JP2020168829A - Recording device - Google Patents

Abstract

To provide an element substrate which can determine a discharge state of a nozzle from a temperature sensor arranged corresponding to each nozzle with high precision, a recording head using the element substrate, and a recording device using the recording head.SOLUTION: An element substrate includes a heater which heats ink and discharges from a nozzle, a temperature sensor arranged corresponding to the heater, and a constant current source which energizes a constant current to the temperature sensor on the basis of a current value a first signal input from an external specifies. A determination circuit determines a discharge state of the ink from the nozzle on the basis of a voltage output from the temperature sensor energized by the constant current and a threshold voltage a second signal input form the external specifies, and outputs a determination result signal.SELECTED DRAWING: Figure 7

Description

The present invention relates to a recording device, and more particularly to a recording device applied to record a recording head incorporating an element substrate including a plurality of recording elements according to an inkjet method.

Among the inkjet recording methods in which ink droplets are ejected from a nozzle and adhered to paper, plastic film or other recording media, there is one that uses a recording head having a recording element that generates thermal energy to eject the ink. In a recording device using a recording head that follows this method, a method of correcting the error of the temperature signal output from the temperature sensor provided corresponding to each heater based on the electrical variation of the circuit and the thermal variation of each nozzle. Has been proposed (see Patent Document 1).

In the recording device disclosed in Patent Document 1, a temperature signal is acquired without applying a drive pulse to the heater, and an offset voltage TEoff indicating electrical variation is acquired. Next, a drive pulse is applied to the heater to acquire a temperature signal, and a coefficient K, which is a thermal variation, is acquired. Then, using the acquired offset voltage TEoff and the coefficient K, the error of the temperature signal is finally corrected and accurate temperature information is output.

Patent No. 4890960

However, in the above-mentioned conventional example, it is premised that the reference for determining the ejection state of the nozzle is a signal of temperature information acquired at a plurality of timings. Therefore, when the ejection state is determined based on the signal indicating the time-dependent change of the temperature information acquired from the temperature sensor, the amount and timing of the tailing (satellite) of the ink droplet ejected from the nozzle crashing into the heater. It is not possible to correct the signal variation caused by the variation of. As a result, it is not possible to determine the discharge state with high accuracy.

The present invention has been made in view of the above-mentioned conventional example, and determines the ejection state of a nozzle with high accuracy from a temperature sensor provided corresponding to each nozzle while suppressing an increase in the circuit scale related to the determination of the ejection state. The purpose is to provide a recording device capable of this.

A plurality of heaters that heat the ink to eject the current from the arranged nozzles, a plurality of temperature sensors provided corresponding to the plurality of heaters, and a first signal input from the outside are designated. A constant current source that energizes the temperature sensor with a constant current based on the current value, a voltage output from the temperature sensor energized by the constant current, and a threshold voltage specified by a second signal input from the outside. Based on this, an element substrate having a determination circuit that determines the ejection state of the ink from the nozzle and outputs a determination result signal, and the first signal and the second signal are generated with respect to the element substrate. A signal generating means for transmitting the current, a receiving means for receiving the determination result signal, and an adjusting means for adjusting the current value energized by the constant current source based on the determination result signal received by the receiving means. A recording device having a memory for storing the current value adjusted by the adjusting means, and the adjusting means is a group of at least a part of the arranged nozzles based on the determination result signal. A recording device characterized in that a common current value for energizing a temperature sensor corresponding to each of a plurality of nozzles constituting the device is adjusted.

According to the present invention, there is an effect that the ejection state of the nozzle can be determined with high accuracy from the temperature sensor provided corresponding to each nozzle while suppressing the increase in the circuit scale related to the determination of the ejection state.

It is a perspective view for demonstrating the structure of the recording apparatus provided with the full-line recording head which is a typical example of this invention. It is a block diagram which shows the control structure of the recording apparatus shown in FIG. It is a figure which shows the multi-layer wiring structure in the vicinity of a recording element formed on a silicon substrate. It is a block diagram which shows the control structure of temperature detection using the element substrate shown in FIG. It is a figure which shows the detailed internal circuit structure of the element substrate 5. It is a time chart of each signal input to the element board. It is a figure which shows the circuit structure which generates the determination result signal RSLT paying attention to one heater (resistor). It is a circuit diagram which shows the detailed structure of the bandpass filter (BPF) 113. 3 is a time chart showing the output waveform Vdiv of the differential amplifier and the output waveform Viv of the inverting amplifier when the constant current Iref0 is applied to the temperature sensor during the latch period T and the pulse of the heater drive signal HT is applied to the heater. It is a time chart which showed the output waveform Vdiv of the differential amplifier and the output waveform Vinv of an inverting amplifier at the time of normal discharge when the constant current Iref is increased by one rank. It is a time chart which showed the output waveform Vdiv of a differential amplifier and the output waveform Vinv of an inverting amplifier at the time of normal discharge when the constant current is increased by 1 rank. It is a flowchart explaining the adjustment process of a constant current. It is a flowchart which shows the detailed process of the acquisition process of the peak voltage shown in step S2 and step S5 shown in FIG. It is a time chart which shows the change of the determination signal when the threshold voltage is changed. It is a figure explaining the method of obtaining the set voltage for three temperature sensors. It is a flowchart which shows the process of determining a set voltage Vpe. 6 is a timing chart showing the output waveform Vdiv of the differential amplifier and the output waveform Vinv of the inverting amplifier when a pulse of the heater drive signal HT is applied to the heater while energizing the temperature sensor with the adjusted constant current Iador. It is a timing chart which shows the output waveform Vdiv of a differential amplifier and the output waveform Vinv of an inverting amplifier when a pulse of a heater drive signal HT is applied to a heater while energizing a temperature sensor with an unadjusted constant current Iref0. 6 is a timing chart showing the output waveform Vdiv of the differential amplifier and the output waveform Vinv of the inverting amplifier when a pulse of the heater drive signal HT is applied to the heater while energizing the temperature sensor with the adjusted constant current Iador. A timing chart showing the output waveform Vdiv of the differential amplifier and the output waveform Vinv of the inverting amplifier when a constant current is applied to the temperature sensor during the ON period of the heater energization signal SE but the pulse of the heater drive signal HT is not applied to the heater. is there. It is a figure explaining the method of obtaining the set current value for three temperature sensors. It is a flowchart which shows the process of determining a set current Iref.

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

In this specification, "record" (sometimes referred to as "print") is not limited to the case of forming significant information such as characters and figures, and may be significant or involuntary. It also refers to the case where an image, pattern, pattern, etc. is widely formed on a recording medium or the medium is processed, regardless of whether or not it is manifested so that it can be visually perceived by humans. ..

The term "recording medium" refers not only to paper used in general recording devices, but also to a wide range of media such as cloth, plastic film, metal plate, glass, ceramics, wood, and leather that can accept ink. Shall be.

Further, "ink" (sometimes referred to as "liquid") should be broadly interpreted as in the definition of "recording (printing)" above. Therefore, by being applied onto the recording medium, the image, pattern, pattern, etc. are formed, the recording medium is processed, or the ink is processed (for example, the colorant in the ink applied to the recording medium is solidified or insolubilized). It shall represent a liquid that can be produced.

Furthermore, the term "nozzle (sometimes referred to as" recording element ")" collectively refers to the ejection port, the liquid passage communicating with the ejection port, and the element that generates energy used for ink ejection, unless otherwise specified. Shall be.

The element substrate (head substrate) for a recording head used below does not indicate a mere substrate made of a silicon semiconductor, but indicates a configuration in which each element, wiring, or the like is provided.

Further, the term “on the substrate” means not only the top of the element substrate but also the surface of the element substrate and the inside side of the element substrate in the vicinity of the surface. Further, the term "build-in" as used in the present invention does not mean that each element of a separate body is simply arranged as a separate body on the surface of a substrate, but that each element is manufactured as a semiconductor circuit. It indicates that it is integrally formed and manufactured on an element plate by a process or the like.

<Recording device equipped with a full-line recording head (Fig. 1)>
FIG. 1 is a diagram showing a schematic configuration of a recording device 1000 using a full-line recording head that ejects ink and records, which is a typical embodiment of the present invention.

As shown in FIG. 1, the recording device 1000 includes a transport unit 1 for transporting the recording medium 2 and a full-line recording head 3 arranged substantially orthogonal to the transport direction of the recording medium 2, and a plurality of recordings are performed. This is a line-type recording device that continuously records while continuously or intermittently transporting the medium 2. The full-line recording head 3 has a negative pressure control unit 230 that controls the pressure (negative pressure) in the ink path, a liquid supply unit 220 that communicates with the negative pressure control unit 230, and ink supply to the liquid supply unit 220. And a liquid connection portion 111A serving as a discharge port is provided.

