JP4359476B2 - High voltage load switchgear - Google Patents

Description

  The present invention relates to an electrical switchgear, and more particularly to a switchgear for controlling a high voltage load with a DC voltage of 36 V or more, which is mounted on a next-generation DC voltage 42V automobile, electric vehicle, or hybrid vehicle.

  An opening / closing device for mechanically opening and closing an electric circuit includes an electric contactor generally called a contact element (sometimes simply referred to as a contact). The electrical contact is required to transmit the current / signal flowing through the contact element without any trouble when the metal contacts the metal, or to be separated without any trouble when disconnected. This contact element is known to cause various physical or chemical phenomena on the contact surface, although the structure itself is relatively simple. For example, adsorption, oxidation, sulfidation, synthesis of organic compounds, and melting, evaporation, consumption, transition with arc discharge, etc., the phenomenon is very complicated Many.

  When the above phenomenon such as arc discharge or consumption occurs, the contact function of the contact element is hindered, and in some cases, the continuity failure or locking occurs, and the opening / closing mechanism cannot operate normally. Serious obstacles may be caused to electronic / electrical devices with built-in devices. This means that the built-in switchgear is one of the important components that determine the life and performance of electronic / electrical equipment.

  In recent years, with the remarkable development of electronic and electrical engineering, the range of use of switchgear has been wide ranging from the weak electric field such as telegraph telephones and various electronic devices to the strong electric field such as electric devices that cut off a large current. . For this reason, the required functions vary widely, and the development of switching mechanisms with characteristics tailored to each purpose of use has been promoted, and a large number of switching devices equipped with these developed switching mechanisms are being supplied to the market. .

Among them, in the field of automobiles, that is, in a switchgear that controls the load on automobiles, Ag—Cu system (alloy consisting of 1 to 40 wt% Cu and the balance Ag) manufactured by melting and casting method, Contact made using an electrical contact material such as an Ag—SnO ₂ system (alloy consisting of 5 to 15% by weight of SnO ₂ and the balance Ag), Ag—SnO ₂ —In ₂ O ₃ system manufactured by an internal oxidation method A device including an element is known (see Patent Documents 1 and 2).
JP 2000-309834 A International Publication No. 01/04368 Pamphlet

  However, in next-generation automobiles, for example, hybrid cars and electric cars, a DC voltage of 42 V (or DC 48 V) is planned for controlling electronic and electric devices mounted on the automobile, and the maximum voltage value is 300 to 400 V. It is said that it is necessary to control very high voltage loads. In this way, for high voltage loads that cannot be compared with conventional DC loads, that is, DC loads of 36 V or more, contact elements using conventionally known electrical contact materials are applied to the current switching mechanism. But it is not adaptable.

  In order to securely interrupt the arc with such a high voltage load, it is necessary to secure a sufficient contact gap, but there is a limit to widening the gap between the contacts with the single break structure used in the current switching mechanism. There is a case where an arc generated at the time of breaking cannot be interrupted at a high voltage load of 36V or more. And in the worst case, it causes an accident that burns down the electronic / electrical equipment to be controlled.

  In order to interrupt such an arc, a switchgear that employs an arc extinguishing method using magnetism is known, but this complicates the switchgear mechanism. In other words, conventional switchgears mounted on automobiles cannot control high DC loads as high as 36 V or more, and there is a strong demand for new switchgears having characteristics that have not been required so far. This is the current situation.

  The present invention has been made in the background as described above, and is a switching device having a switching mechanism applicable to a high voltage load in a next-generation vehicle such as a hybrid vehicle or an electric vehicle, more specifically, 36 V or more. An object of the present invention is to provide a high-voltage load switchgear that can control a direct-current high-voltage load.

  In order to solve the above-mentioned problems, the present inventors have intensively researched and configured a switching mechanism using a contact element formed of an electrical contact material in which MgO is dispersed in an Ag matrix. The inventors have found a phenomenon capable of remarkably shortening the arc continuation time generated in the contact element in the load, and have come up with the present invention.

