JPH0129148B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] This invention relates to a release type dot printer head.

[Technical background of the invention and its problems]

Conventionally, as shown in FIG.
Electromagnetic coils are attached to multiple cores 2 arranged in
A disk-shaped permanent magnet 4 is fixed to the yoke 1, armatures 6 to which needles 5 are fixed are held by leaf springs 7, and the armature 6 is attracted to the core 2 by the magnetic flux of the permanent magnet 4, and then to the electromagnetic coil 3. The magnetic flux of the permanent magnet 4 is canceled by energizing the leaf spring 7.
There is a release type dot printer head in which the armature 6 is moved together with the needle 5 in the printing direction by the force of the dot printer.

However, in such a device, since adjacent cores 2 are magnetically coupled via the yoke 1, magnetic interference occurs. That is, as shown in FIG. 2a, when a specific (center) electromagnetic coil 3 is excited, the magnetic flux of the permanent magnet 4 flows through the yoke 1 to the adjacent core 2, canceling out the magnetic flux of the permanent magnet 4 in the central core 2. To make it easier, as shown in Figure 2b, all the electromagnetic coils 3
When excited, the magnetic flux of the permanent magnet 4 is transferred to the adjacent core 2.
magnetic flux is difficult to cancel. Therefore, the driving conditions differ depending on the number of electromagnetic coils 3 to be excited.
That is, as shown in FIG. 3, the larger the number of electromagnetic coils 3 that are excited, the larger the opening/closing ampere turns. If printing is performed under constant driving conditions, the power consumption increases and the printing speed cannot be increased.

Further, as shown in FIG. 4, a ring-shaped permanent magnet 8 is positioned on the outer periphery of the electromagnetic coil 3 to
There are some that are fixed to the yoke 1, but each core 2 is fixed to the yoke 1.
Since they are magnetically coupled via a . Moreover, since the permanent magnet 8 is fixed to the yoke 1 so as to surround the core 2,
Permanent magnet 8, yoke 1, core 2, armature 6
It has the disadvantage that the magnetic path leading to it is too long.

For this reason, as shown in FIGS. 5 and 6, a donut-shaped permanent magnet 10 is fixed in the housing 9, and a plurality of cores 11 are connected to one surface of the permanent magnet 10 in an annular shape. Arrange and
Pins 12 parallel to the joint surface to the permanent magnet 10 are set up on these cores 11, electromagnetic coils 3 are attached to these pins 12, and a plurality of armatures 13 each having a needle 5 are attached to a block 14.
There is one which is biased in the printing direction by plate springs 15 and 16 fixed in a cross shape.

In operation, the magnetic flux of the permanent magnet 10 is canceled by the excitation action of the electromagnetic coil 3, and the force of the leaf springs 15 and 16 moves the armature 13 in the printing direction. In this case, since each core 11 is independent, the magnetic resistance to adjacent cores 11 is greater than that shown in FIGS. 1 and 3. However, since the area of the facing surface 17 with respect to the adjacent core 11 is large, the magnetic flux leaks to the adjacent core 11 through the air. In addition, since the core 11 has a mounting surface 18 parallel to the pin 12 joined to the permanent magnet 10, the magnetic path from the permanent magnet 10, core 11, and armature 13 to the permanent magnet 10, core 11, and armature 13 becomes long, and the magnetic flux flowing in the air also increases on this surface. This causes magnetic interference to be prevented reliably. Furthermore, since the mounting surface 18 and the end surface of the pin 12 (armature suction surface) are perpendicular to each other, it is difficult to process the parts, and since the pin 12 also faces toward the center of the housing 9 instead of toward the opening surface, the electromagnetic coil 3 cannot be mounted. It's bothersome.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a release type dot printer head that can prevent magnetic interference.

[Summary of the invention]

In this invention, independent cores are fixed at intervals to a permanent magnet facing the armature, and the joint surface of these cores to the permanent magnet is increased, and the cross-sectional area becomes smaller as the distance from the permanent magnet increases. , to prevent leakage of magnetic flux to adjacent cores, and to fix the core to the permanent magnet by positioning it on the surface facing the armature, thereby shortening the length of the magnetic path from the permanent magnet to the armature. This prevents magnetic interference between adjacent cores, and the part where the core is attached to the permanent magnet becomes wider toward the joint surface with the permanent magnet, which increases the magnetic flux density and improves the armature. It is designed to increase suction power.

