JPH10157164A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce positional shift of printing dots and to lower the voltage of a drive power supply. SOLUTION: An emitting electrode 4 provided to each ink nozzle in contact with ink, a control electrode 6 having a passing hole 7 provided thereto so as to prevent the contact with the ink from the ink nozzle, a medium 8 to be printed receiving the ink flying through the passing hole 7 of the control electrode, the opposed electrode 9 provided to the rear of the medium 8 to be printed in opposed relation to the emitting electrode 4, a bias power supply 10 supplying bias voltage across the,emitting electrode and the opposed electrode and the signal source 11 provided between the control electrode and the opposed electrode to control the flight of ink are provided. Since an electric field determining the flight of ink can be stably formed by using three electrodes, that is, the emitting electrode, the control electrode and the opposed electrode, the flight of ink becomes stable and the positional shift of a printing dot can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording head of an ink jet printer which prints on a recording medium by electrostatically flying colored ink.

[0002]

2. Description of the Related Art An electrostatic induction type ink jet printer forms an electric field by applying a voltage between an electrode (ejection electrode) in contact with ink and an electrode (counter electrode) not in contact with ink. By moving the ink to the end of the discharge electrode and further increasing the electric field, the ink flies in the direction of the counter electrode and prints on a printing medium such as paper.

In Japanese Patent Application Laid-Open No. 56-8268, a discharge electrode provided around a small hole and in contact with ink and a counter electrode facing the discharge electrode are provided, and a predetermined voltage or more is applied between the discharge electrode and the counter electrode. It discloses a technique in which an ink is caused to fly on a printing medium by forming an electric field and printing is performed.

In Japanese Patent Application Laid-Open No. 56-8270, a discharge electrode in contact with ink and an external electrode having a hole through which ink passes are provided, and a voltage higher than a predetermined voltage is applied between the discharge electrode and the external electrode to generate an electric field. A technique is disclosed in which the ink is passed through a hole of an external electrode by forming the ink, and is caused to fly on a printing medium to print.

In any case, in the conventional method, the flying of the ink is controlled by controlling the potential of one of the discharge electrode and the counter electrode according to the print information.

[0006]

When the ink is caused to fly from the discharge electrode in contact with the ink as disclosed in JP-A-56-8268, the ink is constantly exposed to the outside air.
There is a disadvantage that the viscosity of the ink tends to increase due to the evaporation of the solvent of the ink, and the ink sticks over time.

Further, since the distance between the two electrodes on which the electric field which determines the ink flight acts is long, it is necessary to increase the potential difference between the two electrodes, and the switching response of the signal source for changing the potential is reduced. is there.

When ink is caused to fly from an electrode in contact with the ink through an external electrode provided with a passage hole through which the ink passes as in JP-A-56-8270, the space from the outside of the external electrode to the printing medium is There is a drawback that dot misalignment is likely to occur because the ink flies regardless of the electric field.

[0009]

SUMMARY OF THE INVENTION The present invention is characterized in that a discharge electrode that comes into contact with ink, a control electrode provided with a passage hole so that ink ejected from an ink nozzle does not touch, and a control electrode that passes through a passage hole of the control electrode. And a bias power supply for providing a bias voltage between the discharge electrode and the counter electrode, wherein a counter electrode is provided on the back of the print medium opposite to the discharge electrode. And that a signal source for controlling the flying of ink by changing the potential of the control electrode is provided.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to FIG.

In a conventional ink jet image forming apparatus,
In contrast to a configuration in which a voltage is applied between two electrodes to drive the ink and the signal source is superimposed on a bias DC power supply and thus tends to be electrically unstable, the present invention provides a bias DC power supply. The electrical stability is increased by connecting the DC voltage and the signal of the signal source to separate electrodes, or by setting the potential of the control electrode that determines the ink flying to the ground potential.

