Temperature sensor

Abstract

A temperature sensor for use in a molding machine, the temperature sensor comprising: a cylindrical optical fiber probe through which an optical fiber is inserted; a housing having a shaft portion into which the optical fiber probe is inserted; a protection window part which is located at the front end side of the optical fiber probe and is formed by glass; and a spacer having a space portion disposed between the fiber-optic probe and the protective window portion and having both surfaces in contact with the fiber-optic probe and the protective window portion, and having a transmission hole formed in the space portion, the transmission hole serving as a path for infrared light to the optical fiber and having a diameter greater than or equal to the outer diameter of the optical fiber.

Description

Technical Field

[0001] The present invention relates to the technical field of a temperature sensor used in a molding machine and using an optical fiber. Background Art

[0002] A molding machine that molds a resin molded product is provided with a sensor for measuring the temperature or pressure of the resin in a cavity, etc. As such a sensor, for example, the following temperature sensor is known: an optical fiber probe is connected to the cavity, an optical fiber for measuring the temperature of the molten resin filled in the cavity is inserted into the optical fiber probe, and infrared light released from the molten resin is transmitted to a detector via the optical fiber (for example, refer to Patent Document 1).

[0003] On the other hand, in the temperature sensor as described above, a protective window covering the incident surface is provided at the front end portion for the purpose of preventing contamination of the incident surface of the optical fiber or protecting the optical fiber (for example, refer to Patent Document 2). In the temperature sensor provided with such a protective window, the protective window is formed of a transparent material, and infrared light passes through the protective window and enters the optical fiber from the incident surface.

[0004] (Prior art literature)

[0005] (Patent Document)

[0006] Patent Document 1: Japanese Patent Application Publication No. 2008-232753

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 62-172228 Summary of the invention

[0008] (Problems to be solved by the invention)

[0009] In a temperature sensor provided with a protective window as described above, infrared light passes through the protective window and enters the optical fiber. Therefore, when an air layer exists between the protective window and the incident surface, the light is sometimes reflected at the interface between the protective window and the air layer or at the interface between the air layer and the incident surface, causing optical interference, depending on the conditions of the air layer.

[0010] In particular, since the protective window or the front end of the optical fiber is 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 will also change, which may affect the measurement results based on the temperature sensor.

[0011] Therefore, an object of the present invention is to suppress the occurrence of optical interference and ensure a stable measurement state.

[0012] (Measures taken to solve the problem)

[0013] The temperature sensor involved in the present invention is used in a molding machine, and the temperature sensor comprises: a cylindrical optical fiber probe, through which an optical fiber is inserted; a housing, which has a shaft portion for inserting the optical fiber probe; a protective window portion, which is located on the front end side of the optical fiber probe and is formed of glass; and a spacer, which has a space portion arranged between the optical fiber probe and the protective window portion and in contact with the optical fiber probe and the protective window portion on both sides, and a transmission hole is formed in the space portion, which serves as a path for infrared light to the optical fiber and has a diameter greater than the outer diameter of the optical fiber.

[0014] Thus, in a state where the space portion of the spacer is arranged between the optical fiber probe and the protection window portion, infrared light is transmitted from the protection window portion through the transmission hole of the spacer and enters the optical fiber.

[0015] (Effects of the Invention)

[0016] According to the present invention, in a state where a space portion with a spacer is arranged between the optical fiber probe and the protective window portion, infrared light is incident on the optical fiber through the transmission hole of the spacer from the protective window portion. Therefore, by means of the space portion, a distance greater than a certain value is maintained between the optical fiber and the protective window portion, and optical interference can be suppressed to ensure a stable measurement state. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is with Figure 2 and Figure 3 The figures together show the embodiment of the present invention, and this figure is a cross-sectional view of a temperature sensor.

[0018] Figure 2 It is an enlarged cross-sectional view showing a part of the temperature sensor.

[0019] Figure 3 This is an enlarged cross-sectional view showing an example in which a spacer is composed of only a space portion. DETAILED DESCRIPTION

[0020] Hereinafter, embodiments of the temperature sensor according to the present invention will be described with reference to the drawings.

[0021] In addition, the temperature sensor shown below has a cylindrical optical fiber probe, and in the following description, the axial direction of the optical fiber probe is set as the up-down direction and the front end side of the optical fiber probe is set as the bottom to indicate the up-down, left-right and right directions. However, the up-down, left-right and right directions shown below are for the convenience of description, and the implementation of the present invention is not limited to these directions.

