JPH0220675A - Welding method for wire dot printer head - Google Patents

Abstract

PURPOSE:To obtain a welding joined part having high fatigue strength by irradiating the surface of an armature part by a laser beam with respect to a corner part between the armature and a plate spring and forming a head fillet. CONSTITUTION:At the time of welding an armature 4 and a plate spring which are integrated into a wire dot printer head, first of all, in a state that the armature 4 has been superposed on a free end side of a plate spring lever piece 5b, spot welding is performed to two parts 13 of the opposed surface. Subsequently, fillet welding is executed by irradiating a corner part between the end face of the armature 4 and the upper face of the lever piece 5b by laser beam 15 from a laser device 14. By this welding, a fillet 16 of a hard alloy which has been generated by a reaction of a molten metal of the armature 4 and a chemical component of a plate spring material is formed. In such a way, a welding joined part having high fatigue strength is obtained, and the durability of a printer head whose printing operation is executed at a high speed and repeatedly is raised.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of welding between a leaf spring and an armature incorporated in a wire dot printer head.

[Conventional technology]

First, in Fig. 0, which explains the structure of a wire dot printer head to which the present invention is applied, with reference to Figs. A thin cemented carbide wire (diameter 0.2 to 0.3
5 is an armature attached to each printing wire 2, 5 is a leaf spring that supports the armature 4, and 6 is a magnetic path for driving the armature assembled integrally with the housing 1. It is.

Here, the armature 4 is a small block piece made of a ferromagnetic material such as silicon iron, and the thin printing wire 2 described above is brazed to the tip of the armature 4. In addition, the leaf spring 5 is made of a spring material such as alloy carbon steel.
Its shape is as shown in FIG. 5, in which a plurality of lever pieces 5b are formed radially extending from a ring-shaped base plate 5a toward the inner circumferential side, and each lever piece 5b has the armature 4 on its free end side. are overlapped and the mating surfaces between the two are spot welded. On the other hand, the closed magnetic path 6 includes a disk-shaped base yoke 7 and a ring-shaped permanent magnet 8 laminated around the outer periphery of the base yoke 7. Yokes 9 and 10 and a degaussing coil 11 installed in the base yoke 7 facing the lower surface of the armature 4
The ring-shaped base plate 5a of the leaf spring 5 is sandwiched between the yokes 9 and 10, and is integrally fastened to the housing 1 by bolts 13.

The operation of such a wire dot printer head is well known, and when the degaussing coil 11 is de-energized, the armature 4 is attracted to the core 12 by the magnetomotive force of the permanent magnet 8 against the spring force of the leaf spring 5 as shown in the figure. ing. On the other hand, if the degaussing coil 11 is excited in response to the print signal, the magnetic flux passing through the core 12 is canceled by the magnetomotive force of the permanent magnet 8, and the magnetic attraction force disappears. The piece 5b is biased and driven by the spring restoring force, and at the same time, the tip of the printing wire 2 protrudes from the housing 1, and printing is performed by the dot matrix method.

[Problem to be solved by the invention]

By the way, in the wire dot printer head mentioned above,
A bending moment is repeatedly applied to the lever piece 5b of the leaf spring 5 for each printing operation. For this purpose, lever piece 5a
In addition to stresses such as shear, compression, and tension due to the notch effect, reaction forces due to collisions between the printing wire 2 and the object to be printed are repeatedly and intensively applied to the spot welding point between the and the armature 4, and as a result, During long-term use, fatigue cracks and fatigue fractures begin to occur at spot weld points.

The present invention has been made in view of the above points, and it is possible to reduce the size of the leaf spring and armature to the minimum required size.

To provide a welding method that provides high fatigue strength and high reliability for the welded joint between a leaf spring and an armature, which is most important in terms of printer head function and durability, while maintaining the shape. With the goal.

(Means for Solving!) In order to solve the above problem, in the welding method of the present invention, a laser beam is irradiated on the surface of the team 1A side of the corner between the armature and the leaf spring. A fillet of hard alloy produced by a reaction between the molten metal of the armature and the chemical components of the leaf spring material is formed at the core.

[Effect]

As mentioned above, by performing fillet welding at the corner between the leaf spring and armature and forming a fillet at the core, stress concentration due to the notch effect is alleviated, and the welded joint due to repeated printing operations is reduced. can prevent fatigue strength from decreasing.

Moreover, when fillet welding, by irradiating the laser beam onto the surface of the armature side rather than directly onto the leaf spring, the chemical components of the leaf spring material can react with the molten metal on the armature side melted by the irradiation heat. A new alloy is produced, and when it solidifies during the cooling process, the crystal structure undergoes transformation, forming a fillet that is harder than the base metal. In addition, in this case, the leaf spring is not easily affected by direct heat from laser irradiation, so there is no risk of the strength and spring characteristics of the leaf spring being impaired, and furthermore, welding rods are not used as in normal welding methods. Therefore, the weight of the moving parts of the printer head does not increase.

