JP5758239B2 - Drum brake device - Google Patents

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. 6 to 8 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. 6 to 8, a strut 11 for automatic gap adjustment is provided so that both the linings 9a in the non-braking state 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 two webs 7a and 7b increases with braking, the sub-plate portion 13 swings around the pivot shaft 14 in the clockwise direction in FIG.

  Of the edge of the sub-plate portion 13, the portion that abuts against the edge of the main plate portion 12 becomes longer from the center of the pivot 14 toward the rear (downward in FIG. 7) in this 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, etc. Has been implemented in 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.

  FIGS. 9 to 10 show an example of a drum brake described in Patent Document 3 in which the service brake is hydraulic and the parking brake is mechanical 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. 6 described above, the same parts are denoted by the same reference numerals, and redundant description is omitted or simplified. The configuration and operation of the brake device portion will be mainly described.

  Of the web 7a constituting one brake shoe 4a, the base end portion of the parking lever 16 is pivotally supported at the end portion near the wheel cylinder 3, and the portion near the base end portion of the parking lever 16 and the other brake shoe 4b. A pressing rod 17 is stretched between a portion of the web 7b that is close to the wheel cylinder 3. Further, the tip of the pulling rod 18 is coupled to the tip of the parking lever 16. Further, the base end portion of the pulling rod 18 can be pulled by an electric actuator 22 including an electric motor 19, a speed reducer 20, and a feed screw device 21.

  When the parking brake device is operated, the actuator 22 causes the parking lever 16 to swing clockwise through the pulling rod 18 in FIG. Then, the other brake shoe 4b is pressed radially outward via the pressing rod 17, and as a reaction, the one brake shoe 4a is displaced radially outward. As a result, the outer peripheral surfaces of the linings 9a and 9b of both the brake shoes 4a and 4b are pressed against the inner peripheral surface of the drum to perform braking.

  In the case of the conventional structure as shown in FIGS. 9 to 10 described above, the reaction force of the braking force generated by pressing the outer peripheral surfaces of the linings 9a and 9b against the inner peripheral surface of the drum is the parking lever 16 and the pulling rod. 18 is applied to the actuator 22 via the switch 18. For this reason, it is necessary to sufficiently increase the rigidity of the portion where the actuator 22 is supported and fixed to the back plate 1, which is disadvantageous in reducing the size and weight of the drum brake device. This also applies to the structures described in Patent Documents 4 and 6.

  Patent Document 2 describes a structure in which a strut 11a that is expanded and contracted by a feed screw device 21a is provided between a pair of brake shoes 4a and 4b as shown in FIG. According to such a conventional structure, the above-described problem of reduction in size and weight can be eliminated. However, unlike the structure shown in FIGS. 9 to 10, the actuator (feed screw device 21a) is placed on the back side of the back plate 1. Cannot be placed. For this reason, the space on the back side of the back plate 1 is effectively used, which is disadvantageous in terms of realizing a structure that secures the reduction ratio of the reduction gear, increases the output of the actuator, and secures the braking force. become.

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 2003-314594 A

  In view of the circumstances as described above, the present invention realizes a structure that can be reduced in size and weight without the reaction force accompanying braking applied to members such as a back plate supporting the expansion / contraction device or the drive device. Invented as much as possible.

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 webs constituting the two 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 strut and first and second expansion levers.
Of these, the first expansion lever has its tip end engaged with the web of one of the brake shoes so that the web can be pressed radially outward.
The second expansion lever has a distal end engaged with a base end of the strut so that the strut can be pressed radially outward.
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 feed screw mechanism and a drive source for driving the feed screw mechanism.
Of these, the feed screw mechanism includes a male screw member and a female screw member.
Among these, the male screw member has a male screw portion on at least a part of the outer peripheral surface, and the front end portion of the male screw member is inserted into the through hole formed in the web of the one brake shoe. The base end portion is disposed on one side with respect to the thickness direction of the web and on the other side with respect to the thickness direction of the web.
The female screw member has a female screw portion, and the female screw portion is screwed into the male screw portion of the male screw member.
Further, one of the male screw member and the female screw member is a rotating side member that is rotationally driven by the driving source, and the other member is displaced in the axial direction along with the rotational movement of the rotating side member. Let it be a side member.
In addition, the base end portions of the first and second expansion levers are engaged with a part of the displacement side member in a state in which the displacement of the displacement side member in accordance with the displacement in the axial direction is possible.
Further, by engaging the rotating side member and the web of the one brake shoe directly or via another member, the action of the axial component of the rotating side member among the reaction force applied during braking is achieved. This displacement of the rotary member in the direction is prevented.

