JP4486283B2 - Dual mode drum brake - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a dual mode drum brake that functions as a leading trailing brake at the time of service braking (normal braking) and functions as a duo-servo brake at the time of parking brake.
[0002]
[Prior art]
(a) a backing plate that is integrally fixed to the vehicle body, and (b) each has a substantially arc shape, and is substantially symmetrically disposed on the backing plate so as to be able to expand to the outer peripheral side. A pair of first and second brake shoes supported by an anchor integrally provided with the backing plate, and (c) other than the pair of first and second brake shoes. The first brake shoe and the second brake shoe are pressed against the drum rotating with the wheel by being arranged on the backing plate so as to be positioned between the end portions, and by separating the other end portions to the outside, respectively. A separation device for generating a braking force as a ring-type drum brake; and (d) disposed substantially along the first brake shoe, A plate-like reaction plate connected to an intermediate portion of a shoe web having a flat plate shape substantially parallel to the backing plate so as to be relatively rotatable around a connection center substantially perpendicular to the backing plate; and (e) the The reaction plate is disposed across one end of the reaction plate and the second brake shoe, and on the second brake shoe side, the reaction plate is disposed on the shoe web in a posture substantially perpendicular to the backing plate. A plate-like second strut member connected to the connecting pin through a mounting hole so as to be relatively rotatable; and (f) an end portion of the second strut member and the reaction plate of the first brake shoe. The plate-like engagement portions that are substantially parallel to the shoe web are held in abutment state in substantially the same plane that is in contact with one surface of the shoe web. A positioning spring; and (g) engaged with one and the other of the second brake shoe and the other end of the reaction plate opposite to the one end with the coupling center of the reaction plate interposed therebetween. A first strut member and a parking lever, and (h) the reaction plate, the first strut member, and the second strut member are interlocked with each other by rotating the parking lever. A dual mode drum brake that expands the brake shoe and the second brake shoe and generates a braking force as a duo-servo brake is described in, for example, Japanese Patent Application Laid-Open No. 2000-170802.
[0003]
FIGS. 3A and 3B are diagrams showing an example of such a dual mode drum brake. FIG. 3A is a front view, FIG. 3B is a cross-sectional view taken along the line BB in FIG. For wheels. In FIG. 3, a substantially disc-shaped backing plate 10 that is integrally fixed to the vehicle body has a pair of brake shoes 12 and 14 having an arc shape (a crescent shape) that can be expanded to the outer peripheral side. In FIG. 3 (a), it is arranged substantially vertically so as to be movable in the left-right direction. The brake shoes 12 and 14 are fixed so that the shoe webs 12a and 14a substantially parallel to the backing plate 10 and the outer peripheral side edges of the shoe webs 12a and 14a are substantially perpendicular, that is, the cross section forms a T-shape. The shoe rims 12b and 14b and the linings 12c and 14c fixed to the outer peripheral surfaces of the shoe rims 12b and 14b are integrally provided, and the shoe hold-down devices 16, 18 is disposed and is pressed against the backing plate 10 so as to be movable in the expanding direction. The pair of shoe webs 12 a and 14 a are positioned in a substantially common plane that is spaced from the backing plate 10 by a predetermined dimension.
[0004]
The opposite end portions of the shoe webs 12a, 14a of the brake shoes 12, 14, that is, the lower end portions in FIG. 3 (a) are brought into contact with the anchor 20 fixed on the backing plate 10. On the other hand, the other end portions of the shoe webs 12a and 14a, that is, the upper end portion in FIG. 3A, are respectively connected to both end portions of the wheel cylinder 22 fixed on the backing plate 10. Engaged. The anchor 20 is a floating type, that is, the shoe webs 12a and 14a are detachably locked, and a tension coil spring 24 disposed between the shoe webs 12a and 14a is always used to fix the shoe webs 12a and 14a. One end is brought into contact with the anchor 20. The wheel cylinder 22 corresponds to a separation device, and includes a pair of pistons that project to both sides by supplying brake hydraulic pressure in accordance with an operation at the time of service braking such as a foot brake, and abut against the anchor 20 by the pistons. The linings 12c and 14c are formed on the inner peripheral surface of the drum 26 that rotates together with the wheels by separating the other end portions of the brake shoes 12 and 14 outward (left and right directions in FIG. When pressed, a braking force is generated. That is, it functions as a leading trailing drum brake during service braking, and when the vehicle moves forward, the drum 26 is rotated in the clockwise direction indicated by arrow A in FIG. The brake shoe 14 on the left side becomes the trailing shoe. 3A is arranged in a posture that is substantially the same as the arrangement state on the vehicle body and in a posture in which the wheel cylinder 22 is positioned on the upper side.
