JP5171095B2 - Inkjet recording device - Google Patents

Description

  The present invention relates to an ink storage unit and an ink jet recording apparatus that performs recording by discharging ink from nozzles communicating with the ink storage unit.

  The ink jet recording method is a method for performing printing or image recording by ejecting minute ink droplets from an ink ejection port of an ink recording head to a recording medium, and can perform a recording operation while being separated from the recording medium. It can be recorded on recording media and articles of various materials and has been used for a wide range of purposes.

  Various types of ink-jet heads used for ink-jet recording have been developed. For example, a pressure chamber filled with ink is expanded and deformed by applying a voltage to a piezoelectric element and deforming it. On-demand type heads have been developed, such as a piezo system that causes pressure fluctuations by contraction, and a thermal system that uses the pressure generated by energizing and heating the heating resistor to foam the ink.

  In such an on-demand type head, ink droplets are ejected as required to record an image. However, since the amount of ink consumed varies from head to head or from color to color, it is necessary to supply ink appropriately. Various improvements have been made. For example, when a recording operation is performed by supplying ink to a nozzle that ejects ink droplets in a negative pressure state, it is necessary to supply the ink while maintaining the negative pressure state when the ink is consumed by the recording operation. For example, Patent Document 1 describes that a pressure control unit that maintains the ink pressure in the head at a desired level when ink is supplied to the print head is described. In Patent Document 2, a print head and a sub tank are provided on a Y cursor movably attached to a Y axis rail, and a negative pressure air pump is connected to the sub tank to prevent ink leakage from the print head in the sub tank. The point of maintaining a negative pressure suitable for the above is described.

Further, when the ink jet head is moved to perform a recording operation, it is necessary to accurately detect the remaining amount of ink in the head to prevent deterioration in recording quality due to a decrease in the remaining amount of ink. In order to cope with such a problem, for example, in Patent Document 3, a partition plate is provided in an ink reservoir in an ink jet head to suppress fluctuations in the ink liquid level and to detect the remaining amount of ink by a photodetector. Points are listed. Japanese Patent Application Laid-Open No. H10-228688 describes that the remaining amount of ink is detected at a timing that matches the movement conditions of the ink cartridge when the ink cartridge reciprocates in the main scanning direction.
JP 7-125254 A JP 2003-182104 A Japanese Patent Laid-Open No. 2-102061 Japanese Patent Laid-Open No. 9-1818

  When a recording operation is performed using the above-described on-demand type inkjet head, recording can be easily performed on various recording media and articles by performing the recording operation while moving the inkjet head. In that case, it is necessary to supply ink to the moving inkjet head, and as described in Patent Documents 1 and 2, ink is supplied to the sub tank while moving the sub tank supplying ink to the head together with the head. By doing so, the recording operation can be continued without running out of ink, and the production efficiency is remarkably improved.

  However, in such an ink supply system, since the subtank also moves, the ink in the subtank fluctuates with the movement, and there is a problem that it is difficult to stably supply ink.

  Patent Documents 3 and 4 describe that the remaining amount of ink in an ink cartridge attached to an ink jet head is detected. However, in the ink jet head described in these documents, ink is supplied to the ink cartridge from the outside. The remaining amount of ink is detected because the ink runs out. In such ink remaining amount detection, there is a large degree of freedom of level setting such as setting a safe level appropriately so as not to run out of ink. However, when ink is supplied from the outside to the ink reservoir of the inkjet head, it depends on the recording operation. It is necessary to maintain the ink in the head in a stable state by accurately detecting the amount of ink consumed and supplying the ink corresponding thereto.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording apparatus that can accurately detect a change in liquid level due to consumption of ink in an ink reservoir and stably supply ink to the ink reservoir. is there.

