JPH07290727A - Impact dot head - Google Patents

Abstract

PURPOSE:To obtain a high resolving power, long life and high reliability, in an impact dot head having a plurality of wires composed of high speed steel and the levers fixed to the wires at one ends thereof and allowing the wires to protrude by the operation of the levers to perform printing action, by setting the surface roughness of the peripheries of the lever fixing parts of the levers to a specific value or less. CONSTITUTION:In an impact dot head having a plurality of wires 1 composed of high speed steel and the levers 2 fixed to the wires 1 at one ends thereof and performing printing action by allowing the wires to protrude by the operation of the levers 2, the surface roughness of the peripheries of the lever fixing parts of the wires 1 is set to 0.4S or less. As a result, the impact dot head high in reliability having the wires capable of withstanding repeated stress of at least two hundred million times or more can be inexpensively obtained.

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 Impact dot matrix printers have been required to have high reliability because they have a wider selection range of print media than other systems and are resistant to environmental changes. On the other hand, the demand for higher resolution has increased due to the demand for printing Chinese characters, etc., and thinner wires have been required.
The wire diameter of about 0.3 mm is about 0.2 mm in a 24-pin printer. Further, as the material of the wire, high speed steel, commonly called HSS material, is widely used from the viewpoint of cost and life.

[0003]

However, the thinner the wire is, the easier it is to break, and in particular, the problem of poor durability, in which the wire is broken at the portion where the wire is connected to the lever due to repeated fatigue associated with the printing operation, becomes a problem. This has caused a serious problem that it is difficult to secure the durability of 200 million strokes per wire required for the actual use of the Todot printer.

It is qualitatively known that the roughness of the wire surface largely affects the fatigue problem.
For example, Japanese Unexamined Patent Publication No. 62-264964 discloses that the surface roughness of the wire is made as small as possible to suppress the stress concentration, thereby making it difficult to break. However, it is not clear what kind of surface roughness management should be performed in the impact dot head to ensure high reliability, and excessive surface roughness management causes a problem of cost increase.

Further, as a technique for reducing the wire diameter for high resolution, there is a taper wire or a stepped wire having a thin tip. However, these wires are difficult to process and, as a result, become very expensive, which is a technology that can be practically used only in some high-end models.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to solve the conventional problems described above, to provide an impact dot head which meets the demand for high resolution and has a long life and high reliability at low cost.

[0007]

In order to solve the above problems, an impact dot head of the present invention has a wire made of a plurality of high speed steels and a lever fixed to one end of the wire, and the lever operates. As a result, in the impact dot head in which the wire protrudes to perform the printing action, the surface roughness around the lever fixing portion of the wire is set to 0.4 S or less.

[0008]

According to the above configuration of the present invention, it is possible to supply an impact dot head in which at least the wire can withstand the repeated stress of 200 million times or more.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic plan view of a mechanical portion of a serial impact dot printer equipped with an impact dot head of the present invention, and FIG. 2 is a schematic side view. In this serial impact dot printer, the impact dot head 6 is mounted on the carriage 7 in order to perform printing while moving the impact dot head 6 in the digit direction parallel to the platen 3 that supports the printing paper 5 as the printing medium. . Dots are printed on the printing paper 5 arranged between the platen 3 and the ink ribbon 4 while moving the carriage 7 in the digit direction, and desired characters, figures, etc. are printed.

An embodiment of the impact dot head of the present invention will be described with reference to FIG. 3 which is a sectional view taken along line AA of FIG.
For printing, when a voltage is applied to the coil 8 and a current flows, a magnetic attraction force is generated. Due to this magnetic attraction force, the armature 9 made of a magnetic material is attracted to the core 10 around the fulcrum a as a rotation center, and the tip of the lever 2 integrated with the armature 9 is also movable. The wire 1 fixed by brazing or the like is located at the tip of the lever 2, and is moved in the printing protrusion direction as the lever 2 is driven. Wire 1
Is a plurality of guides 11, 12, 13, 14, 15, 16
The guide hole provided above positions the wire 1 in the direction of the approximate normal line. In this embodiment, there are 24 wires 1 having a diameter of about φ0.2 mm.

