JP7114404B2 - Liquid ejection device and liquid ejection head - Google Patents

Description

The present invention relates to a liquid ejection apparatus and a liquid ejection head that eject liquid by circulating it through a liquid ejection head.

In a recording apparatus (liquid ejection apparatus) using a recording head (liquid ejection head) capable of ejecting ink (liquid) from ejection openings, an ink flow passing through the ejection openings is generated to remove thickened ink, bubbles, and contaminants. A removal configuration has been proposed in recent years.

Further, Japanese Patent Application Laid-Open No. 2002-200002 describes a configuration that can reverse the direction of ink supply to a print head. Specifically, a switching mechanism consisting of a pump and a plurality of drive valves is provided between the head and the two ink tanks, and the direction of ink flow from one ink tank through the head to the other ink tank is mutually switched. A switchable configuration is disclosed. Ink flow is produced by pumping and switching of flow direction is accomplished by switching valves. Reversing the direction of ink flow agitates the ink within the ink tank and flow path and prevents flow path clogging due to settling and deposition of solids.

WO2017/000997

In the printing apparatus disclosed in Japanese Patent Application Laid-Open No. 2002-100001, refilling (supplementation) of ink to the printing head is performed through a flow path on the upstream side of the printing head in the ink flow direction. Further, a pump located downstream of the print head in the ink flow direction prevents refilling due to reverse flow of ink from the downstream flow path. Therefore, during printing under printing conditions such as high-duty printing, in which a large amount of ink is ejected in a short period of time, refilling of ink from the upstream flow path is insufficient, and the pressure inside the print head is partially increased. There is a risk of change. Specifically, among the plurality of ejection openings in the print head, the ejection openings that repeat the ink ejection operation have a negative pressure on the downstream side of the ejection openings. Due to this negative pressure, the flow rate of ink passing through the vicinity of other ejection openings in the non-ejecting state of ink increases, and the negative pressure at the ejection openings greatly increases, making proper ejection difficult and resulting in poor quality of the recorded image. There is a risk of causing a decrease in Such deterioration in the quality of the printed image becomes more conspicuous as the number of ejection openings in the print head increases, and as the number of ejection openings in the non-ejection state increases during high-duty printing.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid ejection head which is used by circulating liquid inside even when not recording, while maintaining the liquid circulation function and improving the refillability of the liquid to the liquid ejection head. To stabilize the ejection state of liquid in a

A liquid ejecting apparatus according to the present invention includes an ejection port for ejecting liquid, a pressure chamber containing liquid to be ejected from the ejection port, an element for generating energy for ejecting the liquid in the pressure chamber, and liquid. a first tank and a second tank that can accommodate a liquid, a flow path that communicates the first tank and the second tank via the pressure chamber, and a flow direction of the liquid in the flow path in the first tank a switching means for switching between a first direction in which the liquid flows from the pressure chamber to the second tank and a second direction in which the liquid flows from the second tank to the first tank; a pressure compensating means for supplying liquid to the downstream channel portion to compensate for a decrease in pressure in the downstream channel portion when the pressure in the downstream channel portion on the downstream side of is lower than or equal to a predetermined pressure; It is characterized by having

According to the present invention, the pressure is controlled by appropriately replenishing the liquid according to the pressure state inside the liquid ejection head. As a result, it is possible to improve the liquid refill property of the liquid ejection head and stabilize the ejection state of the liquid ejection head.

Further, according to the present invention, pressure control required for a plurality of flow paths can be performed using a common configuration. Therefore, it is possible to provide a compact liquid ejecting apparatus capable of stable ejection operation at low cost with a small number of parts.

1A and 1B are a schematic configuration diagram and a control block diagram of a printing apparatus according to a first embodiment; FIG. 2 is a schematic diagram showing an ink path of the printing apparatus of the first embodiment; FIG. 2 is a schematic diagram showing an ink path of the printing apparatus of the first embodiment; FIG. 2 is a schematic diagram showing an ink path of the printing apparatus of the first embodiment; FIG. 2 is a schematic diagram showing an ink path of the printing apparatus of the first embodiment; FIG. 4 is a schematic diagram showing a liquid supply unit and a valve unit of the first embodiment; FIG. 1 is a schematic diagram showing a liquid ejection head according to a first embodiment; FIG. 1 is an exploded view showing a liquid ejection head according to a first embodiment; FIG. FIG. 3 is a schematic diagram showing a channel member that constitutes the liquid ejection head of the first embodiment; FIG. 10 is an enlarged view of the X portion in FIG. 9; 11 is a cross-sectional view along line XI-XI of FIG. 10; FIG. It is a figure which shows the discharge module of 1st Embodiment. 4A and 4B are diagrams showing the structure of the recording element substrate of the first embodiment; FIG. FIG. 14 is a cross-sectional view along line XIV-XIV in FIG. 13; 4 is a plan view showing adjacent recording element substrates in the first embodiment; FIG. It is a figure which shows the negative pressure control unit of 1st Embodiment. FIG. 4 is a relational diagram between flow resistance and valve opening of the valve portion of the pressure control unit of the first embodiment; FIG. 10 is a schematic diagram showing an ink path of a printing apparatus according to a second embodiment; FIG. 11 is a schematic diagram showing an ink path of a printing apparatus according to a third embodiment; FIG. 11 is a schematic diagram showing ink paths during printing in a printing apparatus according to a fourth embodiment of the present invention; FIG. 11 is a schematic diagram showing ink paths during non-printing in the printing apparatus according to the fourth embodiment of the present invention; FIG. 14 is a schematic diagram showing another state of the ink path during non-printing in the printing apparatus according to the fourth embodiment of the present invention;

Preferred embodiments of the liquid ejecting apparatus of the present invention will be described below with reference to the drawings. However, the scope of the present invention is determined by the claims, and the following description does not limit the scope of the present invention. Moreover, the shape, arrangement, etc. described below do not limit the scope of the present invention.

[First embodiment]
(Inkjet recording device)
1(a) and 1(b) are a schematic configuration diagram and a control block diagram of an inkjet recording apparatus (hereinafter also simply referred to as a recording apparatus or apparatus) 1 that can be used as the liquid ejection apparatus of the present invention. As shown in FIG. 1A, a sheet S as a recording medium is conveyed in the X direction at a predetermined speed by the conveying means 700 so as to pass under the recording section 2 . The recording unit 2 is mainly composed of a liquid ejection head 300 and a liquid circulation unit 504 (not shown in FIG. 1A), which will be described later. Ejection ports for ejecting in the Z direction are arranged at a predetermined pitch in the Y direction.

In FIG. 1B, the CPU 500 controls the entire apparatus 1 according to the program stored in the ROM 501 and using the RAM 502 as a work area. The CPU 500 performs predetermined image processing on image data received from, for example, an externally connected host device 600 in accordance with programs and parameters stored in the ROM 501, thereby causing the liquid ejection head 300 to eject ink. Generate dispensing data. The liquid ejection head is driven according to the ejection data to eject ink at a predetermined frequency. During the ejection operation of the liquid ejection head 300, the transport motor 503 is driven to transport the sheet S in the X direction at a speed corresponding to the ejection frequency. As a result, an image is printed on the sheet S according to the image data received from the host device 600 .

The liquid circulation unit 504 is a unit for supplying the liquid (ink) to the liquid ejection head 300 while circulating it. Under the control of the CPU 500, the liquid circulation unit 504 controls the entire system for circulating ink, including the liquid supply unit 220 described later, the negative pressure control unit 3, the switching mechanism 4, and the like.

(Fluid flow path in recording device)
A fluid flow path of the entire inkjet recording apparatus will be described. 2 to 5 are schematic diagrams showing liquid flow paths (ink flow paths) in the liquid ejection apparatus (inkjet recording apparatus) according to the first embodiment of the invention.

The liquid ejection head 300 is connected to a first tank 21 and a second tank 22 that respectively contain four color inks (liquids) of C (cyan), M (magenta), Y (yellow), and K (black). be. For ease of understanding, the liquid ejection head 300 is shown divided for each color ink in the drawing, but in reality, one liquid ejection head 300 has ink flow paths for all four colors. The ink flow path is connected to the tank for each ink color.

FIG. 2 is a schematic diagram showing a fluid flow path (ink flow path and gas flow path) in a standby state (non-printing state) of a printing operation by the printing apparatus. A main tank 1002 capable of containing a large amount of ink and being replaceable is connected to the first tank 21 for each color ink via a filter 1001 and an ink joint 8 . The main tank 1002 has an air communication hole (not shown). Therefore, when the ink in the ink flow path is consumed due to the ejection operation of the liquid ejection head 300 and maintenance processing (suction recovery, etc.), the signal from the remaining amount detection mechanism (not shown) in the first tank Ink can be replenished from the main tank 1002 to the first tank 21 accordingly.

The first tank 21 and the second tank 22 contain inks of corresponding colors, and in a normal state, there are an air portion (upper layer) and an ink portion (lower layer). An air connection port 23 is provided on the upper walls of the first tank and the second tank to communicate the air portion with the outside, and an ink connection port 20 is provided on the lower side of the side wall to connect the ink portion and the liquid ejection head 300. is provided.

Air can flow in and out of the first tank 21 and the second tank 22 through the respective air connection ports 23 . A gas-liquid separation membrane 24 is provided at each air connection port of the first tank and the second tank. The gas-liquid separation film 24 has a function of preventing ink from entering the air pipe (air path) and causing color mixture when the main body of the recording apparatus is overturned. Therefore, the gas-liquid separation film 24 preferably has low flow resistance and low ink permeability. For example, a water-repellent filter can be preferably used.

The air connection port 23 of the first tank of each color is connected to the common switching mechanism 4 via the individual valve 5 (labeled as V2). The air connection ports 23 of the second tanks of each color are commonly connected to the switching mechanism 4 without intervening another valve. As described above, the air connection port 23 of the first tank 21 is connected to the first pressure adjustment passage 25 for adjusting the pressure in the first tank 21. Similarly, the air connection port 23 of the second tank 22 is connected to is connected to the second pressure regulation passage 26 . Both the first pressure regulation passage 25 and the second pressure regulation passage 26 are connected to the switching mechanism 4 and the negative pressure control unit 3 .

The ink portion of the first tank is liquid-connected to the liquid ejection head 300 via the supply valve 6 (denoted as V3), and communicates with the first common flow path 12 in the liquid ejection head 300 corresponding to each color. there is The ink portion of the second tank 22 is connected to the liquid ejection head 300 without any other valve, and communicates with the second common flow path 13 in the liquid ejection head 300 corresponding to each color.

A portion consisting of the first tank 21, the second tank 22, the filter 1001, and the supply valve (V3) is hereinafter referred to as a liquid supply unit 220. FIG. Although these components of the liquid supply unit 220 are described as integrated in this embodiment, they may be separately provided.

The switching mechanism 4 includes four on-off valves (indicated by V1A, V1B, V1C, and V1D), a circulation path (C) for cyan, a circulation path (M) for magenta, a circulation path (Y) for yellow, They act in common on the circulation path (K) for black. Specifically, one side of each of the first on-off valve V1A and the fourth on-off valve V1D is connected to the four air connection ports 23 of the first tank 21 . One side of each of the second on-off valve V1B and the third on-off valve V1C is connected to the four air connection ports 23 of the second tank 22 . The other side of each of the first on-off valve V1A and the second on-off valve V1B is connected to the first pressure control mechanism 31 (H) in the negative pressure control unit 3 . The other side of each of the third on-off valve V1C and the fourth on-off valve V1D is connected to the second pressure control mechanism 32 (L) in the negative pressure control unit 3 .

