Thermocouple and method for producing same

Abstract

The present disclosure addresses the problem of providing a thermocouple that enables an improvement in durability and a method for producing said thermocouple. A thermocouple 1 according to the present disclosure comprises a graphite molded body 2 which is constituted by an integral article. A method for producing a thermocouple 1 according to the present disclosure comprises a step for compressing a part of a graphite molded body 2. The method for producing a thermocouple 1 according to the present disclosure comprises a step for cutting a part of a graphite base material 10.

Description

Thermocouple and method for manufacturing the same

[0001] This disclosure relates to thermocouples and methods for manufacturing thermocouples, and more particularly to thermocouples composed of graphite molded bodies and methods for manufacturing thermocouples.

[0002] Thermocouples, used as temperature sensors, utilize, for example, two different metal conductors and employ the thermoelectric voltage generated in a closed circuit composed of these metal conductors.

[0003] Furthermore, Patent Document 1 discloses a graphite thermocouple. This graphite thermocouple includes first and second thermoelectric elements made of pyrolytic graphite, which have different thermoelectric properties due to differences in the heat treatment history in pyrolysis, and these first and second thermoelectric elements are joined by conductive pins.

[0004] The conventional graphite thermocouple described above has a structure in which two thermoelectric elements are joined using conductive pins, which results in poor stability of the joint and low durability.

[0005] U.S. Patent No. 3,305,405

[0006] The object of this disclosure is to provide a thermocouple that can improve durability, and a method for manufacturing the thermocouple.

[0007] A thermocouple according to one aspect of this disclosure is composed of a graphite molded body made of a single unit.

[0008] A method for manufacturing a thermocouple according to one aspect of the present disclosure comprises a step of compressing a portion of a graphite molded body.

[0009] A method for manufacturing a thermocouple according to another aspect of the present disclosure comprises a step of cutting a portion of a graphite substrate.

[0010] Figure 1 is a schematic plan view showing an example of a thermocouple according to this embodiment. Figure 2 is a schematic plan view showing another example of a thermocouple according to this embodiment. Figure 3 is a schematic cross-sectional view showing a method for manufacturing a thermocouple according to this embodiment.

[0011] The thermocouple of this embodiment (hereinafter also referred to as thermocouple 1) and the method for manufacturing thermocouple 1 will be described below with reference to the drawings. However, the figures described in the following embodiments are schematic diagrams, and the ratios of the size and thickness of each component do not necessarily reflect the actual dimensional ratios. Furthermore, the configuration described in the following embodiments is merely one example of this disclosure. This disclosure is not limited to the following embodiments, and various modifications are possible depending on the design, etc., as long as the effects of this disclosure can be achieved.

[0012] 1. Overview The thermocouple 1 of this embodiment is composed of a single-piece graphite molded body 2. In other words, the thermocouple 1 is composed of a single-piece graphite molded body 2.

[0013] "Graphite molded body" refers to a tangible object composed of graphite. "Consisting of a single piece" means that the graphite molded body is not formed by using adhesives or other bonding agents or conductive pins to connect multiple graphite molded parts, but rather is a structure in which graphite exists continuously throughout the entire graphite molded body.

[0014] "Graphite" refers to graphite, a type of allotrope of carbon, also known as sphagnum. Graphite is composed of carbon atoms sp ２ A graphite material is formed by bonding layers (graphene layers) arranged in a hexagonal honeycomb lattice pattern, with multiple layers bonded together in the thickness direction by van der Waals forces. Examples of graphite include natural graphite and artificial graphite, as well as pyrolytic graphite obtained by firing resin at high temperatures. Carbon fibers are included in graphite molded products.

[0015] Thermocouple 1 can have improved durability. In other words, thermocouple 1 has good durability. Unlike the thermocouple in Patent Document 1, thermocouple 1 of this embodiment does not have a joint, so the stability of the joint does not decrease, and because it does not have parts or components used in the joint, it can be used at temperatures exceeding the operating temperature caused by these parts or components. If thermocouple 1 is made only of graphite, it can be used up to about 3000°C. Thus, thermocouple 1 has excellent durability.

[0016] As described above, this disclosure provides a thermocouple that can improve durability, and a method for manufacturing the thermocouple.

