JP2021030703A - Injection molding device - Google Patents

Abstract

To provide an injection molding device capable of maintaining product strength and achieving precision of product size.SOLUTION: An injection molding device includes: a first channel 41 formed in a gate body 30 at a hot sprue bottom edge and having a first channel diameter C41; a first diameter reduction part 42 provided on a downstream side of the first channel and on a downstream side than a bottom edge 35a of a heater 35 to reduce the diameter from the first channel diameter to a second channel diameter C42 in a flow direction; a diameter increasing part 43,44,45 provided on a downstream side of the first diameter reduction part to increase the diameter in a flow direction from the second channel diameter to a third channel diameter C43 over the gate body to a cold sprue 3a; and a second diameter reduction part 46 provided in the cold sprue to reduce the diameter in the flow direction from the third channel diameter to a forth channel diameter C44. The second channel diameter is larger than the forth channel diameter, the first channel diameter is larger than the second channel diameter, and the third channel diameter is larger than the first channel diameter.SELECTED DRAWING: Figure 2

Description

The present invention relates to an injection molding device.

In injection molding, from the viewpoint of environmental protection, it is required to reduce waste during molding at the same time as recycling resin products.

Injection molding dies are roughly divided into cold runners and hot runners. Generally, in a cold runner, the sprue runner portion is solidified and an unnecessary portion is formed. In the hot runner mold, the sprue runner portion is heated and controlled by a heater to keep it in a fluidized state at all times, so that only the product is continuously taken out without forming an unnecessary portion.
Hot runners have the advantages of saving materials, eliminating the need for cutting and crushing operations such as sprue, reducing the amount of recycled materials, and shortening the molding cycle, thus improving manufacturing efficiency.

In the hot runner, the gate body is arranged at a position where the resin material is supplied to the cavity side. The tip of the gate body is in contact with the cold side of the cavity or runner.
As described in Patent Document 1, the gate body is heated by a heater or the like.

As described in Patent Document 1, when the temperature drops too much at the tip of the gate body, a problem occurs in which the molten resin solidifies in the gate. Alternatively, even if the temperature drop does not lead to solidification, there is a possibility that problems such as a decrease in the strength of the product or a decrease in the dimensional accuracy of the product may occur as a defect in the injection state into the cavity.

Jikkai Sho 58-3227

However, when the heater is arranged around the gate body, there is a problem that the diameter dimension of the gate body increases and the hot runner itself becomes larger than the product size. Further, in order to solve this problem, it is necessary to incorporate a heater into the gate body, but in this case, there is a problem that the number of parts increases, the number of assembly work steps increases, and the productivity decreases. is there.

Further, in order to prevent the temperature from dropping at the tip of the gate body, it is conceivable to arrange a smaller heater at the tip of the gate body. However, in this case, there is a problem that the number of parts is further increased, the number of assembly work steps is increased, and the productivity is lowered.

Alternatively, in order to prevent the temperature drop at the tip of the gate body, when the temperature drop at the tip of the gate body is suppressed more than necessary, it is necessary to separate the cavity from the cavity that needs cooling. For this reason, the resin flow path between the gate body and the cavity becomes long, which causes a problem that the amount of waste material or recycled material increases.
Regarding the ratio of the recycled material to be mixed, there is an upper limit defined by the product strength and the like, and as a result, there is a problem that the amount of the resin material discharged increases.

Further, when the diameter dimension at the tip of the gate body is reduced in order to reduce the contact area with the cold side for the purpose of optimizing the resin temperature, the strength of the gate body is insufficient and the resin leaks near the tip of the gate body. May occur, which is not preferable. Further, in this case, the injection pressure of the resin material may be insufficient and the dimensional accuracy of the product may not be maintained, which is not preferable.

Further, in order to prevent this, if the diameter dimension at the tip of the gate body is not reduced, the area where the tip of the gate body contacts the cold side cannot be reduced. For this reason, heat escapes from this contact portion, and as described above, there may be a problem that the product strength or the product dimensions do not satisfy the predetermined conditions.

The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent heat escape near the tip of the gate body, maintain the strength of the gate body, maintain the product strength, and ensure the accuracy in the product dimensions. It is something that we are trying to achieve.

The injection molding apparatus of the present invention
It has an injection molding die and an injection molding machine that injects a molten resin material into the injection molding die from an injection nozzle.
The injection molding die is
With a fixed plate
A movable plate that forms a product cavity facing the fixed plate,
A hot sprue that serves as a flow path for the molten resin material,
The gate body as the lower end of the hot sprue,
A heater arranged around the gate body to heat the gate body, and
A cold sprue that becomes a flow path of the molten resin material downstream of the hot sprue and is connected to the product cavity and becomes a cold side of the flow path.
Have,
The flow path is
A first flow path formed inside the gate body in which the heater is arranged around the gate body.
A first diameter-reduced portion located downstream of the lower end of the heater on the downstream side of the first flow path and reducing the diameter from the first flow path to the throttle portion along the flow direction.
A diameter-expanded portion formed from the gate body to the cold sprue on the downstream side of the first diameter-reduced portion and expanded in diameter from the throttle portion along the flow direction.
A second diameter-reduced portion formed on the cold sprue and reduced in diameter from the enlarged-diameter portion along the flow direction, and a second diameter-reduced portion.
Have,
The first flow path has a first flow path diameter, and has a first flow path diameter.
The first reduced diameter portion is reduced in diameter from the first flow path diameter to the second flow path diameter along the flow direction.
The throttle portion has the second flow path diameter and has.
The diameter-expanded portion is expanded from the diameter of the second flow path to the diameter of the third flow path along the flow direction.
The second diameter-reduced portion is reduced in diameter from the third flow path diameter to the fourth flow path diameter along the flow direction.
The second flow path diameter is larger than the fourth flow path diameter,
The first flow path diameter is larger than the second flow path diameter,
The above problem was solved by making the third flow path diameter larger than the first flow path diameter.