The switching mechanism 4 appropriately switches the open/closed states of the four on-off valves V1A to V1D to switch the air portions of the first tanks 21 and the second tanks 22 of each color, the first pressure control mechanism 31 and the second pressure control mechanism 32. and can be switched in various ways. Hereinafter, the on-off valves V1A and V1B connected to the first pressure control mechanism will be referred to as first switching units, and the on-off valves V1C and V1D connected to the second pressure control mechanism will be referred to as second switching units.

The fluid path in this embodiment includes a flow path (path) in which the liquid (ink) used for ejection circulates, and a flow path (path) in which the gas (air) used for pressure control for ejecting the liquid circulates. and exist. Since the directions of flow of liquids and gases correspond, the terms flow direction or flow direction shall be used in common.

Here, the first pressure control mechanism (also referred to as first pressure control section) 31 and the second pressure control mechanism (also referred to as second pressure control section) 32 will be described.

The first pressure control mechanism 31 and the second pressure control mechanism 32 are so-called decompression type regulator mechanism and back pressure type regulator mechanism, each of which includes a valve, a spring, a flexible film, and the like. Both the first pressure control mechanism 31 and the second pressure control mechanism 32 have the function of maintaining the negative pressure of the air portion of the tank connected thereto within a predetermined pressure range (predetermined pressure).

The second pressure control mechanism 32 is connected to a suction pump 1000 (P) via a vacuum joint 9, and by driving the suction pump P, the negative pressure in the space upstream of the second pressure control mechanism 32 is reduced. within a certain range. Aspiration pump 1000 may be a vacuum pump. The first pressure control mechanism 31 is connected to the atmosphere communication port 36 according to the degree of the negative pressure inside, and adjusts the negative pressure in the space downstream of the first pressure control mechanism 31 to a certain range.

Therefore, the first pressure control mechanism 31 and the second pressure control mechanism 32 maintain pressure on the downstream side and the upstream side by the action of internal valves and springs even when the flow rate of ink passing through the ink flow path fluctuates. Pressure can be stabilized within a certain range. Although the details of the first pressure control mechanism 31 and the second pressure control mechanism 32 will be described later, the control pressure of the second pressure control mechanism is set lower than the control pressure of the first pressure control mechanism.

An air buffer 7 is provided between the third on-off valve V1C and the fourth on-off valve V1D and the second pressure control mechanism 32 . The air buffer 7 has a function of preventing ink from dripping from the ejection ports due to environmental changes when the printing apparatus has been unused for a long period of time. That is, when the air in the air section in the tank connected to the second pressure control mechanism 32 expands due to changes in the environmental temperature and atmospheric pressure, the expanded air expands the air buffer 7 communicating with the air section. to prevent pressure from being applied to the liquid ejection head (especially the recording element substrate). As an example, the air buffer 7 can preferably be a bag-shaped rubber or a spring bag-shaped one having a weak spring inside.

In FIG. 2, the upstream ends of the first switching units (V1A and V1D) are connected to the downstream side of the first pressure control mechanism 31 (H), and the downstream ends of the second switching units (V1B and V1C) are It is connected to the upstream side of the second pressure control mechanism 32(L). In FIG. 2, on-off valves V1A and V1C are open and on-off valves V1B and V1D are closed. At this time, the first pressure control mechanism 31 (H) is connected to the first tank 21 of each color through the open valve V1A, and the second pressure control mechanism 32 (L) is connected to the first tank 21 of each color through the open valve V1C. 2 tank 22 is connected.

Contrary to FIG. 2, FIG. 3 shows the case where the on-off valves V1A and V1C are closed and the on-off valves V1B and V1D are open. In this case, the first pressure control mechanism 31 (H) is connected to the second tank 22 of each color through the open valve V1B, and the second pressure control mechanism 32 (L) is connected to the second tank 22 of each color through the open valve V1D. 1 tank 21 is connected.

In this way, by opening and closing the on-off valves V1A to V1D, the first pressure control mechanism 31 (H) and the second pressure control mechanism 32 (L) are connected to the first tanks 21 and the second tanks 22 of each color. Relationships can be switched back and forth.

Such a switching operation is determined by the CPU 500 based on various conditions such as signals from the ink remaining amount detection mechanism (not shown) in the first tank 21 and the second tank 22 of each color. This is done by controlling V1A to V1D. For example, the CPU 500 may perform the above switching at the timing when the remaining amount of liquid in the tank on the upstream side reaches the lower limit, or at the timing when the liquid continues to flow in the same direction for a predetermined time. may be performed. Such a switching operation of the on-off valve is performed while the liquid ejection head 300 is in a state where the ejection operation is stopped. However, since the switching operation itself can be completed in several seconds, downtime of the printing apparatus is not regarded as a problem. .

The switching mechanism 4 only needs to have such a connection state switching function, and is not limited to a simple combination of four on-off valves as in this example. For example, the switching mechanism 4 may have a configuration in which two three-way valves and two slide valves are used as first and second switching units.

(fluid flow path during driving and refilling)
In FIG. 2, the individual valve 5 (V2) and the supply valve 6 (V3) are opened to operate the suction pump 1000 (P). As a result, the tank (first tank 21) connected to the first pressure control mechanism 31 (H) side and the tank (second tank 22) connected to the second pressure control mechanism 32 (L) side are A differential pressure is generated between them. Therefore, inside the liquid ejection head 300, ink flows from the first common channel 12 toward the second common channel 13 (in the direction of the outlined arrow in FIG. 2) through the printing element substrates 10. . Specifically, between the first common flow path 12 and the second common flow path 13, an ink flow is generated that passes near the pressure chambers 123 (FIG. 14) having recording elements therein and the ejection ports communicating with the pressure chambers 123. . Therefore, bubbles, viscous ink, foreign matter, and the like in the vicinity of ejection openings that are not ejecting ink (ejection openings in the non-ejection state) can be discharged to the second tank 22 .

In any one of the second tanks 22 of each color, the amount of ink in the second tank 22 increases due to the ink flowing from the first tank 21 through the liquid ejection head 300, and the ink level rises to a preset high level. When the detection level is exceeded, the switching mechanism 4 functions. That is, the switching mechanism 4 reverses the connection relationship between the first tank 21 and the second tank 22 and the first pressure control mechanism 31 (H) and the second pressure control mechanism 32 (L). This state is shown in FIG. That is, the second tank 22 is connected to the first pressure control mechanism 31 (H) side, and the first tank 21 is connected to the second pressure control mechanism 32 (L) side. As a result, this time, an ink flow is generated from the second common flow path 13 through each recording element substrate 10 toward the first common flow path 12 (in the direction of the white arrow in FIG. 3), causing bubbles, Thickened ink and foreign matter are discharged to the first tank 21 .

After that, when the ink level in the first tank 21 exceeds the high water level detection level, or when the ink level in the second tank 22 falls below the low water level detection level, the switching mechanism switches the connection relationship again. to flip. Considering the stability of the ink ejected from the ejection port, it is preferable to perform such a reversing operation while the printing operation is temporarily stopped. downtime is not a big problem.

It should be noted that the amount of ink in the circulation path decreases as the ink is ejected from the ejection openings of the liquid ejection head 300 . In other words, when the ink level in the second tank 22 is below the low level detection level and the ink level in the first tank 21 is below the high level detection level, the main tank 1002 and the first tank 21 perform an operation to replenish the ink. In this case, first, the supply valve 6 (V3) corresponding to each color is closed and the individual valve 5 (V2) is opened. Next, the switching mechanism 4 is switched to connect the first tank to the second pressure control mechanism and to connect the second tank to the first pressure control mechanism (that is, the state shown in FIG. 3). Then, the suction pump 1000 is operated to open the bypass valve 35 (bypass opening/closing valve; V4) (open the bypass path). That is, in a state in which the first tank 21 and the liquid ejection head 300 are pressure-separated by the supply valve 6 (V3), the inside of the first tank is set to a high negative pressure, and the ink in the main tank 1002 is discharged into the first tank. inhale and replenish. In this case, it is expected that there will be a difference in the required amount of ink replenishment between the first tanks corresponding to the respective colors. However, by closing the individual valve 5 (V2) for each color based on the high water level detection signal of the first tank corresponding to each color, it is possible to prevent excessive replenishment of ink in the first tank. .

During such an ink replenishment operation, static negative pressure is applied to the ejection openings of the recording element substrate 10 by the first pressure control mechanism 31 (H) via the second tank 22. The ink meniscus is held stably. As for the inks of all colors, when the first tank 21 is completely replenished with ink, the ink surface in the second tank 22 of each color is below the low water level detection level. Therefore, ink can flow from the first tank 21 to the second tank 22 simply by reversing the switching mechanism 4 and then opening the supply valve 6 (V3) and the individual valve 5 (V2). Therefore, a stable recording operation can be immediately started by only requiring time (several seconds or less) for the valve switching operation.

The normal state of the individual valve 5 (V2) and/or the supply valve 6 (V3) (the open/closed state when the power supply is stopped) is closed, the first switching section (V1A and V1D) is open to the first tank 21 side, The second switching portions (V1B and V1C) are preferably open to the second tank 22 side. Specifically, in the examples of FIGS. 2 to 5, in the normal state of the four on-off valves (V1A to V1D), V1A and V1C are open and V1B and V1D are closed. With this setting, the liquid ejection head 300 is pressure-separated from the first tank 21 and communicates only with the second tank 22 when the printing apparatus is stopped. Since the second tank is connected to the second pressure control mechanism 32 (L) having a lower control pressure, the negative pressure applied to the nozzle portion of the liquid ejection head can be stopped at a high level. Therefore, it is possible to increase the degree of freedom in layout within the apparatus, such as setting the tank at a position higher than the liquid ejection head, while preventing the ink from dripping from the ejection port. Furthermore, in the case of indoor transportation when the power supply is stopped, ink leakage from the ejection port can be suppressed even if the posture of the recording apparatus is slightly tilted.

As described above, in the ink supply system of this embodiment, the pressure control necessary for the ink flow of each color can be performed using a common pressure control mechanism and pump. For this reason, a highly reliable printing apparatus capable of printing high-quality images by removing bubbles, thickened ink, foreign matter, etc. from the ejection port while having a small number of parts, a low cost, and a small size is required. can provide. Although four colors of ink have been described in the present embodiment, the pressure control mechanism can be used in common even when the types of liquids are further increased, such as light ink, special color ink, and recording-enhancing liquid.

In this embodiment, the mechanical section including the pump 1000, the negative pressure control unit 3, and the switching mechanism 4 is connected to the first tank 21 and the second tank 22 by an air pipe with very small pressure loss. Therefore, it is possible to relatively freely select the layout of the mechanical units in the recording apparatus, and there is an advantage that the size of the recording apparatus can be easily reduced.

