JPH04201344A - inkjet recording device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet recording apparatus used as a copying machine, a facsimile machine, a computer, a word processor, or a composite device thereof.

[Prior Art] An inkjet recording device is known as a device that performs recording by ejecting ink toward a recording material, causing the ink droplets to land and become fixed, and because it is a non-impact type, there is little noise and It has features such as easy recording of color images by using multi-colored inks.
It has become particularly rapidly popular in recent years.

In particular, Canon ■ uses an electrothermal converter to generate energy to eject recording liquid into droplets.
The bubble jet inkjet recording device proposed by the authors is considered to have a more promising future than other recording methods because it is capable of high-speed, high-density recording.

By the way, inkjet recording devices perform recording by directly ejecting ink onto the recording material from fine ink ejection ports, and in order to always obtain stable recorded images, other recording methods are used. Special considerations not found in equipment are required.

Conventionally, for example, in the case of a multi-nozzle type print head in which a large number of ink ejection openings are arranged or a print head unit consisting of a plurality of print heads, ink that is rarely involved in printing during printing operation has been used. Water in the ink evaporates from around the ink ejection ports and the print head, causing ejection failure due to increases in ink viscosity and adhesion of dust. A series of recovery operations have been carried out, such as empty ejection in which ink is ejected all at once.

[Problems to be Solved by the Invention] However, in the conventional inkjet recording apparatus described above, in a multi-nozzle type recording head or a recording head unit consisting of a plurality of recording heads, all the nozzles of all the recording heads are emptied at one time. Since the ink is ejected, if a large number of dry ejections are required, the temperature of the print head will rise significantly compared to immediately before the dry ejection, and the ink viscosity will drop significantly, causing a large density change in the recorded image immediately after that. Furthermore, in full-color images, the color balance may be disrupted and the image quality may be impaired.

The present invention has been made in view of the above circumstances, and its purpose is to perform effective dry ejection to reduce the damage caused by the dry ejection from all nozzles of all print heads, as in the conventional case. An object of the present invention is to provide an inkjet recording device that can prevent changes in image density and collapse of color balance due to temperature rise.

[Means for Solving the Problems] An inkjet recording apparatus of the present invention includes a plurality of recording heads that eject ink, and the plurality of recording heads are divided into at least two groups, and each group is divided into two groups. It is characterized by having a dry ejection control means for performing dry ejection at different time intervals.

Further, in the inkjet recording apparatus of the present invention, in the inkjet recording apparatus equipped with a recording head that ejects ink from a plurality of nozzles, the plurality of nozzles are divided into at least two groups, and each group is separated from each other at a time difference. It may also be characterized by having a dry ejection control means for performing dry ejection.

In this case, when dividing the plurality of nozzles into groups, the idle ejection control means can divide the nozzles into a group of nozzles with even nozzle numbers and a group of nozzles with odd nozzle numbers.

The recording head can be a full-line type recording head that includes a plurality of ejection ports over the entire width of the recording area of the recording medium.

The recording head uses thermal energy to eject ink from an ejection port, and preferably has an electrothermal converter as a means for generating thermal energy.

[Operation] Since the recording heads or nozzles are divided into at least two groups and blank ejection is performed for each group, the number of recording heads or nozzles involved in one idle discharge is reduced compared to the conventional system. Therefore, the amount of heat generated by one dry ejection is reduced, and the temperature rise of the print head due to dry ejection can be suppressed, the decrease in ink viscosity due to the rise in print head temperature can be suppressed, and the density change of the printed image can be suppressed. It can be prevented.

[Examples] Examples of the present invention will be described below in detail and specifically based on the drawings.

