JPH10138513A - Ink jet recording device - Google Patents

Abstract

(57) [Summary] [Problem] When the time during which ink is not ejected from a nozzle exceeds a specified value, the solvent of the ink near the ejection port easily dries, and the pigment or dye in the ink solidifies in the ejection port and clogs. Occurs. A means for generating a print signal of a predetermined clogging detection pattern, a means for reading a pattern printed on a recording medium, and a portion where ink is not ejected based on the result of reading by the reading means And a means for generating a signal for discharging ink for removing clogging from a nozzle at a corresponding location. According to the present invention, clogging can be prevented by printing a clogging detection pattern, detecting the image with an optical sensor, and forcibly discharging ink from a portion where ink is not discharged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus for printing an image by depositing ink droplets discharged from a nozzle opening of a recording head on a recording medium, and more particularly to a device for preventing clogging of a nozzle opening.

[0002]

2. Description of the Related Art An ink jet recording apparatus that prints an image by a set of dots formed by ejecting minute ink droplets from a nozzle opening forms an ink from an ink tank in a recording head into an ink chamber connected to each opening. Guidance,
In this configuration, kinetic energy is given to the ink in the ink chamber, and an ink droplet is ejected from the opening to obtain an image.

There are the following two methods for giving kinetic energy to ink. The first method is to provide a heating resistor near the ink discharge port and apply a pulse voltage thereto to instantaneously boil the ink. This is a method (bubble jet method) in which ink is ejected by the pressure of bubbles generated when the ink is discharged.

In the second method, a part of a wall constituting an ink chamber is adhered to a piezo element, and a piezo element is deformed by applying a pulse voltage to the piezo element, thereby instantaneously reducing the volume of the ink chamber. This is a method of ejecting ink by force.

In both methods, a pulse voltage is generated in accordance with print information and applied to a heating element or a piezo element corresponding to a nozzle opening for discharging ink.

An ink jet recording apparatus as described above can print an image at a higher speed as the number of nozzle openings of the recording head increases.

However, the number of ink droplets that can be ejected per unit time is determined depending on the print data generation speed that determines the presence or absence of ejection of ink droplets. Has been determined.

For this reason, the current ink jet recording head has about several tens of discharge ports, maintains a slight gap with the recording medium, and forms an image by discharging ink while reciprocating on the recording medium surface. There are many things.

However, if the generation speed of print data is increased, the number of nozzles is further increased, and an array-shaped recording head in which the nozzle openings are arranged side by side over the entire printing width is constituted, so that high-speed printing is possible. Becomes practical.

In any of the conventional two types of ink ejection methods, it is necessary to reduce the amount of ink ejected at a time and to reduce the dot diameter in order to obtain a high-quality image. The area of the opening becomes smaller.

Since the ink is a mixture of a pigment or a dye with a solvent such as alcohol, if the time during which the ink droplet is not ejected becomes longer, the ink near the nozzle opening evaporates and dries, and the ink in the ink is dried. Pigments and dyes solidify in the openings, causing clogging. To solve this problem,
If print data is not sent to the inkjet recording apparatus and the time during which ink is not ejected exceeds a specified value, a method of closing the nozzle opening to suppress evaporation of the solvent.
(Japanese Unexamined Patent Publication No. 54-48121), a method of forcibly discharging ink from all ink discharge ports (Japanese Patent Publication No. 3-59833), a method of covering a nozzle opening with a hygroscopic member impregnated with a solvent during non-printing. A method for preventing clogging has been proposed (Japanese Unexamined Patent Publication No. 55-10 / 1979).
No. 1461).

Further, as a method for detecting clogging, a device having a structure in which a member that absorbs ink droplets and expands in volume and detects clogging by means for detecting the expansion is disclosed (Japanese Patent Publication No. 6-65495). ) Has been proposed.

[0013] Furthermore, although not intended to detect clogging, there has been proposed an apparatus having means for reading a printed test print and judging an abnormal image (Japanese Patent Laid-Open No. 3-169640).

[0014]

An array of recording heads in which the nozzle openings are arranged over the entire printing width of the recording medium is installed in a stationary state, and the recording medium is oriented in a direction intersecting the arrangement of the nozzle openings. The ink jet recording apparatus configured to convey the nozzle opening to the recording medium close to the recording medium has an advantage that high-speed printing is possible, but when the printing density of document printing or the like is low, In addition, since there are many nozzles that do not discharge ink and have a long rest period, nozzle clogging is likely to occur.

