JPH05286149A - Print head for dot printer - Google Patents

Abstract

PURPOSE:To prevent the release of a bonded part due to the breakage of a printing wire or the cracking of a fixing material by constituting the fixing material of an armature and printing wire of an inner layer and the inner layer reinforcing outer layer applied to the outer periphery of the inner layer. CONSTITUTION:In a print head, a fixing material 3 is constituted of an inner layer 31 and the outer layer 32 applied to the outer periphery of the inner layer 31 and, since the outer layer 32 reinforces the inner layer 31 to increase the strength of the bonded part of both layers 31, 32, the bonding strength of the bonded part of an armature 2 and a printing wire 1 is enhanced. That is, since the bonded part of the wire 1 and the armature 2 is composed of the double-layered structure of the inner and outer layers 31, 32, even when stress is conc. to the bonded part of the wire 1 and the armature 2 and a crack is generated in the outer layer 32 of the fixing material 3, the inner layer 31 of the fixing material 3 shows the function of a cushion and the spreading of the crack is prevented to stop the crack by the outer layer 32. Therefore, the breakage of the base of the wire 1 or the release of the wire 1 can be prevented. The melting temp. of the silver solder or the fixing material 3 or the outer layer is lower than that of the inner layer in order to prevent the thermal deterioration of the wire 1.

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 a dot impact printer (hereinafter simply referred to as a dot printer) used for printing or drawing a character or a graphic by the tip of a print wire.

[0002]

2. Description of the Related Art In a dot printer, a print head composed of an armature and a print wire fixed to the tip of the armature is fixed mainly to a yoke via a leaf spring, and the armature is attracted by the magnetic force of a permanent magnet to cause the leaf spring to move. It is often used as a structure in which the stand remains bent. Then, when the coil magnet mounted near the permanent magnet is energized and excited, the magnetic force of the permanent magnet is erased,
The return force of the leaf spring causes the print head to jump out rapidly for printing or drawing on the paper.

Further, in order to fix the armature and the printing wire, brazing using silver brazing which can be fixed most simply and surely is adopted. However, as described above, since the print head pops out rapidly and collides with the paper for printing or drawing, stress concentrates in the vicinity of the brazing joint between the armature and the print wire, and the print wire breaks or breaks. Peeling of the joint may occur. Various studies have been made to solve this problem.
No. 0-96041 proposes a structure in which a print head wire is fixed to an armature with a resin so that a position where stress on the wire is generated does not change and breakage occurs.

[0004]

As described above, in the dot printer head, when the coil mounted near the permanent magnet is energized by energizing it, the magnetic force of the permanent magnet is erased,
The armature attracted by the permanent magnet pops out due to the restoring force of the spring, and the printing wire fixed to the tip of the armature prints on the recording medium. At this time, the impact force during printing is concentrated on the joint between the armature and the printing wire. Due to this stress, a crack occurs in the silver solder for joining the armature and the printing wire, and the crack of the silver solder progresses starting from this crack, and further progresses to the crack of the printing wire, and at the root of the printing wire. There is a problem in that it is broken at an early stage, or peeling occurs at the joint portion of the silver brazing material, resulting in early damage. Therefore, in order to prevent the bending of the root of the printing wire and the peeling of the joint from occurring, the stress concentration on the brazed part should be kept low, and the material, length, and amount of deflection of the printing wire should be examined and various Although measures have been taken, all of them have a problem that they are disadvantageous due to high cost, lower workability and the like.

On the other hand, Japanese Utility Model Laid-Open No. 60-96041 proposes a structure in which a printing wire is fixed to an armature with a resin to change the position where stress is applied to the printing wire so that breakage does not occur. ing. However, also in this case, there are problems that the cost is high, the dimensional accuracy is not stable, and the workability is poor. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a dot printer head which does not cause the peeling of the joining portion due to the bending of the printing wire or the cracking of the fixing material in the vicinity of the joining portion between the armature and the printing wire. .

[0006]

DISCLOSURE OF THE INVENTION The present inventors have found that a print head with a broken print wire, a print head with a peeled joint,
As a result of closely observing the print head and the print head during use, it was found that the impact force at the time of printing works like a fatigue and a crack occurs in the fixing material, and the damage of the print head is caused by the development of this crack. It has been found that the phenomenon is that the printing wire cracks and breaks at some times, and the fixing material becomes large cracks at some times leading to peeling.

As a result, the inventors have found that it is sufficient to reduce the number of cracks generated at the joint as much as possible and to suppress the progress of cracks even if cracks occur. is there. More specifically, the present invention comprises an armature that oscillates by magnetism, a printing wire fixed to the end surface of the armature, and a fixing material that fixes the armature and the printing wire, and the fixing material is an inner layer and an inner layer. A print head for a dot printer, which is composed of an outer layer that covers the outer periphery and reinforces the inner layer. And it is desirable that the fixing material is silver solder.