FIG. 1 shows an example of an inkjet recording apparatus using the bubble jet recording method proposed by Canon II to which the present invention is applied. This example is a case of a multicolor recording apparatus, where l is a recording head unit consisting of a plurality of recording heads IA to ID each having multi-nozzles as shown in FIG. ~Recording liquids of different colors are ejected from the ID. In addition, individual recording heads IA to I
At D, electrothermal transducers 40 shown in FIG. 3 to which an applied voltage is supplied in order to generate thermal energy for ejecting the recording liquid are arranged along the liquid path. 2A
-2D are temperature detection means attached to each of the recording heads IA-ID, such as temperature sensors such as a thermistor, thermocouple, or varistor, and 20A-200 are heaters attached to each of the recording heads IA-ID. The temperatures detected by these temperature detection means 2A to 2D are supplied to a temperature control device (not shown) as described later, and the heaters 20A to 20D are turned on and off so as to maintain a predetermined set temperature. Ru.

3 is a carriage on which the recording head unit 1 is mounted and moves in the direction of arrow X along a guide rail 4; 5 is a timing belt that moves the carriage 3; and 6 is a carriage drive motor. The recording sheet 7, which is a recording medium, is held at a recording position by a sheet feed roller 9 driven by a sheet feed motor 8 and a holding roller pair 10 that cooperates with the sheet feed roller 9, and one line of recording is recorded. The sheet is fed in the direction of arrow Y every time the process is completed. 11
12 is a return pipe that returns ink from the recording heads IA to ID to the tank 13, and 14 is a supply pipe that supplies ink to each recording head IA-10. unit 1
This is a recovery device for multiple recording heads that performs an ink non-discharge recovery operation. Further, in FIG. 3, reference numeral 24 denotes an ink pressure feeding means for forcefully feeding ink from the tank 13 to the recording head unit 1. The supply pipe 11 and the return pipe 12
, tank 13, recovery device 14 and ink pressure feeding means 24
constitute the supply system and recovery system of this embodiment.

Next, the algorithm of this embodiment shown in FIGS. 1 to 3 will be explained with reference to FIGS. 4 and 5.

In this embodiment, the recording head unit 1 is capped by the recovery device 14 while the power is turned off.

When the power is turned on and operation starts, first step 5
1 After confirming the capping with the old version, proceed to step 51.
At 03, as an initial recovery operation, the ink is pressurized and circulated by the ink pressure feeding means 24, and henceforth, the printer is in a state where printing is possible at all times.

In step 5103, it is determined whether or not to start recording. If recording has started, in step 104, a plurality of nozzles 51, 52, 53 shown in FIG.
．． Recording is performed by ejecting ink from 54, 55, . . . , respectively.

When recording in step 5104 is performed, in steps 5105 and 3106 eight minutes have elapsed since the initial recovery in step 5102, recording is interrupted and capping is performed, and in step 5107 the nozzle 52 with an even nozzle number,
54. ... (hereinafter referred to as "even number nozzle") is ejected in the air. Next, in steps 5ioa and 5109, after 12 minutes have passed since the initial recovery in step 5102, recording is interrupted again and capping is performed, and in step 5IIO, nozzles with odd nozzle numbers 51, 53, 55, etc.
Hereinafter, these will be referred to as "odd number nozzles." ), then start recording again, and repeat steps 5L05 to 5107 every 8n minutes (n is a natural number), such as 16 minutes and 24 minutes after the initial recovery in step 5102. , 20 minutes later, 28 minutes later, and so on, repeating steps 5108 to 5ILO every 8n+4 minutes (n is a natural number). When recording is completed in step 5111, capping is performed in step 5112, and the process returns to step 5104.

On the other hand, if printing has not started in step 5103, the empty ejection of the even-numbered nozzles is repeated from the initial recovery in step 5102 in steps 5113 and 5114, with the state as it is (capped).
15, 5l16, the idle discharge of the odd numbered nozzles is repeated every 8n+4 minutes from the initial recovery in step 5102.

As is clear from the above explanation, in this embodiment, the number of nozzles at a series of ejection timings is divided into two groups, ie, even numbered nozzles and odd numbered nozzles, but it is also possible to divide the number of nozzles into the first half and the second half of the total nozzle number. can. For example, for a recording head with 128 nozzles, No. 1 to 64 nozzles and No.
, 65 to 128 nozzles may be divided into two groups to control the temperature increase.

