JPH0785388B2 - Overcurrent protector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an overcurrent protector including an overcurrent detection device.

(Prior Art) Generally, in this type of overcurrent protector, an overcurrent detection device for detecting an abnormal current such as an overcurrent or an overload current is provided. This overcurrent detection device includes a bimetal that is warped by heat generated by a flowing current or an electromagnetic device that is movable by magnetic attraction by a flowing current, but the former bimetal is time-delayed by an overload current and the latter The electromagnetic device operates instantaneously due to a short-circuit current, and usually protects the load or the circuit with a combination of both.

In the case of the above, since the bimetal and the electromagnetic device are combined, the time delaying operation of the bimetal is gradually warped, and therefore precise adjustment is required for transmission of the operation. there were.

Therefore, in order to solve this, the present applicant has proposed an overcurrent detection device in which a shape memory alloy that expands at a transformation temperature is interposed between a plunger and a yoke that constitute an electromagnetic device (Japanese Patent Laid-Open No. 58-58). No. 51435), and the specification thereof shows an overcurrent protector using this overcurrent detection device.

This overcurrent protector includes an operating handle, a movable contact having a movable contact connected to the operating handle via a link mechanism, and a fixed contact having a fixed contact facing the movable contact so that the movable contact can be separated from the movable contact. A latch member that latches while maintaining the balance of the link mechanism, and an overcurrent detection device that has a plunger that presses the latch member at one end and drives the movable contact at the other end when an abnormal current flows, When the overcurrent detection device operates due to overload current or short-circuit current while the movable contact is in contact with the fixed contact, the plunger presses the latch member and the link mechanism is out of balance to fix the movable contact. It is moved away from the contactor.

(Problems to be Solved by the Invention) However, according to the above-described overcurrent protector, there is a problem that an extra member such as a link mechanism is required, and the structure itself becomes large and the cost increases. .

The present invention has been made in view of the above problems, and an object thereof is to improve the reliability by reducing the adjustment of the overcurrent detection device, reduce the size of the structure itself, and reduce the cost. An object is to provide an overcurrent protector capable of suppressing the increase.

(Means for Solving the Problem) The present invention relates to a coil cylinder, a coil wound around the outer circumference of the coil cylinder, a yoke surrounding the coil and the coil cylinder, and a coil cylinder located between the yokes. A return spring interposed between the plunger and one end of the yoke, and a shape memory alloy interposed between the plunger and the other end of the yoke and extending at a transformation temperature; The movable plate is movably arranged in a direction orthogonal to the moving direction of the plunger and is latched by the plunger, and the movable contact comes into contact with the fixed contact while the movable plate is latched by the plunger to move the movable plate. And a movable contact plate having a spring force so that the movable contact separates from the fixed contact when the latch of the plate is unlatched.

(Operation) As a result, the plunger momentarily operates against the return spring against the short-circuit current, and the shape memory alloy expands due to heat generation against the overload current and the plunger operates against the return spring. Overcurrent such as short-circuit current or overload current can be dealt with, and since the shape memory alloy operates at a transformation temperature at a stretch, adjustment can be reduced and its reliability can be improved.
Also, when the plunger moves due to an abnormal current, the movable plate is unlatched, the movable contact plate moves the movable plate in a direction orthogonal to the moving direction of the plunger, and the movable plate restrains the movement. The contact plate is moved by the spring force in the direction in which the movable contact is separated from the fixed contact.

(Embodiment) FIG. 1 and FIG. 2 are drawings showing the present invention as an embodiment.
Describing with reference to the drawings, 1 is a coil tube having a cylindrical shape with openings on both sides, and 2 is a coil wound around the outer circumference of the coil tube 1. Reference numeral 3 denotes a yoke that surrounds the coil 2 and the coil cylinder 1, and is a U-shaped magnetic plate 4 including a bottom plate 4a located at one opening of the coil cylinder 1 and a side plate 4b parallel to the coil 2 and the coil cylinder 1, and a side plate. It is composed of an I-shaped magnetic plate 5 attached to the tip of 4b and located in the other opening of the coil cylinder 1. Reference numeral 6 denotes a plunger which is located between the yokes 3 and is housed in the coil cylinder 1, and is composed of a main body 6a and an output end 6b protruding from a hole 3a formed in the yoke 3. A nonmagnetic guide 7 is attached to the hole 3a of the yoke 3 to prevent the sliding friction of the plunger 6 from increasing. Reference numeral 8 is a return spring interposed between the plunger 6 and one end of the yoke 3, and biases the plunger 6 toward the other end of the yoke 3. Reference numeral 9 is a shape memory alloy interposed between the plunger 6 and the other end of the yoke 3, and is adapted to expand at the transformation temperature. The overcurrent detection device X is configured as described above and is housed in the body 10 of the overcurrent protector. Reference numerals 11 and 11 denote a pair of terminal plates attached to the body 10, one end of which is connected to one end of the coil 2, and the other end of which is fixedly secured to a fixed contact 12. 13 is a movable contact facing the fixed contact 12, 14 is a movable contact plate to which the movable contact 13 is fixed, and a spring is applied in a direction in which the movable contact 13 is separated from the fixed contact 12 to fix the base end to the yoke 3. The other end of the coil 2 is connected to this base end. Reference numeral 15 denotes a movable plate, one end of which is fitted with the tip of the movable contact plate 14 and the other end of which is projected from a hole 10a formed in the body 10. Further, the movable plate 15 is formed with a hole 17 into which the output end 6b of the plunger 6 of the overcurrent detection device X is fitted. When the output end 6b is fitted, the movable contact 13 contacts the fixed contact 12 and when the output end 6b is disengaged. The spring force of the movable contact plate 14 causes both contacts 13 and 12 to separate.

To explain this operating state, FIG. 1 shows the closed state, and the plunger 6 is moved by the spring force of the return spring 8 to the yoke 3
Is held at the other end of the movable plate 15, and its output end 6b is fitted into the hole 17 of the movable plate 15 to prevent the movable plate 15 from moving due to the spring force of the movable contact plate 14, so that the fixed contact 12 and the movable contact 13 contact each other. The other terminal plate 11-fixed contact 12-movable contact 13-movable contact plate 14-coil 2-one terminal plate 11 is connected to form a circuit.

When an overload current flows in the circuit in this closed state, the coil 2
Is generated by the current flowing in the shape memory alloy 9 through the coil cylinder 1, and when this temperature reaches the transformation temperature, the spring force of the return spring 8 is increased by the expansion of the shape memory alloy 15 and the magnetic flux of the coil 2. On the contrary, the plunger 6 is pressed against one end side of the yoke 3, and the output end 6b of the plunger 6 is moved to the hole 17 of the movable plate 15.
The movable contact plate 14 is further separated and moved by the spring force of the movable contact plate 14, the movable contact 13 is separated from the fixed contact 12, and the circuit is opened. Incidentally, the return is returned to the original state by the force of the return spring 8, and the output end 6b is fitted into the hole 17 by the manual operation of the movable plate 15 so that the contacts 12 and 13 come into contact with each other to form a circuit.

Next, when a short-circuit current flows in the circuit in the above-mentioned closed state, the plunger 6 is generated by the magnetic flux generated by the current flowing in the coil 2.
The magnetic force acts on the plunger 6 to move it against the return spring 8, and the circuit opens as in the case of the above-mentioned overload current.

Further, if the coil cylinder 1 is first made of ceramic, insulation is ensured, and even if the amount of heat generated by the coil is large, the influence can be reduced, so that the cross-sectional area of the coil can be made small and the size can be reduced.

Next, when the coil cylinder 1 is made of a conductive material, heat conduction due to heat generation of the coil and heat generation due to an overcurrent generated in the coil cylinder 1 are promoted to improve the thermal efficiency of the shape memory alloy 9.

Thirdly, as shown in FIG. 3, the inside of the coil cylinder 1 is a conductive material 1a.
Moreover, when the outer side is formed of the ceramic 16, heat generation due to an overcurrent generated in the conductive material is promoted, thermal efficiency is improved, and insulation with the coil is secured, and further miniaturization can be achieved.

Fourthly, when the coil cylinder 1 described above is a cylinder in which the coil housing groove 1c is formed on the outer periphery as shown in FIG. 4, the position of the coil 1 is stable, the characteristics are stable, and heat transfer can be further improved. .

Incidentally, in FIGS. 3 and 4, the same parts as those of the embodiment of FIGS. 1 and 2 are designated by the same reference numerals, and the description thereof will be omitted.

(Effects of the Invention) As described above, according to the present invention, the plunger operates instantaneously against the return spring against a short-circuit current, and the shape memory alloy expands due to heat generation against an overload current, so that the shape memory alloy expands against the return spring. Since the plunger operates, it is possible to cope with an overcurrent such as a short circuit current or an overload current. Further, since the shape memory alloy operates at a transformation temperature at a stretch, the adjustment amount can be reduced and its reliability can be improved. Also, when the plunger moves due to an abnormal current, the movable plate is unlatched, the movable contact plate moves the movable plate in a direction orthogonal to the moving direction of the plunger, and the movable plate restrains the movement. Since the contact plate moves due to its spring force in the direction in which the movable contact separates from the fixed contact, members such as a link mechanism are not required, and the structure itself can be downsized and cost increase can be suppressed.

[Brief description of drawings]

1 and 2 show an embodiment of an overcurrent protector of the present invention, wherein FIG. 1 is a sectional front view in a closed state, FIG. 2 is a sectional front view in an opened state, and FIG. FIG. 4 and FIG. 4 are sectional front views showing other different embodiments. 1 ... Coil cylinder, 2 ... Coil, 4 ... Yoke, 6 ...
Plunger, 8 ... Return spring, 9 ... Shape memory alloy.

Claims (5)

[Claims] 1. A coil tube, a coil wound around the outer circumference of the coil tube, a yoke surrounding the coil and the coil tube, a plunger located between the yokes and housed in the coil tube, A return spring interposed between the plunger and one end of the yoke, a shape memory alloy interposed between the plunger and the other end of the yoke and extending at a transformation temperature, and orthogonal to the moving direction of the plunger. The movable plate that is movably arranged in the direction that the movable plate is latched by the plunger, and the movable contact contacts the fixed contact when the movable plate is latched by the plunger, and the movable plate is movable when the latch of the movable plate is released. An overcurrent protector comprising: a movable contact plate having a spring force that separates a contact from a fixed contact. 2. The overcurrent protector according to claim 1, wherein the coil cylinder is made of ceramic. 3. The overcurrent protector according to claim 1, wherein the coil cylinder is made of a conductive material. 4. The overcurrent protector according to claim 1, wherein the coil cylinder is formed of a conductive material on the inner side and ceramic on the outer side. 5. The overcurrent protector according to claim 1, wherein the coil cylinder is a cylinder in which a coil housing groove is formed on the outer circumference.