Clearance Sensor

Abstract

To provide a clearance sensor used for a long term in high temperature environment.SOLUTION: A clearance sensor includes: a detection electrode part; a first insulation part provided to cover the outer peripheral surface of the detection electrode part; a shield electrode part provided to cover the outer peripheral surface of the first insulation part; a second insulation part provided to cover the outer peripheral surface of the shield electrode part; an outer wall part provided to cover the outer peripheral surface of the second insulation part; a bond coat provided on the detection side end surface of the detection electrode part and having oxidation resistance; and a topcoat provided on the surface of the bond coat on the detection side end surface of the detection electrode part and having heat-shielding properties.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a clearance sensor. [Background technology]

[0002] Axial flow rotary machines, such as compressors, are known that compress a working fluid using a rotor with multiple rotor blades that rotates inside a cylindrical casing. In these types of axial flow rotary machines, a clearance sensor is provided to measure the clearance between the casing and the rotor blades, and the clearance is controlled by, for example, supplying cooling air to the casing so that the measured clearance value is appropriate. A non-contact type sensor, such as a capacitance type sensor as described in Patent Document 1, is used as this clearance sensor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6431665 Summary of the Invention [Problem to be solved by the invention]

[0004] When such clearance sensors are used for a long period of time in a high-temperature environment, such as in a turbine casing, there is a problem that oxidation thinning occurs, causing damage. Furthermore, when operating in an industrial gas turbine that is subject to repeated start-stops, appropriate high-temperature countermeasures are required accordingly.

[0005] In view of the above problems, the present disclosure Even in high temperature environments, the deterioration of detection accuracy is suppressed by suppressing electrical connection between electrodes. The object is to provide a clearance sensor that can be used for a long period of time in a high-temperature environment. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the clearance sensor of the present disclosure comprises a detection electrode portion, a first insulating portion covering the outer peripheral surface of the detection electrode, a shield electrode portion covering the outer peripheral surface of the first insulating portion, a second insulating portion covering the outer peripheral surface of the shield electrode portion, an outer wall portion covering the outer peripheral surface of the second insulating portion, a bond coat having oxidation resistance provided on the detection side end surface of the detection electrode portion, and a top coat having heat-shielding properties provided on the surface of the bond coat at the detection side end surface of the detection electrode portion. [Effects of the Invention]

[0007] According to the present disclosure, Even in high temperature environments, the deterioration of detection accuracy is suppressed by suppressing electrical connection between electrodes. It is possible to provide a clearance sensor that can be used for a long period of time in a high-temperature environment. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing an application example of a clearance sensor according to the present disclosure. [Figure 2] FIG. 2 is a diagram showing the change in capacitance between electrodes over time when the rotor blade passes. [Figure 3] FIG. 3 is a diagram showing the relationship between the distance between electrodes and the capacitance between the electrodes. [Figure 4] FIG. 4 is a diagram showing a detection side end face of the clearance sensor according to the present disclosure. [Figure 5] FIG. 5 is a cross-sectional view of the clearance sensor according to the first aspect of the first embodiment, taken along line AA. [Figure 6] FIG. 6 is a cross-sectional view of the clearance sensor according to the second aspect of the first embodiment, taken along line AA. [Figure 7] FIG. 7 is a cross-sectional view of the clearance sensor according to the second embodiment taken along line AA. [Figure 8] FIG. 8 is a diagram showing the test results of the thermal cycle test. [Figure 9] FIG. 9 is a diagram illustrating an example of the configuration of a clearance sensor system according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, the present disclosure is not limited to the embodiments described below.

[0010] (Example of application of clearance sensor) Fig. 1 is a schematic diagram showing an application example of a clearance sensor according to the present disclosure. As shown in Fig. 1, a clearance sensor 100 according to the present disclosure is attached to a casing 200 of an axial flow rotating machine such as an industrial gas turbine, and is a sensor for measuring a distance D (clearance) between the casing 200 and a rotor blade 310 attached to a disk 320 of a rotor 300. Here, the axial flow rotating machine to which the clearance sensor 100 is attached may be an industrial gas turbine, a steam turbine, a turbojet engine, a turbofan jet engine, a turboprop engine, or the like. However, the clearance sensor 100 is not limited to being used in an axial flow rotating machine, and may be used to measure the clearance between any members.

