JP2003139168A - Drum brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a parking brake capable of achieving great braking force with small operating force in a drum brake device assuring effective and stable braking force during service braking operation by limiting it to a predetermined magnification of shoe operating force to be input. SOLUTION: In the drum brake device assuring effective and stable braking force during service braking operation by limiting it to the predetermined magnification of the shoe operating force to be input, the parting brake mechanism 51 largely opens brake shoes 3, 4 by the turning of a parking lever 53, not via a service braking shoe driving mechanism 7 or working force generating means 6.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to controlling the pressing force of a brake shoe against a drum in accordance with a braking force to ensure high braking effectiveness and stability. More specifically, the present invention relates to an improvement for realizing a highly effective parking brake mechanism with a small number of components, and more particularly to a drum brake device suitable for electricization of a brake device. 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 press against an inner peripheral surface of a substantially cylindrical drum. Depending on the arrangement of the brake shoes to be performed, 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 in the forward rotation direction of the drum is connected to the inlet side of the secondary shoe via, for example, an adjuster. 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 a braking force (braking torque) acting on the primary shoe and the secondary shoe.
Is received by the anchor section. Thus, when the primary shoe and the secondary shoe are expanded and pressed against the inner peripheral surface of the drum, the braking force acting on the primary shoe is input to the entrance side of the secondary shoe, and the secondary shoe is moved. Since it acts so as to press against the inner peripheral surface of the drum, a self-servo action acts on both the primary shoe and the secondary shoe, so that a very high 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 downsized, and has a parking brake. Has many advantages such as easy integration. 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] Recently, a brake device for a vehicle has been developed to provide an intelligent brake function such as an anti-lock brake system, and to cope with an electric vehicle (EV vehicle) suitable for reducing environmental pollution. Electrification of the brake system is also an important issue. [0007] From such a background, the present applicant has proposed a shoe driving mechanism for expanding the brake shoe during braking.
The pair of brake shoes are expanded and pressed against the drum according to the shoe operating force transmitted from the operating force generating means to the input lever during service braking, while the braking force acting on the anchor portion during braking is reduced by the shoe operating force. A link mechanism has already been proposed in which a braking limiting force in a direction that reduces the action of the shoe operation force when the predetermined magnification is reached is applied to the input lever. By using such a link mechanism, it is possible to stabilize the braking force in the duo-servo type drum brake device. Further, as the above-mentioned operating force generating means, instead of the conventional hydraulic wheel cylinder, an electric motor or the like is used. By simply adopting an electric operating force generating means utilizing the above, the electricization of the brake device could be easily realized. However, in the case of a conventional duo-servo type drum brake device having a shoe drive mechanism for limiting the braking force to a predetermined magnification of the shoe operation force like the above-mentioned link mechanism, the parking As a brake mechanism, a parking lever which is rotated by a braking operation during parking gives a shoe operating force to a shoe driving mechanism, and through this shoe driving mechanism, a pair of brake shoes cause an expansion required for braking. Various things have been developed. However, the above-mentioned shoe driving mechanism limits the braking force generated in accordance with the shoe operating force input from the parking lever. There is a problem that power is required and it is not easy to obtain a large braking force. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to limit the braking force at the time of a service brake to a predetermined ratio of a shoe operating force by a shoe driving mechanism, thereby improving the effectiveness and stability. On the other hand, the braking force at the time of the parking brake can provide a high effect with a small operation force, and it is easy to obtain a large braking force at the time of parking. is there. [0011] To achieve the above object, a drum brake device according to the present invention comprises a pair of brake shoes opposed to each other in a drum. Operating force generating means for generating a shoe operating force in response to a service brake operation; and receiving the shoe operating force generated by the operating force generating means, expanding the pair of brake shoes to generate a braking force and braking. In some cases, the shoe driving mechanism can be controlled so that the braking force from the brake shoe does not exceed a predetermined ratio with respect to the shoe operating force, and the pair of brake shoes are expanded in response to the braking operation during parking braking. A parking brake mechanism for generating power, wherein the parking brake mechanism includes the operating force generating means. In addition, the pair of brake shoes are opened by a rotating operation of a parking lever that rotates in response to a parking brake operation without using the shoe driving mechanism. In the drum brake device configured as described above, at the time of service braking, the shoe driving mechanism controls the effectiveness in accordance with the braking force applied from the brake shoe, and the generated braking force is determined in response to an operation input. By limiting the magnification, it is possible to achieve both braking effectiveness and stability. However, at the time of parking brake, the parking lever does not operate the operating force generating means or the shoe drive mechanism provided for the service brake, and thus the braking force regulation by the shoe drive mechanism does not work. Therefore, the excellent effect peculiar to the drum brake can be sufficiently exerted on the shoe operation force transmitted to each brake shoe by the rotation of the parking lever. Hereinafter, preferred embodiments of a drum brake device according to the present invention will be described in detail with reference to the drawings. FIG. 1 shows a first embodiment of a drum brake device according to the present invention.
