JP2008045655A - Drum brake device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drum brake device easy to assemble on a vehicle, free from over-adjustment, and miniaturizable with the simplified construction of a wheel cylinder and a reduction in the amount of liquid. <P>SOLUTION: In the drum brake device, a clearance between a brake shoe and a drum inner peripheral face is automatically adjusted during non-braking operation by the rotation of an adjuster gear 45 having a second tooth portion 45a gearing with the other end of a strut 41. During braking operation when operating force W of the wheel cylinder 5 is a predetermined value or greater, a lever member 51 laid between the wheel cylinder 5 and the end of the other brake shoe 3 is turned with the operating force W of the wheel cylinder 5 to firmly maintain a gearing condition between the strut 41 and the adjuster gear 45. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a drum brake device having an automatic gap adjustment device that adjusts the position of a brake shoe according to wear. In particular, the present invention can facilitate the assembly work to the vehicle and at the same time after the assembly to the vehicle. The present invention relates to an improvement for easily adjusting a gap between a drum and a brake shoe.

  Conventionally, various types of drum brake devices have been used to brake the running of the vehicle, but these drum brake devices are arranged according to the arrangement of brake shoes pressed against the inner peripheral surface of a substantially cylindrical drum. It is classified as a reading trailing type, a two reading type, or a duo servo type.

  In the case of a drum brake device mounted on an automobile, the gap between the pair of brake shoes arranged opposite to the drum inner space when the brakes are not braked is usually in each brake shoe, regardless of which type is used. In order not to increase due to wear, an automatic gap adjusting device for automatically adjusting the position of each brake shoe according to the wear of each brake shoe is incorporated.

  Conventional automatic gap adjustment devices include a micro-adjuster system that limits the amount of brake shoe feed that can be adjusted during a single braking operation (see, for example, Patent Document 1 or Patent Document 2), and a brake with a single braking operation. It can be broadly classified into a one-shot adjuster type that adjusts the gap between the shoe and the drum at a stretch to a reference value (for example, see Patent Document 3, Patent Document 4, or Patent Document 5).

However, a drum brake device equipped with a conventional micro-adjuster type automatic clearance adjustment device sets a large initial clearance between the drum and the brake shoe when the vehicle is assembled in order to facilitate the assembly work to the vehicle. After installation, it is necessary to repeat the brake pedal operation many times to adjust the gap between the drum and the brake shoe to an appropriate gap, and the gap between the drum and the brake shoe after the vehicle is assembled. There is a problem that adjustment takes time.
Further, in order to solve this problem, if the initial gap between the drum and the brake shoe during assembly to the vehicle is made small, the assembly operation to the vehicle becomes difficult.

On the other hand, in the case of a drum brake device equipped with a conventional one-shot adjuster type automatic gap adjustment device, even if the initial clearance between the drum and the brake shoe is set large when assembled to the vehicle, In order to adjust the gap between the drum and the brake shoe to an appropriate gap, only one or a few brake pedal operations are repeated. Therefore, the assembly to the vehicle can be improved, and at the same time, the adjustment of the gap between the assembled drum and the brake shoe can be simplified.
However, in the case of the conventional one-shot adjuster type automatic gap adjusting device, for example, when the drum is deformed by an excessive braking force and the range of motion of the brake shoe temporarily increases due to the deformation of the drum, Since the position of the brake shoe is adjusted all at once, including the range of motion, over-adjustment occurs where the gap between the drum and the brake shoe to be secured during non-braking is less than or equal to the appropriate gap, and the brake shoe is dragged. There was a risk of inviting.

  Accordingly, a drum brake device 100 shown in FIGS. 15 to 18 has been proposed as a drum brake device that solves the problems in the conventional one-shot adjuster type automatic gap adjusting device.

The drum brake device 100 shown here is disclosed in Patent Document 6 below, and includes a pair of brake shoes 3 and 4 disposed in a space in a substantially cylindrical drum (not shown), and a pair of brake shoes. The wheel cylinder 6 is disposed on one opposite end side of the three and four and generates a shoe operating force for pressing the brake shoes 3 and 4 against the drum, and on the other opposite end side of the pair of brake shoes 3 and 4. A gap between the anchor member 7 that is disposed and receives the braking force of each brake shoe 3, 4, the backing plate 9 that supports these components, and the drum when the pair of brake shoes 3 and 4 are not braked Automatically adjusting the position of each brake shoe 3 and 4 according to wear, and the brake shoe 3 And a parking lever 11 to generate a braking force by expanding the pair of brake shoes 3 by rotatably coupled to the rotation operation at the time of the parking through a pin 11a.
The drum (not shown) is concentric with the backing plate 9 and rotates in the direction of arrow R in FIG. 15 when the vehicle moves forward.

