JP2013050137A - Drum brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a structure reducing the size and the weight and preventing the reaction force accompanying breaking from acting on a back plate.SOLUTION: A first extension lever 33 and a second extension lever 34 are supported for rocking displacement around a pivot 31. The tip part of the first extension lever 33 is engaged with a web 7a of one brake shoe 4a in a depressible state of the web 7a outward in a radial direction. The tip part of the second extension lever 34 is engaged with a base end of a strut 32 in a depressible state of the strut 32 outward in the radial direction. With a transmission mechanism 56 forming a drive device 27a, the first extension lever 33 and the second extension lever 34 are displaced rockingly in opposite directions to each other.

Description

  The present invention relates to an improvement of a drum brake device for keeping a vehicle (automobile) in a stopped state. Specifically, a structure that can efficiently support the reaction force of the braking force is adopted, and a structure that facilitates a reduction in size and weight of the drum brake device is realized.

  Drum brakes are widely used for braking vehicles. Various types of drum brakes are known. Of these, leading / trailing drum brakes are widely used because they provide a stable braking force both forward and backward. 5 to 7 show an example of a leading / trailing drum brake described in Patent Document 1. FIG. The drum brake includes a back plate 1, an anchor 2, a wheel cylinder 3, a pair of brake shoes 4 a and 4 b, and a drum 5.

  Among these, the back plate 1 is supported and fixed to structural members of a suspension device such as a knuckle and an axle housing. The anchor 2 is supported and fixed to a radially outward portion of the back plate 1 in one circumferential direction. The wheel cylinder 3 is fixed at a position on the opposite side of the anchor 2 in the radial direction of the back plate 1 at a portion near the outer diameter of the back plate 1. The wheel cylinder 3 has a pair of pistons oil-tightly fitted to both ends of the cylinder cylinder 6. By introducing hydraulic pressure to the inside of the center of the cylinder cylinder 6, the wheel cylinder 3 can be removed from both ends of the cylinder cylinder 6. The projecting amount of the two pistons is increased (the interval between the two pistons is increased). Further, the brake shoes 4a and 4b can be displaced in the radial direction of the back plate 1 at two positions opposite to the radial direction of the back plate 1 between the anchor 2 and the wheel cylinder 3. I support it.

  Each of the brake shoes 4a and 4b has a substantially arc-shaped web 7a and 7b, and back plates 8a and 8b each having a central portion in the width direction fixed to the outer peripheral edge of the web 7a or 7b by welding or the like, It consists of linings 9a and 9b attached and fixed to the outer peripheral surfaces of the back plates 8a and 8b. Then, one end edge in the circumferential direction of each of the webs 7a and 7b is abutted against the anchor 2, and the other edge in the circumferential direction is abutted against the bottom surfaces of the engaging grooves formed at the tip portions of the two pistons. Further, the drum 5 is formed in a petri dish with cast iron or the like, is provided in a state of covering both the brake shoes 4a and 4b, and rotates together with the wheels.

  When braking is performed with the drum brake configured as described above, hydraulic pressure is introduced into the wheel cylinder 3 by depressing the brake pedal, and the protruding amounts of the two pistons from the cylinder cylinder 6 are increased. Then, the distance between the two webs 7a, 7b abutting against the other end edges in the circumferential direction against the tip ends of the two pistons is widened, and the two brake shoes 4a, 4b are radially centered about the anchor 2. Oscillating displacement outward. As a result, the outer peripheral surfaces of the linings 9a and 9b of both brake shoes 4a and 4b are pressed against the inner peripheral surface of the drum 5 to perform braking. When the hydraulic pressure in the wheel cylinder 3 is removed when the brake is released, both the brake shoes 4a and 4b push the pistons into the cylinder cylinder 6 by the elasticity of the return springs 10a and 10b. Displace towards.

  In the case of the first example of the conventional structure shown in FIGS. 5 to 7, a strut 11 for adjusting the automatic gap is provided, and both the linings 9a in the non-braking state are provided regardless of the wear of the linings 9a and 9b. , 9b and a gap (gap) between the outer peripheral surface of the drum 5 can be maintained at an appropriate value. The strut 11 is formed by connecting a main plate portion 12 and a sub plate portion 13 by a pivot 14. The pivot 14 is fixed to the sub-plate portion 13 and is engaged with a long hole 15 formed in the main plate portion 12 so that the long hole 15 can be displaced in the length direction. When the distance between the webs 7a and 7b is increased along with braking, the sub-plate portion 13 swings around the pivot shaft 14 in the clockwise direction in FIG.

  Of the end edge of the sub-plate portion 13, the portion that abuts against the end edge of the main plate portion 12 becomes longer from the center of the pivot 14 toward the rear (downward in FIG. 6) with respect to the swing direction. Yes. For this reason, the edge of this sub-plate part 13 and the edge of the said main board part 12 engage (it abuts) with the rocking displacement of the said sub-plate part 13 centering on this pivot 14. And even when the distance between the two webs 7a, 7b contracts based on the elasticity of the two return springs 10a, 10b as the brake is released, the contraction amount is larger than the expansion amount for braking. The sub-plate portion 13 shrinks by an amount corresponding to the swing displacement. For this reason, the size of the gap between the outer peripheral surface of both the linings 9a and 9b and the inner peripheral surface of the drum 5 can be maintained at an appropriate value regardless of the wear of the both linings 9a and 9b.

  The operation when using a so-called service brake that decelerates or stops the running vehicle and the operation of the automatic gap adjustment device are as described above, but parking that keeps the vehicle stopped without stepping on the brake pedal. Incorporating the brake device into a drum brake as described above is also widely performed. In addition, it is conventionally known that the service brake is hydraulically performed and the parking brake is mechanically performed by a link mechanism using an electric motor as a drive source, as described in Patent Documents 2 to 3 and 7, etc. It is implemented in some vehicles. Furthermore, Patent Literatures 4 to 6 also disclose an electric brake device that omits the hydraulic mechanism and that exhibits both functions of a service brake and a parking brake using only a mechanical booster mechanism that uses an electric motor as a drive source. It has been described and is conventionally known.

  FIG. 8 shows an example of a drum brake described in Patent Document 7, in which a service brake is hydraulically and a parking brake is mechanically performed by a link mechanism using an electric motor as a drive source. Since the basic structure of the drum brake is the same as the general structure shown in FIG. 5 described above, the redundant description will be omitted or simplified, and the configuration and operation of the parking brake device will be mainly described below.

An expansion / contraction device 16 for expanding / contracting the distance between the pair of brake shoes 4a, 4b is provided between the inner peripheral edges of the webs 7a, 7b constituting both the brake shoes 4a, 4b. 16 is expanded and contracted (driven).
The expansion / contraction device 16 includes a strut 11b, first and second expansion levers 18 and 19, and a coupling link 20 that connects intermediate portions of the first and second expansion levers 18 and 19. .

