Ink supply mechanism and image forming device

Abstract

To provide an ink supply mechanism, which can efficiently perform deaeration of ink even when increasing amounts of ink charged into an ink tank.SOLUTION: An ink supply mechanism 20 provided in a printer 1 comprises: an ink container 14 that stores ink; ink tanks 21 that store ink supplied from the ink container 14 to a recording head 13; a decompression pump 22 which decompresses the inside of the ink tank 21 as well as a first decompression flow path 26a and a second decompression flow path 26b; and a first deaeration flow path 31a and a second deaeration flow path 31b through which ink flown out from the ink tank 21 is circulated and flown into the ink tank 21. The plurality of ink tanks 21 are arranged in parallel with respect to the recording head 13. When one ink tank 21 of the plurality of ink tanks 21 is used for printing, a deaeration tank that performs deaeration is selected out of the other ink tanks 21 whose ink-dissolved oxygen amounts do not reach a predetermined target supply value, in accordance with a predetermined deaeration selection standard, then the deaeration tank is decompressed and is circulated to perform deaeration operation.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an ink supply mechanism and an image forming apparatus that perform printing by ejecting ink from a recording head. [Background technology]

[0002] Conventionally, an inkjet image forming apparatus includes a recording head having nozzles for ejecting ink droplets onto a recording medium such as paper, an ink container for storing ink, and an ink tank for storing the ink supplied from the ink container, and supplies ink to the recording head by utilizing the head pressure between the ink tank and the recording head. In an image forming apparatus, if air bubbles are present in the ink, the nozzles are clogged with the air bubbles, resulting in a decrease in ejection performance. In the ink tank, the ink surface comes into contact with air and is easily dissolved, so it is necessary to suppress the amount of air dissolved in the ink supplied to the recording head.

[0003] For example, some conventional image forming apparatuses use a method of degassing ink by passing the ink through a hollow fiber filter, but this method requires the use of expensive hollow fiber filters for each color of ink, and each hollow fiber filter must be replaced periodically, resulting in high costs for degassing the ink.

[0004] According to Patent Document 1, a degassing device that removes air dissolved in ink used in inkjet printers includes a pump that reduces the pressure inside an ink bottle that contains the ink to -80 kPa or less, and a magnetic field generating unit that generates a magnetic field. The ink bottle contains a magnet rotor in the ink that rotates in response to changes in the external magnetic field, and the magnetic field generating unit applies a magnetic field to the magnet rotor from outside the ink bottle to rotate the magnet rotor, thereby agitating the ink in the ink bottle. The ink in the ink bottle, which has been reduced in pressure by the pump, is agitated by the rotation of the magnet rotor, thereby degassing the air in the ink.

[0005] According to Patent Document 2, an inkjet recording device includes a recording head that ejects ink, a tank that contains ink to be supplied to the recording head, and a float that floats on the ink surface in the tank, and the bottom side of the float that comes into contact with the ink has a slope toward the ink surface, which is the boundary between the ink and air. The ink is stirred under reduced pressure to prevent air from re-dissolving in the degassed ink. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5030305 [Patent Document 2] JP 2019-142189 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the conventional image forming apparatus, as described above, a method of degassing ink in a reduced-pressure ink tank by stirring it with a magnetic stirrer (stirring degassing method) is applied, and the ink degassed near the liquid surface is stirred in the ink tank to improve the degassing efficiency. However, since the stirrer is located at the bottom of the ink tank, if the ink filling depth in the ink tank is increased, the ink replacement performance is reduced between the ink near the liquid surface where there is less dissolved air and the ink near the bottom where there is more dissolved air. Therefore, it is difficult to increase the filling amount of ink in the ink tank. In response to this, some conventional image forming apparatuses apply a method of increasing the rotation speed of the stirrer to increase the stirring efficiency. However, if the stirrer is rotated too fast, the stirrer is not restrained by external magnetism, and stirring is not performed properly, which may result in a decrease in degassing performance.

[0008] SUMMARY OF THE PRESENT DISCLOSURE In consideration of the above circumstances, an object of the present invention is to efficiently degas an ink tank even when the amount of ink filled in the ink tank is increased. [Means for solving the problem]

[0009] The ink supply mechanism of the present invention comprises an ink container for storing ink, an ink tank for storing the ink to be supplied from the ink container to a recording head, a pressure reduction section for reducing the pressure inside the ink tank, and a degassing flow path through which the ink flowing out of the ink tank circulates and flows into the ink tank, and is characterized in that a plurality of ink tanks are arranged in parallel with respect to the recording head, and when one of the plurality of ink tanks is used for printing, a degassing tank to perform degassing is selected from the other ink tanks in which the amount of oxygen dissolved in the ink has not reached a predetermined supply target value in accordance with a predetermined degassing selection criterion, and with the interior of the degassing tank reduced in pressure by the pressure reduction section, the ink inside the degassing tank is circulated using the degassing flow path, thereby performing a degassing operation to degas the ink inside the degassing tank.

[0010] The image forming apparatus of the present invention is characterized by including the ink supply mechanism described above. Effect of the Invention

[0011] According to the present invention, it is possible to efficiently degas the ink tank even when the amount of ink filled in the ink tank is increased. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view illustrating an example of a printer according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram illustrating an example of an ink supply mechanism of a printer according to an embodiment of the present invention. [Diagram 3] 11 is a graph showing an example of the change over time in the amount of oxygen dissolved in ink when degassing an ink tank in an ink supply mechanism. [Figure 4] 10 is a flowchart illustrating an example of an operation for selecting a degassing tank in an ink supply mechanism of a printer according to an embodiment of the present invention. [Diagram 5]10 is a flowchart illustrating an example of a switching tank selection operation of an ink supply mechanism of a printer according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] First, the overall configuration of the printer 1 as an inkjet image forming apparatus will be described with reference to Fig. 1. For ease of explanation, the front side of the paper in Fig. 1 is the front side of the printer 1. Arrows L, R, U, and Lo appropriately added to each figure indicate the left side, right side, upper side, and lower side of the printer 1, respectively.

[0014] As shown in Fig. 1, the printer 1 includes a box-shaped printer main body 2. A paper feed cassette 3 for storing paper is housed in the lower part of the printer main body 2 and can be removed.

[0015] A paper transport path 4 is provided on the right side of the printer body 2, and a paper transport unit 5 that can be raised and lowered is provided above the paper feed cassette 3 in the center of the printer body 2. The transport path 4 runs from the paper feed cassette 3 to the paper transport unit 5, and along the paper transport direction of the transport path 4, a paper feed roller, a transport roller, and a registration roller are provided in this order from upstream.

[0016] The paper transport unit 5 includes a transport frame 6 and an endless transport belt 7 (transport member). A drive roller, a driven roller, and a tension roller are rotatably provided on the transport frame 6, and the transport belt 7 is replaceably attached to the transport frame 6 and wound around the drive roller, the driven roller, and the tension roller. The transport belt 7 is controlled by the control unit 16 described below so as to rotate, for example, counterclockwise when viewed from the front, in response to the rotation of the drive roller, and transport paper on the transport belt 7 from right to left.

