JP2014190353A - Drum brake - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a braking force to be easily released through manual operation of a drum brake for improving it in performance in the case where releasing of the braking force cannot be attained due to returning of a parking lever caused by a certain trouble after the braking force is held by a self-lock mechanism.SOLUTION: This invention comprises: a first member 13a and a second member 13b constituting a part of a shoe strut 13; an insertion member 16 having divided component elements 16a and 16b separably combined; a connecting member 17; and connecting members 18 each of which is arranged between each of the first member 13a and the second member 13b and the insertion member 16. The connecting members 18 are constructed such that the connected state between the first member 13a and the second member 13b is released through separation of the divided component elements 16a and 16b, the divided component elements 16a and 16b include an axial force receiving surface (f) and a braking force forced releasing mechanism 15 having the connecting member 17 arranged to be removable from outside is accompanied to the drum brake.

Description

  The present invention relates to a drum brake mounted on a vehicle, and more particularly to a drum brake having a braking force forcible release mechanism attached thereto.

  One of the brake devices installed in vehicles is a drum-type electric parking brake. The drum-type electric parking brake operates a parking lever provided in the brake assembly by the driving force of the electric actuator.

  By transmitting the pressing force generated by the operation to one brake shoe via a shoe strut, the friction material of one brake shoe is pressed against the inner periphery of the drum fixed to the axle, and the reaction force generated thereby Is transmitted to the other brake shoe via the shoe strut, the friction material of the other brake shoe is also pressed against the inner periphery of the drum to generate a braking force.

  The braking force is held by a self-locking mechanism such as a screw mechanism provided between the electric actuator and the parking lever.

  Such an electric parking brake is described in Patent Document 1 below, for example. An automatic adjuster mechanism for compensating friction material wear in a drum brake is described in Patent Document 2 below.

  The auto-adjuster mechanism of Patent Document 2 uses an adjustment bolt screwed to an adjustment wheel provided at the end of a shoe strut, and uses a pin as a connecting member interposed between the brake shoe and the brake chute. It can be said that a part of the shoe strut is composed of an adjusting bolt.

JP-A-11-105680 Japanese Patent Laid-Open No. 03-20129

  In the case of an electric parking brake, if a failure occurs in an electric system or an electric actuator after the brake is operated and the braking force is held by the self-locking mechanism, the braking force due to the reverse rotation of the electric motor that operates the electric actuator is reduced. Cannot be released.

  For this reason, especially in the case of an electric parking brake, a manual forcible release mechanism for such an emergency is required. In response to the request, Patent Document 1 does not describe any emergency release method for manually forcibly releasing the braking force at the time of failure.

  In addition, the shoe strut of the said patent document 2 can cancel | release connection of the adjustment bolt with respect to a connection member or a brake shoe by extracting the pin for connection, if there is no load.

  However, when the drum brake is operating, the shoe strut receives an axial force (axial compressive load), which causes a strong shearing force to be applied to the pin to which the adjustment bolt is connected. Is extremely difficult.

  Therefore, even if the shoe strut of the parking brake (drum brake) disclosed in Patent Document 1 is replaced with that disclosed in Patent Document 2, it is extremely difficult to forcibly release the braking force in an emergency.

  The present invention has been made in view of the above, and after the braking force is held by the self-locking mechanism in the drum brake, the braking force cannot be released by returning the parking lever due to a failure or the like. Sometimes, the purpose is to make it possible to easily release the braking force by manual operation.

  In order to solve the above-described problems, in the present invention, a parking lever having an input portion, a pair of front and rear brake shoes, and a shoe strut are provided, and the pressing force of the parking lever is applied to one brake shoe via the shoe strut. The friction material of one brake shoe is pressed against the inner periphery of the drum fixed to the axle, and the reaction force generated at this time is transmitted to the other brake shoe via the shoe strut to the other. The brake shoe friction material was pressed against the inner periphery of the drum, and the brake force forcibly releasing mechanism was attached to the drum brake that holds the braking force generated thereby by the self-locking mechanism.

  The braking force forcible release mechanism is a first member and a second member divided in the longitudinal direction, each of which constitutes a part of the shoe strut, and two vertically divided parts are combined in a separable manner. An insertion member, a coupling member that couples the two divided parts and maintains a combined state, a connection provided between the insertion member and the first member, and between the insertion member and the second member. The connecting portion is structured to be able to be disconnected from the first member and the second member by separating the two divided parts, and the first member and the second member are connected to each divided part of the insertion member. An axial force receiving surface that abuts each end surface of the member is included, and the coupling member is detachably disposed from the outside.

