Patent Grant
8939534
The entire disclosures of Japanese Patent Application No. 2009-238989, filed Oct. 16, 2009 is expressly incorporated herein by reference.
1. Technical Field
The present invention relates to a technology of ejecting a liquid from an ejection nozzle.
2. Related Art
A liquid ejection apparatus which ejects a liquid, such as ink, using an ejection nozzle is widely known. Although a number of methods exist for ejecting a liquid from an ejection nozzle, as a typical example, a method is widely used whereby a piezoelectric element mounted on an ejection nozzle acts as an actuator, causing a droplet-like liquid to be ejected from the ejection nozzle by applying a predetermined voltage waveform to the piezoelectric element. Using this method, by changing the voltage waveform applied, it is possible to change the size of a droplet or a liquid ejection amount.
The piezoelectric element, as it is a capacitive load, has the property that, when a voltage is applied to the piezoelectric element, an electric charge is accumulated in the piezoelectric element and a voltage equivalent to the amount of electric charge accumulated appears as an applied voltage between the terminals of the piezoelectric element. For this reason, an electric charge has to be supplied to the piezoelectric element in order to increase the applied voltage, while an electric charge must be emitted from the piezoelectric element in order to decrease the applied voltage.
In order to drive the capacitive load at a high power efficiency, the following kind of technology is proposed. Firstly, a plurality of capacitors are charged by differing voltages. When increasing the applied voltage, an electric charge is supplied to the load by individually switching the capacitors to be connected to the capacitive load to higher voltage capacitors. When decreasing the applied voltage, by individually switching the capacitors to lower voltage capacitors, the electric charge of the capacitive load is recovered by the capacitors. By so doing, it is possible, when increasing the applied voltage again, to supply the capacitive load again with the electric charge recovered by the capacitors when decreasing the applied voltage, and increase the applied voltage, meaning that it is possible to drive the capacitive load at a high efficiency (JP-A-2003-285441).
However, in a case in which the piezoelectric element mounted on the ejection nozzle of the liquid ejection apparatus is driven by applying the technology of JP-A-2003-285441, there is a problem in that it is difficult to adjust the ejection amount of a liquid ejected from the ejection nozzle. That is, because the liquid ejection amount is based on the drive amount of the piezoelectric element, the ejection amount depends heavily on the maximum voltage or minimum voltage of a voltage waveform to be applied, but either a maximum voltage or minimum voltage is applied by connecting a capacitor which has been previously charged by the applied voltage to the piezoelectric element. Consequently, the voltage of the capacitor has to be changed in order to change the maximum voltage or minimum voltage of the voltage waveform. However, in the event that the voltage of the capacitor has been changed, when attempting to apply another voltage waveform, the maximum voltage and minimum voltage of the other voltage waveform also changes.
Of course, it is ideal that the voltage of the capacitor is changed for every voltage waveform, but as the capacitor is set to a large capacitance so that a stable voltage waveform can be output, it is not easy to change the voltage of the capacitor in the short time in which a voltage waveform switches. It is also conceivable, rather than using all the capacitors, to leave out, for example, a maximum voltage capacitor or a minimum voltage capacitor, and to connect the maximum voltage capacitor or minimum voltage capacitor to the piezoelectric element only when applying a higher voltage or a lower voltage, but with this configuration, the maximum voltage or minimum voltage of a voltage waveform fluctuates greatly, and the liquid ejection amount cannot be adjusted finely.
An advantage of some aspects of the invention is to provide a technology capable of adjusting a liquid ejection amount while ejecting a liquid by switching a plurality of voltages, and connecting them to a piezoelectric element which drives an ejection nozzle.
A liquid ejection apparatus according to a first aspect of the invention applies a drive voltage waveform to a piezoelectric element which drives an ejection nozzle, ejects a liquid from the ejection nozzle, includes a reference voltage generating unit which generates a plurality of reference voltages, a drive voltage waveform data storage unit which, classifies the drive voltage waveform as a waveform section comprising either a voltage increasing section, decreasing section, or holding section, stores drive voltage waveform data including a required time of a waveform section configuring the drive voltage waveform, and a voltage, selected from the plurality of reference voltages, at boundary positions of the waveform section, and a drive voltage waveform application unit which, in accordance with information relating to an adjustment of the ejection amount of the liquid ejected from the ejection nozzle, changes the required time included in the drive voltage waveform data, and applies the drive voltage waveform to the piezoelectric element.
With the liquid ejection apparatus of the aspect of the invention, the liquid is ejected from the ejection nozzle by connecting the plurality of reference voltages to the piezoelectric element while switching them in accordance with the drive voltage waveform data. Required times of a plurality of waveform sections configuring the drive voltage waveform, and voltages in the boundary positions of the waveform sections, are stored in the drive voltage waveform data. When applying a drive voltage waveform to the piezoelectric element, a required time of a waveform section included in the drive voltage waveform data is changed in accordance with the information relating to the adjustment of the ejection amount of the liquid. Of course, depending on acquired information, it may also happen that the drive voltage waveform data are not changed. The liquid is ejected by applying the drive voltage waveform in accordance with the drive voltage waveform data obtained in this way.
