JPH11132327A - Bellows - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide bellows mainly for protective boots, etc., blow-moulded of resin material in which an installation condition can be favorably held to secure the optimum seal condition. SOLUTION: In bellows having cylindrical fixture parts at both end parts of a cylindrical bellows part, in at least one cylindrical fixture part 2a, an outer circular groove 3 for tightening a clamp member 10 is provided on an outer circumferential surface, with a circular swollen part 4 to be engaged with a circular engagement groove 21 in a counter installation side member 20 provided at a position within a width of the outer circular groove 3 on an inner circumferential surface, a circular cavity 6 of a roughly W-shaped cross sectional surface having a protrusion 5 at a center of a width (a) is provided with in a range of a part corresponding to the circular swollen part 4, and the width (a) of the circular cavity 6 is set to be similar to or larger than a depth (b) of it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bellows used as a protective boot for a rotary joint structure of an automobile, a protective boot for a steering device, etc., and more particularly to a bellows blow-molded from a resin material.

[0002]

2. Description of the Related Art Bellows of this kind are made of a rubber or resin material having elasticity, and are provided at both ends of a cylindrical bellows having alternating peaks and valleys. The cylindrical fixing part is formed integrally,
In recent years, it is often formed by blow molding from a resin material such as a thermoplastic synthetic resin elastomer.

Usually, an outer annular groove for tightening a clamp member is formed on the outer periphery of the cylindrical fixing portion, and an annular ridge engaged with an annular engaging groove of a member on the mounting side is formed on an inner periphery. A part is formed. That is, in mounting the bellows, axial positioning and sealing properties are secured by the clamping force from the outside by the clamp member and the engagement of the inner annular ridge with the annular engagement groove. I have. The inner annular protrusion is provided at the inner bottom of the outer annular groove for the workability of mounting to the member on the attachment side when the annular annular protrusion is provided, and the formability by blow molding from a thin material. It is conceived to provide a thin groove-shaped annular space at a position corresponding to the above.

For example, in Japanese Patent Application Laid-Open No. 2-221766, as shown in FIG. 5, an inner annular raised portion (54) is formed at an inner bottom of an outer annular groove (53) in a cylindrical fixing portion (52). It has been proposed to provide a single narrow annular space (56) at the corresponding position of (1). In addition, Japanese Patent Publication 5-739
No. 52 discloses a cylindrical fixing portion (5) as shown in FIG.
It has been proposed to increase the axial width of the inner annular ridge (54) in 2) and to provide two narrow annular gaps (56) (56) at the inner bottom of the outer annular groove (53). I have.

[0005] However, in the former case, the axial width of the annular protruding portion (54) on the inner periphery cannot be made large by blow molding from a thin resin material, and the slope of the annular protruding portion (54) is set on the mounting side. The corner portions (71a) and (71a) of both sides of the annular engagement groove (71) of the member (70) may not be able to come into strong contact, and complete sealing may not be obtained. To prevent this, the annular engagement groove (7
The width of 1) may be reduced, but reducing the width of the groove is not suitable for mass production because of the difficulty in processing.

In the latter case, although the above-mentioned problem can be solved, the inner annular ridge (54) has two outer annular gaps (54) due to blow molding from a thin resin material. 56) corresponding to (56), the inner annular ridge (54) has a valley (58) at the center in the width direction of the inner annular ridge (54), so that it is clamped from outside by a clamp member (60). Sometimes two mountain parts (54a)
(54a) escapes inward and the annular ridge (5
4) The contact pressure of the inclined surface with respect to the annular engaging groove (71) becomes low, and an optimum sealing state cannot be obtained.

The present invention has been made in view of the above, and solves the above-mentioned problems by improving the form of an annular space formed in the inner bottom portion of the outer annular groove. It is an object of the present invention to provide a bellows having a structure capable of securing an optimal sealing state and maintaining an optimal sealing state even when molded.

[0008]

The bellows of the present invention for solving the above-mentioned problems are made of a material having elasticity, have a cylindrical fixing portion at both ends of a cylindrical bellows portion, and have at least one cylindrical shape. The fixing portion has, on its outer peripheral surface, an outer annular groove for fastening a clamp member, and on its inner peripheral surface, an annular ridge that engages with the annular engagement groove on the mounting side at a position within the width of the annular groove. Having an inner bottom portion of the outer annular groove,
An annular space having a substantially W-shaped cross section having a projection at the center in the width direction is provided within a range corresponding to the annular ridge, and the width (a) of the annular space is the same as its depth (b); Alternatively, it is characterized by being larger than the depth (b).

