JP2014132181A - Drum brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adopt a common brake lining, restrain increase of the number of components, and avoid a risk of wrong assembly by pressurizing an L-side brake shoe and a T-side brake shoe to a brake drum with a large force to generate a high braking force, and uniformly abrading both of the brake shoes.SOLUTION: The drum brake device 100 according to the present invention includes: a cylindrical brake drum 110; a pair of brake shoes 130, 130' pressurized to an inner periphery 110A of the brake drum 110; and a cam 150 rotated around a rotary driving shaft 151 to drive a tip side of each brake shoe to be enlarged. A characteristic of the cam 150 is made different on a side for driving the brake shoe 130' on a leading side from that on a side for driving the brake shoe 130 on a trailing side.

Description

  The present invention relates to a drum brake device used for braking a vehicle.

  Conventionally, various systems have been adopted as brake devices used for vehicle braking. One of them is a drum brake device, which is a substantially cylindrical brake that rotates substantially integrally with an axle. A pair of brake shoes supported on the inner peripheral surface of the brake drum so as to be swingable with respect to a swing fulcrum fixed to the vehicle side in the circumferential direction of the brake drum inside the drum. By swinging around the swing fulcrum and pressing each brake shoe against the inner peripheral surface of the brake drum, the kinetic energy is converted into thermal energy and the vehicle is braked.

  As an example of this type, in the one described in Patent Document 1, as shown in FIG. 5, the swing fulcrums 24, 24 ′ (attached to the spider so as to be expanded toward the brake drum that rotates substantially integrally with the axle, A pair of brake shoes 18 and 18 ′ that are swingably supported on the vehicle body side) and the pair of brake shoes 18 and 18 ′ are pulled toward each other to separate the pair of brake shoes 18 and 18 ′ from the brake drum. The return spring 26 is connected to the pair of brake shoes 18 and 18 'so that the pair of brake shoes 18 and 18' are pressed against and brought into contact with the brake drum against the return spring 26. And a wheel cylinder 30 that operates as described above. The return spring 26 is attached by hooking hook portions at both ends thereof to latch pins provided on the pair of brake shoes 18 and 18 ′ (refer to reference numerals relating to the description of Patent Document 1). See the drawings attached to Patent Document 1. The same applies hereinafter.

  The wheel cylinder 30 has a piston rod connected between the free ends of the pair of brake shoes 18 and 18 '(opposite sides of the swing fulcrums 24 and 24'). The pair of brake shoes 18 and 18 'are pressed against the brake drum against the return spring 26 to be braked by applying air pressure or hydraulic pressure supplied by depressing the brake pedal.

  Further, in place of a wheel cylinder that supplies a driving force for swinging a pair of brake shoes so as to press the brake shoe against the inner peripheral surface of the brake drum around a swing fulcrum, as shown in FIG. When the brake is applied, the S-shaped cam member 29 is rotated and the cam follower 31 is moved to brake the pair of brake shoes 17 around the anchor pin 15 that is the swing support shaft. A technique is described in which the drum is rocked so as to be pressed against the inner peripheral surface of the drum.

Japanese Utility Model Publication No. 5-96572 JP-A-6-221353

  By the way, a configuration in which the brake drum is braked by swinging and expanding a pair of brake shoes using the S-shaped cam as described above is a cylinder system using a hydraulic piston or the like (Patent Document 1, FIG. For example, since a cam of a forged product can be used, there is an advantage that the configuration is simple and the cost can be reduced.

  However, in the brake structure of the above-described type in which the pair of brake shoes are swung and spread to brake the drum, there is a fear as follows.

  That is, with respect to the brake shoe L on the L side (Leading side, leading side) where the rotation direction and the pressing direction of the drum are the same direction, the T side (Trailing side, Since the brake shoe T on the trailing side tends to be pushed back by the rotation of the drum, the braking force tends to weaken (see FIG. 1 and the like).

  In other words, the L-side brake shoe L that receives the action of being pulled to the drum side during braking has a large self-servo effect (self-boosting effect), but the T-side brake shoe T has a small self-servo effect (self-boosting effect). Brake effectiveness tends to be low.

