Liquid ejection head unit, liquid ejection device, and liquid ejection state determination method

Abstract

The present invention provides a liquid ejection head unit, a liquid ejection device, and a method for determining a liquid ejection state. The liquid ejection head unit is characterized by having: a first energy generating element that generates energy for applying pressure to the liquid in a first pressure chamber; a second energy generating element that generates energy for applying pressure to the liquid in a second pressure chamber; a nozzle flow path that communicates the first pressure chamber with the second pressure chamber and is provided with a nozzle for ejecting the liquid; a drive circuit that drives the first energy generating element and the second energy generating element by applying drive pulses; a detection circuit that detects at least a parameter related to the physical properties of the liquid in the second pressure chamber; and a control unit that controls the operations of the drive circuit and the detection circuit. The control unit performs a first detection operation of driving the first energy generating element by the drive circuit and detecting the parameter in the second pressure chamber by the detection circuit.

Description

Technical Field

[0001] The present invention relates to a liquid ejection head unit, a liquid ejection device, and a method for determining a liquid ejection state of a liquid ejection device. Background Art

[0002] As disclosed in Patent Document 1, a liquid ejection device typified by an inkjet printer has, for example, a pressure chamber for applying pressure to a liquid and a piezoelectric element for applying pressure to the pressure chamber. The device described in Patent Document 1 detects a residual vibration waveform formed based on the vibration of ink after a drive signal is supplied to the pressure element as an electromotive force of the piezoelectric element, and determines an ink state such as ink viscosity or air bubble mixing based on the detection result.

[0003] In the device described in Patent Document 1, since the same piezoelectric element is used in both generation and detection of the residual vibration waveform, it is necessary to switch the piezoelectric element used for detection of the residual vibration waveform from a drive state to a detection state. Therefore, in the device described in Patent Document 1, there is a problem that electrical noise generated by this switching is mixed into the residual vibration waveform, resulting in a decrease in the accuracy of determining the ejection state.

[0004] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2011-189655 Summary of the Invention

[0005] In order to solve the above problems, a liquid ejection head unit according to a preferred aspect of the present invention includes: a first pressure chamber that applies pressure to a liquid; a second pressure chamber that applies pressure to a liquid; a first energy generation element that generates energy for applying pressure to the liquid in the first pressure chamber; a second energy generation element that generates energy for applying pressure to the liquid in the second pressure chamber; a nozzle flow path that connects the first pressure chamber and the second pressure chamber and is provided with a nozzle for ejecting the liquid; a drive circuit that drives the first energy generation element and the second energy generation element by applying drive pulses; a detection circuit that detects at least a parameter related to the physical properties of the liquid in the second pressure chamber; and a control unit that controls operations of the drive circuit and the detection circuit, and the control unit performs the following first detection operation, that is, drives the first energy generation element by the drive circuit and detects the parameter in the second pressure chamber by the detection circuit.

[0006] A liquid ejection device according to a preferred aspect of the present invention includes: the liquid ejection head unit according to the above aspect; and a conveyance mechanism that conveys a printing medium on which an image formed by the liquid from the liquid ejection head unit is printed.

[0007] In the method for judging the liquid ejection state of the liquid ejection device according to the preferred embodiment of the present invention, the liquid ejection device includes: a first pressure chamber that applies pressure to the liquid; a second pressure chamber that applies pressure to the liquid; a first energy generating element that generates energy for applying pressure to the liquid in the first pressure chamber; a second energy generating element that generates energy for applying pressure to the liquid in the second pressure chamber; a nozzle flow path that communicates the first pressure chamber and the second pressure chamber and is provided with a nozzle for ejecting the liquid. In the method for judging the liquid ejection state of the liquid ejection device, the first energy generating element is driven, and a parameter related to the physical properties of the liquid in the second pressure chamber accompanying the driving of the first energy generating element is detected, and the ejection state of the liquid ejected from the nozzle is judged based on the parameter or the physical properties. Description of the Drawings

[0008] Figure 1 A schematic diagram showing a structural example of the liquid ejection device according to the first embodiment.

[0009] Figure 2 A block diagram showing the electrical structure of the liquid ejection device according to the first embodiment.

[0010] Figure 3 A schematic diagram of the flow path in the liquid ejection head according to the first embodiment.

[0011] Figure 4 For Figure 3 The sectional view taken along the line A-A in

[0012] Figure 5 A diagram showing a structural example of the drive circuit in the first embodiment.

[0013] Figure 6 A diagram for explaining the ejection operation in the first embodiment.

[0014] Figure 7 A diagram for explaining the first detection operation in the first embodiment.

[0015] Figure 8 A diagram for explaining the relationship between the detection period and the analysis period.

[0016] Figure 9 A diagram for explaining the second detection operation in the first embodiment.

[0017] Figure 10 A diagram for explaining the third detection operation in the first embodiment.

[0018] Figure 11A diagram showing a structural example of the drive circuit in the second embodiment.

[0019] Figure 12 A diagram for explaining the ejection operation in the second embodiment.

[0020] Figure 13 A diagram for explaining the first detection operation in the second embodiment.

[0021] Figure 14 A diagram for explaining the first detection operation in the third embodiment. Detailed Embodiment

[0022] Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described. In the drawings, the dimensions or ratios of each part are appropriately different from the actual situation, and there are also parts schematically shown for easy understanding. In addition, as long as there is no description in the following explanation that limits the present invention, the scope of the present invention is not limited to these embodiments.

[0023] In addition, the following description is appropriately made using the mutually intersecting X-axis, Y-axis, and Z-axis. In addition, one direction along the X-axis is referred to as the X1 direction, and the direction opposite to the X1 direction is referred to as the X2 direction. Similarly, the directions opposite to each other along the Y-axis are referred to as the Y1 direction and the Y2 direction. In addition, the directions opposite to each other along the Z-axis are referred to as the Z1 direction and the Z2 direction. Here, typically, the Z-axis is a vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. However, the Z-axis may not be a vertical axis. In addition, although the X-axis, Y-axis, and Z-axis typically intersect orthogonally, it is not limited thereto, and they may intersect at an angle within a range of, for example, 80° or more and 100° or less.

[0024] A: First Embodiment

[0025] A1: Overall Structure of the Liquid Ejection Device

[0026] Figure 1 A schematic diagram showing a structural example of the liquid ejection device 100 according to the first embodiment. The liquid ejection device 100 is an inkjet printing device that ejects a liquid such as ink as droplets onto the medium 11. The medium 11 is an example of a printing medium, such as printing paper. In addition, the medium 11 is not limited to printing paper, and for example, it may be any material to be printed such as a resin film or a cloth.

[0027] A liquid container 12 is installed on the liquid ejection device 100. The liquid container 12 stores ink. Specific examples of the liquid container 12 include a cartridge that is detachable from the liquid ejection device 100, a bag-shaped ink bag made of a flexible film, and an ink tank that can be refilled with ink. Additionally, the type of ink stored in the liquid container 12 can be any type.

[0028] As Figure 1 shown in the figure, the liquid ejection device 100 includes a control module 21, a conveyance mechanism 22, a moving mechanism 23, and a liquid ejection head module 20. The control module 21 controls the operations of the various elements of the liquid ejection device 100.

[0029] The conveyance mechanism 22 conveys the medium 11 along the Y-axis under the control of the control module 21. The moving mechanism 23 moves the liquid ejection head module 20 back and forth along the X-axis under the control of the control module 21. The moving mechanism 23 includes a substantially box-shaped conveyance body 231 that houses the liquid ejection head module 20 and a seamless conveyor belt 232 that fixes the conveyance body 231. Additionally, the number of liquid ejection head modules 20 mounted on the conveyance body 231 is not limited to one and can be multiple. Furthermore, on the conveyance body 231, in addition to the liquid ejection head module 20, the above-mentioned liquid container 12 can also be mounted.

[0030] The liquid ejection head module 20 ejects the ink supplied from the liquid container 12 from a plurality of nozzles onto the medium 11 under the control of the control module 21. By performing this ejection in parallel with the conveyance of the medium 11 achieved by the conveyance mechanism 22 and the back-and-forth movement of the liquid ejection head module 20 achieved by the moving mechanism 23, an image is formed on the surface of the medium 11.

[0031] A2: Electrical Structure of the Liquid Ejection Device

[0032] Figure 2 It is a block diagram showing the electrical structure of the liquid ejection device 100 according to the first embodiment. Figure 2 Among the structural elements of the liquid ejection device 100 shown, the above-mentioned control module 21 and liquid ejection head module 20 constitute the liquid ejection head unit 10.

[0033] As Figure 2 shown in the figure, the liquid ejection head module 20 includes a liquid ejection head 24, a drive circuit 45, and a detection circuit 46. Hereinafter, an overview of them will be described. Additionally, based on Figures 3 to 8 , the liquid ejection head 24, drive circuit 45, and detection circuit 46 will be described in detail.