[0017] The paper transport unit 5 also has an elevation mechanism (not shown) capable of raising and lowering the transport frame 6 and the transport belt 7 in the vertical direction, and moves the transport frame 6 and the transport belt 7 to a printing position close to the recording head 13 described below during printing operation, and moves them to a retracted position away from the recording head 13 during non-printing operation. The paper transport unit 5 also has an air intake section 5a on the inside of the transport belt 7. The transport belt 7 has many air intake holes, and the air intake section 5a draws air from above the transport belt 7 to the inside through the air intake holes.

[0018] On the left side of the printer body 2, a paper transport section 8, a drying device 9, and discharge rollers 10 are provided to the left of the paper transport unit 5 at the printing position in order to discharge paper after printing. On the left side of the printer body 2, a discharge outlet 11 is formed near the discharge rollers 10, and below the discharge outlet 11, a paper output tray 12 is provided protruding to the left.

[0019] Additionally, within the printer body 2, there are provided four recording heads 13 (13K, 13C, 13M, 13Y) that eject ink corresponding to the four colors of ink, black, cyan, magenta, and yellow, respectively, and four ink containers 14 (14K, 14C, 14M, 14Y) that store the ink. Each recording head 13 is connected to each ink container 14 via an ink supply mechanism 20 that has a plurality of ink tanks 21 (sub-tanks). Note that in FIG. 1, the ink supply mechanism 20 corresponding to black ink is illustrated, and the ink supply mechanisms 20 corresponding to cyan, magenta, and yellow ink are omitted.

[0020] A plurality of nozzles 13a that eject ink droplets are formed on the undersides of the recording heads 13K, 13C, 13M, and 13Y. The recording heads 13K, 13C, 13M, and 13Y are arranged side by side above the paper transport unit 5 in the center of the printer body 2, and are arranged, for example, in order from the upstream side (right side) in the paper transport direction. The recording heads 13K, 13C, 13M, and 13Y face the upper surface of the transport belt 7 of the paper transport unit 5 during printing operation, and eject black, cyan, magenta, and yellow ink, respectively, onto the paper on the transport belt 7.

[0021] The ink containers 14K, 14C, 14M, and 14Y are arranged side by side in the lower left corner of the printer main body 2, for example, arranged in order from the bottom up. The ink containers 14K, 14C, 14M, and 14Y are, for example, removably stored in respective container storage units (not shown) provided in the lower left corner of the printer main body 2. The ink containers 14K, 14C, 14M, and 14Y store black, cyan, magenta, and yellow ink, respectively.

[0022] Also provided within the printer main body 2 is a control unit 16 that controls each part of the printer 1. The control unit 16 is a computer consisting of a CPU and the like, and controls each part of the printer 1 connected to the control unit 16 by executing calculations based on control programs and control data stored in a storage unit (not shown) consisting of a ROM, RAM, HDD, etc.

[0023] The control unit 16 controls the replenishing operation, deaeration operation, supply operation, and circulation operation, which will be described later, in the ink supply mechanism 20. When printing, the control unit 16 performs a supply operation to supply ink to the recording head 13 from one ink tank 21 to be used for printing (hereinafter referred to as a printing tank) among the multiple ink tanks 21, and can simultaneously perform a replenishing operation or a deaeration operation in preparation for the other ink tanks 21 other than the printing tank.

[0024] Particularly in this embodiment, the control unit 16 selects a degassing tank to perform degassing from among the ink tanks 21 (hereinafter referred to as standby tanks) other than the tank used for printing, in which the amount of oxygen dissolved in the ink has not reached a predetermined supply target value, according to a predetermined degassing selection criterion, and performs a degassing operation on the selected degassing tank. The control unit 16 also selects a switching tank to be switched to next, from among the ink tanks 21 other than the tank used for printing, in which the amount of oxygen dissolved in the ink has reached a predetermined supply target value, according to a predetermined switching selection criterion. Details of the control of the refilling operation, degassing operation, supply operation, and circulation operation of the ink supply mechanism 20 by the control unit 16, and details of the selection of the degassing tank and the selection of the switching tank will be described later.

[0025] Next, the ink supply mechanism 20 will be described in detail.

[0026] The ink supply mechanism 20 is a mechanism that supplies ink from each ink container 14 (14K, 14C, 14M, 14Y) to each recording head 13 (13K, 13C, 13M, 13Y). In this embodiment, the ink supply mechanism 20 includes, in addition to the recording head 13 and the ink container 14, a plurality of ink tanks 21, a pressure reducing pump 22, a suction pump 23, a degassing pump 24, and a circulation pump 25, as shown in FIG.

[0027] The ink supply mechanism 20 includes, for example, a first ink tank 21a and a second ink tank 21b as the multiple ink tanks 21 that store ink supplied from the ink container 14. The ink supply mechanism 20 is configured to supply ink toward the recording head 13 by utilizing the hydraulic head pressure of the ink stored in the first ink tank 21a and the second ink tank 21b. Note that, in this embodiment, an example will be described in which the ink supply mechanism 20 includes two ink tanks 21 (the first ink tank 21a and the second ink tank 21b), but the present invention is not limited to this example, and the ink supply mechanism 20 may include three or more ink tanks 21.

[0028] The ink supply mechanism 20 has a first pressure reduction flow path 26a connected to the first ink tank 21a and communicating with the internal space above the ink liquid level, and a second pressure reduction flow path 26b connected to the second ink tank 21b and communicating with the internal space above the ink liquid level, as pressure reduction flow paths for reducing the pressure inside the ink tank 21. The upstream portions of the first pressure reduction flow path 26a and the second pressure reduction flow path 26b are partially shared as a common pressure reduction flow path 26c, and the pressure reduction pump 22 is provided in the common pressure reduction flow path 26c.

[0029] The first pressure reduction flow path 26a and the pressure reduction pump 22 function as a pressure reduction section for the first ink tank 21a, and the second pressure reduction flow path 26b and the pressure reduction pump 22 function as a pressure reduction section for the second ink tank 21b. The pressure reduction pump 22 is a negative pressure generating source controlled by the control section 16 to reduce the pressure inside the first ink tank 21a and the second ink tank 21b. The first pressure reduction flow path 26a is provided with a first pressure reduction valve 27a that opens and closes the first pressure reduction flow path 26a, and the second pressure reduction flow path 26b is provided with a second pressure reduction valve 27b that opens and closes the second pressure reduction flow path 26b. The first pressure reduction valve 27a and the second pressure reduction valve 27b are opened and closed under the control of the control section 16.

[0030] The first ink tank 21a is provided with a first atmospheric valve 28a that opens and closes communication between the first ink tank 21a and the atmosphere, and the second ink tank 21b is provided with a second atmospheric valve 28b that opens and closes communication between the second ink tank 21b and the atmosphere. The first atmospheric valve 28a and the second atmospheric valve 28b are opened and closed under the control of the control unit 16.

