ELECTROMAGNETIC CONTACTOR

Abstract: Electromagnetic contactor for effecting ON/OFF control of electric wiring of an electric motor or the like. The contactor is made easy to house inside a mount for a circuit device adapted to convert the AC voltage applied to an actuating coil to a DC voltage and to lower the power consumption of the actuating coil after a movable core is attracted. The contactor includes: a printed board assembly (63) on which are mounted an actuating coil (35), a diode (34), a changeover switch (31) and so forth, the printed board assembly (63) being housed within a mount (50); a fixed core (47) of a rod-like magnetic material received by the actuating coil (35); and a movable core shaped substantially like a 'U'. The actuat­ ing coil (35) is housed within a recess in the movable core when the movable core is attracted, thereby to ensure mount­ ing space for the printed board assembly (63).

Description: This invention relates to an electromagnetic contactor for controlling the opening and closing of an electric circuit for an electric motor or the like. More particularly it concerns an electromagnetic contactor comprising a mounting pedestal having a rectifier circuit disposed therein, a stationary iron core disposed on the mounting pedestal and having an operating coil wound around the same, and a movable iron core disposed opposite this stationary iron core, spaced therefrom by a predetermined spacing and always urged away from the stationary iron core side by means of a kickout spring. Figure 1 shows a structural view of a conventional electromagnetic contactor. In the Figure, 1 is a mounting pedestal consisting of an insulating material and made up in the form of a box, which pedestal is provided with a plurality of mounting holes 1a in order to mount the main body of the electromagnetic contactor on a mounting panel or the like. 2 is a base fixed to the mounting pedestal 1 by fastening screws 3, the base being composed of an insulating material. 4 is a stationary iron core in the form of an E having silicon steel laminations stacked on one another, 5 a buffer spring disposed between this stationary iron core 4 and the mounting pedestal 1, and 6 is an operating coil disposed around a central leg of the E-shaped stationary iron core 4 and held by having its lower surface abutting against the stationary iron core 4 and its upper surface abutting against the base 2. 7 is leads for connecting this operating coil 6 to coil terminals 8, and 9 is a movable iron core disposed opposite the stationary iron core 4 to have a predetermined spacing therebetween and constructed so that, when a driving voltage is applied to the operating coil 6, it is attracted by the stationary iron core 4. 10 is a cross bar formed of an insulating material and connected to the movable iron core 9 through a pin 11. 12 is a kickout spring disposed between the cross bar 10 and the mounting pedestal 1 and acting to urge the cross bar 10 upward as viewed in Figure 1c. 13 is a movable contact support provided with a movable contact 14, inserted into a holding hole 10a provided in the cross bar 10 and pressurized by a contact spring 16 held by a spring support 15. 17 is a stationary contact support provided with a stationary contact 18 facing the movable contact 14 and fixed to the base 2 by means of its elasticity while having a terminal screw 19 for the connection to an electrical wire for the main circuit. 20 is an arc runner consisting of a magnetic metal and provided for a purpose of extinguishing an electric arc which runner is fixed to the base 2 by means of its resilience. In the conventional electromagnetic contactor of the structure described above, the application of a driving voltage to the operating coil 6 causes the generation of an electromagnetic attraction between the stationary iron core 4 and the movable iron core 9 due to a magnetic flux generated by this operating coil 6 thereby to attract the movable iron core 9 by the stationary iron core 4 against the kickout spring 12. This is followed by the cross bar 10 connected to the movable iron core 9 being moved towards the stationary iron core 4 to cause the movable contact 14 on the movable contact support 13 held by the cross bar 10 to abut against the stationary contact 18 on the stationary contact support 17. An iron core gap between the movable iron core 9 and the stationary iron core 4 is larger than a contact gap between the movable contact 14 and the stationary contact 18. Therefore, upon the closure of the iron cores, the cross bar 10 is moved further towards the stationary iron core 4 than the position where said contacts abut against each other. This causes the contact spring 16 to be compressed and deformed. This spring pressure is