JP3478294B2 - Ink jet recording device - Google Patents

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 for recording an image or the like by ejecting ink droplets from a nozzle opening by using pressure fluctuation in a pressure chamber.

[0002]

2. Description of the Related Art Various ink jet recording apparatuses such as ink jet printers and ink jet plotters are equipped with a recording head that ejects ink droplets by supplying drive pulses. Then, the recording head is reciprocated along the main scanning direction, and ink droplets are ejected in conjunction with this movement to record an image on the recording paper.

In this type of recording apparatus, in order to improve the recording speed while improving the image quality, recording is performed by variable dots for ejecting plural kinds of ink droplets having different ink amounts from the same nozzle opening. .

When performing recording using variable dots, for example, a drive signal in which a plurality of types of drive pulses having different ejected ink amounts are arranged in time series is generated, and a necessary drive pulse signal is selected from this drive signal. Supply to the pressure generating element.

In this recording operation, the amount of ink droplets to be ejected is determined, for example, according to the image to be recorded.
For example, a large ink droplet (large dot) is recorded in a portion where the image gradation is relatively dark, a small ink droplet (micro dot) is recorded in a relatively light portion, and a gradation portion corresponding to the middle thereof is recorded. Recording is performed with medium ink droplets (middle dots).

As a result, it is possible to prevent a decrease in recording speed due to the density of pixels being unnecessarily increased, and four values of one pixel are large, medium, small, and 0 (non-ejection). Since it is possible to provide the gradation property of, it becomes possible to record a higher quality image faster and more beautifully.

Further, by performing bidirectional recording in which dots in the backward scanning are recorded between dots printed in the forward scanning of the recording head, a high density image can be recorded in a short time. There is.

[0008]

By the way, when recording with variable dots as described above, each drive pulse forming the drive signal is optimized in accordance with the amount of ink to be ejected. , Bias level (reference potential), waveform shape, drive voltage (peak value), etc. are different.

Therefore, in order to generate a series of drive signals, it is necessary to match the bias level of each drive pulse. For example, with reference to the drive pulse of the high bias level, the low bias is applied to the high potential level. It is conceivable to adopt a method of superimposing level drive pulses.

However, if the drive pulse of the low bias level is simply superposed on the drive pulse of the high bias level, the maximum potential of the drive signal may exceed the upper limit of the drive circuit.

The present invention has been made in view of the above circumstances, and can properly generate a drive signal having a plurality of drive pulses having different bias levels within a limited potential level range. It is an object of the present invention to provide an inkjet recording device.

[0012]

DISCLOSURE OF THE INVENTION The present invention has been proposed to achieve the above object. According to a first aspect of the present invention, a pressure chamber communicating with a nozzle opening and a pressure fluctuation in this pressure chamber are provided. A recording head having a pressure generating element capable of generating a reciprocating motion, and a plurality of drive pulses for ejecting ink droplets arranged in time series and a drive signal adjusted to a reference bias level. And a drive pulse selecting means for selecting a drive pulse from the drive signal generated by the drive signal generating means, and the drive pulse selected by the drive pulse selecting means is supplied to the pressure generating element. In the ink jet recording apparatus that ejects ink droplets from the opening, the drive signal generated by the drive signal generation unit is the first drive pulse of the reference bias level. , A second drive pulse having an individual bias level different from the reference bias level, a preparation waveform for changing the potential from the reference bias level to the individual bias level, and a return waveform for changing the potential from the individual bias level to the reference bias level. Including a waveform element that is not selected during the selection of the second drive pulse before and after the second drive pulse, and the preparatory waveform is selected during the selection of the second drive pulse before the second drive pulse. Are arranged so as to sandwich a waveform element that is not selected, and the return waveform is arranged after the second drive pulse so as to sandwich a waveform element that is not selected when the second drive pulse is selected. An inkjet recording apparatus, characterized in that when a second drive pulse is selected, a preparatory waveform and a return waveform are selected together. .

According to a second aspect of the present invention, the second
The waveform elements that are not selected during the drive pulse selection are the connection elements that are not applied as a drive waveform to the piezoelectric generating element and the
The ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus is the first drive pulse .

According to a third aspect of the present invention, the drive signal generating means generates a forward drive signal in which a plurality of drive pulses are arranged in a predetermined order during forward scan of the recording head, and each drive pulse is forward drive signal. A backward drive signal, which is arranged in the reverse order to, is generated during the backward scan of the recording head, and the period from the end of the preparation waveform in the forward drive signal to the start of the second drive pulse and the end of the preliminary waveform in the backward drive signal 3. The ink jet recording apparatus according to claim 1 or 2, wherein the period from to the starting end of the second drive pulse is aligned.

According to a fourth aspect of the present invention, there is provided the ink jet recording apparatus according to any one of the first to third aspects, wherein the preparatory waveform is arranged at a frontmost portion of the drive signal. is there.

According to a fifth aspect of the present invention, the time width of the preparatory waveform is set to be equal to or greater than the Helmholtz resonance period in the pressure chamber, and the ink jet according to any one of the first to fourth aspects. It is a type recording device.

According to a sixth aspect of the present invention, the time width of the return waveform is set to be equal to or greater than the Helmholtz resonance period in the pressure chamber. It is a type recording device.

The ink jet recording apparatus according to any one of claims 1 to 6, wherein the preparatory waveform and the return waveform are set to a potential gradient that does not eject ink droplets. It is a type recording device.

An eighth aspect of the present invention is the ink jet recording apparatus according to any one of the first to seventh aspects, wherein the individual bias level is set to a ground potential.

According to a ninth aspect of the present invention, the second drive pulse is a reference drive pulse capable of ejecting an ink droplet serving as a position reference in a pixel area, and the drive signal generating means sets a plurality of drive pulses to a predetermined value. The forward drive signals arranged in this order are generated during the forward scan of the print head, and the backward drive signals in which the respective drive pulses are arranged in the reverse order of the forward drive signals are generated during the backward scan of the print head. Set the sum of the interval from the start of the printing cycle in the drive signal to the start of the ejection element of the reference drive pulse and the interval from the start of the printing cycle in the backward drive signal to the start of the ejection element of the reference drive pulse in one printing cycle 9. The ink jet recording apparatus according to claim 1, wherein the series of drive signals is generated.

Here, the "ejection element" means a waveform portion which constitutes a part of the driving pulse and operates the piezoelectric vibrator so as to eject an ink droplet.

According to a tenth aspect of the present invention, the drive signal generating means generates a forward drive signal in which a plurality of drive pulses are arranged in a predetermined order during forward scan of the recording head, and each drive pulse is forward drive signal. The reverse drive signal, which is arranged in the reverse order of the above, is generated during the backward scan of the print head, and the distance between the ejection elements of the adjacent drive pulses in the forward drive signal and the corresponding ejection elements between the backward drive signals are generated. The ink jet recording apparatus according to any one of claims 1 to 9, wherein drive signals having the same interval are generated.

According to the eleventh aspect of the present invention, the preparatory waveform and the return waveform are used as the in-print micro-vibration waveform for causing the in-print micro-vibration. The ink jet recording apparatus according to any one of claims.

According to a twelfth aspect of the present invention, the second drive pulse is positioned at the center of a plurality of drive pulses arranged in time series within one printing cycle. The inkjet recording apparatus according to claim 10.

Here, the "fine vibration in printing" means that the meniscus (the free surface of the ink exposed at the nozzle opening) is vibrated to the extent that ink droplets are not ejected, and non-ejection due to thickening of ink. The operation to prevent the state,
It means the operation executed within the printing cycle.

[0026]

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described by taking an ink jet printer (hereinafter referred to as a printer), which is a typical ink jet recording apparatus, as an example.

As shown in FIG. 1, the printer 1 includes a carriage 4 having a cartridge holder portion 2 and a recording head 3.
Have. The carriage 4 is movably attached to a guide member 6 that is provided in the left-right direction of the housing 5. Further, the carriage 4 is connected to a timing belt 9 which is stretched between a drive pulley 7 and an idler pulley 8, and the drive pulley 7 is joined to a rotary shaft of a pulse motor 10. Therefore, the carriage 4 moves the recording paper 11 by the operation of the pulse motor 10.
It moves along the main scanning direction which is the width direction of the.

