Temperature sensor

Abstract

To prevent the occurrence of optical interference to ensure a stable measurement state.SOLUTION: A temperature sensor is used in a molding machine, and comprises: a cylindrical fiber probe into which an optical fiber is inserted; an outer casing that has a shaft part into which the fiber probe is inserted; a protective window part that is located on a leading end side of the fiber probe and formed of glass; and a spacer that is arranged between the fiber probe and the protective window part and has a space part in contact with the fiber probe on one surface and the protective window part on the other surface. The space part is formed with a transmission hole that serves as a path of infrared light to the optical fiber and has a diameter equal to or larger than the outer diameter of the optical fiber.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to the technical field of optical fiber based temperature sensors used in molding machines. [Background technology]

[0002] A molding machine that molds a resin molded product is provided with a sensor for measuring the temperature and pressure of the resin in a cavity, etc. One such sensor known is a temperature sensor in which a fiber probe through which an optical fiber for measuring the temperature of the molten resin filled in the cavity is inserted is connected to the cavity, and infrared light emitted from the molten resin is transmitted to a detector through the optical fiber (see, for example, Patent Document 1).

[0003] Meanwhile, some of the above-mentioned temperature sensors are provided with a protective window that covers the incident surface at the tip in order to prevent contamination of the incident surface of the optical fiber and to protect the optical fiber (see, for example, Patent Document 2). In a temperature sensor provided with such a protective window, the protective window is made of a transparent material, and infrared light is transmitted through the protective window and enters the optical fiber from the incident surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-232753 A [Patent Document 2] Japanese Patent Application Laid-Open No. 62-172228 Summary of the Invention [Problem to be solved by the invention]

[0005] In a temperature sensor provided with a protective window as described above, infrared light passes through the protective window and enters the optical fiber. If an air layer exists between the protective window and the incident surface, depending on the conditions of the air layer, the light may be reflected at the interface between the protective window and the air layer or at the interface between the air layer and the incident surface, resulting in optical interference.

[0006] In particular, since the protective window and the tip of the optical fiber are exposed to a high-temperature environment, if the thickness of the air layer changes due to, for example, thermal expansion of the protective window, the degree of optical interference may also change, which may affect the measurement results obtained by the temperature sensor.

[0007] Therefore, an object of the present invention is to suppress the occurrence of optical interference and ensure a stable measurement state. [Means for solving the problem]

[0008] The temperature sensor of the present invention is a temperature sensor used in a molding machine, and comprises a cylindrical fiber probe through which an optical fiber is inserted, an outer casing having a shaft portion into which the fiber probe is inserted, a protective window portion formed of glass and positioned at the tip side of the fiber probe, and a spacer disposed between the fiber probe and the protective window portion and having a space portion whose both sides contact the fiber probe and the protective window portion, and a transmission hole whose diameter is equal to or greater than the outer diameter of the optical fiber and which serves as a path for infrared light to the optical fiber is formed in the space portion.

[0009] With this, in a state where the space portion of the spacer is disposed between the fiber probe and the protective window portion, infrared light passes through the transmission hole of the spacer from the protective window portion and enters the optical fiber. Effect of the Invention

[0010] According to the present invention, when the space portion of the spacer is positioned between the fiber probe and the protective window portion, infrared light passes through the protective window portion through the transmission hole of the spacer and enters the optical fiber, so that the space portion maintains a certain distance or more between the optical fiber and the protective window portion, thereby suppressing the occurrence of optical interference and ensuring a stable measurement condition. [Brief description of the drawings]

[0011] [Figure 1] 2 and 3, this figure shows an embodiment of the present invention, and is a cross-sectional view of a temperature sensor. [Diagram 2] FIG. 4 is an enlarged cross-sectional view showing a part of the temperature sensor. [Diagram 3] 11 is an enlarged cross-sectional view showing an example in which a spacer is composed only of a space portion. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a temperature sensor according to the present invention will be described with reference to the accompanying drawings.

[0013] The temperature sensor described below has a cylindrical fiber probe, and in the following description, the axial direction of the fiber probe is the up-down direction, and the tip side of the fiber probe is the downside, and the up-down, left-right directions are described. However, the up-down, left-right directions described below are for the convenience of description, and the implementation of the present invention is not limited to these directions.

[0014] <Temperature sensor configuration> First, the configuration of the temperature sensor will be described (see FIGS. 1 to 3).

