JP2012250472A - State monitoring device of inkjet recording head and inkjet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a state monitoring circuit of an inkjet recording head that accurately monitors the state of the drive voltage applied to the discharge energy generating element by a composition as much as of high speed and low cost, and monitoring accurately as a result the state of the inkjet recording head by the composition as much as of high speed and low cost, and to provide an inkjet recording apparatus using this state monitoring circuit.SOLUTION: The above problem is solved by including: a plurality of nozzles; drive circuits that are provided corresponding to respective nozzles and apply drive waveform voltage signals to make the discharge energy generating elements discharge the ink droplets in the resolution unit in order to monitor the state of the inkjet recording head that has the discharge energy generating element to discharge the ink droplet from each nozzle; and comparators that are connected in parallel with the discharge energy generating elements and compare the drive waveform voltage signals applied directly to the discharge energy generating elements with the given reference voltage, and monitoring the state of the inkjet recording head and the drive circuit based on the comparison results of the comparator.

Description

  The present invention relates to an ink jet recording head state monitoring apparatus and an ink jet recording apparatus, and more particularly to an ink jet recording head state monitoring apparatus capable of monitoring the state of an ink jet recording head that ejects ink droplets for recording an image on a recording medium. And an ink jet recording apparatus using the same.

Conventionally, as a printer for recording an image on a recording medium such as recording paper, ink jet recording in which ink droplets are ejected from a plurality of nozzles of an ink jet recording head (hereinafter also simply referred to as a recording head) to form an image on the recording paper The device is used.
Ink droplets can be ejected by applying electrical energy to the recording head ejection energy generating element. However, when the recording head ejection energy generating element is viewed electrically, the piezoelectric element is a capacitor. And, the heater can be regarded as resistance. Further, when the ink is viewed electrically, it can be regarded as a resistance having a low resistance value.

This ink jet recording apparatus includes an ink jet printer using a piezo actuator (piezoelectric element) as an ejection energy generating element for ejecting ink droplets.
In this ink jet printer, nozzle control data for forming an image by performing ON / OFF control of piezoelectric displacement for a plurality of piezoelectric elements (nozzle piezoelectric bodies) provided corresponding to a plurality of nozzles provided in the recording head. Is transferred to the head control unit according to a pixel-unit discharge trigger from the outside, and then the piezoelectric element is selectively driven to finely displace it by applying a driving voltage, based on the dynamic pressure of each piezoelectric actuator. Ink droplets are ejected from the nozzles onto the recording paper, and dots are formed on the recording paper, thereby printing at a desired resolution (for example, 1200 dpi).

  Considering the structure of a recording head using such a piezo actuator, it is natural that the piezoelectric element and the ink are positioned in the immediate vicinity, and the structure of the recording head is actually configured as such. Therefore, in such a recording head, the ink chamber and the electric circuit are close to each other due to the driving structure of the piezo actuator, and it is caused by defects in the manufacturing, structure, and material of the recording head, aging, or ink supply pressure. If an ink leak (leakage) occurs due to a factor and the ink and the piezoelectric element are in direct contact with each other, the piezoelectric element is electrically short-circuited (short-circuited), causing the wiring of the electric circuit in the recording head to be short-circuited. Failure may occur. Since this short circuit (electrical short circuit) is caused by the liquid ink itself, the short circuit location in the electric circuit is complicated.

  For this reason, Patent Document 1 proposes a recording head drive control unit including the recording head state detection device shown in FIG. The recording head drive control unit includes a driving circuit C1 for driving the recording head for applying electrical energy to the piezoelectric element C7, which is an energy generating element, and discharging ink, and a power input terminal for supplying power to the driving circuit. C15, a switch part C12 in which one is connected to the power supply input terminal C15 and the other is connected to the power supply C10, a resistor C16 in which one is connected to the power supply input terminal C15 and the other is connected to the power supply C10, and the voltage of the resistor C16 A comparator (comparator) C9, which is detection means for detecting the state of the recording head by observing, is provided.

  In the figure, C2 is a recording head state detection device comprising transistors C13 and C14 and comprising a switch unit C12 and a state detection unit C17 that switch between a recording operation and a state detection operation of the recording head according to input data VHcont. Further, the drive circuit C1 is supplied with the output voltage VLPSU from the low voltage power supply C11, and generates a voltage signal by the input data WAVDATA, an amplifier circuit C4 that amplifies the voltage signal, a push-pull circuit C5, and its output It comprises an analog switch control unit C8 having an analog switch C6 for controlling on / off of each piezoelectric element 7 of the recording head with a voltage VCOM.

  In the recording head drive control unit disclosed in Patent Document 1, the piezoelectric element C7 has a high resistance, and the current (2.85 mA) flowing through the state detection resistor (360Ω) C16 of the state detection device is small when the detection mode is normal. Therefore, the input voltage VH on the side of the power supply input terminal C15 to the comparator C9 is 36V which is only lower by the voltage drop due to the resistor C16 from the output voltage VHPSU (37V) from the high voltage power supply C10. The comparison result from the comparator C9 is higher than the reference voltage Vref (30V), for example, outputs an L (low) level, VHcont becomes an H (high) level, and a normal recording operation mode is set.

  On the other hand, when ink adheres to the piezoelectric element C7, the ink can be regarded as a low resistance element of about 10Ω added in parallel to the piezoelectric element C7, and therefore the resistance is 100Ω even if the on resistance of the analog switch C6 is added. Since the current flowing from the high voltage power source C10 through the state detection resistor C16 is 80 mA (= 37 × 1000/460), the input voltage VH to the comparator C9 is 8 V, which is lower than the reference voltage Vref (30 V). Thus, the comparison result from the comparator C9 outputs, for example, H level, VHcont becomes L level, the high voltage power supply C10 is turned off, and the drive of the recording head is stopped.

Note that Patent Document 1 also discloses that an AD converter is used in place of the comparator C9 in the recording head state detection device.
Thus, in the recording head state detection device disclosed in Patent Document 1, there is a state detection resistor C16 having a resistance higher than that of ink, and an excessive current does not flow through the drive circuit C1, so the circuit of the drive system is damaged. The state of the recording head can be detected accurately and at high speed.

JP 2008-260164 A

By the way, as described above, the piezoelectric element corresponding to the nozzle of the recording head of the ink jet recording apparatus is substantially equivalent to a capacitor component as an electric circuit, and when the drive circuit and the piezoelectric element (piezoelectric body) are normal, An ink discharge operation can be generated by applying a voltage within a certain range. However, when the drive voltage is out of a certain range due to an abnormality in the physical properties of the piezoelectric body or a circuit failure, the ejection operation becomes abnormal. For example, the above-described inkjet printer cannot eject sufficient ink droplets on a printed matter, resulting in serious quality defects such as blurring and density differences, and the more paper is lost the more the abnormal ejection detection is delayed during mass printing. turn into.
For this reason, in an ink jet printer system, it is essential to detect an abnormal ejection state of the recording head.

In the recording head state detection apparatus disclosed in Patent Document 1, in the detection mode, the voltage at a point on the power input terminal 15 side of the driving circuit C1 of the recording head via the state detection resistor C16 from the high voltage power source C10 is also compared. It is detected at C9 and compared with the reference voltage, and the state of the recording head can be detected according to the comparison result. In particular, if the detected voltage is lower than the reference voltage, an abnormality is detected and the high voltage power supply C10 is turned off. Thus, the drive of the recording head can be stopped.
However, the voltage detected by the recording head state detection apparatus disclosed in Patent Document 1 to detect an abnormality is the voltage of the state detection resistor C16 connected to the power source C10, which is away from the piezoelectric element C7. There is a problem that the voltage is not directly applied to the piezoelectric element C7 but detected at high speed near the piezoelectric element C7.

Further, it is in the detection mode that the state detection device of Patent Document 1 can detect an abnormality, and there is a problem that the abnormal discharge state cannot be detected in the recording operation mode.
Further, the recording head state detection apparatus of Patent Document 1 has a problem that its configuration is complicated.
Furthermore, in the state detection device disclosed in Patent Document 1, if an AD converter is used instead of the comparator C9, there is a problem that the cost increases.