[0034] The liquid ejection head 24 has a plurality of piezoelectric elements 41, and ink is ejected from the nozzles by appropriately driving the plurality of piezoelectric elements 41. Here, each piezoelectric element 41 has a function of receiving the supply of a drive signal Vin and applying pressure to the ink, and a function of receiving the pressure from the ink and outputting an output signal Vout.

[0035] The drive circuit 45 drives the piezoelectric elements 41 under the control implemented by the control module 21. In the present embodiment, the drive circuit 45 also serves as a switching circuit. Specifically, the drive circuit 45 switches, under the control implemented by the control module 21, for each of the plurality of piezoelectric elements 41 included in the liquid ejection head 24, whether to supply the drive signal Com output from the control module 21 as the supply drive signal Vin. Further, in the present embodiment, the drive circuit 45 switches, under the control implemented by the control module 21, for each of the plurality of piezoelectric elements 41 included in the liquid ejection head 24, whether to supply the electromotive force in the piezoelectric element 41 to the detection circuit 46 as the output signal Vout.

[0036] The detection circuit 46 detects a parameter related to the physical properties of the ink flowing in the flow path provided in the liquid ejection head 24. The physical properties of the ink in the present embodiment may be any value as long as the ejection state of the ink described later can be judged, and preferably the viscosity of the ink from the viewpoint of the high correlation with the ejection state of the ink. Moreover, in the case of using a piezoelectric element as in the present embodiment, it is preferable to detect the residual vibration described later as a parameter related to the physical properties of the ink. The detection circuit 46 of the present embodiment generates a residual vibration signal NVT based on the output signal Vout generated by each piezoelectric element 41. For example, the detection circuit 46 generates a residual vibration signal NVT by amplifying the output signal Vout after noise removal. As will be described in detail later, the residual vibration signal NVT represents the vibration remaining in the ink flow path in the liquid ejection head 24 after the drive of the piezoelectric element 41, that is, the residual vibration.

[0037] In addition, although in Figure 2In the example shown, the number of liquid ejection heads 24 in the liquid ejection head module 20 is one, but it is not limited thereto, and the number of liquid ejection heads 24 in the liquid ejection head module 20 may also be two or more. Hereinafter, when the number of piezoelectric elements 41 in the liquid ejection head 24 is set to M, in order to distinguish each of the M piezoelectric elements 41, the suffix [m] is sometimes used and the piezoelectric element 41 is described as the piezoelectric element 41[m]. Here, M is a natural number of 1 or more, and m is a natural number of 1 or more and M or less. In addition, regarding the M other structural elements or signals corresponding to the piezoelectric element 41 in the liquid ejection device 100, the suffix [m] is sometimes also used to indicate the correspondence with the piezoelectric element 41[m].

[0038] As Figure 2 shown, the control module 21 includes a control circuit 51, a storage circuit 52, a power supply circuit 53, a drive signal generation circuit 54, and a determination circuit 55.

[0039] The control circuit 51 has a function of controlling the operations of each part of the liquid ejection device 100 and a function of processing various data. Here, the control circuit 51 is an example of a control unit, and controls the operations of the above-described drive circuit 45 and detection circuit 46. The control circuit 51 includes, for example, one or more processors such as a CPU (Central Processing Unit). In addition, the control circuit 51 may replace the CPU, or may include programmable logic devices such as an FPGA (field-programmable gate array) in addition to the CPU. Furthermore, when the control circuit 51 is composed of a plurality of processors, the operations of the drive circuit 45 and the detection circuit 46 may be controlled by, for example, separately independent processors. That is, both the case where the operations of the drive circuit 45 and the detection circuit 46 are performed by the same processor and the case where the operations of the drive circuit 45 and the detection circuit 46 are performed by separately independent processors are included in the description that the control unit controls the operations of the drive circuit 45 and the detection circuit 46. In addition, when the control circuit 51 is composed of a plurality of processors, the plurality of processors may be mounted on different substrates or the like from each other.

[0040] The storage circuit 52 stores various programs executed by the control circuit 51 and various data such as the printed data Img processed by the control circuit 51. The storage circuit 52 includes, for example, a volatile memory such as a RAM (Random Access Memory) and one or both of non-volatile memories such as a ROM (Read Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), or a PROM (Programmable ROM). The printed data Img is supplied from an external device 200 such as a personal computer or a digital camera. In addition, the storage circuit 52 may be configured as part of the control circuit 51.

[0041] The power supply circuit 53 receives power supply from a commercial power supply (not shown) and generates various predetermined potentials. The generated various potentials are appropriately supplied to each part of the liquid ejecting device 100. For example, the power supply circuit 53 generates a power supply potential VHV and a bias potential VBS. The bias potential VBS is supplied to the liquid ejection head module 20. In addition, the power supply potential VHV is supplied to the drive signal generation circuit 54.

[0042] The drive signal generation circuit 54 is a circuit that generates a drive signal Com for driving each piezoelectric element 41. Specifically, the drive signal generation circuit 54 includes, for example, a DA conversion circuit and an amplification circuit. In the drive signal generation circuit 54, the waveform designation signal dCom from the control circuit 51 is converted from a digital signal to an analog signal by the DA conversion circuit, and the amplification circuit amplifies the analog signal using the power supply potential VHV from the power supply circuit 53 to generate the drive signal Com. Here, the signal of the waveform actually supplied to the piezoelectric element 41 in the waveform included in the drive signal Com is the above-described supply drive signal Vin. The waveform designation signal dCom is a digital signal for specifying the waveform of the drive signal Com.

[0043] The determination circuit 55 determines the ejection state of the ink in the nozzle N (to be described later) based on the residual vibration signal NVT and generates determination information Stt indicating the determination result. The determination information Stt is used, for example, for ejection control of ink ejected from the nozzle during printing. The determination circuit 55 is an example of a determination unit. In addition, the determination circuit 55 may be configured as part of the control circuit 51.

[0044] In the above control module 21, the control circuit 51 controls the operations of the respective parts of the liquid ejection device 100 by executing the program stored in the storage circuit 52. Here, by executing this program, the control circuit 51 generates control signals Sk1 and Sk2, control signal SI, and waveform designation signal dCom as signals for controlling the operations of the respective parts of the liquid ejection device 100.

[0045] The control signal Sk1 is a signal for controlling the drive of the conveyance mechanism 22. The control signal Sk2 is a signal for controlling the drive of the moving mechanism 23. The control signal SI is a digital signal for designating the operating state of the piezoelectric element 41. Additionally, the control signal SI may also include a timing signal for regulating the drive timing of the piezoelectric element 41. This timing signal is generated, for example, based on the output of an encoder that detects the position of the above-described conveyance body 231.

[0046] A3: Flow path of the liquid ejection head

[0047] Figure 3 It is a schematic diagram of the flow path in the liquid ejection head 24 according to the first embodiment. As Figure 3 shown, in the liquid ejection head 24, a plurality of nozzles N, a plurality of independent flow paths P, a first common liquid chamber R1, and a second common liquid chamber R2 are provided, and a circulation mechanism 26 is connected.

[0048] Specifically described, the liquid ejection head 24 has a surface facing the medium 11, and as Figure 3 shown, a plurality of nozzles N are provided on this surface. The plurality of nozzles N are arranged along the Y axis. The plurality of nozzles N each eject ink in the Z2 direction.

[0049] Here, the collection of the plurality of nozzles N constitutes a nozzle row L. In addition, the pitches θ of the plurality of nozzles N are arranged at equal intervals. The pitch θ is the distance between the centers of the plurality of nozzles N in the direction along the Y axis.

[0050] Independent flow paths P communicate with the plurality of nozzles N respectively. The plurality of independent flow paths P each extend along the X axis and communicate with different nozzles N. The collection of the plurality of independent flow paths P constitutes an independent flow path row 25. In addition, the plurality of independent flow paths P are arranged along the Y axis.

[0051] As Figure 3As shown, each independent flow path P has a pressure chamber Ca, a pressure chamber Cb, and a nozzle flow path Nf. Here, the pressure chamber Ca is an example of a first pressure chamber. The pressure chamber Cb is an example of a second pressure chamber. The pressure chamber Ca and the pressure chamber Cb in each independent flow path P are spaces that extend along the X-axis and store the ink to be ejected from the nozzle N communicating with the independent flow path P. Therefore, the direction along the X-axis is also referred to as the extending direction of the pressure chamber Ca or the extending direction of the pressure chamber Cb. In Figure 3 the example shown, a plurality of pressure chambers Ca are arranged along the Y-axis. Similarly, a plurality of pressure chambers Cb are arranged along the Y-axis. Therefore, the direction along the Y-axis is also referred to as the arranging direction of the pressure chamber Ca or the arranging direction of the pressure chamber Cb. In addition, although in each independent flow path P, the positions of the pressure chamber Ca and the pressure chamber Cb in the direction along the Y-axis are Figure 3 the same as each other in the example shown, they may also be different from each other. In addition, hereinafter, when the pressure chamber Ca and the pressure chamber Cb are not particularly distinguished, they are simply referred to as "pressure chamber C".

