JP2021006393A - Liquid discharge device and temperature detection method - Google Patents

Abstract

To provide a liquid discharge device which can be simplified in circuit configuration although having an advantage that a temperature abnormality of a print head can be detected with high accuracy.SOLUTION: A liquid discharge device includes a print head which discharges liquid. The print head has a fluctuation voltage signal output circuit for outputting a fluctuation voltage signal whose voltage value fluctuates by depending on temperature, a stable voltage signal output circuit for outputting a stable voltage signal of the stable voltage value without depending on temperature, a reference voltage signal output circuit for outputting a reference voltage signal which adjusts the voltage value of the stable voltage signal, and a temperature abnormality signal output circuit for outputting a temperature abnormality signal indicating the presence or absence of a temperature abnormality of the print head. The reference voltage signal output circuit adjusts the voltage value of the stable voltage signal on the basis of a voltage value of the fluctuation voltage signal at a prescribed temperature so as to output the reference voltage signal. The temperature abnormality signal output circuit outputs the temperature abnormality signal on the basis of the fluctuation voltage signal and the reference voltage signal.SELECTED DRAWING: Figure 11

Description

The present invention relates to a liquid discharge device and a temperature detection method.

An inkjet printer (liquid ejection device) that ejects ink as a liquid to print an image or a document is known to use a piezoelectric element such as a piezo element. In such an inkjet printer, the piezoelectric element is provided corresponding to each of a plurality of nozzles in the print head. Then, when the drive signal is supplied to the piezoelectric elements at a predetermined timing, each piezoelectric element is driven, a predetermined amount of ink is ejected from the nozzle, and an image or a document is formed on the print medium.

In such an inkjet printer, when an abnormality occurs in the temperature of the print head, the physical characteristics of the ink change and the ejection accuracy deteriorates. Therefore, a configuration is used in which the temperature of the print head is detected and whether or not a temperature abnormality has occurred in the print head is determined based on the detected temperature.

For example, Patent Document 1 discloses a liquid discharge device equipped with a temperature detection method capable of detecting the temperature of a print head using a clock signal.

Japanese Unexamined Patent Publication No. 2014-076593

However, the temperature detection method described in Patent Document 1 has an advantage that it is possible to detect a temperature abnormality of the print head with high accuracy, but there is room for improvement in terms of simplifying the circuit configuration. there were.

One aspect of the liquid discharge device according to the present invention is
Equipped with a print head that discharges liquid
The print head
A fluctuating voltage signal output circuit that outputs a fluctuating voltage signal whose voltage value fluctuates depending on the temperature,
A stable voltage signal output circuit that outputs a stable voltage signal with a stable voltage value regardless of temperature,
A reference voltage signal output circuit that outputs a reference voltage signal in which the voltage value of the stable voltage signal is adjusted, and
A temperature abnormality signal output circuit that outputs a temperature abnormality signal indicating the presence or absence of a temperature abnormality of the print head, and
Have,
The reference voltage signal output circuit outputs the reference voltage signal by adjusting the voltage value of the stable voltage signal based on the voltage value of the fluctuating voltage signal at a predetermined temperature.
The temperature abnormality signal output circuit outputs the temperature abnormality signal based on the fluctuation voltage signal and the reference voltage signal.

In one aspect of the liquid discharge device,
The fluctuating voltage signal may have a negative temperature characteristic in which the voltage value decreases as the temperature rises.

In one aspect of the liquid discharge device,
The stable voltage signal output circuit may be a bandgap reference circuit.

In one aspect of the liquid discharge device,
The reference voltage signal output circuit includes an amplifier circuit and an amplification factor adjustment circuit.
The amplifier factor adjusting circuit adjusts the amplification factor in the amplifier circuit,
The amplifier circuit may output the reference voltage signal by amplifying the voltage value of the stable voltage signal based on the amplification factor adjusted by the amplification factor adjusting circuit.

In one aspect of the liquid discharge device,
The reference voltage output circuit includes a fuse.
The amplification factor may be adjusted depending on whether or not the fuse is blown.

In one aspect of the liquid discharge device,
A plurality of the printheads including the first printhead and the second printhead are provided.
The first printhead outputs a first temperature abnormality signal based on the first fluctuating voltage signal as the fluctuating voltage signal and the first reference voltage signal adjusted by adjusting the first stable voltage signal as the stable voltage signal. It has a first temperature abnormality signal output circuit to output,
The second printhead outputs a second temperature abnormality signal based on the second fluctuating voltage signal as the fluctuating voltage signal and the second reference voltage signal adjusted by adjusting the second stable voltage signal as the stable voltage signal. It has a second temperature abnormality signal output circuit to output,
The adjusted value of the first stable voltage signal for outputting the first reference voltage signal in the first printhead and the second stable voltage for outputting the second reference voltage signal in the second printhead. It may be different from the adjustment value of the signal.

One aspect of the temperature detection method according to the present invention is
A method for detecting the temperature of a liquid discharge device equipped with a first print head for discharging a liquid.
The process of outputting a fluctuating voltage signal whose voltage value fluctuates depending on the temperature,
The process of outputting a stable voltage signal with a stable voltage value regardless of temperature,
A step of outputting a reference voltage signal by adjusting the stable voltage signal based on the voltage value of the fluctuating voltage signal at a predetermined temperature.
A step of outputting an abnormal temperature signal based on the fluctuating voltage signal and the reference voltage signal, and
including.

It is a figure which shows the schematic structure of the liquid discharge device. It is a block diagram which shows the electrical structure of a liquid discharge device. It is a figure which shows the schematic structure of one of a plurality of discharge parts. It is a figure which shows an example of the waveform of the drive signal COM. It is a figure which shows an example of the waveform of the drive signal VOUT. It is a figure which shows the structure of the drive signal selection circuit. It is a figure which shows the decoding content in a decoder. It is a figure which shows the structure of the selection circuit corresponding to one discharge part. It is a figure for demonstrating operation of a drive signal selection circuit. It is a figure which shows the structure of the temperature abnormality detection circuit. It is a figure which shows the structure of the reference voltage output circuit. It is a figure which shows the decoding content in a decoder. It is a figure which shows the equivalent circuit of the non-inverting amplifier circuit. It is a figure which shows the relationship between the resistors Ra, Rb and the resistors R0-R8 corresponding to the switching information. It is a figure for demonstrating the adjustment method of the amplification factor in the temperature abnormality detection circuit, and the temperature detection method which outputs the temperature abnormality signal XHOT. It is a figure for demonstrating the detail of step S140.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The drawings used are for convenience of explanation. It should be noted that the embodiments described below do not unreasonably limit the contents of the present invention described in the claims. Moreover, not all of the configurations described below are essential constituent requirements of the present invention.

1. 1. Overview of the liquid discharge device FIG. 1 is a diagram showing a schematic configuration of the liquid discharge device 1. In the liquid ejection device 1, a carriage 20 on which a head unit 21 for ejecting ink as an example of a liquid is mounted reciprocates to eject ink to a medium P to be conveyed, thereby producing an image with respect to the medium P. It is a serial printing type inkjet printer that forms the above. In the following description, the direction in which the carriage 20 moves is the X direction, the direction in which the medium P is conveyed is the Y direction, and the direction in which the ink is ejected is the Z direction. The X, Y, and Z directions will be described as being orthogonal to each other. Further, as the medium P, any printing target such as printing paper, resin film, or cloth can be used.

The liquid discharge device 1 includes a liquid container 2, a control mechanism 10, a carriage 20, a moving mechanism 30, and a transport mechanism 40.

The liquid container 2 stores a plurality of types of ink to be ejected to the medium P. Examples of the color of the ink stored in the liquid container 2 include black, cyan, magenta, yellow, red, and gray. As the liquid container 2 in which such ink is stored, an ink cartridge, a bag-shaped ink pack made of a flexible film, an ink tank capable of replenishing ink, and the like are used.

The control mechanism 10 includes, for example, a processing circuit such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array) and a storage circuit such as a semiconductor memory, and controls each element of the liquid discharge device 1.

A head unit 21 is mounted on the carriage 20. Further, the carriage 20 is fixed to the endless belt 32 included in the moving mechanism 30. The liquid container 2 may also be mounted on the carriage 20.

