JP6378938B2 - Drum brake device - Google Patents

Description

  The present invention relates to a drum brake device.

  Conventionally, a drum brake device has been adopted as a kind of wheel brake used in industrial vehicles such as forklifts. A drum brake device brakes the rotation of a wheel by a pair of arc-shaped brake shoes pressed against the inner surface of a brake drum that rotates as the wheel rotates, and a frictional force is generated. is there. This brake shoe is attached to the back plate of the drum brake device.

  At the time of braking the wheel, the brake shoe pressed against the brake drum receives a force to rotate with the brake drum. At this time, when the protrusion (anchor) formed on the back plate receives the brake shoe to be rotated, the position of the brake shoe is fixed in a state of frictional contact with the brake drum. However, if the rigidity of the back plate is low, the back plate may be deformed when receiving a force from the brake shoe via the anchor. If the back plate is deformed, the contact surface between the brake shoe and the brake drum also becomes uneven, and vibration is likely to occur when the drum brake device is operated. And when the contact surface of a brake shoe and a brake drum vibrates, there existed a possibility that the unpleasant sound of a brake squeal might generate | occur | produce.

  In order to prevent the occurrence of such a brake squeal, Patent Document 1 provides an elongated annular continuous rib portion on the outer side in the circumferential direction of a plurality of mounting holes formed in the back plate. By providing this rib, the natural frequency of the back plate is changed so that the back plate does not resonate when the contact surface between the brake shoe and the brake drum vibrates.

JP-A-10-148230

  Here, a hole for attaching the wheel cylinder must be formed in the back plate of the drum brake device. However, since the rib portion is continuously extended on the back plate of the drum brake device of Patent Document 1, the position where the wheel cylinder hole is formed is limited to the radially outer side of the rib portion. Therefore, the hole for the wheel cylinder cannot be formed at the same position in the radial direction with respect to the rib portion, and accordingly, the degree of freedom in designing the drum brake device is lowered. Further, as shown in FIGS. 1 and 2 of Patent Document 1, the portion where the hole for the wheel cylinder is formed is formed so as to partially protrude from the back plate, and accordingly, the entire drum brake device is enlarged in the radial direction. Therefore, the installation space had to be large.

  The present invention is made to solve such a problem, and provides a drum brake device capable of preventing the occurrence of brake squeal, ensuring the degree of design freedom, and reducing the installation space. With the goal.

In order to solve the above-described problems, a drum brake device according to the present invention includes a brake drum that can be rotated as a vehicle wheel rotates, a back plate that is fixed to the vehicle, a back plate, and a brake drum. A brake shoe provided opposite to the inner peripheral surface of the motor, and an operating mechanism that is attached to the back plate through an operating mechanism mounting hole formed in the back plate and presses the brake shoe against the brake drum. Is formed with a plurality of solid rib portions on the side opposite to the side on which the operating mechanism is attached, and each of the rib portions has an arc-shaped belt shape along the circumferential direction around the rotation center of the brake drum. And a protrusion formed integrally with the back plate, and the operating mechanism mounting hole faces each other among the ends of the plurality of ribs. It is disposed between at least a pair of said end portion.

Further, the back plate of the drum brake device according to the present invention is formed with a plurality of fastening member mounting holes used for mounting on the vehicle, and the plurality of fastening member mounting holes are centered on the rotation center of the brake drum. are placed along the circumferential direction, the rib portion may extend to overlap one or more portions of the plurality of fastening member mounting holes or the position of the radially outer total.

Further, the tension angle Θ1 of each rib portion may be 90 degrees or more and 130 degrees or less starting from the center of the operation mechanism mounting hole.
Further, the ratio α = W / H of the width W to the height H of the rib portion may be 1 or more and 2.5 or less.

  Furthermore, the height H of the rib portion may be 24 mm, and the width W of the rib portion may be 45 mm.

  According to the drum brake device of the present invention, the occurrence of brake squeal can be prevented, the degree of design freedom is ensured, and the installation space can be reduced.