The greatest feature of the present invention is that the provision of the three electrodes of the discharge electrode, the control electrode, and the counter electrode enables the flying ink to fly on the printing medium more stably. .

As described above, in the technique disclosed in Japanese Patent Application Laid-Open No. 56-8270, ink is caused to fly from an electrode in contact with ink to an external electrode not in contact with ink by an electric field. Since the electric field is hardly formed before the external electrode which is not used, the ink during the flight flies without receiving the electrostatic force, and it is difficult to stably reach the desired position on the paper as the printing medium. difficult.

On the other hand, according to the method of the present invention, since an electric field is applied from the discharge electrode to the counter electrode through the passage hole formed in the control electrode, the ink is applied to the paper to be printed by electrostatic force. Can be reached stably.

A control electrode for controlling the flight of the ink is
By arranging it between the ejection electrode and the counter electrode, the control potential difference of the control electrode required for controlling the flying of the ink can be reduced.

FIG. 1 shows an embodiment of the present invention in which a cylindrical discharge electrode such as an injection needle having a truncated tip is used.
First, this configuration will be described.

In this image forming apparatus for performing direct recording, a paper 8 as a printing medium is arranged on a counter electrode 9.

The control electrode 6 is disposed at a position approximately 0.2 mm to 1 mm away from the paper surface. The control electrode 6 is divided in units of one dot, and is connected to the signal source 11 so that the potential can be changed individually.

Further, the ink nozzle 3 is arranged at a position separated from the control electrode 6 by 0.1 mm to 1 mm. At this time, when the meniscus 5 formed at the tip of the ink nozzle comes into contact with the control electrode 6 or when the ink leaks, the ink is applied to the control electrode 6.
Must not come into contact with

The ink 1 is supplied from the inside of the ink tank 2 and supplied into the ink nozzle 3 using the ink pressure adjusting means 13.

The ink pressure adjusting means 13 may be made of a material capable of holding ink such as felt or a means of adjusting the ink pressure in an ink tank using a pump or the like. Does not leak from the ink nozzles.

Discharge electrodes are arranged in the ink nozzle to form a meniscus of ink. In the case of FIG. 1, the ink nozzle has a cylindrical shape as shown in FIG. 6 and the inside is a discharge electrode. The other shapes will be described later.

Since the ink easily flies in the axial direction of the ink nozzle, the passage hole 7 is formed in the control electrode in a range of about the nozzle diameter or more around the point where the extension of the axis of the ink nozzle intersects the control electrode. Open so that the flying ink does not hit the control electrode 6. As a result, the ink adheres from the ink nozzle 3 having the ejection electrode 4 to the paper 8 in front of the counter electrode 9 through the passage hole 7 provided in the control electrode 6.

Of the three types of electrodes characteristic of the present invention,
A bias power supply is connected to the ejection electrode and the counter electrode to apply a bias voltage to both electrodes, and a signal source is connected to the control electrode so as to control the flight of ink.

The printing method of the above embodiment will be described.

First, the ink 1 is introduced from the ink tank 2 into the inner cylinder of the ink nozzle 3, whereby the ink comes into contact with the discharge electrode 4.

Next, a potential difference is generated between the ejection electrode 4 and the control electrode 6 or between the ejection electrode 4 and the counter electrode 9 to generate an electric field, whereby the ink in contact with the ejection electrode 4 is separated from the control electrode 6 and the opposite electrode. The ink meniscus 5 is drawn out to the electrode 9 side to form.

Next, a method of applying a voltage to each electrode when the ink is caused to fly and when the ink is not caused to fly will be described.

To fly ink, first, the counter electrode 9
Is grounded to make the control electrode 6 a ground potential or a potential close thereto, and a high voltage is applied to the ejection electrode 4 to form an electric field between the electrodes to move the ink to the tip of the ink nozzle to form the meniscus 5. Further, by applying a high voltage to the ejection electrode, the ink can be made to fly from the tip of the ink nozzle.