Since an array-shaped recording head having a large number of nozzles has a high manufacturing cost, it is necessary to extend the life and improve the reliability.

Therefore, in addition to performing the clogging prevention by the above-described prior art method, the presence or absence of clogging is detected and
If clogging is present, a means to recover is needed. In the clogging detection method disclosed in Japanese Patent Publication No. 6-65495 of the related art, in the case of a device using a recording head having a large resolution, the detection accuracy is reduced due to a narrow nozzle interval, and the position of the clogging is specified. It is difficult.

The method disclosed in Japanese Patent Application Laid-Open No. 3-169640 is
Reading the image state of an area of about 1 mmφ, detecting density fluctuations with the surroundings, detecting abnormal ink ejection,
This is a method in which the dot diameter of ink ejected from individual nozzles onto a recording medium is measured, and the amount of ink ejected from each ejection port is corrected. In this method, since the dot diameter on the recording medium is larger than the interval between the nozzle openings, it is not possible to identify the nozzle openings that have not been ejected.

An object of the present invention is to individually detect clogging of a large number of nozzle openings formed in a recording head and recover the nozzle openings in an ink jet recording apparatus using a stationary recording head. Accordingly, it is an object of the present invention to provide an ink jet recording apparatus capable of preventing clogging during normal printing and obtaining a high quality image without image defects.

Another object of the present invention is to provide a highly reliable ink jet recording apparatus which detects an abnormal state in which an ink droplet is not ejected from a nozzle opening due to a cause other than clogging and notifies a user of the abnormal state. It is to be.

[0020]

According to the present invention, when printing has been interrupted for a long period of time, such as when the apparatus is started (when power is turned on), a predetermined image pattern for detecting clogging is recorded on a recording medium. Is printed, the pattern is read by an image reading means (optical sensor), and the clogging of the nozzle opening and the sign thereof are detected, and by recovering the corresponding portion, a high-quality image without image defects can be obtained. An object of the present invention is to provide an obtained ink jet recording apparatus.

More specifically, a stationary recording head in which a number of nozzles from which ink droplets are ejected are arranged and opened, and the recording head is opposed to the nozzle opening of the recording head in a close state, and intersects the arrangement direction of the nozzle openings. In the ink jet recording apparatus having a recording medium transport means for transporting a recording medium in a direction to be performed and a control device for controlling ink ejection from each nozzle opening of the recording head based on print information, a predetermined clogging detection is performed. Means for generating a print signal of a pattern for use, a means for reading a pattern printed on a recording medium, and a portion where ink is not ejected is detected based on the result of reading by the above-described reading means, and a nozzle from the corresponding portion is used to detect Means for generating a signal for performing ink ejection for clogging removal, and forcibly ejecting ink from the nozzle opening. To remove the clogging by the.

Further, at the time of ink ejection, the nozzle opening is shielded by a shielding member so that the inside of the recording apparatus is not contaminated.

In an apparatus using a recording head having a group of nozzle openings for a plurality of colors, a pattern is printed for each color to detect clogging and recover the nozzle openings.

[0024]

FIG. 1 shows an embodiment of an ink jet recording apparatus according to the present invention. Reference numeral 1 denotes a recording head, 2 denotes a shielding member, 3a and 3b denote recording medium transport rolls, and 4 denotes a recording medium. The medium 5 is an optical sensor, and 6 is a shielding member elevating means.

The recording head 1 has a large number of nozzle openings arranged in an array over the entire printing width. The nozzle openings are directed downward, and the arrangement direction of the openings is the same as the transport direction of the recording medium 4. It is installed stationary so as to be in the crossing direction.

In the color ink jet recording apparatus, nozzle groups for four colors of cyan, magenta, yellow and black are formed. Each nozzle opening has a diameter of tens of microns
m, and is driven by a method such as a bubble jet method or a piezo method to eject ink droplets onto a recording medium.

An electric pulse applied to a driving member for ejecting ink droplets from each nozzle opening is generated by a print control unit in the ink jet recording apparatus in accordance with a data signal from a host device such as a personal computer.

The shielding member 2 is excellent in hygroscopicity because it catches and absorbs ink droplets for preventing clogging (recovering the nozzle openings) discharged from each nozzle opening of the recording head 1 and has excellent hygroscopicity. A soft shielding member is provided so as not to damage the nozzle opening of the recording head 1 when it comes into contact with the recording head.

The shielding member 2 is detachably attached so that it can be replaced after long-term use.

The shielding member 2 is driven up and down by the shielding member lifting / lowering means 6, moves upward and downward across the recording medium transport path, approaches the nozzle opening of the recording head 1, or opposes the contact state.

