JP2005053048A - Inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording device which realizes circulation recovery of a recording head by a smaller waste ink amount. <P>SOLUTION: In a first ink passage 117 and a second ink passage 118 which couple a sub tank 102 and the recording head 107 with each other, a pump 101 set at the first ink passage 117 is operated in a state with the second ink passage 118 shut, and ink in the sub tank 102 is supplied to the recording head 107 by the pressure of the pump 101. An ink liquid chamber and a passage in the recording head 107 are after pressured, whereby bubbles remaining in the ink liquid chamber and the like are made to flow from an ink discharge opening. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ink jet recording apparatus that forms an image by supplying ink to a recording head and ejecting the ink from the recording head, and particularly relates to a recovery sequence of the recording head.

  2. Description of the Related Art In an ink jet recording apparatus that has been widely used in recent years, an image is recorded by applying energy corresponding to a driving pulse to each of a plurality of recording elements and ejecting ink from each recording element. There are several methods for applying energy in such an ink jet recording apparatus, but by applying a rapid thermal energy to the ink supplied to each recording element, film boiling occurs in the ink, There is a method in which a predetermined amount of ink is ejected from a recording element as the generated bubbles grow. This method is widely used because it is particularly advantageous in terms of drive frequency and recording element integration density.

  Further, as an arrangement form of the recording elements for improving the recording speed, a so-called line head is known in which a plurality of recording elements are arranged in the direction different from the conveyance direction of the recording medium by the recording area width of the recording medium. . In a line printer to which this line head is applied, an image is formed by ejecting ink from a line head fixed in the recording apparatus at a predetermined cycle and transporting the recording medium at a predetermined speed. It is.

  By the way, in the recording apparatus of the above-described type, foaming is generated in each recording element at a high frequency, and since the number of recording elements itself is large, residual bubbles generated accompanying recording accumulate in the ink flow path, There may be concerns about maintaining stable records.

  Therefore, in general, consideration is given to removing bubbles, and recovery processing is often employed (see, for example, Patent Document 1).

JP 2001-232807 A (2nd page, FIG. 1)

  However, in a general recording device recovery mechanism, the ink flow path is long and complicated, so that a large amount of ink is discharged from the head in the recovery operation performed by circulating ink, which increases the running cost of the recording device itself. Therefore, reducing the amount of discharged ink by optimizing the recovery operation has been a major issue.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an ink jet recording apparatus that realizes circulation recovery of a recording head with a smaller amount of waste ink.

  Therefore, in the present invention, in an ink jet recording apparatus that performs recording using recording means for ejecting ink from a plurality of recording elements, tank means for supplying ink to the recording means, the tank means, and the recording means A first and second ink flow path for connecting the ink, a pump provided in the first ink flow path for supplying ink from the tank means to the recording means, and provided in the second ink flow path. When performing a recovery operation for maintaining the ink discharge state of the recording means in a good state, the valve means capable of controlling the flow of ink in the second ink flow path, the valve means performs the second operation. By operating the pump in a state where the flow of ink in the ink flow path is stopped, the tank means is connected to the recording means via the first ink flow path. A recovery control means for supplying ink and causing the ink to flow out of the recording element by the pressure of the supplied ink; and means for detecting and controlling the temperature in the ink flow path, the recovery control means comprising the recording head In order to detect air bubbles remaining in the inside of the ink flow path, the pump is driven by making a determination based on a temperature change amount by temperature control in the ink flow path.

  According to the present invention, bubbles remaining in the ink liquid chamber or the like in the recording head can be accurately detected, so that the remaining bubbles in the recording head can be removed with fewer recovery times than in the past, and recovery processing is performed. It is possible to reduce the amount of waste ink required.

  The first embodiment of the present invention will be described below.

  FIG. 1 is a conceptual diagram showing an example of an ink flow path in a line printer type ink jet recording apparatus applicable to the present invention together with a recovery processing system. Here, the circulation processing of the recovery processing system will be briefly described.

