Detection device and fluid heating device

Abstract

This invention provides a technology that can suppress dry-boiling without using a thermistor. [Solution] The present invention relates to a detection device and a fluid heating device for detecting leakage current in a sheathed heater. The detection device 2 comprises a conductive wire 20 attached to the surface of the outer tube 14 of the sheathed heater 10, and a detection unit 2 that detects the current flowing through the outer tube of the sheathed heater through the conductive wire.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a detection device for detecting the leakage current of a sheathed heater and a fluid heating device.

Background Art

[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 sheathed heater provided so as to penetrate the fluid heating container, a thermistor provided outside the fluid heating container for detecting the temperature of the sheathed heater, and control means for controlling the sheathed heater. According to the fluid heating device of Patent Document 1, safety measures such as temperature control of the fluid and prevention of dry burning can be performed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the configuration of Patent Document 1, since a thermistor is used, the configuration of the device becomes complicated. Also, the weight and cost of the device may increase. Therefore, this specification provides a technology that can suppress dry burning without using a thermistor.

Means for Solving the Problems

[0005] A first aspect of this technology relates to a detection device for detecting leakage current of a sheathed heater. The sheathed heater comprises a metal outer tube, a heating element housed within the outer tube, and an insulating material made of magnesium oxide filling the area around the heating element within the outer tube. The detection device comprises a conductive wire attached to the surface of the outer tube of the sheathed heater, and a detection unit that detects the current flowing through the outer tube of the sheathed heater via the conductive wire.

[0006] When a sheathed heater is dry-heated, the heat from the heating element is not absorbed by the fluid being heated, which can cause it to overheat. When a sheathed heater overheats, the electrical resistance of the magnesium oxide insulating material decreases, and the current flowing through the heating element may leak through the insulating material to the outer tube of the sheathed heater. With the above configuration, the current leaking to the outer tube of the sheathed heater can be detected through a conductive wire. This makes it possible to detect when the sheathed heater is dry-heating, and dry-heating can be suppressed without using a thermistor.

[0007] In a second embodiment, the detection device may further include a control unit that cuts off the power supply to the heating element when the detection unit detects a current flowing through the outer tube of the sheathed heater. This configuration can prevent the sheathed heater from becoming even hotter and can prevent dry heating.

[0008] In a third embodiment, in the first or second embodiment, the sheath heater may be mounted on the housing containing the fluid to be heated in a manner that is electrically insulated from the housing. This configuration makes it possible to suppress the leakage of current leaking from the outer tube of the sheath heater to the housing.

[0009] In a fourth embodiment, in the third embodiment, the sheath heater may be electrically insulated from the housing by a sealing member disposed between the sheath heater and the housing.

[0010] This configuration ensures reliable insulation between the sheathed heater and the housing. Furthermore, it prevents leakage of the fluid to be heated, contained within the housing, through the gap between the sheathed heater and the housing.

[0011] In a fifth embodiment, in the fourth embodiment, the conductive wire may be attached to the surface of the outer tube of the sheath heater on the axial end side of the sheath heater, relative to the sealing member. This configuration allows the conductive wire to be easily pulled out to the outside.

[0012] In a sixth aspect of this technology, the fluid heating device comprises a housing for containing a fluid to be heated, a sheath heater attached to the housing for heating the fluid contained in the housing, and a detection device for detecting the leakage current of the sheath heater. The sheath heater comprises a metal outer tube, a heating element housed within the outer tube, and an insulating material made of magnesium oxide filling the area around the heating element within the outer tube. The detection device comprises a conductive wire attached to the surface of the outer tube of the sheath heater, and a detection unit for detecting the current flowing through the outer tube of the sheath heater via the conductive wire. [Brief explanation of the drawing]

[0013] [Figure 1] A schematic diagram showing the detection device and fluid heating device of the embodiment. [Figure 2] Cross-sectional view of the sheathed heater in the example. [Figure 3] Section III-III in Figure 2 [Figure 4] Enlarged view of section IV of Figure 1. [Modes for carrying out the invention]

[0014] The detection device 2 and fluid heating device 4 of the embodiment will be described with reference to the drawings. As shown in Figure 1, the detection device 2 of the embodiment is applied to a 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 comprises a housing 50 that houses the fluid to be heated, a sheath heater 10 attached to the housing 50 that heats the fluid housed in the housing 50, and a detection device 2 that detects the leakage current of the sheath heater 10.