[0052] A nozzle flow path Nf is disposed between the pressure chamber Ca and the pressure chamber Cb in each independent flow path P. In each independent flow path P, the nozzle flow path Nf extends along the X-axis and connects the pressure chamber Ca and the pressure chamber Cb. In addition, a plurality of nozzle flow paths Nf are arranged along the Y-axis at intervals from each other. A nozzle N is provided on each nozzle flow path Nf. In each nozzle flow path Nf, the ink is ejected from the nozzle N by the change in pressure in the pressure chamber Ca and the pressure chamber Cb described above.

[0053] A first common liquid chamber R1 and a second common liquid chamber R2 are connected to the plurality of independent flow paths P. The first common liquid chamber R1 and the second common liquid chamber R2 are spaces that straddle the entire range where the plurality of nozzles N are distributed and extend along the Y-axis. When observing in the direction along the Z-axis, the above-described independent flow path row 25 and the plurality of nozzles N are located between the first common liquid chamber R1 and the second common liquid chamber R2. In addition, hereinafter, observing in the direction along the Z-axis is also referred to as "planar observation".

[0054] Here, the first common liquid chamber R1 is connected to the end portion E1 in the X2 direction of each independent flow path P. Ink for supplying to each independent flow path P is stored in the first common liquid chamber R1. On the other hand, the second common liquid chamber R2 is connected to the end portion E2 in the X1 direction of each independent flow path P. Ink that has not been supplied for ejection and has been discharged from each independent flow path P is stored in the second common liquid chamber R2.

[0055] A circulation mechanism 26 is connected to the first common liquid chamber R1 and the second common liquid chamber R2. The circulation mechanism 26 is a mechanism that supplies ink to the first common liquid chamber R1 and recovers the ink discharged from the second common liquid chamber R2 for re-supplying it to the first common liquid chamber R1. The circulation mechanism 26 includes a first supply pump 261, a second supply pump 262, a storage container 263, a recovery flow path 264, and a supply flow path 265.

[0056] The first supply pump 261 is a pump that supplies the ink stored in the liquid container 12 to the storage container 263. The storage container 263 is a sub-tank that temporarily stores the ink supplied from the liquid container 12. The recovery flow path 264 connects the second common liquid chamber R2 and the storage container 263, and is a flow path for recovering the ink from the second common liquid chamber R2 into the storage container 263. In the storage container 263, in addition to the ink supplied from the first supply pump 261 and stored in the liquid container 12, the ink discharged from each independent flow path P into the second common liquid chamber R2 is also supplied via the recovery flow path 264. The second supply pump 262 is a pump that sends out the ink stored in the storage container 263. The supply flow path 265 connects the first common liquid chamber R1 and the storage container 263, and is a flow path for supplying the ink from the storage container 263 to the first common liquid chamber R1.

[0057] A4: Specific structure of the liquid ejection head

[0058] Figure 4 is Figure 3 a cross-sectional view taken along line A-A in Figure 4 which shows a cross-section of the liquid ejection head 24 cut by a plane parallel to the X-axis and the Z-axis along the independent flow path P. As Figure 4 shown, the liquid ejection head 24 includes a flow path structure body 30, a plurality of piezoelectric elements 41, a frame portion 42, a protection substrate 43, and a wiring substrate 44.

[0059] In the flow path structure body 30, the above-mentioned first common liquid chamber R1, second common liquid chamber R2, a plurality of independent flow paths P, and a plurality of nozzles N are provided. Specifically, the flow path structure body 30 is a structure in which a nozzle substrate 31, a communication plate 33, a pressure chamber substrate 34, and a vibration plate 35 are laminated in this order toward the Z1 direction. Each of the nozzle substrate 31, the communication plate 33, the pressure chamber substrate 34, and the vibration plate 35 extends along the Y-axis, and is manufactured, for example, by processing a single crystal substrate of silicon using semiconductor processing technology. In addition, these components are joined to each other by an adhesive or the like. In addition, other layers or substrates such as a bonding layer may be appropriately interposed between two adjacent components among the plurality of components constituting the flow path structure body 30.

[0060] A plurality of nozzles N are provided on the nozzle substrate 31. The plurality of nozzles N are through-holes that penetrate the nozzle substrate 31 and allow ink to pass through.

[0061] On the communication plate 33, a part of each of the first common liquid chamber R1 and the second common liquid chamber R2 and a part of the plurality of independent flow paths P that excludes the pressure chambers Ca and Cb are provided. Here, each independent flow path P has a supply flow path Ra1 and a discharge flow path Ra2 in addition to the above-mentioned pressure chambers Ca, Cb, and nozzle flow path Nf. Among the elements constituting such an independent flow path P, the nozzle flow path Nf, the supply flow path Ra1, and the discharge flow path Ra2 are provided on the communication plate 33.

[0062] A part of each of the first common liquid chamber R1 and the second common liquid chamber R2 is a space that penetrates the communication plate 33. On the surface of the communication plate 33 facing the Z2 direction, vibration absorbers 361 and 362 that block the openings of this space are provided.

[0063] The vibration absorbers 361 and 362 are each a layered member made of an elastic material. The vibration absorber 361 forms a part of the wall surface of the first common liquid chamber R1 and absorbs pressure fluctuations in the first common liquid chamber R1. Similarly, the vibration absorber 362 forms a part of the wall surface of the second common liquid chamber R2 and absorbs pressure fluctuations in the second common liquid chamber R2.

[0064] As described above, the nozzle flow path Nf is a space that connects the pressure chamber Ca and the pressure chamber Cb. In Figure 4 the example shown, the nozzle flow path Nf has a cross-flow path Nf1, a first longitudinal flow path Na1, and a second longitudinal flow path Na2.

[0065] The cross-flow path Nf1 is a space in a groove provided on the surface of the communication plate 33 facing the Z2 direction. Here, the nozzle substrate 31 forms a part of the wall surface of the cross-flow path Nf1.

[0066] The first longitudinal flow path Na1 and the second longitudinal flow path Na2 are each a space that extends along the Z axis and penetrates the communication plate 33. The first longitudinal flow path Na1 connects the pressure chamber Ca and the cross-flow path Nf1 and guides the ink from the pressure chamber Ca to the cross-flow path Nf1. On the other hand, the second longitudinal flow path Na2 connects the pressure chamber Cb and the cross-flow path Nf1 and guides the ink from the cross-flow path Nf1 to the pressure chamber Cb. In addition, the first longitudinal flow path Na1 and the second longitudinal flow path Na2 can be designed as needed and can also be omitted. In this case, the cross-flow path Nf1 forms the nozzle flow path Nf that connects the pressure chamber Ca and the pressure chamber Cb.

[0067] The supply flow path Ra1 and the discharge flow path Ra2 are spaces that extend along the Z-axis and penetrate the connection board 33. The supply flow path Ra1 connects the first common liquid chamber R1 to the pressure chamber Ca and supplies the ink from the first common liquid chamber R1 to the pressure chamber Ca. Here, one end of the supply flow path Ra1 opens on the surface of the connection board 33 facing the Z1 direction. In contrast, the other end of the supply flow path Ra1 is the upstream end E1 of the independent flow path P and opens on the wall surface of the first common liquid chamber R1 in the connection board 33. On the other hand, the discharge flow path Ra2 connects the second common liquid chamber R2 to the pressure chamber Cb and discharges the ink from the pressure chamber Cb to the second common liquid chamber R2. Here, one end of the discharge flow path Ra2 opens on the surface of the connection board 33 facing the Z1 direction. In contrast, the other end of the discharge flow path Ra2 is the downstream end E2 of the independent flow path P and opens on the wall surface of the second common liquid chamber R2 in the connection board 33.

[0068] On the pressure chamber substrate 34, there are provided the pressure chamber Ca and the pressure chamber Cb of a plurality of independent flow paths P. The pressure chamber Ca and the pressure chamber Cb are respectively gaps that penetrate the pressure chamber substrate 34 and are between the connection board 33 and the vibration plate 35.

[0069] The vibration plate 35 is a plate-like member that can vibrate elastically. The vibration plate 35 is, for example, a laminate including a first layer made of silicon oxide (SiO2) and a second layer made of zirconium oxide (ZrO2). Here, other layers such as metal oxides may be interposed between the first layer and the second layer. In addition, a part or all of the vibration plate 35 may also be integrally formed of the same material as the pressure chamber substrate 34. For example, by selectively removing a part in the thickness direction of a region corresponding to the pressure chamber C in a plate-like member of a predetermined thickness, the vibration plate 35 and the pressure chamber substrate 34 can be integrally formed. In addition, the vibration plate 35 may also be composed of a single material layer.

