JP2006310168A - Electric contact mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric contact mechanism improving durability of a contact material by reducing mechanical wear and electrical wear. <P>SOLUTION: A solidified carbon fiber solid material is formed as a contact material by using high flexibility of a carbon fiber body, the flexibility-rich contact material excelling in destruction resistance against bending while each carbon fiber is a material having very large strength, and a contact area to a mating material is ensured by following the surface shape of the mating material because its surface is flexible. Even when vibration or rotation is unexpectedly generated in a moving contact, a stable contact further surely following it and hardly causing a contact failure is secured. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrical contact mechanism capable of reducing mechanical wear and electrical wear.

  2. Description of the Related Art Conventionally, in an electrical contact mechanism, particularly an electrical contact mechanism that involves sliding, a plurality of noble metal multi-component alloys, graphite, and electrical contact materials such as pressure and fired bodies mainly composed of Cu have been widely used. These materials are generally appropriately selected depending on applied voltage, power consumption, and the like.

  At this time, since the electrical contact mechanism with sliding slides while being energized, there is a problem due to a wear mechanism involving mechanical sliding wear and electrical wear (electric corrosion). In particular, when operating in a mode in which the power consumption is relatively large, arc energy increases and electric corrosion tends to be dominant.

The arc that causes this electrical wear occurs when the electrical connection between the contacts is interrupted. Residual current I _e remaining without being completely rectified during electrical connection interruption, the arc is generated when a minimum arc current I _min or a material eigenvalue. Further, the arc energy E _a which is considered to have a correlation with the contact wear is L _c as a circuit inductance.

(Equation 1)
^{_{E a = L c (I e}} 2 -I min 2) / 2

  It is indicated by. As the residual current decreases, the arc energy decreases, so that it is considered that wear due to electrical wear is suppressed. Further, in order to reduce the total arc energy, it is desirable that the two are always in contact with each other stably in a wide range as much as possible during energization between the contacts.

  Various attempts have been made from the material side to reduce the residual current, and from the structural side to reduce the total arc energy. Generally, however, melting or damage is caused to a larger arc energy. A material having high strength and high heat resistance is not applied. A typical example is a carbon-based material.

  Due to its extremely excellent heat resistance, it is possible to suppress weakening of the brush sliding surface due to heat generation related to arc energy, Joule heat resulting from contact resistance, or frictional heat generated during mechanical sliding. In addition, since the carbon-based material has self-lubricating properties, it has low friction. Therefore, even in an electrical contact mechanism in which switching with sliding frequently occurs, a conductive lubricant such as contact grease is used. It becomes possible to apply without using.

  However, due to its layered structure, carbon-based materials such as graphite have a high rate of wear due to mechanical sliding for high hardness and are brittle materials. Since a defect may occur depending on the size, a larger volume is required, and as a result, an electric contact mechanism using the same has to be enlarged. More broadly speaking, this means that devices and devices themselves having an electrical contact mechanism must be increased in size, and there is a dimensional limit as devices and devices become smaller. It is the cause.

  In addition, because carbon-based materials such as graphite are poor in flexibility, the movable contacts in the electrical contact mechanism that frequently undergo switching with sliding are subject to vibration caused by dimensional variations within the design range. I can't follow up. Therefore, even if the contact is energized by applying spring pressure, the contact always jumps at a minute interval, causing the contact to open and close, resulting in excessive contact resistance and arcing. The contact life has been significantly reduced.

  In recent years, a lot of fibrous carbon-based materials have been discovered among carbon-based materials, and research has been actively conducted. There are many basic researches on these carbon fiber materials, and there are very few examples applied to devices and equipment at present. However, in some cases, attempts have been made to use this carbon fiber material as an electrical contact. The typical means and effects are shown below.

  In FIG. 6, at least one of the conductive metal particles and the conductive metal fibers whose outer peripheral surfaces are modified with carbon nanofibers or carbon nanotubes is disposed in the contact layer through which current flows, thereby reducing wear and wear. A contact material that can be reduced has been proposed (Patent Document 1).