  Specifically, when the drum brake device of the present invention as described above is implemented, the rotating side member is the male screw member as in the invention described in claim 2. On the other hand, the displacement side member is the female screw member. Then, the female screw member is screwed onto the distal end portion of the male screw member in a state in which the rotation is prevented (however, the rotation with respect to the male screw member is allowed) and in a state where axial displacement is possible. .

Further, when carrying out the invention described in claim 2 as described above, more specifically, as in the invention described in claim 3, the male screw member includes a shaft portion and a base of the shaft portion. A large-diameter portion provided on the end side.
An engaging member and a bearing member are provided between the large diameter portion and the other side surface in the thickness direction of the web of the one brake shoe.
Of these members, the engaging member is formed in a cylindrical shape in which the shaft portion of the male screw member can be inserted in a state where a clearance is provided on the inner peripheral surface thereof. Further, one end surface of the engaging member is engaged with the web of the one brake shoe. A spherical concave surface portion is formed on the other end surface of the engaging member.
Further, the bearing member is formed in an annular shape in which the shaft portion of the male screw member can be inserted in a state where a gap is provided on the inner peripheral surface thereof. In addition, a spherical convex surface portion that is spherically engageable with the spherical concave surface portion of the engagement member is formed on one end surface of the bearing member. Further, the other end surface of the bearing member is brought into contact with the large diameter portion of the male screw member. The male screw member is supported so as to be swingable relative to the web of the one brake shoe.

  In the case of implementing the drum brake device of the present invention as described above, preferably, both the brake shoes are formed on the rotating side member and the both side surfaces of the back plate as in the invention described in claim 4. The drive source installed on the back surface, which is the surface opposite to the side on which is installed, is connected to a state in which the rotational force can be transmitted directly or through another member through the through hole formed in the back plate.

  When the drum brake device of the present invention as described above is implemented, the feed screw mechanism is irreversible as in the fifth aspect of the present invention.

  The drum brake device of the present invention configured as described above acts as follows and exhibits braking force. At the time of braking, with the displacement in the predetermined direction with respect to the axial direction of the displacement side member that constitutes the feed screw mechanism that is driven by the drive source, the base ends of the first and second expansion levers that constitute the expansion / contraction device are Swings in opposite directions. And between the front-end | tip parts (the engaging part of the web of a 1st expansion lever and one brake shoe, and the engaging part of a 2nd expansion lever and a strut) of these 1st, 2nd expansion levers Increase the spacing. And the tip of the first extension lever is directly or through the other brake shoe web, the tip of the second extension lever is the other brake shoe web through the strut, Each is displaced radially outward. As a result, braking is performed by pressing the linings of both brake shoes against the inner peripheral surface of the drum.

  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 transmitted to the displacement side member constituting the feed screw mechanism via the base end portions of the first and second expansion levers. Of the reaction force, the component relating to the arrangement direction of the struts, and the component trying to swing the first and second expansion levers in the direction opposite to the swinging direction for braking described above, respectively, Is applied to the displacement side member as a force in the opposite direction. As a result, the components in these directions, which occupy most of the reaction force, cancel each other out inside the displacement side member. On the other hand, the component of the reaction force related to the axial direction of the displacement-side member is a force acting on the displacement-side member via the first and second expansion levers in the axial direction (with the predetermined direction). As a force in the opposite direction) and further transmitted to the rotation side member. However, the rotation-side member is prevented from being displaced in the acting direction of the component in the axial direction by the engagement between the displacement-side member and the web of the one brake shoe. For this reason, the component regarding the said axial direction is supported by this web. As a result, a large force is not applied to the portion supporting the expansion / contraction device or the driving device, such as the back plate, due to braking.

