JP7698285B2 - Method for forming insulator for slot coil of rotating electric machine - Google Patents

Description

The present invention relates to a molding method for an insulator for a slot coil of a rotating electric machine. More specifically, the present invention relates to a plastic molding method that can stably mold an insulator (plastic molded product) for a slot coil of a rotating electric machine, which is a thin-walled rectangular prism with a long axis and a plurality of through holes whose interior is divided by a plurality of partition walls.

In electric motors (rotating electric machines) such as motors, the stator plays a role in generating a magnetic field. The stator of an induction motor (AC motor) driven by AC power generates a rotating magnetic field, so an electromagnet with a conductor wound around a magnetic material is used. In order to reduce iron loss (eddy current loss), the magnetic material (stator core) is made of laminated magnetic material, for example, thin plate material such as silicon steel, and has elongated grooves (slots) formed radially (in the radial direction) for winding the coil.

The coils wound around the stator core may be wound for each slot using a dedicated coil winding machine, but in recent years, so-called formed coils have been used, in which a circular winding coil is formed into a circular waveform using a press forming machine (see, for example, Patent Document 1).

On the other hand, a split molded coil (segment coil) is known in which the molded coil is divided into multiple segments and a coil is molded for each segment (see, for example, Patent Document 2). The segment coil is composed of multiple segment coils, such as a coil side segment coil (coil portion that passes through the inside of the stator core), a coil upper end segment coil (coil portion that passes through the upper end of the stator core), and a coil lower end segment (coil portion that passes through the lower end of the stator core). In particular, the coil of the coil side segment that passes through the inside of the stator core is housed in a rectangular (long-axis square prism) plastic molded product that can be inserted into a slot and has multiple through holes that run through in the longitudinal direction to allow the coil to pass through the inside (see, for example, Patent Document 2).

A coil that is modularized and housed in a plastic molded product is called a slot coil. The plastic molded product that houses the coils also functions to bundle multiple coils together and to electrically insulate the stator core from the coils or from one coil to another. The thicker the plastic molded product, the higher the insulation between the stator core and the coils or from one coil to another. However, the thickness of the plastic molded product acts as a resistance to the magnetic flux (magnetic lines of force) generated in the coil, so if the plate is thick, fewer magnetic lines of force pass through the stator core, and the strength of the magnetic field generated in the stator core is weakened. As a result, the induced current induced in the rotor is smaller, and as a result, the rotational force (torque) generated in the rotor is smaller.

Therefore, the thickness of the plastic molded parts used in slot coils must be as thin as possible (e.g., 0.3 mm or less) while still satisfying the required insulation properties. Furthermore, because the torque of an electric motor depends on the magnetic flux density, the length of the coil sides, and the current, the overall length (height) of the plastic molded parts must be as long as possible (e.g., 200 mm or more) while still satisfying the required heat resistance.

JP 2009-296815 A JP 2008-35687 A JP 2019-161964 A JP 2018-125924 A

In plastic molded products that house coils, the elongated through holes for passing the coils through are formed by core pins with a rectangular cross section and long axis. If the plate thickness of the plastic molded product is, for example, 0.3 mm and the overall length is, for example, 200 mm, the core pins are arranged in parallel in the mold with a gap of 0.3 mm between them, with an effective length of 200 mm, and with both ends supported.

Therefore, the molten resin needs to be evenly filled by the injection molding machine into a cavity with a gap of 0.3 mm and a length of 200 mm.

However, because each core pin, arranged in parallel, is supported at both ends within the mold, the core pins will bend at a certain section due to the injection pressure of the molten resin. When the core pins bend, the flow path for the molten resin narrows, or in some cases, the core pins get too close to each other, preventing the molten resin from flowing and resulting in a short shot (a phenomenon in which holes form). Plastic molded products that experience short shots are disposed of as defective products.

The present invention was made in consideration of the problems with the above-mentioned conventional technology, and its purpose is to provide a plastic molding method that can stably mold an insulator (plastic molded product) for a slot coil of a rotating electric machine, which is a thin-walled rectangular prism with a long axis and a plurality of through holes whose interior is divided by a plurality of partitions.