[0011] Let's take an industrial gas turbine as an example of an axial flow rotary machine. When the distance D (clearance) between the rotor blades and the casing of a compressor or turbine becomes large, leakage flow occurs. This prevents the rotor blades from transmitting power to the air, preventing proper interaction between the rotor blades and the air in the compressor or turbine. Furthermore, when the temperature of the casing or rotor blades rises, thermal expansion occurs, causing the clearance D between the casing and rotor blades to change. For this reason, it is necessary to control the clearance D to an appropriate value while the industrial gas turbine is operating.

[0012] 1, when the rotor blade 310 passes, the capacitance C between the clearance sensor 100 and the rotor blade 310 changes. In other words, when the metal part of the clearance sensor 100 and the metallic rotor blade 310 are not in contact with each other, no charge flows between them, and they function as a capacitor that stores charge.

[0013] 2 is a diagram showing the change in capacitance between the electrodes over time when the rotor blade 310 passes by. As shown in FIG. 2, when the rotor blade 310 passes the tip end of the clearance sensor 100, the capacitance C between them becomes the largest.

[0014] 3 is a diagram showing the relationship between the distance between electrodes and the capacitance between the electrodes. As shown in FIG. 3, the smaller the clearance D between the clearance sensor 100 and the rotor blade 310, the larger the capacitance C. Therefore, the clearance D can be calculated by measuring the capacitance C between the two. Specifically, the clearance D is calculated based on the following formula (1).

[0015]

number

[0016] Here, C in equation (1) represents the capacitance between the clearance sensor 100 and the rotor blade 310, A represents the projected area of ​​the electrode of the clearance sensor 100 onto the rotor blade 310, D represents the distance (clearance) between the clearance sensor 100 and the rotor blade 310, εr represents the dielectric constant of a vacuum, and ε0 represents the relative dielectric constant of the working fluid.

[0017] (Clearance sensor configuration) The configuration of clearance sensor 100 will be described with reference to Fig. 4. Fig. 4 is a diagram showing the detection side end face of the clearance sensor according to the present disclosure. As shown in Fig. 4, clearance sensor 100 includes detection electrode portion 110, insulating portion 120, shield electrode portion 130, and outer wall portion 140.

[0018] The detecting electrode unit 110 is a cylindrical electrode, but its shape is not limited to a cylindrical shape and may be any shape, such as a polygonal pillar. The detecting electrode unit 110 has a detecting end surface 110A at one end in the axial direction of the central axis AX of the clearance sensor 100. The detecting electrode unit 110 is made of a conductive material. The detecting electrode unit 110 may be made of a Ni-based alloy, which has excellent corrosion resistance and heat resistance. This makes it possible to properly measure the current flowing through the detecting electrode unit 110 for a long period of time, even in a high-temperature environment.

[0019] The insulating portion 120 includes a first insulating portion 121 and a second insulating portion 122 .

[0020] The first insulating part 121 is an insulating part provided to cover the outer peripheral surface of the detecting electrode part 110. The first insulating part 121 has a detection-side end face 121A at one end in the axial direction of the central axis AX of the clearance sensor 100. The first insulating part 121 is provided between the detecting electrode part 110 and the shield electrode part 130 to electrically insulate them from each other. The first insulating part 121 is formed of an insulator such as ceramics. The first insulating part 121 may be made of alumina, for example. By providing the first insulating part 121 between the detecting electrode part 110 and the shield electrode part 130, it is possible to prevent current from flowing between the detecting electrode part 110 and the shield electrode part 130. Therefore, the current flowing through the detecting electrode part 110 and the current flowing through the shield electrode part 130 can be clearly separated.

[0021] The shield electrode portion 130 is a cylindrical component provided to cover the outer peripheral surface of the first insulating portion 121. That is, the shield electrode portion 130 is provided between the first insulating portion 121 and the second insulating portion 122. The shape of the shield electrode portion 130 is not limited to a cylindrical shape and may be, for example, a polygonal cylindrical shape. The shield electrode portion 130 has a detection-side end face 130A at one end in the axial direction of the central axis AX of the clearance sensor 100. The shield electrode portion 130 is formed of a conductive material. The shield electrode portion 130 may be formed of, for example, a Ni-based alloy that has excellent corrosion resistance and heat resistance. This makes it possible to properly measure the current flowing through the shield electrode portion 130 for a long period of time, even in a high-temperature environment.

