Detection device and fluid heating device

Abstract

This invention provides a detection device and a fluid heating device. This invention provides a technique for suppressing dry burning without using a thermistor. The detection device includes: a conductive wire mounted on the surface of the outer tube of a sheathed heater; and a detection unit that detects the current flowing to the outer tube of the sheathed heater via the conductive wire.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a detection device for detecting leakage current in a sheath heater and a fluid heating device. Background Technology

[0002] Patent Document 1 discloses a fluid heating device. The fluid heating device of Patent Document 1 includes: a fluid heating container having a fluid inlet and an outlet; a sheath heater disposed through the fluid heating container; a thermistor disposed outside the fluid heating container to detect the temperature of the sheath heater; and a control unit that controls the sheath heater. According to the fluid heating device of Patent Document 1, safety measures such as fluid temperature control and prevention of dry burning are possible.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2005-90872 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In the structure of Patent Document 1, the use of a thermistor makes the device structure relatively complex. Furthermore, it increases the weight and cost of the device. Therefore, this specification provides a technique that can suppress dry burning without using a thermistor.

[0008] Solution for solving the problem

[0009] The first technical solution of this invention relates to a detection device for detecting leakage current in a sheathed heater. The sheathed heater comprises: a metal outer tube; a heating element housed within the outer tube; and an insulating material, composed of magnesium oxide, filling the space around the heating element within the outer tube. The detection device comprises: a conductive wire mounted on the surface of the outer tube of the sheathed heater; and a detection unit that detects the current flowing to the outer tube of the sheathed heater via the conductive wire.

[0010] When the sheathed heater is in a dry-burning state, the heat from the heating element is not absorbed by the fluid being heated, thus potentially leading to high temperatures. If the sheathed heater reaches a high temperature, the resistance of the insulating material made of magnesium oxide decreases, and the current flowing in the heating element may leak through the insulating material to the outer tube of the sheathed heater. Based on the above structure, the leakage current to the outer tube of the sheathed heater can be detected by a conductive wire. Therefore, it is possible to detect when the sheathed heater is in a dry-burning state, and dry-burning can be suppressed without using a thermistor.

[0011] In the second technical solution, according to the first technical solution described above, the detection device further includes a control unit that, upon detecting current flowing to the outer tube of the sheath heater, cuts off the power supply to the heating element. This structure can suppress the sheath heater from becoming too hot and can prevent dry burning.

[0012] In the third technical solution, according to the first or second technical solution described above, the sheath heater is installed in the housing in a state of electrical insulation from the housing containing the fluid to be heated. With this structure, leakage of current from the outer tube of the sheath heater to the housing can be suppressed.

[0013] In the fourth technical solution, it is also possible that, according to the third technical solution above, the sheath heater is electrically insulated from the housing by a sealing member disposed between the sheath heater and the housing.

[0014] This structure reliably insulates the sheathed heater from the housing. Furthermore, it prevents leakage of the fluid being heated, housed within the housing, from the gap between the sheathed heater and the housing.

[0015] In the fifth technical solution, or according to the fourth technical solution described above, the conductive wire is mounted on the surface of the outer tube of the sheath heater at an end position closer to the axial direction of the sealing member. With this structure, the conductive wire can be easily led outwards.

[0016] In the sixth technical solution of this technology, the fluid heating device includes: a housing containing a fluid to be heated; a sheath heater installed on the housing to heat the fluid contained in the housing; and a detection device for detecting the leakage current of the sheath heater. The sheath heater includes: a metal outer tube; a heating element housed within the outer tube; and an insulating material, composed of magnesium oxide, filling the space around the heating element within the outer tube. The detection device includes: a conductive wire installed on the surface of the outer tube of the sheath heater; and a detection unit that detects the current flowing to the outer tube of the sheath heater via the conductive wire. Attached Figure Description

[0017] Figure 1 This is a schematic diagram illustrating the detection device and fluid heating device of an embodiment.

[0018] Figure 2 This is a cross-sectional view of the sheath heater of an embodiment.

[0019] Figure 3 yes Figure 1 Sectional view III-III.

[0020] Figure 4 yes Figure 1 A magnified view of part IV.

