JPH09201841A - Injection molded product and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reinforce effectively a part main body by a reinforcing rib without making a sink on the surface of the part main body and to simplify the structure of a mold. SOLUTION: A reinforcing rib 4 is provided to the wall surface of a part main body such as a bamper main body 1 in order to reinforce the part main body and the base end part of the reinforcing rib 4 becoming the connection part to the part main body is formed so as to be reduced in wall thickness to reduce the amt. of the molten resin charged in the base end part of the reinforcing rib 4 at a time of the molding of an injection molded part such as a car bamper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molded part made of a synthetic resin such as a bumper for an automobile, which is molded by injecting a molten resin into a cavity of a molding die, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 5-24491, a pair of upper and lower horizontal ribs extending in the horizontal direction are provided on the back surface of an injection molded part composed of a bumper for an automobile, and A vertical rib for connecting and reinforcing the both horizontal ribs is provided in the corner portion, the vertical rib is installed in a direction orthogonal to the tangential direction of the corner portion, and the vertical rib is provided in the bumper body. Is provided separately from the back surface of the.

[0003]

The above injection-molded parts are
Since the vertical ribs that connect and reinforce the horizontal ribs that are vertically opposed to each other are provided apart from the back surface of the bumper body to provide a space between the bumper body and the vertical ribs, As in the case where the base ends of the vertical ribs are connected to the bumper body, the bumper is caused by heat shrinkage that occurs when the molten resin filled in the connection portion between the vertical ribs and the bumper body is cured during the molding of the injection-molded part. Although it has an advantage that sink marks are not generated on the surface of the main body, there is a problem that the reinforcing action of the horizontal ribs by the vertical ribs tends to be insufficient.

Further, as will be described later, it is necessary to provide the mold with a slide mold having a protrusion for forming a space between the bumper body and the vertical ribs. At the time of removal, the projection must be separated from the space of the injection-molded part by sliding the slide mold to the side to a large extent,
There is a problem that the slide driving mechanism for driving the slide die becomes large and the structure of the molding die becomes complicated.

In view of such circumstances, the present invention can effectively reinforce the component body with the reinforcing ribs without causing sink marks on the surface of the component body.
(EN) An injection-molded part capable of simplifying the structure of a molding die and a method for manufacturing the same.

[0006]

The invention according to claim 1 is
A reinforcing rib is provided on the wall surface of the component body, and the base end portion of the reinforcing rib serving as a connecting portion to the component body is formed thin.

According to the above construction, the base end portion of the reinforcing rib is connected to the wall surface of the component body, so that the component body is effectively reinforced by the reinforcing rib, and at the time of molding an injection molded component, The amount of molten resin filled in the base end portions of the reinforcing ribs, which are the connecting portions to the bumper body, is reduced, and the occurrence of sink marks due to heat shrinkage when the molten resin is cured is effectively prevented. It will be.

According to a second aspect of the present invention, a plurality of reinforcing ribs extending in directions intersecting with each other are provided on the wall surface of the component body, and the base end portion of the reinforcing rib extending in one direction on the surface of the component body. The hollow portion is formed to prevent the occurrence of sink marks, and the base end portion of the reinforcing rib extending in the other direction of the component body is formed thin.

According to the above construction, the base end portions of the respective reinforcing ribs are connected to the wall surface of the component main body, so that the component main body is effectively reinforced by the respective reinforcing ribs, and at the time of molding an injection molded component. The hollow portion formed at the base end portion of the reinforcing rib extending in one direction of the component body effectively prevents sink marks from being generated on the surface of the component body. Also,
Since the base end portion of the reinforcing rib extending in the other direction of the component body is formed thin, the amount of molten resin filled in the base end portion of the reinforcing rib at the time of molding an injection-molded component is reduced, and this melting The occurrence of sink marks due to heat shrinkage when the resin is cured is effectively prevented.

According to a third aspect of the present invention, the structure according to the second aspect is applied to an injection molded part composed of a bumper for an automobile.

