JPH01262604A - Electromagnetic actuator - Google Patents

Abstract

PURPOSE:To reduce magnetic resistance and increase a difference between the attractive force by a permanent magnet and the repulsive force of a spring in order to obtain a small-sized electromagnetic actuator by forcedly making a leakage magnetic circuit between a fixed iron core and a yoke. CONSTITUTION:A face in contact with a permanent magnet 1 of a fixed iron core 2 has a flange part 2f having a larger diameter than the permanent magnet, the part of a yoke 4a, whereinto the permanent magnet 1 is to be inserted, is phasedly pushed and a distance to a flange part of the fixed iron core 2 is shorter than the distance at the part holding the magnet 1. Consequently, the magnetic resistance between the yoke and the fixed iron core is reduced near the magnet 1, while a magnetic flux generated by the magnetomotive force of a coil is increased. As a result, operation is performed by a low current without increasing the number of coil winding, while a difference between the magnetic attractive force by the permanent magnet and the repulsive force of a spring 6 can be increased. That is to say, a shock-proof property and a power-saving property coexist with each other while a small-sized and low- priced electromagnetic actuator can be simply constituted.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electromagnetic actuator whose state is maintained by a permanent magnet and a spring, and whose coil is instantaneously excited by applying a pulsed current only during driving. .

Conventional technology In order to avoid heat generation in the coil and save power on the drive circuit side, self-holding electromagnetic actuators use permanent magnets and springs to hold the state and use the coil only for instantaneous excitation. is being used. Particularly in recent years, electromagnetic actuators built into household electrical appliances have become more power-saving, and gas cutoff valves and gas meters in household gas appliances have been fitted with termites to monitor the gas flow rate and use microcomputers to determine the gas usage status. There has been an increasing need for self-holding electromagnetic actuators for use as gas cutoff valves in microcomputer gas cutoff devices powered by battery power.

An example of the conventional electromagnetic actuator mentioned above will be described below with reference to the drawings.

FIG. 6 shows a cross section of a conventional electromagnetic actuator. In FIG. 6, a cylindrical permanent magnet 1 is magnetized in the direction of the central axis, and a surface facing the permanent magnet 1 is a permanent magnet 1.
It has a multistage cylindrical fixed iron core 2 having a diameter approximately equal to that of the permanent magnet 1 and arranged concentrically with the permanent magnet 1, and an attraction surface 10 that is movable in the direction concentric with the permanent magnet 1 and can come into contact with the fixed iron core 2. Yokes 4m and 4b which form a magnetic circuit by the permanent magnet 1 by sandwiching the permanent magnet 1 between the cylindrical movable iron core a and the fixed iron core 2 and placing the other end near the movable iron core 3. and,
A spring 6 is arranged at an end other than the attraction surface 10 of the movable iron core a in a direction concentric with the permanent magnet 1 and has a reaction force in a direction to separate the movable iron core a from the attraction surface 10, and a yoke 4m. , 4b
An electromagnetic actuator is constituted by a coil 5 which is surrounded by the movable iron core 3 and is arranged around the movable iron core 3, and which excites the movable iron core 3 by applying an electric current. The coil bobbin 5b on which the coil 5 is wound has a cylindrical hole and guides the movable iron core 3 in the movement direction, and holds the fixed iron core 2, the permanent magnet 1, and the movable iron core 3, and the fixed iron core 2 , the permanent magnets 1 are fixed so that their central axes are equal.

The operation of the electromagnetic actuator having the above configuration will be explained below.

When no normal current is applied, the movable iron core 3 is applied to the fixed iron core 2 on the attraction surface 10 against the reaction force f of the spring 6 by the magnetic attraction force Fo caused by the magnetic flux Φm of the permanent magnet 1. It is retained by adsorption. That is, Fo>fs
It is p. During driving, by applying a pulsed current - to the coil 5 to excite the movable iron core 3 in the opposite direction to the magnetic flux Φm, a magnetic flux ΦC is generated by the coil 5, and the magnetic flux Φ passing through the attraction surface 10 is Φ=Φm -ΦG, and the magnetic attraction force F is Fo
) F and decreases. If a sufficient current is applied to F (f, ,), the movable iron core 3 separates from the fixed iron core 2 at the attraction surface 10, and the electromagnetic actuator operates. The equivalent magnetic circuit is approximately shown in Fig. 7. In Fig. 7, the magnetic resistance of the magnetic gap G1 is Rgl, the magnetic resistance of the permanent magnet 1 is Rm, the magnetomotive force of the permanent magnet 1 is Fm, and the magnetomotive force of the coil 5. is Fc, and the leakage magnetic flux, the magnetic resistance at the attraction surface 10, the magnetic resistance of the yokes 4m, 4b, and the fixed iron core 3 are omitted.Furthermore, the equivalent magnetic circuit in FIG. FIG. 8 shows an equivalent magnetic circuit formed by the coil 5.

