Patent Application
20070291090
The nature of this invention, as well as other objects and benefits thereof, will be explained in the following with reference to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures and wherein:
Preferred embodiments of the present invention are described below with reference to the accompanying drawings. In the present specification, the “upward” direction in the liquid ejection apparatus indicates a direction toward an air connection channel, whereas the “downward” direction indicates a direction toward an ejection head (hereinafter referred to also as “head”).
As shown in
The sub tank 11 includes: an ink storage section 18 which forms a liquid storage chamber for storing ink; and an air connection channel 19 which serves as a connection path to the atmosphere. A dividing plate 21 is interposed between the ink storage section 18 and the air connection channel 19. The ink storage section 18 is provided for each color, and a relatively small quantity of ink, corresponding to an amount for printing images on several sheets or several tens of sheets, is stored in the ink storage section 18 provided for each color.
A connection port is provided in the dividing plate 21, and the connection port is filled with an air-liquid separating member 22 through which only air to pass and liquid is inhibited from passing. The air-liquid separating member 22 has a surface which is adjacent to the ink storage section 18 (is located on the-side of the ink storage section 18) and coated with a hydrophobic material. A plurality of fine pores are formed in the air-liquid separating member 22 so that air can pass through the air-liquid separating member 22, and these fine pores are formed by laser processing using irradiation of laser light. Furthermore, the air-liquid separating member 22 may be a multifilament fiber body formed by bonding together sheets made of a fibrous resin, a fibrous metal, or the like, to form a laminated body, and then calcining this laminated body.
Moreover, in the present embodiment, an air bubble incorporation member 25 is provided inside the ink storage section 18. The air bubble incorporation member 25 is a porous member that has a function of allowing both air and liquid to pass through the air bubble incorporation member 25. Therefore, air is allowed to pass through the air bubble incorporation member 25 and to be absorbed in the member 25, and moreover, the liquid can also be absorbed in the member 25 due to the capillary force. Consequently, the absorbed air is incorporated into the absorbed liquid in the form of air bubbles. The air bubble incorporation member 25 may be disposed in any position inside the ink storage section 18, and desirably, the air bubble incorporation member 25 is disposed in a position such that the air and ink pass in the air bubble incorporation member 25 and air bubbles can be incorporated into the ink in a reliable fashion even when the amount of the increase or decrease of the liquid level in the ink storage section 18 is minute. In the present embodiment, as shown in
A suction port 23 for suctioning the air from the exterior is provided with the air connection channel 19, while on the other hand, a supply port 24 for supplying ink from the exterior is provided with each ink storage section 18. The ink storage section 18 is preferably filled with an ink holding member (such as a sponge) in order that the negative pressure of the head 17 can be controlled to a very high degree of accuracy.
During printing, the head 17, which is coupled integrally with the sub tank 11, ejects ink droplets in accordance with image signals while moving reciprocally back and forth over a scanning print region A1 shown in
The silicon substrate 34 is provided with a heater 42 which is a heating element and arranged at a position corresponding to a bubble generation chamber 26 (including a first bubble generation chamber 26A and a second bubble generation chamber 26B) described below. When a prescribed drive signal is supplied to the heater 42, an ejection bubble (a bubble that is generated from evaporation of the ink) is generated and is expanded inside the bubble generation chamber 26 because of the heat generated by the heater 42, and an ink droplet is then ejected from the nozzle 32 because of the pressure created by this ejection bubble. Furthermore, a supply channel 46 and a common flow channel 44 for supplying ink to the bubble generation chamber 26 from the ink storage section 18 of the sub tank 11 are formed in the head 17. The supply channel 46 is formed in the silicon substrate 34.
