1. Technical Field
The present invention relates to a liquid ejecting apparatus, such as an ink jet recording apparatus, as well as a control method therefor, and in particular, it relates to a liquid ejecting apparatus employing a configuration which causes a meniscus of a nozzle to slightly oscillate to a degree that does not cause any liquid ejection, as well as a control method therefor.
2. Related Art
A liquid ejecting apparatus is an apparatus which is provided with a liquid ejection head capable of ejecting liquid as liquid droplets through nozzles, and which causes this liquid ejection head to eject various kinds of liquid. Representative examples of this liquid ejecting apparatus include an image recording apparatus, such as an ink jet recording apparatus (a printer) which is provided with an ink jet type record head (hereinafter, referred to as just a record head), and which performs printing by causing liquid-state ink to be ejected as ink droplets through nozzles of this record head. Besides, this liquid ejecting apparatus has been used for ejection of various kinds of liquid, such as a color material used in a color filter for a liquid crystal display and the like, an organic material used in an organic electro-luminescence (EL) display, and an electrode material used in an electrode formation. Further, a record head for an image recording apparatus ejects liquid-state inks, and a color material ejection head for a display manufacturing apparatus ejects solutions of color materials each for a corresponding one of red (R), green (G) and blue (B) colors. Further, an electrode material ejection head for an electrode formation apparatus ejects liquid-state electrode materials, and a living organic material head for a chip manufacturing apparatus ejects solutions of living organic materials.
With respect to this kind of liquid ejection head, in a nozzle, liquid (meniscus) is exposed to outside air, and thus, the evaporation of solvent components included in the liquid, or the like, sometimes, causes a viscosity increase of the liquid. This viscosity increase of liquid is likely to cause a situation where the liquid is not normally ejected through the nozzle. In order to suppress such a viscosity increase of liquid, during a liquid ejecting operation (for example, during a printing operation regarding a printer), with respect to a nozzle through which liquid is not ejected, liquid contained in a pressure chamber corresponding to the nozzle as well as a meniscus of the nozzle are caused to slightly oscillate to a degree that does not cause the liquid to be ejected through the nozzle by driving a pressure generation means (for example, a piezoelectric element, a heater element or the like) corresponding to the nozzle through applying a slight oscillation pulse to the pressure generation means. That is, this slight oscillation operation causes agitation of liquid existing in an area around the nozzle, so that the viscosity increase is suppressed (for example, refer to JP-A-2000-037867).
In a technology disclosed in JP-A-2000-037867, a driving pulse for the slight oscillation is a pulse whose driving voltage is set so as to be lower than that of an ejection driving pulse which, when performing printing, causes ink to be ejected by driving a pressure generation means.
Meanwhile, recently, such a printer as described above has been used for ejection of various types of ink. Among these types of ink, there are some types of ink each having viscosity likely to increase. Further, the some types of ink include a type of ink in which a particularly large amount of a solid component, such as a color material or a resin, is contained, or a type of ink whose viscosity is relatively high. When the viscosity of ink has increased to a certain level, it is necessary to perform a cleaning process to forcibly suck and discharge the ink from a nozzle. Such a cleaning process consumes a large amount of ink, and thus, it is preferable to reduce the frequency of performing the cleaning process to a level as low as possible. In order to improve a so-called intermittent capability, which is related to a tolerable time within which a state where any cleaning process and any ink ejection are not performed can be kept as it is, it is necessary to improve an effect of agitating ink by raising a voltage of a slight oscillation pulse to a certain degree. Nevertheless, the raise of a voltage of the slight oscillation pulse results in an increase of the oscillation of a meniscus by a degree corresponding to a raised voltage of the slight oscillation pulse, and thus, there has been a disadvantage in that the resultant residual oscillation of the meniscus is likely to give an adverse effect on an ejection stability in subsequent printing operations. Specifically, there has been a disadvantage in that, with respect to ink ejected through a nozzle, the variation of an ink amount, the occurrence of flight bending and the like are likely to occur.
