Barrel and injection molding machine

Abstract

To provide a barrel where a heating temperature of the barrel by a heater can be accurately measured.SOLUTION: A barrel 21 includes: a heater (19) heating a resin material injected between an inner peripheral face (21A) and a plasticizing screw (17) and built in a middle body part (21C) along a central axis (C); and a temperature sensor (30) measuring a temperature of the middle body part (21C) and built in the middle body part (21C) along the central axis in a different position from the heater (19).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to temperature measurement in a barrel of an injection molding machine.

Background Art

[0002] An injection molding machine includes a screw for kneading and plasticizing a resin material, and a cylindrical barrel for housing the screw. Further, the injection molding machine includes a heater for heating the resin material. The resin material moves toward the tip of the barrel while melting by heating with the heater and frictional heat generated by the screw. By the backward movement of the screw, the melted resin is injected from the tip of the barrel into the cavity of the molding die. As the heater, a cartridge heater or a sheathed heater is applied.

[0003] Patent Document 1 proposes to form a plurality of longitudinal through-holes for accommodating heaters at equal intervals in the circumferential direction of the barrel, and insert a cartridge heater or a sheathed heater into the longitudinal through-holes. The longitudinal through-holes are formed along the axial direction of the barrel. By arranging heaters at equal intervals in the circumferential direction of the barrel as in Patent Document 1, the inside of the barrel can be heated evenly.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] It is necessary to adjust the heating temperature by the heater according to the progress stage of injection molding. To accurately adjust the heating temperature, it is necessary to accurately measure the heating temperature. From the above, an object of the present invention is to provide a barrel capable of accurately measuring the heating temperature of the barrel by the heater.

Means for Solving the Problem

[0006] The barrel of the injection molding machine according to the present invention includes an inner peripheral surface, an outer peripheral surface facing the inner peripheral surface, a solid portion between the inner peripheral surface and the outer peripheral surface, and a hollow portion inside the inner peripheral surface, and a plasticizing screw is inserted into the hollow portion. The barrel of the present invention includes a heating heater built into the solid portion along the central axis for heating the resin material introduced into the hollow portion between the inner peripheral surface and the plasticizing screw, and a temperature sensor built into the solid portion along the central axis at a position different from the heating heater for measuring the temperature of the solid portion.

[0007] The temperature sensor according to the present invention preferably includes a heat-sensitive element, a lead wire connected to the heat-sensitive element, a first protective tube covering the heat-sensitive element, and a second protective tube covering the lead wire. The first protective tube and the second protective tube are made of the same or different metal materials.

[0008] The temperature sensor according to the present invention preferably has a part of the first protective tube inserted into the second protective tube.

[0009] The barrel according to the present invention preferably includes a heat-sensitive element, a lead wire connected to the heat-sensitive element, and a sheath made of a resin material covering the heat-sensitive element and the lead wire.

[0010] In the barrel according to the present invention, preferably, a sensor accommodation groove for accommodating the temperature sensor is formed in the solid portion so as to have a closed end extending along the central axis. The temperature sensor has the tip of the first protective tube or the tip of the sheath pressed against the closed end by an elastic force.

[0011] In the barrel according to the present invention, preferably, the elastic force is generated by a coil spring disposed around the lead wire or the sheath.

[0012] In the barrel according to the present invention, preferably, a plurality of heater accommodation grooves arranged in the circumferential direction for accommodating a heater are formed in the solid portion so as to extend along the central axis. Each heater accommodation groove is partitioned into a plurality of regions along the central axis, and a heating heater is arranged corresponding to the plurality of regions.

[0013] In the barrel according to the present invention, preferably, a temperature sensor is arranged corresponding to each of the plurality of regions.

[0014] The injection molding machine according to the present invention includes a mold clamping unit and a plasticizing unit provided corresponding to the mold clamping unit. The plasticizing unit comprises an inner peripheral surface, an outer peripheral surface facing the inner peripheral surface, a solid portion between the inner peripheral surface and the outer peripheral surface, and a hollow portion inside the inner peripheral surface, and is composed of any one of the barrels in which a plasticizing screw is inserted into the hollow portion.

