JPH05238019A - Structure of magnetic path for impact print head - Google Patents

Abstract

PURPOSE:To improve printing speed with moment of inertia acting on an armature reduced by a method wherein a magnetic path is constructed in a structure in which attraction force generated on faces of both of magnetic poles by electrifying a coil acts to produce moment against a support point that supports turning of the armature. CONSTITUTION:Magnetic flux, generated by electrifying a coil 1, penetrates through a core 2 and a magnetic path 3c of an armature 3. As a result, faces of both of magnetic poles 2a and 2b attract the armature 3. When the attraction force exceeds the energizing force of a return spring 8, the armature 3 starts, together with a printing wire 7, turning round a turning support point 4. Considering the turning support point of the armature 3 as 0, points on which the attraction force acts on the faces of the magnetic poles respectively as P and Q, the attraction force acting on the points P as F, the attraction force acting on the point Q as G, the distance between 0 and Q as L, the angle made by the armature 3 and the line O-P as theta, and the angle made by the armature 3 and the line O-Q as alpha, the following equations can be obtained: Mp=RXFcostheta, with Mp = moment produced on the point P side. Mq=LXGsinalpha, with Mq = moment produced on the point Q side. As the above-mentioned two are in the same direction, they can be added together.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print head for an impact dot printer, and more particularly to improvement of a magnetic circuit for high speed printing and large printing power.

[0002]

2. Description of the Related Art The technical field of the present invention belongs to "a magnetic circuit having two magnetic pole faces in one magnetic path loop", and the technical characteristics are achieved by devising mutual arrangement of the two magnetic pole faces. This is to reduce the moment of inertia of the armature.
The following two examples have been proposed as conventional examples featuring the "magnetic circuit having two magnetic pole faces in one magnetic path loop" relating to the present invention.

