JP4032338B2 - Ink jet recording apparatus and ink jet recording head driving method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet recording apparatus capable of discharging a plurality of types of ink droplets having different ink volumes from the same nozzle opening, and a method for driving an ink jet recording head used in the ink jet recording apparatus.
[0002]
[Prior art]
An ink jet recording apparatus includes a recording head having a large number of nozzle openings formed in a row, a carriage mechanism that moves the recording head in the main scanning direction (recording paper width direction), A paper feed mechanism for moving in the scanning direction (paper feed direction).
[0003]
The recording head includes a pressure chamber communicating with the nozzle opening and a pressure generating element that changes the ink pressure in the pressure chamber. In this recording head, the ink pressure in the pressure chamber is changed by supplying a drive pulse to the pressure generating element, and the ink droplet is ejected from the nozzle opening.
[0004]
The carriage mechanism moves the recording head in the main scanning direction. During this movement, the recording head ejects ink droplets at a timing specified by the dot pattern data. When the recording head reaches the end of the moving range, the paper feed mechanism moves the recording paper in the sub-scanning direction. When the recording paper is moved, the carriage mechanism moves the recording head again in the main scanning direction, and the recording head ejects ink droplets during the movement.
[0005]
By repeating the above operation, an image based on the dot pattern data is recorded on the recording paper.
[0006]
This recording apparatus constitutes an image based on whether or not ink droplets are ejected, that is, the presence or absence of dots. For this reason, this recording apparatus employs a method of expressing an intermediate gradation by expressing one pixel by a plurality of dots such as 4 × 4 and 8 × 8. In order to record a high-quality image by this method, it is necessary to eject ink droplets having a very small volume from the recording head. However, when the volume of the ink droplet is made extremely small, another problem that the recording speed becomes slow arises.
[0007]
In view of such circumstances, a technique for ejecting ink droplets of different sizes from the same nozzle has been proposed in order to satisfy the opposing demands of improved image quality and improved recording speed.
[0008]
For example, in the techniques disclosed in Japanese Patent Publication No. 4-15735 and US Pat. No. 5,285,215, by supplying a plurality of pulse signals capable of generating minute ink droplets, minute ink droplets are supplied from the same nozzle. Are ejected, and the ink droplets are combined before landing on the recording paper to generate large ink droplets.
[0009]
However, with these techniques, the number of ink droplets that can be combined is limited, so the size of the ink droplets is limited and the variable range of the size is also narrow. Furthermore, since a plurality of ink droplets must be combined before landing, control is difficult.
[0010]
Therefore, a technique is considered in which a drive signal in which a plurality of types of drive pulses corresponding to the volume of ink droplets to be ejected are connected in series is generated, and the drive pulse obtained from the drive signal is supplied to the pressure generating element. .
[0011]
[Problems to be solved by the invention]
However, in this technique, the following problem arises simply by connecting a plurality of types of drive pulses.
[0012]
The first problem is that the drive cycle necessary for recording one dot becomes long. That is, in this technique, it is necessary to connect drive pulses for the types of ink volumes to be ejected, and the drive cycle becomes longer by the number of connected drive pulses. If the drive cycle becomes longer, the recording speed becomes slower.
[0013]
The second problem is that the flying speed of ink droplets varies with the difference in ink volume. For example, comparing a large ink droplet that forms a large dot with a medium ink droplet that forms a medium dot, the large ink droplet has a faster flight speed than the medium ink droplet. When the volume difference between the ink droplets is increased, a large difference in the flight speed occurs. Then, the difference in flight speed causes a deviation in the landing position of the ink droplet, and the image quality is impaired.
[0014]
The present invention has been proposed in view of the above. An object of the invention is to efficiently store drive pulses for generating a plurality of types of ink droplets having different ink volumes within a limited drive cycle.
[0015]
Another object of the present invention is to reduce a difference in flying speed of ink droplets due to a difference in ink volume.
[0016]
[Means for Solving the Problems]
The present invention has been proposed in order to achieve the above object, and includes a recording head having a pressure generating element provided corresponding to a pressure chamber communicating with a nozzle opening, and operates the pressure generating element. In an ink jet recording apparatus that supplies a driving pulse of 1 to a pressure generating element and ejects ink droplets from each nozzle opening,
Drive signal generating means for generating a drive signal, and drive pulse generating means for generating a drive pulse from the drive signal,
The drive signal generated by the drive signal generating means includes a waveform element that operates the pressure generating element and a connection element that does not operate the pressure generating element, and the connection element connects different voltage levels between the waveform elements,
The drive pulse generation means is an ink jet recording apparatus that generates a plurality of types of drive pulses by selecting a waveform element.
[0017]
Preferably, the generation time of the inclined portion of the connecting element in the drive signal generating means is set to be equal to or less than the generation time of the inclined portion of the waveform element that operates the pressure generating element.
[0018]
Preferably, the waveform element includes a plurality of ejection waveform elements that actuate the pressure generating element to eject ink droplets,
The discharge waveform elements are connected to each other by the connection element.
[0019]
Preferably, the corrugated element includes a filling corrugated element that operates a pressure generating element to fill the pressure chamber with ink,
The drive pulse generating means generates a plurality of types of drive pulses at the timing when selecting the ejection waveform element and the filling waveform element.
[0020]
Preferably, the waveform element includes a plurality of ejection waveform elements that actuate the pressure generating element to eject ink droplets at different timings,
The drive pulse generator generates multiple types of drive pulses so that the volume of ejected ink droplets is different and the ejection timing of small volume ink droplets is earlier than the ejection timing of large volume ink droplets. To do.
[0021]
Preferably, the waveform element includes a plurality of ejection waveform elements that actuate the pressure generating element to eject ink droplets at different timings,
The drive pulse generating means can form a small dot drive pulse capable of ejecting a small ink droplet capable of forming a small dot, a medium dot drive pulse capable of ejecting a medium ink droplet capable of forming a medium dot, and a large dot. A large dot drive pulse that can eject large ink droplets,
Each drive pulse generated by the drive pulse generating means is arranged such that one of the ejection waveform element of the large dot drive pulse or the ejection waveform element of the medium dot drive pulse is arranged before the ejection waveform element of the small dot drive pulse. After the ejection waveform element of the dot drive pulse, the other of the ejection waveform element of the large dot drive pulse or the ejection waveform element of the medium dot drive pulse is arranged.
[0022]
Preferably, the waveform element includes a first large dot waveform discharge element and a second large dot waveform discharge element that discharge a large ink droplet capable of forming a large dot, and ink for forming other dots. Another dot discharge waveform element for discharging droplets, and disposing another dot discharge waveform element between the first large dot discharge waveform element and the second large dot discharge waveform element,
The drive pulse generating means generates a drive pulse composed of a first large dot ejection waveform element and a second large dot ejection waveform element.
[0023]
Preferably, the waveform element includes a plurality of large dot discharge waveform elements that discharge large ink droplets capable of forming large dots, and another dot discharge waveform element that discharges ink droplets for forming other dots. In addition, other dot discharge waveform elements are arranged between the large dot discharge waveform elements,
Preferably, the drive pulse generating means generates a drive pulse composed of at least one ejection waveform element.
[0024]
Preferably, the plurality of waveform elements that can eject the large ink droplets are waveforms having substantially the same shape.
[0025]
Preferably, the two large dot ejection waveform elements are arranged at equal intervals.
[0026]
Preferably, the waveform element includes a plurality of filling waveform elements that actuate the pressure generating element so as to fill ink in the pressure chamber, and an ejection waveform element that activates the pressure generating element so as to eject ink droplets. Including
Connect the filling waveform elements by connecting elements,
The drive pulse generating means generates one drive pulse from the selected one filling waveform element and ejection waveform element.
[0027]
Preferably, the connection end of the connection element connected to the waveform element is a constant voltage part having a constant voltage.
[0028]
The present invention has an ink jet type recording having a pressure generating element that expands and contracts a pressure chamber by a drive pulse and thereby changes an ink pressure in the pressure chamber, and discharges ink droplets from a nozzle opening by the pressure change. A device,
Drive signal generating means for generating a drive signal, and drive pulse generating means for generating a drive pulse from the drive signal,
The drive pulse generating means expands the pressure chamber and maintains the expanded state after the change, a first filling waveform element that further expands the pressure chamber in which the expanded state is maintained by the expanded waveform element, And an ink jet recording apparatus that generates a first drive pulse including a first ejection waveform element that ejects ink droplets by contracting a pressure chamber expanded by one filling waveform element.
[0029]
Preferably, the expansion state holding time by the expansion waveform element is set longer than the natural vibration period of the pressure chamber.
[0030]
Preferably, the drive pulse generating means contracts the pressure chamber, expands the contraction waveform element that maintains the contracted state, and the pressure chamber that maintains the contracted state by the contraction waveform element, and fills the ink with the first pulse. The second drive pulse including the second filling waveform element and the second ejection waveform element for ejecting the ink droplets by contracting the pressure chamber expanded by the second filling waveform element is generated.
[0031]
Preferably, the expansion waveform element is constituted by a stepwise expansion waveform element that expands the pressure chamber in a plurality of stages.
[0032]
Preferably, the contraction waveform element is configured by a stepwise contraction waveform element that contracts the pressure chamber in a plurality of stages.
[0033]
Preferably, at least one drive pulse is divided into a plurality of waveform elements, and a series of drive signals are configured by mixing waveform elements constituting other drive pulses between the divided waveform elements,
The drive pulse generating means generates a drive pulse by selectively connecting the divided waveform elements.
[0034]
Preferably, the expansion waveform element of at least one drive pulse is divided into a plurality of expansion subelements, and a series of drive signals are generated by mixing ejection waveform elements of other drive pulses between these expansion subelements. Constitute.
[0035]
Preferably, the contraction waveform element of at least one drive pulse is divided into a plurality of contraction subelements, and a series of drive signals are generated by mixing ejection waveform elements of other drive pulses between these contraction subelements. Constitute.
[0036]
Preferably, the expansion element that constitutes a part of the expansion waveform element is disposed at the head portion of the drive signal, and the first ejection waveform element is disposed at the end portion of the drive signal.
[0037]
Preferably, different voltage levels between the divided waveform elements are connected by the connection element.
[0038]
Preferably, the pressure generating element is constituted by a flexural vibration mode piezoelectric vibrator.
[0039]
Preferably, the pressure generating element is constituted by a piezoelectric vibrator in a longitudinal vibration mode.
[0040]
Preferably, the pressure generating element is configured by a longitudinal vibration mode piezoelectric vibrator,
Set the end of the waveform element that drops the voltage from the intermediate voltage within the voltage range of 5V or less from the ground voltage,
The end of the waveform element is connected by a connection element.
[0041]
The present invention generates a series of drive signals in which divided waveform elements are connected to each other by a connection element, and drives the waveform element arranged before the connection element and the waveform element arranged after the connection element. And a drive pulse is generated by connecting the selected waveform elements to each other, and the generated drive pulse is supplied to a pressure generating element to eject ink droplets. .
[0042]
The present invention expands the pressure chamber, holds the expanded state for a predetermined time, further expands the pressure chamber in which the expanded state is maintained, and then contracts and ejects ink droplets to generate pressure. This is a method of driving an ink jet recording head that supplies ink to an element and ejects ink droplets.
[0043]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a functional block diagram of an ink jet recording apparatus to which the present invention is applied.
[0044]
The ink jet recording apparatus includes a printer controller 1 and a print engine 2. The printer controller 1 includes an interface 3 that receives print data from a host computer (not shown), a RAM 4 that stores various data, a ROM 5 that stores control routines for various data processing, and the like. A control unit 6 composed of a CPU or the like, an oscillation circuit 7, a drive signal generation circuit 9 that generates a drive signal to be supplied to the recording head 8, print data and drive signals developed in dot pattern data (bitmap data), etc. Is sent to the print engine 2. The drive signal generation circuit 9 is a kind of drive signal generation means in the present invention.
[0045]
The interface 3 receives, for example, print data composed of one or more data of a character code, a graphic function, and image data from a host computer or the like. The interface 3 can output a busy (BUSY) signal, an acknowledge (ACK) signal, and the like to the host computer.
[0046]
The RAM 4 is used as a reception buffer 4a, an intermediate buffer 4b, an output buffer 4c, a work memory (not shown), and the like. Print data from the host computer received by the interface 3 is temporarily stored in the reception buffer 4a. The intermediate buffer 4b stores intermediate code data converted into an intermediate code by the control unit 6. In the output buffer 4c, the dot pattern data after decoding the gradation data is developed. This will be described later.
[0047]
The ROM 5 stores various control routines executed by the control unit 6, font data, graphic functions, and the like.
[0048]
The control unit 6 reads the print data in the reception buffer 4a and converts it into an intermediate code. Then, the control unit 6 stores the converted intermediate code data in the intermediate buffer 4b. Further, the control unit 6 expands the intermediate code data read from the intermediate buffer 4b into dot pattern data with reference to font data and graphic functions in the ROM 5. The developed dot pattern data is stored in the output buffer 4c after necessary decoration processing is performed.
[0049]
When dot pattern data corresponding to one line of the recording head 8 is obtained, the dot pattern data for one line is serially transmitted to the recording head 8 via the interface 10. When dot pattern data for one line is output from the output buffer 4c, the contents of the intermediate buffer 4b are erased and conversion for the next intermediate code is performed.
[0050]
The print engine 2 includes a recording head 8, a paper feed mechanism 11, and a carriage mechanism 12. The paper feed mechanism 11 includes a paper feed motor and a paper feed roller, and sequentially feeds a print recording medium such as a recording paper. That is, the paper feed mechanism 11 performs sub-scanning in the recording operation. The carriage mechanism 12 includes a carriage on which the recording head 8 is mounted, and a pulse motor that drives the carriage via a timing belt or the like. The carriage mechanism 12 performs main scanning in the recording operation.
[0051]
The recording head 8 has nozzle openings 13 (shown in FIG. 2) formed in a large number (for example, 64) arranged in the sub-scanning direction, and ejects ink droplets from the nozzle openings 13.
[0052]
The print data (SI) developed into the dot pattern data is serially transmitted to the selection signal generator 22 through the interface 10 in synchronization with the clock signal (CK) from the oscillation circuit 7. The selection signal generator 22 generates a selection signal corresponding to the print data by receiving the latch signal (LAT), and supplies the generated selection signal to the level shifter 23 that is a voltage amplifier. Here, the selection signal is a signal for selecting a necessary part from the drive signal (COM) from the drive signal generation circuit 9.
