JP5055738B2 - Liquid ejecting apparatus and control method thereof - Google Patents

Description

  The present invention relates to a liquid ejecting apparatus such as an ink jet printer and a control method therefor, and in particular, a liquid ejecting head that ejects liquid droplets from a nozzle opening by supplying a driving signal and operating a pressure generating means. And a control method thereof.

  The liquid ejecting apparatus is an apparatus that includes a liquid ejecting head capable of ejecting liquid as droplets and ejects various liquids from the liquid ejecting head. As a typical example of this liquid ejecting apparatus, for example, an ink jet recording head (hereinafter simply referred to as a recording head) as a liquid ejecting head is provided, and recording paper is used as ink droplets from a nozzle opening of the recording head. Examples thereof include an image recording apparatus such as an ink jet printer that performs recording by forming dots by ejecting and landing on an ejection target such as the above. In recent years, liquid ejecting apparatuses have been applied not only to this image recording apparatus but also to various manufacturing apparatuses such as a manufacturing apparatus for color filters such as liquid crystal displays.

  Here, taking the ink jet printer (hereinafter simply abbreviated as “printer”) as an example, this printer has a series of ink flow paths including a pressure chamber for introducing ink, and nozzle openings leading to the pressure chamber. And a drive for generating a drive signal to be supplied to the pressure generating means, and a recording head having a pressure generating means (for example, a piezoelectric vibrator) provided corresponding to each nozzle array. A signal generation circuit is provided, and a drive signal from the drive signal generation circuit is supplied to the pressure generation means to drive the pressure generation means, thereby ejecting ink as ink droplets from the nozzle openings.

  In the recording head, the liquid amount (weight or volume) of ink droplets ejected from the nozzle opening and the flying speed increase or decrease in accordance with the driving voltage value of the driving signal supplied to the pressure generating means and the waveform shape. ing. Therefore, at the time of manufacturing the recording head, the drive voltage of the drive signal and the shape of the waveform are set so that the average value of the liquid volume and the flying speed of the ejected ink droplets is a design value (design value). (For example, refer to Patent Document 1).

  The drive signal having the drive voltage and waveform set as described above is commonly used for the pressure generating means of each nozzle row, but the amount of liquid when the ink droplet is ejected using this drive signal is determined by the nozzle. May vary between columns. This variation is caused by various factors such as individual differences in pressure generating means. Here, in this type of printer, normally, different color inks correspond to each nozzle row. Therefore, if the amount of ink droplets ejected from each nozzle row varies, the hue of the image on the recording paper is affected. In other words, the color of the nozzle row where the liquid amount is larger than the design value becomes dark, and the color of the nozzle row where the liquid amount is smaller than the design value becomes light. For example, when the discharge liquid amount of the nozzle row corresponding to magenta is larger than the design value, the recorded image becomes more reddish than the image that should originally be obtained.

  In order to correct such a variation between nozzle rows, a printer has been proposed in which information indicating a deviation from a design value for the amount of ink droplets actually ejected is set as a color ID for each nozzle row in a recording head. (For example, patent document 2). In this printer, the number of ink droplet ejections (dot formation rate) per unit area is increased or decreased based on the set color ID, and the image density and hue are adjusted as designed.

JP-A-11-277737 JP 2003-11369 A

  However, when the printer is used for a long period of time, the amount of displacement of the pressure generating means may fluctuate. For this reason, even if the number of ejections is corrected based on the color ID, there is a possibility that variations may occur. As a result, there is a problem that the density and hue of the image cannot be obtained as designed.

  The present invention has been made in view of such circumstances, and an object of the present invention is to reduce the influence on droplet discharge control caused by fluctuations in the amount of displacement of the pressure generating means associated with long-term use.

The liquid ejecting apparatus of the present invention has been proposed in order to achieve the above object, and a plurality of nozzle rows in which nozzle openings communicating with the pressure chambers are arranged, and the liquid in the pressure chambers are subjected to pressure fluctuations. A liquid ejecting head having pressure generating means for generating, and ejecting liquid droplets from the nozzle openings by operation of the pressure generating means;
Identification information storage means for storing identification information about the discharge liquid amount specific to each nozzle row;
With
A liquid ejecting apparatus that adjusts the number of ejections of droplets per unit area by the liquid ejecting head for each nozzle row based on identification information stored in the identification information storage unit,
Drive waveform generating means for generating a waveform including a displacement waveform element for displacing the pressure generating means for discharging a droplet from the nozzle for the purpose of measuring a counter electromotive force signal;
Waveform supply means for supplying the waveform to the pressure generating means;
Back electromotive force amplitude measuring means for measuring the amplitude of the back electromotive force signal based on the residual vibration of the pressure generating means caused by the supply of the displacement waveform element;
Identification information correction means for correcting the identification information stored in the identification information storage means based on the magnitude of the amplitude of the measured back electromotive force signal,
The waveform includes the displacement waveform element and a damping element that restores the potential changed by the displacement waveform element to the original potential, and includes another displacement waveform element before the displacement waveform element. Without
The time from the end of the displacement waveform element to the start of the damping element is set to several times the period of the residual vibration of the pressure generating means .

According to the above configuration, the identification information stored in the identification information storage unit is corrected based on the amplitude of the back electromotive force signal based on the residual vibration after displacement of the pressure generation unit. Variations in the amount of displacement of the generating means can be reflected in the discharge control. For this reason, the density and hue of the discharge target can be maintained as designed. In addition, since the waveform does not include other displacement waveform elements before the displacement waveform element that displaces the pressure generating means for the purpose of measuring the back electromotive force signal, more accurate measurement of the amplitude of the back electromotive force signal is possible. It becomes possible.

  In the above-described configuration, it is desirable that the waveform supply unit supply a displacement waveform element to the pressure generation unit in a state where the residual vibration of the pressure generation unit during the previous drive has converged.

  According to this configuration, the amplitude of the back electromotive force signal can be accurately measured without being affected by the residual vibration caused by the previous drive.