The housing 80 is provided with a negative pressure control unit 230, a liquid supply unit 220, and a liquid connection portion 111A.

The recording medium 2 is not limited to the cut sheet, and may be a continuous roll sheet.

The full-line recording head (hereinafter, recording head) 3 can perform full-color recording with cyan (C), magenta (M), yellow (Y), and black (K) inks. A liquid supply unit 220, which is a supply path for supplying ink to the recording head 3, and a main tank are connected to the recording head 3. Further, an electric control unit (not shown) for transmitting electric power and discharge control signals to the recording head 3 is electrically connected to the recording head 3.

Further, the recording medium 2 is conveyed by rotating two transfer rollers 81, 82 provided so as to be separated by a distance of length F in the transfer direction.

The recording head of this embodiment employs an inkjet method that uses heat energy to eject ink. Therefore, each discharge port of the recording head 3 is provided with an electric heat conversion element (heater). The electric heat conversion element is provided corresponding to each discharge port, and ink is discharged from the corresponding discharge port by applying a pulse voltage to the corresponding electric heat conversion element according to a recording signal. The recording device is not limited to a recording device using a full-line recording head having a recording width corresponding to the width of the recording medium described above. For example, it can be applied to a so-called serial type recording device in which a recording head in which ejection ports are arranged in a transport direction of a recording medium is mounted on a carriage, and ink is ejected to the recording medium while scanning the carriage reciprocatingly for recording.

<Explanation of control configuration (Fig. 2)>
FIG. 2 is a block diagram showing a configuration of a control circuit of the recording device 1000.

As shown in FIG. 2, the recording device 1000 is mainly composed of a print engine unit 417 that controls the recording unit, a scanner engine unit 411 that controls the scanner unit, and a controller unit 410 that controls the entire recording device 1000. ing. The print controller 419 having a built-in MPU or non-volatile memory (EEPROM or the like) controls various mechanisms of the print engine unit 417 according to the instruction of the main controller 441 of the controller unit 410. Various mechanisms of the scanner engine unit 411 are controlled by the main controller 441 of the controller unit 410.

The details of the control configuration will be described below.

In the controller unit 410, the main controller 441 composed of the CPU controls the entire recording device 1000 while using the RAM 406 as a work area according to the programs and various parameters stored in the ROM 407. For example, when a print job is input from the host device 400 via the host I / F 402 or the wireless I / F 403, the image processing unit 408 performs predetermined image processing on the received image data according to the instruction of the main controller 441. Give. Then, the main controller 441 transmits the image data subjected to the image processing to the print engine unit 417 via the print engine I / F405.

The recording device 1000 may acquire image data from the host device 400 via wireless communication or wired communication, or may acquire image data from an external storage device (USB memory or the like) connected to the recording device 1000. Is also good. The communication method used for wireless communication and wired communication is not limited. For example, Wi-Fi (Wireless Fidelity) (registered trademark) and Bluetooth (registered trademark) can be applied as a communication method used for wireless communication. Further, as a communication method used for wired communication, USB (Universal Serial Bus) or the like can be applied. Further, for example, when a read command is input from the host device 400, the main controller 441 transmits this command to the scanner engine unit 411 via the scanner engine I / F409.

The operation panel 404 is a unit for the user to input / output to / from the recording device 1000. The user can instruct operations such as copying and scanning via the operation panel 404, set the recording mode, and recognize the information of the recording device 1000.

In the print engine unit 417, the print controller 419 composed of the CPU controls various mechanisms of the print engine unit 417 with the RAM 421 as a work area according to the programs and various parameters stored in the ROM 420.

When various commands and image data are received via the controller I / F418, the print controller 419 temporarily stores them in the RAM 421. The print controller 419 is converted into the image processing controller 422, and the saved image data is converted into the recording data so that the recording head 3 can be used for the recording operation. When the recorded data is generated, the print controller 419 causes the recording head 3 to execute a recording operation based on the recorded data via the head I / F 427. At this time, the print controller 419 drives the transfer rollers 81 and 82 via the transfer control unit 426 to transfer the recording medium 2. According to the instruction of the print controller 419, the recording operation by the recording head 3 is executed in conjunction with the conveying operation of the recording medium 2, and the recording process is performed.

The head carriage control unit 425 changes the direction and position of the recording head 3 according to an operating state such as a maintenance state or a recording state of the recording device 1000. The ink supply control unit 424 controls the liquid supply unit 220 so that the pressure of the ink supplied to the recording head 3 falls within an appropriate range. The maintenance control unit 423 controls the operation of the cap unit and the wiping unit in the maintenance unit (not shown) when performing the maintenance operation on the recording head 3.

In the scanner engine unit 411, the main controller 441 controls the hardware resources of the scanner controller 415 according to the programs and various parameters stored in the ROM 407, using the RAM 406 as a work area. As a result, various mechanisms included in the scanner engine unit 411 are controlled. For example, the main controller 441 controls the hardware resources in the scanner controller 415 via the controller I / F 414, and the document loaded on the ADF (not shown) by the user is conveyed via the transfer control unit 413, and the sensor. Read by 416. Then, the scanner controller 415 stores the read image data in the RAM 412.

The print controller 419 can cause the recording head 3 to execute a recording operation based on the image data read by the scanner controller 415 by converting the image data acquired as described above into the recording data.

<Explanation of the configuration of the temperature detection element (Fig. 3)>
FIG. 3 is a diagram showing a multilayer wiring structure in the vicinity of a recording element formed on a silicon substrate.

FIG. 3A is a top view in which the temperature detection element 606 is arranged in a sheet shape under the recording element 609 via the interlayer insulating film 607. FIG. 3 (b) is a cross-sectional view taken along the broken line xx'in the top view shown in FIG. 3 (a), and FIG. 3 (c) shows the broken line yy'shown in FIG. 3 (a). It is a cross-sectional view along.

In the xx'cross-sectional view shown in FIG. 3 (b) and the yy' cross-sectional view shown in FIG. 3 (c), a wiring 603 made of aluminum or the like is formed on the insulating film 602 laminated on the silicon substrate. Further, an interlayer insulating film 604 is formed on the wiring 603. The wiring 603 and the temperature detection element 606 of a thin film resistor made of titanium, a titanium nitride laminated film, or the like are electrically connected via a conductive plug 605 made of tungsten or the like embedded in the interlayer insulating film 604.

Next, an interlayer insulating film 607 is formed on the lower side of the temperature detection element 606. Then, the wiring 603 and the recording element 609 of the heat generating resistor made of the tantalum nitride silicon film or the like are electrically connected via the conductive plug 608 made of tungsten or the like penetrating the interlayer insulating film 604 and the interlayer insulating film 607. To.

When connecting the lower conductive plug and the upper conductive plug, it is common that they are connected by sandwiching a spacer composed of an intermediate wiring layer. When applied to this embodiment, since the film thickness of the temperature detection element that is the intermediate wiring layer is a thin film of about several tens of nm, the accuracy of overetch control for the temperature detection element film that is the spacer is required during the via hole process. .. In addition, it is disadvantageous for miniaturizing the pattern of the temperature detection element layer. In view of such circumstances, in this embodiment, a conductive plug in which the interlayer insulating film 604 and the interlayer insulating film 607 are penetrated is adopted.

Further, in order to ensure the reliability of conduction according to the depth of the plug, in this embodiment, the conductive plug 605 having a single layer of interlayer insulating film has a diameter of 0.4 μm, and the conductive plug in which the interlayer insulating film penetrates the two layers. In 608, the larger diameter is 0.6 μm.

Next, a protective film 610 such as a silicon nitride film and a cavitation resistant film 611 such as tantalum are formed on the protective film 610 to form a head substrate (element substrate). Further, the discharge port 613 is formed by the nozzle forming material 612 made of a photosensitive resin or the like.

As described above, the multi-layer wiring structure is provided in which an independent intermediate layer of the temperature detection element 606 is provided between the layer of the wiring 603 and the layer of the recording element 609.

From the above configuration, in the element substrate used in this embodiment, it is possible to obtain temperature information for each recording element by a temperature detecting element provided immediately below each recording element.

Then, from the temperature information detected by the temperature detection element and the temperature change, a determination result signal RSLT indicating the ink ejection state from the corresponding recording element can be obtained by the logic circuit provided inside the element substrate. .. The determination result signal RSLT is a 1-bit signal, where "1" indicates normal discharge and "0" indicates defective discharge.