The plastic molding method according to the present invention for achieving the above object includes a fixed mold (201) for molding the head (10) of a plastic molded product (100) whose interior is divided by a plurality of partition walls (11), a movable mold (202) for molding the body (20) of the plastic molded product (100), a first insert (204) for molding a plurality of through holes (21) along the longitudinal direction inside the body (20), a core mold (203) attached to the movable mold (202) for fixing the first insert (204), and an injection molding machine (207) for injecting molten resin into the plastic molded product (10). The plastic molding method for molding the molded product (150) includes a step of pushing the first insert (204) from both sides with the first slide piece (205) while the first insert (204) is engaged with the fixed mold (201), and a step of molding a plastic molding intermediate (150) having a plurality of openings (20a) in the body (20) by pouring molten resin into the gap between the first insert (204) and the first slide piece (205) and the mold (201, 202, 203) while the first slide piece (205) pushes the first insert (204) from both sides.

In the above configuration, the first insert (204) is pushed from both sides by the first slide piece (205), making it possible to prevent the first insert (204) from bending due to the injection pressure. Since the pitch (spacing) between adjacent first inserts (204) is stable, the flow of the molten resin is also stabilized. As a result, the cavity in the mold is filled evenly with molten resin all the way to the very end.

The second feature of the plastic molding method according to the present invention is that it includes the steps of: pulling out the first insert (204) from the through hole (21) of the plastic molding intermediate (150); inserting a second insert (208) having a smaller cross section than the first insert (204) into the through hole (21) of the plastic molding intermediate (150); pushing the opening (20a) and its vicinity from both sides with a second slide piece (209) having a pushing surface (209a) that envelops the opening (20a) when the second insert (208) is inserted into the through hole (21); and using the second slide piece (209) to pour molten resin into the multiple openings (20a) to block the openings (20a) with molten resin.

In the above configuration, taking into consideration the shrinkage of the plastic molding intermediate (150), a second insert (208) with a smaller cross section than the first insert (204) is inserted into the through hole (21), and the second slide piece (209) pushes through the vicinity including the opening (20a) from both sides. This makes it possible to close the opening (20a) with molten resin while maintaining the new plate thickness after shrinkage.

The third feature of the plastic molding method according to the present invention is that a convex portion (205a) is formed on the surface of the first slide piece (205), and a concave portion (204a) into which the convex portion (205a) fits is formed on the surface of the first insert (204) facing the first slide piece (205).

In the above configuration, the convex portion (205a) of the first slide piece (205) fits into the concave portion (204a) of the first insert (204), thereby making it possible to stably fix the first insert (204). This makes it possible to effectively prevent the first insert (204) from bending due to the injection pressure.

The fourth feature of the plastic molding method according to the present invention is that the second slide piece (209) is configured to be connectable from a lateral direction perpendicular to the longitudinal direction of the second insert (208) at a height position where a film gate that injects molten resin into the opening (20a) communicates with the opening (20a).

In the above configuration, the opening (20a) can be filled with molten resin (20b) so that it is flush with the outer and inner surfaces of the body (20).

The fifth feature of the plastic molding method according to the present invention is that the injection molding machine (207) is configured with a separate plasticization section (210) that plasticizes the resin using a screw and an injection section (211) that injects the molten resin using a plunger.

In the above configuration, the screw only rotates to plasticize the resin. On the other hand, the plunger only reciprocates without receiving any reaction force from the screw, ensuring accurate measurement and injection pressure of the molten resin.

The sixth feature of the plastic molding method according to the present invention is that the fixed mold (201) is configured to be connectable to the injection molding machine (207), and the resin flow path (201c) through which the molten resin injected from the injection molding machine (207) flows is connected to the flange cavity (201a) that molds the flange portion (12) of the plastic molded product (100).

In the above configuration, the flange cavity (201a) of the fixed mold (201) serves as a reservoir for the molten resin, allowing the molten resin to be stably poured evenly into the narrow gap between the first insert (204) and the movable mold (202) all the way to the very end.

The seventh feature of the plastic molding method according to the present invention is that the resin (20b) used to close the opening (20a) of the plastic molding intermediate (150) has the same or higher heat resistance as the resin used to mold the body (20).

In the above configuration, the sealing resin (20b) is less likely to peel off from the body portion (20b).

The plastic molding method of the present invention makes it possible to stably mold a plastic molded product that is a thin-walled rectangular prism with multiple through holes, the interior of which is divided by multiple partitions.

