JP2004296130A - Electrical contact and thermal protector using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrical contact unmelts it even at the end of its service life, and a thermal protector using the contact and having extremely improved reliability and safety. <P>SOLUTION: An electrical contact 10 having a first main face and a second main face opposite each other is used for the thermal protector, wherein a conductive layer 13 is formed between the first and the second main faces 11, 12; a surface layer 13a on the side of the first main face 11 of the conductive layer 13 mainly contains a conductive substance; and a surface layer 13d on the side of the second main face 12 of the conductive layer 13 contains an electrical insulating substance and the conductive substance by a volume ratio of 30:70-70:30. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrical contact with improved welding resistance and a thermal protector using the same.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a thermal protector has been used as a device that protects an electric device by detecting a thermal change occurring when an electric device such as a small motor is abnormal and opening and closing a contact.
[0003]
FIG. 3 is a partially cutaway sectional view of a conventional glass-sealed thermal protector. In the thermal protector 30 shown in FIG. 3, a fixed inner lead wire 33 having a fixed contact 32 at the tip and a movable contact 34 at the tip and a movable contact 34 at the other end are provided in the glass container 31. The thermally responsive element 36 to which the internal lead wire 35 is connected is arranged to face the same, and the fixed contact 32 and the movable contact 34 are arranged so as to be able to contact and separate from each other. The fixed-side internal lead 33 and the movable-side internal lead 35 are supported by a glass bead 37, and the fixed-side internal lead 33 and the movable-side internal lead 35 are fixed to a fixed-side external lead 38 in the sealing portion 31a. And the movable side external lead wire 39 by welding or the like. One ends of the fixed external lead wire 38 and the movable external lead wire 39 are led out of the glass container 31.
[0004]
Such conventional thermal protectors are used for electrical equipment such as small motors. When the equipment malfunctions, the self-heating due to overcurrent and the rise in ambient temperature cause the fixed contact and movable contact to return by reversing the thermal response element. The device is protected by opening and closing to shut off the current.
[0005]
Originally, as the frequency of opening and closing of electrical contacts increases, the surface damage due to arc discharge progresses, and it is not possible to predict whether the failure mode of the conventional thermal protector is non-conducting or welding when the switching operation is repeated until the end of its life. Is the current situation. Here, if the welding of the contacts occurs, there is a danger of damaging the electrical equipment to be protected.
[0006]
For this reason, in order to make the final failure mode of the thermal protector non-conductive, there has been proposed a thermal protector including a contact having a configuration in which insulating fibers are sandwiched inside (for example, see Patent Document 1).
[0007]
However, in the thermal protector having the above-described configuration, the contact is made by sandwiching a foreign substance called insulating fiber, so that the mechanical strength of the contact is inferior, and the end of the insulating fiber is exposed outside the contact. With the opening and closing of the device, fiber waste falls between the contacts, and the contacts become non-conductive even though the thermal protector is in a sufficiently normal state, so that there is a problem that the electric device equipped with the thermal protector does not operate.
[0008]
[Patent Document 1]
JP 2000-311574 A
[Problems to be solved by the invention]
The thermal protector that has been activated once due to an abnormality in the electrical equipment repeatedly opens and closes the contacts at a constant cycle until the cause of the abnormality is eliminated. Essentially, the electrical contacts have the danger that their surface wears out as the switching frequency increases and eventually fuses with each other. However, if the contacts of the thermal protector are welded by a frequent opening / closing operation, the function as a safety element is lost, and there is a possibility that electrical equipment may be damaged.
[0010]
The present invention solves such a problem and provides an electric contact that does not weld even at the end of life and a thermal protector using the same.
[0011]
[Means for Solving the Problems]
The present invention is an electrical contact comprising a first main surface and a second main surface facing each other,
A conductive layer is formed between the first main surface and the second main surface;
The conductive layer includes a layer mainly containing a conductive substance on the first main surface side,
The conductive layer may include a layer containing an electrically insulating material and a conductive material on the second main surface side.
[0012]
Further, the present invention includes a conductor portion having an electric contact at a tip thereof, and a thermo-responsive element having an electric contact at a tip, wherein the electric contact of the conductor portion and the electric contact of the thermo-responsive element are separated from each other. A thermal protector that is arranged as possible,
A thermal protector is provided, wherein the electrical contact is used for at least one selected from an electrical contact of the conductor portion and an electrical contact of the thermally responsive element, and the first main surface is a contact surface. .