Further, the part consisting of the liquid ejection head 300 and the liquid supply unit 220 may be unitized as a liquid ejection head and installed replaceably on the carriage of the printing apparatus main body. By unitizing (integrating) the liquid ejection head 300 and the liquid supply unit 220, the liquid ejection head can be easily replaced simply by removing the main tank 1002 and the air pipe. In addition, since the liquid ejection head is connected to the mechanical section in the main body of the printing apparatus only by an air pipe, the main tank 1002 is also unitized as the liquid ejection head. Therefore, it is possible to replace the liquid ejection head more easily.

Further, although the liquid ejection head in the present embodiment is in the form of a page-wide type line head, it may be in the form of a so-called serial head. When the liquid ejection head is in the form of a serial head, the mechanical portion is installed outside the carriage, the head portion and the mechanical portion are connected by an air pipe, and only the head portion is mounted on the carriage and reciprocated. configured to As a result, printing can be performed while the thickened ink and the foreign matter are being discharged to the tank.

(Negative pressure compensation function)
In the ink supply system of this embodiment, the pressure difference between the first tank 21 and the second tank 22 causes the ink to flow in the liquid ejection head 300 . When ink is ejected from the ejection openings of the liquid ejection head, the pressure chambers are refilled with ink.

Hereinafter, the flow rate of ink passing through the ink flow path in the recording element substrate 10 when the ejection operation from the ejection port is not performed (hereinafter also referred to as "during non-ejection operation") will be referred to as the ink flow rate during the non-ejection operation. It says. Further, the ink ejection amount during the ejection operation (hereinafter also referred to as “during the ejection operation”) is referred to as the ink ejection amount during the ejection operation.

When the ink flow rate during the non-ejection operation is equal to or greater than the ink ejection amount during the ejection operation, refilling of each pressure chamber substantially occurs from the tank side connected to the first pressure control mechanism 31(H). do.

On the other hand, when the ink ejection amount during ejection is larger than the ink flow rate during non-ejection operation, not only the tank side connected to the first pressure control mechanism 31 (H) but also the second pressure control mechanism 32 (L) ), refilling to each pressure chamber also occurs from the tank side connected to . For example, the second pressure control mechanism 32 (L ) is prone to refilling from the tank side connected to

However, the second pressure control mechanism 32 (L) (general back pressure type regulator) automatically closes the internal valve at the time of reverse flow, so that reverse flow does not occur. Also, in the pump 1000, backflow is prevented by an internal check valve. Therefore, when high-duty printing is performed, the pressure on the side of the tank connected to the second pressure control mechanism 32(L) becomes too low in the ink flow path in the printing element substrate 10, resulting in insufficient refilling. As a result, the ejection amount from the ejection port is reduced, and the image may become thin or blurred.

In addition, in other printing element substrates 10 and ejection openings where high-duty printing is not performed, the flow rate of ink passing through increases, negative pressure rises and temperature excessively lowers, and image quality also deteriorates. may be lost.

In this embodiment, in order to avoid the situation described above, a negative pressure fluctuation compensating mechanism (hereinafter also referred to as a negative pressure compensating mechanism, a negative pressure compensating section, or a pressure compensating means) 37 is provided. The negative pressure compensating mechanism 37 is provided in a path for gas communication between the first tank 21 and the second tank 22 . The negative pressure compensation mechanism 37 is composed of a passive valve 33 and an on-off valve 34 (indicated by V5), and directly connects the downstream flow path of the first pressure control mechanism 31 and the upstream flow path of the second pressure control mechanism 32. It is provided in a connecting path (communication path).

The passive valve 33 has a differential pressure on both sides thereof, that is, the difference between the pressure on the side of the first pressure control mechanism 31 and the pressure on the side of the second pressure control mechanism 32 is a predetermined value or more. It is designed to open when the difference between the control pressure and the control pressure of the second pressure control mechanism 32 is exceeded. In the example of FIG. 4 , the pressure on the side of the first pressure control mechanism 31 corresponds to the internal pressure of the channel between the first pressure control mechanism 31 and the first tank 21 . Also, the pressure on the side of the second pressure control mechanism 32 corresponds to the internal pressure of the channel between the second pressure control mechanism 32 and the second tank 22 . With such a configuration, even if the pressure on the second pressure control mechanism 32 side decreases (negative pressure increases) due to the ejection operation of the liquid ejection head 300, the passive valve 33 is opened to reduce the negative pressure. Fluctuations are compensated to prevent excessive underpressure build-up. For example, when the pressure on the side of the second pressure control mechanism 32 is equal to or lower than a predetermined pressure, the liquid is supplied from the flow path on the side of the first pressure control mechanism 31 to the side of the second pressure control mechanism 32, and the second pressure control mechanism The pressure on side 32 can be increased, thus compensating for such a pressure drop. As a result, ink can be stably ejected from the ejection openings of the printing element substrate 10 even during high-duty printing.

Of all the printing element substrates 10 in FIG. 4, the printing element substrates 10 displayed in white are in a state where high-duty printing is being performed. In addition, in the recording element substrate 10 displayed by black shading, it is in a state in which no ejection operation is performed (non-ejection state) or in a state in which the recording elements are driven at a low duty.

High-duty printing is performed in most of the C (cyan) recording element substrate (outlined portion) and in all portions of the Y recording element substrate (outlined portion). Refilling of ink from the 22 side occurs. Therefore, in order to suppress the increase in the negative pressure in the second tanks 22 for C and Y colors, air corresponding to the ink refill is supplied from the first pressure control mechanism 31 through the differential pressure valve 33 . , negative pressure rise is suppressed. Therefore, the internal pressures of the second tanks 22 for the M and K colors in the standby state hardly change, and stable ink flow is continued. In a liquid ejection head provided with a plurality of printing element substrates, such as the page-wide type of this embodiment, each printing element substrate 10 is provided as an example of the liquid ejection head 300 of C (cyan) in FIG. The form of refill differs depending on the recording duty in the. That is, the low duty printing element substrate is refilled only from the first tank 21 side, and the high duty printing element substrate is refilled from both the first tank 21 and the second tank 22 side.

As described above, in this embodiment, an excessive increase in negative pressure in the tank connected to the second pressure control mechanism 32 can be suppressed in any state.

(strong recovery mode)
Further, in this embodiment, a strong recovery mode is executed to discharge bubbles, thickened ink, foreign substances, etc. in the discharge ports and flow paths in the liquid discharge head 300 that could not be discharged with the normal ink flow rate. be able to.

FIG. 5 is a schematic diagram showing the state of paths in the strong recovery mode. A bypass valve 35 (indicated by V4) connected between the upstream and downstream flow paths of the second pressure control mechanism 32(L) is opened. Thereby, the differential pressure between the first tank 21 and the second tank 22 can be controlled according to the rotation speed of the suction pump 1000 regardless of the control pressure of the second pressure control mechanism 32 . That is, the flow rate of the ink passing through the liquid ejection head 300 can be increased compared to the normal circulation described above. The flow rate of ink passing through the liquid ejection head 300 can be selected in consideration of the recoverability of the ejection performance of the liquid ejection head within a range where the meniscus of the ink at the ejection port can be maintained. Since this strong recovery mode is performed in a non-printing state, there is no problem even if the flow rate of ink passing through the inside of the liquid ejection head 300 is equal to or higher than the appropriate negative pressure that can provide ejection characteristics suitable for printing. .

Normally, the flow path of the ejection port is the finest flow path in the liquid ejection head. Also, it is difficult to eject foreign matter from the ejection port. Therefore, after executing the strong recovery mode for a predetermined time, it is preferable to operate the switching mechanism 4 to reverse the ink flow direction in the liquid ejection head 300 and then execute the strong recovery mode again. According to such a strong recovery mode, unlike the conventional recovery operation of the liquid ejection head by the suction operation and the pressurization operation, the recovery operation of the ejection port can be performed without generating a large amount of waste ink. , reduction of waste ink and simplification of the recovery mechanism can be realized.

When executing the strong recovery mode, it is necessary to perform control so as to close the on-off valve 34 (indicated by V5) of the negative pressure compensating mechanism. This is because, in the strong recovery mode, pressure is applied so as to generate a larger differential pressure than usual between the first tank and the second tank. This is because 33 is opened and the differential pressure cannot be increased. Alternatively, the passive valve 33 itself may have a closing function.

(liquid supply unit and valve unit)
6A to 6C are diagrams showing specific configurations of the liquid supply unit 220, the valve unit 400, and the negative pressure control unit 3. FIG.

2 to 5 (V1A, V1B, V1C, V1D, V2, V3, V4, V5), an air buffer 7, an ink joint 8, a vacuum joint 9, and an ink/air flow A mechanical section including a path member. As shown in FIG. 6A, the valve unit 400 is provided with an ink joint 8 connected to the main tanks of the four colors of ink and a vacuum joint 9 connected to the suction pump 1000, each of which is a unit It communicates with the internal ink and air channels.

FIG. 6(b) is a perspective view of the state where the liquid supply unit 220 and the valve unit 400 are separated. As can be seen from this figure, the supplied ink flowing from the ink joint 8 passes through the filter 1001 and is supplied to the internal first tank 21 in order to remove foreign substances in the ink. Also, the air portions of the first tank 21 and the second tank 22 of the liquid supply unit are connected to an air flow path (not shown) inside the valve unit 400 via the air connection port 23 .

FIG. 6C is a top view of the valve unit 400. FIG. The valve unit 400 includes a negative pressure control unit 3, a switching mechanism 4 (on-off valves 41 to 44), four individual valves 5 consisting of electromagnetic valves, a negative pressure compensating mechanism 37 consisting of a passive valve 33 and an on-off valve 34, a bypass A valve 35, four supply valves 6 and an air buffer 7 are arranged in a plane. Of these, the on-off valves 41 to 44, 34, the bypass valve 35, and the supply valve 6 are mechanically connected to a gear cam mechanism (not shown) of the main body of the recording apparatus, and are controlled to open and close. It's becoming For these valves, similarly to the individual valves 5, even if electromagnetic valves are used, there is no functional problem. Further, the individual valve 5 may be controlled to open and close by a gear/cam mechanism of the main body. Since the four supply valves 6 open and close simultaneously for all colors of ink, it is less costly to control them mechanically than to use individual electromagnetic valves. Since the individual valves 5 must be controlled to open and close for each ink color (liquid type), electrical control is less costly than preparing motors and mechanical mechanisms for each ink color.

As shown in FIG. 2, the negative pressure control unit 3 arranged on the valve unit 400 incorporates both the first pressure control mechanism 31(H) and the second pressure control mechanism 32(L). Valves and spring members provided inside the first pressure control mechanism 31 (H) and the second pressure control mechanism 32 (L) operate to reduce the negative pressure in the flow path of the liquid ejection head 300 within a certain range. can be stabilized within Details of the structure of the negative pressure control unit 3 will be described later with reference to FIG.

(Specific Configuration of Liquid Ejection Head)
A specific configuration of the liquid ejection head 300 according to the present embodiment will be described with reference to FIGS. 7 and 8. FIG.

7A and 7B are perspective views of the liquid ejection head 300 according to this embodiment. The liquid ejection head 300 of this example is a line-type liquid ejection head in which 15 recording element substrates 10 are linearly arranged (arranged in-line). One recording element substrate 10 is configured to be capable of ejecting four color inks of C (cyan)/M (magenta)/Y (yellow)/K (black).