[0015] The temperature sensor 1 is attached to an injection molding machine (not shown) and is used to measure the temperature of molten resin in an injection unit, for example. Note that the molding machine to which the temperature sensor 1 is attached is not limited to an injection molding machine, and the temperature sensor 1 may be attached to an extrusion molding machine, a blow molding machine, or the like.

[0016] The temperature sensor 1 has an outer casing 2 for protecting each component, and necessary components protected by the outer casing 2 (see FIG. 1).

[0017] The outer casing 2 has a shaft portion 3, a window support portion 4, a mounting portion 5, and a cover portion 6. Each portion of the outer casing 2 is formed, for example, from a metal material.

[0018] The shaft portion 3 is formed into a cylindrical shape with its axial direction in the up-down direction. An installation nut 50 for mounting the temperature sensor 1 to an injection molding machine is attached to the shaft portion 3 except for the upper and lower ends. The lower end surface of the shaft portion 3 is formed as a pressing surface 3a (see Figures 1 and 2).

[0019] The window support part 4 is tubular with its axial direction in the up-down direction, and is composed of a fitting part 7, a holding part 8, and a receiving part 9. Both the fitting part 7 and the holding part 8 are formed in a cylindrical shape, and the diameter of the fitting part 7 is larger than the diameter of the holding part 8. However, the diameter of the fitting part 7 and the diameter of the holding part 8 may be the same. The holding part 8 is provided below the fitting part 7, continuing from the lower end part of the fitting part 7. The receiving part 9 is formed in a flange shape that protrudes inward from the lower end part of the holding part 8, and the space inside the receiving part 9 is formed as an insertion hole 9a. The fitting part 7 of the window support part 4 is attached to the lower end part of the shaft part 3 in an externally fitted manner, and the holding part 8 and the receiving part 9 are located below the shaft part 3.

[0020] The mounting portion 5 has a flange portion 10 that projects outward from the upper end of the shaft portion 3, and a substantially cylindrical annular portion 11 that projects upward from the outer periphery of the flange portion 10. The mounting portion 5 is formed, for example, integrally with the shaft portion 3. The annular portion 11 is formed with a notch 11a that opens upward and penetrates in the radial direction. The upper end of the annular portion 11 is formed with a plurality of mounting holes 11b that open upward and are spaced apart in the circumferential direction.

[0021] The lid portion 6 is formed in an annular shape and has a screw hole 6a in the center. An adjustment screw 12 is screwed into the screw hole 6a. Screw insertion holes 6b penetrating vertically are formed at the outer periphery of the lid portion 6 at intervals in the circumferential direction. The lid portion 6 is attached to the placement portion 5 from above by inserting a mounting screw 60 through the screw insertion hole 6b and screwing it into the mounting hole 11b.

[0022] A fiber probe 13 is disposed inside the outer casing 2. The fiber probe 13 is formed, for example, from a metal material, and has a cylindrical portion 14 whose axial direction is in the up-down direction, and a flange portion 15 that is continuous with the upper end portion of the cylindrical portion 14. The outer diameter of the flange portion 15 is larger than the outer diameter of the cylindrical portion 14. The upper surface of the flange portion 15 is formed as a pressed surface 15a.

[0023] With the cover portion 6 attached to the placement portion 5 , an elastic member 16 is placed between the lower surface of the adjustment screw 12 and the pressed surface 15 a of the fiber probe 13 .

[0024] For example, a compression coil spring is used as the elastic member 16. The fiber probe 13 is urged downward by the urging force of the elastic member 16. Note that a disc spring, a leaf spring, or the like may also be used as the elastic member 16, and the elastic member 16 may also be made of a rubber material or the like.

[0025] In the temperature sensor 1, the biasing force of the elastic member 16 against the fiber probe 13 can be adjusted by rotating the adjustment screw 12 to change the screwing position relative to the screw hole 6a.

[0026] An optical fiber 17 is inserted and held in the fiber probe 13. One end 17a of the optical fiber 17 is inserted into the cylindrical portion 14, and a bent portion 17b connected to the one end 17a is bent, for example, at a substantially right angle inside the flange portion 15. In the optical fiber 17, a portion between the bent portion 17b and the other end is provided as an intermediate portion 17c, and the intermediate portion 17c passes through the notch 11a and is positioned outside the fiber probe 13 from the outer circumferential surface of the flange portion 15. A detector or the like (not shown) is connected to the other end of the optical fiber 17. An end face (lower end face) of the one end 17a of the optical fiber 17 is formed as an incident surface 17d into which infrared light is incident.

[0027] A protective window portion 18 is supported on the window support portion 4.