An ink jet recording apparatus according to the present invention includes an ink storing portion in which ink is stored and a liquid level of the ink fluctuates due to movement, and a nozzle that communicates with a bottom surface of the ink storing portion and has an opening formed toward a lower surface. A head, a pressure control unit that keeps the upper space of the ink in the ink reservoir in a negative pressure state lower than atmospheric pressure at all times, and prevents ink from leaking from the nozzle, and a state in which ink is pressurized from the ink tank An ink supply control unit that supplies ink into the ink storage unit, wherein the ink jet head moves in a predetermined movement direction and pressure is applied to the ink from the nozzles to perform recording, and the ink jet recording apparatus performs recording. It is provided exposed on the outer surface of the inkjet head and is stored in the ink storage section. A communicating pipe the other end in the upper space of the ink communicated with one end portion in the ink communicating, receiving element light light from the light emitting element is irradiated to said communicating pipe is reflected from the communicating pipe And a liquid level detecting unit that detects a liquid level position of the ink in the communication pipe, and the communication pipe is arranged at a substantially central portion of the width of the ink storage part in the movement direction and the movement. The internal width in the direction is set to be narrower than the internal width of the ink reservoir, and the ink supply control unit determines the ink liquid level position in the ink reservoir based on a detection signal from the liquid level detector. The ink supply to the ink reservoir is controlled so as to be set within a range. Further, the communication pipe is set to be substantially perpendicular to the moving direction.

  With the above-described configuration, one end communicates with the ink that is exposed on the outer surface of the ink jet head and is stored in the ink reservoir, and the other end communicates with the upper space of the ink. Since the communication pipe and the liquid level detection part for detecting the liquid level position of the ink in the communication pipe are provided, the ink liquid level position in the ink storage part can be accurately detected from the outside.

  In other words, the communicating pipe has one end communicating with the ink stored in the ink storing portion and the other end communicating with the upper space of the ink. The ink liquid level appears at the position of the communication pipe, and the ink liquid level position can be easily detected from the outside by exposing the communication pipe to the outer surface of the inkjet head.

  If the ink is supplied so that the detected ink liquid level position is set within a predetermined range, the ink in the ink reservoir can be kept stable at all times and can be constantly stabilized from the nozzle communicating with the ink reservoir. Ink droplets can be ejected in this state.

  Further, by setting the width inside the communication tube in the moving direction of the ink jet head to be narrower than the width inside the ink storing portion, the communication is made in comparison with the fluctuation of the ink level in the ink storing portion that occurs when the ink jet head moves. Variations in the ink level in the tube can be reduced, and variations in the ink level in the ink reservoir due to ink consumption can be detected more accurately.

  Ink fluctuations that occur in the ink reservoir when the inkjet head is moved are greatest at both ends of the width in the scanning direction (corresponding to the wall surface of the ink reservoir), and are smallest at the center. Is arranged at the center, the influence of the change in the ink level in the ink reservoir on the ink level in the communication pipe can be reduced.

  If the communicating pipe is set so as to be substantially perpendicular to the moving direction, it is possible to reduce the fluctuation of the ink level in the communicating pipe that occurs when the inkjet head is moved.

  In addition, a liquid level detection unit is provided by providing a pressure control unit that maintains the ink upper space in the ink storage unit in a negative pressure state lower than atmospheric pressure, and supplying ink from the ink tank to the ink storage unit in a pressurized state. Ink can be quickly supplied into the ink reservoir according to the ink liquid level detected in step 1, and the ink in the ink reservoir is always kept in a negative pressure state to reliably prevent problems such as ink leakage from the nozzles. can do.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments described below are preferable specific examples for carrying out the present invention, and thus various technical limitations are made. However, the present invention is particularly limited in the following description. Unless otherwise specified, the present invention is not limited to these forms.

  FIG. 1 is a schematic configuration diagram relating to an embodiment of the present invention. A recording medium T such as a fabric is conveyed in the sub-scanning direction Y by the endless conveyance belt 3. The inkjet head 1 is positioned and fixed on the upstream side in the sub-scanning direction Y of the carriage 11 supported by the guide rail 10, and the carriage 11 has a width across the recording medium T via the timing belt 13 by driving the carriage motor 12. Reciprocally move in the main scanning direction X across the direction. Note that a moving mechanism using a linear motor or a ball screw may be used instead of the moving mechanism using the carriage motor and the timing belt.

