JP2011183762A - Liquid ejector - Google Patents

Abstract

The present invention sufficiently discharges bubbles adhering to an ejection head.
When fine bubbles adhere to the ejection head, a negative pressure is generated from the ejection nozzle into the ejection head with the on-off valve provided on the liquid passage connecting the liquid storage portion and the ejection head closed. Apply pressure. By reducing the pressure in the ejection head in this way, the liquid is ejected from the ejection nozzle while increasing the size of the fine bubbles attached in the ejection head. Since the resonance frequency decreases as the size of the bubble increases, the bubble is resonated by the operation of ejecting the liquid and detached from the ejection head. As a result, it is possible to sufficiently discharge the bubbles attached in the ejection head.
[Selection] Figure 5

Description

  The present invention relates to a technique for ejecting liquid from an ejection head.

A so-called inkjet printer can print a high-quality image by ejecting an accurate amount of ink to a precise position from a fine ejection nozzle. In addition, by utilizing this technique and ejecting various liquids instead of ink toward the substrate, it is also possible to manufacture electrodes, sensors, biochips, and the like.

In such a technique, the ejection nozzle is provided in the ejection head. In addition, liquid cannot be ejected from the ejection nozzle when the ejection head is not filled with liquid, such as when shipped from the factory. The filling operation (initial filling operation) is performed. At the time of initial filling, bubbles are mixed into the liquid by entraining air in the flow path for supplying the liquid to the ejection head or entraining air in the ejection head. If the liquid is ejected from the ejection nozzle in this state, bubbles are clogged in the ejection nozzle and the liquid cannot be ejected well. Therefore, by driving the suction pump connected to the cap while the spray nozzle is covered with the cap, bubbles mixed in the liquid are sucked from the spray nozzle. In addition, prior to the initial filling, a technique for making it difficult for bubbles to remain in the ejection head during initial filling by moistening the flow path for guiding the liquid to the ejection head and the ejection head with a cleaning liquid has been proposed (Patent Document). 1).

JP 2009-112885 A

However, the above-described prior art has a problem that bubbles in the ejection head cannot be sufficiently removed. That is, a certain amount of bubbles can be discharged from the jet head by the conventional technique, but fine bubbles are difficult to discharge sufficiently by adhering to the jet head. For this reason, the remaining bubbles may block the ejection nozzle during the ejection of the liquid and suddenly cause the liquid to be unable to be ejected.

The present invention has been made to solve the above-described problems of the prior art,
An object of the present invention is to provide a technique for sufficiently discharging bubbles adhering to an ejection head.

In order to solve at least a part of the problems described above, the liquid ejecting apparatus of the present invention employs the following configuration. That is,
A liquid ejecting apparatus that ejects liquid from an ejection nozzle provided in an ejection head,
A liquid passage that guides the liquid from the liquid storage portion in which the liquid is stored to the ejection head;
Negative pressure acting means for applying a negative pressure from the ejection nozzle into the ejection head in a state where the on-off valve provided on the liquid passage is closed;
The present invention includes a bubble discharging unit that discharges bubbles in the ejection head by ejecting a liquid from the ejection nozzle in a state where a negative pressure is applied to the ejection head.

In such a liquid ejecting apparatus of the present invention, when the bubbles in the ejecting head are discharged, the on-off valve on the liquid passage is closed and negative pressure is applied from the ejecting nozzle to the ejecting head,
In this state, liquid is ejected from the ejection nozzle.

When negative pressure acts in the ejection head, the pressure in the ejection head decreases. Along with this, the volume of fine bubbles adhering in the ejection head increases, and the resonance frequency of the bubbles decreases. Although the detailed mechanism will be described later, when the resonance frequency of the bubble is lowered, the bubble is likely to be resonated due to the pressure fluctuation of the liquid generated in the ejection head in association with the operation of ejecting the liquid from the ejection nozzle. Therefore, even when fine bubbles adhere to the ejection head, the bubbles can be easily discharged from the ejection nozzle by detaching the adhered bubbles by resonance. By doing so, it is possible to suppress a situation in which bubbles adhering to the inside of the jet head peel off during jetting of the liquid and block the jet nozzle.

In the liquid ejecting apparatus of the present invention described above, the liquid may be ejected from the ejecting nozzle while applying a negative pressure to the ejecting head by the negative pressure acting unit.