  When the braking force is generated by the parking brake device having such a structure, the base end portions of the first and second extension levers 18 and 19 are used as the first and second pressing members 21 constituting the driving device 16. , 22 from the opposite sides. Then, the first expansion lever 18 swings and displaces around a pivot portion 23a with one end of the coupling link 20 (the right side in FIG. 8), while the second expansion lever 19 is coupled with the coupling link 20. The link 20 is oscillated and displaced in the direction opposite to that of the first extension lever 18 around the pivot 23b with the other end (left side in FIG. 8). Then, the tip of the first extension lever 18 presses one brake shoe 4a radially outward, and the tip of the second extension lever 19 passes through the strut 11b to the other brake shoe. 4b is pressed radially outward. As a result, braking is performed by pressing the linings 9a, 9b of the brake shoes 4a, 4b against the inner peripheral surface of the drum 5.

  In the case of such a structure, the link type boosting mechanism constituted by the first and second expansion levers 18 and 19 and the coupling link 20 uses an electric motor having a relatively small output because of a small transmission loss. Can be reduced in size and weight. Further, the reaction force accompanying the braking is canceled in the booster (the connecting link 20 portion), and a large reaction force accompanying the braking is applied to the back plate 1 that supports and fixes the driving device 17. Can be prevented. However, the first and second expansion levers 18 and 19 are arranged adjacent to each other in the arrangement direction of the struts 11b (left and right direction in FIG. 8). For this reason, from the viewpoint of reducing the dimensions of the first and second expansion levers 18 and 19 in the direction in which the strut 11b is disposed, or the base end portions of the first and second expansion levers 18 and 19 There is room for improvement from the viewpoint of securing a large amount of rocking.

JP 2009-168228 A JP-A-8-244596 JP-A-11-105680 JP 2003-28215 A JP 2006-336868 A US Pat. No. 5,310,0026 JP 2011-99458 A JP 2003-314594 A

  In view of the circumstances as described above, the present invention can use an electric motor with a relatively small output by adopting a link-type booster with little transmission loss, and the reaction force accompanying braking is the booster, Alternatively, a structure that does not add to a member such as a back plate that supports the drive device, and that can reduce the size of the booster in the strut arrangement direction in order to further reduce the size and weight. It was invented to realize.

The drum brake device of the present invention includes a back plate, a pair of brake shoes, a drum, an expansion / contraction device, and a drive device for driving the expansion / contraction device, as in the above-described drum brake device conventionally known. With.
Among these, the back plate is supported and fixed to structural members of the suspension device such as a knuckle and an axle housing.
The two brake shoes are supported at two positions opposite to the back plate in the radial direction so as to be capable of displacement in the radial direction of the back plate.
The drum is provided so as to cover the brake shoes and rotates together with the wheels.
The expansion / contraction device is provided between the inner peripheral edges of the webs constituting both brake shoes in order to expand and contract the distance between the two brake shoes.

In particular, in the drum brake device of the present invention, the expansion / contraction device includes a pivot, a strut, and first and second expansion levers.
Of these, the pivots support the first and second expansion levers in a state in which they can swing around the pivots.
In addition, the first extension lever has a first through hole for inserting the pivot, and a tip portion of the first extension lever is formed between the web of one brake shoe and the strut of the two brake shoes. The one member is engaged with the one member so as to be able to press outward in the radial direction.
Further, the second extension lever has a second through-hole for inserting the pivot, and the tip thereof is the other member of the web of the one brake shoe and the strut, The other member is engaged so as to be able to press outward in the radial direction.
For this purpose, a part of the first extension lever and a part of the second extension lever are arranged so as to overlap each other in the axial direction of the pivot.
Moreover, the front-end | tip part of the said strut is engaged with the web of the other brake shoe of the said both brake shoes so that this web can be pressed to radial direction outward.

The drive device includes a transmission mechanism and a drive source for driving the transmission mechanism.
The transmission mechanism includes a first transmission portion that engages with the first expansion lever and swings the first expansion lever about the pivot. Furthermore, a second transmission portion that engages with the second expansion lever and swings the second expansion lever in the direction opposite to the first expansion lever about the pivot is provided.

When implementing the drum brake device of the present invention as described above, preferably, as in the invention described in claim 2, the pair of plates provided with the first extension levers spaced apart in parallel to each other. And a connecting part that connects these two plate parts.
Further, a pair of the first through holes are formed at positions where the both plate portions of the first extension lever are aligned with each other. In addition, a pair of first engaging portions that can be engaged with the one member are provided at the tip portions of the two plate portions.
On the other hand, the second through hole is formed in the second expansion lever. Further, a second engaging portion that can be engaged with the other member is provided at the tip of the second expansion lever. Further, the second expansion lever is disposed between the two plate portions of the first expansion lever. Then, the pivot is inserted through the first through holes and the second through holes.

  When the invention described in claim 2 as described above is carried out, it is preferable that, as in the invention described in claim 3, the second member is engaged with the second extension lever by the second engagement. The engaging portion with the portion is disposed in a portion between the two plate portions of the first expansion lever.

When the drum brake device of the present invention as described above is implemented, for example, as in the invention described in claim 4, the transmission mechanism includes a male screw member having a male screw portion at a part thereof, and the male screw portion and the screw. A feed screw mechanism including a female screw member having a mating female screw portion is provided.
The first transmission portion is provided on the male screw member or a member that can be displaced in the axial direction of the male screw member in conjunction with the male screw member.
Further, the second transmission portion is provided on the female screw member or a member that can be displaced in the axial direction of the male screw member in conjunction with the female screw member.
And said 1st expansion lever and said 1st transmission part are engaged.
Further, the second extension lever and the second transmission portion are engaged.

Further, when the drum brake device of the present invention as described above is implemented, preferably, the rotational force of the drive source is applied to the base end portion of the male screw member, as in the invention described in claim 5. A connecting member capable of transmitting to the member is slidably engaged with the male screw member.
Further, the first extension lever and the first transmission portion of the feed screw mechanism are engaged with each other in a swingable state.
Further, the second extension lever and the second transmission portion of the feed screw mechanism are engaged with each other in a swingable state.

When implementing the drum brake device of the present invention as described above, preferably, as in the invention described in claim 6, from the center of the first through hole, the tip of the first expansion lever and the The distance to the engaging part with one member is made smaller than the distance from this center to the engaging part between the first extension lever and the first transmission part.
Further, the distance from the center of the second through hole to the engaging portion between the tip of the second expansion lever and the other member is determined from the center of the second expansion lever and the second expansion lever. It is made smaller than the distance to the engaging part with the transmission part.