An advantage of some aspects of the invention is to provide a liquid ejecting apparatus and a control method therefor which enable realization of both of the improvement of an intermittent capability and an ejection stability.
A liquid ejecting apparatus according to a first aspect of the invention, which is a liquid ejecting apparatus to be provided, includes a liquid ejection head that includes a nozzle through which liquid is ejected, a pressure chamber which communicates with the nozzle, and a pressure generation means which causes liquid contained in the pressure chamber to be subjected to a pressure variation, and that causes liquid to be ejected through the nozzle by driving the pressure generation means; and a drive waveform generation means that generates a slight oscillation waveform which does not cause liquid to be ejected through the nozzle, wherein the slight oscillation waveform includes a first variation element which varies up to a first electric potential of a first polarity relative to a reference electric potential and thereby causes liquid contained in the pressure chamber to be subjected to a pressure variation, a second variation element which varies up to a second electric potential of a second polarity, which is different from the first polarity, relative to the reference electric potential and thereby causes liquid contained in the pressure chamber to be subjected to a pressure variation, a third variation element which varies up to a third electric potential of the first electric potential and thereby causes liquid contained in the pressure chamber to be subjected to a pressure variation, and a fourth variation element which varies up to the reference electric potential and thereby causes liquid contained in the pressure chamber to be subjected to a pressure variation.
According to the first aspect of the invention, the slight oscillation waveform includes the first variation element which varies up to a first electric potential of a first polarity relative to a reference electric potential and thereby causes liquid contained in the pressure chamber to be subjected to a pressure variation, the second variation element which varies up to a second electric potential of a second polarity, which is different from the first polarity, relative to the reference electric potential and thereby causes liquid contained in the pressure chamber to be subjected to a pressure variation, the third variation element which varies up to a third electric potential of the first electric potential and thereby causes liquid contained in the pressure chamber to be subjected to a pressure variation, and the fourth variation element which varies up to the reference electric potential and thereby causes liquid contained in the pressure chamber to be subjected to a pressure variation. Thus, it becomes possible to cause the pressure chamber to be contracted to a greater degree by the second variation element, so that the effect of agitation of liquid is improved. Further, it becomes possible to allow the third variation element and the fourth variation element to function as waveform elements for suppressing pressure oscillation caused in the pressure chamber by the first variation chamber and the second variation chamber. Accordingly, when slight oscillation using the relevant slight oscillation waveform is applied, the viscosity increase of liquid can be suppressed and the intermittent capability can be improved, and concurrently therewith, the behavior of the meniscus after the completion of the slight oscillation operation can be suppressed, and thus, it becomes possible to ensure the stability of ejection of liquid in a subsequent ejection operation.
Further, a liquid ejecting apparatus according to a second aspect of the invention includes a liquid ejection head that includes a nozzle through which liquid is ejected, a pressure chamber which communicates with the nozzle, and a pressure generation means which causes liquid contained in the pressure chamber to be subjected to a pressure variation, and that causes liquid to be ejected through the nozzle by driving the pressure generation means; and a drive waveform generation means that generates a slight oscillation waveform which does not cause liquid to be ejected through the nozzle, wherein the slight oscillation waveform includes a first variation element which varies from a reference electric potential up to a first electric potential of a first polarity relative to the reference electric potential and thereby causes liquid contained in the pressure chamber to be subjected to a pressure variation, a second variation element which varies from the first variation element up to a second electric potential of a second polarity, which is different from the first polarity, relative to the reference electric potential and thereby causes liquid contained in the pressure chamber to be subjected to a pressure variation, a third variation element which varies from the second variation element up to a third electric potential of the first electric potential and thereby causes liquid contained in the pressure chamber to be subjected to a pressure variation, and a fourth variation element which varies from the third variation element up to the reference electric potential and thereby causes liquid contained in the pressure chamber to be subjected to a pressure variation.