  Due to the difference in the pressing effect on the drum between the L-side brake shoe L and the T-side brake shoe T, for example, the brake lining volume and area of the T-side brake shoe T are reduced as compared with the L-side brake shoe L and are asymmetric. Although measures such as increasing the surface pressure of the T-side brake shoe T have been taken, problems such as an increase in cost, an increase in the number of parts, and parts with a relatively high replacement frequency For this reason, in the case where the L-side brake shoe L and the T-side brake shoe T are different parts, there is a risk of erroneous assembly.

  The present invention has been made in view of such circumstances, and generates a high braking force by pressing both the L-side brake shoe and the T-side brake shoe against the brake drum with a large force while having a simple and low-cost configuration. In addition, the brake shoe on the L side and the brake shoe on the T side can be evenly worn so that a common brake lining can be adopted, thereby suppressing an increase in the number of parts. An object of the present invention is to provide a drum brake device that can avoid the risk of erroneous assembly.

For this reason, the first invention is
A cylindrical brake drum that rotates integrally with the axle;
A pair of brake shoes, the base end of which is pivotally supported by a swinging fulcrum attached to the vehicle body side, the distal end of which is swung around the swinging fulcrum and pressed against the inner peripheral surface of the brake drum; ,
A cam disposed between the distal ends of the pair of brake shoes and driven around the rotational drive shaft so as to act on the distal ends of the respective brake shoes and to spread the distal ends of the brake shoes; ,
A drum brake device comprising:
The cam characteristics are driven by driving the leading brake shoe that is pressed along the rotation direction of the brake drum and the trailing brake shoe that is pressed from the direction facing the rotation direction of the brake drum. It is characterized by the difference between the two.

  Further, the second invention relates to the characteristics of the cam, characterized in that the displacement of the side that drives the brake shoe on the trailing side to the side of the brake drum is larger than the side that drives the brake shoe on the leading side. To do.

  According to the present invention, while having a simple and low-cost configuration, the L-side brake shoe and the T-side brake shoe are both pressed against the drum with a large force to achieve a high braking force. A drum brake device that allows the brake shoes to be evenly worn, enables the use of a common brake lining, thereby suppressing an increase in the number of parts and avoiding the possibility of erroneous assembly. Can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front cross-sectional view (a cross-sectional view seen from an axle direction) schematically showing an overall configuration of a drum brake device according to an embodiment of the present invention. It is side sectional drawing (right side sectional drawing of FIG. 1) which shows schematically the whole structure of the drum brake device which concerns on embodiment same as the above. It is a schematic diagram for demonstrating the outer peripheral profile of the cam of the drum brake device which concerns on embodiment same as the above. It is a schematic diagram for demonstrating the outer peripheral profile of the cam of the conventional drum brake apparatus. It is a whole block diagram (sectional drawing seen from the axle direction) for demonstrating an example (cylinder system) of the conventional drum brake apparatus. It is a whole block diagram (sectional drawing seen from the axle direction) for demonstrating another example (cam system) of the conventional drum brake apparatus.

  Hereinafter, an embodiment of a drum brake device according to the present invention will be described with reference to the accompanying drawings. The present invention is not limited to the embodiments described below.

  As shown in FIGS. 1 and 2, the drum brake device 100 according to the present invention expands leading end sides (free ends) 130 a and 130 a ′ toward the inner peripheral surface 110 </ b> A of the brake drum 110 that rotates integrally with the axle 101. A pair of brake shoes 130, 130 ′ is provided so that the base end sides 130 b, 130 b ′ are swingably attached to the support pins 104, 104 ′ that are substantially integral with the spider 103.

  The pair of brake shoes 130, 130 ′ includes brake linings 131, 131 ′ as friction elements attached to the surface facing the brake drum 110.

  As shown in FIGS. 1 and 2, the pair of brake shoes 130, 130 ′ are attached to a spider 103 fixed to an axle housing 102 (vehicle body side) that rotatably supports the axle 101. It is configured to be pivotally supported by support pins (swinging fulcrum) 104, 104 ′ so as to be swingable.

  Here, the brake pins 130 and 130 ′ are provided with support pins (swinging fulcrums) 104 and 104 ′, respectively. For example, both brake shoes 130 and 130 ′ are provided on a common support pin (swinging fulcrum). It can also be set as the structure which supports 130 'so that rocking | fluctuation is possible.