[0022] The second insulating portion 122 is an insulating component provided to cover the outer peripheral surface of the shield electrode portion 130. The second insulating portion 122 has a detection-side end face 122A at one end in the axial direction of the central axis AX of the clearance sensor 100. The second insulating portion 122 is provided between the shield electrode portion 130 and the outer wall portion 140 to provide electrical insulation therebetween. The second insulating portion 122 is formed of an insulator such as ceramics. The second insulating portion 122 may be made of alumina, for example. By providing the second insulating portion 122 between the shield electrode portion 130 and the outer wall portion 140, it is possible to prevent current from flowing between the shield electrode portion 130 and the outer wall portion 140. This reduces the influence of the external environment on the current flowing through the detection electrode portion 110.

[0023] The outer wall portion 140 is a cylindrical component provided to cover the outer peripheral surface of the second insulating portion 122. That is, the outer wall portion 140 is electrically insulated from the shield electrode portion 130 by the second insulating portion 122. The outer wall portion 140 has a detection-side end surface 140A at one end in the axial direction of the central axis AX of the clearance sensor 100. The outer wall portion 140 is formed of a conductive material. The outer wall portion 140 may be formed of, for example, a Ni-based alloy that has excellent corrosion resistance and heat resistance. By providing the outer wall portion 140 outside the detection electrode portion 110 and the shield electrode portion 130, the influence of the environment outside the clearance sensor 100 on the current flowing through the detection electrode portion 110 and the shield electrode portion 130 can be reduced.

[0024] (First embodiment) 5 is a diagram showing a cross-sectional view of the clearance sensor according to the first aspect of the first embodiment taken along line AA. In addition to the above-described configuration, the clearance sensor 100 according to the first aspect of the first embodiment includes a bond coat 150 and a top coat 160.

[0025] The bond coat 150 is an oxidation-resistant coating provided on the detection-side end surface 110A of the detection electrode unit 110. In this embodiment, the bond coat 150 is also provided on the detection-side end surface 140A of the outer wall unit 140. The bond coat 150 prevents oxidation and improves adhesion of the top coat 160. The bond coat 150 may be formed of, for example, CoNiCrAlY. CoNiCrAlY is a material that has an excellent balance of oxidation resistance and sulfidation resistance. In addition to CoNiCrAlY, the bond coat 150 may also be CoCrAlY, which has excellent high-temperature corrosion resistance, or NiCrAlY, which has excellent oxidation resistance. The bond coat 150 may be formed by, for example, low-pressure plasma spraying (LPS), atmospheric plasma spraying (APS), high-velocity oxygen-fuel (HVOF) spraying, or the like. The bond coat 150 may have a thickness of, for example, 0.01 to 0.50 mm.

[0026] The top coat 160 is a thermally insulating coating provided on the surface of the bond coat 150 at the detection-side end surface 110A of the detection electrode 110. The top coat 160 may be formed, for example, from yttria-stabilized zirconia (YSZ). Yttria-stabilized zirconia is a zirconia-based oxide in which yttrium oxide is added to stabilize the zirconia crystal structure at room temperature. Yttria-stabilized zirconia has a thermal conductivity of 1.2 to 2.3 W / mK, significantly lower than that of metals. Therefore, forming the top coat 160 on the surface of the bond coat 150 at the detection-side end surface 110A of the detection electrode 110 can improve thermal insulation. Like the bond coat 150, the top coat 160 may be formed by low-pressure plasma spraying, atmospheric plasma spraying, high-velocity oxygen flame spraying, or the like. The thickness of the topcoat 160 may be, for example, 0.1 to 1.0 mm.

[0027] According to this configuration, the bond coat 150 prevents oxidation of the detection electrode portion 110, and the top coat 160 provides heat insulation, so that the clearance sensor 100 can be used for a long period of time in a high-temperature environment.

