JP2888771B2 - Drum brake for vehicles with squeal prevention mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle drum brake provided with a "squeal" preventing mechanism.

[0002]

2. Description of the Related Art Various studies have been made on so-called "squeal" which is generated during braking in a vehicle drum brake during braking, and many inventions and ideas have been developed as a measure against "squeal". Brake squeal
It is considered appropriate to consider the mechanism of the "squeal" generated by the study of the present invention as a coupled vibration between a brake drum and two brake shoes. In other words, this will be described with reference to a leading-trailing (LT) type drum brake shown in FIG. 1. A pair of brake shoes, one end of which is rotatably supported on a bracket 3 by a pin 2, for example, inside a brake drum 1. 4 and 5, the other ends of both brake shoes 4 and 5 are expanded by a cam 6 which is rotated by an actuator (not shown), and a lining 7 affixed to the outer surfaces of the shoes 4 and 5 is applied to the inner periphery of the brake drum 1. In the case of a vehicle drum brake that presses against a surface to perform braking, when the "squeal" occurs, the brake drum 1 vibrates in a mode as shown by a solid line 8 in FIGS. 9 and 10 (FIG. Mode, FIG. 10 shows the fourth mode), and the brake shoes 4, 5 vibrate in the mode shown by the solid line 9 in FIG. Such complicated vibration of the brake drum 1 and the brake shoes 4 and 5 causes the coupled vibration between the brake drum 1 and the two brake shoes 4 and 5.

[0003] This is a double-acting two-leading (2
The same applies to the L) type drum brake. That is, the drum brake comprises wheel cylinders 14, 15 having two pistons moving in opposite directions between opposing ends of a pair of brake shoes 12, 13 symmetrically arranged in a brake drum 11. And the cylinder 1
At the time of the operation of the shoes 4 and 15, the shoes 12,
The entire linings 17 and 17 ′ are pressed against the drum 11 by opening both ends of 13.
When “squealing” occurs, the solid line 8 in FIGS.
11 and the vibration of the brake shoes 12 and 13 shown by the solid line 9 in FIG. 11 also cause the coupled vibration between the brake drum 11 and the two brake shoes 12 and 13. Then, the brake drum 1 or 11 and the brake shoes 4, 5, or 12,
Each of the 13 has a large natural frequency that causes the coupled vibration. In the conventional countermeasures against "squeal", the natural frequency of each of the brake drum 1 or 11 or the pair of brake shoes 4, 5, 12 or 13 (mostly the brake shoes) is changed.

[0004]

However, as described above, since the brake drum 1 or 11 and the pair of brake shoes 4, 5, 12, and 13 each have a large natural frequency, the brake drum and / or the pair of brakes Even if one natural frequency that causes "squeal" in the shoe is changed, the coupled vibration may occur again at another natural frequency, and "squeal" may occur. As a result of research, the present inventors differed in the natural frequencies of a pair of left and right brake shoes, which is one of the factors that cause the coupled vibration, to generate the coupled vibration at a plurality of natural frequencies. It was found to be difficult, and the applicant filed an application as Japanese Patent Application No. 6-225828. Further, the inventor has continued his research, and by making the width of one of the pair of brake shoes different from the other, it has become difficult to generate the coupled vibration at a plurality of natural frequencies, and the occurrence rate of “squeal” has been reduced. The inventor of the present invention has invented a method of reducing the number, and has also filed an application as Japanese Patent Application No. 6-309673 by the present applicant. The present invention was devised as a result of further research conducted by the present inventor. As in the case of the above-mentioned application, the present invention absorbs the vibration that causes “squeal” with a simple structure, and further “squeezes” compared to the conventional one. It is an object of the present invention to provide a vehicle drum brake provided with a squeal prevention mechanism that hardly generates noise. Another object of the present invention is to provide a vehicle drum brake provided with an easily produced squeal prevention mechanism capable of effectively suppressing the squeal by merely processing one of the brake shoes of the same size. Is to provide.

