JP2001171115A - Ink jet recorder and its driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress difference in the flying speed of ink drop due to difference in the volume of ink. SOLUTION: The ink jet recorder comprises means for generating a driving signal, and means for generating a driving pulse from the driving signal. The driving pulse generating means generates a first driving pulse having expansion waveform elements (P98-P100) for inflating a pressure chamber and sustaining the inflated state, first filling waveform elements (P100-P102) for further inflating the pressure chamber sustained in an inflated state by the expansion waveform elements, and first ejection waveform elements (P102-P103) for ejecting ink drops by contracting the pressure chamber inflated by the first filling expansion waveform elements.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field 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 to driving an ink jet recording head used in the ink jet recording apparatus. About the method.

[0002]

2. Description of the Related Art An ink jet recording apparatus includes a recording head having a large number of nozzle openings formed in a row, a carriage mechanism for moving the recording head in a main scanning direction (a recording paper width direction). And a paper feeding mechanism for moving the recording paper in the sub-scanning direction (paper feeding direction).

The above-described recording head includes a pressure chamber communicating with the nozzle opening and a pressure generating element for changing the ink pressure in the pressure chamber. In this recording head, the driving pulse is supplied to the pressure generating element to change the ink pressure in the pressure chamber, and eject the ink droplet from the nozzle opening.

The above-mentioned carriage mechanism moves the recording head in the main scanning direction. During this movement, the recording head ejects ink droplets at the timing specified by the dot pattern data. When the recording head reaches the end of the movement range, the paper feed mechanism moves the recording paper in the sub-scanning direction. After moving the recording paper, the carriage mechanism moves the recording head again in the main scanning direction,
The recording head ejects ink droplets during movement.

[0005] By repeating the above operation, an image based on the dot pattern data is recorded on the recording paper.

This recording apparatus forms an image based on whether or not to eject ink droplets, that is, whether or not there are dots. Therefore, in this recording apparatus, one pixel is 4 ×
A method of expressing an intermediate gradation by expressing a plurality of dots such as 4, 8 × 8 is adopted. In order to print a high-quality image by this method, it is necessary to eject an extremely small volume of ink droplets from the print head. However, when the volume of the ink droplet is extremely small, another problem that the recording speed is reduced occurs.

In view of such circumstances, a technique for ejecting ink droplets of different sizes by the same nozzle has been proposed in order to satisfy the opposing requirements of improving image quality and recording speed.

For example, in the technology disclosed in Japanese Patent Publication No. 4-15735 and US Pat. No. 5,285,215, a plurality of pulse signals capable of generating minute ink droplets are supplied, so that a minute nozzle is supplied from the same nozzle. A large number of ink droplets are ejected, and the ink droplets are united before landing on recording paper to generate a large ink droplet.

However, in these techniques, the number of ink droplets that can be combined is limited, so that the size of the ink droplet is limited, and the variable range of the size is narrow. Further, control is difficult because a plurality of ink droplets must be united before landing.

In view of the above, there is considered a technique of generating a drive signal in which a plurality of types of drive pulses corresponding to the volume of the ink droplet to be ejected are connected in series, and supplying the drive pulse obtained from the drive signal to the pressure generating element. Have been.

[0011]

However, in this technique, simply connecting a plurality of types of driving pulses causes the following problem.

The first problem is that the driving cycle required for recording one dot becomes long. That is,
In this technique, it is necessary to connect drive pulses for the number of ink volumes to be ejected, and the drive cycle becomes longer by the number of connected drive pulses. If the driving cycle becomes longer, the recording speed becomes slower.

A second problem is that the flying speed of ink droplets varies with the difference in ink volume. For example, comparing a large ink droplet forming a large dot with a medium ink droplet forming a medium dot, the large ink droplet has a higher flying speed than the medium ink droplet. If the difference between the volumes of the ink droplets is increased, a large difference occurs in the flight speed. Then, the landing position of the ink droplet is shifted due to the difference in the flying speed, and the image quality is impaired.

The present invention has been proposed in view of the above. An object of the present invention is to efficiently include drive pulses for generating a plurality of types of ink droplets having different ink volumes within a limited drive cycle.

Another object of the present invention is to reduce the difference in flying speed of ink droplets due to the difference in ink volume.

[0016]

SUMMARY OF THE INVENTION The present invention has been proposed to achieve the above object, and has a recording head having a pressure generating element provided corresponding to a pressure chamber communicating with a nozzle opening. A driving signal generating means for generating a driving signal in an ink jet recording apparatus which supplies a driving pulse for operating the pressure generating element to the pressure generating element and ejects ink droplets from each nozzle opening; A drive pulse generating means for generating a drive pulse, wherein the drive signal generated by the drive signal generating means includes a waveform element for operating the pressure generating element and a connecting element for not operating the pressure generating element, and the connecting element Connects different voltage levels between waveform elements, and the driving pulse generating means
An ink jet recording apparatus characterized in that a plurality of types of drive pulses are generated by selecting a waveform element.

Preferably, the generation time of the inclined portion of the connection 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 for operating the pressure generating element.

Preferably, the waveform element includes a plurality of ejection waveform elements for operating a pressure generating element so as to eject ink droplets, and the ejection waveform elements are connected by a connection element.

Preferably, the waveform element includes a filling waveform element for operating a pressure generating element so as to fill the pressure chamber with ink, and the driving pulse generating means selects a discharge waveform element and a filling waveform element. At this time, a plurality of types of drive pulses are generated.

Preferably, the waveform element includes a plurality of ejection waveform elements for operating a pressure generating element so as to eject ink droplets at different timings, and the driving pulse generating means includes a volume of the ejected ink droplet. And a plurality of types of drive pulses are generated such that the ejection timing of the small volume ink droplet is earlier than the ejection timing of the large volume ink droplet.

Preferably, the waveform element includes a plurality of ejection waveform elements for operating a pressure generating element so as to eject ink droplets at different timings, and the driving pulse generating means includes a small driving pulse generating means. A small dot drive pulse capable of ejecting ink droplets, a medium dot drive pulse capable of ejecting medium ink droplets capable of forming medium dots, and a large dot drive pulse capable of ejecting large ink droplets capable of forming large dots Each of the drive pulses generated and generated by the drive pulse generation means is arranged with one of the discharge waveform element of the large dot drive pulse or the discharge waveform element of the medium dot drive pulse before the discharge waveform element of the small dot drive pulse. The ejection waveform element of the large dot drive pulse or the ejection waveform element of the medium dot drive pulse is provided after the ejection waveform element of the small dot drive pulse. The other is located.

Preferably, the waveform element forms a first large dot discharge waveform element and a second large dot waveform discharge element for discharging a large ink droplet capable of forming a large dot, and another dot. The other large-dot ejection waveform element and the second large-dot ejection waveform element, the other-dot ejection waveform element for ejecting ink droplets for The generating means includes:
A drive pulse including the large dot ejection waveform element and the second large dot ejection waveform element is generated.

Preferably, the waveform element includes a plurality of large dot ejection waveform elements for ejecting large ink droplets capable of forming large dots and another dot ejection waveform element for ejecting ink droplets for forming other dots. And the other dot ejection waveform elements are arranged between the large dot ejection waveform elements, and preferably, the drive pulse generation means generates a drive pulse composed of at least one ejection waveform element. I do.

[0024] Preferably, the plurality of waveform elements capable of discharging the large ink droplet have waveforms of substantially the same shape.

Preferably, there are two large dot ejection waveform elements, which are arranged at equal intervals.

Preferably, the waveform element includes a plurality of filling waveform elements for operating a pressure generating element so as to fill the pressure chamber with ink, and a discharge element for operating the pressure generating element to discharge an ink droplet. The driving pulse generating means includes a waveform element and connects the filling waveform elements with each other by a connection element, and the driving pulse generation means generates one driving pulse from the selected one filling waveform element and the selected ejection waveform element.

Preferably, the connection end of the connection element connected to the waveform element is a constant voltage part having a constant voltage.

According to the present invention, there is provided a pressure generating element which expands and contracts the pressure chamber by inputting a driving pulse to fluctuate the ink pressure in the pressure chamber, and ejects ink droplets from the nozzle opening by the pressure fluctuation. An ink jet recording apparatus, comprising: a driving signal generating unit for generating a driving signal; and a driving pulse generating unit for generating a driving pulse from the driving signal. And a first filling waveform element for further expanding the pressure chamber maintained in the expanded state by the expansion waveform element, and a pressure chamber expanded by the first filling waveform element for contracting. An ink jet recording apparatus that generates a first drive pulse including a first ejection waveform element for ejecting ink droplets through the first ejection pulse.

[0029] Preferably, the expansion state holding time by the expansion waveform element is set longer than the natural oscillation period of the pressure chamber.

Preferably, the drive pulse generating means contracts the pressure chamber, contracts a waveform element for maintaining the contracted state, and expands the pressure chamber for which the contracted state is maintained by the contracted waveform element, to thereby discharge ink. A second drive pulse including a second filling waveform element to be filled and a second ejection waveform element that causes the pressure chamber expanded by the second filling waveform element to contract to eject an ink droplet is generated.

Preferably, the expansion waveform element is
The pressure chamber is constituted by a stepwise expansion waveform element that expands in multiple stages.

Preferably, the contraction waveform element is
The pressure chamber is constituted by a stepwise contraction waveform element that contracts in a plurality of steps.

Preferably, at least one drive pulse is divided into a plurality of waveform elements, and a waveform element constituting another drive pulse is mixed between the divided waveform elements to form a series of drive signals. The drive pulse generation means generates a drive pulse by selectively connecting the divided waveform elements.

Preferably, the expansion waveform element of at least one drive pulse is divided into a plurality of expansion sub-elements,
A series of drive signals are formed by mixing other drive pulse ejection waveform elements between these expanded partial elements.

Preferably, a contraction waveform element of at least one drive pulse is divided into a plurality of contraction partial elements,
A series of driving signals are formed by mixing ejection waveform elements of other driving pulses between these contracted partial elements.

Preferably, an expansion element constituting a part of the expansion waveform element is arranged at the head of the drive signal, and the first ejection waveform element is arranged at the end of the drive signal.

Preferably, different voltage levels between the divided waveform elements are connected by connecting elements.

Preferably, the pressure generating element is constituted by a piezoelectric vibrator in a flexural vibration mode.

Preferably, the pressure generating element is constituted by a piezoelectric vibrator in a longitudinal vibration mode.

Preferably, the pressure generating element is constituted by a piezoelectric vibrator in a longitudinal vibration mode, and a terminal of a waveform element which drops the voltage from the intermediate voltage is 5 V from the ground voltage.
The voltage is set within the following range, and the ends of the waveform elements are connected by connecting elements.

According to the present invention, a series of drive signals in which divided waveform elements are connected to each other by a connection element are generated, and a waveform element arranged before the connection element and a waveform element arranged after the connection element are generated. Is selected from the drive signal, a drive pulse is generated by connecting these selected waveform elements together, and the generated drive pulse is supplied to the pressure generating element to drive an ink jet recording head that ejects ink droplets. Is the way.

According to the present invention, a drive pulse for expanding a pressure chamber, holding the expanded state for a predetermined time, further expanding the pressure chamber in which the expanded state is maintained, and then contracting to discharge an ink droplet is provided. This is a method for driving an ink jet recording head that supplies ink to a pressure generating element to eject ink droplets.

[0043]

Embodiments of the present invention will be described below 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.

This ink jet type recording apparatus comprises a printer controller 1 and a print engine 2. The printer controller 1 includes an interface 3 for receiving print data and the like from a host computer (not shown) and a RAM 4 for storing various data and the like.
A ROM 5 storing control routines for various data processing, a control unit 6 including a CPU and the like, and an oscillation circuit 7
A drive signal generating circuit 9 for generating a drive signal to be supplied to the recording head 8, an interface 10 for transmitting print data, drive signals, and the like developed into dot pattern data (bitmap data) to the print engine 2. It has. The drive signal generation circuit 9 is a kind of drive signal generation means in the present invention.

The interface 3 receives, for example, any one of character codes, graphic functions, and image data or print data including a plurality of data from a host computer or the like. The interface 3 is busy (BU) to the host computer.
SY) signal or acknowledge (ACK) signal.

The RAM 4 is used as a receiving buffer 4a, an intermediate buffer 4b, an output buffer 4c, a work memory (not shown), and the like. Receive buffer 4
In a, print data from the host computer received by the interface 3 is temporarily stored. The intermediate buffer 4b stores the intermediate code data converted into the intermediate code by the control unit 6. In the output buffer 4c, the dot pattern data after the gradation data is decoded is developed. This will be described later.

