Injection device, injection molding machine, and method for adjusting injection device

Abstract

To realize proper heat retaining properties corresponding to molding conditions or a molding cycle in an injection device.SOLUTION: The injection device 3 has an injection cylinder 31, a heater 34 which is attached to the side surface 31A of the injection cylinder 31 along the X-direction of the injection cylinder 31, and a heat insulating material 35 which covers at least a portion in the X-direction of the outer circumferential surface 34A of the heater 34. The injection cylinder 31 has a feeding part H1 and H2 to which the plastic is fed, a compressing part H3 which compresses the plastic, and a measuring part H4 and H5 which measure the compressed plastic. The heat retaining property for the heater 34 provided in the compression portion H3 is lower than the heat retaining property for the heater 34 provided in the feed portions H1 and H2 and the heat retaining property for the heater 34 provided in the metering portions H4 and H5.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an injection unit, an injection molding machine, and a method for adjusting an injection unit. [Background technology]

[0002] An injection molding machine is equipped with an injection device for injecting an injection material. Patent Document 1 describes an injection device that has an injection cylinder with a built-in screw, a heater attached to the injection cylinder, and a heat-retaining cover wrapped around the heater. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-115015 Summary of the Invention [Problem to be solved by the invention]

[0004] The thermal insulation cover prevents the heat generated by the injection cylinder and heater from radiating, improving the thermal insulation of the injection unit and contributing to reducing power consumption. However, since the distribution of heat generated by the injection cylinder varies depending on the axial position of the injection cylinder, the thermal insulation material may have excessive thermal insulation in some areas. If the thermal insulation material has excessively high thermal insulation, it may cause the injection material to overheat. The appropriate temperature of the injection material varies depending on the molding conditions and molding cycle of the injection material.

[0005] An object of the present disclosure is to provide an injection device that can achieve appropriate heat retention according to molding conditions and molding cycles. [Means for solving the problem]

[0006] The injection device of the present disclosure includes a heater attached to a side surface of an injection cylinder, and a heat insulating material covering at least a portion of the outer peripheral surface of the heater in the axial direction. The heat insulating property for the heater in the compression section is lower than the heat insulating property for the heater in the supply section and the heat insulating property for the heater in the metering section. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide an injection device that can achieve appropriate heat retention according to molding conditions and molding cycles. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic front view of an injection molding machine according to a first embodiment. [Figure 2] FIG. [Figure 3] FIG. 10 is a diagram showing a change over time in the operation amount of a heater in a comparative example. [Figure 4] FIG. 10 is a diagram showing temperature changes in various parts of an injection cylinder in a comparative example. [Figure 5] 5A and 5B are diagrams illustrating temperature changes in various parts of an injection cylinder according to an embodiment. [Figure 6] FIG. 2 is a schematic perspective view of an outer heat insulating material. [Figure 7] FIG. 1 is a side view of the outer insulation attached to the inner insulation. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Overall configuration of injection molding machine 1> FIG. 1 shows a schematic front view of an injection molding machine 1 according to a first embodiment. The injection molding machine 1 is a horizontal injection molding machine that injects resin. The injection molding machine 1 is generally composed of a mold clamping unit 2 that supports the mold and opens and closes it, and an injection unit 3 that heats, melts, and injects the resin. The injected material may be molten metal. In the following description, the X direction refers to the axial direction of the injection cylinder 31. In the X direction, the direction from the injection unit 3 toward the mold clamping unit 2, or the direction in which the material is injected, is referred to as the +X direction, and the direction from the mold clamping unit 2 toward the injection unit 3 is referred to as the -X direction. For convenience of illustration, the dimensions of the devices and elements shown in the drawings may differ from the actual dimensions.

[0010] <Mold clamping device 2> The mold clamping unit 2 includes a fixed platen 21 fixed on a bed 26 and having a fixed mold M1 attached thereto, and a movable platen 22 slidable on the bed 26 and having a movable mold M2 attached thereto. A mold clamping housing 23 slidable on the bed 26 is provided on the opposite side of the fixed platen 21 with respect to the movable platen 22, and the fixed platen 21 and the mold clamping housing 23 are connected by a plurality of tie bars 24. The movable platen 22 is movable along the tie bars 24. A link mechanism 25 for opening and closing the molds M1 and M2 is provided between the movable platen 22 and the mold clamping housing 23. The link mechanism 25 is driven by an electric ball screw. A hydraulic mold clamping injection cylinder may be provided instead of the link mechanism 25. A cavity to be filled with resin is formed between the fixed mold M1 and the movable mold M2.

