JPH10196694A - Worm shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent adhesion of rust to a worm shaft and the like even when some water penetrates into a body by arranging a slight clearance between the side wall of a ball groove formed in a worm shaft and a ball. SOLUTION: A worm shaft 6 used in a slack adjuster is prevented from rotating by means of a plurality of ball grooves 11 arranged in the outer circumference of the worm shaft 6 and a ball 7 engaged in the ball groove 11. In this case, although the worm shaft 6 is positioned with the ball 7 brought into contact with V-shaped bottom parts 11b, 11b which make a large obtuse angle, a slight clearance (g) is provided between the ball 7 and a side wall 11a. As a result, when great force is applied to a worm gear 5 via a cam shaft 3 and a worm wheel 4 because of application of a brake and the like, for example, the worm gear 5 can be slightly rotated with the worm shaft 6 by the clearance (g) between the ball 7 and the side wall 11a. Therefore, the worm shaft 6 is always moved slightly, and adhesion of rust can be prevented even if water penetrates into the inside a body 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a worm wheel and a worm gear meshing with the worm wheel are provided on a cam shaft mounted on a body, and the worm gear is provided with a ball groove and a ball groove provided on the outer periphery of the worm shaft. The present invention relates to a slack adjuster that is prevented from rotating by an engaging ball. More particularly, the present invention relates to improvements in worm shafts used in slack adjusters.

[0002]

2. Description of the Related Art In a drum type air brake of a vehicle, for example, as shown in FIG. 3, a wheel side brake chamber 20 and a brake cam 21 for operating a brake shoe 22 are connected to operate a brake, and not shown. There is known a slack adjuster 1 in which brake adjustment for adjusting a gap between a brake drum and a brake shoe 22 is performed by rotating the brake shoe 22 around an anchor pin 23 by a brake cam 21.

Referring to FIGS. 4 and 5, the gap adjustment is performed by moving the relative position between the body 2 of the slack adjuster 1 and the cam shaft 3 on which the brake cam 21 is mounted. . That is, a worm wheel 4 meshes with a cam shaft 3 rotatably provided on the body 2, and a worm gear 5 press-fitted on a worm shaft 6 rotatably supported by the body 2 meshes with the worm wheel 4. .

A ball groove 1 is provided at an end of the worm shaft 6.
1 (or a concave portion) is provided, and the ball 7 urged in the direction of the worm shaft 6 by the spring 8 engages with the ball groove 11 to prevent the worm shaft 6 from rotating. Then, by rotating the worm shaft 6 against the ball 7, the brake cam 21 is rotated via the worm gear 5 and the worm wheel 4, and the brake shoe 22 is moved radially outward or inward to form a gap. Has been adjusted.

Referring to FIG. 6, the sectional shape of the ball groove 11 (or concave portion) engaged with the ball 7 is such that the ball 7 has a V-shaped bottom B (for example, an intersection angle of 120 degrees). The camshaft 6 is completely locked by contacting the side portion A without contacting.

Further, covers 10 are provided on both sides of the body 2.
10 is attached by a rivet 10a to protect the inside of the body 2. Here, reference numeral 9 denotes a blind lid, and reference numeral 12 denotes a grease nipple.

[0007]

However, in the above technique, the cover is fixed with rivets or the like. However, even if the cover is mounted via a gasket, the mounting position of the slack adjuster is close to the tire. When running in a pool, water may enter even if there is a gasket, and rust may occur between the worm shaft and the body due to long-term use, causing a problem that brake adjustment cannot be performed. I do.

The present invention has been proposed in view of the above-mentioned problems of the prior art. Even if a small amount of water enters the body, rust does not occur on the worm shaft and the like, and the structure is simple. The purpose is to provide a worm shaft that can be used as a technology to prevent rust adhesion of slack adjusters.

[0009]

SUMMARY OF THE INVENTION A worm shaft according to the present invention comprises:
A worm wheel and a worm gear meshing with the worm wheel are provided on a cam shaft attached to the body,
The worm gear is a worm shaft used in a slack adjuster stopped by a plurality of ball grooves provided on the outer periphery of the worm shaft and a ball engaged with the ball groove. The bottom portion is formed so as to be in contact with the ball and to form a gap between the side wall of the ball groove and the ball.

If the slack adjuster is constituted by the worm shaft according to the present invention having the above-described structure, the worm shaft is always operated by the operation of the brake or the like due to a small gap formed between the side wall of the ball groove and the ball. It turns slightly. Therefore, even if water enters the inside of the body, the worm shaft does not stick to the worm shaft (rust sticks). In addition, since the rust sticking of the worm shaft is prevented, the air brake provided with the slack adjuster using the present invention does not hinder the brake adjustment.

Here, the bottom of the ball groove is formed in a V-shape, and the bottom formed in the V-shape forms a relatively large obtuse angle, and is formed by extending opposing side walls of the ball groove. The angle of intersection is preferably an acute angle.

