Patent Grant
8033644
This application claims priority to and the benefit of Japanese Patent Application No. 2007-192033, filed Jul. 24, 2007, and Japanese Patent Application No. 2007-192032, filed Jul. 24, 2007, the entire disclosures of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a liquid droplet ejecting apparatus, such as an ink jet printer, which ejects liquid to a recording medium.
2. Description of Related Art
An ink jet printer needs to eject ink from nozzles of an ink jet head onto target pixels on a sheet. Therefore, a nozzle surface of the ink jet head is located close to the sheet. On this account, if the sheet moving in a printing area bends, it may contact the nozzle surface of the ink jet head. If the sheet contacts the nozzle surface, the nozzle surface is rubbed to be worn away, and the sheet gets dirty. To solve this problem, a cover member may be disposed around the nozzle surface of the ink jet head. The cover member is disposed to project beyond the nozzle surface toward the sheet, and is formed so as not to block the orbit of the ink ejected from the nozzles (see Japanese Laid-Open Patent Application Publication 2003-72041 for example).
The cover member is required not to obstruct a wiping operation of wiping excess ink and stains from the nozzle surface. Therefore, the cover member can move up and down by an electric-powered cylinder. To be specific, when the wiping operation starts, the cover member is caused to move up by the electric-powered cylinder while being guided by a guide rail of a base. Thus, the cover member moves away from the sheet to be located more distant from the sheet than the nozzle surface.
However, since the cover member is driven by the electric-powered cylinder, the entire apparatus increases in size. In addition, it is difficult to precisely control the distance from the cover member to the sheet by the electric-powered cylinder.
An object of the present invention is to realize precise control of the position of a nozzle protector without increasing the size of the apparatus.
A liquid droplet ejecting apparatus of the present invention, which ejects liquid to a recording medium, includes: a liquid droplet ejecting head including a nozzle surface in which a plurality of nozzles are formed, the nozzles being configured to eject liquid droplets; a dielectric elastomer disposed around the nozzle surface; a pair of electrodes configured to sandwich the dielectric elastomer; and a nozzle protector formed integrally with the dielectric elastomer on a recording medium side of the dielectric elastomer.
In accordance with this configuration, when an electric field is generated by applying the voltage between the pair of electrodes, the dielectric elastomer contracts in an electric field direction, thereby changing the position of the nozzle protector. Even if the volume of the dielectric elastomer is small, the dielectric elastomer can deform greatly. Therefore, it is possible to significantly suppress the increase in size of the apparatus. Moreover, since the dielectric elastomer precisely changes its deformation amount in accordance with the value of the voltage applied between the electrodes, the position of the nozzle protector connected to the dielectric elastomer can also be controlled precisely. The dielectric elastomer may be attached to a member (such as a reinforcing frame, a carriage or a base) formed integrally with the liquid droplet ejecting head or may be attached to the liquid droplet ejecting head itself. Moreover, the nozzle protector may be attached to a member formed integrally with the dielectric elastomer of may be attached to the dielectric elastomer itself.
A direction in which the pair of electrodes sandwich the dielectric elastomer may substantially conform to a normal direction of the nozzle surface.
In accordance with this configuration, since the dielectric elastomer contracts in the normal direction of the nozzle surface, it is possible to easily change the distance of the nozzle protector from the nozzle surface.
The nozzle protector may be attached indirectly to a surface of the dielectric elastomer which is orthogonal to a direction in which the dielectric elastomer mainly contracts.
In accordance with this configuration, the amount of displacement of the nozzle protector can be increased.
The dielectric elastomer may be disposed such that a main surface thereof is opposed to the nozzle protector, one of the pair of electrodes may be formed on a surface of the dielectric elastomer which surface is located on a side of the nozzle protector, and the other one of the pair of electrodes may be formed on a surface of the dielectric elastomer which surface is located on a side opposite the side of the nozzle protector.
In accordance with this configuration, since a main surface that is a largest flat surface of the dielectric elastomer is opposed to the nozzle protector, and the electrode is stacked on the main surface, it is possible to stabilize displacement accuracy of the nozzle protector.