Next, in order to stop the flying of the ink from the state in which the ink is flying, the potential of the control electrode 6 may be brought close to the potential of the discharge electrode 4, and by changing the potential of the control electrode 6, the vicinity of the discharge port is changed. This is because the electric field weakens and ink cannot fly.

As described above, the method of controlling the flight of ink only by changing the potential of the control electrode 6 has a feature that the control can be performed with a lower voltage than the conventional case where a pulse voltage or an AC voltage is superimposed on a DC voltage.

By the way, the ink continuously flies when the electric field becomes stronger than a certain electric field, and the ink does not fly at all below the certain electric field.

Since the strength of these electric fields varies depending on the configuration of the ink nozzles, there is an optimum electric field strength depending on each configuration, and this must be considered in advance. Specific examples for determining the potential of each electrode will be described below.

First, when the counter electrode is grounded, the control electrode is also grounded, and the voltage applied to the ejection electrode is increased until the ink continuously flies, to determine a stable voltage V0.

As a result, the voltage of the discharge electrode is determined to be V0, and thereafter, the potential of the control electrode is increased until the ink stops flying, and the voltage V1 is determined.

Next, the voltage of the control electrode is lowered, and the potential V2 at which the ink flies stably is obtained again.

As described above, the flying of the ink can be controlled by controlling the potential of the control electrode between the potentials V1 and V2, but the potential V2 is not necessarily the ground potential.

FIG. 2 shows an embodiment in which the potential V2 is not the ground potential, in which an auxiliary bias power supply is provided between the control electrode and the counter electrode.

For example, an injection electrode of the injection needle type (having a diameter of 150)
μm), a counter electrode, and a control electrode (having a diameter of 600 μm) having a hole between them, and the interval between them is 500 μm.
When it is set to μm, a potential of 250 V is applied to the control electrode, and 1.5 kV is applied to the ejection electrode.

As a result, the ink stops at the discharge port without flying, and when the potential of the control electrode approaches the ground potential, the ink starts flying and printing can be performed.

As described above, to control the potential of the control electrode, a signal source capable of turning on and off a voltage of several hundred volts in accordance with an image signal from an image signal source such as a computer is used.

When an image is actually formed, ink is ejected in accordance with image information. In this case, when power is turned on, a voltage of several hundred volts is applied to a control electrode in advance, and then a voltage of several kV is applied to an ejection electrode. This eliminates the risk of accidentally ejecting ink.

This is because if a potential of several hundred volts is applied to the control electrode in advance, the ink cannot fly on the paper.

As described above, in the embodiment of the present invention in which the electric field reaches from the discharge electrode through the through hole of the control electrode to the counter electrode, a specific example of the method of determining the potential of each electrode is as follows. There is.

The first method is a method of controlling the potential of the control electrode after grounding the counter electrode and setting the potential of the discharge electrode to the potential at which the ink stably flies to the counter electrode as described above.

In this method, since the counter electrode is set to the ground potential, disturbance of ink flying due to disturbance can be reduced.

The second method is a method in which the potential of the counter electrode is set to a potential close to the ground, among which the electric field can be further formed between the control electrode and the counter electrode. It is possible to stably fly the ink to the paper.

Specifically, as shown in FIG. 3, an auxiliary bias power supply 12 is used to prevent the counter electrode and the control electrode from having the same potential.

In the third method, the voltages applied to the discharge electrode and the counter electrode are reversed in polarity, and a potential difference between the counter electrode and the discharge electrode is set so that ink can fly. There is a method of changing the potential from the potential to the potential of the counter electrode.

In the case of this method, printing is not performed when the control electrode is at the ground potential, so that there is no startup sequence when the power is turned on, and control of the control electrode in accordance with print information is facilitated.

More specifically, the position set to the ground potential changes as shown in FIG.

In order to stably fly the ink, it is necessary to make the positional relationship between the counter electrode and the control electrode appropriate in addition to improving the electrical stability.

