As described above, the rotation of the linear motion portion 31 around the central axis Ax is limited by the brake shoe 3L. Accordingly, the rotation of the linear motion portion 23 around the central axis Ax is limited by the brake shoe 3L. Note that the rotation of the linear motion portion 23 around the central axis Ax may be limited by a member other than the brake shoe 3T, such as the housing 10. The connecting portion 23a and the connecting portion 31b are connected in a state that restricts relative rotation around the central axis Ax and allows relative movement in the direction along the central axis Ax.

The linear motion part 23 and the rotatable part 22 are connected via a screw mechanism. In the present embodiment, as an example, the linear motion portion 23 is provided with a male screw portion 23b, and the rotatable portion 22 is provided with a female screw portion 22e that meshes with the male screw portion 23b. However, conversely, the linearly-moving portion 23 may be provided with a female screw portion, and the rotatable portion 22 may be provided with a male screw portion.

In such a configuration, when the rotatable portion 22 rotates according to the operation of the rotation drive mechanism 50 described later, since the rotation of the linear motion portion 23 is restricted, the male screw portion 23b and the female screw portion 22d. , The total length of the sub-assembly of the linear motion portion 23 and the rotatable portion 22 changes. Here, in the present embodiment, the total length of the sub-assembly of the linear motion portion 23 and the rotatable portion 22 by the rotation of the rotatable portion 22 in the predetermined direction (direction Rs in FIG. 4) by the rotation drive mechanism 50. The direction of the spiral of the screw in the screw mechanism is set so that is longer. When the total length of the sub-assembly of the linear motion portion 23 and the rotatable portion 22 increases, the total length of the movable part 110 pushed from the

brake shoes

3L, 3T to both sides in the axial direction also increases in the pressure chamber Rp depressurization state. It will be. That is, the second extending mechanism 42 is constituted by the male screw portion 23b and the female screw portion 22d. The amount of increase in the length of the sub-assembly of the linear motion portion 23 and the rotatable portion 22 per unit rotation angle of the rotatable portion 22 in the second extension mechanism 42 is determined by the pitch of the screw portion. In the present embodiment, the first elongating mechanism 41 and the second elongating mechanism 42 have opposite screw spiral directions.

In the present embodiment, the first extension mechanism 41 and the second extension mechanism 42 have a ratio of the increase amount of the length of the movable part 110 corresponding to the increase amount of the stroke of the first piston 20 or the second piston 30. Is different. Therefore, when the brake shoe 3L and the brake shoe 3T have different wear speeds of the lining 3c over time, the rate of increase in the length of the movable part 110 in one axial direction and the length in the other axial direction are increased. By making the increase rate different from this, it is possible to set the change (shift) with time of the relative position (for example, the central position in the axial direction) of the movable part 110 with respect to the housing 10 to be smaller.

Further, in the present embodiment, the rate of increase of the first extension mechanism 41 located near the brake shoe 3L serving as the leading shoe for the forward rotation of the wheel and the drum 2 is higher than the rate of increase of the second extension mechanism 42. It is configured as follows. Specifically, the screw pitch of the first extension mechanism 41 (that is, the advance amount per one screw rotation) is set to be larger than the screw pitch of the second extension mechanism 42. In the brake device 1, the wear speed of the lining 3 c of the brake shoe 3 L serving as a leading shoe against forward rotation may be greater than the wear speed of the lining 3 c of the brake shoe 3 T serving as a trailing shoe. In such a case, with the configuration in which the increase rate of the first extension mechanism 41 is higher than the increase rate of the second extension mechanism 42, the relative position (for example, the axial center position) of the movable part 110 with respect to the housing 10 over time. The change (deviation) can be set smaller. In this case, for example, the ratio of the wear speed of the lining 3c of the leading shoe and the wear speed of the lining 3c of the trailing shoe is known by, for example, a statistical method for each vehicle type, vehicle, region, etc. In this case, the increasing rate of the first extension mechanism 41 and the second extension mechanism 42, for example, the screw pitch in the screw mechanism, can be set according to the ratio, for example, in proportion to the ratio.

