JPH07251440A - Blow molding method - Google Patents

Abstract

PURPOSE:To produce a molding having a main hollow part and a sub-hollow part communicating with each other and high in the bonding strength at the boundary part of both hollow parts while reducing a molding process and a deburring process. CONSTITUTION:A tubular parison having a cross-sectional shape of which the size can be received in the cavity of a blow mold consisting of upper and lower molds 5, 6 at least one of which has a slide core 51 and forming a cavity having a product shape and consisting of a main cavity 81 and a sub-cavity 82 is formed. This parison is set to the cavity of the lower mold 6 so that the side surface thereof does not protrude from the cavity of the lower mold 6 and, after the lower mold 6 and the upper mold 5 are clamped, the parison is subjected to primary blow molding under low pressure to be expanded as a whole and the slide core 51 is allowed to protrude into the cavity from the upper mold 5. Thereafter, secondary blow molding is performed under high pressure to mold the parison into the shape of the cavity to obtain a blow molded product.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a blow molding method,
More specifically, it relates to a blow molding method for molding a molded product having a crushed portion from a tubular parison. The method of the present invention is
For example, it can be preferably used when molding a duct with a resonator used for an intake system and an exhaust system duct of an engine of an automobile or the like.

[0002]

2. Description of the Related Art Conventionally, an intake system of an automobile engine,
In an exhaust system, a duct with a resonator is used for the purpose of reducing sound of a certain specific frequency. This is composed of a tubular duct body that forms a gas passage, and a resonator that is connected to the duct body and forms a resonance chamber that communicates with the gas passage of the duct body.

As a method of manufacturing such a duct with a resonator, for example, as disclosed in Japanese Utility Model Laid-Open No. 59-68130, the duct body and the resonator are separately molded and fastened via an elastic member or the like. A method of joining the two by a member is general. Further, for example, in Japanese Examined Patent Publication No. 4-30900 and Japanese Examined Patent Publication No. 4-25131, one member of the duct body and the resonator is prepared in advance, and blow molding is performed to mold the other member. A method is disclosed in which both members are integrated by blow-molding the other member while being housed in a mold.

Further, Japanese Patent Application Laid-Open No. 64-4318 discloses a method of simultaneously blow molding a duct body and a resonator by using a single blow molding die.

[0005]

However, the conventional method disclosed in Japanese Utility Model Application Laid-Open No. 59-68130, in which the duct main body and the resonator are separately molded and then the two are joined by using different members, is a resonator. It takes a lot of steps and man-hours to assemble the attached duct, and it cannot be said that the reliability of the airtightness and the joint strength at the joint is sufficient.

In the conventional methods disclosed in Japanese Patent Publication No. 4-30900 and Japanese Patent Publication No. 4-25131, one member is previously molded and both members are blow-molded when the other member is blow-molded. Since these are integrated, two or more molding processes are required, and the cost increases as the number of processes increases. On the other hand, in the conventional method disclosed in JP-A-64-4318, the molding process itself is one process, but since it is a total burr molding, a parting line on the outer peripheral surface is required to obtain a practical product. Since a process for removing burrs that occurs along the line is required, and another work process is generated by this amount, the productivity is not sufficiently excellent and there is a risk of economical disadvantage.

The present invention has been made in view of the above circumstances, and it is possible to mold a blow-molded product having a main hollow portion and a sub-hollow portion that are in communication with each other, and further simplify the molding process and reduce the deburring process. And to provide a blow molding method capable of molding a blow molded product having high reliability such as airtightness and bonding strength at the boundary between the main hollow portion and the sub hollow portion. This is a technical issue.