A control signal Ctrl-H for controlling the head unit 21 output by the control mechanism 10 and one or a plurality of drive signal COMs for driving the head unit 21 are input to the head unit 21. Then, the head unit 21 ejects the ink supplied from the liquid container 2 based on the control signal Ctrl-H and the drive signal COM.

The moving mechanism 30 includes a carriage motor 31 and an endless belt 32. The carriage motor 31 operates based on the control signal Ctrl-C input from the control mechanism 10. The endless belt 32 rotates according to the operation of the carriage motor 31. As a result, the carriage 20 fixed to the endless belt 32 reciprocates in the X direction.

The transport mechanism 40 includes a transport motor 41 and a transport roller 42. The transfer motor 41 operates based on the control signal Ctrl-T input from the control mechanism 10. The transfer roller 42 rotates according to the operation of the transfer motor 41. The medium P is conveyed in the Y direction as the transfer roller 42 rotates.

As described above, the liquid ejection device 1 ejects ink from the head unit 21 mounted on the carriage 20 in conjunction with the conveying of the medium P by the conveying mechanism 40 and the reciprocating movement of the carriage 20 by the moving mechanism 30. , The ink is landed at an arbitrary position on the surface of the medium P to form a desired image on the medium P.

2. 2. Electrical configuration of the liquid discharge device FIG. 2 is a block diagram showing an electrical configuration of the liquid discharge device 1. The liquid discharge device 1 includes a control mechanism 10, a head unit 21, a carriage motor 31, a transfer motor 41, and a linear encoder 90.

The control mechanism 10 includes a drive signal output circuit 50, a control circuit 100, and a power supply circuit 110. The control circuit 100 includes a processor such as a microcontroller, for example. Then, the control circuit 100 generates and outputs data and various signals for controlling the liquid discharge device 1 based on various signals such as image data input from the host computer.

Specifically, the control circuit 100 grasps the scanning position of the head unit 21 based on the detection signal input from the linear encoder 90. Then, the control circuit 100 generates and outputs various signals according to the scanning position of the head unit 21. Specifically, the control circuit 100 generates a control signal Ctrl-C for controlling the reciprocating motion of the head unit 21 and outputs it to the carriage motor 31. Further, the control circuit 100 generates a control signal Ctrl-T for controlling the transfer of the medium P, and outputs the control signal Ctrl-T to the transfer motor 41. The control signal Ctrl-C may be input to the carriage motor 31 after being signal-converted via a carriage motor driver (not shown). Similarly, the control signal Ctrl-T is a transport motor driver (not shown). After the signal is converted via the above, the signal may be input to the transfer motor 41.

Further, the control circuit 100 uses the print data signal SI1 as a control signal Clock-H for controlling the head unit 21 based on various signals such as image data input from the host computer and the scanning position of the head unit 21. ~ SIn, change signal CH, latch signal LAT, and clock signal SCK are generated and output to the head unit 21.

Further, the control circuit 100 outputs a drive control signal dA, which is a digital signal, to the drive signal output circuit 50.

The drive signal output circuit 50 includes a drive circuit 50a. The drive control signal dA is input to the drive circuit 50a. The drive circuit 50a converts the drive control signal dA into a digital / analog signal, and then amplifies the converted analog signal to class D to generate a drive signal COM. That is, the drive control signal dA is a digital signal that defines the waveform of the drive signal COM, and the drive circuit 50a generates the drive signal COM by amplifying the waveform defined by the drive control signal dA in class D. That is, the drive signal output circuit 50 outputs the drive signal COM generated by the drive circuit 50a. Therefore, the drive control signal dA may be any signal that can define the waveform of the drive signal COM, and for example, the drive control signal dA may be an analog signal. The drive circuit 50a may be configured by a class A amplification circuit, a class B amplification circuit, a class AB amplification circuit, or the like, as long as the waveform defined by the drive control signal dA can be amplified.

Further, the drive signal output circuit 50 outputs a reference voltage signal CGND indicating a reference potential of the drive signal COM. The reference voltage signal CGND may be, for example, a ground potential signal having a voltage value of 0 V, or a DC voltage signal having a voltage value of 6 V or the like.

The drive signal COM and the reference voltage signal CGND are branched by the control mechanism 10 and then output to the head unit 21. Specifically, the drive signal COM is branched into n drive signals COM1 to COMn corresponding to each of the n drive signal selection circuits 200 described later in the control mechanism 10, and then output to the head unit 21. .. Similarly, the reference voltage signal CGND is branched into n reference voltage signals CGND1 to CGNDn by the control mechanism 10 and then output to the head unit 21. Here, the drive signal output circuit 50 may include n drive circuits 50a corresponding to each of the n drive signals COM1 to COMn, and in this case, the control circuit 100 may include n drive circuits 50a. You may output n drive control signals dA for each of.

The power supply circuit 110 generates and outputs voltages VHV, VDD, and ground signals GND. The voltage VHV is a DC voltage signal having a voltage value of, for example, 42 V. Further, the voltage VDD is a signal of a DC voltage having a voltage value of, for example, 3.3 V. The ground signal GND is a signal indicating a reference potential of voltages VHV and VDD, and is, for example, a signal having a ground potential having a voltage value of 0 V. The voltage VHV is used as a voltage for amplification in the drive signal output circuit 50 or the like. Further, the voltage VDD is used for the power supply voltage, the control voltage, and the like of various configurations in the control mechanism 10. The voltages VHV, VDD, and ground signal GND are also output to the head unit 21. The voltage values of the voltages VHV, VDD, and ground signal GND are not limited to the above-mentioned 42V, 3.3V, and 0V. Further, the power supply circuit 110 may generate signals having a plurality of voltage values other than the voltages VHV, VDD, and the ground signal GND.

The head unit 21 includes print heads 22-1 to 22-n. Each of the print heads 22-1 to 22-n includes a drive signal selection circuit 200-1 to 200-n, a temperature abnormality detection circuit 250-1 to 250-n, and a plurality of discharge units 600.

Voltages VHV, VDD, corresponding drive signals COM1 to COMn, corresponding print data signals SI1 to SIn, clock signal SCK, latch signal LAT, and change signal CH are used in each of the drive signal selection circuits 200-1 to 200-n. Is entered. The voltages VHV and VDD are used as the respective power supply voltages of the drive signal selection circuits 200-1 to 200-n and the voltages for generating various control signals. Each of the drive signal selection circuits 200-1 to 200-n selects or does not select the drive signals COM1 to COMn based on the input print data signals SI1 to SIn, clock signal SCK, latch signal LAT, and change signal CH. By doing so, drive signals VOUT1 to VOUTn are generated.

The drive signals VOUT1 to VOUTn generated by each of the drive signal selection circuits 200-1 to 200-n are supplied to the piezoelectric element 60, which is an example of the drive element included in the corresponding discharge unit 600. The piezoelectric element 60 is displaced by being supplied with drive signals VOUT1 to VOUTn. Then, an amount of ink corresponding to the displacement is ejected from the ejection unit 600.

Specifically, the drive signal COM1, the print data signal SI1, the latch signal LAT, the change signal CH, and the clock signal SCK are input to the drive signal selection circuit 200-1. Then, the drive signal selection circuit 200-1 generates the drive signal VOUT1 by selecting or not selecting the waveform of the drive signal COM1 based on the print data signal SI1, the latch signal LAT, the change signal CH, and the clock signal SCK. To do. The drive signal VOUT1 is supplied to one end of the piezoelectric element 60 of the corresponding discharge unit 600. A reference voltage signal CGND1 is supplied to the other end of the piezoelectric element 60. Then, the piezoelectric element 60 is displaced by the potential difference between the drive signal VOUT1 and the reference voltage signal CGND1.

Similarly, the drive signal COMi, the print data signal SIi, the latch signal LAT, the change signal CH, and the clock signal SCK are input to the drive signal selection circuit 200-i (i is any one of 1 to n). Then, the drive signal selection circuit 200-i generates the drive signal VOUTi by selecting or not selecting the waveform of the drive signal COMi based on the print data signal SIi, the latch signal LAT, the change signal CH, and the clock signal SCK. .. The drive signal VOUTi is supplied to one end of the piezoelectric element 60 of the corresponding discharge unit 600. A reference voltage signal CGNDi is supplied to the other end of the piezoelectric element 60. Then, the piezoelectric element 60 is displaced due to the potential difference between the drive signal VOUTi and the reference voltage signal CGNDi.

