JPH0699595A - Printing head - Google Patents

Abstract

PURPOSE:To ensure the moldability and handling property of a buffer sheet and to obtain a required printer operation characteristic by reducing the thickness only of the collision part with an armature of the buffer sheet when the buffer sheet is formed from a carbon fiber-containing thermoplastic resin. CONSTITUTION:The buffer sheet 19 interposed between an armature 9 and a core 14 is formed by the injection molding of a carbon short fiber-containing thermoplastic resin and the collision part 19a with the armature 9 of the buffer sheet is thin as compared with other part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print head used in a dot impact printer.

[0002]

2. Description of the Related Art In a print head, a leaf spring is biased by the magnetic force of a permanent magnet, and the magnetic force of the permanent magnet is canceled by energizing a coil to drive the printing element by releasing the biased leaf spring. There is something I did.

In this type of print head, an armature is provided on a leaf spring, a core is arranged so as to face the armature, and a coil is wound around the core. When the coil is not energized, the armature is attracted to the core by the magnetic force of the permanent magnet and the leaf spring is biased. By this, the biased leaf spring is released.

Among such print heads, there is known one in which a non-magnetic sheet is interposed between the core and the armature for the purpose of improving durability and response speed (for example, Japanese Utility Model Publication No. 57-153543). , Jitsukai Sho 61-152
No. 438). That is, the non-magnetic sheet reduces the attraction force of the armature to the core in the non-energized state, and the biased leaf spring can be quickly released when the coil is energized. This non-magnetic sheet is generally made of metal such as stainless steel, which is harder than the core and the armature, in order to prevent abrasion.

[0005]

In this type of print head, it is necessary to supply a lubricating oil such as silicone oil to the collision part in order to reduce the wear of the collision part. An oil impregnated material such as felt impregnated with a lubricating oil such as is disposed. Therefore, the structure is complicated and the cost is high. In addition, an initial dot omission may occur due to an oil film interposed between the core and the armature at the initial stage of printing.

On the other hand, a non-magnetic sheet made of a thin metal has a problem that the non-magnetic sheet has a short durability life because it may be plastically deformed or destroyed by long-term use.

Further, the impact when the armature is adsorbed by the core cannot be sufficiently absorbed, and this impact causes fatigue damage to the brazing portion of the printing element fixed to the armature or the printing lever, and the non-magnetic sheet is Since it is harder than the core and the armature, there is a problem that the core and the armature are significantly worn.

Therefore, it is conceivable to use a thermoplastic resin containing short carbon fibers as the buffer sheet. However,
If the sheet thickness of the material is set to be thick, the cushioning performance will be sufficient, but the required thickness will be exceeded, and the magnetic attraction between the yoke frame and the movable yoke will not be adjusted properly. , The desired operating characteristics of the printer cannot be obtained.

According to the present invention, when the cushioning sheet is formed of the thermoplastic resin containing carbon fiber, only the portion where the armature collides is made thin to secure the formability and handleability of the cushioning sheet, and at the same time, the required printer operating characteristics can be obtained. The purpose is to do so.

[0010]

SUMMARY OF THE INVENTION The present invention drives a printing element by biasing a leaf spring by the magnetic force of a permanent magnet and canceling the magnetic force of the permanent magnet by energizing a coil to release the biased leaf spring. Print head,
A buffer sheet is arranged between an armature provided at the free end of the leaf spring and a core on which the armature is arranged and a coil is wound, and the buffer sheet contains carbon short fibers. It is injection-molded from a thermoplastic resin, and the part where the armature collides is formed thinner than the other parts.

[0011]

According to the present invention, since the cushioning sheet is made of carbon used as a solid lubricant, the cushioning sheet is rich in smoothness and can prevent wear of the core and the armature without supplying lubricating oil. However, the buffer sheet of this structure is
Since only the part where the armature collides is thin,
It solves the problem of difficult molding of thermoplastic resin containing short carbon fibers and obtains sufficient operating characteristics required for a printer.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A print head to which the present invention is applied will be described with reference to the drawings. As shown in FIG. 1, the print head is provided with a wire frame 1 at a front end thereof, and a plurality of print wires 5 as an example of print elements are provided on the wire frame 1 via wire guides 2, 3 and 4. It is slidably supported in all directions.

A leaf spring 6 is provided on the back surface of the wire frame 1, and a donut-shaped permanent magnet 7 and a core 14 are provided behind the leaf spring 6, and a coil 8 is wound around each core 14. There is. Then, the leaf spring 6 is biased by the magnetic force of the permanent magnet 7, and the coil 8 is energized to cause the permanent magnet 7 to move.
The printing wire 5 can be driven by canceling the magnetic force of the above and releasing the leaf spring 6 in the biased state.

The leaf spring 6 is connected to the outer peripheral portion in a ring shape, and a plurality of arms 6a extending in a centripetal manner corresponding to the number of the printing wires 5 are formed inside. Each arm 6a
An armature 9 made of a magnetic material is fixed to the front end of the print wire 5, and the rear end of the print wire 5 is fixed by brazing via a print lever 10 fixed to the armature 9. The leaf spring 6 is sandwiched between a stopper plate 11 located on the front surface thereof, a ring-shaped support plate 12 and a yoke plate 13 located on the back surface thereof, and is fixed to the wire frame 1 via screws 15. The stopper plate 11, the leaf spring 6 and the support plate 12 are
In this embodiment, it is made of a non-magnetic material.

