1. Technical Field
The present invention relates to a liquid ejecting apparatus on which a liquid ejecting head which ejects liquid through nozzle openings is mounted.
2. Related Art
With the development of a personal computer, a graphic processing can be executed relatively easily. Therefore, a liquid ejecting apparatus capable of outputting a hard copy of a color image, for example, which is displayed on a display, with high quality has been demanded. In order to meet such demand, there has been provided an ink jet recording apparatus on which an ink jet recording head which ejects ink droplets, for example, as liquid is mounted.
The ink jet recording apparatus gives noises of relatively small at the time of printing, and can form small dots at a high density. Therefore, the ink jet recording apparatus is used in various types of printing including color printing.
Such ink jet recording apparatus includes an ink jet recording head and a paper feeding unit. The ink jet recording head receives ink supply from an ink storage unit. The paper feeding unit moves a recording paper relatively with respect to the ink jet recording head. In the ink jet recording apparatus, ink droplets are discharged onto the recording paper from the ink jet recording head in accordance with a printing signal to form dots so that recording is performed.
Further, nozzle openings through which inks of black, yellow, cyan, and magenta can be discharged are provided on a common head holder (carriage). With this, not only text printing with the black ink but also full color printing can be performed by changing each discharge ratio of the inks.
Such ink jet recording head discharges ink pressurized in a pressure generation chamber as ink droplets onto a recording paper through the nozzle openings so as to perform printing. Therefore, there arises a problem that clogging is caused on the nozzle openings because of increase in ink viscosity due to the evaporation of a solvent from the nozzle openings, solidification of ink, adherence of dusts, mixing of air bubbles, or the like, resulting in printing failure.
In order to solve such problem, the ink jet recording apparatus includes a capping device and a cleaning device in many cases. The capping device seals peripheries of the nozzle openings of the ink jet recording head while printing is not performed. The cleaning device cleans a nozzle plate as needed.
The capping device not only has a function as a cap which prevents ink in the nozzle openings from being dried but also has a so-called cleaning function. To be more specific, the capping device also has the cleaning function of eliminating clogging of the nozzle openings by sealing the peripheries of the nozzle openings on the nozzle plate with a cap member and sucking ink from the nozzle openings with a negative pressure from a suction pump when the clogging occurs on the nozzle openings.
A discharge processing of forcibly discharging ink in order to eliminate clogging of the ink jet recording head is called a cleaning operation. Such cleaning operation is executed when printing is restarted after printing has not been performed for a long time or when a user presses a cleaning switch for eliminating clogging of the ink jet recording head. Further, the cleaning operation is a processing including a wiping operation by a cleaning member formed by an elastic plate such as a rubber after ink droplets have been discharged.
Further, the ink jet recording apparatus also includes a function of applying a driving signal, which does not relate to printing, to the ink jet recording head so as to make the ink jet recording head discharge ink droplets. This function is called a flushing operation. The flushing operation is executed every constant period for recovering an abnormal state of a meniscus in the vicinity of the nozzle openings of the head so as to prevent the clogging of the nozzle openings through which small ink droplets are discharged at the time of the printing from occurring (for example, see JP-A-2005-335404). The abnormal state of the meniscus in the vicinity of the nozzle openings is caused by the wiping operation or the like at the time of the cleaning operation.
In the configuration as described in JP-A-2005-335404, when a cap opening operation is performed, if liquid adheres to an abutment face of a cap member against a nozzle face (face on which the nozzle openings are formed) or the vicinity of the abutment face, a liquid film is formed on a space between the abutment face of the cap member against the nozzle face and the nozzle face when the cap member and the nozzle face are separated from each other. Note that the cap opening operation is an operation of separating the cap member from peripheries of the nozzle openings on a nozzle plate. The liquid film is formed when a capillary force acts on the space due to viscosity of the liquid droplets and the space has such a size that the capillary force acts thereon even if the abutment portion of the cap member against the nozzle face and the nozzle face do not abut against each other.
In a process where the cap member and the nozzle face are further separated from each other, the liquid film formed on the space is elongated. With this, a sealed space formed by the nozzle face and the cap member is enlarged so that a pressure in the sealed space is lowered.
If the pressure in the sealed space is lowered, the liquid film formed on the space is broken while being drawn to the inner side of the sealed space and scatters as splashing droplets. The pressure in the sealed space is a negative pressure immediately before the liquid film is broken. Therefore, almost all the splashing droplets fly toward the inner side of the sealed space. The splashing droplets fly while catching air present around the liquid film. Accordingly, fine air bubbles are contained in the splashing droplets.
