JP2016050631A - Drum brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drum brake device which can reduce the deterioration of brake effectiveness, and makes the layout of an expansion mechanism compact.SOLUTION: A drum brake device 11 includes: a gear housing 41 which has an anchor portion interposed between adjacent ends of one of a pair of brake shoes 21 and 23 and on which the adjacent ends of the one abut; an expansion mechanism 15 which is arranged in the gear housing 41, and has a projecting screw 58 driven to expand the pair of the brake shoes 21 and 23; a switch lever 64 rotated by the operation force of the projecting screw 58; and a coupling member 13 which follows rotations of the switch lever 64 and expands the other adjacent ends of the pair of the brake shoes 21 and 23. A predetermined clearance d is provided between the one adjacent end of the brake shoe 21 and the projecting screw 58.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a drum brake device.

  An electric parking brake device is known in which a parking lever that frictionally engages a brake lining of a brake shoe with a brake drum is rotated by a motor (see, for example, Patent Document 1).

This type of electric parking brake device 501 shown in FIG. 10 includes a drum brake 510 having a parking brake mechanism and a drive unit 520 that drives the parking brake mechanism.
The drum brake 510 is roughly constituted by a pair of brake shoes 503 and 505 arranged to face an inner peripheral surface of a brake drum (not shown), a parking lever 513, a connecting member 533, a backing plate 511, and an anchor portion 517. It is configured.
The pair of brake shoes 503 and 505 are elastically supported by the first shoe hold device 507 and the second shoe hold device 509 so as to be relatively movable within a limited range, and the one end portions 503a and 505a are supported by the backing plate. It is supported by an anchor portion 517 fixed to the inner surface of 511.
The parking lever 513 is disposed along one brake shoe 505 such that a rotation support portion 513 a on one end side is rotatably supported by one brake shoe 505. A coupling member 533 is interposed between the parking lever 513 and the other brake shoe 503.

  The drive unit 520 is roughly configured by a motor 521, a rotation-linear motion conversion mechanism 522, a motion transmission member 523, and a case 524. A portion on the rotating shaft side of the motor 521 is accommodated and fixed in the case 524. The rotation-linear motion conversion mechanism 522 is a mechanism that converts the rotational motion of the rotation shaft of the motor 521 into the linear motion of the screw shaft member 527 in the axial direction. The motion transmission member 523 is a member that transmits a motion transmission force due to the linear motion of the screw shaft member 527 in the axial direction to the parking lever 513.

And when operating the electric parking brake apparatus 501, the switch for parking brakes provided in the driver's seat of the vehicle is operated. When the parking brake switch is pushed in the ON direction, the motor 521 rotates, and this rotational motion is transmitted to the rotation-linear motion conversion mechanism 522. The transmitted rotational motion is moved in the right direction in FIG. Converted to linear motion. Accordingly, the parking lever 513 rotates counterclockwise in FIG.
The parking lever 513 pushes the brake shoe 505 toward the brake drum with one end portion 505a supported by the anchor portion 517 of the case 524 as a fulcrum, and also pushes the brake shoe 503 via the connecting member 533 to the anchor portion of the case 524. The one end portion 503a supported by 517 is used as a fulcrum to push toward the brake drum.
Therefore, the parking brake is applied by frictionally engaging the pair of expanded brake shoes 503 and 505 with the inner peripheral surface of the brake drum.

JP 2012-21647 A

  The above-described electric parking brake device 501 that rotates the parking lever 513 via the rotation-linear motion conversion mechanism 522 simply replaces the mechanical forward pull with electric operation. Therefore, the brake shoes 503 and 505 that are expanded by the rotation of the parking lever 513 are only pushed to the brake drum side with the one end portions 503a and 505a supported by the anchor portion 517 as fulcrums. For this reason, there is a problem that the input portions for applying the brake shoes 503 and 505 to the brake drum are one place (two places in total), and the amount of reduction in the brake effect due to the external force after the parking brake is actuated is large. Further, in order to mount the rotation-linear motion conversion mechanism 522 driven by the motor 521, the anchor portion 517 must be configured as a member separate from the rotation-linear motion conversion mechanism 522. For this reason, there is a problem that the layout of the rotation-linear motion conversion mechanism 522 cannot be made compact and the electric parking brake device 501 is enlarged.

  The present invention has been made in view of the above situation, and an object of the present invention is to provide a drum brake device that can reduce a decrease in braking effectiveness and that has a compact layout of an expansion mechanism.