[0017] 2. Details <Thermocouple> The thermocouple 1 of this embodiment is composed of a graphite molded body 2 made of a single piece. The graphite molded body 2 may contain other components, such as a resin binder, which are dispersed substantially uniformly within the graphite molded body 2, to the extent that the effects of this disclosure are not impaired, but it is preferable that the graphite molded body 2 consists only of graphite.

[0018] The shape and size of the graphite molded body 2 are not particularly limited and can be appropriately selected depending on the object to which the thermocouple 1 will be used. Examples of shapes include three-dimensional shapes such as block-shaped, tubular, or combinations thereof, two-dimensional shapes such as sheet-shaped or plate-shaped, and one-dimensional shapes such as linear or rod-shaped.

[0019] When the graphite molded body 2 is in sheet form, its planar shape is, for example, rectangular or U-shaped. Furthermore, its thickness is preferably, for example, 1 μm or more and 1 cm or less, and 10 μm or more and 5 mm or less.

[0020] An example of thermocouple 1 is shown in Figures 1 and 2. The graphite molded body 2, which is made as a single piece, has, for example, a first graphite portion 2A and a second graphite portion 2B, and usually the end of the first graphite portion and the end of the second graphite portion are integrated. In this way, thermocouple 1 has a structure in which the two parts, the first graphite portion 2A and the second graphite portion 2B, are integrated. As a result, thermocouple 1 can improve durability while exhibiting better measurement performance for temperature and other parameters.

[0021] When the graphite molded body 2 has a first graphite portion 2A and a second graphite portion 2B, the ratio of the volume of the first graphite portion 2A to the volume of the second graphite portion 2B (2A / 2B) is preferably, for example, 0.1 or more and 10 or less, and preferably 0.2 or more and 5 or less. This "volume" refers to the apparent volume.

[0022] When the graphite molded body 2 is in the form of a sheet, the ratio of the planar area of ​​the first graphite portion 2A to the second graphite portion 2B (2A / 2B) is, for example, 0.1 or more and 10 or less, preferably 0.8 or more and 1.25 or less, more preferably 0.98 or more and 1.02 or less, and even more preferably 1.

[0023] In thermocouple 1, the first graphite portion 2A and the second graphite portion 2B typically have different Seebeck coefficients. This allows thermocouple 1 to better measure temperature and other parameters. The "Seebeck coefficient" is a value defined as the thermoelectric power per unit temperature difference (unit: μV / K) in the Seebeck effect, where, when a temperature difference exists between the ends of a substance, electrons diffuse according to the temperature gradient, generating a potential difference (thermoelectric power) between the high-temperature and low-temperature ends of the substance.

[0024] Preferably, the first graphite portion 2A and the second graphite portion 2B differ in at least one of the properties selected from the group consisting of density, electrical conductivity, and thermal conductivity. In this case, the Seebeck coefficients of the first graphite portion 2A and the second graphite portion 2B can be made different, thereby improving the measurement performance of the thermocouple 1, such as temperature.

[0025] Among these, it is more preferable that their densities are different. The densities of the first graphite part 2A and the second graphite part 2B can be easily and surely made different, for example, by compressing one of them or by using the surface dense layer 12 existing on the surface of the graphite molded body 2.

[0026] When the density of the second graphite part 2B is greater than that of the first graphite part 2A, the density of the first graphite part 2A is, for example, 0.05 g / cm ３ or more and 0.3 g / cm ３ or less, and preferably 0.1 g / cm ３ or more and 0.2 g / cm ３ or less. The density of the second graphite part 2B is preferably 0.4 g / cm ３ or more and 2.2 g / cm ３ or less, more preferably 0.5 g / cm ３ or more and 2.0 g / cm ３ or less, and even more preferably 0.6 g / cm ３ or more and 1.8 g / cm ３ or less.

[0027] When the density of the second graphite part 2B is greater than that of the first graphite part 2A, the ratio (2B / 2A) of the density of the second graphite part 2B to the density of the first graphite part 2A is preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more. The above ratio is, for example, 20 or less, and preferably 15 or less.