Advantages of the Invention

[0015] According to the present invention, since the heating heater is built in the barrel, the heating heater is close to the hollow portion which is the heating target region of the barrel. Moreover, the temperature sensor related to the temperature control by the heating heater is also built in the barrel. Therefore, since the temperature sensor is also close to the heating target region, the temperature measured by this temperature sensor has accuracy and can promote rapid and accurate temperature control by the built-in heating heater.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

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Figure 9

Mode for Carrying Out the Invention

[0017] Hereinafter, the present invention will be described in detail based on the embodiments shown in the accompanying drawings. The injection molding machine 1 in the present embodiment includes a molding machine main body 10 and a control device 50 that controls the operation of the molding machine main body 10.

[0018] [Molding Machine Main Body 10: FIG. 1] As shown in FIG. 1, the molding machine main body 10 includes a mold clamping unit 11 and a plasticizing unit 15. The mold clamping unit 11 includes a fixed die plate 12 to which a fixed mold (not shown) is attached and a movable die plate 13 to which a movable mold (not shown) is attached. The mold clamping unit 11 includes, for example, a hydraulic mechanism or an electric mechanism that moves the movable die plate 13 toward the fixed die plate 12. Prior to injection molding, the movable die plate 13 is moved to bring the movable mold into contact with the fixed mold. Then, further, for example, by increasing the pressure of the hydraulic oil of the hydraulic mechanism, the movable mold and the fixed mold are clamped to perform mold clamping. After that, molten resin is injected from the plasticizing unit 15 into the cavity formed between the movable mold and the fixed mold to obtain a molded product.

[0019] As shown in FIG. 1, the plasticizing unit 15 includes a barrel 21 having a discharge nozzle (not shown) formed on the front side, which is the side of the clamping unit 11, a plasticizing screw 17 provided inside the barrel 21, and a raw material hopper 18 for supplying a resin material into the barrel 21. The plasticizing unit 15 also includes a configuration (not shown) such as a drive source for advancing or retracting the plasticizing screw 17 and a drive source for rotating the plasticizing screw 17 forward or backward. Further, the barrel 21 is provided with a heating heater 19 inside, and the heating heater 19 heats the inside of the barrel 21 at a controlled temperature while the power is ON. Furthermore, the barrel 21 is provided with a temperature sensor 30 for measuring the temperature of the barrel 21 heated by the heating heater 19. The configuration of the temperature sensor 30 and the arrangement of the heating heater 19 will be described in detail later. The plasticizing screw 17 includes a tip side 17A and a base 17B, and the base 17B is arranged on the side of the raw material hopper 18.

[0020] When the plasticizing screw 17 rotates, the plasticizing unit 15 conveys, for example, pellet-shaped thermoplastic resin supplied from the raw material hopper 18 to the front side of the barrel 21. In this conveying process, the resin pellets are gradually heated and melted and stored in front of the plasticizing screw 17. Under the pressure of the resin generated by the storage, the plasticizing screw 17 conveys and measures a predetermined amount of molten resin forward while retreating toward the raw material hopper 18 side. Then, the measured molten resin is injected and filled into the cavity formed between the fixed mold and the movable mold of the clamping unit 11 by a predetermined amount from the discharge nozzle.

[0021] As shown in Fig. 1, the barrel 21 includes an inner peripheral surface 21A, an outer peripheral surface 21B facing the inner peripheral surface 21A, a solid portion 21C between the inner peripheral surface 21A and the outer peripheral surface 21B, and a hollow portion 21D inside the inner peripheral surface 21A. The barrel 21 has a heater 19 built into the solid portion 21C along the axial direction C for heating the resin material introduced into the hollow portion 21D between the inner peripheral surface 21A and the plasticizing screw 17, and a temperature sensor 30 built into the solid portion 21C along the axial direction C at a position different from the heater 19 for measuring the temperature of the solid portion 21C.

[0022] [Control device 50: Fig. 1] As shown in Fig. 1, the control device 50 generates operation command information so that the molding machine body 10 performs the operations required for each process such as the mold clamping process, the plasticizing process, and the injection process, using the sensing information sent from the molding machine body 10 or the information previously provided in the control device 50. The control device 50 transmits the generated operation command information to each drive unit of the molding machine body 10. This is the basic operation of the control device 50. Each drive unit of the molding machine body 10 executes the operations necessary for injection molding based on the received operation command information.