[0053]
The level shifter 23 outputs a switch signal to the switch circuit 24 based on the supplied selection signal. A drive signal is input to the input side of the switch circuit 24, and a piezoelectric vibrator 25 is connected to the output side of the switch circuit 24. And this switch circuit 24 will be in a connection state, if a switch signal is input. The piezoelectric vibrator 25 is a kind of pressure generating element of the present invention.
[0054]
The print data controls the operation of the switch circuit 24. For example, during a period in which the print data is “1”, a selection signal is output from the selection signal generator 22 and a switch signal is output from the level shifter 23. As a result, a drive signal is supplied to the piezoelectric vibrator 25, and the piezoelectric vibrator 25 is deformed in accordance with the drive signal. On the other hand, while the print data applied to the switch circuit 24 is “0”, the supply of the drive signal to the piezoelectric vibrator 25 is cut off.
[0055]
As the piezoelectric vibrator 25 is deformed, ink droplets are ejected from the nozzle opening 13.
[0056]
Next, the recording head 8 will be described in detail. First, the structure of the recording head 8 will be described. The recording head 8 illustrated in FIG. 2 is the recording head 8 to which the piezoelectric vibrator 25 in the flexural vibration mode is attached.
[0057]
The recording head 8 includes an actuator unit 32 having a plurality of pressure chambers 31, a flow path unit 34 having a nozzle opening 13 and a common ink chamber 33, and a piezoelectric vibrator 25. The flow path unit 34 is joined to the front surface of the actuator unit 32, and the piezoelectric vibrator 25 is provided on the back surface of the actuator unit 32.
[0058]
The pressure chamber 31 expands and contracts as the piezoelectric vibrator 25 is deformed, and changes the ink pressure in the pressure chamber 31. Then, an ink droplet is ejected from the nozzle opening 13 by the change of the ink pressure in the pressure chamber 31. For example, the inside of the pressure chamber 31 is pressurized by abruptly contracting the pressure chamber 31, and ink droplets are ejected from the nozzle opening 13.
[0059]
The actuator unit 32 includes a pressure chamber forming substrate 35 in which a void forming the pressure chamber 31 is formed, a lid member 36 joined to the front surface of the pressure chamber forming substrate 35, and a back surface of the pressure chamber forming substrate 35. It is comprised from the diaphragm 37 which is joined and block | closes the opening surface of an empty part. The lid member 36 includes a first ink channel 38 for communicating the common ink chamber 33 and the pressure chamber 31 and a second ink channel 39 for communicating the pressure chamber 31 and the nozzle opening 13. It is.
[0060]
The flow path unit 34 includes an ink chamber forming substrate 41 in which empty portions forming the common ink chamber 33 are formed, and a nozzle plate in which a large number of nozzle openings 13 are formed and joined to the front surface of the ink chamber forming substrate 41. 42 and a supply port forming plate 43 joined to the back surface of the ink chamber forming substrate 41.
[0061]
The ink chamber forming substrate 41 is formed with a nozzle communication port 44 that communicates with the nozzle opening 13. The supply port forming plate 43 includes an ink supply port 45 that communicates the common ink chamber 33 and the first ink channel 38, and a communication port 46 that communicates the nozzle communication port 44 and the second ink channel 39. Has been drilled.
[0062]
Therefore, a series of ink flow paths from the common ink chamber 33 through the pressure chamber 31 to the nozzle opening 13 are formed in the recording head 8.
[0063]
The piezoelectric vibrator 25 is formed on the opposite side of the pressure chamber 31 with the diaphragm 37 interposed therebetween. The piezoelectric vibrator 25 has a flat plate shape. A lower electrode 48 is formed on the front surface of the piezoelectric vibrator 25, and an upper electrode 49 is formed on the back surface so as to cover the piezoelectric vibrator 25.
[0064]
Further, at both ends of the actuator unit 32, connection terminals 50 whose base end portions are electrically connected to the upper electrodes 49 of the piezoelectric vibrators 25 are formed. The front end surface of the connection terminal 50 is formed higher than the piezoelectric vibrator 25. A flexible circuit board 51 is bonded to the distal end surface of the connection terminal 50, and a drive waveform is supplied to the piezoelectric vibrator 25 via the connection terminal 50 and the upper electrode 49.
[0065]
Although only two pressure chambers 31, piezoelectric vibrators 25, and connection terminals 50 are shown in the drawing, a large number are provided corresponding to the nozzle openings 13.
[0066]
In the recording head 8, when a drive pulse is input, a voltage difference is generated between the upper electrode 49 and the lower electrode 48. Due to this potential difference, the piezoelectric vibrator 25 contracts in a direction orthogonal to the electric field. At this time, since the lower electrode 48 side of the piezoelectric vibrator 25 bonded to the vibration plate 37 is not shrunk but only the upper electrode 49 side is shrunk, the piezoelectric vibrator 25 and the vibration plate 37 protrude toward the pressure chamber 31 side. And the volume of the pressure chamber 31 is contracted.
[0067]
And when discharging an ink drop from the nozzle opening part 13, the pressure chamber 31 is contracted rapidly, for example. That is, when the pressure chamber 31 is rapidly contracted, the ink pressure increases in the pressure chamber 31, and ink droplets are ejected from the nozzle openings 13 along with this pressure increase. Further, when the voltage difference between the upper electrode 49 and the lower electrode 48 is eliminated after the ink droplets are ejected, the piezoelectric vibrator 25 and the diaphragm 37 return to their original states. As a result, the contracted pressure chamber 31 expands, and ink is supplied from the common ink chamber 33 to the pressure chamber 31 through the ink supply port 45.
[0068]
Next, the electrical configuration of the recording head 8 will be described.
[0069]
As shown in FIG. 1, the recording head 8 includes a selection signal generator 22, a level shifter 23, a switch circuit 24, a piezoelectric vibrator 25, and the like. The selection signal generator 22, the level shifter 23, and the switch circuit 24 function as drive pulse generation means in the present invention.
[0070]
As shown in FIG. 3, the level shifter 23 includes a plurality of level shifter elements 23 a to 23 n provided corresponding to the nozzle openings 13. Similarly, the switch circuit 24 includes a plurality of switch elements 24a to 24n. The piezoelectric vibrator 25 is also composed of a plurality of piezoelectric vibrators 25a to 25n.
[0071]
The selection signal from the selection signal generator 22 is selectively supplied to the level shifter elements 23a to 23n based on the print data. The switch elements 24a to 24n are selectively controlled in connection state based on this selection signal.
[0072]
A drive signal (COM) generated by the drive signal generation circuit 9 is input to each of the switch elements 24a to 24n. When the switch elements 24a to 24n are connected, the piezoelectric elements connected to the switch elements 24a to 24n are connected. A drive signal is selectively supplied to the vibrators 25a to 25n.
[0073]
As described above, in the recording head 8, it is possible to control whether or not to input a drive signal to the piezoelectric vibrator 25 by the print data. For example, since the switch circuit 24 is in the connected state during the period when the print data is “1”, the drive signal is supplied to the piezoelectric vibrator 25. The piezoelectric vibrator 25 is deformed by this drive signal. Further, since the switch is not connected during the period when the print data is “0”, the supply of the drive signal to the piezoelectric vibrator 25 is cut off. Note that, during the period in which the print data is “0”, each piezoelectric vibrator 25 holds the previous charge, and the previous deformed state is maintained.
[0074]
Next, control of the recording head 8 will be described. In the following description, for ease of explanation, the case of four gradations of “large dot”, “medium dot”, “small dot”, and “non-printing” will be described as an example. Here, “large dots” in the present embodiment means relatively large dots formed by large ink droplets having an ink volume of about 20 pL (picoliter). “Medium dot” means a medium-sized dot formed by a medium ink droplet having an ink volume of about 8 pL. “Small dots” means relatively small dots formed by small ink droplets having an ink volume of about 4 pL.
[0075]
FIG. 4A shows the waveform of the drive signal generated by the drive signal generation circuit 9. The exemplified drive signal is a series of signals that can eject three types of ink droplets, which are a large ink droplet, a medium ink droplet, and a small ink droplet, from the same nozzle opening 13.
[0076]
Then, the drive signal generation circuit 9 generates this drive signal at a printing cycle T of 7.2 kHz. This printing cycle T defines the printing speed in the recording apparatus. Further, the selection signal generator 22, the level shifter 23, and the switch circuit 24, that is, the drive pulse generator, discharges a small dot drive pulse for discharging a small ink droplet and a medium ink droplet from a series of drive signals. A medium dot drive pulse or a large dot drive pulse that can eject a large ink droplet is generated.
[0077]
Hereinafter, a procedure for generating a drive pulse from the drive signal will be described in detail.
[0078]
The drive signal shown in FIG. 4A includes a waveform element and a connection element. The waveform element is an element that is supplied to the piezoelectric vibrator 25 and deforms the piezoelectric vibrator 25. The connection element is an element that does not operate the piezoelectric vibrator 25 and connects different voltage levels between the waveform elements.
[0079]
The waveform elements in this embodiment include a contraction waveform element, a filling waveform element, a discharge waveform element, a vibration suppression waveform element, and the like. Here, the contraction waveform element is an element that deforms the piezoelectric vibrator 25 so that the pressure chamber 31 contracts to such an extent that ink droplets are not ejected. The filling waveform element is an element that operates the piezoelectric vibrator 25 so as to expand the pressure chamber 31 and fill the pressure chamber 31 with ink. The ejection waveform element is an element that deforms the piezoelectric vibrator 25 so that the pressure chamber 31 is rapidly contracted to eject ink from the nozzle opening 13. The vibration suppression waveform element is an element that quickly stops meniscus undulation immediately after ink droplet ejection. The meniscus means a curved surface (free surface) of ink in the nozzle opening 13.
[0080]
In the drive signals shown in FIGS. 4A and 4B, the portions from P1 to P10 ′ and P12 ′ to P24 are waveform elements. Moreover, the part from P10 'to P12' is a connection element. Further, the portion from P1 to P2 'in the waveform element is the contraction waveform element, the portion from P2' to P5 is the first filling waveform element, the portion from P5 to P9 is the first discharge waveform element, and from P9 to P10 ' The part is a first damping waveform element. The portion from P12 ′ to P15 is the second filling waveform element, the portion from P15 to P17 is the second discharge waveform element, the portion from P17 to P18 is the second damping waveform element, and the portion from P18 ′ to P21. Is a third filling waveform element, a portion from P21 to P23 is a third discharge waveform element, and a portion from P23 to P24 is a third damping waveform element.
[0081]
In addition, the part of P2 'to P3 is a connection end part in a 1st filling waveform element, and the part of P10 to P10' is a connection end part in a 1st damping waveform element. Similarly, P12 ′ to P13 are connection end portions in the second filling waveform element, P18 to P18 ′ portions are connection end portions in the second damping waveform element, and P18 ′ to P19 portions are the first end portions. 3 is a connection end in a filled corrugated element.
[0082]
The drive pulse generating means appropriately selects these contraction waveform elements, filling waveform elements, ejection waveform elements, and vibration suppression waveform elements, and generates a plurality of types of drive pulses by connecting the selected waveforms.
[0083]
As shown in the enlarged view of FIG. 4B, the above-described connecting element connects between the terminal end P10 ′ of the first damping waveform element and the terminal end P12 ′ of the second filling waveform element. That is, this connection element connects between the intermediate voltage VM, which is the voltage level of the terminal end 10 'in the first damping waveform element, and the maximum voltage VH, which is the voltage level of the start end P12' in the second filling waveform element. ing.
[0084]
Incidentally, since the waveform elements (P1 to P10 ′, P12 ′ to P24) of the drive signal are signal elements supplied to the piezoelectric vibrator 25, the response characteristics of the piezoelectric vibrator 25 and the ink state in the pressure chamber 31 are shown. Is set according to For this reason, the waveform element is limited in the voltage gradient, the timing for changing the voltage, and the like. That is, it is necessary to set the voltage gradient below a predetermined gradient, and it is necessary to set the voltage change timing to a predetermined timing suitable for ink droplet ejection.
[0085]
For example, if the voltage gradient becomes too steep, the deformation of the piezoelectric vibrator 25 cannot follow the voltage change of the waveform element, and there is a possibility that a desired volume of ink droplets cannot be ejected. Further, even if the deformation of the piezoelectric vibrator 25 can follow, the pressure chamber 31 may rapidly expand as the piezoelectric vibrator 25 deforms rapidly, and cavitation may occur in the pressure chamber 31. There is. Then, there is a possibility that the ejection amount of the ink droplets is not stabilized by this cavitation. Furthermore, the diaphragm 37 may be damaged by applying excessive mechanical stress to the diaphragm 37.
[0086]
Further, regarding the voltage change timing, in the case of “pulling” in which the pressure chamber 31 is expanded and then contracted to eject ink droplets, the pressure chamber 31 is expanded and then the pressure chamber 31 is contracted. The timing at which the pressure chamber 31 is contracted is determined by the state of the ink flowing into the pressure chamber 31 from the common ink chamber 33, and the timing at which the ink state in the pressure chamber 31 becomes a state suitable for ink droplet ejection. Thus, the pressure chamber 31 is contracted.
[0087]
For example, when the pressure chamber 31 is expanded to make the inside of the pressure chamber 31 a negative pressure and the ink is sucked, the pressure is adjusted in accordance with the generation timing of the pressure wave in the opposite direction (ink discharge direction) generated when the ink flows. The chamber 31 is contracted. As a result, ink droplets can be ejected in an optimal state. On the other hand, when the pressure chamber 31 is contracted at a timing that is not suitable for ink droplet ejection, for example, when the pressure chamber 31 is contracted at a time deviated from the generation timing of the pressure wave in the reverse direction, the ejection is performed. Variations in the size of the ink droplets cause deterioration in image quality.
[0088]
Then, as in this embodiment, by connecting between different voltage levels of the waveform elements with the connection elements, even if the number of waveform elements included in the drive signal is increased as compared to the conventional case, one print cycle T Can fit inside.