1 is a perspective view showing a plastic molded product molded by the plastic molding method of the present invention. 1 is a cross-sectional view illustrating a main portion of a plastic molding die for molding a plastic molded product from molten resin. This is a cross-sectional view taken along line AA in FIG. This is a cross-sectional view taken along line B-B of FIG. This is a cross-sectional view taken along the line CC of FIG. This is a cross-sectional view taken along the line D-D of FIG. 1 is a cross-sectional explanatory view showing a main part of an injection molding machine used in a plastic molding method of the present invention. FIG. 2 is a flow diagram showing a method for molding a plastic molded product using a plastic molding die. 11 is an explanatory view showing a state in which the slide piece in the primary molding has completely pressed the core pin from both sides. FIG. FIG. 2 is a perspective view showing a plastic molding intermediate body molded in the primary molding. 1 is a cross-sectional explanatory view of a main portion of a plastic molding die for secondary molding that closes an opening of a plastic molding intermediate body with resin. FIG. 13 is an explanatory diagram showing a state in which the slide pieces for secondary molding have pressed the vicinity of the opening of the plastic molding intermediate body from both sides. FIG. FIG. 2 is a perspective view showing a plastic molded product in which an opening of a plastic intermediate molded product is sealed with a different resin. FIG. 2 is a cross-sectional view illustrating a main portion of a fixed mold having a fan gate. FIG. 4 is a cross-sectional explanatory view showing a main part of a fixed mold having a reservoir portion. 13 is an explanatory diagram showing a sliding piece in which the length in the longitudinal direction of the pushing surface excluding the protruding portion of the sliding piece is shortened. FIG. 1 is an explanatory diagram showing a plastic molding intermediate body molded by a plastic molding die incorporating a slide piece in which the longitudinal length of the pressing surface excluding the protrusion of the slide piece is shortened. FIG. 1 is a cross-sectional view of a main portion of a slide piece in which the flow resistance is reduced by increasing the area of the gap through which molten resin passes. FIG. FIG. 1 is an explanatory diagram showing a plastic molding intermediate body molded by a plastic molding die incorporating a slide piece that reduces flow resistance by increasing the area of the gap through which molten resin passes.

The following describes an embodiment of the present invention in detail with reference to the attached drawings.

FIG. 1 is a perspective view showing a plastic molded product 100 molded by the plastic molding method of the present invention.
This plastic molded product 100 is composed of a head portion 10 above a lower surface 12a of the flange portion 12, and a body portion 20 below the lower surface 12a. The plastic molded product 100 is used, for example, as a slot coil insulator that is inserted into a slot (not shown) of a stator core of a rotating electrical machine to provide insulation between the stator core and the coil or between the coils themselves.

The inside is divided by multiple (e.g., five) partition walls 11, forming a thin-walled rectangular prism with multiple (e.g., six) through holes 21. The plate thickness t is 0.3 mm or less, preferably 0.2 mm, and the total length L is, for example, 200 mm or more. The through holes 21 are used to wire the rectangular conductors (not shown) that make up the slot coils (not shown) of the rotating electrical machine.

Flange portions 12 are formed near the long sides of the head 10. The plastic molded product 100 is engaged with a slot (not shown) in the stator core via these flange portions 12. The flange portions 12 are L-shaped to allow for the fluidity of the resin. The material for the plastic molded product 100 may be any thermoplastic synthetic resin that is heat resistant and electrically insulating, and for example, a thermoplastic synthetic resin such as liquid crystalline fully aromatic polyester may be used.

The plate thickness portion corresponds to the spatial volume (cavity) into which the molten resin flows in the molding die 200 described below. The flange portion 12 also functions as a resin reservoir for pouring the molten resin evenly into the cavity in the die to the very end, as will be described in detail later with reference to FIG. 3. The molding method of this plastic molded product 100 will be described below.

FIG. 2 is an explanatory cross-sectional view of a main portion of a plastic molding die 200 for molding a plastic molded product 100 from molten resin.
This plastic molding die 200 is comprised of a fixed die 201 that is engaged with the tip of a core pin 204 to mold the head 10 of the plastic molded product 100, a movable die 202 through which the core pin 204 passes and is joined to the fixed die 201 to mold the body 20 of the plastic molded product 100, a core die 203 that fixes the core pin 204 as a unit, the core pin 204 that molds the through hole 21 of the plastic molded product 100, a slide top 205 that pushes the core pin 204 from both sides, a hydraulic cylinder 206 that pushes the slide top 205 with a predetermined force, and an injection molding machine 207 that injects molten resin into the gap between the dies. Each component will be described below.