In this way, as the pressure in the ejection head decreases, the bubbles that have started to resonate are desorbed, so that the bubbles attached to the ejection head can be quickly discharged.

In the liquid ejecting apparatus of the present invention described above, the liquid may be ejected from the ejecting nozzle after the pressure in the ejecting head is reduced by the negative pressure acting unit.

In a state where the resonance frequency of the bubble is not lowered (that is, a state in which a negative pressure for enlarging the bubble is not acting in the ejection head), even if liquid is ejected from the ejection nozzle, the bubble does not resonate. Bubbles are not discharged. Therefore, if the liquid is ejected from the ejection nozzle after the resonance frequency of the bubbles is lowered, it is possible to avoid wasteful ejection of the liquid.

It is explanatory drawing which showed the rough structure of the liquid-jet apparatus of a present Example. It is explanatory drawing which showed the internal mechanism of the carriage. It is explanatory drawing which showed the mode in the jet head after initial filling. It is explanatory drawing which showed the reason why it is difficult to detach | desorb the bubble in an ejection head with the harmonic component of flushing operation | movement. It is explanatory drawing which showed the bubble removal | desorption method of a present Example. It is explanatory drawing shown about the relationship between the resonant frequency of a bubble and the magnitude | size of a bubble. It is explanatory drawing which showed the bubble removal | desorption method of the modification.

Hereinafter, in order to clarify the contents of the present invention described above, examples will be described in the following order.
A. Device configuration:
B. The bubble desorption method of this example:
C. Variations:

A. Device configuration :
FIG. 1 is an explanatory diagram showing a rough configuration of a liquid ejecting apparatus according to the present embodiment, using a so-called ink jet printer as an example. As shown, inkjet printer 1
0 is a carriage 2 that forms ink dots on the print medium 2 while reciprocating in the main scanning direction.
0, a drive mechanism 30 for reciprocating the carriage 20, a platen roller 40 for feeding the print medium 2, and a maintenance mechanism 50 for performing maintenance so that printing can be normally performed. The carriage 20 is provided with an ink cartridge 26 that contains ink, a carriage case 22 in which the ink cartridge 26 is mounted, an ejection head 24 that ejects ink, and the like. A plurality of ejection nozzles are provided on the bottom side of the ejection head 24 (the side facing the print medium 2). The ink in the ink cartridge 26 is guided to the ejection head 24, and is directed from the ejection nozzle toward the print medium 2. Thus, it is possible to eject ink.

In the illustrated inkjet printer 10, it is possible to print a color image using four types of inks of cyan, magenta, yellow, and black. An ejection nozzle is provided for each type of ink. And
Each ejection nozzle is supplied with ink from a corresponding ink cartridge 26 via a passage.

The drive mechanism 30 for reciprocating the carriage 20 includes a timing belt 32 having a plurality of tooth shapes formed therein, a drive motor 34 for driving the timing belt 32, and the like. A part of the timing belt 32 is fixed to the ejection head 24. When the timing belt 32 is driven, the carriage 20 is reciprocated in the main scanning direction while being guided by the guide rail 36 extended in the main scanning direction. Is possible. In addition, the platen roller 40 that feeds the print medium 2 is driven by a drive motor or a gear mechanism (not shown), and can feed the print medium 2 by a predetermined amount in the sub-scanning direction.

The maintenance mechanism 50 is provided in a region called a home position outside the printing region, and the cap 52, the suction pump 54 provided at a position below the cap 52, and the waste liquid provided further below the suction pump 54. It consists of a tank 56 and the like. In the maintenance mechanism 50, various maintenance operations for discharging ink whose properties have deteriorated in the ejection head 24 are performed. That is, the cap 52 is pressed against the bottom surface of the ejection head 24 by a lifting mechanism (not shown), and the suction pump 54 is driven in this state to generate a negative pressure in a closed space formed between the cap 52 and the ejection head 24. . By doing so, it is possible to perform an operation (cleaning operation) of sucking out ink having deteriorated properties from the ejection nozzle.
In addition, an operation (flushing operation) of discharging the ink having deteriorated properties into the cap 52 by ejecting ink from the ejection head 24 toward the cap 52 in a state where the ejection head 24 and the cap 52 are separated from each other. It is also possible to do.