<Explanation of temperature detection configuration seen from the recording device side (Fig. 4)>
FIG. 4 is a block diagram showing a control configuration for temperature detection using the element substrate shown in FIG.

As shown in FIG. 4A, the print engine unit 417 has a print controller 419 with a built-in MPU and a head I connected to the recording head 3 in order to detect the temperature of the recording element mounted on the element substrate 5. It includes / F427 and RAM 421. Further, the head I / F 427 has a signal generation unit 7 that generates various signals for transmission to the element substrate 5, and a determination result signal RSLT output from the element substrate 5 based on the temperature information detected by the temperature detection element 606. Includes a determination result extraction unit 9 for inputting.

When the print controller 419 issues an instruction to the signal generation unit 7 for temperature detection, the signal generation unit 7 issues a clock signal CLK, a latch signal LT, a block signal BLE, a recorded data signal DATA, and a heat enable to the element substrate 5. Output the signal HE. The signal generation unit 7 further outputs the sensor selection signal SDATA, the constant current signal Diref, and the discharge inspection threshold signal Dds.

The sensor selection signal SDATA includes selection information for selecting a temperature detection element for detecting temperature information, information for specifying the amount of electricity supplied to the selected temperature detection element, and information related to an output instruction of the determination result signal RSLT. For example, when the element substrate 5 is configured to mount five rows of recording elements composed of a plurality of recording elements, the selection information included in the sensor selection signal SDATA includes the column selection information for designating the rows and the recording elements of the rows. Includes designated recording element selection information. On the other hand, the element substrate 5 outputs a 1-bit determination result signal RSLT based on the temperature information detected by the temperature detection element corresponding to one recording element in the row specified by the sensor selection signal SDATA.

In this embodiment, a configuration is adopted in which a 1-bit determination result signal RSLT is output per recording element for 5 columns. Therefore, in the configuration in which the element substrate 5 mounts 10 rows of recording elements, the determination result signal RSLT has 2 bits, and this 2-bit signal is serially output to the determination result extraction unit 9 via one signal line. Will be done.

As can be seen from FIG. 4A, the latch signal LT, the block signal BLE, and the sensor selection signal SDATA are fed back to the determination result extraction unit 9. On the other hand, the determination result extraction unit 9 receives the determination result signal RSLT output from the element substrate 5 based on the temperature information detected by the temperature detection element, and determines in each latch period in synchronization with the falling edge of the latch signal LT. Extract the results. Then, when the determination result is a discharge failure, the block signal BLE and the sensor selection signal SDATA corresponding to the determination result are stored in the RAM 421.

Then, the print controller 419 erases the signal for the ejection failure nozzle from the recorded data signal DATA of the corresponding block based on the block signal BLE and the sensor selection signal SDATA used to drive the ejection failure nozzle stored in the RAM 421. .. Then, instead, a nozzle for ejection failure complement is added to the recorded data signal DATA of the corresponding block, and the nozzle is output to the signal generation unit 7.

In the configuration shown in FIG. 4A, the constant current signal Diref and the discharge inspection threshold signal Dds are output to the element substrate 5 by separate signal lines, but the present invention is not limited thereto. Absent. As shown in FIG. 4B, the constant current signal Diref and the discharge inspection threshold signal Dds may be output to the element substrate 5 via a common signal line. In this case, for example, the signal generation unit 7 serially outputs the constant current signal Diref and the discharge inspection threshold signal Dds.

<Explanation of the circuit configuration of the element substrate and the temperature detection configuration in the element substrate (FIGS. 5 to 8)>
FIG. 5 is a diagram showing a detailed internal circuit configuration of the element substrate 5.

As can be seen from the multilayer wiring structure in the vicinity of the recording element shown in FIG. 3, the temperature detection element 606 is formed in the lower layer of the recording element 609. Correspondingly, the element substrate 5 shown in FIG. 5A is provided with a plurality of heaters 101 operating as recording elements 609 and a plurality of temperature sensors 102 operating as temperature detecting elements 606 in pairs. Further, a switch element 105 for turning on / off the heater 101 and a switch element 106 for turning on / off the temperature sensor 102 are connected to the heater 101 and the temperature sensor 102, respectively.

The plurality of heaters 101 and the plurality of temperature sensors 102 are grouped by a plurality of adjacent heaters for time-division driving. In FIG. 5A, this group is designated as G1, G2, G3 ....

A power supply 103 provided outside the element substrate 5 is connected in parallel to the plurality of heaters 101, and a constant current source 104 provided inside the element substrate 5 is connected in parallel to the plurality of temperature sensors 102. Further, a constant current control circuit 240 that drives the constant current source 104 based on the input constant current signal Diref is connected to the constant current source 104. Further, a determination circuit 250 for determining the discharge state of the recording element (nozzle) is connected in parallel to the plurality of temperature sensors 102 based on a temperature detection signal output from any of these heaters, and the determination circuit 250 determines. The result signal RSLT is output.

In order to drive each heater 101, the recorded data signal DATA is received according to the clock signal CLK and input to the shift register (SR) 701, which is latched by the latch circuit (LAT) 703 according to the latch signal LT. Then, this is output to the AND circuit 705 as a heater selection signal D. The heater selection signal D is held for a period T until the next latch timing, during which the next recorded data signal DATA is transferred to the shift register 701. For example, if the group to which the nozzle to be driven belongs is G2, only the heater selection signal D input to the AND circuit 705 belonging to group G2 is valid (High active), and the others are Low.

On the other hand, the block signal BLE is input to another shift register (SR) 708 according to the clock signal CLK, and this is latched by another latch circuit (LAT) 709 according to the latch signal LT. Then, the decoder 710 decodes the block signal BLE to generate the block selection signal BL, which is output to the AND circuit 705. The block selection signal BL output from the decoder 710 is output to the wiring for the number of block divisions. Then, the block selection signal BL corresponding to the nozzle to be driven becomes valid (High active) and is held for a period T until the next latch timing, during which the next block signal BLE is transferred to the shift register 708. Will be done.

The logical product of the recorded data signal DATA and the block selection signal BL is calculated by the AND circuit 705, and the calculation result is output to the AND circuit 706. If both of the two input signals to the AND circuit 705 are valid (High active), the output signal from the AND circuit 705 is valid (High active). Then, it is input to the AND circuit 706 as a signal for permitting the driving of the heater 101. When the heat enable signal HE is input to the AND circuit 706, the AND circuit 706 outputs a heater drive signal HT based on the heat enable signal HE, and the switch element 105 is turned on only during the period when the heater drive is turned on. As a result, a current flows through the corresponding heater 101, and the heat generated by the heater 101 heats the ink and ejects the ink.

In this embodiment, one temperature sensor 102 is selected at one timing by the sensor selection signal SDATA input at that time. The sensor selection signal SDATA is received by the shift register (SR) 702 according to the clock signal CLK, latched by the latch circuit (LAT) 704 according to the latch signal LT, and output to the AND circuit 707 as the selection signal SD. The selection signal SD is held for a period T until the next latch timing, during which time the next sensor selection signal SDATA is transferred to the shift register 702. For example, if the group to which the nozzle to be detected for temperature information belongs is G2, only the selection signal SD input to the AND circuit 707 belonging to group G2 is valid (High active), and the others are Low.

On the other hand, the block selection signal BL is input to the AND circuit 707. That is, the signal for selecting the temperature sensor 102 that operates as the temperature detection element is shared with the block selection signal BL for selecting the heater 101. Therefore, when both the selection signal SD and the block selection signal BL are valid (High active), the AND circuit 707 outputs a sensor energization signal SE that is valid (High active) during the latch period T. One switch element 106 is turned on by the sensor energization signal SE, a constant current Iref flows through one temperature sensor 102 corresponding to the switch element 106, and a potential difference (voltage) appearing at both ends of the temperature sensor (resistance) 102 is transmitted to the determination circuit 250. Entered.

In order to output the temperature detection signal from the temperature sensor 102 when the heater 101 is not driven, all the heater selection signals D are Low, and only one selection signal SD is valid (High active). Just do it.

As can be seen from the above configuration, one constant current control circuit 240 and one determination circuit 250 common to the plurality of temperature sensors 102 that serve as temperature detection elements provided in the element substrate 5 are provided. Therefore, at a certain timing, the determination result signal RSLT based on the temperature information detected by the one temperature sensor 102 selected by the sensor selection signal SDATA is output.