According to this configuration, the slight oscillation waveform includes the first variation element which varies from a reference electric potential up to a first electric potential of a first polarity relative to the reference electric potential and thereby causes liquid contained in the pressure chamber to be subjected to a pressure variation, the second variation element which varies from the first variation element up to a second electric potential of a second polarity, which is different from the first polarity, relative to the reference electric potential and thereby causes liquid contained in the pressure chamber to be subjected to a pressure variation, the third variation element which varies from the second variation element up to a third electric potential of the first electric potential and thereby causes liquid contained in the pressure chamber to be subjected to a pressure variation, and the fourth variation element which varies from the third variation element up to the reference electric potential and thereby causes liquid contained in the pressure chamber to be subjected to a pressure variation, and thus, it becomes possible to cause the electric potential to vary across the boundary of the opposite polarities. Accordingly, the intermittent capability can be improved by suppressing the viscosity increase of liquid further effectively, and at the same time, the behavior of the meniscus after the completion of the slight oscillation operation can be suppressed, and thus, it becomes possible to ensure the stability of ejection of liquid in a subsequent ejection operation.
Further, in the above configurations, it is preferable to employ a configuration in which the first electric potential and the third electric potential are equal to each other.
According to this configuration, the behavior of the meniscus after the completion of the slight oscillation operation can be suppressed, and thus, it becomes possible to ensure the stability of ejection of liquid in a subsequent ejection operation.
Further, in the above configurations, it is preferable to employ a configuration in which the first electric potential and the third electric potential are different from each other.
According to this configuration, it is possible to set the third electric potential appropriately, and thus, it becomes possible to improve a capability of suppressing the behavior of the meniscus after the completion of the slight oscillation operation.
Further, in the above configurations, it is preferable to employ a configuration in which the second variation element is applied to the pressure generation means at timing of generating pressure oscillation capable of activating pressure oscillation which is excited inside liquid contained in the pressure chamber by the first variation element.
According to this configuration, the second variation element is applied to the pressure generation means at timing of generating pressure oscillation capable of activating pressure oscillation which is excited inside liquid contained in the pressure chamber by the first variation element, and thus, the meniscus is caused to oscillate and the liquid is effectively agitated, so that it becomes possible to improve the intermittent capability.
Further, in the above configurations, it is preferable to employ a configuration in which a period of time from a start of the second variation element to an end of the fourth variation element is equal to a period of time resulting from multiplying a natural oscillation cycle of liquid contained in the liquid chamber by a natural number.
According to this configuration, it is possible to agitate the liquid by allowing the second variation element to activate oscillation of the meniscus, having arisen during the operation of the first variation element, and further, allow the third variation element and the fourth variation element to suppress the oscillation of the meniscus, so that it becomes possible to ensure the intermittent capability and the ejection stability further efficiently.
Further, a control method for controlling a liquid ejecting apparatus, according to a third aspect of the invention, is a control method for a liquid ejecting apparatus including a liquid ejection head that includes a nozzle through which liquid is ejected, a pressure chamber which communicates with the nozzle, and a pressure generation means which causes liquid contained in the pressure chamber to be subjected to a pressure variation, and that causes liquid to be ejected through the nozzle by driving the pressure generation means; and a drive waveform generation means that generates a slight oscillation waveform which does not cause liquid to be ejected through the nozzle. Further, this control method includes causing a slight oscillation operation to be performed by applying a slight oscillation waveform to the pressure generation means, the slight oscillation waveform including a first variation element which varies up to a first electric potential of a first polarity relative to a reference electric potential and thereby causes liquid contained in the pressure chamber to be subjected to a pressure variation, a second variation element which varies up to a second electric potential of a second polarity, which is different from the first polarity, relative to the reference electric potential and thereby causes liquid contained in the pressure chamber to be subjected to a pressure variation, a third variation element which varies up to a third electric potential of the first electric potential and thereby causes liquid contained in the pressure chamber to be subjected to a pressure variation, and a fourth variation element which varies up to the reference electric potential and thereby causes liquid contained in the pressure chamber to be subjected to a pressure variation.
According to this configuration, it becomes possible to provide a high-quality liquid ejecting apparatus.