A home position is set in an end region within the movement range of the carriage 4 and outside the printing region. In this home position, the recording head 3
A wiper mechanism 12 for wiping the nozzle surface and a capping mechanism 13 for capping the recording head 3 are arranged side by side on the left and right sides.

Below the carriage 4, the recording paper 1
A platen (paper feed roller) 14 for moving 1 in the paper feed direction (sub-scanning direction) is provided. This platen 1
The rotation of No. 4 is controlled by the paper feed motor 15.

When recording characters or images on the recording paper 11, ink droplets are ejected from the recording head 3 in synchronization with the movement of the carriage 4 in the main scanning direction. Further, the recording paper 11 is moved in the paper feed direction in synchronization with the movement of the carriage 4.

Further, the printer 1 is adapted to perform bidirectional printing. That is, recording can be performed both during the forward scan of the recording head 3 moving from the home position toward the far end on the opposite side and during the backward scan of the print head 3 returning from the far end toward the home position. ing.

Next, the structure of the recording head 3 will be described. The recording head 3 illustrated in FIG. 2 is a box-shaped case 2
The flow path unit 22 is joined to the front end surface of 1. Then, the vibrator unit 23 housed inside the case 21 causes a pressure fluctuation in the pressure chamber 24 in the flow path unit 22 to eject ink droplets from the nozzle openings 25.

The case 21 is in the form of a box in which a housing chamber 26 for housing the transducer unit 23 is formed, and is made of, for example, a resin material. This accommodation room 26
Are connected from the opening on the side of the joint surface with the flow path unit 22 to the opposite surface.

The flow path unit 22 has a structure in which the nozzle plate 28 is joined to one surface of the spacer 27 and the diaphragm 29 is joined to the other surface of the spacer 27.

The spacer 27 is formed of a silicon wafer or the like, and is divided into a predetermined pattern by etching the silicon wafer. The plurality of pressure chambers 24, the common ink chamber 31, and the common ink chamber 31, which communicate with each nozzle opening 25, are formed. Partition walls that form a plurality of ink supply paths 32 and the like that connect the ink chambers 31 to the pressure chambers 24 are appropriately formed.

The common ink chamber 31 is provided with a connection port connected to the ink supply pipe 33, and the ink stored in the ink cartridge 34 (see FIG. 1) is supplied through the connection port to the common ink chamber 31. Is supplied to.

The nozzle plate 28 is provided with a plurality of nozzle openings 25 ... In a row at a pitch corresponding to the dot formation density.

The vibrating plate 29 has a stainless steel plate 35 and a PPS.
A double structure in which an elastic film 36 such as a film is laminated is adopted, and the stainless plate side of the portion corresponding to each pressure chamber 24 is etched into a ring shape, and an island portion 37 is formed in the ring.

The vibrator unit 23 includes a piezoelectric vibrator 40.
It is composed of (a kind of pressure generating element) and a fixing member 41. The piezoelectric vibrator 40 is formed by forming slit portions on a single piezoelectric vibrator plate in which piezoelectric bodies and electrode layers are alternately laminated at a predetermined pitch corresponding to each pressure chamber 24 of the flow path unit 22. It is configured like a tooth. Also, the fixing member 4
1 is fixed to the base end portion of the comb-shaped oscillator.

This vibrator unit 23 includes the piezoelectric vibrator 4
The accommodation chamber 26 of the case 21 with the tip of 0 facing the opening
It is accommodated by being inserted into the inside and fixing the fixing member 41 to the inner wall of the accommodation chamber 26. In this housed state, the tips of the piezoelectric vibrators 40 are brought into contact with and bonded to the corresponding island portions 37 of the diaphragm 29.

Each piezoelectric vibrator 40 expands and contracts in the element longitudinal direction orthogonal to the stacking direction by applying a potential difference between the opposing electrodes, and displaces the elastic film 36 partitioning the pressure chamber 24. That is, in this recording head 3, the piezoelectric vibrator 4
By extending 0 in the element longitudinal direction, the island portion 37 is pushed toward the nozzle plate 28 side, the elastic film 36 around the island portion 37 is deformed, and the pressure chamber 24 contracts. Further, when the piezoelectric vibrator 40 is contracted in the element longitudinal direction, the displacement of the elastic film 36 causes the pressure chamber 24 to expand.
With the expansion and contraction of the pressure chamber 24, the pressure of the ink filled in the pressure chamber 24 changes, and an ink droplet is ejected from the nozzle opening 25 of the flow path unit 22.

Next, the electric drive system of the printer 1 will be described. As shown in FIG. 3, the electric drive system of the printer 1 includes a printer controller 44 and a print engine 45.
It is composed of and.

The printer controller 44 includes an external interface 46 (hereinafter referred to as an external I / F 46).
A RAM 47 that temporarily stores various data, a ROM 48 that stores a control program, a control unit 49 that includes a CPU, an oscillation circuit 50 that generates a clock signal, and a supply to the recording head 3. Drive signal (CO
M) for generating a drive signal, and an internal interface 52 (hereinafter, internal I / F 5) for supplying the print engine 45 with dot pattern data (bitmap data) developed based on the drive signal and print data.
2 ) And.

The external I / F 46 receives, for example, print data including a character code, a graphic function, image data, etc. from a host computer (not shown) or the like. Also, a busy signal (BUSY) and an acknowledge signal (ACK) are sent through the external I / F 46.
Is output to the host computer or the like.

The RAM 47 functions as a reception buffer, an intermediate buffer, an output buffer, and a work memory (not shown). The receiving buffer temporarily stores the print data received via the external I / F 46, the intermediate buffer stores the intermediate code data converted by the control unit 49, and the output buffer stores the dot pattern data.
The dot pattern data is composed of a plurality of bits of print data obtained by decoding (translating) the gradation data.

The ROM 48 stores font data, graphic functions, etc. in addition to a control program (control routine) for performing various data processing.

In addition to performing various controls, the control section 49 reads the print data in the reception buffer and stores the intermediate code data obtained by converting the read print data in the intermediate buffer. In addition, the intermediate code data read from the intermediate buffer is analyzed, and it is developed into dot pattern data by referring to the font data and the graphic function stored in the ROM 48. Further, the control unit 49
Performs necessary decoration processing on the developed dot pattern data and stores this data (print data) in the output buffer.

When the dot pattern data for one line which can be printed by one main scan of the print head 3 is obtained, the control section 49 outputs the dot pattern data (print data) for this one line. , To the recording head 3 through the internal I / F 52. When one line of dot pattern data is output from the output buffer, the expanded intermediate code data is erased from the intermediate buffer, and expansion processing is performed on the next intermediate code data.

The drive signal generation circuit 51 functions as drive signal generation means according to the present invention, and a plurality of drive pulses capable of ejecting ink droplets are arranged in time series and a drive signal adjusted to a reference bias level is generated. Drive signal (COM) for

The drive signal generation circuit 51 generates a forward drive signal COM1 in which a plurality of drive pulses are arranged in a predetermined order in time series during forward scan of the recording head 3.
In the present embodiment, as shown in FIG. 7A, the preparation signal D
P0, a large dot drive pulse DP1, a micro dot drive pulse DP2, a middle dot drive pulse DP3, and a return signal DP4 are arranged in this order to generate a signal.

On the other hand, during the backward scanning of the recording head 3, the drive signal generating circuit 51 generates the backward driving signal COM2 in which the driving pulse generation order is reversed from the forward driving signal COM1. In the present embodiment, as shown in FIG.
A signal in which the preparation signal DP0, the middle dot drive pulse DP3, the micro dot drive pulse DP2, the large dot drive pulse DP1, and the return signal DP4 are arranged in this order is generated.

The structure of the drive signal generating circuit 51,
And each drive signal COM generated by the drive signal generation circuit 51
1 and COM2 will be described later in detail.

