JP2002337334A - Ink jet recorder and its driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recorder in which troubles, e.g. abnormal ejection, can be prevented by limiting the oscillator voltage to a low level during interruption period of a driving signal. SOLUTION: A driving signal generating circuit 9 generates an ejection pulse having a set of an element for lowering the potential from an intermediate level down to a base level, an element for raising the potential from the base level to the intermediate level, and an ejection waveform element between the potential lowering element and the potential raising element. A shift register circuit 41, a latch circuit 42, a decoder 43, a control logic 44, a level shifter 45 and a switch circuit 46 select the ejection waveform element when recording is performed using that ejection pulse and select a pair of the potential lowering element and the potential raising element when recording is not performed.

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 having a recording head capable of ejecting ink droplets from nozzle openings by operating a piezoelectric vibrator, and a driving method thereof.

[0002]

2. Description of the Related Art Ink jet recording apparatuses such as printers, plotters, and facsimile apparatuses perform recording by ejecting ink droplets from a recording head and landing the ink droplets on a print recording medium such as recording paper or a print film. . As a recording head used in this recording apparatus, a recording head using a piezoelectric vibrator (so-called PZT) as a pressure source is suitably used.

[0003] This piezoelectric vibrator operates like a capacitor, and when the supply of the drive signal is cut off, holds the potential just before the cutoff. In the recording apparatus utilizing this operation characteristic, recording is performed by using a drive signal composed of a plurality of waveform elements and selectively supplying the waveform elements to the piezoelectric vibrator. For example, when an ejection waveform element for ejecting an ink droplet is included in a drive signal and an ink droplet is ejected, the ejection waveform element is supplied to a piezoelectric vibrator. On the other hand, when the ink droplet is not ejected, the supply of the drive signal to the piezoelectric vibrator is interrupted immediately before the ejection waveform element is generated, and the supply of the drive signal to the piezoelectric vibrator is restarted after the generation period. In this case, no drive signal is supplied to the piezoelectric vibrator during the period during which the ejection waveform element is generated.

[0004]

By the way, the piezoelectric vibrator can hold the potential just before the cutoff, but the potential gradually decreases due to spontaneous discharge or the like. It is known that the degree of decrease in the potential is higher as the potential immediately before the interruption is higher, and is higher as the humidity of the use environment is higher. And
If the vibrator potential drops significantly, the vibrator potential sharply rises to the drive signal potential when supply of the drive signal is restarted, and the piezoelectric vibrator is deformed. As a result, the ink pressure in the pressure chamber is disturbed, or abnormal ejection of ink droplets occurs.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an ink jet recording apparatus capable of suppressing the potential of a vibrator during a drive signal cut-off period and preventing problems such as abnormal ejection. And a driving method thereof.

[0006]

SUMMARY OF THE INVENTION The present invention has been proposed to achieve the above-mentioned object, and a piezoelectric vibrator capable of causing a pressure fluctuation in a pressure chamber and a pressure transducer according to the first aspect of the present invention. A recording head having a nozzle opening communicating with a chamber, a driving signal generating means for generating a series of driving signals including a plurality of waveform elements, and a driving signal generated by the driving signal generating means in accordance with recording data. A drive element generating means for selecting a waveform element and supplying the selected waveform element to the piezoelectric vibrator; Element, a potential rising element for increasing the potential from the base potential to the intermediate potential, and a discharge pulse having a set of a discharge waveform element sandwiched between the potential lowering element and the potential rising element The waveform element supply means selects an ejection waveform element when recording is performed by the ejection pulse, and selects a pair of a potential lowering element and a potential increasing element when not performing recording. It is an ink jet recording apparatus characterized by the following.

According to a second aspect of the present invention, the connection between the potential lowering element and the discharge waveform element and between the discharge waveform element and the potential rise element by a connection element that is not supplied to the piezoelectric vibrator. The ink jet recording apparatus according to claim 1, wherein:

According to a third aspect of the present invention, there is provided the ink jet recording apparatus according to the first or second aspect, wherein the base potential is set to the lowest potential in the drive signal.

According to a fourth aspect of the present invention, the generation times of the potential decreasing element and the potential increasing element are set to be equal to the natural oscillation period of the pressure chamber.
An ink jet recording apparatus according to any one of the above.

According to a fifth aspect of the present invention, the driving signal generating means generates a series of driving signals including a plurality of ejection pulses within a recording cycle. An ink jet recording apparatus according to any one of the above.

According to a sixth aspect of the present invention, there is provided the ink jet recording apparatus according to any one of the first to fifth aspects, wherein the ejection pulse includes a plurality of ejection waveform elements. .

An ink jet recording apparatus according to claim 7, wherein a series of drive signals including a plurality of waveform elements are generated and a waveform element selected from the drive signals is supplied to a piezoelectric vibrator of an ink jet type recording head. In the driving method, the driving signal includes a potential decreasing element for decreasing the potential from the intermediate potential to the base potential, a potential increasing element for increasing the potential from the base potential to the intermediate potential, and a potential decreasing element and a potential increasing element. An ejection pulse having a set of selected ejection waveform elements is included. When recording is performed using the ejection pulse, the ejection waveform element is selected. When recording is not performed, a potential decreasing element and a potential increasing element are paired. And a selection method.