It is a front view of an embodiment. The drum brake device 1 according to the first embodiment is a so-called duo-servo type drum brake device.
A pair of brake shoes 3, 4 of a primary shoe 3 and a secondary shoe 4, which are disposed opposite to each other in a substantially cylindrical inner space of the drum, and are arranged on one of the opposed ends of the pair of brake shoes 3, 4. Operating force generating means 6 for generating a shoe operating force for pressing each of the brake shoes 3 and 4 against the drum during a service brake operation;
And a shoe drive cam 7 serving as a shoe drive mechanism for transmitting the operating force generated by the operating force generating means 6 to each of the brake shoes 3 and 4, and the other opposing end of each of the brake shoes 3 and 4. An adjuster unit 8 also having a link function of inputting the output of the primary shoe 3 to the secondary shoe 4, a backing plate 9 for supporting these components, and an anchor pin 10 erected on the backing plate 9. , A parking brake mechanism 51 that operates when parking. 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 brake shoes 3, 4 are attached to the backing plate 9 by a shoe hold-down device 91 so as to be movable toward the inner periphery of the drum. The ends of the brake shoes 3 and 4 on the operating force generating means 6 side are connected via shoe return springs 92 and 93, respectively.
It is connected to a spring support pin 10a formed integrally with the upper end of the anchor pin 10, and the ends of the respective shoes are urged in a direction approaching each other (that is, a direction away from the drum). Further, the ends of the brake shoes 3 and 4 on the adjuster unit 8 side are urged by the urging force of the shoe-to-shoe spring 95 so as to maintain the state in contact with the end of the adjuster unit 8. I have. In the case of this embodiment, the operating force generating means 6
As shown in FIG. 2, a wheel cylinder that outputs a pressing force that becomes the shoe operating force W by causing the output rod 6 a to advance in the direction of the arrow (a) in response to a brake operation of a service brake brake pedal or the like. is there. The adjuster unit 8 is supposed to operate in accordance with the progress of wear of the lining of each of the brake shoes 3 and 4.
The gap between the ends of the brake shoes 3 and 4 is adjusted, and the biasing force of the adjuster spring 81 rotates the adjuster lever 82 whose tip abuts on the adjustment gear 8 a on the adjuster unit 8. The distance between the ends of the brake shoes 3 and 4 is automatically adjusted. An adjuster driving mechanism 84 is connected to the adjuster lever 82. In the case of the present embodiment, the adjuster drive mechanism 84 includes a relaying means 85 rotatably supported by the web of the secondary shoe 4, and one end connected to the spring support pin 10 a on the anchor pin 10 and the other end connected. It has a first adjuster rod 86 connected to the relay means 85, and a second adjuster rod 87 one end of which is connected to the relay means 85 and the other end of which is connected to an adjuster lever 82 via an adjuster spring 81. With this configuration, the extension power of the adjuster unit 8 is controlled by applying a rotating force to the adjuster lever 82 in accordance with the amount of movement of the secondary shoe 4 during braking. The shoe driving cam 7 according to the present embodiment is similar to that shown in FIG.
As shown in FIG. 4, a pair of upper and lower cam plates 76 and 77 having the same shape to be fitted to the anchor pin 10 are connected to each other by a primary cam pin 21 as a shoe engaging cam portion abutting on the primary shoe 3 and a secondary cam pin 21. Secondary cam pin 23 as a shoe engaging cam portion abutting on shoe 4
And an input pin 25 as an input receiving portion that receives the shoe operating force W from the operating force generating means 6. The anchor pin 10, the primary cam pin 21, the secondary cam pin 23 and the input pin 25
As shown in FIG. 3A, it is fitted and fixed to the lower cam plate 76. The anchor pin 10 is connected to the lower cam plate 76.
