JP2001093394A - Circuit breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit breaker with improved breaking performance by preventing the lowering of insulating resistance after arcing without impairing the stability and reliability of a current with secular creep deformation. SOLUTION: A cross bar 146 for holding a movable contact 144 of a circuit breaker is an integral molding of a thermosetting resin molding 146A and a thermoplastic resin molding 146B, constructed with the thermoplastic resin molding 146B placed at a portion opposed to a contact of a holding portion 146a of the cross bar 146.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit breaker for interrupting a large current, and more particularly to an improvement in insulation performance.

[0002]

2. Description of the Related Art FIG.
FIG. 1 is a side sectional view showing the inside of a conventional circuit breaker disclosed in Japanese Patent No. 35333 with a part cut away, showing a closed state. In the figure, 40 is a cover, 41 is a base,
Both are made of synthetic resin. 42 is a housing composed of the cover 40 and the base 41, and 43 is a fixed contact mounted on the base 41, and has a fixed contact 43a. Reference numeral 44 denotes a movable contact 44 facing the fixed contact 43a.
This is a movable contact having a, and is rotatably supported by a pivot pin 45. Reference numeral 46 denotes a crossbar made of an insulator connecting one end of each movable contact 44 arranged in parallel with all poles. 47 is interposed between the movable contact 44 and the cross bar 46 to fix the movable contact 44 to the fixed contact 43a.
A contact pressure spring that is constantly urged in the direction and applies a predetermined contact pressure between both contacts 43a and 44a. A flexible conductor 48 has one end connected to the movable contact 44 and the other end connected to a trip device (not shown). 49 is both contacts 43a, 44
This is an arc extinguishing device for extinguishing an arc generated between a and a plurality of arc extinguishing magnetic plates 51 arranged inside a pair of arc extinguishing side plates 50. Reference numerals 52 to 61 denote components constituting the opening / closing mechanism, and reference numeral 53 denotes a connecting pin for rotating the crossbar 46 by the operation of the opening / closing mechanism. Reference numeral 62 denotes a handle formed of a synthetic resin.
4a is approached and separated.

When the fixed contact 43 and the fixed contact 43a fixed to the fixed contact 43 are removed from the closed state shown in the drawing, the movable contact 44 is pressed by the contact pressure spring 47 so that the pivot pin 4 is pressed.
5 is rotated around the center of rotation until it hits the locking portion 46a of the crossbar 46. The amount of movement of the movable contact 44a at this time is the amount of overtravel, and the overtravel is usually about 1 to 2 times the contact thickness. This is provided in order to obtain the stability of the contact even when the contact is mechanically and electrically worn or worn due to the repetition of the switching operation or the arc at the time of the current switching.

In a closed state shown in the figure, when a terminal (not shown) is connected to a power source and a load by an electric wire or the like,
A current flows through a path of the fixed contact 43, the fixed contact 43a, the movable contact 44a, the movable contact 44, the flexible conductor 48, and a trip device (not shown). At this time, due to the electric resistance of each conductive part and the contact resistance of both movable and fixed contacts, heat is generated in proportion to the square of the supplied current, but the insulating members such as the crossbar 46 and the base 41 that support these conductive parts are:
A material that can withstand the temperature increase due to the heat generation is used.

Next, the shutoff operation will be described. If an overcurrent or a short-circuit current flows in the circuit in the closed state, a trip device (not shown) operates to operate the opening / closing mechanism,
The cross bar 46 pivotally supporting the movable contact 44 is rotated to separate the fixed and movable contacts 43a, 44a. At this time,
An arc is generated between the two contacts, but is cooled and extinguished by the arc extinguishing device 49.

[0006] JP-A-8-171847 describes a crossbar of a circuit breaker in which a structural composition is covered with an organic-inorganic composite composition. The molded article of the organic-inorganic composite composition contains 15 to 5 inorganic compounds such as aluminum hydroxide.
0 wt%, and 5 to 50 wt% of a reinforcing material such as glass fiber.

[0007]

In the conventional circuit breaker shown in FIG. 3 as described above, when the circuit breaker is closed, the opening / closing mechanism presses the cross bar 46 via the connecting pin 53,
The shaft portion 46d of the crossbar 46 is received at the bottom of the substantially U-shaped groove 41a provided in the base 41. At this time, crossbar 4
6 acts in a direction to reduce the amount of overtravel. Thermosetting resin such as phenolic resin is used as the crossbar material of conventional circuit breakers, but this is mainly a material that can withstand the temperature rise of conductive parts as described in the conventional technology. This is because the amount of deformation of the crossbar is small even after aging, and the amount of overtravel for obtaining the stability of contact is ensured.

