JP2010194823A - Ink circulation mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink circulation mechanism in which ink mixed in a sub-tank flows backward when the amount of the ink stored in the sub-tank is excessively stored and the positive pressure of atmospheric pressure or higher acts on a joint position of an ink passage through which the ink which is discarded in a discarding tank passes. <P>SOLUTION: The ink circulation mechanism of an image recording device has the sub-tank for temporarily storing ink discharged from a recording head in each color and the discarding tank for discarding the ink excessively stored in the sub-tank, and further has a common air chamber arranged between the sub-tank and the discarding tank, arranged opposite to an inlet port into which the excessively stored ink in each ink color flows from the sub-tank, and provided with a float member floating according to the level of the ink which has flowed in, the float member closes the inlet port, adjusts the flow in amount of the ink from the sub-tank, and prevents the backward flow to the sub-tank when the level of the ink flowing from the sub-tank reaches a predetermined level or higher in the common air chamber. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink circulation mechanism mounted on an inkjet image recording apparatus.

  As a conventional ink jet type image recording apparatus, for example, a recording medium such as recording paper or OHP paper is transported by a recording medium transporting means, and is moved by scanning or ejects ink from a plurality of nozzles provided in a fixed recording head. Thus, an image recording apparatus that forms a high-quality image is known.

  As such an image recording apparatus, for example, in Patent Document 1, in order to eject ink from nozzles of a recording head, a sub tank that temporarily holds ink is provided below the recording head and communicated with a tube. A configuration is disclosed. In addition, in the case of full color, a main tank for supplying ink to the sub tank is connected by a tube. In the case of full color, a sub tank of the number of colors is provided. In order to control the pressure in the sub tank of each color, one generation source is provided. A common route is used.

  In such a configuration, when an excessive amount of ink is supplied to the sub tank, inks of different colors flow in and mix in the common path, and the mixed ink flows back to the sub tank. There is a risk that a problem called color mixing may occur.

  In order to solve such a problem, a negative pressure generating pump is provided in the middle of the tube connected to the waste ink tank.

  The negative pressure generating pump has a negative pressure in the tube, and a suction force to the waste ink tank is generated. Further, in the middle of the tube, each sub tank is connected to each sub tank by a connecting tube via a joint disposed at a position lower than the sub tank. In this way, color mixing due to backflow is prevented by arranging the joint provided between the negative pressure tube connected to the waste ink tank and the connection tube connected to each sub tank at a position lower than the sub tank. Yes.

JP-A-11-115203

  In Patent Document 1 described above, even when excessive ink flows into the sub tank and the ink is discharged through the connection tube, the joint position is lower than the sub tank even if the inside of the tube becomes atmospheric pressure. The remaining ink does not flow back to the sub tank and mix colors.

  However, in this configuration, color mixing due to backflow can be prevented only when the inside of the tube is from negative pressure to atmospheric pressure, and when the inside of the tube becomes positive pressure above atmospheric pressure, the joint position is set. It is assumed that a mixed color occurs due to passing through and flowing into sub-tanks of different ink colors.

  Therefore, the present invention prevents ink from flowing into the sub-tank when excessive ink flows into the sub-tank, even if the inside of the ink path connecting the sub-tank and the waste tank changes to either the negative pressure or the positive pressure. It is an object of the present invention to provide an ink circulation mechanism that prevents the occurrence of the ink.

  In order to solve the above-described problems, the present invention is an image recording apparatus including an image recording unit having a recording head that records an image on a recording medium by discharging different color inks for each of a plurality of nozzle groups. A first tank section for storing ink to be supplied to the recording head for each ink color, a second tank section for storing ink discharged from the recording head for each ink color, and the second tank. A circulation pump that circulates the ink so as to return to the first tank part, a waste tank that discards the excessively stored ink that is stored in the second tank part, and the second tank part The float is disposed between the waste tank and the inflow port into which the excessively stored ink flows from the second tank portion for each ink color, and floats according to the liquid level of the ink that has flowed in. Part And the float member closes the inflow port when the ink flowing from the second tank portion into the common air chamber reaches a predetermined liquid level or more. An ink circulation mechanism that adjusts the amount of ink flowing from the second tank portion is provided.

  In the present invention, when excessive ink flows into the sub-tank, even if the inside of the ink path connecting the sub-tank and the waste tank changes to either the negative pressure or the positive pressure, the ink is prevented from flowing into the sub-tank. An ink circulation mechanism for preventing the occurrence of the ink circulation is provided.

