JP4825647B2 - Inkjet recording device - Google Patents

Description

The present invention relates to an ink circulation type ink jet recording apparatus.

  For example, the following are known as inkjet recording apparatuses. The ink jet recording apparatus includes an ink jet head for ejecting ink onto a recording medium, an ink flow path for supplying ink to the ink jet head, a tank for supplying ink to the ink flow path, A pressure pump that circulates ink in the reverse direction and a filter provided in the middle of the ink flow path are provided.

  In this ink jet recording apparatus, when ejecting ink droplets, the pressure pump is driven in the forward rotation direction to supply ink to the ink jet head. At this time, dust is removed from the ink through a filter, thereby preventing nozzle clogging and the like from occurring in the inkjet head. On the other hand, if the dust in the ink is removed through the filter, the filter will be clogged. However, in this ink jet recording apparatus, the pressure pump is driven in reverse after a predetermined number of ejections to circulate the ink in the reverse direction. The discharge recovery operation is performed. As a result, the dust trapped in the filter is returned to the tank to prevent the filter from being clogged (see, for example, Patent Document 1).

  Other examples of the ink jet recording apparatus include the following. The ink jet recording apparatus includes a print head, an ink tank that stores ink to be supplied to the print head, an ink flow path that connects these, and an ink circulation mechanism that circulates ink in the ink flow path. . The ink circulation mechanism is an ink circulation pump that can rotate forward and backward.

  In this ink jet recording apparatus, ink is supplied from the ink tank to the print head by rotating the pump in the forward direction. Then, after the pump is rotated 20 times in the forward direction, the pump is rotated once in the reverse direction to change the ink flow velocity. As a result, the bubbles adhering to the inner wall in the ink flow path are shaken so that the bubbles are easily removed (see, for example, Patent Document 2).

Further, other examples of the ink jet recording apparatus include the following. An ink jet recording apparatus includes a full line type ink jet head having a width substantially equal to a recording medium, an ink tank storing ink, a liquid flow path connecting an inlet and an outlet of the ink jet head to the ink tank, and And a liquid circulation device for flowing ink from the inlet to the outlet. This ink jet recording apparatus can circulate ink in the head even when the ink jet head is in an ejection operation. As a result, the temperature rise of the inkjet head is prevented, and density unevenness is prevented from occurring in the printed image (see, for example, Patent Document 3).
JP-A-7-52398 JP 2000-33714 A JP 2006-175651 A

  However, in the ink jet recording apparatus described in Patent Document 1, no ink discharge operation can be performed during the discharge recovery operation, which may reduce the printing speed. In addition, the ink jet recording apparatus described in Patent Document 2 has a problem that the ink discharge amount becomes unstable and the print quality deteriorates because the pressure in the vicinity of the nozzles changes abruptly when the pump rotates backward. Furthermore, there has been a problem that no measures have been taken to prevent deterioration in print quality, such as stopping printing when the pump is rotated in reverse.

  Further, in the flow path inside the ink jet head, there is a place where the diameter of the flow path is narrower than other places of the ink flow path, and there is a possibility that dust is clogged in this place. In particular, as in the ink jet recording apparatus described in Patent Document 3, when ink is circulated only in one direction, there is a problem that dust is easily clogged at a portion where the flow path diameter is narrow. However, the inkjet recording apparatuses described in the above-mentioned Patent Documents 1, 2, and 3 have a problem that no measures are taken on this point.

  An object of the present invention is to provide an ink jet recording apparatus capable of eliminating clogging of ink chambers and flow paths in an ink jet head while preventing a decrease in printing speed.

