JPH09226485A - Thermoplastic resin made automobile shock absorbing member and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shape for an automobile shock absorbing member which is excellent in shock absorbing effect and provide a highly productive integral molding method for the member. SOLUTION: A shock absorbing member 1 is constructed of a long curved part, which is provided with a hollow part, and installation parts, which are arranged in the longitudinal both ends, to an automobile main body. In the curved part, an outline of a cross section vertical to the longitudinal direction is formed into a trapezoid tapering toward the automobile front side from the installation side to the automobile main body, and in the center of the trapezoidal cross section, two or more rectangular hollow parts 9 continuing in the longitudinal direction are arranged, and at least one hollow part 10, which is smaller than the hollow part 9 and continues in the longitudinal direction, is arranged in the vicinity of a taper part 7 adjacent to the hollow parts 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock absorbing member for automobiles having a high shock absorbing effect, which is made of a thermoplastic resin, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, metal shock absorbing members such as bumpers and bumper beams have been widely used. However, although they have no problem in strength, they are heavy and easily corroded. was there. Therefore, in recent years, plastic bumpers, bumper beams and the like have been adopted from the viewpoint of resource saving and weight reduction.

It is effective that the plastic bumper, bumper beam and the like have a hollow structure in order to improve shock absorption.
There is a method in which the front side and the back side are separately molded by blow molding or injection molding, and these are bonded by secondary processing to mold a hollow structure molded product. However, in the integral molding by blow molding, a molded product having a hollow structure can be easily obtained, but there are problems that productivity is limited and the degree of freedom in shape is poor.

Further, in the injection molding, there are problems that the molding machine becomes large in size and the die that can withstand high injection pressure becomes expensive, and the cost increases due to the secondary processing.

[0005]

SUMMARY OF THE INVENTION The present invention provides a shape of a shock absorbing member for automobiles having a high shock absorbing effect, and at the same time, makes use of the productivity and the degree of freedom of shape by injection molding, and a molding machine for low pressure molding. An object of the present invention is to provide a method for integrally molding a shock absorbing member for an automobile, which enables miniaturization.

[0006]

DISCLOSURE OF THE INVENTION As a result of various studies on the method for achieving the above-mentioned object, the present inventors found that an automobile shock absorbing member having a specific shape has a high shock absorbing property and is hard to buckle or has a rectangular shape. The present invention has been completed by discovering that an integrated molding method for a shock-absorbing member for automobiles can be achieved by gas injection injection molding using the moving core of (1).

The present invention is as follows. (1) In a shock-absorbing member for an automobile made of a thermoplastic resin, which comprises a long curved portion having a hollow portion and mounting portions provided on both ends in the longitudinal direction to the automobile body, the curved portion has an outer contour of a cross section perpendicular to the longitudinal direction. Is a trapezoidal shape that forms a taper that narrows from the side where it is attached to the car body toward the front of the car, and there are two or more hollow parts that are approximately rectangular and communicate with each other in the longitudinal direction at the center of the trapezoidal cross section, and the taper part adjacent to them. A shock-absorbing member for a vehicle made of a thermoplastic resin, characterized in that it has at least one hollow portion which is smaller than the hollow portion and communicates in the longitudinal direction. (2) The shock-absorbing member for automobiles according to (1) above, which has three hollow portions that are substantially rectangular and communicate with each other in the longitudinal direction at the center of the trapezoidal cross section.

(3) A long curved portion having a hollow portion,
A method of manufacturing a shock-absorbing member for a vehicle made of a thermoplastic resin, the method comprising a mounting portion to be attached to an automobile body provided at both ends in a longitudinal direction, wherein at least two rectangular molds installed in a mold with the mold closed are provided. At least two hollows that protrude from the moving core, retract the moving core while introducing pressurized gas between the tip of the moving core and the mold, and have a substantially rectangular cross section perpendicular to the longitudinal direction and that communicate with each other in the longitudinal direction. A method for manufacturing a shock-absorbing member for a thermoplastic resin automobile by gas injection injection molding so as to form a partition between a hollow portion and the hollow portion.