  In FIG. 7, at least the outermost layer contains carbon nanofibers having conductivity or carbon fibers made of carbon nanotubes, and is improved in electrical conductivity by a brush that is pressed and fired (more preferably containing graphite). In addition, reduction of mechanical sliding wear and contact resistance between commutators and improvement of corrosion resistance due to improvement of brush surface roughness by filling carbon nanofibers or carbon nanotubes between material particles have been proposed (Patent Document 2). ).

In FIG. 8, the contact is formed of a carbon nanotube bundle composed of a plurality of carbon nanotubes having one end fixed to the movable body and the other free end facing the electrode, thereby mechanically sliding the electrical contact. It has been proposed that dynamic wear can be reduced, corrosion resistance can be improved, and elasticity can be adjusted (Patent Document 3).
JP 2004-179021 A JP2004-032963 JP 2003-284304 A

  However, the above Patent Documents 1 and 2 are structures based on the premise that a solid material such as a metal or a graphitic carbon material is filled with a carbon fiber body. Therefore, in a movable contact in an electrical contact mechanism that frequently switches between open and close with sliding, an electrical contact mechanism that cannot easily follow the vibration caused by dimensional variation within the design range and easily generates an arc. can not deny. For the same reason, significant wear can be caused by mechanical sliding, so there is a limit to downsizing, and an electric contact mechanism using the same must be enlarged. Although metal fibers are also mentioned, metal fibers are not desirable because they are extremely weak against arcs and easily cause fusing, adhesion, etc., particularly in a mode with high power consumption.

  Moreover, in patent document 3, since the length of a carbon nanotube is several 100 micrometers at the maximum, it is difficult to always contact with the rotating commutator. In addition, it has a structure that can change the rigidity of the entire bundle of carbon nanotubes by changing the density. On the other hand, it tends to occur when the overall length with respect to the nano-order diameter has a high aspect ratio of several tens to several hundreds of micrometers. Not enough consideration is given to unexpected bending near the free end of the carbon nanotube, which is not only disadvantageous for energization, but especially when an unexpected load is applied, the movable contact and the carbon nanotube are fixed. If the conductive plate may be touched directly, and an arc is generated at that time, the conductive plate itself may be melted and damaged, and the possibility of causing welding cannot be denied.

  Due to the above problems, the problem of the present invention arises between materials and forms suitable for electrical contact mechanisms used in devices and devices that require a large applied voltage or power consumption, and between both contacts. An object of the present invention is to obtain an electrical contact mechanism having a structure that suppresses generation of an arc itself.

  In order to solve the above problems, it has good conductivity, excellent heat resistance, is flexible in terms of structure, and reliably follows vibrations that occur unexpectedly at movable contacts that cause rocking or rotation. It is necessary to secure a stable contact. In addition, the thermal conductivity is high, and it is necessary to efficiently disperse various heats and suppress heat generation.

  For this purpose, it is preferable to use a carbon fiber body for either one of the contact materials. Carbon fiber bundles used in the electrical contact mechanism in the present invention are graphite fiber bodies, carbon nanotubes (SWNT, MWNT), peapod nanotubes, carbon nanofibers (CNF), fullerene nanowhiskers (FNW), fullerene shell tubes, carbon amorphous. It consists of any one of tubes (glassy carbon tubes) or a hybrid of these. Since these carbon fiber bodies have high heat resistance, frictional heat generated during mechanical sliding, heat generation related to arc energy, or Joule heat due to brush-commutator contact resistance weakens the sliding surface of the brush. Can be suppressed. Moreover, since heat conductivity is favorable, various heat can be efficiently disperse | distributed from a brush-commutator sliding surface.

  Furthermore, since the carbon fiber body is a reaction-inactive material and adhesion or the like is unlikely to occur, the coefficient of friction against the counterpart material is small, and heat generation can be suppressed. Moreover, since it is rich in flexibility, it has excellent fracture resistance to bending.

  The invention described in claim 1 is an electrical contact mechanism characterized in that a carbon fiber solid material formed by solidifying a carbon fiber bundle composed of a plurality of carbon fiber bodies is used as a contact material.

  The carbon fiber solid material of the present invention is solidified by utilizing the high flexibility of the above-described bundle of carbon fiber bodies having extremely excellent characteristics. Therefore, although each carbon fiber is a very strong material, it is possible to form a contact material that is rich in flexibility and excellent in fracture resistance against bending.