1 is a perspective view of a drum brake device according to an embodiment of the present invention. It is a top view which shows a mode that the back plate of the drum brake apparatus shown in FIG. 1 was seen from the X-axis positive direction side. It is a figure which shows the shape of the rib part of the backplate of the drum brake apparatus shown in FIG. 1, FIG.3 (i) shows the top view which looked at the rib part from the X-axis positive direction side, FIG.3 (ii) is a figure. It is sectional drawing which cut | disconnected the rib part of 3 (i) by the cutting line II-II. It is a graph which shows the relationship of the ratio (W / H) of the width with respect to the height of the rib part in the drum brake apparatus shown in FIG. 1, the rigidity of a backplate, and squealing performance. It is a top view which shows a mode that the back plate of the drum brake apparatus shown in FIG. 1 was seen from the X-axis negative direction side.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
As shown in FIG. 1, the drum brake device 1 includes a substantially cylindrical brake drum 30 and a substantially donut-shaped casting back plate 10 disposed at one end inside the brake drum 30. The brake drum 30 is attached to the vehicle so as to be rotatable with rotation of a tire (not shown) as a wheel, and rotates about the rotation center X. On the other hand, the back plate 10 is fixedly attached to the vehicle. That is, the brake drum 30 can rotate relative to the back plate 10. The back plate 10 is provided with a pair of substantially crescent shaped brake shoes 14. The brake shoe 14 is disposed so that the outer surface faces the inner peripheral surface of the brake drum 30. A friction member 14 a is attached to the outer surface of the brake shoe 14. Further, a wheel cylinder 11 is provided between the pair of brake shoes 14. One wheel cylinder 11 is provided for the drum brake device 1. A cylinder mounting hole 16 is formed in the back plate 10 at a position corresponding to the mounting position of the wheel cylinder 11. The wheel cylinder 11 is attached to the back plate 10 via the cylinder attachment hole 16.
Here, the side on which the back plate 10 is disposed with respect to the brake drum 30 is defined as the X-axis positive direction (see arrow x1 in FIG. 1). Further, the opposite side to the positive direction of the X axis, that is, the side on which the wheel cylinder 11 is attached to the back plate 10 is defined as the negative direction of the X axis (see arrow x2 in FIG. 1).
The wheel cylinder 11 constitutes an operating mechanism. Further, the cylinder mounting hole 16 constitutes an operating mechanism mounting hole.

  Details of the structure of the back plate 10 on the X axis positive direction side will be described with reference to FIGS. In the following description, the center of the cylinder mounting hole 16 is Y, and the straight line connecting the rotation center X of the brake drum 30 and the center Y of the cylinder mounting hole 16 is the XY line. Further, a range in which the distance from the center Y of the cylinder mounting hole 16 is equal to or less than r is defined as a vicinity N of the cylinder mounting hole 16. It is assumed that the vicinity N of the cylinder mounting hole 16 includes a later-described anchor (see FIG. 5) provided on the X-axis negative direction side of the back plate 10.

As shown in FIGS. 1 and 2, a pair of substantially arc-shaped strip-shaped rib portions 21 are formed on the surface of the back plate 10 on the X axis positive direction side with the cylinder mounting hole 16 interposed therebetween.
Further, a shaft hole 18 through which an axle (not shown) of the vehicle passes is formed at the center of the back plate 10. The center of the shaft hole 18, that is, the rotation center of the vehicle axle coincides with the rotation center X of the brake drum 30. Around the shaft hole 18, eight bolt mounting holes 17 are formed along the circumferential direction around the rotation center X. Four bolt mounting holes 17 are provided so as to be symmetrical with respect to the XY line. Further, the bolt mounting hole 17 is disposed in a range excluding the vicinity N of the cylinder mounting hole 16.
The back plate 10 is fixed to a vehicle fixing member (not shown) through a bolt mounting hole 17 by a fastener such as a bolt.
The bolt mounting hole 17 constitutes a fastening member mounting hole.
In this embodiment, the outer diameter D of the back plate 10 is 310 mm.

