JP2009101668A - Ink supply control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem in which foreign matter and high-viscosity ink can not be removed by reversing an ink flow in forward and backward directions because the ink supply mechanism of a general inkjet image forming apparatus has no circulation pump for circulating an ink flow forward and backward. <P>SOLUTION: In an ink supply control method, the foreign matter or the high-viscosity ink inside a recording head can be removed by circulating ink in forward and backward directions using pressurization and balance inside an upstream ink port and a downstream ink port, regardless of a type of ink circulation pump that is used in the ink circulation mechanism of an inkjet image forming apparatus. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink supply control method for an inkjet image forming apparatus that forms an image by ejecting ink.

  In general, as an inkjet image forming apparatus, there is known an image forming apparatus equipped with a recording head that drives an actuator such as a piezoelectric element or a heat generating element to eject ink onto a recording medium to form an image. A recording head that uses ink may clog the nozzles and prevent normal image formation if bubbles or foreign matter are mixed into the ink in the actuator, or if the viscosity of the ink increases in the actuator due to evaporation of moisture. appear.

  In order to prevent such a situation, it is necessary to remove foreign matter in the recording head. As a countermeasure, a method of providing a circulating ink supply path is known. If the pressure of the ink applied to the recording head is increased, the removal efficiency of foreign matter in the recording head can be improved. However, in this case, since a high pressure is applied also to the nozzles of the head from the inside of the head, a large amount of ink is discharged from the nozzles and becomes waste ink.

On the other hand, as a technique for efficiently removing the foreign matter in the recording head without increasing the amount of waste ink, for example, in Patent Document 1, a tube pump capable of forward and reverse rotation is used as a circulation pump to change the direction of ink circulation. A technique for reversing and removing foreign matter in the recording head has been proposed.
JP 2000-33714 A

  It is necessary to improve the removal efficiency of the foreign matter in the recording head described above when large foreign matter is generated in the recording head or the nozzle is seriously clogged. As one of the causes, it is conceivable that the viscosity of the ink in the recording head is increased by leaving it for a long period of time without carrying out maintenance involving large-scale bubbles entering from the nozzles and image formation and ink ejection. In order to avoid such a situation, it is possible to add a new component member and cope with it by a maintenance process. However, the apparatus is increased in size and cost.

  In addition, an ink circulation pump capable of reversing the ink circulation direction is provided in the ink flow path existing in the image forming apparatus, the maintenance sequence is changed, and the foreign matter caught in the recording head is removed by flowing ink in the reverse direction. Can be removed. However, since there are few types of circulation pumps, the design specifications are limited by the standards. Generally, in order to reduce the cost of the apparatus, the circulation pump used in the ink flow path should be judged from the advantages and costs during normal circulation. The recovery of the recording head that caused the abnormal clogging is not possible. It is undesirable to increase the demand for functions.

  Accordingly, the present invention focuses on the above problems, and performs ink circulation in the opposite direction to the foreign matter in the recording head regardless of the type of ink circulation pump used in the ink circulation mechanism of the inkjet image forming apparatus. It is an object of the present invention to provide an ink supply control method for removing water.

  In order to achieve the above object, the present invention provides a recording head having a plurality of nozzles for ejecting ink, a pump for supplying the ink to the recording head, and supplying the ink from the pump to the recording head. An ink supply channel, an ink discharge channel for supplying the ink from the recording head to the pump, a first sub-ink tank provided on the ink supply channel, and an ink discharge channel. A second sub-ink tank and a flow path resistance member provided on the ink supply flow path side between the first sub-ink tank and the recording head and serving as a flow path resistance of the supplied ink A first atmosphere release valve provided in the first sub ink tank, a second atmosphere release valve provided in the second sub ink tank, and the first atmosphere And a controller that controls the opening and closing of the second air release valve and the driving of the pump, and the flow path resistance of the ink when the pump is stopped sandwiches the pump. In the ink supply control method in the ink circulation path, the flow path between the first and second sub ink tanks sandwiching the recording head is lower than the flow path between the first and second sub tanks. The first air release valve is closed and the pump is driven with the second air release valve open, and after the pressure in the first sub ink tank reaches a predetermined pressure, the first Step 2 for closing the air release valve 2, Step 3 for stopping the driving of the pump, and the pressure in the first sub ink tank and the pressure in the second sub ink tank are in equilibrium. And Step 4 to detect whether, after reaching the equilibrium state, and the step 5 to open the first air release valve, to provide an ink supply control method having.

  Further, the recording head, the pump, the ink supply channel, the ink discharge channel, the first sub ink tank, the second sub ink tank, and the ink supply channel side. A flow path resistance member provided between the first sub ink tank and the recording head and capable of varying a flow path resistance of the supplied ink, the first atmosphere release valve, and the second And the controller, and the flow path resistance of the ink when the pump is stopped is greater than the flow path between the first and second sub-tanks sandwiching the pump. In the ink supply control method in the ink circulation path in which the flow path between the first and second sub ink tanks sandwiching the recording head is lower, the first atmosphere release valve is closed and the second atmosphere is closed. Open the release valve Step 1 of driving the pump with the flow path resistance of the flow path resistance member being increased, and closing the second atmosphere release valve after the pressure in the first sub ink tank reaches a predetermined pressure At the same time, the step 2 for reducing the flow resistance value of the flow path resistance member, the step 3 for stopping the driving of the pump, the pressure in the first sub ink tank, and the pressure in the second sub ink tank There is provided an ink supply control method comprising: a step 4 for detecting whether or not the pressure has reached an equilibrium state; and a step 5 for opening the first atmosphere release valve after the equilibrium state is reached.