The above object of the present invention is achieved by the following configuration.
(1) A pair of brake shoes disposed so as to oppose the inner peripheral surface of the brake drum and elastically supported so as to be movable on a backing plate, and interposed between adjacent ends of the pair of brake shoes, A gear housing that is fixed to the backing plate and has an anchor portion with which one of the adjacent ends abuts, and a thrust that is disposed in the gear housing and is driven to expand each of the pair of brake shoes. An expansion mechanism having a generation mechanism, a switching lever that is rotatably provided on one of the brake shoes by a fulcrum pin, and rotated by the acting force of the thrust generation mechanism, and the other adjacent end of the pair of brake shoes And a connecting member that expands the other adjacent end of the pair of brake shoes in accordance with the rotation of the switching lever. A drum brake device characterized in that a predetermined gap is provided between one adjacent end of the one brake shoe and the thrust generating mechanism.

According to the drum brake device having the above configuration (1), when the thrust generating mechanism of the expansion mechanism is driven during braking, a predetermined gap is provided between one adjacent end of one brake shoe. Therefore, first, the switching lever is pressed by the thrust generating mechanism and rotated around the fulcrum pin, and the connecting member side of the other brake shoe is pushed to the outer peripheral side by the connecting member, and the other brake shoe is pressed by the thrust generating mechanism. The gear housing side is pushed toward the outer peripheral side and is pressed against the inner peripheral surface of the brake drum. And the supporting part of the fulcrum pin of one brake shoe is also pushed out to the outer peripheral side by the reaction force. Therefore, the supporting portion of the fulcrum pin in one brake shoe, the connecting member side and the gear housing side in the other brake shoe are pressed against the inner peripheral surface of the brake drum, respectively, and the brakes are braked at a total of three locations in the pair of brake shoes A pressing force in the direction toward the drum is applied, and a braking force is generated. Therefore, in the drum brake device having the above configuration, when the brake is operated, first, the connecting member side of the other brake shoe is pushed out to the outer peripheral side by the switching lever that is pressed and rotated by the thrust generating mechanism of the spreading mechanism, so that At the same time, the gear housing side of the other brake shoe is pushed out to the outer peripheral side by the expansion mechanism and pressed against the brake drum, and then the supporting portion of the fulcrum pin of one brake shoe also moves to the outer peripheral side by the reaction force A high braking force is obtained as a duo-servo that generates a braking force by being pushed out and pressed against the brake drum, and a decrease in braking effectiveness due to an external force after the brake operation is prevented.
In the drum brake device having the above-described configuration, the gear housing that accommodates the expansion mechanism is interposed between the adjacent ends of the pair of brake shoes and is fixed to the backing plate. One adjacent end of the pair of brake shoes comes into contact with the anchor portion of the gear housing. The anchor portion of the gear housing with which one adjacent end of the pair of brake shoes abuts acts to receive the brake reaction force. As a result, the anchor portion of the gear housing works in the same manner as a conventional anchor member, and it is not necessary to configure the anchor member and the gear housing as separate members, and the layout of the expansion mechanism becomes compact.

(2) The drum brake device according to (1), wherein the thrust generation mechanism is driven by an electric motor.

According to the drum brake device having the configuration (2) above, the thrust generating mechanism of the expansion mechanism driven by the electric motor is disposed in the gear housing interposed between the adjacent ends of the pair of brake shoes. And disposed inside the backing plate, a small electric drum brake can be provided.
(3) The switching lever is rotatably supported on the one brake shoe by the first fulcrum pin and is rotatably supported on the one brake shoe by the first fulcrum pin and the second fulcrum pin. The drum brake device according to (1) or (2), further comprising: a second switching lever that is an output side that rotates following the first switching lever.