[0005]
Between the brake shoes 12 and 14, the other end, that is, the vicinity of the upper end, specifically, the portion close to the inside of the wheel cylinder 22, is substantially parallel to the wheel cylinder 22, that is, the brake shoes 12, 14 are expanded. The first strut member 28 is bridged in a posture that is substantially parallel to the direction. The both ends of the first strut member 28 and the shoe webs 12a, 14a are provided with notches or the like to prevent the first strut member 28 from being displaced or detached. A return spring 30 is disposed around the first strut member 28, and both ends of the return spring 30 are hooked to the brake shoes 12 and 14, so that when the hydraulic pressure of the wheel cylinder 22 decreases, the return spring 30 The two brake shoes 12 and 14 are brought close to each other according to the urging force, and are brought into contact with both end portions of the first strut member 28 to define an approach position (standby position). The first strut member 28 can be expanded and contracted by a screw, and is extended by the shoe gap automatic adjusting mechanism 32 as the amount of movement of the brake shoe 12 increases, so that the standby positions of the brake shoes 12 and 14 are separated from each other. As a result, the gap with the drum 26 is maintained within a predetermined range regardless of the wear of the linings 12c, 14c.
[0006]
A reaction plate 34 is disposed on the brake shoe 14 so as to be substantially parallel to the shoe web 14 a and on the opposite side of the backing plate 10, and the reaction plate 34 is rotated relative to the brake shoe 14 via a first connecting pin 35. The shoe web 14a is movably connected. The axis of the first connection pin 35 corresponds to the connection center (first connection center) and is substantially perpendicular to the backing plate 10. The upper end of the reaction plate 34 reaches the vicinity of the wheel cylinder 22, and the second connecting pin 36 is arranged at the upper end of the reaction plate 34 substantially parallel to the first connecting pin 35, that is, substantially perpendicular to the backing plate 10. It is installed. The reaction plate 34 has a flat plate shape, and a portion 34a corresponding to the first strut member 28 slightly below the upper end where the second connecting pin 36 is provided protrudes away from the shoe web 14a. Although it floats in a shape so that interference with the first strut member 28 is avoided, the other portions are substantially brought into surface contact with the shoe web 14a. A parking lever 38 is coupled to the second coupling pin 36 so as to be capable of relative rotation about a second coupling center that is the axis of the second coupling pin 36.
[0007]
The parking lever 38 is disposed so as to overlap the backing plate 10 side, that is, on the opposite side of the reaction plate 34, substantially parallel to the shoe web 14a of the brake shoe 14, and is locked to the tip end portion (the second connecting pin 36). The other side of the reaction plate 34 reaches the vicinity of the lower end of the reaction plate 34 and the parking brake cable 40 is connected. The second connecting pin 36 is inserted through an insertion hole 14d formed in the shoe web 14a. The insertion hole 14d is sufficiently larger than the diameter of the second connecting pin 36 and is second to the shoe web 14a. The connecting pin 36 and the reaction plate 34 are allowed to relatively rotate around the first connecting pin 35. The brake shoe 14 corresponds to a first brake shoe, and the brake shoe 12 on the opposite side corresponds to a second brake shoe. The parking brake cable 40 is taken out to the vehicle body side from a take-out hole 42 provided on the lower side of the backing plate 10, that is, on the anchor 20 side and in the vicinity of the brake shoe 12, and is provided in the vehicle interior. It is connected to a brake operation member such as a parking brake operation lever and a foot pedal (not shown).
