JP2724158B2 - Ink jet recording device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus, and more particularly, to an ink jet recording apparatus having a plurality of recording heads provided with ink ejection ports in correspondence with ink colors or ink densities. In the apparatus, the means for preventing clogging of the ink discharge port is improved.

2. Description of the Related Art An ink jet recording apparatus is an apparatus that performs recording by ejecting ink from an ink ejection port provided in a recording head to form ink droplets and attaching the ink droplets to a recording material. Widely applied to facsimile or copier.

In such a device, a method of ejecting ink is to provide a heating element (electric heat energy conversion element) in the vicinity of the ejection port and supply an electric signal to the heating element to locally heat the ink to foam. And a method in which ink is ejected from an ejection port by a change in pressure accompanying the pressure, and a method in which an electromechanical transducer such as a piezoelectric element is provided.

In a mode in which ink is ejected only during such recording, that is, an on-demand type ink jet recording apparatus, if the recording pause time is long, the viscosity of the ink increases due to evaporation of the ink solvent and the ink ejection port of the recording head is clogged. For this reason, a capping means for covering the ejection port surface of the recording head with a cap when recording is stopped is provided.

Further, an increase in the viscosity of the ink is also caused by a decrease in the ink temperature at a low temperature in winter or the like. As a countermeasure, the printhead is provided with a temperature detecting means and a heating means for heating the printhead based on the temperature detection signal. A method of providing the recording head at a predetermined temperature or setting the recording head at a predetermined temperature or higher is also adopted.

However, in such an apparatus, even if the above-described capping and the temperature control of the recording head are performed in a recording suspension or a low-humidity environment for a long period of time, an increase in the viscosity of the ink may be unavoidable. In some cases, it is difficult to prevent the problem.

In order to eliminate such inconvenience, a pump unit is provided in the ink supply system before the recording is started to pressurize the ink, and an unsuitable ink such as a thickened ink is ejected from the ejection port of the recording head into the capping unit. Ink is sucked from the ejection port of the recording head via the capping unit, or an electric signal is supplied to the recording head when facing the capping unit to eject the ink in the same manner as during recording (empty). An ink jet recording apparatus provided with an ejection recovery means such as an ink jet recording apparatus has been proposed.

[Problems to be Solved by the Invention] However, when the ejection recovery means is operated in this way, particularly in an ink jet recording apparatus having a plurality of recording heads, for example, a multi-color ink jet recording apparatus, the following problems occur. was there.

That is, in a multi-color ink jet recording apparatus, for example, a full-color ink jet recording apparatus using a recording head of four colors of cyan, magenta, yellow, and black, the recording duty of the recording head is much larger than that of a single-color apparatus, and In some cases, the print duty differs greatly between the print heads of each color. For example, when the recorded image is mostly filled with red, the duties of the magenta and yellow recording heads are much larger than those of cyan and black. Conventionally, in such a case, the recording recovery unit is operated for all four color recording heads before the start of recording or at a predetermined timing during recording, but this is an economical problem that ink is wasted. This may cause a problem particularly in full-color printing with many ink colors. In addition, there is a problem that the waste ink amount increases and the replacement of the waste ink storage member becomes complicated.

The present invention solves such a problem, and enables stable ink discharge without clogging of a discharge port of a print head even after printing has been stopped for a long time or in a low-humidity environment. It is an object of the present invention to provide an ink jet recording apparatus in which the occurrence is suppressed.

[Means for Solving the Problems] For this purpose, the present invention provides a plurality of recording heads that perform recording by discharging ink liquid, and a recovery unit that discharges ink from the recording head and recovers a discharge state of the recording head. A temperature detecting unit for detecting a temperature of the plurality of recording heads, wherein the temperature detecting unit detects a temperature of the plurality of recording heads; In the recovery operation after the predetermined amount of recording operation is performed, the recovery unit discharges a predetermined amount of ink for the recording head that does not reach the predetermined temperature based on the detection result by the temperature detection unit. For a recording head having a temperature equal to or higher than a predetermined temperature, the recovery means may cause the recovery means to discharge a smaller amount of ink than the predetermined amount, or Control means for controlling not to perform the recovery operation by the means.

Further, the present invention is characterized in that in the above-mentioned ink jet recording apparatus, the recovery means discharges ink to recover the discharge state of the recording head.

