Patent Application
20100073433
The present application claims priority from Japanese Patent Application No. 2008-245456, which was filed on Sep. 25, 2008, the disclosure of which is herein incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates in general to a liquid ejecting head for ejecting a liquid therefrom.
2. Description of the Related Art
The viscosity of a liquid such as ink ejected from a liquid ejecting head varies depending upon the temperature of the liquid. In general, the viscosity of the liquid is increased under a low temperature condition. Accordingly, under the low temperature condition, a resistance against a flow of the liquid at a time when the liquid flows into a pressure chamber becomes large, so that it is difficult to obtain a satisfactory ejection effect even if a drive frequency is increased. Further, in order to obtain, under the low temperature condition, the same ejection characteristic (including the ejection amount and the ejection speed) as obtained under an ordinary temperature condition, it is needed to give, to the liquid in the pressure chamber, ejection energy larger than that given under the ordinary temperature condition, by increasing a drive voltage. In this instance, however, it is needed to increase a withstand voltage of an actuator configured to give the ejection energy to the liquid in the head and a withstand voltage of a driver IC configured to drive the actuator. Thus, ejection of the liquid having high viscosity entails some difficulty.
In view of the above, the following Patent Document 1 discloses an ink-jet recording apparatus in which a sub tank, an ink supply pipe connecting the sub tank and a head chip, and a flow-passage substrate provided on the head chip are provided with respective heating devices, for the purpose of lowering the viscosity of the ink under the low temperature condition.
Patent Document 1: JP-A-2002-264362
The ink-jet recording apparatus disclosed in the above-indicated Patent Document 1 is provided with the three heating devices, and one of the three heating devices is disposed outside the head chip, rendering the structure of the apparatus complicated. Further, even though the heating device is disposed on the upper surface of the flow-passage substrate, it is impossible to effectively warm the ink in the head chip, so that the viscosity of the ink in the head cannot be sufficiently lowered.
A need has arisen for a liquid ejecting head capable of effectively warming a liquid that flows thereinto.
According to one embodiment herein, a liquid ejecting head for ejecting a liquid from a plurality of ejection holes may comprise: a first flow-passage member in which is formed a first liquid-supply passage to which the liquid is supplied from an exterior of the liquid ejecting head; a second flow-passage member in which is formed a second liquid-supply passage connected to the first liquid-supply passage and which has a plurality of outflow ports for dispensing the liquid from the second liquid-supply passage; a third flow-passage member in which are formed (a) at least one common liquid passage each communicating with at least one of the plurality of outflow ports of the second flow-passage member and (b) a plurality of individual liquid passages which are provided so as to respectively correspond to the plurality of ejection holes, each of which is connected to any one of the at least one common liquid passage, and which respectively have pressure chambers formed therein, each of the plurality of individual liquid passages introducing the liquid to a corresponding one of the plurality of ejection holes via a corresponding one of the pressure chambers; and at least one energy giving member configured to give ejection energy to the liquid in each of the pressure chambers that are formed respectively in the plurality of individual liquid passages, wherein the first flow-passage member, the second flow-passage member, and the third flow-passage member are superposed in this order on each other, and wherein the liquid ejecting head further comprises a heater disposed between one surface of the first flow-passage member that faces the second flow-passage member and facing surface of the second flow-passage member as one surface thereof that faces the first flow-passage member.
In the liquid ejecting head described above, the liquid in the head can be effectively warmed by the heater disposed between the one surface of the first flow-passage member and the facing surface of the second flow-passage member which faces that one surface, whereby the viscosity of the liquid in the head can be sufficiently lowered.
The above and other objects, features, advantages and technical and industrial significance of the present invention will be better understood by reading the following detailed description of a preferred embodiment of the invention, when considered in connection with the accompanying drawings, in which:
Referring to the drawings, there will be explained an embodiment of the present invention.