As a first conventional example, there is US Pat. No. 4109776 shown in FIG. Two pole faces 2 in it
An embodiment is disclosed in which there are a and 2b. The two magnetic pole surfaces are arranged in the same plane, and the magnetic path is connected by the iron core 2. On the other hand, the magnetic pole surfaces 2a and 2b
A magnetic path is formed by the attracted piece 13 on the side of the armature 3 opposite to the armature 3. When the attracted piece 13 is attracted to the magnetic pole surfaces 2a and 2b, a closed magnetic circuit loop is formed by the iron core 2 and the attracted piece 13. It The coil 1 for generating magnetic force is arranged on the outer circumference of the iron core 2. Also, the main body 14
Is composed of a non-magnetic material, and has an iron core 2 and an armature 3
To maintain the mutual positional relationship. When the coil 1 is in the non-energized state, the attracted piece 13 of the armature is separated from the magnetic pole surfaces 2a and 2b. The armature 3 is attached to the main body 14 by a leaf spring 15, and a part of the leaf spring 15 is constricted and thin, and the bending rigidity of the portion is reduced to form a pivotal support point 16.
The above is the main configuration. To explain the operation briefly,
When the coil 1 is energized, the magnetic pole surfaces 2a and 2b attract the attracted piece 13, and the armature 3 rotates the supporting point 1
Print needle 7 is rotated about 6 to obtain print energy and print needle 7
The leading edge of the sheet collides with the print target sheet through the ink ribbon and prints. The feature of the above configuration is that there are two magnetic pole faces in one magnetic path loop, and therefore, there is a maximum of 2 magnetic pole faces as compared with the case where there is only one magnetic pole face 2a in one magnetic path loop as shown in FIG. It is possible to obtain double the suction power. Here, in comparison with FIG.
The description will be made by substituting the example shown in FIG. Figure 1
The difference between the conventional example shown in FIG. 7 and the example shown in FIG. 19 is that the direction in which the two magnetic pole surfaces 2a and 2b are connected is the same as the direction in which the rotation support point 16 of the armature and the print needle 7 are connected. Or is it arranged at right angles. However, both purposes in magnetic circuits are the same. FIG.
19 and FIG. 19, it is possible to make the dimensional conditions around the magnetic pole faces 2a and 2b the same, and if the same magnetic flux passes through all the magnetic pole faces under that condition, the magnetic pole faces If there are two places, twice the suction force will be generated. However, in the case where there are two magnetic pole surfaces, the resistance of the magnetic circuit is doubled as compared with the case where there is one magnetic pole surface, so the magnetomotive force must be doubled in order to pass the same magnetic flux. That is, the one having two magnetic pole surfaces has a characteristic that a double attraction force can be produced by applying a double power. Such characteristics are effective for the following uses. When the dimensions of the product are limited due to the specifications of the product and the cross-sectional area of the magnetic path cannot be sufficiently taken, there is a case where a sufficient attraction force cannot be obtained even if excitation is performed until the magnetic path is saturated at one magnetic pole surface. At that time, if the two magnetic pole surfaces are excited until they are saturated to the same saturation, a double attractive force may be obtained. That is, there is an advantage in that the constraint of size restriction can be replaced by the factor of electric power. However, in order to put together a product with a structure as shown in FIG. 19, it is necessary to arrange a plurality of print needles 7 (24 as an example) in proximity to the product specifications. Since the two magnetic pole surfaces 2a and 2b are arranged at right angles to the direction connecting the print needle 7, there is a drawback that the lateral width becomes too large and the distance between adjacent print needles becomes large. Therefore, in reality, the arrangement shown in FIG. 17 has no choice but to be arranged. However, the structure as shown in FIG. 17 has the following drawbacks. Two pole faces 2a and 2b
Is arranged in the direction connecting the rotation support point 16 of the armature 3 and the print needle 7 and in the middle thereof, the armature must be lengthened accordingly, and as a result, the moment of inertia of the armature increases. To reduce the printing speed. Further, the length of the attracted piece 13 needs to be a length connecting both outer ends of both magnetic pole surfaces 2a and 2b, and its cross-sectional area is close to that of the iron core 2 in terms of preventing magnetic saturation of the magnetic path. However, as a result, there is a structural defect that the mass of the suction target piece 13 itself becomes large. Moreover, the attracted piece 1 is attached to the rotation support point 16 of the armature.
3 are arranged apart from each other, and the moment of inertia becomes larger under the influence of the square of the distance. Further, the magnetic pole surface 2b farther from the rotation support point 16 of the armature.
Since there is a large air gap during standby, the permeance of the entire magnetic circuit is reduced and the electromechanical conversion efficiency is reduced. As described above, the US patent US shown in FIG.
It can be said that P4109776 is a structure in which the characteristics of a magnetic circuit having two magnetic pole faces in one magnetic path loop are not fully utilized.

As a second conventional example, there is Japanese Patent Laid-Open No. 56-104073 shown in FIG. There is disclosed an embodiment in which the two pole faces 2a and 2b are arranged at a right angle. A magnetic path is connected to both magnetic pole surfaces 2a and 2b by an iron core 2 having a permanent magnet 17 inserted in the middle, and a coil 1 is arranged in a part of the iron core 2. The iron core 2 is fixed to the non-magnetic main body 14, and the positional relationship with the armature 3 is maintained. A part of the armature 3 forms a magnetic path connecting both magnetic pole surfaces 2a and 2b. One end of the armature 3 holds the print needle 7, and the other end is supported by a leaf spring 15 fixed to the main body 14. The imaginary center point of the flexure of the leaf spring 15 is made to coincide with the rotation support point 16 of the armature, and its position is set equidistant from both magnetic pole surfaces 2a and 2b and on the intersection of the extended surfaces of the magnetic pole surfaces. is there. The air gap between the armature 3 and the magnetic pole surfaces 2a and 2b is such that a predetermined air gap is maintained when there is no magnetic flux in the magnetic path and the stress of the leaf spring 15 is zero. However (normally, the coil is in a non-energized state), the armature 3 is attracted to the magnetic pole surfaces 2a and 2b by the permanent magnet 17 in the magnetic path, and the leaf spring 15 is in a state in which the bending energy is accumulated. There is. When the coil 1 is energized so as to cancel the magnetic flux of the permanent magnet 17 from that state, the attraction force by the permanent magnet disappears, so the armature 3 is driven by the restoring energy of the leaf spring 15 with the rotation support point 16 as the rotation center. It The feature of this embodiment is that the relationship between the two magnetic pole faces is arranged at a right angle, and the pivotal support point 16 of the armature is set equidistant from both magnetic pole faces and on the intersection of the extension faces of the respective magnetic pole faces. Therefore, the air gaps on both magnetic pole surfaces can be made the same, and the air gap on one magnetic pole surface does not become too large as in the case of US Pat. There is a point that can be raised. However, in this structure, the magnetic pole surfaces are too far apart from each other, the magnetic path on the armature 3 side connecting them becomes long, the inertia moment of the armature becomes large, and there is a problem in high-speed printing.

