JPS583952A - Material for flat spring of wire dot head - Google Patents

Abstract

PURPOSE:To obtain a material for the flat spring of a wire dot head reducing the occurrence of voids and microcracks due to welding by specifying the contents of Cr, Ni, Al, C, Mn and Si in a steel and precipitating an Ni-Al compound. CONSTITUTION:A hardened material consisting of, by weight, 16.4-17.5% Cr, 6.5-7.5% Ni, 0.9-1.4% Al, 0.06-0.08% C, 0.4-0.9% Mn, 0.15-0.64% Si and the balance Fe and contg. a precipitated Ni-Al compound is used as a material for the flat spring of a wire dot head. By making use of the hardened material, the width of melting and the depth of penetration can be made larger in welding, and the occurrence of microcracks is reduced. Accordingly, the fatigue life of the part of the flat spring joined to an armature is elongated, and the wire dot head causes hardly a breakdown.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a leaf spring material for a wire dot head that biases a leaf spring to release the biasing force of the leaf spring to drive a print wire.

Conventionally, this kind of wire dot head was made by spot welding,
The armature was welded to the free end of the leaf spring using laser welding. In addition, carbon tool steel with excellent spring properties and fatigue strength, such as JIS steel grades 5K-3 to 5K-5, was selected as the leaf spring material, and low carbon steel was selected as the armature material due to its magnetic properties. Due to melting during welding, supersaturated carbon in the leaf spring material made of carbon tool steel segregates, and minute cracks occur in the molten part due to volume changes due to changes in crystal structure due to melting, and the print wire is driven and the printing paper is damaged. Each time printing is performed, the bending force that acts on the welded part is extremely harmful to the fatigue life of the weld, leading to breakage of the leaf spring and failure of the print head.

In order to eliminate these drawbacks, this invention has a spring property,
Fatigue resistance is equivalent to conventional carbon tool steel.

and a material with less thermal deterioration due to welding, that is, Cr content of 1
6.4-17.5 wt%, Nl 6.5-7.5 wt%, AI 0.9-1.4 wt%, C 0.0
6 to 0.08% by weight, Mn 0.4 to 0.9% by weight,
81 at 0.15-0.644% by weight! The amount of Fe
It is characterized by the use of 17-7Ph steel, commonly known as 17-7Ph steel, as the leaf spring, and its purpose is to reduce the occurrence of holes and microcranks that occur during welding, and to increase the strength of the welded part. . This invention was developed based on the detailed drawings and experimental data.

FIG. 1 is a cross-sectional view showing an embodiment of the wire dot head according to the present invention, in which 1 is a first yoke forming a common magnetic path, 2 is a core fixed to the upper surface of the first yoke 1, and 3 is a first yoke that forms a common magnetic path. A permanent magnet, which also serves as a housing; 4 is a degaussing coil that is in the magnetic path of the permanent magnet 3 and cancels the magnetic field of the permanent magnet 3; 5 is a spacer with a plate thickness equal to the desired camp; 6 is a brushed circular shape at the center. A leaf spring having a plurality of arms extending radially in the direction, T is welded near the free end of the leaf spring 6. A printed wire 7.8 is welded to the tip of the armature T, 9 10 is a second yoke laminated on the upper surface of the leaf spring 6, and 10 is a guide frame laminated on the second yoke 9.

Next, the operation in the above configuration will be explained.

First, when the degaussing coil 4 is de-energized, the magnetic flux of the permanent magnet 3 is transferred to the spacer 5. Board splash6. Second yoke9. The armature 7 passes through the armature 7, the core 2, and the first yoke 1, and the armature 7 is attracted to the core 2 by its repelling magnetic attraction force, and the leaf spring 6 is biased. Then degaussing coil 4
When energized, the magnetic field of the permanent magnet 3 is canceled out, so the magnetic attraction force is reduced or completely eliminated. Therefore, the restoring force of the leaf spring 6 causes the armature T to move toward the core 2.
The printed wire 8 moves away from the guide frame 10.
protrude from Thereafter, when the demagnetizing coil 4 is de-energized again, the armature 7 is attracted to the core 2 again as described above, and the leaf spring 6 is biased.

In this way, the leaf spring 6 is added to FIGS. 2(,) and 2(b), but if the leaf spring material according to the present invention is used, there is less deterioration due to melting of the welded part 6a, and the leaf spring 6 is attached to the welded part 6a.
There is little chance of cutting loss.

