Ink jet recording apparatus

Abstract

To provide an ink jet recording apparatus capable of improving accuracy of ink ejection from each ink head arranged in an ink circulation path.SOLUTION: An ink jet recording apparatus comprises a plurality of ink circulation paths different in path length, and an ink head that is provided midway through each of the ink circulation paths. The ink jet recording apparatus is constituted so that approximately equal ink pressures can be applied to the ink heads, respectively.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an inkjet recording apparatus. [Background technology]

[0002] An inkjet recording device forms an image on a recording medium by ejecting ink from a plurality of nozzles provided on a head. Some of such inkjet recording devices are provided with a circulation path for circulating and supplying ink to a plurality of heads. For example, the following Patent Document 1 describes a configuration in which a side fluid resistance variable part capable of changing fluid resistance is provided in each individual supply path and each individual recovery path connected to each head. These fluid resistance variable parts include a liquid path that can be restored and deformed, and a vacuum chamber that covers the periphery of the liquid path, and by pressurizing the vacuum chamber, the liquid path is crushed to increase the fluid resistance. As a result, during maintenance work on the circulation path, ink can be sucked only from the specific head to be maintained, and the suction of ink from other heads can be suppressed, so that the amount of liquid (ink amount) wasted can be suppressed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-127007 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, the ink circulation path is configured such that the heads are connected in parallel between a common ink supply path and an ink recovery path via individual supply paths and individual recovery paths. Therefore, the ink circulation path for each head has a different path length depending on the connection position of the head to the common ink supply path and the ink recovery path. Furthermore, since the ink branches off and flows for each head, there is a difference in the ink flow rate between the common ink supply path for the upstream head and the common ink supply path for the downstream head. This also causes a difference in the ink pressure loss for each head. Such a difference in pressure loss makes it difficult to control the ink pressure applied to each head, and is a factor that hinders improvement of the ink ejection accuracy from each head.

[0005] SUMMARY OF THE PRESENTLY PREFERRED EMBODIMENTS An object of the present invention is to provide an inkjet recording apparatus capable of improving the accuracy of ink ejection from each ink head arranged in an ink circulation path. [Means for solving the problem]

[0006] To achieve this objective, the present invention provides an inkjet recording device that includes a plurality of ink circulation paths with different path lengths and ink heads provided midway along each of the ink circulation paths, and is configured so that the ink pressure applied to each of the ink heads is approximately equal. Effect of the Invention

[0007] According to the present invention, it is possible to provide an inkjet recording apparatus capable of improving the accuracy of ink ejection from each ink head arranged in an ink circulation path. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a configuration diagram of a main part of an inkjet recording apparatus according to an embodiment. [Diagram 2] FIG. 2 is a configuration diagram of a head unit of the inkjet recording apparatus according to the embodiment. [Diagram 3] FIG. 3 is a diagram showing the relationship between the head position and the length of the narrowed portion. [Figure 4] FIG. 4 is a diagram showing the configuration of the narrowed portion. [Diagram 5] FIG. 5 is a diagram showing a first modified example of the constriction portion. [Figure 6] FIG. 6 is a diagram showing a second modified example of the constriction portion. [Figure 7] FIG. 7 is a diagram showing a third modified example of the constriction portion. [Figure 8] FIG. 8 is a diagram showing a fourth modified example of the constriction portion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An embodiment of an inkjet recording apparatus to which the present invention is applied will be described in detail with reference to the drawings. Fig. 1 is a configuration diagram of the main part of an inkjet recording apparatus 1 according to an embodiment, showing the configuration of an ink supply part. As shown in Fig. 1, the inkjet recording apparatus 1 includes a head unit 10, an ink supply unit 20, and a pressure adjustment unit 30.

[0010] Of these, the head unit 10 and the ink supply unit 20 constitute an ink path 100. The ink paths 100 are provided corresponding to each color, such as cyan (C), magenta (M), yellow (Y), black (K), and red (R). Although only one ink path 100 is illustrated here, the ink paths 100c, 100m, 100y, 100k, and 100r corresponding to each color share one pressure adjustment unit 30.

[0011] The configuration of each unit will be described below in the order of the ink supply unit 20, the head unit 10, and the pressure adjustment unit 30.

