JPH11254693A - Method and apparatus for preventing clogging of ink jet head, and image forming method and system employing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress occurrence of nozzle clogging furthermore by an arrangement wherein a liquid having lower concentration than the composition of a recording material permeates the nozzle of an ink jet head through a semipermeable membrane from the outside. SOLUTION: When a chamber 14 receiving a low concentration liquid 12 on the back of a semipermeable membrane 11 is provided with a passage 16 for supplying the low concentration liquid 12, consumption of the low concentration liquid 12 can be dealt with by supplying the liquid 12 at an appropriate time through the supply passage 16 and a cover member 13 is not discarded. When an image is formed while preventing clogging of an ink jet head 2 utilizing the cover member 13, head face 2a of the ink jet head 2 is applied with the cover member 13 having a cushion material and/or the semipermeable membrane 11 at the time of nonprinting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for preventing clogging of an ink jet head used for image formation with a liquid recording material in a printer or the like, and an image forming method and apparatus using the same.

[0002]

2. Description of the Related Art An image forming method using an ink-jet head has the characteristics that the sound is quiet, a plurality of colors can be combined or a combined image can be formed in a short time, and the apparatus is simple and inexpensive. It is becoming widespread as machines.

The liquid recording material to be used, so-called ink,
While quick drying after printing is desired, high resolution of, for example, 300 dpi or more is desired. Therefore, it is necessary to miniaturize the printing dot diameter, for example, to 35 μm, and it is necessary to fly ink from a very small nozzle. It is of utmost importance that it does not clog. Accordingly, the first condition is to prevent clogging, and the type, ratio, and viscosity of the solvent are set so that the quick-drying property can be satisfied to the extent that it can be practically used.

However, the ink comes into contact with the air at the nozzle portion of the ink jet head, and the solvent component easily evaporates.
For this reason, nozzle clogging occurs, which causes poor ink flight during printing and, consequently, poor image quality. This clogging occurs because non-volatile components such as dyes and pigments in the ink are dried and solidified by evaporation of the solvent and fixed to the nozzle portion.

This drying phenomenon occurs not only when printing is stopped in an image forming apparatus such as a printer, but also when a specific nozzle, for example, a nozzle using black ink, such as a nozzle using a color other than black, frequently prints. This is also likely to occur when printing an image pattern that is not used for printing.

Therefore, conventionally, when printing is stopped, as shown in FIG. 8, a cap member d is placed over the head surface c where the nozzle b of the ink jet head is opened to close the head surface c, thereby suppressing the ink drying speed. ing. A suction path e is connected to the cap member d, and during printing of an image pattern in which a specific nozzle is not used for a long time, the inkjet head is moved to a portion outside the recording material range in a timely manner for the specific nozzle. In some cases, ink is intentionally ejected to prevent clogging.

[0007]

However, the method in which the nozzle is closed by the cap member sometimes causes clogging when printing is not performed for a long time, and cannot cope with long-term storage in a printer or the like. In addition, intentional ejection of ink by unused nozzles wastes ink and causes time loss in printing.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and an apparatus for preventing clogging of an ink jet head which can further reduce the occurrence of clogging of nozzles of the ink jet head, and an image forming method and apparatus using the same.

[0009]

In order to achieve the above object, a method for preventing clogging of an ink jet head according to the present invention comprises the steps of: One feature is that a low-concentration liquid having a lower concentration than the composition of the recording material is penetrated from the outside into the semipermeable membrane to prevent clogging of the inkjet head.

With this arrangement, during non-printing, the liquid recording material in the nozzle is opposed to the low-concentration liquid having a lower concentration than the recording material outside the nozzle via the semi-permeable film, and the semi-permeable film is not printed. By nature, the low-concentration liquid with low concentration induces penetration into the recording material with high concentration, the concentration decreases from the opening side of the nozzle, and the nozzle opening or the nozzle where the solvent is likely to evaporate when exposed to the atmosphere. Since the non-volatile components are prevented from drying and solidifying at the nozzles, clogging of the nozzles can be sufficiently prevented even if the non-printing state is long or long.