Next, the rib part 21 is demonstrated using FIG. The pair of rib portions 21 are arranged so as to be symmetric with respect to the XY line. Here, the end of the pair of ribs 21 on the cylinder mounting hole 16 side is defined as an end 21b, and the end opposite to the end 21b is defined as an end 21a.
The end portions 21b are disposed so that the cylinder mounting holes 16 are disposed between the pair of end portions 21b facing each other. That is, as indicated by a one-dot chain line L in FIG. 2, the end portion 21b is provided in the vicinity of the cylinder mounting hole 16 so that the cylinder mounting hole 16 exists on a straight line connecting the pair of end portions 21b.
Further, the end portion 21 a is provided so that the rib portion 21 overlaps the position on the radially outer side of the pair of bolt mounting holes 17 a closest to the cylinder mounting hole 16. That is, the rib portion 21 overlaps the position on the radially outer side of the bolt mounting hole 17a.
Here, the phase (angle) Θ1 of the end portion 21a of the rib portion 21 starting from the center Y of the cylinder mounting hole 16 with the rotation center X as the center is defined as the tension angle of the rib portion 21.
In addition, in this invention, a rib part means the protrusion part integrally formed in the member.

The shape of the rib portion 21 will be specifically described with reference to FIG.
If the width of the rib portion 21 is W as shown in FIG. 3 (i), the cross-sectional shape of the rib portion 21 is a trapezoid whose base is W and height is H, as shown in FIG. 3 (ii). Make a shape. That is, the height (thickness) of the rib portion 21 is H.

Here, FIG. 4 shows the relationship between the ratio W / H of the width W and height H of the rib portion 21, the rigidity Bs of the back plate 10, and the squealing performance Bn of the brake. The squeal performance is based on a numerical value based on whether the operator feels uncomfortable (noisy) when hearing the sound (brake squeal) emitted from the brake when the brake is actually applied to a vehicle equipped with a brake. It is what I did.
In FIG. 4, it can be seen that when the ratio W / H of the width W to the height H of the rib portion 21 increases, the squealing performance Bn deteriorates and the rigidity Bs of the back plate 10 also decreases. When the ratio W / H between the width W and the height H of the rib portion 21 is a value P slightly smaller than 3, there is a reference point Cn for determining whether or not the squealing performance is determined in the above determination. Since the back plate 10 is manufactured as a casting, a manufacturing error may occur. Therefore, in order not to exceed the reference point due to the error, the upper limit of W / H is preferably set to 2.5.
As can be seen from FIG. 4, the squealing performance Bn is improved by reducing the value of W / H. Finally, the brake noise is not felt. However, since the width W of the rib portion 21 is required to some extent from the viewpoint of the rigidity Bs of the back plate 10, in order to reduce the value of W / H, the height H of the rib portion 21 is increased. Therefore, the volume of the rib portion 21 is increased. Enlarging the rib portion 21 requires more material, which is disadvantageous in terms of cost. Therefore, considering the squeal performance Bn and cost, the lower limit of W / H is preferably set to 1. That is, in order to achieve both prevention of brake squealing and reduction in manufacturing cost of the drum brake device 1, the optimum value α = W / H of the ratio of the width W to the height H of the rib portion 21 is 1 or more. 5 or less.
In this embodiment, the width of the rib portion 21 is W = 45 mm and the height of the rib portion 21 is H = 24 mm as optimum values in consideration of the squeal performance Bn and cost.