[0008]

In the print head for a dot printer of the present invention, since the fixing material is composed of the inner layer and the outer layer covering the outer periphery of the inner layer, the outer layer can reinforce the inner layer and increase the strength of the joint portion. The joint between the armature and the printing wire has high joint strength. That is,
Since the joint between the print wire and the armature has a two-layer structure consisting of the inner layer and the outer layer, even if stress concentrates on the joint between the print wire and the armature and cracks occur in the outer layer of the adhesive, the inner layer of the adhesive By acting as a cushion, the development of cracks can be prevented and the cracks can be stopped at the outer layer to prevent the print wire from being fundamentally broken or the print wire from being peeled off. The melting temperature of the silver brazing material which is the fixing material of the outer layer is preferably lower than the melting temperature of the silver brazing material of the fixing material of the inner layer in order to prevent thermal deterioration of the printing wire. The hardness of the fixing material is preferably lower than the hardness of the fixing material of the inner layer.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to embodiments and drawings. Adjusted to a specified hardness C-1.3%, Cr-
In order to improve the flow of the printing wire 1 of φ0.2 mm made of powder high-speed tool steel containing 4.0% and Mo5.0% as main components and the fixing material 3, electroless nickel plating was applied to the surface 1 The armature 2 made of% Si-Fe was brazed using the high-frequency brazing machine using the silver brazing material shown in Table 1. Two high-frequency brazing machines are used for brazing,
The inner layer 31 was brazed with the first unit and the outer layer 32 was brazed with the second unit. For comparison, a conventional print head fixed by brazing was also prepared. FIG. 1 shows a conceptual diagram of the vicinity of the joint between the print head of the present invention and the conventional print head in FIG.

[0010]

[Table 1]

[0011]

[Table 2]

[0012]

[Table 3]

[0013]

[Table 4]

After selecting the five print heads manufactured in this way and measuring the state of hardness decrease at the root of the print wire 1 at the joint and peeling strength, 24 print heads were installed in a printer and used as an actual machine. The life test by The peeling strength of the bonded portion was evaluated by the load when the wedge was pressed into the fixing material 3 to break it. As shown in Table 2, the conventional product has an average strength of 2.5 kg, while the product of the present invention has a strength of 5.5 kg.
It was confirmed that the strength in kg and the strength were remarkably improved. As shown in Table 3, the degree of decrease in hardness of the root of the printing wire 1 at the joint is about HV55 for both the product of the present invention and the conventional product, and there is almost no difference between the two. Next, Table 4 shows the results of the life test using an actual machine. With the conventional product, one of the 24 print heads has one breakage at the root of the print wire 1 when printing 500 million characters.
Two peelings occurred on the fixing material 3 at the joining portion, whereas the product of the present invention did not cause breakage of the root of the printing wire 1 nor peeling of the fixing material 3 at the end of printing of 500 million characters. . Furthermore, as a result of observing with a microscope after filling the joint portion of the print head that completed printing 500 million characters with a microscope, as shown in FIGS. 3 and 4,
In the conventional product, the crack generated in the fixing material 3 is the printing wire 1
It was observed that there were cracks in the fixing material 3 along the boundary between the printing wire 1 and the armature 2. On the other hand, the print head of the present invention has the outer layer 32.
It was confirmed that although cracks were observed, the crack did not extend to the inner layer 31 and the crack stopped only in the outer layer 31.

[0015]

As described above, according to the present invention, the joint strength between the print wire and the armature of the print head for a dot printer can be increased and breakage of the root of the print wire and peeling of the print wire can be prevented. The life of the print head, which was sufficient, can be significantly improved. Therefore, it has a remarkable effect as a print head used in a dot impact type printer that requires high speed and long life.

[Brief description of drawings]

FIG. 1 is a view showing a joint portion between a print wire and an armature of a print head for a dot printer according to the present invention.

FIG. 2 is a diagram showing a joint portion between a print wire and an armature of a conventional print head for a dot printer.

FIG. 3 is a diagram showing a state of a joint portion when 100 million characters are printed on a print head for a dot printer of the present invention.

FIG. 4 is a diagram showing a state of a joint portion when printing 100 million characters of a conventional print head for a dot printer.

[Explanation of symbols]

 1 printing wire 2 armature 3 fixing material 31 inner layer 32 outer layer 4 crack

Claims (1)

[Claims] 1. An armature magnetically oscillating, a print wire fixed to an end surface of the armature, and a fixing material for fixing the armature and the printing wire. The fixing material includes an inner layer and an inner layer. A print head for a dot printer, characterized in that the print head is composed of an outer layer which is covered on the outer periphery and reinforces the inner layer.