As the liquid is ejected by the piezoelectric element deforming, the ejection amount of the liquid depends heavily on the amplitude of a drive voltage waveform applied to the piezoelectric element. In the case of applying a drive voltage waveform to the piezoelectric element by switching the preset plurality of reference voltages and connecting them to the piezoelectric element, it is not easy to finely change the amplitude of the drive voltage waveform. However, the ejection amount of the liquid also depends partially on the required time of the waveform section configuring the drive voltage waveform. Consequently, by changing the required time of the waveform section configuring the drive voltage waveform, it is possible to finely adjust the ejection amount of the liquid ejected from the ejection nozzle.
The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
Hereafter, in order to clarify the heretofore described details of the invention, an embodiment will be described in accordance with the following sequence.
A. Apparatus Configuration
B. Configuration of Ejection Head
C. Ejection Amount (Discharge Weight) Adjusting Method
D. Ejection Nozzle Drive Process
E. Modification Examples
The drive mechanism 30 which reciprocates the carriage 20 is configured of a timing belt 32 stretched by pulleys, a step motor 34 which drives the timing belt 32 via the pulleys, and the like. One portion of the timing belt 32 is fixed to the carriage case 22, making it is possible to reciprocate the carriage case 22 by driving the timing belt 32. The platen roller 40, configuring a paper feed mechanism which carries out a feed of the printing medium 2, together with an drive motor (not shown) and gear mechanism, feed the printing medium 2 in a sub-scanning direction by a predetermined amount at a time.
A printer control circuit 50 which controls an overall operation and an ejection nozzle drive circuit 200 for driving the ejection nozzles provided in the ejection head 24 are also mounted on the inkjet printer 10. The ejection nozzle drive circuit 200, drive mechanism 30, paper feed mechanism, and the like, drive the ejection nozzles, and eject ink while feeding the printing medium 2 under the control of the printer control circuit 50, thereby printing an image on the printing medium 2.
After being generated by the ejection nozzle drive circuit 200 under the control of the printer control circuit 50, a drive voltage waveform is supplied to the piezoelectric element 104 via a gate unit 300. The gate unit 300 is a circuit unit wherein a plurality of gate elements 302 are connected in parallel, and the gate elements 302 can be individually put into a conducting condition or a cut-off condition under a control from the printer control circuit 50. Consequently, after a gate element 302 has been preset to either the conducting condition or cut-off condition by the printer control circuit 50, by outputting a drive voltage waveform from the ejection nozzle drive circuit 200, the drive voltage waveform, passing through only the gate element 302 preset to the conducting condition, is applied to a corresponding piezoelectric element 104, thus enabling an ink droplet to be ejected from its nozzle.
As shown in
The piezoelectric element is an electrical load (a capacitive load) having a so-called capacitance component, and when a voltage is applied, an electric charge in accordance with the voltage applied is accumulated inside the piezoelectric element. The higher the voltage applied, the more the quantity of electric charge accumulated increases. Conversely, when the voltage applied decreases, the quantity of electric charge accumulated decreases, and the electric charge is emitted. In the embodiment, the ejection nozzle drive circuit 200 of a configuration to be described hereafter is employed in order to efficiently drive the piezoelectric element 104 which drives the ejection nozzle 100.
Of the seven stages of voltage V0 to V6 (reference voltages) generated in the reference voltage generating circuit 204, the voltage V0 is connected to the switch S0 of the drive voltage waveform application section 202. In the same way, the voltage V1 generated in the reference voltage generating circuit 204 is connected to the switch S1 of the drive voltage waveform application section 202, the voltage V2 is connected to the switch S2, the voltage V3 to the switch S3, the voltage V4 to the switch S4, the voltage V5 to the switch S5, and the voltage V6 to switch S6. Consequently, it is possible to switch the voltages to be applied to the piezoelectric element 104 depending on which one of the switches S0 to S6 is to be connected. For example, it is possible to apply the voltage V0 to the piezoelectric element 104 by connecting the switch S0, and it is possible to apply the voltage V1 to the piezoelectric element 104 by connecting the switch S1.
The waveform data storage section 206 is configured of a memory, and data relating to a sequence in which the switches S0 to S6 are connected, and to connection times, are stored therein as the drive voltage waveform data. The controller of the drive voltage waveform application section 202, by controlling the operation of the switch control circuit in accordance with the drive voltage waveform data stored in the waveform data storage section 206, switches the connection condition of the switches S0 to S6. By so doing, it is possible to apply a drive voltage waveform in accordance with the drive voltage waveform data to the piezoelectric element 104, as will be described more fully below.