[0011] <Injection device 3> The injection device 3 is provided on a base 39. The injection device 3 includes a hollow cylindrical injection cylinder 31 for heating, melting, and injecting resin, a screw 32 housed in the injection cylinder 31, and a drive mechanism 33 for driving the screw 32. An injection nozzle 31A is attached to the tip of the injection cylinder 31 in the +X direction, and supplies resin to a cavity formed between the molds M1 and M2. The screw 32 includes a screw head 32A (see Figure 2) at its tip in the +X direction. The screw 32 is driven to rotate and in the X direction by the drive mechanism 33.

[0012] 2 is a partial cross-sectional view of the injection unit 3, showing the injection cylinder 31, screw 32, heater 34, and heat insulating material 35. The injection cylinder 31 is roughly divided into supply sections H1 and H2 to which resin is supplied, a compression section H3 that compresses the resin, and metering sections H4 and H5 that meter the compressed resin. A material input section 38 to which resin is input is connected to the end of the injection cylinder 31 in the -X direction. The material input section 38 is equipped with a hopper 38A for inputting the resin.

[0013] The supply sections H1 and H2 are divided into an upstream supply section H1 on the upstream side and a downstream supply section H2 on the downstream side in relation to the resin injection direction (+X direction). The boundary between the upstream supply section H1 and the downstream supply section H2 can be determined as appropriate, but for example, it can be the center in the X direction of the combined portion of the upstream supply section H1 and the downstream supply section H2. The metering sections H4 and H5 are divided into an upstream metering section H4 on the upstream side and a downstream metering section H5 on the downstream side in relation to the resin injection direction. The boundary between the upstream supply section H4 and the downstream metering section H5 can be determined as appropriate, but the downstream metering section H5 can have a shorter length in the X direction than the upstream supply section H4.

[0014] Pellet-shaped resin is fed from the material feed section 38 to the upstream supply section H1. The resin gradually melts as it is heated by the heater 34 and is sent to the compression section H3. The resin is compressed, heated, and kneaded in the compression section H3 to become molten, and is then transferred to the metering sections H4 and H5. The metering sections H4 and H5 meter the amount of resin to be injected in one injection cycle (shot).

[0015] <Heater 34> The injection unit 3 has a heater 34 for heating the resin. The heater 34 is attached to the side surface 31A of the injection cylinder 31 along the X direction of the injection cylinder 31. The heater 34 is an electric band heater, and is provided in each of the supply sections H1 and H2, the compression section H3, and the metering sections H4 and H5. Because the heaters 34 for the supply sections H1 and H2, the compression section H3, and the metering sections H4 and H5 are provided separately, the amount of heat applied to the supply sections H1 and H2, the compression section H3, and the metering sections H4 and H5 can be individually controlled. At least one of the heaters 34 for the supply sections H1 and H2, the heater 34 for the compression section H3, and the heaters 34 for the metering sections H4 and H5 may be separated in the X direction. The supply sections H1 and H2, the compression section H3, and the metering sections H4 and H5 are each provided with a thermocouple (not shown) that can detect the temperature of the side surface 31A of the injection cylinder 31.

[0016] <Heat insulation material 35> The injection device 3 has a heat insulating material 35 that covers at least a portion of the outer peripheral surface 34A of the heater 34 in the X direction. The heat insulating material 35 has a plurality of inner heat insulating materials 36 that cover at least a portion of the heater 34 in the X direction, and a plurality of outer heat insulating materials 37 that cover at least a portion of the inner heat insulating materials 36 in the X direction. As will be described later, the inner heat insulating materials 36 can be attached to only a portion of the heater 34 in the X direction. In places where the inner heat insulating materials 36 are not attached, the outer heat insulating materials 37 are not attached either, so the heater 34 is exposed. The lengths of the individual inner heat insulating materials 36 and outer heat insulating materials 37 in the X direction are not limited, but the inner heat insulating materials 36 and outer heat insulating materials 37 can be appropriately divided in the X direction to facilitate attachment.

