JP3871564B2 - Drum brake device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drum brake device that can control the pressing force of a brake shoe to a drum in accordance with the braking force to ensure high effectiveness and stability of the brake and is also suitable for electrification of the brake device. More specifically, the present invention relates to an improvement for preventing the occurrence of dragging due to a brake shoe return failure when braking is released.
[0002]
[Prior art]
Conventionally, various types of drum brake devices have been used to brake the running of the vehicle, but these drum brake devices are arranged according to the arrangement of brake shoes pressed against the inner peripheral surface of a substantially cylindrical drum. It is classified as a reading trailing type, a two reading type, or a duo servo type.
[0003]
A duo-servo type drum brake device generally includes a pair of brake shoes of a primary shoe and a secondary shoe disposed in a cylindrical drum so as to face each other.
In the primary shoe, the forward rotation direction inlet side of the drum is used as an input unit, and the forward rotation direction outlet side 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 the anchor portion provided on the backing plate, and the anchor portion receives the braking force (braking torque) acting on the primary shoe and the secondary shoe. .
[0004]
As a result, 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 inlet side of the secondary shoe and the secondary shoe is Since it acts so as to press against the surface, the self-servo action acts on both the primary shoe and the secondary shoe, and a braking force with a very high gain can be obtained.
[0005]
The above-mentioned duo-servo type drum brake device not only can obtain extremely high braking force, but also is easy to miniaturize and incorporates a parking brake as compared with a leading trailing type or two-leading type drum brake device. It has many advantages such as being easy.
However, such a duo-servo drum brake device is sensitive to changes in the friction coefficient of the brake shoe lining, and therefore tends to be difficult to stabilize the braking force, and a device for stabilizing the braking force is required. .
[0006]
Also, recent brake devices for vehicles are equipped with an anti-lock brake system to make the brake function intelligent and to deal with electric vehicles (EV vehicles) suitable for reducing environmental pollution. Electrification is also an important issue.
[0007]
Against this background, the applicant of the present application has expanded the pair of brake shoes according to the shoe operating force transmitted from the operating force generating means to the input lever during service braking as a shoe drive mechanism for expanding the brake shoes during braking. A link mechanism that opens and presses against the drum, and applies a braking limiting force to the input lever in a direction that reduces the action of the shoe operating force when the braking force acting on the anchor pin during braking reaches a predetermined magnification with respect to the shoe operating force. Have already proposed.
By using this link mechanism, it is possible to stabilize the braking force in the duo-servo type drum brake device, and use an electric motor or the like instead of the conventional hydraulic wheel cylinder as the operation force generating means. By simply adopting the electric operating force generating means, it was possible to easily realize the electrification of the brake device.
[0008]
[Problems to be solved by the invention]
By the way, in the drum brake device, in general, each brake shoe is returned when the brake is released by a tensile force by a shoe return spring. In the conventional case, the shoe return spring is stretched between the anchor pin and a position away from the anchor pin on the brake shoe web by a predetermined distance.
[0009]
However, at the time of braking, the end of the brake pin on the input side on the anchor pin side is displaced to the drum side having a larger diameter than the anchor pin mounting position due to the diameter expanding operation, and from the line of action of the return force of the shoe return spring. It will come off.
Therefore, when the brake is released, in order to accurately return the end of the brake shoe on the input side to the anchor pin, a turning force is required to turn the end of the brake shoe toward the anchor pin, and only a linear tensile force by the shoe return spring is required. It is difficult to accurately return to the anchor pin, and there is a possibility that the brake shoe may be dragged due to a return failure or the like.
[0010]
The present invention has been made in view of the above circumstances, and can control the braking force according to the braking force, ensure a stable effect of the brake, and at the same time ensure the return of the brake shoe when releasing the brake, An object of the present invention is to provide a highly reliable drum brake device that does not cause drag.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a drum brake device according to a first aspect of the present invention comprises a pair of brake shoes disposed opposite to each other in the drum, and stands on a backing plate on one opposed end side of the pair of brake shoes. A shoe having an anchor pin provided, an operating force generating means for generating a shoe operating force in response to a braking operation, and a cam plate that rotates around the anchor pin in response to a shoe operating force generated by the operating force generating means A drive cam,
The shoe drive cam has a pair of cam pins on the cam plate that abut against one end of the pair of brake shoes and press the brake shoes in the expanding direction when the cam plate is rotated. In the drum brake device that applies a rotational moment to the cam plate in a direction that reduces the action of the shoe operating force according to the braking force that the cam pin receives from the brake shoe,
The return line of the return force of the shoe return spring that returns each brake shoe to the non-braking position when the brake is released is substantially non-overlapping so that it overlaps on a straight line passing through the contact portion of each brake shoe with each cam pin and the center of the cam pin The anchor pin is equipped with a spring bracket provided with a locking portion of the shoe return spring near the center of each cam pin during braking.