[0028] The protective window portion 18 is provided as a contact portion 19 formed in a cylindrical shape except for the lower end portion, and the lower end portion is provided as a supported portion 20. In the protective window portion 18, the contact portion 19 and the supported portion 20 are integrally formed from, for example, sapphire glass.

[0029] The upper surface of the contact portion 19 is formed as a contact surface 19a, and the lower surface at the outer periphery is formed as a regulated surface 19b. The diameter of the contact portion 19 is equal to or larger than the diameter of the fiber probe 13. The supported portion 20 is formed in a disk shape whose diameter is one size smaller than that of the contact portion 19.

[0030] The contact portion 19 of the protective window portion 18 is disposed inside the window support portion 4, and the supported portion 20 is inserted into the insertion hole 9a of the receiving portion 9. Therefore, the regulated surface 19b of the contact portion 19 of the protective window portion 18 is in contact with the upper surface of the receiving portion 9, preventing the protective window portion 18 from falling off from the window support portion 4. The lower end of the supported portion 20 protrudes downward from the insertion hole 9a. However, the lower end of the supported portion 20 may not protrude downward from the insertion hole 9a.

[0031] In addition to the protective window portion 18, a spacer 21 is also supported by the window support portion 4.

[0032] The spacer 21 is made of a metal material such as stainless steel, and is composed of a plate-shaped space portion 22 facing the vertical direction and a cylindrical tubular portion 23 protruding upward from the outer periphery of the space portion 22, which are integrally formed.

[0033] The space portion 22 has a circular outer shape and has a through hole 22a formed in the center. The diameter of the through hole 22a is equal to or larger than the diameter of the optical fiber 17. The space portion 22 has an upper surface formed as a first contact surface 24 and a lower surface formed as a second contact surface 25.

[0034] The upper end surface (tip surface) of the cylindrical portion 23 is formed as a pressed surface 23a.

[0035] The spacer 21 is placed in a state where the first contact surface 24 of the space portion 22 is in contact with the tip surface (lower surface) 13a of the fiber probe 13, and the second contact surface 25 of the space portion 22 is in contact with the contact surface 19a of the protective window portion 18. Since the fiber probe 13 is urged downward by the elastic member 16, the tip surface 13a is pressed against the first contact surface 24 and the second contact surface 25 is pressed against the contact surface 19a. At this time, the center of the transmission hole 22a of the space portion 22 is aligned with the center of the optical fiber 17.

[0036] In addition, the cylindrical portion 23 of the spacer 21 is placed in a state where its inner surface is in contact with the outer peripheral surface of the fiber probe 13, and its outer peripheral surface is in contact with the inner peripheral surface of the holding portion 8 in the window support portion 4, and the pressing surface 3a of the shaft portion 3 is pressed against the pressed surface 23a.

[0037] In this way, the spacer 21 is disposed inside the window support part 4 with its outer peripheral surface in contact with the inner peripheral surface of the retaining part 8, ensuring a stable arrangement without rattling relative to the window support part 4. Therefore, high positional accuracy of the spacer 21 relative to the window support part 4 and the protective window part 18 can be ensured.

[0038] Moreover, since the spacer 21 is disposed inside the window support portion 4 with its inner peripheral surface in contact with the outer peripheral surface of the fiber probe 13, a stable arrangement is ensured without any rattling relative to the fiber probe 13. Therefore, high positional accuracy of the spacer 21 relative to the fiber probe 13 and the protective window portion 18 can be ensured.

[0039] As described above, high positional accuracy of the spacer 21 is ensured, so that the positional accuracy of the space portion 22 relative to the fiber probe 13 and the protective window portion 18 is increased, and the first abutment surface 24 of the space portion 22 is closely adhered to the tip surface 13a of the fiber probe 13 and the second abutment surface 25 of the space portion 22 is closely adhered to the contact surface 19a of the protective window portion 18, making it difficult for the distance between the tip surface 13a and the contact surface 19a to change.

[0040] Furthermore, since the first abutment surface 24 of the space portion 22 is closely attached to the tip surface 13a of the fiber probe 13 and the second abutment surface 25 of the space portion 22 is closely attached to the contact surface 19a of the protective window portion 18, the optical fiber 17, the spacer 21, and the protective window portion 18 are positioned in the axial direction of the fiber probe 13, and high positional accuracy between the optical fiber 17, the spacer 21, and the protective window portion 18 can be ensured.