Continuing, as shown in
Next, as well as the switch S3 being turned off, the switch S4 is turned on. By so doing, the capacitor connected to the piezoelectric element 104 switches from the capacitor C3 which generates the voltage V3 (to be exact, the capacitors C1 to C3) to the capacitor C4 which generates the voltage V4 (to be exact, the capacitors C1 to C4). As a result of this, an electric charge is supplied to the piezoelectric element 104 from the capacitor C4 newly switched, and the applied voltage of the piezoelectric element 104 increases from the voltage V3 to the voltage V4 (refer to
Similarly, by turning off the switch S4, and turning on the switch S5, an electric charge is supplied to the piezoelectric element 104 from the capacitor C5 (to be exact, the capacitors C1 to C5) to increase the applied voltage from the voltage V4 to the voltage V5, and furthermore, by turning off the switch S5, and turning on the switch S6, the applied voltage of the piezoelectric element 104 is increased from the voltage V5 to the voltage V6. An electric charge necessary when increasing the applied voltage from the voltage V4 to the voltage V5 is supplied from the capacitor C5 (to be exact, the capacitors C1 to C5), and an electric charge necessary when increasing the applied voltage from the voltage V5 to the voltage V6 is supplied from the capacitor C6 (to be exact, the capacitors C1 to C6).
After the switches to be tuned on have been switched in order from the switch S2 to the switch S6, as previously described, to increase the applied voltage of the piezoelectric element 104 from the voltage V2 to the voltage V6, this time, by switching the switches to be turned on in a reverse direction, the applied voltages of the piezoelectric element 104 is decreased. That is, from the condition in which the switch S6 is on, the switch S6 is turned off, and the switch S5 is turned on. By so doing, the capacitor connected to the piezoelectric element 104 switches from the capacitor C6 which generates the voltage V6 (to be exact, the capacitors C1 to C6) to the capacitor C5 which generates the voltage V5 (to be exact, the capacitors C1 to C5), as a result of which the electric charge accumulated in the piezoelectric element 104 is supplied to the capacitor C5 (to be exact, the capacitors C1 to C5), and the applied voltage of the piezoelectric element 104 decreases from the voltage V6 to the voltage V5. In
Similarly, by turning off the switch S5, and turning on the switch S4, the electric charge of the piezoelectric element 104 is recovered by the capacitor C4 (to be exact, the capacitors C1 to C4) to decrease the applied voltage from the voltage V5 to the voltage V4. Furthermore, by turning off the switch S4, and turning on the switch S3, the applied voltage of the piezoelectric element 104 is decreased from the voltage V4 to the voltage V3, and by turning off the switch S3, and turning on the switch S2, the applied voltage of the piezoelectric element 104 is decreased from the voltage V3 to the voltage V2. When the applied voltage decreases from the voltage V4 to the voltage V3, the electric charge of the piezoelectric element 104 is recovered by the capacitor C3 (to be exact, the capacitors C1 to C3), and when the applied voltage decreases from the voltage V3 to the voltage V2, the electric charge of the piezoelectric element 104 is recovered by the capacitor C2 (to be exact, the capacitors C1 and C2). By switching the switches to be turned on in order in this way, thus eventually turning off the switch S1 and turning on the switch S0, it is possible to decrease the applied voltage of the piezoelectric element 104 to the voltage V0.
As illustrated in the configuration of the drive voltage waveform application section 202 shown in
After the applied voltage of the piezoelectric element 104 has been decreased to the voltage V0 by switching the switches to be turned on in order from the switch S6 to the switch S5, from the switch S5 to the switch S4, from the switch S4 to the switch S3, from the switch S3 to the switch S2, from the switch S2 to the switch S1, and from the switch S1 to the switch S0 in the way heretofore described, this time, the switches to be turned on are switched from the switch S0 to the switch S1, and from the switch S1 to the switch S2. By so doing, it is possible to increase the applied voltage of the piezoelectric element 104 from the voltage V0 to the voltage V2.
As shown in
When increasing the applied voltage of the piezoelectric element 104 from the voltage V2 to the voltage V3, as an electric charge is supplied to the piezoelectric element 104 from the capacitor C3 (to be exact, the capacitors C1 to C3) which generates the voltage V3, the electric charge of the capacitor C3 (to be exact, the capacitors C1 to C3) decreases. However, when the applied voltage of the piezoelectric element 104 decreases from the voltage V4 to the voltage V3, the capacitor C3 (to be exact, the capacitors C1 to C3) can recover an electric charge from the piezoelectric element 104 (refer to
By way of comparison, the capacitor C6 which generates the voltage V6 is slightly different from the other capacitors C1 to C5. That is, the capacitor C6 supplies an electric charge to the piezoelectric element 104 when increasing the applied voltage of the piezoelectric element 104 from the voltage V5 to the voltage V6, but the electric charge is recovered by the capacitor C5 (to be exact, the capacitors C1 to C5) when the applied voltage of the piezoelectric element 104 decreases from the voltage V6 to the voltage V5. In this way, with regard to the capacitor C6 which generates the voltage V6 which is the highest voltage, as it cannot recover an electric charge from the piezoelectric element 104, the electric charge accumulated therein decreases while the voltage waveform is being output. Consequently, there occurs a need to gradually replenish the capacitor C6 with an electric charge from an external power supply. However, there is little need to replenish the other capacitors C1 to C5 with an electric charge. Moreover, as it is sufficient to supply the capacitor C6 with only an electric charge for increasing the applied voltage from the voltage V5 to the voltage V6 despite the applied voltage being changed within a range of the voltage V0 to the voltage V6, it is possible to drive the piezoelectric element 104 very efficiently.
On the voltage waveform generated in the way heretofore described being applied, the piezoelectric element 104 of the ejection nozzle 100 carries out the following kind of operation.
