JPH0465249A - Ink-jet recorder - 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 [Industrial Application Field 1] The present invention relates to a drop-on-demand type inkjet recording device that can be used as a copier, facsimile, computer, word processor, or a composite device thereof.

[Prior Art] Inkjet recording apparatuses that record information such as characters and images by ejecting ink from a recording head are widely known.

Many of these types of devices are configured to perform printing by ejecting ink directly from the ejection ports of the print head. In some cases, various configurations were added to the . For example, there have been cases in which a configuration has been added that performs a so-called capping operation in which the ejection surface of the recording head is covered with a cap means to prevent ink existing near the ejection ports from drying or evaporating.

However, in a low-humidity environment or during long-term suspension, it is difficult to maintain a ready state for ejecting with just the capping operation. A recovery operation was also performed in which the ink was discharged from the ejection port by applying pressure or suction force. During this recovery operation, approximately the same amount of ink is normally ejected as ejecting the entire surface of a recording medium of size 4 in the Japanese Industrial Standards A column.
It had been abandoned.

[Problem to be solved by the invention]

However, the above conventional example has the following problems.

In the recovery operation, a non-negligible amount of ink is discarded compared to the amount of ink used during printing, leading to wasted ink.

When starting recording from a standby state, it takes time to start recording because the pump needs to restore pressure or suction before starting recording.

The present invention has been made in view of these circumstances, and its purpose is to provide inkjet recording that can reduce ink waste while keeping ink in a ready-to-discharge state at all times, and shorten the time from standby to start of recording. The goal is to provide equipment.

[Means for Solving the Problems] An inkjet recording apparatus of the present invention is a drop-on-demand type inkjet recording apparatus that performs recording by ejecting ink from an ejection port of a recording head onto a recording medium, wherein the recording head is on standby. While in this position, the ink pressure in the nozzle of the recording head is maintained at a pressure equal to or higher than the meniscus destruction pressure, and the ink is discharged from the nozzle. It is characterized by having an ink recovery means for returning the ink.

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

The recording head uses thermal energy to eject ink from the ejection ports, and may include an electrothermal transducer as a means for generating thermal energy.

[Effect]

While the recording head is in the standby position, the ink pressure in the nozzles of the recording head is maintained at a pressure equal to or higher than the meniscus destruction pressure by the pressurizing means, so that ink flows out from the nozzles. The ink that has flowed out is returned to the ink supply tank by the ink recovery means, and is again supplied to the recording head by the pressure means. In this way, while the print head is in the standby position, ink always flows out from the nozzles of the print head.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

1 to 3 show a first embodiment of the present invention, FIG. 1 is a perspective view of the main part, FIG. 2 is an explanatory diagram showing the recording head and its vicinity when the carriage is in a standby position, 1g
FIG. 3 is an explanatory diagram showing the recording head and its vicinity when the carriage is in the standby position.

Here, 1 is a carriage on which a recording head 2 is mounted, and 3 and 4 are carriage guides that hold the carriage 1 so as to be movable back and forth in the six directions of arrows. An endless heald 5 is connected to the carriage 1, and the carriage 1 is moved along the surface of a recording medium 31 by a heald motor 6. Reference numeral 9 denotes a paper feed roller that feeds the recording medium 31 in the direction of arrow B, and is driven by the paper feed motor 7. A tension roller 11 presses the recording medium 31 together with a pinch roller 12 and rotates at a linear speed slightly higher than that of the paper feed roller 9, thereby applying tension to the recording medium 31 on the platen 8. Note that the tension roller 11 is driven by the paper feed motor 7 via a gear train (not shown). 10 is a recording medium guide that guides the recording medium 31.

Here, the head 81 constituting the recording head 2 will be explained based on FIG. 7.

The head 81 has a plurality of discharge ports 82 arranged in a row.
In order to eject ink from the ink, an electrothermal converter 83 that generates thermal energy to which an applied voltage is supplied is provided for each liquid path. By applying a drive signal, the electrothermal transducer 83 generates thermal energy to cause film boiling and form bubbles in the ink liquid path. The growth of this bubble causes ink droplets to be ejected from the ejection port 82.

Ink is supplied to the recording head 2 from an ink supply tank 14 via an ink supply tube 15 and an ink pump 17 as a pressurizing means. An ink recovery tank 13 is provided at the bottom of the recording head 2 for recovering ink pushed out by the ink pump 17 via an ink guide 25, and the ink recovery tank 13 and the ink supply tank 14 are connected to an ink recovery tube 16 and They are communicated via a first valve 26. These ink recovery tank 13, ink recovery tube 16, and first valve 26 constitute ink recovery means. The water head of the ink supply tank 14 is kept lower than the water head of the ink recovery tank 13, and the ink accumulated in the ink recovery tank 13 is configured to return to the ink supply tank 14 due to the difference in water head.

