JPH0257319A - Manufacture of resin boot - Google Patents

Abstract

PURPOSE:To obtain a boot in which the thickness of a crested part is not thinner than the other part by heating a blow-molded form having longer bellows than that of bellows of a final product shape in a state that the bellows are compressed to the size of the bellows in the final product shape in a thermally deforming temperature atmosphere of a material to be molded for a predetermined period of time, and then cooling it to fix the shape. CONSTITUTION:A blow-molded form M having longer size l2 of bellows than that l of bellows of a final product shape is obtained. Then, the form M is so held by a jig 11 in a compressed state that the bellows of the form M becomes the size l of the final product shape. A plurality of the forms M held by the jig 11 in the compressed state are set in many stage pallets 15, stored in a heating tank 16, and held at the thermally deforming temperature of a material to be molded for a predetermined period of time. (In case of polyolefin thermoplastic elastomer, it is held, for example, at 150 deg.C for 10 - 15 min), the pallet 15 is then removed from the tank 16, cooled to ambient temperature, and the molded forms M are then removed from the jig 11. Thus, the forms M are secured in shape to the compressed set state by thermally working, and a boot having the size l of the bellows in a final product shape is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to a method for manufacturing resin boots by blow molding.

<Prior art> Here, as shown in FIG.
The large diameter ring part 1 is fitted to the output @23, the small diameter ring part 2 is fitted to the output @23, and both ring parts! , and a bellows part 3 formed between two parts, and will be explained by taking as an example a resin rack boot B which is attached to a steering rack part of a steering device of an automobile as shown in FIG. However, it is also applicable to boots for other mechanical shaft couplings.

Rack boots like the one above have long compression and expansion strokes. Therefore, when trying to blow mold rack boots using a resin material, the characteristics of the material (the elongation rate of the material itself is much lower than that of rubber).

), it is necessary to make the membrane length of the bellows part longer than that of rubber, that is, to increase the number of ridges, and to reduce the elongation when the boot is extended.

Therefore, as shown in Fig. 4, the resin rack boot is molded to a length ℃1 which is longer than the bellows dimension 1 in the neutral mounting state (steering position when the vehicle is running straight).
Neutral mounting was used by compressing and attaching it to the state bellows dimension book.

Incidentally, examples of publicly known publications describing techniques related to blow molding of resin boots include Japanese Patent Publication No. 42619/1983.

<Problems to be Solved by the Invention> As described above, rack boots made of resin have a longer total boot length than those made of rubber. This means that boots 1
This is undesirable from the viewpoint of storage and transportation, as it increases the space occupied by each unit.

In addition, neutral mounting requires compression from a longer state than before and mounting on the actual vehicle, and installation workability is not as good as with rubber boots.

Further, the distance from the free state to the maximum compression state (the state where the steering angle is maximized) is relatively large, and the bellows portion is likely to be laterally bent (buckled) deformed, which is undesirable in terms of the operating characteristics of the boot.

Furthermore, by shortening the mountain pitch of the bellows part, the membrane length can be relatively increased (that is, the compression/expansion stroke of the boot can be ensured), and the free length of the boot, that is, the product dimensions of the boot can be shortened. . However, if the peak pitch is shortened (the peak angle is small), when blow molding is performed, the thickness of the peak will become thinner than the other parts, as shown in Figure 5, which is undesirable from the viewpoint of strength. , commercialization was considered difficult.

The reason why the mountain top part is thinner than other parts is presumed to be as follows.

During blow molding, at the start of blowing, the parison first hits the trough forming part of the blow mold, where it is cooled and elongation stops at an early stage, while the crests contact up to the crest forming part of the blow mold. It continues to grow until it reaches ↑. Therefore, in blow molding, the peaks are usually formed to be thinner than the valleys. This tendency is more pronounced as the crest angle becomes smaller (the crest pitch is shorter; the difference between the ridge diameter and the valley diameter is larger).

In view of the above, it is an object of the present invention to provide a method for manufacturing resin boots that can produce boots with a short mountain pitch without making the wall thickness at the top part thinner than other parts. do.

Means for Solving the Problems> The method for manufacturing resin boots of the present invention solves the above problems with the following configuration.

In a method for manufacturing a resin boot consisting of a large-diameter ring part, a small-diameter ring part, and a bellows part formed between both ring parts by blow molding, the blow molding has a bellows part dimension longer than the bellows part dimension in the final product shape. A molded product is obtained, and the blow molded product is heated in an atmosphere at the heat deformation temperature of the molding material for a predetermined period of time in a state where the bellows part is compressed to the size of the bellows part in the final product shape, and then heat-processed by cooling and fixing the shape. and manufacturing resin boots.

