JPS63194954A - Wire dot printer head - Google Patents

Abstract

PURPOSE:To improve fatigue resistance strength of a connection part between a plate spring and an armature, by a method wherein at least one or more welding points among the welding points weld a face conforming the rear end face of the armature to an edge face forming a hole provided to an armature fitting part of the plate spring. CONSTITUTION:A welding point position to which maximum bending moment is applied is transferred onto a face for conforming an edge face forming a hole provided to an arm part of a plate spring 6 to a rear end face of an armature 7 and laser spot welding is carried out at five positions 13a', 13b, 13c, 13d, 13e. At the welding point 13a' where the plate spring 6 is laser-welded to an edge end face of the armature 7, no micro crack 15 occurs near a bending moment side 18 of a border part 16 between the plate spring 6 on which peeling force acts by bending moment and the armature 7. A micro crack constituting a starting cause of fatigue failure can be prevented from occurrence thereby and the fatigue failure resistance of the plate spring is improved. Then, the durability of a wire dot printer head of a spring charge type can be remarkably improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spring-charged wire dot printer print head used as an output terminal for various computers.

[Prior Art] Wire dot printers have been widely used recently because they are highly adaptable to various types of printing, are capable of graphic processing, and also have copying capabilities.

A spring-charged wire dot printer head creates a closed magnetic path consisting of a core, armature, yoke, and permanent magnet, and the armature is always attracted to the core by the magnetic flux from the permanent magnet, and when printing is performed. The magnetic flux of the permanent magnet is canceled by passing a current through the coil wound around the core, and the magnetic attraction force between the core and the armadure is reduced to zero. The armature moves in the opposite direction to the core due to the restoring force of the armature support spring, thereby performing a printing operation.

Spring-charged wire dot printer heads, which utilize the elastic energy of leaf springs, are widely used because of their high-speed printing, low power consumption, and simultaneous copying capability (overprinting copy sheets), and efforts are being made to improve their performance.

[Problems to be solved by the invention] Blink heads are generally required to have a durability of 100 million characters or more, but when using a spring-charged printer head for high-speed printing, the durability of the joint between the armature and the leaf spring is important. Gender becomes an issue.

If the drive speed of the head is increased, the impact force applied to the movable body composed of the spring, armature, and wire increases, making the operation unstable, so it is necessary to increase the strength of the joint, especially the fatigue strength.

The leaf spring is made of carbon tool steel, which has excellent spring properties, magnetic properties, and fatigue strength, such as JIS steel grade 5K-3 or 5K-5.
The armature is made of electromagnetic mild steel or 1-3% St steel due to its magnetic properties.

The joining between the leaf spring and armature is done using laser spot welding, which can heat a minute range, to avoid degrading the spring properties due to heating of the leaf spring.

The joints (nuggets) of leaf springs made of laser-welded carbon tool steel have microscopic cracks in the nuggets due to segregation of supersaturated carbon, changes in volume due to changes in structure of crystals due to melting, and rapid heating and cooling. The bending and horns that act on the nugget portion each time the print wire is driven and prints on the print paper are extremely harmful to the fatigue life, and the plate springs may break, resulting in failure of the print head.

SUMMARY OF THE INVENTION An object of the present invention is to provide a wire dot printer head which has a moving body and which improves the fatigue strength of the joint between a leaf spring and an armature.

Means for Solving Problem E] The present invention provides a spring-charged wire dot printer head comprising a movable body in which an armature and a plate spring are welded at a plurality of locations by spot welding, in which at least one of the welding points is welded. The foregoing is a spring-charged wire dot printer head characterized in that the rear end surface of the armature and the edge of the leaf spring that forms the hole provided in the armature mounting portion are welded together.

[Example] The present invention will be explained below based on examples.

FIG. 2 is a partial sectional view showing an example of a wire dot head, in which 1 is a core forming a common magnetic path, 2 is a permanent magnet, 3 is a degaussing coil that cancels the magnetic field of the permanent magnet, 4 is a first yoke, 5 is a spacer with a thickness equal to the desired gap; 6 is a substantially circular plate spring having a plurality of arms extending in a split direction toward the center; 7 is an armature bonded to the plate spring; and 8 is bonded to the armature. 9 is a second yoke laminated on the upper surface of the leaf spring, 10 is a guide frame laminated on the second yoke, 11 is a wire guide, and 12 is a wire bearing.

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

First, when the degaussing coil 3 is de-energized, the magnetic flux of the permanent magnet 2 is transferred to the first yoke 4. Spacer 5. Leaf spring 6. Second yoke9. The armature 7 passes through the armature 7 and the core 1, and the armature 7 is attracted to the core 1 by the magnetic attraction force generated at that time, and the leaf spring 6 is biased. Thereafter, when the degaussing coil 3 is energized, the magnetic field of the permanent magnet 2 is canceled out, so that the magnetic attraction force is reduced or completely eliminated. Therefore, the armature 7 moves away from the core 1 due to the restoring force of the leaf spring 6, and the printed wire 8 protrudes from the wire bearing 12. Thereafter, when the demagnetizing coil 3 is deenergized again, the armadure 7 is again attracted to the core 1 and the leaf spring 6 is biased as described above.

