US3838370A

US3838370A - Solenoid magnet

Info

Publication number: US3838370A
Application number: US00393041A
Authority: US
Inventors: T Ueno; Y Konakawa
Original assignee: AKUTO GIKEN KK
Current assignee: AKUTO GIKEN KK
Priority date: 1972-09-02
Filing date: 1973-08-30
Publication date: 1974-09-24
Anticipated expiration: 1991-09-24
Also published as: JPS4943155A

Abstract

The armature of an electromagnet moves axially in two coaxial, annular pole pieces axially separated by the coil of the magnet when the coil is energized. In another electromagnet, radially projecting pole pieces of a rotor may be aligned simultaneously with corresponding pole pieces equiangularly spaced on the stator against the restraint of a return spring when the stator pole pieces are excited by an energized coil.

Description

United States Patent 1191 Ueno et al. Sept. 24, 1974 SOLENOID MAGNET 2,575,153 11/1951 Wightman 310/261 x 3,119,940 1/1964 Pettit et al. [75] Inventors Km'akawar 3,221,191 11/1965 Cuches et al. 335/279 x both of Tokyo, Japan [73] Assignee: Kabushiki Kaisha Akuto Giken,

Tokyo, Japan Primary ExaminerG. Harris [22] Filed: g 30 1973 Attorney, Agent, or F1rmHans Berman [21] Appl. No.: 393,041

30 Foreign Application Priority Data 1571 ABSTRACT Sept. 2, 1972 Japan 47-88147 The armature of an electromagnet moves axially in [52] US. Cl 335/255, 335/272, 310/259, two x nn r pole pie es axially separated by 310/269 the coil of the magnet when the coil is energized. In [51] Int. Cl. H01t 7/08 another electromagnetr radially p j g po e p e es [58] Field of Search 335/255, 272, 279; of a rotor may be aligned Simultaneously with corre- 310/254, 258, 262, 269, 259, 261 sponding pole pieces equiangularly spaced on the stator against the restraint of a return spring when the [56] References Cited stator pole pieces are excited by an energized coil.

UNITED STATES PATENTS 2,560,560 7/1951 Doherty 310/259 10 Claims, 15 Drawing Figures PAIEMEB EPMM memo SHEEF 1 My I? /4d 14 Megnefic aifracfive force Magnefic affraciive force SOLENOID MAGNET This invention relates to electromagnetic driving apparatus, and particularly to apparatus in which a force of attraction is exerted on an armature when a core is excited by current flowing in a coil.

In conventional electromagnetic devices in which an armature moves linearily toward and away from a core, the force of attraction is smallest initially when the ar mature is farthest from the core and greatest when the armature is nearest the core at the end of its movement. If the attracted armature abuttingly engages the core, damage to both elements may occur in continued use.

In known devices, in which the armature rotates within an enveloping stator toward a position in which radially projecting pole pieces of the stator and rotor are aligned, the initial force of attraction exerted on the armature is not as weak as in the first-described device, but greater initial torque than is available in the known devices would be desirable.

It is an important object of this invention to provide electromagnetic driving apparatus of the general type described in which the driving component of the magnetic force of attraction is high initially and decreases almost to zero as the armature reaches the end of its stroke.

Other features, objects, and advantages of this invention will appear more fully from the following description when considered in connection with the appended drawing in which:

FIG. 1(A) shows a known electromagnet arrangement in section;

FIG. 1(B) graphically illustrates the relationship between the linear displacement of the armature and the driving magnetic force exerted on the same in the apparatus of FIG. 1(A);

FIG. 2 shows an electromagnet arrangement of the invention in side elevation and partly in section;

FIG. 3 is a fragmentary view of another electromagnet arrangement according to the invention;

FIG. 4 shows the relationship of armature displacement and magnetic foce in the apparatus of FIG. 3 and FIG. 9 in the manner of FIG. 1(8);

FIG. 5(A) illustrates the stator frame of a rotary magnet arrangement of the invention in section on its axis;

FIG. 5(B) shows the device of FIG. 5(A) in section on the line 5-5;

FIG. 5(C) shows the stator frame of FIG. 5(A) assembled with the associated rotor and exciting coil in a corresponding view;

FIG. 6(A) illustrates the rotor of the apparatus of FIG. 5(C);

FIG. 6(B) shows the same rotor in a view corresponding to FIG. 5(B);

FIG. 7(A) shows the coil of the apparatus of FIG. 5(C) partly in elevation and partly in axial section;

FIG. 7(B) is aplan view of the coil of FIG. 7(A);

FIG. 8 shows a modified stator and the associated rotor in a view corresponding to that of FIG. 5(C);

FIG. 9 is a perspective view of a modified rotor; and

FIG. 10 is a perspective, exploded view of the apparatus of FIG. 5(C).