[0012] <Ink supply unit 20> The ink supply unit 20 includes a main tank 21 in which the ink 2 is stored, a common sub-tank 23, a supply side sub-tank 25, and a return side sub-tank 26.

[0013] The main tank 21 and the common sub-tank 23 are connected by a pipe 22. The pipe 22 has a pump 22p. The pump 22p operates based on a signal from a float sensor in the common sub-tank 23, and supplies ink 2 from the main tank 21 to the common sub-tank 23. This keeps the amount of ink in the common sub-tank 23 at a predetermined amount.

[0014] The common sub-tank 23 and the supply side sub-tank 25 are connected by a pipe 24. The pipe 24 has a pump 24p and a degassing module 24f. The pump 24p operates based on a signal from a float sensor in the supply side sub-tank 25, and supplies ink from the common sub-tank 23 to the supply side sub-tank 25. This maintains the amount of ink in the supply side sub-tank 25 at a predetermined amount. The degassing module 24f also removes air bubbles dissolved in the ink.

[0015] The common sub-tank 23 and the return side sub-tank 26 are connected by a pipe 27. The pipe 27 has a pump 27p. The pump 27p operates based on a signal from a float sensor in the return side sub-tank 26, and returns ink from the return side sub-tank 26 to the common sub-tank 23. This maintains a predetermined amount of ink in the return side sub-tank 26. The supply side sub-tank 25 and the return side sub-tank 26 may be a common sub-tank.

[0016] <Head Unit 10> Fig. 2 is a configuration diagram of a head unit 10 of an inkjet recording device according to an embodiment, and is an enlarged view of the head unit 10 portion in Fig. 1. As shown in Fig. 1 and Fig. 2, the head unit 10 includes a plurality of ink heads 11, a common ink supply path 12, individual supply paths 13, a common ink recovery path 14, and individual recovery paths 15. These are as follows.

[0017] <Ink head 11> The ink head 11 has an ink supply port 110 and an ink discharge port 111. Although not shown in the figure, each ink head 11 has a pressure chamber communicating with the supply port 110 and a plurality of nozzles communicating with the pressure chamber. Each ink head 11 controls the ejection of ink from each nozzle by applying a drive voltage to ink supplied from a pressure chamber inside the ink head 11. Each pressure chamber also communicates with an ejection port 111, and air bubbles and viscous ink inside the pressure chamber are ejected from the ejection port 111 to the outside of the ink head 11. As a result, each ink head 11 is constantly kept in a state where the pressure chamber is filled with ink, and is configured to always eject ink normally.

[0018] The ink heads 11 are connected in parallel between a common ink supply path 12 and a common ink recovery path 14, which will be described later, via individual supply paths 13 and individual recovery paths 15. As a result, ink circulation paths with different path lengths are formed by the common ink supply path 12, each individual supply path 13, each ink head 11, each individual recovery path 15a, and the common ink recovery path 14. Each ink circulation path is an ink circulation path that includes the ink head 11 from the supply side sub-tank 25 to the return side sub-tank 26. The ink circulation paths that include each ink head 11 have different path lengths and the amount of ink flowing between the branching parts of each individual supply path 13 in the common ink supply path 12 is different, resulting in differences in pressure loss.

[0019] <Common ink supply path 12> The common ink supply path 12 is a pipe for supplying ink to each ink head 11. The common ink supply path 12 is a pipe common to each ink head 11, and is connected to a supply side sub-tank 25.

[0020] <Individual supply route 13> The individual supply paths 13 are pipes branched off from the common ink supply path 12, and connect the supply ports 110 of the ink heads 11 in parallel to the common ink supply path 12. Each individual supply path 13 has a narrowed portion 131. The narrowed portion 131 is as follows.

[0021] [Stenosis 131] The narrowed portion 131 is for adjusting the ink pressure in the individual supply path 13. The narrowed portion 131 is provided so that the ink pressure applied to each ink head 11 is approximately equal, regardless of the path length from the supply side sub-tank 25 to each ink head 11. Such narrowed portion 131 is provided according to the difference in pressure loss that occurs in ink circulation paths with different path lengths.