[0031] The ink supply mechanism 20 has a first suction flow path 29a that sucks ink from the ink container 14 to the first ink tank 21a, and a second suction flow path 29b that sucks ink from the ink container 14 to the second ink tank 21b. The upstream portions of the first suction flow path 29a and the second suction flow path 29b are partially shared as a common suction flow path 29c, and the suction pump 23 is provided in the common suction flow path 29c.

[0032] The suction pump 23 is composed of a diaphragm pump or the like, and is controlled by the control unit 16 to supply ink from the ink container 14 to the first ink tank 21a and the second ink tank 21b via the first suction flow path 29a and the second suction flow path 29b. A first suction valve 30a that opens and closes the first suction flow path 29a is provided in the downstream portion of the first suction flow path 29a, and a second suction valve 30b that opens and closes the second suction flow path 29b is provided in the downstream portion of the second suction flow path 29b. The first suction valve 30a and the second suction valve 30b are opened and closed under the control of the control unit 16.

[0033] The ink supply mechanism 20 has a first degassing flow path 31a for circulating the ink flowing out of the ink tank 21 to the first ink tank 21a and a second degassing flow path 31b for circulating the ink to the second ink tank 21b as degassing flow paths through which the ink flowing out of the ink tank 21 circulates and flows into the ink tank 21. The midstream portions of the first degassing flow path 31a and the second degassing flow path 31b are partially shared as a common degassing flow path 31c, and the degassing pump 24 is provided in the common degassing flow path 31c.

[0034] The degassing pump 24 is controlled by the control unit 16 to cause the ink stored in the first ink tank 21a and the second ink tank 21b to flow into the first degassing flow path 31a and the second degassing flow path 31b, and to cause the ink that has flowed into the first degassing flow path 31a and the second degassing flow path 31b to flow into the first ink tank 21a and the second ink tank 21b, thereby circulating and degassing the ink stored in the first ink tank 21a and the second ink tank 21b. First degassing valves 32a and 33a that open and close the first degassing flow path 31a are provided in the upstream and downstream parts of the first degassing flow path 31a, and second degassing valves 32b and 33b that open and close the second degassing flow path 31b are provided in the upstream and downstream parts of the second degassing flow path 31b. The first degassing valves 32a and 33a and the second degassing valves 32b and 33b are opened and closed under the control of the control unit 16.

[0035] The ink supply mechanism 20 has a first supply flow path 34a that supplies ink from the first ink tank 21a to the recording head 13, and a second supply flow path 34b that supplies ink from the second ink tank 21b to the recording head 13. The downstream portions of the first supply flow path 34a and the second supply flow path 34b are partially shared as a common supply flow path 34c, and the common supply flow path 34c is connected to the recording head 13.

[0036] The first supply flow path 34a and the second supply flow path 34b receive the hydraulic head pressure of the ink stored in the first ink tank 21a and the second ink tank 21b in order to supply ink to the recording head 13. A first supply valve 35a for opening and closing the first supply flow path 34a is provided in the upstream portion of the first supply flow path 34a, and a second supply valve 35b for opening and closing the second supply flow path 34b is provided in the upstream portion of the second supply flow path 34b. The first supply valve 35a and the second supply valve 35b are opened and closed under the control of the control unit 16.

[0037] The middle part of the common supply flow path 34c is branched into a supply branch path 34c1 used for ink supply and a circulation branch path 34c2 used for ink circulation, and the circulation pump 25 is provided in the circulation branch path 34c2. The circulation pump 25 is controlled by the control unit 16 to supply ink to the recording head 13 via the circulation branch path 34c2 in order to circulate the ink remaining in the recording head 13. The supply branch path 34c1 is provided with a supply branch valve 34c3 that opens and closes the supply branch path 34c1, and the circulation branch path 34c2 is provided with a circulation branch valve 34c4 that opens and closes the circulation branch path 34c2. The supply branch valve 34c3 and the circulation branch valve 34c4 are opened and closed under the control of the control unit 16.

[0038] The ink supply mechanism 20 has a first circulation flow path 36a that circulates ink from the recording head 13 to the first ink tank 21a, and a second circulation flow path 36b that circulates ink from the recording head 13 to the second ink tank 21b. The upstream portions of the first circulation flow path 36a and the second circulation flow path 36b are partially shared as a common circulation flow path 36c, and the common circulation flow path 36c is connected to the recording head 13. A first circulation valve 37a that opens and closes the first circulation flow path 36a is provided in a downstream portion of the first circulation flow path 36a, and a second circulation valve 37b that opens and closes the second circulation flow path 36b is provided in a downstream portion of the second circulation flow path 36b. The first circulation valve 37a and the second circulation valve 37b are opened and closed under the control of the control unit 16.

[0039] <Example of ink supply mechanism operation> Next, an example of the operation of the ink supply mechanism 20 of this embodiment will be described.

[0040] <Replenishment operation> The ink supply mechanism 20 performs either a first supply operation of supplying ink from the ink container 14 to the first ink tank 21a, or a second supply operation of supplying ink from the ink container 14 to the second ink tank 21b.

[0041] When performing the first refill operation, the ink supply mechanism 20 opens the first atmosphere valve 28a and the first suction valve 30a for the first ink tank 21a, operates the suction pump 23, and refills the first ink tank 21a with ink from the ink container 14 via the first suction flow path 29a. At this time, the second suction valve 30b for the second ink tank 21b is closed, and the first pressure reducing valve 27a, the first degassing valves 32a and 33a, the first supply valve 35a, and the first circulation valve 37a for the first ink tank 21a are closed.

[0042] During the first supply operation, the supply branching valve 34c3 and the circulation branching valve 34c4, as well as the pressure reducing pump 22, the degassing pump 24, and the circulation pump 25 can be used for the second degassing operation, the second supply operation, the second circulation operation, etc. of the second ink tank 21b. In other words, in the ink supply mechanism 20, during the first supply operation of the first ink tank 21a, printing can be performed by the second supply operation using the second ink tank 21b.

[0043] When performing the second refill operation, the ink supply mechanism 20 opens the second atmosphere valve 28b and the second suction valve 30b for the second ink tank 21b, and operates the suction pump 23 to refill the second ink tank 21b with ink from the ink container 14 via the second suction passage 29b. At this time, the first suction valve 30a for the first ink tank 21a is closed, and the second pressure reducing valve 27b, the second degassing valves 32b and 33b, the second supply valve 35b, and the second circulation valve 37b for the second ink tank 21b are closed.

[0044] During the second supply operation, the supply branching valve 34c3 and the circulation branching valve 34c4, as well as the pressure reducing pump 22, the degassing pump 24, and the circulation pump 25 can be used for the first degassing operation, the first supply operation, the first circulation operation, etc. of the first ink tank 21a. In other words, in the ink supply mechanism 20, during the second supply operation of the second ink tank 21b, it is possible to perform printing by the first supply operation using the first ink tank 21a.