  According to the present invention, there is provided an ink supply control method for removing foreign matter in a recording head by performing ink circulation in the opposite direction to the normal direction regardless of the type of ink circulation pump used in the ink circulation mechanism of the inkjet image forming apparatus. Can be provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a conceptual configuration example of an ink jet image forming apparatus for realizing the ink supply control method of the present invention. Here, the components of the ink supply mechanism necessary for understanding the ink supply control method are shown. For example, the medium supply mechanism and the medium discharge mechanism in the transport mechanism are not shown, but in general, It is assumed that at least the constituent parts included in the device having the widespread configuration are provided.

  The image forming apparatus 1 is roughly divided into a plurality of recording heads 10 each provided with an upstream ink port 10b and a downstream ink port 10c, and transport for transporting the recording medium 31 so as to face the nozzles 10a of the recording head 10. A mechanism 30 and an ink supply mechanism 2 that supplies ink to the recording head 10 are configured.

  These recording heads 10 are short recording heads having nozzle rows shorter than the width of the recording medium 31, and are arranged so as to be equal to or larger than the width of the recording medium. In these recording heads 10, a large number of nozzles 10 a are formed as nozzle rows arranged in a direction orthogonal to the conveyance direction of the recording medium 31.

  These recording heads 10 are short recording heads having nozzle rows shorter than the width of the recording medium 31, and are arranged so as to be equal to or larger than the width of the recording medium. As shown in FIG. 1, for example, using six short recording heads, when viewed from the conveyance direction, the end portions are alternately arranged so as to overlap each other and arranged so as to be orthogonal to the conveyance direction. . Each nozzle 10a is provided with an actuator formed of a piezoelectric element between the ink chamber. These actuators are driven by a drive unit (not shown), and ink is ejected from each nozzle 10a. The nozzle 10a discharges ink to the recording medium 31 at a facing position that is approximately 2 mm away.

  The ink supply mechanism 2 circulates the upstream sub tank (first sub ink tank) 15 that supplies ink from the upstream side, the flow path resistance member 17 that adjusts the pressure of ink supply, and the ink that is supplied to the recording head 10. A supply tube (ink supply flow path) 16 a, a collection tube 16 a that distributes ink collected from the recording head 10, a downstream sub tank (second sub ink tank) 11 that stores the collected ink, and an upstream from the downstream sub tank 11 A return tube (ink discharge flow path) 16c for circulating ink returning to the sub tank 15, a circulation pump 12 for supplying pressure for circulating ink connected to the return tube 16c, and a temperature regulator for adjusting the ink temperature. 13 and a filter 14 for removing foreign matter in the circulating ink.

  Among these, the upstream sub tank 15 is disposed above the nozzle 10 a of the recording head 10 in the gravity direction, and supplies ink through the supply tube 16 a and the flow path resistance member 17. The flow path resistance member 17 is provided on the path of the tube 16 a and adjusts the pressure of the ink supplied to the recording head 10. The downstream sub-tank 11 is disposed below the position of the nozzle 10a in the direction of gravity, and ink that has not been used for image formation by the recording head 10 is collected and stored via the collection tube 16a. The ink in the downstream sub tank 11 is sucked up by the circulation pump 12, adjusted in temperature by the temperature regulator 13, foreign matter in the ink is removed by the filter 14, and returned to the upstream sub tank 15.

  Further, an ink bottle 19 is provided above the upstream sub tank 15 via a tube 18. When the amount of ink stored in the ink circulation path decreases due to ink ejection, ink is replenished from the ink bottle 19 to the ink upstream sub tank 15. A valve 20b is provided on the path of the tube 18, and the valve 20b is closed except when the upstream sub tank 15 is replenished with ink from the ink bottle 19. The inside of the ink bottle 19 is maintained at atmospheric pressure by the atmospheric communication pipe 19 a provided in the ink bottle 19.

  The downstream sub-tank 11 is provided with a downstream atmospheric release valve (second atmospheric release valve) 11a for releasing the internal space to the atmosphere. At the time of image formation, the downstream air release valve 11a is open, and the internal space is at atmospheric pressure. The downstream sub-tank 11 can also be sealed by closing the downstream air release valve 11a.

  A liquid level adjuster 11b is provided at the end of the tube 16c on the downstream sub tank 11 side, and controls the amount of ink flowing from the downstream sub tank 11 toward the tube 16c. The downstream atmosphere release valve 11a is provided with a filter (not shown) to prevent foreign matters from entering the ink supply mechanism 2 through the downstream atmosphere release valve 11a.

  A circulation pump 12 that supplies pressure for circulating ink, a temperature regulator 13 that adjusts the ink temperature, and a filter 14 that removes foreign matter in the circulating ink are provided on the path of the tube 16c. ing.

