JP2000065100A - Drum brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability against impact load such as anchor reaction in relation to a driving source of an action lever, in a drum brake device for generating shoe operating force for pressing a pair of brake shoes against a drum by an action lever. SOLUTION: In a drum brake device 1 having an electric action lever 6 for generating shoe operating force in braking, and a link mechanism 7 for transmitting shoe operating force generated by the action lever 6 to respective brake shoes 3, 4 and for making anchor reaction as brake limiting force in a direction to reduce the action of shoe operating force from the brake shoes act on the action lever 6, a damper spring 81 for absorbing impact force is interposed between the link mechanism 7 and the action lever 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an action lever for pressing a pair of brake shoes, which are opposed to a space in a drum, against a drum surface, and transmits a shoe operating force generated by the action lever to each brake shoe. ,
And a link mechanism for applying a braking limiting force to the action lever in a direction to reduce the shoe operating force when the anchor reaction force from the brake shoe reaches a predetermined magnification with respect to the shoe operating force generated by the action lever. It is.

[0002]

2. Description of the Related Art Conventionally, various types of drum brake devices have been used to brake the running of a vehicle, and these drum brake devices are brakes pressed against the inner peripheral surface of a substantially cylindrical drum. Depending on the arrangement of the shoe, it is classified into a leading trailing type, a two-leading type, a duo servo type, or the like.

A duo-servo type drum brake device is
Generally, a pair of brake shoes, a primary shoe and a secondary shoe, are provided in a cylindrical drum so as to face each other. The primary shoe has an input portion on the inlet side in the forward rotation direction of the drum, and the outlet side on the forward rotation direction of the drum is connected to the inlet side of the secondary shoe via an adjuster, for example. On the other hand, the outlet side of the secondary shoe is brought into contact with an anchor portion provided on the backing plate, and an anchor reaction force acting on the primary shoe and the secondary shoe is received by this anchor portion.

Thus, when the primary shoe and the secondary shoe are expanded and pressed against the inner peripheral surface of the drum, an anchor reaction force acting on the primary shoe is input to the entrance side of the secondary shoe, and the secondary shoe is opened. Acts on the inner peripheral surface of the drum, so that both the primary shoe and the secondary shoe operate as a leading shoe, and a very high gain braking force can be obtained.

The above-described duo-servo type drum brake device not only can obtain an extremely high braking force than a leading trailing type or a two-leading type drum brake device, can be easily miniaturized, and can park. It has many advantages such as easy installation of brakes. However, since such a duo-servo type drum brake device is sensitive to a change in the friction coefficient of the lining of the brake shoe, it tends to be difficult to stabilize the braking force, and a device for stabilizing the braking force is required. .

[0006] From such a background, the output of a hydraulic wheel cylinder for operating the pair of brake shoes to open and close is
Attempts to stabilize the braking force by controlling according to the anchor reaction force have been studied. On the other hand, in recent vehicle brake devices, intelligent brake functions such as an anti-lock brake system and a traction control system are actively being implemented. And, in order to respond to intelligentization, the electrification of brake devices is being promoted.

Therefore, the applicant of the present application generates a shoe operating force for pressing the brake shoe against the drum surface by an electric action lever during braking, and the shoe operating force generated by the action lever is transmitted via a link mechanism. Research and development of drum brake devices that transmit to each brake shoe. The brake device having such a configuration is suitable for making the brake function intelligent by electrifying the drive source, and if the link mechanism interposed between the electric action lever and the brake shoe is devised, the action lever can be generated. It is also possible to stabilize the braking force by limiting the shoe operation force to be performed in accordance with the anchor reaction force, and this can be applied to both the electrification of the duo-servo type drum brake device and the stabilization of the braking force.

[0008]

However, when braking,
When researching a drum brake device that transmits the shoe operating force generated by an electric action lever to each brake shoe via a link mechanism, a function that controls the shoe operating force output by the action lever in accordance with the anchor reaction force Has been an important and difficult task how to incorporate the above into the link mechanism, and at the same time, how to simplify the link mechanism.

