JP2006170235A - Drum brake device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drum brake device capable of well suppressing the lowering of a braking force and the squeal of a brake by stably pressing brake shoes against the inner surface of a brake drum. <P>SOLUTION: This drum brake device 1 generating the braking force by pressing the pair of brake shoes 6 against the inner surface of the brake drum 2 comprises an inner wheel cylinder 14a disposed on the inner inside of the brake drum 2 and an outer wheel cylinder 14b disposed on the inner outside of the brake drum 2. The cylinder hollow part 16a of the inner wheel cylinder 14a is allowed to communicate with the cylinder hollow part 16b of the outer wheel cylinder 14b. The cross sectional areas of the cylinder hollow part 16a and the cylinder hollow part 16b are different from the cross sectional areas of a piston 18a and a piston 18b, respectively. <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, a drum brake device for a vehicle includes a plurality of pairs of brake shoes and a plurality of wheel cylinders provided independently for each pair of brake shoes (for example, Patent Document 1). reference.). In this drum brake device, normally, when the pressure of the hydraulic fluid to the wheel cylinder arranged inside the drum exceeds the set value, the pressure of the hole cylinder arranged outside the drum (backing plate side) also operates. To come.
JP-A-9-156482

  However, even in the conventional drum brake device as described above, particularly when the brake temperature is increased, the end of the outer peripheral cylindrical portion of the brake drum may be expanded by the brake shoe. In such a state, the brake shoe whose one end is supported by the anchor block swings with the anchor block as a fulcrum, and the surface pressure distribution of the brake lining becomes non-uniform, resulting in a decrease in braking force. There is a risk of inviting or brake noise.

  In view of the above, an object of the present invention is to provide a drum brake device that can press the brake shoe stably against the inner surface of the brake drum to satisfactorily suppress a reduction in braking force and a squeal of the brake.

  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, and applies a pressing force applied to the brake shoe between the inside and outside of the brake drum. It is configured to be changeable.

  In this drum brake, the pressing force applied to the brake shoe can be changed between the inside and outside of the brake drum. As a result, even if the end of the outer peripheral cylindrical part of the brake drum is slightly expanded by the brake shoe, the brake shoe is stabilized on the inner surface of the brake drum by changing the pressing force applied to the brake shoe. Can be pressed against. Therefore, according to this drum brake device, it is possible to satisfactorily suppress a reduction in braking force and a squeaking of the brake.

  Further, the drum brake device according to the present invention may include an inner wheel cylinder disposed inside the brake drum and an outer wheel cylinder disposed outside the brake drum, and a cylinder cavity of the inner wheel cylinder. Preferably, the portion and the cylinder cavity of the outer wheel cylinder are communicated with each other, and the inner wheel cylinder and the outer wheel cylinder preferably have different cylinder cavity portions and piston cross-sectional areas.

  By adopting such a configuration, it is possible to change the pressing force applied to the brake shoe between the inside and outside of the brake drum by simple hydraulic pressure control.

  Furthermore, when the drum brake device according to the present invention includes an inner wheel cylinder disposed inside the brake drum and an outer wheel cylinder disposed outside the brake drum, the inner wheel cylinder and the outer The wheel cylinder may be controlled independently.

  By adopting such a configuration, it is possible to finely adjust the pressing force applied to the brake shoe from the inner wheel cylinder and the outer wheel cylinder and press the brake shoe against the inner surface of the brake drum very stably.

  In addition, when a pair of brake shoes are disposed inside and outside the brake drum, the inner wheel cylinder for applying a pressing force to the inner pair of brake shoes and the outer pair of brake shoes are pressed. You may provide the outer wheel cylinder for providing a pressure.

  In this way, by using a plurality of pairs of brake shoes and a wheel cylinder provided for each pair of brakes, it becomes possible to press each pair of brake shoes against the inner surface of the brake drum stably and without difficulty. It is possible to satisfactorily suppress power reduction and brake noise.

  In this case, it is preferable that the brake lining included in the pair of outer brake shoes has a higher coefficient of friction than the brake lining included in the pair of inner brake shoes.

