JP2013248799A - Inspection device, inspection method and program - Google Patents

Abstract

A reference value for determining an injection abnormality is appropriately obtained.
A plurality of ejection units that eject a liquid in a cavity by driving a drive element, and a plurality of ejection units based on a result of comparing a detection signal obtained by driving the drive element and a reference value An inspection unit that performs the inspection of, and the reference value is extracted from the plurality of injection units based on a value related to the inspection value of the cavity filled with the liquid, An inspection apparatus obtained based on a detection signal obtained by driving the drive element of the extracted specific injection unit.
[Selection] Figure 15

Description

  The present invention relates to an inspection apparatus, an inspection method, and a program.

A liquid ejecting apparatus that ejects a liquid such as ink from an ejecting unit such as a nozzle has been developed. In such a liquid ejecting apparatus, an inspection is performed as to whether or not the liquid is appropriately ejected from the ejecting unit.
Patent Document 1 discloses that a nozzle driving actuator is also used as a sensor to detect a nozzle state such as thickening and bubbles from the waveform phase, period, and amplitude.

Japanese Patent No. 4114638

  The inspection of the injection unit as described above is performed based on whether or not the vibration period of the injection unit is within a predetermined range. In order to perform such an inspection, it is necessary to appropriately obtain a reference range in advance. That is, it is desirable to appropriately obtain a reference value for determining an injection abnormality.

  The present invention has been made in view of such circumstances, and an object of the present invention is to appropriately obtain a reference value for determining an injection abnormality.

The main invention for achieving the above object is:
A plurality of ejection units that drive the drive element to eject the liquid in the cavity;
An inspection unit that inspects the plurality of injection units based on a result of comparing a detection signal obtained by driving the drive element and a reference value;
With
The reference value is obtained by extracting a specific injection unit from the plurality of injection units based on a value related to an inspection value of the cavity in a state filled with the liquid, and driving elements of the extracted specific injection unit It is an inspection apparatus calculated | required based on the detection signal obtained by driving.

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

1 is a block diagram of an overall configuration of a printer 1 according to an embodiment. FIG. 2A is a perspective view of the printer 1, and FIG. 2B is a cross-sectional view of the printer 1. 3 is a diagram illustrating an example of a nozzle arrangement on a lower surface (nozzle surface) of a head 41. FIG. FIG. 4 is a cross-sectional view around the nozzles of the head 41. FIG. 10 is a diagram illustrating another example of a piezoelectric actuator 422. It is a figure which shows the calculation model of the single vibration which assumed the residual vibration of the diaphragm 421. FIG. 3 is a circuit diagram showing an example of a configuration of a residual vibration detection circuit 55. FIG. 6 is a diagram illustrating an example of a relationship between an input and an output of a comparator 57 of the residual vibration detection circuit 55. FIG. It is explanatory drawing of the vibration period regarding a nozzle. It is a table | surface which shows the nozzle state by the position NtF and the period NtC. 3 is an explanatory diagram illustrating an example of a configuration of a head control unit HC of the head unit 40. FIG. It is explanatory drawing of the timing of each signal. It is explanatory drawing of the reference | standard range of vibration period NtC. This is an example in which it is difficult to determine the reference range. It is a flowchart of the reference | standard range determination process for a test | inspection. It is explanatory drawing of the method of determining the reference | standard range for a test | inspection. It is a figure which shows an example of the correction value by environmental temperature. It is a figure which shows an example of the correction value by the kind of ink. It is a figure which shows an example of the correction value by the number of nozzles driven simultaneously.

At least the following matters will become clear from the description of the present specification and the accompanying drawings. That is,
A plurality of ejection units that drive the drive element to eject the liquid in the cavity;
An inspection unit that inspects the plurality of injection units based on a result of comparing a detection signal obtained by driving the drive element and a reference value;
With
The reference value is obtained by extracting a specific injection unit from the plurality of injection units based on a value related to an inspection value of the cavity in a state filled with the liquid, and driving elements of the extracted specific injection unit It is an inspection apparatus calculated | required based on the detection signal obtained by driving.
The vibration period of the cavity filled with the liquid has a correlation with the inspection value. Therefore, based on the value related to the inspection value of the cavity filled with the liquid, an appropriate ejection unit is extracted, and the inspection is performed based on the detection signal obtained by driving the plurality of extracted ejection units. By obtaining the reference value, it is possible to appropriately obtain the reference value for determining the injection abnormality.

In such an inspection apparatus, it is preferable that the value related to the inspection value of the cavity is corrected according to the temperature related to the liquid in the cavity.
By doing in this way, since the value relevant to the inspection value of the cavity considered to change according to the temperature can be appropriately corrected, the reference value can be obtained more appropriately.

The value related to the inspection value of the cavity is preferably corrected according to the type of liquid in the cavity.
Since the inspection value of the cavity filled with liquid varies depending on the liquid to be filled, an appropriate reference value can be obtained by correcting the value related to the inspection value of the cavity according to the type of liquid. it can.

Further, the reference value is obtained a plurality of times, and when the reference value is obtained for the second and subsequent times, it is desirable that the reference value is obtained based on the previously obtained reference value.
By doing in this way, the reference value for the second and subsequent times is obtained based on the previously obtained reference value, so that a more accurate reference value can be obtained.

In addition, it is preferable that the driving element is driven when the plurality of injection units are inspected and when the reference value is obtained.
By doing in this way, since each process can be performed based on the detection signal obtained when it drives by each of an inspection process and a reference value calculation process, it is not necessary to memorize a detection signal. Therefore, the memory usage can be reduced.

