JP4448305B2 - Drum brake - Google Patents

Description

  The present invention relates to a drum brake of a vehicle, and more particularly to a drum brake using a C-shaped brake shoe.

  There are various types of vehicle brakes, and one of them is a drum brake using a C-shaped brake shoe (see, for example, Patent Document 1).

  FIG. 12 is an exploded perspective view showing a main part of the drum brake assembly described in Patent Document 1. As shown in FIG. The drum brake assembly 101 mainly includes a support body 102, a piston mechanism 103, a brake shoe 104, a tightening spring 105, and a brake drum 106 (see FIG. 13). The illustrated drum brake assembly 101 is for the right rear wheel of a vehicle (automobile).

The piston mechanism 103 fixed to the support body 102 supports opposite ends of the C-shaped brake shoe 104. The piston mechanism 103 spreads the brake shoe 104 and presses the linings 104 a and 104 b attached to the outer peripheral surface of the brake shoe 104 against the brake drum 106. Such a drum brake assembly 101 has the advantage that the number of parts is small and the processing of the lining shape is easy compared to various drum brakes such as a leading / trailing type and a duo / servo type. ing.
Japanese Patent No. 2629059 (page 4, right column, 21st line to page 6, right column, 5th line, FIGS. 1 and 2)

  The drum brake assembly 101 described above may be used as a parking brake for a vehicle. When starting the vehicle, the parking brake may be released in a state where the vehicle gear is put in a forward direction on a flat road, or in a state where forward torque is input to the brake drum 106 such as a downhill (FIG. 13). (See (a)). In such a case, the brake shoe 104 may be reduced in diameter while the lining 104a on the side functioning as the leading shoe is in contact with the brake drum 106 due to the self-servo action (see FIG. 13B). And since the brake drum 106 rotates with a tire with the lining 104a contact | abutting, the lining 104a will be worn out. A similar situation occurs in the lining 104b when the vehicle is traveling backward, but since the forward departure of the vehicle is more frequent than the backward departure, the lining 104a on the side that functions as a leading shoe when the vehicle moves forward is earlier than the lining 104b. It will wear out. Under normal use conditions, the amount of wear of the lining 104a in such a situation is very small, so that no particular problem occurs. However, when a large amount of sand or the like enters between the brake shoe 104 and the support body 102 and gets caught, the brake shoe 104 is pushed toward the tightening spring 105 side. In some cases, the frictional force increases, that is, the resistance to the diameter-reducing operation of the brake shoe 104 when the brake is released may increase. Under such conditions, when the usage frequency of the parking brake (drum brake assembly 101) with respect to the travel distance of the vehicle is further increased (for example, the drum brake assembly 101 is rotated 100 times for the travel distance of 100 km under the above conditions). Under such very limited conditions (when used above), there is a possibility that the amount of wear of the lining 104a increases.

  The present invention was devised to solve the above-described problem, and in a drum brake having a C-shaped brake shoe, when the brake is released, the side that functions as a leading shoe when the vehicle moves forward is surely separated from the brake drum. It is an object to provide a drum brake that can be separated.

In order to solve the above problems, a drum brake according to claim 1 of the present invention is a brake shoe comprising a back plate, a C-shaped shoe body, and a lining attached to the outer peripheral surface of the shoe body. A wheel cylinder fixed to the back plate and provided between two opposing ends of the shoe body so as to support these ends, and a cylindrical brake drum surrounding the brake shoe. The wheel cylinder expands the diameter of the shoe body by pushing the two ends of the shoe main body, presses the lining against the inner peripheral surface of the brake drum, and pushes the two ends. In the drum brake formed so as to release the pressure contact by reducing the diameter of the shoe body by stopping the spreading operation. , The wheel cylinder, in the state in which the shoe body is reduced in diameter, is greater than the natural length between said two ends, and, as the lining is away with the brake drum, the brake shoe The first urging means is provided to support between the two end portions and to urge the side of the brake shoe that functions as a leading shoe when the vehicle moves forward in the reduced diameter direction.

  The wheel cylinder supports two ends of the C-shaped shoe body, and also has a function as an anchor. Therefore, in the present invention, the “side that functions as a leading shoe when the vehicle moves forward” refers to a brake shoe having a C-shaped shoe body, in which a force is applied in the direction in which the brake drum is pressed against the wheel cylinder when the vehicle moves forward. Refers to the end side.

