JP2008025736A - Drum brake - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drum brake favorably operable even when it is formed more compactly, and preventing a partial load of a brake shoe. <P>SOLUTION: The drum brake is provided with: a backing plate 19 fixed to a car body; a brake drum 10 fixed to a rotary shaft; and first and second brake shoes 11, 12 attached to the backing plate 19 such that they separate from and contact with its inner circumference face. It is also provided with: a parking lever 13 with one end turnably fixed to the first brake shoe 11; a strut 14 with one end abutting on the second brake shoe 12 and the other end abutting on the parking lever 13; a shaft 17 passing through the backing plate 19 from between the brake shoes 11, 12; a link member 16 connected to the shaft 17 and the parking lever 13; and a lever 18 transmitting torque to the shaft 17 connected to a cable 6. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a drum brake device that can be formed more compactly and is suitable for use in, for example, a parking brake for a vehicle.

5 and 6 illustrate a brake device as a first example of a conventional drum brake device, FIG. 5 schematically shows a side view of the drum brake device, and FIG. 6 shows a drum brake. FIG. 2 is a diagram schematically showing the apparatus in a top view with a part broken away. In FIG. 5, the brake drum is not shown. In FIG. 6, cross-sectional hatching is omitted.
As shown in FIGS. 5 and 6, the drum brake device includes a brake drum 101, a pair of brake shoes 102 and 103, a cam 104, a lever 105, and a cable 106.

When the brake operation is performed, the cable 106 is pulled in the direction of arrow P in the drawing, and the cam 104 is rotated by displacing the lever 105 in the direction indicated by the two-dot chain line.
As the cam 104 rotates, the brake shoes 102 and 103 are displaced in a direction indicated by a two-dot chain line in FIG. 5 and are pushed into the brake drum 101 side so that the brake shoes 102 and 103 are placed on the inner peripheral surface of the brake drum 101. Pressed. As a result, a frictional force is generated between the brake drum 101 and each of the brake shoes 102 and 103, and the rotation of the brake drum 101 is regulated by this frictional force.

However, in such a drum brake device, there is a difference in the pressing force of the brake shoes 102 and 103 against the brake drum 101, which is a so-called one-sided state of the brake shoe, and the braking force may vary and the braking force may be insufficient. There is.
This is because the pressing force due to the rotation of the cam 104 is not evenly distributed to the brake shoes 102 and 103 due to the processing accuracy and assembly accuracy of the brake shoes 102 and 103 or the cam 104 and the like. Conceivable.

  For example, when the drum brake device is used for an application in which the brake shoes 102 and 103 are relatively easily worn, such as a service brake, the brake shoe having a strong pressing force against the brake drum 101 is used. Since the wear degree of the brake shoe is larger than that of the other brake shoe, the pressing force of the brake shoes 102 and 103 against the brake drum 101 is gradually and evenly distributed due to the difference in the wear amount. Is gradually resolved and the lack of braking force is resolved.

  However, for example, when the brake shoes 102 and 103 are used for an application where the wear of the brake shoes 102 and 103 is extremely small, such as a parking brake, the brake shoes 102 and 103 are hardly worn. The difference in pressing force is not adjusted, and the inconvenience that the braking force is insufficient due to contact with each other is difficult to be solved.

  A drum brake device shown in FIGS. 7 and 8 is a second example of a conventional drum brake device. As shown in FIGS. 7 and 8, the drum brake device 120 includes a pair of brake shoes 112 and 113, a strut 114, a parking lever 115, a brake drum 117, and a backing plate 118.

The parking lever 115 is rotatably connected to the brake shoe 112 at one end by a pin 115A, the strut 114 is interposed between the brake shoe 113 and the parking lever 115, and both ends of the strut 114 are respectively connected to the brake shoe 113 and the parking shoe. It is in contact with the middle part of the lever 115.
A cable 116 is inserted into the drum brake device 120 from the outside through an opening provided in the backing plate 118, and the cable 116 is connected to the other end of the parking lever 115.