FIG. 1 is a schematic sectional view of an image recording apparatus according to the first embodiment of the present invention. FIG. 2 is a schematic diagram showing an ink circulation system in the image recording apparatus. FIG. 3 is a diagram illustrating an example of a path from the second tank unit to the waste liquid bottle. FIG. 4 is an enlarged view of the periphery of the cylindrical guide member. FIG. 5 is a cross-sectional view of a broken line n portion of the cylindrical guide member shown in FIG. FIG. 6 is a diagram illustrating a state in which the inflow of ink before the ink overflows is started. FIG. 7 is a diagram illustrating a state where ink is flowing. FIG. 8 is a diagram illustrating a state in which the float blocks the opening of the port due to overflow. FIG. 9 is a diagram illustrating a state where the overflow has ended and the float has been lowered. FIG. 10 is a diagram illustrating a plurality of cylindrical guide members provided in the common air chamber. FIG. 11 is a diagram illustrating an example of a path from the second tank unit to the waste liquid bottle in the modified example of the first embodiment. FIG. 12 is a diagram showing a cross-sectional configuration of the common air chamber taken along the broken line P shown in FIG. FIG. 13 is a diagram illustrating a state in which the inflow of ink before the ink overflows is started. FIG. 14 is a diagram illustrating a state in which the float blocks the opening of the port due to overflow. FIG. 15 is a diagram illustrating a state in which the stored ink is discharged from the common air chamber, the float descends, and the ink flows again from the port. FIG. 16 is a diagram illustrating a state of ink in the common air chamber when the ink overflows.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic sectional view of an image recording apparatus according to the first embodiment of the present invention. In the following description, in the drawings, the conveyance direction of the recording medium is the X-axis direction or the sub-scanning direction, and the direction orthogonal to the conveyance direction is the Y-axis direction, the main scanning direction, or the width direction of the recording medium. A direction orthogonal to the axis and the Y-axis direction is referred to as a Z-axis direction or a vertical direction.

  The image recording apparatus 1 is roughly classified into a medium supply unit 2, a medium transport unit 3, an image recording unit 4, a maintenance unit 5, an ink bottle unit (main tank) 6, a first tank unit (upstream sub tank) 7, a heat The replacement unit 8, the second tank unit (downstream sub-tank) 9, the negative pressure adjustment unit 10, the circulation pump unit 11, the waste liquid bottle 12, the medium discharge unit 13, and the control unit 14 are configured. In the image recording apparatus 1 of the present embodiment, the image recording unit 4, the first tank unit 7, the heat exchange unit 8, the second tank unit 9, the negative pressure adjusting unit 10, the circulation pump unit 11, and each part are connected. An ink circulation path for circulating ink is formed by a tube (not shown) to be connected.

  The medium supply unit 2 includes a storage tray 15 that stores a plurality of recording media 17 and a pickup roller 16 that contacts the recording media 17. For example, a cut sheet is used as the recording medium 17 stored in the storage tray 15. The pickup roller 16 contacts the recording medium 17 accommodated, picks up one sheet at a time, and feeds it to the medium conveyance unit 3 downstream in the conveyance direction.

  The medium conveyance unit 3 includes a medium guide 18, a registration roller pair 19, and a belt conveyance mechanism 20. The belt conveyance mechanism 20 is configured by a conveyance belt 24 being wound around a driven roller 21, a tension roller 22, and a driving roller 23 so that tension is applied. A platen 25 and a suction fan 26 are provided inside the belt. It has been.

  The registration roller pair 19 comes into contact with the leading end portion of the recording medium 17 fed by the pickup roller 16, temporarily stops the conveyance, corrects the conveyance posture, and starts conveyance designated by the control unit 14. Based on this timing, the recording medium 17 is transferred to the transport belt 24.

  The transport belt 24 is, for example, a belt-like endless belt, and a large number of holes (not shown) are opened. The conveyor belt 24 is rotatably held by the driven roller 21, the two tension rollers 22, and the four rollers of the driving roller 23 in a tensioned state. Among these, a drive motor (not shown) is connected to the drive roller 23, and the conveyance belt 24 is rotated in the arrow direction m by rotating the drive motor.

  The platen 25 is formed so that at least a region facing the image recording unit 4 is a flat surface, and a large number of holes (not shown) are opened. The suction fan 26 is disposed inside the platen 25 and sucks air from the numerous holes of the platen 25 and the numerous holes of the conveying belt 24. By this suction, the recording medium 17 delivered from the registration roller pair 19 is adsorbed on the transport belt 24 from the leading end and transported to the downstream side at the moving speed of the transport belt 24.

  When transported, the image recording unit 4 disposed opposite to the platen 25 ejects ink onto the recording medium 17 to record an image. The image recording unit 4 includes head units 27, 28, 29, and 31 (K color head unit 27, C color head unit 28, M color head unit 29, and Y color head unit 31), and ink distributors 32, 33, 34, 35 (K color ink distributor 32, C color ink distributor 33, M color ink distributor 34 and Y color ink distributor 35) and ink recovery units 36, 37, 38, 39 (K color ink recovery units) 36, a C color ink recovery device 37, an M color ink recovery device 38, and a Y color ink recovery device 39), and a head unit holding member 42.