Although it is necessary to prevent the ink flying from the ink nozzles from adhering to the passage hole provided in the control electrode as described above, the size of the passage hole will be described with reference to FIG.

The size of the passage hole provided in the control electrode needs to be substantially the same as the size of the ink nozzle, at least.

If the size of the passage hole is smaller than the above-mentioned size (a), there is a case where the ink flying at a high speed cannot pass through the passage hole.

If the ink flies at the width of the inner diameter of the ink nozzle, it will hit the control electrode. Therefore, the size of the passage hole needs to be larger than the inner diameter (b) of the ink nozzle.

However, when the meniscus of the ink formed in the ink nozzle grows, the distance between the meniscus and the end of the passage hole becomes short, and the ink is not directed to the counter electrode where the ink should fly but to the end of the passage hole, that is, the control electrode. May fly.

This is because the electric field formed between the meniscus formed on the ejection electrode and the control electrode is extremely strong and the amount of electric flux reaching the counter electrode is small, so that the ink cannot fly to the counter electrode. It is preferable that the diameter is larger than the outer diameter (c) of the ink nozzle. Here, it is desirable to keep the distance between the control electrode and the meniscus formed in the ink nozzle constant.

This is because if there is a position near any one point, the electric field is biased in that direction, and the ink is deflected in that direction.

When the size of the passage hole is close to the outer diameter of the ink nozzle, special care must be taken. At least two opposing points must be equidistant.

In order to more easily reduce the deflection of the ink, it is desirable to increase the distance between the meniscus and the control electrode, that is, to increase the size of the passage hole.

The better diameter of the passage hole is about twice (d) the outer diameter of the ink nozzle. With this, the electric flux spreads like a trumpet, and the electric field reaches the counter electrode.

If the width is further expanded, the potential difference of the signal source applied to the control electrode becomes large, and it becomes difficult to switch the signal source that applies the potential that determines the ink flight.

It is desirable that the distance between the meniscus at the tip of the ink nozzle and the control electrode is shorter than the distance between the meniscus and the counter electrode.

If the former distance is longer than the latter by the same distance (f) or longer (g), the influence of the potential of the control electrode on the electric field of the ink nozzle becomes small, and it is difficult to control the flying of ink by the control electrode. It is because it becomes.

Specifically, the inner diameter is 150 μm and the outer diameter is 400 μm.
When the gap between the electrodes is 500 μm or more with respect to each of the m ink nozzles, the distance between the ink nozzle and the control electrode is preferably 800 μm or less.

Next, the shape of the ink nozzle will be described.

First, a cylindrical shape as shown in FIG. 10 will be described.

When the ink nozzle has a cylindrical shape, the ink forms a meniscus of the ink at a position facing the counter electrode through the inside of the cylinder.

In forming a meniscus, there is a method in which the pressure is adjusted in the ink tank and the ink is constantly projected from the ink nozzle. However, basically, the ink is drawn out by an electric field to form a meniscus, and the ink flies.
A good method is to print.

In the case of a cylindrical shape, the surface tension of the ink is evenly applied to the tip of the nozzle, so that the ink can be easily discharged and the frequency of the ink drive can be improved.

Further, the prismatic shape as shown in FIG. 11 has a feature that it has a nozzle characteristic similar to that of the cylindrical nozzle and facilitates machining.

Next, the arrangement of the discharge electrodes will be described.

To apply a sufficient electric field to the ink so that the ink can fly more efficiently, it is preferable to first install an ejection electrode on the inner wall of the ink nozzle to make sufficient contact with the ink.

Thus, an electric field can be formed from the ejection electrode, through the ink, through the tip of the ink, and toward the counter electrode. This is particularly effective when conductive ink is used.