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
The electric contact of the present invention includes a layer containing a conductive material as a main component on a first main surface side, and includes a layer containing an electric insulating material and a conductive material on a second main surface side. As a result, as the surface layer of the contact wears due to the repetition of opening and closing, the proportion of the electrically insulating material on the contact surface increases, and finally the contact is in a non-conductive state, thereby avoiding welding of the contact at the end of life. be able to. Here, containing a conductive material as a main component means containing at least 80% by volume in volume ratio.
[0014]
The volume ratio between the electrically insulating substance and the conductive substance contained in the layer on the second main surface side is preferably 30:70 to 70:30, more preferably 45:55 to 65:35. is there. Within this range, welding at the end of life can be more reliably prevented while ensuring the electrical conductivity of the electrical contact in normal operation.
[0015]
Further, the conductive layer may include a plurality of layers in which the amount of the electrically insulating substance increases stepwise from the layer on the first main surface side to the layer on the second main surface side.
[0016]
Further, the proportion of the electrically insulating substance in the conductive layer can be continuously increased from the first main surface side to the second main surface side.
[0017]
The concentration gradient of the electrically insulating substance in the conductive layer can be obtained without the effect of the present invention even if the gradient is stepwise or continuously inclined. It is preferable that
[0018]
Furthermore, since the thermal protector of the present invention uses the electrical contact of the present invention and uses the first main surface as a contact surface, the contact becomes nonconductive at the end of the life of the thermal protector as described above, Avoiding welding can ensure the safety of the equipment.
[0019]
In addition, the electrical contact of the present invention may be used for both of the opposed contacts of the thermal protector, or may be used for any one of them. In particular, in the case of a device with a DC power supply, the degree of wear of the contacts may be greatly affected by the polarity of the contacts.
[0020]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0021]
FIG. 1 is a perspective view (A) showing an example of the electric contact of the present invention and a partially enlarged sectional view (B) thereof. As shown in FIG. 1, the electric contact 10 of the present embodiment includes a first main surface 11 and a second main surface 12 facing each other, and the first main surface 11 and the second main surface 12 are opposed to each other. The conductive layer 13 is formed between them. The conductive layer 13 is formed, for example, from a plurality of layers 13a, 13b, 13c, 13d having different compositions from the first main surface 11 side to the second main surface 12 side. The layer 13a is formed of a conductive material. From this layer 13a, toward the layer 13d, the ratio of the electrically insulating material in each of the layers 13b, 13c, and 13d increases stepwise, and the electrical insulation in the layer 13d is increased. The volume ratio between the conductive material and the conductive material is, for example, 50:50. That is, the conductive layer 13 is formed of a graded material in which the proportion of the electrically insulating substance increases stepwise. Further, the ratio of the electrically insulating substance in the conductive layer 13 can be continuously increased from the first main surface 11 side to the second main surface 12 side. However, it is sufficient that the first main surface 11 side includes a layer mainly including a conductive substance and the second main surface 12 side includes a layer including an electrically insulating substance and a conductive substance. There is no need to use materials.
[0022]
As the conductive material, for example, a single metal powder such as Ag and W, or an alloy powder such as Ag-Ni, Ag-Cd, Ag-W, Ag-Cu, Ag-Pd, Ag-Sn, and Cu-W Can be used. As the electrically insulating material, for example, oxide powder of alumina, silica, magnesia, zirconia, titania, etc. can be used alone or as a mixture of two or more kinds. Not only oxides but also nitrides may be used.
[0023]
As a method for producing the above-mentioned gradient material, various methods are already widely known mainly for a powder metallurgy / ceramic manufacturing process, for example, a sheet laminating method, a powder filling press method, a centrifugal casting method, a plating method, a thin film method, A plasma method or the like can be employed. In the case where an electric contact having a surface with a curvature is produced, it can be produced by a powder filling press method or the like.