  In response to the image signal, the carriage 11 is moved in the main scanning direction X, and a drive signal is input to the inkjet head 1 via the flexible cable 14 and ink droplets are ejected toward the surface of the recording medium T.

  An ink supply pipe 15 is attached to the lower part of the ink jet head 1 to communicate with the inside of the ink storage part and supplies ink, and an air pipe is connected to the upper part of the ink jet part 1 to adjust the atmospheric pressure. 16 is attached.

  A communication pipe 17 is attached to the outer surface of the inkjet head 1 along the vertical direction, and is provided so as to protrude upstream in the sub-scanning direction Y of the inkjet head 1 and is set in an exposed state. ing. The communication pipe 17 is a cylindrical straight pipe made of a transparent material, and the inner surface has water repellency that allows ink to run out. The lower end portion of the communication tube 17 communicates with the ink in the ink storage portion, and the upper end portion communicates with the upper space of the ink in the ink storage portion. For this reason, ink is introduced into the communication pipe 17 and an ink liquid level is generated at the same height as the ink liquid level in the ink reservoir.

  At one end of the range in which the carriage 11 reciprocates in the main scanning direction X, a liquid level detection unit 18 is disposed at a position facing the communication pipe 17. The liquid level detection unit 18 reciprocates the carriage 11. The ink level in the communication pipe 17 is detected each time it moves to face the communication pipe 17. As the liquid level detection unit 18, a light emitting element and a light receiving element are provided, and the light from the light emitting element is irradiated onto the communication pipe 17, and the light reflected from the communication pipe 17 is received by the light receiving element to detect the liquid level position of the ink. You just have to do it. In that case, if a reflecting plate is attached to the outer surface of the inkjet head 1 which is the back surface of the communication pipe 17, the detection accuracy of the liquid surface position can be improved. A method other than such optical detection may be used, and any method that can detect the ink liquid surface position of the communication pipe 17 can be used and is not particularly limited.

  The liquid level detection unit 18 may be attached to the inkjet head 1, and in that case, the liquid level detection unit 18 can always detect the ink liquid level position of the communication pipe 17.

  The liquid level detector 18 detects whether the liquid level position exists within a predetermined range by detecting the upper limit position and the lower limit position of the liquid level position (height). For example, the presence or absence of ink is detected by a pair of light receiving elements arranged corresponding to the upper limit position and the lower limit position when the light emitted from the light emitting element is detected to detect whether the ink level is within a predetermined range. You can do it.

  In addition, a planar heater 19 is attached to the side surface of the inkjet head 1, and heat generated from the heater 19 is conducted through the metal inkjet head body to heat the ink in the ink reservoir. Can be done.

  In the above example, the case where one inkjet head is provided has been described, but the same applies to the case where a plurality of inkjet heads are provided for color recording.

  2 is a cross-sectional view (FIG. 2A), a front view (FIG. 2B), and a bottom view (FIG. 2C) of the inkjet head 1 cut in the sub-scanning direction Y. The ink jet head 1 is made of a metal casing, and has an ink reservoir 20 formed therein. The lower part in the ink storage part 20 is defined as an ink area B where ink is stored up to a predetermined height, and the upper part is defined as a gas area A into which air is introduced.

  The ink supply pipe 15 communicates with the ink region B via a connection member 15a fixed to the outer surface of the inkjet head 1, and the connection member 16a fixed to the upper surface of the inkjet head 1 communicates with the gas region A. The air pipe 16 communicates with each other.

  Further, a communication tube 17 is attached to the outer surface of the inkjet head 1 via a pair of connecting members 17a and 17b. The lower end portion of the communication tube 17 communicates with the ink region B, and the upper end portion communicates with the gas region A. Communicate. Therefore, the ink liquid level S1 is formed in the communication pipe 17 at the same height as the ink liquid level S formed in the ink reservoir 20. Since the communication pipe 17 is made of a transparent or translucent material, the ink liquid level S1 can be visually recognized from the outside as shown in FIG. As a material used for the communication pipe 17, for example, a transparent or translucent material having water repellency and chemical resistance such as a fluororesin is preferable.