Furthermore, in order to suppress temperature rise, the nozzles involved in air ejection can be divided into three or more groups. For example, if there are 3 groups, No, 3n nozzle group, No.
, 3n-1 nozzle group, No., 3n-2 nozzle group! ! +. One group of dry ejections may be performed at the timing of one dry ejection.

In addition, in the case of a multi-head system, half of the recording heads may be used for idle ejection at one time.

Actually, 400dpi (dots per inch), 1
FIG. 6 shows the results of a comparison of the head temperatures (temperatures of the print head) in Examples and Comparative Examples using an inkjet printing apparatus equipped with a 28-nozzle bubble jet print head.

In FIG. 6, the embodiment uses 64 nozzles every 4 minutes at a frequency of 4 kHz according to the algorithm shown in FIG.
, 3000 empty shots were performed from each nozzle.

On the other hand, in the comparative example, the frequency was 4 kHz, and each nozzle was 3000
This is the same as in the example in that the initial dry ejection was performed, but the difference is that the dry ejection was performed from all nozzles (128 nozzles) every 8 minutes.

As shown in FIG. 6, the temperature of the recording head in the example changes less and is stable compared to the comparative example.

The optical reflection density (Optical
Table 1 shows the results of measuring the density.

Table 1 As shown in Table 1, the density change in the example immediately before and immediately after the dry ejection is smaller than that in the comparative example.

The present invention particularly applies to a bubble jet recording head proposed by Canon ■ among inkjet recording systems.
This provides excellent effects in recording devices.

As for typical configurations and principles thereof, it is preferable to use the basic principles disclosed in, for example, US Pat. No. 4,723,129 and US Pat. No. 4,740,796. This method can be applied to both the so-called on-demand type and continuous type, but especially in the case of the on-demand type, it is necessary to arrange the liquid (ink) in accordance with the sheet and liquid path that hold it. By applying at least one drive signal that corresponds to recorded information and causes a rapid temperature rise exceeding nucleate boiling to the electrothermal transducer, the electrothermal transducer generates thermal energy, and the recording head This is effective because it causes film boiling on the heat acting surface of the liquid (ink), resulting in the formation of bubbles in the liquid (ink) in one-to-one correspondence with this drive signal. The growth and contraction of the bubble causes liquid (ink) to be ejected through the ejection opening to form at least one drop. It is more preferable to use this drive signal in a pulse form, since the growth and contraction of bubbles can be carried out immediately and appropriately, so that ejection of liquid (ink) with particularly excellent responsiveness can be achieved. Examples of this pulse-shaped drive signal include those described in US Pat. No. 4,463,359 and US Pat. No. 4,345,262. Incidentally, U.S. Patent No. 431 for the invention related to the temperature increase of the heat acting surface
If the conditions described in specification No. 3124 are adopted,
Even better recording can be performed.

The configuration of the recording head includes, in addition to the combination configuration of an ejection port, a liquid path, and an electrothermal converter (straight liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned specifications, a heat acting part. U.S. Pat. No. 4 discloses an arrangement in which the
558333 and US Pat. No. 4,459,600, respectively. In addition, JP-A No. 1236 of 1982 discloses a configuration in which a common slit is used as a discharge part of a plurality of electrothermal converters.
No. 70 and Japanese Patent Application Laid-Open No. 1384 of 1982, which discloses a configuration in which a discharge portion has an opening that absorbs pressure waves of thermal energy.
The present invention is also effective with a configuration based on Publication No. 61.

Furthermore, as a full-line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus, the length can be increased by combining multiple recording heads as disclosed in the above-mentioned specification. Either a configuration that satisfies the above requirements or a configuration as a single recording head formed integrally may be used, but the present invention can more effectively exhibit the above-mentioned effects.

In addition, a replaceable chip-type recording head that is attached to the device body enables electrical connection to the device body and ink supply from the device body, or a chip-type recording head that is installed integrally with the recording head itself. The present invention is also effective when a cartridge type recording head is used.