[0023] [Temperature sensor 30: Figs. 1 and 2] The temperature sensor 30 will be described with reference to Figs. 1 and 2. First, an example of the arrangement of the temperature sensor 30 in the barrel 21 will be described. As shown in Fig. 1, the temperature sensor 30 is provided at a position symmetric to the illustrated heater 19 with respect to the central axis C. As shown in Figs. 2(a) and 2(b), the barrel 21 is provided with a sensor accommodation groove 22 for accommodating the temperature sensor 30. As shown in Fig. 2(b), the sensor accommodation groove 22 includes a first groove 22A extending along the axial direction X of the barrel 21 and a second groove 22B extending along the radial direction Y of the barrel 21. The rear end 23A of the first groove 22A and the inner end 23B of the second groove 22B are connected to form the sensor accommodation groove 22. The front end of the first groove 22A is provided with a closed end 23C, while the outer end 23D of the second groove 22B is open to the outside. As shown in Fig. 2(a), a first protective tube 34 for accommodating the heat-sensitive element 31 provided at the tip of the temperature sensor 30 is pressed against the closed end 23C to be closed. Also, the rear end side of the lead wire 32 is drawn out from the open outer end 23D. In this way, most of the temperature sensor 30, excluding a part drawn out from the outer end 23D and including the heat-sensitive element 31, is accommodated, that is, built in, inside the barrel 21. Note that the sensor accommodation groove 22 according to the present embodiment has a so-called hole shape with a closed outer peripheral line, but it may have a shape in which a part of the outer peripheral line is open. The sensor accommodation groove in the present invention includes both. However, if the hole shape is adopted, the outer peripheral surface 21B becomes a continuous surface continuous in the circumferential direction. Therefore, it is possible to achieve high strength against the internal pressure applied to the inner peripheral surface 21A from the plasticizing screw 17 and the circumferential tensile stress generated during the expansion in the radial direction when compressed in the axial direction by the injection output.

[0024] Here, an example in which the sensor accommodation groove 22, that is, the temperature sensor 30 is provided at the lowermost part of the barrel 21 is shown, but the present invention is not limited to this. For example, it is allowed to provide the temperature sensor 30 at a position adjacent to the heater 19 shown in Fig. 1. However, it is preferable that the temperature sensor 30 is arranged below the central axis C of the barrel 21. This is because the heated air in the periphery rises and the heat dissipation environment is constantly updated, so heat is less likely to accumulate and the temperature is stable.

[0025] Next, the structure of the temperature sensor 30 will be described with reference to FIG. 2(a). The temperature sensor 30 includes a heat-sensitive element 31, a lead wire 32 electrically connected to the heat-sensitive element 31, and a first protective tube 34 that houses the heat-sensitive element 31. The heat-sensitive element 31 is composed of, for example, a thermocouple, a thermistor, or the like. Although not shown in the figure, the lead wire 32 includes a pair of core wires and an insulating coating that covers each of the pair of core wires. The core wires are made of, for example, copper or a copper alloy with excellent conductivity, and the insulating coating is made of a resin material, which is an electrically insulating material, such as polyethylene, polypropylene, or the like. A terminal 33 is connected to the rear end of the lead wire 32, and the terminal 33 is exposed outside the barrel 21. The first protective tube 34 protects the heat-sensitive element 31 housed therein from the surrounding environment and serves to transmit the heat of the barrel 21 to the heat-sensitive element 31 by being pressed against the closed end 23C of the sensor housing groove 22. Therefore, the first protective tube 34 is made of a metal material with excellent thermal conductivity, such as copper or a copper alloy. When corrosion resistance is required in an atmosphere where there is a risk of rust, it may be made of a material with corrosion resistance such as stainless steel. Since the closed end 23C of the sensor housing groove 22 is closed, an atmosphere where there is a risk of rust is likely to remain and the atmosphere concentration is likely to increase. For this reason, when the sensor housing groove is in an atmosphere where there is a risk of rust, it is preferable that the first protective tube 34 is made of a material with corrosion resistance such as stainless steel.

[0026] The temperature sensor 30 includes a fixture 35 that holds the lead wire 32 via a coil spring 37, and a coil spring 37 disposed around the lead wire 32 between the first protective tube 34 and a second protective tube 39 described later. The coil spring 37 has a function of continuously pressing the first protective tube 34 that houses the heat-sensitive element 31 against the closed end 23C of the first groove 22A even when thermal expansion in the axial direction X of the barrel 21 and elongation due to the injection force during injection occur. The pressing function of the heat-sensitive element 31 will be described in detail later.

