JP5439511B2 - Ink supply device - Google Patents

Description

  Embodiments described herein relate generally to an ink supply device that supplies ink to an inkjet head.

  2. Description of the Related Art Conventionally, in an inkjet recording apparatus that forms an image on a recording medium with an inkjet head, a method of supplying ink to the inkjet head while circulating the ink is used to remove bubbles and foreign matters stagnating around the ink ejection port of the inkjet head. ing.

  As an ink circulation system, a system in which ink is pressurized by a direct pump and circulated is known. In this method, since the ink passes through the pump, the ink is easily deteriorated, and the deteriorated ink is refluxed to the ink jet head, resulting in an unstable image.

  In addition, the above problem can be solved by adopting a system in which the ink is circulated by changing the pressure of the tank in which the ink is stored with the pump without directly pressurizing the ink with the pump. In this method, it is necessary to repeatedly switch the tank pressure from negative pressure to positive pressure, and from positive pressure to negative pressure. During this switching, circulation temporarily stops or pressure fluctuations near the nozzles of the inkjet head occur. Thus, there is a problem that the image quality is adversely affected.

US Patent Application Publication No. 2011/007105

  The problem to be solved by the present invention is to provide an ink supply device that stably circulates ink in a flow path including an inkjet head and enables good image formation by the head.

  An ink supply apparatus according to an embodiment includes a first tank provided upstream of the ink jet head with respect to the ink flow in a flow path including an ink jet head that discharges ink to a recording medium, and the ink flow. On the other hand, a second tank and a third tank provided downstream of the inkjet head, a first flow path connecting the first tank and the inkjet head, the inkjet head, the second tank, and the third tank. A second flow path for connecting a tank, a third flow path for connecting the second tank and the third tank and the first tank, a first pressure adjusting mechanism for adjusting the pressure of the second tank, A second pressure adjusting mechanism for adjusting a pressure in the third tank; and controlling the first pressure adjusting mechanism and the second pressure adjusting mechanism. A controller that repeatedly executes the operation of alternately raising and lowering the pressures of the second tank and the third tank with respect to the reference pressure while keeping the ink flow rate of the heads constant, and circulating the ink between the tanks. .

1 is a diagram illustrating a schematic configuration of an ink supply device according to an embodiment. FIG. 3 is a diagram illustrating an initial state of the ink supply device. FIG. 4 is a diagram showing a part of the circulation operation of the ink supply device. 6 is a flowchart of an initial ink filling operation by the ink supply device. 6 is a flowchart of ink replenishment operation by the ink supply device. 5 is a flowchart of ink circulation operation by the ink supply device. 4 is a time chart showing a second tank flow rate, a third tank flow rate, a circulation flow rate, and a circulation flow rate generated by the ink circulation operation. FIG. 8 is an enlarged view of a part of the time chart shown in FIG. 7. 9 is a time chart for use in comparison with FIG. 7 and FIG.

Hereinafter, an embodiment will be described with reference to the drawings.
[Configuration of ink supply device]
1, 2, and 3 are schematic views illustrating a schematic configuration of an ink supply device according to the present embodiment. The arrows shown in each figure represent the flow of ink and air.
The ink supply device according to the present embodiment includes, for example, a transport mechanism that transports a recording medium such as paper, and an ink jet recording that includes an ink jet head 200 that forms an image by ejecting ink onto the recording medium transported by the transport mechanism. It is included in the device.

  As shown in FIGS. 1, 2, and 3, the ink supply apparatus according to the present embodiment is provided on the upstream side of the inkjet head 200 with respect to the flow direction of the ink 201 and supplies the ink 201 to the inkjet head 200. 1 tank 1, a second tank 2 and a third tank 3 provided on the downstream side of the ink jet head 200 with respect to the flow direction and collecting ink 201, an ink tank 4 such as a replaceable ink cartridge, and the tank 1 A first flow path 5 for supplying the ink 201 inside the ink jet head 200, a second flow path 6 for collecting the ink 201 that has passed through the ink jet head 200 into the tanks 2, 3, and ink in the tanks 2, 3. A third flow path 7 for returning 201 to the first tank 1 and a first port as a first pressure adjusting mechanism for adjusting the pressure in the second tank 2. A flop 8, and a second pump 9 serving as a second pressure adjusting mechanism for adjusting the pressure of the third tank 3, a.

