JP2020124817A - Ink jet recording device - Google Patents

Abstract

To enable the downsizing of an ink jet head.SOLUTION: An ink jet recording device includes a liquid supply path, a liquid discharge path, first and second pressure chambers, first and second actuators, and a control unit. The liquid supply is equipped with a liquid supply port at one end portion in an extending direction. The liquid discharge path is provided side by side with the liquid supply path, and is equipped with a liquid discharge port at the other end portion in the extending direction. The first and second pressure chambers connect the liquid supply path and the liquid discharge path. The second pressure chamber is farther from the liquid supply port than the first pressure chamber. The first and second actuators change the pressure of a liquid in the first and second pressure chambers to discharge the liquid in the first and second pressure chambers through a nozzle. The control unit applies a first driving waveform to the first actuator, and applies a second driving waveform whose liquid discharging force is larger than that of the first driving waveform to the second actuator, thereby discharging the liquid in the first and second pressure chambers from the nozzle.SELECTED DRAWING: Figure 2

Description

Embodiments of the present invention relate to an inkjet recording device.

An inkjet recording device such as an inkjet printer includes an inkjet head that ejects a liquid such as ink. In a liquid circulation type ink jet recording apparatus, the conventional ink jet head is configured so that the pressure of the liquid at the nozzle position is substantially uniform and the flow path resistance from the liquid inlet and the outlet to the actuator is substantially equal. It is arranged.

JP2012-40776A

The inkjet head is desired to be downsized. However, the inkjet head having the above-described structure has a large number of inflow ports and outflow ports, and requires a flow path for distributing and connecting the inflow ports and outflow ports, and thus it is difficult to downsize.

A problem to be solved by the embodiments of the present invention is to provide an inkjet recording apparatus capable of miniaturizing an inkjet head.

The inkjet recording apparatus according to the embodiment includes a liquid supply path, a liquid discharge path, a first pressure chamber, a second pressure chamber, a first actuator, a second actuator, and a controller. The liquid supply path has a liquid supply port at one end in the extending direction. The liquid discharge path is provided side by side with the liquid supply path, and has a liquid discharge port at the other end in the extending direction. The first pressure chamber connects the liquid supply passage and the liquid discharge passage. The second pressure chamber connects the liquid supply path and the liquid discharge path and is farther from the liquid supply port than the first pressure chamber. The first actuator causes the liquid in the first pressure chamber to be ejected from the nozzle by changing the pressure of the liquid in the first pressure chamber. The second actuator causes the liquid in the second pressure chamber to be ejected from the nozzle by changing the pressure of the liquid in the second pressure chamber. The control unit applies the first drive waveform to the first actuator to eject the liquid in the first pressure chamber from the nozzle. The controller applies a second drive waveform, which has a larger force for ejecting the liquid than the first drive waveform, to the second actuator, thereby ejecting the liquid in the second pressure chamber from the nozzle.

FIG. 3 is a schematic diagram showing an example of the configuration of the inkjet recording apparatus according to the first to third embodiments. FIG. 2 is an exploded perspective view showing an example of the inkjet head in FIG. 1. The top view which shows an example of the inkjet head in FIG. 1 from the upper surface side. FIG. 2 is a schematic diagram showing an example of the liquid supply device in FIG. 1. FIG. 2 is a diagram showing liquid flow paths in the inkjet head shown in FIG. 1. FIG. 3 is a block diagram showing an example of a circuit configuration of essential parts of the inkjet recording apparatus according to the first to third embodiments. FIG. 3 is a diagram showing an example of drive waveforms according to the first embodiment. 2 is a flowchart showing an example of processing by the processor in FIG. 1. The figure which shows the example of the drive waveform which concerns on 2nd Embodiment. FIG. 8 is a diagram showing a liquid flow path in an inkjet head according to a modified example of the embodiment.

Hereinafter, inkjet recording apparatuses according to some embodiments will be described with reference to the drawings. In the drawings used for the description of the embodiments below, the scale of each part may be changed as appropriate. Further, the drawings used for the description of the following embodiments may be illustrated with the configuration omitted for the sake of description.
[First Embodiment]
FIG. 1 is a schematic diagram showing an example of the configuration of the inkjet recording apparatus 1 according to the first embodiment.
The inkjet recording apparatus 1 forms an image on the image forming medium S or the like using a liquid recording material such as ink. The inkjet recording apparatus 1 includes, as an example, a plurality of liquid ejection units 2, a head support mechanism 3 that movably supports the liquid ejection units 2, and a medium support mechanism 4 that movably supports the image forming medium S. Prepare The image forming medium S is, for example, sheet-shaped paper.

As shown in FIG. 1, the plurality of liquid ejection units 2 are supported by the head support mechanism 3 in a state of being arranged in parallel in a predetermined direction. The head support mechanism 3 is attached to a belt 3b that is wound around a roller 3a. The inkjet recording apparatus 1 can move the head support mechanism 3 in the main scanning direction A orthogonal to the transport direction of the image forming medium S by rotating the roller 3a. The liquid ejecting section 2 performs an ejecting operation of ejecting a liquid I such as ink from the inkjet head 10. In the first embodiment, the liquid I is ink. The liquid ejection unit 2 includes an inkjet head 10 and a circulation device 20.
As an example, the inkjet recording apparatus 1 performs a liquid ejection operation while reciprocally moving the head support mechanism 3 in the main scanning direction A, thereby forming a desired image on the image forming medium S that is arranged to face the scanning method. Is. Alternatively, the inkjet recording apparatus 1 may be of a single-pass type in which the liquid ejection operation is performed without moving the head support mechanism 3. In this case, it is not necessary to provide the roller 3a and the belt 3b. In this case, the head support mechanism 3 is fixed to, for example, the housing of the inkjet recording device 1.