In order to achieve the above object, an ink jet recording apparatus according to one aspect of the present invention includes a head main body, an ink chamber formed in the head main body, an inlet port connected to the ink chamber, an outlet port connected to the ink chamber, An ink jet head having a constricted portion provided in an ink chamber, a first tank storing ink therein, a second tank storing ink inside, and connecting the first tank and the ink jet head A first flow path, a second flow path connecting the inkjet head and the second tank, a third flow path connecting the second tank and the first tank, In the first direction that rotates in the order of the first flow path, the second flow path, and the third flow path, the ink circulation flow path is provided in the middle of the third flow path. Circulating the ink That a first pump, in the middle of the third flow path, a filter device which is positioned between the first tank and the first pump, with stores ink therein, the A main tank that supplies ink to the ink circulation flow path, a supply flow path that connects the main tank and the third flow path, and is provided in the middle of the supply flow path. A second pump for sending to the ink circulation flow path, a first valve provided in the middle of the first flow path, and a position between the first valve and the ink jet head. A recovery flow path connecting the flow path and the main tank, a second valve provided in the middle of the recovery flow path, the inkjet head, the first pump, the second pump, the first The second valve and the second valve Comprising control device and, wherein the controller is configured to open the first valve, the closed second valve, the ink circulation passage by driving the first pump, the filter A first discharge that circulates the ink in the first direction through the apparatus, and discharges the ink from the inkjet head in this circulation state; and the first pump is stopped, and the first valve And the second valve is opened, and the second pump is driven to drive the second pump in a second direction opposite to the first direction in the ink circulation channel and not through the filter device. Then, the ink is circulated and the second ejection for ejecting the ink from the inkjet head is driven in this circulation state.

  According to the present invention, it is possible to eliminate clogging of a flow path in an inkjet head while preventing a decrease in printing speed. In addition, printing can be performed while stably maintaining the pressure in the vicinity of the discharge nozzle of the ink chamber of the ink jet head.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The ink jet recording apparatus according to this embodiment is a so-called ink circulation type ink jet recording apparatus. As shown in FIGS. 1 and 2, the ink jet recording apparatus 11 includes an ink jet head 12, a first tank 13, a second tank 14, an ink circulation channel 15, a first pump 16, a main tank 17, a supply flow. A passage 18, a second pump 19, a first valve 20, a recovery passage 21, a second valve 22, a first filter device 23, a second filter device 24, and a control device 25 are provided.

As shown in FIG. 2, the inkjet head 12 is formed so as to correspond to the head body 31, the ink chamber 32 formed inside the head body 31, the nozzle plate 34 having a plurality of nozzles 33, and the nozzles 33. And an actuator 35 of the discharge pressure generating means (only one nozzle 33 is shown in FIG. 2). In addition, the inkjet head 12 has an inlet 51 a that is continuous with the ink chamber 32 and an outlet 52 a that is continuous with the ink chamber 32. The actuator 35 is composed of a piezoelectric element such as piezo (PZT), for example. The ink chamber 32 has a narrowed portion 36 where the actuator 35 is provided. The narrowed portion 36 has a smaller channel cross-sectional area than other portions of the ink chamber 32. However, the inkjet head 12 is not limited to the piezoelectric element actuator 35 as an ejection energy generating element, and, for example, generates pressure using thermal energy such as a heater to eject ink droplets. There may be.

  The main tank 17 is an ink tank that is open to the atmosphere. Ink 37 is stored in the main tank 17. The main tank 17 can supply the ink 37 stored therein to the ink circulation channel 15. The main tank 17 has a larger capacity than the first tank 13 and the second tank 14. The main tank 17 has a third liquid level sensor 43. The third liquid level sensor 43 can detect the height of the liquid level of the ink 37 stored in the main tank 17. As shown in FIG. 3, the main tank 17 is placed on the upper side of the fixed base 44.

  The first tank 13 is a so-called sub tank, and stores ink 37 therein. The first tank 13 has a first liquid level sensor 41. The first liquid level sensor 41 can detect the height of the liquid level of the ink 37 stored in the first tank 13. As shown in FIG. 3, the first tank 13 is placed on the upper side of the fixed base 45. The first liquid level sensor 41 monitors the liquid level of the ink 37 in the first tank 13 so that the ink 37 stored in the first tank 13 is equal to or greater than a certain amount of liquid.

The second tank 14 is a so-called sub tank and stores ink 37 therein. Similarly, the second tank 14 has a second liquid level sensor 42. The second liquid level sensor 42 can detect the height of the liquid level of the ink 37 stored in the second tank 14. As shown in FIG. 3, the second tank 14 is placed on the upper side of an adjustment mechanism 61 described later. The second liquid level sensor 42 monitors the liquid level of the ink 37 in the second tank 14 so that the ink 37 stored in the second tank 14 becomes equal to or greater than a certain amount of liquid.