A control unit 60 that controls the overall operation of the inkjet printer 10 is mounted on the back surface of the inkjet printer 10. Operations such as reciprocating the ejection head 24, feeding the print medium 2 and ejecting ink from the ejection nozzles, and various maintenance operations performed by the maintenance mechanism 50 are all performed by the control unit 60. It is controlled. Under such a control unit 60, the inkjet printer 10 drives the ejection head 24 while ejecting the print medium 2 to eject paper, thereby ejecting ink.
Print the image on top.

FIG. 2 is an explanatory view showing an internal mechanism by taking a cross section of the carriage 20.
As described above, the ejection head 24 of the present embodiment is provided with a plurality of ejection nozzles for each type of ink. However, in order to avoid complication of the drawing, in FIG. Only one ejection nozzle corresponding to this ink and a mechanism for supplying ink from the ink cartridge 26 to the ejection nozzle are shown as representatives.

The ink cartridge 26 is connected to a common ink chamber 72 provided in the ejection head 24 via an internal passage 70 of the carriage case 22, and the common ink chamber 72 is an individual ink chamber 74 provided for each ejection nozzle. Connected to each other through a passageway. Therefore, the ink supplied from the ink cartridge 26 to the ejection head 24 is distributed to the individual ink chamber 74 via the common ink chamber 72. A piezo element 76 is provided on the individual ink chamber 74, and when a voltage is applied to the piezo element 76, the piezo element is deformed to pressurize the individual ink chamber 74, thereby It is possible to eject ink from a connected ejection nozzle. An on-off valve 78 is provided on the internal passage 70 connecting the ink cartridge 26 and the common ink chamber 72, and the on-off valve 78 is normally open. The reason why the on-off valve 78 is provided on the internal passage 70 will be described in detail later.

The ink jet printer 10 of the present embodiment as described above is not yet filled with ink in the ejection head 24 when shipped from the manufacturer's factory. Therefore, before the inkjet printer 10 starts printing, an operation (initial filling operation) for filling ink into the ejection head 24 for the first time is performed. That is, when the ink cartridge 26 is mounted on the carriage case 22, the ejection head 24 moves to the home position where the maintenance mechanism 50 is provided. Subsequently, the cap 52 is pressed against the bottom surface of the ejection head 24, and the suction pump 54 is driven in this state. When the negative pressure generated in the cap 52 is applied to the ejection nozzle in this way, air in the ejection head 24 is sucked out of the ejection nozzle,
The ink sucked from the ink cartridge 26 is supplied to the ejection head 24. As a result, the ink supplied from the ink cartridge 26 fills the ejection head 24, so that the ejection head 24 is filled with ink.

Here, in the process of supplying ink from the ink cartridge 26 to the ejection head 24,
Bubbles are mixed in the ink by the air in the ejection head 24 being entrained. If ink is ejected from the ejection nozzle in this state, bubbles are clogged in the ejection nozzle, making it impossible to eject the ink well. Therefore, at the initial filling of ink, after the ejection head 24 is filled with ink, the suction pump 54 is driven for a while to continue the cleaning operation, whereby the bubbles in the ejection head 24 can be discharged together with the ink. Done. By doing so, bubbles that are somewhat large are discharged from the ejection head 24. On the other hand, as shown below,
It is difficult to sufficiently discharge even fine bubbles in the ejection head 24.

FIG. 3 is an explanatory view showing the inside of the ejection head 24 after the initial ink filling is completed. As described above, the common ink chamber 72 and the individual ink chambers 7 are provided inside the ejection head 24.
4 is provided (see FIG. 2). By providing the common ink chamber 72 and the individual ink chamber 74 in this manner, the inside of the ejection head 24 has a complicated structure, and therefore, there are places where fine bubbles are likely to adhere in the ejection head 24. . Therefore, as shown in FIG. 3, after the initial filling is finished, fine bubbles are attached in the ejection head 24. When the ink jet printer 10 is used in this state, the bubbles are peeled off from the ejection head 24 during printing, and the bubbles enter the individual ink chamber 74. As a result, if the air bubbles block the ejection nozzle provided in the individual ink chamber 74, ink cannot be ejected.

