CA1111902A - Ac type electromagnetic device - Google Patents

Abstract

Abstract of the Disclosure AC type electromagnetic device with simplified electromagnetic exciting coil circuit is provided. The coil for electromagnetically driving an armature comprises a first coil of a relatively larger winding number and excited during every half cycle of AC source current and a second coil of a relatively smaller winding number and wound in reverse direction to that of the first coil, so that the armature will be driven by a composite magnetic flux of both fluxes occurring every half cycles due to the first and second coils. For said excitation of the first coil, a single diode is connected in-series with the first coil with the second coil connected in parallel therewith, or in parallel with the first coil with the second coil connected in series therewith.

Description

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This invention relates to AC-type electromagnetic devices to be used, for example, for electromagnetic relays.
In such conventional AC-type electromagnetic devices, a full-wave rectifying curcuit or a rectifying circuit and smoothing condenser are required. United States Patent No. 3,968,406, Chauvin Arnoux, issued 6 July, 1976, is illustrative of such devices. In the known art, there have been disadvantages in that such electromagnetic devices are large and their manufacturing costs are high. The present invention overcomes these disadvantages, in part, by the use of two reversely wound coils, and requires a single diode (or other suitable rectifying means) instead of a full-wave rectifier.
According to the present invention, an AC-driven electromagnetic device comprising a permanent magnet, yokes, a movable armature and an electromagnetic coil for driving the armature are provided. High production costs and excessive size have been eliminated by substituting for the typical single electromagnetic coil surrounding the of armatuYe, ~ first exciting coil excited during every tw~
I_~ c~e half ~-clcs of the AC source current and a second exciting coil generating magnetic flux less than and opposite in phase to the magnetic flux generated by the first exciting coil. By employing a single diode associated with the coils, an effect equivalent to the case where the AC source is full-wave rectified can be achieved.
The present invention provides an AC-driven electromagnetic device which is significantly smaller in size than previous similar devices. This invention also provides an electromagnetic device which can be inexpensively manufactured. Other advantages of the present invention will be apparent from the following descriptions of its preferred embodiments.

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BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates a structure and circuitry arrangement oE a conventional AC type electromagnetic device;
Figure 2 is a diagram graphically illustrating the variation in magnetic flux generated in the device of Fig. l;
Figure 3 illustrates the structure and circuitry arrangement of the preferred embodiment of an AC type electromagnetic device according to the present invention; -~
Figure 4 is a circuit dragram of a preferred embodiment of the invention;
Figure 5 is a diagram showing the various magnetic fluxes generated in the device of Figure 3 and the relation-ship between said fluxes;
, Figures 6 to 9 are sequential views of the various operational positions of the device of Figure 3;
Figure 10 illustrates another embodiment of the present invention;
Figure 11 is a circuit diagram of the embodiment of Figure 10;
Figure 12 is a diagram showing the various magnetic fluxes generated in the embodiment of Figure 10 and the relationship between said fluxes; and Figure 13 is a perspective viaw showing a practical embodiment of the electromagnetic device of the present invention.

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~ DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
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` ~ Electromagnetic devices comparable to those of the present invention have conventionally been driven by a 30~ direct current source. In the case where an alternating ~ ~ current source is utilized, a full-wave rectifying ; ~device has conventionally been used. Figure 1 illustrates ~ ~ 3 ~

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a typical AC-driven electromagnetic device utilizing a full-wave rectifier, and Figure 2 illustrates the variations in magnetic flux intensity generated by such a device. As shown in Figure 1, yokes 2a and 2b are connected respectively to both polarized ends of a permanent magnet 1 and an armature