The electric action lever generally has a structure in which an electric motor is connected to the lever member via an appropriate power transmission mechanism such as a gear train. Since the power transmission mechanism interposed between the motor and the motor is a small-sized mechanism, if the impact action of a large load such as an anchor reaction force is repeated, the power transmission mechanism and the electric motor itself are likely to be damaged by fatigue.
Therefore, it is also very important to improve the durability of a power transmission mechanism and an electric motor for driving the lever member against an impact load. It should be noted that a system combining an electric drive source and a hydraulic anchor reaction force control mechanism can be considered, but such a structure complicates the brake device and, at the same time, causes a flash for the electric brake device. This is excluded based on the design concept that it is not preferable to combine hydraulic mechanisms that may possibly be integrated. In addition, the above-described problem with respect to a load such as an anchor reaction force also occurs, for example, even when the driving source is a mechanical type using a link mechanism. Therefore, measures to increase the strength of the link mechanism with respect to an impact load are required. .

[0010] The present invention has been made in view of the above circumstances, the shoe operating force for pressing the pair of brake shoes on the drum surface is generated by action lever, a link mechanism shoe operating force generated by the action lever drum brake capable of reducing a drum brake device for transmitting to the brake shoes through for power transmission mechanism and an electric motor for driving the action lever, the improvement in durability against impact loads such as anchor reaction force It is intended to provide a device.

[0011]

According to the present invention, there is provided a drum brake device for generating a shoe operating force for pressing a pair of brake shoes, which are disposed opposite to each other in a drum inner space, against a drum surface during braking. and to luer transfection lever, while transmitting the shoe operating force to the brake shoes, reduce shoe operating force when the anchor reaction force from the brake shoe reaches a predetermined magnification with respect to generated shoe operating force of the action lever In the drum brake device having a link mechanism that applies a braking restriction force in the direction to the action lever, a damper spring that absorbs an impact force such as the anchor reaction force is interposed between the link mechanism and the action lever. It is characterized by having.

According to the above construction, when power is transmitted from the action lever to the link mechanism, or when power is transmitted from the link mechanism to the action lever, the damper spring interposed between these members absorbs the impact force. Do. Therefore, even when a large load such as an anchor reaction force is transmitted from the link mechanism to the action lever, a shocking action is avoided, and for example, an electric motor that drives the action lever or a power transmission mechanism interposed between the electric motor and the electric motor. In contrast, a large load can be prevented from acting in a shocking manner.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a drum brake device according to the present invention will be described below in detail with reference to the drawings. 1 to 3 show a first embodiment of a drum brake device according to the present invention. FIG. 1 is a front view of the drum brake device of the first embodiment, and FIG. 2 is an enlarged front view of a main part of FIG. FIG. 3 is a perspective view of the portion shown in FIG.

The drum brake device 1 is a so-called duo-servo type drum brake device, which comprises a pair of primary shoes 3 and a secondary shoe 4 which are disposed opposite to each other in a substantially cylindrical space in a drum (not shown). An electric action lever 6 disposed between one of the opposite ends of the brake shoes 3 and 4 to generate a shoe operating force for pressing the brake shoes 3 and 4 against the drum surface during braking; A link mechanism 7 for transmitting the generated operating force to each of the brake shoes 3, 4;
4 is disposed between the other opposing ends of the primary shoe 3
Adjuster 8 also serving as a link function for inputting the output of the secondary shoe 4 to the secondary shoe 4, a backing plate 9 for supporting these components, and an anchor reaction force from each of the brake shoes 3, 4 standing on the backing plate 9 Receiving anchor pins 70 and 75.

The brake shoes 3, 4 are attached to the backing plate 9 by a shoe support shaft 10 so as to be movable toward the inner periphery of the drum. The end of the brake shoes 3, 4 on the action lever 6 side is connected to a spring end pin 22 erected on the backing plate 9 above the action lever 6 via shoe springs 12, 13, respectively. Of the shoes 3 and 4 are urged in a direction approaching each other (that is, a direction away from the drum). In addition, each brake shoe 3, 4
The ends of the adjusters 8 are biased by the biasing force of the adjuster spring 14 so that the end portions of the adjusters 8 are kept in contact with the ends of the adjusters 8.

