Liquid discharge head and liquid discharge device

Abstract

The present invention provides a liquid dispensing head capable of acquiring the deterioration status of the heater. [Solution] The liquid discharge head includes a discharge port for discharging liquid, a heater 305 that generates energy for discharging liquid from the discharge port, a discharge switch element 405 connected to the heater 305 for energizing the heater 305, a current measuring element 416 with one end connected to a wiring that connects the heater 305 and the discharge switch element 405, and a measuring switch element 406 connected to the other end of the current measuring element 416 for energizing the heater 305 and the current measuring element 416. Switching the discharge switch element 405 to a conductive state and switching the measuring switch element 406 to a conductive state are performed exclusively.

Description

Technical Field

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

Background Art

[0002] A liquid ejection head provided with an energy generating element (hereinafter referred to as a heater) that generates energy for ejecting a liquid from a discharge port is known. In this liquid ejection head, the heater may deteriorate by repeatedly ejecting the liquid, or excessive heat may be generated by driving the heater in a state where there is no liquid, resulting in disconnection of the heater or wiring.

[0003] Patent Document 1 describes an inkjet recording head that can detect disconnection of a heater or wiring. This inkjet recording head includes a detection wiring provided adjacent to the wiring of the heater and a resistor for measuring the potential of the detection wiring. Since a parasitic capacitance exists between the wiring of the heater and the detection wiring, the voltage value at the resistor end changes via the parasitic capacitance by electrostatic induction in response to a change in the current value flowing through the wiring of the heater. This voltage value at the resistor end is compared with a preset threshold value, and when the voltage value exceeds the threshold value, it is determined that a disconnection has occurred in either the wiring of the heater or the detection wiring.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The deterioration state of a heater can be obtained by detecting changes in the heater's resistance in response to minute changes in the current flowing through it. However, in the inkjet recording head described in Patent Document 1, the detection wiring is not connected to the heater, and the current flowing through the heater is measured indirectly using electrostatic induction. With such indirect measurement, although large changes in the heater current can be detected, minute changes in the heater current cannot be detected, making it difficult to obtain the deterioration state of the heater.

[0006] The object of the present invention is to provide a liquid dispensing head capable of acquiring the deterioration state of a heater. [Means for solving the problem]

[0007] A liquid discharge head according to one aspect of the present invention comprises: a discharge port for discharging liquid; a heater for generating energy to discharge liquid from the discharge port; a discharge switch element connected to the heater for energizing the heater; a current measuring element, one end of which is connected to wiring connecting the heater and the discharge switch element, for measuring the current flowing through the heater; and a measuring switch element connected to the other end of the current measuring element for energizing the heater and the current measuring element. The switching of the discharge switch element to a conductive state and the switching of the measuring switch element to a conductive state are performed exclusively. A liquid dispensing head according to another aspect of the present invention includes a heater that generates energy for dispensing liquid from a nozzle, and a current measuring element for measuring the current flowing through the heater. When dispensing the liquid, the power supply is grounded via the heater, and when measuring the current, the power supply is grounded via the portion connecting the heater and the current measuring element. [Effects of the Invention]

[0008] According to the present invention, it is possible to detect changes in the resistance value of a heater in response to minute changes in the current flowing through the heater, thereby enabling the acquisition of the heater's degradation state. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic perspective view of an inkjet recording apparatus to which the present invention can be applied. [Figure 2] This is a block diagram of the control system of a liquid dispensing device equipped with a liquid dispensing head according to a first embodiment of the present invention. [Figure 3] This is a schematic diagram of the recording element substrate of a liquid discharge head according to the first embodiment of the present invention. [Figure 4] Figure 3 is a schematic diagram showing the ejection electrical circuit of the recording element substrate. [Figure 5] This block diagram shows the ejection element drive circuit of the recording element substrate shown in Figure 3. [Figure 6] This block diagram shows the current measurement circuit of the recording element substrate shown in Figure 3. [Figure 7] This is a flowchart illustrating an example of a process for determining the deterioration status of a heater. [Figure 8] This is a schematic diagram of the recording element substrate of a liquid discharge head according to a second embodiment of the present invention. [Figure 9] Figure 8 is a schematic diagram showing the ejection electrical circuit of the recording element substrate. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below with reference to the drawings. However, these embodiments are merely illustrative and are not intended to limit the scope of the present invention to these embodiments.