  Further, in the above configuration, the back electromotive force amplitude measuring unit performs peak detection for detecting the maximum value and the minimum value of the back electromotive force signal, and the potential difference between the detected adjacent maximum value and minimum value is determined as the back electromotive force. It is desirable to obtain it as the amplitude of the signal.

The said structure WHEREIN: The said identification information can take the structure which is the information which shows the deviation with respect to the design value of the discharge liquid amount of each nozzle row.
In the above configuration, it is also possible to employ a configuration in which the identification information is the amplitude of a back electromotive force signal measured in advance for each pressure generating unit corresponding to each nozzle row.

In each of the above configurations, when a predetermined operating condition is reached, a series of processing by the drive waveform generation means, waveform supply means, counter electromotive force amplitude measurement means, and identification information correction means may be executed. desirable.
The “operating condition” means conditions such as the operating time of the liquid ejecting apparatus, the number of printed recording sheets, the number of replacements of the liquid storage member, and the like.

Further, the control method of the liquid ejecting apparatus of the present invention has a plurality of nozzle rows in which nozzle openings communicating with the pressure chambers are arranged, and pressure generating means for causing pressure fluctuations in the liquid in the pressure chambers, A liquid ejecting head that ejects liquid droplets from a nozzle opening by the operation of the pressure generating means;
Identification information storage means for storing identification information about the discharge liquid amount specific to each nozzle row;
With
A control method for a liquid ejecting apparatus that adjusts the number of droplets ejected per unit area by a liquid ejecting head for each nozzle row based on identification information stored in an identification information storage unit,
An element driving step for driving the pressure generating means by supplying the pressure generating means with a waveform including a displacement waveform element for displacing the pressure generating means for discharging a droplet from the nozzle for the purpose of measuring a counter electromotive force signal; ,
A back electromotive force amplitude measuring step for measuring an amplitude of a back electromotive force signal based on residual vibration of the pressure generating means generated by supplying the displacement waveform element;
An identification information correction step of correcting the identification information stored in the identification information storage means based on the magnitude of the amplitude of the measured back electromotive force signal,
The waveform used in the element driving step includes the displacement waveform element and a damping element that restores the potential changed by the displacement waveform element to the original potential, but before the displacement waveform element, Does not include other displacement waveform elements
The time from the end of the displacement waveform element to the start of the damping element is set to several times the period of the residual vibration of the pressure generating means .

According to the above configuration, the identification information stored in the identification information storage unit is corrected based on the amplitude of the back electromotive force signal based on the residual vibration after displacement of the pressure generation unit. Variations in the amount of displacement of the generating means can be reflected in the identification information. For this reason, the density and hue of the discharge target can be maintained as designed. In addition, since the waveform does not include other displacement waveform elements before the displacement waveform element that displaces the pressure generating means for the purpose of measuring the back electromotive force signal, more accurate measurement of the amplitude of the back electromotive force signal is possible. It becomes possible.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. In the embodiments described below, various limitations are made as preferred specific examples of the present invention. However, the scope of the present invention is not limited to the following description unless otherwise specified. However, the present invention is not limited to these embodiments. In the following, an ink jet printer (hereinafter abbreviated as a printer) shown in FIG. 1 will be exemplified as the liquid ejecting apparatus of the invention.

  The printer 1 includes a recording head 2 that is a type of liquid ejecting head, a carriage 4 to which an ink cartridge 3 (a type of liquid storage member) is detachably attached, and a platen disposed below the recording head 2. 5, a carriage moving mechanism 7 that moves the carriage 4 on which the recording head 2 is mounted in the paper width direction of the recording paper 6 (a kind of discharge target), and a recording paper in a paper feeding direction that is orthogonal to the head moving direction. 6 schematically includes a paper feed mechanism 8 for transporting 6. Here, the paper width direction is the main scanning direction, and the paper feed direction is the sub-scanning direction. The ink cartridge 3 may be a type that is mounted on the carriage 4 or a type that is mounted on the housing side of the printer 1 and is supplied to the recording head 2 via an ink supply tube.

  The carriage 4 is attached while being supported by a guide rod 9 installed in the main scanning direction, and is configured to move in the main scanning direction along the guide rod 9 by the operation of the carriage moving mechanism 7. ing. The position of the carriage 4 in the main scanning direction is detected by the linear encoder 10, and a detection signal is transmitted as position information to a printer controller (not shown). Accordingly, the printer controller can control the recording operation (discharge operation) by the recording head 2 while recognizing the scanning position of the carriage 4 (recording head 2) based on the position information from the linear encoder 10.

  In addition, a home position serving as a scanning start point of the recording head 2 is set within the moving range of the recording head 2 and outside the platen 5. A capping mechanism 11 is provided at this home position. The capping mechanism 11 seals the nozzle surface of the recording head 2 with a cap member 11 ′ to prevent the ink solvent from evaporating from the nozzle openings 28 (see FIG. 2). The capping mechanism 11 is used for a cleaning operation in which negative pressure is applied to the sealed nozzle surface to forcibly suck and discharge ink from the nozzle openings 28.

  FIG. 2 is a partial cross-sectional view illustrating the configuration of the recording head 2. The recording head 2 includes a case 12, an actuator unit 13 (in a broad sense, pressure generating means) housed in the case 12, a flow path unit 14 joined to the bottom surface (tip surface) of the case 12, and the like. Yes. The case 12 is made of, for example, an epoxy-based resin, and a housing empty portion 15 for housing the actuator unit 13 is formed therein. The actuator unit 13 includes a plurality of piezoelectric vibrators 16 (pressure generating means in a narrow sense) cut into comb teeth and a fixing plate 17 to which the piezoelectric vibrators 16 are joined. As will be described later, the recording head 2 in the present embodiment is configured to be able to eject a total of four colors of ink, and a total of four nozzle rows corresponding to each color are formed on the nozzle plate 22. The recording head 2 is mounted with a total of four actuator units 13 corresponding to each nozzle row.