At the time of descending, the recording medium 4 is retracted below the recording medium transport path (the back side of the transported recording medium) so as not to hinder the movement of the recording medium 4 transported in the recording medium transport path.

The recording medium transport rolls 3a and 3b are driven and rotated by a motor (not shown) so that the recording medium 4 is opposed to the recording head 1 at an interval of about 1 mm and the arrangement direction of the nozzle openings of the recording head. Is transported in a direction that intersects with

The optical sensor 5 includes a recording medium transport roll 3
The printing state on the recording medium 4 conveyed by a and 3b is detected.

The optical sensor 5 emits a light beam toward the surface of the recording medium 4, detects the reflected light, and detects a printed image such as a fine line on the recording medium.

The shielding member lifting / lowering means 6 is constructed using a lifting / lowering drive mechanism combining a motor and a cam.

The print control unit 7 is mainly composed of a microcomputer, controls the generation of electric pulses in accordance with print data provided from a host device such as a personal computer, and causes the recording head 1 to eject ink droplets.

The printing medium also has a print control function of rotating the recording medium transport rolls 3a and 3b to transport the recording medium 4.

Further, the printing operation is stopped between every page or between pages every predetermined time, and the shielding member lifting / lowering means 6 is controlled so that the shielding member 2 is brought close to or in contact with the recording head 1 to shield the nozzle opening. At the same time, clogging prevention control for supplying an electric pulse to a drive circuit is performed so that ink droplets for clogging prevention are forcibly ejected from the nozzle openings of the recording head 1, and then the shielding member 2 is retracted. Has a control function of controlling the shielding member elevating means 6 and then shifting to the next printing operation.

After the printing, a control function is provided for keeping the nozzle opening of the recording head 1 shielded by the shielding member 2.

In such an ink jet recording apparatus, when the apparatus is not used, the nozzle opening surface of the recording head 1 is shielded by the shielding member 2. As in the case where ejection is not performed during printing, the solvent in the ink dries and clogging occurs.

Since the array recording head has a large number of nozzle openings, the probability of clogging is high.

Therefore, in addition to the forced ejection of ink during printing, the presence or absence of clogging is detected in all nozzle openings before printing starts. If there is a clogged nozzle opening, the nozzle opening is detected. By providing a mechanism for performing recovery, the problem of occurrence of clogging is solved.
The process of clogging detection and recovery will be described with reference to FIG.

FIG. 3 is a block diagram showing the above control method. During normal printing, print data is sent from the personal computer, and the print control unit sends a signal to the ink droplet ejection drive circuit based on the data in the memory to eject ink from the nozzle openings of the recording head.

A method for detecting clogging at the start of printing (or when power is turned on) is as follows. First, a printing control unit fetches a printing pattern from a reference pattern memory and sends a signal to an ink droplet ejection driving circuit based on the data to record. Ink is ejected from the nozzle opening of the head.

The recording medium 4 on which the reference pattern is printed is
The recording medium is conveyed by the recording medium conveying means 3a and 3b, and the optical sensor 5
To detect the printing status. The result read by the optical sensor 5 is transmitted to an image evaluation unit, and the image evaluation unit compares the reference pattern with the measurement result to verify whether ink is ejected to a predetermined position.

A portion where ink is not ejected is recognized as a nozzle clogging, and data to be transmitted to an ink droplet ejection circuit in order to recover the recognized nozzle opening clogging is prepared and sent to the print controller. Can be

FIG. 2 is a view of the ink jet recording apparatus shown in FIG. 1 as viewed from above. The recording medium 4 on which the reference pattern is printed is the recording medium transporting means 3a, 3b, 3c, 3
The paper is transported by d, and the printing state is detected by the optical sensor 5.

The detection method is as follows.
Is temporarily stopped, the optical sensor 5 moves right and left to detect the printing state, and the result is transmitted to the image evaluation unit.

If the optical sensors 5 have a structure in which they are arranged in an array, it is not necessary to stop the recording medium 4 halfway, and the printing state can be detected.

FIG. 4 shows an example of a reference pattern for detecting clogging. This example is an image of a thin line configured so that ink is ejected from all the nozzle openings in about 10 cycles.

If the recording density is 400 dpi, the dot interval is about 63 μm, but the line width of one fine dot line on plain paper is 150 to 200 μm.

Printing periodic vertical thin lines facilitates reading by the sensor. If the clogging has occurred, it is easy to detect because the periodically printed thin line is missing.