[0011] (First embodiment) Figure 1 is a schematic perspective view of an inkjet recording apparatus to which the present invention can be applied. The inkjet recording apparatus shown in Figure 1 is a so-called full-line type recording apparatus and is equipped with a liquid ejection head 101, which is a long inkjet recording head that extends in the width direction of the recording medium 100. The liquid ejection head 101 is equipped with four inkjet recording heads 101Y, 101M, 101C, and 101B that eject liquid such as ink. The recording medium 100 is transported in the direction of arrow A (transport direction) by a transport unit 102 which is composed of a transport belt or transport rollers. The inkjet recording heads 101Y, 101M, 101C, and 101B are arranged in parallel along the transport direction and eject yellow ink, magenta ink, cyan ink, and black ink, respectively, to the recording medium 100. Note that the recording apparatus to which the present invention can be applied is not limited to a full-line type recording apparatus. The present invention can also be applied to so-called serial scan type recording apparatuses, etc.

[0012] Figure 2 is a block diagram of the control system of a liquid dispensing device equipped with a liquid dispensing head according to the first embodiment of the present invention. The MPU (Micro-Processing Unit) 200 performs control processing and data processing of the liquid dispensing device. The ROM 201 stores programs such as processing procedures to be executed by the MPU 200. The RAM 202 is used as a work area for executing control processing and data processing. The head control circuit 203 controls the operation of the liquid dispensing head 101 (including the operation of the heater 305 and the current measuring element 416) according to control signals and data from the MPU 200. For example, when dispensing liquid from the liquid dispensing head 101, the MPU 200 supplies drive data for the heater 305 to the head control circuit 203, and the head control circuit 203 drives the heater 305 according to the drive data. The MPU 200 also controls the transport motor 204 of the transport unit 102 via the motor driver 205.

[0013] The liquid ejection head 101 has a memory element 206, which is a storage means that stores information such as the resistance value of the heater 305 in advance. For example, information including the resistance value (Rref[Ω]) and the standard value (±M[Ω]) of the heater 305 may be stored in the memory element 206 when the liquid ejection head 101 is manufactured. Rref±M[Ω] is set as the standard range for the resistance value of the heater 305, and the deterioration state of the heater 305 can be determined by whether or not the resistance value of the heater 305 is within this standard range. Details of the determination of the deterioration state will be described later. As the memory element 206, a fuse ROM (Read Only Memory) or an EEPROM (Electrically Erasable Programmable ROM) can be used, but is not limited to these.

[0014] Figure 3 is a schematic diagram of the recording element substrate constituting the liquid ejection head 101. Arrow Y indicates the longitudinal direction of the recording element substrate 300, and arrow X indicates the short direction of the recording element substrate 300. The recording element substrate 300 has an ink supply port 301 extending in the direction of arrow Y in the central part. Multiple pressure chambers 304 are formed on both sides of the ink supply port 301. Each pressure chamber 304 communicates with an ejection port 303 for ejecting ink, and a heater 305 is provided in the region facing the ejection port 303. The heater 305 generates energy for ejecting ink from the ejection port 303. Ink supplied from the ink supply port 301 is supplied to each pressure chamber 304, and any ink that remains undischarged is then recovered from the ink recovery port 302.

[0015] When the heater 305 generates heat, the ink in the pressure chamber 304 is foamed, and the foaming energy is used to discharge the ink from the discharge port 303. As the heater 305, an electric heat conversion element (or a heating resistance element) can be used. A plurality of discharge ports 303 are arranged at a predetermined interval along the arrow Y direction, and a discharge port row extending in the arrow Y direction is formed by these discharge ports 303. Here, the arrow Y direction is a direction that intersects (in this case, is orthogonal to) the conveyance direction (arrow A) of the recording medium 100 shown in FIG. 1. A plurality of pads 306 are provided at both ends of the recording element substrate 300 in the arrow Y direction. A selection data signal for selecting the discharge port 303 for discharging the ink and a power supply voltage are supplied to these pads 306 from the recording apparatus main body. The liquid discharge head 101 can discharge the ink at an arbitrary timing from the discharge port 303 selected based on the selection data signal.

