Molding Method for Insulator for Slot Coil of Rotating Electric Machine

Abstract

To provide a plastic molding method capable of stably molding thin-walled long-axis square pole body plastic molded products, for example, with a thickness of 0.3 mm or less and a length of 200 mm or more, whose interior is separated by a plurality of partition walls.SOLUTION: In the molding method of the present invention, a plastic molding intermediate 150 is molded by filling the space volume between a core pin 204 and a fixed mold 201 and a movable mold 202 with molten resin by an injection molding machine 207 while a core pin 204, which molds a through hole 21 of a plastic molding 100, is pushed off from both sides by a slide piece 205. Subsequently, the core pin 204 and the slide piece 205 are replaced with a secondary molding core pin 208 and a secondary molding slide piece 209, respectively, and while the vicinity including an opening 20a is pushed through by the secondary molding slide piece 209 while being supported by the secondary molding core pin 208, the opening 20a is closed with a sealing resin 20b having the same or equal or higher heat resistance than the resin of the body portion 20.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a method for molding an insulator for a slot coil of a rotating electrical machine. More specifically, the present invention relates to a plastic molding method capable of stably molding an insulator (plastic molded product) for a slot coil of a rotating electrical machine having a thin-walled long-axis rectangular prism shape provided with a plurality of through holes partitioned by a plurality of partition walls inside.

Background Art

[0002] In an electric motor (rotating electrical machine) such as a motor, a stator plays a role of generating a magnetic field. In an induction motor (AC motor) driven by AC power, an electromagnet in which a conducting wire is wound around a magnetic material is used to generate a rotating magnetic field. The magnetic material (stator core) is composed of a laminated magnetic material obtained by laminating thin plate materials such as silicon steel sheets in order to reduce iron loss (eddy current loss), and vertically long grooves (slots) for winding coils are formed radially (in the radial direction).

[0003] The coil wound around the stator core may be wound for each slot by a dedicated coil winding machine, but in recent years, a so-called molded coil formed into an annular waveform by a press molding machine from an annular winding coil has been used (see, for example, Patent Document 1).

[0004] On the other hand, a split molded coil (segment coil) in which this molded coil is divided into a plurality of segments and the coil is molded for each segment is known (see, for example, Patent Document 2). The segment coil is composed of a plurality of segment coils such as a coil side segment coil (coil portion passing through the inside of the stator core), a coil upper end segment coil (coil portion passing through the upper end portion of the stator core), and a coil lower end segment (coil portion passing through the lower end portion of the stator core). In particular, the coil of the coil side segment passing through the inside of the stator core is housed in a plastic molded product having a rectangular vertical long shape (long-axis rectangular prism) provided with a plurality of through holes penetrating in the longitudinal direction through which the coil can be inserted and the coil passes through inside (see, for example, Patent Document 2).

[0005] The coil that is housed in this plastic molded product and modularized is called a slot coil. Further, the plastic molded product that houses the coil has a function of bundling a plurality of coils and electrically insulating the stator core from the coil or between the coils. The thicker the plate thickness of the plastic molded product, the higher the insulation between the stator core and the coil or between the coils. However, since the plate thickness of the plastic molded product becomes a resistance to the magnetic flux (magnetic lines of force) generated in the coil, when the plate thickness is thick, the number of magnetic lines of force passing through the stator core decreases, and the strength of the magnetic field generated in the stator core becomes weak. As a result, the induced current induced in the rotor becomes small, and as a result, the rotational force (torque) generated in the rotor becomes small.

[0006] Therefore, regarding the plate thickness of the plastic molded product used in the slot coil, it is required to be as thin as possible (for example, 0.3 mm or less) within the range that satisfies a predetermined insulation property. Further, since the torque of the electric motor depends on the magnetic flux density, the length of the coil side, and the current, regarding the overall length (height) of the plastic molded product, it is required to be as long as possible (for example, 200 mm or more) within the range that satisfies a predetermined heat resistance.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0008] In a plastic molded article for housing a coil, a vertically long through-hole for passing the coil is formed by a core pin having a long axis with a rectangular cross-section. When the plate thickness of the plastic molded article is, for example, 0.3 mm and the overall length is, for example, 200 mm, the cores pins are arranged in parallel in the mold in a state of being supported at both ends with an effective length of 200 mm with a gap of 0.3 mm between the core pins.

