Liquid dispensing device

Abstract

To provide a liquid discharge device capable of detecting whether discharge droplets are obliquely discharged.SOLUTION: A liquid discharge device 2 includes a recording element substrate 1 which has a discharge port 111 for discharging liquid and a heating element 101 for heating liquid in order to discharge liquid from the discharge port 111. The liquid discharge device 2 further has at least a first temperature detecting element 104 and a second temperature detecting element 107 and, in a plan view of the recording element substrate 1, the first temperature detecting element 104 and the second temperature detecting element 107 are formed on a position as an object around the heating element 101 as a center.SELECTED DRAWING: Figure 1

Description

Technical Field

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[0001] The present invention relates to a liquid ejection device that ejects a liquid.

Background Art

[0002] As a method of ejecting a liquid (ink) from a discharge port to perform recording on a recording medium such as paper, a thermal liquid ejection device that ejects ink from the discharge port by thermal energy generated by a heating element (heater) that heats the liquid is known.

[0003] Patent Document 1 discloses a configuration in which two temperature detection elements (temperature sensors) are arranged on one heater in a thermal liquid ejection device. By comparing the magnitude relationship of the output signals from the two temperature sensors, it is determined whether or not the liquid is being normally ejected from the discharge port. Hereinafter, the case where the liquid is being normally ejected is referred to as the normal ejection state, and the case where the liquid is not being normally ejected is referred to as the non-ejection state.

[0004] Specifically, in Patent Document 1, for example, one temperature sensor is arranged at the center of the heater and one temperature sensor is arranged at the periphery of the heater in a plan view. The voltage between both terminals of the temperature sensor at the center of the heater is V1, the voltage between both terminals of the temperature sensor at the periphery of the heater is V2, and V1 and V2 are compared by a comparator. In the non-ejection state, V1 > V2 always holds, whereas in the normal ejection state, there is a period when V1 < V2. Utilizing this difference, it is possible to determine whether or not the liquid is being normally ejected from the discharge port.

Prior Art Documents

Patent Documents

[0007] SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a liquid ejection device that can detect whether ejected droplets are being ejected obliquely. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides a liquid ejection device comprising a recording element substrate having ejection ports for ejecting liquid and heating elements for heating the liquid to eject it from the ejection ports, the liquid ejection device further comprising a first temperature detection element, a second temperature detection element, a first constant current source and a second constant current source which generate constant currents from the same reference current source, a first switching means which switches whether or not a current from the first constant current source is supplied to the first temperature detection element, a second switching means which switches whether or not a current from the second constant current source is supplied to the second temperature detection element, and a differential signal output means which outputs a differential signal between an output signal from the first temperature detection element and an output signal from the second temperature detection element, and when the recording element substrate is viewed in plan, the first temperature detection element and the second temperature detection element are arranged around the heating element, Symmetry It is characterized in that it is formed at a position where [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a liquid ejection device that can detect whether or not ejected droplets are being ejected obliquely. [Brief explanation of the drawings]

[0010] [Figure 1]FIG. [Figure 2] Cross section of Figure 1. [Figure 3] FIG. 2 is a block diagram showing a drive circuit and a processing circuit for an output signal from a temperature detection element. [Figure 4] FIG. 4 is a timing chart of the logic circuit section. [Figure 5] This is a circuit diagram showing the detailed circuit configuration of a differential amplifier. [Figure 6] 5A and 5B are schematic cross-sectional views of a discharge port showing the state during normal discharge and oblique discharge. [Figure 7] FIG. 4 is a timing chart showing output waveforms during normal ejection and oblique ejection. [Figure 8] Plan view of two temperature detection elements arranged symmetrically in the vertical direction. [Figure 9] Plan view showing four temperature detection elements arranged symmetrically. [Figure 10] A plan view of four temperature detection elements symmetrically arranged on the same layer as the heating element. [Figure 11] Cross section AA of Figure 10. [Figure 12] A plan view of four temperature detection elements symmetrically arranged on the same layer as the layer with the anti-cavitation film. [Figure 13] Cross section AA of Figure 12. [Figure 14] FIG. 4 is a timing chart showing each output waveform during oblique ejection. [Figure 15] FIG. 2 is a block diagram illustrating a control configuration of the liquid ejection device. DETAILED DESCRIPTION OF THE INVENTION

[0011] (First embodiment) This embodiment will be described below with reference to the drawings. Fig. 15 is a block diagram showing the control configuration of an oblique discharge inspection device 2 that inspects whether liquid is being discharged obliquely from the discharge ports. In response to instructions from the control unit 4, the signal generation unit 3 outputs a clock signal (CLK), a latch signal (LT), a block signal (BLE), a heater selection signal (DATA), and a heat enable signal (HE) to the recording element substrate 1. In addition, it outputs a sensor selection signal (SDATA), a constant current signal (Diref), a threshold signal 1 (Dth1), and a threshold signal 2 (Dth2) that are related to the selection of two temperature sensors provided for each discharge port, the amount of current flow, and output signal processing.

[0012] The determination result extraction unit 5 receives a determination result signal (RSLT) output from the recording element substrate 1 based on temperature information detected by two temperature sensors (a first temperature detection element and a second temperature detection element), and extracts the determination result for each latch period in synchronization with the falling edge of the latch signal LT. If the determination result is oblique ejection, the block signal BLE and sensor selection signal SDATA corresponding to the determination result are recorded in memory 6.

[0013] The control unit 4 receives the block signal BLE and sensor selection signal SDATA of the misaligned ejection outlet recorded in the memory 6, and if the heater to be driven includes an oblique ejection outlet, it deletes the oblique ejection outlet from the heater selection signal DATA of the corresponding block. Then, it adds an outlet for complementing the oblique ejection to the heater selection signal DATA of the corresponding block instead, and outputs the result to the signal generation unit 3.