Further, the driving element may be driven either when inspecting with the plurality of injection units or when obtaining the reference value.
By doing in this way, each process can be performed using the detection signal obtained when it drives by either an inspection process or a reference value calculation process in common. Thus, both the inspection process and the reference value calculation process can be executed by driving the drive element once.

In addition, at least the following matters will become clear from the description of the present specification and the accompanying drawings. That is,
Obtaining a detection signal by driving each of the drive elements of the plurality of ejection units;
Comparing the detection signal with a reference value and inspecting the plurality of injection units;
Including
The reference value is obtained by extracting a specific injection unit from the plurality of injection units based on a value related to an inspection value of the cavity in a state filled with the liquid, and driving elements of the extracted specific injection unit This is an inspection method that is obtained based on a detection signal obtained by driving.
The vibration period of the cavity filled with the liquid has a correlation with the inspection value. Therefore, based on the value related to the inspection value of the cavity filled with the liquid, an appropriate ejection unit is extracted, and the inspection is performed based on the detection signal obtained by driving the plurality of extracted ejection units. By obtaining the reference value, it is possible to appropriately obtain the reference value for determining the injection abnormality.

In addition, at least the following matters will become clear from the description of the present specification and the accompanying drawings. That is,
Obtaining a detection signal by driving each of the drive elements of the plurality of ejection units;
Comparing the detection signal with a reference value and inspecting the plurality of injection units;
A program for causing an inspection apparatus to
The reference value is obtained by extracting a specific injection unit from the plurality of injection units based on a value related to an inspection value of the cavity in a state filled with the liquid, and driving elements of the extracted specific injection unit Is a program obtained based on a detection signal obtained by driving the.
The vibration period of the cavity filled with the liquid has a correlation with the inspection value. Therefore, based on the value related to the inspection value of the cavity filled with the liquid, an appropriate ejection unit is extracted, and the inspection is performed based on the detection signal obtained by driving the plurality of extracted ejection units. By obtaining the reference value, it is possible to appropriately obtain the reference value for determining the injection abnormality.

=== Embodiment ===
FIG. 1 is a block diagram of the overall configuration of the printer 1 of the present embodiment. 2A is a perspective view of the printer 1, and FIG. 2B is a cross-sectional view of the printer 1. Hereinafter, a basic configuration of the printer 1 of the present embodiment will be described.

  The printer 1 according to the present embodiment includes a transport unit 20, a carriage unit 30, a head unit 40, a detector group 50, and an ASIC (Application Specific Integrated Circuit) 60 (detector group residual vibration detection circuit 55 and ASIC 60 include an inspection unit. Corresponding to). The printer 1 that has received print data from the computer 110 that is an external device controls each unit (the conveyance unit 20, the carriage unit 30, and the head unit 40) by the ASIC 60. The ASIC 60 controls each unit based on the print data received from the computer 110 and prints an image on paper. The situation in the printer 1 is monitored by the detector group 50, and the detector group 50 outputs the detection result to the ASIC 60. The ASIC 60 controls each unit based on the detection result output from the detector group 50.

  The transport unit 20 is for transporting a medium (for example, paper S) in a first direction (hereinafter referred to as a transport direction). The transport unit 20 includes a paper feed roller 21, a transport motor 22 (also referred to as a PF motor), a transport roller 23, a platen 24, and a paper discharge roller 25. The paper feed roller 21 is a roller for feeding the paper inserted into the paper insertion slot into the printer. The transport roller 23 is a roller that transports the paper S fed by the paper feed roller 21 to a printable region, and is driven by the transport motor 22. The platen 24 supports the paper S being printed. The paper discharge roller 25 is a roller for discharging the paper S to the outside of the printer, and is provided on the downstream side in the transport direction with respect to the printable area.

  The carriage unit 30 is for moving (also referred to as “scanning”) the head in a second direction (hereinafter referred to as a moving direction). The carriage unit 30 includes a carriage 31 and a carriage motor 32 (also referred to as a CR motor). The carriage 31 can reciprocate in the moving direction and is driven by a carriage motor 32. Further, the carriage 31 detachably holds an ink cartridge that stores ink.

  The head unit 40 is for ejecting ink onto the paper S. The head unit 40 includes a head 41 having a plurality of nozzles and a head controller HC. Since the head 41 is provided on the carriage 31, when the carriage 31 moves in the movement direction, the head 41 also moves in the movement direction. Then, dot heads (raster lines) along the moving direction are formed on the paper S by intermittently ejecting ink while the head 41 is moving in the moving direction.

The head controller HC is for controlling the driving of the head 41 and the like. The head controller HC selectively drives the piezoelectric actuator corresponding to each nozzle of the head 41 in accordance with the head control signal from the ASIC 60. Thereby, ink is ejected from the nozzles of the head 41.
Details of the head unit 40 will be described later.

  The detector group 50 includes a residual vibration detection circuit 55 for performing nozzle injection inspection (hereinafter, also referred to as nozzle inspection, which corresponds to inspection of an injection unit). Although the details of the residual vibration detection circuit 55 will be described later, it is assumed that the inspection by the ink viscosity variation detection in the ejection unit inspection is included in the ejection unit inspection.