[0008]
A second strut member 44 is bridged between the lower end portion 34 b which is one end portion of the reaction plate 34 and the vicinity of the lower end portion of the brake shoe 12. The second strut member 44 is a flat plate-like member that is substantially parallel to the shoe webs 12a, 14a located in substantially the same plane, and has an arcuate shape so as to bypass the anchor 20, and one end thereof is The shoe web 12 a is substantially in surface contact with the upper surface (the surface opposite to the backing plate 10) and is substantially parallel to the first connecting pin 35 and the second connecting pin 36, that is, substantially perpendicular to the backing plate 10. The shoe web 12a is attached to the third connecting pin 46 disposed on the shoe web 12a in the posture through the mounting hole 44h so as to be relatively rotatable around the third connecting center that is the axis of the third connecting pin 46. It is connected to. The other end portion 44a of the second strut member 44 and the lower end portion 34b of the reaction plate 34 correspond to engaging portions, and are positioned in substantially the same plane that is substantially parallel to and in contact with the upper surface of the shoe web 14a. They are abutted against each other by positioning springs 48. The other end portion 44a is provided with an arc-shaped recess, while the lower end portion 34b is provided with an arc-shaped protrusion having substantially the same curvature as the recess, and the positioning spring 48 and the like. By being fitted, relative rotation is possible within a plane substantially parallel to the backing plate 10 while maintaining the engaged state. The positioning spring 48 is used to prevent the generation of noise due to rattling between the lower end 34b and the other end 44a when the vehicle is running, and to return the reaction plate 34 to a certain initial position when the parking brake is released. , A tension coil spring stretched between the latching portion 34c provided integrally with the reaction plate 34 so as to be separated from the shoe web 14a and the third connecting pin 46, and the coil portion 48a is a second strut. By engaging with the member 44, the second strut member 44 is pressed against the shoe web 14 a of the brake shoe 14.
[0009]
When a brake operating member such as a parking brake operating lever is operated to the parking brake position, the parking lever 38 is centered on the second connecting pin 36 and the brake shoe 12 side (second connecting pin 36) via the parking brake cable 40. When the brake operation member is returned to the brake release position, the parking lever 38 is returned to the original position by a return spring (not shown). When the parking lever 38 is rotated toward the brake shoe 12 at the start of braking of the parking brake, the parking lever 38 is engaged with the first strut member 28 in the vicinity of the second connecting pin 36, and the first strut The brake shoe 12 is displaced outward (to the right in FIG. 3A) via the member 28, and the second connecting pin 36 is outward (to the left in FIG. 3A) by the reaction force. Be displaced. When the second connecting pin 36 is displaced leftward, the reaction plate 34 is rotated counterclockwise of the first connecting pin 35 and the lower end portion 34b is displaced toward the brake shoe 12 side, so that the second strut member 44, the lower end side of the brake shoe 12 is displaced outward (to the right in FIG. 3A), and the reaction plate 34 is engaged with the second strut member 44 as a fulcrum by the reaction force. The brake shoe 14 is rotated counterclockwise in FIG. 3A, and the brake shoe 14 is displaced outward (leftward in FIG. 3A) through the first connecting pin 35.
[0010]
That is, when the parking lever 38 is rotated around the second connecting pin 36 toward the brake shoe 12 when braking of the parking brake is started, the upper end portion (the other end portion) of the brake shoe 12 is moved via the first strut member 28. The second connecting pin 36 is displaced outward by the reaction force while being displaced outward, and the reaction plate 34 is rotated counterclockwise around the first connecting pin 35 as a result. The lower end portion (one end portion) of the brake shoe 12 is displaced outward through the strut member 44, and the brake shoe 14 is displaced outward by the reaction force. As a result, both brake shoes 12, 14 are paired with a pair of strut members. 28, 44, reaction plate 34, parking lever 38 in a operatively connected state, 26 and of being pressed, generates a braking force to the duo-servo type. When functioning as a duo-servo brake, the length of the second strut member 44, the reaction plate 34, the lever ratio of the parking lever 38, etc. are set such that the braking force is received by the anchor 20. When the forward torque indicated by the arrow A is applied, the left brake shoe 14 functions as a primary shoe, the right brake shoe 12 functions as a secondary shoe, and one end of the brake shoe 12 is anchored. 20 is contacted. The insertion hole 14d provided in the shoe web 14a of the brake shoe 14 is set to a size that does not interfere with the second connecting pin 36 when functioning as a duo-servo brake as described above.
