Electromagnetic Relay

Abstract

Electromagnetic relay having a balancing spring for the armature and engaged between an end of the armature and a stationary part of the electromagnetic device so that as the armature is attracted toward the core of electromagnetic device the force of said balancing spring will be reduced and entire spring load characteristic will be kept small. This invention relates to electromagnetic relays. As a balancing spring for a conventional electromagnetic relay has been used to have a gradient in the direction of increasing the elasticity of the balancing spring as the armature is attracted, it has been necessary to increase the electromagnetic attraction that much and to necessarily enlarge the electromagnetic device. Therefore, it has been difficult to make the electromagnetic relay small. According to the present invention, a balancing spring is used to have a gradient reverse to that of a conventional one so that the electromagnet may be small and therefore the problem of making the entire structure of the electromagnetic relay small may be solved. A main object of the present invention is to make a magnetic relay small by using a balancing spring so as to have a gradient reverse to that of a conventional one. Another object of the present invention is to simply and cheaply provide an electromagnetic relay wherein the balancing spring characteristic can be regulated. A further object of the present invention is to provide an electromagnetic relay wherein the chattering of contacts is reduced by reducing the energy of the total spring loads. Another object of the present invention is to provide an electromagnetic relay which having a high sensitivity. A further object of the present invention is to provide a small electromagnetic relay by contriving the shape and incorporating structure of a balancing spring.

Description

The present invention shall be explained in the following with reference to the drawings, in which:

FIG. 1 is a sectional view of an electromagnetic relay of the present invention;

FIG. 2 is a disassembled perspective view;

FIG. 3 is a perspective view with the case, contact spring assembly, base and card removed;

FIG. 4 is an explanatory view showing a balancing spring as engaged;

FIG. 5 is a characteristic view of the spring system;

FIG. 6 is a perspective view showing the shape of a balancing spring;

FIG. 7 is an explanatory view of the balancing spring as the engaging position is varied.

In FIG. 1 showing a sectioned view of a relay of the present invention, 1 is a yoke, 2 is an iron core fixed to the above mentioned yoke, 3 is a coil bobbin arranged around the core 2, 4, is a coil wound on the above mentioned coil bobbin, 5 is a base made of an insulator, 6 is a coil terminal inserted into the above mentioned base 5,7 is a lead wire and 8 is an L-shaped balancing spring supporting frame fixed to the base 5 with a fitting screw.

9 IS AN L-shaped armature engaged in the extention 10 rotatably with the lower end of the yoke 1 (See FIG. 2). 11 is a balancing spring engaged between a projection 12 provided on the armature 9 and a spring receiving part 13 provided on the upper part of the supporting frame 8. Said spring receiving part 13 on the supporting frame 8 is provided on the bridging part at the free of the supporting frame 8 so that the biasing force of the above mentioned balancing spring 11 may be adjusted by plastically deforming the bridging part. 14 is a stationary contact. 15 is a stationary contact spring. 16 is a stationary contact spring block molded integrally with the lower part of the stationary contact spring. 17 is a first moving contact. 18 is a first moving contact spring. 19 is a terminal. 20 is a first moving spring block made of an insulator. 21 is a second moving contact. 22 is a second moving contact spring. 23 is a terminal. 24 is a second moving spring block. 25 is a terminal of the stationary contact. 26 is a contact spring assembly frame made of an insulator. The first and second moving spring blocks 20 and 24 and stationary contact spring block 16 are pressed into a space in the center of said assembly frame 26 and are fixed to the base 5 with the supporting frame 8. 27 is a card fixed to the upper part of the armature 9 so that the moving springs 18 and 22 may be moved on both sides of a spacer part 28 provided on a driving piece. 29 is a case.

In FIG. 2 showing a disassembled perspective view, the fitting relations are indicated with the arrows. What must be particularly explained here is the fitting state of the armature 9. A notch provided in the extension 10 of the armature 9 is loosely fitted with a projection 30 provided on the lower part of the yoke 1 so that the armature 9 may be rotated by the excitation of the coil 4 at this pivoting point. Further, a projection 31 of the yoke 1 is fitted in a hole 32 made on the side wall of the balancing spring supporting frame 8 and a projection 33 of the yoke 1 is fitted in a hole 34 made on each side wall of the supporting frame 8 and is secured to the frame 8 which is fixed to the base 5 with a screw. The balancing spring 11 is ring-shaped and is rotatably engaged at the open end with a projection 12 provided on the armature 9 and also rotatably engaged on the side opposite the open ends with a receiving part 13 on the supporting frame 8.