[0005]

SUMMARY OF THE INVENTION In order to improve the printing speed and the printing force, the present invention has a basic structure of a magnetic circuit having two magnetic pole faces in one magnetic path loop. The challenge is how to reduce the moment.

[0006]

In order to improve the printing speed and the printing force, it is sufficient that a lighter armature can be sucked with a larger force. That is, it depends on how large the driving acceleration of the armature can be. The suction power is
It is almost determined by the dimensionally allowed magnetic path cross-sectional area. Therefore, in order to generate a large attractive force, it is an effective means to employ a magnetic circuit having two magnetic pole faces in one magnetic path loop as described above. However, in the arrangement of the magnetic pole surfaces as in the conventional example, the moment of inertia of the armature becomes rather large, which leads to the improvement of the printing force but not the improvement of the printing speed. Therefore, the present invention reduces the moment of inertia of the armature by the following two means.

The first means is to arrange the two magnetic pole faces as close to each other as possible and shorten the magnetic path on the armature side to reduce the moment of inertia. For example, as shown in FIG. 3, when a hollow hollow cylinder is used as an iron core 2 and a coil 1 is wound around the iron core 2, a closed magnetic circuit is formed. However, as shown in FIG. Inner circumference 5 to become
From the outer circumference 6 to the magnetic pole surface 2a and 2b formed by dividing the magnetic path, the angle formed by the two magnetic pole surfaces 2a and 2b is approximately 80 degrees to 120 degrees.
Angle (90 degrees in FIG. 1), and an armature 3 facing the magnetic pole surfaces 2a and 2b and having attracted surfaces 3a and 3b equal to the angle formed by the magnetic pole surfaces. By forming the magnetic path portion 3c between the attracted surfaces 3a and 3b of the armature so as not to obstruct magnetic permeability, the magnetic path on the armature side can be shortened and the moment of inertia can be reduced. In this example, the position of the rotation support portion 4 of the armature is set to the one magnetic pole surface 2a or 2b.
(2a in FIG. 1) and around the outer circumference 6 of the magnetic path loop of the iron core 2, and when the coil 1 is energized, the attraction force generated on both magnetic pole surfaces 2a and 2b is applied to the rotation support portion 4 of the armature. A moment in the same direction is generated.

The second means is to reduce the moment of inertia of the armature by the shape of the magnetic path portion 3c connecting the attracted surfaces 3a and 3b of the armature 3. The cross-sectional area of the magnetic path loop formed by the iron core 2 and the magnetic path portion 3c of the armature 3 shown in FIG. 1 is preferably the same at any position for the purpose of preventing local saturation of the magnetic path. Therefore, both sides 3 of the armature to be attracted
The cross-sectional area of the magnetic path portion 3c connecting a and 3b should be the same within that range. On the other hand, the magnetic flux is generated by the attracted surfaces 3a and 3a.
Since it passes perpendicularly to b, the direction of the magnetic flux is bent between the attracted surfaces by an angle formed by the attracted surfaces. The direction of the center of curvature is the direction in which both surfaces to be attracted intersect, so that the outer shape on the diagonal side should have a necessary cross-sectional area along the curvature of the magnetic flux as in the slope 3f portion shown in FIG. Become. From the above, as shown in FIG. 1, the magnetic path on the diagonal side of the point where the attracted surfaces 3a and 3b of the armature 3 intersect is reduced, and the magnetic path portion 3c connecting the attracted surfaces 3a and 3b. Unnecessary mass was reduced by making the cross-section area of each to be almost equal.