In a color ink jet recording apparatus for printing in four colors of cyan, magenta, yellow, and black, clogging is detected for each color by printing four sets of patterns shown in FIG.

The ink ejection for recovering the nozzle opening is as follows.
The drive pulse and the waveform shape during normal printing are the same, and if a large period or voltage is applied, a power supply during normal printing can be used, so that cost increases are small and effective.

The voltage pulse applied to the ink droplet ejection driving circuit will be described for each ink ejection method with reference to FIGS.

FIG. 5 is a cross-sectional view of a recording head of a bubble jet system, and FIG. 6 is a cross-sectional view taken along line AA 'of FIG. 11 is a common ink passage, 12 is an individual ink passage, 13 is a nozzle opening, and 14 is a heating resistor.

The common ink passage 11 stores ink sent from an ink container (not shown) and guides the ink to the individual ink passages 12 connected to the nozzle openings 13.

The heating resistor 1 is located near the nozzle opening 13.
When a pulse voltage of several μS is applied based on print data, the ink on the surface of the heating resistor 14 boils to generate bubbles. Ink is ejected from the nozzle opening at the rate at which the bubbles are generated.

FIG. 7 shows an example of an electric pulse applied to the heating resistor 14 of the recording head shown in FIGS. 5 and 6 in a normal printing state.

The pulse train in FIG. 7 shows a case where ink is continuously ejected from one nozzle opening.

The frequency of the pulse is determined by the time from when the ink is replenished from the common ink passage 11 to the individual ink passage 12 after the ink is ejected, and when the ink can be newly ejected.

The frequency of this pulse is called the maximum ejection frequency. The pulse at the time of recovery of the nozzle opening is similar to the pulse train in FIG. 7, and is applied to the heating resistor 14 in which clogging is detected by appropriately increasing the magnitude and frequency of the voltage.

By continuously applying a pulse, the generation of bubbles is repeated in a short time, and the clogged portion is recovered by the pressure to prepare for normal printing.

As described above, when an array-shaped recording head having a very large number of nozzle openings is used, the effect of detecting and recovering clogging can be economically achieved with a minimum necessary amount of ink. is there.

FIG. 8 is a sectional view of a piezo type recording head. Reference numerals 11 to 13 are the same as those in FIG. 5, and reference numeral 15 is a piezo element. In a piezo type recording head, the individual ink chamber 1
The piezo element 15 is bonded to a part of the wall constituting the second element 2.

When a voltage is applied between the electrodes connected to the piezo element 15, the piezo element contracts and deforms the wall of the individual ink chamber 12. By steepening the rise time of the voltage, the volume of the individual ink chamber 12 is instantaneously reduced, and an ink droplet is ejected from the nozzle opening 13 by the action.

When the application of the voltage to the piezo element 15 is stopped, the piezo element 15 returns to the original state,
2 returns, the ink flows from the common ink passage 11 into the individual ink chambers 12, and prepares for the next ink ejection.

FIG. 9 shows a voltage waveform applied to the piezo element used in the recording head of FIG. In order to eject ink droplets from the nozzle openings, the individual ink chambers 1
Since it is necessary to reduce the volume of No. 2, a sharp change is required when applying a voltage. Individual ink chamber 1 after ink ejection
When the ink is led to 2, the voltage needs to be changed more slowly than the rise.

The reason for this is that the volume of the ink chamber is gradually returned to guide the ink to the individual ink chamber 12 to prevent the ink from vibrating in the ink chamber and to prevent the ink from flowing from the nozzle opening to the individual ink chamber 12. This is to prevent the suction of air.

The voltage application time of this triangular wave is 100 to 30.
It is about 0 μS.

As for the pulse at the time of recovery of the nozzle opening, a pulse whose waveform magnitude and frequency used in normal printing are appropriately increased as in the bubble method is used.

By continuously applying a pulse voltage, the ink in the ink chamber vibrates and the clogged portion is removed, and it is possible to prepare for normal printing.

As in the case of the bubble method, the clogging of the nozzle opening can be detected and recovered economically.

By the way, even if the clogging of the nozzle opening is detected every time printing is started (or when the power is turned on) and a recovery process is performed based on the result, no ink is ejected from the nozzle opening. There can be.

In this case, factors other than nozzle clogging
For example, a failure such as a case where the drive pulse is not transmitted to the heating resistor or the piezo element or a case where the heating resistor or the piezo element is damaged is considered.

Means for storing the nozzle position detected each time clogging is performed is provided, and if clogging is determined many times in succession, it is determined that a failure has occurred and the user is notified. Is provided, a highly reliable inkjet recording apparatus can be provided.

