JP2016050630A - Drum brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drum brake device equipped with an electric parting brake device which can reduce the deterioration of brake effectiveness in parking braking, and makes the layout of a motor gear unit compact.SOLUTION: A drum brake device 11 includes: a wheel cylinder 13 interposed between adjacent ends of one of a pair of brake shoes 21 and 23; a gear housing 41 which has an anchor portion on which the adjacent ends of the other of the brake shoes 21 and 23 abut; an expansion mechanism 15 which is arranged in the gear housing 41, and expands the pair of the brake shoes 21 and 23 by an electric motor 39; a switch lever 64 rotated by the operation force of the expansion mechanism 15; and a coupling member 17 which follows rotations of the switch lever 64, and expands the adjacent ends on the wheel cylinder side of the pair of the brake shoes 21 and 23.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. 6 includes a drum brake 510 provided with 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. As a result, 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 circumstances, and an object thereof is to provide a drum brake device including an electric parking brake device that can reduce a decrease in braking effectiveness of a parking brake and that has a compact layout of a motor gear unit. There is to do.

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 wheel cylinder for expanding each of the pair of brake shoes, and an anchor that is interposed between the other adjacent ends of the pair of brake shoes and fixed to the backing plate, and the other adjacent ends abut against each other A gear housing having a portion, an expansion mechanism disposed in the gear housing and driven by an electric motor to expand each of the pair of brake shoes, and the one brake shoe is rotatable. And a switching lever that is rotated by the acting force of the expansion mechanism and a wheel cylinder of the pair of brake shoes. And a connecting member that is provided between adjacent ends on the driver side and expands adjacent ends on the wheel cylinder side of the pair of brake shoes in accordance with rotation of the switching lever.

According to the drum brake device having the above configuration (1), when the expansion mechanism is driven by the electric motor during parking brake, the switching lever is pressed and rotated by the expansion mechanism. Moved to the inside of the brake shoe. Thereby, one adjacent end side of the other brake shoe is pushed out to the outer peripheral side and pressed against the brake drum, and one adjacent end side of one brake shoe is also pushed out to the outer peripheral side by the reaction force. Therefore, one adjacent end side of the one brake shoe and the other brake shoe is pressed against the brake drum to generate a braking force. Furthermore, the expansion mechanism presses the other adjacent end side of the pair of brake shoes substantially simultaneously with the pressing to the switching lever. As a result, the pair of brake shoes are applied with a pressing force in a direction toward the brake drum at two locations (four locations in total) on one adjacent end side and the other adjacent end. Therefore, when the parking brake is operated, the drum brake device having the above-described configuration is first opened by the switching lever that is pressed and rotated by the expansion mechanism, and the wheel cylinder side of the pair of brake shoes is expanded and pressed by the brake drum. As a duo servo that generates braking force when the gear housing side of the pair of brake shoes is expanded and pressed against the brake drum by the expansion mechanism, a high parking braking force can be obtained, and the braking effect by external force after parking operation can be obtained. Is prevented.
In the drum brake device configured as described above, the motor gear unit is configured by the gear housing and the expansion mechanism, and is interposed between the other adjacent ends of the pair of brake shoes and is fixed to the backing plate. . The other 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 the other 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 motor gear unit as separate members, and the layout of the motor gear unit becomes compact.

(2) The expansion mechanism is integrated with the first worm shaft rotated by the electric motor, the first worm wheel rotated by meshing with the first worm shaft, and the first worm wheel. A second worm shaft that is rotated, a second worm wheel that is rotated by meshing with the second worm shaft, and a second worm wheel that is coaxially disposed in the second worm wheel and screwing the rotation of the second worm wheel A projecting screw for expanding and contracting the other adjacent end of the pair of brake shoes by moving both ends projecting from the gear housing forward and backward by converting into linear motion by a mechanism; (1) Drum brake device.

