Non-contact-type temperature sensor

Abstract

Provided is a non-contact-type temperature sensor which makes it possible to facilitate improvement in thermal responsiveness and temperature measurement accuracy. The present invention provides: a temperature sensor which makes it possible to ensure reliability and improve thermal responsiveness; and a device equipped with the temperature sensor.　A non-contact-type temperature sensor 1 includes a holder 2, a lead part 3 that is held by the holder, and a temperature sensitive element 10 that is electrically connected to the lead part 3. The non-contact-type temperature sensor is characterized by comprising a glass substrate 11 which is made of a glass material and on which the temperature sensitive element 10 is formed, and is characterized in that the glass substrate 11 does not cause phase transition within an operating temperature range.

Description

Non-contact temperature sensor

[0001] The present invention relates to a non-contact temperature sensor suitable for detecting the surface temperature of an object without contacting the surface of the object.

[0002] Conventionally, electronic devices such as office automation equipment such as copiers and printers, information and communication equipment such as mobile communication terminals and personal computers, video equipment, consumer equipment, and automotive electrical equipment are equipped with temperature sensors to detect the temperature of an object to be detected (see Patent Documents 1 to 4).

[0003] For example, temperature sensors are used to detect the surface temperature of a target object, which is a rotating or stationary object such as a heating roller used in a fixing device of a copying machine, printer, etc., without contact, and to control the temperature of the heating roller. Specifically, the surface temperature of the target object is detected by a temperature-sensitive element formed on a ceramic substrate such as an alumina substrate.

[0004] Patent No. 5707081 Patent No. 6502588 Patent No. 6842600 Patent No. 6282526

[0005] In the case of conventional temperature sensors such as those described above, the temperature sensor detects the surface temperature of the object being detected without contacting the surface, which results in poor thermal response and temperature measurement accuracy of the temperature sensor, and there is a demand for improvements in thermal response and temperature measurement accuracy.

[0006] The present invention has been made in view of the above problems, and has as its object to provide a non-contact temperature sensor that can improve thermal response and temperature measurement accuracy.

[0007] The non-contact temperature sensor of this embodiment is a non-contact temperature sensor having a holder, a lead portion held by the holder, and a temperature-sensing element electrically connected to the lead portion, and is characterized in that it is provided with a glass substrate made of a glass material on which the temperature-sensing element is formed, and the glass substrate does not undergo a phase transition within the operating temperature range.

[0008] According to this invention, the non-contact temperature sensor has an extremely thin glass substrate, a small heat capacity, and a good infrared absorption rate, making it possible to improve the thermal response and temperature measurement accuracy.

[0009] According to the embodiments of the present invention, it is possible to provide a non-contact temperature sensor that can improve thermal response and temperature measurement accuracy.

[0010] 1 is a plan view showing a non-contact temperature sensor according to a first embodiment of the present invention. FIG. 2 is a plan view showing a non-contact temperature sensor according to a second embodiment. FIG. 3 is a plan view showing a non-contact temperature sensor according to a third embodiment. FIG. 4 is a plan view showing a non-contact temperature sensor according to a fourth embodiment. FIG. 5 is a plan view showing a non-contact temperature sensor according to a fifth embodiment. FIG. 6 is a plan view showing a non-contact temperature sensor according to a sixth embodiment. FIG. 7 is a configuration diagram for explaining a temperature sensing element according to the present invention. FIG. 8 is a plan view showing a connection mode between a temperature sensing element and a lead wire according to the present invention. FIG. 9 is a plan view showing a connection mode between the temperature sensing element and a lead wire. FIG. 10 is a plan view showing a connection mode between the temperature sensing element and a lead wire. FIG. 11 is a table showing evaluations of the heat capacity of a glass substrate according to the present embodiment and an alumina substrate as a comparative example. FIG. 12 is a graph showing evaluations of the infrared transmittance of the glass substrate. FIG. 13 is a table showing evaluations of the performance of the glass substrate. FIG. 14 is an explanatory diagram schematically showing an installation state of a non-contact temperature sensor according to an embodiment of the present invention. FIG. 15 is an explanatory diagram schematically showing an installation state of the non-contact temperature sensor. FIG. 16 is a table showing evaluations of performance depending on the installation state of a non-contact temperature sensor.