The ROM 5 stores various control routines executed by the control unit 6, font data, graphic functions, and the like.

The control section 6 reads out 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.
To memorize. Further, the control section 6 develops 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.

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 one line of dot pattern data is output from the output buffer 4c, the contents of the intermediate buffer 4b are deleted, and the conversion for the next intermediate code is performed.

The print engine 2 includes a recording head 8 and
It comprises a paper feed mechanism 11 and a carriage mechanism 12. The paper feed mechanism 11 includes a paper feed motor, a paper feed roller, and the like, and sequentially feeds a print recording medium such as a recording paper. That is, the paper feed mechanism 11 performs the sub-scan in the recording operation. The carriage mechanism 12 includes a carriage on which the recording head 8 is mounted, and a pulse motor or the like for running the carriage via a timing belt or the like. The carriage mechanism 12 performs main scanning in a printing operation.

The recording head 8 has a large number (for example, 64) of nozzle openings 13 arranged in the sub-scanning direction.
(Shown in FIG. 2), and ejects ink droplets from each nozzle opening 13.

The print data (SI) developed into the dot pattern data corresponds to the clock signal (C
K), the data is serially transmitted to the selection signal generator 22 through the interface 10. The selection signal generator 22 generates a selection signal corresponding to print data by receiving a latch signal (LAT), and supplies the generated selection signal to a level shifter 23, which is a voltage amplifier. here,
The selection signal is a drive signal (C) from the drive signal generation circuit 9.
OM) to select a necessary part.

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 an input side of the switch circuit 24, and a piezoelectric vibrator 25 is input to an output side of the switch circuit 24.
Is connected. And this switch circuit 24
When the switch signal is input, the connection state is established. The above-described piezoelectric vibrator 25 is a kind of the pressure generating element of the present invention.

The above-described 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 generation unit 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 according to 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.

Then, with the deformation of the piezoelectric vibrator 25,
Ink droplets are ejected from the nozzle openings 13.

Next, the recording head 8 will be described in detail. First, the structure of the recording head 8 will be described. FIG.
Is a recording head 8 to which a piezoelectric vibrator 25 in a flexural vibration mode is attached.

The recording head 8 has an actuator unit 32 in which a plurality of pressure chambers 31 are formed, and a channel unit 34 in which a nozzle opening 13 and a common ink chamber 33 are formed.
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 rear surface of the actuator unit 32.

The pressure chamber 31 expands and contracts with the deformation of the piezoelectric vibrator 25, 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 rapidly contracting the pressure chamber 31, and an ink droplet is ejected from the nozzle opening 13.

The actuator unit 32 includes the pressure chamber 3
A pressure chamber forming substrate 35 in which a space for forming 1 is formed;
Lid member 36 joined to the front surface of pressure chamber forming substrate 35
And a vibrating plate 37 joined to the back surface of the pressure chamber forming substrate 35 to close the opening surface of the empty space. A first ink flow path 38 for communicating the common ink chamber 33 and the pressure chamber 31 and a second ink flow path 39 for communicating the pressure chamber 31 and the nozzle opening 13 are formed in the cover member 36. I have.

The flow path unit 34 has an ink chamber forming substrate 41 in which a space for forming the common ink chamber 33 is formed, and a plurality of nozzle openings 13 are formed.
1 and a supply port forming plate 43 bonded to the back surface of the ink chamber forming substrate 41.

In the ink chamber forming substrate 41, a nozzle communication port 44 communicating with the nozzle opening 13 is formed. The supply port forming plate 43 has an ink supply port 45 that connects the common ink chamber 33 and the first ink channel 38, and a communication port 4 that connects the nozzle communication port 44 and the second ink channel 39.
6 is drilled.

Therefore, a series of ink flow paths from the common ink chamber 33 to the nozzle opening 13 through the pressure chamber 31 are formed in the recording head 8.

The piezoelectric vibrator 25 is formed on the opposite side of the pressure chamber 31 with the vibration plate 37 interposed therebetween. This piezoelectric vibrator 2
Reference numeral 5 denotes a flat plate. A lower electrode 48 is formed on the front surface of the piezoelectric vibrator 25, and an upper electrode 49 is formed on the rear surface so as to cover the piezoelectric vibrator 25.

At both ends of the actuator unit 32, connection terminals 50 whose base ends are electrically connected to the upper electrode 49 of each piezoelectric vibrator 25 are formed. The distal end face of the connection terminal 50 is formed higher than the piezoelectric vibrator 25. Then, a flexible circuit board 51 is joined to the end surface of the connection terminal 50, and supplies a drive waveform to the piezoelectric vibrator 25 via the connection terminal 50 and the upper electrode 49.

Although only two pressure chambers 31, two piezoelectric vibrators 25, and two connection terminals 50 are shown in the figure, a large number are provided corresponding to the nozzle openings 13.

In the recording head 8, when a driving pulse is input, a voltage difference is generated between the upper electrode 49 and the lower electrode. 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 joined to the vibration plate 37 does not contract but only the upper electrode 49 side contracts, the piezoelectric vibrator 25 and the vibration plate 37 project toward the pressure chamber 31 side. So that the volume of the pressure chamber 31 is contracted.

When ejecting ink droplets from the nozzle openings 13, for example, the pressure chamber 31 is rapidly contracted. That is, when the pressure chamber 31 is rapidly contracted, an increase in the ink pressure occurs in the pressure chamber 31, and an ink droplet is ejected from the nozzle opening 13 with the increase in the pressure. After the ink droplets are ejected, the upper electrode 49 and the lower electrode 48
Is eliminated, the piezoelectric vibrator 25 and the diaphragm 37 return to the original state. As a result, the inside of 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.

Next, the electrical configuration of the recording head 8 will be described.

This recording head 8 is, as shown in FIG.
It 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 a drive pulse generator in the present invention.

As shown in FIG. 3, the level shifter 23 includes a plurality of level shifter elements 23a to 23n provided corresponding to the nozzle openings 13. Similarly, the switch circuit 24 includes a plurality of switch elements 24a to 24n. In addition, the piezoelectric vibrator 25 also includes a plurality of piezoelectric vibrators 25a to 25a.
25n.

The selection signal from the selection signal generating section 22 is supplied to the level shifter elements 23a to 23n based on the print data.
Are selectively supplied to Switch elements 24a-2
4n, the connection state is selectively controlled based on this selection signal.

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 connection to the switch elements 24a to 24n is established. A drive signal is selectively supplied to the driven piezoelectric vibrators 25a to 25n.

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 based on the print data. For example, during a period in which the print data is “1”, the switch circuit 24 is in a connected state, so that a drive signal is supplied to the piezoelectric vibrator 25. Then, the piezoelectric vibrator 25 is deformed by the drive signal. In addition, since the switch is in a disconnected state during the period when the print data is “0”, the supply of the drive signal to the piezoelectric vibrator 25 is cut off. This print data is "0"
During the period of, each piezoelectric vibrator 25 holds the charge immediately before,
The last deformed state is maintained.

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-print” will be described as an example. here,
The “large dot” in this embodiment means that the ink volume is about 2
It means a relatively large dot formed by a large ink droplet of 0 pL (picoliter). "Medium dot" means a medium-sized dot formed by medium ink droplets 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.

FIG. 4A is a diagram showing the waveform of the drive signal generated by the drive signal generation circuit 9. The illustrated drive signal is a series of signals that can cause three types of ink droplets, that is, a large ink droplet, a medium ink droplet, and a small ink droplet, to be ejected from the same nozzle opening 13.

Then, the drive signal generation circuit 9 generates this drive signal at a printing cycle T of 7.2 kHz. The printing cycle T defines a printing speed in the recording device. In addition, the selection signal generation unit 22, the level shifter 23, and the switch circuit 24, that is, the drive pulse generation unit, generate a small dot drive pulse for discharging small ink droplets and a medium for discharging medium ink droplets from a series of drive signals. A medium dot drive pulse or a large dot drive pulse capable of discharging a large ink droplet is generated.

Hereinafter, a procedure for generating a drive pulse from a drive signal will be described in detail.

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 that connects different voltage levels between the waveform elements.

The waveform element in this embodiment is:
It comprises 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 as to contract the pressure chamber 31 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 and ink is ejected from the nozzle opening 13. The damping waveform element is an element for stopping the waving of the meniscus immediately after the ejection of the ink droplet in a short time. The meniscus is a curved surface (free surface) of the ink in the nozzle opening 13.
Means that

In the drive signals shown in FIGS. 4A and 4B, P1 to P10 'and P12' to P24
The parts up to are waveform elements. Also, from P10 'to P1
Portions up to 2 'are connection elements. Further, the portion from P1 to P2 'in the waveform element is a contraction waveform element, P2
'To P5 are the first filling waveform elements, and P5 to P5
The portion up to 9 is the first ejection waveform element, and the portion from P9 to P10 'is the first damping waveform element. The portion from P12 ′ to P15 is the second filling waveform element, and the portion from P15 to P15.
The portion up to 17 is the second ejection waveform element, from P17 to P18
Is the second damping waveform element, P18 'to P21 is the third filling waveform element, P21 to P23 is the third ejection waveform element, and P23 to P24 is the third damping waveform element. Element.

The portions from P2 'to P3 are connection ends in the first filling waveform element, and the portions from P10 to P10' are connection ends in the first vibration damping waveform element. Similarly, a portion from P12 'to P13 is a connection end in the second filling waveform element, and a portion from P18 to P18' is the second end.
This is the connection end of the damping waveform element,
The portion 19 is the connection end of the third filling wave element.

The drive pulse generation means generates a plurality of types of drive pulses by appropriately selecting the contraction waveform element, the filling waveform element, the discharge waveform element, and the vibration suppression waveform element, and connecting the selected waveforms. I do.

As shown in the enlarged view of FIG. 4B, the connection element described above has a termination P10 'in the first vibration suppression waveform element.
And the start end P12 'of the second filling waveform element. That is, by this connection element, the intermediate voltage VM which is the voltage level of the terminal end 10 'in the first vibration suppression waveform element,
The second filling waveform element is connected to the maximum voltage VH which is the voltage level of the start point P12 '.

By the way, the waveform elements (P1 to P
10 ′, P12 ′ to P24) are signal elements supplied to the piezoelectric vibrator 25, and are set according to the response characteristics of the piezoelectric vibrator 25 and the state of the ink in the pressure chamber 31. For this reason, the waveform element has restrictions on the voltage gradient, the timing of changing the voltage, and the like. That is, the voltage gradient needs to be set to a predetermined gradient or less, and the voltage change timing needs to be set to a predetermined timing suitable for ink droplet ejection.

For example, if the voltage gradient is too steep, the deformation of the piezoelectric vibrator 25 cannot follow the voltage change of the waveform element, and there is a possibility that an ink droplet of a desired volume cannot be ejected. Further, even if the deformation of the piezoelectric vibrator 25 can be followed, the pressure chamber 31 may expand rapidly due to the sudden deformation of the piezoelectric vibrator 25, and cavitation may occur in the pressure chamber 31. There is. The ejection amount of ink droplets may not be stable due to the cavitation. Furthermore, there is a possibility that the diaphragm 37 may be damaged by applying excessive mechanical stress to the diaphragm 37.

Regarding the timing of voltage change, 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 contracted after the pressure chamber 31 is expanded. . The timing of contracting the pressure chamber 31 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 state of the ink in the pressure chamber 31 becomes a state suitable for ejecting ink droplets. , The pressure chamber 31 is contracted.

For example, when the pressure chamber 31 is expanded to expand the pressure chamber 31 so that the pressure inside the pressure chamber 31 is reduced to a negative pressure and ink is sucked in, the generation timing of the pressure wave in the opposite direction (ink discharge direction) generated when the ink flows in is determined. At the same time, the pressure chamber 31 is contracted. This makes it possible to discharge ink droplets in an optimal state. On the other hand, when the pressure chamber 31 is contracted at a timing that is not suitable for discharging the ink droplets, for example, when the pressure chamber 31 is contracted at a time point shifted from the generation timing of the above-described pressure wave in the opposite direction, the ejection is performed. Variations occur in the size of the ink droplets, resulting in deterioration of image quality.

By connecting the different voltage levels of the waveform elements with the connection elements as in the present embodiment, even if the number of waveform elements included in the drive signal is larger than that of the related art, a single series of signals is obtained. It can be contained within the printing cycle T.

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 to a short time. Therefore, waveform elements having different voltage levels at the connection terminals, such as the first vibration suppression waveform element and the second filling waveform element, can be connected in a very short time. With respect to the inclined portion (P11 to P12) of the connection element, the time (generation time) of the inclined portion is determined by the inclined portion of the waveform element that deforms the piezoelectric vibrator 25 (for example, P5 to P6, P15 to P16).
Is set to be the same as the time (occurrence time) or shorter than the time of the slope portion of the waveform element.