  With such a configuration, when a tensile force is input to the cable 116, the drum brake device 120 rotates the parking lever 115 clockwise around the pin 115 </ b> A, and the brake shoe 113 is moved radially outward via the strut 114. The brake shoe 113 is brought into contact with the brake drum 117. When the brake shoe 113 comes into contact with the brake drum 117, a reaction force is generated from the brake drum 117 to the brake shoe 113 side, and the parking lever 115 is pushed rightward in the drawing via the strut 114. As a result, the brake shoe 112 is pushed outward in the radial direction via the pin 115A, and the brake shoe 112 is brought into contact with the brake drum 117 to generate a braking force.

  In this way, the other brake shoe 112 is pressed against the brake drum 117 by the reaction force when one brake shoe 113 is pressed against the brake drum 117 via the strut 114, so that each brake shoe 112, 113 is pressed. Is pressed against the brake drum 117 with a uniform pressing force, preventing the above-mentioned one-side contact and preventing the braking force from being insufficient.

Another example of the drum brake device provided with such struts is disclosed in Patent Document 1.
JP-A-64-069831

By the way, the drum brake device may be required to form the drum brake device more compactly due to a problem in the layout of the attachment site.
In this regard, in the drum brake device described as the first example of the prior art with reference to FIGS. 5 and 6, the device can be formed relatively compact, but there is a possibility that the braking force is insufficient due to the contact of the brake shoe described above. In this respect, the brake shoe is not suitable for use in a parking brake or the like with little wear.

  Further, in the drum brake device described as the second example of the prior art with reference to FIGS. 7 and 8, there is no possibility that the braking force is insufficient due to the one-sided contact, but when the drum brake device is formed in a small size, the drum brake device It is difficult to secure a space for connecting a cable for inputting a braking force from the outside to the parking lever 115 in the drum brake device. For example, if the cable is forced to be inserted into a small space, it is necessary to bend the cable greatly. If the deformation of the cable is too large, the tensile force cannot be transmitted sufficiently and the drum brake device operates well. There is a possibility that it cannot be made, and since it is necessary to insert the cable into a small space such as the opening of the backing plate 118, it cannot be said that the workability for assembly is good.

  The present invention was devised in view of such a problem, and can be operated well even if formed more compactly and can prevent the brake shoe from hitting one side and preventing insufficient braking force. An object is to provide a drum brake device.

  In order to achieve the above-mentioned object, a brake device according to a first aspect of the present invention includes a backing plate fixed to a vehicle body, a brake drum fixed to a rotating shaft, and an inner peripheral surface of the brake drum. And a pair of brake shoes including a first brake shoe and a second brake shoe that are attached to the backing plate so as to be detachable and abut against the inner peripheral surface of the brake drum and brake the rotation of the rotary shaft. A drum brake device, one end of which is rotatably fixed to the first brake shoe, one end of which is disposed so as to be in contact with the second brake shoe, and the other end of which is in contact with the parking lever. A strut disposed in a possible manner and a shaft disposed so as to penetrate the backing plate between the pair of brake shoes. And a link member that rotates integrally with the shaft and has a tip connected to the parking lever, one end connected to a cable for inputting a braking force, and the other end connected to the vehicle body side portion of the shaft. And a lever connected to be able to transmit rotational force.

  According to the drum brake device of the present invention, since the shaft and the lever protrude outward in the axial direction of the brake drum, it is not necessary to wire a cable for inputting the braking force in the backing plate, thereby preventing the one-sided contact. Even a drum brake device equipped with mechanisms to prevent insufficient braking force can be made more compact (small), and the assembly workability when assembling the cable to the lever is good, and Since the mounting angle of the lever and the length of the lever can be set arbitrarily, the degree of freedom of cable wiring until it is assembled to the lever is increased, and the effect that the braking force can be easily set is obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, the drum brake device is applied to a parking brake system of a vehicle.
1 to 4 are diagrams for explaining a drum brake device according to an embodiment of the present invention. FIG. 1 is a diagram schematically showing a configuration of the drum brake device in a side view, and FIG. 2 is a parking brake. FIG. 3 is a diagram schematically showing a schematic configuration of the system, FIG. 3 is a diagram schematically showing a top view of the drum brake device with a partially broken configuration, and FIG. 4 is a schematic diagram showing the upper portion of the drum brake device as viewed from below the side surface. FIG. In FIG. 3, only the cross section of the main part is hatched.

