JPH09254239A - Production of flexible boots made of resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce flexible boots which is easily assembled at relatively low cost and equipped with a positioning structure sufficient in strength. SOLUTION: The end part shape of flexible boots consists of an attaching part 2, a recessed part 3 and a flat part 4 and these parts are molded by injection molding and other parts are subsequently continuously subjected to blow molding. Since the recessed part 3 engaged with the protruding part 8 of a partner member can be molded with high dimensional accuracy and a corner part is certainly formed, even if the difference in level of the protruding part 8 of the partner member is small, the recessed part 3 can be certainly engaged with the protruding part 8 and, even if the protruding end part 9 of the partner member has a polygonal shape, it can be easily attached without caring about directionality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a resin-made flexible boot for covering a connecting portion of two mechanical elements which are displaced relative to each other and preventing dust and water from entering.

[0002]

2. Description of the Related Art FIG. 6 shows an example of a conventional flexible boot of this type. This is the actual Kaihei 3-124072
It is described in Japanese Patent Application Publication No. JP-A-2003-187, and is used for a steering device of an automobile. In FIG. 6, reference numeral 23 is a rack shaft, 24 is a socket, 25 is a tie rod, 26 is a ball fitted in the socket 24, and 29 is a cylinder tube. The flexible boot 27 is fixed by a band 30 by locking one end 28 having a large diameter to a convex portion 29 a provided on the cylinder tube 29, and the other end 31 having a small diameter is connected to a connecting portion 32 of the tie rod 25. It is fixed by a band 33. An intermediate portion connecting the end portions 28 and 31 is a bellows portion 34.

The large diameter end 28 has a cylinder tube 29.
The mounting portion 28a fixed to the upper portion by the band 30 and the convex portion 2
9a and a recess 28b that is engaged with the recess 9b.
From this, a tubular portion 35 reaching the bellows portion 34 is continuously formed. The cylindrical portion 35 has a wide width which is depressed inward in the radial direction at a plurality of positions in the circumferential direction, for example, at four or six positions at equal intervals, and the depth of which gradually decreases toward the bellows part 34. A depression 36 is provided. This depression 3
6 cooperates with the concave portion 28b to partially clamp the convex portion 29a in the circumferential direction. A flexible boot used for a steering device of an automobile receives a force of expansion and contraction and bending at the time of steering a wheel, and therefore requires a positioning structure having sufficient strength and cost reduction as much as possible. The flexible boot shown in the above-mentioned conventional example has required strength and positioning accuracy due to its structure and can be formed by blow molding, so that low cost can be realized.

[0004]

However, the above-mentioned conventional flexible boot has a problem associated with blow molding. That is, as shown in FIG.
No. 6 is that at the time of blow molding, the meat at the corners is pulled to both sides and a large R is attached. Convex portion 29a and protruding end portion 2
When the step a with 9b is large, the concave portion 28b and the convex portion 29
Since the engagement margin b with a can be made large, there is no problem. However, when the step a is small, the engagement margin b becomes short, so that the amount of catching on the convex portion 29a becomes small, and the engagement in the axial direction is small. The stop function will be inferior. Further, as shown in FIG. 8, in this type of steering device, the projecting end portion 29b is often formed in a hexagon, and the step a with respect to the convex portion 29a is small at the top of the hexagon and large at the sides. Therefore, for example, it is necessary to attach the boots by aligning the recessed portions 36 provided at six locations with the hexagonal side portions of the projecting end portion 29b, and there is a problem that the assembly takes time. The present invention solves such a conventional problem, and provides a method for manufacturing a resin flexible boot that is relatively low in cost, has a positioning structure with sufficient strength, and is easy to assemble. The purpose is to

[0005]