In addition, when irradiating the laser beam, a good fillet can be formed by using a YAG laser, controlling the irradiation voltage to 360 to 400 V, and controlling the defocus amount to about 4 to 4.5 mr*. On the other hand, if the irradiation voltage and defocus amount conditions are below the above range, the fillet shape will be undercut, and if the conditions are exceeded, problems such as molten metal scattering and pinholes may occur. Caution is required.

〔Example〕

FIG. 1 is an explanatory diagram of a welding method between an armature and a leaf spring according to the present invention, and FIGS. 2 and 3 are diagrams showing configurations of embodiments with different fillet shapes.
4 is an armature made of silicon iron, and 5b is a lever piece of the leaf spring 5 made of alloyed carbon steel shown in FIG. There is.

Here, in order to weld and join the armature 4 and the lever piece 5b of the leaf spring, first the armature 4 is connected to the lever piece 5b of the leaf spring.
2 of the opposing surfaces between the two
Spot welding is performed as indicated by point number 13. Next, a laser beam 15 is applied from the YAG laser device 14 to the corner between the end surface of the armature 4 and the upper surface of the lever piece 5b.
is irradiated to perform fillet welding, and a fillet 16 is formed at the core. In the embodiment shown in FIG. 2, the fillets 16 are formed at two locations in the corner along the width direction of the armature 4, and in the embodiment shown in FIG. 3, the fillets 16 are formed continuously over the entire length of the corner. In addition, the shape of the fillet 16 is formed to swell with a radius of curvature of about 0.3 mm.

On the other hand, as the laser irradiation conditions when performing the fillet welding described above, the laser beam irradiation point is set on the end run of the armature 4, and the irradiation voltage of the YAG laser is set at 360 to 400V.
, the results are shown when fillet welding is performed with a defocus amount of 4 to 4.5 mm. Armature 4 made of silicon iron has a Vickers hardness of 100 to 150, and a leaf spring made of alloyed carbon steel. Fillet 16 has a Vickers hardness of 700 to 800, while Fillet 16 has a Vickers hardness of 550 to 600.
Met. In other words, the fillet 16 is the base material of the armature 4. It has been confirmed that the hardness value is higher than that of leaf spring 5, and the fatigue strength is also higher. The reason for this is that the molten metal melted from the base armature 4 by laser beam irradiation reacts with the chemical components of the leaf spring 5 to create a new alloy, which undergoes a transformation in the crystal structure during the cooling and solidification process. It is presumed that it will harden.

In this way, the armature 4 and the lever piece 5b of the leaf spring 5
By forming a highly hard fillet 16 in the corner between the two by laser beam irradiation, the stress concentration caused by the notch effect is alleviated, resulting in a welded joint with high fatigue strength, and the printing operation can be repeated at high speed. The durability of the printer head increases.

〔Effect of the invention〕

As explained above, the wire dot printer head welding method according to the present invention involves irradiating a laser beam onto the surface of the armature side of the corner between the armature and the leaf spring so that the molten metal of the armature and the plate are bonded to the core part. Since the fillet of hard alloy produced by reaction with the chemical components of the spring material is formed, the following effects are achieved.

(1) A welded joint with high fatigue strength can be obtained by alleviating stress concentration due to the notch effect in the welded joint between the armature and the leaf spring due to repeated printing operations.

(2) Since the leaf spring is not directly irradiated with the laser beam, the strength and spring characteristics are hardly affected by the laser irradiation.

(3) Since a portion of the armature is melted by laser irradiation to form a fillet, the weight of the movable part of the printer head does not increase and the printing function is not affected.

A wire dot printer head with excellent functionality and durability can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the welding method of the present invention, and FIG. FIG. 3 is a perspective view of the main parts of embodiments of the present invention having different fillet shapes, FIG. 4 is a sectional view of the entire wire dot printer head, and FIG. 5 is a leaf spring in FIG.
FIG. 3 is an assembled plan view of the armature. In each figure, 2: Print wire, 4: Armature, 5: Leaf spring, 13
Nispot welding point, 14: laser device, 15: laser beam, 16: fillet. Figure 3 Figure 6

Claims (1)

[Claims] 1) In a wire dot printer head in which a printing wire is attached to a ferromagnetic armature that is overlapped and welded to the free end side of a leaf spring, and the printing wire is driven by controlling the magnetic force attracted to the armature. In the corner between the armature and the leaf spring, a laser beam is irradiated onto the surface of the armature to form a fillet of hard alloy produced by the reaction between the molten metal of the armature and the chemical components of the leaf spring material. A method for welding a wire dot printer head, characterized in that a wire dot printer head is formed.