When the drum brake device of the present invention as described above is implemented, for example, as in the invention described in claim 7, the base end portions of the first and second extension levers are formed on the back plate. Through the through-hole, the back plate is protruded from the back surface, which is the opposite surface of the both sides of the back plate, to the side where the brake shoes are installed.
In addition, an electric motor as a drive source is installed in a portion that covers the through hole on the back surface of the back plate.
Further, the base end portion of the first extension lever is engaged with the first transmission portion.
Further, the base end portion of the second expansion lever is engaged with the second transmission portion.

  Further, when the drum brake device of the present invention as described above is implemented, preferably, as in the invention described in claim 8, the engaging portion between the first extension lever and the one member, The engaging portion between the second expansion lever and the other member is disposed on the opposite side with respect to the arrangement direction of the struts with the pivot shaft interposed therebetween in a non-braking state.

  Alternatively, as in the invention described in claim 9, the engaging portion between the first extension lever and the one member, and the engaging portion between the second extension lever and the other member are provided. In the non-braking state, the pivot is arranged at substantially the same position as the strut arrangement direction (for example, within a range of 1 mm with respect to the displacement direction accompanying the braking).

  Further, when the drum brake device of the present invention as described above is implemented, preferably, as in the invention described in claim 10, the tip of the second expansion lever is moved to the one member side during non-braking. In a state where the displacement to is restricted, it is engaged with this one member.

  When the drum brake device of the present invention as described above is implemented, the transmission mechanism is irreversible as in the invention described in claim 11.

  The drum brake device of the present invention configured as described above acts as follows and exhibits braking force. At the time of braking, the first and second expansion levers constituting the expansion / contraction device by the drive device are oscillated and displaced in directions opposite to each other around the pivot axis, and the distance between the tip portions of the first and second expansion levers Expand. Then, the tip of the first extension lever is directly connected to one member of the web and strut of one brake shoe or the other member, and the tip of the second extension lever is the one of the one of the brake shoes. The other member of the brake shoe web and the strut is pressed radially outwardly directly or via another member. As a result, both the brake shoes are displaced radially outward, and the linings of both the brake shoes are pressed against the inner peripheral surface of the drum to perform braking.

  Along with this braking, reaction forces in directions approaching each other are applied to the distal ends of the first and second expansion levers. This reaction force is applied as forces in opposite directions to the transmission mechanism constituting the drive device via the pivots constituting the expansion / contraction device and the base ends of the first and second expansion levers. Therefore, the forces in the opposite directions applied to the pivot and the transmission mechanism are canceled out in the expansion / contraction device and the transmission mechanism. As a result, a large force is not applied to the portion supporting the driving device such as the back plate with braking.

  According to the drum brake device of the present invention having the above-described configuration and operation, by adopting a link type boosting device that includes the first and second expansion levers and the pivot shaft and has a small transmission loss, It is possible to reduce the size and weight by using an electric motor with a small output. In addition, a structure in which a large force is not applied to the expanding / contracting device or the connecting portion between the driving device and the back plate can be realized by canceling out the reaction force accompanying braking in the expanding / contracting device and the driving device. For this reason, even each member (the pivot, first and second expansion levers, etc.) constituting the expansion / contraction device and each member (a male screw member, a female screw member, etc. described later) constituting the drive device have sufficient rigidity. In addition, if the strength is given, it is not necessary to particularly increase the rigidity and strength of the portion supporting the expansion / contraction device or the driving device such as the back plate. Thus, it is easy to reduce the weight of the drum brake device.

  Furthermore, in the case of this invention, a part of said 1st, 2nd expansion lever is arrange | positioned in the state superimposed on the axial direction of the said pivot. For this reason, it is possible to reduce the size of the force-increasing device which is a combination of the first and second expansion levers occupying the strut arrangement direction. As a result, the drum brake device can be further reduced in size and weight. Further, when the first and second expansion levers swing, the first and second expansion levers are unlikely to interfere with each other in the arrangement direction of the struts. For this reason, it is easy to ensure the swinging amount of the first and second expansion levers. In addition, it is easy to ensure the rigidity of the tip portions by increasing the dimensions of the tip portions of the first and second expansion levers in the direction in which the struts are disposed. Furthermore, in the case of the invention described in claim 2, a pair of first engaging portions formed at the tip portions of both plate portions of the first extension lever, the web of the one brake shoe, and the struts Since one of the members is engaged at two positions, a stable pressing force can be applied to the one member by the first extension lever.

  Further, in the case of the invention described in claim 3, an engagement portion between the web of the one brake shoe and the other member of the strut and the second engagement portion of the second expansion lever, It arrange | positions in the part between both board parts of said 1st expansion lever. For this reason, positioning with respect to the arrangement direction of the strut and the axial direction of the pivot can be achieved between the other member and the second expansion lever. Furthermore, the dimension regarding the arrangement direction of the said strut can be restrained small. Therefore, the drum brake device can be further reduced in size and weight.

  In the case of the invention described in claim 5, the male screw member constituting the feed screw mechanism and the connecting member engaged with the base end portion of the male screw member are slidably engaged. The first and second expansion levers and the first and second transmission portions of the feed screw mechanism with which the first and second expansion levers are engaged are engaged in a swingable state. For this reason, when the first and second expansion levers swing about the pivot, the members constituting the feed screw mechanism also swing corresponding to the swing. As a result, the rotational force from the drive source can be smoothly transmitted to each member constituting the feed screw mechanism via the connecting member.

  In the case of the invention described in claim 6, the centers of swinging of the first and second expansion levers are biased toward the respective leading ends which are the output side. For this reason, even when a driving force for swinging is applied to the first and second expansion levers using a relatively small drive source, the tip portions of the first and second expansion levers are large. The distance is expanded by force.

  Further, in the case of the invention described in claim 8, the engaging portion between the first expansion lever and the one member, and the engaging portion between the second expansion lever and the other member, The struts are positioned on opposite sides with respect to the arrangement direction of the struts with the pivot interposed therebetween. Therefore, the change in the lever ratio between the first and second expansion levers before and after the drum brake device generates the braking force is reduced, and a stable braking force can be exhibited.

  Further, in the case of the invention described in claim 9, the engaging portion between the first extension lever and the one member, and the engaging portion between the second extension lever and the other member, It is arranged at substantially the same position as the position of the pivot with respect to the arrangement direction of the strut. Even if such a structure is adopted, the change in the lever ratio between the first and second expansion levers before and after the drum brake device generates a braking force can be suppressed.

  Further, in the case of the invention described in claim 10, the distal end portion of the second expansion lever is engaged with the one member in a state in which displacement to the one member side during non-braking is restricted. Yes. Therefore, the positioning of the second expansion lever in the non-braking state with respect to the arrangement direction of the strut is achieved by the engagement between the tip of the second expansion lever and the one brake shoe and the strut. I can do things.