  A flexible cable 18 is connected to each piezoelectric vibrator 16 of the actuator unit 13, and a drive signal from the drive signal generation circuit 43 (see FIG. 3) is supplied through the flexible cable 18. Note that the piezoelectric vibrator 16 in the present embodiment is a so-called longitudinal vibration mode piezoelectric vibrator that is displaced in a direction orthogonal to the electric field direction, and is orthogonal to the stacking direction of the piezoelectric body and the electrodes when a drive signal is supplied. Displaces (stretches) in the direction. Details of the piezoelectric vibrator 16 will be described later.

  The flow path unit 14 is configured by joining a nozzle plate 22 (a kind of nozzle forming member) to one surface of the flow path forming substrate 21 and a diaphragm 23 to the other surface of the flow path forming substrate 21. Yes. The flow path unit 14 is provided with a reservoir 24, an ink supply port 25, a pressure chamber 26, a nozzle communication port 27, and a nozzle opening 28. A series of ink flow paths from the ink supply port 25, the pressure chamber 26, and the nozzle communication port 27 to the nozzle opening 28 are formed corresponding to each nozzle opening 28.

  The nozzle plate 22 is a thin metal plate having a plurality of nozzle openings 28 formed in a row at a pitch (for example, 180 dpi) corresponding to the dot formation density. In the present embodiment, the nozzle plate 22 is made of a stainless steel plate, and a plurality of rows (nozzle rows) of nozzle openings 28 are provided. One nozzle row is composed of, for example, 180 nozzle openings 28. The recording head 2 in the present embodiment has different colors of ink (one type of liquid in the present invention), specifically cyan (C), magenta (M), yellow (Y), and black (K). Four ink cartridges 3 storing a total of four colors of ink can be mounted, and a total of four nozzle rows are formed on the nozzle plate 22 corresponding to these colors.

  The diaphragm 23 has a double structure in which the elastic film 30 is laminated on the surface of the support plate 29. In the present embodiment, the vibration plate 23 is manufactured using a composite plate material in which a stainless plate, which is a kind of metal plate, is used as the support plate 29 and a resin film is laminated on the surface of the support plate 29 as the elastic film 30. The diaphragm 23 is provided with a diaphragm portion 31 that changes the volume of the pressure chamber 26 and a compliance portion 32 that seals a part of the reservoir 24.

  The diaphragm portion 31 is produced by partially removing the support plate 29 by etching or the like. That is, the diaphragm portion 31 includes an island portion 33 to which the tip end surface of the piezoelectric vibrator 16 is joined, and a thin elastic portion 34 surrounding the island portion 33. The compliance section 32 is produced by removing the support plate 29 in the region facing the opening surface of the reservoir 24 by etching processing or the like in the same manner as the diaphragm section 31, and reduces the pressure fluctuation of the liquid stored in the reservoir 24. Functions as a damper to absorb.

  Since the tip surface of the piezoelectric vibrator 16 is joined to the island portion 33, the volume of the pressure chamber 26 can be changed by extending and contracting the free end portion of the piezoelectric vibrator 16. As the volume changes, pressure fluctuations occur in the ink in the pressure chamber 26. The recording head 2 ejects ink droplets from the nozzle openings 28 using this pressure fluctuation.

  FIG. 3 is a block diagram illustrating an electrical configuration of the printer 1. The printer 1 in the present embodiment is schematically configured by a printer controller 35 and a print engine 36. The printer controller 35 stores an external interface (external I / F) 37 to which print data from an external device such as a host computer is input, a RAM 38 for storing various data, and a control program for various controls. ROM 39, timer circuit 40 that functions as a time measuring means and performs a time measuring operation, control unit 41 that performs overall control of each unit according to a control program stored in ROM 39, and oscillation circuit 42 that generates a clock signal, , A drive signal generation circuit 43 (a kind of drive waveform generation means) for generating a drive signal to be supplied to the recording head 2, and ejection data, a driving signal, and the like obtained by developing print data for each dot. And an internal interface (internal I / F) 44 for outputting the data.

  The print engine 36 includes a recording head 2, a carriage moving mechanism 7, a paper feed mechanism 8, and a linear encoder 10. The recording head 2 generates pulse selection data by translating the discharge data from the latch circuit 47, the latch circuit 47 that latches the discharge data set in the shift register 46, the shift register 46 in which the discharge data is set. A decoder 48, a level shifter 49 that functions as a voltage amplifier, a switch circuit 50 that controls supply of drive signals to the piezoelectric vibrator 16, and the piezoelectric vibrator 16 are provided. In the present embodiment, these shift register 46, latch circuit 47, decoder 48, level shifter 49, and switch circuit 50 function as waveform supply means in the present invention, and the printer controller 35 according to the gradation information of the ejection data. Each drive pulse included in the drive signal COM from is selected and supplied to the piezoelectric vibrator 16.

  The recording head 2 in this embodiment includes a nonvolatile storage element 51 made of an EEPROM, a flash ROM, or the like. The nonvolatile storage element 51 (corresponding to the identification information storage means in the present invention) includes, for example, identification information (color ID) relating to the specific discharge liquid amount of each nozzle row, and the piezoelectric vibrator 16 of each actuator unit 13. Information on the amount of displacement (displacement amount information) is stored. The control unit 41 can appropriately read each piece of information stored in the nonvolatile storage element 51, and can perform control according to the read information. Further, the recording head 2 in the present embodiment includes a back electromotive force amplitude measuring circuit 52 that functions as a back electromotive force amplitude measuring unit. The back electromotive force amplitude measuring circuit 52 is configured to receive a back electromotive force signal based on the residual vibration after displacement of the piezoelectric vibrator 16 and measure the amplitude of the back electromotive force signal in an inspection mode to be described later. .