  The coupling member may be a pin, a bolt, a clip, or the like. A bolt that can apply a forced separating force to the two divided parts constituting the insertion member can also be used.

  In this braking force forcible release mechanism, the axial force receiving surface has a direction in which the axial length of the surface on which the two divided parts abut each other is shorter than the axial length of the outer periphery of each divided part. It is preferable to incline.

  It is also preferable to include an element (positioning means) for positioning the coupling member at a fixed position. In the case of using the insertion member having the inclined axial force receiving surface, the inclined axial force receiving surface effectively functions for positioning.

  The positioning of the coupling member is provided between the insertion member and the first member and between the insertion member and the second member in correspondence with a non-circular convex portion and a concave portion whose fitting direction is regulated, A structure in which the insertion direction of the insertion member between the first member and the second member is defined using the convex and concave portions is also possible.

  The coupling member is preferably provided with a working window (hole) in the backing plate of the drum brake to which the brake assembly is assembled, and is extracted therefrom. When a bolt is used as the coupling member in this structure, it is preferable to use a hexagonal bolt as the operation hole in the head.

  In the drum brake of the present invention, when the coupling member is removed, the coupling of the two divided parts is released, the two divided parts can be separated, and the insertion member constituted by the divided parts is defined as the first member. It becomes possible to remove from between the second members. The removal removes the axial force applied to the shoe struts, allowing the pair of brake shoes to return to the position away from the drum and releasing the braking force.

  According to the forcible release mechanism of the braking force provided in the drum brake of the present invention, the axial force applied to the shoe strut is transmitted to the insertion member via the axial force receiving surface included in each divided part of the insertion member. Therefore, no shearing force is applied to the coupling member, and no strong force is required to remove the coupling member, so that manual forcible release can be easily performed without any trouble.

  In addition, since the connecting member is not required to have the strength to withstand the shearing force, the strength can be ensured with a small size.

  In the case where the axial force receiving surface is inclined in the above-described direction, the component force of the axial force applied to the shoe strut is generated on the inclined axial force receiving surface, and the component force separates the two divided parts from each other. Work as power. Therefore, it becomes easy to extract the insertion member from between the first member and the second member.

  In addition, the coupling member can be positioned at a fixed position by using the inclined axial force receiving surface.

  The coupling member can be pulled out by inserting a work tool from the drum brake backing plate and inserting the work tool from it, and the coupling member can be pulled out of the working window if it is positioned at a fixed position. The workability of the forced cancellation | release can be improved by providing in the position to make.

  When the coupling member is a bolt having a hexagonal hole, a hexagonal wrench is used as the work tool. Therefore, the work window provided in the backing plate may be a small hole, and the protective effect of the brake assembly by the backing plate. Is not impaired.

The front view which shows the whole structure of an example of the drum brake of this invention 1 is an exploded perspective view of a strut set provided on the drum brake of FIG. Side view of the strut set of FIG. Sectional view along line IV-IV in FIG. Sectional view along line VV in FIG. Sectional drawing which shows the other example of a coupling member Sectional drawing which shows the further another example of a coupling member Exploded perspective view showing another example of strut set

  An embodiment of a drum brake according to the present invention will be described with reference to FIGS. The illustrated drum brake 1 is an electric parking brake. This drum brake (electric parking brake) 1 pushes out an electric actuator 2, a parking lever 3 having an input portion from the electric actuator 2, a pair of front and rear brake shoes 4, 4, and a pair of brake shoes 4, 4. A brake assembly 9 combining a wheel cylinder 5, a strut set 6, a shoe return spring 7 and an anchor spring 8 is incorporated inside a backing plate 10.

  The electric actuator 2 is a known actuator that converts the rotation of the electric motor into a linear motion by a ball screw mechanism or the like to advance and retract the slide shaft. A screw mechanism (not shown) inside the actuator functions as a self-locking mechanism that holds the generated braking force.

  11 is a shoe hold down, and 12 is a drum inserted between the brake assembly 9 and the peripheral wall of the backing plate 10. The drum 12 is fixed to the axle.

  The strut set 6 is engaged with one brake shoe (the left brake shoe in FIG. 1) 4 and the parking lever 3 at one end and the other brake shoe (the right brake shoe in FIG. 1) 4 at the other end. A combination of a shoe strut 13 to be operated and an auto adjuster mechanism 14 is shown.