According to the above structure, the base end portions of the reinforcing ribs are connected to the wall surface of the bumper body forming the automobile bumper, so that the bumper body is effectively reinforced by the reinforcing ribs. When forming a bumper for an automobile, the hollow portion formed at the base end portion of the reinforcing rib extending in one direction of the bumper body effectively prevents the sink mark from being generated on the surface of the bumper body, and forms the bumper for the automobile. At times, this is because the amount of molten resin filled in the connection between the base end of the reinforcing rib extending in the other direction of the bumper body and the bumper body becomes small, and the thermal contraction occurs when the molten resin cures. The occurrence of sink marks will be effectively prevented.

According to a fourth aspect of the invention, in the injection-molded component comprising the automobile bumper according to the third aspect, a first reinforcing rib extending in the longitudinal direction is formed on the wall surface of the component body comprising the bumper body, and the first reinforcing rib. The first reinforcing rib is provided with a second reinforcing rib extending in a direction intersecting with the first reinforcing rib, and a hollow portion for preventing a sink from being generated on the surface of the bumper body is formed at the base end portion of the first reinforcing rib. It is characterized in that the base end portion of the second reinforcing rib is formed thin.

According to the above construction, a sink mark is generated on the surface of the bumper body due to the hollow portion formed so as to extend in the longitudinal direction of the bumper body along the base end portion of the first reinforcing rib when the automobile bumper is molded. Is effectively prevented, and the amount of molten resin filled in the base end portions of the second reinforcing ribs extending in the direction intersecting with the first reinforcing ribs is reduced, and when the molten resin is cured, The occurrence of sink marks due to heat shrinkage is effectively prevented.

According to a fifth aspect of the present invention, a plurality of reinforcing ribs are arranged on the wall surface of the component body so as to intersect with each other, and the component body is provided at the base end portion of the first reinforcing rib extending in one direction of the component body. A method for manufacturing an injection-molded component, in which a hollow portion is formed on the surface of the component to prevent the occurrence of sink marks and the base end portion of the second reinforcing rib extending in the other direction of the component body is formed thin Then, in a state where the molding die forming the cavity corresponding to this injection-molded part is closed, after filling the cavity with the molten resin, gas is injected into the installation portion of the first reinforcing rib to 1) The hollow portion is formed at the base end portion of the reinforcing rib.

According to the above construction, by filling the cavity of the molding die with the molten resin, an injection-molded component in which a plurality of reinforcing ribs are arranged in an intersecting state on the wall surface of the component body is molded. become. Further, after the molten resin is injected, gas is injected into the installation portion of the first reinforcing rib extending in one direction of the component body, so that the hollow portion formed at the base end thereof causes sink marks on the surface of the component body. Is effectively prevented, the amount of molten resin filled in the connecting portion between the base end of the reinforcing rib extending in one direction of the component body and the bumper body at the time of molding the injection-molded component is reduced, The occurrence of sink marks due to heat shrinkage when the molten resin is cured is prevented.

[0016]

1 and 2 show an automobile bumper as an embodiment of an injection-molded part according to the present invention. This automobile bumper includes a bumper body 1 having a U-shaped cross section, a pair of upper and lower first reinforcing ribs 2 protruding from an inner wall surface of the bumper body 1 and extending in a longitudinal direction thereof, that is, a horizontal direction. A pair of upper and lower auxiliary ribs 3 extending in the longitudinal direction of the bumper body 1 along the reinforcing ribs 2, and a plurality of second reinforcing ribs 4 extending in the direction intersecting the first reinforcing ribs 2 and the auxiliary ribs 3, that is, in the vertical direction. have.

The bumper body 2 has a front wall portion 5 made of a synthetic resin material having a plate thickness of about 5 mm, an upper wall portion 6 projecting rearward from the upper end portion thereof, and the upper wall portion 6. And a bottom wall portion 7 installed substantially in parallel with each other, and the first reinforcing ribs 2, the auxiliary ribs 3 and the second reinforcing ribs 4 project from the inner wall surface of the front wall portion 5.

The first reinforcing rib 2 has an average plate thickness of about 7 mm and is formed to be thicker than the bumper body 1, and can be easily demolded at the time of releasing from the mold described later. As described above, it is formed in a tapered shape. Further, the protrusion amount of the first reinforcing rib 2 is set to be substantially equal to the width dimension of the upper wall portion 6 and the bottom wall portion 7 of the bumper body 1. Further, at the base end portion of the first reinforcing rib 2, that is, the connecting portion of the first reinforcing rib 2 to the front wall portion 5 of the bumper body 1, a hollow portion 8 and a bulging portion 9 extending in the longitudinal direction of the bumper body 1 are provided. And are formed.