The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
Hereinafter, an embodiment to practice the invention will be described with reference to the accompanying drawings. It is to be noted here that, although an embodiment described below is subjected to various limitations as a preferable specific example of the invention, the scope of the invention is not limited to this embodiment described below, except for portions each being particularly given a notice indicating a limitation of the invention. Further, in the following description, an ink jet recording apparatus (hereinafter referred to as just a printer) will be exemplified as a liquid ejecting apparatus according to an aspect of the invention.
The carriage 4 is attached to a guide rod 9, which is installed across the housing of the printer 1 in the main scanning direction, in a state of being pivotably supported by the guide rod 9, and is configured so as to move in the main scanning direction along the guide rode 9 by being actuated by the carriage movement mechanism 7. The location of the carriage 4 in the main scanning direction is detected by a linear encoder 10, and the detected signal, that is, encoder pulses (a kind of location information), are sent to a control unit 41 (refer to
A home position, which is a base point of the carriage scanning, is provided in an edge area located outer than a recording area falling within a movement range of the carriage 4. At the home position in this embodiment, there are disposed a capping member 11 for sealing a nozzle forming face (a nozzle forming substrate 15: refer to
A not-illustrated platen heater (a heating means) is provided inside the platen 5 of the printer 1 according to this embodiment. Record paper or a recording medium on the platen 5 is heated by this platen heater, so that fixing and drying of ink having been landed on the record paper or the recording medium is accelerated.
The pressure chamber substrate 14 is a board formed from, for example, a silicon single crystal substrate. In this pressure chamber substrate 14, a plurality of pressure chambers 20 are arranged in parallel in its width direction (in a nozzle row direction) such that every two adjacent ones of the pressure chambers 20 interpose a partition wall 33. In an area outer than the pressure chamber 20 in a direction along the long side of the pressure chamber 20 of the pressure chamber substrate 14 (i.e., in a direction perpendicular to the nozzle row direction), a communicating portion 21 is formed, and this communicating portion 21 and each of the pressure chambers 20 are communicated with each other via an ink feeding path 22 which is provided for each of the pressure chambers 20. In addition, the communicating chamber 21 communicates with a reservoir portion 26 included in the protection substrate 19 described below, and thereby constitutes part of a reservoir 27 which is an ink chamber common to the individual pressure chambers 20. The ink feeding path 22 has a width smaller than that of the pressure chamber 20, and thereby gives a flowing path resistance to ink flowing into the pressure chamber 20 from the communicating chamber 21. These pressure chambers 20, the ink feeding paths 22 and the like included in the pressure chamber substrate 14 are each formed by means of an anisotropic etching method.
The nozzle forming substrate 15, in which a plurality of nozzles 23 are each formed in an opening state, and are arranged in rows such that each of the nozzles 23 is associated with a corresponding one of the pressure chambers 20, is adhered to the lower face of the pressure chamber substrate 14 by using an adhesive agent 34. In this way, an opening at the lower face of each of the pressure chambers 20 is sealed by the nozzle forming substrate 15, and a bottom portion of each of the pressure chambers 20 is defined. That is, the nozzle forming substrate 15 also functions as a material for the bottom portion of each of the pressure chambers 20. The elastic film 16 composed of, for example, silicon dioxide (SiO2) is formed on the upper face (a first opening face) of the pressure chamber substrate 14. Portions sealing the openings of the pressure chambers 20 in the elastic film 16 function as actuation faces.
