Inspection method for optical temperature sensors

Abstract

To make it easy to confirm the orientation of the protective window. [Solution] A method for inspecting the surface orientation of the first surface of an optical temperature sensor comprising a cylindrical fiber probe through which an optical fiber is inserted, and a protective window portion made of sapphire and located on the tip side of the fiber probe, wherein the surface of the protective window portion opposite to the optical fiber in the axial direction of the fiber probe is formed as the first surface and the surface on the optical fiber side is formed as the second surface, wherein coaxial incident illumination is shone on the first surface.

Description

Technical Field

[0001] The present invention relates to the technical field of a method for inspecting the surface orientation of sapphire in an optical temperature sensor using sapphire.

Background Art

[0002] An optical temperature sensor is known which measures temperature and the like by facing a fiber probe through which an optical fiber is inserted to a cavity of a molding machine or the like and transmitting infrared light radiated from a measurement object through the optical fiber to a detector. Some of such optical temperature sensors are provided with a protection window portion formed of sapphire on the tip side of the fiber probe (optical fiber) in order to protect the optical fiber (see, for example, Patent Document 1).

[0003] In the optical temperature sensor described in Patent Document 1, by setting the front end surface of the protection window portion as the a-plane of sapphire, damage prevention of the protection window portion in a high-temperature and high-pressure environment is achieved as compared with a configuration in which the front end surface is the c-plane.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, in the manufacturing process of optical temperature sensors as described above, an inspection step is required to confirm whether the leading edge of the protective window matches the desired surface orientation (for example, surface a). Methods for confirming the surface orientation of sapphire include, for example, X-ray diffraction (XRD). However, since XRD generally assumes that the sapphire crystal itself is placed in the apparatus for inspection, confirming the surface orientation of the protective window becomes difficult when it is assembled on the fiber probe along with other components, requiring a large-scale inspection device and considerable effort. Therefore, even if the protective window is installed in the wrong orientation after the assembly process, this could not be detected.

[0006] Therefore, the present invention aims to enable easy confirmation of the surface orientation of the protective window portion formed of sapphire, even when it is assembled to an optical temperature sensor. [Means for solving the problem]

[0007] The present invention relates to an optical temperature sensor inspection method, comprising a cylindrical fiber probe through which an optical fiber is inserted, and a protective window portion made of sapphire and located on the tip side of the fiber probe, wherein the surface of the protective window portion opposite to the optical fiber in the axial direction of the fiber probe is formed as a first surface and the surface on the optical fiber side is formed as a second surface, and the first surface is illuminated with coaxial incident illumination.

[0008] This allows the surface orientation inspection to be performed with the protective window section assembled in its designated position. [Effects of the Invention]

[0009] According to the present invention, since the surface orientation inspection is performed with the protective window portion assembled in a predetermined position, the surface orientation of the protective window portion in the optical temperature sensor can be easily confirmed at a stage after the assembly process. [Brief explanation of the drawing]

[0010] [Figure 1] Figures 2 and 4 together illustrate embodiments of the present invention, and this figure is a cross-sectional view of an optical temperature sensor. [Figure 2] This is an enlarged cross-sectional view showing a part of an optical temperature sensor. [Figure 3] This is a diagram illustrating the crystal planes of sapphire. [Figure 4] This is a conceptual diagram illustrating a method for inspecting the surface orientation of a protective window. [Modes for carrying out the invention]

[0011] The embodiments for implementing the optical temperature sensor of the present invention will be described below with reference to the attached drawings (see Figures 1 to 4).

[0012] <Configuration of an optical temperature sensor> First, the configuration of an optical temperature sensor that is inspected by the inspection method according to an embodiment of the present invention will be described (see Figures 1 to 3).

[0013] The optical temperature sensor described below has a cylindrical fiber probe, and in the following description, the axial direction of the fiber probe is considered the vertical direction, with the tip of the fiber probe facing downwards, and the directions of up, down, left, and right are indicated accordingly. However, the directions of up, down, left, and right shown below are for convenience of explanation, and the invention is not limited to these directions.