18 is a head standby hook, and the recording head 2 is in a standby position opposite to this head standby hook 18 when not recording. There is a drain tank 28 below the head standby hook 18, which stores ink from a drain tube 29 (see Figures M2 and 3) via a second valve 27. 1
Reference numeral 9 denotes an air nozzle which, when the orifice surface (discharge surface) of the recording head 2 is in the head standby hook 18, moves the air pump 2 in an oblique direction toward the orifice surface.
It is provided to blow air (indicated by arrow X in Figure 3) from zero.

Next, the operation of the embodiment shown in FIGS. 1 to 3 will be explained with reference to FIG. 4.

When the power is turned on (step 41), the first valve 26 is closed and the second valve 27 is set to oven, while the recording head 2 remains in a standby state, in order to discard the ink that has increased in viscosity within the recording head 2. Then, drive the ink pump 17 (
Step 42) Let the ink flow out and ink collection tank 1
3 through a drainage tube 29 into a drainage tank 28. Thereafter, the ink pump 17 is turned off (step 43) to stop ink from flowing out, and the air pump 20 is turned on (step 44) to jet air obliquely from the air nozzle 19 onto the ejection surface of the recording head 2. After blowing away the ink attached to the ejection surface, the air pump 20 is turned off (step 45), and the carriage 1 is moved to the first position.
It is driven in the direction of the arrow in the figure (step 46) to start recording. During recording, the carriage 1 moves in the direction of the arrow claw, and droplets are selectively ejected from the ejection ports of the recording head 2 to print one line (steps 47 and 48).
). After the carriage 1 is transported by a distance corresponding to the width of the recording medium 31 by the belt motor 6, it is driven in the opposite direction to the direction of the arrow claw, and a photo sensor (not shown) detects the recording start position, and starts the recording. Return to position.

Here, the recording medium 31 is fed by the nozzle width of the recording head 2 by the paper feed motor 7 (step 49), and the operations of the above-mentioned steps 47, 48 and 49 are repeated again.

When recording is completed, the carriage 1 is moved to a standby position where the recording head 2 faces the head standby box 8 (step 50).

In the standby position, the first valve 26 is connected to the oven and the second valve 2
7 is closed (step 51).

The ink pump 17 is turned on immediately from this state (
Step 52). At this time, the ink pump 17 is maintained at a pressure higher than the meniscus breaking pressure in the nozzles of the recording head 2. The meniscus is destroyed and the ink flows out from the ejection ports of the recording head. This spilled ink is guided to the head standby box 18 and the ink guide 25 and reaches the ink recovery link 13. The ink recovery tank 13 and the ink supply tank 14 are communicated by an ink recovery tube 15, and the water head of the ink recovery tank 13 is set higher than the water head of the ink supply tank 14.
Ink The ink in the ink recovery tank 13 immediately returns to the ink supply tank 14, so that the ink always flows out from the ejection ports while the recording head 2 is in the standby position.

In addition, the ejection surface of the recording head 2 is the head standby box]8
The recording head 2 is placed in a substantially closed space formed by the ink recovery tank 13 and the ink recovery tank 13, and the ink is flowing.
The evaporation of ink inside the nozzle is almost negligible. When a print signal indicating restart of printing is input from the standby state (step 53), the ink pump 17 is immediately turned off.

57), the process returns to step 44 and resumes recording in a short time.

As a result, ink can always be kept in a dischargeable state without wasting ink, and printing can be restarted from a standby state in a short time.

5 and 6 show a second embodiment of the invention.

In the first embodiment, an ink pump was used to drain the ink, but in this embodiment, the ink supply tank 64 is configured to be vertically movable by a tank drive mechanism (not shown). A one-way valve 61 is provided inside. As a result, as shown in FIG. 5, when the ink supply tank 64 is raised, the ink in the ink supply tank 64 is supplied to the recording head 62 via the ink supply tube 65, and the ejection openings of the recording head 62 are supplied. Ink flows out and accumulates in the ink recovery tank 63.

On the other hand, as shown in FIG. 6, when the ink supply tank 64 is lowered, the ink accumulated in the ink recovery tank 63 flows into the ink recovery tube, and further this ink passes through the one-way valve 6 in the ink supply tank 64. and return to the ink supply tank 64. As a result, the same effects as in the first embodiment can be expected. Note that the head standby box 68 can be the same as the head standby box 18 shown in FIGS. 1 to 3.

In the first embodiment, both the ink recovery tank and the ink supply tank are mounted on the carriage, but one or both of them may be fixed to the main body of the inkjet recording apparatus.

Furthermore, even in a color inkjet recording device that requires a large number of recording heads, if the number of head standby boxes and ink collection tanks is divided according to the number of recording heads,
Similar effects can be expected.

Furthermore, the print head can be used not only for serial scan types that perform printing while moving the print head, but also for full line types that have multiple ejection ports over the entire recording width of the print medium. The present invention can be applied by making it movable from the position to the standby position.

The present invention brings about excellent effects particularly in recording heads and recording apparatuses of the bubble jet method proposed by Canon 1 among ink jet recording methods.

