JP2019031098A - Ink supply device and inkjet device - Google Patents

Abstract

To form images on a recording medium with high accuracy.SOLUTION: An ink supply device according to an embodiment includes: a first ink tank in which an ink to be supplied to an inkjet head is stored; a pump for circulating the ink between the inkjet head and the first ink tank; and a first buffer tank which is disposed between the inkjet head and the first ink tank and stores the ink.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to an ink supply device and an ink jet device.

  In an ink jet printer that performs printing by spraying liquid ink onto a recording medium such as paper, the ink in the nozzles provided in the ink jet head dries when the standby time during which printing is not performed is prolonged. When the ink in the nozzles is dried, the viscosity of the ink is increased or the ink is solidified to cause clogging of the nozzles.

  Therefore, various techniques for preventing the ink from drying in the inkjet head have been proposed. In the conventional apparatus, a circulation system for circulating ink between the ink jet head and the ink tank is formed. For this reason, ink does not stay for a long time inside the ink jet head, and drying of the ink in the ink jet head can be prevented.

  For this type of circulation system, there is a technique for maintaining the pressure inside the inkjet head constant.

  However, when the amount of ink ejected from the ink jet head increases or when an ink jet head having a relatively large amount of ejection per time is used, the pressure inside the ink jet head may drop sharply. In such a case, the pressure inside the inkjet head fluctuates, or it takes time to recover after the pressure drops, so it is considered that printing loss may occur in the image formed on the recording medium. It is done.

JP 2007-313848 A

  An object of the present invention is to accurately form an image on a recording medium.

  In order to solve the above problems, an ink supply apparatus according to the present embodiment includes a first ink tank that stores ink to be supplied to an inkjet head, and a pump that circulates ink between the inkjet head and the first ink tank. And a first buffer tank disposed between the inkjet head and the first ink tank and storing ink.

It is a block diagram of the ink jet device concerning this embodiment. It is sectional drawing of a tank unit. It is an expansion perspective view of a tank unit. It is a figure which shows the pressure change of the ink in an inkjet head. It is a figure which shows the pressure change of the ink in an inkjet head. It is a figure which shows the pressure change of the ink in an inkjet head.

  Hereinafter, the present embodiment will be described with reference to the drawings. FIG. 1 is a diagram schematically illustrating an inkjet apparatus 1 according to the present embodiment.

  As shown in FIG. 1, the inkjet apparatus 1 is a monochrome inkjet apparatus that includes an inkjet head 20 and an ink supply device 10 that supplies ink 70 to the inkjet head 20.

  The inkjet head 20 is a piezo inkjet head that ejects ink 70 using a piezo element. The inkjet head 20 has a plurality of nozzles and a flow path for circulating the ink 70 to each nozzle. Regarding the inkjet head 20, the structure and the manufacturing method are disclosed in detail in Japanese Unexamined Patent Application Publication No. 2009-202475.

  The ink supply device 10 includes an upstream tank 11 that is a first ink tank, a downstream tank 12 that is a second ink tank, an adjustment tank 13, a buffer tank 14 that is a first buffer tank, and a second buffer tank. 5, the two ink tanks of the buffer tank 15, the two pumps of the circulation pump P 1 and the pressure adjustment pump P 2, and the control system including the calculator 51, the control device 52, and the pump drive device 53.

  The upstream tank 11 and the downstream tank 12 are connected by a pipe line PL1. Further, the buffer tank 14 is connected to the upstream tank 11 via the pipe line PL2, and is connected to the inkjet head 20 via the pipe line PL3. The buffer tank 15 is connected to the downstream tank 12 via the pipe line PL5, and is connected to the inkjet head 20 via the pipe line PL4.

  The upstream tank 11 and the downstream tank 12 have the same size and shape, and the ink 70 supplied to the inkjet head 20 is stored. The upstream tank 11 and the downstream tank 12 are supported so that the height from the floor surface on which the ink supply device 10 is placed is equal. The pressures in the upstream tank 11 and the downstream tank 12 are controlled so as to be negative with respect to the outside air.

  The buffer tanks 14 and 15 are equal in size and shape, and have a smaller capacity than the upstream tank 11 and the downstream tank 12. For example, the capacity of the buffer tanks 14 and 15 is about 25 ml to 100 ml. The buffer tanks 14 and 15 contain about half the capacity of ink 70.

