Heating device

Abstract

In particular, the objective is to provide a heating device that enables efficient heating of the object to be heated and can be freely positioned within a confined space. [Solution] A heating device comprising at least a positive-resistance thermistor heating element having a pair of electrode layers, first and second electrode terminals, and a cover, wherein the first and second electrode terminals are fixed to the cover, the cover is fixed to the object to be heated, and the positive-resistance thermistor heating element is positioned on the side of the cover that is on the object to be heated, wherein one end of the first and second electrode terminals is in contact with the electrode layer of the positive-resistance thermistor heating element, the cover has an external connector connection portion on a surface that does not contact the positive-resistance thermistor heating element, the other end of the first and second electrode terminals is exposed, the external connector connection portion has a substantially flat surface perpendicular to the exposed end of the first and second electrode terminals, and the substantially flat surface of the external connector connection portion is inclined at an angle with respect to the horizontal plane of the positive-resistance thermistor heating element.

Description

Technical Field

[0001] The present invention relates to a heating device using a positive temperature coefficient thermistor heating element (hereinafter referred to as a PTC heating element) used for purposes such as heat preservation heating, heating, and freezing prevention. In particular, it relates to a device that enables efficient heating of an object to be heated and allows for free placement in a narrow space.

Background Art

[0002] Conventionally, in the field of heating elements, PTC heating elements have been used. This is because the PTC heating element has a specific resistance value at low temperatures and acts as a heating element, and above a predetermined temperature (Curie temperature), the resistance value rapidly increases and power supply is cut off, having a self-temperature control function with extremely high safety. By connecting a pair of electrode terminals to a PTC heating element having such characteristics and appropriately performing insulation treatment or arranging it in various housings, a heating device suitable as a heater for heat preservation heating or freezing prevention of various devices can be obtained. And such a heating device can be attached to a pipe for transporting a liquid, gas, etc., and can also be used for heat preservation heating, heating, freezing prevention, etc. of the pipe. As technologies related to the present invention, for example, Patent Documents 1 to 6, etc. can be cited.

[0003] In recent years, when arranging a heating device inside an internal combustion engine, with the downsizing of the internal combustion engine, there may be a requirement for downsizing of the heating device and a high degree of design freedom in arranging it in a narrow space. Therefore, for example, structures in which the external connector connection part of the heating device is bent at a right angle are cited as Patent Documents 7 to 10, etc.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

[0005] Heating devices utilizing PTC heating elements as described above are already on the market and in practical use because they can self-regulate their temperature and be made compact. However, because the angle of the external connector connection part is uniform, the constraints on securing connection with the external connector prevent them from being freely placed in narrow spaces, and there has been a desire to solve this problem.

[0006] The present invention was made to solve the problems of the prior art, and its objective is to provide a heating device that can be freely arranged in a confined space. [Means for solving the problem]

[0007] To achieve the above objective, the present invention provides a heating device comprising at least a positive-resistance thermistor heating element having a pair of electrode layers, a first electrode terminal, a second electrode terminal, and a cover, wherein the first electrode terminal and the second electrode terminal are fixed to the cover, the cover is fixed to the object to be heated, and the positive-resistance thermistor heating element is positioned on the side of the cover facing the object to be heated, wherein one end of the first electrode terminal and the second electrode terminal are in contact with the electrode layer of the positive-resistance thermistor heating element, and the cover has an external connector connection portion on a surface that does not contact the positive-resistance thermistor heating element, with the other end of the first electrode terminal and the second electrode terminal exposed, the external connector connection portion having a substantially flat surface perpendicular to the exposed end of the first electrode terminal and the second electrode terminal, and the substantially flat surface of the external connector connection portion is at an angle inclined with respect to the horizontal plane of the positive-resistance thermistor heating element. Furthermore, the lid portion has a substantially straight body portion that directly fixes the first electrode terminal and the second electrode terminal, and it is conceivable that the virtual extension line of the body portion and the horizontal plane of the positive characteristic thermistor heating element intersect at an angle of 20 to 30 degrees. Furthermore, it is conceivable that the first electrode terminal and the second electrode terminal are inserted into the body portion and directly fixed from a side different from the external connector connection portion. Furthermore, it is possible that a thermal conductive sheet is adjacent to the positive characteristic thermistor heating element mentioned above. Furthermore, it is conceivable that the first electrode terminal and the second electrode terminal each have three or more elastic bending points, and that the positive characteristic thermistor heating element is biased against the heat conductive sheet by the elastic force of the first electrode terminal and the second electrode terminal. [Effects of the Invention]