[0028] Hereinafter, the laminate in which the bond coat 150 and the top coat 160 are stacked will be referred to as the laminate 165. In this case, the laminate 165 (the bond coat 150 and the top coat 160) is provided so as to disconnect the detection electrode portion 110 from the shield electrode portion 130, and the detection electrode portion 110 and the shield electrode portion 130 are not connected via the laminate 165. In other words, the laminate 165 is not provided from the detection-side end surface 110A of the detection electrode portion 110 to the detection-side end surface 130A of the shield electrode portion 130. In other words, the laminate 165 is provided so as to be discontinuous between the detection-side end surface 110A and the detection-side end surface 130A. Similarly, the laminate 165 is provided so as to disconnect the outer wall portion 140 from the shield electrode portion 130, and the outer wall portion 140 and the shield electrode portion 130 are not connected via the laminate 165. In other words, the laminate 165 is not provided from the detection side end face 140A of the outer wall portion 140 to the detection side end face 130A of the shield electrode portion 130; in other words, the laminate 165 is provided so as to be discontinuous between the detection side end face 140A and the detection side end face 130A.

[0029] As shown in FIG. 5 , in the first aspect of the first embodiment, the laminate 165 is spaced apart from the shield electrode section 130, and more specifically, from the detection-side end face 130A of the shield electrode section 130. The distance between the laminate 165 and the detection-side end face 130A of the shield electrode section 130 is preferably, for example, 0.1 mm or more. In this embodiment, the detection-side end face 130A of the shield electrode section 130 is not provided with the laminate 165 and is exposed to the outside. Furthermore, the laminate 165 is spaced apart from the first insulating section 121, and more specifically, from the detection-side end face 121A of the first insulating section 121. Furthermore, the laminate 165 is spaced apart from the second insulating section 122, and more specifically, from the detection-side end face 122A of the second insulating section 122. In the first mode of the first embodiment, the detection side end surface 121A of the first insulating part 121 and the detection side end surface 122A of the second insulating part 122 are not provided with the laminate 165 and are exposed to the outside.

[0030] Thus, in the first aspect of the first embodiment, the laminate 165 is provided on the detection side end surface 110A of the detection electrode portion 110 and on the detection side end surface 140A of the outer wall portion 140, but is not provided on the detection side end surface 130A of the shield electrode portion 130, the detection side end surface 121A of the first insulating portion 121, or the detection side end surface 122A of the second insulating portion 122.

[0031] However, as shown in FIG. 6, for example, the laminate 165 may be provided on the detection-side end surface 130A of the shield electrode section 130 while disconnecting the detection electrode section 110 from the shield electrode section 130. FIG. 6 is a cross-sectional view of a clearance sensor according to a second aspect of the first embodiment, taken along line AA. As shown in FIG. 6, the laminate 135 is provided on the detection-side end surface 130A of the shield electrode section 130, but is not provided on at least a portion of the detection-side end surface 121A of the first insulating section 121 or the detection-side end surface 122A of the second insulating section 122. Even if the laminate 135 is provided on the detection-side end surface 130A of the shield electrode section 130, the laminate 135 is discontinued at the detection-side end surface 121A, and therefore the detection electrode section 110 and the shield electrode section 130 are disconnected. Similarly, in this case, since the laminate 135 is discontinued at the detection-side end surface 121A, the outer wall portion 140 and the shield electrode portion 130 are not connected to each other.

[0032] In yet another embodiment, laminate 165 is provided on detection-side end surface 121A of first insulating part 121 and detection-side end surface 122A of second insulating part 122, but does not necessarily have to be provided on detection-side end surface 130A of shield electrode part 130. Even in this case, laminate 135 is discontinued at detection-side end surface 130A, so that detection electrode part 110 and shield electrode part 130 are not connected, and outer wall part 140 and shield electrode part 130 are not connected.