[0017] <Heat retention against heater 34> 3 shows the change over time in the operation amount (ratio to the maximum heat generation amount) of the heater 34 in the injection device 3 of the comparative example. In the comparative example, a heat-retaining material having the same heat-retaining properties regardless of the position in the X direction is attached to the heater 34 over the entire length in the X direction. The heat-retaining properties required by the heater 34, i.e., the allowable value of the amount of heat dissipation from the outer peripheral surface 34A of the heater 34, differ depending on the location on the injection cylinder 31.

[0018] The upstream supply section H1 is the area where the resin is preheated. Since the resin must be heated quickly, the heater 34 is operated most frequently. Furthermore, because the upstream supply section H1 is adjacent to the low-temperature material input section 38, it is easily cooled by heat conduction between the injection cylinder 31 and the material input section 38. Therefore, the upstream supply section H1 requires the highest heat retention. The reason for the low temperature of the material input section 38 is to prevent the resin temperature from rising excessively. If the resin temperature in the upstream supply section H1 rises excessively, the resin may adhere to the inner wall of the injection cylinder 31 or become clogged between the injection cylinder 31 and the screw 32. To prevent the material input section 38 from heating up excessively, the material input section 38 may be cooled with cooling water.

[0019] The downstream supply section H2, like the upstream supply section H1, is a region where the resin is preheated, and so is required to heat the resin quickly. However, since the downstream supply section H2 is located away from the low-temperature material input section 38 and is heated by heat conduction from the upstream supply section H1, it is not required to have as high a heat retention as the upstream supply section H1.

[0020] The compression section H3 is an area where the resin is kneaded while being heated. Since the resin temperature is still low, it needs to be heated continuously. If the resin temperature is low, there is a possibility that unmelted resin may be mixed into the molded product or the fluidity of the resin may decrease, resulting in a decrease in the shape accuracy of the molded product. However, in the compression section H3, shear heat is generated in the resin, so heat is generated not only by the heater 34 but also by the resin itself. For this reason, the operation amount of the heater 34 is smaller than that of the upstream supply section H1. The metering sections H4 and H5 are areas where the molten resin is held after heating. The operation amount of the heater 34 only needs to be the amount necessary to keep the resin warm, and the heat retention also only needs to be the amount necessary to keep the resin warm.

[0021] Therefore, the heater 34 generally requires the highest heat retention in the upstream supply section H1, followed by the downstream supply section H2, compression section H3, metering section H4, and H5, in that order. However, the inventors discovered that, depending on the molding conditions and molding cycle, the resin may generate too much heat in the compression section H3, resulting in overheating. Overheating can lead to resin burning (discoloration) and separation. The resin temperature can also be controlled by the operating amount of the heater 34. However, because the heat-retaining effect of the heat-retaining material tends to trap heat inside the material, the resin temperature changes slowly in response to changes in the operating amount of the heater 34, making it difficult to appropriately control the resin temperature using this method. Figure 4 shows the temperature change on the side surface 31A of the injection cylinder 31 in a comparative example. Due to the high heat-retaining effect of the heat-retaining material, the temperature in each section exceeds the set temperature, but the temperature rise is particularly large in the compression section H3.

[0022] For the above reasons, in this embodiment, the heat retention of the heater 34 provided in the compression section H3 is set lower than the heat retention of the heaters 34 provided in the supply sections H1 and H2 and the heat retention of the heaters 34 provided in the metering sections H4 and H5. Because the amount of heat dissipated in the compression section H3 is increased, the resin is less likely to overheat in the compression section H3. When the possibility of the resin overheating is low and it is desired to heat the resin quickly, the mounting pattern of the heat-insulating material 35 can be changed as described below, and the operation amount of the heater 34 can be increased. This allows the temperature of the resin in the compression section H3 to be appropriately controlled regardless of the molding conditions or molding cycle.

