JP5516339B2 - Method for measuring droplet weight of liquid jet head and method for calculating appropriate voltage of liquid jet head - Google Patents

Description

The present invention relates to a droplet weight measuring method for a liquid ejecting head and a method for calculating an appropriate voltage for the liquid ejecting head.

2. Description of the Related Art Conventionally, there is known a liquid ejecting head that ejects liquid droplets from nozzles by applying pressure to a liquid by pressure generating means such as a piezoelectric element or a heating element. A typical example is an ink jet recording head that ejects ink droplets from nozzles. In general, such an ink jet recording head supplies ink from an ink cartridge (liquid storing means) filled with ink to a pressure generating chamber of the ink jet recording head main body via an ink passage (liquid passage). It is configured to be. Ink droplets are ejected from nozzles communicating with the pressure generating chamber by applying pressure to the pressure generating chamber by the pressure generating means.

The ink jet recording head is required to print with high resolution and high image quality. However, in order to obtain high quality printing, it is necessary that the weight of the ejected ink droplets does not vary from nozzle to nozzle. For this reason, the voltage applied to the piezoelectric element is calculated for each head so that the weight of the ink droplet becomes the target weight. Specifically, different voltages are applied to the piezoelectric element, the ink drop weight at that time is measured, the correlation between this voltage and the ink drop weight is obtained, and the target weight is handled based on the correlation. The voltage to be used is the appropriate voltage.

As a method of obtaining the weight of the ink droplet, there is a method of measuring using an electronic balance or a flow sensor. Also, there is a method of measuring the ink droplet ejection speed and obtaining the weight of the ink droplet from the correlation between the speed and the weight (for example, see Patent Document 1). In Patent Document 1, it is possible to irradiate a laser beam so as to block the path where the ink droplet falls, monitor the received light amount of the irradiated laser light, and measure the speed of the ink droplet based on the received light amount. It is disclosed.

JP 2008-221759 A (Claim 1, paragraphs 0039-0044, 0049, etc.)

However, when measuring an ink drop with an electronic balance or a flow sensor, there is a possibility that an error or impurities other than the ink drop are mixed, and an accurate weight cannot be measured. Further, since a small ink droplet (called mist or satellite) may be generated from the ejected ink droplet, there is a possibility that the technique according to Patent Document 1 cannot accurately measure the speed. That is, not only the ink droplets block the laser beam, but also the mist and satellites separated from the laser beam block the laser beam, making it difficult to accurately obtain the ink droplet velocity based on the amount of received laser beam. It is also difficult to gain weight.

Such a problem exists not only in the ink jet recording head unit but also in a liquid ejecting head unit that ejects liquid other than ink.

In view of such circumstances, an object of the present invention is to provide a droplet weight measuring method for a liquid ejecting head that can accurately measure the weight of the droplet ejected from the liquid ejecting head. According to another aspect of the invention, there is provided a liquid ejecting head capable of calculating an appropriate voltage for discharging a droplet having a target weight by using an accurate droplet weight obtained based on the droplet weight measuring method. An object is to provide a method for calculating an appropriate voltage.

The present invention that solves the above-mentioned problems includes a pressure generating means for causing a pressure change in a pressure generating chamber that communicates with a nozzle opening, and a first drive signal that includes a plurality of drive pulses is supplied to the pressure generating means. A droplet weight measuring method for a liquid ejecting head that discharges droplets from a nozzle opening by being supplied, wherein the pressure generating means has the same voltage as the voltage Vh of the first drive signal, and one drive A second drive signal including a pulse is supplied, a flying speed of a droplet ejected by the second driving signal is measured, and the flying speed and the correlation between the weight of the droplet and the flying speed are measured. On the basis of the first driving signal, a first weight of the liquid droplets ejected by the second driving signal is obtained, and the first weight is obtained.
Based on the correlation between the weight and the total weight of the plurality of droplets ejected by the first drive signal and the weight of one droplet ejected by the second drive signal, the first drive According to another aspect of the invention, there is provided a droplet weight measuring method for a liquid ejecting head, wherein a second weight of a plurality of droplets ejected by a signal is obtained.
In this aspect, since the second weight is obtained from the first weight based on the correlation between the first weight and the second weight, it is more accurate than simply multiplying the first weight by a plurality of times to obtain the equivalent of the second weight. It is.