An object of the present invention is to solve the above-described problems of the prior art and drive voltage state applied to an ejection energy generating element constituting the recording head for stable control of the ink jet recording head, which is indispensable for stable printing. Can be accurately monitored with a configuration as fast and inexpensive as possible, and an abnormal ejection state can be detected with high accuracy. As a result, the state of the ink jet recording head can be monitored with a configuration as fast and inexpensive as possible. An object of the present invention is to provide a state monitoring circuit for an ink jet recording head.
Another object of the present invention is to improve the ejection control reliability and stability control of the ink jet recording head in the ink jet printer system using the ink jet recording head state monitoring circuit in addition to the above object. An object of the present invention is to provide an ink jet recording apparatus capable of realizing stable printing and image recording.

  In order to solve the above problems, an ink jet recording head state monitoring circuit according to the present invention includes a plurality of nozzles and an ejection energy generating element that is provided corresponding to each nozzle and ejects ink droplets from each nozzle. A state monitoring circuit for monitoring a state of an ink jet recording head, wherein the ejection energy generating element applies a drive waveform voltage signal for ejecting the ink droplets in units of resolution to the ejection energy generating element. And a comparator for comparing the drive waveform voltage signal applied to the ejection energy generating element with a predetermined reference voltage, and based on a comparison result of the comparator, The state of the drive circuit is monitored.

  Here, the comparator outputs a pulse having a different voltage level depending on the magnitude of the drive waveform voltage signal with respect to the predetermined reference voltage as the comparison result, and the state monitoring circuit further includes the state monitoring circuit, The voltage level counted by the pulse counter is provided with a pulse counter that counts the number of changes in the voltage level output from the comparator as the number of changes in which the drive waveform voltage signal changes beyond the predetermined reference voltage. It is preferable to monitor the state of the ink jet recording head and the drive circuit based on the number of times of the change.

The comparison result of the comparator is preferably such that the voltage level is output as binary judgment data.
The binary determination data of the comparison result of the comparator indicates a digital value of 1 when the drive waveform voltage signal is greater than the predetermined reference voltage, and the drive waveform voltage signal is greater than the predetermined reference voltage. When the value is small, it indicates a digital value of 0, and the pulse counter counts the number of changes from the digital value 1 to the digital value 0 and the number of changes from the digital value 1 to the digital value 0 as the number of changes. Preferably there is.
The voltage level of the binary determination data is preferably a TTL level.

The ejection energy generating element starts ejection of the ink droplet by an external pixel unit ejection trigger signal, and a signal waveform of the drive waveform voltage signal in one cycle between the pixel unit ejection trigger signals. Are the same, the count value of the pulse counter is cleared to 0 at the input timing of the pixel unit discharge trigger signal, and the pulse counter in one cycle until the next pixel unit discharge trigger signal is input. It is preferable to generate an error signal when the count value does not reach a predetermined predetermined value.
The error signal is preferably notified to an ink jet recording apparatus that records an image on a recording medium by discharging the ink droplets from the plurality of nozzles of the ink jet recording head.

  The drive circuit includes a waveform data memory for storing drive waveform voltage data, a D / A converter for digital / analog (D / A) conversion of the drive waveform voltage data output from the waveform data memory, and the D And an amplifier that amplifies an analog signal output from the A converter to generate the drive waveform voltage signal, and the state monitoring circuit is configured to detect the nozzle of the ink jet recording head based on a comparison result of the comparator. It is preferable to detect an abnormality in the ejection energy generating element, the drive circuit, and the drive waveform voltage data.

The state monitoring circuit further includes a reference voltage data memory for storing predetermined reference voltage data, and digital / analog (D / A) conversion of the predetermined reference voltage data output from the reference voltage data memory. And a D / A converter that outputs the predetermined reference voltage, wherein the state monitoring circuit is configured to output the nozzle and the ejection energy generating element of the inkjet recording head based on a comparison result of the comparator, and the driving circuit. In addition, it is preferable to detect an abnormality in the drive waveform voltage data.
Further, the comparator has a resistance value higher than that of the ejection energy generating element so as not to affect a voltage value necessary for driving the ejection energy generating element in the drive waveform voltage signal. preferable.

  In order to solve the above-described problem, an inkjet recording apparatus of the present invention includes an inkjet recording apparatus including a plurality of nozzles and an ejection energy generating element that is provided corresponding to each nozzle and ejects ink droplets from each nozzle. A head, a state monitoring circuit of the ink jet recording head, and a discharge control unit that selectively controls driving / non-driving of the discharge energy generating element based on image data, based on the image data, An image is recorded on a recording medium by discharging the ink droplets from the plurality of nozzles of the inkjet recording head.

The ink jet recording head preferably includes a plurality of head modules each having the plurality of nozzles and the ejection energy generating elements provided corresponding to the nozzles.
Further, it is preferable that the ink jet recording head is a line type head that is elongated by arranging a plurality of the head modules in the width direction of the recording medium.
Further, it is preferable that one or more ink jet recording heads are arranged for each of a plurality of colors.

According to the state monitoring circuit of the ink jet recording head of the present invention, with the above configuration, in order to realize stable printing and image recording in the ink jet printer system, in order to improve ejection control reliability and stability control of the ink jet recording head. The drive voltage state applied to the ejection energy generating element can be accurately monitored with a configuration as fast and inexpensive as possible, and the abnormal ejection state can be accurately detected. As a result, the state of the inkjet recording head can be accurately detected. It is possible to monitor with a configuration that is as fast and inexpensive as possible.
Further, according to the ink jet recording apparatus of the present invention, it is possible to improve the ejection control reliability and the stability control of the ink jet recording head in the ink jet printer system using the state monitoring circuit of the ink jet recording head. Printing and image recording can be realized.

1 is a block diagram illustrating an example of a device configuration of a head control device of an ink jet recording apparatus including a state monitoring time of an ink jet recording head according to an embodiment of the present invention. FIG. 2 is a block diagram of a schematic configuration of a state monitoring circuit of the inkjet recording head shown in FIG. 1. (A)-(e) is a timing chart of an example of the signal of each part of the state monitoring circuit of the inkjet recording head shown in FIG. 2, respectively. 1 is a schematic configuration diagram illustrating an apparatus configuration of an example of an ink jet recording apparatus according to an embodiment of the present invention. (A) And (b) is a plane schematic diagram which shows the example of 1 structure of the inkjet recording head of the inkjet recording device shown in FIG. 4, respectively. (A) And (b) is a plane schematic diagram which shows one structural example of the line-type head which arrange | positions the several head module used for the inkjet recording device shown in FIG. 4, respectively. It is an AA arrow directional view of FIG. FIG. 5 is a block diagram illustrating a configuration example of a control system of the ink jet recording apparatus illustrated in FIG. 4. 10 is a circuit diagram illustrating a configuration of a recording head drive control unit including a recording head state detection device disclosed in Patent Literature 1. FIG.

An ink jet recording head state monitoring circuit and an ink jet recording apparatus according to the present invention will be described below in detail based on preferred embodiments shown in the accompanying drawings.
FIG. 1 is a block diagram showing an apparatus configuration of an example of a head control apparatus of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram of a schematic configuration of the state monitoring circuit of the ink jet recording head of the head control apparatus shown in FIG. FIGS. 3A to 3E are timing charts showing examples of signals at various parts of the state monitoring circuit of the ink jet recording head shown in FIG.

As shown in FIG. 1, an ink jet recording apparatus (hereinafter referred to as a recording apparatus) 10 according to the present embodiment includes an ink jet recording head (hereinafter referred to as a recording head) 12, a head control apparatus 14, a device control section 16, And a recording medium transport unit 18.
Although not shown, the recording head 12 has a plurality of nozzles (ink ejection ports) arranged on its ink ejection surface, for example, two-dimensionally arranged at high density, and records ink droplets according to the image data of the image to be recorded. A droplet is ejected onto a medium, and includes a piezo actuator 20 and a switch circuit 22.

The piezo actuator 20 is provided corresponding to each nozzle, is driven according to image data, and ejects ink droplets from each nozzle. The piezo actuator 20 is an ejection energy generating element composed of a piezoelectric element (piezo element). Composed.
The switch circuit 22 is for performing drive selection (ON / OFF control) of each piezo actuator 20 provided corresponding to each nozzle.