The above brake shoes 3 and 4 are attached to the backing plate 9 by a shoe support mechanism 14 so as to be movable toward the inner periphery of the drum.
The ends of the brake shoes 3 and 4 on the wheel cylinder 6 side are urged by shoe-to-shoe springs 15 in directions in which the ends of the shoes approach each other (that is, in directions away from the drum). The end of the shoe is maintained in contact with the piston of the wheel cylinder 6.
The ends of the brake shoes 3 and 4 on the anchor member 7 side are urged by the anchor springs 16 in directions in which the ends of the shoes approach each other (that is, in directions away from the drum). The end of the shoe is maintained in contact with the anchor member 7.

  As shown in FIG. 16, the automatic gap adjusting device 10 has a contact portion 21 a for positioning one brake shoe 3 via the parking lever 11 at one end and a first tooth portion 21 b at the other end. The strut 21, the first tension spring 23 that biases one end of the strut 21 toward the one brake shoe 3 so that the contact portion 21 a is in contact with the parking lever 11, The second end 25a meshed with the first tooth 21b and the web 4a of the other brake shoe 4 are supported at the other end so as to be rotatable and movable in the longitudinal direction of the strut 21. An adjuster gear 25 having an engagement arm portion 25b that fits loosely in the mating hole 26, and the adjuster gear 25 and the stroke in a direction in which the second tooth portion 25a meshes with the first tooth portion 21b. A second tension spring 27 that applies a weaker tensile force than the first tension spring 23 between the first tension spring 23 and the adjuster gear 25 when the operating force from the wheel cylinder 6 exceeds a predetermined value during braking. And an over-adjustment preventing means 29 for preventing over-adjustment by restricting the rotation.

The adjuster gear 25 is rotatably supported by the strut 21 by a support pin 31 inserted through the other end side of the strut 21. Further, the mounting hole on the strut 21 through which the support pin 31 is inserted is formed as a long hole that is long in the longitudinal direction of the strut 21, so that the adjuster gear 25 can move in the longitudinal direction of the strut 21. .
Since the adjuster gear 25 is movably attached along the longitudinal direction of the strut 21, the adjuster gear 25 is meshed with the second tooth portion 25a meshed with the first tooth portion 21b as shown in FIG. From the state, it can move to the drum inner peripheral surface 33 side against the tensile force of the second tension spring 27 to shift to the state where the meshing is released.

  In the drum brake device 100 described above, at the time of braking, the piston of the wheel cylinder 6 pushes the end of each brake shoe 3, 4, so that each brake shoe 3, 4 expands, and the outer periphery of each brake shoe 3, 4. The linings 3b and 4b equipped on the surface are pressed against the drum inner peripheral surface 33 (see FIG. 16) to generate a braking force.

  As shown in FIG. 16, the gap s1 between the drum inner circumferential surface 33 and each of the linings 3b and 4b during non-braking is less than a predetermined value, and the engagement arm portion 25b loosely fitted in the engagement hole 26 is engaged. When the gap s2 is smaller than the inner end edge of the joint hole 26, the inner end edge of the engagement hole 26 is engaged with the engagement arm during the expanding operation in which the brake shoe 4 is pressed against the drum inner peripheral surface 33. The adjuster gear 25 maintains the state where the second tooth portion 25a is engaged with the first tooth portion 21b by the urging force of the second tension spring 27 without contacting the portion 25b. Accordingly, the adjustment of the gap s1 between the drum inner peripheral surface 33 and each of the linings 3b and 4b is not performed.

  On the other hand, due to wear of the linings 3b and 4b, the gap s1 between the drum inner circumferential surface 33 and the linings 3b and 4b is larger than the gap s2 between the engagement arm portion 25b and the inner end edge of the engagement hole 26. If it becomes larger, the inner edge of the engagement hole 26 pushes the engagement arm portion 25 toward the drum inner peripheral surface 33 during the expanding operation in which the brake shoe 4 is pressed against the drum inner peripheral surface 33. As a result, the adjuster gear 25 moves on the strut 21 toward the drum inner circumferential surface 33, and the engagement between the second tooth portion 25a and the first tooth portion 21b is released. Further, the adjuster gear 25 rotates on the strut 21 in the direction of arrow B in FIG. 16 around the support pin 31 by the pressing force acting on the engagement arm portion 25 from the inner end edge of the engagement hole 26. By the rotation of the adjuster gear 25, the position of the second tooth portion 25a meshing with the first tooth portion 21b is changed, and the distance L1 from the first tooth portion 21b to the tip of the engaging arm portion 25b is increased. Therefore, the distance between the pair of brake shoes 3 and 4 whose position is regulated by the strut 21 and the adjuster gear 25 is increased, and the gap s1 between the drum inner peripheral surface 33 and each of the linings 3b and 4b becomes the engagement arm portion 25b. It is automatically adjusted to a value smaller than the gap s2 between the inner end edge of the engagement hole 26.