(Outline configuration)
As shown in FIG. 2, a drum brake device 4 that constitutes a parking brake is attached to the vehicle 1 in the vicinity of the axial center on the inner side in the vehicle width direction of each rear wheel (rear wheel) 2.
Each drum brake device 4 is connected to a parking brake trigger 5 via a cable 6, and a tensile force (braking force) from the parking brake trigger 5 is equally input to each drum brake device 4 via the cable 6. It is comprised so that.

(Drum brake configuration)
Here, the configuration of the drum brake device will be described with reference to FIGS. 1 and 3. 1 and 3, the drum brake device 4 includes a brake drum 10, a brake shoe (first brake shoe) 11, a brake shoe (second brake shoe) 12, a parking lever 13, a strut 14, a wire 15, The arm 16, the shaft 17, the lever 18, the backing plate 19, and the return spring 20 are configured.

  The brake drum 10 has a cylindrical shape, and the brake drum 10 forms an outline of the drum brake device 4 together with the backing plate 19. The brake drum 10 is connected to a drive shaft 3 as a rotation shaft so as to be able to transmit a rotational force, and the drive shaft 3 is connected to the wheels 2 so as to be able to transmit a rotational force. The inner peripheral surface of the brake drum 10 faces the peripheral surface of a shoe flange portion described later of the pair of brake shoes 11 and 12.

The brake shoes 11 and 12 are arranged on the left and right sides, and are attached to the backing plate 19 by pins 11E and 12E, respectively, so as to be displaceable in directions away from each other. The backing plate 19 is fixed to the body (vehicle body) of the vehicle 1.
The brake shoes 11 and 12 are plate-like shoe flange portions 11A and 12A each formed in a semicircular arc shape along the cylindrical inner peripheral surface of the brake drum 10, and the arcuate shapes of the shoe flange portions 11A and 12A. The cross-sectional shape is formed in a substantially T shape (refer to the shaded portion in FIG. 3) by the plate-like shoe web portions 11B and 12B orthogonal to the inner side in the radial direction along the inner peripheral surface. Further, friction materials (linings) 11C and 12C are disposed on the peripheral surfaces of the shoe flange portions 11A and 12A of the brake shoes 11 and 12 that face the inner peripheral surface of the brake drum 10, respectively.

One end of a parking lever 13 is connected to the brake shoe 11 by a pin 13A, and the parking lever 13 is rotatable about the pin 13A.
As shown in FIG. 4, notches 14 </ b> A and 14 </ b> B corresponding to the shoe webs 11 </ b> B and 12 </ b> B of the brake shoes 11 and 12 are formed at both ends of the strut 14. The shoe web portion 12B of the brake shoe 12 is inserted into the notch portion 14B so that the strut 14 and the brake shoe 12 can come into contact with each other. Further, a step portion 14C is formed in the notch portion 14A. The parking lever 13 is inserted into the notch portion 14A together with the shoe web portion 12B of the brake shoe 12, so that the strut 14 and the intermediate portion of the parking lever 13 come into contact with each other at the step portion 14C. Further, the tip portion of the shoe web portion 12B does not interfere with the bottom portion of the cutout portion 14B.

  A protrusion 13B is formed at the other end of the parking lever 13, and the protrusion 13B is connected to the wire 15. That is, the other end portion of the parking lever 13 is connected to the tip portion of the arm 16 via the wire 15 and can transmit a tensile force to each other. The base end portion of the arm 16 is formed integrally with or coupled to the shaft 17 so that the arm 16 and the shaft 17 rotate together. That is, the wire 15 and the arm 16 function as a link member that displaces the parking lever 13 in conjunction with the rotation of the shaft 17.

