JP2007005008A - Casing structure of element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely operate an element whose feature depends on environmental temperatures. <P>SOLUTION: The element 10 comprises a fusible alloy 1, a flux 2, lead terminals 3a, 3b, an insulating case 4, and sealing materials 6a, 6b. The fusible alloy 1 and the flux 2 are a fuse element functioning as a fuse. The fuse elements are shielded from the outside by means of the insulating case 4 and the sealing materials 6a, 6b. The sealing materials 6a, 6b comprise a first layer L<SB>1</SB>, and a second layer L<SB>2</SB>made of a material having a larger coefficient of thermal expansion than that of the first layer L<SB>1</SB>. By this configuration, even if cracks or pinholes are generated in the first layer L<SB>1</SB>, the second layer L<SB>2</SB>blocks them, thereby maintaining good airtightness in the element 10. As a result, the fuse element is prevented from contacting with the atmosphere, and thus the element 10 perform its feature at the expected temperature. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for operating an element such as a fuse in a predetermined temperature environment.

  Some elements constituting electronic devices change their operation depending on temperature, and an expected function is realized at a predetermined temperature. For example, elements such as a fuse, a coil, a capacitor, a resistor, and a crystal resonator are used. For these elements, it may be necessary to shield the elements from the outside and use them for durability and other reasons. Here, a fuse will be described as an example.

  FIG. 7 is a cross-sectional view showing an element 90 having a protective member. In the figure, the fusible alloy 1 realizes the function of the fuse, and the fusible alloy 1 is joined to the ends of the pair of lead terminals 3a and 3b. The lead terminal 3a is electrically connected to a supply device such as a power source, and the lead terminal 3b is electrically connected to an object to be detected (heating body or the like) that is a temperature detection target. The surface of the fusible alloy 1 is covered with a flux 2 and the whole is covered with an insulating case 4 such as ceramics. The insulating case 4 has openings at both ends, and the openings are sealed with sealing materials 5a and 5b such as epoxy resin. The element 90 has internal airtightness secured by the insulating case 4 and the sealing materials 5a and 5b. Note that this type of fuse has been conventionally used as a non-reset type overheat prevention element (see, for example, Patent Documents 1, 2, and 3).

In the element 90, when the ambient temperature exceeds the melting point of the fusible alloy 1, the fusible alloy 1 melts and aggregates at the ends of the lead terminals 3a and 3b, and as shown in FIG. 8, the lead terminals 3a and 3b Make the connection non-conductive. When the lead terminal is in a non-conducting state, the temperature rise of the object to be detected stops, the ambient temperature also decreases, and the aggregated lead terminals 3a and 3b are solidified as they are. As a result, the space between the lead terminals 3a and 3b remains open, and the object to be detected is prevented from being damaged due to excessively high temperature.
Japanese Patent No. 3173077 (FIGS. 2, 3, etc.) Japanese Patent Laid-Open No. 6-2437657 (FIG. 6 etc.) JP 2003-318306 A (FIG. 2 etc.)

  However, when such an element 90 is used in an environment where the temperature changes drastically, the sealing materials 5a and 5b may be cracked due to repeated heating and cooling. Further, when each member repeatedly expands and contracts due to heat, a gap may be generated at the boundary surface between the lead terminals 3a and 3b and the sealing materials 5a and 5b or the insulating case 4 and the sealing materials 5a and 5b.

  Such cracks and gaps cause the element 90 to lose its airtightness and allow the outside air to flow into it. When the flux 2 comes into contact with the outside air, the activity is lost, and the heat responsiveness of the fusible alloy 1 is lowered. As a result, the element 90 can no longer function as a fuse at a predetermined temperature, causing a problem that the detected object is heated to an unnecessarily high temperature and thermally damaged. It was.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a technique for reliably operating an element whose function depends on an environmental temperature.

To achieve the above object, the present invention provides an element whose function depends on the ambient temperature, a protective member having at least one opening and surrounding the element, and one end bonded to the element. A pair of lead terminals whose other ends extend from the opening to the outside of the protection member, and a sealing member that closes the opening of the protection member, the sealing member including the lead terminal and the protection A first layer interposed in a gap between the member and a material having a different thermal expansion coefficient from that of the first layer, and covers the first layer so that the first layer is not exposed to the outside. And a casing structure of the element.
By setting it as this structure, the tolerance with respect to the crack of a sealing member increases and internal airtightness can be ensured favorable.

