JPH02223455A - Print head for dot printer - Google Patents

Abstract

PURPOSE:To obtain a highly reliable print head for dot printer by arranging a polyimide sheet applied with magnetic fluid at the contact section of an armature and a core, thereby relieving impact force and preventing abrasion of the armature and the core. CONSTITUTION:When current is fed to a coil in order to produce a magnetic field for cancelling the magnetic field of a permanent magnet 14, an armature 17 is biased and separated from the core 16 through a leaf spring 6 and a print wire 4 springs out from the tip of the nose 8 and collides against an ink ribbon and a printing medium, thus forming a dot. Upon interruption of current supply to the coil 13, the armature 17 is attracted to the core 16 by means of the permanent magnet 14, thus bringing about non-printing condition. A sheet member 20 in which magnetic fluid 19 is placed between polyimide sheets 18 is fixed to the portion of a print hammer 7 where the armature 17 contacts with the core 16 in order to relieve impact force, upon contact of the armature 17 and the core 16, through viscous damping of the magnetic fluid 19, thus protecting the polyimide sheet 18 from breaking.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) This invention relates to a print head for a wire dot printer.

(Future technology) The energy of a spring that was deflected by the attractive force of a permanent magnet can be
It is released by excitation of the coil and operates the printing hammer.
In so-called spring-charged print heads, contact wear due to collision between the armature and the iron core during the return operation of the print hammer has become a problem. This wear increases the operating stroke of the printing hammer, causing malfunction of the printing hammer and increased stress in the spring, making it impossible to perform stable printing. Therefore, methods have been devised to prevent wear, such as applying a resin such as Teflon to the surface of the iron core, and placing a polyimide sheet between the armature and the iron core.Printing hammers are required to print more than 100 million times. It is not a wear prevention method that can be applied to operations.

(Problems to be Solved by the Invention) This invention has been made in view of the above points, and its purpose is to improve the drawbacks of the conventional device described above, and to create a highly reliable DoSoto printer. The purpose is to provide a print head.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a dot printer in which two polyimide sheets are arranged between the contact portion of a printing hammer and an iron core, and a magnetic fluid is applied between the polyimide sheets. is the print head,
Furthermore, the present invention is a print head for a dot printer in which a bag-shaped sheet member, in which the outer peripheries of two polyimide sheets are adhered and a magnetic fluid is sealed, is arranged between the printing nozzle and the contact portion of the iron core.

(Function) In this way, by arranging the polyimide sheet coated with magnetic fluid between the contact area of the armature and the iron core, the damping when the armature of the printing hammer collides with the iron core is increased and the impact force is alleviated. This can prevent armature and iron core wear.

Furthermore, the magnetic fluid always gathers at the contact area between the armature and the iron core, where the magnetic flux density is highest, and unlike oil, it does not escape outside the contact area due to impact force.

(Example) The present invention will be described in detail below using examples shown in the drawings.

FIG. 1 is a schematic sectional view showing one embodiment of a print head of a dot printer according to the present invention. The print head 1 consists of a driven 3 and a core 2. Driven 3 is printing wire 4,
Printing hammer 7 consisting of lever 5, armature 17, leaf spring 6, wire guide 12, nose 8, spacers 9, 1
0, yoke plate 11. Core 2 is iron core 16,
It consists of a coil 13, a permanent magnet 14, and a yoke 15. Between the core 2 and the driven 3 is a sheet member 1 in which a magnetic fluid 19 is applied between polyimide sheets 18.

Next, a method for assembling and processing the print head 1 will be explained. First, the armatures 17 to which the printing wire 4 is attached are brazed to the tongues of the leaf spring 6, and then attached by laser welding or the like to assemble the printing hammer 7. Next, the printing wire 4 is passed through the wire guide 12, the yoke plate 11, the spacers 9 and 10, and the nose 8 are assembled using screws or the like, and the wire guide 12 is adhered to the nose 8.

After configuring as described above, the printing wire 4 is pushed into the iron core side by a predetermined amount using a jig (not shown) and fixed, and the armature 1
The back surface of 7 is milled using a milling machine or the like so that it becomes flush with the surface of the yoke plate 11 on the iron core side.

By performing the above assembly and processing, the driven side 3 of the print head is completed.