[0070] On the surface of the vibrating plate 35 facing the Z1 direction, a plurality of piezoelectric elements 41 corresponding to different pressure chambers C are provided. Here, the piezoelectric element 41 corresponding to each pressure chamber Ca is an example of a first energy generating element. The piezoelectric element 41 corresponding to each pressure chamber Cb is an example of a second energy generating element. The piezoelectric elements 41 corresponding to each pressure chamber C overlap the pressure chamber C in a plan view. Each piezoelectric element 41 is constituted, for example, by laminating a first electrode and a second electrode facing each other and a piezoelectric body layer disposed between the two electrodes. Each piezoelectric element 41 ejects the ink in the pressure chamber C from the nozzle N by changing the pressure of the ink in the pressure chamber C. The piezoelectric element 41 vibrates the vibrating plate 35 along with its own deformation by being supplied with a drive signal Com. As the pressure chamber expands and contracts along with this vibration, the pressure of the ink in the pressure chamber C changes.

[0071] The housing portion 42 is a housing for storing ink. In the housing portion 42, spaces are provided that are formed in the remaining portions other than a part of the communication plate 33 for the first common liquid chamber R1 and the second common liquid chamber R2, respectively. In addition, a supply port 421 and a discharge port 422 are provided on the housing portion 42. The supply port 421 is a pipe communicating with the first common liquid chamber R1 and is connected to the supply flow path 265 of the circulation mechanism 26. Therefore, the ink sent from the second supply pump 262 to the supply flow path 265 is supplied to the first common liquid chamber R1 via the supply port 421. On the other hand, the discharge port 422 is a pipe communicating with the second common liquid chamber R2 and is connected to the recovery flow path 264 of the circulation mechanism 26. Therefore, the ink in the second common liquid chamber R2 is discharged to the recovery flow path 264 via the discharge port 422.

[0072] The protective substrate 43 is a plate-like member provided on the surface of the vibrating plate 35 facing the Z1 direction, which protects the plurality of piezoelectric elements 41 and enhances the mechanical strength of the vibrating plate 35. Here, a space for accommodating the plurality of piezoelectric elements 41 is formed between the protective substrate 43 and the vibrating plate 35.

[0073] The wiring substrate 44 is a mounting member that is mounted on the surface of the vibrating plate 35 facing the Z1 direction and is used to electrically connect the control module 21 and the liquid ejection head 24. For example, it is preferable to use a flexible wiring substrate 44 such as an FPC (Flexible Printed Circuit) or an FFC (Flexible Flat Cable). The above-mentioned drive circuit 45 is mounted on the wiring substrate 44. In addition, the above-mentioned detection circuit 46 may also be mounted on the wiring substrate 44 in addition to the drive circuit 45.

[0074] Here, when viewed in the Z2 direction which is the ejection direction of the ink ejected from the nozzle N, the drive circuit 45 is located between the piezoelectric element 41 corresponding to the pressure chamber Ca and the piezoelectric element 41 corresponding to the pressure chamber Cb. In other words, the drive circuit 45 is located between the piezoelectric element 41 corresponding to the pressure chamber Ca and the piezoelectric element 41 corresponding to the pressure chamber Cb in the direction along the X axis. Therefore, compared with the structure where the drive circuit 45 is in other positions, the supply path for supplying the drive signal Com to both of these piezoelectric elements 41 from the drive circuit 45 can be shortened.

[0075] In the liquid ejection head 24 having the above structure, due to the operation of the above-described circulation mechanism 26, the ink circulates in the first common liquid chamber R1, the supply flow path Ra1, the pressure chamber Ca, the nozzle flow path Nf, the pressure chamber Cb, the discharge flow path Ra2, and the second common liquid chamber R2 in this order.

[0076] In addition, by simultaneously driving the piezoelectric element 41 corresponding to both the pressure chamber Ca and the pressure chamber Cb using the drive signal Com from the drive circuit 45, the pressures in the pressure chamber Ca and the pressure chamber Cb are changed, and the ink is ejected from the nozzle N along with this pressure change. In Figure 4 the path and direction of the ink flow in the case where the piezoelectric element 41 corresponding to both the pressure chamber Ca and the pressure chamber Cb is simultaneously driven are indicated by dashed lines and arrow marks. In addition, the operation period or operation timing of the circulation mechanism 26 is arbitrary, and whether it repeats with the period or timing of ejecting the ink from the nozzle N is also arbitrary.

[0077] As described above, the liquid ejection head unit 10 has a supply flow path Ra1 and a discharge flow path Ra2. As described above, the supply flow path Ra1 communicates with the pressure chamber Ca and supplies ink to the pressure chamber Ca. The discharge flow path Ra2 communicates with the pressure chamber Cb and discharges ink from the pressure chamber Cb. Through such a supply flow path Ra1 and a discharge flow path Ra2, the retention of ink in the flow path between the supply flow path Ra1 and the discharge flow path Ra2 can be reduced. Therefore, the thickening of the ink or the precipitation of components near the nozzle N can be reduced. As a result, the deterioration of ejection characteristics such as the ejection amount or ejection speed of the ink in the liquid ejection head 24 can be prevented.

[0078] Here, as described above, the supply of the ink from the supply flow path Ra1 to the pressure chamber Ca and the discharge of the ink from the pressure chamber Cb to the discharge flow path Ra2 are performed by the operation of the circulation mechanism 26. In addition, the connection mode of the circulation mechanism 26 to the liquid ejection head 24 may be reversed in the supply side and the discharge side with respect to the above connection mode. In this case, the supply flow path Ra1 functions as a discharge flow path for discharging the ink from the pressure chamber Ca, and the discharge flow path Ra2 functions as a supply flow path for supplying the ink to the pressure chamber Cb.

[0079] A5: Details of the drive circuit

[0080] Figure 5 FIG. shows a structural example of the drive circuit 45 in the first embodiment. As Figure 5 shown, a wiring LHd, a wiring LHa, and a wiring LHs are connected to the drive circuit 45. The wiring LHd is a feeder line to which a bias potential VBS is supplied. The wiring LHa is a signal line for transmitting the drive signal Com. The wiring LHs is a signal line for transmitting the output signal Vout.

[0081] The drive circuit 45 includes M switches SWa (SWa[1] to SWa[M]), M switches SWs (SWs[1] to SWs[M]), and a connection state specifying circuit 451 that specifies the connection states of these switches.

[0082] The switch SWa[m] is a switch that switches between conduction (ON, closed) and non-conduction (OFF, open) between the wiring LHa for transmitting the drive signal Com and the piezoelectric element 41[m]. The switch SWs[m] is a switch that switches between conduction (ON, closed) and non-conduction (OFF, open) between the wiring LHs for transmitting the output signal Vout and the piezoelectric element 41[m]. These switches are, for example, transmission gates. Here, the piezoelectric element 41[1] is the piezoelectric element 41 corresponding to the above-described pressure chamber Ca. In addition, the piezoelectric element 41[2] is the piezoelectric element 41 corresponding to the above-described pressure chamber Cb. Further, in Figure 5 one of the first electrode and the second electrode of the above-described piezoelectric element 41 is shown as an electrode Zd[m], and the other is shown as an electrode Zu[M].

[0083] Based on the control signal SI, the connection state specifying circuit 451 generates connection state specifying signals SLa[1] to SLa[M] that specify the ON or OFF of the switches SWa[1] to SWa[M], and connection state specifying signals SLs[1] to SLs[M] that specify the ON or OFF of the switches SWs[1] to SWs[M].

[0084] The connection state specifying signal SLa[m] generated in the above-described manner switches the on / off state of the switch SWa[m]. For example, the switch SWa[m] is in the on state when the connection state specifying signal SLa[m] is at a high level, and is in the off state when it is at a low level. As described above, the drive circuit 45 supplies a part or all of the waveform included in the drive signal Com to one or more of the piezoelectric elements 41 selected from the plurality of piezoelectric elements 41 as the supply drive signal Vin.

[0085] In addition, the on / off state of the switch SWs[m] is switched according to the connection state specifying signal SLs[m]. For example, the switch SWs[m] is in the on state when the connection state specifying signal SLs[m] is at a high level, and is in the off state when it is at a low level. As described above, the drive circuit 45 supplies the output signal Vout from one or more of the piezoelectric elements 41 selected from the plurality of piezoelectric elements 41 to the detection circuit 46.