After the condition in which the ink is suctioned in this way has been held during the time T2, this time, the applied voltage decreases, and the piezoelectric element 104 deforms in a direction in which it reduces the volume of the ink chamber 102. As a result of this, the ink suctioned into the ink chamber 102 is discharged in a droplet form from the ejection nozzle 100 in such a way as to be pushed out. This discharge operation is carried out by taking the time T3 to decrease the applied voltage in six stages, from the voltage V6 to the voltage V5, from the voltage V5 to the voltage V4, from the voltage V4 to the voltage V3, from the voltage V3 to the voltage V2, from the voltage V2 to the voltage V1, and from the voltage V1 to the voltage V0. As a result of this, the piezoelectric element 104 deforms by an amount equivalent to six stages' worth of voltage difference (the voltage V6−the voltage V0), and ink of a volume in accordance with this deformation amount is discharged from the ejection nozzle 100.
As described above, the ejection amount of a liquid ejected from the ejection nozzle 100 (herein, the size of an ink droplet discharged, or a discharge weight) depends upon the quantity of stages in which the applied voltage is changed in the discharge operation (a discharge stage quantity). Consequently, in order to increase the liquid ejection amount (ink discharge weight), it is sufficient to increase the discharge stage quantity, and conversely, in order to reduce the ejection amount (discharge weight), it is sufficient to reduce the discharge stage quantity. In order to increase the discharge stage quantity, there occurs a need to change the applied voltage by a certain stage quantity of the suction operation too which is carried out prior to the discharge operation. Similar to the quantity of stages in which the applied voltage is changed in the discharge operation being called the discharge stage quantity, the quantity of stages in which the applied voltage is changed in the suction operation may hereafter be called a suction stage quantity.
In the example shown in
Heretofore, an example has been described as one in which the stage quantity of the suction operation (the suction stage quantity) is performed before the discharge operation is changed, by which amount the stage quantity of the discharge operation (the discharge stage quantity) is changed. For example, in the example shown in
Typically, when the discharge stage quantity is changed, the ink ejection amount (discharge weight) undergoes a large change. Consequently, while it is possible to change the ejection amount (discharge weight) roughly, it is not possible to adjust it finely. Therein, with the inkjet printer 10 of the embodiment, by using the following kind of method, it is possible to adjust the ink ejection amount (discharge weight) finely.
As shown in
As is obvious from the measurement results shown in
By predetermining and storing the discharge stage quantity and discharge time (time T3) for each discharge weight in this way, it is possible to easily carry out a fine adjustment of the ink ejection amount (discharge weight). For example, it is taken that there occurs a need to slightly increase the ejection amount (discharge weight) when the piezoelectric element 104 is being driven with one drive voltage waveform. In this case, it is sufficient to check the discharge stage quantity and discharge time (time T3) of the drive voltage waveform, obtain a combination of discharge stage quantity and discharge time (time T3) wherein the discharge weight is slightly greater than that in the combination of discharge stage quantity and discharge time (time T3) obtained, and change the drive voltage waveform. As heretofore described using
Data including the discharge stage quantity and discharge time (time T3) determined for each ink discharge weight in this way are stored in advance, as the drive voltage waveform data, in the waveform data storage section 206 of the ejection nozzle drive circuit 200. The drive voltage waveform application section 202 of the ejection nozzle drive circuit 200, by controlling the switch switching operation based on the drive voltage waveform data retrieved from the waveform data storage section 206, generates a voltage waveform corresponding to the drive voltage waveform data, and applies it to the piezoelectric element 104. Hereafter, a description will be given of a process in which the ejection nozzle drive circuit 200 of the embodiment generates a drive voltage waveform, and applies it to the piezoelectric element 104 of the ejection nozzle 100.
As shown in the diagram, once the ejection nozzle drive process starts, first of all, the previously used drive voltage waveform data are retrieved (step S100). Herein, drive voltage waveform data, which is data for generating a drive voltage waveform, is stored in the waveform data storage section 206.