[0011]
[Problems to be solved by the invention]
However, in the dual mode drum brake configured as described above, play between the first connecting pin 35 and the reaction plate 34 (play) and play between the third connecting pin 46 and the second strut member 44 ( Due to the looseness, the engaging portions (the lower end portion 34b and the other end portion 44a) may be displaced in the plate thickness direction and the contact between them may be disengaged. That is, the mounting hole 44h of the second strut member 44 is provided by punching with a press. However, when the punching side, that is, the shearing surface side of the punching start side is arranged in a posture that is the shoe web 12a side, the opposite side is a fracture surface. Since the hole diameter is large and a pressing force acts in the direction of pressing the lower end portion 34b and the other end portion 44a during braking, the side in contact with the shoe web 12a having the smaller hole diameter becomes the third connecting pin 46. There is a possibility that a moment is generated in the direction in which the other end 44a is lifted from the shoe web 14a with the pressing point S as the center, and the coil portion 48a is lifted only by the pressing action as shown in FIG. 3 (b). There was. In particular, the second strut member 44 has a short dimension in the direction opposite to the other end portion 44a side from the third connecting pin 46 (the right direction in FIG. 3B), so that the other end portion 44a is greatly lifted to lower the lower end portion. There is a possibility to ride on 34b.
[0012]
In this way, if the contact between the lower end portion 34b and the other end portion 44a is released, the braking action cannot be obtained. For example, in Japanese Patent Laid-Open No. 2000-170802, the brake shoe 14 is provided with a spring plate for positioning displacement and positioning. Pins and the like are disposed and both members are positioned on the shoe web 14a to prevent the lifting. However, in this case, the number of parts increases, the number of assembling steps increases, and the manufacturing cost increases.
[0013]
The present invention has been made against the background of the above circumstances, and the purpose of the present invention is to disengage the engaging portion between the reaction plate and the second strut member without using a separate part such as a positioning pin. It is to prevent that.
[0014]
[Means for Solving the Problems]
In order to achieve such an object, the first invention includes (a) a backing plate integrally fixed to the vehicle body, and (b) each having a substantially circular arc shape. A pair of first brake shoes and second brake shoes which are arranged substantially symmetrically and whose opposite ends are supported by an anchor provided integrally with the backing plate; and (c) the A drum that is disposed on the backing plate so as to be positioned between the other end portions of the pair of first brake shoes and the second brake shoe, and that separates the other end portions to the outside so that the drum rotates together with the wheels. A separating device that presses the brake shoe and the second brake shoe to generate a braking force as a leading trailing drum brake; and (d) the first brake The shoe web is arranged substantially along the shoe, and is connected to an intermediate portion of the shoe web having a flat plate shape substantially parallel to the backing plate so as to be relatively rotatable around a coupling center substantially perpendicular to the backing plate. A plate-like reaction plate; and (e) disposed across one end of the reaction plate and the second brake shoe, and on the second brake shoe side, is substantially the same as the backing plate. A plate-like second strut member connected to a connecting pin disposed on the shoe web in a vertical posture through a mounting hole so as to be relatively rotatable; and (f) the second strut member and the reaction plate. Plate-like engaging portions that are substantially parallel to the shoe web of the first brake shoe and are in contact with one surface of the shoe web. A positioning spring that is held in a state of being abutted within the plane of (b), and (g) the other end of the reaction plate opposite to the one end with respect to the connection center, and one and the other of the second brake shoe. A first strut member and a parking lever which are engaged with each other, and (h) the reaction plate, the first strut member, and the second strut member by rotating the parking lever. In a dual mode drum brake that generates a braking force as a duo-servo brake by expanding the pair of first brake shoes and second brake shoes in conjunction with each other, (i) the mounting holes of the second strut members are Die-side surface where the hole diameter is increased by punching with a press Is arranged in a posture facing the shoe web of the second brake shoe.
[0015]
According to a second aspect of the present invention, in the dual mode drum brake of the first aspect, the second strut member is taken out by a punching process using a press, and the die is located on the same surface side as the die side when the mounting hole is punched. When the punching process is performed at the position, the surface on the die side whose outer peripheral shape becomes large is made to face the shoe web.
