DC high voltage current protector

Abstract

To provide a DC high voltage current protector that can be used stably for a long time by immediately attenuating sparks generated between contacts to suppress ignition and fire spread, even when used with DC high voltage currents of 500 V or more.SOLUTION: A DC high voltage current protector includes a movable contact 21 that approaches and moves away from a fixed contact 11 in response to the reversing action of a bimetal 31 made of a reversing bimetal. A magnet 40 is arranged around the fixed contact 11 and the movable contact 21. The contact opening dimension between the two contacts is 6 mm or more, and the magnet 40 is arranged continuously over the entire area in the vertical direction of the contact opening dimension. The magnet 40 is a ferrite magnet or a samarium cobalt magnet with a heat resistance of 500°C or more, and is configured such that the contact opening dimension is obtained by one reversing action of the reversing bimetal, and at least the surfaces of the fixed contact 11 and the movable contact 21 are made of a binary alloy or a ternary alloy.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a protector (overheat preventer) for direct current high voltage current.

Background Art

[0002] Conventionally, as a proposal for a thermal protector, the one described in Patent Document 1 is known. This proposed disposing a bimetal between a fixed contact and a movable contact and enclosing an inert gas in a casing. However, enclosing an inert gas in the casing causes an increase in the manufacturing process and the quality control process, which also becomes a factor in cost increase.

[0003] On the other hand, in recent years, it has been desired to provide a thermal protector for direct current high voltage current of 500 V or more. When targeting such direct current high voltage current, if a spark or arc (hereinafter referred to as a spark without distinction between the two) occurs between the contacts, the surrounding members will be immediately burned. To solve this problem, although enclosing an inert gas in the casing as in Patent Document 1 is also an effective means, as described above, there are problems such as cost increase.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention aims to provide a protector for direct current high voltage current that can immediately attenuate the spark generated between contacts, suppress ignition and burning, and stably use for a long time even when targeting direct current high voltage current, especially direct current high voltage current of 500 V or more, regardless of whether it is an inert gas atmosphere.

Means for Solving the Problems

[0006] As a result of intensive research, the inventor has completed a protector for direct-current high-voltage current, which is described in each claim and has the following features in particular. 1. Place a ferrite magnet or a samarium cobalt magnet (heat resistance: 500 to 700°C) only on the front side in the diffusion direction of the spark between the fixed contact and the movable contact. 2. Use a binary alloy, preferably a ternary alloy, for each of the fixed contact and the movable contact. 3. The contact opening dimension between the fixed contact and the movable contact shall be 6 mm or more, preferably 10 mm or more. 4. Eliminate the chattering of the contact when the contact is opened and closed, and configure it so that the contact opening dimension in item 3 above can be obtained by one reverse operation of the bimetal. 5. Make the terminal on the movable contact side the negative pole grounded.

Advantages of the Invention

[0007] The present invention can immediately attenuate the spark generated between contacts, suppress ignition and burning, and enable long-term stable use even when targeting direct-current high-voltage current, particularly direct-current high-voltage current of 500 V or more, regardless of whether it is in an inert gas atmosphere, and thus provides a protector for direct-current high-voltage current.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Overview) In the protector for DC high-voltage current of this embodiment, a bimetal switch is assembled inside a cylindrical casing 41. Hereinafter, in the description of the present invention, the relationships of up and down, front and back, left and right only indicate relative positional relationships, and it does not prevent the implementation by changing the positional relationships without departing from the gist of the present invention.

[0010] The bimetal switch mainly includes a fixed contact 11, a movable contact 21, a contact plate 22 having the movable contact 21 at the free end of its tip, a bimetal 31 disposed below the contact plate 22, and a magnet 40 disposed around the periphery between the fixed contact 11 and the movable contact 21. As shown in FIG. 2, the magnet 40 is disposed in three directions, i.e., the front side, the left side, and the right side of its periphery, so as to surround the fixed contact 11 and the movable contact 21. However, as shown in FIG. 5(A), it may be implemented by disposing it only on the front side of its periphery, which is the main diffusion direction of the spark.

[0011] This bimetal switch is configured such that when the fixed contact 11 and the movable contact 21 are in a closed state (the state shown by the solid line in FIG. 1 and refer to FIG. 4(B)), as the temperature rises, the bimetal 31 reverses, pushing up the tip side of the contact plate 22 so that the contact opening dimension between the two contacts opens to 6 to 10 mm or more, reaching an open state (the state shown by the two-dot chain line in FIG. 1 and refer to FIG. 4(A)).