As heretofore described using
A detailed description will be given, while referring to
When the drive voltage waveform is simplified into a polygonal line form in this way, a total of six inflection points appear in positions indicated as “L0”, “L1”, “L2”, “L3”, “L4”, and “L5” in
Following this kind of specification of the voltage at the inflection point L0 and the time T0 until the leading voltage switches to the voltage at L0, furthermore, a voltage at the next inflection point L1 and a time (the time T1) until the voltage at the inflection point L0 switches to the voltage at L1 are specified. In the event that the voltage at the inflection point L0 and the voltage at the inflection point L1 are the same, the voltage is maintained in the waveform section (the waveform section of the time T1) while, in the event that the voltage at the inflection point L1 is higher than the voltage at the inflection point L0, the voltage takes the time T1 to increase in the waveform section, and conversely, in the event that the voltage at L1 is lower than the voltage at L0, the voltage takes the time T1 to decrease. Hereafter, in the same way, by specifying a voltage at an inflection point L2 and the time T2 until the voltage at L1 switches to the voltage at L2, a voltage at an inflection point L3 and the time T3 until the voltage at L2 switches to the voltage at L3, a voltage at an inflection point L4 and the time T4 until the voltage at L3 switches to the voltage at L4, and a voltage at an inflection point L5 and the time T5 until the voltage at L4 switches to the voltage at L5, it is possible to describe the kind of polygonal line shaped drive voltage waveform shown in
Herein, as heretofore described, the reference voltages can only take the preset plurality of voltages (herein, the voltage V0 to the voltage V6). Consequently, not the values themselves of the reference voltages, but the stage quantities of the reference voltages are set in the drive voltage waveform data. For example, stage quantities “0” to “6” are set, such as “0” stage in the event of the voltage V0, “1” stage in the event of the voltage V1, and “2” stages in the event of the voltage V2. When increasing or decreasing the voltage, a timing to switch to a voltage of a partway stage quantity is calculated using the computation equation shown in
As heretofore described, the voltages at the starting point and inflection points when describing a drive voltage waveform using a polygonal line, and the times for switching the voltages, are set in the drive voltage waveform data, and by retrieving the drive voltage waveform data, and applying the computation equation of
As illustrated in
Next, it is determined whether or not to adjust the ejection amount of ink ejected from the ejection nozzle 100 (step S102). In the embodiment, when starting a printing, an operator of the inkjet printer 10, by operating an operating button (not shown) of the inkjet printer 10, or a computer connected to the inkjet printer 10 from the screen (not shown) thereof, can instruct the inkjet printer 10 whether or not to adjust the density when printing, and in the event of adjusting it, whether to darken or lighten it. Then, the printer control circuit 50 of the inkjet printer 10, in response to these instructions, outputs an instruction to the ejection nozzle drive circuit 200. Consequently, the ejection nozzle drive circuit 200, based on the existence or otherwise of an instruction from the printer control circuit 50, can determine whether or not to adjust the ejection amount.
As a result of this, if the ejection nozzle drive circuit 200 determines to adjust the ejection amount (step S102: yes), it determines whether or not the content of the adjustment is an increase in ejection amount (step S104). This determination can also be easily made according to the content of an instruction received from the printer control circuit 50. If the ejection nozzle drive circuit 200 determines that the content is an increase in ejection amount (step S104: yes), it retrieves an item of drive voltage waveform data which is one serial number larger (step S106). As shown in
The ejection nozzle drive circuit 200, after retrieving a new item of drive voltage waveform data in this way, by switching the switches S0 to S6 in accordance with the retrieved item of drive voltage waveform data, outputs a drive voltage waveform (step S110).
For example, in the event that the ejection nozzle drive circuit 200 has retrieved the item of drive voltage waveform data of the serial number “1” illustrated in
After holding the voltage V4 in a condition in which it is being output for 2.5μ seconds (the time T2), the ejection nozzle drive circuit 200, in order to take 2.4μ seconds (the time T3) to decrease the output voltage from the voltage V4 to the voltage V0, switches the switches from the condition in which the switch S4 is on to the condition in which the switch S3 is on, to the condition in which the switch S2 is on to a condition in which the switch S1 is on, and then to a condition in which the switch S0 is on, each switching process taking 0.6μ seconds to elapse. Henceforth too, in the same way, the ejection nozzle drive circuit 200, by switching the connection condition of the switches S0 to S6 in accordance with the drive voltage waveform data, can output a drive voltage waveform corresponding to the drive voltage waveform data.
Meanwhile, if the ejection nozzle drive circuit 200 determines not to adjust the ejection amount (step S102 of
The ejection nozzle drive circuit 200, after outputting the drive voltage waveform in the way heretofore described, determines whether or not the printing has finished (step S112). When the printing finishes, as an instruction to that effect is output from the printer control circuit 50, the ejection nozzle drive circuit 200 immediately determines whether or not the printing has finished. If the printing has not finished yet (step S112: no), the ejection nozzle drive circuit 200, by switching the switches S0 to S6 again in accordance with the drive voltage waveform data, outputs a drive voltage waveform toward the piezoelectric element 104 (step S110). The ejection nozzle drive circuit 200 determines whether or not the printing has finished (step S112). The ejection nozzle drive circuit 200 repeats this of process until it receives an instruction to finish the printing from the printer control circuit 50, and if it is determined that the printing has finished (step S112: yes), the ejection nozzle drive circuit 200 stores the serial number of the drive voltage waveform data used in outputting the drive voltage waveform (S114), and finishes the ejection nozzle drive process of
For example, a first item of drive voltage waveform data is data indicated as “A” in the diagram, and on an adjustment to reduce the ejection amount therefrom (a minus adjustment) being carried out, the first item switches to data indicated as “B” in the diagram. When looking at a result of a printing in accordance with the item of drive voltage waveform data, in the event that there is still a need to lighten the printing density, a minus adjustment is made again to start printing an image. By so doing, the ejection nozzle drive process shown in
In this way, a certain amount of adjustment is made by lengthening the discharge time (time T3) little by little while maintaining the discharge stage quantity of the drive voltage waveform, but as a result of this, on the discharge time (time T3) reaching a certain length, a further adjustment is made by making the discharge stage quantity of the drive voltage waveform smaller by one stage. In a case of an adjustment to increase the ejection amount (a plus adjustment) too, in the same way, a certain amount of adjustment is made by shortening the discharge time (time T3) little by little while maintaining the discharge stage quantity of the drive voltage waveform, but as a result of this, on the discharge time (time T3) reaching a certain length, a further adjustment is made by making the discharge stage quantity of the drive voltage waveform larger by one stage.