[0089]
That is, since this connecting element is a signal element that does not deform the piezoelectric vibrator (pressure generating element) 25, the voltage gradient can be set steeply. Since the voltage gradient can be set steeply, the period TS required by the connection element can be set in a short time. For this reason, waveform elements having different voltage levels at the connection ends, such as the first damping waveform element and the second filling waveform element, can be connected in a very short time. In addition, regarding the inclined portion (P11 to P12) of this connection element, the time (occurrence time) of this inclined portion is that of the inclined portion (for example, P5 to P6, P15 to P16) of the waveform element that deforms the piezoelectric vibrator 25. The time is set equal to the time (occurrence time) or shorter than the time of the inclined portion of the waveform element.
[0090]
Therefore, as described above, more waveform elements whose voltage gradient and voltage change timing are defined by the balance with the piezoelectric vibrator 25 are included in one printing cycle T whose time is limited by the printing speed. be able to.
[0091]
Accordingly, the variable range of the ink droplet volume can be increased depending on how the waveform elements are selected. That is, since the degree of freedom of selection of the waveform element is expanded, it can be generated from one drive signal and a drive pulse for ejecting a very small volume ink droplet, a drive pulse for ejecting a large volume ink droplet.
[0092]
Moreover, regarding the start end portions P10 ′ to P11 and the end portions P12 to P12 ′, which are connection end portions in this connection element, in the present embodiment, a constant voltage portion having a constant voltage is provided. By providing this constant voltage section, when connecting the waveform elements, the switching time of the switch circuit 24 can be secured, and the elements can be easily connected. Further, the voltage level difference between the waveform elements to be connected can be eliminated, and the inrush current at the connection portion between the elements can be eliminated. As a result, it is possible to prevent damage to electrical components such as transistors constituting the switch circuit 24. In addition, it is desirable to set this constant voltage part to at least 2 μs or more.
[0093]
In order to generate the small dot driving pulse shown in FIG. 5 from the above driving signal, the driving pulse generating means includes the contraction waveform element (P1 to P2 ′), the first filling waveform element (P2 ′ to P5), the first The discharge waveform elements (P5 to P9) and the first vibration suppression waveform elements (P9 to P10 ′) are selected, and the selected waveform elements are connected in series.
[0094]
Similarly, in order to generate the medium dot drive pulse from the drive signal, the drive pulse generating means includes a contraction waveform element, second filling waveform elements (P12 ′ to P15), second ejection waveform elements (P15 to P17), The second vibration suppression waveform elements (P17 to P18 ′) are selected, and the selected waveform elements are connected in series.
[0095]
Furthermore, in order to generate a large dot drive pulse from the drive signal, the drive pulse generating means includes a contraction waveform element, a second filling waveform element, a second ejection waveform element, a second damping waveform element, and a third filling waveform element. (P18 ′ to P21), the third discharge waveform elements (P21 to P23), and the third vibration suppression waveform elements (P23 to P24) are selected, and the selected waveform elements are connected in series.
[0096]
The drive pulse generation means selects and connects the waveform elements based on the 5-bit print data. For this reason, in the present embodiment, the drive signals are divided into the first waveform elements (P1 to P2 ′) in the period T1, the second waveform elements (P2 ′ to P10 ′) in the period T2, and the third waveform elements in the period T3. (P12 ′ to P18 ′) and fourth waveform elements (P18 ′ to P24) in the period T4.
[0097]
Then, as shown in FIG. 4C, when generating the small dot drive pulse, the drive pulse generating means switches the switch circuit between the period T1 and the period T2 based on the print data set to “11000”. 24 is connected, and the first waveform element and the second waveform element are selectively supplied to the piezoelectric vibrator 25. Similarly, when generating the medium dot drive pulse, the drive pulse generating means sets the switch circuit 24 in the connection state in the period T1 and the period T3 based on the print data set to “10010”, and the first waveform. The element and the third waveform element are selectively supplied to the piezoelectric vibrator 25. When generating a large dot drive pulse, the drive pulse generating means sets the switch in the connected state in the period T1, the period T3, and the period T4 based on the print data set to “10011”, and the first waveform element The third waveform element and the fourth waveform element are selectively supplied to the piezoelectric vibrator 25.
[0098]
In the case of non-printing that does not eject ink droplets, the print data is “00000”, and the switch circuit 24 remains in a disconnected state. The relationship between the print data and the switch connection state will be described later.
[0099]
As shown in FIG. 5, in the small dot drive pulse, the voltage is increased from the intermediate voltage VM at a predetermined voltage gradient θ1 (P1 to P2), and when the maximum voltage VH is reached, the maximum voltage VH is maintained for a predetermined time (P2). ~ P3). Then, the voltage is decreased from the maximum voltage VH to the minimum voltage VL at a predetermined voltage gradient θ2 (P3 to P4), and the voltage is increased from the minimum voltage VL to the maximum voltage VH along the voltage gradient θ3 set to a steep gradient. (P5 to P6). Immediately thereafter, the voltage is lowered to the second intermediate voltage VM2 set between the intermediate voltage VM and the minimum voltage VL (P7 to P8), and the second intermediate voltage VM2 is maintained for a predetermined time (P8 to P9). Then, the voltage is increased along the voltage gradient θ4 to return to the intermediate voltage VM (P9 to P10).
[0100]
In this small dot drive pulse, the voltage gradients θ1, θ2, and θ4 are set to such a gradient that ink droplets are not ejected.
[0101]
By applying this small dot drive pulse, the piezoelectric vibrator 25 is charged and discharged, and the piezoelectric vibrator 25 is deformed. The volume of the pressure chamber 31 changes due to the deformation of the piezoelectric vibrator 25.
[0102]
That is, when the piezoelectric vibrator 25 is charged from the intermediate voltage VM, the volume of the pressure chamber 31 gradually decreases from the reference volume (volume at the intermediate voltage VM). The pressure chamber 31 maintains the minimum volume corresponding to the maximum voltage VH for a predetermined time, and then expands to the maximum volume corresponding to the minimum voltage VL as the piezoelectric vibrator 25 is discharged (P1 to P5).
[0103]
Subsequently, the pressure chamber 31 rapidly contracts from the maximum volume to the minimum volume (P5 to P6). By this contraction, the ink pressure in the pressure chamber 31 is increased, and ink droplets are ejected from the nozzle openings 13. Here, the holding time of the minimum potential VL is made extremely short, and the pressure chamber 31 immediately expands (P7 to P8). Thus, since the pressure chamber 31 is immediately expanded, the volume of the ink droplet ejected from the nozzle opening 13 is extremely small.
[0104]
If the pressure chamber 31 is expanded, the pressure chamber 31 is contracted so that the meniscus undulation is stopped in a short time, and the pressure chamber 31 is returned to the reference volume (P8 to P10).
[0105]
In the middle dot drive pulse, the voltage is increased from the intermediate voltage VM to the maximum voltage VH with the voltage gradient θ1 (P1 to P2), and the maximum voltage VH is maintained for a predetermined time (P2 to P13). Then, the voltage is lowered to the lowest voltage VL at a predetermined voltage gradient θ5, and ink is filled into the pressure chamber 31 (P13 to P14). After ink filling, the voltage is rapidly increased to the maximum voltage VH along the voltage gradient θ6, and the pressure chamber 31 is rapidly contracted to eject ink droplets (P15 to P16). Thereafter, the maximum voltage VH is maintained for a predetermined time (P16 to P17), and the voltage is lowered to the intermediate voltage VM (P17 to P18).
[0106]
In the medium dot drive pulse, the pressure chamber 31 is expanded after the maximum voltage VH is maintained in the period from P16 to P17. Therefore, the amount of ink droplets ejected from the nozzle opening 13 can be adjusted by the maintenance time of the maximum voltage VH, and ink droplets having a volume suitable for medium dots can be ejected.
[0107]
Further, in the large dot drive pulse, following the medium dot drive pulse (P1 to P18), the voltage is lowered to the lowest voltage VL along a predetermined voltage gradient θ7, and the pressure chamber 31 is filled with ink (P19 to P20). ). When the ink is filled, the voltage is increased to the maximum voltage VH along the voltage gradient θ8, the pressure chamber 31 is rapidly contracted, and the second ink droplet is ejected (P21 to P22). Thereafter, the maximum voltage VH is maintained for a predetermined time (P22 to P23), and the voltage is lowered to the intermediate voltage VM (P23 to P24).
[0108]
In this large dot drive pulse, the first ink droplet is ejected in the portion from P1 to P18 which overlaps with the medium dot drive pulse, and the second ink droplet is ejected in the subsequent portion from P19 to P24. Yes. A large dot is formed by the sum of these two ink droplets.
[0109]
As described above, in this embodiment, the drive signal is configured to include the waveform element that operates the piezoelectric vibrator 25 and the connection element that does not operate the piezoelectric vibrator 25, and the waveform is generated by the connection element. Connecting different voltage levels between elements. Further, the drive pulse generation means can select a waveform element and generate a plurality of types of drive pulses. Therefore, even if there are many waveform elements, it can be formed as a series of drive signals within one printing cycle.
[0110]
For this reason, the variable range of the ink droplet size can be made larger than before depending on how the waveform elements are selected, and ink droplets of various sizes can be ejected while maintaining a high recording speed. it can.
[0111]
Next, a procedure for supplying print data for generating a drive pulse to the piezoelectric vibrator 25 will be described.
[0112]
As described above, the dot pattern data is composed of 4-bit print data. That is, the control unit 6 translates the 2-bit gradation value in the intermediate code data into 5-bit print data, and stores the translated print data in the output buffer 4c.
[0113]
When transmitting these print data to the recording head 8, first, the print data corresponding to the first waveform element is sent to all nozzle openings immediately before the selection timing of the first waveform element arrives. The 13-minute selection signal generator 22 is set. For example, it is set during the period T4 in the printing cycle of the previous dot. When the print data is set, the control unit 6 outputs a latch signal in synchronization with the generation timing of the first waveform element.
[0114]
In response to this latch signal, the selection signal generator 22 generates a selection signal in correspondence with the print data “1”. This selection signal is boosted to a predetermined voltage value by the level shifter 23 and supplied to the switch circuit 24. Thereby, the switch circuit 24 is in a connected state, and the portion of the first waveform element in the drive signal is supplied to the corresponding piezoelectric vibrator 25 (25a to 25n).
[0115]
In the supply period T1 of the first waveform element, print data corresponding to the second waveform element is set in the selection signal generating unit 22 for all nozzle openings 13 minutes. Then, at the end of the period T1, the control unit 6 outputs a latch signal. As a result, the second waveform element is applied to the piezoelectric vibrator 25 whose print data is “1”. In the same manner, processing for the connection element, the third waveform element, and the fourth waveform element is performed.
[0116]
When the processing for the fourth waveform element is completed, printing for one dot for all the nozzle openings 13 is completed. When printing for one dot is completed, the next dot process is repeated.
[0117]
By the way, in the first embodiment described above, the second ejection waveform element that ejects ink droplets capable of forming large dots is arranged in the period T3, and the third ejection waveform element is arranged in the period T4. Elements are arranged close to each other in time.
[0118]
In this case, when ink droplets are ejected by the third ejection waveform element, there is a possibility that the influence of ejection of the ink droplet by the second ejection waveform element remains. If the effect remains, there is a possibility that the volume of the ink droplet due to the third ejection waveform element becomes unstable. The second embodiment focusing on this point will be described below.
[0119]
FIG. 6 is a diagram illustrating an example of a drive signal and a drive pulse in the second embodiment. Since the configuration other than the drive signal is the same as that of the first embodiment described above, the description thereof is omitted.
[0120]
In the illustrated driving signal, the period T1 (P31 to P32) is the first waveform element, and the period T2 (P32 to P35) is the second waveform element. The portion of the period T3 (P36 to P39) is the third waveform element, and the portion of the period T4 (P39 to P42) is the fourth waveform element. Further, the portion (P35 to P36) of the period TS is a connection element that does not deform the piezoelectric vibrator 25. The connection elements in this embodiment also connect waveform elements having different voltage levels. With this connection element, even if the number of waveform elements is increased, a series of drive signals can be formed within a limited printing cycle T.
[0121]
Here, the first waveform elements (P31 to P32) in the present embodiment are the same as the first waveform elements (P1 to P2 ′) in the first embodiment, and include contraction waveform elements. The second waveform elements (P32 to P35) are the same as the third waveform elements (P12 ′ to P18 ′) in the first embodiment, and include ejection waveform elements (P33 to P34) that eject medium ink droplets. Yes. The third waveform elements (P36 to P39) are the same as the second waveform elements (P2 ′ to P10 ′) in the first embodiment, and include ejection waveform elements (P37 to P38) that eject small ink droplets. . The fourth waveform elements (P39 to P42) are the same as the fourth waveform elements (P18 ′ to P24) in the first embodiment, and include ejection waveform elements (P40 to P41) that eject large ink droplets. Yes.
[0122]
In order to generate a small dot drive pulse from such a drive signal, the drive pulse generation means (that is, the selection signal generator 22, the level shifter 23, and the switch circuit 24) uses the first waveform element and the third waveform element. Select and concatenate the selected waveform elements. Specifically, the waveform element is selected based on the print data set to “10010”. Further, when generating the medium dot drive pulse, the drive pulse generating means selects the first waveform element and the second waveform element based on the print data set to “11000”, and the selected waveform element Are connected. Similarly, when generating a large dot drive pulse, the drive pulse generation means selects the first waveform element, the second waveform element, and the fourth waveform element based on the print data set to “11001”. Connect the selected waveform elements.
[0123]
In the drive pulse generated in this way, the large dot drive pulse has two discharge waveform elements that discharge two ink droplets, that is, the previous discharge waveform elements (P33 to P34, the first large dot discharge of the present invention). And a subsequent discharge waveform element (P40 to P41, corresponding to the second large dot discharge waveform element of the present invention). The small dot drive pulse includes ejection waveform elements (P37 to P38, corresponding to other dot ejection elements in the present invention) for ejecting small ink droplets.
[0124]
In the drive signal, the ejection waveform element of the small dot drive pulse is arranged between the ejection waveform element before and after the large dot drive pulse.