Further, it is difficult to discharge the bubbles adhering in the ejection head 24 even if the flushing operation is executed. This is due to the following reason. That is, from the viewpoint of detaching bubbles attached to the ejection head 24, the effect obtained by performing the flushing operation is the same as the effect of generating the ink flow in the ejection head 24 and the ejection head 24. And the effect of causing pressure fluctuations in the ink inside. here,
When the flow of ink generated in the ejection head 24 is considered, the flow of ink due to the flushing operation is considered to be slower than the flow of ink generated by the above-described cleaning operation. From this, bubbles remaining in the ejection head 24 after the cleaning operation are
It is difficult to separate by the flow of ink by the flushing operation.

In addition, it is difficult to desorb bubbles adhering to the ejection head 24 due to the effect of causing pressure fluctuations in the ink in the ejection head 24 by the flushing operation.
That is, since the fine bubbles adhering in the ejection head 24 are very small (typically about 40 μm in diameter), the period of the pressure fluctuation due to the flushing operation is too long, and the bubbles simply increase or decrease slowly. The attached bubbles cannot be detached. Of course, as will be described below, the pressure fluctuation generated in the ejection head 24 by the flushing operation includes a component having a shorter frequency and higher frequency (harmonic component) than the frequency of the flushing operation. However, because the magnitude of the harmonic component is small,
It is difficult to detach bubbles attached to the ejection head 24. This point will be described in detail below.

FIG. 4 is an explanatory diagram showing the reason why it is difficult to detach bubbles in the ejection head 24 due to harmonic components of the flushing operation. In FIG. 4, the voltage waveform (drive pulse) applied to the piezo element 76 for the purpose of driving the ejection head 24 during the flushing operation will be described first with reference to FIG. 4B, frequency components included in the pressure fluctuation in the ejection head 24 when a driving pulse for the flushing operation is applied will be described.

As shown in FIG. 4A, the driving pulse of the flushing operation of the present embodiment is a voltage waveform in which a substantially trapezoidal waveform is periodically repeated over time. When this drive pulse is applied to the piezo element 76, the piezo element 76 contracts in a portion where the applied voltage increases, and the piezo element 76 expands in a portion where the applied voltage decreases. Thus, the piezo element 7
6 repeats the expansion and contraction movement, whereby the individual ink chamber 74 is periodically pressurized, and the ejection head 2
Pressure fluctuations occur in 4. Here, the driving pulse for the flushing operation includes a plurality of components having different frequencies. As a result, as shown in FIG. 4B, the frequency of the pressure fluctuation in the ejection head 24 due to the flushing operation is also increased. A plurality of different components are included.

Here, as described above, since the fine bubbles adhering in the ejection head 24 are very small, the low frequency component included in the flushing operation is hardly affected. Therefore, the component that effectively acts on the fine bubbles adhering to the inside of the ejection head 24 is a harmonic component included in the flushing operation. Further, in order to remove fine bubbles adhering to the ejection head 24 using the harmonics of the flushing operation, it is necessary that the amount of harmonic components is a certain amount. From this point, looking at the amount of the frequency component included in the flushing operation, as shown by the hatching in FIG. 4B, the low frequency component (basic) within the pressure fluctuation of the ejection head 24 Waves and harmonics close to the frequency of the fundamental wave) have a certain size, but more harmonic components do not have a sufficient size. As a result, it is difficult to remove fine bubbles adhering to the ejection head 24 by the flushing operation.

As described above, when the printing operation is performed in a state where fine bubbles in the ejection head 24 are attached, the bubbles attached in the ejection head 24 may be peeled off, and the above-described adverse effects may occur. Therefore, in the ink jet printer 10 of the present embodiment, the fine bubbles attached in the ejection head 24 at the initial filling of the ink are desorbed by employing the following bubble desorbing method.

B. Bubble elimination method of this example:
FIG. 5 is an explanatory view showing a method for detaching fine bubbles adhering to the ejection head 24. As described above, when the ink is initially filled in the ejection head 24, the suction pump 54 is driven with the cap 52 pressed against the bottom surface of the ejection head 24. Injection head 24
After the ink is filled in, since fine bubbles are adhered in the ejection head 24 (see FIG. 3), the bubbles in the ejection head 24 are desorbed as follows. First, as shown in FIG. 5A, the suction pump 54 is stopped while the cap 52 is pressed against the bottom surface of the ejection head 24. Then, the internal passage 7 connecting the ink cartridge 26 and the ejection head 24 is used.
After closing the on-off valve 78 provided on 0, the flushing operation is executed by driving the ejection head 24.