  According to the drum brake device of the present invention having the above-described configuration and operation, there is little transmission loss including the first and second expansion levers constituting the expansion / contraction device and the displacement side member constituting the driving device. By adopting a link-type booster (toggle mechanism), it is possible to reduce the size and weight by using an electric motor with a relatively small output. In addition, as described above, a large part of the reaction force associated with braking is canceled in the expansion / contraction device and the drive device, and the remaining small component is removed from the rotary member constituting the drive device and the one of the ones. The brake shoe can be supported by the engaging portion with the web. Accordingly, it is possible to realize a structure in which a large force is not applied to the portion supporting the driving device such as the back plate with braking. For this reason, each member (first, second expansion lever, etc.) constituting the expansion / contraction device, each member (displacement side member, rotation side member, etc.) constituting the drive device, and the rotation side member If the engagement portion of one of the brake shoes with the web has sufficient rigidity and strength, the rigidity and strength of the portion supporting the expansion / contraction device or the drive device such as the back plate is particularly good. There is no need to make it bigger. Thus, it is easy to reduce the weight of the drum brake device.

  Furthermore, the feed screw mechanism that constitutes the drive device is arranged using the space around the web of the one brake shoe. For this reason, the space that is not used in the conventional drum brake device is effectively used to reduce the size and weight of the drum brake device and to design the arrangement, structure, etc. of other members constituting the drum brake device. The degree of freedom can be improved.

  Further, in the case of the invention described in claim 4, the driving source for rotationally driving the rotating side member is a back surface which is a surface opposite to the side where the both brake shoes are installed among the both side surfaces of the back plate. It is installed. For this reason, by effectively utilizing the space on the back side of the back plate, the reduction ratio of the reduction gear can be secured, the output of the actuator such as the feed screw mechanism can be increased, and the braking force can be secured. .

  In the case of the invention described in claim 5, the feed screw 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 one example of embodiment of this invention in the state similar to FIG. 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 X section enlarged view of FIG. 4 for demonstrating the structure and effect | action of a toggle mechanism which show an example of embodiment of this invention. The front view which shows the 1st example of a conventional structure. BB sectional drawing of FIG. CC sectional drawing of FIG. The schematic front view which shows the 2nd example of conventional structure in the state which abbreviate | omitted the drum. FIG. 10 is an enlarged DD cross-sectional view of FIG. 9. The schematic front view which shows the 3rd example of conventional structure.

  1 to 5 show an example of an embodiment of the present invention corresponding to all claims. 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 conventional leading / trailing drum brake device, 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. 6), an expansion / contraction device 23, and a driving device 24 for driving the expansion / contraction device 23.

In particular, in the case of the parking brake device constituting the drum brake device of this example, the expansion / contraction device 23 includes a strut 25 and first and second expansion levers 26 and 27.
Of these, the strut 25 has substantially the same structure as the strut 11 for automatic gap adjustment of the first example of the conventional structure shown in FIGS. As the structure of the automatic gap adjusting device, various structures known in the art described in Patent Document 7 and the like can be applied in addition to the structure of this example. Regardless of which structure is applied, the structure and operation of such an automatic gap adjusting device have been widely known, for example, as described in Patent Documents 6 to 7, etc. Since it is not a characteristic part, further detailed explanation is omitted.

The first extension lever 26 has a generally square shape as a whole. In addition, the distal end portion (the lower end portion in FIG. 4) of the first extension lever 26 has a substantially L shape from the distal end portion, and the other brake shoe 4b side of the two brake shoes 4a and 4b. A leading end side locking claw portion 28 protruding to the left (in FIG. 4) is formed.
Further, a first spherical concave surface portion 31 that can be spherically engaged with an outer peripheral surface (first spherical convex surface portion 50) of a nut 39 described later is formed on the base end surface of the first expansion lever 26.
Further, the first extension lever 26 protrudes in a substantially square shape from this edge at the middle of the edge of one of the brake shoes 4a, 4b on the brake shoe 4a side (the right side in FIG. 4). The intermediate latching claw portion 30 is formed. Further, a partial arc portion 29 is formed in a portion closer to the tip (lower end in FIG. 4) than the intermediate locking claw portion 30 in the end edge. The partial arc portion 29 has a longer distance from the first spherical concave surface portion 31 as it goes in the distal direction (downward in FIG. 4).

