JP2000280475A - Ink-jet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent recording failure by specifying the time interval between the micro dot waveform and the middle dot waveform in terms of a cavity vibration cycle in a device for ejecting large dot ink droplets by applying a micro dot waveform and a middle dot waveform on a pressure generating element. SOLUTION: A print controller 1 is provided with a driving signal generating circuit 9 for generating driving waveform signals including a printing slight vibration waveform 13, a micro dot waveform 14, and a middle dot waveform 15. By applying a series of driving waveform signals continuously to a piezoelectric vibrator of a recording head 8 via an I/F 10, large dot ink droplets are ejected. At the time, the time interval T μm of the micro dot waveform and the middle dot waveform is set in the vicinity of a value obtained from the formula T μm=Tc×(n/2). In the formula, Tc is a cavity vibration cycle, and n is an odd number of 3 or more. Accordingly, generation of recording failure is prevented even in the case of recording a recording pattern of a high recording density.

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 provided with a recording head for performing recording by discharging ink droplets from nozzle openings, and more particularly, to preventing a defect of a recorded image such as missing dots from occurring. About what you did.

[0002]

2. Description of the Related Art In order to improve image quality, an ink-jet recording device such as an ink-jet printer (hereinafter referred to as a recording device) is provided with a plurality of types of inks having different ink weights such as micro dots, middle dots, and large dots. In some cases, droplets are ejected from the same nozzle opening.

[0003] A recording head used in this recording apparatus includes:
For example, it includes a piezoelectric vibrator that is deformed by an applied waveform signal, a pressure chamber that expands and contracts due to deformation of the piezoelectric vibrator, and a nozzle opening that communicates with the pressure chamber.

[0004] A series of drive waveform signals in which a middle dot waveform for ejecting a heavy ink droplet forming a middle dot is arranged after a microdot waveform for ejecting a heavy ink droplet for forming a microdot is generated by a pressure generating element. , A plurality of types of ink droplets are ejected from the same nozzle opening.

That is, when recording micro dots on recording paper, a micro dot waveform is applied to the pressure generating element, and when recording middle dots, a middle dot waveform is applied to the pressure generating element.

In recording large dots,
The micro dot waveform and the middle dot waveform are continuously applied to the pressure generating element. In this case, immediately after the microdot waveform is applied, the residual vibration due to the microdot waveform remains in the pressure chamber. Therefore, by continuously applying the middle dot waveform, the weight of the ink droplet ejected by the middle dot waveform is reduced. Is larger than when the middle dot waveform is applied alone. Therefore, an ink droplet having a weight that forms a large dot is ejected together with the ink droplet ejected by the microdot waveform.

[0007]

In such a recording apparatus, a large dot is formed by continuously applying a microdot waveform and a middle dot waveform, so that the interval between the microdot waveform and the middle dot waveform is increased to some extent. You need to get closer. The time interval between the micro dot waveform and the middle dot waveform affects the quality of a recorded image.

That is, if the time interval deviates from the optimum value, recording defects such as thickening of dots (a phenomenon that a dot larger than the original dot diameter is formed) and missing dots will occur.

In order to prevent this recording failure, a recording pattern in which a recording failure is likely to occur, for example, in a recording head in which one row is composed of 96 nozzle openings, a large dot ink is provided for every eight nozzle openings. A single ejection pattern for ejecting droplets, three adjacent nozzle openings for every eight nozzle openings, and a three ejection pattern for ejecting large dot ink droplets from the selected nozzle openings; An alternate ejection pattern in which large-dot ink droplets are alternately ejected from the odd-numbered nozzle openings and the even-numbered nozzle openings is actually recorded and evaluated, and the microdot waveform and the middle dot are determined based on the evaluation results. The time interval with the dot waveform is determined.

However, it has been found that a recording failure may occur even at a time interval determined by the evaluation based on these recording patterns.

For example, when the time interval between the micro dot waveform and the middle dot waveform is determined by these recording patterns, a single-punch pattern, that is, a nozzle opening that does not discharge ink droplets for every eight nozzle openings When a pattern with a high ratio of nozzle openings (recording density), such as a recording pattern for discharging large dot ink droplets from the nozzle openings other than the set nozzle openings, is printed, In some cases, the recording failure described above may occur.

The present invention has been made in view of such circumstances, and it is possible to reduce recording defects even when recording a recording pattern having a high recording density, such as a single-punch pattern, and to achieve stable recording. It is an object of the present invention to provide an ink jet recording apparatus capable of improving the performance.

[0013]

SUMMARY OF THE INVENTION The present invention has been proposed to achieve the above-mentioned object. According to the first aspect of the present invention, there is provided a pressure generating element deformed by application of a waveform signal, A pressure generating element that includes a pressure chamber that expands and contracts due to deformation of the element, and a nozzle opening that communicates with the pressure chamber, and continuously generates at least a microdot waveform and a middle dot waveform that form a series of drive waveform signals. In the ink jet recording apparatus configured to eject large-dot ink droplets from the nozzle openings by applying to the nozzle, the time interval between the micro dot waveform and the middle dot waveform is
The following equation Tμm = Tc × (n / 2) where Tμm is the time interval between the microdot waveform and the middle dot waveform Tc is the cavity oscillation period n is set to a value close to an odd number of 3 or more An ink jet recording apparatus characterized by the following.

According to a second aspect of the present invention, there is provided an ink jet recording apparatus according to the first aspect, wherein n is set to "3".