  Further, since the surface is also flexible, it is possible to ensure a large contact area with the counterpart material following the surface shape of the counterpart material. Therefore, even if the movable contact is unexpectedly vibrated or rotated, the follow-up is more reliably followed, and it is possible to secure a stable contact that is unlikely to cause a contact failure. Furthermore, damage to the mating material due to sliding or mechanical contact can be reduced.

Here, even if a large contact area is ensured, if the true contact area does not increase, the contact resistance cannot be improved. Therefore, it is necessary to increase the true contact area between the carbon fiber solid material and the counterpart material. The true contact area can be considered as the total number of contact points. When the total number is n, the contact resistance r _i at the i-th contact point, and the current I _i , 1 / r _sum = Σ (1 / r _i ), I _sum = ΣI _i (1 ≦ i ≦ n). That is, with the same type of material, the larger the total number n of contact points, the lower the contact resistance and the higher the maximum applied current. The electrical contact mechanism of the present invention can form an electrical contact mechanism having a larger true contact area than a conventional electrical contact mechanism because a large number of carbon fiber bodies protrude from the carbon fiber solid material surface.

  Furthermore, in order to further increase the above-mentioned n, it is desirable that one end of a larger number of carbon fiber bundles in the solidified structure is brought into contact with the counterpart material as substantially perpendicularly as possible.

  According to a second aspect of the present invention, there is provided an electrical contact mechanism characterized in that a carbon fiber bundle composed of a plurality of carbon fiber bodies is directly fixed by plastically deforming a metal plate surface on which minute irregularities exist.

  By plastically deforming the surface of the metal plate on which the minute uneven portions are present, a carbon fiber body or a carbon fiber body bundle made of a plurality of carbon fiber bodies is caulked by the minute uneven portions, and is fixed onto the metal plate. Therefore, a strong fixing strength is obtained between the metal plate and the carbon fiber body, and since the metal plate and the carbon fiber body are reliably in contact with each other, more ideal energization can be realized.

  The invention described in claim 3 is the electrical contact mechanism according to claim 1 or 2, wherein the carbon fiber body is a carbon nanotube.

The heat dissipation characteristics due to heat conduction of carbon nanotubes are comparable to diamond, the current capacity is a maximum of 10 ⁹ A / cm ² , and the electric conductivity is a maximum of 10 ⁻⁴ Ω · cm. By using carbon nanotubes as the carbon fiber body, it is possible to show the effects of the present invention more remarkably. From the above, an ideal electrical contact mechanism can be formed. For example, among carbon nanotubes, it is more desirable to use single-walled carbon nanotubes that are particularly excellent in mechanical characteristics and electrical characteristics.

  According to a fourth aspect of the present invention, there is provided the electric contact mechanism according to any one of the first to third aspects, wherein a metal and a metal compound are interposed in the carbon fiber bundle or carbon fiber solid material. It is.

  Since a conductive compound containing a metal and a metal element is interposed in the carbon fiber bundle, an electrical contact between the metal and the metal occurs, so that the contact resistance is lowered and smoother conduction is obtained. It is possible to suppress electrical noise often seen in contact materials. As a result, it is possible to reduce the power consumption of the entire apparatus and equipment, and to further improve the reliability against electrical failure. In addition, since the mechanical characteristics are largely dependent on the carbon fiber bundle in principle, the mechanical wear characteristics are extremely good.

  Furthermore, since the voids present in the carbon fiber solid material can be filled with a conductive compound containing a metal and a metal element, the true contact area is further increased. On the other hand, the presence of the carbon fiber body, which is a carbon-based material, suppresses metal welding. The conductive compound containing a metal and a metal element also serves as a binder to bind the carbon fiber bundles more firmly.

  According to a fifth aspect of the present invention, there is provided an electronic apparatus and an electric machine which are configured by using the electric contact mechanism according to the first to fourth aspects.

  By using the electrical contact mechanism of the present invention for relays, switches, DC motors, and other various electronic devices and electrical machines, contact characteristics are less likely to occur due to various features of the contact material, and power consumption is suppressed. It is possible to obtain a long-life electronic device and an electric machine that have both rigidity and flexibility, can efficiently dissipate heat, and have less electrical noise caused by arc generation.