  According to the drum brake device having the configuration (3), the first switching lever is rotatably supported by the one brake shoe by the first fulcrum pin. The second switching lever is rotatably supported on one brake shoe by the second fulcrum pin. And the switching lever which has a 1st switching lever and a 2nd switching lever comprises the booster mechanism. When the thrust generating mechanism of the expansion mechanism is driven during braking, a predetermined gap is provided between one adjacent end of one brake shoe, so first the first switching lever is the expansion mechanism. The thrust generating mechanism is pressed and rotated around the first fulcrum pin, and the second switching lever is rotated counterclockwise around the second fulcrum pin. When the second switching lever is rotated around the second fulcrum pin, the connecting member side of the other brake shoe becomes the ratio of the booster mechanism by the connecting member abutting between the first switching lever and the second fulcrum pin. In response, the drive force is boosted to the outer peripheral side, and the thrust generating mechanism pushes the gear housing side of the other brake shoe to the outer peripheral side to be pressed against the inner peripheral surface of the brake drum. The reaction force also pushes the support portions of the first fulcrum pin and the second fulcrum pin of one brake shoe to the outer peripheral side. Therefore, the supporting portions of the first and second fulcrum pins in one brake shoe, the connecting member side and the gear housing side in the other brake shoe are respectively pressed against the inner peripheral surface of the brake drum, and the pair of brake shoes A pressing force in the direction toward the inner peripheral surface of the brake drum is applied at a total of four locations, and a braking force is generated. Therefore, in the switching lever having the first switching lever and the second switching lever, the positions of the first fulcrum pin and the second fulcrum pin, and the sliding contact position where the first switching lever and the second switching lever abut each other are set. By setting appropriately, it is possible to easily select an appropriate transmission ratio of the first and second switching levers, and it becomes easy to obtain optimum adhesion between the pair of brake shoes and the drum sliding surface.

  According to the drum brake device of the present invention, since the brake is operated by the duo servo, the brake effect can be generated with less operating force (current, gear ratio, etc.) than the brake operation by leading trailing, Decreasing brake effectiveness due to external force after brake operation can be reduced, and the layout of the expansion mechanism can be compactly compiled.

  The present invention has been briefly described above. Further, the details of the present invention will be further clarified by reading through a mode for carrying out the invention described below (hereinafter referred to as “embodiment”) with reference to the accompanying drawings. .

1 is a schematic perspective view of a drum brake device according to a first embodiment of the present invention. (A) is a front view of the drum brake device shown in FIG. 1, (b) is a side view of (a). FIG. 2 is a rear perspective view in which a part of the drum brake device shown in FIG. 1 is omitted. (A) is the front view which notched a part of principal part of the drum brake apparatus shown in FIG. 2, (b) is the rear view which abbreviate | omitted a part of drum brake apparatus shown in FIG. (A) is a front view of the expansion mechanism shown to (a) of FIG. 4, (b) is a side view of (a). It is a schematic perspective view of the drum brake device concerning a 2nd embodiment of the present invention. (A) is a front view of the drum brake device shown in FIG. 6, (b) is a bottom view of (a). FIG. 7 is a rear perspective view in which a part of the drum brake device shown in FIG. 6 is omitted. (A) is the front view which abbreviate | omitted a part of drum brake device shown in FIG. 7, (b) is a rear view of (a). It is a front view of the conventional drum brake device.

Embodiments according to the present invention will be described below with reference to the drawings.
As shown in FIGS. 1 and 2, the drum brake device 11 according to the first embodiment of the present invention has a duo-servo (DS) type drum brake structure, for example, incorporated as a parking brake inside a disc brake. It is. The drum brake device 11 according to the first embodiment includes a first brake shoe 21 and a second brake shoe 23 that are a pair of brake shoes, and one of the first brake shoe 21 and the second brake shoe 23 (in FIG. 1, (Lower) adjacent gear housing 41, expansion mechanism 15 accommodated in the gear housing 41, switching lever 64 rotatably provided on the first brake shoe 21, and first brake shoe 21 and the connecting member 13 provided between the adjacent ends of the other of the second brake shoe 23 (upward in FIG. 1).

  The drum brake device 11 is integrally fixed to the vehicle body in such a posture that the backing plate 19 is substantially perpendicular to a rotation axis of a wheel (not shown). On the backing plate 19, a first brake shoe 21 and a second brake shoe 23, which are a pair of brake shoes each having a substantially arc shape, are arranged vertically along the left and right outer peripheral edges.

  The 1st brake shoe 21 and the 2nd brake shoe 23 are arrange | positioned so as to oppose the internal peripheral surface of the brake drum 25 (refer (a) of FIG. 2). The first brake shoe 21 and the second brake shoe 23 are elastically supported movably on the backing plate 19 by the first shoe hold device 27 and the second shoe hold device 29, and can be expanded. The first brake shoe 21 and the second brake shoe 23 are elastically urged in a direction approaching each other by a pair of first shoe return spring 31 and second shoe return spring 33.