  The first extension lever 26 is inserted in a state where the partial arc portion 29 is in contact with a portion near the back plate 8a in the inner surface of the pressing through hole 32 of the web 7a. In this state, the first spherical concave surface portion 31 is spherically engaged with the outer peripheral surface of the nut 39 so as to be swingably displaceable. Furthermore, the front end portion of the intermediate locking claw portion 30 is on one side surface (upper surface in FIGS. 4 to 5) in the thickness direction of the web 7a, and the front end portion of the front end side locking claw portion 28 is on the web 7a. It is made to contact | abut each other side surface (lower surface of FIGS. 4-5) regarding the thickness direction. In this manner, the first extension lever 26 is positioned during non-braking as shown in FIGS.

On the other hand, the second extension lever 27 is separated from the substantially L-shaped lever body 33 and the edge of the lever body 33 on the other brake shoe 4b side (left side in FIGS. 4 to 5). A pair of plate portions 34, 34 projecting in a parallel state is provided.
Of these, the base end surface of the lever body 33 is formed with a second spherical concave surface portion 35 that can be spherically engaged with the outer peripheral surface of the nut 39 (second spherical convex surface portion 51 described later). Further, a portion of the lever main body 33 that is close to the tip end of the other brake shoe 4b side and that is sandwiched between the two plate portions 34, 34 is engageable with the base end portion of the strut 25. A concavity 36 is formed.
Such a second extension lever 27 has a spherical engagement between the second spherical concave surface portion 35 and the outer peripheral surface of the nut 39 so as to be able to swing and displace between the two plate portions 34, 34. The engaging recess 36 and the base end portion of the strut 25 are engaged and assembled with the base end portion of the strut 25 sandwiched therebetween. In this manner, the second expansion lever 27 is positioned during non-braking as shown in FIGS.

  In the case of this example, as shown in FIG. 5, the center point A of the nut 39, the partial arc portion 29 of the first expansion lever 26, and the inner peripheral surface of the pressing hole 32 of the web 7a are contacted. The contact point B and the engagement point C between the engagement recess 36 of the second extension lever 27 and the base end portion of the strut 25 increase the force while converting the direction of the force to a right angle direction. It constitutes a toggle mechanism.

  That is, in the case of this example, as will be described later, the center point A of the nut 39 moves to the center point A ′ as the nut 39 is displaced in the other axial direction (downward in FIGS. 4 to 5). As the nut 39 is displaced in the other axial direction, the first expansion lever 26 swings counterclockwise in FIGS. 4 to 5, and the contact point B moves to the contact point B ′. . Similarly, the second extension lever 27 swings clockwise in FIGS. 4 to 5, and the engagement point C moves to the engagement point C ′.

With such movement of each point, an angle θ ₁ formed by an imaginary line connecting the center point A and the contact point B and an imaginary line connecting the contact point B and the engagement point C is The angle θ ′ ₁ formed by a virtual line connecting the center point A ′ and the contact point B ′ and a virtual line connecting the contact point B ′ and the engagement point C ′ is continuously reduced. . On the other hand, an angle θ ₂ formed by a virtual line connecting the center point A and the engagement point C and a virtual line connecting the engagement point C and the contact point B is also the center point A ′ and the relationship. An angle θ ′ ₂ formed by a virtual line connecting the joining point C ′ and a virtual line connecting the engagement point C ′ and the contact point B ′ continuously decreases. As a result, the boost ratio (lever ratio) of the first and second expansion levers 26 and 27 is continuously increased. As described above, since the increase ratio of the first and second expansion levers 26 and 27 changes in a direction continuously increasing as the nut 39 is displaced in the other axial direction, the screw 38 to be described later is rotationally driven. Therefore, the output of the drive source can be reduced with the change in the boost ratio. In other words, when the output is the same, the force in the expansion direction of the expansion / contraction device 23 can be increased to exert a large braking force.

The drive device 24 includes a feed screw mechanism 37 and a drive source (not shown) that drives the feed screw mechanism 37.
Of these, the feed screw mechanism 37 includes a screw 38 corresponding to the rotation side member and the male screw member in the claims, a nut 39 corresponding to the displacement side member and the female screw member, and a rotation for preventing the rotation of the nut. A nut holder 40.