[0045] <Degassing operation> The ink supply mechanism 20 performs either a first degassing operation for degassing the ink stored in the first ink tank 21a, or a second degassing operation for degassing the ink stored in the second ink tank 21b.

[0046] Incidentally, as a method for degassing the air dissolved in the ink stored in the ink tank 21, an agitation degassing method has been conventionally applied, in which an agitator is provided in the ink tank 21 to agitate the ink stored in the ink tank 21 to perform degassing. In contrast, the present invention applies a circulation degassing method in which the ink stored in the ink tank 21 is drained, and the drained ink is circulated and flows back into the ink tank 21, thereby creating a flow throughout the ink in the ink tank 21 and stirring the ink to perform degassing. FIG. 3 shows a graph of the time change in the amount of oxygen dissolved in the ink when the ink tank 21 is degassed by each of the agitation degassing method and the circulation degassing method. As shown in FIG. 3, the circulation degassing method takes less time for the amount of oxygen dissolved in the ink to reach a predetermined supply target value than the agitation degassing method.

[0047] When performing the first degassing operation, the ink supply mechanism 20 closes the first atmosphere valve 28a, the first suction valve 30a, the first degassing valves 32a and 33a, the first supply valve 35a, and the first circulation valve 37a for the first ink tank 21a, opens the first pressure reduction valve 27a, and operates the pressure reduction pump 22 to reduce the pressure inside the first ink tank 21a through the first pressure reduction flow path 26a. At this time, the ink supply mechanism 20 closes the second pressure reduction valve 27b for the second ink tank 21b. Then, while the pressure inside the first ink tank 21a is reduced, the ink supply mechanism 20 opens the first degassing valves 32a and 33a for the first ink tank 21a, and operates the degassing pump 24 to degas the ink stored in the first ink tank 21a through the first degassing flow path 31a. At this time, the second degassing valves 32b and 33b are closed for the second ink tank 21b, and the first pressure reduction valve 27a, the first atmosphere valve 28a, the first suction valve 30a, the first supply valve 35a, and the first circulation valve 37a are closed for the first ink tank 21a.

[0048] During the first degassing operation, the supply branching valve 34c3 and the circulation branching valve 34c4, as well as the suction pump 23 and the circulation pump 25, can be used for the second refill operation, the second supply operation, the second circulation operation, etc. of the second ink tank 21b. In other words, in the ink supply mechanism 20, while the first degassing operation of the first ink tank 21a is being performed, printing can be performed by the second supply operation using the second ink tank 21b.

[0049] When performing the second degassing operation, the ink supply mechanism 20 closes the second atmosphere valve 28b, the second suction valve 30b, the second degassing valves 32b and 33b, the second supply valve 35b, and the second circulation valve 37b for the second ink tank 21b, opens the second pressure reduction valve 27b, and operates the pressure reduction pump 22 to reduce the pressure inside the second ink tank 21b through the second pressure reduction flow path 26b. At this time, the ink supply mechanism 20 closes the first pressure reduction valve 27a for the first ink tank 21a. Then, while the pressure inside the second ink tank 21b is reduced, the ink supply mechanism 20 opens the second degassing valves 32b and 33b for the second ink tank 21b, and operates the degassing pump 24 to degas the ink stored in the second ink tank 21b through the second degassing flow path 31b. At this time, the first degassing valves 32a and 33a are closed for the first ink tank 21a, and the second pressure reducing valve 27b, the second atmosphere valve 28b, the second suction valve 30b, the second supply valve 35b, and the second circulation valve 37b are closed for the second ink tank 21b.

[0050] During the second degassing operation, the supply branching valve 34c3 and the circulation branching valve 34c4, as well as the suction pump 23 and the circulation pump 25, can be used for the first refill operation, the first supply operation, the first circulation operation, etc. of the first ink tank 21a. In other words, in the ink supply mechanism 20, during the second degassing operation of the second ink tank 21b, printing can be performed by the first supply operation using the first ink tank 21a.

[0051] <Supply operation> When printing is performed by the recording head 13, the ink supply mechanism 20 performs either a first supply operation to supply ink from the first ink tank 21a to the recording head 13, or a second supply operation to supply ink from the second ink tank 21b to the recording head 13.

[0052] When performing the first supply operation, the ink supply mechanism 20 opens the first atmosphere valve 28a, the first supply valve 35a, and the supply branch valve 34c3 for the first ink tank 21a, and supplies ink from the first ink tank 21a to the recording head 13 through the first supply flow path 34a via the supply branch path 34c1. At this time, the second supply valve 35b for the second ink tank 21b is closed, the first pressure reducing valve 27a, the first suction valve 30a, the first degassing valves 32a and 33a, the circulation branch valve 34c4, and the first circulation valve 37a for the first ink tank 21a are closed, and the operation of the circulation pump 25 is stopped.

[0053] During the first supply operation, the decompression pump 22, the suction pump 23, and the degassing pump 24 can be used for the second supply operation and the second degassing operation of the second ink tank 21b, etc. In other words, in the ink supply mechanism 20, while printing is being performed by the first supply operation using the first ink tank 21a, it is possible to perform the second supply operation and the second degassing operation of the second ink tank 21b.

[0054] When performing the second supply operation, the ink supply mechanism 20 opens the second atmosphere valve 28b, the second supply valve 35b, and the supply branch valve 34c3 for the second ink tank 21b, and supplies ink from the second ink tank 21b to the recording head 13 through the second supply flow path 34b via the supply branch path 34c1. At this time, the first supply valve 35a for the first ink tank 21a is closed, and the second pressure reducing valve 27b, the second suction valve 30b, the second deaeration valves 32b and 33b, the circulation branch valve 34c4, and the second circulation valve 37b for the second ink tank 21b are closed, and the operation of the circulation pump 25 is stopped.

[0055] During the second supply operation, the pressure reducing pump 22, the suction pump 23, and the degassing pump 24 can be used for the first supply operation and the first degassing operation of the first ink tank 21a, etc. In other words, in the ink supply mechanism 20, while printing is being performed by the second supply operation using the second ink tank 21b, it is possible to perform the first supply operation and the first degassing operation of the first ink tank 21a.

[0056] <Circulation operation> The ink supply mechanism 20 performs either a first circulation operation for circulating ink from the recording head 13 to the first ink tank 21a, or a second circulation operation for circulating ink from the recording head 13 to the second ink tank 21b.

[0057] When the ink supply mechanism 20 performs the first circulation operation, it opens the first atmosphere valve 28a, the first supply valve 35a, the circulation branch valve 34c4, and the first circulation valve 37a for the first ink tank 21a, operates the circulation pump 25, and supplies ink from the first ink tank 21a to the recording head 13 through the first supply flow path 34a via the circulation branch path 34c2, and recovers ink from the recording head 13 to the first ink tank 21a through the first circulation flow path 36a, thereby circulating ink from the recording head 13 to the first ink tank 21a. At this time, it closes the second supply valve 35b and the second circulation valve 37b for the second ink tank 21b, and closes the first pressure reducing valve 27a, the first suction valve 30a, the first degassing valves 32a and 33a, and the supply branch valve 34c3 for the first ink tank 21a.