As a result, if the splashing droplets reach to the nozzle openings, the fine air bubbles are drawn to a flow path from the nozzles with a negative pressure applied for maintaining shapes of the meniscuses on the nozzle openings. If the air bubbles are present in the liquid flow path, a pressure applied to a pressure generation chamber is reduced by the air bubbles before liquid is ejected. This causes ejection failure so that a problem arises.
An advantage of some aspects of the invention is to provide a liquid ejecting apparatus which can effectively prevent ejection failure from occurring by making the liquid ejecting apparatus take a configuration in which splashing droplets are made difficult to be generated or a configuration in which a generation source of the splashing droplets and nozzle openings can be shielded from each other even if the splashing droplets scatter such that the splashing droplets do not reach to the nozzle openings.
It is preferable that a liquid ejecting apparatus according to an aspect of the invention include a liquid ejecting head that has a nozzle face on which nozzle openings for ejecting liquid are formed and a cap member that forms a space by abutting against the nozzle face and receives liquid ejected through the nozzle openings in a state where the space is in a negative pressure. In the liquid ejecting apparatus, it is preferable that the cap member include an outer cap portion that abuts against the nozzle face, and an inner cap portion that is provided at the inner side of the outer cap portion, and a cutout be formed at least on the inner cap portion at the side of the nozzle face.
With the liquid ejecting apparatus configured as described above, when liquid is ejected toward the cap member in a state where the cap member abuts against the liquid ejecting head, the liquid ejected through the nozzle openings mainly hits the inner cap portion and is difficult to reach to the outer cap portion.
Further, a liquid film formed between the inner cap portion and the nozzle face is divided into a plurality of films by the cutout formed on the inner cap portion. Therefore, the liquid films are gathered on the divided regions. As a result, the liquid films formed between the inner cap portion and the nozzle face are relatively thicker than a liquid film formed between the outer cap portion and the nozzle face. Accordingly, when the liquid film formed by the outer cap portion becomes splashing droplets and flies into the space formed between the cap member and the nozzle face, the liquid films formed by the inner cap portion are still formed. Therefore, the splashing droplets are absorbed by the liquid films.
Further, the cutout is provided on the inner cap portion. Therefore, the space surrounded by the inner cap portion and the space between the inner cap portion and the outer cap portion communicate with each other. If the outer cap portion is separated from the nozzle face, a negative pressure in the space between the inner cap portion and the outer cap portion is released and the space formed by the inner cap portion communicates with the external environment through the cutout. With this, a negative pressure in the space surrounded by the inner cap portion is also released. Therefore, even if the liquid film between the inner cap portion and the nozzle face is broken, liquid is suppressed from traveling to the space surrounded by the inner cap portion with the negative pressure and liquid is suppressed from adhering to the nozzle face. As described above, the liquid ejected through the nozzle openings can be suppressed from adhering to the outer cap portion. Further, a liquid film can be suppressed from being formed between the cap member and the nozzle face as much as possible. This makes it possible to prevent ejection failure from occurring.
In the ink jet recording apparatus according to another aspect of the invention, it is preferable that a distance between a front end of the inner cap portion and the nozzle face during capping be the same as or longer than a distance between a front end of the outer cap portion and the nozzle face.
With the liquid ejecting apparatus configured as described above, the distance between the front end of the inner cap portion and the nozzle face during the capping is the same as or longer than the distance between the front end of the outer cap portion and the nozzle face. Therefore, when or before the front end of the inner cap portion reaches to the nozzle face, sealing by the outer cap portion is reliably performed in the configuration in which the inner cap portion is additionally provided inside the outer cap portion. Note that the sealing by the outer cap portion can be performed in that the front end of the outer cap portion reliably reaches to and abuts against the nozzle face. This makes it possible to prevent ejection failure from occurring.
Further, in the ink jet recording apparatus according to still another aspect of the invention, it is preferable that an absorbing member be provided in the cap member in a state of being separated from the nozzle face, and a part of the absorbing member also serve as the inner cap portion.
With the liquid ejecting apparatus configured as described above, when the nozzle face hits the inner cap portion or a space having such size that a capillary force acts is generated between the inner cap portion and the nozzle face under a condition that liquid is ejected in a state where the liquid ejecting head is capped with the cap member, the liquid ejected through the nozzles smoothly moves to the inner cap portion formed by the absorbing member with the capillary force. Therefore, the liquid which possibly adheres to the outer cap portion is absorbed by the inner cap portion. Accordingly, adherence of the liquid to the outer cap portion does not physically occur. This makes it possible to suppress splashing droplets from being generated when the outer cap portion and the nozzle face are separated from each other and prevent ejection failure from occurring.
