JPH023324A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE:To enable the stable discharge of ink without causing clogging of a discharge port of a recording head and to suppress a wasteful use of ink by making a discharge-recovery means of the recording head operate selectively in accordance of the respective states of recording heads in a plurality. CONSTITUTION:Based on detection signals of thermistor 10C to 10K provided for recording heads 5C to 5K of separate colors, the temperature T of each recording head is measured. In the case when T is lower than T1, an idle discharge A of 200 droplets in made, for instance, from each discharge port of the heads to a cap which is left separated when the recording heads 5C to 5K return to home positions. In the case when T is T1<=T<=T2, an idle discharge B of 50 droplets is made, for instance, from each discharge port to the cap 9 at the home positions, and when T is higher than T2, no idle discharge is made. The selective drive of the recording heads is enabled by repeating these procedures for each head or by setting data on the idle discharge A, the idle discharge B and on no demand for discharge in RAM in accordance with a detected temperature and conducting discharge recovery in parallel.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an inkjet recording device, and more specifically, an inkjet recording device having a plurality of recording heads provided with ink ejection ports corresponding to ink colors, ink concentrations, etc. In the apparatus, the means for preventing the ink discharge port from glancing is improved.

[Prior Art] An inkjet 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 depositing the droplets on a recording material.
Widely applied to printers, facsimiles, copying machines, etc.

In such devices, the method of ejecting ink involves providing a heating element (electrothermal energy converter) near the ejection port, and supplying an electric signal to this heating element to locally heat the ink and foam it. There is a method in which ink is ejected from an ejection port by the resulting pressure change, and a method in which an electromechanical transducer such as a piezoelectric element is provided.

In such an on-demand type ink jet recording device, which discharges ink only during recording, if the recording pause time is long, the viscosity of the ink increases due to evaporation of the ink solvent, and the ink discharge ports of the recording head may become clogged. Therefore, a capping means is provided to cover the ejection port surface of the print head with a cap when printing is stopped.

Furthermore, an increase in ink viscosity is also caused by a drop in ink temperature during low temperatures such as winter, and as a countermeasure, a temperature detection means is installed in the recording spatula, and the recording head is heated based on the temperature detection signal. There is also a method of providing a heating means to maintain the recording head at a predetermined temperature, or setting the recording head to a predetermined temperature or higher.

However, in such devices, when recording is stopped for a long time or in a low humidity environment, the viscosity of the ink may unavoidably increase even if the above-mentioned capping and recording head temperature control are performed. In some cases, it was difficult to prevent defects.

In order to eliminate this inconvenience, a pump means is provided in the ink supply system to pressurize the ink before the start of recording, and ink unsuitable for recording, such as additional ink, is pushed out from the ejection opening of the recording head into the capping means. Ink can be suctioned from the ejection ports of the recording head through a capping means, or an electrical signal can be supplied to the recording head when facing the caving means to eject ink in the same way as during recording (dry ejection). ) An inkjet recording apparatus has also been proposed that is provided with an ejection recovery means that prevents the ejection from occurring.

[Problems to be Solved by the Invention] However, when the ejection recovery means is operated in this manner, the following problems arise, especially in an inkjet recording apparatus equipped with a plurality of recording heads, for example, a multicolor inkjet recording apparatus. There was.

In other words, in a full-color inkjet recording device that uses a multicolor inkjet recording device, for example, a recording blade with four colors of cyan, magenta, yellow, and black, the recording duty of the recording head is much larger than in a monochrome device. In addition, there are cases where the printing duty differs significantly between the printing heads of each color. For example, if the recorded image is mostly filled with red, the duty of the magenta and yellow recording heads will be much higher than that of cyan and black. Conventionally, in such cases, the recording recovery means was operated for all four color recording heads before recording started or at predetermined timings during recording, but this had the economical problem of wasting ink. This can sometimes be a problem, especially in full-color recording where there are many ink colors. Further, there is a problem in that the amount of waste ink increases and the replacement of the waste ink storage member becomes complicated.

