JPS6115564B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic actuator that magnetically attracts or releases a magnetic pole piece, and in particular, a magnetic actuator that attracts a magnetic pole piece with the magnetic flux of a permanent magnet and is provided in a magnetic circuit. This invention relates to a magnetic actuator that releases the attraction of an armature by energizing a coil to cancel the magnetic flux of a permanent magnet.

Such magnetic actuators are conventionally used in relays, printing hammers for printers, and the like.

FIG. 1 shows an example of a conventional magnetic actuator as described above, which is applied to a printing mechanism of a dot matrix type printer.

In Figure 1, 1 is a permanent magnet, 2 is a yoke, and 3 is a permanent magnet.
is a movable magnetic pole piece composed of a leaf spring made of magnetic material, 4 is a coil wound around the yoke 2, 5 is a dot hammer fixed to the leaf spring 3, 6 is an ink ribbon, 7 is printing paper, and 8 is a platen. are shown respectively.

When the coil 4 is not energized, the tip of the movable magnetic pole piece 3 is attracted by the magnetic flux of the permanent magnet 1 and is in close contact with the tip of the yoke 2. (This state is shown in FIG. 1.) In this state, the movable magnetic pole piece 3 is bent as shown. Now coil 4
If a current sufficient to cancel the magnetic flux of the permanent magnet 1 is applied to the magnet 1, the attractive force to the movable magnetic pole piece 3 disappears. Therefore, the movable magnetic pole piece 3 starts moving to the right by the energy of its own deflection. Therefore, the dot hammer 5 fixed to the tip of the movable magnetic pole piece 3 presses the ink ribbon 6 and printing paper 7 against the platen 8.
Print dots on printing paper 7. Immediately after printing, if the current in the coil 4 is cut off, the magnetic flux of the permanent magnet 1 flows through the yoke 2 again, and the movable magnetic pole piece 3 is attracted again and returns to the state shown in Fig. 1, returning to the next printing point. Be prepared. By moving the entire magnetic actuator shown in FIG. 1 left and right and moving the printing paper 7 up and down, the dot position on the printing paper 7 is controlled, thereby marking desired characters on the printing paper. It can be printed as a combination of

The magnetic behavior of the permanent magnet 1 in such a magnetic actuator will be explained. FIG. 2 shows a demagnetization curve of the permanent magnet 1. The permanent magnet 1 assumes a state on a curve indicated by O→S depending on the permeance of the external magnetic path. When the coil 4 is not energized, the operating point of the permanent magnet 1 is at point P in FIG. Next, when the coil 4 is energized to cancel the attractive force against the movable magnetic pole piece 3, no magnetic flux flows through the yoke 2, so the permeance of the external magnetic path becomes apparently very small. Become. Therefore, permanent magnet 1
The operating point of moves to Q. Point R in the demagnetization curve of permanent magnet 1 (Figure 2) where the slope starts to increase
If the operating point moves further to the left, the permanent magnet will be demagnetized and its characteristics will deteriorate, so the operating point Q when the above-mentioned current is applied must be to the right of point R.

In order to meet these conditions, the permanent magnet 1 of the magnetic actuator shown in Fig. 1 is a magnet with extremely excellent magnetic properties (high coercive force) such as a rare earth cobalt magnet.
Currently, permanent magnets are used.

In recent years, there has been a strong demand for downsizing and lowering prices for relays, printers, etc., and demands for downsizing and lowering prices for magnetic actuators as shown in FIG. 1 have become stronger.

In the configuration shown in FIG. 1, when the coil 4 is energized to cancel the attractive force as described above, the permanent magnet 1
Since the operating point of the magnet moves leftward from P to Q, the length of the permanent magnet must be increased to prevent demagnetization at that time. The drawback was that magnets could not be used.

It is an object of the present invention to provide a compact and inexpensive magnetic actuator by eliminating the drawbacks of the conventional magnetic actuator as described above.

FIG. 3 shows an embodiment of the present invention, in which 11 is a permanent magnet, 12 is a first yoke, 13 is a movable magnetic pole piece composed of a leaf spring made of magnetic material, and 14 is a movable magnetic pole piece that is wound around a second yoke 19. 15 is a dot hammer, 16 is an ink ribbon, 17 is printing paper, 18 is a platen, 19 is a second yoke, and 20 is a fixed gap.

A first magnetic path 21 is formed by the permanent magnet 11, the first yoke 12, and the movable magnetic pole piece 13, and the permanent magnet 11, the first yoke 12, and the second yoke 19
A second magnetic path 22 having an air gap 20 is formed therebetween. Furthermore, the above two magnetic paths are connected in parallel.

FIG. 4 is a diagram showing a demagnetization curve of the permanent magnet 11, similar to FIG. 2, and is for explaining the magnetic behavior of the permanent magnet 11.