In such a method, when printing is not performed, a device for closing the nozzle by covering the head surface where the nozzle of the ink jet head is open with a nozzle is provided, and a semi-permeable membrane facing the head surface is provided on the lid member. This can be realized by disposing a low-concentration liquid having a lower concentration than the ink composition on the back of the semipermeable membrane. In principle, the semi-permeable membrane is made to be a contact surface that directly contacts the head surface, but if a recording material-permeable cushioning material is provided on the surface of the semi-permeable membrane so that it comes into contact with the head surface, A large head that makes it difficult to adhere to the lid member, that is, to the semipermeable membrane, because the adhesion of the lid member to the head surface is improved to prevent the low-concentration liquid and the recording material from leaking from the gap to the outside. It is effective when it is a plane.

In addition, by providing a replenishment path for replenishing the low-concentration liquid in the low-concentration liquid chamber in which the low-concentration liquid is disposed at the back of the semipermeable membrane, the replenishment path is provided even when the low-concentration liquid is consumed. It can be handled by replenishing the low-concentration liquid through the channel, and the lid member is not disposable.

In order to form an image using the above-described method and apparatus, the density of the liquid supplied to the nozzles of the inkjet head through the semi-permeable film during the non-printing period is higher than the composition of the recording material supplied to the inkjet head. Low-concentration liquid with a low concentration is supplied from the outside to permeate the ink side inside the nozzle,
The clogging of the inkjet head is prevented, the clogging prevention operation is canceled during printing, and printing is performed by causing ink to fly from the nozzles of the inkjet head in response to a print signal.

Thus, even if the non-printing state continues for any period of time, the clogging prevention operation is released whenever necessary while preventing clogging of the ink-jet head, and the clogging-free ink-jet is not affected by this operation. By starting printing by the head, it is possible to form a high-quality image without a recording material flying defect or image defect.

At the start of printing in this image formation, the low-density portion where the low-concentration liquid of the ink in the nozzles of the ink jet head has penetrated out of the printing area before the clogging prevention operation is released and the subsequent printing is performed. By performing the preliminary discharge process of discharging, even if the low-density portion in which the low-density liquid has penetrated in the nozzle opening or the entire nozzle of the recording material in the nozzle is only a small amount, it can be used at the beginning of printing. It is possible to avoid image noise caused by insufficient density used in image formation.

The image forming apparatus for forming an image as described above includes a conveying means for conveying the recording sheet, an ink jet head for printing on the recording sheet conveyed by the conveying means, and an ink jet head outside the printing operation range of the ink jet head. A cover member that is provided, covers the head surface where the nozzle of the inkjet head is opened with a semipermeable membrane, closes the nozzle, and arranges a low-concentration liquid having a lower concentration than the ink composition behind the semipermeable membrane; A head drive mechanism that moves the ink jet head to a cover member outside the printing operation range during printing and moves it to a predetermined printing position during printing, if necessary, while preventing clogging of the ink jet head during non-printing. Forming an image each time is automatically achieved.

In this case, the low-density portion in which the low-concentration liquid of the ink in the nozzle of the ink-jet head has permeated is ejected before the head drive mechanism moves the ink-jet head from the position facing the lid member to the printing position. By providing the preliminary ejection processing means, it is also possible to avoid the problem that the low-density portion in which the low-density liquid has penetrated in the nozzle opening portion of the recording material in the nozzle or the entire nozzle portion is used for image formation at the beginning of printing. It is achieved automatically, and the low-concentration liquid is supplied by the low-concentration liquid replenishing means through a supply path for supplying the low-concentration liquid to the low-concentration chamber in which the low-concentration liquid in the lid member is disposed. It can automatically respond to the low-concentration liquid being consumed over time.

Further objects and features of the present invention will become apparent from the following detailed description and drawings.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, typical embodiments of the present invention will be described in detail with reference to the drawings.

