JP2003011370A - Ink jet recorder and its driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the image quality of a recording employing a small quantity of ink drops. SOLUTION: The ink jet recorder comprises a recording head 1 provided with a plurality of nozzle arrays ejecting ink drops from nozzle openings through action of a piezoelectric oscillator 2, a circuit 47 generating a drive signal being fed to the piezoelectric oscillator 2, and a section 45 for controlling ejection of ink drops from the recording head 1 wherein a nozzle array among the plurality of nozzle arrays having the smallest ejection quantity of ink drop is referred to a reference nozzle array and the drive signal generating circuit 47 generates a drive signal having a drive voltage value set to increase the quantity of an ink drop being ejected from the reference nozzle array to a decision reference level or above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet type recording apparatus such as a printer or a plotter and a driving method thereof, and more particularly, to an apparatus having a recording head having a plurality of nozzle rows.

[0002]

2. Description of the Related Art Some ink jet type recording apparatuses (hereinafter simply referred to as recording apparatuses) such as printers and plotters have a recording head having a plurality of nozzle arrays for color recording, high speed recording and the like.

In this recording head, the amount of ink droplets ejected increases or decreases in accordance with the drive voltage value of the drive signal, and the density of the image deviates from the designed standard value. Therefore, the optimum drive voltage value is set. It is important to. Therefore, conventionally,
The ink drop amount for each nozzle row is acquired, and the drive voltage value of the drive signal is set so that the average value of the acquired ink drop amounts becomes the target value.

For example, when an ink droplet of 8.0 pL (picoliter, hereinafter the same) as a target value is ejected using a recording head having a total of seven nozzle rows, the ink droplet for the first nozzle row is ejected. Amount a1, the ink drop amount a2 for the second nozzle line, ..., The ink drop amount a7 for the seventh nozzle line are acquired, and the ink drop amounts a1 to a1 are obtained.
The drive voltage value is set so that the value obtained by dividing the total up to 7 by 7 is 8.0 pL.

Further, since the amount of ink droplets ejected from the recording head tends to vary from nozzle row to nozzle row, identification information indicating variation in ink amount for each nozzle row is given to each nozzle row.

Then, a drive signal having a set drive voltage value is supplied to a pressure generating element (for example, a piezoelectric vibrator) of the recording head to eject ink droplets, and at the same time, a unit area is referred to by referring to the above identification information. The number of times the ink droplet is ejected is increased or decreased. As a result, an image whose image density and color balance have been adjusted is recorded.

[0007]

By the way, in recent years, there is a strong demand for high image quality in this type of recording apparatus, and the amount of the minimum ink droplet is extremely small, for example, 4 to 2 pL. Since such a small amount of ink drop has a larger speed difference between nozzle rows than before, if the above adjustment method is applied as it is, an ink drop flying at a speed lower than the minimum required speed may occur. understood.

Due to this lack of flight speed, the landing position of the ink droplet may deviate from the normal position. This is because the recording apparatus ejects the ink droplets while moving the recording head in the main scanning direction, and it is considered that the flight trajectory of the ink droplets deviates from the regular trajectory due to insufficient flight speed. It has been found that the deviation of the landing position causes the image quality to be deteriorated such that the recorded image has a feeling of roughness and the line is curved. It was also found that there is a risk that the ink droplets will not land on the print recording medium and become a mist.

Further, in a small amount of ink droplets, the variation in the ink amount among the nozzle rows also becomes large. However, when the variation in the ink amount exceeds the allowable range,
It was also found that the solid ink cannot be filled in the nozzle row on the side with a small amount of ink, resulting in white streaks.

The present invention has been made in view of such circumstances, and an object thereof is to improve image quality of recording using a small amount of ink droplets.

[0011]

According to the present invention, there is a high correlation between the ejection rate of ink drops and the flight speed, and when the ejection rate of ink drops is increased or decreased, the flight speed changes according to the increase or decrease. It was made paying attention to the change, and the nozzle row with the smallest amount of ink droplet ejection is set as the reference nozzle row,
The drive voltage value of the drive signal is set so that the amount of ink droplets ejected from the reference nozzle array becomes equal to or larger than the determination reference amount. It should be noted that the “determination reference amount” means the amount of ink that can obtain the velocity required for the ejected ink droplet to normally land on the print recording medium along the planned flight trajectory.

That is, the invention according to claim 1 is provided with a plurality of nozzle rows in which the nozzle openings are provided in rows, the recording head capable of ejecting ink droplets from the nozzle openings by the operation of the pressure generating element, and the pressure generating element. In an ink jet recording apparatus having a drive signal generating unit capable of generating a drive signal supplied to a recording head and an ejection control unit controlling an ejection of an ink droplet by a recording head, the ejection of the ink droplet among the plurality of nozzle rows The nozzle row with the smallest amount is used as the reference nozzle row,
The drive signal generating means is an ink jet recording apparatus characterized by generating a drive signal having a drive voltage value set so that the amount of ink droplets ejected from the reference nozzle array is equal to or larger than the determination reference amount.

According to a second aspect of the present invention, in the recording head, ink amount identification information indicating a ratio of the nozzle rows to each other with respect to the ink droplet amount, and an average ink droplet amount resulting from the set driving voltage value are recorded. The ink jet recording apparatus according to claim 1, wherein average ink amount identification information indicating a difference from the target value is added.

According to a third aspect of the present invention, the ejection control means adjusts the number of ink droplet ejections per unit area for each nozzle row based on the ink amount identification information and the average ink amount identification information. The inkjet recording apparatus according to claim 1 or 2, further comprising an image density correction unit that corrects the image density.

According to a fourth aspect of the invention, the recording head is provided with a Tc rank determined based on the natural vibration period of the ink in the pressure chamber, and the driving voltage value is set in consideration of the Tc rank. Claims 1 to 3 characterized in that
The inkjet recording apparatus according to any one of 1.

According to a fifth aspect of the present invention, there is provided recording mode setting means for selecting one recording mode from a plurality of recording modes determined according to the ink droplet amount, and the ink amount identification information and the average ink amount identification information are provided. Prepare for each recording mode,
The ink jet recording apparatus according to any one of claims 2 to 4, wherein the image density correcting unit performs adjustment based on the ink amount identification information and the average ink amount identification information corresponding to the set recording mode. Is.

The ink jet recording apparatus according to any one of claims 1 to 5, wherein the recording head includes a pressure generating element unitized for each nozzle row. It is a type recording device.

The invention according to claim 7 is the ink jet recording apparatus according to any one of claims 1 to 6, wherein the pressure generating element is a piezoelectric vibrator.

According to an eighth aspect of the present invention, there is provided a plurality of nozzle rows in which nozzle openings are provided, and a recording head capable of ejecting ink droplets from any nozzle opening by the operation of the pressure generating element, and the pressure generating element. In a method of driving an ink jet recording apparatus having a drive signal generating unit capable of generating a drive signal supplied to, a nozzle row having the smallest ink droplet ejection amount among the plurality of nozzle rows is used as a reference nozzle row, The drive signal generating means generates a drive signal having a drive voltage value set so that the amount of ink droplets ejected from the reference nozzle array is equal to or greater than the determination reference amount, and the drive signal having the drive voltage value is supplied to the recording head. And a method for driving an ink jet recording apparatus.

According to a ninth aspect of the invention, based on the amount of ink droplets ejected by the drive signal of the drive voltage value,
9. The method for driving an ink jet recording apparatus according to claim 8, wherein the number of ink droplets ejected per unit area is adjusted for each nozzle row to correct the image density.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. First, the structure of an inkjet recording head (hereinafter referred to as a recording head) will be described. As shown in FIG. 1, the illustrated recording head 1 includes a vibrator group 3 including a plurality of piezoelectric vibrators 2, ..., A fixing plate 4, and a vibrator unit 6 in which a flexible cable 5 and the like are unitized, and the vibration unit 6. A case 7 capable of accommodating the child unit 6 and a flow path unit 8 joined to the front end surface of the case 7.
It has and.