[Operation] According to the present invention, a recovery operation is selectively performed for each of a plurality of recording heads in accordance with the temperature of each of the plurality of recording heads. The discharge recovery process is performed by discharging a predetermined amount of ink, and discharging a smaller amount of ink than the predetermined amount for a print head having a predetermined temperature or higher. Since it is performed, the amount of ink consumed in the ejection recovery process is reduced.

EXAMPLES Hereinafter, the present invention will be described in detail based on examples shown in the drawings.

FIG. 1A shows an example of a configuration of a main part of a full-color ink jet recording apparatus as one embodiment of the present invention.

A guide shaft 3 is disposed in front of a recording material 2 supported by a platen 1, and a carriage 4 that moves along the guide shaft 3 corresponds to a total of four colors of cyan, magenta, yellow, and black. Recording head 5C, 5
M, 5Y and 5K are installed. The recording head of each color has, for example, 128 ink ejection ports arranged in a direction perpendicular to the drawing, and each ink flow path communicating with each ink ejection port has an ejection energy generating means, such as an electrothermal energy converter. Is provided.

A gear pump 6 is installed on each recording head 5C, 5M, 5Y, 5K.
Ink is supplied from the ink tanks 8C, 8M, 8Y, 8K via four pipes 7C, 7M, 7Y, 7K provided with C, 6M, 6Y, 6K.
Although not shown, each color recording head and the ink tank are also connected by a pipe that does not pass through a gear pump.

A cap member 9 is provided at a predetermined position outside the recording range, for example, at a home position of the carriage 4. The cap member 9 is a member that is driven to advance and retreat in the F direction with respect to the recording heads 5C to 5K, and that is joined to and covers the ejection surface at the time of recording suspension or an ejection recovery operation.

On the sides of the recording heads 5C, 5M, 5Y, 5K, temperature detectors 10C, 10M, 10Y, 10K such as thermistors and heaters 11C, 11M, 11K are provided.
Y, 11K are provided. The detection signals from these temperature detectors are input to the control circuit shown in FIG. 1 (B), and the energization control of the heater is performed to maintain the recording head at a predetermined temperature or higher.

FIG. 1 (B) shows a configuration example of a control system according to the above configuration. Here, 100 is a control circuit for controlling each unit,
The CPU has a CPU for executing a processing procedure described later with reference to FIG. 3, a ROM storing programs and other fixed data corresponding to the processing procedure, and a RAM for work such as calculation.

A transport unit 101 transports the recording medium 2 in the sub-scanning direction.
This is a carriage drive unit for driving the carriage. Reference numeral 105 denotes a head driver for driving an electrothermal energy conversion element of a recording head (the components 5C to 5K are collectively indicated by reference numeral 5).
Reference numeral 6 denotes a pump driving unit for driving a pump (the components 6C to 6K are collectively indicated by reference numeral 6).
This is a cap driving unit that moves the recording head 5 in the direction to join / remove the recording head 5. 10 and 11 are thermistors 10C to 10K and the heater 11C shown in FIG.
~ 11K is shown collectively.

FIG. 2 is a characteristic diagram showing a change in temperature of the print head when the print head is warmed up in a normal temperature environment and when continuous printing is performed at three print duties. _{Here, T C, T l, T} h is 0 recording duty respectively%
(That is, when a print signal is not output, and is equal to the warm-up temperature), and is the ultimate temperature of the print head at 20% and 60%. With such recording duty increases, the recording head temperature is greater than the warm-up temperature T _C.

Incidentally, T ₁ and T ₂ of FIG. 2 is a recording head temperature to be a reference of the ejection recovery operations to be described later.

FIG. 3 is a flowchart illustrating an example of a recording processing procedure performed by the apparatus according to the present embodiment.

When the power is turned on, first, in step S1, each unit is initialized. At this time, if the cap 9 is not joined to the surface (ejection surface) of the recording heads 5C to 5K where the ejection openings are provided, the joining is performed.

Next, in step S3, the temperature of the recording head is
Judged by detection output of ～10K, waits until a predetermined warm-up temperature T _C by heating the heater 11C～11K. When the recording head temperature reaches _TC , an affirmative determination is made and the process proceeds to step S5. Note that, by this point on the temperature control by the control circuit 100 performs a recording head 5C~5K in response to the detection output of the thermistor 10 so as not turn down the temperature T _C heater 11
ON / OFF is controlled.