(4) A method for manufacturing a shock-absorbing member for automobiles, which is made of a thermoplastic resin as described in (1) or (2) above,
With the mold closed, at least two rectangular moving cores installed in the mold are projected, pressurized gas is introduced and pressure is maintained until the desired hollow portion is formed in the taper part, and the moving core Injecting gas while introducing pressurized gas between the tip and the mold so that the moving core is retracted so that at least two hollow portions communicating with each other in the longitudinal direction have a substantially rectangular cross section perpendicular to the longitudinal direction. A method for manufacturing a shock-absorbing member made of a thermoplastic resin for automobiles by injection molding. Note that the front of the vehicle in the present invention does not mean only the traveling direction of the vehicle, but means the external space of the vehicle, and the thermoplastic resin shock-absorbing member for an automobile of the present invention includes a front portion and a rear portion of a vehicle body. It is applicable to both.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The shock-absorbing member for an automobile in the present invention is a shock-absorbing member for an automobile made of a thermoplastic resin, which has a long curved portion having a hollow portion and a mounting portion to the automobile body, and the curved portion is perpendicular to the longitudinal direction. The cross-section has a trapezoidal shape that forms a taper that narrows from the side where it is attached to the car body toward the front of the car. At the center of the cross-section, there are two or more hollow parts that are approximately rectangular and communicate with each other in the longitudinal direction, and a taper adjacent to them. A thermoplastic resin shock-absorbing member for automobiles, characterized in that it has at least one hollow portion that is smaller than the hollow portion and communicates in the longitudinal direction. In the above-mentioned cross section, the wall between the rectangular hollow portions of the curved portion and the wall formed by the hollow portion and the hollow portion of the taper portion adjacent thereto serve as ribs and are useful for shock absorption.

The taper portion is necessary for at least one side, and it is preferable that it is on both sides from the viewpoint of shock absorption.
The inclination angle of the taper portion is preferably set in the range of 2 to 20 °, and more preferably in the range of 5 to 10 °. It is preferable that there are three rectangular hollow portions having the above-mentioned cross-section, from the viewpoints of the effect of shock absorbing, the limitation in manufacturing the molding die, and the total weight of the shock absorbing member. Further, the wall thickness between the rectangular hollow portions in the central portion and the wall formed by the hollow portions and the hollow portion of the taper portion adjacent thereto is preferably about 5 mm.
In addition, the wall thickness of the above-mentioned cross section is thicker on the front side and gradually becomes thinner toward the mounting side to the vehicle body, or in the longitudinal direction, the wall thickness at the central portion becomes thicker and gradually becomes thinner toward both end sides. You may want to do it. This is considered to be useful for reducing the weight of the shock absorbing member and improving the shock absorbing effect depending on the form of the shock.

Further, mounting portions are provided near both ends. It is preferable that the mounting portion is provided with unevenness so as to fit with the vehicle body so that the mounted shock absorbing member does not rub. For example, as shown in FIG. 3, the shock absorbing member may be provided with a concave portion, and the automobile body may be provided with a convex portion so that the convex portion can be held. Also, a through hole may be provided in the shock absorbing member so that the shock absorbing member can be mounted from the front side of the vehicle, and the shock absorbing member may be mounted by a joining means such as a bolt, a rivet, or a caulking member. The method for manufacturing the shock absorbing member for automobiles of the present invention will be described below with reference to the drawings. The mold used in the present invention is a metal mold for gas injection injection molding which can be applied to a molded article having a hollow portion having a rectangular cross section perpendicular to the longitudinal direction in addition to the shock absorbing member for automobiles having the above structure. It has a mold structure and is characterized by having a moving core and a portion for introducing pressurized gas. For example, the fixed mold 2 on the injection molding machine side
5 to 9, has a shape corresponding to a shock absorbing member for automobiles, and the moving die 3 has a rectangular moving core 4 and a movement control mechanism for the moving die. The hot runner 6 is used up to the mold cavity to enable the resin to be kept in a molten state. Further, the cavity shape of the fixed mold in the above figures may be reversed to the left and right, and the movable core and its movement control mechanism may be provided on the fixed mold side. The shape and volume of the protruding portion of the moving core 4 substantially correspond to the shape and volume of the rectangular hollow portion 9. Further, this moving core is capable of temperature adjustment, and is preferably divided into multiple parts as necessary, and it is preferable that the moving core has a mechanism capable of individually controlling the movement thereof.