  The ink jet head 200 includes an ink supply port 200a connected to the first flow path 5, an ink recovery port 200b connected to the second flow path 6, and a nozzle in which a large number of nozzles for discharging the ink 201 are arranged. And an ink ejection mechanism that selectively ejects ink from the nozzles arranged on the nozzle surface 200c to form an image on a recording medium conveyed by the conveyance mechanism.

  The first tank 1 includes a valve 10 that opens and seals the air layer in the tank 1 to the atmosphere, and a liquid level sensor 11 that detects the liquid level of the ink 201 in the tank 1. Yes.

  The second tank 2 includes a valve 20 that opens and seals the air layer in the tank 2 to the atmosphere, a liquid level sensor 21 that detects the liquid level of the ink 201 in the tank 2, and the tank 2. And a conduit 22 communicating with the inner air layer. The pipe line 22 is connected to either the suction port or the compression port provided in the first pump 8.

  The third tank 3 includes a valve 30 that opens and seals the air layer in the tank 3 to the atmosphere, a liquid level sensor 31 that detects the liquid level of the ink 201 in the tank 3, and the tank 3. And a conduit 32 communicating with the inner air layer. The pipe line 32 is connected to either the suction port or the compression port provided in the second pump 9.

  An upper limit 11a and a lower limit 11b of the liquid level height are set in the liquid level sensor 11, and an upper limit 21a and a lower limit 21b of the liquid level height are set in the liquid level sensor 21, and the liquid level sensor 31 is set. Is set with an upper limit 31a and a lower limit 31b of the liquid level. The lower limit 11b is set above the opening portions of the pipelines 5 and 73 in the first tank 1, and the lower limit 21b is set above the opening portions of the pipelines 62 and 71 in the second tank 2, The lower limit 31 b is set above the opening portions of the pipes 63 and 72 in the third tank 3. Accordingly, the liquid level of the ink 201 in the first tank 1 is controlled within the upper limit 11a and the lower limit 11b, the liquid level of the ink 201 in the second tank 2 is controlled within the upper limit 21a and the lower limit 21b, and the third tank 3 As long as the liquid level of the ink 201 is controlled within the upper limit 31a and the lower limit 31b, ink leakage does not occur from the tanks 1, 2, 3, and the pipes 5, 62, 63, 71, 72, 73 There is no possibility that air bubbles are mixed into the flow path because the opening is exposed to the air layer.

  Each liquid level sensor 11, 21, 31 outputs a signal indicating that when the liquid level of the ink 201 in each tank 1, 2, 3 reaches the upper limit 11a, 21a, 31a, respectively. When the liquid level of the ink 201 in the tanks 1, 2, 3 reaches the lower limit 11b, 21b, 31b, a signal indicating that is output.

  The first tank 1 and the ink tank 4 are connected via a supply pipe 40. The supply pipe 40 is provided with a partition valve 41 which is, for example, an electromagnetic valve. By opening and closing the partition valve 41, the amount of ink introduced from the ink tank 4 to the first tank 1 is adjusted. A part of the ink tank 4 is open to the atmosphere.

  The first flow path 5 is constituted by a conduit 50 that connects the first tank 1 and the ink supply port 200 a of the inkjet head 200.

  The second flow path 6 includes a branch pipe 60, a pipe 61 connecting the ink recovery port 200b of the inkjet head 200 and the branch pipe 60, a pipe 62 connecting the branch pipe 60 and the second tank 2, the branch pipe 60, and the second pipe 60. A pipe 63 connecting the three tanks 3, a backflow prevention mechanism 64 that suppresses the flow from the second tank 2 toward the inkjet head 200, and a backflow prevention mechanism that suppresses the flow from the third tank 3 toward the inkjet head 200. 65 etc.

