JPH0826779B2 - Sound insulation cover member manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method of manufacturing a cover member manufactured by a double injection molding method.

(Prior Art) In recent years, as a cover member for a timing belt cover, a cylinder head cover or the like of an internal combustion engine, a synthetic resin cover member has been used in place of an integrally molded aluminum product or a metal cover. No. 63160 proposes a cover member in which the main part of the cover member is molded of rigid hard synthetic resin and the sealing side surface of the flange is formed of flexible soft synthetic resin.

(Problems to be solved) However, in order to ensure the rigidity of the entire cover member, when the cover member is made of a hard rigid resin, the cover wall surface, which is a wide flat surface, vibrates and transmits sound, especially in the timing gear cover. This causes a problem that gear noise cannot be effectively blocked. Also, with this type of conventional cover member, a separately manufactured seal rubber is attached to the mating surface and then the cover member is attached. There was a problem.

Therefore, it is an object of the present invention to provide a member which is basically made of a hard synthetic resin and has excellent sound insulation and sealing properties.

(Means for Solving the Problems) The present invention focuses on the sound insulation performance of soft plastics, and uses the double injection type method to form the entire cover member with rigid hard plastic, while providing a high sound insulation effect. A soft plastic part is formed on the cover wall, and has a substantially flat cover wall surface 10 parallel to the cover mounting surface, and a rim wall surface 20 that rises at a right angle from the peripheral edge of the wall surface and has a mounting seal surface 21 at its tip. In the cover member 1 having a U-shaped cross-section, as shown in FIG. 1 and FIG. 2 which is a cross-sectional view taken along the line II-II of FIG.
At least abutment of the mounting first sealing surface 21 and the thermoplastic first soft plastic body 30 for injection-molding a thermoplastic hard plastic molding main body having a part of the central portion of 10 as an opening in the first step Second thermoplastic forming surface
The soft plastic body 40 is injection-molded in the second step, and a double injection molding method of a sound-insulating cover member formed by integrating the two is used.

In the above means, the thermoplastic hard plastic molding-based injection molding in the first step is carried out using a raw material whose main component is polypropylene containing an inorganic substance, while the thermoplastic soft plastic bodies 30, 40 in the second step are Injection molding is performed using a raw material containing an olefin-based elastomer as a main component. Further, in the above means, in the first step, an opening is formed in a portion where mechanical vibration is largely generated when the cover member is molded from hard plastic, and in the second step, the cover is closed with a soft plastic lid. Although the sound insulation is performed, the cover member is formed without forming the opening in the first step,
In the second step, the same result can be obtained by injecting the soft plastic into the inner surface of the wall surface of the cover, which is easily affected by mechanical noise, and performing double molding. Therefore, according to the present invention, as shown in FIG. 3, in the first step, the thermoplastic hard plastic main body 10 'constituting the entire cover member is injection-molded using a raw material containing polypropylene containing an inorganic substance as a main component. ,
Then, in a second step, the first soft plastic molding layer 30 covering one surface of the main body wall surface, for example, the inner surface, and the second soft plastic layer 40 forming at least the contact surface of the mounting seal surface are mixed with an olefin elastomer. A solution is a double injection molding method of a sound insulation cover member obtained by injection molding using a raw material as a main component and integrating both.

(Operation) According to the method of the present invention, the hard member and the soft member can be integrally molded by the double injection molding method by using the thermoplastic resin, so that the mounting member is covered with the second soft plastic. The member is mounted in a vibration-relieving state while closely contacting the mounting surface, and since at least the main part of the inner surface of the cover wall surface is made of soft plastic, it is made of rigid hard plastic that absorbs mechanical vibration. The vibration of the wall surface of the cover is suppressed and the machine noise is insulated.

Further, in this case, since the hard member (mainly made of hard plastic) and the soft member (first soft plastic molding layer and second soft plastic layer) are injection-molded by using the same type of raw material, the joining between them is performed. Good adhesion is obtained for the parts.

Hereinafter, the present invention will be described in detail based on specific examples shown in the accompanying drawings.

(Example) FIG. 4 is a plan view showing the inside of a cover member for a timing belt cover according to the present invention, FIG. 5 is a left side view, FIG. 6 is a right side view, and FIG. 7 is a lower end view. The cover member 1 has a substantially flat cover wall surface 10 which is parallel to the cover mounting surface, a rim wall surface 20 which rises at a right angle from the peripheral edge of the wall surface, and a mounting seal surface 21 which is located at the tip thereof, and has a substantially U-shaped cross section. Make up.

The cover member 1 is made of a hard plastic, for example, a first step of injection-molding a raw material containing polypropylene as a main component containing an appropriate amount of an inorganic material, and a soft plastic, for example, a raw material containing an olefin elastomer as a main component, in the same direction. It is molded by a double injection molding method including a second step of injection molding.

That is, in the first step, almost the entire cover member 1 is molded from hard plastic. Therefore, the cover wall surface 10 of the cover member 1 is formed of hard plastic, and has a circular opening 11 in the central portion from above and a rectangular opening 12 as a whole divided by a plurality of ribs 14 extending in the axial direction. A semicircular opening 13 as a whole divided by a rib 14 is formed, and the cover wall surface is formed.
A rim wall surface 20 reinforced at right angles from the peripheral edge of the rim 10 and reinforced by the ribs 14 and a mounting bolt socket 22 projecting to a peripheral portion thereof are formed of hard plastic.