In FIG. 1, for the sake of simplicity, only one piezo actuator 20 and one switch circuit 22 provided in the recording head 12 are shown. However, in practice, the piezo actuators 20 corresponding to a plurality of nozzles and There are a plurality of switch circuits 22.
A plurality of recording heads 12 can be connected to form one ink jet recording head. For example, by connecting a plurality of recording heads 12 with respect to the width direction of a recording medium (not shown), a predetermined recording resolution (for example, the entire drawing possible width) in the paper width direction (for example, the entire drawing width) A long line head (a page wide head capable of single-pass printing) having a nozzle row capable of recording at 1200 dpi) may be configured.

  Further, in FIG. 1, only one recording head 12 (for one color) is shown for ease of explanation. In the case of monochrome printing, one recording head 12 may be used. However, the present invention is not limited to this, and in the case of color printing, a plurality of (for each color) corresponding to each color of a plurality of colors of ink is used. In the case of the recording apparatus 10 including the recording head 12, the head control apparatus 14 is provided individually (in units of heads) for the recording heads 12 of each color. For example, in the recording apparatus 10 including the recording heads 12 for each color corresponding to the four colors of ink of cyan (C), magenta (M), yellow (Y), and black (K), the recording heads 12 for CMYK colors are used. A head controller 14 is provided for each. The head control devices 14 for these colors are preferably managed by a single device control unit 16.

Next, the head control device 14 is connected to the recording head 12 and controls the driving of the piezo actuator 20 corresponding to each nozzle of the recording head 12, thereby ejecting ink from the nozzles (presence / absence of ejection, droplet ejection amount). It functions as a control means for controlling.
As shown in FIG. 1, the head controller 14 includes an image data memory 24, an image data transfer control circuit 26, an ejection timing control unit 28, and an ink jet recording head state monitoring circuit 30 according to the embodiment of the present invention. And having.

The image data memory 24 is used for storing image data developed in print image data (dot data) of an image recorded on a recording medium.
Image data input to the image data memory 24 is managed by the device control unit 16 of the recording apparatus 10 which is a data control unit higher than the head control device 14.

Based on the image data stored in the image data memory 24, the image data transfer control circuit 26 supplies the nozzle control data (here, image data corresponding to the dot arrangement of the recording resolution) of each recording head 12 to each recording head 12. This is for carrying out control to transfer to the switch circuit 22. Here, the nozzle control data is image data (dot data) for determining whether the switch circuit 22 is ON (ejection drive) / OFF (non-drive). The image data transfer control circuit 26 controls opening / closing (ON / OFF) of the switch circuit 22 for each nozzle by transferring the nozzle control data to the switch circuit 22 of each recording head 12.
The image data transfer control circuit 26 can be constituted by a central processing unit (CPU) or a field programmable gate array (FPGA).

  Since the image data signal (nozzle control data) transferred from the image data transfer control circuit 26 is set in the recording head 12, for example, at a necessary timing from the image data transfer control circuit 26 to the recording head 12, for example, It is transmitted in response to a discharge timing signal described later. When a certain amount of image data is transmitted to the recording head 12, a signal called a data latch (latch signal) is transmitted to the recording head 12. At the timing of this data latch signal, on (ON) / off (OFF) data of the displacement of the piezo actuator 20 (piezoelectric element) in the recording head 12 is determined. Thereafter, by applying a driving voltage to the recording head 12, the piezoelectric element of the piezo actuator 20 according to the ON setting is slightly displaced, and ink droplets are ejected. In this manner, the ejected ink droplets are attached (landed) on the paper, and printing with a desired resolution (for example, 1200 dpi) is performed. Note that the piezoelectric element of the piezo actuator 20 set to OFF is not displaced even when a drive voltage is applied, and no droplet is ejected.

The ejection timing control unit 28 receives an ink droplet ejection trigger signal from the recording medium transport unit 18 that transports the recording medium of the recording apparatus 10 during a recording (printing) operation, and as shown in FIG. This is for outputting a discharge timing signal (pixel unit discharge trigger pulse) serving as a start trigger of the discharge operation to the image data transfer control circuit 26, a drive voltage control circuit 34 of the state monitoring circuit 30 described later, and a pulse counter 36. is there.
In the recording apparatus 10 shown in the drawing, the digital data of the image data and the driving voltage waveform is received in units of resolution from the image data transfer control circuit 26 and the driving voltage control circuit 34 described later to the recording head 12 in response to the ejection timing signal from the ejection timing controller 28. By transferring the data, a selective discharge operation (on-demand discharge drive control) corresponding to the image data can be performed to realize printing of one page.

  As shown in FIGS. 1 and 2, the state monitoring circuit 30 of the recording head 12 of the present invention includes a data controller 40 including a waveform data memory 32, a drive voltage control circuit 34, a pulse counter 36, and a reference voltage data memory 38; D / A converters (converters) 42 and 44, an amplifier circuit 46, and a comparator 48 are included.

The waveform data memory 32 is for storing digital data of a drive voltage waveform (hereinafter also referred to as drive voltage waveform data) for driving the piezo actuator 20. Here, for example, as shown in FIG. 3B, the drive voltage waveform is obtained when the nozzle switch circuit 22 of the recording head 12 is turned on (discharge drive) in response to the discharge timing signal from the discharge timing control unit 28. The drive voltage applied to the piezo actuator (piezoelectric element) 20 to intermittently drive the piezo actuators 20 of the respective recording heads 12 in accordance with the discharge timing signal and discharge a plurality of ink droplets continuously from the nozzles. It is a pulse waveform.
The drive voltage waveform data input to the waveform data memory 32 is managed by the host device control unit 16 in the same manner as the image data input to the image data memory 24.

The drive voltage control circuit 34 reads drive voltage waveform data for driving the piezo actuator 20 of each recording head 12 from the waveform data memory 32, and adjusts the D / A according to the discharge timing signal from the discharge timing control unit 28. This is for output to the converter 42.
The D / A converter 42 converts the drive voltage waveform data output from the drive voltage control circuit 34 into an analog drive pulse having a predetermined voltage value and / or current value, that is, an analog voltage waveform (drive having a predetermined current value). Voltage analog pulse).
The amplifier circuit 46 is a power amplifier circuit for amplifying the output analog voltage waveform from the D / A converter 42 to a predetermined current / voltage suitable for driving the piezo actuator 20 finally. For example, as shown in FIG. 3B, the analog voltage waveform amplified by the amplifier circuit 46 to a current / voltage capable of driving the piezoelectric actuator 20 is supplied to the recording head 12 (piezoactuator 20).

That is, in the head control device 14, the drive voltage control circuit 34 receives the ink droplet discharge trigger signal input from the external recording medium transport unit 18 and matches the discharge timing signal output from the timing control unit 28. Is output to the D / A converter 42, the D / A converter 42 converts the drive voltage waveform data into an analog voltage waveform. The output waveform (analog voltage waveform) of the D / A converter 42 is applied to the piezo actuator (piezoelectric element) 20 of the recording head 12 by applying the drive voltage waveform amplified by the amplifier circuit (power amplification circuit) 46. In response to the drive voltage waveform, ink droplets are continuously ejected from the corresponding nozzles.
Here, as shown in FIG. 3B, in the case of normal ejection, ink droplets are ejected in accordance with the ejection timing signal, but the drive voltage waveform per cycle between ejection timings is always the same. It is.

The reference voltage data memory 38 is for storing digital data (reference voltage data) of a predetermined reference voltage set in advance. Here, the predetermined reference voltage data is set as a digital value of a threshold value between ink droplet ejection and non-ejection.
The D / A converter 44 is for converting predetermined reference voltage data output from the reference voltage data memory 38 into a reference voltage (analog reference voltage value) Vref. Thus, as the D / A converter 44 generating the reference voltage input to the comparator 48, an inexpensive low-speed D / A converter can be used. For example, the D / A converter built in the CPU or the like can be used. An A / A converter, that is, a D / A converter built in a host data controller 40 composed of a CPU or the like can be used.
By changing predetermined reference voltage data output from the reference voltage data memory 38, the reference voltage (analog reference voltage value) Vref output from the D / A converter 44, which becomes a detection threshold, can be easily obtained. Can be changed.

