Temperature sensor and method for manufacturing same

Abstract

A temperature sensor (1) according to the present invention comprises a sensor element (10) and a resin covering body (20) that extends in a prescribed direction (L). The covering body (20) includes: a first covering body (30) that covers a heat-sensitive body (11), a pair of electrodes (11a, 11a), and portions of a pair of conductive wires (12, 12); and a second covering body (40) that is laminated onto the first covering body (30) and covers a portion of the first covering body (30). The first covering body (30) includes: an inner covering part (30A) that covers the heat-sensitive body (11), the pair of electrodes (11a, 11a), and the portions of the pair of conductive wires (12, 12) inside the second covering body (40); and a pair of conductive wire covering parts (30B, 30B) that individually cover the portions of the pair of conductive wires (12, 12) outside the second covering body (40). The inner covering part (30A) and the conductive wire covering parts (30B, 30B) are integrally formed.

Description

Temperature Sensor and Method for Manufacturing the Same

[0001] The present invention relates to a temperature sensor and a method for manufacturing the same.

[0002] Temperature sensors equipped with heat-sensitive elements such as thermistors are widely used. Among these, there are temperature sensors that seal the heat-sensitive element and the like with a coating made of a resin material in order to protect the heat-sensitive element from the surrounding environment. Temperature sensors are used for various applications, and among them, there is a demand for a thin-type temperature sensor with a small dimension in the thickness direction. The thin-type temperature sensor is used, for example, by being inserted into a narrow space.

[0003] As a thin-type temperature sensor, for example, the temperature sensor of Patent Document 1 is known. This temperature sensor includes a heat-sensitive element including a heat-sensitive body, a lead wire having one end electrically connected to the heat-sensitive body, and a sealing body made of an insulating material covering a part of the lead wire and the heat-sensitive body, a lead wire electrically connected to the other end of the lead wire, and a resin coating covering a part of the lead wire and the heat-sensitive element and having a rectangular cross section. In the short side direction, the dimension of the region covering the heat-sensitive element is set smaller than the dimension of the region covering the lead wire.

[0004] Japanese Patent No. 7058377

[0005] In recent years, in the medical field, for example, for endoscopes, there is a demand for a temperature sensor with a smaller diameter while having water resistance.

[0006] The present invention has been made to solve the above problems, and an object thereof is to provide a temperature sensor with a smaller diameter while having water resistance.

[0007] The temperature sensor of the present invention comprises a sensor element having a pair of electrodes and a heat-sensitive element whose resistance changes in response to a change in temperature, and a pair of conductive wires, each having one end electrically connected to the pair of electrodes, and a resin covering that covers at least one end of the heat-sensitive element and the pair of conductive wires and extends in a predetermined direction, wherein the covering comprises a first covering that covers a portion of the heat-sensitive element, the pair of electrodes, and the pair of conductive wires, and a second covering laminated on the first covering that covers a portion of the first covering, wherein the first covering comprises an inner covering portion that covers a portion of the heat-sensitive element, the pair of electrodes, and the pair of conductive wires inside the second covering, and a pair of conductive wire covering portions that individually cover a portion of the pair of conductive wires outside the second covering, and the inner covering portion and the conductive wire covering portion are integrally formed.

[0008] The covering portion of the pair of conductive wires preferably consists of a tubular insulator provided on each of the pair of conductive wires.

[0009] The pair of conductive wire coatings preferably include a fused portion that is integrated by fusion in a predetermined range exposed from the second coating.

[0010] Preferably, the sensor element comprises a pair of electrodes, a heat-sensitive element, and a seal covering a portion of a pair of conductive wires connected to the heat-sensitive element, wherein the second seal extends in one predetermined direction from the seal.

[0011] Preferably, a filler is provided in the void of the second covering to seal the opening on one side.

[0012] Preferably, the inner resin material constituting the first coating has a lower melting point than the outer resin material constituting the second coating.

[0013] Preferably, the first coating is made of PFA (perfluoroalkoxyalkane), and the second coating is made of PTFE (polytetrafluoroethylene).