The print engine 45 uses the paper feed motor 1
5, a pulse motor 10, and a recording head 3.

The paper feed motor 15 is used for the platen 14 described above.
Is a paper feed drive source for rotating the recording head 3
The recording paper 11 is moved in the sub-scanning direction in synchronism with the recording operation.

The pulse motor 10 is a carriage drive source for moving the carriage 4 on which the recording head 3 is mounted along the main scanning direction.

The recording head 3 is provided with a shift register 54, a latch circuit 55, a level shifter 56, a switch 57, a piezoelectric vibrator 40 and the like. Then, as shown in FIG. 4, the shift register 54, the latch circuit 55, the level shifter 56, the switch 57, and the piezoelectric vibrator 40 are
The shift register elements 54A to 54N and the latch elements 55A to 55 are made to correspond to the respective nozzle openings 25.
N, level shifter elements 56A to 56N, switch element 5
7A to 57N and piezoelectric vibrators 40A to 40N.

The recording head 3 appropriately ejects ink droplets having different ink amounts based on the print data (SI) from the printer controller 44.

That is, during the recording operation, the control unit 49
First, in synchronization with the clock signal (CK) from the oscillation circuit 50, the data of the most significant bit string of the print data (SI) for one dot is serially transmitted from the output buffer, and the shift register elements 54A to Set to 54N.

When the print data for all the nozzle openings 25 ... Has been set in the shift register elements 54A to 54N, the control section 49 sets the latch element 55 at a predetermined timing.
A latch signal (LAT) is output to A to 55N. By this latch signal, the latch elements 55A to 55N latch the print data set in the shift register elements 54A to 54N. The latched print data is supplied to the level shifter elements 56A to 56N which are voltage amplifiers.

When the print data is, for example, "1", each level shifter element 56A to 56N boosts the print data up to a voltage value at which the switch 57 can be driven, for example, several tens of volts. Then, the boosted print data is applied to the switch elements 57A to 57N, and
A to 57N are connected by this print data.
When the print data is "0", for example, the corresponding level shifter elements 56A to 56N do not boost the voltage.
The drive signal (COM) from the drive signal generation circuit 51 is applied to each of the switch elements 57A to 57N, and when the switch elements 57A to 57N are in the connected state,
A drive signal is supplied to the piezoelectric vibrators 40A to 40N connected to the switch elements 57A to 57N.

When the drive signal is applied based on the data of the most significant bit string, the controller 49 subsequently serially transmits the data of the lower one bit string and sets it in the shift register elements 54A to 54N.

The shift register elements 54A to 54
When data is set in N, a latch signal is applied to latch the set data and drive signals are supplied to the piezoelectric vibrations 40A to 40N.

After that, the same operation is repeated up to the least significant bit string while shifting the print data to the lower bit string one bit string at a time. When the operation up to the least significant bit of the print data is performed, the same operation is repeated for the print data of the next dot.

As described above, in the illustrated recording head 3,
Whether or not to apply the drive signal to the piezoelectric vibrator 40 can be controlled by the print data from the controller 49. That is, the drive signal can be applied to the piezoelectric vibrator 40 by setting the print data to "1", and the application of the drive signal to the piezoelectric vibrator 40 can be stopped by setting the print data to "0".

Therefore, the forward drive signal COM of FIG.
1 and the backward drive signal COM2 of FIG. 7B, the drive pulses DP1 to DP3 and the preparation signal DP arranged in time series.
By setting each bit of the print data in correspondence with 0 and the return signal DP4, each signal can be selectively applied to the piezoelectric vibrator 40.

By selecting the drive pulse to be applied to the piezoelectric vibrator 40, a plurality of types of ink droplets having different amounts can be ejected from the same nozzle opening 25.

In the ejection control of ink drops,
The control unit 49, the shift register 54, the latch circuit 55, the level shifter 56, and the switch 57 function as drive pulse selecting means according to the present invention.

Next, the drive signal generating circuit 51 described above will be described. The drive signal generation circuit 51 of this embodiment is
As shown in the block diagram of FIG. 5, the waveform generation circuit 61 and the current amplification circuit 62 are roughly configured.

The waveform generation circuit 61 includes a waveform memory 63,
First waveform latch circuit 64 and second waveform latch circuit 65
An adder 66, a digital-analog converter (D / A converter) 67, and a voltage amplifier circuit 68.

The waveform memory 63 functions as a change amount data storage means for individually storing a plurality of types of voltage change amount data output from the control section 49. This waveform memory 6
A first waveform latch circuit 64 is electrically connected to 3.

Then, the first waveform latch circuit 64 is
The voltage change amount data stored in a predetermined address of the waveform memory 63 is held in synchronization with the timing signal.

The output of the first waveform latch circuit 64 and the output of the second waveform latch circuit 65 are input to the adder 66, and the output side of the adder 66 has the second waveform latch circuit 65.
Are electrically connected. And this adder 66
Functions as change amount data adding means, adds output signals to each other, and outputs the added signals.

The second waveform latch circuit 65 is an output data holding means for holding the data (voltage information) output from the adder 66 in synchronization with the second timing signal. D / A
The converter 67 is electrically connected to the output side of the second waveform latch circuit 65 and converts the output signal held by the second waveform latch circuit 65 into an analog signal. Voltage amplifier circuit 6
Reference numeral 8 is electrically connected to the output side of the D / A converter 67 and amplifies the analog signal converted by the D / A converter 67 up to the voltage of the drive signal.

The current amplifying circuit 62 is electrically connected to the output side of the voltage amplifying circuit 68, performs current amplification on the signal whose voltage is amplified by the voltage amplifying circuit 68, and drives signals COM (COM1, COM2). Is output.

The drive signal generation circuit 51 having the above configuration
Then, prior to the generation of the drive signal, a plurality of change amount data indicating the voltage change amount are individually stored in the storage area of the waveform memory 63. For example, the control unit 49 outputs the change amount data and the address data corresponding to the change amount data to the waveform memory 63. Then, the waveform memory 63 stores the change amount data in the storage area designated by the address data. In the present embodiment, the change amount data is composed of data containing positive and negative information (increase / decrease information), and the address data is composed of a 4-bit address signal.

When a plurality of types of change amount data are stored in the waveform memory 63 in this way, it becomes possible to generate a drive signal.

To generate the drive signal, the change amount data is set in the first waveform latch circuit 64, and the change amount data set in the first waveform latch circuit 64 is set to the second waveform latch circuit 64 at a predetermined update cycle.
It is performed by adding to the output voltage from the waveform latch circuit 65.

In the present embodiment, the first waveform latch circuit 64
Change amount data set to the first waveform latch circuit 6 and the 4-bit address signal input to the waveform memory 63.
4 and the first timing signal input to the input terminal 4. That is, in the waveform memory 63, the target change amount data is selected based on the address signal. Then, when the first timing signal is input, the selected change amount data is read from the waveform memory 63 and held in the first waveform latch circuit 64.

The change amount data held in the first waveform latch circuit 64 is input to the adder 66. Since the output voltage held by the second waveform latch circuit 65 is also input to the adder 66, the output data from the adder 66 is the change amount data held by the first waveform latch circuit 64 and the second value. The output voltage held by the waveform latch circuit 65 has a voltage value that is added. Here, since the change amount data includes positive and negative information, when the change amount data has a positive value, the output data from the adder 66 has a voltage value higher than the output voltage (increases). ). On the other hand, when the change amount data has a negative value, the output data from the adder 66 has a voltage value (decreases) lower than the output voltage. When the change amount data has the value “0”, the output data from the adder 66 has the same voltage value as the output voltage.

The output data from the adder 66 is
The second waveform latch circuit 65 is synchronized with the second timing signal.
It is captured and retained in. That is, the output voltage from the second waveform latch circuit 65 is updated in synchronization with the second timing signal.

