LIQUID SUPPLY DEVICE, LIQUID DISCHARGE UNIT, AND DEVICE FOR DISCHARGING LIQUID

Abstract

To provide a liquid supply device equipped with a circulation mechanism, which is downsized and can reduce occurrence of pressure variation caused by the downsizing and prevent occurrence of poor discharging in a liquid discharge head.SOLUTION: The liquid supply device comprises: a liquid discharge head 8 that discharges liquid; a main tank 1 that stores liquid to be supplied to the liquid discharge head 8; a first sub tank 2, connected to the main tank 1 and the liquid discharge head 8, which stores gas and liquid; a second sub tank 3, connected to the first sub tank and the liquid discharge head 8, which stores gas and liquid; a first air tank 10, connected to the first sub tank, which stores gas; and a second air tank 9, connected to the second sub tank, which stores gas.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a liquid supplying device, a liquid ejection unit, and an apparatus for ejecting liquid. [Background technology]

[0002] As image forming apparatuses such as printers, facsimiles, copiers, plotters, and combination machines thereof, for example, ink ejection type recording apparatuses (apparatuses that eject liquid) having a liquid ejection head are known. As liquid ejection heads, circulation type heads are known that have a supply flow path to an individual liquid chamber that communicates with a nozzle and a discharge flow path that communicates with the individual liquid chamber, and that are provided with a liquid supply port that communicates with the supply flow path and a liquid discharge port that communicates with the discharge flow path.

[0003] A known circulation type liquid ejection head has a liquid tank on the supply side and a discharge side (recovery side), and uses the pressure difference caused by positive and negative air in the two liquid tanks to send liquid from the positive pressure side to the negative pressure side, and then uses a pump to send liquid from the negative pressure side to the positive pressure side, thereby circulating liquid between the liquid tanks and the head that ejects the liquid (see, for example, Patent Document 1). Such a circulation mechanism can prevent the nozzle from drying out and the pigment with high density from settling.

[0004] In conventional devices, the ejection operation is stopped when refilling the liquid tank with ink, and then resumed after refilling, which reduces productivity. In particular, when the volume of the liquid tank is small, the operation of refilling the liquid tank with ink from the refill liquid tank is required frequently, which inevitably reduces productivity. However, increasing the volume of the tank leads to an increase in the size of the device, which is not desirable for a liquid supply device equipped with a circulation type head, for which miniaturization is an issue.

[0005] In response to this, Patent Document 1 discloses a technology that includes a circulation section that circulates liquid between the liquid chamber and the liquid ejection section, a liquid replenishment section that replenishes new liquid into the liquid chamber, and a gas replenishment section that replenishes gas into the liquid chamber, in order to prevent the ejection operation from stopping and improve productivity, and adjusts the pressure in the liquid ejection section by switching between replenishing new liquid from the liquid replenishment section and replenishing gas from the gas replenishment section. Summary of the Invention [Problem to be solved by the invention]

[0006] However, even if the technology of Patent Document 1 can prevent the stop of the ejection operation, the air volume also becomes smaller as the tank capacity is reduced as the size is reduced, resulting in larger pressure fluctuations (pulsations) caused by the pump when ink is supplied, and there is an issue that significant pressure fluctuations that exceed the pulsation range occur when ink is ejected. The occurrence of pressure fluctuations may cause liquid overflow or entrapment of air bubbles, which may lead to poor ejection from the liquid ejection head due to dissolved gas. In addition, the occurrence of pressure fluctuations may cause the volume and speed of the ejected liquid to become unstable. Therefore, when the liquid ejection head is installed in an image forming apparatus, it may lead to a deterioration in image quality.

[0007] Therefore, an object of the present invention is to provide a liquid supplying device that can reduce the occurrence of pressure fluctuations that accompany miniaturization while also miniaturizing a device equipped with a circulation mechanism, and prevent the occurrence of ejection defects in a liquid ejection head. [Means for solving the problem]

[0008] In order to solve the above problems, a liquid supplying device of the present invention includes a liquid ejection head that ejects liquid, a main tank that contains liquid to be supplied to the liquid ejection head, a first sub-tank that contains gas and liquid and is connected to the main tank and the liquid ejection head, a second sub-tank that contains gas and liquid and is connected to the first sub-tank and the liquid ejection head, a first air tank that contains gas and is connected to the first sub-tank, and a second air tank that contains gas and is connected to the second sub-tank. The volume of the first air tank is larger than the volume of the first sub-tank, or the volume of the second air tank is larger than the volume of the second sub-tank. It is characterized by:

[0009] Furthermore, a liquid supplying device of the present invention includes a first liquid ejection head and a second liquid ejection head that eject liquid, a main tank that contains liquid to be supplied to the first liquid ejection head and the second liquid ejection head, a first sub-tank that contains a gas and a liquid and is connected to the main tank and the first liquid ejection head, a second sub-tank that contains a gas and a liquid and is connected to the first sub-tank and the first liquid ejection head, a third sub-tank that contains a gas and a liquid and is connected to the main tank and the second liquid ejection head, a fourth sub-tank that contains a gas and a liquid and is connected to the third sub-tank and the second liquid ejection head, a negative pressure air tank that contains a gas and supplies negative air pressure, and a positive pressure air tank that contains a gas and supplies positive air pressure. The negative pressure air tank is connected to two of the first sub-tank, the second sub-tank, the third sub-tank, and the fourth sub-tank, and the positive pressure air tank is connected to the two sub-tanks other than the sub-tank connected to the negative pressure air tank. It is characterized by: Effect of the Invention