Here, the flying speed of the droplets ejected by the second drive signal is determined by imaging the droplets at at least two different times to form an image, and the difference between the times when the images are captured and the image. It is preferable to obtain from the amount of movement of the liquid droplets. As a result, by ejecting droplets with the second drive signal including one drive pulse, it is possible to obtain an image in which the droplets do not overlap, and an accurate speed is obtained from the image. An accurate first weight can be obtained. And since 2nd weight is calculated | required based on this exact 1st weight, more exact 2nd weight can be calculated | required.

Furthermore, according to another aspect of the present invention, n different voltages Vh _n (n is a natural number) are determined, and the second weight when the voltage of the first drive signal is each voltage Vh _n is set to the liquid ejection. determined by the droplet weight measurement method of the head, based on the correlation of the voltage Vh _n and the second weight, the weight of the droplets ejected by the first driving signal determine the suitability voltage to the target weight In the characteristic voltage calculating method of the liquid jet head.
In this aspect, an appropriate voltage that can discharge the target weight can be easily obtained. By using the first drive signal of the appropriate voltage, droplets with a target weight are ejected during printing, and high-quality printing can be performed.

1 is a schematic perspective view of an ink jet recording apparatus according to an embodiment of the present invention. 1 is a cross-sectional view of an ink jet recording head according to an embodiment of the present invention. FIG. 2 is a functional block diagram of an ink jet recording apparatus and a liquid ejecting head. It is a waveform of the 1st drive signal concerning this embodiment. It is a waveform of the 2nd drive signal concerning this embodiment. It is a schematic block diagram of the imaging means and image processing apparatus which measure the speed of an ink drop. It is a principal part enlarged view of FIG. It is a conceptual diagram which shows the method of calculating | requiring the speed of an ink drop based on an image. It is a graph which shows the correlation with the 1st weight of an ink drop, and the flying speed of an ink drop. It is a graph which shows the correlation of the 1st weight of an ink drop, and a 2nd weight. It is a graph which shows the correlation of the weight of an ink drop, and a voltage.

Hereinafter, the present invention will be described in detail based on embodiments.
A liquid ejecting head that ejects droplets to be measured for speed and a liquid ejecting apparatus including the liquid ejecting head will be described.
FIG. 1 is a schematic perspective view of an ink jet recording apparatus that is an example of a liquid ejecting apparatus, FIG. 2 is a cross-sectional view illustrating an ink jet recording head that is an example of a liquid ejecting head, and FIG. 3 is a functional block diagram of a recording apparatus and a liquid ejecting head.

As shown in FIG. 1, an ink jet recording apparatus I which is an example of a liquid ejecting apparatus includes a recording head unit 1 having an ink jet recording head 10. The recording head unit 1 is provided with a cartridge 2 constituting an ink supply means so that it can be attached and detached. A carriage 3 on which the recording head unit 1 is mounted is provided on a carriage shaft 5 attached to the apparatus main body 4 so as to be movable in the axial direction. It has been. The recording head unit 1 ejects, for example, a black ink composition and a color ink composition.

The driving force of the driving motor 6 is transmitted to the carriage 3 through a plurality of gears and timing belt 7 (not shown), so that the carriage 3 on which the ink jet recording head 10 is mounted is moved along the carriage shaft 5. . On the other hand, the apparatus body 4 has a carriage shaft 5.
A recording sheet S that is a recording medium such as paper fed by a paper feed roller (not shown) is wound around the platen 8 and conveyed.

An ink jet recording head 10 shown in FIG. 2 is a type having a longitudinal vibration type piezoelectric element, and a plurality of pressure generating chambers 12 are arranged in parallel on a flow path substrate 11, Sealed by a nozzle plate 14 having a nozzle opening 13 corresponding to the pressure generating chamber 12 and a vibration plate 15. In addition, the flow path substrate 11 is formed with a manifold 17 that communicates with each pressure generation chamber 12 via an ink supply port 16 and serves as a common ink chamber for the plurality of pressure generation chambers 12. The cartridge 2 is connected.