With this configuration, when releasing the brake, the side that functions as the leading shoe when the vehicle moves forward can be separated from the brake drum by the biasing force of the first biasing means. Therefore, it is possible to reduce wear of the lining on the side that functions as a leading shoe when the vehicle moves forward.
The wheel cylinder has two ends of the brake shoe so that when the shoe body is in a reduced diameter, the distance between the two ends of the shoe body is larger than the natural length and the lining is separated from the brake drum. Can be supported.

  The drum brake according to claim 2 is the drum brake according to claim 1, wherein the first urging means further reverses a side of the brake shoe that functions as a leading shoe when the vehicle moves forward. It was set as the structure urged | biased in the gravity direction.

  With this configuration, the urging force of the first urging means can prevent the brake shoe from shifting downward in the brake released state and coming into contact with the lower side of the inner peripheral surface of the brake drum.

  The drum brake according to claim 3 is the drum brake according to claim 1 or 2, wherein the side of the brake shoe that functions as a trailing shoe when the vehicle moves forward is reduced in diameter. It was set as the structure provided with the 2nd biasing means to bias.

  In the present invention, the “side functioning as a trailing shoe when the vehicle moves forward” refers to an end portion of the brake shoe having a C-shaped shoe body, where force is applied in the direction away from the wheel cylinder by the brake drum when the vehicle moves forward. Refers to the side.

  With this configuration, when releasing the brake, in addition to the side that functions as the leading shoe when the vehicle moves forward, the side that functions as the trailing shoe can be separated from the brake drum. It should be noted that the urging force of the first urging means is more than the urging force of the second urging means in order to more surely separate the side functioning as the leading shoe when the vehicle moves forward from the brake drum. .

  With this configuration, in addition to the effects of claim 1 or claim 2, when releasing the brake, the side that functions as the trailing shoe when the vehicle moves forward is separated from the brake drum by the biasing force of the second biasing means. Can do.

  The second urging means may be configured to further urge the side of the brake shoe that functions as a trailing shoe when the vehicle moves forward in the antigravity direction.

  The drum brake according to claim 4 is the drum brake according to any one of claims 1 to 3, wherein the brake shoe has a reduced diameter on a side that functions as a leading shoe when the vehicle moves forward. A return amount restricting means for restricting the return amount of the operation is provided.

  By providing such a return amount regulating means, it is possible to prevent the side functioning as the leading shoe from returning too much when the vehicle moves forward, and to optimize the position of the brake shoe after releasing the brake.

The drum brake according to claim 5 is fixed to the back plate, a brake shoe comprising a back plate, a C-shaped shoe body, and a lining attached to an outer peripheral surface of the shoe body, A wheel cylinder provided between the two opposing ends of the brake shoe so as to support the ends; and a cylindrical brake drum surrounding the brake shoe, wherein the wheel cylinder includes the shoe The shoe body is expanded by expanding two ends of the body, the lining is pressed against the inner peripheral surface of the brake drum, and the operation of expanding the two ends is stopped. In the drum brake formed by reducing the diameter of the main body and releasing the pressure contact, the brake shoe , By one or more of the sliding means, so as to be slidable with respect to the sliding contact means, the is biased to the back plate direction, the frictional force acting between said brake shoe sliding means The side of the brake shoe that functions as a trailing shoe when the vehicle moves forward is configured to be larger than the side that functions as a leading shoe when the vehicle moves forward.

  The “sliding contact means” in the present invention may be a leaf spring having one end attached to the back plate, for example.

  With this configuration, when the brake is released, the frictional force acting between the brake shoe and the sliding contact means acts in a direction that interferes with the diameter reduction operation of the brake shoe. And since the frictional force on the side that functions as the trailing shoe is larger than the frictional force on the side that functions as the leading shoe when the vehicle moves forward, the force that attempts to reduce the diameter on the side that functions as the leading shoe is greater. Thus, the side that functions as the leading shoe when the vehicle moves forward can be separated from the brake drum. Therefore, it is possible to reduce wear of the lining on the side that functions as a leading shoe when the vehicle moves forward.

  According to the present invention, in a drum brake having a C-shaped brake shoe, when the brake is released, the side of the brake shoe that functions as a leading shoe when the vehicle moves forward is prevented from being in contact, and functions as a leading shoe. It is possible to reduce the wear of the lining on the side to be worn.