[0015] First, let's describe the sheathed heater 10. As shown in Figure 2, the sheathed heater 10 comprises an outer tube 14, a heating element 12 located inside the outer tube 14, and an insulating material 13 filled inside the outer tube 14. The sheathed heater 10 also comprises a terminal 17 inserted into the opening 14b of the outer tube 14, and a sealing body (first sealing body 15 and second sealing body 16) that seals the opening 14b of the outer tube 14. The sheathed heater 10 can heat a fluid to be heated by the heating element 12 generating heat. The fluid to be heated by the sheathed heater 10 is not particularly limited, but can be a liquid such as water or coolant.

[0016] The outer tube 14 is made of a metal material such as stainless steel (SUS), and has thermal conductivity and electrical conductivity. The type of metal material of the outer tube 14 is not particularly limited. The axial ends of the outer tube 14 are sealed by sealants (first sealant 15 and second sealant 16). Both axial ends of the outer tube 14 are also sealed by sealants. As shown in Figure 3, the cross-sectional shape of the outer tube 14 in a cross section perpendicular 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 cross section perpendicular to the axial direction of the outer tube 14 may be, for example, elliptical or polygonal. The cross-sectional shape of the outer tube 14 is not particularly limited.

[0017] The heating element 12 is made of, for example, a nichrome wire wound in a spiral. The heating element 12 extends along the axial direction of the outer tube 14. The heating element 12 has thermal conductivity and electrical conductivity and generates heat when an electric current is passed through it.

[0018] The insulating material 13 is composed of magnesium oxide (MgO) powder. The insulating material 13 is filled between the outer tube 14 and the heating element 12. The insulating material 13 is filled around the heating element 12 inside the outer tube 14. The insulating material 13 electrically insulates the heating element 12 and the outer tube 14, but its electrical resistance may decrease at high temperatures. As a result, when the insulating material 13 reaches a high temperature, the current flowing through the heating element 12 may leak to the outer tube 14 through the insulating material 13.

[0019] The terminal 17 extends across the inside and outside of the outer tube 14. One end of the terminal 17 is connected to the heating element 12 inside the outer tube 14, and the other end of the terminal 17 is connected to the bus bar 62 outside the outer tube 14 (see FIG. 1).

[0020] The bus bar 62 has conductivity and is electrically connected to an external power source (not shown). The terminal 17 of the sheathed heater 10 is electrically connected to the power source (not shown) through the bus bar 62. Electric power is supplied from the external power source to the heating element 12 through the bus bar 62 and the terminal 17.

[0021] As shown in FIG. 2, the terminal 17 of the sheathed heater 10 is supported by a sealing body (the first sealing body 15 and the second sealing body 16) that seals the outer tube 14. In the axial direction of the sheathed heater 10, the first sealing body 15 is disposed inside the outer tube 14 more than the second sealing body 16 (the second sealing body 16 is disposed outside the outer tube 14 more than the first sealing body 15). The first sealing body 15 is made of, for example, a glass material. The second sealing body 16 is made of, for example, a ceramic material. The material of the sealing body (the first sealing body 15 and the second sealing body 16) is not particularly limited.

[0022] Next, the housing 50 (see FIGS. 1 and 4) that houses the fluid to be heated by the sheath heater 10 will be described. The housing 50 is made of a metal material such as an alloy containing aluminum, for example. The housing 50 has thermal conductivity and electrical conductivity. The housing 50 includes an insertion hole 56 into which the sheath heater 10 is inserted, a support portion 52 that supports the sheath heater 10, and a flow path 55 through which the fluid to be heated by the sheath heater 10 flows. The sheath heater 10 is supported by the support portion 52 while being inserted into the insertion hole 56 of the housing 50. The sheath heater 10 heats the fluid flowing through the flow path 55 while being supported by the support portion 52. Further, the sheath heater 10 is attached to the housing 50 in a state of being electrically insulated from the housing 50.

