JP2000301573A - Structure of injection molding die for bent resin tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hold an increase in the manufacturing cost of a bent resin tube. SOLUTION: This injection molding die comprises a molding die 15 with an outer peripheral forming part 11 for forming the outer periphery of a bent resin tube, an upper and a lower split core 20, 25 which are housed in the molding die 15 and split in order to have the cores 20, 25 drawn out of the bent resin tube, a gate 32 for injecting a molten resin into a cavity 30 formed by the split cores 20, 25 and the molding die 15 and a pin 35 which protrudes from the molding die 15 side so as to support the split cores 20, 25 which are deflected by the injection pressure of the molten resin and supports a spot near the butting parts 29 of the split cores 20, 25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection mold structure of a bent resin pipe used as, for example, an intake pipe of an engine.

[0002]

2. Description of the Related Art FIG. 6 is a plan view of a conventional engine room, in which an air cleaner 101 and an engine 102 are arranged in an engine room 100, and an outlet 1 of the air cleaner 101 is provided.
01a is connected to one end 105a of the bent resin pipe 105, and the other end 105b of the bent resin pipe 105 is connected to the inlet 103a of the throttle valve 103 of the engine 102.
The bent resin pipe 105 is an airflow tube that guides the air purified by the air cleaner 101 to the throttle valve 103. Hereinafter, a method of manufacturing the bent resin tube 105 will be described.

FIGS. 7A and 7B are views for explaining a conventional method for forming a bent resin pipe, and FIG. 7B is an enlarged view of a portion b of FIG. 3A, a pair of split cores 111 and 112 are placed in a molding die 110 in a state of being abutted to form a cavity 114, and molten resin is injected into the cavity 114 from a gate 115 as shown by arrows a and a. . The molten resin injected from the gate 115 flows into the cavity 114 a on the gate 115 side, and then the cavity 114 a
Wrap around. At this time, a pair of split cores 111,
The injection pressure F1 acts on a portion of the butting portion 113 of the 112 close to the gate 115 as shown by a white arrow.

[0004] In FIG. 1B, the injection pressure F1 is changed to the butt 1
13 to act locally, the split cores 111 and 112
May be opened and a gap S may occur. As a result, the molten resin may enter the gap S, causing burrs on the inner wall of the bent resin pipe 105 (shown in FIG. 6), or changing the thickness of the peripheral wall of the bent resin pipe 105.

Returning to FIG. 6, since the bent resin pipe 105 is mounted on the upstream side of the throttle valve 103, the bent resin pipe 1
If burrs remain in the area 05, the air intake resistance increases, and there is a possibility that air cannot be smoothly sucked into the engine. For this reason, it is necessary to remove burrs generated in the bent resin tube 105 at the time of injection molding in a subsequent step, which causes an increase in cost.

An apparatus for preventing the core from bending due to the injection pressure of the molten resin when the molded article is injection-molded is disclosed in Japanese Patent Application Laid-Open No. 8-207,055. Method and Apparatus for Forming Centrifugal Impeller ". In this technology, the core is supported by pushing the core support pins from the mold so that the core does not bend due to the injection pressure. Immediately after this, the core support pins were withdrawn, and the traces withdrawn were filled with a molten resin so that no trace of the core support pins remained on the molded product.

[0007]

However, the operation of "pulling out the core support pin immediately after the injection pressure becomes uniform" requires an extremely advanced technique. The conditions change depending on the temperature of the molten resin, the pressure, the temperature of the molding die, and changes in the ambient temperature, that is, the conditions change depending on the day and night, summer and winter,
It is considered that the conditions under which the injection pressure becomes uniform vary depending on external factors.

If the core support pin is pulled out early, the core is displaced and the quality of the molded product is degraded, and if the core support pin is pulled out lately, pin marks remain. Therefore, in order to realize the technique disclosed in the above publication, a precise molding machine and advanced operations are required, which leads to an increase in the manufacturing cost of the bent resin pipe.

Further, according to the technique disclosed in the above publication, core support pins are individually prepared for a plurality of cores.
Core support pins are required for the number of cores. For this reason, the number of core support pins increases, which causes an increase in manufacturing cost.

Accordingly, an object of the present invention is to provide a technique capable of preventing burrs from being generated on the inner periphery of a bent resin pipe and suppressing an increase in manufacturing cost of the bent resin pipe.

[0011]

In order to solve the above-mentioned problems, a first aspect of the present invention is a mold having an outer periphery forming portion for forming an outer periphery of a curved resin tube, and a mold having a curved resin tube. A pair of split cores split for pulling out of the tube, a gate for injecting the molten resin into the cavity formed by the split core and the molding die, and a split core for supporting the split core bent by the injection pressure of the molten resin. It consists of a support pin that protrudes from the molding die side and supports the vicinity of the butted portion of the divided cores, and the pair of divided cores forms a recess in one of the butting surfaces of each other,
On the other hand, a convex portion that can be fitted into the concave portion is formed.