In addition, the present invention provides an element whose function depends on the ambient temperature, a protective member that has at least one or more openings and surrounds the element, one end is joined to the element, and the other end is the opening. A pair of lead terminals extending from the portion to the outside of the protection member, and a sealing member that closes the opening of the protection member, and the sealing member is covered around at least a part of the lead terminal An element comprising: a first layer; and a second layer made of a material having a different thermal expansion coefficient from that of the first layer and interposed in a gap between the first layer and the protective member. A casing structure is provided.
By adopting such a structure, it is difficult to generate a gap between the sealing member and the lead terminal, and the internal airtightness can be ensured satisfactorily.

  In addition, this invention is used suitably when the said element is a fuse. Here, the fuse may be an electric fuse that is blown by heat generated by an abnormal current, or may be a temperature fuse that is blown by an increase in ambient temperature. The element is not limited to a fuse, and may be an element such as a coil, a capacitor, a resistor, or a crystal resonator.

  As described above, according to the present invention, it is possible to reliably operate an element whose function depends on the environmental temperature even in an environment where the temperature changes drastically.

  From here, some embodiments will be described as examples for carrying out the present invention. Here, a case where the present invention is applied to a fuse similar to the above-described element 90 will be described. In the following description, components having the same structure as the components of the element 90 described above are denoted by the same reference numerals, and description thereof is omitted as appropriate.

[1: First embodiment]
FIG. 1 is a cross-sectional view showing a configuration of an element 10 according to the first embodiment of the present invention. The element 10 includes a fusible alloy 1, a flux 2, lead terminals 3a and 3b, an insulating case 4, and sealing materials 6a and 6b. The elements 10 and 90 have substantially the same structure except for the seal material.

  The element 10 of the present embodiment is a fuse for protecting a heating device provided in an electrophotographic image forming apparatus. The element 10 is connected to a heating rotator (heating roll) inside the heating device, and melts to make the heating rotator nonconductive when the heating rotator is likely to exceed a predetermined temperature.

  The soluble alloy 1 is a soluble material, and an appropriate material is selected so as to melt at a predetermined temperature. Specifically, an alloy of tin (Sn) and lead (Pb) can be used as the fusible alloy 1. Although the melting temperature can be changed by changing the ratio of tin and lead, a soluble alloy that melts at 180 to 220 ° C. is used in this embodiment. The flux 2 is a thin film formed on the surface of the fusible alloy 1 and covers the fusible alloy 1 to shield the fusible alloy 1 from the outside air. The flux 2 is made of a so-called flux resin such as rosin resin.

When the fusible alloy 1 reaches a predetermined temperature, it melts to bring the lead terminals 3a and 3b into a non-conductive state. At this time, the meltable soluble alloy 1 becomes spherical due to the action of the flux 2 and adheres to the ends of the lead terminals 3a and 3b.
In the following description, the fusible alloy 1 and the flux 2 are collectively referred to as a “fuse element” as necessary.

  One of the lead terminals 3a and 3b is electrically connected to a supply device such as a power source, and the other is electrically connected to a detected object that is a temperature detection target. As the lead terminals 3a and 3b, metals such as copper (Cu) and nickel (Ni) are often used. The lead terminals 3a and 3b of the present embodiment have copper surfaces that are tin-plated.

The insulating case 4 is a protective member that protects the fuse element. The insulating case 4 has two openings, and lead terminals 3a and 3b extend from the openings to the outside, respectively. Although the material of the insulating case 4 is not particularly limited, the heat resistance according to the temperature at which the element 10 functions as a fuse (180 to 220 ° C. in the present embodiment) and the thermal conductivity for quickly heating the fuse element Is required. From these viewpoints, the material of the insulating case 4 is preferably a heat resistant resin such as aluminum nitride (AlN) or alumina ceramics (Al ₂ O ₃ ). In this embodiment, cylindrical aluminum nitride having a thermal conductivity of 150 (W / m · K) is used for the insulating case 4 in order to improve the thermal responsiveness to the fuse element.

  When the insulating case 4 is pressed against the body to be detected, it is desirable to cover the contact surface with a thin film according to wear resistance, slidability, heat resistance, and the like. As this thin film, for example, a film made of fluororesin or polyimide is suitable. In the present embodiment, for the purpose of improving slidability, a polyimide film having a thickness of 50 μm to which an adhesive is applied is provided.

