Patent Application
20080297546
This application claims priority under 35 U.S.C. ยง119(a) from Korean Patent Application No. 2007-0051376, filed on May 28, 2007 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present general inventive concept relates to an ink jet image forming apparatus, and more particularly to an ink jet image forming apparatus which is improved in a structure of an ink supply device so as to stably eject an ink from a print head.
2. Description of the Related Art
An ink jet image forming apparatus is an apparatus that forms an image by ejecting an ink to a printing medium. The ink jet image forming apparatus commonly includes an ink supply device to supply an ink stored in an ink tank to an ink channel in a print head. The ink supplied to the print head is ejected to a printing medium by the print head to print an image. At this time, if the ink stored in the ink tank contains a gas component dissolved therein, or if bubbles are generated in the ink while passing through the ink supply device, the ink is not ejected stably, and this causes deterioration of an image quality.
In order to solve this problem, Korean Patent Registration No. 708195 relates to a method of removing bubbles from the print head by forming an ink circulation passage between the print head and the ink tank and performing a circulation process and a purging process by operating a pump whenever necessary. Here, the circulation process is a process of periodically circulating the ink by the pump to collect the bubbles from the print head into the ink tank, and separating the bubbles from the ink tank. The purging process is a process of operating the pump while closing a valve mounted in the ink circulation passage to apply a large pressure to the print head, thereby exhausting the bubbles to the outside with a small amount of ink.
In order to stably eject the ink from the print head, besides removing the bubbles from the print head through the ink circulation and purging processes, minimizing an influence due to a pressure loss generated in the ink circulation passage when the ink is supplied to the print head through the ink circulation passage is also important. If the ink is ejected from the print head to print an image on the printing medium, a pressure in the print head drops corresponding to a consumed volume of the ink, and accordingly the ink is supplied to the print head through the ink circulation passage. When the ink is supplied to the print head, a pressure loss is generated due to a flow friction or components (e.g., a filter) mounted in the ink circulation passage. Such a pressure loss is transferred to the print head through the ink filled in the ink circulation passage, and acts as a resistance to the ink ejection.
The present general inventive concept to provide an ink jet image forming apparatus which is improved in a structure of an ink supply device so as to minimize an influence due to a pressure loss generated in an ink flow passage.
Additional aspects and/or advantages of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present general inventive concept.
The foregoing and/or other aspects and utilities of the general inventive concept may be achieved by providing an ink jet image forming apparatus including a print head, an ink tank to store ink, an ink circulation passage through which the ink circulates between the ink tank and the print head, a pressure controller having an ink storage unit communicating with the ink circulation passage, and an air storage unit to communicate with external air, a valve mounted in the ink circulation passage between the ink tank and the pressure controller, a pump mounted in the ink circulation passage, and a control unit to control operations of the valve and the pump.
The air storage unit may include an air bag of which a volume is changed according to a pressure change of the ink storage unit.
The pressure controller may include a press member to press the air bag, and an elastic member to elastically support the press member.
The pressure controller may further include a sensor to detect a position of the press member.
The pump may perform bidirectional pumping.
When a printing operation is performed, the control unit closes the valve to interrupt the ink supply to the ink storage unit.
The control unit may perform a first pressure controller charging mode in which the control unit closes the valve and may operate the pump to expand the air bag.
The control unit may perform a second pressure controller charging mode in which the control unit stops the operation of the pump after the first pressure controller charging mode and opens the valve to charge the ink in the ink storage unit.
The control unit may perform a third pressure controller charging mode in which the control unit closes the valve after a predetermined period of time to maintain a negative pressure in the ink storage unit.
The foregoing and/or other aspects and utilities of the general inventive concept may also be achieved by providing an ink jet image forming apparatus including a print head having nozzles to eject an ink to a printing medium, and a channel unit to guide the ink supplied to the nozzles, an ink tank to store the ink, an ink supply passage to connect the ink tank and one side of the channel unit, an ink return passage to connect an other side of the channel unit and the ink tank, a pressure controller having an ink storage unit disposed in the ink supply passage, and an air bag communicating with external air to expand and contract, a valve mounted in the ink supply passage between the ink tank and the ink storage unit, a pump mounted in the ink return passage, and a control unit to control operations of the valve and the pump.
When a printing operation is performed, the control unit closes the valve to interrupt the ink supply to the ink storage unit through the ink supply passage.
The control unit may perform a first pressure controller charging mode in which the control unit closes the valve and operates the pump to expand the air bag.
The control unit may perform a second pressure controller charging mode in which the control unit stops an operation of the pump after the first pressure controller charging mode and opens the valve to supply the ink to the ink storage unit through the ink supply passage.
The control unit may perform a third pressure controller charging mode in which the control unit closes the valve after a predetermined period of time to maintain a negative pressure in the ink storage unit.