The liquid ejection head 300 includes signal input terminals 91 and power supply terminals 92 electrically connected to each recording element substrate 10 via the flexible wiring substrate 40 and the electric wiring substrate 90 . The signal input terminal 91 and the power supply terminal 92 are electrically connected to the control section of the printing apparatus 1 to supply the printing element substrate 10 with an ejection driving signal and electric power necessary for ejection. By consolidating wiring by means of electric circuits in the electric wiring board 90 , the number of signal output terminals 91 and power supply terminals 92 can be reduced compared to the number of recording element boards 10 . This reduces the number of electrical connections that need to be removed when assembling the liquid ejection head 300 to the recording apparatus 1 or when replacing the liquid ejection head 300 .

The liquid connection portions 111 provided at both ends of the liquid ejection head 300 are connected to the first tank and the second tank of each color of the liquid supply unit 220 .

FIG. 8 is an exploded perspective view of each component and unit that constitute the liquid ejection head 300. As shown in FIG.

The housing 80 includes a support portion 81 that supports the liquid ejection head 300 and a support portion 82 that supports the electric wiring board 90, and ensures the rigidity of the entire liquid ejection head. A channel member 210 on which the ejection module 200 is mounted is attached to the support portion 81 . The support portion 82 and the support portion 81 are fixed to the housing 80 with screws. The support portion 81 corrects the warp and deformation of the liquid ejection head 300 and ensures the relative positional accuracy of the plurality of element substrates 10, thereby suppressing the occurrence of streaks and density unevenness in the recorded image. Therefore, it is preferable that the support portion 81 has sufficient rigidity, and the material thereof is preferably a metal material such as SUS or aluminum, or a ceramic such as alumina. The support portion 81 is provided with openings 83 and 84 for inserting the joint rubber 100 . Ink supplied from the ink supply unit 220 is guided to the third flow path member 70 that constitutes the ink discharge unit 300 through holes in the joint rubber 100 .

A cover member 130 is attached to the surface of the liquid ejection head 300 on the recording medium side. The cover member 130 is a frame-shaped member provided with an elongated opening 131, as shown in FIG. Through the opening 131, the recording element substrate 10 and the sealing material 110 (see FIG. 12A) included in the ejection module 200 are exposed. A frame portion around the opening 131 functions as a contact surface with which a cap member that caps the liquid ejection head 3 contacts during standby for recording. Therefore, an adhesive, a sealing material, a filler, or the like is applied along the periphery of the opening 131 to fill the irregularities and gaps on the ejection port surface of the liquid ejection head 300, thereby forming a closed space at the time of capping. It is preferable to configure

Next, details of the flow path member 210 included in the liquid ejection head 300 will be described. As shown in FIG. 8, the flow path member 210 is obtained by stacking the first flow path member 50, the second flow path member 60, and the third flow path member . The channel member 210 is a channel member for distributing the liquid supplied from the liquid supply unit 220 to each ejection module 200 and for returning the liquid circulated from the ejection module 200 to the liquid supply unit 220 . The channel member 210 is fixed to the liquid ejection head support portion 81 by screwing, thereby suppressing warpage and deformation of the channel member 210 .

FIGS. 9(a) to 9(f) are diagrams showing the front and back surfaces of the first, second and third channel members. 9A shows the surface of the first flow path member 50 on the side where the ejection module 200 is mounted, and FIG. 3 shows the surface of the channel member 70. FIG. The first flow path member 50 and the second flow path member 60 are joined so that the surfaces of FIG. 9(b) and the surface of FIG. 9(c), which are their contact surfaces, face each other. The second flow path member and the third flow path member are joined so that the surface of FIG. 9(d) and the surface of FIG. 9(e), which are their contact surfaces, face each other. By joining the second flow path member 60 and the third flow path member 70, common flow grooves 62 and 71 formed in them form eight common flow paths extending in the longitudinal direction of the flow path members. be done. Thereby, a set of the first common channel 12 and the second common channel 13 is formed in the channel member 210 for each color. The communication port 72 of the third channel member 70 fluidly communicates with the liquid supply unit 220 through each hole of the joint rubber 100 . A plurality of communication ports 61 are formed in the bottom surface of the common channel groove 62 of the second channel member 60 , and the communication port 61 communicates with one end of the individual channel groove 52 of the first channel member 50 . ing. A communication port 51 is formed at the other end of the individual channel groove 52 of the first channel member 50 , and the communication port 51 fluidly communicates with the plurality of discharge modules 200 . The individual channel grooves 52 enable the channels to be collectively formed on the central side of the channel member.

It is preferable that the first, second, and third channel members are made of a material having corrosion resistance against liquid and a low coefficient of linear expansion. As materials, for example, composite materials (resin material) can be preferably used. As a method for forming the flow path member 210, three flow path members may be laminated and adhered to each other, or when a resin composite resin material is selected as the material, a joining method by welding may be used. .

Next, with reference to FIG. 10, the connection relationship between the channels in the channel member 210 will be described. FIG. 10 shows a portion of the flow path in the flow path member 210 formed by joining the first, second, and third flow path members to the first flow path member 50 on which the ejection module 200 is mounted. It is an enlarged perspective view seen from the surface side of. The flow channel member 210 includes first common flow channels 12 (12a, 12b, 12c, 12d) and second common flow channels 13 (13a, 13b, 13c) extending in the longitudinal direction of the liquid ejection head 3 for each color. , 13d) are provided. A plurality of first individual channels (213a, 213b, 213c, 213d) formed by individual channel grooves 52 are connected to the first common channel 12 of each color through communication ports 61. As shown in FIG. A plurality of second individual channels (214a, 214b, 214c, 214d) formed by the individual channel grooves 52 are connected to the second common channel 13 of each color through the communication ports 61. As shown in FIG. With such a flow path configuration, ink is concentrated to the recording element substrate 10 located in the central portion of the flow path member through a series of flow paths from each of the first common flow paths 12 to the first individual flow paths 213. can lead. In addition, ink can be recovered from the recording element substrate 10 to each of the second common channels 13 via a series of channels of the second individual channels 214 .

11 is a cross-sectional view taken along line XI-XI of FIG. 10. FIG. As shown in this figure, each of the second individual flow paths (214a, 214c) communicates with the discharge module 200 through the communication port 51. As shown in FIG. Although only the second individual channels (214a, 214c) are shown in the cross section of FIG. 11, in another cross section, the first individual channels 213 and the ejection module 200 are in communication as shown in FIG. . In the support member 30 and the recording element substrate 10 included in each ejection module 200, flow paths for supplying ink from the first flow path member 50 to the recording elements 115 (see FIG. 14) of the recording element substrate 10 are formed. It is Further, a channel is formed for recovering (circulating) part or all of the liquid supplied to the recording element 115 to the first channel member 50 .

When ink circulates as shown in FIG. 2, the first common channel 12 for each color is connected to the pressure control mechanism (high pressure side) 31 via the liquid supply unit 220, and the second common channel 13 is connected to the pressure control mechanism (high pressure side) 31. It is connected to the force control mechanism (low pressure side) 32 via a liquid supply unit 220 . A pressure difference (pressure difference) between the first common flow path 12 and the second common flow path 13 is caused by the negative pressure control unit 3 including the pressure control mechanism (high pressure side) 31 and the pressure control mechanism (low pressure side) 32. occurs. Therefore, in the liquid ejection head configured as shown in FIGS. 10 and 11, there are a first common flow path 12, a first individual flow path 213a, a recording element substrate 10, and a second individual flow path 213b for each color. , and the second common flow path 13 in that order.

When the ink circulates as shown in FIG. 3, the first common channel 12 for each color is connected to the pressure control mechanism (low pressure side) 32 via the liquid supply unit 220, and the second common channel 13 is , is connected to the pressure control mechanism (high pressure side) 31 via the liquid supply unit 220 . A pressure difference (pressure difference) between the first common flow path 12 and the second common flow path 13 is caused by the negative pressure control unit 3 including the pressure control mechanism (high pressure side) 31 and the pressure control mechanism (low pressure side) 32. occurs. Therefore, in the liquid ejection head configured as shown in FIGS. 10 and 11, the second common flow path 13, the second individual flow path 213b, the recording element substrate 10, and the first individual flow path 213a are provided for each color. , and the first common flow path 12 in that order.

(dispensing module)
FIG. 12(a) shows a perspective view of one ejection module 200, and FIG. 12(b) shows an exploded view thereof. As a method of manufacturing the ejection module 200, first, the recording element substrate 10 and the flexible wiring substrate 40 are adhered onto the support member 30 in which the liquid communication port 31 is provided in advance. After that, the terminals 16 on the recording element substrate 10 and the terminals 41 on the flexible wiring substrate 40 are electrically connected by wire bonding, and then the wire bonding portion (electrical connection portion) is covered with a sealing material 110 for sealing. . Terminals 42 of the flexible wiring board 40 on the opposite side of the recording element substrate 10 are electrically connected to connection terminals 93 (see FIG. 8) of the electric wiring board 90 . The support member 30 is a support member that supports the recording element substrate 10 and is a flow path member that fluidly communicates between the recording element substrate 10 and the flow path member 210. Therefore, the flatness of the support member 30 is high and sufficiently high. A material that can be reliably bonded to the recording element substrate is preferable. As the material, for example, alumina or a resin material is preferable.

(Structure of recording element substrate)
The configuration of the recording element substrate 10 in this embodiment will be described.

FIG. 13(a) shows a plan view of the surface of the recording element substrate 10 on which the ejection ports 113 are formed, and FIG. 13(b) shows an enlarged view of the portion indicated by XIIIb in FIG. 13(a). , FIG. 13(c) shows a plan view of the back surface of FIG. 13(a). As shown in FIG. 13A, the ejection port forming member 112 of the recording element substrate 10 is formed with four ejection port arrays corresponding to each ink color. Hereinafter, the direction in which the ejection port row in which the plurality of ejection ports 113 are arranged will be referred to as the “ejection port row direction”.

As shown in FIG. 13B, printing elements 115, which are heat generating elements for foaming the liquid with thermal energy, are arranged at positions corresponding to the ejection ports 113. As shown in FIG. A partition wall 122 defines a pressure chamber 123 having a recording element 115 therein. The recording element 115 is electrically connected to the terminal 16 in FIG. 13A by electrical wiring (not shown) provided on the recording element substrate 10 . The printing element 115 heats and boils the liquid based on a pulse signal input from the control circuit of the printing apparatus 1 via the electric wiring board 90 (FIG. 8) and the flexible wiring board 40 (FIG. 12). . The liquid is ejected from the ejection port 113 by the bubbling power (bubbling pressure) caused by this boiling. As shown in FIG. 13B, a liquid supply path 18 extends on one side and a liquid recovery path 19 extends on the other side along each ejection port row. The liquid supply path 18 and the liquid recovery path 19 are flow paths extending in the ejection port array direction provided on the recording element substrate 10, and communicate with the ejection port 113 via the supply port 17a and the recovery port 17b, respectively.