In this embodiment, an ink jet printer 1 as shown in FIG.
This is an example of a case where an ink 3 as a liquid recording material is caused to fly on a recording sheet 10 or the like according to an image signal to perform printing, thereby forming an image. The image signal can be obtained from any data source such as a personal computer, an image reader, or a host computer, or a web, or an external or internal storage medium, and requires a single or image forming function. The present invention can be used for various printers incorporated in information equipment and the like.

If data obtained by reading a document image is used, the present invention can be applied to a copying machine other than a printer.

The ink jet head 2 is, for example, shown in FIG.
Those having the structure as in each embodiment shown in FIG. 2 are used.
The outline thereof will be described with reference to FIGS.
A piezoelectric element (PZT) 4 is used in combination with a diaphragm 4a as an energy source for flying the laser beam. A voltage is applied to the piezoelectric element 4 through the head ejection drive unit 74 in accordance with the print data, causing distortion. This distortion changes the volume of the channel 5 filled with the ink 3. Due to this change in volume, the ink 3 is ejected from the nozzles 6 provided in the channel 5 toward the recording sheet 10 and flies, and printing on the recording sheet 10 is performed. As shown in FIGS. 5 and 6, a plurality of these printing mechanisms are provided for one ink jet head 2, and the channels 5 of each printing mechanism are supplied with ink 3 through a common ink chamber 5a at the back provided to communicate with each channel. Is supplied. In an ink jet printer that forms a color image, the combination of the piezoelectric element 4 and the channel 5 forms three colors of yellow, magenta, and cyan in order to form a color image by color synthesis.
It is provided corresponding to the nozzle row for each of the inks 3 of four colors, or black and black. There are various numbers and arrangement pitches of a plurality of nozzles 6 provided in one ink-jet head 2, and actually, based on specific conditions of these, the ink-jet head 2 and the recording sheet 1 are provided.
The main scanning and the sub-scanning by the relative movement with respect to 0 are performed in various states, and a planar image is formed. The ink 3 may be a commonly used dye or pigment.

However, as described above, when the non-printing state lasts for a long time or when the printer is stored for a long period of time, clogging is likely to occur, and this cannot be prevented conventionally.

Therefore, in this embodiment, in order to prevent this clogging, the nozzle 6 of the ink jet head 2 is attached to the nozzle 6 of the ink jet head 2 as shown in FIG. 1 and FIG.
A clogging prevention operation is performed by externally penetrating the low-concentration liquid 12 having a lower concentration than the ink composition as shown in FIG. It is preferable that the low-concentration liquid 12 has the same composition as that of the ink 3 in order to perform the permeation. However, the ink 3 may be of any type other than those currently in use, including those to be developed or provided, and the low-concentration liquid 12 may have a different composition from the ink 3. can do.

When the clogging prevention operation is performed as described above, the ink 3 in the nozzle 6 faces the low-concentration liquid 12 having a lower concentration than the ink 3 outside the nozzle 6 via the semi-permeable membrane 11 during non-printing. Then, due to the nature of the semipermeable membrane 11, the low-concentration liquid 12 having a low concentration is moved toward the ink 3 having a high concentration in FIG.
And the concentration decreases from the portion of the nozzle 6 on the opening 6a side. Therefore, since the non-volatile components are prevented from drying and solidifying at the opening 6a of the nozzle 6 where the solvent is likely to evaporate upon contact with the atmosphere, the clogging of the nozzle 6 can be sufficiently prevented even if the non-printing state is long or long. Can be prevented. Thereby, while preventing clogging of the inkjet head 2 during non-printing,
By driving the inkjet head 2, an appropriate image can be formed without the problem of clogging.