3 is rotatably arranged between the respective ends of the yokes 2a and 2b extended from the magnet 1. An electromagnetic coil 4 is provided around the armature 3, and the coil 4 is connected with an alternating current source 5 through a full-wave rectifying device 6 to drive the armature 3 with a rectified source power. Figure 2 diagramatically illustrates the half-wave magnetic flux pattern generated in relation to the AC source current and the magnetizing direction of the armature 3 when positioned as shown in Figure 1.
The present invention is directed to the AC-driven type of such electromagnetic device, and eliminates the requirement for a full-wave rectifier.
Referring to Fig. 3, an AC type electromagnetic device according to the present invention is illustrated showing a short upper yoke 12 and a long lower yoke 12 affixed respectively to each polarized end of a permanent magnet 11 so as to extend their ends 12a and 13b from the magnet.
A plate-shaped armature 14 is rQckably arranged between the extended end 12a of the short yoke 12 and the extended end 13b of the long yoke 13. Around this armature 14, there is provided a first exciting coil 15 and a second exciting coil 16 which are wound reversely to each other so as to generate magnetic fluxes of phases reverse to each other. A diode 17 is connscted in series with the first exciting coil 15. As shown in Fig. 4, the second exciting coil 16 is connected in parallel with the series circuit of the diode 17 and the first exciting coil 15. An alternating current source 18 is connected to both ends of the foregoing combined circuit.

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As illustrated, the number of windings of the first exciting coil 15 is preferably larger than that of the second exciting coil 16.
The operation of the electromagnetic device of the present invention is explained below.
As seen in Fig. 5 the intensities of the magnetic fluxes generated by the respective first and second exciting coils 15 and

- 4~ -~ 9~2 16 in relations to respective half cycles of the AC source current and magnetizing direction of the armaturs, the coils 15 and 16 wound around the armature 14 respectively in reverse direction to each other will cause the respective magnetic flux ~1 of the first coil 15 and the magnetic flux ~2 of the second coil 16 to be of phases reverse to each other and, as the number of windings of the first coil 15 is larger than that of the second coil 16, respective magnitude or amount of these magnetic fluxes will be ~ 2 Further, as the diode 17 is connected in series with the first coil 15, the magnetic flux ~1 generated by the first coil 15 ~~~ o~ ' c~c /e V will appear during every ~ half oy~c~, for example, during each odd numbered half cycles of the AC source as shown in Fig. 5, whereas the flux ~2 due to the second coil 16 which is directly connected to the source will appear during every half cycles but in rev~rse phase during, for example, each of~the odd num~ered half cycles with reqpect to the flux ~1- The flux ~2 in each of the odd numbered half cycles is, however, cancelled by the larger and reverse-phased flux ~1' so that the armature l4 is to be disposed eventually in a magnetic field of such a composite magne~c flux ~
as ~hown by the solid line in Fig. 5 ~hich will magnetize the armature iN the same d~rection during each half cycle of the AC source.
Referring more in detail to the operation of the device of Figs~ 3 and 4 with reference to Figs. 6 through 9, Fig 6 shows a state in which the respective coil~ 15 and 16 are not excited and the armature 14 iq being attracted at an end c to the extended end 12a of the yoke 12 magnetized by the N-pole of the magnet 11 and at the other end d to the extended end 13b of the yoke 13 m~gnetized by S-pole of the magne~ 11 in the present in~tance.

- 5 -When an electric current is fed to the first and second coils 15 and 16, the armature 14 will be excited by the composite magnetic flux ~of Fig. 5 and, if the armature 14 is ma~letized to have the N-pole at the end c in the state of Fig, 6,depending on flowing direction of the current through the respective coils, the armature 14 will be repulsed at the end c by the N-pole of the magnet 11 so as to shift to a state ~hown in Fig. 8 through an intermediate state shown in Fig, 7 of the armature 14 being separated at its N-polarized end c from the yoke end 12a. Incident~J
though the composite magnetic flux ~ fluctuates during, for example, each even numbered half cycle as seen in Fig. 5, the state of Fig. 8 of the armature 14 will be well retained.since magnetic resistance in the ~agnetic circuit formed with the armature 14 and yoke 13 i9 caused to be very small due to that the armature-is completely attracted to the yoke and, additionally, that the compo~ite flux ~ does not vary in the magnetizing direction.
Accordingly, the armature 14 will not vibrate at all on the yoke 13.
When the current flowing through the firct and second coils 15 and 16 is interrupted, the armature 14 is no longer excited by the coils but i9 subjected to the magnetic flux between the yoke 12 and the yoke 13, 90 that the armature 14 will be attracted at the end c by the extended end 12a of the yoke 12 while the other end d of the armature 14 will remain as attracted by the extended end 13b of the yoke 13, whereby the armAture L4 is returned through a state shown in Fig. 9 to the initial state of Fig. 6.
In Fig. lO, there is shown another embodiment of the : . ~
present invention, wherein a permanent magnet 21~ yokes 22 and 23, ~` an armature 24, a ~irst exciting cQil 25, a second exciting coil