[0041] The spacer 21 may be formed only by the space portion 22 (see FIG. 3). In this case, the pressing surface 3a of the shaft portion 3 is pressed against the upper surface of the outer periphery of the space portion 22.

[0042] When the temperature sensor 1 configured as described above is attached to a molding machine such as an injection molding machine and used to measure the temperature of molten resin, infrared light passes from the protective window portion 18 through the transmission hole 22a of the spacer 21, enters the optical fiber 17, and is transmitted to a detector through the optical fiber 17, thereby measuring the temperature.

[0043] Although the above describes an example in which the elastic member 16 for biasing the fiber probe 13 is provided, the temperature sensor 1 may also be configured without the elastic member 16 .

[0044] <Spacer function, etc.> As described above, in the temperature sensor 1, the space portion 22 of the spacer 21 is disposed between the fiber probe 13 and the protective window portion 18, and the distance between the tip surface 13a of the fiber probe 13 and the contact surface 19a of the protective window portion 18 is kept constant by the space portion 22 (see Figs. 1 and 2). Therefore, a constant distance is also kept between the contact surface 19a of the protective window portion 18 and the incident surface 17d of the optical fiber 17 via the air layer 26.

[0045] In general, it is known that there is a possibility that optical interference (thin film interference) may occur when light passes through a thin film, as described in, for example, Japanese Patent Application Laid-Open Nos. 2011-141372 and 2009-276398.

[0046] Optical interference is a natural phenomenon in which light (light waves) reflected at the interfaces on both sides of a thin film in the thickness direction interfere with each other, enhancing or reducing the reflected light of a specific wavelength. Specifically, when light is incident on a thin film, it is reflected at both interfaces, but if the thickness of the thin film is an odd multiple of 1 / 4 the wavelength of light, the two reflected lights interfere with each other and cancel each other out, and if the thickness of the thin film is an odd multiple of 1 / 2 the wavelength of light, the two reflected lights reinforce each other, and these phenomena are called optical interference.

[0047] The optical interference also occurs when the thin film is an air layer, and optical interference may occur due to light reflection at one interface and another interface of the air layer.

[0048] This type of optical interference occurs when the thickness of the thin film (air layer) is extremely small, and becomes less likely to occur as the thickness increases; for example, it can occur in the thickness range of the order of nanometers (nm) to micrometers (μm), for example, thicknesses of 1 μm or less, but it rarely occurs in thickness ranges greater than this.

[0049] Meanwhile, the temperature sensor 1 is provided with a spacer 21, but conversely, in a configuration in which the spacer 21 is not provided and the contact surface 19a of the protective window portion 18 is in contact with the incident surface 17d of the optical fiber 17, microscopically, due to minute irregularities on the contact surface 19a and the incident surface 17d, an air layer (air gap) with a minute thickness on the order of nanometers (nm) to micrometers (μm) exists between the two.

[0050] As described above, optical interference occurs when the thickness of the air layer is extremely small, so in a configuration in which such a minute air layer exists, optical interference may occur when infrared light is incident on the incident surface 17d, which may affect the measurement results. In addition, the thickness of the air layer between the contact surface 19a and the incident surface 17d may change due to the pressure that the protective window portion 18 receives from the molten resin, and the change in the thickness of the air layer may change the degree of optical interference, which may cause fluctuations (variations) in the measurement results.

[0051] On the other hand, in the temperature sensor 1, a spacer 21 is disposed between the fiber probe 13 and the protective window portion 18, and a certain distance is maintained between the contact surface 19a of the protective window portion 18 and the incident surface 17d of the optical fiber 17 via an air layer 26 (transmission hole 22a). Because the spacer 21 is a structure, the thickness of this air layer 26 is not on the order of nanometers or micrometers, but on the order of millimeters (mm) or more.

[0052] Specifically, in the temperature sensor 1, the thickness of the air layer 26 (the thickness of the space portion 22) is set to, for example, 1 mm or more.

[0053] As described above, in the temperature sensor 1, the spacer 21 is disposed between the fiber probe 13 and the protective window portion 18, and the infrared light passes through the transmission hole 22a and enters the incident surface 17d of the optical fiber 17. Therefore, the space portion 22 maintains a certain distance or more between the optical fiber 17 and the protective window portion 18, thereby suppressing the occurrence of optical interference and ensuring a stable measurement state.

[0054] Furthermore, the thickness of the space portion 22 is not limited to 1 mm or more as long as a certain level of strength can be ensured, and may be, for example, 0.5 mm or more, and may be less than 0.5 mm as long as sufficient strength can be ensured and no optical interference occurs.