Here, each of the drive signal selection circuits 200-1 to 200-n has a similar circuit configuration. Therefore, when it is not necessary to distinguish the drive signal selection circuits 200-1 to 200-n in the following description, the drive signal selection circuit 200 is referred to. In this case, the drive signals COM1 to COMn input to the drive signal selection circuit 200 are referred to as drive signals COM, the print data signals SI1 to SIn are referred to as print data signal SI, and the drive signals output from the drive signal selection circuit 200. VOUT1 to VOUTn are referred to as drive signals VOUT. The configuration and operation details of the drive signal selection circuit 200 will be described later.

The temperature abnormality detection circuits 250-1 to 250-n are provided corresponding to the drive signal selection circuits 200-1 to 200-n, respectively. Then, the temperature abnormality detection circuits 250-1 to 250-n determine the presence or absence of a temperature abnormality in the corresponding drive signal selection circuits 200-1 to 200-n. Specifically, the temperature abnormality detection circuits 250-1 to 250-n operate using the voltage VDD as the power supply voltage. Then, when each of the temperature abnormality detection circuits 250-1 to 250-n detects the temperature of the corresponding drive signal selection circuit 200-1 to 200-n and diagnoses that the temperature is normal, a high level ( The temperature abnormality signal XHOT of (H level) is generated and output to the control circuit 100. On the other hand, each of the temperature abnormality detection circuits 250-1 to 250-n has a low level (L level) temperature abnormality when it is diagnosed that the temperature of the corresponding drive signal selection circuits 200-1 to 200-n is abnormal. The signal XHOT is generated and output to the control circuit 100.

Here, each of the temperature abnormality detection circuits 250-1 to 250-n has a similar circuit configuration. Therefore, when it is not necessary to distinguish the temperature abnormality detection circuits 250-1 to 250-n in the following description, the temperature abnormality detection circuit 250 is referred to. The details of the temperature abnormality detection circuit 250 will also be described later.

Here, each of the drive signal selection circuit 200-1 to 200-n and the temperature abnormality detection circuit 250-1 to 250-i is configured as an integrated circuit device. Further, the temperature abnormality detection circuit 250-i and the drive signal selection circuit 200-i may be configured as one integrated circuit device.

3. 3. Configuration of Discharge Unit Next, the configuration of the discharge unit 600 will be described with reference to FIG. FIG. 3 is a diagram showing a schematic configuration of one of the plurality of discharge units 600. FIG. 3 shows an ejection unit 600, an ink supply port 661 for supplying ink to the ejection unit 600, and a reservoir 641.

Ink introduced from the ink supply port 661 is stored in the reservoir 641. Further, the discharge unit 600 includes a piezoelectric element 60, a vibrating plate 621, a cavity 631 and a nozzle 651. The diaphragm 621 is deformed with the displacement of the piezoelectric element 60 provided on the upper surface in FIG. The diaphragm 621 functions as a diaphragm that expands / reduces the internal volume of the cavity 631. The inside of the cavity 631 is filled with ink. The cavity 631 functions as a pressure chamber whose internal volume changes due to the displacement of the piezoelectric element 60. The nozzle 651 is an opening portion formed in the nozzle plate 632 and communicating with the cavity 631. Then, the ink stored inside the cavity 631 is ejected from the nozzle 651 according to the change in the internal volume of the cavity 631. Then, after the ink is ejected from the nozzle 651, the ink stored in the reservoir 641 is supplied to the cavity 631.

The piezoelectric element 60 has a structure in which the piezoelectric body 601 is sandwiched between a pair of electrodes 611 and 612. In the piezoelectric body 601 having this structure, the central portions of the electrodes 611 and 612 and the vibrating plate 621 bend in the vertical direction in FIG. 3 with respect to both end portions in response to the voltage supplied to the electrodes 611 and 612. Specifically, the drive signal VOUT is supplied to the electrode 611, and the reference voltage signal CGND is supplied to the electrode 612. Then, when the voltage of the drive signal VOUT becomes high, the central portion of the piezoelectric element 60 bends upward, and when the voltage of the drive signal VOUT becomes low, the central portion of the piezoelectric element 60 bends downward. That is, if the piezoelectric element 60 bends upward, the internal volume of the cavity 631 expands. Therefore, ink is drawn from the reservoir 641. Further, if the piezoelectric element 60 is bent downward, the internal volume of the cavity 631 is reduced. Therefore, an amount of ink corresponding to the degree of reduction of the internal volume of the cavity 631 is ejected from the nozzle 651. As described above, the piezoelectric element 60 is driven by the drive signal VOUT based on the drive signal COM. Then, by driving the piezoelectric element 60, ink is ejected from the nozzle 651. The piezoelectric element 60 is not limited to the structure shown in the drawing, and may be of a type capable of ejecting ink as the piezoelectric element 60 is displaced. For example, the piezoelectric element 60 may have a configuration that vibrates vertically. ..

4. Example of Drive Signal Waveform Next, an example of the drive signal COM waveform generated by the drive signal output circuit 50 and an example of the drive signal VOUT waveform supplied to the piezoelectric element 60 are used with reference to FIGS. 4 and 5. explain.

FIG. 4 is a diagram showing an example of the waveform of the drive signal COM. As shown in FIG. 4, the drive signal COM includes a trapezoidal waveform Adp1 arranged in the period T1 from the rise of the latch signal LAT to the rise of the change signal CH, and after the period T1 until the next change signal CH rises. This is a continuous waveform of the trapezoidal waveform Adp2 arranged in the period T2 and the trapezoidal waveform Adp3 arranged in the period T3 after the period T2 until the next latch signal LAT rises. Then, when the trapezoidal waveform Adp1 is supplied to one end of the piezoelectric element 60, a medium amount of ink is ejected from the ejection unit 600 corresponding to the piezoelectric element 60. Further, when the trapezoidal waveform Adp2 is supplied to one end of the piezoelectric element 60, a small amount of ink, which is less than a medium amount, is ejected from the ejection unit 600 corresponding to the piezoelectric element 60. Further, when the trapezoidal waveform Adp3 is supplied to one end of the piezoelectric element 60, ink is not ejected from the ejection unit 600 corresponding to the piezoelectric element 60. The trapezoidal waveform Adp3 is a waveform for slightly vibrating the ink in the vicinity of the nozzle opening portion of the ejection portion 600 to prevent an increase in ink viscosity. Here, the period Ta from the rise of the latch signal LAT shown in FIG. 4 to the rise of the latch signal LAT corresponds to the printing cycle for forming new dots on the medium P.

Further, the voltage at the start timing and the end timing of the trapezoidal waveforms Adp1, Adp2, and Adp3 are all common to the voltage Vc. That is, each of the trapezoidal waveforms Adp1, Adp2, and Adp3 is a waveform that starts at a voltage Vc and ends at a voltage Vc. The drive signal COM may be a signal having a continuous waveform of one or two trapezoidal waveforms in the period Ta, or a signal having a continuous waveform of four or more trapezoidal waveforms.

FIG. 5 is a diagram showing an example of the waveform of the drive signal VOUT corresponding to each of “large dot”, “medium dot”, “small dot”, and “non-recording”.

As shown in FIG. 5, the drive signal VOUT corresponding to the “large dot” is arranged in the trapezoidal waveform Adp1 arranged in the period T1, the trapezoidal waveform Adp2 arranged in the period T2, and the period T3 in the period Ta. It is a waveform that is continuous with a constant waveform at the voltage Vc. When this drive signal VOUT is supplied to one end of the piezoelectric element 60, a medium amount of ink and a small amount of ink are ejected from the ejection unit 600 corresponding to the piezoelectric element 60 in the cycle Ta. .. Therefore, large dots are formed on the medium P by landing and coalescing the respective inks.

The drive signal VOUT corresponding to the "medium dot" is a waveform in which a trapezoidal waveform Adp1 arranged in the period T1 and a constant waveform in the voltage Vc arranged in the periods T2 and T3 are continuous in the period Ta. There is. When this drive signal VOUT is supplied to one end of the piezoelectric element 60, a medium amount of ink is ejected from the ejection unit 600 corresponding to the piezoelectric element 60 in the period Ta. Therefore, the ink lands on the medium P to form medium dots.