Here, the drive signal generating operation will be described based on the specific example of FIG. In this example, the waveform memory 6
The change amount data of “0” is stored in the address A of 3,
The change amount data of + ΔV1 is stored in the address B, and the change amount data of −ΔV2 is stored in the address C.

When the first timing signal is input while the address signal designating the address B is input to the waveform memory 63 (t1), the first waveform latch circuit 64 changes the value of + ΔV1 stored at the address B. The quantity data is read from the waveform memory 63 and held. After that, at the update timing defined by the second timing signal, for example,
At the rising timing of the second timing signal, the second waveform latch circuit 65 takes in and holds the output data from the adder 66 (t2). Here, at the first timing after the supply of the first timing signal, ΔV1 is obtained by adding ΔV1 to the ground potential GND which is the output voltage up to that point.
1 is held as a new output voltage.

After that, when the next update timing arrives after the period ΔT has passed, the second waveform latch circuit 65 adds 2V to the output voltage ΔV1 up to that point, which is ΔV1.
1 (ΔV1 + ΔV1) is held as new output voltage data (t3).

When the next update timing arrives after the period ΔT further elapses, the second waveform latch circuit 65 outputs V
(2ΔV1 + ΔV1) is held as new output voltage data (t4).

With respect to the above address signal, when the change amount data corresponding to the address B is held in the first waveform latch circuit 64, the content of the address signal is switched to the address A after that.

The address signal designating the address A is referred to by the next input of the first timing signal (t5). That is, the first waveform latch circuit 64 reads the change amount data of the value “0” stored in the address A in accordance with the input of the first timing signal from the waveform memory 63 and holds it.

When the change amount data of the value “0” is held in the first waveform latch circuit 64, the output data from the adder 66 has the same voltage value as the output voltage from the second waveform latch circuit 65. Therefore, during the period when the change amount data of the value “0” is held in the first waveform latch circuit 64, even if the update timing defined by the second timing signal arrives, the second waveform latch circuit 65 outputs the data. The output voltage maintains the previous voltage value V (t6, t7).

With the input of the next first timing signal, the change amount data of −ΔV2 corresponding to the address C is held in the first waveform latch circuit 64 (t.
8).

When the change amount data is held, the output voltage from the second waveform latch circuit 65 decreases by ΔV2 each time the update timing defined by the second timing signal arrives (t9 to t14). .

Further, with the input of the next first timing signal, the change amount data of the value "0" which is the change amount data corresponding to the address A is held in the first waveform latch circuit 64 (t.
15) Therefore, at the next update timing, the output voltage from the second waveform latch circuit 65 maintains the previous voltage value (t16).

In this way, the exemplified drive signal generation circuit 5
In No. 1, the waveform of the drive signal COM can be set to a free shape only by outputting the address signal and the timing signal from the control unit 49.

When the voltage value of the drive signal COM is increased, the piezoelectric vibrator 40 of the recording head 3 is charged and contracts in the element longitudinal direction, and the volume of the pressure chamber 24 increases. On the contrary, when the voltage value is reduced, the piezoelectric vibrator 40 discharges electric charges and extends in the element longitudinal direction to reduce the volume of the pressure chamber 24.

Next, the drive signal COM generated by the drive signal generation circuit 51 will be described in detail.

During the forward scan of the recording head 3, the drive signal generating circuit 51, as shown in FIG. 7A, prepare signal DP0, large dot drive pulse DP1, microdot drive pulse DP2, middle dot drive pulse DP3,
Forward drive signal COM arranged in series in order of return signal DP4
1 is generated.

On the other hand, during the backward scan of the recording head 3, the drive signal generation circuit 51 uses the preparation signal DP0, the middle dot drive pulse DP3, the micro dot drive pulse DP2, and the large dot drive pulse as shown in FIG. 7B. D
A backward drive signal COM2 is generated in which P1 and the return signal DP4 are arranged in series.

In these forward drive signal COM1 and backward drive signal COM2, the printing cycle T is, for example, 92.
It is set to 6 μs (microsecond). This printing cycle T is a time given for recording one pixel.

The bias levels of the forward drive signal COM1 and the backward drive signal COM2 are both adjusted to the intermediate potential Vm. This intermediate potential Vm corresponds to the reference bias level in the present invention.

The drive pulses DP1, DP2, DP3 included in these drive signals COM1 and COM2 are
Each of them is configured as a drive pulse capable of ejecting different amounts of ink droplets, and its waveform shape is the same for the forward drive signal COM1 and the backward drive signal COM2.

The microdot drive pulse DP2 is applied to small ink droplets capable of forming microdots (eg, about 3 pL).
(Picoliter) ink droplet] is ejected from the nozzle opening 25.

The exemplified microdot drive pulse DP2
Has a bias level adjusted to the ground potential GND, and the intermediate potential V that is the bias level of the drive signal COM.
It is different from m. That is, this microdot drive pulse DP2 corresponds to the second drive pulse according to the present invention, and its bias level corresponds to the individual bias level according to the present invention.

Then, this microdot drive pulse D
P2 is a second expansion element P6 that raises the potential from the ground potential GND to the second maximum potential Vh2 at a constant gradient that does not eject ink drops, and a second expansion hold that holds the second maximum potential Vh2 for an extremely short time. The element P7, the second ejection element P8 that drops (discharges) the potential from the second maximum potential Vh2 to the discharge potential Vh3 with a steep gradient, the discharge hold element P9 that holds the discharge potential Vh3 for an extremely short time, and the discharge potential Vh.
Discharge element P that lowers the potential from 3 to the ground potential GND
10 and 10.

The microdot drive pulse DP
The microdots formed by the supply of 2 are the dots serving as the position reference of the pixel region (the region where the dots forming one pixel can land). Therefore, the microdot drive pulse DP2 functions as a reference drive pulse.

Then, the drive signal generation circuit 51 generates the microdot drive pulse DP2 at a timing almost midway between the forward drive signal COM1 and the backward drive signal COM2. In other words, the microdot drive pulse DP2
Are arranged in the central portion of the drive signal COM.
Thereby, the microdots are formed in substantially the center of the pixel area in the main scanning direction.

Further, the interval T3 from the start of the printing cycle T in the forward drive signal COM1 to the start end of the second ejection element P8 of the microdot drive pulse DP2 is 45.5 μs.
And the interval T4 from the start of the printing cycle T in the backward drive signal COM2 to the start end of the second ejection element P8 of the microdot drive pulse DP2 is set to 47.1 μs,
The sum of the interval T3 in the forward drive signal COM1 and the interval T4 in the return drive signal COM2 is one printing cycle T (9
It is set to be 2.6 μs).

Further, the middle dot drive pulse DP3 is
Medium ink drops that can form middle dots (eg, about 10
It is configured as a waveform for ejecting a pL ink droplet) from the nozzle opening 25.

The bias level of the illustrated middle dot drive pulse DP3 is adjusted to the intermediate potential Vm which is the bias level (reference bias level) of the drive signal COM. That is, the middle dot drive pulse DP3 corresponds to the first drive pulse according to the present invention.

Then, this middle dot drive pulse DP
The third expansion element P11 increases the potential from the intermediate potential Vm to the third maximum potential Vh4 with a constant gradient that does not eject ink drops, and the third expansion element P11 that holds the third maximum potential Vh4 for a predetermined short time. The third expansion holding element P12 and the third ejection element P13 for decreasing (discharging) the potential from the third maximum potential Vh4 to the intermediate potential Vm at a steep gradient are included.

The generation timing of this middle dot drive pulse DP3 (arrangement location in the drive signal COM) is defined with reference to the micro dot drive pulse DP2.

That is, the cycle of the middle dot drive pulse DP3 and the micro dot drive pulse DP2 in the forward drive signal COM1 and the cycle of the middle dot drive pulse DP3 and the micro dot drive pulse DP2 in the backward drive signal COM2 are set to the same cycle. is doing.

Specifically, the microdot drive pulse D
A second ejection element P8 forming a part of P2 and a third ejection element P13 forming a part of the middle dot drive pulse DP3.
, More specifically, the time from the discharge start timing of the second ejection element P8 to the discharge start timing of the third ejection element P13 is aligned with the same cycle T2 for the forward drive signal COM1 and the backward drive signal COM2.