  A plate-like nozzle portion 21 is disposed on the bottom surface of the inkjet head 1, and nozzles 21 a that are formed to open downward are linearly arranged in the nozzle portion 21. A communication passage communicating with the nozzle portion 21 is formed on the bottom surface of the ink storage portion 20, and ink in the ink storage portion 20 is supplied into the nozzle portion 21 via the communication passage. A pressure control device, which will be described later, communicates with the gas region A in the ink reservoir 20 via the air pipe 16, and the pressure in the gas region A is reduced to a predetermined negative pressure state (pressure lower than atmospheric pressure). Is controlled). For this reason, ink is not leaked from the nozzle 21a formed on the bottom surface of the nozzle portion 21 to which ink is supplied. The ink is ejected from the nozzle 21a by applying pressure to the ink in the flow path communicating with the nozzle 21a using a pressure means such as a piezoelectric element provided for each nozzle 21a.

  A heater 19 is in close contact with the outer surface of the inkjet head 1, and the heat transferred to the head body while heating the metal head body is also transmitted to the plate 22 standing from the bottom in the ink reservoir 20. Thus, the ink is also heated from the central portion of the ink region B. For this reason, the ink in the ink reservoir 20 is uniformly heated and always maintained at a predetermined viscosity.

  FIG. 3 is a schematic cross-sectional view relating to the ink reservoir 20 and the communication pipe 17 when the inkjet head 1 is viewed from the front. The width d in the main scanning direction X, which is the inner diameter of the communication pipe 17, is set to be narrower than the width D in the main scanning direction X of the ink reservoir 20, and the midpoint of the width D and the communication pipe 17 are viewed from the front. A communication pipe 17 is attached so that the central axes overlap. When the ink-jet head 1 reciprocates in the main scanning direction X, as shown in FIG. 4, the liquid level of the ink in the ink storage unit 20 varies greatly vertically and horizontally like the liquid level S ′ and the liquid level S ″. However, the influence of the liquid level fluctuation can be reduced by attaching the communication pipe 17 to the center in the main scanning direction X of the ink reservoir 20. Also, by reducing the inner diameter of the communication pipe 17, the communication is achieved. Variations in the ink level in the tube 17 can be suppressed, and changes in the level of the liquid according to ink consumption can be more accurately detected. The inner diameter is preferably set to 2 to 6 mm.

  In this example, the communication pipe 17 is attached in the vertical direction so as to be perpendicular to the main scanning direction X. However, by setting it vertically, it is possible to reduce the influence of the liquid level fluctuation in the ink reservoir 20. . When the ink viscosity is large and the liquid level fluctuation is small, or when the width D of the ink reservoir 20 is narrow and the liquid level fluctuation can be suppressed to a small level, the communication pipe 17 is attached while being inclined with respect to the main scanning direction X. In this case, the liquid level in the communication pipe 17 is widened and the liquid level position can be easily detected.

  FIG. 5 is a block configuration diagram relating to ink supply control to the inkjet head 1 and pressure control in the ink reservoir 20. Ink is supplied from an ink bottle 31 through an ink supply pipe 15 to which an on-off valve 33 is attached. The ink bottle 31 is provided with a pressure pump 32. The air pressure in the ink bottle 31 is increased by the pump 32 to pressurize the ink. Then, the supply operation of the pressurized ink is performed by opening and closing the on-off valve 33.

  Regarding pressure control, a negative pressure adjusting container 34 to which an air pipe 16 communicating with the ink reservoir 20 is attached, a negative pressure holding container 38 communicating with the negative pressure adjusting container 34 via an on-off valve 37, and inside the negative pressure holding container 38. Is provided with a suction pump 39 for bringing the pressure to a predetermined negative pressure state. A pressure gauge 35 and an air release valve 36 for detecting the internal pressure are attached to the negative pressure adjusting container 34.