[0010] According to the present invention, it is possible to provide a liquid supplying device that can reduce the size of a device equipped with a circulation mechanism, while reducing the occurrence of pressure fluctuations that accompany miniaturization, and prevent ejection defects in a liquid ejection head. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic diagram showing a first embodiment of a liquid supply device according to the present embodiment. [Diagram 2] 1 is an external view showing an example of a liquid supply apparatus according to an embodiment of the present invention. [Diagram 3] 11 is a graph conceptually showing the difference in pressure fluctuation depending on whether or not an air tank is connected. [Figure 4] 5 is a schematic diagram showing a second embodiment of a liquid supply apparatus according to the present embodiment. FIG. [Diagram 5] 10A and 10B are schematic diagrams showing a modified example of the second embodiment of the liquid supply device according to the present embodiment. [Figure 6] 10A and 10B are schematic diagrams showing a modified example of the second embodiment of the liquid supply device according to the present embodiment. [Figure 7] 10A and 10B are schematic diagrams showing a modified example of the second embodiment of the liquid supply device according to the present embodiment. [Figure 8] FIG. 13 is a schematic diagram showing a third embodiment of a liquid supply apparatus according to the present embodiment. [Figure 9] FIG. 1 is a schematic diagram showing a conventional liquid supplying device (comparative example). [Figure 10] FIG. 2 is a side view illustrating an example of a liquid ejection unit. [Figure 11] FIG. 2 is a top view illustrating an example of a liquid ejection unit. [Figure 12] FIG. 2 is a side view illustrating an example of a liquid ejection unit. [Figure 13] FIG. 2 is a plan view illustrating a mechanism of an example of a device for discharging liquid. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] A liquid supplying device, a liquid ejection unit, and a device for ejecting liquid according to the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the following embodiments, and may be modified within the scope of what a person skilled in the art can imagine, such as other embodiments, additions, modifications, deletions, etc., and any aspect is within the scope of the present invention as long as it provides the functions and effects of the present invention.

[0013] [Liquid supply device] Figures 1 and 3 to 8 are schematic diagrams showing a liquid supplying device according to the present invention, and Figure 2 is an external view showing one example of a liquid supplying device according to the present invention. Arrows in the drawings indicate the flow direction of liquid or gas. The liquid supply device of this embodiment comprises a liquid ejection head 8 that ejects liquid, a main tank 1 that contains liquid to be supplied to the liquid ejection head 8, sub-tanks 2, 3 that contain at least gas and are connected to the main tank 1 and the liquid ejection head 8, and air tanks 9, 10 that contain gas and are connected to the sub-tanks 2, 3, and the sub-tanks 2, 3 comprise at least a positive pressure sub-tank 3 that supplies liquid to the liquid ejection head 8, and a negative pressure sub-tank 2 that recovers liquid from the liquid ejection head 8.

[0014] [First embodiment] Example 1 An example of a liquid supplying apparatus according to a first embodiment is shown in FIG. The liquid supply device of Figure 1 (A) comprises a liquid ejection head 8 that ejects liquid, a main tank 1 that contains liquid to be supplied to the liquid ejection head 8, a first sub-tank that contains gas and liquid and is connected to the main tank 1 and the liquid ejection head 8, a second sub-tank that contains gas and liquid and is connected to the first sub-tank and the liquid ejection head, a first air tank that contains gas and is connected to the first sub-tank, and a second air tank that contains gas and is connected to the second sub-tank.

[0015] In the liquid supply device of this embodiment, the first sub-tank is a negative pressure sub-tank 2 that recovers liquid from the liquid ejection head 8, the second sub-tank is a positive pressure sub-tank 3 that supplies liquid to the liquid ejection head 8, the first air tank is a negative pressure air tank 9 that supplies negative air pressure, and the second air tank is a positive pressure air tank 10 that supplies positive air pressure.

[0016] In addition, the liquid supply device of this embodiment further includes a first liquid supply pump 4 connected between the main tank 1 and the negative pressure subtank 2 and supplying liquid from the main tank 1 to the negative pressure subtank 2, and a second liquid supply pump (circulation pump) 5 connected between the negative pressure subtank 2 and the positive pressure subtank 3 and supplying liquid from the negative pressure subtank 2 to the positive pressure subtank 3.

[0017] The liquid supply device according to this embodiment includes a decompression air pump 7 connected to a negative pressure air tank 9 to decompress the negative pressure air tank 9, and a pressurization air pump 6 connected to a positive pressure air tank 10 to pressurize the positive pressure air tank 10.

[0018] In addition, the liquid supply device of this embodiment is equipped with a liquid supply path 11 connecting the main tank 1 and the negative pressure subtank 2, a circulation path 14 connecting the positive pressure subtank 3 and the negative pressure subtank 2, a recovery path 12 connecting the negative pressure subtank 2 and the liquid ejection head 8, and a supply path 13 connecting the positive pressure subtank 3 and the liquid ejection head 8. Furthermore, it is provided with a first negative pressure air flow path 15 connecting the negative pressure sub-tank 2 and the negative pressure air tank 9, a second negative pressure air flow path 17 communicating with the negative pressure air tank 9 and connected to the reduced pressure air pump 7, a first positive pressure air flow path 16 connecting the positive pressure sub-tank 3 and the positive pressure air tank 10, and a second positive pressure air flow path 18 communicating with the positive pressure air tank 10 and connected to the pressurized air pump 6.

[0019] The volume of the air tanks (positive pressure air tank 10 and negative pressure air tank 9) of the liquid supplying device according to this embodiment is preferably larger than the volume of the sub-tanks (positive pressure sub-tank 3 and negative pressure sub-tank 2). The specific volume of the air tanks (positive pressure air tank 10 and negative pressure air tank 9) can be appropriately selected depending on the type of device to be installed and the volume of the subtank, but for example, in a subtank containing 20 mL of liquid, it is preferable that the volume is 50 mL or more. In this case, if the volume of the air tank is less than 50 mL, a sufficient damping effect cannot be obtained.

[0020] In this manner, in the liquid supply device of this embodiment, the miniaturized positive pressure sub-tank 3 and negative pressure sub-tank 2 are arranged on top of the liquid ejection head 8, and the large-capacity positive pressure air tank 10 and negative pressure air tank 9 are arranged as separate components in positions separate from the positive pressure sub-tank 3 and negative pressure sub-tank 2, respectively.