The liquid droplet ejecting head may include: a passage unit having the nozzle surface, and a plurality of liquid chambers which are respectively disposed to communicate with the plurality of nozzles; and an actuator having a plurality of driving portions configured to independently change volumes of the plurality of liquid chambers. A reinforcing frame may be attached to a surface of the passage unit opposite the nozzle surface so as to project from the surface of the passage unit; and the nozzle protector may be disposed such that the dielectric elastomer is sandwiched between the nozzle protector and a portion of the reinforcing frame which portion projects from the surface of the passage unit.
In accordance with this configuration, the dielectric elastomer can be disposed by effectively utilizing a space on a side of the passage unit.
The liquid droplet ejecting apparatus may further include: a voltage generator configured to apply a voltage between the pair of electrodes; and a controller configured to control the voltage generator.
In accordance with this configuration, the dielectric elastomer can be suitably automatically controlled.
The controller may be configured to control the voltage generator such that the nozzle protector moves between a projecting position in which the nozzle protector projects beyond the nozzle surface toward the recording medium and a non-projecting position in which the nozzle protector does not project beyond the nozzle surface toward the recording medium. The non-projecting position includes a position in a case where a surface of the nozzle protector which surface is located on a side of the recording medium is flush with the nozzle surface, and a position in a case where the surface of the nozzle protector which surface is located on the side of the recording medium moves away from the recording medium to be located more distant from the recording medium than the nozzle surface.
In accordance with this configuration, it is possible to easily adjust a priority balance between a nozzle protecting function of causing the nozzle protector to project so as not to cause the recording medium to contact the nozzle surface, and an ejecting accuracy improving function of decreasing the amount of projection of the nozzle protector so as to cause the nozzle surface and the recording medium to get close to each other.
In a state where a voltage is not applied between the pair of electrodes, the nozzle protector may be located at the projecting position, and when the voltage is applied between the pair of electrodes, the dielectric elastomer may contract in a normal direction of the nozzle surface, and the nozzle protector may move to the non-projecting position.
In accordance with this configuration, since the nozzle protector usually projects due to its functions, it is set to project in a state where the voltage is not applied between the electrodes. With this, a time during which the voltage is applied can be reduced, and thereby the power consumption can be suppressed.
The liquid droplet ejecting apparatus may further include a wiping device configured to carry out an operation of wiping the nozzle surface, wherein the controller may control the voltage generator such that the voltage is applied between the pair of electrodes during the operation of the wiping device.
In accordance with this configuration, the voltage may be applied in the wiping operation which is much less frequently carried out than printing. With this, the time during which the voltage is applied can be reduced significantly, and thereby the power consumption can be suppressed.
The voltage applied between the pair of electrodes during the operation of the wiping device may be a voltage causing the nozzle protector to move to the non-projecting position.
In accordance with this configuration, since the nozzle protector moves away from the recording medium to be located more distant from the recording medium than the nozzle surface, it is possible to easily wipe the nozzle surface.
The liquid droplet ejecting head may be an ink jet head, the recording medium may be a printing sheet, and the controller may control the voltage generator such that an amount of projection of the nozzle protector which projects beyond the nozzle surface toward the recording medium than is changed in accordance with a printing condition.
In accordance with this configuration, since the amount of projection of the nozzle protector from the nozzle surface can be changed in accordance with the printing condition, the amount of projection of the nozzle protector can be optimized in accordance with a printing state. To be specific, it is possible to adjust in accordance with the printing condition a priority balance between the nozzle protecting function of causing the nozzle protector to project so as not to cause the recording medium to contact the nozzle surface, and an image quality improving function of decreasing the amount of projection of the nozzle protector so as to cause the nozzle surface and the recording medium to get close to each other. Therefore, it is possible to suitably achieve both the protection of the nozzle surface and the improvement of the image quality. The printing condition is not limited to a condition input by a user, and may be a condition detected by, for example, a detecting device, and received by a control device.
The controller may control the voltage generator such that the amount of projection of the nozzle protector toward the recording medium decreases as the printing condition increases a degree of contribution to an improvement of image quality.
In accordance with this configuration, generally, the recording medium becomes less likely to contact the nozzle surface as the printing condition is associated with high image quality. Therefore, by decreasing the amount of projection of the nozzle protector, it is possible to suppress contact between the recording medium and the nozzle protector. On this account, it is possible to effectively decrease the gap between the nozzle surface and the recording medium.