The control unit may perform a circulation mode in which the control unit opens the valve and controls the pump to circulate the ink in a first direction.
The pump may perform bidirectional pumping, and the control unit performs a purging mode in which the control unit closes the valve and controls the pump to pump the ink in a second direction so that the air bag contracts and the ink is ejected through the nozzles.
The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an ink jet image forming apparatus including a print head having nozzles to eject ink onto a printing medium, an ink tank to store the ink, an ink storage unit to receive the ink from the ink tank and to supply the ink to the print head and an air storage unit to expand and contract corresponding to a change in pressure of the ink storage unit.
The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an ink jet image forming apparatus having a plurality of modes, the apparatus including a print head, an ink tank to store ink, an ink circulation passage to circulate the ink between the ink tank and the print head, a pressure controller having an ink storage unit to communicate with the ink circulation passage and an air bag to communicate with air, a valve having a plurality of states, and disposed in the ink circulation passage between the ink tank and the pressure controller, a pump having a plurality of states, and disposed in the ink circulation passage, wherein one of the plurality of modes is selected based on the respective state of each of the valve and the pump.
The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an ink jet printing method including ejecting ink through nozzles of a print head to print an image on a printing medium, increasing negative pressure in the print head, supplying the ink from an ink storage unit of a pressure controller to the print head, and compensating for a pressure change in the ink storage unit by air flowing into an air bag of the pressure controller.
The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing a computer-readable recording medium having embodied thereon a computer program to execute a method, wherein the method includes ejecting ink through nozzles of a print head to print an image on a printing medium, increasing negative pressure in the print head, supplying the ink from an ink storage unit of a pressure controller to the print head, and compensating for a pressure change in the ink storage unit by air flowing into an air bag of the pressure controller.
These and/or other aspects and utilities of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, of which:
Reference will now be made in detail to embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures.
As illustrated in
The paper supply unit 10 includes a paper supply tray 11 on which the printing medium M is loaded, and a pick up roller 12 to pick up the printing medium loaded on the paper supply tray 11 sheet by sheet. The feeding unit 20 feeds the printing medium picked up by the pickup roller 12 to an area below the print head 30, and includes a feeding roller 21 which is mounted near an inlet of the print head 30, and an auxiliary roller 22 which is mounted between the feeding roller 21 and the pickup roller 12.
In this embodiment, the print head 30 is configured as an array print head which is provided with a nozzle unit 31 (
Referring to
The discharge unit 40 includes a discharge roller 41 which is mounted in a downstream side of the print head 30 with respect to a feeding direction of the printing medium M, and a star wheel 42 which is mounted opposite to the discharge roller 41. The star wheel 42 functions to prevent the printing medium M passing below the nozzle unit 31 from contacting the nozzle unit 31, or prevent a gap between the printing medium M and the nozzle unit 31 from being changed.
The ink supply device 100 is connected to the channel unit 34 of the print head 30 by the ink circulation passage 120 through which the ink circulates. The ink supply device 100 is conceptually illustrated in
As illustrated in
The ink stored in the ink tank 110 is supplied to the print head 30 through the ink supply passage 121, and the ink collected from the print head 30 is stored in the ink tank 110 via the ink return passage 122. The ink tank 110 has an atmosphere communication hole 111 through which the ink tank 110 communicates with the atmosphere. When the ink is collected from the print head 30, bubbles in the print head 30 are also collected into the ink tank 110, and are exhausted to the outside through the atmosphere communication hole 111.
An ink filter 123 is mounted in the ink supply passage 121 between the ink tank 110 and the valve 140. The ink filter 123 removes foreign substances from the ink which is supplied from the ink tank 110 to the print head 30.
The pressure controller 130 applies a negative pressure within a predetermined range to the print head 30 so that the ink does not leak from the print head 30, and supplies the ink to the print head 30 while the ink supply through the ink supply passage 121 is interrupted by the valve 140 in the printing operation.
Referring to
The air storage unit 136 communicates with the external air through the air flow hole 134, and the volume of the air storage unit 136 is changed according to the change of the pressure in the ink storage unit 135. The air storage unit 136 may be defined by an air bag 136a which is made of a flexible material capable of expanding and contracting and is mounted inside the housing 131. If the ink is exhausted from the ink storage unit 135 and the pressure in the ink storage unit 135 drops, the air flows into the air bag 136a to compensate for the pressure change in the ink storage unit 135. For example, if the printing operation is performed while the valve 140 is closed and the ink in the ink storage unit 135 is supplied to the print head 30, the pressure in the ink storage unit 135 drops. At this time, the air bag 136a expands by the air flowing into the air bag 136a, thereby compensating for the pressure change.