The low-concentration liquid 12 is basically good as long as it can prevent the nozzles 6 from being clogged with the ink 3. However, taking into consideration that natural leakage from the ink jet head 2 and the semi-permeable membrane 11 can be prevented, It is preferred to determine the low ratio of density to 3. A material containing no coloring material such as a pigment or a dye can also be used. In addition, low concentration liquid 1
2 penetrates into the nozzle 6 side when the liquid concentration on both sides of the semi-permeable membrane 11 becomes one at a stage where the nozzle 6 may be clogged, for example, as shown in FIG. It is preferable to set the conditions of the ink 3, the low-concentration liquid 12, and the semipermeable membrane 11 so that they are balanced and there is no further penetration.

In one embodiment, when the ink 3 is a dye-based ink, the concentration is about 4% and the viscosity at room temperature is about 3 cP, whereas the low-concentration liquid 12 has a concentration of about 0.5%. And the viscosity at room temperature is about 2 cP. When the ink 3 is a pigment, the concentration is about 5% and the viscosity is about 4 cP, whereas the low-concentration liquid 12 has a concentration of about 0.5% and a viscosity of 3 cP.
It should be about P. Solvents used include water, ethylene glycol, diethylene glycol, triethylene glycol, diethylene glycol-n-butyl ether, glycerin, polyethylene glycol, ethanol, propanol, butanol.

Examples of the semipermeable membrane 11 include a cellophane film, a collodion film, a denitration collodion film, a gel cellophane film, parchment paper, a polyvinyl alcohol film, a bacterial cellulose film, a fat film, a biological film, an ultracella filter film, a silflab film, and a molecular film. Sieve, and so on. However, various other known or provided ones can be adopted.

As shown in FIG. 1, the above-described method for preventing clogging is performed when the ink jet head 2 is not printed.
A device that covers the head surface 2a where the nozzle 6 is open with the lid member 13 and closes the nozzle 6 can be used. The form and specific shape of the cover member 13 are not particularly limited as long as the cover member 13 can be closed by covering the nozzle. As the embodiment shown in FIG. 1, a cap-type one having a low-concentration liquid chamber 14 is used, and a semi-permeable membrane 11 is provided at an opening 14a at the tip end facing the head surface 2a. The low-concentration liquid 12 is stored in the low-concentration liquid chamber 14 located at the bottom, so that the low-concentration liquid 12 is disposed on the back of the semi-permeable membrane 11. Each time the ink 11 is put on the ink jet head 2 so as to be in contact with the head surface 2a, the low-concentration liquid 12 is applied to the ink 3 in the nozzle 6 of the ink jet head 2 through the semipermeable membrane 11 as described above. By penetrating from the 6a side, clogging can be prevented. At the time of printing, the lid member 13 may be separated from the head surface 2a so that the positional relationship does not interfere with printing. The separation and connection of the ink jet head 2 and the cover member 13 may be achieved by relative movement by either or one of the movements, and the separation and connection method is not particularly limited.

In principle, the semipermeable film 11 may be a contact surface that directly contacts the head surface 2a as described above. However, as shown in FIG. A material-permeable cushioning material 15 is provided so that the head surface 2
a. Thereby, the lid member 1
3 improves the adhesion to the head surface 2a and prevents the low-concentration liquid 12 and the ink 3 from leaking out of the gap to the outside. This is effective when the large head surface 2a is difficult.

The cushioning material 15 itself may not have a function as a semi-permeable membrane, and can move toward the semi-permeable membrane 11 by transmitting the ink 3 as a liquid recording material. By allowing the low-concentration liquid 12 to penetrate into the ink material 3 in the cushion material 15 and the nozzles 6 without impeding the above-described clogging prevention effect, and retaining the liquid by soaking. It is possible to prevent the ink 3 and the low concentration liquid 12 from oozing out.

For example, foam rubber (cellular) obtained by foaming natural rubber, synthetic rubber, or the like by a mechanical stirring method, a foaming method, a pressurized gas method, a soluble substance blending method, or the like is used for the cushion material 15. Rubber), natural rubber, synthetic rubber, and polyvinyl chloride or phenol resin may be used in combination. Further, PE, PP, PUS, ABS, PV foamed by the decomposition type foaming agent method and the evaporation type foaming agent method.
Plastic foams such as C and polyurethane can also be employed. However, they need to have continuous foaming, not closed foaming.