  Subsequently, a drum brake according to an embodiment of the present invention will be described with reference to the drawings as appropriate. Hereinafter, the case where the drum brake of the present invention is used as a parking brake (also referred to as a parking brake, a hand brake, and a side brake) of a vehicle (automobile) will be described by taking an example applied to the left rear wheel. As an example of operation, a case will be described in which the drum brake is released after the vehicle is stopped and the drum brake is activated and the gear is engaged in the forward direction (the forward torque is input to the brake drum). Expressions such as position and direction are based on the state in which the drum brake is installed in the vehicle unless otherwise specified. Similar parts are denoted by the same reference numerals, and redundant description is omitted. Moreover, in each figure, although the force which acts on each member is represented by the arrow, this shows the direction of force roughly and does not show even the relationship of the magnitude | size of force. Also, it does not represent all the forces acting on the member.

(First embodiment)
FIG. 1 is an exploded perspective view showing a main part of a drum brake according to a first embodiment of the present invention. The drum brake 1A mainly includes a back plate 11, a wheel cylinder 21, a brake shoe 31, a brake drum 41 (see FIG. 2), a first biasing means 51A, and a sliding contact means 61A.

  The back plate 11 includes a main body portion 12, a sleeve 13, and an attachment portion 14.

  The main body 12 is a plate attached to the vehicle body and has a hole 12a. The lever 24 of the wheel cylinder 21 is inserted through the hole 12a.

  The sleeve 13 is a member for supporting the wheel cylinder 21 on the back plate 11, and is provided on the lower side of the main body 12.

  The attachment portion 14 is a member to which one end of the first urging means 51 </ b> A is attached, and is erected from the main body portion 12. The end has a hole, and one end of the first urging means 51A is hung.

  The wheel cylinder 21 includes a screw 22, an adjustment nut 23, a lever 24, and a tappet 25.

  The screw 22 is a male screw having a groove 22a at the head. An end T1 of the brake shoe 31 is fitted in the groove 22a. The head of the screw 22 is provided so as to protrude from the sleeve 13 toward the front of the vehicle.

  The adjustment nut 23 is a female screw that is screwed into the screw 22. The opposite end of the screw 22 is in contact with the lever 24.

  The lever 24 is a member for expanding the screw 22 (adjustment nut 23) and the tappet 25. A part of the lever 24 protrudes beyond the back plate 11 from the hole 12b.

  The tappet 25 is a member that is in contact with the side of the lever 24 opposite to the screw 22 and has a groove 25a at the head. An end T2 of the brake shoe 31 is fitted in the groove 25a. The head of the tappet 25 is provided so as to protrude from the sleeve 13 toward the rear of the vehicle.

  The wheel cylinder 21 indicates a state in which the lever 24 is not operated (the screw 22 and the tappet 25 are retracted into the sleeve 13. Refer to FIG. 3B). The screw 22 and the adjustment nut 23 are adjusted so as to be slightly larger than the natural length between the end portions T1 and T2 of the brake shoe 31. In this way, the wheel cylinder 21 supports the brake shoe 31 so that the diameter of the brake shoe 31 is slightly increased from the natural state and the linings 33 and 34 are separated from the brake drum 41 when the lever 24 is not operated. is doing.

  The brake shoe 31 includes a shoe body 32 and linings 33 and 34.

  The shoe main body 32 is a metal member having a C-shaped side view and a U-shaped cross section, and includes a web 32a and flanges 32b and 32c. The shoe body 32 is supported by the wheel cylinder 21 in such a posture that the C-shaped end portions T1 and T2 are on the lower side. Here, the end portion T1 is an end portion on the front side of the vehicle, and the end portion T2 is an end portion on the rear side of the vehicle. Opposing ends T1 and T2 are fitted into the groove 22a of the screw 22 and the groove 25a of the tappet 25, respectively.

  Linings 33 and 34 are affixed to the outer peripheral surface of the web 32a.

  The flanges 32b and 32c are erected inward from the end of the web 32a. The flange 32b is on the back plate 11 side and is urged toward the back plate 11 by the sliding contact means 61A. The flange 32c has a hole for attaching the first urging means 51A.

  The shoe main body 32 is preferably formed of a mild steel material having moderate elasticity capable of expanding and reducing the diameter as described later.