[Embodiments of the invention]

An embodiment of the present invention will be explained based on FIGS. 7 to 10. Reference numeral 20 denotes a yoke having fins 21, and this yoke 20 is made of a 3% SiFe sintered alloy from the viewpoints of dimensional accuracy, magnetic efficiency, and economical efficiency. A donut-shaped permanent magnet 22 is fixed to the bottom of this yoke 20, and a plurality of cores 25 are fixed at intervals to a core holding surface 24 of the permanent magnet 22 facing the armature 23. These cores 25 are formed of a sintered alloy of 2.5 to 3.5% SiFe in consideration of eddy current loss and saturation magnetic flux density. These cores 25 have an attachment part 26 to the core holding surface 24 and a columnar protrusion 28 on which an electromagnetic coil 27 is attached.
When viewed from the side, the mounting portion 26 has a maximum width of the joint surface with respect to the core holding surface 24, and the width of the joint surface with respect to the core holding surface 24 is
The core 25 is defined in a trapezoidal shape whose width becomes narrower as it moves away from the core 4, and a distance S between the adjacent cores 25 is secured;
In addition, when viewed from the center line of the yoke 20, it is formed in a fan-shape in which the width on the outer circumferential side is wide and the width on the inner circumferential side is narrow. 22 magnetic flux density is increased. A plurality of plunger yokes 30 are held between the yoke 20 and the guide holder 29.
The armature 23 is molded from plastic with a plunger 31 and a needle 32 that are fitted into the plunger yoke 30 buried therein, and one side of the armature 23 has a fulcrum 3 connected to the plunger yoke 30.
3 is formed protrudingly. These armatures 23 are urged in the printing direction by springs 34. The armature 23 is attached to the guide holder 29.
A guide rib 35 and a needle guide 36 are provided to guide the operation.

In such a configuration, the plunger 31 of the armature 23 is attracted to the core 25 by the permanent magnet 22, but the magnetic flux of the permanent magnet 22 is canceled by exciting the electromagnetic coil 27, and the armature 23 is pulled by the force of the spring 34. Fulcrum 33
It moves in the printing direction centering on . Each core 25 is arranged with an interval S, and the width becomes narrower as the distance from the permanent magnet 22 increases.
The intervals between 5 are wide. Therefore, leakage of magnetic flux between the cores 25 can be eliminated. Since the permanent magnet 22 is joined to the core 25 with the surface facing the armature 23, the length of the magnetic path from the permanent magnet 22 to the armature 23 is short, and leakage of magnetic flux due to magnetic flux flowing through space is also prevented. sell. Therefore, it is possible to prevent an increase in power consumption due to magnetic interference and increase printing speed. Since the columnar protrusion 28 of the core 25 is also perpendicular to the permanent magnet 22 and faces toward the open end of the yoke 20, assembly of the electromagnetic coil 27 is also easy. The cores 25 are spaced apart to prevent magnetic interference, but the joint surface with the core holding surface 24 is large, increasing the magnetic flux density of the permanent magnet 22 and attracting the armature 23 quickly with a strong attraction force. Is possible. Furthermore, by using the permanent magnet 22 made of rare earth cobalt, the linearity of the B-H curve (characteristic showing the relationship between magnetic flux density and magnetomotive force) is improved in the fourth quadrant, and the magnetic force does not decrease even when the demagnetizing field is strong. .

〔Effect of the invention〕

As described above, this invention maintains the magnetic flux density of the permanent magnet at a high level by arranging a plurality of cores at intervals and fixing them to a permanent magnet, and by decreasing the cross-sectional area of the cores as they move away from the permanent magnet. It is possible to prevent leakage of magnetic flux between adjacent cores while satisfying the above conditions, and by fixing the core to the permanent magnet with the surface facing the armature, the length of the magnetic path from the permanent magnet to the armature can be reduced. This has the effect of reducing power consumption and increasing printing speed, as well as preventing magnetic interference caused by magnetic flux flowing in the air.

[Brief explanation of drawings]

Figure 1 is a partially cutaway side view of a conventional example, Figure 2 is an explanatory diagram showing the state in which magnetic flux leaks, and Figure 3 shows the relationship between the number of excited electromagnetic coils and open ampere turns. Figure 4 is a partially cutaway side view showing the second conventional example, Figure 5 is a partially cutaway side view showing the third conventional example, and Figure 6 is the permanent magnet. FIGS. 7 to 10 are exploded perspective views showing the relationship between the core and the armature.
The figures show one embodiment of the present invention; FIG. 7 is a partially cutaway side view, FIG. 8 is a plan view showing part of the yoke, FIG. 9 is a perspective view of the core, and FIG. 10 is a partially cutaway side view. FIG. 2 is a side view showing an expanded state of the arrangement of the cores. 22... Permanent magnet, 23... Armature, 2
4... Core holding surface, 25... Core, 26... Mounting surface, 27... Electromagnetic coil, 28... Column-shaped protrusion, 3
2...Needle, 34...Spring.

Claims (1)

[Scope of Claims] 1. A permanent magnet having a plurality of armatures connected to needles which are biased in the printing direction by a spring and arranged in an up-and-down manner, and whose core holding surfaces facing the armatures are formed on the same plane. and a plurality of mounting parts having a maximum area of the joint surface with respect to the core holding surface and a cross-sectional area gradually decreasing as the distance from the core holding surface increases, and a columnar protrusion that stands up from the mounting part and holds the electromagnetic coil. 1. A release type dot printer head, characterized in that the cores are arranged at intervals and fixed to the core holding surface. 2. The release type according to claim 1, characterized in that the width of the core mounting portion is gradually increased from the center of the permanent magnet toward the outer periphery, and the cores are arranged in an annular manner on the core holding surface. Dot printer head.