[0021] As a comparative example, a conventional liquid supplying device is shown in FIG. 9, the negative pressure sub-tank 2 and the decompression air pump 7 are directly connected without an air tank, and similarly the positive pressure sub-tank 3 and the pressurized air pump 6 are directly connected without an air tank, which results in large pressure fluctuations when ink is supplied.

[0022] FIG. 3 shows the difference in pressure fluctuations between the state in which the air tank of this embodiment is connected as shown in FIG. 1(A) and the state in which the conventional air tank is not connected as shown in FIG. Figure 3 is a graph conceptually showing the pressure fluctuations in the recovery flow path 12 connecting the negative pressure subtank 2 and the liquid ejection head 8, and the supply flow path 13 connecting the positive pressure subtank 3 and the liquid ejection head 8, with the example of this embodiment shown by the solid line C1 and the conventional example shown by the dashed line C2. In Figure 3, P0 is the set circulation pressure value, the pulsation range during circulation in the conventional example is shown as V1 (fluctuation between pressures P1 and P2), and the pressure fluctuation during liquid ejection is shown as V2 (fluctuation between pressures P1 and P3). 3, in the period S from T1 when the liquid ejection starts to T2 when the ejection ends, the conventional example C2 to which the air tank is not connected generates a significant pressure fluctuation V2 that exceeds the pulsation range V1. In contrast, the example C1 of this embodiment reduces both the pressure fluctuation during ejection and the width of the pulsation during circulation.

[0023] In this way, in the liquid supply device of this embodiment, by connecting the subtanks (positive pressure subtank 3 and negative pressure subtank 2) and the air tanks (positive pressure air tank 10 and negative pressure air tank 9), the apparent volume of gas in the subtanks becomes the sum of the volume of gas in the large-capacity air tank. This provides a large air damping effect, making it possible to reduce the amplitude of pulsation during circulation by pump drive and the occurrence of large pressure fluctuations during liquid ejection. Furthermore, by reducing the occurrence of pressure fluctuations, ejection defects in the liquid ejection head can be prevented.

[0024] Example 2 A liquid supplying device according to a modified example of the first embodiment is shown in FIG. In the liquid supplying device of the first embodiment described above, the main tank 1 is connected to the negative pressure sub-tank 2, but in the liquid supplying device of the present embodiment, the main tank 1 is connected to the positive pressure sub-tank 3.

[0025] The liquid supply device in Figure 1 (B) comprises a main tank 1 that contains liquid to be supplied to a liquid ejection head 8, a first sub-tank that contains gas and liquid and is connected to the main tank 1 and the liquid ejection head 8, a second sub-tank that contains gas and liquid and is connected to the first sub-tank and the liquid ejection head, a first air tank that contains gas and is connected to the first sub-tank, and a second air tank that contains gas and is connected to the second sub-tank, where the first sub-tank is a positive pressure sub-tank 3 that supplies liquid to the liquid ejection head, the second sub-tank is a negative pressure sub-tank 2 that recovers liquid from the liquid ejection head, the first air tank is a positive pressure air tank 10 that supplies positive air pressure, and the second air tank is a negative pressure air tank 9 that supplies negative air pressure.

[0026] In this way, the sub-tank connected to the main tank 1 may be either the negative pressure sub-tank 2 or the positive pressure sub-tank 3. However, from the viewpoint of suppressing the occurrence of pressure fluctuations, the configuration of the first embodiment in which the sub-tank connected to the main tank 1 is the negative pressure sub-tank 2 is more preferable.

[0027] [Second embodiment] The liquid supply device of this embodiment comprises a plurality of communicating negative pressure subtanks 2, a negative pressure air tank 9 connected to the plurality of negative pressure subtanks 2, and a plurality of communicating positive pressure subtanks 3, and a positive pressure air tank 10 connected to the plurality of positive pressure subtanks 3. The air conditioner further includes a decompression air pump 7 connected to the negative pressure air tank 9 to decompress the negative pressure air tank 9, and a pressurization air pump 6 connected to the positive pressure air tank 10 to pressurize the positive pressure air tank 10.

[0028] Example 3 An example of a liquid supply device according to this embodiment is shown in FIG. The liquid supply device of Figure 4 includes a first liquid ejection head 8a and a second liquid ejection head 8b that eject liquid, a main tank 1 that contains liquid to be supplied to the first liquid ejection head 8a and the second liquid ejection head 8b, a first sub-tank that contains gas and liquid and is connected to the main tank 1 and the first liquid ejection head 8a, a second sub-tank that contains gas and liquid and is connected to the first sub-tank and the first liquid ejection head 8a, a third sub-tank that contains gas and liquid and is connected to the main tank 1 and the second liquid ejection head 8b, a fourth sub-tank that contains gas and liquid and is connected to the third sub-tank and the second liquid ejection head 8b, a negative pressure air tank 9 that contains gas and supplies negative air pressure, and a positive pressure air tank 10 that contains gas and supplies positive air pressure.

[0029] In the liquid supply device of this embodiment, the first sub-tank and third sub-tank are negative pressure sub-tanks 2 (2a, 2b) that recover liquid from the liquid ejection head 8 (8a, 8b), and the second sub-tank and fourth sub-tank are positive pressure sub-tanks 3 (3a, 3b) that supply liquid to the liquid ejection head 8 (8a, 8b). The negative pressure air tank 9 is connected to the first sub-tank (negative pressure sub-tank 2a) and the third sub-tank (negative pressure sub-tank 2b), and the positive pressure air tank 10 is connected to the second sub-tank (positive pressure sub-tank 3a) and the fourth sub-tank (positive pressure sub-tank 3b).