In this way, with the ejection nozzle drive circuit 200 of the embodiment, by changing the discharge time (time T3) of a drive voltage waveform applied to the piezoelectric element 104, and the discharge stage quantity, little by little, it is possible to adjust the ink ejection amount (discharge weight) finely, and moreover, it is possible to continuously change the ink ejection amount.
In the event of the fine adjustment, in most cases, it is possible to make the adjustment using only the discharge time (time T3) of the drive voltage waveform, and in a case of making a rough adjustment, it is sufficient to make the adjustment using the discharge stage quantity and discharge time (time T3) of the drive voltage waveform.
In the heretofore described embodiment, an example has been described as one in which the adjustment of the ink ejection amount (discharge weight) is carried out stage by stage, and consequently, the drive voltage waveform data can switch to items of data whose serial numbers are different from one another. Of course, without being limited to the step-by-step adjustment, it is also acceptable, by making an adjustment of a plurality of stages specifiable, to enable a switching to an item of drive voltage waveform data whose serial number is placed a plurality of numbers ahead in accordance with a specified content.
Various modification examples exist in the heretofore described embodiment. Hereafter, a description will be given of the modification examples. With regard to each modification example to be described hereafter, as well as component portions similar to those of the heretofore described embodiment being given identical reference numerals and characters, a detailed description of the relevant portions will be omitted, and a description will be given centered on differences.
In the heretofore described embodiment, an example has been described as one in which whether or not to adjust the ink ejection amount (discharge weight) is specified by the operator of the inkjet printer 10, and with the ejection nozzle drive circuit 200 of the inkjet printer 10, the ink ejection amount (discharge weight) is adjusted in accordance with a specified content. However, the inkjet printer 10 itself may also acquire information relating to the necessity or otherwise of an adjustment of the ink ejection amount (discharge weight), determine whether or not the adjustment is necessary based on a result of the information, and adjust the ink ejection amount (discharge weight).
In the ejection nozzle drive process of the second embodiment, the process begins by detecting an environmental temperature of the inkjet printer 10 (step S200). As the temperature detector 110 which detects an environmental temperature is mounted on the ejection head 24, as heretofore described using
Next, adjustment parameters with respect to the environmental temperature detected are acquired (step S202). Herein, the adjustment parameters are parameters used to adjust the ink ejection amount (discharge weight). In the second embodiment, the discharge stage quantity and discharge time (time T3) of a drive voltage waveform are used as the adjustment parameters, and appropriate adjustment parameters (the discharge stage quantity and discharge time T3) are stored in advance in a condition in which they are correlated with the environmental temperature.
After acquiring adjustment parameters in the way heretofore described, drive voltage waveform data are generated based on the adjustment parameters (step S204). That is, as heretofore described using
For example, as illustrated in
After generating drive voltage waveform data corresponding to adjustment parameters in this way, a drive voltage waveform is output by switching the switches S0 to S6 in accordance with the drive voltage waveform data generated (step S206). After outputting the drive voltage waveform, it is determined whether or not a printing has finished (step S208). Whether or not the printing has finished can be immediately determined depending on whether or not an instruction from the printer control circuit 50 has been received. If the printing is not yet finished (step S208: no), after outputting a drive voltage waveform again based on the drive voltage waveform data (step S206), it is determined whether or not the printing has completed (step S208).
The ejection nozzle drive circuit 200 repeats this kind of process until it receives an instruction to finish the printing from the printer control circuit 50 and, if it is determined that the printing has finished (step S208: yes), finishes the ejection nozzle drive process of the second embodiment.
In the heretofore described second embodiment, it is possible to detect an environmental temperature of the inkjet printer 10, generate drive voltage waveform data in accordance with the environmental temperature, and drive the ejection nozzle 100. For this reason, even in the event that the viscosity of ink changes due to a change in environmental temperature, as it is possible to counteract the effect thereof by changing the drive voltage waveform data, it is possible to constantly print an image at a stable quality without having the effect of an environmental temperature fluctuation.
In the heretofore described second embodiment, as shown in
Of course, in the event that an environmental temperature is very high, or in the event that an environmental temperature is very low, an item of drive voltage waveform data which is two serial numbers smaller, or an item of drive voltage waveform data which is two serial numbers larger, may also be selected. By so doing, once a preferable printing density is set, it is possible, without having the effect of an environmental temperature after that, to constantly print an image at the preferable printing density.
In the heretofore described first embodiment and second embodiment, an example has been described as one in which the ink ejection amount (discharge weight) is adjusted using only the discharge time (time T3), apart from the discharge stage quantity. However, actually, it is possible to adjust the ink ejection amount (discharge weight) by changing a time other than the discharge time (time T3).