  The third flow path 7 includes a branch pipe 70, a pipe 71 connecting the second tank 2 and the branch pipe 70, a pipe 72 connecting the third tank 3 and the branch pipe 70, the branch pipe 70 and the first tank 1. A pipe 73 to be connected, a backflow prevention mechanism 74 for suppressing the flow in the direction from the first tank 1 to the second tank 2, a backflow prevention mechanism 75 for suppressing the flow in the direction from the first tank 1 to the third tank 3, It is configured by a filter 76 or the like that removes foreign matter from the ink 201 flowing in the pipe 73. The arrangement position of the filter 76 may be another place, for example, the pipe line 50 or the like.

  The backflow prevention mechanisms 64, 65, 74, and 75 are, for example, check valves and valves that can switch the flow direction of the ink 201 to be suppressed.

  As the first pump 8 and the second pump 9, for example, a tube pump or a roots pump is used. The first pump 8 and the second pump 9 can perform a switching operation in which the direction of air flow is reversed and switched. That is, the suction port and the compression port can be reversed. Moreover, the 1st pump 8 and the 2nd pump 9 are comprised so that the inflow of air can be interrupted | blocked during a stop.

  In addition to the configuration described above, the ink supply apparatus according to the present embodiment includes a controller 100 including a processor and a memory, and valve driving circuits 101 and 102 that drive the valves 10, 20, and 30 and the gate valve 41. , 103, 104, and speed control circuits 105, 106 connected to motors for driving the first pump 8 and the second pump 9, respectively.

  The signals output from the liquid level sensors 11, 21, 31 are input to the controller 100. The controller 100 issues commands to the valve drive circuits 101, 102, 103, and 104 to open and close the valves 10, 20, and 30 and the gate valve 41, and inputs from the liquid level sensors 11, 21, and 31. Based on the above signals, commands are sent to the speed control circuits 105 and 106 to drive the pumps 8 and 9 to change the pressure in the tanks 2 and 3.

[Ink filling operation]
Next, the initial filling operation of the ink 201 to the ink supply device according to the present embodiment will be described with reference to the flowchart of FIG. At the beginning of the operation, the liquid level height of the first tank 1 is the upper limit 11a or less, the liquid level height of the second tank 2 is the lower limit 21b or less, and the liquid level height of the third tank 3 is the upper limit. It is assumed that it is 31a or less.

  In starting the filling operation, the controller 100 first starts (ON) the power supply to each of the circuits 101 to 106, the pumps 8 and 9, the valves 10, 20, and 30, the gate valve 41, and the like. A transition is made to a standby state (Act 1). Next, the controller 100 issues a command to the valve drive circuit 101 to open the valve 10 (Act 2), and issues a command to the valve drive circuit 104 to open the gate valve 41 (Act 3). At this time, the ink 201 is supplied from the ink tank 4 to the first tank 1 through the supply pipe 40.

  In this state, the controller 100 monitors the output from the liquid level sensor 11 (Act 4). When the liquid level height of the first tank 1 eventually reaches the upper limit 11a and a signal is output from the liquid level sensor 11 (Act4 YES), the controller 100 issues a command to the valve drive circuit 104 to shut off the gate valve. 41 is closed (Act 5).

  After filling the first tank 1 with the ink 201 up to the upper limit 11a, the controller 100 issues a command to the valve drive circuit 102 to close the valve 20 (Act 6) and issues a command to the speed control circuit 105. Then, the first pump 8 is driven to suck the air in the second tank 2 and discharge it outside (Act 7). As a result, a negative pressure is generated in the second tank 2, and the ink 201 in the first tank 1 flows in the order of the pipe 50, the inkjet head 200, the pipe 61, the branch pipe 60, and the pipe 62. (Act 8).

  In this state, the controller 100 monitors the output from the liquid level sensor 21 (Act 9). When the liquid level of the second tank 2 eventually reaches the lower limit 21b and a signal is output from the liquid level sensor 21 (Yes in Act 9), the controller 100 issues a command to the speed control circuit 105 to The pump 8 is stopped (Act 10), and a command is issued to the valve drive circuit 102 to open the valve 20 (Act 11). At this time, the negative pressure in the second tank 2 is released. After the negative pressure is released, for example, after a predetermined time has elapsed since the valve 20 was opened, the controller 100 issues a command to the valve drive circuit 102 to close the valve 20 (Act 12).