  The ink circulation channel 15 includes a first channel 51 that connects the first tank 13 and the inkjet head 12, a second channel 52 that connects the inkjet head 12 and the second tank 14, And a third flow path 53 that connects the second tank 14 and the first tank 13. In other words, the inkjet head 12, the first tank 13, and the second tank 14 are disposed independently in the middle of the looped ink circulation flow path 15. The supply flow path 18 connects the main tank 17 and the third flow path 53. The recovery flow path 21 connects the first flow path 51 and the main tank 17 at a position between the first valve 20 and the inkjet head 12.

  The first pump 16 is provided in the middle of the third flow path 53. As shown in FIG. 1, the first pump 16 has a first direction D <b> 1 in the ink circulation channel 15, that is, a first channel 51, a second channel 52, and a third channel 53. Ink 37 can be circulated in the direction of rotation in this order.

  The second pump 19 is provided in the middle of the supply flow path 18. The second pump 19 can send the ink 37 from the main tank 17 into the ink circulation channel 15 and supply the ink 37 into the ink circulation channel 15. Further, as will be described later, when performing the second discharge, the second pump 19 causes the second direction D2 opposite to the first direction D1, that is, the supply flow path 18 and the second flow path. The ink 37 can be circulated in the direction of rotating in the order of the flow path 52, the first flow path 51, and the recovery flow path 21.

  The first valve 20 and the second valve 22 are each constituted by an electromagnetic valve. The first valve 20 is provided in the middle of the first flow path 51. The second valve 22 is provided in the middle of the recovery channel 21. The first valve 20 and the second valve 22 can open or close the flow path under the control of the control device 25. In the present embodiment, the first valve 20 and the second valve 22 are installed, but a three-way flow path switching valve is provided at the connection portion 46 between the first flow path 51 and the recovery flow path 21. The circulation path of the ink 37 may be switched when switching between first discharge and second discharge, which will be described later.

The supply channel 18 connects the third channel 53 of the ink circulation channel 15 and the main tank 17. The recovery channel 21 connects the first channel 51 of the ink circulation channel 15 and the main tank 17. The recovery channel 21 is connected to the first channel 51 at a position between the first valve 20 and the inkjet head 12.

  The maintenance device 56 includes, for example, a cap member 56A that covers the nozzle plate 34, a suction pump 56B that sucks the nozzle 33 through the cap member 56A, and a wipe mechanism (not shown) that wipes the surface of the nozzle plate 34, that is, the nozzle surface 38. ,have. For example, the maintenance device 56 performs maintenance (maintenance) such as suction of the nozzle 33 on the inkjet head 12 to prevent nozzle clogging and the like, and to restore the function of the inkjet head 12. Further, the wiping mechanism cleans the nozzle surface 38 at intervals of about 10 minutes, for example.

  As shown in FIGS. 3 and 5, the adjustment mechanism 61 supports the second tank 14. The adjustment mechanism 61 includes, for example, a “U” -shaped fixing piece 62, a “U” -shaped elevating piece 63, a screw mechanism 64 that raises and lowers the elevating piece 63, and the screw mechanism 64 in the forward direction or the reverse direction. And a motor unit 65 to be rotated. The motor unit 65 can raise the installation position of the second tank 14 or lower the installation position of the second tank 14 by rotating the screw mechanism 64.

  The first filter device 23 is provided in the middle of the third flow path 53 at a position between the first tank 13 and the first pump 16. The first filter device 23 includes a mesh-shaped filter main body, a housing surrounding the filter main body, and the like. The second filter device 24 is provided in the middle of the recovery channel 21. The second filter device 24 includes a mesh-shaped filter body, a housing surrounding the filter body, and the like. The first and second filter devices 23 and 24 can remove dust contained in the ink 37.

  The control device 25 is configured by a computer, for example. The control device 25 includes, for example, a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and various drivers. The control device 25 can control the ejection of the ink 37 from the nozzle 33 by driving the actuator 35 of the inkjet head 12. Further, the control device 25 can control the operation and stop of the first pump 16 and the second pump 19. The control device 25 can switch between opening and closing of the first valve 20. The control device 25 can switch between opening and closing of the second valve 22. The control device 25 can drive the motor unit 65 of the adjustment mechanism 61 to control the rising and lowering of the installation position of the second tank 14.