[0013]

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 printer to which the present invention is applied.

The illustrated printer 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 or the like (not shown).
(Hereinafter referred to as an external I / F 3), a RAM 4 for storing various data, a ROM 5 for storing routines for various data processing, and a control unit 6 including a CPU and the like.
Oscillating circuit 7 for generating a clock signal (CK), a driving signal generating circuit 9 for generating a driving signal (COM) to be supplied to the recording head 8, and transmitting dot pattern data and driving signals to the print engine 2. (Hereinafter referred to as an internal I / F 10).

The external I / F 3 receives, for example, any one of character code, graphic function, and image data or print data including a plurality of data from a host computer or the like. The external I / F3 is
It outputs a busy signal (BUSY), an acknowledge signal (ACK), and the like to the host computer.

The RAM 4 is used as a reception buffer, an intermediate buffer, an output buffer, a work memory (not shown), and the like. An external I / O
The print data from the host computer received by F3 is temporarily stored. The intermediate buffer stores the intermediate code data converted into the intermediate code by the control unit 6. In the output buffer, dot pattern data, that is, print data indicating print / non-print for each dot is developed. The ROM 5 stores various control routines executed by the control unit 6, font data and graphic functions, various procedures, and the like.

The drive signal generation circuit 9 functions as drive signal generation means in the present invention, and as shown in FIG. 3, a series of drive signals (COM) having a single ejection pulse PS1 in the recording cycle T. Occurs. This ejection pulse P
S1 is a potential decreasing element P1 for decreasing the potential at a constant gradient from the intermediate potential VM to the minimum potential VL (a kind of base potential of the present invention), an ejection waveform element P2 for ejecting ink droplets, and a minimum potential VL. Rising element P3 that raises the potential at a constant gradient from to a middle potential VM, and a first connection element P that connects the potential falling element P1 and the ejection waveform element P2.
4 and a second connection element P5 for connecting the ejection waveform element P2 and the potential increasing element P3, and each of these waveform elements P1
To P5 are one set. Then, the drive signal generation circuit 9 repeatedly generates the drive signal for each recording cycle T. The drive signal will be described later in detail.

The control section 6 reads out the print data in the reception buffer, converts it into an intermediate code, and stores the intermediate code data in the intermediate buffer. The control unit 6 analyzes the intermediate code data read from the intermediate buffer,
With reference to the font data and graphic functions in the OM5, the intermediate code data is converted into the recording data (S
Expand to I). Note that the recording data in the present embodiment is configured by 1-bit data.

The developed print data is stored in the output buffer and is stored in one line (one raster corresponding to one main scan).
Is obtained, this one row of print data is serially transmitted to the print head 8 via the internal I / F 10. When one line of print data is output from the output buffer, the contents of the intermediate buffer are deleted, and the control unit 6 generates the next line of print data.

The control section 6 constitutes a part of timing signal generating means, and supplies a latch signal (LAT) and a channel signal (CH) to the recording head 8 through the internal I / F 10. These latch signals and channel signals define supply start timings of the waveform elements P1 to P5 constituting the drive signal. In other words, the latch signal and the channel signal serve as triggers for defining the generation timing of the timing signal supplied from the control logic to the decoder.

More specifically, as shown in FIG. 3, the latch signal LAT defines the supply start timing of the potential falling element P1, which is the first waveform element in the ejection pulse PS1. The first channel signal CH1 defines the supply start timing of the first connection element P4, which is the second waveform element, and the second channel signal CH2, the discharge waveform element P2 of the third waveform element. Specifies the supply start timing. Similarly, the third channel signal CH3
Defines the supply start timing of the second connection element P5, which is the fourth waveform element, and specifies the fourth channel signal CH4
Specifies the supply start timing of the potential rising element P3 which is the fifth waveform element.

The first connection element P4 and the second connection element P
5 is not supplied to the piezoelectric vibrator irrespective of the content of the recording data, as described later. Therefore, the first channel signal CH1 and the third channel signal CH3 can be rephrased as signals for defining the cutoff timing of the drive signal.

Further, the control section 6 also functions as a total vibrator potential adjusting means, and supplies a driving signal to all the piezoelectric vibrators 11 at once in the initial period of the recording cycle T. Therefore, the control unit 6 appropriately supplies an enable signal (EN) and an N-charge signal (NCHG) to the gate circuit 12.

The print engine 2 includes a recording head 8 and
A carriage mechanism 13 and a paper feed mechanism 14 are provided.

The carriage mechanism 13 includes a carriage on which the recording head 8 is mounted, a pulse motor for moving the carriage via a timing belt or the like, and moves the recording head 8 in the main scanning direction. The paper feed mechanism 14 includes a paper feed motor, a paper feed roller, and the like.
Sub-scanning is performed by sequentially sending out recording paper (a type of print recording medium).

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 11 in a so-called flexural vibration mode is attached, and is schematically constituted by a channel unit 21 and an actuator unit 22.