[0012] The protector for DC high voltage current equipped with this bimetal switch is attached to the object to be measured for temperature, such as a hot water tank, and detects the temperature rise of the object to be measured. When it detects that the temperature of the object to be measured has risen above a predetermined temperature, it is arranged in an external circuit to perform predetermined operations such as emitting a detection signal or cutting off the power supply to the heating heater of the hot water tank. (Regarding the fixed contact 11)

[0013] As shown in FIGS. 1 and 4, the fixed contact 11 is attached to a contact base 46 that is one step higher from the right side of the bottom 43 of the casing 41 by fixing means such as screws or press-fitting. The fixed contact 11 can be connected to the positive-pole side power supply etc. of an external circuit (not shown) by a fixed terminal 12 that is connected inside the casing 41 and protrudes from the right side wall portion 42 to the outside. (Regarding the movable contact 21)

[0014] The movable contact 21 is arranged above the fixed contact 11 so as to face the fixed contact 11. The movable contact 21 is attached to the lower surface of the tip (free end) of a contact plate 22 made of a plate-shaped body of a conductor. The base end of the contact plate 22 is fixed to a stepped portion 45 that is one step higher from the left side of the bottom 43 of the casing 41 by a fixture 23. The contact plate 22 can be connected to an external circuit via the fixture 23 and the movable-side terminal 27. In the external circuit, the movable contact 21 and the movable-side terminal 27 are grounded and are the negative pole.

[0015] The fixed contact 11 and the movable contact 21 preferably have a shape that makes point contact. Also, although it can be composed of various conductors for contacts, it is desirable to be composed of a binary alloy of silver and nickel, or further a ternary alloy. The movable contact 21 can also be fixed to the contact plate 22 by caulking, but in this example, it is fixed by high-temperature solder. Thereby, when a temperature rise above the melting temperature of the high-temperature solder occurs, a fail-safe mechanism in which the movable contact 21 and the contact plate 22 become non-conductive can be realized. (Regarding the bimetal 31)

[0016] The bimetal 31 is a plate-shaped body (disc-shaped in FIG. 2 and rectangular-shaped in FIG. 4) made of a reversing bimetal that reverses as the temperature rises, and is disposed below the contact plate 22. An opening 44 is formed in the bottom 43 of the casing below it. Thus, when this protector is attached to the object to be measured (not shown), the heat thereof is configured to be efficiently applied to the bimetal 31.

[0017] In particular, in the example of FIG. 1, the periphery of the bimetal 31 is slidably and loosely fitted and supported between the bottom 43 and the bottom cover 52 having a central opening attached thereto, so that the heat of the object to be measured is most easily transmitted. As the slidable support structure, a structure may be shown in which a holding groove is formed in the peripheral wall near the opening 44 of the casing 41, and the periphery of the bimetal 31 is loosely fitted in the holding groove. However, as long as the bimetal 31 can reverse, a fixed structure may be used.

[0018] In the example of FIG. 1, since the bimetal 31 is disposed on the bottom surface of the casing 41 as described above, a distance can be formed between the bimetal 31 and the contact plate 22. Therefore, in this example, a contact leg 28 is provided on the lower surface of the contact plate 22. The contact leg 28 is implemented such that its length can be finely adjusted. Specifically, the contact leg 28 is composed of a lower leg 28a that contacts the upper surface of the bimetal 31 and an upper leg 28b that is fixed to the lower surface of the contact plate 22, and has a structure in which the male screw at the upper part of the lower leg 28a is screwed into the female screw in the upper leg 28b. However, as long as the bimetal 31 can surely push up the contact plate 22 via the contact leg 28 by one reversing operation of the bimetal 31, it may be implemented with a structure that cannot be finely adjusted.

[0019] In the example of FIG. 4, the proximal end 32 on the left side of the rectangular bimetal 31 is fixed together with the contact plate 22 by the fixture 23. Specifically, in this example, the lower spacer 25a is placed on the stepped portion 45, the proximal end 32 of the bimetal 31 is placed on the lower spacer 25a, and the proximal end of the contact plate 22 is disposed thereon via the upper spacer 25b, and they are fixed by the male screw 24 and the female screw 26 passing through them. The male screw 24 is composed of a conductor, and the movable-side terminal 27 connected inside the casing 41 protrudes from the left wall portion 42 to the outside, whereby it is connected to an external circuit. In the external circuit, the movable contact 21 and the movable-side terminal 27 are grounded and are the negative pole. (Opening and closing of contacts)

[0020] As shown in FIG. 1 and FIG. 4(A), at normal temperature, the bimetal 31 is not inverted and does not push up the contact plate 22. As the temperature rises, the bimetal 31 performs an inversion operation. Specifically, the free end 33 rises and suddenly pushes up the lower surface of the contact plate 22, raising the contact plate 22. Thereby, the distance between the fixed contact 11 and the movable contact 21 opens to a predetermined contact opening dimension. When targeting a DC high voltage current of 500V or more, and further 1000V or more, the contact opening dimension is desirably 6mm or more, preferably 10mm or more. To obtain such a contact opening dimension, a large bimetal is required. In that case, as the temperature rises, the bimetal gradually begins to extend and becomes substantially linear, and at the stage when the inversion operating temperature is reached, the bimetal 31 tends to finally invert and stabilize. If the free end 33 of the bimetal 31 contacts the contact plate 22 and slightly pushes it up at the stage when it becomes substantially linear before inversion, it will cause chattering.