The case 7 is a block-shaped member made of synthetic resin in which a storage space 9 whose front and rear ends are open is formed. The vibrator unit 6 is housed and fixed in the storage space 9. That is, in the vibrator unit 6, the fixing plate 4 is adhered to the wall surface of the storage space 9 in a state where the comb-teeth-shaped tip of the piezoelectric vibrator 2 (that is, the tip end surface portion) faces the opening on the tip side.

The piezoelectric vibrator 2 is a kind of the pressure generating element of the present invention and has a comb tooth shape elongated in the vertical direction. For example, it is cut into a needle shape having an extremely narrow width of about 30 μm to 100 μm. This piezoelectric vibrator 2 is a laminated piezoelectric vibrator 2 configured by alternately stacking piezoelectric bodies 10 and internal electrodes 11, and is expandable and contractable in a vertical direction orthogonal to the electric field direction (that is, in the longitudinal direction). It is a piezoelectric vibrator 2 in a longitudinal vibration mode that can vibrate. Then, each piezoelectric vibrator 2 ...
The base end side portion is joined to the fixed plate 4, and the piezoelectric vibrator 2 is attached in a cantilever state in which the free end portion of the piezoelectric vibrator 2 is projected outward from the edge of the fixed plate 4.

In this vibrator group 3, for example, one piezoelectric plate having piezoelectric layers and internal electrode layers alternately laminated is joined to the fixed plate 4, and then the comb group is formed by a cutting tool such as a wire saw. It is made by cutting. In this way, the transducer group 3
Are cut out from the same piezoelectric plate and are unitized, so that the expansion and contraction characteristics of each piezoelectric vibrator 2 can be aligned at a high level.

The tip end surface of each piezoelectric vibrator 2 is fixed to the island portion 12 which is a predetermined portion of the flow path unit 8 by contact, and the flexible cable 5 is on the opposite side of the fixing plate 4. The piezoelectric vibrator 2 is electrically connected to the side surface of the base end portion of the vibrator.

As shown in FIG. 2, in the flow path unit 8, the nozzle plate 16 is disposed on one surface side of the flow path forming substrate 15 with the flow path forming substrate 15 sandwiched therebetween, and the elastic plate 17 is used as the nozzle plate 16. Are arranged and laminated on the other side, which is the opposite side.

The nozzle plate 16 is a thin plate made of stainless steel in which a plurality of nozzle openings 18 are opened in a row at a pitch corresponding to the dot formation density. In this embodiment, 96 nozzle openings 18 are arranged at a pitch of 180 dpi.
Are arranged in rows, and these nozzle openings 18 form a nozzle row. Then, as shown in FIG.
9 are formed in a plurality of rows corresponding to the types of ink that can be ejected (for example, colors).

In this embodiment, a total of seven nozzle rows, from the first nozzle row 19A located at the left end to the seventh nozzle row 19G located at the right end, are formed side by side, and each nozzle row 19A to 19G is formed. The inks of different colors can be ejected.

For example, dark yellow ink is supplied from the first nozzle array 19A, black ink is supplied from the second nozzle array 19B, and cyan ink is supplied from the third nozzle array 19C.
Each is capable of discharging. In addition, light cyan ink is supplied from the fourth nozzle row 19D and the fifth nozzle row 19D.
E is capable of ejecting magenta ink, the sixth nozzle row 19F is capable of ejecting light magenta ink, and the seventh nozzle row 19G is capable of ejecting yellow ink. And in this embodiment, each of these nozzle rows 19A-1
The vibrator unit 6 is provided for each 9G. That is,
The recording head 1 includes seven vibrator units 6 ...

The flow path forming substrate 15 includes a nozzle plate 16
Is a plate-like member in which an empty portion which becomes the pressure chamber 20 is formed corresponding to each of the nozzle openings 18, and an empty portion which becomes the ink supply port 21 and the common ink chamber 22 is formed. For example, a silicon wafer is etched. It is formed by processing.

The pressure chamber 20 is an elongated chamber in a direction orthogonal to the direction in which the nozzle openings 18 are arranged (nozzle row direction), and is composed of a flat concave chamber divided by a weir. The ink supply port 21 is formed by the dam portion in the form of a narrowed portion having a narrow channel width. Further, at a position farthest from the common ink chamber 22 in the pressure chamber 20, a nozzle communication port 23 that communicates the nozzle opening 18 with the pressure chamber 20.
Are provided so as to penetrate in the plate thickness direction.

The elastic plate 17 also serves as a diaphragm portion that seals one opening surface of the pressure chamber 20 and a compliance portion that seals one opening surface of the common ink chamber 22, and is a stainless steel support plate. It has a double structure in which a resin film 25 such as PPS (polyphenylene sulfide) is laminated on 24. Then, the support plate 24 in the portion functioning as the diaphragm portion, that is, the portion corresponding to the pressure chamber 20 is annularly etched to form the island portion 12 for fixing the tip end surface portion of the piezoelectric vibrator 2 in contact with each other. The portion of the support plate 24 functioning as the compliance portion, that is, the portion corresponding to the common ink chamber 22 is removed by etching to leave only the resin film 25.

In the recording head 1 having the above structure, the island portion 12 is pressed against the nozzle plate 16 side by discharging the piezoelectric vibrator 2 and extending the piezoelectric vibrator 2 in the vibrator longitudinal direction (that is, the vertical direction), and the diaphragm. The resin film 25 forming the portion is deformed and the pressure chamber 20 contracts. Further, when the piezoelectric vibrator 2 is charged and contracted in the vibrator longitudinal direction,
The elasticity of the resin film 25 causes the pressure chamber 20 to expand.
By controlling the expansion and contraction of the pressure chamber 20, the ink pressure in the pressure chamber 20 fluctuates and the nozzle opening 1
Ink droplets are ejected from 8.

However, in this recording head 1, the ejection characteristics of the ink droplets (the amount of the ink droplet, the flight speed, etc.) vary depending on the dimensional accuracy of the parts, the assembly accuracy, and the like. That is, even if the ink droplets are ejected under the same conditions, the ejection characteristics of the ink droplets differ for each recording head 1. In particular, in the configuration having different transducer units 6 for each nozzle row 19 as in this embodiment, the characteristic difference (individual difference) of the transducer units 6 affects the ejection characteristics of ink droplets. There is a tendency for each row 19 to vary. It is possible to improve the dimensional accuracy and the assembly accuracy of the parts in order to reduce the variation in the ejection characteristics. However, since each part of the recording head has an extremely fine shape, it is possible to improve the dimensional accuracy and the assembly accuracy. That is not realistic.

Regarding the flight speed of the ink droplets, if the flight speed is higher than a required speed, that is, a speed required for the ejected ink droplets to normally land on the print recording medium along a predetermined flight trajectory. There is no problem, but if it is slower than this required speed, problems such as landing position deviation may occur.
That is, in this type of printer, the ink droplets are ejected while the recording head 1 is moved in the main scanning direction.
When the flight speed of the ink droplet becomes lower than the required speed, the ink droplet deviates from the regular flight trajectory due to viscous resistance of air and the like. This is one of the causes of deterioration of the image quality of a recorded image, such as a feeling of roughness.

In particular, when a very small amount of ink droplets such as 2 pL is ejected, the variation of the displacement amount of the piezoelectric vibrator 2 is amplified to cause the variation of the flight speed, and the influence of the viscous resistance of air is further increased. Since it is received, the amount of deviation of the landing position also becomes large and the image quality deterioration becomes remarkable. Further, there is a possibility that the ink droplets cannot land on the recording paper and become mist.

