JP2021024197A - Liquid discharge device - Google Patents

Abstract

To suppress the occurrence of image defect due to an erroneous operation of drive waveform signal selection when driving a piezoelectric element in a drive waveform signal suitable to the cross talk characteristic for each nozzle.SOLUTION: A liquid discharge device having a plurality of nozzles for discharging liquid by driving a piezoelectric element with a drive waveform signal comprises: a drive waveform generation unit which generates the plurality of drive waveform signals; a selection signal generation unit which generates a selection signal for selecting any of the drive waveform signals for each of the plurality of nozzles on the basis of selection data of associating the drive waveform signal suitable to the characteristic of the nozzle out of the plurality of drive waveform signals with each of the plurality of nozzles; and a waveform switching unit which switches the drive waveform signal transmitted to the piezoelectric element to any of the plurality of drive waveform signals on the basis of the selection signal.SELECTED DRAWING: Figure 1

Description

The present invention relates to a liquid discharge device.

Conventionally, as a liquid ejection device, a drive waveform signal is applied to a piezoelectric element (piezo element), and the piezoelectric element is deformed to pressurize and depressurize the ink chamber to raise and lower the pressure in the ink chamber, thereby causing ink droplets as a liquid. There is known an inkjet recording device that ejects ink toward an object such as paper.

In such an inkjet recording device, variations in the flight speed of ink droplets, which is called crosstalk, may occur for each nozzle depending on the ink droplet ejection conditions. Examples of crosstalk include mechanical crosstalk due to changes in the physical structure of the head and electric crosstalk in which the drive waveform signal (analog signal for driving the piezoelectric element) fluctuates. Since crosstalk affects the image quality by changing the amount of ejected ink and the ejection speed, it is desirable to reduce it, and various such techniques have been conventionally devised.

As a technique for improving crosstalk as described above, for example, there is a technique of generating a plurality of analog signals (drive waveform signal, hereinafter VCOM) for driving a piezoelectric element and selecting one of the VCOMs for each nozzle (for example). Patent Document 1). In this technique, the VCOM has a waveform with a different voltage (that is, a different flying speed of ink droplets ejected from a nozzle), and for a piezoelectric element in which the flying speed suitable for ink tends to be slow due to the influence of crosstalk. By selecting a VCOM that increases the flight speed, and by selecting a VCOM that decreases the flight speed for the piezoelectric element that increases the flight speed due to the influence of crosstalk, variation among nozzles is reduced. ..

However, if the configuration provides a control signal (selection signal) for selecting the VCOM corresponding to each nozzle, in addition to the demerit that the volume and cost of the harness increase due to the increase in the number of signal lines, the selection signal and the VCOM Due to electrical interference between the wiring paths, a malfunction in which an unintended VCOM is selected occurs, which tends to lead to an image defect.

The present invention has been made in view of the above, and when driving a piezoelectric element with a drive waveform signal suitable for crosstalk characteristics for each nozzle, it is possible to suppress the occurrence of image defects due to a malfunction of drive waveform signal selection. The purpose.

In order to solve the above-mentioned problems and achieve the object, the present invention is a liquid discharge device including a plurality of nozzles for discharging liquid by driving a piezoelectric element with a drive waveform signal, and a plurality of drive waveform signals. To select one of the drive waveform signals based on the drive waveform generator for generating the above and the selection data of the plurality of drive waveform signals suitable for the characteristics of the nozzles associated with each of the plurality of nozzles. A selection signal generation unit that generates the selection signal of the above for each of the plurality of nozzles, and a waveform switching unit that switches the drive waveform signal transmitted to the piezoelectric element based on the selection signal to any one of the plurality. And.

According to the present invention, when driving a piezoelectric element with a drive waveform signal suitable for crosstalk characteristics for each nozzle, it is possible to suppress the occurrence of image defects due to a malfunction of drive waveform signal selection.

FIG. 1 is a block diagram showing a schematic configuration of an inkjet recording device according to the first embodiment. FIG. 2 is a block diagram showing an example of the configuration of an inkjet recording device. FIG. 3 is a block diagram illustrating switching control of VCOM. FIG. 4 is a diagram showing an example of a waveform image of VCOM. FIG. 5 is a block diagram showing a schematic configuration of the inkjet recording device according to the second embodiment.