  In the automatic gap adjusting device 10 described above, adjustment of the separation distance between the brake shoes 3 and 4 via the strut 21 and the adjuster gear 25 is performed by moving the brake shoes 3 and 4 until they contact the inner peripheral surface of the drum. As is the case with a drum brake device equipped with a conventional one-shot adjuster type automatic gap adjustment device, the initial stage between the drum and the brake shoes 3 and 4 is assembling to the vehicle. Even if the gap is set to be large, only one brake pedal operation is required to adjust the gap between the drum and the brake shoes 3 and 4 to an appropriate gap after assembly. Therefore, by setting a large initial gap when assembled to the vehicle, the ease of assembling to the vehicle can be improved, and between the drum and the brake shoes 3 and 4 after being assembled to the vehicle. Clearance adjustment can be simplified.

  The over-adjustment preventing means 29 provided in the automatic gap adjusting device 10 includes an escape hole 35 communicating with the engagement hole 26 and extending along the longitudinal direction of the strut 21 so as to be away from the drum inner peripheral surface 33, and a wheel cylinder. 6 and a side piston 6a additionally provided in the middle portion.

  As shown in FIG. 17, the side piston 6a is operated when the operating force from the wheel cylinder 6 to the brake shoes 3 and 4 is greater than or equal to a predetermined value during braking (that is, the hydraulic pressure in the wheel cylinder 6 is greater than or equal to a predetermined value). ), A piston that advances against the tension spring 6b installed inside.

  When the hydraulic pressure in the wheel cylinder 6 reaches a predetermined level or higher, the side piston 6a presses the strut 21 and engages with the engagement hole 26 as shown in FIG. The part 25 b is moved to the escape hole 35. Since the inner end edge of the escape hole 35 extends in a direction away from the drum inner peripheral surface 33 as compared with the engagement hole 26, the inner end of the escape hole 35 can be obtained even if the amount of movement of the brake shoe 4 is large. The edge does not press the engagement arm portion 25b, and the clearance adjustment operation by the rotation of the adjuster gear 25 does not occur.

  That is, in the automatic gap adjusting device 10, even if a situation occurs in which the drum is deformed by an excessive braking force, for example, when the brake is suddenly applied during high-speed traveling, the over-adjustment prevention means 29 is generated at that time. Therefore, an adjusting operation is not generated in which the brake shoe follows the deformation of the drum. Therefore, it is possible to prevent the occurrence of over-adjustment that causes dragging of the brake shoe.

Japanese Examined Patent Publication No. 56-34733 Japanese Patent Publication No. 63-33567 Japanese Patent Publication No.43-21822 Japanese Patent Publication No. 51-12882 Japanese Examined Patent Publication No. 2-21456 JP-A-5-1731

However, in the over-adjustment prevention means 29 disclosed in Patent Document 6, the structure of the wheel cylinder 6 is complicated and enlarged due to the provision of the side piston 6a, or the wheel cylinder is activated by the operation of the side piston 6a. There is a possibility that the braking force fluctuates during braking due to a change in volume in the cylinder 6 and a change in the amount of liquid in the wheel cylinder 6 due to the operation of the side piston 6a.
Further, as shown in FIG. 18, when releasing the brake, a return spring 37 is required to return the strut 21 displaced by the side piston 6a to its original position, and the increase in the number of parts causes an increase in cost. It was.

  Therefore, the object of the present invention is to solve the above-mentioned problems, and it is possible to facilitate the assembly work to the vehicle, and at the same time, to easily adjust the gap between the drum and the brake shoe after the assembly to the vehicle, In addition, it is possible to prevent the occurrence of over-adjustment that causes dragging of the brake shoes, and further, downsizing by simplifying the structure of the wheel cylinder and at the same time suppressing changes in the fluid amount in the wheel cylinder during braking. It is to provide a drum brake device.

The above object is achieved by the following configuration.
(1) A drum brake device including an automatic gap adjustment device that automatically adjusts the position of a pair of brake shoes arranged in a drum inner space according to wear,
The automatic gap adjusting device includes a strut provided with a shoe contact portion that contacts one brake shoe at one end and a first tooth portion at the other end,
A first tension spring that biases the strut so as to maintain the shoe contact portion in contact with the brake shoe;
The other end of the strut is supported so as to be rotatable and movable in the longitudinal direction of the strut, and in a second tooth portion meshing with the first tooth portion and an engagement hole formed in the other brake shoe. An engaging arm portion that loosely fits, and when the other brake shoe moves more than a predetermined amount in the expanding direction, the engaging arm portion is pushed against the inner end edge of the engaging hole to An adjuster gear that can rotate,
A second tension spring that applies a weaker tensile force than the first tension spring in a direction in which the second tooth portion meshes with the first tooth portion;
Over-adjustment preventing means for restricting the rotation of the adjuster gear when the operating force from the wheel cylinder is greater than or equal to a predetermined value during braking,
The over-adjustment prevention means is a lever member interposed between the piston of the wheel cylinder and the end of the other brake shoe,
The lever member is rotatably supported by the other brake shoe at a position where the base end is radially outward from the operating force acting point of the wheel cylinder, and an operating force from the wheel cylinder is provided at an intermediate portion. An operating force receiving portion for receiving the first tension spring is provided. The front end engages with the strut and rotates when the operating force from the wheel cylinder exceeds a predetermined value. A drum brake device, further comprising a strut operating portion that is moved to the adjuster gear side to keep the meshing state between the first tooth portion and the second tooth portion.