[0008] According to the present invention, by tilting the angle of the external connector connection part with respect to the PTC heating element, it is possible to freely arrange the heating device in a narrow space compared to conventional heating devices. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view showing the configuration of a disassembled heating device according to one aspect of the present invention. [Figure 2] This is a side view showing the configuration of a disassembled heating device according to one aspect of the present invention. [Figure 3] This is a side view showing electrode terminals according to one aspect of the present invention. [Figure 4] This is a side view of an electrode terminal and a PTC heating element according to one aspect of the present invention. [Figure 5] This is a plan view showing a PTC heating element according to one aspect of the present invention. [Best Mode for Carrying Out the Invention]

[0010] The embodiments of the present invention will now be described with reference to the figures. This embodiment shows an example in which the object to be heated is a pipe, and the heating device according to the present invention is attached to the pipe. The XYZ notations in the figures are angle notations common to all figures.

[0011] The PTC heating element 11 is made of a barium titanate-based ceramic element formed in a roughly rectangular plate shape with dimensions of 14.0 mm in length, 16.5 mm in width, and 1.5 mm in thickness. Two electrodes made of silver paste are formed in an alternating comb-like pattern on one main surface, and these are designated as electrode layer 1a and electrode layer 1b. One of these electrode layers 1a and electrode layer 1b is the positive electrode, and the other is the negative electrode. The material of the PTC heating element should be appropriately set according to the required heating characteristics (e.g., Curie temperature).

[0012] The heating device 1 includes a lid portion 2, and the lid portion 2 fixedly holds a first electrode terminal 21 and a second electrode terminal 22. Further, the lid portion 2 is fixed to the object to be heated, and a PTC heating element 11 is disposed on the object-to-be-heated side of the lid portion 2. At this time, one end portion of the first electrode terminal 21 and the second electrode terminal 22 is in contact with the PTC heating element 11, and the other end portion thereof is exposed to an external connector connection portion 7 formed on a surface of the lid portion 2 that does not abut against the PTC heating element 11. The external connector connection portion 7 has a substantially flat surface 41 that is orthogonal to the end portions of the first electrode terminal 21 and the second electrode terminal 22, and this substantially flat surface 41 has an angle inclined with respect to the horizontal surface 43 of the PTC heating element 11. Here, the end portions of the first electrode terminal 21 and the second electrode terminal 22 referred to herein refer to the electrode insertion portions 52 in FIG. 3. In this way, as shown in FIG. 2, the substantially flat surface 41 has an angle inclined with respect to the horizontal surface 43 of the PTC heating element 11. The heating device 1 having such a structure can freely design the arrangement of an external connector (not shown) connected to the external connector connection portion 7, and enables arrangement in an internal combustion engine that is becoming more compact, that is, free arrangement in a narrow space of the heating device 1. Hereinafter, the first electrode terminal 21 and the second electrode terminal 22 are appropriately grouped together and described as electrode terminals 21, 22.