  Ink supply control and pressure control are performed by the control unit 30. The control unit 30 performs control based on the detection signal from the liquid level detection unit 18 and the detection signal from the pressure gauge 35. With respect to ink control, the liquid level detection unit 18 detects that ink has been consumed by the recording operation, the ink level in the ink reservoir 20 has fallen, and the ink level in the communication tube 17 has deviated from a predetermined range. Then, the on-off valve 33 is opened and ink is supplied from the ink bottle 31. Since the inside of the ink reservoir 20 is always kept in a negative pressure state, the pressurized ink is smoothly introduced into the ink reservoir 20 and supplied. When the ink level is detected by the liquid level detector 18 detecting that the ink level in the ink reservoir 20 has risen and the liquid level in the communication pipe 17 has risen outside the predetermined range. The on-off valve 33 is closed and the supply of ink is stopped.

  As for the pressure control, a control operation is performed to maintain the negative pressure state in the negative pressure adjusting container 34 that communicates with the gas region A in the ink reservoir 20. The volume of the negative pressure adjustment container 34 is set to be sufficiently larger than the volume of the ink storage unit 20, so that the pressure fluctuation in the ink storage unit 20 is absorbed by the negative pressure adjustment container 34. .

  The pressure in the negative pressure adjusting container 34 is constantly monitored by a pressure gauge 35. When the internal pressure becomes larger than a predetermined negative pressure state, the open / close valve 37 is opened to communicate with the negative pressure holding container 38. Return to the negative pressure state by sucking the air inside. When the internal pressure falls below a predetermined negative pressure state, the atmosphere release valve 36 is opened to introduce air into the inside and return to the predetermined negative pressure state. The pressure in the negative pressure holding container 38 is always maintained in a predetermined negative pressure state by the suction pump 39.

  The pressure fluctuation in the gas region A accompanying the reciprocation of the inkjet head 1 is absorbed by connecting to the negative pressure adjusting container 34. Further, when ink is introduced into the ink reservoir 20 and the pressure in the gas region A increases, the pressure in the negative pressure adjustment container 34 increases, and the on-off valve 37 is opened to decrease the pressure to maintain a predetermined negative pressure state. To do. When the pressure in the gas region A decreases as the ink is consumed, the pressure in the negative pressure adjustment container 34 also decreases, and the atmospheric pressure release valve 36 is opened to increase the pressure to maintain a predetermined negative pressure state. To do.

  As described above, by performing pressure control through the negative pressure adjusting container 34 and the negative pressure holding container 38, a certain amount of pressure fluctuation in the ink reservoir 20 can be communicated with these containers to adjust the pressure. It is possible to maintain the negative pressure state by reducing the number of times the suction pump 39 is operated.

  A plurality of ink reservoirs 20 may be connected to the negative pressure adjusting container 34. In that case, all the ink reservoirs 20 can be adjusted to the same negative pressure state.

  In the example described above, when ink is consumed by the recording operation, the ink is supplied from the ink bottle into the ink reservoir and is controlled so that the ink liquid surface position is always within a predetermined range. By providing it, it is possible to constantly detect the position of the ink liquid level in the ink reservoir, and to suppress fluctuations in the ink liquid level accompanying ink supply and ink consumption.

  In the nozzle provided on the bottom surface of the ink jet head, the pressure in the gas area A in the ink reservoir and the ink pressure based on the height of the ink area to the ink liquid level act, so that both pressures can be kept as constant as possible. Although normal ink discharge operation can be performed by preventing ink leakage or drawing from the nozzle, the ink level in the ink reservoir is maintained by detecting the level in the communication pipe described above. In this way, the ink pressure fluctuation is minimized, and the pressure in the gas region A is minimized by the above-described pressure control, so that the normal recording operation can be performed while always replenishing the ink consumption accompanying the printing operation. Will be able to continue.

  FIG. 6 is a schematic perspective view of another embodiment. Parts having the same functions as those of the above-described embodiment are denoted by the same reference numerals, and description of overlapping parts is omitted.

