JP5263183B2 - electromagnetic switch - Google Patents

Description

  The present invention relates to an electromagnetic switch, and more particularly to an improvement in arc extinguishing performance of an electromagnetic switch having a contact.

In an electromagnetic switch, an arc is generated between a fixed contact and a movable contact when current is interrupted. The arc may melt both contacts and directly affect the life of the electromagnetic switch. Therefore, it is desired to develop an electromagnetic switch that can quickly extinguish the generated arc and has a long contact life. For the purpose of improving the arc extinguishing performance, a structure in which a part that generates cracked gas by arc heat in the case is newly installed in each AC phase, and the arc is extinguished by the cracked gas is disclosed in Patent Document 1 and It is disclosed in Patent Document 2. Patent Document 3 deals with a technique for extinguishing an arc by installing a metal arc extinguishing plate on an arc cover and drawing the arc to the metal arc extinguishing plate and stretching it. Patent Document 4 proposes forming an arc extinguishing grid on the arc cover. The arc is drawn to this grid and extinguishes.

JP 63-133420 A Japanese Patent Publication 8-21277 JP 59-94313 Patent 3411206

In order to improve the arc extinguishing performance of the electromagnetic switch, in the structure in which the components that generate cracked gas by arc heat are installed for each phase in the case, even if the arc is extinguished by the generated cracked gas, In this case, since the number of parts increases, the structure becomes complicated. The present application aims to improve the arc extinguishing performance of an electromagnetic switch with a simple structure while avoiding the complexity of the structure.

The electromagnetic switch according to the present invention includes a plurality of fixed contacts to which fixed contacts are joined, a plurality of movable contacts to which movable contacts are joined, a crossbar that presses the movable contacts against the fixed contacts, A plurality of independent arc extinguishing units provided on the top plate of the arc cover corresponding to the fixed contacts are provided with a casing to which the stationary contacts are attached and a thermoplastic resin arc cover that covers the casing. Walls are erected, and each arc extinguishing wall surrounds a fixed contact and a portion facing the crossbar is open.

The arc extinguishing performance is improved while maintaining the mechanical strength and withstand voltage characteristics of the electromagnetic switch having a contact. Since it has a simple structure, a small and inexpensive electromagnetic switch can be provided. In addition, since parts that generate cracked gas can be easily replaced, it is excellent from the viewpoint of maintenance.

It is a figure which shows the cross section of the electromagnetic switch corresponding to Embodiment 1 by this invention. It is a perspective view showing the external appearance of an arc cover. It is a perspective view which shows the external appearance of the electromagnetic switch by this invention. It is a figure which shows the relationship between an arc-extinguishing chamber and an interphase wall. It is a figure which shows the cross section of the electromagnetic switch corresponding to Embodiment 2 by this invention. It is a figure which shows the cross section AA in FIG.

Embodiment 1 FIG.
The first embodiment will be described with reference to FIGS. FIG. 1 shows an overall cross-sectional view of the electromagnetic switch 100. A fixed iron core 2 in which silicon steel plates are laminated is fixed to a mounting base 1a formed of an insulator. Similarly, a fixed contact 8 is attached to a base 1b formed of an insulator. The movable iron core 3 is an iron core obtained by laminating silicon steel plates in the same manner as the fixed iron core 2, and both iron cores are arranged to face each other. The operation coil 4 generates a driving force that attracts the fixed iron core 2 and the movable iron core 3 against the tripping spring 31 during excitation. The cross bar 5 provided with the square window 32 is formed of an insulator, and holds the movable iron core 3 at its lower end.

The movable contact 6 is inserted into the square window 32 of the cross bar 5 and is held by a holding spring 7. Three square windows 32 are provided on the cross bar 5, and one movable contact 6 is inserted into each square window 32. The fixed contact 8 is provided to face the movable contact 6, and a current flows when both contact with each other. Three sets of the movable contact 6 and the fixed contact 8 are provided in order to correspond to each phase of three-phase alternating current. A movable contact 20 is joined to the movable contact 6, and a fixed contact 21 is joined to the fixed contact 8. The terminal screw 9 is used to connect the electromagnetic switch 100 to an external circuit. The arc cover 11 is provided with an arc extinguishing chamber 11a. In the electromagnetic switch 100, an arc 30 is generated between the movable contact 20 and the fixed contact 21.