The backing plate 19 between one adjacent end of the first brake shoe 21 and the second brake shoe 23 in the upper part of FIG. 1 has an expansion mechanism 15 (FIG. 4A and FIG. 4) having a speed reduction mechanism and a thrust generation mechanism. 5) is fixed. The expansion mechanism 15 constitutes a motor gear unit together with the electric motor 39. The expansion mechanism 15 is driven by the electric motor 39 to expand the space between one adjacent end of the first brake shoe 21 and the second brake shoe 23.
The gear housing 41 fixed to the backing plate 19 has anchor portions 42 and 44 with which one adjacent end of the first brake shoe 21 and the second brake shoe 23 abuts. That is, the gear housing 41 supports one adjacent end of the first brake shoe 21 and the second brake shoe 23 by the anchor portions 42 and 44.

A connecting member 13 is interposed between the other adjacent ends of the first brake shoe 21 and the second brake shoe 23 in the upper part of FIG. When the switching lever 64 is rotated around the fulcrum pin 67 by the first projecting end portion 55 of the projecting screw 58 that is the thrust generating mechanism of the spreading mechanism 15 and the connecting member 13 is pressed, the second brake shoe 23 is moved to the brake drum 25. It is moved to the inner surface. The connecting member 13 of the first embodiment is formed between the other adjacent ends of the first brake shoe 21 and the second brake shoe 23 as the lining wear of the first brake shoe 21 and the second brake shoe 23 progresses. It is an adjuster that can adjust the interval.
An expansion mechanism 15 is provided inside the gear housing 41 fixed to the backing plate 19. Since the gear housing 41 is fixed to the backing plate 19, the gear housing 41 has sufficient strength to receive the brake reaction force when the first brake shoe 21 and the second brake shoe 23 generate the braking force by the anchor portions 42 and 44. .

As shown in FIGS. 5A and 5B, the expansion mechanism 15 of the first embodiment is engaged with the first worm shaft 47 rotated by the electric motor 39 and the first worm shaft. A first worm wheel 49 that rotates, a second worm shaft 51 that rotates together with the first worm wheel 49, a second worm wheel 53 that rotates while meshing with the second worm shaft 51, A speed reduction mechanism having
Further, the first worm shaft 47 arranged obliquely intersecting with the rotation axis of the second worm wheel 53 rotatably supported by the gear housing 41 is mounted in parallel with the rotation axis of the second worm wheel 53. The gear housing 41 is rotatably supported by a pair of shaft support members 46 having an outer peripheral surface. The second worm shaft 51 arranged orthogonal to the rotation axis of the second worm wheel 53 is rotatably supported by the gear housing 41.

  As shown in FIGS. 4A and 5, the expansion mechanism 15 is rotated by the electric motor 39 to expand each of the first brake shoe 21 and the second brake shoe 23. In the second worm wheel 53, a projecting screw 58 that is a thrust generating mechanism is arranged coaxially. The protruding screw 58 includes a first protruding screw 57 having a first protruding end 55 at one end and a male threaded portion 57a at the other end, a second protruding end 59 at one end, and a fitting shaft portion 61a at the other end. A second projecting member 61 having

  The first projecting screw 57 and the second projecting member 61 are disposed coaxially with the second worm wheel 53, and the male threaded portion 57a of the first projecting screw 57 is screwed into the female threaded portion at one end of the second worm wheel 53. The fitting shaft portion 61 a of the second projecting member 61 is rotatably fitted in the fitting hole at the other end of the two worm wheel 53.

  Between the other end of the second worm wheel 53 and the second projecting end portion 59 of the second projecting member 61, a thrust bearing 62 for facilitating mutual relative rotation is interposed. The first projecting end portion 55 of the first projecting screw 57 is engaged with the web 69 of the first brake shoe 21 and is prevented from rotating. When the second worm wheel 53 is rotated, the first projecting screw 57 is The screw is fed to move to the first brake shoe 21 side.

When the first projecting end portion 55 of the first projecting screw 57 contacts the web 69 of the first brake shoe 21, the reaction force causes the second worm wheel 53 to move along with the second projecting member 61 to the second brake shoe 23 side. Move to. Therefore, the protruding screw 58 converts the rotation of the second worm wheel 53 into a linear motion by a screw mechanism. As a result, the projecting screw 58 moves the first projecting end 55 and the second projecting end 59, which are both ends projecting from the gear housing 41, forward and backward, and rotates the switching lever 64 around the fulcrum pin 67. Then, the connecting member 13 moves the connecting member 13 side of the second brake shoe 23 to the inner peripheral surface of the brake drum 25, and moves the gear housing 41 side of the second brake shoe 23 to the inner peripheral surface of the brake drum 25.
As shown in FIG. 4B, when the brake is not operated, the first projecting end 55 is in contact with a switching lever 64 described later, and the web 69 at one adjacent end of the first brake shoe 21 is in contact. A predetermined gap d is provided between the two and no contact. The second projecting end portion 59 is in contact with the web 68 at one adjacent end of the second brake shoe 23.