[0016] FIG. 4 is a schematic diagram of a discharge electric circuit 400 that performs discharge and measurement constituting the recording element substrate 300. The discharge electric circuit 400 includes a heater 305, a discharge switch element 405 for controlling the heater 305, a current measurement element 416 for measuring the current flowing through the heater 305, and a measurement switch element 406 for controlling the current measurement element 416. One end of the heater 305 is connected to a discharge power supply (VH) 403, and the other end of the heater 305 is connected to the discharge switch element 405. Although only one discharge electric circuit 400 is shown in FIG. 4 for the sake of convenience, actually, a plurality of discharge electric circuits 400 are provided, and discharge and measurement are performed in each discharge electric circuit 400.

[0017] The ejection switch element 405 is for energizing the heater 305 and is composed of, for example, a switch element of a MOS type FET. In this case, the other end of the heater 305 is connected to one terminal (source or drain) of the switch element, and the other terminal (source or drain) is grounded. When the voltage value supplied to the gate terminal exceeds the threshold value, the switch element transitions from the non-conductive state to the conductive state. When the ejection switch element 405 becomes conductive, the ejection power supply 403 is grounded via the heater 305, and a current flows from the ejection power supply 403 to the heater 305. MOS is an abbreviation for Metal-Oxide Semiconductor. FET is an abbreviation for Field-Effect Transistor.

[0018] One end of the current measurement element 416 is connected to the wiring 404 that connects the heater 305 and the ejection switch element 405. The other end of the current measurement element 416 is connected to the measurement switch element 406. The measurement switch element 406 is for energizing the heater 305 and the current measurement element 416 and is composed of, for example, a switch element of a MOS type FET. In this case, the other end of the current measurement element 416 is connected to one terminal (source or drain) of the switch element, and the other terminal (source or drain) is grounded. When the voltage supplied to the gate terminal exceeds the threshold value, the switch element transitions from the non-conductive state to the conductive state. When the ejection switch element 405 is in the non-conductive state and the measurement switch element 406 is in the conductive state, the ejection power supply 403 is grounded via the portion connecting the heater 305 and the current measurement element 416, and a current flows from the ejection power supply 403 to the heater 305 and the current measurement element 416.

[0019] The current measuring element 416 measures the current flowing through the heater 305. For example, the current measuring element 416 includes a resistor 416a and a differential amplifier 416b that amplifies the voltage across the resistor 416a. One end of the resistor 416a is connected to wiring 404, and the other end of the resistor 416a is connected to a measuring switch element 406. When the discharge switch element 405 is non-conductive and the measuring switch element 406 is conductive, current flows from the discharge power supply 403 to the heater 305 and the resistor 416a, and the differential amplifier 416b outputs a voltage Vout which is the amplified voltage difference across the resistor 416a.

[0020] In addition to the above configuration, the discharge electrical circuit 400 includes a heater drive unit 400A and a current measuring element drive unit 400B. The heater drive unit 400A includes a discharge level converter unit 401 and a discharge AND gate group 407. The discharge AND gate group 407 is formed from a plurality of AND gates. The discharge AND gate group 407 receives a discharge block selection signal (BE) 409, a discharge data selection signal (DATA) 410, and a discharge time signal (HE) 411 as input signals. The output of the discharge AND gate group 407 is supplied to the discharge switch element 405 via the discharge level converter unit 401. The discharge level converter unit 401 is for driving the discharge switch element 405 and converts the level of the output signal of the discharge AND gate group 407 to a desired signal level. The desired signal level is, for example, a signal level suitable for driving the MOS-type FET switch element described above.