  By solidifying the carbon fiber body bundle, it is possible to form a contact material which is rich in flexibility and excellent in fracture resistance against bending even though each carbon fiber is a very strong material.

  Further, since the surface is also flexible, it is possible to ensure a large contact area with the counterpart material following the surface shape of the counterpart material. Therefore, even if the movable contact is unexpectedly vibrated or rotated, the follow-up is more reliably followed, and it is possible to secure a stable contact that is unlikely to cause a contact failure. Furthermore, damage to the mating material due to sliding or mechanical contact can be reduced.

  In addition, since a large number of carbon fiber bodies protrude from the surface of the solid material, an electrical contact mechanism having a larger true contact area than that of a conventional electrical contact mechanism can be formed. Increase can be achieved.

  Further, by plastically deforming the surface of the metal plate on which the minute uneven portions are present, a carbon fiber body or a carbon fiber bundle composed of a plurality of carbon fiber bodies is caulked at the minute uneven portions and fixed on the metal plate. . Therefore, a strong fixing strength is obtained between the metal plate and the carbon fiber body, and since the metal plate and the carbon fiber body are reliably in contact with each other, more ideal energization can be realized.

  In addition, since a conductive compound containing a metal and a metal element is interposed in the carbon fiber bundle, electrical contact between the metal and the metal occurs, so that the contact resistance is lowered and smoother conduction is obtained. It is possible to suppress electrical noise often seen in carbon contact materials. As a result, it is possible to reduce the power consumption of the entire apparatus and equipment, and to further improve the reliability against electrical failure. In addition, since the mechanical characteristics are largely dependent on the carbon fiber bundle in principle, the mechanical wear characteristics are extremely good.

  From the above, by using the electrical contact mechanism of the present invention for relays, switches, DC motors, and other various electronic devices and electric machines, contact failure is less likely to occur due to various features of the contact material, and power consumption is reduced. Thus, it is possible to obtain a long-life electronic device and electric machine that are suppressed, have both rigidity and flexibility, can efficiently dissipate heat, and have less electrical noise caused by arc generation.

  FIG. 1 is a schematic diagram showing an embodiment of an electrical contact according to the present invention. This electrical contact 1 is obtained by fixing a carbon fiber solid material 3 obtained by solidifying a carbon fiber bundle to a fixed plate 2 made of a conductor such as a leaf spring. Here, the manufacturing method of carbon fiber solid material produced by embodiment of this invention and its various characteristics are demonstrated. Moreover, this embodiment is an example regarding this manufacturing method, and is not limited to this. Moreover, although the result of using SWNT (single-walled carbon nanotube) as the carbon fiber will be described as a representative example, the present invention can also be applied to various carbon fiber bodies.

  First, a mass in which carbon fiber bodies were intertwined in a complicated manner, having a length of several μm to several tens of μm, containing carbon impurities of several percent to several tens of percent was obtained using a thermal vapor synthesis method. In order to make the obtained mass into a predetermined shape, it is dispersed using ultrasonic waves in a solution such as ethanol or DMF (dimethylformamide), dried, and dispersed and dried repeatedly until it becomes a powder form on the visual level. A carbon fiber bundle composed of a plurality of carbon fiber bodies was obtained.

For solidification of the carbon fiber bundle, a hydraulic pressure molding machine having a molding die was used. After a phosphor bronze plate as a fixing plate was inserted into the lowermost part of the mold, a carbon fiber bundle was sealed in the mold, and a load was applied so as to be 5 t / cm ^{2 at} room temperature. By pressing, the carbon fiber bundles entered the fine irregularities present on the surface of the phosphor bronze plate, and were fixed on the surface of the phosphor bronze plate and solidified. Thereby, an electrical contact in which a carbon fiber solid material of 2 mm (W) × 3 mm (D) × 1.0 mm (H) was integrally fixed to the phosphor bronze plate was obtained. Here, the size can be made larger or smaller depending on the shape of the mold and the amount of the carbon fiber bundle.

  An SEM photograph of the surface of the carbon fiber solid material in the electrical contact thus obtained is shown in FIG. This photograph also shows that many carbon fiber bundles protrude on the surface. From this, it can be seen that an electrical contact mechanism having a large true contact area can be formed as compared with the conventional electrical contact mechanism.