[0014] The covering is preferably formed in a cylindrical shape.

[0015] According to the present invention, a method for manufacturing a temperature sensor is provided, comprising a sensor element having a pair of conductive wires electrically connected to a heat-sensitive element, and a covering made of a resin material that individually covers the heat-sensitive element and the pair of conductive wires, the method comprising the steps of: inserting each of the pair of conductive wires of the sensor element into a pair of first insulating tubes; inserting the heat-sensitive element and the first insulating tube, within a predetermined range from the heat-sensitive element side, into a second insulating tube that is heat-shrinkable; and heating the second insulating tube from its periphery to melt and integrate the second insulating tube and the overlapping first insulating tube, and shrinking the second insulating tube.

[0016] The first covering of the temperature sensor of the present invention comprises an inner covering portion that covers a portion of the heat-sensitive element, a pair of electrodes, and a pair of conductive wires inside the second covering portion, and a pair of conductive wire covering portions that individually cover a portion of the pair of conductive wires outside the second covering portion, with the inner covering portion and the conductive wire covering portions being integrally formed. This makes it possible to provide a smaller diameter temperature sensor while maintaining water resistance.

[0017] This is a side view and a partial side cross-sectional view showing a temperature sensor according to an embodiment. This is a diagram showing a sensor element 10 applied to the temperature sensor according to an embodiment. These are cross-sectional views taken along the lines IIA-IIA, IIB-IIB, IIC-IIC, and IID-IID in Figure 1. This is a diagram showing the manufacturing procedure of the temperature sensor according to an embodiment. Following Figure 4, this is a diagram showing the manufacturing procedure of the temperature sensor according to an embodiment. This is a diagram showing a temperature sensor according to a modified example.

[0018] Embodiments of the present invention will be described below with reference to the drawings.

[0019] [Configuration of Temperature Sensor 1: Figure 1] The temperature sensor 1 comprises a sensor element 10, which will be described later using Figure 2, and a covering 20 made of a resin material that seals the sensor element 10. As shown in the right figure, the covering 20 consists of a first covering 30 and a second covering 40 which is laminated on the outside of the first covering 30. The first covering 30 is configured to individually cover the front (F) side of the sensor element 10 and a pair of conductive wires 12, 12, which will be described later. The second covering 40 is configured to cover a part of the front (F) side of the first covering 30.

[0020] In the following, the longitudinal direction L and the width direction W of the temperature sensor 1 are defined as shown in each figure. Furthermore, in the temperature sensor 1, the side of the longitudinal direction L on which the heat-sensitive element 11 is provided is defined as the front or forward (F), and the opposite side is defined as the rear or backward (R). These definitions of front and rear have a relative meaning.

[0021] [Sensor element 10: Figure 2] The sensor element 10 comprises a heat-sensitive element 11 for detecting the temperature of an object to be detected (not shown), a pair of conductive wires 12, 12 whose front (F) ends 12a, 12a in the longitudinal direction L are electrically connected to the heat-sensitive element 11, and a sealant 13 made of an insulating material that seals a part of these conductive wires 12, 12 and the entirety of the heat-sensitive element 11.

[0022] [Thermal Sensing Element 11: Figure 2] The thermal sensing element 11 is made of a metal oxide or metal that has the characteristic of changing electrical resistance with temperature changes. A thermally sensitive resistor is preferably used as the metal oxide, and typically an NTC thermistor (negative temperature coefficient thermistor) is used. Platinum (e.g., Pt100; JIS-C1604) is preferably used as the metal. The thermal sensing element 11 is formed in the shape of a rectangular parallelepiped, and electrodes 11a, 11a are provided on two opposing surfaces.