In this specification, the terms "supply" and "recovery" are used to describe the configuration, such as the liquid supply path 18 and the liquid recovery path 19. However, in the embodiment of the present invention, for example, As shown in FIGS. 2 and 3, the direction of liquid flow can be reversed. Therefore, depending on the flow direction of the liquid, the liquid is recovered in the liquid supply path and supplied from the liquid recovery path. It should be noted that similarly, in the explanations elsewhere in this specification, the relationship between "supply" and "collection" can be reversed if the liquid flow direction (ink flow direction) is reversed. sea bream.

As shown in FIGS. 13C and 14, a sheet-like lid member 200 is layered on the back surface of the recording element substrate 10 on which the ejection ports 113 are formed. The lid member 200 will be described later. A plurality of openings 21 communicating with the liquid supply channel 18 and the liquid recovery channel 19 are provided. In this embodiment, the lid member 200 is provided with three openings 21 for one liquid supply path 18 and two openings 21 for one liquid recovery path 19 . Each opening 21 of the lid member 200 shown in FIG. 13(b) communicates with a plurality of communication ports 51 shown in FIG. 9(a). FIG. 14 is a perspective view showing a cross section of the recording element substrate 10 and the lid member 200 cut along line XIV-XVI in FIG. 13(a). As shown in FIG. 10, the lid member 200 functions as a lid that forms part of the walls of the liquid supply path 18 and the liquid recovery path 19 formed on the substrate 111 of the recording element substrate 10 . The lid member 200 preferably has sufficient corrosion resistance to the liquid, and from the viewpoint of preventing color mixture, the opening shape and opening position of the opening 21 are required to have high accuracy. In this way, the cover member changes the pitch of the flow path by means of the openings 21, and considering the pressure loss, it is desirable that the thickness of the cover member is thin. For this reason, it is preferable to use a photosensitive resin material or a silicon thin plate as the material of the lid member 200 and to form the opening 21 by a photolithography process.

Next, the flow of liquid within the recording element substrate 10 will be described. The recording element substrate 10 is formed by laminating a substrate 111 made of Si and an ejection port forming member 112 made of a photosensitive resin. A printing element 115 is formed on one side of the substrate 111 (FIG. 13B), and a liquid supply path 19 and a liquid recovery path 18 extending along the ejection port array are formed on the back side. Constituent grooves are formed. The liquid supply channel 18 and the liquid recovery channel 19 formed by the substrate 111 and the lid member 200 are connected to the common supply channel 211 and the common recovery channel 212 in the channel member 210, respectively. A differential pressure is generated with the liquid recovery path 19 . During printing in which liquid is ejected from a plurality of ejection openings 113 of the liquid ejection head 3, the liquid in the liquid supply path 18 provided in the substrate 111 is discharged from the ejection openings that are not performing an ejection operation due to this differential pressure. 17a, the pressure chamber 123, and the recovery port 17b to the liquid recovery path 19. The flow is indicated by arrow C in FIG. Due to this flow, thickened ink, bubbles, foreign substances, etc. caused by evaporation from the ejection ports 113 and the pressure chambers 123 where printing is suspended can be recovered to the liquid recovery path 19 . Further, thickening of the ink in the ejection port 113 and the pressure chamber 123 can be suppressed.

The liquid recovered in the liquid recovery channel 19 passes through the opening 21 of the lid member 200 and the liquid communication port 31 of the support member 30 to the communication port 51 in the channel member 210, the individual recovery channels 214, and the second common channel 113. It is collected in order and finally collected into the first tank 21 or the second tank 22 .

That is, the liquid supplied from the first tank or the second tank of the liquid supply unit 220 to the liquid ejection head 300 flows in the following order and is supplied and recovered. The liquid first flows into the liquid ejection head 300 from the liquid supply unit 220 via the liquid connection portion 111 and the joint rubber 100 . After that, the communication port 72 and the common flow channel groove 71 provided in the third flow channel member, the common flow channel groove 62 and the communication port 61 provided in the second flow channel member, and the communication port 61 provided in the first flow channel member The individual channel grooves 52 and the communication ports 51 are supplied in this order. After that, the liquid is supplied to the pressure chamber 123 sequentially through the liquid communication port 31 provided in the support member 30, the opening 21 provided in the cover member, the liquid supply path 18 provided in the substrate 111, and the supply port 17a. Of the liquid supplied to the pressure chamber 123 , the liquid that has not been discharged from the discharge port 13 passes through the recovery port 17 b provided in the substrate 111 and the liquid recovery path 19 , the opening 21 provided in the cover member, and the support member 30 . It flows through the provided liquid communication port 31 in order. After that, the communication port 51 and the individual channel grooves 52 provided in the first channel member, the communication port 61 and the common channel groove 62 provided in the second channel member, and the It flows through the common channel groove 71, the communication port 72, and the joint rubber 100 in order. It is then collected from the liquid connection 111 into the second or first tank of the supply unit 220 .

(Positional relationship between recording element substrates)
FIG. 15 is a partially enlarged plan view showing adjacent portions of recording element substrates in two adjacent ejection modules. As shown in FIG. 13, this embodiment uses a substantially parallelogram recording element substrate. As shown in FIG. 15, the ejection port arrays (L1, L2, L3, L4) in which the ejection ports 113 are arranged in each recording element substrate 10 are arranged so as to be inclined at a certain angle with respect to the conveying direction of the recording medium. . As a result, at least one of the ejection openings in the adjacent portions of the recording element substrates 10 overlaps in the conveying direction of the recording medium. In FIG. 15, two outlets on line D are in an overlapping relationship. With such an arrangement, even if the position of the recording element substrate 10 is slightly deviated from the predetermined position, it is possible to make black streaks and white spots in the recorded image inconspicuous by controlling the driving of the overlapping ejection ports. can. The same is true when a plurality of recording element substrates 10 are arranged not in a zigzag arrangement but in a straight line (inline). That is, with the configuration shown in FIG. 15, it is possible to prevent black streaks and white spots at the joints between the recording element substrates 10 while suppressing an increase in the length of the liquid ejection head 300 in the recording medium conveying direction. In this embodiment, the main plane of the recording element substrate is a parallelogram, but the present invention is not limited to this. A configuration can be preferably applied.

(First pressure control mechanism and second pressure control mechanism)
16(a) to 16(c) are explanatory diagrams of the negative pressure control unit 3 including the first pressure control mechanism 31 and the second pressure control mechanism 32. FIG. 16(a) is a perspective view of the negative pressure control unit 3, FIG. 16(b) is a cross-sectional view along line XVIb-XVIb of FIG. 13(a), and FIG. 16(a) is a cross-sectional view along line XVIc-XVIc.

The first pressure control mechanism 31 as a decompression regulator mechanism and the second pressure control mechanism 32 as a back pressure regulator mechanism are configured within a common body 310, and can be integrally attached and replaced. can. By symmetrically disposing the two pressure control mechanisms 31 and 32 as shown in FIG. 16(c), the space of the negative pressure control unit 3 can be saved.

(First pressure control mechanism)
As shown in FIG. 16B, the first pressure control mechanism 31 as a decompression type regulator mechanism includes a first pressure chamber 305 located on one side of the body 310 (lower side in the figure) and a pressure chamber 305 on the other side of the body 310. and a second pressure chamber 306 located on the side (upper side in the figure). The first pressure chamber 305 is sealed by a flexible film 303A, and the second pressure chamber 306 is sealed by a pressure receiving plate (pressure receiving portion) 302 and a flexible film 303B. An orifice (orifice portion) 308 is formed between the first pressure chamber 305 and the second pressure chamber 306 . A valve 307 mechanically connected to the pressure receiving plate 302 by a shaft 304 is located in the first pressure chamber 305. When the liquid ejection head 300 is driven, the shaft 304, the valve 307, and the pressure receiving plate 302 are integrated. move. The pressure receiving plate 302 is biased by a load in the direction in which the valve 307 closes the orifice 308 by a biasing member (spring) 301B. The valve 307 is urged in the direction of closing the orifice 308 and the flexible film 303A is urged in the direction of being pressed against the negative pressure adjusting member 311 by the urging member (spring) 301A provided in the first pressure chamber 305. be done.

The main function of valve 307 is to change the gap with orifice 308 to adjust and vary the flow resistance of the airflow. Valve 307 preferably closes the gap with orifice 308 when the circulation of ink stops. When the circulation of ink is stopped (when the printing operation is stopped), by fluidly sealing the space (boundary) between the valve 307 and the orifice 308, negative pressure is continuously applied to the ink in the ejection port 113, thereby Ink leakage from 113 can be prevented. As the material of the valve 307, an elastic material such as rubber or elastomer having sufficient corrosion resistance is preferable.

In this example, the springs as the biasing members 301A and 301B are two coupled springs. However, it suffices if the desired negative pressure can be obtained by the combined spring force. Therefore, for example, a configuration using only one spring or a configuration using three or more springs can be adopted. In the example of FIG. 16(b), among the biasing members 301A and 301B (two coupled springs), one biasing member 301B is separately provided in the second pressure chamber 306 so that the pressure receiving plate 302 and It is configured so that it can be separated from the shaft 304 . Even when the pressure receiving plate 302 and the shaft 304 are separated, the biasing force of the biasing member 301B in the second pressure chamber acts on the pressure receiving plate 302 . Therefore, even when the valve 307 closes the orifice 308, the pressure receiving plate 302 is separated from the shaft 304 by the biasing force of the biasing member 301B in the second pressure chamber 306, and the volume in the second pressure chamber 306 is further increased. It is possible to move in the increasing direction. As a result, when the liquid ejection head 300 is not driven for a long period of time and bubbles are trapped in the liquid ejection head 300, the second pressure chamber 306 functions as a buffer that absorbs the volume increase of the bubbles. As a result, it is possible to prevent the ink in the liquid ejection head 300 from becoming positive pressure.

The first pressure chamber 305 and the second pressure chamber 306 communicate with an inlet 312A and an outlet 312B (see FIG. 16(a)), respectively. The valve 307 is located upstream of the orifice 308 in the ink flow direction, and the gap between the valve 307 and the orifice 308 is reduced by moving the pressure receiving plate 302 upward in FIG. do. The air (airflow) entering the first pressure chamber 305 from the inlet 312A flows into the second pressure chamber 306 through the gap between the valve 307 and the orifice 308. is transmitted to The air in the second pressure chamber 306 is supplied to the liquid supply unit 220 through the outlet 312B.

The pressure P2 inside the second pressure chamber 306 is determined from the following relational expression (1), which indicates the balance of forces applied to each part.
P2=P0-(P1.Sv+k1.x)/Sd (1)

Sd is the pressure receiving area of the pressure receiving plate 302, Sv is the pressure receiving area of the valve 307, P0 is the atmospheric pressure, P1 is the pressure inside the first pressure chamber 305, and P2 is the pressure inside the second pressure chamber 306. k1 is the spring constant of the biasing member 301 (301A, 301B), and x is the displacement (spring displacement) of the biasing member 301 (301A, 301B).

Since the second term on the right side of the above equation (1) always takes a positive value, P2<P0 and P2 is a negative pressure. By changing the biasing force of the biasing member 301 (301A, 301B), the pressure P2 inside the second pressure chamber 306 can be set to a desired control pressure. The biasing force of the biasing member 301 can be changed according to the spring constant K and the spring length during operation.