[0022] <Structure of temperature sensor>

[0023] First, the structure of the temperature sensor is described (refer to Figures 1 to 3 ).

[0024] The temperature sensor 1 is mounted on an injection molding machine (not shown) and is used to measure the temperature of molten resin in an injection unit, for example. The molding machine to which the temperature sensor 1 is mounted is not limited to the injection molding machine, and the temperature sensor 1 may also be mounted on an extrusion molding machine or a blow molding machine.

[0025] The temperature sensor 1 includes a housing 2 for protecting various parts and various parts required to be protected by the housing 2 (see Figure 1 ).

[0026] The housing 2 includes a shaft portion 3, a window support portion 4, a placement portion 5, and a cover portion 6. Each portion of the housing 2 is formed of a metal material, for example.

[0027] The shaft portion 3 is formed into a cylindrical shape with the axial direction in the vertical direction. A setting nut 50 for mounting the temperature sensor 1 on the injection molding machine is installed on the portion other than the upper and lower ends of the shaft portion 3. The lower end surface of the shaft portion 3 is formed into a pressing surface 3a (refer to Figure 1 and Figure 2 ).

[0028] The window support portion 4 is in the shape of a cylinder with the axial direction being in the up-down direction, and is composed of a fitting portion 7, a retaining portion 8 and a receiving portion 9. The fitting portion 7 and the retaining portion 8 are both formed in a cylindrical shape, and the diameter of the fitting portion 7 is larger than the diameter of the retaining portion 8. However, the diameter of the fitting portion 7 and the diameter of the retaining portion 8 may be the same. The retaining portion 8 is arranged to be continuous with the lower end portion of the fitting portion 7 on the lower side of the fitting portion 7. The receiving portion 9 is formed in the shape of a flange bulging inward from the lower end portion of the retaining portion 8, and the inner space of the receiving portion 9 is formed as a through hole 9a. In the window support portion 4, the fitting portion 7 is mounted on the lower end portion of the shaft portion 3 in an externally fitted state, and the retaining portion 8 and the receiving portion 9 are located at a position lower than the shaft portion 3.

[0029] The arrangement portion 5 includes a flange portion 10 bulging outward from the upper end portion of the shaft portion 3 and a substantially cylindrical annular portion 11 protruding upward from the outer circumference of the flange portion 10. The arrangement portion 5 is formed integrally with the shaft portion 3, for example. A notch 11a is formed on the annular portion 11, which is open upward and penetrates in the radial direction. A plurality of mounting holes 11b are formed in the upper end portion of the annular portion 11 and are separated in the circumferential direction and open upward.

[0030] The cover 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 are formed in the outer peripheral portion of the cover 6 in a circumferential direction and penetrate up and down. The cover 6 is mounted on the configuration portion 5 from the upper side by screwing the mounting screw 60 inserted through the screw insertion hole 6b into the mounting hole 11b.

[0031] An optical fiber probe 13 is disposed inside the housing 2. The optical fiber probe 13 includes, for example, a cylindrical portion 14 formed of a metal material and having an axial direction in the up-down direction, and a flange portion 15 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.

[0032] In a state where the cover 6 is attached to the placement portion 5 , the elastic member 16 is disposed between the lower surface of the adjustment screw 12 and the pressed surface 15 a of the optical fiber probe 13 .

[0033] For example, a compression coil spring is used as the elastic member 16. The optical fiber probe 13 is urged downward by the urging force of the elastic member 16. Alternatively, a disc spring or a leaf spring may be used as the elastic member 16, and the elastic member 16 may be formed of a rubber material or the like.

[0034] In the temperature sensor 1 , the force applied by the elastic member 16 to the optical fiber probe 13 can be adjusted by rotating the adjustment screw 12 to change the screwing position with respect to the screw hole 6 a .

[0035] An optical fiber 17 is inserted and held in the optical fiber probe 13. One end 17a of the optical fiber 17 is inserted into the cylindrical portion 14, and a curved portion 17b continuous with the one end 17a is bent, for example, at a substantially right angle inside the collar portion 15. In the optical fiber 17, a portion between the curved portion 17b and the other end is provided as an intermediate portion 17c, and the intermediate portion 17c is located outside the optical fiber probe 13 from the outer peripheral surface of the collar portion 15 through the notch 11a. A detector not shown in the figure is connected to the other end of the optical fiber 17. The end face (lower end face) of the one end 17a of the optical fiber 17 is formed as an incident face 17d for incident infrared light.