When such an annular gap is formed,
When tightened by the clamp member fitted in the outer annular groove,
The cylindrical fixing portion is compressed against the elastic force by the tightening force, and both side wall portions of the annular gap are pushed inwardly of the annular gap and elastically deformed. At this time, the annular gap has a cross section. Since it is substantially W-shaped and its width (a) is equal to or greater than the depth (b), deformation of both side wall portions of the annular gap causes the bottom surface of the outer annular groove ( On the other hand, the side surface of the annular gap is in contact with both sides of the central projection, and the projection serves as a wall to suppress excessive deformation of a certain degree or more. The contact pressure with the inner peripheral surface of the mounting-side annular engagement groove can be favorably maintained.

In particular, the contact portions between both side surfaces of the annular space and both side surfaces of the protrusion are inclined to both sides with the protrusion being in the middle, so that a substantially triangular section is formed at the center, The tightening force acts along the contact portion toward the corner of the annular engagement groove on the attachment side, and as a result, the annular ridge forms a corner with respect to the inner peripheral surface of the annular engagement groove. Can be tightly fitted up to

[0011] Thereby, it can be firmly attached and fixed to the member on the side to be attached, and good sealing performance can be secured.

In particular, the central projection in the annular space is
If it is formed lower than the clamp surface of the clamp member, the tightening force of the clamp member will not be impaired by this, and the above-mentioned attached state will be more favorably maintained.

In addition, the annular space has a substantially W-shaped cross section and the central projection is lowered, so that even in the blow molding from a thin resin material, the center of the inner circumferential annular raised portion in the width direction can be formed. A valley portion is not formed, and one cross section can be formed into a mountain shape. For this reason, when tightened by the clamp member, the peak portion of the annular raised portion does not escape inward, so that the pressing force can be favorably held.

[0014]

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

FIG. 1 is a longitudinal sectional view of a bellows (A) according to the present invention.

The bellows (A) is formed by blow molding a resin material having a moderate elasticity such as a thermoplastic synthetic resin elastomer.
As shown in FIG. 1, a cylindrical bellows (1) having alternating peaks (1a) and valleys (1b), and a cylindrical fixing part (2a) formed continuously and integrally with the openings at both ends thereof. ) (2b).

The cylindrical fixing portions (2a) and (2b) at both ends.
At least one (both in the figure) has an outer circumferential groove having a relatively shallow and flat cross section for tightening by a tightening clamp member (10) such as a boot band made of a metal plate such as iron. 3) is formed. The inner peripheral surface has an annular engaging groove (2) formed in the member (20) on the mounted side.
An annular ridge (4) engaging 1) is formed at a position within the axial width of the outer annular groove (3). FIG. 2 shows a part of the large-diameter cylindrical fixing portion (2a) in an enlarged manner. The small-diameter cylindrical fixing portion (2b) also has substantially the same configuration as described below. ing. FIG. 3 is a cross-sectional view of the same portion when tightened.

The inner bottom of the outer annular groove (3) has a projection (5) having a substantially triangular cross section at the center in the width direction within a range corresponding to the inner annular ridge (4). A substantially W-shaped annular gap (6) is provided. In particular, in the case of the drawing, both side surfaces of the annular gap (6) continuous from both side slopes of the projection (5) having a substantially triangular cross section are slightly inclined and the corners are rounded to form the outer annular groove (3). It is formed to have a substantially W-shaped cross section continuous with the bottom surface and slightly expanding on the opening side.

As shown in the enlarged view of FIG. 2, the annular space (6) has a width (a) of the opening which is equal to or less than the depth (b). Large, a ≧
It is formed so as to satisfy b.

The projection (5) at the center of the annular space (6) can be formed at the same height as the bottom of the outer annular groove (3). Say,
The bottom surface of the outer annular groove (3), that is, the clamp member (1)
It is preferable to keep it lower than the clamping surface according to 0),
In particular, it is preferable to form it so as to be lower than the clamp surface at the time of tightening. As a result, a valley is not formed at the center in the width direction of the annular protruding portion (4) even by blow molding from a thin resin material, and the cross section is formed by a relatively gentle circular arc as shown in the figure. It can be formed in a mountain shape.

The width of the base of the annular protrusion (4) is set slightly larger than the width of the annular engagement groove (21) on the mounting side, and the annular engagement groove (21) is tightened by the clamping member (10). ).

In mounting the bellows (A) having the above structure, the cylindrical fixing portions (2a) and (2b) are fitted to the member (20) on the mounting side, and the annular raised portion (4) on the inner circumference is covered. The fitting engagement is performed by being positioned corresponding to the annular engagement groove (21) on the mounting side,
Tighten and fix with a clamp member (10) such as a boot band fitted in the outer annular groove (3).