[0086] A6: Ejection operation in the liquid ejection device

[0087] Figure 6 This is a diagram for explaining the ejection operation in the first embodiment. As Figure 6 shown, the drive signal Com includes drive pulses PD and repeats with a unit period Tu. The unit period Tu is divided into a preceding period Tu1 and a subsequent period Tu2. In Figure 6 the example shown, the lengths of the period Tu1 and the period Tu2 are equal to each other. In the present embodiment, the period Tu1 and the period Tu2 are each used as a control period for switching the switches SWa[1], SWa[2], SWs[1], and SWs[2].

[0088] In addition, the switching of the switches SWa[1], SWa[2], SWs[1], and SWs[2] can also be performed within a control period shorter than the period Tu1 or the period Tu2. Furthermore, the lengths of the period Tu1 and the period Tu2 may be different from each other.

[0089] The drive pulse PD is a pulse of a waveform included within the period Tu1 and spanning the period from the first timing t1 to the second timing t2. In Figure 6 the example shown, the potential of the drive pulse PD takes the bias potential VBS as the reference potential, and after dropping to a potential lower than this reference potential, it rises to a potential higher than this reference potential. Such a waveform of the drive pulse PD is more suitable for the ejection of ink from the nozzle N compared to the case where the drive pulse PD is composed only of a potential higher than the reference potential. Also, although inFigure 6 In the example shown, the potential of the drive signal Com during the period Tu2 is the reference potential, but it is not limited thereto, and pulses for ejection or inspection may be appropriately included during the period Tu2.

[0090] The control circuit 51 performs an ejection operation of ejecting ink from the nozzle N during printing or the like. In this ejection operation, the drive circuit 45 drives both the piezoelectric element 41[1] and the piezoelectric element 41[2], so that ink is ejected from the nozzle N.

[0091] During Figure 6 In the example shown, during the period Tu1, the switches SWa[1] and SWa[2] are respectively set to ON, and the switches SWs[1] and SWs[2] are respectively set to OFF. Further, during the period Tu2, the switches SWa[1], SWa[2], SWs[1], and SWs[2] are respectively set to OFF.

[0092] By switching the switches in this way, drive pulses PD are applied to both the piezoelectric element 41[1] and the piezoelectric element 41[2] during the period Tu1. Additionally, in Figure 6 In the example shown, since no pulses are included in the drive signal Com during the period Tu2, the switches SWa[1] and SWa[2] may also be respectively set to ON.

[0093] A7: Detection operation in the liquid ejection device

[0094] The control circuit 51 performs a detection operation of detecting physical property changes of the ink flowing through the flow path provided in the liquid ejection head 24 by the detection circuit 46. As this detection operation, the control circuit 51 of the present embodiment can perform the following first detection operation, second detection operation, and third detection operation. Additionally, the selection or execution timing of these detection operations is appropriately determined according to a preset program or an operation from the user or the like.

[0095] Figure 7 This is a diagram for explaining the first detection operation in the first embodiment. In the first detection operation, the drive circuit 45 drives the piezoelectric element 41[1], and the detection circuit 46 detects a parameter related to the physical properties of the ink in the pressure chamber Cb accompanying the drive of the piezoelectric element 41[1], here the residual vibration.

[0096] During Figure 7In the example shown, during period Tu1, switch SWa[1] and switch SWs[2] are respectively set to ON, and switch SWa[2] and switch SWs[1] are respectively set to OFF. Further, during period Tu2, switch SWs[2] is set to ON, and switch SWa[1], switch SWa[2], and switch SWs[1] are respectively set to OFF.

[0097] By such switching of the switches, a drive pulse PD is applied to the piezoelectric element 41[1] during period Tu1, and for the detection circuit 46, an output signal Vout from the piezoelectric element 41[2] is input across period Tu1 and period Tu2.

[0098] A third timing t3 which is the start timing of the detection in the first detection operation is earlier than a second timing t2 which is the end timing of the drive pulse PD. Figure 7 In the example shown, the third timing t3 is earlier than a first timing t1 which is the start timing of the drive pulse PD, and coincides with the start timing of the unit period Tu or period Tu1. Further, the third timing t3 only needs to be earlier than the second timing t2, and is not limited to Figure 7 the example shown, but in order to more appropriately perform the first detection operation, it is preferable that the third timing t3 is earlier than the first timing t1.

[0099] A fourth timing t4 which is the end timing of the detection in the first detection operation is later than the second timing t2 which is the end timing of the drive pulse PD. Figure 7 In the example shown, the fourth timing t4 coincides with the end timing of the unit period Tu or period Tu2. Further, the fourth timing t4 only needs to be later than the second timing t2, and is not limited to Figure 7 the example shown.

[0100] Figure 8 It is a diagram for explaining the relationship between the detection period and the analysis period. As Figure 8 shown, during the detection period from the third timing t3 to the fourth timing t4, an output signal Vout including a residual vibration signal NVT is input to the detection circuit 46.

[0101] The determination circuit 55 determines the ejection state of the ink in the nozzle N based on the residual vibration signal NVT during the analysis period from a fifth timing t5 to a sixth timing t6 within the detection period. Here, the fifth timing t5 is the second timing t2 or a timing immediately following it. The sixth timing t6 is a timing earlier than the fourth timing t4. Further, the fifth timing t5 and the sixth timing t6 are not limited to Figure 8 the example shown, and can be arbitrary timings.

[0102] The residual vibration signal NVT is a signal representing the residual vibration. The residual vibration is a vibration with a natural frequency determined by the flow path resistance of the flow path through which the ink in the liquid ejection head 24 flows, the inertia of the ink in the flow path, the compliance of the vibration plate 35, etc. Here, the residual vibration of the vibration plate 35 is equivalent to the residual vibration of the ink (liquid).

[0103] The determination circuit 55 determines the ejection state of the ink ejected from the nozzle N based on the period or amplitude of the residual vibration signal NVT. For example, when the period of the residual vibration signal NVT becomes equal to or greater than a reference value, the determination circuit 55 determines that air bubbles are mixed into the ink and the ejection state of the nozzle N becomes poor. In addition, when the attenuation rate of the amplitude of the residual vibration signal NVT becomes equal to or greater than a reference value, the determination circuit 55 determines that the degree of ink thickening exceeds the allowable range and the ejection state of the nozzle N becomes poor.

[0104] The first embodiment may be a system that only performs the above-described first detection operation, but may further perform a second detection operation. Figure 9 This is a diagram for explaining the second detection operation. In the second detection operation, the drive circuit 45 drives the piezoelectric element 41[2], and the detection circuit 46 detects parameters related to the physical properties of the ink in the pressure chamber Ca accompanying the drive of the piezoelectric element 41[2].

[0105] In Figure 9 In the example shown, during the period Tu1, the switch SWa[2] and the switch SWs[1] are respectively set to ON, and the switch SWa[1] and the switch SWs[2] are respectively set to OFF. In addition, during the period Tu2, the switch SWs[1] is set to ON, and the switch SWa[1], the switch SWa[2], and the switch SWs[2] are respectively set to OFF.

[0106] By switching the switches in this way, a drive pulse PD is applied to the piezoelectric element 41[2] during the period Tu1, and for the detection circuit 46, the output signal Vout from the piezoelectric element 41[1] is input over the periods Tu1 and Tu2.

[0107] The start timing of the detection in the second detection operation is the same as the start timing of the first detection operation, both being the third timing t3. The end timing of the detection in the second detection operation is the same as the end timing of the first detection operation, both being the fourth timing t4. Additionally, the start timing of the detection in the second detection operation may be different from the start timing of the detection in the first detection operation. Similarly, the end timing of the detection in the second detection operation may be different from the end timing of the detection in the first detection operation.

[0108] The second detection operation described above is performed during a period different from the first detection operation described above, that is, before or after the first detection operation. Then, the determination circuit 55 uses the detection results obtained from these detection operations to determine the ejection state of the ink ejected from the nozzle N. For example, the determination circuit 55 calculates the difference between the detection results obtained from these detection operations, and determines that there is an abnormality such as poor ejection when the difference is equal to or greater than a predetermined value. That is, the determination circuit 55 uses one of the detection results obtained from these detection operations as a reference for the other, and determines the presence or absence of an abnormality such as poor ejection. Here, the determination circuit 55 appropriately stores the detection results obtained from these detection operations in the storage circuit 52, or reads these detection results from the storage circuit 52.

[0109] The first embodiment may be a system that only performs the first detection operation described above, but may further perform a third detection operation. Figure 10 FIG. is used to illustrate the third detection operation in the first embodiment. In the third detection operation, the drive circuit 45 drives the piezoelectric elements 41[1] and 41[2], and the detection circuit 46 detects the physical property changes of the ink in the pressure chambers Ca and Cb caused by the driving of the piezoelectric elements 41[1] and 41[2].

