JP2673583B2 - Method of manufacturing article having bellows - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing an article having a bellows portion such as a headrest having a boot.

[Prior Art] As a headrest of an automobile, a bellows-shaped boot 1 is interposed between a headrest 2 and a seat 3 as shown in FIG. 1 in order to improve the feeling of unity with the seat and the appearance. Things are known. A stay extending from the headrest 2 and engaged with the seat 3 is provided inside the boot 1.
20 is inserted, and both ends of the boot 1 are fixed to the headrest 2 and the seat 3, respectively. By this, stay
It is possible to adjust the height and angle of the headrest 2 without exposing 20. Since the headrest 2 may be removed from the seat 3, the boot 1
Is integrally fixed to the headrest 2, and an attachment fitting or the like that is detachably attached to the seat 3 is fixed to the end portion on the seat 3 side.

In order to manufacture this boot, it is usual to manufacture it by injection molding using a molding die composed of an outer die and a core. Then, it is usually molded into a shape elongated from the state of use and mounted on the headrest in a compressed state from the time of molding. As a result, during molding, the difference in height between the peaks and valleys of the bellows becomes small, and the core is easily removed.

[Problems to be Solved by the Invention] By the way, as shown in FIG. 1, due to design restrictions,
The boot 1 may be mounted so that the axial direction of the boot 1 is inclined from the vertical movement direction of the headrest 2. In such a case,
When the height of the headrest 2 is adjusted, the boot 1 may be deformed and may not look good. Further, at the design stage of the boot 1, it is not known at which expansion / contraction position this deformation will occur, and it takes a lot of man-hours and time to determine the shape.

The present invention has been made in view of such circumstances, and an object thereof is to manufacture an article having a bellows portion that surely looks good at a desired expansion / contraction position.

[Means and Actions for Solving the Problem] As a result of researching the mechanism of expansion and contraction of an article having a bellows part, the present inventors have found that there is a deviation between the natural expansion and contraction direction of the bellows part. Have found that it is difficult to improve the appearance at all stretch positions. Therefore, the inventors have completed the present invention as a result of earnest research, in consideration of improving the appearance at the stretchable position where the appearance is most required.

That is, according to the method for manufacturing an article having a bellows portion of the present invention, two peaks or valleys each having both ends fixed to two articles having a cylindrical bellows shape and capable of relatively moving in a direction in which they approach each other and a direction in which they move away from each other. A method of manufacturing an article having a bellows part that expands and contracts in a direction different from the direction orthogonal to the plane surrounded by the parts, wherein the bellows part is compressed to a predetermined length when used, and the bellows part is used as a reference shape. Molding process to form a molded product in an elongated shape from the reference shape in the direction orthogonal to the plane surrounded by one peak or one valley, and the molded product to one peak or one valley A fixing step of fixing both ends to two articles in a state of being compressed to a reference shape in a direction orthogonal to a plane surrounded by the parts, respectively.

The reference shape refers to the shape of the bellows portion at the expansion / contraction position where the best appearance is required as described above. In the case of a headrest boot, for example, the state of the boot when the headrest is in the normal position (neutral), the stretchable shape of the boot at that time is called the reference shape, and that state is called the reference state.

The bellows portion has a tubular shape, but the cross-sectional shape thereof is not particularly limited, such as a circular shape, an elliptical shape, or an irregular shape.

The greatest feature of the present invention is that the bellows part has a reference shape that is contracted to a predetermined length when in use, and the bellows part is orthogonal to a plane surrounded by one peak or one trough from the reference shape. It is in the molding process to form a stretched shaped molded body.

This will be schematically described with reference to FIG. First, assume that a bellows part having a substantially trapezoidal longitudinal section is manufactured. The cross section of the reference shape is the quadrilateral ABCD shown in FIG. 2, and in this state the appearance should be particularly improved. At this time, the peaks and valleys of the bellows are parallel to the planes AB and CD. Next, one end face CD in this reference shape is fixed at that position, and the other end face AB is stretched in the direction in which the bellows naturally expand and contract, that is, in the direction orthogonal to the face AB. This makes the plane
AB moves to plane EF. Then, an elongated molded body having a quadrilateral EFCD cross section is manufactured by injection molding, transfer molding, or the like.