The first bubble generation chamber forming layer 36 made from a photosensitive resin, or the like, is stacked on the silicon substrate 34, and the first bubble generation chamber 26A is formed in the first bubble generation chamber forming layer 36. The second bubble generation chamber forming layer 38 is stacked on the first bubble generation chamber forming layer 36, and the second bubble generation chamber 26B connected to the first bubble generation chamber 26A is formed in the second bubble generation chamber forming layer 38. The bubble generation chamber 26, which is filled with ink that is to be ejected from the nozzle 32 (before the ejection), is constituted by the first bubble generation chamber 26A and the second bubble generation chamber 26B. The second bubble generation chamber forming layer 38 forms a side wall 38A of the second bubble generation chamber 26B. The side wall 38A is inclined at an angle of approximately 10 to 40 degrees with respect to the central axis of the second bubble generation chamber 26B, and thus forms a circular conical tapered shape in which the internal diameter decreases in terms of a direction toward the nozzle 32. Therefore, in the second bubble generation chamber 26B, the liquid flow direction in which the ink is caused to flow due to the expansion of the ejection bubble 48 is regulated to be a direction toward the nozzle 32, and therefore the ejection efficiency of the ink can be improved and the ejection volume can be stabilized.
The nozzle plate 40 is stacked on the second bubble generation chamber forming layer 38, and the nozzles 32 forming ink ejection ports are formed in this nozzle plate 40.
Moreover, as shown in
As shown in
The ink supply system having the above-described composition functions as follows.
Firstly, when the remaining amount of ink in the ink storage section 18 in the sub tank 11 becomes low, then the head 17 moves from the scanning print region A1 to a maintenance region A2, and the sub tank 11 is coupled with the coupling unit 12. In this case, the suction port 23 is coupled to the joint 27 that is connected to the suction pump 16 for suctioning air, while on the other hand, the supply port 24 is coupled to the joint 28 that is connected to the main tank 13. In this situation, air passes through and is absorbed in the air bubble incorporation member 25.
Next, when the valve 31 (shown in
When the ink surface in the ink storage section 18 makes contact with the air-liquid separating member 22, then the rise of the ink level is halted since the air-liquid separating member 22 has a function for inhibiting the passage of liquid. The suction force of the suction pump 16 is set to be lower than the liquid passage inhibiting force (liquid repelling force) of the air-liquid separating member 22.
Moreover, a configuration is adopted in which the ink storage sections 18 are arranged in alignment independently for the color inks, and the air connection channel 19 is provided for all the color inks as a single common chamber. In this case, when the suction operation is carried out by the suction pump 16, the ink supply operations from the main tanks 13 are started simultaneously for all the color inks stored in the ink storage sections 18. It is often the case that the remaining ink amount varies between the ink storage sections 18 storing the color inks; however, since the air-liquid separating member 22 has a function for inhibiting the passage of the liquid, as stated previously, then the ink supply terminates sequentially as the ink storage sections of the respective inks become full and the inks comes into contact with the air-liquid separating member 22.
Furthermore, as printing starts and the ink in the ink storage section 18 is consumed, the liquid level of the ink descends in the air bubble incorporation member 25 from a level such that the liquid contacts with the air-liquid separating member 22 and the liquid level further descends in the ink storage section 18. Therefore, the empty region 18A is formed again, air passes through the air bubble incorporation member 25, and consequently the air is absorbed in the air bubble incorporation member 25 again.
In the present embodiment, as shown in
By means of the operations described above, air and ink alternately permeate the air bubble incorporation member 25, and the air that has been absorbed in the air bubble incorporation member 25 is thereby incorporated into the ink in the form of air bubbles.
Next, the function and beneficial effects according to the present embodiment are described in more detail with reference to
Thereupon, when heat is further generated from the heater 42, as shown in
Subsequently, as shown in
As described above, it is possible to reliably incorporate the air bubbles into the ink inside the bubble generation chamber 26 by means of a simple structure, and the formation of the liquid pool 70 can be reliably prevented from occurring. Consequently, it is possible to prevent the occurrence of the satellite droplet 52, and an image can be formed by means of dots having desired shapes.