Therefore, as described above, the waveform element in which the voltage gradient or the voltage change timing is defined due to the balance with the piezoelectric vibrator 25 is changed within one printing cycle T in which the time is limited by the printing speed. Many can be included.

Accordingly, regarding the volume of the ink droplet,
The variable range can be increased depending on how the waveform element is selected. That is, since the degree of freedom in selecting the waveform element is increased, it is possible to generate a drive pulse for ejecting an ink droplet having a very small volume and a drive pulse for ejecting an ink droplet having a large volume, from one drive signal.

[0092] In addition, start end portions P10 'to P11 and end portions P12 to P12, which are connection ends of the connection element.
In this embodiment, the voltage is a constant voltage part. By providing this constant voltage section, when connecting the waveform elements, the switching time of the switch circuit 24 can be secured, and the connection between the elements can be easily performed. Further, it is possible to eliminate a difference in voltage level between waveform elements to be connected, and to eliminate an inrush current at a connection portion between elements. Thus, it is possible to prevent the electrical components such as the transistors constituting the switch circuit 24 from being damaged. Note that this constant voltage section has at least 2 μm.
It is desirable to set it to s or more.

In order to generate the small dot drive pulse shown in FIG. 5 from the above drive signal, the drive pulse generation means must
The contraction waveform element (P1 to P2 '), the first filling waveform element (P
2 ′ to P5), first ejection waveform elements (P5 to P9), first
The damping waveform elements (P9 to P10 ') are selected, and the selected waveform elements are connected in series.

Similarly, in order to generate a medium dot drive pulse from the drive signal, the drive pulse generating means includes a contraction waveform element, a second filling waveform element (P12 'to P15), and a second ejection waveform element (P15 to P15). P17), the second damping waveform element (P
17 to P18 '), and the selected waveform elements are connected in series.

Further, 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 vibration suppression waveform element, and a third vibration waveform element. A filling waveform element (P18 ′ to P21), a third ejection waveform element (P21 to P23), and a third vibration suppression waveform element (P23 to P24) are selected, and the selected waveform elements are connected in series.

The drive pulse generating means selects and connects the waveform elements based on the 5-bit print data. For this reason, in the present embodiment, the drive signal is divided into the first waveform element (P1 to P2 ′) in the period T1, the second waveform element (P2 ′ to P10 ′) in the period T2, and the third waveform element in the period T3. (P12 ′ to P18 ′) and the fourth waveform element (P18 ′ to P24) in the period T4.

Then, as shown in FIG. 4C, when a small dot drive pulse is generated, the drive pulse generation means determines the period T1 and the period T2 based on the print data set to "11000". To switch the switch circuit 24 to the connected state, and selectively supply the first waveform element and the second waveform element to the piezoelectric vibrator 25. Similarly, when generating a medium-dot drive pulse, the drive pulse generation unit sets “1001
In the period T1 and the period T3, the switch circuit 24 is connected based on the print data set to “0”, and the first
The waveform element and the third waveform element are selectively supplied to the piezoelectric vibrator 25. When generating a large dot drive pulse, the drive pulse generation unit determines the period T1, the period T3, and the period T3 based on the print data set to “10011”.
In step 4, the switch is connected, and the first, third, and fourth waveform elements are selectively switched to the piezoelectric vibrator 25.
To supply.

In the case of non-printing in which ink droplets are not ejected, the print data becomes "00000", and the switch circuit 24 remains in a non-connected state. The relationship between the print data and the connection state of the switch will be described later.

As shown in FIG. 5, in the small dot drive pulse, the voltage is increased from the intermediate voltage VM by 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 to P3). And
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 steeply set voltage gradient θ3 (P5). ~ P6). Then, immediately, the second intermediate voltage V set between the intermediate voltage VM and the minimum voltage VL.
The voltage is decreased to M2 (P7 to P8), and after maintaining the second intermediate voltage VM2 for a predetermined time (P8 to P9), the voltage is increased along the voltage gradient θ4 to return to the intermediate voltage VM (P9). ~ P10).

In this small dot drive pulse,
The voltage gradients θ1, θ2, and θ4 are set to such gradients that ink droplets are not ejected.

By applying the small dot drive pulse, the piezoelectric vibrator 25 is charged or discharged, and the piezoelectric vibrator 25 is deformed. Then, due to the deformation of the piezoelectric vibrator 25, the volume of the pressure chamber 31 changes.

That is, as the piezoelectric vibrator 25 is charged from the intermediate voltage VM, the volume of the pressure chamber 31 gradually decreases from the reference volume (the volume at the intermediate voltage VM).
Then, after maintaining the minimum volume corresponding to the maximum voltage VH for a predetermined time, the pressure chamber 31 expands to the maximum volume corresponding to the minimum voltage VL with the discharge of the piezoelectric vibrator 25 (P
1 to P5).

Subsequently, the pressure chamber 31 rapidly contracts from the maximum volume to the minimum volume (P5 to P6). Due to this contraction, the ink pressure in the pressure chamber 31 increases and the nozzle opening 1
3 ejects ink droplets. Here, the holding time of the lowest potential VL is extremely short, and the pressure chamber 31 expands immediately (P7 to P8). Thus, immediately the pressure chamber 3
1 is expanded, the volume of the ink droplet ejected from the nozzle opening 13 is extremely small.

After the pressure chamber 31 is expanded, the pressure chamber 31 is contracted so that the waving of the meniscus is stopped in a short time, and the pressure chamber 31 is returned to the reference volume (P8 to P1).
0).

In the medium dot driving 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 decreased to the minimum voltage VL at a predetermined voltage gradient θ5 to fill the pressure chamber 31 with the ink (P13 to P14). After the ink is filled, the voltage is rapidly increased along the voltage gradient θ6 to the maximum voltage VH,
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 decreased to the intermediate voltage VM (P17 to P18).

In the medium dot drive pulse, the pressure chamber 31 is expanded after maintaining the maximum voltage VH during the period from P16 to P17. Therefore, the nozzle opening 1
The amount of ink droplets to be ejected from No. 3 can be adjusted by the maintenance time of the maximum voltage VH, and ink droplets of a volume suitable for medium dots can be ejected.

In the large dot driving pulse, the ink is filled in the pressure chamber 31 by lowering the voltage to the minimum voltage VL along the predetermined voltage gradient θ7 following the medium dot driving pulse (P1 to P18) ( P19-P20). After the ink is filled, the voltage is increased to the maximum voltage VH along the voltage gradient θ8, and the pressure chamber 31 is rapidly contracted to eject the second ink droplet (P21 to P22). Thereafter, the maximum voltage VH is maintained for a predetermined time (P22 to P2).
3) Lower the voltage to the intermediate voltage VM (P23 to P23)
24).

In this large dot driving pulse, 1 is applied to the portion from P1 to P18 which overlaps with the medium dot driving pulse.
The second ink droplet is ejected, and subsequent P19 to P24
The second ink droplet is ejected at the portion. And
A large dot is formed by the sum of these two ink droplets.

As described above, in the present embodiment, the drive signal is configured to include the waveform element for operating the piezoelectric vibrator 25 and the connecting element that does not operate the piezoelectric vibrator 25, and Elements connect different voltage levels between waveform elements. Further, a plurality of types of driving pulses can be generated by selecting a waveform element by the driving pulse generating means. Therefore, even if there are many waveform elements, they can be formed as a series of drive signals within one printing cycle.

Therefore, the variable range of the ink droplet size can be made larger than before depending on the manner of selecting the waveform element, and ink droplets of various sizes can be ejected while maintaining a high recording speed. Can be done.

Next, a procedure for supplying print data for generating a drive pulse to the piezoelectric vibrator 25 will be described.

As described above, the dot pattern data is constituted by 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.

When transmitting these print data to the recording head 8, first, immediately before the first waveform element selection timing arrives, the print data corresponding to the first waveform element is completely transferred. The nozzle opening 13 is set in the selection signal generator 22. 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.

The selection signal generating section 22 is provided by the latch signal.
Generates a selection signal corresponding to 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. As a result, the switch circuit 24 is in the 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).

During the supply period T1 of the first waveform element, the second
The print data corresponding to the waveform elements of
It is set in the 3-minute selection signal generator 22. And period T
At the end of Step 1, the control unit 6 outputs a latch signal.
Thus, the piezoelectric vibrator 25 whose print data is “1”
Is applied to the second waveform element. Similarly,
Processing for the connection element, the third waveform element, and the fourth waveform element is performed.

When the processing for the fourth waveform element is completed, printing of one dot for all the nozzle openings 13 is completed. When printing for one dot is completed, the process for the next dot is repeated.

In the first embodiment, the second ejection waveform element for ejecting ink droplets capable of forming large dots is arranged in the period T3, and the third ejection waveform element is used in the period T4.
And both ejection waveform elements are arranged temporally close to each other.

In this case, when an ink droplet is ejected by the third ejection waveform element, the influence of the ejection of the ink droplet by the second ejection waveform element may remain. If the effect remains, the volume of the ink droplet due to the third ejection waveform element may become unstable. Hereinafter, a second embodiment focusing on this point will be described.

FIG. 6 is a diagram showing an example of a drive signal and a drive pulse in the second embodiment. Note that the configuration other than the drive signal is the same as that of the first embodiment described above, and a description thereof will be omitted.

In the illustrated drive signal, the part (P31 to P32) of the period T1 is the first waveform element, and the part of the period T2
(P32 to P35) are the second waveform elements. The portion of the period T3 (P36 to P39) is a third waveform element, and the portion of the period T4 (P39 to P42) is a fourth waveform element. Further, the period TS portion (P35 to P3)
6) is a connection element that does not deform the piezoelectric vibrator 25.
The connection element in the present embodiment also connects waveform elements having different voltage levels. With this connection element,
Even if the number of waveform elements is increased, it can be formed as a series of drive signals within a limited printing cycle T.

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 are ejection waveform elements (P
33 to P34). Third waveform element (P36 ~
P39) is the second waveform element (P2) in the first embodiment.
'To P10') and includes ejection waveform elements (P37 to P38) for ejecting 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 the ejection waveform elements (P40 to P41) for ejecting large ink droplets.
Contains.

In order to generate a small dot drive pulse from such a drive signal, the drive pulse generator (ie, the selection signal generator 22, the level shifter 23, and the switch circuit 24) requires the first waveform element and the third waveform element. Select an element and connect the selected waveform element. Specifically, “1001
A waveform element is selected based on the print data set to "0". When generating the medium dot drive pulse, the drive pulse generation means selects the first waveform element and the second waveform element based on the print data set to “11000”, and selects the selected waveform element. Concatenate. Similarly, when generating a large dot drive pulse, the drive pulse generator selects the first waveform element, the second waveform element, and the fourth waveform element based on the print data set to “11001”. , Concatenate the selected waveform elements.

In the drive pulse generated in this manner, the large dot drive pulse has two ejection waveform elements for ejecting two ink droplets, that is, the previous ejection waveform element (P3
3 to P34, corresponding to the first large dot ejection waveform element of the present invention) and the subsequent ejection waveform elements (P40 to P41, corresponding to the second large dot ejection waveform element of the present invention). I have. 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.

In the driving 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.

In this drive signal, the large dot drive pulse ejects two ink droplets, and the time interval from the timing of ejecting the preceding ink droplet to the timing of ejecting the subsequent ink droplet should be set relatively long. Can be. For this reason, after the previous ink droplet is ejected, the ink state can be stabilized before the subsequent ink droplet can be ejected. Therefore, it is possible to eliminate the variation in the ink volume of the subsequent ink droplet, and to further improve the image quality.

In the first and second embodiments, the damping waveform element and the filling waveform element are connected by the connection element, but the 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.
An embodiment will be described.

FIG. 7 is a diagram showing an example of a drive signal and a drive pulse in the third embodiment. Note that the configuration other than the drive signal is the same as that of the first embodiment described above, and a description thereof will be omitted.

In the illustrated driving signal, the part (P51 to P52) of the period T1 is the first waveform element, and the part of the period T2
(P52 to P54) is the second waveform element, the part (P55 to P57) of the period T3 is the third waveform element,
The part of the period T4 (P57 to P60) is the fourth waveform element, and the part of the period T5 (P60 to P62) is the fifth waveform element. The part of the period TS (P54 to P55)
Connection element.