[0016]
【The invention's effect】
In such a dual mode drum brake, the surface on the die side in the mounting hole punching process, that is, the surface on the side where the hole diameter of the mounting hole becomes larger due to the fracture surface is arranged in a posture facing the shoe web. Therefore, when a pressing force is applied to the engaging portion of the reaction plate and the second strut member during braking of the parking brake, the opposite side of the mounting hole to the shoe web having the small hole diameter is pressed by the connecting pin, and the second strut member A moment in the direction in which the other end of the shoe is pressed toward the shoe web is generated, and the other end is lifted off the shoe web and is prevented from coming into contact with the reaction plate to prevent the braking action from being obtained. The In addition, since it is only necessary to appropriately set the pressing direction when pressing the mounting hole and the posture when assembling the second strut member, the reaction plate and the second strut member are both attached to the shoe web using separate parts. Compared to positioning, the number of parts is reduced, and the structure is simple and inexpensive.
[0017]
The second invention is a case where the second strut member itself is also taken out by punching by pressing, and the die is positioned on the same surface side as the die side at the time of punching of the mounting hole. The die side surface having a larger outer peripheral shape is made to face the shoe web, and the reaction plate is brought into contact with the shoe web side portion having a larger outer peripheral shape, whereby the other end of the second strut member Lifting of the portion (engagement portion) is more effectively prevented.
[0018]
The reaction plate has an end opposite to the engaging portion engaged with the second strut member engaged with the first strut member or the parking lever and connected to the shoe web at an intermediate portion. Therefore, while the posture change is restricted, the moment in the direction of pressing the engaging portion against the shoe web can be generated by separating the latching portion of the positioning spring from the shoe web. Thus, there is no fear that the engaging part will rise up. However, when the reaction plate is attached to the connecting pin of the first brake shoe via the attachment hole, it does not prevent the pressing direction of the attachment hole from being set similarly to the attachment hole of the second strut member.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
According to a first preferred embodiment of the present invention, (a) the parking lever is disposed substantially along the first brake shoe, and the other end of the reaction plate is connected to the connection center (first connection). The second connection center that is substantially parallel to the center of the second connection center so as to be rotatable relative to the second connection center. During parking braking, the second connection center is rotated to the second brake shoe side via the parking brake cable or the like. (B) The first strut member has a second brake shoe that is rotated when the parking lever is rotated toward the second brake shoe about the second connection center during the parking brake. The parking lever and the second brake so that the second connecting center is displaced outward by the reaction force. (C) The second strut member is displaced outwardly during the parking brake so that the reaction plate rotates about the first connection center. Accordingly, the second brake shoe is displaced outward, and the first brake shoe is displaced outward together with the first connection center by the reaction force. The conventional example of FIG. 3 is according to the first embodiment.
[0020]
In the second embodiment, (a) the parking lever is disposed substantially along the second brake shoe, and the second brake shoe has a second substantially parallel to the connection center (first connection center). 2 is connected so as to be capable of relative rotation around a connection center, and is configured to be rotated to the first brake shoe side around the second connection center via a parking brake cable or the like during the parking brake, (b ) The first strut member displaces the other end portion of the reaction plate to the outside when the parking lever is rotated toward the first brake shoe around the second connection center during the parking brake. At the same time, the reaction force causes the parking lever and the reaction plate to displace the second connection center outward. And (c) the second strut member is configured such that the other end of the reaction plate is displaced outward during the parking brake and is rotated about the first connection center. The second brake shoe is displaced outward, and the first brake shoe is displaced outward together with the first connection center by the reaction force.
[0021]
In both the first and second embodiments, the second connection center is substantially parallel to the first connection center. However, in implementing the present invention, the second connection center is not necessarily parallel to the first connection center. For example, it may be parallel to the backing plate. Further, the first brake shoe on which the reaction plate is disposed may be either a leading shoe or a trailing shoe.
[0022]
The reaction plate may be disposed on the backing plate side of the shoe web of the first brake shoe, or may be disposed on the opposite side of the backing plate across the shoe web. In the case of being disposed on the side (the first embodiment), it is desirable to dispose the reaction plate and the parking lever on opposite sides of the shoe web of the first brake shoe. In the case of the second embodiment, it is desirable that the reaction plate and the parking lever are arranged on the same side with respect to the upper and lower sides of the shoe web (whether or not the backing plate side).
