JP2011037196A - Short circuit inspection device for inkjet system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To protect an output circuit in a driving circuit side, from various unexpected short-circuiting abnormalities between wires caused by liquid leakage in a head, in constitution of floating-connecting the inkjet head using a piezoelectric actuator to a driving circuit. <P>SOLUTION: This short circuit inspection device includes an electric power source short-circuiting inspection circuit (44) for inspecting a short circuit in a load electric power source line (22), a signal short-circuiting inspection circuit (46) for inspecting a short circuit in a signal line (18) of transmitting a drive selection signal of the piezoelectric actuator (12), a monitor selecting circuit (42) for selecting an inspection-target line, an inspection switching circuit (48) for permitting an operation of the monitor selecting circuit (42) at the time of an inspection mode, and for starting up the electric power source short-circuiting inspection circuit (44) or the signal short-circuiting inspection circuit (46), in response to the inspection-target line concerned in the selection, and a short-circuiting determination circuit (50) for detecting a potential on the inspection-objective line, to determine the presence of a line short circuit, and the short circuit inspection device stops supply of a load electric power to the head, the transmission of the drive selection signal, and supply of a negative drive electric power, when detecting the short-circuiting abnormality. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a short circuit inspection apparatus for an ink jet system, and more particularly, means for detecting a short circuit (electric short) abnormality in an electric circuit inside an ink jet head and avoiding destruction of circuit components on a driving substrate connected to the head. The present invention relates to a suitable circuit protection technique.

  In an ink jet printer using a piezo actuator (piezoelectric element) as a pressure generating element for ejecting ink, a plurality of piezoelectric elements provided corresponding to a plurality of nozzles provided in an ink jet head are selectively driven. Thus, ink droplets are ejected from the nozzles based on the dynamic pressure of each piezoelectric actuator. The ink droplets thus ejected are attached to the recording paper, whereby dots are formed on the recording paper and printing is performed.

  Here, the circuit configuration of a conventional inkjet head will be outlined with reference to FIG. As shown in the figure, a plurality of piezoelectric actuators 302 are provided in the inkjet head 300 corresponding to a plurality of nozzles (not shown). Each piezo actuator 302 is individually connected to an analog switch 304, and one terminal of each analog switch 304 is connected to the output line 322 of the drive circuit 320.

  In addition, an image data transmission circuit 326 that transmits image data (dot data representing a dot arrangement form) for on / off control of each analog switch 304 in the head is provided on the drive board 324 on which the drive circuit 320 is mounted. Is provided. The image data transmission circuit 326 includes an isolator driver and performs voltage level conversion of the image data signal generated by the signal processing circuit 330. Serial transfer is adopted for transmission of image data representing the nozzle ON / OFF pattern from the image data transmission circuit 326, and a shift register 308 (serial input parallel output type for serial / parallel conversion) is provided in the inkjet head 300; Serial-In, Parallel-Out (SIPO).

  On the other hand, regarding generation of a drive signal for driving the piezo actuator 302, a digital data string is sequentially read from the storage element 340 storing digital data of the drive waveform, and converted into an analog signal by the D / A converter 332. This analog signal is amplified by the operational amplifier 334. A boost circuit 336 composed of two power transistors (Tr1, Tr2) is connected to the output of the operational amplifier 334 so that a large output current can flow. This is because when a voltage pulse signal is applied to the plurality of piezo actuators 302 in the inkjet head 300, it is necessary to instantaneously flow a large current for charging and discharging the capacitor.

  The interface between the drive substrate 324 and the inkjet head 300 includes a line 350 for transmitting a drive signal for driving the piezoelectric actuator 302 and a line 352 for transmitting an image (dot) data signal for controlling the analog switch 304. Including.

  Since the number of nozzles in the inkjet head 300 is large, a signal for driving the piezo actuator 302 is a group of a plurality of nozzles grouped by an appropriate number of nozzles in one drive system, and the inkjet head is connected via a cable 360. Sent to the 300 side. The image (dot) data signal for controlling the analog switch 304 is configured to serially transfer a plurality of nozzles. A drive waveform signal transmitted to one drive system line is applied to each piezo actuator 302 by switching the analog switch 304 in accordance with image (dot) data. Thereby, ink is ejected from the corresponding nozzle.

  In the ink jet head 300 using the piezo actuator 302 as described above, the ink chamber and the electric circuit are close to each other due to the drive structure of the piezo actuator 302, and there are problems such as head unit manufacturing, structure, and material, and aging deterioration. Or, due to factors such as ink supply pressure, ink leakage (leakage) may occur, causing the electrical circuit in the head to be short-circuited. Since this electric short circuit is caused by the liquid ink itself, the short circuit in the electric circuit is complicated.

  In general, a drive board equipped with a drive circuit for driving a piezo actuator outputs at least a power source, drive power, and image data (signals for controlling ON / OFF of each piezo actuator) to the head. . In particular, in the case of a multi-nozzle head having hundreds to thousands of nozzles, a plurality of data lines may be used because image data must be transferred at a necessary timing. For this reason, if an unpredictable electrical short circuit occurs due to ink leaks in the head or the like, the output circuit in the drive circuit is greatly damaged (component burnout). That is, an electrical short causes the output circuit to exceed the absolute rated current and destroys circuit components.

  For example, Patent Documents 1 to 4 include conventional techniques relating to protection measures against a short circuit abnormality in a connection line between an inkjet head and a drive unit.

  In Patent Document 1, when differential transmission such as an LVDS (Low Amplitude Differential Signaling) driver is adopted as a signal transmission method in an inkjet head, the power supply current is transferred to the differential transmission line due to an ink short in the head. There has been proposed a method for protecting a circuit against the problem that the transmission system is broken. Specifically, taking advantage of the characteristics of differential transmission, a capacitor is provided in series on the plus and minus lines, and the data accumulated in both directions is manipulated to cancel the charge accumulated in the capacitor with the previous data with the next data. It is systemized. With this configuration, the driver is protected so that an overcurrent does not flow through the capacitor even when a power supply voltage is applied due to an ink short in the head.

  In Patent Document 2, a short circuit to a ground (GND) of a data line and an address line sent to a thermal ink jet head using a heating resistor as a pressure generating element is detected, and when a short circuit is detected, the driver output is stopped or the power supply is shut off. Proposed a method for protecting the driver circuit.

  Japanese Patent Application Laid-Open No. 2004-228688 proposes detecting a short circuit abnormality of a drive line sent from a drive circuit to a thermal ink jet head and an abnormality of a drive power element (heating resistor). Specifically, charging and discharging is performed using a charging circuit in which a resistor and a capacitor are connected in series as a short-circuit detection circuit, and the abnormality is detected by measuring the potential of the capacitor over time in the state of the load being tested. .

  Patent Document 4 proposes a means for detecting a short circuit between a data line to be sent to an inkjet head and GND. According to the literature 4, the data line is connected in parallel to the head and the short detection circuit, and whether the voltage flowing through each data line exceeds the predetermined value when the voltage is transmitted by the driver used in the normal mode. If it does not exceed (short), a binary code specifying the line is transmitted to the control unit, and data is not transmitted to the corresponding short line.

JP 2003-72074 A JP-A-10-128965 JP-A-9-322380 JP 2000-263765 A

  However, the method described in Patent Document 1 is effective when a differential method is used as a signal transmission method, but cannot be applied to a single-ended transmission method. Further, this system protects the driver from destruction only when the power supply voltage is applied to the signal transmission path due to an ink short circuit, and is a limited protection function. Furthermore, the method of Patent Document 1 does not detect an abnormality due to a short circuit.

  Although the method described in Patent Document 2 performs short circuit detection, the detection target is limited. That is, in Patent Document 2, only a short circuit between the data line and the address line and the ground (GND) can be dealt with. For example, the case where the drive voltage of the data line is short-circuited to the address line is not considered. Moreover, with the technique of the cited reference 2, it is not possible to confirm short-circuits individually for a plurality of lines. Furthermore, it cannot cope with a circuit that is floatingly connected to the head in terms of voltage. As another circuit contradiction, the address line short-circuit detection circuit constantly applies a voltage to the address line. This has a problem that the FET (Field-Effect Transistor) of the heater switch always connected to the address is always in an ON state during normal operation other than short circuit detection.

  The method described in Patent Document 3 is applicable only when the inkjet head is a thermal type and the load is a heater resistor. Therefore, the technique of the literature 3 cannot be applied to an inkjet head in which the load is a piezo actuator, that is, a capacitor (capacitive load).

  The technique described in Patent Document 4 is to detect a shorted data line and use only the remaining line without using that line next time. In other words, it is a technique that does not protect the drive circuit but aims to widen the range of correspondence after a short circuit. Moreover, in patent document 4, the level determination method of a short circuit detection circuit is not specified clearly. Furthermore, as in Patent Document 3, it can only cope with GND in short circuit detection.

  The present invention has been made in view of such circumstances, and in a configuration in which an inkjet head using a piezo actuator and a drive circuit are connected in a floating manner, short circuit between various unexpected wires due to liquid leakage in the head or the like. It is an object of the present invention to provide a short-circuit inspection device for an ink jet system that can protect an output circuit on a drive circuit side from an abnormality.

  In order to achieve the above object, the following invention modes are provided.