The large dot drive pulse DP1 is formed as a waveform for ejecting a large ink droplet (for example, an ink droplet of about 20 pL) capable of forming a large dot from the nozzle opening 25.

The bias level of the illustrated large dot drive pulse DP1 is also adjusted to the intermediate potential Vm which is the bias level of the drive signal COM. That is, this large dot drive pulse DP1 also corresponds to the first drive pulse according to the present invention.

Then, this large dot drive pulse DP
The first expansion element P1 increases the potential from the intermediate potential Vm to the first maximum potential Vh1 with a constant gradient that does not eject ink drops, and the first expansion hold element P2 that holds the first maximum potential Vh1 for a predetermined time. And the first maximum potential Vh1
To the ground potential GND, the first ejection element P3 that steeply drops (discharges) the potential, the contraction hold element P4 that holds the ground potential GND for a predetermined time, and the vibration suppression that raises the potential from the ground potential GND to the intermediate potential Vm. And element P5.

The generation timing of the large dot drive pulse DP1 is also defined with reference to the microdot drive pulse DP2.

That is, the cycle of the large dot drive pulse DP1 and the micro dot drive pulse DP2 in the forward drive signal COM1 and the cycle of the large dot drive pulse DP1 and the micro dot drive pulse DP2 in the backward drive signal COM2 are set to the same cycle. is doing.

Specifically, the microdot drive pulse D
Second ejection element P8 of P2 and large dot drive pulse DP
Cycle of the first ejection element P3, specifically, the second ejection element P
The time from the discharge start timing of No. 8 to the discharge start timing of the first ejection element P3 is set to the same cycle T1 for the forward drive signal COM1 and the backward drive signal COM2.

The preparation signal DP0 is a signal selected when the microdot drive pulse DP2 is supplied to the piezoelectric vibrator 40 or when the meniscus (the free surface of the ink exposed at the nozzle openings 25) is slightly vibrated. There is a first correction element P0 that changes the potential from the intermediate potential Vm, which is the bias level of the drive waveform COM, to the ground potential GND, which is the bias level of the microdot drive pulse DP2, with a gentle constant gradient that does not eject ink droplets. I have it.

The first correction element P0 is a waveform element corresponding to the preparatory waveform according to the present invention, and its time width (pulse width) is set to be equal to or greater than the Helmholtz resonance period in the pressure chamber 24 of the recording head 3. There is. In this embodiment,
Since the natural vibration period Tc of the pressure chamber 24 is about 6.5 μs, the time width of the first correction element P0 is set to 6.5 μs which is equal to the Helmholtz resonance period.

As described above, by setting the time width (supply time) of the first correction element P0 in alignment with the Helmholtz resonance period of the pressure chamber 24, the pressure chamber 24 remains when the first correction element P0 is applied. Vibration can be prevented, and the volume of the pressure chamber 24 can be appropriately changed.

This preparation signal DP0 corresponds to which drive signal C
The OM1 and COM2 are also arranged at the forefront of the drive signal. That is, the first correction element P0 as the preparation waveform
Are arranged before the microdot drive pulse DP2 (second drive pulse).

The period from the end of the first correction element P0 in the preparation signal DP0 to the start of the second expansion element P6 in the microdot drive pulse DP2 is the same period T5 for the forward drive signal COM1 and the backward drive signal COM2.
Is set to. The period T5 is set to such a length that the vibration of the meniscus accompanying the supply of the first correction element P0 can be sufficiently converged. In this example, the period T5 is set to 29 μs.

Regarding the preparation signal DP0, the preparation signal DP0 need not be the frontmost portion of the drive signal as long as it is arranged (generated) before the microdot drive pulse DP2. When the drive signal is arranged at the forefront as in the present embodiment, the interval (period) from the first correction element P0 to the second expansion element P6 can be made sufficiently long.
The vibration of the meniscus accompanying the supply of the preparation signal DP0 can be sufficiently converged. This makes it possible to stabilize the amount of small ink droplets (described later).

The return signal DP4 is the same as the preparation signal DP0.
Is a signal to be selected when supplying the electric current to the ground potential or slightly vibrating the meniscus, and is a signal from the ground potential GND to the intermediate potential Vm.
The second correction element P14 that changes the potential with a gentle constant gradient that does not eject ink droplets.

The second correction element P14 is a waveform element corresponding to the return waveform according to the present invention, and its time width (pulse width) is similar to that of the first correction element P0 in the pressure chamber 24 of the recording head 3. It is set to be longer than the Helmholtz resonance period. In the present embodiment, the time width of the second correction element P14 is set to 6.5 μs, which is equal to the Helmholtz resonance period, so that the residual vibration of the pressure chamber 24 due to the application of the second correction element P14 is prevented. There is.

This return signal DP4 is any drive signal C
Also in OM1 and COM2, they are arranged at the end of the drive signal. That is, the first correction element P0 as the return waveform
Are arranged after the microdot drive pulse DP2 (second drive pulse).

Regarding the return signal DP4, the return signal DP4 need not be the last part of the drive signal as long as it is arranged (generated) after the microdot drive pulse DP2. For example, as shown in FIG. 11, the return signal DP4 may be arranged instead of the first connection element Pgm described later.

Then, the above drive pulses DP1 and DP
When the drive signal COM in which 2, 2, DP3, the preparation signal DP0, and the return signal DP4 are arranged in series is generated, there occurs a time when the potential level becomes discontinuous between adjacent signals.

For this reason, the drive signal generation circuit 51 uses the first connection element Pgm that raises the potential level in a very short time or the second connection element that lowers the potential level in a very short time when the potential level becomes discontinuous. The connection element Pmg is appropriately generated and the potential level is changed to achieve matching.

For example, since the termination potential of the preparation signal DP0 is the ground potential GND and the beginning potential of the large dot drive pulse DP1 generated next to this preparation signal DP0 is the intermediate potential Vm, the drive signal generation circuit 51 , Preparation signal D
The first connection element Pgm is generated between P0 and the large dot drive pulse DP1 to raise the ground potential GND to the intermediate potential Vm in an extremely short time.

Similarly, the termination potential of the large dot drive pulse DP1 is the intermediate potential Vm, and the beginning potential of the microdot drive pulse DP2 generated next to this large dot drive pulse DP1 is the ground potential GND, so that the drive is performed. The signal generation circuit 51 generates the second connection element Pmg between the large dot drive pulse DP1 and the microdot drive pulse DP2, and lowers the intermediate potential Vm to the ground potential GND in an extremely short time.

The first connecting element Pgm and the second connecting element Pgm
The connecting element Pmg is a waveform element that is not actually selected, and is not applied as a drive waveform to the piezoelectric vibrator 40.
Will not be damaged or the bonded portion between the piezoelectric vibrator 40 and the island portion 37 or the island portion 37 and the elastic film 36 will not be peeled off.

The drive signal COM (COM1, COM1,
COM2), the bias level of the large dot drive pulse DP1 and the middle dot drive pulse DP3 whose bias level is adjusted to the bias level of the drive signal (intermediate potential Vm, corresponding to the reference bias level of the present invention) and the bias level of the drive signal The microdot drive pulse DP2 adjusted to different bias levels (ground potential GND, corresponding to the individual bias level of the present invention) is mixed, and the preparation signal DP0 is arranged before the microdot drive pulse DP2 to drive the microdot drive. The return signal DP4 is arranged after the pulse DP2. Further, at the time when the potential levels of adjacent signals become discontinuous, the first connection element Pgm
The second connection element Pmg is generated to match the potential level.

Then, the microdot drive pulse DP2
When supplying the electric field to the piezoelectric vibrator 40, drive pulse selecting means (control section 49, shift register 54, latch circuit 5
5, the level shifter 56 and the switch 57) select the preparation signal DP0 and the return signal DP4 together as described later.