FIG. 3 is a perspective view showing the balancing spring 11 as engaged. The tail part 36 of the armature 9 is rotatably arranged in a space 35 provided in the side part of the yoke 1. The spring 11 is, further, arranged in parallel to side surface of the yoke 1.

The operation of the electromagnetic relay of the present invention shall be explained in the following.

FIG. 4A shows a view in which the resiliency of the balancing spring is decomposed into a component F.sub.3 vertical to the yoke and a component parallel with the yoke.

FIG. 4B shows a spring force of the balancing spring in the initial state in which the coil is not excited. In the drawing, a is a rotating center of the armature, b is a rotating center of the balancing spring and c.sub.1 is a point of rotation with a radius of i.sub.2 with the point a as a center. l.sub.1 is a distance from the point a to the center of the core and L is a distance between the armature and core in the center position of the core. Further, the angle formed by a line connecting a and c.sub.1 and a line connecting b and c.sub.1 is .theta..sub.1.

If the spring force given to the point c of the balancing spring is F.sub.1 ', the direction of the force line of F.sub.1 ' will be on the line bc.

If the component in the tangential direction at the point C of F.sub.1 ' is T.sub.1 ' and the component in the normal direction is P.sub.1 ',

T.sub.1 '= f.sub.1 'sin.theta..sub.1 and

P.sub.1 '=f.sub.1 ' cos.theta..sub.1 .

Here, T.sub.1 ' will be a torque tending to separate the armature from the core and P.sub.1 ' will be a force pressing the armature to the yoke hinge part.

If the force in the core position of T.sub.1 ' is T.sub.1,

T.sub.1 l.sub.1 = T.sub.1 'l.sub.2

That is, T.sub.1 = (l.sub.2 /l.sub.1)T.sub.1 ' = (l.sub.2 /l.sub.1)F.sub.1 'sin.theta..sub.1 .

FIG. 4C shows a spring force of the balancing spring in the final state in which the coil is excited and the attraction of the armature is finished. In this case,

T.sub.2 = (l.sub.2 /l.sub.1)F.sub.2 'sin.theta..sub.2 .

Therefore, the smaller the distance of the armature from the core, the smaller the angle .theta..

If various amounts are set so that F.sub.2 ' - F.sub.1 ' < sin.theta..sub.1 - sin.theta..sub.2, there will be obtained a negative characteristic that, the smaller the distance between the core and armature, the smaller the force tending to separate the armature from the core.

In FIG. 5, the abscissa represents the clearance between the armature and core, L represents the case that the armature and core separate from each other most and L = O represents the case that the armature has attracted the core. As the excited core attracts the armature, L will reduce gradually and the card 28 will move in the direction indicated by the arrow X (in FIG. 4). The load characteristic F.sub.2 of the second contact spring 22 shows that, at L = a, the right end of the card 28 contacts the second contact spring 22 and that, at L = b, the fixed contact 14 and second moving contact 21 tend to separate from each other. The load characteristic F.sub.2 of the first contact spring 18 shows that, at L = c, the fixed contact 14 and first moving contact 17 contact each other and that, at L = d, the left end of the card 28 tends to separate from the first contact spring 18.

In the drawing, F.sub.2 is a spring load characteristic by the first contact spring 18, F.sub.1 is a spring load characteristic by the second contact spring 22, F is a sum of the first contact spring load characteristic F.sub.2, and second contact spring load characteristic F.sub.1, that is,

F = f.sub.1 + f.sub.2 ,

f.sub.3 .sup.- is a characteristic of the balancing spring having a negative characteristic (that, the smaller the clearance between the core surface and armature, the smaller the force) (the case of the conventional example), F.sup.- is a combined spring characteristic, that is, F.sup.- = F.sub.1 + F.sub.2 + F.sub.3 .sup.- (the case of the present invention), F.sub.3 .sup.+ is a characteristic of the balancing spring having a positive characteristic (that, the smaller the clearance between the core surface and armature, the larger the force) (the case of the conventional example) and F.sup.+ is a combined spring characteristic, that is,

F.sup.+ = f.sub.1 + f.sub.2 + f.sub.3.sup.+

(the case of the conventional example).

As evident from the drawing, F.sup.- < F.sup.+. Therefore, for the electromagnetic attraction, there are required f.sup.+ for F.sup.+ and f.sup.- for F.sup.-. Therefore, f.sup.-< f.sup.+. According to the present invention, the electromagnetic attraction is so small that it is possible to make the electromagnetic relay small and to increase the sensitivity.

FIG. 6 shows the shape of the balancing spring. By the way, though this balancing spring has open ends, such open ends are not always necessary and the spring may be ring-shaped.

In this balancing spring, by applying a plastic deformation to the bridging part of the supporting frame receiving part, the balancing spring supporting state can be varied and the direction and magnitude of the spring force can be easily varied.