  (Invention 1): The short-circuit inspection apparatus for an inkjet system according to Invention 1 includes a piezo actuator provided corresponding to a nozzle, and a load control circuit that selectively switches driving / non-driving of the piezo actuator, By driving the piezo actuator selected for driving by the load control circuit, an inkjet head that discharges droplets from the corresponding nozzle, a load power source, a drive selection signal, and driving power necessary for driving the piezo actuator are provided. A short circuit inspection device mounted on an ink jet system having a structure in which an electrical connection between the ink jet head and the drive circuit is a floating connection, the driving circuit including an electric circuit for outputting to the ink jet head. A power generation circuit for supplying the load power to the control circuit; A power supply short circuit inspection circuit that is connected to a load power supply line that transmits the load power generated by the power generation circuit to the inkjet head and performs a short circuit inspection with the load power supply line as an inspection target, and driving / non-driving of the piezoelectric actuator A signal short circuit inspection circuit for performing a short circuit inspection with the signal line as an inspection target, and a short circuit inspection by the power supply short circuit inspection circuit or the signal short circuit inspection circuit. A control circuit for stopping the supply of the load power from the power generation circuit during the inspection mode to be performed, and either the load power line or the signal line as the inspection target of the short-circuit inspection in the inspection mode The monitor selection circuit that selects the monitor selection circuit and the monitor selection circuit can operate in the inspection mode. The monitor selection circuit, the power supply short circuit inspection circuit, and the signal short circuit inspection circuit can be operated in the drive mode in which droplets are ejected from the nozzles while enabling the operation of the power supply short circuit inspection circuit or the signal short circuit inspection circuit. An inspection switching circuit that disables the operation of the monitor selection circuit in the inspection mode, a power supply for inspection connected to the line to be inspected according to the selection of the monitor selection circuit, and detecting a potential on the line to be inspected A short-circuit determination circuit for determining the presence or absence of a short-circuit, and when a line short-circuit is detected by the short-circuit determination circuit, supply of the load power to the inkjet head, transmission of the drive selection signal, and supply of the drive power Is stopped.

  According to the present invention, the presence or absence of a line short circuit can be inspected by shifting to the inspection mode at an appropriate timing before the driving operation in the driving mode or after the driving operation in the driving mode. When a short circuit between wirings is detected, supply of load power to the inkjet head is stopped, transmission of a drive selection signal is stopped, and supply of drive power (load drive power) to the piezoelectric actuator is also stopped. . As a result, overcurrent can be prevented from flowing into the drive circuit, and circuit components can be protected.

  As a specific countermeasure example when a short circuit abnormality is detected, for example, a control circuit performs control to stop the power output of the power generation circuit or the like. By stopping the power output of the power generation circuit, the supply of load power to the head is stopped and the circuit that receives power supply from the power generation circuit in the drive circuit (circuit components connected to the load power line) ) Is also stopped. As a result, power supply to a drive selection signal output circuit (such as an isolator / driver IC) can be stopped, and transmission of the drive selection signal to the head is stopped. Similarly, the supply of load drive power is stopped by stopping the power supply to the drive power amplifier circuit by the control circuit.

  According to the present invention, each of the load power supply line and the signal line can be an inspection target, and various short forms in the head can be dealt with. According to the present invention, the drive circuit can be protected from a short circuit abnormality between various connection lines that may occur in an unexpected manner, such as an electrical short due to liquid leakage in the head.

  The number of piezoelectric actuators in the ink jet head is not particularly limited. In the case of an inkjet head having a plurality of nozzles, a plurality of piezoelectric actuators are provided corresponding to each nozzle.

  (Invention 2): The short-circuit inspection apparatus for an inkjet system according to Invention 2, in Invention 1, the drive circuit includes a drive power amplification circuit that outputs a drive power signal having a voltage waveform for driving the piezoelectric actuator, and the drive The drive waveform voltage output from the power amplifier circuit is a reference potential for the load power supply and the drive selection signal.

  As described in Invention 2, the present invention can also cope with a mode in which a relatively high voltage is applied to the connection line.

  (Invention 3) The short circuit inspection apparatus for an inkjet system according to Invention 3 is characterized in that, in Invention 1 or 2, the control circuit stops power supply to the drive power amplifier circuit in the inspection mode.

  At the time of inspection, the supply of the load power supply is stopped and the output of the drive power signal is also stopped, so that it is possible to prevent the circuit components from being destroyed when a short circuit occurs.

  (Invention 4): The short-circuit inspection apparatus for an inkjet system according to Invention 4, in Invention 3, when the control circuit detects a line short-circuit by the short-circuit determination circuit, the output of the power generation circuit is stopped, The power supply of the drive power amplifier circuit is stopped.

  When the short circuit abnormality is detected, the supply of load power to the inkjet head from the drive circuit side is stopped, and the supply of drive power to the piezo actuator is stopped, thereby preventing the overcurrent from flowing into the drive circuit side and circuit components. Prevent the destruction of.

  (Invention 5): The short-circuit inspection device for an inkjet system according to Invention 5, in any one of Inventions 1 to 4, wherein the inspection switching circuit is based on an input of a trigger signal indicating transition to an inspection mode. A power supply short circuit inspection circuit and a start permission signal for permitting activation of the signal short circuit inspection circuit are output, and a wiring line through which a current flows from the line to be inspected according to the selection of the monitor selection circuit by a line short circuit of the drive circuit It is characterized in that it is terminated with a switch connection to the ground.

  When a trigger signal is input to the inspection switching circuit, a start permission signal is output from the inspection switching circuit, and the selection function of the monitor selection circuit is enabled by the start permission signal, and the power supply short circuit inspection circuit or the signal short circuit inspection circuit The inspection function is activated. The trigger signal may be output by the control circuit or may be output from a higher-level control device.

  (Invention 6): The short-circuit inspection apparatus for an inkjet system according to Invention 6 has a signal processing circuit for generating a signal for selecting driving / non-driving of the piezoelectric actuator according to any one of Inventions 1 to 5, The drive selection signal is generated by voltage-converting the signal output from the signal processing circuit, while the signal processing circuit is configured to inspect the load power supply line or the signal to be inspected in the short-circuit inspection in the inspection mode. A monitor selection signal for selectively activating the power supply short circuit inspection circuit or the signal short circuit inspection circuit is generated as a signal for selecting one of the lines, and the monitor selection signal is used to drive / not drive the piezoelectric actuator. The signal is inputted to the monitor selection circuit using a signal line for transmitting a signal for selecting driving.

  According to this aspect, it is possible to transmit an inspection target line selection signal (monitor selection signal) using an existing signal line. As a result, wire saving and circuit mounting space saving are possible.

  (Invention 7): The short-circuit inspection apparatus for an ink-jet system according to the seventh aspect of the present invention is the short-circuit inspection device according to the sixth aspect, wherein the monitor selection signal selectively activates one short-circuit inspection circuit among the power supply short-circuit inspection circuit and the signal short-circuit inspection circuit. It is a logic binary signal of (H) level and low (L) level that selectively activates the other short circuit inspection circuit.

  According to this aspect, it is possible to selectively activate two inspection objects with simple logic control.

  (Invention 8): The short-circuit inspection apparatus for an inkjet system according to Invention 8 is the invention 6 or 7, wherein a plurality of the signal lines are provided, and one of the plurality of lines is connected to the inspection target line and the other lines. On the other hand, a different monitor selection signal is transmitted, and an individual line can be inspected.

  According to this aspect, it is possible to detect the presence or absence of a short circuit abnormality for each line by selecting the inspection target for each line.

  (Invention 9): The short-circuit inspection device for an inkjet system according to Invention 9 is the short-circuit inspection device according to any one of Inventions 6 to 8, wherein the monitor selection circuit includes the power supply short-circuit inspection circuit and the signal short-circuit inspection from the inspection switching circuit. The power supply short circuit inspection circuit or the short circuit inspection circuit corresponding to the monitor selection signal is activated by an activation permission signal for permitting circuit activation.

  According to this aspect, the monitor selection signal functions effectively on the condition that the start of the power supply short circuit inspection circuit and the signal short circuit inspection circuit is permitted by the inspection switching circuit, and the power supply short circuit inspection circuit corresponding to the monitor selection signal. Alternatively, the short circuit inspection circuit operates.

  (Invention 10): The short-circuit inspection device for an ink jet system according to the invention 10 is the short-circuit inspection device for the ink-jet system according to the ninth aspect, wherein the power supply short-circuit inspection circuit By receiving, the signal line is switched to the inspection switching circuit, the signal line is connected to the ground of the drive circuit via the inspection switching circuit, and the inspection power source is switched to the load power line. It is characterized by doing.

  According to this aspect, it is possible to perform a short circuit inspection of the load power supply line in accordance with the start permission of the inspection switching circuit and the monitor selection signal input to the monitor selection circuit.

  (Invention 11): The short-circuit inspection apparatus for an inkjet system according to Invention 11 is the load driving power for transmitting the drive power signal having a voltage waveform for driving the piezoelectric actuator to the inkjet head in Invention 9 or 10. The signal short-circuit inspection circuit receives the signal short-circuit inspection start signal from the monitor selection circuit in response to the start permission signal from the inspection switch circuit, so that the load drive power line is connected to the inspection switch circuit. The load drive power line is connected to the ground of the drive circuit through the test switching circuit by switch connection, and the test power supply is switch-connected to the signal line.