  The circulation pump 12 has a feature that the flow path resistance when stopped is large. If the heights of the downstream sub-tank 11 and the upstream sub-tank 15 are not taken into consideration, the direction opposite to that when flowing from the downstream sub-tank 11 that is a normal ink flow path to the upstream sub-tank 15 via the circulation pump 12 when stopped. The flow path resistance is smaller when flowing from the downstream sub tank 11 to the upstream sub tank 15 via the recording head 10. As such a circulation pump 12, for example, a bellows pump using a one-way valve using a spring, a gear pump, or a tube pump that crushes a tube with a tooth (a protrusion provided on a pulley) and stops in a sealed state. Etc. can be used. The flow path resistance here refers to a state in which the flow of ink is difficult to flow, and the state in which the flow path resistance is high refers to a state in which pressure is applied to the ink in each tube, or the circulation pump 12 and the valve. Or the like, it means that the ink hardly passes through. Therefore, the ink flows from the higher flow path resistance to the lower flow resistance.

  Further, an upstream atmosphere release valve (second atmosphere release valve) 15 a is provided at the upper portion of the upstream sub tank 15. At the time of image formation, the upstream air release valve 15a is opened and the inside of the tank is kept at atmospheric pressure. Further, the upstream sub tank 15 is provided with a liquid level sensor 20a for detecting the liquid level height, and the liquid level in the tank is always appropriate in order to maintain an appropriate head value for ink ejection. It is kept at a certain height.

  A filter (not shown) provided in the upstream atmosphere release valve 15a prevents foreign matter from entering the ink supply mechanism 2 from the outside through the upstream atmosphere release valve 15a. The upstream atmosphere release valve 15a, the downstream atmosphere release valve 11a, and the circulation pump 12 are controlled by the controller 32 according to a circulation method described later.

Hereinafter, a procedure for recording an image on the recording medium 31 by the image forming apparatus 1 will be described.
First, the recording medium 31 is conveyed by the conveyance mechanism 30 at a predetermined conveyance speed so as to pass in front of the nozzle 10a. An encoder (not shown) or the like outputs the count number according to the transport speed. Based on this count number, an ejection signal synchronized with the conveyance speed is generated. Based on this ejection signal, the recording head 10 ejects ink, whereby an image is formed on the recording medium 31. Here, ink supply to the recording head 10 will be described.
The ink passes from the upstream sub tank 15 through the tube 16a and is supplied to the recording head 10 from the upstream ink port 10b. The ink that has not been ejected by the nozzle 10a exits from the downstream ink port 10c and flows through the tube 16b to the downstream sub tank 11. The ink in the downstream sub-tank 11 is sucked up by the circulation pump 12 and returns to the upstream sub-tank 15 through the tube 16c. A case where ink flows in such a normal circulation direction is referred to as “normal circulation”, and a case where ink flows in the reverse circulation direction is referred to as “reverse circulation”.

  While the ink flows through the tube 16 c, the temperature of the ink is adjusted by the temperature adjuster 13 to a temperature suitable for image formation, and impurities in the ink are filtered by the filter 14. The liquid level height of the downstream sub-tank 11 is always maintained at an appropriate height by the liquid level adjuster 11b so as to maintain an appropriate head value. As the liquid level adjuster 11b, for example, a floating member that narrows the outlet channel to the tube 16c when the liquid level decreases can be used. When the circulation pump 12 circulates ink at a constant pressure, when the liquid level in the downstream sub-tank 11 is lowered, the floating member that is the liquid level adjuster 11b is lowered, and the outlet flow path to the tube 16c is narrowed.

  This increases the flow path resistance when the circulation pump 12 sucks ink from the downstream sub tank 11. As a result, the amount of ink sucked from the downstream sub tank 11 per unit time decreases, and the ink level in the downstream sub tank 11 rises due to the ink flowing from the recording head 10 side.

  As described above, even if the liquid level in the downstream sub-tank 11 fluctuates temporarily, it returns to a certain height by the action of the liquid level adjuster 11b. As a result, when ink is ejected from the nozzle 10a, the ink in the upstream sub tank 15 is reduced and the liquid level is lowered. When the liquid level sensor 20a detects a drop in the liquid level in the upstream sub tank 15, the ink supply controller 20c opens the valve 20b. As a result, ink is supplied from the ink bottle 19 through the tube 18 to the upstream sub tank 15.

  Generally, in order to maintain high image formation quality, it is necessary that no foreign matter exists in the recording head 10. This is because the presence of foreign matter near the actuator in the recording head 10 prevents normal ink supply to the actuator and the nozzle 10a. Also, if bubbles exist near the actuator, the volume modulus of elasticity of the bubbles is extremely smaller than that of ink, so even if the pressure inside the actuator is increased, the pressure is absorbed by the bubbles, and normal ink ejection is difficult. become.

  In addition, when the ink is water-based, moisture may evaporate from the ink filled in the recording head 10 through the nozzle 10a. The viscosity of the water-based ink in which moisture has evaporated increases, which hinders the discharge operation and ink circulation. As described in the prior art, these foreign substances can be efficiently removed by using the circulation ink path or reversing the circulation direction.

