JPH07125265A - Dot impact type printing head - Google Patents

Abstract

PURPOSE:To remove a difference in printing quality caused by a difference in a platen gap being a gap between a tip of a printing wire and a platen by a position of the printing wire. CONSTITUTION:When an armature 15 is attracted with a permanent magnet 18, a grinding amount of the armature is varied so that a bending amount of a leaf spring 14 is made large for an upper and lower part printing wire 12a and is made small for an intermediate part printing wire 12b, and a bypass plate 21 is provided by conforming a tongue like part 21a to a part wherein the bending amount of the leaf spring 14 is large via a spacer 20 on an opposite side to a surface facing a yoke 16b of the leaf spring 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dot impact type print head, and more particularly to an improved dot impact type print head capable of optimally maintaining a distance (platen gap) between a print wire and a platen.

[0002]

2. Description of the Related Art Conventionally, a print head of this type is shown in FIG.
As shown in (a), the head frame 11 having a cylindrical front surface (the left side in the drawing) and the head frame 11
A plurality of printing wires 12 are arranged inside. The tip portion of the print wire 12 is guided by a guide 13 provided at the tip of the head frame 11. Further, the print wire 12 is driven by a driving device including a magnetic circuit described later. The magnetic circuit of this drive device is provided in correspondence with the disc-shaped leaf springs 14 having internal teeth provided continuously to the rear surface (right side in the drawing) of the head frame 11 and the individual print wires 12, Also, an armature 15 fixed to the leaf spring 14, a yoke 16b having a suction surface 16a on a core portion facing the armature 15, an annular electromagnetic coil 17 mounted on the core portion of the yoke 16b, and a yoke 16
a permanent magnet 18 connected to the end face of the outer peripheral portion of b,
It is composed of an annular ring yoke 16c disposed between the leaf spring 14 and the permanent magnet 18. An arm 19 is fixed to the armature 15, and the base end of the print wire 12 is fixed to the arm 19.

In the non-printing state in the operation of such a print head, the armature 15 is attracted to the attraction surface 16a of the yoke 16b by the attraction force of the permanent magnet 18. Here, the magnetic flux generated by the permanent magnet 18 and the electromagnetic coil 17 forms a magnetic loop by the yoke 16, the permanent magnet 18, the leaf spring 14, and the armature 15, as shown in FIG. Passing through. Since the leaf spring 14 is a thin plate, a leakage magnetic flux 22A is generated. The leaf spring 14 is held in a bent state by this magnetic attraction force. When a current is applied to the electromagnetic coil 17 in this state, a magnetic flux in the opposite direction to the magnetic flux generated by the permanent magnet 18 is generated on the attraction surface 16a, and these magnetic fluxes cancel each other out, so that the attraction force of the attraction surface 16a disappears. For this reason, the print wire 12 fixed to the armature 15 is guided by the guide 13 and protrudes from the tip of the head frame 11. Then, the printing wire 12 collides with the platen 4 via the ink ribbon 2 and the printing paper 3 serving as a recording medium, and at this time, the ink applied to the ink ribbon 2 is transferred to the printing paper 3 to perform a printing operation. . When the current applied to the electromagnetic coil 17 is cut off in the state where the printing operation is completed, the armature 15 is again attracted to the attraction surface 16a of the yoke 16b by the magnetic flux of the permanent magnet 18 to perform the return operation.
In this way, a series of printing operations are completed by the opening operation and the suction operation of the armature 15 from the suction surface 16a.

[0004]

In this conventional print head, a plurality of print wires 12 are arranged in a zigzag pattern in the vertical direction (vertical direction in FIG. 4) by guides 13.
Further, since the platen 4 with which the print wire 12 collides during printing has a center on an extension of the center line C of the print head and has a predetermined curvature, the platen gap is defined by the vertical direction of the print wire 12. It changes according to the position in the direction. That is, the platen gap of the intermediate portion printing wire 12b located in the vicinity of the center line C is small, and the platen gap becomes large as it goes away from the center line upward.

Therefore, there is a difference in the moving distance between the print wire 12 at the intermediate position and the print wire 12 at the upper and lower positions apart from the center line. Therefore, for all wires, 1 permanent magnet
In the conventional print head in which the attraction with the same magnetic flux by 8 and the same amount of deflection of the leaf spring 14 are applied, the print wire 12 in the middle portion having a small moving distance performs a series of printing operations. Further, since the platen 4 is hit with the plate spring 14 bent, the printing pressure becomes strong, and the ink ribbon 2 may be caught by the printing wire 12 in the middle portion. Further, since the printing wire 12 having a large moving distance is slow in a series of printing operations and the platen 4 is hit with the plate spring 14 having a small bending amount, the printing pressure is weakened and printing may be blurred. As described above, the conventional print head has a drawback that the print quality is different between the portion having a large platen gap and the portion having a small platen gap.