  FIG. 2 is a view showing a cross section of the tank unit 100 constituting the buffer tanks 14 and 15. FIG. 3 is an exploded perspective view of the tank unit 100. As shown in FIG. 2, the two buffer tanks 14 and 15 are formed as one tank unit 100. The tank unit 100 includes a tank main body 101 that stores ink 70 and a lid 102 that is attached to the tank main body 101.

  As shown in FIG. 3, the tank body 101 is a rectangular parallelepiped member that is open at the top. Two spaces 140 and 150 are formed in the tank body 101, the space 140 functions as the buffer tank 14, and the space 150 functions as the buffer tank 15.

  The tank body 101 is formed with a flange portion 101 a that protrudes outward along the outer edge of the upper surface of the tank body 101. As shown in FIG. 2, the tank body 101 is formed with protrusions 104 and 105 in which a passage leading to the space 140 is formed, and protrusions 106 and 107 in which a passage leading to the space 150 is formed. Has been.

  The protrusions 105 and 107 are formed on the lower surface of the tank main body 101. Pipe lines PL3 and PL4 extending to the inkjet head 20 are connected to the protrusions 105 and 107, respectively.

  The protrusions 104 and 106 are formed on the side surface of the tank body 101. A pipe line PL <b> 2 extending to the upstream tank 11 is connected to the protruding portion 104. Further, a pipe line PL <b> 5 extending to the downstream tank 12 is connected to the protruding portion 106.

  As shown in FIG. 3, the lid 102 is a rectangular plate member. The lid 102 is disposed on the upper surface of the tank main body 101, and is fixed to the flange portion 101a of the tank main body 101 with, for example, bolts or screws. The lid 102 seals the two spaces 140 and 150 formed in the tank main body 101.

  As shown in FIG. 2, the ink 70 is stored in the spaces 140 and 150 of the tank unit 100, and the liquid level of the ink 70 is located higher than the protrusions 104 and 106. Yes.

  In the ink jet apparatus 1, the circulation path C1 is formed by the upstream tank 11, the downstream tank 12, the buffer tanks 14 and 15, and the pipe lines PL1 to PL5 described above. The pipelines PL3 and PL4 are shorter than the other pipelines PL1, PL2, PL5 and the like, and are about 15 cm. On the other hand, the pipelines PL2 and PL5 are about 65 cm. Compared to the upstream tank 11 and the downstream tank 12, the buffer tanks 14 and 15 are disposed closer to the inkjet head 20.

  Returning to FIG. 1, pressure sensors 31 and 32 are provided in the pipes PL3 and PL4, respectively. The pressure sensors 31 and 32 are sensors using a diaphragm, for example. The pressure sensors 31 and 32 measure the pressure of the ink flowing through the pipelines PL3 and PL4, and output signals SP1 and SP2 corresponding to the measurement results to the calculator 51.

  Circulation of the ink 70 in the circulation path C1 is performed by a circulation pump P1 provided in the pipe line PL1. The circulation pump P1 is driven by the pump drive unit 53. When the circulation pump P1 is driven, the ink 70 in the circulation path C1 is supplied to the upstream tank 11, the buffer tank 14, the inkjet head 20, the buffer tank 15, and the downstream tank. Circulate in order of twelve. Further, in the circulation path C1, as the ink 70 circulates, particles and bubbles included in the ink 70 are removed by the filter FL provided in the pipe line PL1.

  The adjustment tank 13 is a tank for adjusting the amount of ink 70 circulating in the circulation path C1. The adjustment tank 13 is connected to the circulation path C1 by a pipe line PL6 branched from the pipe line PL1.

  The supply of the ink 70 from the adjustment tank 13 to the circulation path C1 and the supply of the ink 70 from the circulation path C1 to the adjustment tank 13 are performed by a pressure adjustment pump P2 provided in the pipe line PL4. The pressure adjustment pump P2 is driven by the pump drive unit 53, and when the pressure adjustment pump P2 rotates forward, the ink 70 is sent from the adjustment tank 13 to the circulation path C1. Further, when the pressure adjustment pump P2 is reversely rotated, the ink 70 is sent out from the circulation path C1 to the adjustment tank 13.