Furthermore, the drum brake device 11 according to the first embodiment includes a switching lever 64 as shown in FIG. The switching lever 64 is rotatably provided on the web 69 of the first brake shoe 21 and is rotated by the acting force of the spreading mechanism 15. The switching lever 64 of the first embodiment is rotatably supported on the web 69 of the first brake shoe 21 by a fulcrum pin 67.
When the switching lever 64 is braked, its lower end is pressed by the first projecting screw 57 and rotated clockwise about the fulcrum pin 67 in FIG. The connecting member 13 pushes the connecting member 13 side of the second brake shoe 23 to the outer peripheral side (right direction in FIG. 4B) by the driving force corresponding to the lever ratio, and the second protruding member 61 causes the second brake The gear housing 41 side of the shoe 23 is pushed out to the outer peripheral side and pressed against the inner peripheral surface of the brake drum 25. And the fulcrum pin 67 which is a connection part of the 1st brake shoe 21 and the switching lever 64 is pushed out to the outer peripheral side (left direction of FIG.4 (b)) with the reaction force. Therefore, the supporting portion of the fulcrum pin 67 in the first brake shoe 21 and the connecting member 13 side and the gear housing 41 side in the second brake shoe 23 are pressed against the inner peripheral surface of the brake drum 25, and the first brake shoe 21. In addition, a pressing force in the direction toward the brake drum 25 is applied at a total of three locations in the second brake shoe 23, and a braking force is generated.

  When the switching lever 64 is rotated by the acting force of the expansion mechanism 15, the adjacent end of the first brake shoe 21 and the second brake shoe 23 on the connecting member 13 side is used as the biasing force of the first shoe return spring 31. The distances between the fulcrum, the force point, and the action point are set so as to be expanded against each other.

  The switching lever 64 transmits a driving force to the connecting member 13 by an input from the expanding mechanism 15 to expand the connecting member 13 side of the second brake shoe 23 first, and abuts the inner peripheral surface of the brake drum 25. . The expansion mechanism 15 side of the second brake shoe 23 is brought into contact with the inner peripheral surface of the brake drum 25 by the input from the expansion mechanism 15, and the reaction force from the connecting member 13 and the expansion mechanism 15 to the first brake shoe 21. The acting force is transmitted to the support portion of the fulcrum pin 67.

Next, the operation of the drum brake device 11 having the above configuration will be described.
In the drum brake device 11 according to the first embodiment, when the thrust generating mechanism (protruding screw 58) of the expansion mechanism 15 is driven by the electric motor 39 during braking, at the one adjacent end of the first brake shoe 21. Since a predetermined gap d is provided between the web 69 and the first projecting end portion 55 of the first projecting screw 57, first, the switching lever 64 is pressed by the thrust generating mechanism to center on the fulcrum pin 67. The connecting member 13 pushes the connecting member 13 side (the upper side in FIG. 1) of the second brake shoe 23 to the outer peripheral side, and the thrust generating mechanism causes the second brake shoe 23 to the gear housing 41 side (FIG. 1). Middle, lower side) is pushed to the outer peripheral side and is pressed against the inner peripheral surface of the brake drum 25. And the support part of the fulcrum pin 67 of the 1st brake shoe 21 is also pushed out to the outer peripheral side with the reaction force. Therefore, the supporting portion of the fulcrum pin 67 in the first brake shoe 21 and the connecting member 13 side and the gear housing 41 side in the second brake shoe are pressed against the inner peripheral surface of the brake drum 25, respectively. In addition, a pressing force in the direction toward the inner peripheral surface of the brake drum 25 is applied at a total of three locations in the second brake shoe 23, and a braking force is generated.
Therefore, in the drum brake device 11 according to the present embodiment, when the brake is operated, first, the connecting member 13 side of the second brake shoe 23 is pushed to the outer peripheral side by the switching lever 64 that is pressed and rotated by the expansion mechanism 15. While being pressed by the brake drum 25, the expansion mechanism 15 pushes the gear housing 41 side of the second brake shoe 23 toward the outer peripheral side and presses the brake drum 25, and then the reaction force of the first brake shoe 21 The support portion of the fulcrum pin 67 is also pushed to the outer peripheral side and pressed against the brake drum 25, whereby a high parking braking force is obtained as a duo servo that generates a braking force, and the braking effectiveness is reduced by an external force after parking operation. Is prevented.