The drive signal VOUT corresponding to the "small dot" is a waveform in which a constant waveform at the voltage Vc arranged in the periods T1 and T3 and a trapezoidal waveform Adp2 arranged in the period T2 are continuous in the period Ta. There is. When this drive signal VOUT is supplied to one end of the piezoelectric element 60, a small amount of ink is ejected from the ejection unit 600 corresponding to the piezoelectric element 60 in the period Ta. Therefore, the ink lands on the medium P to form small dots.

The drive signal VOUT corresponding to "non-recording" is a waveform in which a constant waveform at the voltage Vc arranged in the periods T1 and T2 and a trapezoidal waveform Adp3 arranged in the period T3 are continuous in the period Ta. There is. When this drive signal VOUT is supplied to one end of the piezoelectric element 60, the ink in the vicinity of the nozzle opening portion of the ejection portion 600 corresponding to the piezoelectric element 60 only slightly vibrates in the cycle Ta, and the ink is not ejected. Therefore, the ink does not land on the medium P and dots are not formed.

Here, the constant waveform at the voltage Vc is from the voltage at which the immediately preceding voltage Vc is held by the capacitance component of the piezoelectric element 60 when none of the trapezoidal waveforms Adp1, Adp2, and Adp3 is selected as the drive signal VOUT. It is a waveform. Therefore, when none of the trapezoidal waveforms Adp1, Adp2, and Adp3 are selected as the drive signal VOUT, the voltage Vc is supplied to the piezoelectric element 60 as the drive signal VOUT.

The waveforms of the drive signal COM and the drive signal VOUT shown in FIGS. 4 and 5 are merely examples, and are supplied to the print head 22 at the moving speed of the carriage 20 on which the head unit 21 including the print head 22 is mounted. Signals with various waveform combinations may be used depending on the physical characteristics of the ink, the material of the medium P, and the like.

5. Configuration of Drive Signal Selection Circuit Next, the configuration and operation of the drive signal selection circuit 200 will be described with reference to FIGS. 6 to 9. FIG. 6 is a diagram showing the configuration of the drive signal selection circuit 200. As shown in FIG. 6, the drive signal selection circuit 200 includes a selection control circuit 220 and a plurality of selection circuits 230.

The print data signal SI, the latch signal LAT, the change signal CH, and the clock signal SCK are input to the selection control circuit 220. Further, the selection control circuit 220 is provided with a pair of a shift register (S / R) 222, a latch circuit 224, and a decoder 226 corresponding to each of the plurality of discharge units 600. That is, the drive signal selection circuit 200 includes a set of shift registers 222, a latch circuit 224, and a decoder 226, which are the same number as the total number m of the corresponding discharge units 600. Here, the clock signal SCK is a clock signal for defining the timing at which the print data signal SI is input.

Specifically, the print data signal SI is a signal synchronized with the clock signal SCK, and has "large dots", "medium dots", "small dots", and "small dots" for each of the m ejection units 600. It is a signal of a total of 2 mbits including 2-bit print data [SIH, SIL] for selecting any of "non-recording". The print data signal SI is held in the shift register 222 for each of the two bits of print data [SIH, SIL] included in the print data signal SI corresponding to the ejection unit 600. Specifically, the m-stage shift registers 222 corresponding to the ejection unit 600 are vertically connected to each other, and the serially input print data signal SI is sequentially transferred to the subsequent stage according to the clock signal SCK. In addition, in FIG. 6, in order to distinguish the shift register 222, it is described as 1st step, 2nd step, ..., M step in order from the upstream side where the print data signal SI is input.

Each of the m latch circuits 224 latches the 2-bit print data [SIH, SIL] held by each of the m shift registers 222 at the rising edge of the latch signal LAT.

Each of the m decoders 226 decodes the 2-bit print data [SIH, SIL] latched by each of the m latch circuits 224. Then, the decoder 226 outputs the selection signal S for each period T1, T2, T3 defined by the latch signal LAT and the change signal CH.

FIG. 7 is a diagram showing the contents of decoding in the decoder 226. The decoder 226 outputs the selection signal S according to the latched 2-bit print data [SIH, SIL]. For example, when the 2-bit print data [SIH, SIL] is [1,0], the decoder 226 outputs the logic level of the selection signal S as H, H, L levels in each of the periods T1, T2, and T3. To do.

The selection circuit 230 is provided corresponding to each of the discharge portions 600. That is, the number of selection circuits 230 included in the drive signal selection circuit 200 is the same as the total number m of the corresponding discharge units 600. FIG. 8 is a diagram showing a configuration of a selection circuit 230 corresponding to one discharge unit 600. As shown in FIG. 8, the selection circuit 230 has an inverter 232 which is a NOT circuit and a transfer gate 234.

The selection signal S is input to the positive control end not marked with a circle at the transfer gate 234, while it is logically inverted by the inverter 232 and input to the negative control end marked with a circle at the transfer gate 234. To. Further, a drive signal COM is supplied to the input end of the transfer gate 234. Specifically, the transfer gate 234 makes the input end and the output end conductive (on) when the selection signal S is H level, and when the selection signal S is L level, the input end and the output end are connected. The interval is non-conducting (off). Then, the drive signal VOUT is output from the output end of the transfer gate 234.

Here, the operation of the drive signal selection circuit 200 will be described with reference to FIG. FIG. 9 is a diagram for explaining the operation of the drive signal selection circuit 200. The print data signal SI is serially input in synchronization with the clock signal SCK, and is sequentially transferred in the shift register 222 corresponding to the discharge unit 600. Then, when the input of the clock signal SCK is stopped, the 2-bit print data [SIH, SIL] corresponding to each of the ejection units 600 is held in each shift register 222. The print data signal SI is input in the order corresponding to the m-stage, ..., 2-stage, and 1-stage discharge unit 600 of the shift register 222.

Then, when the latch signal LAT rises, each of the latch circuits 224 latches the 2-bit print data [SIH, SIL] held in the shift register 222 all at once. In FIG. 9, LT1, LT2, ..., LTm are 2-bit print data [SIH, SIL] latched by the latch circuit 224 corresponding to the shift register 222 of the 1st stage, 2nd stage, ..., M stage. Shown.

The decoder 226 shows the logic level of the selection signal S in each of the periods T1, T2, and T3 according to the dot size defined by the latched 2-bit print data [SIH, SIL]. Output with.

Specifically, when the print data [SIH, SIL] is [1,1], the decoder 226 sets the selection signal S to the H, H, L levels in the periods T1, T2, and T3. In this case, the selection circuit 230 selects the trapezoidal waveform Adp1 in the period T1, selects the trapezoidal waveform Adp2 in the period T2, and does not select the trapezoidal waveform Adp3 in the period T3. As a result, the drive signal VOUT corresponding to the "large dot" shown in FIG. 5 is generated.

Further, when the print data [SIH, SIL] is [1,0], the decoder 226 sets the selection signal S to the H, L, L levels in the periods T1, T2, and T3. In this case, the selection circuit 230 selects the trapezoidal waveform Adp1 in the period T1, does not select the trapezoidal waveform Adp2 in the period T2, and does not select the trapezoidal waveform Adp3 in the period T3. As a result, the drive signal VOUT corresponding to the "middle dot" shown in FIG. 5 is generated.

Further, when the print data [SIH, SIL] is [0,1], the decoder 226 sets the selection signal S to the L, H, L level in the periods T1, T2, and T3. In this case, the selection circuit 230 does not select the trapezoidal waveform Adp1 in the period T1, selects the trapezoidal waveform Adp2 in the period T2, and does not select the trapezoidal waveform Adp3 in the period T3. As a result, the drive signal VOUT corresponding to the "small dot" shown in FIG. 5 is generated.

Further, when the print data [SIH, SIL] is [0,0], the decoder 226 sets the selection signal S to the L, L, H levels in the periods T1, T2, and T3. In this case, the selection circuit 230 does not select the trapezoidal waveform Adp1 in the period T1, does not select the trapezoidal waveform Adp2 in the period T2, and selects the trapezoidal waveform Adp3 in the period T3. As a result, the drive signal VOUT corresponding to the "non-recording" shown in FIG. 5 is generated.