  Each head unit 27, 28, 29, 31 is configured to be equal to or larger than the width of the recording medium 17 in a direction orthogonal to the transport direction, and each is held by a head unit holding member 42. In the present embodiment, each head unit 27, 28, 29, 31 uses a plurality of short recording heads each having a nozzle row length less than the width of the recording medium. These short recording heads are alternately arranged in a zigzag manner in a direction orthogonal to the transport direction, so that the entire recording head is larger than the width of the recording medium.

  The ink distributors 32, 33, 34, and 35 shown in FIG. 1 are distributors for evenly distributing ink to six recording heads provided for each ink color. The ink collectors 36, 37, 38, and 39 are collectors for temporarily collecting ink that has not been ejected from the six short heads at one place.

  The maintenance unit 5 includes a moving mechanism (not shown), and when recording is performed by the head unit, as shown in FIG. 1, the four head units 27, 28, 29, and 31 are respectively set at the retracted positions on the downstream side in the medium conveyance direction. It is retracted so as to be arranged in parallel with each head unit. On the other hand, when maintenance is performed, the maintenance unit 5 moves onto the lowered belt conveyance mechanism 20 and moves in the medium conveyance direction. After facing the head units, the maintenance units 5 are raised and assigned to the head units. The maintenance unit 5 cleans each short head of the head unit. Although not shown, the maintenance unit 5 includes members known in the image recording apparatus such as a blade member for wiping the nozzle plate of the short head and a cap member for capping the nozzle plate.

  The ink bottle unit 6 is a detachable main tank that supplies ink to each short head. In this example, the K color ink cartridge 43, the C color ink cartridge 44, the M color ink cartridge 45, and the Y color for each ink color. An ink cartridge 46 is provided. From these ink cartridges 43 to 46, the respective color inks are supplied to the short head via the second tank unit 9, the heat exchange unit 8, the first tank unit 7 and the ink distributors 32 to 35. .

  The first tank unit 7 includes a first K color tank 47, a first C color tank 48, a first M color tank 49, and a first Y color tank 50 for each ink color. In each of these first tanks 47 to 50, a filter and a liquid level detector (not shown) are provided. Further, each of these first tanks 47 to 50 is configured to be open to the atmosphere.

  For each ink color, the heat exchanging unit 8 heat exchangers 63 to 66 (K color ink heat exchanger 63, C color ink heat exchanger 64, M color ink heat exchanger 65, and Y color ink heat exchanger. 66). The heat exchanging unit 8 constantly monitors the temperature of the ink flowing in the head units 27 to 31 with a temperature sensor, and if the ink temperature is out of the preset allowable range, the ink temperature is within the allowable range. Adjust the temperature to fit. By this temperature adjustment, it is possible to record an image with ink having an optimum ink temperature.

  The ink is pumped up from the lower ink paths of the heat exchangers 63 to 66 of the respective colors, temporarily stored in the upper first tanks 47 to 50, and then supplied to the short head so as to flow out by gravity. Is done.

  The second tank unit 9 includes a second K color tank 73, a second C color tank 74, a second M color tank 75, and a second Y color tank 76 for each ink color. In each of these second tanks 73 to 76, a liquid level detector for detecting the liquid level is provided. A K color circulation pump 77, a C color circulation pump 78, an M color circulation pump 79, and a Y color circulation pump 81 of the circulation pump unit 11 are connected to the second tanks 73 to 76, respectively. .

  The waste liquid tank 12 is a tank for collecting the waste ink collected by the maintenance unit 5 or the like. Usually, the waste liquid tank 12 is open to the atmosphere.

  The control unit 14 controls the entire components of the image recording apparatus 1. In the image recording apparatus 1 configured as described above, the image recording unit 4 is configured such that the recording medium 17 to be conveyed is below the K color head unit 27, the C color head unit 28, the M color head unit 29, and the Y color head unit 31. The ink is ejected from each short head and the image is recorded on the recording medium 17. The recording medium 17 on which the image is recorded by the image recording unit 4 is discharged to the discharge tray 84 by the discharge roller 83 of the medium discharge unit 13.

Next, the configuration of the ink circulation system will be described with reference to FIG.
FIG. 2 is a schematic diagram showing an ink circulation system in the image recording apparatus 1. FIG. 2 representatively shows the ink path of K-color ink. Here, the ink circulation system connects the image recording unit 4, the first tank unit 7, the heat exchange unit 8, the second tank unit 9, the negative pressure adjustment unit 10, the circulation pump 11, and each shown in FIG. 1. It is made up of tubes. The configurations of the image recording unit 4, the heat exchange unit 8, and the circulation pump unit 11 are as described above.