FIG. 1 shows an example in which the ejection electrode is arranged inside the ink nozzle in the shape of the ejection electrode shown in FIG. 6, but the ejection electrode does not have to reach the tip of the ink nozzle but an electric field is formed through the ink to the opposite electrode. Therefore, there is no problem in flying the ink.

However, in order to concentrate the electric field more efficiently, it is preferable that the ejection electrode is extended to the tip of the ink nozzle as shown in FIG.

Further, as shown in FIG. 7, when the discharge electrode is extended to the outer periphery at the distal end portion, it is possible to concentrate the electric field in the surrounding area. As shown in FIG. 8, a method in which the ink nozzle itself is used as a discharge electrode may be used.

Further, when the ejection electrode is provided at the tip of the nozzle, the electric field can be more concentrated on the tip of the ink nozzle, and the electric field can affect the ink reaching the tip of the ink nozzle. By doing so, the ink can be made to fly at a lower voltage.

Up to now, the case where only the cylindrical ink nozzle is used has been described. However, as another embodiment, when a protruding member is inserted into the ink nozzle, a meniscus is easily formed, and the voltage at which the ink starts to fly is reduced. There is a feature that it becomes lower.

The tip of the projection member is preferably at the same position as the tip of the ink nozzle or slightly protruded.

When the projecting member is used, the ink is slightly drawn out to the outside as shown in FIG. 12 even when there is no or weak electric field, and a predetermined voltage is applied to each electrode to immediately before the ink flies. In this state, the ink is filled up to the tip of the protruding member as shown in FIG.

In the state of the potential relation at which the ink flies, the ink flies rightward in the figure as shown in FIG. 14, and when a stronger electric field is supplied, the cross section of the meniscus becomes a small triangular shape as shown in FIG. .

Normally, the ink flight control is performed in accordance with FIGS.
Is realized by alternately reproducing the state of.

As described above, when the projection member is provided, the firing point of the ink can be specified, and even when the electric field formed at the tip of the ink nozzle is low, a meniscus is easily formed, and the ink is formed from the vicinity of the tip. Can be stably ejected and the flying amount of ink can be reduced, so that a small diameter ink dot can be formed.

In order to realize the above state more stably,
There is a method of making the projecting member conductive, the potential of the conductive projecting member becomes a potential slightly lower than the potential of the ejection electrode,
Since the electric field can be more stably collected on the conductive protrusion member, it is possible to realize a stable ink jet at a low electric field.

Further, by connecting an assist power source to the conductive projection member and supplying a slightly lower potential than the discharge electrode, the ink can be moved to the tip of the conductive projection member by the potential difference, and the meniscus of the ink can be reduced. It can be formed without depending on the potential difference between the conductive projection member and the counter electrode.

Although the case where the ink nozzles are divided into print dot units has been described above, the present invention can be practiced as another embodiment using slit-shaped ink nozzles that are not individually divided.

FIG. 16 shows an embodiment using a slit-shaped ink nozzle.

As shown in the figure, there is no partition forming the nozzle as described above, and it is necessary to arrange a projection member such as a needle electrode inside the slit in order to specify the ink discharge point. is there.

The projection members are arranged so as to correspond one-to-one with the control electrodes corresponding to the printing dots so that the ink can pass through the gap provided in the control electrodes.

Since the wall area of the ink nozzle can be reduced by providing the slit-shaped ink nozzle and the projecting member as described above, the mark which is likely to be generated in the ink nozzle due to the drying of the solvent of the ink is caused. It is possible to reduce the diameter of the image dots and improve dot omission.

The above is the case where a projecting member such as a needle electrode is used. However, when a slit-shaped ink nozzle is used,
In particular, it is effective to use a plate-shaped projection member.

By using a plate-shaped projection member, the meniscus of the ink can be easily formed, and the interval between the protruding points can be easily determined.

Needless to say, the discharge electrode is arranged on the plate-like projection member, and the ink is caused to fly by an electric field between the discharge electrode and the control electrode.

