JPH05193138A - Ink-jet press - Google Patents

Abstract

PURPOSE: To provide an inkjet printer having a simple construction and a high quality printing performance. CONSTITUTION: The printer incorporates a nozzle unit 1 which continuously delivers ink drops A, an electric charge electrode 7 which is disposed in front of the nozzle unit 1 and gives electric charge to the ink drops A on the basis of printing information, and a pair of deflecting electrodes 9, 10 which are disposed in front of the electric charge electrode 7 and deflect the flying direction of the charged ink drops. The printer also incorporates a detector 13 disposed in front of a pair of deflecting electrodes 9, 10 and comprising a detecting electrode to detect deviation in flying direction of ink drops as fluctuation in resistance value, and a controller 6 to correct a deviation in deflection by controlling on the basis of the output from the detector 13 at least one of the flow of ink supplied to the nozzle unit 1, the voltage applied to the charge electrode, and the voltage applied between a pair of deflecting electrodes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printing machine capable of improving print quality.

[0002]

2. Description of the Related Art Ink jet printers include a nozzle unit for continuously ejecting ink droplets flying toward a printing sheet, a charging electrode for giving a predetermined charge to the ink droplets based on print information, and a charged ink droplet. And a pair of deflection electrodes for deflecting the flight direction of the light in accordance with the charge level. Therefore, the ink droplets ejected from the nozzle unit reach the predetermined position on the printing paper by deflecting the flying directions thereof according to the printing information, thereby forming a desired print or image on the printing paper. Will be done.

Therefore, in order to improve the print quality, it is necessary to control the flight direction of the ink droplet with high precision.
However, if the ink viscosity changes with temperature,
The flight speed of the ink droplets ejected from the nozzle unit and the mass thereof change, and the deflection control of the ink droplets cannot be performed with high accuracy. In such a situation, the print width that enables printing cannot be accurately maintained. This is particularly important in the case of a multi-nozzle unit in which a plurality of nozzle units are arranged. If the print widths of the individual nozzle units are incorrect, the print widths of adjacent nozzle units may overlap each other, On the other hand, there will be gaps and gaps.

[0004]

Therefore, in this type of device, a detector for detecting the deflection amount of the ink droplet in the flight direction and the deflection amount of the ink droplet based on the data from the detector are detected. It is general that each of them is provided with a control means for compensating for the above, and an apparatus provided with such a detector is disclosed in, for example, JP-A-55-67481 and JP-A-58-58.
It is disclosed in Japanese Patent No. 22179.

The detector disclosed in Japanese Patent Application Laid-Open No. 55-67481 has three charge detection electrodes arranged in the flight path of the ink droplet, and the charged ink droplet is one of these charge detection electrodes. When the ink droplets collide with each other and adhere, the detection signal of the ink droplets is output from the charge detection electrode to which the ink droplets adhere, and the deflection amount of the ink droplets can be detected based on this detection signal.

On the other hand, the detector disclosed in Japanese Patent Application Laid-Open No. 58-22179 has an image sensor for detecting flying ink drops, and the deflection amount of the ink drops can be detected based on the output from the image sensor. Has become. However, the above-mentioned known detector is limited in its arrangement, and the deflection amount can be detected only for a few ink droplets at most, so that it is not possible to obtain an apparatus with improved print quality.

The present invention has been made under the circumstances described above, and an object of the present invention is to provide an ink jet printer capable of improving print quality.

[0008]

SUMMARY OF THE INVENTION An ink jet printer according to the present invention has a nozzle unit for continuously ejecting flying ink droplets, and a printing unit arranged in front of the nozzle unit to print information on ink droplets ejected from the nozzle unit. And a charging electrode that gives a predetermined charge based on the above, and is arranged in front of the charging electrode with a flight path of the ink droplet interposed therebetween. A pair of deflection electrodes that reach a predetermined position above, a detector that is arranged in front of the pair of deflection electrodes and that detects a deviation in the flight direction of ink droplets, and a nozzle based on the output from this detector. The deflection deviation is controlled by controlling at least one of the flow rate of ink supplied to the unit, the voltage applied to the charging electrode, and the voltage applied between the pair of deflection electrodes. Comprising a positive control means, the detector, the resistance value is configured to include a detection electrode changes when ink droplets having passed through the or at or near to adhere.