  The linings 33 and 34 are affixed on the outer peripheral surface of the web 32a. The lining 33 is affixed over a predetermined range on the end T1 side. The lining 34 is affixed over a predetermined range on the end T2 side.

  The brake drum 41 (see FIG. 2) is a cylindrical member that rotates forward and backward around the rotation axis together with the wheels. The inner peripheral surface has a slightly larger diameter than the brake shoe 31 and is disposed so as to surround the brake shoe 31.

  The first urging means 51A is a member made of a coil spring. One end thereof is fixed to a mounting portion 14 provided in a portion of the main body portion 12 of the back plate 11 that is inside the brake shoe 31. The other end is fixed to the end T1 side of the flange 32c of the brake shoe 31. The first urging means 51A is provided horizontally and urges the end portion T1 side of the brake shoe 31 in the diameter reducing direction (right direction in FIG. 2).

  The sliding contact means 61A is a member made of a leaf spring. One end thereof is fixed to the upper side of the main body 12 of the back plate 11 by a bolt (not shown), and biases the flange 32b of the brake shoe 31 toward the back plate 11.

  In the drum brake 1 </ b> A, the brake shoe 31 is supported by the wheel cylinder 21. That is, the wheel cylinder 21 has a function as an anchor. When the vehicle moves forward, the end T1 is pressed against the wheel cylinder 21 (see FIG. 2B), so that the lining 33 on the end T1 side serves as a leading shoe, and the lining 34 on the end T2 side serves as a trailing shoe. Will work.

  Subsequently, an operation example of the drum brake 1A will be described with reference to FIGS. 2 and 3 (see FIG. 1 as appropriate). 2A and 2B are schematic views showing an example of the operation of the drum brake of FIG. 1, wherein FIG. 2A is a view showing a brake operation time, and FIG. 2B is a view showing a state where forward torque is generated in the brake drum. FIGS. 3A and 3B are schematic diagrams illustrating an example of the releasing operation of the drum brake of FIG. 1, in which FIG. 3A is a diagram illustrating the start of brake release, and FIG. 3B is a diagram illustrating the end of brake release. 2 to 11 used in the description of each embodiment below are schematic diagrams for explaining an operation example of the drum brake according to each embodiment, and therefore, the size of each part is exaggerated.

  First, the case where the drum brake 1A is operated will be described with reference to FIG. 2 (see FIG. 1 as appropriate). When the driver pulls the parking brake lever, the lever 24 is actuated to separate the screw 22 and the tappet 25. First, the screw 22 is pushed out from the sleeve 13 toward the front of the vehicle, and the lining 33 is pressed against the brake drum 41. Next, the tappet 25 is pushed out from the sleeve 13 toward the rear of the vehicle, and the lining 34 is pressed against the brake drum 41. In this way, the wheel cylinder 21 presses and widens the ends T1, T2 of the brake shoe 31 with the forces F1, F2, whereby the linings 33, 34 can be pressed against the brake drum 41, and the drum brake 1A serves as a parking brake. It works (FIG. 2 (a)).

  The vehicle is stopped with the driver operating the parking brake (drum brake 1A). Therefore, when the gear is put in the forward direction, the forward torque is input to the brake drum 41. Due to this forward torque, the end T1 pushes the wheel cylinder 21 with a force F6, and the screw 22 is retracted (FIG. 2B). At this time, the lining 33 of the brake shoe 31 functions as a leading shoe, and the lining 34 functions as a trailing shoe. That is, the lining 33 has a self-servo action and tries to stick to the brake drum 41.

  A case where the driver releases the parking brake in this state will be described. First, the wheel cylinder 21 stops pushing the brake shoe 31 with the forces F1 and F2 (FIG. 3A). The shoe body 32 is reduced in diameter by its restoring forces F3 and F4 (F3 and F4 are forces of the same magnitude and opposite directions, the same applies hereinafter), and the original shape (the shape of FIG. 3B). ). At that time, since the urging force F5 of the first urging means 51A acts on the leading shoe side, the force (F3 + F5) on the leading shoe side becomes larger than the force (F4) on the trailing shoe side. For this reason, the lining 33 on the leading shoe side can be separated from the brake drum 41 against the force of the lining 33 that sticks to the brake drum 41 caused by the self-servo action (FIG. 3B). Therefore, wear of the lining 33 when the vehicle moves forward can be reduced.