In the case of a slit-shaped nozzle, a firing point of ink can be formed by using a projection on the wall surface as shown in FIG.

The embodiment of the present invention configured as described above can be assembled in an array by connecting a plurality of them as shown in FIGS. 18 and 19, and printed in a plane on paper or the like. be able to.

At this time, the distance between the adjacent control electrodes must be such that when the adjacent control electrodes are at different potentials, an electric field weaker than the electric field formed between the ink nozzle and the counter electrode must be generated. , Must be spaced above a predetermined value. The interval is several hundreds μm or more, and more specifically, the distance between the ink nozzle and the counter electrode as described above is about 1 mm, and the distance must be about 200 μm.

[0099] Although the influence of the adjacent electrodes can be reduced as the interval is wider, the degree of integration of the nozzles is reduced, and it is difficult to print with high resolution.

As an improvement method, there is a method of reducing a potential difference between ON and OFF of a signal source applied to a control electrode.

That is, if the potential difference is small, the influence on the adjacent electrode is reduced, and the electrode interval can be narrowed.

If the potential difference can be reduced, ON and OF
The cost of the element for switching F can be greatly reduced.

For example, if the potential difference can be set to about 200 V, an array of power FETs and power transistors can be used, the cost of the element for switching the signal source applied to the control electrode can be reduced, and the inkjet image forming apparatus can be manufactured at a low cost. Can be. As a method for keeping the distance between the ink nozzle and the control electrode constant, a spacer may be inserted between the two.

The spacer may be provided on the front surface of the ink tank as shown in FIG. 20, or a plate member may be provided on the front surface of the ink tank as shown in FIG.

Further, a method may be adopted in which the plate-like member, the spacer and the front surface of the ink tank are integrated, a hole is made in the center of the control electrode as shown in FIG. 22, and an ink nozzle is formed in the center.

Although the configuration of the ink head including the ink nozzles and the control electrode and the counter electrode has been described above, the voltage for switching the ink can be obtained even in a printed circuit board shape as shown in FIG. 5 in which the ink nozzles do not protrude from the ink tank. Can be set to a low voltage.

In the case of a printed circuit board, the through holes serve as ejection electrodes, and the board itself can constitute one surface of the ink tank.

When the shape of the printed circuit board is used, the processing becomes easy, and the ink jet head can be supplied at low cost.

An embodiment in which the above-described ink jet head is mounted on an actual image forming apparatus will be described below.

In the configuration in which ink leakage is taken into consideration, the ink jet head is installed beside the paper transport position as shown in FIG.

In this case, there is little danger of ink leaking and soiling the printing medium, such as paper, but it is difficult to transport the paper because the surface on which the ink is placed is oriented horizontally.

The same applies to the case where the ink jet head is installed below the paper transport position. This problem can be improved by providing a fixing device for drying the ink at the paper discharge portion.

Further, if the configuration is such that paper transport and ink bleeding are taken into account, the ink jet head is installed above the paper transport position as shown in FIG.

In this case, the ink is conveyed with the surface on which the ink is attached facing upward, so that the ink does not bleed. However, when the ink leaks, it may fall on paper or the counter electrode and contaminate the printed image. This problem can be dealt with by properly adjusting the ink pressure inside the ink tank.

In any case, the orientation in which the ink jet head is mounted causes a unique problem, but a high quality printed image can be obtained by optimizing various conditions.

In order to realize a printed image having a dot gradation, it is preferable to apply pulse width modulation to a voltage mainly applied to an electrode for ejecting ink.

According to this, since the bias voltage is kept constant, the flying amount per time when the ink is flying becomes constant, and an image with gradation is obtained by changing the flying time.

By changing the bias voltage over time, the amount of ink flying can be changed per unit time, and the amount of flying can be controlled more easily.

In the above, the potential polarity of the ejection electrode has not been clarified, but may be either positive or negative. In short, the polarity of the potential applied to the ejection electrode is determined by the charging characteristics of the ink.