  The ASIC 60 is a control unit for controlling the printer. The ASIC 60 includes an interface (not shown), a CPU, a memory, and a drive signal generation circuit in addition to a circuit for performing a specific function. The interface unit transmits and receives data between the computer 110 which is an external device and the printer 1. The CPU is an arithmetic processing unit for controlling the entire printer, and also executes a program. The memory is for securing an area for storing a program of the CPU, a work area, and the like, and includes a storage element such as a RAM or an EEPROM. The drive signal generation circuit generates a drive signal COM that drives the head 41.

  Further, the ASIC 60 of the present embodiment also performs processing for determining whether each nozzle is normal or abnormal based on the detection result of the residual vibration detection circuit 55.

  FIG. 3 is a diagram illustrating an example of the nozzle arrangement on the lower surface (nozzle surface) of the head 41. In the head 41, a plurality of nozzles are arranged as shown in FIG. The example of FIG. 3 shows an arrangement pattern of nozzles when four colors of ink (Y: yellow, M: magenta, C: cyan, K: black) are used, and full color printing is possible by combining these colors. It becomes possible.

  There are n (for example, 180) nozzles for each color. In the figure, numbers (Y (1) to Y (n)) are assigned to the nozzles of the Y (yellow) nozzle row.

  The head 41 of this embodiment uses a piezoelectric actuator (so-called piezo method), and a piezoelectric actuator is provided for each nozzle.

  FIG. 4 is a cross-sectional view around the nozzles of the head 41. As shown in FIG. 4, the head 41 includes a vibration plate 421, a piezoelectric actuator 422 that displaces the vibration plate 421, and ink inside that is liquid inside, and the internal pressure increases or decreases due to the displacement of the vibration plate 421. A cavity (pressure chamber) 423, and a nozzle 424 that communicates with the cavity 423 and ejects ink as droplets by increasing or decreasing the pressure in the cavity 423. The piezoelectric actuator 422, the cavity 423, and the nozzle 424 correspond to an injection unit. Further, the injection unit can include a diaphragm 421. As will be described later, the ejecting unit is not limited to ejecting ink droplets by the piezoelectric element 427, and may eject ink droplets by a heating element, and may be driven without including the piezoelectric actuator 422. What is necessary is just to include an element.

  More specifically, the head 41 includes a nozzle substrate 425 on which a nozzle 424 is formed, a cavity substrate 426, a vibration plate 421, and a laminated piezoelectric actuator 422 in which a plurality of piezoelectric elements 427 are laminated. . The cavity substrate 426 is formed in a predetermined shape as shown in the figure, whereby a cavity 423 and a reservoir 428 communicating with the cavity 423 are formed. The reservoir 428 is connected to the ink cartridge CT via the ink supply tube 429. The piezoelectric actuator 422 is alternately arranged with comb-shaped first electrodes 431 and second electrodes 432 arranged in opposition to each other and each comb tooth of the electrodes (first electrode 431 and second electrode 432). And a piezoelectric element 427. In addition, the piezoelectric actuator 422 has one end joined to the diaphragm 421 via an intermediate layer 430 as shown in FIG.

  In the piezoelectric actuator 422 having such a configuration, a mode in which the drive signal COM is applied between the first electrode 431 and the second electrode 432 so as to expand and contract vertically as indicated by arrows in FIG. Is used. Therefore, in the piezoelectric actuator 422, when the drive signal COM is applied, the diaphragm 421 is displaced by the expansion and contraction of the piezoelectric actuator 422, the pressure in the cavity 423 is changed, and an ink droplet is ejected from the nozzle 424. It has become so. Specifically, as described later, the volume of the cavity 423 is enlarged to draw ink, and then the volume of the cavity 423 is reduced to eject ink droplets.

  FIG. 5 is a diagram illustrating another example of the piezoelectric actuator 422. In addition, the code | symbol in a figure has diverted the thing of FIG. The piezoelectric actuator shown in FIG. 5 is generally called a unimorph actuator and has a simple structure in which a piezoelectric element 427 is sandwiched between two electrodes (first electrode 431 and second electrode 432). In the case of the configuration of FIG. 5, the piezoelectric element 427 bends in the vertical direction in the drawing when a drive signal is applied. As a result, similarly to the stacked actuator of FIG. 4, the vibration plate 421 is displaced and ejects ink droplets. Also in this case, the volume of the cavity 423 is enlarged to draw ink, and then the volume of the cavity 423 is reduced to eject ink droplets from the nozzle 424.

  In the printer 1 equipped with such a head 41, ink droplet ejection that does not eject when ink droplets should be ejected from the nozzles 424 (non-ejection) due to causes such as out of ink, ink thickening, and bubble generation. Abnormalities (so-called dot dropout phenomenon) may occur. In order to detect such an abnormality, it is necessary to perform a nozzle inspection.

<About nozzle inspection>
When a drive signal COM is applied to the piezoelectric actuator 422 corresponding to each nozzle 424, after the pressure fluctuation at that time, residual vibration (more precisely, free vibration of the vibration plate 421 in FIG. 4) occurs. The state of each nozzle 424 (including the state in the cavity 423) can be detected from this residual vibration state.