[0033] The laminate 165 has insulating properties at room temperature, for example, but may lose its insulating properties in a high-temperature environment. Specifically, the bond coat 150 may be conductive even at room temperature because its main component is a metal such as nickel (Ni) or cobalt (Co). The top coat 160 has insulating properties at room temperature, for example, but may lose its insulating properties in a high-temperature environment. This is because yttria-stabilized zirconia exhibits the properties of a solid electrolyte in a high-temperature environment. Therefore, if the laminate 165 is formed from the shield electrode portion 130 to the detection electrode portion 110, the conductive laminate 165 may electrically connect the detection electrode portion 110 and the shield electrode portion 130, or the shield electrode portion 130 and the outer wall portion 140, in a high-temperature environment, for example, thereby reducing the detection accuracy of the clearance sensor 100. Therefore, in this embodiment, by providing the laminate 165 so that the shield electrode portion 130 and the detection electrode portion 110 are not connected by the laminate 165, electrical connection between the detection electrode portion 110 and the shield electrode portion 130 and between the shield electrode portion 130 and the outer wall portion 140 is suppressed, and a decrease in the detection accuracy of the clearance sensor 100 is suppressed, while durability at high temperatures can be maintained by providing the laminate 165 on the detection electrode portion 110 and the outer wall portion 140.

[0034] As described above, in the first embodiment, the laminate 165 is provided so as to disconnect the detection electrode portion 110 from the shield electrode portion 130 and so as to disconnect the outer wall portion 140 from the shield electrode portion 130, but this is not limiting. For example, the laminate 165 may be provided so as to cover the entire detection-side end faces of the detection electrode portion 110, the shield electrode portion 130, and the outer wall portion 140. Even in this case, the clearance sensor 100 can be used for a long period of time in a high-temperature environment.

[0035] (Second embodiment) 7 is a cross-sectional view of the clearance sensor according to the second embodiment taken along line AA. The clearance sensor 100 according to the second embodiment includes an insulating coating 170 in addition to the configuration of the clearance sensor 100 according to the first aspect of the first embodiment.

[0036] The insulating coating 170 is a coating having insulating properties. As shown in Fig. 7, the insulating coating 170 may be formed on the detection-side end surface 130A of the shield electrode section 130 and on the detection-side end surfaces 121A and 122A of the first insulating section 121 and the second insulating section 122. Although not shown in Fig. 7, the insulating coating 170 may be formed only on the detection-side end surface 130A of the shield electrode section 130. The insulating coating 170 may be made of, for example, spinel, yttria, alumina, or the like.

[0037] Spinel has the general formula A 2+ B2 3+ O4 2- It is a type of mineral represented by the formula: Spinel may be, for example, magnesium aluminate (MgAl2O4), zinc spinel (ZnAl2O4), or iron spinel (FeAl2O4). Magnesium aluminate has a high melting point of 2135°C and excellent electrical insulation properties. Yttria (Y2O3) is an oxide ceramic with a melting point of 2425°C and a thermal conductivity of 27 W / mK. Alumina (Al2O3) is an oxide ceramic with a melting point of 2072°C and a thermal conductivity of 30 W / mK.

[0038] The top coat 160 and the insulating coat 170 provided on the detection-side end surface 110A of the detection electrode unit 110 are preferably formed to eliminate any step between them. Furthermore, the top coat 160 and the insulating coat 170 provided on the detection-side end surface of the shield electrode unit 130 are preferably formed to eliminate any step between them. In this case, for example, the arithmetic mean roughness Ra of the surface extending from the top coat 160 to the insulating coat 170 is preferably 20 μm or less. The arithmetic mean roughness Ra can be measured in accordance with JIS B 0601:2001. The thickness of the insulating coat 170 may be, for example, 0.1 to 1.0 mm. The resistance value of the insulating coat 170 may be 100 kΩ or more in a temperature environment of 800°C or higher, and preferably 1 MΩ or more. Furthermore, it is more preferable that the resistance value of the insulating coat 170 remains the same even in a temperature environment of 600°C or higher.

[0039] According to this configuration, the insulating coating 170, which has a lower thermal conductivity than metal, is formed on the detection-side end surface 130A of the shield electrode unit 130, so that the shield electrode unit 130 can be protected in a high-temperature environment. Also, conduction of current between the detection electrode unit 110 and the shield electrode unit 130 can be prevented.

[0040] In the second embodiment, no member is provided on the insulating coating 170, and the insulating coating 170 is exposed to the outside. However, the laminate 165 may be provided on the insulating coating 170. Even in this case, the insulating coating 170 exists between the shielded electrode section 130 and the laminate 165, and between the first insulating section 121 and the second insulating section 122 and the laminate 165, so that insulation between the detecting electrode section 110 and the shielded electrode section 130 can be ensured. Furthermore, with this configuration, the heat resistance of the shielded electrode section 130 can also be improved.