[0058] During the first circulation operation, the decompression pump 22, the suction pump 23, and the degassing pump 24 can be used for the second refill operation and the second degassing operation of the second ink tank 21b.

[0059] When the ink supply mechanism 20 performs the second circulation operation, it opens the second atmosphere valve 28b, the second supply valve 35b, the circulation branch valve 34c4, and the second circulation valve 37b for the second ink tank 21b, operates the circulation pump 25, and supplies ink from the second ink tank 21b to the recording head 13 through the second supply flow path 34b via the circulation branch path 34c2, and recovers ink from the recording head 13 to the second ink tank 21b through the second circulation flow path 36b, thereby circulating ink from the recording head 13 to the second ink tank 21b. At this time, it closes the first supply valve 35a and the first circulation valve 37a for the first ink tank 21a, and closes the second pressure reducing valve 27b, the second suction valve 30b, the second deaeration valves 32b and 33b, and the supply branch valve 34c3 for the second ink tank 21b.

[0060] During the second circulation operation, the decompression pump 22, the suction pump 23, and the degassing pump 24 can be used for the first refill operation and the first degassing operation of the first ink tank 21a.

[0061] <Measurement of remaining ink level> Next, a description will be given of the measurement of the remaining amount of ink in the ink tank 21 by the control unit 16. The control unit 16 measures the remaining amount of ink in the ink tank 21 by prediction and / or actual measurement.

[0062] The control unit 16 may obtain remaining ink amount prediction information as described below, and predict the remaining ink amounts in the first ink tank 21a and the second ink tank 21b based on at least one of the remaining ink amount prediction information.

[0063] For example, the control unit 16 detects the amount of ink flowing out from the first ink tank 21a and the second ink tank 21b via the first supply flow path 34a and the second supply flow path 34b using flow rate sensors provided in the first supply flow path 34a and the second supply flow path 34b as predicted information on the remaining ink amount. Then, the control unit 16 may predict the remaining ink amount in the first ink tank 21a and the second ink tank 21b based on the detection results of the amount of ink flowing out from the first ink tank 21a and the second ink tank 21b.

[0064] Alternatively, the control unit 16 calculates the amount of ink used for printing based on print settings such as print density and image data to be printed as predicted information on the remaining ink amount, and in particular calculates the amount of ink used for each of the first ink tank 21a and the second ink tank 21b.The control unit 16 may then predict the remaining ink amounts in the first ink tank 21a and the second ink tank 21b based on the calculation results of the amount of ink used.

[0065] Alternatively, the control unit 16 can calculate the amount of ink used in print jobs that have been completed up to the present time, and predict the amount of ink remaining in the first ink tank 21a and the second ink tank 21b at the present time. The control unit 16 can also calculate the amount of ink used in print jobs that have been completed up to the present time, and the amount of ink used in the next print job, and predict the amount of ink remaining in the first ink tank 21a and the second ink tank 21b at the time the next print job is completed.

[0066] When measuring the remaining amount of ink in the ink tank 21, the control unit 16 may detect the remaining amount of ink or the free capacity of the first ink tank 21a and the second ink tank 21b using remaining ink sensors provided in the first ink tank 21a and the second ink tank 21b, and the control unit 16 may measure the remaining amount of ink in the ink tank 21 based on the detection results. Note that any type of sensor, such as an optical type, a capacitance type, an electrode type, a differential pressure type, or a float type, may be used as the remaining ink sensor.

[0067] The control unit 16 may use either the predicted result or the actual measurement result of the remaining ink amounts in the first ink tank 21a and the second ink tank 21b as the measurement result, or may use a combination of the predicted result and the actual measurement result as the measurement result.

[0068] <Measurement of the amount of oxygen dissolved in ink> Next, a description will be given of the measurement of the amount of oxygen dissolved in the ink in the ink tank 21 by the control unit 16. The control unit 16 measures the amount of oxygen dissolved in the ink in the ink tank 21 by prediction and / or actual measurement.

[0069] The control unit 16 may acquire prediction information on the amount of dissolved oxygen in the ink, as described below, and predict the amount of dissolved oxygen in the ink in the first ink tank 21a and the second ink tank 21b based on at least one of the pieces of prediction information on the amount of dissolved oxygen in the ink.

[0070] For example, the control unit 16 detects the environmental temperature and atmospheric pressure in the installation environment of the printer 1 using a temperature sensor and an atmospheric pressure sensor provided in the printer 1 as predicted information on the amount of oxygen dissolved in the ink. The control unit 16 also measures the elapsed time since the first ink tank 21a and the second ink tank 21b were completely refilled with ink as predicted information on the amount of oxygen dissolved in the ink. The control unit 16 also calculates the amount of ink used for printing based on print settings such as print density and image data to be printed as predicted information on the amount of oxygen dissolved in the ink, and in particular calculates the amount of ink used for each of the first ink tank 21a and the second ink tank 21b.

[0071] For example, when the environmental temperature is low (below a predetermined temperature threshold) and the environmental pressure is low (below a predetermined pressure threshold), the saturated dissolved oxygen amount is low, and therefore the control unit 16 predicts that the dissolved oxygen amount in the ink is low. In addition, since the first ink tank 21a and the second ink tank 21b are replenished with degassed ink from the ink container 14, if the time elapsed since the end of ink replenishment is short (below a predetermined time threshold), the control unit 16 predicts that the dissolved oxygen amount in the ink is low. In addition, when the print density is high (above a predetermined density threshold) or when the print volume in the image data is large (above a predetermined print volume threshold), the supply of degassed ink from the ink container 14 to the first ink tank 21a and the second ink tank 21b becomes active, and therefore the control unit 16 predicts that the dissolved oxygen amount in the ink is low.

[0072] The control unit 16 can predict the amount of oxygen dissolved in the ink in the first ink tank 21a and the second ink tank 21b at the current time, and can also predict the amount of oxygen dissolved in the ink in the first ink tank 21a and the second ink tank 21b at the time the next print job is completed.

[0073] When measuring the amount of oxygen dissolved in the ink in the ink tank 21, the control unit 16 may detect air bubbles in the ink using an air bubble sensor provided in the first degassing flow path 31a or the second degassing flow path 31b, or the first ink tank 21a or the second ink tank 21b, and the control unit 16 may measure the amount of oxygen dissolved in the ink in the ink tank 21 based on the detection result. For example, the control unit 16 may measure the amount of oxygen dissolved in the ink in the ink tank 21 based on the detection result of the air bubble sensor when the printer 1 is turned on or after it has been left unused for a long period of time (for example, when no printing has been performed for a predetermined period of time or more). Note that any type of sensor, such as a photoelectric type, a capacitance type, or an ultrasonic type, may be used as the air bubble sensor.