Here, when the circuit breaker is left for a long period of time with the contacts closed, the resin crossbar undergoes creep deformation due to stress received from the contact pressure spring of the switching mechanism and the movable contact. Creep deformation is proportional to the time during which stress is applied, and is accelerated at high temperatures. When the crossbar is made of a thermoplastic resin, the creep resistance is generally worse than that of the thermosetting resin, and the amount of creep deformation, that is, the warp at both ends of the crossbar, gradually increases, thereby resulting in abrasion of the contact,
Even if there is no wear, the overtravel amount is gradually reduced, and the reliability of energization is impaired. In addition, the amount of deformation does not saturate as long as stress is applied, and eventually leads to creep rupture.

However, the surface of the crossbar formed of the thermosetting resin material, after being exposed to the arc,
When the insulation resistance is significantly reduced due to the formation of a carbonized layer or the adhesion of a molten metal or free carbon, particularly in the case of a crossbar that supports the movable contacts of each phase in a state where an inter-phase voltage is applied. However, there is a problem that short-circuiting between the phases and interruption of disconnection may be caused, and it is difficult to improve interruption performance.

A crossbar of a circuit breaker described in Japanese Patent Application Laid-Open No. Hei 8-171847 includes an organic-inorganic composite composition containing 15 to 50 wt% of an inorganic compound such as aluminum hydroxide and 5 to 50 wt% of a reinforcing material. Since it is brittle, it is difficult to reduce the thickness of the organic-inorganic composite composition, and it is necessary to cover the entire surface of the structural composition with the organic-inorganic composite composition, and molding is also difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and has a circuit having a crossbar with a small amount of creep deformation, high contact stability, high reliability, and excellent insulation against arc exposure. It is intended to provide a circuit breaker.

[0012]

The circuit breaker of the present invention comprises:
A fixed contact having a fixed contact, a movable contact having a movable contact, a crossbar for holding the movable contact, and a movable contact of the movable contact being a fixed contact, In the apparatus having an opening / closing mechanism for making contact / separation, the crossbar has a structure in which a thermoplastic resin molded product is disposed on an outer surface of a thermosetting resin molded product.

Further, the thermoplastic resin molded product has a structure arranged on a holding portion of the movable contact of the crossbar. Further, the thickness of the thermoplastic resin molded product is 0.5 mm to 1.6 mm. The sliding surface between the base and the crossbar has a structure in which a thermoplastic resin molded product is not provided. Furthermore, the thermoplastic resin which is the main component of the thermoplastic resin molded product is polyamide,
Polyacetal or polyketone.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a perspective view of a crossbar of a circuit breaker according to one embodiment of the present invention, and shows an energized state (on state) of the circuit breaker. Note that only the left pole of the movable contact 144 is shown.
In FIG. 1, the movable contact 144 has a movable contact 144a fixed to one end, and a rotating shaft (not shown) provided at the other end, and the rotating shaft is used as a holding portion 146a of the crossbar 146.
Is held rotatably. The crossbar 146 includes a thermosetting resin molded product 146A including a large part of the holding portion 146a, a main body 146b, and a sliding portion 146c with a base (not shown), and an arm 146a1 of the holding portion 146a.
Molded article 146 provided at the contact-facing portion of
B. In the energized state of the circuit breaker shown in FIG. 1, the lower end of the movable contact 144 and the holding portion 146a
Is in a non-contact state with the bottom part 146a2 of the. On the other hand, when the circuit breaker is in the cut-off state (open circuit state), the crossbar 146 is moved by the toggle link mechanism (not shown) of the mechanism section in FIG.
, The lower end of the movable contact 144 comes into contact with the bottom 146a2 of the holding portion 146a.

Next, a method of manufacturing the crossbar 146 will be described. First, a thermosetting resin molded product 146A is molded by compression heating molding or injection molding. Next, the thermosetting resin molded product 146A is arranged so that the holding portion 146a of the crossbar 146 is surrounded by a mold (not shown) at a predetermined position. That is, the thermosetting resin molded product 146A is arranged at a position where the distance between the contact surface of the holding portion 146a of the thermosetting resin molded product 146A and the mold surface is separated by a distance of 1 mm. Thereafter, a resin containing a thermoplastic resin as a main component is injected into a mold and molded, whereby the crossbar 146 is formed.
A thermoplastic resin molded product 146B having a thickness of 1 mm is integrally formed with the thermosetting resin molded product 146A on the contact-facing portion of the holding portion 146A.