The printing condition may include printing resolution information, and the controller may control the voltage generator such that the amount of projection of the nozzle protector decreases as a printing resolution of the printing resolution information increases.
In accordance with this configuration, the degree of abrasion of the recording medium with respect to the nozzle surface differs depending on the printing resolution. Therefore, by decreasing the amount of projection of the nozzle protector as the printing resolution increases, it is possible to effectively balance the prevention of abrasion and the improvement in printing accuracy.
The printing condition may include recording medium type information, and the controller may control the voltage generator such that the amount of projection of the nozzle protector decreases as flexibility of the recording medium of the recording medium type information decreases.
In accordance with this configuration, by increasing the amount of projection of the nozzle protector as the flexibility of the recording medium increases, it is possible to effectively prevent or reduce the contact between the recording medium and the nozzle surface.
The printing condition may include printing speed information, and the controller may control the voltage generator such that the amount of projection of the nozzle protector decreases as a printing speed of the printing speed information decreases.
In accordance with this configuration, the contact of the recording medium with respect to the nozzle surface decreases as the printing speed decreases as in high-quality image printing. Therefore, decreasing the amount of projection of the nozzle protector can contribute to the improvement of the image quality. Meanwhile, by increasing the amount of projection of the nozzle protector as the printing speed increases as in low-quality image printing, it is possible to effectively prevent or reduce the contact of the recording medium with respect to the nozzle surface. The printing speed includes a scanning speed of the head and a feeding speed of the recording medium.
The liquid droplet ejecting apparatus may further include: a gap adjusting mechanism configured to displace the ink jet head in a normal direction of the nozzle surface; and a gap controller configured to control the gap adjusting mechanism such that a gap between the nozzle surface and the recording medium decreases as the printing condition increases a degree of contribution to an improvement of image quality.
In accordance with this configuration, since the gap between the nozzle surface and the recording medium decreases at the time of the high-quality image printing, it is possible to effectively improve the ejecting accuracy of the ink, thereby improving the image quality.
The liquid droplet ejecting apparatus may further includes a flexible cable connected to the liquid droplet ejecting head, wherein the liquid droplet ejecting head may include a passage unit having a plurality of liquid chambers which are respectively disposed to communicate with the plurality of nozzles, and an actuator having a plurality of driving portions configured to independently change volumes of the plurality of liquid chambers, and the flexible cable may include a plurality of actuator driving wires connected to the plurality of driving portions of the actuator, and a dielectric elastomer driving wire connected to at least one of the pair of electrodes.
In accordance with this configuration, since the flexible cable connected to the ink jet head also functions as a wire member connected to the electrode of the dielectric elastomer, it is possible to reduce the number of components.
The nozzle protector may be attached to a surface of the dielectric elastomer, which is orthogonal to a direction in which the dielectric elastomer mainly contracts.
In accordance with this configuration, the amount of displacement of the nozzle protector can be increased.
The nozzle protector may be made of an electrically-conductive material, and the nozzle protector may function as one of the pair of electrodes.
In accordance with this configuration, since the nozzle protector made of the electrically-conductive material also functions as the electrode, it is possible to reduce the number of components.
Embodiments of the invention now are described with reference to the accompanying drawings, which are given by way of example only, and are not intended to limit the present invention.
Preferred embodiments of the present invention, and their features and advantages, may be understood by referring to accompanying drawings, like numerals being used for corresponding parts in the various drawings. In the following description, a direction in which an ink jet head ejects ink is referred to as “downward” or “below”, and its opposite direction is referred to as “upward”.
As shown in
As shown in
An area in which the image recording unit 16 reciprocates includes: a printing area in which an image is recorded on a printing sheet 30 (see
The image recording unit 16 includes a carriage 24 that is a casing. The carriage 24 includes four buffer tanks 25 which temporality store the ink. The cartridge mounting portion 26 is provided on a right front side of the guide rail 15. Four-color (black, cyan, magenta and yellow) ink cartridges 27 are detachably attached to the cartridge mounting portion 26. The ink cartridges 27 attached to the cartridge mounting portion 26 are connected to the buffer tanks 25, respectively, via ink supply tubes 28.