[0009] Therefore, it is necessary to uniformly fill the cavity with a gap of 0.3 mm and a length of 200 mm with molten resin by an injection molding machine.

[0010] However, since each of the core pins arranged in parallel is supported at both ends in the mold, the core pins will bend in a certain section due to the injection pressure of the molten resin. When the core pins bend, the flow path of the molten resin becomes narrower, or in some cases, the core pins come too close to each other and the molten resin does not flow, resulting in a short shot (void phenomenon). The plastic molded article with a short shot will be disposed of as a defective product.

[0011] Therefore, the present invention has been made in view of the problems of the above prior art, and an object thereof is to provide a plastic molding method capable of stably molding an insulator (plastic molded article) for a slot coil of a rotating electric machine having a thin-walled long-axis rectangular prism shape with a plurality of through-holes internally partitioned by a plurality of partition walls.

Means for Solving the Problems

[0012] The plastic molding method according to the present invention for achieving the above object is a plastic molding method for molding a plastic molded product (100) using a fixed mold (201) for molding a head (10) of the plastic molded product (100) whose interior is partitioned by a plurality of partition walls (11), a movable mold (202) for molding a body portion (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 portion (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, comprising: a step of pushing the first insert (204) from both sides by a first slide piece (205) with the first insert (204) locked to the fixed mold (201); and a step of molding a plastic molding intermediate (150) having a plurality of openings (20a) in the body portion (20) by pouring molten resin into the gaps between the first insert (204), the first slide piece (205), and the molds (201, 202, 203) with the first slide piece (205) having pushed the first insert (204) from both sides.

[0013] In the above configuration, since the first insert (204) is pushed from both sides by the first slide piece (205), it is possible to prevent the first insert (204) from being deflected by the injection pressure. Since the pitch (interval) between adjacent first inserts (204) is stabilized, the flow of the molten resin also becomes stable. As a result, the cavity in the mold is uniformly filled with the molten resin up to the very end.

[0014] The second feature of the plastic molding method according to the present invention is a step of pulling out the first insert (204) from the through hole (21) of the plastic molding intermediate (150), a step of 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), and a step of pressing the vicinity including the opening (20a) from both sides by a second slide piece (209) having a pressing surface (209a) that envelopes the opening (20a) with the second insert (208) inserted into the through hole (21), and a step of closing the opening (20a) with molten resin by flowing the molten resin into a plurality of the openings (20a) using the second slide piece (209).

[0015] In the above configuration, in consideration of the shrinkage of the plastic molding intermediate (150), a second insert (208) having a smaller cross section than the first insert (204) is inserted into the through hole (21), and the vicinity including the opening (20a) is pressed from both sides by the second slide piece (209). As a result, it becomes possible to close the opening (20a) with molten resin while maintaining the new plate thickness after shrinkage.

[0016] 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).

[0017] In the above configuration, by fitting the convex portion (205a) of the first slide piece (205) into the concave portion (204a) of the first insert (204), it becomes possible to stably fix the first insert (204). As a result, it becomes possible to suitably prevent the first insert (204) from being deflected by the injection pressure.

[0018] The fourth feature of the plastic molding method according to the present invention is that the second slide member (209) is configured to be connectable from a lateral direction orthogonal to the longitudinal direction of the second insert (208) at a height position where a film gate for injecting molten resin into the opening (20a) communicates with the opening (20a).

[0019] In the above configuration, the outer peripheral surface and the inner peripheral surface of the body portion (20) can be flush with each other, and the molten resin (20b) can be filled into the opening (20a).

[0020] The fifth feature of the plastic molding method according to the present invention is that the injection molding machine (207) is separately configured with a plasticizing portion (210) for plasticizing the resin by a screw and an injection portion (211) for injecting the molten resin by a plunger.