And a portion protruding from the back side of the cam plate 76 is rotatably held by the backing plate 9. Grooves 21a, 23a, 25a are provided at the upper ends of the pins 21, 23, 25 which pass through the pin fitting holes formed in the upper cam plate 77.
Is provided around. The upper cam plate 77 fitted to the upper ends of the pins 21, 23, 25 is provided with the above-mentioned grooves 21a, 23a,
The retaining ring portions 27a, 27b, and 27c that engage with 25a are prevented from coming off by a spring 27 that is formed by bending a single spring wire, and are integrated with the lower cam plate 76. The above-described shoe driving cam 7 inputs a shoe operating force from the operating force generating means 6 to the input pin 25 in response to the brake operation during forward braking or reverse braking when the brake pedal for the service brake is operated. . When the shoe operation force is input, the shoe operation force
The shoe drive cam 7 rotates counterclockwise in FIG. 2 around the anchor pin 10, and the brake shoes 3, 4 are expanded by the primary cam pin 21 and the secondary cam pin 23 provided between the pair of cam plates 76, 77. To the drum. On the other hand, at the time of braking by the service brake, a braking force is applied to the secondary cam pin 23 or the primary cam pin 21 from the brake shoe. The brake force acting on the secondary cam pin 23 or the primary cam pin 21 changes the rotational moment around the anchor pin 10 in a direction (clockwise in FIG. 2) in which the action of the shoe operating force from the operating force generating means 6 is reduced. Work. By this braking force, the rotational moment acting on the shoe drive cam 7 becomes a braking limiting force, and the braking force at the time of service braking is controlled so as not to exceed a predetermined magnification of the shoe operating force input by the brake operation. Excellent braking performance that balances both effectiveness and stability is ensured. The parking brake mechanism 5 of the present embodiment
Reference numeral 1 denotes brake shoes 3 and 4 by rotating a parking lever 53 that rotates in response to a parking brake operation without using an operating force generating means 6 for a service brake and a shoe driving cam 7 as a shoe driving mechanism. Can be expanded. That is, the parking lever 53 is connected to the web 4a of the secondary shoe 4 at one end by the connecting pin 52.
A shoe connecting portion 53a rotatably connected via
A shoe pressing portion 53b that engages with the lever engaging portion 3b of the primary shoe 3 protrudes to a position opposite to the primary cam pin 21 with the anchor pin 10 interposed therebetween. The other end of the parking lever 53 is connected to a wire (not shown) for parking brake operation, and is pulled in the direction of arrow C in FIG. 2 by the braking operation during parking. When the parking lever 53 is pulled in the direction of arrow C in FIG. 2, it rotates clockwise about the connecting pin 52 in FIG. 4 and the shoe pressing portion 53b
Pushes the lever engaging portion 3b of the primary shoe 3 through the
The primary shoe 3 is expanded in a direction away from the primary shoe 3 to generate a braking force. In the initial stage in which the brake shoes 2 and 3 are expanded with the rotation of the parking lever 53, a load acts on the shoe drive cam 7 from each brake shoe via the cam pins 21 and 23. There is. However, in this case, the load acting on the shoe drive cam 7 is
In FIG. 2, the shoe driving cam 7 itself is restricted from rotating clockwise by contact with the operating force generating means 6 by the rotational moment rotating clockwise around the anchor pin 10. The drive cam 7 does not rotate. Then, by operating the parking lever 53,
In the braking state at the time of parking in which the brake shoes 2 and 3 are pressed against the drum, the ends of the brake shoes 2 and 3 are completely separated from the cam pins 21 and 23 on the shoe driving cam 7 to perform the braking operation. The operating force generating means 6 and the shoe driving cam 7 do not participate in the operation. In the drum brake device 1 configured as described above, at the time of service braking, the shoe drive cam 7 provided as a shoe drive mechanism controls the effectiveness according to the braking force applied from the brake shoe.