[0024]
FIG. 2 is a partially cutaway sectional view showing an example of the thermal protector of the present invention. As shown in FIG. 2, the thermal protector 20 of the present embodiment includes a fixed inner lead wire 23 having a fixed contact 22 at a distal end in a glass container 21 and a movable contact 24 at a distal end. A thermally responsive element 26 having a movable internal lead wire 25 connected to the other end thereof is disposed to face, and the fixed contact 22 and the movable contact 24 are disposed so as to be able to contact and separate from each other. The fixed-side internal lead 23 and the movable-side internal lead 25 are supported by a glass bead 27, and the fixed-side internal lead 23 and the movable-side internal lead 25 are fixed to a fixed-side external lead 28 in the sealing portion 21a. And to the movable external lead wire 29 by welding or the like. One ends of the fixed external lead 28 and the movable external lead 29 are led out of the glass container 21.
[0025]
As the fixed contact 22, the electric contact of the present embodiment shown in FIG. 1 described above is used, and the first main surface 11 is used as a contact surface, and the second main surface 12 is used as a connection surface with the thermally responsive element 26. I have. The movable contact 24 is made of, for example, an alloy such as Ag-Ni, Ag-Cd, Ag-W, Ag-Cu, Ag-Pd, Ag-Sn, or Cu-W, or a single metal such as Ag or W. Can be formed from
[0026]
The thermally responsive element 26 includes a bimetal in which two metal plates having different coefficients of thermal expansion are bonded, or a trimetal in which three metal plates are bonded. Generally, a Ni-Fe alloy or the like can be mainly used as the metal on the low expansion side. Further, as the metal on the high expansion side, various alloys such as Ni-Cr-Fe, Ni-Mn-Fe, Ni-Mo-Fe, and Ni-Cu-Mn can be used.
[0027]
【Example】
Next, the present invention will be described more specifically based on examples. However, the present invention is not limited to the following examples.
[0028]
(Example 1)
First, an electrical contact was manufactured using a sheet lamination method as follows.
[0029]
Silver powder having an average particle diameter of 4 μm was prepared as a conductive substance, and alumina powder having an average particle diameter of 2 μm was prepared as an electrically insulating substance. A mixture was prepared by mixing the silver powder and the alumina powder at four different volume ratios. To 100 parts by mass of each mixture, 3 parts by mass of butyral as a binder, 0.1 part by mass of ammonium polyacrylate as a dispersant, and 30 parts by mass of butyl acetate as a solvent were added to prepare four types of slurries. The volume ratio of alumina powder to silver powder (alumina powder / silver powder) was four types: 0/100, 10/90, 30/70, and 50/50.
[0030]
Each slurry was applied on a polyethylene terephthalate (PET) film to produce four types of sheets having a thickness of about 100 μm. The PET film was peeled off from the sheet and cut into sheet pieces of a predetermined size. Here, the volume ratio of alumina powder / silver powder is 0/100 for sheet A, 10/90 for sheet B, 30/70 for sheet C, and 50/50 for sheet. D. Subsequently, four sheet pieces A were laminated to form a sheet layer A. Similarly, sheet layers B, C, and D were formed.
[0031]
Next, these sheet layers are successively laminated and pressed in the order of A, B, C, and D to produce a laminated molded body, and then cut to obtain a 2.5 mm long, 2.5 mm wide, 1.5 mm thick. I got a chip. The obtained chip was heated to 400 ° C. in an electric furnace to remove the binder, and then fired at 800 ° C. for 2 hours to produce an electric contact.
[0032]
Next, as shown in FIG. 2, this electric contact is used for both the fixed contact and the movable contact, and the layers having a volume ratio of alumina powder / silver powder of 0/100 are arranged so as to face each other. A thermal protector was made. Note that a bimetal in which a Ni-Fe alloy plate and a Ni-Cr-Fe alloy plate were bonded together was used as the thermally responsive element. Further, a Mn-Ni wire was used as a material for the lead wire.
[0033]
(Example 2)
A thermal protector was manufactured in the same manner as in Example 1, except that a conventional electrical contact formed of an Ag-Ni alloy was used as the movable contact.
[0034]
(Example 3)
A thermal protector was manufactured in the same manner as in Example 1 except that a conventional electrical contact formed of an Ag-Ni alloy was used as the fixed contact.
[0035]
(Comparative example)
A thermal protector was manufactured in the same manner as in Example 1, except that both the fixed contact and the movable contact were formed from an Ag-Ni alloy.