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. In particular, in the case of the on-demand type applied to the present invention, the electrothermal transducer arranged corresponding to the sheet holding the liquid (ink) or the liquid path corresponds to recorded information. By applying at least one drive signal that causes a rapid temperature rise above boiling, the electrothermal transducer generates thermal energy that causes Bboiling to occur on the thermally active surface of the recording head, resulting in this drive signal This is effective because it allows bubbles to be formed in the liquid (ink) in one-to-one correspondence. 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 because the growth and contraction of the bubbles can be carried out immediately and appropriately, so that liquid (ink) ejection with particularly excellent response can be achieved. This pulse-shaped drive signal is described in US Pat. No. 44,633.
Those described in Japanese Patent No. 59 and Japanese Patent No. 4,345,262 are suitable. Furthermore, if the conditions described in US Pat. No. 4,313,124 concerning the temperature increase rate of the heat acting surface are adopted, even more excellent recording can be achieved.

The configuration of the recording head includes, in addition to the combined configuration of ejection ports, liquid paths, and electrothermal converters (straight liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned specifications, a heat acting section. US Pat. No. 4,558,333 and US Pat. No. 4,459,600 disclose a configuration in which the
They may be those described in the respective specifications. In addition,
Japanese Unexamined Patent Publication No. 123670 of 1981 discloses a configuration in which a common slit is used as a discharge part of a plurality of electrothermal converters, and an aperture that absorbs pressure waves of thermal energy is used as a discharge part. The present invention is also effective as a configuration based on Japanese Unexamined Patent Application Publication No. 138461 of 1981, which discloses a configuration corresponding to.

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 a recovery means for the recording head, a preliminary auxiliary means, etc., which are provided as a configuration of the recording device of the present invention, because the effects of the present invention can be further stabilized. Specifically, these include 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 a recording mode in which only the mainstream color such as black is used; the recording head may be configured integrally or in combination with a plurality of recording heads; 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 explained as a liquid, but it is 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. That is, it is sufficient if the ink is in a liquid state when the recording signal is applied. In addition, it is possible to actively prevent temperature rise due to thermal energy by using it as energy to transform the ink from a solid state to a liquid state, or to use ink that solidifies when left in order to prevent ink evaporation. Iruka,
In any case, some types of ink liquefy when thermal energy is applied in accordance with the recording signal and are ejected as liquid ink, and some types of ink that begin to solidify by the time they reach the recording medium, are liquefied only by thermal energy. The use of ink having such properties is also applicable to the present invention. In such a case, the ink is held as a liquid or solid in the recesses or through-holes of the porous sheet and is heated by electric heat as described in JP-A-5456-847 or JP-A-60-71260. It may also be in a form such that it faces the converting body. In the present invention, the most effective method for each of the above-mentioned inks is to implement the above-mentioned film boiling method.

[Effects of the Invention] As explained above, the present invention maintains the ink pressure in the nozzle of the recording head at a pressure equal to or higher than the meniscus destruction pressure while the recording head is in the standby position, and causes the ink to flow out from the nozzle. In addition, by collecting the spilled ink and returning it to the ink collection tank, the following effects can be achieved.

A recovery operation is required only immediately after the power is turned on, and after that, ink is not wasted for anything other than printing. Therefore, it is possible to reduce running costs.

When starting recording from a standby state, no recovery operation is required, so the time required to start recording can be shortened.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of main parts showing the first embodiment of the present invention, and FIG.
The figure is an explanatory diagram showing the print head and its vicinity when the carriage is in the standby position, FIG. 3 is an explanatory diagram showing the print head and its vicinity when the carriage is in the standby position, and FIG. 4 is an explanatory diagram showing the print head and its vicinity when the carriage is in the standby position. A flowchart showing example operation,
5 and 6 are explanatory diagrams showing a second embodiment of the present invention, respectively, and FIG. 7 is a partially cutaway perspective view of the head. 1... Carriage, 2... Recording head, 3.4... Carriage guide, 5... Endless belt, 6... Belt motor 7... Paper feed motor 8... Platen, 9. ...Paper feed roller O...Recording medium guide, 1...Tension roller 2...Pinch roller 3...Ink collection tank, 4...Ink supply tank, 5...Ink supply tube, 6... Ink collection tube, 7... Ink pump, 8... Head standby box, 9... Air nozzle, O... Air pump, 6.27... Valve, 8... Exhaust Liquid tank, 29.--Drainage tube.

Claims (1)

[Scope of Claims] 1. In a drop-on-demand type inkjet recording apparatus that performs recording by ejecting ink from an ejection port of a recording head onto a recording medium, while the recording head is in a standby position, the recording head is It is characterized by comprising a pressurizing means for maintaining the ink pressure in the nozzle at a pressure equal to or higher than the meniscus destruction pressure and causing the ink to flow out from the nozzle, and an ink collecting means for collecting the flowing out ink and returning it to the ink collection tank. Inkjet recording device. 2. The inkjet recording apparatus according to claim 1, wherein the recording head is a full-line type recording head having a plurality of ejection ports over the entire recording width of the recording medium. 3. 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.
The inkjet recording device described above.