The auxiliary ribs 3 are formed between the first reinforcing ribs 2 facing each other and below the first reinforcing ribs 2 and the bumper body 1.
And the bottom wall portion 7 of each. And
The auxiliary rib 3 is formed to have a thickness of about 1/3 of the thickness of the bumper body 1, for example, a thin thickness of about 1.5 mm, and the protrusion amount thereof is set to a value shorter than that of the first reinforcing rib 2. For example, the protrusion amount of the auxiliary rib 3 is determined by the first reinforcing rib 2
It is set to about 1/3 of the protrusion amount of.

The second reinforcing rib 4 has a plate thickness of 1.5 mm.
The base portion 10 set to a certain degree and the middle portion where the plate thickness changes from 1.5 mm to 6 mm by forming a tapered wall surface on the center side (inward side in the left-right direction) of the bumper body 1 11 and a tip 12 formed to have a plate thickness of about 6 mm. Then, the second reinforcing rib 4
Is installed in the vertical direction between the upper wall portion 6 and the bottom wall portion 7 of the bumper main body 1, so that the first reinforcing rib 2
And the auxiliary rib 3 are connected by the second reinforcing rib 4.

The structure of a molding die for forming an injection-molded part composed of the bumper body 1 will be described with reference to FIGS. 3 and 4. The molding die 13 includes a movable die 14 having a core portion 20 having a molding surface corresponding to the back surface of the bumper body 1, a fixed die 15 having a molding surface corresponding to the surface of the bumper body 1, A movable die 14 supported by the movable die 14; and the movable die 14 and the fixed die 1.
5 and the slide die 16 constitute a cavity 17 for bumper molding.

That is, a molding portion for molding the bumper body 1 is formed between the upper surface of the movable die 14 and the lower surface of the fixed die 15, and is provided on the core portion 20 of the movable die 14. The formed first slit 18 and the second slit 19 form a forming portion for forming the first reinforcing rib 2 and the auxiliary rib 3. further,
The core portion of the movable mold 14 is formed with an upwardly widening concave portion having a tapered inclined surface 21 whose upper end portion is inclined toward the central portion side of the bumper body 1 and a side wall surface 22 extending in the vertical direction. The slide die 16 is retractably housed in the recess.

On the outer side surface of the slide die 16, that is, the side wall surface located on the outer side in the left-right direction of the bumper body 1,
The base end portion 10 of the second reinforcing rib 4 is formed thin, and a protrusion 29 for forming the tapered wall surface is formed on the intermediate portion 11 of the second reinforcing rib 4 (see FIG. 6). . A molding portion for molding the second reinforcing rib 4 is formed between the side wall surface of the slide die 16 and the side wall surface 22 of the recess formed in the movable die 14.

The movable die 14 is formed with a support hole for the eject pin 23 which is inclined in the same direction as the inclined wall 21, and the eject pin 23 is slidably supported along the support hole. This eject pin 2
An eject plate 24 for raising and lowering 3 is provided. Then, by driving the eject plate 24 up and down by a driving means (not shown), the slide die 16 is pushed through the eject pin 23, and the slide die 16 is vertically driven along the inclined wall 21 of the recess. It has become so.

Further, in the movable die 14, a gas supply passage 25 for injecting gas at a predetermined timing into the installation portion of the first reinforcing rib 2 formed of the first slit 18 to form the hollow portion 8. Are formed. In addition, the fixed mold 1
A sprue 26, a runner 27, and a gate 28 for filling the cavity gate 17 with molten resin discharged from an injection molding machine (not shown) are formed on the member 5.

A method of manufacturing an injection-molded part comprising an automobile bumper using the molding die 13 will be described below. In order to manufacture the injection-molded part, as shown in FIGS. 3 and 4, the cavity gate 17 is filled with the molten resin discharged from the injection molding machine while the molding die 13 is closed. Next, before the molten resin is cured, gas is supplied from a gas supply source (not shown) to the installation portion of the first reinforcing rib 2 via the gas supply passage 25,
As shown in FIG. 2, a hollow portion 8 extending in the longitudinal direction of the bumper body 1 is formed along the base end portion of the first reinforcing rib 2.
That is, at the base end portion of the first reinforcing rib 2, that is, at the connection portion with respect to the bumper body 1, the filled resin material tends to stay in the molten state. By flowing in the longitudinal direction of the bumper body 1, a hollow portion 8 extending in the longitudinal direction of the bumper body 1 is formed at the base end portion of the first reinforcing rib 2.

