JPH0722947B2 - Manufacturing method of fiber reinforced plastic bolt - Google Patents

Description

The present invention relates to a method for manufacturing a fiber-reinforced plastic bolt.

(Prior Art) Hexagon bolts (hereinafter referred to as bolts) are widely used as fastening members. Conventionally, the material of these bolts has been mainly metal, but metallic bolts are heavy and easily rusted,
Moreover, it has a drawback that it lacks heat insulation and electrical insulation. On the other hand, a plastic bolt, which is light and has excellent corrosion resistance, heat insulation, electric insulation, and productivity, has been put into practical use. However, such a plastic bolt can only express the strength of the plastic material itself and cannot satisfy the strength normally used as a bolt.

In order to improve the strength of plastic bolts, bolts made of fiber reinforced plastic containing reinforcing fibers have been developed. "High-strength bolts made of glass fiber reinforced plastic" (Japan Screw Research Association, Vol. 11, No. 8, 1980)
According to the method, in order to manufacture a material having excellent strength using fiber reinforced plastic, firstly, the reinforcing fibers are oriented in the longitudinal direction of the bolt material shaft portion, and secondly, inside the bolt material and It is described that it is important to prevent the formation of cavities and shrinkage due to the solidification shrinkage of the plastic resin on the surface. However, in normal injection molding, the molten plastic resin is filled into the mold cavity at a high speed from a thin gate, so that the resin flow becomes an extremely expanded flow in the cavity. Therefore, the shaft portion of the obtained bolt material is not uniformly oriented in the axial direction of the reinforcing fiber. In injection molding, the resin in the gate portion usually tends to solidify faster than the resin in the cavity portion. Therefore, cavities and shrinkage due to solidification shrinkage occur inside the molding resin in the cavity. In particular, since the head portion of the bolt material is thick, a nest or shrinkage is likely to occur in this head portion.

In order to solve these drawbacks of the conventional injection molding method,
In Japanese Patent Application No. 60-264210 and Japanese Patent Application Laid-Open No. 60-264237, a part of the bolt shaft portion or just before the bolt shaft end is heated to a temperature higher than the melting point of the resin material, By injecting and filling the molten resin material toward the head and then cooling and solidifying while applying pressure with the subsequent molten resin material, the fiber orientation of the shank is excellent and there is no nest or shrinkage in the head. Is proposed.

However, when a bolt having a hexagonal columnar head is to be manufactured by the above method, the resin flow becomes an expanding flow between the shaft cavity and the head cavity, and the resin flow is generated on the hexagonal head cavity wall. By hitting, in the hexagonal head, as shown in FIG. 6, more fibers 42 are oriented at an angle close to the direction perpendicular to the longitudinal direction of the shaft. Therefore, the reinforcing effect of the reinforcing fiber is not sufficiently exerted on the head,
When a load is applied to such a bolt, the bolt is often broken at the head, which causes variations in strength.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned conventional drawbacks, improves the reinforcing effect of the reinforcing fiber at the bolt head, and is excellent in strength and strength stability. The present invention has been made for the purpose of providing a manufacturing method of.

(Structure of the invention) The gist of the present invention is to provide a shaft cavity and a head cavity from the gate side in this order in the head cavity of a mold provided with a bolt cavity composed of these cavities. Manufacture of a fiber-reinforced plastic bolt having a step of injecting a reinforcing fiber-containing molten resin material into the bolt cavity, in which a protrusion having a diameter gradually reduced from the center of the end face toward the top of the shaft cavity is provided. In the way.

Hereinafter, the present invention will be described with reference to the drawings.

An example of a bolt forming die for embodying the manufacturing method of the present invention is shown in FIG. 1, and another example is shown in FIG.

The molds 2 and 3 are composed of fixed-side mold plates 21 and 31 and movable-side mold plates 22 and 32, and spruces 25 and 35 and runners 26 and 36 are followed by bolt cavities 24 and 34. Bolt cavity 24,
34 is the shaft cavity 242, 342 and the hexagonal head cavity 241, 3
41 and consists of shaft cavities 242,3 from the sprue 25,35 side
42 and head cavities 241 and 341 are provided in this order. twenty three,
Reference numeral 33 denotes a protrusion, which has a tip portion whose diameter is gradually reduced toward the top, and the tip portion projects into the head cavities 241 and 341 from the center of the end surface toward the shaft cavities 242 and 342. It is provided.

In the case of the mold 3, the sprue 35 and the runner 36 are kept at a temperature equal to or higher than the melting point of the molding resin material by the heating means 37 provided in the vicinity thereof, and the bolt cavities 24, 34 are provided in the cooling means 38 provided in the vicinity thereof. As a result, the temperature is kept below the melting point of the molding resin material. As the heating means 37 and the cooling means 38, for example, heater heating, a combination of heater heating and cooling water circulation, or a means usually used for resin molding such as oil circulation is appropriately selected.

The molds 2 and 3 are used by being attached to an injection molding machine usually used for resin molding. The reinforcing fiber-containing resin material used for molding is melted and plasticized in the cylinder of the injection molding machine.

