Sealed cased magnetic switch

A sealed cased magnetic switch includes: a first contact pressure spring having one end supported by the movable contactor and applying an elastic force to the movable contactor to provide a contact pressure in a direction in which the movable contactor is brought into contact with the fixed electrode; a spring seat member supporting the other end of the first contact pressure spring and fixedly installed on the driving shaft; and a second contact pressure spring having a diameter larger than that of the first contact pressure spring and applying an elastic force at an outer position in a radial direction compared with the first contact pressure spring to the movable contactor in a direction in which the movable contactor is brought into contact with the fixed electrode.

CROSS-REFERENCE TO A RELATED APPLICATION

Pursuant to 35 U.S.C. §119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2009-0136230, filed on Dec. 31, 2009, the contents of which is incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sealed cased magnetic switch and, more particularly, to a sealed cased magnetic switch capable of reducing noise of a switching operation.

2. Description of the Related Art

A magnetic switch, a device used for switch a power supply line, is a relatively low voltage electric power switch utilized for extensive purposes including an industrial purpose, a household purpose, electric vehicle purpose, and the like. The magnetic switch is configured to switch a power supply circuit by moving a movable contact connected to a movable core, to a circuit opening position where a movable contactor connected to the movable core is separated from a corresponding fixed electrode, or to a circuit closing position where the movable contactor is brought into contact with the corresponding fixed electrode, by moving the movable core by using magnetic force of a coil magnetized or demagnetized according to supply or interruption of control electric power source. If the contact of the movable contactor at the position where the movable contactor is in contact with the fixed electrode becomes poor due to an external factor such as vibration, an impact, and the like, at the circuit closing position, the contact may be fused, damaged, and the like to possibly cause a more critical electrical incident, so a contact pressure spring is employed to apply elastic force to the position at which the movable contactor is in contact with the corresponding fixed electrode.

However, in the magnetic switch, the use of the contact pressure spring having a high elastic force to obtain the operational reliability during the contact operation increases an impact when the movable contactor is brought into contact with the fixed electrode during the circuit closing operation, causing severe impact noise.

In particular, the magnetic switch used for homes or electric vehicles urgently needs to have a low-noise structure that does not generate such impact noise.

Meanwhile, the related art sealed cased magnetic switch includes one contact pressure spring installed around a driving shaft of a movable contactor, in which one end of the contact pressure spring is supported by a central portion of the movable contactor and the other end of the contact pressure spring is supported by a spring seat fixedly installed on the driving shaft. The related art sealed cased magnetic switch has a structure in which the contact pressure spring and the driving shaft providing a contract driving force are placed at the central portion of the movable contactor, while an outer portion of the movable contactor collides with the fixed electrode during a contact operation. Thus, a large impact is applied to the portion of the movable contactor which is brought into contact with the fixed electrode, and as shown inFIG. 1, as the stroke of the distance along which the movable contactor is moved during the contact operation increases, a total contact pressure has a lengthy nonlinear interval (i.e., the interval in which the total contact pressure is stationary without a variation inFIG. 1) starting from a collision. As the nonlinear interval is lengthy, more severe noise is generated. Thus, in the related art sealed cased magnetic switch, the nonlinear interval is lengthy in terms of the variation characteristics of the total contact pressure as the contact operation of the movable contactor is performed, generating severe noise.

SUMMARY OF THE INVENTION

Therefore, in order to address the above matters, the various features described herein have been conceived.

An aspect of the present invention provides a sealed cased magnetic switch capable of reducing noise generation when a movable contactor performs a contact operation by shortening a nonlinear interval in terms of variation characteristics of a total contact pressure as the contact operation of the movable contactor is performed.

According to an aspect of the present invention, there is provided a sealed cased magnetic switch, which includes a sealed container with one side opened, a fixed electrode air-tightly attached to the side opposite to the opened side of the sealed container, a movable contactor movable to a position at which it is brought into contact with the fixed electrode and to a position at which it is separated from the fixed electrode, a driving shaft supporting the movable contactor and being movable along with the movable contactor, a movable core coupled with the driving shaft so as to be movable together, a fixed core installed to face the movable core, a bobbin accommodating the fixed core and the movable core in the interior of a hollow thereof, a coil wound around the bobbin, a yoke installed near the coil to form a magnetic path, and an iron plate forming the magnetic path along with the yoke and installed at an upper portion of the bobbin, including: a first contact pressure spring having one end supported by the movable contactor and applying an elastic force to the movable contactor to provide a contact pressure in a direction in which the movable contactor is brought into contact with the fixed electrode; a spring seat member supporting the other end of the first contact pressure spring and fixedly installed on the driving shaft; and a second contact pressure spring having a diameter larger than that of the first contact pressure spring and applying an elastic force at an outer position in a radial direction compared with the first contact pressure spring to the movable contactor is in a direction in which the movable contactor is brought into contact with the fixed electrode.