[0023] The heat retention for the heater 34 provided in the compression section H3 can be lower than that for the heater 34 provided in the downstream supply section H2. The heat retention for the heater 34 provided in the downstream supply section H2 can be lower than that for the heater 34 provided in the upstream supply section H1. The heat retention for the heater 34 provided in the compression section H3 can be lower than that for the heaters 34 provided in the metering sections H4 and H5. The heat retention for the heaters 34 provided in the metering sections H4 and H5 can be lower than that for the heater 34 provided in the upstream supply section H. The heat retention for the heater 34 provided in the downstream supply section H2 can be lower than that for the heaters 34 provided in the metering sections H4 and H5. That is, the heat retention ability for the heater 34 increases in the order of compression section H3, downstream supply section H2, metering sections H4 and H5, and upstream supply section H1.

[0024] The heat retention of the heater 34 is the resistance to the escape of heat dissipated from the outer peripheral surface 34A of the heater 34, and can be defined as T=(Q1-Q2) / Q1. Q1: Heat flux radiating from the outer surface 34A of the heater 34 when the heat insulating material 35 is not present Q2: What is the heat flux radiating from the outer surface 34A of the heater 34 when the heat insulating material 35 is present? The larger T is, the less heat escapes from the heater 34, and the smaller T is, the more heat escapes from the heater 34. When the heat insulating material 35 is not present (when the heater 34 is exposed), Q1 = Q2, so T = 0. When the heat insulating material 35 is provided, T corresponds to the insulating properties of the heat insulating material 35. However, T can be defined even when the heat insulating material 35 is not provided. In this specification, the magnitude of the heat retention for the heater 34 corresponds to the magnitude of T.

[0025] <Installation pattern for insulation material 35> Based on the above, specific mounting patterns of the heat insulating material 35 will be described. Table 1 shows examples of mounting patterns of the heat insulating material 35. In all patterns, multiple inner heat insulating materials 36 and multiple outer heat insulating materials 37 are mounted at least in the upstream supply section H1 and the metering sections H4 and H5. Pattern 1 is the configuration shown in Figure 1, in which the inner heat insulating materials 36 are mounted in the upstream supply section H1, the downstream supply section H2, the compression section H3, and the metering sections H4 and H5, and the outer heat insulating materials 37 are mounted only in the upstream supply section H1, the downstream supply section H2, and the metering sections H4 and H5.

[0026] 2, for convenience, the thickness of the inner thermal insulation material 36 is constant regardless of location, and the thickness of the outer thermal insulation material 37 is also constant regardless of location, but as mentioned above, the thermal insulation required in each section differs. The thickness, material (thermal conductivity), etc. of at least one of the outer thermal insulation material 37 and the inner thermal insulation material 36 can be changed depending on the thermal insulation required in each section. For example, in pattern 1, the outer thermal insulation material 37 is provided in the upstream supply section H1, the downstream supply section H2, and the metering sections H4 and H5, but if the thermal insulation required in the downstream supply section H2 is to be reduced, the thickness of the outer thermal insulation material 37 provided in the downstream supply section H2 can be made thinner.

[0027] [Table 1]

[0028] In pattern 2, the inner thermal insulation 36 is attached only to the upstream supply section H1, the downstream supply section H2, and the metering sections H4 and H5, and the outer thermal insulation 37 is attached only to the upstream supply section H1 and the metering sections H4 and H5. In pattern 3, the inner thermal insulation 36 and the outer thermal insulation 37 are attached only to the upstream supply section H1, the downstream supply section H2, and the metering sections H4 and H5. In pattern 4, the inner thermal insulation 36 is attached only to the upstream supply section H1, the downstream supply section H2, the compression section H3, and the metering sections H4 and H5, and the outer thermal insulation 37 is attached only to the upstream supply section H1 and the metering sections H4 and H5. In pattern 5, the inner thermal insulation 36 and the thermal insulation 35 are attached only to the upstream supply section H1 and the metering sections H4 and H5.

[0029] Figure 5 shows the temperature change at each part of the injection cylinder 31 in the configuration (pattern 1) shown in Figure 1. Because the heat retention of the heat-retaining material 35 is adjusted for each part, it is possible to control the temperature of each part so that it is approximately the set temperature.