By the way, in the recording head 1, when the drive signals having the same waveform are used, the drive voltage value, that is,
The ejection amount of the ink droplet can be changed according to the potential difference from the maximum potential to the minimum potential in the drive signal. In this case, it has been found that there is a high correlation between the ink droplet ejection amount and the flight speed, and that when the ink droplet ejection amount is increased or decreased, the flight speed changes according to the increased or decreased amount.

In the present invention, attention is paid to this point, and the nozzle row 19 with the smallest ink droplet ejection amount is used as the reference nozzle row.
The drive voltage value of the drive signal is set so that the amount of ink droplets ejected from the reference nozzle array becomes equal to or larger than the determination reference amount. Here, the “determination reference amount” is an ink amount defined by the above required speed, and is an ink amount that provides a flight speed that is higher than this required speed.

In this way, the necessary flight speed can be secured for the ink droplets ejected from the reference nozzle row, so that even a very small amount of ink droplets such as 2 pL can be reliably landed at a predetermined position. It is possible to prevent the formation of mist. Then, the nozzle row 19 other than the reference nozzle row
The amount of ink droplets ejected from is at least equal to or higher than the reference nozzle row, and the flight speed is equal to or higher than the reference nozzle row. For this reason, the flight speed of the ink droplets becomes higher than the required speed even in the entire recording head 1. This makes it possible to ensure the accuracy of the ink droplet landing position and prevent mist formation.

However, since the drive voltage value is set in accordance with the reference nozzle row having the smallest ink droplet ejection amount,
The drive voltage value is determined according to each recording head 1, and the amount of ejected ink droplets (average ink amount) varies. This difference in ejection amount causes variation in light and shade of the image. For example, when there are two recording heads 1 and 1 having different ejection amounts of ink droplets, an image recorded by the recording head 1 having a larger ejection amount of ink droplets is the recording head 1 having a smaller ejection amount. It is darker than the image recorded in. Therefore, if images of the same print data are recorded by these recording heads 1, there will be differences in the shade of the images.

Further, as described above, the ejection amount of ink droplets varies from nozzle row to nozzle row even with one recording head 1. The variation in the ejection amount between the nozzle rows affects the hue of the image. That is, when printing is performed under the same condition for each nozzle row 19, the nozzle row 1 whose ejection amount is larger than the average ejection amount in the recording head 1
Nozzle row 1 in which 9 colors are darker and less than the average discharge amount
The color of 9 becomes light. For example, when the ink amount in the magenta row is larger than the average ejection amount, the recorded image becomes redder than the standard image.

In order to correct such a variation for each print head 1 and a variation for each nozzle row 19, a color adjust ID indicating a relative ratio of the ink droplet amount for each nozzle row.
(Corresponding to the ink amount identification information of the present invention) and an offset ID indicating the difference from the target value of the average ink drop amount due to driving with the set drive voltage value (corresponding to the average ink amount identification information of the present invention) And are applied to the recording head 1. Then, when the recording head 1 is incorporated in a printer, the ink amount per unit area, that is, the number of ink droplet ejections is increased or decreased by using the color adjustment ID and the offset ID, and the image density and hue (color balance) are obtained. ) According to the design.

The procedure for setting the drive voltage value of the drive signal, the color adjust ID, and the offset ID will be described below with reference to FIG.
And it demonstrates in detail based on the flowchart of FIG.
The drive voltage value, the color adjustment ID, and the offset ID are set, for example, in the inspection process for the recording head 1 that has been assembled.

In setting these voltage values and ID, first, the Tc rank of the recording head 1 is determined (S
1). This "Tc rank" is a rank determined based on the natural vibration period Tc, and in the present embodiment, the natural vibration period Tc is standard "rank 0", shorter than the standard "rank 1", longer than the standard. It consists of three ranks, "Rank 2". Here, the natural vibration period Tc is the pressure vibration reciprocating in the ink in a series of empty parts (a pressure chamber in a broad sense, which is the pressure chamber in the present invention) including the pressure chamber 20 and the nozzle communication port 23. Is the cycle of.

The Tc rank is measured because there is a high correlation between the natural vibration period Tc and the flight speed of the ink drop, and the flight speed of the ink drop is the natural vibration cycle even if the ejection amount of the ink drop is the same. It depends on the variation with Tc. The fact that the flight speed of the ink droplet fluctuates according to the natural vibration cycle Tc means that the above-described determination reference amount changes according to the natural vibration cycle Tc. Therefore, Tc
When the driving voltage value is set in consideration of the rank, it is possible to make an appropriate setting that reflects the characteristics of the recording head 1.

For example, as shown in FIG. 6, when the ejection amount of ink droplets is adjusted to a target value (for example, 2.0 pL), the recording head 1 of Tc rank 1 having a short natural vibration period Tc has an average flight of ink droplets. In the recording head 1 of the Tc rank 2 where the velocity Vm is sufficiently faster than the required velocity and the natural vibration period Tc is long, the average flight velocity Vm is about the same as or slightly faster than the required velocity. Furthermore, the natural vibration period Tc is standard Tc.
In the recording head 1 of rank 0, the average flight speed Vm is almost between Tc rank 1 and Tc rank 2.

From FIG. 6, since the average flying speed Vm of the recording head 1 classified into Tc rank 1 is sufficiently higher than the required speed Vm0, even if the deviation of the reference nozzle row is large,
That is, even if the flight speed of the reference nozzle array greatly varies toward the lower side than the average flight speed, the flight speed Vm of the ink droplets from the reference nozzle array is faster than the required speed Vm0. Therefore, the recording head 1 of Tc rank 1 has a temporary driving voltage value Vh ′ determined based on the target value of the ink droplet amount.
It can be seen that the necessary and sufficient flight speed Vm can be obtained even when driven by (described later), in other words, without performing the adjustment based on the determination reference value.

For the recording head 1 classified into Tc rank 0, the average flight speed Vm is slightly higher than the required speed Vm0. However, when the deviation of the reference nozzle row is large, the flight speed of the ink droplets from the reference nozzle row may be slower than the required speed. Therefore, the determination reference amount for the recording head 1 having Tc rank 0 is set so that the drive voltage value is adjusted with respect to the provisional drive voltage value Vh ′ when the deviation of the reference nozzle row is large. For example, when the determination reference amount is set to be 10% less than the target value of the ink droplet amount, and the ink droplet amount of the reference nozzle row is less than this determination reference amount, the provisional drive voltage value Vh ′ is set. It is corrected to the + side so as to have a normal drive voltage value Vh so that the ink droplet amount equal to or larger than the determination reference amount is ejected.

In the recording head 1 classified into the Tc rank 2, the average flight speed Vm is about the same as the required speed Vm0. Therefore, the nozzle row 19 having a flight speed lower than the average flight speed Vm has ink droplets. The flight speed may be slower than the required speed Vm0. Therefore, the determination reference amount for the recording head 1 of Tc rank 2 is set so that the drive voltage value is adjusted with respect to the provisional drive voltage value Vh ′ regardless of the deviation of the reference nozzle row. For example, the judgment reference amount is set to the target value of the ink droplet amount, and the provisional drive voltage value Vh ′ is corrected to the + side so that the ink droplet amount of the reference nozzle row is equal to or larger than this target value, and the normal drive voltage is corrected. The value Vh,
The amount of ink droplets equal to or larger than the determination reference amount is ejected from all the nozzle rows 19.

Next, a method of measuring the Tc rank will be described.

As shown in FIG. 7, the Tc rank is measured by
The evaluation pulse generation circuit 30 and the electronic balance 31 are used. In the present embodiment, the evaluation pulse generation circuit 30 and the recording head 1 are electrically connected, and the evaluation pulse TP1 generated by the evaluation pulse generation circuit 30 is supplied to the piezoelectric vibrator 2 to eject ink droplets from the recording head 1. Let Then, the weight of the ejected ink droplet is measured by the electronic balance 31, and the natural vibration period Tc is determined based on the measured ink weight.