The known magnet arrangement shown in FIG. l(A) has a rod-shaped armature l0 coaxially movable in a cylindrical coil 12. The coil is enveloped by a unitary, cup-shaped frame 14 of magnetic material. When the coil 12 is energized, a cylindrical wall portion 14a and a radial end wall of the frame 14 provide a yoke connecting an annular flange 14b constituting one pole piece of the electromagnet and another pole piece Me which projects centrally from the end wall 140 and is formed with a recess 14d shaped to receive one end of the armature rod III.

The attracted armature I0 strikes the pole piece Me.

As is shown in FIG. 1(8), the force of attraction acting in the direction of movement on the armature 10 in the initial position of FIG. 1(A) is at its minimum value and increases until the armature strikes the pole piece l4e. During extended use of the known device, the engagement faces of the armature l0 and of the pole piece l4e are worn and deformed. They may become heated sufficiently to make the device inoperative.

The improved electromagnet arrangement of the invention shown in FIG. 2 avoids this shortcoming.

The frame of the arrangement is formed by a cylindrical, tubular casing 20 of magnetizable material.

Brackets

22, 24 of non-magnetic material project radially inward from the axial ends of the casing 20. Two axially spaced, annular pole pieces 26, 28 are coaxially fastened to the inner face of the casing 20.

A coil 32 is wound on a cylindrical carrier tube 30 of non-magnetic material between radial flanges 30a, 30b. The inner diameter of the tube 30 is slightly smaller than the corresponding dimension of the pole pieces 26, 28 which are separated by the coil 32 and the tube 30. An armature 34 passes coaxially through the casing 20, through central apertures in the pole pieces 26, 28 and in the coil 32. It is mounted on non-illustrated bearings for axial movement. It consists of a rod 36 carrying two

annular bodies

38, 40 of magnetizable material arranged and dimensioned to be received simultaneously in the central openings of the pole pieces 26, 28 when the coil 32 is energized, as shown in FIG. 2. Only the portion of the rod 36 between the

annular bodies

38, 40 consists of or is coated with magnetizable material. A helical compression spring 42 wound about the rod 36 between the body 40 and the bracket 24 returns the armature to the rest position partly indicated in broken lines when the coil 12 is deenergized.

The magnetic force of attraction axially exerted on the armature 34 is at its maximum in the rest postion and decreases as the armature approaches the position shown in FIG. 2.

The rotary electromagnet arrangement of the invention shown in FIG. 3 has a generally cylindrical, tubular stator frame 44 of magnetizable material from whose inner face four equiangularly spaced integral pole pieces 46a 46d project radially. A generally cylindrical rotor 48 of magnetizable material is coaxially arranged in the frame 44 and carries four integral pole pieces 50a 50d projecting radially outward and simultaneously alignable with the pole pieces of the frame 44 by angular displacement of the rotor 48. The frame 44 carries a non-illustrated coil for exciting the pole pieces 46a 46d, as will presently become apparent.

The rotor 48 is biased toward the illustrated position by a non-illustrated return spring and turns clockwise, as viewed in FIG. 3, through an angle 01 from the position indicated by a broken line F to a position indicated by a broken line P in which the pole pieces 50a 50d are radially aligned with the pole pieces 46a 46d, whereupon the rotor stops.

When the angle a" is smaller than the complementary angle B, the rotor 48 is turned clockwise when the stator is excited. When the angle 01 is greater than the angle B, the rotor is turned counterclockwise.

When constant current flows through the nonillustrated coil of the stator, the circumferential distance between associated pole pieces of the stator and rotor decreases during angular movement of the rotor 48. As indicated by the line a in FIG. 4, the circumferential component of the magnetic force exerted on the rotor which causes rotation of the rotor has its maximum value in the illustrated rest postiion and becomes zero when the pole pieces of the stator and rotor are aligned in the final position.