The shaft 17 passes through the backing plate 19 and projects outward in the axial direction (inward in the vehicle width direction) from the space surrounded by the brake drum 10 and the backing plate 19.
A lever 18 is connected to the other end of the shaft 17, and the lever 18 is connected to the cable 6.
The return spring 20 is a coil spring, and is interposed between the brake shoes 11 and 12 and constantly urges the brake shoes 11 and 12 in a direction to approach each other. More specifically, the return spring 20 has hook portions 20A and 20B each having a hook shape, and a locking portion 11D formed inside the shoe flange portions 11A and 12A of the brake shoes 11 and 12. , 12D are hooked between the brake shoes 11 and 12 by engaging the hook portions 20A and 20B (see FIG. 4).

Since the drum brake device according to one embodiment of the present invention is configured as described above, the following operations and effects are achieved.
First, when the driver pulls the parking brake trigger 5, a tensile force is equally input to the levers 18 of the left and right drum brake devices 4 via the cable 6.
The lever 18 is rotated in the direction indicated by the two-dot chain line in FIG. 1 by the tensile force of the cable 6, and the shaft 17 and the arm 16 that rotates together with the shaft 17 in accordance with this are shown in the direction indicated by the two-dot chain line (that is, , Clockwise). Then, as the arm 16 rotates, the parking lever 13 swings around the pin 13A, and the strut 14 is displaced toward the brake shoe 12 side.

Then, the brake shoe 12 is pushed from the strut 14 by the displacement of the strut 14, the brake shoe 12 is displaced leftward in the figure, and the friction material 12 </ b> C comes into contact with and presses against the inner peripheral surface of the brake drum 10. As a result, a braking force (frictional force) is generated between the brake shoe 12 and the brake drum 10.
Further, when the brake shoe 12 comes into contact with the brake drum 10, a reaction force from the brake drum 10 generates an axial force on the strut 14 in the long axis direction. As a result, a force is generated on the strut 14 to push the parking lever 13 rightward in the drawing.

Here, the parking lever 13 is pushed in the right direction in the drawing at the portion in contact with the strut 14, and the wire 15 pulls the parking lever 13 in the left direction in the drawing at the protrusion 13 </ b> B. An attempt is made to rotate clockwise with the contacting portion (step portion 14C) as a fulcrum.
By this rotation, the pin 13A pushes the brake shoe 11 in the right direction in the figure at the pin 13A portion, and when the brake shoe 11 is pushed by the pin 13A, the friction material 11C of the brake shoe 11 comes into contact with the inner peripheral surface of the brake drum 10, Pressed. Thereby, a braking force is generated between the brake shoe 11 and the brake drum 10.

  That is, when the brake shoe 12 is first pressed against the brake drum 10 by the strut 14, the brake shoe 11 is pressed against the brake drum 10 by the reaction force transmitted from the brake drum 10 to the strut 14. Is pressed against the brake drum 10 with an even pressing force and restricts the rotation of the brake drum 10.

  When the driver operates the parking brake trigger 5 to release the parking brake, the cable 6 is loosened and the brake force input to the lever 18 is released. The brake shoes 11 and 12 are displaced in a direction in which the brake shoes 11 and 12 approach each other (that is, a direction away from the brake drum), and the friction agents 11C and 12C and the inner peripheral surface of the brake drum 10 are separated from each other.

  As described above, according to the drum brake device of the present invention, when the shaft 17 rotates, the arm 16 disposed inside the brake drum 10 rotates and the parking lever 13 is pulled by the wire 15 to thereby turn the parking lever 13. Therefore, even if the size of the drum brake device 4 is made compact, the rotational force of the shaft 17 can be reliably transmitted and the brake shoes 11 and 12 can be pressed against the brake drum 10. Furthermore, the parking brake can be housed in a space as small as the parking brake is compactly formed as described above, and the degree of freedom in designing the layout of the vehicle 1 can be improved.