As a result, the microdot drive pulse D
Since the preparation signal DP0 is supplied before P2 is supplied, the microdot drive pulse DP2 is supplied with the potential of the piezoelectric vibrator 40 lowered from the intermediate potential Vm to the ground potential GND. Then, since the return signal DP4 is supplied after the microdot drive pulse DP2 is supplied, the potential of the piezoelectric vibrator 40 that has dropped to the ground potential GND with the supply of the microdot drive pulse DP2 is restored to the intermediate potential Vm. It

As a result, even if a plurality of drive pulses having different bias levels are included in the drive signal, the maximum potential of the drive signal can be suppressed to a low level, and the drive signal can be kept within a limited potential level range. it can. In addition, it is possible to prevent damage to the elements forming the drive circuit, and to use an inexpensive element having a low breakdown voltage as the element forming the drive circuit.

Further, as in this embodiment, by setting the individual bias level to the ground potential GND, the maximum potential of the drive signal COM (V in the exemplified drive signal is
h2) can be kept low.

Next, the recording operation of the printer 1 will be described.

In this recording operation, the type of ink droplet to be ejected is selected according to the image data. For example, a large dot (large ink droplet) is recorded in a portion where the image gradation is relatively dark, and a micro dot (small ink droplet) is recorded in the comparatively light portion, and a gradation corresponding to the middle thereof is recorded. Recording is performed by middle dots (medium ink droplets) on the portion.

Further, in this recording operation, the dots (pixels) in the backward scan are recorded between the dots (pixels) recorded in the forward scan. For example, as shown in FIG. 10, during the forward scan of the recording head 3, dots during the forward scan indicated by a white circle are printed. Then, during the backward scan of the recording head 3, the backward scan dots indicated by the shaded circles are recorded between the adjacent forward scan dots.

Then, at the time of forward scanning of the recording head 3,
Print data (forward print data) corresponding to each signal forming the forward drive signal COM1 is used.

As shown in FIG. 8, the print data includes the data D0 as the preparation signal DP0, the data D1 as the large dot drive pulse DP1, the data D2 as the microdot drive pulse DP2, and the data D3 as the middle dot drive pulse. 5-bit data D0, D1, D2, D3, D in which data D4 is made to correspond to the return signal DP4, respectively, at DP3
It is composed of four.

During forward scanning of the recording head 3, the control section 49 selects ink droplets to be ejected by appropriately changing the print data D0, D1, D2, D3, D4.

That is, when recording microdots on the recording paper 11, the control unit 49 sets the print data to D0 = 1, D.
Set 1 = 0, D2 = 1, D3 = 0, D4 = 1. When recording the middle dots, the control unit 49 sets the print data to D0 = 0, D1 = 0, D2 = 0, D3 = 1, D4 = 0.
Set to. When recording large dots, the control unit 49
Print data D0 = 0, D1 = 1, D2 = 0, D3
= 0 and D4 = 0. When the meniscus is slightly vibrated, the control unit 49 sets the print data to D0 =
1, D1 = 0, D2 = 0, D3 = 0, D4 = 1.

On the other hand, at the time of the backward scan of the recording head 3, the print data (return pass print data) corresponding to each signal forming the backward drive signal COM2 is set.

As shown in FIG. 9, this print data includes data D0 as a preparation signal DP0, data D1 as a middle dot drive pulse DP3, data D2 as a micro dot drive pulse DP2, and data D3 as a large dot drive pulse. 5-bit data D0, D1, D2, D3, D in which the data D4 is made to correspond to the return signal DP4 in the DP1
It is composed of four.

Then, even during the backward scan of the recording head 3, the control section 49 controls the print data D0, D1, D2, D
The ink to be ejected is selected by appropriately changing 3 and D4.

That is, when recording microdots, the control section 49 sets the print data to D0 = 1, D1 = 0, D2 =
1, D3 = 0 and D4 = 1 are set. When recording the middle dots, the control unit 49 sets the print data to D0 = 0, D
Set 1 = 1, D2 = 0, D3 = 0, D4 = 0. When recording a large dot, the control unit 49 sets the print data to D0 = 0, D1 = 0, D2 = 0, D3 = 1, D4 = 0.
Set to. When the meniscus is slightly vibrated, the control unit 49 sets the print data to D0 = 1, D1 = 0,
Set D2 = 0, D3 = 0, and D4 = 1.

Drive pulse selecting means (49, 54, 55, 56, based on the above-mentioned microdot print data)
57) selects the preparation signal DP0, the microdot drive pulse DP2, and the return signal DP4. By this selection, these signals DP0, DP2, and DP4 are sequentially supplied to the piezoelectric vibrator 40.

In this case, first, the pressure chamber 24 is contracted relatively slowly by the first correction element P0 from the reference volume corresponding to the intermediate potential Vm to the minimum volume corresponding to the ground potential GND, and this pressure chamber 24 is maintained over the period T5. The minimum volume is maintained.

Then, the second expansion element P6 expands the pressure chamber 24 from the minimum volume to the second maximum volume corresponding to the maximum potential Vh2. As a result, the pressure chamber 24 expands relatively rapidly and the inside of the pressure chamber 24 becomes negative pressure, and the meniscus is largely drawn into the inside of the pressure chamber 24.

Here, the pressure chamber 24 maintains a constant volume over a period T5 from the supply of the first correction element P0 to the supply of the second expansion element P6. This is to sufficiently converge the vibration of the meniscus accompanying the supply of the first correction element P0. That is, this microdot drive pulse D
Since a very small amount of ink droplets are ejected at P2, if the microdot drive pulse DP2 is supplied in a state where the meniscus is vibrating greatly, the amount of ink droplets will vary due to the vibration of the meniscus.

Therefore, after the first correction element P0 is supplied, the constant volume of the pressure chamber 24 is maintained for a period T5 to sufficiently converge the vibration of the meniscus before the second expansion element P6.
Is supplied so that the ink amount of the small ink droplets is made uniform.

Further, in this embodiment, the first correction element P
The period from when 0 is supplied to when the second expansion element P6 is supplied is the forward drive signal COM1 and the backward drive signal COM.
Both 2 and 2 are aligned in the period T5. Accordingly, the vibration state of the meniscus at the time of starting the supply of the second expansion element P6 can be made the same in the forward scan and the backward scan, and the ink amount of the small ink droplets can be made uniform in the forward scan and the backward scan. You can

When the second expansion element P6 is supplied, the second expansion hold element P7 is supplied for a very short time. After that, the pressure chamber 24 is rapidly contracted by the second discharge element P8 to the intermediate volume corresponding to the discharge potential Vh3, and this intermediate volume is maintained by the discharge hold element P9 for a very short time. With the supply of the second ejection element P8 and the discharge hold element P9, small ink droplets are generated in the nozzle opening 2
Discharge from 5.

After that, the pressure chamber 24 is contracted by the discharge element P10 at such a speed as not to eject ink droplets from the intermediate volume to the minimum volume, maintains this minimum volume, and is expanded to the reference volume by the second correction element P14. Return.

Based on the above-mentioned print data of the middle dots, the drive pulse selecting means determines the middle dot drive pulse D
Select P3. Then, the selected middle dot drive pulse DP3 is supplied to the piezoelectric vibrator 40.

When the middle dot drive pulse DP3 is supplied, first, the pressure chamber 2 is moved by the third expansion element P11.
4 expands from the reference volume corresponding to the intermediate potential Vm to the third maximum volume corresponding to the third maximum potential Vh4. Then, after the expansion state of the pressure chamber 24 is maintained for an extremely short time by the third expansion hold element P12, the pressure chamber 24 is rapidly contracted from the third maximum volume to the reference volume by the third discharge element P13. To do. Due to the rapid contraction of the pressure chamber 24, the ink pressure in the pressure chamber 24 increases, and a medium ink droplet is ejected from the nozzle opening 25.

On the basis of the above-mentioned large dot print data, the drive pulse selecting means sets the large dot drive pulse D
Select P1. Then, the selected large dot drive pulse DP1 is supplied to the piezoelectric vibrator 40.