According to a third aspect of the present invention, there is provided a pressure generating element which is deformed by application of a waveform signal, a pressure chamber which is expanded and contracted by the deformation of the pressure generating element, and a nozzle opening communicating with the pressure chamber. Ink-jet recording comprising a large dot ink droplet ejected from a nozzle opening by continuously applying a micro dot waveform and a middle dot waveform constituting a series of drive waveform signals to a pressure generating element. An ink jet recording apparatus, characterized in that at least a time interval between a microdot waveform and a middle dot waveform is set to a length approximately halfway between defective times occurring at a cavity oscillation period interval.

According to a fourth aspect of the present invention, a series of drive waveform signals is configured by including a micro-vibration waveform in a print for micro-vibrating a meniscus before a micro-dot waveform, and the micro-vibration waveform in a print and the The ink jet recording apparatus according to any one of claims 1 to 3, wherein the time interval of the dot waveform is set long enough not to be affected by the vibration due to the minute vibration waveform in the print.

According to a fifth aspect of the present invention, the waveform interval is T
5. The ink jet recording apparatus according to claim 4, wherein c is three times or more.

According to a sixth aspect of the present invention, there is provided a pressure generating element deformed by application of a waveform signal, a pressure chamber expanded and contracted by deformation of the pressure generating element, and a nozzle opening communicating with the pressure chamber. An ink jet type comprising a large dot ink droplet ejected from a nozzle opening by continuously applying at least a micro dot waveform and a middle dot waveform constituting a series of drive waveform signals to a pressure generating element. An ink jet recording apparatus, wherein the time interval between the micro dot waveform and the middle dot waveform is set to an interval at which no ejection failure occurs.

According to a seventh aspect of the present invention, there is provided the ink jet recording apparatus according to the sixth aspect, wherein the interval is an interval mainly represented by a linear function of Tc.

According to an eighth aspect of the present invention, there is provided an ink jet recording apparatus according to the third aspect, wherein the defective time appears periodically.

According to a ninth aspect of the present invention, the pressure generating element is constituted by a comb-shaped vibrator in which a piezoelectric body and an electrode are laminated in a direction perpendicular to the direction of expansion and contraction of the vibrator. An ink jet recording apparatus according to any one of claims 1 to 8.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to an ink jet printer (hereinafter, referred to as a printer) as a typical ink jet recording apparatus. As shown in FIG. 1, the printer is schematically composed of a printer controller 1 and a print engine 2.

The microdots, middle dots, and large dots in this specification represent dots in which the weight of ink forming the dots increases in the order of microdots, middle dots, and large dots.

The printer controller 1 includes an external interface 3 (hereinafter referred to as an external I / F 3), a RAM 4 for temporarily storing various data, a ROM 5 for storing a control program and the like, a CPU and the like. A control unit 6, an oscillation circuit 7 for generating a clock signal, a drive signal generation circuit 9 for generating a drive waveform signal (COM) to be supplied to the recording head 8, and a development based on the drive waveform signal and print data And an internal interface 10 (hereinafter, referred to as an internal I / F 10) for supplying the printed dot pattern data (bitmap data) and the like to the print engine 2.

The external I / F 3 receives print data composed of, for example, a character code, a graphic function, and image data from a host computer (not shown). In addition, a busy signal (BUSY) and an acknowledge signal (ACK) are output to the host computer and the like through the external I / F3.

The RAM 4 functions as a receiving buffer 4A, an intermediate buffer 4B, an output buffer 4C, and a work memory (not shown). The receiving buffer 4A temporarily stores the print data received via the external I / F 3, the intermediate buffer 4B stores the intermediate code data converted by the control unit 6, and the output buffer 4C stores the dot pattern data. Remember. The dot pattern data is composed of print data obtained by decoding (translating) gradation data.

The ROM 5 includes a control program (control routine) for performing various data processing,
Font data, graphic functions, etc. are stored.

The control unit 6 performs various controls, reads out the print data in the reception buffer 4A, and stores the intermediate code data obtained by converting the print data in the intermediate buffer 4B. Further, the intermediate code data read from the intermediate buffer 4B is analyzed, and is expanded into dot pattern data with reference to font data and graphic functions stored in the ROM 5. After performing the necessary decoration processing, the control unit 6 stores the dot pattern data in the output buffer 4C.

If one line of dot pattern data that can be recorded is obtained by one main scan of the recording head 8, this one line of dot pattern data is output from the output buffer 4C to the internal I / F 10C. Are sequentially output to the recording head 8. When one line of dot pattern data is output from the output buffer 4C, the expanded intermediate code data is deleted from the intermediate buffer 4B, and the expansion processing for the next intermediate code data is performed.

The drive signal generation circuit 9 generates a drive waveform signal as described above. In the present embodiment, as shown in FIG. 6, the print medium includes a micro-vibration waveform 13, a micro-dot waveform 14, and a middle-dot waveform 15, and a middle-dot waveform 15 is arranged after the micro-dot waveform 14. A series of signals in which the in-print micro-vibration waveform 13 is arranged earlier than this is generated as a drive waveform signal.

Here, the in-print micro-vibration waveform 13 is a waveform for stirring the ink in the nozzle opening 16 (see FIG. 3), and the micro-dot waveform 14 is a micro-dot ink droplet (for example, about 3 μm). .. 3 ng of ink droplets are ejected from the nozzle openings 16, and the middle dot waveform 15 is used to eject middle dot ink droplets (for example, approximately 10 ng ink droplets) from the nozzle openings 16. It is a waveform.

In the present embodiment, as will be described later, the microdot waveform 14 and the middle dot waveform 15 are successively recorded on the recording head 8 (that is, the piezoelectric vibrator 3 described later).
5), the weight of the ink droplet by the middle dot waveform 15 is increased from the weight of the ink droplet when the middle dot waveform 15 is applied alone,
A large dot ink droplet (a total of approximately 20 ng of a microdot ink droplet and a middle dot ink droplet) is ejected.