Figure 3 is a cross-sectional view taken along line A-A in Figure 2. As shown in Figure 3, the fixed mold 201 has a flange cavity 201a that forms the flange 12 (Figure 1) of the plastic molded product 100, a core pin locking cavity 201b that locks the tip of the core pin 204 (hatched portion), a head cavity 201c that forms the head 10 of the plastic molded product 100, and a resin supply flow path 201c that supplies molten resin to the flange cavity 201a. Therefore, the space excluding the core pin 204 (hatched portion) from the head cavity 201c forms the plate thickness portion (plate thickness t portion) of the head 10 of the plastic molded product 100.

Figure 4 is a cross-sectional view taken along line B-B in Figure 2. As shown in Figure 4, the movable mold 202 has a body cavity 202a that molds the body 10 of the plastic molded product 100. Therefore, the space excluding the core pin 204 (hatched portion) from the body cavity 202a forms the plate thickness portion (portion of plate thickness t) of the body 20 of the plastic molded product 100. In addition, the movable mold 202 is connected to a moving mechanism (not shown) and is configured to be able to move back and forth in the horizontal direction.

Figure 5 is a cross-sectional view taken along the line C-C in Figure 2. Figure 5(a) shows the state in which the slide top 205 has been separated from the core pin 204. Figure 5(b) shows the state in which the slide top 205 has fully pressed the core pin 204.

As shown in FIG. 5(a), the slide piece 205 has a convex portion 205a formed on the surface facing the core pin 204. This convex portion 205a is configured to fit into the concave portion 204a formed in the core pin 204.

The shape of the convex portion 205a can be, for example, an R-shape (hemispherical), a prism (square prism), a rounded column (cylindrical, elliptical column), a pyramid (square pyramid), a cone, or a wedge, but is not limited to these shapes. In addition, the slide top 205 is attached to the movable mold 202 at a position where it can press through the center of the core pin 204 in the longitudinal direction (axial direction). The shape of the concave portion 204a of the core pin 204 is uniquely determined from the shape of the convex portion 205a.

The recesses 204a of the core pin 204 are attached at two locations, for example, at the top and bottom or at two locations at the left and right, facing the protrusions 205a of the slide top 205. The cross-sectional shape of the body of the core pin 204 that does not face the protrusions 205a of the slide top 205 is a solid rectangle.

As shown in FIG. 5(b), the convex portion 205a of the slide piece 205 fits into the concave portion 204a of the core pin 204, so that the core pin 204 is firmly fixed from above and below by the slide piece 205. This makes the core pin 204 less likely to bend due to the injection pressure of the molten resin, and allows the molten resin to flow sufficiently all the way to the end.

The molten resin does not flow into the overlapping portion of the body cavity 202a (Fig. 4) of the movable mold 202 with the core pin 204 and the slide piece 205. Therefore, a through hole 21 (Fig. 1) is formed in the overlapping portion with the core pin 204, while an opening 20a (Fig. 10) is formed in the overlapping portion with the slide piece 205. Since the conductor is exposed in this opening 20a (Fig. 10), it is necessary to block the opening 20a (Fig. 10) with resin. The process of blocking the opening 20a (Fig. 10) with resin will be described later with reference to Figs. 11 to 13.

Figure 6 is a cross-sectional view taken along the line D-D in Figure 2. As shown in Figure 6, the core mold 203 has a core pin fixing cavity 202a for fixing the core pin 204. The joint surface of the core mold 203 with the movable mold 202, excluding the core pin fixing cavity 202a, forms the lower end surface of the body 20 of the plastic molded product 100.

FIG. 7 is an explanatory cross-sectional view of a main portion of an injection molding machine 207 used in the plastic molding method of the present invention.
This injection molding machine 207 is equipped with a plasticizing section 210 that plasticizes resin and an injection section 211 that injects the plasticized molten resin, which are separate and independent of each other. Conventional injection molding machines inject the plasticized molten resin by the screw while plasticizing the resin with the screw. That is, the screw moves forward while rotating. Therefore, a part of the molten resin flows out in the opposite direction to the injection direction from the gap between the screw and the inner peripheral surface of the cylinder, and this backflow of the molten resin becomes a force that pushes down the screw. This force that pushes down the screw acts in a direction that prevents the screw from injecting the molten resin, but it is difficult to quantitatively predict the magnitude of this force. As a result, the load that pushes the screw becomes unstable, which deteriorates the filling accuracy of the molten resin. In addition, this force that pushes down the screw can also cause problems with the screw.