[0023] [Conductive wires 12, 12: Figure 2] The pair of conductive wires 12, 12 have their front (F) ends 12a, 12a electrically connected to the electrodes 11a, 11a of the heat-sensitive element 11, respectively, and their rear (R) ends 12b, 12b are drawn out towards the rear (R) from the sealing body 13, which will be described later. The conductive wires 12 are used to pass a constant current through the heat-sensitive element 11. A metal material with high electrical conductivity, typically copper, is used for the conductive wires 12, and Dumet wire is preferably used. Dumet wire is a composite wire clad with an inner layer made of iron-nickel alloy and an outer layer made of copper. While current is passed through this pair of conductive wires 12, 12, the voltage between the pair of electrodes of the heat-sensitive element 11 (not shown in the figure) is measured, the resistance value is determined from Ohm's law (E = IR), and the temperature is detected.

[0024] [Sealing body 13: Figure 2] The sealing body 13 is provided to prevent chemical and physical changes from occurring in the heat-sensitive element 11 by surrounding it and sealing it in an airtight state. Glass can be used as the sealing body 13. In particular, when a dumette wire is used for the conductive wire 12, the coefficients of linear expansion of the iron-nickel alloy and glass are approximate, so it is preferable to use glass for the sealing body 13. In this invention, a material other than glass, such as a resin material, may be used as the sealing body 13, and the sealing body 13 may be omitted depending on the environment in which the temperature sensor 1 is used. The shape of the sealing body 13 is formed, for example, in a spindle shape.

[0025] [Coating 20: Figures 1 and 3] The coating 20 is designed to improve water resistance, dust resistance, and insulation by sealing the sensor element 10. This coating 20 consists of a first coating 30 and a second coating 40.

[0026] The first coating 30 and the second coating 40 are made of a resin material having electrical insulating properties. Preferably, fluororesins are used for the first coating 30 and the second coating 40. This is because fluororesins have excellent water repellency, chemical resistance, and electrical insulating properties. Examples of fluororesins include PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane), and FEP (perfluoroethylene-propene copolymer). The melting points of PTFE, PFA, and FEP are 327°C, 310°C, and 260°C, respectively, and are appropriately selected according to the heating temperature when fusing the resin material constituting the first coating 30. For example, when PFA, which has a relatively low melting point, is used as the first coating 30, it is preferable to make the second coating 40 out of PTFE, which has a relatively high melting point. In this embodiment, the case in which PFA is used for the first coating 30 and PTFE is used for the second coating 40 is illustrated.

[0027] [First covering 30: See Figures 1, 3, and 4] As shown in Figure 1, the first covering 30 consists of an inner covering portion 30A extending in the longitudinal direction L, and a pair of conductive wire covering portions 30B, 30B formed continuously on the rear (R) side of the inner covering portion 30A, which individually cover a pair of conductive wires 12, 12. The inner covering portion 30A is covered by the second covering 40, but the conductive wire covering portions 30B, 30B are exposed to the outside of the second covering 40.

[0028] [Inner covering portion 30A: Figures 1 and 3] The inner covering portion 30A hermetically seals the front (F) side of the longitudinal direction L of the sealant 13 and the conductive wires 12, 12. The inner covering portion 30A is formed in a substantially cylindrical shape and, in addition to covering and sealing the sealant 13 and the conductive wires 12, 12 from the outside in the width direction W, it also fills the space between the conductive wires 12, 12 as shown in the IIC-IIC cross-sectional view of Figure 3. Therefore, the inner covering portion 30A not only electrically insulates the pair of conductive wires 12, 12 but also maintains the distance between them. In this embodiment, the inner covering portion 30A is described as being formed in a substantially cylindrical shape, but the present invention is not limited to this. The shape of the inner covering portion 30A can be formed in any shape, such as a prismatic or triangular prismatic shape. The front (F) end 30a of the inner covering portion 30A in the longitudinal direction L coincides with the contact line CL with the sealant 13 of the sensor element 10, which will be described later, and the rear (R) end 30b coincides with the rear (R) end 40b of the second covering portion 40. A pair of conductive wire covering portions 30B, 30B are provided extending rearward (R) from the rear (R) end 30b of the inner covering portion 30A. The contact line CL is the line segment in contact between the maximum diameter portion of the sealant 13 and the inner circumference of the second covering portion 40, as shown in the figure.