On the backing plate 9, a parking brake mechanism 90 is also incorporated. Parking brake mechanism 9
When the parking lever 92 is rotated with the parking pin 91 as a rotation fulcrum, the operating force is transmitted to the primary shoe 3 via the strut 93, and the pair of brake shoes 3, 4 are pressed against the drum. It has become. The drum (not shown) is concentric with the backing plate 9 and rotates in the direction of arrow R in FIG. 1 when the vehicle moves forward.

The adjuster 8 originally adjusts the interval between the ends of the brake shoes 3, 4 in accordance with the progress of wear of the linings 3c, 4c of the brake shoes 3, 4, and comprises an adjuster spring. The spacing between the ends of the brake shoes 3 and 4 is automatically adjusted by the turning operation of the adjuster lever 17 whose tip abuts on the adjustment gear 8a on the adjuster 8 by the urging force of 14. . The adjuster lever 17 is connected to an end of an adjuster cable 19 that passes from a spring end pin 22 via a cable guide 18 mounted on the secondary shoe 4. This adjuster cable 19
Turns the adjuster lever 17 in accordance with the amount of movement of the secondary shoe 4 when the secondary shoe 4 is expanded, thereby causing the adjuster lever 17 to perform a predetermined turning operation.

In the case of the present embodiment, the electric action lever 6 has an electric motor connected to the lever member 61 via a power transmission mechanism such as a gear train (not shown) disposed on the back side of the backing plate 9. With this configuration, the lever member 61 is advanced in the direction of the arrow (a) in FIG. 2 during braking. The advance output of the lever member 61 is a shoe operating force for pressing the brake shoes 3, 4 against the drum surface. In the case of the present embodiment, the power transmission mechanism for driving the lever member 61 and the electric motor are provided by a geared motor in which a reduction gear train as a power transmission mechanism is incorporated in a case of the electric motor.

As shown in FIGS. 2 and 3, the link mechanism 7 has a lever pin 71 erected near one end on the primary shoe 3, an intermediate portion rotatably supported by the lever pin 71, and a base end. The input side 72a receives a shoe operation force from the action lever 6 on the side thereof. The input portion 72a rotates in the arrow (b) direction of FIG. One end of the control lever 73 is brought into contact with the distal end portion 72b of the input lever 72 and the other end of the control lever 73 is brought into contact with the distal end portion 73a of the control lever 73 to control the shoe operating force input from the input lever 72. A pressure plate 74 transmitting to the secondary shoe 4 via a lever 73; Anchor pin 7 to receive the anchor reaction force
5, an anchor pin 70 receiving an anchor reaction force from the primary shoe 3 during reverse braking, a reaction anchor pin 76 protruding from the backing plate 9 between the previous anchor pin 75 and the pressure plate 74, and one end. Is connected to the lever pin 71, and the other end is provided so as to pass between the anchor pin 75 and the reaction anchor pin 76, and can reciprocate between the opposed ends of the pair of brake shoes 3 and 4 integrally with the lever pin 71. Reaction strut 77 and reaction strut 7
And a reaction lever 79 rotatably supported by a lever pin 78 provided at the other end of the motor 7.

The distal end of the control lever 73 comes into contact with the pressure plate 74 and the end of the secondary shoe 4 so as to be sandwiched between the pressure plate 74 and the end of the secondary shoe 4, and the input lever The shoe operation force transmitted from the second gear 72 via the pressure plate 74 is transmitted to the secondary shoe 4.

The base end of the control lever 73 has a concave arc-shaped anchor contact portion 73c circumscribing the anchor pin 75 and a concave arc-shaped shoe circumscribing the convex arc portion formed on the secondary shoe 4. And a contact portion 73d. When the anchor reaction force from the secondary shoe 4 is received by the shoe contact portion 73d, the control lever 73 rotates around the anchor pin 75 and distributes the anchor reaction force to the anchor pin 75 and the pressure plate 74. . In the control lever 73, the contact center C1 with the anchor pin 75, the secondary shoe 4
Contact center C2 with the convex arc portion of the pressure plate 7
The lever ratio determined by the contact center C3 with the lever 4 is the distribution ratio of the anchor reaction force. When the control lever 73 rotates around the anchor pin 75 by the action of the anchor reaction force, the distal end of the control lever 73 moves away from the secondary shoe 4.