As described above, the drive signal selection circuit 200 selects the waveform of the drive signal COM based on the print data signal SI, the latch signal LAT, the change signal CH, and the clock signal SCK, and outputs the drive signal VOUT. In other words, the drive signal selection circuit 200 controls the supply of the drive signal COM to the piezoelectric element 60.

6. Configuration of Temperature Abnormality Detection Circuit Next, the configuration and operation of the temperature abnormality detection circuit 250 will be described. FIG. 10 is a diagram showing the configuration of the temperature abnormality detection circuit 250. FIG. 11 is a diagram showing the configuration of the reference voltage output circuit 270. FIG. 12 is a diagram showing the contents of decoding in the decoder 285. As described above, the temperature abnormality detection circuits 250-1 to 250-n all have the same configuration. Therefore, in FIGS. 10 to 12, only the temperature abnormality detection circuit 250-1 is shown as a representative, and the detailed configuration of the temperature abnormality detection circuits 250-2 to 250-n is omitted.

As shown in FIGS. 10 and 11, the temperature abnormality detection circuit 250 included in the printhead 22 includes a temperature-dependent voltage output circuit 260, a BGR (Band Gap Reference) circuit 271, a non-inverting amplifier circuit 272, and a temperature. It has an abnormal signal output circuit 280.

Then, the temperature-dependent voltage output circuit 260 outputs a temperature-dependent voltage signal Vf whose voltage value fluctuates depending on the temperature. Further, the BGR circuit 271 outputs the original reference voltage signal Vbgr having a stable voltage value regardless of the temperature. The non-inverting amplification circuit 272 outputs a reference voltage signal Vref in which the voltage value of the original reference voltage signal Vbgr is adjusted. Specifically, the non-inverting amplifier circuit 272 outputs a reference voltage signal Vref by adjusting the voltage value of the original reference voltage signal Vbgr based on the voltage value of the temperature-dependent voltage signal Vf at a predetermined temperature.

The temperature-dependent voltage signal Vf and the reference voltage signal Vref are input to the temperature abnormality signal output circuit 280. The temperature abnormality signal output circuit 280 outputs the temperature abnormality signal XHOT based on the temperature-dependent voltage signal Vf and the reference voltage signal Vref. In other words, the temperature abnormality signal output circuit 280 outputs the temperature abnormality signal XHOT indicating the presence or absence of the temperature abnormality of the print head 22.

Here, the temperature-dependent voltage output circuit 260 is an example of a fluctuating voltage signal output circuit, and the temperature-dependent voltage signal Vf output by the temperature-dependent voltage output circuit 260 is an example of a fluctuating voltage signal. Further, the BGR circuit 271 which is a bandgap reference circuit is an example of a stable voltage signal output circuit, and the original reference voltage signal Vbgr output by the BGR circuit 271 is an example of a stable voltage signal. The non-inverting amplifier circuit 272 is an example of a reference voltage signal output circuit, and the reference voltage signal Vref output by the non-inverting amplifier circuit 272 is an example of a reference voltage signal. The temperature abnormality signal output circuit 280 is an example of the temperature abnormality signal output circuit, and the temperature abnormality signal XHOT output by the temperature abnormality signal output circuit 280 is an example of the temperature abnormality signal.

The configuration and operation of the temperature abnormality detection circuit 250 will be specifically described with reference to FIGS. 10 to 12.

As shown in FIG. 10, the temperature abnormality detection circuit 250 includes a temperature-dependent voltage output circuit 260, a reference voltage output circuit 270, a temperature abnormality signal output circuit 280, and a resistor 255. A voltage VDD is supplied to one end of the resistor 255, and the other end is connected to the temperature-dependent voltage output circuit 260.

The temperature-dependent voltage output circuit 260 includes a plurality of diodes 254. The plurality of diodes 254 are connected in series with each other. The anode terminal of the diode 254 located on the highest potential side of the plurality of diodes 254 connected in series is connected to the other end of the resistor 255, and the cathode terminal of the diode 254 located on the lowest potential side is , The ground signal GND is connected to the propagation path.

Specifically, the temperature-dependent voltage output circuit 260 has diodes 254-1,254-2, 254-3, 254-4 as a plurality of diodes 254. The anode terminal of the diode 254-1 is connected to the other end of the resistor 255. The cathode terminal of the diode 254-1 is connected to the anode terminal of the diode 254-2. The cathode terminal of the diode 254-2 is connected to the anode terminal of the diode 254-2. The cathode terminal of the diode 254-3 is connected to the anode terminal of the diode 254-4. The cathode terminal of the diode 254-4 is connected to a propagation path through which the ground signal GND propagates. Further, the anode terminal of the diode 254-1 is connected to the temperature abnormality signal output circuit 280.

A voltage VDD is supplied to the temperature-dependent voltage output circuit 260 via a resistor 255.

In this case, the temperature-dependent voltage signal Vf, which is the sum of the forward voltages of the plurality of diodes 254, is supplied to the temperature abnormality signal output circuit 280 as the output of the temperature-dependent voltage output circuit 260. The forward voltage of the plurality of diodes 254 fluctuates with respect to temperature fluctuations. Specifically, the forward voltage of the plurality of diodes 254 in the present embodiment has a characteristic that the voltage decreases as the temperature rises. Therefore, the voltage value of the temperature-dependent voltage signal Vf output from the temperature-dependent voltage output circuit 260 decreases as the temperature rises. In other words, the voltage value of the temperature-dependent voltage output circuit 260 decreases as the temperature rises. A temperature-dependent voltage signal Vf having a negative temperature characteristic is output. The number of the plurality of diodes 254 included in the temperature-dependent voltage output circuit 260 is not limited to four.

The reference voltage output circuit 270 generates a reference voltage signal Vref and outputs it to the temperature abnormality signal output circuit 280. As shown in FIG. 11, the reference voltage output circuit 270 includes a BGR circuit 271 and a non-inverting amplifier circuit 272.

The BGR circuit 271 generates and outputs a source reference voltage signal Vbgr having a stable voltage value independent of temperature by utilizing the band cap voltage generated on the substrate or the like of the integrated circuit device in which the temperature abnormality detection circuit 250 is configured.

The non-inverting amplifier circuit 272 includes an amplifier 273 and an amplification factor adjusting circuit 274.

The original reference voltage signal Vbgr is input to the amplifier 273. Then, the amplifier 273 generates and outputs a reference voltage signal Vref by amplifying the original reference voltage signal Vbgr according to the amplification factor G defined by the amplification factor adjustment circuit 274. In other words, the amplifier 273 outputs the reference voltage signal Vref by amplifying the original reference voltage signal Vbgr based on the amplification factor G adjusted by the amplification factor adjusting circuit 274. Here, the amplifier 273 is an example of an amplifier circuit.

The amplification factor adjusting circuit 274 adjusts the amplification factor G in the amplifier 273. As shown in FIG. 12, the amplification factor adjusting circuit 274 includes fuses 281-1 to 281-3, 282-1 to 282-3, switches 283 to 283-7, resistors R0 to R8, and a decoder 285. ..

One end of the fuse 281-1 is connected to a propagation path through which the voltage VDD propagates. The other end of the fuse 281-1 is connected to one end of the fuse 282-1. The other end of the fuse 282-1 is connected to a propagation path through which the ground signal GND propagates. Then, the voltage at the connection point where the other end of the fuse 281-1 and one end of the fuse 282-1 are connected is input to the decoder 285 as switching information P1. Similarly, each end of the fuses 281-2 and 281-3 is connected to a propagation path through which the voltage VDD propagates. The other ends of the fuses 281-2, 281-3 are connected to the respective ends of the fuses 282-2, 282-3. The other ends of the fuses 282-2 and 282-3 are connected to a propagation path through which the ground signal GND propagates. Then, the voltage at the connection point where the other end of the fuse 281-2 and one end of the fuse 282-2 are connected is input to the decoder 285 as switching information P2, and the other end of the fuse 281-3 and the fuse 282-3 The voltage at the connection point to which one end is connected is input to the decoder 285 as switching information P3.

