JPS61213168A - Ink-type wire dot printer - Google Patents

Abstract

PURPOSE:To obtain an ink-type wire dot printer with high printing quality in which dot density is stable and appropriate, by a construction wherein an ink negative-pressure based on the atmospheric pressure is in a specified range in the vicinity of the front end surface of a wire. CONSTITUTION:With a coil 17 energized, a plunger 15 opposed to a coil core 16 is attracted, whereby a clapper 14 with the plunger 15 fixed thereto is turned, and a wire 11 engage to the tip of the clapper 14 is protruded. The tip surface of the wire penetrates through an ink menisucus, whereby an ink is adhered to the tip surface, and the wire collides against a recording paper, thereby transferring the ink onto the paper. In view of the face that the position of an ink tank is ordinarily within about + or -1 cm from the position of the tip surface of the wire in an ink-type wire dot printer, it is necessary that the average pore diameter of a porous material be 200-600mum in order to maintain the ink pressure in such a range as to ensure favorable printing quality i.e., in the range of 2,000-8,000dyn/cm<2>.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an ink-type wire dot printer that prints by depositing ink on the tip of a wire.

<Technical Background of the Invention> The conventionally known wire dot recording method, in which dots are formed by striking recording paper with a wire through a ribbon impregnated with ink, is capable of relatively high-speed printing and high printing quality. It is widely used because it provides high quality at low cost.

However, in this wire dot recording method, the ink impregnated in the ink ribbon is permeated into the recording paper by the impact pressure when the wire collides, forming dots on the recording paper, so it is difficult to obtain sufficient dot density. If so, it is necessary to increase the striking force of the wire, which causes problems such as printing noise and increased energy consumption.

Also.

Woven cloth is generally used as the material for the ink ribbon, taking into consideration its durability, ink impregnability, etc.

If the diameter of the wire is smaller than the size of the weave of the woven fabric, the wire will penetrate the weave.

In this state, the ink ribbon and the printer head move acoustically, causing ribbon breakage and even wire breakage. Therefore, there is a limit to increasing the recording density by reducing the diameter of the wire.

Therefore, an ink-type wire dot recording method was devised in which ink is directly supplied to the tip of the wire without using an ink ribbon, and the ink adhering to the front end of the wire is transferred to recording paper with the wire protruding. There is. With this method, the problems caused by using an ink ribbon, as described above, can be solved. That is, since almost no impact force is required, printing noise and energy consumption can be reduced, and the weight of the movable parts can be reduced.

This allows for faster printing. Also.

By reducing the diameter of the wire, high-density and high-quality printing is possible.

By the way, the biggest difference between the above-mentioned ink-type wire dot recording method and the ribbon-type wire dot recording method is that the fluid behavior of the ink has a decisive effect on printing quality. In other words, in the ink wire dot recording method, the shape, density, etc. of the dots formed are similar to the ink that adheres to the tip of the wire! It depends on the IVC, and its appearance depends on the wire end and
The value h near the end depends on properties such as capillary force acting on the ink in the channel or ink tank i, a meniscus formed near the tip of the wire, and viscous resistance acting on the ink flowing through the channel. Among these, the most fundamental factor that determines print quality is the state of the meniscus formed by the ink filled near the tip of the wire. Depending on this state, printing may not be performed at all, or an excessive amount of ink may be transferred, forming irregularly shaped dots with large smearing around the periphery. Incidentally, the state of the meniscus formed at the tip of the wire depends on the ink pressure at that portion.

Therefore, good print quality cannot be obtained unless the ink pressure is set to an appropriate value.

<Object of the Invention> The present invention has been made in view of the above-mentioned points, and its object is to provide an ink-type wire dot printer with high printing quality in which the dot density is stable and appropriate. It is. Another object of the present invention is to provide an ink type wire dot printer that is high speed, has low noise, and has low power consumption.

Means for Solving the Problems> The ink-type wire dot printer of the present invention includes an ink tank and an ink guide means having one end connected to the ink tank and the other end connected to the vicinity of the front end surface of the wire, Near the surface, the ink negative pressure based on atmospheric pressure is 2000 d71 or more 8000 dyn7 excellent 8
It is characterized by being configured as follows. Still more preferably, the ink tank includes a porous material that is an ink-impregnated member.