[0009]

1 shows the armature 3 in a standby state, in which the coil 1 is in a non-energized state. Since the armature 3 is pressed against the armature stopper 9 side by the urging force of the return spring 8, both the attracted surfaces 3 of the armature 3
a and 3b are both magnetic pole surfaces 2a and 2b facing them.
Keeps a predetermined gap away from. When the coil 1 is energized in this state, the generated magnetic flux penetrates the magnetic core 3 and the magnetic path portion 3c of the armature 3. As a result, both magnetic pole surfaces 2a and 2b attract the armature 3, but when the attraction force exceeds the urging force of the return spring 8, the armature 3 starts to rotate around the rotation support point 4 together with the print needle 7. To do. When the attraction force is further increased, the armature 3 is accelerated to obtain a predetermined energy, and finally collides with the magnetic pole faces 2a and 2b. However, in the actual printing state, the tip of the print needle 7 collides with the print target paper via the ink ribbon just before the armature 3 collides with the magnetic pole surfaces 2a and 2b, and the movement of the armature is restricted at that time. The two will not collide. The return of the armature 3 after printing is returned to the standby state by the reaction of the collision of the print needle 7 and the restoring force of the return spring 8, but if the suction force remains at that time, the return time is Since it is delayed, the coil energization time is adjusted so that the suction force disappears when the print needle 7 collides with the print paper.

Next, the moment of the armature 3 shown in FIG. 1 with respect to the rotation support portion 4 will be described. As shown in FIG. 15, the rotation support portion of the armature 3 is O, the attraction force acting points of the magnetic pole surfaces are P and Q, the attraction force of the P point is F, and the attraction force of the Q point is between G and OP. If the distance is R, the distance between OQ is L, the angle between the armature 3 and the line OP is θ, and the angle between the armature 3 and the line OQ is α, the moment Mp generated on the P point side is Mp = R × Fcos θ, Q
The moment Mq generated on the point side is Mq = L × Gsinα
become. Since the moments are in the same direction with respect to the rotation support portion O, they are added.

[0011]

1 is a sectional view showing a first embodiment of the present invention, and FIG. 2 is a perspective view thereof. In FIG. 1, a part of a ring-shaped iron core 2 having a square cross section is cut out so as to open in a fan shape from the inner circumference 5 to the outer circumference 6, and the magnetic path is divided to form two magnetic pole surfaces 2a and 2b. However, the angle formed by both magnetic pole surfaces 2a and 2b is set to fall within the range of 80 to 120 degrees (90 degrees in FIG. 1). A predetermined number of coils 1 are wound around the iron core 2 formed as described above. On the other hand, the armature 3 rotates the magnetic path portion 3c forming both the attracted surfaces 3a and 3b, the arm 3d connecting the magnetic path portion 3c and the print needle 7, and the magnetic path portion 3c and the arm portion together. It is composed of a connecting portion 3e for movably supporting, and the angle between the attracted surfaces 3a and 3b is equal to the angle between the magnetic pole surfaces 2a and 2b, and they are arranged so as to face each other between the magnetic pole surfaces 2a and 2b. .. In this arrangement, the connecting portion 3e fits into the rotation support portion 4 which is a semicircular recess formed on the outer peripheral surface 6 of the iron core 2 and holds the armature 3 rotatably at a predetermined position. The relationship between the armature 3 and the magnetic pole surfaces 2a and 2b is such that when the magnetic pole surface 2b and the attracted surface 3b are attracted, there is a slight gap between the other magnetic pole surface 2a and the attracted surface 3a. ing. The reason is that, in terms of processing accuracy, it is not possible for both the attracted surfaces 3a and 3b to contact the magnetic pole surface at the same time, so the processing error on the magnetic pole surface 2a side that is easily affected by the dimensional error from the rotation support portion 4 This is because it is necessary to have a gap that absorbs. Since the influence on the moment of inertia increases as the distance from the rotation support portion 4 increases, the mass of the arm 3d is made as small as possible as shown in FIG. However, since it is necessary to obtain bending rigidity, as a result, the arm 3d is configured to have a large width in the rotation direction and a small thickness. Further, also in the magnetic path portion 3c, the outermost circumference of the magnetic path is formed by an arc that matches the outer circumference 6 of the iron core 2 to reduce unnecessary mass.

