JP4310169B2 - Drum brake device - Google Patents

Description

  The present invention relates to a drum brake used in an automobile, and more particularly to a drum brake device for a large commercial vehicle.

  2. Description of the Related Art Conventionally, a drum brake device for a large commercial vehicle that is generally used in practice is, for example, an anchor bracket that is a stationary member attached to a non-rotating member of a vehicle axle, and a shoe operating member that is fixed to the anchor bracket. An actuator, a pair of brake shoes whose one adjacent end is operatively engaged with the actuator and whose other adjacent end is supported by an anchor provided on the anchor bracket, and always urges the brake shoe in the return direction A so-called leading-trailing type (hereinafter referred to as LT type) brake is known which uses a shoe return spring as a main component.

  Various studies have been made on so-called “brake squealing”, which is generated when braking in this type of drum brake device and becomes noise, and many inventions and devices have been made to prevent it. In particular, it has been found that effective squealing can be prevented by suppressing complex coupled vibrations of the brake drum and the brake shoe.

Japanese Patent No. 2916395

The conventional drum brake device described above has the following problems.
(1) In order to make the natural frequency of a pair of brake shoes different, one brake shoe is made of cast iron and the other is made of steel plate, but cast iron is inferior in material strength to steel plate and the required strength of brake shoe In addition, there is a problem of increasing the weight to ensure rigidity.
(2) Since one of the pair of brake shoes is made of cast iron and the other is made of a steel plate, their manufacturing processes are different and there is a problem of high cost.

The present invention is arcuate and shoe rim of affixing the lining on the outer circumferential surface, the shoe web Toka et formed was natural frequency different pair of brake shoes to be juxtaposed with a spacing in the width direction of the inner peripheral surface of the shoe rim in the opposite disposed, leading trailing type drum brake device that applies a pivot anchor portion of the adjacent end of the other adjacent ends in commercial vehicles diverging operating the fulcrum one of the two brake shoes, a pair of brake shoes The shoe rim and shoe web are made of steel plate, and only the trailing side brake shoe of the trailing side brake shoe and the leading side brake shoe when moving forward is folded at both ends in the width direction of the shoe rim toward the inside of the brake. The bent part is formed integrally, and the bent part is moved from the center of the maximum surface pressure of the lining to the anchor side. By providing a notch in only one place around the position close to the following degrees 28 degrees, it made different each natural frequency of the pair of brake shoes, suppresses coupled vibration described above.

The present invention, among a pair of steel plate brake shoes, by simply changing the shoe rim of the trailing brake shoe at the time of advancement by simply providing a bent portion and a notch, preventing the brake device from squeaking, and There are the following unique effects.
(1) Both of the pair of brake shoes are made of steel plates, and are much lighter than conventional cast iron brake shoes.
(2) Further, since the pair of brake shoes are made of steel plates, there is no great difference in the manufacturing process of both brake shoes, and the manufacturing equipment can be shared, so there is no possibility of incurring high manufacturing costs.
(3) Further, since the notch is provided in the bent portion of the shoe rim, the bent portion can be easily bent and the manufacturing cost can be further reduced.

  Hereinafter, an example of a drum brake device according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a plan view of a leading / trailing type (LT type) drum brake device for a large commercial vehicle, FIG. 2 is a longitudinal sectional view thereof, and FIG. 3 is a plan view of a brake shoe applied to a trailing shoe.

  The anchor bracket 10 is a stationary member in which the central hole 13 is fitted to a stationary part of a vehicle body (not shown), and the peripheral part of the central hole 13 is fixed by a plurality of fastening members. The upper side of FIGS. The anchor portion 11 is formed in a shape to mount the actuator 40, and the anchor portion 11 positioned on the lower side is formed in a forked shape with an interval in the axle direction, and anchor holes 14 and 14 penetrating in the axle direction are arranged in parallel here Has been drilled.