FIG. 4 shows an operation diagram accompanying the driving of the wire 1 of this embodiment. The solid line shows the standby state of the lever 2, and the broken line shows the print protruding state. The wire 1 can be regarded as a cantilever whose fixed end is the fixed portion b with the lever 2.
With a series of movements of the wire 1 from the standby state to the print protruding state and to the standby state again, the guide 11 closest to the lever 2 repeats the forced displacement ± δ.

FIG. 5 shows a stress distribution on the wire 1 during suction as an example of this operation. As can be seen from this, it is understood that the maximum stress applied to the wire 1 is generated at the fixing portion b with the lever 2.

FIG. 6 is a graph showing the stress amplitude σ _a applied to the wire at the fixed portion a with a series of changes in the forced displacement ± δ from the standby state of the wire 1 to the end of the printing operation. In the setting of the structure, this stress value σ _a is
It must be set in consideration of the fatigue limit of 70 Kgf / mm ² or less.

FIG. 7 shows a graph in which the load stress applied to the wire 1 is plotted on the vertical axis and the number of repetitions of the load stress is plotted on the horizontal axis, and the surface roughness of the wire 1 is plotted. In the present embodiment, the surface roughness of the wire 1 is set to 0.4 S or less, and as shown in the graph of FIG. 7, the durability against the repeated stress amplitude is 200 million times or more. Can be secured. Moreover, the surface roughness of the wire 1 may be controlled only around the fixing portion with the lever 2 where the stress is highest.

As for the adjustment of the surface roughness, the barrel treatment is generally known, and the impact dot which secures stable durability without the cost increase due to unnecessary excessive treatment according to the regulations of this embodiment. A head can be provided.

In the present embodiment, the so-called direct attraction type head has been described, but an impact dot head using a wire is also used for a spring charge type head using a permanent magnet or a piezo type head using a piezoelectric element. Needless to say, the same effect can be obtained.

[0017]

As described above, the impact dot head of the present invention has a wire made of a plurality of high-speed steels and a lever fixed to one end of the wire. In an impact dot head that has a wire protruding and performs a printing action, the surface roughness around the lever fixing part of the wire is 0.4 S or less, so at least the wire has a repeated stress of 200 million times or more. There is an effect that it is possible to provide a highly reliable impact dot head that can withstand the above cost at a low cost.

[Brief description of drawings]

FIG. 1 is a schematic plan view of a mechanical portion of a serial impact dot printer equipped with an impact dot head of the present invention.

FIG. 2 is a schematic side view of a mechanical portion of a serial impact dot printer equipped with the impact dot head of the present invention.

FIG. 3 is a sectional view taken along the line AA of FIG. 1 showing an embodiment of the impact dot head of the present invention.

FIG. 4 is a partial view showing a wire operation in one embodiment of the impact dot head of the present invention.

FIG. 5 is a diagram showing a stress distribution applied to a wire of the impact dot head of the present invention.

FIG. 6 is a graph showing a stress amplitude applied to a wire of the impact dot head of the present invention.

FIG. 7 is a graph showing the correlation between the load stress and the number of repetitions regarding the surface roughness of the wire of the impact dot head of the present invention.

[Explanation of symbols]

 1 Wire 2 Lever 3 Platen 4 Ink Ribbon 5 Printing Paper 6 Impact Dot Head 7 Carriage 8 Coil 9 Armature 10 Core 11 Guide 12 Guide 13 Guide 14 Guide 15 Guide 16 Guide

Claims (1)

[Claims] 1. An impact dot head having a wire made of a plurality of high-speed steels and a lever fixed to one end of the wire, wherein the lever is actuated to project the wire to perform a printing operation. In the impact dot head, the surface roughness of the wire around the lever fixing portion in the previous period is 0.4 S or less.