[0125]
With this drive signal, the large dot drive pulse ejects two ink droplets, but the time interval from the timing of ejecting the previous ink droplet to the timing of ejecting the subsequent ink droplet can be set relatively long. For this reason, after discharging the previous ink droplet, the ink state can be stabilized and then the subsequent ink droplet can be discharged. Accordingly, it is possible to eliminate the variation in the ink volume for the subsequent ink droplets, and it is possible to further improve the image quality.
[0126]
By the way, in said 1st Embodiment and 2nd Embodiment, although the damping waveform element and the filling waveform element were connected by the connection element, a connection element is not limited to this. For example, the discharge waveform elements may be connected to each other by a connection element. Hereinafter, the third embodiment configured as described above will be described.
[0127]
FIG. 7 is a diagram illustrating an example of a drive signal and a drive pulse in the third embodiment. Since the configuration other than the drive signal is the same as that of the first embodiment described above, the description thereof is omitted.
[0128]
In the illustrated drive signal, the period T1 (P51 to P52) is the first waveform element, the period T2 (P52 to P54) is the second waveform element, and the period T3 (P55 to P57) is the second waveform element. The third waveform element is a fourth waveform element in the period T4 (P57 to P60), and the fifth waveform element is a part in the period T5 (P60 to P62). Moreover, the part (P54-P55) of the period TS is a connection element.
[0129]
This drive signal is intended to eject a very small volume of ink droplets by rapidly expanding the contracted pressure chamber 31. That is, by supplying the maximum voltage VH, the piezoelectric vibrator 25 is bent so as to protrude toward the pressure chamber 31 and the pressure chamber 31 is contracted, and then the voltage is drastically lowered to the minimum voltage VL. The pressure chamber 31 is rapidly expanded by returning and deforming the vibrator 25.
[0130]
By controlling in this way, the pressure chamber 31 suddenly becomes a negative pressure, and the meniscus is drawn into the pressure chamber 31 at a high speed. Due to the movement of the meniscus, very small ink droplets are separated from the central portion of the meniscus. The ink droplets fly in the opposite direction to the inside of the pressure chamber 31 and are ejected from the nozzle opening 13.
[0131]
Therefore, in this drive signal, the portions from P51 to P52 are contraction waveform elements. Further, a portion from P52 to P54 is a first discharge waveform element, a portion from P55 to P57 is a second discharge waveform element, and a portion from P58 to P59 is a third discharge waveform element. Further, a portion from P57 to P58 is a filling waveform element, and a portion from P59 to P62 is a damping waveform element.
[0132]
The connection elements (P54 to P55) connect the first ejection waveform element and the second ejection waveform element, and the drive pulse generation means (that is, the selection signal generation unit 22, the level shifter 23, and the switch circuit 24) A plurality of types of drive pulses are generated by appropriately selecting the discharge waveform elements.
[0133]
That is, when generating the small dot drive pulse, the drive pulse generating means sets the switch circuit 24 in the connection state in the period T1, the period T2, and the period T5, and the first waveform element, the second waveform element, and the fifth waveform element. The waveform element is selectively supplied to the piezoelectric vibrator 25. Similarly, when generating the medium dot drive pulse, the drive pulse generation means sets the switch circuit 24 in the connection state in the period T1, the period T3, and the period T5, and the first waveform element, the third waveform element, and the fifth waveform element. The waveform element is selectively supplied to the piezoelectric vibrator 25. Further, when generating a large dot drive pulse, the drive pulse generating means sets the switch circuit 24 in the connection state in the period T1, the period T3, the period T4, and the period T5, and the first waveform element and the third waveform. The element, the fourth waveform element, and the fifth waveform element are selectively supplied to the piezoelectric vibrator 25.
[0134]
In the present embodiment, the selection of the waveform element is performed by 6-bit print data. That is, when generating a small dot drive pulse, the print data is set to “110001” to supply waveform elements in the periods T 1, T 2, and T 5 to the piezoelectric vibrator 25. Similarly, when generating a medium dot drive pulse, the print data is set to “100101” to supply waveform elements in the periods T 1, T 3, and T 5 to the piezoelectric vibrator 25. When generating a large dot drive pulse, the waveform data in the periods T1, T3, T4, and T5 are supplied to the piezoelectric vibrator 25 by setting the print data to “100111”.
[0135]
And in this embodiment, since the 1st discharge waveform element (P52-P54) and the 2nd discharge waveform element (P55-P57) are connected by the connection element (P54-P55), between discharge waveform elements The time interval can be shortened. Thereby, even within a limited time, many ejection elements can be included in the drive signal. Therefore, many types of drive pulses can be generated from one drive signal.
[0136]
Further, the time interval between the discharge waveform elements can be adjusted by the connection element. Thereby, the ejection timing of the ink droplets can be adjusted at a minute level. Accordingly, it is possible to reduce the deviation of the ink droplet landing center position.
[0137]
Moreover, in this embodiment, the 1st discharge waveform element and the 2nd discharge waveform element use the contraction waveform element (P51-P52) which is common. In other words, one drive pulse is generated by the contraction waveform element and the first discharge waveform element, and another drive pulse is generated by the contraction waveform element and the second discharge waveform element.
[0138]
In this configuration, the size of the ink droplet can be adjusted by the time interval from the contraction waveform element to the ejection waveform element. And this space | interval can be adjusted with the inclination of a connection element, or the length of a flat part. Therefore, the size of the ink droplet can be controlled at a minimum level. Thereby, the image quality can be further improved.
[0139]
In the above configuration, the same applies to the case where a filling waveform element is used in place of the contraction waveform element and a plurality of types of drive pulses are generated at the timing when the discharge waveform element and the filling waveform element are selected.
[0140]
Further, in the drive signal described above, the drive signal includes a plurality of ejection elements that actuate the piezoelectric vibrator 25 so as to eject ink droplets at different timings. That is, the drive signal includes a first ejection waveform element (P53 to P54) for ejecting small ink drops, a second ejection waveform element (P56 to P57) for ejecting medium ink drops, and a third for ejecting large ink drops. Discharge waveform elements (P58 to P59).
[0141]
Then, the drive pulse generating means generates a plurality of types of drive pulses so that the discharge timing of the small ink droplets is earlier than the discharge timing of the large ink droplets. For example, when a small dot drive pulse for ejecting a small ink droplet is compared with a medium dot drive pulse for ejecting a medium ink droplet, the smaller dot drive pulse than the ejection waveform elements (P56 to P57) in the medium dot drive pulse. The discharge waveform elements (P53 to P54) are earlier.
[0142]
Thereby, an ink droplet having a smaller ink volume is ejected earlier. In this case, the flying speed of the ejected ink droplet varies slightly depending on the size of the ink droplet, and the flying speed is faster for larger ink droplets and slower for smaller ink droplets. For this reason, the time from the ejection to the landing on the recording paper is also slightly different depending on the size of the ink droplet. That is, it takes a short time to land with a large ink droplet, and a long time to land with a small ink droplet.
[0143]
Therefore, by ejecting small ink droplets earlier than large ink droplets, it is possible to reduce the difference in landing timing due to the size of each ink droplet, in other words, the difference in landing center position on the recording paper. Therefore, the image quality can be further improved.
[0144]
By the way, in this 3rd Embodiment, although discharge waveform elements were connected with a connection element, you may make it connect filling waveform elements with a connection element. Hereinafter, the fourth embodiment configured as above will be described.
[0145]
FIG. 8 is a diagram illustrating an example of drive signals and drive pulses in the fourth embodiment. Since the configuration other than the drive signal is the same as that of the first embodiment described above, the description thereof is omitted.
[0146]
In the drive signal shown in FIG. 8, the period T1 (P71 to P72) is the first waveform element, and the period T2 (P72 to P74) is the second waveform element. Further, the period T3 (P75 to P76) is the third waveform element, the period T4 (P77 to P78) is the fourth waveform element, and the period T5 (P78 to P81) is the fifth waveform element. It is. Further, the portion (P74 to P75) of the period TS1 is a first connection element, and the portion (P76 to P77) of the period TS2 is a second connection element.
[0147]
This drive signal includes a plurality of filling waveform elements and one ejection waveform element, and changes the volume of ink droplets to be ejected by changing the combination of the filling waveform element and the ejection waveform element. That is, a plurality of filling elements having different ink filling states are prepared, and the volume of ink droplets to be ejected is varied depending on which filling element is selected.
[0148]
In this drive signal, the portion from P71 to P72 is the contraction waveform element, the portion from P72 to P74 is the first filling waveform element, the portion from P75 to P76 is the second filling waveform element, and the portion from P77 to P78 Is the third filling waveform element. Further, the portions from P79 to P80 are ejection waveform elements, and the portions from P80 to P81 are vibration damping elements.
[0149]
The first connection element (P74 to P75) connects the first filling waveform element and the second filling waveform element, and the second connection element (P76 to P77) is the second filling waveform element and the third filling waveform element. Connect the element.
[0150]
As described above, since the plurality of filling waveform elements are connected by the connecting element, the interval between the filling waveform elements can be narrowed, and a large number of filling waveform elements can be included in the drive signal within one printing cycle.
[0151]
Then, the drive pulse generation means (that is, the selection signal generator 22, the level shifter 23, and the switch circuit 24) generates a plurality of types of drive pulses by appropriately selecting the filling waveform elements.
[0152]
That is, in order to generate the small dot drive pulse, the drive pulse generation means sets the switch circuit 24 in the connection state in the period T1, the period T4, and the period T5, and the first waveform element, the fourth waveform element, and the fifth waveform element. Select. As a result, a small dot drive pulse in which the contraction waveform element and the third filling waveform element are coupled is generated and supplied to the piezoelectric vibrator 25.
[0153]
Similarly, in order to generate the medium dot drive pulse, the drive pulse generation means sets the switch circuit 24 in the connection state in the period T1, the period T3, and the period T5, and the first waveform element, the third waveform element, and the fifth waveform. Select an element. As a result, a medium dot drive pulse in which the contraction waveform element and the second filling waveform element are coupled is generated and supplied to the piezoelectric vibrator 25.
[0154]
Further, in order to generate the large dot drive pulse, the drive pulse generation means sets the switch circuit 24 in the connection state in the period T1, the period T2, and the period T5, and the first waveform element, the second waveform element, and the fifth waveform element. Select. As a result, a large dot drive pulse in which the contraction waveform element and the first filling waveform element are connected is generated and supplied to the piezoelectric vibrator 25.
[0155]
In the present embodiment, the selection of the waveform element is performed by 7-bit print data. That is, when generating a small dot drive pulse, the waveform data in the periods T1, T4, and T5 are supplied to the piezoelectric vibrator 25 by setting the print data to “1000011”. Similarly, when generating a medium dot drive pulse, the print data is set to “1001001” to supply waveform elements in the periods T 1, T 3, and T 5 to the piezoelectric vibrator 25. When generating a small dot drive pulse, the waveform data in the periods T1, T2, and T5 are supplied to the piezoelectric vibrator 25 by setting the print data to “1100001”.
[0156]
In this embodiment, since the ink droplets are ejected using the same ejection waveform element, the first filling waveform element (P72 to P74), the second filling waveform element (P75 to P76), and the third filling waveform element. The size of the ink droplet can be determined by selecting one filling waveform element from (P77 to P78). For this reason, control is easy.
[0157]
Furthermore, since a plurality of types of ink droplets having different ink volumes are ejected using the same ejection waveform element, the control can be simplified from this point.
[0158]
For this reason, the variable range of the ink droplet size can be expanded while maintaining a high recording speed.
[0159]
Next, the pressure chamber 31 of the reference volume is expanded to hold the expanded state after the change for a predetermined time, and the pressure chamber 31 in which the expanded state is held is further expanded and then contracted to discharge ink droplets. The fifth embodiment configured as described above will be described.
[0160]
The drive signal shown in FIG. 9 is a signal for ejecting large ink droplets and medium ink droplets having different ink volumes from the same nozzle opening 13.
[0161]
Since the configuration other than the drive signal is the same as that of the first embodiment described above, the description thereof is omitted.
[0162]
In this drive signal, the period T1 (P91 to P97) is the first waveform element, and the period T2 (P97 to P106) is the second waveform element.
[0163]
The first waveform element includes a filling waveform element (P91 to P93, corresponding to the second filling waveform element of the present invention) for deforming the piezoelectric vibrator 25 so as to fill the ink in the pressure chamber 31, and a nozzle. The ejection waveform element (P93 to P95, corresponding to the second ejection waveform element of the present invention) for deforming the piezoelectric vibrator 25 so as to eject ink from the opening 13 and the meniscus undulation immediately after ejection are short. It consists of vibration suppression waveform elements (P95 to P96) for stopping in time.
[0164]
The voltages at the start point (P91) and end point (P97) of the first waveform element are set to the intermediate voltage VM that is the reference voltage. This intermediate voltage VM is also the start point (P97) and end point (P106) of the second waveform element. Thus, by setting the start point and the end point of a plurality of waveform elements to the intermediate voltage VM, the waveform elements can be smoothly connected.
[0165]
The second waveform element is an expansion waveform element (P98 to P100) that expands the pressure chamber 31 in the reference state of the intermediate voltage VM slightly and holds the ink in the pressure chamber 31 for a predetermined time. The pressure chamber 31 expanded by the waveform element is further expanded to fill the pressure chamber 31 with ink (P100 to P102, corresponding to the first filling waveform element of the present invention), and the nozzle opening 13. Discharge waveform elements (P102 to P104, corresponding to the first discharge waveform element of the present invention) for discharging ink droplets from, and vibration suppression elements (P104 to P105) for suppressing meniscus undulation immediately after discharge. Yes.
[0166]
In the expansion waveform element (P98 to P100) of the second waveform element, the holding time for holding the expanded pressure chamber 31, that is, the supply time Tc for the expansion hold element (P99 to P100), causes the pressure chamber 31 to expand. It is preferable to set the time sufficiently long so that the vibration of the meniscus when the piezoelectric vibrator 25 is deformed converges to reach a steady state.