[0021] In the above configuration, the screw only performs a rotational movement to plasticize the resin. On the other hand, since the plunger only performs a reciprocating movement without receiving a reaction force from the screw, accurate metering of the molten resin and injection pressure can be ensured.

[0022] 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 a resin flow path (201c) through which the molten resin injected from the injection molding machine (207) flows communicates with a flange portion cavity (201a) for molding the flange portion (12) of the plastic molded product (100).

[0023] In the above configuration, since the flange portion cavity (201a) of the fixed mold (201) becomes a reservoir portion of the molten resin, the molten resin can be evenly and stably poured to the very end into the narrow gap between the first insert (204) and the movable mold (202).

[0024] The seventh feature of the plastic molding method according to the present invention is that the resin (20b) used to block the opening (20a) of the plastic molding intermediate (150) has the same or higher heat resistance than the resin used for molding the body portion (20).

[0025] In the above configuration, the sealing resin (20b) is less likely to peel off from the body portion (20b).

Effects of the Invention

[0026] According to the plastic molding method of the present invention, it becomes possible to stably mold a plastic molded product in the form of a thin-walled long-axis rectangular prism provided with a plurality of through holes whose interior is partitioned by a plurality of partition walls.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Embodiments for Carrying Out the Invention

[0028] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0029] 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 the 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 an insulating body for a slot coil that is inserted into a slot (not shown) of a stator core of a rotating electrical machine to insulate between the stator core and a coil or coils.

[0030] The interior is partitioned by a plurality (for example, five) of partition walls 11 and forms a thin-walled long-axis rectangular prism having a plurality (for example, six) of through-holes 21. The plate thickness t is 0.3 mm or less, desirably 0.2 mm, and the overall length L has, for example, 200 mm or more. The through-holes 21 are used for wiring a square conductor (not shown) that constitutes a slot coil (not shown) of a rotating electrical machine.

[0031] Also, flange portions 12 are respectively formed near the long sides of the head portion 10. Through this flange portion 12, the plastic molded product 100 is to be locked to a slot (not shown) of the stator core. The flange portion 12 has an L shape in consideration of the fluidity of the resin. As the material of the plastic molded product 100, any thermoplastic synthetic resin having heat resistance and electrical insulation may be used, and for example, a thermoplastic synthetic resin of liquid crystalline wholly aromatic polyester can be used.

[0032] Also, the plate-thickness portion corresponds to the space volume (cavity) into which the molten resin flows in the molding die 200 described later. Although details will be described later with reference to FIG. 3, the flange portion 12 also functions as a resin reservoir for evenly flowing the molten resin to the very end of the cavity in the die. Hereinafter, the molding method of this plastic molded product 100 will be described.

[0033] FIG. 2 is a cross-sectional explanatory view of a main part showing a plastic molding die 200 for molding the plastic molded product 100 from molten resin. This plastic injection mold 200 includes a fixed mold 201 where the tip of the core pin 204 locks to form the head 10 of the plastic molded product 100, a movable mold 202 where the core pin 204 penetrates through and joins to the fixed mold 201 to form the body 20 of the plastic molded product 100, a core mold 203 that integrally fixes the core pin 204, a core pin 204 that forms the through hole 21 of the plastic molded product 100, a slide piece 205 that pushes the core pin 204 from both sides, a hydraulic cylinder 206 that pushes the slide piece 205 with a predetermined force, and an injection molding machine 207 that injects molten resin into the gap between the molds. Hereinafter, each component will be described.

[0034] Figure 3 is a cross-sectional view taken along line A-A of Figure 2. As shown in Figure 3, the fixed mold 201 includes a flange portion cavity 201a that forms the flange portion 12 (Figure 1) of the plastic molded product 100, a core pin locking cavity 201b where the tip of the core pin 204 (hatched portion) locks, a head cavity 201c that forms the head 10 of the plastic molded product 100, and a resin supply passage 201c that supplies molten resin to the flange portion cavity 201a. Therefore, the space excluding the core pin 204 (hatched portion) from the head cavity 201c forms the plate thickness portion (portion with plate thickness t) of the head 10 of the plastic molded product 100.