[0008]

The blow molding method of the present invention for solving the above-mentioned problems has a slide core in at least one of an upper mold and a lower mold, and the slide core has the above-mentioned upper core depending on a desired product shape. In a blow molding method for molding a tubular parison using a blow molding die that is provided so as to be retractable with respect to a cavity formed in a mold and a lower mold,
A setting step in which the tubular parison having a shape that can be accommodated in the cavity is set without protruding from the cavity side wall of the lower mold, and at the same time, a part of the tubular parison is made to exist in the cavity space where the slide core projects, After clamping the upper mold and the lower mold, a primary blow step of supplying air of a predetermined pressure into the tubular parison, and a core for advancing the slide core into the cavity from at least one of the upper mold and the lower mold. A discharging step, and a secondary blowing step of supplying a higher pressure air than the air supplied in the primary blowing step to the inside of the tubular parison to form a molded product following the outer shape of the cavity. It is a feature.

In a preferred aspect of the method of the present invention, the blow mold has a parison guide portion that can be retracted into and out of the cavity, and the setting step includes the parison guide portion with the parison guide portion protruding into the cavity. Can be mentioned as a step of contacting with the parison guide portion and setting. As a further preferred embodiment of the method of the present invention,
The tubular parison of the present invention is a parison in which the material is switched at least once between one material having a high limit value of blow-up rate and another material having a lower limit value of blow-up rate than the one material. The blow-up rate of the maximum blow-up portion of the portion made of one material before and after the blow molding is larger than the blow-up rate of the maximum blow-up portion of the portion made of another material. I can mention that.

[0010]

In the blow molding method of the present invention, first, a tubular parison having a size that can be accommodated in the cavity of the blow mold is formed. The parison is set in the cavity of the lower mold so that the side surface of the parison does not protrude from the cavity of the lower mold. At this time, the parison is set in the cavity of the lower mold so that at least a part of the parison exists in the cavity space where the slide core provided so as to be retractable from the mold protrudes. This allows
It is possible to prevent burrs from being generated on the outer peripheral side surface of the blow-molded product except for both ends.

After the lower die and the upper die are clamped, the parison is entirely swollen by primary blow molding at a relatively low pressure. This causes the parison to gradually expand in the cavity. While the parison is expanding, the slide core is projected into the cavity from at least one of the upper mold and the lower mold. As a result, the parison at the position where the slide core projects is crushed by the slide core and the cavity surface facing the tip of the slide core. After that, if the secondary blow molding is performed at a high pressure, the parison that is not bitten by the slide core is blown up in the cavity. As a result, the part blown up by directly blowing air is the main hollow part, the part bitten by the slide core is the rib, and the part blown up as a partial partition with the main hollow part is the sub-part. It can be a blow-molded product having a hollow portion. This blow-molded product is demolded after cooling.

As described above, according to the blow molding method of the present invention, the rib serving as the boundary between the main hollow portion and the sub hollow portion can be formed by the crushed portion by the slide core.
Its strength is high, and the bond strength at the ribs is highly reliable. Further, the main hollow portion and the sub hollow portion of the blow-molded product can be integrally formed at the same time. Further, the blow molding die is provided with a parison guide portion that can be retracted into and out of the cavity, and in the step of setting the parison, the parison is brought into contact with the parison guide portion while the parison guide portion is projected into the cavity. When the parison is set, the parison can be quickly and surely set in the cavity.

Further, in order to stably mold a blow-molded product having a large blow-up rate only in a certain part and the parison blow-up even in a narrow part, as in the molding method of the present invention, After the mold is clamped and the pinch-off part is closed, it is an effective means to perform a two-stage blow of a low pressure primary blow and a high pressure secondary blow. That is, since the partition wall that partitions the interior of the parison begins to form in the state where the parison is gradually expanding due to the primary blow, the parison is blown up smoothly even in the narrow cavity portion, and also at a large blow up rate. Because it can endure.

In the method of the present invention, the parison of the blow-molded product is composed of a plurality of materials having different blow-up limit values, and a part of the parison composed of one material having a high blow-up limit value is This is a particularly suitable molding method when molding a blow-molded product that requires a higher blow-up rate than the part (1).