On the other hand, on the side opposite to the pressure generation chamber 12 of the diaphragm 15, the tip of the piezoelectric element 18 is provided in contact with a region corresponding to each pressure generation chamber 12. These piezoelectric elements 18 are
The piezoelectric material 19 and the electrode forming materials 20 and 21 are stacked vertically and alternately sandwiched, and an inactive region that does not contribute to vibration is fixed to the fixed substrate 22. Fixed substrate 2
2, the vibration plate 15, the flow path substrate 11, and the nozzle plate 14 are integrally fixed via a base 23.

In the ink jet recording head 10 configured as described above, ink is supplied to the manifold 17 via the ink flow path communicating with the cartridge 2, and is distributed to each pressure generating chamber 12 via the ink supply port 16. Actually, the piezoelectric element 18 is contracted by applying a voltage to the piezoelectric element 18. Thereby, the diaphragm 15 is deformed together with the piezoelectric element 18 (
The volume of the pressure generation chamber 12 is expanded (in the upward direction in the figure), and ink is drawn into the pressure generation chamber 12. Then, after filling the inside to the nozzle opening 13 with ink, the voltage applied to the electrode forming materials 20 and 21 of the piezoelectric element 18 in accordance with a first drive signal (details will be described later) from the drive circuit. When is released, the piezoelectric element 18 is expanded to return to the original state. As a result, the diaphragm 15 is also displaced to return to the original state, so that the pressure generating chamber 12 is contracted,
The internal pressure increases and ink droplets (droplets) are ejected from the nozzle openings 13. That is, in the present embodiment, the longitudinal vibration type piezoelectric element 18 is provided as a pressure generating means for causing a pressure change in the pressure generating chamber 12.

As shown in FIG. 3, the ink jet recording apparatus I of the present embodiment is schematically configured by a printer controller 111 and a print engine 112. The printer controller 111 includes an external interface 113 (hereinafter referred to as an external I / F 113), a RAM 114 that temporarily stores various data, and a ROM 115 that stores a control program and the like.
A control unit 116 including a CPU and the like, and an oscillation circuit 117 for generating a clock signal
A drive signal generation circuit 119 for generating a first drive signal supplied to the ink jet recording head 10, and dot pattern data (bitmap data) developed based on the first drive signal and print data. An internal interface 120 (hereinafter referred to as an internal I / F 120) that transmits to the print engine 112 is provided.

The external I / F 113 receives print data including, for example, a character code, a graphic function, image data, and the like from a host computer (not shown). Further, a busy signal (BUSY) and an acknowledge signal (A
CK) is output to the host computer or the like. The RAM 114 functions as a reception buffer 121, an intermediate buffer 122, an output buffer 123, and a work memory (not shown). The reception buffer 121 temporarily stores print data received by the external I / F 113, the intermediate buffer 122 stores intermediate code data converted by the control unit 116, and the output buffer 123 stores dot pattern data. . This dot pattern data is constituted by print data obtained by decoding (translating) gradation data.

The ROM 115 has a control program (control routine) for performing various data processing.
In addition, font data, graphic functions, and the like are stored. The control unit 116 reads the print data in the reception buffer 121 and stores the intermediate code data obtained by converting the print data in the intermediate buffer 122. Further, the intermediate code data read from the intermediate buffer 122 is analyzed, and the intermediate code data is developed into dot pattern data by referring to the font data and graphic functions stored in the ROM 115.
Then, the control unit 116 stores the developed dot pattern data in the output buffer 123 after performing necessary decoration processing.

If dot pattern data corresponding to one line of the ink jet recording head 10 is obtained, the dot pattern data for one line is output to the ink jet recording head 10 through the internal I / F 120. When dot pattern data for one line is output from the output buffer 123, the developed intermediate code data is stored in the intermediate buffer 12.
2 is erased, and the next intermediate code data is expanded.

The print engine 112 includes the ink jet recording head 10, a paper feed mechanism 124, and a carriage mechanism 125. The paper feed mechanism 124 includes a paper feed motor and a paper feed motor that rotates the paper feed roller, a platen 8, and the like. A print storage medium such as a recording paper is sequentially linked with a recording operation of the ink jet recording head 10. Send it out. That is, the paper feed mechanism 124 relatively moves the print storage medium in the sub-scanning direction.