[0167]
For example, it is preferable to set it longer than the natural vibration period of the pressure chamber 31, and it is more preferable if it is at least twice this natural vibration period. Here, the natural vibration period of the pressure chamber 31 is determined by factors such as the capacity and size of the pressure chamber 31 and refers to the vibration period of the meniscus inherent in each type of the recording head 8 and is approximately about 8 to 10 μsec. Takes the value of
[0168]
Then, the drive pulse generation means (that is, the selection signal generator 22, the level shifter 23, and the switch circuit 24) selectively generates one drive pulse from the drive signal. For example, when generating a medium dot drive pulse (corresponding to the second drive pulse of the present invention) for ejecting a medium ink droplet from the drive signal, as shown in FIG. 10, the first waveform elements (P91 to P97) are generated. ) And the second waveform element (P98 to P106) is selected when generating a large dot drive pulse (corresponding to the first drive pulse of the present invention) for ejecting a large ink droplet.
[0169]
In the present embodiment, the selection of the waveform element is performed by 2-bit print data. Therefore, the drive signal is divided into first waveform elements (P91 to P97) in the period T1 and first waveform elements (P97 to P106) in the period T2. When generating the medium dot drive pulse, the print data is set to “10”, so that the switch circuit 24 is connected in the period T1, and the first waveform element is selectively supplied to the piezoelectric vibrator 25. To do. Similarly, when generating a large dot drive pulse, by setting the print data to “01”, the switch circuit 24 is connected in the period T2, and the second waveform element is selectively selected by the piezoelectric vibrator 25. To supply. Further, in the case of non-printing in which no dot is formed, the print data is set to “00” to put the switch circuit 24 in a non-connected state.
[0170]
By supplying the medium dot drive pulse generated in this way to the piezoelectric vibrator 25, ink droplets are ejected as follows.
[0171]
As shown in FIG. 10, in the state of the intermediate voltage VM (P91), the piezoelectric vibrator 25 is slightly bent while protruding toward the pressure chamber 31, and the pressure chamber 31 is slightly contracted. This state is an initial state and is set as a reference volume of the pressure chamber 31.
[0172]
Next, the voltage is dropped from the intermediate voltage VM at a predetermined voltage gradient θ11 (P91 to P92), and when the minimum voltage VL is reached, the minimum voltage VL is maintained for a predetermined time (P92 to P93). At this time, the piezoelectric vibrator 25 is deformed as the voltage drops, and the pressure chamber 31 expands more than the reference volume, and ink is filled into the pressure chamber 31.
[0173]
Next, the voltage is rapidly increased from the minimum voltage VL to the maximum voltage VH along the voltage gradient θ12 set to be steep (P93 to P94). At this time, the piezoelectric vibrator 25 is rapidly deformed, and the volume of the pressure chamber 31 is also rapidly contracted. Due to the contraction of the pressure chamber 31, the ink pressure in the pressure chamber 31 increases and ink droplets are ejected from the nozzle opening 13.
[0174]
Then, after maintaining the maximum voltage VH for a predetermined time (P94 to P95), the pressure chamber 31 is expanded from the maximum voltage VH so that the meniscus undulation is stopped in a short time, and returned to the reference volume (P95). ~ P96). At this time, since the pressure chamber 31 is expanded after maintaining the maximum voltage VH, the ink is returned to the pressure chamber 31 after the ink is pushed out from the nozzle opening 13 to some extent. The volume of the ink droplet ejected from the nozzle opening 13 can be adjusted by the maintenance time (P94 to P95) of the maximum voltage VH, and the ink droplet having a volume suitable for forming the medium dot can be ejected. .
[0175]
Further, by supplying a large dot drive pulse to the piezoelectric vibrator 25, ink droplets are ejected as follows.
[0176]
First, the voltage is dropped from the intermediate voltage VM at a predetermined voltage gradient θ13 (P98 to P99). When the intermediate voltage VM reaches the second intermediate voltage VML that is substantially intermediate between the minimum voltage VL and the second intermediate voltage VML. Is maintained for a predetermined time (P99 to P100). At this time, the pressure chamber 31 expands slightly from the reference volume as the piezoelectric vibrator 25 expands and deforms, and ink is filled into the pressure chamber 31 to some extent. Since the second intermediate voltage VML is held for a sufficiently long time Tc, a steady state is obtained in which the vibration of the meniscus is sufficiently converged when the pressure chamber 31 is expanded.
[0177]
Next, the voltage is further lowered from the second intermediate voltage VML at a predetermined voltage gradient θ14 (P100 to P101), and when the minimum voltage VL is reached, the minimum voltage VL is maintained for a predetermined time (P101 to P102). At this time, the pressure chamber 31 slightly expanded further expands, and ink is filled in the pressure chamber 31. Next, the voltage is rapidly increased from the minimum voltage VL to the maximum voltage VH along the voltage gradient θ15 set to a steep slope (P102 to P103), and held at the maximum voltage VH for a predetermined time (P103 to P104). The pressure chamber 31 is expanded from the maximum voltage VH so as to stop the meniscus wave in a short time and returned to the reference volume (P104 to P105). At this time, due to the rapid deformation of the piezoelectric vibrator 25, the volume of the pressure chamber 31 is rapidly contracted, and ink droplets are ejected from the nozzle openings 13.
[0178]
With this large dot drive pulse, the voltage is once lowered from the intermediate voltage VM to the second intermediate voltage VML and held for a predetermined time until the meniscus vibration converges (P98 to P100), and the pressure chamber 31 is further expanded from this state. Since the ink is filled (P100 to P102), the pressure fluctuation in the pressure chamber 31 when the ink is filled can be reduced, and the meniscus can be prevented from retreating to the pressure chamber 31 side.
[0179]
Therefore, when ejecting a large ink droplet having a large ink volume, the pressure change width in the pressure chamber 31 can be made smaller than before, and the flying speed of the ink droplet becomes excessively high. Can be prevented. As a result, it is possible to prevent the deviation of the landing center position due to the difference in ink volume.
[0180]
The flying speed of the ink droplets can be adjusted by setting the degree of expansion of the pressure chamber 31 and the holding time of the expanded state. For this reason, it is possible to adjust the flight speed suitable for the volume of ink droplets to be ejected. Therefore, also in this respect, the difference in the flying speed of the ink droplets accompanying the difference in the ink volume can be reduced. As a result, it is possible to more reliably prevent the deviation of the landing center position.
[0181]
In addition, a difficult operation of combining a plurality of minute ink droplets is not required, and a large dot can be formed on the recording paper with one ink droplet, and the variable range of the dot diameter is also increased.
[0182]
Next, a description will be given of a sixth embodiment in which one drive pulse is divided into a plurality of waveform elements, and a series of drive signals are configured by mixing other drive pulses between the divided waveform elements.
[0183]
The drive signal shown in FIG. 11 is also a signal for ejecting large ink droplets and medium ink droplets having different ink volumes from the same nozzle opening 13. Since the configuration other than the drive signal is the same as that of the first embodiment described above, the description thereof is omitted.
[0184]
This drive signal includes two drive pulses, a large dot drive pulse for ejecting large ink droplets and a medium dot drive pulse for ejecting medium ink droplets. Here, in the present embodiment, the large dot drive pulse corresponds to the first drive pulse of the present invention, and the medium dot drive pulse corresponds to the second drive pulse of the present invention.
[0185]
And the waveform element which comprises a large dot drive pulse is divided | segmented into two, and is arrange | positioned in the period T1 and the period T3. In addition, the waveform elements constituting the medium dot drive pulse are arranged in the period T2. That is, the first waveform element (P111 to P113) in the period T1 and the third waveform element (P128 to P135) in the period T3 constitute a large dot drive pulse, and medium dots are generated in the period T2 between the period T1 and the period T3. Second waveform elements (P116 to P125) constituting the driving pulse are arranged.
[0186]
Also, in the period TS1 between the period T1 and the period T2, the first connection elements (P113 to P116) shown in FIG. 11B are arranged, and the end of the first waveform element (P113) and the second waveform element Are connected at different voltage levels. Similarly, in the period TS2 between the period T2 and the period T3, the second connection elements (P125 to P128) shown in FIG. 11C are arranged, and the end of the second waveform element (P125) and the third waveform. Different voltage levels are connected at the beginning (P128) of the element.
[0187]
The drive pulse generation means (that is, the selection signal generation unit 22, the level shifter 23, and the switch circuit 24) is arranged in the period T1 and the period T3 from the drive signal based on the print data set to “10001”. A large dot drive pulse is generated by selecting and connecting waveform elements. Further, the drive pulse generation means generates a medium dot drive pulse by selecting the second waveform element arranged in the period T2 based on the print data set to “00100”.
[0188]
The large dot drive pulse is expanded from the intermediate voltage VM with expansion waveform elements (P111 to P113, P128 to P129) that slightly expand the pressure chamber 31 and fill the pressure chamber 31 with ink to some extent and hold it for a predetermined time. A filling waveform element (P129 to P131, corresponding to the first filling waveform element of the present invention) for expanding the pressure chamber 31 a little further to fill with ink, and an ejection waveform element (for ejecting ink droplets from the nozzle opening 13) ( P131 to P133 (corresponding to the first discharge waveform element of the present invention) and vibration suppression waveform elements (P133 to P134) for stopping meniscus undulation immediately after discharge.
[0189]
On the other hand, the medium dot drive pulse is filled with the contraction waveform element (P117 to P119) that temporarily contracts the pressure chamber 31 from the intermediate voltage VM and holds it for a predetermined time, and expands the contracted pressure chamber 31 to fill the ink. Waveform elements (P119 to P121, corresponding to the second filling waveform element of the present invention), and discharge waveform elements (P121 to P123, the present invention) for causing the expanded pressure chamber 31 to contract and ejecting ink from the nozzle openings 13 And a damping element (P123 to P124) for stopping meniscus undulation immediately after ejection.
[0190]
By inputting the medium dot drive pulse generated in this way to the piezoelectric vibrator 25, ink droplets are ejected as follows. First, the voltage is increased at a predetermined voltage gradient θ16 set so as not to eject ink droplets from the intermediate voltage VM (P117 to P118), and when the maximum voltage VH is reached, the maximum voltage VH is maintained for a predetermined time (P118 to P118). P119). At this time, the pressure chamber 31 is temporarily contracted from the reference volume, and a margin for expansion when the pressure chamber 31 is expanded next is secured. Further, the pressure chamber 31 can be expanded at a timing when the meniscus is once pushed outward from the nozzle opening 13 and the pushed-out meniscus returns in response to the maintenance time of the maximum voltage VH. As a result, the meniscus can be drawn into the pressure chamber 31, and the contraction of the pressure chamber 31 can be started from the drawn-in state.
[0191]
Next, the voltage is lowered from the maximum voltage VH with a predetermined voltage gradient θ17 (P119 to P120), and when the minimum voltage VL is reached, the minimum voltage VL is maintained for a predetermined time (P120 to P121), and the ink is put into the pressure chamber 31. Fill. Next, the voltage is rapidly increased from the lowest voltage VL to the voltage VMH set to a substantially intermediate level between the reference voltage VM and the maximum voltage VH along the voltage gradient θ18 set to a steep slope (P121 to P122). At this time, the volume of the pressure chamber 31 rapidly shrinks and ink droplets are ejected from the nozzle opening 13. Here, as described above, the contraction of the pressure chamber 31 is started from the state in which the meniscus is drawn into the pressure chamber 31, and the ink is ejected by increasing the voltage to a voltage VMH slightly lower than the maximum voltage VH. Ink droplets having an ink volume suitable for forming medium dots can be ejected.
[0192]
Then, after maintaining the voltage VMH for a predetermined time (P122 to P123), the pressure chamber 31 is expanded from the voltage VMH so that the meniscus wave is stopped in a short time, and returned to the reference volume (P123 to P124). ).
[0193]
The operation of ejecting large ink droplets having a large ink volume by supplying large dot drive pulses to the piezoelectric vibrator 25 is the same as in the fifth embodiment. Therefore, the description is omitted.
[0194]
In this embodiment, the waveform element constituting the large dot drive pulse is divided into two waveform elements at the portion of the expansion waveform element. That is, the expansion waveform element is divided into a previous expansion waveform element (P111 to P113) and a subsequent expansion waveform element (P128 to P129). A series of drive signals is configured by arranging waveform elements constituting the medium dot drive pulse between the divided waveform elements (corresponding to the expanded partial elements in the present invention). For this reason, the holding time (time from P112 to P129) in the expansion waveform element can be made sufficiently long. Further, since the drive signal itself can be configured to be short, a plurality of drive waveforms can be easily accommodated within a limited printing cycle.
[0195]
Further, since the ejection waveform elements (P121 to P122) of the medium dot drive pulse and the ejection waveform elements (P131 to P133) of the large dot drive pulse can be arranged close in time, the deviation of the landing position of the ink droplet is small. High print quality can be secured.
[0196]
Next, a plurality of drive pulses are each divided into a plurality of waveform elements, and a series of drive signals are configured by mixing the waveform elements of other drive pulses between the waveform elements of one drive pulse. A form is demonstrated.
[0197]
The drive signal shown in FIG. 12A is a signal for ejecting large ink droplets and small ink droplets from the same nozzle opening 13. Since the configuration other than the drive signal is the same as that of the first embodiment described above, the description thereof is omitted.
[0198]
In this drive signal, the waveform elements constituting the small dot drive pulse (corresponding to the second drive pulse of the present invention) are divided into two and arranged in the periods T1 and T3. Further, the waveform elements constituting the large dot drive pulse (corresponding to the first drive pulse of the present invention) are also divided into two and arranged in the period T2 and the period T4. That is, the first waveform elements (P141 to P143) in the period T1 and the third waveform elements (P152 to P159) in the period T3 constitute a small dot drive pulse. Further, the second waveform elements (P146 to P149) in the period T2 and the fourth waveform elements (P162 to P169) in the period T4 arranged between the periods T1 and T3 constitute a large dot drive pulse.
[0199]
Further, in the period TS1 between the period T1 and the period T2, the first connection elements (P143 to P146) shown in FIG. 12B are arranged. The first connection element connects different voltage levels at the end of the first waveform element (P143) and the start of the second waveform element (P146). Similarly, in the period TS2 between the period T2 and the period T3, the second connection elements (P149 to P152) shown in FIG. 12C are arranged, and in the period TS3 between the period T3 and the period T4, FIG. The 3rd connection element (P159-P162) shown to 12 (d) is arranged.
[0200]
The drive pulse generation means (that is, the selection signal generator 22, the level shifter 23, and the switch circuit 24) has waveforms arranged in the periods T1 and T3 from the drive signal based on the print data set to “1000100”. Select and connect elements. Thereby, a small dot drive pulse is generated. Further, the drive pulse generating means selects and connects the waveform elements arranged in the periods T2 and T4 based on the print data set to “0010001”. Thereby, a large dot drive pulse is generated.