The control lever 73 moves the anchor pin 75 by the anchor reaction force from the secondary shoe 4.
Is rotated in the direction of arrow (c) in FIG.
The pressure plate 74 that is in contact with the distal end 73a of the control lever 73 returns in the direction of the arrow (d). The reaction lever 79 rotates in the direction of the arrow (e) around the lever pin 78 as the pressure plate 74 returns, with the rotating control lever 73 contacting one end edge. Then, when the return amount of the pressure plate 74 due to the anchor reaction force exceeds a certain value,
That is, when the control lever 73 rotates by a predetermined amount or more, the reaction lever 79 that rotates with the control lever 73 contacts the other end of the reaction lever pin 76 with the reaction anchor pin 76, and the further rotation force causes the lever pin 78 to turn to the arrow (f). ) Direction, that is, a force to slide the reaction strut 77 toward the secondary shoe 4 (arrow (F) side). When the reaction strut 77 is displaced in the direction of the arrow (f), the lever pin 71 is moved in the direction of the arrow (f).
Pull in the direction.

In this embodiment, a damper spring 81 is interposed between the lever member 61 of the action lever 6 and the input portion 72a of the input lever 72. The damper spring 81 is a compression coil spring that is elastically held in a cylindrical spring housing case 83 on a frame member 82 fixed to the backing plate 9. The base end side of the damper spring 81 is in contact with the lever member 61 via a spring seat 84. Further, the distal end side of the damper spring 81 is connected to the input section 72a via a spring seat 86 having an input rod 85 engaged with the input section 72a. Therefore, power transmission between the lever member 61 and the input portion 72a is performed through the damper spring 81.

Next, in the drum brake device 1 having the above structure, the action lever 6 and the link mechanism 7 during braking are used.
Will be described with reference to FIGS. 2 and 3. During forward braking, the lever member 61, which is the action lever 6, is driven to advance in the direction of the arrow (a) to generate a shoe operating force. The shoe operation force is transmitted to the input portion 72a of the input lever 72 via the spring seat 84, the damper spring 81, the spring seat 86, and the input rod 85.

When the primary shoe 3 is separated from the drum at the initial stage of braking, the input lever 7
2 rotates in the direction of the arrow (g) in FIG. 2 with the tip 72b as a fulcrum by the shoe operation force input to the input unit 72a, and the lever pin 71 moves with the rotation of the input lever 72. , The primary shoe 3 is brought into contact with the inner peripheral surface of the drum. After the primary shoe 3 comes into contact with the inner peripheral surface of the drum, the rotation of the input lever 72 by the shoe operation force input to the input section 72a replaces the operation using the lever pin 71 as a rotation fulcrum. The rotation of the input lever 72 around the lever pin 71 is
The pressure plate 74 is displaced toward the secondary shoe 4, and the secondary shoe 4 is displaced toward the inner peripheral surface of the drum via the control lever 73 with which the end of the pressure plate 74 is in contact. As a result, the shoe operating force causes the pair of brake shoes 3, 4 to press against the drum surface to generate a predetermined braking force.

At the time of forward braking operation, the anchor reaction force from the secondary shoe 4 is distributed to the anchor pin 75 and the pressure plate 74 via the control lever 73. When the anchor reaction force from the secondary shoe 4 reaches a predetermined magnification, the pressure plate 7
When the anchor reaction force acting on the lever 4 becomes larger than the shoe operation force input from the input lever 72 to the pressure plate 74, the control lever 73 rotates about the anchor pin 75 in the direction of the arrow (c) in FIG. To move the pressure plate 74 in the direction indicated by the arrow (d) in FIG.
Push back to the primary shoe 3 side indicated as the direction.

On the other hand, when the displacement of the pressure plate 74 due to the return operation to the primary shoe 3 side becomes a predetermined value or more, the reaction turned in the direction of the arrow (e) in FIG. The lever 79 contacts the reaction anchor pin 76.
Reaction lever 79 is reaction anchor pin 7
6, the reaction strut 77 cooperates with this, via the lever pin 78, and the arrow (f) in FIG.
Initiate displacement in the direction.