[0009]

The ink droplets ejected from the nozzle unit are selectively charged by the charging electrode based on the print information. After that, when the charged ink droplet passes through the electric field between the pair of deflection electrodes, the flight direction of the ink droplet is deflected by the electric field toward the print medium, and reaches the predetermined position of the print medium. ..

Then, at an appropriate time, the detection electrode of the detector is used as a target to cause the ink droplet to fly, thereby determining whether or not the flight direction of the ink droplet is appropriately deflected. That is, since the flight distance of the ink droplets defined between the nozzle unit and the detection electrode of the detector and the deflection position of the detection electrode with respect to the nozzle unit are known, the detection ink droplets that fly toward the target are detected. It collides with and adheres to the detection electrode of the detector, or
When passing through the vicinity of the detection electrode, due to the influence of the detection ink droplet itself or the accompanying airflow accompanying the flight of the detection ink droplet,
The resistance value of the detection electrode changes, which makes it possible to determine that the deflection amount of the ink droplet in the flight direction is appropriately controlled. However, if the detection ink droplets do not adhere to the detection electrodes of the detector, or if the detection electrodes are not affected by the entrained airflow, the flight direction deflection amount of the ink droplets is appropriately controlled. Therefore, it can be determined that there is a deviation in the flight direction. In this case, the control means
Based on the output of the detection electrode, at least one of the flow velocity of the ink supplied to the ink nozzle, the voltage applied to the charging electrode, and the voltage applied between the pair of deflection electrodes is controlled. The deflection amount in the flight direction is corrected so that the ink droplet adheres to the detection electrode or passes through the vicinity.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, an ink jet printer according to the present invention is schematically shown. The print head of this apparatus is provided with a nozzle unit 1, and this nozzle unit 1 is composed of an ejection nozzle 2 and a piezoelectric vibrating element 3. The discharge nozzle 2 is connected to an ink supply source, that is, an ink tank 5 via a supply pump 4, and therefore the ink sucked up by the supply pump 4 from the ink tank 5 is pressurized to a predetermined pressure. Is supplied to the nozzle unit 1, that is, the discharge nozzle 2, and then discharged from the nozzle port of the discharge nozzle 2.

On the other hand, the piezoelectric vibrating element 3 includes a controller 6
The controller 6 periodically applies a voltage to the piezoelectric vibrating element 3, whereby the ejection nozzle 2 vibrates at a predetermined frequency.
When the ejection nozzle 2 is vibrated in this way, the ink ejected from the ejection nozzle 2 becomes a continuous ink droplet A which is separated from each other at a predetermined interval and flies.

The supply pump 4 is also a controller 6
The controller 6 can also control the drive of the supply pump 4. A charging electrode 7 having a cylindrical shape is arranged immediately in front of the discharge nozzle 2. The charging electrode 7 is positioned coaxially with the ejection nozzle 2, and therefore the ink droplet A ejected from the ejection nozzle 2 flies through the charging electrode 7. The charging electrode 7 is also connected to the controller 6, and the controller 6 controls the charging electrode 7 at a predetermined timing,
A predetermined pulse voltage is applied.

Here, the pulse voltage applied to the charging electrode 7 is applied at the time when the ink ejected from the ejection nozzle 2 is divided to generate an ink droplet A, whereby the generated ink droplet A is electrostatically charged. It is charged by induction. Also,
When the individual ink droplet A is generated, the level of the pulse voltage applied to the charging electrode 7 is set based on the print information. That is, the controller 6 is connected to a print pattern generating circuit 8 such as a character generator, and based on the print signal supplied from the print pattern generating circuit 8, the controller 6 changes the level of the pulse voltage to the charging electrode 7. decide. Therefore, each ink droplet A that has passed through the charging electrode 7 has a charge determined based on the print information.