[0014] Fig. 1 is a plan view of one of the multiple ejection ports provided on a recording element substrate 1 in this embodiment, viewed from the substrate side in the ink ejection direction. Fig. 2 is a cross-sectional view of the ejection port in Fig. 1, with Fig. 2(A) showing the AA cross-sectional view and Fig. 2(B) showing the BB cross-sectional view. An ink flow path 112 is formed in an orifice plate 212 formed on the recording element substrate 1, and an ink supply port 113 and an ink discharge port 114 are formed in the recording element substrate 1 perpendicular to the ink flow path 112. Above the ink flow path 112, one ejection port 111 is formed in the orifice plate 212 for each ejection port.

[0015] A rectangular heater 101 made of a thin-film resistor with high resistivity and thermal stability, such as TaSiN, is provided in the recording element substrate 1 directly below the ejection orifice 111. Furthermore, temperature sensors (temperature detection elements) 104 and 107 made of a thin-film resistor are provided below the heater 101 near the center of the long sides of the heater 101, with an insulating layer 202 between them, so that they partially overlap the heater 101 in the plan view of FIG. 1. The temperature detection element 104 (first temperature detection element) and the temperature detection element 107 (second temperature detection element) are provided symmetrically around the heater 101. Here, "symmetric" means that, when the recording element substrate is viewed in plan, the ratio of the distance between the center of the second temperature detection element 107 and the center of the heating element 101 to the distance between the center of the first temperature detection element 104 and the center of the heating element 101 is 0.95 or more and 1.05 or less. 1, the first temperature detection element 104 and the second temperature detection element 107 are arranged in the short direction of the heating element 101. To increase the output voltage, the temperature sensors 104 and 107 preferably have a high resistivity similar to that of the heater 101 and are made of a material with a high temperature coefficient of resistance.

[0016] A protective film 201 made of an insulating material such as SiN is formed on the heater 101 and the temperature sensors 104 and 107. A cavitation-resistant film 110 made of, for example, Ta is further formed thereon so as to cover the heater 101 in the plan view of FIG.

[0017] 1, the temperature sensors 104 and 107 are provided at positions overlapping the ink flow path 112 via a protective film 201 and an anti-cavitation film 110. The recording element substrate 1 is configured by providing multiple wiring layers on an insulating member 202 on a substrate 211. The insulating member 202 is configured by laminating multiple interlayer insulating films, and each of the wiring layers is provided between the interlayer insulating films. The substrate 211 is made of a semiconductor material such as silicon, and the insulating member 202 is made of an insulating material such as silicon oxide.

[0018] The heater 101 and temperature sensors 104 and 107 are electrically connected via wiring patterns and conductive plugs provided on the multiple wiring layers to form a circuit capable of realizing a recording function. In this embodiment, two wiring layers are provided: a first layer closest to the substrate 211 and a second layer above it.

[0019] The heater 101 is connected at one end of the short side of the heater 101 to a wiring pattern 209 of the second layer via a conductive plug 102, and at the other end to a wiring pattern 210 of the second layer via a conductive plug 103. The wiring pattern 209 is connected to a power supply line, and the wiring pattern 210 is grounded via a switch element 319 (see FIG. 3) described below.

[0020] 1, the temperature sensor 104 is connected to a predetermined wiring pattern via conductive plugs 105 and 106. For example, as shown in FIG. 2A, the temperature sensor 104 is connected to a pad 204 on the second layer via a conductive plug 106 provided at one end thereof, and is further connected to a wiring pattern 208 on the first layer via a conductive plug 206.

[0021] Similar to temperature sensor 104, temperature sensor 107 is connected to a predetermined wiring pattern via conductive plugs 108 and 109. For example, as shown in FIG. 2A, temperature sensor 107 is connected to pad 203 on the second layer via conductive plug 108 provided at one end thereof, and is further connected to wiring pattern 207 on the first layer via conductive plug 205.

[0022] In addition, a heat dissipation pattern 207 is disposed on the second layer below the heater 101, and the pattern 207 is connected to a heat dissipation pattern 208 on the first layer via a plug 209, and the pattern 208 is connected to a substrate 211 via a plug 210. With this configuration, when the heater 101 is driven to generate heat and then the driving is suppressed, the heat is quickly released to the substrate 211.

[0023] 3 is a block diagram of a heater drive circuit and a circuit for processing output signals from temperature sensors mounted on the printing element substrate 1 in this embodiment. For ease of explanation, it is assumed here that the printing element substrate 1 has four heaters 101a-d and eight temperature sensors 104a-d, 107a-d in each ejection port array 301, and that they are arranged in the order shown in FIG.

[0024] The printing element substrate 1 includes a constant voltage source 302 for driving the heaters 101a-d, a constant current source 304 for energizing the temperature sensors 104a-104d and 107a-107d, and an input / output unit (pads or terminals) for inputting and outputting signals and information to and from the outside. A constant voltage source 303 serves as a power supply source for the constant current source 304, and applies, for example, 5V VHTA to the high voltage side of the constant current source 304 and VSS as GND to the low voltage side.

[0025] The constant current source 304 is composed of two current sources, a constant current source 309 (first constant current source) and a constant current source 310 (second constant current source). Using the same current-type DAC 307 as a reference current source, a mirroring circuit 308 mirrors the current Iref to the constant current sources 309 and 310 at the same amplification factor.

[0026] Switch element (MOS transistor) 319a, together with heater 101a and gate circuits 317a and 318a, constitutes one drive circuit 316a, and controls the application of voltage from constant voltage source 302 to heater 101a. When switch element 319a is turned on, a VH of, for example, 24 V is applied to the high-voltage side of heater 101a, and a GNDH is applied to the low-voltage side. The other three heaters 101b to 101d are also controlled by similar switch elements.