  Here, the head management and its principle in the inkjet recording apparatus 11 will be described. As shown in FIG. 3, the liquid level height A of the inkjet head 12 is higher than the liquid level height B of the first tank 13 and the liquid level height C of the second tank 14. Therefore, the pressure in the ink chamber 32 of the inkjet head 12 is maintained at a negative pressure due to the water head difference between the liquid level height A and the liquid level height B. In this case, the pressure in the vicinity of the nozzle 33 is managed constant within a range of 0 to -3 kPa.

  Also in the liquid level height shown in FIG. 5, the pressure in the ink chamber 32 is maintained at a negative pressure as described above due to the water head difference between the liquid level height A and the liquid level height B.

  More specifically, in order to stabilize the ejection amount of ink droplets, the pressure in the ink chamber 32 in the vicinity of the nozzles 33 is managed to be constant in the following manner.

  Usually, in an ink jet recording apparatus, the discharge flow rate is sufficiently smaller than the circulation flow rate. For this reason, the value of the pressure loss in the ink supply system and the ink jet head greatly depends on the circulation flow rate rather than the discharge flow rate. Further, the dynamic pressure due to the circulating flow in the vicinity of the nozzle 33 is generally sufficiently small and can be ignored. In such an ink supply system of the inkjet head 12, the Reynolds number is usually sufficiently small, and the influence of turbulence can be ignored.

  In the present embodiment, it is assumed that the first tank 13 has energy P1 per unit volume with reference to the nozzle surface 38, and the second tank 14 has energy P2 per unit volume with reference to the nozzle surface 38. The energy per unit volume with reference to the nozzle surface 38 is the energy per unit volume of the Bernoulli equation of the ink in the tank when the nozzle surface 38 is used as a reference. When the dynamic pressure is negligible, the energy P per unit volume is the sum of the static pressure Pi of the ink in the tank and the potential pressure ρ · g · h of the tank, that is, P = Pi + ρ · g · h. Is done. Where ρ is the density of the ink, g is the gravitational acceleration, and h is the height of the pressure source viewed from the nozzle.

  The ink 37 in the second tank 14 is returned to the first tank 13 via the first pump 16 and the first filter device 23. The first pump 16 is operated so that the liquid level of the ink 37 in the first tank 13 is constant. The second pump 19 increases or decreases the amount of ink in the ink circulation channel 15 so that the liquid level of the ink 37 in the second tank 14 is constant. In this case, the liquid level of the ink 37 in the first tank 13 is detected by the first liquid level sensor 41, and the liquid level of the ink 37 in the second tank 14 is detected by the second liquid level sensor 42. ing.

  If P1> P2 in this state, a flow is generated from the first tank 13 toward the second tank 14 via the nozzle position. At this time, the energy P1 per unit volume of the ink 37 in the first tank 13 creates a flow of the ink 37 flowing toward the nozzle position, and the energy P2 per unit volume of the ink 37 in the second tank 14 is A flow of ink 37 flowing from the nozzle position to the second tank 14 is created.

  Here, when the flow resistance from the first tank 13 of the ink circulation flow path to the nozzle surface 38 of the inkjet head 12 is R1, and the flow resistance from the nozzle surface 38 to the second tank 14 is R2, the circulation is performed. The flow rate Q is Q = (P1−P2) / (R1 + R2). The increase / decrease in the circulation flow rate Q is adjusted by increasing / decreasing the energy P 1 per unit volume of the first tank 13.

The value of energy P2 per unit volume of the second tank 14 is
P2 = {(R1 + R2) / R1} * Pn- (R2 / R1) * P1 (1)
Set to be. Pn is a constant indicating an appropriate pressure at the nozzle surface 38.

At this time, the pressure at the location of the nozzle surface 38 is
P2 + Q × R2
= P2 + {(P1-P2) / (R1 + R2)} * R2
= {1-R2 / (R1 + R2)} * P2 + {R2 / (R1 + R2)} * P1
= {R1 / (R1 + R2)} × P2 + {R2 / (R1 + R2)} × P1
= Pn- {R1 / (R1 + R2) * (R2 / R1) * P1} + {R2 / (R1 + R2)} * P1
= Pn (2)
It becomes. That is, by controlling in this way, the pressure at the location of the nozzle surface 38 can always be kept at a constant value Pn. The pressure Pn is managed at about 0 to -3 kPa. This is because the ink 37 may leak from the nozzle surface 38 when the pressure Pn is 0 or more, and air may be drawn from the nozzle surface 38 on the negative pressure side of −3 kPa.