  After filling the second tank 2 with the ink 201 to the lower limit 21b, the controller 100 issues a command to the valve drive circuit 103 to close the valve 30 (Act 13) and issues a command to the speed control circuit 106. Then, the second pump 9 is driven, and the air in the third tank 3 is sucked and discharged to the outside (Act 14). Then, negative pressure is generated in the third tank 3, and the ink 201 in the first tank 1 flows in the order of the pipe 50, the inkjet head 200, the pipe 61, the branch pipe 60, and the pipe 63 to the third tank 3. (Act 15).

  In this state, the controller 100 monitors the output from the liquid level sensor 31 (Act 16). When the liquid level height of the third tank 3 eventually reaches the upper limit 31a and a signal is output from the liquid level sensor 31 (YES in Act 16), the controller 100 issues a command to the speed control circuit 106 to output the second value. The pump 9 is stopped (Act 17), and a command is issued to the valve drive circuit 103 to open the valve 30 (Act 18). At this time, the negative pressure in the third tank 3 is released. After the negative pressure is released, for example, after a predetermined time has elapsed since the valve 30 was opened, the controller 100 issues a command to the valve drive circuit 103 to close the valve 30 (Act 19). In this way, the third tank 3 is filled with the ink 201 up to the upper limit 31a.

  While the operations of Act6 to Act19 are executed, the ink amount in the first tank 1 decreases. In order to replenish the first tank 1 with this ink decrease amount, the controller 100 repeatedly executes the replenishment operation shown in the flowchart of FIG. 5 in parallel with the operations of Act6 to Act19.

  That is, first, the controller 100 determines whether or not a signal is output from the liquid level sensor 11 in response to the liquid level of the first tank 1 reaching the lower limit 11b (Act 20). If no signal is output from the liquid level sensor 11 (NO in Act 20), the operation shown in this flowchart ends.

  On the other hand, if the signal is output from the liquid level sensor 11 (YES in Act 20), the controller 100 issues a command to the valve drive circuit 104 to open the gate valve 41 (Act 21). At this time, the ink 201 is supplied from the ink tank 4 to the first tank 1 through the supply pipe 40.

In this state, the controller 100 monitors the output from the liquid level sensor 11 (Act 22). When the liquid level of the first tank 1 eventually reaches the upper limit 11a and a signal is output from the liquid level sensor 11 (YES in Act 22), the controller 100 issues a command to the valve drive circuit 104 to shut off the gate valve. 41 is closed (Act 23). This completes the operation shown in the flowchart.
By the operation described above, ink is filled in each of the tanks 1, 2 and 3 as shown in FIG.

[Ink circulation]
The controller 100 controls the first pump 8 and the second pump 9 to keep the pressure of the second tank 2 and the third tank 3 alternately with respect to the atmospheric pressure (reference pressure) while keeping the ink flow rate of the inkjet head 200 constant. The ink is circulated in each of the tanks 1, 2, 3 by repeatedly executing the operation of moving up and down. Details of this circulation operation will be described with reference to FIGS. 6, 7 and 8. FIG.

  FIG. 6 is a flowchart of the ink circulation operation. FIG. 7 shows the flow rate of ink 201 flowing into the second tank 2 [(a) second tank flow rate], the flow rate of ink 201 flowing into the third tank 3 [(b) third tank flow rate], and the first. The flow rate of the ink 201 supplied from the tank 1 to the first flow path 5 and flowing through the inkjet head 200 [(c) circulation flow rate], the flow rate of the ink 201 returning from the second tank 2 and the third tank 3 to the first tank 1 [ It is a time chart which shows the time change of (d) recirculation flow volume]. FIG. 8 is an enlarged view of a part of the time chart of FIG. The circulating flow rate is a value obtained by adding the positive portions of the second tank flow rate and the third tank flow rate, and the circulating flow rate is a value obtained by adding the negative portions of the second tank flow rate and the third tank flow rate.

  The liquid level height of each of the tanks 1, 2, 3 at the start of the circulation operation is a state immediately after the filling operation is completed, that is, as shown in FIG. 2, the upper limit 11 a for the first tank 1 and the lower limit 21 b for the second tank 2. The third tank 3 is assumed to have an upper limit 31a. From this state, first, the controller 100 starts supplying power to the circuits 101 to 106, the pumps 8, 9, the valves 10, 20, 30 and the gate valve 41, etc., and waits for the operation. (Act 24). Next, the controller 100 issues a command to the valve drive circuit 101 to open the valve 10 (Act 25), issues a command to the valve drive circuit 102 to close the valve 20 (Act 26), and issues a command to the valve drive circuit 103. And the valve 30 is closed (Act 27).