It will look like Figure 9. From Figures 8 and 9, it becomes a permanent magnet, and the magnetic flux Φ passing through the attraction surface 10 is Fo = N, where Φ = Φm- is N. (4), and the magnetic attraction force F is the square of the magnetic flux. Since it is proportional to , if the proportionality constant is K, then %' = Φ
Because it becomes 2... (5) 1 current J and attraction surface 10
The relationship between the magnetic attraction force F and Fm is expressed as follows. In FIG. 5, the reaction force f of the spring 6 is represented by a chain line.

Since the balance of forces on the attracting surface 10 is F - f when the attracting direction is positive, point B in FIG. 5 is the operating point of the electromagnetic actuator.

Problems to be Solved by the Invention However, in the above-described configuration, the magnetic attraction force Fo when the current is 00 in FIG. The difference Fo f from the reaction force fs of the spring 6
Since op is small, the movable iron core 3 may easily separate from the suction surface 10 due to loads such as external impacts, which may cause malfunction. On the other hand, in order to obtain a certain level of impact resistance, the reaction force fsp of the spring 6 can be set to a small value to reduce Fo.
It is possible to increase fop, but in this case, as shown in Fig. 5, the current IB at the operating point increases.
Power saving is sacrificed. What if the above formula (3) is used to achieve both impact resistance and power saving? (5) From coil 5
It is sufficient to increase the rate of change of the magnetomotive force Fc with respect to the current I, that is, from equation (4) or (6), the number of turns N of the coil 5 can be increased.
It would be better to make it larger. However, in order to make the current value equal to the voltage across the coil 5, the electrical resistance of the coil 5 must not be changed, so the diameter of the winding of the coil 5 increases, and when added to the increase in the number of turns N, the diameter of the coil 5 increases. Size and weight increase dramatically. In other words, both compactness and low cost are sacrificed.

In view of the above problems, the present invention can increase the difference Fo fop between the magnetic attraction force Fo due to the magnetic flux Φm of the permanent magnet and the spring reaction force fs with a low current flow without increasing the number of coil turns. i.e. impact resistance.

The present invention provides an electromagnetic actuator with a simple configuration that is both power saving, compact, and inexpensive.

Means for Solving the Problems In order to solve the above problems, the electromagnetic actuator of the present invention includes at least a cylindrical permanent magnet magnetized in the direction of the central axis, and a surface in contact with the permanent magnet that is larger than the permanent magnet. a multistage cylindrical fixed iron core having a diameter and arranged concentrically with the permanent magnet; a cylindrical movable iron core that is movable in a direction concentric with the permanent magnet and has an adsorption surface that can come into contact with the fixed iron core; A permanent magnet is sandwiched between the fixed iron core and the part of the fixed iron core that is in contact with the permanent magnet and has a diameter larger than the diameter of the permanent magnet has a distance between the fixed iron core and the part where the permanent magnet is sandwiched. A yoke that forms a magnetic circuit using a permanent magnet by placing the other end near the movable iron core with a shape smaller than the distance between a spring arranged to have a reaction force in the direction of separating the movable iron core from the suction surface; and a coil surrounded by the yoke and arranged around the movable iron core to excite the movable iron core by applying a current. It consists of

Furthermore, as a means for aligning the central axes of the fixed iron core, the permanent magnet, and the movable iron core, the electromagnetic actuator of the present invention uses a coil bobbin around which a coil is wound and has a hole in the center, and aligns the centers of the fixed iron core and the movable iron core with the hole. By aligning the axes and engaging a portion of the coil bobbin with a portion of the yoke, the central axes of the fixed iron core and the permanent magnet are aligned.