As shown in
A platen 34 is disposed below the image recording unit 16. A feed roller 35 and a pinch roller 36 are provided upstream from the image recording unit 16 in a direction where a sheet is fed (hereinafter referred to as a sheet feeding direction). The feed roller 35 and the pinch roller 36 are configured to sandwich therebetween the printing sheet 30 being fed through the feed path 32 and to feed the printing sheet 30 onto the platen 34. A sheet discharge roller 37 and a pinch roller 38 are provided downstream of the image recording unit 16 in the sheet feeding direction. The sheet discharge roller 37 and the pinch roller 38 are configured to sandwich therebetween the printed printing sheet 30 and to feed the printed printing sheet 30 onto the sheet discharge tray 7 (see
An ink jet head 41 (liquid droplet ejecting head) is attached to a lower portion of the carriage 24 via a frame-plate-shaped reinforcing frame 40 having a central opening 40a. Note that the reinforcing frame 40 may have any shape as long as it does not block the orbit of the ink ejected from the nozzles 84.
The ink jet head 41 includes: a passage unit 42 having a plurality of liquid chambers 85 (see
A frame-shaped protector driving device 44 is bonded to a lower surface of the reinforcing frame 40 which projects from the passage unit 42. The protector driving device 44 includes: a frame-plate-shaped dielectric elastomer 45; a thin-film upper electrode 46 formed on an upper surface, i.e, a main surface of the dielectric elastomer 45; and a thin-film lower electrode 47 formed on a lower surface, i.e., a main surface of the dielectric elastomer 45. A frame-plate-shaped nozzle protector 48 is bonded to a lower surface of the protector driving device 44 which surface is located on the platen 34 side (that is, on the printing sheet side). To be specific, the dielectric elastomer 45 is disposed such that the upper surface thereof is attached to the reinforcing frame 40 via the upper electrode 46, and the lower surface thereof is attached to the nozzle protector 48 via the lower electrode 47. Therefore, the dielectric elastomer 45 is sandwiched between the projecting portion of the reinforcing frame 40 and the nozzle protector 48 via the electrodes 46 and 47 around the passage unit 42 (see
Further, the carriage 24 includes a head control device 49 which is connected to the ink jet head 41 via a flat flexible cable 51 (see
Moreover, the nozzle protector 48 is disposed around the nozzle surface 42a of the ink jet head 41 in plan view so as to be spaced apart from the ink jet head 41 by a very short distance. The nozzle protector 48 projects, for example, 0.3 mm below the nozzle surface 42a in a state where the voltage is not applied between the upper electrode 46 and the lower electrode 47. When the voltage is applied between the upper electrode 46 and the lower electrode 47, the dielectric elastomer 45 contracts in the normal direction of the nozzle surface 42a, and thereby the nozzle protector 48 moves away from the platen 34 (printing sheet) side to a non-projecting position side in which the nozzle protector 48 does not project beyond the nozzle surface 42a toward the platen 34 (printing sheet).
As shown in
Moreover, the actuator driving wire portion 51a extends through the large opening 24a to be connected to the actuator 43 of the ink jet head 41. The dielectric elastomer driving wire portion 51b extends through the small opening 24b to be connected to the upper electrode 46 of the protector driving device 44. The grounding wire portion 51c extends through the small opening 24b to be connected to the lower electrode 47 of the protector driving device 44.
As shown in
The actuator 43 is formed by stacking a plurality of sheet-shaped piezoelectric elements 70 made of, for example, PZT. The actuator 43 is disposed to cover the pressure chambers 82. Among the piezoelectric elements 70, each of even numbered piezoelectric elements 70 counted from bottom is provided on an upper surface thereof with individual electrodes 71 at positions corresponding to the pressure chambers 82. Moreover, each of odd numbered piezoelectric elements 70 counted from bottom is provided on an upper surface thereof with a common electrode 72 which corresponds to a plurality of the pressure chambers 82. To be specific, the individual electrode 71 and the common electrode 72 are disposed to sandwich therebetween one piezoelectric element 70 except for the lowermost and uppermost piezoelectric elements 70. An area sandwiched by the individual electrode 71 and the common electrode 72 is a driving portion. The voltage is applied between the individual electrode 71 and common electrode 72 of the actuator 43 from the head control device 49 via the flexible cable 51. With this, a necessary portion of the piezoelectric element 70 is bent in the stack direction to change the volume of the necessary pressure chamber 82, thereby ejecting the ink from the nozzle 84.