(2) The drum brake device according to (1), wherein the lever member includes a pair of bent pieces that sandwich a web of the other brake shoe.

  In the drum brake device described in (1) above, a gap between the drum inner peripheral surface and each lining is formed between the engagement arm portion and the inner end edge of the engagement hole due to wear of the lining of each brake shoe. When the clearance is larger than the gap, the inner edge of the engagement hole pushes the engagement arm portion toward the drum inner peripheral surface during the expanding operation in which the other brake shoe is pressed against the drum inner peripheral surface. As a result, the adjuster gear moves on the drum inner peripheral surface side on the strut, and the engagement between the second tooth portion and the first tooth portion is disengaged from the inner end edge of the engagement hole. The adjuster gear rotates on the strut by the pressing force acting on the arm portion. By the rotation of the adjuster gear, the engagement position between the second tooth portion and the first tooth portion is changed to adjust the separation distance between the pair of brake shoes via the strut and the adjuster gear. The gap between the peripheral surface and each lining is maintained below a predetermined dimension.

  And the over-adjustment preventing means of the automatic gap adjusting device according to the present invention moves the strut to the adjuster gear side by a lever member that is rotatably interposed between the wheel cylinder and the other brake shoe. Since the rotation of the adjuster gear is restricted and no improvement of the wheel cylinder such as addition of a side piston is required, the size of the apparatus can be reduced by simplifying the structure of the wheel cylinder.

  In the drum brake device according to the above (2), the lever member used for the over-adjustment prevention means is configured such that the web of the other brake shoe is sandwiched between the pair of bent pieces, so that it is difficult for the lever member to fall off during assembly. Assembling property can be improved.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a drum brake device according to the invention will be described in detail with reference to the drawings.
1 is a front view of a drum brake device according to a first embodiment of the present invention, FIG. 2 is a perspective view of the drum brake device shown in FIG. 1, and FIG. 3 is a pair of brake shoes shown in FIG. FIG. 4 is an enlarged front view showing a positional relationship between the automatic gap adjusting device shown in FIG. 3 and a pair of brake shoes.

The drum brake device 200 according to the first embodiment includes a pair of brake shoes 3 and 4 disposed opposite to a space in a substantially cylindrical drum (not shown), and one of the pair of brake shoes 3 and 4. The wheel cylinder 5 that generates a shoe operating force that presses the brake shoes 3 and 4 against the drum and the other opposing end side of the pair of brake shoes 3 and 4. The gap between the anchor member 7 that receives the braking force of the brake shoes 3 and 4, the backing plate 9 that supports these components, and the drum when the pair of brake shoes 3 and 4 are not braked is each brake shoe 3. , 4 so as not to increase due to wear, an automatic gap adjusting device 201 that automatically adjusts the position of each brake shoe 3, 4 according to wear, and a pin 11 a on the brake shoe 4. And a parking lever 11 to generate a braking force by expanding the pair of brake shoes 3, 4 by rotating operation during parking is rotatably coupled to.
A drum (not shown) is concentric with the backing plate 9 and rotates in the direction of arrow R in FIG. 1 when the vehicle moves forward.

The brake shoes 3, 4 are backing plates that are movable toward the inner periphery of the drum by shoe support shafts 14 that are mounted in attachment holes 3 c, 4 c (see FIG. 3) formed through the webs 3 a, 4 a. 9 is attached.
The ends of the brake shoes 3 and 4 on the wheel cylinder 5 side are urged by shoe-to-shoe springs 15 in directions in which the ends of the shoes approach each other (i.e., away from the drum). The end of the shoe is maintained in contact with the piston of the wheel cylinder 5.
The ends of the brake shoes 3 and 4 on the anchor member 7 side are urged by the anchor springs 16 in directions in which the ends of the shoes approach each other (that is, in directions away from the drum). The end of the shoe is maintained in contact with the anchor member 7.

  The pin 11a that connects the parking lever 11 to the brake shoe 4 is prevented from coming off by a clip (retaining ring) 12 that is fitted to the pin 11a.

  As shown in FIGS. 4 to 7, the automatic gap adjusting device 201 of the present embodiment includes a shoe contact portion 41 a that contacts the strut engagement portion 4 d of one brake shoe 4 and positions the brake shoe 4. The strut 41 is provided at one end and the first tooth portion 41b is provided at the other end, and one end of the strut 41 is connected to the strut 41 so that the shoe contact portion 41a is in contact with the strut engagement portion 4d. In a first tension spring 43 urged toward the brake shoe 4 side, a second tooth portion 45a meshing with the first tooth portion 41b, and an engagement hole 47 formed in the web 3a of the other brake shoe 3 A first tension spring 45 between the adjuster gear 45 and the strut 41 in a direction in which the adjuster gear 45 provided with the engagement arm portion 45b to be loosely fitted and the second tooth portion 45a meshes with the first tooth portion 41b. 43 A second tension spring 48 that exerts a weaker tensile force and an over-adjustment that prevents over-adjustment by restricting the rotation of the adjuster gear 45 when the operating force from the wheel cylinder 5 exceeds a predetermined value during braking. Prevention means 51.