The comparator 48 is a drive voltage (analog voltage) of the drive voltage waveform (analog voltage waveform) amplified by the amplifier circuit 46 and directly applied to the piezo actuator 20, and the reference voltage Vref output from the D / A converter 44. And a voltage comparator for outputting a comparison result. That is, the drive voltage applied to the recording head 12 is directly input to the comparator 48 and is compared with a preset reference voltage by the comparator 48.
Since the comparison result of the comparator 48 is detected as a voltage value on the pulse, that is, a detection voltage pulse, the pulse counter 36 of the host data controller 40 can count (count) the change point of the voltage pulse. It becomes possible.

  Therefore, the comparison result is preferably output as a voltage value that can be binary-determined from the comparator 48 so that it can be digitally counted by the pulse counter 36. For example, as shown in FIG. It is preferable to output a binary determination voltage value detection pulse, for example, TTL level binary determination data (digital value 1: 3.3 V and digital value 0: 0 V). Here, for example, when the driving voltage> Vref, the output of the comparator 48 becomes 3.3V and indicates a digital value 1, and when the driving voltage <Vref, the output becomes 0V and indicates a digital value 0. Is good.

Since the comparator 48 has a very high resistance value compared to the piezo actuator (piezoelectric element) 20 and the amplifier circuit 46 has a sufficient current capacity, the comparator 48 includes a drive of the piezo actuator 20. No current is generated that affects the voltage value required.
Therefore, the comparator 48 can be connected in parallel with the piezo actuator 20 and can directly monitor the voltage value applied to the piezo actuator 20, thus enabling more accurate voltage detection.

  As shown in FIG. 3D, the pulse counter 36 receives the discharge timing signal shown in FIG. 3A from the discharge timing control unit 28, clears the count value to 0, and receives the next discharge timing signal. Until this time, the number of changes in which the output of the comparator 48 changes from the digital value 1 to 0 and / or the number of changes in the change from the digital value 0 to 1 is counted. Note that the pulse counter 36 has a predetermined number of preset pulse count values between the preceding and subsequent ejection timing signals. In the example shown in FIG. 3D, the change from the digital value 1 to 0 and the change from 0 to 1 If the six times of counting both changes cannot be obtained, an error signal as shown in FIG. 3E is sent from the data controller 40 as shown in FIG. Send to.

In this way, the data controller 40 monitors the change point of the voltage value of the comparator 48, that is, the point where the drive voltage waveform crosses the reference voltage Vref serving as the detection threshold, and the output data of the comparator 48 starts from 1. An internal pulse counter 36 counts the number of changes that change from 0, 0 to 1. On the other hand, as described above, since ink is ejected by a pixel unit ejection trigger (ejection timing signal), the drive voltage waveform per cycle is always the same. Therefore, the number of times the comparator 48 changes across the reference voltage Vref serving as the detection threshold is always a constant value. For this reason, when the number of changes counted by the pulse counter 36 is less than a certain value, it becomes possible for the data controller 40 to detect that an abnormal state has occurred, and an error (as shown in FIG. fail) signal can be output.
Therefore, in the data controller 40, when the count of the pulse counter 36 reaches a predetermined count value in a certain time, the normal state is assumed, and when the count value does not reach, the abnormal state is notified to the user. Can do.

  In the state monitoring circuit 30 of the recording head 12 of the present invention, the waveform data memory 32, the drive voltage control circuit 34, the pulse counter 36 and the reference voltage data memory 38 are configured as a data controller 40. That is, the data controller 40 includes a waveform data memory 32 that stores drive voltage waveform data output to the D / A converter 42, a pulse counter 36 that counts the number of ejection pulse changes, and a reference that is input to the voltage comparator 48. The reference voltage data memory 38 has a function of storing reference voltage data to be output to the D / A converter 44 that outputs a voltage. The data controller 40 can be configured by a CPU or hardware called FPGA. The data controller 40 and the above-described image data transfer control circuit 26 may be configured by the same CPU or FPGA as a controller for controlling the driving of the recording head 12, or the data controller 40 may be an image data transfer control circuit. 26 may be included.

Next, as will be described in detail later, the apparatus control unit 16 is a part that controls digital data on the recording apparatus 10 side, which is higher than the head control apparatus 14, and can be configured by, for example, a personal computer or a host computer. . The head control device 14 preferably includes a USB (Universal Serial Bus) or other communication interface as data communication means for receiving data from the host device control unit 16.
Here, when the system is started, it is preferable that waveform data and image data are transferred from the device control unit 16 to the head control device 14 of each color. Note that image data may be transferred in synchronism with recording medium conveyance during execution of printing (image recording).
The recording medium transport unit 18, which will be described in detail later, includes various transport drums (cylinders) and processes for transporting a recording medium on which an image is recorded by the recording head 12 and various processes are performed. Consists of transport means such as drums, transport rollers, and transport belts, and can acquire and output ink droplet ejection trigger signals for obtaining ejection timing signals in accordance with the transport of recording media. is there.

In the state monitoring circuit 30 of the recording head 12 of the present invention, the drive voltage waveform data output from the waveform data memory 32 is converted into a constant voltage or current value by the D / A converter 42, and finally the amplifier. The circuit 46 amplifies the driving voltage to a predetermined piezoelectric actuator (piezo element) 20. The amplified drive voltage is applied to the piezo actuator 20 piezo element for ink ejection, and further input to a comparator 48 connected in parallel with the piezo actuator 20 for voltage detection. During the discharge operation, a drive voltage is input to the comparator 48, and a voltage comparison process is performed with the reference voltage (Vref) input at the same time.
For this reason, in contrast to Patent Document 1 in which a comparator is input in parallel to a drive circuit that drives the head and a power supply input terminal that supplies power to the drive circuit, in the present invention, a piezo actuator (piezo element) 20 is used. Since the voltage detection comparator 48 is connected in parallel to compare the voltage value input to the piezo actuator 20, the voltage value itself applied to the piezo actuator 20 can be monitored.

In the state monitoring circuit 30 of the recording head 12 of the present invention, the comparison result by the comparator 48 is input to the pulse counter 36 as the voltage value from the comparator 48 as binary determination data (0: 1) of TTL level. The pulse counter 36 counts the number of changes of 1 to 0 data and / or 0 to 1 data, and whether the recording head 12 is in a normal state or not depending on whether the count value is a predetermined specified value or not. Determine if it is in a state.
For this reason, in contrast to Patent Document 1 that monitors the comparator (comparator) output itself, in the present invention, the number of change points of the comparator output is counted, so that any one of the piezo element, the drive circuit, and the drive memory data is abnormal. Even in this case, it can be detected with high accuracy, at high speed and at low cost.

Also in the state monitoring circuit 30 of the recording head 12 in the illustrated example, the comparator 48 converts the voltage value detected from the input drive voltage waveform into a digital value by the A / D converter without using the comparator 48. In the state monitoring circuit 30 of the recording head 12 according to the present invention, it is possible to detect an abnormality with higher accuracy, but the A / D with high speed and high resolution (several tens of MHz, 8 bits) is possible. The conversion element is very expensive and is undesirable because it increases the equipment cost.
On the other hand, in the state monitoring circuit of the present invention, the detection circuit configuration can be realized by a very inexpensive element called a comparator, which is effective for device development.
In the state monitoring circuit of the present invention, since the detection current may be weak, it is possible to monitor in real time whether the recording head made of the piezoelectric element is in the printing operation or in the standby state. is there.

FIG. 4 is an overall configuration diagram showing a configuration example of the ink jet recording apparatus according to the embodiment of the present invention.
As shown in the figure, an ink jet recording apparatus (hereinafter referred to as a recording apparatus) 100 according to the present embodiment includes a paper feeding unit 112, a treatment liquid application unit (precoat unit) 114, a drawing unit 116, and a drying unit 118. A fixing unit 120 and a paper discharge unit 122.
The recording apparatus 100 according to this embodiment includes an ink jet recording head (hereinafter referred to as a recording head) 172M on a recording medium (hereinafter also referred to as recording paper or paper) 124 held on an impression cylinder (drawing drum) 170 of the drawing unit 116. , 172K, 172C, and 172Y, a single-pass recording apparatus that forms a desired color image by ejecting a plurality of colors of ink, and a processing liquid (here, aggregating treatment) is applied to the recording medium 124 before the ink is ejected. This is an on-demand type image forming apparatus to which a two-liquid reaction (aggregation) method in which an image is formed on a recording medium 124 by reacting a processing liquid and an ink liquid.