[0012]
In the drum brake device configured as described above, during the braking operation, the cam plate of the shoe drive cam that receives the shoe operating force output from the operating force generating means rotates around the anchor pin, and the cam plate rotates. Along with this, each cam pin on the cam plate expands each brake shoe to generate a braking force. During braking, the braking force that acts on the cam pin from the brake shoe on the output side generates a rotational moment in a direction that reduces the rotation of the cam plate due to the shoe operating force, thereby limiting the braking force.
[0013]
Further, since the shoe drive cam is disposed between the operating force generating means and each brake shoe and mechanically controls the braking force, the operating force generating means is a hydraulic type such as a conventional hydraulic wheel cylinder. In addition to this actuator, an electric actuator such as an electric motor can be used.
[0014]
In addition, the line of action of the return force of the shoe return spring is set so that it substantially overlaps on a straight line passing through the contact portion of each end of the brake shoe with each cam pin and the center of the cam pin. The end on the side is always kept in contact with the cam pin. Therefore, when the brake is released, the end of each brake shoe follows the cam pin when the cam pin returns to the initial position integrally with the cam plate of the shoe drive cam, even if it is separated from the anchor pin to the drum side radially outward. Surely return to the initial position.
[0015]
The drum brake device according to claim 2 is the drum brake device according to claim 1, wherein the spring bracket is prevented from rotating with respect to the anchor pin by fitting into a non-circular cross section formed in the anchor pin 10. It is characterized by.
[0016]
In such a drum brake device, when the spring bracket that locks one end of the shoe return spring is fixed to the anchor pin, the spring bracket is prevented from rotating only by being fitted to the non-circular cross section of the anchor pin. Separate parts are omitted.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a drum brake device according to the invention will be described in detail with reference to the drawings.
FIG. 1 is a front view of an embodiment of a drum brake device according to the present invention.
The drum brake device 1 of this embodiment is a so-called duo-servo type drum brake device, and is a pair of brakes of a primary shoe 3 and a secondary shoe 4 that are arranged to face each other in a space in a substantially cylindrical drum (not shown). The shoes 3, 4 and one of the pair of brake shoes 3, 4 are arranged on one opposing end side, and generate a shoe operating force for pressing the brake shoes 3, 4 against the drum when operating the service brake. The operating force generating means 6, the shoe driving cam 7 that is a shoe driving mechanism for transmitting the operating force generated by the operating force generating means 6 to each brake shoe 3, 4, and the other opposing end of each brake shoe 3, 4 An adjuster unit 8 which is disposed between them and also serves as a link function for inputting the output of the primary shoe 3 to the secondary shoe 4, and supports these components. A backing plate 9 which is provided with a anchor pin 10 provided upright on the backing plate 9, and a parking brake mechanism 51 for actuating the parking time.
[0018]
The drum (not shown) is concentric with the backing plate 9 and rotates counterclockwise in FIG. 1 when the vehicle moves forward. Further, as shown in FIG. 2, the anchor pin 10 is fixedly mounted on an anchor block 11 that is fastened and fixed to the backing plate 9.
[0019]
The above brake shoes 3 and 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 end portions of the brake shoes 3 and 4 on the side of the operating force generating means 6 are in directions in which the end portions of the respective shoes approach each other via shoe return springs 92 and 93 (that is, directions away from the drum). Is being energized.
Further, the ends of the brake shoes 3 and 4 on the side of the adjuster unit 8 are urged by the urging force of the shoe-to-shoe spring 95 so that the state in contact with the end of the adjuster unit 8 is maintained. Yes.
[0020]
In the case of the present embodiment, as shown in FIG. 5, the operating force generating means 6 causes the output rod 6a to advance in the direction of the arrow (A) in response to a brake operation such as a brake pedal for service brakes, thereby operating the shoe. It is a wheel cylinder that outputs a pressing force with a force W (see FIG. 5).
