JP5950731B2 - Parking brake mechanism and electric parking brake - Google Patents

Description

  The present invention relates to a parking brake mechanism and an electric parking brake.

  The drum brake device is classified into a leading trailing type, a two-leading type, a duo servo type, and the like depending on a difference between a fulcrum position where the brake shoe opens and an anchor structure.

  For example, as shown in FIG. 17, the duo servo drum brake 501 includes a pair of brake shoes, a first brake shoe 503 and a second brake shoe 505, disposed in a cylindrical brake drum 509 so as to face each other. In the first brake shoe 503, the forward rotation direction inlet side (upper side in the figure) of the brake drum 509 is an input portion, and the forward rotation direction outlet side (lower side in the figure) of the brake drum 509 is provided via an adjuster 515, for example. The second brake shoe 505 is connected to the inlet side (the lower side in the figure). On the other hand, the outlet side (the upper side in the figure) of the second brake shoe 505 is brought into contact with the anchor portion 507 provided on the backing plate, and the anchor reaction force acting on the first brake shoe 503 and the second brake shoe 505 is generated. The anchor unit 507 is adapted to receive it.

  As a result, when the first brake shoe 503 and the second brake shoe 505 are expanded and pressed against the inner peripheral surface 511 of the brake drum 509, the anchor reaction force acting on the first brake shoe 503 is applied to the inlet of the second brake shoe 505. Since the second brake shoe 505 acts to press the second brake shoe 505 against the inner peripheral surface 511 of the brake drum 509, both the first brake shoe 503 and the second brake shoe 505 operate as leading shoes, and the gain is very high. High braking force can be obtained.

  Such a duo-servo type drum brake 501 not only can obtain a very high braking force, but also can be easily reduced in size compared to a leading trailing type or a two leading type drum brake device, and can be incorporated into a disc brake. It may be incorporated as a parking brake mechanism (see, for example, Patent Document 1).

JP 2003-28212 A

  However, the duo-servo type drum brake 501 as the parking brake mechanism has a first brake shoe from the state before the operation shown in FIG. 17 (A) by the unfolding force of the unillustrated unfolding mechanism (the white arrow in the figure). When the anchor portion 507 side of 503 and the second brake shoe 505 is expanded, the first brake shoe 503 and the second brake shoe 505 that are expanded at the initial stage of operation shown in FIG. Away from the inner surface 511 of the brake drum 509. At this time, the first brake shoe 503 and the second brake shoe 505 move to the adjuster 515 side by a reaction force (arrow in the figure) from the inner peripheral surface 511.

  At the end of the operation shown in FIG. 17C, the first brake shoe 503 and the second brake shoe 505 move along the curvature of the inner peripheral surface 511 of the brake drum 509, and the brake drum 509 opposite to the anchor portion 507. Is in pressure contact with the inner peripheral surface 513. Therefore, from the inner peripheral surface 513, an upward reaction force (arrow in the figure) toward the anchor portion 507 acts on the first brake shoe 503 and the second brake shoe 505.

At this time, since the first brake shoe 503 and the second brake shoe 505 do not have a spreading function on the side opposite to the anchor portion 507 (generally, the adjuster 515 side), the first brake shoe 503 and the second brake shoe 505 have close adhesion to the inner peripheral surface 513 of the brake drum 509. There may be a shortage.
As a result, the first brake shoe 503 and the second brake shoe 505 are slightly displaced in the direction in which the outlet side of the second brake shoe 505 contacts the anchor portion 507 until the parking braking force shown in FIG. Since the expansion force of the expansion mechanism is reduced, a so-called loosening phenomenon may occur when the parking braking force is generated.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a parking brake mechanism and an electric parking brake that can prevent a loosening phenomenon that occurs when a parking braking force is generated in a duo-servo parking brake. .

The above object of the present invention is achieved by the following configuration.
(1) A first brake shoe disposed along the inner peripheral surface of the brake drum, one end of which is an input side from the expansion mechanism, and an inner peripheral surface of the brake drum facing the first brake shoe. And a second brake shoe, one end of which is an input side from the expansion mechanism and the other end is connected to the other end of the first brake shoe via an adjuster, and a backing plate. An anchor portion that is in contact with one end side of the first brake shoe and one end side of the second brake shoe, and is rotatably supported by the first brake shoe, and an input side end is in contact with the expansion mechanism. and a transmission lever which abuts the adjuster output end is connected to the other end of the second brake shoe with a second end of said first brake shoe and the adjuster A parking brake mechanism, wherein a predetermined gap is provided between the two.