[0021] During the period when the ejection time signal (HE) 411 is applied to the ejection AND gate group 407, the ejection switch element 405 becomes conductive, and current flows to the heater 305. If the current flowing through the heater 305 is I, then I = VH / R [A]. Here, "VH" represents the voltage value [V] of the ejection power supply 403, and "R" represents the resistance value [Ω] of the heater 305. Also, if the Joule heat generated by the heater 305 is Q, then Q = VH·I·T [J]. Here, "T" represents the time during which the ejection time signal (HE) 411 is applied to the ejection AND gate group 407. As the heater 305 generates Joule heat Q, the ink foams and is ejected from the ejection port 303.

[0022] The current measuring element drive unit 400B includes a measuring level converter unit 402 and a measuring AND gate group 408. The measuring AND gate group 408 is formed from a plurality of AND gates. The measuring AND gate group 408 receives a measuring block selection signal (S_BE) 412, a measuring data selection signal (S_DATA) 413, and a measuring signal (S_E) 414 as input signals. The output of the measuring AND gate group 408 is supplied to the measuring switch element 406 via the measuring level converter unit 402. The measuring level converter unit 402 is for driving the measuring switch element 406 and converts the level of the output signal of the measuring AND gate group 408 to a desired signal level. The desired signal level is, for example, a signal level suitable for driving the MOS-type FET switch element described above.

[0023] When the measurement signal (S_E) 414 is supplied to the measurement AND gate group 408, the measurement switch element 406 changes to a conductive state. When the discharge switch element 405 is in a non-conductive state and the measurement switch element 406 becomes conductive, current flows through the heater 305 and the resistor 416a. If the current flowing through the heater 305 and the resistor 416a is Is, then Is = VH / (R+Rs)[A]. Here, "Rs" represents the resistance value [Ω] of the resistor 416a. If the voltage across the resistor 416a is Vs, then Vs = Is·Rs[V]. Here, it is assumed that the differential amplifier 416b amplifies the voltage across the resistor 416a by a factor of K, and the amplification factor of the differential amplifier 416b is K. The output voltage Vout of the differential amplifier 416b is Vout = K·Vs[V].

[0024] From the relationship described above, the resistance value R of heater 305 is given by R = Rs·(K·VH-Vout) / Vout[Ω] (hereinafter referred to as resistance value R conversion formula 1). Here, VH, Rs, and K are all known design values. Therefore, by measuring the output voltage Vout of differential amplifier 416b, the resistance value R of heater 305 can be obtained based on resistance value R conversion formula 1. For example, suppose the voltage VH of the power supply 403 is 24.0[V], the resistance value Rs of resistor 416a is 10.0[Ω], and the amplification factor K of differential amplifier 416b is 10 times. If the output voltage Vout of differential amplifier 416b is 2.96[V], then based on resistance value R conversion formula 1, a resistance value R of heater 305 of 800.0[Ω] can be obtained.

[0025] In the discharge electrical circuit 400, the switching of the discharge switch element 405 to a conductive state and the switching of the measurement switch element 406 to a conductive state are performed mutually exclusive. Even if the discharge switch element 405 and the measurement switch element 406 become conductive at the same time, the potential of the wiring 404 will be the same as that of ground, so the heater 305 will generate Joule heat Q, and no current will flow to the current measurement element 416. In other words, the discharge electrical circuit 400 is configured so that the discharge operation takes priority when the discharge operation by the heater 305 and the measurement operation by the current measurement element 416 occur simultaneously.

[0026] Figure 5 is a block diagram showing the configuration of the ejection element drive circuit 10 included in the recording element substrate 300. The ejection element drive circuit 10 shown in Figure 5 is configured to drive multiple heaters 305 assigned to four blocks. The ejection element drive circuit 10 includes an ejection data supply unit 501 and an ejection block selection unit 504.

[0027] The discharge data supply unit 501 includes an M-bit shift register 502 and a latch circuit 503. The M-bit shift register 502 stores the discharge data DATA in synchronization with the transfer clock CLK. The latch circuit 503 temporarily holds the same bit data (M-bit data) in the M-bit shift register 502 in response to the data latch signal LATCH.