However, in the injection molding machine 207 used in the plastic molding die 200, the plasticizing section 210 and the injection section 211 are configured as separate mechanisms. Therefore, the screw 210a only performs rotational motion to plasticize the resin.

On the other hand, the injection of the molten resin is performed by the plunger 211a. The plunger 211a only reciprocates within the injection cylinder 211b and does not rotate. In addition, since the surface of the plunger 211a does not have a helical projection such as a screw thread, it is possible to attach a seal material such as an O-ring to the surface of the plunger 211a. This prevents the molten resin from flowing in the opposite direction through the gap between the plunger 211a and the injection cylinder 211b. In other words, the force of the molten resin pushing down the plunger 211a is not generated. As a result, the load pushing the plunger 211a by the actuator 211c is stabilized, and the amount of molten resin injected can be suitably controlled by the pushing load. This significantly improves the filling accuracy of the molten resin compared to conventional injection molding machines.

The following describes a method for molding the plastic molded product 100 using the plastic molding die 200.

FIG. 8 is a flow diagram showing a molding method for the plastic molded product 100 using the plastic molding die 200.
First, in process P 1 , a core pin 204 is attached to a core die 203 .

Next, in process P2, the core die 203 with the core pin 204 attached is attached to the movable die.

Next, in process P3, the movable mold 202 is joined to the fixed mold 201.

Next, in process P4, the sliding piece 205 pushes the core pin 204 all the way from both sides. Figure 9 shows the state in which the sliding piece 205 has pushed the core pin 204 all the way from both sides.

Next, in process P5, the injection molding machine 207 fills the mold with molten resin.

Next, in process P6, the slide piece 205 is separated from the core pin 204.

Figure 10 is an explanatory diagram showing the plastic molded intermediate 150 molded in the primary molding from process P1 to process P6. The slide piece 205 pushes through the core pins 204 from both sides, forming six openings 20a on each side of the wide side of the body 20, for a total of twelve openings 20a on both sides. The twelve openings 20a are sealed with resin in the secondary molding from process P7 to process P14. The secondary molding process for sealing the twelve openings 20a with resin is described below.

Returning to Figure 8, in process P7, the core mold 203 is separated from the movable mold 202.

Next, in process P8, the core pin 204 of the core mold 203 is replaced with a secondary molding core pin 208. The secondary molding core pin 208 has a cross section smaller than that of the core pin 204 in accordance with the degree of shrinkage of the plastic molding intermediate 150.

Next, in process P9, the core mold 203 with the secondary molding core pin 208 attached is reattached to the movable mold 202.

Next, in process P10, a secondary molding slide piece 209 is attached to the movable mold 202 in place of the slide piece 205.

FIG. 11 is an explanatory cross-sectional view of a main part of a plastic molding die 200A for secondary molding, which closes the opening 20a of the plastic molding intermediate body 150 with resin.
In this plastic molding die 200A, the above-mentioned core pin 204 and slide piece 205 are replaced with a secondary molding core pin 208 and a secondary molding slide piece 209, respectively.

This secondary molding slide piece 209 has a pushing surface 209a for pushing through the vicinity including the opening 20a of the body 20. The secondary molding slide piece 209 is configured so that a film gate (not shown) that injects molten resin into the opening 20a can be connected from a lateral direction perpendicular to the longitudinal direction of the secondary molding core pin 208. Therefore, when the opening 20a is blocked with resin in the process P12 described below, the film gate (not shown) is connected to the secondary molding slide piece 209, and molten resin is injected from the film gate (not shown) into the opening 20a. Molten resin is supplied to each film gate (not shown) from the injection molding machine 207.

Returning to FIG. 8, in process P11, the secondary molding slide piece 209 pushes through the vicinity of the opening 20a of the plastic molding intermediate body 150 from both sides. FIG. 12 shows the state in which the secondary molding slide piece 209 pushes through the vicinity of the opening 20a of the plastic molding intermediate body 150 from both sides.