The injection molding apparatus of the present invention is the above-mentioned injection molding apparatus.
The injection molding die has a gate bush that comes into contact with the cold side.
The tip of the gate body can be inserted inside the gate bush.

In the injection molding apparatus of the present invention
The tip surface of the gate body can be separated from the opposite surface of the gate bush.

In the injection molding apparatus of the present invention
The thermal conductivity of the gate body can be lower than that of the gate bush.

The injection molding apparatus of the present invention is the injection molding apparatus according to any one of the above.
A bushing is placed inside the gate bush.
The bushing can be disposed around the tip surface of the gate body with the gate bushing.

In the injection molding apparatus of the present invention
The bushing may have a lower thermal conductivity than the gate bush.

In the injection molding apparatus of the present invention
The bushing is provided with a contact portion that contacts the inner peripheral surface of the gate bush and a relief portion that does not contact the gate bush on the downstream side of the contact portion on the outer periphery thereof.
The relief portion may be arranged on the downstream side of the flow path with respect to the contact portion.

In the injection molding apparatus of the present invention
In the gate body, the first reduced diameter portion may be made of a spherical surface, and the enlarged diameter portion may be made of a tapered surface.

According to the present invention, it is possible to prevent heat escape at the tip of the gate body, maintain the strength of the gate body, maintain the product strength, and secure the accuracy in the product dimensions.

It is sectional drawing of the main part which shows the embodiment of the injection molding apparatus which concerns on this invention. It is an enlarged sectional view which shows the vicinity of the gate body in embodiment of the injection molding apparatus which concerns on this invention. It is sectional drawing which shows the gate body in embodiment of the injection molding apparatus which concerns on this invention. It is sectional drawing which shows the bushing in embodiment of the injection molding apparatus which concerns on this invention. It is a schematic diagram which shows the measurement of the overall diameter in the Example which concerns on this invention. It is a figure which shows the measurement result of the inner diameter-outer diameter wall thickness in the Example which concerns on this invention. It is a figure which shows the measurement result of the inner diameter-outer diameter wall thickness in the Example which concerns on this invention.

Hereinafter, embodiments of the injection molding apparatus according to the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing an injection molding apparatus according to the present embodiment, in which reference numeral 100 is an injection molding apparatus.

The injection molding die 110 includes a fixed plate 1, an intermediate plate 4 and a movable plate 2 provided so as to be in contact with and separated from the fixed plate 1. The fixed plate 1, the intermediate plate 4, and the movable plate 2 move at least to each other in the vertically shown vertical direction (mold opening / closing direction) to open and close, and form a product cavity 3 that forms a molded product when the mold is closed. To do. The opening and closing of the intermediate plate 4 and the movable plate 2 with respect to the fixed plate 1 can be appropriately set according to the shape of the product to be molded.

The fixed plate 1 includes a fixed-side template 6 as a substrate, and a fixed-side receiving plate 7 as a substrate fixed to a surface (upper surface in the drawing) opposite to the movable plate 2 in the fixed-side template 6. A fixed-side mounting plate 9 fixed via a spacer block 8 is provided on a surface of the fixed-side receiving plate 7 opposite to the movable plate 2. The fixed-side mounting plate 9 is mounted on the fixed-side platen of the injection molding machine 103. Further, a manifold 11 is arranged in the space between the fixed side receiving plate 7, the spacer block 8 and the fixed side mounting plate 9. A support pad 12 is interposed between the manifold 11 and the fixed side receiving plate 7 and the fixed side mounting plate 9.

A tubular hot sprue bush (sprue bush) 13 is fixed to the surface of the manifold 11 facing the fixed side mounting plate 9. The hot sprue bush 13 penetrates the fixed side mounting plate 9 and is connected to the injection nozzle 103a of the injection molding machine 103. The inside of the hot sprue bush 13 forms a hot sprue 14 which is an inlet portion of a flow path (material passage) 40 described later. Further, a heater 15 as a heating means is provided on the outer periphery of the hot sprue bush 13. A tubular heater cover that covers the heater 15 may be provided on the outer periphery of the heater 15. Further, a locating ring 17 is fixed to the outer surface of the fixing plate 9 so as to surround the hot sprue bush 13.

The manifold 11 has a runner 21 formed inside, which is a branch path of the flow path (material passage) 40. The runner 21 branches from one inlet portion 21a communicating with the hot sprue 14, and has an outlet portion 21b corresponding to each toward the product cavity 3 on a surface close to the fixed side receiving plate 7. Further, the manifold 11 is provided with a heater (not shown) as a heating means for heating the runner 21.