  In the case of the invention described in claim 11, the transmission mechanism is irreversible. For this reason, even when energization to a drive source such as an electric motor is stopped, a state in which a braking force is exerted can be maintained without providing a separate lock structure in the speed reducer or the like. As a result, the cost of the drum brake device can be reduced.

The perspective view which shows one example of embodiment of this invention. The perspective view shown in the state which abbreviate | omitted the backplate, the wheel cylinder, and the anchor which shows an example of embodiment of this invention. The front view which shows an example of embodiment of this invention. FIG. 4 is a cross-sectional view taken along line AA in FIG. 3, showing an example of the embodiment of the present invention. The front view which shows the 1st example of a conventional structure. BB sectional drawing of FIG. 5 which shows the 1st example of a conventional structure. CC sectional drawing of FIG. 5 which shows the 1st example of a conventional structure. Sectional drawing of a drum brake which shows the 2nd example of conventional structure.

  1 to 4 show an example of an embodiment of the present invention corresponding to claims 1 to 8 and 10 to 11. In this example, the structure of the drum brake device of the present invention is applied to a parking brake device. The structure and operation other than the parking brake device are the same as those of the leading and trailing drum brake devices that have been widely known, including the conventional structure shown in FIGS. Therefore, the illustration and description regarding the equivalent parts are omitted or simplified, and the following description will focus on the characteristic parts of the present invention. The structure of the service brake is constituted by a hydraulic mechanism, similar to the conventional structure described above. However, the structure of the drum brake device of the present invention can also be applied to a service brake device.

  The parking brake device constituting the drum brake device of the present example is similar to the conventionally known drum brake type parking brake device described above, and includes a back plate 1, a pair of brake shoes 4a and 4b, and a drum 5 (see FIG. 8), an expansion / contraction device 16a, and a drive device 17a for driving the expansion / contraction device 16a.

In particular, in the case of the parking brake device constituting the drum brake device of this example, the expansion / contraction device 16 a includes a pivot 24, a strut 25, and first and second expansion levers 26 and 27.
Among these, the pivot 24 is in a state in which a part of the first and second expansion levers 26 and 27 are overlapped with each other with respect to the axial direction of the pivot 24, and swings around the pivot 24. It is supported in a possible state.

The strut 25 is formed by combining a holding cylinder 28, a screw rod 29, and a screw cylinder 30 as is widely known as described in Patent Document 7 and the like. When the linings 9a and 9b are worn, the screw rod 29 is rotated by the lever 31 and the strut 25 is extended. In the case of this example, the first engagement flat portion 32 is formed by performing press molding or the like on the base end portion (the right end portion in FIGS. 1 to 4) of the screw cylinder 30. Further, the second engagement flat portion 33 is formed by performing press molding or the like on the distal end portion (the left end portion in FIGS. 1 to 4) of the holding cylinder 28. In addition, a notch 34 is formed at the tip of the second engagement flat portion 33 so that the web 7b of the other brake shoe 4b of the two brake shoes 4a and 4b can be engaged in a radially outwardly pressable manner. doing.
As the structure of the automatic gap adjusting device, the structure of the conventional automatic gap adjusting device described in FIGS. 5 to 8 can be applied. Regardless of which structure is applied, the structure and operation of such an automatic gap adjusting device have been widely known in the past, as described in Patent Documents 6 to 8, and the like. Since it is not a part, further detailed explanation is omitted.

  The first extension lever 26 is formed by bending a plate-like material, and is provided with a pair of first plate portions 35, 35 provided in parallel and isolated from each other. It consists of the 1st connection part 36 which connects a part of 1st board parts 35 and 35. As shown in FIG.

  A pair of first through-holes 37 penetrating these first plate portions 35, 35 in the thickness direction at positions that are aligned with each other among the intermediate portions of both first plate portions 35, 35, They are concentric with each other. Further, a web 7a of one brake shoe 4a of the two brake shoes 4a and 4b and a web 7a of the first brake plate 4a and 4b are provided at the leading ends (the upper ends of FIGS. A pair of first engaging portions 38, 38 that can be engaged with each other in a state that can be pressed radially outward is formed.

Further, an intermediate portion and a base end portion (lower end portions in FIGS. 1 to 2 and 4) of the first plate portions 35 and 35 are connected to a base of the first plate portions 35 and 35 through a step portion 39. The interval between the end portions is continuous in a state where it is larger than the interval between the intermediate portions. Further, a pair of first notches 40 having a partial arc shape opened on the one brake shoe 4a side at the edge of the one brake shoe 4a side of the base end portions of the first plate portions 35, 35. Is forming. The center of the first through holes 37 (center of the pivot 24 in the assembled state) and the first engaging portions 38, 38 (both first engagements in the assembled state). The distance between the joint portions 38, 38 and the engagement portion between the one brake shoe 4a and the web 7a) is set so that the center of the first through hole 37 and the first notches 40 (in the assembled state). The so-called lever of the first expansion lever 26 is made sufficiently smaller than the distance between the first cutouts 40 and the engagement portions of the first projections 60 of the bearing member 51 described later. The ratio is sufficiently large (larger than 1, for example, about 3 to 6).
Further, the first connecting portion 36 connects the intermediate portions of the end surfaces (left end surface in FIG. 4) of the first brake plates 4b side of the first plate portions 35, 35. When the first and second expansion levers 26 and 27 are oscillated and displaced from each other, the first connecting portion 36 is connected to the first connection portion 36 within a range in which the first and second expansion levers 26 and 27 do not interfere with each other. It can also be provided at the end edge (the right end edge in FIG. 4) of both the first plate portions 35, 35 on the one brake shoe 4a side.

On the other hand, the second extension lever 27 is formed by bending a plate-like member or the like, and a pair of second plate portions 41 and 41 closely overlapped with each other except for a base end portion to be described later. It consists of the 2nd connection part 42 which connects a part of 2nd board parts 41 and 41 mutually.
A pair of (but continuous with) the second plate portions 41, 41 passing through the second plate portions 41, 41 in the thickness direction at positions where they are aligned with each other among the intermediate portions of the second plate portions 41, 41. A second through hole 43 is formed. Further, the first engaging flat portion of the screw cylinder 30 constituting the strut 25 is provided on the end surface of the distal end portions (the upper end portions in FIGS. 1 to 2 and 4) of the second plate portions 41 and 41 on the strut 25 side. 32 and a pair of (but continuous with each other) second engaging portions 44 that can engage with the struts 25 in a state in which the struts 25 can be pressed radially outward. Further, in the non-braking state shown in FIG. 4, a part of the tip of each of the second plate portions 41, 41 is engaged with a locking groove 45 formed in the web 7a of the one brake shoe 4a. Yes. In this manner, the displacement of the second expansion lever 27 toward the one brake shoe 4a is restricted during non-braking.
In addition, the engaging part which can engage with the web 7a of said one brake shoe 4a can also be provided in the front-end | tip part of both said 2nd board parts 41 and 41. FIG.