[0023] The insertion hole 56 penetrates the side surface portion 50a of the housing 50, and the inside and outside of the housing 50 communicate with each other through the insertion hole 56. The sheath heater 10 is inserted into the insertion hole 56 of the housing 50. There is a gap between the inner peripheral surface 56a of the insertion hole 56 and the outer peripheral surface 14a of the outer tube 14 of the sheath heater 10. The inner peripheral surface 56a of the insertion hole 56 and the outer peripheral surface 14a of the outer tube 14 of the sheath heater 10 are not in contact with each other and are separated. Therefore, the housing 50 and the sheath heater 10 are not in contact with each other and are separated.

[0024] The support portion 52 supports the outer peripheral surface 14a of the outer tube 14 of the sheath heater 10 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 via a seal member 70. The support portion 52 and the sheath heater 10 are not in contact with each other and are separated via the seal member 70. The support portion 52 includes a housing recess 53 that houses the seal member 70.

[0025] The seal member 70 is made of an insulating material such as resin, for example. The seal member 70 has elasticity and insulation. The seal member 70 is disposed between the sheath heater 10 and the housing 50 and electrically insulates the sheath heater 10 and the housing 50. The seal member 70 is housed in the housing recess 53 provided in the support portion 52 of the housing 50.

[0026] The sealing member 70 is in close contact with the outer circumferential surface 14a of the outer tube 14 of the sheath heater 10. The sealing member 70 encircles the outer circumferential surface 14a of the outer tube 14 of the sheath heater 10, surrounding it. The sealing member 70 seals the gap between the outer circumferential surface 14a of the outer tube 14 of the sheath heater 10 and the support portion 52. The sealing member 70 seals the gap between the outer circumferential surface 14a of the outer tube 14 of the sheath heater 10 and the inner circumferential surface 56a of the insertion hole 56. As shown in Figure 3, the sealing member 70 is composed of an O-ring with an O-shaped cross-section.

[0027] Next, the detection device 2 for detecting the leakage current of the sheath heater 10 will be described. As shown in Figure 1, the detection device 2 comprises a conductive wire 20 attached to the outer tube 14 of the sheath heater 10 and a control device 100.

[0028] One end of the conductive wire 20 is electrically connected to the outer tube 14 of the sheath heater 10, and the other end is electrically connected to the control device 100. When current flows through the outer tube 14 of the sheath heater 10, current also flows through the conductive wire 20. One end of the conductive wire 20 is attached to the outer circumferential surface 14a of the outer tube 14 of the sheath heater 10. One end of the conductive wire 20 is attached to the outer circumferential surface 14a of the outer tube 14 of the sheath heater 10 on the axial end side of the sheath heater 10, closer to the sealing member 70. One end of the conductive wire 20 is attached to the outer circumferential surface 14a of the outer tube 14 of the sheath heater 10 via the sealing member 70, on the side opposite to the flow path 55 of the housing 50. In a modified example, one end of the conductive wire 20 may be attached to a surface other than the outer circumferential surface 14a of the outer tube 14 of the sheath heater 10 (for example, the axial end face of the outer tube 14).

[0029] The control device 100 is fixed to the circuit board 120. The circuit board 120 is supported by the busbar 62. The control device 100 detects the current flowing through the outer tube 14 of the sheath heater 10 through the conductive wire 20. This allows the control device 100 to detect the leakage current of the sheath heater 10. In addition, when the control device 100 detects the current flowing through 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 turning off the power supply (not shown) of the sheath heater 10. When the power supply to the heating element 12 is cut off, the heating element 12 stops generating heat. As a result, the sheath heater 10 stops heating the fluid to be heated.