[0041] (Experimental example) FIG. 8 shows the results of a thermal cycle test. A coating was formed on the front surface of a metal plate, and while the back surface was cooled, the front surface was irradiated with a laser beam of a predetermined intensity to heat it. This process was repeated a predetermined number of times, and the number of times the coating peeled off was counted. The horizontal axis of FIG. 8 represents the number of thermal cycles at which the coating peeled off from the test specimen. The vertical axis of FIG. 8 represents the temperature difference between the front and back surfaces of the test specimen coating. The square plots in FIG. 8 represent the test results of a test specimen in which a CoNiCrAlY bond coat 150, an yttria-stabilized zirconia (YSZ) top coat 160, and yttria were formed on the front surface of a metal plate in the manner shown in FIG. 7. The triangle plots in FIG. 8 represent the test results of a test specimen in which a CoNiCrAlY bond coat and an yttria-stabilized zirconia (YSZ) top coat 160 were formed on the front surface of a metal plate in the manner shown in FIG. 5. The ∘ plots in Figure 8 show the test results for test specimens in which CoNiCrAlY was used as the bond coat 150, yttria-stabilized zirconia was used as the top coat 160, and spinel was used as the insulating coat 170 on the surface of a metal plate in the manner shown in Figure 7, and then the test specimens were treated to eliminate any unevenness between the top coat 160 and the insulating coat 170. As shown in Figure 8, compared to the test specimens in which yttria-stabilized zirconia (YSZ) and yttria were coated (square plots in Figure 8), the test specimens in which yttria-stabilized zirconia (YSZ) with an uneven surface (triangle plots in Figure 8) and the test specimens in which yttria-stabilized zirconia (YSZ) and spinel were coated (circle plots in Figure 8) showed a higher number of thermal cycles. It can be seen that coating yttria-stabilized zirconia (YSZ) and spinel with minimal unevenness is preferable because it increases the number of thermal cycles and improves heat resistance. However, this is just one experimental example, and the present disclosure is not limited to this experimental example.

[0042] (Configuration of clearance sensor system) Next, the configuration of the clearance sensor system will be described with reference to Fig. 9. Fig. 9 is a diagram showing the configuration of the clearance sensor system according to the present disclosure. As shown in Fig. 9, the clearance sensor system 500 according to the present disclosure includes a clearance sensor 100 and a processing device 400. The configuration of the clearance sensor 100 will be described later, so here, the relationship between the clearance sensor 100 and the processing device 400, and the configuration of the processing device 400 will be described.

[0043] 9, a clearance sensor system 500 according to the present disclosure includes a clearance sensor 100 and a processing device 400. The detection electrode portion 110, the shield electrode portion 130, and the outer wall portion 140 of the clearance sensor 100 are connected to the processing device 400.

[0044] An AC voltage is applied to the detection electrode unit 110 from an AC power supply 410 included in the processing device 400 via an inorganic insulated (MI) cable and a flexible cable. The MI cable has a conductor portion, a tubular member, and a tubular component, and is used in high-temperature or harsh environments. The MI cable has a triple structure consisting of the conductor portion, the tubular member, and the tubular component, and an insulator such as magnesium oxide is filled between each component. Magnesium oxide is a non-reactive insulator, so it can prevent the current flowing through the conductor portion from being affected by external factors. Furthermore, the tubular member and the tubular component of the MI cable are made of a Ni-based alloy, so long-term measurements are possible even in high-temperature environments.

[0045] Similarly, an AC voltage is applied to the shielded electrode section 130 from an AC power supply 410 provided in the processing device 400 via an MI cable and a flexible cable. The MI cable connected to the outer wall section 140 is connected to the ground. The flexible cable connected to the MI cable connected to the outer wall section 140 is connected to the ground of the processing device 400.

[0046] The processing device 400 includes a CPU (Central Processing Unit) and a storage device, and executes various types of arithmetic processing. The storage device stores various types of information, such as programs related to the arithmetic processing executed by the CPU, and includes, for example, a main storage device such as a RAM (Random Access Memory) and a ROM (Read Only Memory), and an external storage device such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive).