The drive waveform signal will be described later in detail.

The print engine 2 includes a paper feed mechanism 19
, A carriage mechanism 20, and the recording head 8.

As shown in FIG. 2, the paper feed mechanism 19 comprises a paper feed motor 21, a paper feed roller 22, and the like.
Are sequentially sent out in conjunction with the recording operation by That is, the paper feed mechanism 19 moves the recording paper 23 in the recording paper feed direction, which is the sub-scanning direction.

The carriage mechanism 20 is capable of mounting the recording head 8 and the ink cartridge 24 and is bridged between a driving pulley 27 and a driven pulley 28 while being movably mounted on a guide member 25. A timing belt 29 connected to the carriage 26 and a pulse motor 3 for rotating the drive pulley 27
0.

In the carriage mechanism 20, the carriage 26 is reciprocated along the width direction of the recording paper 23 by the operation of the pulse motor 30. That is, the recording head 8 mounted on the carriage 26 is moved in the main scanning direction.

Next, the recording head 8 will be described. As shown in FIG. 3, the illustrated recording head 8 has a comb-shaped piezoelectric vibrator 35 (comb-shaped vibrator 35) in one opening in a storage chamber 34 of a box-shaped case 33 made of, for example, plastic. And the comb-shaped tip 35a faces the other opening, and the flow path unit 36 is joined to the surface (lower surface) of the case 33 on the opening side. It is schematically configured by abutting and fixing to a predetermined portion.

The piezoelectric vibrator 35 is formed by cutting a plate-like vibrator plate in which common internal electrodes 38 and individual internal electrodes 39 are alternately laminated with a piezoelectric body 37 interposed therebetween in a comb-teeth shape corresponding to the dot formation density. It is configured. Then, by giving a potential difference between the common internal electrode 38 and the individual internal electrode 39,
Each piezoelectric vibrator 35 (that is, the comb-shaped vibrator 35) expands and contracts in the vibrator longitudinal direction orthogonal to the lamination direction.

The channel unit 36 is constructed by laminating a nozzle plate 43 and an elastic plate 44 on both sides with a channel forming plate 42 interposed therebetween.

The flow path forming plate 42 has a plurality of cavities (pressure chambers) 45 which are communicated with the plurality of nozzle openings 16 formed in the nozzle plate 43 and are arranged in rows with pressure chamber partition walls therebetween. Is a plate member in which an elongated common ink chamber 47 communicating with a plurality of ink supply units 46 communicating with at least one end is formed. In this embodiment, an elongated common ink chamber 47 is formed by etching a silicon wafer, and cavities 45 are formed along the longitudinal direction of the common ink chamber 47 in accordance with the pitch of the nozzle openings 16. And common ink chamber 47
And a groove-shaped ink supply section 46 is formed between them. The ink supply section 46 is connected to one end of the cavity 45, and the nozzle supply section 46 is arranged near the end opposite to the ink supply section 46. The common ink chamber 47 is a chamber for supplying the ink stored in the ink cartridge 24 to the cavities 45. An ink supply pipe 48 communicates with substantially the center in the longitudinal direction.

The elastic plate 44 is laminated on the other surface of the flow path forming plate 42 on the opposite side of the nozzle plate 43, and is formed by laminating a polymer film such as PPS as an elastic film 50 on a stainless steel plate 49. It has a double structure. Then, the stainless plate 49 corresponding to the cavity 45
Is etched to form an island portion 51 for abutting and fixing the piezoelectric vibrator 35.

In the recording head 8 having the above configuration, the island portion 51 is pressed toward the nozzle plate 43 by extending the piezoelectric vibrator 35 in the longitudinal direction of the vibrator, and the elastic film 50 around the island portion 51 is formed. The cavity 45 is deformed and contracted. Also, the piezoelectric vibrator 35
Is contracted in the longitudinal direction of the vibrator, the volume of the cavity 45 expands due to the elasticity of the elastic film 50. Then, by controlling expansion and contraction of the volume of the cavity 45, ink droplets are ejected from the nozzle openings 16.

The natural vibration of the ink in the cavity 45 in the recording head 8 having such a configuration can be represented by an equivalent circuit shown in FIG. It is known that the natural vibration period Tc of the ink in the cavity 45 can be calculated by the following equation.

Tc = 2π√ [[(Mn × Ms) / (Mn
+ Ms)] × C] In this equation, the symbol M is the inertance [Kg / m4], which is the mass of the medium per unit length, Mn is the inertance at the nozzle opening 16, and Ms is the inertance at the ink supply unit 46. is there. The symbol C is the compliance [m5 / N] of the cavity 45 (pressure chamber).
It is.

The natural vibration period Tc of the ink in the cavity 45 calculated based on this equation is about 8 μsec in this embodiment.

Next, the electrical configuration of the recording head 8 and control for discharging ink droplets will be described.

This recording head 8 is, as shown in FIG.
Shift register 54, latch circuit 55, level shifter 5
6, a switch 57, a piezoelectric vibrator 35, and the like.
Further, as shown in FIG.
4. Latch circuit 55, level shifter 56, switch 57
And the piezoelectric vibrator 35 are each provided with a shift register element 54A provided for each nozzle opening 16 of the recording head 8.
To 54N, latch elements 55A to 55N, level shifter elements 56A to 56N, switch elements 57A to 57N, and piezoelectric vibrators 35A to 35N.

To cause the recording head 8 to eject ink droplets, the control unit 6 first synchronizes with the clock signal (CK) from the oscillation circuit 7 and outputs the most significant bit of the print data (SI). The data is transmitted serially from the output buffer 4C and sequentially set in the shift register elements 54A to 54N. If print data for all the nozzle openings 16 are set in the shift register elements 54A to 54N,
The control unit 6 sends a latch signal (LAT) to the latch circuit 55, that is, the latch elements 55A to 55N at a predetermined timing.
Output. With this latch signal, the latch element 55
A 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 56, which is a voltage amplifier, that is, the level shifter elements 56A to 56N.