(Rotation drive mechanism)
As shown in FIGS. 2 to 5, the rotation drive mechanism 50 includes a linear motion member 51, a swing member 52, a biasing member 53, and a one-way rotation portion 54. The linear motion member 51 is supported by the first piston 20 and reciprocates along the central axis Ax together with the first piston 20. The rotation of the linear motion member 51 around the central axis Ax is limited by other members. The swing member 52 is swingably supported by the housing 10 and swings about the swing center C 3 according to a linear reciprocation along the central axis Ax of the linear motion member 51. The biasing member 53 biases the linear motion member 51 or the swing member 52 so that the linear motion member 51 follows the return of the first piston 20. The linear motion member 51, the swing member 52, and the urging member 53 constitute a direct motion swing conversion mechanism. An annular seal member 55 is interposed between the linear motion member 51 and the first piston 20 (projecting portion 22b) to prevent foreign matter from entering.

The one-way rotating portion 54 is configured to rotate mainly in one direction by rotating by the forward movement of the swinging member 52 and not rotating by the backward movement of the swinging member 52. Specifically, a claw 52a (latch) provided on the swinging member 52 and a plurality of teeth 54a provided on the one-way rotating portion 54 (gear) are used in one rotation direction (clockwise direction in FIG. 4). , A ratchet mechanism that engages in the direction Rs) but does not engage in the other rotation direction (counterclockwise direction in FIG. 4, the direction opposite to the direction Rs).

The pivotable part 22 is configured to rotate in accordance with the rotation of the one-way rotating part 54. In the present embodiment, as an example, as shown in FIG. 5, the one-way rotating part 54 is fixed to the rotatable part 22. Note that the rotatable portion 22 only needs to rotate according to the rotation of the one-way rotating portion 54, and may not be integrated with the one-way rotating portion 54.

In the brake device 1, as the gap (shoe clearance) between the outer peripheral surface of the lining 3c of the

brake shoes

3L and 3T and the inner peripheral surface 2a of the drum 2 increases with time, the amount of movement of the

brake shoes

3L and 3T increases. . In this case, the stroke of the linear motion member 51 that operates in conjunction with the first piston 20, that is, the stroke between the pressure-removed state and the pressurized state of the pressure chamber Rp increases.

Here, in the present embodiment, as described above, both the first extension mechanism 41 and the second extension mechanism 42 are movable according to the rotation of the rotatable portion 22 by setting the screw spiral direction in the screw mechanism. The length of the part 110 in the direction along the central axis Ax is increased. Therefore, according to the present embodiment, the length of the movable part 110 increases as the shoe clearance increases due to the operation of the rotation drive mechanism 50, the first extension mechanism 41, and the second extension mechanism 42, and the shoe clearance Can be reduced. Therefore, according to the present embodiment, the shoe clearance can be maintained within a certain range. The range includes an appropriate value depending on the specifications of each part of the rotation drive mechanism 50, the first extension mechanism 41, and the second extension mechanism 42, including the interval (angular interval) between the teeth 54 a of the unidirectional rotation unit 54. Can be adjusted.

As described above, in the present embodiment, as the stroke between the pressure-removed state and the pressurized state of the first piston 20 is larger, the first extension mechanism 41 has the linear motion portion 21 and the rotatable portion 22. The second extension mechanism 42 increases the length of the subassembly (two parts) of the linear motion part 23 and the rotatable part 22. That is, in both the first extension mechanism 41 and the second extension mechanism 42, the length of the movable part 110 is increased as the stroke between the pressure-removed state and the pressurized state of the first piston 20 is increased. In other words, the pivotable portion 22 of the first piston 20 is rotationally displaced by the ratchet mechanism, so that the axial interval between the first piston 20 and the second piston 30 and the