(Second embodiment)
The drum brake according to the second embodiment will be described focusing on the differences from the drum brake 1A according to the first embodiment. FIG. 4 is a schematic diagram illustrating an example of a drum brake releasing operation according to the second embodiment. FIG. 4A is a diagram illustrating a brake release start time, and FIG. 4B is a diagram illustrating a brake release end time. The drum brake 1B has first urging means 51B instead of the first urging means 51A.

  The first biasing means 51B biases the side of the brake shoe 31 that functions as the leading shoe with a force F7 in the upper right direction in the figure (FIG. 4A). Thus, the first urging means 51B urges the shoe in the anti-gravity direction, so that the brake shoe 31 is further displaced downward in the brake released state, and is applied to the lower side of the inner peripheral surface of the brake drum 41. It is possible to prevent contact.

(Third embodiment)
The drum brake according to the third embodiment will be described focusing on the differences from the drum brake 1A according to the first embodiment. FIG. 5 is a schematic diagram illustrating an example of a drum brake release operation according to the third embodiment, where (a) illustrates a brake release start time and (b) illustrates a brake release end time. The drum brake 1C is installed in a vehicle with the drum brake 1A slightly tilted counterclockwise in the drawing. By installing in this way, the first urging means 51A urges the brake shoe 31 with the force F5 in the upper right direction in the figure (FIG. 5A), and the brake shoe 31 in the brake released state. Can be prevented from shifting downward and coming into contact with the lower side of the inner peripheral surface of the brake drum 41.

(Fourth embodiment)
The drum brake according to the fourth embodiment will be described focusing on the differences from the drum brake 1A according to the first embodiment. FIGS. 6A and 6B are schematic diagrams illustrating an example of operation of the drum brake according to the fourth embodiment, where FIG. 6A is a diagram illustrating the start of brake release, and FIG. 6B is a diagram illustrating the end of brake release. The drum brake 1D includes a second urging unit 52 in addition to the first urging unit 51A.

  The second urging means 52 is a member made of a coil spring. One end thereof is fixed to a mounting portion 14 erected on a portion of the main body portion 12 of the back plate 11 that is inside the brake shoe 31. The other end is fixed to the end T2 side of the flange 32c of the brake shoe 31. The second urging means 52 is provided horizontally and urges the end portion T2 side of the brake shoe 31 in the diameter reducing direction (left direction in the figure).

  The second urging means 52 urges the brake shoe 31 functioning as a trailing shoe when the vehicle moves forward with a force F8 in the left direction in the figure (FIG. 6A). Sometimes the side functioning as the trailing shoe as well as the side functioning as the leading shoe can be separated from the brake drum 41 (FIG. 6B). Therefore, wear of the lining 34 when the vehicle is traveling backward can be reduced.

  It is desirable that the urging force F5 of the first urging means 51A is greater than or equal to the urging force F6 of the second urging means 52. This is because the lane 33 needs to be separated from the brake drum 41 more reliably because the vehicle has more opportunities for forward departure than the reverse departure.

(Fifth embodiment)
The drum brake according to the fifth embodiment will be described focusing on differences from the drum brake 1A according to the first embodiment. FIG. 7 is a schematic diagram showing an example of a drum brake release operation according to the fifth embodiment, where (a) is a diagram showing the start of brake release, and (b) is a diagram showing the end of brake release. The drum brake 1E includes return amount regulating means 71 in addition to the first urging means 51A.

  The return amount regulating means 71 includes a friction ring 72, a rod 73, a first wall portion 74, and a second wall portion 75.

  The friction ring 72 is a member for generating a frictional force between the friction ring 72 and the rod 73. The axial thickness is smaller than the width of the gap between the first wall portion 74 and the second wall portion 75.

  One end of the rod 73 is attached to the flange 32c of the brake shoe 31 and is movably inserted into the first wall 74, the friction ring 72, and the second wall 75.

  The first wall portion 74 and the second wall portion 75 are erected from the main body portion 12 of the back plate 11 at a predetermined interval, and the rod 73 is inserted therethrough. Between these wall portions 74 and 75, a friction ring 72 into which a rod 73 is inserted is provided.

  An example of the releasing operation of the drum brake 1E provided with the return amount regulating means 71 will be described.