The present invention solves these problems and enables stable ink ejection without clogging of the ejection ports of the print head even after a long printing pause or during printing in a low humidity environment, and wastes ink. An object of the present invention is to provide an inkjet recording device that suppresses

[Means for Solving the Problems] To achieve this, the present invention provides a plurality of printheads, an ejection recovery means provided corresponding to each of the plurality of printheads, and an ejection recovery means that corresponds to the state of each of the plurality of printheads. The present invention is characterized by comprising means for selectively operating the ejection recovery means of the recording head.

[Function 1] According to the present invention, ejection recovery processing is performed on the plurality of recording heads according to their respective states, so that the amount of ink consumed during the ejection recovery processing is reduced.

[Example] Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIG. 1 (8) shows an example of the main part configuration of a full color inkjet recording apparatus as an embodiment of the present invention.

A kite shaft 3 is arranged in front of the recording material 2 supported by the platen 1, and the carriage 4, which moves along the kite shaft 1-3, is compatible with a total of four colors: cyan, macenta, yellow, and black. recording head 5
C, 5M, 5Y and 5K are installed. For example, 128 ink ejection ports are arranged in the recording head of each color in the direction perpendicular to the drawing, and each ink flow path communicating with each ink ejection port is equipped with an ejection energy generating means, such as electrothermal energy. A converter is provided.

Each color recording head 5C, 5N+, 5Y, 5K is connected to an ink tank 8G via four wooden pipes 707M, 7Y, 7K with gear pumps 6C, 6M, 6Y, 5K installed in the middle.
Ink is supplied from 8M, 8Y, and 8K. Although not shown, each color recording head and ink tank are also connected by a pipe that does not involve a gear pump.

A cap member 9 is provided at a predetermined position outside the recording range, for example at the Baum position of the carriage 4. This cap member 9 is a portion A that is driven forward and backward in the direction F relative to the recording media 5C to 5K, and is joined to and covers the ejection surface during a recording pause or an ejection recovery operation.

On the sides of the recording heads 5C, 5M, 5Y, 5, there are temperature detectors 10c such as thermistors, IOM, IOY, IOK.
and heaters 11C, IIM, lIY, ]lK are provided. Detection signals from these temperature detectors are input to the control circuit shown in FIG. 1B, and the heater is controlled to be energized 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 that controls each part,
It has a CPU that executes a processing procedure to be described later with reference to FIG. 3, a ROM that stores programs and other fixed data corresponding to the processing procedure, and an RΔ14 for operations such as calculations.

Reference numeral 101 denotes a conveying section for conveying the recording medium 2 in the sub-scanning direction, and 104 denotes a carriage drive section for driving the carriage 4 in the scanning direction S relative to the recording medium 2. 105 is a recording head (each part 50 to 5K is collectively indicated as 5)
Spatula 1-1 for driving the electrothermal energy conversion element of
- driver, 106 is a pump drive unit 107 for driving the pump (each part 66 to 6K is collectively indicated by the reference numeral 6);
1 is a cap driving unit that moves the cap member 9 in the F direction to attach/detach the cap member 9 to/from the recording head 5. Further, 10 and II collectively indicate the thermistors IOc to 10 and heaters IIC to IIK shown in the first diagram, respectively.

FIG. 2 is a characteristic diagram showing the temperature transition of the print head when the print head is warmed up in a normal temperature environment and when continuous printing is performed with three different print duties.

Here, as shown in TC9, Th is the temperature reached by the recording head when the recording duty is 0% (that is, no recording signal is output, and is equal to the ohm-up temperature), 20%, and 50%, respectively. As the recording duty increases in this manner, the recording head temperature becomes much higher than the temperature up temperature TC.

Note that 11 and T2 in FIG. 2 are recording head temperatures that serve as a reference for the ejection recovery operation described later.

FIG. 3 is a flowchart showing an example of the recording processing procedure by the apparatus related to the tree seed layer side.

When the power is turned on, each part is first initialized in step S1. If the cap 9 is not bonded to the surface (discharge surface) on which the discharge ports of the scraping recording heads 5C to 5 are provided, the cap 9 is bonded.

Next, in step S3, the temperature of the recording head is measured using the thermistor IO.
Judging from the detection output of C to IOH, heater 11C-1
1 to a predetermined warm-up temperature T. Wait until you hear it. When the recording head temperature reaches Tc, an affirmative determination is made and the process proceeds to step S5.