Each of the plurality of liquid ejection units 2 corresponds to, for example, any one of the four color inks of CMYK (cyan, magenta, yellow, and key(black)). That is, each of the plurality of liquid ejection units 2 corresponds to any one of cyan ink, magenta ink, yellow ink, and black ink. Then, each of the plurality of liquid ejection units 2 ejects the ink of the corresponding color.

The configuration of the inkjet head 10 will be described. FIG. 2 is an exploded perspective view showing an example of the inkjet head 10. The inkjet head 10 includes, for example, a manifold (support member) 11, a liquid supply pipe 12, a liquid discharge pipe 13, a base material 14, a drive unit 15, a frame member 16, and a nozzle plate 17.

The manifold 11 includes, for example, a main body portion 111, two upper step portions 112, a lower step portion 113, four partition walls 114, two brackets 115, two fixing holes 116, a liquid supply port 117, and two liquid discharge ports 118. ..

The main body portion 111 is, for example, a rectangular parallelepiped portion. However, the upper surface of the main body 111 is
A step is formed. As a result, two upper step portions 112 and one lower step portion 113 are formed. Both ends in the longitudinal direction of the upper surface of the main body portion 111 are upper step portions 112. The portion of the upper surface of the main body 111 sandwiched by the upper step 112 is the lower step 113. The boundary between the upper step portion 112 and the lower step portion 113 is a step. As a result, the height of the lower step portion 113 is lower than that of the upper step portion 112. In addition, when it is necessary to distinguish the two upper steps 112, they are referred to as an upper step 112a and an upper step 112b.

Two partition walls 114 are formed on each upper surface of the upper step portion 112. The partition wall 114 is formed at a position in contact with the drive unit 15 in the extending direction of the drive unit 15.

The support 115 is formed on each side surface of the main body 111 in the longitudinal direction. The support 115 is provided to fix the inkjet head 10 to the head support mechanism 3 or the casing of the inkjet recording apparatus 1. Further, the support 115 has a fixing hole 116 through which a screw or the like for fixing the inkjet head 10 is inserted.

The liquid supply port 117 is a supply port for supplying the liquid I into the inkjet head 10. The liquid supply port 117 is formed between the partition 114 and the partition 114 of the upper part 112a. The liquid supply port 117 penetrates to the lower surface of the manifold 11 (main body 11) and communicates with the liquid supply pipe 12 connected to the manifold 11.
The liquid discharge port 118 is a discharge port through which the liquid I is discharged from the inside of the inkjet head 10. The liquid discharge port 118 is formed between the partition wall 114 and the frame member 16 of the upper step portion 112b. The liquid discharge port 118 penetrates to the lower surface of the manifold 11 (main body 11) and communicates with the liquid discharge pipe 13 connected to the manifold 11.

The liquid supply pipe 12 connects the manifold 11 and the circulation device 20. As a result, the liquid I sent from the circulation device 20 is supplied into the inkjet head 10 through the liquid supply pipe 12 and the liquid supply port 117. As a result, the inside of the inkjet head 10 is filled with the liquid I.
The liquid discharge pipe 13 connects the manifold 11 and the circulation device 20. As a result, the liquid I in the inkjet head 10 is sent to the circulation device 20 through the liquid discharge port 118 and the liquid discharge pipe 13.

The base material 14 is a plate-shaped substrate. The base material 14 is bonded to the manifold 11 so as to be in contact with the two steps that are the boundaries between the upper step portion 112 and the lower step portion 113 and the upper surface of the lower step portion 113. That is, the base material 14 is sandwiched between the two upper step portions 112 and adhered while being placed on the lower step portion 113. The thickness of the base material 14 is about the same as the height of the step. As a result, the upper surface of the base material 14 and the upper surfaces of the two upper steps 112 are substantially flush with each other.

The drive unit 15 is formed on the base material 14 so as to extend from the longitudinal end of the base material 14 to the opposite end. Further, two drive units 15 are formed on the base material 14 side by side with an interval.

The frame member 16 is bonded onto the manifold 11 and the base material 14 so as to surround the drive unit 15, the four partition walls 114, the liquid supply port 117, and the two liquid discharge ports. The frame member 16 is provided so that the inside of the frame member 16 contacts the side surfaces of the four partition walls 114. The drive unit 15, the frame member 16, and the four partition walls 114 have approximately the same thickness.

The nozzle plate 17 is bonded onto the drive unit 15, the frame member 16 and the four partitions 114. The nozzle plate 17 is made of polyimide, for example. In the nozzle plate 17, two rows in which the plurality of nozzles 171 are arranged in one row are formed. The rows are formed at positions on the drive unit 15, respectively.
The nozzle 171 is a hole through which the liquid I in the inkjet head 10 is discharged.

The configuration of the inkjet head 10 will be further described. FIG. 3 is a plan view showing an example of the inkjet head 10 from the upper surface side. However, in FIG. 3, the nozzle plate 17 is not shown so that the inside of the inkjet head 10 can be seen.

As shown in FIG. 3, a plurality of wirings 141 are provided on the base material 14. Each of the wirings 141 is formed so as to extend from the side end portion of the upper surface of the base material 14 to the drive unit 15.

In the inkjet head 10, the base member 14, the driving unit 15, the frame member 16 and the four partition walls 114 form three spaces, an inner flow path 142 and two outer flow paths 143. The inner flow path 142 is a space sandwiched by the two drive units 15 and the four partition walls 114. Each of the outer flow paths 143 is a space surrounded by one drive unit 15, two partition walls 114, and the frame member 16.

The drive unit 15 has a structure in which two plate-shaped piezoelectric bodies are bonded together. The two piezoelectric bodies are attached so that the polarization directions thereof are opposite to each other in the thickness direction of the drive unit 15. The material of the piezoelectric body is, for example, lead zirconate titanate (PZT:Pb(Zr,Ti)O ₃ ), lithium niobate (LiNbO ₃ ), or lithium tantalate (LiTaO ₃ ).