FIG. 2 is a perspective view showing the external appearance of the arc cover 11. The arc cover 11 is obtained by integrally molding an arc extinguishing chamber 11a and a top plate 11b with a thermoplastic resin. Six arc extinguishing chambers 11a are provided, each corresponding to six sets of contacts (movable contact 20 and fixed contact 21). The arc extinguishing chambers 11a are arranged in a front row and a rear row, and the arc extinguishing chambers in the same row are aligned in the same direction. The rear row arc extinguishing chambers 11a and the front row arc extinguishing chambers 11a are opposed to each other, and the crossbar 5 is accommodated therebetween.

Each arc extinguishing chamber 11a includes side walls 40a to 40c arranged in a U-shape and a ceiling wall 40d. The side walls 40a to 40c are erected vertically to the top plate 11b or the ceiling wall 40d. The reason why the ceiling wall 40d is one step higher than the top plate 11b of the arc cover 11 is to increase the strength of the arc extinguishing chamber 11a, and the top plate 11b can be used as it is as the ceiling wall 40d. The side walls 40a to 40c are continuously bent so that the side wall 40a and the side wall 40c face each other. The central side wall 40b is arranged so as to be parallel to the cross bar 5.

The U-shaped arc extinguishing chamber 11a shields the arc 30 generated between the movable contact 20 and the fixed contact 21 from four directions. The side walls 40a to 40c are integrated, but a gap or a hole may be provided to release heat. The side wall 40 is partially cut away so as not to close in order to release arc heat. The opening of the opened side wall 40 (the surface facing the side wall 40b) faces the cross bar 5. In order to enhance the arc confinement effect, the side walls 40a to 40c of the continuous arc-extinguishing chamber 11a are widened (for example, the side wall 40a and the side wall 40c are arranged in the shape of a narrow C on the side wall 40b side, Even if the side wall 40c is arranged in a V-shape directly in contact with the side wall 40b and the side wall 40a and the side wall 40c are arranged in a U-shape in direct contact with the side wall 40b. Good. The reason why the bottom surface of the arc extinguishing chamber 11a facing the top plate 11b is opened is to release arc heat. In addition to the U-shape, the side wall 40 may have a C-shape, a tapered tip, or the like.

The arc cover 11 is preferably made of a thermoplastic resin that generates hydrogen gas when arc heat is applied. For example, polymethylpentene resin, polymethyl methacrylate resin, and polybutylene resin are preferably applied. In the present invention, it is particularly preferable to use PA6 (Polyamide 6), PA46 (Polyamide 46), and PA66 (Polyamide 66) in order to ensure high arc extinguishing performance. Polyamide is a thermoplastic resin having no aromatic ring, and the number indicates the C (carbon) number. PA46 obtained by polycondensation of diaminobutane and adipic acid has a high melting point of 290 ° C. and a glass transition temperature (Tg) of about 78 ° C., which is a high characteristic value. The melting points of PA66 and PA6 are 262 ° C. and 222 ° C., respectively.

In order to use PA6, PA46, and PA66 in the arc cover 11, particularly in the arc extinguishing chamber 11a, it is preferable to use one of these as a base material and to include glass fiber in the filler. In addition, it preferably contains one or more flame retardants selected from magnesium hydroxide, aluminum hydroxide, antimony trioxide, antimony tetroxide, and antimony pentoxide, and is made of a material that does not contain a bromine component. It is more desirable.

FIG. 3 is a perspective view schematically showing the outer shape of the electromagnetic switch 100. A casing 1 of the electromagnetic switch 100 is composed of a mounting base 1a and a base 1b, and houses a fixed iron core 2, a movable iron core 3, an operation coil 4, and a cross bar 5. The arc cover 11 covers the upper surface (attachment surface 1d) of the housing 1, and can be easily attached and detached from the housing 1 (base 1b). Cover protection walls 11 c and 11 d are attached to the arc cover 11. The four interphase walls 35a to 35d are plate members formed of the same highly insulating thermoplastic resin as the arc cover 11 (the arc extinguishing chamber 11a), and are arranged in parallel with the cover protective walls 11c and 11d. Has been. Here, the cover protection walls 11c and 11d and the interphase walls 35a to 35d are configured to be detachable from the arc cover 11, but may be integrally molded.