Next, the tension angle Θ1 will be described. The tension angle Θ1 must be provided at a minimum so that the rib portion 21 overlaps the radially outer position of the pair of bolt mounting holes 17a closest to the cylinder mounting hole 16, and more specifically, the tension angle Θ1 is 90 degrees or more. It is good to set it as 130 degrees or less. When the tension angle Θ1 is small, the squealing performance Bn is deteriorated and the rigidity Bs of the back plate 10 is also lowered. In order to satisfy the pass / fail criterion Cn for the determination of the squealing performance Bn, it is necessary to provide at least the rib portion 21 so as to overlap the radially outer position of the pair of bolt mounting holes 17a closest to the cylinder mounting hole 16. . However, in consideration of manufacturing errors, the tension angle Θ1 is preferably 90 degrees or more.
And the squealing performance Bn is improved by increasing the tension angle Θ1. Finally, the brake noise is not felt. However, increasing the tension angle Θ1 increases the volume of the rib portion 21. Therefore, increasing the tension angle Θ1 at the tension angle Θ1 is disadvantageous in terms of cost. Therefore, considering the squeal performance Bn and the cost, the upper limit of the tension angle Θ1 is preferably 130 degrees.
In this embodiment, the tension angle Θ1 is 90 degrees as an optimum value in consideration of the squealing performance Bn and the cost.

Details of the structure on the X axis negative direction side of the back plate 10 will be described with reference to FIG.
The pair of brake shoes 14 are supported on the back plate 10 by a pair of shoe hold springs 19. A band-shaped anchor 12 is formed integrally with the back plate 10 adjacent to the inner side in the radial direction of the wheel cylinder 11 provided between the pair of brake shoes 14. A pair of return springs 13 are bridged between the anchor 12 and the pair of brake shoes 14. Here, the return spring 13 applies a force to the brake shoe 14 in a direction away from the inner peripheral surface of the brake drum 30. Further, an auto adjuster 15 is connected to the end of the pair of brake shoes 14 opposite to the side to which the wheel cylinder 11 is connected. The auto adjuster 15 adjusts the gap between the outer peripheral surface of the brake shoe 14 and the inner peripheral surface of the brake drum 30.

Next, the operation of the drum brake device 1 will be described with reference to FIGS. It is assumed that the brake drum 30 rotates in the direction of arrow A.
First, when the drum brake device 1 is operated, hydraulic pressure is introduced into the wheel cylinder 11. A piston (not shown) in the wheel cylinder 11 presses the pair of brake shoes 14 to rotate outwardly against the elastic force of the return spring 13. As a result, the friction member 14 a of the brake shoe 14 is pressed against the inner peripheral surface of the brake drum 30. At this time, the brake shoe 14 tries to move in the direction of the arrow A along with the rotation of the brake drum 30, but the end 14 b on the wheel cylinder 11 side of the brake shoe 14 disposed on the left side of the drawing comes into contact with the anchor 12. Therefore, the brake shoe 14 cannot move in the direction of the arrow A, and the position is fixed. As a result, a large frictional force acts between the friction member 14a of the brake shoe 14 and the inner peripheral surface of the brake drum 30, and the rotation of the brake drum 30 stops.

  As described above, in the drum brake device 1 according to this embodiment, the pair of rib portions 21 allows the cylinder mounting holes 16 of the one wheel cylinder 11 provided in the drum brake device 1 to be between the end portions facing each other. It is provided between. The pair of rib portions 21 can increase the rigidity of the back plate 10 of the drum brake device 1 and can provide the cylinder mounting hole 16 at the same position as the rib portion 21 in the radial direction. Accordingly, since the distance (moment distance) from the wheel cylinder 11 to the rib portion 21 can be reduced, the acting force is reduced by the rib portion, the deformation of the back plate 10 is suppressed, and the occurrence of brake squeal is prevented. Furthermore, at the same time, the degree of freedom of design is secured for the position where the wheel cylinder 11 is attached. Further, since it is not necessary to provide the cylinder mounting hole 16 on the radially outer side of the rib portion 21, the size of the entire drum brake device 1 in the radial direction can be suppressed, and the installation space can be reduced.