In order to achieve the above-mentioned object, the present invention changes the production of a resin flexible boot from conventional direct blow molding to injection blow molding. Injection blow molding is one in which the same middle mold is used, injection molding is performed in one mold, and then blow molding is performed in the other mold, so the advantages of injection molding and blow molding can be incorporated. When molding flexible boots, injection molding the end parts that require high precision and blow molding the middle part to manufacture resin flexible boots with sufficient positioning strength at relatively low cost and easy to assemble. can do.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In order to facilitate injection blow molding, a method of manufacturing a resin flexible boot according to the present invention has a shape such that at least one end portion of the flexible boot is attached to a connecting portion of a mechanical element. A portion, a concave portion provided adjacent to the mounting portion and capable of engaging with a convex portion formed in the coupling portion of the mechanical element, and a concave portion provided adjacent to the concave portion and continuously on the circumference. Alternatively, the flat portion is provided at two or more places at equal intervals, and at least the mounting portion, the concave portion, and the flat portion are injection-molded, and then the other portions are blow-molded. This makes it possible to mold the concave portion that engages with the convex portion of the mating member with high dimensional accuracy,
Since the corners are formed reliably, even if the step is small,
The concave portion can be reliably engaged with the convex portion, and even if the protruding end portion of the mating member has a polygonal shape, it can be easily attached without worrying about the directionality.

According to the present invention, the flexible boot further includes a tubular portion between the concave portion and the bellows portion, and the tubular portion is depressed radially inward so as to form the other wall surface of the concave portion. It has a plurality of recesses provided,
The strength of the end portion of the flexible boot can be further improved.

[0008]

FIG. 1 shows one end of a flexible boot in one embodiment of the present invention, and FIG. 2 shows an enlarged cross section of the end. This flexible boot 1
The overall shape is similar to that shown in FIG. 6, and is used for a steering device of an automobile. One end of the flexible boot 1
A mounting portion 2 fixed to a cylinder tube of a steering device with a band, an annular concave portion 3 engaged with an annular convex portion 8 provided on the cylinder tube, and a flat portion provided adjacent to the concave portion 3. 4, a tubular portion 5 provided continuously to the flat portion 4, and six recessed portions provided in the tubular portion 5 at regular intervals in the circumferential direction so as to widen radially inwardly. 6 and a bellows portion 7 provided continuously to the tubular portion 5. The depressed portion 6 is gradually shallowed toward the bellows portion 7.

One end of the flexible boot 1 is pushed into the cylinder tube and covered therewith, and after the recess 3 is fitted into the projection 8 of the connecting portion, the mounting portion 2 is fixed with a band. Since the concave portion 3 fits into the convex portion 8, even if the flexible boot 1 is subjected to the force of expansion and contraction and bending, the positional displacement does not occur. Further, since the flat portion 4 is provided adjacent to the concave portion 3, the corner portion of the concave portion 3 can be surely formed, so that the engagement margin for the convex portion 8 can be taken as designed. For this reason, even if the protruding end 9 of the coupling portion is polygonal, even a portion of the corner portion having a small step is sufficiently locked, so that the mounting can be easily performed without worrying about the directionality. it can. Further, since the tubular portion 5 is provided with the plurality of recesses 6, the strength of the tubular portion 5 is increased, and it is possible to reliably prevent abnormal operation and deformation of the flexible boot 1 and deterioration of durability.

The flexible boot 1 is formed of a synthetic resin material by injection blow molding. The process will be described below with reference to FIGS. 3 and 4. In FIG. 3A, two identical middle dies 12 and 13 are fixed in the 180-degree radial direction of the shaft 11, and the injection die 14 and the blow die 15 respectively.
To be housed in them by closing. The injection mold 14 has a cavity for forming the mounting portion 2, the concave portion 3 and the flat portion 4 of the flexible boot 1, a straight tubular portion and a cavity for forming the opposite end portion. In the state of (a), the molten resin is injected into the injection mold 14 from the nozzle 16 under pressure. As a result, a cylindrical semi-molded product 17 in which the mounting portion 2, the concave portion 3 and the flat portion 4 are formed around the middle die 12 of the injection die 14 is formed. Next, in (b), the nozzle 16 is retracted and both molds 14 and 15 are opened. Then, in (c), the shaft 11 is rotated 180 degrees,
The semi-molded product 17 around 2 is placed at the position of the blow mold 15. Next, in FIG. 4D, both molds 14 and 15 are closed, compressed air is blown into the blow mold 15 to press the semi-molded product 17 against the inner surface of the blow mold 15, and then cooled. Let it solidify. As a result, the tubular portion 5, the depressed portion 6, and the bellows portion 7 of the flexible boot 1 are blow-formed. At this time, since the concave portion 3 and the flat portion 4 are already formed and the flat portion 4 is formed between the blown portion and the concave portion 3, the corner portion of the concave portion 3 is not affected by the blow molding and is surely formed. Is formed. At the same time, the molten resin is injected from the nozzle 16 into the other injection mold 14 for injection molding. Then, in (e), both molds 14 and 15 are opened to take out a molded product 18 from the blow molding mold 15, and a semi-molded product 17 is molded in the injection mold 14 as in the step (b). Therefore, the same steps are repeated thereafter.