[0014] The optical temperature sensor 1 is attached to, for example, an injection molding machine (not shown) and used, for example, to measure the temperature of the molten resin in the nozzle. The optical temperature sensor 1 may also be attached to various other molding machines besides injection molding machines, such as extrusion molding machines and blow molding machines.

[0015] The optical temperature sensor 1 is configured such that each required part is arranged or supported in the outer housing 2 (see Fig. 1). The outer housing 2 has a housing 3 and a window support portion 4. The outer housing 2 is formed of, for example, a metal material for all parts.

[0016] The housing 3 has a shaft portion 5, an arrangement portion 6, and a lid portion 7.

[0017] The shaft portion 5 is formed in a cylindrical shape with its axial direction being the vertical direction. An installation nut 50 for attaching the optical temperature sensor 1 to an injection molding machine is attached to a portion of the shaft portion 5 excluding both upper and lower end portions. The lower end surface of the shaft portion 5 is formed as an abutment surface 5a (see Figs. 1 and 2).

[0018] The arrangement portion 6 has a flange portion 8 that projects outward from the upper end portion of the shaft portion 5 and an approximately cylindrical annular portion 9 that projects upward from the outer peripheral portion of the flange portion 8. The arrangement portion 6 is formed integrally with the shaft portion 5, for example. A notch 9a that is open upward and penetrates in the radial direction is formed in the annular portion 9. A plurality of attachment holes 9b that are open upward are formed at intervals in the circumferential direction at the upper end portion of the annular portion 9.

[0019] The lid portion 7 is formed in an annular shape and has a screw hole 7a at the center. An adjustment screw 10 is screwed into the screw hole 7a. Screw insertion holes 7b that penetrate vertically are formed at intervals in the circumferential direction on the outer peripheral portion of the lid portion 7. The lid portion 7 is attached to the arrangement portion 6 from above by screwing an attachment screw 60 inserted through the screw insertion hole 7b into the attachment hole 9b.

[0020] The window support portion 4 is formed in a cylindrical shape with its axial direction being the vertical direction, and has a fitting portion 11, a holding portion 12, and a receiving portion 13. The fitting portion 11, the holding portion 12, and the receiving portion 13 of the window support portion 4 are, for example, integrally formed. Both the fitting portion 11 and the holding portion 12 are formed in a cylindrical shape, and the diameter of the fitting portion 11 is made larger than the diameter of the holding portion 12. The holding portion 12 is provided continuously to the lower end portion of the fitting portion 11 on the lower side of the fitting portion 11. The upper surface of the holding portion 12 is formed as a pressed surface 12a, and the lower surface is formed as a front end surface 12b. In the window support portion 4, the fitting portion 11 is externally fitted to the lower end portion of the shaft portion 5, and the pressing surface 5a of the shaft portion 5 is pressed against the pressed surface 12a of the holding portion 12.

[0021] The receiving portion 13 is provided in a state of protruding inward at an intermediate portion in the vertical direction of the holding portion 12 (see FIG. 2). The upper surface of the receiving portion 13 is formed as a first receiving surface 13a, and the lower surface is formed as a second receiving surface 13b. The space inside the receiving portion 13 is formed as a through hole 14. The diameter of the through hole 14 is made larger than or equal to the diameter of an optical fiber described later.

[0022] The space above the receiving portion 13 in the internal space of the holding portion 12 is formed as a first insertion space 15, and the space below the receiving portion 13 is formed as a second insertion space 16. The portion of the inner peripheral surface of the holding portion 12 that forms the first insertion space 15 is formed as a first inner peripheral surface 12c, and the portion that forms the second insertion space 16 is formed as a second inner peripheral surface 12d. The first insertion space 15 and the second insertion space 16 are communicated through the through hole 14.

[0023] A sleeve material 17 and a protective window portion 18 are arranged in the second insertion space 16.