FIG. 4 is a diagram schematically showing a state where the top plate 11b of the arc cover 11 is virtually removed from the electromagnetic switch 100, and the relationship between the interphase walls 35a to 35d and the arc extinguishing chamber 11a is displayed. The interphase walls 35 a to 35 d are arranged in a direction perpendicular to the cross bar 5. The interphase walls 35a and 35b are arranged in the lower stage, and the interphase walls 35c and 35d are arranged in the upper stage, and the six arc extinguishing chambers 11a corresponding to each phase are isolated from each other. When the arc 30 is generated, the interphase wall 35 blocks the arc 30 from moving to the adjacent arc extinguishing chamber. The arc-extinguishing chamber 11a has an open surface facing the crossbar 5. There are six arc extinguishing chambers 11a, and each chamber is provided independently. However, the side wall 40a of the arc extinguishing chamber in the middle and the side wall 40c of the arc extinguishing chamber on the left side may be integrated. Similarly, the side wall 40c of the middle arc-extinguishing chamber and the side wall 40a of the arc-extinguishing chamber adjacent to the right may be integrated.

Six fixed contacts 8 are fixed to the mounting surface 1 d of the housing 1. Three fixed contacts 8 are arranged on each of the upper and lower stages, and correspond to each phase of the three-phase alternating current. The crossbar 5 is provided with three square windows 32 in parallel. Each of the three movable contacts 6 inserted into the cross bar 5 is disposed above the fixed contact 8. The movable contact 20 and the fixed contact 21 are opposed to each other. The stationary contacts 8 arranged separately in the upper stage and the lower stage form a pair, and conduct when the movable contact 6 moves downward. Each stationary contact 8 is surrounded by a side wall 40 of the arc extinguishing chamber 11a when viewed from the upper surface (mounting surface 1d) of the housing 1.

Next, the operation will be described. When the operation coil 4 is excited, the movable iron core 3 is attracted to the fixed iron core 2 against the tripping spring 31. As a result, the cross bar 5 and the movable contact 6 move, and the movable contact 20 contacts the fixed contact 21. Although the movable iron core 3 and the cross bar 5 continue to move even after contact, the movement of the movable contact 6 is restricted because the movable contact 20 is in contact with the fixed contact 21, and the holding spring 7 is contracted. The movable contact 20 and the fixed contact 21 are pressurized, the contact resistance between the contacts is reduced, and a current flows. When the operation coil 4 is demagnetized, the movable iron core 3 is separated from the fixed iron core 2 by the trip spring 31. With this operation, the cross bar 5 also moves upward, and the fixed contact 21 and the movable contact 20 are separated. At this time, an arc 30 is generated between the two contacts.

The generated arc 30 is pulled outward by electromagnetic force and reaches the vicinity of the arc extinguishing chamber 11 a of the arc cover 11. The components of the arc cover 11 are evaporated by the heat and light of the arc, and gas is released from the arc cover 11. Since the arc cover 11 is made of a thermoplastic resin whose base material is one selected from PA6, PA46, and PA66, hydrogen gas is likely to be generated. Since the hydrogen gas has a high thermal conductivity, the arc gas can be easily cooled, and the arc extinguishing chamber 11a is formed in a U shape so as to cover the fixed contact 21, so that the arc 30 has a thermal conductivity from the surroundings. Cooled with high hydrogen gas. The diameter of the arc 30 gradually decreases, and the voltage increases and is cut off.

The interruption of the arc 30 does not necessarily occur simultaneously for all three phases. One phase could be blocked, but another phase could not be blocked. The correlation walls 35a to 35d are provided to prevent a short circuit between the phases. Since the interphase wall 35 is disposed between the adjacent arc extinguishing chambers 11a, the insulation between the phases is strengthened and the arc cover 11 can be prevented from being damaged.

Since PA6, PA46, and PA66 are heat-resistant thermoplastic resins, insulation failure due to surface carbonization is suppressed. Moreover, the absence of an aromatic ring also suppresses insulation failure due to surface carbonization, and suppresses arc extinguishing failure due to scattering of free carbon around. Further, when the material of the arc cover 11 does not contain a bromine component, bromine having a high conductivity is not included in the vaporized gas due to the arc, so that the arc extinguishing performance is improved.

Evaporated gas (arc-extinguishing gas) generated by the arc 30 increases the internal pressure of the arc-extinguishing chamber 11a. Since the bottom surface and one side surface of the arc extinguishing chamber are open, the evaporated gas is discharged from here. Since the arc cover 11 is filled with glass fiber, the arc cover 11 has a high pressure resistance and can be prevented from being damaged by the pressure of the evaporating gas.