When the print data is, for example, "1", each of the level shifter elements 56A to 56N boosts the print data to a voltage value at which the switch 57 can be driven, for example, several tens of volts. The boosted print data is applied to the switch 57, that is, the switch elements 57A to 57N, and the switch elements 57A to 57N are connected by the print data. The print data is, for example, “0”.
, The corresponding level shifter elements 56A to 56A
N does not boost. Then, each switch element 57A-
The drive waveform signal (COM) from the drive signal generation circuit 9 is applied to the switch elements 57A to 57N.
When 7N is connected, the switch elements 57A to 57A
The drive waveform signal is supplied to the piezoelectric vibrators 35A to 35N connected to the 7N.

When the drive waveform signal is applied based on the data of the most significant bit, subsequently, the control unit 6 serially transmits the data of one bit lower and sets the data in the shift register elements 54A to 54N. Then, if data is set in the shift register elements 54A to 54N,
By applying the latch signal, the set data is latched, and the drive waveform signal is converted to the piezoelectric vibrators 35A to 35A.
5N. Thereafter, the same operation is repeated up to the least significant bit while shifting the print data to lower bits one bit at a time.

As described above, in the illustrated printer, whether or not the drive waveform signal is applied to the piezoelectric vibrator 35 can be controlled by the print data. That is, the drive waveform signal can be applied to the piezoelectric vibrator 35 by setting the print data to “1”, and the application of the drive waveform signal to the piezoelectric vibrator 35 can be stopped by setting the print data to “0”. it can.

Therefore, the driving waveform signal is changed to the micro-vibration waveform 13 in printing, the micro-dot waveform 14, the middle-dot waveform 1
5 in the direction of the time axis so that each waveform signal 13
By setting each bit of the print data corresponding to 14 and 15, each of the waveform signals 13, 14 and 15 can be selectively applied to the piezoelectric vibrator 35.

For example, in the example shown in FIG. 6, the print data is composed of 3-bit data D1, D2 and D3. The print data D1 is a micro vibration waveform 13 in the print, and the print data D2 is a micro dot waveform 14 And print data D3
Are respectively associated with the middle dot waveforms 15. Then, by appropriately changing the data D1, D2, and D3, a plurality of types of ink droplets having different amounts are supplied to the nozzle opening 1.
6 can be discharged.

For example, if the print data is D1 = 1, D2 =
1, when D3 = 0, the in-print minute vibration waveform 13 and the microdot waveform 14 are applied to the piezoelectric vibrator 35,
Microdot ink droplets are ejected from the nozzle openings 16. Each data is represented by D1 = 1, D2 = 0, D3 =
When it is set to 1, the in-print minute vibration waveform 13 and the middle dot waveform 15 are applied to the piezoelectric vibrator 35, and a middle dot ink droplet is ejected from the nozzle opening 16. Similarly, by setting each data to D1 = 1, D2 = 1, and D3 = 1, the in-print minute vibration waveform 13 and the microdot waveform 1
4 and the middle dot waveform 15 are applied to the piezoelectric vibrator 35, and an ink droplet with the microdot waveform 14 and an ink droplet with the middle dot waveform 15 are ejected to form a large dot. Each data is represented by D1 = 1, D2 = 0,
By setting D3 = 0, the in-print minute vibration waveform 13 is applied to the piezoelectric vibrator 35, and the meniscus at the nozzle opening 16, that is, the free surface of the ink exposed at the nozzle opening 16, vibrates minutely. Thereby, the ink in the nozzle opening 16 is agitated, and the viscosity of the ink is prevented from increasing.

Next, each waveform will be described in detail with reference to FIG. First, the in-print minute vibration waveform 13 will be described.

The micro-vibration waveform 13 in the print includes a first charging element 60 for increasing the voltage at a constant gradient from the GND level V0, which is the reference voltage, to the micro-vibration driving potential V1, and holding the micro-vibration driving potential V1 for a certain time. First holding element 61
And a first discharge element 62 that lowers the voltage at a constant gradient from the micro-vibration drive potential V1 to the GND level V0.

In the present embodiment, the potential difference Vkp between the micro-vibration drive potential V1 and the GND level V0 is set based on the potential difference VHμ in the microdot waveform 14, and is set to 40% of the potential difference VHμ. . Further, the application time (charging time) of the first charging element 60 is set to 7 μsec, and the application time (holding time) of the first holding element 61 is set.
Is set to 2 μsec, and the application time (discharge time) of the first discharge element 62 is set to 7 μsec.

By applying such an in-print minute vibration waveform 13 to the piezoelectric vibrator 35, the piezoelectric vibrator 35 contracts and expands slightly, and the cavity 45 expands and contracts slightly. The meniscus vibrates slightly with the expansion and contraction.

The micro dot waveform 14 includes a second charging element 64 for increasing the voltage at a constant gradient from the GND level V0 to the micro driving potential V2, a second holding element 65 for holding the micro driving potential V2 for a certain time, A second discharging element 66 for decreasing the voltage at a constant gradient from the driving potential V2 to the first intermediate potential V3, a third holding element 67 for holding the first intermediate potential V3 for a fixed time, and a GND level from the first intermediate potential V3. This is constituted by a substantially trapezoidal signal composed of a third discharge element 68 for decreasing the voltage at a constant gradient to V0.