The evaluation pulse generating circuit 30 is, for example, as shown in FIG.
The evaluation pulse TP1 shown in FIG. This evaluation pulse T
P1 is an excitation element P1 that raises the potential from the intermediate potential VM to the maximum potential VH with a constant gradient, a first hold element P2 that is generated following the excitation element P1 and maintains the maximum potential VH, and a first hold element P2. The ejection element P3 that is generated following the ejection element P3 that ejects an ink droplet from the nozzle opening 18 by lowering the potential from the maximum potential VH to the minimum potential VL at a constant gradient, and the ejection element P3 that is generated subsequent to the ejection element P3 The second hold element P4 to maintain and the lowest potential V
It is composed of a damping element P5 that raises the potential from L to the intermediate potential VM with a constant gradient.

The above-mentioned first hold element P2 is supplied to the discharge element P3 at the supply start timing, in other words, the exciting element P1.
This is an element that defines the time from the end of to the start of the ejection element P3, and a plurality of types of generation time Pwh1 (supply time) are set when measuring the ink weight. That is, a plurality of types of evaluation pulses TP1 having different generation times Pwh1 of the first hold element P2 are used, and the ink amount is measured a plurality of times.

In this embodiment, the first evaluation pulse in which the generation time Pwh1 is set to the first standard time serving as a reference and the second evaluation pulse in which the generation time Pwh1 is set to the second standard time shorter than the first standard time are used. And the third evaluation pulse in which the generation time Pwh1 is set to the third standard time which is longer than the first standard time, the ink amount is measured three times.

The above-mentioned first standard time is set to the time when the ejected ink amount becomes the smallest when the assembled recording head 11 has the natural vibration period Tc as designed. That is, the generation time Pwh1 is set such that the sum with the generation time of the excitation element P1 is aligned with the design value of the natural vibration period Tc. Further, the second standard time is set to a time shorter than the first standard time by a predetermined time, and the third standard time is set to a time longer than the first standard time by a predetermined time.

As a specific example, the design value of the natural vibration period Tc is about 8.4 μs (microsecond), and the excitation element P
When the generation time of 1 is 4.2 μs, as shown in FIG. 10, the first standard time (M) of the generation time Pwh1 is 4.2 μs, and the second standard time (S) is the first standard time. 3.4 μs, which is 0.8 μs shorter than the time, and 5.0 μs in which the third standard time (L) is 0.8 μs longer than the first standard time
Becomes

Then, in measuring the ink weight,
The three types of evaluation pulses TP1 determined as described above are supplied to the piezoelectric vibrator 2. When these evaluation pulses TP1 are supplied to the piezoelectric vibrator 2, first, the pressure chamber 20 expands as the excitation element P1 is supplied, and pressure vibration is excited in the ink in the pressure chamber 20. Then, the expanded state of the pressure chamber 20 is the first
It is maintained for the supply time Pwh1 of the hold element P2, and the pressure chamber 20 contracts with the supply of the discharge element P3,
Ink droplets are ejected from the nozzle openings 18. The ejected ink droplets are collected, and the collected amount (weight) of each evaluation pulse is measured using the electronic balance 31.

At this time, the ejection amount of the ink drop differs for each evaluation pulse. For example, if the first evaluation pulse is used when the assembled recording head 1 has the natural vibration period Tc as designed, the ejection element P3 is supplied at the timing indicated by the symbol M in FIG. . In this case, the pressure applied to the ink by the ejection element P3 is canceled by the pressure vibration of the ink excited by the excitation element P1, so that the ejection amount of the ink droplet is minimized. Further, when the second evaluation pulse is used, the ejection element P3 is supplied at the timing shown by reference symbol S in FIG. 9, and when the third evaluation pulse is used, the ejection element P3 is supplied at the timing shown by reference symbol L in FIG. . In these cases, it is possible to pressurize the ink more efficiently than when the first evaluation pulse is used, so that the ink amount
More than the evaluation pulse.

Further, when the assembled recording head 1 has the natural vibration period Tc shorter than the design value, the first hold that minimizes the ejected ink amount, as shown by the broken line in FIG. The supply time Pwh1 of the element P2 becomes shorter than that in the case of the recording head 1 whose natural vibration period Tc is as designed. Therefore, regarding the ink amount, the case where the second evaluation pulse is used is the smallest, the case where the first evaluation pulse is used is the second smallest, and the case where the third evaluation pulse is used is the largest.

On the contrary, when the assembled recording head 1 has the natural vibration period Tc longer than the design value,
As shown by the alternate long and short dash line in FIG. 9, the supply time Pwh1 of the first hold element P2 at which the ejected ink amount is the minimum is longer than that of the recording head 1 whose natural vibration period Tc is the designed value. Therefore, regarding the ink amount, the case where the second evaluation pulse is used is the largest, the case where the first evaluation pulse is used is the second largest, and the case where the third evaluation pulse is used is the smallest.

After measuring the ink amount for each evaluation pulse TP, the Tc rank is set based on the measurement result. That is, as shown in FIGS. 10 and 11, the ink amount Iw corresponding to the first evaluation pulse (Pwh1 = 4.2 μs)
1, the ink amount Iw2 corresponding to the second evaluation pulse (Pwh1 = 3.4 μs), and the third evaluation pulse (Pwh1 =
The Tc rank is set by comparison with the ink amount Iw3 corresponding to 5.0 μs.

These ink amounts Iw1, Iw2, Iw3
In the case of the recording head 1 in which the ink amount Iw1 is the smallest and the ink amounts Iw2 and Iw3 are larger than the ink amount Iw1 (indicated by the circled line in FIG. 10), Since the natural vibration period Tc of the recording head 1 in (1) is equal to the design value, it is classified into Tc rank 0. Similarly, the ink amounts Iw1 and Iw2 are substantially equal to each other, and the ink amount Iw3 is larger than the ink amount Iw1.
And the ink amounts Iw1 and Iw3 are substantially equal, the ink amount Iw
The recording head 1 having the ink amount 2 larger than the ink amount Iw1 is also classified as Tc rank 0.

Further, in the case of the recording head 1 in which the ink amount Iw2 is the smallest, the ink amount Iw1 is the second smallest, and the ink amount Iw3 is the largest (in the case of the line marked with a square in FIG. 10), , Recording head 1 after assembly
The natural vibration period Tc of is shorter than the design value. Therefore, the recording head 1 is classified into Tc rank 1.

Further, in the case of the recording head 1 in which the ink amount Iw2 is the largest, the ink amount Iw1 is the second largest, and the ink amount Iw3 is the smallest (in the case of the line marked with X in FIG. 10), The natural vibration period Tc of the recording head 1 after assembly is longer than the design value. Therefore, the recording head 1 is classified into Tc rank 2.

After the Tc rank is determined, the temporary drive voltage value Vh 'in the drive signal is set (S2).

In the present embodiment, the drive voltage in the drive signal corresponds to the potential difference from the maximum potential VH to the minimum potential VL of the small dot drive pulse DP1 shown in FIG. 12 (b). The tentative drive voltage value Vh ′ is the ejection amount of the ink droplets obtained by supplying the small dot drive pulse DP1 to the piezoelectric vibrator 2, more specifically, the average ink droplet amount (1 drop) per unit of the recording head. Per volume) is the target value of 2.0 pL
It is a voltage value determined so that

Here, the small dot drive pulse DP1 will be briefly described. This small dot drive pulse DP1 is
First charge element P11, second charge element P12, first hold element P13, first discharge element P14, second hold element P15, second discharge element P16, third hold element P1
7 and the third discharge element P18 are sequentially connected to form a series of signals.