The thermosetting resin molded product 146A is composed of a thermosetting resin as a main component of 40 wt% to 85 wt% and a filler of 60 wt% to 15 wt%. When any of melamine phenol, phenolic resin and unsaturated polyester is used as the thermosetting resin, the creep resistance is good, and the stability and reliability of contact can be ensured for a long period of time. The filler is a reinforcing material such as glass fiber for strengthening the strength. In addition, as a filler, heat deformation temperature,
Inorganic substances such as calcium carbonate, clay and talc for improving the dimensional stability and inorganic compounds such as calcium hydroxide for the purpose of improving the insulating property against arc may be mixed.

The thermoplastic resin molded product 146B is composed of 75 wt% to 100 wt% of a thermoplastic resin as a main component and 25 wt% to 0 wt% of a filler. From the viewpoint of the dimensional accuracy of the molded product, the thermoplastic resin is 80 wt% to 85 wt%, and the filler is 20 w
What consists of t%-15wt% is preferred. When any one of non-aromatic polyamide, polyacetal, and polyketone is used as the thermoplastic resin, the surface insulation resistance after the arc exposure is hardly reduced, and a higher circuit voltage and higher breaking performance for breaking a short circuit current can be achieved. In particular, polyketone is preferable from the viewpoint of flame retardancy of a molded article and dimensional stability after molding. The filler is an inorganic substance such as calcium carbonate, clay, and talc that improves the heat distortion temperature and dimensional stability. The filler may be mixed with an inorganic compound such as calcium hydroxide or the like for the purpose of improving the insulation property against the arc, or a reinforcing material such as glass fiber for the purpose of strengthening the strength, and may be mixed with several wt%.

In the circuit breaker using the crossbar 146 according to the first embodiment, the thermoplastic resin molded product 146B disposed on the arm 146a1 of the holding portion 146a, which is the contact-facing portion, mainly performs arc exposure. As a result, the insulation resistance on the surface of the crossbar 146 is prevented from lowering, and the crossbar 146 is made of the thermosetting resin molded product 1.
The other portion is formed by 46A, which has better creep resistance than a crossbar formed only of a thermoplastic resin, and can secure stability and reliability of contact with the base.

Further, since the thermoplastic resin molded product 146B contains 75% by weight to 100% of the thermoplastic resin as a main component, the molding accuracy is good, the thickness is excellent, the molding is easy, and the molding is easy. The crossbar 146 can be obtained at low cost without covering the entire circumference of the crossbar. Further, the crossbar 146 is formed so that a substantially flat thermoplastic resin molded product 146B is arranged on a part of the arm portion 146a1 of the holding portion 146a of the thermosetting resin molded product 146A. In spite of the thin shape of the resin, the positioning of the thermosetting resin molded product 146A to the mold is easy and accurate compared to the case where the entire circumference of the thermosetting resin molded product is covered with the thermoplastic resin molded product. A thermoplastic resin article 146B can be provided.

Further, regarding the molding of the crossbar 146, since the thermoplastic resin molded product 146B has a thin-walled shape with a thickness of 1 mm, it mainly causes moisture absorption when casting with the thermosetting resin molded product 146A. Dimensional change of molded product due to difference in thickness of thermoplastic resin (dimensional change due to sink mark)
Is less likely to occur, the dimensional stability is good, and there is no problem that peeling or cracking is caused by residual stress due to shrinkage.
In the above description, the case where the thermoplastic resin molded product 146B has a thickness of 1 mm has been described.
The same effect can be obtained even in the range of 1.6 mm.

Further, since the sliding portion 146c of the crossbar 146 with the base is formed of a thermosetting resin molded product 146A, in other words, the sliding portion 146c has a structure in which the thermoplastic resin molded product 146B is not provided. Therefore, it is possible to provide the crossbar 146 which is small and has excellent wear resistance and creep resistance. Here, in order to dispose the thermoplastic resin molded product 146B on the sliding portion 146c, mechanical strength is required. Therefore, a large amount of reinforcing material is mixed with the thermoplastic resin and the thickness is relatively large. A thickness of 6 mm or more is required. In the first embodiment, as shown in FIG. 1, a thermosetting resin molded product 146A is formed on an inner surface of a holding portion 146a that slides when the movable contact 144a and the fixed contact (not shown) are opened and closed. Has been described, but the thermoplastic resin molded product 146B has excellent slidability, and therefore, the holding component 146 having no problem of creep resistance is used.
The structure in which the thermoplastic resin molded product 146B is arranged on the inner side surface of a is more preferable.