[0011] A non-contact temperature sensor according to an embodiment of the present invention will be described below with reference to Figures 1 to 10. Note that in each figure, the scale of each component has been appropriately changed for the purpose of explanation so that each component can be recognized. Furthermore, the same or corresponding parts are given the same reference numerals, and duplicate explanations will be omitted.

[0012] (First embodiment) A first embodiment will be described with reference to Fig. 1. Fig. 1 is a plan view showing a non-contact temperature sensor.

[0013] The non-contact temperature sensor 1 includes a holder 2 , a lead frame 3 which is a lead portion, and a temperature sensitive element 10 .

[0014] The holder 2 is made of an insulating resin material, such as PPS (polyphenylene sulfide), and is formed in a horizontally elongated, approximately rectangular parallelepiped shape with a rectangular opening 21 approximately in the center, forming a frame shape. A hook hole 21a is formed at one longitudinal end of the holder 2, and a screw hole 21b is formed at the other longitudinal end. The hook hole 21a and the screw hole 21b are used, for example, when attaching the non-contact temperature sensor 1 to a fixing device. Furthermore, a pair of grooves are formed at the other longitudinal end, and a pair of external lead wires 22 are arranged in these grooves. The external lead wires 22 are, specifically, lead wires with an insulating coating.

[0015] A lead frame 3 serving as a lead portion is fixed and held by insert molding in the holder 2. The lead frame 3 is an elastic body having elasticity formed by means of chemical etching, pressing, or the like, and is a thin, plate-shaped metal plate made of, for example, constantan.

[0016] The temperature-sensing element 10 is a thermal resistance element, specifically a thin-film thermistor formed on an insulating substrate 11, the details of which will be described later. The temperature-sensing element 10 is electrically connected to an electrical connection 12 connected to a lead frame 3. The insulating substrate 11 is a glass substrate made of a glass material, and the thickness of the insulating substrate 11 is 200 μm or less, preferably 150 μm or less. A thin glass substrate can be more effectively prevented from cracking during substrate fabrication than a ceramic substrate. A wiring pattern (not shown) for connecting the temperature-sensing element 10 to the electrical connection 12 is appropriately formed on the insulating substrate 11.

[0017] The insulating substrate 11 is disposed in a bridge shape across the lead frame 3, and both ends of the insulating substrate 11 are connected to electrical connection parts 12 connected to the lead frame 3 using brazing material, conductive paste, etc. In this embodiment, the insulating substrate 11 is disposed, for example, perpendicular to the direction of rotation of a heating roller used in a fixing device.

[0018] Additionally, a heat-resistant insulating coating 23 such as a polyimide film is attached to the surface facing the temperature sensing element 10 so as to cover part of the opening 21. The insulating coating 23 insulates the temperature sensing element 10 and the exposed portions (electrical connection portions 12) of the lead frame 3, which are the lead portions. The insulating coating 23 is provided so as to contact only two opposing sides of the holder 2. Therefore, thermal loss is minimal. In this embodiment, the insulating coating 23 is provided to ensure electrical insulation and prevent dust from adhering.

[0019] The insulating coating may sandwich and cover both sides of the temperature sensing element 10 and the exposed portion (electrical connection portion 12) of the lead frame 3, which is the lead portion. It is also preferable that the insulating coating has infrared absorption capability, which contributes to improving thermal response and temperature measurement accuracy. Specifically, it is desirable that the insulating coating be configured to absorb at least a portion of infrared rays in the wavelength range of 1 μm to 6 μm. Additionally, since the glass substrate of the insulating substrate 11 has insulating properties, it is possible to omit the insulating coating 23.