[0027] Temperature sensors 104a and 107a, together with switch elements 324a to 327a, constitute one temperature acquisition circuit 323a. Switch element 324a controls the current supply from constant current source 309 to temperature sensor 104a. Switch element 325a controls the output of the voltage generated in temperature sensor 104a to voltage follower 328. Similarly, switch element 326a controls the current supply from constant current source 310 to temperature sensor 107a. Switch element 327a controls the output of the voltage generated in temperature sensor 107a to voltage follower 329.

[0028] The switch elements 324a to 327a are simultaneously turned on, and at this time, the temperature sensors 104a and 107a output temperature signals to buffer amplifiers 328 and 329 to inspect the state of distortion of ink droplets ejected from the ejection port corresponding to the heater 101a. The other six temperature sensors 104b to 104d and 107b to 107d are also controlled by similar switch elements.

[0029] 3 includes four drive circuits 316a-316d and four temperature acquisition circuits 323a-323d. The four drive circuits 316a-316d and four temperature acquisition circuits 323a-323d are divided into two groups G1 and G2. Each group is made up of two drive circuits and two temperature acquisition circuits.

[0030] 4 is a timing chart showing the timing of control in the logic circuit section of the recording element substrate 1. Hereinafter, the operation of the logic circuit section of the recording element substrate 1 of this embodiment will be described with reference to FIGS.

[0031] The recording element substrate 1 receives a clock signal (CLK), a latch signal (LT), a block signal (BLE), a heater selection signal (DATA) which is 2-bit serial data, and a heat enable signal (HE) which are transferred from the misaligned ejection inspection device 2. Note that the block signal (BLE) is usually multi-bit serial data, but in this embodiment it is 1-bit data.

[0032] Furthermore, a sensor selection signal (SDATA) consisting of 2-bit serial data is also received. Signals other than the clock signal (CLK) are received at intervals of a block period tb. Specifically, the four drive circuits 316a-316d and the four temperature acquisition circuits 323a-323d are controlled in two blocks in a time-division manner, and this process is repeated twice to complete acquisition of the temperature signals from the eight temperature sensors 104b-104d and 107b-107d.

[0033] The block signals BL1 to BL4 are transferred to the shift register 311 in synchronization with a clock signal (CLK), latched by the latch circuit 312 at timings t0 to t3, respectively, decoded by the decoder 313, and output to the wires B1 and B2. In this embodiment, the shift register 311 is a 1-bit register. The signals on the wires B1 and B2 are held for a period tb until the next latch timing, during which time the next block signal is transferred to the shift register 311.

[0034] The signals on wires B1 and B2 are used to select the heaters to be driven simultaneously, with only one of the signals being valid. In FIG. 3, wire B1 is connected to gate circuits 317a and 317c. Therefore, when the signal on wire B1 is valid (high active), heaters 101a and 101c can be driven simultaneously. Similarly, when the signal on wire B2 is valid, heaters 101b and 101d can be driven simultaneously.

[0035] As shown in FIG. 4, in this embodiment, a case will be handled where B1 is activated between t0 and t1 and between t2 and t3, and B2 is activated between t1 and t2 and between t3 and t4 in a time-division manner.

[0036] The heater selection signals DT1 to DT4 are transferred to the shift registers 314a and 314b in synchronization with the clock signal (CLK), latched by the latch circuits 315a and 315b at times t0 to t3, and output to the wires D1 and D2. The signals on the wires D1 and D2 are held for a period tb until the next latch timing, during which time the next heater selection signal is transferred to the shift registers 314a and 314b.

[0037] The signals on the wires D1 and D2 are used to select the heater groups G1 and G2. In FIG. 1, the wire D1 is connected to the gate circuits 317a and 317b. Therefore, when the signal on the wire D1 is enabled (high active), the heaters 101a and 101b of the group G1 can be selected. Similarly, when the signal on the wire D2 is enabled, the heaters 101c and 101d of the group G2 can be selected.

[0038] In this embodiment, we will deal with the case where heaters in group G1 are selected in the first two blocks and heaters in group G2 are selected in the last two blocks, meaning that driving of all four heaters is completed in four blocks.

[0039] The signals on the wires B1 and B2, together with the signal on the wire D1, are input to the gate circuits 317a and 317b, respectively. The output signals of the gate circuits 317a and 317b, together with a heat enable signal (HE), are further input to the gate circuits 318a and 318b, respectively. The gate circuits 318a and 318b output pulse signals 401 and 402 to the wires H1 and H2, respectively. The wires H1 and H2 are connected to the switch elements 319a and 319b, respectively, and the pulse signals 401 and 402 drive the heaters 101a and 101b, respectively.

[0040] Similarly, pulse signals 403 and 404 are output to wirings H3 and H4 by gate circuits 318c and 318d, respectively. Wirings H3 and H4 are connected to switch elements 319c and 319d, respectively, and heaters 101c and 101d are driven by pulse signals 403 and 404, respectively.

[0041] The sensor selection signals SDT1 to SDT4 are transferred to the shift registers 320a and 320b in synchronization with the clock signal (CLK), latched by the latch circuits 321a and 321b at times t0 to t3, and output to the wires SD1 and SD2. The signals on the wires SD1 and SD2 are held for a period of time tb until the next latch timing, during which time the next sensor selection signal is transferred to the shift registers 320a and 320b.

[0042] The signals on the lines SD1 and SD2 are used to select one of the groups G1 and G2 that includes the temperature sensor corresponding to the heater to be driven. In FIG. 3, the line SD1 is connected to the gate circuits 322a and 322b. Therefore, when the signal on the line SD1 is enabled (high active), the temperature sensors 104a, 104b, 107a, and 107b in the group G1 can be selected as the temperature sensor corresponding to the heater to be driven. Similarly, when the signal on the line SD2 is enabled, the temperature sensors 104c, 104d, 107c, and 107d in G2 can be selected as the temperature sensor corresponding to the heater to be driven.