In the present embodiment, with respect to the potential difference VHμ between the micro drive potential V2 and the GND level V0, individual voltages are set for each recording head so that the weight of the ejected ink becomes 3.3 ng. Further, the first intermediate potentials V3 and G
The potential difference Vcμ from the ND level V0 is set based on the potential difference VHμ, and specifically, 65% of the potential difference VHμ
Is set to The application time of the second charging element 64 is set to 8 μsec, the application time of the second holding element 65 is set to 1 μsec, and the second discharging element 66
Is set to 1.5 μsec. The application time of the third hold element 67 is set to 1 μsec,
The application time of the third discharge element 68 is set to 5.4 μsec.

When the microdot waveform 14 is applied to the piezoelectric vibrator 35, the piezoelectric vibrator 35 contracts due to the application of the second charging element 64, and the cavity 45 expands. Drawn into the inside of the Then, a very small amount (3.3) is generated by the force of the drawn meniscus to return in the ejection direction.
ng) of the ink droplet is ejected.

The middle dot waveform 15 has the GND level V
A third charging element 70 for increasing the voltage at a constant gradient from 0 to the middle driving potential V4, a fourth holding element 71 for holding the middle driving potential V4 for a certain time, and a middle driving potential V
A fourth discharging element 72 for decreasing the voltage at a constant gradient from 4 to the GND level V0, a fifth holding element 73 for holding the GND level V0 for a fixed time, and a constant gradient from the GND level V0 to the second intermediate potential V5. A fourth charging element 74 for increasing the voltage, a sixth holding element 75 for holding the second intermediate potential V5 for a certain time, and a GN from the second intermediate potential V5.
The signal is constituted by a signal in which two large and small trapezoidal waveforms each including a fifth discharge element 76 for decreasing the voltage at a constant gradient to the D level V0 are arranged.

In this embodiment, the middle drive potentials V4 and G
The potential difference VHM from the ND level V0 is set for each head so that the large dot ink weight ejected by continuously applying the microdot waveform 14 and the middle dot waveform 15 becomes 20 ng. Also, the potential difference Vs between the second intermediate potential V5 and the GND level V0
p is set based on the potential difference VHM, and specifically, is set to 20% of the potential difference VHM.

The application time of the third charging element 70 is 7.
The application time of the fourth hold element 71 is set to 2 μsec, and the fourth discharge element 72 is set to 5 μsec.
Is set to 4 μsec. The application time of the fifth hold element 73 is set to 4 μsec.
The application time of the charging element 74 is set to 4 μsec,
The application time of the sixth hold element 75 is set to 2 μsec, and the application time of the fifth discharge element 76 is set to 4 μsec.

When such a middle dot waveform 15 is applied to the piezoelectric vibrator 35, the piezoelectric vibrator 35 contracts due to the application of the third charging element 70, and the cavity 45 expands.
The cavity 45 expanded by the extension of the piezoelectric vibrator 35 by the application of the fourth discharge element 72 is contracted, and ink droplets are ejected with the contraction of the cavity 45. And
By applying the fourth charging element, the sixth holding element 75, and the fifth discharging element 76, the meniscus is given an anti-phase vibration to suppress the meniscus vibration.

Next, each waveform signal (micro-vibration waveform 1 in printing)
3, micro dot waveform 14, middle dot waveform 15)
The arrangement interval between them will be described.

First, the time interval between the micro dot waveform 14 and the middle dot waveform 15 will be described. In this embodiment, the micro dot waveform 14 and the middle dot waveform 15
, Ie, the time from the end of the application of the third discharge element 68 to the start of the application of the third charge element 70 is about 1.5 times the cavity oscillation period Tc (8 μsec in the present embodiment). .5 μsec.

Hereinafter, the reason why the interval between the two waveforms is determined will be described.

FIG. 8 shows a single discharge pattern, a three discharge pattern, an alternate discharge pattern, and a single discharge pattern while changing the time interval Tμm between the micro dot waveform 14 and the middle dot waveform 15.
FIG. 9 is a diagram illustrating evaluation of a printing result when each of the main blanking patterns is printed by large dots.

Here, the single-ejection pattern corresponds to FIG.
As shown in (a), this is a recording pattern for discharging large dot ink droplets for each of the eight nozzle openings 16,
The nozzle openings 16 to be ejected of ink droplets are switched at regular intervals. FIG. 9 shows a three-ejection pattern.
As shown in (b), three adjacent nozzle openings 16 are selected for each of the eight nozzle openings 16, and a large dot ink droplet is ejected from the selected nozzle openings 16 in a recording pattern. The nozzle openings 16 to be ejected of ink droplets are switched at regular intervals. As shown in FIG. 9C, the alternate ejection pattern is a recording pattern in which large-dot ink droplets are alternately ejected from the odd-numbered nozzle openings 16 and the even-numbered nozzle openings 16 at regular intervals. is there. In addition, the one-off pattern is
As shown in FIG. 9D, a nozzle opening 16 that does not discharge ink droplets is set for each of the eight nozzle openings 16, and large dot ink droplets are discharged from the nozzle openings 16 excluding the set nozzle opening 16. Is a recording pattern for discharging.
Even in this single-punch pattern, the nozzle openings 16 that do not discharge ink droplets are switched at regular intervals.

In other words, one ejection pattern is a recording pattern in which the ratio of the nozzle openings 16 for recording (hereinafter, referred to as recording density) is the lowest among the four patterns.
The three-ejection pattern is a recording pattern having the second lowest recording density. The alternate ejection pattern is a recording pattern having the second highest recording density among the four patterns,
The one-off pattern is a recording pattern having the highest recording density.

