Patent Grant
7905573
This application claims priority under 35 USC §119 to Japanese Patent Application No. 2007-160858, filed on Jun. 19, 2007, and Japanese Patent Application No. 2008-105277, filed on Apr. 15, 2008, the entire contents of which are incorporated by reference.
1. Technical Field
This disclosure relates to a liquid ejection head and an image forming apparatus, and in particular to a liquid ejection head ejecting liquid drops and an image forming apparatus employing the liquid ejection head.
2. Discussion of the Background Art
An image forming apparatus, such a printer, a facsimile, a copier, a complex machine configured by combining these devices, etc., sometimes employs a liquid ejection device that includes a printing head having a liquid ejection head for ejecting and adhering liquid drops onto a medium, such as a paper, a string, a texture, a towel, a leather, a metal, a plastic, a glass, woods, ceramics, etc., while conveying the printing sheet to form an image.
The image formation includes not only a meaningful image, such as a character, a figure, etc., but also a meaningless image, such as a pattern, etc. The liquid is not limited to printing liquid or ink, but includes every type of liquid as far it is capable of executing image formation. The liquid ejection device generally ejects liquid from a liquid ejection head.
As one example of such a liquid ejection head employed in an image forming includes a heater in a nozzle plate to eject liquid drops from the nozzle while deforming the nozzle plate using a difference in heat expansion has been known as discussed in Japanese Patent Application Laid Open No. 2001-105590.
Various types of a liquid ejection head that deforms a nozzle plate including a flexible film by heat are described in the Japanese Patent Application Laid Open Nos. 2002-359981 and 2004-160650 as well as the Japanese Patent Registration No. 2827544.
There is a type that changes a fluidity resistance by connecting a vibration plate and a piezoelectric element to a bottom of the fluidity resistance flow path communicated with one end of the pressurizing chamber as described in the Japanese Patent Application Laid Open No. 2001-063047.
Since a liquid ejection head generally ejects liquid drops from a nozzle by pressurizing a liquid chamber or a flow path, pressure preferably does not leak from the liquid chamber when the pressure in the liquid chamber is to be efficiently increased and is applied to the liquid drops to be ejected. Thus, a liquid resistance section is arranged in the flow path that supplies liquid to the liquid chamber. In this point of view, the Japanese Patent Application Laid Open No. 2001-063047 employs a device capable of increasing the fluidity resistance when liquid drops are ejected.
However, these prior arts are still insufficient.
In an aspect of this disclosure, there is provided a liquid ejection head that includes a nozzle plate having a nozzle for ejecting liquid drops, an actuator for deforming a nozzle plate portion surrounding the nozzle, and a flow path member opposing the nozzle plate and forming a flow path for guiding liquid to the nozzle.
In another aspect, a fluidity resistance path is formed in the flow path between the nozzle plate portion and a portion of the flow path member opposing the nozzle plate portion. A fluidity resistance of the fluidity resistance path is changed by deforming the nozzle plate portion.
In another aspect, the flow path member includes at least one convex opposing either the nozzle or the nozzle plate portion in the fluidity resistance path.
In yet another aspect, the flow path member includes an inlet opposing the nozzle across the convex and configured to take in the liquid to the flow path.
In yet another aspect, the flow path member includes at least one concave opposing the nozzle plate portion in the fluidity resistance path.
In yet another aspect, the liquid ejection head includes a nozzle plate having a nozzle that ejects liquid drops, a deformable member including a wall opposing the nozzle, which guides liquid to the nozzle, and an actuator that deforms the deformable member. A holding member opposing the nozzle via the deformable member is provided to form a flow path guiding the liquid to the nozzle. A fluidity resistance path is formed in the flow path between a nozzle plate portion surrounding the nozzle and a surface of the deformable member opposing the nozzle plate portion. A fluidity resistance of the fluidity resistance path is changed by deforming the deformable member.
A more complete appreciation of the aforementioned and other aspects, features and advantages will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
Referring now to the drawing, wherein like reference numerals designate identical or corresponding parts throughout several views, in particular, in
A nozzle 3 is formed on the nozzle plate 1 to eject liquid drops. The nozzle plate 1 includes three layers. Specifically, an upper layer 11 is made of material having a large thermal expansion coefficient, such as Ni—Cr of 16×10E-6/° C. An inner layer 12 is made of material having a small thermal expansion coefficient, such as Cr of 8×10E-6/° C. A heater layer 4 is provided as an intermediate layer 4 between the layers 11 and 12 to serve as an actuator device. The intermediate layer 4 has a circular planner shape and surrounds the nozzle 3. The intermediate layer forms a bimetallic structure. Thus, an electrode 5 is connected to the heater layer 4 so as to supply power.