  In FIG. 1, 106 is an ink tank for storing ink, 102 is a sub-tank for temporarily storing ink supplied from the ink tank, 107 is a recording head including a plurality of recording elements for discharging ink, Reference numeral 104 denotes a recovery tank for receiving ink ejected from the recording head 107 by the recovery operation, and 119 denotes a waste ink tank for collecting ink from the recovery tank 104 and storing the ink. Reference numerals 101 and 105 denote pumps, respectively, and portions indicated by thick solid lines in the figure indicate paths through which ink flows. Reference numerals 108, 110, and 111 denote electromagnetic valves that can be opened and closed at appropriate timings. Reference numerals 112, 113, and 114 denote filters for preventing foreign matters from circulating in the ink flow path.

  The ink stored in the ink tank 106 is supplied to the sub tank 102 by the pump 105. In addition to the ink introduction path for introducing ink from the ink tank 106, the sub tank 102 is supplied with a supply path 117 for supplying ink to the recording head 107 and ink that has not been used for recording from the recording head 107. A recovery path 118 for recovery is connected. With respect to the recovery path 118, a part of the bubbles generated by the recording head are also recovered together with the ink not used by the recording head 107. Since the sub tank 102 is provided with the air communication port 103, the sub tank is maintained at the same pressure as the atmospheric pressure, and the recovered bubbles are discharged upward in the sub tank.

  Each recording element of the recording head 107 includes an ejection port for ejecting ink and an ink path communicating with the ejection port, and ink is filled to the vicinity of the ejection port by the capillary force of the ink path. A meniscus is formed on the ink surface in the vicinity of the discharge port due to the negative pressure generated by the water head difference between the ink liquid level of the sub tank 102 and the discharge port. Then, the capillary force and the negative pressure are kept in an equilibrium state at a preferable position, so that the ejection from the recording element is stably performed. During recording, the pumps 101 and 105 are stopped and the electromagnetic valve 108 is opened. The ink in the sub tank 102 is gradually consumed with recording, but the ink remaining amount in the sub tank 102 is managed by the ink remaining amount detection sensor 115 including electrodes. Ink is supplied from the ink tank 106 using the pump 105.

  When the recovery process of the recording head 107 is performed, the ink is forcibly circulated by the pump 101 and the pump 105. While ink is supplied to the recording head by the pump 101, continuous ink is discharged from each recording element of the recording head 107 toward the recovery bowl 104, and the ink stored in the recovery bowl 104 is sucked by the pump 105. The waste ink tank 115 is discarded. The ink remaining on the surface of the ejection port of the recording head 107 is wiped off by a blade 116 made of an elastic member disposed on the recovery rod 104, and then the recording head 107 is preliminarily ejected into the recovery rod 104. Recording is enabled by performing.

  Each of the mechanisms described above corresponds to a recovery mechanism portion of the ink jet recording apparatus that is not shown, and is arranged inside the ink jet recording apparatus main body.

  FIG. 2 is a conceptual diagram for explaining the configuration of the inkjet recording head 107 applied in this embodiment. A plurality of recording elements 205 for discharging ink are formed in the recording head 107 at a predetermined density, and the discharge ports 208 provided in each of the recording elements 205 are the surface of the recording head on which the discharge ports are provided. Many (orifice surfaces) 209 are arranged at a predetermined density. As the ink flow, first, the ink supplied from the sub tank 102 passes through the filter 113 from the ink supply port 201 and then enters the common liquid chamber 204 through the supply path 203. The ink stored in the common liquid chamber 204 is then divided into each recording element 205 and used for ejection, and does not go to the recording element 205 but passes through the common liquid chamber 204 as it is, and returns the supply path 206. Through the filter 207 and return to the sub tank 102 from the ink suction port 208. During recording, the ink consumed by being discharged from the discharge port 208 is refilled from the sub tank 102 through the ink supply port 201. At this time, the orifice surface 209 is arranged at a higher position between the ink liquid level in the sub tank 102 and the orifice surface 209 of the recording head 107, and the head surface 209 always has a uniform water head difference. Thus, the meniscus in the recording element is suitably maintained and stable ejection is possible.