[0043] 4, in this embodiment, of the four blocks, the first and second blocks deal with the case where the signal on the line SD1 is enabled to select the temperature sensor of group G1, and the third and fourth blocks deal with the case where the signal on the line SD2 is enabled to select the temperature sensor of group G2.

[0044] The signals on the wires B1 and B2 are used as block signals for selecting the temperature sensor. That is, the signals on the wires B1 and B2 are input to the gate circuits 322a and 322b, respectively, together with the signal on the wire SD1. Similarly, the signals on the wires B1 and B2 are input to the gate circuits 322c and 322d, respectively, together with the signal on the wire SD2.

[0045] The set value Diref of the constant current Iref is determined as a 5-bit digital value that can be set in 32 steps, and is transferred to a shift register 305 in synchronization with a clock signal CLK. Then, it is latched by a latch circuit 306 in synchronization with a latch signal LT, and output to a current output type digital-to-analog converter (DAC) 307. That is, the DAC 307 outputs an output current Irefin based on the set value Diref.

[0046] The output signal of the latch circuit 306 is held until the next latch timing, during which time the next set value Diref is transferred to the shift register 305 .

[0047] The output current Irefin of the DAC 307 is mirrored to the constant current sources 309 and 310, amplified by, for example, 12 times, and output as the constant current Iref.

[0048] As a result, in the first block, the gate circuit 322a outputs a pulse signal 405 that is valid between t0 and t1 to the wiring S1. The wiring S1 is connected to the switch elements 324a and 325a, and the pulse signal 405 causes the constant current Iref to be supplied from the constant current source 309 to the temperature sensor 104a between t0 and t1.

[0049] Resistance Rs1 of temperature sensor 104a at temperature T1 is expressed by the following equation (1), where room temperature is T0, resistance at that time is Rs0, and temperature coefficient of resistance of temperature sensor 104a is TCR. Rs1=Rs0·{1+TCR·(T1-T0)} (1) The temperature signal Vs1 generated at the constant current supply side terminal of the temperature sensor 104a is expressed by the following equation (2). Vs1=Iref·Rs1=Iref·Rs0·{1+TCR·(T1-T0)} ···(2) The temperature signal Vs1 expressed by the above equation (2) is output to the voltage follower 328 via the wiring V1.

[0050] The wiring S1 is also connected to the switch elements 326a and 327a, and the pulse signal 405 causes the constant current Iref to be supplied from the constant current source 310 to the temperature sensor 107a during the period from t0 to t1.

[0051] The resistance Rs2 of the temperature sensor 107a at the temperature T2 is expressed by the following equation (3). Rs2=Rs0·{1+TCR·(T2-T0)} (3) The temperature signal Vs2 generated at the constant current supply side terminal of the temperature sensor 107a is expressed by the following equation (4). Vs2=Iref·Rs2=Iref·Rs0·{1+TCR·(T2-T0)} ···(4) The temperature signal Vs2 expressed by the above equation (4) is output to the voltage follower 329 via the wiring V2.

[0052] In this embodiment, the temperature sensors 104a and 107a are configured to have the same room temperature resistance Rs0, but the room temperature resistances may be different. In this case, the constant current values ​​supplied to the temperature sensors 104a and 107a are adjusted by constant current sources 309 and 310 so that the temperature signals Vs1 and Vs2 at room temperature T0 are equal.

[0053] In the second block, gate circuit 322b outputs pulse signal 406, which is valid between t1 and t2, to wiring S2. Wiring S2 is connected to switch elements 324b and 325b, and constant current Iref is supplied from constant current source 309 to temperature sensor 104b between t1 and t2 by pulse signal 406. At the same time, temperature signal Vs1 generated at the constant current supply terminal of temperature sensor 104b is output to voltage follower 328 via wiring V1.

[0054] Wire S2 is also connected to switch elements 326b and 327b, and constant current Iref is supplied to temperature sensor 107b from constant current source 310 during the period from t1 to t2 in response to pulse signal 406. At the same time, temperature signal Vs2 generated at the constant current supply terminal of temperature sensor 107b is output to voltage follower 329 via wire V2.

[0055] In the third block, gate circuit 322c outputs pulse signal 407, which is valid between t2 and t3, to wiring S3. Wiring S3 is connected to switch elements 324c and 325c, and constant current Iref is supplied from constant current source 309 to temperature sensor 104c between t2 and t3 in response to pulse signal 407. At the same time, temperature signal Vs1 generated at the constant current supply terminal of temperature sensor 104c is output to voltage follower 328 via wiring V1.

[0056] Wire S3 is also connected to switch elements 326c and 327c, and constant current Iref is supplied to temperature sensor 107c from constant current source 310 during the period from t2 to t3 in response to pulse signal 407. At the same time, temperature signal Vs2 generated at the constant current supply terminal of temperature sensor 107c is output to voltage follower 329 via wire V2.

[0057] In the fourth block, gate circuit 322d outputs pulse signal 408, which is valid between t3 and t4, to wiring S4. Wiring S4 is connected to switch elements 324d and 325d, and constant current Iref is supplied from constant current source 309 to temperature sensor 104d between t3 and t4 in response to pulse signal 408. At the same time, temperature signal Vs1 generated at the constant current supply terminal of temperature sensor 104d is output to voltage follower 328 via wiring V1.

[0058] Wire S4 is also connected to switch elements 326d and 327d, and constant current Iref is supplied to temperature sensor 107d from constant current source 310 during the period from t3 to t4 in response to pulse signal 408. At the same time, temperature signal Vs2 generated at the constant current supply terminal of temperature sensor 107d is output to voltage follower 329 via wire V2.