[0036]
Next, a life test up to the end of life was performed using each of the 30 thermal protectors of Example 1, Example 2, Example 3, and Comparative Example. The life test was performed under the conditions of AC 120 V, 10 A, and a power factor of 80%.
[0037]
As a result, in each of the thermal protectors of Example 1, Example 2, Example 3, and Comparative Example, there was a certain variation in the number of times the contacts were opened and closed until the life end, but in Comparative Example, 30 samples were used. Twelve of them reached the end of life due to contact welding, whereas in Example 1, Example 2 and Example 3, no contact welding occurred, and all of the contacts reached the life end in a non-conductive state. . Thus, in the thermal protectors of Examples 1 to 3 according to the present invention, it was proved that even if the contacts were repeatedly opened and closed until the end of the service life, the non-conductive state of the contacts could be finally secured.
[0038]
In designing a contact material using an inclined material, a predetermined conductivity is required even in a layer containing the largest amount of an electrically insulating substance in order to secure the function of the electric contact. In this embodiment, the volume% of the alumina powder in the layer containing the largest amount of the electrically insulating substance is set to 50% by volume. However, if the volume% of the alumina powder is within 70% by volume, the quality of the thermal protector is not affected. Confirmed conductivity.
[0039]
In the case of a contact having a conventional structure, a relatively high-resistance joining layer made of a Cu—Ni alloy or the like may be provided on the lead wire side in order to facilitate joining by resistance welding. % Layer on the fixed-side internal lead wire side, a moderate rise in resistance appears, and resistance welding can be easily performed without the above-mentioned bonding layer. Was also confirmed.
[0040]
Finally, although the present invention has been described using a glass container type thermal protector, it is clear that the same effect can be obtained in a resin container type thermal protector, and furthermore, the electric contact of the present invention reduces the risk of contact welding. It can be applied to any contact relay equipment to be borne.
[0041]
【The invention's effect】
As described above, the present invention can provide an electrical contact that does not weld even at the end of its life, and a thermal protector using the electrical contact that has greatly improved reliability and safety.
[Brief description of the drawings]
FIG. 1 is a perspective view (A) showing an example of an electric contact of the present invention and a partially enlarged sectional view (B) thereof.
FIG. 2 is a sectional view showing an example of the thermal protector of the present invention.
FIG. 3 is a sectional view of a conventional thermal protector.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Electric contact 11 1st main surface 12 2nd main surface 13 Conductive layer 13a, 13b, 13c, 13d Layer 20, 30 Thermal protector 21, 31 Glass container 21a, 31a Sealing part 22, 32 Fixed side contact 23, 33 Fixed internal lead wire 24, 34 Movable contact 25, 35 Movable internal lead wire 26, 36 Thermal response element 27, 37 Glass bead 28, 38 Fixed external lead wire 29, 39 Movable external lead wire

Claims (5)

An electrical contact comprising a first main surface and a second main surface facing each other,
A conductive layer is formed between the first main surface and the second main surface;
The conductive layer includes a layer containing a conductive substance as a main component on the first main surface side,
The electric contact, wherein the conductive layer includes a layer containing an electrically insulating substance and a conductive substance on the second main surface side. 2. The electrical contact according to claim 1, wherein a volume ratio between the electrically insulating substance and the conductive substance contained in the layer on the second main surface side is 30:70 to 70:30. 3. 2. The conductive layer includes a plurality of layers in which the amount of the electrically insulating substance increases stepwise from the layer on the first main surface side toward the layer on the second main surface side. 3. 3. The electrical contact according to 2. 3. The electrical contact according to claim 1, wherein a ratio of the electrically insulating substance in the conductive layer continuously increases from the first main surface side to the second main surface side. 4. A thermal section including a conductor portion having an electrical contact at a distal end and a thermoresponsive element having an electrical contact at a distal end, wherein the electrical contact of the conductor portion and the electrical contact of the thermal responsive element are arranged so as to be capable of coming and going. A protector,
At least one selected from the electrical contact of the conductor portion and the electrical contact of the thermally responsive element uses the electrical contact according to any one of claims 1 to 4, and the first main surface is a contact surface. A thermal protector characterized in that:

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