[0074] For example, a photoelectric air bubble sensor is composed of a transmitter that transmits a beam and a receiver that receives the beam, and transmits a beam from one side of the first degassing flow path 31a or the second degassing flow path 31b, or the first ink tank 21a or the second ink tank 21b, and receives the beam on the other side. When the beam is blocked by ink or air bubbles, the received beam signal changes, and the photoelectric air bubble sensor confirms the presence of air bubbles according to the received beam signal.

[0075] The capacitance type air bubble sensor is composed of a detection electrode and a ground electrode that are insulated from each other, and the detection electrode is arranged on one side inside the first degassing flow path 31a or the second degassing flow path 31b, or the first ink tank 21a or the second ink tank 21b, and the ground electrode is arranged on the other side. The capacitance type air bubble sensor detects the state of air bubbles in the ink according to the change in capacitance generated between the detection electrode and the ground electrode. Note that the capacitance type air bubble sensor is applicable to the first degassing flow path 31a or the second degassing flow path 31b that are composed of a wider range of materials and diameters than the photoelectric type air bubble sensor. Furthermore, the capacitance type air bubble sensor is constructed at a lower cost than the ultrasonic type air bubble sensor, and is therefore a cost-effective method for air bubble detection.

[0076] The ultrasonic air bubble sensor is composed of a generator such as a transducer that generates ultrasonic waves and a receiver such as a transducer that receives ultrasonic waves. The ultrasonic waves are generated from one side of the first degassing flow path 31a or the second degassing flow path 31b or the first ink tank 21a or the second ink tank 21b, and are received on the other side. The ultrasonic air bubble sensor checks for the presence of air bubbles according to the signal strength of the received ultrasonic waves, utilizing the characteristic that ultrasonic waves pass through liquid but cannot pass through air bubbles and are reflected. The ultrasonic air bubble sensor is applicable to the first degassing flow path 31a or the second degassing flow path 31b, which have a small diameter, and is also suitable for detecting microbubbles in ink, and is capable of more accurate measurements than photoelectric air bubble sensors and capacitive air bubble sensors.

[0077] The control unit 16 may use either the predicted result or the actual measurement result of the amount of oxygen dissolved in the ink in the first ink tank 21a and the second ink tank 21b as the measurement result, or may use a combination of the predicted result and the actual measurement result as the measurement result.

[0078] <Selecting a degassing tank> Next, the selection of a degassing tank of the ink supply mechanism 20 by the control unit 16 in the printer 1 of this embodiment will be described.

[0079] When one of the ink tanks 21 is being used for printing as a printing tank, and there are multiple other ink tanks 21 that are standby tanks in which the amount of oxygen dissolved in the ink has not reached a predetermined supply target value, the control unit 16 selects a degassing tank to perform degassing from these other ink tanks 21 in accordance with a predetermined degassing selection criterion. For example, the control unit 16 determines that the supply target value has not been reached when the amount of oxygen dissolved in the ink of the ink tank 21 exceeds a predetermined supply oxygen amount value. Note that when there is only one other ink tank 21 in which the amount of oxygen dissolved in the ink has not reached the supply target value, the control unit 16 may select the other ink tank 21 as a degassing tank regardless of the degassing selection criterion.

[0080] Then, the control unit 16 performs a degassing operation to degas the ink inside the degassing tank by circulating the ink inside the degassing tank using the degassing paths (the first degassing path 31a and the second degassing path 31b) while depressurizing the inside of the ink tank 21, which is a degassing tank that satisfies the degassing selection criteria, using the degassing unit (the degassing pump 22 and the first degassing path 26a and the second degassing path 26b). After starting the degassing operation of the degassing tank, the control unit 16 ends the degassing operation when the amount of oxygen dissolved in the ink in the degassing tank falls below a predetermined supply oxygen amount value and satisfies a predetermined supply target value.

[0081] The control unit 16 selects a degassing tank during printing or while waiting for printing using one of the ink tanks 21 used for printing, and, for example, periodically at a predetermined time interval or at the timing of a print job (start timing or end timing), predicts and / or actually measures the amount of oxygen dissolved in the ink of the other ink tanks 21 to select a degassing tank. Note that if a long period of waiting for printing has elapsed since completing the degassing operation of the selected degassing tank, causing the amount of oxygen dissolved in the ink in the degassing tank to exceed a predetermined supply oxygen amount value, the control unit 16 may perform the degassing operation of the degassing tank again.

[0082] For example, the control unit 16 may set a degassing order for the multiple ink tanks 21 as the degassing selection criterion in advance, and select the ink tanks 21 as degassing tanks according to the degassing order. In other words, the control unit 16 determines that the ink tank 21 whose degassing order has arrived is the ink tank 21 that satisfies the degassing selection criterion.

[0083] Alternatively, the control unit 16 may select, as the degassing tank, the ink tank 21 that is predicted to have the amount of dissolved oxygen in the ink reach the supply target value most quickly through the degassing operation among the other ink tanks 21 that are standby tanks, as the degassing tank. In other words, the control unit 16 selects the ink tank 21 that will have the amount of dissolved oxygen in the ink reach the supply target value most quickly as the ink tank 21 that satisfies the degassing selection criterion. This allows the ink tank 21 to be prepared for the next printing more quickly.

[0084] Alternatively, the control unit 16 may select the ink tank 21 with the largest ink volume as the degassing tank among the other ink tanks 21 that are standby tanks as the degassing selection criterion. In other words, the control unit 16 selects the ink tank 21 with the largest ink volume as the ink tank 21 that satisfies the degassing selection criterion. This makes it possible to prepare an ink tank 21 that can be used for a longer period of time.

[0085] <Selection of switching tank> Next, selection of a switching tank of the ink supply mechanism 20 by the control unit 16 in the printer 1 of this embodiment will be described.

[0086] When one of the ink tanks 21 is being used for printing as a printing tank, and there are multiple other ink tanks 21 that are standby tanks in which the amount of dissolved oxygen in ink has reached a predetermined supply target value, the control unit 16 selects from these other ink tanks 21 a switching tank to be switched to next after the first ink tank 21 in accordance with a predetermined switching selection criterion. For example, the control unit 16 determines that the supply target value has been reached when the amount of dissolved oxygen in ink in the ink tank 21 is equal to or less than a predetermined supply oxygen amount value. Note that when there is only one other ink tank 21 in which the amount of dissolved oxygen in ink has reached the supply target value, the control unit 16 may select the other ink tank 21 as the switching tank regardless of the switching selection criterion.

[0087] The control unit 16 selects a switching tank when it becomes necessary to switch from one ink tank 21, which is a printing tank, to another ink tank 21, which is a standby tank. For example, the control unit 16 measures the remaining ink amount and / or the amount of ink-dissolved oxygen in the printing tank by prediction and / or actual measurement at regular intervals or at the timing of a print job (start timing or end timing) during printing or standby using the one ink tank 21, which is a printing tank. The control unit 16 selects a switching tank when the remaining ink amount in the one ink tank 21 becomes low and approaches a predetermined switching target value, or when the amount of ink-dissolved oxygen increases and approaches a predetermined switching target value. For example, the control unit 16 determines that the switching target value has been reached when the remaining ink amount is equal to or less than the predetermined switching remaining amount value, and determines that the switching target value has been reached when the amount of ink-dissolved oxygen is equal to or more than the predetermined switching oxygen amount value.

