JPS6036465B2 - Wire dot head leaf spring material - Google Patents

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 used for spot welding,
The armature was attached to the free end of the leaf spring by laser welding.

In addition, as a leaf spring material, carbon tool steel with excellent spring properties and fatigue strength, such as JIS steel grades SK-3 to SK-
5, low carbon steel was selected as the armature material due to its magnetic properties, so the melting during welding may segregate the saturated carbon of the leaf spring material made of carbon tool steel, or the volume may change due to changes in crystal structure due to melting. This causes minute cracks in the welded part, which is extremely harmful to the fatigue life due to the bending force that acts on the welded part every time the print wire is driven and prints on printing paper, and can lead to breakage of the leaf spring. This had the disadvantage of indicating a print head failure. In order to eliminate these drawbacks, this invention uses a material with spring properties and fatigue strength equivalent to those of conventional carbon tool steel, and less thermal deterioration due to welding, that is, a material with a weight of 16.4 to 17.5 Cr. %
, 6.5 to 7.5% by weight of Ni, 0.9 to 1.4% by weight of peaks, and 0.06 to 0.0% of C. Female weight%, Mn 0.4-0
．． It is characterized by using a material commonly known as 17-7Ph steel, which contains 9% by weight of Si, 0.15 to 0.64% by weight of Si, and the remaining amount of Fe, as a leaf spring. The purpose is to reduce the occurrence of holes and microcracks and increase the strength of the welded part.

The present invention will be explained below based on drawings and experimental data. FIG. 1 is a 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 It is a permanent magnet and also serves as a housing; 4 is an extinguishing 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 smoother having a plate thickness equal to that of the desired cap; 6 is a substantially circular center; a leaf spring having a plurality of arms extending radially in the direction; 7 an armature disposed near the free end of the leaf spring 6; 8 a printed wire welded to the tip of the armature 7; 9 a wire of the leaf spring 6; The second yoke 10 laminated on the upper surface 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 passes through the spacer 5, the leaf spring 6, the second yoke 9, the armature 7, the core 2, and the first yoke 1, and the magnetic attraction force generated at this time. The armature 7 is attracted to the core 2, and the leaf spring 6
But I'm biased.

When the degaussing coil 4 is then excited, the magnetic field of the permanent magnet 3 is canceled out. The magnetic attraction is reduced or completely eliminated. Therefore, the armature 7 moves away from the core 2 due to the force of the leaf spring 6, and the printed wire 8
protrudes from the guide frame 10. Thereafter, when the demagnetizing coil 4 is deenergized again, the armature 7 is attracted to the core 2 again as described above, and the leaf spring 6 is biased.
When the leaf spring 6 is bent in this manner as shown in FIGS. 2a and 2b, a large bending moment is applied to the welded part 6a of the leaf spring 6 where the armature 7 has fallen, but when the leaf spring material according to the present invention is used, For example, there is less deterioration due to melting of the welded portion 6a, and the leaf spring 6 is less likely to be damaged at the welded portion 6a.

Figures 3a and 3b 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.

If the leaf spring material is carbon tool steel, a third
As shown in Figure a, pores 6b and fine cracks 6c are generated. Although the generation of holes 6b can be suppressed by reducing the laser output, the generation of fine cracks 6c cannot be suppressed. On the other hand, as will be described later, the welding area and penetration depth 6e are reduced for low laser output,
Strength against bending force decreases. Furthermore, as shown in FIG. 3b, the hardness distribution at this time shows an increase in hardness in the welded part 6a, but the Vickers hardness is 650 to 7.
It shows the variation of 5 plates v and 5 nagi v. When analyzing the components of the deposited portion 6a at this hardness measurement position, significant segregation of carbon was observed, particularly in the area where fine cracks 6c were generated. That is, the reason for this is that the carbon already contained in the carbon tool steel is originally supersaturated due to the melting of the leaf spring 6 and armature 7 due to laser irradiation.
This is probably due to segregation due to cooling. FIG. 4 shows a cross section of a welded part and hardness distribution under the same laser welding conditions as in FIGS. 3a and 3b, using Muraya (SUS631) according to the present invention as a plate spring. No formation of voids 6b in the carbon tool steel is observed. The fine cracks 6c are much smaller than that of carbon tool steel. Further, although an increase in hardness is observed in the welded portion 6a, the variation in the welded portion 6a is small. FIG. 5 shows the difference in welding width 6d and 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 1 and 1 indicate the experimental values for the material according to the present invention (S
Experimental values for US631) are shown. FIG. 6 shows the bending strength of a statically welded portion when the focus of the laser light 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 o mark indicates an experimental value using the material of the present invention. From these results, it can be seen that the material according to the present invention, which has a larger welding width 6d and a larger 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 is more advantageous because it has fewer microcracks. The above case was for the case where one molten part is formed due to laser irradiation, but since the bending force acting on the leaf spring is large, laser irradiation is performed multiple times and multiple deposits are formed as shown in Figure 2b. When an attempt is made to increase the welding area and the bending strength with 6a, the difference between the two materials becomes even more remarkable.