[0027] Further, the temperature sensor 30 includes a second protective tube 39 that covers from the rear end of the coil spring 37 to the rear end side of the lead wire 32. The second protective tube 39 protects the lead wire 32 with poor heat resistance from the surrounding environment. A locking tool 38 is interposed between the rear end of the coil spring 37 and the second protective tube 39, and the locking tool 38 supports the coil spring 37 at its rear end. By this support, the position of the rear end of the coil spring 37 is fixed. The second protective tube 39 is preferably made of a metal material with low thermal conductivity, for example, 20 to 40 W / (m·K). This low thermal conductivity is effective for suppressing heat conduction to the first protective tube 34. Examples of this metal material include martensitic stainless steels such as JIS SUS420J2. This stainless steel has high strength and wear resistance in addition to corrosion resistance.

[0028] [Pressing function of the heat-sensitive element 31 by the coil spring 37: FIGS. 3, 4, 5, 6] Next, the pressing function of the heat-sensitive element 31 by the coil spring 37 will be described with reference to FIGS. 3 to 6. First, based on FIG. 3, the first pressing form will be described. In the first pressing form, as shown by the white arrow, a pressing force 35F is applied to the coil spring 37 from the outside in the radial direction by the fixture 35. In FIG. 3, the lead wire 32 and the coil spring 37 are clamped together by the fixture 35. By this clamping, the lead wire 32 and the coil spring 37 are fixed at their positions by the fixture 35. The part of the coil spring 37 behind the fixture 35 is compressed more than in the free state, and the reaction force 37RF due to this compression pushes the free region FA in front of the compression region CA forward as shown by the black arrow. Since the lead wire 32 and the coil spring 37 are fixed at the position of the fixture 35, the lead wire 32 is pushed forward by the reaction force 37RF. Therefore, the first protective tube 34 (heat-sensitive element 31) attached to the tip of the lead wire 32 is pressed against the closed end 23C. Thus, according to the temperature sensor 30, even if thermal expansion and elongation due to the injection force occur during injection in the barrel 21, the temperature measurement of the barrel 21 can be continuously performed.

[0029] Next, the second pressing form will be described with reference to FIG. 4(a). In the second pressing form, the lead wire 32 and the coil spring 37 are not fixed by the fixture 35. Without using a fixture, the following structure is adopted. In the second pressing form, a coil spring 37 is interposed between the enlarged diameter portion 34B at the rear end of the first protective tube 34 and the front end of the second protective tube 39. The lead wire 32 is accommodated inside the coil spring 37. When the tip of the first protective tube 34 is pressed against the closed end 23C of the first groove 22A, the coil spring 37 is allowed to expand and contract in a compressed state where it is contracted more than in the free state. As a result, the first protective tube 34 is continuously pressed against the closed end 23C. In the second pressing form, the rear end of the first protective tube 34 may be extended to the locking tool 38, and the extended first protective tube 34 may be provided inside the coil spring 37.

[0030] Next, the third pressing form will be described with reference to FIG. 4(b). In the third pressing form, instead of using the first protective tube 34, a sheath 36 that covers up to the heat-sensitive element 31 is provided. Here, the sheath 36 covers the outside of the electrical insulating layer that covers the core wire described above. In the third pressing form, the front end of the coil spring 37 abuts against the enlarged diameter portion 36B of the sheath 36, so that the tip of the sheath 36 is pressed against the closed end 23C by the elastic force. Generally, a wire having a core wire and an electrical insulating layer is called an electric wire, and a wire further having a sheath 36 is called a cable. Note that the sheath 36 may be provided so as to cover the entire length of the lead wire 32, or may be provided so as to partially cover the lead wire 32. When provided partially, for example, the tip region exposed from the second protective tube 39 can be covered with the sheath 36. FIG. 4(b) is based on the second pressing form, but a sheath 36 can also be provided in the first pressing form.

[0031] Next, the fourth pressing form will be described with reference to FIG. 5. As shown in FIG. 5, in the fourth pressing form, a sheath 36 is provided along substantially the entire length of the barrel 21 for the temperature sensor 30, and a base fixture 41 is provided at the rear end thereof, thereby supporting the temperature sensor 30 in a cantilever structure. This cantilever support supports the sheath 36 so that a compressive force is generated in the longitudinal direction thereof, thereby causing the tip of the temperature sensor 30 to be pressed against the closed end 23C. Fixing at the rear end can also be performed for the second protective tube 39.