[0028] When the electrical conductivity or the thermal conductivity of the second graphite part 2B is greater than that of the first graphite part 2A, the ratio (2B / 2A) of these values of the second graphite part 2B to the first graphite part 2A is, for example, 1.1 or more, and preferably 2 or more. The above ratio is, for example, 10 or less, and preferably 7 or less.

[0029] An example of the thermocouple 1 of this embodiment is shown in the plan view of Figure 1. The thermocouple 1 in Figure 1 is composed of a sheet-like graphite molded body 2, and its plan view shape is an elongated rectangle, with the first graphite portion 2A and the second graphite portion 2B being integrated at their respective ends. In this embodiment, the density of the second graphite portion 2B is greater than that of the first graphite portion 2A. Due to its flexibility, the thermocouple 1 in Figure 1 can be bent at the boundary between the first graphite portion 2A and the second graphite portion 2B, and can be used in a bent state.

[0030] Another example of the thermocouple 1 of this embodiment is shown in the plan view of Figure 2. The thermocouple 1 in Figure 2 is composed of a sheet-like graphite molded body 2, and its plan view shape is U-shaped, with the first graphite portion 2A and the second graphite portion 2B being integrated at their respective ends. In this embodiment, the density of the second graphite portion 2B is greater than the density of the first graphite portion 2A.

[0031] As an example of the thermocouple 1 of this embodiment, one can be said to be one manufactured by the manufacturing method shown in Figure 3, which will be described later. This thermocouple 1 is composed of a graphite molded body 2 obtained by cutting a graphite substrate 10, and its cross-sectional shape is U-shaped, with the first graphite portion 2A and the second graphite portion 2B being integrated at their respective ends. In other words, this thermocouple 1 has a structure in which the sheet-like first graphite portion 2A and the second graphite portion 2B are laminated. As shown in Figure 3, the first graphite portion 2A consists of the middle layer 11 of the graphite substrate 10, and the second graphite portion 2B includes a surface dense layer 12 present on the surface of the graphite substrate 10. The surface dense layer 12 is denser and more oriented than the middle layer 11.

[0032] <Method for Manufacturing Thermocouples> The thermocouple 1 of this disclosure can be manufactured simply and reliably, for example, by the manufacturing methods A and B shown below.

[0033] [Manufacturing Method A] Manufacturing Method A includes a step of compressing a part of the graphite molded body 2 (hereinafter also referred to as the compression step). The graphite molded body 2 whose part is to be compressed is preferably made of an integral body.

[0034] (Compression Step) In this step, a part of the graphite molded body 2 is compressed. As a result, a first graphite portion 2A and a second graphite portion 2B are formed in the graphite molded body 2, and for example, their densities and the like can be made different from each other.

[0035] The graphite molded body 2 to be used is preferably made of an integral body. That is, in this step, it is preferable to compress a part of the graphite molded body 2 made of an integral body.

[0036] The range of the part of the graphite molded body 2 to be compressed can be appropriately selected in consideration of the measurement performance such as the temperature of the thermocouple 1 to be obtained. In the graphite molded body 2 before the compression step, the volume of the part to be compressed is, for example, 10% by volume or more and 90% by volume or less with respect to the total volume of the graphite molded body 2, preferably 30% by volume or more and 70% by volume or less, and more preferably 45% by volume or more and 55% by volume or less. This "volume" means the apparent volume.

[0037] As the compression method, for example, a method using a press device or the like, a method of crushing a part of the graphite molded body 2 using a roller or the like can be mentioned.

[0038] As the degree of increase in the density of the graphite molded body 2 in the compressed part, for example, it is 1.1 times or more, preferably 2 times or more, more preferably 3 times or more, and even more preferably 4 times or more. The degree of increase in the above density is, for example, 10 times or less.

[0039] [Manufacturing Method B] Manufacturing Method B includes a step of cutting a part of the graphite base material 10 (hereinafter also referred to as the cutting step). Manufacturing Method B may further include a step of compressing either the first graphite portion 2A or the second graphite portion 2B after the cutting step (hereinafter also referred to as the post-compression step).

[0040] (Cutting Process) In this process, a part of the graphite base material 10 is cut. The "graphite base material" refers to a base material containing graphite as the main component.