As shown in FIGS. 1 and 2, a low-concentration liquid chamber 14 for disposing a low-concentration liquid 12 behind the semipermeable membrane 11.
If a replenishment path 16 for replenishing the low-concentration liquid 12 is provided, the low-concentration liquid 12 is consumed.
By replenishing the low-concentration liquid 12 in a timely manner through 6,
It is possible to cope with the consumption of the low concentration liquid 12, and the cover member 13 is not disposable. In the case of disposables, a supply structure is not required.

Further, in order to form an image with an operation for preventing clogging of the ink-jet head 2 using the lid member 13 shown in each of the above-described embodiments of FIGS. As shown in b), the head surface 2a of the ink jet head 2 is covered with a semipermeable membrane 11 or a lid member 13 having the semipermeable membrane 11 and the cushion material 15 to perform a clogging prevention operation. (C), the lid member 13 is separated from the ink jet head 2 to release the clogging prevention operation, and the positional relationship is set so as not to hinder the printing. Thereafter, the ink 3 is transferred from the nozzle 6 of the ink jet head 2 according to the print signal. To print.
In this way, regardless of the time and period in which the non-printing state lasts, the clogging of the inkjet head 2 is prevented, and the clogging prevention operation is released whenever necessary, and the clogging-free inkjet head 2 is not affected by this operation. , Printing can be started to form a high-quality image free from flying defects of the ink 3 and image defects.

In this embodiment, in particular, at the start of printing in this image formation, the ink 3 in the nozzles 6 of the ink jet head 2 is not used until the clogging prevention operation is released and the subsequent printing is performed. A preliminary ejection process for ejecting the low-concentration portion 3a in which the low-concentration liquid 12 permeates as shown in FIG. Thus, even if the low-concentration portion 3a in which the low-concentration liquid 12 has permeated the opening 6a of the nozzle 6 of the ink 3 in the nozzle 6 is a very small amount, it is used for image formation at the beginning of printing. Thus, it is possible to avoid image noise due to insufficient density. in this case,
Considering that the low-concentration liquid 12 varies in the permeation area of the nozzle 6 toward the nozzle 6 due to the difference in the elapsed time of the operation for preventing the clogging, the ink 3 having the normal concentration finally becomes as shown in FIG. However, even if one drop is preliminarily ejected, it is difficult to perform the predischarge operation to slightly exceed the low-density portion 3a of the volume corresponding to the maximum permeation area shown in FIG. It is preferable to prevent the density portion 3a from affecting the image.

The ink jet printer 1 shown in FIG. 7 includes a conveying unit 31 that conveys the recording sheet 10 in order to form an image with the above-described clogging prevention operation;
An ink-jet head for printing on a recording sheet conveyed by the conveying means, and a semi-permeable membrane 11 covering the head surface 2a provided outside the printing operation range of the ink-jet head 2 and opening the nozzle 6 of the ink-jet head 2 A cover member 13 for performing the above-described clogging prevention operation, and a cover member 13 outside the printing operation range when the inkjet head is not printed.
And a head drive mechanism 32 that moves the ink jet head 2 to a predetermined printing position during printing by preventing the inkjet head 2 from being clogged during non-printing. However, forming an image whenever necessary is automatically achieved. Moreover,
Before the head drive mechanism 32 moves the inkjet head 2 from the position facing the lid member 13 to the printing position,
A preliminary ejection processing unit 33 is provided for ejecting the low-concentration portion 3a in which the low-concentration liquid 12 of the ink 3 in the nozzle 6 of the inkjet head 2 has penetrated. Thereby, it is also possible to automatically avoid the problem that the low-density portion 3a in which the low-density liquid 12 has penetrated into the opening 6a of the nozzle 6 of the ink 3 in the nozzle 6 is used for image formation at the beginning of printing. Is achieved. Further, a replenishment path 1 for replenishing the low-concentration liquid 12 into the low-concentration liquid chamber 14 in which the low-concentration liquid 12 of the lid member 13 is disposed.
6, the low-concentration liquid 12
Is supplied appropriately. This makes it possible to automatically cope with the low-concentration liquid being consumed over time.