By supplying the first charging element P11 to the piezoelectric vibrator 2, the pressure chamber 20 is slowly expanded to such an extent that the meniscus (the free surface of the ink exposed at the nozzle opening 18) is not excessively vibrated. After that, the second charging element P12 is supplied to rapidly expand the pressure chamber 20 to the maximum volume, and the central portion of the meniscus is locally expanded to the pressure chamber 20.
Pull to the side. Next, the pressure chamber 20 is maintained in the expanded state by the supply of the first hold element P13, and the central portion of the meniscus is raised in a convex shape in the ejection direction by a reaction. Then, the first discharge element P14 is supplied to rapidly contract the pressure chamber 20, and the ink column is pushed out in the ejection direction.
After that, the second hold element P15 and the second discharge element P1
6, third hold element P17, and third discharge element P1
8 are sequentially supplied to gradually contract the pressure chamber 20. As a result, the tip portion of the ink column is torn from the main body and flies in the ejection direction, and an extremely small amount of ink droplet of about 2.0 pL is ejected from the nozzle opening 18.

Even with the small dot drive pulse DP1, the amount of ink droplets ejected changes according to the drive voltage. Therefore, when setting the tentative drive voltage value Vh ′, as shown in FIG. 12A, the lowest voltage value Vh1 in the ink drop ejectable range and the ink drop amount corresponding to this lowest voltage value Vh1 are set. And the maximum voltage value Vh2
Then, a calibration curve is created using the ink droplet amount corresponding to the maximum voltage value Vh2. Then, the temporary drive voltage value Vh ′ is set using this calibration curve. That is, the voltage value corresponding to the target value of 2.0 pL is acquired from the created calibration curve, and the acquired voltage value is set as the temporary drive voltage value Vh ′.

As the ink drop amount when creating this calibration curve, the ink drop amount of one unit of the recording head, that is, the average value obtained by ejecting the ink drops from all the nozzle openings 18 is used. This average value is, for example, the electronic balance 3 described above.
1 is used to measure the amount of collected ink, and the amount of collected ink is divided by the number of ink droplet ejections and the number of all nozzle openings to calculate.

After the provisional drive voltage value Vh 'is set, the ejection amount of the ink droplet at the provisional drive voltage value Vh' is measured for each nozzle row 19 (S3).

The measurement of the ink drop amount is also performed by using the electronic balance 31. For example, the amount of collected ink is measured by ejecting ink droplets a predetermined number of times from all the nozzle openings 18 belonging to the nozzle row 19 to be measured. Number (eg 9
The amount of ink per drop is obtained by dividing by 6).

When the ink ejection amount for each nozzle row 19 is measured, the color adjust ID is set (S4).

As described above, this color adjust ID is information indicating the relative ratio of the ink drop amount for each nozzle row 19, and corresponds to the ink amount identification information of the present invention. The color adjust ID is set based on the ink droplet amount for each nozzle row 19 and indicates a deviation from the target ink amount. In the present embodiment, the case where the deviation from the target value is 0% is set to “50”, and is increased by 1 point each time the deviation increases to 1% plus side, and decreased by 1 point each time the deviation increases to 1% minus side. ing.

For example, if the target amount of ink drops is 2.0 pL
When the ink drop amount of the nozzle row 19 for which the color adjustment ID is set is also 2.0 pL, there is no difference from the target value of the ink drop amount, and the deviation is 0%. In this case, the color adjust ID for the nozzle row 19 is “50”.

When the ink drop amount of the nozzle row 19 for which the color adjust ID is set is 1.9 pL, the difference from the target value of the ink drop amount is 0.1 pL, which is the target value. On the other hand, it is deviated to the minus side by 5%. In this case, the color adjustment ID for the nozzle row 19
Is 45, which is 5 points lower than 50. Similarly,
The ink droplet amount of the nozzle row 19 for which the ID is set is 1.
If it is 8 pL, the difference in ink drop amount is 0.2 pL (-
10%), the color adjust ID is "40".
Becomes

The same applies when the amount of ink droplets is larger than the target value. That is, when the ink drop amount of the nozzle row 19 for which the ID is set is 2.1 pL, the difference between the ink drop amounts is 0.1 pL (+ 5%), so the color adjust ID is “55”, and the ink drop When the amount is 2.2 pL, the difference between the ink droplet amounts is 0.2 pL (+ 10%), so the color adjust ID is “60”.

Recording head 1A illustrated in FIG. 13 (a)
Indicates that the color adjust ID of the first nozzle row 19A and the fourth nozzle row 19D is "45", and the ink drop amount is 1.9.
It is shown to be pL. Then, the second nozzle row 1
The color adjust ID of 9B, the fifth nozzle row 19E, and the sixth nozzle row 19F is “50”, which indicates that the ink droplet amount is 2.0 pL, which is the same as the target value. Further, the color adjust ID of the third nozzle row 19C and the seventh nozzle row 19G is "55", indicating that the ink droplet amount is 2.1 pL. In this setting method, since the average ink droplet amount for each recording head is used to set the temporary drive voltage value Vh ′, each nozzle row 19
When the color adjust IDs of A to 19G are averaged, the value is “50”.

In the recording head 1B illustrated in FIG. 13B, the color adjustment ID of the first nozzle row 19A is "35" (ink droplet amount = 1.7 pL), and the color of the second nozzle row 19B is the same. The adjust ID is “40” (ink droplet amount = 1.8 pL), and the color adjust ID of the third nozzle row 19C is “55” (ink droplet amount = 2.1 pL).
L). The color adjust ID of the fourth nozzle array 19D and the seventh nozzle array 19G is “60” (ink droplet amount = 2.2 pL), and the color adjust IDs of the fifth nozzle array 19E and the sixth nozzle array 19F are “ 50 "
(Ink drop amount = 2.0 pL).

Recording head 1A and recording head 1B
Comparing with, it can be seen that the print head 1B has a larger variation among the nozzle rows 19A to 19G than the print head 1A.

When the color adjust ID is set,
The reference nozzle row is set (S5).

The setting of the reference nozzle array is performed based on the ejection amount of the ink droplet, and the nozzle array 19 with the smallest ejection amount is used.
Is a reference nozzle row. In the present embodiment, since the above-mentioned color adjust ID indicates the relative ratio of the ink droplet ejection amount, the nozzle row 19 to which the smallest color adjust ID is given is set as the reference nozzle row. For example, in FIG.
In the recording head A of (a), the first nozzle row 19A and the fourth nozzle row 19A
The IDs of the nozzle rows 19D are both “45”, which is the lowest among all the nozzle rows 19A to 19G. Therefore, one of the first nozzle row 19A and the fourth nozzle row 19D is set as the reference nozzle row. Further, in the recording head B of FIG. 13B, the ID of the first nozzle row 19A is “35”,
The lowest among all the nozzle rows 19A to 19G. For this reason,
This first nozzle row 19A is set as the reference nozzle row.

After the reference nozzle row is set, the drive voltage value Vh (voltage value used for printing) and the offset ID are set (S6 to S11).

In this case, first, the set Tc rank is confirmed (S6). This is because, as described with reference to FIG. 6, the flight speed of the ink drop differs depending on the set Tc rank, and the determination reference value is changed according to this Tc rank.

In step S6, the recording head 1 to be measured is set to Tc.
When it is determined that the rank is 1, the process proceeds to S7, where “0” is set as the offset ID and the temporary drive voltage value Vh ′ is set as the drive voltage value Vh. This is because the recording head 1 of Tc rank 1 has a sufficient margin with respect to the required speed Vm0 with respect to the flight speed of the ink droplets, and thus the temporary drive voltage value set by the target value (2.0 pL) of the ink droplet amount. This is because even if Vh ′ is used, the flying speed Vm of the ink droplet is less likely to be lower than the required speed Vm0.