With the mold clamping mechanism of the injection molding machine, the molten resin material is sprued while the fixed mold plate 21 and the movable mold plate 22 are engaged in a liquid-tight manner.
From the ends 251, 351 of the 25, 35 are injected into the molds 25, 35 by the injection molding machine of the injection molding machine. Molten resin material is sprue 25,35
Through the runners 26, 36 from the ends of the shaft cavities 242, 342 into the bolt cavities 24, 34. After the injection, holding pressure and cooling are appropriately performed.

The cooled and solidified molded product is removed from the mold as follows.

In the case of the mold 2, first, the movable side mold plate 22 is retracted, so that the solidified molded product is released from the fixed side metal plate 21 together with the sprue portion and the runner portion. Subsequently, the forward movement of the protruding rod 29 of the injection molding machine advances the lock pin 28,
The molded product is released from the movable side mold plate 22.

In the case of the mold 3, first, the movable side mold plate 32 is retracted so that the solidified shaft portion is discharged from the fixed side mold plate 31. Subsequently, the protrusion 33 advances by the advancing operation of the protruding lot 39, and the molded product is ejected from the movable side mold plate 32.

When the mold release of the molded product is completed, the protruding rods 29 and 39 retreat,
The lock pin 27 and the protrusion 33 are retracted by a spring to prepare for the next molding.

The molded product taken out from the mold is provided as a bolt as follows.

In the case of the mold 2, the sprue portion and the runner portion are cut from the molded product that has been taken out, so that it can be directly provided as a bolt.

In the case of the mold 3, the end portion of the shaft portion of the taken-out molded product is threaded by a required length to serve as a bolt.

As the screw working method, a method which is usually used for forming a screw thread, such as rolling or cutting, is appropriately selected.

As described above, the screw thread is formed in the shaft cavity in advance, and when the screw thread is formed at the time of injection molding and is also used as a bolt, the screw is formed on the cylindrical shaft portion obtained by injection molding. The thread may be formed by post-processing and used as a bolt.

In the head of the bolt manufactured according to the present invention, the reinforcing fiber-containing molten resin material flows along the protrusions 23 and 33 as shown in FIG. 5, so that the reinforcing fiber is contained in a considerable amount in the longitudinal direction of the shaft. Orient at an angle close to. On the other hand, as shown in FIG. 6, in the case of manufacturing without the conventional projections, the amount of those oriented at an angle close to a direction perpendicular to the longitudinal direction of the axis of the reinforcing fiber is overwhelmingly large. The head portion of the bolt manufactured by this conventional manufacturing method is weak because the reinforcing effect of the reinforcing fiber is low against the stress in the direction perpendicular to the longitudinal direction of the shaft, and the head portion is easily damaged. On the other hand, the bolt manufactured by the manufacturing method of the present invention is strong because the reinforcing effect oriented in the longitudinal direction of the shaft of the reinforcing fiber effectively acts on the stress in the direction perpendicular to the longitudinal direction of the shaft. Parts are not easily damaged.

The protrusions 23, 33 provided so as to protrude into the head cavities 241, 341 may be provided in the form of a pin-shaped object as shown in FIGS. 1 and 2, and the head cavities 241, 341 may be provided.
It may be provided integrally with a member constituting 341.

It is preferable that the projections 23 and 33 satisfy the following conditions in order to exert the effect of the present invention.

As shown in FIGS. 3 (a) and (b) and FIGS. 4 (a) to (c), the protrusion height h from the end surface of the head cavities 241 and 341 is the axial length H of the head cavities 241 and 341. (1) is satisfied, the angle θ of the outer peripheral surface with respect to the axis is satisfied (2), and the diameter d of the circumscribed circle of the projections 23, 33 on the end faces of the head cavities 241, 341 is the head. Cavity 2
41,341 hexagonal inscribed circle diameter D1 and shank cavity 24
Satisfy the formula (3) for the outer diameter D2 of 2,342.

0.25H ≦ h ≦ 0.85H (1) 20 ° ≦ θ ≦ 65 ° (2) 0.5D2 ≦ d <D1 (3) The molding resin material used in the present invention is a thermoplastic resin having reinforcing fibers. It is a synthetic resin composition. As the reinforcing fiber, for example,
There are known fibers used for reinforcing thermoplastic resins such as glass fiber, carbon fiber, aramid fiber, potassium titanate fiber, alumina fiber, boron fiber, silicon carbide fiber and various metal fibers, and these are single or It is used in the form of a mixture of two or more kinds. As the thermoplastic synthetic resin, a thermoplastic synthetic resin that can obtain a reinforcing effect by mixing reinforcing fibers can be used. For example, a polyamide resin, a thermoplastic polyester resin, a polyacetal resin, a polycarbonate resin, a polypropylene resin, a polyethylene resin, a vinyl chloride resin, a polyphenylene sulfide resin or the like is used alone or in the form of a mixture of two or more kinds. Various molding auxiliaries or resin modifiers may be appropriately added to the thermoplastic synthetic resin.