[0013] The lid portion 2 may have a substantially straight body portion 4 for directly fixing the first electrode terminal 21 and the second electrode terminal 22. An external connector connection portion 7 is formed at the end of this body portion 4, and it is conceivable that one end of the first electrode terminal 21 and the second electrode terminal 22 is exposed at the external connector connection portion 7 (not shown in Figure 1). The body portion 4 is made up of a substantially straight cylindrical, elliptical, or prismatic shape, and it is preferable that a virtual extension line 42 extending from its substantially straight shape intersects the horizontal plane 43 of the PTC heating element 11 at an angle of 20 to 30 degrees. In this embodiment, the virtual extension line 42 of the body portion 4 and the horizontal plane 43 of the PTC heating element 11 intersect at an angle of 25 degrees. By forming the body portion 4 at an angle of 20 to 30 degrees with respect to the horizontal plane 43 of the PTC heating element 11, it is possible to reduce the height of the lid portion 2 while ensuring ease of inserting the external connector into the external connector connection portion 7, that is, the heating device 1 can be freely positioned in a narrow space.

[0014] Forming the body portion 4 at an angle of 20 to 30 degrees with respect to the horizontal plane 43 of the PTC heating element 11 is particularly preferable for fixing the first electrode terminal 21 and the second electrode terminal 22 having a complex bent shape (hereinafter referred to as bent electrode terminals only in this paragraph) to the body portion 4. In the insert molding method, there is a method in which the electrode terminal is fixed inside the mold, the mold is clamped, and the resin is filled. However, in order to clamp the mold by covering the lid, the shape of the electrode terminal exposed from the filled resin is required to be a linear shape (hereinafter referred to as a linear electrode terminal only in this paragraph). In order to provide a bent electrode terminal in this method, a process of bending the linear electrode terminal after insert molding or a process of connecting the bent electrode terminal to the linear electrode terminal after insert molding is required, but the adoption of these processes is costly and not preferable. Also, simply bending the linear electrode terminal into an L shape results in insufficient pressing of the electrode terminal against the PTC heating element 11, so the electrode terminal is required to be at least a bent electrode terminal such as an S shape. If the pressing is insufficient, the temperature rising performance of the heating device and the fixing of each component are not stable, which is not preferable. In the insert molding method, it is difficult to fix the bent electrode terminal to the body portion 4, so a method such as a post-press fitting method in which the bent electrode terminal is inserted into the body portion 4 after molding is preferable. At this time, by forming the body portion 4 at an angle of 20 to 30 degrees with respect to the horizontal plane 43 of the PTC heating element 11, it is possible to achieve both the lowest possible profile of the lid portion 2 and the fixing of the bent electrode terminal to the body portion 4 by the post-press fitting method. Since the bent electrode terminal adopted in this method and structure has a bent structure such as an S shape, the pressing of the electrode terminal against the PTC heating element 11 is sufficient and stable, and the temperature rising performance of the heating device and the fixing of each component can be stabilized.

[0015] Furthermore, it is preferable that the first electrode terminal 21 and the second electrode terminal 22 are inserted into the body 4 from a different side than the external connector connection portion 7 formed on the body 4 and directly fixed. In a manufacturing method in which the first electrode terminal 21 and the second electrode terminal 22 are fixed to the body 4 by insert molding, cost constraints are imposed on design changes to the first electrode terminal 21 and the second electrode terminal 22, which is undesirable. If the manufacturing method involves inserting the first electrode terminal 21 and the second electrode terminal 22 into the body 4 that has been molded by injection molding or the like, the design of the first electrode terminal 21 and the second electrode terminal 22 can be changed at any time, improving the versatility of the heating device 1. In addition, the first electrode terminal 21 and the second electrode terminal 22 have multiple bent portions. By inserting the first electrode terminal 21 and the second electrode terminal 22 into the body 4 from a different side than the external connector connection portion 7, the bent portions act as stoppers, preventing them from falling out towards the external connector and preventing the generation of foreign matter after the heating device 1 has been assembled.