The carriage mechanism 125 is a carriage 3 on which the ink jet recording head 10 can be mounted.
And a carriage driving unit that causes the carriage 3 to travel along the main scanning direction. By moving the carriage 3, the ink jet recording head 10 is moved in the main scanning direction. The carriage drive unit is composed of the drive motor 6 and the timing belt 7 as described above.

The ink jet recording head 10 has a large number of nozzle openings 13 along the sub-scanning direction, and ejects ink droplets from the nozzle openings 13 at a timing defined by dot pattern data or the like. The piezoelectric element 18 of the ink jet recording head 10 is supplied with an electrical signal, for example, a first drive signal (described later), print data (SI), and the like via an external wiring (not shown). The printer controller 111 configured in this way
In the print engine 112, a latch 132, a level shifter 133, a switch 134, and the like, which selectively input the first drive signal having a predetermined waveform output from the printer controller 111 and the drive signal generation circuit 119 to the piezoelectric element 18. Shift register (S
R) A drive circuit (not shown) having 131 or the like serves as a control means for applying a predetermined first drive signal to the piezoelectric element 18.

These shift register (SR) 131, latch 132, and level shifter 13
3, the switch 134 and the piezoelectric element 18 are provided for each nozzle opening 13 of the ink jet recording head 10, and the shift register 131, the latch 132,
The level shifter 133 and the switch 134 generate a drive pulse from the first drive signal generated by the drive signal generation circuit 119. Here, the drive pulse is an applied pulse that is actually applied to the piezoelectric element 18.

In such an ink jet recording head 10, first, print data (SI) constituting dot pattern data is serially transmitted from the output buffer 123 to the shift register 131 in synchronization with the clock signal (CK) from the oscillation circuit 117. Are set sequentially.
In this case, first, the most significant bit data in the print data of all the nozzle openings 13 is serially transmitted. When the most significant bit data serial transmission is completed, the second most significant bit data is serially transmitted. . Similarly, the lower bit data is serially transmitted sequentially.

When the print data of the bit is set in each shift register 131 for all nozzles, the control unit 116 sends a latch signal (LAT) to the latch 132 at a predetermined timing.
Is output. In response to this latch signal, the latch 132 latches the print data set in the shift register 131. Print data latched by the latch 132 (LATo
ut) is applied to a level shifter 133 which is a voltage amplifier. This level shifter 1
When the print data is “1”, for example, 33 boosts the print data to a voltage value that can drive the switch 134, for example, several tens of volts. The boosted print data is applied to each switch 134, and each switch 134 is connected by the print data.

Each switch 134 has a first drive signal generated by the drive signal generation circuit 119 (
COM) is also applied, and when the switch 134 is selectively connected, the first drive signal is selectively applied to the piezoelectric element 18 connected to the switch 134.

In the ink jet recording head 10 exemplified as described above, whether or not the first drive signal is applied to the piezoelectric element 18 is controlled by the print data. For example, during the period when the print data is “1”, the switch 134 is connected by the latch signal (LAT).
The drive signal (COM) is supplied to the piezoelectric element 18, and the piezoelectric element 18 is displaced (deformed) by the first drive signal (COM). Further, since the switch 134 is not connected during the period when the print data is “0”, the supply of the first drive signal to the piezoelectric element 18 is cut off.
Note that, during the period in which the print data is “0”, each piezoelectric element 18 holds the previous potential, so the previous displacement state is maintained.

In the longitudinal vibration type piezoelectric element 18, the piezoelectric element 18 contracts in the longitudinal direction by charging and the pressure generating chamber 1.
2 is expanded, and the piezoelectric element 18 is elongated in the longitudinal direction by the electric discharge to contract the pressure generating chamber 12. In such an ink jet recording head 10, the volume of the corresponding pressure generation chamber 12 changes with charging / discharging of the piezoelectric element 18, so that ink droplets are ejected from the nozzle openings 13 using the pressure fluctuation of the pressure generation chamber 12. Discharged.

The first drive signal supplied to the ink jet recording head 10 will be described. FIG. 4 is a waveform of the first drive signal according to the present embodiment.

The figure shows the waveform of the first drive signal with the vertical axis representing voltage and the horizontal axis representing time.
The first drive signal is composed of a plurality of drive pulses. One first drive signal is generated by the drive signal generation circuit 119 at a predetermined cycle T, and such a first drive signal is continuously generated by the drive signal generation circuit 119 every cycle T.