In FIG. 1, with respect to the brake drum 50 indicated by a two-dot chain line rotating in the direction of the arrow, the brake shoe 20 expanded in the same direction is a leading shoe, and the brake shoe 30 expanded in the opposite direction. It is a trailing shoe.
One brake shoe 20 includes a shoe rim 21 in which a flat plate is bent in an arc shape, a lining 24 attached to the outer peripheral surface of the shoe rim 21, and a shoe web 22 provided in parallel with an interval on the inner peripheral surface of the shoe rim 21. 23, a pressure receiving member 25 that is operatively engaged with the actuator 40 is spanned at one end of the shoe webs 22, 23, and a cylindrical anchor boss 26 is fixed to the lower end. Has been.
The shoe rim 31 of the other brake shoe 30 has integrally a bent portion 31a bent toward the brake inward at both ends in the width direction, and the bent portion 31a has a maximum surface pressure center position of the lining, On the anchor side, a notch 31b centered at a position close to 22 degrees or more and 28 degrees or less is provided to present an arc shape. Note that the lining 24 attached to the outer peripheral surface of the shoe rim 31 and the shoe webs 22, 23, the pressure receiving member 25, and the anchor boss 26 arranged side by side with an interval on the inner peripheral surface are the lining 24 of one brake shoe 20. The shoe webs 22, 23, the pressure receiving member 25, and the anchor boss 26 are the same.
That is, one brake shoe 20 and the other brake shoe 30 are different from each other only in the shoe rims 21 and 31.
The anchor bosses 26 and 26 are rotatably supported by anchor pins 12 and 12 inserted into the anchor holes 14 of the anchor bracket 10, and the anchor pins 12 and 12 are screwed to the anchor bracket 10. The plate 16 is fixed so that it cannot be removed and cannot be rotated.

  Next, effects of the bent portion 31a and the notch 31b provided on the shoe rim 31 of the other brake shoe 30 will be described.

<Effect of bent part height>
The height of the bent portion 31a provided on the shoe rim 31 of the other brake shoe 30 requires a dimension that is 1.5 times or more the plate thickness of the shoe rim 31 in terms of the accuracy of press bending. The dimension within 2.0 times the plate | board thickness of the shoe rim 31 is requested | required from the surface of brake maintainability accompanying attachment or detachment. Here, a change in the natural frequency of the brake shoe 30 due to a difference in height of the bent portion 31a provided on the shoe rim 31 is shown by a line A in FIG.

<Effect of notch>
If uniform bent portions 31a are provided at both ends in the width direction of the shoe rim 31 and the shoe rim 31 is bent into an arc shape, wrinkles and distortion are generated at the tip of the bent portion 31a whose circumferential length is shortened, and cannot be practically processed. The problem occurs. As a countermeasure, this problem can be solved by providing a notch 31b having a length necessary for bending at the central portion in the circumferential direction of the bent part 31a. However, this notch 31b causes a decrease in the natural frequency.

  Furthermore, the decrease in the natural frequency due to the difference in the center position of the notch 31b is minimized at the position of the node of the vibration mode of the brake shoe, and is maximized at the position of the antinode of the vibration mode. As a result of the inventors' research, there is a vibration mode node at a position of 25 degrees on the brake anchor side from the maximum surface pressure center position as shown in FIG. 5, and the bent portion is provided by providing the center of the notch 31b here. It was found that it is closest to the center in the circumferential direction and the decrease in natural frequency can be minimized. The change in the natural frequency of the brake shoe at this time is shown by line B in FIG. However, the shoe rim 31 is joined to the shoe webs 22 and 23 by welding, and manufacturing tolerances are required for the relative positions of both members. In the case of this type of brake, the relative position fluctuation between the shoe rim and the shoe web requires a maximum of 3 degrees. Therefore, the center of the notch 31b is in the range of 22 degrees to 28 degrees. The natural frequency of the brake shoe at this time is indicated by a line C in FIG.