[0088] For example, the control unit 16 may set a switching order for switching the ink tanks 21 in advance as a switching selection criterion, and select an ink tank 21 as a switching tank according to the switching order. In other words, the control unit 16 determines that the ink tank 21 whose switching order has arrived is the ink tank 21 that satisfies the switching selection criterion.

[0089] Alternatively, the control unit 16 may use the switching selection criterion to select as the switching tank, among the other ink tanks 21 that are standby tanks, the ink tank 21 that is predicted to take the longest time for the amount of dissolved oxygen in the ink to reach a predetermined switching target value when used for printing. In other words, the control unit 16 selects the ink tank 21 that will take the longest time to reach the switching target value as the ink tank 21 that satisfies the switching selection criterion. This allows the ink tank 21 to be used for a longer period of time when the selected switching tank is switched to the tank to be used in the next printing, and reduces the effort required to switch ink tanks 21 thereafter.

[0090] Furthermore, during printing or while waiting to print, the control unit 16 determines whether or not to perform a refill operation for the standby tank based on the remaining ink amount and the amount of oxygen dissolved in the ink measured by prediction and / or actual measurement in the standby tank. Note that the control unit 16 calculates the refill time required for the refill operation and the degassing time required for the degassing operation based on the remaining ink amount and the amount of oxygen dissolved in the ink in the standby tank, and preferably performs the refill operation and degassing operation for the ink tank 21 with the shortest total refill time and degassing time among the multiple ink tanks 21 that are standby tanks.

[0091] Thereafter, if the amount of oxygen dissolved in the ink in the standby tank exceeds the predetermined oxygen supply amount value due to a long period of time having passed since the completion of the refilling operation and degassing operation of the standby tank and the standby tank requires degassing, the control unit 16 may perform the degassing operation on the standby tank again, or may perform the degassing operation on another standby tank. Also, when the printer 1 is on standby for printing, the control unit 16 may perform the degassing operation on each ink tank 21 as appropriate, depending on the amount of ink remaining in each ink tank 21 and / or the amount of oxygen dissolved in the ink.

[0092] <Example of degassing tank selection> Next, an example of an operation for selecting a degassing tank in the printer 1 of this embodiment will be described with reference to the flowchart in FIG.

[0093] When one of the multiple ink tanks 21 is used as a printing tank and is printing or waiting to print, the other ink tanks 21 are standby tanks. Then, the control unit 16 measures the amount of oxygen dissolved in the ink of the other ink tank 21 that is the standby tank (step S1). At this time, the control unit 16 predicts and / or actually measures the amount of oxygen dissolved in the ink of the standby tank at the current time.

[0094] The control unit 16 determines whether or not there is a standby tank in which the amount of oxygen dissolved in the ink has not reached a predetermined supply target value (step S2).

[0095] If there are no standby tanks in which the amount of dissolved oxygen in the ink has not reached the predetermined supply target value, i.e., if the amount of dissolved oxygen in the ink in all standby tanks has reached the predetermined supply target value (step S2: No), the control unit 16 does not select a degassing tank or perform a degassing operation.

[0096] On the other hand, if there is a standby tank in which the amount of dissolved oxygen in the ink has not reached the predetermined supply target value (step S2: Yes), the control unit 16 determines whether there are multiple standby tanks in which the amount of dissolved oxygen in the ink has not reached the predetermined supply target value (step S3).

[0097] If there is even one standby tank in which the amount of oxygen dissolved in the ink has not reached the predetermined supply target value (step S3: No), the control unit 16 selects that standby tank as a degassing tank (step S4).

[0098] On the other hand, if there are multiple standby tanks in which the amount of oxygen dissolved in ink has not reached the specified supply target value (step S3: Yes), the control unit 16 selects a degassing tank to perform degassing from among those standby tanks in accordance with specified degassing selection criteria (step S5).

[0099] The control unit 16 performs a degassing operation on the degassing tank selected as described above (step S6).

[0100] <Example of switching tank selection> Next, an example of the switching tank selection operation in the printer 1 of this embodiment will be described with reference to the flowchart in FIG.

[0101] When one of the multiple ink tanks 21 is used as a printing tank during printing or standby for printing, the other ink tanks 21 are standby tanks. When it becomes necessary to switch from one ink tank 21 used for printing to another ink tank 21 which is a standby tank, the control unit 16 measures the amount of oxygen dissolved in the ink of the standby tank (step S11). At this time, the control unit 16 predicts and / or actually measures the amount of oxygen dissolved in the ink of the standby tank at the current time.

[0102] The control unit 16 determines whether or not there is a standby tank in which the amount of oxygen dissolved in the ink has reached a predetermined supply target value (step S12).

[0103] If there is no standby tank in which the amount of dissolved oxygen in the ink has reached the predetermined supply target value, i.e., if the amount of dissolved oxygen in the ink in all standby tanks has not reached the predetermined supply target value (step S12: No), the control unit 16 does not select a switching tank, but instead selects a degassing tank as described above and performs the degassing operation.

[0104] On the other hand, if there is a standby tank in which the amount of dissolved oxygen in ink has reached the predetermined supply target value (step S12: Yes), the control unit 16 determines whether there are multiple standby tanks in which the amount of dissolved oxygen in ink has reached the predetermined supply target value (step S13).

[0105] If there is only one standby tank in which the amount of oxygen dissolved in the ink has reached the predetermined supply target value (step S13: No), the control unit 16 selects that standby tank as a switching tank (step S14).

[0106] On the other hand, if there are multiple standby tanks whose ink-dissolved oxygen amount has reached the predetermined supply target value (step S13: Yes), the control unit 16 selects a switching tank to perform switching from among those standby tanks according to a predetermined switching selection criterion (step S15).

[0107] The control unit 16 switches the tank used for printing to the switching tank selected as described above (step S16).

[0108] As described above, in this embodiment, the ink supply mechanism 20 of the printer 1 includes an ink container 14 that contains ink, an ink tank 21 that stores ink to be supplied from the ink container 14 to the recording head 13, a pressure reducing unit (a pressure reducing pump 22 and a first pressure reducing flow path 26a and a second pressure reducing flow path 26b) that reduces the pressure inside the ink tank 21, and a degassing flow path (a first degassing flow path 31a and a second degassing flow path 31b) that circulates ink flowing out of the ink tank 21 and flows into the ink tank 21. In the ink supply mechanism 20, a plurality of ink tanks 21 are arranged in parallel with respect to the recording head 13, and when one ink tank 21 out of the plurality of ink tanks 21 is used for printing, a degassing tank to be degassed is selected from the other ink tanks 21 in which the amount of oxygen dissolved in the ink has not reached a predetermined supply target value according to a predetermined degassing selection criterion, and a degassing operation is performed to degas the ink inside the degassing tank by circulating the ink inside the degassing tank using the degassing flow path while the pressure inside the degassing tank is reduced by the pressure reducing unit.