[0021] Explanation of reference numerals in the attached figures

[0022] 2. Detection device; 4. Fluid heating device; 10. Sheath heater; 12. Heating element; 13. Insulating material; 14. Outer tube; 15. First sealing body; 16. Second sealing body; 17. Terminal; 20. Conductive wire; 50. Housing; 52. Support part; 53. Receiving recess; 55. Flow path; 56. Insertion hole; 62. Busbar; 70. Sealing component; 100. Control device. Detailed Implementation

[0023] The detection device 2 and the fluid heating device 4 of the embodiment will be described with reference to the accompanying drawings. Figure 1 As shown, the detection device 2 of the embodiment is applied to the sheath heater 10. The detection device 2 is a device for detecting the leakage current of the sheath heater 10. The fluid heating device 4 of the embodiment includes: a housing 50 that contains the fluid to be heated; a sheath heater 10 that is mounted on the housing 50 and heats the fluid contained in the housing 50; and a detection device 2 that detects the leakage current of the sheath heater 10.

[0024] First, the sheath heater 10 will be described. For example... Figure 2 As shown, the sheathed heater 10 includes an outer tube 14, a heating element 12 disposed within the outer tube 14, and an insulating material 13 filled within the outer tube 14. Furthermore, the sheathed heater 10 includes a terminal 17 inserted into an opening 14b of the outer tube 14, and sealing bodies (a first sealing body 15 and a second sealing body 16) sealing the opening 14b of the outer tube 14. The sheathed heater 10 can heat a fluid by means of heat generated by the heating element 12. The fluid to be heated by the sheathed heater 10 is not particularly limited; for example, it can be a liquid such as water or coolant.

[0025] The outer tube 14 is made of a metallic material such as stainless steel (SUS), which has thermal and electrical conductivity. The type of metallic material used for the outer tube 14 is not particularly limited. The axial ends of the outer tube 14 are sealed by sealing bodies (first sealing body 15 and second sealing body 16). Both axial ends of the outer tube 14 are sealed by sealing bodies. Figure 3 As shown, the cross-sectional shape of the outer tube 14 in a section orthogonal to the axial direction of the outer tube 14 is circular. In a modified example, the cross-sectional shape of the outer tube 14 in a section orthogonal to the axial direction of the outer tube 14 may also be elliptical or polygonal. The cross-sectional shape of the outer tube 14 is not particularly limited.

[0026] The heating element 12 is, for example, made of a nickel-chromium alloy wire wound into a spiral shape. The heating element 12 extends along the axial direction of the outer tube 14. The heating element 12 is thermally and electrically conductive and generates heat by passing an electric current through it.

[0027] The insulating material 13 is composed of magnesium oxide (MgO) powder. The insulating material 13 fills the space between the outer tube 14 and the heating element 12. The insulating material 13 is filled inside the outer tube 14, surrounding the heating element 12. The insulating material 13 electrically insulates the heating element 12 from the outer tube 14, but its resistance decreases at high temperatures. Therefore, when the insulating material 13 reaches a high temperature, current flowing in the heating element 12 may leak through the insulating material 13 to the outer tube 14.

[0028] Terminal 17 extends both inside and outside the outer tube 14. One end of terminal 17 is connected to the heating element 12 inside the outer tube 14, and the other end of terminal 17 is connected to the busbar 62 outside the outer tube 14 (see reference). Figure 1 ).

[0029] Busbar 62 is conductive and electrically connected to an external power source (not shown). Terminal 17 of the sheathed heater 10 is electrically connected to the power source (not shown) via busbar 62. Power is supplied from the external power source to the heating element 12 through busbar 62 and terminal 17.

[0030] like Figure 2 As shown, the terminal 17 of the sheathed heater 10 is supported by the sealing bodies (first sealing body 15 and second sealing body 16) of the sealing outer tube 14. Axially, the first sealing body 15 is positioned inside the outer tube 14 (the second sealing body 16 is positioned outside the outer tube 14) compared to the second sealing body 16. The first sealing body 15 is made of, for example, glass. The second sealing body 16 is made of, for example, ceramic. The materials of the sealing bodies (first sealing body 15 and second sealing body 16) are not particularly limited.

[0031] Next, the housing 50 (refer to) that houses the fluid to be heated by the sheath heater 10 is... Figure 1 and Figure 4 The housing 50 is made of a metallic material, such as an alloy containing aluminum. The housing 50 is thermally and electrically conductive. The housing 50 includes an insertion hole 56 for inserting the sheath heater 10, a support portion 52 for supporting the sheath heater 10, and a flow path 55 for the fluid to be heated by the sheath heater 10. The sheath heater 10 is supported by the support portion 52 while inserted into the insertion hole 56 of the housing 50. The sheath heater 10 heats the fluid flowing in the flow path 55 while supported by the support portion 52. Furthermore, the sheath heater 10 is mounted to the housing 50 in an electrically insulated manner relative to the housing 50.