[0015]

EXAMPLES Specific examples of the present invention will be described below. (First Embodiment) In this embodiment, a duct with a resonator for an automobile is manufactured. A sectional view of the duct manufactured according to this embodiment is shown in FIG. 1, and a sectional view taken along the line AA of FIG. 1 is shown in FIG. To
FIG. 3 shows a sectional view taken along the line BB of FIG.

The duct with the resonator according to this embodiment is
A box-shaped resonator 2 having a tubular duct body 1 having a gas passage 1a therein and a resonance chamber 2a formed integrally with the duct body 1 and communicating with the gas passage 1a of the duct body 1.
And a pair of plate-shaped ribs 3 and 3 connecting the duct body 1 and the resonator 2. The duct body 1 is formed by blow molding of a method in which burrs do not occur on the outer peripheral side surfaces except for both ends, and the first soft end portion 11 connected to a carburetor, an air cleaner, etc., and the resonator 2
Is integrally formed, and a second soft end portion 13 connected to an intake manifold of the engine, an air flow meter, and the like. The first,
The second soft ends 11 and 13 are both made of a soft material such as a thermoplastic elastomer, specifically, TPO. Further, the hard central portion 12 is made of a material having a higher swale ratio and blow-up ratio than the soft material, specifically P
It is made of P (polypropylene) natural material.

The resonator 2 is made of the same material as the hard center portion 12 of the duct body 1, and is integrated with the duct body 1 via a neck portion 21 which is also made of the same material as the hard center portion 12. Has been done. A communication hole 21 a that connects the gas passage 1 a of the duct body 1 and the resonance chamber 2 a of the resonator 2 is formed in the neck portion 21. The sectional shape of the resonator 2 is substantially trapezoidal as shown in FIG.

The rib 3 is made of the same material as that of the hard central portion 12 of the duct body 1 and is integrally formed with the duct body 1 and the resonator 2. As will be described later, the rib 3 is formed by being pressed and bitten by the mold surface of a blow molding die (slide core), and has a thickness of about 5 to 30 mm. A method for manufacturing the duct with a resonator having the above configuration will be described with reference to FIGS. 4 to 8.

In this embodiment, a blow molding machine having a blow molding die including an upper die 5 and a lower die 6 and a pouring head 7 is used. The blow mold composed of the upper mold 5 and the lower mold 6 is formed with a cavity corresponding to the product shape, and the duct main body 1
Main cavity 81 and resonator 2 corresponding to the shape of
Sub cavities 82 corresponding to the shape of are respectively formed. The upper die 5 is provided with a slide core 51 at a position corresponding to the rib 3 so as to be retractable in the cavity.
The tip of the slide core 51 has the same shape as the plan shape of the rib 3 and has a notch 51a for forming the neck 21 at a position corresponding to the neck 21 (see FIG. 8). Further, the lower mold 6 is also provided with a convex portion 61 facing the slide core 51 at a position corresponding to the rib 3 and having the same tip shape as the planar shape of the rib 3, and this convex portion 61 is also formed on the neck portion 21 similarly. A notch 61a for forming the neck 21 is provided at a corresponding position (see FIG. 8).

At the time of molding, first, the parison P1 made of a soft material having a small blow-up limit value corresponding to the first soft end portion 11 is poured out from the pouring head 7 of the blow molding machine, and then the hard central portion 12 and the resonator. 2 and neck 21
The parison P2 made of a hard material having a large blow-up limit value corresponding to the above was poured out, and the parison P3 made of a soft material having a small blow-up limit value corresponding to the second soft end 13 was poured out (see FIG. 4). . In addition, parison P
The sizes of the diameters of 1 to P3 are controlled so that the side surfaces of the parison P1 to P3 do not stick out of the cavity of the blow molding die. That is, the parison P1 and P3 have a sectional shape that can be accommodated in the main cavity 81 of the blow mold, and the parison P2 has the main cavity 8 of the blow mold.
1 and the size of the diameter thereof are controlled so that the cross-sectional shape can be stored in the sub-cavity 82. Also, parison P
Depending on the product shape, the diameter of 2 is the parison P as needed.
1 or larger than P3. In order to make the diameter of the parison P2 larger than that of the parisons P1 and P3, there is a means for selecting a material having a swell ratio larger than that of the parisons P1 and P3 as the material for the parison P2.