transmitted to the movable contact support 13 to close the contacts with a predetermined contact pressure. Then, upon removing the driving voltage applied to the operating coil 8, the electromagnetic force disappears between the stationary iron core 4 and the movable iron core 9 and the cross bar 10 moves away from the stationary iron core by means of the spring force of the kickout spring 12 in its compressed state. Thus the contacts are separated from each other. At that time, an electric arc is generated between the movable contact 14 and stationary contact 18 but this electric arc stretches along the arc runner 20 adjacent to said contact portions to be cooled and divided until it is extinguished. In said electromagnetic contactor, however, the driving voltage is of an alternating current and therefore, in order to prevent the iron cores from vibrating due to its alternating magnetic flux, a shading coil 21 has been disposed on a pole surface of the iron core to smooth the pulsating attraction due to the alternating magnetic flux. However, the effectiveness of the shading coil 21 has a limit. For example, upon the occurrence of rust on the pole surface of the iron core, the smoothing effect decreases, causing vibrations of the iron cores. Thus noise has been generated. To this end, there has been proposed a rectifier circuit included in the mounting pedestal to change an AC voltage applied to the operating coil 6 to a direct current. However, since the mounting pedestal 1 has the stationary iron core 4, the buffer spring 5 and the operating coil 6 and other components included therein as shown in the Figure, it has been difficult to sufficiently ensure enough mounting space for said rectifier circuit. GB-A-2109164 an intermediate document : publication date : 25-5-83, discloses a contactor generally similar to that of Figure 1 but with a U-shaped stationary core. GB-A-2109164 also discloses the provision of a starting circuit to rectify a large capacity electric current from an AC power source, and to supply the rectified current to said operating coil; a holding circuit including a converting means to supply said large capacity current from said power source to said operating coil through said converting means to convert the large capacity current to a small capacity when said iron cores are in contact; and a change-over switch to change an energizing current for said operating coil from said starting circuit over to said holding circuit, said change-over switch including a hysteresis means to cause it to activate said holding circuit only after closure of said both contact points, and to deactivate said holding circuit only after separation of both contact points. In GB-A-2109164, the relay drive control circuit is provided on a printed circuit board in the mounting pedestal. This contactor also suffers from lack of space for the starting circuit and holding circuit. DE-A-1807241 discloses a relay device with a rectifier mounted on a protective cap of the relay, the entire assembly being potted within a sheet metal housing. The object of the present invention is to provide an electromagnetic contactor which has eliminated said problems of conventional relays with rectifiers and to provide improvements in assembling and handling abilities concerning the accommodation of the rectifier circuit and its accessories in the interior of a mounting pedestal. The present invention provides an electromagnetic contactor comprising a stationary iron core disposed opposite a movable iron core for effecting an opening and a closing contact movement and an operating coil disposed so as to surround this stationary iron core, disposed on a box-shaped mounting pedestal, said coil being supplied with electric power which is a direct current converted from an alternating current from an AC electric source; a change-over switch put in a closed state upon the closure of the electric source and in an open state after said stationary iron core has attracted said movable iron core; and a circuit board located in the vicinity of said stationary iron core and fixed within said mounting pedestal, said circuit board having thereon a rectifier circuit for rectifying said alternating current into the direct current, and a voltage dropping circuit connected in parallel to this change-over switch to reduce the voltage applied to said coil, the said rectifier circuit, change-over switch and voltage dropping circuit being disposed in a space formed between said stationary iron core and a lateral wall part of said mounting pedestal, characterized in that the stationary iron core is bar-shaped and is disposed on a central portion of said mounting pedestal, the circuit board is mounted between the base of the mounting pedestal and the underside of the stationary core and coil, and the changeover switch is mounted on the circuit board. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a structural view of an outline of a conventional electromagnetic contactor wherein Figure 1(a) is a plan and a sectional view in half; Figure 1(b) is a front elevational and a sectional view in half; and Figure 1(c) is a side elevational and a sectional view in half. Figures 2 to 11 are views illustrating one embodiment of an electromagnetic contactor according to the present invention wherein Figure 2 is a diagram of a control circuit for an operating coil; Figure 3 is a plan view, partly in section, of the electromagnetic contactor; Figure 4 is a sectional view taken on the line IV-IV of Figure 3; Figure 5 is a sectional view taken on the line V-V of Figure 3; Figure 6 is an exploded perspective view of an electromagnetic portion; Figure 7 is a perspective view as viewed in the arrow on the line VII-VII of Figure 6; Figure 8 is an enlarged perspective view of a change-over switch; Figure 9 is an enlarged perspective view of a stationary iron core; Figure 10 is an enlarged perspective view illustrating an alternative stationary iron core support; Figure 11 is an exploded perspective view illustrating an alternative manner in which a kickout spring bearing is mounted to a mounting pedestal; Figure 12 is a plan view illustrating that portion of a printed circuit board inserted into the mounting pedestal according to another embodiment of the present invention; and Figure 13 is a sectional view of the mounting pedestal of Figure 12. The description of embodiments of the present invention will hereinafter be made with reference to the drawings. Referring first to Figure 2, the description will be made in conjunction with a circuit for an electromagnet. The circuit components are composed of a varistor 30, a change-over switch 31, a resistor 32, a capacitor 33, a rectifier 34 and an operating coil 35. The change-over switch 31 is closed when the main contacts are open and is open when the main contacts are closed. The capacitor 33 and the resistor 32 are serially connected and also connected in parallel to the change-over switch 31. The rectifier 34 full-wave rectifies an AC voltage AC and is connected at DC output terminals thereof to the operating coil 35 and the varistor 30 is connected to the AC side in order to prevent an intrusion of an external surge. When an AC voltage is applied to the contruction as described above, the operating coil 35 is first applied with the entire voltage formed only of the full-wave rectified AC voltage because the change-over switch 31 is closed. Thus a movable part of the electromagnetic contactor is driven with an electromagnetic force to close the main contacts and simultaneously open the change-over switch 31. With the change-over switch 31 open, the AC voltage is applied to the diode 34 through the capacitor 33. Since the operating coil 35 is supplied with an AC voltage dropped in voltage due to the capacitor 33, the movable part is held with a weak electromagnetic force as compared with the closure. Thus, the power consumed by the operating coil 35 becomes low. In electromagnets having the operating coil 35 directly applied with an AC voltage, the operating coil 35 has a magnetomotive force and a consumed electric power changed with a variation in reactance between the closing and holding, but for the DC excitation, it is required to change the voltage applied to the operating coil 35 by the change-over switch 31 or the like as described above. Then, upon removing the AC voltage, said movable part is returned back to its original state while at the same time the change-over switch 31 is closed to discharge an electric charge remaining on the capacitor 33 to the change-over switch 31 through the resistor 32 to electrically remove electrical insulation produced on the contact surfaces of the change-over switch 31. The resistance 32 limits the magnitude of the discharge current so as not to weld the contacts. Subsequently, referring to Figures 3 to 11 the construction of the electromagnetic contactor according to the present invention will be described. The main contacts comprise a movable contact 40 and a stationary contact 41 and the movable contact 40 is pressed by a contact spring 42 and held by a cross bar 43. A tripping or kick-out spring 80 acts on the cross bar 43 to urge the contacts apart. The cross bar 43 is connected to a movable iron core 44 in the form of a substantially angular U forming a magnetic path, by means of a pin 45, and therewith is slidably assembled into an upper housing part 46. A bar-shaped stationary iron core 47 having a section substantially in the form of a trapezoid is disposed facing the movable