  Further, an intermediate portion and a base end portion (lower end portions in FIGS. 1 to 2 and 4) of both the second plate portions 41 and 41 are connected to a base of the both second plate portions 41 and 41 through a step portion 46. The interval between the end portions is continuous in a state where it is larger than the interval between the intermediate portions. The second plate portions 41 and 41 are provided in such a manner that the intermediate portions are overlapped with each other from the front end portion, while the base end portions are parallel to each other and separated from each other. It is provided in the state.

  Further, a pair of second arcuate or U-shaped pairs of second end portions of the second plate portions 41, 41 are opened on the other brake shoe 4b side edge of the second brake shoe 4b side. A second notch 47 is formed. The center of the second through holes 43 (the center of the pivot 24 in the assembled state) and the second engaging portions 44 (the two engaging portions in the assembled state). 44 and the engagement portion of the screw cylinder 30 constituting the strut 25 with the first engagement flat portion 32), the distance between the center of the second through holes 43 and the second notches 47 ( In the assembled state, the distance between the second notches 47 and the engagement portions of the nuts 52, which will be described later, with the second convex portions 65, 65) is set to be sufficiently smaller than the second. The lever ratio of the expansion lever 27 is sufficiently large (greater than 1, for example, about 3 to 6). In this example, the lever ratio of the first extension lever 26 and the lever ratio of the second extension lever 27 are substantially the same.

Further, the second connecting portion 42 connects the intermediate portions of the end surfaces (the right end surface in FIG. 4) of the second brake plate 4a side of the second plate portions 41, 41. The second connecting portion 42 can also be provided at an end edge (left end edge in FIG. 4) of the second brake shoe 4b side of the second plate portions 41, 41.
Such first and second expansion levers 26 and 27 are disposed between the first plate portions 35 and 35 of the first expansion lever 26 and the second plate portions of the second expansion lever 27. 41 and 41 are combined. In addition, the first through holes 37 of the first plate portions 35 and 35 and the second through holes 43 of the second plate portions 41 and 41 are aligned with each other. The pivot 24 is inserted into the second through holes 37 and 43, and the two expansion levers 26 and 27 are combined so as to be swingable and displaceable.

  Further, in such a combined state, the inner surfaces of the first plate portions 35, 35 of the first expansion lever 26 and the second surfaces of the second expansion lever 27 facing the both inner surfaces. A slight gap is provided between the outer surfaces of the plate portions 41 and 41. Therefore, in the combined state, when the first and second expansion levers 26 and 27 exhibit or release the braking force, the pivot 24 is not interfered with each other within a predetermined range. Oscillating displacement around the center is possible.

  Further, the engaging portion between the second engaging portions 44 of the second expansion lever 27 and the first engaging flat portion 32 of the screw cylinder 30 constituting the strut 25 is used as the first expansion lever. It is located in the part between 26 both the 1st board parts 35 and 35. FIG.

  Further, in the case of this example, the first engaging portions 38, 38 of the first extension lever 26 and the engaging portion A (see FIG. 4) between the web 7a of the one brake shoe 4a, and the second The engagement portion b (see FIG. 4) between the second engagement portion 44 of the expansion lever 27 and the first engagement flat portion 32 of the screw cylinder 30 constituting the strut 25 is denoted by α in FIG. The positions of the pivots 24 with respect to the direction in which the struts 25 are arranged are shifted to positions opposite to each other by approximately the same distance (installed in the opposite direction). The first engagement portions 38, 38 of the first extension lever 26 and the engagement portion between the web 7a of the one brake shoe 4a and the second engagement portion of the second extension lever 27 are provided. 44 and the engaging part of the first engaging flat part 32 of the screw cylinder 30 constituting the strut 25 are arranged at substantially the same position as the position α of the pivot 24 in the arrangement direction of the strut 25. You can also.

  In the case of this example, the base end portions of the first and second expansion levers 26 and 27 are formed in the back plate 1 and have a rectangular through hole 48 (FIG. 1) that is long in the length direction of the strut 25. 1), the back plate 1 protrudes from the back surface (the lower surface in FIG. 1) which is the surface opposite to the side where the brake shoes 4a and 4b are installed. Then, the first and second expansion levers 26 and 27 are placed on the back surface portion of the back plate 1 so as to swing and displace around the pivot 24. The driving device 17a is provided to expand and contract the distance between the base end portions of the 27.

The drive device 17a includes a transmission mechanism 49 and an electric motor (not shown) that corresponds to a drive source in claims and that drives the transmission mechanism.
Of these, the transmission mechanism 49 corresponds to a male screw member in the claims, a screw 50 that is driven to rotate by the output of the electric motor, a bearing member 51, and a nut 52 that corresponds to a female screw member in the claims. And.

Of these, the screw 50 includes a shaft portion 53 (see FIG. 4) and a large-diameter portion 54 having a larger diameter than the shaft portion 53.
Among these, the shaft part 53 has a male screw part 55 formed on the outer peripheral surface from the intermediate part to the tip part (left end part in FIG. 4).
The large-diameter portion 54 is provided at the base end portion (right end portion in FIG. 4) of the screw 50, and is continuous with one end (right end in FIG. 4) of the shaft portion 53 via the step portion 56. ing. Further, a hexagonal hole 57 opened in one axial direction is formed at the center of the large-diameter portion 54, and the distal end portion of the connecting member 58 capable of transmitting the output of the electric motor is engaged with the hexagonal hole 57. Match. In such an assembled state, the connecting member 58 is capable of relative displacement in the axial direction with respect to the screw 50 and swinging displacement with respect to the screw 50, while preventing relative rotation with respect to the screw 50. (It is possible to rotate in synchronization with the screw 50).

  Further, by providing a reduction gear (not shown) between the connecting member 58 and the electric motor, the output (rotational force) of the electric motor is reduced and the increased torque is transmitted via the connecting member 58. To be transmitted to the screw 50. Note that the base end portion (the right end portion in FIG. 4) of the connecting member 58 is supported so as to be capable of axial displacement and swing displacement with respect to the output shaft of the speed reducer. Since the structure and installation method of such an electric motor and reduction gear are the same as the structure described in Patent Document 7 except that the connecting member 58 is provided, illustration and detailed description thereof are omitted. .