Firstly, in a waveform section (the waveform section of the time T0) in which the drive voltage waveform is held at the initial voltage, as shown at the left end of the middle portion of
As a result, ink from the ink cartridge 26 is suctioned into the ink chamber 102, and at the same time, ink in the vicinity of the orifice of the ejection nozzle 100 is also suctioned, along with which the ink interface is drawn inward (as shown in the center of the middle portion of
After the ink has been discharged in this way, the voltage of the drive voltage waveform returns to the initial voltage after it has been held at the minimum voltage for the time T4. As the ink interface temporarily comes into a condition in which it bulges out largely when the ink is discharged, the ink interface tends to return to the original position after that, and a kind of resonance phenomenon occurs due to this force. As a result of this, while the voltage of the drive voltage waveform is being held, or even after it has returned to the initial voltage, the amplitude of vibration of the ink interface decreases gradually while the ink interface is vibrating at a constant frequency.
After the drive voltage waveform has increased, in a waveform section (the waveform section of the time T2) in which the maximum voltage is held, the same ink vibration phenomenon occurs in the vicinity of the orifice of the ejection nozzle 100. That is, the ink in the vicinity of the orifice of the ejection nozzle 100 flows inward while the drive voltage waveform is increasing, and the piezoelectric element 104 is carrying out a suction operation (the waveform section of the time T1), and still tends to flow inward due to the inertia of the ink for a while even immediately after the drive voltage has been held at a constant voltage to stop the suction operation. However, as the suction operation of the piezoelectric element 104 has finished, the flow of the ink tending to flow inward attenuates quickly, and this time, the ink tends to flow toward the vicinity of the orifice of the ejection nozzle 100 due to the action of a force pushing back the ink in an opposite direction. Consequently, in the waveform section (the waveform section of the time T2) in which the drive voltage waveform has finished increasing, and is held at the maximum voltage, at first, the ink in the vicinity of the orifice of the ejection nozzle 100 is flowing inward, but after a while, starts flowing outward (that is, in the direction of the orifice).
In the event that a suction operation is carried out in the condition in which the ink in the vicinity of the orifice of the ejection nozzle 100 is flowing inward, it is considered that the amount of ink discharged decreases, and conversely, in the event that a suction operation is carried out in the condition in which the ink is flowing outward, it is considered that the amount of ink discharged increases.
When the ink ejection amount (discharge weight) is measured during the time (the time T2) for which the drive voltage waveform is held at the maximum voltage is changed, it can be confirmed that the ink ejection amount (discharge weight) increases gradually as the time T2 is lengthened, and decreases after having eventually reached a maximum ejection amount. This is because, in the case in which the time T2 is extremely short, as it happens that the piezoelectric element 104 tends to push out the ink against the inward flow of ink, the ink ejection amount (discharge weight) decreases. Since the inward flow of ink weakens as the time T2 becomes longer, the ink ejection amount (discharge weight) increases, and in the event that the time T2 is further lengthened, the condition in which the ink in the vicinity of the orifice of the ejection nozzle 100 is flowing outward (in the direction of the orifice), a discharge operation is carried out in such a way as to push out the ink from behind, the ink ejection amount (discharge weight) further increases. However, in the event that the time T2 is made too long, as it happens that the outward flow of the ink in the vicinity of the orifice also attenuates, or that the ink flows inward again, the ink ejection amount (discharge weight) decreases.
As is obvious from the above description, it is also possible to adjust the ink ejection amount (discharge weight) by changing the time (time T2) for which the drive voltage waveform is held at the maximum voltage. Heretofore, a description has been given of the case of changing the time T2, but it is conceivable that, by also changing another time, it is possible to adjust the ink ejection amount (discharge weight). That is, a mechanism of adjusting the ink ejection amount (discharge weight) by changing the time T2 lies in changing the ejection amount (discharge weight) utilizing the flow of ink in the ink chamber 102 (at least in the vicinity of the orifice of the ejection nozzle 100). For example, in the event that the ink in the vicinity of the orifice of the ejection nozzle 100 flows inward, the flow of the ink acts in a direction in which it counteracts a discharge operation of the piezoelectric element 104, and in the event that the ink flows outward, the flow of the ink acts in a direction in which it accelerates a discharge operation of the piezoelectric element 104. The extent of their effects depends on the intensity of ink flow.
In the heretofore described second embodiment, the direction and intensity of an ink flow at a point at which the piezoelectric element 104 starts a discharge operation are adjusted by changing the time T2, as a result of which the ink ejection amount (discharge weight) is changed. Consequently, when it is possible to affect the flow of ink in the ink chamber 102 (at least in the vicinity of the orifice of the ejection nozzle 100), it is possible to change not only the time T2, but the ink ejection amount (discharge weight) on the same principle.
For example, the length of a time (the time T1) for which the piezoelectric element 104 carries out a suction operation directly affects the intensity of an inward ink flow caused by the suction operation. Naturally, the effect also reaches the waveform section (the waveform section of the time T2) in which the drive voltage waveform is held. Consequently, by also changing the length of the time T1, it is possible to change the ink ejection amount (discharge weight).
As shown in
For example, on the piezoelectric element 104 starting a suction operation when ink is flowing toward the orifice of the ejection nozzle 100, the ink flow acts in a direction in which it counteracts the suction operation, and conversely, when the ink is flowing inward, the ink flow acts in a direction in which it accelerates the suction operation.