In the above description, the printing medium is mainly paper, but it is particularly preferable to use paper such as ink-jet paper, which hardly bleeds ink.

[0121]

According to the present invention, the use of the three electrodes of the discharge electrode, the control electrode, and the counter electrode enables the electric field that determines the ink flight to be stably formed, so that the ink flight is stabilized and printing is performed. The displacement of the dot can be reduced.

Further, since the driving power supply can be reduced in voltage and simplified, including that the potential difference used for ink flight control can be reduced, a small-sized and low-cost inkjet image forming apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view using a columnar ink nozzle according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view in which an auxiliary bias power supply is added to FIG.

FIG. 3 is a sectional view in which a counter electrode is grounded.

FIG. 4 is a cross-sectional view in which a control electrode can be set to a ground potential.

FIG. 5 is a cross-sectional view when an ink nozzle is formed in a printed circuit board shape.

FIG. 6 is a cross-sectional view in which an ejection electrode is provided inside an ink nozzle.

FIG. 7 is a cross-sectional view in which a discharge electrode is provided up to the tip of an ink nozzle.

FIG. 8 is a cross-sectional view when the entire ink nozzle is used as a discharge electrode.

FIG. 9 is a cross-sectional view of a control electrode passage hole between an ink nozzle and a counter electrode.

FIG. 10 is a perspective view showing a relationship between a cylindrical nozzle, a control electrode, and a counter electrode.

FIG. 11 is a perspective view showing a relationship between a prismatic nozzle, a control electrode, and a counter electrode.

FIG. 12 is a cross-sectional view when a protrusion member is placed inside the ink nozzle.

FIG. 13 is a cross-sectional view showing a state before ink is ejected using a projection member.

FIG. 14 is a cross-sectional view illustrating a state where the ink is flying using the protrusion members.

FIG. 15 is a cross-sectional view illustrating a state of ink flying when a strong electric field is formed.

FIG. 16 is an external view in which a projection member is provided on a slit-shaped ink nozzle.

FIG. 17 is an external view in which a projection is provided on a slit-shaped ink nozzle itself.

FIG. 18 is an external view of ink heads arranged in an array using cylindrical ink nozzles.

FIG. 19 is an external view of an ink head in which a slit-shaped ink nozzle is arranged in an array using a projection member.

FIG. 20 is a sectional view in which a spacer is inserted between an ink tank and a control electrode.

FIG. 21 is a sectional view in which a spacer is inserted between an ink tank and a control electrode.

FIG. 22 is an external view when a control electrode is mounted on a spacer.

FIG. 23 is a diagram illustrating the entire apparatus when the ink head is placed horizontally.

FIG. 24 is a diagram showing the entire apparatus when the ink head is placed on the upper side.

[Explanation of symbols]

1, 24: ink, 2: ink tank, 3, 16, 2
8, 38 ink nozzle, 4 discharge electrode, 5, 15, 1
9, 21, 27 ... meniscus, 6, 17, 30, 35,
39: control electrode, 7: passage hole, 8: printing medium (paper),
9, 32, 45 ... counter electrode, 10, 29 ... bias power supply, 11, 31 ... signal source, 12 ... auxiliary bias power supply, 1
3 ... ink pressure adjusting means, 14 ... ejection electrode (through hole), 18 ... tip of ink nozzle, 20, 34 ... projection member, 22 ... tip of projection member, 23 ... ink column, 25, 33
... Slit, 26 ... Slit protrusion, 36, 37 ... Spacer, 40 ... Ink tank wall, 41,46 ... Ink head, 42 ... Drive power supply, 43 ... Paper, 44 ... Fixing device.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshinobu Fukano 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Inside the Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Akira Shimada 7-1 Omikamachi, Hitachi City, Ibaraki Prefecture No. 1 Hitachi, Ltd. Hitachi Research Laboratories (72) Inventor Keiji Nagae 1-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratories Hitachi Research Laboratory (72) Inventor Li San, Hitachi City, Oita City, Ibaraki Prefecture 7-1-1, Machi-cho, Hitachi Research Laboratory, Ltd.