Here, the energy P1 per unit volume is used to increase / decrease the circulation flow rate Q, and the energy P2 per unit volume is controlled to maintain the pressure at the location of the nozzle surface 38. It is also possible to maintain the pressure at the location of the nozzle face 38 by using the energy P2 per unit volume and controlling the energy P1 per unit volume.
In particular, when R1 = R2, the calculation formula of energy P2 per unit volume becomes simpler, and P2 = 2Pn-P1.

By the way, if R2 / R1 = r, the above equation (1) is
P2 = (1 + r) * Pn-r * P1 (3)
It becomes. That is, the control condition for the value of energy P2 per unit volume is not affected by the absolute values of R1 and R2, but is determined only by the ratio of R1 and R2.

  For example, when the viscosity of the ink 37 changes due to a difference in ambient temperature or when another type of ink 37 having a different viscosity is used, the absolute values of the channel resistances R1 and R2 change greatly. Unless the physical shape of the circulation channel 15 is changed, the ratio of R1 and R2 is kept substantially constant.

  For example, if the cross-sectional area of the flow path upstream of the nozzle and the flow path downstream of the nozzle can be considered to be the same, the ratio of the length of the upstream flow path to the downstream flow path is the ratio of R1 and R2, and this is expressed as r P2 can be determined from the above equation (3). As a result, the meniscus 33a is always formed in the opening of the nozzle 33 on the nozzle surface 38, and the pressure in the vicinity of the nozzle 33 in the ink chamber 32 can be kept constant.

  If the absolute values of the channel resistances R1 and R2 change, the circulation flow rate Q changes. However, in the ink jet head 12 of the type that prints while circulating the ink 37, the circulation flow is given in a direction that does not affect the ejection operation of the ink 37. Even if the circulation flow rate Q changes, almost no problem occurs. However, if the change is too large, problems such as insufficient capacity of the pump to be used and the size of the tank and reduction of the circulation effect occur. Therefore, in order to prevent the change in the circulation flow rate Q from becoming too large, The value of the pressure P1 of the first tank may be corrected according to the viscosity of 37.

The circulation flow rate Q is
Q = (P1-P2) / (R1 + R2) = (1 + r) (P1-Pn) / (R1 + R2) (4)
Therefore, in order to make Q constant, for example, if the viscosity of the ink 37 increases and (R1 + R2) increases, the energy P1 per unit volume is increased so that (P1−Pn) increases accordingly. Should be increased.

If the total flow resistance is R1 + R2 = R and the value of energy P1 per unit volume to be controlled is calculated backward,
P1 = Q.R / (1 + r) + Pn (5)
It becomes. Since the total flow path resistance R is proportional to the viscosity of the ink 37, the energy P1 per unit volume may be adjusted according to the viscosity of the ink 37 as shown in equation (5). This adjustment is not required to be so strict. Even if correction is not performed, the pressure in the vicinity of the nozzle opening on the nozzle surface 38 does not change if the method for controlling the energy P2 per unit volume is maintained.
In this way, the pressure in the vicinity of the nozzle 33 in the ink chamber 32 can always be constant regardless of the circulation flow rate of the ink 37 with a simple configuration.

  Based on this principle, an actual printing operation using the inkjet recording apparatus 11 of the present embodiment will be described. The ink jet recording apparatus 11 of the present embodiment includes a first discharge that discharges the ink 37 while circulating the ink 37 in the forward direction, that is, the first direction D1 in the ink circulation channel 15, and the ink circulation channel 15. By switching between the second ejection in which the ink 37 is ejected while the ink 37 is circulated in the reverse direction, that is, the second direction D2, the printing process can be performed by changing the circulation direction of the ink 37.

  As shown in FIG. 1, when the operation of the inkjet recording apparatus 11 is started, the control device 25 opens the first valve 20 and closes the second valve 22. The control device 25 drives the first pump 16 to send the ink 37 in the third flow path 53 to the first tank 13. At that time, the ink 37 is filtered by the first filter device 23 to remove dust contained therein. Further, as shown in FIG. 3, the control device 25 drives the adjustment mechanism 61 so that the liquid level height of the second tank 14 is C lower than the liquid level height B of the first tank 13. . The control device 25 also appropriately drives the second pump 19 to send the ink 37 from the main tank 17 to the ink circulation channel 15 and is stored in the first tank 13 and the second tank 14. The ink 37 is maintained at a predetermined liquid amount.