In the ink-jet printer 101, there is formed a sheet delivery path through which a sheet P is delivered along solid arrows in
The sheet conveying mechanism 16 includes: two belt rollers 6, 7; an endless sheet conveyor belt 8 wound around the two rollers 6, 7 so as to be stretched therebetween; a tension roller 10 which is in contact with the inner circumferential surface of the sheet conveyor belt 8 at the lower half portion of the loop of the sheet conveyor belt 8 while being biased downwardly, thereby applying tension to the sheet conveyor belt 8; and a platen 18 which is disposed in a region enclosed by the sheet conveyor belt 8. The platen 18 supports, at a position where the platen 18 is opposed to the ink-jet heads 1, the sheet conveyor belt 8 so as to prevent the sheet conveyor belt 8 from sagging downward. The belt roller 7 is a drive roller configured to be rotated clockwise in
The outer circumferential surface 8a of the sheet conveyor belt 8 is silicone-treated so as to have adhesion property. A nip roller 4 is disposed at a position on the sheet delivery path at which the nip roller 4 faces the belt roller 6 with the sheet conveyor belt 8 interposed therebetween. The nip roller 4 is configured to press the sheet P supplied from the sheet-supply unit 101b onto the outer circumferential surface 8a of the sheet conveyor belt 8. The sheet P pressed onto the outer circumferential surface 8a of the sheet conveyor belt 8 is conveyed in a sheet conveyance direction, namely, in a sub scanning direction, (in the rightward direction in
A separation plate 5 is disposed at a position on the sheet delivery path where the separation plate 5 faces the belt roller 7. The separation plate 5 separates the sheet P held on the outer circumferential surface 8a of the sheet conveyor belt 8 therefrom. The separated sheet P is delivered upward while being guided by sheet guides 29a, 29b and nipped by rollers of each of two feed roller pairs 28. Subsequently, the sheep P is ejected from an outlet 30 formed at the upper portion of the casing 101a to the sheet receiving recessed portion 15 formed on the upper surface of the casing 101a.
The four ink-jet heads 1 respectively eject inks of the mutually different colors, i.e., magenta, yellow, cyan, and black. Each ink-jet head 1 has a generally rectangular parallepiped shape having a longer dimension in a main scanning direction that is perpendicular to the sub scanning direction. The dimension of each head 1 as measured in the main scanning direction is larger than the width of the sheet. The four ink-jet heads 1 are arranged side by side in the sheet conveyance direction and immovable in the main scanning direction. That is, the ink jet printer 101 is a printer of a line type.
The bottom surface of each ink-jet head 1 is made as an ejection surface 2a in which are formed a plurality of ejection holes 108 (FIG. 9) through which the ink is ejected. When the sheet P being conveyed passes right below the four ink-jet heads 1, the inks of the different colors are ejected from the ejection holes 108 toward the upper surface of the sheet P, whereby an intended color image is formed on the upper surface, i.e., on the print surface, of the sheet P.
The four ink-jet heads 1 are connected respectively to four ink tanks 17 disposed in the ink tank unit 101c. The inks of the mutually different four colors are stored in the respective four ink tanks 17. The inks are supplied from the ink tanks 17 to the respective ink-jet heads 1 via respective tubes.
Referring to the cross sectional view of
There is formed, in the filter support member 41, an ink flow passage 73 as the first liquid-supply passage that includes the vertically extending inlet 71 in which an ink inlet opening is formed and two vertically extending outlets 72a, 72b in each of which an ink outlet opening is formed. The ink flow passage 73 includes an intermediate portion 93 between the inlet 71 and the two outlets 72a, 72b. In the intermediate portion 93, there is formed an elongate, rectangular opening 74a opening downward.
To the filter support member 41, there is attached a filter 79 in which a plurality of minute through-holes are formed for filtering the ink. The filter 79 divides the intermediate portion 93 into: a first space 74 which is held in communication with the inlet 71 and which is defined by the rectangular opening 74a; and a second space 75 which is held in communication with the outlets 72a, 72b. A region of the second space 75 which does not face the filter 79, i.e., a non-facing region 76, horizontally extends at a height level that is slightly higher than a height level of a region of the second space 75 which faces the filter 79. The two outlets 72a, 72b extend from the non-facing region 76 in the vertically downward direction so as to open to a lower surface 70e of the filter support member 41.