According to the drum brake device having the configuration (2) above, the expansion mechanism is constituted by a two-stage worm gear mechanism including a first worm shaft and a second worm shaft, so that the size is small and a high reduction ratio is easy. Can get to. As a result, the electric motor can be downsized and power consumption can be reduced.
Further, at the time of parking brake, first, the wheel cylinder side of the pair of brake shoes is expanded and pressed against the brake drum by the switching lever rotated by the projecting screw projecting from the gear housing, and then the pair of the projecting screws is paired by both ends of the projecting screw. When the gear housing side of the brake shoe is expanded and pressed against the brake drum, a braking force is generated. During service braking, the wheel cylinder side of the pair of brake shoes is expanded by the wheel cylinder and pressed against the brake drum to generate a braking force, and the brake reaction force acts on the anchor portion of the gear housing.
Therefore, the expansion mechanism having the above-described configuration for expanding the wheel cylinder side and the gear housing side of the pair of brake shoes during parking brake is interposed between the other adjacent ends of the pair of brake shoes and fixed to the backing plate. By disposing in the gear housing, the anchor part that receives the brake reaction force and the motor gear unit can coexist, and the motor gear unit can be easily placed inside the backing plate even with a small brake size. Become.
(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 first switching lever is pressed and rotated by the expansion mechanism, the second switching lever is rotated in the opposite direction. When the second switching lever is rotated, the connecting member abutting between the first switching lever and the second fulcrum pin is driven by one of the brake shoes with a driving force boosted according to the ratio of the boosting mechanism. Move inward. 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, the service brake is operated by leading / trailing and the parking brake is operated by duo-servo. Therefore, the operating force (current, gear ratio, etc.) is smaller than that of the parking operation by leading / trailing. ) Can generate the braking effectiveness of the parking brake, reduce the braking effectiveness of the parking brake due to the external force after the parking brake is activated, and have an electric parking brake device with a compact motor gear unit layout. Can do.

  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 an 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). (A) And (b) is the front view and back view which abbreviate | omitted a part of drum brake device shown in FIG. (A) is the perspective view which abbreviate | omitted a part of drum brake device shown in FIG. 2, (b) is the front view which notched a part of principal part shown in (a). (A) is a front view of the expansion mechanism shown to (b) of FIG. 4, (b) is a side 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 an embodiment of the present invention operates as a leading / trailing (LT) type during service braking by the operation of the wheel cylinder 13 when the foot brake pedal is depressed. In addition, a dual mode structure that operates as a duo-servo (DS) type is provided at the time of parking brake by the operation of the electric motor 39 when the parking switch is operated. The drum brake device 11 including the electric parking brake device according to the present 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. The wheel cylinder 13 interposed between adjacent ends (upper in FIG. 1) and the other adjacent end (lower in FIG. 1) of the first brake shoe 21 and the second brake shoe 23 are interposed. The wheel cylinder side of the gear housing 41, the expansion mechanism 15 accommodated in the gear housing 41, the switching lever 64 provided rotatably on the first brake shoe 21, and the first brake shoe 21 and the second brake shoe 23. The connecting member 17 provided between adjacent ends of the main member is configured as a main member.

  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.

  A wheel cylinder 13 as a fluid actuator is interposed between adjacent ends of the first brake shoe 21 and the second brake shoe 23 in the upper part of FIG. The wheel cylinder 13 is attached to the backing plate 19, and the first piston 35 and the second piston 37 push the one adjacent end away from each other to expand the first brake shoe 21 and the second brake shoe 23. Let

A gear housing 41 containing an expansion mechanism 15 (see FIG. 4B) is fixed to the backing plate 19 between the other adjacent ends of the first brake shoe 21 and the second brake shoe 23 in the lower part of FIG. Is done. The expansion mechanism 15 and the electric motor 39 constitute a motor gear unit in the electric parking brake device. The expansion mechanism 15 is driven by the electric motor 39 to expand the other 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 the other adjacent ends of the first brake shoe 21 and the second brake shoe 23 abut. That is, the gear housing 41 supports the other adjacent ends of the first brake shoe 21 and the second brake shoe 23 by the anchor portions 42 and 44.

  When the service brake is performed by depressing the foot brake pedal, the wheel cylinder 13 is operated by pressurizing the wheel cylinder 13 and the first piston 35 and the second piston 37 that advance from both ends thereof are used for the first brake shoe 21 and the second brake. The shoe 23 is expanded and rotated from the position shown in FIG. 2 around the contact points with the anchor portions 42 and 44. As a result, the first brake shoe 21 and the second brake shoe 23 are frictionally engaged with the inner peripheral surface of the brake drum 25 to brake it. At this time, one of the first brake shoe 21 and the second brake shoe 23 is a leading shoe with respect to the rotation direction of the brake drum 25 and has a self-servo property, and the other is a trailing shoe with respect to the rotation direction of the brake drum 25. Thus, the drum brake device 11 acts as a leading / trailing drum brake. When the service brake is applied with the vehicle backed, the opposite action is obtained, so the same braking action can be obtained.

  A connecting member 17 is interposed between adjacent ends of the first brake shoe 21 and the second brake shoe 23 in the vicinity of the wheel cylinder 13 via an auto adjuster 45 that adjusts the shoe interval (FIG. 4 ( b)). The connecting member 17 is moved to the inside of the first brake shoe 21 following the rotation of the switching lever 64.