  Further, in the drum brake device 11 configured as described above, the gear unit is configured by the gear housing 41 and the expansion mechanism 15, and is interposed between one adjacent end of the first brake shoe 21 and the second brake shoe. It is fixed to the backing plate 19. One adjacent end of the first brake shoe 21 and the second brake shoe 23 abuts on the anchor portions 42 and 44 of the gear housing 41. The anchor portions 42 and 44 of the gear housing 41 with which one adjacent end of the first brake shoe 21 and the second brake shoe 23 abuts act to receive the brake reaction force. As a result, the anchor portions 42 and 44 of the gear housing 41 work in the same manner as a conventional anchor member, and it is not necessary to configure the anchor member and the gear unit (expansion mechanism 15) as separate members, and the layout of the gear unit is compact. become.

  Further, the gear housing 41 accommodates an expansion mechanism 15 that constitutes a gear unit. The expansion mechanism 15 has a projecting screw 58 as a thrust generation mechanism that expands each of the first brake shoe 21 and the second brake shoe 23 by being rotated by the electric motor 39 when the brake is operated. That is, since the expansion mechanism 15 is composed of a two-stage worm gear mechanism including the first worm shaft 47 and the second worm shaft 51, it is small and a high reduction ratio can be easily obtained. As a result, the electric motor 39 can be downsized and power consumption can be reduced. In addition, the structure of the gear of the expansion mechanism 15 is not limited to the said worm gear, The structure of gears other than a worm may be sufficient.

  Further, when the brake is operated, first, the connecting member 13 side of the second brake shoe 23 is pushed to the outer peripheral side by the switching lever 64 rotated by the protruding screw 58 protruding from the gear housing 41 and is pressed against the brake drum 25. The gear housing 41 side of the second brake shoe 23 is pushed outward by the second projecting end portion 59 of the projecting screw 58 and is pressed against the inner peripheral surface of the brake drum 25, and then the first brake shoe 21 is caused by the reaction force. The supporting portion of the fulcrum pin 67 is also pushed to the outer peripheral side and is pressed against the brake drum 25 to generate a braking force.

  Therefore, the expansion mechanism 15 having the above-described configuration for expanding the connection member 13 side and the gear housing 41 side of the first brake shoe 21 and the second brake shoe 23 during braking is the first brake shoe 21 and the second brake shoe. 23 and disposed in the gear housing 41 that is interposed between the other adjacent ends and fixed to the backing plate 19, the anchor portions 42 and 44 that receive the brake reaction force and the gear unit (the electric motor 39 and the expansion unit). The opening mechanism 15) can coexist and the gear unit can be easily arranged inside the backing plate 19 even with a small brake size.

  As a result, in the drum brake device 11 according to the present embodiment, the dimension H of the protruding portion of the gear housing 41 in which the expansion mechanism 15 is accommodated is reduced on the vehicle attachment surface side shown in FIG. That is, a small electric drum brake can be provided.

Next, a drum brake device 111 according to a second embodiment of the present invention will be described.
As shown in FIGS. 6 to 9, the drum brake device 111 according to the second embodiment has a duo-servo drum brake structure, similarly to the drum brake device 11 according to the first embodiment. It is built into the disc brake as a parking brake. In addition, the same code | symbol is attached | subjected to the structural member equivalent to the structural member of the drum brake apparatus 11 shown in the said 1st Embodiment, and the overlapping description is abbreviate | omitted.

In the drum brake device 111 according to the second embodiment, a switching lever 64A is used instead of the switching lever 64 used in the drum brake device 11 according to the first embodiment.
As shown in FIGS. 8 and 9, the switching lever 64 </ b> A includes a first switching lever 63 on the input side and a second switching lever 65 on the output side that rotates following the first switching lever 63. . The first switching lever 63 is rotatably supported on the web 69 of the first brake shoe 21 by the first fulcrum pin 67A. The second switching lever 65 is rotatably supported on the web 69 of the first brake shoe 21 by the second fulcrum pin 71. The first shoe return spring 31 urges the first switching lever 63 to rotate in the direction in which the lever end 63 a contacts the web 69 via the second switching lever 65.