Although not shown in the drawing, the introduction portion of the pressurized gas has a function of introducing the pressurized gas into the resin of the front portion of the shock absorbing member and the taper portion. For example, it is a mold in which a pin that can be retracted forward is installed so that the pressurized gas can be efficiently introduced into those parts. As the pressurized gas, an inert gas such as nitrogen or helium, or air is used, but nitrogen gas is generally used. The pressure is usually in the range of 3 to 15 MPa. In the molding of the shock absorbing member, the pin is moved at the same time as introducing the pressurized gas after the molten resin is injected and filled, or after a predetermined time, using a hydraulic device or the like. The amount of protrusion into the mold and the pressure of the gas used depend on the melt viscosity of the molten resin and the like, and are appropriately determined depending on the gas introduction state. The shape of the pin is not particularly limited. The injection molding machine that can be used in the present invention may be any molding machine to which the above-mentioned mold is attached so that the mold function can be sufficiently exhibited, and a normal molding machine for gas injection injection molding may be used. The target resin includes thermoplastic resins such as polyethylene, polypropylene, ABS, polycarbonate and polyamide, or elastomers such as ethylene / α-olefin copolymer elastomers, talc, mica, calcium carbonate and glass fibers to these thermoplastic resins. It is possible to adopt a material to which an inorganic filler such as carbon fiber is added, and polypropylene resin is mainly used in many cases.

In the present invention, the hollow portion 10 is also provided in the taper portion.
According to the procedure, the method of manufacturing the shock absorbing member having
This will be described below. (1) As shown in FIG. 5, the molds 2 and 3 are closed so that the moving core 4 projects to a predetermined position. The molten resin 5 injected into the mold cavity is appropriately plasticized and melted, and the resin is filled in the mold cavity, as in ordinary injection molding. The amount to be filled is appropriately determined depending on the mold cavity volume that is substantially determined by the fixed mold 2 and the moving core 4 and the final shape of the shock absorbing member 1. (2) As shown in FIG. 6, the introduction of the pressurized gas is started when the molten resin 5 injected and filled in the mold cavity is in a molten state. The introduction may be started in parallel with a part of the molten resin, or after the molten resin is injection-filled into the mold cavity, that is, immediately after the injection filling or after a certain period of time. This pressurized gas is first introduced into the molten resin of the taper portion 7 of the shock absorbing member.

(3) Next, as shown in FIGS. 7 and 8, a pressurized gas is introduced into the molten resin in the front surface portion 8 of the shock absorbing member, and the moving core 4 is retracted while the front surface of the shock absorbing member is retracted. The introduction of the pressurized gas into the molten resin in the portion 8 is continued so that a predetermined rectangular hollow portion 9 can be formed. Further, the introduction of the pressurized gas into the taper portion 7 is intended to maintain the pressure after the desired hollow portion 10 is formed, and the hollow portion may be maintained. The amount and pressure of the pressurized gas introduced into each are appropriately adjusted so as not to break the wall between the hollow portions.
Since the molten resin 5 in contact with the moving core 4 whose temperature is adjustable has started cooling, this cooled part forms a kind of wall, and when the moving core is retracted and pressurized gas is introduced, the wall The hollow portion grows along with the movement of the molten resin 5. (4) As shown in FIG. 9, the retreat of the moving core 4 is completed, and the desired rectangular hollow portion 9 is formed. After sufficiently cooling and solidifying this, the mold is opened and the molded shock absorbing member 1 is taken out. At that time, pressurizing gas is released from the mold,
The molded shock absorbing member may be easily taken out.

Of the present invention, the method of manufacturing the shock absorbing member having no hollow portion in the taper portion is as follows.
It suffices to follow the procedure without introducing pressurized gas into the taper section. According to the gas injection injection molding of the present invention, since molding can be performed under a low resin pressure, a mold capable of withstanding high pressure unlike ordinary injection molding is not required, and the mold can be downsized, and at the same time cost can be reduced. it can. Also, the injection molding machine to which it is attached can be used even if it is small. Furthermore, the gas injection injection molding enables high productivity, which is a characteristic of injection molding, and has a large degree of freedom in shape.