  In this embodiment, the ink supply control mechanism proposed in the first embodiment is used for the ink supply mechanism 2 having a general configuration, and the ink circulation and reverse circulation are repeated, so that the inside of the recording head 10 can be efficiently performed. Remove foreign material.

  Hereinafter, the operation procedure, operation, and effect of the ink supply control method according to the present embodiment will be described with reference to FIGS. FIG. 2 conceptually shows an extracted circulation ink path in the ink supply mechanism 2 shown in FIG. 1 in order to explain the operation procedure of the ink supply control method. FIG. 3 is a flowchart for explaining the ink supply control method of the present embodiment, and FIG. 4 is a timing chart for explaining the procedure of the ink supply control.

When the ink is circulated in the reverse direction by the ink supply mechanism 2, the circulation pump 12 is driven in a state where the upstream atmosphere release valve 15a is closed and the downstream atmosphere release valve 11a is opened in the first process. By these operations, the ink is difficult to flow from the upstream sub tank 15 to the recording head 10 by the flow path resistance member 17, so that the ink is accumulated in the upstream sub tank 15, and as a result, the space in the upstream sub tank 15 is pressurized (FIG. 2 ( a) see)
In the second process, the downstream air release valve 11a is closed after a predetermined time T1 [second] has elapsed, and at the same time, the circulation pump 12 is stopped. At this time, the pressure from the upstream sub-tank 15 is not yet transmitted to the downstream sub-tank 11 by the flow path resistance member 17 or is not easily transmitted. Accordingly, the inside of the upstream sub tank 15 is in a pressurized state, and the inside of the downstream sub tank 11 is in an atmospheric pressure state.

  Therefore, as time passes, the ink passes from the upstream sub tank 15 through the flow path resistance member 17 and flows into the downstream sub tank 11 via the recording head 10 (see FIG. 2B). Further, by controlling the time T1 [seconds] until the circulation pump 12 is stopped, the circulation pressure in this case can be adjusted. That is, when the time T1 is [large], the circulating pressure is [large], and when T1 is [small], the circulating pressure is [small].

  Then, after the circulation pump 12 is stopped, when the preparation time T2 [second] for reverse circulation elapses, the pressure in the upstream sub tank 15, the pressure in the downstream sub tank 11, and the water head between the upstream sub tank 15 and the downstream sub tank 11. The pressure is balanced. The preparation time T2 [seconds] until reaching the equilibrium state is measured in advance.

  In the third process, after the circulation pump 12 is stopped, the upstream atmosphere release valve 15a is opened after the preparation time T2 [seconds] has elapsed.

  When the upstream atmospheric release valve 15a is opened, the equilibrium state is lost, the upstream sub tank 15 is in an atmospheric pressure state, and the downstream sub tank 11 is in a pressurized state. Further, at this time, due to the internal pressure of the downstream sub tank 11, the liquid level in the downstream sub tank 11 is larger than the water head difference to the liquid level in the upstream sub tank 15. For this reason, the ink flows backward from the downstream sub tank 11 to the upstream sub tank 15 via the recording head 10 (see FIG. 2C). At this time, the flow path resistance of the stopped circulation pump 12 is larger than that of the flow path resistance member 17, so that no ink flows from the downstream sub tank 11 to the upstream sub tank 15 via the circulation pump 12.

  In the present embodiment, since the downstream sub tank 11 is located below the nozzle 10a in the gravity direction, the ink pressure applied to the downstream ink port is kept at a negative pressure. Thereby, the circulation speed of the ink is increased, the time required to reach the equilibrium state in FIG. 2B is shortened, and the positive pressure applied to the nozzle 10b in the process is reduced. As a result, the amount of ink discharged from the nozzle 10b to the outside can be reduced in the process until the equilibrium state is reached.

  According to the present embodiment, by applying the ink supply control method according to the present embodiment to an ink supply mechanism having a general configuration that does not include an ink circulation pump that can reverse the ink circulation direction, the reverse circulation of ink is achieved. Can be implemented. Thus, the ink circulation and reverse circulation are repeated, and the foreign matter in the recording head 10 can be efficiently removed. By removing the foreign matter using the reverse circulation of the ink flow, the foreign matter is removed from the nozzle 10a, and normal ink ejection can be maintained and the image forming quality can be kept high.

  In addition, the flow path resistance member 17 is better as the flow path resistance is higher as long as it is lower than the flow path resistance of the circulation pump 12. As the flow path resistance member 17, for example, an ink flow path in the recording head 10 having a structure in which ink flows in an actuator constituted by a piezoelectric element can be considered. The ink flow path constituted by the actuator for ejecting ink is narrow, and the flow path resistance of this flow path is very large. Further, the flow path resistance value of the flow path resistance member 17 is preferably variable. As an example, a mechanism for increasing flow path resistance by interposing an electromagnetic valve or a tube 16a can be considered.