From now on, the temperature control performed by the control circuit 100 controls whether the heater 11 is turned on or off in accordance with the detection output of the thermistor 10 in the recording heads 56 to 5 so that the temperature does not fall below Tc.

In step S5, the bonds 76C to 5 corresponding to each color are
For example, if K is operated for 1 second at the same time, the recording head 50-5
The ink in the nozzle is discharged into the cap 9 from the discharge port. Note that since the ejection surfaces of the scraping recording heads 50 to 5 are wetted with ink, a cleaning member (not shown) provided in the cap 9 is brought into contact with the ejection surfaces to absorb the ink that has landed on the ejection surfaces. At this time, it is more effective if a pump is connected to the cap 9 to perform suction in order to improve cleaning performance. When this cleaning operation is completed, the recording head is covered again with the cap 9 in step S9, and enters a standby state in which recording operation is possible.

Next, in the determination process of step 511, when a recording start command is input manually, the cap 9 is moved to the recording spatula l"5C to 5K.
Immediately before this, in step 513, the four color recording heads 50 to 5 are driven to eject, for example, 100 droplets of ink from all the ejection ports.

After performing this idle ejection, a home position is created in the recording heads 56 to 5, the recording medium is scanned, and recording is performed based on the image signal in step S15.

Next, in step S17, it is determined whether or not a predetermined amount of recording, for example, recording for 5 scans has been completed, and if the determination is negative, the process returns to step 515 to continue recording, and if the determination is affirmative, step 519 Proceed to.

In step 519, the temperature T of each print head is measured based on the detection signals of the thermistors IOC to IOH disposed in the print heads 50 to 5K of each color. Next step 5
21, if the temperature T of the recording head is less than T1 and an affirmative determination is made, the process advances to step S23, and when the recording heads 5C to 5K return to the Baum position, the cap that remains separated is For example, 200 droplets are idle-ejected A from each ejection port of the head for which the determination has been made, and the process proceeds to step S29.

If a negative determination is made in step S2+, step S
25, it is determined whether or not the recording head temperature T is T1≦T<T2. If the determination is affirmative, the process advances to the next step 527, where each of the heads for which the affirmative determination has been made for the cap 9 at the home position is For example, 50 empty discharges B are performed from the discharge port, and the process proceeds to step 529.

If the recording head temperature T is 12 or higher and a negative determination is made in step S25, no idle ejection is performed, and step S5
Proceed to step 29.

By repeating these steps S19 to S27 for each head, or by setting data for dry ejection A, dry ejection B, and no ejection in the RAM according to the detected temperature, and performing ejection recovery in parallel. , it becomes possible to selectively drive the recording head.

In step S29, recording is continued, and then in step S3
] It is determined whether recording of all the output image signals has been completed. If an affirmative determination is made in step 531, the process returns to step S9, and the cap 9 is bonded to the ejection surface of the print heads 50 to 5 in preparation for the next print start command. If a negative determination is made in step 531, that is, if printing is to be continued, the process proceeds to step 533, returns the print heads 5C to 51 (to their home positions, and, while keeping the caps apart, discharges all four colors from all ejection ports to the caps. In each case, for example, 100 drops are idle-discharged, and the process returns to step S15.

Further, in steps 523 and 527 described above, as an ejection recovery operation, a dry ejection was performed in which a print signal was applied to perform full ejection from the print head ejection ports. Any one of the pumps 66 to 6 connected to the head may be driven to perform the discharge recovery operation by pressurization. In this case, the cap is attached to the recording head as described in the pump drive in step S5, and the pump is driven for, for example, 2 seconds instead of the dry discharge A in step S23, and the pump is driven for 2 seconds instead of the dry discharge B in step S27. The drive is performed, for example, for one second, and the ink is forcibly discharged from the ejection port. After this, a step of cleaning the ejection surface can be performed.

Although this ejection recovery operation by driving the pump consumes more ink than empty ejection, it is much more effective.

FIG. 4 shows an apparatus according to another embodiment of the present invention,
FIG. 1 is a plan view showing an example of the configuration of a main part of a blue color inkjet recording apparatus capable of multi-tone recording. Here, corresponding parts are given the same reference numerals to the parts configured similarly to the apparatus shown in the first figure, and the explanation thereof will be omitted.