[0005]

According to the present invention, there is provided a vehicle drum brake provided with a squeal preventive mechanism for achieving the above object. The present invention relates to a vehicle drum brake which presses a pair of brake shoes of the same size against the inner surface of a brake drum for braking. In the drum brake, a first invention in which the center of the point of application of one of the pair of brake shoes at the time of braking is decentered in the width direction of the shoe, and a pair of brake shoes on the inner surface of the brake drum In a vehicle drum brake that presses and brakes a brake shoe of the same size, a center of an applied point at the time of braking of one of the pair of brake shoes is eccentric to a depth side of the brake drum in a width direction of the shoe. The second invention is characterized in that the second invention is performed.

[0006]

In the vehicle drum brake according to the first aspect of the invention, the center of the point of application of one of the pair of brake shoes during braking is eccentric in the width direction of the shoe, so that the two shoes can be used with respect to the brake drum. The point of application is different, and the vibration of the drum is changed as compared to the case where the point of application is the same, so that the coupled vibration is less likely to occur, and thus the chance of generating "squeal" is reduced. Further, in the vehicle drum brake according to the second aspect of the invention, the eccentricity according to the first aspect of the present invention is applied to the inner side of the brake drum, whereby vibration is suppressed at a position where the amplitude of the brake drum is small. The suppression effect can be increased. In the first and second aspects of the present invention, when the widths of the pair of brake shoes are different from each other, the natural frequencies of the two shoes are different from each other. Together with this, the vibration suppressing effect is further enhanced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a vehicle drum brake according to the present invention will be described in detail with reference to FIGS. 1 to 8. In the "leading-trailing drum brake" shown in FIG. As shown in FIGS. 3 and 4, both the brake shoe 4 serving as a leading shoe and the brake shoe 5 serving as a trailing shoe have webs 4b, 4c or rims 4a, 5a on which linings 7, 7 'are attached. In the embodiment shown in FIGS. 3 and 4, the anchor block 18 connected to the lower ends of the webs 5b and 5c is connected to the brake shoe 5 serving as a trailing shoe when the shoe 5 is assembled. As shown in FIG. 3, it is eccentric to the front side by a predetermined distance e, that is, eccentric to the opening side of the brake drum 1, and is fixed to the lower ends of the webs 5b and 5c by welding or the like. Things. Thereby, when the brake shoe 5 is mounted on the bracket 3 by the anchor pin 2, the brake shoe 5 is eccentric to the rear side of the brake drum 1 by a distance E as shown in FIG. The applied point at the time is a position different from the applied point on the brake shoe 4 serving as the leading shoe.

In the drum brake shown in FIG. 2, both brake shoes 12 and 13 become leading shoes regardless of the rotation direction of the brake drum 11 [2].
A leading shoe type drum brake ", in which both brake shoes 12 and 13 have webs 12b and 13b on the back surfaces of rims 12a and 13a to which linings 17 and 17 'are attached. The position of the brake shoe in the width direction can be adjusted by, for example, eccentricity of the one shoe 13 in the width direction of the web 13b. However, the embodiments shown in FIGS. 3 to 8 all describe a brake shoe for a "leading-trailing drum brake".

In the embodiment shown in FIGS. 5 to 8, the width of the brake shoe 5 'serving as a trailing shoe is set to the rim 5'.
a and the lining 7 "are smaller than the rim 4a and the lining 7 of the brake shoe 4 which is the leading shoe. This can also be carried out by the" 2 leading shoe drum brake "shown in FIG. The extent to which the width of the brake shoe 5 'is made smaller than the width of the brake shoe 4 can be determined by experiments or the like. According to the research conducted by the present inventors, the width of the brake shoe 5 is determined by the width of the brake shoe 4. On the other hand, setting the primary natural frequency so as to differ (increase) by about 10 to 30% produced a good result. According to the experiments of the present inventors, the “squealing” occurrence rate is reduced by the difference in the natural frequency between the left and right brake shoes 4 and 5 having different widths at the above ratio. 30 drum brakes using brake shoes
%, Whereas that of the present invention was drastically reduced to 0%.