The displacement of the reaction strut 77 acts to pull back the lever pin 71 on the primary shoe 3 in the direction of the arrow (f). As a result, the input lever 72 receives the force acting via the lever pin 71 due to the displacement of the reaction strut 77 and the force acting from the pressure plate 74 due to the return operation of the pressure plate 74, and operates the shoe from the action lever 6. A rotating force is generated in a direction to cancel the force, and the increase in the force pressing the primary shoe 3 against the drum surface is suppressed, and the effectiveness of the braking force is limited to a predetermined magnification.

The force acting on the input lever 72 so as to cancel the shoe operation force from the action lever 6 due to the anchor reaction force, instantaneously stops the rotation of the input lever 72 due to the shoe operation force. Or reverse rotation, resulting in an impact load. Since the damper spring 81 interposed between the input lever 72 and the lever member 61 absorbs the impact force, the impact load is transmitted to the action lever 6 side. Not done. Therefore, even when a large load such as an anchor reaction force is transmitted from the link mechanism 7 to the action lever 6, a large load is imposed on the electric motor that drives the action lever 6 and the power transmission mechanism interposed between the electric motor and the electric motor. Is prevented from acting in a shocking manner. As a result, it is possible to improve the durability of the power transmission mechanism and the electric motor that are the driving sources of the action lever 6. In addition, the durability of the power transmission mechanism and the electric motor against an impact load can be improved only by adding the damper spring 81 without depending on the strength of these components and the like. It is also possible to expect a reduction in cost due to the improvement and a reduction in the size and weight of the mechanism for driving the action lever 6.

FIGS. 4 and 5 show a second embodiment of the drum brake device according to the present invention. FIG. 4 is an enlarged front view of a main part of the drum brake device according to the present invention, and FIG.
FIG. 3 is a perspective view of a portion shown in FIG. The drum brake device 101 includes the action lever 6 and the spring seat 84 in the drum brake device 1 of the first embodiment.
With the action lever 106 and the spring seat 184
The configuration other than these changes is common to the first embodiment. Therefore, the configuration common to the first embodiment such as the link mechanism 7 and the damper spring 81 is as follows.
The same reference numerals as in the first embodiment denote the same parts, and a description thereof will be omitted.

The action lever 106 of the drum brake device 101 includes a lever member 161 and a shaft 162.
This is similar to the first embodiment in that the lever member 161 is rotated by an electric motor or a gear train by rotating the lever member 161 around in the direction of the arrow (i) in FIG. It is. In accordance with the structure of the lever member 161, the spring seat 184 interposed between the lever member 161 and the damper spring 81 has a structure having a projection 184a that comes into contact with the arm portion 161a of the lever member 161.

The drum brake device 1 of the second embodiment
01, the lever member 1 of the action lever 106
61 and the input lever 72 of the link mechanism 7,
Since the damper spring 81 that absorbs the impact force is provided, the action lever 10 is provided similarly to the first embodiment.
6, the power transmission mechanism and the electric motor for driving the motor 6 can be improved in durability against impact load.
In addition, it is possible to expect a reduction in cost due to an improvement in durability and a reduction in size and weight of a mechanism for driving the action lever 106.

FIGS. 6 and 7 show a third embodiment of the drum brake device according to the present invention. FIG. 6 is an enlarged front view of a main part of the drum brake device of the third embodiment, and FIG. FIG. 3 is a perspective view of a portion shown in FIG. The drum brake device 201 according to the third embodiment includes an electric action lever 206 that generates a shoe operation force for pressing a pair of brake shoes 3 and 4 disposed opposite to the inner space of the drum against the drum surface during braking, The shoe operating force generated by the lever 206 is transmitted to each of the brake shoes 3 and 4, and when the anchor reaction force from the secondary shoe 4 reaches a predetermined magnification with respect to the shoe operating force, the action of the shoe operating force is reduced. Brake limiting force of the action lever 206
And a damper spring 281 for absorbing an impact force such as an anchor reaction force is interposed between the link mechanism 207 and the action lever 206.