[0029] [Conductive wire covering portion 30B, 30B: Figures 1, 3] The pair of conductive wire covering portions 30B, 30B are hermetically sealed except for the rear (R) side in the longitudinal direction L of the pair of conductive wires 12, 12, thereby preventing moisture and other substances from entering the inside of the sensor element 10 while ensuring insulation between the two wires and between the conductive wires 12 and the outside. In this embodiment, the conductive wire covering portions 30B, 30B are made of the same fluororesin material as the inner covering portion 30A. As shown in the IID-IID cross-sectional views of Figures 1 and 3, the pair of conductive wire covering portions 30B, 30B are formed in a tubular shape extending in the longitudinal direction L. The pair of conductive wire covering portions 30B, 30B are arranged side by side in the width direction W, and the front (F) end portion 30c is formed seamlessly and continuously with the rear (R) end portion 30b of the inner covering portion 30A. The pair of conductive wire covering portions 30B, 30B are in contact with each other at the center 30bc in the width direction W of the end portion 30b of the inner covering portion 30A. In this embodiment, the case in which the pair of conductive wire covering portions 30B, 30B are in contact at the center 30bc of the end portion 30b of the inner covering portion 30A is described as an example, but the present invention is not limited to this. The pair of conductive wire covering portions 30B, 30B do not necessarily need to be in contact at the center 30bc of the end portion 30b, and a small gap may be formed. Also, the pair of conductive wire covering portions 30B, 30B exposed from the second covering body 40 are in contact with each other but are not connected, for example, fused. In other words, in the temperature sensor 1, the pair of conductive wire covering portions 30B, 30B are independent.

[0030] The pair of conductive wire covering portions 30B, 30B each cover a predetermined range on the rear (R) side of the ends 12a, 12a of the pair of conductive wires 12, 12, from the end 30b of the inner covering portion 30A. The ends 12b, 12b of the conductive wires 12, 12 are exposed from the respective rear (R) ends (lower ends in the figure) of the pair of conductive wire covering portions 30B, 30B in the longitudinal direction L, and the ends 12b, 12b of the pair of conductive wires 12, 12 are connected to a subsequent electrical circuit (not shown).

[0031] The longitudinal dimension L of the pair of conductive wire covering portions 30B, 30B can be set to any dimension as needed, depending on the usage environment of the sensor element of the present invention. For example, the length of both conductive wire covering portions 30B, 30B may be set to be the same, or one conductive wire covering portion 30B may be set to be longer than the other conductive wire covering portion 30B. Furthermore, if it is possible to ensure that moisture does not enter the inside of the temperature sensor and that the pair of conductive wires 12, 12 and the outside are insulated, the conductive wire covering portion 30B may be provided on only one of the conductive wires 12. In this embodiment, the case in which the outer circumference of the pair of conductive wire covering portions 30B, 30B is formed in a circular tube shape is described as an example, but the outer shape can be set arbitrarily. For example, similar to the shape of the inner covering portion 30A, the shape of the conductive wire covering portion 30B can be formed into any shape, such as a rectangular prism or a triangular prism.

[0032] [Second Covering 40: Figures 1 and 3] The second covering 40 is provided on the outside of the first covering 30 in the width direction W, and is formed in a cylindrical shape extending in the longitudinal direction L. As shown in the IIB-IIB cross-sectional view, it is in direct contact with the outer circumference of the sealant 13 at the contact line CL. Here, the contact line CL indicates the contact portion between the inner circumference of the second covering 40 and the outer circumference of the sealant 13 of the sensor element 10. As described above, since the sealant 13 is formed in a spindle shape, the contact line CL is a collection of contact points with the second covering 40 that are continuous in the outer circumference direction of the sealant 13.