A brake shoe 5 'shown in FIG. 5 has a width smaller than that of the other brake shoe 4, and has an anchor block 18 connected to the lower ends of the webs 5'b and 5'c as in FIG. When the shoe 5 'is assembled, it is eccentrically moved forward by a predetermined distance e as shown in FIG. 5, that is, eccentric to the opening side of the brake drum 1, and fixed to the lower ends of the webs 5b and 5c by welding or the like. Thereby, when the brake shoe 5 is mounted on the bracket 3 by the anchor pin 2, the brake shoe 5 is moved to a distance E as shown in FIG.
Eccentric to the back side of the brake drum 1 and the web 5
The applied point at the time of braking between b and 5c is different from the applied point on the brake shoe 4 serving as the leading shoe.

The width of the brake shoe 5 'shown in FIG. 7 is smaller than that of the other brake shoe 4, and the webs 5'b and 5'c normally hold the anchor block 18 at the lower end thereof when the shoe 5' is assembled. In the connected state, as shown in FIG. 7, it is eccentric to the rear side by a predetermined distance e, that is, eccentric to the closed side (rear side) of the brake drum 1, and is fixed to the rim 5'a by welding or the like. Thereby, when the brake shoe 5 'is mounted on the bracket 3 by the anchor pin 2, the brake shoe 5' is eccentric to the far side of the brake drum 1 by a distance E as shown in FIG.
The applied point at the time of braking between 5'c is different from the applied point in the brake shoe 4 which is the leading shoe.

Although the width of the brake shoe 5 'shown in FIG. 8 is smaller than that of the other brake shoe 4, when the shoe 5' is assembled, an anchor having a slightly shorter length is attached to the lower ends of the webs 5'b and 5'c. When the shoe 5 'is normally used, the spacers 19, 20 having the reduced thickness are applied to the front and rear of the short anchor block 18', and the pins 2 'are connected. When the brake shoe 5 'is eccentric for the purpose of the present invention, if the spacers 19 and 20 are overlapped and applied to the front of the short anchor block 18' as shown in FIG. The brake shoe 5 'is eccentric to the back side of the brake drum 1 by a distance E, and the webs 5'b, 5'c
The intermediate point of braking during braking is different from the point of application of the brake shoe 4 serving as the leading shoe.
If the anchor blocks 18 and 18 'are internally threaded and the pins 2 are threaded and the two are screwed together, the brake shoe 5' can adjust the point of application at the time of braking to an optimum position. Can be eccentric.

[0014]

According to the present invention, there is provided a vehicle drum brake provided with a squeal prevention mechanism, wherein a pair of brake shoes of the same size are pressed against the inner surface of a brake drum to brake the vehicle. A first invention in which the center of the applied point of one shoe during braking is eccentric in the width direction of the shoe, and a pair of brake shoes of the same size are pressed against the inner surface of the brake drum to perform braking. In a vehicle drum brake, a second invention is characterized in that the center of the point of application of one of the pair of brake shoes during braking is eccentric to the depth side of the brake drum in the width direction of the shoe. According to the first aspect of the present invention, the center of the point of application of the braking force of one of the pair of brake shoes is set in the width direction of the shoe. By eccentricity, the points of application of the two shoes to the brake drum are different, and the vibrations of the drums are changed as compared with the case where the points of application of the brakes are the same, so that the coupled vibration is less likely to occur. The chance of "squealing" can be reduced. Further, by performing the eccentricity of the brake shoe on the back side of the brake drum according to the second invention, vibration is suppressed at a place where the amplitude of the brake drum is small, and thereby the resonance suppressing effect can be further enhanced. In the case where the widths of the pair of brake shoes are different from each other,
Since the respective natural frequencies of the two shoes differ, the vibration suppressing effect can be further enhanced in combination with the above-mentioned high cost in which the point of application to the brake drum is different.