[0030] <Composition of Heat Insulation Material 35> The outer heat insulating material 37 is detachable from the inner heat insulating material 36, and the inner heat insulating material 36 is detachable from the heater 34 so that the attachment pattern of the heat insulating material 35 can be changed depending on the molding conditions and molding cycle. When adjusting the injection device 3, the multiple outer heat insulating materials 37 can be detachably attached to all or part of the multiple inner heat insulating materials 36 in the X direction. The configuration of the outer heat insulating material 37 will be described below, but the inner heat insulating material 36 can also be configured in the same way as the outer heat insulating material 37.

[0031] FIG. 6 shows a schematic perspective view of the outer thermal insulation material 37, and FIG. 7 shows a side view of the outer thermal insulation material 37 attached to the inner thermal insulation material 36. Each of the multiple outer thermal insulation materials 37 has a flexible main portion 37A that is integral in the X direction and two flexible tongue portions 37B that are separated from each other in the X direction. The main portion 37A is wrapped around a portion of the inner thermal insulation material 36 in the circumferential direction C, and the two tongue portions 37B are wrapped around the remaining portion of the inner thermal insulation material 36 in the circumferential direction C. Each of the two tongue portions 37B is connected to the main portion 37A at one end 36F in the circumferential direction C and includes a joining element 37C near the other end 36G in the circumferential direction C that can be detachably joined to the main portion 37A. The main portion 37A also has another joining element 37D that can be joined to the joining element 37C of the tongue portion 37B. The joining element 37C can be formed, for example, by a hook-and-loop fastener.

[0032] Referring to Figure 7, the heater 34 has a terminal block 34B and a cable 34C extending from the terminal block 34B to the outside. The cable 34C and the terminal block 34B are preferably installed in a location with high heat dissipation to suppress the effects of heat. Therefore, the outer heat insulating material 37 is arranged so that the terminal block 34B straddles the two tongue portions 37B, and the cable 34C is led out through a gap 37E formed between the two tongue portions 37B. When the inner heat insulating material 36 and the outer heat insulating material 37 are arranged overlapping each other, the inner heat insulating material 36 and the outer heat insulating material 37 can be arranged so that the gap (not shown) in the inner heat insulating material 36 and the gap 37E in the outer heat insulating material 37 coincide with each other.

[0033] The heat retention of the tongue portion 37B against the heater 34 can be made lower than the heat retention of the main portion 37A against the heater 34. The heat dissipation property can be easily adjusted by the thickness and materials of the tongue portion 37B and the main portion 37A. Although most of the terminal block 34B is covered by the tongue portion 37B, the tongue portion 37B has a higher heat dissipation property than the main portion 37A, so the thermal influence on the terminal block 34B is mitigated. [Explanation of symbols]

[0034] 1 injection molding machine 3 Injection device 31 Injection cylinder 34 Heater 34B terminal block 34C cable 35 Heat insulation material 36 Inner insulation material 37 External insulation material 37A Main section 37B Tongue 37C, 37D joining element H1 Upstream supply section H2 Downstream supply section H3 compression section H4, H5 Measuring section

Claims

1. An injection cylinder; a heater attached to a side surface of the injection cylinder along the axial direction of the injection cylinder; a heat insulating material that covers at least a portion of an outer peripheral surface of the heater in the axial direction, the injection cylinder has a supply section to which the injection material is supplied, a compression section to compress the injection material, and a metering section to meter the compressed injection material, an injection device in which heat retention for the heater in the compression section is lower than heat retention for the heater in the supply section and heat retention for the heater in the metering section;

2. 2. The injection device according to claim 1, wherein the supply section has an upstream supply section on the upstream side with respect to the injection direction of the injection material and a downstream supply section on the downstream side, and the heat retention property of the downstream supply section is lower than the heat retention property of the upstream supply section.

3. The injection device according to claim 2 , wherein the heat retention of the metering section is lower than the heat retention of the upstream supply section.

4. 2. The injection device according to claim 1, wherein the heat insulating material includes a plurality of inner heat insulating materials that cover at least a portion of the heater in the axial direction, and a plurality of outer heat insulating materials that cover at least a portion of the inner heat insulating materials in the axial direction.