As shown in FIGS. 6 and 7, a lever abutting portion 41 c with which the parking lever 11 abuts is formed at one end of the strut 41 continuously with the shoe abutting portion 41 a.
The parking lever 11 is a traction force transmitted from a cable (not shown), rotates around the pin 11a in the direction of the arrow X in FIG. 3, and presses and displaces the strut 41 toward the brake shoe 3 so that a pair of brakes The shoes 3 and 4 are expanded to generate a braking force.

  As shown in FIGS. 7 and 14, the strut 41 is an elongated stick-like plate material along the opposing direction of the pair of brake shoes 3 and 4. The other end side of the strut 41 is a first arm portion 411 having a first tooth portion 41b formed at the tip thereof, and is substantially parallel to the first arm portion 411 and extends beyond the first arm portion 411. The second arm 412 branches off into two arms. A thin long hole 413 is formed in the longitudinal direction of the strut 41 on the distal end side of the second arm portion 412.

The adjuster gear 45 is supported on the other end of the strut 41 so as to be rotatable and movable in the longitudinal direction of the strut 41 by a cylindrical pin 451 fitted into the elongated hole 413 of the second arm portion 412.
The engagement hole 47 of the brake shoe 3 into which the engagement arm portion 45b of the adjuster gear 45 is loosely fitted is formed on the lining 3b of the brake shoe 3 when the brake shoe 3 is expanded by the operating force of the wheel cylinder 5. When the amount of displacement until the brake shoe 3 is pressed against the inner peripheral surface of the drum is less than a specified amount with little wear, the dimensions are set so that the inner edge 47a of the engagement hole 47 does not contact the engagement arm portion 45b. Is set.

When wear of the lining 3b of the brake shoe 3 progresses and the brake shoe 3 is expanded by the operating force of the wheel cylinder 5, the amount of displacement until the brake shoe 3 is pressed against the inner peripheral surface of the drum is a specified amount. In such a case, the inner end edge 47a of the engagement hole 47 of the brake shoe 3 that is displaced pushes the engagement arm portion 45b.
When the engagement arm portion 45b is pushed by the inner end edge 47a of the engagement hole 47, the adjuster gear 45 moves along the elongated hole 413, thereby attaching the second tension spring 48 as shown in FIG. From the state where the second tooth portion 45a meshes with the first tooth portion 41b by the force, the meshing of these tooth portions 45a and 41b is released as shown in FIG.

  Then, when the pressing force from the inner end edge 47a acts on the engaging arm portion 45b in the state where the engagement is further released, the adjuster gear 45 rotates as indicated by an arrow Y in FIG. The rotation of the adjuster gear 45 increases the distance L2 from the first tooth portion 41b to the tip of the engaging arm portion 45b, so that the position of the pair of brake shoes 3 and 4 regulated by the strut 41 and the adjuster gear 45 is increased. The separation distance is increased, and the gap between the drum inner peripheral surface 33 and each of the linings 3b and 4b is smaller than the gap between the engagement arm portion 45b and the inner end edge 47a of the engagement hole 47 during non-braking. Automatically adjusted to the value.

In the case of the present embodiment, the over-adjustment preventing means 51 is a lever member that is interposed between the piston of the wheel cylinder 5 and the end of the other brake shoe 3 as shown in FIGS. is there.
As shown in FIG. 4, the lever member as the over-adjustment preventing means 51 (hereinafter simply referred to as the lever member 51) is located at a position where the base end 51 a is outside the operating force application point P <b> 1 of the wheel cylinder 5. An operation force receiving portion 51 b that receives the operation force W from the wheel cylinder 5 is provided at the middle portion while being rotatably supported by the brake shoe 3. Further, the lever member 51 is engaged with the strut 41, and when the operating force W from the wheel cylinder 5 exceeds a predetermined value, the strut 41 is first pulled by turning around the base end 51a. A strut operating portion 51c is provided that moves toward the adjuster gear 45 against the urging force of the spring 43. By the pressing by the strut operation part 51c, the meshing state of the first tooth part 41b and the second tooth part 45a is firmly maintained.