[0022] Here, the individual supply paths 13 are referred to as individual supply paths 13a, 13b, ... in the order of proximity to the supply side sub-tank 25 (see FIG. 2). The narrowed portions 131 arranged in the individual supply paths 13a, 13b, ... are referred to as narrowed portions 131a, 131b, ..., and the ink heads 11 connected to the individual supply paths 13a, 13b, ... are referred to as ink heads 11a, 11b, ....

[0023] FIG. 3 is a diagram showing the relationship between the head position and the narrowed portion length. In FIG. 3, the head position [x] on the horizontal axis indicates the order of the distance from the supply side subtank 25 to each ink head 11, that is, the order of the path length of the ink circulation path (see FIG. 2). The head position [x] of the ink head 11 arranged farthest from the supply side subtank 25 is head position [x] = 1. In the example shown in FIG. 3, one head unit 10 is equipped with eight ink heads 11, and the head position [x] of the ink head 11a arranged closest to the supply side subtank 25 is 8. Also in FIG. 3, the narrowed portion length [L] on the vertical axis is the length of the narrowed portion 131 in the individual supply path 13 connected to each ink head 11.

[0024] 3, the larger the head position [x], i.e., the closer the ink head 11 is to the supply-side sub-tank 25, the longer the narrowed portion length [L] of the narrowed portion 131 of the individual supply path 13 connected to this ink head 11. In other words, the shorter the ink circulation path length, the higher the degree of narrowing of the narrowed portion 131 due to the long narrowed portion length [L], and the greater the degree of narrowing, the greater the pressure loss due to the narrowing.

[0025] The length of the constriction [L] is the square of the head position [x] ([x 2 ]). In this case, however, the opening area of ​​each of the individual supply paths 13a, 13b, ... and the opening area of ​​the narrowed portions 131a, 131b, ... are the same, and each of the individual supply paths 13a, 13b, ... is connected to the common ink supply path 12 at equal intervals [d]. Furthermore, the narrowed portion length [L] is proportional to the connection interval [d] of each ink head 11 to the common ink supply path 12.

[0026] Fig. 4 is a diagram showing the configuration of the narrowed portion in the individual flow path. As shown in Fig. 4, each of the narrowed portions 131a, 131b, ... is formed of, for example, a cylindrical member provided inside each of the individual supply paths 13a, 13b, .... In the cylindrical members constituting the narrowed portions 131a, 131b, ..., when the opening diameter [r] of the through hole 130a is the same, the respective lengths [La], [Lb], ... are each calculated by multiplying the head position [x] by the square ([x 2 ]). The head position [x] is the position of the ink head 11 to which each of the individual supply paths 13a, 13b, ... having the narrowed portions 131a, 131b, ... is connected. The narrowed portions 131a, 131b, ... using such a cylindrical member are easy to mold.

[0027] <Common ink recovery path 14> 1 and 2, the common ink recovery path 14 is a pipe for recovering ink from each ink head 11. This common ink recovery path 14 is a pipe common to each ink head 11, and is connected to a return side sub-tank 26.

[0028] <Individual Collection Route 15> The individual recovery paths 15 are pipes branched off from the common ink recovery path 14, and connect the discharge ports 111 of the ink heads 11 in parallel to the common ink recovery path 14. Each individual recovery path 15 has a narrowed portion 151.

[0029] The narrowed portion 151 is similar to the narrowed portion 131 of the individual supply path 13 described above. This narrowed portion 151 is provided so that the ink pressure applied to each ink head 11 is approximately equal, regardless of the path length from the return side sub-tank 26 to each ink head 11. That is, as described with reference to Figs. 2 to 4, the narrowed portion length [L] of the narrowed portion 151 of the individual recovery path 15 connected to the ink head 11 is longer for the ink head 11 closer to the return side sub-tank 26. The length [L] of each narrowed portion 151a, 151b, ... is set to an appropriate value depending on the length of the common ink recovery path 14 and each individual recovery path 15a, 15b, ..., similar to the length [L] of the narrowed portion 131 of the individual supply path 13.

