JP2006138432A - Drum brake device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drum brake device capable of excellently restraining generation of an abnormal sound when expanding brake shoes. <P>SOLUTION: This drum brake device 1 generates braking force by pressing a pair of brake shoes 11 and 12 to an inner surface of a brake drum 2; and has a wheel cylinder 5 arranged on one end part side of the respective brake shoes 11 and 12 and expanding and contracting the brake shoes 11 and 12, an anchor block 7 arranged between the mutual other end parts of the respective brake shoes 11 and 12 and receiving the other end parts of the respective brake shoes 11 and 12, and a friction reducing member 8 arranged between the other end parts of at least the respective brake shoes 11 and 12 and the anchor block 7 and reducing a static friction coefficient between the respective brake shoes 11 and the anchor block 7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a drum brake device that generates a braking force by pressing a pair of brake shoes against an inner surface of a brake drum.

2. Description of the Related Art Conventionally, drum brake devices that generate a braking force by pressing a pair of brake shoes against the inner surface of a brake drum have been widely adopted, mainly in small vehicles. In such a drum brake device, a wheel cylinder for expanding and contracting the pair of brake shoes is provided on one end portion side of each brake shoe, and other brake shoes are provided between the other end portions of each brake shoe. An anchor block that receives the end is disposed. Here, in the drum brake device in which the anchor block is disposed between the other ends of the pair of brake shoes, particularly when the brake is released, the brake shoe and the anchor block may collide and generate an abnormal noise. is there. For this reason, conventionally, in order to suppress the generation of abnormal noise caused by the collision between the brake shoe and the anchor block, an elastic buffer member has been arranged between the other end of each brake shoe and the anchor block. A drum brake device is known (for example, refer to Patent Document 1).
Japanese Patent Laid-Open No. 11-117965

  However, in the vehicle equipped with the drum brake device as described above, when the brake operation is further performed in the stopped state, that is, the end of each brake shoe and the anchor block are in direct or indirect contact with each other. When the pair of brake shoes is further expanded from the state, abnormal noise may be generated from the brake device.

  Therefore, an object of the present invention is to provide a drum brake device that can satisfactorily suppress the generation of abnormal noise when the brake shoe is extended.

  The drum brake device according to the present invention is a drum brake device that generates a braking force by pressing a pair of brake shoes against the inner surface of the brake drum. The drum brake device is provided on one end side of each brake shoe. Expansion / contraction means, and an anchor block that is disposed between the other ends of each brake shoe and receives the other end of each brake shoe, and at least between the other end of each brake shoe and the anchor block And a friction reducing member for reducing a coefficient of static friction between each brake shoe and the anchor block.

  When the pair of brake shoes is further expanded from the state in which the end of each brake shoe and the anchor block are in direct or indirect contact with each other, Alternatively, a relative displacement occurs between a portion such as an anchor block that is indirectly in contact. That is, when the drum brake device is further operated in the stop state, the friction state between each brake shoe and the anchor block shifts from the static friction state to the dynamic friction state, and noise is generated due to the so-called stick-slip phenomenon. End up. The larger the difference between the static friction coefficient in the static friction state and the dynamic friction coefficient in the dynamic friction state, the greater the noise that is generated when the stored energy is released. In this case, in order to reduce the difference between the static friction coefficient in the static friction state and the dynamic friction coefficient in the dynamic friction state, it is conceivable to fill a lubricant such as grease between each brake shoe and the anchor block. However, it is not easy to properly hold the lubricant between the brake shoe and the anchor block, and it takes time to refill the lubricant.

  In view of these points, in this drum brake device, a friction reducing member for reducing a coefficient of static friction between each brake shoe and the anchor block is provided at least between the other end portion of each brake shoe and the anchor block. Be placed. This makes it possible to reduce the difference between the static friction coefficient in the static friction state and the dynamic friction coefficient in the dynamic friction state between each brake shoe and the anchor block. Therefore, when the brake shoe is expanded, even if a relative displacement occurs between the brake shoe and the anchor block that have been stationary until then, it is possible to satisfactorily suppress the generation of abnormal noise. It becomes possible.