[0024] The sleeve material 17 is formed in an annular shape with its axial direction being the vertical direction. The sleeve material 17 is formed of a material having a coefficient of thermal expansion smaller than that of the window support portion 4, for example, Kovar. It is desirable that the sleeve material 17 is formed of a material having a coefficient of thermal expansion close to that of the protective window portion 18.

[0025] The sleeve material 17 is inserted almost entirely into the second insertion space 16 with its upper surface in contact with the second receiving surface 13b, and its lower surface is positioned on the same plane as the tip surface 12b of the retaining portion 12, or slightly below the tip surface 12b. When the sleeve material 17 is inserted into the second insertion space 16, its outer peripheral surface 17a is in contact with the second inner peripheral surface 12d of the retaining portion 12. The sleeve material 17 is bonded to the retaining portion 12, for example, by welding. However, the sleeve material 17 and the retaining portion 12 may also be bonded by brazing or a heat-resistant adhesive.

[0026] The protective window portion 18 is cylindrical with its axial direction running vertically, with the lower surface formed as the first surface 18a and the upper surface formed as the second surface 18b. The first surface 18a and the second surface 18b are substantially parallel. The protective window portion 18 is made of, for example, sapphire. As shown in Figure 3, sapphire has crystal planes such as c-planes, m-planes, a-planes, and r-planes with the c-axis as the growth axis, and the first surface 18a and the second surface 18b are the a-planes in the sapphire crystal plane. The protective window portion 18 may have a chamfered edge at the continuous portion between the outer peripheral surface 18c and the first surface 18a.

[0027] The outer diameter of the protective window portion 18 is larger than the diameter of the through-hole 14 and is approximately the same as or slightly smaller than the inner diameter of the sleeve material 17 (see Figure 2). The protective window portion 18 is inserted into the sleeve material 17 and attached to the window support portion 4 with the outer circumference of the second surface 18b in contact with the second receiving surface 13b. The outer circumference 18c of the protective window portion 18 is bonded to the inner circumference 17b of the sleeve material 17 by, for example, brazing with silver solder. However, the sleeve material 17 and the protective window portion 18 may also be bonded by low-melting-point glass or a heat-resistant adhesive.

[0028] When the protective window portion 18 is attached to the window support portion 4, its lower end protrudes downward from the sleeve material 17. This makes it less likely for molten resin to accumulate at the tip when the optical temperature sensor 1 is attached to a molding machine such as an injection molding machine and used to measure the temperature of molten resin.

[0029] The thermal expansion coefficient of the protective window portion 18 is smaller than that of the window support portion 4 and larger than that of the sleeve material 17.

[0030] A fiber probe 19 is positioned inside the outer casing 2 (see Figure 1). The fiber probe 19 is formed, for example, from a metal material and has a cylindrical portion 20 whose axial direction is vertical and a flange portion 21 that is continuous with the upper end of the cylindrical portion 20. The outer diameter of the flange portion 21 is larger than the outer diameter of the cylindrical portion 20. The upper surface of the flange portion 21 is formed as the pressure-bearing surface 21a.

[0031] An optical fiber 23 is inserted through and held in the fiber probe 19. One end 23a of the optical fiber 23 is inserted into the cylindrical portion 20, and a bent portion 23b, which is continuous with the one end 23a, is bent, for example, at a nearly right angle inside the flange portion 21. In the optical fiber 23, the portion between the bent portion 23b and the other end is provided as an intermediate portion 23c, and the intermediate portion 23c is located outside the fiber probe 19 from the outer circumferential surface of the flange portion 21 through the notch 9a. A detector or the like (not shown) is connected to the other end of the optical fiber 23. The end face (lower end face) of the one end 23a of the optical fiber 23 is formed as the incident surface 23d into which infrared light is incident (see Figure 2).