Next, a second embodiment is shown in FIG. One end surface of the core 10 having the coil 1 arranged on the outer circumference is used as a first magnetic pole surface 2b for attracting the armature 3, and the yoke 11 forming a magnetic path is connected to the core on the opposite side of the first magnetic pole surface 2b. The yoke 11 passes through the outside of the coil 1 and the core 1
The extension yoke portion 1 extends along the central axis of 0 to extend beyond the extension surface of the first magnetic pole surface 2b and extends beyond the extension surface.
A side surface of the core la on the core 10 side is a second magnetic pole surface 2a, and an angle formed by the second magnetic pole surface 2a and the first magnetic pole surface 2b is 90 degrees. Suction surface 3
The armature 3 having a and 3b is arranged, and the rotation support portion 4 of the armature 3 is provided on the upper end surface of the extension yoke portion 11a adjacent to the second magnetic pole surface 2a. The above is the magnetic path configuration corresponding to one print needle 7, but FIG. 5 shows a plan view when a plurality of magnetic needles are arranged. A plurality of magnetic paths are arranged on the circumference around the center point O of the print head, and the armatures 3 are oriented in the direction of the center point O, respectively. Multiple core pole faces 2
Although a is independently arranged, the yoke 11 is integrally connected to form a ring on the outermost periphery of the center point O. The shape of the armature 3 is as shown in FIG. Suctioned surface 3
The a and 3b are orthogonal to each other, and the magnetic path portion 3c on the diagonal side thereof is cut away to form a slope 3f. The base end of the arm 3d is connected to the slope 3f, and the print needle 7 is brazed to the tip of the arm 3d. In order to support the armature 3, the convex portion having a semicircular cross section of the connecting portion 3e connected to the magnetic path portion 3c is formed by the extension yoke portion 1.
It is performed by fitting with the rotation support portion 4 provided on the upper end surface of the la 1a. The connecting portion 3e forms a magnetic flux leakage path for the magnetic flux passing through the attracted surface 3a, but since the cross-sectional area is small, magnetic saturation occurs and the influence is small. Rather, in the range where the magnetic flux density is low, since the permeance on the attracted surface 3a side is increased, it acts so as to increase the attractive force of the other attracted surface 3b, and overall the magnetic flux is slightly leaked to this portion. The better the performance. The above is the second embodiment, but the difference from the first embodiment is that the magnetic path configuration is changed from a ring shape to a rectangular shape. The reason is that there is a demand to combine a plurality of magnetic path constituent parts into one or a very small number of parts in order to reduce the cost. In the embodiment shown in FIGS. 4 and 5, the plurality of cores 10 and the yoke 11 can be formed by one component. As shown in FIG. 4, the feature of this embodiment from the machined surface is that the side surface 11b of the yoke 11 on the core 10 side and the surface of the second magnetic pole surface 2a are aligned with each other, facilitating die cutting during processing and extending the yoke portion. This means that 11a can also be made integrally.