  FIG. 3 is a schematic diagram for explaining the configuration of the recording element 205 of the recording head 107 applied in this embodiment in more detail. An ink path 307 that communicates with the ejection port 208 that ejects ink includes an element substrate 301, a top plate 303 joined to the element substrate 301, and an orifice plate 304 joined to these from the front end surface.

  The element substrate 301 is provided with a heating element 302 that gives thermal energy for generating bubbles in the liquid (here, ink), and the heating element 302 is obtained by patterning an electric resistance layer and wiring. . When recording is performed, the heating element 302 generates heat by applying a voltage from the wiring to the electric resistance layer and causing a current to flow through the electric resistance layer. Due to the rapid heat generation of the heating element 302, bubbles are generated in the ink existing in the ink path 307, and an amount of ink corresponding to the volume of the generated bubbles is discharged from the discharge port 298. Although not shown in the figure, a sensor for detecting the heat storage temperature of the element substrate 301 and the heating element 302 is arranged on the element substrate 301, and the head of the head is set according to the detected temperature of the sensor. Driving conditions are determined.

  Further, a sub-heater 306 is provided in the common liquid chamber on the element substrate 301. This is provided for the purpose of performing stable ejection within a predetermined range by keeping the temperature of the ink in the recording head 107 constant and stabilizing the viscosity of the ink.

  The top plate 303 is for constituting a common liquid chamber 204 for supplying a liquid in common to the ink path 307 and the plurality of ink paths 307 in which the heat generating body 302 is arranged. Correspondingly, a partition 309 is integrally provided to define an ink path.

  The orifice plate 304 is bonded to the end portion of each ink path 307, thereby forming a plurality of ejection ports 208 communicating with the common liquid chamber 204 via the respective ink paths 307.

  FIGS. 4A to 4D are diagrams for explaining the generation state of bubbles accumulated in the common liquid chamber 204 when the recording head 107 performs recording.

  In FIG. 4A, when a recording signal is input, application of voltage to the heating element 302 is started.

  In FIG. 4B, the heating element 302 to which a voltage is applied generates heat, and bubbles 401 are generated in the ink existing in the ink path 307. At the same time, the ink in the flow path is gradually pushed out toward the discharge port due to the pressure of the bubbles expanding.

  In FIG. 4C, the expanded bubble finally reaches the discharge port 208 and collapses. At this timing, the ink in the vicinity of the heating element is ejected.

  In FIG. 4D, in the liquid chamber after ejection, the ink consumed for ejection is refilled by the capillary force of the ink path 307 to prepare for the next ejection. However, some small bubbles that are generated when the foam is abruptly accumulated as residual bubbles 402 in the liquid chamber.

  FIGS. 5A to 5C show a state in the common liquid chamber that changes over time by repeating the foaming and discharging described in FIG.

  In FIG. 5A, only the ink is filled in the initial state before starting the recording.

  In FIG. 5B, when recording is started from the state of FIG. 5A and discharge is repeated for a while, residual bubbles 501 that are not excluded from the discharge ports 208 gradually accumulate in the common liquid chamber 204. . In this state, it is possible to eject ink, but since there is a possibility that stable ejection cannot be performed, it is preferable to actually perform a recovery process before this state is reached.

  FIG. 5C shows a state in the liquid chamber when the discharge is continued without performing the recovery process from the state of FIG. 5B. Here, many residual bubbles 501 that are small bubbles are accumulated, and the large bubbles 502 occupy the common liquid chamber 204. In such a situation, the path for supplying ink to the vicinity of the ejection port is blocked, so that not only stable ejection cannot be performed, but also the large bubble 502 makes the ejection itself impossible.

  In this embodiment, in order to avoid such a discharge failure due to bubbles accumulated in the liquid chamber, a recovery operation is performed as needed before falling into the situation as shown in FIG. A recovery method for removing bubbles in the liquid chamber performed in the present embodiment will be described below.