The first space 74 has an elongate, rectangular shape. The opening 74a is sealed by a damper film 78 as a seal member. The damper film 78 has generally the same shape as the opening 74a in plan view. Thus, the damper film 78 cooperates with the filter support member 41 to define the ink flow passage 73. A peripheral wall 74b that defines the opening 74a extends downward to a predetermined height level throughout its periphery, so that the damper film 78 fixed to the lower end of the peripheral wall 74b extends horizontally.
In the second space 75, a downward opening 75a is defined by a recess. The opening 75a faces a part of the damper film 78 that extends from a position on a right side of the center of the damper film 78 to the right-side end of the same 78. The opening 75a has a shape, in plan view, that tapers in both of a direction of the ink flow and a direction opposite to the ink flow direction. The filter 79 has a shape substantially similar to that of the opening 75a and has a size in plan view somewhat larger than the opening 75a. The filter 79 is fixed in the first space 74 so as to cover the opening 75a. In other words, the filter 79 is fixed to the filter support member 41 so as to be opposed to the opening 74a and the damper film 78.
The ink introduced from the inlet 71 initially flows substantially horizontally in the first space 74 from the left to the right in
The damper film 78 is a flexible resin film. Between the damper film 78 and the upper surface of the plate 42, there is formed a clearance that allows deflection of the damper film 78 in accordance with vibration of the ink. According to the structure described above, the damper film 78 is deflected in the substantially vertical direction in accordance with the vibration of the ink, whereby the vibration of the ink can be absorbed and damped.
An opening is formed in an upper surface 70f of the filter support member 41 to define the non-facing region 76. The opening is sealed by a film 76a having flexibility, and the film 76a is deflected in accordance with the vibration of the ink, whereby the vibration of the ink is absorbed and damped.
In the filter support member 41, there is further formed a discharge passage connecting the first space 74 and an outlet opening of the cylindrical projection 70b. The discharge passage initially extends below the non-facing region 76 in the width direction of the filter support member 41, then extends in the longitudinal direction of the filter support member 41 after having extended upward to the same height level as the non-facing region 76, and finally communicates with the cylindrical projection 70b on the downstream side of a position at which the discharge passage comes down to a height level lower than the filter 79. A region 77 having the same height level as the non-facing region 76 is defined by sealing an opening formed in the upper surface 70f of the filter support member 41 with a film 76b. The discharge passage is utilized for discharging air bubbles staying in a portion of the filter support member 41 located on the upstream side of the filter 79.
The laminar body 37 including the plates 42-47 and the small-plate group 48 constitutes the second flow-passage member. Each of the plates of the laminar body 37 is formed of a metal material having a higher degree of heat conductivity than the resin material of the filter support member 41. In the plates of the laminar body 37, there are formed through-holes, openings, and a recess which provide the second liquid-supply passage and eighteen outflow ports described below.
More specifically, two through-holes 42a, 42b are formed through the thickness of the plate 42 in the vicinity of the central portion of the same 42, so as to be opposed to the inlets 72a, 72b, respectively. The two through-holes 42a, 42b are connected to the ink flow passage 73 as the first liquid-supply passage. The upper surface of the plate 42 faces the lower surface 70e of the filter support member 41. In the following description, the upper surface of the plate 42 is referred to as a “facing surface”.
Two openings 43a, 43b are formed through the thickness of the plate 43. The opening 43a extends from the vicinity of the central portion of the plate 43 to one of longitudinal ends of the same 43 while the opening 43a extends from the vicinity of the central portion of the plate 43 to the other of the longitudinal ends of the same 43. Each opening 43a, 43b has a tapered section that tapers in a direction toward the central portion of the plate 43. The openings 43a, 43b are opposed, around ends of the respective tapered sections, to the through-holes 42a, 42b, respectively. Two through-holes 44a, 44b are formed through the thickness of the plate 44 so as to be located at respective longitudinal end portions of the plate 44. The through-holes 44a, 44b are respectively opposed to outer ends of the respective openings 43a, 43b.