The drive pulse drives the piezoelectric element 18 so as to eject ink droplets. In the present embodiment, three drive pulses COM _{1 to} COM ₃ constitute a drive signal. Each of the drive pulses COM _{1 to} COM ₃ has the same waveform as described below with the same period (T ₁ , T ₂ , T ₃ ), but the first drive signal has a plurality of different waveforms. You may be comprised from the pulse.

The drive pulses COM _{1 to} COM ₃ are output from the state where the intermediate potential Vm is maintained to the first expansion potential V.
A first expansion element P1 that is expanded to time 1 at time t1 to expand the pressure generating chamber 12, a first hold element P2 that maintains the first expansion potential V1 for a time t2, and a first contraction from the first expansion potential V1. A first contraction element P3 that contracts the pressure generation chamber 12 by dropping steeply to the potential V2 at time t3, a second hold element P4 that maintains the first contraction potential V2 for the time t4, and a first contraction potential V2 To the intermediate potential Vm, and a first damping element P5 that restores the potential with a constant gradient (time t5) that does not cause ink droplets to be ejected. Incidentally, the potential difference from the first expansion potential V1 to the first contraction potential V2 is represented by a voltage Vh.

When such a first drive signal is supplied to the piezoelectric element 18, the first expansion element P1
As a result, the piezoelectric element 18 is deformed in the direction in which the volume of the pressure generating chamber 12 is expanded, and the meniscus in the nozzle opening 13 is drawn to the pressure generating chamber 12 side, and ink is supplied to the pressure generating chamber 12 from the manifold 17 side. Is done. The expanded state of the pressure generation chamber 12 is maintained by the first hold element P2. Thereafter, the first contraction element P3 is supplied and the piezoelectric element 18 expands. As a result, the pressure generation chamber 12 is rapidly contracted from the expansion volume to the contraction volume corresponding to the first contraction potential V2, the ink in the pressure generation chamber 12 is pressurized, and ink droplets are ejected from the nozzle openings 13. The contraction state of the pressure generation chamber 12 is maintained by the second hold element P4, and the ink pressure in the pressure generation chamber 12 decreased by the ejection of ink droplets during this time rises again due to its natural vibration. The first damping element P5 is supplied at the rising timing,
The pressure generation chamber 12 returns to the reference volume, and the pressure fluctuation in the pressure generation chamber 12 is absorbed. That is, the first drive signal of this embodiment is a pull-push type.

Thus, since the first drive signal of the present embodiment is composed of three drive pulses,
From the piezoelectric element 18 to which the first drive signal is supplied, the drive pulses COM _{1 to} COM _{3 are} output.
Accordingly, three ink droplets are ejected.

The period T of the first drive signal is set so that a plurality of ink droplets ejected and landed by the drive pulses COM _{1 to} COM ₃ form dots having a predetermined shape. That is, the first
The period T is set so that the three ink droplets ejected by the driving signal lands on substantially the same region of the recording sheet S to form one dot. Therefore, one dot is formed from three ink droplets ejected based on one first drive signal. The first
By selectively applying an arbitrary drive pulse in the drive signal to the piezoelectric element 18, not only a large dot composed of three ink droplets is formed, but also a small or medium composed of one or two ink droplets. About a dot can be formed.

Thus, when printing on the recording sheet S, the piezoelectric element 18 is based on the first drive signal.
To eject ink droplets.

Further, the weight of the ink droplet has a correlation with the voltage Vh of the drive pulse (the voltage of the first drive signal in the claims). Therefore, it is necessary to set an appropriate voltage Vh in order to eject ink droplets having a desired weight. A method for setting the voltage Vh will be described later.

Here, a method for measuring the weight of ink droplets will be described. As described above, when an image based on the print data is printed on the recording sheet S by the ink jet recording head 10, the first
These drive signals are used. On the other hand, when measuring the weight of the ink droplet, the second drive signal is used. In this embodiment, two voltages Vh to be set for the first drive signal are selected, and the weights of the ink droplets when ejected with the two voltages Vh are obtained. Hereinafter, these two voltages are referred to as Vh ₁ and Vh ₂ .