Although the specific configuration of each of these means and devices is not particularly limited, in the embodiment shown in FIG.
1 feeds the recording sheets 10 stacked on the paper feed tray 35 one by one by a paper feed roller 36,
The sheet is conveyed onto the platen 37 by 6a, and is used for printing by the inkjet head 2 here. Each time printing is performed for one main scan, a sub-scan is carried out in which the recording sheet 10 is conveyed by one pitch by the conveying roller 36a. By repeating this, an image corresponding to the print data is formed. The printed recording sheet 10 is discharged by a paper discharge roller 38 arranged downstream of the printing unit and a spur roller 39 pressed against the paper discharge roller 38.

The head drive mechanism 32 is provided with a carriage 42 which is moved in the main scanning direction along a guide 41, and is equipped with an ink jet head 2 together with an ink cartridge 43 for supplying ink to the carriage 42. Further, movement between the printing area and the maintenance unit 44 provided with the lid member 13 and the suction and cleaning mechanism 431 outside the printing area is performed. To this end, a drive pulley 45 directly connected to a motor (not shown) or the like and a timing belt 47 stretched over an idle pulley 46 provided opposite to the drive pulley 45 are moved between the print area and the maintenance section 44 between the print area and the maintenance section 44. The timing belt 47 causes the carriage 42 to perform main scanning in the forward direction or in both the forward and reverse directions.
Move it to the required position.

The ink jet head 2 includes a head 21 for black ink and a head 2 for ink of three colors of yellow, magenta and cyan which are used together when printing a color image.
2, the cover member 13 is also provided with the head 21.
A cover member 13a for the head 22 and a cover member 13b for the head 22 are provided. However, they may be formed integrally, or may be divided in any color. When the ink jet head 2 faces the lid member 13, the lid member 13 is slightly moved up and down to come into contact with the head surface 2a to perform the clogging prevention operation or cancel the clogging prevention operation. Thereby, when the inkjet head 2 moves to or moves away from the maintenance unit 44, it is possible to prevent damage due to contact between the head surface 2a, the semipermeable membrane 11, and the like. However, instead of moving the lid member 13 up and down, the ink jet head 2 may be moved up and down. For example, this can be achieved even when the carriage 42 is tilted or raised.

The pre-ejection processing means 33 receives a pre-ejection signal issued prior to a print data or a print start signal from a control device 49 using a microcomputer or the like for controlling the operation of the printer 1, and outputs a head ejection drive unit. At 74, a preliminary ejection operation is performed. The preliminary ejection processing unit 33 may be an external device of the control device 49, but may use the internal function thereof. Further, the preliminary ejection processing means 33 includes:
When the maintenance unit 44 has the suction and cleaning mechanism 431 as described above, when the head driving mechanism 32 is also driven and controlled so as to perform the preliminary ejection, the low-density portion 3a from which the ink 3 has been preliminary discharged is suctioned out. Can be automatically discarded. In addition, the suction and cleaning mechanism 431 controls the inkjet head 2 after printing under the operation control of the control device 49 and before printing by releasing the clogging prevention operation.
The head surface 2a and the nozzle 6 can be cleaned by suction and cleaning, and the reliability of printing is further improved.

The low-concentration liquid replenishing means 34 uses a pump 51 provided in the replenishment path 16 and operates the pump 51 in response to a replenishment signal from the control device 49 or the like to cause the low-concentration liquid 12 to flow from the storage section 52 to the low-concentration liquid chamber. Replenish to 14. The replenishment signal may be counted by the control device 49 by counting the number of times of the clogging prevention operation, the time, and the like, and may be performed for a predetermined time each time the signal reaches a predetermined value. When there is a delivery pressure of the low-concentration liquid 12 in the storage unit 52, an on-off valve such as an electromagnetic valve that can be electrically controlled can be used instead of the pump 51.