The insulating film 17 composed of zirconium oxide (ZrO2) is formed on the elastic film 16 described above. Further, on this insulating film 17, piezoelectric elements 18 are arranged such that each of the piezoelectric elements 18 is associated with a corresponding one of the pressure chambers 20. The exemplified piezoelectric element 18 is a so-called piezoelectric element in a bending oscillation mode, and is configured such that a piezoelectric material 18c is interposed between a driving electrode 18a and a common electrode 18b. Further, a lead electrode 24 composed of, for example, gold (Au) or the like is connected to the driving electrode 18a of each of the piezoelectric elements 18. Further, when a driving signal (a driving pulse) has been applied to the driving electrode 18a of the piezoelectric element 18, electric field in accordance with an electric-potential difference arises between the driving electrode 18a and the common electrode 18b. This electric field is applied to the piezoelectric material 18c, so that the piezoelectric material 18c is deformed in accordance with the strength of the electric field. That is, the higher the electric-potential of the driving electrode 18a is made, the central portion of the piezoelectric material 18c in its width direction (i.e., in the nozzle row direction) bends towards the inner side of the pressure chamber 20 (i.e., towards a side nearer the nozzle forming substrate 15) to an increasing degree, so that this bending deforms the elastic film 16 so as to make the volume of the pressure chamber 20 smaller. In contrast, the lower the electric-potential of the driving electrode 18a is made (that is, the nearer zero the electric-potential of the driving electrode 18a is made), the central portion of the piezoelectric material 18c in its short-side direction bends towards the outer side of the pressure chamber 20 (i.e., towards a side farther from the nozzle formation substrate 15) to an increasing degree, so that this bending deforms the elastic film 16 so as to make the volume of the pressure chamber 20 larger.
The protection substrate 19 is adhered to the piezoelectric element 18 side face of the pressure chamber substrate 14. Further, the protection substrate 19 includes piezoelectric element retaining portions 25 each being a space having a size of a degree sufficient not to disturb the displacement of the piezoelectric element 18, and being located at an area facing the piezo electric element 18. Moreover, the protection substrate 19 is provided with a reservoir portion 26 in an area corresponding to the communicating portion 21 of the pressure chamber substrate 14. This reservoir portion 26 is formed in the protection substrate 19 as a penetrating hole of a rectangular opening shape having a long side along the direction in which the pressure chambers 20 are arranged. Further, as described above, this reservoir portion 26 defines the reservoir 27 together with the communicating portion 21 of the pressure chamber substrate 14, which communicates with the reservoir portion 26 itself. This reservoir 27 is provided for each kind of ink (for each color), and reserves ink common to more than two ones of the pressure chambers 20.
Further, a penetrating hole 28 which penetrates the protection substrate 19 in its thickness direction is provided in an area between the piezoelectric retaining portion 25 and the reservoir portion 26 which are included in the protection substrate 19, and a portion of the common electrode 18b and an edge of the lead electrode 24 are exposed within this penetrating hole 28. A compliance substrate 31 including a sealing film 29 and a fixing plate 30 is adhered onto the protection substrate 19. This sealing film 29 is composed of a material having flexibility (for example, a polyphenylene sulfide film), and this sealing film 29 seals one of the faces of the reservoir portion 26. Further, the fixing plate 30 is composed of a hard material, such as a metallic material (for example, a stainless steel material or the like). An area facing the reservoir 27, included in the fixing plate 30, is an opening 32 penetrating in the thickness direction of the fixing plate 30. Thus, one of the faces of the reservoir 27 is sealed by only the sealing film 29 having flexibility.
In the record head 2 configured in such a way as described above, ink is fed from an ink feeding means, such as an ink cartridge, so that portions from the reservoir 27 up to the nozzle 23 are filled with the ink. Further, the supply of a driving signal from the main frame of the printer causes electric field in accordance with an electric-potential difference of the common electrode 18b and the driving electrode 18a, between the common electrode 18b and the driving electrode 18a which correspond to each of the pressure chambers 20, so that the piezoelectric element 18 and the actuation face (the elastic film 16) bend and are deformed, and this deformation causes a pressure variation inside the pressure chamber 20. Through control of this pressure variation, ejection of ink through the nozzle 23 is controlled.
The control unit 41 functions as a timing pulse generation means for generating a timing pulse PTS (refer to
The above driving signal generation circuit 43 generates a driving signal COM including a plurality of ejection driving pulses every receipt of the timing pulse PTS. In other words, the driving signal generation circuit 43 repeatedly generates the driving signal COM at intervals of a cycle (hereinafter, referred to as a unit cycle T) based on the above timing pulse PTS.