At this time, pressure fluctuations occur in the ink in the ejection head 24 due to the flushing operation, but as described above, the frequency at which the fine bubbles attached to the ejection head 24 are effectively desorbed in the components of the flushing operation. The component is not sufficiently contained (see FIG. 4B).
Therefore, fine bubbles are not detached due to pressure fluctuation in the ejection head 24.

From this state, as shown in FIG. 5B, the suction pump 54 is driven while continuing the flushing operation. At this time, since the on-off valve 78 on the internal passage 70 is closed, the connection between the ejection head 24 and its upstream side is cut off. Accordingly, when air is sucked out from the cap 52 by the cleaning operation, negative pressure is accumulated in a closed space formed between the cap 52 and the ejection head 24.

When the negative pressure is accumulated in the cap 52, the negative pressure acts on the ejection head 24 via the ejection nozzle, so that the pressure in the ejection head decreases. As a result, the pressure applied to the fine bubbles in the ejection head 24 decreases, and as a result, the fine bubbles in the ejection head 24 gradually increase. Thus, the flushing operation is continued while the bubbles in the ejection head 24 become larger. And when the bubble adhering in the ejection head 24 reaches a certain size, the bubble itself starts to vibrate greatly. The phenomenon that the bubbles vibrate in this way is a phenomenon called “resonance” of the bubbles. The reason why the bubbles in the ejection head 24 resonate at this time will be described in detail later.

When the bubbles adhering in the ejection head 24 are resonated in this way, the bubbles themselves vibrate to generate a force that repels the adhesion location in the ejection head 24. When this force increases, as shown in FIG. 5C, bubbles attached to the common ink chamber 72 in the ejection head 24 and the wall surface in the individual ink chamber 74 are detached from the ejection head 24.

When the bubbles adhering to the ejection head 24 are removed as described above, finally, the internal passage 7
Open on-off valve 78 on zero. In this way, the ejection head 24 and its upstream side are connected,
Ink can be supplied from the ink cartridge 26 to the ejection head 24. As a result, the ink is strongly sucked out of the ejection nozzle by the negative pressure accumulated in the cap 52. At this time, bubbles are generated in the common ink chamber 72 or the individual ink chamber 7 in the ejection head 24.
4 is detached from the wall surface in FIG. 4 (see FIG. 5C), and it is easier to suck out the bubbles as compared with the state in which the bubbles are attached in the ejection head 24. Accordingly, bubbles are sucked out from the ejection nozzle together with the ink and discharged out of the ejection head 24.

As described above, in the inkjet printer 10 according to the present embodiment, when the fine bubbles attached in the ejection head 24 are removed, the on-off valve 7 is used while performing the flushing operation.
By executing the cleaning operation in a state where 8 is closed, the bubbles in the ejection head 24 are enlarged. In this way, since the bubbles resonate when they grow to a certain size, they can be detached from the ejection head 24. Hereinafter, this point will be described in detail.

FIG. 6 is an explanatory diagram showing the relationship between the bubble resonance frequency and the bubble size. Although detailed explanation is omitted, according to the Minnaert formula that defines the resonance frequency of the bubble,
The resonant frequency of the bubble is inversely proportional to the radius of the bubble. Therefore, as shown in FIG. 6, the larger the bubble, the lower the resonance frequency of the bubble.

Further, in FIG. 6, among the components included in the above-described flushing operation, a region including the frequency of a component that can sufficiently resonate a bubble (that is, a component having a large content, see FIG. 4B),
It is indicated by the shaded area. As shown in the figure, if the fine bubbles adhering in the ejection head 24 become large, the resonance frequency of the bubbles can be lowered to the frequency of the component that can sufficiently resonate the bubbles. As a result, when the bubbles in the ejection head are resonated by the flushing operation, they are detached from the ejection head 24. For the reasons described above, in the inkjet printer 10 of this embodiment, when fine bubbles adhering to the ejection head 24 are removed, the ejection operation is performed by performing the cleaning operation with the on-off valve 78 closed. The flushing operation is performed while enlarging the bubbles in the head 24.