  First, the vehicle is stopped with the parking brake (drum brake 1E) being activated. At this time, the friction ring 72 is in contact with the first wall portion 74. Therefore, when the gear is put in the forward direction, the forward torque is input to the brake drum 41 (FIG. 7A).

  The leading shoe side is separated from the brake drum 41 by the forces F3 and F5. At this time, the rod 73 moves in the diameter reducing direction. Accordingly, the friction ring 72 moves from the first wall 74 side to the second wall 75 side (FIG. 7B).

  When the friction ring 72 comes into contact with the second wall portion 75, a frictional force F9 is generated between the friction ring 72 and the rod 73. The frictional resistance between the friction ring 72 and the rod 73 is large enough to prohibit relative movement between the friction ring 72 and the rod 73 in such a state. That is, the return amount on the leading shoe side when the diameter is reduced is an amount obtained by subtracting the axial width of the friction ring 72 from the width of the gap between the first wall portion 74 and the second wall portion 75 (FIG. 7A ) And w), it is possible to prevent the leading shoe side from returning too much.

  When the drum brake 1E is operated again, the force F1 (see FIG. 2 (a)) that pushes the wheel cylinder 21 is sufficiently larger than the frictional force between the friction ring 72 and the rod 73. ), The friction ring 72 moves to the first wall 74 side together with the rod 73.

  Such a drum brake 1E prevents excessive return on the side that functions as a leading shoe when the vehicle moves forward by the frictional force F9 generated between the friction ring 72 and the rod 73, and optimizes the position of the brake shoe 31 after releasing the brake. can do.

(Sixth embodiment)
The drum brake according to the sixth embodiment will be described focusing on differences from the drum brake 1A according to the first embodiment. FIG. 8 is a schematic diagram illustrating an example of a drum brake release operation according to the sixth embodiment, where (a) illustrates a brake release start time and (b) illustrates a brake release end time. The drum brake 1F does not have the first urging means 51A and the attachment portion 14. In addition to the sliding contact means 61A, sliding contact means 61B is provided.

  The sliding contact means 61B is a member made of a leaf spring. One end thereof is fixed to the upper side of the main body 12 of the back plate 11 by a bolt (not shown), and biases the end T2 side of the flange 32b (see FIG. 1) toward the back plate 11.

  When the brake is released, the frictional force F10 acts rightward in the figure between the sliding contact means 61B and the flange 32b (FIG. 8A). Since this frictional force F10 works in a direction to cancel the restoring force F4, the force in the reduced diameter direction (F3) on the side that functions as the leading shoe when the vehicle moves forward is reduced in the reduced diameter direction on the side that functions as the trailing shoe. It becomes larger than force (F4-F10). Accordingly, the lining 33 can be separated from the brake drum 41 against the force that the lining 33 tries to stick to the brake drum 41 caused by the self-servo action (FIG. 8B).

  The ratio of the magnitude of the frictional force generated between the sliding contact means 61A and 61B and the flange 32b can be, for example, 1: 0.5.

(Seventh embodiment)
The drum brake according to the seventh embodiment will be described focusing on the differences from the drum brake 1A according to the first embodiment. FIG. 9 is a schematic diagram illustrating an example of a drum brake release operation according to the seventh embodiment, where (a) illustrates a start of brake release, and (b) illustrates an end of brake release. The drum brake 1G does not include the first urging means 51A, the attachment portion 14, and the sliding contact means 61A, but includes the sliding contact means 61C and the sliding contact means 61D.

  The sliding contact means 61C is a member made of a leaf spring. One end of the flange 32b (see FIG. 1) is fixed to the upper side of the main body 12 of the back plate 11 by a bolt (not shown) and biases the end T1 side of the flange 32b (see FIG. 1) toward the back plate 11.

  The sliding contact means 61D is a member made of a leaf spring. One end thereof is fixed to the upper side of the main body 12 of the back plate 11 by a bolt (not shown), and biases the end T2 side of the flange 32b (see FIG. 1) toward the back plate 11. The frictional force F12 generated between the sliding contact means 61D and the flange 32b is formed larger than the frictional force F11 generated between the sliding contact means 61C and the flange 32b. For example, F12: F11 = 1: 0.75 can be set.