The screw 38 includes a shaft portion 41 and a large-diameter portion 42 having a larger diameter than the shaft portion 41.
Of these, the shaft portion 41 is formed with a male screw portion 43 at a portion extending from the intermediate portion of the outer peripheral surface to the tip portion (the upper end portion in FIGS. 4 to 5).
The large-diameter portion 42 is connected to the base end side (the lower end side in FIGS. 4 to 5) of the screw 38 via the other end (the lower end in FIGS. 4 to 5) and the stepped portion 44. It is provided in the state. Further, a hexagonal hole 45 is formed in the central portion of the large-diameter portion 42 and opens in the other axial direction (downward in FIG. 4).

  Such a screw 38 has its middle portion inserted into a long hole 47 formed in the web 7a and extending in the direction in which the strut 25 is disposed (left and right in FIGS. 4 to 5). Is disposed on one side (upper side of FIGS. 4 to 5) with respect to the thickness direction of the web 7a, and the base end portion is disposed on the other side (lower side of FIGS. 4 to 5) with respect to the thickness direction of the web 7a. doing. In this state, the screw 38 can be oscillated and displaced in the arrangement direction of the strut 25 in the elongated hole 47. The length of the elongated hole 47 in the direction in which the struts 25 are arranged is larger than the maximum amount of displacement that the one brake shoe 4a is displaced radially outward during braking.

  In addition, the hexagonal hole 45 of the screw 38 is engaged with a distal end portion of a connecting member 46 capable of transmitting the output of the electric motor. In such an assembled state, the connecting member 46 can be displaced relative to the screw 38 in the axial direction and swinging relative to the screw 38, while preventing relative rotation with respect to the screw 38. (It is possible to rotate in synchronization with the screw 38). For this reason, the shape seen from the axial direction of both ends of the connecting member 46 is a hexagon.

Further, in the case of this example, the base end portion of the connecting member 46 is passed through a through hole 48 (see FIG. 1) formed in the back plate 1, and the brake shoes 4a on both sides of the back plate 1 are formed. It protrudes from the back surface, which is the surface opposite to the side on which 4b is installed.
And the base end part (lower end part of FIGS. 4-5) of the said connection member 46 and the electric motor arrange | positioned at the back surface of the said backplate 1 are connected via the reduction gear (illustration omitted). Note that the base end portion of the connecting member 46 is engaged with the output shaft of the speed reducer in a state where it can be displaced in the axial direction and oscillated. The structure for rotationally driving the connecting member 46 with such an electric motor and speed reducer can be easily designed in various ways, and therefore illustration and detailed description thereof are omitted.

The nut 39 has a cylindrical shape in which an internal thread portion 49 is formed on the inner peripheral surface. Further, a pair of nut side plane portions (not shown) parallel to each other are formed at positions opposite to the circumferential direction of the outer peripheral surface. Furthermore, the first and second spherical concave surface portions 31 of the first and second expansion levers 26 and 27 are respectively formed between the nut-side flat portions in the circumferential direction of the outer peripheral surface. The first and second spherical convex surface portions 50 and 51 that can engage with the spherical surface 35 are formed.
Such a nut 39 is coupled to a portion near the tip of the screw 38 in a state where the female screw portion 49 and the male screw portion 43 of the screw 38 are screwed together.

  The nut holder 40 is made by bending a plate-shaped material, and has a rectangular holder base portion 52 and a pair of holder side plate portions 53 and 53 bent from the holder base portion 52 at a substantially right angle. Consists of. A holder-side through hole 54 having a diameter that does not interfere with the tip of the screw 38 is formed at the center of the holder base 52. The distance between the inner side surfaces of the holder side plate portions 53 and 53 is substantially the same as or slightly smaller than the width between the nut side flat portions of the nut 39.

  In such a nut holder 40, the tip end portion of the screw 38 is inserted into the holder side through hole 54, and the nut side of the nut 39 is inserted between the inner side surfaces of the holder side plate portions 53, 53. They are arranged with the flat part in between. In this way, the nut 39 is prevented from rotating.

  Further, the base end portion of the first extension lever 26 is arranged on the one brake shoe 4a side (the right side in FIGS. 4 to 5) of the portion between the inner side surfaces of the holder side plate portions 53, 53. doing. On the other hand, the base end portion of the second extension lever 27 is arranged on the other brake shoe 4b side (the left side in FIGS. 4 to 5) of the portion between the inner side surfaces of the holder side plate portions 53, 53. doing. In this manner, even when a moment is generated that causes the two expansion levers 26 and 27 to tilt in the front and back directions in FIGS. 4 to 5 during braking, the two expansion levers 26 and 27 do not tilt. For this reason, the postures of the two expansion levers 26 and 27 are stabilized, and the two expansion levers 26 and 27 can apply a stable pressing force to the both webs 7a and 7b.