Then, the cavity 17 of the molding die 13 is formed.
At the time when the automobile bumper is formed by hardening the molten resin filled in the inside, as shown in FIG. 5, the movable mold 14 is lowered to open the mold 13, and the driving outside the drawing is performed. Ejector plate 24 by means
Drive the slide die 16 to displace the ejector pin 23 upward to slide the slide die 16 into the inclined wall 2.
Push up diagonally along 1.

As the slide die 16 rises, the automobile bumper is released from the movable die 14, and
As the slide die 16 moves toward the central portion of the bumper body 1, as shown in FIG. 6, the thin portion and the intermediate portion 11 formed at the base end portion 10 of the second reinforcing rib 4 are tapered. Since the projection 29 of the slide die 16 is separated from the wall surface, the automobile bumper can be easily removed from the slide die 16.

As described above, the second reinforcing rib 4 is provided on the wall surface of the bumper body 1 which constitutes the injection-molded part including the automobile bumper, and the base end portion of the second reinforcing rib 4 which is a connecting portion to the bumper body 1. Since 10 is formed thin, by reducing the amount of the molten resin filled in the base end portion 10 of the second reinforcing rib 4, the sink mark caused by the heat shrinkage of the molten resin when the molten resin is cured is generated. While being effectively prevented from being formed on the surface of No. 1, the second reinforcing rib 4 can effectively improve the rigidity of the automobile bumper.

That is, as in the conventional example shown in FIG. 7, when the second reinforcing ribs 4'are separated from the bumper body 1'constituting the injection-molded part and a space is provided therebetween, this Since the bumper body 1'cannot be directly reinforced by the second reinforcing ribs 4 ', the bumper body 1'
However, in the case where the thin portion provided on the base end portion 10 of the second reinforcing rib 4 is connected to the back surface of the bumper body 1 as described above, , The bumper body 1 by the second reinforcing ribs 4
Since it can be directly reinforced, the bumper rigidity for automobiles can be effectively increased.

Moreover, in the above-mentioned conventional example, the second reinforcing rib 4 is used.
Between the bumper body 1'and the second reinforcing rib 4'by providing the projection 29 'having the same protrusion amount T'as the second reinforcing rib 4'on the slide mold 16' constituting the molding part of ' Since it is necessary to configure the above-mentioned space portion in the
When the 9'is separated from the second reinforcing rib 4 ', the slide mold 16' must be largely moved laterally. For this reason, it is unavoidable that the eject pin for driving the slide die 16 'and the slide drive mechanism having the drive means for the slide die 16 are large and the structure of the molding die is complicated.

On the other hand, in the above embodiment of the present invention,
Since the thin portion provided on the base end portion 10 of the second reinforcing rib 4 is configured to be connected to the back surface of the bumper body 1, the protrusion 29 of the slide mold 16 that constitutes the molding portion of the second reinforcing rib 4 is formed. The protrusion amount T can be made smaller than that of the conventional example. Therefore, by setting the drive amount of the slide drive unit that moves the slide mold 19 to the side to separate the protrusion 29 from the second reinforcing rib 4 from the above-mentioned conventional example, the slide drive mechanism is downsized and molded. The structure of the mold can be simplified.

Further, in the above embodiment, the bumper body 1
Since the first reinforcing rib 2 extending in the longitudinal direction is provided on the inner wall surface of the, and the second reinforcing rib 4 is arranged in the direction intersecting with the first reinforcing rib 2, the bumper body 1
The bending rigidity of the automobile bumper can be increased by the first reinforcing ribs 2 extending in the longitudinal direction, and the first reinforcing ribs 2 can be reinforced by the second reinforcing ribs 4. Therefore, the bumper body 1 can be effectively reinforced by the first and second reinforcing ribs 2 and 4, and the load bearing capacity of the injection-molded component including the automobile bumper can be effectively increased.