At this time, as shown in FIG. 3, the cylindrical fixing portion (2a) is compressed against the elastic force by the tightening force of the clamp member (10), and both side wall portions of the annular space (6) are compressed. The annular space (6) is pushed inward and deforms elastically. The annular space (6) has a substantially W-shaped cross section, and its width (a) is equal to or greater than the depth (b). (B) The deformation of the side walls of the annular space (6) is larger on the bottom (clamping surface) side of the outer annular groove (3), because it is larger.
Since both side surfaces of the annular space (6) are in contact with both sides of the central projection (5), the projection (5) serves as a wall to suppress a certain degree of excessive deformation, and the annular ridge (4). And the contact pressure between the mounting surface and the inner peripheral surface of the annular engagement groove (3) on the mounting side can be favorably maintained.

In particular, the contact portions between both side surfaces of the annular space (6) and both side surfaces of the projection (5) are inclined on both sides with the projection (5) being in the middle, and a substantially triangular section is formed at the center. And the clamping force acts along the abutting portion (7) toward the corner of the annular engagement groove (21) on the mounting side, so that the annular ridge (4) is annularly engaged. The inner peripheral surface of the mating groove (3) can be surely tightly fitted to both corners of the bottom surface. In particular, if the projection (5) is formed lower than the clamp surface of the clamp member (10), the clamp member (1)
Thus, the tightening force according to 0) is not impaired by this, and the above-mentioned mounting state is more favorably maintained.

FIG. 4 shows an analysis diagram of a deformed state (compressed state) of the cylindrical fixing portion (2a) at the time of tightening by a finite analysis method (FEM analysis method). According to FIG. 4, the bottom wall portion of the outer annular groove (3) is compressed and the member (20) on the mounting side is compressed.
It can be seen that the outer circumferential surface of the annular engaging groove (3) is strongly compressed in the vicinity of the base of the annular ridge (4), and is strongly pressed near the opening side corner of the annular engaging groove (3). Furthermore, both side wall portions of the annular space (6) are pushed inward to abut on both sides of the central projection (5), and this abutting portion (7) is located on both sides with the projection (5) in the middle. Inclined, the tightening force is applied along the contact portion (7) along the annular engagement groove (2
It can be seen that the annular protrusion (4) is strongly pressed against the inner surface of the annular engaging groove (3), particularly on both side surfaces.

As described above, the cylindrical fixing portion (2a) can be firmly attached to and fixed to the member (21) on the mounting side, and a good sealing property can be secured.

[0027]

As described above, according to the bellows of the present invention, the inner bottom of the outer annular groove is provided with an annular space having a W-shaped cross section. The annular protruding portion can be securely and closely fitted to the annular engaging groove on the attachment side, can be firmly attached and fixed, and a good sealing state can be ensured.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of the entire bellows according to the present invention.

FIG. 2 is an enlarged sectional view of a cylindrical fixing portion.

FIG. 3 is an enlarged sectional view at the time of tightening the same.

FIG. 4 shows an analysis diagram in a finite analysis method of a compression state at the time of tightening in the above.

FIG. 5 is an enlarged cross-sectional view showing an example of a conventional tubular fixing portion of a bellows.

FIG. 6 is an enlarged cross-sectional view showing another example of a conventional bellows cylindrical fixing portion.

[Explanation of symbols]

 (A) Bellows (1) Tubular bellows (2a) (2b) Tubular fixing part (3) Outer annular groove (4) Annular ridge (5) Projection (6) Annular gap (7) Contact part (10) ) Clamping member (20) Member on the mounting side (21) Annular engagement groove

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Katsushi Saito 1-17-18 Edobori, Nishi-ku, Osaka-shi, Osaka Toyo Tire & Rubber Co., Ltd. (72) Inventor Shinichi Ito 1-1-1 Toyota-cho, Toyota-shi, Aichi (72) Inventor Keishi Mochizuki 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation

Claims (3)

[Claims] 1. A bellows formed of a material having elasticity and having cylindrical fixing portions at both ends of a cylindrical bellows portion, wherein at least one of the cylindrical fixing portions has an outer peripheral surface on which a clamp member is tightened. An outer annular groove for engaging an annular protrusion on an inner peripheral surface of the outer annular groove at a position within the width of the outer annular groove. Has an annular space having a substantially W-shaped cross section having a projection at the center in the width direction within a region corresponding to the annular ridge, and the width (a) of the annular space is determined by its depth (b) and its depth (b). Bellows characterized by being the same or greater than depth (b). 2. The bellows according to claim 1, wherein a central projection in the width direction of the annular gap is formed lower than a clamp surface of the outer annular groove formed by the clamp member. 3. The bellows according to claim 1, wherein the inner annular protrusion has a single cross section in a mountain shape.