Further, in S6, the recording head 1 to be measured is set to T
When it is determined that the c rank is 0, the process proceeds to S8, and it is determined whether or not the color adjust ID of the reference nozzle array is equal to or less than "39". That is, in the recording head 1 of Tc rank 0, as described above, when the nozzle row 19 having a large variation in flight speed on the low speed side exists, the flight speed of the ink droplets ejected from the nozzle row 19 is higher than the required speed Vm0. May be low. Then, since there is a high correlation between the ink droplet ejection amount and the flight speed, is the flight speed lower than the required speed based on the color adjust ID given to the reference nozzle row having the smallest ink drop amount? You can judge whether or not. In this embodiment, it is determined whether or not the ink droplet amount of the reference nozzle array is 11% or more smaller than the target value.

When the color adjustment ID of the reference nozzle array is "40" or more, that is, the deviation from the target value of the ink droplet amount from the reference nozzle array is minus 10.
If it is within%, it is determined that there is no nozzle row 19 that greatly varies on the low speed side. Therefore, similarly to the case of the Tc rank 1, the process proceeds to S7, the offset ID is set to "0", and the drive voltage value Vh is set to the value of the temporary drive voltage value Vh '.

On the other hand, the color adjustment I of the reference nozzle array
When D is "39" or less, that is, the deviation from the target value for the ink droplet amount from the reference nozzle row is minus 11%.
If it is above, the process proceeds to S9, and the offset ID and the drive voltage value Vh are set so that the color adjust ID of the reference nozzle array becomes "40". This is based on the idea that if the color adjust ID is “40” or more, the flight speed Vm of the ink droplet becomes the required speed Vm0 or more. Therefore, this color adjust ID "4
"0" corresponds to the judgment reference value of the present invention, and if the ink droplet amount from the reference nozzle row is set to 1.8 pL or more, the required speed Vm
It means that 0 can be secured.

The processes of S8 and S9 will be described by taking the recording head A and the recording head B of FIG. 13 as an example. First, for the print head A, a reference nozzle array (for example,
The color adjust ID of the first nozzle row 19A) is "4.
Since it is "5", it is determined in the process of S8 that it is not "39" or less, the offset ID "0" is set in the process of S7, and the temporary drive voltage value Vh 'becomes the drive voltage value Vh as it is.

On the other hand, regarding the recording head 1B, the color adjust ID of the reference nozzle row (first nozzle row 19A)
Is "35", it is determined that the value is "39" or less in the process of S8, and the process proceeds to S9. Then, in the processing of S9, the offset amount "5" required for setting the color adjust ID of the reference nozzle row to "40" is the offset ID.
Is set as. That is, from the judgment reference value “40” to the color adjustment ID “35” of the reference nozzle row.
The value “5” obtained by subtracting is set as the offset ID.

The drive voltage value Vh is the offset ID
It is set corresponding to the increased amount of the ink drop indicated by. Here, the offset ID “5” means increasing the target value of the ink droplet amount by 5%. In this embodiment, since the target value is 2.0 pL, 5% of the target value is 0.1 pL.
Only the amount of ink drops will be increased. Therefore, when “5” is set as the offset ID, FIG.
Based on the calibration curve of (a), the voltage value corresponding to the ink drop amount of 2.1 pL is set as the drive voltage value Vh.

When the offset ID is other than "5", the drive voltage is set in the same way. For example, when the offset ID is “10”, the voltage value corresponding to 2.2 pL which is 10% higher than the target value is set as the drive voltage value Vh, and when the offset ID is “15”, 15% from the target value is set. A voltage value corresponding to a high 2.3 pL is set as the drive voltage value Vh.

In S6, the recording head 1 to be measured is set to T
If it is determined to be c rank 2, the process proceeds to S10, and the offset ID and the drive voltage are set so that the color adjust ID of the reference nozzle row is "50" (corresponding to the determination reference value of the present invention). This is because the Tc rank 2 head has an ink droplet flight speed Vm close to the required speed Vm0, and the nozzle row 19 in which the ink droplet flight speed is slower than the average has a lower ink droplet flight speed than the required speed. This is because there is a high possibility that it will end up. That is, by adjusting the ink droplet amount of the reference nozzle row to the target value of 2.0 pL, the flight speed of the ink droplets ejected from this reference nozzle row can be made higher than the required speed.

The process of S10 will be described by taking the recording head A and the recording head B of FIG. 13 as an example. First, regarding the print head A, since the color adjust ID of the reference nozzle array (for example, the first nozzle array 19A) is "45", the offset amount "5" necessary to set this color adjust ID to "50". Is set as the offset ID. In addition, the drive voltage value Vh is the increased amount (0.1 pL) of the ink drop indicated by the offset ID as described above.
The voltage value corresponding to the ink drop amount of 2.1 pL is set as the drive voltage value Vh based on the calibration curve of FIG. 12A.

On the other hand, for the print head B, since the color adjust ID of the reference nozzle array (first nozzle array 19A) is "35", this color adjust ID is "5".
The offset amount "15" required for setting "0" is set as the offset ID. Further, the drive voltage value Vh is
Increasing amount of ink drop indicated by offset ID (0.3p
L), the voltage value corresponding to the ink drop amount of 2.3 pL is set as the drive voltage value Vh based on the calibration curve of FIG.

Then, the offset ID and drive voltage set in any of the above S7, S9, and S10 are determined in S11. For example, in the case where the above-described recording heads A and B are given Tc rank 1, FIG.
The color adjustment ID, offset ID, and
Also, the drive voltage is set. Similarly, when Tc rank 0 is given, the contents are as shown in FIG. 14B, and when Tc rank 2 is given, FIG. 14C is shown.
Color adjustment ID and offset I
D and the drive voltage are set.

According to the setting method described above, since the nozzle row 19 (that is, the reference nozzle row) having the slowest flight speed of the ink droplet is determined based on the ejection amount of the ink droplet, the flight of the ink droplet is performed. It is simpler than measuring the velocity directly, and the configuration of the measuring device can be simplified. Therefore, it is suitable for mass production. Similarly, the flight speed of the ink droplets ejected from the reference nozzle array is also adjusted based on the ejection amount of the ink droplets, which is also simple.

The color adjustment ID, the offset ID, and the driving voltage set by the above method are, for example, the identification information storage element 32 (FIG. 15) in the recording head 1.
(Refer to FIG. 4) or by an identification information notifying member (not shown) provided on the recording head 1.
The identification information storage element 32 is configured by an element (for example, ROM) capable of electrically storing information. Also,
The identification information notation member described above is, for example, composed of a seal member or a plate member whose back surface is coated with an adhesive, and the surface of which is provided with mark information composed of symbols such as letters, numbers, and figures, and an optical scanner. The coded information that can be read is written in.

Therefore, when the identification information storage element 32 is used, each information of the color adjust ID, the offset ID, and the driving voltage can be directly sent to the printer controller 40 (see FIG. 15), Control based on each of these pieces of information can be performed. When the identification information notation member is used, based on the mark information and the encoded information,
Since each information of the color adjust ID, the offset ID, and the driving voltage can be given to the printer controller 40, the control based on each of these information can be performed.

Next, a method of using each information (color adjust ID, offset ID, drive voltage) attached to the recording head 1 will be described. Here, FIG. 15 is a block diagram illustrating the electrical configuration of an ink jet recording apparatus such as a printer or plotter.

The illustrated recording apparatus includes a printer controller 40 and a print engine 41. The printer controller 40 includes an interface 42 that receives print data and the like from a host computer (not shown), a RAM 43 that stores various data, and a ROM 4 that stores control routines for various data processing.
4, a control unit 45 including a CPU and the like, and an oscillation circuit 46.
And a drive signal generation circuit 47 that generates a drive signal to be supplied to the recording head 1 (corresponding to drive signal generation means of the present invention).
And an interface 48 for transmitting to the print engine 41 print data, drive signals, etc. obtained by developing print data for each dot. In addition,
The control unit 45 also functions as the ejection control unit of the present invention, and controls the ejection of ink droplets by the recording head 1.