According to the parking brake mechanism having the above configuration (1), when the parking brake is operated, the one end sides of the first brake shoe and the second brake shoe which are spread apart are separated from the anchor portion, and the inner peripheral surface of the brake drum. Press contact. At this time, the input from the spreading mechanism to the one end side of the first brake shoe and the input side end of the transmission lever is input to the other end side of the second brake shoe connected to the adjuster via the output side end of the transmission lever. Communicated.
After the parking brake operation is completed, until the parking braking force is generated by the self-boosting effect of the duo-servo drum brake, one end of the first brake shoe or the second brake shoe comes into contact with the anchor portion and the brake drum When closely contacting the inner peripheral surface, these brake shoes are slightly displaced, but the reaction force generated on the adjuster side by the parking braking force is transmitted to the expansion mechanism via the transmission lever and the other end side of the first brake shoe. The gap provided between the adjuster and the adjuster absorbs this minute displacement. Therefore, the expansion force of the expansion mechanism does not decrease, and the loosening that occurs when the parking braking force is generated is prevented. As a result, the safety of the parking brake is improved.

(2) The parking brake mechanism having the configuration of (1), wherein a stepped sleeve is penetrated through the first web of the first brake shoe, and the stepped sleeve is penetrated and supported by the backing plate. The lift of the first brake shoe is regulated by the pressing of a spring seat and a sleeve pressing spring that are penetrated by the pin and sandwiched between the stepped portion on the opposite side of the backing plate across the first web. The transmission lever is sandwiched between the first web and the backing plate through the stepped sleeve so as to be rotatable around the stepped sleeve and partially bent into a U shape. A parking brake machine that is held by the first brake shoe with the first web sandwiched by one part. .

  According to the parking brake mechanism having the above configuration (2), the stepped sleeve regulates the lifting of the first brake shoe through the spring seat and the sleeve pressing spring by the through pin supported by the backing plate. . The transmission lever is disposed between the first web and the backing plate, and is rotatable around a stepped sleeve that is passed therethrough. The transmission lever that is rotatable about the stepped sleeve is held on the first web by the sandwiching piece that sandwiches the first web. Therefore, both the first web and the transmission lever are supported via the stepped sleeve, and the first brake shoe is prevented from being lifted and the transmission lever is rotatably supported.

(3) A first brake shoe disposed along the inner peripheral surface of the brake drum, one end of which is the input side from the spreading mechanism, and an inner peripheral surface of the brake drum facing the first brake shoe. And a second brake shoe, the other end of which is connected to the other end of the first brake shoe via an adjuster, and a backing plate, and one end of the first brake shoe and the second brake An anchor portion that is in contact with one end of the shoe, and is rotatably supported by the first brake shoe, an input side end is in contact with the expansion mechanism, and an output side end is in contact with the adjuster, And a switching lever that expands the other end side before one end side of the first brake shoe and the second brake shoe by an input from the expanding mechanism. Parking brake mechanism.

According to the parking brake mechanism having the above configuration (3), when the parking brake is operated, the other end side (adjuster side) of the first brake shoe and the second brake shoe is one end by the input from the expansion mechanism via the switching lever. It is expanded before the side (anchor part side). Therefore, the one end side of the first brake shoe and the second brake shoe is moved to the anchor portion side at the time of expansion, and does not leave the anchor portion. Accordingly, since the first brake shoe and the second brake shoe have an expanding force on both the other end side and the one end side, the adhesion between the first brake shoe and the second brake shoe and the drum sliding surface is improved. In addition, loosening that occurs when parking braking force is generated is prevented. As a result, the safety of the parking brake is improved.
(4) The parking brake mechanism configured as described in (3) above, wherein the switching lever is rotatably supported by the first brake shoe by a first fulcrum pin and serves as an input side; A second switching lever that is rotatably supported by the first brake shoe by a fulcrum pin and that is an output side that rotates following the first switching lever, and the first switching lever includes the expansion mechanism. And the first web is sandwiched in the direction of the rotation axis, and the second switching lever is sandwiched in the direction of the rotation axis between the adjuster projection end provided in the adjuster and the first web. A parking brake mechanism characterized by that.