The porous material is characterized in that the average pore diameter is 200#1 or more and 600#1 or less.

Function> The present invention will be described in detail below, and Figure 1 shows an outline of the ink supply mechanism of the ink type wire dot printer of the present invention.

In Figure WN2, the wire 11 is projected from the standby position shown by an i-wire drive device (not shown), collides with the platen 31 via the recording paper 3o, and transfers the ink on the front end surface 11-α onto the recording paper. It returns to the standby position again. Ink is consumed as the ink is consumed each time the wire 11 moves back and forth.
1 Ink guide path B from the ink tank by capillary action
i The wire flows through the front end surface 11 a of the wire indicated by m in Fig. 2.
is filled in the front part of the The ink filled in the room is 1
A meniscus ft is formed by surface tension, and part or all of the front end surface 11α of the wire rMi! jl[In The ink that adheres to the tip end surface of the wire 11 at the next printing dot i and is transferred to the paper.

Next, the behavior of the ink when it is attached to the wire and transferred to the paper will be explained with reference to FIGS. 2, 8, and 4. Predicament 2
The figure shows the state of the ink liquid level when the wire is on standby, FIG. 8 shows the state of the ink adhering to the wire 11 just before it collides with the paper, and FIG. 4 shows the state of the ink transferred to the paper.

Also, (a), (6),
(c) shows the amount of ink. In other words, the wire tip 11 a K: The amount of ink that adheres and is transferred to the paper is determined by the wire tip surface l1α and the ink meniscus m when the wire is on standby.
Depends on the relative position. When a meniscus is formed behind the wire tip surface 11α as shown in FIG. 2 et al. and the wire tip surface 11α is in a dry state, ink will not adhere to the wire tip surface 11α as shown in FIG. 8 (b)). Either no dots are formed, or the dots are incomplete as shown in Figure 4). 2. As shown in Figure (6), a meniscus is formed forward of the wire tip surface 11α, and the wire tip surface 1
If there is a considerable amount of ink thickness between 1α and
As shown in 6), an excessive amount of ink adheres to the tip of the wire, and as shown in FIG. 4(6), the ink soaks toward the periphery of the paper and bleeds around the dot, resulting in irregular dots. Furthermore, ink that collides with the recording paper together with the wire 11 may not be absorbed by the recording paper, but may be scattered around due to the impact of the wire and adhere to the ink, resulting in so-called satellites. If the meniscus thinly covers the wire tip surface 11a or partially exposes the wire tip surface 11a as shown in FIG. 2(C), the wire tip The ink adheres thinly and uniformly to the area, and as shown in Figure 4(c), the dot shape roughly matches the shape of the wire tip surface 11α, and no satellites are observed.

As described above, in the ink supply mechanism of the ink-type Y/Y dot printer, the print quality is greatly influenced by the state of the meniscus formed by the ink filled at the tip of the wire during the wire standby condition.

Incidentally, the meniscus formed at the tip of the wire described above changes depending on the pressure within the ink.

This situation will be explained using a t-eiES diagram. The meniscus SO cedar shape is the intersection line of the wire guide hole 13-α side surface or the wire front end surface 11-α and the meniscus m! In,
FL, where the contact angle θ of the meniscus determined by the physical properties of the ink and the physical properties of the wire guide or wire is given.
'Lt The equation that is generally known as a positive equation as a boundary condition is Pα -]-/Snow = p= γ (jz-=tj--;) Pa = Atmospheric pressure Pβ: Pressure in the ink P Two atmospheric pressures as a reference Negative ink pressure r: Surface tension of ink 1 a R1: It can be found by solving the principal radius of curvature of the meniscus. In other words, this means that the radius of curvature of the meniscus is determined according to the pressure of the ink. 7L
, R2, and the radius of curvature of tn@ are R1s and R2, respectively.
m"3, and the negative pressure of the ink at that time t-Pl, P
If the goose is s'l, then -Rs<Rs<Rs, so from Laplace's equation above, l Pll > I P2I > l Pg 1. As mentioned above, the appropriate position of the meniscus for forming a proper dot is around m2 in Figure 5, and m
Near 1, the ink around the dot bleeds, and near 3, no dot is formed.Therefore, there are upper and lower limits of ink pressure for forming proper dots.