[0016] As shown in Figure 3, the electrode terminals 21 and 22 are thought to have an electrode vertical portion 51 formed roughly along the Y-axis, and it is preferable that this electrode vertical portion 51 is formed at an angle of 10 to 45 degrees with respect to the Y-axis, with an angle of 10 to 30 degrees being most desirable. If it is formed at an angle greater than the predetermined angle with respect to the Y-axis, the elastic force of the electrode terminals 21 and 22 that biases the PTC heating element 11 against the heat conductive sheet 3 will be insufficient, which is undesirable. Also, if it is formed at an angle less than the predetermined angle with respect to the Y-axis, i.e., formed more parallel to the Y-axis, a catching force may be generated during the assembly process, causing the electrode terminals 21 and 22 to generate unintended pressure on the PTC heating element 11. Referring also to Figure 3, it is preferable that the straight portion of the electrode terminals 21 and 22 located in the lower Y-axis direction, surrounded by the two elastic bending portions 5, be designed to be relatively long. Designing this to be long is preferable because it allows the electrode terminals 21 and 22 to contact the PTC heating element 11 with appropriate pressure. "Relatively long" refers to a length that is 5-20% of the total length of the electrode terminals 21 and 22.

[0017] The heating device 1 may have a thermally conductive sheet 3. When the thermally conductive sheet 3 is present, the PTC heating element 11 and the thermally conductive sheet 3 are in contact. The thermally conductive sheet 3 is made of graphite particles and a polymer compound, and is used in which the long axis direction of the graphite particles is formed to be substantially perpendicular to the contact surface with the PTC heating element 11. As the thermally conductive sheet 3, for example, those described in the above-mentioned Patent Documents 5 and 6 can be used. By having the thermally conductive sheet 3, the thermal conductivity of the PTC heating element 11 to the object to be heated can be improved, resulting in good thermal efficiency. As the thermally conductive sheet 3, a sheet of silicone resin with metal added, or thermal conductive grease applied to the CPU of a PC, or any other material with excellent thermal conductivity may be used as appropriate. The heating device 1 may also have legs 6. In actual use, it is conceivable that the heat generated by the PTC heating element 11 is transferred to the object to be heated via the thermally conductive sheet 3 and the legs 6.

[0018] When the PTC heating element 11 and the thermal conductive sheet 3 are in contact, it is preferable that the first electrode terminal 21 and the second electrode terminal 22 each have three or more elastic bending portions 5. If there are two or fewer elastic bending portions 5, it becomes difficult to stably bias the PTC heating element 11 against the thermal conductive sheet 3. Furthermore, the first electrode terminal 21 and the second electrode terminal 22 do not necessarily have clearly defined bending portions; they may have an arc shape along their entire length or a straight shape without bending portions. However, in order to stably bias the PTC heating element 11 against the thermal conductive sheet 3, it is preferable that the first electrode terminal 21 and the second electrode terminal 22 have straight lines perpendicular to the horizontal plane 43 of the PTC heating element 11. The elastic bending portions 5 may be formed by cutting, but they can also be formed by bending. The position of the elastic bending portions 5 is designed considering the distance between the lid portion 2 and the PTC heating element 11, the elastic force of the first electrode terminal 21 and the second electrode terminal 22, and the pressure required for the thermal conductive sheet 3. This structure allows the thermal conductive sheet 3 to be stably biased to the PTC heating element 11, improving thermal conductivity, resulting in good thermal efficiency and a more uniform heat distribution. When directional graphite particles are incorporated into the thermal conductive sheet 3, and the long axis direction of the graphite particles is formed to be approximately perpendicular to the contact surface with the PTC heating element 11, the heat transfer performance improves in proportion to the amount of pressure applied to the thermal conductive sheet 3. Furthermore, if the thermal conductive sheet 3 is fluid, it flows when pressurized and fills the voids caused by fine surface irregularities in the PTC heating element 11 and the object being heated, thereby improving heat transfer performance. For these reasons, it is preferable that the PTC heating element 11 is biased to the thermal conductive sheet 3.