One or more flame retardants selected from magnesium hydroxide, aluminum hydroxide, antimony trioxide, antimony tetroxide, and antimony pentoxide have an effect of suppressing the generation of free carbon and improve arc extinguishing performance. As the flame retardant, a halogenated phosphate ester or red phosphorus, which is a phosphorus flame retardant having no aromatic ring, may be used to suppress poor insulation due to surface carbonization and deterioration of arc extinguishing performance due to generation of free carbon.

When the movable iron core 3 is attracted to the fixed iron core 2, the fixed iron core 2 and the movable iron core 3 collide, and the impact is transmitted to the mounting base 1a, the base 1b, and the cross bar 5. The electromagnetic switch 100 is required to have mechanical strength for the mounting base 1a, the base 1b, and the crossbar 5 in order to perform an open / close circuit test for 30,000 times in the AC4 class electrical test and 2 million times in the AC3 class electrical test. It is said. In addition, a withstand voltage is required for the base 1 b on which the fixed contact 8 is disposed and the cross bar 5 that supports the movable contact 6. If the material and shape of the base 1b and the cross bar 5 are changed in order to improve the arc extinguishing performance, the mechanical strength and withstand voltage of the base 1b may be impaired. However, the arc cover 11 is only put on the base 1b, and does not require high mechanical strength, and withstand voltage performance is not required as much as the base 1b and the crossbar 5. You can choose.

Since the side walls 40a to 40c of the arc cover 11 that covers the fixed contact 21 in a U-shape are integrated with the top plate 11b, the arc-extinguishing gas generating component is separately provided for each fixed connector 8 corresponding to each phase. The structure is simpler than arranging it inside the case. The arc cover 11 is originally a part of the electromagnetic switch 100 and has a structure that can be easily removed.

  In the above structure, the consumable parts are only the movable contact 6 including the movable contact 20, the fixed contact 8 including the fixed contact 21, and the arc cover 11. The electromagnetic switch 100 can be used if only these parts are replaced during maintenance. It becomes possible.

Embodiment 2. FIG.
FIG. 5 is a diagram for explaining the second embodiment, and FIG. 6 is a diagram showing a cross section AA in FIG. The difference from the first embodiment is that the metal arc extinguishing plate 32 is arranged inside the side walls 40a to 40c provided in the U-shape of the arc cover 11. The metal arc extinguishing plate 32 has one or more holes 32a. The fixed contact 8 is bent in a U shape in order to reinforce the force of pulling the arc outward by electromagnetic force. Compared to the first embodiment, the height of the fixed contact 21 from the mounting surface 1d of the housing 1 is higher.

  By installing the metal arc extinguishing plate 32, the arc 30 is attracted to the metal arc extinguishing plate 32 by electromagnetic force. The arc cover 11 emits evaporating gas by the heat of the drawn arc 30. This gas passes through a hole 32 a provided in the metal arc extinguishing plate 32 and extinguishes the arc 30. The arc extinguishing performance is further improved by the second embodiment.

DESCRIPTION OF SYMBOLS 1 Housing | casing, 2 Fixed iron core, 3 Movable iron core, 5 Crossbar, 6 Movable contactor, 8 Fixed contactor, 11 Arc cover, 11a Arc extinguishing chamber, 11b Top plate, 20 Movable contact, 21 Fixed contact, 35 Interphase wall 40a-40c Side wall, 40d Ceiling wall

Claims (5)

A plurality of fixed contacts to which fixed contacts are joined, a plurality of movable contacts to which movable contacts are joined, a cross bar that presses the movable contacts against the fixed contacts, and a housing to which the fixed contacts are attached. And an arc cover made of a thermoplastic resin. The arc cover is formed by integrally molding a plurality of arc extinguishing chamber side walls and a top plate, and between the adjacent arc extinguishing chamber side walls. A gap is provided, a side wall of the arc extinguishing chamber is disposed on the top plate so as to surround the fixed contact, and a portion facing the cross bar is opened. Switch. The electromagnetic switch according to claim 1, wherein a thermoplastic resin plate is provided in the gap as an independent member that is detachable from the arc cover . 2. The electromagnetic switch according to claim 1, wherein the arc extinguishing chamber is formed by using one kind selected from polyamide 6, polyamide 46, and polyamide 66 as a base material, and the base material is filled with glass fiber. . 4. The electromagnetic switch according to claim 3, wherein the base material of the arc extinguishing chamber contains one or more compounds selected from magnesium hydroxide, aluminum hydroxide, and (three, four, five) antimony oxide. The electromagnetic switch according to claim 3, wherein the base material of the arc extinguishing chamber includes one or more compounds selected from a halogenated phosphate ester and red phosphorus.

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