FIG. 5 shows the waveform of the second drive signal with the vertical axis representing voltage and the horizontal axis representing time.
The cycle T of the second drive signal is the same as that of the first drive signal, and includes the same one as the drive pulse COM ₁ of the first drive signal.

Since such a second drive signal is composed of one drive pulse, one ink droplet is ejected by the second drive signal.

The voltage Vh of the second drive signal is the same as the voltage Vh of the first drive signal. In the present embodiment, since two voltages to be set for the first drive signal are selected, the voltages of the second drive signal are also Vh ₁ and Vh ₂ , respectively.

First, the speed of one ink droplet ejected is determined based on the second drive signal.
A method for measuring the speed of the ink droplet ejected by the second drive signal will be described in detail with reference to FIGS. 6 is a schematic configuration diagram of an image pickup unit and an image processing apparatus for measuring the speed of ink droplets, FIG. 7 is an enlarged view of a main part of FIG. 6, and FIG. 8 shows an image obtained by the image pickup unit. It is a conceptual diagram which shows the method of calculating | requiring the speed of an ink drop based on.

As shown in FIG. 6, the vicinity of the nozzle opening 13 is set within the imaging range of the camera 30 that is the imaging means so that the ink droplet 50 ejected from the nozzle opening 13 of the ink jet recording head 10 can be imaged from the side. To fix. The camera 30 may be any camera that can obtain a plurality of images while the ink droplets 50 are dropped or can obtain a continuous image (moving image).

An image processing device 40 is connected to the camera 30. The image processing apparatus 40 is connected to the camera 3
This is an apparatus that transmits an image obtained at 0 and calculates the velocity of ink droplets based on this image. The image processing apparatus 40 is connected to the printer controller 111, transmits a predetermined signal to the printer controller 111 to eject ink droplets from the ink jet recording head 10, and outputs the first drive signal or the second drive signal. The operation of the ink jet recording apparatus I can be controlled, for example, by switching the driving signal.

Using these camera 30 and image processing apparatus 40, the speed of the ink droplet is measured as follows.

First, the image processing apparatus 40 transmits a control signal to the printer controller 111 so as to supply the second drive signal to the piezoelectric element 18. There is no particular limitation on the frequency of the second drive signal.

Next, the image processing apparatus 40 is caused to transmit a signal for ejecting the ink droplets 50 to the printer controller 111, and as shown in FIG. 7, a plurality of images including one ejected ink droplet 50 are captured. Let In addition, the time when each image is captured is also recorded.

In this embodiment, two images are taken. That is, the first ink droplet 50u at time t _1, was created an image of the first ink droplets 50d from time t ₁ at time t ₂ advanced minute time.

A method for obtaining an image including the ejected ink droplet 50 is not particularly limited. For example, after a signal for ejecting the ink droplet 50 is transmitted to the printer controller 111, a moving image is captured for a certain period of time, and two images in which the first ink droplet 50 is reflected can be selected from the moving image. .

Here, as described above, the ink droplet 50 was ejected by the second drive signal. The second drive signal includes one drive pulse.

When the second drive signal is given to the piezoelectric element 18, the ink droplet 50 is ejected from the nozzle opening 13.
Is ejected, and the occurrence of mist and satellite from the ink droplet 50 is suppressed.
Thus, ink droplets 50, no mist or satellite therearound, further since there is no overlap with the next ink droplet 50, the ink droplets 50u at time t _1, the ink droplets 50d at time t ₂ is Ya mist An image captured without overlapping the other ink droplets 50 can be obtained.

Next, the speed of the ink droplet is calculated based on the obtained image. 8, the image _{I 2} and are shown in the image _{I 1} and the time _{t 2} at time _{t 1.}

Ink droplets 50u and 50d are respectively captured in the images I ₁ and I ₂ . Image processing is performed on these images to recognize the ink droplets 50u and 50d. For this image processing, a known method such as edge detection can be used.

Next, the distance D (movement amount) between the recognized ink droplets 50u and 50d is measured. Here, the distance in the vertical direction was measured. By obtaining the actual length corresponding to one pixel in the image I ₁ in advance, the actual distance D of the ink droplets 50u and 50d can be obtained.