  The bearing member 51 is, for example, a sliding bearing or the like, and is made of a material that is easy to slide, such as oil-impregnated metal or high-functional resin, and that has a high compressive strength. Such a bearing member 51 has a substantially rectangular parallelepiped bearing body 59 and a pair of first convex portions 60 corresponding to the first transmission portion in the claims. Of these, the bearing body 59 is formed with an insertion hole 61 (see FIG. 4) so as to penetrate from one side surface to the other side surface, and the inner peripheral surface of the insertion hole 61 is the shaft portion of the screw 50. Of the portion near the base end of the outer peripheral surface of 53, it is possible to make sliding contact with a portion where the male screw portion 55 is not formed.

Further, each of the first convex portions 60 has a columnar shape, and a pair of side surfaces (side surfaces other than the side surface on which the insertion hole 61 is formed) of the bearing body 59 that are located on opposite sides. Are provided concentrically with each other in a state protruding from both side surfaces.
In such a bearing member 51, the shaft portion 53 of the screw 50 is inserted into the insertion hole 61, and one end surface (the right end surface in FIG. 4) of the bearing body 59 and the stepped portion 56 of the screw 50 are brought into contact with each other. Assembled in contact.

The nut 52 has a substantially rectangular parallelepiped nut main body 62 and a pair of second convex portions 65 and 65 corresponding to the second transmission portion of the claims. Among these, the nut main body 62 penetrates from one side surface to the other side surface, and a screw hole 64 having a female screw portion 63 that can be screwed with the male screw portion 55 of the screw 50 is formed on the inner peripheral surface thereof. .
Each of the second convex portions 65 and 65 has a columnar shape, and a pair of side surfaces (other than the side surface on which the screw hole 64 is formed) of the nut main body 62 located on the opposite sides. Are provided concentrically with each other in a state protruding from both side surfaces. Such a nut 52 is assembled to the distal end portion of the screw 50 in a state where the female screw portion 63 and the male screw portion 55 of the screw 50 are screwed together.

In the drive device 17 a configured as described above, both the first protrusions 60 of the bearing member 51 are engaged with both first notches 40 of the first expansion lever 26. In this assembled state, the first expansion lever 26 and the bearing member 51 can be oscillated and displaced with the first convex portion 60 as the center. Further, the displacement of the screw 50 in the other axial direction (the left direction in FIG. 4) is caused by the first step 60 of the screw 50 and the first convex portions 60 of the bearing member 51. This is transmitted to the expansion lever 26.
When the screw 50 is displaced in one axial direction (the right direction in FIG. 4), the bearing member 51 is moved together with the base end of the first expansion lever 26 by the elasticity of the return springs 10a and 10b. Displace in one direction. In this way, the contact state between the stepped portion 56 of the screw 50 and one end surface of the bearing body 59, both the first convex portions 60 of the bearing member 51, and the first extension lever 26 The engaged state with both first notches 40 is maintained.

  On the other hand, the second protrusions 65 and 65 of the nut 52 are engaged with the second notches 47 and 47 of the second expansion lever 27 to prevent the nut 52 from rotating. . Further, in the assembled state, the second extension lever 27 and the nut 52 can be oscillated and displaced around the second convex portions 65 and 65 with respect to each other. Further, the displacement of the nut 52 in one axial direction (the right side in FIG. 4) based on the rotational movement of the screw 50 causes the second expansion through the second convex portions 65, 65 of the nut 52. It is transmitted to the lever 27. When the nut 52 is displaced in the other axial direction (left side in FIG. 4), the base end portion of the second extension lever 27 is displaced in the other axial direction by the elasticity of the return springs 10a and 10b. In this manner, the engagement state between the second convex portions 65 and 65 of the nut 52 and the second notches 47 and 47 of the second expansion lever 27 is maintained.

  Such a transmission mechanism 49 is a normal feed screw mechanism having irreversibility (self-locking function). For this reason, even when energization of the electric motor is stopped, it is possible to maintain a state where the braking force is exerted without energizing any part. The transmission mechanism 49 may be reversible such as a ball nut type feed screw mechanism. However, in this case, a lock structure for securing the braking force even after the energization of the electric motor is stopped is provided separately in, for example, the speed reducer.

  The parking brake which constitutes the drum brake device of the present example constructed as described above acts as follows and exhibits braking force. During braking, the output of the electric motor is transmitted to the screw 50 via the speed reducer and the connecting member 58, and the screw 50 is rotated in a predetermined direction. Then, the screw 50 is displaced in the other axial direction (the left side in FIG. 4) based on the threaded engagement between the male threaded portion 55 of the screw 50 and the female threaded portion 63 of the nut 52. The displacement of the screw 50 in the other axial direction is transmitted to the bearing member 51 via the stepped portion 56 of the screw 50, and further, the first first via the first convex portions 60 of the bearing member 51. To the expansion lever 26. As a result, the first extension lever 26 swings clockwise about the pivot 24.

  On the other hand, the nut 52 is displaced in one axial direction (the right side in FIG. 4) based on the threaded engagement with the male threaded portion 55 of the screw 50. The displacement of the nut 52 in one axial direction is transmitted to the second expansion lever 27 via both second convex portions 65 and 65 of the nut 52. As a result, the second extension lever 27 swings counterclockwise about the pivot 24.

  The tip portions of the first and second expansion levers 26 and 27 that are oscillated and displaced in the opposite directions in this way oscillate in directions away from each other, and the interval between these tip portions increases. The position of the swing center (the pivot axis 24) of the first and second expansion levers 26 and 27 is biased toward the respective distal end sides that are the output side (the respective lever ratios are large). The distance between the distal ends of the second extension levers 26 and 27 is increased by a large force. In the case of this example, the tip of the first extension lever 26 is directly on the web 7a of the one brake shoe 4a, and the tip of the second extension lever 27 is on the other brake shoe. The webs 7b of 4b are displaced radially outward through the struts 25, respectively. Then, the linings 9a and 9b of the brake shoes 4a and 4b are pressed against the inner peripheral surface of the drum 5 to perform braking. Such a force-increasing mechanism including the first and second expansion levers 26 and 27 and the pivot 24 has a small friction loss and an excellent transmission efficiency. The gear-type speed reducer used in the structure of this example inevitably causes a certain amount of friction loss, but the speed reduction by the amount increased by the first and second expansion levers 26 and 27. The increase ratio in the speed reduction part can be kept small, and the friction loss in the reduction part can be kept low accordingly. For this reason, it is possible to reduce the size and weight by using an electric motor having a relatively small output. Note that another member capable of transmitting a pressing force may be interposed between the distal end portion of the first extension lever 26 and the web 7a of the one brake shoe 4a.