[0032] Next, the fifth pressing form will be described with reference to FIG. 6. As shown in FIG. 6, the fifth pressing form is different from the second pressing form in that the rear end 34E of the first protective tube 34 is inserted into the tip 39F of the second protective tube 39, and the enlarged diameter portion 34B is provided near the tip of the first protective tube 34. Thereby, since the rear end portion of the first protective tube 34, which is the tip portion of the temperature sensor 30, can be horizontally supported by the highly rigid second protective tube 39, the tip portion of the temperature sensor 30 can be prevented from sagging downward due to its own weight and hitting the bottom surface of the sensor accommodation groove 22 and thus being unable to reach the closed end 23C, which is the original temperature measurement position.

[0033] [Arrangement Forms of the Heating Heater 19 and the Temperature Sensor 30: FIGS. 7, 8, and 9] Next, the arrangement forms of the heating heater 19 and the temperature sensor 30 will be described with reference to FIGS. 7 to 9. Note that FIG. 7 shows an example in which there is one (single) temperature sensor 30, and FIGS. 8 and 9 show examples in which there are two (plural) temperature sensors 30.

[0034] In the first arrangement form shown in FIGS. 7(a) and (b), as an example, six heating heaters 19 are arranged at equal intervals along the circumferential direction Z of the barrel 21, and while measuring the temperature with one temperature sensor 30, the six heating heaters 19 are controlled based on the measured temperature by one temperature sensor 30. Note that the heating heaters 19 may be arranged at unequal intervals along the circumferential direction Z of the barrel 21. In the example of FIG. 4, the heating heaters 19 are continuous in the axial direction X, and the temperature measurement by the temperature sensor 30 is preferably performed at an intermediate position in the axial direction X of the heating heaters 19.

[0035] In the second arrangement shown in FIGS. 8(a-1), (a-2), and (b), as an example, the axial direction X of the barrel 21 is divided into a first region A and a second region B, and three first heaters 19A corresponding to the first region A and three second heaters 19B corresponding to the second region B are provided. The second heater 19B is not arranged in the second region B of the axial direction X where the first heater 19A is arranged, and conversely, the first heater 19A is not arranged in the first region A of the axial direction X where the second heater 19B is arranged. That is, in the circumferential direction Z of the barrel 21, the first heaters 19A are arranged with one heater skipped in the first region A, and the second heaters 19B are arranged with one heater skipped in the second region B. In this example, a first temperature sensor 30A is arranged corresponding to the first region A, and a second temperature sensor 30B is arranged corresponding to the second region B. The first temperature sensor 30A measures the temperature at an intermediate position in the axial direction X of the first region A, and the second temperature sensor 30B measures the temperature at an intermediate position in the axial direction X of the second region B.

[0036] As shown in FIG. 8(a-1), in the second arrangement, the plurality of first heaters 19A and the plurality of second heaters 19B can be arranged at positions having the same radial distance from the central axis C. Also, as shown in FIG. 8(a-2), in the second arrangement, the plurality of first heaters 19A and the plurality of second heaters 19B can be arranged at positions having different radial distances from the central axis C.

[0037] The third arrangement form shown in Fig. 9 divides the axial direction X of the barrel 21 into a first region A and a second region B as an example, and six first heaters 19A are provided corresponding to the first region A and six second heaters 19B are provided corresponding to the second region B. The second heaters 19B are also arranged in the second region B in the axial direction X where the first heaters 19A are arranged, and the first heaters 19A are arranged in the first region A in the axial direction X where the second heaters 19B are arranged. In this third arrangement form, a first temperature sensor 30A is arranged corresponding to the first region A, and a second temperature sensor 30B is arranged corresponding to the second region B. The first temperature sensor 30A measures the temperature at an intermediate position in the axial direction X of the first region A, and the second temperature sensor 30B measures the temperature at an intermediate position in the axial direction X of the second region B.