  According to this aspect, it is possible to perform a short circuit inspection of the signal line according to the start permission of the inspection switching circuit and the monitor selection signal input to the monitor selection circuit.

  (Invention 12): The short-circuit inspection apparatus for an inkjet system according to Invention 12, according to any one of Inventions 1 to 11, is an isolator as a transmission circuit that outputs the drive selection signal to the inkjet head via the signal line. A driver IC is used.

  The present invention can effectively prevent destruction of the isolator / driver IC when there is a possibility that a leakage current when an electrical short between the wirings occurs exceeds the rating of the isolator / driver IC.

  (Invention 13): The short-circuit inspection device for an inkjet system according to Invention 13 is the short-circuit determination circuit according to any one of Inventions 1 to 12, wherein the short-circuit determination circuit tests the inspection target line from the inspection power source in the inspection mode. A voltage is applied, the potential on the line is compared with a threshold value to determine the presence or absence of a line short circuit, and a signal indicating the determination result is output.

  According to this aspect, if there is a short circuit abnormality between the lines, a current flows from the line to be inspected to the ground via the short circuit path. Therefore, the potential of interest on the inspection target line when the short circuit abnormality occurs is lower than that in a normal case (when there is no short circuit abnormality). Based on this potential change, the presence or absence of a line short circuit can be determined.

  (Invention 14): The short-circuit inspection apparatus for an inkjet system according to Invention 14, in Invention 13, wherein the voltage application of the inspection power supply is set to be equal to or less than the rated current in the transmission circuit output of the line of the inspection target line. It is characterized by being.

  The current for inspection is limited so that the circuit is not destroyed by the current flowing in the inspection mode. When there are multiple circuit components that can be destroyed by short circuit abnormality on the drive circuit side, set the current value for inspection within the range that satisfies the most severe conditions (those with the lowest rated current). Is desirable.

  (Invention 15): In the short-circuit inspection apparatus for an inkjet system according to Invention 15, in the invention 13 or 14, the threshold value for comparing the potential on the line to be inspected is a voltage of the inspection power supply applied to the line. From the ground to the ground, the voltage is divided by a resistor.

  According to this aspect, it is possible to determine the presence or absence of a circuit short circuit with a simple circuit configuration.

  According to the present invention, in a configuration in which an inkjet head and a drive circuit are connected in a voltage floating relationship, the presence or absence of a short circuit abnormality between connection lines due to liquid leakage in the head is inspected at an appropriate timing. be able to. When a short circuit abnormality is detected, the supply of the load power supply is stopped, and the sending of the drive selection signal and the supply of the drive power (load drive power) are also stopped, so that the leakage current returns via the short circuit path. It is possible to prevent destruction of circuit components due to the above.

The circuit block diagram which showed the example of the short circuit inspection apparatus of the inkjet system which concerns on embodiment of this invention The figure which shows the more specific circuit example of the short circuit inspection apparatus of this example Equivalent circuit diagram of the input side of the comparison discriminating circuit in the short circuit judgment circuit Timing chart of signals flowing in image signal line in inspection mode Main part circuit diagram for explaining operation of power supply short circuit inspection circuit Main part circuit diagram for explaining the operation of the signal short circuit inspection circuit 1 is a configuration diagram of an ink jet recording apparatus equipped with a short circuit inspection apparatus according to an embodiment of the present invention. Diagram showing an example of the structure of an inkjet head Plane perspective view showing another structural example of the inkjet head Sectional drawing which follows the AA line in FIG. Main block diagram showing the system configuration of the inkjet recording apparatus Outline diagram of circuit configuration of conventional inkjet head

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a circuit block diagram showing a configuration example of a short-circuit inspection apparatus for an inkjet system according to an embodiment of the present invention.

  As shown in FIG. 1, an inkjet head unit (hereinafter referred to as “head unit”) 10 is provided with a piezoelectric actuator 12 corresponding to each nozzle. In FIG. 1, only the circuit of one piezo actuator 12 is shown in the head unit 10 for the sake of simplicity, but actually there are a plurality of piezo actuators 12 corresponding to a plurality of nozzles. There is also an aspect in which a plurality of head units 10 are connected to form one ink jet head.

  Each piezo actuator 12 in the head unit 10 is provided with a load control circuit 16 (switch circuit) including a switch element 14 for performing drive selection (ON / OFF control) of each piezo actuator 12. . As for the load control circuit 16, only one circuit is shown in FIG. 1, but there are a plurality of similar circuits corresponding to the individual piezoelectric actuators 12.

  Further, in order to switch-control a plurality of piezo actuators 12 in a short time, a signal (image data) for controlling the load control circuit 16 is sent from the drive substrate 20 to the head unit 10 through a plurality of lines (reference numeral 18). . In FIG. 1, only one signal line for transmitting the image data indicated by reference numeral 18 is shown, but in reality, it has a plurality of lines.

  Further, as described with reference numerals 352 and 308 in FIG. 12, one signal (image data) line serially transfers a signal (corresponding to a “drive selection signal”) for turning on / off a plurality of piezoelectric actuators 12. It has become a thing. Hereinafter, the signal line indicated by reference numeral 18 is referred to as an “image signal line”.

  In FIG. 1, in addition to the image signal line 18, electrical wiring necessary for driving each piezo actuator 12 is a load power line 22, a load drive power line 24, and a common (COM) line 26.

  In the illustrated circuit, the electrical connection between the head unit 10 and the drive substrate 20 is a floating connection. That is, the ground (GND) on the drive substrate 20 side and the ground in the head unit 10 are completely separated (insulated state). The electric circuits mounted on the drive substrate 20 may be collectively referred to as “drive circuit”.

  The internal circuit of the head unit 10 uses the reference potential as the drive waveform voltage of the piezo actuator 12 due to the drive structure of the piezo actuator 12. For this reason, the power supply of the head unit 10 (the load power supply supplied from the load power supply line 22) becomes a potential based on the drive waveform voltage of the load drive power line 24. Accordingly, on the drive circuit side, the voltage level of the drive selection signal (image data) of the piezo actuator 12 transmitted to the head unit 10 from the GND (reference numeral 30) of the reference potential of the drive substrate 20 to the drive waveform voltage of the head reference potential. Conversion is in progress. The drive waveform voltage required for driving the piezo actuator 12 is about several tens of volts [V], and the drive waveform requires skew, so that an expensive isolation component ( The isolator / driver IC indicated by reference numeral 34 in the figure is used.

  With this configuration, the driving power is commonly supplied to the plurality of piezoelectric actuators 12 corresponding to each nozzle through the load driving power line 24, and which pixel nozzle is driven (discharged) based on the image data. A drive selection signal for selection is sent to the head unit 10. In the head unit 10, a switch element 14 corresponding to each piezo actuator 12 is provided, and the ON / OFF of the switch element 14 is controlled according to the drive selection signal sent through the image signal line 18. The drive of the piezo actuator 12 to be selected is selected. Thereby, ink can be ejected from the nozzles of the pixels corresponding to the image data.

  In the ink jet system having such a circuit configuration, ink leaks (leakage) from an ink chamber (an individual pressure chamber corresponding to each nozzle or a common liquid chamber communicating with a plurality of pressure chambers) inside the head unit 10. ), Electrical shorts may occur at various points in each wiring of the electric circuit inside the head unit 10. For example, an electrical short between the wiring of the load power supply line 22 and the image signal line 18 in FIG. 1 (symbol <1>), an electrical short between the wiring of the image signal line 18 and the load driving power line 24 (symbol <2>), An electrical short (symbol <3>) between the load driving power line 24 and the common (COM) line 26, or a combination thereof may occur.

  As a result, if no measures are taken, a short circuit occurs in the wiring between the head unit 10 and the drive board 20, and thus an overcurrent flows in the output circuit of the drive board 20, and the components constituting the circuit may be destroyed. There is. For example, the range leading to component destruction includes a load power generation circuit (corresponding to a “power generation circuit”) 32 that supplies load power, and an image data transmission circuit that drives and selects each piezo actuator 12 (an isolator indicated by reference numeral 34). A driving power amplification (amplifier) circuit 36 for outputting a driving power signal for driving the piezoelectric actuator 12.

  A driving power signal for driving the piezo actuator 12 is transmitted as a voltage waveform from 0 V to several tens of V [volts] through the load driving power line 24. The load power supply supplied to the head unit 10 is a digital power supply (for example, +3.3 V) based on this drive waveform voltage. Therefore, when viewed from the reference potential GND (reference numeral 30) of the drive substrate 20, the drive power supply potential is a drive waveform voltage (0V to several tens of volts) plus a digital power supply (for example, + 3.3V).

  On the other hand, a signal (image data) for selecting driving of the piezo actuator 12 is digitally transmitted by an isolator / driver IC 34 based on the driving waveform potential. This driver IC 34 has an output current of several tens of mA [milliamperes] at the maximum, and the leakage current when the wiring is short-circuited due to ink leakage or the like flows exceeding the ratings for both Sink (suction) and Source (discharge). The cause of destruction in Sink (suction) is mainly a short mode between the load power supply line 22 and the image signal line (reception input side) 18 inside the head. On the other hand, the cause of destruction at the source is mainly the short mode between the image signal line 18 and the load driving power line 24 inside the head or the short mode between the image signal line 18 and the common (COM) line 26. .