(First Embodiment)
Hereinafter, embodiments of the liquid discharge device will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing a schematic configuration of an inkjet recording device (an example of a liquid ejection device) according to the first embodiment. The inkjet recording device includes a head drive substrate 100 and an inkjet head 200. The head drive board 100 includes an ASIC (Application Specific Integrated Circuit) 101 and a plurality of VCOM generation circuits 102. Further, the inkjet head 200 includes a RAM (Random Access Memory) 201, a VCOM selection circuit 202, a selection signal generation circuit 203, and a plurality of piezoelectric elements 31. The piezoelectric element 31 is deformed by receiving a voltage application, whereby ink droplets are ejected from the nozzle.

The ASIC 101 is an integrated circuit designed for a specific application, and here, processing for input image data (for example, image processing, sorting processing, various signal processing) and input / output for controlling the entire device. Performs signal processing, etc.

The VCOM generation circuit 102 is an example of a drive waveform generation unit, and is provided in association with the piezoelectric element 31 to generate a VCOM according to the output of the ASIC 101 and output the VCOM to the inkjet head 200. The VCOM is an analog signal (driving waveform signal) having a predetermined time width for driving the piezoelectric element 31, and the waveform shows the fluctuation of the voltage applied to the piezoelectric element 31. In the inkjet recording device, the size of the ink droplets ejected by the nozzle is changed by adjusting the voltage applied to the piezoelectric element 31, and a desired gradation expression is performed.

The RAM 201 is a volatile memory, and stores data (VCOM selection data) used for selecting (switching) VCOM, for example, in the form of a table. The writing of the VCOM selection data to the RAM 201, that is, the transmission of the control signal from the head drive substrate 100 to the inkjet head 200 is performed in a state where the VCOM is not output. The VCOM selection data (an example of selection data) associates a nozzle with a drive waveform signal (any of a plurality of options) suitable for the characteristics of the nozzle for each of the plurality of nozzles.

The selection signal generation circuit 203 is an example of the selection signal generation unit, and generates a selection signal used for switching the VCOM according to the drive conditions of the piezoelectric element 31 obtained from the image data transmitted from the head drive substrate 100. , The generated selection signal is output to the VCOM selection circuit 202.

The VCOM selection circuit 202 is an example of a waveform switching unit, and among a plurality of VCOMs input from the VCOM generation circuit 102, the one corresponding to the selection signal input from the selection signal generation circuit 203 is selected and selected. The VCOM is output to the corresponding piezoelectric element 31.

According to the configuration as described above, a plurality of VCOMs are generated in the head drive substrate 100, and a VCOM selection signal is generated based on the VCOM selection data stored in the RAM 201 in the inkjet head 200. This makes it possible to reduce crosstalk. As a result, it is possible to reduce the conventional inconvenience that an unintended VCOM is selected due to the VCOM noise overlapping the selection signal and an image defect occurs.

If the selection signal generation circuit 203 (selection signal generation unit) and the VCOM selection circuit 202 (waveform switching unit) are provided on the same substrate or housed in the same IC, further crosstalk will occur. It can be reduced and the above-mentioned inconvenience can be less likely to occur.

Hereinafter, the schematic configuration shown in FIG. 1 will be specifically described. FIG. 2 is a block diagram showing an example of the configuration of an inkjet recording device. The inkjet head 200 includes a head substrate 21, a piezoelectric element support substrate 22, and a plurality of piezoelectric elements 31-1, 31-2, ..., 31-n. The piezoelectric element support substrate 22 includes a piezoelectric element drive IC (Integrated Circuit) 204. The head substrate 21 includes a control unit 210 and a ROM 205.

The head drive board 100 includes a control unit 110, VCOM generation units 103a, 103b, ..., 103x, and AMP circuits 104a, 104b, ..., 104x. The control unit 110, the VCOM generation units 103a, 103b, ..., 103x are provided in the ASIC 101. Further, the AMP circuits 104a, 104b, ..., 104x in the configuration of FIG. 2 correspond to the VCOM generation circuit 102 in FIG.