  Then, the controller 100 issues a command to the speed control circuit 105 to drive the first pump 8 so as to suck air from the second tank 2 (Act 28). When the first pump 8 is driven in this way, negative pressure is generated in the second tank 2, and the ink 201 flows from the first tank 1 to the conduit 50, the inkjet head 200, and the conduit 61 as indicated by the arrows in FIG. 2. Then, a flow that flows into the second tank 2 through the branch pipe 60 and the pipe line 62 is generated. The force that causes the flow of the ink 201 into the second tank 2 from the first tank 1 through the pipe 73, the branch pipe 70, and the pipe 71 also works, but this flow is suppressed by the action of the backflow prevention mechanism 74. Hereinafter, when the first pump 8 is driven so as to suck air from the second tank 2, a similar ink flow is generated, and detailed description thereof is omitted. In Act 28, the target value of the driving speed of the motor of the first pump 8 is set to a speed at which the second tank flow rate is stabilized at the flow rate A.

  At the same time as driving the first pump 8, the controller 100 issues a command to the speed control circuit 106 to drive the second pump 9 so as to compress the air in the third tank 3 (Act 29). When the second pump 9 is driven in this way, a positive pressure is generated in the third tank 3, and the ink 201 flows from the third tank 3 to the pipe 72, the branch pipe 70, and the pipe 73 as shown by the arrows in FIG. 2. The flow which flows in into the 1st tank 1 through this occurs. A force that causes a flow of ink to flow out from the third tank 3 to the first tank 1 through the pipe 63, the branch pipe 60, the pipe 61, the ink jet head 200, and the pipe 50 also acts. It is suppressed by the action of. Hereinafter, when the second pump 9 is driven so as to compress the air in the third tank 3, it is assumed that the same ink flow occurs, and detailed description thereof is omitted. In Act 29, the target value of the driving speed of the motor of the second pump 9 is set to a speed at which the third tank flow rate is stabilized at the flow rate −A.

  Act 28 changes the pressure of the second tank 2 from the atmospheric pressure to the negative pressure, and with this change, the second tank flow rate gradually increases from zero as shown in FIGS. 7 (a) and 8 (a). And stabilize at flow rate A. Further, the operation of Act 29 changes the pressure of the third tank 3 from the atmospheric pressure to the positive pressure, and the third tank flow rate gradually decreases from zero as shown in FIGS. 7B and 8B. And stabilize at flow rate -A.

  With the first pump 8 and the second pump 9 thus operated, the controller 100 monitors the output from the liquid level sensor 31 (Act 30). When the liquid level height of the third tank 3 reaches the lower limit 31b and a signal is output from the liquid level sensor 31 (YES in Act 30), the controller 100 eventually sends the speed control circuit 106, as shown in FIG. A command is issued to drive the second pump 9 so as to suck air from the third tank 3 (Act 31). When the second pump 9 is driven in this way, a negative pressure is generated in the third tank 3, and the ink 201 flows from the first tank 1 to the pipe 50, the inkjet head 200, and the pipe 61 as shown by the arrows in FIG. Then, a flow that flows into the third tank 3 through the branch pipe 60 and the pipe line 63 is generated. The force that causes the flow of the ink 201 into the third tank 3 from the first tank 1 through the pipe 73, the branch pipe 70, and the pipe 72 also works, but this flow is suppressed by the action of the backflow prevention mechanism 75. Hereinafter, when the second pump 9 is driven so as to suck air from the inside of the third tank 3, it is assumed that a similar ink flow occurs, and detailed description thereof is omitted. In Act 31, the target value of the driving speed of the motor of the second pump 9 is set to a speed at which the third tank flow rate is stabilized at the flow rate A.