As mentioned above, in the ink-type wire dot printer h, the print quality depends on the relative position of the ink meniscus m formed at the tip of the wire and the wire tip surface 11a, and the ink meniscus usually changes depending on the ink pressure. do. Therefore, it is found that it is better to use the ink pressure and the depth of the wire tip m1la from the wire guide hole opening end 136 as parameters representing conditions for maintaining good print quality. However, in order to generalize the wire tip surface depth for various wire guide diameters, the normalized value L/d (wire The degree of attraction) is determined.

The inventors of the present invention conducted repeated experiments using various ink-type wire dot heads, and succeeded in finding appropriate ranges for ink pressure and wire retraction to obtain good print quality.

The results are shown in Figure 6.

In Figure 116, in the area I above curve C, no dots are formed at all, or in the area ■ between curves CI and C, no dots are formed at all, or the dots are incompletely printed. Missing dots are formed, resulting in somewhat faint printing. Curve C,
In the area (3) between C3 and C3, dots with a cross-sectional shape almost the same as the wire cross-sectional shape are stably obtained, and good printing quality is ensured.

In the area (3) between and C4, dots with some smearing are formed around the periphery, resulting in dark i printing. When dots are continuously printed at a high printing frequency (approximately 1 KHg) under these conditions, the ink transfer amount determined by the dynamic ink supply process and the ink transfer determined by the static conditions described above. In the region V below the 0 curve C4, where there is a slight difference in the density of the dots after that point compared to the beginning of printing, a large amount of bleeding occurs around the dots.Also, when the wire collides with the paper, Satellites occur due to ink scattering.Furthermore, the density change during continuous printing, as seen in the above area (■), is significant.

As mentioned above, in order to obtain good printing quality, the ink negative pressure and the wire retraction degree need to satisfy the conditions in the sixth region (1), (2), and (2) in the figure. More desirably, it is necessary to satisfy the range of area (3).

Incidentally, the relative position between the tip end surface of the wire and the front end surface of the wire guide hole is determined via the movable body of the wire drive device or the like. Therefore, it is not impossible to suppress the error to about ±0.02axr, but it is not preferable from the viewpoint of manufacturing costs, etc. Therefore, the wire guide hole diameter is usually 0.2axr.
vsa ~ 0.8 m.

It is necessary to take a range of about ±0.1 or more in terms of the wire pull-in degree.

From the above point of view, when compared with the graph in Figure 6, in order to fall within the ranges n, m, and ■ while allowing an error of ±0.1 in the wire retraction degree, the ink pressure must is 2
000 dyn/an” or more, 8000 dyn/(
7) It is necessary to be below the proverbial level, and more preferably 4000 dyn/cm in order to fall within the range of area m.
It is necessary that the speed be not less than 8000 dyn/cm.

In ink-type wire dot printers, various configurations of ink tanks are possible, but the method of storing ink in an ink-impregnated member is widely used because it has a simple configuration and can realize a highly reliable ink tank without ink leakage. I'm here. Porous members are generally used as ink-impregnated members in view of ink storage efficiency.

Now, the negative pressure P at the tip of the wire is calculated using the negative ink pressure PT in the ink tank and the height 5 of the ink tank based on the position of the tip of the wire.
g h Next, an implementation fl of an ink-type wire dot printer head according to the present invention! will be explained with reference to the cross-sectional view of the head shown in Figure 7 and the exploded perspective view of the ink supply device shown in Figure 8.

The head has an ink tank 2 removably disposed above the head, and an ink impregnating member 60 made of a porous material filled in the ink tank 2 is impregnated with ink. As shown in FIG. 8, the ink supply guide 12 has an ink guiding groove 126'i extending in the axial direction, and the ink guiding groove 126 and the tank filling material 60 are in contact with each other. The width and depth of the ink guide groove 12b are set to appropriate values to ensure stable supply of ink from the ink tank 60. There is a circumferential groove 12a in the front part of the ink supply guide 12, which is internally connected to the ink guide groove 126. A wire guide 13 is incorporated in the first circumferential groove 12a, and the combination of the two leads to a seventh groove. Gaps shown in Figures A and B are provided. Furthermore, the gap between the wire 11 and the wire guide hole 13α of the wire guide 13 is small, and the ink is guided from the ink tank 2 to the ink supply guide 12 @126. The wire 1 is guided by capillary force through the gap B between the wire guide 13 and the tip of the wire 1.