As shown in
To be specific, the main control device 50 includes an input receiving section 53, a resolution determining section 54, a printing sheet determining section 55, a printing speed determining section 56, a wiping command receiving section 58, a control section 59 and an output section 60. The input receiving section 53 receives a printing condition input by a user using the operation panel 10, a printing condition sent from an external personal computer (not shown), or a printing condition detected by some kind of detecting device (for example, an optical sensor which determines a type of printing sheet).
The resolution determining section 54 determines a printing resolution from the printing condition received by the input receiving section 53. The printing sheet determining section 55 determines a type of printing sheet (e.g., standard, inkjet, glossy, and transparency) from the printing condition received by the input receiving section 53. The printing speed determining section 56 determines a scanning speed and a sheet feeding speed of the image recording unit 16 from the printing condition received by the input receiving section 53. The wiping command receiving section 58 receives from a wiping command section (not shown) a wiping command for starting an operation of wiping the nozzle surface 42a with the wiper blade 21.
The control section 59 transmits via the output section 60 to the head control device 49 a control signal for reducing an amount to cause the nozzle protector 48 to project toward the printing sheet 30 as the printing conditions determined by the resolution determining section 54, the printing sheet determining section 55 and the printing speed determining section 56 are associated with a higher degree of contribution to an improvement of image quality. The head control device 49 includes a voltage applying section 61 that is a voltage generator for applying a voltage between the upper electrode 46 (see
To be specific, the control section 59 transmits to the voltage applying section 61 a control signal for reducing an amount to cause the nozzle protector 48 to project from the nozzle surface 42a toward the printing sheet 30 as the printing resolution determined by the resolution determining section 54 is higher. Moreover, the control section 59 transmits to the voltage applying section 61a control signal for reducing an amount to cause the nozzle protector 48 to project from the nozzle surface 42a toward the printing sheet 30 as the printing sheet determined by the printing sheet determining section 55 has less flexibility. Further, the control section 59 transmits to the voltage applying section 61 a control signal for reducing an amount to cause the nozzle protector 48 to project from the nozzle surface 42a toward the printing sheet 30 as the printing speed determined by the printing speed determining section 56 is lower. In addition, the control section 59 transmits via the output section 60 to the voltage applying section 61a control signal for causing the nozzle protector 48 to retract until the lower surface of the nozzle protector 48 becomes flush with the nozzle surface 42a, that is, causing the nozzle protector 48 to move up to the non-projecting position, when the wiping command receiving section 58 receives the wiping command.
Next, an up-down operation of the nozzle protector 48 will be explained. As shown in
As shown in
As shown in
As shown in
In accordance with the above configuration, the position of the nozzle protector 48 can be changed easily by applying the voltage between the upper electrode 46 and the lower electrode 47 to contract the dielectric elastomer 45 in the normal direction of the nozzle surface 42a. Even the dielectric elastomer 45 having a small volume can deform greatly. Therefore, it is possible to significantly suppress the increase in size of the apparatus. Moreover, since the dielectric elastomer 45 precisely changes its deformation amount in accordance with the value of the voltage applied between the upper electrode 46 and the lower electrode 47, the position of the nozzle protector 48 integrally connected to the dielectric elastomer 45 can also be controlled precisely. Further, since the dielectric elastomer 45 is disposed around the entire periphery of the nozzle surface 42a, the nozzle protector 48 can be moved while maintaining its posture without using a guide.
Moreover, the nozzle protector 48 can continuously change its amount of projection toward the printing sheet 30 in the normal direction of the nozzle surface 42a. Therefore, it is possible to easily adjust a priority balance between a nozzle protecting function of causing the nozzle protector 48 to project so as not to cause the printing sheet 30 to contact the nozzle surface 42a, and an image quality improving function of decreasing the amount of projection of the nozzle protector 48 so as to cause the nozzle surface 42a and the printing sheet 30 to get close to each other.