The relationship between the flow resistance R in the gap between the valve 307 and the orifice 308 and the flow rate Q passing through the negative pressure control unit 3 (specifically, the orifice 308) is given by the following equation (2). To establish.
P2=P1-QR (2)

The gap between the valve 307 and the orifice 308 (hereinafter also referred to as "valve opening") and the flow resistance R have a relationship such as shown in FIG. set to a relationship that P2 is determined by adjusting the valve opening so that the equations (1) and (2) are satisfied at the same time.

When the flow rate Q increases, the flow resistance upstream of the first pressure control mechanism 31 increases due to the increase in the flow rate Q. Therefore, the pressure P1 in the first pressure chamber 305 is reduced by the increase in flow resistance. Therefore, the force (P1·Sv) that closes the valve 307 decreases, and the pressure P2 in the second pressure chamber 306 rises instantaneously, as is clear from equation (1).

Also, the formula R=(P1-P2)/Q is derived from the formula (2). As the flow rate Q and the pressure P2 increase and the pressure P1 decreases, the flow resistance R decreases. As the flow resistance R decreases, the valve opening degree increases according to the relationship shown in FIG. Since the length of the biasing member 301 decreases as the valve opening increases, the displacement x from its free length increases. Therefore, the acting force (k1·x) of the biasing member 301 increases, and the pressure P2 in the second pressure chamber 306 instantly decreases, as is clear from the equation (1).

On the other hand, when the flow rate Q of air flowing into the first pressure control mechanism 31 decreases, the first pressure control mechanism 31 acts in the opposite manner to when the flow rate Q increases. That is, the pressure P2 in the second pressure chamber 306 decreases instantaneously due to the increase in the pressure P1 in the first pressure chamber 305, and the decrease in pressure P2 decreases the flow resistance R. As a result, the second pressure chamber 305 The pressure P2 inside the pressure chamber 306 increases instantaneously.

Also, R=(P1−P2)/Q is derived from (Equation 2). Since Q and P2 are now increasing and P1 is decreasing, R will decrease. When R decreases, the valve opening degree increases from the relationship shown in FIG. As can be seen from FIG. 16(b), the length of the biasing member (spring) 301 decreases as the valve opening increases, so x, which is the displacement from the free length, increases. As a result, the acting force k1x of the spring increases. Therefore, P2 decreases instantaneously from (Equation 1).

In this way, the instantaneous increase and decrease of the pressure P2 are repeated, the valve opening degree changes according to the flow rate Q, and the equations (1) and (2) are compatible. Pressure P2 is controlled constant. Therefore, the pressure in the downstream channel portion (inlet side of the liquid ejection head) of the first pressure control mechanism 31 is autonomously controlled to be constant.

A negative pressure adjusting member 311 fixed to the body 310 is for changing the accommodation length and the biasing force of the biasing member 301A in the first pressure chamber 305 . A protrusion is provided at a position of the negative pressure adjusting member 311 facing the first pressure chamber 305 . By selectively fixing the negative pressure adjusting member 311 having different projection heights to the body 310, the biasing force of the biasing member 301A is changed to change or adjust the control pressure of the first pressure control mechanism 31. be able to. Therefore, even if the head difference between the negative pressure control unit 3 and the surface of the liquid ejection head 300 on which the ejection ports are formed is different, it is possible to replace the negative pressure adjusting member 311 with one having a different projection height. , can be handled by the same first pressure control mechanism 31 .

(Second pressure control mechanism)
The second pressure control mechanism 32 as a back pressure regulator mechanism is configured in the same manner as the first pressure control mechanism 31 described above, except for the differences described below. are denoted by the same reference numerals, and description thereof is omitted.

One of their differences is that the valve 307 of the second pressure control mechanism 32 is located within the second pressure chamber 306 . Another difference is that when the pressure receiving plate 302 of the second pressure control mechanism 32 moves in the biasing direction of the biasing member 301B (downward in FIG. 16B), the gap between the valve 307 and the orifice 308 is The difference is that the gap (valve opening degree) expands. Still another difference is that the second pressure chamber 306 of the second pressure control mechanism 32 communicates with the inlet 313A (see FIG. 16(a)), and the first pressure chamber 305 of the second pressure control mechanism 32 communicates with the outlet. 313B (see FIG. 16(a)). Therefore, in the second pressure control mechanism 32 , air flows from the second pressure chamber 306 toward the first pressure chamber 305 , contrary to the first pressure control mechanism 31 . Yet another difference is that valve 307 of second pressure control mechanism 32 is integrated with pressure plate 302 via shaft 304 . Furthermore, the shaft 304 of the second pressure control mechanism 32 passes through the orifice 308 and contacts the shaft holder 309 . Since the valve 307 and the pressure receiving plate 302 are integrated via the shaft 304, not only the biasing force of the biasing member 301A in the first pressure chamber 305 but also the biasing force of the biasing member 301B in the second pressure chamber 306 is applied. It also receives an urging force.

The mechanism of pressure adjustment in the second pressure control mechanism 32 is the same as that of the first pressure control mechanism 31 described above. Determined by relational expression (3).
P1=P0-(P2.Sv+k1.x)/Sd (3)

Sd is the pressure receiving area of the pressure receiving plate 302, Sv is the pressure receiving area of the valve 307, P0 is the atmospheric pressure, P1 is the pressure inside the second pressure chamber 306 on the upstream side, and P2 is the first pressure chamber 305 on the downstream side. is the internal pressure. k1 is the spring constant of the biasing member 301 (301A, 301B), and x is the displacement (spring displacement) of the biasing member 301 (301A, 301B). Since the second term on the right side of equation (3) always takes a positive value, P1<P0 and P1 is a negative pressure.

Also, between the flow resistance R in the gap between the valve 307 and the orifice 308 and the flow rate Q passing through the orifice 308, the following equation (4) holds.
P1=P2-QR (4)

The gap (valve opening) between the valve 307 and the orifice 308 and the flow resistance R are set to have the relationship shown in FIG. 17, that is, the flow resistance R decreases as the valve opening increases. The pressure P1 in the second pressure chamber 306 on the upstream side is determined by adjusting the valve opening so that the equations (3) and (4) are satisfied at the same time.

When the flow rate Q increases, the pressure of the suction pump 1000 (see FIG. 2) connected downstream of the negative pressure control unit 3 is constant. Flow resistance increases between up to 1000. Therefore, the pressure P2 in the first pressure chamber 305 rises by the increase in flow resistance. Therefore, the force (P2·Sv) that closes the valve 307 increases, and the pressure P1 in the second pressure chamber 306 on the upstream side instantaneously decreases, as is clear from the equation (3).

Also, the formula R=(P1-P2)/Q is derived from the formula (4). As the flow rate Q and the pressure P2 increase and the pressure P1 decreases, the flow resistance R decreases. As the flow resistance R decreases, the valve opening degree increases according to the relationship shown in FIG. Since the length of the biasing member 301 increases as the valve opening increases, the displacement x from its free length decreases. Therefore, the acting force (k1·x) of the biasing member 301 becomes smaller, and the pressure P1 in the second pressure chamber 306 on the upstream side instantaneously increases, as is clear from the equation (3).

On the other hand, when the flow rate Q of air decreases, the second pressure control mechanism 32 acts in the opposite manner to when the flow rate Q increases. That is, when the pressure P2 in the first pressure chamber 305 on the downstream side drops, the pressure P1 in the second pressure chamber 306 on the upstream side instantaneously increases, and the increase in the pressure P1 increases the flow resistance R. As a result, the pressure P1 in the second pressure chamber 306 on the downstream side is instantaneously reduced.

In this way, the instantaneous increase and decrease of the pressure P1 in the second pressure chamber 306 on the upstream side are repeated, the valve opening degree changes according to the flow rate Q, and the equations (3) and (4) are compatible. As a result, the pressure P1 inside the second pressure chamber 306 on the upstream side is controlled to be constant. Therefore, the pressure in the upstream channel portion (exit side of the liquid ejection head) of the second pressure control mechanism 32 is autonomously controlled to be constant.

Also, the retracted length and biasing force of the biasing member 301A in the first pressure chamber 306 are determined by the negative pressure adjusting member 311 of the second pressure control mechanism 32, similarly to the negative pressure adjusting member 311 of the first pressure control mechanism 31. can be changed. Therefore, the same negative pressure control unit 3 can be used for various recording apparatuses with different operating conditions, thereby reducing costs.

In this embodiment, the flow direction of the ink flowing through the ink flow path that communicates the first tank and the second tank via the pressure chamber is the first direction (forward direction) and the opposite second direction (return direction). ) can be switched between Therefore, bubbles, viscous ink, foreign matter, and the like in the flow path and near the ejection port can be discharged to the downstream side of the ejection port in the flow direction.

According to the configuration of this embodiment, even if the flow direction of the ink flowing through the ink flow path that communicates the first tank and the second tank via the pressure chamber is the first direction (forward direction), it is the second direction. Even in the (reverse direction), it is possible to stabilize ink refilling during ejection.

[Second embodiment]
A configuration according to the second embodiment of the present invention will be described. It should be noted that in the following description, portions different from the first embodiment will be described, and descriptions of portions similar to the first embodiment will be omitted.

FIG. 18 is a schematic diagram showing a fluid flow path (ink flow path, air flow path) of the printing apparatus according to the second embodiment of the invention. The differences from the first embodiment are that a replaceable main tank 1002 is connected to the liquid ejection head instead of the first tank, and that the air communication port of the main tank 1002 is connected to an individual supply valve (V2). The only difference is that it is connected to the switching mechanism 4 via .

The main tank 1002 of this embodiment has a remaining amount detection mechanism (not shown) for detecting information regarding the remaining amount of ink inside, and includes an inner bag for storing ink and an air communication port opened in the tank housing. It is preferable to have a configuration having Although such a main tank configuration itself is common, by connecting a negative pressure control unit to the atmosphere communication port of the main tank 1002 via a switching mechanism, unlike a normal main tank, ink can be supplied. It is possible to use it in and out. In addition, since the ink inner bag is provided, it is possible to avoid the risk of ink color mixture occurring in the air pipe due to overturning or the like while maintaining the internal pressure control performance via the air pressure. Furthermore, by installing a residual amount detection mechanism that detects, for example, the collapse displacement of the inner bag, highly accurate residual amount detection that is not affected by the installation angle of the recording apparatus is also possible.

Some conventional main tanks have a system of providing a biasing means in the inner bag to generate a negative pressure in order to prevent ink leakage. When such a method is applied to the present embodiment, the negative pressure generated by the internal mechanism of the main tank must be lower than the control pressure of the first pressure control mechanism, or the negative pressure in the tank when setting the tank must be reduced. It is preferable from the point of view of handling that the pressure generating mechanism is disabled.

Although not shown, the second tank 23 can also be configured to use a tank having a similar bag configuration. However, in this case, since the second tank is not replaced unlike the main tank side, part of the foam discharged from the liquid ejection head 300 accumulates in the inner bag of the second tank, and the remaining amount detection accuracy gradually decreases. There is a fear that it will decline.