  The control unit 41 (control unit) controls the ejection of ink droplets by the recording head 2 and other units of the printer 1 in accordance with an operation program stored in the ROM 39. The control unit 41 converts print data (RGB data) input from an external device via the external I / F 37 into discharge data (dot pattern data) used for discharging ink droplets in the recording head 2. In this embodiment, each dot (large, medium, small) of each ink color (C, M, Y, K) is an ejection target in any proportion with respect to the gradation value of the image of the print data. A look-up table (dot formation rate table) that defines the dot formation rate of each dot on the discharge target is stored in the ROM 39, and the control unit 41 controls the look. Data conversion is performed based on the up table. The converted ejection data is transferred to the recording head 2 through the internal I / F 44, and the recording head 2 controls the supply of a drive signal COM (driving pulse) to the piezoelectric vibrator 16 based on the ejection data, thereby causing ink to flow. A droplet discharge, that is, a recording operation (discharge operation) is performed.

  The drive signal generation circuit 43 generates a drive signal COM having a predetermined waveform shape. The printer 1 according to the present embodiment can perform multi-tone recording in which dots having different sizes are formed on a recording paper (a kind of ejection target) by ejecting ink droplets having different liquid amounts. The recording operation is possible with four gradations of dots, small dots, and non-recording. Then, as shown in FIG. 4, for example, the drive signal generation circuit 43 connects the ejection pulse DP1, the ejection pulse DP2, the ejection pulse DP3, and the micro-vibration pulse DP4 for causing micro-vibration of the meniscus during non-recording. A drive signal COM configured as described above is generated.

  The drive signal COM illustrated in FIG. 4 is a drive signal used for relatively high-speed recording such as text printing, and the ejection pulses DP1 to DP3 have the same waveform shape. For example, by supplying only the ejection pulse DP2 to the piezoelectric vibrator 16, small dots are formed on the recording paper 6. Similarly, by supplying two pulses of the ejection pulses DP1 and DP3 to the piezoelectric vibrator 16, a medium dot is formed, and three pulses of the ejection pulses DP1, DP2, and DP3 are supplied to the piezoelectric vibrator 16. Thus, a large dot is formed. Further, during non-recording when no dots are formed, the fine vibration DP4 is supplied to the piezoelectric vibrator 16, and the meniscus exposed to the nozzle opening 28 vibrates finely to the extent that ink droplets are not ejected. Here, the amount of ink droplets ejected by supplying the ejection pulses DP1 to DP3 and the flying speed are determined by the shape of each ejection pulse and the magnitude of the drive voltage Vh (potential difference from the lowest potential to the highest potential). It is prescribed. Therefore, the shape of each ejection pulse of the drive signal COM and the drive voltage Vh are set so that the target liquid amount (design value) is obtained on the average for the ink droplets ejected from all the nozzle openings 28. The drive signal COM is used in common for each actuator unit 13 mounted on the recording head 2.

  Further, the drive signal generation circuit 43 in the present embodiment generates a test drive pulse (evaluation pulse) used in a test mode of the actuator unit 13 described later. This evaluation pulse will be described later together with the inspection mode of the actuator unit 13.

  Next, the piezoelectric vibrator 16 will be described. As shown in FIG. 5, the piezoelectric vibrator 16 in the present embodiment is a stacked piezoelectric vibrator formed by alternately laminating a common internal electrode 55 and individual internal electrodes 56 with a piezoelectric body 57 interposed therebetween. is there. Here, the common internal electrode 55 is an electrode set to the same potential level with respect to all the piezoelectric vibrators 16. The individual internal electrode 56 is an electrode in which a potential level is set for each piezoelectric vibrator 16 in accordance with a supplied drive signal. In the present embodiment, a portion from the tip of the vibrator in the piezoelectric vibrator 16 to about two thirds of the vibrator longitudinal direction (direction perpendicular to the stacking direction) is defined as the free end portion 16a. The remaining portion of the piezoelectric vibrator 16, that is, the portion from the end of the free end portion 16a to the base end of the vibrator is used as a base end portion 16b.

  In the free end portion 16a, an active region (overlap portion) in which the common internal electrode 55 and the individual internal electrode 56 overlap each other is formed. When a potential difference is applied to these internal electrodes 55 and 56, the piezoelectric body 57 in the active region L is actuated and deformed, and the free end portion 16a is displaced in the longitudinal direction of the vibrator to expand and contract. The base end of the common internal electrode 55 is electrically connected to the common external electrode 58 at the base end surface portion of the piezoelectric vibrator 16. On the other hand, the tip of the individual internal electrode 56 is electrically connected to the individual external electrode 59 at the tip surface portion of the piezoelectric vibrator 16. Note that the distal end of the common internal electrode 55 is located slightly in front of the distal end surface portion of the vibrator of the piezoelectric vibrator 16, and the base end of the individual internal electrode 56 is the boundary between the free end portion 16a and the base end portion 16b. Is located.

  The individual external electrode 59 is an electrode formed in series on the tip surface portion of the piezoelectric vibrator 16 and a wiring connection surface (upper face in FIG. 5) which is one side surface of the piezoelectric vibrator 16 in the stacking direction. The wiring pattern of the cable 18 is electrically connected to each individual internal electrode 56. And the part by the side of the wiring connection surface of this separate external electrode 59 is continuously formed toward the front end side from the base end part 16b. The common external electrode 58 is formed on the base end surface portion of the piezoelectric vibrator 16, the above-described wiring connection surface, and a fixed plate mounting surface (lower surface in FIG. 5) which is the other side surface of the piezoelectric vibrator 16 in the stacking direction. It is an electrode formed in series, and conducts between the wiring pattern of the flexible cable 18 and each common internal electrode 55. The portion on the wiring connection surface side of the common external electrode 58 is continuously formed from slightly before the end portion of the individual external electrode 59 toward the base end surface portion side, and the portion on the fixed portion mounting surface side is It is continuously formed from a position slightly ahead of the distal end surface portion of the vibrator toward the proximal end side.