[0110] In Figure 10 In the example shown, during the period Tu1, the switches SWa[2] and SWs[1] are respectively set to ON, and the switches SWa[1] and SWs[2] are respectively set to OFF. In addition, during the period Tu2, the switches SWs[1] and SWs[2] are respectively set to ON, and the switches SWa[1] and SWa[2] are respectively set to OFF.

[0111] By switching the switches in this way, drive pulses PD are applied to the piezoelectric elements 41[1] and 41[2] during the period Tu1, and output signals Vout from the piezoelectric elements 41[1] and 41[2] are input to the detection circuit 46 during the period Tu2.

[0112] The start timing of the detection in the third detection operation immediately follows the second timing t2 described above. The end timing of the detection in the third detection operation is the same as the end timing of the first detection operation, which is the fourth timing t4. In addition, the start timing and the end timing of the detection in the third detection operation are not limited to Figure 10 the example shown. For example, the end timing of the detection in the third detection operation may also be earlier than the fourth timing t4.

[0113] As described above, in the above third detection operation, both the piezoelectric element 41[1] and the piezoelectric element 41[2] are driven simultaneously during the period Tu1, and since the same drive pulse PD as that in the above ejection operation is used, ink is ejected from the nozzle N. Therefore, the third detection operation can be used instead of the above ejection operation. Thus, both printing and detection can be performed by the third detection operation. Further, the detection result obtained by the third detection operation can be used in combination with the detection result obtained by the above first detection operation or second detection operation and used for the determination in the determination circuit 55. Here, the determination circuit 55 appropriately stores the detection results obtained by these detection operations in the storage circuit 52 or reads these detection results from the storage circuit 52.

[0114] As described above, the above liquid ejection head unit 10 includes a pressure chamber Ca as an example of a first pressure chamber, a pressure chamber Cb as an example of a second pressure chamber, a piezoelectric element 41[1] as an example of a first energy generating element, a piezoelectric element 41[2] as an example of a second energy generating element, a nozzle flow path Nf, a drive circuit 45, a detection circuit 46, and a control circuit 51 as an example of a control unit.

[0115] The pressure chamber Ca and the pressure chamber Cb apply pressure to ink as an example of a liquid, respectively. The piezoelectric element 41[1] generates energy for applying pressure to the ink in the pressure chamber Ca. The piezoelectric element 41[2] generates energy for applying pressure to the ink in the pressure chamber Cb. The nozzle flow path Nf connects the pressure chamber Ca and the pressure chamber Cb, and a nozzle N for ejecting ink is provided on the nozzle flow path Nf. The drive circuit 45 drives the piezoelectric element 41[1] and the piezoelectric element 41[2] by applying the drive pulse PD. The detection circuit 46 detects a parameter related to the physical properties of the ink in at least one of the pressure chamber Ca and the pressure chamber Cb. The control circuit 51 controls the operations of the drive circuit 45 and the detection circuit 46.

[0116] In particular, the control circuit 51 performs a first detection operation in which the piezoelectric element 41[1] is driven by the drive circuit 45, and a parameter related to the physical properties of the ink in the pressure chamber Cb accompanying the drive of the piezoelectric element 41[1] is detected by the detection circuit 46.

[0117] In the above-described liquid ejection head unit 10, since in the first detection operation, parameters related to the physical properties of the ink in the pressure chamber Cb accompanying the driving of the piezoelectric element 41[1] are detected by the piezoelectric element 41[2], the piezoelectric element 41[1] does not need to be used in this detection. Therefore, there is no need to switch the piezoelectric element 41[2], which is an element for this detection, from the driving state to the detection state, thereby preventing the mixing of noise due to this switching of the detection waveform. As a result, the determination accuracy of the ejection state can be improved compared with the prior art.

[0118] Here, the control circuit 51 performs an ejection operation of ejecting ink from the nozzle N by driving both the piezoelectric element 41[1] and the piezoelectric element 41[2] using the driving circuit 45. In such an ejection operation, the ejection efficiency can be improved compared with an operation of ejecting ink from the nozzle N by driving either the piezoelectric element 41[1] or the piezoelectric element 41[2]. In addition, drive pulses PD that do not eject ink from the nozzle N during the driving of either the piezoelectric element 41[1] or the piezoelectric element 41[2] can be used in the ejection operation. Therefore, the same drive pulses PD can be used in the first detection operation and the ejection operation.

[0119] In the present embodiment, the drive pulse PD applied to the piezoelectric element 41[1] in the first detection operation has the same waveform as the drive pulse PD applied to the piezoelectric element 41[1] in the ejection operation. Therefore, compared with a configuration in which different drive pulses are used in the first detection operation and the ejection operation, the structure of the liquid ejection head unit 10 can be simplified. Here, by appropriately setting the waveform of the drive pulse PD, ink can be ejected from the nozzle N in the first detection operation.

[0120] Preferably, in the first detection operation, ink is not ejected from the nozzle N. In this case, even if the first detection operation is used as a detection-only operation, waste of ink can be reduced.

[0121] As described above, in the first detection operation, the drive circuit 45 applies the drive pulse PD to the piezoelectric element 41[1]. Here, the drive pulse PD has a waveform that spans the period from the first timing t1 to the second timing t2. The first detection operation detects changes in the physical properties of the ink in the pressure chamber Cb by the detection circuit 46 during a period starting from the third timing t3 before the second timing t2. Therefore, changes in the physical properties of the ink in the pressure chamber Cb accompanying the driving of the piezoelectric element 41[1] can be detected from the start of their generation.

[0122] In addition, during the period from the second timing t2 to the fourth timing t4, the first detection operation detects the physical property change of the ink in the pressure chamber Cb by the detection circuit 46. Therefore, it is possible to detect the parameters related to the physical properties of the ink in the pressure chamber Cb associated with the driving of the piezoelectric element 41[1] within the range required for judgment from the start of the generation thereof.

[0123] In the present embodiment, the detection circuit 46 detects the residual vibration generated in the pressure chamber Cb as a parameter related to the physical properties. After the driving of the piezoelectric element 41[1], with the pressure change of the ink in the pressure chamber Ca, a residual vibration is generated as the vibration remaining in the pressure chamber Cb. For example, the amplitude or period of the residual vibration varies depending on the presence or absence of the generation of bubbles or the degree of viscosity increase in the ink in the pressure chamber Cb. Therefore, by detecting the residual vibration, it is possible to judge the ejection state of the nozzle N using the detection result.

[0124] As described above, the liquid ejection head unit 10 further includes a judgment circuit 55 as an example of a judgment unit. The judgment circuit 55 judges the ejection state of the ink ejected from the nozzle N based on the detection result of the parameter related to the physical properties obtained from the first detection operation. Therefore, it is possible to perform ejection control of the ink ejected from the nozzle N or inform the ejection state of the ink ejected from the nozzle N using the judgment result of the judgment circuit 55 to improve the image quality.

[0125] Here, in the present embodiment, as described above, the control circuit 51 not only performs the first detection operation but also performs the second detection operation. The second detection operation is to drive the piezoelectric element 41[2] by the drive circuit 45 and detect the parameters related to the physical properties of the ink in the pressure chamber Ca associated with the driving of the piezoelectric element 41[2] by the detection circuit 46. The judgment circuit 55 judges the ejection state of the ink ejected from the nozzle N based on the detection result obtained from the first detection operation and the detection result obtained from the second detection operation. For example, by using the difference between the detection result obtained from the first detection operation and the detection result obtained from the second detection operation, it is possible to judge an abnormality such as poor ejection when the difference is equal to or greater than a predetermined value. In addition, by using this difference, it is also possible to cancel or reduce useless components such as noise included in these detection results. Therefore, compared with the case of using only the detection result obtained from the first detection operation, the judgment accuracy of the ejection state of the ink ejected from the nozzle N can be improved. In addition, the second detection operation may be performed as needed. Further, the control circuit 51 may be configured not to perform the second detection operation.

[0126] In addition, as described above, the control circuit 51 may also perform a third detection operation in addition to the first and second detection operations. The third detection operation is to drive the piezoelectric element 41[1] through the drive circuit 45 and detect, through the detection circuit 46, parameters related to the physical properties of the ink in the pressure chamber Ca accompanying the driving of the piezoelectric element 41[1]. Therefore, by using in combination the detection results obtained from at least one of the first and second detection operations and the detection result obtained from the third detection operation, the detection accuracy in the detection circuit 46 can be improved.

[0127] Here, the third detection operation preferably further includes the following operation in addition to the above-described operations, that is, driving the piezoelectric element 41[2] through the drive circuit 45 and detecting, through the detection circuit 46, parameters related to the physical properties of the ink in the pressure chamber Cb accompanying the driving of the piezoelectric element 41[2]. In this case, similar to the case of using in combination the detection results obtained from the first and second detection operations, by using the difference between the two detection results obtained from the third detection operation, the determination accuracy in the determination circuit 55 can be improved. In addition, the third detection operation may be performed as needed. Furthermore, the control circuit 51 may be configured not to perform the third detection operation.