[0030] In addition, the liquid supply device of this embodiment further includes a first liquid supply pump 4a connected between the main tank 1 and the first subtank and supplying liquid from the main tank 1 to the first subtank, a second liquid supply pump 4b connected between the main tank 1 and the third subtank and supplying liquid from the main tank 1 to the third subtank, a third liquid supply pump (circulation pump) 5a connected between the first subtank and the second subtank and supplying liquid from the first subtank to the second subtank, and a fourth liquid supply pump (circulation pump) 5b connected between the third subtank and the fourth subtank and supplying liquid from the third subtank to the fourth subtank.

[0031] The liquid supply device shown in Figure 4 is equipped with a first liquid supply pump 4a connected between the main tank 1 and one of the negative pressure subtanks 2a and supplies liquid from the main tank 1 to the one of the negative pressure subtanks 2a, a second liquid supply pump 4b connected between the main tank 1 and the other negative pressure subtank 2b and supplies liquid from the main tank 1 to the other negative pressure subtank 2b, a third liquid supply pump (circulation pump) 5a connected between one of the negative pressure subtanks 2a and one of the positive pressure subtanks 3a and supplies liquid from one of the negative pressure subtanks 2a to one of the positive pressure subtanks 3a, and a fourth liquid supply pump (circulation pump) 5b connected between the other negative pressure subtank 2b and the other positive pressure subtank 3b and supplies liquid from the other negative pressure subtank 2b to the other positive pressure subtank 3b.

[0032] The liquid supply device shown in FIG. 4 also includes a circulation flow path 14a connecting the positive pressure subtank 3a and the negative pressure subtank 2a, a circulation flow path 14b connecting the positive pressure subtank 3b and the negative pressure subtank 2b, a recovery flow path 12a connecting the negative pressure subtank 2a and the liquid ejection head 8a, a recovery flow path 12b connecting the negative pressure subtank 2b and the liquid ejection head 8b, a supply flow path 13a connecting the positive pressure subtank 3a and the liquid ejection head 8a, and a supply flow path 13b connecting the positive pressure subtank 3b and the liquid ejection head 8b.

[0033] Furthermore, the liquid supply device shown in Figure 4 is equipped with a first negative pressure air flow path 15 connecting the negative pressure sub-tanks 2a and 2b with the negative pressure air tank 9, a second negative pressure air flow path 17 communicating with the negative pressure air tank 9 and connected to the reduced pressure air pump 7, a first positive pressure air flow path 16 connecting the positive pressure sub-tanks 3a and 3b with the positive pressure air tank 10, and a second positive pressure air flow path 18 communicating with the positive pressure air tank 10 and connected to the pressurized air pump 6.

[0034] In this way, even in an embodiment having a plurality of sub-tanks, the air volume in each sub-tank can be increased by connecting the air tank.

[0035] Example 4 A liquid supply device according to a modified example of the second embodiment is shown in FIG. In the liquid supplying device of the above-mentioned embodiment 3, the main tank 1 is connected to the negative pressure sub-tank 2a and the negative pressure sub-tank 2b, whereas in the liquid supplying device of this embodiment shown in Figure 5, the main tank 1 is connected to the negative pressure sub-tank 2a and the positive pressure sub-tank 3b.

[0036] In the liquid supply device of Figure 5, the first sub-tank and fourth sub-tank are negative pressure sub-tanks 2 (2a, 2b) that recover liquid from the liquid ejection head 8 (8a, 8b), the second sub-tank and third sub-tank are positive pressure sub-tanks 3 (3a, 3b) that supply liquid to the liquid ejection head 8 (8a, 8b), a negative pressure air tank 9 is connected to the first sub-tank and fourth sub-tank, and a positive pressure air tank 10 is connected to the second sub-tank and third sub-tank. The other configurations are the same as those in the third embodiment.

[0037] Example 5 A liquid supply device according to another modified example of the second embodiment is shown in FIG. In the liquid supplying device of the above-mentioned embodiment 3, the main tank 1 is connected to the negative pressure sub-tank 2a and the negative pressure sub-tank 2b, whereas in the liquid supplying device of this embodiment shown in Figure 6, the main tank 1 is connected to the positive pressure sub-tank 3a and the positive pressure sub-tank 3b.

[0038] In the liquid supply device of Figure 6, the second sub-tank and the fourth sub-tank are negative pressure sub-tanks 2 (2a, 2b) that recover liquid from the liquid ejection head 8 (8a, 8b), the first sub-tank and the third sub-tank are positive pressure sub-tanks 3 (3a, 3b) that supply liquid to the liquid ejection head 8 (8a, 8b), a negative pressure air tank 9 is connected to the second sub-tank and the fourth sub-tank, and a positive pressure air tank 10 is connected to the first sub-tank and the third sub-tank. The other configurations are the same as those in the third embodiment.

[0039] Example 6 A liquid supply device according to another modified example of the second embodiment is shown in FIG. In the liquid supplying device of the above-mentioned embodiment 3, the main tank 1 is connected to the negative pressure sub-tank 2a and the negative pressure sub-tank 2b, whereas in the liquid supplying device of this embodiment shown in Figure 7, the main tank 1 is connected to the positive pressure sub-tank 3a and the negative pressure sub-tank 2b.

[0040] In the liquid supply device of Figure 7, the second sub-tank and the third sub-tank are negative pressure sub-tanks 2 (2a, 2b) that recover liquid from the liquid ejection head 8 (8a, 8b), the first sub-tank and the fourth sub-tank are positive pressure sub-tanks 3 (3a, 3b) that supply liquid to the liquid ejection head 8 (8a, 8b), a negative pressure air tank 9 is connected to the second sub-tank and the third sub-tank, and a positive pressure air tank 10 is connected to the first sub-tank and the fourth sub-tank. The other configurations are the same as those in the third embodiment.

[0041] In an embodiment in which a plurality of sub-tanks are provided, such as in the present embodiment (Examples 3 to 6), the negative pressure sub-tank and the positive pressure sub-tank can be connected as appropriate to increase the air volume in each sub-tank. The increased air volume in the sub-tank provides an air damper effect, making it possible to reduce the amplitude of pulsation during circulation by pump drive and the occurrence of large pressure fluctuations during liquid ejection.