[0109] As a result, by applying the circulation degassing method, the ink supply mechanism 20 can complete degassing in a shorter time than when applying the stirring degassing method. Also, by degassing one ink tank 21 while printing is being performed using the other ink tank 21, when it becomes necessary to switch one ink tank 21, it is possible to immediately switch to the other ink tank 21. At this time, there is no need to wait for the degassing operation, and printing efficiency can be improved. Also, when there are multiple other ink tanks 21, the degassing tank to perform degassing can be appropriately selected by following the degassing selection criteria. Thus, according to the present invention, efficient degassing can be achieved even if the amount of ink filled in the ink tank 21 is increased.

[0110] In the present embodiment, the ink supply mechanism 20 sets the degassing selection criterion for selecting a degassing tank as the ink tank 21 in which the amount of oxygen dissolved in the ink is predicted to reach the supply target value most quickly through the degassing operation.

[0111] This allows the degassing operation of the degassing tank to be completed more quickly, so that the ink tank 21 to be used for the next printing can be prepared more quickly.

[0112] In this embodiment, the ink supply mechanism 20 uses the ink tank 21 with the largest ink volume as the degassing selection criterion for selecting a degassing tank.

[0113] In this way, by completing the degassing operation of the degassing tank with a larger ink capacity, it is possible to prepare an ink tank 21 that can be used for a longer period of time.

[0114] Furthermore, in this embodiment, when one of the multiple ink tanks 21 is used for printing, the ink supply mechanism 20 selects a switching tank to be switched to next after the one ink tank 21 from the other ink tanks 21 in which the amount of dissolved oxygen in the ink has reached a predetermined supply target value, in accordance with predetermined switching selection criteria.

[0115] In this way, when there are multiple other ink tanks 21, it is possible to appropriately select a tank to be switched to in place of the tank used for printing by following the switching selection criteria. Therefore, it is possible to smoothly switch the ink tanks 21 and improve printing efficiency.

[0116] Furthermore, in this embodiment, the ink supply mechanism 20 sets the switching selection criterion for selecting a switching tank as the ink tank 21 that is predicted to take the longest time for the amount of dissolved oxygen in the ink to reach a predetermined switching target value when used for printing.

[0117] As a result, when the selected switch tank is switched to be the tank to be used for the next printing, the ink tank 21 can be used for a longer period of time, and the trouble of switching the ink tank 21 thereafter can be reduced.

[0118] In this embodiment, the ink supply mechanism 20 includes a degassing pump 24 in a degassing flow path common to the ink tanks 21, and performs the degassing operation of each of the ink tanks 21 using the degassing pump 24.

[0119] This makes it possible to improve space efficiency by eliminating the need to provide a degassing pump 24 for each of the multiple ink tanks 21. In order to suppress degassing noise, the degassing operation is performed on each of the multiple ink tanks 21 one by one, and the degassing operation is not performed on multiple ink tanks 21 at the same time.

[0120] In the above embodiment, the ink supply mechanism 20 is provided with a degassing flow path (first degassing flow path 31a and second degassing flow path 31b) and a degassing pump 24 for the ink tank 21, and circulates ink flowing out of the ink tank 21 and causes it to flow into the ink tank 21, thereby degassing the ink tank 21. However, the present invention is not limited to this example. In the present invention, the ink supply mechanism 20 may be configured to be provided with a degassing flow path and a degassing pump for the ink container 14, and to degas the ink container 14 by circulating ink flowing out of the ink container 14 and causing it to flow into the ink container 14.

[0121] The present invention is not limited to the configurations of the printer 1 and ink supply mechanism 20 in the above-described embodiment, and the specifications and combinations of the operations of the printer 1 and ink supply mechanism 20 may be changed according to the usage environment. This allows the optimal degassing operation to be performed according to the conditions of the printer 1, and downtime of the printer 1 can be reduced.

[0122] In this embodiment, the configuration of the present invention is applied to a printer 1 as an image forming apparatus. However, in other different embodiments, the configuration of the present invention can also be applied to other different image forming apparatuses such as copiers, facsimiles, multifunction machines, etc., so long as they are equipped with an inkjet type ink supply mechanism. [Explanation of symbols]

[0123] 1. Printer (image forming device) 13, 13K, 13C, 13M, 13Y recording head 14, 14K, 14C, 14M, 14Y ink container 20 Ink supply mechanism 16 Control section 20 Ink supply mechanism 21 Ink tank 21a First ink tank 21b Second ink tank 22 Pressure reducing pump (pressure reducing section) 23 Suction Pump 24 Degassing Pump 25 Circulation Pump 26a First pressure reducing passage (pressure reducing section) 26b Second pressure reducing passage (pressure reducing section) 26c Common pressure reducing passage (pressure reducing section) 27a First pressure reducing valve (pressure reducing section) 27b Second pressure reducing valve (pressure reducing section) 31a First degassing channel (degassing channel) 31b Second degassing channel (degassing channel) 31c Common degassing channel (degassing channel) 32a, 33a First degassing valve 32b, 33b Second degassing valve

Claims

1. an ink container for storing ink; an ink tank that stores the ink to be supplied from the ink container to a recording head; a pressure reducing unit for reducing the pressure inside the ink tank; a degassing flow path through which the ink flowing out of the ink tank circulates and flows into the ink tank, A plurality of the ink tanks are arranged in parallel with respect to the recording head, an ink supply mechanism for performing a degassing operation to degas the ink inside the degassing tank by selecting a degassing tank to perform degassing from the other ink tanks in which the amount of oxygen dissolved in the ink has not reached a predetermined supply target value according to a predetermined degassing selection criterion, and circulating the ink inside the degassing tank using the degassing flow path while the inside of the degassing tank is depressurized by the depressurization section when one of the ink tanks is used for printing.

2. 2. The ink supply mechanism according to claim 1, wherein the degassing selection criterion is the ink tank in which the amount of oxygen dissolved in the ink is predicted to reach the supply target value most quickly through the degassing operation.

3. 2. The ink supply mechanism according to claim 1, wherein the ink tank having the largest ink volume is selected as the degassing selection criterion.

4. 2. The ink supply mechanism according to claim 1, wherein when one of the plurality of ink tanks is used for printing, a switching tank to be switched to next after the one ink tank is selected from the other ink tanks in which the amount of dissolved oxygen in the ink has reached a predetermined supply target value, according to a predetermined switching selection criterion.

5. 5. The ink supply mechanism according to claim 4, wherein the switching selection criterion is the ink tank that is predicted to take the longest time for the amount of oxygen dissolved in the ink to reach a predetermined switching target value when used for printing.

6. a degassing pump common to the ink tanks is provided in the degassing flow path; 2. The ink supply mechanism according to claim 1, wherein the degassing operation for each of the ink tanks is performed by using the degassing pump.

7. An image forming apparatus comprising the ink supply mechanism according to claim 1.

Images