[0021]
The adjuster unit 8 originally adjusts the distance between the ends of the brake shoes 3 and 4 according to the progress of the lining wear of the brake shoes 3 and 4, and is adjusted by the biasing force of the adjuster spring 81. The interval between the ends of the brake shoes 3 and 4 is automatically adjusted by the rotation of the adjuster lever 82 whose tip is in contact with the adjusting gear 8a on the adjuster unit 8.
[0022]
An adjuster drive mechanism 84 is connected to the adjuster lever 82. In the case of the present embodiment, the adjuster drive mechanism 84 includes a relay means 85 rotatably supported on the web 4a of the secondary shoe 4, and one end connected to the upper end portion 10a of the anchor pin 10 and the other end connected to the relay means. And a second adjuster rod 87 having one end connected to the relay means 85 and the other end connected to an adjuster lever 82 via an adjuster spring 81. Thus, a rotating force is applied to the adjuster lever 82 in accordance with the amount of movement of the secondary shoe 4 during braking to control the extension of the adjuster unit 8.
[0023]
As shown in FIGS. 2 to 5, the shoe drive cam 7 according to the present embodiment has a shoe engagement mechanism in which a pair of upper and lower identical cam plates 76 and 77 fitted to the anchor pin 10 are brought into contact with the primary shoe 3. A primary cam pin 21 as a combined cam portion, a secondary cam pin 23 as a shoe engagement cam portion that contacts the secondary 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 Join with.
[0024]
The primary cam pin 21, the secondary cam pin 23, and the input pin 25 have a reduced-diameter portion that is inserted through the pin fitting holes of the upper and lower cam plates 76 and 77 at both ends. Then, as shown in FIG. 4, these pins 21 and 23 are inserted into the pin fitting holes of the upper and lower cam plates 76 and 77 after the diameter-reduced portions at both ends are inserted from the upper and lower cam plates 76 and 77. By attaching a retaining ring 27 such as an E-ring to the protruding end, it is possible to prevent the upper and lower cam plates 76 and 77 from coming off.
[0025]
Further, the primary cam pin 21 and the secondary cam pin 23 are disposed at a position radially outside the drum, and a secondary cam pin 23 is positioned radially inside the drum, with the anchor pin 10 interposed therebetween. As shown in FIG. 5, the input pin 25 is arranged at a position spaced further to the radially inner diameter side than the secondary cam pin 23 and receives the shoe operating force of the operating force generating means 6 from the left side of the pin. Thus, the cam plates 76 and 77 are caused to rotate counterclockwise in the drawing.
[0026]
A spring bracket 28 is fitted and attached to the upper end portion of the anchor pin 10 protruding on the upper cam plate 77.
The spring bracket 28 is made of sheet metal, and as shown in FIG. 5, a main body 28b having an anchor fitting hole 28a for fitting to the upper portion of the anchor pin 10, and a pair of arm portions 28c extending from the main body 28b, 28d, and the distal end of the arm portion 28c is bent as an engaging portion 28e for engaging the hook portion at one end of the shoe return spring 92, and the distal end of the arm portion 28d is one end of the shoe return spring 93. It is bent as a locking portion 28f for locking the hook portion.
[0027]
As shown in FIG. 5, in the spring bracket 28, the action line of the return force of the shoe return springs 92, 93 causes the contact portions of the brake shoes 3, 4 to contact the cam pins 21, 23 and the cam pins 21, 23. The locking portion 28e is provided in the vicinity of the center of the primary cam pin 21 during non-braking, and the locking portion 28f is the secondary cam pin 23 during non-braking so as to substantially overlap the straight lines 31, 32 passing through the center of the secondary cam pin 23. It is provided so that it may be located in the center vicinity of, and the dimension of each part is set.
[0028]
As shown in FIG. 2, a non-circular cross-sectional portion 10b having a part of a side surface cut flat is provided on the anchor pin 10, and a first adjuster rod 86 is provided on the non-circular cross-sectional portion 10b. A support pin 10c for locking is integrally formed.
And the anchor fitting hole 28a of the spring bracket 28 is finished in the shape corresponding to the non-circular cross section 10b.
The spring bracket 28 is fitted to a non-circular cross section 10b formed on the top of the anchor pin 10 so that the positions of the respective locking portions 28e and 28f are not inadvertently shifted from the top of each pin. The detent is against.
[0029]
The upper and lower cam plates 76 and 77 are integrally formed with an input receiving arm 78 that receives the shoe operating force from the parking brake mechanism 51.
