AN ELECTROMAGNET

Abstract: The present invention provides an improvement for noise suppression, in an electromagnet constructed of the parts including a yoke, a fixed iron core (2) fixed relative to the yoke, a movable iron core (4) capable of being attracted toward and coming apart from the fixed iron core and a coiled wire wound around the magnetic path formed of the yoke, fixed iron core and movable iron core which serves to attract the movable iron core toward the fixed iron core by means of the magnetic flux induced by passing an electric current therethrough, which comprises dividing either one of the fixed iron core and the movable iron core into a body member (2b) and an end-surface member (2a), at which the fixed and movable iron cores are contacted with each other, providing an elastic insert member (6) between the body member and the end-surface member of the iron core in such a manner as not to interrupt the path of the magnetic flux and, optionally, providing a spring means which urges a stem supporting the end-surface member in such a manner that the end-surface member is pressed against the elastic insert member with a predentermined pressure.

Description: BACKGROUND OF THE INVENTION The present invention relates to an electromagnet or, more particularly, to an electromagnet which is characterized by the greatly decreased noise when the movable iron core hits the fixed iron core by being attracted thereby and by the uniformity of the ampere-turns required for holding the movable iron core attracted on the fixed iron core. A conventional electromagnet is known by JP-A-59-181003. As is illustrated in Figure 9 of the accompanying drawing, the conventional electromagnet is typically constructed of the parts including a yoke 1, a fixed iron core 2 fixed relative to the yoke 1, a movable iron core 4 which is attracted by and coming apart from the fixed iron core 2 and a coiled wire 3 wound around the magnetic path formed of the yoke 1, fixed iron core 2 and movable iron core 4 which serves to attract the movable iron core 4 toward the fixed iron core 2 by means of the magnetic flux 5 induced by passing an electric current therethrough. When the coil 3 is energized and movable iron core 4 is attracted toward and hits the fixed iron core 2, a sharp noise is unavoidably caused more or less by the bumping of the two metal-made parts. This noise generation can sometimes be a serious problem, especially, when the electromagnet is built in a household electric appliance. A conventional measure undertaken to reduce the noise generation in the electromagnet is to provide a covering member 6 made of an elastic material such as rubbers and plastics on the end surface 2a of the fixed iron core 2 or on the end surface 4a of the movable iron core 4. Such an electromagnet having an elastic covering member 6 on the end surface of the fixed iron core 2 or movable iron core 4 has several problems. For example, the elastic covering member 6 made of a non-magnetic material such as rubbers is provided across the path of the magnetic flux 5 so that the permeance is decreased consequently resulting in a decrease of the attracting force. Since the elastic covering member 6 is repeatedly bumped directly by the fixed iron core 2 or movable iron core 4 made of a magnetic material, the elastic covering member 6 is unavoidably worn out in the long run which produces dust so that the attracting behavior of the electromagnet is degraded with a decrease in the serviceable life of the electromagnet. Moreover, the noise-suppressing effect and the value of ampere-turn required for obtaining a desired attracting force are not always reproducible when a large number of electromagnets are mass-produced. SUMMARY OF THE INVENTION The present invention accordingly has the object to provide an electromagnet in which the above described problems and disadvantages in the prior art electromagnets have been solved. Namely, the present invention has the object to provide an electromagnet having good characteristics relative to the attracting force and a long serviceable life with greatly decreased noise generation by bumping of the fixed and movable iron cores along with uniform reproducibility of the noise-suppressing effect and the value of ampere-turns required for obtaining a desired attracting force. The electromagnet comprises a yoke, a fixed iron core fixed relative to the yoke, a movable iron core capable of being attracted toward and coming apart from the fixed iron core; and a coiled wire wound around the magnetic path formed of the yoke, fixed iron core and movable iron core for attracting the movable iron core toward the fixed iron core by means of the magnetic flux induced by passing an electric current through the coiled wire. According to the present invention, either one of the fixed iron core and the movable iron core is divided into a body member and an end-surface member, at which the fixed and movable iron cores are contacted with each other when the movable iron core is attracted toward the fixed iron core, and is provided with at least an elastic insert member between the body member and the end-surface member of the iron core in such a manner as not to interrupt the magnetic flux along the magnetic path and not to cause any adverse influences on the magnetically attacking behaviour of the electromagnet. Advantageously, the divided iron core is provided with a stem which supports the end-surface member and with a spring means to urge the stem for pressing the end-surface member against the elastic