JP2017019212A - Liquid volume measurement device, ink supply device, and inkjet device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce cost related to a device.SOLUTION: A liquid volume measurement device includes: a float moving in accordance with a level of liquid in a tank; a metal plate attached to the float, of which dimension crossing with a direction of float movement changes along a moving direction; and a guiding-type sensor disposed facing the metal plate, thereby eliminating the need of using an expensive sensor and reducing manufacturing cost of product and running cost.SELECTED DRAWING: Figure 3

Description

  Embodiments described herein relate generally to a liquid amount measurement device, an ink supply device, and an ink jet device.

  Various techniques for preventing ink drying in an 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.

  In the above circulation system, the ink pressure fluctuates when the head is operating. For this reason, in the circulation system, control is performed to control the pressure of the circulating ink to prevent the output image from being lost. This type of control is performed, for example, by adjusting the pressure of each ink tank so that the difference in pressure between the ink tanks arranged on the upstream side and the downstream side of the head becomes constant. Therefore, it is necessary to detect the amount of ink stored in the ink tank with a certain degree of accuracy.

  For detecting the amount of ink, a sensor that detects the amount of liquid based on a capacitance that changes in accordance with the amount of ink, a sensor that detects the height of the liquid surface using ultrasonic waves, and the like are known. . However, since these sensors are expensive, there is a disadvantage that the manufacturing cost of the apparatus increases.

JP 2007-313848 A

  An object of the present invention is to reduce the cost associated with the apparatus.

  In order to solve the above problems, the liquid amount measuring device according to the present embodiment has a float that moves in accordance with the liquid level of the liquid in the tank, and a dimension that is attached to the float and intersects the moving direction of the float. A metal plate that changes along the moving direction; and an inductive sensor that is disposed opposite the metal plate.

It is a block diagram of the ink jet device concerning this embodiment. It is a perspective view of a tank unit. It is sectional drawing of a tank unit. It is a perspective view of a float. It is a figure for demonstrating the operation | movement of a float. It is a perspective view of a proximity sensor. It is a figure which shows the positional relationship of the coil of a proximity sensor, and the float target. It is a figure which shows the output characteristic of a proximity sensor.

  Hereinafter, the present embodiment will be described with reference to the drawings. FIG. 1 is a block diagram schematically showing 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 five ink tanks, an upstream tank 11, a downstream tank 12, a regulation tank 13, and buffer tanks 14 and 15, two pumps, a circulation pump P1 and a pressure regulation pump P2, a calculator 51, And a control system including a control device 52 and a 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 perspective view of the tank unit 100 constituting the buffer tanks 14 and 15. As shown in FIG. 2, the tank unit 100 measures the amount of ink stored in the tank unit 100, a tank body 101 having a hollow inside, a lid 102 for sealing a space formed in the tank body 101, and the tank unit 100. Proximity sensors 33A and 33B.

  FIG. 3 is a view showing a cross section of the tank unit 100. The tank main body 101 of the tank unit 100 is a member made of, for example, a resin such as plastic and opened upward. Two spaces 140 and 150 are formed inside the tank body 101. The spaces 140 and 150 constitute buffer tanks 14 and 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. Further, as shown in FIG. 3, 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. 2, the lid 102 is a rectangular plate member whose longitudinal direction is the X-axis direction. 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. 3, the float units 200 are respectively disposed in the spaces 140 and 150 formed in the tank main body 101. FIG. 4 is a perspective view of the float unit 200. As shown in FIG. 4, the float unit 200 is a member composed of two parts, a float 202 and a support part 201.

  The float 202 is made of a resin such as plastic. The float 202 is a pentagonal hollow member whose longitudinal direction is the Y-axis direction and floats on the ink. The float 202 is shaped into a taper shape with the width in the X-axis direction becoming narrower downward. A target 203 made of, for example, a stainless steel plate having a thickness of 0.2 mm is attached to the −Y side surface of the float 202. The target 203 is shaped into an isosceles triangle shape whose width (dimension in the X-axis method) decreases toward the lower end of the float 202.