Next, a third embodiment is shown in FIG. The basic magnetic path structure of this embodiment is the same as that of the second embodiment shown in FIG. 4, but the only difference is that the magnetic pole surface 2a is closer to the core 10 side. Therefore, the side surface 11 of the yoke 11 is
There is a step between b and the magnetic pole surface 2a, and the length of the armature 3 can be shortened by that step, and the moment of inertia can be reduced. The side surface 11b of the yoke 11 needs to be separated from the core 10 by the winding thickness of the coil 1 plus a margin, and the distance cannot be reduced in the portion where the coil 1 exists, so that the magnetic pole surface 2a does not have the coil 1. The magnetic pole surface 2a located above the magnetic pole surface 2b which is the range is brought close to the core 10 side. Extension yoke part 1
The lower surface of 1a coincides with the extension surface of the magnetic pole surface 2b. The extension yoke portion 11a is formed separately from the yoke 11.

Next, a fourth embodiment is shown in FIG. In this embodiment, a step is provided on the lower surface of the extension yoke portion 11a, and the lower surface of the extension yoke portion 11a, which is one surface of the extension yoke portion 11a, is separated from the magnetic pole surface 2b above the magnetic pole surface 2a. The armature 3 is further shortened by making it closer to the core 10 side than in the example shown to reduce the moment of inertia.
The magnetic pole surface 2a is approached until the magnetic pole surface 2a and the side surface of the core 10 near the yoke 11 coincide with each other. Since the magnetic pole surface 2b is separated from the lower surface of the extension yoke portion 11a on the magnetic pole surface 2a side, a coil is also wound in that space to reduce the copper loss of the coil.

Next, a fifth embodiment is shown in FIG. In this embodiment, the magnetic pole surface 2a is moved closer to the core 10 side to shorten the armature and reduce the moment of inertia. At that time, in order to prevent the magnetic pole surface 2a and the magnetic pole surface 2b from approaching each other to cause magnetic flux leakage, the core 1 including a part of the magnetic pole surface 2b is prevented.
A portion 2c near the magnetic pole surface 2b of 0 was cut out. The state of the cut-out core 10 is shown in the perspective view of FIG. Since the cross-sectional area of the core 10 can be increased with respect to the area of the magnetic pole surface 2b, the permeance of the core 10 is increased and a magnetic circuit with good efficiency can be constructed. In the embodiment shown in FIG. 9, the armature 3 is supported by fitting the pin 12 and a recess having a semicircular cross section of the connecting portion 3e of the armature 3. On the other hand, the shape of the armature 3 is considered from the viewpoint of processing cost so that press punching can be performed from the direction of arrow A as shown in FIG. 11, and is slightly different from the example shown in FIG. In this embodiment, the diagonal surface of the magnetic path portion 3c at which the attracted surfaces 3a and 3b are orthogonal to each other is cut away to form the slope 3f, but the direction of the slope is opposite to the arm 3d. (The direction to reduce the reduction amount) to increase the dimension from the attracted surface 3b to increase the arm 3
The bond strength at the base end of d is increased.

Next, a sixth embodiment is shown in FIG. This embodiment is different from the above five embodiments in the method of reducing the moment of inertia of the armature 3. In the above five embodiments, the size and mass of the armature 3 are reduced to reduce the moment of inertia. On the other hand, in this embodiment, the rotation support portion 4 of the armature 3 is set at a position where the moment of inertia of the armature 3 becomes small. When the shape of the armature 3 is fixed, the moment of inertia at the center of gravity of the armature 3 is minimized, so that the rotation support portion 4 is provided as close to the position as possible. Since the print needle 7 is connected to the armature 3, the entire mass configuration is the magnetic path portion 3c, the arm 3d, and the print needle 7. Since the magnetic path portion 3c has the largest mass among them, the arm 3 near the magnetic path portion 3c
The center of gravity is in d. The center of gravity may exist in the space depending on the shape, but in any case, it exists in the middle between the print needle 7 and the magnetic path portion 3c. Therefore, the yoke 11 which also serves as a support portion of the armature 3 is arranged closer to the print needle 7 than the core 10 and is formed by a pin protruding in a direction perpendicular to the plane of the drawing from the arm 3d penetrating the groove provided in the extension yoke portion 11a. Is supported so that it can be rotated. A side surface of the extension yoke portion 11a on the core side forms a second magnetic pole surface 2a, and the second magnetic pole surface 2a is the other first magnetic pole surface 2a.
It is arranged on a plane perpendicular to b. Both pole faces 2
The magnetic path portion 3c of the armature 3 having two attracted surfaces 3a and 3b facing each magnetic pole surface between a and 2b.
To place. Also in this example, the slope 3 is formed by cutting away the diagonal side of the intersection of the attracted surfaces 3a and 3b of the magnetic path portion 3c.
f is formed to reduce the mass.