Next, an electric configuration of this record head 2 will be described. As shown in
This record head 2 performs ejection control of ink (a kind of liquid) on the basis of print data (pixel data) SI sent from the printer controller 36. In this embodiment, the print data SI, each piece thereof being composed of two bits, is sent to the record head 2 in synchronization with a clock signal CLK in order of a series of upper bits of the print data SI and a series of lower bits of the print data SI, and thus, first, a series of upper bits of the print data SI is set in the second shift register 46. When a series of upper bits of the print data SI has been completely set in the second sift register 46 for each of all the nozzles 23, next, this series of upper bits begins to shift into the first shift register 45. Concurrently therewith, a series of lower bits of the print data SI begins to shift into the second shift register 46.
The first latch circuit 47 is electrically connected to the first shift register 45 as a subsequent stage of the first shift register 45, and the second latch circuit 48 is electrically connected to the second shift register 46 as a subsequent stage of the second shift register 46. Further, when a latch pulse from the printer controller 36 side has been inputted to each of the latch circuits 47 and 48, the first latch circuit 47 latches the series of upper bits, and the second latch circuit 48 latches the series of lower bits. Groups of pieces of record data, each of the groups being latched in a corresponding one of the latch circuits 47 and 48, (i.e., the series of upper bits and the series of lower bits), are outputted to the decoder 49. This decoder 49 generates a piece of pulse selection data for selecting a corresponding one of the driving pulses included in the driving signal COM on the basis of the series of upper bits and the series of lower bits of the record data.
The driving signal COM from the driving signal generation circuit 43 is inputted to the input side of the switch 52. Further, the output side of the switch 52 is connected to the piezoelectric element 18. The switch 52 selectively supplies each of the driving pulses included in the driving pulse COM to the piezoelectric element 18 on the basis of the above piece of pulse selection data. The switch 52 performing such an operation as described above functions as a kind of selective supply means.
Here, in this embodiment, as shown in
The contraction element p3 is a waveform element which is generated subsequent to the first hold element p2. Further, the contraction element p3 is a waveform element whose electric potential varies (rises) with a constant gradient from the first slight expansion electric potential E3, across the reference electric potential Eb and up to the slight oscillation contraction electric potential E4 (corresponding to the second electric potential in any one of the aforementioned aspects of the invention) at the positive polarity side relative to the reference electric potential Eb. The second hold element p4 is a waveform element for holding the slight oscillation contraction electric potential E4, which is a termination electric potential of the contraction element p3, during a constant period of time Δt2. The second expansion element p5 is a waveform element whose electric potential varies from the slight oscillation contraction electric potential E4 up to the first slight oscillation expansion electric potential E3 (corresponding to the third electric potential in any one of the aforementioned aspects of the invention), that is, up to the negative polarity side. Further, the third hold element p6 is a waveform element for holding the first slight oscillation expansion electric potential E3 during a constant period of time Δt3. Further, the return element p7 is a waveform element which returns with a constant gradient from the first slight expansion electric potential E3 up to the reference electric potential Eb.
When the slight oscillation driving pulse Pv configured in such a way as described above has been applied to the piezoelectric element 18, this application causes operation described below.