FIG. 12 shows a vehicle drum brake of the above embodiment in which the widths of a pair of brake shoes are different from each other and the widths of the left and right brake shoes are the same, and there is no "squeal". "Squealing" when a vehicle equipped with a vehicle drum brake that did not take measures was run at a speed of 10 km / h to 40 km / h and stopped at a deceleration of 0.1 G to 0.35 G / h. It is a comparison of the occurrence situation of
The vehicle equipped with the latter conventional vehicle has a sound level of 1; "squeal" small to 5; "squeak" high (the number in parentheses indicates the level), especially at a vehicle speed of 20 km / h or more and 0. "Squeal" mainly composed of 3 levels at deceleration of 2G or more
On the other hand, in the vehicle equipped with the vehicle drum brake of the present invention, the "squeal" is 1 level or less at all vehicle speeds and decelerations, and the effectiveness of the present invention can be confirmed. FIG. 13 shows a vehicle drum brake in which the widths of a pair of brake shoes are different from each other and a vehicle in which the widths of a pair of brake shoes are simply different from each other, similarly to FIG. The vehicle equipped with the drum brakes
Drive from 0km at 40km / h,
This is a comparison of the occurrence of "squeal" when the vehicle is stopped at a deceleration of 0.1 G to 0.35 G. In vehicles equipped with the latter, 1; "squeal" from small to 5; "
At a large sound level (the number in parentheses indicates the level), "squeal" mainly consisting of 2 and 3 levels occurs at some speeds and decelerations, whereas the vehicle drum brake of the present invention is mounted. In the vehicle, "squeal" is almost one level or less at all vehicle speeds and decelerations, which confirms the effectiveness of the present invention.

[Brief description of the drawings]

FIG. 1 is a front view of an embodiment of a vehicle drum brake provided with a squeal prevention mechanism according to the present invention.

FIG. 2 is a front view of another embodiment of the vehicle drum brake provided with the squeal prevention mechanism of the present invention.

FIG. 3 is a front view of a brake shoe having a squeal prevention mechanism according to the present invention.

4 is a sectional view taken along the line AA of FIG. 1 when the brake shoe shown in FIG. 3 is mounted.

FIG. 5 is a front view of a reduced-width brake shoe having a squeal prevention mechanism according to the present invention.

6 is a sectional view taken along the line AA of FIG. 1 when the brake shoe shown in FIG. 5 is mounted.

FIG. 7 is a front view of another reduced brake shoe having a squeal prevention mechanism according to the present invention.

FIG. 8 is a front view of still another brake shoe having a reduced width having a squeal prevention mechanism according to the present invention.

FIG. 9 is a diagram showing a mode of a tertiary vibration of the brake drum.

FIG. 10 is a diagram showing a fourth-order vibration mode of the brake drum.

FIG. 11 is a diagram showing a vibration mode of a brake shoe.

FIG. 12 is a view showing an effect on “squeal” of a vehicle drum brake provided with the squeeze prevention mechanism of the present invention.

FIG. 13 is a diagram showing an effect on “squeal” of a vehicle drum brake provided with the squeeze prevention mechanism of the present invention. 1, 11; brake drum, 2; pin 4, 5, 5 ', 12, 13; brake shoe, 6; cam, 7, 7', 17, 17 '; lining. 18, 18 '; anchor block.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F16D 65/08 F16D 51/18

Claims (3)

(57) [Claims] 1. A vehicle drum brake for braking by pressing a pair of brake shoes of the same size against the inner surface of a brake drum, wherein the center of the point of application of one of the pair of brake shoes during braking is set to the shoe. A vehicle drum brake provided with a squeal prevention mechanism characterized by being eccentric in the width direction of the vehicle. 2. A vehicle drum brake for braking by pressing a pair of brake shoes of the same size against the inner surface of a brake drum, wherein the center of the point of application of one of the pair of brake shoes during braking is set to the shoe. A vehicle drum brake provided with a squeal prevention mechanism, which is eccentric in the width direction of the brake drum toward the back side of the brake drum. 3. The brake shoe according to claim 1, wherein one of said pair of brake shoes has a different width from the other.
A vehicle drum brake provided with the squeal prevention mechanism described in the above.