  In the illustrated drum brake (electric parking brake) 1 having the above elements, when the brake switch is operated, the electric actuator 2 is actuated and the parking lever 3 is pulled, and the pressing force generated thereby passes through the shoe struts 13. Thus, the friction material 4a of the brake shoe 4 is transmitted to one brake shoe (right brake shoe in FIG. 1) 4 and pressed against the inner periphery of the drum 12.

  Further, the reaction force generated at this time is transmitted to the other brake shoe 4 via the shoe struts 13, and therefore the friction material 4a of the other brake shoe is also pressed against the inner periphery of the drum 12 to generate a braking force. The braking force is held by the aforementioned self-locking mechanism.

  As shown in FIGS. 2 to 4, the shoe strut 13 includes a first member 13 a and a second member 13 b that are divided in the longitudinal direction, each constituting a part of the shoe strut. Both the first member 13a and the second member 13b have a clevis portion, the first member 13a is on the brake shoe 4 and the parking lever 3 on the left side of FIG. 1, and the second member 13b is on the right side of FIG. The brake shoes 4 are engaged with each other so as not to rotate.

  The auto-adjuster mechanism 14 is a combination of an adjusting bolt 14a, a sleeve 14b for screwing the adjusting bolt 14a, and a spring 14c for rotating the adjusting bolt 14a as necessary. A part of the adjusting bolt 14a is a first one. The two members 13b are rotatably fitted in the holes having the clevis portions.

  For the strut set without the auto adjuster mechanism 14, a second member is used in which a portion corresponding to the sleeve 14b shown in the drawing and the clevis portion at the right end in FIG. 1 are integrally formed.

  A brake force forcible release mechanism 15 is incorporated in the brake assembly 9. The forcible release mechanism 15 of the braking force includes an insertion member 16, a coupling member 17, an insertion member 16, and a first member 13a that are inserted between the sleeves 14b that are part of the first member 13a and the second member 13b. And a connecting portion 18 provided between the insertion member 16 and the sleeve 14b.

  The insertion member 16 is configured by combining two divided parts 16a and 16b divided vertically (separated into left and right) into a cylindrical shape so as to be separable. The coupling member 17 is a component that maintains the cylindrical combination state of the two divided components 16a and 16b, and employs a clip that bundles pins, bolts, and divided components.

  The pins used as the coupling member 17 are not limited to the split pins shown in FIGS. 2 to 4 (which are inserted into the pin holes 16c provided in the split parts 16a and 16b), and press-fit pins may be used. it can.

  The insertion member 16 shown in FIG. 2 to FIG. 4 has two axial parts 16a and 16b at both ends, and the axial length of the surface on the side where the divided parts 16a and 16b abut each other is the outer circumference of each divided part. Inclined in a direction that is shorter than the axial length of the shaft, and the surfaces of the inclined ends are set as axial force receiving surfaces f, and the axial force receiving surfaces f are abutted against the end surfaces of the first member 13a and the sleeve 14b, respectively.

  According to this structure, no shearing force is applied to the coupling member 17 inserted into the holes of the divided parts 16a and 16b. On the other hand, in a state where the braking force is held, a component force of the axial force applied to the shoe strut 13 is generated on the axial force receiving surface f, and the component force is a force that causes the divided parts 16a and 16b to separate both. Join. Therefore, when it is assumed that the separation force is increased, the coupling member 17 may be a bolt, a split pin, a clip, or the like that can easily withstand the separation force.

  The connecting portion 18 is provided by projecting a small-diameter angular shaft portion 18b having a flange 18a formed at the tip of the first member 13a and the second member 13b, and the flanges 18a and the small-diameter angular shaft portion are provided on the divided parts 16a and 16b. A concave portion 18c for fitting 18b from the side is provided.

  In the illustrated structure, the insertion of the small-diameter angle shaft portion 18b into the concave portion 18c is allowed when in a specified posture, and the assembly posture of the insertion member 16 is restricted by the insertion restriction, thereby the coupling member 17 is positioned at a fixed position. The one having the inclined axial force receiving surface f can determine the assembling posture of the insertion member 16 by using the axial force receiving surface f and the mating surface that abuts the axial force receiving surface f for positioning.

  As shown in FIG. 5, the backing plate 10 of the exemplary drum brake is provided with a work window (hole) 19 from which a working tool is inserted into the shoe strut installation portion and the coupling member 17. Can be extracted. The convex part 20 shown with the chain line in FIG. 5 can be provided as needed, and can be used to push and move the divided parts 16a and 16b.