  The support part 201 is a member whose longitudinal direction is the X-axis direction. The −X side end portion of the support portion 201 is connected to the float 202, and a cylindrical portion 204 whose busbar is parallel to the Y axis is formed at the + X side end portion, for example.

  As shown in FIG. 3, the cylindrical portion 204 of the float unit 200 configured as described above is rotatably supported around an axis parallel to the Y axis by a support column 102 a extending downward from the bottom surface of the lid 102. Yes. As shown in FIG. 5, the float 202 of the float unit 200 moves along a circle CR <b> 1 centering on the central axis S <b> 1 of the cylindrical portion 204. Similarly, the target 203 provided on the float 202 moves along the circle CR1 together with the float 202.

  As can be seen with reference to FIG. 5, for example, the float unit 200 is located at the position indicated by the phantom line when the tank main body 101 does not contain ink 70. Further, when the liquid level of the ink 70 is indicated by a straight line LV1, it is positioned at a solid line, and when the liquid level of the ink 70 is indicated by a straight line LV2, it is indicated by a broken line. Located in the place. In the tank unit 100, the liquid level of the ink 70 stored in the spaces 140 and 150 is in the vicinity of the position indicated by the normal straight line LV1. In this state, as shown in FIG. 3, the liquid level of the ink 70 is positioned higher than the protrusions 104 and 106.

  The proximity sensors 33A and 33B are inductive sensors that output voltage signals SL1 and SL2 corresponding to the distance and size of the approaching metal material, for example. The proximity sensors 33A and 33B can detect a conductor located within a distance of approximately 5 mm from the proximity sensors 33A and 33B.

  FIG. 6 is a perspective view of the proximity sensor 33A. As shown in FIG. 6, the proximity sensor 33 </ b> A includes a substrate 331, an IC chip 333 mounted on the substrate 331, and a coil 332. The IC chip 333 oscillates the coil 332 and generates an electromagnetic field of about several hundred kHz in the vicinity of the coil 332. When the current of the coil 332 is attenuated, the IC chip 333 outputs a signal having a value corresponding to the degree of attenuation.

  FIG. 7 is a diagram illustrating a positional relationship between the coil 332 of the proximity sensor 33 </ b> A and the target 203 of the float unit 200. As can be seen from FIG. 7, the proximity sensor 33A is attached to the outer surface of the tank main body 101 so that the coil 332 is positioned on the circle CR1.

  As shown in FIG. 8, for example, when the target 203 is at the position indicated by the arrow A in FIG. 7, the value of the signal SL1 output from the proximity sensor 33A is V1. When the target 203 is at the position indicated by the arrow B in FIG. 7, the value of the signal SL1 output from the proximity sensor 33A is V2. In addition, the voltage V (x) of the signal SL1 with respect to the position x on the circle CR1 from the position indicated by the arrow A to the position indicated by the arrow B of the target 203 changes substantially linearly from V1 to V2.

  The proximity sensor 33B also includes a substrate 331, an IC chip 333, and a coil 332, like the proximity sensor 33A. The proximity sensor 33B is disposed so as to face the float unit 200 provided in the space 150 of the tank body 101. The coil 332 of the proximity sensor 33B faces the target 203 of the float unit 200.

  As shown in FIG. 1, 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 70 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 computing unit 51 computes the amount of ink 70 stored in the buffer tanks 14 and 15 based on the signals SL1 and SL2 output from the proximity sensors 33A and 33B. When the calculator 51 calculates the amount of ink 70 stored in the buffer tanks 14 and 15, the signal SV 1 indicating the amount of ink 70 stored in the buffer tank 14 and the signal indicating the amount of ink 70 stored in the buffer tank 15. SV2 is output to the 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 Pth2 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.