  When the pressure of the first tank 13 becomes higher than that of the second tank 14 by driving the first pump 16, the ink 37 flows toward the second tank 14, and the ink 37 flows in the ink circulation channel 15. Circulate in the first direction D1. In a state where the circulation has occurred, after a predetermined time has passed and the pressure near the nozzle 33 in the ink chamber 32 has stabilized, the control device 25 instructs the inkjet head 12 to eject ink droplets. Thus, the first discharge is executed. During the first discharge, the second valve 22 is closed, so that the recovery channel 21 and the second filter device 24 are separated from the circulation path of the ink 37. In the first discharge, the control device 25 monitors the liquid level of the ink 37 in the first tank 13 via the first liquid level sensor 41, and the first tank When the amount of ink 37 in the ink 13 is reduced, the first pump 16 and the second pump 19 are driven to supply the ink 37 from the main tank 17 to the first tank 13. Further, the control device 25 monitors the liquid level of the ink 37 in the second tank 14 via the second liquid level sensor 42, and the amount of the ink 37 in the second tank 14 is determined. When the amount is low, the second pump 19 is driven to supply ink 37 from the main tank 17 to the second tank 14.

  For example, after about 10 minutes have passed since the first ejection, the second ejection in which the circulation direction of the ink 37 is reversed is performed. When switching to the second ejection, the control device 25 performs maintenance. The apparatus 56 is instructed to maintain the inkjet head 12. Specifically, the cap member 56 </ b> A comes into contact with the inkjet head 12 facing the maintenance device 56. In this state, the control device 25 drives the suction pump 56B to suck the nozzle 33 opening and forcibly discharge the ink 37. Further, the wiping device cleans the nozzle surface 38 by wiping the surface of the nozzle plate 34. In the present embodiment, when the maintenance device 56 performs maintenance of the inkjet head 12, switching between the first ejection and the second ejection is performed.

  In the middle of this maintenance process, the control device 25 stops the driving of the first pump 16. Then, the first valve 20 is closed and the second valve 22 is opened. As shown in FIG. 5, the adjustment mechanism 61 is driven to raise the position of the second tank 14, and the liquid level height of the second tank 14 is equivalent to the liquid level height of the first tank 13 from C. B. Thereby, the liquid level height of the second tank 14 is made higher than the liquid level height of the main tank 17. By this operation, the pressure in the vicinity of the nozzle 33 of the inkjet head 12 can be kept constant in the second ejection. In this state, the second pump 19 is driven to send ink from the main tank 17 to the second tank 14.

  Thus, as shown in FIG. 4, when the pressure in the second tank 14 becomes higher than the pressure in the main tank 17, the direction from the second tank 14 to the main tank 17, that is, the supply flow path 18 and the second flow path. The ink 37 circulates in the second direction D2 that reaches the path 52, the first flow path 51, and the recovery flow path 21 in this order. The second direction D2 is a direction opposite to the first direction D1. The circulation of the ink 37 and the pressure of the ink 37 at the nozzle position are stable when the maintenance process is completed, for example. In this way, with the circulation of the ink 37 stabilized, the control device 25 ends the maintenance process and instructs the inkjet head 12 to eject ink droplets. During the second discharge, the first tank 13 and the first filter device 23 are disconnected from the circulation path of the ink 37 by closing the first valve 20 and stopping the driving of the first pump 16. It is.

  After about 10 minutes have passed since the second ejection, the inkjet head 12 is again maintained, and the second ejection is switched to the first ejection during the maintenance process. That is, the control device 25 drives the adjustment mechanism 61 to lower the installation position of the second tank 14, and again sets the liquid level height of the second tank 14 to C, so that the liquid in the second tank 14 The surface position is set lower than that of the first tank 13. By this operation, the pressure in the vicinity of the nozzle 33 of the ink chamber 32 of the inkjet head 12 can be kept constant in the first ejection. Then, the first valve 20 is opened and the second valve 22 is closed, and the first pump 16 is driven to perform the first discharge. In this way, in the ink jet recording apparatus 11, the first discharge and the second discharge are alternately switched every predetermined time, and a printing process is realized in which the circulation direction of the ink 37 in the ink circulation channel 15 is changed. .