[0030] (effect) The detection device 2 and 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 dry-heated, the heat from the heating element 12 is not absorbed by the fluid to be heated, so the sheath heater 10 may become hot. When the sheath heater 10 becomes hot, the electrical resistance of the insulating material 13 made of magnesium oxide decreases, and the current flowing through the heating element 12 may leak through the insulating material 13 to the outer tube 14 of the sheath heater 10.

[0031] The detection device 2 of the embodiment includes a conductive wire 20 attached to the outer surface 14a of the outer tube 14 of the sheath heater 10, and a control device 100 (an example of a detection unit) that detects the current flowing through the outer tube 14 of the sheath heater 10 via the conductive wire 20.

[0032] With this configuration, the current leaking into the outer tube 14 of the sheathed heater 10 can be detected through the conductive wire 20. This makes it possible to detect when the sheathed heater 10 is dry-heating, and thus dry-heating can be suppressed. Dry-heating can be suppressed without using a thermistor.

[0033] The control device 100 (an example of a control unit) cuts off the power supply to the heating element 12 when it detects a current flowing through the outer tube 14 of the sheathed heater 10. This configuration prevents the sheathed heater 10 from becoming even hotter and prevents dry heating.

[0034] The sheathed heater 10 is mounted to the housing 50, which contains the fluid to be heated, in a state of electrical isolation from the housing 50. This configuration makes it possible to suppress the leakage of current leaking from the outer tube 14 of the sheathed heater 10 to the housing 50.

[0035] The sheathed heater 10 is electrically insulated from the housing 50 by a sealing member 70 positioned between the sheathed heater 10 and the housing 50. This configuration ensures reliable insulation between the sheathed heater 10 and the housing 50. Furthermore, it prevents leakage of the fluid to be heated contained within the housing 50 through the gap between the sheathed heater 10 and the housing 50.

[0036] The conductive wire 20 is attached to the outer surface 14a of the outer tube 14 of the sheath heater 10 on the axial end side of the sheath heater 10, relative to the sealing member 70. With this configuration, the conductive wire 20 can be easily pulled out to the outside.

[0037] (modified version) In the above embodiment, the housing 50 of the fluid heating device 4 was configured to include a flow path 55, but the configuration is not limited to this. In a modified example, the housing 50 of the fluid heating device 4 may be configured to include a storage section (not shown) for storing the fluid in the heating device of the sheath heater 10. The fluid in the heating device of the sheath heater 10 does not necessarily have to be flowing during heating by the sheath heater 10.

[0038] Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. The technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives itself constitutes technical usefulness. [Explanation of Symbols]

[0039] 2: Detection device, 4: Fluid heating device, 10: Sheath heater, 12: Heating element, 13: Insulating material, 14: Outer tube, 15: First seal, 16: Second seal, 17: Terminal, 20: Conductive wire, 50: Housing, 52: Support part, 53: Retaining recess, 55: Flow path, 56: Insertion hole, 62: Busbar, 70: Sealing member, 100: Control device

Claims

1. 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 made of magnesium oxide filling the area around the heating element within the outer tube. The detection device is A conductive wire attached to the surface of the outer tube of the sheathed heater, A detection device comprising: a detection unit that detects the current flowing through the outer tube of the sheathed heater through the conductive wire.

2. A detection device according to claim 1, A detection device further comprising a control unit that cuts off the power supply to the heating element when the detection unit detects a current flowing through the outer tube of the sheathed heater.

3. A detection device according to claim 1 or 2, The detection device is such that the sheath heater is attached to the housing containing the fluid to be heated, in a manner that electrically insulates it from the housing.

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

5. A detection device according to claim 4, A detection device in which the conductive wire is attached to the surface of the outer tube of the sheath heater at the axial end of the sheath heater, closer to the sealing member than the sheath heater.

6. A housing that contains the fluid to be heated, A sheathed heater is attached to the aforementioned housing and heats the fluid contained within the housing, The system includes a detection device for detecting 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 made of magnesium oxide filling the area around the heating element within the outer tube. The detection device is A conductive wire attached to the surface of the outer tube of the sheathed heater, A fluid heating device comprising: a detection unit that detects the current flowing through the outer tube of the sheathed heater via the conductive wire.

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