As described above, the electric action lever 206 for generating the shoe operating force, the link mechanism 207 for transmitting the shoe operating force generated by the action lever 206 to the brake shoes 3, 4, and the link mechanism 207 between the action lever 206 and the link mechanism 207. It is common to each of the above-described embodiments in that it has a damper spring 281 interposed therebetween to absorb an impact force. The drum brake device 201 of the present embodiment is a so-called duo-servo type drum brake device similar to the above-described embodiments, and although not shown, the output of the primary shoe 3 , 4 is transmitted to the secondary shoe 4 via an adjuster arranged between the other opposite ends.

The drum brake device 2 of the third embodiment
01, the action lever 206 is
The rotation of the cam member 261 by the electric motor or the gear train is performed by rotating the cam member 261 by rotating the cam member 261 around the shaft 262 in the direction of the arrow (nu) in FIG. This is the same as in each embodiment. The cam member 261 has a concave portion 261a for engaging the base end of the damper spring 281.

As shown in FIGS. 6 and 7, the link mechanism 207 has a lever pin 271 erected near one end on the primary shoe 3, an intermediate portion rotatably supported by the lever pin 271 and a base end. The input side 272a which receives a shoe operation force from the action lever 206 is provided on the side, and the input lever 272 which rotates in the direction of the arrow (R) in FIG.
And one end of the control lever 273 is in contact with the tip 272b of the input lever 272, and the other end is in contact with the tip 27 of the control lever 273.
The pressure plate 274 is transmitted to the secondary shoe 4 via the control lever 273 by contacting the shoe 3a with the input lever 272 and receives an anchor reaction force from the secondary shoe 4 during forward braking. An anchor pin 275, an anchor pin 270 receiving an anchor reaction force from the primary shoe 3 during reverse braking, and an elongated hole 230 formed in the web of the primary shoe 3 are provided to pass through the secondary shoe 4. Input lever 2 by anchor reaction force
And a feedback pin 277 that regulates the rotation of the rotation lever 72.

The tip 273 of the control lever 273
a comes into contact with the pressure plate 274 and the end of the secondary shoe 4 so as to be sandwiched between the pressure plate 274 and the end of the secondary shoe 4, and passes through the pressure plate 274 from the input lever 272. The transmitted shoe operation force is transmitted to the secondary shoe 4.

The base end of the control lever 273 has a concave arc-shaped anchor contact portion 273c circumscribing the anchor pin 275 and a concave arc-shaped shoe circumscribing the convex arc portion formed on the secondary shoe 4. And a contact portion 273d. The control lever 273 transmits the anchor reaction force from the secondary shoe 4 to the shoe contact portion 273.
When receiving at d, it rotates around the anchor pin 275 and distributes the anchor reaction force to the anchor pin 275 and the pressure plate 274. In this control lever 273, the contact center C with the anchor pin 275
1. Contact center C of secondary shoe 4 with convex arc portion
2. The lever ratio determined by the contact center C3 with the pressure plate 274 is the distribution ratio of the anchor reaction force.
Control lever 273 by the action of the anchor reaction force
Is rotated around the anchor pin 275, the distal end side of the control lever 273 moves away from the secondary shoe 4.

The control lever 273 is moved by the anchor pin 2 by the anchor reaction force from the secondary shoe 4.
6, the pressure plate 274 in contact with the distal end portion 273a of the control lever 273 is pushed back in the direction of the arrow (W), and contacts the pressure plate 274. The contact input lever 272 is rotated in the direction of the arrow (f).

The rotation of the input lever 272 due to the anchor reaction force from the secondary shoe 4 is restricted by the input lever 272 contacting the feedback pin 277. During forward braking,
As described above, the anchor reaction force from the secondary shoe 4 acts on the input lever 272 via the control lever 273 and the pressure plate 274,
The input lever 272 is turned in the direction of arrow (f), but the anchor reaction force of the primary shoe 3 is received by the anchor pin 270 during reverse braking. At this time, the tip end portion 272b of the input lever 272 directly abuts on the anchor pin 270, whereby the rotation of the input lever 272 due to the shoe operation force is regulated, and the braking force is stabilized.