Here, the respective logic levels of the switching information P1, P2, and P3 are one of the fuse 281-1 and the fuse 282-1 connected in series, and the fuse 281-2 and the fuse 282- connected in series. It is defined by cutting either one of the two and one of the fuse 281-2 and the fuse 282-2 connected in series. For example, when the fuse 282-1, the fuse 282-2, and the fuse 281-3 are disconnected, the decoder 285 has the voltage VDD as the H level switching information P1 and the voltage as the H level switching information P2. VDD and the ground signal GND as the L level switching information P3 are input.

The decoder 285 decodes the input switching information P1, P2, P3, and outputs the switch control signals D0 to D7 according to the decoded contents shown in FIG. For example, in the decoder 285, when the input switching information P1, P2, and P3 are H level, H level, and L level, respectively, the H level switch control signals D3 and L are according to the decoding contents shown in FIG. The level switch control signals D0 to D2 and D4 to D7 are output.

The resistors R0 to R8 are connected in series between the propagation path in which the reference voltage signal Vref propagates and the propagation path in which the ground signal GND propagates. Further, among the resistors R0 to R8 connected in series, one end of the switch 283 to 283-7 is connected to the other end of each of the resistors R0 to R7.

Specifically, one end of the resistor R0 is connected to a propagation path through which the reference voltage signal Vref propagates. The other end of the resistor R0 is connected to one end of the resistor R1 and one end of the switch 283-0. Similarly, the other end of the resistors R1 to R7 are connected to one end of the resistors R2 to R8 and one end of the switches 283-1 to 283-7. The other end of the resistor R8 is connected to a propagation path through which the ground signal GND propagates.

The switch control signal D0 output from the decoder 285 is input to the control terminal of the switch 283-0. Similarly, the corresponding switch control signals D1 to D7 output from the decoder 285 are input to the respective control terminals of the switches 283-1 to 283-7. When the logic level of the switch control signals D0 to D7 input to the control terminal is H level, each of the corresponding switches 283 to 283-7 controls the continuity between one end and the other end. On the other hand, when the logic level of the switch control signals D0 to D7 input to the control terminal is L level, each of the corresponding switches 283-1 to 283-7 controls non-conduction between one end and the other end. To do.

Here, as shown in FIG. 12, as for the logic level of the switch control signals D0 to D7 output by the decoder 285, only one of the switch control signals D0 to D7 becomes the H level, and the other switch control signals D0. ~ D7 is the L level. That is, only one of the switches 283 to 283-7 is controlled to be conductive, and the other switches 283 to 283-7 are controlled to be non-conductive.

The other ends of the switches 283-0 to 283-7 are commonly connected. The other ends of the switches 283 to 283-7 are connected to the negative input terminal of the amplifier 273.

Here, the adjustment of the amplification factor G in the non-inverting amplifier circuit 272 will be described with reference to FIG. FIG. 13 is a diagram showing an equivalent circuit of the non-inverting amplification circuit 272. As shown in FIG. 13, the equivalent circuit of the non-inverting amplifier circuit 272 in the present embodiment, the output terminal of the amplifier 373 corresponding to the amplifier 273, has a ground signal GND via a resistor Ra and a resistor Rb connected in series. It is connected to the propagation path to be propagated. Further, the connection point between the resistor Ra and the resistor Rb is connected to the negative input terminal of the amplifier 273. In other words, the output end of the amplifier 273 is connected to the ground via the resistor Ra and the resistor Rb, and returns to the − side input terminal from the connection point between the resistor Ra and the resistor Rb.

The amplification factor G in the non-inverting amplification circuit 272 configured as described above, that is, the voltage ratio of the reference voltage signal Vref to the original reference voltage signal Vbgr input to the non-inverting amplification circuit 272 is determined by the following equation (1). Can be shown as

Here, the resistor Ra shown in FIG. 13 is a resistance component of the resistors R0 to R8 up to one end of the switches 283-0 to 283-7 conducting by the switch control signals D0 to D7, and the resistor Rb is a resistor Rb. It is a resistance component from one end of the switches 283 to 283-7 conducting by the switch control signals D0 to D7 to the ground.

FIG. 14 is a diagram showing the relationship between the resistors Ra and Rb corresponding to the switching information P1, P2 and P3 and the resistors R0 to R8. As shown in FIG. 14, the amplification factor adjusting circuit 274 in the present embodiment sends switch control signals D0 to D7 based on whether or not the fuses 281 to 281-3 and 282-1 to 282-3 are cut. By specifying, the amplification factor G is specified by generating a combination of resistors Ra and Rb corresponding to eight states. In other words, the non-inverting amplifier circuit 272 includes a fuse 281-1 to 281-3, 282-1 to 282-3, and the amplification factor G is adjusted depending on whether or not the fuse is blown.

For example, when the fuses 282-1,282-2,281-3 are blown, H level, H level, and L level switching information P1, P2, and P3 are input to the decoder 285. In this case, the decoder 285 outputs the H level switch control signal D3 and the L level switch control signals D0 to D2, D4 to D7 according to the decoding contents shown in FIG. Therefore, only the switch 283-3 corresponding to the switch control signal D3 is controlled to be conductive. As a result, the resistor Ra is a resistance component of the resistors R0 to R8 up to one end of the switch 283-3 which is conducted by the switch control signal D3, and the resistor Rb is a switch which is conducted by the switch control signal D3. It is a resistance component from one end of 283-3 to the ground. In other words, the resistance Ra is the combined resistance of the resistors R0, R1, R2, and R3, and the resistance Rb is the combined resistance of the resistors R4, R5, R6, R7, and R8. Therefore, the amplification factor G of the non-inverting amplifier circuit 272 is represented by the equation (2).

As described above, in the non-inverting amplifier circuit 272, the amplification factor adjustment circuit 274 adjusts the voltage value of the original reference voltage signal Vbgr by the amplifier 273 adjusting the amplification factor G defined by the amplification factor adjustment circuit 274. , The reference voltage signal Vref is generated and output.

Returning to FIG. 10, the temperature anomaly signal output circuit 280 includes a comparator 251, a transistor 253, and a resistor 256. The comparator 251 operates by the potential difference between the voltage VDD and the ground signal GND. A reference voltage signal Vref is supplied to the + side input terminal of the comparator 251 and a temperature-dependent voltage signal Vf is supplied to the − side input terminal. Then, the comparator 251 compares the reference voltage signal Vref with the temperature-dependent voltage signal Vf, and outputs a signal based on the comparison result from the output terminal.

A voltage VDD is supplied to the drain terminal of the transistor 253 via a resistor 256. Further, the gate terminal of the transistor 253 is connected to the output terminal of the comparator 251 and the ground signal GND is supplied to the source terminal. The voltage supplied to the drain terminal of the transistor 253 connected as described above is output from the temperature abnormality detection circuit 250 as a temperature abnormality signal XHOT.

Here, the temperature abnormality detection circuit 250 in the present embodiment may output the signal output from the comparator 251 as the temperature abnormality signal XHOT, but as shown in FIG. 10, the output signal of the comparator 251 is output to the transistor 253. It is preferable that the signal is inverted by the above and output as a temperature abnormality signal XHOTO. As shown in FIG. 10, the propagation paths through which the temperature abnormality signals XHOT output from each of the n temperature abnormality detection circuits 250-1 to 250-n are propagated are commonly connected. The temperature abnormality detection circuits 250-1 to 250-n are wired or connected. As a result, even when a plurality of temperature abnormality detection circuits 250 are provided in the head unit 21, the presence or absence of a temperature abnormality in the head unit 21 can be determined without increasing the number of wires for propagating the temperature abnormality signal XHOT. The indicated temperature anomaly signal XHOT can be propagated.

As described above, the temperature abnormality detection circuit 250 includes the reference voltage signal Vref, the temperature-dependent voltage signal Vf, and the temperature abnormality generated by amplifying the original reference voltage signal Vbgr having a stable voltage value independent of the temperature. The signal output circuit 280 is compared, and the temperature abnormality signal XHOT is output based on the comparison result. In this case, by making it possible to adjust the amplification factor G that amplifies the original reference voltage signal Vbgr, it is possible to reduce the variation in the temperature threshold value at which the temperature abnormality signal XHOT is output.