  Further, if the flow path resistance of the flow path resistance member 17 is variable, the circulation pump 12 is stopped, and at the same time, the flow path resistance of the flow path resistance member 17 is reduced, so that the inside of the upstream sub tank 15 described above can be reduced. The time until the pressure in the downstream sub tank 11 reaches the equilibrium state can be shortened. By reducing the time, the frequency of switching between normal forward circulation and reverse circulation is improved, so that the foreign matter removal efficiency in the recording head 10 is improved. Further, when charging the pressure to the upstream sub tank 11, the pressure charged to the upstream sub tank 11 can be further increased by setting the flow path resistance of the flow path resistance member 17 high. As a result, the pressure in the downstream sub-tank 15 after reaching the equilibrium state is also increased, and the ink flow can be reversely circulated by a stronger pressure.

  In the present embodiment, the circulation pump 12 preferably makes the ink flow speed variable. When the circulation pump 12 is driven in order to charge the upstream sub-tank 15, the circulation pump 12 is increased at a higher speed, preferably higher than the ink supply (circulation) amount at the time of image formation. Can drive the upstream sub-tank 15 to charge a higher pressure.

In the above-described operation for reverse ink circulation, it has been described that the timing at which the pressures of the upstream sub-tank 15 and the downstream sub-tank 11 reach the equilibrium state is measured in advance. However, the present invention is not limited to this, for example, the pressure in the upstream sub-tank 15 An upstream pressure sensor that can measure the pressure and a downstream pressure sensor that can measure the pressure in the downstream sub-tank 11, and whether or not an equilibrium state has been reached by directly measuring the pressure in each sub-tank by each pressure sensor Can be detected. That is, in the second process, after the upstream pressure sensor detects that the pressure in the upstream sub-tank 15 has reached a predetermined pressure, the downstream air release valve 11a may be closed and the circulation pump 12 may be stopped. Then, in the third process, if the pressure in the upstream sub-tank 15 and the pressure in the downstream sub-tank 11 are in equilibrium from the detection results of the upstream pressure sensor and the downstream pressure sensor, the upstream atmospheric release valve 15a is turned on. You may make it open. A modification of the first embodiment will be described.
In the first embodiment described above, an arrangement in which the upstream tank 15 is located above the nozzle 10a is taken as an example. However, the present invention is not limited to this, and may be located below the downstream sub-tank 11 as shown in FIG. . The other constituent parts are the same as those in the first embodiment described above, and the same reference numerals are assigned to omit the description thereof.

  In this modification, ink circulation by normal normal circulation is performed with the upstream air release valve 15a closed. In this case, the space in the upstream sub tank 15 is pressurized to a positive pressure by the circulation pump 12. Ink is supplied to the upstream ink port 10b with this pressure. Here, when reverse circulation is performed, first, the downstream atmosphere release valve 11a is closed, and at the same time, the circulation pump 12 is stopped. Then, after a predetermined preparation time [T2] or more has elapsed, the upstream atmospheric release valve 15a is opened after the pressure in the downstream sub tank 11 and the pressure in the upstream sub tank 15 reach an equilibrium state. Due to this opening, the ink in the downstream sub tank 11 flows to the upstream sub tank 11 via the recording head 10.

  According to this modification, since the downstream sub-tank 11 is disposed above the upstream sub-tank 15, the water head difference acts as a pressure for reverse circulation. By this action, reverse circulation can be performed at a higher pressure than in the first embodiment.

Next, a second embodiment will be described.
6A to 6D are conceptual diagrams for explaining an ink supply control method according to the second embodiment. The components in this embodiment are the same as those in the first embodiment described above, and the ink supply control method is different. Therefore, in the description of the present embodiment, the same reference numerals are used to refer to the configuration shown in FIG. Here, FIG. 7 is a flowchart for explaining the ink supply control method of this embodiment, and FIG. 8 is a timing chart for explaining the ink supply control of this embodiment.

  The first embodiment described above is an example in which the circulation pump 12 is stopped simultaneously with the closing of the downstream atmosphere release valve 11a (see FIGS. 2B and 4). On the other hand, in this embodiment, the operation of the circulation pump 12 is continued even after the downstream atmosphere release valve 11a is closed. (See FIGS. 6B and 8).

  In the first embodiment, the ink is circulated by the water head difference between the upstream sub tank 15 and the downstream sub tank 11. On the other hand, in the ink supply control method according to this embodiment, the ink in the ink supply mechanism 2 is operated at a pressure higher than the circulation pressure of the first embodiment by further operating the circulation pump 12 to circulate the ink. Circulate. Thereby, the removal efficiency of the foreign matter in the recording head is improved.

  Further, when the image forming apparatus 1 is left unused for a long period of time and the thickened aqueous ink is clogged in the recording head 10, the ink cannot flow in the recording head 10 in a normal circulation. Ink does not fall into the downstream sub tank 11. In such a case, when ink is circulated by the ink supply control method of the present embodiment, the circulation pump 12 transfers the ink in the sealed downstream sub-tank 11 to the upstream sub-tank 15, but the alternative ink is transferred to the downstream sub-tank 11. Since it does not enter, the inside of the downstream sub tank 11 is depressurized and becomes negative pressure.

  As a result, the pressure difference between the upstream ink port 10b and the downstream ink port 10c increases, and the circulating pressure that pushes the thickened ink in the recording head 10 increases. Only by increasing the circulation pressure, foreign matter in the recording head 10 can be removed with higher efficiency than the normal ink circulation operation.