  In this example, the head unit 40 is a line head (full line type inkjet head) in which a plurality of nozzles are formed in the main scanning direction over the entire width of the image forming region intersecting with the sub scanning direction Y. Are arranged with recording heads 40Y, 40M, 40C, and 40K. Color ink is supplied to the recording heads 40Y, 40M, 40C, and 40K, respectively, so that full-color recording is performed.

  Each recording head is configured by arranging a plurality of head block portions 40a to 40f in the main scanning direction. Each head block portion has the same structure as the ink jet head 1 shown in FIG. Ink is ejected from the nozzles and recorded. FIG. 7 is a side view of the recording head as viewed from the sub-scanning direction. An ink supply pipe L1 and an air pipe L2 are connected to the upper portions of the head block portions 40a to 40f. The ink supply pipe L1 and the air pipe L2 are connected to each head block unit so that pressure control and individual ink supply can be performed. Further, like the inkjet head 1 in FIG. 1, communication pipes 17 a to 17 f for detecting the liquid level of the ink storage part in the block part are attached to the side surface of each head block part. Each communication pipe is provided with liquid level detectors 18a to 18f to detect whether or not the liquid level in the communication pipe is at a level within a predetermined range. Then, ink supply control is performed based on detection signals from the liquid level detection units 18a to 18f, the liquid level of the ink storage unit in the head block unit is maintained within a predetermined range, and fluctuations in ink pressure due to liquid level fluctuations are minimized. It will be limited to the limit. In addition, since the communication pipe is attached to the side surface, even when air bubbles enter the ink reservoir, accurate liquid level detection can be performed without bubbles entering the communication pipe.

It is a schematic block diagram regarding embodiment which concerns on this invention. It is sectional drawing of an inkjet head, a front view, and a bottom view. It is a schematic sectional drawing which shows the state which attached the communicating pipe. It is explanatory drawing which shows the fluctuation | variation of the ink when an inkjet head reciprocates. It is a block block diagram regarding ink supply control and pressure control. It is a schematic perspective view regarding another embodiment which concerns on this invention. It is the side view which looked at the recording head of Drawing 6 from the subscanning direction.

Explanation of symbols

1 Inkjet head
15 Ink supply pipe
16 Air pipe
17 Communication pipe
18 Liquid level detector
20 Ink reservoir
21 Nozzle
30 Control unit
31 Ink bottle
32 pumps
33 On-off valve
34 Negative pressure adjustment container
35 Pressure gauge
36 Air release valve
37 On-off valve
38 Negative pressure holding container
39 Suction pump
40 recording head

Claims (2)

An ink storage section that stores ink therein and has an ink liquid level that fluctuates due to movement, an ink jet head that communicates with the bottom surface of the ink storage section and that has an opening formed toward the bottom surface, and ink in the ink storage section A pressure control unit that constantly maintains the inside of the upper space in a negative pressure state lower than atmospheric pressure so that ink does not leak from the nozzles, and ink that supplies ink from an ink tank into the ink storage unit in a pressurized state An ink jet recording apparatus that performs recording by ejecting the ink jet head by applying pressure to the ink by moving the ink jet head in a predetermined movement direction and providing the supply control unit, And one end communicates with the ink stored in the ink storage section. A communicating pipe in the upper space and the other end communicating with the liquid level of ink in the communicating pipe by receiving light reflected light from the light emitting element from the communicating tube by irradiating the communicating pipe by the light receiving element A liquid level detection unit that detects a position, and the communication pipe is disposed at a substantially central portion of the width of the ink storage unit in the movement direction, and an internal width in the movement direction is within the ink storage unit. The ink supply control unit is set to be narrower than the width, and the ink supply control unit sets the ink liquid level position in the ink storage unit within a predetermined range based on a detection signal from the liquid level detection unit. An ink jet recording apparatus that controls ink supply to the ink jet recording apparatus.   2. The ink jet recording apparatus according to claim 1, wherein the communication pipe is set to be substantially perpendicular to the moving direction.

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