The lever member 51 of the present embodiment is formed by press forming a metal plate. As shown in FIGS. 3 to 5, the base end 51 a of the lever member 51 has a plate shape perpendicular to the web 3 a and is loosely fitted into the notch groove 53 formed in the web 3 a so as to be attached to the web 3 a. . The operating force receiving portion 51b is set on an intermediate plate 51d extending from the end edge of the base end 51a to the strut 41 side. A boundary portion 51e between the intermediate plate 51d and the base end 51a is processed into a predetermined bend R. The bend R of the boundary portion 51e covers the protruding curved portion 54 of the web 3a connected to the entrance portion of the notch groove 53, and the lever member 51 is smoothly rotated.
The strut operating portion 51c is a protrusion formed at the tip of a plate portion 51f that is parallel to the web 3a and continues to the side edge of the base end 51a and the intermediate plate 51d. The strut operating portion 51 c is in contact with a protrusion 414 that is formed to protrude on the second arm portion 412 of the strut 41.

As shown in FIG. 4, the distance from the contact point c1 during rotation of the lever member 51 that is rotatably engaged with the web 3a to the operating force application point P1 is S1, and from the contact point c1 during rotation to the strut operating portion 51c. If the distance is S2, the length of the plate portion 51f is set so that S1 <S2.
Further, when the operating force W from the wheel cylinder 5 is below a predetermined value, the force F by which the strut operating portion 51c pushes the projection 414 is applied to the first tension spring 43 that biases the strut 41 toward the brake shoe 4 side. The dimensions of each part of the lever member 51 are set so as to be smaller than the urging force.

In the case of the present embodiment, the threshold value when the operating force W from the wheel cylinder 5 is less than or equal to a predetermined value is set to the drum inner peripheral surface, for example, when a sudden brake is applied during high speed running. This means an operating force when the inner peripheral surface of the drum is deformed because the pressing force of the brake shoes 3 and 4 is too strong.
Accordingly, each brake shoe 3 or 4 immediately after the start of the brake pedal operation until the brake shoes 3 and 4 come into contact with the drum inner peripheral surface, the operation force output by the wheel cylinder 5 during the expansion operation of each brake shoe, The operating force output by the wheel cylinder 5 when the shoes 3 and 4 are pressed against the drum inner peripheral surface is less than a predetermined value.

Next, the operation of the lever member 51 during braking will be described with reference to FIG.
When the operating force W is applied from the wheel cylinder 5 to the operating force application point P1, the lever member 51 is moved according to the ratio of the distances S1 and S2 from the contact point c1 when the lever member 51 is rotated to the web 3a to each operating point. A force F that pushes the protrusion 414 on the strut 41 is generated in the strut operating portion 51c.
When the operating force W from the wheel cylinder 5 is less than or equal to a predetermined value, the force F acting on the projection 414 of the strut 41 from the strut operating portion 51c is smaller than the tensile force of the first tension spring 43. Is maintained in contact with the brake shoe 4. Therefore, the position of the strut operating portion 51 c of the lever member 51 is not displaced, and the base end 51 a is displaced together with the brake shoe 3 toward the drum inner peripheral surface side in accordance with the operating force W from the wheel cylinder 5.

  When the operating force W becomes greater than or equal to a predetermined value due to sudden braking or the like, the force F acting on the projection 414 of the strut 41 from the strut operating portion 51c becomes larger than the tensile force of the first tension spring 43. The strut 41 is moved toward the adjuster gear 45 against the tensile force of the first tension spring 43 by the force F from the strut operating portion 51c. By the movement of the strut 41, as shown in FIG. 9, the state where the first tooth portion 41b is engaged with the second tooth portion 45a is firmly held, and the engaging arm portion is engaged by the inner end edge 47a of the engaging hole 47. Even if 45b is pushed, the adjuster gear 45 is held in a state where it cannot rotate.

In the drum brake device 200 of the first embodiment described above, the gap between the drum inner peripheral surface and each lining 3b, 4b is engaged by the wear of the linings 3b, 4b of each brake shoe 3, 4. When the clearance is larger than the gap between the arm portion 45b and the inner end edge of the engagement hole 47, the inner end edge 47a of the engagement hole 47 is expanded during the expansion operation in which the other brake shoe 3 is pressed against the drum inner peripheral surface. Pushes the engagement arm portion 45b toward the drum inner peripheral surface.
As a result, the adjuster gear 45 moves to the drum inner peripheral surface side on the strut 41, and the second tooth portion 45a and the first tooth portion 41b are disengaged as shown in FIG. The adjuster gear 45 rotates on the strut 41 by the pressing force acting on the engagement arm portion 45 b from the inner end edge 47 a of the engagement hole 47. By the rotation of the adjuster gear 45, the meshing position of the second tooth portion 45a and the first tooth portion 41b is changed, so that the pair of brake shoes 3 and 4 are separated from each other via the strut 41 and the adjuster gear 45. The distance is adjusted, and the gap between the drum inner peripheral surface and each of the linings 3b and 4b is maintained below a predetermined dimension.