  In the following description, since the other colors C, M, and Y have the same configuration, only the ink path of the K color ink shown in FIG. 2 is described, and the ink paths of the other colors C, M, and Y Will not be described. In FIG. 2, the same reference numerals as those in FIG. 1 are assigned to the same constituent portions or the same functional portions as those shown in FIG. 1, and detailed description thereof will be omitted.

  The K color ink cartridge 43 of the ink bottle unit 6 shown in FIG. 1 communicates with the second K color tank 73 via an ink path 86 and an ink supply valve 87 as shown in FIG. Ink is supplied to the second K color tank 73 by opening and closing the valve 87. The second K color tank 73 includes a liquid level detector 119. The liquid level detector 119 is turned off when the ink level drops, and based on this signal, the ink supply valve 87 is opened and closed to supply ink from the K color ink cartridge 43 to the second K color ink tank 73. .

  The ink supplied to the second K color tank 73 is pumped by the K color circulation pump 77 to the first K color tank 47 via the ink path 88 and the heat exchanger 63. The K color circulation pump 77 is driven by a motor 82. The first K color ink tank 47 includes a liquid level detector 108.

  The liquid level detector 108 is turned on when the ink pumped up by the K color circulation pump 77 exceeds a preset liquid level position, and the K color circulation pump 77 is stopped by an instruction from the control unit 14 (not shown). To do. In the present embodiment, the liquid level position set in the second K color tank 73 is lower than the surface position of the nozzle plate 55 of the short recording head 51 of the head unit 27 in the direction of gravity. Two K-color tanks 73 are arranged.

  As shown in FIG. 2, the negative pressure adjusting unit 10 shown in FIG. 1 includes a common air chamber 94, a pressure bellows 95, a weight 96, a position adjusting member 97, and a drive source 98. The pressure bellows 95 has an upper end opening communicated with the common air chamber 94 via the tube 101, and a weight 96 is attached to the lower end sealing portion. The position adjusting member 97 is provided to adjust the position of the weight 96 at the lower end of the pressure bellows 95, that is, the position of the pressure bellows 95.

  The position adjusting member 97 is moved up and down by the drive source 98. When the image recording apparatus 1 is not in operation, the pressure bellows 95 is raised and moved to the initial position compressed to the maximum contracted position. This initial position is an open position where the movement of the lower end of the pressure bellows 95 is freely released as shown in FIG.

  When the pressure bellows 95 is freely released, the pressure bellows 95 is pulled down by the weight 96 to generate a negative pressure in the pressure bellows 96 to make the common air chamber 94 communicated by the tube 101 a negative pressure. Since the common air chamber 94 communicates with the second K-color tank 73 through the tube 99, the second K-color tank 73 similarly has a negative pressure.

  The negative pressure adjusting unit 10 can respond to negative pressure fluctuation due to the image recording operation of the recording head of the K color head unit 27 and pressure fluctuation due to the K color circulation pump 77 by the weight of the weight 96 and the elasticity of the pressure bellows 96. It is configured. The appropriateness of the response can be adjusted by increasing / decreasing the weight of the weight 96 during assembly and selecting from a plurality of elastic members having different elasticity as the material of the pressure bellows 96.

  The common air chamber 94 of the negative pressure adjusting unit 10 communicates with the second K-color tank 73 via the tube 99 on the one hand and the ink pan 115 via the other tube 118 and the atmosphere release valve 102 on the other hand. It is connected to the. Further, the ink pan 115 communicates with the waste liquid tank 103 via the tube 114. The atmosphere release valve 102 is an atmosphere release valve of the second K color tank 73. The pressure generation unit 105 is formed as a whole by the negative pressure adjustment unit 10, the second K color tank 73, the K color circulation pump 77, and the motor 82.

  In the present embodiment, the liquid feeding capacity of the K color circulation pump 77 is designed so that an ink amount larger than the ink amount flowing into the second K color tank 73 can be fed. This is to prevent the overflow of the second K color tank 73. If an overflow occurs, the liquid level detector 116 is turned on and notified to the control unit 14 to temporarily stop the operation of the image forming apparatus 1.

  In a normal use state, the second K color tank 73 is prevented from overflowing by increasing the ink flow rate that can be pumped by the K color circulation pump 77 rather than the ink flow rate flowing into the second K color tank 73. To do. Further, the pressure generation unit 105 opens the inside of the second K-color tank 73 by opening the tube 99 and the atmosphere release valve 102 during non-ink circulation. On the other hand, when the ink is circulated, the atmosphere release valve 102 is closed, and the second K color tank 73 is set to a negative pressure in a sealed state. With this setting, the second K color tank 73 applies a negative pressure to the recording head of the K color head unit 27 via the ink discharge path 106 and the K color ink collector 36 during ink circulation.