A gate body 30 is connected to the outlet portion 21b of the runner 21 in the manifold 11. The gate body 30 projects substantially vertically toward the movable plate 2 from the surface 7a of the fixed side receiving plate 7 facing the intermediate plate 4 side. The gate body 30 is fixed to the fixed side receiving plate 7.
The gate body 30 has a tubular portion 31 and a flange portion 32 having an enlarged diameter around the end portion on the upstream side of the tubular portion 31, that is, the manifold 11 side.

The flange portion 32 of the gate body 30 is fitted in the recess 27 formed on the surface of the fixed side receiving plate 7 on the manifold 11 side. The flange portion 32 is sandwiched and fixed by the manifold 11 and the fixed side receiving plate 7. The gate body 30 is inserted into the recess 27 of the fixed side receiving plate 7 and the gate bush 33 of the fixed side template 6.
The tubular portion 31 of the gate body 30 is arranged in the gate bush 33 of the fixed side template 6. A portion of the tubular portion 31 that is close to the flange portion 32 in the axial direction penetrates the fixed side receiving plate 7. A portion of the tubular portion 31 that is separated from the flange portion 32 is inserted into the gate bush 33 of the fixed side template 6.

The fixed-side template 6 includes a positioning cylinder 61 fixed to the surface of the fixed-side receiving plate 7 on the intermediate plate 4 side, and a gate bush 33 as a hot sprue forming member fitted inside the positioning cylinder 61. doing.
The positioning cylinder 61 is fitted in a tubular inner peripheral presser penetrating the fixed side template 6. A gate bush 33 is fitted in the positioning cylinder 61. The gate bush 33 penetrates the fixed side template 6. The tip surface 33a of the gate bush 33 faces the cold runner 3a communicating with the product cavity 3.

A heater 35, which is a heating means for heating the flow path (material passage) 40, is provided around the tubular portion 31 of the gate body 30. The lower end 35a side of the heater 35 is located inside the gate bush 33. The outer peripheral surface of the heater 35 and the inner peripheral surface of the gate bush 33 are separated from each other. A gap is formed between the outer peripheral surface of the heater 35 and the inner peripheral surface of the gate bush 33. The gate bush 33 acts as a tubular heater cover that covers the heater 35.

The front end surface 30a of the gate body 30 faces the bottom surface 33b of the gate bush 33. The front end surface 30a of the gate body 30 is separated from the bottom surface 33b of the gate bush 33. A gap g is formed between the front end surface 30a of the gate body 30 and the bottom surface 33b of the gate bush 33.
The thermal conductivity of the gate body 30 is lower than that of the gate bush 33. Further, the gate body 30 can be formed of hot tool steel having high strength, high hardness, high toughness, and high specific heat as compared with other components of the fixed plate 1.

A bushing 34 is arranged at the bottom position of the gate bush 33. The bushing 34 is arranged around the tip surface 30a of the gate body 30. The bushing 34 is arranged between the bushing 34 and the gate bush 33 at the tip of the gate body 30. The bushing 34 is separated from the lower end 35a of the heater 35 in the axial direction of the tubular portion 31. The bushing 34 is located closer to the intermediate plate 4 than the lower end 35a of the heater 35 in the axial direction of the tubular portion 31.
The thermal conductivity of the bushing 34 is lower than that of the gate bushing 33. The thermal conductivity of the bushing 34 is lower than the thermal conductivity of the gate body 30. The bushing 34 can be formed from, for example, SUS material.

The intermediate plate 4 is located between the fixed plate 1 and the movable plate 2. The intermediate plate 4 has a cavity block for forming a product cavity 3 on the movable plate 2 side. Further, the intermediate cylinder 4a is fitted in the tubular inner peripheral presser penetrating the cavity block. A cold runner 3a is formed in the intermediate cylinder 4a. A temperature control passage for passing the temperature control fluid may be formed in the cavity block.

The movable plate 2 includes a movable side mounting plate attached to the fixed side platen of the injection molding machine 103, a movable side receiving plate fixed to the surface of the movable side mounting plate on the intermediate plate 4 side close to the fixed plate 1, and the movable side receiving plate. It is provided with a movable side template fixed to the surface of the intermediate plate 4 in the movable side receiving plate. The movable side template is composed of a positioning frame fixed to the surface of the movable side receiving plate on the intermediate plate 4 side and a core block as a cavity forming member fitted inside the positioning frame. Each of these core blocks forms a product cavity 3. Further, the positioning frame is tapered and fitted to the positioning frame of the fixed plate 1. A temperature control passage for passing a temperature control fluid such as cooling water is formed in the core block.
The intermediate plate 4 and the movable plate 2 are formed with a product cavity 3 and a cold runner 3a communicating with the product cavity 3.

The gate body 30 communicates with the hot sprue 14 of the hot sprue bush 13 and the runner 21 of the manifold 11, and forms a flow path (material passage) 40 together with the gate bush 33. The gate body 30 and the gate bush 33 form the lower end of the hot sprue as a flow path. The hot sprue as a flow path communicates with the product cavity 3 via the cold runner 3a.

FIG. 2 is an enlarged cross-sectional view showing the vicinity of the gate body and the gate bush in the present embodiment.
Inside the gate body 30 and the gate bush 33, a flow path (material passage) 40 from the manifold 11 side to the tip surface 33a of the gate bush 33 is formed.
This flow path (material passage) 40 communicates with the product cavity 3.