  In this case, it is preferable that the friction reducing member is formed so as to be engageable with the anchor block by a thin metal plate.

  Accordingly, it is possible to satisfactorily reduce the coefficient of static friction between each brake shoe and the anchor block, and to easily dispose the friction reducing member between each brake shoe and the anchor block.

  In the drum brake device of the present invention, a lubricant may be filled between the anchor block and the friction reducing member.

  By adopting such a configuration, it is possible to further reduce the coefficient of static friction between each brake shoe and the anchor block, so it is possible to very well suppress the occurrence of abnormal noise when the brake shoe is expanded. It becomes.

  In this case, the drum brake device of the present invention may further include a lubricant holding means for holding the lubricant between the anchor block and the friction reducing member.

  According to the present invention, it is possible to realize a drum brake device that can satisfactorily suppress the generation of abnormal noise when the brake shoe is extended.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an embodiment of a drum brake device according to the present invention. The drum brake device 1 shown in the figure is suitable for application as a rear brake unit of a vehicle, for example, and is disposed on a brake drum 2 attached to an axle (not shown) of the vehicle and a backing plate 3. A pair of brake shoes 11 and brake shoes 12 are included. The brake shoe 11 on the left side in the figure includes a web 13 extending in parallel with the plate surface of the backing plate 3, a rim 15 fixed to the outer peripheral surface of the web 13, and a brake lining 17 fixed to the outer peripheral surface of the rim 15. And have. Similarly, the brake shoe 12 on the right side in the figure is also fixed to the web 14 extending parallel to the plate surface of the backing plate 3, the rim 16 fixed to the outer peripheral surface of the web 14, and the outer peripheral surface of the rim 16. And a brake lining 18.

  One end portions (upper end portions in the figure) of the brake shoe 11 and the brake shoe 12 are fixed on the backing plate 3 by the urging force of the shoe return spring 4 that connects the one end portion side of the web 13 and the one end portion side of the web 14. It is made to engage with the both ends of the wheel cylinder 5 as the expanded / contracted means. Further, the other end portions (lower end portions in the drawing) of the brake shoe 11 and the brake shoe 12 are placed on the backing plate 3 by the biasing force of the spring 6 that connects the other end portion of the web 13 and the other end portion of the web 14. It is made to contact | abut on the both sides | surfaces of the anchor block 7 fixed.

  When the brake pedal is operated by the driver and hydraulic oil is supplied to the wheel cylinder 5, the pair of pistons 5 a are protruded from the holes of the wheel cylinder 5, whereby both brake shoes 11 are used with the anchor block 7 as a fulcrum. 1 and 12 are extended outward (to the left and right in the figure), respectively. As a result, the brake lining 17 of the brake shoe 11 and the brake lining 18 of the brake shoe 12 are pressed against the inner peripheral surface of the brake drum 2 that rotates integrally with the wheel, whereby a braking force is obtained.

  Here, from the state where the other ends of the webs 13 and 14 of the brake shoes 11 and 12 and the anchor block 7 are in direct contact with each other or indirectly via a predetermined buffer member or the like, the brake shoes are further removed. When 11 and 12 are expanded, a relative displacement is generated between the brake shoes 11 and 12 that have been stationary with respect to each other and the anchor block 7 that is in direct or indirect contact therewith. That is, when the brake pedal is further depressed while the vehicle is stopped, the friction state between the brake shoes 11 and 12 and the anchor block 7 shifts from the static friction state to the dynamic friction state, and an abnormal noise is caused by a so-called stick-slip phenomenon. Will occur. And the larger the difference between the static friction coefficient in the static friction state and the dynamic friction coefficient in the dynamic friction state, the greater the noise that is generated when the stored energy is released.