When the ink is pumped up to the first K color tank 47, the ink is adjusted to a temperature suitable for ejection from the recording head via the K color ink heat exchanger 63. The first K color tank 47 includes a filter 107 and a liquid level detector 108.
In the present embodiment, the ink liquid level of the first K color tank 47 (the first tank unit 7 in FIG. 1) is higher than the surface of the nozzle plate 55 of the K color head unit 27 in the gravity direction. One K color tank 47 is arranged.

  The ink passes from the second K color tank 73 through the filter 107, is cleaned by removing dust and the like, and flows into the recording head via the ink path 109 and the K color ink distributor 32. Here, when the liquid level detector 108 is turned off for a certain time, a signal is sent to the control unit 14, the ink supply valve 87 is opened, and a necessary amount of ink is supplied to the second K color tank 73. Supplied.

  The first K color tank 47 is provided with an air release valve 113 through a discharge passage 110, a common air chamber 111, and an air release passage 112. In the present embodiment, the air release valve 113 is closed during non-ink circulation, and the first K color tank 47 is set in a sealed state. On the other hand, during the ink circulation, the atmosphere release valve 113 is opened, and the first K color tank 47 is opened to the atmosphere through the atmosphere release valve 113, the atmosphere release path 112, the common air chamber 111, and the discharge path 110. Is set to

  With this setting, the first K color tank 47 applies a positive pressure to the recording head of the K color head unit 27 during ink circulation. That is, when the ink is not circulated, an appropriate negative pressure is generated in the nozzle portion due to the water head difference between the second K color ink tank 73 and the nozzle surface 55, and when the ink is circulated, the water head between the K color ink tank 73 and the nozzle surface 55 is generated. The negative pressure due to the difference, the negative pressure of the pressure generation unit 105, and the positive pressure of the first K color ink tank are added together to generate an appropriate negative pressure for image recording.

  Since the atmosphere release path 112 communicates with the ink pan 115, in the unlikely event that the ink in the first K color tank 47 becomes excessive, excess ink passes through the atmosphere release path 112 and the ink pan 115. Then, it is collected in the waste liquid tank 103. During the head maintenance, the air release valves 102 and 113 are closed and the position adjusting member 97 of the negative pressure adjusting unit 10 is raised to compress the pressure bellows 95 so that the pressure in the ink circulation path is positive. Then, the ink is pushed out from the nozzle 54 of the recording head to the maintenance unit 5. The extruded ink is collected in the waste liquid tank 103 through the waste liquid path 107.

  Next, the route from the second tank unit 9 to the waste liquid bottle will be described in detail with reference to FIG. FIG. 3 shows the ink paths of the K color ink path 120, the C color ink path 121, the M color ink path 122, and the Y color ink path 123. Here, a common part in each color ink path will be described using the K color ink path 120 as a representative.

  The K-color ink path 120 includes an ink path 86 for supplying ink to the second K-color tank 73, a K-color circulation pump 77 and an ink path 88 for pumping ink to the first K-color ink tank 47, An ink discharge path 106 for collecting ink from the K color ink collector 36 communicates. Furthermore, it communicates with a common air chamber 94 via a tube 99. A cylindrical guide member 124 is formed in the common air chamber 94.

In the hollow portion of the cylindrical guide member 124, a spherical float 125 lighter than the specific gravity of the ink is provided so as to be movable in the vertical direction in the cylindrical guide member 124.
Next, the common air chamber 94 will be described in detail with reference to FIGS. 4 and 5. FIG. 4 is an enlarged view around the cylindrical guide member 124. FIG. 5 is a cross-sectional view of the broken line n portion of the cylindrical guide member 124.

  The tube 99 is inserted into a port 127 made of a highly rigid member provided on the upper surface of the common air chamber 94. The port 127 extends downward (inward) from the upper surface of the common air chamber. On the bottom surface of the common air chamber 94, a cylindrical guide member 124 is disposed at a position facing the port 127 so that the hollow portion is located.

  A float 125 that can float up and down is fitted in the hollow of the cylindrical guide member 124. The float 125 is made of a material having a specific gravity smaller than the specific gravity of the ink. The outer shape of the float 125 is set to be larger than the inner diameter of the port 127 and smaller than the inner diameter of the cylindrical guide member 124. The float 125 is guided by the hollow portion of the cylindrical guide member 124 in the horizontal (lateral) direction, and can move up and down (up and down) in the vertical direction.

  Further, the movable range due to the raising and lowering of the float 125 is from the bottom surface of the common air chamber 94 to the lower end of the port 127, and the cylindrical guide member 124 is high so that the float 125 can be guided over this movable range. Is set. In the present embodiment, the height of the cylindrical guide member 124 is set lower than the lower end of the port 127, but the distance from the lower end of the port does not allow the float 125 to escape from the hollow front end of the cylindrical guide member 124. Set to distance.