As shown in FIG. 4B, when the constant current signal Diref and the discharge inspection threshold signal Dds are transferred to the element substrate 5 via a common signal line, the inside of the element substrate 5 is configured to correspond to this. The circuit configuration may be the configuration shown in FIG. 5B. That is, FIG. 5 (a) shows a configuration in which separate and independent terminals are provided for receiving the constant current signal Diref and the discharge inspection threshold signal Dds. However, as shown in FIG. 5 (b), the constant current signal is provided. A common terminal may be provided for receiving the Diref and the discharge inspection threshold signal Dds.

FIG. 6 is a time chart of each signal input to the element substrate.

As shown in FIG. 6, the element substrate 5 is ejected from the signal generation unit 7 of the recording device: clock signal CLK, latch signal LT, heat enable signal HE, recorded data signal DATA, sensor selection signal SDATA, constant current signal Diref, and discharge. Receives the inspection threshold signal Dds. Other than the clock signal CLK, it is received once every latch period T.

Next, a circuit configuration for generating a determination result signal RSLT inside the element substrate 5 from the temperature information detected by one temperature sensor 102 will be described.

FIG. 7 is a diagram showing a circuit configuration for generating a determination result signal RSLT focusing on one heater (resistor). In FIG. 7, the same reference numbers and reference symbols are assigned to the components and signals already described above, and the description thereof will be omitted.

In FIG. 7, (a) shows the input / output state of the circuit that processes the signal output from the temperature sensor 102 when the heater drive signal HT is applied to the heater 101. Further, (b) represents the input / output state of the circuit that processes the signal output from the temperature sensor 102 when the heater drive signal HT is not applied to the heater 101. The temperature sensor 102 is composed of a thin film resistor.

In FIG. 7A, when the heater drive signal HT is turned ON (High active), the switch element 105 is closed (ON) and a constant voltage VH is applied to the heater 101. Further, when the heater drive signal HT is turned OFF (Low), the switch element 105 is opened (OFF), and the application of the constant voltage VH to the heater 101 is cut off. In this way, the constant voltage VH is applied to the heater 101 in a square pulse shape by turning on / off the heater drive signal HT.

On the other hand, when the sensor energization signal SE is turned ON (High active), the switch element 106 is closed (ON) and the constant current Iref is supplied to the temperature sensor 102. At the same time, the switch element 107 is closed (ON), and the voltage signals VSS and VSS + VSS at both ends of the temperature sensor 102 are input to the differential amplifier 111.

Further, when the sensor energization signal SE is turned OFF (Low), the switch element 105 is opened (OFF), the supply of the constant current Iref to the temperature sensor 102 is cut off, and the difference between the voltage signals at both ends of the temperature sensor 102. The input to the dynamic amplifier 111 is also cut off.

The constant current Iref can be set in 32 steps from 0.6 mA to 3.7 mA in steps of 0.1 mA, for example. Hereinafter, the setting width of one step is referred to as one rank. If it is one rank larger, the current value is larger. The constant current signal Diref, which determines the set value of the constant current Iref, is defined as a 5-bit digital value that can be set in 32 steps, and is transferred from the signal generator 7 to the shift register (SR) 108 in synchronization with the clock signal CLK. ..

Then, the set value determined by the constant current signal Diref is latched by the latch circuit 109 in synchronization with the latch signal LT, and is output to the current output type digital-to-analog converter (DAC) 110. The output signal of the latch circuit 109 is held for a period T until the next latch timing, during which the set value determined by the next constant current signal Diref is transferred from the signal generation unit 7 to the shift register 108. The output current Iref of the DAC 110 is input to the constant current source 104, amplified 12 times, and output as a constant current Iref.

The resistance Rs at the temperature T of the temperature sensor 102 is represented by the equation (1), where T0 is the normal temperature, Rs0 is the resistance value at that time, and the temperature resistance coefficient of the temperature sensor 102 is TCR. That is,
Rs = Rs0 {1 + TCR (T-T0)} …… (1)
Is. When the constant current Iref is supplied to the temperature sensor 102, the difference voltage VS at both ends is represented by the equation (2). That is,
VS = Iref ・ Rs = Iref ・ Rs0 {1 + TCR (T-T0)} …… (2)
Is. The difference voltage VS is inverting and input to the differential amplifier 111, but if it is left as it is, the output Vdiv becomes a negative voltage equal to or less than the ground potential GND, and in reality Vdim = 0V and feedback to the-terminal of the operational amplifier inside the differential amplifier 111. Will be done. Therefore, an unexpected signal is finally output. In order to avoid this, an offset voltage Vref sufficient for the output Vdiv to be equal to or higher than the ground potential GND is applied to the differential amplifier 111 by the constant voltage source 112.

As a result, assuming that the amplification factor of the differential amplifier 111 is Gdiv, the output Vdiv of the differential amplifier 111 is as shown by the equation (3). That is,
Vdiv = Vref-Gdiv · Vs …… (3)
Is. The output Vdiv of the differential amplifier 111 is input to the bandpass filter (BPF) 113. The BPF 113 is a circuit for suppressing noise in the voltage Vdiv, converting a signal when the change is maximum into a peak, and outputting the signal.

FIG. 8 is a circuit diagram showing a detailed configuration of the bandpass filter (BPF) 113.

As shown in FIG. 8A, the BPF 113 is composed of a bandpass filter in which a secondary lowpass filter 501 and a primary highpass filter 502 are cascaded. The low-pass filter (LPF) 501 is composed of an operational amplifier 503, resistors R1L504 and R2L505, and capacitors C1L506 and C2L507. The LPF501 has a predetermined pass band and attenuates high frequency noise on the high frequency side of the cutoff frequency fcL. The cutoff frequency fcL here is obtained by the equation (4). That is,
fcL = 1 / [2π ・ √ (R1L ・ R2L ・ C1L ・ C2L)] …… (4)
Is.

On the other hand, the high-pass filter (HPF) 502 is composed of an operational amplifier 511, resistors R1H512 and R2H513, a capacitor CH514, and a constant voltage source 114. The HPF502 has a predetermined passband, and the low frequency side of the cutoff frequency fcH is first-order differentiated to extract the gradient at the time of temperature decrease, and the DC component is removed. The cutoff frequency fcH here is obtained by the equation (5). That is,
fcH = 1 / (2π ・ R1H ・ CH) …… (5)
Is.

By the signal processing by the BPF 113 having the above-described configuration, the BPF 113 outputs a signal VF that is a source for determining either normal discharge or discharge failure.

If the + terminal of the operational amplifier 511 is directly grounded, the signal VF may have a negative voltage equal to or lower than the ground potential GND. At that time, VF = 0V and the signal is fed back to the-terminal of the operational amplifier 511. An unexpected signal VF is output. In order to avoid this, in this embodiment, an offset voltage Vofs sufficient for the signal VF to be equal to or higher than the ground potential GND is applied to the + terminal by the constant voltage source 114.

If the LPF501 cannot sufficiently attenuate the high frequency noise contained in the signal Vdiv, the LPF501 may be connected in two stages in a cascade. On the contrary, if the high frequency noise contained in the signal Vdiv is at a level at which there is no problem even if it passes through the HPF502 as it is, as shown in FIG. 8B, the LPF501 may be omitted and the BPF113 may be configured only with the HPF502. good.

Returning to FIG. 7A and continuing the description, the output signal VF of the BPF 113 is amplified by the inverting amplifier (INV) 115 in the subsequent stage because the low frequency signal is attenuated by the HPF 502 and the output voltage is lowered. In the inverting amplifier 115, the positive voltage input signal VF is inverted to become a negative voltage, so the offset voltage Vofs is applied to raise the signal voltage in the same manner as the HPF502. Here, the output of the constant voltage source 114 that applies the offset voltage Vofs to the HPF 502 is branched, and the same offset voltage Vofs is also applied to the inverting amplifier 115. As a result, assuming that the amplification factor of the inverting amplifier 115 is Ginv, the output signal Vinv of the inverting amplifier 115 is as shown in the equation (6). That is,
Vinv = Vofs + Ginv (Vofs-VF) …… (6)
Is.

By the way, as shown in FIG. 7B, if the heater drive signal HT is not applied to the heater 101 and the temperature indicated by the temperature information of the temperature sensor 102 remains at room temperature T0, the output Vdiv of the differential amplifier 111 From equations (2) to (3), is as shown in equation (7). That is,
Vdiv0 = Vref-Gdiv ・ Iref ・ Rs0 …… (7)
Will be. That is, since the output Vdiv becomes a constant voltage and the output signal VF of the BPF 113 becomes the offset voltage Vofs, the second term disappears from the equation (6) and the output signal Vinv of the inverting amplifier 115 also becomes Vofs. That is, by making the offset voltage applied to the inverting amplifier 115 common to the offset voltage Vofs applied to the HPF 502, the reference voltage of the voltage Vinv is affected by the amplification factor Ginv of the inverting amplifier 115 and the variation of the difference voltage between the offset voltages. Stable without receiving.