Next, in process P12, the opening 20a of the plastic molding intermediate 150 is sealed with molten resin. The resin used may be different from the resin used in the plastic molding intermediate 150, as long as it has the same or higher heat resistance.

Next, in process P13, the secondary molding slide piece 209 is separated.

Next, in process P14, the movable mold 202 is separated from the fixed mold 201. FIG. 13 is a perspective view showing a plastic molded product 100A in which the opening 20a of the plastic intermediate molded product 150 is sealed with a different resin (sealing resin 20b). The sealing resin 20b has the same or greater heat resistance and insulating properties as the resin of the body 20. The above-mentioned plastic molded product 100 is a plastic molded product in which the opening 20a of the plastic molded intermediate 150 is sealed with the same resin as the resin of the body 20.

As described above, the plastic molding method of the present invention makes it possible to stably mold a plastic molded product having a thin-walled rectangular prism with a long axis and a thickness of 0.3 mm or less and a length of 200 mm or more, for example, with multiple through holes 21 inside separated by multiple partitions 11.

The plastic molding method of the present invention and the plastic molded product molded by the method have been described above with reference to the drawings, but the present invention is not limited to the above. In other words, various changes and modifications can be made within the technical scope of the present invention. For example, the mounting position and number of slide pieces 205 that push the core pin 204 from both sides can be changed so that not only the center of the core pin 204 is pushed from both sides, but multiple points of the core pin 204 are pushed from both sides at predetermined intervals according to the overall length L of the plastic molded product 100, 100A.

In addition, the six protrusions 205a of the slide piece 205 are arranged in a row along a direction perpendicular to the longitudinal direction of the core pin 204, but they may be arranged in multiple rows.

In addition, various gates other than the gate shown in FIG. 3 can be used as the gate for supplying molten resin to the flange cavity 201a of the fixed mold 201. Below, we will explain a modified example of the fixed mold 201 that uses a fan gate.

Figure 14 is a cross-sectional explanatory diagram of a main part showing a fixed mold 201A equipped with a fan gate 201d. Figure 14(a) is a cross-sectional view taken along the line A-A in Figure 2. Figure 14(b) is a cross-sectional view taken along the line E-E in Figure 14(a).

As shown in FIG. 14(a), the molten resin is supplied to the long side of the flange cavity 201a through the fan gate 201d. In particular, a cylindrical control pin 201e is formed vertically inside the fan gate 201d. The control pin 201e is formed at an appropriate position on the perpendicular bisector (axis of symmetry) of an isosceles triangle with the long side of the flange cavity 201a as its base. In this embodiment, the control pin 201e is formed, for example, near the midpoint on the perpendicular bisector (axis of symmetry). The molten resin injected from the resin supply flow path 201c is divided equally by this control pin 201e in the left and right directions of the control pin 201e.

As shown in FIG. 14(b), the cross-sectional shape of the fan gate 201d has a tapered structure in which the height decreases toward the flange cavity 201a. On the other hand, as shown in FIG. 14(a), the planar shape of the fan gate 201d has a widening structure in which the width increases toward the flange cavity 201a. Therefore, the flow resistance decreases as the distance from the control pin 201e increases laterally. As a result, the movement distance of the molten resin on the outside is longer than that on the inside, but the flow speed of the molten resin on the outside is faster than that on the inside. Conversely, the movement distance of the molten resin on the inside is shorter than that on the outside, but the flow speed of the molten resin on the inside is slower than that on the outside. As a result, the molten resin on the outside and inside reach the flange cavity 201a at almost the same time. In other words, the molten resin injected from the resin supply flow path 201c is supplied evenly along the long side of the flange cavity 201a at almost the same time.

As a result, the molten resin flows evenly into each narrow gap between the core pins 204 at almost the same time, so that the molten resin is filled evenly and stably all the way to the very end. This even flow of molten resin without time lag also greatly reduces the load that the core pins 204 receive from the flow.

However, the flow of molten resin that collides with the control pin 201e may generate a vortex, and the molten resin flowing into the flange cavity 201a may become turbulent. In this case, the molten resin will not flow evenly into the narrow gaps between the core pins 204. Below, we will explain the fixed mold 201B, which has a reservoir (buffer) that calms (calms) the turbulent flow of the molten resin, located behind the fan gate 201d and before the flange cavity 201a.