As described above with reference to
{(D2−D1)/16}≦d≦(D1/8) (1)
where d represents a diameter of the air bubbles incorporated into the bubble generation chamber 26.
In the inequality equation (1), the upper limit value (D1/8) is the limit value for ensuring the ink ejection characteristics from the nozzle 32. If the air bubbles having a larger diameter than this limit value are incorporated into the ink, then there is a possibility that an ejection failure may occur and that the variation in the ejection volume of the ink may increase and the image quality may thus be deteriorated.
Moreover, the lower limit value {(D2−D1)/16} is the lower limit value for achieving effective coalescence of the incorporated air bubbles. If the air bubbles having a smaller diameter than this lower limit value are incorporated into the ink, then it becomes difficult to cause the air bubbles to combine together effectively, the air pool 49 shown in
When air and ink alternately permeate the air bubble incorporation member 25 constituted by a porous member and the air bubbles are thereby incorporated into the ink, then the following relationship is satisfied between the pore diameter in the porous member and the diameter of the air bubbles to be incorporated:
g2≦d≦g1 (2)
where g1 represents the maximum pore diameter of the air bubble incorporation member 25, and g2 represents the minimum pore diameter of the air bubble incorporation member 25. By taking into consideration this relationship, the air bubble incorporation member 25 having the desired pore diameter can be selected so as to adjust the diameter of the air bubbles to be incorporated into the ink.
Another possible embodiment for incorporating the air bubbles into the ink is described below.
Next, the print unit including the aforementioned ink supply system is described below.
The recording paper conveyance amount measurement sensor (conveyance amount sensor) 165 is a device which measures the conveyance amount in the sub-scanning direction of the recording paper 137, and the conveyance amount sensor 165 includes photoelectric sensors arranged following a substantially parallel direction with respect to the sub-scanning direction. The amount of conveyance of the recording paper 137 is measured on the basis of sensor signals obtained from this conveyance amount sensor 165.
As shown in
The sensor width (readable width) of the print determination unit 143 is composed to be broader than the nozzle arrangement width (printable width) of the head 17. Accordingly, even when relative displacement (position error) occurs between the head 17 and the print determination unit 143 mounted on the carriage 162 (shown in
In the case of a configuration in which roll paper is used, a cutter 147 is provided as shown in
The recording paper 137 delivered from the paper supply unit 138 retains curl due to having been loaded in the magazine. In order to remove the curl, heat is applied to the recording paper 137 in the decurling unit 139 by a heating drum 130 in the direction opposite to the curl direction in the magazine.
After decurling, the cut recording paper 137 is delivered to the suction belt conveyance unit 141. The suction belt conveyance unit 141 has a configuration in which an endless belt 133 is set around rollers 131 and 132 so that the portion of the endless belt 133 facing at least the nozzle face of the print unit 29 forms a plane.
The belt 133 has a width that is greater than the width of the recording paper 137, and a plurality of suction holes (not shown) are formed on the belt surface. A suction chamber 134 is disposed in a position facing the nozzle surface of the print unit 29 on the interior side of the belt 133, which is set around the rollers 131 and 132, as shown in
The belt 133 is driven in the clockwise direction in
Since the ink adheres to the belt 133 when a marginless print job or the like is performed, a belt-cleaning unit 136 is disposed in a predetermined position (a suitable position outside the printing area) on the exterior side of the belt 133. A heating fan 140 is disposed on the upstream side of the print unit 29 in the conveyance pathway formed by the suction belt conveyance unit 141. The heating fan 140 blows heated air onto the recording paper 137 to heat the recording paper 137 immediately before printing so that the ink deposited on the recording paper 137 dries more easily.