  In order to confirm the adhesion between the phosphor bronze plate and the carbon fiber solid material, an adhesive peel test in the 90 ° tensile direction was performed using a cellophane adhesive tape specified in JIS Z 1522. As a result, it was confirmed that the carbon fiber solid material was sufficiently caulked without being peeled due to the anchor effect caused by caulking the carbon fiber solid material at the minute uneven portions of the phosphor bronze plate.

The carbon fiber solid material was brought into contact with a silver rivet contact by applying a spring pressure of 5 gf / mm ² , and the results of examining the current-voltage characteristics are shown in FIG. As can be seen from this result, the relationship between the current and the voltage is proportional, indicating a metallic behavior. Further, the resistance value calculated from this result was 850 mΩ. The difference was not recognized or slightly smaller than the results of measuring the resistance values of various carbon contact materials in the same form, and they were excellent conductors at a practical level.

  Next, using a carbon fiber solid material fixed to the phosphor bronze plate and a carbon contact material made of graphite as a comparative example, a mechanical wear test was performed by a mechanical wear tester 4 shown in FIG. The mechanical wear tester 4 includes a drive motor 5, a coupling 6, a shaft 7, and a support material 8 that supports them.

  The output from the drive motor 5 is transmitted to the shaft 7 supported by ball bearings 9 on the left and right via the coupling 6, and a rotating body 10 formed of copper-based metal is fixed to the shaft 7. . A carbon fiber solid material 12 fixed to the fixed plate 11 was brought into contact with the rotating body 10 by using a spring pressure by the spring material 13. Further, as a comparative example, the carbon contact material made of graphite was replaced with the carbon fiber solid material 12, and the test was performed by the same means.

  The test conditions were a rotational speed of 4000 rpm, a load of 20 gf, normal temperature and humidity, and no lubrication. The evaluation was based on the wear volume to the wear rate (wear volume per unit sliding distance) and the specific wear amount (unit sliding distance / unit load). Per wear volume). The results are shown in Table 1.

As a result, in the carbon fiber solid material of the present invention, the wear rate is 2.58 × 10 ⁻¹⁰ mm ² , the specific wear amount is 1.29 × 10 ⁻⁹ mm ² / N, and the carbon contact material made of graphite is worn. The rate is 2.60 × 10 ⁻⁹ mm ² and the specific wear amount is 1.30 × 10 ⁻⁸ mm ² / N. Compared with the conventional carbon contact material made of graphite, both the wear rate and the specific wear amount are Reduced to about 1/10. Furthermore, since the carbon fiber solid material of the present invention has a self-lubricating property and a flexible surface, no significant damage was observed on the surface of the rotating body in this mechanical wear test. As described above, the carbon fiber solid material of the present invention has a flexible surface, has a remarkable durability against mechanical wear, and greatly contributes to the extension of the service life of electrical contacts with sliding.

  Further, using this carbon fiber solid material and a carbon contact material made of graphite and a copper alloy as a comparative example, an electric wear test was performed by a relay type electric wear tester 14 as shown in FIG. In this relay type electric wear tester 14, a fixing plate 18 having a carbon fiber solid material 17 fixed thereto is fixed to a holder 16 having a soft magnetic material 15, and a silver-based one is connected via an inductance 19 and a constant current source 20. Connected to the rivet contact 21. The electromagnet 23 connected to the constant voltage source 22 is repeatedly turned on and off at regular intervals by the sequencer 24. By this ON-OFF operation, the carbon fiber solid material 17 of the present invention repeatedly contacts the silver rivet contact 21. The arc is generated each time. As a comparative example, the carbon contact material made of graphite and a copper alloy was replaced with the carbon fiber solid material 17, and the test was performed by the same means.

The test conditions were a maximum power consumption of 20 W, an applied current of 0.5 A, an ON-OFF frequency of 20 Hz, an insertion inductance of 1 mH (at 1 kHz), and normal temperature and humidity, and the evaluation was per relay terminal resistance and ON-OFF per turn. This was done by determining the wear volume. The inter-terminal resistance was measured using an ohmmeter with a surface pressure of 5 gf / mm ² applied between the fixed plate before and after the test and the silver rivet contact. The results are shown in Table 2.