[0019] Figure 4 shows the PTC heating element 11 with the electrode terminals 21 and 22 biased, and is a side view rotated 90 degrees from the angle in Figure 2, with the X axis in the Z axis direction. More specifically, the PTC heating element 11 is provided with a silver cover electrode 25 and ohmic electrodes 11a and 11b having a comb-like shape as shown in Figure 5, and the PTC heating element 11 and the electrode terminals 21 and 22 are indirectly in contact, forming a conductive structure. The shaded area at the boundary between 11a and 11b in Figure 4 is a schematic representation of the intricate comb-like structure as shown in Figure 5. Here, it is preferable that the electrode terminals 21 and 22 have a curved surface 23, and it is most desirable that the curved surface 23 is in contact with the silver cover electrode 25. When fixing the electrode terminals 21 and 22 by inserting them into the cover portion 2, tolerances may occur in the fixing angle depending on the precision of the machine tool. If the electrode terminals 21 and 22 come into contact with the silver cover electrode 25 while angle tolerances persist, and if the electrode terminals 21 and 22 do not have a curved surface 25, the electrode terminals 21 and 22 may scrape the silver cover electrode 25, potentially causing direct contact between the electrode terminals 21 and 22 and the ohmic electrodes 11a and 11b. Direct contact can lead to increased contact resistance, resulting in power concentration and potentially causing contact failure due to localized heat generation. Since contact failure reduces performance, it is undesirable. The presence of a curved surface 23 on the electrode terminals 21 and 22 is particularly preferable because it prevents the electrode terminals 21 and 22 from scraping the silver cover electrode 25, not only during assembly but also when material shift occurs due to temperature contraction after assembly. Furthermore, the presence of a curved surface 23 is preferable because it stabilizes the contact position with the silver cover electrode 25 during assembly. Furthermore, in the state shown in Figure 4, if the electrode terminals 21 and 22 do not have a curved surface 23 and are rectangular in shape when viewed from the side, the contact position with the silver cover electrode 25 will shift significantly when the electrode terminals 21 and 22 are tilted in the left-right direction in Figure 4. Having a curved surface 23 and contacting the silver cover electrode 25 in an arc is particularly preferable as it suppresses shifts in the contact position due to manufacturing precision. Any known method may be used to form the curved surface 23, but for example, the curved surface 23 can be formed by pressing a strip or ribbon-shaped material against a pipe or the like with its longitudinal direction parallel. This forming process may be performed before or after forming the elastic bending portion 5.

[0020] The lid portion 2 used in this embodiment is made of nylon 66 and has a PTC heating element 11 arranged on it. Screw holes are formed on the surface of the lid portion 2 on which the PTC heating element 11 is arranged, for fastening the lid portion 2 and the object to be heated to an internal combustion engine or the like (not shown).

[0021] In this embodiment, a packing 33 is also used. This packing is made of EPDM (ethylene propylene diene copolymer rubber). The packing 33 is placed around the PTC heating element 11 and the heat conductive sheet 3, and can prevent water droplets and foreign matter from entering the interior of the lid 2 structure from the side of the object to be heated. The packing 33 is formed in a ring shape that conforms to the shape of the inner wall of the lid 2.

[0022] The assembly of these components is described below. The lid 2, which is fixed to the leg portion 6, is positioned with the leg portion 6 as the bottom. The packing 33, the heat conductive sheet 3, and the PTC heating element 11 are arranged sequentially on the leg portion 6, and the lid 2, into which the first electrode terminal 21 and the second electrode terminal 22 are inserted, is then placed over it. In this embodiment, the lid 2 has a recess and the leg portion 6 has a protrusion, and it is preferable to fit the lid 2 over the leg portion while engaging these recesses and protrusions. Claws are formed on the opposite sides of the recesses and protrusions of the lid 2 and leg portion 6 to fix them together. After the lid 2 is placed over the leg portion, the positions of the lid 2, leg portion 6, first electrode terminal 21 and second electrode terminal 22, packing 33, heat conductive sheet 3, and PTC heating element 11 are all fixed. In this state, the heating device 1 is placed on another internal combustion engine, etc. (not shown) and fastened to the internal combustion engine using the screw holes 8 formed in the lid 2. After fastening, it is conceivable that an external connector will be connected to the external connector connection part 7.

[0023] The above embodiment is merely one example; for example, the following embodiments are also conceivable.