This example is shown in FIGS. 7A to 7F. In the drawings, c.sub.1 is an engaging point of the balancing spring with the supporting part 12 before the armature is attracted, c.sub.2 is an engaging point of the balancing spring with the supporting part 12 after the armature is attracted, a is a pivoting point of the armature with the yoke and b is a engaging point of the balancing spring with the spring receiving part 13 on the supporting frame.

FIGS. 7A to 7D show examples in which the balancing spring supporting point b is varied.

FIG. 7E shows the results.

FIG. 7A shows an initial position before the supporting point is adjusted.

FIG. 7B shows the case that the point b is moved toward the point a.

FIG. 7C shows the case that the point b is moved onto ac.sub.2.

FIG. 7D shows the case that the point b is moved leftward from ac.sub.2.

FIG. 7F shows a combined spring load characteristic in case the balancing spring is supported in the state of FIG. 7D.

Depending on the manner of taking the position of the balancing spring supporting point b, during the travel of the armature, the direction of the spring force may change. This manner is shown as F.sub.3 '.sup.- in the drawing. The spring load characteristic will be F'.sup.- , which will be a force generally smaller than F.sup.- shown in FIG. 5 and will never be a bar to the charactistic.

However, as the position in which the direction of the force changes, that is, the point L' is positioned at a point closer to the point L, the points a, b and c will become smaller forces and, in the extreme case, the forces of the points b and c will become negative (the forces of the points a, b and c must be positive), therefore the force of the point l will have to be made large and the force of the point d will happen to be large. As explained also in FIG. 9, this is very disadvantageous to the characteristic of the electromagnetic attraction.

Further, when the force of the point a is smaller than is required, the returning operation of the electromagnetic relay will be hard to make and, in the extreme case, the electromagnetic relay will not return well.

From the above, it is found that the point L' may be present between O and L (that is, the direction of the force may change) but must in a position close to the point O.

As described above, the present invention has the following effects:

a. As the armature is attracted by the core, the balancing spring will be engaged so that the spring force may reduce. Therefore, the combined spring characteristic can be reduced so much that the attraction for the armature can be small, the electromagnetic relay can be made small, the spring load can be kept low and therefore a high sensitivity electromagnetic relay can be realized. Further, as additional effects, the energy of the spring load will reduce and therefore the chattering of the contacts will decrease.

b. By making the balancing spring ring-shaped, the direction of the spring displacement can be made effective and the relay can be made small.

c. By plastically deforming the balancing spring receiving part, the balancing spring supporting point can be varied and the spring characteristic can be freely regulated.

Claims

What is claimed is:

1. An electromagnetic relay comprising the combination of:

a. an electromagnetic device including a coil, a core member, and a pivotally mounted armature,

b. at least one fixed spring contact,

c. a movable contact mounted for making and breaking contact with said fixed contact in response to pivoting movement of said armature,

d. and spring means biasing said armature away from said core, said spring means being responsive to pivotal movement of said armature for reducing said biasing force on said armature as the armature moves toward said core, and for increasing said biasing force as the armature moves away from said core.

2. An electromagnetic relay as set forth in claim 1 wherein said electromagnetic device comprises an L-shaped yoke to which a core having an exciting coil is fixed, and an L-shaped armature rotatably engaged in the end part of said yoke, a part of said armature being arranged rotatably in a space provided in the side part of the yoke.

3. An electromagnetic relay according to claim 1 wherein said spring means is supported on a member of an easily plastically deformable material and shape.

4. An electromagnetic relay according to claim 3 wherein a part of said spring supporting member is formed of a metallic frame fixed to a yoke and has a bridging part in one end part of it and a projection provided substantially in the center of said bridging part is made said spring supporting member.

5. An electromagnetic relay according to claim 1 wherein said spring means is ring-shaped.

6. An electromagnetic relay according to claim 1 wherein said spring means is of a ring-shape having open ends, engaged at said open end with a projection provided on said armature and rotatably engaged on the side opposite the open ends with the receiving part provided to project on the upper part of the supporting frame.

7. An electromagnetic relay according to claim 1 wherein said spring means is of a ring-shape having open ends and engaged in both open end parts with two projections provided on the armature and also on the side opposite the open ends with a spring supporting member.

8. An electromagnetic relay as set forth in claim 1 wherein the combined spring characteristics of said spring contact and said spring means provide a spring load on said armature which varies in proportion to the electromagnetic force on said armature as the armature moves toward said core.

9. An electromagnetic relay as set forth in claim 1 which includes a pair of fixed spring contacts disposed on opposite sides of said movable contact.