Next, a method of assembling the core side 2 will be explained.

The permanent magnet 14 and the yoke 15 are glued to the iron core 16, the coil 13 is attached to each iron core 16, and the iron core 16 and the yoke 1 are attached.
Process the end face of No. 5 into an icicle.

Finally, between the driven 3 and the core 2, a sheet member 20 coated with a magnetic fluid 19 is sandwiched between two polyimide sheets 18 shown in FIG. Complete.

Next, the operation of this print head will be explained. First, when a printing operation is not performed, in the magnetic circuit composed of the permanent magnet 14, yoke 15, yoke plate 11, armature 17, and iron core 16, the armature 17 is attracted to the end face of the iron core 16 by the magnetic force of the permanent magnet 14. Therefore, the printing hammer 7 is biased toward the iron core 16.

Next, when performing a printing operation, a current is applied by a drive circuit (not shown) to the coil 13 paired with the desired printing hammer 7 to generate a magnetic field in the opposite direction to the magnetic field of the permanent magnet 14. By canceling the magnetic field and eliminating the attraction force, the printing hammer 7 is separated from the iron core 16 by the spring force of the biased leaf spring 6, and the printing wire 4 is guided by the guide 12 and protrudes from the tip of the nose 8. It collides with an ink ribbon (not shown) and a printing medium to form a dot. At this time, when the applied flow of the coil 13 is cut off, the printing hammer 7 is attracted to the iron core 13 again by the attractive force of the permanent magnet 14, and becomes in a non-printing state.

Conventionally, in print heads that perform such operations, wear due to the impact force during the return operation at the contact point between the armature of the printing hammer and the core was a problem, so a polyimide sheet was installed between the armature and the core. Although a surface film was formed on the surface of the iron core for lubrication, it was not a sufficient countermeasure against printing operations over 100 million times, resulting in breakage of the polyimide sheet and peeling of the surface film. The armature and iron core were worn out.

In the present invention, a sheet member 20 coated with magnetic fluid 19 is attached between polyimide sheets 18 to this contact portion. This sheet member 20 reduces the impact force upon contact by viscous damping of the magnetic fluid 19 and prevents the polyimide sheet 18 from breaking. In particular, since the magnetic fluid 19 concentrates in areas with high magnetic flux density, it gathers at the contact area between the armature 17 and the iron core 16, where the magnetic flux density is high, and the thickness of the sheet member 20 corresponding to the contact area increases, resulting in this damping effect. becomes larger. Furthermore, the magnetic fluid 19 momentarily flows outside the contact area due to the collision with the printing hammer 7, but returns to the contact area due to the action of magnetic flux, so that the thickness of the sheet member 20 at the contact area is always maintained.

As a result, a print head with a long life can be obtained without wear of the armature and iron core.

Further, the same effect can be obtained by enclosing the magnetic fluid 19 in a bag-shaped sheet member 20 made by bonding the outer peripheries of two polyimide sheets 18 together by thermocompression bonding or the like.

[Effects of the Invention] As detailed above, by installing a polyimide sheet coated with magnetic fluid between the contact portion of the printing hammer and the iron core, a print head with a long life can be realized.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a print head showing an embodiment of the present invention, and FIG. 2 is a schematic sectional view of a sheet member. DESCRIPTION OF SYMBOLS 1... Print head, 4... Print wire, 6... Leaf spring, 7... Print hammer, 13... Coil, 14...
...Permanent magnet, 16... Iron core, 18... Polyimide sheet, 19... Magnetic fluid, 20... Sheet member.

Claims (2)

[Claims] (1) In the print head of a dot printer, a leaf spring is biased by a permanent magnet, the biased leaf spring is released by excitation of a magnetic coil, and the print wire is driven. A print head for a dot printer, characterized in that more than one polyimide sheet is arranged, and a magnetic fluid is applied between the polyimide sheets. (2) In the print head of a dot printer, where a permanent magnet biases a leaf spring and excitation of a magnetic coil releases the biased leaf spring to drive the print wire, there is a wire between the print hammer and the iron core. A print head for a dot printer, characterized in that a bag-shaped sheet member is arranged in which the outer periphery of two polyimide sheets is adhered and a magnetic fluid is sealed.