JPH05116345A - Printing head - Google Patents

Abstract

PURPOSE:To enhance printing quality in a printing head. CONSTITUTION:The distance from a leading end guide hole 25b to a rear end guide hole 25a and the distance (m) up to the fixing part 23 of each of printing wires 10 and a movable piece 18 are made constant in each of the printing wires 10 and the movable piece 18 is arranged on the center line 31 of each of electromagnets 5 which are arranged in a circular shape at an equal interval. By this constitution, since the reaction force and lateral pressure applied to each of the printing wires 10 become constant and flying irregularity and printing force irregularity are eliminated, a printing head imparting good printing quality can be obtained. Since the electromagnets 5 having the same shape can be closely arranged, the small-sized printing head excellent in mass productivity can be obtained at a low cost.

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 matrix printer.

[0002]

2. Description of the Related Art As a conventional print head, for example, one described in Japanese Patent Application Laid-Open No. 2-155748 is known. As disclosed therein, as shown in FIG. 4, the guide hole 101 at the rear end, which is the closest to the movable piece 100, is arranged in a circular shape centering on the head axis 102, and the movable piece 100 is also a head. They are arranged in a circular shape around the axis 102. Therefore, the distance m ′ from the guide hole 101 to the fixed portion 104 of the print wire 103 to which the movable piece 100 is fixed is constant in each print wire 103, and the lateral pressure and reaction force applied to the print wire 103 are made uniform. It was something to try.

As another conventional print head, for example, as shown in FIG. 5, the distance p'from the tip 204 of the print wire 200 to the fixed portion 202 of the movable piece 201 is constant in each print wire 200. The fixed part 202 and the electromagnet 203 are arranged in an elliptical shape so as to form a straight line.

[0004]

However, as shown in FIG. 4, in the conventional print head, the rear end guide hole 101 is formed.
The distance l ′ from the guide hole 105 at the tip to the guide wire 105 at the tip is different for each print wire 103. Therefore, the lateral pressure applied to the print wire 103 is not sufficiently uniform, and the print wire 103 fluctuates in flight and print power, which deteriorates print quality.

Further, in the conventional print head as shown in FIG. 5, since the relative positions of the adjacent electromagnets 203 are not constant, when arranging the electromagnets 203 having the same shape, a wasteful gap is generated between the adjacent electromagnets 203, and the printing is performed. There was a problem that the head could not be made smaller. In addition, when the shape of the electromagnet is changed, the coil of the electromagnet must also have a different shape, so that there is a problem that mass productivity is not excellent and cost is increased.

Therefore, the present invention is intended to solve such a problem, in which the side pressure and reaction force applied to the printing wire are made uniform to obtain good printing quality, and at the same time, the mass productivity is excellent and the cost is low. The purpose is to obtain a small print head.

[0007]

In the print head of the present invention, a plurality of electromagnets having the same shape are arranged on the same plane, each electromagnet drives a corresponding movable piece and is fixed to the tip of the movable piece. In a print head that prints by hitting a print wire slidably held in a guide hole formed in the wire guide on a print medium, electromagnets are circularly arranged at equal intervals, and a guide hole at the tip is provided. The guide holes at the rear end are arranged in an elliptical shape so that the distance from the guide hole at the rear end to the guide hole at the rear end is uniform on the projection surface parallel to the printing surface of the print medium. And a fixed portion on the projection surface parallel to the print surface of the print medium, and the movable piece is arranged on the center line of the electromagnet.

[0008]

The distance between the guide hole at the front end and the guide hole at the rear end on the projection plane parallel to the print surface of the print medium, and the print surface of the print medium from the guide hole at the rear end to the fixing portion of the print wire Since the distances on the parallel projection planes are the same, the side pressure and reaction force applied to the printing wire are constant, and there are no variations in the printing wire flight and variations in the printing force, and uniform printing quality can be obtained. it can. Further, since the electromagnets are arranged in a circle, the electromagnets of the same shape can be arranged without a wasteful gap, the print head can be downsized, and the coil of the same shape can be used, which is excellent in mass productivity, A low cost print head can be obtained.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a front view of an embodiment of the print head of the present invention, and FIG. 1B is a side view. FIG. 2 shows A in FIG.
It is a fragmentary sectional view showing the -A section. FIG. 3 is a view showing the arrangement of the guide hole 25b at the front end, the guide hole 25a at the rear end, the print wire fixing portion 23, the movable piece 18, and the electromagnet 5 in the embodiment of the print head of the present invention.

A print head 1 of an embodiment based on FIGS. 1 to 3.
The configuration and operation of will be described. A coil 4 wound around a coil bobbin 3 is inserted into a core 2 made of a magnetic material having high magnetic permeability to form an electromagnet 5. The coil 4 is connected to a driver circuit (not shown) through the substrate 6 and the connector 7. As shown in FIG. 3, the electromagnet 5 has a trapezoidal shape that tapers in the central direction, and is arranged on the bottom surface of the core block 8 on the same circumference centered on the shaft center 9 of the print head 1 at equal intervals and without gaps. , All have the same shape. In this embodiment, 24 printing wires 10 are provided, and the electromagnets 5 are arranged on the same circle at equal intervals of 15 degrees.

The core 2 has a larger area than the suction surface of the movable piece 18, and has a tapered surface 33 that squeezes the tip in accordance with the position of the corresponding movable piece 18. A yoke 11, a spacer 12, a positioning plate 13, a spacer 14, and a holder 15 are laminated on the core block 8 to form a leaf spring 16
It is fixed by. The heat dissipation member 17 covers the outer periphery of the core block 8. A movable piece 18 made of a magnetic material having a high magnetic permeability is rotatably supported by a fulcrum shaft 19 and guided by a guide portion 32 formed on the coil bobbin 3.