Further, the voltage applied to the upper electrode 46 is set to zero in the frequently-used standard sheet/low resolution mode, while the voltage applied to the upper electrode 46 is set to maximum in the wiping operation which is much less frequently carried out than the printing. Therefore, it is possible to efficiently suppress the power consumption. Moreover, the printing sheet 30 becomes less likely to contact the nozzle surface 42a as the printing condition is associated with high image quality (high resolution, hard printing sheet, low printing speed). Therefore, it is possible to achieve a further improvement of the image quality by decreasing the amount of projection of the nozzle protector 48 to reduce a gap between the nozzle surface 42a and the printing sheet 30.
Further, since a main surface of the dielectric elastomer 45 that is a largest flat surface thereof is opposed to the nozzle protector 48, it is possible to stabilize displacement accuracy of the nozzle protector 48. Moreover, since the flexible cable 51 connected to the actuator 43 of the ink jet head 41 also functions as a wire member connected to the electrodes 46 and 47 formed on upper and lower surfaces, respectively, of the dielectric elastomer 45, it is possible to reduce the number of components.
Embodiment 2 is different from Embodiment 1 in that the gap between the nozzle surface 42a of the ink jet head 41 and the printing sheet 30 is adjustable. In Embodiment 2, same reference numbers are used for members corresponding to the members in Embodiment 1, and same explanations thereof are omitted.
As shown in
Moreover, a solenoid electric-powered actuator 93 is disposed between the first member 91 and the second member 92 to relatively displace the first member 91 in the vertical direction with respect to the second member 92. The electric-powered actuator 93 is supplied with electric power and controlled by a separate control device (not shown) via a wire 94. That is, a gap adjusting mechanism 95 is realized such that the second member 92 can be relatively displaced with respect to the first member 91 by the electric-powered actuator 93.
As shown in
To be specific, the gap control section 96 controls the electric-powered actuator 93 such that the gap between the nozzle surface 42a and the printing sheet 30 decreases as the printing resolution determined by the resolution determining section 54 increases. Moreover, the gap control section 96 controls the electric-powered actuator 93 such that the gap between the nozzle surface 42a and the printing sheet 30 decreases as the flexibility of the printing sheet determined by the printing sheet determining section 55 decreases. Further, the gap control section 96 controls the electric-powered actuator 93 such that the gap between the nozzle surface 42a and the printing sheet 30 decreases as the printing speed determined by the printing speed determining section 56 decreases. Note that the positional control of the nozzle protector 48 is carried out in the same manner as in Embodiment 1.
In accordance with the above configuration, as the printing condition is associated with high image quality (high resolution, hard printing sheet, low printing speed), the gap between the nozzle surface 42a and the printing sheet 30 decreases while the amount of projection of the nozzle protector 48 decreases. Therefore, accuracy of ejecting ink onto the printing sheet 30 improves, thereby further improving the image quality.
Embodiment 3 is different from Embodiment 1 in that a nozzle protector 148 also functions as the lower electrode 47. In Embodiment 3, same reference numbers are used for members corresponding to the members in Embodiment 1, and same explanations thereof are omitted.
As shown in
The actuator driving wire portion 51a of the flexible cable 51 is connected to the actuator 43 of the ink jet head 41. The dielectric elastomer driving wire portion 51b of the flexible cable 51 is connected to the upper electrode 46. The grounding wire portion 51c of the flexible cable 51 is connected to the nozzle protector 48.
In accordance with the above configuration, since the nozzle protector 48 made of the electrically-conductive material also functions as the lower electrode, it is possible to reduce the number of components. The present invention is applied to an ink jet printer in the above-described embodiments, however, the present invention may be applied to a recording apparatus which ejects liquid, such as electrically-conductive liquid, other than ink.
Although embodiments of the present invention have been described in detail herein, the scope of the invention is not limited thereto. It will be appreciated by those skilled in the art that various modifications may be made without departing from the scope of the invention. Accordingly, the embodiments disclosed herein are only exemplary. It is to be understood that the scope of the invention is not to be limited thereby, but is to be determined by the claims which follow.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-192032 | Jul 2007 | JP | national |
| 2007-192033 | Jul 2007 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 6299288 | Abeywardane et al. | Oct 2001 | B1 |
| Number | Date | Country |
|---|---|---|
| 2003072041 | Mar 2003 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20090027451 A1 | Jan 2009 | US |