[0017]

According to the present invention, by adopting a specific hollow structure, it is possible to obtain an automobile shock absorbing member having a high shock absorbing effect. In addition, by gas injection injection molding that features a moving core and pressurized gas introduction, it is possible to integrally mold an automobile shock-cushioning member with high productivity, a large degree of freedom in shape, and a compact molding machine. It will be possible.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional shape of a shock-absorbing member for an automobile of the present invention (a cross-section A at a central portion, and a cross-section C in some cases).

FIG. 2 is a schematic plan view of an automobile shock-cushioning member of the present invention.

FIG. 3 is a schematic cross-sectional shape of a shock-absorbing member for an automobile of the present invention (cross-section B of a mounting portion).

FIG. 4 is a schematic front view of an automobile shock-cushioning member of the present invention.

FIG. 5 is a conceptual diagram of a manufacturing method of the present invention (filling a molten resin with a mold).

FIG. 6 is a conceptual diagram of the manufacturing method of the present invention (filling the taper with gas).

FIG. 7 is a conceptual diagram of the manufacturing method of the present invention (starting gas filling of the front surface portion).

FIG. 8 is a conceptual diagram of a manufacturing method of the present invention (filling the front surface with gas and retracting the moving core).

FIG. 9 is a conceptual diagram of a manufacturing method of the present invention (completion of formation of a rectangular hollow portion).

FIG. 10: Shock-damping member for automobile by blow molding (a)
Outline view (b) Central cross-section

FIG. 11 is a schematic view of a conventional automobile shock-cushioning member formed by injection molding.

[Explanation of symbols]

1 ... Shock absorbing member for automobile 10 ... Hollow part of taper part 2 ... Fixed mold 11 ... Wall between rectangular hollow parts 3 ... Moving mold 12 ... Of taper part Inclination angle 4 ... Moving core 13 ... Car mounting part 5 ... Molten resin 14 ... Mounting hole 6 ... Hot runner 15 ... Rib 7 ... Taper part 16 ... Solid Part 8 ... Front part 17 ... Hollow part 9 ... Rectangular hollow part

Claims (4)

[Claims] 1. In a shock-absorbing member for an automobile made of a thermoplastic resin, which comprises a long curved portion having a hollow portion and mounting portions provided on both ends in the longitudinal direction to the automobile body, the curved portion has a cross section perpendicular to the longitudinal direction. Has a trapezoidal shape that forms a taper that narrows from the side where it is attached to the vehicle body toward the front of the vehicle, and has two or more hollow portions that are approximately rectangular in the center of the trapezoidal cross section and communicate with each other in the longitudinal direction, and the taper that is adjacent to them. A shock-absorbing member made of a thermoplastic resin for automobiles, characterized in that it has at least one hollow portion which is smaller than the hollow portion and communicates with the hollow portion in the longitudinal direction. 2. A shock-absorbing member made of a thermoplastic resin for automobiles according to claim 1, wherein said trapezoidal cross-section has three hollow portions which are substantially rectangular and which communicate with each other in the longitudinal direction. 3. A method of manufacturing a shock-absorbing member for a vehicle made of a thermoplastic resin, comprising: a long curved portion having a hollow portion; and mounting portions provided on both ends in a longitudinal direction to a vehicle body, wherein a mold is closed. In this state, at least two rectangular moving cores installed in the mold are projected, and while the pressurized gas is introduced between the tip of the moving core and the mold, the moving core is retracted, and is perpendicular to the longitudinal direction. Of a shock-absorbing member made of a thermoplastic resin for automobiles by gas injection injection molding, wherein at least two hollow portions having a substantially rectangular cross section and communicating with each other in the longitudinal direction and partition walls of the hollow portions are formed. 4. The method for manufacturing a shock-absorbing member for a thermoplastic resin automobile according to claim 1, wherein at least two rectangular moving cores are installed in the mold with the mold closed. And pressurizing gas until the desired hollow portion is formed in the taper portion and holding the pressure, while moving the pressing gas between the tip of the moving core and the mold, the moving core is retracted, The cross section perpendicular to the longitudinal direction is almost rectangular,
A method for manufacturing a shock-absorbing member made of a thermoplastic resin for automobiles by gas injection injection molding, wherein at least two hollow portions communicating with each other in a longitudinal direction are formed.