A pair of deflection electrodes 9 and 10 is arranged in front of the charging electrode 7. These deflection electrodes 9 and 10
Are positioned so as to sandwich the flight path of the ink droplet A ejected from the nozzle unit 1, one deflection electrode 9 is connected to the controller 6, and the other deflection electrode 10 is grounded. When the ink droplet A has a negative charge, a constant positive voltage is applied to the deflecting electrode 9 by the controller 6, whereby the charged ink that flies passing between the pair of deflecting electrodes 9 and 10 flies. Drop A
Are attracted to the deflection electrode 9 side by the electrostatic field between the deflection electrodes 9 and 10. That is, the flight direction of the ink droplet A is
The deflection is performed by the pair of deflection electrodes 9 and 10, and the deflection amount is determined by the level of electric charge of each ink droplet A. The deflecting electrode 9 is inclined with respect to the deflecting electrode 10 so that the distance between the deflecting electrode 10 and the deflecting electrode 10 increases as the distance from the nozzle unit 1 increases. They may be arranged parallel to each other with respect to the axis line of.

As described above, between the pair of deflection electrodes 9 and 10, each ink droplet A whose flight direction is deflected is
After that, it reaches the printing paper B positioned in front of the deflection electrodes 9 and 10 and adheres to a predetermined position on the printing paper B determined by the deflection amount. Further, a gutter 11 is arranged immediately in front of the deflection electrode 10 of the pair of deflection electrodes 9 and 10. This gutter 11 has an opening 12 at one end facing the charging electrode 7, that is, the discharge nozzle 2, and the other end is connected to the ink tank 5 described above.
Therefore, if such a gutter 11 is provided, the ink droplet A that is not charged by the charging electrode 7 and is not used for printing.
Travels between the pair of deflection electrodes 9 and 10 without being deflected in the flight direction, and is recovered by the gutter 11 through the opening 12, and the recovered ink droplet A is returned to the ink tank 5.

As described above, when the ink droplets A are continuously ejected from the nozzle unit 1, when the print head scans the print sheet B in the direction of the arrow in FIG. A desired print dot pattern is printed on one scanning line of the printing paper B based on the printing information, the printing paper B is sequentially fed by the next scanning line, and then the above-described operation is repeated. As a result, desired printing or printing information including an image is printed on the entire surface of the printing paper B.

In the case of the ink jet printer of this embodiment, the printing paper B is fed in the direction orthogonal to the paper surface of FIG. 1, and therefore the ink droplet A ejected from the ejection nozzle 2 is in the flight direction. Will be deflected in the direction of the scan line described above. Then, the pair of deflection electrodes 9 and 10
A detector 13 according to the first embodiment for detecting the ink droplet A is provided in front of. In the case of this embodiment, as is apparent from FIG. 1, the detector 13 is arranged between the conveyance path of the printing paper B and the deflection electrode 9 so as to be located on the deflection electrode 9 side. The detector 13 may be in a plane including the conveyance path of the printing paper B, or may be arranged on the opposite side of the detector 13 shown in the conveyance path of the printing paper B. Good.

The detector 13 is composed of a bridge circuit, as shown in FIG. 2, and is provided with a rectangular substrate 14. The substrate 14 is arranged so that its plate surface is orthogonal to the discharge nozzle 2. On the surface of the substrate 14 facing the ejection nozzle 2, one detection electrode 1 made of a resistance wire is formed.
5 are arranged, and the detection electrodes 15 extend in the feeding direction of the printing paper B.

One end of the detection electrode 15 is connected to the controller 6 via resistors R1 and R2, and a node 16 between one end of the detection electrode 15 and the resistor R1 is grounded.
On the other hand, the other end of the detection electrode 15 is also connected to the node 17 between the resistor R2 and the controller 6 via the resistor R3. Then, the node 18 between the resistor R1 and the resistor R2
And the node 19 between the detection electrode 15 and the resistor R3 is
The differential amplifier 20 is connected to the input terminals thereof, and the output terminal of the differential amplifier 20 is connected to the node 17 and the controller 6.

Here, the resistors R1, R2 and R3 are made of, for example, a manganin wire having a zero temperature coefficient, and are adjusted so that the bridge circuit is balanced when the detection electrode 15 reaches a predetermined temperature. There is. The output signal from the differential amplifier 20 is processed in the controller 6, and
The controller 6 controls the level of the pulse voltage supplied to the charging electrode 7 based on its output signal, and its control section is shown in FIG.

The control circuit section first detects the detector 13
That is, the discrimination circuit 21 that receives the output signal from the differential amplifier 20 is provided. This discrimination circuit 21 is used for the differential amplifier 2
The change in the output signal from 0 is discriminated and whether or not the charged ink droplet A collides with the detection electrode 15 or whether the charged ink droplet A flies near the detection electrode 15 is determined. Detect.