In FIG. 8, the evaluation results are represented by four types of symbols, “○”, “Δ”, “×”, and “XX”. Here, the symbol “○” means that good recording was performed without any defect, and the symbol “△”
For example, the ejection pattern means that thicker dots with a wider width than normal and dot missing where the ejection pattern is not printed have occurred, and the symbol “x” means that a relatively large number of recording failures have occurred. , The symbol “xx” means that a very large number of recording failures have occurred. Evaluation result is "○"
Only practical.

Note that MPBF is the average number of missing-dot pages during image printing. The average number of missing dots is the average value from the page where a missing dot occurs to the next page where a missing dot occurs when an evaluation image is printed. For example, when the MPBF is “100”, it means that dot missing occurs about every 100 pages.

As shown in FIG. 8, in the single-discharge pattern described above, when the time interval Tμm is 6.5 μsec, some recording defects occur, but good recording can be performed without any recording defects in general. ing.

In the three-ejection pattern, some recording defects occur when the time interval Tμm is in the range of 6.5 to 10.5 μsec. However, when the time interval Tμm is 11.5 μsec or more, there is no recording defect and good recording is performed. Has been done.

In the alternate discharge pattern, a relatively large number of recording failures occur when the time interval Tμm is 6.5 and 8.5 μsec, and the time interval Tμm is 9.5, 10.5 and 1 μm.
Some recording failure occurred at 8.5 μsec.
Then, the time interval Tμm is 11.5 to 16.5 μsec.
In the range, good recording was performed without recording failure.

In the single-punch pattern, the time interval T μm is in the range of 10.5 to 12.5 μsec, 18.5 and 2
At 0.5 μsec, good recording can be performed without recording failure. Then, the time interval Tμm is 6.5 and 16.5μ.
A relatively large number of recording failures occur in sec, and a very large number of recording failures occur when the time interval Tμm is set to 14.5 μsec. In addition, the time interval Tμm is 8.5,9.
In the case of 5, 13.5 and 22.5 μsec, some recording defects occurred.

From the above, it can be seen that as the recording density increases, the time interval that can be favorably used for recording is limited. That is, in the single-ejection pattern having the lowest recording density,
When the time interval Tμm is 8.5 μsec or more, good recording can be performed. On the other hand, in the single-punch pattern having the highest recording density, the time interval Tμm is 10.5 to 12.5 μsec.
Recording can be performed well only in the limited range of c and 18.5 to 20.5 μsec.

It can also be seen that when the recording density increases, periodicity appears in the time interval T μm at which a recording failure occurs. That is, in the single blank pattern, a recording failure occurs when the time interval Tμm is 6.5, 14.5, 16.5, 22.5 μsec, and the time interval T at which the recording failure occurs
8 μsec is approximately equal to the cavity oscillation period Tc
Appears every time. At 22.5 μsec, the evaluation was “△”, and only some recording failure occurred, but the elapsed time from the point of application of the micro waveform was relatively long, and during this time the influence of the vibration due to the micro waveform was reduced. Therefore, it is considered that a recording failure has occurred.

It has been found that the recording failure in the single-punch pattern occurs when recording is performed by the nozzle opening 16 immediately after a state where recording is not performed.
From this, the recording failure in the single-punch pattern is as follows.
It is conceivable that this is caused by the influence of ink ejection from the adjacent nozzle openings 16.

That is, the vibration from the cavities 45, 45 adjacent to each other through the common ink chamber 47 is transmitted to the cavity (pressure chamber) 45 communicating with the nozzle opening 16 where recording is not performed, or the piezoelectric vibrator 35 adjacent to both sides is used. , 35, the piezoelectric vibrator 35 connected to the cavity 45 vibrates, so that unnecessary vibration is applied.

Depending on the timing at which this vibration is applied,
The slightly vibrating meniscus is amplified by the in-print minute vibration waveform 13, and as a result, the amplitude of the meniscus becomes excessively large and bubbles are taken in from the nozzle opening 16. Due to the captured bubbles, the compliance in the cavity 45 is increased, and first, an ink droplet having a large dot diameter is ejected, and the dot becomes thick.
Then, when more bubbles are taken in, dot missing occurs.

The timing (failure time) at which such a recording failure occurs is set at intervals of 8 μsec substantially equal to the cavity vibration period Tc, that is, at a time interval Tμm.
5, 14.5, and 22.5 μsec, the recording failure can be prevented by setting the time interval Tμm to approximately the middle of these failure times. This is because, when the time interval Tμm is set to approximately the middle of the failure time, the propagation of vibration from the adjacent cavities 45 and the effect of the vibration in the cavity 45 caused by the crosstalk of the piezoelectric vibrator 35 become more efficient. It is thought that it can be suppressed well. The setting of the time interval Tμm can also be represented by the following equation.

Tμm = Tc × (n / 2) In this equation, Tμm [μsec] is a time interval between the micro dot waveform 14 and the middle dot waveform 15;
Tc [μsec] is a cavity oscillation period, and n
Is an odd number of “3” or more.

In the present embodiment, n is set to “3”, and the time interval Tμm is set to about 1.5 times the cavity oscillation period Tc. The cavity vibration period Tc is about 8
Since it is μsec, 1.5 times of this is 12 μsec, but 11.5 μsec close to this 12 μsec is set as the time interval Tμm. And the time interval Tμ
When m is set to 11.5 μsec, MPBF
(Average number of missing dots) is 150 pages,
It was confirmed that recording defects can be significantly reduced as compared with the case where the time interval Tμm where the value of PBF is low is 14.5 μsec (MPBF = 10).

The reason why n is set to “3” is that large dots are ejected by continuously applying the microdot waveform 14 and the middle dot waveform 15 to the piezoelectric vibrator 35. I have.