Function: In the electromagnetic actuator of the present invention, the surface of the fixed iron core that contacts the permanent magnet has a diameter larger than that of the permanent magnet, and the surface of the fixed iron core of the yoke that contacts the permanent magnet has a diameter that is larger than the diameter of the permanent magnet. The magnetic resistance between the fixed iron core and the yoke is equal to the distance between the fixed iron core and the permanent magnet. The magnetic resistance of the part and the magnetic resistance of the part whose magnetic gap is smaller than the part of the permanent magnet and larger than the diameter of the permanent magnet become parallel magnetic resistance, and the resultant magnetic resistance is a value smaller than the magnetic resistance of the part of the permanent magnet alone. Become. That is, by forcibly creating a leakage magnetic circuit between the fixed iron core and the yoke, the magnetic resistance between the fixed iron core and the yoke is reduced. Therefore, compared to the case without the leakage magnetic circuit, if the magnetomotive force of the coil is the same, the magnetic flux due to the coil becomes larger, and the difference between the magnetic attraction force of the permanent magnet and the reaction force of the spring can be increased.

In this manner, the electromagnetic actuator of the present invention provides a compact, low-cost electromagnetic actuator with a simple configuration that is both impact resistant and power saving.

EXAMPLE Hereinafter, a self-holding electromagnetic actuator according to an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a cross section of an electromagnetic actuator according to an embodiment of the present invention. In FIG. 1, there is a cylindrical permanent magnet 1 magnetized in the central axis direction, and a multi-stage cylindrical shape whose surface facing the permanent magnet 1 has a larger diameter than the permanent magnet 1 and is arranged concentrically with the permanent magnet 1. a fixed iron core 2 made of a magnetic material; a movable iron core 3 made of a cylindrical magnetic material and having an adsorption surface 10 movable concentrically with the permanent magnet 1 and capable of coming into contact with the fixed iron core 2;
Sandwich the permanent magnet 1 between the fixed iron core 2 and the fixed iron core 2.
The distance between the edge portion 2f that is in contact with the permanent magnet 1 and has a larger diameter than the diameter of the permanent magnet 1 is the distance between the fixed iron core 2 at the part where the permanent magnet is sandwiched, that is, the distance of the permanent magnet 1. The yokes 4a and 4b made of magnetic material, which have a shape smaller than the thickness and whose other end is arranged near the movable iron core 3 to form a magnetic circuit by the permanent magnet 1, are separate from the attraction surface 10 of the movable iron core 3. A spring 6 is disposed at the end in a direction concentric with the permanent magnet and has a reaction force in a direction to separate the movable iron core from the attraction surface 10, and a yoke 4. ．． An electromagnetic actuator is constituted by a coil 5 which is surrounded by the movable iron core 3 and is arranged around the movable iron core 3, and which excites the movable iron core 3 by applying an electric current. The coil bobbin 5b made of a non-magnetic material around which the coil 5 is wound has a cylindrical hole and guides the movable iron core a in the direction of movement and holds the fixed iron core 2, so that the center of the movable iron core 3 and the fixed iron core 2 is The axes of the movable iron core 3 and the fixed iron core 2 are fixed to be equal, and the pin 5p extends downward from the bottom of the coil bobbin 5 and engages with the hole 4h formed in the yoke 411, thereby aligning the central axes of the movable iron core 3 and the fixed iron core 2 to the yoke 4a. It is fixed against. On the other hand, a stepped part is provided on the bottom surface of the yoke 4a, and by fixing the permanent magnet 1, the central axes of the permanent magnet 1, the movable iron core 3, and the fixed iron core 2 are aligned, and the edge of the fixed iron core 2 2f is smaller than the thickness of the permanent magnet. As for processing means, since the fixed iron core 2 has a wide bottom surface, it is possible to finish the surface of the surface in contact with the attraction surface 10 and the permanent magnet 1 by cutting the shaft material with a lathe and then grinding both sides.
- The hole 4h and the stepped part can be processed by sheet metal processing at the same time as bending, etc., and the coil bobbin 5
b can be manufactured by synthetic resin molding. Therefore, the fixed iron core 2, yoke 4, and coil bobbin 5b can be manufactured at a low cost equivalent to that of a conventional electromagnetic actuator.

The operation of the electromagnetic actuator configured as above will be explained with reference to the drawings.

In the electromagnetic actuator shown in FIG. 1, when no normal current is applied, the movable iron core 3 is attached to the fixed iron core 2 on the attraction surface 10 against the reaction force fs of the spring 6 by the permanent magnet 1. It is attracted and held by the magnetic attraction force Fo caused by the magnetic flux Φm.