  The auto adjuster 45 is a shoe gap automatic adjustment mechanism, and defines the standby positions of the first brake shoe 21 and the second brake shoe 23 during non-braking. The auto adjuster 45 includes a guide plate 72 fixed to the web 68 of the second brake shoe 23, a wedge-shaped plate 73 interposed between the one end 17 a of the connecting member 17 and the guide plate 72, and a wedge-shaped plate 73. A tension coil spring 75 that biases the other adjacent end side of the second brake shoe 23 and a tension coil spring 74 that biases the connecting member 17 toward the guide plate 72 are configured. The auto adjuster 45 changes the standby positions of the first brake shoe 21 and the second brake shoe 23 according to the wear of the friction material. That is, when the amount of movement of the first brake shoe 21 and the second brake shoe 23 during braking increases due to wear of the friction material, the guide plate 72 fixed to the second brake shoe 23 is pressed via the wedge-shaped plate 73. The gap between one end of the connecting member 17 and the guide plate 72 is widened, and the standby positions of the first brake shoe 21 and the second brake shoe 23 during non-braking are separated from each other, and the shoe gap (the total size of the shoe gaps on both sides) ) Is maintained substantially constant.

  An expansion mechanism 15 is provided inside the gear housing 41 fixed to the backing plate 19. The gear housing 41 is formed as a block body in which half bodies are combined, and is integrally assembled and fixed to the backing plate 19 so that the first brake shoe 21 and the second brake shoe 23 generate braking force. It has sufficient strength to receive the brake reaction force at the anchor portions 42 and 44.

As shown in FIGS. 5A and 5B, the expansion mechanism 15 of the present 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, a second worm shaft 51 that rotates together with the first worm wheel 49, and a second worm wheel 53 that rotates while meshing with the second worm shaft 51. .
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. Further, the second worm shaft 51 arranged orthogonal to the rotation axis of the second worm wheel 53 is geared by a pair of pivot pins 48 having a mounting outer peripheral surface parallel to the rotation axis of the second worm wheel 53. The housing 41 is rotatably supported.

  As shown in FIGS. 4B 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. A projecting screw 58 is coaxially disposed in the second worm wheel 53. 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. And a second projecting shaft 61 having The first projecting screw 57 and the second projecting shaft 61 are arranged coaxially with the second worm wheel 53, the male threaded portion 57 a of the first projecting screw 57 is screwed into the female threaded portion at one end of the second worm wheel 53, and 2 The fitting shaft portion 61a of the second protruding shaft 61 is rotatably fitted in the fitting hole at the other end of the worm wheel 53. Between the other end of the second worm wheel 53 and the second projecting end 59 of the second projecting shaft 61, a thrust bearing 62 is provided for facilitating mutual relative rotation. 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 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 shaft 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. Thus, 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, so that the first brake shoe 21 and the second brake shoe 23 The other adjacent end is expanded. As shown in FIG. 4B, when the parking brake is not operated, the first protruding end 55 is located at the other adjacent end of the first switching lever 63 and the first brake shoe 21 in the switching lever 64 described later. The second projecting end portion 59 is not in contact with the other adjacent end of the second brake shoe 23.

  Furthermore, the electric parking brake device according to the present embodiment includes a switching lever 64. 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 present embodiment 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 a first fulcrum pin 67. 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 64 having the first switching lever 63 and the second switching lever 65 constitutes a boost mechanism. When the parking brake is actuated, the first switching lever 63 is pressed by the first protruding screw 57 and rotates counterclockwise as shown in FIG. 4B, thereby rotating the second switching lever 65 clockwise. When the second switching lever 65 is rotated clockwise, the connecting member 17 that is in contact between the first switching lever 63 and the second fulcrum pin 71 is boosted in accordance with the ratio of the boost mechanism. The first brake shoe 21 is moved inside by the driving force. As a result, one adjacent end of the second brake shoe 23 is pushed outward (to the left in FIG. 4) and is pressed against the brake drum 25. At the same time, the reaction force causes the second fulcrum pin 71, which is a connecting portion between the first brake shoe 21 and the second switching lever 65, to be pushed outward (to the right in FIG. 4). Is pushed by the brake drum 25, and a braking force is generated by the first brake shoe 21 and the second brake shoe 23.

  When the first switching lever 63 and the second switching lever 65 are rotated by the acting force of the spreading mechanism 15, the connecting member 17 that follows the rotation of the first switching lever 63 and the second switching lever 65 is the first. The distance between the fulcrum, the force point, and the action point is such that the adjacent ends of the brake shoe 21 and the second brake shoe 23 on the anchor portions 42 and 44 side are expanded against the urging force of the second shoe return spring 33. Is set.