[0042] [Third embodiment] The liquid supply device of this embodiment comprises a plurality of communicating negative pressure subtanks 2, a negative pressure air tank 9 connected to the plurality of negative pressure subtanks 2, a plurality of communicating positive pressure subtanks 3, and a positive pressure air tank 10 connected to the plurality of positive pressure subtanks 3, a reduced pressure air pump 7 connected to the negative pressure air tank 9 and depressurizing the negative pressure air tank 9, and a pressurized air pump 6 connected to the positive pressure air tank 10 and pressurizing the positive pressure air tank 10. In addition, an additional negative pressure air tank and an additional positive pressure air tank are provided.

[0043] Example 7 An example of a liquid supply device according to this embodiment is shown in FIG. The liquid supply device of Figure 8 includes an additional negative pressure air tank 9b connected between the negative pressure air tank 9a and the negative pressure sub-tank 2 (2a, 2b), and an additional positive pressure air tank 10b connected between the positive pressure air tank 10a and the positive pressure sub-tank 3 (3a, 3b). The other configurations can be the same as those in the third embodiment.

[0044] The method of connecting the multiple sub-tanks and the multiple air tanks may be either in series or in parallel, and can be appropriately selected according to the required capacity and design restrictions. For example, as shown in Fig. 8, an embodiment can be provided that includes multiple positive pressure sub-tanks 3 (3a, 3b) that communicate in parallel, multiple positive pressure air tanks 10 (10a, 10b) that communicate in series and are connected to the multiple positive pressure sub-tanks 3 (3a, 3b), multiple negative pressure sub-tanks 2 (2a, 2b) that communicate in parallel, and multiple negative pressure air tanks 9 (9a, 9b) that communicate in series and are connected to the multiple negative pressure sub-tanks 2 (2a, 2b). Connecting a plurality of air tanks in series is preferable from the viewpoint of miniaturization, since it is possible to reduce the number and length of flow paths required for connection to the sub-tank.

[0045] The liquid supply device shown in FIG. 8 also includes a circulation flow path 14a connecting the positive pressure subtank 3a and the negative pressure subtank 2a, a circulation flow path 14b connecting the positive pressure subtank 3b and the negative pressure subtank 2b, a liquid circulation pump 5a which is a means for sending liquid from the negative pressure subtank 2a to the positive pressure subtank 3a, a liquid circulation pump 5b which is a means for sending liquid from the negative pressure subtank 2b to the positive pressure subtank 3b, a recovery flow path 12a which connects the negative pressure subtank 2a and the liquid ejection head 8a, a recovery flow path 12b which connects the negative pressure subtank 2b and the liquid ejection head 8b, a supply flow path 13a which connects the positive pressure subtank 3a and the liquid ejection head 8a, and a supply flow path 13b which connects the positive pressure subtank 3b and the liquid ejection head 8b.

[0046] Furthermore, the liquid supply device shown in Figure 8 is equipped with a first negative pressure air flow path 15 connecting the negative pressure sub-tanks 2a and 2b and the negative pressure air tank 9a, a reduced pressure air pump 7 which is a means for reducing the pressure in the negative pressure air tanks 9a and 9b, a second negative pressure air flow path 17 which is connected to the negative pressure air tank 9b and connected to the reduced pressure air pump 7, a third negative pressure air flow path 19 which connects the negative pressure air tanks 9a and 9b, a first positive pressure air flow path 16 which connects the positive pressure sub-tanks 3a and 3b and the positive pressure air tank 10b, a pressurized air pump 6 which is a means for pressurizing the positive pressure air tank 10, a second positive pressure air flow path 18 which is connected to the positive pressure air tank 10 and connected to the pressurized air pump 6, and a third positive pressure air flow path 20 which connects the positive pressure air tanks 10a and 10b.

[0047] In this way, even in an embodiment with multiple sub-tanks, the air volume in each sub-tank can be significantly increased by arranging and connecting multiple air tanks, resulting in a large air damping effect and reducing the amplitude of pulsation during circulation by pump drive and the occurrence of large pressure fluctuations during liquid ejection, thereby preventing ejection defects in the liquid ejection head and preventing degradation of image quality when the liquid is installed in an image forming apparatus.

[0048] [Liquid ejection unit] A liquid ejection unit according to the present invention includes the liquid supply device according to the present invention described above. The term "liquid ejection unit" refers to a liquid ejection head integrated with other functional parts and mechanisms, and is a collection of parts related to the function of ejecting liquid. For example, the "liquid ejection unit" includes the supply mechanism of the liquid supply device according to this embodiment, as well as a combination of at least one of the components of a carriage, a maintenance and recovery mechanism, and a main scanning movement mechanism with a liquid ejection head. Here, integration includes, for example, a liquid ejection head, a functional part, and a mechanism that are fixed to each other by fastening, bonding, engaging, etc., and one is held movably relative to the other. Also, the liquid ejection head, the functional part, and the mechanism may be configured to be detachable from each other.

[0049] The liquid ejection unit may be, for example, one in which the liquid ejection head and the head tank are integrated, or one in which the liquid ejection head and the head tank are integrated by being connected to each other by a tube, etc. A unit including a filter may be added between the head tank and the liquid ejection head of these liquid ejection units.

[0050] FIG. 10 shows an example of a liquid ejection unit in which a liquid ejection head and a carriage are integrated. 10 is mounted on a carriage 403. The carriage 403 is held by a guide member 401 that constitutes a main scanning movement mechanism, and moves back and forth in the main scanning direction. 10 shows a conveyor belt 412, which is a means for conveying a recording medium (e.g., paper, etc.), among the members constituting a device for discharging a liquid, which will be described later. The conveyor belt 412 is an endless belt, and is stretched between a conveyor roller 413 and a tension roller 414.