[0021] Therefore, in the embodiment of FIG. 1, the contact leg portion 28 with adjustable length is adopted so that the free end 33 of the bimetal 31 does not contact the contact plate 22 even when the bimetal 31 is substantially on a straight line. Also, in the example of FIG. 4, the proximal end 32 of the bimetal 31 is disposed at a position higher than the fixed contact 11. By disposing the lower spacer 25a below the proximal end 32 of the bimetal 31, its height can be easily changed and adjusted according to the inversion temperature and behavior characteristics of the bimetal 31.

[0022] Note that, as shown in FIG. 1, the contact plate 22 can be implemented as a substantially linear shape, but in the example of FIG. 4, it is implemented as a plate-like body bent slightly downward near the proximal end of the contact plate 22. Also, the inversion operating temperature of the bimetal 31 can be appropriately changed according to the required detection temperature, but in this example, it can be implemented with an inversion operating temperature of about 120° C. and a return temperature of about -40° C. to 40° C.

[0023] In case it is necessary to make the fixed contact 11 and the movable contact 21 in a closed state before the temperature of the bimetal 31 drops to the return temperature, a manual return switch 50 is provided in these embodiments. The manual return switch 50 presses down the contact plate 22 from above to forcibly make it in a closed state, and the bimetal 31 can be inverted again to the return state before inversion even in the stage until the ambient temperature drops to the return temperature. In this example, a manual return switch 50 having a stem penetrating the upper lid 51 attached to the open upper end of the casing 41 is attached. By manually or mechanically pressing down the stem protruding on the upper lid 51 against the biasing force of the spring, the contact plate 22 and the bimetal 31 are pressed down to a closed state, and a well-known manual return switch 50 is adopted, but it can be changed to other forms or omitted.

[0024] (Regarding the magnet 40) It is desirable that no spark occurs when the contact is opened and closed, but in the case of a protector for DC high voltage current, it is particularly necessary to configure it so that ignition due to this is surely suppressed even if a spark occurs.

[0025] Therefore, in this DC high-voltage current protector, a magnet 40 is disposed at at least one location around between a fixed contact 11 and a movable contact 21. The vertical length of the magnet 40 is continuously disposed over the entire contact opening dimension (see FIGS. 1 and 4). The width of the magnet 40 is made equal to or greater than the diameters of the fixed contact 11 and the movable contact 21. In the examples of FIGS. 2 and 5, the magnet 40 has a rectangular shape in plan view, but a magnet having a planar semi-circular shape or a U-shape may be disposed so as to surround the fixed contact 11 and the movable contact 21.

[0026] Since the magnet 40 is exposed to the high temperature of the spark, it preferably has high heat resistance (the property of maintaining magnetism even at high temperatures). Specifically, a ferrite magnet or a samarium cobalt magnet having a heat resistance of 500° C. or higher is suitable.

[0027] Since the spark attenuation effect is exerted by the magnetic force of the magnet 40, it is desirable that the distance between the fixed contact 11 and the movable contact 21 and the magnet 40 be as small as possible. In this example, the magnet 40 is stored and disposed in a magnet placement portion 47 of a heat insulating casing 41, and by surrounding the periphery thereof, both magnetic proximity and heat insulation are achieved. (Regarding the casing 41)

[0028] The casing 41 can be implemented by various heat-resistant synthetic resins or metal materials. In this example, it is made mass-producible by a heat-resistant synthetic resin. The shape can be variously changed and implemented as long as it can stably incorporate the above-described bimetal switch. In this example, it is implemented as a substantially box-shaped bottomed rectangle in plan view. Since it can be implemented regardless of the presence or absence of an inert gas atmosphere, the casing 41 can be implemented regardless of the presence or absence of gas tightness.

[0029] Specifically, wall portions 42 are erected upward from four sides of a bottom portion 43 having an opening 44 penetrating vertically. Since the wall portion 42 has heat insulation properties, it can be implemented as having a relatively large thickness.