[0035] Figure 4 is a cross-sectional view taken along line B-B of Figure 2. As shown in Figure 4, the movable mold 202 includes a body cavity 202a that forms 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 with plate thickness t) of the body 20 of the plastic molded product 100. Also, the movable mold 202 is connected to a moving mechanism (not shown) and is configured to be reciprocally movable in the horizontal direction.

[0036] Figure 5 is a cross-sectional view taken along line C-C of Figure 2. Figure 5(a) shows a state where the slide piece 205 is separated from the core pin 204. Figure 5(b) shows a state where the slide piece 205 has pushed through the core pin 204.

[0037] 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 on the core pin 204.

[0038] Regarding the shape of the convex portion 205a, for example, an R shape (hemispherical shape), a prism shape (quadrangular prism shape), a round prism shape (cylindrical shape, elliptical cylindrical shape), a pyramid shape (quadrangular pyramid shape), a conical shape or a wedge shape can be adopted, but it is not limited to these shapes. Also, regarding the mounting position of the slide piece 205 on the movable die 202, the slide piece 205 is mounted at a position where it can push past the vicinity of the center in the longitudinal direction (axial direction) of the core pin 204. Note that the shape of the concave portion 204a of the core pin 204 is uniquely determined from the shape of the convex portion 205a respectively.

[0039] Also, regarding the mounting position of the concave portion 204a of the core pin 204, for example, it is formed at two upper and lower positions or two left and right positions facing the convex portion 205a of the slide piece 205. Note that the cross-sectional shape of the body portion of the core pin 204 that does not face the convex portion 205a of the slide piece 205 forms a solid square.

[0040] As shown in Fig. 5(b), when the convex portion 205a of the slide piece 205 fits into the concave portion 204a of the core pin 204, the core pin 204 will be firmly fixed from the up and down directions by the slide piece 205. As a result, the core pin 204 becomes less likely to bend due to the injection pressure of the molten resin, and the molten resin can flow sufficiently to the very end.

[0041] Note that, among the cavity 202a (Fig. 4) of the movable mold 202, the molten resin does not flow into the overlapping portions with the core pin 204 and the slide block 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 block 205. Since the conducting wire is exposed at 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.

[0042] Fig. 6 is a cross-sectional view taken along the line D-D of Fig. 2. As shown in Fig. 6, the core mold 203 includes a core pin fixing cavity 202a for fixing the core pin 204. Note that 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 portion 20 of the plastic molded product 100.

[0043] Fig. 7 is an explanatory sectional view of the main part showing the injection molding machine 207 used in the plastic molding method of the present invention. This injection molding machine 207 separately and independently includes a plasticizing portion 210 for plasticizing the resin and an injection portion 211 for injecting the plasticized molten resin. Conventional injection molding machines inject the molten resin plasticized by the screw while plasticizing the resin with the screw. That is, the screw performs a forward movement while performing a rotational movement. Therefore, a part of the molten resin flows out in the direction opposite 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 hinders the injection of the molten resin by the screw, but it is difficult to quantitatively predict the magnitude of that force. As a result, the load for pushing the screw becomes unstable, deteriorating the filling accuracy of the molten resin. In addition, this force that pushes down the screw also causes defects in the screw.

[0044] 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 a rotational motion to plasticize the resin.

[0045] 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 perform a rotational motion. Also, since no protrusions such as threads are formed spirally on the surface of the plunger 211a, it is possible to attach a sealing material such as an O-ring to the surface of the plunger 211a. As a result, the molten resin does not flow backward from the gap between the plunger 211a and the injection cylinder 211b. That is, the force that pushes down the plunger 211a by the molten resin does not occur. As a result, the load that pushes the plunger 211a by the actuator 211c becomes stable, and it becomes possible to suitably control it by the load that pushes the injection amount of the molten resin. Thereby, the filling accuracy of the molten resin is significantly improved compared to conventional injection molding machines.