  FIGS. 6A to 6D show the recovery operation performed for removing bubbles in the liquid chamber over time. Hereinafter, description of each process is demonstrated, also referring FIG.

  FIG. 6A shows a state in which a certain amount of bubbles are accumulated in the common liquid chamber 204 with recording, as in FIG. 5B. At such a stage, in order to perform the bubble removal recovery operation, the recording apparatus brings the recovery rod 104 and the recording head 107 closer to each other and positions them in an arrangement called a circulation position. The circulation position will be described later with reference to the drawings. Basically, the circulation position is such that the ink flowing out from the ejection port 208 can be efficiently collected in the recovery tank 104.

  When positioned in the proper position, referring to FIG. 1, the pump 101 operates with the solenoid valve 108 closed. As a result, the ink in the sub tank 102 is forcibly supplied to the head 107 via the ink supply path 117 and the filter 113. Since the electromagnetic valve 108 is closed, the common liquid chamber and the flow path in the recording head 107 are pressurized with a relatively strong pressure, and the ink in the vicinity of the ejection port is gradually and forcibly discharged from the ejection port ( FIG. 6 (b)).

  As the pressurization continues, the bubbles present in the common liquid chamber are pushed out from the discharge port (FIG. 6C).

  Then, by flowing down the ink guide in the recovery rod 104, the outflowed ink and bubbles are removed from the common liquid chamber 204 (FIG. 6D).

  (2) In the recovery operation of the present embodiment using the pump with the electromagnetic valve 108 closed as described above, the ink flow path is pressurized by a strong pressure, unlike the refill force due to the capillary phenomenon during recording. Therefore, the bubbles in the liquid chamber can be forcibly moved and discharged toward the discharge port. In addition, if sufficient pressure is applied to remove bubbles, it is not necessary to inject more ink than necessary from the sub tank. Therefore, compared to the recovery operation described in the background section, the amount of ink to be discarded is discarded. The amount can also be reduced. The flow rate of ink fed by the pump 101 is preferably less than the liquid chamber volume of the print head or less than the total volume of the ink paths of a plurality of print elements, and the pump 101 applied in this embodiment realizes this value. It is possible.

  The ink collected in the recovery tank 104 is sucked by the suction pump 105 and is discarded to the waste liquid tank through the filter 111. Thereafter, in order to remove the pressure remaining in the flow path to some extent, the electromagnetic valve 108 is once opened to disperse the pressure. Further, in order to completely remove the pressure in the flow path, the electromagnetic valve 108 is closed again, and preliminary discharge is performed from the discharge port 208 into the recovery rod 104. After the pressure is completely removed in this way, the electromagnetic valve 108 is opened again, and after returning to the state at the time of recording, the ink remaining on the orifice surface of the recording head in which the ejection ports 208 are arranged is used as a blade made of an elastic member. After wiping with 106, final preliminary ejection is performed in the recovery rod 104 to prepare a recording element again, and a normal recording is possible.

  FIG. 7 is a schematic cross-sectional view for explaining the positional relationship between the recording head 107 and the recovery mechanism such as the recovery rod 104 in each operation performed by the ink jet recording apparatus of the present embodiment.

  FIG. 7A shows the circulation position. The circulation position is applied when bubbles in the liquid chamber are removed as described above. Here, when the ink flows from the recording head 107 to the recovery tub 104, the ink is efficiently collected through the ink guide 703 in the tub.

  FIG. 7B shows the blade position. The recovery process of this embodiment includes a recovery process for removing ink mist accumulated on the orifice surface of the recording head 107 during recording in addition to the recovery process for removing bubbles accumulated in the common liquid chamber 204 as described above. is there. The latter recovery process for removing the ink mist is performed at the blade position in FIG. The blade position is a position for the blade 106 made of an elastic member attached to the side of the recovery rod 104 to clean the surface of the recording head 107. From the position in the figure, the recording head 107 and the blade 106 are relatively By horizontally moving in the direction of the arrow, ink mist remaining on the orifice surface of the recording head 107 can be removed.