[0038] The arrangement forms of the heater 19 and the temperature sensor 30 have been described above, but this is only an example of this embodiment, and other arrangement forms can also be adopted. For example, in the second and third arrangement forms, the first temperature sensor 30A and the second temperature sensor 30B are both provided below the central axis C, but either one of the first temperature sensor 30A or the second temperature sensor 30B may be arranged symmetrically with respect to the other first temperature sensor 30A or the second temperature sensor 30B. Specifically, when one temperature sensor is the first temperature sensor 30A and the other temperature sensor is the second temperature sensor 30B, the first temperature sensor 30A may be arranged below the central axis C, and the second temperature sensor 30B may be arranged above the central axis C at a position symmetrical to the first temperature sensor 30A.

[0039] Also, the heater 19 is preferably composed of a cartridge heater or a sheath heater. The cartridge heater is a metal resistance wire, usually a nichrome wire, spirally wound around a ceramic core (not shown) and covered with a metal sheath. A powder made of an electrical insulating material, such as magnesium oxide powder, is interposed in the gap between the metal sheath and the metal resistance wire. This cartridge heater generates heat by resistance heating. For example, by applying a voltage to an alloy wire having a high electrical resistance composed of 80% Ni - 20% Cr and passing an electric current, the alloy wire generates heat and is configured to emit heat from the entire circumference of the sheath. The basic structure of the sheathed heater is the same as that of the cartridge heater. However, a heater with a structure in which lead wires connected to the nichrome wire are drawn out from both sides is called a sheathed heater, and a heater with a structure in which the lead wire is drawn out from one side is called a cartridge heater.

[0040] [Effect] Hereinafter, the effects exhibited by the injection molding machine 1 according to the present embodiment will be described. Since the injection molding machine 1 according to the present embodiment has a built-in heating heater 19 in the barrel 21, the heating heater 19 is close to the hollow portion 21D of the barrel 21, which is the heating target area by the heating heater 19. Therefore, compared with providing a heating heater on the outer periphery of the barrel 21, the temperature of the hollow portion 21D that requires can be controlled quickly and accurately. Moreover, the temperature sensor 30 related to the temperature control by the heating heater 19 is built in the barrel 21 except for a part drawn out from the outer end 23D. Therefore, since the temperature sensor 30 is also close to the hollow portion 21D of the barrel 21, which is the heating target area, it can promote the quick and accurate temperature control by the built-in heating heater 19.

[0041] In addition, the temperature sensor 30 is built in the barrel 21 except for a part thereof and is not exposed to the outside of the barrel 21. Therefore, according to the injection molding machine 1, even if there are various equipment on the outer peripheral surface 21B of the barrel 21, the temperature sensor 30 can be provided without being affected by the equipment. In particular, when wrapping a heat insulating material around the outer periphery of the barrel 21, there is no limitation on the region where the heat insulating material is provided in order to provide the temperature sensor 30. Specifically, holes or gaps penetrating from the outer peripheral side of the heat insulating material to the outer peripheral surface 21B of the barrel 21 (regions where the heat insulating material is not provided on the outer peripheral surface of the barrel 21 and no heat insulating effect can be expected) are provided, and since it is not necessary to allow the temperature sensor 30 to approach the barrel 21 from the outside, the heat insulating effect of the barrel 21 by the heat insulating material is not inhibited. Therefore, according to the present embodiment, the heat insulating material can be provided only in the necessary regions as needed, so that the heat insulating effect by the heat insulating material can be obtained without leakage.

[0042] In the present embodiment, the first protective tube 34 in which the heat sensitive element 31 for detecting temperature is housed and the second protective tube 39 covering the lead wire 32 are separate bodies. Therefore, even if the temperature of the second protective tube 39 rises through the barrel 21, the influence on the temperature measurement by the heat sensitive element 31 inside the first protective tube 34 is negligible or there is no influence. As described above, by configuring the second protective tube 39 with a material having low thermal conductivity, the influence on the temperature measurement of the heat sensitive element 31 can be suppressed.

[0043] The temperature sensor 30 is built in the barrel 21. Therefore, even if molten resin adheres to the outer peripheral surface 21B of the barrel 21 during the operation of the injection molding machine 1, the molten resin does not directly adhere to the first protective tube 34 (heat sensitive element 31) or the lead wire 32 of the temperature sensor 30. Thereby, it is possible to prevent the temperature sensor 30 from erroneously measuring the temperature of the molten resin. Further, since it is not necessary to remove the molten resin from the temperature sensor 30, the temperature sensor 30 is not damaged during the operation of removing the molten resin.