  Further, since the plurality of bolt mounting holes 17 are arranged excluding the vicinity N of the cylinder mounting hole 16, the rigidity around the wheel cylinder 11 and the anchor 12 where rigidity is particularly required in the back plate 10 is ensured. Is done. Further, the rib portion 21 extends so as to overlap a position on the radially outer side of a part of the plurality of bolt mounting holes 17 (bolt mounting holes 17a), so that the rigidity of the back plate 10 near the bolt mounting holes 17a is reduced. Can be prevented.

  Further, the tension angle Θ1 of the rib portion 21 is 90 degrees. Further, in the back plate 10 having an outer diameter D of 310 mm, the height H of the rib portion 21 is 24 mm and the width W is 45 mm. Specifically, by forming the rib portion 21 in such a shape, the brake noise of the drum brake device 1 can be prevented and the manufacturing cost of the back plate 10 can be improved.

In addition, the dimension of the height H and the width W of the rib part 21 is not limited to this embodiment. Specifically, if the ratio α = W / H of the width W of the rib portion 21 to the height H of the rib portion 21 is 1 or more and 2.5 or less, even if the manufacturing cost of the drum brake device 1 is taken into consideration, The brake squeal can be efficiently prevented.
Further, the tension angle Θ1 of the rib portion 21 is not limited to 90 degrees, and may be 90 degrees or more and 130 degrees or less. Even if the tension angle Θ1 is within this range, brake noise can be efficiently prevented even if the manufacturing cost of the drum brake device 1 is taken into consideration.
Further, the number of the rib portions 21 is not limited to two and may be three or more. Moreover, the number of the bolt attachment holes 17 should just be plural, and is not limited to eight.
Further, the rib portion 21 may extend so as to overlap not only the pair of bolt mounting holes 17a but also one or more of the eight bolt mounting holes 17 or all radially outer positions.
Further, the bolt mounting hole 17 has been described in the configuration arranged in the range excluding the vicinity N of the cylinder mounting hole 16, but may be provided for the structure arranged in the vicinity of the cylinder mounting hole 16.

  DESCRIPTION OF SYMBOLS 1 Drum brake device, 10 Back plate, 14 Brake shoes, 16 Cylinder attachment hole (operation mechanism attachment hole), 17 Bolt attachment hole (fastening member attachment hole), 21 Rib part, 21a, 21b End part of rib part, 30 Brake Drum, D Back plate outer diameter, H rib height, W rib width, N Location near cylinder mounting hole (actuation mechanism mounting hole).

Claims (5)

A brake drum that can rotate with the rotation of the wheels of the vehicle;
A back plate fixed to the vehicle;
Brake shoes provided on the back plate so as to face the inner peripheral surface of the brake drum;
A drum brake device including an operation mechanism that is attached to the back plate via an operation mechanism attachment hole formed in the back plate and presses the brake shoe against the brake drum;
A plurality of solid rib portions are formed on the back plate on the side opposite to the side on which the operating mechanism is attached,
Each of the rib portions is a projecting portion integrally formed with the back plate, and has an arcuate belt shape along a circumferential direction around the rotation center of the brake drum.
The operating mechanism mounting hole is a drum brake device disposed between at least a pair of the end portions facing each other among the end portions of the plurality of rib portions. The back plate is formed with a plurality of fastening member mounting holes used for mounting to the vehicle,
The plurality of fastening member mounting holes are arranged along the circumferential direction around the rotation center of the brake drum,
2. The drum brake device according to claim 1, wherein the rib portion extends at one or more or all radially outer positions of the plurality of fastening member mounting holes.   3. The drum brake device according to claim 1, wherein a tension angle Θ <b> 1 of each of the rib portions is 90 degrees or more and 130 degrees or less starting from the center of the operation mechanism mounting hole.   The drum brake device according to any one of claims 1 to 3, wherein a ratio α = W / H of a width W of the rib portion to a height H of the rib portion is 1 or more and 2.5 or less.   The drum brake device according to any one of claims 1 to 4, wherein a height H of the rib portion is 24 mm, and a width W of the rib portion is 45 mm.

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