The black head 21 is frequently used for printing, while the head 22 is used only for color image formation. Accordingly, clogging may occur on the side of the head 22 while black printing is continuously performed for a long time. As described above, when the specific inkjet head is printing an image pattern that is not involved in printing, the head 22 that is the specific inkjet head is printed.
In the case where clogging occurs, it is preferable to continue the clogging prevention operation during printing on this specific inkjet head by another inkjet head. This includes
A specific inkjet head is mounted on the carriage 42 so as to be movable, for example, rotatable, between a position facing the printing side and a position away from the printing side, and a cover member that is positioned away from the printing side when not printing. If a clogging prevention operation is performed with the cover 13, the printing can be realized without disturbing the printing.
Such measures are preferably performed individually for heads that can be specific ink jet heads so that each can be dealt with in a timely manner.

[0043]

According to the method and apparatus for preventing clogging of an ink jet head according to the present invention, it is possible to prevent a low-concentration liquid from penetrating into a recording material in a nozzle through a semipermeable membrane even when a non-printing state is long or long. The clogging of the nozzle can be sufficiently reduced or prevented by the designed clogging prevention operation.

When a recording material-permeable cushioning material is provided on the surface of the semi-permeable membrane so as to come into contact with the head surface, the adhesion of the lid member to the head surface is improved, and the height of the cover member is reduced. Since the concentration liquid and the recording material are prevented from leaking to the outside, it is effective when the head has a large head surface which is difficult to adhere to the cover member, that is, to the semipermeable membrane.

Further, by providing a replenishment path for replenishing the low-concentration liquid in the low-concentration liquid chamber in which the low-concentration liquid is disposed at the back of the semipermeable membrane, the replenishment path can be supplied even when the low-concentration liquid is consumed. It can be handled by replenishing the low-concentration liquid through the channel, and the lid member is not disposable.

According to the image forming method and apparatus of the present invention, clogging of the ink jet head is prevented by a clogging prevention operation at the time of non-printing, and the clogging prevention operation is released at the time of printing, and the ink jet head is responded to a print signal. By performing ink printing by ejecting ink from the nozzles, the clogging prevention operation can be canceled whenever necessary and the clogging operation can be canceled, even if the non-printing state continues for any period of time. Printing can be started by an ink-jet head without clogging without any influence, and a high-quality image free of recording material flying defects and image defects can be formed.

Also, at the start of printing, a pre-ejection process for ejecting a low-density portion where the low-concentration liquid of the ink in the nozzle of the ink jet head has permeated out of the printing area before the clogging prevention operation is released and the subsequent printing is performed. By doing so, even if the low-concentration part in which the low-concentration liquid permeates the nozzle opening of the recording material in the nozzle or the entire nozzle is a very small amount, it is used for image formation at the beginning of printing. Thus, it is possible to avoid image noise due to insufficient density.

In the apparatus, the low-concentration liquid is appropriately replenished by the low-concentration liquid replenishing means through the replenishment path to the low-concentration chamber, so that the low-concentration liquid is automatically consumed as time passes. Can respond.

[Brief description of the drawings]

FIG. 1 shows a method and an apparatus for preventing clogging in an ink jet printer according to a representative embodiment of the present invention.
FIG. 4 is a cross-sectional view showing one embodiment.

FIG. 2 is a cross-sectional view illustrating another embodiment of a method and apparatus for preventing clogging.

FIG. 3 is a flow chart of a process before starting printing in the embodiment shown in FIG. 1;
Two exemplary procedures are shown, in which (a) shows a clogging prevention operation start state, (b) shows a clogging prevention state, and (c) shows a preliminary ejection operation processing state when the clogging prevention operation is canceled.

FIG. 4 is a cross-sectional view illustrating a schematic configuration of an inkjet head unit and a preliminary ejection mechanism of the inkjet printer according to the embodiment of the present invention.