  In order to realize circuit protection corresponding to such electrical shorts between various wirings, the short circuit inspection apparatus according to the present embodiment includes a power supply control circuit 40, a monitor selection circuit 42, a power supply short circuit inspection circuit 44, and a signal short circuit inspection circuit. 46, an inspection switching circuit 48, and a short circuit determination circuit 50.

The power supply control circuit 40 performs on / off control of the load power supply generation circuit 32 configured by an insulated DC-DC converter and on / off control of power supply (+ V ₂ ) supply of the drive power amplification circuit 36. The monitor selection circuit 42 is a circuit that outputs a signal for selecting one of the power supply short circuit inspection circuit 44 and the signal short circuit inspection circuit 46 to be operated. The monitor selection circuit 42 receives a selection signal (corresponding to a “monitor selection signal”) transmitted from the signal processing circuit 60 to a signal line input to the preceding stage 34A of the isolator / driver IC 34, and a signal related to the reception In accordance with the signals, the signals for controlling on / off of the switch elements 44A and 44B in the power supply short circuit inspection circuit 44 and the switch elements 46A and 46B of the signal short circuit inspection circuit 46 ("power supply short circuit inspection start signal", "signal short circuit inspection start signal") Is equivalent). The pair of switch elements 44A and 44B is controlled in conjunction with each other. Similarly, a pair of switch elements 46A and 46B is controlled in conjunction with each other.

The power supply short circuit inspection circuit 44 is means for inspecting the presence of a short circuit for the load power supply line 22 as an inspection target. The switch element 44 </ b> A of the power supply short circuit inspection circuit 44 applies a test power supply voltage (+ V ₃ ) supplied from a power supply (corresponding to a “test power supply”) different from the load power supply generation circuit 32 to the load power supply line 22, Alternatively, the application is canceled.

  The power supply short circuit inspection circuit 44 includes a series circuit of a resistor 44C and a diode 44D connected to the image signal line 18 on the subsequent stage (output side) 34B of the isolator driver IC 34. The cathode (cathode) terminal of the diode 44D is connected to one end of the switch element 48A of the inspection switching circuit 48 via the switch element 44B.

  The signal short circuit inspection circuit 46 is means for inspecting the presence / absence of a short circuit for the image signal line 18 as an inspection target. The signal short circuit inspection circuit 46 is different from the power supply short circuit inspection circuit 44 described above in the wiring line to be inspected, but the main circuit elements are the same as those of the power supply short circuit inspection circuit 44.

The switch element 46A of the signal short circuit inspection circuit 46 is controlled by a signal from the monitor selection circuit 42. When the switch element 46A is turned on, the test power supply voltage (+ V ₃ ) is applied to the image signal line 18. When the switch element 46A is turned off, the application of the test power supply voltage (+ V ₃ ) is released.

  The signal short circuit inspection circuit 46 includes a series circuit of a resistor 46C and a diode 46D connected to the output line (load drive power line 24) of the drive power amplifier circuit 36. The cathode (cathode) terminal of the diode 46D is connected to one end of the switch element 48A of the inspection switching circuit 48 via the switch element 46B.

  The other terminal of the switch element 48A is connected to the ground (GND) line 30 of the drive circuit. The switch element 48A is controlled to be turned on / off by a test mode (TEST_MODE) signal given from the control unit 62 of the host device. Under the control of the switch element 48A, the resistor 44C of the power supply short circuit inspection circuit 44 or the resistor 46C of the signal short circuit inspection circuit 46 is connected to the ground (GND) line 30 in accordance with the selection of the inspection circuit by the monitor selection circuit 42. Alternatively, the connection with the ground (GND) line 30 can be released.

  Since the drive circuit on the drive substrate 20 and the head unit 10 are completely separated from each other in ground, in order to pass an inspection current from the drive substrate 20 to the head unit 10, the ground on the drive circuit side is returned as a return. It is necessary to flow to (reference numeral 30).

  Therefore, in the present embodiment, an inspection switching circuit 48 for connecting an inspection circuit including a line to be inspected to the ground is provided, and the inspection switching circuit 48 and the monitor selection circuit 42 cooperate with each other to supply power. The selective activation of the short circuit inspection circuit 44 or the signal short circuit inspection circuit 46 is realized.

  The signal processing circuit 60 generates image data (dot data) for selecting driving / non-driving of each piezoelectric actuator 12. The signal (image data) output from the signal processing circuit 60 is converted into a voltage by the isolator / driver IC 34, and a drive selection signal for on / off control of the switch element 14 of the load control circuit 16 is generated. In the inspection mode, the signal processing circuit 60 generates an inspection object selection signal (corresponding to a “monitor selection signal”, which will be described later, “TEST_DATAn”) for selecting a line to be inspected.

  The signal processing circuit 60 may be mounted on the drive substrate 20 or may be mounted on a host device that controls the drive circuit. In FIG. 1, the control unit 62 and the signal processing circuit 60 are shown as separate blocks. However, they can be integrated to form an integrated structure. Further, the power supply control circuit 40 and the control unit 62 can be integrated to form a single control circuit. The power supply control circuit 40 or a combination of this and the control unit 62 corresponds to a “control circuit”.

  FIG. 2 shows a more specific circuit example of the configuration described in FIG. 2, elements that are the same as or similar to the elements shown in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted. FIG. 2 shows a state in which a plurality of image signal lines 18 are provided corresponding to a large number of piezoelectric actuators 12 in the head unit 10. The signal bus line 68 for transmitting the image data is connected to a signal processing circuit (reference numeral 60 in FIG. 1) not shown in FIG. The signal bus line 68 branches to n circuits, and each signal line (signal_1, signal_2,... Signal_n) is connected to the load control circuit 16 of the piezo actuator 12 in the head unit 10. ing.

  Since the head unit 10 has a large number of nozzles, the image data transmission line (image signal line 18) has multiple lines. The nozzle groups in the head unit 10 are grouped by an appropriate number, one line is assigned for each group unit, and image data for a plurality of nozzles is transmitted as serial data.

  The signal processing circuit 60 can output a signal for each line for each signal line (signal_1, signal_2,... Signal_n). In this example, by sequentially sending data (selection signal) one line at a time for each line of the first signal line (signal_1), second signal line (signal_1)..., N-th signal line (signal_n), Can be individually inspected.

  In FIG. 2, from the viewpoint of wire saving, since the short circuit determination circuit 50 is combined into one, n lines cannot be inspected at the same time, but by providing a plurality of short circuit determination circuits 50, It is also possible to inspect multiple lines simultaneously.

<About generation of drive waveform>
The drive power amplifier circuit denoted by reference numeral 36 is the same as the drive circuit 320 described with reference to FIG. That is, the digital data string is sequentially read from the storage element 64 (see FIG. 1) storing the digital data of the drive waveform, and converted into an analog signal by a D / A converter (not shown). Then, the analog signal is amplified by the operational amplifier 70. A boost circuit composed of two power transistors (Tr 1, Tr 2) is connected to the output of the operational amplifier 70 so that a large output current can flow through the load drive power line 24. Further, a power switch SW2 for turning on / off the supply of power (+ V ₂ ) to the boost circuit is provided, and the power switch SW2 is controlled by the power control circuit 40.

<Monitor selection circuit 42>
The monitor selection circuit 42 has a configuration in which a PNP transistor Tr3 and an NPN transistor Tr4 are connected in parallel, and a signal (TEST_DATAn) is input from the signal bus line 68 to the bases of the transistors Tr3 and Tr4. This signal (TEST_DATAn) is a monitor selection signal (corresponding to “inspection object selection signal”) for selecting a line to be inspected. When a logic “L” level signal is input as the TEST_DATAn signal, the power supply short circuit inspection circuit 44 can be activated. When a logic “H” level signal is input as the TEST_DATAn signal, the signal short circuit inspection circuit 46 can be activated.

  As described above, the monitor selection circuit 42 performs alternative selection so that the inspection of the load power supply line 22 and the inspection of the image signal line 18 do not work simultaneously. A signal (data) for instructing selection (switching) of the inspection target is output from the signal processing circuit 60 using an image transmission line. When the ejection drive image data is not output (during the ejection drive stop period), the mode shifts to the inspection mode, and a monitor selection signal is sent to the monitor selection circuit 42 using the vacant image transmission line. Thereby, line saving can be achieved.

<About the power supply short circuit inspection circuit 44 and the signal short circuit inspection circuit 46>
Transistors Tr5 and Tr6 in the power supply short circuit inspection circuit 44 of FIG. 2 correspond to the switch elements 44A and 44B described in FIG. The transistor Tr7 in the signal short circuit inspection circuit 46 of FIG. 2 corresponds to the switch element 46A described in FIG. Further, the transistor Tr4 in FIG. 2 functions as the switch element 46B described in FIG.

<About the short circuit determination circuit 50>
The short circuit determination circuit 50 detects the potential of the inspection target line (the load power supply line 22 or the image signal line 18) to which the test power supply voltage (+ V ₃ ) is applied, and compares it with a predetermined reference value (threshold). It has a comparison / discriminating circuit 52 for outputting a signal indicating whether it is normal or abnormal. The short circuit determination circuit 50 includes a voltage dividing circuit (resistance dividing circuit) in which resistors R1, R2, and R3 are combined. A potential divided by the voltage dividing circuit is input to an input terminal of the comparison determination circuit 52. As for the threshold value, a specified voltage set by a voltage dividing circuit (not shown) from the test power supply voltage (+ V ₃ ) is input to the comparison determination circuit 52.