  The above is the embodiment of the inkjet recording apparatus 11. According to the present embodiment, the control device 25 drives the inkjet head 12 to perform the first ejection in a state in which the ink 37 is circulated in the first direction D1, and is opposite to the first direction D1. In the state where the ink 37 is circulated in the second direction D2 on the side, the second ejection for driving the inkjet head 12 is performed.

  According to this configuration, two types of ink can be ejected with different circulation directions of the ink 37, and the ink 37 is circulated in the second direction D2 opposite to the first direction D1. The printing process can be performed. For this reason, even when the ink 37 is circulated in the reverse direction, the ejection of the ink 37 is not delayed, and the printing process can be advanced promptly.

  In this case, the control device 25 switches between the first discharge and the second discharge alternately. According to this configuration, since the circulation direction of the ink 37 in the inkjet head 12 is reversed between the first ejection and the second ejection, for example, in the inkjet head 12 during the first ejection. Even when dust is caught in the constricted portion 36, the ink 37 is allowed to flow in the reverse direction during the second ejection, so that the dust caught in the constricted portion 36 can be removed.

  In this case, the inkjet head 12 has an ink chamber 32 formed in the head body 31 and a narrowed portion 36 provided in the ink chamber 32. According to this configuration, since the flow path cross-sectional area of the ink chamber 32 becomes small in the narrowed portion 36, the flow velocity of the ink 37 is increased at this location. This prevents a situation where dust is clogged in the vicinity of the nozzle 33 in the ink chamber 32. Further, when the ink 37 is circulated in the reverse direction to remove dust, the dust removal efficiency can be improved.

  The control device 25 is configured to switch between the first discharge and the second discharge when the maintenance device 56 performs maintenance of the inkjet head 12. Usually, when the circulation direction of the ink 37 is changed, the pressure temporarily becomes unstable in the vicinity of the nozzle 33 in the ink chamber 32. For this reason, when switching between the first discharge and the second discharge, it is preferable to shift to the next discharge after a predetermined time interval and the pressure has stabilized. On the other hand, the inkjet head 12 requires regular maintenance during use. According to this configuration, since the first discharge and the second discharge are switched when the maintenance device 56 performs the maintenance of the inkjet head 12, there is a time between the first discharge and the second discharge. Can be set at regular intervals. Therefore, in a state where the pressure is stable, the second discharge or the first discharge can be started, and the discharge liquid amount of the ink 37 can be made uniform with high accuracy, thereby improving the print quality. Further, the time for maintenance of the inkjet head 12 can be effectively utilized.

  The control device 25 drives the adjusting mechanism 61 during the first discharge so that the liquid level position of the second tank 14 is lower than the liquid level position of the first tank 13 and the second discharge. At this time, the adjusting mechanism 61 is driven to make the liquid level position of the second tank 14 higher than the liquid level position of the main tank 17. According to this configuration, the position head of the first tank 13 can be made larger than the position head of the second tank 14 at the time of the first ejection, and the ink 37 in the ink circulation channel 15. Can be easily circulated in the first direction D1. At that time, the pressure in the vicinity of the nozzle 33 of the inkjet head 12 can be kept constant. On the other hand, at the time of the second ejection, the position head of the second tank 14 can be made larger than the position head of the main tank 17, and the ink can be easily moved in the second direction in the ink circulation channel 15. It can be circulated to D2. At that time, the pressure in the vicinity of the nozzle 33 of the ink chamber 32 of the inkjet head 12 can be maintained constant. If the pressure becomes constant, the discharge liquid amount of the ink 37 becomes uniform, and the print quality can be improved.

  In this case, the first filter device 23 is provided in the middle of the third flow path 53 at a position between the first tank 13 and the first pump 16. According to this configuration, when the first discharge is performed, the ink 37 flowing from the first pump 16 to the first tank 13 can be filtered to remove dust in the ink 37. Further, when the second discharge is performed, the portion between the first tank 13 and the first pump 16 that has stopped driving is disconnected from the circulation path of the ink 37, and therefore the second direction D2 (reverse direction). Even when the ink 37 is circulated, it is possible to prevent dust from flowing into the ink 37 from the first filter device 23.

