JPH0457505B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to wire dots, and more particularly to wire dot heads with multiple wires.

Prior Art In order to print characters, etc. using dots, as shown in Figure 1, an m x n dot matrix is constructed, and n dots are arranged horizontally at a pitch of P ₁ and vertically at a pitch of P ₂ . If the wire is moved and shifted m times, and the wire is driven for each shift, the desired printing can be performed.

The conventional structure of a wire dot head for performing such dot printing is shown in FIGS. 2 to 5.

In FIGS. 2 to 5, the reference numeral 1 indicates a tip guide, which is fixed to the intermediate guide 2. As shown in FIGS.
The intermediate guide 2 is formed with a notch 2a for a screw for attachment to a carriage (not shown).

A flexible printed circuit board 3 that is integrated with a heat dissipation plate 4 is arranged behind the intermediate guide 2.

The heat dissipation plate 4 is a flexible printed circuit board 3
It also serves as a spacer between the yoke 5 formed in the shape of an elliptical cylinder, and transmits the heat of the yoke 5 to the bag holder described later, and is made of a material with excellent thermal conductivity such as aluminum with a thickness of about 2 mm. .

A plurality of cores 6 are fitted and fixed to the yoke 5, and a bobbin 8 around which a coil 7 is wound is attached to the core 6.

The bobbin 8 has two protruding terminals 8a.
The winding start and winding end portions of the coil 7 are fixed to these by soldering. The terminal 8a passes through the yoke 5 and the heat radiation plate 4 and is soldered and fixed to the flexible printed circuit board 3 side.

On the other hand, the reference numeral 9 denotes a rear guide, which is formed into a cylindrical shape as a whole, and is connected to the yoke 5,
The heat dissipation plate 4 and the flexible printed circuit board 3 are inserted into the intermediate guide 2.

One end of a return spring 10 is fixed to the rear end of this rear guide 9. On the other hand, the open end of the rear end of the yoke 5 is closed by an auxiliary yoke 11. A circular opening is formed in the center of the auxiliary yoke 11, and the rear end of the rear guide 9 corresponds to this opening.

Also, a post 8 protruding from the rear end side of the bobbin 8
b fits into a through hole formed in the auxiliary yoke 11 and projects rearward, and the rear end of the armature 14 is fitted using this post 8b. The number of armatures 14 is the same as the number of wires 22, and a plunger 13 is provided in the middle thereof.

Further, a spacer 12 is arranged between the auxiliary yoke 11 and the armature 14.

This spacer 12 is provided to prevent wear caused by contact between the auxiliary yoke 11 and the armature 14, and to prevent the movement of the armature 14 from becoming unstable due to residual magnetism of the auxiliary yoke 11, which is a problem when forming a closed magnetic path. .

A plurality of armatures 14 are arranged radially as shown in FIG.
The proximal end of is fixed. The return spring 10 is loaded between the free end of the armature 14 and the rear end of the rear guide 9. Due to this return spring 10, the free end of the armature 14 is always positioned behind the rear guide 9. A force is applied in the direction away from the edge.

On the other hand, a stopper 1 is placed behind the armature 14.
5 is arranged and faces a position where it can come into contact with the free end side of the armature 14.
This stopper 15 is fitted into an armature holder 16, and the tip of each arm of the radially formed armature holder 16 is connected to the armature 14.
The proximal end side of the yoke is pressed against the auxiliary yoke 11. This armature holder 16
The pressing force of each arm against the armature 14 is applied by a similarly radial leaf spring 17 arranged at the rear of the armature holder 16. By the way, a damper 18 is arranged behind the leaf spring 17. This damper 18 is made of a material with high specific gravity such as lead, and has a washer 19 and a spring washer 20.
The bag holder 21 is disposed in contact with the bag holder 21 via the bag holder 21.

Since the bag holder 21 has a large effect on the heat dissipation of the head, the surface area of the bag holder 21 is made as large as possible, and a large number of fins are formed on the outside as shown in FIG.

This bag holder 21 is fixed to the intermediate guide 2 by screws 23, and covers the armature and yoke as a whole.