The obtained molded body is fixed to two articles whose both end surfaces are relatively movable while being naturally compressed at the reference position of the quadrilateral ABCD. When it is forcibly expanded and contracted in the O-axis direction deviated from the direction of natural compression, the points A and B are parallel to the axis O and are E'-A-G 'and F'-.
Draw a locus along B-H '. Therefore, the loci E-A-G and F-B- of the points A and B when they naturally expand and contract.
Compared with H, it can be seen that the difference is zero in the reference state and increases as the distance from the reference state increases. That is, in the reference state, the shape is the same as when it naturally expands and contracts, so that the appearance is best.

According to the study by the present inventors, in order to prevent deformation of the bellows portion and further improve the appearance, the corner portion of the cylindrical bellows portion has a small wall thickness, and the straight portion has a large wall thickness. It turned out that it is preferable to do. It was also found that it is preferable that the peaks of the bellows have a large thickness and the valleys have a small thickness.

[Effects of the Invention] Therefore, according to the method for producing an article having a bellows portion of the present invention, an article having a bellows portion that looks particularly good in the standard state can be easily and reliably produced. Further, the reference state can be arbitrarily selected, and the man-hour and time required for determining the shape can be reduced.

[Examples] Hereinafter, specific examples will be described. The present embodiment is an application of the present invention to the manufacture of an automobile headrest.

BACKGROUND ART As a vehicle headrest, a headrest having a shape as shown in FIG. 1 is known. In this headrest, stays 20 hang from both ends of the headrest 2 and engage with the seat 3. This makes it possible to adjust the height of the headrest 2. Bellows-shaped boots 1 are fixed to both sides of the headrest 2 to cover the stay 20 and improve the appearance.

Here, the boot 1 is arranged in a substantially V-shape when viewed from the front, and is configured to naturally expand and contract in the inclined direction. However, the actual expansion / contraction direction is the vertical direction in which the stay 20 extends. The boot 1 has a modified cross section from the viewpoint of design.

The height of the headrest is usually adjusted to a neutral position at a position suitable for a person of standard height, and is normally adjusted in the vertical direction from the neutral position. Therefore, the neutral position is often set to the normal position. Therefore, in this embodiment, the appearance is particularly improved at the neutral position.

A conceptual front view of the boot in the neutral position is shown in FIG. A quadrilateral ABCD with a neutral shape
Is a reference shape, and one end face CD is fixed and the other end face AB is extended in the natural expansion and contraction direction of the bellows, and is referred to as a face EF. As a result, the front view of the molded body to be molded is completed as a quadrilateral EFCD. Then, a side view, a rear view, etc. are similarly prepared, and the shape of the molded body is determined from these. A mold is manufactured based on this shape, and a boot is obtained by injection molding from a mixed material of EPDM and PP. The height of the bellows is 9mm and the pitch is 13.5m.
m.

The formed boot 1 is fixed by welding one end to a PP mounting plate 4 separately formed as shown in FIG. 4, and the mounting plate 4 is fixed to the headrest 2 side with a screw, As shown in FIG. 1, it is attached to the headrest 2 while being inclined with respect to the stay 20. A mounting bracket (not shown) is fixed to the other end of the boot 1 so that the boot 1 is engaged with and held by the seat 3 at a neutral position where the boot 1 is compressed in a direction in which it naturally expands and contracts. As a result, both ends of the boot 1 are fixed to the headrest 2 and the seat 3.

Here, when adjusting the height of the headrest 2, the other end surface AB of the boot 1 in the standard state is in the extending direction O of the stay 20.
Along the E'-AG 'direction. The natural expansion and contraction direction of the boot 1 is the EAG direction.

When the stay 20 is in the upper two-stage position (P), the point A is
Located A ₁ point, 4 from the position A ₁ 'point when the extend and retract spontaneously.
3 mm off. Also, when in the upper 1st position (Q), the point A is at the point A ₂ and the position when it is naturally expanded and contracted.
When it is in the lower 1st step position (R) by 2 mm from the A ₂ ′ point, the A point is at the A ₃ point and the position when it is naturally expanded and contracted.
It is 2 mm off the point A ₃ '. However, at the neutral position (N), the actual expansion / contraction position and the natural expansion / contraction position coincide with each other at point A, and the deviation is zero. Therefore, at the neutral position, no shear stress is generated and the appearance is good.