FIGS. 3(a) and 3(b) show the cross section of the welded part and the hardness distribution of the leaf spring part in laser welding when carbon tool steel, which has been commonly used in the past, is used as the leaf spring material.

When the leaf spring material is carbon tool steel, the welded part 6a has a third
As shown in Figure (a), pores 6b and fine cracks 6c occur, in particular. Although the generation of the voids 6b can be suppressed by reducing the laser output, the generation of the fine cracks 6C cannot be suppressed, but the strength will be reduced. In addition, the hardness distribution at this time is as shown in FIG. 3(b).
Although an increase in hardness is observed in the hardness, the Pinkers hardness shows a variation of 650 to 750 Hv, which is ±50 Hv.

When the components of the welded portion 6a are analyzed at this hardness measuring position, significant segregation of carbon is observed, and this tendency is particularly noticeable in the portion where the fine cranks 6C occur.

That is, the reason for this is thought to be that the carbon already contained in the carbon tool steel was originally supersaturated due to melting of the leaf spring 6 and armature 7 due to laser irradiation, and therefore segregated upon cooling.

FIG. 4 shows a cross section of a welded part and hardness distribution under the same laser welding conditions as in FIGS. 3(a) and (b), using a plate spring made of the material (SUS63) according to the present invention. No formation of voids 6b in the carbon tool steel is observed.

The fine crank 6c is extremely small compared to carbon tool steel. Further, an increase in hardness is observed in the welded part 6a, or the variation in the welded part 6a is small.

FIG. 5 shows the difference in welding width 6d and melt penetration depth 6e representing the welding state of both the leaf spring materials explained in FIGS. 3 and 4. In this figure, the marks * and O indicate experimental values for carbon tool steel (SK-5), and the marks ■ and 0 indicate experimental values for the material according to the present invention (SUS631).

FIG. 6 shows the bending strength of a statically welded portion when the focus of the laser beam is shifted downward from the surface of the leaf spring 6.

In this figure, the * mark indicates an experimental value using carbon tool steel, and the 0 mark indicates an experimental value using the material of the present invention. From these welding width 6d,
It can be seen that the material according to the present invention, which has a large melt penetration depth 6e, is clearly superior. Further, in the print head according to the present invention, fatigue strength due to repeated bending force is a problem, but it is clear that the material according to the present invention has fewer fine cranks, which is more advantageous.

The above was about the case where one weld is formed due to laser irradiation, or the bending force acting on the leaf spring is large,
The difference between the two materials becomes even more remarkable when the weld area is increased by multiple welds 6& and the bending force strength is attempted to be increased by performing radar irradiation multiple times as shown in Figure 2 (bl). .

FIG. 7 shows, as an example, the hardness distribution when laser irradiation is performed four times. As shown in FIGS. 7(a) and 7(b), the carbon tool steel exhibits repeated heat-induced cracking in the vicinity of the weld and an abnormal decrease in hardness. On the other hand, Fig. 7 ((ri, (d)
As shown in FIG. 2, no decrease in hardness near the welded portion is observed in this invention. In FIG. 7(,), a crank 6f is observed at the end of the welded portion, but not in FIG. 7(C). From this, the advantage of the material of the present invention is clear.

Note that by improving the welding method of the joint between the leaf spring 6 and the armature 7, the joint strength can be further increased.

This K will be explained below.

FIG. 8(a) shows the spot positional relationship caused by welding at the joint. In this figure, r is the radius of the spot, d is the center spacing of the spots, and the overlapping diagram (b) shows the welding due to the bending moment when the number of spots and the weight of the spots in Figure 8 (a) are taken as parameters. Indicates strength. 8th
Figure (b) shows carbon tool steel (for example, J
IS steel type 5K-5), the bending moment of weld fracture when low carbon steel is used as the armature material is expressed as a ratio of 1 when the number of spots is 1. In this figure, the 0 mark indicates the overlap rate is 50%, the * mark indicates the same 10%, the x mark indicates the hand O%, and the landmark indicates the same -10%. This shows that in welding by multiple laser irradiations, the bending strength decreases as the overlap ratio increases.

The reason for this is that the leaf spring material during welding was melted by the previous laser irradiation, as shown in Fig. 9(a) (overlap ratio 50 inches, hardness measurement position, number of spots 4).