Figure 15 is a cross-sectional explanatory diagram of a main part showing a fixed mold 201B having a reservoir portion 20f. Figure 15(a) is a cross-sectional view taken along the line A-A in Figure 2. Figure 15(b) is a cross-sectional view taken along the line E-E in Figure 15(a).

In this fixed mold 201B, a reservoir 201f and a film gate 201g are provided adjacent to the outlet of the fan gate 201d. The reservoir 201f is, for example, a box shape with a rectangular cross section and a long axis. The length in the axial direction (longitudinal direction) is longer than the long side of the flange cavity 201a. At the outlet of the reservoir 201f, a film gate 201g of a constant height is formed integrally with the reservoir 201f.

Therefore, if the molten resin flowing out of the fan gate 201d becomes turbulent, the molten resin flows into the reservoir 201f, expands, and calms down, and is then rectified into a laminar flow of a certain thickness (height) by the film gate 201g and supplied to the long side of the flange cavity 201a. As a result, the laminar (stable flow) molten resin flows evenly into each narrow gap between the core pins 204 at almost the same time, and the molten resin is filled evenly all the way to the very end. This even and stable inflow of molten resin without time lag also significantly reduces the load that the core pins 204 receive from the flow.

The pushing-through caused by the projection 205a of the slide top 205 and the recess 204a of the core pin 204 engaging with each other serves as a means for suppressing deflection of the core pin 204 and stabilizing the pitch (spacing) between the core pins 204, but it can also act as a flow resistance that impedes the flow of molten resin. In addition, the surface of the slide top 205 facing the core pin 204, excluding the projection 205a, does not contribute much to suppressing the deflection of the core pin 204.

Therefore, in order to minimize the obstruction of the flow of molten resin while maintaining the deflection suppression function of the slide top 205, it is possible to consider, for example, (1) shortening the longitudinal length of the pushing surface of the slide top 205 excluding the convex portion 205a to shorten the length of the slide top through which the molten resin passes, or (2) increasing the area of the gap in the slide top 205 through which the molten resin passes. Below, we will explain slide top 205' in which the longitudinal length of the pushing surface of the slide top 205 excluding the convex portion 205a is shortened.

Figure 16 is an explanatory diagram showing a slide top 205' in which the length of the pushing surface of the slide top 205, excluding the protrusion 205a, in the longitudinal direction is shortened. Figure 16(a) shows the pushing surface of the slide top 205 against the core pin 204 as a comparative example. Figure 16(b) shows the pushing surface of the slide top 205' against the core pin 204.

As shown in FIG. 16(b), in the slide piece 205', the pushing surface of the convex portion 205a remains the same as that of the slide piece 205, but the longitudinal length L" of the pushing surface excluding the convex portion 205a is made shorter than that of the slide piece 205 (L"<L) to reduce the flow resistance to the molten resin.

Figure 17 is an explanatory diagram showing a plastic molding intermediate 150A molded by a plastic molding die incorporating a slide piece 205'. The openings 20a corresponding to the slide pieces 205' form a single opening that is connected to each other in the horizontal direction. Therefore, when injecting resin to seal the two upper and lower openings 20a of the body 20, the resin is injected from the horizontal direction into each opening 20a by one gate. Next, we will explain slide piece 205'', which reduces flow resistance by increasing the gap through which the molten resin flows in slide piece 205.

Figure 18 is a cross-sectional view of a main part of a slide piece 205" that reduces flow resistance by increasing the area of the gap in the slide piece 205 through which the molten resin passes. Figure 18(a) shows a comparative example in which the slide piece 205 has pressed the core pin 204 from both sides. Figure 18(b) shows the slide piece 205" has pressed the core pin 204 from both sides.

As shown in FIG. 18(b), in the slide top 205'', the protruding height H" of the convex parts 205a" from the bottom surface 205b is made higher than that of the slide top 205 (H">H), so that the six consecutive convex parts 205a" push the core pin 204 from both sides (single pushing by the convex parts 205a"). As a result, a new gap is created between the bottom surface 205b of the slide top 205" and the core pin 204. In addition, the gap between the core pins 204 also increases. As a result, the area of the gap through which the molten resin passes in the slide top 205" is significantly larger than that of the slide top 205, so the flow resistance to the molten resin is significantly lower than that of the slide top 205, and the molten resin is filled to the very end.