The print engine 41 uses the recording head 1
And a carriage mechanism 51 and a paper feed mechanism 52. The recording head 1 includes a shift register 53 in which print data is set, a latch circuit 54 that latches the print data set in the shift register 53, a level shifter 55 that functions as a voltage amplifier, and a drive signal for the piezoelectric vibrator 2. Switch circuit 56 for controlling supply
And a piezoelectric vibrator 2 and an identification information storage element 32.

The control section 45 operates according to the operation program stored in the ROM 44 and controls each section of the recording apparatus. The drive signal generation circuit 47 generates a drive signal COM having a waveform shape determined by the control unit 45. As the drive signal COM, for example, as shown in FIG. 16, a micro-vibration pulse DP for micro-vibrating the meniscus.
Two sets of 2 and the small dot drive pulse DP1 are arranged within one recording cycle T.

The minute vibration pulse DP2 has a trapezoidal shape. Then, the minute vibration pulse DP2 is transmitted to the piezoelectric vibrator 2
Is supplied to the pressure chamber 20, pressure vibration is generated in the pressure chamber 20 to the extent that ink droplets are not discharged, and the meniscus vibrates slightly.

In addition, the above-mentioned small dot drive pulse DP1
Is the small dot drive pulse DP1 described with reference to FIG.
But the drive voltage value is set to Vh. Therefore, when the small dot drive pulse DP1 is supplied to the piezoelectric vibrator 2, the ink droplets of a larger amount than the target value (2.0 pL) are ejected by the set offset ID. For example, the recording head 1 whose offset ID is "5"
The average ejection amount of the ink droplets is 2.1 pL, and the average ejection amount of the ink droplets is 2.3 pL in the recording head 1 having the offset ID “15”.

Since the drive voltage value Vh is a voltage value set so that the amount of ink droplets ejected from the reference nozzle array is equal to or more than the determination reference amount as described above, the drive voltage value Vh is ejected from the reference nozzle array. The flying speed of the ink droplet to be generated is higher than the required speed. As a result, even an extremely small amount of ink droplets can be reliably landed at a predetermined position, image quality can be improved, and mist formation can be prevented. Also,
Since the ejection amount of the ink droplets is equal to or larger than the determination reference amount, it is possible to prevent the white streak defect due to the insufficient ink droplet amount. further,
Since the ink droplets ejected from the other nozzle rows 19 have a flight speed that is at least equal to or higher than that of the reference nozzle row, it is possible to ensure the landing position accuracy and prevent mist formation.

By the way, the drive signal CO having the drive voltage value Vh
When ink droplets are ejected with M, as described above,
The amount of ejected ink droplets (average ink amount) varies for each recording head 1, and the amount of ink droplets ejected from each nozzle array 19 also varies by the amount specified by the color adjust ID. In order to correct such a variation in the ink droplet amount between the recording heads 1 and a variation in the ink droplet amount between the nozzle rows 19, the control unit 45 (image density correction unit) uses the offset ID and the color adjust ID as a basis. The number of ink droplets discharged per unit area is adjusted for each nozzle row 19 to correct the image density.

For example, in the case of setting the ink droplet of 200 pL to be ejected 100 times by ejecting the ink droplet of 2.0 pL per unit area, the nozzle row 19 with the ink droplet amount of 2.1 pL is within this unit area. When ink droplets are ejected 95 times, the ink droplets per unit area is 199.5 p
It becomes L, and is adjusted to 200 pL. Similarly, 2.3p
With respect to the L nozzle row 19, when ink droplets are ejected 87 times within this unit area, the ink amount per unit area becomes 200.1 pL, which is equal to 200 pL. Then, the control unit 45 determines the number of times of ink droplet ejection so that the ink amount per unit area in each of the nozzle rows 19A to 19G is aligned with the set value.

For example, in the case of the print head A classified into Tc rank 0, the number of ejections per unit area is determined based on the color adjustment ID. That is, as shown in FIG. 17A, the first and fourth color adjustment IDs “45” are assigned.
For the nozzle row 19D, the number of ink droplets discharged per unit area is set to 105, and the color adjust ID “5” is set.
For the second, fifth, and sixth nozzle rows 19F of "0", the number of ejections is set to 100, and the color adjustment ID "5" is set.
For the third and seventh nozzle rows 19G of "5", the number of discharges is set to 95 times. As a result, when recording is performed with the recording head 1A, an image in which the density and color balance are aligned with the designed density and color balance is obtained.

In the case of the print head B classified into Tc rank 2, the number of ejections per unit area is determined by using the added value obtained by adding the offset ID to the color ID. That is, as shown in FIG. 17B, the first value of the added value "50"
The number of ejections is set to 100 for the nozzle row 19A, the number of ejections is set to 95 for the second nozzle row 19B of the addition value "55", and the fifth and sixth nozzle rows 19 of the addition value "65" are set.
For, the number of ejections is set to 87 times. Similarly, the number of ejections is set to 8 for the third nozzle row 19C having the added value "70".
The number of ejections is set to 3 and the number of ejections is set to 80 for the fourth nozzle row 19D having the added value “75”. As a result, the recording head B can also record an image in which the density and color balance are aligned with the designed density and color balance.

By the way, the present invention is not limited to the above-mentioned embodiments, but various modifications can be made based on the description of the claims.

For example, in the above-described first embodiment, there is one type of recording mode and one type of color adjustment ID and offset ID, but the present invention is not limited to this configuration. For example, it can be applied to a recording apparatus that can operate in a plurality of recording modes. In this case, a plurality of color adjustment IDs and offset IDs are set according to each recording mode. For example, as shown in FIG.
In a printer capable of selecting two kinds of recording modes, that is, a high speed mode of L and a high resolution mode of an ink drop amount of 2 pL, a set of a color adjust ID and an offset ID for the high speed mode and a color adjust I for the high resolution mode are selected.
A set of D and offset ID is prepared separately. Then, the control unit 45 (recording mode setting unit, image density correction unit) selects a set of corresponding color adjust ID and offset ID according to the set recording mode, and adjusts the number of ejections per unit area described above. I do. With this configuration, the ink amount identification information and the average ink amount identification information suitable for the recording mode can be used, and the image quality can be further improved. Of course, the number of recording modes is not limited to two and may be three or more.

In the above embodiment, the Tc rank I
Although the determination reference amount is set in consideration of D, the determination reference amount may be set only by the ink droplet ejection amount.

Further, in the above embodiment, the drive signal having one type of drive pulse (small dot drive pulse DP1) is illustrated, but the drive signal is not limited to this, and a plurality of types of drive pulses having different ink droplet ejection amounts may be used. The present invention can be applied even if the driving is performed by the provided driving signal. In this case, for example, the above adjustment method is applied to the drive pulse of the minimum ink amount that tends to have large variations, and the drive voltage value, the color adjust ID, and the offset ID are determined.

In the above embodiment, the so-called longitudinal vibration mode piezoelectric vibrator 2 is illustrated as the pressure generating element of the present invention, but the present invention is not limited to this. For example, a piezoelectric vibrator that can vibrate in the electric field direction (the stacking direction of the piezoelectric body 10 and the internal electrode 11) may be used. In addition, each nozzle row 19
The unit is not limited to each unit, but may be a unit provided for each pressure chamber 20, such as a so-called flexural vibration mode piezoelectric vibrator. Furthermore, not only the piezoelectric vibrator,
The pressure generating element may be configured by an electromechanical conversion element such as a magnetostrictive element. The pressure generating element may be constituted by the heating element.