  Further, at least one ink outlet 126 is opened on the side surface of the cylindrical guide member 124. The ink outlet 126 is set at a position higher than the bottom surface of the common air chamber 94. For example, the amount of ink that flows out from one ink outlet 126 per unit time is set to be smaller than the amount of ink that flows down from one port 127.

Further, the amount of ink flowing per unit time from each ink outlet (ink outlet 126 for each color) in the K-color ink path 120, the C-color ink path 121, the M-color ink path 122, and the Y-color ink path 123 is shown. The amount of ink flowing through the atmosphere release valve 102 and the tube 118 is set to be larger than the total. Specifically, the flow path resistance of the ports ^{127, 1.2 × 10 -7 Pa · S} / m 3, the flow path resistance of the ink flow outlet 126 ^{2.0x10 -7 Pa · S / m 3} , the air release The flow path resistance of the valve 102 and the tube 118 is 1.8 × 10 ⁻⁷ Pa · S / m ³ . However, the present invention is not limited to this, and it is only necessary to maintain the relationship of “flow path resistance of the port 127 <flow path resistance of the air release valve 102 and tube 118 <flow path resistance of the ink outlet 126”.

  The reason for having such a relationship is that the atmosphere release valve 102 is required to have high responsiveness in order to realize stable ink circulation and head maintenance. Therefore, a mechanism with a large flow path resistance such as an electromagnetic valve must be employed. However, if the flow path resistance of the port 127 is made smaller than the flow path resistance of the electromagnetic valve, the port diameter becomes very small, This is because clogging causes a drop in pressure generated during head maintenance and causes deterioration in image quality.

The operation when the ink overflows from the second K color tank 73 will be described with reference to FIGS.
FIG. 6 is a diagram illustrating a state in which the inflow of ink before the ink overflows is started. FIG. 7 is a diagram illustrating a state where ink is flowing. FIG. 8 is a diagram illustrating a state in which ink flows in and overflows, and the float 125 blocks the opening of the port 127. FIG. 9 is a diagram illustrating a state where the overflow has ended and the float 125 has been lowered. FIG. 10 is a view showing a plurality of cylindrical guide members 124 provided in the common air chamber 94.

  In FIG. 6, ink does not flow from the port 127 into the common air chamber 94, and the float 125 is placed on the bottom surface of the common air chamber 94 due to its own weight. Next, the ink 129 flows in as indicated by an arrow A, and the hollow portion of the cylindrical guide member 124 is filled with the ink 129. At this time, since the specific gravity of the float 125 is lighter than that of the ink 129, the float 125 rises along the inner wall of the cylindrical guide member 124 in the direction of arrow B as shown in FIG. Thereafter, the hollow portion of the cylindrical guide member 124 is filled with the ink 129, and when the liquid level reaches the ink outlet 126, the ink 129 flows out from the ink outlet 126.

  However, when the amount of ink flowing into the hollow portion from the port 127 is larger than the amount of ink flowing out of the cylindrical guide member 124 through the ink outlet 126 from the hollow portion, the inside of the cylindrical guide member 124 The liquid level gradually rises. When the ink 129 further flows in, the float 125 contacts the lower end of the port 127 and closes the port 127 as shown in FIG. Since the buoyancy of the float 125 is set to be larger than the ink pressure flowing down from the port 127, the float 125 can block the port 127 and stop the ink inflow.

  Even in the state where the float 125 blocks the port 127 and the ink inflow is stopped, the ink outflow from the ink outlet 126 is continued. Therefore, according to the amount of ink flowing out from the ink outlet 126, the liquid level is lowered and the float 125 is also lowered, so that the port 127 is blocked until then, and the ink 129 flows from the port 127. While the ink flows from the port 127 and the ink flows out of the cylindrical guide member 124 from the ink outlet 126, the float 125 moves up and down, and the amount of ink flowing from the port 127 into the common air chamber 94 Is regulated. That is, the ink amount that is the same as the amount of ink that has flowed out from the ink outlet 126 is adjusted to be constant so that the ink 129 flows out of the port 127.

  Thereafter, when the overflow is completed, the ink inflow from the port 127 is reduced or stopped, and only the ink outflow from the ink outlet 126 is performed. The ink level in the cylindrical guide member 124 is gradually lowered, and the ink outlet 126 And maintain the same height. As shown in FIG. 9, the float 125 also floats at the liquid level.