An elongate, rectangular opening 45a is formed through the thickness of the plate 45 so as to extend from one of longitudinal end portions of the plate 45 to the other of the longitudinal end portions thereof. The opening 45a is opposed, at its longitudinally opposite ends, to the respective through-holes 44a, 44b. A circular through-hole 46a is formed through the thickness of the plate 46 around the central portion of the same 46. The through-hole 46 has a diameter slightly smaller than the width of the opening 45a and is opposed to the central portion of the opening 45a.
An elongate recess 47a is formed in the plate 47 so as to extend from one of longitudinal end portions of the plate 47 to the other of the longitudinal end portions of the same 47. The central portion of the recess 47a is opposed to the circular opening 46a. The recess 47a is formed by etching a substantially upper half portion of the plate 47 in its thickness direction.
In addition to the recess 47a, eighteen through-holes 47b are formed through the thickness of the plate 47 so as to be located within the recess 47a. More specifically, the eighteen through-holes 47b are located so as to be contiguous to the periphery of the recess 47a and are arranged, along the longitudinal direction of the plate 47, in two rows each consisting of nine through-holes 47b. The nine through-holes 47b in each of the two rows are disposed such that eight through-holes 47b except for the outermost one of the through-holes 47b form four pairs. Each pair consists of two through-holes 47a that are located adjacent to each other. Further, the eighteen through-holes 47b are disposed so as to have point symmetry with respect to the center of the plate 47.
In each of eight inner small plates 48a in the small-plate group 48, there are formed two through-holes 49a which are to be opposed to corresponding two adjacent through-holes 47b of the plate 47. In each of two outer small plates 49b between which the eight inner small plates 48a are disposed, one through-hole 49b is formed so as to be opposed to a corresponding one of the outermost through-holes 47b in the plate 47.
In the present embodiment, the second liquid-supply passage is constituted by the through-holes 42a, 42b formed in the plate 42; the openings 43a, 43b formed in the plate 43; the through-holes 44a, 44b formed in the plate 44; the opening 45a formed in the plate 45; the through-hole 46a formed in the plate 46; and recess 47a formed in the plate 47, which are in communication with each other. The through-holes 47b in the plate 47 and the through-holes 49a, 49b in the plate 48 constitute a plurality of outflow ports connected to the second liquid-supply passage. More specifically, each outflow port is constituted by a combination of the through-hole 47b formed in the plate 47 and the through-hole 48a formed in a corresponding small plate 48a or the through-hole 49b formed in a corresponding small palate 48b. Each outflow port is connected to a corresponding manifold 105 in the flow-passage unit 9 via a corresponding ink supply hole 105b described below.
The two heaters 34, 35 are fixed to the facing surface 42c of the plate 42 so as to be in contact therewith. The length of each heater 34, as measured in the longitudinal direction of each of the plates 42-47 is not larger than half the length of each of the plates 42-47 as measured in the same direction. Each heater 34, 35 has a generally rectangular shape that extends in the longitudinal direction of the reservoir unit 32, and is disposed on the facing surface 42c such that the longitudinal direction of each heater 34, 35 coincides with the longitudinal direction of the reservoir unit 32. A mid point between a line connecting the two heaters 34, 35 coincides with the center of the laminar body 37, as the second flow-passage member, that includes the plates 42-47 and the small-plate group 48. The arrangement reduces a variation in the temperature in the head 1, thereby reducing a variation in the temperature of the ink. Accordingly, it is possible to minimize nonuniformity in the printed image.
The head main body 33 includes the flow-passage unit 9, ten filters 106, and eight actuator units 21. The filters 106 and the actuator units 21 are fixed to the upper surface of the flow-passage unit 9. Each filter 106 is provided for a corresponding one of the ten small plates 48a, 48b, and covers one or two ink supply holes 105b which will be explained.