  From the conventional research, the difference in natural frequency between the pair of left and right shoes is preferably 20 to 70%. From this, the natural frequency of the other brake shoe having the bent portion 31a provided with the notch portion 31b is within the range where the height of the bent portion 31a is 1.5 to 2.0 times the shoe rim plate thickness. 20% higher than the natural frequency of one of the brake shoes without the bent portion.

The result of confirming the effect of suppressing the occurrence of brake squeal of the drum brake to which the brake shoe according to the present invention is applied is as shown in FIG. 6, and the effect equal to or better than the result of effectively suppressing the brake squeal with the conventional brake of FIG. Was confirmed.
This is because the leading shoe generally has a work amount with respect to the braking force three times that of the trailing shoe, and the brake shoe serving as the leading shoe tends to resonate with the brake drum to generate “brake squeal”. However, in the present invention, the steel sheet trailing shoe having a sufficiently higher resonance frequency than the leading shoe and having superior material strength and rigidity than the cast iron reliably suppresses the resonance between the drum 50 and the leading shoe. That is, the coupled vibration between the brake drum 50 and the pair of brake shoes is cut off, and the “brake squeal” is not generated.
The brake shoe in the present invention has a brake diameter of 406 mm, a shoe width of 216 mm, a rim plate thickness of 6 mm and a mass of 9.0 kg, which is much lighter than the conventional cast iron brake shoe mass of 13.6 kg. .

  As described above, the present invention is an easy change by simply providing a bent portion and a notch in the shoe rim of one brake shoe located on the trailing side when traveling forward, out of a pair of steel plate brake shoes. Suppresses noise and produces the following unique effects.

<A> The pair of brake shoes are both made of a steel plate, and one of the conventional brake shoes is significantly lighter than a cast iron brake shoe.

<B> Furthermore, since the pair of brake shoes are made of steel plates, there is no significant difference in the manufacturing process of both shoes, and the manufacturing equipment can be shared, so there is no possibility of incurring high manufacturing costs.
<C> Further, since the notch is provided in the bent portion of the shoe rim, the bent portion can be easily bent and the manufacturing cost can be further reduced.

Plan view of drum brake according to the present invention II-II sectional view of FIG. The top view of the trailing shoe of the drum brake concerning the present invention Relationship diagram between the height of both ends of shoe rim width direction and natural frequency Relationship between notch position and natural frequency at both ends of shoe rim width direction The figure which shows the brake squeal incidence rate of the drum brake of this invention A diagram showing the occurrence rate of brake squeal in a conventional drum brake

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Anchor bracket 11 Anchor part 11a Flat surface 12 Anchor pin 13 Center hole 14 Anchor hole 15 Extension part 15a Bottomed hole 16 Stop plate 20 Brake shoe 21 Rim 22, 23 Shoe web 24 Lining 25 Pressure receiving member 26 Anchor boss 30 Brake shoe 31 Rim 31a Bent part 31b Notch 40 Actuator 50 Brake drum

Claims (1)

A shoe rim of affixing the lining arcuate outer peripheral surface of the opposing arranged different pair of brake shoes of natural frequencies that shoe web Toka et formation juxtaposed at a distance in the width direction of the inner peripheral surface of the shoe rim In a leading / trailing type drum brake device applied to a commercial vehicle in which a pivot anchor portion at one adjacent end of both brake shoes is used as a fulcrum and the other adjacent end portion is expanded.
Forming a shoe rim and a shoe web of the pair of brake shoes from a steel plate;
Of the trailing brake shoe and the leading brake shoe during forward travel, only the trailing brake shoe is formed integrally with bent portions toward the brake inward at both ends in the width direction of the shoe rim,
The bent portion is provided with a notch only at one place centered on a position closer to 22 to 28 degrees on the anchor side from the maximum surface pressure center position of the lining,
Drum brake device.

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