  According to the present invention, it is possible to realize a drum brake device that can stably press the brake shoe against the inner surface of the brake drum and satisfactorily suppress a reduction in braking force and a squeal of the brake.

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

[First Embodiment]
FIG. 1 is a schematic configuration diagram showing a first embodiment of a drum brake device according to the present invention, and FIG. 2 is an enlarged partial sectional view showing a main part of the drum brake device shown in FIG. The drum brake device 1 shown in these drawings is preferably applied 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 4. A pair of brake shoes 6. Each brake shoe 6 includes two webs 8 a and 8 b, a rim 10 and a brake lining 12. The two webs 8a and 8b of each brake shoe 6 extend in parallel with the plate surface of the backing plate 4, and are fixed to the inner peripheral surface of the rim 10 at a predetermined interval as shown in FIG. ing. The brake lining 12 is fixed to the outer peripheral surface of the rim 10 and faces the inner peripheral surface of the brake drum 2.

  As shown in FIG. 2, the drum brake device 1 includes an inner wheel cylinder 14a disposed on the inner side of the brake drum 2, that is, the right side in FIG. 2, and the outer side of the brake drum 2, that is, the left side in FIG. And an outer wheel cylinder 14b disposed on the (backing plate 4 side). The inner wheel cylinder 14a includes a cylinder cavity portion 16a and a pair of pistons 18a disposed inside the cylinder cavity portion 16a. Further, the outer wheel cylinder 14b includes a cylinder cavity portion 16b and a pair of pistons 18b disposed inside the cylinder cavity portion 16b.

  In the present embodiment, as shown in FIG. 2, the cylinder cavity 16 a of the inner wheel cylinder 14 a and the cylinder cavity 16 b of the outer wheel cylinder 14 b are communicated with each other via the flow path 20. Further, the inner wheel cylinder 14a and the outer wheel cylinder 14b have different cross-sectional areas of the cylinder cavity portion 16a and the cylinder cavity portion 16b and pistons 18a and 18b. That is, in this embodiment, the cross-sectional areas of the cylinder cavity 16a and the piston 18a of the inner wheel cylinder 14a are smaller than the cross-sectional areas of the cylinder cavity 16b and the piston 18b of the outer wheel cylinder 14b.

  One end of the pair of brake shoes 6, that is, the upper ends in FIG. 1 are connected to each other via one or two shoe return springs 22. Due to the urging force of the shoe return spring 22, one end of the web 8a of each brake shoe 6 is engaged with the end of the corresponding piston 18a of the inner wheel cylinder 14a. Further, due to the urging force of the shoe return spring 22, one end of the web 8b of each brake shoe 6 is engaged with the corresponding end of the piston 18b of the outer wheel cylinder 14b. One shoe return spring 22 is preferably provided between the webs 8 a of each brake shoe 6 and between the webs 8 b of each brake shoe 6.

  Further, the other end portions of the pair of brake shoes 6, that is, the lower end portions in FIG. 1 are connected to each other via a spring 24. The other end of the web 8 a of each brake shoe 6 is brought into contact with the corresponding side surface of the anchor block 26 fixed on the backing plate 4 by the biasing force of the spring 24. Similarly, the other end of the web 8 b of each brake shoe 6 is also brought into contact with the corresponding side surface of the anchor block 26 fixed on the backing plate 4 by the biasing force of the spring 24. One spring 24 is preferably provided between the webs 8 a of each brake shoe 6 and between the webs 8 b of each brake shoe 6.

  In the drum brake device 1 configured as described above, when the brake pedal is operated by the driver, hydraulic oil is supplied from the master cylinder (not shown) to the inner wheel cylinder 14a and the outer wheel cylinder 14b. Accordingly, the pair of pistons 18a of the inner wheel cylinder 14a are protruded outward, and the pair of pistons 18b of the outer wheel cylinder 14b are respectively protruded outward. As a result, a pressing force is applied to the pair of brake shoes 6 from the inner wheel cylinder 14a and the outer wheel cylinder 14b, and one end portions of both brake shoes 6 respectively move outward (to the left and right in the figure) with the anchor block 26 as a fulcrum. ) Expanded. As a result, the brake lining 12 of each brake shoe 6 is pressed against the inner peripheral surface of the brake drum 2 that rotates integrally with the wheel, whereby a braking force is obtained.