By limiting the generated braking force to a predetermined magnification with respect to the operation input, both the effectiveness and stability of the brake are achieved. However, at the time of parking brake, the parking lever
Operating force generating means 6 provided for service brake
Also, since the shoe drive cam 7 is not operated, the braking force by the shoe drive cam 7 is not regulated. Therefore, the excellent effect peculiar to the drum brake can be sufficiently exerted on the shoe operating force transmitted to the brake shoes 2 and 3 by the rotation of the parking lever 53. Therefore, during parking, a large braking force can be easily obtained due to a high effect even with a small operating force, and excellent operability of the parking brake can be obtained. The conventional problem that a large operating force is required can be solved. The shoe driving cam 7 is disposed between the operating force generating means 6 and each of the brake shoes 3 and 4 to mechanically control the braking force. It is suitable for not only hydraulic actuators such as hydraulic wheel cylinders but also electric actuators such as electric motors and manual operating force generation means used for parking brakes etc. It is also suitable for electrification for making functions intelligent and for vehicle hybridization. FIG. 5 is a front view of a main part of a second embodiment of the drum brake device according to the present invention. The drum brake device 101 of this embodiment is different from the first embodiment in that the arm-shaped lever engaging portion 3b formed integrally with the end of the web 3a of the primary shoe 3 is used as the primary brake.
The strut 102 is different from the shoe 3, and the other configuration is the same as that of the first embodiment.
The same components as those in the first embodiment are denoted by the same reference numerals, and the description is omitted or simplified. The strut 102 has one end 102a engaged with the engaging recess 3c at the end of the web 3a and the other end 102b at the shoe pressing portion 53 of the parking lever 53.
When the parking lever 53 rotates in the direction indicated by the arrow (d), the primary shoe 3 is pressed in a direction away from the primary cam pin 21. One end 102a and the other end 102b are
It is formed into a smooth convex arc surface so as not to cause undesired catching. In the case of the second embodiment as well, similar to the first embodiment, the braking during parking does not involve the operating force generating means 6 for the service brake or the shoe driving cam 7, and the shoe is driven by the shoe. Since the braking force is not limited by the drive cam 7, a large braking force can be easily obtained with a high effect even with a small operating force, and a large braking force is required for the parking lever or the like to obtain a large braking force during parking. The conventional problem that an operation force is required can be solved. FIG. 6 is a front view of a main part of a third embodiment of the drum brake device according to the present invention. The drum brake device 201 of the present embodiment is different from the switch lever 202 in which one end 202a swingably engages with the input pin 25 instead of the strut 102 shown in the second embodiment.
And the switch lever 202 and the parking lever 53
Input lever 20 interposed between the input lever 20 and the shoe pressing portion 53b.
3 and the other configuration is common to that of the second embodiment. The same components as those of the second embodiment are denoted by the same reference numerals, and the description is omitted or simplified. The switch lever 202 is provided with a shoe contact portion 202b at the tip end thereof, which is in contact with the end of the web 3a of the primary shoe 3, and the input lever 2 at the intermediate portion.
An input receiving portion 202c that receives an operation input from the electronic device 03 protrudes. Shoe contact portion 202b and input receiving portion 202
“c” is formed into a smooth convex arc surface so as not to cause an undesired snagging or the like on the mating surface of the partner. The input lever 203 is provided with an input receiving portion 202c.
An intermediate lever is provided with a concave arcuate lever engaging portion 203a which engages with the web 4 of the secondary shoe 4 at one end.
a shoe contact portion 203b contacting the end of the parking lever 53, and the shoe pressing portion 53 of the parking lever 53 at the other end.
A concave arc-shaped input receiving portion 203c that engages with the input receiving portion 203b is formed. The input lever 203 pushes the input receiving portion 202c of the switch lever 202 toward the primary shoe 3 by turning the parking lever 53 in the direction of the arrow (e) to rotate the switch lever 202 around the input pin 25. And pushes the primary shoe 3 away from the primary cam pin 21 via the switch lever 202. At the same time, the secondary shoe 4 is pushed in a direction away from the secondary cam pin 23 by the shoe contact portion 203b. As described above, when the input lever 203 receives a shoe operating force from the parking lever 53, the input lever 203 swings with the lever engagement portion 203a or the shoe contact portion 203b as a swing fulcrum, and the brake shoes 3, 4 And the braking force is activated. In the braking operation by the rotation of the parking lever 53, the shoe operating force acting on the switch lever 202 acts as a rotational moment on the shoe driving cam 7 via the input pin 25. The output rod 6a of the force generating means 6 is in contact with the shoe driving cam 7 due to the rotational moment.