  Furthermore, after that, if the circulation pump 12 is stopped, the upstream sub-tank 11 reaches a positive pressure, the upstream air release valve 15a is opened, and the ink is reversely circulated, the normal flow of the ink due to the pressure higher than usual is increased. Circulation and reverse circulation can be used together. According to this operation, the upstream side and the downstream side are alternately shaken in the recording head 10 to release the clogged ink and foreign matters, and then they are washed away with a strong force. Therefore, when there are many foreign substances in the recording head 10 or when a large amount of ink with increased viscosity is clogged in the recording head 10, these foreign substances or high-viscosity ink can be separated from the place and efficiently. Can be removed.

  The image forming apparatus adapted to exclude foreign matter and high-viscosity ink using the ink supply control method of the present invention is not limited to a line recording system having a plurality of fixed image forming heads, for example, a single image formation that scans and moves An ink supply mechanism having a serial recording type recording head that forms an image by forming an image by scanning and moving the image forming head in the width direction of the recording medium can be easily applied. .

  In addition, the first embodiment, its modification example, and the second embodiment can be implemented in appropriate combination. These may also be applied to an ink supply mechanism having a serial recording type recording head.

The ink supply control method of the present invention includes the following gist.
(1) An ink supply control method of an ink supply mechanism for supplying the ink to the recording head mounted in an image forming apparatus including a recording head that forms an image by ejecting ink onto a recording medium,
The ink supply mechanism adjusts, from the upstream side, a first sub-tank having a first air release means that can be controlled to open and close, and a pressure of ink provided downstream of the first sub-tank and supplied to the recording head A flow path resistance member that circulates, a supply flow path that circulates ink supplied to the recording head, a recovery flow path that circulates ink recovered from the recording head, and an open / close that stores ink recovered from the recovery flow path A second subtank having a controllable second air release means; and a circulation pump configured to return ink from the second subtank to the first subtank through a return flow path. And
The flow path resistance of the recovery flow path is made higher than the flow path resistance of the supply flow path, and ink containing foreign matter and high-viscosity ink is poured from the second sub tank to the first sub tank via the recording head. An ink supply control method.

(2) The flow path resistance of the recovery flow path and the flow path resistance of the supply flow path are:
After the first atmosphere release means is closed and the second atmosphere release means is opened, the circulation pump is operated for an arbitrary time to increase the pressure in the first sub tank, and then the second The air release means is closed, and after the pressure in the first sub-tank and the pressure in the second sub-tank are balanced, the first air release means is opened to generate the air. The ink supply control method according to item (1).

(3) The flow path resistance of the recovery flow path and the flow path resistance of the supply flow path are:
After the first atmosphere release means is closed and the second atmosphere release means is opened, the circulation pump is operated for an arbitrary time to increase the pressure in the first sub tank, and then the second The circulation pump is stopped simultaneously with closing the atmospheric release means, and after the pressure in the first sub-tank and the pressure in the second sub-tank are balanced, the first atmospheric release means is opened. The ink supply control method according to item (2), wherein:

(4) The flow path resistance of the recovery flow path and the flow path resistance of the supply flow path are:
After the first atmosphere release means is closed and the second atmosphere release means is opened, the circulation pump is operated for an arbitrary time to increase the pressure in the first sub tank, and then the second After the preset time has elapsed, the circulation pump is stopped, and after the pressure in the first sub tank and the pressure in the second sub tank are balanced, the first The ink supply control method according to (2) above, wherein the ink supply control method is generated by opening the air release means.

(5) The flow path resistance member of the ink supply mechanism has a function capable of varying the flow path resistance,
The channel resistance of the recovery channel and the channel resistance of the supply channel are:
The first air release means is closed, the second air release means is opened, and the circulation pump is operated for an arbitrary period of time in a state where the flow resistance of the flow resistance member is increased. After the pressure in the sub-tank is increased, the second atmosphere release means is closed, and after the pressure in the first sub-tank and the pressure in the second sub-tank are balanced, the first atmosphere release means The ink supply control method according to the item (1), wherein the ink supply control method is generated by releasing the.

(6) The circulation pump of the ink supply mechanism has a function capable of changing a circulation speed,
The channel resistance of the recovery channel and the channel resistance of the supply channel are:
With the first atmosphere release means closed and the second atmosphere release means opened, the circulating pump is operated for an arbitrary time at a speed higher than that at the time of image formation, and the pressure in the first sub tank is The second atmosphere release means is closed, and after the pressure in the first sub tank and the pressure in the second sub tank are balanced, the first atmosphere release means is opened. The ink supply control method according to item (1), wherein the ink supply control method is generated.

(7) In the circulation path of the ink supply mechanism,
The ink supply control method according to any one of (1) to (6), wherein the second sub-tank is disposed above the first sub-tank.

(8) In the circulation path of the ink supply mechanism,
The ink supply control method according to any one of (1) to (6), wherein the second sub tank is provided below a nozzle of the recording head.