[0030] Also, on the rear side of the contact base 46, a magnet placement portion 47 is formed so as to dig down the wall portion 42 from above over at least the entire height of the contact opening dimension, and the magnet 40 is mounted from its upper opening.

[0031] The upper end of the wall portion 42 is flat and is closed by an upper lid 51 having an appropriate shape such as a plate-like body, and is fixed by appropriate means such as being screwed to lid holes 48 provided at the four corners of the wall portion 42. The bottom lid 52 in FIG. 1 is also attached with a structure substantially the same as that of the upper lid 51. Also, a main body mounting hole 49 is formed so as to penetrate vertically through the centers of the front and rear wall portions 42, and is fixed by appropriate means such as being screwed to the object to be measured.

Example

[0032] Examples are shown below to assist in understanding the present invention, but the present invention should not be understood as being limited to these examples. As an example, protectors for both DC high voltage currents shown in FIGS. 1 to 3 and FIGS. 4 to 6 were created. A magnet 40 of ferrite or samarium cobalt of about 130 mT was mounted in a magnet placement portion 47 formed about 5 mm away from the fixed contact 11 and the movable contact 21. For the fixed contact 11 and the movable contact 21, a bimetal 31 made of a bimetal adjusted to a reverse operating temperature of about 120 ° C. / a return temperature of about 40 ° C. was used with a general-purpose silver-nickel binary alloy or ternary alloy while ensuring a contact opening dimension of about 10 mm. In these examples, as the magnet 40, as shown in FIGS. 1 and 4(B), the above magnet having a length over the entire height of the contact opening dimension was arranged and implemented. (Power-on heating test)

[0033] The protectors for both DC high voltage currents in the examples were fixed to a test object whose temperature could be adjusted in a natural air environment, and while applying a load of 1000 V 15 A, the temperature was raised and lowered to conduct an ON / OFF repeated test. When it was confirmed that 10,000 times were achieved without any abnormalities such as the occurrence of a flame, the test was terminated. (Comparative example)

[0034] In the comparative example, as the magnet 40 in FIGS. 4 to 6, the magnet having an up-and-down length covering half of the total height of the contact opening dimension was arranged and implemented. The arrangement configurations and conditions of other members were substantially the same as those in the examples of FIGS. 4 to 6. When the same energization heating test as in the example was carried out, a flame occurred at 100 times and the surroundings were burned, so the test was terminated at this stage.

Explanation of Signs

[0035] 11: Fixed contact 12: Fixed terminal 21: Movable contact 22: Contact plate 23: Fixture 24: Male screw 25a: Lower spacer 25b: Upper spacer 26: Female screw 27: Movable-side terminal 28: Contact foot 28a: Lower foot 28b: Upper foot 31: Bimetal 32: Base end 33: Free end 40: Magnet 41: Casing 42: Wall portion 43: Bottom 44: Opening 45: Step portion 46: Contact base 47: Magnet arrangement portion 48: Hole for lid 49: Body mounting hole 50: Manual reset switch 51: Upper lid 52: Bottom lid

Claims

1. A bimetal switch having a movable contact on a contact plate that moves toward and away from a fixed contact in response to reversal of the bimetal is disposed in a casing in a high voltage DC current protector. A magnet is disposed around the fixed contact and the movable contact, so that a spark between the fixed contact and the movable contact is attenuated. A contact gap between the fixed contact and the movable contact is 6 mm or more; A protector for high voltage DC current, characterized in that the magnets are arranged across the entire vertical range of the contact opening dimension.

2. The DC high voltage current is 500 V or more, The magnet is a ferrite magnet or a samarium-cobalt magnet having a heat resistance of 500°C or higher, Three magnets are arranged in three directions around the two contacts, 2. The DC high voltage current protector according to claim 1, wherein the fixed contact is a negative terminal connected to ground, and the movable contact is a positive terminal.

3. a contact plate having the movable contact at a free end thereof, and a contact leg portion disposed on a lower surface of the contact plate; The contact leg extends downward to contact the bimetal when the actuator is reversed. The bimetal is disk-shaped, and the periphery of the bimetal is supported in a retaining groove of the casing, 3. The DC high voltage current protector according to claim 2, wherein the bimetal is configured to push up the abutment leg by one reversal movement of the bimetal, thereby obtaining the contact opening dimension.

4. 4. The DC high voltage current protector according to claim 1, wherein at least the surfaces of said fixed contacts and said movable contacts are made of a binary alloy or a ternary alloy.

5. A DC high voltage current protector as described in any one of claims 1 to 3, characterized in that the movable contact is fixed to the contact plate by high temperature solder, thereby forming a fail-safe mechanism in the event that a temperature rise occurs above the melting temperature of the high temperature solder.

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