According to the parking brake mechanism having the configuration (4), the first switching lever is rotatably held on the first brake shoe by the first fulcrum pin and the second switching lever is held by the second fulcrum pin. Therefore, the position of the first fulcrum pin and the second fulcrum pin, the position of the sliding contact between the expansion mechanism and the first switching lever, the position of the sliding contact between the first switching lever and the second switching lever, the second switching lever By setting the position of the sliding contact between the first brake shoe and the adjuster, an appropriate transmission ratio of the first and second switching levers can be easily selected, and the first brake shoe, the second brake shoe, the drum sliding surface, It becomes easy to obtain the optimum adhesiveness.
Further, the first switching lever is sandwiched in the rotation axis direction between the expansion mechanism protruding end and the first web, and the second switching lever is sandwiched in the rotation axis direction between the adjuster protruding end and the first web. It is. Therefore, even if the first switching lever and the second switching lever have a flat plate shape, their contact points do not come off, and a simple shape and an inexpensive configuration can be achieved.

(5) An electric parking brake including the parking brake mechanism having any one of the above configurations (1) to (4), wherein a parking cable connected to the spreading mechanism is provided on a back side surface of the backing plate. An electric parking brake comprising a drive mechanism for pulling driving.

  According to the electric parking brake having the configuration (5), the parking mechanism is pulled by the driving mechanism disposed on the back side surface of the backing plate, so that the expansion mechanism can be operated electrically.

According to the parking brake mechanism of the present invention, in the duo servo parking brake, it is possible to prevent a loosening phenomenon that occurs when a parking braking force is generated.
Moreover, according to the electric parking brake according to the present invention, the parking brake can be electrified.

  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. .

It is a perspective view of the drum brake which constitutes the parking brake mechanism concerning a 1st embodiment of the present invention. It is a front view of the drum brake shown in FIG. FIG. 3 is a right side view of the drum brake shown in FIG. 2. FIG. 3 is a rear view of the drum brake shown in FIG. 2. FIG. 3 is a top view of the drum brake shown in FIG. 2. FIG. 5 is a VV cross-sectional arrow view of the drum brake shown in FIG. 2. It is a VII-VII cross section arrow expansion mechanism figure of the drum brake shown in FIG. It is a VIII-VIII cross-sectional arrow view of the drum brake shown in FIG. It is action explanatory drawing showing the operation before the drum brake shown in FIG. 2 (A), the operation initial stage (B), operation completion (C), and braking force generation | occurrence | production (D). It is a perspective view of the drum brake which comprises the parking brake mechanism of 2nd Embodiment which concerns on this invention. It is a front view of the drum brake shown in FIG. It is a perspective view of the drum brake shown in FIG. FIG. 12 is a cross-sectional view taken along the line XIII-XIII of the drum brake shown in FIG. 11. It is a schematic block diagram of the drum brake before the 1st switching lever and 2nd switching lever which were shown in FIG. 11 act | operate. It is a schematic block diagram of the drum brake after the 1st switching lever and the 2nd switching lever which were shown in FIG. 11 act | operated. It is action explanatory drawing showing the operation before the drum brake shown in FIG. 11 (A), the operation initial stage (B), operation completion (C), and braking force generation | occurrence | production (D). It is action explanatory drawing showing before operation (A) of the duo servo type drum brake which comprises the conventional parking brake mechanism, the operation initial stage (B), operation completion (C), and braking force generation | occurrence | production (D).

Embodiments according to the present invention will be described below with reference to the drawings.
As shown in FIGS. 1 to 5, the drum brake 11 constituting the parking brake mechanism according to the first embodiment is a so-called duo servo drum brake. The drum brake 11 is integrally fixed to the vehicle body in such a posture that the backing plate 13 is substantially perpendicular to the rotational axis of the wheel. A first brake shoe 15 and a second brake shoe 17, which are a pair of brake shoes each having a substantially arc shape, are arranged on the backing plate 13 vertically along the left and right outer peripheral edges.

  The first brake shoe 15 is disposed along the inner peripheral surface of a brake drum (not shown), and the entrance side (one end side) in the drum forward rotation direction is the input side from the toggle type spreading mechanism 19. The second brake shoe 17 is disposed along the inner peripheral surface of the brake drum so as to face the first brake shoe 15, and the drum forward rotation direction outlet side (one end side) is an input side from the expansion mechanism 19.