That is, Fo ) fsp. During driving, a pulsed current 1 is applied to the coil 5 so as to excite the movable iron core 3 in the opposite direction to the magnetic flux Φm, so that a magnetic flux ΦC is generated in the coil 5, and the magnetic flux Φ passing through the attraction surface 10 is Φ=Φm -ΦC and the magnetic attraction force F becomes Fo)F and decreases. If F <
When a sufficient current i is applied to make f and p, the movable iron core 3 separates from the fixed iron core 2 at the attraction surface 10, and the electromagnetic actuator operates. An equivalent magnetic circuit of the electromagnetic actuator having the configuration shown in FIG. 1 is approximately shown in FIG.

The magnetic resistance of the magnetic gap G1 in FIG. 1 is RQl+
The magnetic resistance of the magnetic gap G2 at the edge 2f of the fixed iron core 2 is Rg2, the magnetic resistance of the permanent magnet 1 is Rm, the magnetomotive force of the permanent magnet 1 is Fm, the magnetomotive force of the coil 5 is Fc, and the magnetic gaps Gl, G2 Leakage magnetic flux other than that, magnetic resistance at the attraction surface 10, magnetic resistance of the yokes 4m and 4b, and the fixed iron core 3 are omitted.

Furthermore, if the equivalent magnetic circuit shown in FIG. 2 is separated into an equivalent magnetic circuit made up of the permanent magnet 1 and an equivalent magnetic circuit made up of the coil 5, they become as shown in FIGS. 3 and 4, respectively.

From FIG. 3, the magnetic flux caused by the permanent magnet 1 is separated into a magnetic flux Φm1 passing through the magnetic gap G1 and a magnetic flux Φm2 passing through the magnetic gap G2, and of each Φm and -, only Φm1 passes through the attraction surface 10.

On the other hand, from Fig. 4, the magnetic flux due to the coil 5 is caused by the magnetic gap G.
1, the magnetic flux Φc1 passing through the permanent magnet 1, and the magnetic flux Φc2 passing through the magnetic gap G2, respectively. Therefore, the magnetic flux ΦC due to the coil 5 passing through the attraction surface 10 is ΦC=Φc
1+Φc2=ru. From the above, the magnetic flux passing through the attraction surface 10 during driving becomes Φ(12), and if the number of turns of the coil 50 is N, then F
a=N...(4), and the magnetic attraction force F is proportional to the square of the magnetic flux, so if we set the proportionality constant to F=Φ2
......β), and the relationship between the current 1 and the magnetic attraction force F on the attraction surface 10 is F=.

Here, the magnetic flux ΦC due to the coil 5 of the conventional electromagnetic actuator in FIG. 6 and the coil 5 of the electromagnetic actuator of the present invention
Compare the magnetic flux ΦG due to For convenience, the conventional ΦC is replaced by ΦC
= Φc /, ΦC of the present invention is Φ◎ = ΦG, and each magnetic resistance and the magnetomotive force Fc of the coil 5 are equal, then ΦC
Since -Φo'=(14), ΦO>ΦC'. Therefore, according to equation (6) or (13), the rate of change of the magnetic attraction force F with respect to the current l of the present invention is larger than the same rate of change in the conventional electromagnetic actuator. therefore,
The magnetic flux Φm caused by the permanent magnet 1 of the present invention is equal to the magnetic flux Φm caused by the permanent magnet 1 of the conventional electromagnetic actuator. That is, the magnetic attraction force F on the attraction surface 10 when the current 1=O
Assuming that o is equal, the relationship between the magnetic attraction force F and the current I on the attraction surface 10 of the present invention is expressed as a solid line FA in FIG. In FIG. 5, the reaction force f□ of the spring 6 is represented by a chain line.

Since the force balance on the attracting surface 10 is F-f,p when the attracting direction is positive, point A in FIG. 5 is the operating point of the electromagnetic actuator.

Operating point A of the electromagnetic actuator of the present invention in FIG.
Comparing the operating points of the conventional electromagnetic actuator and the electromagnetic actuator of the present invention, it is found that the electromagnetic actuator of the present invention operates with a smaller current. If the same current as the current +8 at the operating point of the conventional electromagnetic actuator is applied, the reaction force of the spring 6 can be set to fsp A shown by the two-dot chain line in Fig. 5, so the permanent magnet The difference between the magnetic attraction force Fo due to 1 and the reaction force fs of the spring 6, Fo - tspA
is larger than conventional electromagnetic actuators, improving impact resistance. Moreover, the number of turns of the coil 5 of the electromagnetic actuator of the present invention may be the same as that of a conventional electromagnetic actuator, so that it can be manufactured in a small size and at low cost.

As described above, the present invention has high impact resistance and saves power.

It is possible to provide a small, low-cost electromagnetic actuator with a simple configuration.

