JPH05221B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to wire dot heads.

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 includes a washer 19 and a spring washer 2.
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.

Incidentally, 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.

Further, 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 tip guide 11. 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 yoke 6, and the armature 14 resists the elastic force of the return spring 10 and moves the wire 22.
is made to protrude from the tip guide 1 by a predetermined distance. The wire 22 prints dots on the paper via an ink ribbon (not shown).

By the way, the magnetic circuit of a general wire dot head is composed of a yoke 5, a core 6, a plunger 13, and an auxiliary yoke 11, as shown in FIG.

In such a structure, the responsiveness to printing force and electric signals depends only on the gap G between the core 6 and the plunger 13 when only the drive section of the armature 14 is considered. This gap G is expressed by the following equation.

G=H ₁ +t ₁ +t ₂ −H ₂ −H _3In the above formula, H ₁ is the distance from the bottom surface of the yoke 5 to the end surface, H ₂ is the height of the core 6, H ₃ is the height of the plunger 13, and t ₁ is the thickness of the auxiliary yoke 11, and _t2 is the thickness of the polyester film 12.

By the way, as is clear from FIG. 2, the auxiliary yoke 11 functions as a stopper for the armature 14 in the printing direction. Generally, the printing force of a wire that can make 3 to 4 copies is about 2.5 kg per wire.

Therefore, when all of the plurality of wires are driven at the same time, an extremely large force acts on the side surface of the auxiliary yoke 11.

Here, the amount of displacement of the side surface of the side yoke will be modeled and calculated based on the force acting on the side surface of the auxiliary yoke 11 of a conventional print head.

That is, as shown in FIG. 7, the armature 14
The number of wires (number of armatures) where the suction force is F
Assuming that N is the force F _T acting on the auxiliary yoke 11 due to the N armatures, it is expressed by the following equation.

F _T = NF ...(1) Here, for simplicity, the outer diameter of the auxiliary yoke 11 is
Let Do and the inner diameter be D〓, and assume that a force F _T acts as a uniformly distributed load w on the side surface of the auxiliary yoke 11 as shown in FIG.

It is assumed that the peripheral edge of the auxiliary yoke 11 is simply supported, as is clear from FIG.

In this state, the uniformly distributed load w (Kg/mm ² ) is expressed by the following equation.

w=F _T /π/4(Do ² −D〓 ² ) (2) At this time, the amount of displacement t at the inner peripheral portion of the auxiliary yoke 11 is expressed as follows.

t=α ₁₃ wDo ⁴ /Eh ³ =0.78×wDo ⁴ /Eh ³ ...(3) In equation (3), E is the Young's modulus of the material of the auxiliary yoke, h is the thickness of the auxiliary yoke, and α ₁₃ is In terms of the deflection coefficient, in the relationship D〓/Do, if D〓/Do=0.42, then α ₁₃ =0.78.

Here, assuming that the distance from the plunger position to the outer circumference of the auxiliary yoke 11 is taken as the distance, the displacement amount t _P at the plunger position is expressed by the following equation.

t _P = t/Do-D〓/2 ...(4) When the auxiliary yoke 11 is displaced as described above, the gap between the core 6 and the plunger 13
G ₂ is the gap G ₁ when the auxiliary yoke is not displaced.
Then, it is expressed by the following formula.

G ₂ =G ₁ −t _P (5) As is clear from equation (5), G ₂ =0 in some cases. That is, the core and plunger may come into contact with each other.

In such a case, even if the coil is no longer energized, the core 6 and plunger 13 will be damaged due to residual magnetism.
Since the wire 22 continues to be attracted, the wire 22 continues to protrude, which causes the wire 22 to get stuck in the ink ribbon, causing damage to the ink ribbon, breakage of the wire 22, etc., and making printing impossible.

Purpose The present invention has been made in order to solve the above-mentioned conventional problems. For example, it is possible to reduce the amount of displacement of the auxiliary yoke, and for example, to maintain a substantially constant gap between the core and the plunger. It is an object of the present invention to provide a wire dot head configured so that the wire does not remain protruded.

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

The embodiment described below constitutes a part of the magnetic circuit in a wire dot head that performs printing using a plurality of wires driven through a plurality of armatures operated by a solenoid housed in the head body. This wire dot head is characterized in that a part of the auxiliary yoke is constricted to increase bending rigidity.

FIG. 9 and subsequent figures illustrate one embodiment of the present invention, in which a wire dot head is shown in cross section.

In Fig. 9, 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. 10, the yoke 32 has a large number of
For example, 24 cores 36 are fixed 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. 10, 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. This auxiliary yoke 40 has the core 3
A total of 24 posts 4 in one-to-one correspondence with 6
1 is provided protrudingly.

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 28.
and is guided to the distal end 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. 10, and its tip end is connected to the post 41.
The base end of the armature 43 is pressed against the auxiliary yoke 40.

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.

By the way, in the present invention, as is clear from FIG. 9, a structure is adopted in which the peripheral edge of the auxiliary yoke 40 is bent into an annular shape to increase rigidity.

Auxiliary yoke 4 when adopting such a structure
The displacement amount of 0 is as follows.