  The present invention provides a single break structure opening / closing mechanism comprising a contact element made of an electrical contact material composed of 2.0 to 20.0% by weight of MgO particles and the balance Ag and having MgO particles dispersed in an Ag matrix. A high-voltage load switchgear characterized by controlling a high-voltage load having a DC voltage of 36 to 400 V and a rated current of 0.01 to 15 A.

  The present inventors have investigated a contact element made of an Ag-oxide-based electrical contact material in which various oxides are dispersed in an Ag matrix by forming a single break structure switching mechanism. Among them, only MgO found a phenomenon in which the arc duration was shortened by a larger difference than a pure Ag contact in which no oxide was added. That is, only in a switchgear having a contact element using an Ag-oxide based electrical contact material in which MgO is dispersed in an Ag matrix, a high voltage load of 36 V or more is generated at the time of separation. The arc can be interrupted, and a normal opening / closing operation can be maintained. According to the study by the present inventors, the arc extinction phenomenon at the DC high voltage load of the contact element by the electrical contact material in which MgO particles are dispersed in the Ag matrix is the amount of MgO particles dispersed in the Ag matrix, It has been confirmed that it is affected by the dispersion state and particle size.

  The electrical contact material used for the contact element of the switchgear for a high voltage load according to the present invention does not clearly show the effect of shortening the arc duration when MgO is less than 2.0% by weight. When it exceeds, the increase in contact resistance becomes remarkable, and the workability of the material tends to be remarkably deteriorated. In practice, a more desirable composition is to contain 8.1 to 15% by weight of MgO. Within this range, contact elements having good characteristics in all aspects of arc duration reduction effect, low contact resistance, and material workability can be formed, and a switchgear suitable for high voltage loads can be realized. Because you can.

  Furthermore, as a result of studying the dispersion state of MgO particles in the electrical contact material, the present inventors formed a contact element by using an electrical contact material in which MgO particles are dispersed in layers. It has been found that the arc suppression effect is reduced.

  The electrical contact material of Ag-MgO according to the present invention can be manufactured by a so-called internal oxidation method (see Patent Document 3). However, when the present inventors tried to produce an Ag-MgO electrical contact material by the prior art internal oxidation method, the obtained electrical contact material was either in a state where the oxide was dispersed in layers or very large. Only the agglomerated state was obtained, and it was confirmed that even when a contact element made of such an electrical contact material was used, arcing under a DC high voltage load could not be sufficiently suppressed.

JP 2002-363666 A

  Here, the structure state in the electrical contact material of Ag—MgO will be described specifically by exemplifying a structure cross-sectional photograph. First, in the case of the internal oxidation method, Mg and Ag were dissolved so as to be 3.0% by weight of Mg and the balance Ag, and cast into a plate mold. Thereafter, the plate was rolled and processed to a thickness of 1.5 mm, and cut into 10 mm squares. Next, the contact piece was internally oxidized at an oxygen pressure of 5 atm and a temperature of 750 ° C., and the dispersion state of MgO particles in the obtained Ag—MgO electrical contact material was confirmed. FIG. 1 shows the dispersion state of MgO particles when the internal oxidation method is used. As can be seen from this, MgO is dispersed in layers in the Ag matrix. FIG. 2 shows the dispersion state of MgO particles when the internal oxidation conditions are changed to an oxygen pressure of 0.2 atm and a temperature of 750 ° C. In this case, it can be seen that the MgO particles aggregate to form a large mass and exist in the Ag matrix.

  On the other hand, the present inventors mixed Ag powder and MgO powder with a predetermined particle size in a predetermined composition, compressed, and then sintered to produce an Ag-MgO electrical contact material. It was confirmed that MgO was obtained in a granular state dispersed in the Ag matrix (FIG. 3). The electrical contact material shown in FIG. 3 has the same composition as that prepared by internally oxidizing the above-described Mg 3.0 wt% (in metal conversion) and the remaining Ag alloy, that is, MgO 4.9 wt% and the remaining Ag Ag. -It was obtained by mixing Ag powder and MgO powder so as to be an MgO electrical contact material.