Then, the obtained distance D is divided by time t (t ₂ −t ₁ ), and the velocity of the ink droplet 50 can be obtained.

The speed measurement of the above ink droplets is performed at each of the voltages Vh ₁ and Vh ₂ . Voltage Vh ₁ , V
Vm (Vh ₁ ) and Vm (Vh ₂ ) are the speeds of the ink droplet 50 obtained in h ₂ .

The flying speed of the ink droplet (for one droplet) by the second drive signal has a correlation with the weight of the ink droplet.

FIG. 9 illustrates a correlation in which the vertical axis represents the first weight of the ink droplet (one droplet) and the horizontal axis represents the flying speed of the ink droplet.

Three ink jet recording heads 10 having the structure shown in FIG. 2 were prepared in advance (X, Y, Z
For each head 10, the speed of the ink droplets ejected by the second drive signal is obtained as described above, and the weight at that time is obtained by actual measurement.

Thus, it can be seen that there is a correlation between the flying speed of the ink droplet and the first weight even in different heads 10.

Such correlation and the velocity Vm (Vh ₁ ), Vm (Vm) of the ink droplet obtained as described above.
h first weight _Iw 1 corresponding to _{2) (L 1, Vh 1} ), obtaining the _{Iw 2 (L 1, Vh 2} ) (
L ₁ means one ink drop. ). In this embodiment, y = 0.8 for speed and weight.
Since there is a relationship of 514x + 3.4094 (y is weight, x is speed), the first weight of one ink droplet ejected by the second drive signal of each voltage Vh ₁ and Vh ₂ is obtained based on this equation. .

The weight of the ink droplet (one droplet) by the second drive signal has a correlation with the total weight of the ink droplet ejected by the first drive signal.

FIG. 10 illustrates a correlation in which the vertical axis represents the second weight (the weight of ink drops for three drops) and the horizontal axis represents the first weight.

Three ink jet recording heads 10 having the structure shown in FIG. 2 were prepared in advance (X, Y, Z
) For each head 10, the total weight of the ink droplets ejected by the first drive signal and the weight of the ink droplet ejected by the second drive signal are obtained by actual measurement (each head 10 X, 10 Y).
Two trials (A, B) of 10Z were performed. ).

Thus, it can be seen that there is a correlation between the first weight and the second weight even in different heads 10X to 10Z. It can also be seen that the first weight does not become the second weight even if it is simply tripled.

Such correlation and the first weight Iw ₁ (L ₁ , Vh ₁₎ of the ink droplet obtained as described above.
), Iw ₂ (L ₁ , Vh ₂ ) corresponding to the second weight Iw ₁ (L ₃ , Vh ₁ ), Iw ₂ (L ₃
, Vh ₂ ) (L ₃ means three ink droplets). In the present embodiment, the first weight and the second weight have a relationship of y = 3.3454x + 1.198 (y is the second weight, x is the first weight). Find the weight.

In this way, for the voltages Vh ₁ and Vh ₂ , the second weight Iw ₁ (L ₃ , Vh ₁ ), I
w ₂ (L ₃ , Vh ₂ ) is obtained. That is, when the first weight of the ink droplet ejected by the second drive signal having the voltage Vh ₁ is measured and the predetermined calculation is performed, the first drive signal having the voltage Vh ₁ is ejected. The total weight (second weight) of the ink droplets is obtained. The same applies to the voltage Vh _2.

As described above, according to the ink droplet weight measurement method according to the present embodiment, an image in which ink droplets do not overlap is obtained by ejecting ink droplets with the second drive signal including one drive pulse. Since an accurate speed is obtained from the image, the accurate first weight can be obtained from the correlation with the weight. Then, since the second weight is obtained from the first weight based on the correlation between the first weight and the second weight, it is more accurate than simply multiplying the first weight by three and obtaining the equivalent of the second weight. is there.

Further, as described above, since the weight of the ink droplet is not directly measured with an electronic balance, a flow sensor, or the like, there is no risk of an error due to mixing of impurities, and a more accurate second weight can be obtained. Furthermore, since the velocity is measured using image processing, the velocity of the ink droplet can be measured with a simpler configuration than the velocity measurement using laser light.

In addition, based on the plurality of second weights obtained in this way, it is possible to obtain an appropriate voltage for making the weight of the droplets ejected by the first drive signal the target weight.