Hereinafter, each processing unit will be described.
(Paper Feeder)
A recording medium 124 that is a sheet is stacked on the paper feeding unit 112, and the recording medium 124 is fed one by one from the paper feeding tray 150 of the paper feeding unit 112 to the processing liquid application unit 114. In this example, a sheet (cut paper) is used as the recording medium 124, but a configuration in which continuous paper (roll paper) is cut to a required size and fed is also possible.

(Processing liquid application part)
The processing liquid application unit 114 is a mechanism that applies the processing liquid to the recording surface of the recording medium 124. The treatment liquid contains a color material aggregating agent that agglomerates the color material (pigment in this example) in the ink applied by the drawing unit 116, and the ink comes into contact with the treatment liquid and the ink. And the solvent are promoted.

  The processing liquid application unit 114 includes a paper feed cylinder 152, a processing liquid drum (also referred to as “precoat cylinder”) 154, and a processing liquid coating device 156. The treatment liquid drum 154 is a drum that holds and rotates the recording medium 124. The processing liquid drum 154 includes a claw-shaped holding means (gripper) 155 on the outer peripheral surface thereof, and the recording medium 124 is sandwiched between the claw of the holding means 155 and the peripheral surface of the processing liquid drum 154, thereby recording the recording medium. The tip of 124 can be held. The treatment liquid drum 154 may be provided with a suction hole on the outer peripheral surface thereof and connected to a suction unit that performs suction from the suction hole. As a result, the recording medium 124 can be held in close contact with the peripheral surface of the treatment liquid drum 154.

  A processing liquid coating device 156 is provided outside the processing liquid drum 154 so as to face the peripheral surface thereof. The processing liquid coating device 156 includes a processing liquid container in which the processing liquid is stored, an anix roller (measuring roller) partially immersed in the processing liquid in the processing liquid container, and the anix roller and the processing liquid drum 154. A rubber roller is brought into pressure contact with the upper recording medium 124 and transfers the measured processing liquid to the recording medium 124. According to the processing liquid coating apparatus 156, the processing liquid can be applied to the recording medium 124 while being measured.

  In the present embodiment, the configuration in which the application method using the roller is exemplified, but the present invention is not limited to this. For example, various methods such as a spray method and an ink jet method can be applied.

  The recording medium 124 to which the processing liquid is applied by the processing liquid applying unit 114 is transferred from the processing liquid drum 154 to the drawing drum 170 of the drawing unit 116 via the intermediate transport unit 126.

(Drawing part)
The drawing unit 116 includes a drawing drum (also referred to as “drawing cylinder” or “jetting cylinder”) 170, a paper holding roller 174, and recording heads 172M, 172K, 172C, and 172Y. As the recording heads 172M, 172K, 172C, and 172Y for the respective colors and the control devices thereof, the configuration of the recording head 12 and the configuration of the head control device 14 described with reference to FIGS.

  Similar to the treatment liquid drum 154, the drawing drum 170 includes a claw-shaped holding means (gripper) 171 on the outer peripheral surface thereof. The recording medium 124 fixed to the drawing drum 170 is conveyed with the recording surface facing outward, and ink is applied to the recording surface from the recording heads 172M, 172K, 172C, 172Y.

  Each of the recording heads 172M, 172K, 172C, and 172Y is a full-line ink jet recording head having a length corresponding to the maximum width of the image forming area in the recording medium 124. A nozzle row (two-dimensional array nozzle) in which a plurality of nozzles for ejecting ink are arranged over the entire width of the formation region is formed. Each of the recording heads 172M, 172K, 172C, and 172Y is installed so as to extend in a direction orthogonal to the conveyance direction of the recording medium 124 (the rotation direction of the drawing drum 170).

  A corresponding color ink cassette is attached to each of the recording heads 172M, 172K, 172C, and 172Y. Ink droplets are ejected from the recording heads 172M, 172K, 172C, and 172Y toward the recording surface of the recording medium 124 held on the outer peripheral surface of the drawing drum 170.

  As a result, the ink comes into contact with the treatment liquid previously applied to the recording surface, and the color material (pigment) dispersed in the ink is aggregated to form a color material aggregate. As an example of the reaction between the ink and the treatment liquid, this embodiment uses a mechanism in which an acid is contained in the treatment liquid and the pigment dispersion is destroyed and aggregated by PH down, so that coloring material bleeding, color mixing between inks of each color, ink drop Avoids droplet ejection interference due to liquid coalescence when landing. Thus, the color material flow on the recording medium 124 is prevented, and an image is formed on the recording surface of the recording medium 124.

  The droplet ejection timings of the recording heads 172M, 172K, 172C, and 172Y are synchronized with an encoder (not shown in FIG. 4 and reference numeral 294 in FIG. 8) that detects the rotational speed disposed on the drawing drum 170. An ink droplet ejection trigger signal (pixel trigger) is issued based on the detection signal of the encoder. Thereby, the landing position can be determined with high accuracy. In addition, it learns the speed fluctuation due to the deflection of the drawing drum 170 in advance, corrects the droplet ejection timing obtained by the encoder, and depends on the deflection of the drawing drum 170, the accuracy of the rotation axis, and the speed of the outer peripheral surface of the drawing drum 170. In this case, it is possible to reduce the droplet ejection unevenness. The drawing drum 170 provided with the encoder (294: see FIG. 8) corresponds to the recording medium transport unit 18 described in FIG.

  Further, maintenance operations such as cleaning the nozzle surfaces of the recording heads 172M, 172K, 172C, and 172Y and discharging the thickened ink may be performed by retracting the head unit from the drawing drum 170.

  In this example, the configuration of CMYK standard colors (four colors) is illustrated, but the combination of ink colors and the number of colors is not limited to this embodiment, and light ink, dark ink, and special color ink are used as necessary. May be added. For example, it is possible to add a recording head that discharges light ink such as light cyan and light magenta, and the arrangement order of the color heads is not particularly limited.

  The recording medium 124 on which an image is formed by the drawing unit 116 is transferred from the drawing drum 170 to the drying drum 176 of the drying unit 118 via the intermediate conveyance unit 128.

(Drying part)
The drying unit 118 is a mechanism for drying moisture contained in the solvent separated by the color material aggregating action. As shown in FIG. 4, a drying drum (also referred to as “drying cylinder”) 176, a solvent drying device 178, It has. Similar to the processing liquid drum 154, the drying drum 176 includes a claw-shaped holding unit (gripper) 177 on the outer peripheral surface thereof, and the holding unit 177 can hold the leading end of the recording medium 124.

  The solvent drying device 178 is disposed at a position facing the outer peripheral surface of the drying drum 176, and includes a plurality of halogen heaters 180 and hot air ejection nozzles 182 disposed between the halogen heaters 180. Various drying conditions can be realized by appropriately adjusting the temperature and volume of the hot air blown from the hot air jet nozzles 182 toward the recording medium 124 and the temperature of the halogen heaters 180.

  The recording medium 124 is held on the outer peripheral surface of the drying drum 176 so that the recording surface of the recording medium 124 faces outward (that is, in a state where the recording surface of the recording medium 124 is curved so as to be convex), and is rotated. By drying while being conveyed, the recording medium 124 can be prevented from wrinkling and floating, and drying unevenness caused by these can be surely prevented.

  The recording medium 124 that has been dried by the drying unit 118 is transferred from the drying drum 176 to the fixing drum 184 of the fixing unit 120 via the intermediate conveyance unit 130.

(Fixing part)
The fixing unit 120 includes a fixing drum (also referred to as a “fixing cylinder”) 184, a halogen heater 186, a fixing roller 188, and an inline sensor 190. Like the processing liquid drum 154, the fixing drum 184 includes a claw-shaped holding unit (gripper) 185 on the outer peripheral surface, and the leading end of the recording medium 124 can be held by the holding unit 185.