[0028] The output block selection unit 504 has an L-bit shift register 505 and an L-bit decoder 506. The L-bit shift register 505 stores the output block data BDATA in synchronization with the transfer clock CLK. The L-bit decoder 506 temporarily holds the same bit data (L(L=2) bit data) from the L-bit shift register 505 in response to the input data latch signal LATCH. One of the output block selection signals BE0 to BE3, the output data selection signals DATA0 to DATA(M-1) corresponding to the output dots from the output data supply unit 501, and the output time signal HE are input to the output electrical circuit 400.

[0029] Figure 6 is a block diagram showing the configuration of the current measurement circuit 11 included in the recording element substrate 300. The current measurement circuit 11 shown in Figure 6 is configured to drive multiple current measurement elements 416 by assigning them to four blocks. The current measurement circuit 11 includes a measurement data supply unit 601 and a measurement block selection unit 604.

[0030] The measurement data supply unit 601 includes an M-bit shift register 602 and a latch circuit 603. The M-bit shift register 602 stores the measurement data S_DATA in synchronization with the transfer clock CLK. The latch circuit 603 temporarily holds the same bit data (M-bit data) in the M-bit shift register 602 in response to the data latch signal LATCH.

[0031] The measurement block selection unit 604 has an L-bit shift register 605 and an L-bit decoder 606. The L-bit shift register 605 stores the measurement block data S_BDATA in synchronization with the transfer clock CLK. The L-bit decoder 606 temporarily holds the same bit data (L(L=2) bit data) from the L-bit shift register 605 in response to the input data latch signal LATCH. One of the measurement block selection signals S_BE0 to S_BE3, the measurement data selection signals S_DATA0 to S_DATA(M-1) corresponding to the measurement dot from the measurement data supply unit 601, and the measurement signal S_E are input to the aforementioned output electrical circuit 400.

[0032] In the liquid ejection head 101 of the above-described embodiment, as the heater 305 deteriorates due to repeated ink ejection, the resistance value R of the heater 305 also changes accordingly. For example, the resistance value R of the heater 305 may increase due to damage to the heater 305 caused by periodic impacts or thermal loads due to cavitation. However, the factors causing deterioration of the heater 305 are diverse and not limited to impacts or thermal loads due to cavitation. In this embodiment, the memory element 206 stores the heater's resistance value (Rref[Ω]) and standard value (±M[Ω]) in advance. The deterioration state of the heater 305 can be determined by whether or not the resistance value R of the heater 305 is within the standard range (Rref±M[Ω]).

[0033] Figure 7 is a flowchart showing an example of a process for determining the deterioration state of a heater. First, in step S1, measurement data S_DATA and measurement block data S_BDATA are input to the current measurement circuit 11 (see Figure 6). Based on the measurement data S_DATA and measurement block data S_BDATA, the current measurement circuit 11 selects the current measurement element 416 to be measured from among a plurality of current measurement elements 416. Then, the measurement block selection signal (S_BE) 412 and the measurement data selection signal (S_DATA) 413 are input to the current measurement element drive unit 400B (see Figure 4) corresponding to the current measurement element 416 to be measured.

[0034] In step S2, the measurement signal S_E is input to the current measurement circuit 11. The current measurement circuit 11 causes the current measurement element 416, which is the object to be measured, to perform current measurement according to the measurement signal S_E. When the measurement signal (S_E) 414 is supplied to the measurement AND gate group 408 of the current measurement element drive unit 400B, the measurement switch element 406 becomes conductive, and current flows through the heater 305 and the resistor 416a. The differential amplifier 416b outputs a voltage Vout, which is the amplified voltage difference across the resistor 416a. The head control circuit 203 obtains the resistance value R of the heater 305 from the output voltage Vout of the differential amplifier 416b based on the aforementioned resistance value conversion formula 1.

[0035] In step S3, the head control circuit 203 reads the heater's resistance value (Rref[Ω]) and specification value (±M[Ω]) stored in the memory element 206. Rref±M[Ω] is defined as the specification range for the heater 305's resistance value. In step S4, the head control circuit 203 determines whether the resistance value R of the heater 305 obtained in step S2 is within the specified range (Rref±M[Ω]) of the resistance value of the heater 305 read in step S3.