pistons

20 and 30 correspond to these. The distance between the

brake shoes

3L and 3T in the axial direction can be appropriately adjusted according to the stroke. That is, one wheel cylinder 100 can be provided with a shoe clearance adjusting function for the two

brake shoes

3L and 3T with a simple configuration. In the present embodiment, the movable component 110 functions as a strut that intervenes with the lever 61 between the two

brake shoes

3L and 3T when the lever 61 is braked. Therefore, according to this embodiment, the strut with an adjuster provided separately from the wheel cylinder 100 becomes unnecessary. Therefore, for example, the brake device 1 can be configured more compactly. Further, for example, the labor and cost required for manufacturing the brake device 1 can be reduced by the amount of parts that can be reduced. In the present embodiment, both the first extension mechanism 41 and the second extension mechanism 42 are configured to increase the length of the movable part 110 in accordance with an increase in the stroke of the first piston 20, but this is not limitative. For example, both the first extension mechanism 41 and the second extension mechanism 42 may be configured to increase the length of the movable part 110 in accordance with an increase in the stroke of the second piston 30. Alternatively, the first extension mechanism 41 increases the length of the movable part 110 in accordance with an increase in the stroke of the first piston 20, and the second extension mechanism 42 has a movable part in accordance with an increase in the stroke of the second piston 30. The length of 110 may be increased.

In the present embodiment, the first extension mechanism 41 and the second extension mechanism 42 have a ratio of the increase amount of the length of the movable part 110 corresponding to the increase amount of the stroke of the first piston 20 or the second piston 30. Is different. Therefore, according to this embodiment, when the brake shoe 3L and the brake shoe 3T have different wear speeds of the lining 3c with time, the rate of increase in the length of the movable part 110 in one axial direction is as follows: By changing the rate of increase in the length in the other axial direction, even if the length of the movable part 110 is increased, the change (shift) with time of the relative position of the movable part 110 with respect to the housing 10 is changed. , Can be set smaller.

In the present embodiment, the first extension mechanism 41 and the second extension mechanism 42 have a ratio of the increase amount of the length of the movable part 110 corresponding to the increase amount of the stroke of the first piston 20 or the second piston 30. Is different. Therefore, according to the present embodiment, for example, by appropriately setting the ratio of the increase amount, the change (deviation) with time of the relative position (for example, the central position in the axial direction) of the movable part 110 with respect to the housing 10 is set to be smaller. It becomes possible to do.

Further, in the present embodiment, the ratio of the first extension mechanism 41 positioned near the brake shoe 3 L serving as a leading shoe for the forward rotation of the wheel and the drum 2 is larger than the ratio of the second extension mechanism 42. It is configured as follows. Therefore, according to the present embodiment, for example, when the wear rate of the lining 3c of the brake shoe 3L serving as a leading shoe against forward rotation is higher than the wear rate of the lining 3c of the brake shoe 3T serving as a trailing shoe, the housing Thus, it is possible to set the change with time of the relative position of the movable part 110 with respect to 10 smaller.

(Modification)
FIG. 6 is a cross-sectional view of a modified wheel cylinder 100A at the same position as in FIG. In the present modification, the second piston 30 A has a linear motion portion 31 and a rotatable portion 32. The connecting portion 32a of the rotatable portion 32 and the connecting portion 22f of the rotatable portion 22 of the first piston 20A restrict relative rotation around the central axis Ax and extend in the direction along the central axis Ax. Connected in a state that allows relative movement. The second extension mechanism 42 A includes a female screw part 31 c provided in the linear motion part 31 and a male screw part 32 b provided in the rotatable part 32. Also in this modified example, as the stroke of the first piston 20A increases, the second extension mechanism 42A has a full axial length between the linear motion portion 31 and the rotatable portion 32, that is, the second piston 30A. The total length, and thus the total length of the movable part 110A, is set to increase. Further, the ratio of the increase amount of the length of the movable part 110A to the increase amount of the stroke of the first piston 20A of the first extension mechanism 41 is different from the ratio of the second extension mechanism 42A. Also by such a modification, the same effect as the said embodiment is acquired. In the present modification, the first extension mechanism 41 and the second extension mechanism 42A can have the same screw spiral direction.