As shown in FIG. 2, the flow path (material passage) 40 includes a first flow path 41, a first diameter reduction portion 42, a first diameter expansion portion (diameter expansion portion) 43, and a second diameter expansion portion (a second diameter expansion portion). It has a diameter-expanded portion) 44, a third diameter-expanded portion (diameter-expanded portion) 45, and a second diameter-reduced portion 46.
In the flow path (material passage) 40, the first reduced diameter portion 42 is continuous with the downstream side of the first flow path 41. The first diameter-expanded portion (diameter-expanded portion) 43 is continuous with the downstream side of the first diameter-reduced portion 42. The second diameter-expanded portion (diameter-expanded portion) 44 is continuous with the downstream side of the first diameter-expanded portion (diameter-expanded portion) 43. The third diameter-expanded portion (diameter-expanded portion) 45 is continuous with the downstream side of the second diameter-expanded portion (diameter-expanded portion) 44. The second diameter reduction portion 46 is continuous with the downstream side of the third diameter expansion portion (diameter expansion portion) 45.

The first flow path 41 is formed inside the tubular portion 31 of the gate body 30. The first flow path 41 is formed inside the tubular portion 31 of the gate body 30 at a position where the heater 35 is arranged around it. The first flow path 41 has a first flow path diameter C41, and has a first flow path diameter C41 that is substantially the same in the flow direction of the flow path 40. The first flow path 41 is formed to have a substantially circular cross section, that is, a cylindrical shape.

The first diameter-reduced portion 42 is arranged on the downstream side of the first flow path 41 and on the downstream side of the lower end 35a of the heater 35, and the diameter is reduced from the first flow path 41 to the throttle portion 36 along the flow direction. The first reduced diameter portion 42 is reduced in diameter from the first flow path diameter C41 to the second flow path diameter C42 along the flow direction. The first reduced diameter portion 42 is formed as a spherical surface. The upper end of the first reduced diameter portion 42 is formed at a position equal to the lower end 35a of the heater 35 or upstream of the lower end 35a of the heater 35 in the flow direction of the flow path 40.
The boundary between the first flow path 41 and the first reduced diameter portion 42 coincides with the lower end 35a of the heater 35 in the flow direction of the flow path 40.
The throttle portion 36 is separated from the lower end 35a of the heater 35 and the inner peripheral surface of the gate bush 33 in the flow direction of the flow path 40. The throttle portion 36 is formed at a position downstream of the lower end 35a of the heater 35 in the flow direction of the flow path 40.
The throttle portion 36 has a second flow path diameter C42. The throttle portion 36 is formed at a position downstream of the lower end 35a of the heater 35 in the flow direction of the flow path 40.

The first diameter-expanded portion (diameter-expanded portion) 43 is formed inside the gate body 30 from the throttle portion 36 to the tip surface 30a of the gate body 30 on the downstream side of the first diameter-reduced portion 42. The first diameter-expanded portion (diameter-expanded portion) 43 expands in diameter from the throttle portion 36 to the tip surface 30a along the flow direction. The first diameter-expanded portion (diameter-expanded portion) 43 is formed as a tapered surface.
At a position corresponding to the tip surface 30a of the gate body 30, the flow path 40 has a flow path diameter C30a.

The second diameter-expanded portion (diameter-expanded portion) 44 is formed inside the gate bush 33 from the tip surface 30a of the gate body 30 to the tip surface 33a of the gate bush 33. The second diameter-expanded portion (diameter-expanded portion) 44 expands in diameter to the tip surface 33a along the flow direction. The second diameter-expanded portion (diameter-expanded portion) 44 is formed as a tapered surface.
At a position corresponding to the tip surface 33a of the gate bush 33, the flow path 40 has a flow path diameter C33a.

Both the first diameter-expanded portion (diameter-expanded portion) 43 and the second diameter-expanded portion (diameter-expanded portion) 44 are formed of tapered surfaces. The first diameter-expanded portion (diameter-expanded portion) 43 and the second diameter-expanded portion (diameter-expanded portion) 44 are flush with each other and have the same diameter expansion ratio. The first diameter expansion portion (diameter expansion portion) 43 expands from the second flow path diameter C42 to the flow path diameter C30a along the flow direction, and the second diameter expansion portion (diameter expansion portion) 44 expands from the flow path diameter C30a in the flow direction. The diameter is expanded along the flow path diameter C33a.

The third diameter-expanded portion (diameter-expanded portion) 45 is formed as a cold runner 3a from the tip surface 33a of the gate bush 33 and expands in diameter to the third flow path diameter C43. Here, the third flow path diameter C43 can be a virtual diameter dimension with respect to the total flow path cross section in the cold runner 3a. This is because it is possible to cope with the case where the cold runner 3a is branched into a plurality of flow paths.
The third diameter-expanded portion (diameter-expanded portion) 45 has a larger diameter-expanded ratio than the diameter-expanded ratio of the first diameter-expanded portion (diameter-expanded portion) 43 and the second diameter-expanded portion (diameter-expanded portion) 44. Further, the third diameter-expanded portion (diameter-expanded portion) 45 has a large third flow path diameter C43 by branching as a cold runner 3a.

The second diameter-reduced portion 46 is formed in the cold runner 3a and has a diameter reduced from the third diameter-expanded portion (diameter-expanded portion) 45 to the product cavity 3 along the flow direction. The second reduced diameter portion 46 is reduced in diameter from the third flow path diameter C43 to the fourth flow path diameter C44 along the flow direction.