  That is, the potential for determining the presence or absence of a short circuit based on the input threshold (threshold) level of the comparison determination circuit 52 is divided between the voltage dividing circuit of the resistors R1 to R3 and the circuit that continues up to the test switching circuit 48 when a short circuit occurs. Set by pressure ratio. The configuration diagram is shown by the equivalent circuit of FIG.

  The above-mentioned “circuit continuing to the inspection switching circuit 48 when a short circuit occurs” is a portion indicated by reference numeral 54 in FIG. 3. In the case of inspecting the load power supply line 22, the transistor Tr 5 to the wiring short-circuit portion, The circuit reaches the resistor 44C, the diode 44D, the transistor Tr6, and the transistor Tr8. When the image signal line 18 is inspected, the circuit extends from the transistor Tr7 to the short-circuit portion between the wires, the resistor 46C, the diode 46D, the transistor Tr4, and the transistor Tr8.

The test power supply voltage (+ V ₃ ) is set to + 36V, for example. The test power supply voltage (+ V ₃ ) is applied to the inspection target line selected by the monitor selection circuit 42 in the inspection mode, but the current value is limited by the resistors R1 to R3. Even if a line short circuit occurs, a current that is less than the rated current of the output of the isolator / driver IC 34 flows, and the circuit components on the drive board 20 are not destroyed.

  The comparison determination circuit 52 may employ a digital circuit that outputs whether the input potential is normal or abnormal as a binary value (“0” or “1”). For example, an A / D converter or an analog comparator can be used.

  The comparison determination circuit 52 of this example is configured to output “1” when there is a short circuit abnormality and “0” when normal. The determination result signal is sent to the control unit 62 and used to control the power supply control circuit 40.

  Next, the operation of the inspection apparatus configured as described above will be described.

  In the ink jet recording apparatus of this example, an abnormality due to an electrical short circuit has occurred in the state where ejection driving is not performed, in addition to the normal operation mode (corresponding to “driving mode”) in which the head unit 10 is ejected. It has a mode to check whether there is any. This inspection operation mode (referred to as “inspection mode” or “test mode”) operates in the following procedure.

  (Step 1): First, the power supply control circuit 40 turns off the power supply of the load power supply generation circuit 32 and the drive power amplification circuit 36. Specifically, the power switch SW1 (not shown) of the load power generation circuit 32 is turned off, and the power switch SW2 (see FIG. 2) of the drive power amplifier circuit 36 is turned off. This is performed to prevent destruction and stop operation of the output circuit (image data transmission circuit including the isolator / driver IC 34) at the time of inspection and to guarantee the operation of the inspection circuit.

  (Step 2): Next, in the inspection mode from the signal processing circuit 60, a data signal for selecting whether to perform a power supply short circuit inspection or a signal short circuit inspection (referred to herein as a “monitor selection signal”). Equivalent to “inspection object selection signal”). The signal processing circuit 60 transmits a signal (image data) for selecting the piezo actuator 12 corresponding to the ejection nozzle in a normal operation mode (referred to as “driving mode”) in which droplets are ejected from the head unit 10. However, during the period of the inspection mode, a logic level (“H (high)” or “L (low)” signal) for selecting an inspection target of the power supply short circuit inspection or the signal short circuit inspection is transmitted (FIG. 4). See timing chart).

  (Step 3): The monitor selection circuit 42 receives the monitor selection signal transmitted from the signal processing circuit 60 to the image signal line input to the preceding stage (34A) of the isolator / driver IC 34, and the selection signal related to the reception. Accordingly, the short circuit inspection circuit to be operated is selected from the power supply short circuit inspection circuit 44 and the signal short circuit inspection circuit 46.

  (Step 4): Also, in the inspection mode, a test mode signal (TEST_MODE signal) is input to the inspection switching circuit 48, and the switch element 48A (corresponding to the transistor Tr8 in FIG. 2) is closed by this signal to 44 and the signal short circuit inspection circuit 46 are connected to the GND line 30 to operate the short circuit inspection circuit (44 or 46). The TEST_MODE signal in this example is an “H” level signal and is generated from the control unit 62 (see FIG. 1).

  Thus, when the power supply short circuit inspection circuit 44 and the signal short circuit inspection circuit 46 are GND-connected, the short circuit inspection circuit (44 or 46) enters an operation standby state, and the start signal (the short circuit inspection circuit of the short circuit inspection circuit) is output from the monitor selection circuit 42. Each circuit starts to operate in response to the selection signal.

(Step 5): monitor selection circuit 42 short test circuit selected by (44 or 46), the switch element 44A or 46A to close the test supply voltage _{V 3} inspected load connection line (load power supply line 22 or the image The line (image signal line 18 or load drive power line 24) into which the leakage current of the line to be inspected flows by closing the switch element 44B or 46B while being applied to the signal line 18) together with the terminating resistor (resistor 44C or 46C). Connected to a ground (GND) line 30. Table 1 summarizes the connection relationship between the selected short-circuit inspection circuit and each line.

(Step 6): The short circuit determination circuit 50 compares the potential of the target line when the test power supply voltage (+ V ₃ ) is applied to the inspection target line (the load power supply line 22 or the image signal line 18) with the detector threshold. A circuit for determining normality / abnormality. When an ink leak or the like occurs in the head unit 10 and the inspection target line is electrically short-circuited, a low voltage is detected with respect to the applied voltage, so that “abnormal” is determined and an error result is output. The determination result signal is sent to the control unit 62 described with reference to FIG.

  (Step 7): If an error determination is made in “Step 6” above, the power sources of the load power generation circuit 32 and the drive power amplification circuit 36 are not turned on. That is, the control unit 62 controls the power supply control circuit 40 so that the power switch SW1 of the load power generation circuit 32 is maintained in the off state and the power switch SW2 of the drive power amplifier circuit 36 is maintained in the off state. Thus, the output of the drive signal of the piezo actuator 12 to the head unit 10 is prohibited.

  Further, it is preferable that the error information is communicated to a host device such as a host computer, and warning is performed by appropriate notification means such as display of an error message or warning by voice.

  In this way, when an error occurs, the load power generation circuit 32 and the drive power amplifier circuit 36 are not permitted to be turned on, thereby protecting the output circuit (isolator / driver IC 34, etc.) on the drive substrate 20.

  FIG. 4 is a timing chart of signals flowing in the image signal line 18 in the inspection mode. As shown in the preceding part of FIG. 4A, image data corresponding to the selection signal of each piezo actuator 12 is sent during ejection driving (normal driving) in the normal driving mode. At this time, the test mode (TEST_MODE) signal is at the logic “L” level, the switch element 48A of the inspection switching circuit 48 is in the OFF state, and the short circuit inspection circuits (44, 46) do not operate.

  In a state where transmission of image data in the drive mode is stopped, the test mode (inspection mode) is entered at an appropriate timing during the stop. The timing for shifting to the inspection mode may be before the start of driving in the driving mode, or after the operation in the driving mode, such as between print jobs or after printing a certain number of sheets. When the inspection mode is entered, as described in “Step 1”, the power sources of the load power generation circuit 32 and the drive power amplification circuit 36 are turned off. Then, the “test mode signal (TEST_MODE signal)” becomes the active level (H level). When the test mode signal becomes H level, the data of the inspection selection signal on the image signal line 18 becomes valid.

  Thus, in the inspection mode, the signal processing circuit 60 transmits a signal for selecting the short-circuit inspection circuit (44, 46) to the line of the image signal line 18 (which can be said to be a signal for selecting the wiring line to be inspected). In the example of FIG. 4, a signal (logic “L” level signal) for selecting a power supply short circuit inspection is output first, and then a signal (logic “H” level signal) for selecting a signal short circuit inspection is output. However, the order of inspection is not particularly limited and can be changed.

  In this example, the power supply short circuit inspection circuit 44 for inspecting the load power supply line 22 is active at the L level, and the signal short circuit inspection circuit for inspecting the image signal line 18 is active at the H level.

  As shown in FIG. 4B, when the TEST_MODE signal becomes active level, that is, logic “H” level, the data of the monitor selection signal of the image signal line 18 becomes valid, and the monitor selection circuit 42 validates the selection signal. The data is input as data, and the corresponding short circuit inspection circuit is activated.

  By switching the monitor selection signal between high (H) and low (L) while maintaining the TEST_MODE signal at the active level, it is possible to continuously inspect by changing the inspection target. Further, when testing for a plurality of lines, a monitor selection signal is sent for each target line while the TEST_MODE signal is maintained at an active level, and the tests are sequentially performed.

  Next, for each of the power supply short circuit inspection circuit 44 and the signal short circuit inspection circuit 46, the circuit operation until each circuit is activated and short circuit detection is performed will be described.

<Short-circuit inspection of load power line>
FIG. 5 is a principal circuit diagram for explaining the operation of the power supply short-circuit inspection circuit 44.

  In the case of a power supply short circuit inspection, a logic “L” level monitor selection signal (TEST_DATAn) is transmitted from the output of the signal processing circuit 60 (see FIG. 1) (n = 1, 2,...). This monitor selection signal (TEST_DATAn) is applied to the base terminal of the transistor Tr3 of the monitor selection circuit 42.