[0116]

As described above, the present invention has the following effects. That is, the nozzle row with the smallest ink droplet ejection amount is used as a reference nozzle row, and the drive voltage of the drive signal is set so that the amount of ink droplets ejected from this reference nozzle row is equal to or greater than the determination reference amount. Therefore, the flight speed of the ink droplets ejected from the reference nozzle row can be made higher than the required speed. As a result, even a very small amount of ink droplets can be reliably landed at a predetermined position and mist formation can be prevented. Then, since the ink droplets ejected from the other nozzle rows have a flight speed at least equal to or higher than that of the reference nozzle row, it is possible to ensure the landing position accuracy and prevent mist formation. Further, since the ejection amount of the ink droplets from the reference nozzle array is set to be equal to or larger than the determination reference amount, it is possible to prevent the occurrence of white streaks due to the insufficient ink droplet amount. Further, since the flight speed of the ink droplet is determined based on the ejection amount of the ink droplet, the measuring device can be simplified and the procedure is simple, which is suitable for mass production.

When the ink amount identification information and the average ink amount identification information are given to the recording head, the hue of the recorded image is matched with the designed hue while ensuring the accuracy of the ink droplet landing position. Further, the density of the recorded image can be matched with the designed density. That is, the number of ink droplets ejected per unit area can be adjusted for each nozzle row based on the ink amount identification information, and the ink amount per unit area can be made uniform in each row, which is in the design hue. The recorded image can be recorded. In addition, since the number of ink droplets ejected per unit area can be adjusted based on the average ink amount identification information, the shades of colors can be made uniform, and an image can be recorded at the designed density.

The recording head is given a Tc rank determined based on the natural vibration period of ink in the pressure chamber,
When the drive voltage value is set in consideration of this Tc rank, it is possible to cope with the flight speed of the ink droplet that changes according to this natural vibration period, and therefore, it is possible to make an appropriate setting that further reflects the characteristics of the recording head. .

In the case where the ink amount identification information and the average ink amount identification information are prepared for each recording mode and the adjustment is performed by the ink amount identification information and the average ink amount identification information corresponding to the set recording mode. Can use the ink amount identification information and the average ink amount identification information suitable for the recording mode, and the image quality can be further improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a part of a recording head.

FIG. 2 is a partially enlarged sectional view illustrating cultivation of a flow path unit.

FIG. 3 is a view of the recording head as viewed from the nozzle plate side.

FIG. 4 is a flowchart illustrating a procedure for setting a drive voltage value, a color adjust ID, and an offset ID.

FIG. 5 is a flowchart illustrating a procedure for setting a drive voltage value, a color adjust ID, and an offset ID.

FIG. 6 is a diagram showing a relationship between Tc rank and flight speed.

FIG. 7 is a diagram illustrating a Tc rank measuring device.

FIG. 8 is a diagram illustrating an evaluation pulse.

FIG. 9 is a diagram for explaining pressure fluctuations in the pressure chamber when an excitation element is supplied.

FIG. 10 is a diagram illustrating the correlation between the generation time Pwh1 of the first hold element and the ink amount.

FIG. 11 is a schematic diagram illustrating a relationship between a Tc rank ID and a natural vibration period Tc.

12A is a diagram illustrating a calibration curve for determining a drive voltage value, and FIG. 12B is a diagram illustrating a small dot drive pulse.

13A and 13B are diagrams illustrating a set color adjust ID.

14A to 14C are diagrams showing the set color adjust ID and offset ID for each Tc rank.

FIG. 15 is a block diagram illustrating a configuration of a recording device.

FIG. 16 is a diagram illustrating a drive signal generated by a drive signal generation circuit.

17A and 17B are diagrams illustrating control of the number of ejections per unit area.

FIG. 18 is a diagram illustrating a case having a plurality of recording modes.

[Explanation of symbols]

1 Inkjet recording head 2 Piezoelectric vibrator 3 transducer group 4 fixed plate 5 flexible cable 6 transducer unit 7 cases 8 flow path unit 9 storage space 10 Piezoelectric body 11 internal electrodes 12 islands 15 Flow path forming substrate 16 nozzle plate 17 Elastic plate 18 nozzle openings 19 nozzle row 20 pressure chamber 21 Ink supply port 22 Common ink chamber 23 Nozzle communication port 24 Support plate 25 resin film 30 Evaluation pulse generation circuit 31 Electronic Balance 32 identification information storage element 40 Printer controller 41 print engine 42 Interface 43 RAM 44 ROM 45 control unit 46 oscillator circuit 47 Drive signal generation circuit 48 interfaces 51 Carriage mechanism 52 Paper feed mechanism 53 shift register 54 Latch circuit 55 level shifter 56 switch circuit

Continued front page    (72) Inventor Takemi Hiramoto             Seiko, 3-3-3 Yamato, Suwa City, Nagano Prefecture             -In Epson Corporation F-term (reference) 2C056 EA06 EA07 EA08 EA11 EB08                       EB29 EB59 EC08 EC31 EC42                       EC73 EC75 EC77 EC80 FA04                       KD06                 2C057 AF25 AF28 AF30 AF31 AF91                       AG14 AG47 AL40 AM22 AM40                       AR08 BA03 BA14

Claims (9)

[Claims] 1. A recording head comprising a plurality of nozzle rows having nozzle openings arranged therein, capable of ejecting ink droplets from the nozzle openings by actuation of the pressure generating element, and generating a drive signal supplied to the pressure generating element. In the ink jet recording apparatus having various driving signal generating means and an ejection control means for controlling ejection of ink droplets by the recording head, the nozzle row having the smallest ink droplet ejection amount among the plurality of nozzle rows is used as a reference nozzle. An ink jet recording apparatus, characterized in that the drive signal generating means generates a drive signal having a drive voltage value set so that the amount of ink droplets ejected from the reference nozzle line is equal to or larger than the determination reference amount. 2. The recording head is provided with ink amount identification information indicating a ratio of nozzle rows with respect to an ink droplet amount, and a difference from a target value of an average ink droplet amount caused by the set driving voltage value. The ink jet recording apparatus according to claim 1, wherein average ink amount identification information is added. 3. The image density for correcting the image density by adjusting the number of ink droplets ejected per unit area for each nozzle row based on the ink amount identification information and the average ink amount identification information. The inkjet recording apparatus according to claim 1 or 2, further comprising a correction unit. 4. The recording head is provided with a Tc rank determined based on a natural vibration period of ink in the pressure chamber,
The ink jet recording apparatus according to any one of claims 1 to 3, wherein the driving voltage value is set in consideration of the Tc rank. 5. A recording mode setting means for selecting one recording mode from a plurality of recording modes determined according to the ink droplet amount, wherein the ink amount identification information and the average ink amount identification information are prepared for each recording mode, 3. The image density correction means makes an adjustment based on the ink amount identification information and the average ink amount identification information corresponding to the set recording mode.
5. The ink jet recording apparatus according to claim 4. 6. The ink jet recording apparatus according to claim 1, wherein the recording head includes a pressure generating element unitized for each nozzle row. 7. The ink jet recording apparatus according to claim 1, wherein the pressure generating element is a piezoelectric vibrator. 8. A recording head comprising a plurality of nozzle rows having nozzle openings arranged therein, the recording head capable of ejecting ink droplets from an arbitrary nozzle opening by the operation of the pressure generating element, and a drive signal supplied to the pressure generating element. In a method of driving an inkjet recording apparatus having a drive signal generating means capable of generating, a nozzle row having the smallest ink droplet ejection amount among the plurality of nozzle rows is set as a reference nozzle row, and the nozzle row is ejected from this reference nozzle row. Inkjet, characterized in that a drive signal having a drive voltage value set so that the amount of ink droplets to be discharged is equal to or more than a determination reference amount is generated from a drive signal generating means, and the drive signal having the drive voltage value is supplied to a recording head. Method for driving a recording apparatus. 9. The image density is corrected by adjusting the number of ink droplets ejected per unit area for each nozzle row based on the amount of ink droplets ejected by the drive signal of the drive voltage value. A method for driving an ink jet recording apparatus according to claim 8.