Here, regarding the magnitude relationship of the flow path diameter in the flow path 40, the second flow path diameter C42 is larger than the fourth flow path diameter C44, the first flow path diameter C41 is larger than the second flow path diameter C42, and the first flow path diameter C41 is larger than the first flow path diameter C41. Also, the third flow path diameter C43 is large.

FIG. 3 is a cross-sectional view showing the gate body in the present embodiment. FIG. 4 is a cross-sectional view showing the bushing in the present embodiment.
As shown in FIG. 3, the gate body 30 has a tubular portion 31 and a flange portion 32 having an enlarged diameter around an end portion of the tubular portion 31 on the manifold 11 side.
The flange surface 32a on the manifold 11 side of the flange portion 32 is made flat so as to be in close contact with the lower surface of the manifold 11. On the surface 32b of the flange portion 32 opposite to the manifold 11, a ridge 32b1 protruding toward the opposite side of the manifold 11 is provided around the peripheral edge portion. The ridge 32b1 is in contact with the recess 27 formed on the surface of the fixed side receiving plate 7 on the manifold 11 side.

On the surface 32b of the flange portion 32 opposite to the manifold 11, the inner diameter in the radial direction close to the tubular portion 31 is a recess 32b2 recessed toward the manifold 11 side as compared with the ridge 32b1. The recess 32b2 does not come into contact with the recess 27 formed on the surface of the fixed side receiving plate 7 on the manifold 11 side.

The tubular portion 31 has a cylindrical shape. The tip surface 30a, which is the lower end of the tubular portion 31, is formed in a flat shape. The tip surface 30a is orthogonal to the axial direction of the tubular portion 31. The flange surface 32a of the flange portion 32, which is the upper end of the gate body 30, is formed in a flat shape. The flange surface 32a is a plane orthogonal to the axial direction of the tubular portion 31.
Inside the tubular portion 31, a flow path (material passage) 40 having a substantially circular cross section is formed at the center position. The flow path (material passage) 40 is formed over the entire length along the axial direction of the tubular portion 31. The flow path (material passage) 40 is formed concentrically with the tubular portion 31. The flow path (material passage) 40 opens at the tip surface 30a and the flange surface 32a, respectively.

The flange portion 32 and the cylinder portion 31 have a first flow path 41, a first diameter reduction portion 42, and a first diameter expansion portion (a first diameter expansion portion) as a flow path (material passage) 40 continuous from the flange surface 32a to the tip surface 30a. The enlarged diameter portion) 43 and is formed. A throttle portion 36 is formed between the first diameter reduction portion 42 and the first diameter expansion portion (diameter expansion portion) 43.

A step 31b is formed on the outer periphery of the tubular portion 31 close to the tip surface 30a so as to reduce the diameter toward the tip surface 30a. From the step 31b in the axial direction of the tubular portion 31 to the tip surface 30a is a reduced diameter portion 31c.
The outer diameter of the reduced diameter portion 31c of the tubular portion 31 is substantially equal to the inner diameter of the bushing 34. The length of the reduced diameter portion 31c in the axial direction of the tubular portion 31 corresponds to the thickness dimension of the bushing 34 in order to form the gap g.

The bushing 34 has a ring shape as shown in FIG. The reduced diameter portion 31c of the tubular portion 31 comes into contact with the inner peripheral surface 34c of the bushing 34. The bushing 34 has a ring shape as shown in FIG. The bushing 34 is fitted into the reduced diameter portion 31c of the tubular portion 31 in a concentric state.
The outer peripheral surface 34b of the bushing 34 has a contact portion 34b1 and a relief portion 34b2. The contact portion 34b1 contacts the inner peripheral surface 33c of the gate bush 33. The relief portion 34b2 is formed on the side closer to the bottom surface 33b than the contact portion 34b1. The relief portion 34b2 is reduced in diameter so as not to come into contact with the gate bush 33.

In the bushing 34, the dimensional ratio of the contact portion 34b1 and the relief portion 34b2 in the axial direction (thickness direction) is set so as to reduce the contact area between the bushing 34 and the gate bush 33 as much as possible. The contact area between the bushing 34 and the gate bush 33 may be reduced by forming a recess in the inner peripheral surface 33c of the gate bush 33 in the direction of increasing the diameter.
Further, in order to reduce the contact area between the bushing 34 and the gate bush 33, in the range of the contact portion 34b1 arranged on the upstream side, a recess serving as a relief portion may be further formed in addition to the relief portion 34b2. it can.

The lower surface 34a of the bushing 34 has a flat surface parallel to the front end surface 30a of the gate body 30 and the bottom surface 33b of the gate bush 33.
The thickness dimension of the bushing 34 is set to be slightly larger than the distance from the tip surface 30a to the step 31b in the axial direction of the tubular portion 31.
As a result, the lower surface 34a of the bushing 34 is in contact with the bottom surface 33b which is the bottom of the gate bush 33, but the tip surface 30a of the gate body 30 is separated from the bottom surface 33b which is the bottom of the gate bush 33. As a result, the gap g is formed with the gate body 30 inserted into the gate bush 33.