[0023]
The first strut member and the second strut member are substantially parallel to the expanding direction of the pair of first brake shoes and second brake shoes, i.e., substantially perpendicular to the straight line connecting the separating device and the anchor. It is desirable to dispose them so as to be substantially parallel to each other and to be substantially parallel to each other, and it is desirable to dispose them close to the inner part of the separating device and the anchor. Further, when functioning as a duo-servo type brake during parking brake, it is desirable that the anchoring force be received by the anchor, and the length and arrangement of the first strut member and the second strut member, the reaction plate, and the parking The lever ratio of the lever should be determined so that one end of the brake shoe that becomes the secondary shoe during parking brake comes into contact with the anchor, and there is a gap between the other end of both brake shoes and the wheel cylinder. Is desirable. The anchor is provided integrally with the backing plate, and is fixed to the vehicle body together with the backing plate or alone, for example.
[0024]
A return spring and a strut member that generally define an approach position (standby position) are disposed at the other end portions of the pair of first brake shoes and second brake shoes, that is, the end portions on the side of the separating device. The first strut member and the second strut member are different from the strut member for defining the standby position. However, as shown in FIG. 3, the wheel cylinder side of the first strut member and the second strut member can also be used as the strut member for defining the standby position.
[0025]
A wheel cylinder is widely used as the separation device, but various modes such as an electric separation device using an electric motor can be adopted. For example, the parking lever is configured to be rotated according to the operation force of the driver's parking brake operation, but is configured to be rotated by a drive source such as an electric motor that is operated according to the operation of the parking switch. You can also.
[0026]
As the positioning spring for biasing the engaging portion of the reaction plate and the second strut member in the direction approaching each other, a tension coil spring is preferably used, but a torsion coil spring can also be used. It can also be used to activate. For example, the positioning spring is disposed across the second strut member and the reaction plate, but may be disposed across the second brake shoe and the reaction plate.
[0027]
The engaging portion between the reaction plate and the second strut member is preferably located on one surface of the shoe web of the first brake shoe. It may be made to be located in. The phrase “on one surface of the shoe web” does not mean the upper side in the vertical direction, but means that it overlaps the shoe web in a plan view as viewed from the direction perpendicular to the shoe web.
[0028]
For example, when the reaction plate is disposed on the primary brake shoe as shown in FIG. 3, the engagement portion between the reaction plate and the second strut member is provided with an arc-shaped protrusion on the reaction plate side. An arc-shaped recess having substantially the same curvature as the convex portion is provided on the two strut member side, but conversely, a concave portion may be provided on the reaction plate side and a protrusion may be provided on the second strut member side.
[0029]
In the second invention, the die is positioned on the same surface side as the die side at the time of punching the mounting hole, the second strut member is punched, and the die side surface whose outer peripheral shape is large is opposed to the shoe web. As a result, the reaction plate is brought into contact with the shoe web side portion having a large outer peripheral shape. In the first invention, however, punching is performed so that the outer peripheral shape is substantially constant in the thickness direction, for example. While processing, the thickness of the reaction plate may be partially or entirely reduced so as to contact the shoe web side portion. The reaction plate may be formed so that the outer peripheral shape of the reaction plate becomes larger toward the shoe web by appropriately setting the direction of punching of the reaction plate. Note that the second strut member and the reaction plate can be manufactured by a processing method other than punching with a press.
[0030]
In addition, the engaging portion between the reaction plate and the second strut member is provided with a stopper portion that regulates displacement of the second strut member in a direction away from the shoe web relative to the reaction plate, You may make it prevent reliably that contact | abutting with a 2nd strut member remove | deviates. The stopper portion is integrally provided so as to protrude from the engagement portion of the reaction plate to the opposite side of the shoe web and to the second strut member side, and is engaged with the surface of the second strut member opposite to the shoe web. Protrusions that can be combined are desirable.
[0031]
【Example】
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, the case where the present invention is applied to the dual mode drum brake of FIG. 3 will be described. Components that are substantially the same as those in FIG.