  FIG. 6 is a diagram showing a simple vibration calculation model assuming residual vibration of the diaphragm 421. When the drive signal COM (drive pulse) is applied from the drive signal generation circuit 65 to the piezoelectric actuator 422, the piezoelectric actuator 422 expands and contracts according to the voltage of the drive signal COM. The vibration plate 421 bends in accordance with the expansion and contraction of the piezoelectric actuator 422, whereby the volume of the cavity 423 is expanded and then contracted. At this time, a part of the ink filling the cavity 423 is ejected as an ink droplet from the nozzle 424 by the pressure generated in the ink chamber. During the operation of the series of vibration plates 421, the natural vibration determined by the flow path resistance r due to the shape of the ink supply port, ink viscosity, etc., the inertance m due to the ink weight in the flow path, and the compliance c of the vibration plate 421. The diaphragm 421 causes free vibration at a frequency (residual vibration).

A calculation model of the residual vibration of the diaphragm 421 can be expressed by the pressure P, the inertance m, the compliance C, and the flow path resistance r described above. When the step response when the pressure P is applied to the circuit of FIG. 6 is calculated for the volume velocity u, the following equation is obtained.

<Residual vibration detection circuit>
FIG. 7 is a circuit diagram showing an example of the configuration of the residual vibration detection circuit 55. The residual vibration detection circuit 55 of this embodiment is provided in common for each nozzle of the head 41.

  The residual vibration detection circuit 55 of the present embodiment detects that the pressure change in the cavity 423 is transmitted to the piezoelectric actuator 422. Specifically, the residual vibration detection circuit 55 is based on the mechanical displacement of the piezoelectric actuator 422. A change in the electromotive force (electromotive voltage) generated is detected. This residual vibration detection circuit 55 is configured to open or close the ground end (transistor Q) that grounds or opens the ground end (HGND application side) of the piezoelectric actuator 422 and the drive terminal COM after applying the drive signal COM pulse to the piezoelectric actuator 422. Thus, an AC amplifier 56 that amplifies the AC component of the residual vibration generated by this, and a comparator (comparator) 57 that compares the amplified residual vibration VaOUT and the reference voltage Vref are configured. Among these, the AC amplifier 56 includes a capacitor C that removes a DC component, and an arithmetic unit AMP that inverts and amplifies at a gain determined by the resistors R1 and R2 with the potential of the reference voltage Vref as a reference. The resistor R3 is provided to suppress a rapid voltage change when the transistor Q is switched on and off.

  With the above configuration, when the gate voltage (gate signal DSEL) of the transistor Q in the residual vibration detection circuit 55 becomes high level (hereinafter also referred to as H level), the transistor Q is turned on, and the ground end of the piezoelectric actuator 422 is grounded. Then, the drive signal COM is supplied to the piezoelectric actuator 422. On the contrary, when the gate voltage (gate signal DSEL) of the transistor Q in each residual vibration detection circuit 55 becomes low level (hereinafter also referred to as L level), the transistor Q is turned off, and the electromotive force of the piezoelectric actuator 422 becomes residual vibration. It is taken out by the detection circuit 55. Then, residual vibration is detected by the residual vibration detection circuit 55, and the detection result is output as a pulse POUT. In addition, the code | symbol HGND in a figure is a signal line (grounding line) to the ground end of the piezoelectric actuator 422.

  The detection of the residual vibration is basically performed for each individual piezoelectric actuator 422. However, in the example of FIG. 19 described later, a plurality of piezoelectric actuators 422 are driven, and residual vibrations of the plurality of piezoelectric actuators 422 are acquired.

  Here, the pressure change in the cavity is detected via the piezoelectric actuator 422, but a separate element for detecting vibration may be provided for each nozzle of the head 41. In this case, the element for detecting vibration and the ASIC 60 correspond to the inspection unit.

  FIG. 8 is a diagram illustrating an example of the relationship between the input and output of the comparator 57 of the residual vibration detection circuit 55. The reference voltage Vref is applied to the non-inverting input terminal (+ terminal) of the comparator 57, and the residual vibration VaOUT is applied to the inverting input terminal (−terminal). The comparator 57 outputs an H level if the voltage (Vref) at the + terminal is larger than the voltage (VaOUT) at the − terminal, and becomes L when the voltage (Vref) at the + terminal is smaller than the voltage (VaOUT) at the − terminal. Output level. Therefore, a pulse (COMP output) corresponding to the vibration of the residual vibration VaOUT is output as shown in the figure. In the present embodiment, the position NtF and the vibration period NtC are obtained based on the pulse period of this pulse output (COMP output), and the nozzle 424 is inspected.

  FIG. 9 is an explanatory diagram of the vibration period related to the nozzle. FIG. 10 is a table showing the nozzle state according to the position NtF and the cycle NtC. Hereinafter, the vibration period and nozzle state relating to the nozzle will be described with reference to FIGS. 9 and 10.

  FIG. 9 shows the vibration period after the piezoelectric actuator 422 is driven. The horizontal axis is time, and the vertical axis is amplitude. Further, the position NtF and the vibration period NtC are shown on the time axis of FIG. The position NtF indicates a temporal position from the time zero until the voltage first returns to zero. The vibration period NtC indicates a vibration period for one period. The reason why NtF is indicated as “position” is to distinguish it from “vibration period”.

  In FIG. 9, the vibration cycle of the piezoelectric actuator 422 in a normal nozzle is shown by a solid line. On the other hand, the vibration cycle when bubbles enter the cavity 423 is indicated by a one-dot chain line. The vibration period when bubbles enter the cavity 423 is shorter than that of a normal one. When bubbles are generated in the ink in the cavity 423, the ink in the cavity 423 is reduced, so that the inertance m mainly decreases. When the inertance m is decreased, the angular velocity ω is increased as shown in the above formula. Therefore, as shown in FIG. 9, the position NtF at which the voltage becomes zero arrives early, and the vibration period NtC becomes shorter.