  When the TEST_MODE signal input to the control terminal of the test switching circuit 48 becomes active (logic “H” level), the transistor Tr8 of the test switching circuit 48 is turned on, and the previous signal input to the monitor selection circuit 42 is turned on. The selection signal (TEST_DATAn) becomes valid (see the timing chart in FIG. 4).

That is, the transistor Tr3 of the monitor selection circuit 42 is turned on by a logic “L” level selection signal (TEST_DATAn) input to the monitor selection circuit 42, and from a power supply (+ V ₄ ) different from the load power supply generation circuit 32. A current flows through the transistor Tr3 to the base of the transistor Tr6 of the power supply short circuit inspection circuit 44. Then, this transistor Tr6 is turned on. Further, when a test mode trigger signal TEST_MODE signal (H level) is input to the test switching circuit 48, the transistor Tr8 is switched on, and the path [7] → [8] → [9] in the figure. Is connected to ground. Thereby, the transistor Tr5 of the power supply short circuit inspection circuit 44 is turned on, and a path ([1] → [2]) through which a current flows from the test power supply voltage (+ V ₃ ) to the load power supply line 22 is formed. Thus starts the power supply short test circuit 44, through the path of [1] → [2] from the test power supply voltage in FIG. 5 (+ V _3), the test supply voltage (+ V ₃₎ is applied to the load power supply line 22.

  That is, when the TEST_MODE signal (H level) is input to the test switching circuit 48, the transistor Tr8 is switched on, and the emitter of the transistor Tr6 of the power supply short circuit testing circuit 44 is connected to the ground. This corresponds to the “activation permission signal” from Further, when the transistor Tr3 of the monitor selection circuit 42 is turned on and a voltage is applied to the base of the transistor Tr6 of the power supply short circuit inspection circuit 44 via the collector of the transistor Tr3, the “power supply short circuit from the monitor selection circuit 42”. This corresponds to receiving the “inspection start signal”.

  If the load power supply line 22 and the image signal line 18 are not short-circuited in the head unit 10, no current flows between the wiring of the load power supply line 22 and the image signal line 18 ([3] → [4]). A predetermined divided voltage determined by resistance division of the resistors R1, R2, and R3 is input to the comparison determination circuit 52 of the short circuit determination circuit 50. In this normal state (no short circuit), the short circuit determination circuit 50 detects a logic “H” level and outputs a non-error signal indicating normal. The determination signal output from the short circuit determination circuit 50 is sent to the control unit 62 described with reference to FIG.

  On the other hand, if the load power supply line 22 and the image signal line 18 are short-circuited in the head unit 10, a current flows between the wirings of the load power supply line 22 and the image signal line 18 ([3] → [4]). Therefore, in the route of the resistor 44C → the transistor Tr6 → the transistor Tr8 → the ground (GND) connected to the image signal line 18 ([5] → [6] → [7] → [8] → [9 ] To reach the GND line 30.

  As a result, the location indicated by [1] (the potential of the emitter of the transistor Tr5) is lower than that in the case where no short circuit occurs. In this case, the short circuit determination circuit 50 detects a logic “L” level and outputs an error signal. Upon receiving this error signal, the control unit 62 prohibits supply of load power to the head unit 10 and prohibits supply of power to the drive power amplifier circuit 36. In the inspection mode, the supply of load power and the supply of drive power are stopped and the inspection is performed. Therefore, when a short circuit abnormality is detected, the supply stop state is continuously maintained.

<Image signal line short circuit inspection>
FIG. 6 is a principal circuit diagram for explaining the operation of the signal short circuit inspection circuit 46.

  In the case of signal short-circuit inspection, a logic “H” level selection signal (TEST_DATAn) is transmitted from the output of the signal processing circuit 60 (see FIG. 1). When the TEST_MODE signal indicating the test mode is input to the control terminal of the test switching circuit 48 (when the TEST_MODE signal becomes active), the previous selection signal (TEST_DATAn) input to the monitor selection circuit 42 becomes valid. . Then, the transistor Tr4 of the monitor selection circuit 42 is turned on, and the transistor Tr8 of the inspection switching circuit 48 is turned on. The route [8] → [9] → [10] in FIG. → [7] → [8] → [9] → [10] Current path is formed.

Thus, the signal short circuit inspection circuit 46 is activated, and a current (test current) flows through the image signal line 18 through the path [1] → [2] from the test power supply voltage (+ V ₃ ) in FIG.

  That is, the fact that the transistor Tr8 of the inspection switching circuit 48 is turned on and the emitter of the transistor Tr4 of the monitor selection circuit 42 is connected to the ground corresponds to the reception of the “activation permission signal” from the inspection switching circuit 48. ing. The monitor selection circuit 42 indicates that the transistor Tr4 of the monitor selection circuit 42 is turned on, the base potential of the transistor Tr7 of the signal short circuit inspection circuit 46 connected to the collector of the transistor Tr4 is lowered, and the transistor Tr7 is switched on. This corresponds to the reception of the “signal short circuit inspection start signal”.

  If the image signal line 18 and the load driving power line 24 are not short-circuited in the head unit 10, a current flows between the wirings of the image signal line 18 and the load driving power line 24 ([3] → [4]). Therefore, a predetermined divided voltage determined by the resistance division of the resistors R1, R2, and R3 is input to the comparison determination circuit 52 of the short circuit determination circuit 50. In this normal state (no short circuit), the short circuit determination circuit 50 detects a logic “H” level and outputs a non-error signal indicating normal. The determination signal output from the short circuit determination circuit 50 is sent to the control unit 62 described with reference to FIG.

  On the other hand, if the image signal line 18 and the load driving power line 24 are short-circuited in the head unit 10, a current flows between both wirings ([3] → [4]). Connected resistor 46C → Transistor Tr4 → Transistor Tr8 → Ground (GND) ([5] → [6] → [7] → [8] → [9] → [10] in FIG. 6) Route) to the GND line 30.

  As a result, the location indicated by [1] (the potential of the emitter of the transistor Tr7) is lower than that in the case where no short circuit occurs. In this case, the short circuit determination circuit 50 detects a logic “L” level and outputs an error signal. Upon receiving this error signal, the control unit 62 prohibits supply of load power to the head unit 10 and prohibits supply of power to the drive power amplifier circuit 36.

  As described above, when an abnormality is detected in one of the power supply short circuit inspection and the signal short circuit inspection, the load power supply and the output of the drive power signal are prohibited, so that the drive circuit can be protected. . Note that if no abnormality is detected in either the power supply short circuit inspection or the signal short circuit inspection, the drive circuit can be operated normally, so that the control unit 62 can shift to the normal mode and discharge operation. It can be performed.

<Short-circuit phenomenon between wires other than FIGS. 5 and 6>
5 illustrates the short circuit inspection between the load power supply line 22 and the image signal line 18, and FIG. 6 illustrates the short circuit inspection between the image signal line 18 and the load driving power line 24. A case where a short circuit has occurred can also be detected in either of FIGS.

  For example, when the load driving power line 24 and the common (COM) line 26 are short-circuited, these two lines are at the same potential. Therefore, if a short-circuit occurs between the image signal line 18 and the common (COM) line 26, As in FIG. 6, a current flows from the image signal line 18 to the ground, and the potential of the image signal line 18 decreases. Therefore, it is possible to detect a short circuit abnormality.

  According to this embodiment, it is possible to transmit the selection signal for the inspection target line using the image signal line 18 which is an existing signal line. Thereby, it is not necessary to newly provide a signal line for a selection signal, and the line can be saved. In addition, it is possible to cope with a small circuit, and the mounting space for the inspection parts can be reduced.

  Since this embodiment employs a voltage conversion type inspection circuit, it can be applied to a floating voltage circuit. A circuit configuration in which an inspection circuit according to the present invention is directly connected to a circuit necessary for a normal ejection driving operation is possible. Further, it is possible to detect a short circuit between the image signal line 18 or the load power supply line and the return path line.

  Furthermore, according to this embodiment, the state of the multi-line driver output lines corresponding to a large number of piezoelectric actuators 12 can be inspected at a time. Therefore, inspection can be performed in a short time, and inspection can be performed by shifting to an inspection mode for each normal print sequence. In addition, regarding the signal lines of these multiple lines, it is possible to determine whether the line is abnormal (hardware related abnormality), data is abnormal (software problem), or the cause of the malfunction.

<Configuration example of inkjet recording apparatus>
A configuration example of an ink jet recording apparatus equipped with the short circuit inspection apparatus described with reference to FIGS. 1 to 6 will be described. FIG. 7 is a configuration diagram of an inkjet recording apparatus 100 equipped with a short-circuit inspection apparatus according to an embodiment of the present invention. In the inkjet recording apparatus 100, a plurality of colors are supplied from inkjet heads 172 M, 172 K, 172 C, and 172 Y to a recording medium 124 (sometimes referred to as “paper” for convenience) held on an impression cylinder (drawing drum 170) of the drawing unit 116. Is an impression cylinder direct drawing type ink jet recording apparatus that forms a desired color image by applying ink droplets of the ink. A treatment liquid (in this case, an aggregating treatment liquid) is applied onto the recording medium 124 before ink ejection. This is an on-demand type image forming apparatus to which a two-liquid reaction (aggregation) method for forming an image on a recording medium 124 by reacting a treatment liquid and an ink liquid is applied.