  In this case, in order to reduce the difference between the static friction coefficient in the static friction state and the dynamic friction coefficient in the dynamic friction state, a lubricant such as grease is provided between the webs 13 and 14 of the brake shoes 11 and 12 and the anchor block 7. It is also conceivable to fill However, when traveling in the rain or the like, the lubricant may be washed away by rainwater, and it is not easy to appropriately hold the lubricant between the brake shoes 11 and 12 and the anchor block. Further, it takes time to refill the lubricant, which leads to an increase in the burden on the user.

  In view of these points, in the drum brake device 1, as shown in FIGS. 1 and 2, at least between the other ends of the webs 13 and 14 of the brake shoes 11 and 12 and both side surfaces of the anchor block 7. A friction reducing member 8 for reducing the coefficient of static friction between the brake shoes 11 and 12 and the anchor block 7 is disposed so as to be positioned at the position. As shown in FIG. 3, the friction reducing member 8 is formed by bending a thin plate made of a metal having a relatively small coefficient of static friction such as stainless steel into a substantially C shape, and is engaged with the anchor block 7 from above. It is formed so that it can be combined. In this case, it is preferable that a slight gap is formed between the friction reducing member 8 and at least one of the upper and lower surfaces of the anchor block 7, as shown in FIG.

  Thus, by providing the friction reducing member 8 as described above between the other ends of the webs 13 and 14 of the brake shoes 11 and 12 and the anchor block 7, the brake shoes 11 and 12 are arranged. 12 and the anchor block 7, the difference between the static friction coefficient in the static friction state and the dynamic friction coefficient in the dynamic friction state can be reduced. That is, the friction reducing member 8 formed of stainless steel or the like is interposed between the brake shoes 11 and 12 and the anchor block 7 so that the substantial contact between the brake shoes 11 and 12 and the anchor block 7 is achieved. The area will increase. As a result, when the end portions of the webs 13 and 14 of the brake shoes 11 and 12 and the anchor block 7 are substantially in line contact with each other, the coefficient of static friction between them, which is about 0.5, is about 0.2. It becomes possible to reduce to the extent. As a result, when the pair of brake shoes 11, 12 are expanded, they are in contact with the brake shoes 11, 12 through the friction reducing member 8 and the brake shoes 11, 12 that have been stationary until then. Even if a relative displacement occurs with the anchor block 7, it is possible to satisfactorily suppress the occurrence of abnormal noise.

  The relative displacement between the brake shoes 11 and 12 and the anchor block 7 is basically a vertical displacement along the side surface of the anchor block 7. Therefore, as shown in FIG. 2, if a slight gap is formed between the friction reducing member 8 and at least one of the upper surface and the lower surface of the anchor block 7, the friction reducing member 8 is anchored. It becomes easy to displace with respect to the block 7. Thereby, the displacement of the brake shoes 11 and 12 is absorbed by the friction reducing member 8, and between the brake shoes 11 and 12 and the anchor block 7 in contact with the brake shoes 11 and 12 through the friction reducing member 8. Even if the relative displacement occurs, it is possible to suppress the occurrence of abnormal noise very well.

  If the friction reducing member 8 is formed in a substantially C shape so as to be engageable with the anchor block 7 by a metal thin plate, the coefficient of static friction between the brake shoes 11 and 12 and the anchor block 7 is good. And the friction reducing member 8 can be easily disposed between the brake shoes 11 and 12 and the anchor block. Needless to say, the friction reducing member 8 may be an annular member surrounding the entire circumference of the anchor block 7. As can be seen from FIG. 4, the friction reducing member 8 may be engaged with the anchor block 7 from below.

  Furthermore, like the friction reducing member 8A shown in FIG. 5, the flexibility of the friction reducing member 8A may be increased by providing an opening 80 at a location that does not contact the brake shoes 11 and 12. As a result, the friction reducing member 8A is easily displaced with respect to the anchor block 7, so that the displacement of the brake shoes 11 and 12 can be satisfactorily absorbed by the friction reducing member 8A. It becomes possible to suppress well. Further, in order to increase the flexibility of the friction reducing member 8A, a notch 81 may be provided at a location that does not contact the brake shoes 11 and 12, as in the friction reducing member 8B shown in FIG.