As the hard plastic raw material, specifically, polypropylene alone, a mixture of polypropylene 100 parts by weight and talc 20 parts by weight, polypropylene 100
A mixture of 15 parts by weight of glass fiber and 10 parts by weight of talc can be used with respect to parts by weight.

Next, the second step is applied from the inside to the molding body made of the hard plastic. That is, the openings 11, 1
The first soft plastic body 30 is injection-molded so as to seal the 2 and 13, and the second soft plastic body is provided on at least the contact surface of the mounting seal surface 21 at the tip of the rim wall surface 20.
Injection mold 40. Specifically, the first soft plastic body
30 corresponds to the above openings 11, 12, 13 respectively 31, 32, 33
As shown in FIG. 8A, in contrast to the stepped portion 15 notched inward at the inner peripheral edge of the opening, the stepped portion notched outward at each outer peripheral edge of the first soft plastic body. The attached portion 34 is formed, and injection-molded and joined so that they are engaged with each other. On the other hand, the second soft plastic body 40 changes its shape depending on the shape of the edge of the rim wall surface 20 (see FIGS. 8A to 8H), but includes the seal body (gasket) 41 having the lip 42 on the downward contact surface. Injection molding is performed from the same direction as in one step, and the first soft plastic 30 forming the lid is joined at the same time.

Specific examples of olefin elastomers for soft plastics include PR (propylene rubber) or EPT.
It is possible to use a mixture of (ethylene propylene diene terpolymer), polypropylene and a low molecular weight additive in appropriate amounts.

(Test for confirming soundproofing and soundproofing effect) As shown in FIG. 9, a sound source is placed in a soundproofing wall, and the sound pressure level emitted from the sound source is measured by a level meter through a microphone located above the upper opening of the soundproofing wall. To do so.

Now, when the sound pressure level is 84 dB without closing the soundproof wall upper opening with the cover, if the soundproof cover according to the present invention and the conventional hard cover are used to block the soundproof opening upper opening, the following soundproofing / noiseproofing effect is obtained. Was obtained. The results are shown in Table 1.

Table 1 Types of cover Sound pressure level No cover 84dB Hard cover 69dB Invention cover 62dB (Effect of the invention) As is clear from the above description, according to the present invention, the sound insulation performance of the soft plastic is focused, While the injection-molding method is used to form the entire cover member with rigid hard plastic, the mounting sealing surface of the cover member is integrally molded with the mounting surface of the second soft plastic to reduce vibration while closely adhering. Since it is attached in a state and at least the main part of the inner surface of the cover wall surface is made of soft plastic, it can be mass-produced as compared with separate members, and since both are integrated, it is more mechanical than separate members. It absorbs vibrations and suppresses the vibrations of the wall surface of the cover, which is made of rigid hard plastic. It is possible to eliminate the disadvantages of the cover member made of black. Moreover, since it can be formed by a double injection molding method, it can be provided at low cost.

Further, in this case, since the raw materials of the same system are used for the hard plastic and the soft plastic, it is possible to secure a good adhesion state in the joint portion between the two.

[Brief description of drawings]

FIG. 1 is a plan view of a sound insulation cover member according to the present invention, FIGS. 2 and 3 are cross-sectional side views showing the basic structure of the sound insulation cover member according to the present invention, and FIG. 4 is a timing belt cover according to the present invention. 5 is a left side view, FIG. 6 is a right side view, FIG. 7 is a lower end view, and FIGS. 8A to 8H are lines AA in FIG. BB line, CC line,
D-D line, E-E line, F-F line, G-G line, H-H line cross-sectional view, FIG. 9 is an explanatory diagram of a sound insulation and soundproof effect confirmation test. 1 ... Cover member, 10 ... Cover wall surface, 20 ... Rim wall surface, 21 ... Mounting seal surface, 30 ... First soft plastic, 40 ... Second soft plastic

Claims (2)

[Claims] 1. A cover member having a U-shaped cross section, which has a substantially flat cover wall surface parallel to the cover mounting surface, and a rim wall surface which rises at a right angle from the peripheral edge of the wall surface and has a mounting sealing surface at its tip. In the first step, in the first step, a thermoplastic hard plastic molding main body that constitutes almost the entire cover member and has an opening in a part of the central portion of the cover wall surface is injected using a raw material whose main component is polypropylene containing an inorganic substance. In a second step, a thermoplastic first soft plastic body that closes the opening from the inside and a thermoplastic second soft plastic body that forms at least the abutment surface of the mounting seal surface are mixed with an olefin elastomer. A sound-insulating cover member obtained by injection-molding a raw material as a main component, and integrating the two, is molded by a double injection molding method. Sound insulation cover member manufacturing method. 2. A cover member having a U-shaped cross section, which has a substantially flat cover wall surface parallel to the cover mounting surface, and a rim wall surface which rises at a right angle from the peripheral edge of the wall surface and has a mounting sealing surface at its tip. In the first step, the thermoplastic hard plastic main component that constitutes the entire cover member is injection-molded using a raw material whose main component is polypropylene containing an inorganic substance, and in the second step, the heat is applied to cover one side of the cover wall surface. By injection-molding a plastic first soft plastic molding layer and a thermoplastic second soft plastic layer forming at least the contact surface of the mounting seal surface using a raw material containing an olefin elastomer as a main component, A method for producing a sound insulation cover member, characterized in that the sound insulation cover member formed by integrating the above is molded by a double injection molding method.