  The return spring 105 pulls the free ends 130a and 130a ′ of the pair of brake shoes 130 and 130 ′ toward each other so as to separate the pair of brake shoes 130 and 130 ′ from the inner peripheral surface 110A of the brake drum 110 when not braking. The free ends 130a and 130a ′ are attached to the latch pins 130A and 130A ′.

  Here, the drum brake device 100 according to the present invention has an S-shape as a drive mechanism for expanding the free ends (tip side) 130a, 130a ′ of the pair of brake shoes 130, 130 ′ against the return spring 105. A mechanism for rotating the shaped cam 150 around the rotation drive shaft 151 is provided. The S-shaped cam 150 and the rotation drive shaft 151 can be either an integral part or a separate part.

  When the S-shaped cam 150 is rotated by the rotary drive shaft 151, cam followers 132 and 132 ′ that are rotatably attached to the free ends 130 a and 130 a ′ of the pair of brake shoes 130 and 130 ′ are S-shaped. Is displaced along the outer peripheral profile (outer peripheral shape) of the cam 150, whereby the free ends 130 a, 130 a ′ of the pair of brake shoes 130, 130 ′ are pushed toward the inner peripheral surface 110 </ b> A of the brake drum 110. The brake linings 131 and 131 ′ are pressed against the inner peripheral surface 110 </ b> A of the brake drum 110 to apply the brake.

  As shown in FIG. 2, the rotation drive shaft 151 is rotated by receiving the rotation drive from the actuator 160 to rotate the S-shaped cam 150, and the actuator 160 is operated by a driver using a brake pedal (not shown). ), The reciprocating linear motion of the cylinder that is linearly moved by receiving the air pressure (or hydraulic pressure) supplied when stepping on is converted into a reciprocating motion-rotational motion conversion mechanism (for example, slack adjuster, rack and pinion mechanism, crank mechanism, etc. ) To convert the rotational drive shaft 151 into rotational motion.

  Here, as described above, the pair of brake shoes 130, 130 ′ has the L side (the direction in which the self-servo effect (self-boosting effect) is large) in which the rotation direction and the pressing direction of the brake drum 110 are the same (the direction where the self-servo effect (self-boost effect) is large) The direction in which the rotation direction and the pressing direction of the brake drum 110 are opposed to the brake shoe 130 ′ on the leading side and the leading side (the direction in which the self-servo effect (self-boosting effect) is small and the brake effect is weak) is T. Since the brake shoe 130 on the side (Trailing side, Trailing side) tends to be pushed back by the rotation of the brake drum 110, the braking force tends to be weakened.

  On the other hand, the brake shoe 130 ′ on the L side (Leading side, leading side) tends to be pulled by the rotation of the brake drum 110, so that the braking force tends to increase.

  For this reason, there is a possibility that the wear amount of the brake linings 131 and 131 ′ attached to the pair of brake shoes 130 and 130 ′ may not be uniform.

  For this reason, in the present embodiment, as shown in FIG. 3, the involute basic circle for determining the outer peripheral profile of the S-shaped cam 150 is made different between the T side and the L side. To do.

  Specifically, the center X of the T-side involute foundation circle is offset toward the T-side brake shoe 130 with respect to the center Y of the L-side involute foundation circle. FIG. 4 shows a conventional configuration example in which the involute basic circle is common on the T side and the L side.

  Accordingly, geometrically, the T-side outer peripheral profile of the S-shaped cam 150 always displaces the cam follower 132 first, so that the T-side brake shoe 130 and the T-side brake lining 131 are First, it comes into contact with the inner peripheral surface 110A of the brake drum 110 and presses it.

  That is, in the present embodiment, the outer peripheral profile of the S-shaped cam 150 is made different between the L side and the T side, so that the T side brake shoe 130 and the T side brake lining 131 are connected to the brake drum 110. The characteristics such as the timing of pressing the inner peripheral surface 110A and the magnitude of the force are made different from those of the L-side brake shoe 130 ′ and the L-side brake lining 131 ′.