[0033] The longitudinal dimension L of the second covering 40 is set to be larger than the longitudinal dimension L of the inner covering portion 30A of the first covering 30. As shown in Figure 1, the front (F) end (tip) 40a of the second covering 40 in the longitudinal direction L is located forward (F) of the contact line CL in the longitudinal direction L, and the rear (R) end 40b is formed in the same position as the rear (R) end 30b of the inner covering portion 30A. Therefore, as shown in the IIA-IIA cross-sectional view of Figure 3, a gap G with an opening 40c on the front (F) side is formed on the inside of the front (F) side of the second covering 40, that is, between the contact line CL between the second covering 40 and the sealant 13 and the tip 40a, and the end 40a of the second covering 40 protrudes forward (F) beyond the tip 13a of the sealant 13. This configuration prevents the sealing body 13 from being scratched or damaged by contact with external objects during the manufacturing of the temperature sensor or during installation work on the device.

[0034] Furthermore, at the contact line CL, it is preferable that the second covering 40 is in contact with the outer surface of the sealant 13 under pressure. For this reason, as will be described later, the heat shrink tubing used to form the second covering 40 is such that its width W after shrinkage is smaller than the width W of the sealant 13. In this way, by applying pressure from the second covering 40 to the sealant 13, the second covering 40 and the sealant 13 can be tightly bonded together. As a result, the covering 20 can reduce the intrusion of liquids such as moisture from its front (F) tip 40a side to the rear (R) of the contact line CL.

[0035] The widthwise dimension W of the second covering 40 at the contact line CL is set to be larger than that at the front (F) and rear (R) of the contact line CL. As will be described later, the second covering 40 is formed by shrinking a heat shrink tube, so the widthwise dimension W after heating becomes smaller almost uniformly compared to the original heat shrink tube. However, because the sealing body 13 of the sensor element 10 is present on the inside, the thermal shrinkage of the heat shrink tube at the contact line CL is restricted compared to the front (F) and rear (R). On the other hand, in the parts other than the position in contact with the sealing body 13, i.e., the inner covering portion 30A and the position where the void G exists, there is no sealing body 13 to restrict shrinkage, so the heat shrink tube shrinks more than in the part where the sealing body 13 exists. As a result, as shown in Figure 1, the widthwise dimension W of the covering 20 at the inner covering portion 30A and the void G of the first covering 30 is smaller. As described above, the maximum value of the widthwise dimension W of the second covering 40 is the widthwise dimension W at the contact line CL. In other words, the second covering 40 is made thinner to the width W dimension of the contact line CL while maintaining waterproofness, thereby realizing a thinner temperature sensor 1.

[0036] In this embodiment, the case in which the width W dimension of the inner covering portion 30A of the first covering portion 30 and the gap G is smaller than the portion where the sealant 13 exists is illustrated and described, but the present invention is not limited to this. The second covering portion 40 does not need to be in contact with the sealant 13 as long as the molten PFA (described later) formed during heating does not flow out from the front (F) in the longitudinal direction L of the heat shrink tube. This is because the inner covering portion 30A of the first covering portion 30 and the sealant 13 can prevent water, etc., from entering the inside from the opening 40c of the gap G. In this case, the width W dimension of the second covering portion 40 can be set to be the same as the front (F) and rear (R) of the contact line CL.

[0037] [Manufacturing method for temperature sensor 1: Figures 4 and 5] Next, the manufacturing procedure for temperature sensor 1 will be explained with reference to Figures 4 and 5. Note that the following manufacturing method assumes that the sensor element 10 has already been manufactured. [STEP A: Figure 4] Prepare the sensor element 10 and two first insulating tubes 50, 50 which will form the first covering 30 after manufacturing. The conductive wire 12 of the sensor element 10 is, for example, made of a dumet wire with a diameter of 0.15 mm, and the first insulating tube 50 is, for example, made of PFA and has an inner diameter that allows the conductive wire 12 to be inserted without difficulty.

[0038] [STEP B: Figure 4] The conductive wires 12, 12 are inserted from the rear (R) end 12b, 12b side through the openings at the longitudinal ends 50a, 50a of the two prepared first insulating tubes 50, 50 in the longitudinal direction L. The two first insulating tubes 50, 50 are pushed in until one end (tip) 50a, 50a abuts against the sealant 13. Hereinafter, the sensor element 10 in the state in which these two first insulating tubes 50, 50 are inserted will be referred to as the sensor element 10A. Next, a second insulating tube 51 is prepared, which will form the second covering 40 after manufacturing. As an example, a PTFE tube is used for the second insulating tube 51. The inner diameter of the second insulating tube 51 is set to be equal to or slightly larger than the outer diameter of the sealant 13.