When the large dot drive pulse DP1 is supplied, first, the pressure chamber 24 is moved by the first expansion element P1.
Expands from the reference volume corresponding to the intermediate potential Vm to the first maximum volume corresponding to the first maximum potential Vh1.

After the expanded state of the pressure chamber 24 is maintained for a predetermined time by the first expansion hold element P2, the first expansion hold element P2
The pressure chamber 24 is rapidly contracted by the ejection element P3 to the minimum volume corresponding to the ground potential GND, and the contraction hold element P4 maintains the state of the minimum volume for a predetermined time. Due to the rapid contraction of the pressure chamber 24, the ink pressure in the pressure chamber 24 increases, and a large ink droplet is ejected from the nozzle opening 25.

When a large ink droplet is ejected, the damping element P5
Thereby, the pressure chamber 24 expands and returns from the minimum volume to the reference volume. With the expansion and return of the pressure chamber 24, the vibration of the meniscus converges in a relatively short time.

On the basis of the print data of the above-mentioned slight vibration, the drive pulse selecting means sets the preparation signal DP0 and the return signal DP4.
Select and. Then, the selected preparation signal DP0 and the selected return signal DP4 are sequentially supplied to the piezoelectric vibrator 40. That is, the preparation signal DP0 (the first correction element P0 as the preparation waveform) and the return signal DP4 (the second correction element P14 as the return waveform) are used as the in-print micro-vibration waveform.

When this in-print minute vibration waveform is supplied, first, the pressure chamber 24 is relatively slowly moved from the reference volume corresponding to the intermediate potential Vm to the minimum volume corresponding to the ground potential GND by the first correction element P0. Contract. Along with this contraction, the pressure chamber 24 is slightly pressurized, and the meniscus slightly moves in the ink ejection direction. The contracted state of the pressure chamber 24 is maintained until the second correction element P14 is supplied, during which the meniscus slightly vibrates due to residual vibration. Then, the second correction element P14 causes the pressure chamber 24 to relatively slowly expand and return to the reference volume.

In this embodiment, the forward drive signal COM1 in which the drive pulses DP1, DP2, DP3 are arranged in a predetermined order as described above is generated during the forward scan of the recording head 3, and the drive pulses DP1, DP2 are generated. , DP3 are arranged in the reverse order of the forward drive signal COM1, the backward drive signal C
OM2 is generated during the backward scan of the recording head 3, and bidirectional recording is performed using these drive signals COM1 and COM2.

As a result, as shown in FIG. 10, the intervals between adjacent dots can be made uniform. This is because the ejection order of ink droplets during forward scanning and the ejection order of ink droplets during backward scanning are reversed.

That is, since the scanning direction of the recording head 3 is opposite between the forward scan and the backward scan, the print cycle T
The ink droplets ejected in the early stage land on one end side in the main scanning direction in the pixel region during the forward scan, and land on the other end side in the main scanning direction in the pixel region during the backward scan. Similarly, the ink droplets ejected in the latter part of the printing cycle T land on the other end side of the pixel region in the main scanning direction during the forward scan, and land on one end side of the pixel region in the main scanning direction during the backward scan.

Here, if the order of the drive pulses in the backward drive signal COM2 is reversed from the order of the drive pulses in the forward drive signal COM1, the drive pulse previously arranged in the forward drive signal COM1 during the forward scan. Are arranged later in the backward drive signal COM2 during the backward scan. That is, the ink droplets ejected first during the forward scan of the recording head 3 are ejected later during the backward scan of the recording head 3.

Therefore, for the same amount (type) of ink droplets, the landing positions on the main scanning direction side in the pixel area are aligned with the ink droplets ejected during forward scanning and the ink droplets ejected during backward scanning. Therefore, the intervals between adjacent dots can be made uniform.

Further, the forward drive signal COM during the forward scan is used.
Regarding 1 and the backward drive signal COM2 during the backward scan, in the present embodiment, the cycle between the ejection elements of the adjacent drive pulses in the forward drive signal COM1 during the forward scan corresponds to the drive signal COM2 during the backward scan. The cycle of the discharge elements is set to the same time.

For example, the microdot drive pulse DP2
As for the second ejection element P8 and the first ejection element P3 of the large dot drive pulse DP1, the same period T is used for the forward drive signal COM1 and the backward drive signal COM2 as described above.
1 is aligned. Similarly, the microdot drive pulse D
Second ejection element P8 of P2 and middle dot drive pulse DP
For the third ejection element P13 of No. 3, the forward drive signal C
The same cycle T2 is set for the OM1 and the homeward drive signal COM2.

In this way, if the periods T1 and T2 of the ejection elements of the adjacent drive pulses are made uniform by the forward drive signal COM1 during the forward scan and the backward drive signal COM2 during the backward scan, the type (quantity) It is possible to make the amount of deviation of the landing positions of the ink droplets different from each other the same between the forward scan and the backward scan. For example, the distance W1 from the landing center of a small ink drop to the landing center of a large ink drop and the distance W2 from the landing center of a small ink drop to the landing center of a medium ink drop are the same during forward scanning and backward scanning. Can be set to.

Therefore, by adjusting the ink droplets that serve as the position reference, that is, the small ink droplets in this embodiment, to land at regular intervals, the impact positions of other ink droplets can also be aligned at regular intervals.

With respect to this point, in the present embodiment, as described above, the second drive signal COM1 in the forward drive signal during forward scan is used.
The sum of the period T3 (45.5 μs) to the ejection element P8 and the period T4 (47.1 μs) to the second ejection element P8 in the drive signal COM2 at the time of the backward scan is the printing cycle T.
It is set to be (92.6 μs).

Thus, if the width of the pixel area is W,
During the forward scan of the recording head 3, the microdots
From one end of the pixel area in the main scanning direction to W × (45.5 / 92.
6) Land at position W3. On the other hand, during the forward scan of the recording head 3, the microdots land on the position W4 of W × (47.1 / 92.6) from the other end of the pixel area in the main scanning direction.

The interval between the adjoining forward scanning microdots and the backward scanning microdots is W3 +
W4, that is, W. Therefore, the distance between the microdots recorded during the forward scan and the microdots recorded during the backward scan is constant at W. As a result, it is possible to surely prevent the image from having a rough feeling and further improve the image quality.

In the embodiment described above, the driving pulse for ejecting the ink droplet is set to 3 within one printing cycle T.
Although the description has been given by taking as an example the drive signals provided individually, the number of drive pulses is not limited to three. For example, the drive signal may include four drive pulses within one printing cycle T, or the drive signal may include five or more drive pulses.

Further, regarding the drive signal generation circuit 51, in the present embodiment, the change amount data set in the first waveform latch circuit 64 is changed to the second waveform latch circuit for each predetermined update cycle defined by the second timing signal. An example in which a waveform having an arbitrary shape can be generated by adding to the output voltage of 65 has been described, but the configuration is not limited to this.

For example, an analog circuit constitutes a first drive signal generating circuit for generating the forward drive signal COM1 and a second drive signal generating circuit for generating the backward drive signal COM2, which are provided in the printer controller 44 to perform the forward scan. The forward drive signal COM1 from the first drive signal generation circuit may be supplied to the recording head 3 at times, and the return drive signal COM2 from the second drive signal generation circuit may be supplied to the recording head 3 during the backward scan. .

Further, the pressure generating element that causes the pressure fluctuation in the pressure chamber 24 is not limited to the piezoelectric vibrator 40. For example, a magnetostrictive element may be used as the pressure generating element. Further, the heating element may be used as the pressure generating element, and the pressure fluctuation may be generated in the pressure chamber 24 by the bubbles expanded and contracted by the heat generated by the heating element.

[0181]

As described above, according to the present invention, the following excellent effects are exhibited.