The flow path unit 21 has a supply port forming substrate 25 having a through hole serving as an ink supply port 23 and a part of the first nozzle communication hole 24, and a through hole serving as a common ink chamber 26. An ink chamber forming substrate 28 having a through hole serving as a second nozzle communication hole 27 and a nozzle plate 30 having a plurality of (for example, 64) nozzle openings 29 formed along the sub-scanning direction. Then, the nozzle plate 30 is provided on the front side (the lower side in the figure) of the ink chamber forming substrate 28.
The supply port forming substrate 25 is disposed on the back side (same upper side), and the supply port forming substrate 25, the ink chamber forming substrate 28, and the nozzle plate 30 are integrated.

The actuator unit 22 includes a first lid member 31 functioning as an elastic plate, a pressure chamber forming substrate 33 having a through hole serving as a pressure chamber 32, and a supply side communication hole 34.
A second lid member 35 having a through hole serving as a part of the first nozzle communicating hole 24 and the piezoelectric vibrator 11 is provided. Then, the first lid member 31 is disposed on the back surface of the pressure chamber forming substrate 33 and the second lid member 35 is disposed on the front surface thereof, and the first lid member 31 and the second lid member 35 form the pressure chamber forming substrate. 33 are integrated.

The piezoelectric vibrator 11 is formed on the back side of the first lid member 31. The exemplified piezoelectric vibrator 11 is in the flexural vibration mode as described above, and contracts by charging to reduce the volume of the pressure chamber 32 (the cover member 3).
1) is deformed, and the elastic plate is deformed so as to expand by discharge and increase the volume of the pressure chamber 32. This piezoelectric vibrator 11
Is a common electrode 36 formed on the back surface of the first lid member 31.
And a piezoelectric layer 37 formed in a laminated state on the back surface of the common electrode 36, and a drive electrode 38 formed on the back surface of the piezoelectric layer 37. ) Is formed. And this piezoelectric vibrator 1
1 is a potential difference (voltage) between the common electrode 36 and the drive electrode 38
And the volume of the pressure chamber 32 is varied. Also,
The piezoelectric vibrator 11 functions like a capacitor, and retains the potential immediately before the interruption of the signal supply.

In the recording head 8 having such a configuration,
Nozzle opening 2 from common ink chamber 26 through pressure chamber 32
9 are formed for each nozzle opening 29. When the piezoelectric vibrator 11 is charged or discharged, the corresponding pressure chamber 32 contracts or expands, and the pressure in the ink in the pressure chamber 32 fluctuates. By controlling the ink pressure, an ink droplet can be ejected from the nozzle opening 29.

In brief, when the piezoelectric vibrator 11 is charged, the piezoelectric vibrator 11 shrinks in a direction perpendicular to the electric field and the first cover member 31 is deformed. The pressure chamber 32 contracts. On the other hand, when the charged piezoelectric vibrator 11 is discharged, the piezoelectric vibrator 11 extends in a direction orthogonal to the electric field, the first lid member 31 is deformed in the return direction, and the pressure chamber 32 is expanded. When the pressure chamber 32 in the steady state is once expanded and then rapidly contracted,
Ink droplets are ejected from the nozzle openings 29.

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

This recording head 8 is, as shown in FIG.
Shift register circuit 41, latch circuit 42, decoder 43, control logic 44, gate circuit 12, level shifter 45, switch circuit 46, piezoelectric vibrator 1
1 is provided. Then, the shift register circuit 41,
A plurality of latch circuits 42, decoders 43, gate circuits 12, switch circuits 46, and piezoelectric vibrators 11 are provided corresponding to the nozzle openings 29 of the recording head 8, respectively.

The recording head 8 ejects ink droplets based on the recording data (SI) from the printer controller 1. That is, print data from the printer controller 1 is serially transmitted to the shift register circuit 41 in synchronization with a clock signal (CK) from the oscillation circuit 7.
As described above, this recording data is “1” or “0”.
This is bit data and is set for each dot, that is, for each nozzle opening 29.

When a latch signal (LAT) from the printer controller 1 is input to the latch circuit 42, the latch circuit 42 latches the recording data set in the shift register. Shift register circuit 4 performing such operation
The set of 1 and the latch circuit 42 functions as print data holding means capable of holding print data.

The recording data latched by the latch circuit 42 is input to the decoder 43. The decoder 43 performs translation (decoding) based on the input recording data, and generates waveform element selection data for selecting each of the waveform elements P1 to P5. In the present embodiment, since the driving cycle is composed of five waveform elements, the decoder 43
The 5-bit waveform element selection data is generated from the bit recording data. Then, the decoder 4 that operates as described above
Reference numeral 3 functions as waveform element selection data generation means.

The decoder 43 has a control logic 4
4 is also input. The control logic 44 functions as timing signal generating means together with the control unit 6, and generates a timing signal in synchronization with the input of a latch signal (LAT) or a channel signal (CH).

The 5-bit waveform element selection data translated by the decoder 43 is supplied to the level shifter 45 through the gate circuit 12.