  The first switching lever 63 and the second switching lever 65 expand the wheel cylinder side of the first brake shoe 21 and the second brake shoe 23 first by the input from the expansion mechanism 15 and thereby the inner peripheral surface of the brake drum 25. Abut. After the positions of the first brake shoe 21 and the second brake shoe 23 are determined, a reaction force from the inner peripheral surface of the brake drum 25 acts on the first brake shoe 21 and the second brake shoe 23 to expand the expansion mechanism 15. The first switching lever 63 and the second switching lever 65 are rotated to transmit the acting force to the connecting member 17 when the acting force (expanding force) becomes equal to or greater than a predetermined value.

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 present embodiment, when the expansion mechanism 15 is driven by the electric motor 39 during parking brake, the switching lever 64 is pressed and rotated by the expansion mechanism 15, so that the connecting member 17 is It moves to the inside of the first brake shoe 21. Accordingly, one adjacent end of the second brake shoe 23 is pushed out to the outer peripheral side and pressed against the brake drum 25, and one adjacent end of the first brake shoe 21 is also pushed out to the outer peripheral side by the reaction force. Therefore, one adjacent end side of each of the first brake shoe 21 and the second brake shoe is pressed against the brake drum 25 to generate a braking force. Furthermore, the expansion mechanism 15 also presses the other adjacent end side of the first brake shoe 21 and the second brake shoe 23 substantially simultaneously with the pressing to the switching lever 64. As a result, the first and second brake shoes 21 and 23 are applied with a pressing force in the direction toward the brake drum 25 at two locations (four locations in total) on one adjacent end side and the other adjacent end.
Therefore, the drum brake device 11 including the electric parking brake device according to the present embodiment is configured such that when the parking brake is operated, first, the first brake shoe 21 and the second brake lever 21 are rotated by the switching lever 64 that is pressed and rotated by the expansion mechanism 15. One adjacent end side (wheel cylinder 13 side) of the brake shoe 23 is expanded and pressed by the brake drum 25, and then the other adjacent one of the first brake shoe 21 and the second brake shoe 23 by the expansion mechanism 15. When the end side (gear housing 41 side) is expanded and pressed against the brake drum 25, 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.

  In the drum brake device 11 configured as described above, the motor gear unit is configured by the gear housing 41 and the expansion mechanism 15, and is interposed between the other adjacent ends of the first brake shoe 21 and the second brake shoe. It is fixed to the backing plate 19. The other adjacent ends of the first brake shoe 21 and the second brake shoe 23 abut 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 the other adjacent ends of the first brake shoe 21 and the second brake shoe 23 abut 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 motor gear unit (expansion mechanism 15) as separate members, and the layout of the motor gear unit. Becomes compact.

  Further, the gear housing 41 accommodates an expansion mechanism 15 that constitutes a motor gear unit. The expansion mechanism 15 has a projecting screw 58 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 parking 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.

  When the parking brake is operated, first, the wheel cylinder 13 side of the first brake shoe 21 and the second brake shoe 23 is expanded by the switching lever 64 rotated by the projecting screw 58 projecting from the gear housing 41 to the brake drum 25. Then, the gear housing 41 side of the first brake shoe 21 and the second brake shoe 23 is expanded by the first and second projecting end portions 55 and 59 of the projecting screw 58, and the inner peripheral surface of the brake drum 25. A braking force is generated by being pressed by the. During service braking, the wheel cylinder 13 opens the wheel cylinder 13 side of the first brake shoe 21 and the second brake shoe 23 and presses against the brake drum 25 to generate a braking force. It acts on the anchor portions 42 and 44 of the.

  Therefore, the expansion mechanism 15 configured as described above to expand the wheel cylinder 13 side and the gear housing 41 side of the first brake shoe 21 and the second brake shoe 23 at the time of parking brake is the first brake shoe 21 and the second brake shoe. By being disposed in the gear housing 41 interposed between the other adjacent ends of the shoe 23 and fixed to the backing plate 19, the anchor portions 42 and 44 that receive the brake reaction force and the motor gear unit (electric motor 39 And the expansion mechanism 15) can coexist, and the motor 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.

  Further, the switching lever 64 in the drum brake device 11 of the present embodiment has a first switching lever and a second switching lever to constitute a boosting mechanism. The first switching lever 63 is rotatably supported on the web 69 of the first brake shoe 21 by a first fulcrum pin 67. The second switching lever 65 is rotatably supported on the web 69 of the first brake shoe 21 by the second fulcrum pin 71. When the first switching lever 63 is pressed and rotated by the first projecting screw 57 of the expansion mechanism 15, the first switching lever 63 rotates the second switching lever 65 in the opposite direction. When the second switching lever 65 is rotated, the connecting member 17 that is in contact between the first switching lever 63 and the second fulcrum pin 71 is driven by a driving force that is boosted according to the ratio of the boosting mechanism. Move to the inside of the first brake shoe 21.