[0020] In the following embodiments, the holder 2, lead frame 3, and temperature sensitive element 10 have the same configuration as this embodiment. Therefore, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations will be omitted.

[0021] Second Embodiment A second embodiment will be described with reference to Fig. 2. Fig. 2 is a plan view showing a non-contact temperature sensor.

[0022] In this embodiment, the insulating substrate 11, which is a glass substrate, is disposed along the longitudinal direction of the lead frame 3, approximately in the center of the opening 21 of the holder 2. Both ends of the insulating substrate 11 are electrically connected to the electrical connection portions 12. In this embodiment, for example, the insulating substrate 11 is disposed in a direction parallel to the rotation direction of a heating roller used in a fixing device.

[0023] (Third embodiment) A third embodiment will be described with reference to Fig. 3. Fig. 3 is a plan view showing a non-contact temperature sensor.

[0024] In this embodiment, the temperature sensing element 10 is formed on a glass substrate, and a lead wire 24 is connected to the temperature sensing element 10. The lead wire 24 is formed integrally with the electrical connection portion 12 and is narrower than the electrical connection portion 12. The lead wire 24 is electrically connected to the temperature sensing element 10 by laser welding. Laser welding is preferred, but connection by soldering, conductive paste, or wire bonding is also possible. The lead wire 24 is arranged in a bridge shape so that the temperature sensing element 10 is located approximately in the center of the opening 21 of the holder 2 and is connected to the electrical connection portion 12.

[0025] (Fourth embodiment) A fourth embodiment will be described with reference to Fig. 4. Fig. 4 is a plan view showing a non-contact temperature sensor.

[0026] In this embodiment, a lead wire 24 extends from the external lead wire 22 side, and the temperature sensing element 10 is connected to its tip by laser welding. Although laser welding is preferred, connection by soldering, conductive paste, or wire bonding is also possible. As in the third embodiment, the lead wire 24 is formed integrally with the electrical connection portion 12 and is narrower than the electrical connection portion 12.

[0027] The lead wires 24 extend along the longitudinal direction of the lead frame 3 , and the temperature sensitive element 10 is positioned in the opening 21 of the holder 2 .

[0028] Fifth Embodiment A fifth embodiment will be described with reference to Fig. 5. Fig. 5 is a plan view showing a non-contact temperature sensor.

[0029] This embodiment has the same basic configuration as the third embodiment (see FIG. 3 ), except that the lead wire 24 is configured separately from the electrical connection portion 12. The lead wire 24 is electrically connected to the temperature sensing element 10 and the electrical connection portion 12 by laser welding. Note that while laser welding is preferred, connection by soldering, conductive paste, or wire bonding may also be used.

[0030] Sixth Embodiment A sixth embodiment will be described with reference to Fig. 6. Fig. 6 is a plan view showing a non-contact temperature sensor.

[0031] This embodiment has the same basic configuration as the fourth embodiment (see FIG. 4 ), except that the lead wire 24 is configured separately from the electrical connection portion 12. The lead wire 24 is electrically connected to the temperature sensing element 10 and the electrical connection portion 12 by laser welding. Note that while laser welding is preferred, connection by soldering, conductive paste, or wire bonding may also be used.

[0032] Next, the temperature sensitive element will be described with reference to Fig. 7. Fig. 7 is a configuration diagram for explaining the temperature sensitive element. The temperature sensitive element 10 represented by the third embodiment described above will be described as an example.

[0033] On an insulating substrate 11, a heat-sensitive thin film 10a, a pair of electrode layers 12a and 12b, and a protective film 13 are formed.

[0034] The insulating substrate 11 is a glass substrate having a substantially rectangular shape with dimensions of 1 mm wide x 0.5 mm long and a thickness of 200 μm or less, preferably 150 μm or less, and formed from a glass material. Specifically, the glass substrate of this embodiment has an extremely thin thickness of 100 μm or less, and is made of silicon oxide (SiO ２ ) is contained at 40 to 80%.