[0046] Hereinafter, a method for molding the plastic molded product 100 using the above plastic molding die 200 will be described.

[0047] FIG. 8 is a flowchart showing a method for molding the plastic molded product 100 by the plastic molding die 200. First, in process P1, the core pin 204 is attached to the core die 203.

[0048] Next, in process P2, the core die 203 to which the core pin 204 is attached is attached to the movable die.

[0049] Next, in process P3, the movable die 202 is joined to the fixed die 201.

[0050] Next, in process P4, the core pin 204 is pushed out from both sides by the slide block 205. FIG. 9 shows a state where the core pin 204 is pushed out from both sides by the slide block 205.

[0051] Next, in process P5, the injection molding machine 207 fills the mold with molten resin.

[0052] Next, in process P6, the slide member 205 is separated from the core pin 204.

[0053] FIG. 10 is an explanatory view showing a plastic molding intermediate 150 formed in the primary molding from process P1 to process P6. Due to the slide member 205 pushing out the core pins 204 from both sides, six openings 20a are formed on one side of the wide side surface of the body portion 20, and a total of twelve openings 20a are formed on both sides. The twelve openings 20a are blocked with resin in the secondary molding from process P7 to process P14. Hereinafter, the secondary molding process of blocking the twelve openings 20a with resin will be described.

[0054] Returning to FIG. 8, in process P7, the core mold 203 is separated from the movable mold 202.

[0055] Next, in process P8, the core pin 204 of the core mold 203 is replaced with a core pin 208 for secondary molding. The cross-section of the core pin 208 for secondary molding is smaller than the cross-section of the core pin 204 according to the shrinkage degree of the plastic molding intermediate 150.

[0056] Next, in process P9, the core mold 203 with the core pin 208 for secondary molding attached is attached to the movable mold 202 again.

[0057] Next, in process P10, a slide member 209 for secondary molding is attached to the movable mold 202 instead of the slide member 205.

[0058] FIG. 11 is a sectional view of the main part showing a plastic molding die 200A for secondary molding for blocking the openings 20a of the plastic molding intermediate 150 with resin. In this plastic molding die 200A, the core pin 204 and the slide member 205 are replaced with a core pin 208 for secondary molding and a slide member 209 for secondary molding, respectively.

[0059] This slide member 209 for secondary molding has a pressing surface 209a for cutting through the vicinity including the opening 20a of the body portion 20. The slide member 209 for secondary molding is configured such that a film gate (not shown) for injecting molten resin into the opening 20a can be connected from a lateral direction orthogonal to the longitudinal direction of the core pin 208 for secondary molding. Therefore, when closing the opening 20a with resin in the following process P12, the film gate (not shown) is connected to the slide member 209 for secondary molding, 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.

[0060] Returning to FIG. 8, in process P11, the slide member 209 for secondary molding cuts through the vicinity including the opening 20a of the plastic molding intermediate 150 from both sides. FIG. 12 shows a state where the slide member 209 for secondary molding has cut through the vicinity including the opening 20a of the plastic molding intermediate 150 from both sides.

[0061] Next, in process P12, the opening 20a of the plastic molding intermediate 150 is closed with molten resin. Regarding the resin to be used, it may be different from the resin used in the plastic molding intermediate 150 as long as its heat resistance is equal to or higher.

[0062] Next, in process P13, the slide member 209 for secondary molding is separated.

[0063] Next, in process P14, the movable mold 202 is separated from the fixed mold 201. FIG. 13 is a perspective view showing the plastic molded product 100A in which the opening 20a of the plastic intermediate molded product 150 is closed with a different resin (sealing resin 20b). The sealing resin 20b has heat resistance and insulation properties equal to or higher than those of the resin of the body portion 20. Note that the above plastic molded product 100 is obtained by closing the opening 20a of the plastic molding intermediate 150 with the same resin as the resin of the body portion 20.

[0064] As described above, according to the plastic molding method of the present invention, it is possible to stably mold a plastic molded product in the form of a thin-walled long-axis rectangular prism having a plurality of through holes 21 inside partitioned by a plurality of partition walls 11, for example, having a plate thickness of 0.3 mm or less and a length of 200 mm or more.