As shown in FIG. 7, the spreading mechanism 19 includes a lever member 25 and a strut 27 that are connected to each other by a connecting pin 23 so as to be relatively rotatable, and the connecting pin 23 is substantially parallel to the backing plate 13. It is arranged with the posture.
The lever member 25 is made of a metal plate, and is provided with an engaging portion 29 (concave portion) that is engaged with the second brake shoe 17. Further, a cable latching portion 31 is provided at the other end of the lever member 25, and a latching member fixed to the tip of the parking cable 33 is latched.
The strut 27 is formed by bending two metal plates into a substantially U shape. A lever member 25 is disposed inside the strut 27, and the other end opposite to the connecting pin 23 is in close contact with each other. An engagement portion 29 (concave portion) that is bent inward and integrally overlapped with the first brake shoe 15 is provided. The strut 27 is provided with a leaf spring 35 bent into a predetermined shape.

  The backing plate 13 is equipped with an anchor portion 37. The anchor portion 37 is formed by cutting or forging a metal block and is fixed to the backing plate 13. The anchor portion 37 is in contact with the drum forward rotation direction inlet side (one end side) of the first brake shoe 15 and the drum forward rotation direction outlet side (one end side) of the second brake shoe 17.

  The expansion mechanism 19 is supported by contacting an anchor portion 37 with a head 39 of a plurality of bolts integrally fixed to a vehicle carrier (not shown) together with the backing plate 13. Is provided with an insertion hole 41 through which the parking cable 33 is inserted. The cable latching portion 31 is positioned at a portion that substantially coincides with the insertion hole 41 in a direction substantially perpendicular to the backing plate 13, and the parking cable 33 is inserted into the insertion hole from the vehicle body side (lower side in FIG. 7). By being inserted, it is hooked on the cable hooking portion 31. A tension coil spring 43 shown in FIG. 2 is disposed substantially horizontally between one end sides of the first brake shoe 15 and the second brake shoe 17 supported by the anchor portion 37.

  The adjuster 21 adjusts the distance between the other ends of the first brake shoe 15 and the second brake shoe 17 in accordance with the progress of wear of the lining 45 of the first brake shoe 15 and the second brake shoe 17. The adjuster 21 moves the distance between the other ends of the first brake shoe 15 and the second brake shoe 17 by the operation of an adjuster lever (not shown) whose tip is brought into contact with the adjustment gear 47 on the adjuster by the adjuster spring 85. Configured to automatically adjust.

  Each of the first brake shoe 15 and the second brake shoe 17 is held on the backing plate 13 by a first shoe hold-down device 49 and a second shoe hold-down device 51 so as to be expandable.

  Further, the transmission lever 53 shown in FIGS. 1, 2, and 4 is rotatably supported by the first brake shoe 15. As shown in FIGS. 4 and 8, the transmission lever 53 has an input side end in contact with the expansion mechanism 19 and an output side end in contact with the adjuster 21. The shape of the output side end of the transmission lever 53 is set so that a predetermined gap S1 is formed between the other end side of the first brake shoe 15 and the adjuster 21 (see FIG. 8).

  In the first embodiment, the transmission lever 53 is rotatably supported on the first web 55 of the first brake shoe 15 by the first shoe hold-down device 49. As shown in FIG. 6, the first shoe holddown device 49 includes a stepped sleeve 57, a penetrating pin 59, a spring seat 61, and a sleeve pressing spring 63. A stepped sleeve 57 is passed through the first web 55 of the first brake shoe 15. The stepped sleeve 57 is penetrated by a penetration pin 59 that is penetrated and supported by the backing plate 13. The stepped sleeve 57 has a first brake 55 pressed by a spring seat 61 and a sleeve pressing spring 63 that are interposed between a through pin 59 and a stepped portion 57a opposite to the backing plate 13 across the first web 55. The lifting of the shoe 15 is restricted. The transmission lever 53 passes through the stepped sleeve 57 between the first web 55 and the backing plate 13 and is rotatable around the sleeve 57. Further, the transmission lever 53 is held by the first brake shoe 15 with the first web 55 sandwiched by a sandwiching piece 65 that is partially bent into a U shape.

  Note that the second shoe hold-down device 51 is configured by omitting the stepped sleeve 57 from the configuration of the first shoe hold-down device 49. Accordingly, the second shoe hold-down device 51 is configured such that the sleeve pressing spring 63 directly presses the second web 67.

