Electromagnetic switch element with arcuate pole faces

0001The invention relates to an electromagnetic switching element, in particular, a contactor.

0002Switching elements of this type have essentially a coil to that usually provided with a magnetizable yoke is. Current flows through the coil, a movable armature counter to a restoring force, such as a spring, attracted so moving switching contacts to another Position to be moved. Thereby, contact bridges, which at currentless coil are approximately open, closed. Thus, by the current through the coil in a control circuit of the Main circuit, in which a consumer, such as a motor, is, to be controlled.

0003The embodiments of the yoke and of the armature vary, they are so selected that a case attracted armature closed magnetic circuit forms. Here is the Armature on the pole faces of the yoke. In one embodiment, are the armature and yoke about the two E-shaped, wherein the two side legs of the armature and yoke with tightened Position of the armature abut touching. The Middle leg of the armature and yoke, however, are adapted that with tightened position of the armature an air gap remains between the two central limbs. This Air gap serves, inter alia, when switched off Current flow through the coil and the desired release of the The armature from the pole faces of the yoke sticking of the armature on Yoke due to the residual magnetism stop. a further advantage of the air gap is that in AC operation a hum is avoided, the lying otherwise due to the three in a plane would occur surfaces. To the magnetic flux through the yoke but not to interfere with and anchor too, is the Distance between the two central limb and hence the width of the Air gap a few tenths of a millimeter.

0004Frequent switching operations cause wear of the Pole faces of the side legs of the armature and yoke, so that the pole faces of the center leg in the course of use of the Switching element closer until they touch the end. In this state of the switching element, there may be Malfunction due to residual magnetism come, the reliable separation of the armature from the yoke prevented. Further, due to the now in a plane past three surfaces ripple occur. A depletion of The air gap between the two central limbs due to increasing wear of the pole surfaces of the side legs thus usually means the end of the mechanical Life of the switching element.

0005To the mechanical life of the switching elements to optimize, according to the state of the art initially to a precision grinding of the pole faces of the middle leg respected, an air gap with a precisely defined width ensure. Furthermore, it must to good lubrication of the yoke are respected and the armature, on the one hand a To achieve impact absorption in the course of switching operations and on the other hand to prevent corrosion. These measures however, cause only an optimization of the mechanical life under the given Workpiece geometries of the armature and yoke.

0006In contrast, the aim of the present Invention, a substantial extension of the mechanical Life of electromagnetic switching elements by a Modifying the workpiece geometry of the armature and yoke to to accomplish. It is further object of the invention, the consuming grinding of the pole faces of the armature and yoke to avoid.

0007These objects are achieved by the characterizing features of Claim 1 reached. Claim 1 refers here to electromagnetic switching elements, in particular a contactor, of the type comprising a coil, a fixed set forth above Yoke and an armature, the switching contacts and carries between a first switching position, in which it is spaced from the yoke and a second switching position in which it in close proximity to the yoke is, is movably held. The Switching contacts of the armature act in these two Switching positions with fixed switch contacts to to realize different switching states, the Armature and the yoke facing surface portions have that touch in the second switching position or touch approximately. This facing surface portions questions usually constitute the pole faces of the armature and yoke. According to the invention it is now provided in accordance with claim 1 that at least one of these surface portions of the armature and the him facing surface portion of the yoke a have different curvature. In contrast to the above the prior art shown are thus the mutually facing surface portions of the armature and of him facing surface portion of the yoke extending in the second touch switch position or touching almost, not as plane-parallel surfaces run, but as areas with different curvatures. It is feasible that one of the two surfaces, such as those of the yoke, left as a flat surface is and the pole face of the armature with a convex curvature is provided. Alternatively, the pole face of the Yoke curved be executed, wherein the curvature is advantageously have a concave shape whose Curvature less than that of the armature. The Embodiments may thus vary, each it is achieved that in case of wear of those parts of the armature, which stopping the movement in the direction of the yoke, the mutually facing surface portions of the armature and of him facing surface portion of the yoke extending in the second touch switch position or touching almost, not flat abut, but only along a Contact line. Thereby, the air gap on only one much smaller area than conventional embodiments Closed what functional limitations due to Residual magnetism or hum avoids. It is at a Workpiece geometry of the armature and yoke according to the invention even conceivable that these surface portions of the beginning touch, so that although during oftmaliger shifts may alter the line of contact, a reduction in the Air gap to an extent, the function of the Switching element affected, but much later than occurs in conventional switching elements. By curved design may also be a time-consuming Grinding of the relevant surface portions omitted since lower demands on the surface accuracy are set.

0008Claim 2 refers to a particular embodiment of the electromagnetic switching element, wherein the armature and the Yoke substantially E-shape with one central leg, the in the second switching position within the coil and in each case two side legs which lie outside the coil, are formed, in the second switching position, the Pole faces of the side legs touching. There are therefore the Pole faces of the side legs, which when current flows through stop coil movement of the armature towards the yoke and are most affected by the wear. According to Claim 2 it is provided that the pole faces of the Middle leg having a different curvature.