[0047] As shown in FIG. 9, the processing device 400 includes an AC power supply 410, an ammeter 420, and a voltmeter 430.

[0048] AC power supply 410 is connected to a flexible cable connected to detection electrode unit 110 via an MI cable and to a flexible cable connected to shield electrode unit 130 via an MI cable, and applies an AC voltage to both. That is, the same AC voltage V is applied from AC power supply 410 to detection electrode unit 110 and shield electrode unit 130.

[0049] Ammeter 420 is connected to a flexible cable that is connected to detection electrode unit 110 via an MI cable, and measures AC current Ie that flows through detection electrode unit 110.

[0050] The voltmeter 430 is connected to the ground of the processing device 400 and between the AC power supply 410 and the ammeter 420, and measures the AC voltage V applied by the AC power supply 410 to the detection electrode section 110 and the shield electrode section .

[0051] The capacitance C between the detection electrode unit 110 and the rotor blade 310 is calculated from the AC current Ie flowing through the detection electrode unit 110 and the AC current Ig flowing through the shield electrode unit 130, and the clearance D is calculated using the above formula (1). If the shield electrode unit 130 is not present, the AC current Ie of the detection electrode unit 110 will include not only the capacitance C between the detection electrode unit 110 and the rotor blade 310 but also the effects of other capacitances. Therefore, by using the AC current Ig flowing through the shield electrode unit 130, the capacitance C between the detection electrode unit 110 and the rotor blade 310 can be calculated more accurately.

[0052] (Composition and Effects) The clearance sensor according to the present disclosure comprises a detection electrode portion 110, a first insulating portion 121 provided to cover the outer peripheral surface of the detection electrode portion 110, a shield electrode portion 130 provided to cover the outer peripheral surface of the first insulating portion 121, a second insulating portion 122 provided to cover the outer peripheral surface of the shield electrode portion 130, an outer wall portion 140 provided to cover the outer peripheral surface of the second insulating portion 122, a bond coat 150 provided on the detection side end surface of the detection electrode portion 110 and having oxidation resistance, and a top coat 160 provided on the bond coat 150 on the detection side end surface of the detection electrode portion 110 and having heat-shielding properties.

[0053] According to this configuration, the bond coat 150 prevents oxidation of the detection electrode portion 110, and the top coat 160 provides heat insulation, so that the clearance sensor 100 can be used for a long period of time in a high-temperature environment.

[0054] The bond coat 150 and the top coat 160 (laminate 165) are provided so as to disconnect the detection electrode portion 110 from the shield electrode portion .

[0055] According to this configuration, the detection electrode portion 110 and the shield electrode portion 130 are not connected by the laminate 165, and therefore electrical connection between the detection electrode portion 110 and the shield electrode portion 130 is prevented, thereby preventing a decrease in the detection accuracy of the clearance sensor 100 while maintaining durability at high temperatures.

[0056] The bond coat 150 and the top coat 160 (laminate 165) are spaced apart from the shield electrode portion 130. This configuration prevents electrical connection between the detection electrode portion 110 and the shield electrode portion 130, thereby preventing a decrease in the detection accuracy of the clearance sensor 100 and maintaining durability at high temperatures.

[0057] An insulating coating 170 is provided on the detection side end face of the shield electrode section 130 .

[0058] With this configuration, insulating coating 170, which has lower thermal conductivity than metal, is formed on the detection-side end surface of shield electrode 130, so that shield electrode 130 can be protected in a high-temperature environment. Also, conduction of current between detection electrode 110 and shield electrode 130 can be prevented. This improves the accuracy of clearance measurement.

[0059] The bond coat 150 and the top coat 160 are spaced apart from the first insulating portion 121 and the second insulating portion 122 .

[0060] According to this configuration, the bond coat 150 and the top coat 160 are not formed on the detection side end surfaces of the first insulating portion 121 and the second insulating portion 122, so that the conductive bond coat 150 is prevented from coming into contact with the shield electrode portion 130, preventing electrical continuity between the detection electrode portion 110 and the shield electrode portion 130 via the bond coat 150. This improves the accuracy of the clearance measurement.

[0061] An insulating coating 170 is provided on the detection side end surfaces of the first insulating portion 121 and the second insulating portion 122.