DETAILED DESCRIPTION OF THE INVENTION

A sealed cased magnetic switch according to a preferred embodiment of the present invention will now be described with reference toFIGS. 2 and 3.

FIG. 2is a vertical sectional view showing the configuration of a sealed cased magnetic switch according to the preferred embodiment of the present invention, andFIG. 3is a graph showing a change in an elastic force over a contact position moving stroke of a movable contactor in a sealed cased magnetic switch according to the preferred embodiment of the present invention illustrated inFIG. 2, specifically, showing a change in an elastic force and a total contact pressure of a return spring and first and second contact pressure springs.

As shown inFIG. 2, a sealed cased magnetic switch according to an preferred embodiment of the present invention comprises a sealed container11, a fixed electrode12, a movable contactor13, a driving shaft16, a movable core17, a fixed core15, a bobbin19, a coil, a yoke, and an iron plate14.

The sealed container11is a container having a substantially alphabet “U” shaped vertical section with one side opened. The sealed container11is installed such that the open side points upward and serves as an upper outer casing of the sealed cased magnetic switch.

The fixed electrode12is penetratingly installed on and air-tightly attached to the side opposite to the open side of the sealed container11so as to be supported by the sealed container11. The fixed electrode12has the function of a terminal to which an external electric wire is connected and the function of a fixed electrode which is brought into contact with the movable contactor13or separated from the movable contactor13. A pair of fixed electrodes12are provided.

The movable contactor13is configured as a movable electrode that can be moved to a position at which it is brought into contact with the fixed electrode12and to a position at which it is separated from the fixed electrode12. In order to be brought into contact with the pair of fixed electrodes12or separated therefrom, the movable contactor13may be configured as a conductive plate having a sufficient length equivalent to the length obtained by adding the distance between the pair of fixed electrodes12and the width of the respective fixed electrodes12.

The driving shaft16supports the movable contactor13and is movable along with the movable contactor13. The driving shaft16and the movable contactor13may be connected by fixing the position of an upper end portion, of the driving shaft16, which is press-fit through an opening formed at a central portion of the movable contactor f13so as to penetratingly extend, by using a release preventing washer16a. A spring support protrusion16bis formed at a position away by a predetermined distance from an upper end portion of the driving shaft16such that it extends (or is protruded) to be perpendicular to an axial direction of the driving shaft16. The spring support protrusion16bsupports a lower end of the first contact pressure spring23with a spring support washer (no reference numeral given) having a larger diameter than that of the first contact pressure spring23interposed therebetween, rather than directly supporting the lower end of the first contact pressure spring23.

The movable core17is installed at a lower end portion of the driving shaft16. The movable core17is coupled to the lower end portion of the driving shaft16through press-fitting, screw connection, welding, or the like, so as to be prevented from being released. The movable core17is coupled with the driving shaft16and movable together. The movable core17may be configured as, for example, an iron core.

The fixed core15is installed to face the movable core17. InFIG. 2, the fixed core15positioned at an upper side is installed to face the movable core17positioned at a lower side. The driving shaft16extends penetratingly at the central portion of the fixed core15.

A return spring20is installed around the driving shaft16penetrating the central portion of the fixed core15. An upper end portion of the return spring20is supported by an end portion of an inner circumferential surface of the fixed core15, and a lower end portion of the return spring20is supported by an end portion of an inner circumferential surface of the movable core17. The return spring20applies an elastic force to the movable core17in a direction in which the movable core17is separated from the fixed core15. Accordingly, when a current flow to the coil21is interrupted so the coil21is demagnetized, the movable core17is returned to the position away by a gap (D) inFIG. 2from the fixed core15owing to the elastic force of the return spring20.

The bobbin19is provided to accommodate the fixed core15and the movable core17in a hollow thereof. The bobbin may be made of a synthetic resin material having electrical insulation properties.

A cylinder18is installed between the movable core17and the fixed core18and bobbin18in order to provide a movement path.

The coil21is wound around the bobbin18. When current flows through the coil21, the coil21is magnetized to form a magnetic path together with the yoke22and the iron plate14nearby to provide a magnetic force for moving the movable core17such that it is brought into contact with the fixed core15.