FIG. 7 shows, as an example, the hardness distribution when the laser beam is irradiated four times. As shown in FIGS. 7a and 7b, in carbon tool steel, the vicinity of the welded part is repeatedly affected by heat and exhibits an abnormal decrease in hardness. On the other hand, as shown in FIGS. 7C and 7D, in the present invention, there is no decrease in hardness near the settling part. In Fig. 7a, a crack 6f is observed at the end of the weld.
It is not seen in Figure 7C. From this, the advantage of the material of the present invention is clear. In addition, by improving the welding method of the joint between the leaf spring 6 and the armature 7,
Furthermore, the bonding strength increases.

This will be explained below. FIG. 8a shows the spot positional relationship caused by settling at the joint. In this figure, r
is the spot radius, d is the center spacing of the spots, and the overlap rate is defined as (·−nose)×·dish%. In Figure 8b,
The welding strength according to the bending moment is shown when the number of spots and the weight of the spots in FIG. 8a are used as parameters. Fig. 8b shows carbon tool steel (for example, JI
It is shown as a ratio of 1 when the bending moment of weld breakage is 1 spot when low carbon steel is used as the armature material. In this diagram,
The o mark indicates an overlap rate of 50%, the * mark indicates the same 10%, the x mark indicates the same 0%, and the mouth seal indicates the same 10%. This allows for welding using multiple laser irradiations.
It can be seen that the bending strength decreases as the overlap ratio increases. The reason for this is as shown in Fig. 9a (overlap ratio 50%, hardness measurement position L, number of spots 4), the leaf spring material during welding is not only melted and solidified by the previous laser irradiation, but also melted and solidified subsequently. Due to the solidification, the hardness of the welded overlapped portion is abnormally reduced, and the strength of the overlapped portion is reduced as shown in FIG. 9b.

If the overlap ratio is set to 0% or less, the abnormal distribution of hardness as shown in FIG. 9b disappears, the bending strength becomes sufficiently high, and the life span becomes sufficiently long. Note that, as shown in FIG. 8b, even if the number of spots is increased to six or more, the increase in bending strength becomes smaller. As a result, when welding the print head, it is sufficient to take into account the spring dimensions, armature dimensions, and bending force of the print head, and select the number of spots that will provide a large bending strength. Note that the present invention is not limited to the above-mentioned embodiments; for example, the armature 7 is welded to the free end of the leaf spring 6, and the armature 7 is energized by exciting an excitation coil.
The same effect can be obtained in a wire dot printer in which the printing wire 8 fixed to the armature 7 or the leaf spring 6 is driven by suction, and the printing wire 8 is returned to its original position by the restoring force of the deflected leaf spring 6. be.

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.
The penetration depth is deep and the occurrence of fine cracks is 4.
・Because it is thinner, the fatigue life of the armature and leaf spring joint is increased, which has the advantage of reducing wire dot head failure.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the wire dot head according to the present invention, FIGS. 2a and b are diagrams explaining the operation of the embodiment shown in FIG. 1, and FIGS. Figure 4 is a diagram showing the measurement results of the welded part cross section and hardness distribution when using the leaf spring material of this invention. Figure 5 shows the melt width and penetration depth when welding both materials, Figure 6 shows the experimental values of welding strength for both materials, and Figures 7 a to d show the welding strength of both materials. Figure 8a is a diagram showing the cross section and hardness distribution of the welded part when multiple laser irradiations are performed, Figure 8a is a diagram explaining the overlap of the welded part caused by multiple laser irradiations, and Figure 8b is the diagram showing the hardness distribution depending on the number of laser irradiations. FIG. 9a is a diagram of experimental results showing the bending strength ratio of the fused portion when the number of fused portions generated and the overlap ratio are varied. b is a diagram 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, 7 is the armature, 8 is the printed wire, 9 is the second yoke, 10' or It is a guide frame. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9

Claims (1)

[Claims] 1 A spring charge type in which a leaf spring welded to the armature is biased by a permanent magnet, 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. In the wire dot head, the material of the leaf spring is Cr16.4-17.
．． 5% by weight, Ni6.5~7.5% by weight, A10.9~
1.4% by weight, C0.06-0.08% by weight, Mn0.
4 to 0.9% by weight of Si, 0.15 to 0.64% by weight of Si, the balance being Fe, and a hardened material with a precipitated Ni-AI compound.