The sealing materials 6a and 6b close the gap between the lead terminals 3a and 3b and the insulating case 4 at the two openings of the insulating case 4, and the inside of the element 10 (that is, the space covered with the insulating case 4 and the sealing materials 6a and 6b). It is the sealing member which ensures the airtightness of. Sealing material 6a, 6b, respectively, and has first layer _{L 1} and the second layer _{L 2.} The first layer L ₁ is made of an epoxy resin and is interposed in the gap between the lead terminals 3 a and 3 b and the insulating case 4.

On the other hand, the second layer L ₂ is made greater RTV (Room Temperature Vulcanizing) silicone rubber-based resin called rubber thermal expansion coefficient than the epoxy resin, so that its first layer L ₁ is not exposed to the outside The surface is covered. Here, “external” refers to the outside of the insulating case 4 and the sealing materials 6 a and 6 b covering the fusible alloy 1 and the flux 2.

  The configuration of the element 10 is as described above. Next, referring to FIG. 2, the behavior of the element 10 will be described in comparison with that of the element 90. In FIG. 2, cracks and pinholes, which will be described later, are emphasized in order to facilitate understanding of the contents shown in the figure, but actual cracks and pinholes are smaller.

In the element (10 or 90), each member repeats thermal expansion and thermal contraction when the heating roll as the detection target repeats heating and cooling. At this time, the sealing material (6a, 6b or 5a, 5b) may crack due to repeated expansion and contraction (FIG. 2 (a)). In addition, since some air bubbles are included in the sealing material, one or more air bubbles may penetrate the inside and outside of the sealing material to form a pinhole (FIG. 2B). When such a crack or a pin hole occurs, if the second layer L ₂ is present and airtightness of the inner case is broken, so that the external air flows from cracks or pinholes.

On the other hand, when the second layer L ₂ is present, the second layer L ₂ has a larger thermal expansion coefficient than the first layer L ₁ , so that the second layer L ₂ enters the cracks and pinholes as described above. (FIG. 2 (c)), or acts so as to cover the surface of cracks and pinholes (FIG. 2 (d)).
Thus, by providing the second layer L ₂ than the first layer L ₁ consists of a material having a large thermal expansion coefficient on the outside of the first layer L _1, element 10 is well inside the airtight Can be maintained. As a result, the contact of the fuse element with the outside air is prevented, and the element 10 can perform its function at a predetermined temperature.

[2: Second Embodiment]
Subsequently, a second embodiment of the present invention will be described. In the present embodiment, the same components as those in the first embodiment described above are denoted by the same reference numerals, and description thereof is omitted as appropriate.
FIG. 3 is a cross-sectional view showing the configuration of the element 20 according to the present embodiment. The element 20 includes a fusible alloy 1, a flux 2, lead terminals 3a and 3b, an insulating case 4, and sealing materials 7a and 7b. That is, the elements 10 and 20 have substantially the same structure except for the sealing material.

The sealing members 7a and 7b are sealing members that block the gap between the lead terminals 3a and 3b and the insulating case 4 to ensure the airtightness inside the element 10 (that is, the space covered by the insulating case 4 and the sealing materials 7a and 7b). It is. Sealing material 7a, 7b respectively have a first layer _{L 4} and a second layer _{L 3.} The second layer L ₃ is made of, for example, an epoxy resin, and is interposed between the first layer L ₄ and the insulating case 4. Then, the first layer L ₄ are being coated so as to cover a portion of the lead terminals 3a, 3b the surface of the. First layer L ₄ are formed by a silicone rubber-based resins such as high RTV rubber coefficient of thermal expansion than the epoxy resin.

The configuration of the element 20 is as described above. Next, referring to FIG. 4, the behavior of the element 20 will be described in comparison with that of the element 90.
In the element (20 or 90), each member repeats thermal expansion and thermal contraction when the heating roll as the detection target repeats heating and cooling. At this time, due to repeated expansion and contraction, a gap may be formed between the lead terminals 3a and 3b and the seal material (7a, 7b or 5a, 5b) (FIG. 4A). When such a gap has occurred, if the first layer L ₄ is present, airtightness of the inner case is broken, the external atmosphere is to flow from this gap.