[0065] As described above, the plastic molding method of the present invention and the plastic molded product molded by the method have been described with reference to the drawings. However, the present invention is not limited to the above only. That is, various changes and modifications can be made within the technical scope of the present invention. For example, regarding the mounting position and number of the slide members 205 that push out the core pins 204 from both sides, not only in the form of pushing out only the vicinity of the center of the core pins 204 from both sides, but also a plurality of positions of the core pins 204 may be pushed out from both sides at predetermined intervals according to the overall length L of the plastic molded products 100 and 100A.

[0066] Also, regarding the convex portions 205a of the slide members 205, although the six convex portions 205a are arranged in a row along the direction orthogonal to the longitudinal direction of the core pins 204, they may be arranged in a plurality of rows.

[0067] Also, regarding the gate for supplying the molten resin to the flange portion cavity 201a of the fixed mold 201, various gates other than the gate shown in FIG. 3 can be used. A modified example of the fixed mold 201 using a fan gate will be described below.

[0068] FIG. 14 is a sectional explanatory view of a main part showing a fixed mold 201A provided with a fan gate 201d. FIG. 14(a) is a sectional view taken along the cutting position A-A of FIG. 2. FIG. 14(b) is a sectional view taken along the line E-E of FIG. 14(a).

[0069] As shown in Fig. 14(a), the molten resin is configured to be supplied to the long side of the flange portion cavity 201a through the fan gate 201d. In particular, a cylindrical control pin 201e is vertically formed inside the fan gate 201d. The control pin 201e is formed at an appropriate position on the perpendicular bisector (axis of symmetry) within an isosceles triangle having the long side of the flange portion cavity 201a as the 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 passage 201c is evenly divided in the left - right direction of the control pin 201e by this control pin 201e.

[0070] Note that, as shown in Fig. 14(b), the cross - sectional shape of the fan gate 201d forms a throttle structure in which the height decreases toward the flange portion cavity 201a. On the other hand, as shown in Fig. 14(a), the planar shape of the fan gate 201d forms a width - expanding structure in which the width expands toward the flange portion cavity 201a. Therefore, the flow resistance decreases as the distance from the control pin 201e in the lateral direction increases. As a result, the moving distance of the outer molten resin becomes longer than that of the inner molten resin, but the flow velocity of the outer molten resin becomes faster than that of the inner molten resin. Conversely, the moving distance of the inner molten resin becomes shorter than that of the outer molten resin, but the flow velocity of the inner molten resin becomes slower than that of the outer molten resin. As a result, the outer and inner molten resins reach the flange portion cavity 201a at almost the same timing. That is, the molten resin injected from the resin supply passage 201c is evenly supplied along the long side of the flange portion cavity 201a at almost the same timing.

[0071] Thereby, the molten resin evenly enters each narrow gap between the core pins 204 at almost the same timing, and the molten resin is stably filled evenly to the very end. This uniform inflow of the molten resin without a time difference also significantly reduces the load that the core pins 204 receive from the flow.

[0072] Incidentally, the flow of the molten resin that collides with the control pin 201e generates a vortex, and the molten resin flowing into the flange portion cavity 201a may become turbulent. In this case, the molten resin does not evenly enter the narrow gaps between the core pins 204. Hereinafter, a fixed mold 201B provided with a reservoir portion (buffer portion) for suppressing (calming) the turbulent flow of the molten resin will be described, which is provided at the rear stage of the fan gate 201d and the front stage of the flange portion cavity 201a.

[0073] FIG. 15 is a cross-sectional explanatory view of a main part showing a fixed mold 201B provided with a reservoir portion 20f. FIG. 15(a) is a cross-sectional view taken along the line A-A in FIG. 2. FIG. 15(b) is a cross-sectional view taken along the line E-E in FIG. 15(a).