However, the damper 18 is configured to be movable by the leaf spring 17 and the spring washer 20, thereby increasing the vibration damping effect.

Further, the washer 19 prevents the spring washer 20 from biting into the damper 18.

In addition, the wires 22 are guided by guides 1, 2, and 9 to prevent buckling, and the plurality of wires 22 are gradually guided in a vertical line along these guides, and completely within the distal guide 1. are arranged in a vertical line.

In order to print based on this structure, when the coil 7 is energized according to the printing command,
Since a closed magnetic path is formed by the yoke 5, the auxiliary yoke 11, the plunger 13, and the core 6, the plunger 13 is attracted toward the core 6, and the armature 1
4 causes the wire 22 to protrude a predetermined distance from the tip guide 1 against the elastic force of the return spring 10. The wire 22 prints dots on the paper via an ink ribbon (not shown).

By the way, in the conventional wire dot head having the structure described above, the structure of the auxiliary yoke 11 and the rear guide 9 has been an obstacle to making the head compact, extending its life, and enabling high-speed printing. .

That is, the shape of the auxiliary yoke 11 is approximately elliptical as shown in FIGS. 4 and 5, and its thickness is approximately 1 mm.

This auxiliary yoke is positioned by a post 8b projecting from the rear end of the bobbin 8, and the bobbin 8 is positioned by a core 6 fixed to the yoke 5.

On the other hand, the rear guide 9 is fitted into the groove of the yoke 5 and its rotation is restricted, and as a result, the positional relationship between the auxiliary yoke 11 and the rear guide 9 is restricted by the yoke 5.

Therefore, even if the positional relationship between the hole position of the auxiliary yoke 11 and the rear guide 9 is logically as designed, in practice, a positional deviation occurs due to dimensional errors during processing.

When such a positional shift occurs, the movement of the armature 14 that is integrated with the wire 22 is controlled by the post 8b of the bobbin 8 and the groove 9a that guides the armature 14 formed at the rear end of the rear guide 9. Because of this restriction, the plunger 13 comes into contact with the wall surface of the through hole 11b of the auxiliary yoke 11 into which the plunger 13 of the armature 14 enters.

The through hole 11b of the auxiliary yoke 11 and the plunger 1
The gap between the plunger 13 and the through hole 11b is made extremely small in order to increase the permeance of the magnetic circuit, so that if a slight positional deviation as mentioned above occurs, the plunger 13 and the wall surface of the through hole 11b will definitely come into contact. I will do it.

If the plunger 13 makes contact, the armature 14 will no longer be able to operate in response to the print signal, and the tip of the wire 22 will remain protruding, causing the ink ribbon to be caught or conversely causing the wire 22 to protrude. This results in missing dots and a significant drop in print quality. On the other hand, the guide groove 9a of the armature of the rear guide 9 and the guide hole 9b of the intermediate guide integrated with the rear guide 9
If the armature 14 is not in the correct position,
This also has a large effect on the sliding resistance of the wire 22 that is integrated therewith.

The sliding resistance also increases when the groove 9a and the hole 9b of the intermediate guide are misaligned with respect to the auxiliary yoke 11. In this way, when the positional deviations during assembly of many parts and the errors of the product itself are compounded, the movement of the wire 22 at the speed of light is inhibited, and the grooves 9a and holes 9b are rapidly worn out.
The disadvantages were that the life of the printing head was significantly shortened, assembly was complicated, and the head itself became large.

Purpose The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional head, and is capable of reliably operating a large number of wires without causing misalignment between the members constituting the head. It is an object of the present invention to provide a wire dot head configured to be miniaturized.

Embodiments Hereinafter, details of the present invention will be explained based on embodiments shown in the drawings.

FIG. 6 and subsequent figures illustrate one embodiment of the present invention, in which a wire dot head is shown in cross section.

In FIG. 6, the reference numeral 29 is the body, which is different from the conventional structure and is formed by integrating the supporting parts of the tip guide and the intermediate guide.
A plurality of intermediate guides 25 to 27 are attached to the protruding portion 29a that protrudes forward. A tip guide 24 is fixed to the tip of this protrusion 29a. The material of the intermediate guides 25 to 27 is a linear synthetic resin, such as PBT (polybutylene terephthalate) with carbon fibers, nylon with carbon fibers, PBT with glass fibers, nylon with glass fibers, Teflon, or a mixture thereof.