That is, the drive signal generated by the drive signal generating means is the first drive pulse having the reference bias level which is the bias level in the drive signal and the second drive pulse having the individual bias level different from the reference bias level. ,
Including a preparatory waveform that changes the potential from the reference bias level to the individual bias level, and a return waveform that changes the potential from the individual bias level to the reference bias level,
Waveform elements that are not selected during the second drive pulse selection are included before and after the second drive pulse, and waveform elements that are not selected during the second drive pulse selection before the second drive pulse are included in the preparatory waveform. In the case where the waveforms are arranged so as to sandwich the waveform element that is not selected in selecting the second drive pulse after the second drive pulse and the return waveform is sandwiched, and the drive pulse selecting means selects the second drive pulse. Then, the preparatory waveform and the return waveform are selected together.

Therefore, the preparation waveform is supplied before the second drive pulse is supplied, and the second drive pulse is supplied in the state where the potential changes from the reference bias level to the individual bias level. Further, the return waveform is supplied after the second drive pulse is supplied, and the potential that has become the individual bias level due to the supply of the second drive pulse is returned to the reference bias level.

As a result, even when a plurality of drive pulses having different bias levels are included in the drive signal, the maximum potential of the drive signal can be suppressed to a low level, and the drive signal can be kept within the range of the limited potential level. it can.

[Brief description of drawings]

FIG. 1 is a perspective view illustrating an internal structure of a printer.

FIG. 2 is a sectional view illustrating a configuration of a recording head.

FIG. 3 is a block diagram illustrating an electrical configuration of a printer.

FIG. 4 is a diagram illustrating an electrical configuration of a recording head.

FIG. 5 is a block diagram illustrating an electrical configuration of a drive signal generation circuit.

FIG. 6 is a timing chart illustrating a drive signal generation procedure by the drive signal generation circuit.

7A and 7B are diagrams illustrating drive signals according to the present invention, in which FIG. 7A shows a drive signal during forward scanning, and FIG. 7B shows a drive signal during a return operation.

FIG. 8 is a diagram illustrating a relationship between a drive signal at the time of forward scan and a drive pulse supplied to the print head according to the present invention.

FIG. 9 is a diagram illustrating a relationship between a drive signal and a drive pulse supplied to the recording head during a return operation according to the present invention.

FIG. 10 is a diagram illustrating a positional relationship between dots printed during forward scan and dots printed during return operation.

11A and 11B are diagrams illustrating another drive signal according to the present invention, in which FIG. 11A shows a drive signal during forward scanning, and FIG. 11B shows a drive signal during return operation.

[Explanation of symbols]

1 printer 2 Cartridge holder 3 recording head 4 carriage 5 housing 6 Guide member 7 Drive pulley 8 idle pulley 9 Timing belt 10 pulse motor 11 Recording paper 12 Wiper mechanism 13 Capping mechanism 14 Platen 15 Paper feed motor 21 cases 22 Channel unit 23 Transducer unit 24 Pressure chamber 25 nozzle opening 26 accommodation room 27 spacer 28 nozzle plate 29 diaphragm 31 common ink chamber 32 ink supply path 33 Ink supply pipe 34 ink cartridges 35 stainless steel plate 36 Elastic Membrane 37 Island 40 Piezoelectric vibrator 41 fixing member 44 Printer controller 45 print engine 46 External interface 47 RAM 48 ROM 49 control unit (driving pulse selection means) 50 oscillation circuit 51 drive signal generation circuit (drive signal generation means) 52 Internal interface 54 shift register (driving pulse selection means) 55 Latch circuit (drive pulse selection means) 56 level shifter (drive pulse selection means) 57 switch (drive pulse selection means) 61 Waveform generation circuit 62 Current amplification circuit 63 waveform memory 64 First Waveform Latch Circuit 65 Second Waveform Latch Circuit 66 adder 67 Digital-to-analog conversion circuit 68 Voltage amplification circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-10-193587 (JP, A) JP-A-11-277744 (JP, A) JP-A-3-235668 (JP, A) JP-A-9- 52360 (JP, A) JP-A-8-174868 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B41J 2/045 B41J 2/055

Claims (12)

(57) [Claims] 1. A pressure chamber communicating with a nozzle opening and a pressure generating element capable of generating pressure fluctuation in the pressure chamber,
A recording head capable of reciprocating along the main scanning direction, a drive signal generating means for generating a drive signal adjusted to a reference bias level while a plurality of drive pulses for ejecting ink droplets are arranged in time series, and a drive signal. An ink jet recording apparatus comprising: a drive pulse selecting unit that selects a drive pulse from the drive signal generated by the generating unit; and supplying the drive pulse selected by the drive pulse selecting unit to a pressure generating element to eject an ink droplet from a nozzle opening. In the drive signal generated by the drive signal generating means, a first drive pulse having a reference bias level, a second drive pulse having an individual bias level different from the reference bias level,
Including a preparatory waveform that changes the potential from the reference bias level to the individual bias level, and a return waveform that changes the potential from the individual bias level to the reference bias level,
Before and after the second drive pulse, there are waveform elements that are not selected during the selection of the second drive pulse, and the preparatory waveform is selected during the selection of the second drive pulse before the second drive pulse. Are arranged so as to sandwich a waveform element that is not selected, and the return waveform is arranged after the second drive pulse so as to sandwich a waveform element that is not selected when the second drive pulse is selected. An ink jet recording apparatus, wherein a drive waveform and a return waveform are selected at the same time when the drive pulse is selected. 2. The waveform element that is not selected when selecting the second drive pulse is the connection element that is not applied as a drive waveform to the piezoelectric generating element and the first drive pulse. Inkjet recording device. 3. The drive signal generating means generates a forward drive signal in which a plurality of drive pulses are arranged in a predetermined order during forward scanning of the recording head, and each drive pulse is arranged in the reverse order of the forward drive signal. The moving drive signal is generated during the backward scan of the recording head, and the period from the end of the preparation waveform in the forward drive signal to the start of the second drive pulse and the end of the preliminary waveform in the backward drive signal from the second end of the second drive pulse The ink jet recording apparatus according to claim 1 or 2, wherein the period up to the start end is made uniform. 4. The ink jet recording apparatus according to claim 1, wherein the preparatory waveform is arranged at a foremost portion in the drive signal. 5. The ink jet recording apparatus according to claim 1, wherein a time width of the preparatory waveform is set to be equal to or greater than a Helmholtz resonance period in the pressure chamber. 6. The ink jet recording apparatus according to claim 1, wherein a time width of the return waveform is set to be a Helmholtz resonance period or more in the pressure chamber. 7. The ink jet recording apparatus according to claim 1, wherein the preparatory waveform and the return waveform are set to a potential gradient that does not eject ink droplets. 8. The ink jet recording apparatus according to claim 1, wherein the individual bias level is set to a ground potential. 9. The second drive pulse is a reference drive pulse capable of ejecting an ink droplet that serves as a position reference in a pixel region, and the drive signal generating means is a forward drive in which a plurality of drive pulses are arranged in a predetermined order. A signal is generated during the forward scan of the printhead, and each drive pulse is arranged in the reverse order of the forward drive signal. A backward drive signal is generated during the backward scan of the printhead, and the print cycle of the forward drive signal is started. To the start end of the ejection element of the reference drive pulse and the interval from the start of the printing cycle in the backward drive signal to the start end of the ejection element of the reference drive pulse to generate a series of drive signals with one printing cycle Claim 1 characterized by the above.
9. The inkjet recording device according to claim 8. 10. The drive signal generating means generates a forward drive signal in which a plurality of drive pulses are arranged in a predetermined order during forward scan of the recording head, and each drive pulse is arranged in the reverse order of the forward drive signal. Driving in which the drive signal for movement is generated during the backward scan of the print head, and the interval between ejection elements of adjacent drive pulses in the forward drive signal is the same as the interval between corresponding ejection elements in the backward drive signal. The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus generates a signal. 11. The ink jet system according to claim 1, wherein the preparatory waveform and the return waveform are used as an in-print micro-vibration waveform for performing an in-print micro-vibration. Recording device. 12. The method according to claim 1, wherein the second drive pulse is located at the center of a plurality of drive pulses arranged in time series within one printing cycle. The ink jet recording apparatus described.