  Here, as described above, in the drum brake device 1 of the present embodiment, the cylinder cavity 16a of the inner wheel cylinder 14a and the cylinder cavity 16b of the outer wheel cylinder 14b are communicated with each other via the flow path 20. Moreover, the cross-sectional areas of the cylinder cavity 16a and the piston 18a of the inner wheel cylinder 14a are smaller than the cross-sectional areas of the cylinder cavity 16b and the piston 18b of the outer wheel cylinder 14b. For this reason, when hydraulic fluid is supplied from the master cylinder to the inner and outer wheel cylinders 14 a and 14 b, the pressing force applied to each brake shoe 6 changes between the inside and outside of the brake drum 2. . That is, in this embodiment, basically, the pressing force applied to each brake shoe 6 via the web 8b located outside the brake drum 2 is the web 8a located inside the brake drum 2. It becomes larger than the pressing force applied to each brake shoe 6 via.

  As a result, even if the end of the outer cylindrical portion 2a of the brake drum 2 is slightly expanded by the brake shoe 6 as shown by the arrow in FIG. 6 is larger than the pressure applied to each brake shoe 6 inside the inside of the brake drum 2, so that the brake lining 12 of each brake shoe 6 is stably pressed against the inner surface of the brake drum 2. be able to. Therefore, according to the drum brake device 1, it is possible to make the surface pressure distribution of the brake lining 12 in the drum axis direction uniform, and to satisfactorily suppress a reduction in braking force and a brake squeal.

  Further, the cylinder cavity portion 16a of the inner wheel cylinder 14a and the cylinder cavity portion 16b of the outer wheel cylinder 14b are communicated with each other, and the cross-sectional areas of the cylinder cavity portion 16a and the cylinder cavity portion 16b and the cross-sectional areas of the piston 18a and the piston 18b. Are different from each other, the pressing force applied to each brake shoe 6 can be changed between the inside and outside of the brake drum 2 by simple hydraulic pressure control.

  In the drum brake device 1 described above, the two webs 8a and 8b are provided for each brake shoe 6. However, the present invention is not limited to this. That is, as shown in FIG. 3, the brake shoe 6 may have a single web 8. In such a case, a piston receiver having a plurality of engaging portions 9a and 9b for engaging the plurality of pistons 18a, 18b of the inner and outer wheel cylinders with the web 8 with respect to one web 8. The member 9 may be fixed. Moreover, although the above-mentioned drum brake device 1 was demonstrated as a thing provided with two wheel cylinders, it is not restricted to this. That is, it goes without saying that the drum brake device 1 described above may include three or more wheel cylinders that press the brake shoes 6.

[Second Embodiment]
Hereinafter, a second embodiment of the drum brake device according to the present invention will be described with reference to FIG. The same elements as those described in relation to the first embodiment described above are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 4 is an enlarged partial sectional view showing a main part of a second embodiment of the drum brake device according to the present invention. The drum brake device 1A shown in the figure also has basically the same structure as the drum brake device 1 according to the first embodiment, and applies a pressing force to the pair of brake shoes 6 via the webs 8a or 8b. An inner wheel cylinder 140a and an outer wheel cylinder 140b to be applied are included. However, in the present embodiment, the cross-sectional areas of the cylinder cavity 16a and the piston 18a of the inner wheel cylinder 140a are the same as the cross-sectional areas of the cylinder cavity 16b and the piston 18b of the outer wheel cylinder 140b.

  Further, in the drum brake device 1A of the present embodiment, the cylinder cavity portion 16a of the inner wheel cylinder 140a and the cylinder cavity portion 16b of the outer wheel cylinder 140b are completely separated, and both are independent oil holes (not shown). )have. In the drum brake device 1A, the hydraulic pressures of the inner wheel cylinder 140a disposed inside the brake drum 2 and the outer wheel cylinder 140b disposed outside the brake drum 2 are independently controlled. .