5. The supply unit has an upstream supply unit on the upstream side with respect to the injection direction of the injection material and a downstream supply unit on the downstream side, The injection device according to claim 4 , wherein the plurality of inner thermal insulation materials and the plurality of outer thermal insulation materials are attached to the upstream supply section and the metering section.

6. 6. The injection device according to claim 5, wherein the plurality of inner heat-insulating materials are attached to the upstream supply section, the downstream supply section, the compression section, and the metering section, and the plurality of outer heat-insulating materials are attached only to the upstream supply section, the downstream supply section, and the metering section.

7. 6. The injection device according to claim 5, wherein the plurality of inner heat-retaining materials are attached only to the upstream supply section, the downstream supply section, and the metering section, and the plurality of outer heat-retaining materials are attached only to the upstream supply section and the metering section.

8. The injection device according to claim 5 , wherein the plurality of inner heat insulating materials and the plurality of outer heat insulating materials are attached only to the upstream supply section and the metering section.

9. The injection device according to claim 5 , wherein the plurality of outer thermal insulation materials are detachable from the plurality of inner thermal insulation materials.

10. Each of the plurality of outer thermal insulation materials has a flexible main portion integral in the axial direction, and two flexible tongue portions separated from each other in the axial direction, The main portion is wound around a part of the circumferential direction of the plurality of inner heat-insulating materials, and the two tongue portions are wound around the remaining part of the circumferential direction of the plurality of inner heat-insulating materials, The injection device according to claim 9 , wherein the two tongue portions are connected to the main portion at one end in the circumferential direction and are provided with a joining element near the other end in the circumferential direction that is detachably joinable to the main portion.

11. The injection device of claim 10, wherein the joining element is a hook-and-loop fastener.

12. the heater has a terminal block and a cable extending from the terminal block to the outside, The injection device according to claim 10, wherein the cable is pulled out from between the two tongues.

13. The injection device according to claim 10, wherein the tongue portion has lower heat retention ability relative to the heater than the main portion.

14. An injection molding machine having an injection device and a mold clamping device that supports a mold and opens and closes the mold, The injection device An injection cylinder; a heater attached to a side surface of the injection cylinder along the axial direction of the injection cylinder; a heat insulating material that covers at least a portion of an outer peripheral surface of the heater in the axial direction, the injection cylinder has a supply section to which the injection material is supplied, a compression section to compress the injection material, and a metering section to meter the compressed injection material, an injection molding machine in which the heat retention for the heater in the compression section is lower than the heat retention for the heater in the supply section and the heat retention for the heater in the metering section;

15. 15. The injection molding machine according to claim 14, wherein the supply section has an upstream supply section on the upstream side with respect to the injection direction of the injection material and a downstream supply section on the downstream side, and the heat retention property of the downstream supply section is lower than the heat retention property of the upstream supply section.

16. The injection molding machine according to claim 14, wherein the heat retention of the metering section is lower than the heat retention of the upstream supply section.

17. 15. The injection molding machine according to claim 14, wherein the heat insulating material includes a plurality of inner heat insulating materials that cover at least a portion of the heater in the axial direction, and a plurality of outer heat insulating materials that cover at least a portion of the plurality of inner heat insulating materials in the axial direction.

18. The supply unit has an upstream supply unit on the upstream side with respect to the injection direction of the injection material and a downstream supply unit on the downstream side, 18. The injection molding machine according to claim 17, wherein the plurality of inner thermal insulation materials and the plurality of outer thermal insulation materials are attached to the upstream supply section and the metering section.

19. 19. The injection molding machine according to claim 14, wherein the plurality of outer thermal insulation materials are detachable from the plurality of inner thermal insulation materials.

20. 1. A method for adjusting an injection device having an injection cylinder, a heater attached to a side surface of the injection cylinder along an axial direction of the injection cylinder, and a plurality of inner heat insulating materials covering at least a portion of the heater in the axial direction, the method comprising: A method for adjusting an injection device, comprising removably attaching a plurality of outer thermal insulation materials to at least a portion of the plurality of inner thermal insulation materials in the axial direction.

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