FIG. 5 is a cross-sectional view of the ink-jet head shown in FIG.

FIG. 6 is a front view of the inkjet head unit shown in FIGS. 4 and 5;

FIG. 7 is a perspective view showing a schematic configuration of the entire ink jet printer of the present invention.

FIG. 8 is a cross-sectional view illustrating a method and apparatus for preventing clogging of an inkjet head of a conventional inkjet printer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink jet printer 2 Ink jet head 2a Head surface 3 Ink 3a Low concentration part 6 Nozzle 6a opening 11 Semipermeable membrane 12 Low concentration liquid 13 Cover member 14 Low concentration liquid chamber 15 Cushion material 16 Supply path 31 Transport means 32 Head drive mechanism 33 Reserve Discharge processing means 34 Low-concentration liquid replenishment means 49 Controller

Claims (10)

[Claims] An ink jet head in which a low-concentration liquid having a lower concentration than the composition of a recording material is externally penetrated into a nozzle of an ink jet head to which a liquid recording material is supplied through a semi-permeable membrane during non-printing. A method for preventing clogging of an ink-jet head, characterized by preventing clogging of the ink jet head. 2. A method according to claim 1, further comprising the step of: covering a head surface of the ink jet head where the nozzle is opened with a cover member which covers the nozzle surface during non-printing and closes the nozzle; and providing the cover member with a semipermeable membrane facing the head surface. An apparatus for preventing clogging of an ink-jet head, wherein a low-concentration liquid having a lower concentration than a composition of a liquid recording material supplied to the ink-jet head is disposed on a back portion. 3. The ink jet head clogging prevention device according to claim 2, wherein the semi-permeable membrane forms a contact surface with the head surface. 4. The apparatus for preventing clogging of an ink jet head according to claim 2, wherein a cushioning material permeable to a recording material is provided on a surface of the semipermeable membrane. 5. The ink-jet apparatus according to claim 2, wherein the low-concentration liquid chamber at the back of the semipermeable membrane, in which the low-concentration liquid is disposed, is provided with a supply path for supplying the low-concentration liquid. Head clogging prevention device. 6. A non-printing liquid having a low concentration lower than the composition of a recording material of a liquid supplied to the ink-jet head via a semi-permeable membrane is externally penetrated into a nozzle of the ink-jet head during non-printing, thereby clogging the ink-jet head. An image forming method in which a clogging prevention operation is released during printing, and a recording material is caused to fly from a nozzle of an inkjet head in accordance with a print signal to perform printing, thereby forming an image. 7. At the start of printing, a low-density portion in which a low-density liquid of a recording material in a nozzle of an ink-jet head has permeated is ejected outside a printing area until a clogging prevention operation is canceled and printing is performed afterward. The image forming method according to claim 6, wherein a preliminary ejection process is performed. 8. A conveying means for conveying a recording sheet, an ink jet head for printing on the recording sheet conveyed by the conveying means, and a head provided outside the printing operation range of the ink jet head and having nozzles of the ink jet head opened. A cover member in which a low-concentration liquid having a concentration lower than the composition of the recording material of the liquid supplied to the inkjet head is disposed behind the semi-permeable membrane and the nozzle is closed, and An image forming apparatus, comprising: a head drive mechanism for moving an inkjet head to a predetermined printing position during printing, with the inkjet head facing a cover member outside a printing operation range. 9. A low-density portion where a low-density liquid of a recording material in a nozzle of an ink-jet head has permeated before a head drive mechanism moves the ink-jet head from a position facing the lid member to a printing position. The image forming apparatus according to claim 8, further comprising a preliminary ejection processing unit that performs ejection outside the region. 10. A low-concentration chamber for disposing a low-concentration liquid in a lid member is provided with a supply path for supplying the low-concentration liquid, and a low-concentration liquid replenishing means for appropriately supplying the low-concentration liquid through the supply path. The image forming apparatus according to claim 8.