  FIG. 7C shows a cap position when ink is preliminarily ejected from the recording head 107 at times other than standby and recording. In this case, the cap 706 provided on the upper part of the recovery rod 104 covers the orifice surface of the recording head 107 so that the ink discharged from the discharge port does not scatter to the other.

  FIG. 7D shows a recording position when the recording head 107 actually performs recording. At the recording position, the recording head 107 and the recovery mechanism that are in a positional relationship facing each other in FIGS. 7A to 7C are completely displaced in the horizontal direction, and the recording head 107 records on the recording medium 709. Therefore, the recording medium 709 is lowered to the conveyance surface.

  Next, control performed by the ink jet recording apparatus according to the present embodiment in order to prevent non-ejection due to bubbles will be described.

  FIG. 8 is a block diagram for explaining a configuration of a control system in the ink jet recording apparatus applied in the present embodiment.

  In the figure, reference numeral 801 denotes a CPU which reads out programs and the like stored in a memory ROM provided therein and executes control of the entire recording apparatus such as a flow shown in FIG.

  Reference numeral 802 denotes a conveyance motor drive circuit. The voltage pulse generated by the conveyance motor drive circuit 802 is input to the conveyance motor 805, so that the conveyance motor 805 is driven, whereby the recording medium is conveyed at a predetermined speed.

  Reference numeral 803 denotes a recording head driving circuit. By applying the generated drive pulse to the recording head 107 at a predetermined frequency, ink is ejected at an ejection frequency according to the given frequency, and can be landed on the recording medium being conveyed. The CPU 801 can control the conveyance speed of the conveyance motor 805 and the ejection frequency of the recording head 107 in accordance with the image recording density.

  Reference numeral 806 denotes a counter for counting the number of ejections of the recording head 107.

  Reference numeral 804 denotes a recovery system unit control circuit. The CPU 801 can independently control the solenoid valves (108, 110, 111), the pump 101, and the pump 105 via the recovery system unit control circuit.

  The operation of the recovery sequence having the above configuration will be described below with reference to flowcharts.

  FIG. 9 is a graph showing the difference in temperature rise due to the difference in specific heat between the bubble remaining in the flow path and the ink when the same heat quantity Q (J) is applied to the ink flow path in the recording element. Assuming that the temperature rise in the flow path is ΔT, the remaining ink amount is L (g), and the specific heat of the ink is A (J / g · K), these are expressed by the function shown in Equation 9. Here, assuming that the specific heat A of the ink is constant, the temperature rise ΔT varies depending on the amount of remaining ink. That is, as the amount of bubbles increases, the amount of remaining ink decreases, and the value of the temperature increase ΔT increases. In the graph, time is plotted on the horizontal axis and temperature rise ΔT is plotted on the vertical axis, and there is a relationship as shown in the figure when there are many bubbles (a) and when there are few bubbles (b).

  FIG. 10 is a flowchart for explaining each step in the recovery sequence performed by the ink jet recording apparatus of this embodiment.

  When the recovery sequence is started, first, the temperature (T1) of the flow path in the recording head is detected in step S101. Next, a certain amount of heat (QJ) is applied to the recording head flow path (step S102). Thereafter, the temperature (T2) in the recording head channel is detected again (step S103). Further, a difference (T3) between the detected temperatures T1 and T2 is calculated, and it is determined whether or not this value is larger than Tair (step S104). Here, Tair indicates a temperature rise value when a heat quantity (QJ) is applied just before bubbles are accumulated in the flow path of the recording head and a recording failure occurs. If T3> Tair in step S104, the process proceeds to step S105 to perform recovery processing. If T3 ≦ Tair, the process returns to step S101.

  In the above description, as an embodiment in which bubbles are likely to accumulate in the liquid chamber, an example of an ink jet recording apparatus using a line printer using a line head and performing ejection by applying thermal energy to each recording element is taken as an example. However, the present invention is not limited to this. Even if it is a serial type recording device instead of a line printer, or an ink jet recording device other than a system that applies thermal energy to each recording element, bubbles accumulated in the liquid chamber can be removed without consuming excess ink. The effect of the present invention that it can be efficiently removed is effective.