[0059] If the temperature signals Vs1 and Vs2 are directly input to the differential amplifier 330 (differential signal output means), the resistance of the switch element affects the input impedance of the differential amplifier 330, causing a voltage drop in the temperature signals Vs1 and Vs2 before they are input to the differential amplifier 330. For this reason, the temperature signals Vs1 and Vs2 are first received by voltage followers 328 and 329 provided in the outlet array 101 and then input to the differential amplifier 330.

[0060] 5 is a circuit diagram showing a detailed circuit configuration of the differential amplifier 330 provided outside the ejection port array 101 of the recording element substrate 1. The differential amplifier 330 is made up of an operational amplifier 501, a constant voltage source 502, and resistors 503-506.

[0061] In each of the first to fourth blocks, the differential amplifier 330 amplifies a signal (differential signal) obtained by subtracting the temperature signal Vs1 expressed by equation (2) from the temperature signal Vs2 expressed by equation (4) with the amplification factor Gdif of the differential amplifier, and outputs a signal Vdif expressed by equation (5) below, which is offset by the voltage Vofs of the constant voltage source 502. Vdif=Gdif·(Vs2-Vs1)+Vofs =Vofs-Gdif·Iref·Rs0·TCR·(T2-T1) (5) Here, when the resistance value of the resistors 503 and 504 is RD1 and the resistance value of the resistors 505 and 506 is RD2, the amplification factor Gdif is expressed by the following equation (6).

[0062]

number

[0063] This differential amplifier 133 cancels out two types of noise. One is noise that is superimposed on the temperature signals Vs1 and Vs2 in proportion to the constant current Iref shown in equations (2) and (4) due to current fluctuations in the reference current source 307. The other is crosstalk noise caused by voltage fluctuations in the wiring that intersects with the wiring V1 and V2 via parasitic capacitance. Any other noise remaining in the signal Vdif is suppressed by the low-pass filter 331 and output as the signal VF.

[0064] The signal VF is compared with threshold voltages Vdth1 (first predetermined value) and Vdth2 (second predetermined value) based on two threshold signals Dth1 and Dth2 to determine whether the ejection is distorted (whether it is oblique ejection or not). That is, the signal VF is input to the positive terminal of the comparator 335, and is compared with the threshold voltage Vdth1 input to the negative terminal. Then, if VF>Vdth1, a high-level signal (distorted ejection) is output to the wiring CMP1, and if VF≦Vdth1, a low-level signal (normal ejection) is output.

[0065] On the other hand, the signal VF is input to the negative terminal of the comparator 339, and compared with the threshold voltage Vdth2 input to the positive terminal. If Vdth2>VF, a high-level signal (deformed discharge) is output to the wiring CMP2, and if Vdth2≦VF, a low-level signal (normal discharge) is output to the wiring CMP2.

[0066] The threshold voltages Vdth1 and Vdth2 can be set in 256 steps, for example, from 0.5 V to 2.54 V in 8 mV increments. The setting values ​​Dth1 and Dth2 of the threshold voltages Vdth1 and Vdth2 are determined as 8-bit digital values ​​that can be set in 256 steps, for example, and are transferred from the signal generating unit 3 to the shift registers 332 and 336, respectively, in synchronization with the clock signal CLK.

[0067] The threshold signal Dth1 is latched by the latch circuit 333 in synchronization with the latch signal LT, and is output to the voltage output type DAC 334. The output signal of the latch circuit 333 is held until the next latch timing, during which time the next threshold signal Dth1 is transferred to the shift register 332. Similarly, the threshold signal Dth2 is latched by the latch circuit 336 in synchronization with the latch signal LT, and is output to the voltage output type DAC 338. The output signal of the latch circuit 338 is held until the next latch timing, during which time the next threshold signal Dth2 is transferred to the shift register 336.

[0068] The signals CMP1 and CMP2 are input to an OR gate circuit 340 and output to a line CMP. By inputting the signal CMP to the set input terminal of an RS latch circuit 341, the pulse signal of the signal CMP is held at a high level and output to a line HCMP. By latching this signal HCMP in a flip-flop circuit 342 using the latch signal LT as a trigger, a determination result signal RSLT is obtained that becomes a high level in the next latch period when a misaligned ejection occurs.

[0069] The signal HCMP is reset at the falling edge of the latch signal LT by inputting an inverted signal of the latch signal LT to the reset input terminal of the RS latch circuit 341.

[0070] The decision result signal RSLT is extracted by the decision result extractor 5 shown in FIG. 14 in synchronization with the falling edge of the latch signal LT, together with the block signal BLE delayed by the latch period and the sensor selection signal SDATA.

[0071] In this embodiment, the determination circuit section from the differential amplifier 330 to the flip-flop circuit 342 is configured to be provided inside the recording element substrate 1 outside the ejection port array 301, but it may also be provided inside a control chip provided in the recording head outside the recording element substrate 1. Furthermore, the determination circuit section may also be provided inside a control chip provided in the recording apparatus outside the recording head.

[0072] Fig. 6 is a schematic cross-sectional view of an ejection port showing the state when an ink droplet 601 is ejected from the ejection port 111 and a tail 602 crashes onto the anti-cavitation film 110, with Fig. 6(A) showing normal ejection and Fig. 6(B) showing irregular ejection. Fig. 7 is a timing chart showing the output waveforms of the determination circuit unit of the recording element substrate 1 in the first block shown in Fig. 4, with Fig. 7(A) showing normal ejection and Fig. 7(B) showing irregular ejection. The other blocks have similar timing charts, so they will not be described in this embodiment.