  The switching lever 64A having the first switching lever 63 and the second switching lever 65 constitutes a boost mechanism. In addition, a predetermined gap d is provided between the web 69 at one adjacent end of the first brake shoe 21 and the first protruding end portion 55 of the first protruding screw 57. When the parking switch is operated, the first switching lever 63 is pressed by the first projecting screw 57 and rotated clockwise about the first fulcrum pin 67A in FIG. The second fulcrum pin 71 is rotated counterclockwise. When the second switching lever 65 is rotated counterclockwise around the second fulcrum pin 71, the second brake shoe is brought about by the connecting member 13 that is in contact between the first switching lever 63 and the second fulcrum pin 71. 23 is pushed to the outer peripheral side (rightward in FIG. 9B) by the driving force boosted according to the ratio of the booster mechanism, and the gear of the second brake shoe 23 is projected by the protruding screw 58. The housing 41 side is pushed toward the outer peripheral side and is pressed against the inner peripheral surface of the brake drum 25. The reaction force also pushes the support portion of the first fulcrum pin 67A and the support portion of the second fulcrum pin 71 of the first brake shoe 21 to the outer peripheral side (leftward in FIG. 9B). Therefore, the supporting portions of the first and second fulcrum pins 67A and 71 in the first brake shoe 21 and the connecting member 13 side and the gear housing 41 side in the second brake shoe 23 are pressed against the inner peripheral surface of the brake drum 25, respectively. Then, pressing force in the direction toward the inner peripheral surface of the brake drum 25 is applied at a total of four locations on the first brake shoe 21 and the second brake shoe 23, and a braking force is generated.

  Note that when the first switching lever 63 and the second switching lever 65 are rotated by the acting force of the spreading mechanism 15, the first and second brake shoes 21 and 23 are connected to the adjacent ends of the first brake shoe 21 and the second brake shoe 23 on the connecting member 13 side. A distance between the fulcrum, the force point, and the action point is set so as to expand against the urging force of the shoe return spring 31.

  The first switching lever 63 and the second switching lever 65 transmit the driving force to the connecting member 13 by the input from the expanding mechanism 15 to expand the connecting member 13 side of the second brake shoe 23 first, and the brake drum 25. It is made to contact | abut to the internal peripheral surface. The expansion mechanism 15 side of the second brake shoe 23 is brought into contact with the inner peripheral surface of the brake drum 25 by the input from the expansion mechanism 15, and the reaction force from the connecting member 13 and the expansion mechanism 15 to the first brake shoe 21. The acting force is transmitted to the support portions of the first and second fulcrum pins 67A and 71.

Next, the operation of the drum brake device 111 having the above configuration will be described.
In the drum brake device 111 according to the second embodiment, the switching lever 64 </ b> A includes the first switching lever 63 and the second switching lever 65 to configure a booster mechanism. The first switching lever 63 is rotatably supported on the web 69 of the first brake shoe 21 by the first fulcrum pin 67A. The second switching lever 65 is rotatably supported on the web 69 of the first brake shoe 21 by the second fulcrum pin 71.
During braking, when the thrust generating mechanism (projecting screw 58) of the expansion mechanism 15 is driven by the electric motor 39, the web 69 and the first projecting end of the first projecting screw 57 at one adjacent end of the first brake shoe 21. Since a predetermined gap d is provided between the first and second portions 55, first, the first switching lever 63 is pressed by the first projecting screw 57 of the expansion mechanism 15 and rotated about the first fulcrum pin 67A. Then, the second switching lever 65 is rotated counterclockwise around the second fulcrum pin 71. When the second switching lever 65 is rotated around the second fulcrum pin 71, the connecting member of the second brake shoe 23 is connected by the connecting member 13 that is in contact between the first switching lever 63 and the second fulcrum pin 71. 13 side is pushed out to the outer peripheral side by the driving force boosted according to the ratio of the booster mechanism, and the gear housing 41 side of the second brake shoe 23 is pushed out to the outer peripheral side by the projecting screw 58 and the inner periphery of the brake drum 25 is pushed. Pressed against the surface. The reaction force also pushes the support portions of the first fulcrum pin 67A and the second fulcrum pin 71 of the first brake shoe 21 to the outer peripheral side. Therefore, the support portions of the first and second fulcrum pins 67A and 71 in the first brake shoe 21, and the connecting member 13 side and the gear housing 41 in the second brake shoe 23 are pressed against the inner peripheral surface of the brake drum 25, respectively. Thus, a pressing force in the direction toward the inner peripheral surface of the brake drum 25 is applied at a total of four locations in the first brake shoe 21 and the second brake shoe 23, and a braking force is generated.

  Therefore, in the switching lever 64A having the first switching lever 63 and the second switching lever 65, the positions of the first fulcrum pin 67A and the second fulcrum pin 71 and the first switching lever 63 and the second switching lever 65 are mutually different. An appropriate transmission ratio of the first and second switching levers 63 and 65 can be easily selected by appropriately setting the sliding contact position P to be in contact with the first brake shoe 21 and the second brake shoe 23. It becomes easy to obtain optimum adhesion to the drum sliding surface of the brake drum 25.