Here, the gate circuit 12 functions as data selection supply means, and selectively supplies the waveform element selection data or the N-charge signal to the level shifter 45 (switch circuit 46). For example, when the enable signal is in the ON state (for example, H level), the waveform element selection data is supplied to the level shifter 45. On the other hand, in the OFF state (for example, L level), the waveform element selection data is not supplied to the level shifter 45, and the ON signal (waveform element selection data “1”) is synchronized with the ON state of the N-charge signal. (Equivalent signal) to the level shifter 45.

When the enable signal is in the ON state, the waveform element selection data is sequentially input to the level shifter 45 from the upper bits. This level shifter 4
Reference numeral 5 functions as a voltage amplifier, and outputs an electric signal boosted to a voltage capable of driving the switch circuit 46, for example, a voltage of about several tens of volts, when the waveform element selection data is “1”.

The waveform element selection data of "1" boosted by the level shifter 45 is supplied to a switch circuit 46 functioning as a switch. The input side of this switch circuit 46 has a drive signal (CO
M), and the output side of the switch circuit 46 is connected to the piezoelectric vibrator 11.

The waveform element selection data controls the operation of the switch circuit 46. That is, while the waveform element selection data applied to the switch circuit 46 is “1”, a drive signal is supplied to the piezoelectric vibrator 11, and the vibrator potential of the piezoelectric vibrator 11 changes according to the drive signal. On the other hand, while the waveform element selection data applied to the switch circuit 46 is “0”, the level shifter 45 does not output an electric signal for operating the switch circuit 46. Therefore, no drive signal is supplied to the piezoelectric vibrator 11. In short, the waveform elements P1 to P5 in which “1” is set as the waveform element selection data are selectively supplied to the piezoelectric vibrator 11.

As described above, in the present embodiment, the shift register circuit 41, the latch circuit 42, the decoder 43, the control logic 44, the level shifter 45, and the switch circuit 4
6 functions as a waveform element supply unit of the present invention,
The waveform elements P1 to P5 are selected from the drive signals, and the selected waveform elements are supplied to the piezoelectric vibrator 11.

On the other hand, when the enable signal is off, the supply of the waveform element selection data to the level shifter 45 is not performed. In this case, as described above, the gate circuit 12
Outputs an ON signal to the level shifter 45 over a period in which the N-charge signal is in the ON state. This ON signal is boosted by the level shifter 45, and switches the switch circuit 46 to the connected state. Thereby, all the piezoelectric vibrators 1
The drive signals are supplied to all at once, and the oscillator potential is equalized to the drive signal potential. In the present embodiment, the potential adjustment of the piezoelectric vibrator 11 by the N-charge signal is performed by supplying the potential decreasing element P1 from the beginning of the recording cycle T indicated by the symbol A in FIG. This is done for a very short period until just before.

Next, the drive signal (COM) generated by the drive signal generation circuit 9 and the waveform element P1 in this drive signal
The selection operation of P5 will be described.

First, the drive signal will be described. The drive signal illustrated in FIG. 3 includes one ejection pulse PS1 in the print cycle T, and is a drive signal capable of printing one type of dot. The ejection pulse PS1 includes a potential falling element P1 generated in the first cycle t1, a first connection element P4 generated in the second cycle t2, an ejection waveform element P2 generated in the third cycle t3, The second connection element P5 generated in the fourth cycle t4 and the potential rising element P generated in the fifth cycle t5
And 3. The drive signal has the potential at the start and end in the recording cycle T adjusted to the intermediate potential VM, and is repeatedly generated in the recording cycle T.

The potential lowering element P1 is a waveform element for lowering the potential at a constant gradient from the intermediate potential VM to the lowest potential VL. The intermediate potential VM in the present embodiment is the maximum potential V
H is set to 50 to 60%, and the lowest potential VL is set to a low potential close to the ground potential (GND potential). When the potential lowering element P1 is supplied, the piezoelectric vibrator 11 discharges, and the vibrator potential is adjusted to the minimum potential VL. Further, the diaphragm (first lid member 31) is deformed by the discharge of the piezoelectric vibrator 11, and the pressure chamber 32 expands to the maximum volume.

The generation time of the potential lowering element P1 is determined based on the natural oscillation period Tc of the ink in the pressure chamber 32. In the present embodiment, since the natural oscillation period Tc is about 10 μs, the generation time of the potential falling element P1 is set to 10 μs in accordance with the natural oscillation period Tc. By setting the generation time in this way, it is possible to prevent a problem that unnecessary vibration is excited in the ink when the pressure chamber 32 is expanded.

The first connection element P4 is a waveform element for connecting the potential drop element P1 and the discharge waveform element P2,
A different potential between the lowest potential VL, which is the terminal potential of the potential falling element P1, and the intermediate potential VM, which is the starting potential of the ejection waveform element P2, is connected. Then, the first connection element P4
Is used to connect the waveform elements P1 and P2, and is not supplied to the piezoelectric vibrator 11. For this reason, the potential of the first connection element P4 is set as steep as possible. Thereby, waveform elements having different potentials at the connection terminals can be brought closer to each other (that is, generated in a short time), and the recording cycle T can be shortened. As a result, the recording head 8 can be driven at a high frequency, and images and characters with a high dot density can be recorded at high speed.