First, the application of the first expansion element p1 to the piezoelectric element 18 causes the width-direction central portion of each of the relevant piezoelectric element 18 and a corresponding actuation portion of the elastic film 16 to bend towards the outer side of the pressure chamber 20 (towards a side farther from the nozzle forming substrate 15). This bending causes the pressure chamber 20 to expand from the reference volume corresponding to the reference electric potential Eb to a first expanded volume corresponding to the first slight oscillation expansion electric potential E3. This expansion causes a meniscus in the nozzle 23 to be pulled in towards the pressure chamber 20 side, and concurrently therewith, the expansion causes ink to be fed to the inside of the pressure chamber 20 from the reservoir 27 through a feeding opening. This expansion state of the pressure chamber 20 is kept during a period when the first hold element p2 is applied. Subsequently, the contraction element p3 causes the width-direction central portion of each of the piezoelectric element 18 and the corresponding actuation portion of the elastic film 16 to bend towards the inner side of the pressure chamber 20 (towards a side nearer the nozzle forming substrate 15) to a large degree. This bending causes the pressure chamber 20 to rapidly contract from the expanded volume corresponding to the slight oscillation expansion electric potential E3 up to a contracted volume corresponding to the slight oscillation contraction electric potential E4. This rapid contraction of the pressure chamber 20 causes ink inside the pressure chamber 20 to be pressurized, so that pressure oscillation occurs, and this pressure oscillation causes agitation of ink inside the pressure chamber 20 as well as the meniscus. Here, an electric-potential difference from the reference electric potential Eb to the slight oscillation electric potential E3 is called V3, and an electric-potential difference from the reference electric potential Eb to the slight oscillation contraction electric potential E4 is called V4. With respect to the slight oscillation driving pulse Pv in this embodiment, an electric-potential difference (V3+V4) of the contraction element p3 is set to a larger value as compared with those in conventional methods, and thus, the effect of the agitation of ink is improved to a greater degree.
Further, this expansion state of the pressure chamber 20 is kept during a period when the second hold element p4 is applied. Subsequently, the application of the second expansion element p5 causes the central portion of each of the piezoelectric element 18 and the corresponding actuation portion of the elastic film 16 to bend towards the outer side of the pressure chamber 20. This bending causes the pressure chamber 20 to expand again from the contracted volume to the expanded volume corresponding to the first slight oscillation expansion electric potential E3. Subsequently, the contracted state of the pressure chamber 20 is kept during a period when the third hold element p6 is applied. Subsequent to the application of the third hold element p6, the return element p7 is applied to the piezoelectric element 18. This causes the central portion of each of the piezoelectric element 18 and the corresponding actuation portion of the elastic film 16 to bend towards the inner side of the pressure chamber 20, and return to the reference state.
Here, timing when the contraction element p3 is applied to the piezoelectric element 18 is set such that this timing becomes timing at which pressure oscillation, which arises when the pressure chamber 20 is expanded by the expansion element p1, can be activated. Further, timing points when the second hold element p4, the second expansion element p5, the third hold element p6 and the return element p7 are applied to the piezoelectric element 18 are set such that these timing points become timing points at which the pressure oscillation having been excited by the expansion element p1 and the contraction element p3 are caused to be suppressed. Specifically, a period of time Δt4 regarding the contraction element p3, the period of time Δt2 regarding the second hold element p4, a period of time Δt5 regarding the second expansion element p5, the period of time Δt3 regarding the third hold element p6 and a period of time Δt6 regarding the return element p7 are adjusted such that a period of time from the start of the contraction element p3, at which the activation of pressure oscillation starts, up to the end of the return element p7, which activates pressure oscillation having a phase reverse to that of the pressure oscillation having been excited by the expansion element p1, becomes a value resulting from multiplying a cycle Tc (a natural oscillation cycle) of the pressure oscillation which occurs in ink inside the pressure chamber 20 by a natural number. This adjustment activates the pressure oscillation having been excited by the expansion element p1, thereby causing the meniscus to oscillate and causing the ink to be effectively agitated, and further, reduces the pressure oscillation inside the pressure chamber 20 having been excited by the expansion element p1 and having been activated by the contraction element p3. Accordingly, even when the ink is ejected after the completion of the slight oscillation operation, the influence of the residual oscillation can be suppressed, and thus, it becomes possible to ensure the ejection stability.
Here, in general, the above Tc can be represented by the following formula:
Tc=2π√[(Mn+Ms)/(Mn×Ms×(Cc+Ci))]
In the above formula, Mn is inertance (mass of ink per unit of sectional area) of the nozzle 23; Ms is inertance of the ink feeding path 22; Cc is compliance (a volume variation per unit of pressure, that is, a degree of softness) of the pressure chamber 20; and Ci is compliance of ink (Ci=volume V/[density ρ×acoustic velocity c2]).