The driving unit 15 also includes a plurality of grooves 151, a plurality of electrodes 152, and a plurality of actuators 153.
The groove 151 extends in a direction intersecting the extending direction of the drive unit 15 and is formed from the inner flow path 142 to the outer flow path 143. The plurality of grooves 151 are arranged in the extending direction of the drive unit 15. The upper portion of the groove 151 is covered with the nozzle plate 17. As a result, the pressure chamber 18 surrounded by the groove 151 and the nozzle plate is formed. Further, the nozzle 171 included in the nozzle plate 17 is located above the groove 151. Therefore, the nozzle 171 and the pressure chamber 18 are in communication with each other.

The electrode 152 is formed so as to cover the surface of the groove 151. The electrode 152 is formed by, for example, plating, sputtering, vapor deposition, photolithography, or the like.

The actuator 153 is a part that separates the groove 151 from the groove 151. Therefore, the actuator 153 has a structure in which the piezoelectric body is sandwiched between the electrode 152 and the electrode 152. When the voltage between the electrodes 152 changes, the actuator 153 deforms and the volume of the pressure chamber 18 increases or decreases. As a result, the pressure of the liquid I in the pressure chamber 18 changes, and the liquid I is discharged from the nozzle 171 communicating with the pressure chamber 18. In addition, hereinafter, the actuator 153 may be referred to as an actuator 153-1, an actuator 153-2, an actuator 153-3,... In ascending order of the distance from the liquid supply port 117. Since there are two drive units 15, there are also two actuators 153-1, 153-2, 153-3,...

The circulation device 20 will be described with reference to FIG. FIG. 4 is a schematic diagram showing an example of the circulation device 20. The circulation device 20 is a device that circulates and supplies the liquid I to the inkjet head 10. The circulation device 20 includes, for example, a supply side liquid tank 21, a discharge side liquid tank 22, a supply side pressure adjusting pump 23, a transport pump 24, a discharge side pressure adjusting pump 25, a supply pump 26, and a thermometer 27. These are connected by a tube or the like through which the liquid I can flow.

The supply side liquid tank 21 is connected to the liquid supply pipe 12 via a tube or the like. The supply-side liquid tank 21 supplies the liquid I to the liquid supply pipe 12.
The discharge side liquid tank 22 is connected to the liquid discharge pipe 13 via a tube or the like. The discharge side liquid tank 22 temporarily stores the liquid I discharged from the liquid discharge pipe 13.

The supply-side pressure adjustment pump 23 adjusts the pressure of the supply-side liquid tank 21.
The transport pump 24 recirculates the liquid I stored in the discharge side liquid tank 22 to the supply side liquid tank 21 via the tube. The liquid I circulates in the inkjet head 10 and the circulation device 20 by the action of the transport pump 24 and the like.
The discharge side pressure adjustment pump 25 adjusts the pressure of the discharge side liquid tank 22.
The supply pump 26 sends the liquid I in the ink cartridge 30 to the supply side liquid tank 21 of the circulation device 20. The ink cartridge 30 includes a tank configured to hold the liquid I.
The thermometer 27 measures the temperature of the liquid I circulating in the inkjet head 10 and the circulation device 20. The thermometer 27 is provided in the path in which the liquid I circulates. Further, the thermometer 27 may be provided inside the inkjet head 10.

FIG. 5 is a diagram showing the flow path of the liquid I in the inkjet head 10. The liquid I sent from the circulation device 20 flows out from the liquid supply port 117 to the inner flow path 142 through the liquid supply pipe 12. The liquid I in the inner flow path 142 passes through one of the pressure chambers 18 and flows into the outer flow path 143. The liquid I may be ejected from the nozzle 171 when the liquid ejection operation is performed by the inkjet head 10 while passing through the pressure chamber 18. Therefore, of the liquid I that has flowed into the pressure chamber 18, the liquid I that has not been discharged from the nozzle 171 flows out to the outer flow path 143. The liquid I in the outer flow path 143 flows out from the liquid discharge port 118, passes through the liquid discharge pipe 13, and flows into the circulation device 20.
As described above, the inner flow path 142 is an example of a liquid supply path having a liquid supply port at one end in the extending direction. The outer flow path 143 is an example of a liquid discharge path that is provided alongside the liquid supply path and has a liquid discharge port at the other end in the extending direction.

The liquid I has almost the same flow distance from the liquid supply port 117 to the liquid discharge port 118 regardless of which pressure chamber 18 is passed. Therefore, the flow rate of the liquid I flowing in the pressure chambers 18 is almost the same in all the pressure chambers 18. However, the pressure of the liquid I in the pressure chamber 18 is different for each pressure chamber 18. That is, the pressure of the liquid I in the pressure chamber 18 becomes lower as the pressure chamber 18 is farther from the liquid supply port 117. This is because the farther the pressure chamber 18 is from the liquid supply port 117, the greater the friction loss until the liquid I reaches the pressure chamber 18 from the liquid supply port 117.

FIG. 6 is a block diagram showing an example of the main circuit configuration of the inkjet recording apparatus 1 according to the first embodiment.
The inkjet recording apparatus 1 includes, for example, a processor 101, a ROM (read-only memory) 102, a RAM (random-access memory) 103, an auxiliary storage device 104, a head interface 105, a circulation interface 106, and an ink interface 107. Then, these respective units are connected by a bus 108 or the like.

The processor 101 corresponds to the central part of a computer that performs processing such as calculation and control necessary for the operation of the inkjet recording apparatus 1. The processor 101 controls each unit to realize various functions of the inkjet recording apparatus 1 based on a program such as system software, application software or firmware stored in the ROM 102 or the auxiliary storage device 104. Note that part or all of the program may be incorporated in the circuit of the processor 101. The processor 101 is, for example, a CPU (central processing unit), MPU (micro processing unit), SoC (system on a chip), DSP (digital signal processor), GPU (graphics processing unit), ASIC (application specific integrated circuit), It is a PLD (programmable logic device) or an FPGA (field-programmable gate array). Alternatively, the processor 101 is a combination of a plurality of these.

The ROM 102 corresponds to a main storage device of a computer having the processor 101 as a center. The ROM 102 is a non-volatile memory used exclusively for reading data. The ROM 102 stores the above program. Further, the ROM 102 stores data used by the processor 101 to perform various processes, various set values, and the like.

The RAM 103 corresponds to a main storage device of a computer having the processor 101 as a center. The RAM 103 is a memory used for reading and writing data. The RAM 103 is used as a so-called work area or the like for storing data that is temporarily used by the processor 101 for performing various processes.

The auxiliary storage device 104 corresponds to an auxiliary storage device of a computer having the processor 101 as a center. The auxiliary storage device 104 is, for example, an EEPROM (electric erasable programmable read-only memory), an HDD (hard disk drive), an SSD (solid state drive) or an eMMC (embedded MultiMediaCard). The auxiliary storage device 104 may store the above program. The auxiliary storage device 104 also stores data used by the processor 101 to perform various processes, data generated by the process of the processor 101, various setting values, and the like.

The programs stored in the ROM 102 or the auxiliary storage device 104 include programs for executing the processes described below. As an example, the inkjet recording apparatus 1 is transferred to a manager or the like of the inkjet recording apparatus 1 while the program is stored in the ROM 102 or the auxiliary storage device 104. However, the inkjet recording apparatus 1 may be transferred to the administrator or the like in a state where the program is not stored in the ROM 102 or the auxiliary storage device 104. Further, the inkjet recording apparatus 1 may be transferred to the administrator or the like in a state where a program different from the program is stored in the ROM 102 or the auxiliary storage device 104. Then, a program for executing the process described below may be separately transferred to the administrator or the like, and written in the ROM 102 or the auxiliary storage device 104 under the operation of the administrator or a service person. The transfer of the program at this time can be realized by recording on a removable storage medium such as a magnetic disk, a magneto-optical disk, an optical disk or a semiconductor memory, or by downloading via a network NW or the like.

The head interface 105 is provided for the processor 101 to communicate with the inkjet head 10. The head interface 105 transmits gradation data and control data to the inkjet head 10 under the control of the processor 101.

The circulation interface 106 is provided for the processor 101 to communicate with the circulation device 20. The processor 101 communicates with the circulation pump 24, the thermometer 27, etc. via the circulation interface 106.
The ink interface 107 is provided for the processor 101 to communicate with the ink cartridge 30.

The bus 108 includes a control bus, an address bus, a data bus, and the like, and transmits signals transmitted and received by each unit of the inkjet recording apparatus 1.

The inkjet recording device 1 also includes an inkjet head 10. The inkjet head 10 includes a head driver 19 and an actuator 153.
The head driver 19 is a drive circuit for operating the inkjet head 10. The head driver 19 is, for example, a line driver. Under the control of the processor 101, the head driver 19 applies a drive voltage to each of the plurality of actuators 153 based on the input gradation data and the like. The processor 101 and the head driver 19 work together as an example of a control unit.

The operation of the inkjet recording apparatus 1 according to the first embodiment will be described below. Note that the content of the processing in the following description of the operation is an example, and various processing that can obtain the same result can be appropriately used.

The head driver 19 applies a drive waveform W1 as shown in FIG. 7 to the actuator 153 under the control of the processor 101. FIG. 7 is a diagram showing an example of drive waveforms according to the first embodiment. In FIG. 7, the vertical axis represents voltage and the horizontal axis represents time. Further, the drive waveform W1 shown in FIG. 7 is a waveform for ejecting the liquid I from the nozzle 171 by one drop. Further, FIG. 7 shows a drive waveform W1a and a drive waveform W1b as examples of the drive waveform W1.

The head driver 19 applies the drive waveform W1a to the actuator 153-a. Then, the head driver 19 applies the drive waveform W1b to the actuator 153-b. Here, the actuator 153-a and the actuator 153-b are two actuators 153 selected from the actuator 153-1, the actuator 153-2, the actuator 153-3,.... Therefore, a and b are natural numbers equal to or less than the number of actuators 153 included in the drive unit 15. Further, the actuator 153-a is assumed to be farther from the liquid supply port 117 than the actuator 153-b. Therefore, a is a number larger than b.

The drive waveform W1 includes a first pulse P1 and a second pulse P2. The first pulse P1 is a voltage signal applied to generate pressure oscillation for promoting ejection of droplets. The voltage of the first pulse P1 is, for example, −V1. The application time of the first pulse P1 is t1. The second pulse P2 is a voltage signal applied for ejecting a droplet from the nozzle 171. The voltage of the second pulse P2 is, for example, V1. The application time of the second pulse P2 is t2. The drive waveform W1 has a large force for ejecting the liquid I from the nozzle 171 (hereinafter, “the force for ejecting the liquid I from the nozzle 171” is referred to as “ejection force”) when t1 is 1AL and t2 is 2AL. The ejection force of the drive waveform W1 decreases as t1 deviates from 1AL. Here, AL is a half of the natural vibration period (cycle at the main acoustic resonance frequency) of the liquid I in the pressure chamber 18.

The drive waveform W1a has a larger ejection force than the drive waveform W1b. Therefore, for example, the application time t1a of the first pulse P1a of the drive waveform W1a is longer than the application time t1b of the first pulse P1b of the drive waveform W1b. However, t1a is assumed to be 1AL or less. That is, t1a and t1b have a relationship of 1AL≧t1a>t1b. Alternatively, t1a may be 1AL or more. In this case, t1b is longer than t1a. That is, t1a and t1b have a relationship of 1AL≦t1a<t1b. Note that FIG. 7 shows the drive waveform W1a and the drive waveform W1b when t1a and t1b have a relationship of 1AL≧t1a>t1b.

Further, the application time t2a of the second pulse P2a of the drive waveform W1a and the application time t2b of the second pulse P2b of the drive waveform W1b are, for example, 2AL.

As described above, the actuator 153-b is an example of the first actuator. The actuator 153-a is an example of the second actuator. The drive waveform W1b is an example of the first drive waveform. The drive waveform W1a is an example of the second drive waveform.

The above description is valid for arbitrary a and b. Therefore, the head driver 19 applies to the actuator 153 a drive waveform W1 having a larger ejection force as the actuator 153 located farther from the liquid supply port 117. That is, as the actuator 153 is farther from the liquid supply port 117, the application time t1 of the first pulse of the applied drive waveform W1 is closer to 1AL.

As described above, the pressure of the liquid I in the pressure chamber 18 is lower as it is farther from the liquid supply port 117. Therefore, when the same drive waveform is applied to the actuators 153 of the pressure chambers 18 having different distances from the liquid supply port 117, the liquid I ejected from the pressure chamber 18 far from the liquid supply port 117 has a pressure close to that of the liquid supply port 117. The discharge amount is smaller than the liquid I discharged from the chamber 18. As described above, the inkjet recording apparatus 1 according to the first embodiment applies a drive waveform having a larger ejection force to the actuator 153 that is farther from the liquid supply port 117. As a result, the inkjet recording apparatus 1 according to the first embodiment can make the ejection amount of the liquid I ejected from the pressure chamber 18 uniform regardless of the distance from the liquid supply port 117.

The larger the friction loss pressure, the larger the pressure difference between the two pressure chambers 18 that are different in distance from the liquid supply port 117. The friction loss pressure is proportional to the viscosity of the liquid I and the flow rate of the liquid I. That is, the friction loss pressure increases as the viscosity of the liquid I increases. The friction loss pressure increases as the flow rate of the liquid I increases. Further, the viscosity changes depending on the temperature of the liquid I.

The reason why the friction loss pressure is proportional to the viscosity of the liquid I and the flow rate of the liquid I will be described. Equation (1) below is the Darcy Weissbach formula.
However,
ΔP: Friction loss pressure [Pa]
λ: pipe friction coefficient L: pipe length [m]
ρ: Fluid density [kg/m ³ ]
V: Flow velocity [m/s]
D: Diameter of tube [m]
Is.

Further, the pipe friction coefficient λ can be expressed by the following equation (2).
However,
k: rectangular tube correction coefficient Re: Rey Nozzle number.

Here, the Reynolds number Re can be expressed by the following equation (3).
However,
ν: dynamic viscosity coefficient [m ² /s]
Is.

Further, the kinematic viscosity coefficient ν can be expressed by the following equation (4).
However,
μ: viscosity of liquid I [Pa·s=(N·s)/m ² =kg/(s·m)]
Is.

Therefore, the Reynolds number Re can be expressed by the following expression (5) by substituting the expression (4) into the expression (3).
Then, by substituting the equation (5) into the equation (2), the pipe friction coefficient λ can be expressed by the following equation (6).

Further, the flow rate Q [m ³ /s] of the liquid I can be expressed by the following equation (7).
The flow velocity V can be represented by the following equation (8) by modifying the equation (7).

From the above, the friction loss pressure ΔP can be expressed by the following equation (9).

In the equation (9), the rectangular tube correction coefficient k, the tube diameter D and the tube length L are constants. Therefore, it is understood from the equation (9) that the friction loss pressure ΔP is proportional to the viscosity and the flow rate of the liquid I.

Hereinafter, a method of correcting the drive waveform W1 to cope with the change in the friction loss pressure ΔP based on the change in the viscosity and the flow rate of the liquid I will be described. FIG. 8 is a flowchart showing an example of processing by the processor 101 of the inkjet recording apparatus 1. The processor 101 executes this processing based on a program stored in the ROM 102 or the auxiliary storage device 104, for example.

In Act 11, the processor 101 determines whether to start correction. The processor 101 determines to start the correction when a predetermined condition is satisfied. The predetermined condition is that printing has been performed for a certain amount or more since the previous correction, a certain amount of time has passed since the previous correction, or there has been a temperature change for a certain amount or more since the previous correction. is there. If it is determined that the correction is not started, the processor 101 determines No in Act 11 and repeats Act 11. On the other hand, if the processor 101 determines to start the correction, it determines Yes in Act 11 and proceeds to Act 12.

In Act 12, the processor 101 acquires ink information from the ink cartridge 30 or the like. The ink information includes information about the liquid I in the ink cartridge 30.

In Act 13, the processor 101 acquires the temperature of the liquid I from the thermometer 27.

In ACT14, the processor 101 acquires the circulation amount (flow rate) of the liquid I flowing in the inkjet head 10 and the circulation device 20. For example, the processor 101 acquires the circulation amount by obtaining the circulation amount based on the information acquired from the transportation pump 24, the information controlling the transportation pump 24, or the like. Alternatively, the processor 101 may obtain the circulation amount by obtaining the circulation amount based on information obtained from a sensor such as a flow meter or an anemometer installed in the inkjet head 10 or the circulation device 20.

In Act 15, the processor 101 calculates the viscosity of the liquid I using at least one of the ink information acquired in Act 12 and the temperature acquired in Act 13. The processor 101 obtains the viscosity using, for example, a table or a relational expression stored in advance in the auxiliary storage device 104 or the like. Note that the table is obtained in advance, for example, by an experiment.

In ACT16, the processor 101 obtains a correction value based on the circulation amount and viscosity obtained in ACT14 and ACT15. The correction value is a value for equalizing the ejection amount of the liquid I ejected from the pressure chambers 18 having different distances from the liquid supply port 117. The correction value is a value that determines how much the difference between the ejection forces of the drive waveform W1 applied to the two actuators 153 having different distances from the liquid supply port 117 is set. That is, the correction value is a value that determines the time t1 of each drive waveform W1 applied to each actuator 153. The processor 101 obtains the correction value using, for example, a table stored in the auxiliary storage device 104 or the like in advance or a relational expression. Note that the table is obtained in advance, for example, by an experiment.

In ACT17, the processor 101 controls the head driver 19 to apply the correction value obtained in ACT16. After the processing of Act16, the processor 101 returns to Act11.

According to the inkjet recording apparatus 1 of the first embodiment, the inkjet head 10 has one liquid supply port 117 and two liquid discharge ports 118. Since the number of liquid supply ports and liquid discharge ports is small as described above, the inkjet head 10 can be easily downsized.

Further, according to the inkjet recording apparatus 1 of the first embodiment, the drive waveform W1 having a larger ejection force is applied to the actuator 153 as the distance from the liquid supply port increases. As a result, the ejection amount of the droplets ejected from each pressure chamber 18 becomes uniform regardless of the distance from the liquid supply port. As described above, according to the inkjet recording apparatus 1 of the first embodiment, it is possible to reduce the size of the inkjet head 10 while preventing deterioration of print quality.

Further, the inkjet recording apparatus 1 according to the first embodiment determines the ejection force of the drive waveform W1 applied to each actuator 153 according to the viscosity of the liquid I. As a result, in the inkjet recording apparatus 1 of the first embodiment, even if the temperature of the liquid I changes and the type of the liquid I changes, the ejection amount of the liquid droplets ejected from each pressure chamber 18 can be measured from the liquid supply port. It can be made uniform regardless of.

Further, the inkjet recording apparatus 1 according to the first embodiment determines the ejection force of the drive waveform W1 applied to each actuator 153 according to the circulation amount of the liquid I. Accordingly, in the inkjet recording apparatus 1 according to the first embodiment, even if the circulation amount of the liquid I changes, the ejection amount of the liquid droplets ejected from each pressure chamber 18 is made uniform regardless of the distance from the liquid supply port. be able to.

[Second Embodiment]
The configuration of the inkjet recording apparatus 1 of the second embodiment is the same as that of the first embodiment, and thus the description thereof is omitted. The operation of the inkjet recording apparatus 1 according to the second embodiment will be described below.

The head driver 19 applies the drive waveform W2 as shown in FIG. 9 to the actuator 153 under the control of the processor 101. FIG. 9 is a diagram showing an example of drive waveforms according to the second embodiment. Note that in FIG. 9, the vertical axis represents voltage and the horizontal axis represents time. The drive waveform W2 shown in FIG. 9 is a waveform for ejecting the liquid I from the nozzle 171 by one drop. Further, FIG. 9 shows a drive waveform W2a and a drive waveform W2b as examples of the drive waveform W2.

The head driver 19 applies the drive waveform W2a to the actuator 153-a. Then, the head driver 19 applies the drive waveform W2b to the actuator 153-b. About a and b, it is the same as that of 1st Embodiment.

The drive waveform W2 includes a first pulse P3 and a second pulse P4. The voltage of the first pulse P3 is, for example, -V1. The first pulse P3 is a voltage signal applied to generate pressure oscillation for promoting the ejection of droplets. The application time of the first pulse P3 is t3. The second pulse P4 is a voltage signal applied to eject the liquid droplets from the nozzle 171. The voltage of the second pulse P4 is, for example, V1. The application time of the second pulse P2 is t5. The application of the second pulse P2 starts when the time t4 has elapsed from the end of the application of the first pulse P3. The drive waveform W2 has a large ejection force when t3, t4, and t5 are all 1AL. The ejection force of the drive waveform W2 decreases as t3 deviates from 1AL.

The drive waveform W2a has a larger ejection force than the drive waveform W2b. Therefore, for example, the application time t3a of the first pulse P3a of the drive waveform W2a is longer than the application time t3b of the first pulse P3b of the drive waveform W2b. However, t3a is assumed to be 1AL or less. That is, t3a and t3b have a relationship of 1AL≧t3a>t3b. Alternatively, t3a may be 1AL or more. In this case, t3b is longer than t3a. That is, t3a and t3b have a relationship of 1AL≦t3a<t3b. Note that FIG. 9 shows the drive waveform W2a and the drive waveform W2b when t3a and t3b have a relationship of 1AL≧t3a>t3b.

The application time t5a of the second pulse P4a of the drive waveform W2a and the application time t5b of the second pulse P4b of the drive waveform W2b are 2AL, for example. Further, a time t4a from the end of application of the first pulse P3a of the drive waveform W2a to the start of application of the second pulse P4a, and the time t4b from the end of application of the first pulse P3b of the drive waveform W2b to the start of application of the second pulse P4b. Is, for example, 1AL.

As described above, the drive waveform W2b is an example of the first drive waveform. The drive waveform W2a is an example of the second drive waveform.

The above description is valid for arbitrary a and b. Therefore, the head driver 19 applies to the actuator 153 a drive waveform W2 having a larger ejection force as the distance from the liquid supply port 117 increases. That is, the longer the actuator 153 is from the liquid supply port 117, the closer the application time of the first pulse P3 of the applied drive waveform W2 is to 1AL.

In the second embodiment, the processor 101 executes the processing shown in FIG. 8 as in the first embodiment. However, in the second embodiment, the correction value is a value that determines the time t3 of each drive waveform W2 applied to each actuator 153.

The inkjet recording device 1 of the second embodiment can obtain the same effects as those of the first embodiment.

[Third Embodiment]
The configuration of the inkjet recording apparatus 1 according to the third embodiment is similar to that of the first and second embodiments, and thus the description thereof will be omitted. The operation of the inkjet recording apparatus 1 according to the third embodiment will be described below.

The head driver 19 applies the drive waveform W3 to the actuator 153 under the control of the processor 101. The liquid I is ejected from the nozzle 171 by applying the drive waveform W3. Hereinafter, the drive waveform W3a and the drive waveform W3b will be described as examples of the drive waveform W3. The head driver 19 applies the drive waveform W3a to the actuator 153a. Then, the head driver 19 applies the drive waveform W3b to the actuator 153b. About a and b, it is the same as that of 1st Embodiment and 2nd Embodiment.

The absolute value of the voltage of the drive waveform W3a is larger than the absolute value of the voltage of the drive waveform W3b. Therefore, the drive waveform W3a has a larger ejection force than the drive waveform W3b.

As described above, the drive waveform W3b is an example of the first drive waveform. The drive waveform W3a is an example of the second drive waveform.

The above description is valid for arbitrary a and b. Therefore, the head driver 19 applies to the actuator 153 a drive waveform W3 in which the absolute value of the voltage increases as the distance from the liquid supply port 117 increases. As a result, the head driver 19 applies to the actuator 153 a drive waveform W3 having a larger ejection force as the distance from the liquid supply port 117 increases.

In the third embodiment, the processor 101 executes the processing shown in FIG. 8 as in the first embodiment. However, in the third embodiment, the correction value is a value that determines the magnitude of the absolute value of the voltage of each drive waveform W3 applied to each actuator 153.

The inkjet recording device 1 of the third embodiment can obtain the same effects as those of the first and second embodiments.

The first to third embodiments described above can be modified as follows.
The head driver 19 may apply a drive waveform having a waveform different from those of the above-described first to third embodiments. Even in this case, the head driver 19 applies a drive waveform having a larger ejection force as the actuator 153 located farther from the liquid supply port 117.

In the above-described first embodiment, the head driver 19 changes the ejection force of the drive waveform W1 by changing the application time t1 of the first pulse P1. However, the head driver 19 may change the ejection force of the drive waveform W1 by changing the application time t2 of the second pulse P2. Further, the head driver 19 may change the ejection force of the drive waveform W1 by changing both t1 and t2.

In the second embodiment described above, the head driver 19 changes the ejection force of the drive waveform W2 by changing the application time t3 of the first pulse P3. However, the head driver 19 may change the ejection force of the drive waveform W2 by changing the application time t5 of the second pulse P4. Further, the head driver 19 may change the ejection force of the drive waveform W2 by changing the time t4 from the end of application of the first pulse P3 to the start of application of the second pulse P4. Alternatively, the head driver 19 may change the ejection force of the drive waveform W2 by changing any one of t3, t4, and t5.

In the first and second embodiments described above, the head driver 19 changes the ejection force by changing the duration of the elements included in the drive waveform. Then, in the third embodiment described above, the head driver 19 changes the ejection force by changing the voltage of the drive waveform. However, the head driver 19 may change the ejection force by changing the duration of the elements included in the drive waveform and the voltage of the drive waveform.

The application of the drive waveform W1a and the application of the drive waveform W1b shown in FIG. 7 are started at the same time. However, the drive waveform W1b may be applied after the application of the drive waveform W1a is started, and may be terminated at the same time when the application of the drive waveform W1b is completed. Alternatively, the drive waveform W1b may be applied after the application of the drive waveform W1a is started and ended before the application of the drive waveform W1a is completed.
Further, the application start of the drive waveform W2a and the application start of the drive waveform W2b shown in FIG. 9 are simultaneous. However, the drive waveform W2b may be applied after the application of the drive waveform W2a is started, and may be terminated at the same time when the application of the drive waveform W2b is completed. Alternatively, the drive waveform W2b may be applied after the application of the drive waveform W2a is started and may be ended before the application of the drive waveform W2a is completed.

One pressure chamber 18 is sandwiched by two actuators. Therefore, the head driver 19 may apply the same drive waveform to the two actuators 153 that sandwich the pressure chamber 18 that ejects the droplets.

The head driver 19 outputs the drive waveform W4-1 from the actuator 153-1 to the actuator 153-n_1, the drive waveform W4-2 from the actuator 153-(n_1+1) to the actuator 153-n_2,..., The actuator 153-(n_(k The drive waveform W4-k may be applied from -1)+1) to the actuator 153-k. The drive waveform W4-1, the drive waveform W4-2,..., And the drive waveform W4-k have a large ejection force in the order of drive waveform W4-1<drive waveform W4-2<... Further, n_1, n_2,..., N_(k-1), and n_k are all natural numbers, and have a magnitude relationship of n_1<n_2<...<n_(k-1)<n_k. Then, n_k is the number of actuators 153 included in the drive unit 15. Further, k is a natural number that is 2 or more and is less than the number of actuators 153 included in the drive unit 15. As described above, the head driver 19 may apply the driving waveform W4 at the same stage to the plurality of continuous actuators 153 to apply the driving waveform W4 at the k stages having different ejection forces to the actuator 153.
In the above, the actuator 153-p is an example of the first actuator. The actuator 153-q is an example of the second actuator. The drive waveform W4-p is an example of the first drive waveform. The drive waveform W4-q is an example of the second drive waveform. However, p<q.

In the inkjet heads 10 of the above-described first to third embodiments, the liquid supply port 117 is in the inner flow path 142 and the liquid discharge port 118 is in the outer flow path 143. However, the inkjet recording apparatus 1 may include an inkjet head 10b as shown in FIG. 10 instead of the inkjet head 10. FIG. 10 is a diagram showing liquid flow paths in the inkjet head 10b. In the inkjet head 10b, the liquid supply port 117b is in the outer flow path 143, and the liquid discharge port 118b is in the inner flow path 142. In this case, the liquid I sent from the circulation device 20 flows out from the liquid supply port 117b to the outer flow path 143 through the liquid supply pipe 12. The liquid I in the outer flow path 143 passes through one of the pressure chambers 18 and flows into the inner flow path 142. The liquid I may be ejected from the nozzle 171 when the liquid ejection operation is performed by the inkjet head 10 while passing through the pressure chamber 18. Therefore, of the liquid I that has flowed into the pressure chamber 18, the liquid I that has not been discharged from the nozzle 171 flows out to the inner flow path 142. The liquid I in the inner flow path 142 flows out from the liquid discharge port 118b, passes through the liquid discharge pipe 13, and flows into the circulation device 20.
Further, as described above, when the liquid supply port 117b is in the outer flow path 143 and the liquid discharge port 118b is in the inner flow path 142, the inner flow path 142 is an example of a liquid discharge path. The outer flow path 143 is an example of the liquid supply path.

The head driver 19 may process a part of the processing performed by the processor 101 in the first to third embodiments described above.

The inkjet recording apparatus 1 of the embodiment is an inkjet printer that forms a two-dimensional image with ink on the image forming medium S. However, the inkjet recording apparatus according to the embodiment is not limited to this. The inkjet recording device of the embodiment may be, for example, a 3D printer, an industrial manufacturing machine, or a medical machine. When the inkjet recording apparatus according to the embodiment is a 3D printer, an industrial manufacturing machine, a medical machine, or the like, the inkjet recording apparatus according to the embodiment may be, for example, a substance as a material or a binder for hardening the material. Is ejected from the inkjet head to form a three-dimensional object.

The inkjet recording apparatus 1 according to the embodiment includes four liquid ejecting sections 2, and the liquid I used by each of the liquid ejecting sections 2 is cyan, magenta, yellow, or black ink. However, the number of the liquid ejection units 2 included in the inkjet recording device is not limited to four, and may not be plural. In addition, the color and characteristics of the ink used by each liquid ejection unit 2 are not limited.
The liquid ejection unit 2 can also eject transparent glossy ink, ink that develops color when irradiated with infrared rays or ultraviolet rays, or other special ink. Further, the liquid ejecting unit 2 may be capable of ejecting a liquid other than ink. The liquid ejected by the liquid ejecting unit 2 may be a dispersion liquid such as a suspension liquid. As the liquid other than the ink ejected by the liquid ejecting section 2, for example, a liquid containing conductive particles for forming a wiring pattern of a printed wiring board, a liquid containing cells for artificially forming a tissue or an organ, or the like. , A binder such as an adhesive, a wax, or a liquid resin.

In addition to the above embodiment, the inkjet head may have a structure in which the vibration plate is deformed by static electricity to eject ink, or a structure in which thermal energy of a heater or the like is used to eject ink from the nozzle. In these cases, the diaphragm or heater is an actuator.

The processor 101 may realize a part or all of the processing realized by the program in the above embodiment by a hardware configuration of a circuit.

While some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and the gist of the invention, and are also included in the invention described in the claims and the scope equivalent thereto.

1... Inkjet recording device, 10... Inkjet head, 15... Driving unit, 18... Pressure chamber, 19... Head driver, 24... Transport pump, 27... Thermometer, 101... Processor, 102... ... ROM, 103 ... RAM, 104 ... auxiliary storage device 117, 117b ... liquid supply port, 118, 118b ... liquid discharge port, 142 ... inner flow path, 143 ... outer flow path, 153 ... Actuator, 171... Nozzle

Claims (5)

A liquid supply path having a liquid supply port at one end in the stretching direction,
A liquid discharge path provided alongside the liquid supply path and having a liquid discharge port at the other end in the extending direction;
A first pressure chamber connecting the liquid supply passage and the liquid discharge passage,
A second pressure chamber that connects the liquid supply path and the liquid discharge path and is farther from the liquid supply port than the first pressure chamber;
A first actuator that discharges the liquid in the first pressure chamber from a nozzle by changing the pressure of the liquid in the first pressure chamber by driving;
A second actuator configured to discharge the liquid in the second pressure chamber from a nozzle by changing the pressure of the liquid in the second pressure chamber by driving;
Applying a first drive waveform for driving the first actuator to the first actuator;
A second drive waveform that drives the second actuator and has a larger force for ejecting liquid than the first drive waveform is applied to the second actuator.
An inkjet recording apparatus comprising: a controller. The second drive waveform has a main acoustic resonance of liquid in the first and second pressure chambers in which a pulse width included in the second drive waveform is larger than a pulse width included in the first drive waveform. The inkjet recording apparatus according to claim 1, wherein the force for ejecting the liquid is larger than the first drive waveform because the frequency is close to a half cycle. The inkjet recording according to claim 1 or 2, wherein the second drive waveform has a voltage higher than that of the first drive waveform and thus has a larger force for ejecting liquid than the first drive waveform. apparatus. 4. The controller according to claim 1, wherein the controller increases the difference in the force for ejecting the liquid between the first drive waveform and the second drive waveform as the viscosity of the liquid increases. 2. The inkjet recording device according to item 1. 5. The controller according to claim 1, wherein the controller increases the difference in the force of ejecting the liquid between the first drive waveform and the second drive waveform as the flow rate of the liquid increases. 2. The inkjet recording device according to item 1.