As a result of various studies, the present inventors have found that when implementing the present invention, the relatively large obtuse angle formed by the bottom of the V-shaped ball groove is 140 degrees, 6 crossing angles formed by extending the side walls
It has been found that it is very suitable to set the clearance between the side wall of the ball groove and the ball to 0.2 mm at 0 degree.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

In the drawings, members having the same functions as those of the prior art are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 shows a cross section of a plurality of (six in the illustrated example) grooves 11b of a worm shaft showing an embodiment of a rust sticking prevention device for a slack adjuster according to the present invention. In the figure, each groove 7 has a bottom 11b having a large obtuse angle (for example, 140 degrees) and two planes 11b, 11b in which the ball 7 contacts each surface, and side walls 11a, 11a of the groove connected to those planes. It is formed with.

The side walls 11a are formed so as to form an acute angle with each other (for example, 60 degrees), and a small gap g (for example, 0. 0) is formed between the side walls 11a and the balls 7 in a state where the balls 7 are in contact with the bottoms 11b and 11b. It is configured to have 2 m / m.

There is no problem even if the groove 11 is a concave having the same cross-sectional shape.

The operation will be described below.

Although the worm shaft 3 is positioned in contact with the V-shaped bottoms 11b, 11b of the ball 7 having a large obtuse angle, the worm shaft 3 has a slight gap g between the ball 7 and the side wall 11a. The camshaft 3,
When a large force is applied to the worm gear 5 via the worm wheel 4, the worm gear 6 can be slightly rotated together with the worm shaft 6 by the gap g between the ball 7 and the side wall 11 a. Therefore, the worm shaft 6 always moves only slightly, and even if water enters the body, it does not adhere to rust.

FIG. 2 shows an example of the worm shaft according to the present invention in order to specify its cross-sectional shape, particularly the shape of a ball groove.

In the example shown in FIG. 2, the diameter of the ball 7 is 7-φ.
Is 8 mm, and a slight gap g between the side wall 11a and the ball 7 is 0.2 mm. The intersection angle (large obtuse angle) α formed by the bottom portions 11b of the ball groove 11 is large.
Is 140 degrees, and the vertical line V in FIG.
Are formed at an angle α / 2 of 70 degrees.

Here, reference numeral 11-C in FIG. 2 indicates a crossing point of the bottom portions 11b, 11b, and reference numeral O indicates the center of (the cross section of) the worm axis.

Also, the side walls 11a of the ball groove 11 are provided.
The intersection angle β formed by (an extension of) is 60 degrees, and the angle β formed by (an extension of) one side wall 11a and the vertical line V
/ 2 is 30 degrees.

On the other hand, FIG. 7 shows a cross section of a conventional worm shaft used in combination with a ball having a diameter of 8 mm, similarly to the embodiment of FIGS. In the conventional worm shaft 6 shown in FIG. 7, the angle corresponding to the angle α in FIG. 2 is 120 degrees, the angle corresponding to the angle α / 2 is 60 degrees, and the angle corresponding to the angle β in FIG. 60 degrees,
The angle corresponding to the angle β / 2 is 30 degrees.

[0025]

The present invention is configured as described above,
Due to the slight gap formed between the side wall of the ball groove and the ball, the worm shaft is always slightly rotated by the operation of the brake or the like. Therefore, even if water enters the inside of the body, it does not adhere to rust. As a result, there is no hindrance to the brake adjustment.

[Brief description of the drawings]

FIG. 1 is a sectional view of a groove of a worm shaft according to an embodiment of the present invention.

FIG. 2 is a front view for specifying the shape of one embodiment of the present invention in detail.

FIG. 3 is a side view showing a conventional air brake.

FIG. 4 is a partial cross-sectional front view showing an example of a conventional slack adjuster.

FIG. 5 is a side view showing an example of a conventional slack adjuster.

FIG. 6 is a view showing a cross section of a groove portion of a conventional worm shaft.

FIG. 7 is a front view for specifying the shape of an example of a conventional worm shaft groove in detail.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Slack adjuster 2 ... Body 3 ... Brake cam shaft 4 ... Worm wheel 5 ... Worm gear 6 ... Worm shaft 7 ... Ball 11 ... Groove 20 ... Brake Chamber 21: Brake cam 22: Brake shoe

Claims (3)

[Claims] 1. A worm wheel and a worm gear meshing with the worm wheel are provided on a cam shaft mounted on the body, and the worm gear is provided with a plurality of ball grooves provided on the outer periphery of the worm shaft and balls engaged with the ball grooves. In the worm shaft used in the slack adjuster that is prevented from rotating, the cross-sectional shape of the ball groove is such that the bottom of the ball groove contacts the ball and forms a gap between the ball and the side wall of the ball groove. A worm shaft characterized by being formed. 2. A bottom of the ball groove is formed in a V-shape, and the bottom formed in the V-shape forms a relatively large obtuse angle, and is formed by extending opposing side walls of the ball groove. 2. The worm axis of claim 1, wherein the intersection angle is an acute angle. 3. The worm shaft according to claim 2, wherein the obtuse angle is 140 degrees, the acute angle is 60 degrees, and the gap between the side wall of the ball groove and the ball is 0.2 mm.