  These external electrodes 58 and 59 also function as electrodes for operating the outermost piezoelectric body 57. That is, the individual external electrode 59 is paired with the common internal electrode 55 across the piezoelectric body 57a formed on the outer surface in the stacking direction, and the common internal electrode 55 and the individual external electrode 59 are formed in the active region L. It overlaps. Accordingly, the portion of the active region L of the piezoelectric body 57a is deformed by the potential difference between the common internal electrode 55 and the individual external electrode 59. Similarly, the common external electrode 58 is paired with the individual internal electrode 56 across the piezoelectric body 57b formed on the outer surface in the stacking direction, and the individual internal electrode 56 and the common external electrode 58 are formed in the active region L. It overlaps. Therefore, the active region L of the piezoelectric body 57b is deformed by the potential difference between the individual internal electrode 56 and the common external electrode 58.

  The base end portion 16b is a non-operation portion that does not expand and contract even when the piezoelectric body 57 in the active region L is operated. A flexible cable 18 is arranged on the wiring connection surface side of the base end portion 16b, and the individual external electrode 59 and the common external electrode 58 and the flexible cable 18 are electrically connected on the base end portion 16b. A drive signal is supplied to each electrode through the flexible cable 18. Further, the fixing plate mounting surface of the base end portion 16b functions as a fixing plate joint, and the fixing plate 17 is joined. That is, each piezoelectric vibrator 16 is joined on the fixed plate 17 in a so-called cantilever state.

  By the way, in the printer 1 described above, the amount of ink droplets actually ejected (ejection fluid amount) does not necessarily match the design value due to variations in the dimensional accuracy or assembly accuracy of components. In particular, in the configuration having the actuator unit 13 for each nozzle row as in this embodiment, it is affected by the individual difference of the actuator unit 13, that is, the variation in the displacement amount of the piezoelectric vibrator 16 of each actuator unit 13. Therefore, when the common drive signal COM is used in each actuator unit 13, the discharge liquid amount may vary between the nozzle rows. The variation in the discharge liquid amount affects the hue of the recorded image. That is, when recording is performed with the same conditions for each nozzle row, the color corresponding to the nozzle row having a larger discharge liquid amount than the design value becomes darker, and the nozzle row has a smaller discharge liquid amount than the design value. Corresponding color becomes lighter.

  In order to prevent such a problem, the printer 1 performs the discharge control based on the identification information (color ID) relating to the specific discharge liquid amount of each nozzle row, thereby making the influence of the above variations as much as possible. It comes to suppress. Hereinafter, this point will be described.

The color ID is information indicating how much the liquid amount of each nozzle row is deviated from the design value. Specifically, this color ID is obtained as follows.
First, in the inspection process for the recording head 2 that has been assembled, for each nozzle row (for each ink color), the average value of the amount of liquid discharged from the nozzle openings 28 constituting the nozzle row is measured, and this average value is used as the nozzle. The amount of liquid discharged in the row. Then, a deviation from the design value of the discharge liquid amount of each nozzle row is obtained, and a value indicating the deviation is stored in the nonvolatile storage element 51 of the recording head 2 as a color ID.

  In the present embodiment, for example, ink droplets are ejected a predetermined number of times from all nozzle openings 28 belonging to the nozzle row to be measured, and the ejected ink is collected by an electronic balance and its weight is measured. Then, by dividing this measurement result by the number of discharges and the number of nozzle openings 28, a measurement value for the discharge liquid amount of the nozzle row is obtained. And the deviation with respect to the design value about the measured value of this discharge liquid amount is calculated. For example, if the discharge liquid amount (measured value) corresponding to a small dot is 1.8 ng for a certain nozzle row, it is 10% less than the design value 2 ng of this discharge liquid amount. For example, when the design value is “100”, “90”, which is 10% less than this, is stored in the nonvolatile storage element 51 as the color ID corresponding to the small dot of the corresponding nozzle row. In this way, the color ID for each nozzle row (each ink color) is stored in the nonvolatile storage element 51.

  In the printer 1, ejection control is performed based on the color ID. That is, the control unit 41 as a control unit reads the color ID stored in the nonvolatile storage element 51 and adjusts the dot formation rate on the recording paper 6 for each nozzle row (ink color) based on the color ID. To do. For example, when the color ID for a small dot in a certain nozzle row is “90”, the control unit 41 determines that the amount of ejected liquid in this nozzle row is 10% lower than the design value. The dot formation rate is controlled to increase by 10%. Specifically, for example, when it is set to eject the ink droplets of the small dots 100 times and land a total of 200 ng of ink droplets, the control unit 41 increases the number of ink droplet ejections by 10% to 110 times. Adjust to. In other words, the nozzle formation is adjusted so that the dot formation rate is decreased for a nozzle row with a larger discharge liquid amount than the design value, and the dot formation rate is increased for a nozzle row with a smaller discharge liquid amount than the design value. Thereby, the density and hue of the recorded image can be aligned as designed.

  However, when the printer is used for a long period of time, the piezoelectric vibrator 16 deteriorates, and the displacement amount of the piezoelectric vibrator 16 also varies from the displacement amount at the time of manufacture. Here, with respect to each actuator unit 13, at the time of manufacture, a combination of the piezoelectric vibrators 16 having the same displacement amount is mounted on the recording head 2, but the usage frequency (the number of times of driving) is different for each actuator unit 13. Since they are different, the degree of deterioration is also different for each. Therefore, the variation rate of the displacement amount of the piezoelectric vibrator 16 due to the deterioration also differs for each actuator unit 13. As a result, even if the dot formation rate is adjusted based on the color ID as described above, there may be variations among nozzle rows.