[0073] 6 and 7, the difference in operation between normal and misaligned ejection of the determination circuit unit in the first block of this embodiment will be described below. Fig. 6(A) is a schematic cross-sectional view of the ejection port during normal ejection, in which an ink droplet (ejected droplet) 601 is ejected perpendicular to the surface of the orifice plate 212. The negative pressure inside the foamed bubble acts symmetrically on the tail 602, and the bursting of the meniscus causes the bubble to communicate with the atmosphere simultaneously around the entire circumference of the ejection port 111, causing the tail 602 to crash into the center of the heater 101 in a plan view.

[0074] Therefore, the fallen tail 602 spreads symmetrically about the heater 101 in a plan view, and the temperature sensors 104 and 107, which are arranged symmetrically about the heater 101, are uniformly cooled by the tail 602. Therefore, as shown in Figure 7(A), the output signals Vs1 and Vs2 of the temperature sensors 104 and 107 appear to overlap as shown in waveform 701. Note that waveform 701 rises from an initial voltage Vini due to heating of the heater 101 by the driving pulse 401, and begins to rapidly decrease in temperature from characteristic point 702 due to cooling caused by the fall of the tail 602.

[0075] Since the output signals Vs1 and Vs2 are the same (T1 = T2), the output signals Vs1 and Vs2, including current fluctuation noise and crosstalk noise, cancel each other out according to equation (5), and the output signal Vdif of the differential amplifier 330 becomes a constant voltage Vofs. Therefore, the output signal VF of the low-pass filter 331 also becomes a waveform 703 of a constant voltage Vofs, as shown in FIG. 7(A). The threshold voltages Vdth1 and Vdth2 are set so that they are equal to this Vofs.

[0076] In FIG. 7(A), since Vdth2 ≤ VF ≤ Vdth1, both the signals CMP1 and CMP2 are at the low level (normal ejection), and the output signal CMP of the OR gate circuit 340 is also at the low level, so no pulse is generated (704). Therefore, the signals HCMP (705) and the determination result signal RSLT (706) are also at the low level (normal ejection) and are output to the determination result extraction unit 5.

[0077] On the other hand, FIG. 6(B) is a schematic cross-sectional view of the discharge port during a skew discharge, and the ink droplet 601 represents a state where it is discharged with a skew to the left from the discharge direction in FIG. 6(A). Also, the negative pressure inside the foamed bubble acts asymmetrically on the trailing portion 602, and the atmospheric communication of the bubble also occurs asymmetrically from the portion where the meniscus becomes thin. As a result, the trailing portion 602 sways to the left from the center of the heater 101 and falls.

[0078] Therefore, the fallen trailing portion 60 becomes closer to the temperature sensor 107 than in FIG. 6(A) in a plan view and moves away from the temperature sensor 104. Thus, the temperature sensor 107 is cooled more strongly by the trailing portion 602 than the temperature sensor 104. That is, as shown in FIG. 7(B), the feature point 709 that appears in the waveform 707 of the output signal Vs1 of the temperature sensor 104 has a later appearance timing than the feature point 710 that appears in the waveform 708 of the output signal Vs2 of the temperature sensor 107. Also, the temperature drop rate after the feature point 709 is slower than the temperature drop rate after the feature point 710, and the slope of the waveform becomes gentle.

[0079] However, the time difference in the appearance of the feature point 710 and the feature point 709 is slight. To extract the appearance timing of the feature points 709 and 710, a circuit such as a differential filter is separately required and the accuracy is low, and the time difference in appearance cannot be detected with good accuracy.

[0080] On the other hand, after the feature point 710, the waveform 708 of the output signal Vs2 stably falls slightly below the waveform 707 of the output signal Vs1, and the signal Vdif obtained by taking the difference and amplifying the output signals of the waveforms 708 and 707 can be detected stably with good accuracy. Therefore, the skew discharge state is determined based on the signal Vdif.

[0081] From equation (5), the output signal Vdif of the differential amplifier 330 drops from the constant voltage Vofs after characteristic point 710. Therefore, the output signal VF of the low-pass filter 331 also takes the form of waveform 711, which drops from the constant voltage Vofs after characteristic point 710, as shown in FIG. 7A. The threshold voltages Vdth1 and Vdth2 are set so as to be equal to this Vofs.

[0082] In FIG. 7A, in the section where Vdth2>VF, the signal CMP1 goes low, the signal CMP2 goes high (distortion discharge), and the output signal CMP of the OR gate circuit 340 goes high (distortion discharge), generating a pulse 713.

[0083] Therefore, a pulse 714 that holds the pulse 713 is generated in the signal HCMP, and the determination result signal RSLT (715) becomes high level (distorted discharge) and is output to the determination result extraction unit 5.

[0084] When the ejection direction of the ink droplet 601 is deviated to the right, opposite to the direction shown in FIG. 6B, the waveforms 707 and 708 in FIG. 7B are swapped, and the signal VF becomes waveform 712, which is a reflection of waveform 711 relative to the constant voltage Vofs.

[0085] In this case, in the section where VF>Vdth1, the signal CMP1 goes high (discharge of distortion) and the signal CMP2 goes low, the output signal CMP of the OR gate circuit 340 goes high (discharge of distortion), and a pulse 713 is generated, just as in the case of distortion to the left. Therefore, a pulse 714 that holds the pulse 713 is generated in the signal HCMP, and the judgment result signal RSLT (715) goes high (discharge of distortion) and is output to the judgment result extraction unit 5.

[0086] As explained above, in this embodiment, when the print element substrate is viewed from above, a constant current generated from the same reference constant current source is supplied to two symmetrically arranged temperature sensors, and the differential between the signals of the terminals on the constant current supply side of the two temperature sensors is taken and amplified. This amplifies while canceling out current fluctuation noise and crosstalk noise, making it possible to detect with high accuracy even slight misalignment of ejection in the direction connecting the two temperature sensors.