Carriage 4 has recording hens 1 to 5C1°5C for cyan.
2. A total of eight recording heads are mounted: recording heads 5Ml and 5M2 for macenter, recording heads F5Yl and 5Y2 for yellow, and recording head F5Ml for black; Among these, 5C1, 5MI, 5Yl, 1 in 5
7 is a print head that ejects flame-colored ink (low-density ink), and 5C2, 5M2, 5Y2, and 5 are print heads that eject dark-color ink (high-density ink).

In this way, three-value recording is possible by ejecting dark and light ink for each color, and two-value recording, such as the device shown in Figure 1, is possible.
It is possible to reproduce multiple gradations compared to value recording. The concentration of low concentration ink in a solvent such as water may be, for example, 1%, and the concentration of high concentration ink may be, for example, 3%.

An example of a recording method using the above-mentioned a-light ink will be explained with reference to FIG.

Figure 5 shows the relationship between the recorded dot percentage and the human power signal (ablt), and in recording with low-density ink, the human power level is 0°° and 255°', and the recorded dots are 0.
%, and becomes 100% when the human power level is 100". In other words, the recording is mainly of bright areas and intermediate tones.

Also, recording with high-density ink is at the level of human labor.°'100
”, the recorded dot is 0%, and the human power level is °'2
55" and 100%.

In other words, it mainly records the dark areas.

It is clear that when printing is performed according to the printing characteristics shown in FIG. 5, the amount of low-density ink to be printed increases not only when printing a half-tone image but also when printing a so-called solid image. In particular, when recording halftone images with bright colors, the amount of high-density ink recorded is significantly smaller than the amount of low-density ink.

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

In FIG. 6, step 517 is the same as the procedure shown in FIG. 3, so its explanation will be omitted.

In this procedure, if the recording of a predetermined amount M based on the image signal is completed in step 517 based on the image signal, for example, recording of 2 scans, the process advances to step 5119, and the process proceeds to step 5119, as shown in FIG.
Based on a command from the control circuit similar to (b), when the recording head 5025M2, 5Y2.5 that ejects high-density ink is sent to the cap 9, all of them or the head under unsuitable conditions For example, 100 drops are idly ejected from each ejection port. At this time, the recording heads 5C1, 5M1.5Yl, and 51, which eject low-density ink, are not allowed to perform idle ejection.

Next, the process advances to step 5121 to continue recording, and then, in step 5123, it is determined whether or not recording of a predetermined number of iN, for example, recording for 10 scans has been completed.If the determination is negative, the process returns to step 5121 to continue recording. If the determination is affirmative, the process advances to step 5125.

In step 5125, eight recording heads 5G1 to 58
1, Cap 9 at home position on 5G2-5
For example, loo? Perform a dry discharge of R.

Next, the process advances to step 5127 to continue recording, and then the process advances to step 5129, where it is determined whether or not recording of all output image signals has been completed.

In step 5119 and step 5125, as an ejection recovery operation, a printing signal is given to perform full ejection from the print head ejection port to perform dry ejection, or instead of this dry ejection, each color recording head is connected to each color recording head according to a control signal. The pumps 6C1 to 6C2 may be selectively driven to perform the discharge recovery operation. In this case step 5
Pumps 6C2, 6M2.6Y are connected via pipes to the recording head which connects a cap to the recording head at the home position and discharges high-concentration ink instead of the idle discharge of 119.
In 2.6, the pump in step 2 is driven for one second, and the ink is forcibly discharged from the ejection port. After this, the ejection surface can be cleaned.

Further, instead of the idle ejection in step 5125, the cap 9 is attached to the recording head at the home position, and the pumps [iC1 to 6 and 2 are simultaneously driven for, for example, one second to forcibly eject ink from the ejection ports. After this, the ejection surface can be cleaned.

FIG. 7 shows an apparatus according to still another embodiment of the present invention, which shows the main structure of a full-color ink sheet recording apparatus in which the carriage is equipped with an optical sensor that reads the density of an image recorded in one scan of the carriage. It is a top view showing an example.

Here, corresponding parts are given the same reference numerals as to the parts configured similarly to the apparatus shown in the first figure, and the explanation thereof will be omitted.