  Therefore, the printer 1 according to the present embodiment measures the elapsed time from the previous inspection (including the inspection at the time of manufacture) of the displacement amount of the piezoelectric vibrator 16 by the timer circuit 40, and determines the elapsed time from the previous inspection. On the condition that the reference time (a kind of operating condition in the present invention) has been exceeded, the normal mode in which the normal discharge operation is performed is switched from the inspection mode to the inspection mode, and the change in the displacement amount of the piezoelectric vibrator 16 of each actuator unit 13 is inspected. (Measurement) and color ID correction based on the inspection result. Specifically, the displacement of the piezoelectric vibrator 16 is inspected by measuring the amplitude of the back electromotive force signal based on the residual vibration generated after the displacement of the piezoelectric vibrator 16, and the inspection result is reflected in the color ID. . The determination reference time at this time is set to a time at which the influence of deterioration of the piezoelectric vibrator 16 appears due to normal use. Hereinafter, this inspection mode will be described.

FIG. 6 is a flowchart for explaining a series of processes in the printer 1.
In the normal mode (step S1), the control unit 41 controls a normal ejection operation by the recording head 2, that is, recording of an image or the like on the recording paper 6. The control unit 41 monitors the timer circuit 40 and determines whether or not the time measured by the timer circuit 40 has exceeded the determination reference time (step S2). If the time measured by the timer circuit 40 does not exceed the determination reference time in step S2, the process returns to step S1, and the discharge operation in the normal mode is performed while continuously monitoring the timer circuit 40. On the other hand, when it is determined in step S2 that the time measured by the timer circuit 40 exceeds the determination reference time, the control unit 41 performs mode switching from the normal mode to the inspection mode (step S3). This mode switching is executed, for example, immediately after the printer 1 is turned on or in a standby state, and is executed at that time, and when the discharge operation is in progress, it is executed after the discharge operation is completed.

  In the inspection mode in the present embodiment, a drive pulse (evaluation pulse) for measurement is generated from the drive signal generation circuit 43, and this evaluation pulse TP1 is supplied to the piezoelectric vibrator 16 to cause the piezoelectric vibrator 16 to expand or contract. Thus, ink droplets are ejected from the recording head 2. Then, a back electromotive force signal based on the residual vibration after displacement of the piezoelectric vibrator 16 is output to the back electromotive force amplitude measuring circuit 52, and the back electromotive force amplitude measuring circuit 52 measures the amplitude of the back electromotive force signal.

The drive signal generation circuit 43 generates, for example, the evaluation pulse TP1 shown in FIG. The evaluation pulse TP1 lowers the potential from the intermediate potential Vm to the ejection potential VD, thereby extending and displacing the piezoelectric vibrator 16 and ejecting ink droplets from the nozzle openings 28 (the displacement waveform element of the present invention). 1), a hold element P2 that is generated following the discharge element P1 and maintains the discharge potential VD for a certain period of time, and a damping element P3 that restores the potential from the discharge potential VD to the intermediate potential Vm. That is, evaluation pulse TP1 is the ejection element as the displacement waveform element is including waveform.

  The ejection element P1 is set to a voltage gradient that causes the pressure chamber 26 to contract and pressurize the ink in the pressure chamber. Further, the generation time Pw1 of the ejection element P1 is set to be, for example, ½ or less of the natural vibration period Tc. The hold element P <b> 2 is generated to hold the extended state of the piezoelectric vibrator 16. The amplitude of the back electromotive force signal is measured during the generation period of the hold element P2. Therefore, the generation time Pw2 of the hold element P2 is set to a time sufficient for measuring the amplitude of the back electromotive force signal, for example, about several times the period of the residual vibration of the piezoelectric vibrator 16. Here, if the piezoelectric vibrator 16 is unnecessarily expanded and contracted before the timing of checking the amplitude of the back electromotive force signal, vibrations excited each time are synthesized, and the waveform of the back electromotive force signal becomes complicated. This makes it difficult to accurately measure the amplitude of the back electromotive force signal. Therefore, in the evaluation pulse TP1 in the present embodiment, other waveform elements such as an expansion element that preliminarily expands the pressure chamber are not provided before the discharge element P1.

In the element driving step (step S4), the evaluation pulse TP1 is supplied to the piezoelectric vibrator 16 to drive the piezoelectric vibrator 16. At this time, the piezoelectric vibrator 16 is extended by the supply of the ejection element P 1, the pressure chamber 26 is contracted accordingly. As a result, the ink in the pressure chamber is pressurized and ink droplets are ejected from the nozzle openings 28. Further, residual vibration is generated in the expanded piezoelectric vibrator 16. The residual vibration generates a counter electromotive force as shown in FIG. The counter electromotive force signal CF is output to the counter electromotive force amplitude measuring circuit 52.

Next, in the counter electromotive force amplitude measuring step (step S5), the counter electromotive force amplitude measuring circuit 52 extracts the adjacent maximum value (waveform peak) and minimum value (waveform valley) of the counter electromotive force signal CF. (Peak detection step), the potential difference between the adjacent maximum value and minimum value detected in the peak detection step is acquired as the amplitude of the back electromotive force signal CF (amplitude acquisition step), and the acquired amplitude is output to the control unit 41. In addition, the measurement of the amplitude is performed by the combination of the same maximum value and minimum value for all the actuator units 13. In this embodiment, as shown in FIG. 8, the potential difference A between second local maximum MX2 and third pole minimum value MM3 after the residual vibration is excited, or, a third maximum value MX3 the third potential difference B between the pole minimum value MM3, the amplitude a of the counter electromotive force signal CF, obtained as B. The amplitude of the back electromotive force signal CF is larger at the initial stage and gradually converges with the passage of time. Therefore, in order to improve the measurement accuracy, the initial amplitude of the back electromotive force signal CF is measured as much as possible. It is desirable. Therefore, in the case of the amplitudes A and B, it is preferable to acquire the earlier amplitude A as the amplitude of the back electromotive force signal CF.