[0039] [STEP C: Figure 5] Next, the sensor element 10A is inserted into the second insulating tube 51. The sensor element 10A is inserted through the opening at the rear end (rear end) 51b of the second insulating tube 51, with the front (F) side of the sensor element 10A in the longitudinal direction L with the tip 13a side of the seal 13 of the sensor element 10A with the front (F) side of the longitudinal direction L of the sensor element 10A. In this step C, the case in which the sensor element 10A is inserted through the opening at the rear end (rear end) 51b of the second insulating tube 51 is illustrated, but it may also be inserted through the opening at the front end (tip) 51a of the second insulating tube 51 in the longitudinal direction L of the sensor element 10A. Here, the position of the seal 13 of the sensor element 10A in the longitudinal direction L inside the second insulating tube 51 will be explained. The position of the sealant 13 in the longitudinal direction L is set such that, after the second insulating tube 51 has shrunk due to heat, the tip 13a of the sealant 13 is in front of the tip 40a of the covering 20 (second covering 40), that is, the sealant 13 is not exposed to the outside of the covering 20. In other words, the sealant 13 is positioned such that the tip 51a of the second insulating tube 51 protrudes forward (F) of the tip 13a of the sealant 13. When the sensor element 10A is placed on the second insulating tube 51 as described above, a gap G is provided inside the second insulating tube 51 in front of the sealant 13 (F), and the first insulating tubes 50, 50 overlap with the second insulating tube 51 at a portion of their tip 50a side, while their rear (R) ends 50b, 50b are exposed from the opening at the rear end 51b of the second insulating tube 51. Hereinafter, the portion of the first insulating tube 50, 50 that overlaps with the second insulating tube 51 will be referred to as the overlapping portion 50C.

[0040] [STEP D: Figure 5] While fixing the second insulating tube 51 so that it does not detach from or shift position from the sensor element 10A, the second insulating tube 51 is heated from the width direction W side. This heating is performed at a temperature at which PFA melts, but PTFE shrinks without melting. Specifically, since the melting point of PFA is 310°C and the melting point of PTFE is 327°C, this heating temperature HT is selected from the range of the following equation (1): 310°C < HT < 327°C Equation (1)

[0041] When heating is performed for a predetermined time at a temperature within the range of formula (1) above, the overlapping portion 50C of the first insulating tubes 50, 50 melts inside the second insulating tube 51, and the second insulating tube 51 shrinks in the width direction W. Hereinafter, the PFA formed by melting this overlapping portion 50C will be referred to as molten PFA 30C2. If heating is continued further, the second insulating tube 51 shrinks, and the second insulating tube 51 and the sealant 13 of the sensor element 10A come into contact, forming a contact line CL. In this contact line CL portion, there is no gap between the second insulating tube 51 and the sealant 13 of the sensor element 10A, so the molten PFA 30C2 is blocked at this contact line CL and prevented from moving forward (F). Further heating causes the second insulating tube 51 to shrink further in the width direction W, and only the portion of the second insulating tube 51 that contacts the sealant 13 of the sensor element 10 curves to conform to the outer diameter of the sealant 13, deforming into an external shape similar to the temperature sensor 1 shown in Figure 1. After the second insulating tube 51 has been sufficiently heated, when the heating is stopped, the molten PFA 30C2 dissipates heat and solidifies. The molten PFA 30C2 then solidifies as a single unit from the contact line CL to the rear end 51b on the rear (R) side of the second insulating tube 51, forming the inner covering portion 30A. Meanwhile, at the rear (R) end 30b of this inner covering portion 30A, the first insulating tubes 50, 50 contact each other at the center 30bc, and a pair of conductive wire covering portions 30B, 30B are formed that are continuous with the end 30b and extend towards the rear (R). The solidification of the molten PFA 30C2 can be achieved by forced cooling, such as by spraying a cooling medium after heating, or by natural heat dissipation. By performing the above steps, the temperature sensor 1 shown in Figure 1 is manufactured.