The upper surface 34d of the bushing 34 is formed parallel to the lower surface 34a. The upper surface 34d of the bushing 34 is provided with a relief portion 34d2 on the entire circumference of the inner edge portion. Therefore, on the upper surface 34d of the bushing 34, the outer edge portion of the relief portion 34d2 comes into contact with the step 31b of the gate body 30. Therefore, the relief portion 34d2 reduces both the contact area between the inner peripheral surface 34c of the bushing 34 and the reduced diameter portion 31c and the contact area between the upper surface 34d of the bushing 34 and the step 31b.

The dimensions and contact state of the gate body 30, the gate bush 33, and the bushing 34 are related to each other in a heated state in which the molten resin material is passed through the flow path 40.

The bushing 34 of the present embodiment is made of a material having a lower thermal conductivity than that of the fixed plate 1. That is, the thermal conductivity of the bushing 34 is set to be lower than the thermal conductivity of the gate bush 33 in which the contact portion 34b1 of the bushing 34 and the lower surface 34a are in contact with each other. Specifically, when the gate bush 33 is made of a steel material such as S50C, the material of the bushing 34 can be made of, for example, SUS304 or the like.

As a result, heat escape from the bushing 34 in contact with the gate body 30 to the gate bush 33 in contact with the bushing 34 can be suppressed by the bushing 34. As a result, the temperature drop near the tip of the gate body 30 is suppressed.
The bushing 34 is not limited to the gate bush 33, and can be made of a material having a lower thermal conductivity than any of the members constituting the fixed plate 1.

Further, the bushing 34 of the present embodiment is made of a material having a coefficient of linear expansion larger than that of the fixed plate 1. That is, the coefficient of linear expansion of the bushing 34 is set to a value larger than the coefficient of linear expansion of the gate bush 33 with which the bushing 34 is in contact. Specifically, when the gate bush 33 is made of a steel material such as S50C, the material of the bushing 34 can be made of, for example, SUS304 or the like.

As a result, when the molten resin material that supplies the inside of the flow path 40 that becomes the hot sprue is heated, the tubular portion 31 and the bushing 34 of the gate body 30 are thermally expanded by this heating. That is, the length dimension of the tubular portion 31 of the gate body 30 in the axial direction increases. As a result, the upper surface 34d of the bushing 34 is pressed by the step 31b. Further, the thickness of the bushing 34 is increased by heating.

As a result, the lower surface 34a of the bushing 34 is pressed against the lower surface 33b of the gate bush 33 on the entire circumference of the reduced diameter portion 31c of the gate body 30. At the same time, a state in which a gap g is formed between the front end surface 30a of the gate body 30 and the bottom surface 33b of the gate bush 33 is maintained.

Next, a method of molding a product using the injection molding apparatus in this embodiment will be described.

At the time of molding, first, the fixed plate 1 and the movable plate 2 are molded and closed to form a product cavity 3 between the fixed plate 1 and the movable plate 2. In this closed state, the positioning frames of the movable plate 2 and the fixed plate 1 are fitted to each other. Then, the molten thermoplastic resin, which is a thermoplastic molding material, is injected from the injection nozzle 103a of the injection molding machine 103 into the flow path (material passage) 40.

This resin flows from the hot sprue bush 13 into the runner 21 of the manifold 11, and branches at the runner 21. Further, the resin sequentially passes from the runner 21 through the material passage 40. That is, the resin flows into the product cavity 3 from the gate body 30 heated by the heater 35 via the cold runner 3a.

Then, after the product cavity 3 is filled with the resin, the injection of the resin is stopped. After the resin in the product cavity 3 is cooled and solidified, the fixed plate 1, the intermediate plate 4, and the movable plate 2 are mold-opened, and the molded product is taken out.

At this time, the resin in the cold runner 3a is cooled and solidified integrally with the product. On the other hand, the resin in the gate body 30 is heated by the heater 35 and thus maintains a molten state. As a result, when the product is taken out from the product cavity 3, the molten resin in the gate body 30 can be separated from the solidified product-side resin at the position of the reduced diameter drawing portion 36. ..

Further, since the mutual magnitude relationship between the first flow path diameter C41, the second flow path diameter C42, the third flow path diameter C43, and the fourth flow path diameter C44 in the flow path 40 is set as described above, this flow. The pressure and the flow velocity in the flow path 40 are adjusted according to the path diameter. Specifically, when the flow path diameter is reduced, the flow velocity of the molten resin increases and the pressure decreases. On the contrary, when the flow path diameter is increased, the flow velocity of the molten resin is reduced and the pressure is increased.

As a result, the molten resin material is provided in a state where the pressure is increased in the cold runner 3a having the largest third flow path diameter C43 and the flow velocity in the smallest fourth flow path diameter C44 is maintained so as to be equal to or higher than a predetermined value. It can be supplied to the product cavity 3. Therefore, it is possible to control the inflow state of the resin material in the product cavity 3 to a desired state, improve the transferability, and maintain the strength and dimensional accuracy of the molded product in the desired state.

At the same time, the size of the cold runner 3a can be reduced, the recycling rate can be improved, the amount of waste material can be reduced, and the cost in product manufacturing can be reduced.

Further, the gate body 30 is made of a high-strength material, and the bushing 34 is provided so that the tip surface 30a of the gate body 30 does not abut on the bottom surface 33b of the gate bush 33. It is possible to prevent the tip of 30 from being worn, and it will not be deformed or damaged by an impact similar to the axial direction. As a result, the durability of the gate body 30 can be improved, the maintainability can be improved, and the manufacturing cost can be reduced.