[0032] The fiber probe 19 has a cylindrical portion 20 inserted through the shaft portion 5, and its tip is inserted into and supported in the first insertion space 15 of the holding portion 12. The outer surface of the cylindrical portion 20 is in contact with the first inner surface 12c of the holding portion 12, and the tip surface (bottom surface) 19a of the fiber probe is in contact with the first receiving surface 13a of the receiving portion 13. At this time, the center of the optical fiber 23 (incident surface 23d) is approximately coincident with the center of the through hole 14. In this way, the fiber probe 19 is positioned inside the window support portion 4 with the outer surface of the cylindrical portion 20 in contact with the first inner surface 12c of the holding portion 12, thus ensuring a stable position without rattling relative to the window support portion 4.

[0033] The flange portion 21 is located in the placement portion 6, and with the lid portion 7 attached to the placement portion 6, the elastic member 22 is positioned between the lower surface of the adjustment screw 10 and the pressed surface 21a of the flange portion 21 (see Figure 1).

[0034] For example, a compression coil spring is used as the elastic member 22. The fiber probe 19 is biased downward by the biasing force of the elastic member 22. Therefore, the tip surface 19a of the fiber probe 19 is pressed against the first receiving surface 13a of the receiving portion 13 by the biasing force of the elastic member 22. Note that a disc spring or a leaf spring may be used as the elastic member 22, and the elastic member 22 may be made of a rubber material or the like.

[0035] In the optical temperature sensor 1, the biasing force of the elastic member 22 on the fiber probe 19 can be adjusted by rotating the adjustment screw 10 to change the screwing position with respect to the screw hole 7a. It is also possible to configure the optical temperature sensor 1 without the elastic member 22.

[0036] When the optical 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 emitted from the object to be measured is incident on the protective window portion 18 from the first surface 18a, guided through the inside of the protective window portion 18, and emitted from the second surface 18b. The infrared light emitted from the second surface 18b passes through the through hole 14 and is incident on the optical fiber 23 from the incident surface 23d, and is transmitted to the detector via the optical fiber 23.

[0037] As shown in Patent Document 1, the optical temperature sensor 1 has a first surface 18a of the protective window portion 18 made of sapphire surface a, thereby preventing damage to the protective window portion 18 in high temperature and high pressure environments.

[0038] Furthermore, in the optical temperature sensor 1, a receiving portion 13 is provided on the window support portion 4, so that a certain distance is maintained between the second surface 18b of the protective window portion 18 and the incident surface 23d of the optical fiber 23 via an air layer (transmission hole 14). This suppresses the occurrence of optical interference at the interface between the second surface 18b or the incident surface 23d and the air layer, and ensures a stable measurement state.

[0039] Furthermore, the first receiving surface 13a of the receiving portion 13 is in contact with the fiber probe 19, and the second receiving surface 13b is in contact with the protective window portion 18. This makes it difficult for the biasing force of the elastic member 22 applied to the fiber probe 19 to be transmitted to the protective window portion 18, and when pressure from the molten resin is applied to the protective window portion 18, the pressure from the molten resin is transmitted from the protective window portion 18 to the outer casing 2 via the receiving portion 13, thereby reducing the load on the protective window portion 18 due to the pressure from the molten resin.

[0040] Although the above example shows the receiving portion 13 being provided as part of the window support portion 4, the receiving portion may also be provided as a separate component from the window support portion.

[0041] Furthermore, in the optical temperature sensor 1, a sleeve material 17 is provided between the protective window portion 18 and the window support portion 4. This suppresses the intrusion of molten resin between the protective window portion 18 and the window support portion 4, making it difficult for excessive force to be applied to the protective window portion 18 in the radial direction.

[0042] In addition, by making the thermal expansion coefficient of the sleeve material 17 smaller than and close to that of the protective window portion 18, the protective window portion 18 is slightly tightened by the sleeve material 17 during expansion, thereby further preventing molten resin from entering the space between the protective window portion 18 and the sleeve material 17.

[0043] <Method for inspecting surface orientation> Next, we will explain the inspection method for the surface orientation of the protective window portion 18 (sapphire).