The ejection waveform element P2 is a waveform element for ejecting ink droplets. In the present embodiment, the intermediate potential V
An expansion element Pa that lowers the potential at a constant gradient from M to the minimum potential VL, an expansion hold element Pb that holds the minimum potential VL for a predetermined short period, and a expansion potential VH from the minimum potential VL to the maximum potential VH.
A discharge element Pc that rapidly raises the potential to the maximum, a contraction hold element Pd that holds the maximum potential VH for a predetermined short time,
And a damping element Pe that lowers the potential at a constant gradient from the maximum potential VH to the intermediate potential VM. When the ejection waveform element P2 is supplied to the piezoelectric vibrator 11, the piezoelectric vibrator 11 is deformed, the volume of the pressure chamber 32 changes as follows, and ink droplets are ejected from the nozzle opening 29.

That is, the supply of the expansion element Pa changes the pressure chamber 32 from the steady volume corresponding to the intermediate potential VM to the lowest potential V.
Expand to the maximum volume corresponding to L. This inflated state is maintained over a period corresponding to the inflated hold element Pb,
Thereafter, the pressure chamber 32 contracts rapidly to the minimum volume corresponding to the maximum potential VH with the supply of the ejection element Pc. Due to this rapid contraction, the ink pressure in the pressure chamber 32 increases, and ink droplets are pushed out from the nozzle openings 29. Following the ejection element Pc, the contraction hold element Pd is supplied,
The contracted state of the pressure chamber 32 is maintained for a predetermined short time. After the elapse of the holding period by the discharge holding element, the vibration damping element Pe is supplied, and the pressure chamber 32 is expanded from the minimum volume to the steady volume. The expansion of the pressure chamber 32 absorbs fluctuations in the ink pressure in the pressure chamber 32.
This is because the timing is optimized by the contraction hold element Pd and the potential gradient of the damping element Pe is optimized.

The second connection element P5 is a waveform element for connecting between the ejection waveform element P2 and the potential increasing element P3, and is not supplied to the piezoelectric vibrator 11 like the first connection element P4. For this reason, the potential of the second connection element P5 is also set to be as steep as possible, so that the ejection waveform element P2 and the potential increasing element P3 are brought closer to each other. Thereby, the recording cycle T is shortened, and the recording head 8 can be driven at a high frequency.

The potential increasing element P3 is constituted by a waveform element for increasing the potential at a constant gradient from the lowest potential VL to the intermediate potential VM. When the potential raising element P3 is supplied, the piezoelectric vibrator 11 is charged, and the vibrator potential returns to the intermediate potential VM. Further, the diaphragm is deformed by charging the piezoelectric vibrator 11, and the pressure chamber 32 has a steady volume. The generation time of the potential increasing element P3 is also determined based on the natural oscillation period of the ink in the pressure chamber 32. In the present embodiment, as in the case of the potential lowering element P1,
s.

Next, the operation of selecting each of the waveform elements P1 to P5 constituting the drive signal, that is, the waveform element supply means (shift register circuit 41, latch circuit 42, decoder 43,
Control logic 44, level shifter 45, switch circuit 4
6, and so on. ) Will be described.

In the present embodiment, the waveform element supply means
The waveform elements P1 to P5 to be selected are determined based on the recording data corresponding to the recording cycle T, that is, the recording / non-recording information. In this case, the decoder 43 translates the print data latched by the latch circuit 42 for each nozzle opening 29, and generates waveform element selection data corresponding to the nozzle opening 29.

For example, the recording data is "0" indicating non-recording.
, The decoder 43 outputs the waveform element selection data “10
001 ”is generated. If the recording data is “1” indicating recording, the decoder 43 generates waveform element selection data “00100”.

As a result, when printing is performed, the switch circuit 46 is turned on in the third period t3, and as shown in FIG. 4A, the ejection waveform element P2 is selected from the drive signal and the piezoelectric element is selected. It is supplied to the vibrator 11. on the other hand,
In the case of non-recording, the switch circuit 46 is turned on in the first cycle t1 and the fifth cycle t5, and as shown in FIG. Is selected and supplied to the piezoelectric vibrator 11.

In the case of non-recording as shown in FIGS. 5A and 5B, the drive signal to the piezoelectric vibrator 11 is transmitted over the second period t2 to the fourth period t4 indicated by the reference symbol B. Although the supply is interrupted, in the interruption period B, the first cycle t1
The piezoelectric vibrator 11 is driven by the potential lowering element P1 supplied by
Are adjusted to the lowest potential VL. As described above, since the vibrator potential is actively reduced during the drive signal cutoff period B, the drop in the vibrator potential due to spontaneous discharge can be suppressed. Thereby, at the start of the supply of the potential increasing element P3 in the fifth period t5, the gap between the vibrator potential and the potential of the drive signal is reduced, and abnormal deformation of the piezoelectric vibrator 11 is prevented. Discharge can be prevented. Further, since the vibrator potential is adjusted to the minimum potential VL, the burden on the piezoelectric vibrator 11 can be reduced, and the life of the piezoelectric vibrator 11 can be extended.