[0201]
When the small dot drive pulse generated in this way is supplied to the piezoelectric vibrator 25, ink droplets are ejected as follows.
[0202]
First, the voltage is increased at a predetermined voltage gradient θ19 set so as not to eject ink droplets from the intermediate voltage VM (P141 to P142), and when the maximum voltage VH is reached, the maximum voltage VH is maintained for a predetermined time (P142 to P142). P143, P152 to P153). At this time, the pressure chamber 31 once contracts from the reference volume, and an expansion allowance is secured when the pressure chamber 31 is then expanded.
[0203]
Further, the meniscus is once pushed out from the opening edge of the nozzle opening 13 by the maintenance time of the maximum voltage VH, and the pressure chamber 31 can be expanded at the timing when the pushed meniscus returns by reaction. As a result, the meniscus can be drawn into the pressure chamber 31, and the contraction of the pressure chamber 31 can be started from the drawn-in state.
[0204]
Next, the voltage is lowered from the maximum voltage VH with a predetermined voltage gradient θ20 (P153 to P154). When the minimum voltage VL is reached, the minimum voltage VL is maintained for a predetermined time (P154 to P155), and ink is filled into the pressure chamber 31. Next, the voltage is rapidly increased from the minimum voltage VL to the maximum voltage VH along the voltage gradient θ21 set to a steep slope (P155 to P156). At this time, the volume of the pressure chamber 31 rapidly shrinks, the ink pressure in the pressure chamber 31 increases, and ink droplets are ejected from the nozzle openings 13.
[0205]
In this case, since the ink droplet is ejected by increasing the voltage from the state where the meniscus is deeply drawn to the maximum voltage VH, it is possible to eject a small ink droplet having a small ink volume suitable for forming a small dot.
[0206]
Then, the state in which the maximum voltage VH is supplied is maintained for a predetermined time (P156 to P157), and the pressure chamber 31 is expanded from the maximum voltage VH to return to the reference volume so that the meniscus undulation is stopped in a short time (P157 to P157). P158).
[0207]
The operation for ejecting large ink droplets having a large ink volume by supplying large dot drive pulses to the piezoelectric vibrator 25 is the same as in the fifth embodiment. Therefore, the description is omitted.
[0208]
In this embodiment, a series of drive signals are configured by mixing waveform elements constituting a large dot ejection waveform and waveform elements constituting a small dot ejection waveform. For this reason, the drive signal itself can be shortened, and a plurality of drive waveforms can be easily accommodated within a limited printing cycle. Other than that is the same as that of the said 6th Embodiment, and there exists the same effect.
[0209]
Next, a small dot drive pulse, a medium dot drive pulse, and a large dot drive pulse can be generated, and the degree of contraction of the pressure chamber 31 in the small dot drive pulse and the pressure chamber 31 in the medium dot drive pulse. An eighth embodiment with different degrees of contraction will be described.
[0210]
As shown in FIG. 13, in this drive signal, the waveform element constituting the large dot drive pulse (corresponding to the first drive pulse of the present invention) is divided into two waveform elements, and the period T1 (P180 to P182) and It is arranged in the period T6 (P213 to P220). Further, the waveform elements constituting the medium dot drive pulse (corresponding to the second drive pulse of the present invention) are divided into two and arranged in the period T2 (P185 to P188) and the period T4 (P193 to P200). Yes. Further, the waveform elements constituting the small dot drive pulse (corresponding to the second drive pulse of the present invention) are divided into three, and the periods T2 (P185 to P188), T3 (P188 to P190), and the period T5 (P203 to P203) are divided. P210).
[0211]
Further, in the period TS1 between the period T1 and the period T2, the first connection elements (P182 to P185) shown in FIG. 14A are arranged, and the end of the first waveform element (P182) and the second waveform element Are connected to different voltage levels at the beginning (P185). Similarly, in the period TS2 between the period T3 and the period T4, the second connection elements (P190 to P193) shown in FIG. 14B are arranged, and in the period TS3 between the period T4 and the period T5, The third connection elements (P200 to P203) shown in FIG. 14 (c) are arranged, and the fourth connection elements (P210 to P213) shown in FIG. 14 (d) are arranged in the period TS4 between the periods T3 and T4. Has been.
[0212]
Then, the drive pulse generation means (that is, the selection signal generation unit 22, the level shifter 23, and the switch circuit 24) generates the second waveform element in the period T2 and the second waveform element in the period T3 based on the print data set to “00111000100”. The three waveform elements and the fifth waveform element in the period T5 are selected from the drive signals and connected. Thereby, a small dot drive pulse is generated. Further, the drive pulse generation means selects and connects the second waveform element of the period T2 and the fourth waveform element of the period T4 based on the print data set to “0010010000” from the drive signal. Thereby, a medium dot drive pulse is generated. Similarly, the drive pulse generation means selects and connects the first waveform element in the period T1 and the sixth waveform element in the period T6 based on the print data set to “1000000001”. Thereby, a large dot drive pulse is generated.
[0213]
The large dot drive pulse is basically the same as the first waveform in the fifth embodiment, and an expansion waveform in which the pressure chamber 31 is expanded from the intermediate voltage VM, ink is filled in the pressure chamber 31 to some extent, and is held for a predetermined time. An element (P180 to P182, P213 to P214), a filling waveform element (P214 to P216) for expanding the pressure chamber 31 expanded by the expansion waveform element a little more and filling with ink, and an ink droplet from the nozzle opening 13 Are composed of discharge waveform elements (P216 to P218) for discharging water and vibration suppression waveform elements (P218 to P219) for stopping meniscus undulation immediately after discharge.
[0214]
The small dot drive pulse is a first contraction waveform element that raises the voltage from the intermediate voltage VM to the third intermediate voltage VMH set to a substantially intermediate level between the intermediate voltage VM and the maximum voltage VH to slightly contract the pressure chamber 31. (P185 to P188), the second contraction waveform element (P188 to P190, P203 to P204) that further contracts and holds the pressure chamber 31 contracted by the first contraction waveform element for a predetermined time, and the contracted pressure chamber A filling waveform element (P204 to P206) for inflating 31 and filling ink, an ejection waveform element (P206 to P208) for causing ink droplets to be ejected from the nozzle opening 13 by contracting the expanded pressure chamber 31, and immediately after ejection And a damping waveform element (P208 to P209) for stopping the meniscus undulation.
[0215]
Further, the medium dot drive pulse raises the voltage from the reference voltage VM to the third intermediate voltage VMH to slightly contract the pressure chamber 31 and hold the first contraction waveform elements (P185 to P188, P193 to hold in this contracted state). P194), a filling waveform element (P194 to P196) for expanding the contracted pressure chamber 31 and filling the pressure chamber 31 with ink, and contracting the expanded pressure chamber 31 to drop ink droplets from the nozzle openings 13. A discharge waveform element (P196 to P198) to be discharged and a vibration suppression waveform element (P198 to P199) to stop meniscus undulation immediately after discharge are configured.
[0216]
Here, in the first contraction waveform element of the medium dot driving pulse and the first contraction waveform element of the small dot driving pulse, the second waveform elements (P185 to P188) arranged in the period T2 are used in common. .
[0217]
In this drive signal, the contraction waveform element that contracts the pressure chamber 31 is composed of a two-stage gradual contraction waveform element including a first contraction waveform element in the period T2 and a second contraction waveform element in the period T3. ing.
[0218]
By supplying the small dot drive pulse to the piezoelectric vibrator 25, it is possible to eject a small ink droplet having a small ink volume, as in the seventh embodiment. However, in this embodiment, when the pressure chamber 31 is contracted, the two contraction waveform elements of the first contraction waveform element (P185 to P188) and the second contraction waveform element (P188 to P190) are supplied to the piezoelectric vibrator 25. To do.
[0219]
Further, when the medium dot drive pulse is supplied to the piezoelectric vibrator 25, ink droplets are ejected as follows. First, the voltage is increased from the intermediate voltage VM at a predetermined voltage gradient θ22 set to such an extent that no ink droplets are ejected (P186 to P187), and the third intermediate voltage VMH at a substantially intermediate level between the intermediate voltage VM and the maximum voltage VH. The third intermediate voltage VMH is maintained for a predetermined time (P187 to P188, P193 to P194). At this time, the pressure chamber 31 temporarily contracts slightly from the reference volume, and an expansion allowance is secured when the pressure chamber 31 is then expanded. Next, the voltage is lowered from the third intermediate voltage VMH at a predetermined voltage gradient θ23 (P194 to P195), and when the minimum voltage VL is reached, the minimum voltage VL is maintained for a predetermined time (P195 to P196). Fill inside. Next, the voltage is rapidly increased from the minimum voltage VL to the maximum voltage VH along the voltage gradient θ24 set to a steep slope (P196 to P197). At this time, the volume of the pressure chamber 31 contracts and ink droplets are ejected from the nozzle opening 13. Then, the pressure chamber 31 is maintained for a predetermined time in a state where the maximum voltage VH is supplied (P197 to P198), and the pressure chamber 31 is expanded from the maximum voltage VH so that the meniscus undulation is stopped in a short time and returned to the reference volume (P198 to P199). ).
[0220]
Then, by supplying a large dot drive pulse to the piezoelectric vibrator 25, a large ink droplet having a relatively large ink volume can be ejected as in the fifth embodiment.
[0221]
In the present embodiment, the element that contracts the pressure chamber 31 is composed of a two-stage contraction element of a first contraction waveform element (P186 to P188) and a second contraction waveform element (P188 to P190). For this reason, by selectively connecting the first contraction waveform contraction element and the second contraction waveform element, it is possible to change the voltage in a plurality of stages without providing a plurality of contraction waveform elements. In addition, the drive signal itself can be shortened.
[0222]
In addition, the waveform element of the large dot drive pulse is divided into two waveform elements, the first waveform element and the sixth waveform element, in the waveform width direction, the first waveform element is arranged in the first period T1, and the sixth waveform The element is arranged in the last period T6. Further, the expansion waveform element is also divided into two expansion waveform partial elements, and the previous expansion partial element is arranged in the first waveform element which is the head portion of the drive signal. Further, the subsequent expansion waveform element is arranged in the sixth waveform element.
[0223]
In this way, by allowing other waveform elements to exist during the retention time of the expansion waveform element, the retention time of the expansion element can be made sufficiently long. And the whole drive signal can be shortened.
[0224]
Further, the previous inflating subelement includes an inflating element (P180-P181). That is, the expansion element that constitutes a part of the expansion waveform element is disposed at the head of the drive signal. Further, the ejection waveform elements (P216 to P218) of the large dot drive pulse are arranged at the end of the drive signal. As a result, other waveform elements can be arranged during the retention time of the expansion waveform element, the retention time of the expansion waveform element can be sufficiently long, and the entire time of the drive signal can be shortened.
[0225]
In the present embodiment, the element for contracting the pressure chamber 31 is composed of a two-stage contraction waveform element (stepwise contraction waveform element) of a first contraction waveform element and a second contraction waveform element. Based on the same concept, the element that expands the pressure chamber 31 can be constituted by a plurality of stages of expansion waveform elements (stepwise expansion waveform elements), such as the first expansion waveform element and the second expansion waveform element. .
[0226]
In this embodiment, the waveform elements constituting the medium dot drive pulse are the contraction waveform elements (P185 to P188, P193 to P194), the previous contraction waveform elements (P185 to P188), and the subsequent expansion waveform. It is divided into elements (P193 to P194). A series of drive signals is configured by arranging waveform elements constituting a small dot drive pulse between the divided waveform elements. For this reason, more waveform elements can be easily accommodated within a limited printing cycle.
[0227]
Further, in the present embodiment, each drive pulse generated by the drive pulse generation unit is set so that the ejection waveform elements (P196 to P198) of the medium dot drive pulse precede the ejection waveform elements (P206 to P208) of the small dot drive pulse. ) And the ejection waveform elements (P216 to P218) of the large dot drive pulse are arranged after the ejection waveform elements of the small dot drive pulse.
[0228]
When bidirectional printing is performed with this configuration, the ejection order within the printing cycle T during forward movement is the order of medium ink droplets, small ink droplets, and large ink droplets. Further, the ejection order within the printing cycle T during the backward movement is the order of medium ink droplets, small ink droplets and large ink droplets. That is, at the time of forward movement and at the time of backward movement, the landing positions of the ink droplets are simply exchanged between the large ink droplet and the medium ink droplet. For this reason, the recorded image can be improved in image quality.
[0229]
Next, a ninth embodiment capable of generating a large dot driving pulse, a medium dot driving pulse, a small dot driving pulse, and a fine vibration pulse in printing from a driving signal will be described.
[0230]
As shown in FIG. 15, in this drive signal, the waveform elements constituting the fine vibration pulse in printing are divided into three, and the period T1 (P221 to P225), the period T4 (P240 to P243), and the period T5 are divided. (P243 to P246). Further, the waveform elements constituting the small dot drive pulse (corresponding to the second drive pulse of the present invention) are divided into two and arranged in the periods T2 (P225 to P228) and the period T6 (P247 to P258). Has been. In addition, the waveform elements constituting the medium dot drive pulse (corresponding to the second drive pulse of the present invention) are arranged in the period T3 (P230 to P240) without being divided. Furthermore, the waveform elements constituting the large dot drive pulse (corresponding to the first drive pulse of the present invention) are divided into two, and are divided into periods T4 (P240 to P243) and periods T7 (P260 to P266). Has been placed. The waveform element in the period T4 is commonly used for the large dot drive pulse and the fine vibration pulse in printing.
[0231]
Further, in the period TS1 between the period T2 and the period T3, the first connection elements (P228 to P229) are arranged. Similarly, the second connection elements (P246 to P247) shown are arranged in the period TS2 between the periods T5 and T6, and the third connection elements (P258 to P258) are arranged in the period TS3 between the periods T3 and T4. P259) is arranged.