Here, due to the thermal expansion of the gate body 30 and the thermal expansion of the bushing 34, the bushing 34 is crimped to the bottom surface 33b and the inner peripheral surface 33c of the gate bush 33, and the flow path 40 near the boundary between the hot sprue and the cold sprue is formed. Be sealed.

Further, the gate bush 33 is in a lower temperature state than the gate body 30 heated by the heater 35. Therefore, heat escapes from the gate body 30 to the gate bush 33 via the bushing 34. In particular, heat escapes from the reduced diameter portion 31c of the tubular portion 31 located at the lower end of the lower end 35a of the heater 35, but the bushing 34 is made of a material having low thermal conductivity and the bushing 34 has the escape portions 34b2 and 34d2. By providing the above, the contact area is reduced, so that the temperature in the flow path 40 can be prevented from dropping.

Therefore, it is not necessary to provide a small heater near the tip of the gate body, and it is not necessary to newly install a controller for the small heater. Therefore, the number of parts can be reduced and the required heating state of the molten resin material can be achieved with a simple configuration. It will be possible to maintain.

Further, the throttle portion 36 located at the lower end of the heater 35 with respect to the lower end 35a allows the flow of the molten resin material to flow in the direction along the flow path 40 from the first flow path diameter C41 to the second flow path diameter C42 and the second flow path diameter C42. To the third flow path diameter C43, it is narrowed down once and expanded again. The drawn portion 36 makes it possible to easily cut the molten resin.
Therefore, it is not necessary to provide a movable component configuration such as a valve pin in a state where the molten resin material that is not cooled and solidified is maintained in a molten state without being solidified more than necessary. At the same time, welding can be prevented, the required molten resin material can be reduced with a simple structure, the amount of waste material can be reduced, and the molded product can be easily taken out.

In addition, it is possible to reduce the work time required for manufacturing and improve the efficiency of the manufacturing process.
At the same time, even for product shapes for which gate pins cannot be used, it is possible to easily manufacture products while maintaining strength and dimensional accuracy.

A molten resin material flows into the gap g between the front end surface 30a of the gate body 30 and the bottom surface 33b of the gate bush 33 to form a resin thin film, which can be removed during maintenance of the injection molding apparatus 100. .. In addition, it does not affect the molding of the product.
As a result, by preventing the front end surface 30a of the gate body 30 and the bottom surface 33b of the gate bush 33 from coming into contact with each other, it is possible to prevent heat from flowing out to the gate bush 33.

Further, in the present embodiment, it is possible to obtain the effect of preventing the formation of an extra resin thin film near the tip surface 30a of the gate body 30 and the occurrence of resin leakage.

Hereinafter, examples of the present invention will be described.

A specific example thereof will be described as a confirmation test of the injection molding apparatus in the present invention.

<Experimental example 1>
In the gate body 30 at the lower end of the hot runner described above, a bushing 34 is provided around the tip of the gate body 30. At this time, on the outer peripheral surface 34b of the bushing 34, the dimensional ratio of the contact portion 34b1 and the relief portion 34b2 in the axial direction is set to 5.78: 4.22. Further, the angle formed by the relief portion 34b2 with the lower surface 34a is set to 60 °.
Further, the gear G was formed in the following flow path.
Here, the gate body 30 when the resin is injected into the product cavity 3 from the three gates G0, the flow path 40 in the bushing 34, and other specifications are shown here.

1st flow path diameter C41; Φ6mm
First reduced diameter portion 42 length; 1.6 mm
Second flow path diameter C42; Φ3 mm
Flow path diameter C30a; Φ3.48mm
First enlarged diameter portion 43 length; 4.55 mm
Flow path diameter C33a; Φ4.24 mm
Second diameter expansion part 44 length; Φ6 mm
Third flow path diameter C43; Φ5.21 mm
Fourth flow path diameter C44; Φ1.20 mm

Gate body material;
Resin temperature near the gate body; about 215 ° C. Outer diameter of the reduced diameter part of the gate body: 10 mm
Gate body reduced diameter part Axial length dimension; 4.5 mm
Distance of gap g: 0.05 mm
Bushing inner diameter: Φ10mm
Bushing outer diameter: Φ15mm
Bushing thickness dimension; 4.5 mm

Aim gear radius dimension; about 27 mm Gear thickness dimension; about 9 mm tooth pitch dimension; module: 0.7 mm, number of teeth: 75 mm
Inner diameter: about 17.5 mm Outer diameter: about 54.32 mm

As shown in FIG. 5, the gauge head B1 of the measuring instrument B was inserted between the gear teeth G1 of the gear G which is a molded product, and the overball diameter was measured. As a result at that time, the range width is shown in Table 1. The target overall diameter was set to about 54 mm.
Further, in Table 1, the four numerical values in one set are the measured values (mm) in the four molded products.

<Experimental Examples 2 to 5>
Similar to Experimental Example 1, the gear G was molded using a conventional injection molding machine. The conventional injection molding machine does not have a bushing 34, and the conventional injection molding machine does not have a bushing 34.
Experimental example 2: Cold type No. 6 experimental example before modification 3: Cold type No. 5 experimental example having the same structure as No. 6 type 4: Cold type No. 4 experimental example having the same structure as No. 6 type 5: It is a cold type No. 2 type that has the same structure as the No. 6 type.