Further, since the oscillator potential returns to the intermediate potential VM at the end of the recording cycle T by the potential increasing element P3, the transition to the next recording cycle T can be performed smoothly. That is, at the time of transition from the current recording cycle T to the next recording cycle T,
A sudden change in the oscillator potential can be prevented.

As shown in FIG. 5C, when the recording is continuous, the drive signal is cut off from the end of the third cycle of the current recording cycle T to the start of the third cycle of the next recording cycle T. Although the state continues, as described above, the N-charge signal is supplied immediately after the start of the next recording cycle T (period A), and the drive signal is supplied to all the piezoelectric vibrators 11. At this point, the transducer potential returns to the intermediate potential VM. Therefore, the drive signal cutoff period is the period C1 from the end of the third cycle t3 in the current recording cycle T to the end of the current recording cycle T, and the third cycle t3 from the end of the period A in the next recording cycle T. Period C until just before the start of
As a result, recording can be performed continuously without greatly lowering the potential of the piezoelectric vibrator 11. As a result, abnormal deformation of the piezoelectric vibrator 11 can be prevented, and thus abnormal discharge of ink droplets can be prevented.

By the way, although the ejection pulse element P2 included in the ejection pulse PS1 of the first embodiment is one,
The present invention is not limited to this ejection pulse PS1. For example, a plurality of ejection waveform elements may be included in one ejection pulse.

For example, the ejection pulse P of the modification shown in FIG.
S2 includes two ejection waveform elements, and the first cycle t1
, A first connection element P4 generated in the second cycle t2, a first ejection waveform element P2A generated in the third cycle t3, and a first generation element P2A generated in the fourth cycle t4. It is composed of a two-ejection waveform element P2B, a second connection element P5 generated in the fifth cycle t5, and a potential rise element P3 generated in the sixth cycle t6. Note that, among these waveform elements, the potential falling element P1, the first connection element P4, and the second
The connection element P5 and the potential increasing element P3 are the same as the waveform elements described in the first embodiment. The first ejection waveform element P2A and the second ejection waveform element P2B have the same waveform shape as the ejection waveform element P2 of the first embodiment.

The first ejection waveform element P2A and the second ejection waveform element P2A
The ejection waveform elements P2B are not selected independently but are selected as a set (pair). That is, as shown in FIG. 7, when recording is performed, the first ejection waveform element P2A and the second ejection waveform element P2B are selected and supplied to the piezoelectric vibrator 11. On the other hand, in the case of non-recording, the potential decreasing element P1 and the potential increasing element P3 are selected and supplied to the piezoelectric vibrator 11. When recording is performed with the ejection pulse PS2, two ejection waveform elements P2A and P2B are continuously supplied to the piezoelectric vibrator 11, so that ink droplets are continuously ejected. That is, one dot is recorded by two ink droplets.

The supply of the drive signal to the piezoelectric vibrator 11 is also interrupted in the second period t2 to the fifth period t5 (period B ') in the ejection pulse PS2 as well, but in the first period t1.
The piezoelectric vibrator 11 is driven by the potential lowering element P1 supplied by
Is adjusted to the lowest potential VL, so that a drop in the oscillator potential due to spontaneous discharge or the like can be suppressed during the cutoff period. In particular, in the ejection pulse PS2 of this modified example, the cutoff period of the drive signal during non-printing is longer than the ejection pulse PS1 of the first embodiment. It can be suppressed to the extent. For this reason, at the start of the supply of the potential increasing element P3, the gap between the transducer potential and the drive signal potential can be reduced, and abnormal deformation of the piezoelectric vibrator 11 can be prevented. As a result, abnormal ejection of ink droplets can be prevented.

Incidentally, the first embodiment and the first
In each of the modifications of the embodiment, one type of dot is recorded. However, the present invention is not limited to this configuration, and a plurality of types of dots can be recorded. Hereinafter, a second embodiment configured as described above will be described.

FIG. 8 is a functional block diagram of the printer according to the second embodiment. The printer according to the second embodiment has basically the same configuration as the printer according to the first embodiment, but the shift register circuit includes a first shift register circuit 50 and a second shift register circuit 51. The difference is that the latch circuit is constituted by the first latch circuit 52 and the second latch circuit 53. Further, as shown in FIG. 9, the drive signal generation circuit 9
The three ejection pulses PS3, PS4 and PS5 are recorded in the recording cycle T
A series of drive signals (COM) contained within are generated. Further, the control unit 6 generates 2-bit grayscale data as dot pattern data, and the decoder 43 translates the 2-bit grayscale data to generate 15-bit waveform element selection data.

The lower bits of the gradation data are set in the first shift register circuit 50, and the upper bits of the gradation data are set in the second shift register circuit 51.
Therefore, when the latch signal is input, the first latch circuit 5
2 latches the lower bit of the grayscale data, and the second latch circuit 53 latches the upper bit of the grayscale data. This gradation data is data indicating four gradations of non-printing, small dot, medium dot, and large dot.
0, a small dot is "01", a medium dot is "10", and a large dot is "11". Here, in the present embodiment, small dots are dots formed by one small ink droplet, medium dots are dots formed by two small ink droplets, and large dots are formed by three small ink droplets. Is the dot to be created. Therefore, with this printer, printing can be performed with four gradations having different dot sizes.

