JP2008087355A - Inkjet drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet drive device capable of reducing variation in ink ejection amount and consumption power. <P>SOLUTION: This inkjet device makes D/A conversion of data D0-D7 for setting the ink ejection amount of a corresponding channel at a prescribed value to analogue voltage Va, and the analogue voltage Va is amplified to form a control voltage Vch. The control voltage Vch is added to a reference voltage Vs to form a drive voltage Vchs, and then a piezoelectric element 4 is driven by the drive voltage Vchs. As the drive voltage Vchs is divided into the control voltage Vch and the constant reference voltage Vs and only the control voltage Vch is controlled, it is possible to reduce the consumption power of an operation amplifier 12 compared with the case where the drive voltage Vchs is directly controlled. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inkjet drive device, and more particularly to an inkjet drive device that drives an inkjet head.

2. Description of the Related Art Conventionally, in an inkjet apparatus, a piezoelectric element that is a capacitive load is charged and discharged to expand and contract the piezoelectric element, and ink is ejected by an ejection pressure generated thereby (see, for example, Patent Documents 1 and 2).
JP-A-11-170529 JP-A-11-314364

  However, the conventional ink jet apparatus has a problem that the amount of ink discharged varies between apparatuses and between channels due to variations in characteristics of the ink jet head.

  As a countermeasure, a driving voltage necessary for ejecting a predetermined amount of ink is obtained in advance for each channel, the driving voltage is generated in the apparatus, and the piezoelectric element is charged / discharged with the generated driving voltage. There is. However, this method has a problem that the power consumption of the drive voltage generation circuit increases.

  Therefore, a main object of the present invention is to provide an ink jet driving apparatus with small variations in ink discharge amount and low power consumption.

  An inkjet drive device according to the present invention is an inkjet drive device that drives an inkjet head. An adjustment voltage generation circuit that generates an adjustment voltage for adjusting an ink discharge amount of the inkjet head to a predetermined value, and an adjustment voltage are predetermined. A drive voltage generating circuit for generating a drive voltage in addition to the reference voltage, and a charge / discharge circuit for charging / discharging the piezoelectric element of the inkjet head in response to the drive voltage.

  Preferably, the adjustment voltage generation circuit includes a storage circuit that stores data for generating the adjustment voltage, a D / A conversion circuit that converts the data stored in the storage circuit into an analog voltage, and a D / A conversion circuit And an amplifier circuit that amplifies the output voltage and outputs a regulated voltage.

  Preferably, the drive voltage generation circuit includes a first capacitor, a second capacitor having one electrode connected to the output node of the drive voltage generation circuit and the other electrode receiving the reference voltage, and the first period And a switching circuit that applies a regulated voltage between the terminals of the first capacitor, and a second period includes a voltage between the terminals of the first capacitor between the terminals of the second capacitor.

  Preferably, the inkjet head has a plurality of channels, and the adjustment voltage generation circuit is provided corresponding to each channel and generates an adjustment voltage for adjusting the ink discharge amount of the corresponding channel to a predetermined value. The drive voltage generation circuit is provided corresponding to each channel and generates a drive voltage by adding a corresponding adjustment voltage to the reference voltage. The charge / discharge circuit is provided corresponding to each channel and generates a corresponding drive voltage. The piezoelectric element of the corresponding channel is charged and discharged.

  In the ink jet drive device according to the present invention, an adjustment voltage generating circuit for generating an adjustment voltage for adjusting the ink discharge amount of the ink jet head to a predetermined value, and generating the drive voltage by adding the adjustment voltage to a predetermined reference voltage And a driving voltage generating circuit. Therefore, since the drive voltage is divided into the adjustment voltage and the constant reference voltage and only the adjustment voltage is adjusted, power consumption can be reduced as compared with the case where the entire drive voltage is adjusted.

  FIG. 1 is a block diagram showing a main part of an ink jet apparatus according to an embodiment of the present invention. In FIG. 1, the ink jet apparatus includes a memory circuit 1, a control circuit 2, a plurality of drive circuits 3, and a plurality of piezoelectric elements 4. This ink jet apparatus includes an ink jet head having a plurality of channels, and the piezoelectric element 4 is provided in each channel. When the piezoelectric element 4 expands and contracts, an ejection pressure is generated thereby, and ink is ejected from the nozzle of the corresponding channel.