[0128] As described above, the drive circuit 45 also functions as a switching circuit. That is, the liquid ejection head unit 10 includes a drive circuit 45, which is an example of a switching circuit capable of switching between a first state and a second state. In the first state, the piezoelectric element 41[2] is electrically connected to the drive circuit 45, and the piezoelectric element 41[2] is not electrically connected to the detection circuit 46. Therefore, when the drive circuit 45 is in the first state, the piezoelectric element 41[2] can be used as a drive element in the ejection operation. In contrast, in the second state, the piezoelectric element 41[2] is not electrically connected to the drive circuit 45, and the piezoelectric element 41[2] is electrically connected to the detection circuit 46. Therefore, when the drive circuit 45 is in the second state, the piezoelectric element 41[2] can be used as a detection element in the first detection operation.

[0129] The above-described liquid ejection device 100 includes a liquid ejection head unit 10 and a conveyance mechanism 22 that conveys a medium 11, which is an example of a printing medium on which an image formed by the ink ejected from the nozzle N is printed. In the above-described liquid ejection device 100, by utilizing the excellent detection characteristics of the liquid ejection head unit 10 as described above, the image quality can be improved and the reliability can be enhanced compared to the prior art.

[0130] B: Second Embodiment

[0131] Hereinafter, a second embodiment of the present invention will be described. For elements having the same functions and operations as those in the first embodiment among the embodiments illustrated below, the symbols used in the description of the first embodiment are used, and their detailed descriptions are appropriately omitted.

[0132] Figure 11 FIG. showing a structural example of the drive circuit 45A in the second embodiment. The liquid ejection head unit 10A of the present embodiment has, instead of the drive circuit 45 of the liquid ejection head unit 10A of the above-described first embodiment, Figure 11 the drive circuit 45A shown.

[0133] As Figure 11 shown, in addition to the wiring LHd, the wiring LHa, and the wiring LHs, a wiring LHb is also connected to the drive circuit 45A. The wiring LHb is a signal line for transmitting the drive signal Com-B. In the present embodiment, the wiring LHa is a signal line for transmitting the drive signal Com-A.

[0134] The drive circuit 45A includes M switches SWa (SWa[1] to SWa[M]), M switches SWb (SWb[1] to SWb[M]), M switches SWs (SWs[1] to SWs[M]), and a connection state specifying circuit 451A that specifies the connection states of these switches.

[0135] The switch SWb[m] is a switch that switches between conduction (ON, closed) and non-conduction (OFF, open) between the wiring LHb and the piezoelectric element 41[m]. Based on the control signal SI, the connection state specifying circuit 451A generates, in addition to the connection state specifying signals SLa[1] to SLa[M] and the connection state specifying signals SLs[1] to SLs[M], connection state specifying signals SLb[1] to SLb[M] that specify the on or off states of the switches SWb[1] to SWb[M].

[0136] The on or off state of the switch SWb[m] is switched according to the connection state specifying signal SLb[m]. As described above, the drive circuit 45A supplies a part or all of the waveform included in the drive signal Com-B to one or more of the piezoelectric elements 41 selected from the plurality of piezoelectric elements 41 as the supply drive signal Vin.

[0137] Figure 12 FIG. for explaining the ejection operation in the second embodiment. As Figure 12 shown, the drive signal Com-A includes drive pulses PD in the same manner as the drive signal Com of the above-described first embodiment, and is repeated at a unit period Tu.

[0138] In the ejection operation, similar to the first embodiment described above, the drive circuit 45A applies drive pulses PD to both the piezoelectric element 41[1] and the piezoelectric element 41[2].

[0139] During Figure 12 In the example shown, during the period Tu1, the switches SWa[1] and SWa[2] are respectively set to ON, and the switches SWb[1], SWb[2], SWs[1], and SWs[2] are respectively set to OFF. Further, during the period Tu2, the switches SWa[1], SWa[2], SWb[1], SWb[2], SWs[1], and SWs[2] are respectively set to OFF.

[0140] Figure 13 FIG. is for explaining the first detection operation in the second embodiment. As Figure 13 shown, the drive signal Com - B includes a drive pulse PD1 and repeats at a unit period Tu. In addition, the unit period Tu is divided into a preceding period Tu1 and a subsequent period Tu2 in the same manner as in the first embodiment.

[0141] The drive pulse PD1 is a pulse having a waveform that is included in the period Tu1 and spans the period from the first timing t1 to the second timing t2. However, the waveform of the drive pulse PD1 is different from that of the drive pulse PD. In Figure 13 the example shown, the potential of the drive pulse PD1 takes the bias potential VBS as the reference potential, does not drop to a potential lower than this reference potential, but rises to a potential higher than this reference potential. Such a waveform of the drive pulse PD1 makes it easier to prevent ink from being ejected from the nozzle N compared to the drive pulse PD. Therefore, in the first detection operation, ink is not ejected from the nozzle N, thereby preventing waste of ink.

[0142] In the first detection operation of the present embodiment, the drive circuit 45 applies the drive pulse PD1 to the piezoelectric element 41[1], and the detection circuit 46 detects parameters related to the physical properties of the ink in the pressure chamber Cb accompanying the drive of the piezoelectric element 41[1].

[0143] During Figure 13 In the example shown, during the period Tu1, the switches SWb[1] and SWs[2] are respectively set to ON, and the switches SWa[1], SWa[2], SWb[2], and SWs[1] are respectively set to OFF. Further, during the period Tu2, the switch SWs[2] is set to ON, and the switches SWa[1], SWa[2], SWb[1], SWb[2], and SWs[1] are respectively set to OFF.

[0144] Through the above second embodiment, the same effects as those of the above first embodiment can also be obtained. In addition, in this embodiment, by using the drive pulse PD1 in the first detection operation, it becomes easier for no ink to be ejected from the nozzle N during the first detection operation.

[0145] C: Third Embodiment

[0146] Hereinafter, the third embodiment of the present invention will be described. For the elements having the same functions and operations as those in the first embodiment in the embodiments illustrated below, the symbols used in the description of the first embodiment are used, and the detailed description of each is appropriately omitted.

[0147] Figure 14 FIG. is a diagram for explaining the first detection operation in the third embodiment. This embodiment is the same as the above second embodiment except that a drive signal Com-B including a drive pulse PD2 is used instead of the drive pulse PD1.

[0148] The drive pulse PD2 is a pulse having a waveform included within the period Tu1 and spanning the period from the first timing t1 to the second timing t2. In Figure 14 the illustrated example, the potential of the drive pulse PD2 takes the bias potential VBS as the reference potential, does not rise to a potential higher than this reference potential, but drops to a potential lower than this reference potential. The drive pulse PD2 having such a waveform, like the drive pulse PD1 of the above second embodiment, makes it easier for ink to be difficult to be ejected from the nozzle N as compared with the drive pulse PD. Therefore, no ink is ejected from the nozzle N during the first detection operation, thereby preventing waste of ink.

[0149] According to the above third embodiment, the same effects as those of the above first embodiment can also be obtained. In addition, in this embodiment, by using the drive pulse PD2 in the first detection operation, it becomes easier for no ink to be ejected from the nozzle N during the first detection operation.

[0150] D: Modification Example

[0151] The various embodiments illustrated above can be modified in various ways. Hereinafter, specific modification methods applicable to the above embodiments will be illustrated. The methods arbitrarily selected from the following examples can be appropriately combined within a range where they do not conflict with each other.

[0152] Modification Example 1

[0153] Although in the above-described various methods, a structure in which the ink used in the liquid ejection head is circulated by a circulation mechanism is illustrated, the present invention is not limited to this structure, and may be a structure that does not have such a circulation mechanism.

[0154] Modification Example 2

[0155] Each of the first energy generating element and the second energy generating element that changes the pressure of the ink in the pressure chamber C is not limited to the piezoelectric element 41 illustrated in the above-described various methods. For example, a heating element that changes the pressure of the ink by generating bubbles inside the pressure chamber C by heating may be used as the first energy generating element or the second energy generating element.

[0156] When the heating element is used as the first energy generating element and the second energy generating element, the detection circuit 46 preferably detects the temperature as a parameter related to the physical properties of the ink. The viscosity of the ink changes according to the temperature change. Therefore, by driving the first energy generating element and detecting the temperature in the second pressure chamber at that time by the second energy generating element, it is possible to estimate the viscosity, which is a physical property of the ink, based on the temperature change. Specifically, in a structure in which a heating element is used as the first energy generating element, with the driving of the first energy generating element, the temperature of the liquid in the first pressure chamber rises, and the temperature of the liquid in the second pressure chamber also rises. Further, after the driving of the first energy generating element, the temperature of the liquid in the second pressure chamber drops to return to a stable state. Such a temperature change of the liquid in the second pressure chamber varies depending on the presence or absence of bubble generation or the degree of viscosity increase in the liquid in the second pressure chamber. Therefore, by detecting the temperature in the second pressure chamber, it is possible to use the detection result to determine the presence or absence of bubble generation or the degree of viscosity increase in the liquid in the second pressure chamber.