The core 14 has a number of U-shaped portions corresponding to the number of the print wires 5, one end of which is joined to the back surface of the yoke plate 13 via the permanent magnet 7, the yoke plate 16 and the spacer 17. The other end faces the armature 9, and the coil 8 is attached to the facing portion via the coil bobbin 18.
Is wrapped around. The permanent magnet 7, the yoke plate 16 and the spacer 17 are all formed of a magnetic material in a ring shape, and the permanent magnet 7, the armature 9, the yoke plate 1 are provided.
3, core 14, yoke plate 16 and spacer 17
A loop-shaped magnetic circuit 20 is formed by and.
A gap is formed between the core 14 and the armature 9 by the yoke plate 16, and the spacer 17 serves as the core 14.
It is used to adjust the gap between the armature and the armature 9.

The permanent magnet 7 attracts the armature 9 to the core 14 against the elastic force of the leaf spring 6 and biases the leaf spring 6 when the coil 8 is not energized. When the coil 8 is energized, the magnetic force of the permanent magnet 7 is canceled to cancel the attraction state of the armature 9 to the core 14,
The biased state of the leaf spring 6 is released, and the printing wire 5 is driven by this.
That is, when the coil 8 is not energized, the leaf spring 6 is biased by the magnetic force of the permanent magnet 7 and the printing wire 5
Is located in the retracted position, and when the coil 8 is energized, the magnetic force of the permanent magnet 7 is canceled, the biased state of the leaf spring 6 is released, and the printing wire 5 advances.

A disc-shaped cushioning sheet 19 is interposed between the core 14 and the armature 9.
Due to the existence of the above, the biased leaf spring 6 can be quickly released when the coil 8 is energized. That is, the cushioning sheet 19 reduces the attraction force of the armature 9 to the core 14 when the coil 8 is not energized, and the attraction state of the armature 9 is quickly released by energizing the coil 8. .

FIG. 2 shows an overall plan view of the cushioning sheet 19. The cushioning sheet 19 is manufactured by injection molding a thermoplastic resin containing short carbon fibers. Core 14
A fan-shaped thin portion 19a is formed in each portion where the armature 9 and the armature 9 face each other. The other portion is a thick portion 19b for satisfying the molding conditions. The cushioning sheet 19 is inserted between the core 14 and the armature 9 in a state in which the rotational direction of the cushioning sheet 19 is positioned by several convex pieces 19c provided on the circumferential portion of the cushioning sheet 19, and the printing wire 5
A thin portion 19a is located at a portion where the core 14 and the armature 9 collide with each other during driving, so as to buffer the collision force.

The partial cross-sectional shape of the cushioning sheet 19 is shown in FIG.

According to the above construction, since the buffer sheet 19 itself is made of carbon used as a solid lubricant,
It has high smoothness, and therefore, the wear of the core 14 and the armature 9 can be prevented without supplying lubricating oil. As a result, it is not necessary to provide an oil-impregnated material such as felt impregnated with a lubricating oil such as silicone oil inside the head as in the conventional case, and the structure can be simplified and the cost can be reduced. Also,
Since it is not necessary to use the lubricating oil, the initial dot omission due to the contact of the armature 9 with the oil film unlike the conventional case does not occur.

Further, the shock absorbing property of the cushioning sheet 19 is high, and the shock when the armature 9 is adsorbed by the core 14 can be sufficiently absorbed. Therefore, it is possible to suppress the occurrence of cracks in the brazed portion of the printing wire 5 due to the impact when the armature 9 is attracted to the core 14, and the durability of the entire head is improved.

[0022]

As described above, according to the print head of the present invention, the buffer sheet interposed between the armature and the core is a thermoplastic resin containing short carbon fibers, and only the portion where the armature collides is thin. Since it is formed so as to form a part, it is possible to ensure the moldability and handleability of the cushioning sheet as well as the characteristics required for the printer, thereby supplying the lubricating oil. It has an excellent effect that a high-speed print head having excellent durability can be provided at a lower cost.

[Brief description of drawings]

FIG. 1 is a sectional view of a print head to which the present invention is applied.

FIG. 2 is a plan view of a cushioning sheet.

FIG. 3 is a partial sectional view of a cushioning sheet.

[Explanation of symbols]

 5 printing wire (printing element) 6 leaf spring 7 permanent magnet 8 coil 9 armature 14 core 19 buffer sheet

Claims (1)

[Claims] 1. A print head for driving a printing element by biasing a leaf spring by the magnetic force of a permanent magnet, canceling the magnetic force of the permanent magnet by energizing a coil, and releasing the leaf spring in the biased state. A buffer sheet is disposed between an armature provided on the leaf spring and a core around which the coil is wound and which is disposed so as to face the armature, and the buffer sheet is made of a thermoplastic resin containing short carbon fibers. A print head, which is made of resin and has a portion where the armature collides with is thinner than other portions.