  With the rotation of the fixing drum 184, the recording medium 124 is conveyed with the recording surface facing outward. The recording surface is preheated by the halogen heater 186, fixing processing by the fixing roller 188, and the inline sensor 190. And inspection is performed.

  The halogen heater 186 is controlled to a predetermined temperature (for example, 180 ° C.). Thereby, preheating of the recording medium 124 is performed.

  The fixing roller 188 is a roller member that heats and pressurizes the dried ink to weld the self-dispersing polymer fine particles in the ink to form a film of the ink, and is configured to heat and press the recording medium 124. The Specifically, the fixing roller 188 is disposed so as to be in pressure contact with the fixing drum 184 and constitutes a nip roller with the fixing drum 184. As a result, the recording medium 124 is sandwiched between the fixing roller 188 and the fixing drum 184 and is nipped at a predetermined nip pressure (for example, 0.15 MPa) to perform the fixing process.

  The fixing roller 188 is configured by a heating roller in which a halogen lamp is incorporated in a metal pipe such as aluminum having good thermal conductivity, and is controlled to a predetermined temperature (for example, 60 to 80 ° C.). By heating the recording medium 124 with this heating roller, thermal energy equal to or higher than the Tg temperature (glass transition temperature) of the latex contained in the ink is applied, and the latex particles are melted. As a result, pressing and fixing are performed on the unevenness of the recording medium 124, and the unevenness of the image surface is leveled to obtain glossiness.

  In the embodiment shown in FIG. 4, only one fixing roller 188 is provided. However, a configuration in which a plurality of fixing rollers 188 are provided may be used depending on the image layer thickness and the Tg characteristics of latex particles.

  On the other hand, the inline sensor 190 is a reading unit for measuring an ejection defect check pattern, image density, image defect, and the like for an image (including a test pattern) recorded on the recording medium 124, and is a CCD line sensor. Etc. apply.

  According to the fixing unit 120 configured as described above, the latex particles in the thin image layer formed by the drying unit 118 are heated and pressurized by the fixing roller 188 and are melted. Can be made.

  In addition, instead of the ink containing the high boiling point solvent and the polymer fine particles (thermoplastic resin particles), a monomer component that can be polymerized and cured by ultraviolet (UV) exposure may be contained. In this case, the recording apparatus 100 includes a UV exposure unit that exposes ink on the recording medium 124 to UV light instead of the heat-pressure fixing unit (fixing roller 188) using a heat roller. As described above, when ink containing an actinic ray curable resin such as a UV curable resin is used, an actinic ray such as a UV lamp or an ultraviolet LD (laser diode) array is used instead of the fixing roller 188 for heat fixing. Means for irradiating are provided.

(Output section)
As shown in FIG. 4, a paper discharge unit 122 is provided following the fixing unit 120. The paper discharge unit 122 includes a discharge tray 192. Between the discharge tray 192 and the fixing drum 184 of the fixing unit 120, a transfer drum 194, a transport belt 196, and a stretcher are provided so as to be in contact with each other. A roller 198 is provided. The recording medium 124 is sent to the conveyor belt 196 by the transfer drum 194 and discharged to the discharge tray 192. Although details of the paper transport mechanism by the transport belt 196 are not shown, the recording medium 124 after printing is held at the front end of the paper by a gripper of a bar (not shown) passed between the endless transport belt 196, and the transport belt The sheet is conveyed above the discharge tray 192 by the rotation of 196.

  Although not shown in FIG. 4, in addition to the above-described configuration, the recording apparatus 100 according to the present embodiment includes an ink storage / loading unit that supplies ink to the recording heads 172M, 172K, 172C, and 172Y, and a processing liquid. A head maintenance unit for supplying the processing liquid to the applying unit 114 and cleaning the recording heads 172M, 172K, 172C, and 172Y (nozzle surface wiping, purging, nozzle suction, etc.), on the paper conveyance path You may provide the position detection sensor which detects the position of the recording medium 124, the temperature sensor which detects the temperature of each part of an apparatus, etc.

<Configuration example of recording head>
Next, the structure of the recording head will be described. Since the recording heads 172M, 172K, 172C, and 172Y corresponding to the respective colors have the same structure, the recording head will be denoted by the reference numeral 250 as a representative of them.

  FIG. 5A is a perspective plan view showing a structural example of the head 250, and FIG. 5B is an enlarged view of a part thereof. FIG. 6 is a diagram illustrating an arrangement example of a plurality of head modules constituting the head 250. 7 is a cross-sectional view (A in FIG. 5) showing a three-dimensional configuration of a droplet ejection element (an ink chamber unit corresponding to one nozzle 251) for one channel serving as a recording element unit (ejection element unit). It is sectional drawing which follows the -A line | wire.

  As shown in FIG. 5, the head 250 of this example includes a plurality of ink chamber units (droplet discharge elements) 253 including nozzles 251 serving as ink discharge ports and pressure chambers 252 corresponding to the nozzles 251. The two-dimensionally arranged structure allows the effective nozzle interval (projection nozzle pitch) to be projected (orthogonal projection) so as to be aligned along the head longitudinal direction (direction orthogonal to the paper feed direction). High density is achieved.

  Corresponds to the entire width Wm of the drawing area of the recording medium 124 in a direction (arrow M direction; corresponding to “second direction”) substantially orthogonal to the feeding direction (arrow S direction; corresponding to “first direction”) of the recording medium 124. In order to configure a nozzle row longer than the length, for example, as shown in FIG. 6A, a short head module 250 ′ in which a plurality of nozzles 251 are two-dimensionally arranged is arranged in a zigzag pattern. Construct a line-type head. Alternatively, as shown in FIG. 6B, a mode in which the head modules 250 ″ are arranged in a row and connected is possible. Each head module 250 ′ or 250 ″ shown in FIG. 6 is the head described in FIG. This corresponds to the modules 12a and 12b.

  Note that the full-line print head for single pass printing is not limited to the case where the entire surface of the recording medium 124 is set as the drawing range, but when a part of the surface of the recording medium 124 is the drawing area (for example, paper In the case of providing a non-drawing area (margin part) around the area, it is only necessary to form a nozzle row necessary for drawing in a predetermined drawing area.

  The pressure chamber 252 provided corresponding to each nozzle 251 has a substantially square planar shape (see FIGS. 5A and 5B), and the nozzle 251 is provided at one of the diagonal corners. An outlet for supplying ink (supply port) 254 is provided on the other side. Note that the shape of the pressure chamber 252 is not limited to this example, and the planar shape may have various forms such as a quadrangle (rhombus, rectangle, etc.), a pentagon, a hexagon, other polygons, a circle, and an ellipse.

  As shown in FIG. 7, the head 250 (head modules 250 ′, 250 ″) includes a nozzle plate 251A in which the nozzles 251 are formed, and a channel plate in which channels such as the pressure chambers 252 and the common channel 255 are formed. The nozzle plate 251A constitutes a nozzle surface (ink ejection surface) 250A of the head 250, and a plurality of nozzles 251 communicating with the respective pressure chambers 252 are two-dimensionally formed. ing.

  The flow path plate 252P forms a side wall of the pressure chamber 252 and a flow path that forms a supply port 254 as a narrowed portion (most narrowed portion) of an individual supply path that guides ink from the common flow path 255 to the pressure chamber 252. It is a forming member. For convenience of explanation, the flow path plate 252P has a structure in which one or a plurality of substrates are stacked, although it is illustrated in a simplified manner in FIG.

  The nozzle plate 251A and the flow path plate 252P can be processed into a required shape by a semiconductor manufacturing process using silicon as a material.

  The common flow channel 255 communicates with an ink tank (not shown) as an ink supply source, and the ink supplied from the ink tank is supplied to each pressure chamber 252 via the common flow channel 255.