On the other hand, when the first layer L ₄ is present, the first layer L ₄ has a larger thermal expansion coefficient than the second layer L ₃ , so that the first layer L ₄ expands and the above-described gap is generated. (FIG. 4B).
Thus, by providing the first layer L ₄ between the lead terminals 3 a and 3 b and the second layer L ₃ , the element 20 can maintain good internal airtightness. As a result, the contact of the fuse element with the outside air is prevented, and the element 20 can perform its function at a predetermined temperature.

[3: Modification]
As described above, the contents of the present invention have been described with reference to two embodiments. However, the present invention is not limited to these aspects, and various modifications can be made. Below, a part of the modification is demonstrated.

In the above embodiment, the first layer L ₁ and the second layer L ₂ by coating with the type of device (first embodiment), to coat the first layer L ₄ lead terminals 3a, 3b, the surface Although the device of the type (second embodiment) is shown, the present invention can also be implemented in a combination of these.
FIG. 5 is a sectional view showing the configuration of the element 30 to which this modification is applied. Element 30 is provided with sealing material 8a, the 8b, the sealing material 8a, 8b comprises a first layer _{L 5,} the first layer _{which L 5} is provided so as not to contact the external and the lead terminals 3a, and 3b and and a second layer L _6. By doing in this way, it becomes possible to further improve the airtightness inside a case.

In the element of the present invention, as the sealing member (seal material), various materials can be selected according to the material of other components and the use conditions of the element, and the thermal expansion coefficient of each layer is not constant. Of course, the magnitude relationship between the thermal expansion coefficients of the materials constituting the first layer and the second layer of the sealing member is not limited to the above-described example.
Furthermore, the sealing member does not necessarily have to be two layers, and may have a structure having three or more layers.

Moreover, in the above-mentioned embodiment, although the fuse element was protected by the cylindrical protective member (insulating case 4) which has two opening parts, it is not limited to such an aspect.
FIG. 6 is a cross-sectional view showing a configuration of an element 40 that is a modification of the above-described embodiment. As shown in the figure, the element 40 includes an insulating case 9 having one opening, and the lead terminals 3a and 3b extend from the same opening to the outside. Then, the sealing member 0 as the first layer L ₇ so as to cover the opening and a second layer L ₈ are formed. Such an element can be used, for example, as a type of fuse that is directly attached to the surface of an insulating circuit board.

In the above-described embodiment, the element is described as a so-called thermal fuse that is blown by an increase in ambient temperature. However, the present invention is also applied to a so-called electric fuse in which the fuse element itself generates heat due to an abnormal current. The invention is applicable.
Further, the casing structure of the present invention is not limited to application to a fuse, and the present invention can be applied to elements such as a coil, a capacitor, a resistor, and a crystal resonator. In short, the present invention is a technique used for all elements that exhibit a desired function at a predetermined temperature.

It is sectional drawing which showed the structure of the element which concerns on the 1st Embodiment of this invention. It is a figure explaining the behavior which the element of the embodiment shows. It is sectional drawing which showed the structure of the element which concerns on the 2nd Embodiment of this invention. It is a figure explaining the behavior which the element of the embodiment shows. It is the figure which showed the modification of the element. It is the figure which showed the modification of the element. It is sectional drawing which showed the conventional element. It is sectional drawing which showed the element of a non-conduction state.

Explanation of symbols

10, 20, 30, 40, 90 ... element, 1 ... fusible alloy, 2 ... flux, 3a, 3b ... lead terminal, 4, 9 ... insulating case, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b ... Sealing material

Claims (3)

An element whose function depends on the ambient temperature;
A protective member having at least one opening and surrounding the element;
A pair of lead terminals having one end joined to the element and the other end extending from the opening to the outside of the protective member;
A sealing member that closes the opening of the protective member;
The sealing member is
A first layer interposed in a gap between the lead terminal and the protective member;
An element comprising a second layer that is made of a material having a different thermal expansion coefficient from the first layer and covers the first layer so that the first layer is not exposed to the outside. Casing structure. An element whose function depends on the ambient temperature;
A protective member having at least one opening and surrounding the element;
A pair of lead terminals having one end joined to the element and the other end extending from the opening to the outside of the protective member;
A sealing member that closes the opening of the protective member;
The sealing member is
A first layer coated around at least a portion of the lead terminal;
An element casing structure comprising a second layer made of a material having a different thermal expansion coefficient from that of the first layer and interposed in a gap between the first layer and the protective member. The element casing structure according to claim 1, wherein the element is a fuse.

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