  FIG. 7 is an enlarged view of a main part showing another embodiment of the drum brake device according to the present invention.

  The friction reducing member 8C illustrated in FIG. 7 surrounds the entire circumference of the anchor block 7, and a slight gap is formed between the inner surface of the friction reducing member 8C and the outer peripheral surface of the anchor block 7. Yes. In the example of FIG. 7, a lubricant L such as grease is filled between the inner surface of the friction reducing member 8 </ b> C and the outer peripheral surface of the anchor block 7. Thus, by filling the lubricant L between the anchor block 7 and the friction reducing member 8C, it is possible to further reduce the static friction coefficient between the brake shoes 11 and 12 and the anchor block 7. Therefore, it is possible to very well suppress the generation of abnormal noise when the pair of brake shoes 11 and 12 are expanded. Needless to say, a lubricant may be filled between the substantially C-shaped friction reducing member 8 and the anchor block 7 described with reference to FIG.

  Further, as shown in FIG. 8, a mesh material 9 that functions as a lubricant holding means for holding the lubricant may be disposed between the anchor block 7 and the friction reducing member 8C. As described above, when the lubricant is applied to the mesh material 9 as the lubricant holding means and the mesh material 9 is disposed between the anchor block 7 and the friction reducing member 8C, the lubricant is absorbed by the mesh material 9. It is securely held between the anchor block 7 and the friction reducing member 8C. As a result, it is possible to satisfactorily suppress the lubricant from being washed away by rainwater during running in the rain.

  Further, dimple processing may be performed on the inner surface of the friction reducing member. In the friction reducing member 8D illustrated in FIG. 9, a large number of minute concave portions 82 functioning as lubricant holding means are formed on the inner surface. If a lubricant such as grease is filled between the inner surface of the friction reducing member 8D configured as described above and the outer peripheral surface of the anchor block 7, the lubricant is held in each recess 82 on the inner surface of the friction reducing member 8D. Therefore, the lubricant is reliably held between the anchor block 7 and the friction reducing member 8C, and it is possible to satisfactorily prevent the lubricant from being washed away by rainwater when traveling in the rain. Become.

It is a schematic structure figure showing one embodiment of a drum brake device by the present invention. It is an enlarged view which shows the principal part of the drum brake device of FIG. It is a perspective view which shows the friction reduction member with which the drum brake apparatus of FIG. 1 was equipped. It is a perspective view which shows the other example of the friction reduction member in this invention. It is a perspective view which shows the other example of the friction reduction member in this invention. It is a perspective view which shows the other example of the friction reduction member in this invention. It is a principal part enlarged view which shows other embodiment of the drum brake device by this invention. It is a perspective view which shows the modification in other embodiment of the drum brake device by this invention. It is a perspective view which shows the other modification in other embodiment of the drum brake device by this invention.

Explanation of symbols

1 drum brake device, 2 brake drum, 3 backing plate, 4 shoe return spring, 5a piston, 5 wheel cylinder, 6 spring, 7 anchor block, 8, 8A, 8B, 8C, 8D friction reducing member, 9 mesh material, 11 , 12 Brake shoe, 13, 14 Web, 15, 16 Rim, 17, 18 Brake lining, 80 Opening, 82 Recess

Claims (4)

In a drum brake device that generates a braking force by pressing a pair of brake shoes against the inner surface of the brake drum,
An expansion / contraction means provided on one end side of each of the brake shoes, for expanding / contracting the pair of brake shoes;
An anchor block that is disposed between the other ends of each brake shoe and receives the other end of each brake shoe;
A friction reducing member is disposed between at least the other end of each brake shoe and the anchor block, and reduces a coefficient of static friction between each brake shoe and the anchor block. Drum brake device.   2. The drum brake device according to claim 1, wherein the friction reducing member is formed to be engageable with the anchor block by a metal thin plate.   The drum brake device according to claim 1 or 2, wherein a lubricant is filled between the anchor block and the friction reducing member. The drum brake device according to claim 3, further comprising a lubricant holding means for holding a lubricant between the anchor block and the friction reducing member.

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