[0036] If the result of the judgment in step S4 is "YES", in step S5 the head control circuit 203 determines that the heater 305 is normal. If the result of the judgment in step S4 is "NO", in step S6 the head control circuit 203 determines that the heater 305 has deteriorated.

[0037] According to the process for determining the deterioration state of the heater 305 described above, it is possible to detect changes in the resistance value of the heater 305 in response to minute changes in the current flowing through the heater 305, thereby obtaining the deterioration state of the heater 305. If the heater 305 or wiring is broken, the output voltage Vout of the differential amplifier 416b becomes 0. When the head control circuit 203 detects that the output voltage Vout of the differential amplifier 416b has become 0, it determines that the heater 305 or wiring is broken.

[0038] Furthermore, in recent years, there has been a growing demand for products and manufacturing methods that minimize environmental impact. From the perspective of efficient resource utilization, used liquid dispensing heads are eligible for reuse or recycling. In the regeneration process for used liquid dispensing heads, after being collected from households, the heads undergo a preliminary inspection at the regeneration plant. If the inspection reveals any abnormalities in the heater installed in the liquid dispensing head, reuse becomes difficult, and the heads are then recycled or discarded.

[0039] Since the resistance value of the heater 305 changes depending on the number of ink ejections and usage conditions, it is necessary to determine whether the resistance value of the heater 305 is within an appropriate range when reusing the liquid ejection head 101. By applying the above-described process for determining the deterioration state of the heater 305 to the regeneration process of the used liquid ejection head, it is possible to determine whether or not it can be reused. For example, if the result of the determination in step S4 is "YES", it is determined that it can be reused. If the result of the determination in step S4 is "NO", it is determined that it cannot be reused. In this case, the head control circuit 203 may perform the determination process, or the control device of the regeneration equipment may perform the determination process. In the latter case, for example, an electrical contact for outputting the output of the differential amplifier 416b to the outside is provided on the liquid ejection head 101. The output of the differential amplifier 416b is supplied to the control device of the regeneration equipment via the electrical contact of the liquid ejection head 101. If the liquid ejection head 101 is small, it is preferable to perform the determination process by the head control circuit 203. On the other hand, if the liquid discharge head 101 is large, it is preferable to perform the determination process using the control device of the regeneration equipment.

[0040] Furthermore, if the determination process is performed when the ink is depleted, current will flow to the heater 305 and current measuring element 416 even without liquid, generating excessive heat which may damage the heater 305 and wiring. Therefore, it is preferable to perform the determination process for the deterioration state of the heater 305 when the amount of ink contained in the liquid ejection head 101 decreases, that is, when there is still ink remaining (preferably just before the ink runs out). For example, the head control circuit 203 performs the determination process when the ink decreases and stores the determination result in the memory element 206. The liquid ejection head 101 is equipped with electrical contacts for outputting the information stored in the memory element 206 to the outside. The control device of the regeneration equipment can determine whether or not it is reusable by reading the information (determination result) stored in the memory element 206 via the electrical contacts of the liquid ejection head 101.

[0041] (Second embodiment) Figure 8 is a schematic diagram of a recording element substrate constituting a liquid discharge head according to a second embodiment of the present invention. In Figure 8, arrow Y indicates the longitudinal direction of the recording element substrate 300, and arrow X indicates the short direction of the recording element substrate 300.

[0042] The liquid discharge head 101 of this embodiment is the same as that described in the first embodiment, except that the resistor 616a of the current measuring element 416 is replaced with element 801. The same reference numerals are used for components identical to those in the first embodiment, and a detailed description of their components is omitted.

[0043] Element 801 functions not only as a resistor used to measure current, but also as an electrothermal conversion element (heater) that heats the ink. Element 801 is positioned between the ink supply port 301 and the heater 305. In the direction of ink flow, element 801 is positioned upstream of the heater 305, allowing the ink supplied to the heater 305 to be heated upstream.

[0044] Figure 9 is a schematic diagram of the ejection electrical circuit that performs ejection and measurement, which constitutes the recording element substrate shown in Figure 8. For convenience, Figure 9 shows the ejection electrical circuit 400 for one heater 305, but in reality, the ejection electrical circuit 400 shown in Figure 9 is provided for all heaters 305.