  A piezo actuator (piezoelectric element) 258 provided with individual electrodes 257 is joined to a diaphragm 256 constituting a part of the pressure chamber 252 (the top surface in FIG. 7). The diaphragm 256 of this embodiment is made of silicon (Si) with a nickel (Ni) conductive layer that functions as a common electrode 259 corresponding to the lower electrode of the piezo actuator 258, and is arranged corresponding to each pressure chamber 252. It also serves as a common electrode for the piezo actuator 258. It is also possible to form the diaphragm with a non-conductive material such as resin. In this case, a common electrode layer made of a conductive material such as metal is formed on the surface of the diaphragm member. Moreover, you may comprise the diaphragm which serves as a common electrode with metals (conductive material), such as stainless steel (SUS).

  By applying a driving voltage to the individual electrode 257, the piezoelectric actuator 258 is deformed and the volume of the pressure chamber 252 is changed, and ink is ejected from the nozzle 251 due to the pressure change accompanying this. When the piezo actuator 258 returns to its original state after ink ejection, new ink is refilled into the pressure chamber 252 from the common channel 255 through the supply port 254.

  As shown in FIG. 5B, the ink chamber units 253 having such a structure are arranged in a fixed manner along the row direction along the main scanning direction and the oblique column direction having a constant angle θ that is not orthogonal to the main scanning direction. By arranging a large number of patterns in a lattice pattern, the high-density nozzle head of the present embodiment is realized. In this matrix arrangement, when the interval between adjacent nozzles in the sub-scanning direction is Ls, in the main scanning direction, each nozzle 251 is substantially equivalent to a linear arrangement with a constant pitch P = Ls / tan θ. It can be handled.

  In implementing the present invention, the arrangement form of the nozzles 251 in the head 250 is not limited to the illustrated example, and various nozzle arrangement structures can be applied. For example, in place of the matrix arrangement described with reference to FIG. 5, a V-shaped nozzle arrangement, a zigzag nozzle arrangement (such as a W-shape) having a V-shaped arrangement as a repeating unit, or the like is also possible. .

  The means for generating the discharge pressure (discharge energy) for discharging the droplets from each nozzle in the recording head is not limited to the piezo actuator (piezoelectric element), but the thermal method (the pressure of film boiling due to the heating of the heater) Various pressure generating elements (ejection energy generating elements) such as heaters (heating elements) and other actuators based on other systems can be applied. Corresponding energy generating elements are provided in the flow path structure according to the ejection method of the head.

<Description of control system>
FIG. 8 is a principal block diagram showing the system configuration of the recording apparatus 100.
The recording apparatus 100 shown in the figure includes a communication interface 270, a system controller 272, a print controller 274, an image buffer memory 276, a head driver 278, a motor driver 280, a heater driver 282, and processing liquid application control. A unit 284, a drying control unit 286, a fixing control unit 288, a memory 290, a ROM 292, an encoder 294, and the like.

  The communication interface 270 is an interface unit that receives image data sent from the host computer 350. As the communication interface 270, a serial interface such as USB (Universal Serial Bus), IEEE 1394, Ethernet (registered trademark), a wireless network, or a parallel interface such as Centronics can be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted. Image data sent from the host computer 350 is taken into the recording apparatus 100 via the communication interface 270 and temporarily stored in the memory 290.

  The memory 290 is a storage unit that temporarily stores an image input via the communication interface 270, and data is read and written through the system controller 272. The memory 290 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The system controller 272 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire recording apparatus 100 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. That is, the system controller 272 controls the communication interface 270, the print control unit 274, the motor driver 280, the heater driver 282, the treatment liquid application control unit 284, and the like, and communicates with the host computer 350. Control and read / write control of the memory 290 are performed, and a control signal for controlling the transport motor 296 and the heater 298 is generated.

  The ROM 292 stores programs executed by the CPU of the system controller 272 and various data necessary for control. The ROM 292 may be a non-rewritable storage unit or a rewritable storage unit such as an EEPROM. The memory 290 is used as a temporary storage area for image data, and is also used as a program development area and a calculation work area for the CPU.

  The motor driver 280 is a driver that drives the motor 296 in accordance with instructions from the system controller 272. In FIG. 8, various motors arranged in each part in the apparatus are represented by a reference numeral 296 as a representative. For example, the motor 296 shown in FIG. 8 includes a motor that drives the rotation of the paper feed drum 152, the processing liquid drum 154, the drawing drum 170, the drying drum 176, the fixing drum 184, the transfer drum 194, and the like shown in FIG. A pump drive motor for sucking negative pressure from the suction holes 170, a motor for a retraction mechanism for moving the head units of the recording heads 172M, 172K, 172C, and 172Y to a maintenance area outside the drawing drum 170, and the like are included. .

  The heater driver 282 is a driver that drives the heater 298 in accordance with an instruction from the system controller 272. In FIG. 8, various heaters arranged in each unit in the apparatus are represented by a reference numeral 298. For example, the heater 298 shown in FIG. 8 includes a preheater (not shown) for heating the recording medium 124 to an appropriate temperature in the paper feeding unit 112 in advance.

  The print control unit 274 has a signal processing function for performing various processes and corrections for generating a print control signal from the image data in the memory 290 according to the control of the system controller 272, and the generated print data This is a control unit that supplies (dot data) to the head driver 278.

  The dot data is generally generated by performing color conversion processing and halftone processing on multi-tone image data. In the color conversion process, image data expressed in sRGB or the like (for example, 8-bit image data for each RGB color) is converted into color data for each color of ink used in the recording apparatus 100 (in this example, KCMY color data). It is processing to do.

  The halftone process is a process of converting the color data of each color generated by the color conversion process into dot data of each color (KCMY dot data in this example) by processes such as an error diffusion method and a threshold matrix.

  In the print control unit 274, necessary signal processing is performed, and the ejection amount and ejection timing of the ink droplets of the head 250 are controlled via the head driver 278 based on the obtained dot data. Thereby, a desired dot size and dot arrangement are realized. The dot data here corresponds to “nozzle control data”.

  The print control unit 274 includes an image buffer memory (not shown), and image data, parameters, and other data are temporarily stored in the image buffer memory when image data is processed in the print control unit 274. Also possible is an aspect in which the print control unit 274 and the system controller 272 are integrated to form a single processor.

  An overview of the flow of processing from image input to print output is as follows. Image data to be printed is input from the outside via the communication interface 270 and stored in the memory 290. At this stage, for example, RGB image data is stored in the memory 290. In the recording apparatus 100, a pseudo continuous tone image is formed by changing the droplet ejection density of fine dots with ink (coloring material) and the dot size, so that the input digital image It is necessary to convert to a dot pattern that reproduces the gradation (shading of the image) as faithfully as possible. Therefore, the original image (RGB) data stored in the memory 290 is sent to the print control unit 274 via the system controller 272, and the print control unit 274 performs halftoning processing using a threshold matrix, an error diffusion method, or the like. Is converted into dot data for each ink color. In other words, the print control unit 274 performs processing for converting the input RGB image data into dot data of four colors K, C, M, and Y. In this way, the dot data generated by the print controller 274 is stored in an image buffer memory (not shown).

  The head driver 278 outputs a drive signal for driving an actuator corresponding to each nozzle of the head 250 based on print data (that is, dot data stored in the image buffer memory 276) given from the print control unit 274. . The head driver 278 may include a feedback control system for keeping the head driving condition constant.

  When the drive signal output from the head driver 278 is applied to the head 250, ink is ejected from the corresponding nozzle. An image is formed on the recording medium 124 by controlling ink ejection from the head 250 while conveying the recording medium 124 at a predetermined speed. The recording apparatus 100 shown in the present embodiment applies a common drive power waveform signal to each piezo actuator 258 of the head 250 (head module) in units of modules, and corresponds to the ejection timing of each piezo actuator 258. Thus, a driving method is employed in which ink is ejected from the nozzles 251 corresponding to each piezo actuator 258 by switching on / off of switch elements (not shown) connected to individual electrodes of each piezo actuator 258.

  The head driver 278 and the print controller 274 (with built-in image buffer memory) correspond to the head controller 14 described in FIG. Further, the system controller 272 in FIG. 8 corresponds to the device control unit 16 described in FIG.

  The treatment liquid application control unit 284 controls the operation of the treatment liquid application device 156 (see FIG. 4) according to an instruction from the system controller 272. The drying control unit 286 controls the operation of the solvent drying device 178 (see FIG. 4) in accordance with an instruction from the system controller 272.