The carriage 4 includes four color recording heads 50 to 5 as well as illumination lamps 12 . An image density reading unit consisting of a rod lens array 13 and a color solid-state image sensor 14)
Is it installed? The color solid-state image sensor 14 has a large number of minute light-receiving elements arranged in a row in a direction perpendicular to the plane of the paper in FIG.
, green (G), and red (It) minute filters are provided,
For example, a color CCD line sensor is used. The lens array 13 is also arranged in a direction perpendicular to the plane of the paper in 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 focused on the solid-state image sensor 14. let

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

In FIG. 7, when the carriage 4 moves and starts recording, at the same timing the color CCD line sensor 14
starts reading the recorded image.

In block 10 of FIG. 8, the color CCD line sensor reads the reflected light of the full-color image on the paper, performs photoelectric conversion, and outputs B, G, and H dot-sequential analog signals. This color separation signal is then amplified in block 20, subjected to rough/D conversion, and outputted as, for example, a 4-bit digital signal.

This signal is separated into B, G, and R colors in block 30, converted into logarithmically corrected Y, M, and C signals in block 40, and sent to block 50, where three color signals of Y9M and C are sent. A Bk (black) signal is also generated.

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

The image 7 imaginary reading processing described above is performed by digital signal processing, or else the recorded image is read by four color sensors B, G, R, and Bk, and each color output signal is integrally stored and compared with the reference voltage. processing to perform a discharge recovery operation,
That is, the present invention can be effectively and easily applied even to image density reading processing that is easy to perform in DX1 using analog signal processing.

In each of the above embodiments, the present invention is applied to a serial printer that performs printing by moving and scanning the print head. The present invention can be similarly applied to a multicolor inkjet recording apparatus in the form of a line printer using a so-called full multi-type recording head.

In addition, although the case where the present invention is applied to an inkjet recording device that performs full-color recording using yellow, macenta, cyan, and black inks has been described above, the ink colors to be used may be any desired color, and furthermore, such ink colors may be used as desired. For multi-color ink sheet recording devices, the number of inks is 1
Of course, the present invention can be applied very effectively and easily to any device having a plurality of recording heads corresponding to a plurality of types of ink depending on color or density.

[Effects of the Invention] As explained above, according to the present invention, even when recording is performed after a long pause, stable ejection can be ensured without clogging, and each recording Since recovery processing is performed selectively depending on head conditions,
It was possible to reduce the amount of ink consumed and the amount of waste ink as much as possible.

[Brief explanation of the drawing]

FIG. 1(A) is a plan view showing an example of the configuration of main parts of a full-color inkjet recording apparatus according to an embodiment of the present invention; FIG. 1(B) is a block diagram showing an example of the configuration of its control system; Fig. 3 is a characteristic diagram showing the temperature transition of the recording head of the apparatus shown in Fig. 1; Fig. 3 is a flowchart showing an example of the recording processing procedure by the apparatus shown in Fig. 1; Fig. 4 is a diagram according to another embodiment of the present invention. A plan view showing an example of the main part configuration of a multi-gradation full color ink sheet recording device, and FIG. 5 is a characteristic diagram showing the relationship between the human power signal level of two types of ink and the recorded dots (%) in the device shown in FIG. 4. , FIG. 6 is a neo-flowchart showing an example of the recording processing procedure of the apparatus shown in FIG. FIG. 8 is a block diagram showing an example of signal processing for image density reading or ejection recovery operation of the apparatus shown in FIG. 2... Recording medium, 4... Carriage, 5.5C, 5M, 5Y, 5K... Recording head, 5C,
6M, 6Y, 6K...Pump, 7G, 7M, 7Y, 7
K...pipe, 8G, 8M, 8Y, 8K...ink tank, 9°"° cap, 10, IOC, IOM, IOY, IOK...temperature detection element, 11.11C, lIM, IIY, 11K ...Heater, 100...Control circuit.

Claims (1)

[Claims] 1) A plurality of recording heads, an ejection recovery means provided corresponding to each of the plurality of recording heads, and selectively controlling the ejection recovery means of the recording head according to the state of each of the plurality of recording heads. An inkjet recording device characterized by comprising: means for operating the inkjet recording device.