[0044] The heat-sensitive lead wire 32 is inserted into the second protective tube 39. Therefore, molten resin does not adhere to the lead wire 32, and the second protective tube 39 has a low thermal conductivity and suppresses the transfer of the heat of the barrel 21 to the inserted lead wire 32. Also, the minute space between the inner peripheral surface of the second protective tube 39 and the lead wire 32 exhibits a heat insulation effect. Thus, it is possible to prevent thermal breakage of the lead wire 32 of the heat-sensitive element 31, and maintenance such as removal of the heat-sensitive element 31 from the barrel 21 becomes easy.

[0045] Even if the barrel 21 is thermally expanded in the axial direction X or stretched in the axial direction X by the injection force during injection, the tip of the temperature sensor 30 is continuously pressed against the closed end 23C of the barrel 21 by the elastic force of the elastic body. Therefore, stable and accurate temperature measurement is possible.

[0046] In addition to the above, as long as the gist of the present invention is not deviated from, it is possible to select the configurations exemplified in the above-described embodiment or to appropriately change them to other configurations.

Explanation of Signs

[0047] 1 Injection molding machine 10 Molding machine body 11 Mold clamping unit 12 Fixed die plate 13 Movable die plate 15 Plasticizing unit 17 Plasticizing screw 17A Tip side 17B Base 18 Raw material hopper 19 Heater 19A First heater 19B Second heater 21 Barrel 21A Inner peripheral surface 21B Outer peripheral surface 21C Solid part 21D Hollow part 22 Sensor accommodation groove 22A First groove 22B Second groove 23A Rear end Inner end of 23B Closed end of 23C Outer end of 23D Temperature sensor 30 First temperature sensor 30A Second temperature sensor 30B Thermosensitive element 31 Lead wire 32 Terminal 33 First protective tube 34 Diameter-expanded part 34B Fixture 35 Sheath 36 Diameter-expanded part 36B RF reaction force 37 Locking tool 38 Second protective tube 39 Control device 50 First region A Second region B Central axis C Compression region CA Free region FA X-axis direction Y-diameter direction Z-circumferential direction

Claims

1. An injection molding machine barrel comprising an inner peripheral surface, an outer peripheral surface facing the inner peripheral surface, a solid portion between the inner peripheral surface and the outer peripheral surface, and a hollow portion inside the inner peripheral surface, wherein a plasticizing screw is inserted into the hollow portion, wherein the barrel comprises a heating heater built into the solid portion along a central axis for heating a resin material introduced into the hollow portion between the inner peripheral surface and the plasticizing screw; a temperature sensor built into the solid portion, which measures the temperature of the solid portion, is installed at different positions in the circumferential direction in the solid portion, has a closed outer circumference, and is installed in a hole along the central axis; wherein the temperature sensor comprises a heat-sensitive element, a lead wire connected to the heat-sensitive element, a first protective tube covering the heat-sensitive element, and a second protective tube covering the lead wire; and a coil spring that can expand and contract in a compressed state that is shrunk from a free state between the first protective tube and the second protective tube. The barrel is characterized by this.

2. The temperature sensor is such that a part of the first protective tube is inserted into the second protective tube, The barrel according to claim 1.

3. The hole is formed so as to have a closed end in the solid portion, The temperature sensor is such that the tip of the first protective tube is pressed against the closed end by the elastic force of the coil spring, The barrel according to claim 1.

4. The solid portion is formed with a plurality of heater accommodation grooves arranged in the circumferential direction for accommodating the heating heater so as to extend along the central axis, each of the heater accommodation grooves is partitioned into a plurality of regions along the central axis, and the heating heater is arranged corresponding to the plurality of regions, The barrel according to any one of claims 1 to 3.

5. The temperature sensor is arranged corresponding to each of the plurality of regions, The barrel according to claim 4.

6. The temperature sensor is arranged below the central axis C of the barrel, The barrel according to any one of claims 1 to 5.

7. An injection molding machine comprising a clamping unit and a plasticizing unit provided corresponding to the clamping unit, wherein the plasticizing unit comprises an inner peripheral surface, an outer peripheral surface facing the inner peripheral surface, a solid portion between the inner peripheral surface and the outer peripheral surface, and a hollow portion inside the inner peripheral surface, and is provided with the barrel according to any one of claims 1 to 6, in which a plasticizing screw is inserted into the hollow portion, characterized by this.

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