Moreover, the cavity 1 in the molding die 13
After the molten resin is filled into the inside 7 and before the molten resin is hardened, gas is injected into the installation portion of the first reinforcing rib 2 to prevent the sinker from being generated on the surface of the bumper body 1. Since the hollow portion 8 for forming the first reinforcement rib 2 is formed at the base end portion of the first reinforcement rib 2, even when the bumper body 1 is configured to be effectively reinforced by setting the plate thickness of the first reinforcement rib 2 large, It is possible to reliably prevent the occurrence of sink marks due to the hardening of the molten resin filled in the molded portion of the first reinforcing rib 2.

Further, in the above embodiment, since the thin auxiliary ribs 3 extending along the first reinforcing ribs 2 are provided on the inner wall surface of the bumper body, the first reinforcing ribs 2 and the auxiliary ribs 3 are formed in the longitudinal direction of the bumper body 1. By providing a predetermined number of reinforcing ribs including the ribs 3, the bending rigidity of the automobile bumper can be effectively increased, and at the same time, sink marks can be prevented from being formed on the surface of the bumper body 1. That is, since the thin auxiliary ribs 3 are arranged between the thick first reinforcing ribs 2 which are vertically opposed to each other, the installation interval S between both the first reinforcing ribs 2 is sufficiently secured. At the same time, the space between the installation portions of the first reinforcing ribs 2 is reinforced by the auxiliary ribs 3 to sufficiently secure the bending rigidity of the automobile bumper and effectively increase the load bearing capacity of the automobile bumper. it can.

For example, as shown in FIGS. 1 and 2, the pair of first reinforcing ribs 2 and auxiliary ribs 3 on the inner wall surface of the bumper 1 and the direction in which the first reinforcing ribs 2 and auxiliary ribs 3 intersect. A bumper for an automobile according to an embodiment of the present invention, which is provided with the second reinforcing rib 4 that extends, and an automobile for a comparative example, which has the same configuration as the present invention except that the auxiliary rib 3 is omitted. When a collision test was performed using a bumper, it was confirmed that the load capacity of the automobile bumper according to the above-mentioned example was about 10% larger than that of the comparative example.

Since the molten resin filled in the molding portion of the thin auxiliary rib 3 is hardened early, the amount of heat shrinkage generated at the time of hardening can be suppressed to a small level, and the thick first reinforcing ribs can be suppressed. When the gas is injected into the installation portion of No. 2, the gas is prevented from moving to the installation portion side of the adjacent first reinforcing rib 2, and the gas is supplied over substantially the entire length of the bumper body 1. After the injection, the hollow portion 8 can be formed in a proper state at the base end portion of the first reinforcing rib 2.
Therefore, the hollow portion 8 effectively prevents the sink mark due to the heat shrinkage during the curing of the molten resin from being formed on the surface of the bumper body 1, and the automobile bumper having an excellent appearance is formed. be able to.

Further, in the above embodiment, the bumper body 1
Since the amount of protrusion of the auxiliary rib 3 provided on the inner wall surface of the movable rib 14 is set to be smaller than the amount of protrusion of the first reinforcing rib 2, the core portion 20 of the movable mold 14 is largely divided by the slit 19 serving as the molding portion of the auxiliary rib 3. It is possible to form the auxiliary ribs 3 that supplementarily reinforce the bumper body 1 at a predetermined position without causing the following adverse effects due to the above-mentioned effects.

That is, when a large number of reinforcing ribs having a large protrusion amount are provided on the inner wall surface of the bumper body to increase the bending rigidity of the automobile bumper, the slits for forming the reinforcing ribs are used. Since the core part of the movable mold is largely divided, the core part is largely deformed according to the filling pressure of the molten resin filled in the cavity during the molding of the automobile bumper, and the mold is easily damaged. At the same time, there is an adverse effect that it is difficult to secure a space for disposing the cooling water flow pipe in the core portion.

On the other hand, as shown in the above embodiment,
When the protrusion amount of the auxiliary ribs 3 arranged between the first reinforcing ribs 2 is set to be small, the depth of the slit serving as the forming portion of the auxiliary ribs 3 can be set to be small. It is possible to effectively prevent the core from being largely deformed and the molding die being damaged in accordance with the filling pressure of the molten resin filled in the cavity during the molding of the use bumper.
Moreover, since the cooling water flow pipe can be arranged at a position facing the tip of the slit 19, the installation space can be easily secured in this flow pipe.