[0042] [Effects of Temperature Sensor 1] The effects of temperature sensor 1 are described below. [First Effect]

[0043] According to the temperature sensor 1, it includes two coatings, namely the first coating 30 and the second coating 40. The second coating 40 is directly in contact with the sealing body 13 having the largest dimension in the width direction W in the sensor element 10. That is, according to the temperature sensor 1, in the region where the first coating 30 is provided, it has two layers of coatings, the first coating 30 and the second coating 40. However, in front (F) of the contact line CL of the sealing body 13, only the second coating 40 is provided, so the dimension in the width direction W can be minimized.

[0044] [Second effect] The coating 20 by the temperature sensor 1 is heated and cooled in a state where the first insulating tubes 50, 50 which are the precursors of the first coating 30 exist inside the second insulating tube 51 made of PTFE which is the precursor of the second coating 40. By this heating and cooling, the first insulating tubes 50, 50 are melted and solidified to form the inner coating portion 30A of the first coating 30. In the process of this melting and solidification, the second insulating tube 51 made of PTFE shrinks in the width direction W. As a result, pressure is applied from the second coating 40 to the sealing body 13. By doing so, the second coating 40 and the sealing body 13 can be strongly adhered to each other, and the water resistance can be improved.

[0045] [Third effect] According to the temperature sensor 1, while a part of the first insulating tubes 50, 50 which are the precursors is melted and solidified to form the inner coating portion 30A, the first insulating tubes 50, 50 remain as they are to form the conductive wire coating portions 30B, 30B behind (R) the inner coating portion 30A. These conductive wire coating portions 30B, 30B cover the conductive wires 12, 12 from the surroundings. Thereby, the inner coating portion 30A and the pair of conductive wire coating portions 30B, 30B can be integrally formed. That is, in order to form the first coating 30, there is no need to prepare a member different from the first insulating tubes 50, 50, so the productivity of the temperature sensor 1 can be improved. Moreover, since the first coating 30 integrally forms the inner coating portion 30A and the conductive wire coating portion 30B in the longitudinal direction L, there is no insulating tube inside the coating 20, so the gap between the inner coating portion 30A and the insulating tube can be eliminated. As a result, while reducing the dimension in the width direction W to achieve miniaturization, the water resistance can be ensured.

[0046] [Fourth Effect] According to the temperature sensor 1, since the inside of the second covering 40 in front (F) of the sealing body 13 covering the heat-sensitive body 11 is an air gap G, the tip 40a side of the second covering 40 protrudes to the front (F) side with respect to the tip 13a of the sealing body 13. By configuring it in this way, it is possible to prevent the sealing body 13 from hitting an external object and being damaged or broken during the manufacturing of the temperature sensor or during the attachment work to the device.

[0047] As described above, the preferred temperature sensor 1 in the present invention has been described. However, as will be described below, the present invention can be modified in several ways.

[0048] [Modification Example 1: FIG. 6] In the temperature sensor 1, the conductive wire covering portions 30B, 30B exposed from the second covering 40 are independent without being connected, but the present invention is not limited to this. That is, in a predetermined range exposed from the second covering body 40, the conductive wire covering portions 30B, 30B can be joined by the fusion portion 14.

[0049] In this modification example 1, the case where the fusion portion 14 is provided on the first covering 30 will be described. Regarding the parts common to the temperature sensor 1 shown in the above-described embodiment, the same numbers as those in FIG. 1 are given and the detailed description is omitted. The difference between the temperature sensor 2 shown in this modification example 1 and the temperature sensor 1 is that a fusion portion 14 that protrudes to the rear (R) side with respect to the rear (R) end portion 40b of the second covering 40 is formed on the rear (R) side in the longitudinal direction L of the inner covering portion 30A. This fusion portion 14 is formed integrally with the inner covering portion 30A. Specifically, this fusion portion 14 is formed by melting a predetermined range rearward from the end portion 40b of the second covering 40 on the front (F) side of the pair of conductive wire covering portions 30B, 30B. That is, in the temperature sensor 2 shown in this modification example 1, the end portion 30b on the rear (R) side of the inner covering portion 30A is exposed from the end portion 40b of the second covering 40, and this exposed portion is equivalent to forming the fusion portion 14. If the fusion portion 14 is provided, it can be inferred that the first insulating tubes 50, 50 are melted and solidified with each other inside the second covering 40 to form the inner covering portion 30A.