  The present invention is not limited to the embodiment described above. Of course, various modifications can be made without departing from the scope of the invention. That is, in this embodiment, the main tank 17 is used to supply the ink 37 to the ink circulation flow path 15, but the main tank 17 is not provided, and the first tank 13 and the second tank 14 are provided. It is also possible to perform printing by switching between the first ejection that circulates in the first direction D1 and the second ejection that circulates in the second direction D2. In this case, it is preferable that the first tank 13 and the second tank 14 have sufficient capacity.

FIG. 2 is a schematic diagram illustrating an overall configuration of an ink jet recording apparatus and a case where ink is circulated in a first direction. FIG. 3 is a cross-sectional view illustrating a structure around a nozzle of the inkjet head according to the embodiment. The schematic diagram which shows the liquid level height of an inkjet head and each tank in the inkjet recording device shown in FIG. FIG. 2 is a schematic diagram when ink is circulated in a second direction in the ink jet recording apparatus shown in FIG. 1. The schematic diagram which shows the liquid level height of an inkjet head and each tank in the inkjet recording device shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Inkjet recording device, 12 ... Inkjet head, 13 ... 1st tank, 14 ... 2nd tank, 15 ... Ink circulation flow path, 16 ... 1st pump, 17 ... Main tank, 18 ... Supply flow path, DESCRIPTION OF SYMBOLS 19 ... 2nd pump, 20 ... 1st valve, 21 ... Recovery flow path, 22 ... 2nd valve, 23 ... 1st filter apparatus, 24 ... 2nd filter apparatus, 25 ... Control apparatus, 37 ... Ink, 51 ... first flow path, 52 ... second flow path, 53 ... third flow path, 56 ... maintenance device, 61 ... adjustment mechanism, D1 ... first direction, D2 ... second direction

Claims (4)

An ink jet head having a head main body, an ink chamber formed in the head main body, an inlet port connected to the ink chamber, an outlet port connected to the ink chamber, and a narrowed portion provided in the ink chamber ;
A first tank storing ink therein;
A second tank storing ink therein;
A first flow path connecting the first tank and the inkjet head; a second flow path connecting the inkjet head and the second tank; the second tank; An ink circulation flow path having a third flow path connecting the tank;
The first flow path is provided in the middle of the third flow path and circulates the ink in a first direction that rotates in the order of the first flow path, the second flow path, and the third flow path. A pump,
A filter device provided at a position between the first tank and the first pump in the middle of the third flow path;
A main tank for storing ink inside and supplying ink to the ink circulation channel;
A supply flow path connecting the main tank and the third flow path;
A second pump that is provided in the middle of the supply flow path and sends ink in the main tank to the ink circulation flow path;
A first valve provided in the middle of the first flow path;
A recovery flow path connecting the first flow path and the main tank at a position between the first valve and the inkjet head;
A second valve provided in the middle of the recovery flow path;
A controller for driving the inkjet head, the first pump, the second pump, the first valve, and the second valve;
Comprising
The control device opens the first valve, closes the second valve, drives the first pump, and circulates the filter device in the ink circulation channel. A first discharge that circulates the ink in a direction and discharges the ink from the inkjet head in this circulation state;
The first pump is stopped, the first valve is closed, the second valve is opened, and the second pump is driven to define the first direction in the ink circulation channel. An ink jet characterized in that the ink is circulated in a second direction that does not flow through the filter device on the opposite side, and the second ejection for ejecting the ink from the inkjet head in this circulation state is driven. Recording device.   2. The ink jet recording apparatus according to claim 1, wherein the control device alternately switches between the first ejection and the second ejection. 3. A maintenance device for maintaining the inkjet head;
The ink jet recording apparatus according to claim 2, wherein the control device switches between the first discharge and the second discharge when the maintenance device performs maintenance of the ink jet head. An adjustment mechanism for adjusting the installation height of the second tank;
The control mechanism drives the adjustment mechanism during the first discharge to make the liquid level height of the second tank lower than the liquid level height of the first tank, and 2, the adjustment mechanism is driven so that the liquid level height of the second tank is higher than the liquid level height of the main tank. 4. The ink jet recording apparatus according to claim 2 , wherein the pressure is kept constant.

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