[0232]
Then, the drive pulse generation means (that is, the selection signal generation unit 22, the level shifter 23, and the switch circuit 24) generates the fourth waveform element in the period T4 and the period T7 based on the print data set to “00000100001”. The seventh waveform element is selected from the drive signals and connected to generate a large dot drive pulse. Further, the drive pulse generating means selects the third waveform element of the period T3 from the drive signal based on the print data set to “0000001”, and generates a medium dot drive pulse. The drive pulse generation means selects and connects the second waveform element of the period T2 and the sixth waveform element of the period T6 based on the print data set to “0100000100” from the drive signal, and performs medium dot drive Generate a pulse. The drive pulse generating means selects from the drive signal the first waveform element in the period T1, the fourth waveform element in the period T4, and the fifth waveform element in the period T5 based on the print data set to “1000110000”. Are connected to generate an in-print micro-vibration pulse.
[0233]
As shown in FIG. 16, the large dot drive pulse is basically the same as the large dot drive pulse in the fifth embodiment, and the pressure chamber 31 of the reference volume is slightly expanded to fill the pressure chamber 31 with ink to some extent. An expansion waveform element (P241 to P243, P259 to P260) that is held for a predetermined time, and a filling waveform element (P260 to P262) that expands the pressure chamber 31 expanded by the expansion waveform element a little more and fills it with ink. The discharge waveform elements (P260 to P264) discharge the ink droplets from the nozzle openings 13 by rapidly increasing the voltage from the minimum voltage VL to the second maximum voltage VH ′ set to a voltage level slightly lower than the maximum potential VH. And vibration suppression waveform elements (P264 to P265) for stopping meniscus undulation immediately after discharge.
[0234]
The medium dot drive pulse expands the pressure chamber 31 by lowering the voltage from the intermediate voltage VM along the voltage gradient θ31 to the second lowest voltage VL ′ set at a voltage level slightly higher than the lowest potential VL. The filling waveform elements (P230 to P232) for maintaining the expanded state, the discharge waveform elements (P232 to P234) for contracting the expanded pressure chamber 31, and the portions that become ink droplets by supplying the discharge waveform elements are removed from the meniscus. A pull-in waveform element (P234 to P236) that rapidly expands the pressure chamber 31 immediately before separation to draw the meniscus toward the pressure chamber 31 side, and a vibration suppression waveform element (P236 to P239) that stops the meniscus wave just after discharge. Consists of
[0235]
Further, the small dot drive pulse causes the pressure chamber 31 to slightly contract by raising the voltage from the intermediate voltage VM to the maximum voltage VH, and contraction waveform elements (P226 to P228, P247 to P248) that maintain this contraction state, A filling waveform element (P248 to P250) for expanding the pressure chamber 31 in which the contracted state is held by the contraction waveform element to fill with ink, a discharge waveform element (P250 to P252) for contracting the expanded pressure chamber 31, and Immediately before the portion that becomes ink droplets is separated from the meniscus by supplying the discharge waveform element, the pressure chamber 31 is rapidly expanded to draw the meniscus toward the pressure chamber 31 (P252 to P254), and the meniscus immediately after discharge It is comprised from the damping waveform element (P254-P257) which stops a wave.
[0236]
Further, the fine vibration pulse in printing is composed of first fine vibration waveform elements (P221 to P224) and second fine vibration waveform elements (P241 to P245).
[0237]
It is the same as in the fifth embodiment that a large ink droplet having a large ink volume can be ejected by supplying the large dot drive pulse to the piezoelectric vibrator 25.
[0238]
Further, when the medium dot drive pulse is supplied to the piezoelectric vibrator 25, ink droplets are ejected as follows. First, the voltage is lowered to the second lowest voltage VL ′ with a predetermined voltage gradient θ31 set so as not to eject ink droplets from the intermediate voltage VM (P230 to P231), and when the second lowest voltage VL ′ is reached, the second voltage VL ′ is reached. 2 The minimum voltage VL ′ is maintained for a predetermined time (P231 to P232). As a result, the pressure chamber 31 is filled with ink. Next, the voltage is rapidly increased from the minimum voltage VL to the second maximum voltage VH ′ along the voltage gradient θ32 set to a steep slope (P232 to P234). At this time, the pressure chamber 31 rapidly contracts and the ink pressure in the pressure chamber 31 increases. As the ink pressure increases, the center of the meniscus rises in the ejection direction. Then, at the timing immediately before the ink droplet portion is separated from the meniscus, the voltage is lowered to the pull-in voltage VA along the steeply set θ31 (P234 to P235). As a result, the pressure chamber 31 rapidly expands, the inside of the pressure chamber 31 becomes negative pressure, and the peripheral portion of the meniscus is drawn inside the pressure chamber 31. Therefore, the central part of the meniscus is separated from the meniscus, and this central part flies as an ink droplet. If the ink droplets are ejected, the voltage is raised and then lowered again, the pressure chamber 31 is contracted and expanded, and the meniscus vibration is converged early (P236 to P239).
[0239]
Further, when a small dot drive pulse is supplied to the piezoelectric vibrator 25, the voltage is increased from the intermediate voltage to the maximum voltage VH and held, whereby the pressure chamber 31 expands and an expansion margin is secured ( P226-P228, P247-P248). Thereafter, the same operation as the medium dot drive pulse described above is performed (P248 to P257). With this small dot driving pulse, the ink droplet is ejected in a state where the meniscus is largely drawn inside the pressure chamber 31, so that a smaller volume of the ink droplet can be ejected.
[0240]
When the fine vibration pulse is supplied to the piezoelectric vibrator 25, the pressure chamber 31 is slightly expanded from the reference volume corresponding to the intermediate voltage VM by the first fine vibration waveform and the second fine vibration waveform. Thereafter, the pressure chamber 31 returns to the reference volume after maintaining this expanded state for a predetermined time. As a result, the meniscus is slightly pulled inside the pressure chamber 31 and then returns to the normal state. Accordingly, the ink in the vicinity of the nozzle opening 13 is agitated.
[0241]
Next, a tenth embodiment will be described. In the tenth embodiment, a small dot ejection waveform element as another dot ejection waveform element is disposed between two large dot ejection waveform elements. Further, the waveform shapes of the two large dot drive pulses for ejecting large ink droplets are made the same.
[0242]
In the drive signal shown in FIG. 17, the portion of the period T1 (P270 to P273) is the first waveform element, and the portion of the period T2 (P274 to P281) is the second waveform element. The portion of period T3 (P282 to P289) is the third waveform element, and the portion of period T4 (P289 to P295) is the fourth waveform element. Further, the portion (P273 to P274) of the period TS1 is a first connection element, and the portions (P281 to P282) of the period TS2 are second connection elements.
[0243]
The first waveform element includes contraction waveform elements (P271 to P272). The second waveform element includes a first filling waveform element (P275 to P277), a first large dot ejection waveform element (P277 to P279), and a first damping waveform element (P279 to P280). The third waveform element includes a second filling waveform element (P283 to P285), a small dot ejection waveform element (P285 to P287), and a second vibration suppression waveform element (P287 to P288). The fourth waveform element includes a third filling waveform element (P290 to P292), a second large dot ejection waveform element (P292 to P294), and a third vibration suppression waveform element (P294 to P295).
[0244]
Further, the second waveform element and the fourth waveform element of the present embodiment are waveforms having the same shape. The time from the start point (P270) of the first waveform element to the end point (P280) of the first vibration suppression waveform element and the end point (P280) of the first vibration suppression waveform element to the end point (P295) ) Is set to be the same time. The end point (P295) of the third vibration suppression waveform element is the start point (P270) of the first waveform element in the next printing cycle T.
[0245]
In order to generate a small dot drive pulse from such a drive signal, the drive pulse generation means (that is, the selection signal generator 22, the level shifter 23, and the switch circuit 24) uses the first waveform element and the third waveform element. Select and concatenate the selected waveform elements. Specifically, the waveform element is selected based on the print data set to “100010”. Further, when generating a large dot drive pulse, the drive pulse generating means selects the second waveform element based on the print data set to “001000” or prints set to “000001”. A fourth waveform element is selected based on the data. That is, in the present embodiment, the second waveform element and the fourth waveform element independently constitute a large dot drive pulse.
[0246]
Further, in the case of ejecting large ink droplets continuously, the drive pulse generating means selects the second waveform element and the fourth waveform element based on the print data set to “001001” and selects two large dots. A drive pulse is generated. As for the two large dot drive pulses, the waveform shapes of the previous large dot drive pulses (P275 to P280) and the subsequent large dot drive pulses (P290 to P295) are the same as described above. Further, the time from the start point (P270) of the drive cycle T to the start point (P275) of the previous large dot drive pulse, and the start point (P290) of the subsequent large dot drive pulse from the end point (P280) of the previous large dot drive pulse. Until the same time. That is, the time from the end point of the large dot drive pulse to the start point of the next large dot drive pulse is set to a fixed time.
[0247]
Thereby, when ejecting large ink droplets continuously, large ink droplets can be ejected at regular intervals, that is, at a constant frequency. As a result, it is possible to eliminate variations in landing positions of the large ink droplets caused by the previous large dot drive pulse and the large ink droplets caused by the subsequent large dot drive pulse, thereby improving the print quality. Further, the recording head 8 can be driven at the highest possible frequency.
[0248]
In this embodiment, the drive signal is generated at a printing cycle T of 10.8 kHz, for example. For this reason, when large ink droplets are continuously discharged, the large ink droplets can be discharged twice within the period of the printing cycle T, and the drive frequency of the recording head 8 can be substantially increased. . In addition, since the ejection waveform element constituting the small dot drive pulse as the other dot drive pulse is arranged between the two large dot drive pulses for generating the large ink droplets, the print cycle T in a limited period is used. Even if it exists, many drive waveforms can be included.
[0249]
Furthermore, since the waveforms of the two large dot drive pulses are made the same, the volume of the large ink droplet is the same regardless of which large dot drive pulse is ejected. That is, the size of the large dot can be made the same.
[0250]
In this embodiment, two large dot driving pulses are included in the printing cycle T, but more large dot driving pulses may be included in the printing cycle T.
[0251]
Next, an eleventh embodiment will be described. In the eleventh embodiment, large ink droplets, medium ink droplets, and small ink droplets are ejected from the same nozzle opening 13. In this embodiment, the two large dot ejection waveforms constituting the large dot drive pulse have the same shape, and the large dot ejection waveforms are arranged at regular intervals. Further, a small dot discharge waveform is arranged between the large dot discharge waveforms.
[0252]
In the drive signal shown in FIG. 18, the portion of the period T1 (P300 to P303) is the first waveform element, and the portion of the period T2 (P304 to P311) is the second waveform element. The portion (P312 to P317) of the period T3 is the third waveform element, and the portion (P317 to P323) of the period T4 is the fourth waveform element. Further, the portion (P303 to P304) of the period TS1 is a first connection element, and the portions (P311 to P312) of the period TS2 are second connection elements.
[0253]
The first waveform element includes contraction waveform elements (P301 to P302). The second waveform element includes a first filling waveform element (P305 to P307), a first discharge waveform element (P307 to P309), and a first damping waveform element (P309 to P310). The third waveform element includes a second filling waveform element (P313 to P314), a second discharge waveform element (P314 to P315), and a second vibration suppression waveform element (P315 to P316). The fourth waveform element includes a third filling waveform element (P318 to P320), a third discharge waveform element (P320 to P322), and a third vibration suppression waveform element (P322 to P323). The end point (P323) of the third vibration suppression waveform element is the start point (P300) of the first waveform element in the next printing cycle T.
[0254]
In order to generate a small dot drive pulse from such a drive signal, the drive pulse generation means (that is, the selection signal generator 22, the level shifter 23, and the switch circuit 24) uses the first waveform element and the third waveform element. Select and concatenate the selected waveform elements. Specifically, the waveform element is selected based on the print data set to “100010”. In this small dot drive pulse, the second ejection waveform elements (P314 to P315) of the third waveform element are other dot ejection waveform elements.
[0255]
When generating a medium dot drive pulse, the drive pulse generator selects the fourth waveform element based on the print data set to “000001”. That is, the fourth waveform element alone constitutes a medium dot drive pulse.
[0256]
Further, when generating a large dot drive pulse, the drive pulse generating means selects and connects the second waveform element and the fourth waveform element based on the print data set to “001001”. In this large dot drive pulse, the first discharge waveform elements (P307 to P309) of the second waveform element and the third discharge waveform elements (P320 to P322) of the fourth waveform element are large dot discharge waveform elements.
[0257]
Regarding the two large dot ejection waveforms constituting the large dot drive pulse, the waveform shapes of the previous large dot ejection waveforms (P305 to P310) and the subsequent large dot ejection waveforms (P318 to P323) are the same. Further, the time from the start point (P300) of the driving cycle T to the start point (P305) of the previous large dot discharge waveform, and the start point (P318) of the subsequent large dot discharge waveform from the end point (P310). Until the same time. That is, the time from the end point of the large dot discharge waveform to the start point of the next large dot discharge waveform is set to a fixed time. Further, small dot discharge waveforms (P313 to P316) constituting a small dot drive pulse are arranged between the large dot discharge waveforms.
[0258]
In this drive signal, since the large dot ejection waveform is arranged before and after the small dot ejection waveform, both printing is performed both when the recording head 8 (that is, the carriage) moves forward and backward. In the directional printing, the landing positions of the small ink droplets and the large ink droplets can be aligned by aligning the large ink droplets with reference to the landing positions of the small ink droplets ejected by the small dot drive pulse.
[0259]
In addition, the previous large dot ejection waveform and the subsequent large dot ejection waveform have the same waveform shape, and the volume of the ink droplet ejected by the previous large dot ejection waveform and the ink droplet ejected by the subsequent large dot ejection waveform The volume can be aligned.
[0260]
Further, since the large dot ejection waveform is generated at regular intervals within the printing cycle T, in the case of bidirectional printing, the same recording state can be realized during forward movement and backward movement.
[0261]
As described above, in the present embodiment, a high-quality image can be recorded particularly in the configuration of bidirectional printing.
[0262]
By the way, in each of the above embodiments, the recording head 8 using the flexural vibration mode piezoelectric vibrator 61 as a pressure generating element has been exemplified. However, the present invention uses the longitudinal vibration mode piezoelectric vibrator 61 shown in FIG. The present invention can also be applied to the recording head 62.
[0263]
The recording head 62 includes a base 63 made of synthetic resin and a flow path unit 64 attached to the front surface of the base 63 (corresponding to the left side in the figure). The flow path unit 64 includes a nozzle plate 66 in which a nozzle opening 65 is formed, a vibration plate 67, and a flow path forming plate 68.