  Further, since the shaft 17 penetrates the backing plate 19 and protrudes outward in the axial direction of the brake drum 10, and the lever 17 is connected to the shaft 17, the shape such as the length of the shaft 17 and the lever 18 is appropriately set. As a result, the position where the cable 6 is connected to the lever 17 can be set relatively freely, and there is also an advantage that the degree of freedom of layout of each device of the vehicle 1 is increased. In addition, since the length of the lever 18 is set so that the tip is exposed to the outside in the radial direction of the brake drum 10, there is an effect that the assembly workability when connecting the cable 6 and the lever 18 is good. can get.

  Furthermore, each brake shoe 11 and 12 is pressed against the brake drum 10 by being pushed into the strut 14, so that each brake shoe 11 and 12 is pressed against the brake drum with an equal force. As a result, it is possible to prevent the brake shoes from coming into contact with each other and to obtain a sufficient braking force with a good balance by the brake shoes 11 and 12.

  Further, since the brake shoes 11 and 12 are always urged by the return springs 20 in the direction of separating from the brake drum 10, the brake shoes 11 and 12 are automatically activated when the driver releases the parking brake. And the brake drum 10 can be separated to release the brake.

[Others]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above-described embodiment, the drum brake device is applied to the parking brake of the vehicle as an example. However, the drum brake device is not limited to this, but as a normal drum brake device such as a service brake for a moped bicycle. The present invention can be applied to an appropriate place, and it is particularly effective to apply the present invention as a parking brake of an electric vehicle equipped with an in-wheel motor.

  In other words, in-wheel motors usually have a built-in speed reduction mechanism, and the braking force required for the parking brake is compared to the case without a speed reduction mechanism because the speed reduction mechanism is interposed between the wheel and the parking brake. And small. For this reason, the drum brake device as a parking brake can be made smaller. Further, it is possible to obtain an effect that the unsprung weight of the electric vehicle can be reduced by further downsizing the parking brake.

BRIEF DESCRIPTION OF THE DRAWINGS It is for demonstrating the drum brake device which concerns on one Embodiment of this invention, Comprising: It is a figure which shows a drum brake device typically by side view. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram schematically illustrating a schematic configuration of a parking brake system for a vehicle, for explaining a drum brake device according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is for demonstrating the drum brake device which concerns on one Embodiment of this invention, Comprising: It is a figure which partially fractures | ruptures the structure of a drum brake device, and shows it typically by upper surface view. BRIEF DESCRIPTION OF THE DRAWINGS It is for demonstrating the drum brake device which concerns on one Embodiment of this invention, Comprising: It is the typical perspective view which looked at the drum brake device from the lower side. It is a figure for demonstrating the drum brake apparatus of a prior art, Comprising: It is a figure which shows a drum brake apparatus typically by side view. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure for demonstrating the drum brake apparatus of a prior art, Comprising: The structure of a drum brake apparatus is partially fractured | ruptured, and is a figure typically shown by a top view. It is a figure for demonstrating the drum brake apparatus of a prior art, Comprising: It is a figure which shows a drum brake apparatus typically by side view. It is for demonstrating the drum brake apparatus of a prior art, Comprising: It is typical XX arrow sectional drawing of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Wheel 3 Drive shaft 4 Drum brake device 5 Parking brake trigger 6 Cable 10 Brake drums 11 and 12 Brake shoes (1st brake shoe, 2nd brake shoe)
13 Parking lever 14 Strut 15 Wire 16 Arm 17 Shaft 18 Lever 19 Backing plate 20 Return spring

Claims (1)

A backing plate fixed to the vehicle body, a brake drum fixed to a rotating shaft, and attached to the backing plate so as to be detachable from the inner peripheral surface of the brake drum. A drum brake device comprising a pair of brake shoes including a first brake shoe and a second brake shoe that brake the rotation of the rotary shaft by contact;
A parking lever having one end rotatably fixed to the first brake shoe;
A strut having one end arranged to be in contact with the second brake shoe and the other end arranged to be able to contact the parking lever;
A shaft disposed so as to penetrate the backing plate from between the pair of brake shoes;
A link member that rotates integrally with the shaft and whose tip is connected to the parking lever;
A drum brake device comprising: a lever having one end connected to a cable for inputting a braking force, and the other end connected to the vehicle body side portion of the shaft so as to transmit a rotational force to the shaft. .

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