  In the drum brake device 200 of the present embodiment, such an operation of the automatic gap adjusting device 201 is performed at a time in conjunction with the movement operation until each brake shoe 3, 4 comes into contact with the inner peripheral surface of the drum. As in the case of a drum brake device equipped with a conventional one-shot adjuster type automatic clearance adjustment device, even if the initial clearance between the drum and the brake shoe is set large when assembled to the vehicle, In order to adjust the gap between the drum and the brake shoe to an appropriate gap, it is only necessary to execute one brake pedal operation. Therefore, by setting a large initial gap when assembling to the vehicle, it is possible to improve the ease of assembling to the vehicle and to adjust the gap between the drum and the brake shoe after assembling to the vehicle. Can be simple.

  Further, when the operating force W from the wheel cylinder 5 becomes greater than or equal to a predetermined value during braking, the over-adjustment preventing means 51 prevents over-adjustment by restricting the rotation of the adjuster gear 45, thereby causing the brake shoe to drag. The occurrence of over-adjustment can also be prevented.

  The over-adjustment preventing means 51 in the automatic gap adjusting device 201 of the present embodiment is configured such that the strut 41 is adjusted by the lever member 51 that is rotatably interposed between the wheel cylinder 5 and the other brake shoe 3. By moving to the 45 side, the rotation of the adjuster gear 45 is restricted, and there is no need to improve the wheel cylinder such as the addition of a side piston. Can be realized.

  Further, since it is not necessary to improve the wheel cylinder such as addition of a side piston, fluctuations in the volume in the wheel cylinder can be suppressed.

  In addition, the strut 41 moved by the over-adjustment preventing means 51 to prevent over-adjustment during braking returns to the original position by the first tension spring 43 when the brake is released, and thus returns as the over-adjustment preventing means 51. There is no need to equip a dedicated spring member, and the brake device can be reduced in size and cost by reducing the number of parts.

  The specific structure of the lever member as the over-adjustment preventing means according to the present invention is not limited to the above embodiment. The structure shown in the second embodiment described below can also be adopted.

  10 to 14 show a drum brake device 300 according to a second embodiment of the present invention. FIG. 10 is a front view of the drum brake device according to the second embodiment of the present invention. FIG. 10 is a perspective view of the drum brake device shown in FIG. 10, FIG. 12 is an enlarged front view showing the positional relationship between the automatic gap adjusting device shown in FIG. 10 and a pair of brake shoes, and FIG. 13 (a) is shown in FIG. FIG. 13B is a front view of the lever member, FIG. 13C is a side view of the lever member, and FIG. 14A is a perspective view of the automatic gap adjusting device shown in FIG. 14A and 14B are the front view and FIGS. 14A and 14C are the bottom views.

The drum brake device 300 according to the second embodiment uses a lever member 151 instead of the lever member 51 in the drum brake device 200 according to the first embodiment. This is common with the drum brake device 200 of the embodiment.
Common components are denoted by the same reference numerals and description thereof is omitted.
Hereinafter, the structure of the lever member 151 employed in the second embodiment will be described with reference to FIGS.
In this embodiment, the lever member 151 used in the automatic gap adjusting device 301 is also radially outside the operating force application point P1 of the wheel cylinder 5 as in the first embodiment. An operation force receiving portion 151 b that receives the operation force W from the wheel cylinder 5 is provided at the intermediate portion while being rotatably supported by the brake shoe 3 at the position. Further, the lever member 151 has a first tensile force at the distal end of the lever member 151 by rotating around the base end 151a when the operating force W from the wheel cylinder 5 is greater than or equal to a predetermined value. A strut operating portion 151c is provided that moves toward the adjuster gear 45 against the urging force of the spring 43. By the pressing by the strut operating portion 151c, the meshing state of the first tooth portion 41b and the second tooth portion 45a is firmly maintained.

Similarly to the lever member 51 of the first embodiment, the lever member 151 of the present embodiment is also formed by press forming a metal plate.
However, as shown in FIG. 13, the lever member 151 according to the present embodiment is formed by bending a long and narrow plate material at an intermediate portion thereof, and using the bent portion as a base end 151a, and extending from both ends of the base end 151a. The distal ends of the pair of bent pieces 151 e serve as a strut operating portion 151 c that presses the protrusion 414 of the strut 41.
As shown in FIG. 13B, the lever member 151 is rotatably supported by the web 3a by inserting the base end 151a into the notch groove 53 of the web 3a.
At that time, the pair of bent pieces 151e sandwich the web 3a of the brake shoe 3 and prevent the web 3a from falling off.

In the case of this lever member 151 as well, the distance from the contact point c1 at the time of rotation of the lever member 151 rotatably engaged with the web 3a to the operating force application point P1 is S1, and the strut operating portion 151c from the contact point at the time of rotation c1 to the operating force application point P1. The length of the bent piece 151e is set so that S1 <S2, where S2 is the distance up to.
Further, when the operating force W from the wheel cylinder 5 is less than or equal to a predetermined value, the force F by which the strut operating portion 151c pushes the projection 414 is applied to the first tension spring 43 that biases the strut 41 toward the brake shoe 4 side. The dimension of each part of the lever member 151 is set so as to be smaller than the urging force.