  As a result, the braking effect of the brake lining causes the T-side brake lining 131 to rise in temperature first, increasing its effectiveness, and the braking force is equalized between the L-side and the T-side. The braking force can be increased.

  Further, according to the present embodiment, the difference in the pressing effect on the brake drum between the L-side brake shoe L and the T-side brake shoe T can be suppressed, so that the brake lining volume and area of the T-side brake shoe T are asymmetrical. Therefore, the L-side brake shoe and the T-side brake shoe can be shared.

  For this reason, it is a problem that the cost increases when the L side brake shoe and the T side brake shoe are different parts, the problem that the number of parts increases, and the replacement frequency is relatively high. It is possible to avoid the possibility of erroneous assembly.

  In addition, since wear between the L-side brake shoe L and the T-side brake shoe T can be equalized, the L-side brake shoe and the T-side brake shoe can be shared in the same manner. There is a risk of increased costs when using different parts for the T-side brake shoe, problems such as an increase in the number of parts, and the possibility of erroneous assembly due to relatively high replacement frequency. Can be avoided.

  That is, according to the present embodiment, although the configuration is simple and low-cost, both the L-side brake shoe and the T-side brake shoe can be pressed against the brake drum with a large force to generate a high braking force. In addition, the brake shoe on the L side and the brake shoe on the T side can be evenly worn, so that a common brake lining can be adopted, thereby suppressing an increase in the number of parts and further misassembly. It is possible to provide a drum brake device that can avoid such a fear.

  Since the S-shaped cam 150 can be a forged die product, even if the shape is different between the L side and the T side, it is easy to manufacture and has no disadvantages such as an increase in the number of parts. is there.

  By the way, in the present embodiment, as an example of a method of making the outer peripheral profile of the S-shaped cam 150 different between the L side and the T side, the T side involute foundation with respect to the center Y of the L side involute foundation circle. Although the method of offsetting the center X of the circle toward the T-side brake shoe 130 has been described, the present invention is not limited to this, and the center of the L-side involute foundation circle, the center of the T-side involute foundation circle, , The center of the involute foundation circle is the same (concentric), and the diameter of the T-side involute foundation circle is different from the diameter of the L-side involute foundation circle (T-side involute foundation circle) Can be employed as well.

  In addition, not only the diameter of an involute foundation circle but the outer peripheral profile of the S-shaped cam 150 can be made different between the L side and the T side.

  In the present embodiment, the outer peripheral profile of the S-shaped cam 150 is described as being formed by an involute curve. However, the present invention is not limited to this, and the S-shaped cam 150 is not limited to this. The outer peripheral profile can be any other suitable shape.

  The cam according to the present invention is not limited to the S shape, but can be a Z shape or other shapes.

  The embodiment described above is merely an example for explaining the present invention, and various modifications can be made without departing from the gist of the present invention.

100 Drum brake device 101 Axle
110 Brake drum 110A Inner peripheral surface 104, 104 'Support pin (swinging fulcrum)
130 Brake shoe (trailing side, T side)
130 'Brake shoe (leading side, L side)
130a, 130a 'Free end (tip)
131, 131 ′ Brake lining 150 S-shaped cam (an example of a cam according to the present invention)
151 Rotation drive shaft 160 Actuator

Claims (2)

A cylindrical brake drum that rotates integrally with the axle;
A pair of brake shoes, the base end of which is pivotally supported by a swinging fulcrum attached to the vehicle body side, the distal end of which is swung around the swinging fulcrum and pressed against the inner peripheral surface of the brake drum; ,
A cam disposed between the distal ends of the pair of brake shoes and driven around the rotational drive shaft so as to act on the distal ends of the respective brake shoes and to spread the distal ends of the brake shoes; ,
A drum brake device comprising:
The cam characteristics are driven by driving the leading brake shoe that is pressed along the rotation direction of the brake drum and the trailing brake shoe that is pressed from the direction facing the rotation direction of the brake drum. Drum brake device characterized in that it differs from side to side. 2. The drum according to claim 1, wherein, with respect to the characteristics of the cam, the displacement of the side that drives the brake shoe on the trailing side to the side of the brake drum is larger than the side that drives the brake shoe on the leading side. Brake device.

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