  As shown in the figure, the ink jet recording apparatus 100 mainly includes a paper feeding unit 112, a treatment liquid application unit 114, a drawing unit 116, a drying unit 118, a fixing unit 120, and a paper discharge unit 122.

(Paper Feeder)
The paper feeding unit 112 is a mechanism that supplies the recording medium 124 to the processing liquid application unit 114, and the recording medium 124 that is a sheet is stacked on the paper feeding unit 112. The paper feed unit 112 is provided with a paper feed tray 150, and the recording medium 124 is fed from the paper feed tray 150 to the processing liquid application unit 114 one by one.

  In the inkjet recording apparatus 100 of this example, a plurality of types of recording media 124 having different paper types and sizes (paper sizes) can be used as the recording medium 124. A mode is also possible in which a plurality of paper trays (not shown) for separately collecting various recording media are provided in the paper feeding unit 112 and the paper to be sent to the paper feeding tray 150 is automatically switched from among the plurality of paper trays. In addition, a mode is also possible in which the operator selects or replaces the paper tray as necessary. 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.

  As shown in FIG. 7, the treatment liquid application unit 114 includes a paper feed cylinder 152, a treatment liquid drum 154, and a treatment liquid application device 156. 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. The tip 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 partially immersed in the processing liquid in the processing liquid container, and the recording medium 124 on the anix roller and the processing liquid drum 154. And a rubber roller that 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 170, a paper holding roller 174, and ink jet heads 172M, 172K, 172C, and 172Y. 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 inkjet heads 172M, 172K, 172C, 172Y.

  The inkjet heads 172M, 172K, 172C, and 172Y are full-line inkjet recording heads (inkjet heads) each having a length corresponding to the maximum width of the image forming area on the recording medium 124. Is formed with a nozzle row in which a plurality of nozzles for ink ejection are arranged over the entire width of the image forming area. Each inkjet head 172M, 172K, 172C, 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).

  The droplets of the corresponding color ink are ejected from the inkjet heads 172M, 172K, 172C, and 172Y toward the recording surface of the recording medium 124 held in close contact with the drawing drum 170, whereby the processing liquid application unit 114 performs the processing. 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. Thereby, 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 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.

  As described above, according to the configuration in which the full line head having the nozzle row covering the entire width of the image forming area of the recording medium 124 is provided for each ink color, the recording medium 124 is conveyed at a constant speed by the drawing drum 170. In this transport direction (sub-scanning direction), the recording medium 124 and each of the inkjet heads 172M, 172K, 172C, and 172Y are moved only once (that is, in one sub-scanning operation). Images can be recorded in 124 image forming areas. Single-pass image formation with such a full-line (page wide) head is a multi-pass with a serial (shuttle) type head that reciprocates in the direction (main scanning direction) orthogonal to the recording medium conveyance direction (sub-scanning direction). High-speed printing is possible as compared with the case where the method is applied, and print productivity can be improved.

  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 colors are used as necessary. Ink may be added. For example, it is possible to add an inkjet head that discharges light-colored ink such as light cyan and light magenta, and the arrangement order of the color heads is not particularly limited.

  Further, the application range of the present invention is not limited to a printing method using a line type head, and a short head that is less than the length in the width direction (main scanning direction) of the recording medium 124 is scanned in the width direction of the recording medium 124. Printing in the width direction is performed, and when printing in one width direction is completed, the recording medium 124 is moved by a predetermined amount in the direction perpendicular to the width direction of the recording medium 124 (sub-scanning direction). A serial method in which printing is performed in the width direction and printing is performed over the entire printing area of the recording medium 124 by repeating this operation may be applied.

(Drying part)
The drying unit 118 is a mechanism for drying moisture contained in the solvent separated by the color material aggregating action, and includes a drying drum 176 and a solvent drying device 178 as shown in FIG.

  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 air volume of the hot air blown toward the recording medium 124 from each hot air ejection nozzle 182 and the temperature of each halogen heater 180.

  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 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 by the inline sensor 190. Inspection 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 nipped at a predetermined nip pressure (for example, 0.15 MPa), and the fixing process is performed.

  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 inkjet recording apparatus 100 includes a UV exposure unit that exposes the ink on the recording medium 124 to UV light instead of the heat-pressure fixing unit (fixing roller 188) using a heat roller.

  The in-line sensor 190 is a measuring unit for measuring a check pattern, a moisture content, a surface temperature, a glossiness, and the like for an image fixed on the recording medium 124, and a CCD line sensor or the like is applied.

(Output section)
As shown in FIG. 7, 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 conveyance belt 196, and a stretching roller 198 are in contact with each other. 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 not shown in the drawing, the ink jet recording apparatus 100 of the present example has an ink storage / loading unit for supplying ink to each of the ink jet heads 172M, 172K, 172C, and 172Y in addition to the above-described configuration, and application of processing liquid. A means for supplying a processing liquid to the unit 114, and a head maintenance unit for cleaning each ink jet head 172M, 172K, 172C, 172Y (wiping, purging, nozzle suction, etc. of the nozzle surface), A position detection sensor for detecting the position of the recording medium 124, a temperature sensor for detecting the temperature of each part of the apparatus, and the like are provided.

<Inkjet head structure>
Next, the structure of the inkjet head will be described. Since the inkjet heads 172M, 172K, 172C, and 172Y corresponding to the respective colors have the same structure, the heads are represented by the reference numeral 250 in the following.

  FIG. 8A is a plan perspective view showing an example of the structure of the head 250, and FIG. 8B is an enlarged view of a part thereof. 9 is a perspective plan view showing another structural example of the head 250, and FIG. 10 is a three-dimensional configuration of one-channel droplet discharge elements (ink chamber units corresponding to one nozzle 251) serving as recording element units. FIG. 9 is a cross-sectional view (a cross-sectional view taken along line AA in FIG. 8).

  As shown in FIG. 8, the head 250 of this example has a matrix of 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 nozzle spacing (projection nozzle pitch) is projected (orthogonally projected) so as to be aligned along the longitudinal direction of the head (direction perpendicular to the paper feed direction). High density is achieved.

  A configuration in which nozzle rows having a length corresponding to the full width Wm of the recording medium 124 are configured in a direction (arrow M direction; main scanning direction) substantially orthogonal to the feeding direction (arrow S direction; sub-scanning direction) of the recording medium 124 It is not limited to this example. For example, instead of the configuration of FIG. 8A, as shown in FIG. 9A, short head modules 250 ′ in which a plurality of nozzles 251 are two-dimensionally arranged are arranged in a staggered manner and connected. Thus, there are a mode in which a line head having a nozzle row having a length corresponding to the full width of the recording medium 124 and a mode in which the head modules 250 ″ are arranged in a row and connected as shown in FIG. 9B.

  The pressure chamber 252 provided corresponding to each nozzle 251 has a substantially square planar shape (see FIGS. 8A and 8B), 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. 10, the head 250 has a structure in which a nozzle plate 251A in which nozzles 251 are formed and a flow path plate 252P in which flow paths such as a pressure chamber 252 and a common flow path 255 are formed are laminated and joined. 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 pressure chambers 252 are two-dimensionally formed.

  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, although shown in FIG. 10 in a simplified manner, the flow path plate 252P has a structure in which one or a plurality of substrates are stacked.

  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 ink supplied from the ink tank is supplied to each pressure chamber 252 via the common flow channel 255.

  Piezo actuator 258 (corresponding to “piezo actuator 12” described in FIG. 1) provided with individual electrode 257 is joined to diaphragm 256 constituting a part of the pressure chamber 252 (the top surface in FIG. 10). ing. The diaphragm 256 of this example is made of silicon (Si) with a nickel (Ni) conductive layer functioning as a common electrode 259 corresponding to the lower electrode of the piezoelectric actuator 258, and is arranged corresponding to each pressure chamber 252. It also serves as a common electrode for the 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 piezo 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. 8B, the ink chamber units 253 having such a structure are arranged in a fixed manner along a row direction along the main scanning direction and an 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 this example 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 the implementation of 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, instead of the matrix array described in FIG. 8, a linear array of lines, a V-shaped nozzle array, and a zigzag (W-shaped) nozzle array having a V-shaped array as a repeating unit. Etc. are also possible.

<Description of control system>
FIG. 11 is a principal block diagram showing the system configuration of the inkjet recording apparatus 100. The inkjet recording apparatus 100 includes a communication interface 270, a system controller 272, a memory 274, a motor driver 276, a heater driver 278, a print control unit 280, an image buffer memory 282, a head driver 284, and the like.

  The communication interface 270 is an interface unit that receives image data sent from the host computer 286. 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. The image data sent from the host computer 286 is taken into the inkjet recording apparatus 100 via the communication interface 270 and temporarily stored in the memory 274.

  The memory 274 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 274 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 inkjet 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 memory 274, the motor driver 276, the heater driver 278, and the like, performs communication control with the host computer 286, read / write control of the memory 274, and the like. Control signals for controlling the motor 288 and the heater 289 are generated.

  The ROM 290 stores various control programs, various parameters, and the like, and the control program is read and executed in accordance with a command from the system controller 272.

  The memory 274 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 276 is a driver that drives the motor 288 in accordance with an instruction from the system controller 272. In FIG. 11, various motors arranged in the respective units in the apparatus are represented by reference numeral 288 as a representative.