Embodiment 2 FIG. FIG. 2 is a perspective view of a crossbar of a circuit breaker according to another embodiment of the present invention,
It shows the energized state (ON state) of the circuit breaker. Note that only the left pole of the movable contact 144 is shown. In FIG. 2, the crossbar 146 includes most of the holding portion 146,
A thermosetting resin molded product 146C composed of a sliding portion 146c of the main body 146b on the side opposite to the movable contact 144a, on the movable contact 144a side, and on a base (not shown).
And a thermoplastic resin molded product 146D provided on the outer periphery of the holding portion 146a and the outer periphery of the movable contact 144a side portion of the main body portion 146b. The other configuration is the same as that of the first embodiment, and a description thereof will be omitted.

In the circuit breaker using the crossbar 146 according to the second embodiment, a thermoplastic resin molded product 146D is disposed at a portion opposed to the contact, and the thermoplastic resin molded product 146D receives most of the arc exposure. This prevents the insulation resistance of the surface from being lowered, has excellent creep resistance, and ensures stability and reliability of contact with the base. Further, since the thermoplastic resin molded product 146D is disposed so as to cover the outer periphery of the contact-facing portion of the cross bar 146, as compared with the case where the thermoplastic resin molded product 146D is disposed flat as shown in FIG. Since the bonding is performed on three or more surfaces, the thermoplastic resin molded product 146D can be more firmly integrated with the thermosetting resin molded product 146C.

[0024]

As described above, the circuit breaker according to the present invention has a fixed contact having a fixed contact, a movable contact having a movable contact, and a movable contact in a housing including a base and a cover. And a switching mechanism for bringing the movable contact of the movable contact into and out of contact with the fixed contact, wherein the crossbar is formed of a thermoplastic resin molded on the outer surface of a thermosetting resin molded product. Since the product has a structure in which the components are arranged, it is possible to provide a circuit breaker having a crossbar which has high stability and reliability of contact of the contact and has excellent insulation against arc exposure.

Further, since the thermoplastic resin molded article has a structure arranged on the holding portion of the movable contact of the crossbar, the stability and reliability of the contact of the contact are high, and the insulation property against the exposure to the arc is excellent. It can be molded with high accuracy.

The thickness of the thermoplastic resin molded product is 0.5
mm to 1.6 mm, the contact stability and reliability of the contact are high, and the insulation property against arc exposure is excellent and the molding can be performed with high accuracy.

Further, since the sliding surface between the base and the crossbar has a structure in which no thermoplastic resin molded product is provided, the sliding surface is small and has excellent wear resistance and creep resistance.

Further, since the thermoplastic resin, which is the main component of the thermoplastic resin molded product, is a polyamide, polyacetal or polyketone, it has higher reliability and excellent insulation against arc exposure.

[Brief description of the drawings]

FIG. 1 is a perspective view of a crossbar according to Embodiment 1 of the present invention.

FIG. 2 is a perspective view of a crossbar according to Embodiment 2 of the present invention.

FIG. 3 is a side sectional view showing a structure of a conventional circuit breaker, showing a closed state.

[Explanation of symbols]

144 movable contact, 144a movable contact, 1
46 crossbar, 146A, 146C thermosetting resin molded product, 146B, 146D thermoplastic resin molded product,
146a Holding part 146c Sliding part

Claims (5)

[Claims] 1. A fixed contact having a fixed contact, a movable contact having a movable contact, a crossbar holding the movable contact, and a movable contact of the movable contact in a housing comprising a base and a cover. Wherein the crossbar has a structure in which a thermoplastic resin molded product is disposed on an outer surface of a thermosetting resin molded product. Circuit breaker. 2. The circuit breaker according to claim 1, wherein the thermoplastic resin molded product has a structure arranged on a holding portion of the movable contact of the crossbar. 3. The thickness of a thermoplastic resin molded product is 0.5 mm.
3 to 1.6 mm.
The circuit breaker as described. 4. The circuit breaker according to claim 1, wherein a sliding surface of the base and the crossbar has a structure in which a thermoplastic resin molded product is not provided. 5. The circuit breaker according to claim 1, wherein the thermoplastic resin as a main component of the thermoplastic resin molded product is a polyamide, polyacetal, or polyketone.