  As shown in FIG. 10, from the total amount of ink flowing per unit time from each ink outlet 126 in the K-color ink path 120, the C-color ink path 121, the M-color ink path 122, and the Y-color ink path 123, The amount of ink flowing through the atmosphere release valve 102 and the tube 118 is set large, and each ink outlet 126 is set higher than the bottom surface of the common air chamber 94. That is, when the ink 129 overflows from the port 127, the float 127 and the cylindrical guide member 124 block the port 127, so that a certain amount of ink does not flow. While the amount of ink flowing in by the float 127 is regulated, the ink is discharged from the ink outlet 126, and further, the ink is discharged from the atmosphere release valve 102 and the tube 118 to the overflow pan 115.

  Since the total amount of ink flowing out from each ink outlet 126 is equal to or less than the amount of ink flowing out from the atmosphere release valve 102 and the tube 118, the mixed ink liquid level flowing out to the bottom of the common air chamber 94 will not rise. Absent. Since the ink outlet 126 is set at a position higher than the bottom surface of the common air chamber 94, mixed color ink does not enter the cylindrical guide member 124. Accordingly, since only the same color ink exists between the cylindrical guide member 124 and the port 127, the mixed color ink does not flow back to the upstream side (second tank 9) from the cylindrical guide member 124.

  As described above, according to the present embodiment, even when the ink overflows from the sub tank, the ink circulation path is not contaminated by the mixed color ink, so that it is not necessary to completely replace the ink circulation path, and the ink path is repaired. The site can be kept to a minimum. In the present embodiment, the second tank unit 9 has been described, but the first tank unit 7 has the same configuration.

Next, a modification of the first embodiment will be described.
In this modification, the same components or the same working parts as those of the first embodiment described above are denoted by the same reference numerals, and the description thereof is omitted.
FIG. 11 shows a path from the second tank unit 9 to the waste liquid bottle in this modification. In the first embodiment described above, the cylindrical guide member 124 and the float 128 are provided at a position facing the port 127. However, in order to simplify the structure, a rod-like support 131 and a float 130 are provided. The support 131 is implanted on the bottom surface of the common air chamber 94 at a position facing the port 127. The float 130 is formed in a cap shape with a member that is lighter than the specific gravity of the ink 129, and is attached to the top of the support 131.

  The common air chamber 94 will be described in detail with reference to FIG. FIG. 12 shows a cross-sectional configuration of the common air chamber 94 along the broken line P shown in FIG. As shown in FIG. 11, the float 130 is disposed at a position facing the port 127, and is supported movably in the vertical direction along the support 131. Further, the air release valve 102 and the tube 118 are calculated based on the total amount of ink flowing from the ports 127 in the K color ink path 132, the C color ink path 133, the M color ink path 134, and the Y color ink path 135 per unit time. The amount of ink flowing through is set small.

Specifically, the flow resistance of the port 127 is 1.2 × 10 ⁻⁷ Pa · S / m ³ , and the flow resistance of the air release valve 102 and the tube 118 is 1.8 × 10 ⁻⁷ Pa · S / m ^3. Yes. It is not limited to these, and it is only necessary to maintain the relationship of the flow path resistance of the port 127 <the flow path resistance of the air release valve 102 and the tube 118.

  Here, the operation when the ink overflows from the second K color tank 73 will be described with reference to FIGS. FIG. 13 is a diagram showing a state in which the inflow of ink into the common air chamber 94 is started before the ink overflows. FIG. 14 is a diagram illustrating a state in which the float 130 is lifted by the inflow of ink to block the opening of the port 127. FIG. 15 is a diagram illustrating a state in which the stored ink is discharged from the common air chamber 94, the float 130 is lowered, and the ink flows again from the port 127. FIG. 16 is a diagram illustrating the state of ink in the common air chamber 94 when the ink overflows.

  FIG. 13 shows a state immediately after the ink overflow starts in the common air chamber 94. The ink 129 that has flowed into the common air chamber 94 is applied to the float 130 that is positioned vertically downward with respect to the support 131 as indicated by an arrow E.

  Furthermore, if the inflow of ink continues, the ink liquid level in the common air chamber 94 rises and the float 130 rises. As shown in FIG. 14, when the float 130 rises in the direction of arrow F, the upper surface of the float 130 comes into contact with the port 127, closes the port 127, and stops ink inflow.

  At that time, the ink 129 in the common air chamber 94 is discharged to the waste liquid bottle 12 through the open air release valve 102 and the tube 118. The ink level in the common air chamber 94 is lowered, and the float 130 is lowered as shown by an arrow G in FIG. 15 to release the contact state with the port 127, so that ink flows from the port 127 into the common air chamber 94. To do. While the ink flows from the port 127, the float 125 moves up and down to regulate the amount of ink flowing into the common air chamber 94.