In step S5, the pumps 6C to 6K corresponding to the respective colors are simultaneously operated, for example, for one second, and the ink in the nozzles of the recording heads 5C to 5K is discharged from the discharge ports into the cap 9. At this time, since the ejection surfaces of the recording heads 5C to 5K leak with ink, a cleaning member (not shown) provided in the cap 9 is brought into contact with the ejection surface to absorb the ink attached to the ejection surface. At this time, it is more effective to connect a pump to the cap 9 to perform suction in order to enhance the cleaning property. When the cleaning operation is completed, the recording head is again covered with the cap 9 in step S9, and the recording head enters a standby state in which the recording operation is possible.

Next, in the discrimination processing of step S11, when a recording start command is input, the cap 9 is detached from the recording heads 5C to 5K. Immediately before this, in step S13, all of the four color recording heads 5C to 5K are removed. By driving the ink, for example, 100 drops of ink are ejected from all of the ejection ports, respectively.

After performing the idle discharge, the print heads 5C to 5K leave the home position, scan the print medium, and perform printing based on the image signal in step S15.

Next, in step S17, it is determined whether or not printing of a predetermined amount, for example, printing for five scans, has been completed. If the determination is negative, the process returns to step S15 to continue printing, and if the determination is affirmative, the process proceeds to step S19. move on.

In step S19, the recording head temperatures T are measured based on the detection signals of the thermistors 10C to 10K disposed on the recording heads 5C to 5K of the respective colors. At subsequent step S21, the temperature T of the recording head is less than T _1, if an affirmative determination is made processing proceeds to step S23, with respect to the cap of the left recording head 5C~5K is separated when returning to the home position From each ejection port of the head for which the affirmative determination was made, for example, 200
The idle ejection A of the droplet is performed, and the process proceeds to step S29.

If a negative determination is made in step S21, step S25
Then, it is determined whether or not the recording head temperature T satisfies T ₁ ≦ T <T _2. If the determination is affirmative, the process proceeds to the next step S27, in which the cap 9 at the home position is subjected to the affirmative determination. For example, idle discharge B of 50 drops is performed from each discharge port, and the process proceeds to step S29. If the recording head temperature T in the step S25 is made negative determination be at T ₂ or more idle discharge is not performed, the process proceeds to step S29.

These steps S19 to S27 are repeated for each head, or the idle discharge is performed according to the detected temperature.
By setting A, idle ejection B, and ejection unnecessary data in the RAM and performing ejection recovery in parallel, it is possible to selectively drive the print head.

In step S29, recording is continued, and thereafter, it is determined whether or not recording of all the image signals output in step S31 has been completed. If a positive determination is made in step S31, step S
Then, the cap 9 is joined to the ejection surfaces of the print heads 5C to 5K to prepare for the next print start command. If a negative determination is made in step S31, that is, if recording is to be continued, the process proceeds to step S33, where the recording heads 5C to 5K are returned to their home positions, and 4
For example, 100 drops of idle discharge are performed from all the discharge ports for each color, and the process returns to step S15.

In the above-described step S23 and step S27, as the ejection recovery operation, the idle ejection for giving the recording signal for performing the entire ejection from the ejection head of the recording head is performed. The ejection recovery operation by pressurization may be performed by driving any of the pumps 6C to 6K connected to the head. In this case, the cap is bonded to the recording head as described in the step S5, and the pump drive is performed, for example, for 2 seconds in place of the idle discharge A in step S23, and the pump is driven in place of the idle discharge B in step S27. For example, for 1 second, the ink is forcibly discharged from the ejection port. Thereafter, a step of cleaning the ejection surface can be performed.

The discharge recovery operation by the pump drive requires a larger amount of ink consumption than the idle discharge, but the effect is large. FIG. 4 shows an apparatus according to another embodiment of the present invention, in which multi-gradation recording is possible. FIG. 2 is a plan view illustrating an example of a configuration of a main part of the full-color inkjet recording apparatus. Here, the same components as those of the apparatus shown in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted.

The carriage 4 includes a total of eight recording heads 5C1 and 5C2 for cyan, recording heads 5M1 and 5M2 for magenta, recording heads 5Y1 and 5Y2 for yellow, and recording heads 5K1 and 5K2 for black.
The recording heads are mounted. 5C1,5M1,5Y in this
1,5K1 is a recording head that discharges light color ink (low density ink), and 5C2,5M2,5Y2,5K2 is a recording head that discharges dark color ink (high density ink).

In this manner, tertiary recording is possible by discharging the dark and light inks for each color, and it is possible to reproduce multiple gradations as compared with binary recording as in the apparatus shown in FIG. The low-concentration ink can have an ink concentration of, for example, 1% in a solvent such as water, and the high-concentration ink can have, for example, 3%.