[0087] (Second embodiment) Figure 8 is a plan view of an ejection port in which two temperature sensors 801 and 804 have been added in a vertically symmetrical arrangement on the same layer as the two temperature sensors 104 and 107 in Figure 1 shown in the first embodiment, as viewed from the substrate side in the ink ejection direction.

[0088] As shown in Figure 1, in a configuration in which two temperature sensors 104, 107 are symmetrically arranged near the center of the long side of the heater 101, it was possible to stably detect the twisted discharge state when the falling tail 602 twists horizontally in Figure 1.

[0089] However, when the falling tail 602 is twisted in the vertical direction in FIG. 1, the twisted ejection state cannot be detected even by taking the differential of the output signals of the temperature sensors 104 and 107.

[0090] 8, in this embodiment, temperature sensors 801 and 804 are arranged symmetrically in the vertical direction about the center of the heater 101. In addition to the constant current sources 309 and 310, two new constant current sources corresponding to the added temperature sensors 801 and 804 are added, for a total of four systems.

[0091] By doing so, even if the falling tail 602 is distorted vertically, it is possible to detect the distorted ejection state by taking the difference between the output signals of the temperature sensors 801 and 804. In this case, the threshold voltages Vdth1 and Vdth2 are set by taking into account the signal VF when the falling tail 602 is distorted diagonally in FIG.

[0092] (Third embodiment) 9 is a plan view of the ejection orifices, as viewed from the substrate side in the ink ejection direction, in which four temperature sensors 901, 904, 907, and 910 are arranged symmetrically with respect to the heater 101 so as to overlap the long side of the heater 101, among the multiple ejection orifices arranged on the printing element substrate 1. Note that there are four constant current sources for supplying current to the four temperature sensors, one for each temperature sensor.

[0093] 9, it is possible to obtain the same effect as in the second embodiment by symmetrically arranging two temperature sensors on each side of the long side of the heater 101. That is, if at least one of the differential signal VF1 of the outputs of the temperature sensors 901 and 907 or the differential signal VF2 of the outputs of the temperature sensors 904 and 910 exceeds the threshold voltage, it is determined that deviation in the horizontal direction has occurred.

[0094] Similarly, if at least one of the differential signal VF3 of the outputs of the temperature sensors 901 and 904 or the differential signal VF4 of the outputs of the temperature sensors 907 and 910 exceeds a separately set threshold voltage, it is determined that vertical deviation in ejection has occurred.

[0095] Alternatively, the differential signal VF5 of the outputs of the temperature sensors 901 and 910 and the differential signal VF6 of the outputs of the temperature sensors 904 and 907 may be compared with a separately set threshold voltage. In this case, if either the differential signal VF5 or VF6 exceeds the threshold voltage, it is determined that there is deviation in the oblique direction, and if both exceed the threshold voltage, it is determined that there is deviation in the horizontal or vertical direction.

[0096] (Fourth embodiment) Figure 10 is a plan view of an ejection port in which four temperature sensors 1001, 1004, 1007, and 1010 are arranged symmetrically with respect to the heater 101, two in the longitudinal and two in the lateral directions of the heater 101, on the same layer as the heater 101, as viewed from the substrate side in the ink ejection direction.

[0097] The four temperature sensors 1001, 1004, 1007, and 1010 are arranged so as to overlap the ink flow path 112 in the plan view of Fig. 10. Fig. 11 shows a cross-sectional view of the ejection port taken along line AA in Fig. 10. As shown in Fig. 10, by making the four temperature sensors 1001, 1004, 1007, and 1010 out of the same material as the heater 101, the sheet resistance can be increased, the sensor length can be shortened to obtain temperatures over a narrower range, and the positioning can be relatively free.

[0098] 11, the temperature sensor can be placed closer to the ink flow path 112 than in FIG. 2(A), and the sensitivity to cooling by the ink drop 602 can be increased while receiving heat from the heater 101. Also, by arranging the four temperature sensors 1001, 1004, 1007, and 1010 symmetrically in the vertical and horizontal directions, it is possible to obtain the same effect as in the second embodiment.

[0099] (Fifth embodiment) 12 is a plan view showing four temperature sensors 1201, 1204, 1207, and 1210 arranged symmetrically with respect to the heater 101, adjacent to the centers of the long and short sides of the heater 101 in a plan view, on the same layer as the layer on which the anti-cavitation film 110 is provided. Also, FIG. 13 shows a cross section taken along the line AA of the ejection port in FIG.

[0100] The anti-cavitation film 110 is provided so as to cover the minimum area necessary to protect the heater 101 from cavitation. The gaps between the four temperature sensors 1201, 1204, 1207, and 1210 and the anti-cavitation film 110 are set to be minimum, and the temperature sensors are positioned so as to overlap the ink flow path 112 in the plan view of FIG.

[0101] By arranging them as described above, the four temperature sensors can be provided closest to the heater 101, but they are still too far away to receive sufficient heat from the heater 101.

[0102] Therefore, four auxiliary heaters (auxiliary heating elements) 1213, 1216, 1219, and 1222 for heating the temperature sensors are provided in the same layer as the heater 101, immediately before a significant difference appears in the output signals of a pair of temperature sensors that are differentially detected.

[0103] An auxiliary heater 1213 is provided to heat temperature sensor 1201, an auxiliary heater 1216 to heat temperature sensor 1204, an auxiliary heater 1219 to heat temperature sensor 1207, and an auxiliary heater 1222 to heat temperature sensor 1210. The four auxiliary heaters are connected via conductive plugs to the same power supply line on the second layer as the power supply line to which heater 101 is connected via a conductive plug.

[0104] Fig. 14 is a timing chart showing output waveforms of the determination circuit unit of the recording element substrate 1 in the first block shown in Fig. 4 during misaligned ejection in this embodiment. The ink droplet 601 is misaligned to the left in the horizontal direction as shown in Fig. 6(B).