  Therefore, in the switching lever 64 having the first switching lever 63 and the second switching lever 65, the positions of the first fulcrum pin 67 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 device 11 according to the present embodiment, since the service brake is operated by leading trailing and the parking brake is operated by duo servo, the operating force (current) is smaller than the parking operation by leading trailing. , Gear ratio, etc.) and the parking brake's braking effect due to external force after the parking brake is actuated can be reduced, and the motor gear unit layout is compactly integrated. An apparatus can be provided.
That is, the drum brake device 11 can actuate the parking 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. Thus, the compact motor gear unit in which the electric motor 39 and the expansion mechanism 15 are miniaturized forms the layout of the compact electric parking brake device described above.

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.
The pair of brake shoes (the first brake shoe 21 and the second brake shoe 23) are interposed between adjacent one ends of the pair of brake shoes (the first brake shoe 21 and the second brake shoe 23). A wheel cylinder 13 for expanding,
An anchor portion 42 which is interposed between the other 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 the other adjacent ends abut against each other. , 44 and a gear housing 41 disposed in the gear housing 41 and driven by an electric motor 39 to expand each of the pair of brake shoes (first brake shoe 21 and second brake shoe 23). An expansion mechanism 15 for causing
A switching lever 64 provided rotatably on one of the brake shoes (first brake shoe 21) and rotated by the acting force of the expansion mechanism 15,
Provided between adjacent ends of the pair of brake shoes on the wheel cylinder side and adjacent to the wheel cylinder side of the pair of brake shoes (first brake shoe 21 and second brake shoe 23) following the rotation of the switching lever. A connecting member 17 that widens the end;
A drum brake device 11 comprising:
[2] The expansion mechanism 15 includes a first worm shaft 47 rotated by the electric motor 39, a first worm wheel 49 rotated by meshing with the first worm shaft 47, and the first A second worm shaft 51 that rotates integrally with the worm wheel 49, a second worm wheel 53 that rotates while meshing with the second worm shaft 51, and the second worm wheel 53 are arranged coaxially. The rotation of the second worm wheel 53 is converted into a linear motion by a screw mechanism, whereby both end portions 55 and 59 protruding from the gear housing 41 are moved forward and backward to move the pair of brake shoes (the first brake shoe 21 and the first brake shoe 21). And a projecting screw 58 for expanding the other adjacent end of the two brake shoes 23). 11.
[3] The switching lever 64 is rotatably supported on the one brake shoe (first brake shoe 21) by a first fulcrum pin 67 and is provided on the input side by a first switching lever 63 and a 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 11 of [1] or [2].

DESCRIPTION OF SYMBOLS 11 ... Drum brake device 13 ... Wheel cylinder 15 ... Expansion mechanism 17 ... Connecting member 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 portion 47 ... First worm shaft 49 ... First worm wheel 51 ... Second worm shaft 53 ... Second worm wheel 58 ... Projecting screw 63 ... First Switching lever 64 ... Switching lever 65 ... Second switching lever 67 ... First fulcrum pin 71 ... Second 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 wheel cylinder interposed between one adjacent ends of the pair of brake shoes, and for expanding each of the pair of brake shoes;
A gear housing that is interposed between the other adjacent ends of the pair of brake shoes and is fixed to the backing plate, and having an anchor portion with which the other adjacent end abuts;
An expansion mechanism disposed within the gear housing and configured to expand each of the pair of brake shoes by being driven by an electric motor;
A switching lever provided rotatably on one of the brake shoes and rotated by the acting force of the expansion mechanism;
A connecting member that is provided between adjacent ends of the pair of brake shoes on the wheel cylinder side and that expands the adjacent ends of the pair of brake shoes on the wheel cylinder side according to the rotation of the switching lever;
A drum brake device comprising:   The expansion mechanism is rotated integrally with the first worm wheel rotated by the electric motor, the first worm wheel rotated by meshing with the first worm shaft, and the first worm wheel. A second worm shaft, a second worm wheel meshed with the second worm shaft, and a second worm wheel coaxially disposed in the second worm wheel, wherein the rotation of the second worm wheel is straightened by a screw mechanism. 2. A projecting screw for expanding and contracting the other adjacent end of the pair of brake shoes by moving both ends projecting from the gear housing forward and backward by converting into motion. The drum brake device described.   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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