  Such a feed screw mechanism 37 is a normal feed screw mechanism having irreversibility (self-locking function). For this reason, when energization to 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 37 may be reversible such as a ball nut type feed screw mechanism. However, in this case, a lock structure for ensuring the braking force even after the energization of the electric motor is stopped is separately provided in, for example, the electric motor or the speed reducer portion.

Further, in the case of this example, the engaging cylinder member 55 and the bearing member 56 are arranged in this order from the web 7a side between the stepped portion 44 of the screw 38 and the other side surface in the thickness direction of the web 7a. And are provided.
Among these, the engagement cylinder member 55 has a cylindrical shape into which the shaft portion 41 of the screw 38 can be inserted with a gap provided therein. Further, engaging portions 57 provided at a plurality of circumferential positions (for example, 3 to 4 positions) on the front end face (the upper end face in FIGS. 4 to 5) are engaged with notches or concave grooves provided on the web 7a. The web 7a is prevented from rotating by engaging with the joint. On the other hand, the spherical concave surface part 58 is formed in the base end surface (lower end surface of FIGS. 4-5).

  The bearing member 56 has an annular shape into which the shaft portion 41 of the screw 38 can be inserted with a gap provided therebetween. Further, a spherical convex surface portion 59 that can engage with the spherical concave surface portion 58 of the engagement tube member 55 so as to be swingable is provided on one end surface in the axial direction on the web 7a side (the upper end surface in FIGS. 4 to 5). Forming. On the other hand, the other axial end surface (the lower end surface in FIGS. 4 to 5) is a flat surface.

  The engaging cylinder member 55 as described above is configured so that the engaging portion 57 of the engaging cylinder member 55 is used as the engaging portion of the web 7a while the intermediate portion of the shaft portion 41 of the screw 38 is inserted inside. Engaged. On the other hand, the bearing member 56 has a spherical convex surface portion 59 of the engagement cylinder member 55 in place of the spherical convex surface portion 59 of the engagement cylinder member 55 in a state where the proximal end portion of the shaft portion 41 of the screw 38 is inserted inward. And the other end surface is brought into contact with the stepped portion 44 of the screw 38. In this manner, the displacement of the screw 38 in one axial direction (upward in FIGS. 4 to 5) is restricted, and swinging displacement with respect to the web 7a is enabled.

  The parking brake device constituting the drum brake device of the present example constructed as described above acts as follows and exhibits a braking force. During braking, the output of the electric motor is transmitted to the screw 38 via the speed reducer and the connecting member 46, and the screw 38 is rotated in a predetermined direction. Then, based on the threaded engagement between the male threaded portion 43 of the screw 38 and the female threaded portion 49 of the nut 39 constituting the toggle mechanism as described above, the nut 39 is connected to the other axial direction (the lower side of FIGS. 4 to 5). ). Then, the first spherical convex surface portion 50 of the nut 39 and the first spherical concave surface portion 31 of the first expansion lever 26 slide, and the base end portion of the first expansion lever 26 is It swings counterclockwise in FIGS. As a result, the contact point B (see FIG. 5) between the partial arc portion 29 of the first extension lever 26 and the pressing through hole 32 of the web 7a reaches the contact point B ′. Move while pressing outward.

  On the other hand, as the nut 39 is displaced in the other axial direction (the lower side in FIGS. 4 to 5), the second spherical convex surface portion 51 of the nut 39 and the second spherical concave surface of the second expansion lever 27. As the portion 35 slides, the base end portion of the second expansion lever 27 swings clockwise in FIGS. As a result, the engagement portion C (see FIG. 5) between the engagement recess 36 of the second expansion lever 27 and the base end portion of the strut 25 passes through the strut 25 to the engagement portion C ′. The web 7b of the other brake shoe 4b is moved while being pressed radially outward.