Further, it is preferable to add recovery means and preliminary auxiliary means for the recording head, which are provided as a configuration of the recording apparatus of the present invention, because the effects of the present invention can be further stabilized. Specifically, these include: a preheating means for the recording head using a caving means, a cleaning means, a pressurizing or suction means, an electrothermal transducer or another heating element, or a combination thereof; It is also effective to perform a preliminary ejection mode in which ejection is performed separately from printing in order to perform stable printing.

Furthermore, the recording mode of the recording device is not limited to only the mainstream color such as black (although the recording head may be configured integrally or by a combination of multiple colors, it may also be possible to record multiple colors of different colors or mixed colors). The present invention is also extremely effective for devices equipped with at least one full color image.

In the embodiments of the present invention described above, the ink is described as a liquid, but it may be an ink that solidifies at room temperature or below, but softens or becomes a liquid at room temperature, or an ink that is generally used in inkjet. It may be one that becomes soft or liquid in the temperature range of 30° C. or higher and 70° C. or lower, which is the temperature range for temperature adjustment. In other words, it is sufficient if the ink is in a liquid state when the recording signal is applied.In addition, the temperature increase caused by thermal energy can be actively used as energy to transform the ink from a solid state to a liquid state. Or, in order to prevent ink evaporation, ink that solidifies when left standing is used, and in either case, the ink is liquefied by applying thermal energy in accordance with the recording signal and is ejected as liquid ink. The present invention is also applicable to the use of inks that are liquefied only by thermal energy, such as those that already begin to solidify upon reaching the medium. In such a case, the ink may be ink as described in Japanese Patent Application Laid-Open No. 54-56847 or Japanese Patent Application Laid-Open No. 60-71260.
In the present invention, the most effective ink for each of the above-mentioned inks may be held as a liquid or solid in the porous sheet recesses or through holes, and may face the electrothermal converter. The device implements the film boiling method described above.

[Effects of the Invention] As explained above, the present invention has a plurality of nozzles or
By dividing the print heads into at least two groups and performing idle ejection, it is possible to prevent changes in image density and loss of color balance due to increases in the temperature of the print heads, and to obtain high-quality printed images. It has the effect of

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing an embodiment of an inkjet recording apparatus of the present invention, FIG. 2 is a perspective view of main parts of a recording head of this embodiment, and FIG. 3 is a supply system 8 and a recovery system of this embodiment. 4 is a flowchart showing the algorithm of this embodiment, FIG. 5 is a model diagram for explaining the algorithm of this embodiment, and FIG. 6 is a graph showing head temperatures of the embodiment and comparative example. be. 1... Recording head unit, IA, 2B, IC, 2D... Recording head, 2A,
2B, 2C, 2D... Temperature detection means, 3... Carriage, 4... Guide rail, 5... Timing belt, 6... Carriage drive motor, 7... Recording sheet, 8...・Sheet feed motor,
9... Sheet feed roller, lO... Holding roller pair, 11... Supply pipe, 12... Return pipe, 13...
・Tank, 14...Recovery device, 20A, 20
B, 20 (:, 200--Heater, 24--Ink pressure feeding means, 40--Electrothermal converter, 51.52, 53, 54.55--Nozzle. Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] 1. In an inkjet recording apparatus equipped with a plurality of recording heads that eject ink, the plurality of recording heads are divided into at least two groups, and each group is subjected to idle ejection at a time difference. An inkjet recording apparatus characterized by having a means for controlling idle ejection. 2. In an inkjet recording apparatus equipped with a recording head that discharges ink from a plurality of nozzles, the plurality of nozzles are divided into at least two groups, and each group performs idle discharge at a time difference. An inkjet recording device characterized by having a means. 3. The inkjet recording apparatus according to claim 2, wherein the idle ejection control means, when dividing the plurality of nozzles into groups, divides them into groups of nozzles with even nozzle numbers and groups of nozzles with odd nozzle numbers. 4. The inkjet recording apparatus according to claim 1, 2 or 3, wherein the recording head is a full line type recording head having a plurality of ejection ports over the entire width of the recording area of the recording medium. 5. The recording head uses thermal energy to eject ink from the ejection ports, and has an electrothermal converter as a means for generating thermal energy.
or 4. The inkjet recording device according to 4.