The housing 131 is provided with a press unit 137 thereinside, to press the air bag 136a. The press unit 137 presses the air bag 136a, in which the air is filled, so that the air cannot flow successively into the air bag 136a and the interior of the ink storage unit 135 can keep the negative pressure within a predetermined range. The press unit 137 includes a press member 137a which is in contact with the air bag 136a and presses the air bag 136a, and an elastic member 137b to elastically support the press member 137a.
The pressure controller 130 may further include a sensor 138 to detect the position of the press member 137a. By the sensor 138 detecting the position of the press member 137a, how much ink remains in the ink storage unit 135 can be indirectly estimated. If the amount of ink in the ink storage unit 135 decreases as the ink is supplied from the ink storage unit 135 to the print head 30, the air bag 136a expands, and the press member 137a moves. At this time, by the sensor 138 detecting the moving position of the press member 137a, the amount of ink remaining in the ink storage unit 135 can be estimated.
The valve 140 is mounted in the ink supply passage 121 between the ink tank 110 and the pressure controller 130, i.e., the valve 140 is mounted in the first supply passage 121a. If the valve 140 is closed by the control unit 160, the ink in the pressure controller 130, the second supply passage 121b and the print head 30 is isolated from the ink in the ink tank 110 and the first supply passage 121a between the valve 140 and the ink tank 110.
The pump 150 is mounted in the ink return passage 122, and can perform bidirectional pumping. The pump 150 includes a body 151 which has an inner peripheral surface of a circular arc shape, a pumping motor 152 to rotate in a forward/reverse direction, a roller arm 153 to rotate by the pumping motor 152, and rollers 154 which are mounted to both ends of the roller arm 153 to press the ink return passage 122. If the roller arm 153 rotates in a counterclockwise direction by the pumping motor 152, the ink is pumped in the arrow direction illustrated by a solid line in
By controlling the pump 150 and the valve 140, the control unit 160 controls the overall operation of the image forming apparatus, such as an operation of circulating the ink through the ink circulation passage 120, an operation of charging the ink into the ink storage unit 135 of the pressure controller 130, and the like.
Hereinafter, the operation of the ink jet image forming apparatus according to an embodiment of the present general inventive concept will be described with reference to
Referring to
Referring to
Referring to
In the first pressure controller charging mode as illustrated in
Thereafter, the control unit 160 stops an operation of the pump 150 as illustrated in
When the predetermined period of time elapses, the control unit 160 closes the valve 140 (the third pressure controller charging mode). As illustrated in
After the pressure controller 130 is charged with the ink as described above, the printing mode is performed. Referring to
As the printing operation is performed continuously, an amount of ink in the ink storage unit 135 decreases gradually, and the negative pressure in the ink storage unit 135 increases. At this time, the air bag 136a expands gradually to reduce a degree of increase of the negative pressure in the ink storage unit 135. However, the pressure controller 130 recharges at a proper point of time. The point of time of charging the pressure controller 130 can be known from the sensor 138 mounted in the pressure controller 130. That is, if the air bag 136a expands, the press member 137a moves in the direction of pressing the elastic member 137b. If the press member 137a is sensed by the sensor 138, the pressure controller charging mode is performed. At this time, bubbles in the print head 30 or in the ink circulation passage 120 can be removed by performing the aforesaid circulation mode before performing the pressure controller charging mode.
Besides the method of using the sensor as described above, the point of time of charging the pressure controller 130 can be determined by calculating the amount of ink ejected on the printing medium from the print head 30 (so-called dot count method).
The operational states of the pump 150 and the valve 140 in the respective modes described above can be summarized as the following table 1.
The present general inventive concept can also be embodied as computer-readable codes on a computer-readable medium. The computer-readable medium can include a computer-readable recording medium and a computer-readable transmission medium. The computer-readable recording medium is any data storage device that can store data that can be thereafter read by a computer system. Examples of the computer-readable recording medium include read-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, and optical data storage devices. The computer-readable recording medium can also be distributed over network coupled computer systems so that the computer-readable code is stored and executed in a distributed fashion. The computer-readable transmission medium can transmit carrier waves or signals (e.g., wired or wireless data transmission through the Internet). Also, functional programs, codes, and code segments to accomplish the present general inventive concept can be easily construed by programmers skilled in the art to which the present general inventive concept pertains.
As apparent from the above description, an ink jet image forming apparatus according to various embodiments of the present general inventive concept performs a printing operation while a print head is isolated from an ink supply passage and receives ink from a pressure controller. Accordingly, influence by pressure loss generated in the ink passage is minimized. Accordingly, ink ejection from the print head can be stably achieved, thereby increasing image quality.
Although various embodiments of the present general inventive concept have been illustrated and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the present general inventive concept, the scope of which is defined in the claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-51376 | May 2007 | KR | national |