The fulcrum shaft 19 includes a spacer 12 and a spacer 14.
And is positioned by the positioning plate 13. The movable piece 18 is pressed by the return spring 21 held by the spring holding member 20 and is pressed against the damper 22. The printing wire 10 is fixed to the fixing portion 23 at the tip of the movable piece 18, and is slidably held in guide holes 25a, 25b, 25 formed in the wire guides 24a, 24b, 24. The guide hole 25 at the rear end that is the closest to the movable piece 18
a is formed integrally with the spring holding member 20. The wire guides 24a, 24b, 24 are fixed to a guide holding member 26, a head attaching portion 27 is formed on the guide holding member 26, and attached to a carriage (not shown).

When the coil 4 is energized by a driver circuit (not shown), the electromagnet 5 attracts the movable piece 18, the print wire 10 flies, and the print medium 29 held on the platen 30 via the ink ribbon 28. Hit the
Print. After printing, the movable piece 18 is pressed by the return spring 21 and returns to the standby position.

Next, the guide hole 25b at the front end, the guide hole 25a at the rear end, the fixed portion 23 of the print wire 10 and the movable piece 18,
The arrangement of the electromagnets 5 will be described. Since the print head 1 of this embodiment is symmetrical with respect to the axis 9, the arrangement on one side on a plane orthogonal to the axis 9 is shown in FIG. The axis 9 is substantially orthogonal to the print medium 29 near the print position. The guide holes 25b at the tip end are staggered. The guide hole 25a at the rear end, which is the closest to the movable piece 18, has the electromagnet 5
Is located on the center line 31 and is arranged in an elliptical shape so that the distance 1 from the guide hole 25b at the tip is uniform. The fixing portion 23 of the printing wire 10 is also on the center line 31 of the core 2, and is arranged in an elliptical shape like the rear end guide hole 25b so that the distance m from the rear end guide hole 25a is uniform. There is. Therefore, in all the print wires 10, the distance 1 from the guide hole 25b at the front end to the guide hole 25a at the rear end and the guide wire 25a at the rear end from the guide hole 25a
The distance m to the fixing portion 23 of the
The reaction force applied to 0 and the lateral pressure are constant. Further, since the guide hole 25a at the rear end, the fixed portion 23 of the print wire 10 and the movable piece 18 are on the center line 31 of the electromagnet, the guide portion 32 does not exert a lateral pressure on the movable piece 18, and the movable piece moves. Is made smooth. Further, since the return springs 21 have the same elliptic arrangement and the distance n from the fulcrum shaft 19 to the return springs 21 is constant, the return force applied to the print wires 10 is equal in all the print wires 10, and the flight time and the print force are the same. It is possible to obtain uniform print quality without variation. Further, in the present invention, since the electromagnets 5 are arranged in a circular shape, the electromagnets 5 having the same shape can be arranged without a gap, and the core 2 can be arranged in comparison with the case where they are arranged in an elliptical shape.
Therefore, the print head 1 can be downsized when a certain required suction area is secured. Further, since coils having the same shape can be used, mass productivity is excellent and cost can be reduced.

Although the relative position of the movable piece 18 and the core 2 is different for each printing wire 10, the area of the core 2 is enlarged so that the movable piece 18 is located on the surface of the core 2 in any case. The tapered surface 33 is changed for each core 2 according to the position of the movable piece 18 facing each other, and since the tip is squeezed, the suction force can be made constant and the suction force can be increased.

[0016]

As described above, according to the present invention, the distance from the guide hole at the front end to the guide hole at the rear end and the printing on the print medium from the guide hole at the rear end to the fixed portion of the print wire and the movable piece are performed. Since the distance on the projection plane parallel to the surface is made uniform, the reaction force and the lateral pressure applied to the printing wire become equal, the flight variation and the printing force become constant, and uniform printing quality can be obtained. Also, because the electromagnets are arranged in a circle,
It is possible to obtain a print head that is small in size, excellent in mass productivity, and low in cost.

[Brief description of drawings]

FIG. 1A is a front view and FIG. 1B is a side view of an embodiment of a print head according to the present invention.

FIG. 2 is a partial cross-sectional view of the AA plane shown in FIG. 1A of the embodiment of the print head of the present invention.

FIG. 3 is a front guide hole 25b, a rear guide hole 25a, and a print wire fixing portion 2 of the print head according to the embodiment of the present invention.
FIG. 3 is a diagram showing an arrangement of 3, a movable piece 18, and an electromagnet 5.

FIG. 4 is a diagram showing a prior art arrangement.

FIG. 5 is a diagram showing a prior art arrangement.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 print head 5 electromagnet 10 print wire 18 movable piece 23 fixed part 25a rear end guide hole 25b front end guide hole 29 print medium

Claims (1)

[Claims] 1. A plurality of electromagnets having the same shape are arranged on the same plane, each electromagnet drives a corresponding movable piece, and the electromagnet is fixed to the tip of the movable piece, and is inserted into a guide hole formed in a plurality of wire guides. In a print head that prints by sliding a print wire held slidably on a print medium, the electromagnets are circularly arranged at equal intervals, from the guide hole at the front end to the guide hole at the rear end. The guide holes at the rear end are arranged in an elliptical shape so that the distance on the projection plane parallel to the print surface of the print medium is uniform, and the guide wire and the movable piece are separated from the guide hole at the rear end. A print head, wherein a distance to a fixed portion on a projection plane parallel to a print surface of the print medium is uniform, and the movable piece is arranged on a center line of the electromagnet.