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26 ancl an alternating current source 28 are arranged substantially in the same manner as in the case of Fig. 3, except that a diode 27 is connected in parallel with the first exciting coil 25, the seconci exciting coil 26 is connected in series with this parallel circuit and the alternating current source 28 is connected at both ends to the entire combined circuit of the coils and diode as seen best in Fig. 11 showing the arrangement of this embodiment in an equivalent circuit. The first coil 25 of the larger winding number and the second coil 26 of ~he smaller winding number are also wound respectively reversely to each other around the armature 24.
The magnetic fluxes generated by the two coils shall be explained with reference to Fig. 12. As the diode 27 is connected in parAllel with the first coil 25, the AC source current will flow through the first and second coils 25 and 26 during the half cycle A of the current reverse in the polarity to the direction of the diode 27 to generate the magnetic fluxes ~l and ~2. During the next half cy~le B of the current normal to the diode 27, the current will flow only through the diode 27 and the second coil 26 and no current will flow through the first coil 25. Accordlngly, th~ magnetic flux ~1 will belgenerated at intervals of a half cycle of the AC source current as shown in Fig. 12, whereas the magnetic flux ~2 will be generated in every half cycle. The phase of the flux ~2 during the cycles A in which the flux ~1 is generated is reverse to that of the magnetic flux ~1~ so that a composite magnetic flux ~ shown by the solid line in Fig. 12 will act on the anmature 24. As this composite magnetic flux ha~ the same tendency in the case of Fig. 5, the oper~tion of this electromagnetic 0,~

device is the same as of the'first embodiment, and detailed explanation shall be omitted here.
Referring to the amount of the magnetic flux ~ in this secomd embodiment, for example, when the ratio of the larger number of windings of the first coil 25 to that of the second coil 26 ~s made 3 : 1 and the resistance values of the both coils are made the same, the respective fluxes ~1 and ~2 during the half cycle denoted by A in Fig. 12 will have a relation of ~ 3 x ~j Since the composite magnetic flux ~ during this cycle will be of an amount ~ 2~ when the~above formula is substituted, ~ = 3~1 will be obtained.
During the next half cycle B, the current flow~ only through the second coil 26, as well a9 the diode 27, and the magnitude of the current is determined only by the resistance of the coil 26, ~o that the curren~ will b'e twice as large as in the case when the current i9 flowing through both the coils 25 and 26 ' . and ~ ~ 2 x ~2. Substituting the formula ~2 = 3~1~ then ~ = 23~1, Thus the amount of the generated composite magnetic flux ~ will be the same throughout the respective half cycles A and B, that is, the composite magnetic flux of 3~1 will be continuously generated in the same direction of magnetization of the armature and the armature will not be caused to vibrate at all -on the yoke 23.
In Fig. 13, there is shown an exemplary structure of a practical electromagnetic de~ice embodying the present invention, in which a coil frame 33 having a hollow inner chamber 32 is fixed to a lower yoke 31 acting also as a base plate, as fitted in a central aperture'of the yoke 31, a pair 34 of first and second coils ~re wound on the frame 33 in the ~anner described with reference - 8 ~