[0017]

By using the print head having the magnetic path structure according to the present invention, the magnetic path length on the armature side can be shortened, the moment of inertia of the armature can be reduced, and the printing speed can be improved. Fig. 16 shows the magnetic path length on the armature side.
The example of the conventional magnetic circuit shown in FIG. 1 will be compared with the magnetic circuit of the present invention shown in FIG. In the example shown in FIG. 16, the magnetic pole surfaces 2a and 2b are arranged on a plane, and the magnetic path portion 3c of the armature 3 connecting the magnetic pole surfaces 2a and 2b has a semicircular length. A length connecting the ends on the outer circle of 2b is required. In comparison with this, in the example shown in FIG. 1, since the magnetic pole surfaces 2a and 2b are arranged at right angles, the length of the magnetic path portion 3c of the armature 3 is about half that of the example shown in FIG. .. Along with this, the mass of the magnetic path portion 3c is also halved, so that the moment of inertia of the armature can be reduced. Further, the arm 3d needs to have a certain minimum length in terms of arrangement of peripheral parts. Therefore, if the length of the arm 3d is the same in the example shown in FIG. 16 and the example shown in FIG. 1, the position of the rotation support portion 4 of the armature 3 is shown in FIG.
1 can be set closer to the arm 3d, the total length of the armature and the moment of inertia can be reduced in the example shown in FIG. 1 than in the example shown in FIG.

The suitable angle range formed by the two magnetic pole surfaces according to the present invention is limited to 80 to 120 degrees, but the performance is not extremely deteriorated outside the range. FIG. 13 shows a case where the angle formed by both magnetic pole surfaces 2a and 2b is 80 degrees, but within the range of this angle or less, the component of the attractive force of the magnetic pole surface 2a gradually increases the attractive force of the magnetic pole surface 2b. Since they occur in the direction of canceling each other, the total suction force decreases. Further, in the assembly process, the magnetic pole surface 2a previously assembled and the attracted surface 3a of the armature to be assembled later are likely to interfere with each other. On the other hand, FIG. 14 shows the case where the angle formed by both magnetic pole surfaces 2a and 2b is 120 degrees, but within the range of this angle or more, both attracted surfaces 3a and 3b of the armature 3 are shown.
The length of the magnetic path that connects the two is gradually increased, the mass is increased, the total length of the armature is increased, the moment of inertia is increased, and the difference in performance from the conventional one is reduced. Further, since the distance between the rotation support portion 4 and the magnetic pole surface 2b becomes large, the gap of the magnetic pole surface 2b becomes large during the rotation of the armature, which lowers the permeance of the magnetic circuit and improves the electromechanical conversion efficiency. It tends to decrease. The angle currently considered to be the best is 90 degrees in terms of processing and assembly, armature mass and suction force.

Further, by using the print head having the magnetic path structure according to the present invention, the unnecessary magnetic path of the armature can be reduced,
By reducing the mass, the moment of inertia of the armature is reduced, and the printing speed can be improved. Since both surfaces to be attracted of the armature intersect at approximately 80 to 120 degrees, the cross-sectional area of the magnetic path connecting both surfaces to be attracted is uniform even if a part of the magnetic path on the diagonal side of the intersection is reduced. Can be As shown in FIG. 2, if the slope 3f on the diagonal side of the intersection of the attracted surfaces of the armature is aligned with the outer surface 6 of the iron core 2, the cross-sectional area of the magnetic path portion 3c becomes the cross-sectional area of the iron core 2. Can be matched. In FIG. 2, the slope 3f is formed by a circular arc, but the performance is almost the same even if it is formed by a straight line.