The flow path member 2 includes an ink supply inlet 21 and an ink supply path 22. The flow path member 2 includes a convex part 23 opposing the nozzle 3 and a surrounding area 6 of the nozzle 3 (herein after referred to as a nozzle surrounding section 6). Between a surface 24 of the convex part 23 and the nozzle surrounding section 6, a fluidity resistance path 7 having a larger fluidity resistance than that of the ink supply path 22 or another flowpath section of the ink supply inlet 21 are formed.
As shown by a void arrow in
At this moment, owing to approach of the nozzle surrounding section 6 toward the opposing surface 24, a cross sectional area of the opening of the fluidity resistance path 7 decreases, and the resistance value of the liquid in the fluidity resistance path 7 increases. As a result, an amount of the ink flowing from the nozzle 3 to the ink supply path 22 decreases.
Thus, pressure caused at the nozzle 3 is hardly conveyed to the image supply path 22, and is dedicatedly used as energy for ejecting the ink. As a result, ejection efficiency is significantly improved while low voltage drive can be obtained saving the power.
Thus, a fluidity resistance is changed by a simple construction and thereby capable of efficiently ejecting dink drops.
Now, a modification of the first embodiment of the liquid ejection head is described with reference to
Now, a second embodiment of the liquid ejection head is described with reference to
Now, a driving operation of the liquid ejection head is described. As mentioned above, the liquid ejection head ejects ink by turning on the heater layer 4 while deforming the nozzle surrounding section 6. At that moment, by ejecting liquid drops while disengaging the nozzle surrounding section 6 with the opposing surface 24, a deformation amount of the nozzle plate 1 (i.e., the nozzle surrounding section 6) and accordingly a size of the ink drop can be changed in accordance with an amount of electricity supplied to the heater layer 4. As a result, a multi bit and high quality image having an excellent gray scalability can be printed.
By ejecting the liquid drops while engaging the nozzle surrounding section 6 with the opposing surface 24, the liquid drops can be constantly ejected and a high quality image can be obtained. Because, the amount of deformation of the nozzle surrounding section 6 is substantially constant.
Further, prescribed power is initially supplied to the heater layer 4 to change a size of the fluidity resistance path 7 to have a prescribed fluidity resistance not to eject ink drops, and then larger power can be supplied to eject the ink drops. Thus, a high quality image having an excellent gray scalability can be obtained, because a size of the liquid drops can be previously changed.
Now, an exemplary image forming apparatus including a liquid ejection head is described with reference to
When a duplex unit 207 is attached to the apparatus body to execute duplex printing, the printing sheet 203 is reversely conveyed after one side printing is completed by the conveyance mechanism 205 and is taken in by the duplex unit 207. Then, the printing sheet is reversed to enable the other side to get ready to receive printing and is further launched into the conveyance mechanism 205 again. The printing sheet 203 is then ejected onto the printing sheet ejection tray 206 after the other side receives the printing.
The image formation section 202 includes four printing heads 211k to 211y of a full-line type for ejecting ink of black, cyan, magenta, and yellow mono-colors (K, C, M, and Y), respectively. Herein after, the four printing heads 211k to 211y are referred to as printing heads 211 when mono-color does not matter. Each of the printing heads 211 is attached with its nozzle surface facing downward, which forms a nozzle for ejecting liquid drops.
Four maintenance recovery mechanisms 212k to 212y are provided corresponding to the respective printing heads 211. Herein after, the four maintenance recovery mechanisms 212k to 212y are referred to as a maintenance recovery mechanism 212 when mono-color does not matter. When a performance maintenance operation, such as a purge process, a wiping process, etc., is executed, the printing head 211 and the maintenance recovery mechanism 212 are relatively moved so that four capping members serving as the maintenance recovery mechanism 212 can oppose the nozzle surface of the printing head 211.
As mentioned heretofore, the printing heads 211 are arranged to eject yellow to black colors in turn from the upstream side in the sheet conveyance direction. However, arrangement and number of colors are not limited thereto. One or more number of line type heads each including a plurality of nozzle lines can be employed for ejecting liquid drops of respective colors. An ink cartridge for supplying the head with ink can be integral with or separate from the head. Further, a line head can be formed by arranging straight lines of heads displaced from each other.