The overball diameter was measured in the same manner as in Experimental Example 1. Table 1 shows the range width at that time. The target overall diameter was similarly set to about 54 mm.

From these results, it can be seen that according to the present invention, the range width of the overall diameter can be reduced to about half, that is, the variation in the product diameter can be reduced.

<Experiment 1>
In the gear G in Experimental Example 1, the variation in outer shape was measured.
Here, the value of inner diameter − outer diameter wall thickness is shown in FIG.

<Experiment 2>
In the same manner as in Experiment 1, the variation in outer shape was measured in the gear G in Experimental Examples 2 and 5.
Here, the value of inner diameter − outer diameter wall thickness is shown in FIG. The shape of the gear G is also shown in the figure, and the positions of the three gates G0 are also shown.

From these results, it can be seen that according to the present invention, it is possible to manufacture a product having a shape close to a circle without any bias from the center.

As an example of utilization of the present invention, as a product that requires elimination of abnormal noise or reduction of non-rotation, manufacturing of a rotating product that requires perfect circle (roundness) can be mentioned.

1 ... Fixed plate 2 ... Movable plate 3 ... Product cavity 3a ... Cold runner 4 ... Intermediate plate 6 ... Fixed side template 7 ... Fixed side receiving plate 9 ... Fixed side mounting plate 11 ... Manifold 21 ... Runner 30 ... Gate body 30a ... Tip surface 31 ... Cylinder portion 31b ... Step 31c ... Reduced diameter portion 32 ... Flange portion 32a ... Flange surface 33 ... Gate bush 33a ... Tip surface 33b ... Bottom surface 33c ... Inner peripheral surface 34 ... Bushing 34b1 ... Contact portion 34b2 ... Relief portion 34d2 ... Relief part 35 ... Heater 35a ... Lower end 36 ... Squeezing part 40 ... Flow path (material passage)
41 ... 1st flow path 42 ... 1st diameter reduction portion 43 ... 1st diameter expansion portion (diameter expansion portion)
44 ... Second diameter expansion part (diameter expansion part)
45 ... Third diameter expansion part (diameter expansion part)
46 ... Second reduced diameter portion 100 ... Injection molding device 103 ... Injection molding machine 110 ... Injection molding mold C30a ... Flow path diameter C33a ... Flow path diameter C41 ... First flow path diameter C42 ... Second flow path diameter C43 ... Third flow path diameter C44 ... 4th flow path diameter g ... Gap H ... Hot half

Claims (8)

It has an injection molding die and an injection molding machine that injects a molten resin material into the injection molding die from an injection nozzle.
The injection molding die is
With a fixed plate
A movable plate that forms a product cavity facing the fixed plate,
A hot sprue that serves as a flow path for the molten resin material,
The gate body as the lower end of the hot sprue,
A heater arranged around the gate body to heat the gate body, and
A cold sprue that becomes a flow path of the molten resin material downstream of the hot sprue and is connected to the product cavity and becomes a cold side of the flow path.
Have,
The flow path is
A first flow path formed inside the gate body in which the heater is arranged around the gate body.
A first diameter-reduced portion located downstream of the lower end of the heater on the downstream side of the first flow path and reducing the diameter from the first flow path to the throttle portion along the flow direction.
A diameter-expanded portion formed from the gate body to the cold sprue on the downstream side of the first diameter-reduced portion and expanded in diameter from the throttle portion along the flow direction.
A second diameter-reduced portion formed on the cold sprue and reduced in diameter from the enlarged diameter portion along the flow direction, and a second diameter-reduced portion.
Have,
The first flow path has a first flow path diameter, and has a first flow path diameter.
The first reduced diameter portion is reduced in diameter from the first flow path diameter to the second flow path diameter along the flow direction.
The throttle portion has the second flow path diameter and has.
The diameter-expanded portion is expanded from the diameter of the second flow path to the diameter of the third flow path along the flow direction.
The second diameter-reduced portion is reduced in diameter from the third flow path diameter to the fourth flow path diameter along the flow direction.
The second flow path diameter is larger than the fourth flow path diameter,
The first flow path diameter is larger than the second flow path diameter,
An injection molding apparatus characterized in that the third flow path diameter is larger than the first flow path diameter. In the injection molding apparatus according to claim 1,
The injection molding die has a gate bush that comes into contact with the cold side.
An injection molding apparatus characterized in that the tip of the gate body is inserted inside the gate bush. The injection molding apparatus according to claim 2, wherein the tip surface of the gate body is separated from the facing surface of the gate bush. The injection molding apparatus according to claim 2 or 3, wherein the gate body has a thermal conductivity lower than that of the gate bush. In the injection molding apparatus according to any one of claims 2 to 4.
A bushing is placed inside the gate bush.
The injection molding apparatus, wherein the bushing is arranged between the bushing and the gate bushing around the tip surface of the gate body. The injection molding apparatus according to claim 5, wherein the bushing has a thermal conductivity lower than that of the gate bushing. The bushing is provided with a contact portion that contacts the inner peripheral surface of the gate bush and a relief portion that does not contact the gate bush on the downstream side of the contact portion on the outer periphery thereof.
The injection molding apparatus according to claim 5, wherein the relief portion is arranged on the downstream side of the flow path with respect to the contact portion. The injection molding apparatus according to any one of claims 1 to 7, wherein the gate body has a first reduced diameter portion made of a spherical surface and the enlarged diameter portion made of a tapered surface.