[0105] If the temperature sensors 1201 and 1204 are not heated by an auxiliary heater, sufficient sensitivity to detect misaligned ejection cannot be obtained, as shown by the waveform 1403 in Fig. 14. Therefore, by heating the temperature sensors 1201 and 1204 by an auxiliary heater before the pulse 1409 appears in the signal CMP, the temperature of the output waveform of the temperature sensor rises rapidly from the temperature rise point 1404, and sufficient sensitivity can be obtained.

[0106] A waveform 1401 after the temperature rise point 1404 represents the output signal Vs1 of the temperature sensor 1201, and a waveform 1402 represents the output signal Vs2 of the temperature sensor 1204.

[0107] 6(B), because the crash trail 602 is skewed to the left, the timing of the appearance of feature point 1405 in waveform 1401 is later than that of feature point 1406 in waveform 1402. In addition, the rate of temperature decrease after feature point 1405 is slower than that after feature point 1406, and the slope of the waveform becomes gentler.

[0108] After characteristic point 1406, waveform 1402 of output signal Vs2 falls below waveform 1401 of output signal Vs1, and therefore, from equation (5), output signal Vdif of differential amplifier 330 drops from constant voltage Vofs after characteristic point 710. Therefore, output signal VF of low-pass filter 331 also drops from constant voltage Vofs to waveform 1407 as shown in FIG. 14 after characteristic point 1406. Threshold voltages Vdth1 and Vdth2 are set so as to be equal to this Vofs.

[0109] 14, in the section where Vdth2>VF, the signal CMP1 goes low and the signal CMP2 goes high (distortion discharge), and the output signal CMP of the OR gate circuit 340 goes high (distortion discharge) to generate a pulse 1409. Therefore, a pulse 1410 that holds the pulse 1409 is generated in the signal HCMP, and the judgment result signal RSLT (1411) goes high (distortion discharge) and is output to the judgment result extraction unit 5.

[0110] 13, in this embodiment, the temperature sensor is provided so as to be in contact with the ink flow path 112, and therefore, as explained above, the temperature sensor can receive heat from the auxiliary heater while being more sensitive to cooling by the drop tail 602. In addition, by arranging the four temperature sensors 1201, 1204, 1207, and 1210 symmetrically in the vertical and horizontal directions, it is possible to obtain the same effect as in Example 2.

[0111] (Other embodiments) Although the first to fifth embodiments have been described, the present invention is not limited to the above values ​​and configurations. For example, the two temperature sensors arranged symmetrically in the horizontal direction with respect to the heater and the two temperature sensors arranged symmetrically in the vertical direction with respect to the heater may be arranged on different layers.

[0112] Furthermore, even if the positions of the two temperature sensors are symmetrical with respect to the heater, the shapes of the two temperature sensors do not have to be symmetrical. Furthermore, the number of outlets per outlet array is not limited to four but may be, for example, 512, and the number of outlet arrays may be multiple rather than one. [Explanation of symbols]

[0113] 1. Recording element board 2 Liquid discharge device 101 heating element 104 first temperature detection element 107 Second temperature detection element 111 Discharge port

Claims

1. a discharge port for discharging a liquid; a heating element for heating the liquid so as to eject the liquid from the ejection port; In a liquid ejection apparatus having a recording element substrate having The liquid ejection device a first temperature detection element; a second temperature detection element; a first constant current source and a second constant current source that generate constant currents from the same reference current source; a first switching means for switching whether or not a current from the first constant current source is supplied to the first temperature detection element; a second switching means for switching whether or not a current from the second constant current source is supplied to the second temperature detection element; a differential signal output means for outputting a differential signal between an output signal from the first temperature detection element and an output signal from the second temperature detection element; and A liquid ejection device characterized in that, when the recording element substrate is viewed from above, the first temperature detection element and the second temperature detection element are formed in positions symmetrical with respect to the heating element.

2. A liquid ejection device as described in claim 1, wherein when the recording element substrate is viewed in a plane, the ratio of the distance between the center of the second temperature detection element and the center of the heating element to the distance between the center of the first temperature detection element and the center of the heating element is 0.95 or more and 1.05 or less.

3. The liquid ejection device according to claim 1 , further comprising a determination circuit section that determines whether the liquid ejected from the ejection port is being ejected obliquely by comparing the differential signal with a preset threshold voltage.

4. The liquid ejection device according to claim 3, wherein the determination circuit unit determines that the liquid is being ejected obliquely from the ejection port when the differential signal is greater than a predetermined first threshold voltage or less than a predetermined second threshold voltage.

5. 5. The liquid ejection device according to claim 1, wherein the first temperature detection element and the second temperature detection element are arranged in a lateral direction of the heating element.

6. 5. The liquid ejection device according to claim 1, wherein the first temperature detection element and the second temperature detection element are arranged in a longitudinal direction of the heating element.

7. 7. The liquid ejection device according to claim 1, wherein the first temperature detection element and the second temperature detection element are formed at positions that do not overlap with the heating element when the recording element substrate is viewed in a plan view.

8. 8. The liquid ejection device according to claim 1, wherein the first temperature detection element and the second temperature detection element are thin-film resistors formed below the heating element via an insulating layer.

9. 8. The liquid ejection device according to claim 1, wherein the first temperature detection element and the second temperature detection element are thin-film resistors formed in the same layer as the heating element.

10. 8. The liquid ejection device according to claim 1, wherein the first temperature detection element and the second temperature detection element are thin-film resistors formed in the same layer as the anti-cavitation film.

11. 11. The liquid ejection device according to claim 1, further comprising an auxiliary heating element for heating the first temperature detection element and the second temperature detection element.

Images