insert member with a predetermined pressure. BRIEF DESCRIPTION OF THE DRAWINGS Figures 1(a) and 1(b) are each a partial cross sectional view of an electromagnet as a first embodiment of the invention and Figure 1(c) is a plan view of a part used therein. Figures 2(a) and 2(b) are each a partial cross sectional view of an electromagnet as a second embodiment of the invention. Figures 3(a) and 3(b) are each a partial cross sectional view of an electromagnet as a third embodiment of the invention. Figures 4(a) and 4(b) are each a partial cross sectional view of an electromagnet as a fourth embodiment of the invention and Figure 4(c) is a cross sectional view of the same as cut and viewed along the arrows E-E in Figure 4(a). Figure 5 is a partial cross sectional view of an electromagnet as a fifth embodiment of the invention. Figures 6(a) and 6(b) are each a partial cross sectional view of an electromagnet as a sixth embodiment of the invention and Figure 7 is a partial cross sectional view of the same as cut and viewed along the arrows F-F in Figure 6(a). Figures 8(a) and 8(b) are each a partial cross sectional view of an electromagnet as a seventh embodiment of the invention. Figure 9 is a cross sectional view of a conventional electromagnet in the prior art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As is described above, the most characteristic feature of the inventive improvement is that, in an electromagnet, either one of the fixed iron core and the movable iron core is divided into a body member and an end-surface member to which the other iron core is magnetically attracted and an elastic insert member is provided between the body member and the end-surface member in such a manner that the magnetic flux induced by means of the coiled wire is not interrupted not to cause any adverse influences on the magnetically attracting behavior of the electromagnet. Different from conventional electromagnets in which an elastic member is bonded to the end surface of an iron core, the elastic insert member according to the invention is free from direct bumping of the iron core so that the electromagnet is imparted with a greatly extended serviceable life which otherwise is limited by the degradation of the elastic member as a result of the repeated bumping of the iron core. Another advantage obtained by the inventive improvement is that, when the fixed and movable iron cores are held together in contact after completion of attraction of the movable iron core toward the fixed iron core, a constant-current working performance can be exhibited with a rating magnetization ampereturn or less because the adverse effect due to the variation or unevenness in the dimensions of the contacting surfaces can be absorbed by the contraction and expansion of the elastic member so that the variation in the magnetization ampere-turn required for attraction or attracting force is minimized. Furthermore, the end-surface member is pressed against the body member of the iron core always with a constant pressing force by a spring means so that the vibration of the elastic member caused by bumping of the iron core can be attenuated uniformly and rapidly, when a large number of the electromagnets are manufactured in a mass-production system. In addition, the reproducibility and reliability of the products relative to the uniform requirement for the value of ampere-turn and the noise suppressing effect can be greatly improved due to the minimized variation in the contacting condition of the fixed and movable iron cores unavoidable as a consequence of the dimensional errors of the individual parts as fabricated. In the following, the improvement according to the present invention is described in detail with reference to the accompanying drawing. Figures 1(a) and 1(b) illustrate an electromagnet according to a first embodiment of the improvement, of which Figure 1(a) is a partial cross sectional view of the same as cut and viewed along the arrows A-A in Figure 1(b). The iron cores illustrated in these figures are the same in the structure as those of the conventional electromagnet illustrated in Figure 9 excepting for the following. Namely, the fixed iron core 2 is divided into the end-surface member 2a which is contacted by the movable iron core 4 and the body member 2b connected to the yoke 1. Further, an elastic member 6 is inserted between the end-surface member 2a and the body member 2b in such a disposition that it is not across the magnetic flux 5. The end-surface member 2a and the body member 2b are joined together by means of a clip 7 illustrated in Figure 1(c). Figures 2(a) and 2(b) illustrate a second embodiment according to the invention, of which Figure 2(a) is a partial cross sectional view of the iron core as cut and viewed along the arrows B-B in Figure 2(b). Separate elastic insert members 6 are provided between the end-surface member 2a and the body member 2b. Figures 3(a) and 3(b) illustrate a third embodiment according to the invention, of which Figure 3(a) is a partial cross sectional view of the iron cores as cut and viewed along the arrows C-C in Figure 3(b). Separate elastic insert members 6 are provided between the end-surface member 2a and the body member 2b while the end-surface member 2a is constructed of a ring-like member 2e and a core member 2f adhesively bonded together and the body member 2b is constructed of a ring-like member 2h and a base member 2g adhesively bonded together, the end-surface member 2a and the body member 2b being joined together engagedly. It is of course