The effect thereof also reaches the waveform section (the waveform section of the time T2) in which the drive voltage waveform is held after the suction operation. Consequently, as long as the time T0 is not set to a length such that it is possible to ignore the effect of the previous drive voltage waveform, it is also possible to adjust the ink ejection amount (discharge weight) by setting the time T0. Furthermore, the amplitude of vibration of ink occurring after the piezoelectric element 104 has finished the discharge operation is considered to change by setting the time T4 and time T5. Consequently, it is also possible to adjust the ink ejection amount (discharge weight) by changing the amplitude of vibration persisting during a next suction operation by means of the setting of the time T4 and time T5.
In the case of adjusting the ink ejection amount (discharge weight) by changing the discharge time (time T3), as in the heretofore described first embodiment or second embodiment, the ejection speed of ink (the speed of ink ejected from an ejection nozzle 100) also changes. With the inkjet printer 10, as a change in the ink ejection speed may affect an image quality, it is also acceptable to adopt a configuration such as to counteract the effect of the ink ejection speed by also changing the time T0, in conjunction with the change of the time T3.
With the inkjet printer 10, it is for the following reason that a change in the ink ejection speed may affect an image quality. Firstly, as heretofore described using
That is, in the event that the ink ejection speed becomes higher, as ink flies across the platen gap in a shorter time after the ink is ejected, the positional misalignment becomes smaller. Conversely, in the event that the ink ejection speed becomes lower, as it takes more time from ink being ejected until the ink reaches the surface of the printing medium 2, the positional misalignment becomes larger. For this kind of reason, on the ink ejection speed changing, the size of positional misalignment also changes, thus affecting an image quality.
Therein, in a case of shortening the discharge time (time T3) in order to adjust the ink ejection amount (discharge weight), as the ink ejection speed is considered to become higher, the time T0 is lengthened. By so doing, it is possible to suppress a change in positional misalignment by delaying an ink ejection timing by an amount by which the time of flight across the platen gap has been shortened. Conversely, in a case of lengthening the discharge time (time T3) in order to adjust the ink ejection amount (discharge weight), the time T0 is shortened. By so doing, it is possible to suppress a change in position gap by ejecting ink at an earlier timing by an amount by which the time of flight across the platen gap has been lengthened.
In the heretofore described embodiment and various modification examples, an example has been described as one in which one drive voltage waveform is repeatedly output. However, the invention can also be suitably applied to a case in which a plurality of drive voltage waveforms are made into a set, and the set of drive voltage waveforms is repeatedly output.
In the case in which the plurality of drive voltage waveforms are made into a set in this way, it is difficult to adjust the ink ejection amount (discharge weight) by changing the amount of voltage change (the amount of deformation of a piezoelectric element 104) during a discharge operation. For example, a case will be considered in which the size of the small dot is made slightly smaller (the ejection amount is made smaller). As an ink discharge operation for the small dot is carried out by decreasing the drive voltage from the voltage V4 to the voltage V0 in the waveform 2, by slightly decreasing the voltage V4, or by slightly increasing the voltage V0, it is possible to reduce the ink ejection amount (discharge weight), and make the size of dots smaller. However, as the voltage V5 is generated by adding the inter-terminal voltage of the capacitor C5 to the voltage V4, and the voltage V6 is generated by adding the inter-terminal voltage of the capacitor C5 and the inter-terminal voltage of the capacitor C6 to the voltage V4, as heretofore described using
In the event that the ink ejection amount is adjusted using the discharge time (time T3) or another waveform section time (time T2 or the like) of a drive voltage waveform, it becomes possible to adjust only the ejection amount of a single waveform in the waveform set. For example, in the example shown in
In the ejection nozzle drive circuit 200 of each of the heretofore described embodiment and various modification examples, as shown in
Next, as shown in
Furthermore, as shown in
In this way, with the ejection nozzle drive circuit 500 of the sixth embodiment shown in
With the ejection nozzle drive circuit 500 of the sixth embodiment having the heretofore described configuration, drive voltage waveform data are stored in a waveform data storage section 506, and by changing a time of a waveform section configuring a drive voltage waveform, it is possible to adjust the ink ejection amount (discharge weight) finely.
Heretofore, a description has been given of the embodiment and various modification examples of the invention, but the invention is not limited to these descriptions and can be implemented in various forms without departing from the scope thereof. For example, it is possible to configure an ejection nozzle drive circuit using an electrical accumulator (for example, a secondary battery) which can accumulate an electric charge, in place of a capacitor.
In the heretofore described embodiment or various modification examples, an example has been described as one in which the liquid ejection apparatus is the inkjet printer 10 which ejects ink. However, the invention can also be suitably applied to a liquid ejection apparatus acting as a surgical instrument with which body tissue is incised or excised by ejecting a liquid, such as water or salt water, in a pulsed form.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-238989 | Oct 2009 | JP | national |
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| 5264865 | Shimoda et al. | Nov 1993 | A |
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| 7049756 | Aiba et al. | May 2006 | B2 |
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| European Search Report mailed Feb. 25, 2011 as received in related European Application No. 10187535.9. |
| Number | Date | Country | |
|---|---|---|---|
| 20110090273 A1 | Apr 2011 | US |