According to the drum brake device of this example, it is not necessary to particularly increase the rigidity and strength of the portion supporting the drive device 17a, such as the back plate 1 and the substrate, and it is easy to reduce the weight of the drum brake device.
That is, in the case of the parking brake device that constitutes the drum brake device of the present example, the front and rear ends of the first and second expansion levers 26 and 27 are opposite to each other along with the braking performed as described above. Power is added. This reaction force is applied to the pivot 24 as forces opposite to each other. Further, the reaction force applied to the distal end portion of the first expansion lever 26 is transmitted from the base end portion of the first expansion lever 26 through the drive device 17a (both first convex portions 60 of the bearing member 51). The screw 50) is applied as a force in one axial direction (right direction in FIG. 4). On the other hand, the reaction force applied to the distal end portion of the second expansion lever 27 causes the drive device 17a (the two convex portions 65, 65 of the nut 52 to move from the base end portion of the second expansion lever 27). To the screw 50) as a force directed in the other axial direction (left direction in FIG. 4).

  The forces in the opposite directions applied to the driving device 17a from the first and second expansion levers 26, 27 are the same in the driving device 17a (the screw 50 has the same magnitude in the opposite directions). Negate each other) Therefore, a large force is not applied to the portions of the back plate 1 and the substrate that support the driving device 17a due to braking. Therefore, even the pivot 24 and the first and second expansion levers 26 and 27 constituting the expansion / contraction device 16a, and the screw 50 and the bearing member 51 and the nut 52 constituting the drive device 17a, If sufficient rigidity and strength are provided, it is not necessary to particularly increase the rigidity and strength of the back plate 1, the substrate, and the like supporting the driving device 17a, and the drum brake device can be reduced in weight. easy.

  The screw 50 constituting the transmission mechanism 49 and the connecting member 58 engaged with the base end portion of the screw 50 are engaged with each other so as to be able to swing. Further, the first expansion lever 26 and the bearing member 51 are engaged with each other so as to be swingable. Further, the second extension lever 27 and the nut 52 are engaged with each other so as to be swingable. Therefore, each member (screw 50, bearing member 51, nut 52) constituting the transmission mechanism 49 with respect to the swing of the first and second expansion levers 26, 27 around the pivot 24 is provided. It can follow by swinging displacement. As a result, the rotational force from the electric motor can be smoothly transmitted to the screw 50 via the connecting member 58.

  Further, the position of the pivot 24, which is the swing center of the first and second expansion levers 26, 27, is biased toward the respective distal ends on the output side. For this reason, even when the force applied to the base end portions of the first and second expansion levers 26 and 27 is small, the distance between the tip portions of the first and second expansion levers 26 and 27 is increased by a large force. . As a result, an electric motor having a relatively small output can be used to swing and displace the first and second expansion levers 26 and 27, and the size and weight can be reduced.

Further, by arranging the second expansion lever 27 between the first plate portions 35, 35 of the first expansion lever 26, the first and second expansion levers 26, 27 are arranged. Some of them are arranged in a state of being overlapped with respect to the axial direction of the pivot 24. For this reason, the dimensions of the first and second expansion levers 26 and 27 occupying in the arrangement direction of the strut 25 can be kept small, and the drum brake device can be further reduced in size and weight. it can.
Further, when the first and second expansion levers 26 and 27 swing, the first and second expansion levers 26 and 27 do not interfere with each other in the arrangement direction of the strut 25. For this reason, it is easy to ensure the swinging amount of the first and second expansion levers 26 and 27, and even if the increase ratio of the expansion levers 26 and 27 is increased, the displacement amount of the brake shoes 4a and 4b can be reduced. Easy to secure.
Furthermore, even if the dimensions of the distal end portions of the first and second expansion levers 26 and 27 with respect to the arrangement direction of the struts 25 are relatively large, like the structure shown in FIG. Compared to the case where the first and second expansion levers 24 and 25 are arranged adjacent to each other in the arrangement direction of the struts 11b, the first and second expansion levers 26 and 27 occupying the arrangement direction. The size of can be kept small. As a result, it is possible to reduce the size and weight of the drum brake device and to ensure the rigidity of the tip portions of the first and second expansion levers 26 and 27.

  In addition, a pair of first engaging portions 38 are formed at the distal end portions of the first plate portions 35 35 of the first expansion lever 26. The first engaging portions 38, 38 and the web 7a of the one brake shoe 4a are engaged at two positions. And the engaging part of the 2nd engaging part 44 of the said 2nd expansion lever 27 and the said strut 25 exists in the part between these two locations. For this reason, at the time of braking, there is no moment in the direction in which the two expansion levers 26 and 27 are inclined, and the postures of the two expansion levers 26 and 27 are stabilized. A stable pressing force can be applied to the webs 7a and 7b.

  Further, the engaging portion between the first engaging flat portion 32 of the screw cylinder 30 constituting the strut 25 and the second engaging portions 44 of the second extending lever 27 is used as the first expanding lever. It arrange | positions in the part between 26 both the 1st board parts 35 and 35. Therefore, the strut 25 and the second extension lever 27 can be positioned with respect to the arrangement direction of the strut 25 and the axial direction of the pivot 24. Furthermore, the dimension in the direction in which the struts 25 are arranged can be kept small, and the drum brake device can be further reduced in size and weight.

  Further, the first engaging portions 38, 38 of the first extension lever 26 and the web 7a of the one brake shoe 4a, and the second engaging portion of the second extension lever 27 are provided. 44 and the engagement portion between the first engagement flat portion 32 of the screw cylinder 30 constituting the strut 25 are substantially the same distance on the opposite sides with respect to the arrangement direction of the strut 25 with the pivot 24 interposed therebetween. It is just shifted. Therefore, the change in the lever ratio before and after the first and second expansion levers 26 and 27 exert the braking force is reduced, and a stable braking force can be exhibited. The first engagement portions 38, 38 of the first extension lever 26 and the engagement portion between the web 7a of the one brake shoe 4a and the second engagement portion of the second extension lever 27 are provided. 44 and the engaging portion between the first engaging flat portion 32 of the screw cylinder 30 constituting the strut 25 can be disposed at substantially the same position as the pivot 24 in the arrangement direction of the strut 25. Even in the case of such a structure, the change in the lever ratio before and after the first and second expansion levers 26 and 27 exert the braking force can be suppressed to a small extent even if the structure is not as large as the structure of this example. Can do.

  Further, the tip of the second extension lever 27 is prevented from being displaced toward the one brake shoe 4a when the second extension lever 27 is not braked. Is engaged with the web 7a. For this reason, the positioning of the second expansion lever 27 with respect to the arrangement direction of the strut 25 during non-braking is performed by engaging the distal end portion of the second expansion lever 25 with the proximal end portion of the strut 25. Further, this can be achieved by engaging the tip of the second extension lever 25 with the web 7a of the one brake shoe 4a.