optional that, instead of dividing the fixed iron core 2 into the end-surface member 2a and the body member 2b as in the above described first to third embodiments, the movable iron core 4 is divided into an end-surface member and a body member with an elastic insert member intervening therebetween. Figure 4(a) illustrates an axial cross sectional view of iron cores as a fourth embodiment according to the invention. Figure 4(b) is a cross sectional view of the fixed iron core 2 as cut and viewed along the arrows D-D in Figure 4(a). Figure 4(c) illustrates the movable iron core 4 in Figure 4(a) as viewed along the arrows E-E in Figure 4(a). The fixed iron core 2 has a recess to face the movable iron core 4 which has a conically shaped end portion 4a which fits the recess in the fixed iron core when the movable iron core 4 is attracted to the fixed iron core 2. The end-surface member 2a is joined to the body member 2b by means of a screw 8 with the elastic insert member 6 located therebetween. In the iron core illustrated in Figure 5 as a fifth embodiment of the invention by an axial cross sectional view, the end-surface member 2a is joined to the conically shaped end portion 4a of the movable iron core 4 by means of a screw 8 with the elastic insert member 6 located therebetween to fit the recess in the end portion of the fixed iron core 2 when the movable iron core 4 is attracted to the fixed iron core 2 instead of dividing the fixed iron core 2 illustrated in Figure 4 into an end-surface member and a body member. Figures 6(a) and 6(b) each illustrate a partial cross sectional view of an iron core as a sixth embodiment according to the present invention and Figure 7 illustrates an axial view of the same fixed iron core as viewed along the arrows F-F in Figure 6(a). The fixed iron core 2 is divided into an end-surface member 2a at which the movable iron core 4 is contacted with the fixed iron core 2 and a body member 2b and an elastic insert member 6 is provided between the end-surface member 2a and the body member 2b in such a manner as not to interrupt the magnetic flux along the magnetic path. The end-surface member 2a of the fixed iron core 2 made of a magnetic material is brought into contact with the end surface 4b of the movable iron core 4. The end-surface member 2a is held by a stem 11 which penetrates a hole 2c provided along the axis of the body member 2b and is fixed to the body member 2b by means of a screw 12 and a washer 13 at the end remote from the end-surface member 2a. A coil spring 14 surrounding the stem 11 is provided between the washer 13 and the body member 2b in such a manner that the end-surface member 2a is always pressed against the elastic insert member 6 by way of the elastic resilience of the spring 14. The elastic resilience of the coil spring 14, with which the end-surface member 2a is pressed against the elastic insert member 6, can be controlled as desired by adequately driving the screw 12 into or out of the female screw in the stem 11. Figure 6(a) illustrates the fixed iron core 2 and the movable iron core 4 apart from each other with the electromagnet in an unenergized condition. Figure 6(b) illustrates the fixed and movable iron cores 2, 4 in contact with each other by means of the magnetic flux 5 generated when the electromagnet is energized. Figures 8(a) and 8(b) each illustrate a partial cross sectional view of an iron core as a seventh embodiment according to the present invention. Different from the embodiment illustrated in Figure 6, the movable iron core 4 in these figures is divided into an end-surface member 2a and a body member 2b.

Claims: Electromagnet comprising a yoke (1), a fixed iron core (2) fixed relative to the yoke, a movable iron core (4) capable of being attracted toward and coming apart from the fixed iron core, and a coiled wire (3) wound around the magnetic path formed of the yoke, fixed iron core and movable iron core for attracting the movable iron core toward the fixed iron core by means of the magnetic flux (5) induced by passing an electric current through the coiled wire, characterized in that either one of the fixed iron core and the movable iron core is divided into a body member (2b, 4) and an end-surface member (2a) at which the fixed and movable iron cores are contacted with each other, and is provided with at least an elastic insert member (6) between the body member and the end-surface member in such a manner as not to interrupt the magnetic flux along the magnetic path and not to cause any adverse influences on the magnetically attracting behaviour of the electromagnet. Electromagnet according to claim 1, characterized in that the divided iron core is provided with a spring means (14) which urges a stem (11) supporting the end-surface member (2a) for pressing the end-surface member against the elastic insert member (6) with a predetermined pressure. Electromagnet according to claim 1, characterized that the body member (2b) is constructed of a ring-like member (2h) and a base member (2g) adhesively bonded together, and in that the end-surface member (2a) is constructed of a ring like member (2e) and a core member (2f) adhesively bonded together. Electromagnet according any of the preceding claims, characterized in that the elastic insert member (6) is made of a non-magnetic material.

Inventors: ANDOH, YUICHI C/O KYUSYU OFFICE, IIO, KENJI C/O KYUSYU OFFICE, UETSUHARA, TOKIO
Applicants: MITSUBISHI MINING & CEMENT CO., LTD., OSAKA GAS CO., LTD
Application year: 1988
Main classification: H01F7
IPC codes: H01F7