By adopting the bubble desorption method of the present embodiment as described above, the bubbles can be easily desorbed from the inside of the ejection head 24 to which fine bubbles easily adhere, and the bubbles are discharged by a maintenance operation such as cleaning. It becomes easy. Accordingly, it is possible to suppress a situation in which bubbles remain in the ejection head 24 during maintenance, and as a result, the bubbles remaining in the ejection head 24 block the ejection nozzle during the ejection of the liquid, and the liquid cannot be ejected suddenly. It is possible to make it difficult for the negative effects to occur.

Further, the phenomenon that fine bubbles adhere to the ejection head 24 as described above is not a phenomenon that is limited to the initial ink filling. For example, even when the ink is used up and a new ink cartridge 26 is replaced, fine bubbles may adhere to the ejection head 24. If the inkjet printer 10 has been used for a long time, It is also possible that bubbles generated in the ink adhere to the ejection head 24 due to, for example, the melted air being bubbled due to a temperature change. The bubble detachment method of this embodiment is a method that can cope with any of these situations. Therefore, not only during the initial ink filling, but if the bubble detachment method of this embodiment is periodically executed, bubbles attached to the ejection head 24 can be detached and easily discharged. Is possible.

C. Modified example:
In the above-described embodiment, when bubbles adhering to the ejection head 24 are removed, a flushing operation is performed while performing a cleaning operation with the on-off valve 78 on the internal passage 70 provided in the carriage 20 closed. Explained. However, the cleaning operation and the flushing operation are not necessarily performed at the same time, and may be performed as follows, for example.

FIG. 7 is an explanatory view showing a bubble detachment method according to a modification. As described above, the on-off valve 78
When the cleaning operation is performed in the closed state, the bubbles in the ejection head 24 gradually increase, and the resonance frequency of the bubbles decreases accordingly. Here, since the speed at which the bubbles increase in the ejection head 24 is not so fast, it takes a certain time for the resonance frequency of the bubbles to reach the frequency of the effective component included in the drive pulse of the flushing operation. . Therefore, even if the flushing operation is performed during this period, the bubbles in the ejection head 24 do not resonate. Therefore, when the bubbles in the ejection head 24 are detached, first, as shown in FIG. 7A, only the cleaning operation is performed with the on-off valve 78 closed. After a while, when the bubbles in the ejection head 24 become sufficiently large and the resonance frequency of the bubbles reaches the frequency of the effective component in the drive pulse, the flushing operation is started as shown in FIG. To do.

Also by such a method, bubbles adhering in the ejection head 24 can be sufficiently resonated and detached from the ejection head 24. Further, since the flushing operation is not performed until the bubbles in the ejection head 24 reach a sufficient size, it is possible to save power consumed by performing the flushing operation.

Although various embodiments have been described above, the present invention is not limited to all the above embodiments, and can be implemented in various modes without departing from the scope of the invention.

2 ... print medium, 10 ... inkjet printer, 20 ... carriage,
22 ... Carriage case, 24 ... Ejecting head, 26 ... Ink cartridge,
30 ... Drive mechanism, 32 ... Timing belt, 34 ... Drive motor,
36 ... Guide rail, 40 ... Platen roller, 50 ... Maintenance mechanism,
52 ... Cap, 54 ... Suction pump, 56 ... Waste liquid tank,
60 ... Control unit, 70 ... Internal passage, 72 ... Common ink chamber,
74 ... Individual ink chamber, 76 ... Piezo element, 78 ... Open / close valve

Claims (3)

A liquid ejecting apparatus that ejects liquid from an ejection nozzle provided in an ejection head,
A liquid passage that guides the liquid from the liquid storage portion in which the liquid is stored to the ejection head;
Negative pressure acting means for applying a negative pressure from the ejection nozzle into the ejection head in a state where the on-off valve provided on the liquid passage is closed;
A liquid ejecting apparatus comprising: bubble ejecting means for ejecting air bubbles in the ejecting head by ejecting liquid from the ejecting nozzle in a state where a negative pressure is applied to the ejecting head. The liquid ejecting apparatus according to claim 1,
The liquid discharge means is configured to apply a negative pressure in the ejection head by the negative pressure action means,
A liquid ejecting apparatus which is means for ejecting the bubbles by ejecting liquid from the ejecting nozzle. The liquid ejecting apparatus according to claim 1,
The bubble ejecting unit is a unit for ejecting bubbles by ejecting liquid from the ejection nozzle after reducing the pressure in the ejection head using the negative pressure acting unit.

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