to the first or second embodiment, and the frame 33 is butted at an axial end against a side wall of a permanent magnet 35 placed on an end part of the lower yoke 31. An upper yoke 36 shorter than the lower yoke 31 is stacked on the permanent magnet 35 so as to extend its one end above the lower yoke 31 for a short distance.
A substantially T-shaped armature 37 is rockably inserted in the hollow chamber 32 of the coil fram~ 33 so as to engage both projecting parts 37a of the T-shape onto the other axial end of the coil frame 33. The other end of the armature 37 inserted in the coil frame is disposed at a posltion between the upper and lower yokes 36 and 31. 38 is a terminal base provided on the upper yoke 36 and external terminals 39 are provided on the terminal base 38.
40 is one of four internal terminals fitted to the terminal base 38 and connected to lead wires ~ both ends of the first and second coilg 41 i8 a diode, and 42 is a card for transmitting movements of the armature 37 to, for example, relay contacts (not shown) as driven by the armature 37 to open and close the contacts.
According to the present invention, as described above, the first and second exciting coils a~e wound reversely to each other around the armature and only one diode is used, so that the same operation as if exciting the armature with an electric current rectified with an all-wave rectifier using four diodes is obtained end a small and inexpensive AC type electrom&gnetic device can be produced.
It should be appreciated tha~, whlle ~he invention has been described with reference to the preferred em~odiments. applied to electromagnetic devices of polarized type, the invention should not be limited to such polarized~.~type devices but can be effectively - , _ g _ :' . ' ~, .

applied to all types of the electromagnetic devices adapted to the AC source~
While, further, the invention has been described in~
connection with the preferred embodiments shown, it should be und~rstood that intention is not to limit the invention to the particular embodiments but is to rather include all possible modification, alterations and equivalent arrangements within the scope of the appended claims.

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Claims (2)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An AC-driven electromagnetic device comprising:
a permanent magnet having opposite magnetic poles on longitudinally opposite surfaces thereon;
first and second yokes of different lengths and respectively disposed on each of the magnetic pole surfaces of said permanent magnet and extending in opposed parallel spaced relation to each other;
an armature pivotably disposed between said spaced first and second yokes and normally magnetically engaged at each end thereof to each of the opposing surfaces of the respective yokes; and an electromagnetic coil wound around said armature for causing the armature to pivot between the yokes when said coil is electromagnetically excited, said coil comprising a first exciting coil for generating magnetic flux during every other half cycle of an AC source current and a second exciting coil for continuously generating magnetic flux of lower magnitude than, and opposite phase from, the flux generated by said first exciting coil.

2. In an AC-driven electromagnetic relay construction, the combination comprising:
a permanent magnet of generally rectangular shape and having opposite magnetic poles on longitudinally opposite surfaces thereon;
- Page one of Claims -a first yoke being flat and having a central opening bounded by first and second ends, said first yoke being engaged at its first end to one of the opposite surfaces of said permanent magnet;
a second yoke being flat and shorter than the first yoke, said second yoke being engaged at its first end to the other of the opposite surfaces of the magnet and extending in the same direction as, and parallel to the first yoke;
a flat elongated armature spanning said central opening of the first yoke and normally magnetically engaged at its first end to said second yoke near the other end of said second yoke and at its other end to said first yoke near the other end of said first yoke;
a relay coil surrounding the intermediate body of said armature and fitting into the central opening so that when a current passes through said coil, setting up magnetic flux in the armature in a direction opposite to the flux induced by the permanent magnet, the armature will pivot at its first end and within the coil from the other end of the second yoke to a point on said first yoke intermediate its ends, said relay coil including a first exciting coil for generating magnetic flux during every other half cycle of an AC source current and a second exciting coil having a fewer number of turns than, and wound in the opposite direction from, said first exciting coil for continuously generating magnetic flux of lower magnitude than, and opposite phase from, the flux generated by said first exciting coil; and a contact relay assembly including stationary and movable contactors disposed substantially on the second yoke, said movable contactor being operatively coupled to the first end of the armature.
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