  The present invention can be used in an ink jet recording apparatus that forms an image by supplying ink to a recording head and discharging the ink from the recording head.

It is the conceptual diagram which showed the recovery processing system of the inkjet recording device conventionally applied with this invention. It is a conceptual diagram for demonstrating the structure of the inkjet recording head applied by embodiment of this invention. FIG. 3 is a schematic diagram for explaining a configuration of a recording element of a recording head applied in an embodiment of the present invention. It is a figure for demonstrating the generation | occurrence | production condition of the bubble which accumulates in a common liquid chamber. It is the figure which showed the mode of the time-dependent change in a common liquid chamber. It is a figure for explaining the recovery process in the embodiment of the present invention over time. FIG. 4 is a schematic cross-sectional view for explaining a positional relationship between a recording head and a recovery mechanism. It is a block diagram for demonstrating the structure of the control system in the inkjet recording device applied by embodiment of this invention. It is a figure showing the graph which shows the difference of the temperature rise by the ratio of the bubble and ink with respect to the same calorie | heat amount Q (J). It is a flowchart for demonstrating the recovery sequence which the inkjet recording device of this invention performs.

Explanation of symbols

101, 105 Pump 102 Sub tank 103 Air communication port 104 Recovery tank 106 Ink tank 107 Recording head 108 Solenoid valve 110, 111 Solenoid valve 112, 113, 114 Filter 115 Ink remaining amount sensor 116 Blade 117 Ink supply path 118 Collection path 119 Waste liquid tank 201 Ink supply port 203 Supply path 204 Common liquid chamber 205 Recording element 206 Return supply path 208 Ink outlet 209 Orifice surface 301 Element substrate 302 Heating element 303 Top plate 304 Orifice plate 306 Subheater 307 Channel 309 Channel wall 401 Bubble 402 Residual Bubble 501 Residual bubble 502 Bubble 703 Ink guide 705 Orifice surface 706 Cap 709 Recording medium

Claims (5)

In an inkjet recording apparatus that performs recording using a recording unit that discharges ink from a plurality of recording elements,
Tank means for supplying ink to the recording means;
First and second ink flow paths connecting the tank means and the recording means;
A pump provided in the first ink flow path for supplying ink from the tank means to the recording means;
Valve means provided in the second ink flow path and capable of controlling the flow of ink in the second ink flow path;
When the recovery operation for maintaining the ink discharge state of the recording unit in a good state is performed, the pump is operated in a state where the flow of ink in the second ink channel is stopped by the valve unit. Recovery control means for supplying ink from the tank means to the recording means via the first ink flow path, and causing the ink to flow out of the recording element by the pressure of the supplied ink;
A temperature change detecting means for detecting a temperature rise value by applying a predetermined amount of heat inside the recording means;
And determining whether or not there is a predetermined amount or more of bubbles in the recording means based on the value of the temperature rise obtained by the temperature change detecting means, and determining whether or not there is a predetermined amount or more in the recording means. An ink jet recording apparatus, wherein the recovery control means drives the pump when bubbles are present.   2. The ink jet recording apparatus according to claim 1, wherein the temperature change detecting means is disposed in the vicinity of the ink discharge portion of the recording element or in the flow path thereof.   Utilizing the fact that the value of the temperature rise inside the recording means detected by the temperature change detecting means differs depending on the amount of ink present inside the recording means, the bubbles above the predetermined amount inside the recording means 3. The ink jet recording apparatus according to claim 1, wherein it is determined whether or not there is.   The ink jet recording apparatus according to claim 1, wherein a line head is applied as the recording unit. The recording element is provided with an ejection port for ejecting ink, a liquid path communicating with the ejection port, and a film boiling in the ink as energy used for ejecting the ink. The recording apparatus according to claim 1, further comprising: a heat generating element that generates heat energy.

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