  The heater driver 278 is a driver that drives the heater 289 in accordance with an instruction from the system controller 272. In FIG. 11, various heaters arranged in each unit in the apparatus are represented by reference numeral 289.

  The print control unit 280 has a signal processing function for performing various processes and corrections for generating a print control signal from the image data in the memory 274 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 284.

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

  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.

  The required signal processing is performed in the print control unit 280, and the ejection amount and ejection timing of the ink droplets of the head 250 are controlled via the head driver 284 based on the obtained dot data. Thereby, a desired dot size and dot arrangement are realized.

  The print control unit 280 includes an image buffer memory 282, and image data, parameters, and other data are temporarily stored in the image buffer memory 282 when image data is processed in the print control unit 280. Also possible is an aspect in which the print control unit 280 and the system controller 272 are integrated to form a single processor.

  The head driver 284 includes the drive power amplifier circuit 36 and the isolator / driver IC 34, the monitor selection circuit 42, the power supply short circuit inspection circuit 44, the signal short circuit inspection circuit 46, and the like described in FIG. Note that the head driver 284 shown in FIG. 11 may include a feedback control system for keeping the driving condition of the head 250 constant.

  As described with reference to FIG. 1, the inkjet recording apparatus 100 shown in this example applies a common drive power waveform signal to each piezoelectric actuator 258, and applies to the individual electrodes of each piezoelectric actuator 258 according to the ejection timing of each piezoelectric actuator 258. A drive method is employed in which ink is ejected from the nozzles 251 corresponding to the piezoelectric actuators 258 by switching on and off the connected switch elements 14 (see FIG. 1).

  A print control unit 280 in FIG. 11 corresponds to the signal processing circuit 60 described in FIG. 1, and the system controller 272 in FIG. 11 or a combination of this and the print control unit 280 is added to the control unit 62 described in FIG. It corresponds.

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

  DESCRIPTION OF SYMBOLS 10 ... Head unit, 12 ... Piezo actuator, 14 ... Switch element, 16 ... Load control circuit, 18 ... Image signal line, 20 ... Drive board, 22 ... Load power supply line, 24 ... Load drive power line, 26 ... Common line, 32 ... Load power supply generation circuit, 34 ... Isolator / driver IC, 36 ... Drive power amplifier circuit, 40 ... Power supply control circuit, 42 ... Monitor selection circuit, 44 ... Power supply short circuit inspection circuit, 46 ... Signal short circuit inspection circuit, 48 ... Inspection Switching circuit 50 ... Short circuit determination circuit 60 ... Signal processing circuit 62 ... Control unit 100 ... Inkjet recording apparatus 251 ... Nozzle

Claims (15)

A piezoelectric actuator provided corresponding to the nozzle, and a load control circuit that selectively switches driving / non-driving of the piezoelectric actuator, and driving the piezoelectric actuator selected by the load control circuit An inkjet head that ejects droplets from the corresponding nozzle;
A load circuit necessary for driving the piezoelectric actuator, a drive selection signal, and a drive circuit including an electric circuit that outputs drive power to the inkjet head,
A short-circuit inspection apparatus mounted on an inkjet system having a configuration in which an electrical connection between the inkjet head and the drive circuit is a floating connection,
A power generation circuit for supplying the load power to the load control circuit;
A power supply short circuit inspection circuit that is connected to a load power supply line that transmits the load power generated by the power generation circuit to the inkjet head, and performs a short circuit inspection with the load power supply line as an inspection target;
A signal short circuit inspection circuit that is connected to a signal line that transmits the drive selection signal for selecting driving / non-driving of the piezo actuator, and that performs a short circuit inspection on the signal line as an inspection target;
A control circuit for stopping the supply of the load power from the power generation circuit during an inspection mode for performing a short circuit inspection by the power supply short circuit inspection circuit or the signal short circuit inspection circuit;
A monitor selection circuit that selects either the load power supply line or the signal line as an inspection target of the short-circuit inspection in the inspection mode;
In the inspection mode, the monitor selection circuit can be operated, and the power supply short circuit inspection circuit or the signal short circuit inspection circuit can be operated. On the other hand, in the driving mode in which droplets are ejected from the nozzle, the monitor is operated. An inspection switching circuit for making the selection circuit, the power supply short circuit inspection circuit and the signal short circuit inspection circuit inoperable; and
A short circuit determination circuit for connecting a power supply for inspection to the line to be inspected according to selection of the monitor selection circuit at the time of the inspection mode, and detecting a potential on the line to be inspected to determine the presence or absence of a line short circuit;
An inkjet system characterized in that supply of the load power to the inkjet head, transmission of the drive selection signal, and supply of the drive power are stopped when a short circuit is detected by the short circuit determination circuit Short circuit inspection equipment. In claim 1,
The drive circuit includes a drive power amplification circuit that outputs a drive power signal having a voltage waveform for driving the piezoelectric actuator,
A short-circuit inspection apparatus for an ink jet system, wherein a drive waveform voltage output from the drive power amplifier circuit is a reference potential of the load power supply and the drive selection signal. In claim 1 or 2,
The short circuit inspection apparatus for an ink jet system, wherein the control circuit stops power supply to the driving power amplifier circuit in the inspection mode. In claim 3,
The control circuit, when detecting a circuit short-circuit by the short-circuit determination circuit, stops the output of the power generation circuit and stops the power supply of the drive power amplifier circuit, apparatus. In any one of Claims 1 thru | or 4,
The inspection switching circuit outputs a start permission signal for permitting start of the power supply short circuit inspection circuit and the signal short circuit inspection circuit based on an input of a trigger signal indicating transition to the inspection mode, and the monitor selection circuit A short circuit inspection apparatus for an ink jet system, characterized in that a wiring line into which a current flows from a line to be inspected according to selection due to a short circuit is switched and connected to a ground of the drive circuit. In any one of Claims 1 thru | or 5,
A signal processing circuit for generating a signal for selecting driving / non-driving of the piezoelectric actuator, and the drive selection signal is generated by voltage-converting the signal output from the signal processing circuit; The circuit selectively activates the power supply short circuit inspection circuit or the signal short circuit inspection circuit as a signal for selecting either the load power supply line or the signal line to be inspected for the short circuit inspection in the inspection mode. Generate a monitor selection signal for
The short circuit inspection apparatus for an ink jet system, wherein the monitor selection signal is input to the monitor selection circuit using a signal line for transmitting a signal for selecting driving / non-driving of the piezoelectric actuator.
A short-circuit inspection apparatus for an inkjet system, wherein the signal is transmitted to the monitor selection circuit using the signal line for transmitting the drive selection signal. In claim 6,
The monitor selection signal has a high (H) level for selectively starting one of the power supply short circuit inspection circuit and the signal short circuit inspection circuit, and a low (L) level for selectively starting the other short circuit inspection circuit. A short circuit inspection apparatus for an ink jet system, characterized by being a logic binary signal. In claim 6 or 7,
An ink jet comprising a plurality of signal lines, wherein different monitor selection signals are transmitted to the one line to be inspected and the other lines among the plurality of lines, and individual lines can be inspected. System short circuit inspection device. In any one of Claims 6 thru | or 8,
The monitor selection circuit includes the power supply short-circuit inspection circuit or the short-circuit inspection circuit according to the monitor selection signal in accordance with a start permission signal for permitting start-up of the power supply short-circuit inspection circuit and the signal short-circuit inspection circuit from the inspection switching circuit. A short-circuit inspection device for an ink jet system, In claim 9,
The power supply short circuit inspection circuit receives a power supply short circuit inspection start signal from the monitor selection circuit by a start permission signal from the inspection switching circuit,
The signal line is switch-connected to the inspection switching circuit, the signal line is connected to the ground of the drive circuit via the inspection switching circuit, and the inspection power supply is switch-connected to the load power supply line. Short-circuit inspection device for inkjet system. In claim 9 or 10,
The drive circuit has a load drive power line for transmitting a drive power signal having a voltage waveform for driving the piezoelectric actuator to the inkjet head,
The signal short circuit inspection circuit receives the signal short circuit inspection start signal from the monitor selection circuit by the start permission signal from the inspection switching circuit,
The load driving power line is switched to the inspection switching circuit, the load driving power line is connected to the ground of the driving circuit via the inspection switching circuit, and the inspection power supply is switched to the signal line. A short-circuit inspection device for an inkjet system characterized by the following. In any one of Claims 1 thru | or 11,
A short-circuit inspection apparatus for an ink jet system, wherein an isolator / driver IC is used as a transmission circuit for outputting the drive selection signal to the ink jet head via the signal line. In any one of Claims 1 thru | or 12,
The short circuit determination circuit applies a test voltage from the inspection power source to the inspection target line in the inspection mode, compares the potential on the line with a threshold value, determines the presence or absence of a line short circuit, and the determination result A short-circuit inspection apparatus for an ink jet system, characterized in that In claim 13,
The short-circuit inspection apparatus for an ink jet system, wherein the voltage application of the inspection power supply is set to be equal to or less than a rated current in a transmission circuit output of the line to be inspected. In claim 13 or 14,
The short-circuit inspection of an ink jet system, wherein the threshold value for comparing the potential on the inspection target line is divided by a resistor with reference to the ground from the voltage of the inspection power supply applied to the line apparatus.

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