[0157] Modification Example 3

[0158] Although in the above-described various methods, the serial liquid ejection device 100 in which the carrier 231 carrying the liquid ejection head 24 reciprocates is illustrated, the present invention can also be applied to a line-type liquid ejection device in which a plurality of nozzles N are distributed across the entire width of the medium 11.

[0159] In addition to the equipment dedicated to printing, the liquid ejection device 100 exemplified in the above-described manner can also be used in various devices such as a facsimile device or a copying machine, and the use of the present invention is not particularly limited. However, the use of the liquid ejection device is not limited to printing. For example, a liquid ejection device that ejects a solution of a color material is used as a manufacturing device for a color filter of a display device such as a liquid crystal display panel. In addition, a liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device for wirings and electrodes of a wiring substrate. In addition, a liquid ejection device that ejects a solution of an organism-related organic substance is used, for example, as a manufacturing device for a biochip.

[0160] Reference Signs

[0161] 10... liquid ejection head unit; 10A... liquid ejection head unit; 11... medium (printing medium); 22... conveying mechanism; 41[1]... piezoelectric element (first energy generating element); 41[2]... piezoelectric element (second energy generating element); 45... drive circuit; 45A... drive circuit; 46... detection circuit; 51... control circuit (control unit); 55... determination circuit (determination unit); 100... liquid ejection device; Ca... pressure chamber (first pressure chamber); Cb... pressure chamber (second pressure chamber); N... nozzle; Nf... nozzle flow path; PD... drive pulse; PD1... drive pulse; PD2... drive pulse; Ra1... supply flow path; Ra2... discharge flow path; t1... first timing; t2... second timing; t3... third timing; t4... fourth timing.

Claims

1. A liquid ejection head unit, characterized in that, comprising: a first pressure chamber that applies pressure to a liquid; a second pressure chamber that applies pressure to a liquid; a first energy generating element that generates energy for applying pressure to the liquid in the first pressure chamber; a second energy generating element that generates energy for applying pressure to the liquid in the second pressure chamber; a nozzle flow path that connects the first pressure chamber and the second pressure chamber and is provided with a nozzle for ejecting the liquid; a drive circuit that drives the first energy generating element and the second energy generating element by applying drive pulses; a detection circuit that detects at least a parameter related to the physical properties of the liquid in the second pressure chamber; a control unit that controls the operations of the drive circuit and the detection circuit, the control unit performs a first detection operation as follows, that is, drives the first energy generating element by the drive circuit and detects the parameter in the second pressure chamber by the detection circuit, when the drive pulses having a waveform over a period from a first timing to a second timing are applied to the first energy generating element by the drive circuit, during a period starting from a third timing before the second timing, the parameter in the second pressure chamber is detected by the detection circuit.

2. The liquid ejection head unit according to claim 1, wherein the control unit performs an ejection operation as follows, that is, by driving both the first energy generating element and the second energy generating element using the drive circuit, the liquid is ejected from the nozzle.

3. The liquid ejection head unit according to claim 2, wherein the drive pulses applied to the first energy generating element in the first detection operation and the drive pulses applied to the first energy generating element in the ejection operation have the same waveform.

4. The liquid ejection head unit according to any one of claims 1 to 3, wherein in the first detection operation, no liquid is ejected from the nozzle.

5. The liquid ejection head unit according to claim 1, wherein the third timing is earlier than the first timing.

6. The liquid ejection head unit according to claim 1 or 5, wherein during a period until a fourth timing after the second timing, the parameter in the second pressure chamber is detected by the detection circuit in the first detection operation.

7. The liquid ejection head unit according to claim 1, wherein the detection circuit detects residual vibration generated in the second pressure chamber as the parameter.

8. The liquid ejection head unit according to claim 1, wherein the detection circuit detects the temperature in the second pressure chamber as the parameter.

9. The liquid ejection head unit according to claim 1, wherein the physical property is the viscosity of the liquid.

10. The liquid ejection head unit according to claim 1, wherein It also has a judging section that judges the ejection state of the liquid ejected from the nozzle based on the parameter or the physical property.

11. The liquid ejection head unit according to claim 10, wherein the control section performs the following second detection operation, that is, drives the second energy generating element through the drive circuit, and detects the parameter in the first pressure chamber through the detection circuit, the judging section judges the ejection state of the liquid ejected from the nozzle based on the detection result obtained from the first detection operation and the detection result obtained from the second detection operation.

12. The liquid ejection head unit according to claim 1, wherein It also has: a supply flow path that communicates with the first pressure chamber and supplies liquid to the first pressure chamber; a discharge flow path that communicates with the second pressure chamber and discharges liquid from the second pressure chamber.

13. The liquid ejection head unit according to claim 1, wherein It also has: a supply flow path that communicates with the second pressure chamber and supplies liquid to the second pressure chamber; a discharge flow path that communicates with the first pressure chamber and discharges liquid from the first pressure chamber.

14. The liquid ejection head unit according to claim 1, wherein the control section performs the following third detection operation, that is, drives the first energy generating element through the drive circuit, and detects the parameter in the first pressure chamber accompanying the drive of the first energy generating element through the detection circuit.

15. The liquid ejection head unit according to claim 14, wherein in the third detection operation, the second energy generating element is driven through the drive circuit, and the parameter in the second pressure chamber accompanying the drive of the second energy generating element is detected through the detection circuit.

16. The liquid ejection head unit according to claim 1, wherein it also has a switching circuit that can switch between a first state and a second state. The first state is a state in which the second energy generating element and the drive circuit are electrically connected and the second energy generating element and the detection circuit are not electrically connected. The second state is a state in which the second energy generating element and the drive circuit are not electrically connected and the second energy generating element and the detection circuit are electrically connected.

17. The liquid ejection head unit according to claim 1, wherein the first pressure chamber and the second pressure chamber each extend in an extending direction, and the drive circuit is located between the first energy generating element and the second energy generating element in the extending direction.

18. A liquid ejection device, characterized in that, It has: the liquid ejection head unit according to any one of claims 1 to 17; a conveying mechanism that conveys a printing medium on which an image formed by the liquid from the liquid ejection head unit is printed.

19. A method for judging the ejection state of a liquid ejection device, wherein the liquid ejection device has: a first pressure chamber that applies pressure to the liquid; a second pressure chamber that applies pressure to the liquid; a first energy generating element that generates energy for applying pressure to the liquid in the first pressure chamber; A second energy generating element that generates energy for applying pressure to the liquid in the second pressure chamber; A nozzle flow path that connects the first pressure chamber and the second pressure chamber and is provided with a nozzle for ejecting the liquid, In the method for judging the liquid ejection state of the liquid ejection device, The first energy generating element is driven, and a parameter related to the physical properties of the liquid in the second pressure chamber accompanying the driving of the first energy generating element is detected, Based on the parameter or the physical properties, the ejection state of the liquid ejected from the nozzle is judged, When a drive pulse having a waveform spanning a period from a first timing to a second timing is applied to the first energy generating element, the parameter in the second pressure chamber is detected over a period starting from a third timing before the second timing.

20. A liquid ejection head unit, characterized in that, Comprising: A first pressure chamber that applies pressure to the liquid; A second pressure chamber that applies pressure to the liquid; A first energy generating element that generates energy for applying pressure to the liquid in the first pressure chamber; A second energy generating element that generates energy for applying pressure to the liquid in the second pressure chamber; A nozzle flow path that connects the first pressure chamber and the second pressure chamber and is provided with a nozzle for ejecting the liquid; A drive circuit that drives the first energy generating element and the second energy generating element by applying drive pulses; A detection circuit that detects at least a parameter related to the physical properties of the liquid in the second pressure chamber; A control unit that controls the operations of the drive circuit and the detection circuit; A judgment unit that judges the ejection state of the liquid ejected from the nozzle based on the parameter or the physical properties, The control unit performs the following first detection operation, that is, drives the first energy generating element through the drive circuit and detects the parameter in the second pressure chamber through the detection circuit, The control unit performs the following second detection operation, that is, drives the second energy generating element through the drive circuit and detects the parameter in the first pressure chamber through the detection circuit, The judgment unit judges the ejection state of the liquid ejected from the nozzle based on the detection result obtained from the first detection operation and the detection result obtained from the second detection operation.

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