Further, it is preferable that an ink jet recording apparatus according to still another aspect of the invention include a liquid ejecting head that has a nozzle face on which nozzle openings for ejecting liquid are formed, and a cap member that forms a space by abutting against the nozzle face and receive liquid ejected through the nozzle openings in a state where the space is in a negative pressure. In the ink jet recording apparatus, it is preferable that the cap member include an outer cap portion that abuts against the nozzle face, and an inner cap portion that is provided at the inner side of the outer cap portion, a cutout be formed at least on the inner cap portion at the side of the nozzle face, and a distance between the inner cap portion and the nozzle face be set to be a distance at which a liquid film formed between the inner cap portion and the nozzle face is not broken when a liquid film formed between the outer cap portion and the nozzle face is broken.
With the liquid ejecting apparatus configured as described above, even if a liquid film is broken due to reduction in pressure from the outer cap portion, the liquid film formed on the inner cap portion is kept without being influenced by the reduction in pressure. Therefore, splashing droplets generated from the outer cap portion is absorbed by the liquid film left on the inner cap portion and does not reach to the nozzle openings. This makes it possible to prevent ejection failure from occurring.
The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
Hereinafter, an embodiment and variations are described in the following order in order to clarify contents of the invention.
A. Apparatus Configuration according to the Embodiment
B. Capping Unit according to the Embodiment
C. Variations
C-1. First Variation
C-2. Second Variation
An ink cartridge 26, a carriage case 22, a discharge head 24, and the like are provided on the carriage 20. The ink cartridge 26 accommodates ink. The ink cartridge 26 is mounted on the ink carriage case 22. The discharge head 24 is one type of a liquid ejecting head. The discharge head 24 is mounted on the carriage case 22 at a bottom side (at a side facing to the print medium 2) and discharges ink. Ink in the ink cartridge 26 is introduced to the discharge head 24 and an accurate amount of ink is discharged onto the print medium 2 as a discharge medium from the discharge head 24 through nozzle openings (not illustrated in
The driving mechanism 30 which makes the carriage 20 reciprocate is constituted by a guide rail 38, a timing belt 32, a driving pulley 34, a step motor 36, and the like. The guide rail 38 is provided so as to extend in the main scanning direction. A plurality of teeth are formed on an inner side of the timing belt 32. The driving pulley 34 is engaged with the teeth of the timing belt 32. The step motor 36 drives the driving pulley 34. A portion of the timing belt 32 is fixed to the carriage case 22. If the timing belt 32 is driven, the carriage case 22 can be moved along the guide rail 38. Further, the timing belt 32 and the driving pulley 34 are engaged with each other with the teeth. Therefore, if the driving pulley 34 is driven by the step motor 36, the carriage case 22 can be moved with high accuracy in accordance with a driving amount of the driving pulley 34.
The platen roller 40 which feeds the print medium 2 is driven by a driving motor and a gear mechanism (which are not illustrated) so as to feed the print medium 2 in a sub scanning direction by a predetermined amount at time. The ink jet printer 10 drives the discharge head 24 in the main scanning direction and discharges inks of each color through the nozzle openings while feeding the print medium 2 in the sub scanning direction by the above mechanisms. With this, the ink jet printer 10 prints an image on the print medium 2.
Thus, in the ink jet printer 10, ink of each color is discharged through a plurality of nozzle openings provided on the discharge head 24 so that an image is printed. It is needless to say that it is important to maintain nature of ink in the nozzle openings to be in an appropriate state in order to discharge the ink through the nozzle openings appropriately. If the nature of the ink is changed (for example, viscosity of the ink is increased) due to evaporation of a volatile component in the ink, the ink cannot be discharged through the nozzle openings normally. For this reason, the ink jet printer 10 includes the maintenance mechanism 100 for maintaining a state where ink can be discharged normally in addition to various mechanisms for printing an image.
As illustrated in
Further, even if the capping unit 140 is pressed against the discharge head 24 so as to prevent ink from being dried, water and a volatile component in ink are reduced little by little over long time so that nature of the ink is changed (for example, viscosity of the ink is increased). In this case, an operation (cleaning operation) in which an inner portion of the space 160 is made in a negative pressure by operating the suction pump 150 in a state where the capping unit 140 is mounted so as to suck the ink through the nozzle openings is performed. If the cleaning operation is performed, ink of which nature has been changed can be forcibly discharged through the nozzle openings. This makes it possible to recover the nozzle openings to be in a normal state.
As described above, in the ink jet printer 10, ink can be prevented from being evaporated or ink of which nature has been changed can be forcibly discharged by the maintenance mechanism 100. Accordingly, the discharge head 24 can be kept to be in a normal state.