[0032]
1A and 1B are views corresponding to FIG. 3, in which FIG. 1A is a front view, FIG. 1B is a cross-sectional view taken along line BB in which a part of FIG. 1A is omitted, and a second strut member 50 according to this embodiment. The mounting holes 50h are provided by punching (piercing) using a press, which is the same as the conventional example. However, the surface on the die side where the hole diameter becomes large and the hole diameter becomes large is the shoe web of the brake shoe 12. The side facing 12a, that is, the opposite direction as compared with FIG. The second strut member 50 itself is also taken out by punching (blanking) by a press, but when the die is positioned on the same side as the die at the time of punching the mounting hole 50h, the punching is performed. Of the outer peripheral surface 50f, the surface on the die side whose outer peripheral shape is large is opposed to the shoe web 14a. Further, the latching portion 48b of the positioning spring 48 is wound around the latching groove of the third connecting pin 46 over an angle range larger than 180 °, specifically over an angle range of 200 ° or more.
[0033]
In such a dual mode drum brake, the surface on the die side in the punching process of the mounting hole 50h, that is, the surface on the side where the hole diameter of the mounting hole 50h becomes larger is opposed to the shoe web 12a. Therefore, when a pressing force is applied to the reaction plate 34 and the engaging portion (the lower end portion 34b and the other end portion 50a) of the second strut member 50 during braking of the parking brake, the hole diameter of the mounting hole 50h is reduced. A direction in which the opening opposite to the small shoe web 12a is pressed by the third connecting pin 46, and the other end 50a of the second strut member 50 is pressed toward the shoe web 14a around the pressing point S (FIG. 1). (b) in the counterclockwise direction), and the other end 50a is lifted from the shoe web 14a to the rear. It is prevented that the contact with the friction plate 34 is released and the braking action cannot be obtained. Further, since it is only necessary to appropriately set the pressing direction when pressing the mounting hole 50h and the posture when assembling the second strut member 50, the reaction plate 34 and the second strut member 50 are used by using separate parts. In comparison with the case of positioning on the shoe web 14a, the number of parts is reduced, and the structure is simple and inexpensive.
[0034]
Further, in this embodiment, the second strut member 50 itself is also taken out by punching with a press, but the die is positioned on the same surface side as the die side when the mounting hole 50h is punched, and the punching is performed. Thus, the die-side surface with an increased outer peripheral shape is made to face the shoe web 14a, so that the reaction plate 34 comes into contact with the peripheral portion of the outer peripheral surface 50f on the shoe web 14a side with the larger outer peripheral shape, Lifting of the other end portion 50a of the second strut member 50 is further effectively prevented.
[0035]
Further, in this embodiment, since the latching portion 48b of the positioning spring 48 is wound around the latching groove of the third connecting pin 46 over an angle range of 200 ° or more, the positioning spring 48 is broken by rust or the like. Even in this case, the latching portion 48b is held while being latched by the third connecting pin 46, and the third connecting pin 46 and the second strut member 50 are not likely to fall off the brake shoe 12, and a C-type retaining ring or the like is used. Compared with the case where the third connecting pin 46 is prevented from being detached, the number of parts is reduced, and in this respect as well, the apparatus is configured at low cost.
[0036]
In the above embodiment, the outer peripheral surface 50f of the second strut member 50 is inclined. However, in this embodiment, the plate thickness of the reaction plate 34 is thinner than the plate thickness of the second strut member 50. Is substantially vertical, the reaction plate 34 is brought into contact with the portion on the shoe web 14a side, and a moment in the direction in which the other end portion 50a of the second strut member 50 is pressed toward the shoe web 14a is generated. Lifting of the other end 50a is prevented. When punching out the reaction plate 34, the pressing direction and processing conditions may be set so that the outer peripheral shape increases toward the surface facing the shoe web 14a.
[0037]
In the embodiment of FIG. 2, a protrusion 34 d is provided on the lower end 34 b of the reaction plate 34. The protrusion 34d corresponds to a stopper portion that prevents the second strut member 50 from being displaced relative to the reaction plate 34 in a direction away from the shoe web 14a and coming out of contact with the reaction plate 34. The reaction plate 34 is integrally provided so as to protrude from the lower end 34b of the reaction plate 34 to the side opposite to the shoe web 14a and to extend toward the second strut member 50, and on the surface of the second strut member 50 opposite to the shoe web 14a. It can be engaged. In this embodiment, the outer peripheral surface 50f of the second strut member 50 is substantially vertical.