Generally, a parison having a large swell ratio is
It is a parison that has a large degree of diameter immediately after it is poured from the pouring nozzle. Therefore, parison P
If 2 is made of a material having a larger swell ratio than the parison P1 and P3, it is possible to naturally increase only the diameter of the parison P2 as compared with the parisons P1 and P3 by simply pouring while switching the materials constituting the parison. .

As shown in FIGS. 5 and 6, the parison P thus formed is mainly in the main cavity 81 of the lower mold 6, and the side faces of the parisons P1 to P3 protrude from the cavity of the lower mold 6 to the outside of the mold. I set it not to. At this time, the part of the parison P2 is arranged on the convex portion 61 of the lower mold 6 so that the parison P2 is located over both the main cavity 81 and the sub-cavity 82 of the lower mold 6. Both ends of the parison P1 to P3 are provided at the main cavity 81 of the lower mold 6.
It protrudes from the length direction.

Then, after the upper die 5 with the slide core 51 immersed in the die was clamped to the lower die 6, air blowing (primary blow) was started from the blow pin provided in the die. The air pressure at this time is low pressure (4.9 to 19.6 x 1).
0 ⁴ Pa), the parison P1 to P3 were gradually swollen as a whole. At this time, since the parison P2 corresponding to the hard central portion 12 is made of a material having a swale ratio and a blow-up rate higher than those of the parison P1 and P3 corresponding to the soft ends 11 and 13, from the pouring point of the parison, The parison P2 has a larger diameter than the parison P1 and P3 and is poured out. At the same time, the parison P2 partly bulges largely. As a result, the parison P1 and P3 have the main cavity 8
1 swells to a predetermined size, and the parison P2 also swells to a predetermined size in the main cavity 81 and the sub-cavity 82.

After the start of the primary blow molding at a low pressure (0.1 to 5.0 seconds after the air is blown), the slide core 51 is projected from the upper die 5 into the cavity,
The parison P2 was sandwiched between 1 and the convex portion 61 of the lower mold 6 (see FIG. 7). And the secondary blow at high pressure (34.3 × 1
0 ⁴ Pa) was performed to obtain a blow-molded product by molding into a predetermined cavity shape.

After cooling the above blow-molded product in a blow-molding die, it was released from the mold, and the bag portions at both ends were cut into a product shape. In the blow molding method of this embodiment, the parison P1 to P3 is blow molded in a state where the parison is set so that the side surfaces of the parison P1 to P3 do not protrude from the cavity of the blow molding die. No burr is generated on the outer peripheral side surface such as 2 and the deburring step after blow molding can be omitted.

Further, since the rib 3 for connecting the duct body 1 and the resonator 2 is formed by being pressed and bitten by the mold surfaces of the slide core 51 and the convex portion 61, its strength is high and the rib is The bond strength in 3 is highly reliable. In addition, the ribs 3 are formed by crushing.
Can be taken large. Further, since the ribs 3 are crushed, the rib 3 has no defective portion due to defective rotation of the resin. Furthermore, since the duct body 1, the resonator 2, the rib 3 and the neck portion 21 are all integrally formed by blow molding at the same time,
In addition to simplifying the molding process and reducing the number of parts, it is possible to prevent a defective joint between the duct body 1 and the resonator 2 and prevent foreign matters such as dust and screws from entering the resonator 2. Further, it is possible to prevent a deviation in tuning of the resonator 2 due to a defective joint.