That is, as shown in FIGS. 13 to 15, if the outer diameter of the auxiliary yoke 40 is Do, the inner diameter is D, the force acting on the auxiliary yoke 40 due to one armature is F, and the number of armatures is N. The force F _T acting on the auxiliary yoke 40 is expressed by the following equation.

F _T = NF ... (6) By the way, this force F _T causes a uniformly distributed load w (Kg/mm ² ) on the side surface of the auxiliary yoke 40 as shown in Fig. 15.
Assuming that w acts as , w is expressed by the following equation.

w=F _T /π/4 (Do ² −D〓 ² ) ...(7) When the uniformly distributed load w is applied to the auxiliary yoke 40, the amount of displacement t at the inner circumference of the auxiliary yoke 40 is the first
Since the outer periphery of the auxiliary yoke is deep-drawn by H as shown in FIG. 4, it is considered that the periphery is fixed as shown in FIG. 15, so it is expressed by the following equation.

t=α ₁₄ wDo ⁴ /Eh ³ =0.1×wDo ⁴ /Eh ³ ...(8) In equation (8), E is the Young's modulus of the material of the auxiliary yoke, h is the thickness of the auxiliary yoke, and α ₁₄ is the deflection coefficient. ,
If D〓/Do=0.42, α ₁₄ =0.1 from the diagram.

Here, if the distance from the position of the plunger 46 to the outer periphery of the auxiliary yoke 40 is, then the amount of displacement of the auxiliary yoke 40 at the position of the plunger 46 is
Assuming t _P ′, this is expressed by the following equation.

t _P ′=t/Do−D〓/2 …(9) Now, the core 3 when the auxiliary yoke 40 is not displaced
If the gap between 6 and the plunger 46 is _G1 , the gap when the auxiliary yoke 40 is displaced is _G2.
is expressed by the following equation.

G ₂ =G ₁ −t _P ′ (10) If such a structure is adopted, the ratio α of the displacement amount at the plunger portion of the auxiliary yoke in the conventional structure and the auxiliary yoke according to the present invention will be as follows.

α=t _P ′/t _P =0.1/0.78=0.129 (11) In other words, it can be seen that the amount of displacement when the peripheral edge of the auxiliary yoke is constricted is reduced to 1/8 compared to when it is not constricted.

In this manner, it can be seen that when the outer diameter, inner diameter, and plate thickness of the auxiliary yoke are equal, the restriction of the outer periphery of the auxiliary yoke has a large effect on the amount of displacement of the auxiliary yoke.

Since this embodiment is constructed as described above, by narrowing the outer circumference of the auxiliary yoke, the bending rigidity of the auxiliary yoke can be increased, and the amount of displacement caused by the force acting on the auxiliary yoke by the armature can be significantly reduced. This makes it possible to maintain a constant gap between the core and the plunger, increasing printing duty and enabling high-speed printing.

Further, since the core and the plunger do not come into contact as in the conventional case, the plunger is not held by residual magnetism, the wire does not protrude, and the wire and the ink ribbon are not damaged.
In other words, according to the above embodiment, the bending rigidity of the auxiliary yoke is increased by narrowing the peripheral edge of the auxiliary yoke, so that the amount of displacement caused by the force acting on the auxiliary yoke by the armature can be significantly reduced. Since a constant gap can be maintained between the core and the plunger, the plunger is not attracted by residual magnetism, the wire does not stick out, and the ink ribbon or wire is not damaged, increasing printing duty. A wire dot head capable of high-speed printing can be obtained.

Effects As is clear from the above explanation, according to the present invention, the protruding wire can be quickly retracted, the wire does not remain protruding, and the recording duty can be increased to enable high-speed recording. You can get a dot head.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing a printing method using a wire dot head, Figs. 2 to 8 are explanatory diagrams of the conventional structure, Fig. 2 is a cross-sectional plan view, Fig. 3 is an exploded perspective view, and Fig. 4 is an explanatory diagram showing a printing method using a wire dot head. FIG. 5 is a view taken along line BB in FIG. 2, FIG. 6 is an explanatory view of the yoke, FIG. 7 is a front view of the auxiliary yoke, The figure is an explanatory diagram showing the displacement of the auxiliary yoke. Figure 9 and subsequent figures are explanatory diagrams of one embodiment of the present invention. Figure 9 is a cross-sectional plan view, Figure 10 is a rear view with the bag holder removed, and 11 is a front view, FIG. 12 is a side view, FIG. 13 is a rear view of the auxiliary yoke, FIG. 14 is a vertical side view of the auxiliary yoke, and FIG. 15 is an explanatory view showing displacement of the auxiliary yoke. 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)

[Scope of Claims] 1. A wire dot head for recording on a recording medium, comprising: a wire coupled to a distal end of an armature; a guide for guiding the wire; a coil; a core; a yoke and a second yoke into which a plunger is loosely fitted, the armature is sucked in response to a suction operation between the core and the plunger, and the wire is made to protrude from the guide in the longitudinal direction of the wire. A wire dot head comprising: a drive means for the second yoke, and the bending rigidity of the peripheral edge of the second yoke is increased. 2. The wire dot head according to claim 1, wherein the second yoke has increased bending rigidity by bending the peripheral edge portion into an annular shape. 3. The driving means is characterized in that when the coil is energized, a closed magnetic path is formed by the core, the first yoke, the second yoke, and the plunger. A wire dot head according to claim 1.