The VCOM generation units 103a, 103b, ..., 103x and the AMP circuits 104a, 104b, ..., 104x are provided independently.

The control unit 110 includes a CPU (Central Processing Unit) that controls the entire device, a ROM (Read Only Memory) that stores fixed data such as programs executed by the CPU, and a RAM (Random Access Memory) that temporarily holds the data. Is configured to include.

Further, the control unit 110 receives image data from the CTL (controller board) 300 that performs image treatment installed on the upstream side of the head drive board 100 in the image forming process, and transfers the received image data to the inkjet head 200. Serial transfer.

Further, the control unit 110 transmits the timing data and the selection data to the inkjet head 200. The timing data is data for controlling ON / OFF of the analog switch in the piezoelectric element drive IC 204 and its timing. The analog switch of the piezoelectric element drive IC204 is turned on while receiving the timing data. The piezoelectric element drive IC 204 applies a drive waveform to the piezoelectric elements 31-1, 31-2, ..., 31-n while the analog switch is ON. By transmitting timing data at the timing when the analog switch is desired to be turned ON / OFF, it is possible to eject ink droplets having a plurality of gradations with one drive waveform. The selection data is VCOM selection data.

Further, the VCOM generation units 103a, 103b, ..., 103x generate VCOMs under the control of the control unit 110. The AMP circuits 104a, 104b, ..., 104x amplify the voltage of the analog signal output from the VCOM generation units 103a, 103b, ..., 103x and output it. The amplified and output analog signals (VCOMa, VCOMb, ..., VCOMx) are transmitted to the piezoelectric element drive IC204.

The control unit 210 includes a CPU, a ROM for storing fixed data such as a program executed by the CPU, and a RAM 201 (see FIG. 1) for temporarily holding the data. Further, the control unit 210 includes a configuration corresponding to the selection signal generation circuit 203 in FIG. The control unit 210 deserializes the image data serially transferred from the head drive board 100 and outputs the image data to the piezoelectric element drive IC 204. The control unit 210 may be provided in the piezoelectric element drive IC 204.

The piezoelectric element drive IC 204 corresponds to the VCOM selection circuit 202 in FIG. The piezoelectric element drive IC 204 appropriately turns on / off VCOMa, VCOMb, ..., VCOMx by an analog switch or the like according to the image data received from the head substrate 21, and the piezoelectric element 31-1, 31-2, ..., 31- Apply to n.

The ROM 205 uses data (VCOM selection data) for determining which of a plurality of VCOMa, VCOMb, ..., VCOMx is applied to the piezoelectric elements 31-1, 31-2, ..., 31-n (selection and switching of VCOM). ) Is stored in advance in the form of a table, for example.

The ROM 205 is, for example, a flash ROM, and the control unit 210 updates the VCOM selection data stored in the ROM 205 with the data received from the control unit 110. This reception and update is performed at a time that does not overlap with the reception of VCOMa, VCOMb, ..., VCOMx.

In the configuration as shown in FIG. 2, a plurality of VCOMa, VCOMb, ..., VCOMx for reducing known crosstalk are generated in the head drive substrate 100, and the VCOM stored in advance by the ROM 205 in the inkjet head 200. Based on the selection data, a signal (selection signal) for selecting any of VCOMa, VCOMb, ..., VCOMx is generated. As a result, it is possible to reduce the occurrence of conventional inconveniences such that the VCOM is affected by noise on the head drive substrate 100 and on the transmission line and an unintended VCOM is selected to cause an image defect.

Next, FIG. 3 is a block diagram illustrating switching control of VCOM. The configuration example shown in FIG. 3 is an example in which the configuration of the inkjet head 200 in FIG. 2 is further embodied. In this example, the control unit 210 includes a switching circuit 206, and the piezoelectric element drive IC 204 includes multiplexers 207-1, 207-2, ..., 207-n. The multiplexers 207-1, 207-2, ..., 207-n are provided corresponding to the piezoelectric elements 31-1, 31-2, ..., 31-n.