iron core 44 and stationary iron core supports 48 fitted to both ends thereof are fixed by carrying them between the upper housing part 46 fixed by screws 49 and the mounting pedestal 50. Fixing rubber buffers 51 are disposed at the bottom of the mounting pedestal 50 to support and upwardly press the stationary iron core 47. Thus the core 47 is disposed on a central portion of the mounting pedestal. As shown in the details thereof in Figure 7, the operating coil 35 is composed of a coil spool 52, a winding 53, and coil leads 54. After the winding 53 has been wound around the coil spool 52, it is passed through grooves 55 disposed in the coil spool 52 and is connected to protrusions 56 on electrically conducting coil leads 54. The groove 55 is provided on a flange 57 of the coil spool 52 below the stationary iron core 47 so as not to interfere with the movable iron core 44. A protrusion 58 is disposed on the coil lead 54 to be inserted into and fixed in a hole 59 disposed in the coil spool 52. Also a terminal protrusion 60 protrudes along the flange 57 to the base side whereby the protrustion can be utilized as a terminal for measuring the winding resistance of the operating coil 35. The operating coil 35 constructed as described above is connected to a printed circuit board 61 by the protrusions 58 on the coil leads 54 while being arranged with its axis horizontal, the stationary iron core 47 extending through the coil spool 52. The printed circuit board 61 is equipped, in addition to the operating coil 35, with the varistor 30, the change-over switch 31, the resistor 32, the capacitor 33 and the diode 34 which are the components used for the control of the operating coil 35, and coil terminals 62 for applying the AC voltage. This printed circuit board assembly 63 is assembled into the interior of the mounting pedestal 50, made in the form of a box, while the change-over switch 31 is provided with a female screw 64 (see Figure 5) so that the position of the change-over switch 31 is controlled by fastening it to the mounting pedestal 50 through the printed circuit board 61 by means of a screw 65. The circuit board is placed between the base 50B of the mounting pedestal and the underside of the coil 35 and core 47, with the circuit components 31 - 34 being accommodated in a space defined between the core 47 and coil 35, and the lateral walls of the mounting pedestal. The lateral walls in question are those that do not accommodate the openings 74 receiving the supports 48. Furthermore, the flange 57 of the coil spool 52 is provided on both lateral surfaces thereof with protrusion 66 which is provided with a notch 67. By fastening a screw 68 to a female screw 72 (see Figure 5) formed in the mounting pedestal 50, the heavy operating coil 35 is fixed to the mounting pedestal 50. The coil terminals 62 (see Figure 6) are fastened to relaying terminals 69 forcedly inserted into the mounting pedestal 50 by means of coil terminal screws 70 whereby it is possible to connect the electromagnet to an external electric source. In order to protect each component on the printed circuit board assembly 63 fixed to the mounting pedestal 50 as described above against impulses due to closure of the electromagnetic contactor itself, an epoxy resin 71 is poured into the box-like mounting pedestal 50. The present inventors have experimentally confirmed that the epoxy resin 71 does not leak from the mounting pedestal 50 through which the screws 65 extend. Figure 8 shows a perspective view of the change-over switch 31. This change-over switch 31 has an operating button 31a on the upper portion. This button 31a is disposed so as to be pressed against the lower end of the cross bar 43 so that its contacts are open just before a position of attraction of the iron core. Also it has pin-shaped terminals 31b on the lower portion, which terminals are constructed so as to be connected to the printed circuit board 61 by direct soldering. Also, Figure 9 shows a perspective view of the stationary iron core 47 which is a bar with a trapezoid sectional profile and a pole surface to which a non-magnetic spacer 73 is stuck in order to prevent the iron core from falling with a delay, the spacer 73 being formed of a non-magnetic sheet metal such as stainless steel or the like. This stationary iron core 47 is inserted into the operating coil 35 through an opening 74 (see Figure 6) in the lateral surface of the mounting pedestal 50, the opening being closed by the stationary iron core support 48. Figure 10 is an enlarged perspective view illustrating a stationary iron core support 75 used as an alternative to the core support 48 and consisting of a material having a small Young's modulus (for example, a thermoplastic resin or the like). The core