The parking brake mechanism 51 of the present embodiment abuts one end of the parking lever 53 rotatably supported by the backing plate 9 by the connecting pin 52 to the input receiving arm 78 and parks the other end of the parking lever 53. It is connected to a wire for brake operation, and the parking lever 53 is rotated in the direction of the arrow (d) in FIG. 5 by a braking operation during parking.
The parking lever 53 is rotated in the arrow (d) direction by rotating the shoe drive cam 7 counterclockwise around the anchor pin 10 in FIG. Thus, the brake shoes 3 and 4 are expanded to obtain a braking force.
[0030]
In the drum brake device 1 described above, at the time of forward braking or reverse braking in which the service brake brake pedal is operated, the shoe operating force W is input from the operating force generating means 6 to the input pin 25 according to the brake operation. . When the shoe operation force W is input, the cam operation force W causes the cam plates 76 and 77 to rotate counterclockwise in FIG. 5 around the anchor pin 10 to be installed between the pair of cam plates 76 and 77. The brake shoes 3 and 4 are expanded and pressed against the drum by the primary cam pin 21 and the secondary cam pin 23.
[0031]
On the other hand, at the time of forward braking by the service brake, the secondary cam pin 23 receives a braking force from the secondary shoe 4 that is the output-side brake shoe. The braking force acting on the secondary cam pin 23 exerts on the shoe drive cam 7 a 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.
The rotational moment acting on the shoe drive cam 7 by this braking force becomes a braking limiting force that reduces the effect of the shoe operating force from the operating force generating means 6, and the braking force at the time of service braking is input by the brake operation. Since the braking force is controlled so as not to exceed a predetermined magnification and the braking effect is stabilized, an excellent braking performance in which both the braking effect and the stability are appropriately balanced is ensured.
[0032]
Similarly, during reverse braking, the shoe operating force from the operating force generating means 6 is input to the input pin 25, and the pair of brake shoes 3, 4 are expanded by the rotation of the shoe drive cam 7 to perform braking. When the operation starts, a braking force acts on the primary cam pin 21 from the primary shoe 3 which is the brake shoe on the output side.
The rotational moment acting on the shoe drive cam 7 by the braking force from the primary shoe 3 becomes the braking limiting force that reduces the action of the shoe operating force from the operating force generating means 6, and the braking force at the time of service braking is reduced. In order to stabilize the effectiveness of the brake, it is controlled so as not to exceed the predetermined magnification of the shoe operation force input by the brake operation, and excellent braking performance that balances both braking effectiveness and stability is ensured The
[0033]
The shoe drive cam 7 is disposed between the operating force generating means 6 and the brake shoes 3 and 4 and mechanically controls the braking force. Therefore, the operating force generating means 6 is a conventional hydraulic type. It is easy to use not only hydraulic actuators such as wheel cylinders but also electric actuators such as electric motors, and it is easy to make the brake function intelligent and to make the vehicle hybrid.
[0034]
In addition, the line of action of the return force of the shoe return springs 92, 93 is a straight line 31, 32 passing through a contact portion of each end of each brake shoe 3, 4 with the cam pins 21, 23 and the center of the cam pins 21, 23. The end portions of the brake shoes on the anchor pin 10 side are always kept in contact with the cam pins 21 and 23.
Therefore, the cam pins 21 and 23 are integrated with the cam plates 76 and 77 of the shoe drive cam 7 even if the end portions of the brake shoes 3 and 4 are separated from the anchor pin 10 toward the outer drum side in the radial direction when braking is released. When returning to the initial position, it follows the cam pins 21 and 23 and surely returns to the initial position. Therefore, it is possible to prevent the brake shoe from being dragged due to a return failure only by the linear tensile force by the shoe return springs 92 and 93.
[0035]
Further, in the case of the present embodiment, the spring bracket 28 for locking one end of the shoe return springs 92 and 93 is prevented from rotating with respect to the anchor pin 10 by fitting with the non-circular cross section 10b formed at the upper part of the anchor pin 10. Therefore, when the spring bracket 28 is fixed to the anchor pin, a separate part for preventing rotation is omitted. Therefore, it is possible to prevent a decrease in assemblability due to an increase in the number of parts.
[0036]
In the present invention, the specific structure and the like of the spring bracket are not limited to the above embodiment, and can be appropriately changed in design without departing from the spirit of the present invention.