Figure 19 is an explanatory diagram showing a plastic molding intermediate 150B molded by a plastic molding die incorporating a slide piece 205". The openings 20a corresponding to the protrusions 205a" of the slide piece 205" each form an independent opening. Therefore, when injecting resin to seal the six openings 20a on one side of the body 20, the resin is injected perpendicularly to each opening 20a by a tough gate having six gates.

REFERENCE SIGNS LIST 10 Head 11 Partition 12 Flange 20 Body 20a Opening 20b Sealing resin 21 Through hole 100 Plastic molded product 100A Plastic molded product 150 Plastic molded intermediate 200 Plastic molding die 200A Plastic molding die 201 Fixed die 201A Fixed die A
201B Fixed mold B
201a Flange cavity 201b Core pin locking cavity 201c Resin supply flow path 201d Fan gate 201e Control pin 201f Reservoir 201g Film gate 202 Movable mold 202a Body cavity 203 Core mold 203a Core pin fixing cavity 204 Core pin (first insert)
204a Recess 205 Slider (first slider)
205a: convex portion 206: hydraulic cylinder 207: injection molding machine 208: secondary molding core pin (second insert)
209 Secondary molding slide piece (second slide piece)
209a: Push-off surface 210: Plasticizing section 210a: Screw 210b: Plasticizing cylinder 210c: Plasticizing motor 211: Injection section 211a: Plunger 211b: Injection cylinder 211c: Actuator

Claims (7)

A fixed mold (201) for molding a head (10) of a plastic molded product (100) whose interior is divided by a plurality of partition walls (11);
A movable mold (202) for molding the body portion (20) of the plastic molded product (100);
A first insert (204) for forming a plurality of through holes (21) along the longitudinal direction inside the body (20);
a core mold (203) attached to the movable mold (202) and fixing the first insert (204);
A plastic molding method for molding the plastic molded product (100) using an injection molding machine (207) that injects molten resin, comprising:
a step of pushing the first insert (204) from both sides in a direction perpendicular to the longitudinal direction of the first insert (204) by a first slide piece (205) while the first insert (204) is engaged with the fixed mold (201);
a step of molding a plastic molding intermediate body (150) having a plurality of openings (20a) in the body portion (20) by pouring molten resin into a gap between the first insert (204) and the first slide piece (205) and the mold (201, 202, 203) while the first slide piece (205) is pushing the first insert (204) from both sides in a direction perpendicular to the longitudinal direction of the first insert (204) ;
and closing said plurality of openings (20a) . The plastic molding method according to claim 1,
Pulling the first insert (204) out of the through hole (21) of the plastic molding intermediate body (150);
inserting a second insert (208) having a smaller cross section than the first insert (204) into the through hole (21) of the plastic molding intermediate body (150);
a step of pushing off the vicinity including the opening (20a) from both sides in a direction perpendicular to the longitudinal direction of the second insert (208) by a second slide piece (209) having a pushing-off surface (209a) that envelops the opening (20a) when the second insert (208) is inserted into the through hole (21) ;
and a step of using the second slide piece (209) to pour molten resin into the plurality of openings (20a) to close the openings (20a) with molten resin. The plastic molding method according to claim 1 or 2,
A convex portion (205a) is formed on the surface of the first slide piece (205),
a recess (204a) into which the protrusion (205a) fits is formed on a surface of the first insert (204) facing the first slide piece (205). The plastic molding method according to claim 2,
a film gate for injecting molten resin into the opening (20a) and configured to be connectable to the second slide piece (209) from a lateral direction perpendicular to the longitudinal direction of the second insert (208), at a height position where the film gate communicates with the opening (20a). The plastic molding method according to any one of claims 1 to 4,
The plastic molding method is characterized in that the injection molding machine (207) is configured separately from a plasticization section (210) that plasticizes resin by a screw and an injection section (211) that injects molten resin by a plunger. The plastic molding method according to any one of claims 1 to 5,
The fixed mold (201) is configured to be connectable to the injection molding machine (207);
a resin flow path (201c) through which the molten resin injected from the injection molding machine (207) flows is connected to a flange portion cavity (201a) which molds the flange portion (12) of the plastic molded product (100). The plastic molding method according to claim 2 ,
a resin (20b) used to close the opening (20a) of the plastic molding intermediate body (150) has heat resistance equal to or greater than that of a resin used to mold the body portion (20).