[0035] Glass substrates can be made thinner than ceramic substrates because they are less susceptible to cracking during substrate fabrication. Glass substrates also have a low thermal capacity, low infrared transmittance, and the ability to efficiently absorb infrared rays.

[0036] Furthermore, some thin insulating substrates undergo deformation when left in the operating temperature range. For example, it has been confirmed that zirconia substrates deform, become brittle, and deteriorate after being left in a 150°C temperature environment for 1,000 hours, or in a 200°C temperature environment for 200 hours. This substrate deformation is thought to be due to dimensional changes caused by low-temperature thermal degradation resulting from changes in the zirconia crystal structure. Therefore, thin glass substrates used as temperature sensors should be designed to prevent such dimensional changes from occurring within the operating temperature range.

[0037] The glass substrate of this embodiment is made of a material selected to suppress deformation due to phase transitions that cause changes in the chain polymer structure of the glass within the operating temperature range, thereby reducing the reduction in strength. In other words, there is no phase transition point within the operating temperature range that would cause deformation. The operating temperature range is the temperature range in which the non-contact temperature sensor 1 is used in various situations, and is assumed to be between -40°C and 250°C.

[0038] The thermosensitive thin film 10a is a thermosensitive resistive thin film that functions as a temperature sensor and is a thermistor thin film made of an oxide semiconductor having a negative temperature coefficient. The thermistor thin film is formed by sputtering on the insulating substrate 11 and on the electrode layers 12a and 12b, so as to straddle the electrode layers 12a and 12b, and is electrically connected to the electrode layers 12a and 12b.

[0039] The thermistor thin film is made of a thermistor material containing, as its main component, a composite metal oxide having a spinel structure, which is composed of two or more elements selected from transition metal elements such as manganese (Mn), nickel (Ni), cobalt (Co), and iron (Fe). Subcomponents may also be included to improve characteristics. The composition and content of the main component and subcomponents can be determined appropriately depending on the desired characteristics.

[0040] The pair of electrode layers 12a, 12b are formed on the insulating substrate 11 and are electrically connected to the thermosensitive element 10. They are arranged facing each other with a predetermined gap between them. Specifically, the pair of electrode layers 12a, 12b are formed by sputtering a thin metal film, and the metal material used may be a precious metal such as platinum (Pt), gold (Au), silver (Ag), palladium (Pd), or ruthenium (Ru), or an alloy thereof, such as an Ag-Pd alloy. In this embodiment, the electrode layers 12a, 12b are formed below the thermosensitive thin film 10a, but they may also be formed on or within the thermosensitive thin film 10a.

[0041] The protective film 13 covers the region where the heat-sensitive thin film 10a is formed, and also covers the electrode layers 12a and 12b by forming exposed portions so that at least a part of the electrode layers 12a and 12b is exposed. The protective film 13 is made of silicon dioxide (SiO ２ ), silicon nitride (Si ３ N ４ ) or the like can be formed by sputtering, or lead glass, borosilicate glass, lead borosilicate glass, or the like can be formed by printing.

[0042] Next, connection modes between the temperature sensitive element 10 and the lead wires 24 will be described with reference to Figures 8 to 10. Figures 8 to 10 show plan views of connection modes. In each mode, the lead wires 24 extend in different directions.

[0043] 8 shows that lead wires 24 are electrically connected by laser welding to electrode layers 12a and 12b on both ends in the longitudinal direction of insulating substrate 11. Lead wires 24 are perpendicular to the lateral direction of insulating substrate 11 and extend in opposite directions.

[0044] 9 shows a structure in which lead wires 24 are electrically connected by laser welding to electrode layers 12a and 12b on both ends of the insulating substrate 11 in the longitudinal direction. The lead wires 24 are perpendicular to the longitudinal direction of the insulating substrate 11 and extend in the same direction.

[0045] 10 shows a similar structure in which lead wires 24 are electrically connected by laser welding to electrode layers 12a and 12b on both longitudinal ends of insulating substrate 11. Lead wires 24 are perpendicular to the longitudinal direction of insulating substrate 11 and extend in mutually offset opposite directions.