FIGS. 5(A) to 7(B) and FIG. 10 illustrate an actual embodiment of the rotary electromagnet arrangement shown in FIG. 3. Referring initially to FIGS. 5(A) to 5(C), there is seen a stator 52 consisting of two identical unitary frame bodies 54 of magnetizable material arranged symmetrically relative to the radial plane 5 5 in FIG. 5(A). Each body 54 has an outer, circumferential, cylindrical wall portion 56 axially engaging the corresponding wall portion of the other body and an annular, radial end wall portion 60 axially remote from the other body 54. Six pole pieces 58a 58fare equiangularly distributed about a central aperture 62 in the end wall portion 60. As is best seen in FIG. 10, the pole pieces are circumferentially spaced fragments of a cylindrical tube 64 and axially project from each radial end wall portion 60 toward axially aligned pole pieces on the other wall portion 60, but are axially shorter than the wall portions 56. v

The bodies 54 jointly bound an annular cavity S in which a coil 70 is received. A rotor 66 is journaled in two bearing plates 72 fitted in the openings 62. The axial gap d, between the adjacent ends of aligned pairs of pole pieces of the bodies 54 is greater than the radial gap d between the cylindrical surface p defined by the inner circumferential faces of the pole pieces 58a 58f and the corresponding opposite surface q of the rotor 66. Axially adjacent the gaps 64a 64f which circumferentially separate the pole pieces, the thickness d of the end wall portion 60 is much smaller than its thickness d between the pole pieces and the cylindrical wall portion 56. The magnetic fluxfproduced by the energized coil 70 thus flows almost entirely in the magnetic circuit indicated in FIG. 5(C) by a broken line from the stator 52 across the gap d into the rotor 66 and back through the gap (1, into the stator.

As best seen in FIGS. 7(A) and 7(8), the coil 70 has an excitation winding 73 on a flanged tube 74 of insulating material. It is fastened in the cavity S in a conventional manner not specifically illustrated.

The rotor 66 is shown in FIGS. 6(A) and 6(8). It has six axially elongated pole pieces 68a to 68fradially projecting from an integral, cylindrical body portion 69 of magnetizable material, and are equiangularly spaced for simultaneous radial alignment with the pole pieces of the stator 52. Each pole piece on the rotor is axially coextensive with two aligned pole pieces of the stator. The body portion 69 is mounted on a shaft 67.

In the modified electromagnet arrangement shown in FIG. 8, the rotor 66 is identical with that described above, and the stator has two identical frame units 78 which differ from those of the afore-described embodiment by pole pieces 80 having obliquely inclined faces 82 which radially bound the cavity S for the nonillustrated exciting coil. The pole pieces 80 thus taper in an axial direction toward each other. This further reduces leakage of magnetic fiux between axially aligned pole pieces, provides space for more excitation windings, and facilitates the removal of the units 78 from a mold if they are made by molding.

In the modified rotor 88 shown in FIG. 9, the pole pieces 90 are axially elongated and equiangularly distributed about the circumference of the rotor body, as described above, but the length W2 of the leading axial edge is smaller than the length w of the trailing axial edge so that each pole piece tapers circumferentially. As is shown by broken line b in FIG. 4, this modification delays the decrease of the torque exerted on the rotor as it moves from its rest position to a final position of alignment of the pole pieces on the rotor and stator.

Only preferred embodiment of the electromagnet arrangement of the invention have been described. Modifications will be apparent to those skilled in the art in the light of the above teachings, and it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purpose of the disclosure which do not depart from the spirit and scope of the appended claims. What is claimed is: I. A magnet arrangement comprising: a. a casing of magnetizable material; b. two annular pole pieces having respective, coaxial, central openings, said pole pieces being mounted on said casing in axially spaced relationship; c. an annular coil having an excitation winding about said axis, said coil being axially interposed between said pole pieces and having a central opening axially aligned with the openings of said pole pieces; and d. an armature axially slidable in the aligned openings of said pole pieces and said coil, said armature including 1. two bodies of magnetizable material dimensioned and arranged to be received simultaneously in the central openings of said pole pieces when said winding is energized, and

2. a rod member axially connecting said bodies, a portion of said rod member intermediate said bodies consisting of magnetizable material.

2. An arrangement as set forth in claim 1, wherein said casing is tubular, said pole pieces being mounted on the inner wall of said casing.