The output signal Vinv of the inverting amplifier 115 is input to the positive terminal of the comparator 116, compared with the threshold voltage Dth input to the negative terminal, and if Vinv> Dth, a high level (normal discharge) determination signal is obtained. Output CMP. If Vinv <Dth or Vinv = Dth, the determination signal CMP outputs a low level signal.

The threshold voltage Dth can be set in 256 ranks from 0.5V to 2.54V in increments of 8 mV, for example.

The discharge inspection threshold signal Dds that sets the threshold voltage Dth is defined as, for example, an 8-bit digital value that can be set in 256 ranks, and is transferred from the signal generation unit 7 to the shift register 117 in synchronization with the clock signal CLK. Then, it is latched by the latch circuit 118 in synchronization with the latch signal LT, and is output to the voltage output type DAC119. The output signal of the latch circuit 118 is held for a period T until the next latch timing, during which the discharge inspection threshold signal Dds that sets the next threshold voltage is transferred to the shift register 117.

By inputting the determination signal CMP to the set input terminal (S) of the RS latch circuit 120, the pulse signal of the determination signal CMP is held (HCMP). By latching this signal HCMP with the flip-flop circuit 121 using the latch signal LT as a trigger, a determination result signal RSLT which becomes High in the next latch period at the time of normal discharge is obtained. The signal HCMP is reset at the falling edge of the latch signal LT by inputting the inverted signal of the latch signal LT to the reset input terminal (R) of the RS latch circuit 120.

The determination result signal RSLT is extracted by the determination result extraction unit 9 shown in FIG. 4 together with the block signal BLE and the sensor selection signal SDATA delayed by the latch period T in synchronization with the falling edge of the latch signal LT.

Next, an example of temperature detection of each recording element (heater) in the recording head incorporating the element substrate having the above configuration will be described below.

(Example 1)
FIG. 9A shows the output waveform Vdiv of the differential amplifier 111 and the output waveform Vinv of the inverting amplifier 115 when the constant current Iref0 is applied to the temperature sensor 102 during the latch period T and the pulse 211 of the heater drive signal HT is applied to the heater 101. It is a time chart showing.

In FIG. 9A, the resistance value Rs0 of the temperature sensor 102 at room temperature T0, the temperature resistance coefficient TCR, and the resistance value of the heater 101 are smaller than the standard values, and the film thickness of the interlayer film separating the heater 101 and the temperature sensor 102 is smaller than the standard values. It represents Vdiv and Vinv when it is thick.

In FIG. 9A, the sensor energization signal SE is turned ON (212), the constant current Iref0 (for example, 1.6 mA) is energized to the temperature sensor 102, and the heater 101 is applied with the pulse 211 of the heater drive signal HT. Here, in the case of normal discharge, the output waveform Vdiv becomes the waveform 201. Since the waveform 201 is upside down as a temperature waveform, a negative slope represents a temperature raising process, and a positive slope represents a temperature falling process. In the process of lowering the temperature of the waveform 201, the tail of the ink droplets ejected from the nozzle crashes at the interface of the heater 101 during normal ejection, and the interface is cooled. As a result, the feature point 209 appears, and the temperature lowering rate of the waveform 201 sharply increases after the feature point 209. On the other hand, in the case of a discharge failure, the output waveform Vdiv becomes like the waveform 202, the feature point 209 does not appear like the waveform 201 of the normal discharge, and the temperature lowering rate gradually decreases in the temperature lowering process.

The initial voltage of the waveforms 201 and 202 before applying the pulse 211 of the heater drive signal HT is Vdim0 represented by the equation (7), and the waveforms 201 and 202 gradually approach Vdiv0 through the temperature lowering process. When the waveform 201 is output from the inverting amplifier 115 via the BPF 113, it becomes the waveform 203. Similarly, the waveform 202 becomes the waveform 204 when output from the inverting amplifier 115. The reference voltage of the waveforms 203 and 204 is Vofs, and finally approaches Vofs through the temperature lowering process. In the waveform 203, a peak value 210 due to the maximum temperature drop rate after the feature point 209 of the waveform 201 appears, and the comparator 116 compares it with the threshold voltage Dth, and the determination signal CMP is used in the section exceeding the threshold voltage Dth. Is output as a pulse 213 indicating that the discharge is normal.

On the other hand, since the feature point 209 does not appear in the waveform 202, the temperature lowering rate is low, the peak appearing in the waveform 204 is lower than the threshold voltage Dth, and the pulse 213 does not appear in the determination signal CMP output from the comparator 116. The wider the peak difference Vpdiv between the peak of the waveform 203 and the peak of the waveform 204, the wider the difference between the threshold voltage Dth and the peak can be secured, and the discharge state can be determined with high accuracy. The peak difference Vpdiv can be expanded by amplifying the output Vinv of the inverting amplifier 115 by the amplifier, but the noise also increases in proportion to the amplification factor, so that the determination accuracy is not improved.

Therefore, in this example, the constant current Iref is increased to amplify the difference voltage VS across the temperature sensor 102 without increasing the noise, and the peak voltage Vp is increased to widen the peak difference Vpdiv to improve the determination accuracy. ..

FIG. 9B is a time chart showing the output waveform Vdiv of the differential amplifier 111 and the output waveform Vinv of the inverting amplifier 115 at the time of normal discharge when the constant current Iref is increased by one rank.

In FIG. 9B, the waveform of the output Vdiv corresponding to the initial value Iref1 (reference rank) of the constant current Iref is 221. The output waveform Vinv231 corresponds to the waveform 221 of the output Vdiv. Similarly, the waveform of the output Vdiv corresponding to the constant current Iref2 is set to 222. The output waveform Vinv232 corresponds to the waveform 222 of the output Vdiv. The waveform of the output Vdiv corresponding to the constant current Iref3 is 223. The output waveform Vinv233 corresponds to the waveform 223 of the output Vdiv. Let 224 be the waveform of the output Vdiv corresponding to the constant current Iref4. The output waveform Vinv234 corresponds to the waveform 224 of the output Vdiv.

Since the BPF 113 is a linear filter, when the constant current Iref increases linearly, the output Vdiv of the differential amplifier 111 decreases linearly, and the output Vinv of the inverting amplifier 115 increases linearly.

That is, when the current value of the constant current Iref is increased by one rank, the waveform 221 of the output Vdiv changes to the waveform 222, the waveform 223, and the waveform 224. The peak of the waveform decreases by ΔVdiv corresponding to Iref1 rank.

Further, as the waveform of the output Vdiv changes, the waveform 231 of the output Vinv increases by ΔVinv whose peak voltage Vp corresponds to the Iref1 rank, and changes from the waveform 231 to the waveform 232, the waveform 233, and the waveform 234. At this time, the peak voltage Vp increases linearly with the increase of Iref. As shown in FIG. 9B, the maximum value of the output waveform Vinv231 is Vpmax1, the maximum value of the output waveform Vinv232 is Vpmax2, the maximum value of the output waveform Vinv233 is Vpmax3, and the maximum value of the output waveform Vinv234 is Vpmax4.

However, due to the characteristics of the operational amplifiers that make up the differential amplifier 111, the output Vdiv of the differential amplifier 111 changes non-linearly when the voltage drops below a certain voltage, and when the voltage drops further, it saturates and does not drop any further. Therefore, if the constant current Iref is increased beyond a certain current value Imax, a phenomenon occurs in which the peak voltage Vp is conversely lowered.

FIG. 9C is a time chart showing the output waveform Vdiv of the differential amplifier 111 and the output waveform Viv of the inverting amplifier 115 at the time of normal discharge when the value exceeds the constant current Iref4 and is increased by one rank.

In FIG. 9C, the waveform of the output Vdiv corresponding to the constant current Iref5 is 225. The output waveform Vinv235 corresponds to the waveform 225 of the output Vdiv. Similarly, the waveform of the output Vdiv corresponding to the constant current Iref 6 is set to 226. The output waveform Vinv236 corresponds to the waveform 226 of the output Vdiv.

According to FIG. 9C, when the constant current Imax is increased by one rank, the waveform 224 of the output Vdiv changes non-linearly and decreases from the peak voltage Vpmax4 to become the waveform 235. Specifically, the maximum gradient of the waveform 225 when the temperature is lowered is lower than that of the waveform 224, and the output Vinv is lowered from the waveform 234 whose peak voltage is Vpmax to become the waveform 235. Further, when the constant current Iref is increased by one rank, the peak of the waveform 225 of the output Vdiv is saturated and does not decrease, and becomes the waveform 226. At this time, the maximum gradient of the waveform 226 when the temperature is lowered is further lowered than that of the waveform 225, and the peak of the waveform 235 of the output Vinv is further lowered to become the waveform 236. The maximum value of the output waveform Vinv235 is Vpmax5, and the maximum value of the output waveform Vinv236 is Vpmax6.