  The operation of Act31 changes the pressure in the third tank 3 from positive pressure to atmospheric pressure and from atmospheric pressure to negative pressure. Here, the time at which a signal indicating that the liquid level height of the third tank 3 has reached the lower limit 31b is output from the liquid level sensor 31 is t1 ′, and the time of the third tank 3 that has changed from positive pressure to lowering The time for the pressure to reach atmospheric pressure is defined as t1a ′, and the time for the pressure in the third tank 3 to further decrease and stabilize at negative pressure is defined as t1b ′. As shown in FIGS. 7B and 8B, the third tank flow rate starts to gradually increase from the flow rate −A at time t1 ′, becomes zero at time t1a ′, and continues to increase thereafter. Stable at the flow rate A at time t1b ′.

After Act 31, the controller 100 waits for a time until the pressure in the third tank 3 starts to increase and reaches the atmospheric pressure, that is, (t1a′−t1 ′) (Act32). After the standby, the controller 100 issues a command to the speed control circuit 105 to drive the first pump 8 so as to compress the air in the second tank 2 (Act 33). When the first pump 8 is driven in this way, positive pressure is generated in the second tank 2, and the ink 201 flows into the first tank 1 from the second tank 2 through the pipe 71, the branch pipe 70, and the pipe 73. A flow occurs. The force that generates the flow of the ink 201 flowing into the first tank 1 from the first tank 1 through the pipe 62, the branch pipe 60, the pipe 61, the ink jet head 200, and the pipe 50 also works. 64 is suppressed. Hereinafter, when the first pump 8 is driven so as to compress the air in the second tank 2, it is assumed that a similar ink flow occurs, and detailed description thereof is omitted. In Act 33, the target value of the driving speed of the motor of the first pump 8 is set to a speed at which the second tank flow rate is stabilized at the flow rate −A.
Due to the operation of Act33, the pressure in the second tank 2 changes from negative pressure to atmospheric pressure.

  After Act33, the controller 100 waits for a time from when the pressure in the third tank 3 reaches atmospheric pressure until it further decreases and stabilizes at negative pressure, that is, (t1b'-t1a ') (Act34).

  After the standby, the controller 100 issues a command to the speed control circuit 105 so that the target value of the driving speed of the motor of the first pump 8 is stabilized at the second tank flow rate at the flow rate −B (A <B). Change to speed (Act 35). Along with this, the pressure in the second tank 2 further increases and eventually stabilizes at a positive pressure. Here, a time during which the pressure in the second tank 2 is stabilized at a positive pressure is defined as t1c '.

  After Act 35, the controller 100 waits for a time (t1d'-t1b ') (Act 36). Here, t1d ′ is a time during which the pressure in the second tank 2 should be lowered, and is stored in a memory or the like provided in advance in the controller 100. After the standby, the controller 100 issues a command to the speed control circuit 105 to change the target value of the motor driving speed of the first pump 8 to a speed at which the second tank flow rate is stabilized at the flow rate −A ( Act 37). Accordingly, the pressure is stabilized when the pressure in the second tank 2 is slightly reduced. Here, t1e 'is defined as a time during which the pressure of the second tank 2 is lowered and stabilized.

  In the operations of Acts 33 to 37, the second tank flow rate starts to gradually drop from the flow rate A at time t1a ′ as shown in FIGS. 7A and 8A, and becomes zero at time t1b ′. Thereafter, it continues to descend and stabilizes at a flow rate -B at time t1c ', starts to rise at time t1d', and stabilizes at flow rate -A at time t1e '.

  After Act 37, the controller 100 monitors the output from the liquid level sensor 21 (Act 38). When the liquid level height of the second tank 2 eventually reaches the lower limit 21b and a signal is output from the liquid level sensor 21 (YES in Act 38), the controller 100 issues a command to the speed control circuit 105 to set the second level. The first pump 8 is driven to suck air from the tank 2 (Act 39). At this time, the target value of the driving speed of the motor of the first pump 8 is set to a speed at which the second tank flow rate is stabilized at the flow rate A.

  Here, a time during which a signal indicating that the liquid level of the second tank 2 has reached the lower limit 21b is output from the liquid level sensor 21 is defined as t2 '.

  After that, the controller 100 waits for a time corresponding to (t1a′−t1 ′) as in Act 32 (Act 40). After the standby, the controller 100 issues a command to the speed control circuit 106 to drive the second pump 9 so as to compress the air in the third tank 3 (Act 41). At this time, the target value of the driving speed of the motor of the second pump 9 is set to a speed at which the third tank flow rate is stabilized at the flow rate −A.