[0030] <Pressure adjustment unit 30> 1, the pressure adjustment unit 30 monitors the pressure in the supply side sub-tanks 25 and return side sub-tanks 26 in all of the ink paths 100, and controls the flow rate of ink circulating through the head unit 10 of each ink path 100. Such a pressure adjustment unit 30 has a supply side air tank 31 connected to the supply side sub-tanks 25 of all of the ink paths 100, and a return side air tank 32 connected to the return side sub-tanks 26.

[0031] Supply-side pressure gauges 31a and 31b are connected to the supply-side air tank 31. These supply-side pressure gauges 31a and 31b are the supply-side pressure gauge 31a mounted on the carriage together with the head unit 10, and the supply-side pressure gauge 31b mounted on the printer side. In addition, the supply-side air tank 31 is provided with a pressurized purge chamber 31c and a pressure gauge 31d in parallel with the supply-side pressure gauge 31b. The pressurized purge chamber 31c can purge the head maintenance at a predetermined pressure by maintaining a purge pressure. The pressurized purge chamber 31c and the pressure gauge 31d are mounted on the printer side.

[0032] In addition, return pressure gauges 32a and 32b are connected to the return air tank 32. These return pressure gauges 32a and 32b are the return pressure gauge 32a mounted on the carriage together with the head unit 10, and the return pressure gauge 32b mounted on the printer side.

[0033] In this configuration, the flow of ink 2 will be described with reference to Fig. 1. The main tank 21 installed by the user contains ink 2. The ink 2 in the main tank 21 is passed through a filter (not shown) by the pump 22p and is stored in the common sub-tank 23 until a predetermined amount is detected by a float sensor in the common sub-tank 23.

[0034] The pressure in the supply-side sub-tank 23 is monitored by supply-side pressure gauges 31a and 31b via the supply-side air tank 31. The pressure in the supply-side air tank 31 is controlled by a regulator (not shown) based on the measurement value of the supply-side pressure gauge 31b mounted on the printer side. In this way, the pressure in the supply-side sub-tank 25 is controlled by the pressure in the supply-side air tank 31.

[0035] Similarly, the pressure in the return side sub-tank 26 is monitored by return side pressure gauges 32a and 32b via the return side air tank 32. The pressure in the return side air tank 32 is controlled by a regulator (not shown) based on the measurement value of the return side pressure gauge 32b mounted on the printer side. In this way, the pressure in the return side sub-tank 26 is controlled by the pressure in the return side air tank 32.

[0036] Due to the pressure difference between the supply side air tank 31 and the return side air tank 32, the ink in the supply side sub-tank 25 flows through the common ink supply path 12, and then through each individual supply path 13 to each ink head 11, and is then sent to the return side sub-tank 26 through the common ink recovery path 14.

[0037] Furthermore, as the ink in the supply subtank 25 decreases, a float sensor in the supply subtank 25 detects the drop in the liquid level and operates the pump 24p to keep the amount of ink in the supply subtank 25 constant. When the ink is pumped by the pump 24p, the ink passes through the degassing module 24f, which removes the air dissolved in the ink from the ink. This allows ink suitable for ejection to be supplied to the ink head 11.

[0038] As the ink in the return sub-tank 26 increases, the float sensor in the return sub-tank 26 detects the increase in the liquid level, and operates the pump 27p to return the ink in the return sub-tank 26 to the common sub-tank 23. This forms a path for circulating the ink to each ink head 11.

[0039] Effect of the embodiment According to the embodiment described above, the narrowed portions 131, 151 are provided in the individual supply paths 13 and the individual recovery paths 15 of the ink circulation paths having different path lengths, so that the pressure loss occurring in each ink circulation path is offset by the narrowed portions 131, 151, and the ink pressure applied to the ink heads 11 is configured to be approximately equal. This makes it possible to improve the accuracy of ink ejection from each ink head 11. As a result, it is possible to improve the image quality of printed matter produced by the inkjet recording device 1.

[0040] <<Variation 1>> Fig. 5 is a diagram showing a first modified example of the narrowed portion. As shown in Fig. 5, the narrowed portion 131 provided in the individual supply path 13 may be formed by connecting a plurality of tubular members 130 (three in the illustrated example) each having a predetermined length [L'], so that each narrowed portion has the length [L] shown in Fig. 3. Each tubular member 130 preferably has a through hole 130a in its central axis.