[0038]
In this case, in addition to preventing the other end portion 50a of the second strut member 50 from being lifted from the shoe web 14a by the form of the mounting hole 50h, the protrusion 34d integrally provided on the reaction plate 34 Since the second strut member 50 is prevented from being displaced relative to the reaction plate 34 in the direction away from the shoe web 14a, the contact disengagement between the second strut member 50 and the reaction plate 34 is further ensured. Is prevented.
[0039]
Here, there is a possibility that the reaction plate 34 is displaced in a direction away from the shoe web 14a relative to the second strut member 50. The reaction plate 34 is interposed at the upper end portion thereof via the second connecting pin 36. Since it is connected to the parking lever 38 and is connected to the shoe web 14a by the first connecting pin 35 at the intermediate portion, the posture change is restricted, and the reaction plate 34 rides on and comes into contact with the second strut member 50. There is no fear of coming off.
[0040]
As mentioned above, although the Example of this invention was described in detail based on drawing, these are one embodiment to the last, and this invention is implemented in the aspect which added the various change and improvement based on the knowledge of those skilled in the art. be able to.
[Brief description of the drawings]
1A and 1B are diagrams showing a dual mode drum brake according to an embodiment of the present invention, in which FIG. 1A is a front view, and FIG. 1B is a cross-sectional view taken along line BB in FIG. .
FIG. 2 is a view showing another embodiment of the present invention and corresponding to FIG.
FIGS. 3A and 3B are diagrams for explaining an example of a conventional dual mode drum brake. FIG. 3A is a front view, and FIG. 3B is a cross-sectional view taken along line BB in FIG.
[Explanation of symbols]
10: backing plate 12: brake shoe (second brake shoe) 14: brake shoe (first brake shoe) 12a, 14a: shoe web 20: anchor 22: wheel cylinder (separating device) 28: first strut member 34: reaction Plate 34b: Lower end (one end, engaging portion) 35: First connecting pin (connecting center) 38: Parking lever 46: Third connecting pin (connecting pin) 48: Positioning spring 50: Second strut member 50a: Other End (engagement part) 50h: Mounting hole

Claims (2)

A backing plate integrally fixed to the vehicle body;
Each has a substantially arc shape, and is disposed on the backing plate in a substantially symmetrical manner so as to be able to expand to the outer peripheral side, and opposite one end portions are supported by an anchor provided integrally with the backing plate. A pair of first and second brake shoes,
The drum is configured to be disposed on the backing plate so as to be positioned between the other ends of the pair of first brake shoes and the second brake shoes. A separation device that presses the first brake shoe and the second brake shoe to generate a braking force as a leading trailing drum brake;
Relative rotation about a coupling center that is disposed substantially along the first brake shoe and that is substantially perpendicular to the backing plate at the middle portion of the shoe web that is substantially parallel to the backing plate. A plate-like reaction plate that can be connected,
The reaction plate is disposed across one end portion of the reaction plate and the second brake shoe, and on the second brake shoe side, the reaction plate is disposed on the shoe web so as to be substantially perpendicular to the backing plate. A plate-like second strut member connected to the connecting pin via a mounting hole so as to be relatively rotatable,
End portions of the second strut member and the reaction plate, and plate-like engaging portions that are substantially parallel to the shoe web of the first brake shoe are arranged in substantially the same plane that is in contact with one surface of the shoe web. A positioning spring that holds it in a butted state,
The first strut member and the parking that are engaged with each other while being engaged with one end and the other end of the second brake shoe, and the other end opposite to the one end with the connection center of the reaction plate interposed therebetween. And the reaction lever, the first strut member, and the second strut member are interlocked to expand the pair of first brake shoes and second brake shoes by rotating the parking lever. In a dual mode drum brake that generates braking force as a duo servo brake,
The mounting hole of the second strut member is provided by a punching process using a press, and the die side surface having a larger hole diameter is disposed in a posture facing the shoe web of the second brake shoe. Features a dual mode drum brake. The second strut member is taken out by a punching process using a press, and the outer peripheral shape is increased when the die is positioned on the same surface side as the die side at the time of punching the mounting hole. The dual-mode drum brake according to claim 1, wherein a surface on the die side is made to face the shoe web.

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