  Also, in FIG. 9, the vibration period when the ink is thickened is indicated by a broken line. As the ink in the cavity 423 thickens, the flow path resistance r increases. As the flow path resistance r increases, the angular velocity ω decreases as shown in the above formula. Therefore, as shown in FIG. 9, the position NtF where the voltage becomes zero arrives late, and the vibration period NtC becomes longer.

  FIG. 10 shows these relationships as a table. A nozzle that is within a predetermined reference range for the position NtF and the vibration period NtC can be considered as a normal nozzle (the reference range corresponds to a reference value). On the other hand, a nozzle whose position NtF is not more than the reference range for the position (early) and whose vibration cycle NtC is not more than the reference range for the vibration cycle (short) is considered as a nozzle that contains bubbles and does not normally eject. be able to. Further, nozzles whose position NtF is not less than the reference range for the position (slow) and whose vibration period NtC is not less than the reference range for the vibration period (long) are considered to be nozzles that do not normally eject due to thickening. be able to.

<About the configuration of the head controller>
FIG. 11 is an explanatory diagram of an example of the configuration of the head controller HC of the head unit 40, and FIG. 12 is an explanatory diagram of the timing of each signal.

  The head controller HC shown in FIG. 11 includes a first shift register 81A, a second shift register 81B, a first latch circuit 82A, a second latch circuit 82B, a decoder 83, a control logic 84, and a switch 86 ( Corresponding to the first switch). Each part excluding the control logic 84 (that is, the first shift register 81A, the second shift register 81B, the first latch circuit 82A, the second latch circuit 82B, the decoder 83, and the switch 86) is provided for each piezoelectric actuator 422. (For each nozzle 424).

  The residual vibration detection circuit 55 of the present embodiment is provided in common for each nozzle 424, and the residual vibration detection circuit 55 includes a signal line (ground line HGND) to the ground end side of each piezoelectric actuator 422. ) Is entered.

  In the present embodiment, the transmission lines in the flexible cable 71 include the transmission lines of the drive signal COM, the latch signal LAT, the channel signal CH, the pixel data SI, the transfer clock SCK, and the ground line HGND. Then, the drive signal COM, the latch signal LAT, the channel signal CH, the pixel data SI, and the transfer clock SCK are transmitted from the ASIC 60 to the head controller HC via the transmission lines of the flexible cable 71. Hereinafter, these signals will be described.

  The latch signal LAT is a signal indicating a repetition period T (a period in which the head 41 moves in a section of one pixel). The latch signal LAT is generated by the ASIC 60 based on the signal of the linear encoder 51, and is input to the control logic 84 and the latch circuit (first latch circuit 82A, second latch circuit 82B).

  The channel signal CH is a signal indicating a section in which the drive pulse included in the drive signal COM is applied to the piezoelectric actuator 422. The channel signal CH is generated by the ASIC 60 based on the signal from the linear encoder 51 and input to the control logic 84.

  The pixel data SI is a signal indicating whether or not dots are formed in each pixel (that is, whether or not ink is ejected from the nozzles 424). In the present embodiment, the pixel data SI also indicates the inspection period of the nozzle 424. This pixel data is composed of 2 bits for each nozzle 424. For example, when the number of nozzles is 64, pixel data SI of 2 bits × 64 is sent from the ASIC 60 every repetition period T. The pixel data SI is input to the first shift register 81A and the second shift register 81B in synchronization with the transfer clock SCK.

  The transfer clock SCK is a signal used when the pixel data SI and the channel signal CH sent from the ASIC 60 are set in the control logic 84 and each shift register (first shift register 81A, second shift register 81B).

  As shown in FIG. 12, the drive signal COM of the present embodiment is provided with four periods of a drive period 1, an inspection period 1, a drive period 2, and an inspection period 2 during the repetition period T. Among these, the driving period 1 includes a waveform 1 (hereinafter also referred to as a waveform for fine vibration) that does not eject ink droplets but gives fine vibration to the ink in the pressure chamber 423 of the head 41. The driving period 2 includes a waveform 2 (hereinafter also referred to as an ejection waveform) that is applied to the piezoelectric actuator 422 when dots are formed (ink ejection). An inspection period 1 and an inspection period 2 indicate periods during which nozzle inspection is performed, and are provided immediately after the driving period 1 and the driving period 2, respectively. Note that the drive signal COM is constant during each inspection period.

  The drive signal COM is input to each switch 86 provided for each piezoelectric actuator 422. The switch 86 performs on / off control as to whether or not to apply the drive signal COM to the piezoelectric actuator 422 based on the pixel data SI. With this on / off control, a part of the drive signal COM can be selectively applied to the piezoelectric actuator 422.

  Next, signals generated by the head controller HC will be described. In the head controller HC, selection signals q0 to q3, a switch control signal SW, and an application signal are generated. The selection signals q0 to q3 are generated by the control logic 64 based on the latch signal LAT and the channel signal CH. Then, the generated selection signals q0 to q3 are respectively input to the decoders 83 provided for each piezoelectric actuator 422.

  As for the switch control signal SW, any one of the selection signals q0 to q3 is selected by the decoder 83 based on the pixel data (2 bits) latched in each latch circuit (first latch circuit 82A, second latch circuit 82B). It is a thing. The switch control signal SW generated by each decoder 83 is input to the corresponding switch 86. The application signal is output from the switch 86 based on the drive signal COM and the switch control signal SW. This application signal is applied to each piezoelectric actuator 422 corresponding to each switch 86.