[0036] The protection window portion 18 is supported by the window support portion 4 .

[0037] The portion of the protection window 18 other than the lower end is provided as a contact portion 19 formed in a cylindrical shape, and the lower end is provided as a supported portion 20. The contact portion 19 and the supported portion 20 of the protection window 18 are integrally formed of, for example, sapphire glass.

[0038] The upper surface of the contact portion 19 is formed as a contact surface 19a, and the lower surface of the outer peripheral portion is formed as a restricted surface 19b. The diameter of the contact portion 19 is greater than the diameter of the optical fiber probe 13. The supported portion 20 is formed in a disk shape with a diameter slightly smaller than that of the contact portion 19.

[0039] In the protective window portion 18, the contact portion 19 is arranged 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 protective window portion 18 is in a state where the restricted surface 19b of the contact portion 19 is in contact with the upper surface of the receiving portion 9, thereby preventing it from falling off the window support portion 4. The lower end portion of the supported portion 20 protrudes downward from the insertion hole 9a. However, the supported portion 20 may also be in a state where the lower end portion does not protrude downward from the insertion hole 9a.

[0040] In addition to protecting the window portion 18 , a spacer 21 is also supported by the window support portion 4 .

[0041] The spacer 21 is formed of a metal material such as stainless steel, and is integrally formed of a plate-shaped space portion 22 oriented in the up-down direction and a cylindrical tube portion 23 protruding upward from the outer periphery of the space portion 22 .

[0042] The space portion 22 has a circular outer shape and a transmission hole 22a is formed in the center. The diameter of the transmission hole 22a is equal to or larger than the diameter of the optical fiber 17. The upper surface of the space portion 22 is formed as a first contact surface 24, and the lower surface is formed as a second contact surface 25.

[0043] The upper end surface (front end surface) of the cylindrical portion 23 is formed as a pressed surface 23 a.

[0044] The spacer 21 is in a state where the first contact surface 24 of the space portion 22 contacts the front end surface (lower surface) 13a of the optical fiber probe 13, and the second contact surface 25 of the space portion 22 contacts the contact surface 19a of the protective window portion 18. The optical fiber probe 13 is urged downward by the elastic member 16, so that the front end 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 coincides with the center of the optical fiber 17.

[0045] The inner circumference of the cylindrical portion 23 of the spacer 21 contacts the outer circumference of the optical fiber probe 13 and the outer circumference contacts the inner circumference of the retaining portion 8 in the window support portion 4, and the pressing surface 3a of the shaft portion 3 presses on the pressed surface 23a.

[0046] Thus, the spacer 21 is arranged inside the window support portion 4 with its outer circumferential surface in contact with the inner circumferential surface of the holding portion 8, so that it does not wobble relative to the window support portion 4 and is stably arranged. Therefore, high positional accuracy of the spacer 21 relative to the window support portion 4 and the protective window portion 18 can be ensured.

[0047] Furthermore, the spacer 21 is arranged inside the window support 4 with its inner peripheral surface in contact with the outer peripheral surface of the optical fiber probe 13, so that it does not wobble relative to the optical fiber probe 13 and a stable arrangement is ensured. Therefore, high positional accuracy of the spacer 21 relative to the optical fiber probe 13 and the protective window 18 can be ensured.

[0048] As described above, the high positional accuracy of the spacer 21 can be ensured, so the positional accuracy of the space portion 22 relative to the optical fiber probe 13 and the protective window portion 18 becomes higher, the first abutting surface 24 of the space portion 22 is in close contact with the front end surface 13a of the optical fiber probe 13, and the second abutting surface 25 of the space portion 22 is in close contact with the contact surface 19a of the protective window portion 18, thereby achieving a state in which the distance between the front end surface 13a and the contact surface 19a is not easily changed.

[0049] Furthermore, the first abutment surface 24 of the space portion 22 is in close contact with the front end surface 13a of the optical fiber probe 13, and the second abutment surface 25 of the space portion 22 is in close contact with the contact surface 19a of the protective window portion 18, thereby positioning the optical fiber 17, the spacer 21 and the protective window portion 18 in the axial direction of the optical fiber probe 13, thereby ensuring high positional accuracy among the optical fiber 17, the spacer 21 and the protective window portion 18.