[0006]

A dot impact type print head according to the present invention is mounted on an armature for driving a printing wire supported by an elastic member, a yoke having a suction surface facing the armature, and a yoke. In an annular magnetic circuit including a permanent magnet and an electromagnet, and a wire dot type print head that attracts the armature by the permanent magnet and releases the armature from an attraction surface by energizing the electromagnet, the yoke is provided. It is characterized in that a magnetic bypass plate having a tongue-shaped projection in the center and a spacer are arranged on the side opposite to the surface in accordance with the portion of the elastic member having a large amount of deflection.

[0007]

The present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of an embodiment of the present invention, and FIG. 2 is a dot impact type print head (hereinafter referred to as a print head) 1, an ink ribbon 2, a print sheet 3, and a platen for showing the cross-sectional position of FIG. 4 is a perspective view showing the arrangement of No. 4 in FIG. That is, FIG. 1A is a sectional view taken along the line AA of FIG.
2B is a sectional view taken along the line BB in FIG. 2, the same reference numerals as those in the conventional example of FIG. 5 indicate the same configurations. That is, the bypass plate 21 is provided in this embodiment. FIG. 3 shows FIG.
FIG. 4 is a perspective view of the bypass plate 21 of the embodiment of “a”, and FIG. 4 is an enlarged cross-sectional view of the periphery of the print head tip portion of the embodiment of FIG. 1.

Next, the configuration and operation of this embodiment will be described. The print head 1 is provided with a plurality of print wires 12, and a magnetic circuit corresponding to each print wire 12 is formed. Printing is performed by selectively energizing a predetermined magnetic circuit according to the print information to drive the print wire 12. In this embodiment, the upper and lower print wires 12a and a representative example of the intermediate wire, the intermediate print wire 12b will be described as a typical example of the upper and lower wires, but the operation description common to both the upper and lower print wires 12a and the intermediate print wire 12b will be described. It will be indicated by the print wire 12. The print wire 12 guided and supported by a guide 13 provided at the tip of the head frame 11 is driven by a drive device including a magnetic circuit. The magnetic circuit is a disk-shaped leaf spring 14 having internal teeth provided continuously on the rear surface of the head frame 11, an armature 15 fixed to the leaf spring 14, and a center arranged to face the armature 15. 16b having a suction surface 16a on its core
And the electromagnetic coil 17 mounted on the yoke 16b,
A permanent magnet 18 connected to the end face of the outer peripheral portion of the yoke 16b, a ring yoke 16c arranged between the leaf springs 14 and 18, a spacer 20 connected to the leaf spring 14, and a head frame 11 And a bypass plate 21 fixed by being sandwiched between the spacer 20 and the spacer 20. When the armature 15 is attracted by the permanent magnet 18, the upper and lower print wires 12a of the print head are made larger and the middle print wire 12b is made smaller so that the amount of deflection of the leaf spring 14 is made larger, and the armature 15a for the upper and lower print wires is made smaller.
Is thin, and the armature 15b for the intermediate print wire is thickly polished. The bypass plate 21 is shown in FIG.
As described above, a magnetic substance such as iron is used to attach the tongue-shaped portions 21a vertically so that the cross section C-C corresponds to the cross section of FIG. That is, the tongue portion 21a is arranged so as to match the portion of the leaf spring 14 where the amount of bending is large. Spacer 20
The bypass plate 21 serves as the suction surface 16 of the yoke 16b.
It is formed with a sufficient thickness to maintain a gap that does not hinder the opening and suction operations of the armature 15 by a.

FIG. 1 of the present embodiment is a state before starting the printing operation, FIG. 1 (a) is a state of upper and lower wires, and FIG. 1 (b).
Indicates the state of the intermediate wire. Bypass plate 2
1, the tongue portion 21a is arranged in the upper and lower wire state of FIG. 1 (a). In this state, no current is applied to the electromagnetic coil 17. Therefore, the armature 15 is a permanent magnet 18
Is attracted to the suction surface 16a of the yoke 16b, and the leaf spring 14 is bent. In the upper and lower wires shown in FIG. 1A, the upper and lower print wire armatures 12a are provided.
Since the thickness of the plate spring 14 is thin, the deflection of the leaf spring 14 is large.
In the intermediate wire of (b), since the armature 12b for the intermediate portion printing wire is thick, the deflection of the leaf spring 14 is small. When a current is applied to the electromagnetic coil 17 from this state, the magnetic flux generated by the permanent magnet 18 and the magnetic flux generated by the electromagnetic coil 17 in the opposite direction cancel each other out, and the armature 15 moves to the leaf spring 1
With the release of the elastic strain energy of 4, the suction surface 16
It is released from a. By this opening operation, the printing wire 12
Project from the head frame 11 and collide with the platen 4 via the ink ribbon 2 and the print paper 3 serving as a recording medium, whereby the ink applied to the ink ribbon 2 is transferred to the print paper 4 and predetermined printing is performed. Be seen. Immediately after the printing wire 12 reaches the printing paper 3, the electromagnetic coil 17
When the current applied to the armature 15 is cut off, the armature 15
The recovered attractive force of the permanent magnet 18 promptly causes the yoke 1
It is adsorbed by the suction surface 16a of 6b and returns to its original state.