(Examples) Hereinafter, the present invention will be described with reference to specific examples.

Examples 1 to 7 As the thermoplastic synthetic resin, 100 parts by weight of an aromatic polyamide resin (trade name; Lenny 6002, manufactured by Mitsubishi Gas Chemical Co., Inc.) was used, and 100 parts by weight of glass fiber was used as a reinforcing fiber. Both were mixed to produce a pellet-shaped resin material. First
Using the mold 2 shown in the figure, M16 size bolts having the head shape shown in FIG. 3 were manufactured. At this time, H = 12m
m, D1 = 24 mm, D2 = 16 mm, and θ, d, h were changed as shown in Table 1.

A steel nut having a height of 20.5 mm was attached to the manufactured bolt, and a tensile test was performed with a tensile device. The load when the bolt broke was measured, and this was taken as the tensile strength. The maximum value, the minimum value, and the average value were shown in Table 1 as measured for 5 samples. The fracture site is also shown.

Comparative Example 1 The protrusion 23 protruding into the head cavity 241 was removed,
The same as Examples 1 to 7 except that the end face of the hexagonal head is made flat. The results of the same test are also shown in Table 1.

Examples 8 to 12 Polyphenylene sulfide resin (trade name; Ryton A-100, manufactured by Philips) as a thermoplastic synthetic resin 100
100 parts by weight of glass fiber was used as the reinforcing fiber with respect to parts by weight. Both were mixed to produce a pellet-shaped resin material. Using the mold 3 shown in FIG. 2, a bolt material for M16 size having the head shape shown in FIG. 4 was manufactured, and thread processing was performed by rolling to obtain an M16 size bolt.
At this time, H = 12 mm, D1 = 24 mm, D2 = 14.2 mm, θ1, θ
2, d, h were changed as shown in Table 2. The manufactured bolt was tested in the same manner as in Examples 1-7. The results are shown in Table 2.

Comparative Example 2 The protrusion 33 protruding into the head cavity 341 was removed,
The same as Examples 8 to 12 except that the end face of the hexagonal head was made flat. The results of the same test are also shown in Table 2.

(Effect of the invention) According to the manufacturing method of the present invention, since the reinforcing fibers are oriented not only in the axial portion of the bolt but also in the longitudinal direction of the head, the strength of the head is superior to the conventional one, and the plastic is It is possible to obtain a fiber reinforced plastic bolt having the characteristics such as corrosion resistance, electric insulation and heat resistance.

Further, if the shape of the protrusion protruding into the head cavity satisfies the above expressions (1) to (3), it is possible to obtain a fiber-reinforced plastic bolt having particularly excellent head strength.

[Brief description of drawings]

1 and 2 are sectional views of a mold used in the present invention, FIG. 3 (a) is a plan view of an example of a bolt manufactured according to the present invention, and FIG. 3 (b) is a sectional view. X- in Fig. 3 (a)
FIG. 4 (a) is a cross-sectional view taken along line X, FIG. 4 (a) is a plan view of another example of the bolt manufactured according to the present invention, and FIG. 4 (b) is a cross section taken along line XX of FIG. 4 (a). Fig. 4 (c) is a sectional view taken along line YY of Fig. 4 (a), Fig. 5 is a sectional view of an example of a bolt manufactured according to the present invention, and Fig. 6 is a conventional manufacturing method. It is a sectional view of an example of a bolt manufactured by. Explanation of symbols 2,3 …… Mold, 21,31 …… Fixed side template, 22,32 …… Movable side template, 23,33 …… Projection, 24,34 …… Bolt cavity,
25,35 …… Sprue, 26,36 …… Runner, 27 …… Lock pin, 29,39 …… Projecting rod, 37 …… Heating means, 38 …… Cooling means, 241,341 …… Head cavity, 242,342 …… Shaft cavity.

Claims (2)

[Claims] 1. A shaft cavity and a head cavity are arranged in this order from the gate side, and in the head cavity of a mold provided with a bolt cavity composed of both cavities, the shaft is arranged from the center of the end face of the head cavity. A method for manufacturing a fiber-reinforced plastic bolt, comprising a step of injecting a reinforcing fiber-containing molten resin material into the bolt cavity, in which a projection having a diameter gradually reduced toward the top of the cavity is projected. 2. The protrusion height h of the protrusion from the end face of the head cavity satisfies the formula (1) with respect to the axial length H of the head cavity, and the angle θ of the outer peripheral surface with respect to the axis is: The formula (2) is satisfied, and the diameter d of the circumscribed circle at the end face of the head cavity satisfies the formula (3) with respect to the diameter D1 of the inscribed circle of the head cavity and the outer diameter D2 of the shaft cavity. A method for manufacturing a fiber-reinforced plastic bolt according to claim 1. 0.25H ≤ h ≤ 0.85H (1) 20 ° ≤ θ ≤ 65 ° ...... (2) 0.5D2 ≤ d <D1 ...... (3)