[0050] In addition, the spacer 21 may be composed of only the space portion 22 (see Figure 3 In this case, the pressing surface 3 a of the shaft portion 3 is pressed against the upper surface of the outer peripheral portion in the space portion 22 .

[0051] When the temperature sensor 1 constructed as described above is installed in a molding machine such as an injection molding machine and is used to measure the temperature of molten resin, infrared light is incident on the optical fiber 17 from the protective window portion 18 through the transmission hole 22a of the spacer 21 and is transmitted to the detector through the optical fiber 17, thereby measuring the temperature.

[0052] In addition, although the example in which the elastic member 16 for urging the optical fiber probe 13 is provided is shown above, the temperature sensor 1 may also be configured such that the elastic member 16 is not provided.

[0053] <Function of spacers, etc.>

[0054] As described above, in the temperature sensor 1, the space portion 22 of the spacer 21 is arranged between the optical fiber probe 13 and the protection window portion 18, and the distance between the front end surface 13a of the optical fiber probe 13 and the contact surface 19a of the protection window portion 18 is kept constant by the space portion 22 (refer to Figure 1 and Figure 2 ). Therefore, a constant distance is maintained between the contact surface 19 a of the protection window portion 18 and the incident surface 17 d of the optical fiber 17 via the air layer 26 .

[0055] Generally, it is known 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 No. 2011-141372 or Japanese Patent Application Laid-Open No. 2009-276398.

[0056] Optical interference is a natural phenomenon in which the reflected light (light waves) at the interfaces on both sides of the film in the thickness direction interfere with each other and enhance or reduce the reflected light of a specific wavelength. Specifically, when light is incident on a film, reflections are generated at the interfaces on both sides. However, when the thickness of the film is an odd multiple of 1 / 4 wavelength of light, the reflected light on both sides interferes with each other and cancels each other out. When the thickness of the film is an odd multiple of 1 / 2 wavelength of light, the reflected light on both sides enhances each other. These phenomena are considered optical interference.

[0057] The optical interference is also the same when the thin film is an air layer. Optical interference may occur when light is reflected at one interface and the other interface in the air layer.

[0058] This type of optical interference occurs when the thickness of the film (air layer) is extremely small, and becomes less likely to occur as the thickness increases. For example, it may occur in a thickness range of nanometers (nm) to micrometers (μm), such as a thickness of less than 1 μm, but it almost never occurs in a thickness exceeding this range.

[0059] The temperature sensor 1 is provided with a spacer 21. On the contrary, in a structure where 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, at a microscopic level, due to the tiny unevenness of the contact surface 19a and the incident surface 17d, there will be an air layer (air gap) with a tiny thickness of nanometers (nm) to micrometers (μm) level between the two.

[0060] As described above, optical interference occurs when the thickness of the air layer is extremely small. Therefore, in a structure where such a small air layer exists, when infrared light is incident on the incident surface 17d, optical interference may occur and affect the measurement result. In addition, the thickness of the air layer between the contact surface 19a and the incident surface 17d may change depending on the pressure applied to the protective window 18 by the molten resin, and the change in the thickness of the air layer may also change the degree of optical interference and cause a change (deviation) in the measurement result.

[0061] On the other hand, in the temperature sensor 1, a spacer 21 is arranged between the optical fiber probe 13 and the protective window 18, and a constant distance is maintained between the contact surface 19a of the protective window 18 and the incident surface 17d of the optical fiber 17 via an air layer 26 (transmission hole 22a). Since the spacer 21 is a structure, the thickness of the air layer 26 is not nanometer or micrometer order, but millimeter (mm) or more.

[0062] Specifically, in the temperature sensor 1 , the thickness of the air layer 26 (the thickness of the space portion 22 ) is, for example, 1 mm or more.

[0063] As described above, in the temperature sensor 1, a spacer 21 is arranged between the optical fiber probe 13 and the protective window portion 18, and infrared light is incident on the incident surface 17d of the optical fiber 17 through the transmission hole 22a. Therefore, a certain distance is maintained between the optical fiber 17 and the protective window portion 18 by means of the space portion 22, so that optical interference can be suppressed and a stable measurement state can be ensured.