  According to the drum brake device 1 </ b> A configured as described above, the pressing force applied to each brake shoe 6 from the inner wheel cylinder 140 a and the outer wheel cylinder 140 b is finely adjusted, and the brake shoe 6 is adjusted to the inner surface of the brake drum 2. Can be pressed very stably. As a result, even if the end portion of the outer peripheral cylindrical portion 2a of the brake drum 2 is slightly expanded by the brake shoe 6, the surface pressure distribution in the drum axial direction of the brake lining 12 is made uniform, and the braking force is reduced. It is possible to satisfactorily suppress squealing of the brake. In order to independently control the hydraulic pressures of the inner wheel cylinder 140a and the outer wheel cylinder 140b, for example, together with an appropriate actuator controlled by a brake ECU or the like, each brake shoe as shown by a two-dot chain line in FIG. It is preferable to use an acceleration sensor 28 attached to one end of at least one of the six webs 8a and 8b.

  In this case, the acceleration sensor 28 detects the vibration acceleration of the brake shoe 6, that is, the acceleration in the direction toward the center of the brake drum 2, and gives a signal indicating the detected value to the brake ECU. For example, when the detected value of the acceleration sensor 28 exceeds a predetermined threshold, the brake ECU maintains the hydraulic pressure of the outer wheel cylinder 140b and sets the hydraulic pressure of the inner wheel cylinder 140a to zero. Alternatively, the hydraulic pressure control actuator is operated so that the pressure is lowered by a predetermined amount. As described above, if the hydraulic pressures of the inner wheel cylinder 140a and the outer wheel cylinder 140b are independently controlled based on the vibration acceleration of the brake shoe 6, the surface pressure distribution of the brake lining 12 in the drum axial direction is made uniform. It is possible to satisfactorily suppress power reduction and brake noise.

  Although the above-described drum brake device 1A has been described as including two wheel cylinders 140a and 140b, the present invention is not limited to this. That is, it is needless to say that the above-described drum brake device 1A may include three or more wheel cylinders that are independently controlled to press the brake shoe 6.

[Third Embodiment]
Hereinafter, a third embodiment of the drum brake device according to the present invention will be described with reference to FIG. The same elements as those described in relation to the first embodiment described above are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 5 is an enlarged partial sectional view showing a main part of a third embodiment of the drum brake device according to the present invention. The drum brake device 1B shown in the figure includes a pair of inner brake shoes 6a and a pair of outer brake shoes 6b arranged in parallel in the axial direction of the brake drum 2. Each brake shoe 6a has one web 80a, a rim 10a, and a brake lining 12a. Similarly, each brake shoe 6b has one web 80b, a rim 10b, and a brake lining 12b.

  Further, the drum brake device 1B includes an inner wheel cylinder 140a for applying a pressing force to the pair of inner brake shoes 6a and an outer wheel cylinder 140b for applying a pressing force to the pair of outer brake shoes 6b. Yes. Similar to the drum brake device 1A according to the second embodiment, the cylinder cavity 16a of the inner wheel cylinder 140a and the cylinder cavity 16b of the outer wheel cylinder 140b are completely separated. The hydraulic pressures of the inner wheel cylinder 140a disposed inside the brake drum 2 and the outer wheel cylinder 140b disposed outside the brake drum 2 are independently controlled.

  In the present embodiment, the cross-sectional areas of the cylinder cavity 16a and the piston 18a of the inner wheel cylinder 140a are the same as the cross-sectional areas of the cylinder cavity 16b and the piston 18b of the outer wheel cylinder 140b. The shoe return spring and the spring arranged on the anchor block side are provided at least one for each of the inner brake shoe 6a and the outer brake shoe 6b.

  As described above, when a plurality of pairs of brake shoes 6a and 6b and individually corresponding wheel cylinders 140a and 140b are used, the pairs of brake shoes 6a and 6b are pressed against the inner surface of the brake drum 2 stably and without difficulty. Accordingly, the surface pressure distribution of the brake lining 12 in the drum axis direction can be made uniform, and a reduction in braking force and brake squeal can be satisfactorily suppressed.