However, the tip guide 24 is made of ruby, ceramic, glass, or synthetic resin, which has excellent wear resistance.

A cylindrical deep-drawn yoke 32 is accommodated within the body 29. A spacer 31 formed in a ring shape and serving as a heat dissipation plate is fixed to the side surface of the body 29 of the yoke 32 on the protrusion 29a side, and a printed circuit board 30 also formed in a ring shape is fixed to the outer surface of this spacer 31. Fixed.

The yoke 32 has a cylindrical shape, but has a circular opening formed in its center.

As shown in FIG. 7, a large number of cores 36, for example 24, are fixed to the yoke 32 at equal angular intervals. The edge of the yoke 32 and the edge of the core 36 are polished so as to form the same plane, and consideration is given to making the gap between the plunger and the core uniform, which will be described later.

As shown in FIG. 7, the core 36 has a cross-sectional shape in which both sides of a cylinder are machined symmetrically and parallel to each other.

A coil 34 formed into a cylindrical shape is fitted into these 24 cores 36. The winding start and winding end portions 35 of the coil 34 pass through the yoke 32 and the spacer 31 and are soldered to the printed circuit board 30 side. The end portion 35 of this coil is covered with a heat-resistant insulating column 33 to prevent the occurrence of shoots.

The coil 34 is fixed to the yoke 32 with an epoxy resin adhesive 37 to prevent wire breakage due to vibration of the head, and a thermistor 38 for detecting the temperature of the coil 34 is also bonded to prevent the coil 34 from seizing. It is embedded in the vicinity of the coil 34 by the agent 37.

An auxiliary yoke 40 is fixed to the rear end of this yoke 32 so as to abut against each other. This auxiliary yoke 40 has a narrowed peripheral edge in order to increase its bending rigidity, and the edge of this narrowed area abuts against the yoke 32. A total of 24 posts 41 are protruded from the auxiliary yoke 40 in one-to-one correspondence with the core 36.

On the other hand, what is indicated by the code 43 is an armature,
The rear end is fitted into the post 41, and a plunger 46 is fixed in the middle thereof, and this plunger 46 is slidably fitted into a through hole formed in the auxiliary yoke 40. The core 3
It is facing 6. The auxiliary yoke 40 is formed in a ring shape, and its material is ferrite stainless steel, which does not reduce the permeance of the magnetic circuit and is compatible with the armature 43 in terms of wear resistance.

Further, a polyester sheet 42 is disposed between the auxiliary yoke 40 and the armature 43 to prevent wear caused by contact between the two and to improve magnetic separation between the two.

The center portion of the auxiliary yoke 40 having the above-described structure is integrated with the subbody 47, which also serves as a rear guide, by outsert molding. This subbody 47 is made of synthetic resin with excellent heat resistance and wear resistance. An intermediate guide 28 is fixed to the tip of this subbody 47, and the subbody 47 and yoke 32 are connected with screws 3.
It is integrated by 9.

The material of this subbody 47 is conventionally
POM (polyacetal) was used, but in the present invention, it contains 10% glass fiber.
PBT is used, which reduces wire wear and extends head life by approximately 1.5 times compared to conventional wires.

Also, a return spring 4 is provided at the rear end of the subbody 47.
One end of the return spring 48 is fixed, and the other end of the return spring 48 is pressed into the middle of the armature 43. Therefore, the armature 43 is given a force in a direction away from the subbody 47 by the force of the return spring 48. The rear ends of wires 49 are fixed to the distal ends of a total of 24 armatures 43. The wire 49 is connected to a guide 47a formed in the subbody 47 and intermediate guides 25 to 2.
8 and is guided to the tip guide 24.

In the case of this embodiment, there are 24 wires 49,
There are 12 of them arranged in a staggered pattern. The pitch between the 12 wires 49 is 0.282 mm, and the dot pitch in the printed state is 0.141 mm.