[0051] FIG. 11 shows an example of a liquid ejection unit in which a liquid ejection head and a scanning movement mechanism are integrated. 11, the liquid ejection head 404 is movably held by a guide member 401 constituting a part of the main scanning movement mechanism, and the liquid ejection head 404 is integrated with a main scanning movement mechanism 493. In the liquid ejection unit, the liquid ejection head 404, the carriage 403, and the main scanning movement mechanism 493 may be integrated. It should be noted that the main scanning movement mechanism 493 also includes the guide member alone. 11 shows a housing part made up of side plates 491A, 491B and a back plate 491C, which are among the members constituting a device for discharging liquid, which will be described later. An arrow D1 in the drawing indicates the main scanning direction.

[0052] The liquid ejection unit may have a configuration in which a cap member, which is part of the maintenance and recovery mechanism, is fixed to a carriage on which the liquid ejection head is attached, so that the liquid ejection head, carriage, and maintenance and recovery mechanism are integrated.

[0053] FIG. 12 shows an example of a liquid ejection unit in which a tube is connected to a liquid ejection head having a head tank or a flow path component attached thereto, and the liquid ejection head and a supply mechanism are integrated together. 12, a tube 456 is connected to a liquid ejection head 404 to which a flow path part 444 is attached, and the liquid ejection head 404 and a supply mechanism are integrated. Liquid from a liquid storage source is supplied to the liquid ejection head 404 via this tube 456. The flow path part 444 is disposed inside the cover 442. A head tank 441 may be included instead of the flow path part 444. Furthermore, a connector 443 for electrically connecting with the liquid ejection head 404 is provided on the upper part of the flow path part 444. The integrated supply mechanism includes a tube alone and a loading unit alone.

[0054] [Liquid ejection device] A liquid ejection device according to the present invention includes the above-described liquid supply device according to the present invention. As an example of an apparatus for discharging liquid according to this embodiment, a serial type image forming apparatus is shown in Fig. 13. Fig. 13 is a plan view illustrating the mechanism of the apparatus. The liquid supplying device according to this embodiment constitutes a liquid discharge unit in which the liquid discharge heads 8 (8a and 8b) and a liquid supplying mechanism (not shown) are integrated together, and is mounted as the liquid discharge unit on an image forming apparatus.

[0055] 13, a carriage 103 is movably supported by a main guide member 101 and a sub-guide member (not shown) that are hung on left and right side plates (not shown). A main scanning motor 105 causes the carriage 103 to reciprocate in a main scanning direction (carriage movement direction) D1 via a timing belt 108 hung between a drive pulley 106 and a driven pulley 107.

[0056] A liquid ejection head 8 is mounted on this carriage 103. The liquid ejection head 8 ejects ink droplets of each color, for example, yellow (Y), cyan (C), magenta (M), and black (K). The liquid ejection head 8 has a nozzle row 8n made up of a plurality of nozzles arranged in a sub-scanning direction D2 perpendicular to the main scanning direction D1, and is mounted with the droplet ejection direction facing downward.

[0057] The liquid ejection head constituting the liquid ejection head 8 may be, for example, a piezoelectric actuator such as a piezoelectric element, or a thermal actuator that utilizes a phase change caused by film boiling of liquid using an electrothermal conversion element such as a heating resistor.

[0058] On the other hand, in order to transport the paper P, a paper transport belt 112 is provided as a paper transport means for electrostatically attracting the paper and transporting it to a position facing the liquid ejection head 8. This paper transport belt 112 is an endless belt, and is stretched between a belt transport roller 113 and a tension roller 114.

[0059] The paper conveying belt 112 moves in a circular motion in the sub-scanning direction D2 by the belt conveying roller 113 being rotationally driven by the sub-scanning motor 116 via a timing belt 117 and a timing pulley 118. The paper conveying belt 112 is charged (charged) by a charging roller (not shown) while moving in a circular motion.

[0060] Furthermore, on one side of the carriage 103 in the main scanning direction D1, a maintenance and recovery mechanism (cleaning section) 120 that maintains and recovers the liquid ejection head 8 is arranged beside the paper transport belt 112, and on the other side, an empty ejection receiver 121 that performs empty ejection from the liquid ejection head 8 is arranged beside the paper transport belt 112. The maintenance and recovery mechanism 120 is composed of, for example, a capping member 120a that caps the nozzle surface (the surface on which the nozzles are formed) of the liquid ejection head 8, a wiping mechanism 120b that wipes the nozzle surface, and a blank ejection receiver (not shown) that ejects droplets that do not contribute to image formation. The wiping mechanism 120b includes at least a long wiping member capable of absorbing liquid, which will be described later, and may further include a blade-shaped member made of an elastic material (eg, rubber, etc.).

[0061] Further, a discharge detection unit 100 is disposed outside the recording area between the paper transport belt 112 and the maintenance and recovery mechanism 120 and in an area capable of facing the liquid discharge head 8. Meanwhile, a cleaning unit 200 that cleans the electrode plate of the discharge detection unit 100 is provided on the carriage 103.

[0062] In addition, an encoder scale 123 having a predetermined pattern formed thereon is stretched between both side plates of the carriage 103 along the main scanning direction D1, and the carriage 103 is provided with an encoder sensor 124 consisting of a transmission type photosensor that reads the pattern of the encoder scale 123. The encoder scale 123 and the encoder sensor 124 together constitute a linear encoder (main scanning encoder) that detects the movement of the carriage 103.

[0063] In addition, a code wheel 125 is attached to the shaft of the belt transport roller 113, and an encoder sensor 126 consisting of a transmission type photosensor is provided to detect a pattern formed on this code wheel 125. The code wheel 125 and the encoder sensor 126 constitute a rotary encoder (sub-scanning encoder) that detects the amount of movement and the movement position of the paper transport belt 112.

[0064] In this image forming apparatus configured in this manner, paper P is fed from a paper feed tray (not shown) onto the charged paper conveying belt 112 and adsorbed thereon, and the paper P is conveyed in the sub-scanning direction D2 by the circular movement of the paper conveying belt 112.