  After Act 41, the controller 100 waits for a time corresponding to (t1b'-t1a ') as in Act 34 (Act 42). After the standby, the controller 100 issues a command to the speed control circuit 106 to change the target value of the driving speed of the motor of the second pump 9 to a speed at which the third tank flow rate is stabilized at the flow rate −B ( Act 43).

  After Act 42, the controller 100 waits for a time corresponding to (t1d'-t1b ') as in Act 36 (Act 44). After the standby, the controller 100 issues a command to the speed control circuit 106 to change the target value of the motor driving speed of the second pump 9 to a speed at which the third tank flow rate is stabilized at the flow rate −A ( Act 45).

  When Acts 38 to 45 are performed, after time t2 ′, the second tank flow rate shows the same change as the third tank flow rate change from t1 ′ to t2 ′ as shown in FIG. The flow rate shows the same change as the change in the second tank flow rate from t1 ′ to t2 ′ as shown in FIG.

  After Act 45, the controller 100 determines whether or not the end of the circulation operation has been instructed (Act 46). For example, when the user inputs the end of the operation through the operation panel of the ink jet recording apparatus including the ink supply device, it is determined that the end of the circulation operation is instructed (YES in Act 46), and the series of operations ends. It becomes.

  On the other hand, when the end of the circulation operation is not instructed (NO in Act 46), the operation from Act 30 is repeated. In FIG. 7, after such a repetition, the time during which a signal indicating that the liquid level height of the third tank 3 has reached the lower limit 31 b is first output from the liquid level sensor 31 as t3 ′. The time when a signal indicating that the liquid level height of the second tank 2 has reached the lower limit 21b is output from the liquid level sensor 21 as t4 ′.

  Changes in the circulation flow rate and the circulation flow rate when the above-described circulation operation is executed will be described. It is assumed that the time variation of the pressure in each tank 2 and 3 with respect to the target value of the motor rotation speed of each pump 8 and 9 has the same linearity.

  As is apparent from FIGS. 7, 8A and 8B, the third tank flow rate starts to increase from zero at the time t1a ′ and the second tank flow rate starts to decrease from the flow rate A at the time t1b ′. As the 3 tank flow rate reaches the flow rate A, the second tank flow rate reaches zero. That is, since the decrease in the second tank flow rate is compensated by the increase in the third tank flow rate, the circulation flow rate becomes constant at the flow rate A as shown in FIGS. Also in the subsequent operation, when the positive / negative pressure in each of the tanks 2 and 3 is switched, the decrease in one of the second tank flow and the third tank flow is compensated by the increase in the other, so the circulation flow Becomes constant at the flow rate A.

  As is clear from FIGS. 7 and 8D, the reflux flow rate temporarily decreases at the time t1 '. However, in the present embodiment, when the second tank flow rate or the third tank flow rate is reduced, the flow rate is temporarily reduced to a flow rate -B lower than the flow rate -A. To rise. This increase compensates for the decrease in the recirculation flow rate, and the total circulation flow rate and the total recirculation flow rate coincide with each other. In other words, the value of the flow rate -B and the time t1d 'are determined so that the total amount of the circulating flow rate and the circulating flow rate coincide with each other.

  In particular, in the present embodiment, the amount of ink 201 flowing into the second tank 2 in one cycle of the circulation operation (area S1 in FIG. 7A) and the amount of ink 201 flowing out from the second tank 2 ( And the area of the region S2 in FIG. Similarly, the amount of ink 201 flowing in and out of the third tank 3 is also matched.

  As described above, the ink supply device according to the present embodiment circulates the ink while keeping the flow rate of the ink 201 flowing through the inkjet head 200 constant. With such a configuration, the amount of ink 201 supplied to the ink jet head 200 is stabilized, so that good image formation by the ink jet head 200 is possible.

  If the compression and suction by the first pump 8 and the second pump 9 are switched at the same timing, a time zone in which the circulation flow rate temporarily decreases as shown in FIG. For this reason, the amount of ink 201 supplied to the inkjet head 200 becomes unstable, and the image quality of an image formed by the inkjet head 200 may be deteriorated.