Next, the operation of the drum brake 11 having the above configuration will be described.
In the drum brake 11 that constitutes the parking brake mechanism according to the first embodiment, when the parking brake is activated, the parking cable 33 acts in a direction substantially perpendicular to the backing plate 13 in accordance with the operation of an operation member (such as an operation lever) in the vehicle compartment. (Downward in FIG. 7).

Then, when the lever member 25 is rotated counterclockwise, the second brake shoe 17 is pushed outward (rightward in FIG. 7) and is pressed against the inner peripheral surface of a brake drum (not shown). When the connecting pin 23 is moved in the left direction in FIG. 7 by using the engaging portion 29 with the second brake shoe 17 by the reaction force from the brake drum, the strut 27 is also moved in the left direction.
With this movement, the strut 27 presses one end side of the first brake shoe 15 and the input side end of the transmission lever 53 to the left in FIG. The first brake shoe 15 and the transmission lever 53 pressed by the strut 27 are rotated counterclockwise around the stepped sleeve 57 of the first shoe holddown device 49 of FIG. And the one end side of the 1st brake shoe 15 and the 2nd brake shoe 17 which were expanded is mutually separated from the anchor part 37, and press-contacts to the internal peripheral surface of a brake drum.
At this time, since a predetermined gap S1 is provided between the other end side of the first brake shoe 15 and the adjuster 21, the expansion to the one end side of the first brake shoe 15 and the input side end of the transmission lever 53 is performed. The input from the opening mechanism 19 is transmitted to the other end side of the second brake shoe 17 connected to the adjuster 21 via the output side end of the transmission lever 53.

Next, the operation of the drum brake 11 having the above configuration will be described.
FIG. 9 is an operation explanatory view showing before operation (A), initial operation (B), operation end (C), and braking force generation (D) of the drum brake 11 constituting the parking brake mechanism according to the first embodiment. It is.
In the drum brake 11 constituting the parking brake mechanism according to the first embodiment, the parking cable 33 is pulled according to the operation of an operation member (such as an operation lever) in the vehicle compartment from the state before the operation shown in FIG. As a result, the expansion force of the expansion mechanism 19 (the white arrow in the figure) causes the anchor portions 37 of the first brake shoe 15 and the second brake shoe 17 to be expanded, and the transmission lever 53 is also connected to the first brake shoe. Moved with 15

  Then, at the initial stage of operation shown in FIG. 9B, the first brake shoe 15 and the second brake shoe 17 that have been expanded are separated from the anchor portion 37 and are in pressure contact with the inner peripheral surface 100 of the brake drum. At this time, the first brake shoe 15 and the second brake shoe 17 move to the adjuster 21 side by a reaction force (arrow in the figure) from the inner peripheral surface 100.

  At the end of the operation shown in FIG. 9C, the first brake shoe 15 and the second brake shoe 17 move along the curvature of the inner peripheral surface 100 of the brake drum, and the inside of the brake drum on the side opposite to the anchor portion 37 Press contact with the peripheral surface 101. Accordingly, from the inner peripheral surface 101, an upward reaction force (in the drawing, an arrow) to the anchor portion 37 side acts on the first brake shoe 15 and the second brake shoe 17. A predetermined gap S1 is provided between the other end side of the first brake shoe 15 and the adjuster 21. The reaction force toward the anchor portion 37 side is stepped from the output side end of the transmission lever 53. It is transmitted to the first brake shoe 15 through the attached sleeve 57.

After the operation is completed, one end of the second brake shoe 17 abuts against the anchor portion 37 until the parking braking force shown in FIG. 9D is generated due to the self-boosting effect of the duo servo drum brake. The brake shoes 15 and 17 are slightly displaced when they are in close contact with the peripheral surfaces 100 and 101, but the reaction force generated on the adjuster 21 side by the parking braking force (the white arrow in the figure) expands via the transmission lever 53. While being transmitted to the mechanism 19, the gap S1 provided between the other end of the first brake shoe 15 and the adjuster 21 is reduced to the gap S2 to absorb this minute displacement.
Therefore, in the drum brake 11 of the first embodiment, the expansion force of the expansion mechanism 19 does not decrease, and the loosening that occurs when the parking braking force is generated is prevented. As a result, the safety of the parking brake is improved.