  When the ink 70 is sent from the adjustment tank 13 to the circulation path C1 by the pressure adjustment pump P2, the pressure of the ink flowing through the pipe lines PL3 and PL4 increases. Further, when the ink 70 is sent out from the circulation path C1 to the adjustment tank 13 by the pressure adjustment pump P2, the pressure of the ink flowing through the pipe lines PL3 and PL4 decreases. Therefore, the pressure adjustment pump P2 is operated based on the signals output from the pressure sensors 31 and 32 to control the pressure of the ink flowing through the pipes PL3 and PL4, thereby adjusting the ink pressure of the inkjet head 20. be able to.

  The pump driving device 53 drives the circulation pump P1 and the pressure adjusting pump P2 described above based on instructions from the control device 52. Thereby, the circulation of the ink 70 in the circulation path C1 and the pressure adjustment of the upstream tank 11 and the downstream tank 12 are realized.

  The computing unit 51 calculates the ink jet head 20 from the pressure TP1 of the ink flowing through the pipe line PL3 indicated by the signal SP1 from the pressure sensor 31 and the pressure TP2 of the ink flowing through the pipe line PL4 indicated by the signal SP2 from the pressure sensor 32. The pressure PN of the ink 70 at the nozzle is calculated. The following formula (1) is used as an example for the calculation of the pressure PN.

PN = (TP1 + TP2) / 2 (1)

  When computing unit 51 calculates nozzle pressure PN based on equation (1), it outputs a signal SPN corresponding to the value of pressure PN to control device 52.

  The control device 52 includes a central processing unit (CPU), a main storage unit that is a work area of the CPU, and an auxiliary storage unit that stores a program executed by the CPU. The control device 52 drives the circulation pump P1 via the pump drive device 53 to circulate the ink 70 in the circulation path C1. Further, the control device 52 appropriately performs pressure adjustment control using the pressure adjustment pump P2 based on the signal SPN output from the computing unit 51.

  The pressure adjustment control is control for maintaining the meniscus of ink formed on the nozzles of the inkjet head 20 in an optimal state. In the pressure adjustment control, the control device 52 performs control so that the pressure PN of the nozzles of the inkjet head 20 is about −1.7 kPa.

  In the pressure adjustment control, the control device 52 compares the nozzle pressure PN indicated by the signal SPN from the computing unit 51 with the threshold value Pth1. When the nozzle pressure PN is equal to or higher than the threshold value Pth1, the control device 52 reverses the pressure adjustment pump P2 and sends out the ink 70 from the circulation path C1 to the adjustment tank 13. As a result, the pressure PN of the nozzle decreases until it becomes equal to or less than the threshold value Pth1. In the present embodiment, the value of the threshold value Pth1 may be about −1.7 kPa to −1.6 kPa.

  Further, the control device 52 compares the nozzle pressure PN indicated by the signal SPN from the computing unit 51 with the threshold value Pth2. When the nozzle pressure PN is equal to or less than the threshold value Pth2, the control device 52 rotates the pressure adjustment pump P2 in the normal direction to send the ink 70 from the adjustment tank 13 to the circulation path C1. As a result, the pressure PN of the nozzle rises until it reaches the threshold value Pth2. In the present embodiment, the value of the threshold value Pth1 may be about −1.7 kPa to −1.8 kPa. By the pressure adjustment control described above, the pressure PN of the ink 70 in the inkjet head 20 is maintained constant.

  However, even if the pressure adjustment control described above is performed, the internal pressure of the inkjet head 20 may temporarily decrease when the ink 70 is ejected from the inkjet head 20. Usually, the pressure drop in the ink jet head 20 is eliminated while a certain amount of time elapses due to the action of the upstream tank 11 and the downstream tank 12 which have larger capacities than the ink jet head 20.

  The inkjet apparatus 1 according to the present embodiment includes two buffer tanks 14 and 15 separately from the upstream tank 11 and the downstream tank 12. Therefore, as compared with a conventional ink jet apparatus including only the upstream tank 11 and the downstream tank 12, the pressure drop in the ink jet head 20 can be eliminated in a short time.

  Further, the two buffer tanks 14 and 15 are provided closer to the inkjet head 20 than the upstream tank 11 and the downstream tank 12. Therefore, the pressure drop in the inkjet head 20 can be eliminated with better responsiveness than the conventional inkjet apparatus.