The drive signal generated by the drive signal generation circuit 9 is the first ejection pulse PS generated in the first recording cycle T1.
3 and a second ejection pulse P generated in the second recording cycle T2.
S4 and a third ejection pulse PS5 generated in the third recording cycle T3. Each of these ejection pulses has the same waveform shape. Each of the ejection pulses PS3 to PS5 has the same waveform shape as the ejection pulse PS1 of the above-described first embodiment, and includes a potential decreasing element P1, a first connection element P4, an ejection waveform element P2, and a second connection element P.
5 and a potential increasing element P3. Since these waveform elements have the same functions as the waveform elements of the first embodiment, they are denoted by the same reference numerals and description thereof is omitted.

In the second embodiment, in the case of non-printing, printing by the first to third discharge pulses PS3 to PS5 is not performed. When printing small dots, printing is performed using the second ejection pulse PS4. Further, when printing a medium dot, the first ejection pulse PS
The recording is performed using the third ejection pulse PS5 and the third ejection pulse PS5. When printing a large dot, the recording is performed using the first ejection pulse PS3 to the third ejection pulse PS5. In addition, the ejection pulse that is not used is selected by pairing the potential decreasing element P1 and the potential increasing element P3. Therefore, the decoder 43
Generates “100011000110001” as the waveform selection data in the case of non-recording (gradation data “00”), and “100010010010001” as the waveform selection data in the case of small dots (gradation data “01”).
Generate Similarly, medium dot (gradation data “10”)
In the case of
100100 ”and a large dot (gradation data“ 1
1)), “001000” is selected as the waveform selection data.
010000100 "is generated.

As a result, as shown in FIG. 10, in the case of non-recording, the potential decreasing element P1 and the potential increasing element P3 are selected as a pair in each of the recording periods T1 to T3, and the drive vibration is cut off. At this time, the oscillator potential is adjusted to the minimum potential VL. When printing small dots, the second
In the recording cycle T2, the ejection waveform element P2 is selected, and in the first recording cycle T1 and the third recording cycle T3, the potential decreasing element P1 and the potential increasing element P3 are selected as a pair.
When printing medium dots, the first recording cycle T1
In the third recording cycle T3, the ejection waveform element P2 is selected, and in the second recording cycle T2, the potential decreasing element P1 and the potential increasing element P3 are selected as a pair. Further, when printing a large dot, the ejection waveform element P2 is selected in each of the printing cycles T1 to T3.

As described above, also in the present embodiment, when the cutoff state of the drive signal continues, the vibrator potential is positively lowered, and an excessive drop in the vibrator potential during the cutoff period can be prevented. In the case of non-recording, since the vibrator potential is positively lowered, the load on the piezoelectric vibrator 11 is reduced,
Life can be extended.

By the way, the present invention is not limited to the above embodiment, and various modifications can be made based on the description in the claims.

For example, the base potential in the drive signal is
The potential is not limited to the minimum potential VL, but may be lower than the intermediate potential VM. For example, the minimum potential VL and the intermediate potential V
It may be set in the middle of M.

Each ejection pulse PS3 of the second embodiment
Regarding to PS5, a plurality of ejection waveform elements P2A and P2B may be included as in the modification of the first embodiment. Further, the number of ejection pulses included in the recording cycle T is not limited to three, and may be any number as long as it is plural. For example,
Two ejection pulses may be included, or five ejection pulses may be included. And the ejection pulse to be included is
The shape may not be the same as long as the potential decreasing element P1, the ejection waveform element P2, and the potential increasing element P3 are set. For example, a plurality of types of ejection waveform elements may be prepared, and a different ejection waveform element may be used for each ejection pulse.

Although the recording head 8 of the above embodiment has the piezoelectric vibrator 11 in a so-called bending vibration mode, the present invention can be applied to a piezoelectric vibrator in a so-called longitudinal vibration mode. .

The present invention can be applied not only to a printer but also to a recording device such as a plotter or a facsimile machine.

[0077]

As described above, according to the present invention, the following effects can be obtained. In other words, the waveform element supply means selects a pair of the potential decreasing element and the potential increasing element when recording is not performed, so that the transducer potential when recording is not performed is adjusted to the base potential by the potential decreasing element. You. After that, the supply of the drive signal to the piezoelectric vibrator is interrupted during the generation period of the ejection waveform element. However, since the piezoelectric vibrator has the base potential, an excessive drop in the vibrator potential can be prevented. For this reason, it is possible to prevent the vibrator potential from rapidly increasing at the start of the supply of the potential increasing element, and to prevent abnormal operation of the piezoelectric vibrator. Further, during the non-recording period, since the vibrator potential is actively lowered, the load on the piezoelectric vibrator can be reduced, and the life of the piezoelectric vibrator can be extended.

When the connection between the potential drop element and the discharge waveform element and the connection between the discharge waveform element and the potential rise element by a connection element that is not supplied to the piezoelectric vibrator, the connection element is suddenly connected. Since the gradient can be set, the recording cycle can be shortened while different potentials are connected between the potential lowering element or the potential increasing element and the ejection waveform element, and this is suitable for driving at a high frequency.