  In the first embodiment, the stepped sleeve 57 has the stepped portion 57 a lifted up from the first brake shoe 15 via the spring seat 61 and the sleeve pressing spring 63 by the through pin 59 supported by the backing plate 13. regulate. The transmission lever 53 is disposed between the first web 55 and the backing plate 13 and is rotatable about a stepped sleeve 57 that is penetrated by the sleeve through hole 69. The transmission lever 53 that is rotatable around the stepped sleeve 57 is held on the first web 55 by a clamping piece 65 that sandwiches the first web 55 in the thickness direction. Accordingly, both the first web 55 and the transmission lever 53 are supported via the stepped sleeve 57, and the first brake shoe 15 is prevented from being lifted up and the transmission lever 53 is rotatably supported. Become.

Next, a drum brake 71 constituting a parking brake mechanism according to a second embodiment of the present invention will be described.
As shown in FIGS. 10 to 12, the drum brake 71 constituting the parking brake mechanism according to the second embodiment is called a so-called duo servo drum brake, similarly to the drum brake 11 according to the first embodiment. Is. In addition, the same code | symbol is attached | subjected to the structural member equivalent to the structural member of the drum brake 11 shown in the said 1st Embodiment, and the overlapping description is abbreviate | omitted.

The drum brake 71 of the second embodiment includes a first switching lever 73 and a second switching lever 75 instead of the transmission lever 53 used in the drum brake 11 shown in the first embodiment. Switch lever is used.
The first switching lever 73 is rotatably supported by the first fulcrum pin 77 suspended from the first web 55 of the first brake shoe 15 at the position in the drum forward rotation direction inlet side (one end side) of the first brake shoe 15. To the input side. The second switching lever 75 is rotatably supported at a substantially intermediate position of the first brake shoe 15 by a second fulcrum pin 79 suspended from the first web 55, and rotates on the output side following the first switching lever 73. It becomes.

  As shown in FIG. 13, the first switching lever 73 is sandwiched between the expansion mechanism protruding end 81 provided in the expansion mechanism 19 and the first web 55 in the rotation axis direction. The second switching lever 75 is sandwiched between the adjuster protruding end 83 provided on the adjuster 21 and the first web 55 in the rotation axis direction. The adjuster 21 side of the first brake shoe 15 and the second brake shoe 17 is urged in the approaching direction by an adjuster spring 85.

The first switching lever 73 and the second switching lever 75 are arranged on the adjuster 21 side (the other end) rather than the anchor portion 37 side (one end side) of the first brake shoe 15 and the second brake shoe 17 by the input from the spreading mechanism 19. The distance between the fulcrum, the force point, and the action point is set so that the side) is expanded first.
In the second embodiment, in the non-operating state of the operating member, as shown in FIG. 14, the strut 27 and the first switching lever 73 are in contact with each other at the first sliding contact 87, and the first switching lever 73 and the second switching lever 73 are in contact with each other. The switching lever 75 is in contact with the second sliding contact 89, and the second switching lever 75 and the adjuster 21 are in contact with the third sliding contact 91.
Note that one end sides of the first brake shoe 15 and the second brake shoe 17 supported by the anchor portion 37 are biased in the approaching direction by the tension coil spring 43, but as shown in FIG. The shapes of the first switching lever 73 and the second switching lever 75 are set so that a predetermined gap S is formed between one end side of the shoe 15 and the strut 27 (see FIG. 14).

  The first sliding contact 87 and the first fulcrum pin 77 in the direction along the virtual center line 93 that divides the backing plate 13 in which the first brake shoe 15 and the second brake shoe 17 are arranged on the left and right in FIG. The distance is A, the distance between the first fulcrum pin 77 and the second sliding contact 89 in the direction along the virtual center line 93 is B, and the distance between the second sliding contact 89 and the second fulcrum pin 79 in the direction along the virtual center line 93 C, and the distance between the second fulcrum pin 79 and the third sliding contact 91 in the direction along the virtual center line 93 is D. Each distance is set to (A / B) × (C / D)> 1, and a predetermined gap S is provided between one end of the first brake shoe 15 and the strut 27. As shown in FIG. 15, from the anchor portion 37 side (one end side) of the first brake shoe 15 and the second brake shoe 17 by the input from the spreading mechanism 19 via the first switching lever 73 and the second switching lever 75. Also, the adjuster 21 side (the other end side) is expanded first.