  When the brake is released, the force (F3-F11) on the side that functions as the leading shoe when the vehicle moves forward is greater than the force (F4-F12) on the side that functions as the trailing shoe (FIG. 9A). Therefore, the lining 33 can be separated from the brake drum 41 against the force that the lining 33 tries to stick to the brake drum 41 caused by the self-servo action (FIG. 9B).

(Eighth embodiment)
The drum brake according to the eighth embodiment will be described focusing on differences from the drum brake 1A according to the first embodiment. FIG. 10 is a schematic diagram illustrating an example of a drum brake release operation according to the eighth embodiment, where (a) illustrates a brake release start time and (b) illustrates a brake release end time. The drum brake 1H does not include the first urging means 51A, the attachment portion 14, and the sliding contact means 61A, but includes the sliding contact means 61E.

  The sliding contact means 61E is a member made of a leaf spring. One end thereof is fixed to the upper side of the main body 12 of the back plate 11 by a bolt (not shown), and biases the end T2 side of the flange 32b (see FIG. 1) toward the back plate 11.

  Since the frictional force F13 is generated between the sliding contact means 61E and the flange 32b when the brake is released, the force (F3) on the side that functions as the leading shoe when the vehicle moves forward is on the side that functions as the trailing shoe. It becomes larger than the force (F4-F13) (FIG. 10A). Accordingly, the lining 33 can be separated from the brake drum 41 against the force that the lining 33 tries to stick to the brake drum 41 caused by the self-servo action (FIG. 10B).

(Ninth embodiment)
The drum brake according to the ninth embodiment will be described focusing on differences from the drum brake 1A according to the first embodiment. FIG. 11 is a schematic diagram showing an example of a drum brake release operation according to the ninth embodiment, where (a) shows a start of brake release and (b) shows a end of brake release. The drum brake 1I has a configuration in which the wheel cylinder 21, the brake shoe 31, the first urging means 51A, and the sliding contact means 61A are attached by rotating 180 degrees around the rotation axis of the wheel. Even in such a configuration, the end portion T1 side functions as a leading shoe when the vehicle moves forward, and the drum brake 1I has the same effects as the drum brake 1A according to the first embodiment.

  The design of the drum brake according to the present invention can be changed as appropriate without departing from the gist of the present invention. Its application is not limited to parking brakes, but can also be applied to main brakes (also called service brakes, service brakes, and foot brakes). Further, as a modified example of the fourth to eighth embodiments, a configuration in which the wheel is rotated by 180 degrees around the rotation axis of the wheel may be used similarly to the drum brake 1I according to the ninth embodiment. Note that the mounting angle around the rotation axis of the wheel when the drum brake of the present invention is mounted on the vehicle is not limited to the above-described one, and can be mounted at an arbitrary angle.

  Further, the attachment positions of the urging means and the sliding contact means are not limited to those illustrated. Although one end of each urging means 51A, 51B, 52 is configured to be attached to the mounting portion 14, the bolt head for fixing the sliding contact means 61A to the back plate 11 or the leaf spring body of the sliding contact means 61A. The structure which attaches may be sufficient. Further, the attachment / fixation of each sliding contact means to the back plate is not limited to that using bolts. In the sixth to eighth embodiments, the frictional force acting between the sliding contact means and the brake shoe on the side that functions as the trailing shoe when the vehicle moves forward is larger than the side that functions as the leading shoe. Further, although one or two sliding contact means are mounted, three or more sliding contact means may be used.