Each of the eight actuator units 21 includes a plurality of piezoelectric actuators for giving ejection energy to the ink in respective pressure chambers 110 (
A plurality of electronic components are disposed on the base plate 31 of the head 1. The two heaters 34, 35 and the COFs 51 are connected to the electronic components via connectors 31a attached to the base plate 31. The electronic components disposed on the base plate 31 are connected to the control portion 100 via wires not shown. The operations of the two heaters 34, 35 are controlled by the control portion 100. As shown in
The ink that has flowed from the through-holes 42a, 42b down to the openings 43a, 43b flows in the openings 43a, 43b in mutually opposite directions toward the respective longitudinal end or outer end portions of the plate 43. Each of the openings 43a, 43b is a first extending passage portion in the second liquid-supply passage extending along the facing surface 42c of the plate 42. The opening 43a is opposed to the heater 34 while the opening 43b is opposed to the heater 35, in the direction of lamination of the plates of the laminar body 37. As described above, in the present embodiment, the two heaters 34, 35 are disposed on the facing surface 42c of the plate 42, and the second liquid-supply passage has the two first extending passage portions that are opposed to the respective heaters 34, 35. Accordingly, the liquid (ink) can be effectively warmed by the two heaters 34, 35. Further, the openings 43a, 43b are passage portions that are the closest to the heaters 34, 35 in the above-indicated lamination direction, so that the ink flowing in the openings 43a, 43b can be more effectively warmed owing to the plates 42, 43, 44 that have absorbed the heat of the haters 34, 35.
The ink that has flowed from the openings 43a, 43b down to the opening 45a of the plate 45 via the through-holes 44a, 44b of the plate flows in the opening 45a in mutually opposite directions toward the center of the plate 45. The opening 45a includes two second extending passage portions one of which corresponds to a right half portion of the opening 45a and the other of which corresponds to a left half portion of the same 45b, as seen in
In the present embodiment, a resistance against a flow of the ink that flows from the inlet, i.e., the upstream end, of the through-hole 43a to the merge point (i.e., the upstream end of the through-hole 46a) is equal to a resistance of a flow of the ink that flows from the inlet, i.e., the upstream end, of the through-hole 43b to the merge point (i.e., the upstream end of the through-hole 46a. Therefore, there is not caused a difference between the amount of ink that flows in the through-hole 43a and the amount of ink that flows in the through-hole 43b, whereby it is less likely to be caused a difference in the temperature of the ink in the opening 43a and the temperature of the ink in the opening 43b, which inks are to mix with each other at the merge point. As a result, the temperature of the ink after having mixed tends to be uniform, thereby reducing a variation in the temperature of the ink that flows into the respective eighteen outflow ports. Accordingly, it is possible to minimize nonuniformity in the printed image.
In the present embodiment, the opening 45a has a length about twice as large as each of the openings 43a, 43b. In other words, a length of each of the two second extending passage portions from its inlet (corresponding to one longitudinal end of the opening 45a) to its outlet (corresponding to the central portion of the opening 45a) is equal to a length of the opening 43a or 43b as the first extending passage portion from its inlet (corresponding to the inner end of the opening 43a or 43b) to its outlet (corresponding to the outer end of the opening 43a or 43b). Since the second extending passage portions are long, the temperature of the ink can be easily raised by the heaters 34, 35.
The ink flow as a result of merging of the ink flows in the respective two second extending passage portions at the merge point (i.e., the upstream end of the through-hole 46a) drops into the recess 47a of the plate 47 from the downstream end of the through-hole 46a. Then the ink flows in the recess 47a and subsequently flows into the flow-passage unit 9 via the eighteen outflow ports provided by the through-holes 47b and the through-holes 49a, 49b. In the present embodiment, in the laminar body 37, two downstream portions which are located on the downstream side of the corresponding openings 43a, 43b merge with each other, and the eighteen outflow ports are connected to the second liquid-supply passage on the downstream side of the merge point. Accordingly, it is possible to reduce a variation in the temperature of the ink that flows into the eighteen outflow ports.
In the present embodiment, the laminar body 37 is formed of the material having heat conductivity higher than that of the material of the filter support member 41, and the two heaters 34, 35 are fixed so as to be in contact with the facing surface 42c of the plate 42. Accordingly, the heat generated by the two heaters 34, 35 can be efficiently transmitted to the ink. Moreover, the temperature sensors 34a, 35a are integrally disposed on the respective heaters 34, 35, so that it is possible to directly detect, without delay, changes in the temperature of the plates 42 and so on that are caused by the heat generated by the heaters 34, 35.