[0041] "Cutting" means both making a cut (slice) etc. while keeping the graphite base material 10 as one base material, and cutting a part of the graphite base material 10 to divide it into two or more base materials.

[0042] As a method of cutting, it is preferable to use a method such as using a knife or a slicer, etc., but in addition to that, a laser processing method, a water jet processing method, etc. can also be used.

[0043] In this process, first, a part of the graphite base material 10 may be cut and divided into a graphite molded body 2 made of an integral body and the other part. Thereby, the graphite molded body 2 made of an integral body can be obtained.

[0044] In the graphite molded body 2, the location where cutting is performed can be appropriately selected in consideration of the desired structure of the thermocouple 1.

[0045] By this process, a first graphite part 2A and a second graphite part 2B that are integrated with each other can be formed, and the densities of the first graphite part 2A and the second graphite part 2B can also be made different.

[0046] When using the sheet-like graphite molded body 2, by this process, for example, a thermocouple 1 having a U-shaped planar view shape as shown in FIG. 2 can be obtained.

[0047] Also, in this process, when using the sheet-like graphite molded body 2, cutting can also be performed in a direction parallel to the main surface of the graphite molded body 2.

[0048] As shown in Figure 3, the graphite substrate 10 used has an intermediate layer 11 other than the surface layer and a surface dense layer 12 present on the surface. First, as shown by the first cutting line (X), a cut (slice) is made in a direction parallel to the main surface just below the surface dense layer 12. Next, as shown by the second cutting line (Y), a cut is made in the intermediate layer 11 in a direction parallel to the main surface to separate it from the other parts. With this method, a thermocouple 1 in which the density of the first graphite part 2A and the second graphite part 2B are different can be easily and reliably obtained, as the first graphite part 2A consists only of the intermediate layer 11 and the second graphite part 2B includes the surface dense layer 12.

[0049] (Post-compression step) In this step, the graphite molded body 2 obtained in the cutting step is compressed in either the first graphite portion 2A or the second graphite portion 2B. By performing this step, the thermocouple 1 can be obtained more reliably.

[0050] The compression method in this process is the same as the method in the compression process described above.

[0051] As described above, the thermocouple 1 of this embodiment can be manufactured simply and easily using the thermocouple manufacturing method of this embodiment.

[0052] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0053] <Preparation of Thermocouples> [Examples 1-3] Thermocouples of Examples 1-3 were prepared by the following methods. ・Example 1: A sheet-like graphite substrate (average thickness: 112 μm) was cut into ribbon shapes, and one half of the resulting graphite molded body was crushed with a roller to make the thickness of the second graphite portion 2B 27 μm, thereby producing a thermocouple with the structure shown in Figure 1. First graphite portion 2A: Thickness: 113 μm, Density: 0.15 g / cm³ ３ Second graphite section 2B: Thickness: 27 μm, Density: 0.62 g / cm³ ３

[0054] Example 2: A sheet-like graphite substrate (average thickness: 111 μm) was cut into a U-shape in plan view, and one side of the resulting graphite molded body was crushed with a roller to make the thickness of the second graphite portion 2B 26 μm, thereby producing a thermocouple with the structure shown in Figure 2. First graphite portion 2A: Thickness: 111 μm, Density: 0.15 g / cm³ ３ Second graphite section 2B: Thickness: 26 μm, Density: 0.65 g / cm³ ３

[0055] Example 3: As shown in Figure 3, a graphite substrate having a surface densitically packed layer on its surface was sliced ​​along a first cutting line (X) parallel to the main surface just below the surface densitically packed layer, and then cut along a second cutting line (Y) parallel to the main surface in the middle layer. This resulted in a thermocouple having a U-shaped cross-section and comprising a first graphite portion 2A containing only the middle layer and a second graphite portion 2B mainly containing the surface densitically packed layer.

[0056] <Performance Measurement> For the thermocouples of Examples 1 to 3 prepared above, the relationship between temperature (°C) and the voltage (thermoelectromotive force) (mV) across the ends of the thermocouple was measured as a performance measurement. The measurement results are shown in Table 1 below. In Table 1, "-" indicates that measurement was not performed at that temperature.