Wear volume per ON-OFF1 times, the present invention example 5.3 × ¹⁰ -5 mm ³ / dose, graphite is 5.4 × ¹⁰ -5 mm ³ / dose, approximately equivalent electrical wear characteristics Indicated. Moreover, since the initial value of the inter-terminal resistance is 850 mΩ of the present invention example and 980 mΩ of graphite, these are chemically stable with respect to oxygen and the like. There were no major changes in magnitude. However, the copper alloy was affected by significant electrical wear as compared with the carbon-based material, resulting in fusing. In addition, although the initial resistance of the copper alloy was as small as 25 mΩ, significant oxidation occurred with the generation of the arc, and the resistance between the terminals increased greatly. The resistance between the terminals after the occurrence of the arc was very unstable. This is considered to be because the formation and destruction of the oxide film are repeated every time the arc is generated.

  From the above, it can be seen that the present invention example has at least the same electrical wear characteristics as an electrical contact using a conventional carbon-based material, and the advantages of the conventional carbon-based material are exhibited. . Furthermore, in this electrical wear test, we obtained a result with the same electrical wear characteristics because we intentionally generated an arc structure, but considering an electrical contact mechanism with sliding, it has a flexible surface. Therefore, it is possible to suppress the generation of the arc itself, and it is possible to realize a longer life with respect to electrical wear than the electrical contact material using the conventional carbon-based material. When combined with mechanical wear characteristics, it has wear characteristics that exceed those of conventional carbon-based materials, so it is possible to form superior electrical contact mechanisms that surpass those of conventional carbon-based materials. It becomes.

  Moreover, the carbon fiber solid material which made the carbon fiber bundle bundle interpose a metal particle was produced, and the characteristic was investigated. First, silver nanocrystal particles of 10 nm to 30 nm are dispersed in toluene, and after impregnating silver nanoparticles between carbon fiber bundles solidified by the same method as described above, about 250 ° C. Is fired for 1 hour in the air atmosphere, and this operation is repeated several times. Thereby, the carbon fiber solid material which fully filled silver between the solidified carbon fiber body bundles was obtained.

  The resistance value was calculated | required from the result of having investigated the current-voltage characteristic similar to the above about the obtained metal containing carbon fiber solid material. As a result, the resistance value, which was 850 mΩ in the contact material before interposing the metal, was further improved to several tens of mΩ, and could be improved to a level comparable to that of the noble metal contact.

  Utilizing the above characteristics, it can be applied to various other electrical contact mechanisms including switching terminals and DC motor electrical contacts.

The schematic diagram which shows embodiment of the electrical contact of this invention SEM photograph of the surface of the carbon fiber solid material in the electrical contact of this example Current-voltage characteristic diagram of contact material of this example Schematic diagram showing the configuration of a mechanical wear tester in this example Schematic diagram showing the configuration of the electrical wear tester in this example Explanatory drawing of the conventional electrical contact mechanism in Patent Document 1 Explanatory drawing of the conventional electrical contact mechanism in Patent Document 2 Explanatory drawing of the conventional electrical contact mechanism in Patent Document 3

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrical contact 2, 11, 18 Fixed plate 3, 12, 17 Carbon fiber solid material 4 Mechanical abrasion tester 5 Drive motor 6 Coupling 7 Shaft 8 Support material 9 Ball bearing 10 Rotating body 13 Spring material 14 Relay type electric wear Test machine 15 Soft magnetic material 16 Holder 19 Inductance 20 Constant current source 21 Silver-based rivet contact 22 Constant voltage source 23 Electromagnet 24 Sequencer

Claims (5)

  An electrical contact mechanism characterized in that a carbon fiber solid material formed by solidifying a carbon fiber body bundle made of a plurality of carbon fiber bodies is used as a contact material.   An electrical contact mechanism characterized in that a carbon fiber bundle composed of a plurality of carbon fiber bodies is directly fixed by plastically deforming a metal plate surface on which minute irregularities exist.   3. The electrical contact mechanism according to claim 1, wherein the carbon fiber body is a carbon nanotube.   4. The electric contact mechanism according to claim 1, wherein a metal and a metal compound are interposed in the carbon fiber bundle or the carbon fiber solid material. 5. An electronic apparatus and an electric machine configured by using the electric contact mechanism according to claim 1.