[0044] An inspection device 100 is used to inspect the surface orientation. The inspection device 100 is, for example, a microscope and includes a light source 101 that emits light, a lens 102 that constitutes an imaging optical system, and a beam splitter 103 and a polarizing plate 104 positioned on the optical axis Ax of the lens 102 (see Figure 4). Note that the inspection device 100 is not limited to a microscope and may be configured to observe the image formation via a camera or the like.

[0045] For example, a half-mirror is used as the beam splitter 103. The beam splitter 103 is positioned between the lens 102 and the object to be inspected (protective window portion 18), and is positioned at a predetermined angle with respect to the optical axis Ax, for example, at a 45-degree inclination. The beam splitter 103 has the function of reflecting the light emitted from the light source 101 toward the object to be inspected, and transmitting the reflected light from the object to be inspected toward the lens 102. The inspection device 100 may also be configured to use a cube-shaped beam splitter or the like instead of a half-mirror.

[0046] The polarizing plate 104 is positioned between the lens 102 and the beam splitter 103. While it is possible to omit the polarizing plate 104, reliable identification can be achieved by observing the light through the polarizing plate 104. Furthermore, in addition to the polarizing plate 104, another polarizing plate may be provided in the optical path between the light source 101 and the beam splitter 103.

[0047] During inspection, the optical temperature sensor 1 is installed such that the first surface 18a of the protective window portion 18 faces the beam splitter 103, and the central axis of the protective window portion 18 substantially coincides with the optical axis Ax.

[0048] Light emitted from the light source 101 is reflected by the beam splitter 103 and irradiated onto the first surface 18a approximately perpendicularly, as so-called coaxial incident illumination, with the optical axis coinciding with the optical axis Ax of the lens 102. A portion of the light irradiated onto the first surface 18a is reflected by the first surface 18a and passes through the beam splitter 103 and polarizer 104 towards the lens 102. Another portion of the irradiated light enters the protective window portion 18 from the first surface 18a, is reflected by the second surface 18b, and then passes through the first surface 18a again towards the lens 102. The inspection device 100 determines the surface orientation by observing (receiving) the reflected light from the first surface 18a and the reflected light from the second surface 18b.

[0049] A specific method of identification utilizes the fact that sapphire has its optical axis along the c-axis. When the first surface 18a and the second surface 18b are the a-faces of sapphire, the light emitted from the light source 101 is incident on the protective window 18 from a direction that is at an angle to the optical axis (c-axis). As a result, a phase difference is created between the light reflected by the first surface 18a and the light reflected by the second surface 18b due to birefringence, so, for example, rainbow-colored interference unevenness can be observed.

[0050] In contrast, when the first surface 18a and the second surface 18b are c-planes, light is incident parallel to the optical axis (c-axis) of the sapphire. As a result, there is no phase difference between the light reflected by the first surface 18a and the light reflected by the second surface 18b, and interference unevenness is not observed.

[0051] Therefore, the presence or absence of observed interference irregularities makes it easy to determine whether the first surface 18a of the protective window portion 18 is the a-face or c-face of sapphire.

[0052] Thus, in the inspection method according to this embodiment, since the surface orientation inspection is performed with the protective window portion 18 assembled in a predetermined position, the surface orientation of the protective window portion 18 (sapphire) of the optical temperature sensor 1 can be easily confirmed at a stage after the assembly process. [Explanation of Symbols]

[0053] 1. Optical temperature sensor 18 Protective window section 18a First face 18b Second side 19 Fiber probe 23 Optical Fiber 100 Inspection device 101 Light source 102 Lens 103 Beam Splitter 104 Polarizing plate

Claims

[Claim 1] A method for inspecting the surface orientation of the first surface in an optical temperature sensor comprising a cylindrical fiber probe through which an optical fiber is inserted, and a protective window portion made of sapphire and located on the tip side of the fiber probe, wherein the surface of the protective window portion opposite to the optical fiber in the axial direction of the fiber probe is formed as a first surface and the surface on the optical fiber side is formed as a second surface, Coaxial incident illumination is shone onto the first surface. Testing method for optical temperature sensors.

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