Referring next to
As shown in
The ink supply holes 105b (
As shown in
The nine plates 122-130 are positioned with and stacked on each other, whereby a plurality of individual ink passages 132 as a plurality of individual liquid passages are defined in the flow-passage unit 9 each of which extends from an outlet of a corresponding one of the sub manifolds 105a to a corresponding one of the ejection holes 108 via a corresponding one of the pressure chambers 110. The ink which has supplied from the reservoir unit 32 to the flow-passage unit 9 via the ink supply holes 105b flows into the sub manifolds 105a from the manifolds 105. The ink in the sub manifolds 105a flows into the individual ink passages 132 and reaches nozzle ejection holes 108 via the apertures 112 each functioning as an orifice and the pressure chambers 110.
The actuator unit 21 will be explained. As shown in
As shown in
The common electrode 134 is kept at a ground potential as a basic potential given by the COF 51. The individual electrodes 135 are electrically connected to terminals of the driver IC 52 via the respective lands 136 and respective internal wires of the COF 51. A drive signal for driving the actuator unit 21 is supplied from the driver IC 52 to the individual electrodes 135 independently of each other. Accordingly, respective portions in the actuator unit 21 sandwiched by and between the individual electrodes 135 and the pressure chambers 110 function as individual actuators which are independent of each other. That is, a plurality of actuators, each as an energy giving member, are provided in the actuator unit 21 in the same number as the pressure chambers 110.
There will be next explained a method of driving each actuator unit 21 to permit ink droplets to be ejected from the nozzles. The piezoelectric layer 141 is polarized in its thickness direction. When an electric field is applied to the piezoelectric layer 141 in the polarization direction with one individual electrode 135 kept at a potential different from that of the common electrode 134, a portion of the piezoelectric layer 141 to which the electric field is applied functions as an active portion that undergoes strain owing to a piezoelectric effect. The active portion expands in a direction of thickness of the layer 141 and contracts in a direction parallel to the plane of the layer 141 (i.e., in the plane direction) when the electric field and the polarization are in the same direction. In this instance, the amount of deformation of the active portion upon expansion and contraction is larger in the plane direction than in the thickness direction. In the actuator unit 21, the uppermost one 141 of the three piezoelectric layers that is the most distant from the pressure chambers 110 is an active layer including the active portions while the lower two piezoelectric layers 142, 143 nearer to the pressure chambers 110 are non-active layers. As shown in
In the illustrated embodiment, the ink that flows in the laminar body 37 can be effectively warmed by the heaters 34, 35 disposed between the facing surface 42c of the plate 42 and the lower surface of the filter support member 41. Accordingly, the viscosity of the ink in each head 1 can be sufficiently lowered. Hence, even under the low temperature condition, the resistance against the flow of the ink at a time when the ink flows into the pressure chamber 110 does not become high, so that increasing the drive frequency becomes effective for obtaining a satisfactory ejection effect.
Further, the same ejection characteristic as obtained under the ordinary temperature condition can be obtained under the low temperature condition without increasing the drive voltage, so that it is not required to increase the withstand voltage of the actuator units 21 and the withstand voltage of the driver ICs 52 configured to drive the actuator units 21.
It is to be understood that the invention is not limited to the details of the illustrated embodiment, but may be embodied with various changes and modifications, which may occur to those skilled in the art, without departing from the spirit and scope of the invention defined in the attached claims. For instance, the heaters 34, 35 may be disposed on the lower surface of the filter support member 41. Only one heater or more than three heaters may be used. Only one through-hole may be formed in the plate 42. Only one opening may be formed in the plate 43. Two openings may be formed in the plate 45. Only one common liquid passage may be formed in the flow-passage unit 9. The passage structure in the head 1 is not limited to that in the illustrated embodiment, but may be otherwise modified. The energy giving member is not limited to the one utilizing the piezoelectric body, but the one of a thermal type may be utilized.
It is to be understood that the principle of the invention may be applicable not only to the head for a line printer as in the illustrated embodiment, but also to a head for a serial printer, and further to a head for ejecting a liquid other than the ink.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-245456 | Sep 2008 | JP | national |