[0024] In the above embodiment, a structure was shown in which the heat from the PTC heating element 11 is transferred to the object to be heated. However, the object to be heated may also be made of a thermally conductive material, and the heat from the PTC heating element 11 may be transferred to another location.

[0025] The materials constituting the first electrode terminal 21 and the second electrode terminal 22 are not particularly limited as long as they have spring elasticity and function as electrodes. Examples include stainless steel plates, phosphor bronze plates, beryllium copper plates, nickel-plated brass plates, tin-plated brass plates, and silver-plated brass plates. Among these, stainless steel plates, beryllium copper plates, and phosphor bronze plates are particularly preferred because they can sufficiently maintain their spring elasticity even when subjected to long-term thermal cycling.

[0026] The materials constituting the lid portion 2, the body portion 4, and the external connector connection portion 7 are not particularly limited, but it is preferable that they have excellent heat resistance and insulating properties. For example, various resin materials such as nylon, aramid, polypropylene, polyester, polystyrene, polyphenylene sulfide, and polycarbonate can be used.

[0027] The material constituting the packing 33 is preferably flexible, elastic, and has excellent oil resistance and heat resistance. Examples include various rubber materials such as EPDM (ethylene propylene diene copolymer rubber), fluororubber, silicone rubber, and acrylic rubber. [Industrial applicability]

[0028] As detailed above, the present invention provides a heating device that enables efficient heating of an object to be heated and allows for free placement in a confined space. Such a heating device can be suitably used, for example, as a heater for heat retention, warming, and freeze prevention of home appliances, housing equipment, automobile engines, plants, and piping, as well as as a heater for the evaporation of liquids such as fragrances and various chemicals. [Explanation of Symbols]

[0029] 1. Heating device 2 Lid 3. Thermal conductive sheet 4 Torso 5. Elastic flex section 6 legs 7 External connector connection section 11. Positive characteristic thermistor heating element (PTC heating element) 11a Ohmic electrode 11b Ohmic electrode 21 First electrode terminal 22 Second electrode terminal 23 Curved surface 25 Silver-covered electrodes 33 Packing 41 A nearly flat surface 42 Virtual extension lines 43 Horizontal plane 51 Vertical part of electrode 52 Electrode insertion section

Claims

1. It comprises a positive characteristic thermistor heating element having a pair of electrode layers, a first electrode terminal, a second electrode terminal, and a cover portion, The first electrode terminal and the second electrode terminal are fixed to the cover portion. The lid portion is fixed to the object to be heated. A heating device in which the positive characteristic thermistor heating element is arranged on the side of the lid portion that is heated, One end of the first electrode terminal and the second electrode terminal are in contact with the electrode layer of the positive characteristic thermistor heating element. The cover portion has an external connector connection portion on a surface that does not come into contact with the positive characteristic thermistor heating element, in which the other end of the first electrode terminal and the second electrode terminal are exposed. The external connector connection portion has a substantially flat surface perpendicular to one of the exposed ends of the first electrode terminal and the second electrode terminal. The heating device is characterized in that the substantially flat surface of the external connector connection portion is inclined at an angle with respect to the horizontal plane of the positive characteristic thermistor heating element.

2. The cover portion has a substantially straight body portion that directly fixes the first electrode terminal and the second electrode terminal, The heating device according to claim 1, characterized in that the virtual extension line of the body portion and the horizontal plane of the positive characteristic thermistor heating element intersect at an angle of 20 to 30 degrees.

3. The first electrode terminal and the second electrode terminal described above are The heating device according to claim 1, characterized in that it is inserted into the body portion and directly fixed from a side different from the external connector connection portion.

4. The heating device according to any one of claims 1 to 3, characterized in that a heat conductive sheet is adjacent to the positive characteristic thermistor heating element described above.

5. The first electrode terminal and the second electrode terminal each have three or more elastic bending portions. The heating device according to claim 4, characterized in that the positive characteristic thermistor heating element is biased against the heat conductive sheet by the elastic force of the first electrode terminal and the second electrode terminal.

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