In the print head of this embodiment, by changing the amount of deflection of the leaf spring 14, the elastic energy of the leaf spring 14 can be varied and the printing wire 12 collides with the platen 4 via the ink ribbon 2 and the printing paper 3. It is possible to make the force to be constant regardless of the difference in the wire movement distance. That is, the bending amount of the leaf spring 14 is increased for the upper and lower print wires 12a and smaller for the intermediate print wire 12b with respect to the difference in platen gap between the upper and lower print wires 12a and the intermediate print wire 12b due to the curvature of the platen 4. By making the upper and lower print wire armatures 15a thin and the middle print wire armature 15a thick, the impact force of collision with the platen 4 via the ink ribbon 2 and the printing paper 3 can be made constant for all wires. is there.

Further, when the elastic energy of the leaf spring 14 is increased, the holding force, which is the relative suction force between the upper and lower print wire armatures 15a and the suction surface 16a of the yoke 16b, becomes small. Since the release timing of the elastic energy of the leaf spring 14 is advanced, the bypass plate 21 is prevented from causing the print wire 12a to jump out early or the return operation of the print wire 12a to be delayed due to insufficient suction.
Is arranged on the side opposite to the surface of the leaf spring 14 on which the yoke 16b is provided so that the upper and lower parts are the tongue-like parts 21a. Therefore, the magnetic flux generated by the permanent magnet 18 is shown by the solid line in FIG. 1b, the yoke 16b, the upper and lower print wire armatures 15a, and the leaf spring 14 are penetrated, and the upper and lower portions of the yoke 16b and the upper and lower print wire armatures 15a are indicated by broken line arrows in FIG. ,
It penetrates the bypass plate 21 which allows the leakage magnetic flux described in FIG. Therefore, the attraction force of the upper and lower print wire armatures 15a by the permanent magnets 18 can be increased only to the upper and lower print wires 12a. The thickness of the armature 15 can be adjusted by the armature 1
When polishing 5, the printing wire 12 can be easily constructed by changing the pushing amount. Also, the bypass plate 2
Since No. 1 can be manufactured by punching a magnetic plate material, it is possible to obtain an inexpensive product with good dimensional accuracy.

In the print head constructed as described above, the difference in impact force due to the difference in platen gap due to the curvature of the platen 4 is eliminated, and the relative suction force between the armature 15 and the suction surface 16a of the yoke 16b is applied to all the wires. It is possible to make it constant.

[0014]

As described above, since the print head of the present invention includes the bypass plate and the spacer, any wire has an optimum impact force according to the size of the platen gap due to the curvature of the platen.
Further, since it is possible to eliminate the variation in the relative suction force between the armature and the yoke suction surface that occurs at that time, it is possible to improve the printing quality.

[Brief description of drawings]

1 is a sectional view (a) taken along the line AA shown in FIG. 2 and a sectional view taken along the line BB (b) shown in FIG. 2 according to an embodiment of the present invention.

FIG. 2 is a perspective view of an impact type print head of the present embodiment.

FIG. 3 is a perspective view of a bypass plate of this embodiment.

4 is an enlarged cross-sectional view of the print head tip portion of the embodiment of FIG.

FIG. 5 is a cross-sectional view of a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 print head 2 ink ribbon 3 print paper 4 platen 11 head frame 12 print wire (generic name including upper and lower print wires 12a and intermediate print wire 12b) 12a upper and lower print wires 12b intermediate print wire 13 guide 14 leaf spring 15 , 15a, 15b Armature 16a Suction surface 16b Yoke 16c Ring yoke 17 Electromagnetic coil 18 Permanent magnet 19 Armature arm 20 Spacer 21 Bypass plate

Claims (2)

[Claims] 1. An annular magnetic circuit composed of an armature for driving a printing wire supported by an elastic member, a yoke having a suction surface facing the armature, and a permanent magnet and an electromagnet attached to the yoke. In a wire dot type print head that attracts the armature by the permanent magnet and releases the armature from the attraction surface by energizing the electromagnet, the amount of deflection of the elastic member on the side opposite to the side on which the yoke is provided is A dot impact type print head characterized in that a magnetic bypass plate having a tongue-shaped projection in the center and a spacer are arranged in accordance with a large portion. 2. When the armature is attracted, the amount of deflection of the elastic member is increased by the permanent magnet with respect to the upper and lower print wires of the print head, and decreased with respect to the intermediate print wire. The dot impact type print head according to claim 1, wherein the polishing amount of the armature is changed.