  As shown in FIG. 16, when the amount of ink liquid in the common air chamber 94 increases, the float 130 also rises and closes the port 127, thereby restricting the amount of ink flowing into the common air chamber 94. Further, there is always a difference in height between the top (table) of the float 130 and the ink liquid level flowing into the common air chamber 94. For this reason, even if the relationship of “flow path resistance of the port 127 <flow path resistance of the air release valve 102 and the tube 118” is satisfied, ink of other colors does not adhere to the port 127. Accordingly, the mixed color ink does not flow back into the second tank 9.

  As described above, in this modified example, even if the ink overflows from the sub tank 73, the ink circulation path is not contaminated with the mixed ink, so that it is not necessary to replace the ink circulation path completely, and the repaired portion of the ink path is minimized. Can be fastened. Moreover, although the 2nd tank part 9 was demonstrated in this modification, it is the same structure also in the 1st tank part 7, and can obtain the same effect.

  Therefore, even if the ink overflows from the second tank, the mixed ink does not flow back in the ink circulation path, so that it is not necessary to completely replace the ink circulation path, and the repaired portion of the ink path is kept to a minimum. Can do. In addition, since the mechanism for preventing color mixing in the ink circulation mechanism of the present embodiment does not require electrical control, color mixing can be prevented even when an unexpected situation such as a power failure occurs.

  DESCRIPTION OF SYMBOLS 1 Image recording device ... 2 ... Medium supply part, 3 ... Medium conveyance part, 4 ... Image recording part, 5 ... Maintenance unit, 6 ... Ink bottle unit (main tank), 7 ... 1st tank part (upstream sub tank) , 8 ... Heat exchange section, 9 ... Second tank section (downstream sub-tank), 10 ... Negative pressure adjustment section, 11 ... Circulation pump section, 12 ... Waste liquid bottle, 13 ... Medium discharge section, 14 ... Control section, 15 ... Storage tray, 16 ... pickup roller, 17 ... recording medium, 18 ... medium guide, 19 ... registration roller pair, 20 ... belt conveying mechanism, 21 ... driven roller, 22 ... tension roller, 23 driving roller ..., 24 ... conveying belt, 25 ... Platen, 26 ... Suction fan, 27 ... K color head unit, 28 ... C color head unit, 29 ... M color head unit, 31 ... Y color head unit, 32 ... K color i 33 ... C color ink distributor, 34 ... M color ink distributor, 35Y color ink distributor ..., 36 ... K color ink collector, 37 ... C color ink collector, 38 ... M color ink collector 39 ... Y color ink collector, 42 ... head unit holding member, 43 ... K color ink cartridge, 44 ... C color ink cartridge, 45 ... M color ink cartridge, 46 ... Y color ink cartridge, 47 ... first K Color tank, 48 ... first C color tank, 49 first M color tank, 50 ... first Y color tank, 63 ... K color ink heat exchanger, 64 ... C color ink heat exchanger, 65 ... M color ink heat exchanger, 66 ... Y color ink heat exchanger.

Claims (6)

An image recording apparatus comprising an image recording unit having a recording head for recording an image on a recording medium by ejecting different color inks for each of a plurality of nozzle groups,
A first tank for storing ink to be supplied to the recording head for each ink color;
A second tank section for storing ink discharged from the recording head for each ink color;
A circulation pump that circulates the ink so as to return from the second tank portion to the first tank portion;
A waste tank for discarding ink stored in the second tank part and excessively stored;
An ink liquid which is provided between the second tank part and the waste tank and is disposed opposite to an inlet port into which excessively stored ink flows from the second tank part for each ink color. A common air chamber having a float member that floats according to a surface;
Comprising
The float member closes the inflow port when the ink flowing into the common air chamber from the second tank portion becomes a predetermined liquid level or more, and the inflow amount of ink from the second tank portion. An ink circulation mechanism characterized by adjusting the pressure.   The ink circulation mechanism according to claim 1, wherein the float member is made of a material that is lighter than a specific gravity of the ink.   The float member has a spherical shape, is fitted into a cylindrical guide member planted at the bottom of the common air chamber, moves along the inner wall as the liquid level rises and falls, and exceeds a predetermined liquid level. The ink circulation mechanism according to claim 2, wherein the inflow port is blocked when the ink circulation port is closed. Furthermore, an ink outlet opening opened in a side wall of the cylindrical guide member,
The common air chamber has a discharge port for discharging ink to the waste tank,
Comprising
The ink circulation path according to claim 3, wherein an ink amount flowing from the ink outlet for each ink color is made smaller than an ink amount flowing from the outlet of the common air chamber.   The ink circulation mechanism according to claim 4, wherein the ink outlet is opened at a position higher than a bottom surface of the common air chamber.   The float member has a cap shape, is movably fitted on the top of a rod-like support body planted at the bottom of the common air chamber, and moves along the support body as the liquid level rises and falls. The ink circulation mechanism according to claim 2, wherein when the liquid level exceeds a predetermined level, the inflow port is blocked by the top of the cap shape.

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