This drive signal is designed to cause the pressure chamber 31 in the contracted state to expand rapidly, thereby discharging an extremely small volume of ink droplet. That is, the maximum voltage V
By supplying H, the piezoelectric vibrator 25 is bent so as to protrude toward the pressure chamber 31 to bring the pressure chamber 31 into a contracted state, and thereafter, the voltage is rapidly lowered to the minimum voltage VL, and the piezoelectric vibrator 25 is moved. The pressure chamber 31 is rapidly expanded by the return deformation.

With this control, the pressure in the pressure chamber 31 suddenly becomes negative, and the meniscus is drawn into the pressure chamber 31 at a high speed. Due to the movement of the meniscus, an extremely small ink droplet is separated from the center of the meniscus.
Then, the ink droplet flies in the direction opposite to the inside of the pressure chamber 31 and is ejected from the nozzle opening 13.

Therefore, in this drive signal, P51
The portion from to P52 is a contraction waveform element. Also, P
The portion from 52 to P54 is the first ejection waveform element,
The portion from P55 to P57 is a second ejection waveform element, and the portion from P58 to P59 is a third ejection waveform element. The portions from P57 to P58 are filling waveform elements, and the portions from P59 to P62 are vibration suppression waveform elements.

The connection elements (P54 to P55)
By connecting the first ejection waveform element and the second ejection waveform element, the drive pulse generation means (that is, the selection signal generation unit 22, the level shifter 23, and the switch circuit 24) appropriately selects these ejection waveform elements, Generate multiple types of drive pulses.

That is, when generating a small dot drive pulse, the drive pulse generating means sets the switch circuit 24 in the connection state in the periods T1, T2, and T5, and sets the first waveform element, the second waveform element, The fifth waveform element is selectively supplied to the piezoelectric vibrator 25. Similarly, when generating a medium dot drive pulse, the drive pulse generation means sets the period T
1. In a period T3 and a period T5, the switch circuit 24 is connected, and the first waveform element, the third waveform element, and the fifth 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 circuit 24 in the connection state in the period T1, the period T3, the period T4, and the period T5, and sets the first waveform element, the third
, The fourth waveform element, and the fifth waveform element are selectively supplied to the piezoelectric vibrator 25.

In the present embodiment, the selection of this waveform element
It is configured to perform the printing by using bit print data. That is, when a small dot drive pulse is generated, the print data is set to “110001”, so that the periods T1 and T1
The waveform elements at 2 and T5 are supplied to the piezoelectric vibrator 25. Similarly, when generating a medium dot drive pulse,
By setting the print data to “100101”, the waveform elements in the periods T1, T3 and T5 are
To supply. When generating a large dot drive pulse, the print data is set to “100111” to supply the waveform elements in the periods T1, T3, T4, and T5 to the piezoelectric vibrator 25.

In this embodiment, the connection element (P5
4 to P55), the first ejection waveform element (P52 to P5)
4) and the second ejection waveform element (P55 to P57) are connected, so that the time interval between the ejection waveform elements can be shortened. Thereby, many ejection elements can be included in the drive signal even within a limited time. Therefore, various types of driving pulses can be generated from one driving signal.

The time interval between the ejection waveform elements can be adjusted by the connection element. Thereby, the ejection timing of the ink droplet can be adjusted at a minute level. Therefore, it is possible to reduce the deviation of the landing center position of the ink droplet.

In the present embodiment, the first ejection waveform element and the second ejection waveform element share a common contraction waveform element (P51 to P51).
P52). In other words, one drive pulse is generated by the contraction waveform element and the first ejection waveform element, and another drive pulse is generated by the contraction waveform element and the second ejection waveform element.

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. This interval can be adjusted by the inclination of the connection element and the length of the flat portion. Therefore, the size of the ink droplet can be controlled at a minimum level. Thereby, the image quality can be further improved.

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 ejection waveform element and the filling waveform element are selected. It is.

Further, in the drive signal described above, the drive signal includes a plurality of ejection elements for operating the piezoelectric vibrator 25 so as to eject ink droplets at different timings. That is, the drive signal is the first signal for discharging the small ink droplet.
Discharge waveform elements (P53 to P54), second discharge waveform elements for discharging medium ink droplets (P56 to P57), and third discharge waveform elements for discharging large ink drops (P58 to P59)
And

The driving pulse generating means generates a plurality of types of driving pulses so that the ejection timing of small ink droplets is earlier than the ejection timing of large ink droplets. For example, when a small dot drive pulse for ejecting a small ink droplet and a medium dot drive pulse for ejecting a medium ink droplet are compared, the ejection waveform element (P56 to P57) in the medium dot drive pulse is smaller in the small dot drive pulse. The ejection waveform elements (P53 to P54) are earlier.

Thus, an ink droplet having a smaller ink volume is ejected earlier. In this case, the flying speed of the ejected ink droplet slightly varies depending on the size of the ink droplet. The flying speed of a large ink droplet is high, and the flying speed of a small ink droplet is low. Therefore, the time from ejection to landing on the recording paper slightly varies depending on the size of the ink droplet. That is, a large ink droplet takes a short time to land, and a small ink droplet takes a long time to land.

Therefore, by discharging 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. Can be.
Therefore, the image quality can be further improved.

By the way, in the third embodiment, the discharge waveform elements are connected by the connection elements, but the filling waveform elements may be connected by the connection elements. Hereinafter, a fourth embodiment configured as described above will be described.

FIG. 8 is a diagram showing an example of a drive signal and a drive pulse in the fourth embodiment. Note that the configuration other than the drive signal is the same as that of the first embodiment described above, and a description thereof will be omitted.

In the driving signal shown in FIG.
(P71 to P72) are the first waveform elements, and the part (P72 to P74) of the period T2 is the second waveform element.
Further, the portion of the period T3 (P75 to P76) is a third waveform element, the portion of the period T4 (P77 to P78) is a fourth waveform element, and the portion of the period T5 (P78 to P81) is a fifth waveform element. It is. Also, the portion of the period TS1 (P74 to
P75) is a first connection element, and is a portion (P
76 to P77) are second connection elements.

This drive signal includes a plurality of filling waveform elements and one ejection waveform element, and changes the combination of the filling waveform element and the ejection waveform element to change the volume of the ink droplet to be ejected. is there. That is, a plurality of filling elements having different ink filling states are prepared, and the volume of the ink droplet to be ejected is made different depending on which filling element is selected.

In this drive signal, the portion from P71 to P72 is a contraction waveform element, and the portion from P72 to P74
Are the first filling waveform elements, the parts from P75 to P76 are the second filling waveform elements, and the parts from P77 to P78 are the third filling waveform elements. Also, from P79 to P80
Are the ejection waveform elements, and the parts from P80 to P81 are the vibration damping elements.

Then, the first connection element (P74 to P75)
Connects the first filling waveform element and the second filling waveform element,
The second connection elements (P76 to P77) connect the second filling waveform element and the third filling waveform element.

As described above, since the plurality of filling waveform elements are connected by the connection element, the interval between the filling waveform elements can be reduced, and the driving signal in one printing cycle can include many filling waveform elements. it can.

The driving pulse generating means (ie, the selection signal generating section 22, the level shifter 23, and the switch circuit 2)
4) generates a plurality of types of drive pulses by appropriately selecting a filling waveform element.

That is, in order to generate a 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 sets the first waveform element, the fourth waveform element, and the fourth waveform element. Select 5 waveform elements. As a result, a small dot drive pulse in which the contraction waveform element and the third filling waveform element are connected is generated and supplied to the piezoelectric vibrator 25.

Similarly, in order to generate a medium dot drive pulse, the drive pulse generator turns on the switch circuit 24 in the periods T1, T3 and T5, and sets the first waveform element, the third waveform element and Select the fifth waveform element. As a result, a medium dot drive pulse in which the contraction waveform element and the second filling waveform element are connected is generated and supplied to the piezoelectric vibrator 25.

In order to generate a large dot drive pulse, the drive pulse generating means sets the switch circuit 24 in the connection state during the periods T1, T2 and T5, and sets the first waveform element, the second waveform element and the second waveform element. Select 5 waveform elements. 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.

In this embodiment, the selection of the waveform element is performed by using 7-bit print data. That is, when generating a small dot drive pulse, the print data is set to “1000011” so that the waveform elements in the periods T1, T4 and T5 are
To supply. Similarly, when generating the medium dot drive pulse, the print data is set to “1001001”, so that the waveform elements in the periods T1, T3, and T5 are supplied to the piezoelectric vibrator 25. When generating a small dot drive pulse, the print data is set to “1100001” to supply the waveform elements in the periods T1, T2, and T5 to the piezoelectric vibrator 25.

In this embodiment, since the ink droplets are ejected using the same ejection waveform element, the first filling waveform element (P72 to P74) and the second filling waveform element (P75) are used.
To P76) and the third filling waveform element (P77 to P78), the size of the ink droplet can be determined by selecting one filling waveform element. Therefore, control is easy.

Further, since a plurality of types of ink droplets having different ink volumes are configured to be ejected using the same ejection waveform element, control can be simplified from this point as well.

For this reason, the variable range of the size of the ink droplet can be expanded while maintaining a high recording speed.

Next, the pressure chamber 31 having the reference volume is expanded to hold the changed expansion state for a predetermined time, and the pressure chamber 31 in which the expansion state is maintained is further expanded and then contracted to thereby reduce the ink droplets. A fifth embodiment will be described in which the liquid is ejected.

[0160] The drive signal shown in FIG. 9 indicates that a large ink droplet and a medium ink droplet having different ink volumes are supplied to the same nozzle opening 1.
3 is a signal to be ejected.

Since the configuration other than the drive signal is the same as that of the first embodiment described above, description thereof will be omitted.

In this drive signal, the portion of the period T1 (P91 to P97) is the first waveform element, and the portion of the period T2 (P97 to P106) is the second waveform element.

The first waveform element is a filling waveform element for deforming the piezoelectric vibrator 25 so as to fill the pressure chamber 31 with ink (P91 to P93, corresponding to the second filling waveform element of the present invention). A discharge waveform element (P93 to P95, corresponding to a second discharge waveform element of the present invention) for deforming the piezoelectric vibrator 25 so as to discharge ink from the nozzle opening 13; Vibration suppression waveform element (P95-
P96).

The voltage at the start point (P91) and the end point (P97) of the first waveform element is set to the intermediate voltage VM as the reference voltage. This intermediate voltage VM is also the start point (P97) and end point (P106) of the second waveform element. As described above, by setting the start point and the end point of the plurality of waveform elements to the intermediate voltage VM, the respective waveform elements can be connected smoothly.

The second waveform element is an expansion waveform element (P98 to P100) that slightly expands the pressure chamber 31 in the reference state of the intermediate voltage VM and holds the pressure chamber 31 for a predetermined time with a small amount of ink filled therein. And a filling waveform element (P100 to P102; P100 to P102) for further expanding the pressure chamber 31 expanded by the expansion waveform element and filling the pressure chamber 31 with ink.
A discharge waveform element (corresponding to a first filling waveform element according to the present invention) and an ejection waveform element (P1
02 to P104, corresponding to the first ejection waveform element of the present invention), and damping elements (P104 to P105) for suppressing the waving of the meniscus immediately after the ejection.

The expansion waveform elements of the second waveform element (P98 to P98)
100), the holding time for holding the inflated pressure chamber 31, that is, the expansion hold element (P99 to P10).
The supply time Tc of 0) is preferably set to a sufficiently long time such that the vibration of the meniscus when the piezoelectric vibrator 25 is deformed so as to expand the pressure chamber 31 converges to a steady state. .

For example, it is preferable to set the period longer than the natural oscillation period of the pressure chamber 31, and it is more preferable that the length be at least twice the natural oscillation period. Here, the natural vibration cycle 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 cycle of the meniscus inherently present for each type of the recording head 8, and is generally about 8 to 10 μsec.
Take the value of the degree.

The drive pulse generating means (ie, 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 a second drive pulse of the present invention) for ejecting a medium ink droplet from the drive signal, as shown in FIG.
When selecting the waveform elements (P91 to P97) and generating a large dot drive pulse (corresponding to the first drive pulse of the present invention) for discharging a large ink droplet, the second waveform element (P9
8 to P106).

In the present embodiment, the configuration is such that the selection of the waveform element is made by 2-bit print data. Therefore, the drive signal is divided into the first waveform elements (P91 to P97) in the period T1 and the first waveform elements (P97 to P106) in the period T2. When generating the medium dot drive pulse, the print data is set to “1”.
By setting to “0”, the switch circuit 24 is connected in the period T1, and the first waveform element is selectively set in the piezoelectric vibrator 25.
To supply. Similarly, when generating a large dot drive pulse, the print data is set to “01” so that the switch circuit 24 is connected in the period T2,
The waveform element is selectively supplied to the piezoelectric vibrator 25. Also,
In the case of non-printing in which no dots are formed, the print data is set to “00”, so that the switch circuit 24 is in a non-connected state.