[0062] According to this configuration, insulating coating 170, which has lower thermal conductivity than metal, is formed on the detection-side end surfaces of first insulating portion 121 and second insulating portion 122, so that first insulating portion 121 and second insulating portion 122 can be protected in a high-temperature environment. Also, conduction of current between detecting electrode portion 110 and shield electrode portion 130 can be prevented. Therefore, the accuracy of clearance measurement can be improved.

[0063] The top coat 160 provided on the detection side end face of the detection electrode section 110 and the insulating coat 170 provided on the detection side end face of the shield electrode section 130 are formed so as to eliminate any step between them.

[0064] This configuration reduces stress concentration in the insulating coating 170 and improves the peeling resistance of the insulating coating 170.

[0065] The bond coat 150 material includes CoNiCrAlY.

[0066] This configuration improves the oxidation resistance of clearance sensor 100, allowing it to be used for a long period of time in a high-temperature environment.

[0067] The material of the top coat 160 includes yttria-stabilized zirconia.

[0068] According to this configuration, the heat insulation of the clearance sensor 100 can be improved, and therefore the clearance sensor 100 can be used for a long period of time in a high-temperature environment.

[0069] The material of the insulating coating 170 includes at least one of spinel, yttria, and alumina.

[0070] According to this configuration, the detection electrode section 110 and the shield electrode section 130 can be appropriately insulated from each other.

[0071] The resistance value of the insulating coating 170 is 100 kΩ or more in a temperature environment of 600° C. or more.

[0072] This configuration allows the detection electrode section 110 and the shield electrode section 130 to be appropriately insulated from each other even in a high-temperature environment.

[0073] Although the embodiments of the present disclosure have been described above, the embodiments are not limited to the contents of these embodiments. Furthermore, the above-described components include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the above-described components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the above-described embodiments. [Explanation of symbols]

[0074] 100 Clearance Sensor 110 detection electrode part 120 Insulation 121 First insulation section 122 Second insulating section 130 Shield electrode part 140 Exterior wall 150 Bond Coat 160 Top Coat 170 Insulation Coat 200 casing 300 rotors 310 Moving blade 320 disc 400 Processing Equipment 410 AC power supply 420 ammeter 430 Voltmeter C capacitance D. Clearance

Claims

1. A detection electrode portion; a first insulating portion provided to cover an outer peripheral surface of the detection electrode portion; a shield electrode portion provided to cover an outer peripheral surface of the first insulating portion; a second insulating portion provided to cover an outer peripheral surface of the shield electrode portion; an outer wall portion provided to cover an outer peripheral surface of the second insulating portion; a bond coat having oxidation resistance and provided on a detection side end surface of the detection electrode portion; a top coat having heat insulating properties, the top coat being provided on a surface of the bond coat at a detection side end surface of the detection electrode portion; the bond coat and the top coat are provided so as to disconnect the detection electrode portion from the shield electrode portion, The top coat material includes yttria-stabilized zirconia; an insulating coating is provided on the detection side end surface of the shield electrode portion; an insulating coating is provided on detection side end surfaces of the first insulating portion and the second insulating portion; The insulating coating material contains spinel, The arithmetic mean roughness Ra of the surface extending from the top coat to the insulating coat is 20 μm or less. Clearance sensor.

2. The clearance sensor of claim 1 , wherein the bond coat and the top coat are spaced apart from the shield electrode portion.

3. the bond coat and the top coat are spaced apart from the first insulating portion and the second insulating portion; The clearance sensor according to claim 1 or 2.

4. the bond coat and the top coat are provided in this order on a detection side end surface of the outer wall portion; The clearance sensor according to any one of claims 1 to 3.

5. the top coat provided on the detection side end surface of the detection electrode portion and the insulating coat provided on the detection side end surface of the shield electrode portion are formed so as to eliminate any step therebetween; The clearance sensor according to claim 1 .

6. The bond coat material includes CoNiCrAlY. The clearance sensor according to any one of claims 1 to 5.

7. The material of the insulating coating includes at least one of yttria and alumina. The clearance sensor according to claim 1 .

8. The resistance value of the insulating coating is 100 kΩ or more in a temperature environment of 600°C or more. The clearance sensor according to claim 1 .

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