Also, the diameter of the wire 49 is 0.20 at the tip only.
mm, and the other parts are 0.22 mm, using electrolytically polished tungsten wire.

Incidentally, the plunger 46 fixed to the armature 43 also has a cross-sectional shape in which both sides of a cylinder are cut, similarly to the core 36.

There is a stopper 5 behind the many armatures 43.
0 is placed. This stopper 50 is required to be heat resistant because the temperature of the head rises to about 150°C during operation, and in order to extend the life of the intermediate guide, oil is applied between it and the wire 49. Since it also adheres to the stopper 50, oil resistance and chemical resistance are also required.

In addition, in order to achieve high-speed printing, when the armature 43 is stopped by the stopper 50 after printing, the armature 43 stops while rebounding, but the shorter the time until this vibration is converged to zero, the higher the speed. In order to enable printing, a property with a small rebound coefficient of elasticity is required. For example, fluorocarbon rubber is suitable as a material that satisfies these conditions.

The stopper 50 is fixed to a stopper holder 53 with adhesive or the like. The stopper holder 53 is slidably fitted into the center of a bag holder 60 constituting the rear casing of the head.

The bag holder 60 covers the entire rear half of the head and is fixed to the body 29 with screws 61.

Furthermore, this back holder 60 has a shape with many fins to radiate heat generated in the drive section of the head to the outside, and furthermore, it does not transmit to the outside the noise generated when the armature 43 hits the stopper 50 when it returns. It also has the purpose of

The surface of this bag holder 60 is treated with black alumite in order to improve the heat transfer coefficient.

A leaf spring holder 51 is fixed to the inner surface of the bag holder 60 with screws 52, and a leaf spring 45 is disposed between the leaf spring holder 51 and the bag holder 60.

This leaf spring 45 is also formed radially, as shown in FIG. .

By the way, the material of armature 43 is SPCC.
(cold rolled steel plate), armature 43
During the movement of the armature 4, it will wear out due to contact with the stainless steel plate spring 45.
In order to prevent this, a polyester sheet 44 is interposed between the armature 43 and the leaf spring 45.

On the other hand, a sub-bag holder 58 is fixed to the back side of the bag holder 60 with screws 59.

A disc spring 57 is disposed between the damper 55 fixed to the stopper holder 53 and the sub-back holder 58 with a washer 56 interposed therebetween. The damper 55 is molded from lead and is fixed to the stopper holder 53 by pressure.

By the way, as mentioned above, the stopper holder 53 is slidably fitted to the bag holder 60, and it is possible to change the thickness or number of adjusting washers 54 fitted between the back of the bag holder 60 and the stopper holder 53. Accordingly, stopper 5
The stroke of the wire 49 can be adjusted by regulating the zero position.

In the wire dot head according to the present invention configured as described above, when the coil 34 corresponding to the wire 49 to be driven during printing is energized,
A closed magnetic path is formed by the core 36, yoke 32, auxiliary yoke 40, and plunger 46, the plunger 46 is attracted, the armature 43 is attracted, the target wire 49 protrudes, and it is recorded on the printing paper via the ink ribbon. will be held.

As explained above, the wire dot head of this embodiment has the auxiliary yoke 40 and the subbody 47 integrally molded, so that the through hole 40a and the post 41 formed in the auxiliary yoke 40 are fitted with the plunger 46. Installation position and guide hole 47 for wire 49 formed in guide 47a of sub-body 47
The relative positional relationship with b can be matched as designed. In other words, since the subbody 47 and the auxiliary yoke 40 are not molded separately and then integrated after drilling, etc., it is possible to perform drilling and other operations while they are integrated, and the holes between the two can be processed. This means that the position can be set as designed.

Therefore, the plunger 46 connected to the armature 43 can always trace the same trajectory during its operation.

Therefore, the gap between the wall surface of the through hole 40a of the auxiliary yoke 40 and the plunger 46 can be made extremely small, the permeance between them increases, and the magnetic efficiency is extremely improved.

That is, the magnetic circuit of the wire dot head according to the present invention includes the core 36, the yoke 32, and the auxiliary yoke 4.
0 and the plunger 46, and it is the permeance in the gap between the core 36 and the plunger 46 and the gap between the auxiliary yoke 40 and the plunger 46 that determine the high efficiency of this magnetic circuit.