The main tank 13 includes tanks which store the color inks to be supplied to the heads 17 corresponding to the respective ink storage sections 18K, 18C, 18M and 18Y of the print unit 29 (shown in
The coupling unit 12 shown in
As shown
A heating/pressurizing unit 144 is disposed following the post-drying unit 142. The heating/pressurizing unit 144 is a device to control the glossiness of the image surface, and the image surface is pressed with a pressure roller 145 having a predetermined uneven surface shape while the image surface is heated, and the uneven shape is transferred to the image surface.
The printed matter generated in this manner is outputted from the paper output unit 146. The target print (i.e., the result of printing the target image) and the test print are preferably outputted separately. In the inkjet recording apparatus 10, a sorting device (not shown) is provided for switching the outputting pathways in order to sort the printed matter with the target print and the printed matter with the test print, and to send them to paper output units 146A and 146B, respectively. When the target print and the test print are simultaneously formed in parallel on the same large sheet of paper, the test print portion is cut and separated by a cutter (second cutter) 148. The cutter 148 is disposed immediately before the paper output unit 146, and is used for cutting the test print portion from the target print portion when a test print has been performed in the blank portion of the target print. The structure of the cutter 148 is the same as the first cutter 147 described above, and has a stationary blade 148A and a round blade 148B.
The communication interface 170 is an interface unit for receiving image data sent from a host computer 186. The image data sent from the host computer 186 is received by the inkjet recording apparatus 10 through the communication interface 170, and is temporarily stored in the image memory 174. The image memory 174 is a storage device for temporarily storing an image input via the communication interface 170, and data is written to and read from the image memory 174 via the system controller 172.
The system controller 172 is a control unit for controlling the various sections, such as the communication interface 170, the image memory 174, the motor driver 176, the heater driver 178, and the like. The system controller 172 is constituted by a central processing unit (CPU) and peripheral circuits thereof, and the like, and in addition to controlling communications with the host computer 186 and controlling reading and writing from and to the image memory 174, and the like, it also generates control signals for controlling the heater 42 and the motor 188 in the conveyance system.
The motor driver (drive circuit) 176 drives the motor 188 in accordance with commands from the system controller 172. The heater driver 178 drives the heaters 42 (shown in
The print controller 180 has a signal processing function for performing various tasks, compensations, and other types of processing for generating print control signals from the image data stored in the image memory 174 in accordance with commands from the system controller 172 so as to supply generated print control signals (dot data) to the head driver 184. Prescribed signal processing is carried out in the print controller 180, and the ejection amount and the ejection timing of the ink droplets from the respective print heads 17 are controlled by the head driver 184, on the basis of the print data. By this control of the head driver 184, desired dot size and dot positions can be achieved.
The print controller 180 is accompanied with the image buffer memory 182, and image data, parameters, and other data are temporarily stored in the image buffer memory 182 while the image data is processed in the print controller 180.
The heater driver 178 generates drive signals for driving the heaters 42 (shown in
As stated previously, the print determination unit 143 reads in a test pattern recorded by the heads 17, and it performs prescribed signal processing, and the like, in order to determine the ink ejection status of the heads 17 (the presence or absence of ejection, the dot sizes, the dot depositing positions, and the like) (in other words, in order to determine variations between the nozzles 32). The print determination unit 143 supplies the determination results to the print controller 180. According to requirements, the print controller 180 makes various corrections with respect to the heads 17 on the basis of information obtained from the print determination unit 143.
The conveyance amount sensor 165 measures the amount of conveyance of the recording paper 137 in the sub-scanning direction, and the sensor signals (conveyance amount information) obtained from the conveyance amount sensor 165 are supplied to the print controller 180.
The image forming apparatus according to an embodiment of the present invention is described in detail above, but the present invention is not limited to the aforementioned embodiments, and it is of course possible for improvements or modifications of various kinds to be implemented, within a range which does not deviate from the essence of the present invention.
It should be understood that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the invention is to cover all modifications, alternate constructions and equivalents falling within the spirit and scope of the invention as expressed in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-165116 | Jun 2006 | JP | national |