[0065] Then, the carriage 103 is moved in the main scanning direction D1 while the liquid ejection head 8 is driven in response to an image signal to eject ink droplets onto the stationary paper P to record one line. Then, after the paper P is transported a predetermined distance, the next line is recorded.

[0066] Upon receiving a recording end signal or a signal indicating that the rear end of the paper P has reached the recording area, the recording operation is terminated and the paper P is discharged to a paper discharge tray (not shown).

[0067] In this application, a "liquid ejection device" is a device that includes a liquid ejection head or a liquid ejection unit and ejects liquid by driving the liquid ejection head. In addition to the above examples, liquid ejection devices include not only devices that can eject liquid onto objects to which the liquid can adhere, but also devices that eject liquid into air or liquid. This "liquid ejection device" is a device that is used for the feeding, transporting, and ejection of items to which liquid can be attached. It may also include stages, pre-treatment devices, post-treatment devices, etc.

[0068] For example, an example of a "liquid ejecting device" is a device that ejects ink to form an image on paper. 2. Description of the Related Art There are image forming apparatuses, which are devices for forming a three-dimensional object (a three-dimensional object), and three-dimensional modeling apparatuses, which eject modeling liquid onto a powder layer formed by forming powder into a layer, in order to form a three-dimensional object (a three-dimensional object). In addition, the term "liquid ejection device" is not limited to devices that use ejected liquid to visualize meaningful images such as letters and figures. For example, it also includes devices that form patterns that have no meaning in themselves and devices that create three-dimensional images.

[0069] The above-mentioned "object to which liquid can adhere" means an object to which liquid can adhere at least temporarily, and to which the liquid adheres and sticks, or to which the liquid adheres and penetrates, etc. Specific examples include media such as paper, recording paper, film, cloth, and other recording media, electronic boards, electronic components such as piezoelectric elements, powder layers, organ models, and test cells, and unless otherwise specified, includes all objects to which liquid can adhere.

[0070] The material of the above-mentioned "object to which liquid can adhere" may be any material to which liquid can adhere even temporarily, such as paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, and ceramics.

[0071] The "liquid" may be any liquid having a viscosity and surface tension that allows it to be discharged from the head, and is not particularly limited, but it is preferable that the viscosity of the liquid is 30 mPa·s or less at room temperature and pressure, or by heating or cooling. More specifically, the liquid may be a solution, suspension, emulsion, etc., containing a solvent such as water or an organic solvent, a colorant such as a dye or pigment, a functionalizing material such as a polymerizable compound, a resin, or a surfactant, a biocompatible material such as DNA, amino acids, proteins, or calcium, an edible material such as a natural dye, etc., and these can be used for applications such as inkjet ink, surface treatment liquid, a liquid for forming a component of an electronic element or a light-emitting element, an electronic circuit resist pattern, a material liquid for three-dimensional modeling, etc.

[0072] Furthermore, the "liquid ejection device" may be a device in which a liquid ejection head and an object to which liquid can be attached move relatively, but is not limited to this. Specific examples include a serial type device in which a liquid ejection head moves, a line type device in which a liquid ejection head does not move, etc.

[0073] Other examples of "liquid ejecting devices" include a treatment liquid application device that ejects a treatment liquid onto paper to apply the treatment liquid to the surface of the paper for purposes such as modifying the surface of the paper, and an injection granulation device that ejects a composition liquid in which raw materials are dispersed through a nozzle to granulate fine particles of the raw materials. [Explanation of symbols]

[0074] 1. Main Tank 2 Negative pressure sub-tank 3 Positive pressure sub-tank 4 Liquid supply pump 5 Liquid supply pump (circulation pump) 6. Pressurized air pump 7. Pressure reducing air pump 8 Liquid ejection head 9. Negative pressure air tank 10 Positive pressure air tank 11 Liquid supply path 12 Recovery channel 13 Supply Channel 14 Circulation flow path 15 First negative pressure air flow path 16 First positive air flow path 17 Second negative pressure air flow path 18 Second positive air flow path 19 Third negative pressure air flow path 20 Third positive pressure air flow path [Prior art documents] [Patent documents]

[0075] [Patent Document 1] Patent No. 6280742

Claims

1. A liquid ejection head that ejects liquid; a main tank that contains a liquid to be supplied to the liquid ejection head; a first sub-tank that contains gas and liquid and is connected to the main tank and the liquid ejection head; a second sub-tank that contains gas and liquid and is connected to the first sub-tank and the liquid ejection head; a first air tank that contains gas and is connected to the first sub-tank; a second air tank that contains gas and is connected to the second sub-tank; Equipped with the first sub-tank is a negative pressure sub-tank that recovers liquid from the liquid ejection head, the second sub-tank is a positive pressure sub-tank that supplies liquid to the liquid ejection head, the first air tank is a negative pressure air tank that supplies negative air pressure, the second air tank is a positive pressure air tank that supplies positive air pressure, The volume of the first air tank is larger than the volume of the first sub-tank, and the volume of the second air tank is larger than the volume of the second sub-tank. A liquid supply device comprising:

2. A liquid ejection head that ejects liquid; a main tank that contains a liquid to be supplied to the liquid ejection head; a first sub-tank that contains gas and liquid and is connected to the main tank and the liquid ejection head; a second sub-tank that contains gas and liquid and is connected to the first sub-tank and the liquid ejection head; a first air tank that contains gas and is connected to the first sub-tank; a second air tank that contains gas and is connected to the second sub-tank; Equipped with the first sub-tank is a positive pressure sub-tank that supplies liquid to the liquid ejection head, the second sub-tank is a negative pressure sub-tank that recovers liquid from the liquid ejection head, the first air tank is a positive pressure air tank that supplies positive air pressure, the second air tank is a negative pressure air tank that supplies negative air pressure, The volume of the first air tank is larger than the volume of the first sub-tank, and the volume of the second air tank is larger than the volume of the second sub-tank. A liquid supply device comprising:

3. a first liquid supply pump connected between the main tank and the first sub-tank and configured to supply liquid from the main tank to the first sub-tank; a second liquid supply pump connected between the first sub-tank and the second sub-tank and configured to supply liquid from the first sub-tank to the second sub-tank; The liquid supply device according to claim 1 or 2, further comprising:

4. a pressure reducing air pump connected to the negative pressure air tank and configured to reduce the pressure in the negative pressure air tank; a pressurizing air pump connected to the positive pressure air tank and pressurizing the positive pressure air tank; The liquid supply device according to claim 1 or 2, further comprising:

5. 5. The liquid supplying device according to claim 1, wherein the first air tank and the second air tank have a volume of 50 mL or more.