That is, the charged ink droplet A is detected by the detection electrode 15.
When it collides with and adheres to the detection electrode 15, the heat of the detection electrode 15 is taken away, the temperature adjusted by the resistors R1, R2 and R3 changes, and the equilibrium state of the bridge circuit is broken. At this time, the differential amplifier 20 corrects the potential difference between the nodes 18 and 19 by applying the output current to the node 17, so that the balanced state of the bridge circuit is not broken. In addition, if the heat capacity of the detection electrode 15 is further reduced,
Alternatively, the sensitivity is improved by adjusting the resistors R1, R2, and R3 so that a large temperature difference occurs between the detection electrode 15 and the surroundings. Further, even if the ink droplet A does not adhere to the detection electrode 15, even if the ink droplet A flies in the vicinity of the detection electrode 15, the heat of the detection electrode 15 is taken away by the accompanying airflow accompanying the flight of the ink droplet A, The resistance value will change.

When the temperature of the detection electrode 15, that is, the resistance value changes, an output corresponding to the change is supplied to the determination circuit 21 of the controller 6 to detect whether the ink droplet A has collided or flew. You can Therefore, the ink droplet A from the ejection nozzle 2 to the detection electrode 15 of the detector 13
Since the flight distance of the ink droplet A and the deflection distance of the detection electrode 15 with respect to the ejection nozzle 2 are constant values, when the flight direction of the ink droplet A is controlled by using the detection electrode 15 of the detector 13 as a target, The ink droplet A is the detection electrode 15
If it collides with and adheres to the detection electrode 15 or flies in the vicinity of the detection electrode 15, the change in the resistance value of the detection electrode 15 causes a change in the determination circuit 2.
It is possible to determine that the flight direction of the ink droplet A ejected from the ejection nozzle 2 is appropriately controlled by being detected by No. 1, and in this case, the printing information can be printed on the printing paper B with high accuracy. become.

On the other hand, when the detection ink droplet A does not adhere to the detection electrode 15 or when it does not fly in the vicinity thereof, the resistance value of the detection electrode 15 does not change, so that the direction of flight of the ink droplet A is changed. Regarding the deflection control, the determination circuit 21 can determine that the deflection deviation has occurred in the flight direction. Such a deflection deviation is caused by a change in the flight speed of the ink droplet A due to a change in the viscosity of the ink due to a change in temperature, for example.

When such a situation is reached, the discrimination circuit 21 supplies the above-mentioned signal indicating the deflection deviation to the correction circuit 22. In the correction circuit 22, the correction amount of the pulse voltage supplied to the charging electrode 7 is calculated based on the signal from the determination circuit 21, and the correction amount of the pulse voltage is calculated as follows.
Next, it is supplied to the charging circuit 23 connected to the charging electrode 7. Further, the charging circuit 23 is also connected to the above-described print pattern generating circuit 8, whereby the charging circuit 23 adds a new correction amount to the print signal supplied from the print pattern generating circuit 8. A print signal is generated, and a pulse voltage based on this new print signal is supplied from the charging circuit 23 to the charging electrode 7. In such pulse voltage correction control, the deflection amount of the detection ink droplet A in the flight direction becomes appropriate, and the detection ink droplet A collides with and adheres to the detection electrode 15 of the detector 13, or The correction amount is determined by continuing until the aircraft flies in the vicinity.

When the pulse voltage to the charging electrode 7 is corrected based on the deflection deviation as described above, the flight direction of the ink droplet A ejected from the ejection nozzle 22 is controlled appropriately based on the print information. It is possible to maintain high-precision printing on the printing paper B. The pulse voltage correction control described above is repeatedly performed at an appropriate time. It goes without saying that the correction circuit 22 also calculates the correction amount in consideration of the distance between the detector 13 and the printing paper B.

Further, although not shown, the detection ink droplet A attached to the substrate 14 or the detection electrode 15 of the detector 13 is adapted to be removed from the surface of the substrate 14 or the detection electrode 15 by suction means. The present invention is not limited to the detector 13 of the first embodiment described above, and various modifications are possible.