Furthermore, in the duct with a resonator according to this embodiment, both ends of the duct body 1 are soft end portions 11, 13.
Since it is formed of, the work of connecting with the mating member becomes easy, and the airtightness at the connecting portion also becomes good. Further, since this duct with a resonator is formed by blow molding in which a burr does not occur, there is no V-shaped groove formed by a parting line on the inner peripheral surface of the duct body 1 and the like except for the crushed portion. . Therefore, it further contributes to the improvement of the airtightness of the connection portion.

In the above embodiment, the slide core 51 is provided only on the upper die 5, but the convex portion 61 of the lower die 6 may be a slide core like the upper die. (Second Embodiment) In the second embodiment, as shown in FIG. 9, a parison guide portion 9 is detachably provided on the lower mold 6, and the rest is the same as the first embodiment. The parison guide portion 9 has a plate-shaped guide plate portion 91 at the tip.

In blow molding, the parison guide portion 9 is inserted from the end of the main cavity 81 on the opposite side of the sub-cavity 82 so that the guide plate portion 91 is located substantially in the center of the main cavity 81. Place on top of 6. And
When setting the parison P1 to P3 in the cavity of the lower mold 6, the parison P2 is set while abutting against the guide plate portion 91 of the parison guide portion 9. As a result, the part of the parison P2 bends toward the side of the sub-cavity 82 while being guided by the guide plate portion 91, so that the part of the parison P2 surely and quickly covers the main cavity 81 and the sub-cavity 82. Can be set to. After the parisons P1 to P3 are set in the cavity of the lower mold 6, the parison guide portion 9 is removed, the mold is clamped, and blow molding is performed as in the first embodiment.

The guide plate portion 91 of the parison guide portion 9 may be inclined to facilitate insertion of the parison P2. (Third Embodiment) In the third embodiment, as shown in FIGS. 10 and 11, the parison guide portion 9 is provided in the lower die 6 so as to be capable of reciprocating in the horizontal direction. Second above
It is similar to the embodiment. That is, this parison guide 9
Reciprocates in the horizontal direction, so that the main cavity 8
It is possible to appear and disappear within 1.

At the time of blow molding, the parison guide portion 9 is inserted into the main cavity 81 from the end opposite to the sub cavity 82 of the main cavity 81 so that the guide plate portion 91 is located substantially in the center of the main cavity 81. Make it protrude. As a result, when the parisons P1 to P3 are set in the cavity of the lower die 6, the parison P2 is set as in the second embodiment.
It is possible to surely and quickly set the portion while contacting the guide plate portion 91 of the parison guide portion 9. The part of the parison P2 bends toward the sub-cavity 82 while being guided by the guide plate portion 91, so that the part of the parison P2 can be reliably set so as to straddle both the main cavity 81 and the sub-cavity 82. Then, when the parisons P1 to P3 are set in the cavity of the lower mold 6, the lower mold 6 and the upper mold 5 are clamped, and the parison guide portion 9 is immersed in the lower mold 6 immediately or thereafter. While low pressure blow molding. As a result, the second
Compared with the embodiment, the parison P2 portion can be more surely bulged in both the main cavity 81 and the sub cavity 82.

(Fourth Embodiment) In the third embodiment, as shown in FIG. 12, a plate-shaped parison guide portion 9 is provided on the lower die 6 so as to be capable of reciprocating in a substantially vertical direction. Others are the same as those in the third embodiment, and the same actions and effects as those in the third embodiment are obtained. In addition, in order to insert the parison P2 more easily, the sliding direction of the parison guide portion 9 may be slanted.

In the above embodiment, an example of molding a blow-molded article having a main hollow portion and a sub hollow portion, both of which are integrally connected by a rib formed by a crushed portion, has been described. However, according to the method of the present invention, by disposing the slide core at the end portion in the cavity,
On the side surface of the hollow molded product having a single hollow portion, integrally,
Moreover, it is also possible to mold a blow molded product having a strong and large crushed portion.