By injecting the molten resin into the cavity while supporting the split core with the support pins, the butting portion of the split core does not open due to the injection pressure. Therefore, burrs do not occur on the inner periphery of the bent resin pipe, and the step of removing the burrs can be omitted. In addition, by fitting the butting surfaces of the pair of split cores with the concave and convex portions, displacement of the pair of split cores can be prevented only by supporting the vicinity of the butted portion with the support pins. As a result, the pair of split cores can be efficiently supported by one support pin, so that the number of support pins can be reduced.

According to a second aspect of the present invention, a small hole is formed in the resin tube by bending with a support pin. Since small holes can be formed at the same time when the bent resin tube is injection-molded, the step of forming small holes can be omitted. In addition, since small holes are simultaneously opened when the bent resin tube is injection-molded, there is no need to remove the support pins during the injection molding. For this reason, a precise molding machine and an advanced operation required for suitably removing the support pin are not required.

[0014] According to a third aspect of the present invention, the small holes are bent and arranged outside the bending of the resin tube. By arranging the small hole on the outside of the bent resin pipe, for example, a sensor and a breather pipe can be attached to the outside of the bent resin pipe via the small hole. When a fluid is caused to flow through the bent resin pipe, the fluid flows intensively outside the bending of the bent resin pipe. For this reason, the contact ratio of the fluid to the sensor can be increased, and the breather pipe can be arranged at a location where the fluid flows in a concentrated manner.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings should be viewed in the direction of reference numerals. FIG. 1 is a sectional view of an injection mold structure of a bent resin pipe according to the present invention. Injection mold structure 1 for bent resin pipe
0 is an outer periphery forming portion 11 for forming the outer periphery of the bent resin pipe.
And the upper and lower divisional cores 20 and 25 which are housed in the molding die 15 and which are divided to be extracted from the molding die 15, and formed by these divisional cores 20 and 25 and the molding die 15. A gate 32 for injecting the molten resin into the cavity 30 and a lower and upper divided cores 20 and 25 that bend by the injection pressure of the molten resin protrude from the molding die 15 side to support them.
And a support pin 35 for supporting the vicinity of the butted portion of the upper and lower split cores 20, 25.

The molding die 15 includes a fixed die 16 having one forming portion 11a of the outer peripheral forming portion 11 and a movable die 17 having the other forming portion 11b of the outer peripheral forming portion 11. In this molding die 15, the outer peripheral forming portion 11 is formed by one and the other molding portions 11a and 11b by clamping the fixed die 16 and the movable die 17, and the movable die 17 is connected to the mold opening lines 18 and 18.
It opens from the mold. The outer periphery forming portion 11 includes a curved portion 12 and upper and lower diameter portions 13 and 14 formed at upper and lower ends of the curved portion 12.

The upper split core 20 has an upper step portion 21 formed at the base end in accordance with the upper diameter portion 13 of the outer peripheral portion 11, and the upper step portion 21 covers the upper diameter portion 13 of the outer peripheral portion 11. It is a curved cylindrical body in which a flange 22 is formed and a concave portion 23 a is formed in the abutting surface 23. The lower split core 25 forms a lower step 26 at the base end in accordance with the lower diameter section 14, and forms a lower flange 27 at the lower step 26 to close the lower diameter section 14 of the outer peripheral forming section 11, It is a curved cylindrical body having a projection 28a formed on the surface 28.
The protrusion 28a is formed so as to be inserted into the recess 23a.

The cavity 30 is a space formed by the outer peripheral forming portion 11 and the upper and lower split cores 20 and 25, and is a space for forming a bent resin tube. The gate 32 is a flow path formed in the fixed mold 16 at the bending center side of the bent resin pipe, and extends from the concave portion 33 for pressing a nozzle (not shown) of the molten resin supply means to the cavity 30. It is.

The support pin 35 is slidably attached to the hole 17a of the movable die 17, and is advanced by an actuator (not shown) such as an air cylinder as shown by an arrow so that the pin tip 36 abuts on the upper divided core 20. The pin tip 36 is pulled out of the cavity 30 by retreating as shown by an arrow in contact with the vicinity of 23 (that is, the vicinity of the butting portion 29). The pin tip 36 of the support pin 35 is set to have a diameter d.

The butting portion 2 is formed by the pin tip 36 of the support pin 35.
By supporting the vicinity of 9, it is possible to support a portion that is easily bent and easily displaced. Therefore, the upper and lower split cores 2
0, 25 can be efficiently supported by one support pin 35.