  FIG. 9 is a diagram showing the relationship between the displacement amount of the piezoelectric vibrator 16 (PZT) and the amplitude of the back electromotive force signal CF. In addition, the solid line graph in the figure shows the correlation when the amplitude A in FIG. 8 is measured, and the alternate long and short dash line graph shows the correlation when the amplitude B in FIG. 8 is measured. As shown in the figure, the larger the displacement amount of the piezoelectric vibrator 16 is, the larger the amplitude of the back electromotive force signal CF is. On the contrary, the smaller the displacement amount of the piezoelectric vibrator 16 is, the smaller the amplitude of the back electromotive force signal CF is. Smaller. Therefore, in the present embodiment, the amount of fluctuation (variation) of the amplitude acquired in the current inspection with respect to the amplitude of the back electromotive force signal acquired as displacement information at the time of the previous inspection (manufacturing) (hereinafter referred to as the previous acquired amplitude). Rate) can be a variation amount of the displacement amount of the piezoelectric vibrator 16.

  In step S6, the control unit 41 detects the previous acquired amplitude stored in advance in the nonvolatile storage element 51 as the displacement amount information, that is, the amplitude of the back electromotive force signal obtained at the previous inspection, and the current inspection. Is compared with the amplitude of the back electromotive force signal CF acquired this time (current acquired amplitude), and the fluctuation width (variation rate) of the current acquired amplitude with respect to the previous acquired amplitude exceeds a specified fluctuation rate (for example, ± 5%). Determine whether or not. If it is determined in step S6 that the fluctuation width of the current acquired amplitude with respect to the previous acquired amplitude does not exceed the specified fluctuation rate, the process returns to step S1 and shifts to control in the normal mode.

  On the other hand, when it is determined in step S6 that the fluctuation width of the current acquired amplitude with respect to the previous acquired amplitude exceeds the specified fluctuation rate, the process proceeds to step S7, and a color ID correction process (identification information correction process) is performed. In this color ID correction step, the control unit 41 functions as identification information correction means in the present invention, and is non-volatile based on the amplitude (currently acquired amplitude) of the back electromotive force signal CF obtained in the back electromotive force amplitude measurement step. The color ID stored in the storage element 51 is corrected. Specifically, the value of the color ID is increased or decreased by the amount of fluctuation of the current acquired amplitude with respect to the previous acquired amplitude. For example, regarding the piezoelectric vibrator 16 of the actuator unit 13 corresponding to a certain nozzle row, when the previous acquired amplitude is 100 (mV) and the current acquired amplitude is 95 (mV), the variation of the current acquired amplitude with respect to the previous acquired amplitude. Is -5%. Therefore, when the value of the color ID is “90”, the color ID is reduced by 5% and corrected to “85”. Further, the current acquired amplitude is overwritten and updated to the previous acquired amplitude stored in the nonvolatile memory element 51 as new displacement amount information. And after completion | finish of test | inspection mode, it returns to step S1 and control of normal mode is performed.

  As described above, the amplitude of the counter electromotive force signal CF based on the residual vibration after displacement of the piezoelectric vibrator 16 is measured, and stored in the nonvolatile memory element 51 based on the magnitude of the amplitude of the measured counter electromotive force signal. Since the color ID is corrected, that is, the value of the color ID is increased or decreased by the variation of the current acquired amplitude with respect to the previous acquired amplitude, the variation of the displacement amount of the piezoelectric vibrator 16 due to long-term use is reflected in the discharge control. Can be made. For this reason, the density and hue of the discharge target can be kept constant even during long-term use.

  In addition, this invention is not limited to above-described embodiment, A various deformation | transformation is possible based on description of a claim.

  For example, regarding the color ID, in the above-described embodiment, identification information regarding the specific discharge liquid amount of each nozzle row is stored in the nonvolatile storage element 51 as a color ID, and discharge control (dot formation rate of the dot formation rate) is performed based on this color ID. Although an example in which adjustment is performed is shown, the present invention is not limited to this. For example, the amplitude (previous acquisition amplitude) of the back electromotive force signal measured for each nozzle row (each actuator unit 13) as the displacement amount information at the time of the previous inspection (manufacturing) can be used as the color ID. . That is, it is possible to adjust the dot formation rate based on the deviation of the previous acquired amplitude with respect to the reference amplitude, using the amplitude with which the liquid amount of the design value is obtained as the reference amplitude.

Further, regarding the evaluation pulse, in the above-described embodiment, the evaluation pulse TP1 having a configuration in which no other waveform element is arranged before the ejection element is illustrated, but the present invention is not limited to this. For example, the evaluation pulse TP2 illustrated in FIG. As described above, it is possible to adopt a configuration having other waveform elements before the ejection elements. The evaluation pulse TP2 includes an expansion element Pa that increases the potential from the intermediate potential Vm to the maximum potential VH with a gradient that does not cause ink droplets to be ejected, and an expansion hold element Pb that connects the expansion element Pa and the ejection element P1 at the maximum potential VH. Are provided before the discharge element P1. That is, when the evaluation pulse T2 is supplied to the piezoelectric vibrator 16, the pressure vibrator 16 is first contracted by the expansion element Pa, whereby the pressure chamber 26 is expanded. As the pressure chamber 26 expands, ink flows from the reservoir 24 into the pressure chamber 26. The expansion state of the pressure chamber 26 is maintained over the generation time of the expansion hold element Pb. The generation time Pwb of the expansion hold element Pb is a time sufficient for the residual vibration generated by contracting and displacing the piezoelectric vibrator 16 by the expansion element Pa to converge (for example, the period of the residual vibration of the piezoelectric vibrator 16). 5 times or more). Then, after the residual vibration accompanying the contraction deformation of the piezoelectric vibrator 16 by the expansion element Pa is converged, the ejection element P1 is supplied to the piezoelectric vibrator 16 and ink droplets are ejected. As a result, the amplitude of the back electromotive force signal CF can be accurately measured without being affected by other waveform elements arranged before the ejection element P1.
In short, as long as the evaluation pulse has a configuration in which the displacement waveform element is supplied to the piezoelectric vibrator 16 in a state where the residual vibration of the piezoelectric vibrator 16 at the time of previous driving has converged, one having various waveforms can be adopted. .