When the leaf spring 6 is bent in this way as shown in FIG.
A large bending moment is applied to the

Next, the printing durability test results of this wire tod head will be explained.

The leaf spring 6 was made of carbon tool steel equivalent to 5K-5 which was subjected to quenching and tempering heat treatment to have a hardness of 1V400 to 650, and the armature 7 was made of 1% Sin.

FIG. 1 is an explanatory diagram showing the arrangement of laser spot welding points, and the printing durability test of the head was performed in the following A.

The tests were carried out for two types of B.

The laser spot welding points of Conventional Example A are arranged at 13a, 13b, 13c, and 13d in FIG.

13e, all of which were conducted inside the edges of the leaf spring 6 and armature 7, that is, so that the welding point molten part (nugget) did not touch the edges, but the main movable body was tested for printing durability. When I did this, it turned out to be 80,000,000 characters.
At 25,000,000 characters, as shown in FIG. 1(b), a crack 14 starting from the welding point 13a where the maximum bending moment was applied occurred in the leaf spring 6, making it impossible to operate as a movable body.

When the cross section of the welding point 13a, which was the starting point of crack generation, was observed under a microscope, a plurality of microcracks 15 were observed as shown in FIG.

Furthermore, observation of the fracture surface of the cracks revealed that the cause of the leaf spring failure was fatigue fracture originating from microcracks existing at the laser welding points.

When a bending moment is applied to the leaf spring 6, a peeling force 17 is applied to the leaf spring 6 and the armature 7 in FIG. It was also found that fatigue failure progressed rapidly and the life of the head was short.

In addition, similar microcracks were observed at the other four welding points 13b to 13G, excluding the welding point 13a, which was the starting point of the welding point crack, as shown in FIG. It was also found that this is a common phenomenon when the inner part is used rather than the edge.

Next, Example B according to the present invention in which the durability of the movable body was improved will be described.

In FIG. 1, in Example B, the arrangement of the welding points is changed, and only the welding point position where the maximum bending moment is applied is formed in the holes 13a to 13a' provided in the arms of the leaf spring 6 in the example. 13a', 13b, 13c, 13d, 13e.
Laser spot welding was performed at five locations. Laser welding was performed using a YAG laser processing device, and the output energy, pulse width, pulse waveform, focal length of the lens used, defocus, etc. were the same for both Conventional Example A and Example B.

The result of a printing durability test on the movable body of Example B was 7000.
It is possible to print 10,000 to 200 million characters, which is approximately 100,000 to 200 million characters compared to Example △.
We were able to achieve a 0x improvement in service life.

FIG. 4 is a sectional view of the welding point 13a' where the maximum bending moment is applied in Example B.

When observing the cross section of the welding point 13a' laser-welded to the edge end face of the leaf spring 6 and armature 7 with a microscope, it is found that it is near the bending moment side 18 of the boundary part 16 between the leaf spring 6 and the armature 7, where peeling force acts due to the bending moment. The durability was not adversely affected and no microcracks 15 were observed.

The reason why microcracks do not occur near the 18th part is presumed to be that the solidification form during laser welding of the nugget 13a shown in FIG. 3 of Conventional Example A and the nugget 13a' shown in FIG. 4 of Example B is different.

That is, the nugget 13a in FIG. 3 is located inside the edge and solidifies while being restrained by the surroundings during solidification, whereas the nugget 13a' in FIG. It is possible to terminate coagulation without
It is considered that microcracks are less likely to occur.

[Effects of the Invention] According to the present invention, the occurrence of microcracks, which are the starting point of fatigue fracture at the welding point where the maximum bending moment is applied, is prevented, so the fatigue fracture strength of the leaf spring is improved, and the fatigue fracture strength of the leaf spring is improved. The lifespan of the spring-charged wide dot printer head can be greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the laser spot welding points of the leaf spring and Armadure according to the present invention, and FIG. 2 is a sectional view showing an embodiment of the spring-charged wire tod head according to the present invention.
FIG. 3 is an explanatory view showing the state of the microcrank existing at the laser welding point, and FIG. 4 is a sectional view of the laser welding point at the edge, showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Core, 2... Permanent magnet, 3... Demagnetizing coil, 4... First yoke, 5... Spacer, 6... Leaf spring, 7... Armature, 8...・Printed wire, 9...Second yoke, 10...Guide frame, 1
1... Wire guide, 12... Wire bearing, 13
a, 13a'. 13b, 13c, 13d, 13e--Welding point, 14
...Crack, 15...Micro crack, 16.
...Joining interface, 17... Peeling force, 18... Bending moment side, 19... Hole. □Patent applicant Yasugi Seimitsu Co., Ltd. Figure 1 (b) Figure 2

Claims (1)

[Claims] In a spring-charged wire dot printer head comprising a movable body in which an armature and a leaf spring are welded at multiple locations by spot welding, at least one of the welding points is the rear end face of the armature and the arm of the leaf spring. A wire dot printer head characterized in that a surface that matches an edge surface forming a hole provided in the wire dot printer head is welded.