The wire drive device has a coil 17t-wound coil core 1.
6t- yoke 18, yoke plate 19 and plunger 1
6 constitutes a magnetic circuit. The movement of the plunger 15 is transmitted to the wire 11 via the clapper 14. The wire driving device described above is covered by a cover 21 and the operating length of the clapper 14 is regulated.

Next, the operation will be explained. FIG. 7 shows the state when the coil 17 is energized, and the plunger 15 facing the coil core 16 is attracted. As a result, the clapper 14 to which the plunger 15 is fixed rotates, and the wire 11 engaged at its tip protrudes. The tip end surface of the wire pierces the ink meniscus, causes ink to adhere to the tip end surface, and collides with recording paper (not shown), so that the ink is transferred onto the recording paper.

In order to obtain good print quality as described above in the above configuration, the dimensions of each element are set as follows.

Wire guide hole diameter d O, 22m Wire front end depth A O, 0? ±0.02 The average pore diameter D of the porous material is 850. Also, the surface tension r of the ink is 45 dy? /11. From this, the wire retraction degree 44 is J/d 0.82, and the ink pressure at the tip of the wire is -4060 (dys/m''), which is the portion for the region shown in FIG. 6 mentioned above.

When printing was performed at a printing frequency of 1 KHg under the above conditions, good quality printing with an appropriate ζ% density and a generally circular dot shape was stably obtained. Furthermore, the average pore diameter of the porous material is 200 #m and 800 #m.

When printing was carried out under the same conditions with the thickness changed to 400 am and 500 μm, the results shown in the table below were obtained.

Here, P: Density of ink g: Acceleration of gravity. The ink negative pressure in the ink tank can be expressed as PTli using the average pore diameter of the porous material. Therefore, by appropriately selecting the average pore diameter of the porous material, it is easy to set the ink negative pressure at the wire tip within the above range without changing the basic configuration of the printer head. I can do it.

Considering that in the structure of a normal ink-type wire dot printer, the position of the ink tank is within about ±151 from the position of the wire tip, the ink pressure should be set within the range that can maintain good printing quality as described above, that is, 2000 dytJt.
8000 d from sI, preferably 4000
In order to keep it within the range of 80004ytv'd from ``dlllVns'', the average pore diameter of the porous material should be 200μm or more and 600μm or less, more preferably 400μm or more and 600μm or less, calculated from the previous formula. is necessary. .

<Example>Effects> As explained above, according to the present invention, by setting the ink pressure at the tip of the wire to a predetermined value, it is possible to eliminate blurring and blurring and to stably produce dots of appropriate density. An ink-type wire dot printer with good print quality can be provided.

[BRIEF DESCRIPTION OF THE DRAWINGS] Figure 111 is a sectional view showing the ink supply mechanism for explaining the present invention in detail, and Figure 2 is a schematic diagram illustrating how the tip of the wire is filled with ink in the wire standby state. The cross-sectional view, IF5, is a schematic cross-sectional view showing the state of ink adhesion to the wire in the wire protruding state, and a diagram showing the dot shape of @S Zusha. Figure 6 is a graph showing the conditions for forming proper dots *I
FIG. E7 is a sectional view of a head showing an embodiment of the ink-type wire dot printer according to the present invention, and FIG. 8 is an exploded perspective view showing details of the ink supply and storage. 2-Ink tank 11-Wire Minor-Ink supply guide 13-Wire guide 14-Operating plate 15-Plunger 17-Coil 1g-:i-ri ω-Ink impregnation member. that's all

Claims (1)

[Scope of Claims] 1. A wire dot printer having a protruding wire with ink attached to the tip thereof is connected to an ink tank, and an ink guide means having one end connected to the ink tank and the other end connected to the vicinity of the front end surface of the wire. The ink negative pressure is 2000 dyn/dyn based on atmospheric pressure near the front end surface of the wire.
An ink-type wire dot printer characterized in that the ink-type wire dot printer is configured to have an output of not less than cm^2 and not more than 8000 dyn/cm^2. 2. The ink tank includes a porous material that is an ink-impregnated member, and the porous material has an average pore diameter of 200 μm or more and 600 μm or more.
An ink-type wire dot printer according to claim 1, characterized in that the ink-type wire dot printer has a dot size of μm or less.