  The tip portions (the contact point B and the engagement point C) 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 these tip portions. The distance between them increases. In the case of this example, as described above, the partial arc portion 29 of the first extension lever 26 directly connects the web 7a of the one brake shoe 4a and the engagement recess 36 of the second extension lever 27. The web 7b of the other brake shoe 4b is displaced radially outward through the strut 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 (see FIG. 6) to perform braking. Such a force-increasing mechanism (toggle mechanism) composed of the first and second expansion levers 26 and 27 and the nut 39 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.

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 driving device 24 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. Of the reaction force, the component in the arrangement direction of the strut 25 and the component that causes the first and second expansion levers 26 and 27 to swing in the direction opposite to the above-described swinging direction are respectively described above. It is applied to the nut 39 as a reaction force in the opposite direction. As a result, these reaction forces cancel out in the nut 39. On the other hand, the axial component of the nut 39 is applied to the nut 39 as a force in the same direction (upward in FIGS. 4 to 5) via the first and second expansion levers 26 and 27. This is transmitted to the screw 38. However, the screw 38 has a displacement in the acting direction of the axial component (upward in FIGS. 4 to 5), as described above, the stepped portion 44 of the screw 38 and the other side surface of the web 7a. It is blocked by engaging through the engaging cylinder member 55 and the bearing member 56. Moreover, the magnitude of the axial component that occurs when the braking force is generated is limited (small). The web 7a is originally made of thick metal and has a large strength and rigidity. Accordingly, the axial component can be sufficiently supported by the web 7a, and the portion supporting the driving device 24 such as the back plate 1 that supports the web 7a is accompanied by braking. There is no great power. For this reason, members constituting the part that cancels or supports the reaction force (first and second expansion levers 26 and 27, screw 38, nut 39, web 7a, engagement cylinder member 55, bearing member 56) By providing sufficient rigidity and strength, it is not necessary to particularly increase the rigidity and strength of the portion supporting the driving device 24 such as the back plate 1 and the substrate, and the drum brake device can be reduced in weight. easy.

  Further, the feed screw mechanism 37 is arranged using the space around the web 7a of the one brake shoe 4a. For this reason, the space that is not used in the conventional drum brake device is effectively used to reduce the size and weight of the drum brake device and to design the arrangement, structure, etc. of other members constituting the drum brake device. The degree of freedom can be improved.

  The screw 38 constituting the feed screw mechanism 37 is supported so as to be swingable with respect to the web 7a of the one brake shoe 4a. Further, the screw 38 and the connecting member 46 are connected to each other in a swingable state. For this reason, even when the reaction force accompanying the braking as described above is applied as a force for swinging the screw 38, the screw 38 and the connecting member 46 can follow each other by swinging displacement. As a result, the rotational force from the electric motor can be smoothly transmitted to the screw 38 via the connecting member 46.

  In addition, the base end portion of the first extension lever 26 and the base end portion of the second extension lever 27 are disposed between the holder side plate portions 53 and 53 of the nut holder 40. For this reason, even when a moment occurs in the direction in which the first and second expansion levers 26 and 27 are inclined during braking, the postures of the first and second expansion levers 26 and 27 are stabilized. The first and second expansion levers 26 and 27 can apply a stable pressing force to the webs 7a and 7b.

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.
Also, the structure of the first and second expansion levers constituting the expansion / contraction device of the present invention, the engagement (connection) structure between the first and second expansion levers and the displacement side member, and the first The engagement structure between the extension lever and the web of one brake shoe and the engagement structure between the second extension lever and the strut are not limited to the structure of the example of the embodiment described above. That is, various structures that can constitute a toggle mechanism can be employed by the first and second expansion levers and the displacement side member. Further, the structure of the engaging portion that engages the first and second expansion levers and the displacement side member with each other so as to be able to swing and displace is not limited to the engagement between the spherical convex surface portion and the spherical concave surface portion. (The virtual straight line existing in the front and back direction of FIG. 5 through the point A in FIG. 5 is used as the center axis) and the cylindrical convex surface portion can be engaged with the cylindrical concave surface portion.

  Alternatively, the displacement side member can be a screw and the rotation side member can be a nut. For example, the nut is rotated by the output of the electric motor to displace the screw in the axial direction. Further, a partially spherical (or partially cylindrical) convex surface is provided on a part of the screw, and a toggle mechanism is configured by the screw and the first and second expansion levers. When adopting such a structure, the nut is based on an axial component of the reaction force applied to the screw from the first and second expansion levers during braking, while preventing rotation of the screw. Is prevented by the engagement of the nut and the web of one brake shoe, either directly or via another member.