That is, when discharging large dots,
The residual vibration after the application of the microdot waveform 14 is used, and the weight of the ink droplet of the middle dot becomes larger than the original weight of 10 ng by the residual vibration. If the time interval Tμm is too far away, the effect of the residual vibration is diminished, and even if the microdot waveform 14 and the middle dot waveform 15 are applied, the 13.3 ng ink droplet which is the total value of the original weight is applied. This makes it difficult to widen the weight range of ink droplets that can be ejected from the nozzle opening 16. In addition, since the printing cycle is extended, the printing speed of the printer is also reduced.

As described above, when the time interval Tμm is set to about 1.5 times the cavity oscillation period Tc, it is possible to prevent a recording failure, widen the weight range of ink droplets, and improve the recording speed of the printer. be able to.

Next, the time interval between the in-print minute vibration waveform 13 and the microdot waveform 14 will be described. In the present embodiment, the in-print minute vibration waveform 13 and the microdot waveform 1
The time interval between the fourth dot 4 and the middle dot waveform 15, that is, the time from the end of the application of the first discharge element 62 to the start of the application of the second charge element 64 is set to about 50 μsec.

The time interval between the in-print micro-vibration waveform 13 and the microdot waveform 14 is also the same as the time interval Tμ between the microdot waveform 14 and the middle dot waveform 15 described above.
It is considered that the same relationship as m has occurred. That is, it is considered that the timing (defective time) at which a recording failure occurs appears every 8 μsec substantially equal to the cavity vibration period Tc.

Therefore, in the present embodiment, the time interval between the in-print micro-vibration waveform 13 and the micro-dot waveform 14 is set to be long enough not to be affected by the in-print micro-vibration waveform 13. Specifically, as shown in FIG. 7, this time interval is set to 50 μsec.

Regarding this time interval, as described above, the timing at which a recording failure occurs is set at intervals of 8 μsec substantially equal to the cavity vibration period Tc, specifically, as in the case of FIG. It appears to appear at a time interval of 5,22.5 μsec. Here, in the case of FIG. 8, the evaluation result when the time interval is 22.5 μsec is “Δ”, which is small enough to cause some recording failure. It is considered that this is because the vibration is attenuated due to the longer time interval as described above.

For this reason, if the time interval is set to 30.5 μsec, which is longer than the 22.5 μsec by the cavity vibration period Tc, it is considered that the influence of the vibration due to the in-print minute vibration waveform 13 can be almost ignored. Therefore, regarding the time interval between the micro-vibration waveform 13 in printing and the micro-dot waveform 14, the time interval for which the influence of the vibration by the micro-vibration waveform 13 in printing does not have to be given to the micro-dot waveform 14 (micro-dot) is about 3 × Tc or more. Can be considered. In other words, the micro vibration waveform 13 in the print and the micro dot waveform 1
By setting the time interval of 4 to 3 × Tc or more, it is possible to eliminate the influence of the vibration due to the in-print minute vibration waveform 13 and to stabilize the ejection of the ink droplet by the microdot waveform 14.

In the present embodiment, the pressure generating element is
A so-called d3 in which the vibrator is laminated with the piezoelectric body 37 and the internal electrodes 38 and 39 in a direction orthogonal to the cavity pressing direction.
Although the one constituted by the comb-shaped vibrator 35 in one longitudinal vibration mode has been exemplified, the present invention relates to a so-called d33 longitudinal vibration mode in which the piezoelectric body 37 and the internal electrodes 38 and 39 are laminated in the cavity pressing direction. The present invention can also be applied to a piezoelectric vibrator or a pressure generating element using a flexural vibration mode.

Then, the comb-shaped vibrator 35 in the longitudinal vibration mode
Are integrally joined to the adjacent vibrator at the base end side, and thus are susceptible to the crosstalk from the adjacent vibrator, and recording errors easily occur. Therefore, by applying the present invention to the comb-shaped vibrator 35 in the longitudinal vibration mode, recording failure can be more effectively prevented.

In the present embodiment, microdots, middle dots, and large dots are described. Of course, the diameters of the dots ejected from the ink jet recording head according to the present invention are relative, and the results are obtained. The size of the dot is not particularly limited. That is, the present invention is not limited to only three types of dot modulation of microdots, middle dots, and large dots, but can be applied to an ink jet recording apparatus that adjusts a drive waveform for the purpose of dot modulation. In particular, the effect of the ink jet recording apparatus that realizes dot modulation by utilizing the residual vibration of the meniscus is remarkable.

[0098]

As described above, the present invention has the following effects.

According to the first, third, sixth, seventh, and eighth aspects of the present invention, at least a microdot waveform and a middle dot waveform are continuously applied to the pressure generating element. In the ink jet recording apparatus configured to eject large-dot ink droplets from the nozzle openings, the time interval between the micro dot waveform and the middle dot waveform is set to a length approximately halfway between the defective times occurring at the cavity oscillation period interval. With this setting, propagation of vibration from adjacent cavities and influence of vibration in the cavities caused by crosstalk of the piezoelectric vibrator can be suppressed.

Therefore, even if a recording pattern having a high recording density is recorded, recording defects can be reduced, and recording stability can be improved.

According to the second aspect of the present invention, by setting n to “3”, the time interval Tμm of the middle dot waveform becomes 1.5 times the cavity oscillation period Tc. The middle dot waveform can be arranged at a relatively short time interval. For this reason, when recording a large dot, the residual vibration after application of the microdot waveform can be used for ejection of ink droplets of the middle dot, and the weight of the middle dot during large dot recording can be used alone for the middle dot. Can be made larger than the weight when recording. Therefore, the weight range of the ink droplet can be widened, and recording with a wide dot diameter can be performed.