In this embodiment, as in the first embodiment, the switching mechanism 4 can reverse the direction of ink flow in the liquid ejection head 300 . A negative pressure compensating mechanism 37 is provided as in the first embodiment. Therefore, even when a large amount of ink is ejected from the ejection port 113 of the recording element substrate 10 in a short period of time, the negative pressure in the flow path on the downstream side of the pressure chamber in the ink flow direction is suppressed from dropping too much. A stable recording operation can be performed. That is, in the present embodiment, even if the flow direction of the ink flowing through the ink flow path connecting the first tank and the second tank via the pressure chamber is the first direction (forward direction), it is the opposite direction. Even in the second direction (backward direction), it is possible to stabilize the refilling of the ink during ejection. As a result, a highly reliable recording operation can be performed.

In the second embodiment, the use and mounting of the first tank 21 and the supply valve 6 (V3) on the apparatus can be eliminated, so that the cost and size of the ink supply system can be further reduced. In addition, since many main tanks have conventionally been equipped with a remaining amount detection mechanism, the remaining amount detection mechanism can be reduced by diverting that function to operate the switching mechanism. Moreover, since the refilling operation from the main tank to the first tank is unnecessary, the recording standby time can be reduced, and the recording productivity of the recording apparatus can be improved.

[Third embodiment]
A configuration of the third embodiment of the present invention will be described. In the following description, portions different from the first embodiment will be described, and descriptions of portions similar to the first embodiment will be omitted.

FIG. 19A is a schematic diagram showing an ink flow path and an air flow path for one of four colors of ink in the printing apparatus according to the third embodiment of the present invention. The third embodiment differs from the first embodiment in that a suction pump 1000 and a pressure pump 1003 are used to cause ink to flow through the liquid ejection head 300 . That is, in the third embodiment, the pressure pump 1003 functions as a first pressure control mechanism, and the suction pump 1000 functions as a second pressure control mechanism. According to the configuration of the third embodiment, by controlling the number of revolutions of the pump, the flow rate of ink flowing through the liquid ejection head 300 can be changed for each ink color.

The negative pressure compensating mechanism 37 is composed of a passive valve 33 and an on-off valve 34 (indicated by V5) as in the first embodiment. and the suction pump 1000 are provided in the middle of a path (bypass flow path) that directly connects them.

The passive valve 33 is designed to open when the pressure difference between its two sides, that is, the pressure difference between the pressure on the pressurizing pump 1003 side and the pressure on the suction pump 1000 side reaches or exceeds a predetermined value. In the example of FIG. 19, the pressure on the pressurizing pump 1003 side corresponds to the internal pressure of the ink flow path between the pressurizing pump 1003 and the inlet of the liquid ejection head 300 . The pressure on the side of the suction pump 1000 corresponds to the internal pressure of the ink flow path between the suction pump 1000 and the outlet of the liquid ejection head 300 .

According to the configuration of the third embodiment, even if the ejection operation of the liquid ejection head 300 causes the pressure on the downstream side (outlet side) of the ejection port to decrease (negative pressure increases), , the opening of the passive valve 33 compensates for the negative pressure fluctuations and prevents an excessive rise in the negative pressure. As a result, refilling of the ink during ejection can be stabilized, and a highly reliable printing operation can be performed.

The third embodiment also differs from the first embodiment in that the switching mechanism 4 is arranged between the first and second tanks and the liquid ejection head 300 . In FIG. 19A, the on-off valve V1A and the on-off valve V1D are open, and the on-off valve V1B and the on-off valve V1C are closed. Therefore, the ink is supplied from the first tank 21 to the pressurizing pump 1003 through the on-off valve V1D, and then flows into the liquid ejection head 300 . After that, the ink is sucked out by the suction pump 1000 and recovered into the second tank 22 through the on-off valve V1A. When the amount of ink in the second tank 22 exceeds the specified water level, the switching operation closes the on-off valve V1A and the on-off valve V1D and opens the on-off valve V1B and the on-off valve V1C as shown in FIG. 19(b). . This switching operation reverses the direction of ink flow as viewed from the first tank and the second dunk.

On the other hand, in the first and second embodiments, the direction of ink flow in the liquid ejection head 300 can be switched between reciprocating directions. The ink flow direction is fixed in one direction. From the viewpoint of the layout design of the ink flow path for each color in the liquid ejection head, there are cases where a large difference occurs between the upstream side resistance and the downstream side resistance of the ejection port. In this case, if the direction of ink flow in the liquid ejection head 300 is reversed, the negative pressure value at the ejection port changes greatly depending on the direction of ink flow. . In contrast, if the direction of ink flow in the liquid ejection head 300 is fixed as in the present embodiment, this risk can be reduced.

In the third embodiment, similarly to the first and second embodiments, the liquid is appropriately replenished according to the pressure state inside the liquid ejection head, and the pressure is controlled. As a result, it is possible to improve the liquid refill property of the liquid ejection head and stabilize the ejection state of the liquid ejection head.

[Fourth embodiment]
A configuration according to the fourth embodiment of the present invention will be described. It should be noted that in the following description, portions different from the first embodiment will be described, and descriptions of portions similar to the first embodiment will be omitted. 20 and 21 are schematic diagrams showing fluid flow paths (ink flow paths, air flow paths) of the printing apparatus according to the fourth embodiment of the invention. 20 shows the state during recording, and FIG. 21 shows the state during non-recording.

The difference from the first embodiment is that it has a communication passage 28 that connects the first tank and the second tank of each color, and an on-off valve 14 (indicated by V6) that can open and close the communication passage 28. , and the rest is the same as in the first embodiment. The purpose of providing the communication path 28 and the valve 14 (V6) is to quickly move the ink between the first tank 21 and the second tank 22 without passing through the recording element substrate 10. FIG. In FIG. 21, the second tank 22 is connected to the pressure control mechanism (high pressure side) 31, and the first tank 21 is connected to the suction pump 1000 via the valve V1D and the bypass valve 35 (V4). By driving the suction pump 1000 , the air in the first tank 21 is discharged and ink flows into the first tank 21 from the second tank 22 through the communication passage 28 . At this time, since the supply valve 6 (V3) is closed, the ink inside the liquid ejection head 300 is not recovered inside the first tank 21 . Further, since the internal pressure of the second tank 22 is substantially close to the control pressure of the pressure control mechanism (high pressure side) 31, the meniscus at the ejection port of the recording element substrate 10 is held, and Ink is not collected in the second tank 22 . A check valve (not shown) is built in the main tank 1002, and the ink in the main tank 1002 passes through the check valve, the ink joint 8 and the filter 1001, and the first tank 21 is replenished with ink. be done. Since the pressure for opening the check valve is set lower than the internal pressure of the first tank 21 during transfer of ink as shown in FIG.

In the fourth embodiment, as in the first embodiment, ink flows from the first tank 21 to the second tank 22 via the recording element substrate 10 of the liquid ejection head 300 during printing as shown in FIG. . However, in the fourth embodiment, the movement of ink from the second tank 22 to the first tank 21 is performed via the communication path 28 and the valve 14 (V6) during non-printing as shown in FIG. Therefore, the ink flow direction in the printing element substrate 10 during printing can be limited to one direction, and the temperature distribution in the row direction of the ejection openings can be easily estimated.

For example, in FIG. 10, it is assumed that the first individual flow path 213 is positioned upstream in the ink flow direction of the recording element substrate 10, and the second individual flow path 214 is positioned downstream in the flow direction. In this case, since the temperature of the ink flowing into the recording element substrate 10 is normally low, the temperature of the ink at the ejection openings near the first individual flow paths 213 tends to be low. On the other hand, the ink in the recording element substrate 10 receives heat and rises in temperature, and the temperature of the ink flowing out from the recording element substrate 10 rises, so the temperature of the ink in the ejection openings around the second individual flow path 214 rises. Cheap. Therefore, the recording element substrate 10 has a temperature distribution of low-temperature portions and high-temperature portions in the row direction of the ejection openings, and the temperature distribution is roughly related to the position of the first individual channel 213 and the second individual channel 214 . It will correspond. Based on such an estimated value of the temperature distribution, a control device (not shown) of the main body of the recording apparatus adjusts the number of ink droplets that land per unit area of the recording medium. It is possible to correct the density unevenness of the printed image caused by the volume change of the ink.

When the ink flow direction in the recording element substrate 10 is reversed as in the first embodiment, the temperature distribution of the recording element substrate 10 is also reversed. Therefore, if the control mode for adjusting the number of ejected ink droplets is fixed, it is not possible to deal with such a reversal of the temperature distribution, and it becomes difficult to correct the density unevenness of the printed image. In the first embodiment as described above, by switching to the control mode for adjusting the number of ejected ink droplets according to the flow direction of the ink in the recording element substrate 10, the density of the recorded image can be adjusted according to the inversion of the temperature distribution. Unevenness can be corrected. However, in this case, there is a risk of complicating control on the printing apparatus main body side.

Further, in order to transfer the ink more reliably without taking bubbles in the first tank 21 and the second tank 22 into the communication path 28 as much as possible, the communication position of the communication path 28 with respect to the second tank 22 is set to the second tank 22. A position below the liquid level in 22 is preferred.

In addition, as a preferable point of transferring the ink between the first tank 21 and the second tank 22 via the communication path 28, when the ink is a pigment ink containing a pigment component, the sedimentation of the pigment component can be suppressed. FIG. 22 is a schematic diagram showing fluid flow paths (ink flow path, air flow path) when ink is transferred from the first tank 21 to the second tank 22 via the communication path 28 during non-printing. In FIG. 22, contrary to the case of FIG. 21, the first tank 21 is connected to the pressure control mechanism (high pressure side) 31, and the second tank 22 is sucked through the valve V1C and the bypass valve 35 (V4). It is connected to pump 1000 . Others are the same as in the case of FIG. 21, and ink is transferred from the first tank 21 to the second tank 21 by driving the suction pump 1000 .

During non-printing, the transfer of ink shown in FIG. 21 and the transfer of ink shown in FIG. The ink inside can be stirred. As a result, sedimentation of the pigment component in the ink in the first tank 21 and the second tank 22 can be suppressed without adding a special configuration for stirring the ink. In order to increase the efficiency of ink agitation by the ink flow through the communication path 28, it is preferable to provide a static mixer in the vicinity of the connecting portion of the communication path 28 in the first tank 21 and the second tank 22.

Also in the first embodiment, by reversing the ink flow direction, it is possible to agitate the ink in the first and second tanks in the same manner as in the fourth embodiment. However, in the negative pressure range where the meniscus of the ink formed in the ejection port can be maintained, the flow rate of the ink that can pass through the printing element substrate 10 is not large. Settling can be eliminated.

Further, the communication passage 28 and the valve 14 (V6) in the fourth embodiment 4 can be added to the configurations of the second embodiment and the third embodiment as in the first embodiment.

(Other embodiments)
In the first to third embodiments described above, the bubble jet (registered trademark) method is adopted as the liquid ejection method, but the present invention can also be applied to a liquid ejection head that employs the piezo method. .

The method of the printing apparatus is not limited to the full-line method as in the above-described embodiment, and an image is printed by repeatedly moving the liquid ejection head in the main scanning direction and conveying the printing medium in the sub-scanning direction. A so-called serial scan method may be used.