It does not rotate around. In the case of the third embodiment, similarly to the second embodiment, the braking force during parking does not involve the operating force generating means 6 for the service brake or the shoe driving cam 7 and the shoe is driven by the shoe. Since the braking force is not limited by the drive cam 7, a large braking force can be easily obtained with a high effect even with a small operating force, and a large braking force is required for the parking lever or the like to obtain a large braking force during parking. The conventional problem that an operation force is required can be solved. Incidentally, in the drum brake device of the present invention, the specific structures of the operating force generating means and the shoe driving mechanism are not limited to the above-described embodiments, and do not depart from the gist of the present invention. Thus, appropriate modifications and improvements can be made. For example, in the above-described embodiment, the shoe driving mechanism is a cam mechanism in which cam pins that abut against each brake shoe are erected on a cam plate that is rotatable around an anchor pin. It is also possible to employ a link mechanism that transmits a shoe operation force by a lever. As described above, according to the drum brake device of the present invention, during service braking,
The shoe driving mechanism controls the effectiveness according to the braking force applied from the brake shoe, and limits the generated braking force to a predetermined magnification with respect to the operation input, thereby achieving both the effectiveness and stability of the brake. However, at the time of the parking brake, the operating force generating means and the shoe drive mechanism provided for the service brake are not operated, so that the braking force is not regulated by the shoe drive mechanism. Therefore, the excellent effect peculiar to the drum brake can be sufficiently exerted on the shoe operation force transmitted to each brake shoe by the rotation of the parking lever. Therefore, during parking, a large braking force can be easily obtained with a high effect even with a small operating force, and excellent operability of the parking brake can be obtained. In contrast, the conventional problem that a large operation force is required can be solved.

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 explanatory view of an engagement state between a shoe driving cam and a parking lever shown in FIG. 1 and a brake shoe. 3A and 3B are external views of a cam plate below a shoe driving cam shown in FIG. 1, wherein FIG. 3A is a perspective view and FIG. 3B is a plan view. 4A and 4B are external views of an assembled state of the shoe driving cam shown in FIG. 1, wherein FIG. 4A is a perspective view and FIG. 4B is a plan view. FIG. 5 is a front view of a main part of a second embodiment of the drum brake device according to the present invention. FIG. 6 is a front view of a main part of a third embodiment of the drum brake device according to the present invention. [Description of Signs] 1 Drum brake device 3 Primary shoe (brake shoe) 4 Secondary shoe (brake shoe) 6 Operating force generating means (wheel cylinder) 7 Shoe drive cam (shoe drive mechanism) 8 Adjuster unit 9 Backing plate 10 Main anchor pin 21 Primary cam pin (cam pin) 23 Secondary cam pin (cam pin) 25 Input pin 27 Spring 51 Parking brake mechanism 52 Connection pin 53 Parking lever 53a Shoe connecting part 53b Shoe pressing part 76, 77 Cam plate 101 Drum brake device 102 Strut 201 Drum Brake device 202 Switch lever 203 Input

Claims (1)

Claims: 1. A pair of brake shoes disposed opposite to each other in a drum, operating force generating means for generating a shoe operating force in response to a service brake operation, and the operating force generating means generating the operating force. Shoe drive capable of receiving a shoe operating force, expanding the pair of brake shoes to generate a braking force, and controlling the braking force from the brake shoe to not exceed a predetermined magnification with respect to the shoe operating force during braking. A parking brake mechanism that generates a braking force by expanding the pair of brake shoes in response to a braking operation during parking braking, wherein the parking brake mechanism includes the operating force generation unit and Rotation of the parking lever that rotates in response to the parking brake operation without going through the shoe drive mechanism The work drum brake device, characterized in that for expanding the pair of brake shoes.