6. a first liquid ejection head and a second liquid ejection head for ejecting liquid; a main tank that contains liquid to be supplied to the first liquid ejection head and the second liquid ejection head; a first sub-tank that contains gas and liquid and is connected to the main tank and the first liquid ejection head; a second sub-tank that contains a gas and a liquid and is connected to the first sub-tank and the first liquid ejection head; a third sub-tank that contains gas and liquid and is connected to the main tank and the second liquid ejection head; a fourth sub-tank that contains gas and liquid and is connected to the third sub-tank and the second liquid ejection head; a negative pressure air tank that stores gas and supplies negative air pressure; a positive pressure air tank that stores gas and supplies positive air pressure; Equipped with the negative pressure air tank is connected to two of the first sub-tank, the second sub-tank, the third sub-tank, and the fourth sub-tank; The positive pressure air tank is connected to two sub-tanks other than the sub-tank connected to the negative pressure air tank. A liquid supply device comprising:

7. the first sub-tank is a negative pressure sub-tank that recovers liquid from the first liquid ejection head, the third sub-tank is a negative pressure sub-tank that recovers liquid from the second liquid ejection head, the second sub-tank is a positive pressure sub-tank that supplies liquid to the first liquid ejection head, the fourth sub-tank is a positive pressure sub-tank that supplies liquid to the second liquid ejection head, the negative pressure air tank is connected to the first sub-tank and the third sub-tank, 7. The liquid supply device according to claim 6, wherein the positive pressure air tank is connected to the second sub-tank and the fourth sub-tank.

8. the first sub-tank is a negative pressure sub-tank that recovers liquid from the first liquid ejection head, the fourth sub-tank is a negative pressure sub-tank that recovers liquid from the second liquid ejection head, the second sub-tank is a positive pressure sub-tank that supplies liquid to the first liquid ejection head, the third sub-tank is a positive pressure sub-tank that supplies liquid to the second liquid ejection head, the negative pressure air tank is connected to the first sub-tank and the fourth sub-tank, 7. The liquid supplying device according to claim 6, wherein the positive pressure air tank is connected to the second sub-tank and the third sub-tank.

9. the second sub-tank is a negative pressure sub-tank that recovers liquid from the first liquid ejection head, the fourth sub-tank is a negative pressure sub-tank that recovers liquid from the second liquid ejection head, the first sub-tank is a positive pressure sub-tank that supplies liquid to the first liquid ejection head, the third sub-tank is a positive pressure sub-tank that supplies liquid to the second liquid ejection head, the negative pressure air tank is connected to the second sub-tank and the fourth sub-tank, 7. The liquid supply device according to claim 6, wherein the positive pressure air tank is connected to the first sub-tank and the third sub-tank.

10. the second sub-tank is a negative pressure sub-tank that recovers liquid from the first liquid ejection head, the third sub-tank is a negative pressure sub-tank that recovers liquid from the second liquid ejection head, the first sub-tank is a positive pressure sub-tank that supplies liquid to the first liquid ejection head, the fourth sub-tank is a positive pressure sub-tank that supplies liquid to the second liquid ejection head, the negative pressure air tank is connected to the second sub-tank and the third sub-tank, 7. The liquid supply device according to claim 6, wherein the positive pressure air tank is connected to the first sub-tank and the fourth sub-tank.

11. a first liquid supply pump connected between the main tank and one of the negative pressure sub-tanks and configured to supply liquid from the main tank to the one of the negative pressure sub-tanks; a second liquid supply pump connected between the main tank and the other negative pressure sub-tank for supplying liquid from the main tank to the other negative pressure sub-tank; a third liquid supply pump connected between the one of the negative pressure sub-tanks and the one of the positive pressure sub-tanks for supplying liquid from the one of the negative pressure sub-tanks to the one of the positive pressure sub-tanks; a fourth liquid supply pump connected between the other negative pressure sub-tank and the other positive pressure sub-tank for supplying liquid from the other negative pressure sub-tank to the other positive pressure sub-tank; The liquid supply apparatus according to claim 7, further comprising:

12. a first liquid supply pump connected between the main tank and the first sub-tank and configured to supply liquid from the main tank to the first sub-tank; a second liquid supply pump connected between the main tank and the third sub-tank and configured to supply liquid from the main tank to the third sub-tank; a third liquid supply pump connected between the first sub-tank and the second sub-tank and configured to supply liquid from the first sub-tank to the second sub-tank; a fourth liquid supply pump connected between the third sub-tank and the fourth sub-tank and configured to supply liquid from the third sub-tank to the fourth sub-tank; 11. The liquid supply device according to claim 6, further comprising:

13. a pressure reducing air pump connected to the negative pressure air tank and configured to reduce the pressure in the negative pressure air tank; a pressurizing air pump connected to the positive pressure air tank and pressurizing the positive pressure air tank; 13. A liquid supply apparatus according to claim 6, further comprising:

14. A liquid supply device as described in any one of claims 7 to 11, characterized in that it comprises an additional negative pressure air tank connected between the negative pressure air tank and the negative pressure sub-tank, and an additional positive pressure air tank connected between the positive pressure air tank and the positive pressure sub-tank.

15. A liquid ejection unit comprising the liquid supply device according to claim 1 .

16. A liquid ejecting device comprising the liquid supply device according to any one of claims 1 to 14.

Images