The printing sheets 203 in the sheet feeding tray 204 are separated by a separation pad, not shown, in cooperation with a sheet feeding roller 221 having a half moon shape one by one, and are is launched into the apparatus body 201. The printing sheet 203 is transferred into a gap between the registration roller 225 and the conveyance belt 233 along a guide surface 223a of the conveyance guide member 223. Then, the printing sheet 203 is transferred onto the conveyance belt 233 of the conveyance mechanism 205 via the guide member 226 at a prescribed time.
On the conveyance guide member 223, a guide surface 223b is formed so as to guide a printing sheet 203 launched from the duplex unit 207. Further arranged therein is a guide member 227 to guide the printing sheet 203 returned from a conveyance mechanism 205 to the duplex unit 207 when a duplex printing is executed.
The conveyance mechanism 205 includes an endless conveyance belt 233 wound around a conveyance roller 231 as a driving roller and a driven roller 232, a discharge roller 234 for discharging the conveyance belt 233, and a platen member 235 for maintaining the conveyance belt 233 to be flat at a section opposing the image formation section 235. Also included are a pressure applying roller 236 for depressing the printing sheet 203 toward the conveyance belt 233 and the conveyance roller 231, and a cleaning roller made of spongy member for removing printing liquid, such as ink adhering to the conveyance belt 233 or the like.
On the downstream side of the conveyance mechanism 205, an ejection roller 238 and a spur 239 are provided to launch a printing sheet 203 with an image onto the ejection tray 206.
In such an image forming apparatus, the conveyance belt 233 travels and circulates in a direction as shown by an arrow, and is charged by contacting the discharge roller 334 in a positive polarity, because a voltage of a high potential is applied to the discharge roller 334. Specifically, the discharge roller 234 with a charge voltage discharges the conveyance belt 233 at a prescribed interval while a polarity thereof is switched at the prescribed interval.
When a printing sheet 203 is fed onto the conveyance belt 233 with the charge of the high potential, the inside of the printing sheet 203 becomes a polarity-separated condition. Thus, electrode having a reverse polarity to that on the conveyance belt 233 is induced on the surface of the printing sheet 203 contacting the conveyance belt 233, and the electrode on the conveyance belt 233 and that on the printing sheet 203 electro-statically pull each other. Thus, the printing sheet 203 is electro-statically attracted to the conveyance belt 233. As a result, bent and concavity and convexity on the printing sheet are corrected when the printing sheet is intensely attracted to the conveyance belt 233, thereby highly flat surface can be formed.
By circulating the conveyance belt 233 and thereby conveying the printing sheet 203 while ejecting liquid drops from the printing head 21, a prescribed printing image is formed on the printing sheet 203. Then, the printing sheet 203 with the printing image is ejected onto the sheet ejection tray 206 by the sheet ejection roller 238.
As a result, an image can be formed at high speed highly improving efficiency of ejecting liquid drops.
Now, an exemplary maintenance recovery operation for a printing head of the image forming apparatus is described with reference to
Since the temperature of the nozzle plate surface (i.e. the ejection side surface) increases due to the power supply to the heater serving as an actuator, adhesion ink and plastic are soften, and thereby sticking force decreases. Accordingly, the nozzle plate surface can be easily cleaned by means of the wiping member. As a result, a bias to the wiping member can be decreased, and accordingly, a waterproof layer applied to the nozzle surface or the like hardly wears, thereby a durability of the head is improved. Further, ink can be replenished while preliminary applying prescribed heat to the nozzle plate not to eject drops, similarly.
Now, another exemplary liquid ejection head of a third embodiment according to the present invention is described with reference to
The vibration plate 102 includes a three-layer construction similar to the above-mentioned nozzle plate 1. Specifically, a layer 121 made of material having a relatively low thermal expansion coefficient is arranged on the side of the nozzle 101. A layer 122 made of material having a relatively high thermal expansion coefficient is arranged opposing the nozzle 101. And, a heater layer 124 serving as an actuator is arranged between the layers 121 and 122. Thus, a bimetallic construction is formed. An electrode 125 is connected to the heater layer 124.
In the holding member 103, an ink supply inlet 131 and a flow path 113 are formed. In the flow path member 103, a limit section 133 is provided to limit a deformation of the vibration plate 102 opposing the nozzle 111. Further, in the vibration plate 102, a passage 114 connecting the flow paths 112 and 113 to each other are arranged.