As mentioned above, although embodiment of this invention was illustrated, the said embodiment is an example and is not intending limiting the range of invention. The above embodiment can be implemented in various other forms, and various omissions, replacements, combinations, and changes can be made without departing from the spirit of the invention. In addition, the specifications (structure, type, direction, shape, size, length, width, thickness, height, number, arrangement, position, material, etc.) of each configuration, shape, etc. are appropriately changed. Can be implemented.

In the above embodiment, the configuration in which the operating member that moves the braking member is the cable 62 is exemplified. However, the operating member may be other than the cable 62, such as a rod or a lever. The actuating member may move the braking member by pushing instead of pulling. Further, the extension mechanism only needs to change the length of the movable component in accordance with the stroke of the piston, and is not limited to the disclosed configuration. Moreover, the external thread part and the internal thread part of an extending | stretching mechanism can be comprised by changing suitably. Further, the present invention can also be applied to a parking brake that brakes by moving the lever 61 by manual operation. In this case, the lever 61 is operated via a cable 62 connected to a manual operation member such as a hand lever or a foot pedal.

Claims

A housing provided with a cylinder hole;
A first piston that is movably accommodated in the cylinder hole in the axial direction and that presses the first brake shoe in one of the axial directions in a pressurized state of the pressure chamber in the cylinder hole, and the axial direction in the cylinder hole A second piston that is movably accommodated and presses the second brake shoe against the other in the axial direction in the pressurized state, and is integrated in the axial direction in the cylinder hole in the pressure-removed state of the pressure chamber. A movable part movably interposed between the first brake shoe and the second brake shoe;
As the stroke between the depressurized state and the pressurized state of the first piston or the second piston increases, the rotation angle about the axis relative to the housing increases so that the rotation angle of the first piston and the second piston increases. A ratchet mechanism that rotationally displaces one of them,
A plurality of extension mechanisms that increase the length of the movable part in the axial direction as the rotation angle increases;
With
One extension mechanism is disposed between the one piston rotated and displaced by the ratchet mechanism and the brake shoe pressed against the piston, and the other extension mechanism includes the first piston and the first piston. A drum cylinder for drum brakes arranged between two pistons.
The drum brake wheel according to claim 1, wherein a ratio of an increase amount of the length of the movable part to an increase amount of the stroke of one of the plurality of extension mechanisms is different from the ratio of the other extension mechanisms. Cylinder.
The first brake shoe is a leading shoe for forward rotation of the wheel, and the second brake shoe is a trailing shoe for forward rotation of the wheel,
Of the two extension mechanisms, when the extension mechanism is disposed between the first piston and the first brake shoe, the ratio of the extension mechanism is the ratio of the first piston and the first brake mechanism. When the extension mechanism is not disposed between the brake shoe and the brake shoe, the ratio of the extension mechanism disposed between the first piston and the second piston is greater than the ratio of the other extension mechanism. The wheel cylinder for a drum brake according to claim 2, which is large.
When a lever that is pivotably connected to one of the first brake shoe and the second brake shoe is subjected to a braking operation, the movable part becomes the lever, the first brake shoe, and the second brake shoe. The wheel cylinder for a drum brake according to any one of claims 1 to 3, wherein the wheel cylinder is interposed as a strut between the other and the other.
A wheel cylinder for a drum brake according to any one of claims 1 to 3,
The first brake shoe and the second brake shoe;
Drum brake for vehicles equipped with.
Comprising a lever rotatably connected to one of the first brake shoe and the second brake shoe;
The movable part is configured to be interposed as a strut between the lever and the other of the first brake shoe and the second brake shoe when the lever is braked. Vehicle drum brake.