  In such an ink jet apparatus, since the drive voltage-discharge amount characteristics of a plurality of channels vary, different amounts of ink are discharged from the plurality of channels when the same drive voltage is applied to the plurality of piezoelectric elements 4. Therefore, the ink discharge amounts of the plurality of channels are made uniform as follows.

  First, for each channel, a drive voltage-discharge amount characteristic indicating the relationship between the drive voltage and the ink discharge amount is obtained, and based on the obtained characteristic, in order to discharge the same predetermined amount of ink from a plurality of channels, the piezoelectric of each channel A drive voltage to be applied to the element 1 is obtained. The ink discharge amount is measured by, for example, “WYKO NT3300 surface shape roughness meter measuring device”.

  Next, the drive voltage Vchs of each channel is divided into a reference voltage Vs and an adjustment voltage Vch. However, Vs> Vch. For example, the number of channels is 5, and the drive voltages Vchs required to eject the same predetermined amount of ink from the 5 channels are 18.5V, 18.3V, 17.8V, 18.0V, and 17.9V, respectively. Then, the reference voltage Vs is set to 15V, and the adjustment voltages Vch of the five channels are set to 3.5V, 3.3V, 2.8V, 3.0V, and 2.9V, respectively. Next, the adjustment voltages Vch for a plurality of channels are converted into a plurality of data codes and stored in the storage circuit 1. The data code includes, for example, 8-bit data D0 to D7.

  The control circuit 2 reads a plurality of data codes from the storage circuit 1 and gives the read data codes to the plurality of drive circuits 3 respectively. The drive circuit 3 generates a drive voltage Vchs according to the data code given from the control circuit 2 and applies the generated drive voltage Vchs to the corresponding piezoelectric element 4 in a pulsed manner. In this way, the same predetermined amount of ink is ejected from a plurality of channels.

  FIG. 2 is a circuit block diagram showing the configuration of the drive circuit 3. In FIG. 2, the drive circuit 3 includes a D / A conversion circuit 10, an amplifier circuit 11, a drive voltage generation circuit 15, a reference voltage generation circuit 21, a charge / discharge circuit 22, and an output terminal 27. The D / A conversion circuit 10 converts the data D0 to D7 read from the storage circuit 1 and applied from the control circuit 2 into an analog voltage Va.

  The amplifier circuit 11 includes an operational amplifier 12 and resistance elements 13 and 14, and amplifies the analog voltage Va with a predetermined amplification factor (for example, 2 times) and outputs a regulated voltage Vch (for example, 3.0 V). The amplification factor A of the amplifier circuit 11 is A = 1 + (R13 / R14) when the resistance values of the resistance elements 13 and 14 are R13 and R14, respectively.

  Reference voltage generation circuit 21 outputs a predetermined reference voltage Vs (for example, 15.0 V). Drive voltage generation circuit 15 includes a diode 16, capacitors 17 and 18, a P channel MOS transistor 19, and an N channel MOS transistor 20. The anode of the diode 16 is connected to the output node N12 of the operational amplifier 12 and the cathode thereof is connected to the power supply node N22 of the charge / discharge circuit 22. Capacitor 17 and N channel MOS transistor 20 are connected in series between node N12 and the line of ground voltage GND. Capacitor 18 and P channel MOS transistor 19 are connected in series between node N22 and the drain of N channel MOS transistor 20 (node N19). A reference voltage Vs is applied to the source (node N18) of the P-channel MOS transistor 19. The gates of transistors 19 and 20 both receive control signal φ1 from control circuit 2.

  When control signal φ1 is at “H” level, transistor 19 is turned off, transistor 20 is turned on, and capacitor 17 is charged to adjustment voltage Vch. When the control signal φ1 falls to the “L” level, the transistor 20 is turned off and the transistor 19 is turned on, a current flows from the capacitor 17 to the capacitor 18 via the diode 16, and the voltage across the terminals of the capacitor 18 is adjusted. Vch. When control signal φ1 rises to the “H” level, transistor 19 is turned off and transistor 20 is turned on, and the voltage at power supply node N22 is obtained by adding the voltage across terminals of capacitor 18, that is, adjustment voltage Vch, to reference voltage Vs. Drive voltage Vchs.