In the above embodiment, in order to effectively prevent the sink mark from being formed on the surface of the bumper body 1 corresponding to the connecting portion of the auxiliary rib 3, the thickness of the base end portion 10 is set to the bumper body. The example in which the thickness of the base end portion is set to 1/2 or less of the bumper body 1 can suppress the occurrence of sink marks to some extent. The plate thickness of the base end portion 10 can be arbitrarily set within a range of 1/2 or less.

Further, in the above embodiment, an example in which the present invention is applied to an injection-molded part composed of an automobile bumper has been described, but the present invention is not limited to the above automobile bumper, and a plurality of automobile installation panels and the like. It can be applied to various injection-molded parts having the reinforcing ribs. Further, the installation positions and the number of the first reinforcing ribs 2 and the second reinforcing ribs 4 are not limited to those in the above-described embodiment, and various modifications are possible. For example, the lower first reinforcing ribs 2 and bumpers may be provided. Auxiliary rib 3 between the bottom wall 7 of the main body 1
May be provided.

[0043]

As described above, according to the present invention, a reinforcing rib is provided on a wall surface of a component body which constitutes an injection-molded component such as a bumper for an automobile, and a reinforcing rib serving as a connecting portion to the component body is provided. Since the base end is formed thin, the amount of molten resin filled in the base end of the reinforcing rib is reduced, so that the shrinkage caused by the heat shrinkage of the molten resin causes the shrinkage of the surface of the component body. There is an advantage that the rigidity of the injection-molded part can be effectively improved by the reinforcing ribs and the structure of the molding die can be simplified while effectively preventing the formation of the molding die.

[Brief description of drawings]

FIG. 1 is a plan sectional view showing an embodiment of an injection-molded part according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a front cross-sectional view showing the structure of a molding die.

FIG. 4 is a sectional view taken along line BB of FIG. 3;

FIG. 5 is a front sectional view showing a state in which a molding die is opened.

FIG. 6 is a plan sectional view showing a main part of an injection molded part.

FIG. 7 is a view corresponding to FIG. 6 showing a conventional example of an injection molded part.

[Explanation of symbols]

 1 Bumper Main Body (Component Main Body) 2 First Reinforcing Rib 3 Auxiliary Rib 4 Second Reinforcing Rib 8 Hollow Part 10 Base End 13 Mold Die 17 Cavity

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takahiro Tanaka 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Motor Corporation

Claims (5)

[Claims] 1. An injection-molded component, characterized in that a reinforcing rib is provided on a wall surface of the component body, and a base end portion of the reinforcing rib serving as a connecting portion to the component body is formed thin. 2. A plurality of reinforcing ribs extending in directions intersecting with each other are provided on a wall surface of the component body, and sink marks are generated on the surface of the component body at the base end portions of the reinforcing ribs extending in one direction of the component body. While forming a hollow part to prevent
An injection-molded component, characterized in that a base end portion of a reinforcing rib extending in the other direction of the component body is formed thin. 3. The injection-molded part according to claim 1, wherein the injection-molded part is an automobile bumper. 4. A wall surface of a component body composed of a bumper body is provided with a first reinforcing rib extending in a longitudinal direction thereof and a second reinforcing rib extending in a direction intersecting with the first reinforcing rib,
A hollow portion is formed at the base end portion of the first reinforcing rib for preventing sink marks on the surface of the bumper body, and the base end portion of the second reinforcing rib is formed thin. The injection-molded part according to claim 3. 5. A sink mark is generated on the surface of the component body at the base end portion of the first reinforcing rib extending in one direction of the component body, wherein a plurality of reinforcing ribs are arranged on the wall surface of the component body so as to intersect with each other. A method for manufacturing an injection-molded component, in which a hollow portion is formed to prevent the formation of a hollow portion, and the base end portion of the second reinforcing rib extending in the other direction of the component body is formed to be thin. In a state where a mold forming a cavity corresponding to a component is closed, a molten resin is filled in the cavity, and then a gas is injected into an installation portion of the first reinforcing rib to form a base end of the first reinforcing rib. A method for manufacturing an injection-molded part, characterized in that the hollow part is formed in the part.