[0057]

[0058] As can be seen from the results in Table 1, the thermocouples in Examples 1 to 3 all exhibited good measurement performance for temperature and other parameters.

[0059] (Summary) As is clear from the above embodiments, this disclosure includes the following aspects. In the following, reference numerals are enclosed in parentheses solely to indicate their correspondence with the embodiments.

[0060] The thermocouple (1) of the first embodiment is composed of a single, integrated graphite molded body (2).

[0061] According to the first embodiment, the thermocouple (1) can have improved durability.

[0062] In the thermocouple (1) of the second embodiment, the graphite molded body (2) has a first graphite portion (2A) and a second graphite portion (2B). The end of the first graphite portion (2A) and the end of the second graphite portion (2B) are integrated.

[0063] According to the second embodiment, the thermocouple (1) has a first graphite portion (2A) and a second graphite portion (2B) which are integrated at their ends, thereby improving durability and enabling better measurement performance of temperature and other parameters.

[0064] In the thermocouple (1) of the third embodiment, the first graphite portion (2A) and the second graphite portion (2B) have different Seebeck coefficients, as in the second embodiment.

[0065] According to the third embodiment, the temperature measurement performance of the thermocouple (1) can be better demonstrated.

[0066] In the thermocouple (1) of the fourth embodiment, in the second or third embodiment, the first graphite portion (2A) and the second graphite portion (2B) differ in at least one selected from the group consisting of density, electrical conductivity and thermal conductivity.

[0067] According to the fourth embodiment, the temperature measurement performance of the thermocouple (1) can be better demonstrated.

[0068] A fifth embodiment of the method for manufacturing a thermocouple (1) includes a step of compressing a portion of a graphite molded body (2).

[0069] According to the fifth embodiment, the thermocouple (1) can be manufactured simply and reliably.

[0070] A method for manufacturing a thermocouple (1) according to the sixth embodiment includes a step of cutting a part of the graphite substrate (10).

[0071] According to the sixth embodiment, the thermocouple (1) can be manufactured simply and reliably.

[0072] In the seventh embodiment of the method for manufacturing a thermocouple (1), in the sixth embodiment, a first graphite portion (2A) and a second graphite portion (2B) are formed in the cutting step, and the density of the first graphite portion (2A) and the second graphite portion (2B) are different.

[0073] According to the seventh embodiment, the thermocouple (1) can be manufactured more reliably.

[0074] In the eighth embodiment of the method for manufacturing a thermocouple (1), in the sixth embodiment, a cutting step is made to form a first graphite portion (2A) and a second graphite portion (2B) which are integrated with each other. After the cutting step, the method further comprises a step of compressing either the first graphite portion (2A) or the second graphite portion (2B).

[0075] According to the eighth aspect, the thermocouple (1) can be manufactured more reliably.

[0076] 1 Thermocouple 2 Graphite molded body 2A First graphite section 2B Second graphite section 10 Graphite substrate 11 Middle layer 12 Surface dense layer X First cutting line Y Second cutting line

Claims

1. A thermocouple composed of a single, solid graphite molded body.

2. The thermocouple according to claim 1, wherein the graphite molded body has a first graphite portion and a second graphite portion, and the end of the first graphite portion and the end of the second graphite portion are integrated.

3. The thermocouple according to claim 2, wherein the first graphite portion and the second graphite portion have different Seebeck coefficients.

4. The thermocouple according to claim 2 or 3, wherein the first graphite portion and the second graphite portion differ in at least one selected from the group consisting of density, electrical conductivity and thermal conductivity.

5. A method for manufacturing a thermocouple, comprising a step of compressing a portion of a graphite molded body.

6. A method for manufacturing a thermocouple, comprising a step of cutting a portion of a graphite substrate.

7. The method for manufacturing a thermocouple according to claim 6, wherein in the cutting step, a first graphite portion and a second graphite portion are formed that are integrated with each other, and the density of the first graphite portion and the second graphite portion are different.

8. The method for manufacturing a thermocouple according to claim 6, further comprising the step of forming a first graphite portion and a second graphite portion that are integrated with each other in the cutting step, and compressing either the first graphite portion or the second graphite portion after the cutting step.

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