[0034]

As described above in detail, in the blow molding method of the present invention, it is possible to prevent burrs from being generated on the outer peripheral side surfaces of the blow molded product except for both ends, and the deburring step after blow molding can be performed. It becomes possible to omit. Further, according to the blow molding method of the present invention, an integral blow is formed by the main hollow portion, the sub hollow portion, and the rib that is bitten by the slide core and connects the main hollow portion and the sub hollow portion. A molded product can be molded. Therefore, it is possible to form a blow-molded product having good bonding properties at the ribs connecting the main hollow portion and the sub hollow portion while reducing the number of molding steps and the number of parts.

Further, the blow molding die is provided with a parison guide portion which can be retracted into and out of the cavity, so that the parison is set in contact with the parison guide portion while the parison guide portion is projected into the cavity. In this case, the parison can be set in the cavity quickly and reliably.

[Brief description of drawings]

FIG. 1 is a sectional view of a duct with a resonator manufactured according to a first embodiment.

FIG. 2 relates to the above-mentioned resonator-equipped duct,
It is an A line arrow sectional view.

[Fig. 3] Fig. 3 relates to the duct with a resonator, and
It is a B line arrow sectional view.

FIG. 4 is a sectional view of a parison according to the first embodiment.

FIG. 5 is a perspective view showing how the parison is set in the cavity of the lower mold according to the first embodiment.

FIG. 6 is a cross-sectional view showing a state in which a parison is set in the cavity of the lower mold according to the first embodiment.

FIG. 7 is a cross-sectional view showing a state after high-pressure blow molding according to the first embodiment.

FIG. 8 is a partial cross-sectional view of a lower die convex portion and an upper die slide core according to the first embodiment.

FIG. 9 is a cross-sectional view showing a state in which a parison is set in the cavity of the lower mold according to the second embodiment.

FIG. 10 is a cross-sectional view showing a state in which a parison is set in the cavity of the lower mold according to the third embodiment.

FIG. 11 is a cross-sectional view showing a state after high-pressure blow molding according to the third embodiment.

FIG. 12 is a cross-sectional view showing a state in which a parison is set in the cavity of the lower mold according to the fourth embodiment.

[Explanation of symbols]

1 is a duct main body, 1a is a gas passage, 2 is a resonator, 2
a is a resonance chamber, 21a is a communication hole, 3 is a rib, 5 is an upper die, 5
1 is a slide core, 6 is a lower mold, 61 is a convex part, 81 is a main cavity, 82 is a sub cavity, 9 is a parison guide part,
P1 to P3 are parison.

Claims (3)

[Claims] 1. A slide core is provided in at least one of an upper mold and a lower mold, and the slide core is provided so as to be retractable from a cavity formed in the upper mold and the lower mold according to a desired product shape. In a blow molding method for forming a tubular parison by using a blow mold, the tubular parison having a shape that can be accommodated in the cavity is set without protruding from the cavity side wall of the lower mold, and at the same time, the tubular parison is formed. A step of causing a part of the core to be present in a cavity space where the slide core projects, a primary blow step of supplying a predetermined pressure of air into the tubular parison after the upper and lower molds are clamped, A core-extracting step of advancing the slide core into the cavity from at least one of a mold and a lower mold; A blow molding method comprising: a secondary blowing step of supplying air having a higher pressure than the air supplied at that time to the inside of the tubular parison to form a molded product following the outer shape of the cavity. 2. The blow molding die has a parison guide part that can be retracted into and out of the cavity, and in the setting step, the parison is applied to the parison guide part with the parison guide part protruding into the cavity. The blow molding method according to claim 1, which is a step of contacting and setting. 3. The tubular parison has a material switched between at least one material having a high blow-up rate limit value and another material having a blow-up rate limit value lower than that of the one material. The blow-up rate of the maximum blow-up portion of the part made of one material before and after blow molding is higher than the blow-up rate of the maximum blow-up portion of the part made of another material. The blow molding method according to claim 1.