[0032] The insertion hole 56 penetrates the side portion 50a of the housing 50, connecting the inside and outside of the housing 50. The sheath heater 10 is inserted into the insertion hole 56 of the housing 50. There is a gap between the inner circumferential surface 56a of the insertion hole 56 and the outer circumferential surface 14a of the outer tube 14 of the sheath heater 10. The inner circumferential surface 56a of the insertion hole 56 and the outer circumferential surface 14a of the outer tube 14 of the sheath heater 10 are not in contact but separated. Therefore, the housing 50 and the sheath heater 10 are not in contact but separated.

[0033] The support portion 52 supports the outer peripheral surface 14a of the outer tube 14 of the sheath heater 10, which is inserted into the insertion hole 56. The support portion 52 supports the outer peripheral surface 14a of the outer tube 14 of the sheath heater 10 through the sealing member 70. The support portion 52 is not in contact with the sheath heater 10, but is separated from it through the sealing member 70. The support portion 52 has a receiving recess 53 for receiving the sealing member 70.

[0034] The sealing member 70 is made of an insulating material such as resin. The sealing member 70 is elastic and insulating. The sealing member 70 is disposed between the sheath heater 10 and the housing 50, electrically insulating the sheath heater 10 from the housing 50. The sealing member 70 is housed in a receiving recess 53 provided in the support portion 52 of the housing 50.

[0035] The sealing member 70 is in close contact with the outer peripheral surface 14a of the outer tube 14 of the sheathed heater 10. The sealing member 70 surrounds the outer peripheral surface 14a of the outer tube 14 of the sheathed heater 10. The sealing member 70 seals the gap between the outer peripheral surface 14a of the outer tube 14 of the sheathed heater 10 and the support portion 52. The sealing member 70 also seals the gap between the outer peripheral surface 14a of the outer tube 14 of the sheathed heater 10 and the inner peripheral surface 56a of the insertion hole 56. Figure 3 As shown, the sealing member 70 is composed of an O-ring with a cross-sectional shape of O (letter O).

[0036] Next, the detection device 2 for detecting leakage current of the sheath heater 10 will be described. For example... Figure 1 As shown, the detection device 2 includes a conductive wire 20 installed on the outer tube 14 of the sheath heater 10 and a control device 100.

[0037] One end of the conductive wire 20 is electrically connected to the outer tube 14 of the sheathed heater 10, and the other end is electrically connected to the control device 100. When current flows to the outer tube 14 of the sheathed heater 10, current also flows to the conductive wire 20. One end of the conductive wire 20 is mounted on the outer peripheral surface 14a of the outer tube 14 of the sheathed heater 10. One end of the conductive wire 20 is mounted on the outer peripheral surface 14a of the outer tube 14 of the sheathed heater 10 at a position on the axial end side of the sheathed heater 10 relative to the sealing member 70. One end of the conductive wire 20 is mounted on the outer peripheral surface 14a of the outer tube 14 of the sheathed heater 10 on the side opposite to the flow path 55 of the housing 50, separated by the sealing member 70. Furthermore, in a modified example, one end of the conductive wire 20 may also be mounted on a surface other than the outer peripheral surface 14a of the outer tube 14 of the sheathed heater 10 (e.g., the axial end face of the outer tube 14).

[0038] The control device 100 is fixed to the base plate 120. The base plate 120 is supported by the busbar 62. The control device 100 detects the current flowing to the outer tube 14 of the sheath heater 10 via the conductive wire 20. Thus, the control device 100 can detect the leakage current of the sheath heater 10. Furthermore, when the control device 100 detects current flowing to the outer tube 14 of the sheath heater 10, it cuts off the power supply to the heating element 12 of the sheath heater 10. For example, the control device 100 cuts off the power supply to the heating element 12 by disconnecting the power supply (not shown) to the sheath heater 10. When the power supply to the heating element 12 is cut off, the heating element 12 no longer heats up. Therefore, the sheath heater 10 no longer heats the fluid to be heated.