[0064] The thickness of the space portion 22 is not limited to 1 mm or more as long as it can ensure a certain strength or more, and may be, for example, 0.5 mm or more, or may be less than 0.5 mm as long as it can ensure sufficient strength and does not cause optical interference.

[0065] Furthermore, since the air layer 26 has a sufficient thickness, even if the thickness of the air layer 26 changes slightly due to the pressure of the molten resin, the rate of change is extremely small. Even if optical interference occurs due to a slight change in the thickness of the air layer 26, it is not easy to cause changes (deviations) in the measurement results of the temperature sensor 1.

[0066] In the temperature sensor 1 , the spacer 21 is provided with a cylindrical portion 23 continuous with the outer periphery of the space portion 22 , and the front end surface of the cylindrical portion 23 is formed as a pressed surface 23 a , on which the pressing surface 3 a of the shaft portion 3 is pressed.

[0067] Therefore, the pressure of the molten resin is transmitted from the protection 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 the load on the protection window portion 18 caused by the pressure of the molten resin can be reduced, and the optical fiber 17 can be protected. In particular, since a load is not easily generated on the bent portion 17b of the optical fiber 17, the degree of bending of the bent portion 17b is not easily changed, and the influence of the pressure of the molten resin on the measurement result of the temperature sensor 1 can be reduced.

[0068] Furthermore, the portion of the protection window 18 that contacts the space 22 is provided as a cylindrical contact portion 19 , and the diameter of the contact portion 19 is equal to or larger than the diameter of the optical fiber probe 13 .

[0069] Therefore, the contact portion 19 having a diameter larger than that of the optical fiber probe 13 is in contact with the space portion 22, so that 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 of the spacer 21 and the cylindrical portion 23, thereby further reducing the load on the protective window portion 18 caused by the pressure of the molten resin.

[0070] In addition, an elastic member 16 is provided to apply force in a direction to press the optical fiber probe 13 toward the space portion 22. Therefore, when the load generated by the pressure of the molten resin is transmitted from the protection window portion 18 to the optical fiber probe 13 via the space portion 22, the optical fiber probe 13 resists the force applied by the elastic member 16 and displaces in a direction to reduce the load, thereby protecting the optical fiber probe 13.

[0071] In particular, when the load caused by the pressure of the molten resin is transmitted from the protection window portion 18 to the optical fiber probe 13 via the space portion 22, the optical fiber probe 13 displaces in the direction of reducing the load against the force of the elastic member 16, so that the pressure of the molten resin is easily transmitted from the protection window portion 18 to the shaft portion 3 via the space portion 22 and the cylindrical portion 23 of the spacer 21. Therefore, it is possible to simultaneously achieve a reduction in the load caused by the pressure of the molten resin on the optical fiber 17 and a reduction in the load caused by the pressure of the molten resin on the protection window portion 18.

[0072] (Explanation of Reference Numerals)

[0073] 1: temperature sensor; 2: housing; 3: shaft; 13: optical fiber probe; 16: elastic component;

[0074] 17: optical fiber; 18: protective window; 19: contact part; 21: spacer; 22: space part;

[0075] 22a: transmission hole; 23: cylindrical portion.

Claims

1. A temperature sensor for a molding machine, the temperature sensor comprising: A cylindrical optical fiber probe having an optical fiber inserted therethrough; A housing having a shaft portion for inserting the optical fiber probe; a protective window portion, located at the front end side of the optical fiber probe and formed of glass; and a spacer having a space portion disposed between the optical fiber probe and the protective window portion and having two surfaces in contact with the optical fiber probe and the protective window portion, The space portion has a transmission hole which serves as a path for infrared light to the optical fiber and has a diameter equal to or larger than the outer diameter of the optical fiber.

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

3. The temperature sensor according to claim 2, wherein: The temperature sensor is in a state where the outer peripheral surface of the cylindrical portion is in contact with the inner peripheral surface of the housing.

4. The temperature sensor according to claim 2, wherein: The portion of the protection window portion that contacts the space portion is configured as a cylindrical contact portion. The diameter of the contact portion is greater than or equal to the diameter of the optical fiber probe.

5. The temperature sensor according to claim 1, 2, 3 or 4, wherein: An elastic member is provided, and the elastic member applies force in a direction to press the optical fiber probe into the space portion.

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