Further, when the base potential is set to the lowest potential in the drive signal, a drop in the vibrator potential due to spontaneous discharge or the like can be reliably prevented, and the load on the piezoelectric vibrator can also be reduced.

Further, when the generation times of the potential falling element and the potential rising element are set to be equal to the natural vibration period of the pressure chamber, unnecessary vibration is excited in the pressure chamber while the expansion and contraction of the pressure chamber are performed quickly. It is possible to prevent the problem of being performed.

Further, when a plurality of ejection pulses are included in a recording cycle or when a plurality of ejection waveform elements are included in an ejection pulse, the types of dots to be recorded can be increased.
High quality recording can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an overall configuration of a printer according to a first embodiment.

FIG. 2 is an explanatory diagram illustrating a mechanical structure of a recording head.

FIG. 3 is a diagram illustrating a drive signal.

FIGS. 4A and 4B are diagrams for explaining supply control of waveform elements by the drive signal of FIG. 3, wherein FIG. 4A shows a recording time and FIG.

5A and 5B are diagrams for explaining supply control of a waveform element by the drive signal of FIG. 3; FIG. 5A illustrates a case where non-recording continues;
(B) shows a case where recording is performed following non-recording, and (c) shows a case where recording is continuous.

FIG. 6 is a diagram illustrating a modified example of a drive signal.

7A and 7B are diagrams for explaining supply control of waveform elements by the drive signal of FIG. 6, wherein FIG. 7A shows a recording time and FIG. 7B shows a non-recording time.

FIG. 8 is a block diagram illustrating an overall configuration of a printer according to a second embodiment.

FIG. 9 is a diagram illustrating a drive signal according to the second embodiment.

FIG. 10 is a diagram for explaining supply control of waveform elements by the drive signal of FIG. 9;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printer controller 2 Print engine 3 External I / F 4 RAM 5 ROM 6 Control part 7 Oscillation circuit 8 Recording head 9 Drive signal generation circuit 10 Internal I / F 11 Piezoelectric vibrator 12 Gate circuit 13 Carriage mechanism 14 Paper feed mechanism 21 Flow Path unit 22 Actuator unit 23 Ink supply port 24 First nozzle communication hole 25 Supply port forming substrate 26 Common ink chamber 27 Second nozzle communication hole 28 Ink chamber forming substrate 29 Nozzle opening 30 Nozzle plate 31 First lid member 32 Pressure chamber Reference Signs List 33 pressure chamber forming substrate 34 supply side communication hole 35 second cover member 36 common electrode 37 piezoelectric layer 38 drive electrode 41 shift register circuit 42 latch circuit 43 decoder 44 control logic 45 level shifter 46 switch circuit 50 first shift register circuit 51 No. 2 shift register circuit 52 first latch circuit 53 second latch circuit

Claims (7)

[Claims] A recording head having a piezoelectric vibrator capable of causing pressure fluctuations in a pressure chamber and a nozzle opening communicating with the pressure chamber; a driving signal generating means for generating a series of driving signals including a plurality of waveform elements; A required waveform element is selected from the drive signals generated by the drive signal generation means in accordance with the recording data, and a waveform element supply means capable of supplying the selected waveform element to the piezoelectric vibrator. The drive signal generating means is sandwiched between a potential lowering element for lowering the potential from the intermediate potential to the base potential, a potential increasing element for increasing the potential from the base potential to the intermediate potential, and a potential lowering element and a potential raising element A discharge pulse having a set of discharge waveform elements is generated, and the waveform element supply means selects the discharge waveform element when performing recording using the discharge pulses, An ink jet recording apparatus characterized by selecting as a pair and potential lowering element and the potential rise component in case of no record. 2. The method according to claim 1, wherein the potential drop element and the discharge waveform element and the discharge waveform element and the potential rise element are connected by a connection element that is not supplied to the piezoelectric vibrator. 3. The ink jet recording apparatus according to claim 1. 3. The device according to claim 1, wherein the base potential is set to a lowest potential in a drive signal.
3. The ink jet recording apparatus according to claim 1. 4. The ink jet recording apparatus according to claim 1, wherein the generation times of the potential drop element and the potential rise element are set to the natural oscillation period of the pressure chamber. . 5. The ink jet type apparatus according to claim 1, wherein said drive signal generating means generates a series of drive signals including a plurality of ejection pulses within a recording cycle. Recording device. 6. The ink jet recording apparatus according to claim 1, wherein the ejection pulse includes a plurality of ejection waveform elements. 7. A method of driving an ink jet recording apparatus which generates a series of driving signals including a plurality of waveform elements and supplies a waveform element selected from the driving signals to a piezoelectric vibrator of the ink jet recording head. The signal includes a potential decreasing element for decreasing the potential from the intermediate potential to the base potential, a potential increasing element for increasing the potential from the base potential to the intermediate potential, and an ejection waveform element sandwiched between the potential decreasing element and the potential increasing element. The discharge pulse included in the set is included, and when the recording is performed by the discharge pulse, the discharge waveform element is selected, and when the recording is not performed, the potential decreasing element and the potential increasing element are selected as a pair. Drive method.