The operation of the bent resin tube injection mold structure 10 described above will be described. FIGS. 2 (a) and 2 (b) are views for explaining a first operation of the injection mold structure according to the present invention. In (a), after the mold 15 is clamped, the upper and lower split cores 20 and 25 are placed in the mold 15 and the butting surfaces 23 and
The concave portion 23a of 28 and the convex portion 28a are fitted together. next,
The pin tip 36 of the support pin 35 is pressed near the butting surface 23 of the upper split core 20. Next, molten resin is supplied from the gate 32 to the cavity 30. The molten resin injected from the gate 32 first flows into the cavity 30 on the side of the gate 32 as shown by an arrow, and then flows around the entire cavity 30.

When the molten resin flows into the cavity 30 on the side of the gate 32 as shown by an arrow, an injection pressure F is applied to the butting portion 29 of the upper and lower split cores 20 and 25 as shown by a white arrow. However, since the concave portions 23a and the convex portions 28a of the butting surfaces 23 and 28 are fitted together and the pin tips 36 of the support pins 35 are pressed near the butting surfaces 23 of the upper split core 20, the butting surfaces 23 and 28 are formed. There is no opening, and the upper and lower split cores 20 and 25 do not shift.

In FIG. 3B, after the bent resin tube 40 is formed from the molten resin filled in the cavity, the support pin 35 is moved as shown by the arrow to move the bent resin tube 40 from the pin tip 36 to the pin tip 36.
Withdraw. Here, since it is not necessary to fill the trace of the pin tip 36 with the molten resin, it is not necessary to accurately manage the solidification state of the molten resin. As a result, there is no need to provide a facility for managing the solidification state of the molten resin, and therefore, there is no need to pay for the facility. In addition, since it is not necessary to accurately manage the solidification state of the molten resin, no labor is required. Next, the upper split core 20 is pulled out from the mold 15 as shown by the arrow.

FIGS. 3A and 3B are views for explaining a second operation of the injection mold structure according to the present invention. In (a),
The lower split core 25 is pulled out of the mold 15 as shown by the arrow. Thus, the inside 40a of the bent resin tube 40 becomes hollow. In (b), the movable mold 17 of the mold 15 is moved as shown by the arrow, and the mold 15 is opened. At this time,
The support pin 35 moves together with the movable mold 17 while being attached to the movable mold 17.

FIG. 4 shows a third embodiment of the injection mold structure according to the present invention.
It is an operation explanatory view. One outer peripheral forming portion 11 of fixed mold 16
The curved resin tube 40 is released from the molding die 15 by separating the outer periphery 41 of the curved resin tube 40 from the outer peripheral forming portion 11b of the movable die 17 and the other.

According to the present invention, by using the support member 35 (see FIG. 2), the upper and lower split cores 20, 25 can be formed.
Does not change the shape of the cavity 30 and does not open the butting portion 29. Therefore, the thickness t of the peripheral wall 42 of the bent resin pipe 40 can be formed to be constant, and burrs do not occur on the inner periphery of the bent resin pipe 40. Further, with the pin tip 36 of the support member 35 arranged in the cavity,
Since injection molding is performed, a small hole 43 having a diameter d can be formed in the peripheral wall 42 of the bent resin tube 40.

Next, an example in which the bent resin pipe 40 is used as an intake pipe will be described. FIG. 5 is a diagram illustrating an example of use of a bent resin tube molded by the injection molding structure according to the present invention. A socket 47 is provided at a position corresponding to the small hole 43 of the bent resin pipe 40.
And the temperature sensor 48 is screwed into the socket 47, so that the detecting portion 48a of the temperature sensor 48
And is disposed inside the bent resin tube 40. The air cleaner and the throttle valve are connected by the bent resin pipe 40.

In this state, the throttle valve side is set to a negative pressure, and air is sucked from the air cleaner side to the throttle valve side as shown by an arrow. Since the bent resin pipe 40 is a curved intake pipe, the air that has flowed into the bent resin pipe 40 flows intensively outside the bent resin pipe 40. For this reason, the temperature sensor 48 can increase the contact ratio with the air, so that the temperature of the air can be detected with high accuracy.

In the above-described embodiment, an example has been described in which the temperature sensor 48 is attached to the bent resin pipe 40. However, a breather pipe, a negative pressure joint, a pipe for taking out injector-assisted air, and the like can be attached.
The breather pipe is a pipe that bends the combustion in the incomplete combustion state in the combustion chamber and returns it to the resin pipe 40 in order to re-burn the combustion in the incomplete combustion state in the combustion chamber in the combustion chamber.
The negative pressure joint is a joint for extracting a negative pressure for operating the diaphragm of the actuator.
The injector-assisted air extraction pipe is a pipe for supplying air to the injector.