[0074] In this fixed mold 201B, a reservoir portion 201f and a film gate 201g are continuously provided at the outlet of the fan gate 201d, respectively. The reservoir portion 201f has, for example, a rectangular cross-section and forms a box shape with a long axis. The length in the axial direction (longitudinal direction) is longer than the long side of the flange portion cavity 201a. A film gate 201g with a constant height is integrally formed in the reservoir portion 201f at the outlet of the reservoir portion 201f.

[0075] Therefore, when the molten resin flowing out from the fan gate 201d becomes turbulent, the molten resin flows into and expands in the reservoir portion 201f to be calmed, and is rectified into a laminar flow with a constant thickness (height) by the film gate 201g and supplied to the long side of the flange portion cavity 201a. As a result, the molten resin that has become laminar (the flow has become stable) evenly enters each of the narrow gaps between the core pins 204 at almost the same timing, and the molten resin is stably filled evenly to the very end. This uniform and stable inflow of the molten resin without a time difference also significantly reduces the load on the core pins 204 from the flow.

[0076] Incidentally, the pushing by the engagement of the convex portion 205a of the slide piece 205 and the concave portion 204a of the core pin 204 is a bending suppression means that preferably suppresses the bending of the core pin 204 and stabilizes the pitch (interval) between the core pins 204, but on the other hand, it can also be a flow resistance that hinders the flow of the molten resin. Also, regarding the surface of the slide piece 205 that faces the core pin 204 and excludes the convex portion 205a, it does not contribute much to suppressing the bending of the core pin 204.

[0077] Therefore, in order to prevent the molten resin flow from being inhibited as much as possible while maintaining the bending suppression function in the slide piece 205, for example, (1) shortening the longitudinal length of the pushing surface excluding the convex portion 205a of the slide piece 205 to shorten the length of the slide piece through which the molten resin passes, and (2) increasing the area of the gap through which the molten resin passes in the slide piece 205 can be considered. Below, the slide piece 205' with the longitudinal length of the pushing surface excluding the convex portion 205a of the slide piece 205 shortened will be described.

[0078] FIG. 16 is an explanatory diagram showing a slide piece 205' with the longitudinal length of the pushing surface excluding the convex portion 205a of the slide piece 205 shortened. FIG. 16(a) shows the pushing surface of the slide piece 205 against the core pin 204 as a comparative example. FIG. 16(b) shows the pushing surface of the slide piece 205' against the core pin 204.

[0079] 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, and 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.

[0080] FIG. 17 is an explanatory view showing a plastic molded intermediate body 150A molded by a plastic injection mold incorporating a slide piece 205'. The openings 20a corresponding to the slide piece 205' form one opening that communicates laterally with each other. Therefore, for the injection of resin to seal the upper and lower two openings 20a of the body portion 20, it will be injected laterally from one gate into each opening 20a. Next, the slide piece 205'' will be described, which is designed to reduce the flow resistance by increasing the gap through which the molten resin flows in the slide piece 205.

[0081] FIG. 18 is a cross-sectional explanatory view of the main part showing the slide piece 205'' which is designed to reduce the flow resistance by increasing the area of the gap through which the molten resin passes in the slide piece 205. FIG. 18(a) shows the state where the above slide piece 205 pushes the core pin 204 from both sides as a comparative example. FIG. 18(b) shows the state where the above slide piece 205'' pushes the core pin 204 from both sides.

[0082] As shown in FIG. 18(b), in the slide piece 205'', by making the protruding height H'' from the lower surface 205b of the convex portion 205a'' higher than that of the slide piece 205 (H''>H), the six consecutive convex portions 205a'' push the core pin 204 from both sides (single pushing by the convex portion 205a''). As a result, a new gap will be generated between the lower surface 205b of the slide piece 205'' and the core pin 204. In addition, the gap between the core pin 204 and the core pin 204 will also increase. Thereby, since the area of the gap through which the molten resin passes in the slide piece 205'' increases significantly compared to the slide piece 205, the flow resistance to the molten resin decreases significantly compared to the slide piece 205, and the molten resin will be filled to the very end.