The yoke22is installed near the coil21. When current flows through the coil21, the yoke22forms a magnetic path allowing magnetic flux formed at a right is angle with respect to the current of the coil21to move.

The iron plate14forms the magnetic path together with the yoke22and is installed at an upper portion of the bobbin19. A through hole is formed at a central portion of the iron plate14, in which the upper end portion of the fixed core15is inserted.

With reference toFIG. 2, the sealed cased magnetic switch according to an preferred embodiment of the present invention further comprises a first contact pressure spring23and a second contact pressure spring24.

One end (i.e., upper end inFIG. 2) of the first contact pressure spring23is supported by a lower surface of the movable contactor13, and the first contact pressure spring applies an elastic force to the movable contactor13in a direction in which the movable contactor13is brought into contact with the fixed electrode12in order to provide a contact pressure. The other end (i.e., a lower end inFIG. 2) of the first contact pressure spring23is supported by a spring support washer as a spring seat member25having a larger diameter than that of the first contact pressure spring23. The spring support washer as a spring seat member25is supported by the spring protrusion16bof the driving shaft16, thus being prevented from moving in the axial direction.

The second contact pressure spring24has a diameter larger than that of the first contact pressure spring23and applies an elastic force to the movable contactor13in a direction in which the movable contactor13is brought into contact with the fixed electrode12at an outer position in a radial direction compared with the first contact pressure spring23. One end (i.e., the upper end inFIG. 2) of second contact pressure spring24is supported by the lower surface of the movable contactor13and the other end (i.e., the lower end inFIG. 2) of the is second contact pressure spring24is supported by the iron plate14.

Preferably, the first and second contact pressure springs23and24are configured as coil springs.

The sealed cased magnetic switch according to the preferred embodiment of the present invention configured as described above has the following operation and its effect.

When current for controlling switching is supplied through an extra coil terminal which is not illustrated inFIG. 2to magnetize the coil21, the yoke22and the iron plate14nearby form a magnetic path to allow the moving core17, overcoming the elastic force of the return spring20, to move so as to be brought into contact with the fixed core15.

According to the movement of the movable core17to result in contact with the fixed core15, the movable contact13connected to the movable core17through the driving shaft16is moved to be brought into contact with the fixed electrode12. Thus, the electric power is supplied from an electrical power source to an electrical load through the sealed cased magnetic switch according to an preferred embodiment of the present invention. At this time, the first and second contact pressure springs23and24provide a contact pressure to the movable contactor13so that the movable contactor13can be maintained in the state of being in contact with the fixed electrode12.

When the supply of the current for controlling switching through an extra coil terminal which is not illustrated inFIG. 2is stopped, the coil21is demagnetized and the magnetic path through the yoke22and the iron plate14nearby becomes extinct. Accordingly, the movable core17is separated from the fixed core15due to the elastic force of the return spring20, to become away by the gap (D) illustrated inFIG. 2from the fixed core15.

In this case, according to the downward movement of the movable core17so as to be separated from the fixed core15, the movable contactor13connected to the movable core17through the driving shaft16is also separated from the contact position of the fixed electrode12as shown inFIG. 2.

Accordingly, the electric power supply from the electric power source to the electric load through the sealed cased magnetic switch according to the preferred embodiment of the present invention is interrupted.

Because the sealed cased magnetic switch according to the preferred embodiment of the present invention includes the second contact pressure spring24having a larger diameter than that of the first contact pressure spring23and applies an elastic force to the movable contactor13in a direction in which it is brought into contact with the fixed electrode12at an outer position in a radial direction compared with the first contact pressure spring23, the area of the movable contactor13to which the first and second contact pressure springs23and24apply the elastic force increases, so the stress of the movable contactor13due to the presence of the first and second contact pressure springs23and24can be reduced. Also, because the portion of the movable contactor23which collides with the fixed electrode12is an outer portion corresponding to the outer circumferential portion, not a central portion, of the movable contactor13, the first and second contact pressure springs23and24, in particular, the diameter of the second contact pressure spring24, are/is positioned to be close to the outer portion of the movable contactor13compared with the related art. Thus, when the movable contactor13collides with the fixed electrode12at the electric power supplying position, namely, at an ON position, of the sealed cased magnetic is switch according to the preferred embodiment of the present invention, a reaction force applied to the movable contactor13by the fixed electrode12is mostly absorbed. Thus, as shown inFIG. 3, the interval in which the total contact pressure is nonlinearly stationary by the first and second contact pressure springs23and24can be shortened, and because an impact is absorbed, noise can be reduced.