  When the internal oxidation method and the powder metallurgy method were used for a DC high voltage load, the internal oxidation method could not sufficiently suppress the arc at the time of breaking.

  Furthermore, the Ag-MgO electrical contact material according to the present invention can be obtained by a manufacturing method employing a so-called mechanical alloying method (see Patent Document 4). However, when the present inventors performed mechanical alloying based on Patent Document 4 which is the prior art, the arc at the time of breaking could not be sufficiently suppressed.

Japanese Patent Laid-Open No. 09-111367

  As a result of the examination on the structure of the electrical contact material of Ag-MgO as described above, in the high-voltage load switchgear mounted on an automobile according to the present invention, Ag powder and MgO powder are mixed to obtain an average particle size of 1. It was judged that it was desirable that 1 to 6.0 μm MgO particles were formed so as to be dispersed in the Ag matrix. The switchgear used for a high voltage load having a DC voltage of 36 V or more, which is the subject of the present invention, requires that MgO in the Ag—MgO electrical contact material forming the contact element be present in the Ag matrix as particles. For example, in the case of an electrical contact material that is in an Ag matrix in a state of being alloyed with Ag, it becomes impossible to suppress an arc of a DC high voltage load.

  When the average particle diameter of the MgO particles is less than 1.1 μm in the electrical contact material used in the switchgear of the present invention, the arc suppression effect under a direct current high voltage load tends to be reduced. On the other hand, if the thickness exceeds 6.0 μm, arc concentration tends to occur and local wear is caused. More desirably, the average practical particle size of the MgO particles is 1.5 to 3.0 μm in the most practical range.

  When a contact element is formed of the above-described Ag-MgO electrical contact material and a single break structure switching mechanism is formed by the contact element, the vehicle is mounted with a DC voltage of 36 to 400 V and a rated current of 0.01 to 15 A. High voltage load can be controlled. FIG. 4 shows a schematic diagram of a single break structure, which is the most general structure of an opening / closing mechanism, and electrically controls a high voltage load by opening / closing two contact elements.

  Further, when the contact material formed of the Ag-MgO electrical contact material used in the above-described switchgear of the present invention is used in a switchgear having a so-called double break structure switchgear, a DC voltage of 36 to 400 V, a rated current of 5 It becomes possible to control a high voltage load of 500A. FIG. 5 shows a schematic diagram of a double break structure. Unlike a single break structure, a high voltage load is electrically controlled by opening and closing two sets of four contact elements. The feature is that it can be widened.

  Even in the case of this double break structure switchgear, the Ag-MgO electrical contact material forming the contact element does not clearly show the effect of shortening the arc duration when MgO is less than 2.0% by weight, If it exceeds 20.0% by weight, the increase in contact resistance becomes remarkable, and the workability of the material tends to be remarkably deteriorated. In practice, a more desirable composition is to contain 8.1 to 15% by weight of MgO. Within this range, contact elements having good characteristics in all aspects of arc duration reduction effect, low contact resistance, and material workability can be formed, and a switchgear suitable for high voltage loads can be realized. Because you can. In the same manner as the single break structure opening / closing device described above, Ag powder and MgO powder were mixed to form MgO particles having an average particle size of 1.1 to 6.0 μm dispersed in the Ag matrix. An electrical contact material is desirable.

  According to the present invention, even in the case of a DC high voltage load of 36V to 400V or more, the arc duration time at the time of opening and closing in the electric switching mechanism can be extremely shortened, and it is mounted on a next generation vehicle such as a hybrid vehicle or an electric vehicle. The opening / closing operation for controlling electronic / electrical equipment can be performed stably.

  Hereinafter, the best mode for carrying out the present invention will be described based on Examples 1 to 8 described below.

  Table 1 shows the compositions of the electrical contact materials of Examples 1 to 8 used for the contact elements of the switchgear. In addition, Conventional Examples 1 to 5 and Comparative Example 1 described in Table 1 show the electrical contact material compositions employed for comparison with the examples.