  In the above-described embodiment, the example of measuring the amplitude of the back electromotive force signal based on the residual vibration after the expansion of the piezoelectric vibrator 16 has been described. For example, based on the residual vibration after the piezoelectric vibrator 16 is contracted. It is also possible to measure the amplitude of the back electromotive force signal. In any case, it is not always necessary to eject ink droplets.

  The present invention can also be applied to liquid ejecting apparatuses other than the printer. For example, the present invention can be applied to a display manufacturing apparatus, an electrode manufacturing apparatus, a chip manufacturing apparatus, and the like.

FIG. 2 is a perspective view illustrating a configuration of a printer. FIG. 3 is a cross-sectional view of a main part for explaining the configuration of a recording head. 2 is a block diagram illustrating an electrical configuration of a printer. FIG. It is a figure explaining the structure of a drive signal. It is sectional drawing explaining the structure of a piezoelectric vibrator. 6 is a flowchart illustrating processing of a printer. It is a wave form diagram explaining the structure of an evaluation pulse. It is a wave form diagram explaining the back electromotive force signal accompanying the residual vibration of a piezoelectric vibrator. It is a figure which shows the relationship between the displacement amount of a piezoelectric vibrator, and the amplitude of a back electromotive force signal. It is a wave form diagram explaining the structure of the modification of an evaluation pulse.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Printer, 2 Recording head, 4 Carriage, 13 Actuator unit, 14 Flow path unit, 16 Piezoelectric vibrator, 17 Fixed plate, 18 Flexible cable, 26 Pressure chamber, 28 Nozzle opening, 41 Control part, 43 Drive signal generation circuit, 46 shift register, 47 latch circuit, 48 decoder, 49 level shifter, 50 switch circuit, 51 nonvolatile memory element, 52 counter electromotive force amplitude measurement circuit, 55 common internal electrode, 56 individual internal electrode, 57 piezoelectric layer, 58 common external Electrode, 59 Individual external electrode

Claims (7)

A plurality of nozzle rows in which nozzle openings communicating with the pressure chambers are arranged; and pressure generating means for causing a pressure fluctuation in the liquid in the pressure chambers, and droplets are ejected from the nozzle openings by the operation of the pressure generating means. A liquid jet head for discharging;
Identification information storage means for storing identification information about the discharge liquid amount specific to each nozzle row;
With
A liquid ejecting apparatus that adjusts the number of ejections of droplets per unit area by the liquid ejecting head for each nozzle row based on identification information stored in the identification information storage unit,
Drive waveform generating means for generating a waveform including a displacement waveform element for displacing the pressure generating means for discharging a droplet from the nozzle for the purpose of measuring a counter electromotive force signal;
Waveform supply means for supplying the waveform to the pressure generating means;
Back electromotive force amplitude measuring means for measuring the amplitude of the back electromotive force signal based on the residual vibration of the pressure generating means caused by the supply of the displacement waveform element;
Identification information correction means for correcting the identification information stored in the identification information storage means based on the magnitude of the amplitude of the measured back electromotive force signal,
The waveform includes the displacement waveform element and a damping element that restores the potential changed by the displacement waveform element to the original potential, and includes another displacement waveform element before the displacement waveform element. Without
The liquid ejecting apparatus according to claim 1, wherein the time from the end of the displacement waveform element to the start of the damping element is set to be several times the period of the residual vibration of the pressure generating means .   2. The liquid ejecting apparatus according to claim 1, wherein the waveform supplying unit supplies the displacement waveform element to the pressure generating unit in a state where the residual vibration of the pressure generating unit at the time of previous driving has converged.   The back electromotive force amplitude measuring means detects a peak for detecting a maximum value and a minimum value of a back electromotive force signal, and obtains a potential difference between the detected adjacent maximum value and minimum value as an amplitude of the counter electromotive force signal. The liquid ejecting apparatus according to claim 1, wherein the liquid ejecting apparatus is a liquid ejecting apparatus.   4. The liquid ejecting apparatus according to claim 1, wherein the identification information is information indicating a deviation from a design value of a discharge liquid amount of each nozzle row. 5.   4. The liquid ejection according to claim 1, wherein the identification information is an amplitude of a back electromotive force signal measured in advance for each pressure generating unit corresponding to each nozzle row. 5. apparatus.   2. A series of processes by a drive waveform generation means, a waveform supply means, a back electromotive force amplitude measurement means, and an identification information correction means are executed when a predetermined operating condition is reached. The liquid ejecting apparatus according to claim 5. A plurality of nozzle rows in which nozzle openings communicating with the pressure chambers are arranged; and pressure generating means for causing a pressure fluctuation in the liquid in the pressure chambers, and droplets are ejected from the nozzle openings by the operation of the pressure generating means. A liquid jet head for discharging;
Identification information storage means for storing identification information about the discharge liquid amount specific to each nozzle row;
With
A control method for a liquid ejecting apparatus that adjusts the number of droplets ejected per unit area by a liquid ejecting head for each nozzle row based on identification information stored in an identification information storage unit,
An element driving step for driving the pressure generating means by supplying the pressure generating means with a waveform including a displacement waveform element for displacing the pressure generating means for discharging a droplet from the nozzle for the purpose of measuring a counter electromotive force signal; ,
A back electromotive force amplitude measuring step for measuring an amplitude of a back electromotive force signal based on residual vibration of the pressure generating means generated by supplying the displacement waveform element;
An identification information correction step of correcting the identification information stored in the identification information storage means based on the magnitude of the amplitude of the measured back electromotive force signal,
The waveform used in the element driving step includes the displacement waveform element and a damping element that restores the potential changed by the displacement waveform element to the original potential, but before the displacement waveform element, Does not include other displacement waveform elements
The control method characterized in that the time from the end of the displacement waveform element to the start of the damping element is set to be several times the period of the residual vibration of the pressure generating means .

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