[0264]
The base 63 is a block-like member provided with an accommodation space 69 that is open on the front and back surfaces. The accommodation space 69 accommodates the piezoelectric vibrator 61 fixed to the fixed substrate 70.
[0265]
The nozzle plate 66 is a thin plate member having a large number of nozzle openings 65 formed along the sub-scanning direction. Each nozzle opening 65 is opened at a predetermined pitch corresponding to the dot formation density. The diaphragm 67 is a plate-like member that includes an island portion 71 as a thick portion with which the piezoelectric vibrator 61 abuts, and a thin portion 72 that is provided so as to surround the island portion 71 and has elasticity. .
[0266]
A large number of island portions 71 are provided at a predetermined pitch so that one island portion 71 corresponds to one nozzle opening 65.
[0267]
The flow path forming plate 68 is provided with an opening for forming a pressure chamber 73, a common ink chamber 74, and an ink supply path 75 that connects the pressure chamber 73 and the common ink chamber 74.
[0268]
And while arrange | positioning the nozzle plate 66 in the front surface of the flow-path formation board 68, and arrange | positioning the vibration plate 67 in the back side, the flow-path formation board 68 is pinched | interposed by the nozzle plate 66 and the vibration plate 67, The flow path unit 64 is formed by being integrated by bonding or the like.
[0269]
In the flow path unit 64, a pressure chamber 73 is formed on the back side of the nozzle opening 65, and the island portion 71 of the diaphragm 67 is located on the back side of the pressure chamber 73. Further, the pressure chamber 73 and the common ink chamber 74 communicate with each other through the ink supply path 75.
[0270]
The tip of the piezoelectric vibrator 61 is brought into contact with the island portion 71 from the back side, and the piezoelectric vibrator 61 is fixed to the base 63 in this contact state. The piezoelectric vibrator 61 is supplied with a drive signal (COM), print data (SI), and the like via a flexible cable.
[0271]
The piezoelectric vibrator 61 in the longitudinal vibration mode has a characteristic of contracting in a direction orthogonal to the electric field when charged and extending in a direction orthogonal to the electric field when discharged. Therefore, in the recording head 62, the piezoelectric vibrator 61 contracts backward by being charged, and the island portion 71 is pulled back along with the contraction, and the contracted pressure chamber 73 expands. Along with this expansion, the ink in the common ink chamber 74 flows into the pressure chamber 73 through the ink supply path 75. On the other hand, by discharging, the piezoelectric vibrator 61 extends forward, the island portion 71 of the elastic plate is pushed forward, and the pressure chamber 73 contracts. With this contraction, the ink pressure in the pressure chamber 73 increases.
[0272]
As described above, in the recording head 62, the relationship between the voltage level due to charging / discharging of the piezoelectric vibrator 61 and the expansion / contraction of the pressure chamber 73 is opposite to those in the above embodiments. Therefore, when the recording head 62 is used, the drive signal and drive waveform in which the polarity of the drive signal and drive waveform shown in the previous embodiment are reversed with respect to the intermediate voltage are used. For example, as shown in FIG. 20, the drive signal and drive waveform are used in which the drive signal and drive waveform shown in FIGS. 15 and 16 are reversed in the direction of voltage increase / decrease with the intermediate voltage VM as a boundary. .
[0273]
That is, in the recording head 62, the ink is filled into the pressure chamber 73 by increasing the voltage. Similarly, ink droplets are ejected by lowering the voltage. Even when this recording head 62 is used, the same operational effects as those of the above embodiments can be obtained.
[0274]
In the drive signal of FIG. 20, the minimum voltage VL is set within a voltage range from 0 V that is the ground voltage to about 5 V that is slightly higher than the ground voltage. And the termination | terminus of the first half part (P330-P334) of the contraction waveform element (P332-P334, P339-P334) which drops a voltage from the intermediate voltage VM is set to the minimum voltage VL. Further, the end of the first half of the contraction waveform element and the start of the waveform elements (P335 to P336) constituting the medium dot drive pulse are connected by connection elements (P334 to P335).
[0275]
As described above, when the minimum voltage VL is set within a voltage range of 5 V or less from the ground voltage, the drive signal can be configured by the voltage in the positive direction from the ground voltage with reference to the ground voltage. For this reason, control becomes easy. In addition, since voltage application or voltage maintenance at the voltage level of the maximum voltage VH can be suppressed to a low level, the burden on the piezoelectric vibrator associated with voltage application can be reduced as much as possible.
[0276]
【The invention's effect】
In summary, according to the present invention, the waveform element that operates the pressure generating element and the connection element that does not operate the pressure generating element are included, and different voltage levels between the waveform elements are connected by the connection element. A series of drive signals are generated by the drive signal generation means, the drive pulse generation means selectively connects the waveform elements in the drive signal to generate a drive pulse, and the generated drive pulse is supplied to the pressure generation element. Since the ink droplets are ejected, the connecting element is a signal element that does not operate the pressure generating element, so that the voltage gradient can be set steeply.
[0277]
For this reason, waveform elements having different voltage levels at the connection end can be connected in a short time. Therefore, even in the case of a waveform element in which the voltage gradient and voltage change timing are regulated by the balance with the pressure generating element, the number of elements can be increased more than in the past, and a series of drive signals within one printing cycle can be obtained. Can be included.
[0278]
Therefore, regarding the size of the ink droplet, the variable range can be increased depending on how the waveform element is selected. For this reason, the remarkable effect that ink droplets of various sizes can be ejected while maintaining a high recording speed is exhibited.
[0279]
According to another configuration of the present invention, the pressure chamber is expanded, the expanded state is maintained for a predetermined time, and the pressure chamber in which the expanded state is maintained is further expanded and then contracted to drop the ink droplets. A drive pulse including an expansion waveform element to be ejected is generated by the drive pulse generation means, and the generated drive pulse is supplied to the pressure generating element to eject ink droplets. The pressure in the pressure chamber that has become negative pressure returns to the normal pressure side as the holding time elapses.
[0280]
Since the pressure chamber in a state where the pressure has returned is further expanded by the first filling waveform element to be filled with ink, the pressure fluctuation in the pressure chamber when filling the pressure chamber with ink can be reduced, Meniscus retreat can be suppressed.
[0281]
Therefore, when ejecting ink droplets having a large ink volume, the change width of the pressure in the ink chamber can be made smaller than before, and the flying speed of the ink droplets can be prevented from becoming excessively high. The remarkable effect is demonstrated.
[0282]
Further, the flying speed of the ink droplet can be adjusted by setting the degree of expansion of the pressure chamber and the holding time of the expanded state. For this reason, it is possible to adjust the flight speed suitable for the ink droplets to be ejected. Therefore, the effect that the difference in the flying speed of the ink droplet accompanying the difference in the ink volume can be reduced is also exhibited.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an overall configuration of an ink jet recording apparatus.
FIG. 2 is an explanatory diagram showing a mechanical structure of a recording head.
FIG. 3 is a block diagram illustrating a main part of a recording head driving circuit.
4A and 4B show a first embodiment of the present invention, in which FIG. 4A shows a drive signal, FIG. 4B shows a connection element in the drive signal, and FIG. 4C shows a gradation value and print data; It is a figure which shows a relationship.
FIG. 5 is a diagram showing drive pulses in the first embodiment of the present invention.
FIG. 6 is a diagram showing a drive signal and a drive pulse in the second embodiment of the present invention.
FIG. 7 is a diagram showing drive signals and drive pulses in the third embodiment of the present invention.
FIG. 8 is a diagram showing drive signals and drive pulses in a fourth embodiment of the present invention.
FIG. 9 is a diagram showing drive signals in a fifth embodiment of the present invention.
FIG. 10 is a diagram showing drive signals and drive pulses in a fifth embodiment of the present invention.
11A and 11B show a sixth embodiment of the present invention, in which FIG. 11A is a diagram showing drive signals and drive pulses, and FIGS. 11B and 11C are diagrams showing connection elements, respectively.
12A and 12B show a seventh embodiment of the present invention, in which FIG. 12A is a diagram showing a drive signal and a drive pulse, and FIGS. 12B, C, and D are diagrams showing connection elements, respectively.
FIG. 13 is a diagram showing drive signals and drive pulses in the eighth embodiment of the present invention.
FIGS. 14A, 14B, and 14C are views showing connection elements in an eighth embodiment of the present invention, respectively.
FIG. 15 is a diagram showing drive signals in a ninth embodiment of the present invention.
FIG. 16 is a diagram showing drive pulses in a ninth embodiment of the present invention.
FIG. 17 is a diagram showing drive signals and drive pulses in a tenth embodiment of the present invention.
FIG. 18 is a diagram showing drive signals and drive pulses in an eleventh embodiment of the present invention.
FIG. 19 is a diagram illustrating the mechanical structure of another recording head applicable to the present invention.
20 is a diagram showing drive signals and drive pulses for the recording head described in FIG.
[Explanation of symbols]
1 Printer controller
2 Print engine
3 Interface
4 RAM
5 ROM
6 Control unit
7 Oscillator circuit
8 Recording head
9 Drive signal generation circuit
10 Interface
11 Paper feed mechanism
12 Carriage mechanism
13 Nozzle opening
22 Selection signal generator
23 Level Shifter
24 Switch circuit
25 Piezoelectric vibrator
31 Pressure chamber
32 Actuator unit
33 Ink chamber
34 Channel unit
35 Pressure chamber forming substrate
36 Lid member
37 Diaphragm
38 First ink flow path
39 Second ink flow path
41 Ink chamber forming member
42 Nozzle plate
43 Supply port forming plate
44 Nozzle communication port
45 Ink supply port
46 Communication port
48 Lower electrode
49 Upper electrode
50 connection terminals
51 Flexible circuit board
61 Piezoelectric vibrator
62 Recording head
63 base
64 Channel unit
65 Nozzle opening
66 Nozzle plate
67 Diaphragm
68 Flow path forming plate
69 accommodation space
70 Fixed substrate
71 Island
72 Thin section
73 Pressure chamber
74 Common ink chamber
75 Ink supply path

Claims (11)

An ink jet recording apparatus having a pressure generating element that expands and contracts a pressure chamber when a driving pulse is input to vary ink pressure in the pressure chamber, and ejects ink droplets from a nozzle opening by the pressure variation. ,
Drive signal generating means for generating a drive signal, and drive pulse generating means for generating a drive pulse from the drive signal,
The drive pulse generating means expands the pressure chamber and maintains the expanded state after the change, a first filling waveform element that further expands the pressure chamber whose expansion state is maintained by the expansion waveform element, Generating a first drive pulse including a first ejection waveform element that contracts a pressure chamber expanded by one filling waveform element to eject an ink droplet;
Further, the drive pulse generating means contracts the pressure chamber, a contraction waveform element that maintains the contracted state, and a second filling waveform that fills the ink by expanding the pressure chamber in which the contracted state is maintained by the contraction waveform element. A first drive pulse and a second drive pulse are generated, the second drive pulse including the element and a second ejection waveform element that causes the pressure chamber expanded by the second filling waveform element to contract and eject an ink droplet An ink jet recording apparatus that generates pulses having different gradations. An ink jet recording apparatus having a pressure generating element that expands and contracts a pressure chamber when a driving pulse is input to vary ink pressure in the pressure chamber, and ejects ink droplets from a nozzle opening by the pressure variation. ,
Drive signal generating means for generating a drive signal, and drive pulse generating means for generating a drive pulse from the drive signal,
The drive pulse generating means expands the pressure chamber and maintains the expanded state after the change, a first filling waveform element that further expands the pressure chamber whose expansion state is maintained by the expansion waveform element, Generating a first drive pulse including a first ejection waveform element that contracts a pressure chamber expanded by one filling waveform element to eject an ink droplet;
At least one drive pulse is divided into a plurality of waveform elements, and a series of drive signals is configured by mixing waveform elements constituting other drive pulses between the divided waveform elements,
An ink jet recording apparatus, wherein the drive pulse generating means generates a drive pulse by selectively connecting the divided waveform elements. An ink jet recording apparatus having a pressure generating element that expands and contracts a pressure chamber when a driving pulse is input to vary ink pressure in the pressure chamber, and ejects ink droplets from a nozzle opening by the pressure variation. ,
Drive signal generating means for generating a drive signal, and drive pulse generating means for generating a drive pulse from the drive signal,
The drive pulse generating means expands the pressure chamber and maintains the expanded state after the change, a first filling waveform element that further expands the pressure chamber whose expansion state is maintained by the expansion waveform element, Generating a first drive pulse including a first ejection waveform element that contracts a pressure chamber expanded by one filling waveform element to eject an ink droplet;
The expansion waveform element of at least one drive pulse is divided into a plurality of expansion subelements, and a series of drive signals are configured by mixing ejection waveform elements of other drive pulses between these expansion subelements. An ink jet recording apparatus. It said expansion waveform element, the ink jet recording apparatus according to any one of claims 1 to 3, characterized by being configured by stepwise expansion wave elements for expanding the pressure chamber in a plurality of stages. 2. The ink jet recording apparatus according to claim 1 , wherein the contraction waveform element includes a stepwise contraction waveform element that contracts the pressure chamber in a plurality of stages. A contraction waveform element of at least one drive pulse is divided into a plurality of contraction subelements, and a series of drive signals are configured by mixing ejection waveform elements of other drive pulses between these contraction subelements. The ink jet recording apparatus according to claim 1 . Place the expansion element constituting a part of said expansion waveform element at the beginning of the drive signals, according to claim 2, characterized in that the first ejection wave element is disposed at the end portion of the drive signal, or 6 The ink jet recording apparatus described. The ink jet recording apparatus according to claim 2, wherein different voltage levels between the divided waveform elements are connected by a connection element. An ink jet recording apparatus according to any one of claims 1 to 8, characterized by being configured by a piezoelectric vibrator of a vibration mode bending the pressure generating element. An ink jet recording apparatus according to any one of claims 1 to 8, characterized in that constructed by the piezoelectric vibrator of the longitudinal vibration mode the pressure generating element. 11. The ink jet recording apparatus according to claim 10, wherein the lowest voltage in the drive signal is set in a range of ground voltage to 5V.

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