  FIG. 3 shows a cross-sectional photograph of the structure of Example 2. As can be seen, it was confirmed that MgO particles having an average particle diameter of 2 μm were uniformly dispersed in the Ag matrix.

  The electrical contact materials of Examples 1 to 8 were manufactured by powder metallurgy, and Ag powder with an average particle size of 6 μm and MgO powder with an average particle size of 2 μm were weighed as a raw material powder to a predetermined mixing ratio. Mixed powder was produced with a mold mixer. Next, this mixed powder was placed in a cylindrical container having a diameter of 50 mm, and pressure was applied from the longitudinal direction of the cylinder to compress the cylindrical billet. Subsequent to this compression processing, sintering was performed at 850 ° C. for 4 hours. This compression process and sintering process were repeated four times to finally produce a cylindrical billet with a diameter of 50 mm.

  The electric contact materials of Conventional Examples 1 and 3 to 5 were manufactured by an internal oxidation method, and using a high-frequency melting furnace, an Ag alloy having each composition was cast into an ingot and processed into chips. Then, this chip is subjected to internal oxidation treatment at an oxygen pressure of 5 atm and a temperature of 750 ° C. for 48 hours, the chips after the internal oxidation treatment are collected, placed in a φ50 mm cylindrical container, and pressure is applied from the longitudinal direction of the cylinder. The billet was compressed. Subsequent to this compression processing, sintering was performed at 850 ° C. for 4 hours. This compression process and sintering process were repeated four times to finally produce a cylindrical billet with a diameter of 50 mm.

  In Conventional Example 2, a φ50 mm cylindrical billet was produced according to the method for producing an Ag—Sn based electrical contact material described in JP-A No. 54-110124.

  In Comparative Example 1, casting was performed in a normal high-frequency melting furnace to finally produce a cylindrical billet having a diameter of 50 mm.

  As described above, the billet produced by each manufacturing method was formed into a φ7 mm wire by hot extrusion (extrusion area ratio of about 51: 1). Subsequently, a wire rod having a diameter of 2.3 mm was formed by drawing, and a rivet contact having a head diameter of 3.5 mm and a head thickness of 1 mm was produced by a header machine.

  Each machined rivet contact was measured for arc duration using an ASTM tester. In the ASTM test, as shown in Table 2, voltage and current can be freely selected. The contact opening speed was 80 mm / sec.

  FIG. 6 shows arc durations of the respective voltages and currents of Conventional Example 1, which is the most common electric contact material used in an on-vehicle switchgear. At DC14V, the arc duration did not change much in the region where the current value was 5A to 25A. However, when the voltage is higher than DC42V, a proportional relationship with respect to the current starts to disappear, and when a certain current value is exceeded, a phenomenon in which the arc duration increases rapidly is observed. For this reason, for example, controlling a current of 25 A or more at DC 42 V is considered to indicate that it is difficult to cope with the extension based on the characteristics of the conventional electrical contact material.

  FIG. 7 shows the arc duration of each voltage and each current for the above-described conventional example 1 and examples 3 and 4. As can be seen from FIG. 7, at a voltage value of less than 30 V, both the conventional example 1 and the examples 3 and 4 do not change the arc duration so much. However, when the voltage value is 36V or more, the arc duration time tends to increase abruptly when the current value increases in Conventional Example 1, whereas the arc duration time slightly increases in Examples 3 and 4. Although a trend was seen, it was found to be stable.

  Next, FIG. 8 shows the result when the inductance at the time of DC42V is changed with the contact material of Conventional Example 1. Loads used in automobiles are more inductive loads having inductances such as motors than simple resistance loads, and loads having such inductances are more severe than simple resistance loads. Is.

  Therefore, regarding the matters shown in FIG. 6 and FIG. 8, the relationship between the amount of oxide to be added and the arc duration was investigated based on the Ag contact of Comparative Example 1. The results are shown in FIG. 9 and FIG.