For example, referring to FIG. 4, a detector 24 of the second embodiment is shown. This detector 24 is the substrate 1
4 and a pair of detection electrodes 15a and 15b, which are resistance lines and are arranged in parallel on the substrate 14 so as to be close to each other. One end of one detection electrode 15a is connected to the node 16a between the ground and the resistor R1, and the other end is connected to the resistor R3. One end of the other detection electrode 15b is connected to the node 16b between the node 16a and the ground, and the other end is open.

According to the above-mentioned detector 24, as shown in FIG. 4, when the detection ink droplet A adheres across the pair of detection electrodes 15a and 15b, as a result, the detection electrode The resistance value of 15a can be greatly changed, and the deviation in the flight direction of the detection ink droplet A can be detected more easily. Further, in the first embodiment, when the deviation in the flight direction of the detection ink droplet A is detected without contact with the detection electrode 15, the substrate 14 of the detector 13 is not always necessary. .. In this case, since the detection ink droplet A does not collide with the detection electrode 15, it is possible to prevent generation of mist due to the collision, and
A recovery line for the detection ink droplet A attached to the substrate 14 or the detection electrode 15 is also unnecessary.

Further, in the above-described embodiment, the deviation in the flight direction of the ink droplet A is corrected by controlling the level of the pulse voltage applied to the charging electrode 7, that is, the charge amount of the ink droplet A. The deflection deviation is caused by the pair of deflection electrodes 9 and 10
The deflection voltage applied to the nozzle and the flow velocity of the ink ejected from the ejection nozzle 2 can be corrected by controlling the supply pump 4. When the deflection voltage is controlled, the attracting force of the ink droplet A is adjusted, while when the flow velocity of the ink is controlled, the mass of each ink droplet A is changed, so that the flying speed of the ink droplet A is changed. Will be adjusted.

Furthermore, the print head device of the present invention comprises:
Needless to say, printing is possible not only on printing paper but also on various printing media such as cloth.

[0033]

As described above, according to the ink jet printer of the present invention, the deviation of the flight direction of the ink droplets from the nozzle unit in the flight direction is detected by the detector provided with the detection electrode. The detection is performed, and based on the output signal from this detector, the flying speed of the ink droplet, the pulse voltage applied to the charging electrode, or the deflection voltage of the pair of deflection electrodes is controlled and eliminated. Therefore, stable and high-quality printing can be performed for a long time. Further, since the detector can be easily made small, there is an advantage that it can be easily applied to a multi-nozzle type printing machine.

[Brief description of drawings]

FIG. 1 is a schematic view showing a printing machine.

FIG. 2 is a circuit diagram showing a configuration of a detector of the first embodiment.

FIG. 3 is a block diagram illustrating a control circuit section in a controller for processing a detector output signal.

FIG. 4 is a plan view showing a part of the detector of the second embodiment.

[Explanation of symbols]

 1 Nozzle Unit 2 Ejection Nozzle 3 Piezoelectric Vibration Element 7 Charged Electrode 6 Controller 9,10 Deflection Electrode 11 Gutter 13 Detector 15 Detection Electrode A Ink Drop B Printing Paper

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takashi Yoshiyama 1-1-1, Sonoyama, Otsu City, Shiga Toray Co., Ltd. Shiga Plant (72) Inventor Robert Gerber Ponggrass Australia 2008 New South Wales Sydney Woolara Ocean Street 122

Claims (1)

[Claims] 1. A nozzle unit for continuously ejecting flying ink droplets, a charging electrode disposed in front of the nozzle unit for giving a predetermined charge to the ink droplets ejected from the nozzle unit based on print information, and a charging unit. A pair of deflection electrodes, which are arranged in front of the electrodes with an ink droplet flight path interposed therebetween and which deflects the ink droplet flight direction in accordance with the charge level of the ink droplets and causes the ink droplets to reach a predetermined position on the print medium. , A detector that is arranged in front of the pair of deflection electrodes and detects the deviation in deflection of the ink droplet in the flight direction, and based on the output from this detector, the flow velocity of the ink supplied to the nozzle unit and the application to the charging electrode. Control unit for controlling at least one of the voltage applied to the deflection electrodes and the voltage applied between the pair of deflection electrodes to correct the deflection deviation, and the detector deposits ink droplets. Ink jet printer, characterized in that the resistance value comprises a detection electrode changes when passing through the Luke or near.