[0039] (Effect)

[0040] The detection device 2 and the fluid heating device 4 of the embodiment have been described above. In the fluid heating device 4 described above, if the sheath heater 10 is in a no-heat state, the heat of the heating element 12 will not be absorbed by the fluid being heated, and therefore the sheath heater 10 may become too high. If the sheath heater 10 becomes too high, the resistance of the insulating material 13 made of magnesium oxide will decrease, and the current flowing in the heating element 12 may leak through the insulating material 13 to the outer tube 14 of the sheath heater 10.

[0041] The detection device 2 of the embodiment includes: a conductive wire 20, which is installed on the outer peripheral surface 14a of the outer tube 14 of the sheath heater 10; and a control device 100 (an example of a detection unit), which detects the current flowing to the outer tube 14 of the sheath heater 10 through the conductive wire 20.

[0042] According to this structure, the current leaking to the outer tube 14 of the sheath heater 10 can be detected through the conductive wire 20. Therefore, it is possible to detect if the sheath heater 10 is in a dry-burning state, and dry-burning can be suppressed. Dry-burning can be suppressed without using a thermistor.

[0043] The control device 100 (an example of a control unit) cuts off the power supply to the heating element 12 upon detecting current flowing to the outer tube 14 of the sheath heater 10. This structure prevents the sheath heater 10 from becoming too hot and suppresses dry burning.

[0044] The sheathed heater 10 is mounted on the housing 50 in a state of electrical insulation from the housing 50 containing the fluid to be heated. With this structure, leakage of current from the outer tube 14 of the sheathed heater 10 to the housing 50 can be suppressed.

[0045] The sheathed heater 10 is electrically insulated from the housing 50 by a sealing member 70 disposed between the sheathed heater 10 and the housing 50. This structure reliably insulates the sheathed heater 10 from the housing 50. Furthermore, leakage of the fluid contained within the housing 50 that is to be heated from the gap between the sheathed heater 10 and the housing 50 can be suppressed.

[0046] The conductive wire 20 is mounted on the outer peripheral surface 14a of the outer tube 14 of the sheath heater 10 at a position closer to the axial end of the sealing member 70 than the sheath heater 10. With this structure, the conductive wire 20 can be easily led outward.

[0047] (Modified example)

[0048] In the above embodiments, the housing 50 of the fluid heating device 4 has a flow path 55, but it is not limited to this structure. In a variation, the housing 50 of the fluid heating device 4 may also have a storage section (not shown) for storing the fluid that is to be heated by the sheath heater 10. The fluid that is to be heated by the sheath heater 10 may not need to flow during the heating process of the sheath heater 10.

[0049] The specific examples of the present invention have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes techniques derived from various modifications and alterations of the specific examples described above. The technical elements illustrated in this specification or drawings are technically useful individually or in various combinations, and are not limited to the combinations described in the claims at the time of application. Furthermore, the technology illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives is itself technically useful.

Claims

1. A detection device for detecting the leakage current of a sheathed heater, wherein, The sheathed heater comprises: a metal outer tube; a heating element housed within the outer tube; and an insulating material, composed of magnesium oxide, filling the space around the heating element within the outer tube. The detection device includes: Conductive wires, which are mounted on the surface of the outer tube of the sheathed heater; and The detection unit detects the current flowing to the outer tube of the sheath heater via the conductive wire.

2. The detection device according to claim 1, wherein, The detection device also includes a control unit that cuts off the power supply to the heating element when the detection unit detects current flowing to the outer tube of the sheath heater.

3. The detection device according to claim 1 or 2, wherein, The sheathed heater is installed in the housing in a state of electrical insulation from the housing containing the fluid to be heated.

4. The detection device according to claim 3, wherein, The sheath heater is electrically insulated from the housing by a sealing member disposed between the sheath heater and the housing.

5. The detection device according to claim 4, wherein, The conductive wire is mounted on the surface of the outer tube of the sheath heater at a position on the end side of the sheath heater that is closer to the axial direction than the sealing member.

6. A fluid heating device, wherein, This fluid heating device includes: A housing that contains the fluid that is being heated; A sheathed heater, mounted on the housing, heats the fluid contained within the housing; and The detection device detects the leakage current of the sheath heater. The sheathed heater comprises: a metal outer tube; a heating element housed within the outer tube; and an insulating material, composed of magnesium oxide, filling the space around the heating element within the outer tube. The detection device includes: Conductive wires, which are mounted on the surface of the outer tube of the sheathed heater; and The detection unit detects the current flowing to the outer tube of the sheath heater via the conductive wire.

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