  The fixing control unit 288 controls the operation of the fixing pressure unit 299 including the halogen heater 186 and the fixing roller 188 (see FIG. 4) of the fixing unit 120 in accordance with an instruction from the system controller 272.

  As described with reference to FIG. 4, the inline sensor 190 is a block including an image sensor. The inline sensor 190 reads an image printed on the recording medium 124, performs necessary signal processing, etc. Variation, optical density, etc.) are detected, and the detection results are provided to the system controller 272 and the print controller 274.

  The print controller 274 performs various corrections (non-ejection correction, density correction, etc.) on the head 250 based on information obtained from the in-line sensor 190, and cleaning operations (nozzles, etc.) such as preliminary ejection, suction, and wiping as necessary. Control to implement recovery operation).

  In the above embodiment, an ink jet recording apparatus of a method (direct recording method) in which an ink droplet is directly ejected onto the recording medium 124 has been described. However, the scope of application of the present invention is not limited to this, and once The present invention is also applied to an intermediate transfer type image forming apparatus that forms an image (primary image) on an intermediate transfer member and transfers the image to a recording sheet in a transfer unit to form a final image. can do.

  Further, in the above embodiment, an inkjet recording apparatus using a page-wide full-line head having a nozzle row having a length corresponding to the entire width of the recording medium (single-pass image for completing an image by one sub-scanning). However, the scope of application of the present invention is not limited to this, and an inkjet that performs image recording by scanning a plurality of heads while moving a short recording head such as a serial (shuttle scan) head. The present invention can also be applied to a recording apparatus.

  In the above-described embodiment, the configuration in which the recording medium is transported to the stopped head is exemplified. However, in the implementation of the present invention, a configuration in which the head is moved with respect to the stopped recording medium (the drawing medium) is also possible. is there.

  In the above embodiment, application to an inkjet recording apparatus for graphic printing has been described as a representative example, but the scope of application of the present invention is not limited to this example. For example, a wiring drawing apparatus for drawing a wiring pattern of an electronic circuit, a manufacturing apparatus for various devices, a resist printing apparatus that uses a resin liquid as a functional liquid for ejection, a color filter manufacturing apparatus, and a material deposition material. The present invention can be widely applied to an inkjet system that draws various shapes and patterns using a liquid functional material, such as a fine structure forming apparatus that forms a structure.

  As described above, the ink jet recording head state monitoring circuit and the ink jet recording apparatus using the same have been described in detail. However, the present invention is not limited to the above embodiments, and does not depart from the gist of the present invention. Of course, various improvements and changes may be made within the scope.

10, 100 Inkjet recording apparatus (recording apparatus)
12, 250 Inkjet recording head (recording head)
14 Head control device 16 Device control unit 18 Recording medium transport unit 20 Piezo actuator (piezoelectric element)
22 Switch Circuit 24 Image Data Memory 26 Image Data Transfer Control Circuit 28 Discharge Timing Control Unit 30 Inkjet Recording Head Status Monitoring Circuit (Status Monitoring Circuit)
32 Waveform data memory 34 Drive voltage control circuit 36 Pulse counter 38 Reference voltage data memory 40 Data processor 42, 44 D / A converter 46 Amplifier 48 Comparator 100 Inkjet recording device 124 Recording medium 170 Drawing drum 172M, 172K, 172C, 172Y Inkjet head 190 Inline sensor 251 Nozzle 272 System controller 274 Print controller 294 Encoder

Claims (14)

A state monitoring circuit that monitors a state of an inkjet recording head that includes a plurality of nozzles and a discharge energy generating element that discharges ink droplets from each nozzle.
A drive circuit for applying a drive waveform voltage signal for causing the ink droplets to be ejected in units of resolution to the ejection energy generating element;
A comparator connected in parallel with the ejection energy generating element and comparing the drive waveform voltage signal applied directly to the ejection energy generating element with a predetermined reference voltage;
A state monitoring circuit for an ink jet recording head, wherein the states of the ink jet recording head and the drive circuit are monitored based on a comparison result of the comparator. The comparator outputs, as the comparison result, pulses having different voltage levels depending on the magnitude of the drive waveform voltage signal with respect to the predetermined reference voltage,
The state monitoring circuit further includes a pulse counter that counts the number of changes in the voltage level output from the comparator as the number of changes in which the drive waveform voltage signal changes beyond the predetermined reference voltage.
2. The state monitoring circuit for an ink jet recording head according to claim 1, wherein the state of the ink jet recording head and the drive circuit is monitored based on the number of changes in the voltage level counted by the pulse counter.   The ink jet recording head state monitoring circuit according to claim 2, wherein the comparison result of the comparator is one in which the voltage level is output as binary judgment data. The binary determination data of the comparison result of the comparator indicates a digital value of 1 when the drive waveform voltage signal is greater than the predetermined reference voltage, and when the drive waveform voltage signal is less than the predetermined reference voltage. Indicates a digital value of 0,
The inkjet recording according to claim 3, wherein the pulse counter counts the number of times the digital value 1 changes to the digital value 0 and the number of times the digital value 1 changes to the digital value 0 as the number of changes. Head status monitoring circuit.   The state monitoring circuit for an ink jet recording head according to claim 3 or 4, wherein the voltage level of the binary determination data is a TTL level. The ejection energy generating element starts ejection of the ink droplet by a pixel unit ejection trigger signal from the outside,
The signal waveform of the drive waveform voltage signal in one cycle between the pixel unit ejection trigger signals is the same,
The count value of the pulse counter is cleared to 0 at the input timing of the pixel unit discharge trigger signal, and the count value of the pulse counter in one cycle until the next pixel unit discharge trigger signal is input is a predetermined default value. 6. The state monitor circuit for an ink jet recording head according to claim 2, wherein an error signal is generated when the value is not reached.   The state monitoring circuit of the ink jet recording head according to claim 6, wherein the error signal is notified to an ink jet recording apparatus that records the image on a recording medium by discharging the ink droplets from the plurality of nozzles of the ink jet recording head. The drive circuit includes a waveform data memory for storing drive waveform voltage data, a D / A converter for digital / analog (D / A) conversion of the drive waveform voltage data output from the waveform data memory, and the D / A An amplifier that amplifies an analog signal output from the converter to generate the drive waveform voltage signal,
The state monitoring circuit detects an abnormality in the nozzle and the ejection energy generation element, the drive circuit, and the drive waveform voltage data of the inkjet recording head based on a comparison result of the comparator. The state monitoring circuit of the inkjet recording head of any one of these. The state monitoring circuit further includes a reference voltage data memory for storing predetermined reference voltage data, and digital / analog (D / A) conversion of the predetermined reference voltage data output from the reference voltage data memory for the predetermined voltage A D / A converter that outputs a reference voltage of
The state monitoring circuit detects an abnormality in the nozzle and ejection energy generating element, the drive circuit, and the drive waveform voltage data of the inkjet recording head based on a comparison result of the comparator. The state monitoring circuit of the inkjet recording head of any one of Claims.   2. The comparator has a resistance value higher than that of the ejection energy generating element so as not to affect a voltage value necessary for driving the ejection energy generating element in the drive waveform voltage signal. The state monitoring circuit for an inkjet recording head according to any one of 9. An inkjet recording head having a plurality of nozzles and an ejection energy generating element that is provided corresponding to each nozzle and ejects ink droplets from each nozzle;
A state monitoring circuit for an ink jet recording head according to any one of claims 1 to 10,
An ejection control unit that selectively controls driving / non-driving of the ejection energy generating element based on image data, and ejecting the ink droplets from the plurality of nozzles of the inkjet recording head based on the image data. An ink jet recording apparatus which records an image on a recording medium by discharging.   The inkjet recording apparatus according to claim 11, wherein the inkjet recording head includes a plurality of head modules each having the plurality of nozzles and the ejection energy generating elements provided corresponding to the nozzles. .   The inkjet recording apparatus according to claim 12, wherein the inkjet recording head is a line-type head that is elongated by arranging a plurality of the head modules in the width direction of the recording medium.   The inkjet recording apparatus according to claim 11, wherein at least one inkjet recording head is disposed for each of a plurality of colors.

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