As described above, the temperature abnormality detection circuit 250 in the present embodiment can individually adjust the amplification factor G that amplifies the original reference voltage signal Vbgr. Therefore, as shown in this embodiment, the head unit 21 has n temperature abnormality detection circuits 250-1 to 250-n corresponding to each of n print heads 22-1 to 22-n. Also, it is possible to adjust the amplification factor G to the optimum value for each of the n temperature abnormality detection circuits 250-1 to 250-n.

Specifically, the temperature abnormality signal output circuit 280 included in the temperature abnormality detection circuit 250-p in the print head 22-p (p is any one of 1 to n) depends on the temperature in the temperature abnormality detection circuit 250-p. The reference voltage signal Vref generated by amplifying the original reference voltage signal Vbgr having a stable voltage value is compared with the temperature-dependent voltage signal Vf, and the temperature abnormality signal XHOT is output based on the comparison result. .. On the other hand, in the print head 22-q (q is any of 1 to n other than p), the temperature abnormality signal output circuit 280 included in the temperature abnormality detection circuit 250-q is the temperature in the temperature abnormality detection circuit 250-q. The reference voltage signal Vref generated by amplifying the original reference voltage signal Vbgr having a stable voltage value independent of the above and the temperature-dependent voltage signal Vf are compared, and the temperature abnormality signal XHOT is obtained based on the comparison result. Output.

In this case, the amplification factor G as the adjustment value of the original reference voltage signal Vbgr for outputting the reference voltage signal Vref in the printhead 22-p and the original for outputting the reference voltage signal Vref in the printhead 22-q. It may be different from the amplification factor G as the adjustment value of the reference voltage signal Vbgr. As a result, it is possible to reduce the variation in the temperature threshold value at which the temperature abnormality signal XHOT is output among the n temperature abnormality detection circuits 250-1 to 250-n in the print head 22.

Here, the print head 22-p is an example of the first print head, and the temperature abnormality signal output circuit 280 included in the temperature abnormality detection circuit 250-p included in the print head 22-p is the first temperature abnormality signal output circuit. This is an example. The temperature abnormality signal XHOT output by the temperature abnormality signal output circuit 280 is an example of the first temperature abnormality signal, and the reference voltage signal Vref to be compared in order for the temperature abnormality signal output circuit 280 to output the temperature abnormality signal XHOT. Is an example of the first reference voltage signal, and the temperature-dependent voltage signal Vf is an example of the first fluctuating voltage signal. Further, in the temperature abnormality detection circuit 250-p, the original reference voltage signal Vbgr for outputting the reference voltage signal Vref is an example of the first stable voltage signal.

Similarly, the print head 22-q is an example of the second print head, and the temperature abnormality signal output circuit 280 included in the temperature abnormality detection circuit 250-q of the print head 22-q is the second temperature abnormality signal output circuit. This is an example. The temperature abnormality signal XHOT output by the temperature abnormality signal output circuit 280 is an example of the second temperature abnormality signal, and the reference voltage signal Vref to be compared for the temperature abnormality signal output circuit 280 to output the temperature abnormality signal XHOT. Is an example of the second reference voltage signal, and the temperature-dependent voltage signal Vf is an example of the second fluctuating voltage signal. Further, in the temperature abnormality detection circuit 250-q, the original reference voltage signal Vbgr for outputting the reference voltage signal Vref is an example of the second stable voltage signal.

7. Temperature Detection Method of Temperature Abnormal Signal XHOT in Temperature Abnormality Detection Circuit Next, a method of adjusting the amplification factor G in the temperature abnormality detection circuit 250 and a temperature detection method of outputting the temperature abnormality signal XHOT will be described with reference to FIG. FIG. 15 is a diagram for explaining a method of adjusting the amplification factor G in the temperature abnormality detection circuit 250 and a temperature detection method of outputting the temperature abnormality signal XHOT.

The temperature-dependent voltage output circuit 260 outputs a temperature-dependent voltage signal Vf whose voltage value fluctuates depending on the temperature (step S110). Further, the BGR circuit 271 outputs a source reference voltage signal Vbgr having a stable voltage value independent of temperature (step S120). Then, in an inspection / adjustment facility (not shown) for adjusting the temperature threshold of the temperature abnormality signal XHOT in the temperature abnormality detection circuit 250, the current temperature of the integrated circuit device constituting the temperature abnormality detection circuit 250, the temperature-dependent voltage signal Vf, And the voltage value of the reference voltage signal Vref amplified at an arbitrary amplification factor G is acquired (step S130).

Then, the inspection and adjustment equipment (not shown) adjusts the original reference voltage signal Vbgr by adjusting the amplification factor G based on the voltage value of the temperature-dependent voltage signal Vf at the acquired current temperature. As a result, the reference voltage output circuit 270 outputs a reference voltage signal Vref having a desired voltage value (step S140).

FIG. 16 is a diagram for explaining the details of step S140. In FIG. 16, the horizontal axis shows the temperature of the temperature abnormality detection circuit 250, and the vertical axis shows the voltage. Further, the temperature Txhot shown in FIG. 16 is a threshold temperature for outputting the temperature abnormality signal XHOT required for the liquid discharge device 1, and the temperature Tm is the current temperature of the integrated circuit device acquired in step S130. Further, the voltage Vref1 shown in FIG. 16 is the voltage value of the reference voltage signal Vref at an arbitrary amplification factor G acquired in step S130, and the voltage Vref2 is the voltage value of the reference voltage signal Vref at the adjusted amplification factor G. is there. This voltage Vref2 is the adjustment target voltage value of the reference voltage signal Vref.

The inspection and adjustment equipment stores reference information for outputting a temperature abnormality signal XHOT indicating a temperature abnormality at the temperature Txhot. Specifically, the inspection and adjustment equipment stores the reference temperature Tref and the reference potential difference ΔV between the temperature-dependent voltage signal Vf and the reference voltage signal Vref at the reference temperature Tref. In other words, the temperature abnormality detection circuit 250 generates a temperature abnormality signal XHOT indicating a temperature abnormality at the temperature Txhot when the potential difference between the temperature-dependent voltage signal Vf and the reference voltage signal Vref is the reference potential difference ΔV at the reference temperature Tref. Output.

The inspection adjustment facility calculates the potential difference ΔVm between the temperature-dependent voltage signal Vf and the voltage Vref2 at the temperature Tm according to the equation (3) using the current temperature Tm and the temperature-dependent voltage signal Vf acquired in step 130. ..

Then, the inspection and adjustment equipment sets the amplification factor G when the voltage value of the reference voltage signal Vref acquired in step S130 is the voltage Vref 1 to any of the fuses 281-1 to 281-3, 282-1 to 282-3. Adjust by cutting. As a result, the voltage value of the reference voltage signal Vref is adjusted to the voltage Vref2 in which the potential difference from the temperature-dependent voltage signal Vf at the temperature Tm is the potential difference ΔVm.

Then, the temperature abnormality signal output circuit 280 outputs the temperature abnormality signal XHOT based on the temperature-dependent voltage signal Vf and the reference voltage signal Vref (step S150).

8. Action effect As described above, in the liquid discharge device 1 of the present embodiment, the temperature abnormality signal output circuit 280 has a temperature-dependent voltage signal Vf in which the voltage value fluctuates depending on the temperature and a stable voltage value independent of the temperature. A temperature abnormality signal XHOT indicating the presence or absence of a temperature abnormality of the print head 22 is output based on the reference voltage signal Vref adjusted for the voltage value of the original reference voltage signal Vbgr. Here, since the reference voltage signal Vref is a voltage obtained by adjusting the voltage value of the original reference voltage signal Vbgr, it is a stable voltage value independent of the temperature. Then, the reference voltage output circuit 270 adjusts the voltage value of the reference voltage signal Vref based on the voltage value of the temperature-dependent voltage signal Vf at a predetermined temperature. As a result, the temperature abnormality signal output circuit 280 can adjust the threshold value when outputting the temperature abnormality signal XHOT, and thus it is possible to reduce the variation in the temperature at which the temperature abnormality signal XHOT is output. .. That is, in the liquid discharge device 1 of the present embodiment, the reference voltage output circuit 270 only includes a circuit for adjusting the voltage value of the reference voltage signal Vref, and the temperature abnormality signal output circuit 280 generates the temperature abnormality signal XHOT. It is possible to reduce the variation in temperature at the time of output. Therefore, it is possible to detect the temperature abnormality of the printhead 22 with high accuracy only by providing the printhead 22 with a simple circuit configuration for adjusting the voltage value of the reference voltage signal Vref.