INDUSTRIAL APPLICABILITY The present invention can be widely applied to liquid supply apparatuses that supply various liquids and liquid ejection apparatuses that can eject various liquids. The present invention also relates to an inkjet apparatus that uses an inkjet head capable of ejecting liquid to perform various processes (recording, processing, coating, irradiation, reading, inspection, etc.) on various media (sheets). is also applicable. The medium (including recording medium) includes various media to which liquid including ink is applied regardless of the material, such as paper, plastic, film, fabric, metal, and flexible substrate.

1 Recording Device 3 Negative Pressure Control Unit 4 Switching Mechanism 10 Recording Element Substrate 11 Support 12 First Common Channel 13 Second Common Channel 21 First Tank 22 Second Tank 33 Passive Valve 34 Opening/Closing Valve 37 Negative Pressure Compensation Mechanism ( pressure compensation means)
113 ejection port 123 pressure chamber 220 liquid supply unit 300 liquid ejection head

Claims (26)

an ejection port for ejecting liquid;
a pressure chamber containing a liquid to be ejected from the ejection port;
an element that generates energy for ejecting the liquid in the pressure chamber;
a first tank and a second tank capable of containing a liquid;
a flow path communicating between the first tank and the second tank via the pressure chamber;
switching means for switching the flow direction of the liquid in the channel between a first direction of flow from the first tank to the second tank and a second direction of flow from the second tank to the first tank;
In the flow channel, when the pressure in the downstream flow channel portion on the downstream side of the pressure chamber in the flow direction of the liquid is equal to or lower than a predetermined pressure, the liquid is supplied to the downstream flow channel portion. pressure compensating means for compensating for pressure drop in the
A liquid ejection device comprising: pressure between the downstream channel portion and an upstream channel portion on the upstream side of the pressure chamber in the liquid flow direction so as to cause the fluid to flow through the pressure chamber in the channel; 2. The liquid ejector of claim 1, further comprising pressure control means for creating the difference. The pressure control means includes a first pressure control section that controls the pressure in the upstream flow path section to a first pressure, and a second pressure control section that controls the pressure in the downstream flow path section to a second pressure lower than the first pressure. 3. The liquid ejecting apparatus according to claim 2, further comprising: 2 pressure control units. 4. The liquid ejection device according to claim 3, further comprising a pump at a position downstream of the second pressure control section in the flow direction. 3. A bypass passage connecting upstream and downstream of said second pressure control unit in said flow direction is provided, said bypass passage being provided with a bypass opening/closing valve capable of opening/closing control of said bypass passage. 5. The liquid ejecting apparatus according to 4. The pressure compensating means includes a communication passage that communicates the air portion of the first tank with the air portion of the second tank when the pressure in the downstream channel portion becomes equal to or lower than a predetermined pressure. 6. The liquid ejecting apparatus according to any one of claims 1 to 5, characterized in that: The pressure compensating means is a passive valve that opens and closes the communication path in accordance with a pressure difference between a pressure in an upstream channel portion upstream of the pressure chamber in a liquid flow direction and a pressure in the downstream channel portion. 7. The liquid ejecting apparatus according to claim 6, comprising: 8. The liquid ejecting apparatus according to claim 6, further comprising an open/close valve capable of opening/closing control in the communication path. Each of the first tank) and the second tank has an air connection port that allows air to flow in and out of the air portion in the tank,
The air connection port of the first tank controls, via the switching means, the pressure in the upstream flow path portion on the upstream side of the pressure chamber in the flow direction of the liquid to a first pressure. 1 pressure control unit, and a second pressure control unit that controls the pressure in the downstream channel portion to a second pressure lower than the first pressure,
3. The air connection port of the second tank is switchably connected to the first pressure control section and the second pressure control section through the switching means by an air path. 9. The liquid ejection device according to any one of 8 to 8. 10. The liquid according to claim 9, wherein a gas-liquid separation membrane or a water-repellent filter is provided in at least one of the air connection port and the air path of each of the first tank and the second tank. discharge device. An on-off valve arranged in an air path between the switching means and the first tank, which opens to allow liquid and/or air to enter and exit the first tank, and which closes when the power supply is stopped,
The switching means is
The upstream end is connected to the downstream side of a first pressure control section that controls the pressure in the upstream flow path section on the upstream side in the flow direction of the liquid from the pressure chamber to a first pressure, and the downstream end is connected to the first tank. and a first switching section switchable to be connected upstream of one of said second tank;
The downstream end is connected upstream of a second pressure control section that controls the pressure in the downstream flow path section on the downstream side of the pressure chamber in the flow direction of the liquid to a second pressure lower than the first pressure; is switchable to be connected downstream of one of the first tank and the second tank; and
with
The first switching unit connects its downstream end to the upstream of the first tank, and the second switching unit connects its upstream end to the downstream of the second tank when the power supply is stopped. The liquid ejection device according to any one of claims 8 to 10. 12. The liquid ejecting apparatus according to any one of claims 1 to 11, wherein the flow path communicates with each of the plurality of pressure chambers. The liquid ejection device is capable of ejecting a plurality of liquid types,
A plurality of sets of the first tank and the second tank are provided corresponding to the liquid type,
Each of the first tank and the second tank has an air connection port that allows air to flow in and out of the air portion in the tank,
The air connection port of the first tank for each type of liquid controls the pressure in the common upstream flow path section upstream in the flow direction of the liquid from the pressure chamber via the switching means by the air path. A first pressure control section that controls the pressure to a first pressure, and a common pressure in the downstream flow path section on the downstream side of the pressure chamber in the flow direction of the liquid, a second pressure that is lower than the first pressure. 2 connected to one of the pressure control units,
The air connection port of the second tank for each liquid type is connected to the other of the common first pressure control section or the common second pressure control section via the switching means by an air path. 13. The liquid ejecting apparatus according to any one of claims 8 to 12, characterized by: A first position downstream of the first pressure control section in the flow direction and upstream of the pressure chamber in the flow direction, and a position upstream of the second pressure control section in the flow direction. and a second position downstream of the pressure chamber in the flow direction, and a bypass flow passage in which the pressure compensating means is arranged,
4. The liquid ejecting apparatus according to claim 3, wherein the pressure compensating means opens the bypass channel when the pressure in the downstream channel portion becomes equal to or lower than a predetermined pressure. 15. The method according to claim 14, wherein the pressure compensating means includes a passive valve that opens and closes the bypass flow path according to a pressure difference between the pressure in the upstream flow path section and the pressure in the downstream flow path section. A liquid ejection device as described. 16. The liquid ejecting apparatus according to claim 15, further comprising an open/close valve capable of opening/closing control in the bypass channel. 17. The fuel tank according to any one of claims 1 to 16, further comprising: a communication passage for communicating said first tank and said second tank without passing through said pressure chamber; and a valve capable of opening and closing said communication passage. 2. The liquid ejection device according to item 1. 18. The liquid ejecting apparatus according to claim 17, wherein the communication path allows liquid to flow from the second tank to the first tank, but does not allow liquid to flow from the first tank to the second tank. Recording is performed by ejecting the liquid from the ejection port while the liquid is flowing in the first direction in the flow path, and the ejection port is performed in the state where the liquid is flowing in the second direction in the flow path. 19. The liquid ejecting apparatus according to claim 17, wherein the liquid is ejected from the nozzle to perform no printing. A liquid ejection head mounted and used in the liquid ejection device according to any one of claims 1 to 19,
an element substrate comprising an ejection port for ejecting a liquid, a pressure chamber containing the liquid to be ejected from the ejection port, and an element arranged in the pressure chamber for generating energy necessary for ejecting the liquid; ,
a first tank and a second tank capable of containing a liquid;
a support that supports the element substrate and has a flow path that communicates the first tank and the second tank via the pressure chamber;
A liquid ejection head comprising: 21. A liquid ejection head according to claim 20, wherein the element substrate ejects the liquid by bubbling pressure generated by applying heat to the liquid. 22. A liquid ejection head according to claim 20, wherein the liquid in said pressure chamber is circulated with the outside of said pressure chamber. The liquid discharge head includes the downstream flow path section and the upstream flow path section upstream of the pressure chamber in the flow direction of the liquid so as to cause the flow of the liquid through the pressure chamber in the flow path. and pressure control means for creating a pressure differential between
The pressure control means includes a first pressure control section that controls the pressure in the upstream flow path section to a first pressure, and a second pressure control section that controls the pressure in the downstream flow path section to a second pressure lower than the first pressure. 2 pressure control, and
The first pressure control unit is applied with a pressure higher than the first pressure from the upstream side in the flow direction,
a first pressure chamber communicating with the first tank or the second tank;
a second pressure chamber having a variable volume connected to the flow path upstream of the pressure chamber in the flow direction;
an orifice provided at a boundary between the first pressure chamber and the second pressure chamber;
a valve provided in the first pressure chamber, variable in flow resistance between the first pressure chamber and the second pressure chamber, and urged by a load in a direction to close the gap between the orifice and the orifice; ,
Displacement is possible based on fluctuations in the pressure in the second pressure chamber, and by transmitting the displacement to the valve, the position of the valve is made variable together with the biasing force applied to the valve. 23. The liquid ejection head according to any one of claims 20 to 22, further comprising a pressure receiving portion. The liquid discharge head includes the downstream flow path section and the upstream flow path section upstream of the pressure chamber in the flow direction of the liquid so as to cause the flow of the liquid through the pressure chamber in the flow path. and pressure control means for creating a pressure differential between
The pressure control means includes a first pressure control section that controls the pressure in the upstream flow path section to a first pressure, and a second pressure control section that controls the pressure in the downstream flow path section to a second pressure lower than the first pressure. 2 pressure control, and
The second pressure control unit is applied with a pressure lower than the second pressure from the upstream side in the flow direction,
a first pressure chamber with a variable volume connected to the flow path downstream of the pressure chamber in the flow direction;
a second pressure chamber communicating with the flow path at a position downstream of the second pressure control unit in the flow direction;
an orifice provided at a boundary between the first pressure chamber and the second pressure chamber;
A valve provided in the second pressure chamber, variable in flow resistance between the first pressure chamber and the second pressure chamber, and urged by a load in the direction of closing the gap between the orifice and the orifice. When,
A pressure receiving pressure capable of being displaced based on fluctuations in the pressure in the first pressure chamber, and transmitting the displacement to the valve, together with the biasing force applied to the valve, for varying the position of the valve. 24. The liquid ejection head according to any one of claims 20 to 23, further comprising: an ejection port for ejecting liquid;
a pressure chamber containing a liquid to be ejected from the ejection port;
an element that generates energy for ejecting the liquid in the pressure chamber;
a first tank and a second tank capable of containing a liquid;
a flow path communicating between the first tank and the second tank via the pressure chamber;
switching means for switching the flow direction of the liquid in the channel between a first direction of flow from the first tank to the second tank and a second direction of flow from the second tank to the first tank;
a first pressure regulating passage and a second pressure regulating passage for regulating the pressure in the first tank and the second tank, respectively;
a communicating passage that communicates the first pressure regulating passage and the second pressure regulating passage;
a passive valve that is provided in the communication path and opens and closes the communication path in accordance with a pressure difference between an upstream channel upstream of the pressure chamber in a liquid flow direction and a downstream channel downstream of the pressure chamber;
A liquid ejection device comprising: 26. The liquid ejection device according to claim 25, wherein the liquid in the upstream channel is supplied to the downstream channel through the communication channel by opening the passive valve.

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