0009Claim 3 refers to the above-mentioned possibility, that the pole faces of the center leg in the second touch switch position. According to claim 3 therefore is this Configuration already during the operating period of the Switching element realized and is not only a consequence of Wear. This embodiment is conceivable, as a result of the different curvatures of the pole faces of the middle leg there still remains a sufficient air gap to A malfunctioning residual magnetism or hum to avoid. Claim 4 relates in contrast to an embodiment in which the pole faces of the Center leg approximately in the second switching position, touch.

0010Claim 5, an advantageous embodiment of the Of side legs before the armature and yoke, in which the Side legs of the armature and the yoke in each case with a be closed winding of an electrical conductor (Short ring) are fitted. Thus, in addition to Main field of the coil induces another magnetic field which the Force gaps in the current zero crossing partially compensated. Thereby, the ripple is reduced.

0011The invention will in the following with reference to the accompanying Drawings explained in more detail. show Here<sl><li>FIG. 1 is a contactor,</li><li>a partial cross section of the contactor of Fig. 1 taken along FIG. 2 a vertical center plane in the direction II for a Switching state of the contactor, in which the coil is not current is removed,</li><li>a partial cross section of the contactor of Fig. 1 taken along FIG. 3 a vertical center plane in the direction III of a Switching state of the contactor, in which the coil is not current is removed,</li><li>Fig. 4 shows a cross section of the contactor of Fig. 1 along a vertical center plane in the viewing direction III, the left Half a switching state of the switching element with open Main circuit corresponds to the right half has a Switching state of the switching element closed Main circuit, and</li><li>Fig. 5 is a view of the yoke and the armature.</li></sl>

0012Fig. 1 shows an electromagnetic switching element, in given case, a contactor, with connections 1a, 1b, 2a, 2b (The latter is not visible in Fig. 1) for the Control circuit. The connection of the current-carrying conductor of The control circuit may be about clamping screws 2 and Clamping plate 3 done. According to the embodiment of FIG. 1 are four ports 1a, 1b, 2a, 2b are provided, wherein only two terminals for the control circuit required are. Here is possible to either the two terminals 1a and 1b for the power supply of the coil 14 (Fig. 2 to 4) be used, or the two terminals 2a and 2b. Alternatively, it is also possible, one of the two Terminals 1a or 1b for the connection of a conductor provide and the diagonally opposite Terminal 2a or 2b for the connection of the second conductor. From the terminals 1a, 1b, 2a, 2b lead each electrically conductive connections to a coil 14, so that when closing the control circuit, the coil current flowing through the fourteenth The Opening and closing of the control circuit can be done manually via external buttons done, or even from their own controllers are made that are not shown in FIGS. 1 to 5 are.

0013The connection of the live conductors of the main circuit via the connection openings 4 (those on the opposite side of the contactor are in Fig. 1 does not visible). The switching element shown in Fig. 1 is about the connection of the three phases and the neutral conductor a three phase network. In openings 5 ​​can do this Clamping screws 6 (see also Fig. 4) are used, which cooperate with clamping plate 21 and the current-carrying Head of the main circuit fix. About retaining tabs 7 , the contactor will be attached to external support members (in Fig. 1 is not visible). In the main circuit is the Consumers, in general, an engine (in FIGS. 1 to 5 are not shown). It is also conceivable that the opening and Closing the control circuit from the operating state of the is motor dependent.

0014Fig. 2 shows a partial cross section of the contactor of Fig. 1 along a vertical central plane in the direction II and a partial cross section of the contactor of Fig. 1 taken along FIG. 3 a vertical center plane in the viewing direction III. shown in Fig. 2 an embodiment of a contactor, in which the anchor 8 and the yoke 9 is substantially E-shaped, each having two Side legs 8a, 9a, plus one middle leg 8b, 9b are formed. The armature 8 and the yoke 9 are usually as laminated cores from punched and mutually insulated Single sheets 20 formed to prevent eddy currents. The Laminated cores can about of plastic wrap be partially sheathed. The cohesion of the sheet stack but can also be done by riveting.

0015The center leg 9b of the yoke 9 is of the coil 14 surrounded, which is poured in about a plastic block. The side legs 8a of the armature 8 and 9a of the yoke 9 are outside the coil 14 surround the armature 8 and the yoke 9 Thus the coil 14. The side legs 8a, 9a of the armature 8 and the yoke 9 can here each with a self closed winding of an electrical conductor 19 (Short ring) be equipped. Thus, in addition to Main field of the coil induces another magnetic field which the Force gaps in the current zero crossing partially compensated. Thereby, the ripple is reduced.