As described above, even if the current value is increased from the constant current Iref4, the peak voltage Vp decreases. From this examination, even if the constant current Iref is increased without limit, the peak voltage Vp does not necessarily increase and the judgment accuracy does not improve, but the peak voltage Vp becomes maximum at a certain constant current value, and the Iref value is further increased. However, it can be seen that the peak voltage Vp decreases on the contrary. Therefore, the determination accuracy can be maintained as high as possible by investigating the constant current value that maximizes the peak voltage Vp and adjusting the constant current Iref so as not to deviate significantly from the current value.

FIG. 10 is a flowchart illustrating a constant current adjustment process executed based on the above studies. This process is executed by the print controller 419 shown in FIG. 4 via the head I / F 427. Then, the constant current adjusted by this process becomes the set value determined by the constant current signal Diref.

First, in step S1, the initial value of the constant current Iref is determined for one temperature sensor 102 to be adjusted, and the voltage applied to the temperature sensor 102 is generated by the current value. Next, in step S2, the peak voltage Vp described with reference to FIGS. 9A to 9B is obtained by using a plurality of threshold values for the generated voltage waveform. Then, in step S3, the obtained peak voltage Vp is stored in the RAM 421.

In step S4, the current value of the constant current Iref is increased by one rank, and the voltage applied to the temperature sensor 102 is generated by the current value. Further, in step S5, the peak voltage Vp is obtained by using a plurality of threshold values for the generated voltage waveform. In step S6, it is determined whether the acquired peak voltage Vp is larger than the peak voltage Vp stored in the RAM 421.

Here, if the peak voltage Vp obtained by energizing a constant current obtained by increasing the current value by one rank is larger than the peak voltage Vp already stored in the RAM 421, the process returns to step S3 and the same process is repeated. On the other hand, if the peak voltage Vp obtained by energizing a constant current obtained by increasing the current value by one rank is equal to or less than the peak voltage Vp already stored in the RAM 421, the process proceeds to step S7. Then, in step S7, the peak voltage Vp stored in the RAM 421 is set as the maximum value.

Here, the details of the processes of steps S2 and S5 will be described with reference to FIGS. 11 to 12.

FIG. 11 is a flowchart showing a detailed process of the peak voltage acquisition process shown in steps S2 and S5. Further, FIG. 12 is a time chart showing a change in the determination signal when the threshold voltage is changed. FIG. 12 shows an example in which the threshold voltage is changed from Dth0 to the threshold voltage Dth5 and set.

In step S11, a constant current is applied to the temperature sensor 102, and the threshold voltage is set in step S12. First, Dth0 is set as the threshold voltage Dth. In step S13, the heater 101 is turned on. In step S14, it is determined whether or not the peak voltage Vp from the temperature sensor 102 exceeds the threshold voltage by the time when a certain time (10 μs) elapses.

The circuit shown in FIG. 7 will be described as follows with reference to the configuration of these processes.

First, in the first latch period T, the signal generation unit 7 sets the reference set value Diref0 in the constant current signal Diref, and transmits the threshold voltage Dds to the element substrate 5 as Dds0. Correspondingly, the pulse 211 of the heater drive signal HT is applied to the heater 101 in a state where the temperature sensor 102 is energized with the constant current Iref0 (for example, 1.6 mA) corresponding to the reference set value Diref0. At this time, the reference set value Dds0 corresponding to the reference threshold voltage Dth0 is input to the comparator 116 and compared with the peak value 210 of the peak voltage Vp.

Here, if it is determined that the peak voltage Vp exceeds the threshold voltage Dth0, the process proceeds to step S15. Then, in step S15, the threshold voltage is stored in the RAM 421. In step S16, the threshold voltage Dth1 which is one rank larger is set. Then, the process returns to step S13, and the same process is repeated.

On the other hand, if it is determined that the peak voltage Vp is equal to or less than the threshold voltage Dth0, the process proceeds to step S17. In step S14, No, and the threshold voltage stored in the RAM 421 in step S17 is set as the peak voltage.

In the circuit shown in FIG. 7, when the comparator 116 determines that the peak value 210 of the peak voltage Vp exceeds the threshold voltage Dth0, the comparator 116 outputs a pulse 214 to the determination signal CMP. The element substrate 5 outputs the determination result signal RSLT corresponding to the pulse 214 to the determination result extraction unit 9. After receiving the determination result signal RSLT, the signal generation unit 7 raises the rank of the threshold signal Dth by one to Dth1 in the next latch period T, and compares this with the acquired peak value 210 of the peak voltage Vp.

Considering the example shown in FIG. 12, the above processing is repeated until the threshold voltage Dth5 at which the pulse is not output to the judgment signal CMP, and finally the threshold voltage Dth4 of the rank in which the pulse 215 is output to the judgment signal CMP is peaked. Let the voltage be Vp. When the peak voltage Vp is acquired, the constant current Iref is increased by one rank, the threshold voltage is set in the same manner, and the peak voltage Vp is obtained.

On the other hand, if the determination signal CMP pulse is not output in the first latch period T, the rank of the threshold voltage Dth is lowered by one in the next latch period T, and the peak voltage obtained by performing the same processing as described above is performed. Comparison with the peak value 210 of Vp is performed. Such processing is repeated until a pulse is output to the determination signal CMP, and the threshold voltage of the rank from which the pulse is output is defined as the peak voltage Vp.

The peak voltage Vp described above is detected every time the rank of the constant current Iref is increased one by one. Then, for example, when it is confirmed that the peak voltage Vp drops two ranks in a row, the peak voltage of the waveform before the peak voltage Vp drops is set as the maximum peak voltage Vpmax, and the constant current Iref at that time is set as the maximum constant current. Let it be Imax. Then, the constant current Iref, which is one or two ranks lower than Imax in anticipation of a margin, is determined as the adjusted constant current value Iadj. The threshold voltage Dth is lowered by a predetermined number of ranks (for example, 6 ranks) necessary for determining normal discharge with desired accuracy from the peak voltage Vpadj detected when the constant current Iadj is applied to the temperature sensor 102. Set to the voltage value at the time.

Although the process of adjusting the constant current energizing one temperature sensor 102 has been described in FIG. 10, the same process is also executed for the next temperature sensor 102 mounted on the element substrate 5, and all the processes are performed. Determine the optimum constant current value for each temperature sensor. While the adjustment process is being executed, the adjusted constant current value is stored in the RAM 421, but the adjusted constant current value is the non-volatile memory of the print controller 419 for the temperature detection process in the subsequent recording operation. It is stored in (for example, EEPROM).

Therefore, according to the above-described example, the constant current Imax that maximizes the peak voltage Vp of the output waveform of the inverting amplifier 115 can be investigated, and the constant current Iref can be adjusted so as not to exceed the maximum constant current Imax. As a result, the peak voltage Vp can be adjusted as high as possible to maintain high ejection state determination accuracy, and the ink ejection state of the nozzle can be determined with high reliability.

(Example 2)
Further, by adjusting the constant current Iref so that the peak voltage Vp of the output Vinv is aligned with the set voltage Vpe, it is possible to determine the discharge state of all nozzles with one threshold voltage Dth.

In determining the set voltage Vpe, first, a set of a plurality of constant current values and a threshold voltage is obtained for each nozzle by the method shown in Example 1 above.

FIG. 13 is a diagram illustrating a method of obtaining set voltages for the three temperature sensors.

In FIG. 13, for simplification of explanation, there are three temperature sensors 1, a temperature sensor 2, and a temperature sensor 3 on the element substrate, and three levels of current and voltage will be described as an example.

Here, the temperature sensor 1 detects the discharge of the nozzle 1, the temperature sensor 2 detects the discharge of the nozzle 2, and the temperature sensor 3 detects the discharge of the nozzle 3. As shown in FIG. 13, the peak voltages acquired for the temperature sensor 1 are Vp11, Vp12, and Vp13, and the maximum voltage is Vp13. The peak voltages acquired for the temperature sensor 2 are Vp21, Vp22, and Vp23, and the maximum voltage is Vp23. Further, the peak voltages acquired for the temperature sensor 3 are Vp31, Vp32, and Vp33, and the maximum voltage is Vp33.

FIG. 14 is a flowchart showing a process of determining the set voltage Vpe.