In the case of this embodiment, the damper spring 28 interposed between the cam member 261 of the action lever 206 and the input portion 272a of the input lever 272.
Reference numeral 1 denotes a compression coil spring, and the base end thereof is brought into contact with the cam member 261 via a spring seat 284 having a cam rod 283 engaged with the concave portion 261a of the cam member 261. Further, the distal end of the damper spring 281 is connected to an input rod 285 which engages with the input portion 272a.
Through the spring seat 286 having the
2a. Spring seats 284, 28
6 have cone-shaped projections 284a and 286a that are fitted into the inner periphery of the coil of the damper spring 281 to prevent the damper spring 281 from falling off. Therefore, power transmission between the cam member 261 and the input portion 272a is performed via the damper spring 281.

In the drum brake device 201 described above, the action lever 206 and the link mechanism 2 during braking are used.
The operation of 07 will be described based on FIG. 6 and FIG. During forward braking, the cam member 261 as the action lever 206 is driven to rotate in the direction of the arrow (nu) to generate a shoe operating force. The shoe operation force is transmitted to the input portion 272a of the input lever 272 via the cam rod 283, the spring seat 284, the damper spring 281, the spring seat 286, and the input rod 285.

When the primary shoe 3 is separated from the drum at the initial stage of braking, the input lever 2
The pivot 72 rotates in the direction of the arrow (Y) in FIG. 6 with the tip 272b as a pivot point by the shoe operation force input to the input section 272a, and the lever pin 271 moves with the rotation of the input lever 272. ,primary·
The shoe 3 comes into contact with the inner peripheral surface of the drum. After the primary shoe 3 comes into contact with the inner peripheral surface of the drum, the input section 272a
Input lever 27 by shoe operation force input to
The rotation of 2 replaces the operation using the lever pin 271 as a rotation fulcrum. The rotation of the input lever 272 about the lever pin 271 causes the pressure plate 274 to be displaced toward the secondary shoe 4 and the control lever 2 with which the end of the pressure plate 274 is in contact.
The secondary shoes 4 are displaced toward the inner peripheral surface of the drum via 73, and the pair of brake shoes 3, 4 are pressed against the drum to generate a predetermined braking force.

During the forward braking operation, the anchor reaction force from the secondary shoe 4 is distributed to the anchor pin 275 and the pressure plate 274 via the control lever 273. When the anchor reaction force from the secondary shoe 4 reaches a predetermined magnification and the anchor reaction force acting on the pressure plate 274 becomes larger than the shoe operation force input from the input lever 272 to the pressure plate 274, the control lever 273 is activated. Has the anchor pin 275 as the center of rotation,
6, the pressure plate 274 is pushed back to the primary shoe 3 side indicated by the arrow (W) direction in FIG.

When the pressure plate 274 returns to the primary shoe 3 side, the input lever 272 in contact with the pressure plate 274 is rotated in the direction of the arrow (f). At this time, the rotation of the input lever 272 in the direction of the arrow (f) due to the anchor reaction force is restricted by the input lever 272 abutting on the feedback pin 277. Input lever 272
In the state where the input lever 27 is in contact with the feedback pin 277, when a load in the push-back direction due to the anchor reaction force is further applied from the pressure plate 274, the input lever 27
Reference numeral 2 rotates around a contact point with the feedback pin 277 as a fulcrum. The rotation of the input lever 272 about the feedback pin 277 offsets the shoe operation force from the action lever 206, and the primary
An increase in the pressing force of the shoe 3 against the drum is suppressed, and the effectiveness of the braking force is limited to a predetermined magnification.

During forward braking, as described above, the anchor reaction force from the secondary shoe 4 acts on the input lever 272 via the control lever 273 and the pressure plate 274, causing the input lever 272 to move in the direction indicated by the arrow. ), The anchor reaction force of the primary shoe 3 is received by the anchor pin 270 during reverse braking. At this time, the tip end portion 272b of the input lever 272 directly abuts on the anchor pin 270, thereby restricting the rotation of the input lever 272 due to the shoe operating force from the action lever 206, and the effectiveness of the braking force is determined. Limit to magnification.