  Further, the control device 52 monitors the amount of ink 70 indicated by the signals SV1 and SV2 from the computing unit 51. When it is determined that the amount of the buffer tanks 14 and 15 indicated by the signals SV1 and SV2 has become equal to or less than a predetermined threshold value, the pressure adjustment pump P2 is rotated forward to send the ink 70 from the adjustment tank 13 to the circulation path C1. As a result, the amount of ink 70 circulating in the circulation path C1 is maintained above a certain level. As a result, the control of the nozzle pressure PN of the inkjet head 20 is facilitated.

  As described above, in this embodiment, it is possible to accurately control the pressure PN of the nozzles of the inkjet head 20. Therefore, it is possible to prevent occurrence of printing omission and form a fine image.

  In the present embodiment, the detection of the liquid amounts in the buffer tanks 14 and 15 is performed by the proximity sensors 33A and 33B. For this reason, there is no need to use an expensive sensor such as a sensor for detecting the amount of liquid based on the capacitance or a sensor for detecting the height of the liquid surface using ultrasonic waves, and the manufacturing cost and running cost of the apparatus are reduced. Can be reduced.

  The proximity sensors 33A and 33B according to the present embodiment are disposed outside the tank in which the ink 70 is stored. For this reason, it is not necessary to carry out wiring etc. in the tank, and the structure of the apparatus can be simplified. Moreover, the sealing property in a tank can be improved.

  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.

  In the present embodiment, a liquid amount measuring device is configured by the float unit 200 including the target 203 and the proximity sensors 33A and 33B.

  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 amount of ink 70 in the buffer tanks 14 and 15 is detected using the proximity sensors 33A and 33B has been described. For example, the amount of ink 70 stored in the upstream tank 11, the downstream tank 12, or the adjustment tank 13 may be measured using a proximity sensor. Also in this case, it is not necessary to use an expensive sensor, and the manufacturing cost and running cost of the apparatus can be reduced.

  In the above embodiment, the case where the target 203 is an isosceles triangle has been described. However, the present invention is not limited to this, and the target 203 may be any shape as long as the dimension in the direction orthogonal to the moving direction of the target 203 changes along the moving direction. Specifically, the target 203 does not need to have a specific shape as long as it is trapezoidal or wedge-shaped.

  In the above embodiment, the case where the target 203 is made of stainless steel has been described. Not only this but the target 203 should just be a conductor, and may be formed from metals other than stainless steel.

  In the above embodiment, the case where the float 202 of the float unit 200 moves along the circle CR1 has been described. Not limited to this, the float unit 200 may be configured such that the float 202 moves in the vertical direction.

  The output characteristics of the proximity sensors 33A and 33B according to the present embodiment are not limited to those shown in FIG. Any sensor that outputs a signal having a value corresponding to the approaching state of the target can be used.

  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 20 Inkjet head 33A, 33B Proximity sensor (inductive sensor)
200 Float unit 201 Support part (support member)
202 Float 203 Target (metal plate)

Claims (5)

A float that moves according to the liquid level in the tank;
A metal plate attached to the float and having a dimension in a direction intersecting the movement direction of the float that varies along the movement direction;
An inductive sensor disposed opposite the metal plate;
A liquid quantity measuring device having   The liquid quantity measuring device according to claim 1, wherein one end is supported rotatably around an axis parallel to the liquid surface, and the other end includes a support member connected to the float.   The liquid amount measuring device according to claim 1, wherein the inductive sensor is disposed outside the tank. An ink tank for storing ink to be supplied to the inkjet head;
The liquid amount measuring device according to any one of claims 1 to 3, which measures the amount of the ink in the ink tank.
A circulation pump for circulating the ink between the inkjet head and the ink tank;
A control device for adjusting the amount of the ink circulated by the circulation pump based on the measurement result of the liquid amount measuring device;
An ink supply device comprising: An inkjet head;
An ink supply device according to claim 4,
An inkjet apparatus comprising:

Images