According to the flowchart, first, in step S21, Vp33, which is the lowest voltage among the three maximum voltages Vp13, Vp23, and Vp33, is set as a temporary set voltage Vpe. Next, in step S22, among the peak voltages Vp11, Vp12, and Vp13, the voltage Vp13 close to the provisional set voltage Vpe is selected for the temperature sensor 1, and the current value Iref13 corresponding to Vp13 is set to the current of the temperature sensor 1. Use as a value.

In step S23, the same process is performed for the temperature sensor 2. That is, for the temperature sensor 2, a voltage Vp22 close to the temporary set voltage Vpe is selected, and the current value Iref22 corresponding to Vp22 is set as the current set value of the temperature sensor 2.

In step S24, the same process is performed for the temperature sensor 3. That is, for the temperature sensor 3, a voltage Vp33 close to the temporary set voltage Vpe is selected, and the current value Iref33 corresponding to Vp33 is set as the current set value of the sensor 3.

Further, as the threshold voltage Dth, the threshold voltage Dth of the nozzle in which the peak voltage Vpadj is set as the set voltage Vpe is used.

FIG. 15 shows the output waveform Vdiv of the differential amplifier 111 and the output waveform Vinv of the inverting amplifier 115 when the pulse 211 of the heater drive signal HT is applied to the heater 101 while energizing the temperature sensor 102 with the adjusted constant current Iador. It is a timing chart. The constant current Iador in FIG. 15 is adjusted so that the peak voltage Vp becomes the minimum rank current value at the constant current Iref when the set voltage Vp or more.

When the constant current Iref is raised from the reference set value Iref0 to Iadr, the output waveform 201 of the differential amplifier 111 changes to the waveform 205 at the time of normal discharge. Further, the output waveform 202 of the differential amplifier 111 at the time of ejection failure changes to the waveform 206. Further, the output waveform 203 of the inverting amplifier 115 changes to the waveform 207 during normal discharge, and the output waveform 204 of the inverting amplifier 115 changes to waveform 208 when the discharge is defective.

FIG. 16 shows the output waveform Vdiv of the differential amplifier 111 and the output waveform Vinv of the inverting amplifier 115 when the pulse 211 of the heater drive signal HT is applied to the heater 101 while energizing the temperature sensor 102 with the unadjusted constant current Iref0. It is a timing chart.

FIG. 16 shows a case where the appearance time of the feature point 309 is later than the reference time (for example, 0.4 μsec later) or to the interface of the heater 101 of the tailing (satellite) of the ejected ink droplet which is the cause of the feature point 309. It shows Vdim and Vinv when the amount of crash is less than the standard.

In FIG. 16, since the resistance value Rs0 of the temperature sensor 102, the temperature resistance coefficient TCR, and the resistance value of the heater 101 are standard values, the waveform 302 of the output Vdiv and the waveform 304 of the output Vinv at the time of ejection failure are the same. It is almost the same as the reference waveform.

On the other hand, in the waveform 301 of the output Vdiv in the normal discharge, the temperature lowering rate after the feature point 309 is slower than the reference waveform, and as a result, the peak voltage Vp of the peak 310 of the waveform 303 of the output Vinv of the normal discharge is the peak of the reference waveform. It will be lower than the voltage. As a result, the voltage Vpdim shown in FIG. 16 becomes larger than the voltage Vpdim shown in FIG. 9A.

FIG. 17 shows the output waveform Vdiv of the differential amplifier 111 and the output waveform Vinv of the inverting amplifier 115 when the pulse 211 of the heater drive signal HT is applied to the heater 101 while energizing the temperature sensor 102 with the adjusted constant current Iador. It is a timing chart.

The constant current Iador in FIG. 17 adjusts the current value to be passed through each sensor so that the peak voltage Vp becomes the minimum rank current value in the range of the current value equal to or higher than the set voltage Vpe. For example, as shown in FIG. 13, if three temperature sensors are to be adjusted, the temperature sensor 1 has a current value corresponding to the maximum voltage VP13, and the temperature sensor 2 has a current value corresponding to the maximum voltage VP22 and a temperature sensor. 3 sets the current value corresponding to the maximum voltage VP33, respectively.

When the constant current Iref is changed from the reference setting value Iref0 to Iador, the output waveform 301 of the differential amplifier 111 at the time of normal discharge becomes the waveform 305, and the output waveform 302 of the differential amplifier 111 at the time of poor discharge becomes the waveform 306. Change. Further, the output waveform 303 of the inverting amplifier 115 at the time of normal discharge changes to the waveform 307, and the output waveform 304 of the inverting amplifier 115 at the time of poor discharge changes to the waveform 308.

At this time, the peak voltage Vp of the waveform 303 becomes the peak voltage Vpe of the waveform 307, which coincides with the peak voltage Vpe of the waveform 207 of FIG. On the other hand, the peak of the waveform 308 is multiplied by the ratio 1-Vpdim / Vpb to become Vpe (1-Vpdim / Vpb), which is larger than the peak of the waveform 208 of FIG. As a result, the peak difference Vpdiv after adjusting the constant current Threshold becomes narrower than that shown in FIG. 15, but it is necessary to ensure sufficient accuracy in determining ejection defects, assuming such variations. By setting the threshold voltage Dth to, the discharge state can be accurately determined.

Therefore, as described above, the constant current Iref can be adjusted so that the peak voltage Vp of the output waveform of the inverting amplifier 115 is aligned with the set voltage Vpe. As a result, the ejection state of all nozzles can be determined using one threshold voltage Dth, and it is not necessary for the signal generation unit 7 to output the threshold signal Dds for each nozzle, and the threshold signal Dds stored in the RAM 421 or EEPROM is eliminated. The amount of information can be reduced.

In the above-mentioned example, both the constant current Iref and the threshold voltage Dth are set for each nozzle. Further, for the purpose of reducing the storage area of the threshold signal Dds for all nozzles, by adjusting the constant current Iref so that the peak voltage Vp of the output Vinv is aligned with the set voltage Vpe, all at one threshold voltage Dth. There was also a form in which the ejection state of the nozzle could be determined.

(Example)
Hereinafter, suitable examples will be described.

In this embodiment, a method of reducing the storage area of the constant current signal Diref for all the nozzles will be described by setting the constant current Iref for each nozzle group including a plurality of nozzles which are a part of all the nozzles arranged. The constant current Iref can be set for each temperature sensor group, but by setting the value of the peak voltage Vp of the output waveform for each temperature sensor that is close to each other, it is possible to achieve both relatively high determination accuracy and the effect of reducing the storage area. Since the value of the peak voltage Vp of the output waveform changes mainly due to the output variation of the constant current Iref, it is desirable to set the constant current Iref in units of the temperature sensor group 102 or less belonging to each constant current control circuit 240.

In determining the constant current setting of the temperature sensor group, first, a plurality of constant current values and threshold voltage sets are obtained for each temperature sensor by the method shown in Example 1 above.

FIG. 19 is a diagram illustrating a method of obtaining constant current settings for the three temperature sensors. The three temperature sensors are sensors belonging to a group of nozzles in which the same constant current is set. For the sake of simplicity, the element substrate has three temperature sensors 1, a temperature sensor 2, and a temperature sensor 3, and shows the peak voltage Vp of the output Vinv when the Iref is changed in eight steps.

Here, the temperature sensor 1 detects the discharge of the nozzle 1, the temperature sensor 2 detects the discharge of the nozzle 2, and the temperature sensor 3 detects the discharge of the nozzle 3. In all temperature sensors, when the Iref is increased, the value of the peak voltage Vp increases, and the value of Vp decreases after reaching the peak, but the degree of this decrease is steep. This sharply decreasing Iref value means that the error of the detected voltage is large in the region. This phenomenon is as described in FIG. 9C.

FIG. 20 is a flowchart showing a process of determining a constant current setting to be set in the temperature sensor group.

According to the flowchart, first, in step S31, Iref = Imax at which Vp is maximum is determined with respect to the temperature sensors belonging to the temperature sensor group to be set with the constant current. The Iref at which the Vp of the temperature sensor 1 peaks is 4, the Iref at which the Vp of the temperature sensor 2 peaks is 6, and the Iref at which the Vp of the temperature sensor 3 peaks is 7.

In step S32, the minimum value in Imax of each temperature sensor belonging to the temperature sensor group is calculated. The smallest Iref of the Imaxes of the three temperature sensors is 4.

In step S33, the calculated value is determined as a constant current setting for each temperature sensor belonging to the temperature sensor group. Therefore, the Iref set in this temperature sensor group is 4. By setting the lowest Iref in Imax in the group, the highest Iref value can be set while avoiding the above-mentioned Iref value in the rapidly decreasing region.