[0041] In this case, if the opening areas of the cylindrical members 130 are the same, the total length of the cylindrical members 130 can be the length [L] of each narrowed portion shown in Fig. 3. Furthermore, there may or may not be a gap between the cylindrical members 130 provided inside the individual supply paths 13.

[0042] By adopting such a configuration of Modification Example 1, it is possible to configure narrowed portions 131 of different lengths [L] using one type of tubular member .

[0043] The cylindrical member 130 is not limited to one type of length [L'], and may be prepared in a plurality of different lengths [L']. By using a combination of cylindrical members 130 of a plurality of different lengths [L'], the narrowed portion 131 of various narrowed portion lengths [L] shown in FIG. 3 can be easily realized. The above also applies to the narrowed portion 151 of the individual recovery path 15.

[0044] <<Variation 2>> Fig. 6 is a diagram showing a second modified example of the narrowed portion. As shown in Fig. 6, the narrowed portion 131' provided in the individual supply path 13 adjusts the ink pressure in the individual supply path 13 by the opening area of ​​the through holes 130a. In this case, the closer the ink head 11 (see Fig. 2) is to the supply side sub-tank 25, the fewer the number of through holes 130a of the narrowed portion 131' in the individual supply path 13 connected to this ink head 11.

[0045] 6, a narrowed portion 131' of the individual supply path 13a closest to the supply side sub-tank 25 has one through hole 130a. Also, a narrowed portion 131b' of the individual supply path 13b next closest to the supply side sub-tank 25 has two through holes 130a.

[0046] Even with the configuration of the modified example 2, the same effects as those of the embodiment can be obtained.

[0047] The opening area of ​​the through holes 130a may be adjusted by the number of the through holes 130a as well as the diameter of the through holes 130a. The opening area of ​​the through holes 130a may be adjusted by the number and diameter of the through holes 130a. Furthermore, this modified example 2 may be combined with the configuration of the embodiment shown in FIG. 4 or the configuration of modified example 1 to adjust the ink pressure of the individual supply path 13 by the opening area of ​​the through holes 130a in the narrowed portion 131' and the length of the narrowed portion 131'. The above also applies to the narrowed portion 151 of the individual recovery path 15.

[0048] <Modification 3> 7 is a perspective view and a plan view showing a third modified example of the narrowing portion. As shown in FIG. 7, when the narrowing portion 131 provided in the individual supply path 13 is formed by connecting a plurality of cylindrical members 130, each cylindrical member 130 may be provided in the individual supply path 13 with the phase of the through hole 130a shifted. However, the plurality of cylindrical members 130 are provided in the individual supply path 13 so that the through hole 130a of each cylindrical member 130 is not completely blocked by the adjacent cylindrical members 130.

[0049] According to the configuration of the third modification, an individual supply path 13 in which the ink pressure is adjusted can be obtained by adjusting the degree of phase shift of the through holes 130a in adjacent cylindrical members 130. The above also applies to the narrowed portion 151 of the individual recovery path 15.

[0050] <Modification 4> FIG. 8 is a perspective view and a plan view showing a fourth modified example of the narrowing portion. As shown in FIG. 8, when the narrowing portion 131″ provided in the individual supply path 13 is formed by connecting a plurality of cylindrical members 130″, each cylindrical member 130″ may have a plurality of through holes 130a. Each cylindrical member 130″ may be provided in the individual supply path 13 with the phases of the plurality of through holes 130a shifted. However, the plurality of cylindrical members 130″ are provided in the individual supply path 13 so that the through holes 130a of each cylindrical member 130″ are not blocked by the adjacent cylindrical members 130″.

[0051] Even in the configuration of Modification 4, an individual supply path 13 with adjusted ink pressure can be obtained by adjusting the degree of misalignment of the through holes 130a in adjacent cylindrical members 130". The same applies to the narrowed portion 151 of the individual recovery path 15.