[0055] Furthermore, since the air layer 26 is made sufficiently thick, even if the thickness of the air layer 26 changes slightly due to the pressure of the molten resin, etc., the rate of change is extremely small, and even if optical interference occurs due to a slight change in the thickness of the air layer 26, fluctuations (variations) in the measurement results of the temperature sensor 1 are unlikely to occur.

[0056] Furthermore, in the temperature sensor 1, a cylindrical portion 23 that is continuous with the outer periphery of the space portion 22 is provided in the spacer 21, and the tip surface of the cylindrical portion 23 is formed as a pressed surface 23a, and the pressing surface 3a of the shaft portion 3 is pressed against the pressed surface 23a.

[0057] Therefore, the pressure of the molten resin is transmitted from the protective window portion 18 to the shaft portion 3 via the space portion 22 and the cylindrical portion 23 of the spacer 21, and the pressure of the molten resin on the optical fiber 17 is suppressed, so that it is possible to reduce the load caused by the pressure of the molten resin on the protective window portion 18 and to protect the optical fiber 17. In particular, since a load is unlikely to be generated on the bent portion 17b of the optical fiber 17, the degree of bending of the bent portion 17b is unlikely to change, and the effect of the pressure of the molten resin on the measurement results of the temperature sensor 1 can be reduced.

[0058] Furthermore, the portion of the protective window 18 that comes into contact with the space 22 is provided as a cylindrical contact portion 19 , and the diameter of the contact portion 19 is set to be equal to or larger than the diameter of the fiber probe 13 .

[0059] Therefore, since the contact portion 19, which has a diameter larger than that of the fiber probe 13, is brought into contact with the space portion 22, the pressure of the molten resin is easily dispersed and transmitted from the protective window portion 18 to the shaft portion 3 via the space portion 22 and the tubular portion 23 of the spacer 21, and the load caused by the pressure of the molten resin on the protective window portion 18 can be further reduced.

[0060] In addition, an elastic member 16 is provided which biases the fiber probe 13 in a direction pressing it against the space portion 22. Therefore, when the load due to the pressure of the molten resin is transmitted from the protective window portion 18 through the space portion 22 to the fiber probe 13, the fiber probe 13 is displaced in a direction that reduces the load against the biasing force of the elastic member 16, thereby protecting the fiber probe 13.

[0061] In particular, when the load due to the pressure of the molten resin is transmitted from the protective window portion 18 to the fiber probe 13 via the space portion 22, the fiber probe 13 is displaced in a direction that reduces the load against the biasing force of the elastic member 16, and therefore the pressure of the molten resin is easily transmitted from the protective window portion 18 to the shaft portion 3 via the space portion 22 and the cylindrical portion 23 of the spacer 21. Therefore, the load due to the pressure of the molten resin on the optical fiber 17 and the load due to the pressure of the molten resin on the protective window portion 18 can be reduced simultaneously. [Explanation of symbols]

[0062] 1 Temperature Sensor 2 Outer casing 3 Shaft section 13 Fiber Probe 16 Elastic member 17 Optical Fiber 18 Protective window 19 Contact part 21 Spacer 22 Space Department 22a Transmission hole 23 Cylindrical section

Claims

1. A temperature sensor for use in a molding machine, comprising: a cylindrical fiber probe through which an optical fiber is inserted; an outer casing having a shaft portion into which the fiber probe is inserted; a protective window portion formed of glass and located on a tip side of the fiber probe; a spacer disposed between the fiber probe and the protective window portion and having a space portion whose both surfaces are in contact with the fiber probe and the protective window portion, A transmission hole is formed in the space portion to serve as a path for infrared light to the optical fiber, and the diameter of the transmission hole is set to be equal to or larger than the outer diameter of the optical fiber. Temperature sensor.

2. the spacer is provided with a cylindrical portion continuous with an outer periphery of the space portion, One end surface of the shaft portion in the axial direction is pressed against the tip surface of the cylindrical portion. The temperature sensor according to claim 1 .

3. The outer peripheral surface of the cylindrical portion is in contact with the inner peripheral surface of the outer casing. The temperature sensor according to claim 2.

4. a portion of the protective window that comes into contact with the space portion is provided as a cylindrical contact portion, The diameter of the contact portion is set to be equal to or larger than the diameter of the fiber probe. The temperature sensor according to claim 2.

5. An elastic member is provided to bias the fiber probe in a direction to press the fiber probe against the space. The temperature sensor according to claim 1, 2, 3 or 4.

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