The structure of the drum brake device of the present invention can be applied not only to a parking brake but also to a service brake.
Moreover, the structure of the 1st, 2nd expansion lever which comprises the expansion / contraction apparatus of this invention is not limited to the structure of one example of embodiment mentioned above. For example, the first expansion lever and the second expansion lever are each constituted by a single plate-like member, and the first and second expansion levers can swing around the pivot axis, and Also, a structure can be adopted in which it is supported in a state of being overlapped with respect to the axial direction of the pivot. Also, the distal end of the first expansion lever is engaged with the base end of the strut so that the strut can be pressed radially outward, and the distal end of the second expansion lever is engaged with the web of one brake shoe. It is also possible to engage the web so that it can be pressed radially outward.

DESCRIPTION OF SYMBOLS 1 Back plate 2 Anchor 3 Wheel cylinder 4a, 4b Brake shoe 5 Drum 6 Cylinder cylinder 7a, 7b Web 8a, 8b Back plate 9a, 9b Lining 10a, 10b Return spring 11, 11b Strut 12 Main plate part 13 Sub-plate part 14 Axis 15 Elongated hole 16, 16a Enlargement / contraction device 17, 17a Drive device 18 First expansion lever 19 Second expansion lever 20 Link 21 First pressing member 22 Second pressing member 23a, 23b Pivoting portion 24 Pivot 25 Strut 26 Second One extension lever 27 Second extension lever 28 Holding cylinder 29 Screw rod 30 Screw cylinder 31 Lever 32 First engagement flat part 33 Second engagement flat part 34 Notch 35 First plate part 36 First connection part 37 First One through hole 38 First engaging portion 39 Stepped portion 40 First notch 4 Second plate portion 42 Second connecting portion 43 Second through hole 44 Second engaging portion 45 Locking groove 46 Stepped portion 47 Second notch 48 Through hole 49 Transmission mechanism 50 Screw 51 Bearing member 52 Nut 53 Shaft Part 54 large diameter part 55 male screw part 56 step part 57 hexagonal hole 58 connecting member 59 bearing body 60 first convex part 61 insertion hole 62 nut main body 63 female thread part 64 screw hole 65 second convex part

Claims (11)

A back plate supported and fixed to the structural members of the suspension device;
A pair of brake shoes that support displacement in the radial direction of the back plate at two positions opposite to the radial direction of the back plate;
A drum that is provided in a state of covering both the brake shoes and rotates with the wheel;
In order to expand and contract the distance between the two brake shoes, an expansion / contraction device provided between the inner peripheral edges of the webs constituting the two brake shoes,
In a drum brake device including a driving device for driving the expansion / contraction device,
The expansion / contraction device includes a pivot, a strut, and first and second expansion levers.
Of these, the pivot is to support the first and second expansion levers in a state that allows swinging around the pivot.
The first extension lever has a first through hole for inserting the pivot shaft, and the tip of the first extension lever is one of the web of one of the brake shoes and the strut. The one member is engaged with the member in such a manner that it can be pressed radially outward,
The second expansion lever is arranged in a state where a part of the second expansion lever overlaps with a part of the first expansion lever in the axial direction of the pivot, and a second through hole for inserting the pivot And the front end thereof is engaged with the other member of the web of the one brake shoe and the strut so that the other member can be pressed radially outward,
The strut tip is engaged with the web of the other brake shoe of the two brake shoes so that the web can be pressed radially outward,
The drive device includes a transmission mechanism and a drive source for driving the transmission mechanism,
The transmission mechanism is engaged with the first expansion lever, and a first transmission portion that swings the first expansion lever around the pivot axis;
A second transmission portion that engages with the second expansion lever and swings the second expansion lever in a direction opposite to the first expansion lever about the pivot axis; Drum brake device. The first extension lever includes a pair of plate portions provided in a state of being separated from each other in parallel, and a connecting portion that connects these two plate portions,
A pair of first through holes are formed at positions where both plate portions of the first expansion lever are aligned with each other, and a pair of first engagements that can be engaged with the one member at the distal end portion. Have joints,
The second expansion lever is formed with the second through hole, and has a second engagement portion that can be engaged with the other member at a tip portion. It is arranged in the part between the plate parts,
The drum brake device according to claim 1, wherein the pivot is inserted through the first through hole and the second through hole.   The engagement portion between the other member and the second engagement portion of the second expansion lever is disposed at a portion between both plate portions of the first expansion lever. The drum brake device described. The transmission mechanism is a feed screw mechanism having a male screw member having a male screw part in a part thereof and a female screw member having a female screw part screwed into the male screw part,
The first transmission portion is provided on the male screw member or a member displaceable in the axial direction of the male screw member in conjunction with the male screw member,
The second transmission part is provided on the female screw member or a member displaceable in the axial direction of the male screw member in conjunction with the female screw member,
The first extension lever and the first transmission portion are engaged,
The drum brake device according to any one of claims 1 to 3, wherein the second extension lever and the second transmission portion are engaged. A connection member capable of transmitting the rotational force of the drive source to the male screw member is slidably engaged with the male screw member at a base end portion of the male screw member,
The first expansion lever and the first transmission portion of the feed screw mechanism are engaged with each other in a swingable state,
The drum brake according to any one of claims 1 to 4, wherein the second extension lever and the second transmission portion of the feed screw mechanism are engaged with each other in a swingable state. apparatus. The distance from the center of the first through hole to the engagement portion between the tip of the first expansion lever and the one member is the distance from the center to the first transmission lever and the first transmission. Smaller than the distance to the engaging part with the part,
The distance from the center of the second through hole to the engaging portion between the tip of the second expansion lever and the other member is determined from the center of the second expansion lever and the second transmission. The drum brake device according to any one of claims 1 to 5, wherein the drum brake device is smaller than a distance from the engaging portion to the engaging portion. The back surface which is a surface on the opposite side to the side which installed both the brake shoes among the both sides | surfaces of this back plate through the through-hole formed in the said back plate through the base-end part of said 1st, 2nd expansion lever Protruding from the
An electric motor as a drive source is installed in a portion that covers the through hole on the back surface of the back plate,
The base end portion of the first extension lever and the first transmission portion are engaged,
The drum brake device according to any one of claims 1 to 6, wherein a base end portion of the second extension lever and the second transmission portion are engaged with each other. An engagement portion between the first expansion lever and the one member;
An engagement portion between the second expansion lever and the other member,
The drum brake device according to any one of claims 1 to 7, wherein the drum is sandwiched between the pivots in a non-braking state and arranged on opposite sides with respect to the arrangement direction of the struts. An engagement portion between the first expansion lever and the one member;
An engagement portion between the second expansion lever and the other member,
The drum brake device according to any one of claims 1 to 7, wherein the drum brake device is disposed at substantially the same position as the position of the pivot in the disposing direction of the strut in a non-braking state.   The front end portion of the second extension lever is engaged with the one member in a state where displacement to the one member side is restricted during non-braking. The drum brake device according to item 1.   The drum brake device according to any one of claims 1 to 10, wherein the transmission mechanism has irreversibility.

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