The ROM 205 stores a switching table necessary for generating switching signals 1, switching signals 2, ..., And switching signals n input to multiplexers 207-1, 207-2, ..., 207-n. The switching table corresponds to VCOM selection data. This switching table includes the mechanical crosstalk characteristics of the piezoelectric elements 31-1, 31-2, ..., 31-n on the inkjet head 200 and each nozzle, and the crosstalk characteristics corresponding to the driving conditions of the inkjet head 200. , Nozzle-specific values are stored.

The control unit 210 reads the data of the switching table from the ROM 205 and stores it in the RAM 201, and then generates the switching signal 1, the switching signal 2, ..., The switching signal n by the switching circuit 206, and the multiplexer 207 in the piezoelectric element drive IC 204. It is transmitted to -1,207-2, ..., 207-n. The switching signal 1, switching signal 2, ..., And switching signal n correspond to the selection signals in FIGS. 1 and 2. That is, the switching circuit 206 is an example of the selection signal generation unit.

The switching circuit 206 corresponds to various conditions related to crosstalk characteristics such as image data received from the head drive board 100 and the operating frequency of the inkjet head 200, and a comparison result with the data (switching table) stored in the RAM 201. , VCOMa, VCOMb, ..., VCOMx, which can obtain the optimum discharge characteristics are selected, and switching signal 1, switching signal 2, ..., Switching signal n is output.

The multiplexers 207-1, 207-2, ..., 207-n are composed of analog switches and the like in the piezoelectric element drive IC204, and are suitable for the switching signal 1, switching signal 2, ..., Switching signal n, VCOMa, VCOMb, ..., The VCOMx is output to the piezoelectric elements 31-1, 31-2, ..., 31-n.

FIG. 4 is a diagram showing an example of a waveform image of VCOM. Here, as an example, a case where VCOMa, VCOMb, and VCOMc having three stages of intensity (voltage amplitude) of small, medium, and large are used as the drive waveform signal is taken as an example. In general, the flight speed of ink droplets changes due to various factors such as the peak value and slope of the waveform, but in this example, the difference between the maximum value and the minimum value of the waveform is expressed as the intensity and is shown as an example. ing.

Further, in this example, it is assumed that the inkjet head 200 includes a nozzle 1, a nozzle 2, and a nozzle 3 (not shown), and a piezoelectric element 31-1, a piezoelectric element 31-2, and a piezoelectric element 31-3 are assembled to each of them. Suppose you are. It is assumed that the nozzles 1 to 3 have the following characteristics, respectively.
-The nozzle 1 has a characteristic that the flight speed of ink droplets is faster than the standard.
-The nozzle 2 has a characteristic that the flight speed of ink droplets is slower than the standard.
-The nozzle 3 has a characteristic that the flight speed of ink droplets is standard.

The ROM 205 stores the above-mentioned characteristics. In this case, the control unit 210 generates switching signals 1 to 3 for each nozzle 1 to 3 by making the following determination with reference to the characteristics of each nozzle 1 to 3 stored in the ROM 205.
-To the nozzle 1, a signal instructing to select VCOMa having a low intensity is output as the switching signal 1 in order to slow down the flight speed of the ink droplet.
-To the nozzle 2, a signal instructing to select a high-intensity VCOMc is output as the switching signal 2 in order to increase the flight speed of the ink droplets.
-Since it is not necessary to change the flight speed of the ink droplets to the nozzle 3, a signal instructing to select a VCOMb having a medium intensity is output as the switching signal 3.

Here, a case where it is necessary to apply a high-intensity drive waveform signal (corresponding to VCOMa in the above example) to all the piezoelectric elements 31-1, 31-2, 31-3 of the inkjet head 200 will be considered. In this case, if VCOMa is applied to all the piezoelectric elements 31-1, 31-2, 31-3, the load on VCOMa becomes large. Therefore, the shape of the waveform of VCOMa becomes dull, and the inconvenience that the flight speed of ink droplets becomes slow tends to occur.

Therefore, when it is necessary to apply a high-intensity drive waveform signal (corresponding to VCOMa in the above example) to all the piezoelectric elements 31-1, 31-2, 31-3, all the piezoelectric elements 31-1, Instead of applying VCOMa to 31-2 and 31-3, VCOMa, VCOMb, and VCOMc are shared and applied as the same waveform (in this case, the one having higher intensity).