[0045] One end of element 801 is connected to wiring 404 that connects heater 305 and discharge switch element 405, and the other end of element 801 is connected to measuring switch element 406. Differential amplifier 416b outputs a voltage Vout which is the amplified voltage difference across element 801.

[0046] During the period when the ejection time signal (HE) 411 is applied, the ejection switch element 405 becomes conductive. When the ejection switch element 405 becomes conductive, current flows to the heater 305. Then, the heater 305 generates Joule heat Q1 (Q1 = VH·I·T [J]), causing the ink to foam and be ejected from the ejection port 303.

[0047] When the measurement signal S_E is applied, the measurement switch element 406 becomes conductive. When the ejection switch element 405 is in a non-conductive state, when the measurement switch element 406 becomes conductive, current flows through the heater 305 and the element 801, and a voltage (Vs = Is·Rs [V]) is generated across both ends of the element 801. Here, Rs represents the resistance value of the element 801. Since the differential amplifier 416b amplifies the voltage across both ends of the element 801 by K times, the output voltage of the differential amplifier 416b is Vout = K·Vs [V]. The resistance value of the heater 305 is R = Rs·(K·VH - Vout) / Vout [Ω]. This equation is the same as the conversion formula 1 for the resistance value R described above.

[0048] According to the liquid ejection head 101 of the present embodiment, in addition to the effects described in the first embodiment, the following effects are achieved. When the measurement switch element 406 is made conductive for a period of Tb [seconds], the heater 305 generates Joule heat Q2 (Q2 = R·Is 2 ·Tb [J]), and the element 801 generates Joule heat Qs (Qs = Rs·Is 2 ·Tb [J]). By heating the ink with these heaters 305 and the element 801, the viscosity of the ink in the pressure chamber 304 decreases. As a result, the circulation of the ink and the ejection operation when the ejection switch element 405 is made conductive and the ink is ejected from the ejection port 303 can be preferably performed. In particular, by arranging the element 801 upstream of the heater 305, the ink supplied to the heater 305 can be heated, so that the ejection operation can be performed more preferably. Note that the relationship Qs < Q2 < Q1 and Rs < R holds, and it is preferable that both Qs and Q2 are of a magnitude such that no bubbles are generated.

[0049] Also, usually, a resistor for measuring current and an electrothermal conversion element (heater) for heating ink are provided separately. In the present embodiment, since the element 801 has both a function as a resistor for measuring current and a function as an electrothermal conversion element (heater) for heating ink, the number of elements used on the recording element substrate 300 can be reduced.

[0050] The liquid discharge head 101 of this embodiment can also be subjected to the applications and modifications described in the first embodiment.