Next, the operation of the drum brake 71 having the above configuration will be described.
FIG. 16 is an operation explanatory view showing before operation (A), operation initial (B), operation end (C), and braking force generation (D) of the drum brake 71 constituting the parking brake mechanism according to the second embodiment. It is.
In the drum brake 71 constituting the parking brake mechanism according to the second embodiment, the parking cable 33 is pulled according to the operation of the operation member (operation lever or the like) in the vehicle compartment from the state before the operation shown in FIG. Then, since a predetermined gap S is provided between one end side of the first brake shoe 15 and the strut 27, the first brake is applied by the expansion force of the expansion mechanism 19 (the white arrow in the figure). Before the anchor portion 37 side of the shoe 15 and the second brake shoe 17 is expanded, the first switching lever 73 is rotated counterclockwise about the first fulcrum pin 77.

  16B, the first switching lever 73 presses the second switching lever 75, and the second switching lever 75 rotates counterclockwise around the second fulcrum pin 79. As a result, the second switching lever 75 presses the adjuster 21 side (the other end side) of the second brake shoe 17 via the adjuster 21. As a result, the first brake shoe 15 and the second brake shoe 17 are opened on the adjuster 21 side and pressed against the inner peripheral surface 101 of the brake drum, and then the reaction force from the inner peripheral surface 101 (arrow in the figure). It moves to the anchor part 37 side. That is, when the second switching lever 75 presses the adjuster 21, the adjuster 21 side (the anti-anchor side) of the first brake shoe 15 and the second brake shoe 17 is first expanded. Therefore, the anchor portion 37 side of the first brake shoe 15 and the second brake shoe 17 is moved to the anchor portion 37 side during the expansion, and does not leave the anchor portion 37.

  At the end of the operation shown in FIG. 16C, the first brake shoe 15 and the second brake shoe 17 are pressed against the inner peripheral surface 101 of the brake drum on the adjuster 21 side and the inner peripheral surface 100 of the brake drum on the anchor portion 37 side. To do. Therefore, an inward reaction force (arrow in the figure) toward the adjuster 21 acts on the first brake shoe 15 and the second brake shoe 17 from the inner peripheral surface 101 of the brake drum on the adjuster 21 side, and the anchor portion A downward reaction force (arrow in the figure) acts from the inner peripheral surface 100 of the brake drum on the 37 side toward the adjuster 21 side.

  At this time, the first brake shoe 15 and the second brake shoe 17 are expanded on both the anchor portion 37 and the adjuster 21 side, and adhesion to the brake drum sliding surface is improved. As a result, before the parking braking force shown in FIG. 16 (D) is generated, the anchor portion 37 (one end side) of the first brake shoe 15 or the second brake shoe 17 is displaced in a direction in contact with the anchor portion 37. The loosening phenomenon is prevented.

  As described above, in the drum brake 71 of the second embodiment, the first brake shoe 15 and the second brake are received by the input from the expansion mechanism 19 via the switching lever including the first switching lever 73 and the second switching lever 75. The adjuster 21 side (the other end side) with the shoe 17 is expanded before the anchor portion 37 side (one end side). Therefore, the anchor portion 37 side of the first brake shoe 15 and the second brake shoe 17 is moved to the anchor portion 37 side during the expansion, and does not leave the anchor portion 37. Accordingly, since the first brake shoe 15 and the second brake shoe 17 have an expanding force on both the adjuster 21 side and the anchor portion 37 side, the first brake shoe 15 and the second brake shoe 17 and the drum sliding surface. And the looseness that occurs when parking braking force is generated is prevented. As a result, the safety of the parking brake is improved.

  In the drum brake 71 of the second embodiment, the first switching lever 73 is rotatably held on the first brake shoe 15 by the first fulcrum pin 77 and the second switching lever 75 is held by the second fulcrum pin 79. Therefore, the position of the first fulcrum pin 77 and the second fulcrum pin 79, the position of the first sliding contact 87 between the strut 27 and the first switching lever 73, the second of the first switching lever 73 and the second switching lever 75. By setting the position of the sliding contact 89 and the position of the third sliding contact 91 between the second switching lever 75 and the adjuster 21, it is possible to easily select an appropriate transmission ratio of the first and second switching levers 73 and 75. This makes it easy to obtain optimum adhesion between the first brake shoe 15 and the second brake shoe 17 and the drum sliding surface.

  Further, the first switching lever 73 is sandwiched between the expansion mechanism protruding end portion 81 and the first web 55 in the rotation axis direction, and the second switching lever 75 is interposed between the adjuster protruding end portion 83 and the first web 55. Is sandwiched in the direction of the rotation axis. Therefore, even if the first switching lever 73 and the second switching lever 75 have a flat plate shape, their contact points do not come off, and a simple shape and an inexpensive configuration can be achieved.