Means for informing the user include a method of providing a lamp in the ink jet recording apparatus and a method of displaying characters on the operation panel.

The frequency of use of the ink jet recording apparatus varies depending on the user. If the frequency of use is high, clogging of the nozzle opening hardly occurs, so that detection of clogging may not be necessary in some cases.

In this case, it is preferable to provide a mechanism that can omit the clogging detection and recovery sequence by operating the operation panel of the ink jet recording apparatus.

[0080]

According to the present invention, there is provided an ink jet recording apparatus for conveying a recording medium in front of a nozzle opening of a stationary recording head in a state of approaching the recording medium and discharging ink droplets from the nozzle opening to perform printing. Before starting page printing (or when power is turned on), a clogging detection pattern is printed, the image is detected by an optical sensor, and if there is a portion where ink has not been ejected, the nozzle corresponding to that portion is detected. By recognizing that clogging has occurred in the opening, and performing forced ejection of ink for the purpose of clogging recovery, the ink that has evaporated due to evaporation of the solvent near the nozzle opening has been removed. There is an effect that clogging can be prevented.

When the ink jet recording apparatus is frequently used and clogging of the nozzle opening is unlikely to occur, a mechanism is provided to omit the detection of clogging.
There is an effect that it is economical because unnecessary ink ejection is not performed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view showing an embodiment of an ink jet recording apparatus according to the present invention.

FIG. 2 is a top view showing an embodiment of the ink jet recording apparatus according to the present invention.

FIG. 3 is a flowchart illustrating a method for detecting and recovering from clogging in the inkjet recording apparatus according to the present invention.

4 is an example of an image pattern for detecting clogging in the ink jet recording apparatus shown in FIG.

FIG. 5 is a vertical sectional side view of a bubble jet type ink jet head.

FIG. 6 is a transverse sectional view of the inkjet head shown in FIG.

FIG. 7 is an example of an electric pulse applied to a heating resistor of a bubble jet type inkjet head.

FIG. 8 is a vertical side view of a piezo type inkjet head.

FIG. 9 is an example of an electric pulse applied to a piezo element of a piezo type inkjet head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Recording head, 2 ... Shielding member, 3 ... Recording paper conveyance roll, 4 ... Recording medium, 5 ... Optical sensor, 6 ... Shielding member raising / lowering means.

Claims (7)

[Claims] A stationary recording head in which a number of nozzles for ejecting ink droplets are arranged and opened; a shielding member for absorbing ink; and a shielding member at a position opposed to a nozzle opening of the recording head in a state close to the nozzle opening. An ink jet recording apparatus having a control device for controlling ink ejection from each nozzle opening of the recording head based on print information, wherein a means for reading an image on a recording medium; Means for printing a test pattern capable of detecting the presence or absence of ink ejection from a nozzle opening, detecting the non-ejection nozzle by the reading means, and then controlling to forcibly eject ink from the non-ejection nozzle toward the shielding member. An ink jet recording apparatus comprising: 2. The ink jet recording apparatus according to claim 1, wherein the control is performed such that the ink is ejected at a frequency higher than the maximum ejection frequency during normal printing during forced ejection. 3. The ink jet recording apparatus according to claim 1, wherein the control is performed such that the driving energy per discharge is increased during the forced discharge as compared with the normal printing to discharge the ink. Ink jet recording device. 4. An ink jet recording apparatus according to claim 1, wherein a sequence of printing a test pattern, detecting a non-discharge nozzle, and forcibly discharging ink from the non-discharge nozzle toward a shielding member is controlled by a power supply of the recording apparatus. An ink jet recording apparatus characterized in that it is controlled to be performed at the time of input. 5. An ink jet recording apparatus according to claim 1, wherein a sequence of printing a test pattern, detecting a non-discharge nozzle, and forcibly discharging ink from the non-discharge nozzle toward a shielding member is not repeated. An ink jet recording apparatus comprising means for recognizing an abnormal state when a discharge nozzle is present and displaying the abnormal state. 6. The ink jet recording apparatus according to claim 1, wherein the shield moving means is provided for normal printing.
An ink jet recording apparatus, wherein the shielding member is retracted to a position avoiding a recording medium transport path. 7. An external switch according to claim 1, wherein a sequence of printing a test pattern, detecting a non-discharge nozzle, and forcibly discharging ink from the non-discharge nozzle toward a shielding member can be stopped. An ink jet recording apparatus comprising: