JP2021115769A - Inkjet printer - Google Patents

Abstract

To provide an inkjet printer which can achieve print quality comparable to print quality achieved when a method using a regulator to reduce pulsation of an ink fluid is adopted while adopting a method using a damper and a check valve to reduce the pulsation.SOLUTION: An inkjet printer 1 includes: an ink tank 2; a print head 3; a gutter 51; and a pump 4 which transfers an ink between these components. Pulsation reduction means 10 which reduces pulsation of an ink fluid is attached to a pipe 5 connecting the ink tank 2 with the print head 3. The pulsation reduction means 10 comprises: a damper 11; a static mixer 12, and a check valve 13.SELECTED DRAWING: Figure 1

Description

The present invention relates to a continuous inkjet printer, and more particularly to an inkjet printer provided with means for reducing the pulsation of an ink fluid.

Inkjet printers are roughly classified into continuous type and on-demand type. Of these, the continuous type inkjet printer (hereinafter referred to as "CIJ") ejects ink from the nozzle of the print head by a pump, charges the ink droplets at the position where the ejected ink separates into ink droplets, and further deflects the ink droplets. The trajectory of the ink droplet charged by the electrode is bent so that it collides with a predetermined position on the recording surface.

In CIJ, when the flight speed of the ink droplets ejected from the nozzle changes, the print quality deteriorates and the height of the characters varies. Therefore, the flight speed is kept constant to ensure the print quality.

Two methods have been put into practical use as a method for ensuring print quality by keeping the flight speed constant. The first method is a method in which a regulator is attached to a pipe in front of the nozzle to keep the pressure of the ink fluid constant to keep the flight speed constant (see Patent Document 1). The second method is a method of measuring the flight speed of ink droplets ejected from a nozzle and adjusting the pressure of the ink so that it becomes a predetermined value (see Patent Document 2).

Further, since the flight speed of the ink droplets also changes depending on the viscosity of the ink, in the first and second methods described above, the viscosity is adjusted so that the flight speed becomes constant.

On the other hand, in CIJ, a diaphragm pump is often used to pump the ink fluid from the ink tank to the print head. In that case, due to the nature of the diaphragm pump, pulsation occurs in the ink fluid. When pulsation occurs in the ink fluid, the flight speed of the ink droplets ejected from the nozzle changes and the print quality deteriorates. Therefore, measures to reduce the pulsation are indispensable.

Japanese Unexamined Patent Publication No. 2008-137198 JP-A-2017-42999

In the first method described above, priority is given to reducing pulsation, and a regulator that keeps the pressure of the ink fluid constant is attached to the pipe in front of the nozzle.

On the other hand, the viscosity of ink changes with temperature, and even if the pressure is constant, if the viscosity changes, the flight speed changes in inverse proportion to it. Therefore, the viscosity is regularly measured with a viscometer and adjusted to a predetermined viscosity. Viscosity adjustment is performed by replenishing a solvent or the like.

As described above, the first method can reduce the pulsation to a sufficiently low level, so that high print quality can be realized, but the viscometer is indispensable as an accessory component, so that the cost is high.

On the other hand, the second method utilizes the property that the viscosity of the ink and the pressure of the ink fluid are in a proportional relationship, and the viscosity of the ink is derived from the detected flight speed of the ink droplets and the pressure of the ink fluid pumped from the pump to the nozzle. Is calculated, and the viscosity of the ink is adjusted based on the value.

The second method is advantageous in terms of cost because it does not require a viscometer. Furthermore, in the first method, it takes time to adjust the viscosity, so if the temperature or viscosity changes suddenly during printing, it is difficult to respond to the change in flight speed, whereas in the second method, pressure is applied. By changing it, there is an advantage that it is possible to immediately respond to a change in flight speed during printing.

However, since the second method requires changing the pressure of the ink, that is, changing the rotation speed of the pump, the regulator cannot be used. Therefore, a damper and a check valve are connected in series to the pipe in front of the nozzle to reduce the pulsation of the ink fluid, but a sufficient effect has not been obtained.

The present invention has been made in view of such conventional problems, and reduces pulsation by using a regulator while adopting a second method of reducing pulsation of ink fluid by using a damper and a check valve. It is an object of the present invention to provide an inkjet printer capable of achieving print quality comparable to that of the case where the first method is adopted.

In order to achieve the above object, the inkjet printer according to the present invention
An ink tank that stores ink and
A print head that ejects the ink supplied from the ink tank toward the surface of the printed matter, and
A gutter that collects ink that is not used for printing among the ink ejected from the nozzle of the print head,
A pump for transferring ink from the ink tank to the print head and transferring ink collected by the gutter to the ink tank is provided.
A pulsation reducing means for reducing the pulsation of the ink fluid is attached to the pipe connecting the ink tank and the print head, and the pulsation reducing means is characterized by being composed of a damper, a static mixer and a check valve. ..

Here, in the pulsation reducing means, it is preferable that the damper, the static mixer and the check valve are arranged in this order according to the flow of ink.

Further, it is preferable that the check valve blocks the transfer of ink when the pressure of the ink transferred in the pipe does not exceed a predetermined value, and transfers the ink when the pressure exceeds a predetermined value.

Further, it is preferable to use a diaphragm pump as the pump.

Further, it is preferable that a pressure sensor for detecting the pressure of the ink fluid is attached between the pulsation reducing means and the print head in the pipe, and the pressure sensor detects the pressure of the ink fluid flowing in the pipe.

In the inkjet printer according to the present invention, by combining a static mixer with a damper and a check valve, a practically sufficient pulsation reduction effect is realized, and since it is not necessary to use a regulator, the cost of the printer is significantly reduced. It is possible to reduce it.

It is a piping diagram of the inkjet printer which concerns on embodiment of this invention. It is a figure which shows the schematic structure of the print head of the printer. It is a block diagram which shows the structure of the control system of the printer. It is a figure explaining the operation of the print head of the printer. It is a graph explaining the effect of embodiment of this invention. It is a figure which shows the printing example by the printer.

Hereinafter, the inkjet printer according to the embodiment of the present invention will be described with reference to the drawings.

<Inkjet printer configuration>
FIG. 1 shows a piping diagram of an inkjet printer according to the present embodiment, and FIG. 2 shows a schematic configuration of a print head of the printer. Further, FIG. 3 shows a block diagram of the control system of the printer.

First, the configuration of the printer excluding the printhead will be described with reference to FIG. 1, then the configuration of the printhead will be described with reference to FIG. 2, and finally, the configuration of the controller will be described with reference to FIG. explain.

As shown in the piping diagram of FIG. 1, the inkjet printer (hereinafter abbreviated as “printer”) 1 includes an ink tank 2 for storing ink I, a print head 3 for ejecting ink to print on the surface of an object to be printed. A pump 4 that delivers ink, pipes 5a to 5i that connect these members (hereinafter collectively referred to as "pipe 5"), on-off valves 61 to 65 that are arranged in the middle of the pipe 5 and open and close the pipe, and ink. It is composed of sensors 71 to 73 for detecting various states of the above, tanks 81 and 82 used for replenishing ink and solvent, and means 10 for reducing pulsation of ink fluid.

The ink tank 2 is a rectangular parallelepiped tank body 21 made of reinforced plastic or the like and having an open upper surface, and a flat plate lid 22 made of the same reinforced plastic or the like and installed so as to cover the upper surface of the tank body 21. It is composed of.

As shown in FIG. 1, the lid 22 is formed with holes for passing a plurality of pipes 5 and holes for passing the temperature sensor 72 and the liquid level detection sensor 73. A coagulation tank 83 is attached to the tip of the pipe 5i to collect the vapor of the ink solvent released through the pipe 5i and coagulate and liquefy it to recover the ink solvent.

The holes formed in the lid 22 are sealed between the holes and the pipes. Further, the opening of the tank body 21 and the lid 22 are fastened with bolts, nuts, etc. via packing (not shown), and the tank body 21 and the lid 22 are sealed. Has been done.

In the present embodiment, as the ink I, methyl ethyl ketone (70 to 90%), which is a solvent, is added with a chromium complex salt (5 to 10%), which is a black dye, and a small amount of cyclohexane (5 to 10%) is added thereto. The one to which isopropyl alcohol (0.1 to 1%) is added is used.

A pump 4 is arranged in the middle of the pipe 5a connecting the ink tank 2 and the print head 3, and transfers the ink in the tank to the print head 3. In the present embodiment, four diaphragm units 41 to 44 are integrated as the pump 4, and a diaphragm type pump is used in which these are rotationally driven by one motor 45 (see FIG. 3).

Since the diaphragm unit 41 transfers the ink in the ink tank 2 to the print head 3, the diaphragm units 42 and 43 are used to transfer the ink collected by the gutter 51 to the ink tank 2. Further, the diaphragm unit 44 is used to circulate the ink to stir the ink in the ink tank 2 and to supply the ink or solvent contained in the replenishment tank 81 or 82 to the ink tank 2.

The filters 52, 53 and 54 provided in the middle of the pipes 5a and 5c remove impurities in the ink.

A damper 11, a static mixer 12, and a check valve 13 are arranged in the middle of the pipe 5a connecting the diaphragm unit 41 and the print head 3 as means 10 for reducing ink pulsation. Further, a diaphragm 55 is attached in the middle of the pipe 5b that branches on the upstream side of the damper 11 and returns the ink to the ink tank 2. These functions will be described in detail later with reference to the drawings.

In addition to the above-mentioned members, an on-off valve 61-65 and an ink discharge valve 66 are arranged in the middle of the pipes 5a, 5d, 5e, 5f, and 5g. The on-off valves 61 to 65 are composed of solenoid valves, and open and close the pipe 5 according to the instruction of the controller 9 in FIG. 3 to transfer ink or stop the transfer. The ink discharge valve 66 discharges the ink remaining in the pipe 5a and the ink tank 2 during maintenance and inspection of the printer 1, and is manually opened and closed.

The pressure sensor 71 connected to the pipe 5a detects the pressure of the ink flowing through the pipe 5a. Further, the temperature sensor 72 attached to the lid 22 of the ink tank 2 detects the temperature of the ink in the ink tank 2. Similarly, the liquid level detection sensor 73 attached to the lid 22 uses a plurality of conductive rods having different lengths, and detects the height of the liquid level of the ink depending on the presence or absence of electrical continuity between them.

Next, the configuration of the print head 3 will be described. As shown in FIG. 2, the print head 3 is composed of a gun 30, a charging electrode 34, a pair of detection electrodes 36a and 36b (hereinafter collectively referred to as “detection electrode 36”), and a deflection electrode 38.

The gun 30 ejects ink droplet ID toward the surface of a printed matter (for example, a packing box), and is composed of a gun body 31, an ultrasonic vibrator 32, and a nozzle 33. The ink sent from the ink tank 2 by the pump 41 and supplied to the gun body 31 through the pipe 5a is ejected from the hole of the nozzle 33 in a state where vibration is added by the ultrasonic vibrator 32 built in the gun body 31. NS.

The ink column ejected from the nozzle 33 is separated into individual ink droplet IDs by the vibration applied by the ultrasonic vibrator 32, further charged by the charging electrode 34, and then the ink droplets required for printing by the deflection electrode 38. Only the ID is deflected according to the amount of charge charged and collides with the surface of the printed matter to form dots.

Next, the configuration and functions of the controller will be described. The controller 9 controls the operations of the motor 45 that rotationally drives the pump 4 and the on-off valves 61 to 65 based on the output signals of the voltage detecting means 37, the pressure sensor 71, the temperature sensor 72, and the liquid level detecting sensor 73.

Further, an ultrasonic vibrator 32, a pulse power supply 35, and a DC power supply 39 used for driving the print head 3 are connected to the controller 9.

As shown in FIG. 3, the controller 9 includes a CPU 91, a ROM 92, a RAM 93, an input / display panel 94, a storage device 95, and a bus line 96.

The CPU 91 creates an instruction signal necessary for controlling the operation of each part of the printer 1. The ROM 92 stores a program necessary for the CPU 91 to operate. The RAM 93 temporarily stores data required during the execution of the program.

The storage device 95 is composed of a hard disk drive, a flash memory, or the like, and stores data necessary for controlling the printer 1. The input / display panel 94 is composed of a liquid crystal display or the like, and inputs print contents, set values, etc., and displays the input data, print contents, etc. The bus line 96 transmits a data signal, an address signal, and a control signal of the CPU 91.

A program for calculating the flight speed of ink droplets based on the measured value of the voltage detecting means 37 is installed in the storage device 95 in advance. The calculated flight speed is displayed on the input / display panel 94.

Although the controller 9 and each component to be controlled are connected by a cable for signal transmission, they are omitted in FIG. 2 in order to avoid complication.

<Print head operation>
Next, the operation of the print head 3 will be described with reference to FIGS. 2 and 4. FIG. 4 is a diagram showing an operation when printing on a printed matter using the print head 3 of FIG.

FIG. 4 shows a packing box 100 moving at a constant speed on a belt conveyor (not shown) in the direction indicated by the arrow. When the packaging box 100 is moving in a direction orthogonal to the flight direction of the ink droplet ID, the position of the ink droplet ID that collides with the side surface of the packaging box 100 is changed by changing the deflection amount of the ink droplet ID. When the ink droplet ID is repeatedly deflected in synchronization with the movement of the packing box 100, a character (“A” in the figure) is printed.

On the other hand, the uncharged ink droplet ID and the charged ink droplet ID that is not used for printing are not deflected and jump into the ink recovery gutter 51 as they are and are collected in the ink tank 2. The ink collected by the gutter 51 is transferred to the ink tank 2 through the pipe 5c by the pumps 42 and 43 and reused.

By driving the pump 41, the controller 9 applies pressure to the ink contained in the ink tank 2 and supplies the ink to the gun 30. Further, the controller 9 adjusts the flight speed of the ink droplet ID ejected from the nozzle 23 by controlling the rotation speed of the pump 41.

Further, the controller 9 adjusts the number and timing of the ink droplet IDs to be charged by controlling the timing of the pulse voltage applied from the pulse power supply 35 to the charging electrode 34. Further, the controller 9 adjusts the deflection amount of the ink droplet ID deflected by the deflection electrode 38 by controlling the voltage of the DC power supply 39.

A pair of detection electrodes 36a and 36b arranged at regular intervals L along the flight path of the ink droplet ID measure the velocity of the ink droplet ID during flight. The print head 3 has a built-in voltage detecting means 37 that detects a voltage induced in a pair of detection electrodes 36a and 36b by a charged ink droplet ID. The voltage signal detected by the voltage detecting means 37 is transmitted to the controller 9.

The controller 9 measures the time when the ink droplet ID passes in the vicinity of the detection electrodes 36a and 36b by the voltage signal induced in the pair of detection electrodes 36a and 36b by the charged ink droplet ID. Then, from the difference between the two measured values, the time required for the ink droplet ID to pass between the two detection electrodes 36a and 36b is calculated, and the flight speed of the ink droplet ID is calculated by dividing the distance by that time. do.

<Explanation of ink flow>
Next, the flow of ink in the printer 1 will be described with reference to FIG. 1 described above. The arrows displayed along the pipe 5 in FIG. 1 indicate the direction in which the ink flows.

The ink I contained in the ink tank 2 is sucked by the diaphragm unit 41 and transferred to the print head 3 through the pipe 5a. As described above, a damper 11, a static mixer 12, and a check valve 13 are arranged downstream of the diaphragm unit 41 of the pipe 5a as means 10 for reducing the pulsating flow of ink, and further in front of the damper 11 from the pipe 5a. The pipe 5b is branched and the tip is connected to the ink tank 2.

The ink delivered from the diaphragm unit 41 reaches the check valve 13 after most of the pulsating current is removed by the damper 11 and the static mixer 12.

The check valve 13 supplies ink at a certain pressure or higher to the print head 3, and when the pressure of the ink fluid falls below a value determined by the elastic force of the spring, the check valve 13 remains closed. The ink returns to the ink tank through the branch pipe 5b. The throttle 55 provided in the middle of the branch pipe 5b adjusts the flow rate of the ink collected in the ink tank 2.

The pressure sensor 71 attached to the pipe 5a on the downstream side of the check valve 13 detects the pressure of the ink fluid supplied to the print head 3. The pressure of the ink fluid detected by the pressure sensor 71 is used to adjust the viscosity of the ink.

When the viscosity of the ink is constant, the pressure of the ink transferred through the pipe 5a and the flight speed of the ink droplets are in a proportional relationship. When the pressure for maintaining the flight speed increases, it is determined that the viscosity of the ink has increased, and the solvent is replenished from the replenishment tank 82.

The on-off valve 61 provided in the middle of the pipe 5a opens the flow path of the pipe 5a when driving the pump 4 to start printing by the printer, and pipes when the printing is completed and the operation of the pump 4 is stopped. Close the flow path of 5a.

A part of the ink droplets ejected from the print head 3 is used for printing, and the other ink droplets are collected in the gutter 51. The ink collected in the gutter 51 is transferred by the diaphragm units 42 and 43 through the pipe 5c and returned to the ink tank 2.

The use of two diaphragm units 42 and 43 for ink transfer by the pipe 5c is in consideration of the ink transfer capacity of the diaphragm unit, and when the transfer capacity of the diaphragm unit is large, ink is used by using one diaphragm unit. May be transferred.

The pipe taken out from the lower part of the print head 3 and the ink tank 2 are connected by a pipe 5d, and an on-off valve 62 is arranged in the middle. The pipe 5d is for removing the air remaining in the print head 3 when the power of the printer 1 is turned on. By opening the on-off valve 62, the ink containing air is transferred and the ink tank is used. It is returned to 2.

The pipes 5e and 5h for transferring the ink taken out from the ink replenishment tank 81 to the ink tank 2 by using the diaphragm unit 44 are provided, and an on-off valve 63 is attached in the middle of the pipe 5e.

Similarly, pipes 5f and 5h for transferring the solvent taken out from the solvent replenishment tank 82 to the ink tank 2 using the diaphragm unit 44 are provided, and an on-off valve 64 is attached in the middle of the pipe 5f. ..

Further, pipes 5g and 5h for returning the ink taken out from the ink tank 2 to the ink tank 2 using the diaphragm unit 44 are provided, and an on-off valve 65 is attached in the middle of the pipe 5g. This pipe 5g is used to stir the ink in the ink tank 2.

The three pipes 5e, 5f and 5g described above also serve as a diaphragm unit 44 for ink transfer, so that the pipes 5e, 5f and 5g merge and are connected to the pipe 5h.

When replenishing ink to the ink tank 2, according to the instruction of the controller 9, the on-off valve 63 is opened, the on-off valves 64 and 65 are closed, and the diaphragm unit 44 is driven to charge the ink in the replenishment tank 81 to the ink tank 2. Transfer.

When replenishing the solvent to the ink tank 2, the on-off valve 64 is opened, the on-off valves 63 and 65 are closed, and the diaphragm unit 44 is driven to supply the solvent in the replenishment tank 82 to the ink tank 2 according to the instruction of the controller 9. Transfer.

<Reduction of pulsation of ink fluid>
As described above, the pressure and viscosity of the ink supplied to the print head 3 are adjusted to the optimum values for maintaining the print quality by the control of the controller 9, but the controller 9 causes the pulsation of the ink fluid. It cannot be reduced. In the present embodiment, the pulsation reducing means 10 composed of the damper 11, the static mixer 12, and the check valve 13 is attached in the middle of the pipe 5a.

In the printer described in Patent Document 2 described above, the damper 11 and the check valve 13 are used as means for reducing the pulsating flow of the ink fluid supplied to the print head 3, but the pulsating flow can be sufficiently reduced. There wasn't.

Through experiments, the inventors have found that by arranging the static mixer 12 in addition to these, a practically sufficient pulsating flow reducing effect can be obtained.

The static mixer 12 is a static mixer that does not have a drive unit and agitates by utilizing the flow of a fluid, and a plurality of elements in which a rectangular plate is twisted are arranged in the mixer. The fluid passing through the mixer is sequentially agitated and mixed by a plurality of elements having different twisting directions.

Static mixers are generally used for mixing high-viscosity fluids (adhesives, foodstuffs), heat exchange and soaking of fluids, and never for reducing pulsation of ink fluids. It was found that when the inventors tried to insert a static mixer between the damper and the check valve, it exerted a remarkable effect on reducing pulsation.

FIG. 5 shows the pulsation values measured by the pressure sensor 71 with and without the static mixer 12 inserted between the damper 11 and the check valve 13. Further, FIG. 6 shows a printing example at that time. In the experiment, an example is shown in which a horizontal straight line is printed on the side surface of a packing box that is transferred on a conveyor at a constant speed.

For comparison, FIGS. 5 and 6 show the experimental results when the pulsation of the ink fluid is reduced by using the first method described in the above-mentioned Patent Document 1, that is, a regulator.

In the experiment, a printer manufactured by Kishu Giken Kogyo (model name: CCS2800) was used, and one with a static mixer inserted between the damper and the check valve and one without the static mixer were used. As a printer using a regulator, a printer manufactured by Kishu Giken Kogyo (model name: CCS3000L) was used.

As is clear from FIG. 5, the pulsation value was 0.85 kPa when the static mixer was inserted, and the pulsation was reduced by about 75% as compared with the pulsation value of 3.35 kPa when the static mixer was not inserted. This value is comparable to the pulsation value of 0.70 kPa when the regulator is used.

FIG. 6 shows a printing example when the static mixer is inserted (a) and when it is not inserted (b). When the static mixer is not inserted (b), the dots formed on the surface to be printed are displaced in the vertical direction due to the influence of the pulsation of the ink fluid, and the print quality is clearly deteriorated as compared with the case (a) when the static mixer is inserted. Is. On the other hand, in the printing example of the case where the static mixer is inserted (a), there is no significant difference in the displacement in the vertical direction as compared with the case where the regulator is adopted (c).

As described above, the static mixer has the effect of reducing the pulsation of the ink fluid, and by combining this with the damper and the check valve, a practically sufficient effect as a pulsation reducing means can be obtained, and as a result, a sufficient effect can be obtained. Since no regulator is required, it also contributes to printer cost reduction.

In the above-described embodiment, the experimental results when the damper, the static mixer and the check valve are arranged in this order from the upstream side are shown, but as a result of the experiment, the arrangement of the damper, the static mixer and the check valve is shown. It was found that almost the same effect can be obtained even if the arrangement is changed.

Further, the pulsation reducing means according to the present invention is effective when ink is delivered by using a dial flam pump, but the same effect can be obtained when another pump that causes pulsation in the fluid is adopted. It is clear that.

Further, the structure of the static mixer is not limited to the one in which a plurality of elements obtained by twisting a rectangular plate as described above are arranged. The same effect can be obtained regardless of the structure adopted as long as the stirring is performed by utilizing the flow of the fluid.

1 Ink printer 2 Ink tank 3 Printhead 4 Pump 5, 5a-5i Piping 9 Controller 10 Pulse flow reduction means 11 Damper 12 Static mixer 13 Check valve 21 Tank body 22 Lid 30 Gun 31 Gun body 32 Ultrasonic transducer 33 Nozzle 34 Charging electrode 35 Pulse power supply 36a, 36b Detection electrode 37 Voltage detection means 38 Deflection electrode 39 DC power supply 41-44 Diaphragm unit 51 Gutter 52-54 Filter 55 Squeeze 61-65 On-off valve 66 Ink discharge valve 71 Pressure sensor 72 Temperature sensor 73 Liquid level detection sensor 81, 82 Replenishment tank 83 Coagulation tank 91 CPU
92 ROM
93 RAM
94 Input / Display Panel 95 Storage Device 96 Bus Line I Ink

In order to achieve the above object, the inkjet printer according to the present invention
An ink tank that stores ink and
A print head that ejects the ink supplied from the ink tank toward the surface of the printed matter, and
A gutter that collects ink that is not used for printing among the ink ejected from the nozzle of the print head,
A pump for transferring ink from the ink tank to the print head and transferring ink collected by the gutter to the ink tank is provided.
A pulsation reducing means for reducing the pulsation of the ink fluid is attached to the pipe connecting the ink tank and the print head.
The pulsation reducing means is characterized in that the damper, the static mixer and the check valve are arranged in this order according to the flow of ink .

Here, it is preferable that the check valve blocks the transfer of ink when the pressure of the ink transferred in the pipe does not exceed a predetermined value, and transfers the ink when the pressure exceeds a predetermined value. ..

Claims (5)

An ink tank that stores ink and
A print head that ejects the ink supplied from the ink tank toward the surface of the printed matter, and
A gutter that collects ink that is not used for printing among the ink ejected from the nozzle of the print head,
A pump for transferring ink from the ink tank to the print head and transferring ink collected by the gutter to the ink tank is provided.
A pulsation reducing means for reducing the pulsation of the ink fluid is attached to the pipe connecting the ink tank and the print head, and the pulsation reducing means is characterized by being composed of a damper, a static mixer, and a check valve. Inkjet printer. The inkjet printer according to claim 1, wherein the pulsation reducing means arranges a damper, a static mixer, and a check valve in this order according to the flow of ink. The check valve blocks the transfer of ink when the pressure of the ink transferred in the pipe does not exceed a predetermined value, and transfers the ink when the pressure exceeds a predetermined value, claim 1 or 2. Inkjet printer described in. The inkjet printer according to any one of claims 1 to 3, wherein a diaphragm pump is used as the pump. A pressure sensor for detecting the pressure of the ink fluid is attached between the pulsation reducing means and the print head in the pipe, and the pressure sensor detects the pressure of the ink fluid flowing in the pipe. The inkjet printer according to any one of 4.

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