Note that the shape of the bellows at the neutral position is FEM.
Simulation analysis by (finite element method) is shown in FIG. From FIG. 5, it was also shown by calculation that the bellows part at the neutral position looks good. The actual boots also showed the same behavior as the FEM analysis, and the appearance was particularly good at the neutral position, and no extreme deformation occurred at other positions.

(Comparative Example) In the molding step, the bellows portion was extended from the neutral position, which is the reference state, in the extending direction of the stay 20 to form a molded body. That is, as shown in FIG. 6, the quadrilateral ABCD, which is a neutral shape, is used as a reference shape and
Is fixed and the other end surface AB is extended in the O direction in which the stay extends and is referred to as surface EF. As a result, the front view of the molded body to be molded is completed as a quadrilateral EFCD. Then, a side view, a rear view, etc. are similarly prepared, and the shape of the molded body is determined from these. A mold is manufactured based on this shape, and a boot is obtained by injection molding from a mixed material of EPDM and PP. The obtained boot was fixed to the headrest 2 and the seat 3 without being compressed and without being twisted.

Here, when adjusting the height of the headrest 2, the other end surface AB of the boot 1 is EA along the direction O in which the stay 20 extends.
Move along the -G 'direction. The natural expansion and contraction direction of the boot 1 is the EAG direction.

When the stay 20 is in the upper two-stage position (P), the point A is
It is at A ₁ point, and the position when it is naturally expanded and contracted A ₁ ′ from point 1.
It is offset by 2 mm. Also, when in the upper 1st position (Q), the point A is at the point A ₂ and the position when it is naturally expanded and contracted.
When it is in the lower 1st position (R) by 3.5 mm from point A ₂ ′, point A is at point A ₃ , which is the position when it is naturally expanded and contracted.
It is offset 8mm from A ₃ 'point. Further, at the neutral position (N), the deviation between points A and A'is 6.8 mm.

In the case where the molded body is formed by extending in the extending direction of the stay and the bellows portion is formed from this, the shift amount becomes larger than that of the bellows portion obtained in the example, and the appearance becomes poor. Similar to the example, the results of FEM analysis in the neutral position are shown in FIG. From this, it is clear that the bellows portion formed by the method of the comparative example has a poorer appearance at the neutral position than the bellows portion obtained in the example. The actual boot also showed the same behavior as the FEM analysis.

[Brief description of the drawings]

FIG. 1 is a front view of a headrest device, and FIG. 2 is a diagram explaining the operation of the present invention. 3 to 6 relate to a manufacturing method of an embodiment of the present invention, FIG. 3 is a diagram for explaining the operation, FIG. 4 is a perspective view of a main part of a bellows part, and FIG. 5 is a bellows part. It is a FEM analysis chart. 6 to 7 relate to the manufacturing method of the comparative example, FIG. 6 is a diagram for explaining the action, and FIG. 7 is an FEM analysis diagram of the bellows portion. 1 ... Bellows part, 2 ... Headrest 3 ... Seat, 4 ... Mounting plate N ... Neutral position (standard state)

Claims (1)

(57) [Claims] 1. A flat surface having both ends fixed to two articles each having a cylindrical bellows shape and capable of relatively moving in a direction in which they are close to each other and a direction in which they are away from each other, with respect to a plane surrounded by one mountain portion or one valley portion. A method of manufacturing an article having a bellows part which expands and contracts in a direction different from the orthogonal direction, wherein a shape in which the bellows part is compressed to a predetermined length during use is used as a reference shape, and the bellows part is used as the reference shape. A molding step of molding an elongated shaped body extending in a direction orthogonal to a plane surrounded by one mountain portion or one valley portion, and surrounding the molded body with one mountain portion or one valley portion. And a fixing step of fixing both ends to the two articles in a state of being compressed to the reference shape in a direction orthogonal to a plane to be formed, and a method of manufacturing an article having a bellows portion.