An example of a recording method using the above dark and light inks will be described with reference to FIG.

FIG. 5 shows the relationship between the recording dot% and the input signal (8 bits). In the recording using the low-density ink, when the input levels are "0" and "255", the recording dots become 0% and the input level becomes "100". "100%. That is, the recording of the bright part and the halftone is mainly performed. In the case of recording using high-density ink, the recording dot is 0% when the input level is "100", and is 100% when the input level is "255". That is, the recording of the dark part is mainly performed.

When recording is performed in accordance with the recording characteristics shown in FIG. 5, it is apparent that the recording amount of the low-density ink increases when recording not only a halftone image but also a so-called solid image. In particular, in the printing of a halftone image having a bright color tone, the printing amount of the high-density ink is significantly smaller than the printing amount of the low-density ink.

FIG. 6 is a flowchart showing an example of a recording procedure by the apparatus shown in FIG.

In FIG. 6, the procedure up to step S17 is the same as the procedure shown in FIG.

In this procedure, if the printing of the predetermined amount M based on the image signal by the eight print heads, for example, the printing for two scans, is completed in step S17, the process proceeds to step S119, and FIG.
When the recording heads 5C2, 5M2, 5Y2, and 5K2 ejecting high-density ink return to the home position, all of them, or each of the heads under inappropriate conditions, Empty discharge of, for example, 100 drops is performed from the discharge port. At this time, a recording head that ejects low-density ink
No idle discharge is performed on 5C1, 5M1, 5Y1, and 5K1.

Next, after proceeding to step S121 to continue printing, it is determined in step S123 whether printing of a predetermined amount N, for example, printing for 10 scans, has been completed.
To continue recording, and if the determination is affirmative, the process proceeds to step S125.

In step S125, the eight recording heads 5C1-5K1, 5C2-
For all of 5K2, the cap 9 is caused to discharge, for example, 100 drops from each discharge port to the cap 9 at the home position.

Next, after proceeding to step S127 to continue recording, proceed to step S129 to determine whether or not recording of all output image signals has been completed.

In step S119 and step S125, as a discharge recovery operation, a recording signal for performing full discharge from the recording head discharge port is given to perform idle discharge, but instead of this idle discharge, the recording head is connected to each color recording head according to a control signal. Pumps 6C1 to 6K2 may be selectively driven to perform a discharge recovery operation. In this case, instead of the idle discharge in step S119, the cap is joined to the print head at the home position, and the pump drive of the pumps 6C2, 6M2, 6Y2, 6K2 connected via a pipe to the print head that discharges high-density ink. For example, for 1 second, the ink is forcibly discharged from the ejection port.
Thereafter, the ejection surface can be cleaned.

Further, the cap 9 is joined to the recording head at the home position in place of the idle discharge in step S125, and the pumps 6C1 to 6K2 are simultaneously driven, for example, for one second to forcibly discharge ink from the discharge ports. After that, cleaning of the ejection surface can be performed.

FIG. 7 shows an apparatus according to still another embodiment of the present invention, and shows an example of a main configuration of a full-color ink jet recording apparatus in which an optical sensor for reading an image density recorded by one scan of the carriage is mounted on the carriage. FIG. Here, the same components as those of the apparatus shown in FIG. 1 are denoted by the same reference numerals and the description thereof is omitted.

The carriage 4 has four color recording heads 5C to 5K,
An image density reading unit including an illumination lamp 12, a rod lens array 13, and a color solid-state imaging device 14 is mounted. In the color solid-state imaging device 14, a large number of minute light receiving elements are arranged in a row in a direction perpendicular to the paper surface of FIG. 7, and blue (B), green (G),
A small filter of red (R) is provided.
A D line sensor is used. The lens array 13 is also arranged in the direction perpendicular to the plane of the paper of FIG. 7, and when reading the image density, the reflected light image of the recorded image on the paper 2 illuminated by the illumination lamp 12 is formed on the solid-state imaging device 14. Let it.

FIG. 8 is a block diagram showing an example of signal processing from the image density reading of the apparatus shown in FIG. 7 to the control of the ejection recovery operation.

In FIG. 7, when the carriage 4 is moved and recording is started, reading of the recorded image by the color CCD line sensor 14 is started at the same timing.