When the coil 14 is not energized, the magnetic flux of the permanent magnet 11 is distributed between the first magnetic path 21 and the second magnetic path 22.
It flows to. Therefore, the tip of the movable magnetic pole piece 13 is the first
It is attracted to the yoke 12 of the yoke 12 and is in close contact with its tip. This situation is shown in FIG. In this state, the movable magnetic pole piece 13 is bent as shown. Next, the coil 14 is energized in the direction in which the magnetic flux of the second magnetic path 22 increases, and the magnetic flux of the second magnetic path 22 becomes the magnetic flux corresponding to the permanent magnetization of the permanent magnet 11 (i.e., the fourth
The magnetic flux density at point Q in the figure multiplied by the cross-sectional area of permanent magnet 11).

In this state, the operating point of the permanent magnet moves to point Q in FIG. Therefore, the difference in magnetic potential between both end faces of the permanent magnet 11 becomes zero. Therefore, no magnetic flux flows through the first magnetic path 21. Alternatively, since all the magnetic flux supplied from the permanent magnet 11 flows into the second magnetic path 22,
It may be considered that magnetic flux no longer flows through the first magnetic path 21. Therefore, the attractive force acting on the movable magnetic pole piece 13 disappears, and the tip of the movable magnetic pole piece 13 starts to move to the right due to the energy of the deflection of the movable magnetic pole piece 13. Therefore, the dot hammer 15 fixed to the tip of the movable magnetic pole piece 13 is attached to the ink ribbon 16.
Press the printing paper 17 against the platen 18 and press the printing paper 1
Print a dot at 7. Thus, the magnetic actuator of the present invention shown in FIG. 3 can operate completely with the conventional magnetic actuator shown in FIG.

As mentioned above, in the magnetic actuator of the present invention, when the coil 14 is energized to cancel the attractive force against the movable magnetic pole piece 13, the operating point of the permanent magnet 11 changes from point P to point Q in the demagnetization curve in FIG. Move to the right on top. This point is a major advantage compared to conventional magnetic actuators.

Therefore, there is no need to worry about the Q point going to the left of the R point. This point is a major advantage compared to conventional magnetic actuators. For this reason, in the case of the present invention, it is possible to replace expensive permanent magnets such as rare earth cobalt magnets that have been used in the past with relatively low-grade and inexpensive magnets such as alnico magnets and manganese/aluminum magnets. can. Also, if you use a high-grade magnet such as a rare earth cobalt magnet as before, the dimensions of the permanent magnet 11 (especially the length)
can be made much smaller, making it possible to reduce the size and cost.

FIG. 5 shows another embodiment of the present invention in which the movable magnetic pole piece 32 made of a leaf spring shown in FIG. 3 is replaced with a rigid movable magnetic pole piece 32 rotatably supported around a fulcrum 31. . Since the movable pole piece 32 is pulled to the right by the spring 33, it functions exactly the same as the movable pole piece 13 in FIG.

It is clear that such a magnetic actuator operates in the same way as the magnetic actuator of FIG. 3 and has the same effect.

In addition, the two magnetic paths 21 and 22 installed in parallel in Fig. 3 can be installed so that they partially overlap as shown in Fig. 6, and the same effect can be obtained, as well as having the advantage of being able to be made smaller. . Although various other configurations are possible, any structure may be used as long as the magnetic path having the movable magnetic pole piece and the magnetic path having the fixed air gap and the coil are connected in parallel.

In the above explanation, the case where the magnetic actuator of the present invention is used as a dot hammer drive mechanism of a dot matrix type printer has been explained. It is clear that the invention can be applied to a variety of applications in which suction and release of pieces can be carried out quickly, and the advantages of the present invention can be realized as well.

[Brief explanation of the drawing]

FIG. 1 is a side view showing an example of a conventional magnetic actuator, in which 1 represents a permanent magnet, 2 represents a yoke, 3 represents a movable magnetic pole piece, and 4 represents a coil. 2 is a diagram illustrating the movement of the operating point of the permanent magnet 1 in FIG. is a moving magnetic pole piece, 1
4 is a coil, 19 is a second yoke, and 20 is a fixed air gap, FIG. 4 is a diagram explaining the movement of the operating point of the permanent magnet 11 in FIG. 3, and FIG. 5 is another implementation of the present invention. In a side view showing an example, reference numeral 31 indicates a fulcrum, and reference numeral 32 indicates a movable magnetic pole piece 33, a spring. FIG. 6 is a side view showing still another embodiment of the present invention.

Claims (1)

[Claims] 1. In a magnetic actuator that uses a magnetic circuit having a permanent magnet and a coil, and attracts and releases a movable magnetic pole piece provided in the magnetic circuit by intermittent current in the coil, the magnetic flux of the permanent magnet is It has two magnetic paths installed in parallel to allow the flow to flow, one magnetic path has a fixed air gap and a coil installed to interlink with the magnetic path, and the other magnetic path A magnetic actuator, characterized in that the magnetic actuator is provided with a movable magnetic pole piece that constitutes a part of its magnetic path.