Further, in the liquid discharge device 1 of the present embodiment, the reference voltage output circuit 270 includes an amplifier 273 and an amplification factor adjusting circuit 274. Then, the reference voltage output circuit 270 outputs the reference voltage signal Vref by adjusting the amplification factor G for adjusting the voltage value of the original reference voltage signal Vbgr in the amplification factor adjustment circuit 274. That is, in the liquid discharge device 1 of the present embodiment, the reference voltage output circuit 270 only includes an amplifier 273 and an amplification factor adjustment circuit 274 to adjust the voltage value of the reference voltage signal Vref, and is an abnormal temperature signal output circuit. The 280 can reduce the variation in temperature when outputting the temperature abnormality signal XHOT. Therefore, the temperature of the print head 22 can be detected with high accuracy with a simple circuit configuration that only adjusts the voltage value of the reference voltage output circuit 270.

Further, in the liquid discharge device 1 of the present embodiment, the reference voltage output circuit 270 includes fuses 281-1 to 281-3, 282-1 to 282-3, and fuses 281-1 to 281-3, 282-1. The amplification factor G in the amplification factor adjustment circuit 274 is adjusted depending on whether or not to disconnect ~ 282-3. That is, in the liquid discharge device 1 of the present embodiment, in the reference voltage output circuit 270, the amplification factor G for the amplification factor adjustment circuit 274 to be adjusted is the fuse 281-1 to 281-3, 282-1 to 282-3. It is determined by a simple circuit configuration whether or not to disconnect. Therefore, the temperature of the print head 22 can be detected with high accuracy with a simple circuit configuration that only adjusts the voltage value of the reference voltage output circuit 270.

9. Modification Example In the liquid discharge device 1 described above, the amplification factor adjusting circuit 274 includes nine resistors R0 to R9 connected in series, and is conducted by the switch control signals D0 to D7 among the resistors R0 to R8. The amplification factor G is adjusted by the resistance component up to one end of the switch 283 and the resistance component from one end of the switch 283 conducting by the switch control signals D0 to D7 to the ground. The number of resistors that 274 has is not limited to nine. For example, the amplification factor adjusting circuit 274 may include 17 resistors. In that case, the amplification factor adjusting circuit 274 has 16 switches 283, and the decoder 285 outputs 16 switch control signals D for controlling the 16 switches 283. Therefore, at least 4 bits of switching information P for generating 16 switch control signals D are input to the decoder 285. In the amplification factor adjusting circuit 274 configured as described above, the amplification factor G can be adjusted more delicately. Therefore, the temperature variation when the temperature abnormality signal output circuit 280 outputs the temperature abnormality signal XHOT can be further reduced.

Although the embodiments and modifications have been described above, the present invention is not limited to these embodiments, and can be implemented in various embodiments without departing from the gist thereof. For example, the above embodiments can be combined as appropriate.

The present invention includes a configuration substantially the same as the configuration described in the embodiment (for example, a configuration having the same function, method and result, or a configuration having the same purpose and effect). The present invention also includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. The present invention also includes a configuration that exhibits the same effects as the configuration described in the embodiment or a configuration that can achieve the same object. The present invention also includes a configuration in which a known technique is added to the configuration described in the embodiment.

1 ... Liquid discharge device, 2 ... Liquid container, 10 ... Control mechanism, 20 ... Carriage, 21 ... Head unit, 22 ... Print head, 30 ... Movement mechanism, 31 ... Carriage motor, 32 ... Endless belt, 40 ... Conveyance mechanism, 41 ... Conveyor motor, 42 ... Conveyor roller, 50 ... Drive signal output circuit, 50a ... Drive circuit, 60 ... Piezoelectric element, 90 ... Linear encoder, 100 ... Control circuit, 110 ... Power supply circuit, 130 ... Step, 200 ... Drive signal Selection circuit, 220 ... Selection control circuit, 222 ... Shift register, 224 ... Latch circuit, 226 ... Decoder, 230 ... Selection circuit, 232 ... Inverter, 234 ... Transfer gate, 250 ... Temperature abnormality detection circuit, 251 ... Comparator, 253 ... Transistor, 254 ... Diode, 255, 256 ... Resistance, 260 ... Temperature dependent voltage output circuit, 270 ... Reference voltage output circuit, 271 ... BGR circuit, 272 ... Non-inverting amplifier circuit, 273 ... Amplifier, 274 ... Amplification rate adjustment circuit , 280 ... Temperature anomaly signal output circuit, 281-1 to 281-3 ... Fuse, 282-1 to 282-3 ... Fuse, 283 to 283-7 ... Switch, 285 ... Decoder, 373 ... Amplifier, 600 ... Discharge Unit, 601 ... Piezoelectric body, 611, 612 ... Electrode, 621 ... Vibration plate, 631 ... Cavity, 632 ... Nozzle plate, 641 ... Reservoir, 651 ... Nozzle, 661 ... Ink supply port, P ... Medium, R0 to R8, Ra, Rb ... Resistance

Claims (7)

Equipped with a print head that discharges liquid
The print head
A fluctuating voltage signal output circuit that outputs a fluctuating voltage signal whose voltage value fluctuates depending on the temperature,
A stable voltage signal output circuit that outputs a stable voltage signal with a stable voltage value regardless of temperature,
A reference voltage signal output circuit that outputs a reference voltage signal in which the voltage value of the stable voltage signal is adjusted, and
A temperature abnormality signal output circuit that outputs a temperature abnormality signal indicating the presence or absence of a temperature abnormality of the print head, and
Have,
The reference voltage signal output circuit outputs the reference voltage signal by adjusting the voltage value of the stable voltage signal based on the voltage value of the fluctuating voltage signal at a predetermined temperature.
The temperature abnormality signal output circuit outputs the temperature abnormality signal based on the fluctuation voltage signal and the reference voltage signal.
A liquid discharge device characterized by this. The fluctuating voltage signal has a negative temperature characteristic in which the voltage value decreases as the temperature rises.
The liquid discharge device according to claim 1. The stable voltage signal output circuit is a bandgap reference circuit.
The liquid discharge device according to claim 1 or 2. The reference voltage signal output circuit includes an amplifier circuit and an amplification factor adjustment circuit.
The amplifier factor adjusting circuit adjusts the amplification factor in the amplifier circuit,
The amplifier circuit outputs the reference voltage signal by amplifying the voltage value of the stable voltage signal based on the amplification factor adjusted by the amplification factor adjusting circuit.
The liquid discharge device according to any one of claims 1 to 3, wherein the liquid discharge device is characterized. The reference voltage signal output circuit includes a fuse.
The amplification factor is adjusted depending on whether or not the fuse is blown.
The liquid discharge device according to claim 4. A plurality of the printheads including the first printhead and the second printhead are provided.
The first printhead outputs a first temperature abnormality signal based on the first fluctuating voltage signal as the fluctuating voltage signal and the first reference voltage signal adjusted by adjusting the first stable voltage signal as the stable voltage signal. It has a first temperature abnormality signal output circuit to output,
The second printhead outputs a second temperature abnormality signal based on the second fluctuating voltage signal as the fluctuating voltage signal and the second reference voltage signal adjusted by adjusting the second stable voltage signal as the stable voltage signal. It has a second temperature abnormality signal output circuit to output,
The adjusted value of the first stable voltage signal for outputting the first reference voltage signal in the first printhead and the second stable voltage for outputting the second reference voltage signal in the second printhead. Different from the signal adjustment value,
The liquid discharge device according to any one of claims 1 to 5, wherein the liquid discharge device is characterized. A temperature detection method for a liquid discharge device equipped with a first print head that discharges liquid.
The process of outputting a fluctuating voltage signal whose voltage value fluctuates depending on the temperature,
The process of outputting a stable voltage signal with a stable voltage value regardless of temperature,
A step of outputting a reference voltage signal by adjusting the stable voltage signal based on the voltage value of the fluctuating voltage signal at a predetermined temperature.
A step of outputting an abnormal temperature signal based on the fluctuating voltage signal and the reference voltage signal, and
A temperature detection method comprising.

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