support 75 has a convex curved lower surface abutting against the pole surface of the stationary iron core 47 to position the latter. Accordingly, said stationary iron core 47 can be rotated in the direction of the arrow A shown in Figure 4 and therefore it is possible to intimately contact the pole surface of the U-shaped movable iron core 44 disposed opposite it without any clearance therebetween. Thus the attraction characteristics can be arranged to be stabilized under the state of attraction of the iron cores. The core support has a pair of spaced legs adjacent to the convex surface, and facing lateral surfaces of the iron core. An elastically deformable leg part extends in the opposite direction, and incorporates teeth 75a by which it is fixed to the upper housing part 46 with a snap action. Figure 11 is an enlarged perspective view illustrating a spring seat 76 for for the tripping spring 80, used instead of that shown in Figures 4 and 6. The fixing is effected by fitting its protrusion 76a into a dovetail groove 50b provided in the mounting pedestal 50 with the tripping spring 80 compressed and disposed between the spring seat 76 and the lower surface of the cross bar 43 to urge the cross bar 43 upwards. The electromagnetic contactor of the present embodiment constructed as described above is constructed so that the stationary iron core 47 is formed of a magnetic bar-shaped member while the movable iron core 44 disposed facing the side thereof is made in the form of U and during the attraction of the iron cores, that portion of the operating coil 35 on the side of the movable iron core is accommodated in a recessed portion of said movable iron core 44. This permits a sufficient space for mounting the rectifier circuit to be provided within the mounting pedestal 50. The stationary iron core 47 is laid by its side during the assembling and the stationary iron core support 75 for positioning this stationary iron core 47 is made up into the form of a gate. Thus after the electromagnetic contactor has been assembled, the insertion and removal of the stationary iron core 47 can be effected through a gate type inner space of the stationary iron core support 75. At that time, the contact pole surface thereof can can readily be distinguished from the lower surface thereof because the sectional profile of the stationary iron core 47 is trapezoid. In the electromagnetic contactor of the present embodiment, the wiring of the rectifier circuit shown in Figure 2 for the operating coil 35 is entirely effected within the printed circuit board 61 without any lead wiring and furthermore, the operating coil 35 and the changeover switch 31 are arranged to be capable of being directly mounted on the printed substrate 61. Moreover, their positions and heights can readily be set by the screws 65. Thus the assembling ability is much improved to render the entire device inexpensive. Furthermore, in the electromagnetic contactor of the present embodiment, the electronic components 30, 33, 32 and 34 and the wiring specification for the operating coil 35 in Figure 2 have parameters which change with variations in driving voltage. However, all of them are fixed within the mounting pedestal 50 by means of a potting casting material 71, for example an epoxy resin. Thus when the user reconstructs the device at a different driving voltage, the reconstruction can be very conveniently effected because only the replacement of the mounting pedestal 51 is required without any erroneous combination of the electronic components with the operating coil 35. Also since the electromagnetic contactor of the present embodiment includes the change-over switch 31 fixed to the mounting pedestal 50 by the screws 65 and having the accurate changing-over position, stability of operation is obtained. Furthermore said embodiment has shown the printed circuit board 61 mounted to the mounting pedestal 50 by the screws 65 and fixed by the casting material 71, but it may be fixed by disposing protrusions 50c having sloping surfaces narrow in width at several positions on a seat 50a for the mounting pedestal 50 as shown in Figures 12 and 13, setting a dimension between the tops of these protrusions 50c to be smaller than that of the printed circuit board 61 and utilizing the flexibility of this printed circuit board 61 upon the insertion. As described above, and according to the present invention, the stationary iron core is composed of a bar-shaped magnetic member while the movable iron core disposed opposite thereto is in the form of a U. Thus an electromagnetic contactor can be provided which improves the assembling and handling abilities concerning the accommodation of the rectifier circuit and its accessories in the interior of said mounting pedestal.