  Further, the first pump 8 and the second pump 9 circulate the ink 201 by adjusting the pressure of the second tank 2 and the third tank 3 without directly pressurizing the ink 201, so that the ink 201 is altered. Nor.

  Moreover, since the total amount of the circulation flow rate and the total amount of the recirculation flow rate coincide with each other in one cycle of the circulation operation described above, the circulation operation can be continuously performed for a long time without stopping.

[Modification]
The configuration disclosed in the above embodiment can be modified as appropriate.
For example, in the above-described embodiment, the backflow prevention mechanisms 64, 65, 74, and 75 are arranged after the branch pipes 60 and 70 are branched. However, the flow paths of the branch pipes 60 and 70 can be selectively switched. The branch pipes 60 and 70 may serve as a backflow prevention mechanism. That is, the branch pipes 60 and 70 have a mechanism for selectively allowing a flow in one direction and blocking a flow in the other direction, and interlocking with the pumps 8 and 9 to serve as a backflow prevention mechanism. The backflow prevention mechanisms 64, 65, 74, and 75 can be omitted.

  In the above embodiment, the liquid level sensor 11, 21, 31 is used to control the timing of the switching operation. However, each tank 1, 1 is replaced with the liquid level sensor 11, 21, 31. A weight sensor that detects the weight of the ink 201 in the second and third inks may be used. In this case, an upper limit and a lower limit of the weight detected by the weight sensor are set, and when the weight of the ink 201 in each of the tanks 1, 2, 3 reaches the upper limit or the lower limit, each pump 8, 9 or each valve 10. , 20, 30 and the gate valve 41 may be variously controlled.

  Although several embodiments of the present invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... 1st tank, 2 ... 2nd tank, 3 ... 3rd tank, 4 ... Ink tank, 5 ... 1st flow path, 6 ... 2nd flow path, 7 ... 3rd flow path, 8 ... 1st pump ( (First pressure adjusting mechanism), 9 ... second pump (second pressure adjusting mechanism), 10, 20, 30 ... valve, 11, 21, 31 ... liquid level sensor, 40 ... supply pipe, 41 ... gate valve, 60, 70 ... Branch pipe, 64, 65, 74, 75 ... Backflow prevention mechanism, 76 ... Filter, 100 ... Controller, 101-104 ... Valve drive circuit, 105, 106 ... Speed control circuit, 200 ... Inkjet head, 201 ... ink

Claims (3)

A first tank provided upstream of the ink jet head with respect to the ink flow in the flow path including the ink jet head for discharging ink to the recording medium;
A second tank and a third tank provided downstream of the inkjet head with respect to the ink flow;
A first flow path connecting the first tank and the inkjet head;
A second flow path connecting the inkjet head, the second tank, and the third tank;
A third flow path connecting the second tank and the third tank to the first tank;
A first pressure adjusting mechanism for adjusting the pressure of the second tank;
A second pressure adjusting mechanism for adjusting the pressure of the third tank;
An operation of controlling the first pressure adjusting mechanism and the second pressure adjusting mechanism to alternately raise and lower the pressures of the second tank and the third tank with respect to a reference pressure while keeping the ink flow rate of the inkjet head constant. A controller that repeatedly executes and circulates ink between the tanks;
An ink supply device comprising: The controller is
The first pressure adjusting mechanism and the second pressure adjusting mechanism are controlled, the pressure of one of the second tank and the third tank is lowered below a reference pressure, and the pressure of the other tank is set to the reference The operation of supplying the ink in the tank whose pressure has been increased to the third flow path while supplying the ink in the tank whose pressure has been increased to the third flow path by increasing the pressure above the pressure. , While switching between the tank that raises the reference pressure and the tank that lowers it,
2. The ink supply according to claim 1, wherein, at the time of the switching, the timing at which the pressure of the tank whose pressure has been reduced starts to rise is delayed by a certain time from the timing at which the pressure of the tank whose pressure has increased has fallen. apparatus.   The ink supply apparatus according to claim 2, wherein the predetermined time is a time from when the pressure of the tank that has increased the pressure starts to decrease until the reference pressure is reached.

Images