Effects of the Invention As described above, in the present invention, the surface of the fixed iron core that comes into contact with the permanent magnet has an edge portion with a diameter larger than that of the permanent magnet,
The part of the yoke into which the permanent magnet is inserted is stepped, etc., and the distance from the edge of the fixed iron core is smaller than the distance between the fixed iron core and the part where the permanent magnet is inserted, so it is not permanent. Since the magnetic resistance between the yoke and the fixed iron core near the magnet decreases, the magnetic flux generated by the magnetomotive force of the coil increases. Therefore, it is possible to operate with a low current without increasing the number of coil turns, and to increase the difference between the magnetic attraction force of the permanent magnet and the spring reaction force. In other words, it is possible to provide an electromagnetic actuator with a simple configuration that is compact and inexpensive and has both impact resistance and power saving properties.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the electromagnetic actuator of the present invention, and FIGS. 2, 3, and 4 are equivalent magnetic circuit diagrams and equivalent magnetic circuit diagrams using permanent magnets in the electromagnetic actuator of the present invention, respectively. An equivalent magnetic circuit diagram using a coil; FIG. 5 is a diagram showing the relationship between current and magnetic attraction force on the attraction surface in the electromagnetic actuator of the present invention and the conventional one; FIG. 6 is a cross-sectional view of the conventional electromagnetic actuator;
8 and 9 are an equivalent magnetic circuit diagram, an equivalent magnetic circuit diagram using a permanent magnet, and an equivalent magnetic circuit diagram using a coil, respectively, in a conventional electromagnetic actuator. 1...Permanent magnet, 2...Fixed iron core, 3
......Movable iron core, 4m, 4b...Yoke, 5...Coil, 5b...Coil bobbin, 6...Spring, 7. ...Splash catcher, 2
f...Edge of fixed iron core, 5p...pin, 4h...hole, Gl, G2...magnetic gap, Φrn1. Φm2...Magnetic flux due to permanent magnet, Φc. ΦC...Magnetic flux due to coil, fsp...
・Spring reaction force, F...Magnetic attraction force, Fo...
...Magnetic attraction force by permanent magnet, ...Current, R
gl, Rg2, Rm...Magnetic resistance, F
m... Magnetomotive force of permanent magnet, Fo... Magnetomotive force of coil, A... Operating point. Name of agent: Patent attorney Toshio Nakao and 1 other person1-
Permanent magnet 2 ・-! ! I Cooking 2f-・-3, Ra graduate 3-・Yoke a 4b-・-Yoke b Sen-・-hole 5- Coil 5b・-・Coil pot 5P-do Solo・・-Ba Year 7-・Ba Year-bearing Gr1G2-・Pussaki〒Tub 1-+, ht--To the magnetic flux by Ichinei Su arsenite +, kz-
- Magnetic flux φm2 due to the coil; Fig. 2 Fig. 3 Fig. 4 Fig. 5 Current L Fig. 6 Fig. 7 Fig. 8 Fig. 9

Claims (2)

[Claims] (1) A cylindrical permanent magnet magnetized at least in the central axis direction, and a multistage cylindrical permanent magnet whose surface facing the permanent magnet has a larger diameter than the permanent magnet and which is arranged concentrically with the permanent magnet. A fixed iron core, a cylindrical movable iron core that is movable in a direction concentric with the permanent magnet and has an adsorption surface that can come into contact with the fixed iron core, and the permanent magnet is sandwiched between the fixed iron core. The distance between a portion of the fixed iron core that is in contact with the permanent magnet and has a diameter larger than the diameter of the permanent magnet is smaller than the distance between the fixed iron core and a portion that sandwiches the permanent magnet. a yoke whose other end is arranged in the vicinity of the movable iron core to form a magnetic circuit by the permanent magnet; , and a spring arranged to have a reaction force in a direction to separate the movable iron core from the attracting surface, and a spring surrounded by the yoke and arranged around the movable iron core, and the spring is arranged to have a reaction force in a direction in which the movable iron core is separated from the attraction surface, and the spring is surrounded by the yoke and is arranged around the movable iron core, and the movable iron core is An electromagnetic actuator consisting of a coil that excites the core. (2) By using a coil bobbin around which the coil is wound and having a hole in the center, the central axes of the fixed iron core and the movable iron core are aligned through the hole, and a part of the coil bobbin is engaged with a part of the yoke. The electromagnetic actuator according to claim 1, wherein the fixed iron core and the central axis of the permanent magnet are aligned.