Through the employment of the slight oscillation driving pulse Pv having been described above, it becomes possible to allow the contraction element p3 to contract the pressure chamber 20 to a great degree, so that the effect of agitation of ink is improved. Further, it is possible to allow the second hold element p4, the second expansion element p5, the third hold element p6, the return element p7 to function as waveform elements for suppressing the pressure oscillation having been excited inside the pressure chamber 20. Accordingly, in the case where slight oscillation using the slight oscillation pulse Pv is excited, the viscosity increase is suppressed, so that the intermittent capability can be improved, and further, the behavior of the meniscus after the completion of the slight oscillation operation can be suppressed, and thus, it becomes possible to ensure the stability of ink ejection in a subsequent ejection operation. Further, through the employment of a control method for allowing slight oscillation to be excited in such a way as described above, it becomes possible to provide a printer of high reliability.
The table of
In the case of comparison example 1, an ink agitation capability is relatively small, and although V3 was caused to vary from 9% to 27%, an intermittent capability higher than a required level could not be obtained. Further, with respect to the printing stability, only in the case where V3 was 9%, the result was “G”, and in each of the other cases, the result was “NG”, and thus, any good result could not be obtained. Further, in the case of comparison example 2, in the case where V3 was larger than or equal to 21%, the intermittent capability was good, but in contrast, the ejection stability was “A” or “NG”, and in the case where V3 was smaller than or equal to 18%, reversely, the ejection stability was good, but in contrast, the intermittent capability was “A” or “NG”. Accordingly, the result was such that, in both of comparison example 1 and comparison example 2, it was difficult to realize both of the improvement of the intermittent capability and the improvement of the ejection stability. In contrast, in the case where slight oscillation using the slight oscillation driving pulse Pv was excited, the result was such that, within a range between 15% and 21%, both of the intermittent capability and the ejection stability were “G”, and a range in which both of the intermittent capability and the ejection stability were higher than their corresponding required levels (the range corresponding to a portion enclosed by a heavy-line frame in
Meanwhile, the invention is not limited to the aforementioned embodiment, and may be subjected to various modifications based on description in appended claims.
In a slight oscillation driving pulse shown in
Further, a slight oscillation driving pulse shown in
Further, a slight oscillation driving pulse Pv shown in
Moreover, with respect to the slight oscillation driving pulse Pv in the above first embodiment and the slight oscillation driving pulse Pv in each of the modification examples, a magnitude relation between V3 and V4 is not limited to the exemplifications, and may be reversed.
Further, although, in the above first embodiment, there has been exemplified the configuration in which two ejection driving pulses PD and one slight oscillation driving pulse Pv are included, the invention is not limited to this configuration, and a configuration therefor is sufficient merely provided that at least one ejection driving pulse and at least one slight oscillation driving pulse are included in the driving signal COM. Further, although there has been exemplified the configuration in which any one of the ejection driving pulses Pd has the same waveform, it is possible to employ ejection driving pulses having various waveforms.
Moreover, although, in the above first embodiment, there has been exemplified a so-called slight oscillation inside a printing operation, in which slight oscillation is excited by a slight oscillation driving pulse during a recording operation (a printing operation) with respect to a nozzle which is in a state where no ink is to be ejected through the nozzle itself, the invention is not limited to this slight oscillation inside a printing operation, and the slight oscillation driving pulse according to the first embodiment can be also applied to a so-called slight oscillation outside a printing operation, in which the slight oscillation is continuously excited during a period when no printing operation is performed.
In addition, the invention can be applied to not only the printer, but also liquid ejecting apparatuses each capable of performing slight oscillation control using a slight oscillation pulse. That is, the invention can be also applied to various kinds of ink jet recording apparatus, such as a plotter, a facsimile machine and a copying machine, as well as liquid ejecting apparatuses other than the recording apparatuses, such as a display manufacturing apparatus, an electrode manufacturing apparatus and a chip manufacturing apparatus.
The entire disclosure of Japanese Patent Application No. 2012-241577, filed Nov. 1, 2012 is expressly incorporated by reference herein.
Number | Date | Country | Kind |
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2012-241577 | Nov 2012 | JP | national |