[0037]
【The invention's effect】
As described above, according to the drum brake device of the present invention described in claim 1, the cam plate of the shoe drive cam that receives the shoe operating force output from the operating force generating means moves around the anchor pin during the braking operation. As the cam plate rotates, each cam pin on the cam plate expands each brake shoe to generate a braking force. During braking, the braking force that acts on the cam pin from the brake shoe on the output side generates a rotational moment in a direction that reduces the rotation of the cam plate due to the shoe operating force, thereby limiting the braking force. Effectiveness can be secured.
[0038]
Further, since the shoe drive cam is disposed between the operating force generating means and each brake shoe and mechanically controls the braking force, the operating force generating means is a hydraulic type such as a conventional hydraulic wheel cylinder. It is easy to use not only this actuator but also an electric actuator such as an electric motor, and it is easy to make the brake function intelligent and to make the vehicle more hybrid for hybrid purposes.
[0039]
Also, the line of action of the return force of the shoe return spring is set so that it almost overlaps on a straight line that passes through the cam pin contact portion at one end of the brake shoe and the center of the cam pin. The end of this is always kept in contact with the cam pin. Therefore, when the brake is released, the end of each brake shoe follows the cam pin when the cam pin returns to the initial position integrally with the cam plate of the shoe drive cam, even if it is separated from the anchor pin to the drum side radially outward. Surely return to the initial position. Therefore, it is possible to prevent the brake shoe from being dragged due to a return failure only by a linear tensile force by the shoe return spring.
[0040]
According to the drum brake device of the present invention, the spring bracket is fitted to the non-circular cross-section of the anchor pin when the spring bracket for locking one end of the shoe return spring is fixed to the anchor pin. Only the rotation prevention is made, and another part for the rotation prevention is omitted. Therefore, it is possible to prevent a decrease in assemblability due to an increase in the number of parts.
[Brief description of the drawings]
FIG. 1 is a front view of an embodiment of a drum brake device according to the present invention.
FIG. 2 is a perspective view of the shoe drive cam shown in FIG.
FIG. 3 is a plan view showing a state before the upper and lower cam plates of the shoe drive cam shown in FIG.
4 is a plan view showing a state after the upper and lower cam plates of the shoe drive cam shown in FIG.
5 is an explanatory view of a positional relationship among a shoe drive cam and a parking lever, each brake shoe, and a spring bracket of the drum brake device shown in FIG. 1. FIG.
6 is a view as seen from an arrow A in FIG. 5;
7 is a view taken in the direction of arrow B in FIG.
[Explanation of symbols]
1 Drum brake device 3 Primary shoe (brake shoe)
4 Secondary shoe (brake shoe)
6 Operating force generation means (wheel cylinder)
7 Shoe drive cam (Shoe drive mechanism)
8 Adjuster unit 9 Backing plate 10 Anchor pin 10b Non-circular cross section 10c Support pin 21 Primary cam pin (cam pin)
23 Secondary cam pin (cam pin)
25 Input pin 27 Retaining ring 28 Spring bracket 28a Anchor fitting hole 28c, 28d Arm portion 28e, 28f Locking portion 51 Parking brake mechanism 52 Connection pin 53 Parking lever 76, 77 Cam plate 78 Input receiving arm

Claims (2)

A pair of brake shoes arranged opposite to each other in the drum, an anchor pin erected on the backing plate on one opposite end side of the pair of brake shoes, and an operation force generation that generates a shoe operation force according to the braking operation And a shoe drive cam having a cam plate that rotates around the anchor pin in response to a shoe operating force generated by the operating force generating means,
The shoe drive cam has a pair of cam pins on the cam plate that abut against one end of the pair of brake shoes and press the brake shoes in the expanding direction when the cam plate is rotated. In the drum brake device that applies a rotational moment to the cam plate in a direction that reduces the action of the shoe operating force according to the braking force that the cam pin receives from the brake shoe,
The return line of the return force of the shoe return spring that returns each brake shoe to the non-braking position when the brake is released is substantially non-overlapping so that it overlaps on a straight line passing through the contact portion of each brake shoe with each cam pin and the center of the cam pin. A drum brake device characterized in that a spring bracket provided with a locking portion for the shoe return spring is provided on the anchor pin in the vicinity of the center of each cam pin during braking. The drum brake device according to claim 1, wherein the spring bracket is prevented from rotating with respect to the anchor pin by fitting into a non-circular cross section formed on the anchor pin.

Images