By supplying the medium dot drive pulse generated as described above to the piezoelectric vibrator 25, ink droplets are ejected as follows.

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 the initial state, and is set as the reference volume of the pressure chamber 31.

Next, a predetermined voltage gradient θ is applied from the intermediate voltage VM.
11, the voltage is decreased (P91 to P92), and the minimum voltage V
L, the minimum voltage VL is maintained for a predetermined time (P9
2 to P93). At this time, the piezoelectric vibrator 25 is deformed as the voltage drops, and the pressure chamber 31 expands beyond the reference volume, and the pressure chamber 31 is filled with ink.

Next, the voltage is rapidly increased from the minimum voltage VL to the maximum voltage VH along the steeply set voltage gradient θ12 (P93 to P94). At this time, the piezoelectric vibrator 25 is rapidly deformed, and the volume of the pressure chamber 31 is also rapidly reduced. 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.

After maintaining for a predetermined time in the state where the maximum voltage VH is applied (P94 to P95), the maximum voltage VH is applied.
The pressure chamber 31 is expanded so that the waving of the meniscus stops in a short time from H, and returns to the reference volume (P95 to P9).
6). At this time, after maintaining the maximum voltage VH, the pressure chamber 3
Since the ink 1 is expanded, the ink is returned to the inside of the pressure chamber 31 after the ink is pushed out from the nozzle opening 13 to some extent. Maintaining time of this maximum voltage VH (P94-P95)
Accordingly, the volume of the ink droplet ejected from the nozzle opening 13 can be adjusted, and the ink droplet having a volume suitable for forming the medium dot can be ejected.

The large dot drive pulse is applied to the piezoelectric vibrator 2.
5, ink droplets are ejected as follows.

First, a predetermined voltage gradient θ is calculated from the intermediate voltage VM.
13, the voltage is decreased (P98 to P99), and the intermediate voltage V
When the second intermediate voltage VML reaches a substantially intermediate level between M and the minimum voltage VL, the second intermediate voltage VML is maintained for a predetermined time (P99 to P100). At this time, the pressure chamber 31 expands slightly more than the reference volume with the extension deformation of the piezoelectric vibrator 25, and the ink is filled in the pressure chamber 31 to some extent. Then, since the second intermediate voltage VML is held for a sufficiently long time Tc, the steady state in which the vibration of the meniscus when the pressure chamber 31 is expanded sufficiently converges.

Next, the voltage is further decreased from the second intermediate voltage VML by a predetermined voltage gradient θ14 (P100 to P10
1) 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 that has expanded a little further expands, and ink flows into the pressure chamber 3.
1 is filled. Next, the voltage is rapidly increased from the minimum voltage VL to the maximum voltage VH along the steeply set voltage gradient θ15 (P102 to P103), and the maximum voltage V
After maintaining the pressure at H for a predetermined time (P103 to P104), the pressure chamber 31 is expanded from the maximum voltage VH so as to stop the meniscus undulation in a short time, and returned to the reference volume (P1).
04-P105). At this time, due to the sudden deformation of the piezoelectric vibrator 25, the volume of the pressure chamber 31 contracts rapidly, and ink droplets are ejected from the nozzle openings 13.

In this large dot drive pulse, the intermediate voltage V
From M, the voltage is once decreased to the second intermediate voltage VML and held for a predetermined time until the meniscus oscillation converges (P98
Since the pressure chamber 31 is further expanded from this state and filled with ink (P100 to P10).
2) Fluctuations in the pressure in the pressure chamber 31 during ink filling can be reduced, and the meniscus pressure chamber 31
Retreat to the side can be suppressed.

Therefore, when a large ink droplet having a large ink volume is ejected, the width of change of the pressure 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 landing center position from being shifted due to the difference in the ink volume.

The flying speed of the ink droplet is controlled by the pressure chamber 3
It can be adjusted by setting the degree of expansion and the holding time of the expanded state. For this reason, it is possible to adjust the flight speed to be suitable for the volume of the ink droplet to be ejected. Therefore, also in this respect, the difference in the flying speed of the ink droplet due to the difference in the ink volume can be reduced. As a result, the displacement of the landing center position can be more reliably prevented.

Further, it is not necessary to perform a difficult operation for combining a plurality of minute ink droplets, a large dot can be formed on a recording paper with one ink droplet, and the variable range of the dot diameter becomes large.

Next, a sixth embodiment in which one drive pulse is divided into a plurality of waveform elements, and another drive pulse is mixed between these divided waveform elements to form a series of drive signals will be described. I do.

The driving signal shown in FIG. 11 is also a signal for ejecting a large ink droplet and a medium ink droplet having different ink volumes from the same nozzle opening 13. Note that the configuration other than the drive signal is the same as that of the first embodiment described above, and a description thereof will be omitted.

This drive signal includes two drive pulses, a large dot drive pulse for discharging large ink droplets and a medium dot drive pulse for discharging medium ink droplets. Here, in the present embodiment, the large dot drive pulse is the first pulse of the present invention.
The medium dot drive pulse corresponds to the drive pulse, and the medium drive pulse corresponds to the second drive pulse of the present invention.

The waveform element forming the large dot drive pulse is divided into two and arranged in the period T1 and the period T3. Further, a waveform element constituting the medium dot drive pulse is arranged in the period T2. That is, the first waveform element (P111 to P113) in the period T1 and the third waveform element in the period T3
The waveform elements (P128 to P135) constitute the large dot drive pulse, and the second waveform elements (P116 to P116) which constitute the medium dot drive pulse during the period T2 between the period T1 and the period T3.
125).

A period TS between the period T1 and the period T2
1 includes first connection elements (P113 to P113) shown in FIG.
P116) is arranged to terminate the first waveform element (P11).
3) and different voltage levels at the beginning (P116) of the second waveform element are connected. 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 (P125) of the second waveform element and the third waveform Different voltage levels at the beginning of the element (P128) are connected.

Then, the drive pulse generation means (ie, the selection signal generator 22, the level shifter 23, and the switch circuit 24) change the drive signal from the drive signal to the periods T1 and T3 based on the print data set to "10001". A large dot drive pulse is generated by selecting and connecting the arranged waveform elements. Further, the driving pulse generating means includes:
By selecting the second waveform element arranged in the period T2 based on the print data set to “00100”,
Generate a medium dot drive pulse.

The large dot drive pulse is generated by expanding waveform elements (P111 to P113, P128 to P129) for slightly expanding the pressure chamber 31 from the intermediate voltage VM, filling the pressure chamber 31 with ink to some extent, and holding the ink for a predetermined time. A filling waveform element (P129 to P131, corresponding to the first filling waveform element of the present invention) for further inflating the expanded pressure chamber 31 a little more to fill the ink, and the nozzle opening 13
Waveform elements (P131-P
133, which corresponds to the first ejection waveform element of the present invention);
And vibration suppression waveform elements (P133 to P134) for suppressing meniscus undulation immediately after ejection.

On the other hand, the medium dot drive pulse is generated by the intermediate voltage V
From M, a contraction waveform element (P117 to P119) for temporarily contracting the pressure chamber 31 and holding it for a predetermined time, and a filling waveform element (P119 to P121) for expanding the contracted pressure chamber 31 and filling the ink, A discharge waveform element (corresponding to a second filling waveform element) and a discharge waveform element (P) for discharging the ink from the nozzle opening 13 by contracting the expanded pressure chamber 31.
121 to P123, which correspond to the second ejection waveform element of the present invention), and damping elements (P123 to P124) for suppressing waving of the meniscus immediately after ejection.

By inputting the medium dot drive pulse generated as described above to the piezoelectric vibrator 25, ink droplets are ejected as follows. First, the intermediate voltage VM
The voltage is increased by a predetermined voltage gradient θ16 set so that no ink droplets are ejected from (P117 to P11).
8) When the maximum voltage VH is reached, the maximum voltage VH is maintained for a predetermined time (P118 to P119). At this time, the pressure chamber 31 temporarily contracts from the reference volume, and an expansion margin when the pressure chamber 31 is expanded next is secured. Further, the meniscus is once pushed out of the nozzle opening 13 by the maintenance time of the maximum voltage VH, and the pressure chamber 31 can be expanded at a timing at which the pushed meniscus returns by reaction. Thereby, the meniscus is moved to the pressure chamber 31.
The contraction of the pressure chamber 31 can be started from the retracted state.

Next, the voltage is decreased from the maximum voltage VH at a predetermined voltage gradient θ17 (P119 to P120). When the voltage reaches the minimum voltage VL, the minimum voltage VL is maintained for a predetermined time (P120 to P121), and the ink is transferred to the pressure chamber. 31 is filled. Next, along the steeply set voltage gradient θ18, the voltage is rapidly increased from the lowest voltage VL to a voltage VMH set at a substantially intermediate level between the reference voltage VM and the maximum voltage VH (P121 to P122). At this time, the pressure chamber 3
1 rapidly contracts, 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 where the meniscus is drawn into the pressure chamber 31, and the voltage is increased to a voltage VMH slightly lower than the maximum voltage VH to eject ink droplets. In addition, ink droplets having an ink volume suitable for forming medium dots can be ejected.

After maintaining the voltage VMH applied for a predetermined period of time (P122 to P123), the pressure chamber 31 is expanded from the voltage VMH so as to stop the meniscus undulation in a short time, and returns to the reference volume (see FIGS. P123-P12
4).

Note that the large dot drive pulse is applied to the piezoelectric vibrator 2
The operation of ejecting a large ink droplet having a large ink volume by supplying the ink to the nozzle 5 is the same as that of the fifth embodiment. Therefore, the description is omitted.

In this embodiment, the waveform element constituting the large dot drive pulse is divided into two waveform elements at the expansion waveform element. That is, the expansion waveform element is divided into the first expansion waveform element (P111 to P113) and the second expansion waveform element (P128 to P129). Then, a series of drive signals is formed by arranging the waveform elements constituting the medium dot drive pulse between the divided waveform elements (corresponding to the expansion part elements in the present invention).
Therefore, 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 contained within a limited printing cycle.

Furthermore, 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 landing position of the ink droplet can be determined. The deviation is small, and high print quality can be secured.

Next, a plurality of drive pulses were divided into a plurality of waveform elements, and a series of drive signals was formed by mixing one drive pulse waveform element with another drive pulse waveform element. A seventh embodiment will be described.

The drive signal shown in FIG. 12A is a signal for ejecting a large ink droplet and a small ink droplet from the same nozzle opening 13. Note that the configuration other than the drive signal is the same as that of the first embodiment described above, and a description thereof will be omitted.

In this drive signal, a waveform element constituting a small dot drive pulse (corresponding to the second drive pulse of the present invention) is divided into two and arranged in a period T1 and a period T3. Further, a waveform element constituting a large dot drive pulse (corresponding to the first drive pulse of the present invention) is also divided into two and arranged in a period T2 and a period T4. That is, the first waveform element (P141 to P143) in the period T1 and the third waveform element (P152 to P159) in the period T3 constitute a small dot drive pulse. Further, the period T1 and the period T3
Of the second waveform element of the period T2 (P146-
P149) and the fourth waveform element of the period T4 (P162 to P1)
69) constitute a large dot drive pulse.

A period TS between the period T1 and the period T2
1 includes first connection elements (P143 to P143) shown in FIG.
P146). The first connection element connects different voltage levels at the end (P143) of the first waveform element and the start (P146) of the second waveform element.
Similarly, in a period TS2 between the period T2 and the period T3, the second connection elements (P149 to P152) illustrated in FIG.
Are disposed, and in a period TS3 between the period T3 and the period T4, the third connection elements (P159 to P1) illustrated in FIG.
62) are arranged.

Then, the drive pulse generation means (ie, the selection signal generation section 22, the level shifter 23, and the switch circuit 24) are arranged in the periods T1 and T3 from the drive signal based on the print data set to "1000100". The selected waveform elements are connected. As a result, a small dot drive pulse is generated. Further, the drive pulse generation means outputs “0
Based on the print data set to “010001”, the waveform elements arranged in the periods T2 and T4 are selected and connected. As a result, a large dot drive pulse is generated.

When the small dot drive pulse generated as described above is supplied to the piezoelectric vibrator 25, ink droplets are ejected as follows.