  As the coupling member 17, a bolt as shown in FIG. 6 can be used instead of the above-described split pin. In the bolt of FIG. 6, the operation hole 17 a on the head is a hexagonal hole, and when this bolt is used as the coupling member 17, the work window 19 may be a small-sized hole into which a hexagon wrench can be inserted.

  In addition, as shown in FIG. 7, the bolt used as the coupling member 17 may be a so-called double screw in which a reverse screw is cut at a portion screwed into the divided component 16a and a portion screwed into the divided component 16b. When the double screw is used, it is possible to facilitate the separation of the two divided parts by applying a forced separating force to the divided parts 16a and 16b using the thrust of the screw.

  The flange 18a is a square flange, but this may be a round flange. What is necessary is just to be able to maintain the connection state of the insertion member 16 with respect to the 1st member 13a and the 2nd member 13b, and it can substitute with a latching protrusion etc.

  In addition, the axial force receiving surface f of the insertion member 16 may be a surface perpendicular to the axis as shown in FIG. In this configuration, the force that separates the divided parts 16a and 16b from each other cannot be obtained, but even in this structure, by removing the insertion member 16, the axial force applied to the shoe strut 13 is released and the braking force is forcibly released. can do.

  Although the present invention is particularly effective when applied to an electric parking brake, the drum brake to which the present invention is applied is not limited to the electric parking brake. Even in a normal drum brake, if an adjustment wheel that functions as a self-locking mechanism rusts, forcible release is required. Therefore, all drum brakes including shoe struts are applicable to the present invention.

DESCRIPTION OF SYMBOLS 1 Drum brake 2 Electric actuator 3 Parking lever 4 Brake shoe 5 Wheel cylinder 6 Strut set 7 Shoe return spring 8 Anchor spring 9 Brake assembly 10 Backing plate 11 Shoe hold down 12 Drum 13 Shoe strut 13a First member 13b Second member 14 Auto Adjuster mechanism 14a Adjustment bolt 14b Sleeve 14c Spring 15 Forced release mechanism 16 Insertion member 16a, 16b Split part 16c Pin hole f Axial force receiving surface 17 Connection member 17a Operation hole 18 Connection portion 18a Flange 18b Small diameter angle shaft portion 18c Recess 19 Work window 20 Convex

Claims (5)

A parking lever (3) having an input section, a pair of front and rear brake shoes (4, 4), and a shoe strut (13), and the pressing force by the parking lever (3) is transmitted via the shoe strut (13). The friction material (4a) of one brake shoe is transmitted to one brake shoe (4) and pressed against the inner periphery of the drum (12) fixed to the axle, and the reaction force generated at this time is applied to the shoe. A self-lock mechanism that transmits the braking force generated by the other brake shoe (4a) to the other brake shoe (4) via the strut (13) and presses against the inner periphery of the drum (12). A drum brake held by
A first member (13a) and a second member (13b), each of which is part of the shoe strut (13) divided in the longitudinal direction, and two vertically divided parts (16a, 16b). An insertion member (16) configured to be separable, a coupling member (17) that holds the two divided parts (16a, 16b) in a combined state, the insertion member (16), and the The connecting portion (18) is provided between the first member (13a) and between the insertion member (16) and the second member (13b), and the connecting portion (18) includes the two pieces. The first member (13a) and the second member (13b) can be disconnected from each other by separating the divided parts (16a, 16b), and the first member is attached to each divided part (16a, 16b) of the insertion member. (13a) and No. An axial force receiving surface (f) that abuts each end surface of the member (13b) is included, and the coupling member (17) is provided with a braking force forcibly releasing mechanism (15) having a structure that is detachably arranged from the outside. Let the drum brake.   In the axial force receiving surface (f), the axial length of the surface on the side where the two divided parts (16a, 16b) face each other is longer than the axial length of the outer periphery of each divided part (16a, 16b). The drum brake according to claim 1, wherein the drum brake is tilted in a direction of shortening.   The drum brake according to claim 1 or 2, further comprising an element for positioning the coupling member (17) in a fixed position.   A brake assembly (9) combining the parking lever (3), a pair of front and rear brake shoes (4, 4), and shoe struts (13) is incorporated inside a backing plate (10), and the backing plate (10 The drum brake according to any one of claims 1 to 3, wherein a work window (19) is provided in which the coupling member (17) can be removed from the outside.   As the coupling member (17), there are two male screw portions that are screwed to the two divided parts (16a, 16b) on the same axis, and the threading directions of the two male screw portions are reversed. The drum brake according to any one of claims 1 to 4, wherein a bolt is used.

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