In block 10 in FIG. 8, the color CCD line sensor reads the reflected light of the full-color image on the paper, and after photoelectric conversion, outputs B, G, R point-sequential analog signals. This color separation signal is then amplified in block 20 and further
It is A / D converted and output as a 4-bit digital signal, for example.

This signal is color-separated into B, G, and R colors in block 30,
In the next block 40, the signals are converted into logarithmically corrected Y, M, C signals and sent to the block 50, where the three color signals of Y, M, C are converted to Bk (black).
A signal is also generated.

The image density signals of the four colors Y, M, C, and Bk thus obtained are stored in the memory in the next block 60, and the recording area ratio is calculated for each color. Based on the result of this calculation, the ejection recovery operation as described for the apparatus shown in FIG. 1 is controlled.

The image density reading process described above is based on digital signal processing. In addition, a recorded image is read by four color sensors B, G, R, and Bk, and each color output signal is integrated and stored, and compared with a reference voltage. The present invention can be effectively and easily applied to a process for performing an ejection recovery operation by performing a simple image density reading process by analog signal processing.

In each of the embodiments described above, the case where the present invention is applied to a serial printer in which printing is performed by moving and scanning the print head has been described.However, the present invention provides that the discharge ports of the print head are arranged in parallel over the entire width of the print medium. The present invention can be similarly applied to a line printer type multi-color ink jet recording apparatus using a so-called full multi-type recording head.

Further, in the above example, the case where the present invention is applied to an ink jet recording apparatus that performs full color recording using yellow, magenta, cyan, and black inks has been described, but the ink color used is arbitrary and desired. The present invention is very effective and easy to apply not only to a multi-color ink jet recording apparatus but also to an apparatus having a plurality of recording heads corresponding to a plurality of kinds of inks depending on the density even if the ink is one color. Of course you can.

[Effects of the Invention] As described above, according to the present invention, even when printing is performed after a long pause, clogging or the like does not occur, stable ejection can be ensured, and the recording head of each print head can be secured. Since the recovery process is selectively performed according to the conditions, the amount of ink consumption and the amount of waste ink can be reduced as much as possible.

[Brief description of the drawings]

FIG. 1A is a plan view showing a configuration example of a main part of a full-color ink jet recording apparatus according to an embodiment of the present invention, FIG. 1B is a block diagram showing a configuration example of a control system thereof, FIG. FIG. 3 is a characteristic diagram showing a change in temperature of the recording head of the apparatus shown in FIG. 1, FIG. 3 is a flowchart showing an example of a recording processing procedure by the apparatus shown in FIG. 1, and FIG. FIG. 5 is a plan view showing a configuration example of a main part of a multi-tone full-color ink jet recording apparatus. FIG. 5 is a characteristic diagram showing a relationship between input signal levels of two types of ink and recording dots (%) in the apparatus shown in FIG. 6 is a flowchart showing an example of a recording processing procedure of the apparatus shown in FIG. 4, FIG. 7 is a plan view showing an example of a configuration of a main part of a full-color ink jet recording apparatus according to still another embodiment of the present invention, and FIG. Image density of the device shown in FIG. Is a block diagram showing an example of signal processing of the ejection recovery operations do not take. 2 ... recording medium, 4 ... carriage, 5,5C, 5M, 5Y, 5K ...... recording head, 6C, 6M, 6Y, 6K ... pump, 7C, 7M, 7Y, 7K ... pipe, 8C, 8M , 8Y, 8K ... ink tank, 9 ... cap, 10, 10C, 10M, 10Y, 10K ... temperature detecting element, 11, 11C, 11M, 11Y, 11K ... heater, 100 ... control circuit.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display B41J 2/185

Claims (2)

(57) [Claims] A plurality of recording heads for performing recording by discharging ink liquid; and a recovery unit for discharging ink from the recording heads to recover a discharge state of the recording heads. In an ink jet recording apparatus that performs a recovery operation by the recovery unit after performing a recording operation, a temperature detection unit that detects a temperature of the plurality of recording heads, and after performing a predetermined amount of recording operation by the plurality of recording heads. In the recovery operation, based on the detection result by the temperature detection unit, for the recording head that does not reach the predetermined temperature, the recovery unit discharges a predetermined amount of ink,
Control means for controlling the recording head having the predetermined temperature or higher to cause the recovery means to discharge a smaller amount of ink than the predetermined amount or to prevent the recovery means from performing the recovery operation. An ink jet recording apparatus comprising: 2. An ink jet recording apparatus according to claim 1, wherein said recovery means recovers the discharge state of the recording head by discharging ink.