First, the voltage is increased from the intermediate voltage VM with a predetermined voltage gradient θ19 set so as not to eject ink droplets (P141 to P142). When the voltage reaches the maximum voltage VH, the maximum voltage VH is maintained for a predetermined time. (P142-
P143, P152 to P153). At this time, the pressure chamber 3
The reference numeral 1 indicates that an expansion allowance for temporarily contracting from the reference volume and then expanding the pressure chamber 31 is secured.

Further, the meniscus is once pushed outward 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 this drawn state.

Next, the voltage is decreased from the maximum voltage VH at a predetermined voltage gradient θ20 (P153 to P154). When the voltage reaches the minimum voltage VL, the minimum voltage VL is maintained for a predetermined time (P154 to P155), and the pressure chamber 31 is filled with ink. Next, the voltage is rapidly increased from the minimum voltage VL to the maximum voltage VH along the steeply set voltage gradient θ21 (P155 to P156). At this time, the volume of the pressure chamber 31 contracts rapidly, the ink pressure in the pressure chamber 31 increases, and ink droplets are ejected from the nozzle openings 13.

In this case, since the voltage is raised from the state where the meniscus is deeply drawn to the maximum voltage VH and the ink droplet is ejected, a small ink droplet having a small ink volume suitable for forming a small dot can be ejected.

Then, the state where the maximum voltage VH is supplied is maintained for a predetermined time (P156 to P157), and the maximum voltage VH is supplied.
The pressure chamber 31 is expanded and returned to the reference volume so that the waving of the meniscus can be stopped in a short time from (P157 to P1).
58).

Note that the large dot drive pulse is applied to the piezoelectric vibrator 2
The operation of ejecting a large ink droplet having a large ink volume by supplying the ink to the fifth ink droplet is the same as that of the fifth embodiment. Therefore, the description is omitted.

In this embodiment, a series of drive signals is formed by mixing waveform elements constituting a large dot ejection waveform and waveform elements constituting a small dot ejection waveform. Therefore, the drive signal itself can be shortened, and a plurality of drive waveforms can be easily contained within a limited printing cycle. Other than that, it is the same as the sixth embodiment,
It has the same effect.

Next, a small dot drive pulse, a medium dot drive pulse, and a large dot drive pulse can be generated.
An eighth embodiment will be described in which the degree of contraction of the pressure chamber 31 during the small dot drive pulse is different from the degree of contraction of the pressure chamber 31 during the medium dot drive pulse.

As shown in FIG. 13, 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 is divided into a period T1 (P180 to P182) and a period T6 (P2).
13 to P220). Further, the waveform element constituting the medium dot drive pulse (corresponding to the second drive pulse of the present invention) is divided into two, and a period T2 (P185 to P185) is applied.
P188) and a period T4 (P193 to P200). Further, the waveform element constituting the small dot drive pulse (corresponding to the second drive pulse of the present invention) is divided into three and divided into periods T2 (P185 to P188) and T3 (P
188-P190) and period T5 (P203-P21)
0).

Also, a period TS between the period T1 and the period T2
1 includes first connection elements (P182 to P182) shown in FIG.
P185) is arranged to terminate the first waveform element (P18).
2) and different voltage levels at the beginning (P185) of the second waveform element are connected. Similarly, in a period TS2 between the period T3 and the period T4, the second connection elements (P190 to P193) shown in FIG.
The third connection element (P200 to P203) shown in FIG. 14C is arranged in the period TS3 between 5 and 5. In the period TS4 between the period T3 and the period T4, the third connection element shown in FIG. 4
Connection elements (P210 to P213) are arranged.

Then, the drive pulse generation means (ie, the selection signal generation unit 22, the level shifter 23, and the switch circuit 24) outputs the second waveform element of the period T2, the period T2 based on the print data set to "00111000100". T3
And the fifth waveform element in the period T5 are selected from the drive signals and connected. As a result, a small dot drive pulse is generated. Further, the drive pulse generation means outputs “0
The second waveform element in the period T2 and the fourth waveform element in the period T4 are selected from the drive signals and connected based on the print data set to “0100100000”. As a result, a medium dot drive pulse is generated. Similarly, the drive pulse generation unit 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 “100000000001” from the drive signal. As a result, a large dot drive pulse is generated.

The large dot drive pulse is basically the same as the first waveform in the fifth embodiment, and expands the pressure chamber 31 from the intermediate voltage VM, fills the pressure chamber 31 with ink to some extent, and holds it for a predetermined time. Expanding waveform element (P180
To P182, P213 to P214), and a filling waveform element (P214 to P214) for further inflating the pressure chamber 31 expanded by the expansion waveform element to fill ink.
216), an ejection waveform element (P216 to P218) for ejecting ink droplets from the nozzle opening 13, and a vibration suppression waveform element (P218 to P219) for suppressing wavy meniscus immediately after ejection.

Further, the small dot drive pulse is applied to the intermediate voltage V
M to a third intermediate voltage VMH which is set to a substantially intermediate level between the intermediate voltage VM and the maximum voltage VH to increase the pressure chamber 3
1 contraction waveform element (P185-P1
88) and a second contraction waveform element (P188 to P190, P203 to P204) for further contracting and holding the pressure chamber 31 contracted by the first contraction waveform element for a predetermined time.
A filling waveform element (P204 to P206) for expanding the contracted pressure chamber 31 to fill with ink, and a discharge waveform element (P206) for contracting the expanded pressure chamber 31 to discharge ink droplets from the nozzle opening 13. ~ P208)
And vibration suppression waveform elements (P208 to P209) for suppressing waving of the meniscus immediately after ejection.

Further, the medium dot drive pulse increases the voltage from the reference voltage VM to the third intermediate voltage VMH to slightly contract the pressure chamber 31, and holds the first contraction waveform element (P185 to P188) held in this contracted state. , P193-P19
4), the contracted pressure chamber 31 is expanded to form a pressure chamber 3
1 is filled with ink.
196) and an ejection waveform element (P1) for contracting the expanded pressure chamber 31 to eject ink droplets from the nozzle opening 13.
96 to P198), and a damping waveform element (P198 to P199) for suppressing waving of the meniscus immediately after ejection.

Here, the first contraction waveform element of the medium dot drive pulse and the first contraction waveform element of the small dot drive pulse include the second waveform element (P185 to P185) arranged in the period T2.
188) are commonly used.

In this drive signal, the contraction waveform element for contracting the pressure chamber 31 is a two-stage stepwise contraction waveform element consisting of a first contraction waveform element in the period T2 and a second contraction waveform element in the period T3. It is composed of

The above-mentioned small dot drive pulse is applied to the piezoelectric vibrator 2
5, small ink droplets having a small ink volume can be ejected as in the seventh embodiment.
However, in the present embodiment, when the pressure chamber 31 is contracted,
The two-stage contraction waveform element of the first contraction waveform element (P185 to P188) and the second contraction waveform element (P188 to P190) is supplied to the piezoelectric vibrator 25.

Also, the medium dot drive pulse is applied to the piezoelectric vibrator 2
5, ink droplets are ejected as follows. First, the voltage is increased from the intermediate voltage VM by a predetermined voltage gradient θ22 set so as not to eject ink droplets (P1
86 to P187), when the third intermediate voltage VMH reaches 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, P1).
93-P194). At this time, the pressure chamber 31 temporarily contracts slightly from the reference volume, and an expansion allowance when the pressure chamber 31 is expanded next is secured. Next, the voltage is decreased from the third intermediate voltage VMH at a predetermined voltage gradient θ23 (P194 to P194).
(P195) When the minimum voltage VL is reached, the minimum voltage VL is maintained for a predetermined time (P195 to P196), and the pressure chamber 31 is filled with ink. Next, the voltage is rapidly increased from the minimum voltage VL to the maximum voltage VH along the steeply set voltage gradient θ24 (P196 to P197). At this time, the volume of the pressure chamber 31 contracts, and the ink droplet is ejected from the nozzle opening 13. Then, a predetermined time is maintained while the maximum voltage VH is supplied (P197 to P198),
The pressure chamber 31 is expanded from the maximum voltage VH so that the meniscus undulation stops in a short time, and returns to the reference volume (P
198-P199).

By supplying a large dot drive pulse to the piezoelectric vibrator 25, large ink droplets having a relatively large ink volume can be ejected, as in the fifth embodiment.

In this embodiment, the element for contracting the pressure chamber 31 is the first contraction waveform element (P186 to P18).
8) and 2 of the second contraction waveform element (P188 to P190)
It consists of a stepwise contraction element. For this reason, by selectively connecting the first contraction waveform element and the second contraction waveform element, it is possible to perform a voltage change in a plurality of stages without providing a plurality of contraction waveform elements. Then, the drive signal itself can be shortened.

The waveform element of the large dot drive pulse is
In the direction of the waveform width, the waveform element is divided into a first waveform element and a sixth waveform element, and the first waveform element is arranged in the first period T1 and the sixth waveform element is arranged in the last period T6. . Further, the expansion waveform element is also divided into two expansion waveform sub-elements, and the previous expansion sub-element is arranged in the first waveform element which is the head of the drive signal. Further, the later expansion waveform element is arranged in the sixth waveform element.

As described above, the existence of another waveform element during the holding time of the expansion waveform element makes it possible to make the holding time of the expansion element sufficiently long. And the whole drive signal can be shortened.

Further, the above-mentioned expansion element is an expansion element (P
180 to P181). That is, the expansion element forming a part of the expansion waveform element is arranged at the head of the drive signal. Also, the ejection waveform elements (P216 to P218) of the large dot drive pulse are arranged at the end of the drive signal. Thus, another waveform element can be arranged during the holding time of the expansion waveform element, so that the holding time of the expansion waveform element can be made sufficiently long and the entire time of the drive signal can be shortened.

In the present embodiment, the element for contracting the pressure chamber 31 is composed of a two-stage contraction waveform element (a stepwise contraction waveform element) of a first contraction waveform element and a second contraction waveform element. Based on a similar concept, the element that expands the pressure chamber 31 may be configured by a plurality of stages of expansion waveform elements (stepwise expansion waveform elements), such as a first expansion waveform element and a second expansion waveform element. .

Further, in this embodiment, the waveform element constituting the medium dot drive pulse is a contraction waveform element (P18
5 to P188, P193 to P194) are divided into a first contraction waveform element (P185 to P188) and a second expansion waveform element (P193 to P194). Then, a series of drive signals is formed by arranging waveform elements constituting the small dot drive pulse between the divided waveform elements. For this reason, more waveform elements can be easily contained within a limited printing cycle.

In the present embodiment, each drive pulse generated by the drive pulse generation means is provided with a medium dot drive pulse discharge waveform element (P206 to P208) before a small dot drive pulse discharge waveform element (P206 to P208). P196 ~
P198), and the ejection waveform elements of the large dot drive pulse (P216 to P218) are arranged after the ejection waveform element of the small dot drive pulse.

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. The ejection order in the printing cycle T at the time of the backward movement is the order of the medium ink droplet, the small ink droplet, and the large ink droplet. In other words, in the forward movement and the backward movement, the landing positions of the ink droplets are simply that the large ink droplets and the medium ink droplets are switched. For this reason, the quality of the recorded image can be improved.

Next, from the drive signals, a large dot drive pulse, a medium dot drive pulse, a small dot drive pulse, and
A ninth embodiment capable of generating an in-print microvibration pulse will be described.

As shown in FIG. 15, with this drive signal,
The waveform element forming the micro-vibration pulse in the print is divided into three, and a period T1 (P221 to P225) and a period T4 (P
240 to P243) and a period T5 (P243 to P2)
46). Further, the waveform element constituting the small dot driving pulse (corresponding to the second driving pulse of the present invention) is divided into two, and the period T2 (P225 to P22)
8) and a period T6 (P247 to P258). Further, 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. Further, the waveform element constituting the large dot drive pulse (corresponding to the first drive pulse of the present invention) is divided into two, and is divided into a period T4 (P240 to P243) and a period T4.
7 (P260 to P266). The waveform element in the period T4 is commonly used for the large dot drive pulse and the in-print fine vibration pulse.

Further, the period TS between the period T2 and the period T3
1, the first connection elements (P228 to P229) are arranged. Similarly, a period TS between the period T5 and the period T6
2, a second connection element (P246 to P247) is arranged, and a third connection element (P258 to P259) is arranged in a period TS3 between the period T3 and the period T4.

The drive pulse generation means (ie, the selection signal generation section 22, the level shifter 23, and the switch circuit 24) outputs the fourth waveform element in the period T4 based on the print data set to "00000100001", and , Selecting and connecting the seventh waveform element of the period T7 from the drive signal,
Generate a large dot drive pulse. Further, the drive pulse generation means selects the third waveform element in the period T3 from the drive signal based on the print data set to “00100000” to generate a medium dot drive pulse. The drive pulse generation means selects and connects the second waveform element in the period T2 and the sixth waveform element in the period T6 from the drive signal based on the print data set to “0100000100”, and drives the medium dot. Generate a pulse. In addition, the drive pulse generation unit determines the first waveform element of the period T1 and the period T1 based on the print data set to “1000110000”.
The fourth waveform element of No. 4 and the fifth waveform element of the period T5 are selected from the drive signals and connected to generate a micro-vibration pulse in printing.