  4 to 6 are diagrams showing a change in pressure of the ink 70 in the inkjet head 20. The graph shown in each figure shows the pressure PN calculated by the calculator 51. The time t1 is the time when the ejection of the ink 70 from the inkjet head 20 starts, and the time t2 is the time when the ejection of the ink 70 is completed.

  As shown in FIG. 4, in the ink jet apparatus that does not have the buffer tanks 14 and 15, the pressure of the ink 70 is reduced by about 1.43 kPa immediately after the time t <b> 1 when the ejection of the ink 70 starts.

  As an example, as shown in FIG. 5, in the inkjet apparatus 1 having the buffer tanks 14 and 15 having a capacity of 25 ml, the pressure of the ink 70 decreases by about 0.22 kPa immediately after the time t <b> 1 when the ejection of the ink 70 starts. Stay. As an example, as shown in FIG. 6, in the inkjet apparatus 1 having the buffer tanks 14 and 15 having a capacity of 100 ml, the pressure of the ink 70 decreases by about 0.16 kPa immediately after the time t <b> 1 when the ejection of the ink 70 starts. Stay on.

  From the above results, in the ink jet apparatus 1 according to the present embodiment, a decrease in the internal pressure of the ink jet head 20 is suppressed by the two buffer tanks 14 and 15 provided separately from the upstream tank 11 and the downstream tank 12. I understand that Therefore, the ink jet device 1 can eliminate the pressure drop in the ink jet head 20 in a short time compared to the conventional ink jet device including only the upstream tank 11 and the downstream tank 12.

  In the present embodiment, the buffer tanks 14 and 15 are configured as one tank unit 100. Therefore, it is possible to reduce the size of the inkjet device 1 and simplify the device configuration.

  As mentioned above, although embodiment of this invention was described, this invention is not limited by the said embodiment. For example, in the above embodiment, the case where the inkjet apparatus 1 includes the two buffer tanks 14 and 15 has been described. The present invention is not limited to this, and the ink jet apparatus 1 may include only one of the two buffer tanks 14 and 15. In this case, the inkjet apparatus 1 preferably includes a buffer tank 14 on the upstream side of the inkjet head 20.

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

DESCRIPTION OF SYMBOLS 1 Inkjet apparatus 10 Ink supply apparatus 11 Upstream tank (1st ink tank)
12 Downstream tank (second ink tank)
13 Adjustment tank 14 Buffer tank (first buffer tank)
15 Buffer tank (second buffer tank)
20 Inkjet head

In order to solve the above problems, an ink supply device according to the present embodiment includes a first ink tank, a circulation pump, a first buffer tank, a second ink tank, a second buffer tank, and a first pressure sensor. And a second pressure sensor and a control unit . The first ink tank stores ink supplied to the inkjet head. The circulation pump circulates ink between the inkjet head and the first ink tank. The first buffer tank is directly connected to the downstream side of the first ink tank between the inkjet head and the first ink tank, and ink is stored in the first buffer tank. The second ink tank stores ink that flows out from the ink jet head after flowing into the ink jet head from the first ink tank. The second buffer tank is connected between the inkjet head and the second ink tank and stores ink. The first pressure sensor measures the pressure of the ink flowing through the first flow path connecting the first buffer tank and the inkjet head, and outputs a signal according to the measurement result. The second pressure sensor measures the pressure of the ink flowing in the second flow path connecting the second buffer tank and the inkjet head, and outputs a signal corresponding to the measurement result. The control unit controls the ink pressure of the inkjet head based on signals output from the first pressure sensor and the second pressure sensor.

Claims (5)

A first ink tank that stores ink to be supplied to the inkjet head;
A pump for circulating the ink between the inkjet head and the first ink tank;
A first buffer tank disposed between the inkjet head and the first ink tank and storing the ink;
An ink supply device comprising:   The ink supply device according to claim 1, wherein the first buffer tank is disposed between the first ink tank and the inkjet head.   The ink supply device according to claim 1, further comprising a second ink tank in which the ink flowing out from the first ink tank to the ink jet head and then flowing out from the ink jet head is stored.   The ink supply device according to claim 3, further comprising a second buffer tank that is disposed between the inkjet head and the second ink tank and stores the ink. An inkjet head;
An ink supply device according to any one of claims 1 to 4,
An inkjet apparatus comprising:

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