Claims: An electromagnetic contactor comprising a stationary iron core (47) disposed opposite a movable iron core (44) for effecting an opening and a closing contact movement and an operating coil (35) disposed so as to surround this stationary iron core (47), disposed on a box-shaped mounting pedestal (50), said coil (35) being supplied with electric power which is a direct current converted from an alternating current from an AC electric source; a change-over switch (31) put in a closed state upon the closure of the electric source and in an open state after said stationary iron core (47) has attracted said movable iron core (44); and a circuit board (61) located in the vicinity of said stationary iron core (47) and fixed within said mounting pedestal (50), said circuit board (61) having thereon a rectifier circuit (34) for rectifying said alternating current into the direct current, and a voltage dropping circuit (32, 33) connected in parallel to this change-over switch (31) to reduce the voltage applied to said coil (35), the said rectifier circuit (34), change-over switch (31) and voltage dropping circuit (32, 33) being disposed in a space formed between said stationary iron core (47) and a lateral wall part of said mounting pedestal (50), characterized in that the stationary iron core (47) is bar-shaped and is disposed on a central portion of said mounting pedestal (50), the circuit board (61) is mounted between the base of the mounting pedestal (50) and the underside of the stationary core (47) and coil (35), and the changeover switch (31) is mounted on the circuit board (61). An electromagnetic contactor according to claim 1, characterized in that said stationary iron core (47) has a cross section in the form of a trapezoid. An electromagnetic contactor according to claim 2, characterized in that said mounting pedestal (50) has a support unit (51) in the interior of said mounting pedestal (50) to elastically receive said stationary iron core (47), an upper housing part (46) is combined with said mounting pedestal (50) to make up a case for the entire electromagnetic contactor, said upper housing part (46) having disposed thereon an iron core support (75) for carrying said stationary iron core (47) by the same and said support unit (75), and a portion (75b) of said iron core support (75) abutting against said stationary iron (47) core is a convex surface. An electromagnetic contactor according to claim 3, characterised in that said iron core support (75) has leg parts adjacent to the abutting convex surface thereof and facing lateral surfaces of said stationary iron core (47). An electromagnetic contactor according to claim 3 or 4, characterized in that said iron core cupport (75) has an elastically deformable leg part having a snap-action tooth (75a) and is disposed on said upper housing part (46) by this leg part. An electromagnetic contactor according to claim 1 or 2 characterized in that a pair of opposite lateral walls of said mounting pedestal (50) have respective openings (74) therein and both ends of said stationary iron core (47) are located in a pair of stationary iron core supports (48) disposed in these openings. An electromagnetic contactor according to claim 6, characterized in that said openings (74) are in lateral walls different from the lateral walls which bound the space for accommodating said rectifier circuit (34), the change-over switch (31) and the voltage dropping circuit (32, 33). An electromagnetic contactor according to any one of claims 2 to 7, characterized in that a contact pole surface of said stationary iron core (47) has a non-magnetic spacer (73) stuck to it. An electromagnetic contactor according to any preceding claim characterized in that said change-over switch (31) is fixed at a predetermined position on said mounting pedestal. An electromagnetic contactor according to any preceding claim characterized in that one part of a cross bar (43) driven by said movable iron core (44) faces an operating button (31a) of said change-over switch (31) thereby to operate said change-over switch (31). An electromagnetic contactor according to any preceding claim characterized in that a spring (80) for imparting a separating force between said movable iron core (44) and said stationary iron core (47) is disposed between a cross bar (43) driven by said movable iron core and said mounting pedestal (50), and a spring seat (76) for supporting one end of this spring is fitted into and disposed on said mounting pedestal. An electromagnetic contactor according to claim 11, characterized in that a groove (50b) is provided in a lateral surface part of said mounting pedestal (50) and a protrusion (76a) is provided on said spring seat (76), this protrusion being fitted into said groove thereby to dispose said spring bearing on said mounting pedestal. An electromagnetic contactor according to any preceding claim characterized in that said circuit board (61) is fixed on said mounting pedestal by resin potting mold to form a unitary structure.

Inventors: KAKIZOE, MASAHIRO MITSUBISHI DENKI K. K., NISHIZAKO, SHIZUTAKA MITSUBISHI DENKI K. K., OKADO, HIROYUKI MITSUBISHI DENKI KABUSHIKI KAISHA, SAKO, YUJI MITSUBISHI DENKI KABUSHIKI KAISHA
Applicants: MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1983
Main classification: H01H50
IPC codes: H01H50