  In the drum brake device 1B having a plurality of pairs of brake shoes 6a and 6b, the friction coefficients of the brake linings 12a and 12b can be changed for each brake shoe 6a and 6b. Thereby, it becomes possible to adjust the braking force by each brake shoe 6a, 6b, without changing the capacity | capacitance of the inner side wheel cylinder 140a or the outer side wheel cylinder 140b. In the present embodiment, considering the rigidity of the brake drum 2, the brake lining 12b of the outer brake shoe 6b positioned outside where the rigidity of the drum 2 is low is used as the brake of the inner brake shoe 6a positioned inside where the rigidity of the drum 2 is high. A material having a higher friction coefficient than the lining 12a is employed. As a result, even if the end of the outer peripheral cylindrical portion 2a of the brake drum 2 is slightly expanded by the brake shoes 6a and 6b, the brake lining 12b of the outer brake shoe 6b and the inner surface of the brake drum 2 come into contact with each other. If this is the case, a sufficient braking force can be applied from the outer brake shoe 6b to the brake drum 2, so that the surface pressure distribution in the drum axial direction of the brake lining 12 can be made uniform so that the braking force can be reduced and the brake squealed well. It becomes possible to suppress.

  Although the above-described drum brake device 1B has been described as including two pairs of brake shoes 6a and 6b and two wheel cylinders 140a and 140b, the present invention is not limited to this. That is, the above-described drum brake device 1B may include three or more pairs of brake shoes and three or more wheel cylinders corresponding to each brake shoe. The plurality of wheel cylinders of the drum brake device 1B may not be individually hydraulically controlled. That is, in the above-described drum brake device 1B, the cylinder cavities of the hole cylinders may be communicated with each other, and the cylinder cavities and the cross-sectional areas of the pistons may be different among the plurality of wheel cylinders.

It is a schematic structure figure showing a 1st embodiment of a drum brake device by the present invention. It is an expanded partial sectional view which shows the principal part of the drum brake device of FIG. It is a perspective view for demonstrating the modification in 1st Embodiment of the drum brake device by this invention. It is an expanded partial sectional view which shows 2nd Embodiment of the drum brake device by this invention. It is an expanded partial sectional view which shows 3rd Embodiment of the drum brake device by this invention.

Explanation of symbols

1, 1A, 1B Drum brake device, 2 Brake drum, 2a Outer cylindrical part, 4 Backing plate, 6 Brake shoe, 6a Inner brake shoe, 6b Outer brake shoe, 8, 8a, 8b, 80a, 80b Web, 9 Piston Receiving member, 9a engaging portion, 10, 10a, 10b rim, 12, 12a, 12b brake lining, 14a, 140a inner wheel cylinder, 14b, 140b outer wheel cylinder, 16a, 16b cylinder cavity, 18a, 18b piston, 20 Flow path, 22 Shoe return spring, 24 Spring, 26 Anchor block, 28 Acceleration sensor

Claims (5)

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,
A drum brake device configured to change a pressing force applied to the brake shoe between an inside and an outside of the brake drum. An inner wheel cylinder disposed inside the brake drum;
An outer wheel cylinder disposed outside the inside of the brake drum,
The cylinder cavity of the inner wheel cylinder and the cylinder cavity of the outer wheel cylinder are in communication with each other, and the inner wheel cylinder and the outer wheel cylinder have different cylinder cavity portions and piston cross-sectional areas. The drum brake device according to claim 1, wherein: An inner wheel cylinder disposed inside the brake drum;
An outer wheel cylinder disposed outside the inside of the brake drum,
The drum brake device according to claim 1, wherein the inner wheel cylinder and the outer wheel cylinder are independently controlled.   A pair of brake shoes are arranged inside and outside the brake drum, an inner wheel cylinder for applying a pressing force to the inner pair of brake shoes, and a pressing force to the outer pair of brake shoes. The drum brake device according to claim 1, further comprising an outer wheel cylinder for providing 5. The drum brake according to claim 4, wherein a brake lining included in the pair of outer brake shoes has a higher coefficient of friction than a brake lining included in the pair of inner brake shoes. apparatus.

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