FIG. 11 shows a correlation in which the vertical axis represents the ink drop weight and the horizontal axis represents the voltage Vh.
As shown, the second weights Iw ₁ (L ₃ , Vh ₁ ), Iw ₂ (L ₃ ) obtained as described above are obtained.
, Vh ₂ ) (abbreviated as Iw ₁ and Iw _{2 in the} figure) and two points A and B of the voltages Vh ₁ and Vh ₂ are plotted.

From the two points A and B, a straight line connecting the points, that is, a voltage-weight characteristic L is obtained. The slope a of the characteristic L is (Iw ₂ −Iw ₁ ) / (Vh ₂ −Vh ₁ ), and the intercept b is Iw ₁ −
aVh ₁

Here, the total weight (target weight) of ink droplets to be ejected by the first drive signal is represented by Iw (L
₃ ), an appropriate voltage VhL is obtained from the characteristic L.

According to the calculation method of the appropriate voltage according to the present embodiment, the appropriate voltage VhL that can discharge the target weight.
Can be easily obtained. By using the first drive signal of the appropriate voltage VhL, a target weight of ink droplets is ejected during printing, and high-quality printing can be performed.

As mentioned above, although one Embodiment of this invention was described, the basic composition of this invention is not limited to what was mentioned above.

In the embodiment described above, the number of drive pulses included in the first drive signal is not limited to three, but may be plural. Further, the waveform of the drive pulse is not limited to that described above. In measuring the appropriate voltage of the ink droplet, two second weights based on the two voltages Vh ₁ and Vh ₂ are used, but two or more may be used.

In addition, although an ink jet recording head has been described as an example of the liquid ejecting head,
The present invention is widely intended for all liquid ejecting heads, and can of course be applied to liquid ejecting heads that eject liquids other than ink. Other liquid ejecting heads include, for example, various recording heads used in image recording apparatuses such as printers, color material ejecting heads used for manufacturing color filters such as liquid crystal displays, organic EL displays, and FEDs.
Electrode material ejection head used for electrode formation for (field emission display), bio chi
Examples include bio-organic matter ejecting heads used for manufacturing p, and can also be applied to liquid ejecting apparatuses including such liquid ejecting heads.

I ink jet recording apparatus (liquid ejecting apparatus), 1 recording head unit, 10
Inkjet recording head (liquid ejecting head), 13 nozzle opening, 18 piezoelectric element, 30 camera, 40 image processing device, 50, 50u, 50d ink droplet, 1
19 Drive signal generation circuit

Claims (3)

Pressure generating means for causing a pressure change in a pressure generating chamber communicating with the nozzle opening is provided, and a first driving signal configured to include a plurality of driving pulses is supplied to the pressure generating means so that the liquid is discharged from the nozzle opening. A droplet weight measuring method of a liquid ejecting head for discharging droplets,
A second driving signal having the same voltage as the voltage Vh of the first driving signal and including one driving pulse is supplied to the pressure generating means;
Measuring the flying speed of the droplets discharged by the second drive signal;
Based on the flight speed and the correlation between the droplet weight and the flight speed, the first weight of the droplets discharged by the second drive signal is obtained,
Based on the correlation between the first weight and the total weight of the plurality of droplets ejected by the first drive signal and the weight of one droplet ejected by the second drive signal, A method for measuring a weight of a droplet of a liquid ejecting head, comprising: obtaining a second weight of a plurality of droplets ejected by one drive signal. In the liquid jet head droplet weight measuring method according to claim 1,
The flying speed of the droplet ejected by the second drive signal is such that the droplet is imaged at at least two different times to form an image, and the difference between the time when the image is captured and the droplet in the image A liquid drop weight measurement method for a liquid ejecting head, characterized in that the liquid weight is obtained from the movement amount of the liquid jet head. N different (n is a natural number) voltages Vh _n are defined, and the voltage of the first drive signal is set to each voltage V
The second weight when h _n is determined by the droplet weight measuring method for a liquid jet head according to any one of claims 1 to 2,
Based on the correlation of the voltage Vh _n and the second weight, the suitability voltage of a liquid ejecting head weight of droplets ejected by the first driving signal and obtains the suitability voltage to the target weight Calculation method.

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