The force acting on the input lever 272 so as to cancel the shoe operation force from the action lever 206 due to the anchor reaction force immediately stops the rotation of the input lever 272 due to the shoe operation force. , Or reverse, it becomes an impact load,
Since the damper spring 281 interposed between the input lever 272 and the cam member 261 absorbs the impact force, the impact load is not transmitted to the action lever 206 side. Therefore, even when a large load such as an anchor reaction force is transmitted from the link mechanism 207 to the action lever 206, a large load is imposed on the electric motor driving the action lever 206 or the power transmission mechanism interposed between the electric motor and the electric motor. Is prevented from acting in a shocking manner. As a result, it is possible to improve the durability of the power transmission mechanism or the electric motor that is the driving source of the action lever 206. And for the power transmission mechanism and the electric motor,
The durability against an impact load can be improved only by adding the damper spring 281 without relying on the increase in the strength of these components and the like. The driving mechanism can be expected to be smaller and lighter.

In the drum brake device of the present invention, the drive source of the action levers 6, 106, 206 is
In the case of the electric type, it is not limited to the electric motor. For example, as a driving source of the action levers 6, 106, and 206, a giant magnetostrictive element capable of controlling a linear displacement operation by feeding power,
A solenoid or the like can also be used. In each of the above embodiments, the action levers 6, 106, 206
Although the drive source is described as an electric drive source, in the drum brake device of the present invention, the drive source may be, for example, a mechanical type using a link mechanism. Is absorbed by the damper spring and is not transmitted to the link mechanism. Further, as the power transmission mechanism, various known mechanisms such as a gear train that transmits the rotational force and a cam mechanism that converts the rotational force into a linear motion can be considered.

In the present invention, the specific structure of the link mechanism for transmitting the shoe operating force output from the action lever to each brake shoe and feeding back the anchor reaction force to the action lever is the same as that of the above-described embodiment. It is not limited to. Link mechanism 7, 20
The components constituting 7 can be appropriately changed and improved as long as equivalent functions can be obtained.

[0050]

According to the drum brake device of the present invention,
When power is transmitted from the action lever to the link mechanism, or when power is transmitted from the link mechanism to the action lever, the damper spring interposed between these members absorbs the impact force. Therefore, even when a large load such as an anchor reaction force is transmitted from the link mechanism to the action lever, the large load may impact the electric motor driving the action lever or the power transmission mechanism interposed between the electric motor and the electric motor. Is prevented. As a result, the durability of the power transmission mechanism and the electric motor for driving the action lever against the impact load can be improved. For the power transmission mechanism and the electric motor for driving the action lever, it is possible to reduce the impact load only by adding a damper spring without depending on the strength of the components such as the power transmission mechanism and the electric motor. Since the durability can be improved, it is possible to expect a reduction in cost due to the improvement in the durability and a reduction in size and weight of a mechanism for driving the action lever.

[Brief description of the drawings]

FIG. 1 is a front view of a first embodiment of a drum brake device according to the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a perspective view of the part of FIG. 2;

FIG. 4 is an enlarged front view of a main part of a second embodiment of the drum brake device according to the present invention.

FIG. 5 is a perspective view of the part of FIG. 4;

FIG. 6 is an enlarged front view of a main part of a third embodiment of the drum brake device according to the present invention.

FIG. 7 is a perspective view of the part of FIG. 6;

[Explanation of symbols]

 1, 101, 201 Drum brake device 3 Primary shoe (brake shoe) 4 Secondary shoe (brake shoe) 6, 106, 206 Action lever 7, 207 Link mechanism 61, 161 Lever member 72, 272 Input lever 73, 273 Control Lever 81, 281 Damper spring 261 Cam member

Claims (1)

[Claims] 1. An action lever for generating a shoe operating force for pressing a pair of brake shoes, which are disposed opposite to each other in a drum internal space, against a drum surface during braking, transmitting the shoe operating force to each brake shoe, A link mechanism for applying a braking limiting force to the action lever in a direction to reduce the shoe operation force when the anchor reaction force from the shoe reaches a predetermined magnification with respect to the shoe operation force generated by the action lever, A drum brake device, wherein a damper spring that absorbs an impact force such as the anchor reaction force is interposed between the link mechanism and the action lever.