  Charge / discharge circuit 22 includes a P-channel MOS transistor 23, an N-channel MOS transistor 24, and diodes 25 and 26. P channel MOS transistor 23 is connected between power supply node N22 and output terminal 27, and N channel MOS transistor 24 is connected between output terminal 27 and the line of ground voltage GND. The gates of transistors 23 and 24 both receive control signal φ2 from control circuit 2. Diode 25 is connected between output terminal 27 and power supply node N 22, and diode 26 is connected between the ground voltage GND line and output terminal 27. The diodes 25 and 26 protect the transistors 23 and 24 from an excessive voltage generated at the output terminal 27. The piezoelectric element 4 is connected between the output terminal 27 and the ground voltage GND line.

  When control signal φ2 falls to “L” level, transistor 24 is turned off and transistor 23 is turned on, and current flows from power supply node N22 to piezoelectric element 4 via transistor 23 and output terminal 27. 4 is charged and stretched. When the control signal φ2 rises to the “H” level, the transistor 23 is turned off and the transistor 24 is turned on, and a current flows from the piezoelectric element 4 through the output terminal 27 and the transistor 24 to the ground voltage GND line. The piezoelectric element 4 is discharged and contracts.

  Next, the operation of the ink jet apparatus shown in FIGS. 1 and 2 will be briefly described. A plurality of data codes for ejecting the same amount of ink from a plurality of channels are read from the storage circuit 1, and the plurality of read data codes are respectively supplied to the plurality of drive circuits 3 via the control circuit 2. . Data D0 to D7 included in the data code are converted into the analog voltage Va by the D / A conversion circuit 10, and the analog voltage Va is amplified to the adjustment voltage Vch by the amplifier circuit 11.

  The adjustment voltage Vch is added to the reference voltage Vs by the drive voltage generation circuit 15 to generate the drive voltage Vchs. The charge / discharge circuit 22 repeats the operation of charging the piezoelectric element 4 to the drive voltage Vchs and the operation of discharging the piezoelectric element 4 to the ground voltage GND to discharge ink. In this way, the same amount of ink is ejected from a plurality of channels.

  FIG. 3 is a circuit block diagram showing a comparative example of this embodiment, and is a diagram to be compared with FIG. In FIG. 3, the drive circuit 30 includes a D / A conversion circuit 31, an amplifier circuit 32, a capacitor 36, a charge / discharge circuit 37, and an output terminal 38. In this comparative example, the drive voltage Vchs is not divided into the adjustment voltage Vch and the reference voltage Vs. The storage circuit 1 stores a plurality of data codes indicating a plurality of drive voltages Vchs for ejecting the same amount of ink from a plurality of channels. The data code includes, for example, 12-bit data D0 to D11.

  The D / A conversion circuit 31 converts data D0 to D11 included in the data code read from the storage circuit 1 and supplied from the control circuit 2 into an analog voltage Va. The amplifier circuit 32 includes an operational amplifier 33 and resistance elements 34 and 35, amplifies the analog voltage Va with a predetermined amplification factor (for example, 5 times), and outputs a drive voltage Vchs (for example, 18.0V). The amplification factor A of the amplifier circuit 32 is A = 1 + (R34 / R35) when the resistance values of the resistance elements 34 and 35 are R34 and R35, respectively.

  The capacitor 36 is connected between the output node N33 of the operational amplifier 33 and the line of the ground voltage GND, and is charged to the drive voltage Vchs. The charge / discharge circuit 37 is the same circuit as the charge / discharge circuit 22 of FIG. 2, and when the control signal φ2 is at “H” level, the piezoelectric element 4 is charged to the drive voltage Vchs via the output terminal 38, and the control signal φ2 When is at the “L” level, the piezoelectric element 4 is discharged to the ground voltage GND. Therefore, even when this drive circuit 30 is used, the same amount of ink can be ejected from a plurality of channels.

  The driving circuit 3 in FIG. 2 differs from the driving circuit 30 in FIG. 3 in the power consumption of the operational amplifiers 12 and 33. Here, the power consumption of the operational amplifier will be described. As shown in FIG. 4, the power supply voltage V1 is applied to the positive power supply terminal 40a of the operational amplifier 40, the power supply voltage V2 is applied to the negative power supply terminal 40b, and the voltage Vo and current Io are output from the output terminal 40c. It is assumed that the circuit current Icc flows through the operational amplifier 40 itself. At this time, the power consumption Pt of the operational amplifier 40 is the sum of the power consumption Icc × (V1−V2) for the circuit current Icc and the power consumption Io × (V1−Vo) for the output current Io.