0016Figs. 2 and 3 show the contactor in a first switching state, in which the coil 14 is not current is flowing through the armature and 8 is therefore spaced from the yoke. 9 If the coil 14 due a closed control circuit current flowing through it, so inducing a magnetic field whose magnetic flux in Inside the spool 14 is at its greatest and the center leg 8, 9 magnetized. The 8b in the two central limbs, 9b induced magnetic flux is divided into two Side legs 8a, 9a and causes different polarity at the opposite pole faces 10 and 11 of Center leg 8b and 9b and at the opposite Pole faces 12 and 13 of the side legs 8a and 9a. The armature 8 is consequently attracted to the yoke 9, until the pole faces 12 of the armature 8 to the opposite pole surfaces of the yoke 13 9 abut. This movement takes place against a restoring force, as a result of springs in the Fig. 1-5 are not shown. The contactor is thus in its second switching state in which the Pole faces 12 and 13 abut one another and the pole faces 10 and 11 of the central leg 8, 9 only slightly spaced.

0017These two switching states of the contactor are in Fig. 4 displayed simultaneously, with the left half a first Switching state of the switching element with open main circuit shows and the right half of a second switching state of the Switching element with a closed main circuit. The live conductor of the main circuit are represented by the Connection openings 4 and out using the clamping screws 6 and the clamping plate 21 is fixed. This are the electrical conductors to fixed contacts 15, with movable switch contacts 16 form contact bridges. The movable switch contacts 16 are in this case in a Support frame 17 is held with the support of the switching contacts 16 in the support frame 17 advantageously by springs 18 takes place. The support frame 17 is in turn fixed to the armature 8 connected (in Fig. 4 graphically not run). A Movement of the armature 8 therefore transfers over the Support frame 17 on the switching contacts 16th

0018If, for example, the control circuit is closed and the coil 14 thus current flowing through it, the armature 8 is attracted and Direction yoke 9 is moved until it is at in its respect Fig. 4 lower position, as second the Switch state according to the right half of FIG. 4 corresponds. The movable switching contacts 16 are characterized by a by springs 18 variable pressure on the fixed contacts 15 is pressed so that the contact bridge and thus the main circuit is closed. If the Control circuit interrupted, then the magnetic field is the Coil 14 and the yoke 9 and the armature 8 from. By means of a restoring force, as a result of in FIGS. 1 to 5 not shown springs, the armature 8 is returned to its brought in relation to FIG. 4, upper position, as the first switching state shown in the left half of FIG. 4 equivalent. The movable switching contacts 16 are characterized also upwards and the contact bridge is moved back opened so that the main circuit is interrupted.

0019After interrupting the control circuit and thus switching off the current through the coil 14 remains in the armature 8 and the yoke 9 in the magnetic circuit a residual magnetism. This state of affairs also referred to as remanence and can cause after interruption of the control circuit of the armature 8 to the yoke 9 adheres to are instead moved away from him. Therefore is also generally between pole faces 10 of the armature 8 and Pole faces 11 of the yoke 9, an air gap is provided, wherein the Air gap also acts reductively on the ripple. By Wear of the side legs 8a of the armature 8 and the Side arms 9a of the yoke 9, the air gap but over the operating life of the contactor can be reduced, and finally largely disappear. This usually occur Brumm and problems with the remanence. The wear of the Side legs 8a, 9a are thus the mechanical life the contactor before.

0020As is apparent from FIG. 2 and FIG. 5, the Pole faces 10 and 11 of the center leg 8, 9 according to the Invention each has a curvature. The pole face 11 of the Yoke 9 here is convex curved and has a greater Curvature than the concave curved pole face 10 of the armature 8. Even with a displacement of the armature 8 relative to the yoke 9 be a result of wear of the side legs 8 8a and 9a the pole faces 10 and 11 practically never touch completely, but always form an air gap. Apart from in the Fig. 1 to 5 shown design of the pole faces 10 and 11 other shapes are also conceivable, such as a can of Pole faces 10, 11 have no curvature and the second Pole surface may be curved correspondingly convex. these Configuration is "different, the formulation Curvatures of the pole faces 10 and 11, "Furthermore. FIG. 1 shows only one possible embodiment of a contactor, so could about the relative position of the contact apparatus with the Contacts 15, 16 and the magnetic drive can also be interchanged are, so that in contrast to the embodiment shown by is FIG. 1 of the contact system in the lower part of the contactor and the magnet drive the top of the contactor.

0021As mentioned, it is even conceivable, from the outset Contact of the two pole faces 10 and 11 of the middle leg 8b and 9b to allow, as the touch due to the rocker-like design of the pole faces 10 and 11 only can be carried out along lines of contact, but which do not sufficient residual magnetism due to adhesion of the Armature 8 to cause the yoke. 9 The Mechanical life the switch is thereby significantly extended. Furthermore , the production of the pole faces 10 and 11 with lower Accuracy done, in particular, the time-consuming Grinding process accounts. The setting of the air gap is Instead, by the punching precision for the individual sheets certainly.