The drum brake 11 and the drum brake 71 according to the first and second embodiments are disposed on the backing plate rear side surface 97 and are motor gears as a drive mechanism that pulls and drives the parking cable 33 connected to the expansion mechanism 19. By attaching the unit 95 (see FIG. 13), an electric parking brake can be obtained.
According to the electric parking brake, when the parking cable 33 is pulled by the motor gear unit 95 disposed on the back side surface 97 of the backing plate, the expansion mechanism 19 can be operated electrically.

  Therefore, according to the drum brake 11 or the drum brake 71 constituting the parking brake mechanism according to the present embodiment, it is possible to prevent the loosening phenomenon that occurs when the parking braking force is generated in the duo servo parking brake.

  Moreover, according to the electric parking brake which concerns on this embodiment, a parking brake can be motorized.

DESCRIPTION OF SYMBOLS 13 ... Backing plate 15 ... 1st brake shoe 17 ... 2nd brake shoe 19 ... Expansion mechanism 21 ... Adjuster 33 ... Parking cable 37 ... Anchor part 53 ... Transmission lever 55 ... 1st web 57 ... Stepped sleeve 59 ... Through pin 61 ... Spring seat 63 ... Sleeve pressing spring 65 ... Nipping piece 73 ... First switching lever 75 ... Second switching lever 77 ... First fulcrum pin 79 ... Second fulcrum pin 81 ... Expansion mechanism protruding end 83 ... Adjuster protruding End 95: Motor gear unit (drive mechanism)
97 ... Back side of backing plate

Claims (5)

A first brake shoe disposed along the inner peripheral surface of the brake drum and having one end side as an input side from the expansion mechanism, and disposed along the inner peripheral surface of the brake drum facing the first brake shoe. A second brake shoe having one end side as an input side from the expansion mechanism and the other end side connected to the other end side of the first brake shoe via an adjuster, and a backing plate, An anchor portion that is in contact with one end side of one brake shoe and one end side of the second brake shoe, and is rotatably supported by the first brake shoe, and an input side end is in contact with the expansion mechanism and an output side comprising a transmission lever which end is brought into contact with the adjuster which is connected to the other end of the second brake shoe, and between the other end side to the adjuster of the first brake shoe Parking brake mechanism, characterized in that the constant gap is provided. The parking brake mechanism according to claim 1,
A stepped sleeve is passed through the first web of the first brake shoe,
The stepped sleeve is penetrated by a through pin that is penetrated and supported by the backing plate, and a stepped portion opposite to the backing plate across the first web is interposed between the through pin and a spring seat Restricting the lifting of the first brake shoe by pressing the sleeve pressing spring;
The transmission lever is passed through the stepped sleeve between the first web and the backing plate so as to be rotatable around the stepped sleeve, and a sandwiching piece portion partially bent into a U shape The parking brake mechanism is held by the first brake shoe with the first web interposed therebetween. A first brake shoe disposed along the inner peripheral surface of the brake drum, and having one end side as an input side from the spreading mechanism;
A second brake shoe disposed along the inner peripheral surface of the brake drum so as to face the first brake shoe and having the other end connected to the other end of the first brake shoe via an adjuster;
An anchor portion mounted on a backing plate and in contact with one end side of the first brake shoe and the second brake shoe;
The first brake shoe is rotatably supported, the input side end is in contact with the expansion mechanism and the output side end is in contact with the adjuster, and the first brake shoe is input by the input from the expansion mechanism. And a switching lever that widens the other end before the one end of the second brake shoe,
A parking brake mechanism comprising: The parking brake mechanism according to claim 3, wherein
The switching lever is rotatably supported on the first brake shoe by a first fulcrum pin and is an input side. The switching lever is rotatably supported by the first brake shoe by a second fulcrum pin. A second switching lever on the output side that rotates following the switching lever,
The first switching lever is sandwiched in the rotation axis direction between the expansion mechanism protruding end provided in the expansion mechanism and the first web;
The parking brake mechanism, wherein the second switching lever is sandwiched between the protruding end of the adjuster provided on the adjuster and the first web in the rotation axis direction. An electric parking brake comprising the parking brake mechanism according to any one of claims 1 to 4,
An electric parking brake, wherein a driving mechanism for pulling and driving a parking cable connected to the spreading mechanism is disposed on the back side surface of the backing plate.

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