Claims (16)

[Claims] 1. An ink jet image forming apparatus having an ink, an ink tank containing the ink, and an ink nozzle for introducing the ink, wherein the discharge nozzle is provided in the ink nozzle and contacts the ink, and the ink is discharged from the ink nozzle. A control electrode provided with a passage hole so that ink does not touch, a printing medium receiving ink flying through the control electrode through hole, and a back surface of the printing medium facing the ejection electrode; An ink jet image forming apparatus comprising: an electrode; a bias power supply for supplying a bias voltage between the ejection electrode and the counter electrode; and a signal source for controlling the flight of ink on the control electrode. 2. An ink jet image forming apparatus having an ink, an ink tank containing the ink, and an ink nozzle for introducing the ink, wherein the discharge nozzle is provided in the ink nozzle and contacts the ink, and the ink is discharged from the ink nozzle. A control electrode provided with a passage hole so that ink does not touch, a printing medium receiving ink flying through the control electrode through hole, and a back surface of the printing medium facing the ejection electrode; A bias power supply for supplying a bias voltage to the ejection electrode, an auxiliary bias power supply for supplying a bias voltage to the counter electrode, and a signal source for supplying a signal voltage to the control electrode for controlling the flight of ink. An inkjet image forming apparatus comprising: 3. The ink-jet image forming apparatus according to claim 1, wherein the size of the through-hole of the control electrode is larger than the size of the discharge port of the ink nozzle. 4. An ink jet image forming apparatus according to claim 1, wherein a shortest distance between the tip of the ink nozzle and the control electrode is shorter than a shortest distance between the tip of the ink nozzle and the counter electrode. . 5. The ink jet image forming apparatus according to claim 1, further comprising a discharge electrode on an inner wall of the ink nozzle. 6. An ink jet image forming apparatus according to claim 1, further comprising a discharge electrode at a tip of a discharge port of an ink nozzle. 7. An ink-jet image forming apparatus according to claim 1, wherein the potential applied to the control electrode is between the potential of the discharge electrode and the potential of the counter electrode. 8. The ink-jet image forming apparatus according to claim 1, wherein the counter electrode is grounded, and a potential applied to the control electrode according to print information is a potential between a discharge electrode potential and a counter electrode potential. An ink-jet image forming apparatus, which is controlled between a potential close to a potential or a ground potential. 9. The ink-jet image forming apparatus according to claim 1, wherein the potential of the discharge electrode and the potential of the counter electrode are opposite in polarity, and the potential applied to the control electrode according to print information is opposite to the ground potential. An ink-jet image forming apparatus characterized by being controlled between the potential of an electrode and the potential of an electrode. 10. An ink jet image forming apparatus according to claim 1, wherein a voltage application time or an applied voltage of a signal voltage generated by a signal source is changed in accordance with a print image signal. 11. An ink-jet image forming apparatus according to claim 1, further comprising a spacer for maintaining a space between a member supporting said ink nozzle and a member supporting said control electrode. . 12. An ink jet image forming apparatus according to claim 1, wherein said ink nozzle has a cylindrical shape or a slit shape. 13. An ink-jet image forming apparatus according to claim 11, further comprising a projection member inside the ink nozzle. 14. The ink-jet image forming apparatus according to claim 13, wherein a bar-shaped member or a plate-shaped member having a convex portion is used as the projecting member. 15. An ink-jet image forming apparatus according to claim 13, wherein said projecting member is conductive. 16. An ink-jet image forming apparatus according to claim 14, wherein an assist power supply for applying a potential between the potential of the discharge electrode and the potential of the control electrode is provided on the conductive projection member. Image forming device.