1 is a diagram illustrating a conceptual configuration example of an ink jet type image forming apparatus for carrying out an ink supply control method according to a first embodiment of the present invention. 2A to 2C are conceptual diagrams for explaining the ink supply control method according to the first embodiment. 4 is a flowchart for explaining an ink supply control method according to the first embodiment; 4 is a timing chart for explaining ink supply control according to the first embodiment; It is a figure which shows the modification in 1st Embodiment. 6A to 6D are conceptual diagrams for explaining an ink supply control method according to the second embodiment. It is a flowchart for demonstrating the ink supply control method of 2nd Embodiment. 10 is a timing chart for explaining ink supply control according to the second embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Ink supply mechanism, 10 ... Recording head, 10a ... Nozzle, 10b ... Upstream ink port, 10c ... Downstream ink port, 11 ... Downstream sub tank, 11a ... Downstream air release valve, 11b ... Liquid level adjustment 12 ... circulation pump, 13 ... temperature regulator, 14 ... filter, 15 ... upstream sub tank, 15a ... upstream air release valve, 16a, 16b, 16c, 18 ... tube, 17 ... flow path resistance, 19 ... ink bottle , 19a ... atmosphere communication pipe, 20a ... liquid level sensor, 20b ... valve, 20c ... ink supply controller, 30 ... transport mechanism, 31 ... recording medium, 32 ... controller.

Claims (10)