<Performance Example> An example of the method for manufacturing resin boots of the present invention will be described below with reference to FIG. 1.

(1) Obtain a blow-molded product M having a bellows part dimension 12 longer than the bellows part dimension (normally the length in the neutral mounting state) i in the final product shape.

That is, when blow molding is performed, the pitch of the ridges is such that the crests do not become thinner than other areas.

The molding method at this time may be direct blow or injection blow. Further, as the molding material, thermoplastic elastomer materials such as polyester and polyolefin are used.

(2) Next, using the jig 11, the molded product M obtained above is
The jig 1 is held in a compressed state such that the bellows part becomes the bellows part dimension 2 in the final product shape (Fig. 1B).
1, a plurality of holding rods 13 are protruded at equal intervals on a base plate 12, an engaging groove t3a is formed at a predetermined height position of each holding rod 13, and a retaining ring (for example, a ball) is formed in the engaging groove 13a. 14 equipped with a plunger mechanism can be engaged. The above compression ratio flail 2 is usually o, 6
5~0°85.

(3) Set the plurality of molded products M held on the jig 11 with the bellows parts in a compressed state on the multi-stage pallet 15 (FIG. 1C), and store them in the heating tank 16 to thermally deform the molding material. The temperature is maintained for a predetermined time (FIG. 1D). This thermal deformation temperature holding condition is applicable when the molding material is a polyolefin thermoplastic elastomer, for example! The temperature is 50°C for 10 to 15 minutes.

(4) Next, the above multi-tiered pallet! 5 was removed from the heating chamber 16 and cooled at room temperature (e.g., 25°C
minutes) (FIG. 1E), the molded product M is removed from the jig 11 (FIG. 1F). In this way, the shape of the molded product M is fixed in a compressed set state by heat processing, and a boot having the bellows part dimension l in the final product shape is obtained (FIG. 1G).

The resin boot produced in this way is mounted in a neutral state in its free state, ie without compression.

<Operations and Effects of the Invention> As described above, the method for manufacturing a resin boot of the present invention obtains a blow molded product having a bellows part dimension longer than the bellows part dimension in the final product shape, and The resin boots are manufactured by compressing the resin to the bellows dimensions of the final product shape and heating the molded material for a predetermined time in an atmosphere at the heat distortion temperature of the molding material, followed by subsequent cooling to fix the shape. This configuration provides the following effects.

When manufacturing a resin boot having a bellows portion with a short crest pitch by blow molding, it is necessary to obtain the boot with the thickness of the crest portion being substantially concave compared to the other portions.

Therefore, (1) boots with the same membrane length can be obtained with relatively short free lengths, and - the space occupied by each boot is reduced, which is desirable from the standpoint of storage and transportation.

■Since the length of the bellows part in the free state and the length of the bellows part when installed on an actual vehicle are approximately concave, there is no need to attach the bellows part while it is in a compressed state, which improves workability during installation.

■The distance difference between the bellows part from the free state to the maximum compression state is short, making it difficult for lateral bending deformation (buckling deformation) to occur when mounted on an actual vehicle, improving the operating characteristics of the boot.

[Brief explanation of the drawing]

Fig. 1 is a process schematic diagram showing an example of the method for manufacturing resin boots of the present invention, Fig. 2 is a half-sectional view of the mounting mode showing an example of rack boots to which the present invention is applied, and Fig. 3 is the same as that of Fig. 2. A schematic perspective view showing the steering part showing the part where the boots are attached. Figure 4 is an explanatory diagram of the manner in which the boots are attached using the conventional manufacturing method. Figure 5 is the case where boots with a short pitch are manufactured using the conventional manufacturing method. FIG. 2. Figure 1... Large diameter ring part, 2... Small diameter ring part, 3... Bellows part, 11... Jig, 13... Holding rod, 16... Heating tank, B. ...Rack boots, λ...Dimensions of bellows part in neutral state, (dimensions of bellows part in final product) f! , 2...Dimensions of the bellows part during molding. Figure 3

Claims (1)

[Claims] A method for manufacturing a resin boot consisting of a large-diameter ring portion, a small-diameter ring portion, and a bellows portion formed between the two ring portions by blow molding, which is longer than the size of the bellows portion in the final product shape. A blow molded product having a bellows part size is obtained, and the blow molded product is heated in an atmosphere at the heat distortion temperature of the molding material for a predetermined time in a state in which the bellows part is compressed to the bellows part size in the final product shape, and then cooled. 1. A method for manufacturing resin boots, which comprises manufacturing resin boots by performing heat processing to fix the shape.