As a result, the load on each VCOM (VCOMa, VCOMb, VCOMc) can be reduced to 1/3, the dullness of the VCOM waveform due to the load fluctuation can be reduced, and the influence on the flight speed of the ink droplet can be suppressed. This is because the control unit 210 determines the magnitude of the load based on the image data received from the head drive board 100, and the switching circuit 206 generates a switching signal (selection signal) based on the image data. It can be realized.

(Second Embodiment)
Next, a second embodiment, which is a modification of the first embodiment, will be described. Since this embodiment is a modification of the previous embodiment, the same reference numerals are used for the same parts as those of the previous embodiment, and detailed description thereof will be omitted. FIG. 5 is a diagram corresponding to FIG. 1, and is a block diagram showing a schematic configuration of an inkjet recording device according to a second embodiment.

In the present embodiment, the head drive board 100 is provided with a selection signal generation circuit 109 that performs processing corresponding to the selection signal generation circuit 203 of the previous embodiment. The selection signal generation circuit 109 serially transmits the control signal (selection signal) used for selecting the VCOM for each nozzle (piezoelectric element 31). The selection signal generation circuit 109 also transmits a clock signal (CLK) to the VCOM selection circuit 202.

Further, in the present embodiment, since the selection signal generation circuit 109 is provided instead of the selection signal generation circuit 203, it is not necessary to transfer and store the VCOM selection data in the inkjet head 200.

Even with this configuration, the same effect as in the previous embodiment can be obtained. That is, in the head drive substrate 100, a plurality of VCOMs are generated, and further, a VCOM selection signal is generated based on the VCOM selection data. As a result, the number of signal lines can be suppressed as compared with the conventional case, so that crosstalk can be reduced, and the possibility of data garbled due to noise can be reduced. As a result, it is possible to reduce the conventional inconvenience that an unintended VCOM is selected due to the VCOM noise overlapping the selection signal and an image defect occurs.

100: Head drive board 101: ASIC
102: VCOM generation circuit (example of drive waveform generation unit)
103a, 103b, ..., 103x: VCOM generation unit 104a, 104b, ..., 104x: AMP circuit 109: Selection signal generation circuit (an example of the selection signal generation unit)
110: Control unit 200: Inkjet head 201: RAM (example of storage unit)
202: VCOM selection circuit (example of waveform switching unit)
203: Selection signal generation circuit (example of selection signal generation unit)
204: Piezoelectric element drive IC
205: ROM (an example of a storage unit)
206: Switching circuit (example of selection signal generator)
207-1, 207-2, ..., 207-n: multiplexer 210: Control unit 21: Head substrate 22: Piezoelectric element support substrate 31-1, 31-2, ..., 31-n: Piezoelectric element

Japanese Unexamined Patent Publication No. 2002-120366

Claims (6)

A liquid discharge device having a plurality of nozzles for discharging a liquid by driving a piezoelectric element with a drive waveform signal.
A drive waveform generator that generates multiple drive waveform signals,
A selection signal for selecting one of the drive waveform signals based on the selection data in which the plurality of drive waveform signals suitable for the characteristics of the nozzle are associated with each of the plurality of nozzles is selected from the plurality of nozzles. The selection signal generator that is generated for each of
A waveform switching unit that switches the drive waveform signal to be transmitted to the piezoelectric element to any one of a plurality of the selection signals.
A liquid discharge device equipped with. The liquid discharge device according to claim 1, wherein the selection signal generation unit generates the selection signal based on image data. The liquid discharge device according to claim 1 or 2, wherein the selection data used by the selection signal generation unit is a value unique to the nozzle. The liquid discharge device according to any one of claims 1 to 3, wherein the drive waveform generation unit generates a plurality of the drive waveform signals having different intensities. A claim that the drive waveform generation unit generates a plurality of the same drive waveform signals when the selection signal generation unit generates selection signals for selecting the same drive waveform signal for a plurality of the nozzles. The liquid discharge device according to any one of 1 to 3. The liquid discharge device according to any one of claims 1 to 5, wherein the selection signal generation unit and the waveform switching unit are provided on the same substrate.

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