In the liquid ejection head with such a construction, liquid (e.g. ink) is supplied from the ink supply inlet 131 to the fluidity resistance path 107 via the flow paths 113 and 112, and the passage 114. Thus, the nozzle 111 is fulfilled with the ink. Then, by supplying power to the heater layer 124 and causing the heat layer 124 to generate heat, the vibration plate 102 is heated. Thus, a central section of the vibration plate 102 deforms toward the nozzle 111 and ink within the nozzle 111 is pressurized, thereby liquid drops are ejected from the nozzle 111.
Due to bending of the vibration plate 102 toward the nozzle surrounding section 106, an area of the opening of the fluidity resistance path 107 decreases while a fluidity resistance of the fluidity resistance path 107 increases. Thus, an amount of the ink flowing from the nozzle 111 to the flow path 112 is reduced. Accordingly, since pressure caused by deformation of the vibration plate member is almost spent as ink ejection energy, ejection efficiency is significantly improved. Further, low voltage driving is achieved while suppressing consumption of the power.
Since the vibration plate 102 including the heater layer 124 as an actuator device is arranged in the liquid, heat transmission from the heater layer 124 is hardly accumulated in the holding member 103 and the nozzle plate 101. As a result, driving can be steady and continuous.
Now, an exemplary liquid ejection head of a fourth embodiment is described with reference to
Also in this configuration, since the vibration plate 102 including the heater layer 124 is arranged in the ink as liquid, heat transmission from the heater layer 124 is hardly accumulated in the holding member 103 and the nozzle plate 101, thereby capable of steadily and continuously driving the liquid ejection head.
Any of the liquid ejection head described in these third and fourth embodiment can be built-in in an image forming apparatus.
Now, a fifth embodiment of an exemplary liquid ejection head according to the present invention is described with reference to
Further, a convex section 306 is formed on the nozzle plate 301 around the nozzle 311 and thereby forming the pressuring chamber 312. Between the convex section 306 and the portion of the vibration plate member 302 opposing the convex section 306, a fluidity resistance path 307 having larger fluidity resistance than the fluidity path 313 that communicated with the pressurizing chamber 312 is formed. A supply inlet, not shown, supplies liquid to the fluidity path 313.
As shown in
Since the vibration plate member 302 extends in parallel to its plane when the heater layer 304 is supplied with power, and the vibration plate member 302 is deformed and contacts the stopper member 305 as shown in
At this moment, since the vibration plate member 302 is bent toward the convex section 306, a cross sectional area of the opening of the fluidity resistance path 307 decreases, and a fluidity resistance on the fluidity resistance path 307 increases, ink flowing into the pressurizing chamber 312 from the nozzle 311 decreases. As a result, the bending force is mainly used for ink ejection energy, and accordingly, ejection efficiency is significantly improved while saving a head driving voltage and power.
Now, one example of a manufacturing process for manufacturing the above-mentioned vibration plate member 302 is described with reference to
Now, a sixth embodiment of an exemplary liquid ejection head is described with reference to
Specifically, the vibration plate member 302 is deformed as shown in
Now, a seventh embodiment of an exemplary liquid ejection head is described with reference to
The above-mentioned various embodiments of the present invention can be applied to a facsimile, a copier, a multifunction machine having functions of a printer, the facsimile and the copier beside the printer. Further, the invention is also applied to an image forming apparatus that ejects liquid other than the ink, such as resist, DNA sample used in a medical field, or the like. Numerous additional modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise that as specifically described herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-160858 | Jun 2007 | JP | national |
| 2008-105277 | Apr 2008 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4505604 | Takemoto | Mar 1985 | A |
| 4530280 | Kaneko et al. | Jul 1985 | A |
| 4569607 | Takemoto | Feb 1986 | A |
| 4619536 | Takemoto | Oct 1986 | A |
| 4708501 | Takemoto | Nov 1987 | A |
| 6267469 | Silverbrook | Jul 2001 | B1 |
| 6367914 | Ohtaka et al. | Apr 2002 | B1 |
| 6874867 | DeBar et al. | Apr 2005 | B2 |
| 20070002122 | Murano et al. | Jan 2007 | A1 |
| 20070160383 | Matsumoto et al. | Jul 2007 | A1 |
| Number | Date | Country |
|---|---|---|
| 2827544 | Sep 1998 | JP |
| 2001-63047 | Mar 2001 | JP |
| 2001-105590 | Apr 2001 | JP |
| 2001-277502 | Oct 2001 | JP |
| 2002-359981 | Dec 2002 | JP |
| 2004-160650 | Jun 2004 | JP |
| 2006-297688 | Nov 2006 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20080316279 A1 | Dec 2008 | US |
