JPH06135016A - Dot impact print head - Google Patents

Abstract

PURPOSE:To obtain a print head having high print quality by employing a coil spring and a leaf spring as armature reset means for a clapper type print head thereby allowing high speed printing while furthermore extending a ring yoke, interposed between a yoke and the fulcrum of armature, to the vicinity of armature attracting section thereby restraining magnetic interference. CONSTITUTION:A leaf spring 10 has one end fixed to the vicinity of the center of rotation 2a of an armature 2 and the other free end extending to the vicinity of the part 2b of armature contacting with the leaf spring 10. When the armature 2 is attracted magnetically to decrease an attraction gap Ga below a predetermined dimension, the armature 2 abuts on the leaf spring 10. A ring yoke 9 is disposed through a slight gap with respect to a protrusion of the armature and forming a magnetic path B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dot impact print head used in a dot matrix printer.

[0002]

2. Description of the Related Art FIG. 7 is a sectional view of a conventional dot impact print head. In this example, as shown in FIG. 7, a plurality of armatures 2 each having a print wire 1 attached to the tip thereof are provided.
And a yoke 3 having a plurality of cores 3a each having a coil 4 corresponding to each armature, a return spring 5 for pushing the armature 2 in a direction opposite to the core 3a, and a rotation center 2a of the armature 2 being pushed against the yoke 3 side. It has a hold spring 6.

[0003]

In this conventional dot impact print head, in order to perform high-speed printing operation, the magnetic attraction force is strong and the return spring force is weak during the armature attraction operation, and the residual magnetic flux is returned when the armature is restored. However, it is difficult to satisfy both of them, and if both the magnetic attraction force and the return spring force are increased, the shape of the print head becomes large. There was a problem.

FIG. 8 is a diagram for explaining the operation of the conventional example shown in FIG. This conventional dot impact print head has a suction gap Ga and a stopper gap G as shown in FIG.
Since the operating distance and the operating performance of the armature depend on s, it is necessary to accurately manufacture these two gaps Ga and Gs. However, it is important to accurately process the step between the outer peripheral portion of the yoke and the inner core portion. It was difficult and expensive.

On the other hand, when the coil is energized, the magnetic flux generated thereby passes through the path A shown in FIG. 8 and the path C shown in FIG. 5 which is a cross section taken along line LM in FIG. When the magnetic reluctance is large, there is a problem that the magnetic flux passing through the path C increases and magnetic interference with the adjacent magnetic circuit occurs to make the armature operation unstable.

[0006]

A dot impact print head according to the present invention has a plurality of coils, an armature having a print wire attached to its tip, and a yoke integrally formed with a plurality of cores. In a dot impact print head that selectively drives the armature to print characters and figures, the armature is rotatable about an end opposite to the end to which the print wire is attached, and the rotation is performed. A leaf spring extending from the center of the armature toward the tip of the armature is provided, and the leaf spring is a cantilever with its free end being fixed near the rotation center of the armature. It is characterized by

A coil spring for applying a force in a direction opposite to the magnetic attraction force of the armature is provided, and the size is set so that the force by the coil spring is always applied in the direction for returning the armature, and the leaf spring is used. The force is dimensioned so as to be applied in the same direction as the force of the coil spring when the armature is magnetically attracted and approaches the yoke.

Further, the armatures are arranged in a circular shape, and the leaf spring is a flat plate having a circular outer periphery and having the same number of protrusions as the armatures on the inner side.

Further, a ring-shaped plate made of a magnetic material is provided between the center of rotation of the armature and the yoke, and the magnetic attraction portion of the armature has a protrusion toward the coil mounting portion of the yoke, The plate thickness of the plate and the size of the protrusion of the armature are substantially the same, and when the yoke, the ring plate, the plate spring, and the armature are stacked, the armature and the suction surface of the yoke are parallel to each other. It is characterized by being configured.

Further, a ring-shaped spacer made of a magnetic material is provided between the ring-shaped plate and the yoke,
When the attraction surfaces of the armature and the yoke are parallel to each other, a gap is created between the attraction surface of the armature and the yoke by the thickness of the spacer, and the armature abuts the yoke due to magnetic attraction. Sometimes, the armature is tilted by the gap to bend the leaf spring.

The straight line connecting the leaf spring abutting portion of the armature with which the free end tip of the leaf spring abuts and the rotation center of the armature is parallel to the suction surface of the armature, and the leaf spring contact is made. A recess is provided between the contact portion and the center of rotation of the armature, and the armature and the leaf spring are in contact with each other only at the two points.