[0046] Next, the evaluation of heat capacity and infrared transmittance will be described with reference to Figures 11 and 12. Figure 11 is a table showing the evaluation of heat capacity of the glass substrate of this embodiment and an alumina substrate as a comparative example. The shape of the insulating substrate 11 of the thermosensitive element 10 (dimensions: width 1 mm x length 0.5 mm) represented by the third embodiment will be used as an example.

[0047] When the thickness is 70 μm, the heat capacity of the alumina substrate of the comparative example is 1.1×10 －４(J / K), whereas the heat capacity of the glass substrate of this embodiment is 0.64×10 －４ (J / K). When the thickness of the substrate is 150 μm, the heat capacity of the alumina substrate of the comparative example is 2.3×10 －４ (J / K), whereas the heat capacity of the glass substrate of this embodiment is 1.4×10 －４ (J / K). Therefore, the heat capacity can be reduced by using a glass substrate.

[0048] 12 is a graph showing the evaluation of infrared transmittance. The horizontal axis represents wavelength [μm], and the vertical axis represents infrared transmittance [%]. This graph shows the cases where the thickness of the glass substrate is 70 μm and 150 μm, and the thickness of the alumina substrate is 150 μm.

[0049] As can be seen from the graph, when comparing infrared transmittance at wavelengths of 20 μm or less, the comparative thin-film thermistor formed on an alumina substrate exhibits a large loss of approximately 70% transmittance for infrared rays at wavelengths of approximately 6.5 μm, which have the highest energy radiation in the wavelength range. This results in a problem of poor temperature measurement accuracy. However, the thin-film thermistor formed on an ultra-thin glass substrate exhibits an infrared transmittance of approximately 0% for wavelengths of approximately 6.5 μm or more, demonstrating that the use of a glass substrate allows for efficient absorption of infrared rays. This means that improved temperature measurement accuracy can be expected.

[0050] Next, performance evaluation will be described with reference to FIG. 13. FIG. 13 is a table showing the thermal time constant (seconds) and the reached temperature (°C). The temperature of the object to be detected is set to 200°C, and the distance between the object to be detected and the non-contact temperature sensor 1 is set to 1 mm. The reached temperature (°C) is the temperature 2 minutes after the start of temperature measurement. In this embodiment, the heat capacity of the glass substrate is small, which shortens the time required to reach the specified temperature, shortens the thermal time constant, and improves thermal response. Furthermore, because the glass substrate efficiently absorbs infrared rays, the reached temperature approaches the temperature of the object to be measured.

[0051] As described above, according to this embodiment, it is possible to provide a non-contact temperature sensor that can improve thermal response and temperature measurement accuracy.

[0052] Next, an example of the mounting state of the non-contact temperature sensor 1 will be described with reference to Figures 14 and 15. In this example, the non-contact temperature sensor 1 is mounted in a fixing device of a copying machine, printer, or the like.

[0053] 14, a heating roller 20 and a pressure roller (not shown) are supported rotatably, and the heating roller 20 receives a rotational driving force from a driving means. The pressure roller is in pressure contact with the surface of the heating roller 20 and is arranged to rotate due to the frictional force at the pressure contact portion (nip portion).

[0054] Non-contact temperature sensor 1 is attached to a support part with a distance of approximately 0.5 mm to 1.5 mm from heat roller 20. Heat roller 20 is set to 200°C. Non-contact temperature sensor 1 receives heat from heat roller 20, detects changes in resistance, and controls the surface temperature of heat roller 20 to a predetermined temperature.

[0055] In this case, the temperature sensitive element 10 formed on one surface of the glass substrate of the insulating substrate 11 is disposed facing the heating roller 20, which is the object to be detected, and is directed toward the heating roller 20 side.