As described above, according to this embodiment, by setting the constant current setting for each temperature sensor group, it is not necessary for the signal generation unit 7 to output the constant current setting value Diref for each nozzle, and each nozzle is set in the RAM 421 or EEPROM. It is possible to reduce the information of the current set value EEPROM. While realizing this, it is possible to improve the discharge determination accuracy of each temperature sensor.

On the other hand, when the number of nozzles belonging to the temperature sensor group is large (for example, 5120 nozzles), it is necessary to temporarily hold the value of Vp for each constant current setting Iref for all the temperature sensor groups, which requires a huge memory and processing time. I need. Therefore, the temperature sensor group is divided into a plurality of groups (for example, 512 nozzles × 10 groups), the Imax at which the representative value of the Vp value for each constant current setting Iref of each group becomes the maximum is determined, and the Imax of all the groups is determined. By setting the minimum value of to the constant current set value Diref of this temperature sensor group, the number of data to be temporarily held can be significantly reduced. Here, the above-mentioned representative value may be the maximum value, minimum value, average value, median value, mode value, etc. of the peak voltage Vp of each temperature sensor belonging to the group, but it is not affected by the discharge state of each nozzle. It is desirable to use the median to understand the behavior of the entire group.

Further, while calculating the amount of change in the value of Vp when the constant current Iref of each group is sequentially changed, the number of nozzles in which this amount of change becomes negative is counted, and the value of this count is compared with a predetermined threshold value. It is also possible to determine the Imax of each group with, and the same effect can be obtained by setting the minimum value of Imax of all groups as the constant current set value Threshold of this temperature sensor group.

(Example 3)
In the following example, if a peak difference Vpdiv sufficient to achieve the required determination accuracy can be secured, the rank of the constant current Iref is not raised any more.

The wider the peak difference Vpdiv of the output Vinv of the inverting amplifier shown in FIG. 9A, the wider the difference between the threshold voltage Dth and the peak can be secured, and the discharge state can be determined with high accuracy. Therefore, although the necessary determination accuracy can be ensured by confirming that the peak difference Vpdim secures a desired voltage range, it is generally difficult to reproduce the discharge defective state at an arbitrary timing. Therefore, instead of the peak difference Vpdim, a method of adjusting the constant voltage Iref so that the peak voltage Vp of normal discharge becomes a predetermined voltage can be considered, but in reality, the reference voltage Vofs of the inverting amplifier varies, so the peak voltage Vp is used. The peak difference Vpdim cannot be replaced. That is, an unexpected offset voltage may be superimposed on the output VF and the output Vinv due to a slight variation in the symmetry of the differential amplification stage of the operational amplifier constituting the BPF 113 and the inverting amplifier 115.

As a result, even if the peak voltage Vp is higher than the predetermined set voltage Vpe, it may be apparently high due to the unexpected offset voltage being superimposed in the positive direction. Therefore, there is a possibility that the determination accuracy is deteriorated by adjusting the constant current Iref.

Based on the above studies, in this example, the reference voltage Vpref of the output Vinv including an unexpected offset voltage is detected in advance, and the difference voltage between the reference voltage Vpref and the peak voltage Vp of the output Vinv is set to a predetermined voltage Vpe. Adjust the constant current Iref so that it is aligned with.

FIG. 18 shows the output waveform Vdiv of the differential amplifier 111 and the output of the inverting amplifier 115 when a constant current is applied to the temperature sensor 102 during the ON period of the sensor energization signal SE but no pulse of the heater drive signal HT is applied to the heater 101. It is a timing chart which shows the waveform Vinv.

As shown in FIG. 18, consider a case (broken line 211) in which the heater 101 is not applied with the pulse 211 of the heater drive signal HT while the constant current Iref0 (for example, 1.6 mA) is energized in the temperature sensor 102. In this case, the temperature sensor 102 does not raise the temperature at room temperature T0, and the waveform 401 of the output voltage Vdif becomes a constant voltage as shown in the equation (7). At this time, the output VF of the BPF 113 becomes Vofs + Vofs1 by superimposing the unexpected offset voltage Vofs1 on the offset voltage Vofs applied by the constant voltage source 114.

Therefore, assuming that the unexpected offset voltage superimposed on the output Vinv of the inverting amplifier 115 is Vofs2, the output Vinv is expressed as in the equation (8) from the equation (6). That is,
Vinv = Vpref = Vofs + Vofs2-Ginv · Vofs1 …… (8)
Will be. That is, the reference voltage Vpref of the output Vinv varies from the constant voltage Vofs by Vofs2-Ginv · Vofs1. Therefore, in this embodiment, the temperature sensor 102 is energized with a constant current Iref0 in the same manner as when the peak voltage Vp was detected in the first embodiment. Then, in a state where the pulse of the heater drive signal is not applied to the heater 101, the output voltage Vinv and the threshold voltage are compared, and the reference voltage Vpref is detected using the comparator 116.

Separately, the temperature sensor 102 is energized with a constant current Iref0, and the peak voltage Vp when the heater drive signal pulse 211 is applied to the heater 101 is detected by the same method as in the first embodiment using the comparator 116. .. Since the difference voltage Vp-Vpref between the peak voltage Vp and the reference voltage Vpref is proportional to the constant current Ireff, the constant current value Iadj corresponding to the target set voltage Vpe can be obtained by the equation (9). That is,
Iadj = Iref0 × {(Vpe-Vpref) / (Vp-Vpref)} ... (9). The constant current value Iadj has been adjusted by confirming that the difference voltage Vp-Vpref between the peak voltage Vp and the reference voltage Vpref detected when the temperature sensor 102 is energized with the constant current Iadj matches Vpe-Vpref. It can be determined as a constant current value.

Therefore, according to the above-described embodiment, the reference voltage Vpref can be detected in addition to the peak voltage Vp of the inverting amplifier 115, and the constant current Ireff can be adjusted based on the difference voltage. Therefore, even if an unexpected offset voltage is superimposed on the output of the HPF 502 or the inverting amplifier 115 due to manufacturing variations, it is possible to secure a peak difference Vpdim sufficient to achieve the required ejection state determination accuracy. As a result, the constant current Iref can be satisfactorily adjusted without being unnecessarily increased, and the deterioration of the temperature sensor 102 can be prevented from being accelerated.

Although the examples have been described above, the present invention is not limited to the above-mentioned values and forms. For example, the low-pass filter and high-pass filter constituting the bandpass filter may be composed of a digital filter such as an FIR filter or an IIR filter composed of a digital circuit instead of an analog filter composed of an analog circuit.

Claims (5)

A plurality of heaters that heat the ink to eject the ink from the arranged nozzles, a plurality of temperature sensors provided corresponding to the plurality of heaters, and a first signal input from the outside are designated. A constant current source that energizes the temperature sensor with a constant current based on the current value, a voltage output from the temperature sensor energized by the constant current, and a threshold voltage specified by a second signal input from the outside. Based on this, an element substrate having a determination circuit that determines the ejection state of the ink from the nozzle and outputs a determination result signal, and
A signal generation means for generating and transmitting the first signal and the second signal to the element substrate.
A receiving means for receiving the determination result signal and
An adjusting means for adjusting the current value energized by the constant current source based on the determination result signal received by the receiving means, and
A memory for storing the current value adjusted by the adjusting means, and
It is a recording device having
The adjusting means adjusts a common current value for energizing a temperature sensor corresponding to each of a plurality of nozzles constituting at least a part of the arranged nozzles based on the determination result signal. A recording device characterized in that. The recording device according to claim 1, further comprising a constant current control circuit for driving the constant current source based on a current value designated by the first signal. The determination circuit
A differential amplifier that amplifies the voltage output from the temperature sensor,
A filter that suppresses noise contained in the voltage signal output from the differential amplifier,
An inverting amplifier that inverts the signal output from the filter,
Includes a comparator that compares the signal output from the inverting amplifier with the threshold voltage specified by the second signal.
The recording device according to claim 1 or 2, wherein the determination result signal is output based on the result of comparison by the comparator. The current value specified by the first signal can be set in a plurality of steps with a predetermined step size.
The recording device according to any one of claims 1 to 3, wherein the threshold voltage designated by the second signal can be set in a plurality of ranks with a predetermined step size. A first switch that turns on / off the energization of the temperature sensor,
It further has a second switch that turns on / off the energization of the heater.
The first switch is turned on / off by a sensor energization signal input from the outside, and the second switch is turned on / off by a recorded data signal input from the outside. 4. The recording device according to any one of 4.

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