<Operation of the head controller HC>
The head controller HC performs control for ejecting ink based on the pixel data SI from the ASIC 60. That is, the head controller HC controls the on / off of the switch 86 based on the print data, and selectively applies a necessary portion (period) of the drive signal COM to the piezoelectric actuator 422. In other words, the head controller HC controls the driving of each piezoelectric actuator 422. In the present embodiment, the pixel data SI is composed of 2 bits. The pixel data SI is sent to the head 41 in synchronization with the transfer clock SCK. Further, the upper bit group of the pixel data SI is set in each first shift register 81A, and the lower bit group is set in each second shift register 81B. A first latch circuit 82A is electrically connected to the first shift register 81A, and a second latch circuit 82B is electrically connected to the second shift register 81B.

  When the latch signal LAT from the ASIC 60 becomes H level, each first latch circuit 82A latches the upper bit (SIH) of the corresponding pixel data SI, and each second latch circuit 82B receives the lower bit ( SIL) is latched. Pixel data SI (a set of upper bits and lower bits) latched by the first latch circuit 82A and the second latch circuit 82B is input to the decoder 83, respectively. The decoder 83 selects one of the selection signals q0 to q3 output from the control logic 84 (for example, the selection signal q1) according to the pixel data SI latched by the first latch circuit 82A and the second latch circuit 82B. ) And outputs the selected selection signal as the switch control signal SW. Each switch 86 is turned on / off according to the switch control signal SW, and selectively applies a necessary portion (period) of the drive signal COM to the piezoelectric actuator 422.

<How to find the reference range>
As described with reference to FIG. 9 and FIG. 10 described above, it is possible to detect a nozzle ejection abnormality based on the position NtF and the vibration period NtC. For example, as shown in FIG. 10, the position NtF enters an area within the reference range for the position, enters an area below the reference range for the position, or enters an area above the reference range for the position. It is classified by. Further, the cycle NtC is classified according to whether it enters a region within the reference range for the vibration cycle, enters a region below the reference range for the vibration cycle, or enters a region above the reference range for the vibration cycle. Yes.

  FIG. 13 is an explanatory diagram of the reference range of the vibration period NtC. In FIG. 13, the horizontal axis represents the vibration period, and the vertical axis represents the appearance frequency. In the figure, reference ranges Lts to Hts in which the vibration period NtC is normal are shown. Moreover, Cts which is the median of these is shown.

  When the vibration period NtC is acquired by the method as described above, based on these reference ranges Lts to Hts, whether the acquired vibration period NtC enters the region within the reference range or enters the region below the reference range, Or it can classify | categorize into the area | region beyond a reference | standard range. As a result, the acquired vibration period NtC can be classified as “normal”, “short”, or “long”.

  Here, the reference range has been described by taking the vibration period NtC as an example, but similarly, based on the reference range for the position NtF, it can be classified as either “normal”, “slow”, or “early”. .

  The reference range for the vibration period NtC can be obtained, for example, as follows. First, the vibration period NtC for all nozzles in a certain nozzle row is obtained. Then, the appearance frequency graph as shown in FIG. 10 can be obtained for the vibration period NtC. Basically, since the frequency of appearance of nozzles that can eject ink normally is high, a provisional reference range is determined by obtaining a mountain-shaped center Cts and defining a predetermined width 2 Wt from the center Cts. Can do. Here, the reference range for the vibration period NtC has been described, but the reference range can be similarly determined for the position NtF.

  By appropriately determining the reference range, it is possible to determine whether or not the nozzles normally eject ink by the above-described method. On the other hand, unless these reference ranges are properly obtained, it is impossible to properly determine whether the nozzle is normal or abnormal.

  In general, the reference range can be appropriately determined by the above-described method. However, in the following cases, it may be difficult to appropriately determine the reference range.

  FIG. 14 is an example in which it is difficult to determine the reference range. As described above, as a result of obtaining the vibration period NtC for all the nozzles in a certain nozzle row, a graph of appearance frequency as shown in FIG. 14 may be obtained. In such a case, it is difficult to determine which peak shape median should be adopted. Therefore, it is necessary to estimate the reference range to some extent.

  In the present embodiment, the reference range is estimated based on the vibration period TC of the cavity in a state where ink is filled, and then the reference range is obtained. Below, how to obtain it will be described.

  FIG. 15 is a flowchart of the reference range determination process for inspection. FIG. 16 is an explanatory diagram of a method for determining a reference range for inspection. The reference range for inspection needs to be obtained for both the position NtF and the vibration period NtC, but since both are obtained in substantially the same manner, the vibration period NtC will be described as an example here.

  First, a temporary reference range is set based on the vibration period TC of the head cavity (S102). In order to set the temporary reference range, first, the median value Ctm of the temporary reference range is obtained. The median value Ctm of the temporary reference range is obtained based on the vibration period TC of the head cavity 423. More specifically, it is obtained based on the vibration period TC in a state where the cavity 423 is filled with a liquid such as ink.

  The vibration period TC is a value close to the median value of the reference range or a value related to the median value Cts of the reference range. The median value Cts of the reference range is a value related to the temporary median value Ctm of the reference range. That is, the median value Ctm of the temporary reference range can be expressed as a function F (TC) of the cavity vibration period TC. The vibration period TC of the cavity 423 can be obtained based on a vibration model of the cavity in a state where ink is filled.