[0050] [Modification 2: Sealing of the void G: See Figures 1 and 6] In temperature sensors 1 and 2, a void G is provided in front of (F) the sealing body 13 in the second covering 40, but the present invention is not limited to this. The same resin material as the first covering 30 may be filled into this void G. By filling the void G with resin material in this way, the void G on the front (F) side in the longitudinal direction L of temperature sensors 1 and 2 can be sealed, thereby improving airtightness, dustproofness, water resistance, and weather resistance.

[0051] 1,2 Temperature sensor 10,10A Sensor element 11 Heat-sensitive element 12 Conductive wire 13 Encapsulation 14 Fusion part 20 Covering 30 First covering 30A Inner covering 30B Conductive wire covering 40 Second covering 50 First insulating tube 51 Second insulating tube CL Contact wire G Gap L Longitudinal direction W Width direction F Front R Rear

Claims

1. A temperature sensor comprising: a heat-sensitive element having a pair of electrodes and whose resistance changes in response to a change in temperature; a pair of conductive wires, each having one end electrically connected to the pair of electrodes; and a resin covering that covers at least the heat-sensitive element and the one end of the pair of conductive wires and extends in a predetermined direction, wherein the covering comprises: a first covering that covers a portion of the heat-sensitive element, the pair of electrodes, and the pair of conductive wires; and a second covering laminated on the first covering and covering a portion of the first covering, wherein the first covering comprises: an inner covering portion that covers a portion of the heat-sensitive element, the pair of electrodes, and the pair of conductive wires inside the second covering; and a pair of conductive wire covering portions that individually cover a portion of the pair of conductive wires outside the second covering, wherein the inner covering portion and the conductive wire covering portion are integrally formed.

2. The temperature sensor according to claim 1, wherein the pair of conductive wire coverings consist of tubular insulators provided on each of the pair of conductive wires.

3. The temperature sensor according to claim 1 or claim 2, wherein the pair of conductive wire coverings are fused together by fusion in a predetermined area exposed from the second covering.

4. The temperature sensor according to claim 2, wherein the sensor element comprises a pair of electrodes, a heat-sensitive element, and a sealing body covering a portion of a pair of conductive wires connected to the heat-sensitive element, the second covering body extends beyond the sealing body in one of the predetermined directions, and the inside of the extended second covering body is a void.

5. The temperature sensor according to claim 4, wherein a filler is provided in the void of the second covering to seal the opening on one side.

6. The temperature sensor according to claim 1, wherein the inner resin material constituting the first coating has a lower melting point than the outer resin material constituting the second coating.

7. The temperature sensor according to claim 6, wherein the first coating is made of PFA (perfluoroalkoxyalkane) and the second coating is made of PTFE (polytetrafluoroethylene).

8. The temperature sensor according to claim 4, wherein the covering is formed in a cylindrical shape.

9. A method for manufacturing a temperature sensor comprising a sensor element having a pair of conductive wires electrically connected to a heat-sensitive element, the sensor element having a covering made of a resin material that individually covers the heat-sensitive element and the pair of conductive wires, the method comprising: inserting each of the pair of conductive wires of the sensor element into a pair of first insulating tubes; inserting the heat-sensitive element and the first insulating tube, within a predetermined range from the side of the heat-sensitive element, into a second insulating tube that is heat-shrinkable; and heating the second insulating tube from its periphery to melt and integrate the second insulating tube and the overlapping first insulating tube, and to shrink the second insulating tube.

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