As can be seen from FIGS. 9 and 10, the electrical contact material in which SnO ₂ + In ₂ O ₃ , SnO ₂ , and CuO is added to Ag tends to have a longer arc duration than the Ag contact. found. On the other hand, the electrical contact material in which ZnO, CdO, and MgO are added to Ag tends to have a shorter arc continuation time than the Ag contact, and especially in the case of MgO, the arc continuation is at a level that cannot be predicted from the conventional example. I found out that the time was shortened.

  In FIG. 11, the result at the time of changing the addition amount of MgO is shown. When the current value was 15 A or less, it was found that the arc duration time was the shortest at 13 wt%. On the other hand, when the current value was 25 A, it was found that the arc duration was the shortest at 8 wt% MgO. When the composition in which the arc duration is shortened at all current values was examined from FIG. 11, it was determined that the range of 5 to 15 wt% MgO was a practical composition. In particular, it was expected that the arc duration could be shortened efficiently in the range of 8.1 to 10.0% by weight.

  Next, the contact gap was considered. In the case of a single break structure, the device is generally designed with a contact gap of 4 mm or less for a switch and 2 mm or less for a relay. Therefore, in such a single break structure, it is appropriate to use in the range of DC voltage 36-400V and rated current 0.01-15A. When considering use in a region with a high rated current, it is necessary to use a double break structure. In such a switch, it can be used with a DC voltage of 36 to 400 V and a rated current of 5 to 500 A. It is judged.

  Below, the result which the present inventors considered about why only MgO has such an arc suppression effect is demonstrated. According to the study by the present inventors, the mechanism of the effect of suppressing the arc of the DCO high voltage load of MgO is estimated as follows.

  The inventors of the present invention have found that the arc phenomenon under a DC high voltage load is due to the photoemission of a substance (a phenomenon in which electrons are ejected when light having a photon energy larger than the work function is applied to the substance) and thermionic emission (the substance temperature is high It was thought that this is related to the phenomenon that electrons are excited and the electrons jump out when they have energy larger than the work function. That is, in order to grasp these phenomena, it was necessary to measure the work function of each substance, and actually measured. Table 3 shows the measurement results. It shows that a substance having a lower work function is more likely to emit photoelectrons and thermionic electrons. Note that. For reference, the melting point and boiling point of each substance are also listed. Some oxides do not show a clear boiling point when they have the property of sublimation, and in that case they are indicated by-.

Table 3 shows that each oxide can be classified into MgO having a work function value lower than Ag, and conversely, SnO ₂ , In ₂ O ₃ , CuO, ZnO, and CdO having high work function values. I understand.

  In addition, the arc generated when the contact is released first generates a metal phase arc composed of metal ions and electrons having a duration of 2 ms or less, and subsequently to a gas phase arc composed of nitrogen ions and oxygen ions. It is known to migrate. As is clear from the results at 42V in FIG. 6, the arc at the DC high voltage load is almost dominated by the gas phase arc, and how the hindrance of the gas phase arc is prevented is the DC high voltage. It can be seen that this is a breakthrough to achieve the purpose of controlling the load.

Considering an Ag—MgO electrical contact material here, it is considered that electrons are intensively emitted from MgO having a low work function in the metal phase arc, and the generation of ionized Mg ²⁺ accompanying it is also generated. . Next, in the arc, nitrogen and oxygen in the atmosphere are ionized and the arc shifts to a gas phase arc. At this time, Mg ²⁺ generated by the metal phase arc is combined with O ²⁻ to generate MgO. Therefore, the concentration of gas ions is significantly reduced, and the persistence of the gas phase arc is hindered. From such a phenomenon, it can be explained that the electrical contact material of Ag—MgO has a characteristic that the arc duration is shorter than that of Ag.

Next, in the case of an electric contact material made only of Ag, Ag is ionized to Ag ⁺ by a metal phase arc generated when the contact is opened. Next, when transitioning to a gas phase arc, Ag ⁺ does not react with the ionized N ₂ and O _2, so it has no effect on the gas phase arc. It is considered that the suppressing property is not shown.