Now, assuming that the permeance is P, the magnetic permeability of the gap is μ, the opposing area between the gaps is S, and the gap interval is l, the permeance P, which is the reciprocal of magnetic resistance, is expressed by the following equation.

P=Sμ/l Therefore, the larger the permeance P, the better the magnetic efficiency, and the smaller the gap or interval l, the smaller the area S.
It can be seen that the larger P becomes larger.

That is, the plunger 46 and the auxiliary yoke 40
The smaller the gap between the gap and the wall of the hole 40a into which the plunger 46 is inserted, the better.

However, as a practical matter, since the plunger 46 reciprocates in the plunger hole 40a, it is usually necessary to provide a gap with a sufficient margin so that the plunger 46 does not come into contact with the wall surface of the hole 40a.

Therefore, in the past, the gap was made larger, which lowered the magnetic efficiency, but in the present invention, the position of each hole can be set accurately, so the gap can be made smaller and the magnetic efficiency can be increased.

Furthermore, the sliding resistance of the armature 43 integrated with the wire 49 is minimized because the movement of the armature 43 is ideally regulated, making it easier to respond to electrical signals and enabling high-speed printing.

In addition, the material of the subbody 47 used to be POM, etc., but in the present invention, PBT containing 10% glass fiber is used, so it has a lifespan of about 1.5 times that of the conventional head. be able to.

Furthermore, since the auxiliary yoke 40 and the subbody 47 are integrally molded, there is no need to make each part large for assembly, so that the head can be made compact and the entire head can be made compact.

Effects As is clear from the above explanation, according to the present invention, the structure in which the subbody and the auxiliary yoke are integrated by outsert molding is adopted, so the hole positions of the auxiliary yoke and the subbody can be adjusted as designed. The gap between the plunger and the through hole into which the plunger of the auxiliary yoke fits can be made extremely small. The head structure can be made small and downsized.

In addition, the subbody is made of glass fiber.
Since PBT is used, a long life can be achieved.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing a printing method using a wire dot head, Figs. 2 to 5 are explanatory diagrams of a conventional structure, Fig. 2 is a cross-sectional plan view, Fig. 3 is an exploded perspective view, and Fig. 4 is a view taken along the line A-A in FIG. 2, FIG. 5 is a view taken along the line B-B in FIG. A cross-sectional plan view, Fig. 7 is a rear view with the bag holder removed, Fig. 8 is a front view, Fig. 9 is a side view, Fig. 10 is a front view of the integrated auxiliary yoke and subbody, Fig. 11 is a plan view of an integrated auxiliary yoke and subbody. 29...Body, 32...Yoke, 36...Core, 40...Auxiliary yoke, 41...Post, 43
... Armature, 45 ... Leaf spring, 46 ... Plunger, 47 ... Subbody, 49 ... Wire, 60 ... Back holder.

Claims (1)

[Claims] 1. In a wire dot head that performs printing by a plurality of wires driven via a plurality of armatures operated by a solenoid housed in the head body, forming part of a magnetic path. A wire dot head characterized in that an auxiliary yoke and a subbody having a wire guide function are integrated by outsert molding. 2. The wire dot head according to claim 1, wherein the material of the subbody is a linear structure synthetic resin. 3 Linear structure synthetic resin contains carbon fiber
The wire dot head according to claim 2, characterized in that it is made of PBT (polybutylene terephthalate). 4. The wire dot head according to claim 2, wherein the linear synthetic resin is carbon fiber-filled nylon. 5 Linear structure synthetic resin contains glass fibers
The wire dot head according to claim 2, which is made of PBT. 6. The wire dot head according to claim 2, wherein the linear synthetic resin is glass fiber-filled nylon. 7 Linear structure synthetic resins include PBT with carbon glass fibers, nylon with carbon fibers,
3. The wire dot head according to claim 2, which is a mixture or compound of two or more of PBT containing glass fibers and nylon containing glass fibers. 8. The wire dot head according to claim 1, wherein the material of the subbody is Teflon.