According to the fourth and fifth aspects of the present invention, the time interval between the micro-vibration waveform in printing and the micro-dot waveform is set long enough not to be affected by the vibration due to the micro-vibration waveform in printing. In addition, it is possible to stabilize the ejection of the ink droplet by the micro dot waveform.

According to the ninth aspect of the present invention, since the pressure generating element is constituted by the comb-shaped vibrator in which the piezoelectric body and the electrode are laminated in the direction orthogonal to the direction of expansion and contraction of the vibrator, recording failure can be reduced. It can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an ink jet printer.

FIG. 2 is a perspective view illustrating an internal mechanism of the ink jet printer.

FIG. 3 is a cross-sectional view illustrating a structure of a recording head.

FIG. 4 is an equivalent circuit for explaining natural vibration of ink in a cavity.

FIG. 5 is a block diagram illustrating an electrical configuration of the recording head.

FIG. 6 is a diagram illustrating a relationship between a driving waveform signal and a recording dot.

FIG. 7 is a diagram illustrating a drive waveform signal.

FIG. 8 is a diagram showing an evaluation of a printing result when each pattern is printed while changing the time interval Tμm between the microdot waveform and the middle dot waveform.

FIG. 9 is a diagram illustrating a recording pattern for evaluation.
(A) shows a single ejection pattern, (b) shows a three ejection pattern, (c) shows an alternate ejection pattern, and (d) shows a single ejection pattern.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printer controller 2 Print engine 3 External interface 4 RAM 5 ROM 6 Control part 7 Oscillation circuit 8 Recording head 9 Drive signal generation circuit 10 Internal interface 13 Fine vibration waveform in printing 14 Micro dot waveform 15 Middle dot waveform 16 Nozzle opening 19 Paper Feed mechanism 20 Carriage mechanism 21 Paper feed motor 22 Paper feed roller 23 Recording paper 24 Ink cartridge 25 Guide member 26 Carriage 27 Drive pulley 28 Follower pulley 29 Timing belt 30 Pulse motor 33 Case 34 Storage chamber 35 Piezoelectric vibrator 36 Flow path unit 37 Piezoelectric body 38 Common internal electrode 39 Individual internal electrode 42 Flow path forming plate 43 Nozzle plate 44 Elastic plate 45 Cavity (pressure chamber) 46 Ink supply unit 47 Common ink chamber 48 Ink supply pipe 49 Stainless steel plate 50 Elastic film 51 Island part 54 Shift register 55 Latch circuit 56 Level shifter 57 Switch 60 First charging element 61 First holding element 62 First discharging element 64 Second charging element 65 Second holding element 66 First 2 discharge element 67 third hold element 68 third discharge element 70 third charge element 71 fourth hold element 72 fourth discharge element 73 fifth hold element 74 fourth charge element 75 sixth hold element 76 fifth discharge element

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 2C057 AF39 AF40 AG12 AG48 AG53 AG55 AM03 AM15 AM18 AM21 AM22 AN01 AR04 AR08 BA03 BA14 2C062 AA02 AA08 AA14

Claims (9)

[Claims] A pressure generating element that is deformed by application of a waveform signal; a pressure chamber that expands and contracts due to deformation of the pressure generating element; and a nozzle opening that communicates with the pressure chamber. In an ink jet recording apparatus configured to discharge at least a large dot ink droplet from a nozzle opening by continuously applying at least a micro dot waveform and a middle dot waveform constituting a micro dot waveform, the micro dot waveform And the time interval between the middle dot waveform
The following equation Tμm = Tc × (n / 2) where Tμm is the time interval between the microdot waveform and the middle dot waveform Tc is the cavity oscillation period n is set to a value close to a value based on an odd number of 3 or more. An ink jet recording apparatus characterized by the above-mentioned. 2. The ink-jet recording apparatus according to claim 1, wherein n is set to “3”. 3. A driving waveform signal comprising a pressure generating element deformed by application of a waveform signal, a pressure chamber expanded and contracted by deformation of the pressure generating element, and a nozzle opening communicating with the pressure chamber. In an ink jet recording apparatus configured to discharge at least a large dot ink droplet from a nozzle opening by continuously applying at least a micro dot waveform and a middle dot waveform constituting a micro dot waveform, the micro dot waveform And the time interval between the middle dot waveform
An ink jet recording apparatus, wherein the length is set to a substantially intermediate length between the defective times generated at the cavity vibration period interval. 4. A series of driving waveform signals is formed by including a micro-vibration waveform in print for micro-vibrating the meniscus before the micro-dot waveform, and a time interval between the micro-vibration waveform in print and the micro-dot waveform is set. ,
4. The ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus is set to be long enough not to be affected by the vibration due to the minute vibration waveform in the print. 5. The ink jet recording apparatus according to claim 4, wherein the time interval is 3 × Tc or more. 6. A driving waveform signal comprising a pressure generating element deformed by application of a waveform signal, a pressure chamber expanded and contracted by deformation of the pressure generating element, and a nozzle opening communicating with the pressure chamber. In an ink jet recording apparatus configured to discharge at least a large dot ink droplet from a nozzle opening by continuously applying at least a micro dot waveform and a middle dot waveform constituting a micro dot waveform, the micro dot waveform An ink jet recording apparatus characterized in that a time interval between the middle dot waveform and the middle dot waveform is set to an interval at which ejection failure does not occur. 7. The ink jet recording apparatus according to claim 6, wherein the interval is an interval mainly represented by a linear function of Tc. 8. The ink jet recording apparatus according to claim 3, wherein said defective time appears periodically. 9. The pressure generating element according to claim 1, wherein the pressure generating element is constituted by a comb-shaped vibrator in which a piezoelectric body and an electrode are laminated in a direction orthogonal to a direction in which the vibrator expands and contracts. An ink jet recording apparatus according to any one of the above.