And it is considered as follows in the electrical contact material of Ag-CuO. In the metal phase arc generated when the contact is released, Ag with a low work function value is concentrated and released, so that Ag is ionized and released as Ag ⁺ . Next, even when the gas phase arc is changed, Ag ⁺ does not react with the ionized N ₂ and O _2, and thus has no effect. However, when CuO is exposed to a high temperature by an arc, CuO undergoes thermal decomposition, and oxygen released at that time is ionized, contributing to the persistence of the gas phase arc. This explains that Ag—CuO has a longer arc duration than Ag. It can also be understood that this phenomenon becomes more remarkable as the current value increases.

The phenomenon in the contact material of Conventional Example 1 in which SnO ₂ + In ₂ O ₃ is added and in Conventional Example 2 in which SnO ₂ is added is also considered to be the same as the phenomenon in the electrical contact material of Ag—CuO described above.

  For the reasons as described above, it is assumed that only MgO has an effect of suppressing the arc of such a specific direct current high voltage load. Therefore, it can be assumed that a substance other than MgO having the same effect has a work function value lower than Ag and has a strong binding force with oxygen.

  According to the switchgear of the present invention, it is possible to control a DC high-voltage load mounted on a hybrid vehicle or an electric vehicle that is a next-generation vehicle. This greatly contributes to further improvement of next-generation vehicles, and greatly contributes to the popularization of next-generation vehicles in the future.

The structure cross-sectional photograph (400-times multiplication factor) of the electrical contact material of Ag-MgO manufactured by the internal oxidation method. The structure cross-sectional photograph (400-times multiplication factor) of the electrical contact material of Ag-MgO manufactured by the internal oxidation method. The structure cross-sectional photograph (400-times multiplication factor) of the electrical contact material of Ag-MgO manufactured by the powder metallurgy method. Schematic diagram of single break structure. The schematic diagram of a double break structure. The graph which shows the measurement result of the arc duration of the voltage-current in the electrical contact material of the prior art example 1. The electric contact material of the prior art example 1, Example 3, and 4 is a graph which shows the measurement result of the arc duration when changing a current value with each voltage. The graph which shows the measurement result of the arc continuation time at the time of changing the inductance at the time of DC42V in the electrical contact material of the prior art example 1. FIG. The electric contact material of the prior art examples 1-3, the comparative example 1, and Example 4 is a graph which shows the measurement result of the arc duration when changing a current value by DC42V. The graph which shows the measurement result of the arc duration when the electric current value is changed by DC42V in the electrical contact materials of Conventional Examples 4 and 5, Comparative Example 1 and Example 4. The electric contact material of Examples 1-8 WHEREIN: The graph which shows the relationship between the addition amount of MgO at the time of changing an electric current value by DC42V, and an arc duration.

Claims (4)

A switching device having a single break structure switching mechanism comprising a contact element made of an electrical contact material composed of 2.0 to 20.0% by weight of MgO particles and the balance Ag, and in which MgO particles are dispersed in an Ag matrix. There,
The electrical contact material is obtained by dispersing MgO particles having an average particle size of 1.1 to 6.0 μm in an Ag matrix by mixing Ag powder and MgO powder.
A high-voltage load switchgear that controls a high-voltage load having a DC voltage of 36 to 400 V and a rated current of 0.01 to 15 A. The switchgear for high voltage loads according to claim 1, wherein MgO is 8.1 to 15.0% by weight. A switching device having a switching mechanism of a double break structure comprising a contact element made of an electrical contact material composed of 2.0 to 20.0% by weight of MgO particles and the balance Ag, and in which MgO particles are dispersed in an Ag matrix. There,
The electrical contact material is obtained by dispersing MgO particles having an average particle size of 1.1 to 6.0 μm in an Ag matrix by mixing Ag powder and MgO powder.
A high-voltage load switchgear that controls a high-voltage load having a DC voltage of 36 to 400 V and a rated current of 5 to 500 A. The switchgear for a high voltage load according to claim 3 , wherein MgO is 8.1 to 15.0% by weight.

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