Since the magnetic circuit of the present invention has two magnetic pole faces, the attraction force of the armature becomes large, and a large printing force can be obtained. In addition, since the distance from the armature rotation support portion to both magnetic pole surfaces can be shortened, the air gap on both magnetic pole surfaces is reduced, and as a result, the permeance of the magnetic circuit is increased, so there are two magnetic pole surfaces. The electromechanical conversion efficiency is improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a perspective view of the embodiment shown in FIG.

FIG. 3 is an illustration of a magnetic circuit relating to FIG.

FIG. 4 is a sectional view showing a second embodiment of the present invention.

5 is a plan view of the embodiment shown in FIG.

6 is a perspective view of the armature 3 shown in FIG.

FIG. 7 is a sectional view showing a third embodiment of the present invention.

FIG. 8 is a sectional view showing a fourth embodiment of the present invention.

FIG. 9 is a sectional view showing a fifth embodiment of the present invention.

10 is a see-through perspective view around the magnetic pole surface 2b shown in FIG.

11 is a perspective view of the armature 3 shown in FIG. 9. FIG.

FIG. 12 is a sectional view showing a sixth embodiment of the present invention.

FIG. 13 is a cross-sectional view of an example in which the angle formed by the magnetic pole surfaces 2a and 2b is 80 degrees.

FIG. 14 is a cross-sectional view of an example in which the angle formed by the magnetic pole faces 2a and 2b is 120 degrees.

FIG. 15 is an explanatory diagram of a moment acting on the armature of the present invention.

FIG. 16 is an explanatory diagram showing an example of a conventional magnetic circuit as viewed from the side.

FIG. 17 is an explanatory diagram of a first conventional example.

FIG. 18 is an explanatory diagram of a magnetic circuit having one magnetic pole surface.

FIG. 19 is an explanatory diagram of a magnetic circuit having two magnetic pole surfaces.

FIG. 20 is an explanatory diagram of a second conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 coil 2 iron core 2a magnetic pole surface 2b magnetic pole surface 3 armature 3a attracted surface 3b attracted surface 3c magnetic path part 3d arm 3e connecting part 3f sloped surface 4 rotation support part 7 print needle 8 return spring 9 armature stopper 10 core 11 yoke 11a Extension yoke part 12 pin 13 attracted piece 14 body 15 leaf spring 16 rotation support point 17 permanent magnet

Claims (2)

[Claims] 1. In a print head for driving an armature by a magnetic attraction force to obtain an impact force required for printing by kinetic energy applied to the armature, a magnetic core of an iron core in which a coil is wound and a closed magnetic path is formed. An iron core having two magnetic pole faces formed by cutting a part of the iron core and dividing the magnetic path so as to open in a fan shape from the inner side to the outer side of the road loop at an angle in the range of 80 to 120 degrees. , Two magnetic attraction surfaces that form an angle equal to the angle formed by the two magnetic pole surfaces and a magnetic path that does not impede magnetic permeability between the magnetic attraction surfaces, and each of the two magnetic attraction surfaces has the two magnetic attraction surfaces. And an armature rotatably supported in the vicinity of the one magnetic pole surface of the iron core and in the vicinity of the outer peripheral surface of the magnetic path loop of the iron core so as to face one magnetic pole surface, and to energize the coil. By both A magnetic path structure of an impact print head, characterized in that a magnetic path structure is formed such that a suction force generated on a magnetic pole surface generates a moment with respect to a rotation support portion of an armature. 2. The magnetic path structure of the impact print head according to claim 1, wherein a magnetic path on a diagonal side of a point where both surfaces to be attracted of the armature according to claim 1 intersect is reduced.