  Therefore, according to the drum brake devices 11 and 111 according to the present embodiment, since the brake is operated by the duo servo, the braking effect is generated with less operating force (current, gear ratio, etc.) than the brake operation by the leading trailing. In addition, the reduction in brake effectiveness due to external force after the brake is actuated can be reduced, and the layout of the gear unit can be made compact.

  In other words, the drum brake devices 11 and 111 can actuate a brake with a duo servo having a braking effect larger than that of leading / trailing, and can generate the braking effect with a small operating force. Therefore, the above-described compact drum brake device layout is established by the compact motor gear unit in which the electric motor 39 and the expansion mechanism 15 are miniaturized.

Here, the features of the embodiment of the drum brake device according to the present invention described above will be briefly summarized below.
[1] A pair of brake shoes (a first brake shoe 21 and a second brake shoe 23) that are disposed so as to face the inner peripheral surface of the brake drum 25 and are elastically supported by the backing plate 19 so as to be movable.
An anchor portion 42 which is interposed between one adjacent ends of the pair of brake shoes (the first brake shoe 21 and the second brake shoe 23) and fixed to the backing plate 19 and which one adjacent end abuts against. , 44, and a thrust generation mechanism that is disposed in the gear housing 41 and that is driven to expand each of the pair of brake shoes (the first brake shoe 21 and the second brake shoe 23). An expansion mechanism 15 having a (protruding screw 58);
A switching lever 64 that is rotatably provided on one of the brake shoes (first brake shoe 21) by a fulcrum pin 67 and rotated by the acting force of the thrust generating mechanism (projecting screw 58);
Provided between the other adjacent ends of the pair of brake shoes, and the other adjacent ends of the pair of brake shoes (the first brake shoe 21 and the second brake shoe 23) are expanded by the rotation of the switching lever. A connecting member 13 to be
A drum brake device (11), wherein a predetermined gap (d) is provided between one adjacent end of the one brake shoe (first brake shoe (21)) and the thrust generating mechanism (projecting screw (58)).
[2] The drum brake device 11 according to [1], wherein the thrust generation mechanism is driven by an electric motor 39.
[3] The switching lever 64A is rotatably supported on the one brake shoe (first brake shoe 21) by the first fulcrum pin 67A and is input to the first switching lever 63 and the second fulcrum pin 71. And a second switching lever 65 that is rotatably supported by the one brake shoe (first brake shoe 21) and that is an output side that rotates following the first switching lever 63. The drum brake device 111 of [1] or [2].

DESCRIPTION OF SYMBOLS 11 ... Drum brake device 13 ... Connecting member 15 ... Expansion mechanism 19 ... Backing plate 21 ... 1st brake shoe (brake shoe)
23 ... Second brake shoe (brake shoe)
25 ... Brake drum 39 ... Electric motor 41 ... Gear housing 42, 44 ... Anchor section 47 ... First worm shaft 49 ... First worm wheel 51 ... Second worm shaft 53 ... Second worm wheel 58 ... Projecting screw (thrust generating mechanism) )
63 ... 1st switching lever 67 ... fulcrum pin

Claims (3)

A pair of brake shoes disposed so as to face the inner peripheral surface of the brake drum and elastically supported so as to be movable on the backing plate;
A gear housing interposed between one adjacent ends of the pair of brake shoes and fixed to the backing plate, and having an anchor portion with which the one adjacent end abuts,
An expansion mechanism having a thrust generating mechanism that is disposed in the gear housing and is driven to expand each of the pair of brake shoes;
A switching lever that is rotatably provided on one of the brake shoes by a fulcrum pin and is rotated by the acting force of the thrust generating mechanism;
A connecting member that is provided between the other adjacent ends of the pair of brake shoes and expands the other adjacent end of the pair of brake shoes by following the rotation of the switching lever;
A drum brake device, wherein a predetermined gap is provided between one adjacent end of the one brake shoe and the thrust generating mechanism.   The drum brake device according to claim 1, wherein the thrust generation mechanism is driven by an electric motor.   The switching lever is rotatably supported on the one brake shoe by a first fulcrum pin and is an input side, and the first fulcrum pin is rotatably supported by the one brake shoe by a second fulcrum pin. The drum brake device according to claim 1, further comprising: a second switching lever that is an output side that rotates following the switching lever.

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