It is a principal part disassembled perspective view which shows the drum brake which concerns on 1st embodiment of this invention. 2A and 2B are schematic diagrams illustrating an operation example of the drum brake of FIG. 1, in which FIG. 1A is a diagram illustrating when the brake is operated, and FIG. 2B is a diagram illustrating a state in which forward torque is generated in the brake drum. 2A and 2B are schematic diagrams illustrating an example of a release operation of the drum brake in FIG. 1, in which FIG. 1A is a diagram illustrating a brake release start time, and FIG. It is a schematic diagram which shows the release operation example of the drum brake which concerns on 2nd embodiment of this invention, (a) is a figure which shows the time of brake release start, (b) is a figure which shows the time of brake release completion. It is a schematic diagram which shows the release operation example of the drum brake which concerns on 3rd embodiment of this invention, (a) is a figure which shows the time of brake release start, (b) is a figure which shows the time of brake completion | finish. It is a schematic diagram which shows the release operation example of the drum brake which concerns on 4th embodiment of this invention, (a) is a figure which shows the time of brake release start, (b) is a figure which shows the time of brake release completion | finish. It is a schematic diagram which shows the release operation example of the drum brake which concerns on 5th embodiment of this invention, (a) is a figure which shows the time of brake release start, (b) is a figure which shows the time of brake release completion. It is a schematic diagram which shows the release operation example of the drum brake which concerns on 6th embodiment of this invention, (a) is a figure which shows the time of brake release start, (b) is a figure which shows the time of brake release completion | finish. It is a schematic diagram which shows the release operation example of the drum brake which concerns on 7th embodiment of this invention, (a) is a figure which shows the time of brake release start, (b) is a figure which shows the time of brake completion | finish. It is a schematic diagram which shows the releasing operation example of the drum brake which concerns on 8th embodiment of this invention, (a) is a figure which shows the time of brake release start, (b) is a figure which shows the time of completion | finish of brake release. It is a schematic diagram which shows the release operation example of the drum brake which concerns on 9th embodiment of this invention, (a) is a figure which shows the time of brake release start, (b) is a figure which shows the time of brake release completion | finish. It is a principal part disassembled perspective view which shows the drum brake assembly of patent document 1. FIG. FIG. 13 is a schematic diagram illustrating an example of a releasing operation of the drum brake assembly of FIG. 12, (a) is a diagram illustrating when the brake is released, and (b) is a diagram illustrating when the brake is released.

Explanation of symbols

1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I Drum brake 11 Back plate 12 Body portion 13 Sleeve 14 Mounting portion 21 Wheel cylinder 31 Brake shoe 32 Shoe body 32a Web 32b Flange 32c Flange 33 Lining 34 Lining 41 Brake drum 51A, 51B First urging means 52 Second urging means 61A, 61B, 61C, 61D, 61E Sliding contact means 71 Return amount restricting means 72 Friction ring 73 Rod 74 First wall 75 Second Wall

Claims (5)

Back plate,
A brake shoe comprising a C-shaped shoe body and a lining attached to the outer peripheral surface of the shoe body;
A wheel cylinder fixed to the back plate and provided between the two opposing ends of the shoe body so as to support these ends;
A cylindrical brake drum surrounding the brake shoe,
The wheel cylinder expands the diameter of the shoe body by expanding the two ends of the shoe body, presses the lining against the inner peripheral surface of the brake drum, and expands the two ends. In the drum brake formed by reducing the diameter of the shoe body by stopping the operation and releasing the pressure contact,
The wheel cylinder is configured so that when the shoe body is in a reduced diameter state, the distance between the two ends is larger than a natural length, and the lining is separated from the brake drum. Support between the two ends,
A drum brake comprising a first urging means for urging a side of the brake shoe that functions as a leading shoe when the vehicle moves forward in a diameter-reducing direction.   2. The drum brake according to claim 1, wherein the first urging unit further urges a side of the brake shoe that functions as a leading shoe when the vehicle moves forward in an anti-gravity direction.   The drum according to claim 1 or 2, further comprising second urging means for urging a side of the brake shoe that functions as a trailing shoe when the vehicle moves forward in a diameter reducing direction. brake.   4. A return amount regulating means for regulating a return amount of a diameter-reducing operation on a side of the brake shoe that functions as a leading shoe when the vehicle moves forward. Drum brake described in. Back plate,
A brake shoe comprising a C-shaped shoe body and a lining attached to the outer peripheral surface of the shoe body;
A wheel cylinder fixed to the back plate and provided between two opposing ends of the brake shoe so as to support these ends;
A cylindrical brake drum surrounding the brake shoe,
The wheel cylinder expands the diameter of the shoe body by expanding the two ends of the shoe body, presses the lining against the inner peripheral surface of the brake drum, and expands the two ends. In the drum brake formed by reducing the diameter of the shoe body by stopping the operation and releasing the pressure contact,
The brake shoe is urged toward the back plate by one or more sliding contact means so as to be slidable with respect to the sliding contact means, and between the brake shoe and the sliding contact means. The drum brake according to claim 1, wherein a frictional force to be applied is formed such that a side of the brake shoe that functions as a trailing shoe when the vehicle moves forward is larger than a side that functions as a leading shoe when the vehicle moves forward.

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