In the above-described embodiment, the example in which the gate 32 is bent and formed on the bending center side of the resin tube 40 and the support pin 35 is bent and attached to the outside of the resin tube 40 has been described. A support pin 3 formed outside the tube 40
5 may be bent and attached to the bending center side of the resin tube 40.

Further, in the above-described embodiment, after the bent resin tube 40 is formed, first, the support pin 35 is extracted, and then the upper and lower split cores 20 and 25 are extracted.
The step of opening the mold 5 and releasing the bent resin tube 40 has been described. For example, after extracting the support pin 35,
May be opened to release the bent resin tube 40, and then the upper and lower split cores 20, 25 may be pulled out. Further, the example in which the bent resin pipe 40 is used as the intake pipe of the engine has been described, but the same effect can be obtained by using the bent resin pipe 40 as another pipe.

[0032]

According to the present invention, the following effects are exhibited by the above configuration. According to the first aspect, when the bent resin tube is injection-molded, the molten resin is injected into the cavity while supporting the divided core with the support pin, so that the butting portion of the divided core is not opened by the injection pressure. . As a result, burrs do not occur on the inner periphery of the bent resin pipe, the step of removing burrs can be omitted, and an increase in cost can be suppressed. In addition, by fitting the butting surfaces of the pair of split cores with the concave and convex portions, displacement of the pair of split cores can be prevented only by supporting the vicinity of the butted portion with the support pins.
As a result, the pair of split cores can be efficiently supported by one support pin, so that the number of support pins can be reduced and the increase in manufacturing cost can be suppressed.

According to a second aspect of the present invention, a small hole is formed in the resin tube by bending with a support pin. Therefore, when the bent resin tube is injection-molded, a small hole for mounting the sensor can be formed at the same time. As a result, the step of forming a small hole can be omitted, so that the productivity of the bent resin pipe can be increased. In addition, since small holes are simultaneously opened when the bent resin tube is injection-molded, there is no need to remove the support pins during the injection molding. For this reason, it is not necessary to use a precise molding machine and sophisticated operation necessary for suitably removing the support pin, and it is possible to suppress an increase in the manufacturing cost of the bent resin pipe.

According to a third aspect of the present invention, the small holes are arranged outside the bending of the bent resin tube, so that, for example, a sensor and a breather pipe can be attached to the outside of the bending resin tube through the small holes. When a fluid is caused to flow through the bent resin pipe, the fluid flows intensively outside the bend of the bent resin pipe. Therefore, the contact rate of the fluid with respect to the sensor can be increased. As a result, the state of the fluid can be detected with high accuracy. In addition, since the breather pipe can be arranged at a location where the fluid flows in a concentrated manner, an efficient breather effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of an injection mold structure of a bent resin pipe according to the present invention.

FIG. 2 is an explanatory view of a first operation of the injection mold structure according to the present invention.

FIG. 3 is an explanatory view of a second operation of the injection mold structure according to the present invention.

FIG. 4 is an explanatory view of a third operation of the injection mold structure according to the present invention.

FIG. 5 is a diagram illustrating an example of use of a bent resin pipe molded by the injection molding die structure according to the present invention.

FIG. 6 is a plan view of a conventional engine room.

FIG. 7 is a view illustrating a conventional method of forming a bent resin pipe.

[Explanation of symbols]

10: Injection mold structure of bent resin tube, 11: Outer periphery forming part, 15: Mold, 20: Split core (upper split core), 2
3, 28 butting surface, 23a recess, 25 split core (lower split core), 28a projection, 29 ... butting part, 30
... cavity, 32 ... gate, 35 ... support pin, 40 ...
Bent resin tube, 41 ... outer periphery, 43 ... small hole.

Claims (3)

[Claims] 1. A molding die having an outer periphery forming portion for forming an outer periphery of a curved resin pipe, a pair of divided cores which are housed in the molding die and are pulled out from the curved resin pipe, and A gate for injecting the molten resin into the cavity formed by the core and the molding die, and a projection protruding from the molding die side to support the divided core that is bent by the injection pressure of the molten resin, and supports the vicinity of the butted portion of the divided core. A pair of split cores, wherein the pair of split cores have a concave portion formed on one of the abutting surfaces thereof and a convex portion which can be fitted into the concave portion on the other side thereof. . 2. The injection molding die structure of a bent resin pipe according to claim 1, wherein a small hole is formed in the bent resin pipe with the support pin. 3. The injection molding structure of a bent resin pipe according to claim 2, wherein said small hole is arranged outside a bent resin pipe.