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, 11c Strut 12, 12a Main plate part 13, 13a Sub-plate part 14 Axis 15 Long hole 16 Parking lever 17 Press rod 18 Pull rod 19 Electric motor 20 Reducer 21, 21a Feed screw device 22 Actuator 23 Expansion / contraction device 24 Drive device 25 Strut 26 First expansion lever 27 Second expansion Lever 28 Tip side locking claw portion 29 Partial arc portion 30 Intermediate locking claw portion 31 First spherical concave portion 32 Pressing hole 33 Lever body 34 Plate portion 35 Second spherical concave portion 36 Engaging concave portion 37 Feed screw Mechanism 38 Screw 39 40 nut holder 41 shaft portion 42 large diameter portion 43 male screw portion 44 stepped portion 45 hexagonal hole 46 connecting member 47 long hole 48 through hole 49 female screw portion 50 first spherical convex surface portion 51 second spherical convex surface portion 52 holder base 53 Holder side plate part 54 Holder side through hole 55 Engaging cylinder member 56 Bearing member 57 Engaging part 58 Spherical concave part 59 Spherical convex part

Claims (5)

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 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 strut and first and second expansion levers.
The first extension lever is engaged with a web of one brake shoe of the two brake shoes so that the web can be pressed radially outward.
The second extension lever is engaged with the distal end of the second extension lever at the base end of the strut so as to be able to press the strut radially outward.
The front end of the strut is engaged with the web of the other brake shoe of the two brake shoes so as to be able to press the web radially outward.
The drive device includes a feed screw mechanism and a drive source for driving the feed screw mechanism,
Of these, the feed screw mechanism consists of a male screw member and a female screw member,
Of these, the male screw member has a male screw portion on at least a part of the outer peripheral surface, and a tip portion of the male screw member is inserted into a through hole formed in the web of the one brake shoe. On one side with respect to the thickness direction of the web, and a base end portion on the other side with respect to the thickness direction of the web,
The female screw member has a female screw portion, and the female screw portion is screwed to the male screw portion of the male screw member,
One of the male screw member and the female screw member is a rotating side member that is rotationally driven by the drive source, and the other member is a displacement side member that is displaced in the axial direction along with the rotational movement of the rotating side member. age,
A part of the displacement side member is engaged with the base end portions of the first and second expansion levers in a state in which the displacement of the displacement side member in accordance with the displacement in the axial direction is possible.
By engaging the rotation side member and the web of the one brake shoe directly or via another member, out of the reaction force applied at the time of braking, in the direction of action of the axial component of the rotation side member A drum brake device that prevents the rotation side member from being displaced. The rotation-side member is the male screw member;
The displacement side member is the female screw member;
2. The drum brake device according to claim 1, wherein the female screw member is screwed to a distal end portion of the male screw member in a state in which the rotation is prevented and the axial displacement is possible. The male screw member has a shaft portion and a large-diameter portion provided on the proximal end side of the shaft portion,
An engagement member and a bearing member are provided between the large diameter portion and the other side surface of the web of the one brake shoe,
Of these members, the engaging member has a cylindrical shape in which the shaft portion of the male screw member can be inserted in a state where a gap is provided on the inner peripheral surface thereof, and one end surface thereof is engaged with the web of the one brake shoe. It has a spherical concave part on the other end face,
The bearing member has an annular shape in which the shaft portion of the male screw member can be inserted in a state where a clearance is provided on the inner peripheral surface thereof, and can be spherically engaged with the spherical concave surface portion of the engagement member on one end surface. It has a spherical convex surface part, the other end surface is in contact with the large diameter part of the male screw member,
The drum brake device according to claim 2, wherein the male screw member is supported in a swingable manner with respect to the web of the one brake shoe.   Through the through hole formed in the back plate, the rotation side member and the drive source installed on the back surface, which is the opposite side of the both side surfaces of the back plate, to the side where the both brake shoes are installed, The drum brake device according to any one of claims 1 to 3, wherein the drum brake device is connected to a state in which a rotational force can be transmitted directly or via another member.   The drum brake device according to any one of claims 1 to 4, wherein the feed screw mechanism has irreversibility.

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