However, as described above, when the cap opening operation is performed, if ink adheres to an upper end of an inner wall face of an outer cap 141 of the capping unit 140, that is, to the outer cap 141 at a position near the nozzle face 241, a capillary force is generated and an ink film as a liquid film is formed between the outer cap 141 and the nozzle face 241 immediately after the outer cap 141 and the nozzle face 241 are separated from each other. Then, if the outer cap 141 and the nozzle face 241 are further separated from each other, ink scatters as splashing droplets. If the splashing droplets reach to the nozzle openings, there is a risk that discharge failure is caused, resulting in a problem. In order to eliminate such risk, in the ink jet printer 10 according to the embodiment, the capping unit 140 has the following configuration for suppressing ink from adhering to the outer cap 141 or suppressing splashing droplets from reaching to the nozzle openings so as to prevent discharge failure from occurring.
As illustrated in
Further, in
The inner cap 142 is formed at the inner side of the outer cap 141 at a position between an inner wall of the outer cap 141 and the nozzle rows 243. Cutouts 146 are provided at least a part of the inner cap 142 at the side of the nozzle face 241 unlike the configuration of the outer cap 141. Therefore, a part of the inner cap 142 does not abut against the nozzle face 241. Accordingly, when liquid adheres to an interface between the inner cap 142 and the nozzle face 241, an ink film is divided into a plurality of films by the cutouts 146. The divided liquid films attract ink with the capillary forces thereof so as to be relatively thicker than the ink film formed on an interface between the outer cap 141 and the nozzle face 241.
An ink film 210 formed on the inner cap 142 is not broken at the time when an ink film 200 formed on the outer cap 141 is broken to the inner side with the negative pressure. Therefore, splashing droplets 220 can be suppressed from traveling to the nozzle rows 243. This will be described in detail below.
The ink film 200 formed on the interface between the nozzle face 241 and the outer cap 141 is broken mainly due to the negative pressure generated on the thin ink film 200 and the space 160. Directions of the force applied to the ink film 200 with the negative pressure are indicated by black arrows in
In the embodiment, when the cap opening operation is performed, the ink film 210 formed between the inner cap 142 and the nozzle face 241 is not broken when the ink film 200 formed between the outer cap 141 and the nozzle face 241 is broken for the following reason. That is, when the ink film 200 formed between the outer cap 141 and the nozzle face 241 is broken, a negative pressure is not generated on the space 160 formed by the inner cap 142 because the ink film 210 formed between the inner cap 142 and the nozzle face 241 is formed to be thick and the space 160 communicates with the outside environment by the cutouts 146 as described above. Accordingly, the ink film 210 formed on the inner cap 142 is not broken at the time where the ink film 200 formed on the outer cap 141 is broken to the inner side with the negative pressure. This makes it possible to suppress the splashing droplets 220 from traveling to the nozzle openings 242 and the nozzle rows 243.
A distance between the inner cap 142 and the nozzle face 241 is required to be set such that the ink film 210 is not broken when the ink film 200 formed due to a distance between the outer cap 141 and the nozzle face 241 is broken. That is, the distance between the inner cap 142 and the nozzle face 241 may be the same as or slightly longer than the distance between the outer cap 141 and the nozzle face 241. The distance between the inner cap 142 and the nozzle face 241 can be set to be slightly longer than the distance between the outer cap 141 and the nozzle face 241 by making the adjustment of setting the widths of the cutouts 146 to be larger, increasing the number of cutouts 146, or the like in consideration of the viscosity of ink since the ink film 210 divided by the cutouts 146 is required to be thick.
Several variations of the above embodiment can be considered. Hereinafter, these variations are simply described. It will be understood that the variation has the same configuration unless a difference in the configuration between the above embodiment and the variation is otherwise particularly defined.
In the above embodiment, the inner cap is formed with a material which is the same as that of the outer cap. However, a portion of an absorbing member may be made higher so as to have a function of the inner cap.
A distance between the portions 145a of the absorbing member and the nozzle face 241 as illustrated in
Hereinbefore, the liquid ejecting apparatus has been described. However, the invention is not limited to all of the above embodiment and variations. The invention can be realized in various modes within the range without departing from the scope of the invention. For example, the liquid ejecting apparatus may be a printing apparatus (so-called line head printer or the like) including a larger ejecting head.
The entire disclosure of Japanese Patent Application No. 2010-292057, filed Dec. 28, 2010 is expressly incorporated by reference herein.
Number | Date | Country | Kind |
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2010-292057 | Dec 2010 | JP | national |
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