[0056] Next, in Figure 15, the installation state of the non-contact temperature sensor 1 is the same as in Figure 14. In this case, however, the other surface of the glass substrate of the insulating substrate 11 faces the heating roller 20, which is the object to be detected, and the other surface of the glass substrate is disposed facing the heating roller 20.

[0057] As shown in Figure 16, we evaluated the case where the temperature-sensitive element 10 formed on one side (mounting side) of the glass substrate faces the heating roller 20 (see Figure 14) and the case where the other side (rear side) of the glass substrate faces the heating roller 20 (see Figure 15).

[0058] 16 is a table showing the thermal time constant (seconds) and the temperature (°C) reached. The temperature (°C) reached is the temperature two minutes after the start of temperature measurement.

[0059] As a result, it was found that in the mounting state shown in Figure 15, where the other side (rear side) of the glass substrate faces the heating roller 20, the thermal time constant (seconds) is short, the temperature rise is fast, and the thermal response is good. This is thought to be due to the good infrared absorption rate of the glass substrate.

[0060] The temperature sensor 20 in each of the embodiments described above can be provided and applied to various devices for detecting the temperature of electronic devices such as fixing devices in copiers and printers, information and communication devices such as mobile communication terminals and personal computers, video devices, consumer devices, and automotive electrical devices, but is not limited to specific devices.

[0061] The present invention is not limited to the configurations of the above-described embodiments, and various modifications are possible within the scope of the invention. Furthermore, the above-described embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the inventions and their equivalents as set forth in the claims.

[0062] REFERENCE SIGNS LIST 1 Non-contact temperature sensor 2 Holder 3 Lead portion (lead frame) 10 Temperature-sensing element 11 Insulating substrate (glass substrate) 12 Electrical connection portion 12a, 12b Electrode layer 13 Protective film 20 Heating roller 21 Opening 22 External lead wire 23 Insulating coating portion 24 Lead wire

Claims

1. A non-contact temperature sensor having a holder, a lead portion held by the holder, and a temperature-sensing element electrically connected to the lead portion, characterized in that the non-contact temperature sensor further comprises a glass substrate made of a glass material on which the temperature-sensing element is formed, and the glass substrate does not undergo a phase transition within the operating temperature range.

2. The non-contact temperature sensor according to claim 1, wherein the glass substrate has a thickness of 200 μm or less.

3. A non-contact temperature sensor according to claim 1 or 2, characterized in that the temperature-sensing element is a thin-film thermistor.

4. A non-contact temperature sensor as described in claim 1, characterized in that a lead wire is connected to the temperature sensing element, and the lead wire is formed integrally with an electrical connection portion connected to the lead portion.

5. A non-contact temperature sensor as described in claim 1, characterized in that a lead wire is connected to the temperature sensing element, and the lead wire is configured separately from the electrical connection portion connected to the lead portion.

6. A non-contact temperature sensor according to claim 4 or 5, characterized in that the lead wires are electrically connected to the temperature-sensitive element by welding.

7. A non-contact temperature sensor according to claim 1 or 2, characterized in that the temperature-sensing element is formed on one side of a glass substrate, and the other side of the glass substrate is arranged facing the object to be sensed.

8. A non-contact temperature sensor as claimed in claim 1 or 2, characterized in that at least both ends of the glass substrate are electrically connected to electrical connection parts connected to the lead parts by means of conductive paste.

9. A non-contact temperature sensor according to claim 1 or 2, characterized in that the temperature sensing element and at least a part of the lead portion are insulated by an insulating coating portion.

10. The non-contact temperature sensor according to claim 9, wherein the insulating coating portion sandwiches and covers at least a portion of the temperature sensing element and the lead portion from both sides.

11. The non-contact temperature sensor according to claim 9, wherein the insulating coating has an infrared absorbing ability.

12. The non-contact temperature sensor according to claim 9, wherein the insulating coating absorbs at least a part of infrared rays in the wavelength range of 1 μm to 6 μm.

13. The non-contact temperature sensor according to claim 9, wherein the insulating coating portion is provided in contact with only two opposing sides of the holder.

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