[0051] This embodiment includes the following configuration. (Composition 1) A nozzle for dispensing liquid, A heater that generates energy for discharging liquid from the aforementioned outlet, A discharge switch element connected to the heater and for energizing the heater, One end is connected to the wiring connecting the heater and the discharge switch element, and a current measuring element is used to measure the current flowing through the heater, The system comprises a measuring switch element connected to the other end of the current measuring element for energizing the heater and the current measuring element, A liquid dispensing head characterized in that the switching of the dispensing switch element to a conductive state and the switching of the measuring switch element to a conductive state are performed exclusively. (Configuration 2) The liquid dispensing head according to configuration 1, characterized in that the current measuring element comprises a resistor and a differential amplifier that amplifies the voltage generated across the resistor. (Composition 3) The liquid dispensing head according to configuration 2, characterized in that one end of the resistor is connected to the wiring connecting the heater and the dispensing switch element, and current flows through the heater and the resistor when the dispensing switch element is non-conductive and the measuring switch element is conductive. (Composition 4) The liquid dispensing head according to configuration 3, characterized by having an electrical contact for outputting the output of the differential amplifier to the outside. (Composition 5) The liquid dispensing head according to any one of configurations 2 to 4, characterized in that the resistor heats the liquid. (Composition 6) The liquid discharge head according to configuration 5, comprising a pressure chamber that communicates with the discharge port and to which the liquid is supplied, wherein the heater and resistor are provided in the pressure chamber, and the resistor is positioned upstream of the heater in the direction of liquid flow. (Composition 7) A liquid dispensing head according to any one of configurations 1 to 6, characterized in that it is equipped with a plurality of heaters and current measuring elements, and has a current measuring circuit that selects the current measuring element to be measured from among the plurality of current measuring elements according to an input signal. (Composition 8) A heater that generates energy to discharge liquid from the outlet, It includes a current measuring element for measuring the current flowing through the heater, When the aforementioned liquid is discharged, the power supply is grounded via the heater. A liquid dispensing head characterized in that, when measuring the current, the power supply is grounded via the portion connecting the heater and the current measuring element. (Composition 9) A liquid dispensing head as described in any one of configurations 1 to 8, The system includes a head control circuit that controls the operation of the liquid discharge head, The head control circuit is characterized by obtaining the resistance value of the heater based on the output of the current measuring element, determining that the heater is normal if the obtained resistance value of the heater is within a predetermined range, and determining that the heater is deteriorated if the obtained resistance value of the heater falls outside the predetermined range. (Composition 10) The liquid dispensing device according to configuration 9, characterized in that it has a memory element that holds information indicating whether the heater is normal or deteriorated. (Composition 11) The liquid dispensing device according to configuration 10, characterized in that the liquid dispensing head has an electrical contact for outputting information held in the memory element to the outside. [Explanation of Symbols]

[0052] 101 Liquid dispensing head 305 Heater 404 Wiring 405 Discharge switch element 406 Measuring switch element 416 Current measuring element

Claims

1. A nozzle for dispensing liquid, A heater that generates energy for discharging liquid from the aforementioned outlet, A discharge switch element connected to the heater and for energizing the heater, One end is connected to the wiring that connects the heater and the discharge switch element, and the heater A current measuring element for measuring the current flowing through it, It is connected to the other end of the current measuring element and is used to energize the heater and the current measuring element. A measuring switch element is provided, Switching of the discharge switch element to a conductive state and the conductive state of the measuring switch element A liquid dispensing head characterized by exclusive switching between modes.

2. The current measuring element comprises a resistor and a differential amplifier that amplifies the voltage across the resistor. The liquid dispensing head according to claim 1, characterized by having ,

3. One end of the resistor is connected to the wiring that connects the heater and the discharge switch element. Furthermore, when the discharge switch element is in a non-conductive state and the measuring switch element is in a conductive state The liquid discharge device according to claim 2, characterized in that current flows through the heater and the resistor. Head out.

4. The differential amplifier is characterized by having an electrical contact for outputting the output to an external source. A liquid dispensing head as described in item 3.

5. The liquid discharge head according to claim 2, characterized in that the resistor heats the liquid. 。

6. It is equipped with a pressure chamber that communicates with the discharge port and to which the liquid is supplied, and the heater and resistor are The resistor is provided in the pressure chamber, and in the direction of the liquid flow, the resistor is positioned above the heater. The liquid discharge head according to claim 5, characterized in that it is positioned on the flow side.

7. The system is equipped with multiple heaters and current measuring elements, and according to the input signal, multiple The circuit has a current measuring circuit that selects the current measuring element to be measured from among the aforementioned current measuring elements. The liquid dispensing head according to claim 1, characterized in that... (Former claim 8 deleted)

8. A liquid dispensing head according to any one of claims 1 to 7, The system includes a head control circuit that controls the operation of the liquid discharge head, The head control circuit acquires the resistance value of the heater based on the output of the current measuring element. If the acquired resistance value of the heater falls within a predetermined range, it is determined that the heater is functioning normally. If the resistance value of the heater is determined and obtained falls outside the predetermined range, the heater A liquid dispensing device characterized by its ability to determine if a liquid has deteriorated.

9. The heater is characterized by having a memory element that holds information indicating whether the heater is functioning normally or is degraded. The liquid dispensing device according to claim 8.

10. The liquid dispensing device according to claim 9, characterized in that the liquid dispensing head has an electrical contact for outputting the information held in the memory element to the outside of the liquid dispensing head.

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