In FIG. 2, the axial length d of the inner peripheral surface 4a of the flat portion 4 is preferably 5 mm or more.
If it is less than mm, it may be pulled by the blow portion and affect the corner portion of the step. In addition, the inner peripheral surface 4a of the flat portion 4
The angle θ with respect to the axis is preferably within ± 10 °. If it exceeds 10 ° on the outer diameter side, it becomes difficult to release it from the middle dies 12, 13, and if it exceeds 10 ° on the inner diameter side, it interferes with other parts. There is a fear.

FIG. 5 shows a modification of the shape of the end portion of the flexible boot according to the present invention. In the flexible boot 1A of (a), the recessed portion 6 is formed at a substantially uniform depth with respect to the tubular portion 5, and the flexible boot 1 of (b) is formed.
In B, the depression 6 is not formed in the tubular portion 5, and (c)
The flexible boot 1C is characterized in that the outer peripheral surface of the concave portion 3 and the outer peripheral surface of the flat portion 4 are formed on the same surface. As described above, the shape of the flexible boot of the present invention can be variously changed on condition that the mounting portion 2, the concave portion 3, and the flat portion 4 are provided.

[0013]

As described above, according to the present invention, the shape of the end portion of the flexible boot is the mounting portion, the concave portion and the flat portion, which are injection molded, and then the other portion is blow molded. Therefore, the concave portion that engages with the convex portion of the mating member can be molded with high dimensional accuracy, and the corner portion is reliably formed, so that the concave portion can be reliably engaged with the convex portion even if the step is small. Even if the projecting end of the mating member has a polygonal shape, it can be easily attached without worrying about the directionality.

[Brief description of drawings]

FIG. 1 is a perspective view of one end of a flexible boot according to an embodiment of the present invention.

FIG. 2 is an enlarged partial sectional view of one end of a flexible boot according to an embodiment of the present invention.

FIG. 3 is a mold cross-sectional view for explaining an injection blow molding process in one embodiment of the present invention.

FIG. 4 is a mold cross-sectional view (continuation) for explaining an injection blow molding step in one embodiment of the present invention.

FIG. 5 is an enlarged partial sectional view showing a modified example of the end shape of the flexible boot according to the present invention.

FIG. 6 is a partial cross-sectional view of a steering device using a conventional flexible boot.

FIG. 7 is an enlarged partial sectional view of one end of a conventional flexible boot.

FIG. 8 is a side end view of a mating member for explaining the problems of the conventional flexible boot.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flexible boot 2 Mounting part 3 Recessed part 4 Flat part 5 Cylindrical part 6 Cavity part 7 Bellows part 8 Convex part of mating member 9 Projecting end part of mating member 11 Shaft 12, 13 Medium size 14 Injection mold 15 Blow mold 16 Nozzle 17 Semi-molded product 18 Molded product

Claims (3)

[Claims] 1. A method for producing a resin flexible boot having injection-molding, the end portions of which are joined to a joining portion of two mechanical elements that are relatively displaced, and a resin-made flexible boot having a bellows portion capable of expansion and contraction and bending in an intermediate portion. hand,
The flexible boot, at least one end thereof,
An attachment portion attached to the connecting portion of the machine element, a recessed portion provided adjacent to the attachment portion and engageable with a protrusion formed on the connection portion of the mechanical element, and adjacent to the recessed portion. And a flat portion provided on the circumference continuously or at equal intervals at two or more places, and at least the mounting portion, the concave portion and the flat portion are injection molded,
A method for producing a flexible boot made of resin, characterized in that the other part is then blow-molded. 2. The method for producing a flexible boot made of resin according to claim 1, wherein the flexible boot has a tubular portion between the concave portion and the bellows portion. 3. The flexible boot has a cylindrical portion,
The method for manufacturing a flexible boot made of resin according to claim 2, further comprising a plurality of recesses which are recessed inward in the radial direction so as to form the other wall surface of the recess.