  Next, the lower limit value Ltm and the upper limit value Htm are set around the median value Ctm of the calculated temporary reference range. These values are set by providing an arbitrary predetermined width from the median value Ctm. By doing so, provisional reference ranges Ltm to Htm can be set based on the vibration period TC of the head cavity 423 (S102).

  Next, residual vibration is detected for each nozzle. Then, the vibration period NtC is obtained from the detected residual vibration (S104). Since the method for obtaining the residual vibration and the method for obtaining the vibration period NtC have already been described, description thereof will be omitted.

  Next, a reference range for inspection is set based on the acquired vibration cycle NtC and the temporary reference range (S106). Specifically, the vibration period NtC within the temporary reference range Ltm to Htm is extracted. Then, an average value of the vibration periods NtC within the temporary reference range Ltm to Htm is obtained. And let the calculated | required average value be the median value Cts of the reference | standard range for a test | inspection. Further, Cts−Wt is set as the lower limit value Lts of the reference range for inspection with the median value Cts of the reference range as a reference. Further, Cts + Wt is set as the upper limit value Hts of the reference range for inspection.

  In this way, the inspection reference ranges Lts to Hts can be obtained. In the above-described embodiment, the average value of the vibration periods NtC in the provisional reference range is the median value Cts of the inspection reference range, but the embodiment is not limited thereto. For example, instead of the average value, the median value or mode value may be used as the median value Cts of the reference range for inspection.

  In the above-described embodiment, the procedure from step S102 to step S106 is performed only once, but may be performed a plurality of times. In the case of performing a plurality of times, the median value Cts of the reference range for inspection obtained last time in step S102 after the second time can be used as a temporary reference range.

  In addition, the vibration cycle for each nozzle is acquired in step S104, but this vibration cycle is acquired in step S104, stored in a memory or the like, and reused in actual nozzle inspection. It is good as well. That is, the driving of the piezoelectric actuator 422 can be performed only once in total at the time of actual inspection and when the reference value is obtained. By doing in this way, it is not necessary to acquire vibration data again, so that time can be shortened at the time of inspection.

  On the other hand, the vibration cycle for each nozzle may be acquired in step S104, and furthermore, the piezoelectric actuator 422 may be driven during actual inspection to individually acquire the vibration cycle for each nozzle. By doing so, it is possible to prevent the memory from being occupied by vibration cycle data.

  Further, here, the vibration period NtC has been described as an example, but the reference range for the position NtF can also be appropriately obtained by the same method. In this case, the “vibration period” described above may be read as “position”.

  FIG. 17 is a diagram illustrating an example of the correction value based on the environmental temperature. The reference value when the nozzle is normal also varies depending on changes in the environmental temperature. Therefore, the environmental temperature is also taken into account when determining the temporary reference range. Here, the environmental temperature is, for example, the temperature of ink filled in the cavity.

  FIG. 17 shows a correction value that is added (or subtracted) to the temporary median value Ctm of the position NtF corresponding to the environmental temperature. Moreover, the correction value added (or subtracted) to the temporary median value Ctm of the vibration period NtC corresponding to the environmental temperature is shown.

  These correction values are added (or subtracted) to the temporary median value in step S102 in FIG. Thereby, since the temporary reference range according to environmental temperature can be calculated | required, based on this, the more suitable reference range for a test | inspection can be calculated | required.

  FIG. 18 is a diagram illustrating an example of correction values depending on the type of ink. The reference value when the nozzle is normal also varies depending on the type of liquid filled in the cavity. This is because the specific gravity and viscosity of the liquid to be filled are different. Therefore, when obtaining the provisional reference range, the type of liquid filled in the cavity is also taken into consideration. Here, the type of liquid is the type of ink that fills the cavity 423 of the head.

  FIG. 18 shows a correction value that is added (or subtracted) to the provisional median value Ctm of the position NtF corresponding to the type of ink. In addition, a correction value that is added (or subtracted) to the temporary median value Ctm of the vibration period NtC corresponding to the type of ink is shown.

  These correction values are also added (or subtracted) to the temporary median value in step S102 in FIG. As a result, a provisional reference range corresponding to the type of ink to be filled can be obtained. Based on this, a more appropriate reference range for inspection can be obtained.

  FIG. 19 is a diagram illustrating an example of correction values based on the number of nozzles that are driven simultaneously. In the above description, the piezoelectric actuator 422 of each nozzle is driven in units of nozzles, and the vibration period and the like are individually acquired. However, here, the piezoelectric actuators 422 of a plurality of nozzles are driven, and the vibration periods NtC of the plurality of piezoelectric actuators 422 are acquired.

  When acquired in this way, the vibration period NtC (position NtF) is obtained as a vibration period in which the vibrations of the plurality of piezoelectric actuators 422 are superimposed. The vibration period obtained in this way is also correlated with the median value Ctm of the temporary reference range. Therefore, the median value Ctm of the temporary reference range can be obtained based on the vibration cycle obtained in this way.

  By doing in this way, when calculating | requiring the median value Ctm of a temporary reference | standard range, since the several piezoelectric actuator 422 is driven simultaneously, the time required for acquisition of the vibration period NtC can be shortened. Further, by simultaneously driving the plurality of piezoelectric actuators 422, the amplitude of the composite waveform of the residual vibration is increased, so even if a small number of abnormal nozzles are mixed, the influence on the vibration cycle NtC (position NtF) is small. There is also an advantage.