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 slightly expands the pressure chamber 31 of the reference volume to a certain extent inside the pressure chamber 31. The expansion waveform elements (P241 to P243, P259 to
P260), a filling waveform element (P260 to P262) for further inflating the pressure chamber 31 expanded by this expansion waveform element to fill ink, and a maximum potential V
A discharge waveform element (P260 to P264) for rapidly increasing the voltage from the minimum voltage VL to a second maximum voltage VH 'set to a voltage level slightly lower than H to discharge ink droplets from the nozzle opening 13; Immediately after the meniscus undulation (P264-P2)
65).

[0234] The medium dot drive pulse has the lowest potential V
A filling waveform that expands the pressure chamber 31 by lowering the voltage from the intermediate voltage VM along the voltage gradient θ31 to the second minimum voltage VL ′ set to a voltage level slightly higher than L, thereby maintaining the expanded state. Element (P230-P232)
And a discharge waveform element (P) for contracting the expanded pressure chamber 31.
232 to P234), and withdrawal waveform elements (P234 to P236) for rapidly expanding the pressure chamber 31 and pulling the meniscus to the pressure chamber 31 side immediately before the portion that becomes an ink droplet by the supply of the discharge waveform element separates from the meniscus. , And damping waveform elements (P236 to P239) for suppressing waving of the meniscus immediately after the ejection.

Further, the small dot drive pulse has the intermediate voltage V
Pressure chamber 3 by increasing the voltage from M to the maximum voltage VH
1 is slightly contracted, and contraction waveform elements (P226 to P228, P247 to P248) for maintaining the contracted state, and the pressure chamber 3 in which the contracted state is maintained by the contracted waveform element
Filling waveform element (P2
48 to P250), the discharge waveform element (P250 to P252) for contracting the expanded pressure chamber 31, and the pressure chamber 31 is rapidly expanded just before a portion that becomes an ink droplet by the supply of the discharge waveform element is separated from the meniscus. Waveform element (P252 to P2) that draws the meniscus to the pressure chamber 31 side
54), and a damping waveform element (P254 to P257) for suppressing waving of the meniscus immediately after the ejection.

Further, the in-print micro-vibration pulse includes a first micro-vibration waveform element (P221 to P224) and a second micro-vibration waveform element (P241 to P245).

The above-described large dot drive pulse is applied to the piezoelectric vibrator 2
The same as in the fifth embodiment, a large ink droplet having a large ink volume can be ejected by supplying the ink to the fifth ink droplet.

Further, the medium dot drive pulse is applied to the piezoelectric vibrator 2
5, ink droplets are ejected as follows. First, the voltage is decreased from the intermediate voltage VM to a second minimum voltage VL 'with a predetermined voltage gradient θ31 set so as not to eject ink droplets (P230 to P231), and when the voltage reaches the second minimum voltage VL', (2) The minimum voltage VL 'is maintained for a predetermined time (P231 to P232). Thereby, the pressure chamber 3
1 is filled with ink. Next, the voltage is rapidly increased from the lowest voltage VL to the second maximum voltage VH 'along the steeply set voltage gradient θ32 (P232 to P232).
234). At this time, the pressure chamber 31 contracts rapidly, 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 a timing immediately before the portion that becomes an ink droplet separates from the meniscus, the voltage drops to the pull-in voltage VA along the steeply set θ31 (P
234-P235). As a result, the pressure chamber 31 rapidly expands, and the inside of the pressure chamber 31 becomes a negative pressure, and the peripheral portion of the meniscus is drawn into the inside of the pressure chamber 31. Therefore, the central portion of the meniscus is separated from the meniscus, and the central portion flies as an ink droplet. When the ink droplets are ejected, the voltage is raised and then lowered again, so that the pressure chamber 3
1 is contracted and expanded, and the vibration of the meniscus is converged early (P236 to P239).

Also, the small dot drive pulse is applied to the piezoelectric vibrator 2.
5, the voltage rises from the intermediate voltage to the maximum voltage VH and is held, whereby the pressure chamber 31 expands and the expansion allowance is secured (P226 to P228, P24).
7 to P248). After that, the same operation as the above-described medium dot drive pulse is performed (P248 to P25).
7). With this small dot drive pulse, ink droplets are ejected in a state where the meniscus is largely drawn into the inside of the pressure chamber 31, so that ink droplets of smaller volume can be ejected.

When a micro vibration pulse is supplied to the piezoelectric vibrator 25, the pressure chamber 31 slightly expands from the reference volume corresponding to the intermediate voltage VM by the first micro vibration waveform and the second micro 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 drawn into the pressure chamber 31, and then returns to the normal state. Therefore, the ink near the nozzle opening 13 is stirred.

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 two large dot drive pulses for ejecting large ink droplets are made identical.

In the driving signal shown in FIG.
The portion of P1 (P270 to P273) is the first waveform element, and the portion of period T2 (P274 to P281) is the second waveform element.
It is a waveform element. Then, the portion of the period T3 (P282 to
P289) is the third waveform element, and the portion (P
289-P295) is the fourth waveform element. Further, the portion of the period TS1 (P273 to P274) is the first connection element, and the portion of the period TS2 (P281 to P282) is the second connection element.
Connection element.

The first waveform element is a contraction waveform element (P
271 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 vibration suppression waveform element (P279 to P280). Also,
The third waveform element is a second filling waveform element (P283 to P28).
5) and small dot ejection waveform elements (P285 to P287)
And second vibration suppression waveform elements (P287 to P288). The fourth waveform element is a third filling waveform element (P290).
To P292) and the second large dot ejection waveform element (P292).
To P294) and the third vibration suppression waveform element (P294 to P29).
5).

Further, the second waveform element and the fourth
The waveform element is a waveform having the same shape. Then, the time from the start point (P270) of the first waveform element to the end point (P280) of the first vibration control element, and the end point (P280) of the first vibration control element to the end point (P295) of the third control element. )
It is set so that the time until the same time. Note that the end point (P295) of the third damping waveform element is the start point (P270) of the first waveform element in the next printing cycle T.

In order to generate a small dot drive pulse from such a drive signal, the drive pulse generation means (ie, the selection signal generation unit 22, the level shifter 23, and the switch circuit 24) requires the first waveform element and the third waveform element. Select an element and connect the selected waveform element. Specifically, “10001
A waveform element is selected based on the print data set to "0". When generating a large dot drive pulse, the drive pulse generation means selects the second waveform element based on the print data set to “001000” or prints the print data 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.

Further, when continuously ejecting large ink droplets, the drive pulse generation means selects the second waveform element and the fourth waveform element based on the print data set to “001001”, and Generates two large dot drive pulses. Regarding these two large dot drive pulses, the waveforms of the preceding large dot drive pulse (P275 to P280) and the subsequent large dot drive pulse (P290 to P295) are the same as described above. Further, the starting point (P2) of the large dot driving pulse ahead of the starting point (P270) of the driving cycle T
75) and the starting point (P2) of the subsequent large dot drive pulse from the end point (P280) of the previous large dot drive pulse.
The time up to 90) is set to 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.

Thus, in the case of continuously ejecting large ink droplets, large ink droplets are ejected at regular intervals, that is,
Discharge can be performed at a constant frequency. As a result, it is possible to eliminate variations in landing positions of large ink droplets caused by the first large dot drive pulse and large ink droplets caused by the subsequent large dot drive pulse, thereby improving print quality. Further, the recording head 8 can be driven at a frequency as high as possible.

In this embodiment, the drive signal is generated at a print cycle T of, for example, 10.8 kHz. For this reason, when large ink droplets are continuously ejected, large ink droplets can be ejected twice during the printing cycle T, and the driving frequency of the recording head 8 can be substantially increased. . In addition, 2 which generates large ink droplets
Since a discharge waveform element constituting a small dot drive pulse as another dot drive pulse is arranged between two large dot drive pulses, many drive waveforms are included even in a print cycle T of a limited period. Can be made.

Furthermore, since the waveforms of the two large dot drive pulses have the same shape, the volume of the large ink droplet is the same regardless of which large dot drive pulse ejects a large ink droplet. That is, the size of the large dot can be made the same.

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.

Next, an eleventh embodiment will be described.
In the eleventh embodiment, a large ink droplet, a medium ink droplet, and a small ink droplet 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, small dot ejection waveforms are arranged between large dot ejection waveforms.

In the driving signal shown in FIG.
The portion of P1 (P300 to P303) is the first waveform element, and the portion of period T2 (P304 to P311) is the second waveform element.
It is a waveform element. Then, the part of the period T3 (P312 to P312)
P317) is a third waveform element, and the portion (P
317 to P323) are the fourth waveform elements. Further, the portion of the period TS1 (P303 to P304) is the first connection element, and the portion of the period TS2 (P311 to P312) is the second connection element.
Connection element.

The first waveform element is a contraction waveform element (P
301 to P302). The second waveform element includes a first filling waveform element (P305 to P307), a first ejection waveform element (P307 to P309), and a first vibration suppression waveform element (P309 to P310). The third waveform element is a second filling waveform element (P313 to P314).
And second ejection waveform elements (P314 to P315)
And damping waveform elements (P315 to P316).
The fourth waveform element is a third filling waveform element (P318 to P32).
0), the third ejection waveform element (P320 to P322),
And third vibration suppression waveform elements (P322 to P323). Note that the end point (P323) of the third damping waveform element is the start point (P300) of the first waveform element in the next printing cycle T.
It is.

In order to generate a small dot drive pulse from such a drive signal, the drive pulse generation means (ie, the selection signal generation unit 22, the level shifter 23, and the switch circuit 24) requires the first waveform element and the third waveform element. Select an element and connect the selected waveform element. Specifically, “10001
A waveform element is selected based on the print data set to "0". 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.

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 forms a medium dot drive pulse.

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 ejection waveform element (P307-P2) of the second waveform element
P309) and a third ejection waveform element (P3
20 to P322) are large dot ejection waveform elements.

[0257] Regarding the two large dot ejection waveforms constituting the large dot drive pulse, the first large dot ejection waveform (P305 to P310) and the second large dot ejection waveform (P3
18 to P323) are the same. The time from the start point (P300) of the driving cycle T to the start point (P305) of the previous large dot ejection waveform, and the start point (P318) of the subsequent large dot ejection waveform from the end point (P310) of the previous large dot ejection waveform. Time until the same time. That is, the time from the end point of the large dot ejection waveform to the start point of the next large dot ejection waveform is set to a fixed time. Further, between the large dot ejection waveforms, small dot ejection waveforms (P313 to P316) constituting a small dot drive pulse are arranged.

In this drive signal, since the large dot ejection waveform is arranged before and after the small dot ejection waveform, printing is performed both when the recording head 8 (that is, the carriage) moves forward and backward. In bidirectional printing, the landing positions of small ink droplets and large ink droplets can be aligned by aligning large ink droplets with reference to the landing positions of small ink droplets ejected by small dot drive pulses. .

Also, the first large dot ejection waveform and the second large dot ejection waveform have the same waveform, and the volume of the ink droplet ejected by the first large dot ejection waveform and the second large dot ejection waveform are ejected. The volume of the ink droplet can be made uniform.

Further, since the large dot ejection waveform is generated at regular intervals within the printing cycle T, the same recording state can be realized in the forward movement and the backward movement in bidirectional printing.

As described above, in this embodiment, a high-quality image can be recorded particularly in a bidirectional printing configuration.

In each of the above embodiments, the recording head 8 using the flexural mode piezoelectric vibrator 61 as a pressure generating element has been described. Recording head 6 using 61
2 can also be applied.

The recording head 62 has a base 63 made of a synthetic resin, and a flow path unit 64 attached to the front surface (corresponding to the left side in the figure) of the base 63. And
The flow path unit 64 includes a nozzle plate 66 having a nozzle opening 65 formed therein, a vibration plate 67, and a flow path forming plate 6.
And 8.

The base 63 is a block-shaped member provided with a housing space 69 opened at the front and back. In the housing space 69, the piezoelectric vibrator 6 fixed to the fixed substrate 70 is provided.
1 is accommodated.