Further, the ring-shaped plate is characterized in that the inner diameter is such that a slight clearance is maintained within a range in which the ring-shaped plate does not come into contact with the outer peripheral portion of the suction projection of the armature arranged in a circular shape.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. 1 is a sectional view of an embodiment of the dot impact print head of the present invention, FIG. 2 is a cutaway perspective view of the embodiment shown in FIG. 1, FIG. 3 is a perspective view of the leaf spring in FIG. 1, and FIG. FIG. 6 is an operation explanatory diagram of the embodiment shown in FIG.

As shown in FIGS. 1 and 2, in this embodiment, a plurality of armatures 2 having a print wire 1 fixed to the tip thereof are provided.
And a yoke 3 having a plurality of cores 3a having coils 4 corresponding to the individual armatures 2 and having an integrated outer periphery.
A return spring 5 for pushing the armature 2 in the direction opposite to the core 3a, a ring-shaped spacer 8 made of a magnetic material stacked between the armature 2 and the yoke 3, a ring-shaped yoke 9, a leaf spring 10, and the armature 2. A hold spring 6 installed so as to press the end portion against the leaf spring 10 and a stopper 7 for stopping the operation of the armature 2 pushed by the return spring 5 are provided.

Here, as shown in FIG. 3, the leaf spring 10 is a flat plate having a circular outer periphery and having the same number of protrusions toward the inner side as the number of armatures. As shown in FIG. 4, the outer peripheral portion is the center of rotation of the armature 2. It is sandwiched between 2a and the ring-shaped yoke 9, and the tip end portion of the protrusion is configured to contact the leaf spring contact portion 2b of the armature when the armature 2 is attracted to the core 3a. On the other hand, the armature 2 has a recess between the rotation center 2a of the armature 2 and the leaf spring contact portion 2b, and the surface connecting the rotation center 2a and the leaf spring contact portion 2b is parallel to the armature suction surface 2c. ing.

Here, the distance between the two parallel planes is equal to the total thickness of the leaf spring 10 and the ring-shaped yoke 9. Further, the surfaces of the yoke 3 and the core 3a on the armature 2 side are processed to be the same plane. Therefore, when the armature 2 is in a horizontal state as shown in FIG.
0, the suction surface gap Ga at this time becomes equal to the plate thickness of the ring-shaped spacer 8. The inner circumference of the ring-shaped yoke 9 is dimensioned so as to have a slight clearance within a range where it does not come into contact with the protrusion of the armature.

In the present embodiment having such a structure, the armature 2 is pressed against the stopper 7 by the return spring 5 at the time of non-printing, and when the coil 4 is energized, the magnetic attraction force causes the armature attraction surface 2c to become the core attraction surface. 3c, the armature 2 rotates clockwise around the armature center 2a in FIG. Then, when the armature 2 becomes horizontal, it hits the leaf spring 10 and is further attracted to print at the tip of the print wire 1. When the energization is cut off thereafter, the armature 2 rotates counterclockwise by the force of the leaf spring 10 and the return spring 5, collides with the stopper 7, absorbs the impact, and stands still.

FIG. 6 is a diagram showing the relationship between the magnetic attraction force and the armature return force and the attraction gap in this embodiment. In FIG. 6, the horizontal axis represents the air gap x on the suction surface,
The vertical axis is magnetic attraction force and spring force (armature return force)
F, the straight line A0-P1-P2-Fc (0) shows the force of the return spring, the straight line P2-Fa (0) shows the force of the leaf spring 10 added to the force of the return spring, and thus the polygonal line Fa (X) shows the restoring force of the armature. On the other hand, the curve Fb (x) shows the magnetic attraction force when the coil 4 is energized.

Here, the suction gap x = A1 when not printing, x = A2 when the armature is in the horizontal state, and x = 0 when the armature is in contact with the core 3a. Therefore, when the coil 4 is energized, the force F acting on the armature 2 is Fb.
(X) −Fa (x) = f (x), that is, f (A1) at the start of operation and f (0) at the time of contact with the core 3a. When the energization is cut off after magnetic attraction, the above-mentioned restoring force Fa (x) acts on the armature and returns to the position of A1.

Since the conventional print head does not have a leaf spring, the armature return force is A0-P1-P2-Fc.
Since it is a straight line of (0), the restoring force when the power is turned off is F
Since it is c (0) and the restoring force is small, the printing operation is slow.

On the other hand, in this embodiment, even if the magnetic attraction force is the same, the restoring force can be increased to Fa (0), and high-speed printing can be performed. Further, the position of A2 needs to be assembled with high precision, but in this embodiment, since it is determined by the plate thickness of the ring-shaped spacer 8, high precision can be obtained.