In addition to solidification, the subsequent melting and solidification causes the hardness of the welded portion to be abnormally reduced, resulting in a reduction in the strength of the overlapped portion as shown in FIG. 9(b). This is an overlap rate of 0%
If the following conditions are met, the abnormal distribution of hardness as shown in FIG. 9(b) will be eliminated, the bending strength will be sufficiently high, and the life span will be sufficiently long.

As shown in Figure 8(b), even if the number of spots is increased to 6 or more, the bending strength increases only slightly. The number of spots should be determined by taking the force into consideration and thereby obtaining a certain degree of bending strength.

Note that the present invention is not limited to the above-mentioned embodiments. For example, the armature 77 is welded to the free end of the leaf spring 6, the exciting coil is excited to attract the 1-mature T, and the armature 7
Or drive the printed wire 8 fixed to the leaf spring 6,
At this time, the print wire 8 is returned to its original position by the restoring force of the biased leaf spring 6. This is similarly effective in a wire dot printer.

As explained in detail above, since the present invention has the above-mentioned composition, it can be used as a leaf spring material and has a wide melting width during welding.
Since the welding depth can be deep and the occurrence of microcracks is reduced, the fatigue life of the armature and leaf spring joint is increased, and there are fewer failures of the wire dot head.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the wire dot head according to the present invention, FIGS. 2(a) and 2(b) are views explaining the operation of the embodiment shown in FIG. ) and (b
) is a diagram showing the measurement results of the welded part cross section and hardness distribution when using the conventional leaf spring material, and Figure 4 shows the welded part cross section and the measurement results of the hardness distribution when the material of this invention is used as the spring material. Figure 5 is a diagram showing the fusion width and penetration depth when welding with both materials, Figure 6 is a diagram showing experimental values of welding strength with both materials, Figure 7 (,) ~(f) is a diagram showing the cross section and hardness distribution of the welded part when multiple laser irradiations are applied to both materials, FIG. 8(a) is a diagram illustrating the overlap of the welded part caused by multiple laser irradiations, FIG. 8(b) is a diagram of experimental results showing the bending strength ratio of the melted part when the number of melted parts and the overlap ratio are changed depending on the number of laser irradiations,
FIGS. 9(a) and 9(b) are diagrams showing the hardness distribution measurement results of the leaf spring in the welded cross section. In the figure, 1 is the first yoke, 2 is the core, 3 is the permanent magnet, 4 is the degaussing coil, 5 is the spacer, 6 is the leaf spring, T is the armature, 8 is the printed wire, 9 is the second yoke, and 10 is the guide. It is a frame. Figure 1 Figure 2 (a) 290- Figure 8 (a) (b) Number of N spots (pieces) Figure 9 (a) Number of N spots (pieces) Procedural amendment (method) February 1982 Mr. Commissioner of the Japan Patent Office on the 3rd 1, Indication of the case *HFe 56-1 ooss 1 No. 2
, Title of the invention: Plate repellent for wire dot head 3.
Relationship with the person making the amendment Patent applicant address 1-1-6 Uchisaiwai-cho, Chiyoda-ku, Tokyo Name (4
22) Nippon Telegraph and Telephone Public Corporation Representative Tsune Shinfuji 4, Agent 6th floor, Okunomatsu Building, 31-16 Sakuragaoka-cho, Shibuya-ku, Tokyo 150 November 24, 1981 6 Drawings of the specification subject to amendment Brief Explanation Column 7, Statement of Contents of Amendment No.] Day 0, line 19 [Figure 7 (a) to (f)
J is corrected as [Fig. 7(,) to (d)]. that's all

Claims (1)

[Claims] In the spring-charged wire dot head, the wire dot head is biased by a permanent magnet in the form of a leaf spring welded to the armature, and the magnetic field of the permanent magnet is canceled by excitation of a magnetic coil to release the biased leaf spring and drive the printed wire. The material of the leaf spring is Cr l 6.4~1
7.5% by weight, Ni6.5-7.5% by weight, AIo, 9
~1.4% by weight, C0.06~0.088% by weight,
Mn 0.4-0.9 F IIF%, SIO, 15-0.
A leaf spring material for a wire dot head, characterized in that it is a hardened material in which the remaining amount is Fe and a N1-Al compound is precipitated.