[0083] FIG. 19 is an explanatory view showing a plastic molded intermediate body 150B molded by a plastic injection mold incorporating a slide piece 205”. The openings 20a corresponding to the convex portions 205a of the slide piece 205” each form independent openings. Therefore, with respect to the injection of resin for sealing the six openings 20a on one side of the body portion 20, it is injected from a direction perpendicular to each opening 20a by a tuff gate having six gates.

Explanation of Signs

[0084] 10 Head 11 Partition Wall 12 Flange Portion 20 Body Portion 20a Opening 20b Sealing Resin 21 Through Hole 100 Plastic Molded Product 100A Plastic Molded Product 150 Plastic Molded Intermediate 200 Plastic Injection Mold 200A Plastic Injection Mold 201 Fixed Mold 201A Fixed Mold A 201B Fixed Mold B 201a Flange Portion Cavity 201b Core Pin Locking Cavity 201c Resin Supply Flow Path 201d Fan Gate 201e Control Pin 201f Storage Portion 201g Film Gate 202 Movable Mold 202a Body Portion Cavity 203 Core Mold 203a Core Pin Fixing Cavity 204 Core Pin (First Insertion) 204a Concave Portion 205 Slide Piece (First Slide Piece) 205a Convex Portion 206 Hydraulic Cylinder 207 Injection molding machine 208 Core pin for secondary molding (second insert) 209 Slide piece for secondary molding (second slide piece) 209a Pressing surface 210 Plasticizing section 210a Screw 210b Plasticizing cylinder 210c Plasticizing motor 211 Injection section 211a Plunger 211b Injection cylinder 211c Actuator

Claims

1. A fixed mold (201) for molding the head (10) of a plastic molded product (100) whose interior is partitioned 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 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) for fixing the first insert (204), An injection molding machine (207) for injecting molten resin, and a plastic molding method for molding the plastic molded product (100) using the same, A step of pushing out the first insert (204) from both sides in a direction orthogonal to the longitudinal direction of the first insert (204) by a first slide member (205) with the first insert (204) locked to the fixed mold (201), A step of forming a plastic molding intermediate (150) having a plurality of openings (20a) in the body (20) by pouring molten resin into the gaps between the first insert (204), the first slide member (205), and the molds (201, 202, 203) with the first slide member (205) pushing out the first insert (204) from both sides in a direction orthogonal to the longitudinal direction of the first insert (204), And a step of closing the plurality of openings (20a). A plastic molding method characterized by the above.

2. In the plastic molding method according to Claim 1, A step of pulling out the first insert (204) from the through hole (21) of the plastic molding intermediate (150), A step of 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), A step of pushing out the vicinity including the opening (20a) from both sides in a direction orthogonal to the longitudinal direction of the second insert (208) by a second slide member (209) having a pressing surface (209a) that envelopes the opening (20a) with the second insert (208) inserted into the through hole (21), And a step of closing the opening (20a) with molten resin by pouring molten resin into the plurality of openings (20a) using the second slide member (209). A plastic molding method characterized by the above.

3. In the plastic molding method according to Claim 1 or 2, Protrusions (205a) are formed on the surface of the first slide member (205), A recess (204a) into which the convex portion (205a) fits is formed on the surface of the first insert (204) facing the first slide piece (205). A plastic molding method characterized by this.

4. In the plastic molding method according to claim 2, The second slide piece (209) is configured to be connectable to the second slide piece (209) from a lateral direction orthogonal to the longitudinal direction of the second insert (208) at a height position where a film gate for injecting molten resin into the opening (20a) communicates with the opening (20a). A plastic molding method characterized by this.

5. In the plastic molding method according to any one of claims 1 to 4, The injection molding machine (207) has a plasticizing portion (210) for plasticizing the resin by a screw and An injection portion (211) for injecting the molten resin by a plunger is separately configured. A plastic molding method characterized by this.

6. In 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 communicates with a flange portion cavity (201a) for molding the flange portion (12) of the plastic molded product (100). A plastic molding method characterized by this.

7. In the plastic molding method according to claim 2, 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 for molding the body portion (20). A plastic molding method characterized by this.

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