On the other hand, when the coil is energized, the magnetic flux passes through the paths A and B shown in FIG. 4 and the path C shown in FIG. Here, the route C passes through the adjacent armature 2 and core 3a and is not a preferable route due to the problem of magnetic interference. However, since the route B which is not provided in the conventional print head is added, the route C is added. The magnetic flux passing through can be reduced and the magnetic interference is reduced.

[0023]

As described above, according to the present invention, the printing speed can be increased by providing the leaf spring that acts to strengthen the armature return force when the armature is magnetically attracted and approaches the core. Has the effect. In addition, the contact position of the leaf spring is determined by the thickness of the ring-shaped spacer, and a recess is provided in the armature between the center of rotation and the contact portion of the leaf spring, so that a high-quality print head with stable armature return force characteristics. Has the effect of being able to provide. Further, by bringing the inner diameter of the ring-shaped yoke close to the armature within a range where it does not come into contact with the armature, there is an effect that it is possible to provide a print head having good print quality with less magnetic interference.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a dot impact print head of the present invention.

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

3 is a perspective view of the leaf spring in FIG. 1. FIG.

FIG. 4 is an operation explanatory diagram of the embodiment shown in FIG.

5 is a cross-sectional view taken along line LM in FIGS. 4 and 8. FIG.

FIG. 6 is a diagram showing a relationship between a magnetic attraction force and an armature return force and an attraction gap in the present embodiment.

FIG. 7 is a cross-sectional view of a conventional dot impact print head.

FIG. 8 is an operation explanatory diagram of the conventional example shown in FIG. 7.

[Explanation of symbols]

 1 Print wire 2 Armature 2a Armature rotation center 2b Leaf spring contact part 2c Armature suction surface 3 Yoke 3a Core 4 Coil 5 Return spring 6 Hold spring 7 Stopper 8 Ring spacer 9 Ring yoke 10 Leaf spring

Claims (7)

[Claims] 1. A character or a graphic having a plurality of coils, an armature having a print wire attached to a tip thereof, and a yoke integrally molded with a plurality of cores, and selectively driving the armature by a magnetic attraction force. In the dot impact print head for printing, the armature is rotatable about an end opposite to the end on which the print wire is attached, and the armature extends from the yoke side of the center of rotation toward the tip of the armature. A dot impact print head, comprising a leaf spring, wherein the leaf spring is a cantilever having a free end in a vicinity of a center of rotation of the armature and a free end. 2. A coil spring that applies a force in a direction opposite to the magnetic attraction force of the armature, is dimensioned so that the force of the coil spring is always applied in a direction of returning the armature, and the leaf spring is used. 2. The dot impact print head according to claim 1, wherein the force is dimensioned so as to be applied in the same direction as the force of the coil spring when the armature is magnetically attracted and approaches the yoke. 3. The armatures are arranged in a circle, and the leaf spring is a flat plate having a circular outer periphery and having the same number of protrusions as the armatures on the inner side.
The dot impact print head described. 4. A ring-shaped plate made of a magnetic material is provided between the center of rotation of the armature and the yoke, and the magnetic attraction portion of the armature has a protrusion toward the coil mounting portion of the yoke, and the ring. The plate thickness of the plate and the size of the protrusion of the armature are substantially the same, and when the yoke, the ring plate, the plate spring, and the armature are stacked, the armature and the suction surface of the yoke are parallel to each other. The dot impact print head according to claim 1 or 3, wherein the dot impact print head is configured. 5. A ring-shaped spacer made of a magnetic material is provided between the ring-shaped plate and the yoke, and when the attraction surfaces of the armature and the yoke are parallel to each other, the spacer has a thickness corresponding to the plate thickness. A gap is created between the armature and the suction surface of the yoke, and when the armature abuts the yoke due to magnetic attraction, the armature is tilted by the gap to bend the leaf spring. The dot impact print head according to claim 1 or 4, characterized in that: 6. A straight line connecting a leaf spring contact portion of the armature with which a free end tip of the leaf spring abuts and a rotation center of the armature and a suction surface of the armature are parallel to each other, and 2. The dot impact print head according to claim 1, wherein a recess is provided between the contact portion and the center of rotation of the armature, and the armature and the leaf spring contact each other only at the two points. 7. The inner diameter of the ring-shaped plate has a size with a slight clearance provided that it does not come into contact with the outer peripheral portion of the protrusion of the suction portion of the armature arranged in a circular shape. 4. The dot impact print head according to 4.