3. A magnet arrangement comprising:

a. a stator including 1. An annular frame of magnetizable material, said frame having an axis, two axially spaced, radially extending end walls, and an outer circumferential wall connecting said end walls, said end walls being formed with respective central openings,

2. a plurality of pole pieces of magnetizable material circumferentially spaced about the central opening of each of said end walls and extending from the associated end wall toward a pole piece on the other end wall, the pole pieces on one end wall being axially spaced from the pole pieces on the other end wall, said walls and said pole pieces jointly bounding an annular cavity, and

3. a coil having excitation windings in said cavity;

and

b. a rotor mounted for rotation about said axis, said rotor including 1. a body portion of magnetizable material and 2. a plurality of pole pieces of said material radially projecting from said body portion in circumferentially spaced relationship for simultaneous radial alignment with the pole pieces on said end walls.

4. An arrangement as set forth in claim 3, wherein said frame consists essentially of two substantially identical bodies, each body including one of said end walls and an axial portion of said circumferential wall, the

pole pieces on the end wall of each body being axially 5 aligned with the pole pieces on the other body and equiangularly spaced about said axis.

5. An arrangement as set forth in claim 4, wherein said pole pieces of said rotor are axially coextensive with the pole pieces on both end walls.

6. An arrangement as set forth in claim 3, wherein the axial spacing of the pole pieces on each end wall from the pole pieces on the other end wall is greater than the radial spacing of the pole pieces of said rotor from the pole pieces of said stator during said simultaneous radial alignment.

7. An arrangement as set forth in claim 3, wherein the pole pieces on said end walls have respective faces opposite said circumferential wall, said faces bounding said cavity and being obliquely inclined relative to said axis, and each of the pole pieces on said end walls tapers axially away from the associated end wall.

8. An arrangement as set forth in claim 3, wherein the pole pieces of said rotor are each axially elongated and taper circumferentially.

9. A frame for a magnet arrangement comprising two substantially identical, approximately cup-shaped bodies of magnetizable material having a common axis and being axially juxtaposed in abutting engagement along a plane of symmetry radial relative to said axis, each body including a. an outer circumferential wall portion axially engaging the corresponding wall portion of the other body.

b. a radially extending wall portion axially remote from the other body and formed with a central aperture, and

c. a plurality of pole pieces projecting axially from said end wall toward the pole pieces on the end wall of the other body,

1. said pole pieces being circumferentially spaced about said central aperture,

2. each pole piece being axially aligned with a pole piece on the other end wall and axially spaced from the axially aligned pole piece.

10. A frame as set forth in claim 9, wherein said pole pieces are equiangularly spaced about the central aperture of the associated end plate.

Claims

1. A magnet arrangement comprising: a. a casing of magnetizable material; b. two annular pole pieces having respective, coaxial, central openings, said pole pieces being mounted on said casing in axially spaced relationship; c. an annular coil having an excitation winding about said axis, said coil being axially interposed between said pole pieces and having a central opening axially aligned with the openings of said pole pieces; and d. an armature axially slidable in the aligned openings of said pole pieces and said coil, said armature including 1. two bodies of magnetizable material dimensioned and arranged to be received simultaneously in the central openings of said pole pieces when said winding is energized, and 2. a rod member axially connecting said bodies, a portion of said rod member intermediate said bodies consisting of magnetizable material.

2. a plurality of pole pieces of said material radially projecting from said body portion in circumferentially spaced relationship for simultaneous radial alignment with the pole pieces on said end walls.

3. a coil having excitation windings in said cavity; and b. a rotor mounted for rotation about said axis, said rotor including

3. A magnet arrangement comprising: a. a stator including

4. An arrangement as set forth in claim 3, wherein said frame consists essentially of two substantially identical bodies, each body including one of said end walls and an axial portion of said circumferential wall, the pole pieces on the end wall of each body being axially aligned with the pole pieces on the other body and equiangularly spaced about said axis.

9. A frame for a magnet arrangement comprising two substantially identical, approximately cup-shaped bodies of magnetizable material having a common axis and being axially juxtaposed in abutting engagement along a plane of symmetry radial relative to said axis, each body including a. an outer circumferential wall portion axially engaging the corresponding wall portion of the other body. b. a radially extending wall portion axially remote from the other body and formed with a central aperture, and c. a plurality of pole pieces projecting axially from said end wall toward the pole pieces on the end wall of the other body,