The nozzle plate 66 is a thin plate-like member having a large number of nozzle openings 65 formed in the sub-scanning direction. Each nozzle opening 65 is opened at a predetermined pitch corresponding to the dot formation density. The diaphragm 67 has an island portion 71 as a thick portion with which the piezoelectric vibrator 61 contacts.
And a thin plate member 72 provided to surround the periphery of the island portion 71 and having elasticity.

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.

The flow path forming plate 68 includes a pressure chamber 73, a common ink chamber 74, and the pressure chamber 73 and the common ink chamber 7.
An opening for forming an ink supply path 75 that communicates with the nozzle 4 is provided.

The nozzle plate 66 is disposed on the front surface of the flow path forming plate 68, and the vibration plate 67 is disposed on the rear side. The flow path forming plate 68 is sandwiched between the nozzle plate 66 and the vibration plate 67. In this state, the flow path unit 64 is formed integrally by bonding or the like.

In the flow path unit 64, a pressure chamber 73 is formed on the back side of the nozzle opening 65, and the pressure chamber 73 is formed.
The island portion 71 of the diaphragm 67 is located on the back side of the. The pressure chamber 73 and the common ink chamber 74 communicate with each other via an ink supply path 75.

The tip of the piezoelectric vibrator 61 is
1 is contacted from the back side, and in this contact state, the piezoelectric vibrator 6
1 is fixed to the base 63. A drive signal (C) is supplied to the piezoelectric vibrator 61 via a flexible cable.
OM) and print data (SI) are supplied.

[0271] The piezoelectric vibrator 61 in the longitudinal vibration mode has the property of contracting in the direction perpendicular to the electric field when charged, and extending in the direction perpendicular to the electric field when discharged. Therefore, in the recording head 62, the piezoelectric vibrator 61 contracts rearward by being charged, and the island portion 71 is pulled back along with the contraction, and the contracted pressure chamber 73 expands. 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, the electric discharge causes the piezoelectric vibrator 61 to extend forward, the island 71 of the elastic plate is pushed forward, and the pressure chamber 73 contracts. With the contraction, the ink pressure in the pressure chamber 73 increases.

As described above, in the recording head 62, the relationship between the voltage level due to the charging and discharging of the piezoelectric vibrator 61 and the expansion and contraction of the pressure chamber 73 is opposite to that of the above embodiments. Therefore, when the recording head 62 is used, the driving signal and the driving waveform in which the polarity of the driving signal and the driving waveform shown in the previous embodiment are opposite to each other with respect to the intermediate voltage are used. For example, as shown in FIG.
The drive signal and the drive waveform shown in FIG. 16 and the drive signal and the drive waveform in which the rising and falling directions of the voltage are reversed with respect to the intermediate voltage VM are used.

That is, in the recording head 62, the pressure chamber 73 is filled with ink by increasing the voltage. Similarly, ejection of ink droplets is performed by lowering the voltage. Then, even when this recording head 62 is used, the same operation and effect as those of the above-described embodiments can be obtained.

In the driving signal shown in FIG. 20, the lowest voltage V
L is set in a voltage range from 0 V, which is the ground voltage, to about 5 V, which is slightly higher than the ground voltage. Then, the end of the first half (P330 to P334) of the contraction waveform element (P332 to P334, P339 to P334) that drops the voltage from the intermediate voltage VM is set to the lowest voltage VL. Further, the end of the first half of the contraction waveform element and the waveform element (P335) forming the medium dot drive pulse
To P336) and the connection elements (P334 to P33).
5).

As described above, when the minimum voltage VL is set within a voltage range of 5 V or less from the ground voltage, a drive signal can be constituted by a voltage in the positive direction from the ground voltage with respect to the ground voltage. Therefore, control becomes easy. Further, since the voltage application or the voltage maintenance at the voltage level of the maximum voltage VH can be suppressed low, the load on the piezoelectric vibrator due to the voltage application can be reduced as much as possible.

[0276]

As described above, in summary, according to the present invention, a wave element for operating the pressure generating element and a connecting element that does not operate the pressure generating element are included, and the connecting element makes it possible to connect the wave elements to each other. A series of drive signals to which different voltage levels are connected are generated by the drive signal generation means, and the drive pulse generation means selectively connects waveform elements in the drive signal to generate drive pulses, and the generated drive pulses are pressure-generated. Since the ink droplets are ejected by supplying to the elements, the connection element is a signal element in which the pressure generating element does not operate, so that the voltage gradient can be set steeply.

For this reason, it is possible to connect waveform elements having different voltage levels at the connection ends in a short time.
Therefore, even with a waveform element in which a voltage gradient or a voltage change timing is defined by a balance with a pressure generating element, the number of elements can be increased as compared with the related art, and a series of drive signals in one printing cycle can be used. Can be included.

Therefore, the variable range of the size of the ink droplet can be increased depending on the method of selecting the waveform element. Therefore, a remarkable effect that ink droplets of various sizes can be ejected while maintaining the recording speed at a high speed is exhibited.

Further, according to another configuration of the present invention, the pressure chamber is expanded, and this expanded state is maintained for a predetermined time.
The drive pulse generating means generates a drive pulse including an expansion waveform element for discharging the ink droplets by further contracting the pressure chamber in which the expanded state is maintained, and then supplying the generated drive pulse to the pressure generating element. As a result, the pressure in the pressure chamber, which has become negative due to expansion by the expansion waveform element, returns to the normal pressure side after the elapse of the holding time.

Since the pressure chamber in the state where the pressure has returned is further expanded by the first filling waveform element to fill the ink, the pressure fluctuation in the pressure chamber when the pressure chamber is filled with the ink can be reduced. And the retraction of the meniscus can be suppressed.

Therefore, when ejecting an ink droplet having a large ink volume, the width of change in the pressure in the ink chamber can be made smaller than before, and the flying speed of the ink droplet becomes excessively high. It has a remarkable effect that it can be prevented.

Furthermore, the flying speed of the ink droplet can be adjusted by setting the degree of expansion of the pressure chamber and the time for which the expanded state is maintained. For this reason, it is possible to adjust the flying speed to be suitable for the ink droplet to be ejected. Therefore, the effect that the difference in the flying speed of the ink droplet due to the difference in the ink volume can be reduced is also exerted.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating 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 drive 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 relationship between a gradation value and print data. It is a figure showing a relation.

FIG. 5 is a diagram illustrating a driving pulse according to the first embodiment of the present invention.

FIG. 6 is a diagram illustrating a drive signal and a drive pulse according to a second embodiment of the present invention.

FIG. 7 is a diagram illustrating a drive signal and a drive pulse according to a third embodiment of the present invention.

FIG. 8 is a diagram illustrating a drive signal and a drive pulse according to a fourth embodiment of the present invention.

FIG. 9 is a diagram illustrating a drive signal according to a fifth embodiment of the present invention.

FIG. 10 is a diagram showing a drive signal and a drive pulse according to a fifth embodiment of the present invention.

11A and 11B show a sixth embodiment of the present invention, in which FIG. 11A shows a drive signal and a drive pulse, and FIGS. 11B and 11C show connection elements, respectively.

12A and 12B show a seventh embodiment of the present invention, in which FIG. 12A shows a drive signal and a drive pulse, and FIGS. 12B, 12C and 12D show connection elements, respectively.

FIG. 13 is a diagram illustrating a drive signal and a drive pulse according to an eighth embodiment of the present invention.

FIGS. 14 (a), (b) and (c) are diagrams each showing a connection element in an eighth embodiment of the present invention.

FIG. 15 is a diagram showing drive signals according to a ninth embodiment of the present invention.

FIG. 16 is a diagram showing a drive pulse according to a ninth embodiment of the present invention.

FIG. 17 is a diagram showing a drive signal and a drive pulse according to a tenth embodiment of the present invention.

FIG. 18 is a diagram showing a drive signal and a drive pulse in an eleventh embodiment of the present invention.

FIG. 19 is a diagram illustrating a mechanical structure of another recording head applicable to the present invention.

FIG. 20 is a diagram illustrating a drive signal and a drive pulse for the recording head illustrated in FIG. 19;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printer controller 2 Print engine 3 Interface 4 RAM 5 ROM 6 Control part 7 Oscillation circuit 8 Recording head 9 Drive signal generation circuit 10 Interface 11 Paper feed mechanism 12 Carriage mechanism 13 Nozzle opening 22 Selection signal generation part 23 Level shifter 24 Switch circuit 25 Piezoelectric vibrator 31 Pressure chamber 32 Actuator unit 33 Ink chamber 34 Flow path unit 35 Pressure chamber forming substrate 36 Cover member 37 Vibration plate 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 terminal 51 Flexible circuit board 61 Piezoelectric vibrator 62 Recording head 63 Base 64 Flow path unit 65 Nozzle open Part 66 nozzle plate 67 diaphragm 68 the passage forming plate 69 housing space 70 fixing substrate 71 island portion 72 thin portion 73 the pressure chamber 74 common ink chamber 75 ink supply path

Claims (14)

[Claims] A pressure generating element for expanding and contracting a pressure chamber by inputting a driving pulse to vary ink pressure in the pressure chamber, and ejecting an ink droplet from a nozzle opening by the pressure fluctuation. A recording apparatus, comprising: a driving signal generating unit that generates a driving signal; and a driving pulse generating unit that generates a driving pulse from the driving signal, wherein the driving pulse generating unit expands the pressure chamber and expands after the change. An expansion waveform element for maintaining the state, and a first chamber for further expanding the pressure chamber in which the expansion state is maintained by the expansion waveform element.
An ink jet recording apparatus that generates a first drive pulse including a filling waveform element of (1) and a first ejection waveform element that causes a pressure chamber expanded by the first filling waveform element to contract to eject ink droplets. 2. The ink jet recording apparatus according to claim 1, wherein an expansion state holding time by the expansion waveform element is set longer than a natural oscillation period of the pressure chamber. 3. A driving pulse generating means for contracting a pressure chamber, a contraction waveform element for maintaining the contracted state, and a pressure chamber for filling the ink by expanding the pressure chamber maintained in a contracted state by the contraction waveform element. And generating a second drive pulse including a second filling waveform element and a second ejection waveform element for ejecting ink droplets by contracting the pressure chamber expanded by the second filling waveform element. Item 3. An ink jet recording apparatus according to item 1 or 2. 4. The ink jet recording apparatus according to claim 1, wherein said expansion waveform element comprises a stepwise expansion waveform element for expanding a pressure chamber in a plurality of stages. 5. The ink jet recording apparatus according to claim 1, wherein the contraction waveform element is constituted by a stepwise contraction waveform element for contracting the pressure chamber in a plurality of steps. 6. A drive pulse is formed by dividing at least one drive pulse into a plurality of waveform elements, and interposing a waveform element constituting another drive pulse between the divided waveform elements. The ink jet recording apparatus according to any one of claims 1 to 5, wherein the generation unit generates a drive pulse by selectively connecting the divided waveform elements. 7. An expansion waveform element of at least one drive pulse is divided into a plurality of expansion partial elements, and a discharge signal of another drive pulse is mixed between these expansion partial elements to generate a series of drive signals. The ink jet recording apparatus according to any one of claims 1 to 6, wherein the apparatus is configured. 8. A contraction waveform element of at least one drive pulse is divided into a plurality of contraction part elements, and a discharge signal element of another drive pulse is mixed between these contraction part elements to generate a series of drive signals. The ink jet recording apparatus according to any one of claims 1 to 7, wherein the apparatus is configured. 9. An apparatus according to claim 6, wherein an expansion element forming a part of said expansion waveform element is arranged at a leading portion of the drive signal, and a first ejection waveform element is arranged at an end portion of the drive signal. 9. The ink jet recording apparatus according to any one of items 8. 10. The ink jet recording apparatus according to claim 6, wherein different voltage levels between the divided waveform elements are connected by connecting elements. 11. The pressure generating element according to claim 1, wherein said pressure generating element comprises a piezoelectric vibrator in a flexural vibration mode.
11. The ink jet recording apparatus according to any one of items 1 to 10. 12. An ink jet recording apparatus according to claim 1, wherein said pressure generating element is constituted by a piezoelectric vibrator in a longitudinal vibration mode. 13. The pressure generating element is constituted by a piezoelectric vibrator in a longitudinal vibration mode, and the end of a waveform element that drops a voltage from an intermediate voltage is set within a voltage range of 5 V or less from a ground voltage. 13. The ink jet recording apparatus according to claim 1, wherein the terminals are connected by connecting elements. 14. A drive pulse for inflating the pressure chamber, maintaining the expanded state for a predetermined time, further expanding the pressure chamber in which the expanded state is maintained, and then contracting to discharge ink droplets. A method of driving an ink jet recording head that supplies ink to a generating element to discharge ink droplets.