  However, when a plurality of piezoelectric actuators 422 are driven, some correction may be required depending on the number of piezoelectric actuators 422 that are driven simultaneously. For such correction, a correction value as shown in FIG. 19 is employed.

  FIG. 19 shows a correction value that is added (or subtracted) to the provisional median value Ctm of the position NtF corresponding to the piezoelectric actuator 422 that is driven simultaneously. In addition, a correction value that is added (or subtracted) to the provisional median value Ctm of the vibration period NtC corresponding to the piezoelectric actuator 422 that is simultaneously driven is shown.

  These correction values are also added (or subtracted) to the temporary median value in step S102 in FIG. As a result, a provisional reference range corresponding to the number of piezoelectric actuators 422 that are driven simultaneously can be obtained, so that a more appropriate reference range for inspection can be obtained.

  In the above embodiment, a so-called serial type printer that discharges ink while moving the head in a direction intersecting the conveyance direction of the paper S has been described as an example. However, a head that is long in the paper width direction of the paper S is fixed to the printer. Needless to say, the above-described method can be performed even for a so-called line head type printer that forms an image by ejecting ink onto the conveyed paper S.

=== Other Embodiments ===
In the above-described embodiment, the printer 1 has been described as the liquid ejecting apparatus. However, the present invention is not limited to this, and other fluids other than ink (liquid, liquids in which functional material particles are dispersed, gel Such a fluid can also be embodied in a liquid ejection device that ejects or ejects the fluid. For example, color filter manufacturing apparatus, dyeing apparatus, fine processing apparatus, semiconductor manufacturing apparatus, surface processing apparatus, three-dimensional modeling machine, gas vaporizer, organic EL manufacturing apparatus (especially polymer EL manufacturing apparatus), display manufacturing apparatus, film formation You may apply the technique similar to the above-mentioned embodiment to the various apparatuses which applied inkjet technology, such as an apparatus and a DNA chip manufacturing apparatus. These methods and manufacturing methods are also within the scope of application.

  The above-described embodiments are for facilitating the understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof.

<About the head>
In the above-described embodiment, ink is ejected using a piezoelectric element. However, the method for discharging the liquid is not limited to this. For example, other methods such as a method of generating bubbles in the nozzle by heat may be used.

  In this case, in a printer that discharges ink by bubbles generated by generating heat from the heat generating element, the pressure fluctuation may be detected as described above, or the ink in the nozzle is not discharged and the temperature of the heat generating element is increased along with the temperature. An inspection may be performed depending on whether or not the drive voltage changes by utilizing the increase in the resistance value.

1 printer,
20 transport units, 21 paper feed rollers, 22 transport motors,
23 transport roller, 24 platen, 25 discharge roller,
30 Carriage unit, 31 Carriage,
40 head units,
50 detector groups, 55 residual vibration detection circuit,
60 ASIC,
81A first shift register, 81B second shift register,
82A first latch circuit, 82B second latch circuit,
83 Decoder, 84 Control logic, 86 Switch,
421 diaphragm, 422 piezoelectric actuator, 423 cavity,
424 nozzle, 425 nozzle substrate, 426 cavity substrate,
427 Piezoelectric element, 428 reservoir, 429 ink supply tube,
430 Intermediate layer, 431 first electrode, 432 second electrode

Claims (8)

A plurality of ejection units that drive the drive element to eject the liquid in the cavity;
An inspection unit that inspects the plurality of injection units based on a result of comparing a detection signal obtained by driving the drive element and a reference value;
With
The reference value is obtained by extracting a specific injection unit from the plurality of injection units based on a value related to an inspection value of the cavity in a state filled with the liquid, and driving elements of the extracted specific injection unit An inspection apparatus which is obtained based on a detection signal obtained by driving the.   The inspection apparatus according to claim 1, wherein a value related to the inspection value of the cavity is corrected according to a temperature related to a liquid in the cavity.   The inspection apparatus according to claim 1, wherein a value related to the inspection value of the cavity is corrected according to a type of liquid in the cavity.   The inspection apparatus according to any one of claims 1 to 3, wherein the reference value is obtained a plurality of times, and the reference value is obtained on the basis of the reference value obtained last time when the reference value is obtained after the second time.   5. The inspection device according to claim 1, wherein the driving element is driven when the plurality of ejection units are inspected and when the reference value is obtained.   The inspection device according to any one of claims 1 to 4, wherein driving of the drive element is performed either when inspecting with the plurality of injection units or when determining the reference value. Obtaining a detection signal by driving each of the drive elements of the plurality of ejection units;
Comparing the detection signal with a reference value and inspecting the plurality of injection units;
Including
The reference value is obtained by extracting a specific injection unit from the plurality of injection units based on a value related to an inspection value of the cavity in a state filled with the liquid, and driving elements of the extracted specific injection unit An inspection method obtained based on a detection signal obtained by driving. Obtaining a detection signal by driving each of the drive elements of the plurality of ejection units;
Comparing the detection signal with a reference value and inspecting the plurality of injection units;
A program for causing an inspection apparatus to
The reference value is obtained by extracting a specific injection unit from the plurality of injection units based on a value related to an inspection value of the cavity in a state filled with the liquid, and driving elements of the extracted specific injection unit A program obtained based on a detection signal obtained by driving the.

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