  When the lever member 151 of the present embodiment is used, for example, when the automatic gap adjusting device 301 is assembled to the pair of brake shoes 3 and 4 by a pre-assembly or the like, the lever member 151 is attached to the notch groove 53 of the web 3a. Since the lever member 151 sandwiches the web 3a of the brake shoe 3 between the pair of bent pieces 151e, it is difficult for the lever member 151 to fall off during assembly, and the assembly of the brake device can be improved.

It is a front view of a 1st embodiment of a drum brake device concerning the present invention. It is a perspective view of the drum brake device shown in FIG. FIG. 2 is a perspective view of a state in which the pair of brake shoes and the automatic gap adjusting device shown in FIG. 1 are partially assembled. FIG. 4 is an enlarged front view showing a positional relationship between the automatic gap adjusting device shown in FIG. 3 and a pair of brake shoes. (A) is the perspective view of the lever member shown in FIG. 4, (b) is the same front view, (c) is the same side view, (d) is the same plan view. It is CC sectional drawing of FIG. It is DD sectional drawing of FIG. FIG. 7 is an enlarged view of the automatic gap adjusting device shown in FIG. 6 when the adjuster gear rotates to adjust the gap. FIG. 7 is an enlarged view showing a state in which the rotation of the adjuster gear is restrained by the operation of the over-adjustment preventing means in the automatic gap adjusting device shown in FIG. 6. It is a front view of 2nd Embodiment of the drum brake device which concerns on this invention. It is a perspective view of the drum brake device shown in FIG. FIG. 11 is an enlarged front view showing a positional relationship between the automatic gap adjusting device shown in FIG. 10 and a pair of brake shoes. (A) is a perspective view of the lever member shown in FIG. 12, (b) is the front view, and (c) is the side view. (A) is the perspective view seen from diagonally downward of the automatic clearance gap adjustment apparatus shown in FIG. 11, (b) is the front view, (c) is the bottom view. It is a front view of the conventional drum brake device provided with the automatic clearance gap adjustment device. It is AA sectional drawing of FIG. FIG. 16 is an enlarged view of the wheel cylinder shown in FIG. 15. It is explanatory drawing of the state which the over adjustment prevention means shown in FIG. 15 act | operated.

Explanation of symbols

3, 4 Brake shoe 3a, 4a Web 3b, 4b Lining 4d Strut engaging part 5 Wheel cylinder 7 Anchor member 9 Backing plate 11 Parking lever 15 Shoe-to-shoe spring 16 Anchor spring 41 Strut 41a Shoe contact part 41b First tooth Part 41c Lever contact part 43 First tension spring 45 Adjuster gear 45a Second tooth part 45b Engaging arm part 47 Engaging hole 47a Inner edge 48 Second tension spring 51 Lever member (over-adjustment preventing means)
51a Base end 51b Operation force receiving portion 51c Strut operation portion 53 Notch groove 151a Base end 151b Operation force receiving portion 151c Strut operation portion 151e Bending piece 200 Drum brake device 201 Automatic gap adjustment device 300 Drum brake device 301 Automatic gap adjustment device 413 Long hole 414 Projection 451 Pin

Claims (2)

A drum brake device including an automatic gap adjusting device that automatically adjusts the position of a pair of brake shoes arranged in the drum inner space according to wear,
The automatic gap adjusting device includes a strut provided with a shoe contact portion that contacts one brake shoe at one end and a first tooth portion at the other end,
A first tension spring that biases the strut so as to maintain the shoe contact portion in contact with the brake shoe;
The other end of the strut is supported so as to be rotatable and movable in the longitudinal direction of the strut, and in a second tooth portion meshing with the first tooth portion and an engagement hole formed in the other brake shoe. An engaging arm portion that loosely fits, and when the other brake shoe moves more than a predetermined amount in the expanding direction, the engaging arm portion is pushed against the inner end edge of the engaging hole to An adjuster gear that can rotate,
A second tension spring that applies a weaker tensile force than the first tension spring in a direction in which the second tooth portion meshes with the first tooth portion;
Over-adjustment preventing means for restricting the rotation of the adjuster gear when the operating force from the wheel cylinder is greater than or equal to a predetermined value during braking,
The over-adjustment prevention means is a lever member interposed between the piston of the wheel cylinder and the end of the other brake shoe,
The lever member is rotatably supported by the other brake shoe at a position where the base end is radially outward from the operating force acting point of the wheel cylinder, and an operating force from the wheel cylinder is provided at an intermediate portion. An operating force receiving portion for receiving the first tension spring is provided. The front end engages with the strut and rotates when the operating force from the wheel cylinder exceeds a predetermined value. A drum brake device, further comprising a strut operating portion that is moved to the adjuster gear side to keep the meshing state between the first tooth portion and the second tooth portion.   The drum brake device according to claim 1, wherein the lever member includes a pair of bent pieces that sandwich a web of the other brake shoe.

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