A recording head having a plurality of nozzles for discharging ink;
A pump for supplying the ink to the recording head;
An ink supply flow path for supplying the ink from the pump to the recording head;
An ink discharge channel for supplying the ink from the recording head to the pump;
A first sub-ink tank provided on the ink supply channel;
A second sub-ink tank provided on the ink discharge channel;
A flow path resistance member on the ink supply flow path side, provided between the first sub ink tank and the recording head, and serving as a flow path resistance of the supplied ink;
A first air release valve provided in the first sub-ink tank;
A second atmosphere release valve provided in the second sub ink tank;
A controller that controls opening and closing of the first atmosphere release valve and the second atmosphere release valve and driving of the pump;
Have
The flow path resistance of the ink when the pump is stopped is greater than the flow path between the first and second sub-tanks that sandwich the pump, and the first and second subs that sandwich the recording head. In the ink supply control method in the ink circulation path where the flow path between the ink tanks is lower,
Step 1 of driving the pump with the first atmosphere release valve closed and the second atmosphere release valve open;
Closing the second atmosphere release valve after the pressure in the first sub-ink tank reaches a predetermined pressure;
Step 3 for stopping the driving of the pump;
Detecting whether or not the pressure in the first sub ink tank and the pressure in the second sub ink tank are in an equilibrium state;
After reaching the equilibrium state, opening the first atmosphere release valve; and
An ink supply control method comprising:   The ink supply control method according to claim 1, wherein the control unit closes the second atmosphere release valve and simultaneously stops driving the pump.   The ink supply control method according to claim 1, wherein the control unit continues driving the pump even after the second atmosphere release valve is closed. A recording head having a plurality of nozzles for discharging ink;
A pump for supplying the ink to the recording head;
An ink supply flow path for supplying the ink from the pump to the recording head;
An ink discharge channel for supplying the ink from the recording head to the pump;
A first sub-ink tank provided on the ink supply channel;
A second sub-ink tank provided on the ink discharge channel;
A flow path resistance member on the ink supply flow path side, provided between the first sub ink tank and the recording head, and capable of varying a flow path resistance of the supplied ink;
A first air release valve provided in the first sub-ink tank;
A second atmosphere release valve provided in the second sub ink tank;
A controller that controls opening and closing of the first atmosphere release valve and the second atmosphere release valve, driving of the pump, and a flow path resistance value of the flow path resistance member;
Have
The flow path resistance of the ink when the pump is stopped is greater than the flow path between the first and second sub-tanks that sandwich the pump, and the first and second subs that sandwich the recording head. In the ink supply control method in the ink circulation path where the flow path between the ink tanks is lower,
Closing the first atmosphere release valve and opening the second atmosphere release valve to drive the pump in a state in which the flow path resistance of the flow path resistance member is increased; and
After the pressure in the first sub ink tank reaches a predetermined pressure, the step of closing the second atmosphere release valve and simultaneously reducing the flow resistance value of the flow path resistance member;
Step 3 for stopping the driving of the pump;
Detecting whether the pressure in the first sub-ink tank and the pressure in the second sub-ink tank are in an equilibrium state;
After reaching the equilibrium state, opening the first atmosphere release valve; and
An ink supply control method comprising: A recording head having a plurality of nozzles for discharging ink;
A pump for supplying the ink to the recording head and making the ink supply amount variable;
An ink supply flow path for supplying the ink from the pump to the recording head;
An ink discharge channel for supplying the ink from the recording head to the pump;
A first sub-ink tank provided on the ink supply channel;
A second sub-ink tank provided on the ink discharge channel;
A flow path resistance member on the ink supply flow path side, provided between the first sub ink tank and the recording head, and serving as a flow path resistance of the supplied ink;
A first air release valve provided in the first sub-ink tank;
A second atmosphere release valve provided in the second sub ink tank;
A controller for controlling opening and closing of the first atmosphere release valve and the second atmosphere release valve, and driving of the pump;
Have
The flow path resistance of the ink when the pump is stopped is greater than the flow path between the first and second sub-tanks that sandwich the pump, and the first and second subs that sandwich the recording head. In the ink supply control method in the ink circulation path where the flow path between the ink tanks is lower,
Step 1 of closing the first atmosphere release valve and opening the second atmosphere release valve to drive the pump in a state where the ink supply amount is higher than that during image formation;
Closing the second atmosphere release valve after the pressure in the first sub-ink tank reaches a predetermined pressure;
Step 3 for stopping the driving of the pump;
Detecting whether the pressure in the first sub-ink tank and the pressure in the second sub-ink tank are in an equilibrium state;
After reaching the equilibrium state, opening the first air release valve; and
An ink supply control method comprising: A recording head having a plurality of nozzles for discharging the ink;
A pump for supplying the ink to the recording head;
An ink supply flow path for supplying the ink from the pump to the recording head;
An ink discharge channel for supplying the ink from the recording head to the pump;
A first sub-ink tank provided on the ink supply channel;
A second sub-ink tank provided on the ink discharge channel;
A flow path resistance member on the ink supply flow path side, provided between the first sub ink tank and the recording head, and serving as a flow path resistance of the supplied ink;
A first air release valve provided in the first sub-ink tank;
A second atmosphere release valve provided in the second sub ink tank;
A controller that controls opening and closing of the first atmosphere release valve and the second atmosphere release valve and driving of the pump;
Have
The flow path resistance of the ink when the pump is stopped is greater than the flow path between the first and second sub tanks that sandwich the pump, and the first and second sub inks that sandwich the recording head. In the ink supply control method in the ink circulation path where the flow path between the tanks is lower,
Step 1 of driving the pump for a predetermined time T1 with the first atmosphere release valve closed and the second atmosphere release valve opened;
Step 2 of closing the second atmosphere release valve after a predetermined time T1 has elapsed;
Step 3 for stopping the driving of the pump;
Opening the first atmosphere release valve after the closing time of the second atmosphere release valve reaches a predetermined time T2, and
An ink supply control method comprising:   The ink supply control method according to claim 6, wherein the control unit closes the second atmosphere release valve and simultaneously stops driving the pump.   The ink supply control method according to claim 6, wherein the control unit continues driving the pump even after the second atmosphere release valve is closed. A recording head having a plurality of the nozzles for discharging the ink;
A pump for supplying the ink to the recording head;
An ink supply flow path for supplying the ink from the pump to the recording head;
An ink discharge channel for supplying the ink from the recording head to the pump;
A first sub-ink tank provided on the ink supply channel;
A second sub-ink tank provided on the ink discharge channel;
A flow path resistance member on the ink supply flow path side, provided between the first sub ink tank and the recording head, and capable of varying a flow path resistance of the supplied ink;
A first air release valve provided in the first sub-ink tank;
A second atmosphere release valve provided in the second sub ink tank;
A controller that controls opening and closing of the first atmosphere release valve and the second atmosphere release valve, driving of the pump, and a flow path resistance value of the flow path resistance member;
Have
The flow path resistance of the ink when the pump is stopped is greater than the flow path between the first and second sub-tanks that sandwich the pump, and the first and second subs that sandwich the recording head. In the ink supply control method in the ink circulation path where the flow path between the ink tanks is lower,
A step 1 of driving the pump for a predetermined time T1 in a state where the first atmosphere release valve is closed and the second atmosphere release valve is opened to increase the flow path resistance of the flow path resistance member;
Step 2 of closing the second atmosphere release valve after a predetermined time T1 and simultaneously reducing the flow resistance value of the flow path resistance member;
Step 3 for stopping the driving of the pump;
Opening the first atmosphere release valve after the closing time of the second atmosphere release valve reaches a predetermined time T2, and
An ink supply control method comprising: A recording head having a plurality of nozzles for discharging ink;
A pump for supplying the ink to the recording head and making the ink supply amount variable;
An ink supply flow path for supplying the ink from the pump to the recording head;
An ink discharge channel for supplying the ink from the recording head to the pump;
A first sub-ink tank provided on the ink supply channel;
A second sub-ink tank provided on the ink discharge channel;
A flow path resistance member on the ink supply flow path side, provided between the first sub ink tank and the recording head, and serving as a flow path resistance of the supplied ink;
A first air release valve provided in the first sub-ink tank;
A second atmosphere release valve provided in the second sub ink tank;
A controller for controlling opening and closing of the first atmosphere release valve and the second atmosphere release valve, and driving of the pump;
Have
The flow path resistance of the ink when the pump is stopped is greater than the flow path between the first and second sub-tanks that sandwich the pump, and the first and second subs that sandwich the recording head. In the ink supply control method in the ink circulation path where the flow path between the ink tanks is lower,
A step 1 of closing the first atmosphere release valve and opening the second atmosphere release valve to drive the pump for a predetermined time T1 in a state where the ink supply amount is higher than that during image formation;
Step 2 of closing the second atmosphere release valve after a predetermined time T1 and simultaneously reducing the flow resistance value of the flow path resistance member;
Step 3 for stopping the driving of the pump;
Opening the first atmosphere release valve after the closing time of the second atmosphere release valve reaches a predetermined time T2, and
An ink supply control method comprising:

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