[0052] The above-described first to fourth modified examples can be combined with one another, and by combining them, fine adjustment of the ink pressure becomes easier. [Explanation of symbols]

[0053] 1...Inkjet recording device 2. Ink 11, 11a to 11d…Ink head 12...Common ink supply path 13, 13a to 13d...Individual supply paths (individual paths) 14…Common ink recovery passage 15, 15a-15d...Individual collection route (individual route) 23...Common subtank (ink tank) 25...Supply subtank (ink tank) 26...Return subtank (ink tank) 110…Supply port (ink head) 111…Discharge port (ink head) 130,130"...Cylindrical member 130a...Through hole 131,131',131”,131a~131c,131a'~131b'...Stenosis 151,131a~131c...Stricture area [d]…Interval [L], [La]~[Ld]…Length of the constricted part [r]…Aperture diameter [x]…Rank

Claims

1. The ink supply device includes a plurality of ink circulation paths having different lengths, and an ink head provided in the middle of each of the ink circulation paths, The ink pressure applied to each of the ink heads is substantially equal. Inkjet recording device.

2. By adjusting the pressure of the ink flowing through each of the ink circulation paths, the ink pressure applied to each of the ink heads is configured to be approximately equal. The inkjet recording apparatus according to claim 1 .

3. the ink circulation paths share an ink supply path and an ink recovery path as a common path; Each of the ink circulation paths includes an individual path for connecting each of the ink heads between the ink supply path and the ink recovery path. The inkjet recording apparatus according to claim 1 .

4. The ink pressure applied to each of the ink heads is adjusted by providing a narrowed portion in each of the ink circulation paths. The inkjet recording apparatus according to claim 3 .

5. the individual paths include individual supply paths that connect the ink supply paths and each of the ink heads, and individual recovery paths that connect the ink recovery paths and each of the ink heads, The narrowed portion is provided in both the individual supply path and the individual recovery path. The inkjet recording apparatus according to claim 4.

6. The ink circulation path having a shorter path length among the plurality of ink circulation paths has a higher degree of narrowing caused by the narrowing portion, so that the ink pressure applied to each of the ink heads is adjusted to be approximately equal. The inkjet recording apparatus according to claim 4.

7. The degree of narrowing of the plurality of ink circulation paths is adjusted by changing the length of the narrowing portion. The inkjet recording apparatus according to claim 6.

8. When the ink heads are connected to the common path at equal intervals, and the ink circulation paths are ranked [x] in order of the longest path length, the length [L] of the narrowed portion provided in the [x]th ink circulation path is proportional to the square of the rank [x]. The inkjet recording apparatus according to claim 7.

9. Furthermore, the length [L] of the narrowed portion is proportional to the connection interval [d] of each of the ink heads with respect to the common path. The inkjet recording apparatus according to claim 8.

10. The narrowed portion is made of a tubular member provided inside the individual path. The inkjet recording apparatus according to claim 4.

11. The degree of narrowing of the narrowed portion of each of the plurality of ink circulation paths is adjusted by changing the length of the cylindrical member. The inkjet recording apparatus according to claim 10.

12. The degree of narrowing of the narrowed portion of each of the plurality of ink circulation paths is adjusted by the number of the cylindrical members provided in series with respect to the individual paths. The inkjet recording apparatus according to claim 10.

13. The plurality of ink circulation paths are each configured such that the degree of narrowing of the narrowed portion is adjusted by the opening area of ​​the cylindrical member. The inkjet recording apparatus according to claim 10.

14. The plurality of ink circulation paths are each configured such that the degree of narrowing of the narrowed portion is adjusted by the opening diameter of the cylindrical member. The inkjet recording apparatus according to claim 13.

15. The degree of narrowing of the narrowed portion of each of the plurality of ink circulation paths is adjusted by the number of through holes provided in the cylindrical member. The inkjet recording apparatus according to claim 13.

16. Among the plurality of ink circulation paths, in the ink circulation path in which the plurality of cylindrical members are disposed in series, the degree of narrowing of the narrowed portion is adjusted by shifting the phase of the through holes of the cylindrical members. The inkjet recording apparatus according to claim 10.

17. The ink supply path supplies ink stored in an ink tank to each of the ink heads, and the ink recovery path allows ink recovered from each of the ink heads to be stored in the ink tank. The inkjet recording apparatus according to claim 3 .

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