  In the operational amplifier 33 of the comparative example, as shown in FIG. 5, if V1 = + 30V, V2 = 0V, Vo = + 20V, Io = + 10mA, Icc = 1mA, the power consumption for the circuit current is 1mA × (30V-0V). = 30 mW, the power consumption for the output current is 10 mA × (30V-20V) = 100 mW, and the total power consumption is 30 mW + 100 mW = 130 mW.

  On the other hand, in the operational amplifier 12 of the embodiment, as shown in FIG. 6, the circuit current Icc is the same as that in the comparative example, but the output voltage Vo is lowered to 5V, so the power supply voltage V1 is lowered to + 10V. Since V1-Vo is ½ of the comparative example, the output current Io can be halved. Therefore, V1 = + 10 V, V2 = 0 V, Vo = + 5 V, Io = + 5 mA, Icc = 1 mA, the power consumption for the circuit current is 1 mA × (10 V−0 V) = 10 mW, and the power consumption for the output current is 5 mA × (10V-5V) = 25 mW, and the total power consumption is 10 mW + 25 mW = 35 mW. Therefore, the power consumption of the operational amplifier 12 of the embodiment is about ¼ of the power consumption of the operational amplifier 33 of the comparative example.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a block diagram which shows the principal part of the inkjet apparatus by one Embodiment of this invention. FIG. 2 is a circuit block diagram illustrating a configuration of a drive circuit illustrated in FIG. 1. It is a circuit block diagram which shows the comparative example of this embodiment. It is a figure for demonstrating generally the power consumption of an operational amplifier. It is a figure for demonstrating the power consumption of the operational amplifier shown in FIG. It is a figure for demonstrating the power consumption of the operational amplifier shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Memory circuit, 2 Control circuit, 3,30 Drive circuit, 4 Piezoelectric element, 10,31 D / A converter circuit, 11,32 Amplifier circuit, 12,33,40 Operational amplifier, 13,14,34,35 Resistance element, 15 drive voltage generating circuit, 16, 25, 26 diode, 17, 18, 36 capacitor, 19, 23 P channel MOS transistor, 20, 24 N channel MOS transistor, 21 reference voltage generating circuit, 22, 37 charge / discharge circuit, 27 , 38 Output terminal.

Claims (4)

In an inkjet drive device that drives an inkjet head,
An adjustment voltage generating circuit for generating an adjustment voltage for adjusting the ink discharge amount of the inkjet head to a predetermined value;
A drive voltage generation circuit for generating a drive voltage by adding the adjustment voltage to a predetermined reference voltage;
An ink jet drive apparatus comprising: a charge / discharge circuit that receives the drive voltage and charges / discharges a piezoelectric element of the ink jet head. The adjustment voltage generation circuit includes:
A storage circuit for storing data for generating the adjustment voltage;
A D / A conversion circuit for converting data stored in the storage circuit into an analog voltage;
The inkjet driving apparatus according to claim 1, further comprising: an amplification circuit that amplifies an output voltage of the D / A conversion circuit and outputs the adjustment voltage. The drive voltage generation circuit includes:
A first capacitor;
A second capacitor having one electrode connected to the output node of the drive voltage generating circuit and the other electrode receiving the reference voltage;
A switching circuit that applies the adjustment voltage between the terminals of the first capacitor during the first period and supplies a voltage between the terminals of the first capacitor during the second period. The ink jet driving apparatus according to claim 1, wherein the ink jet driving apparatus is provided. The inkjet head has a plurality of channels,
The adjustment voltage generation circuit is provided corresponding to each channel and generates the adjustment voltage for adjusting the ink ejection amount of the corresponding channel to a predetermined value.
The drive voltage generation circuit is provided corresponding to each channel and generates a drive voltage by adding a corresponding adjustment voltage to the reference voltage,
The charge / discharge circuit is provided corresponding to each channel, receives a corresponding drive voltage, and charges / discharges the piezoelectric element of the corresponding channel. The ink jet drive device described in 1.

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