JP2007105907A - Inkjet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stir ink in an ink tank and to disperse ink components by carrying out suction and ejection by connecting a diaphragm pump as a stirring means to the ink tank. <P>SOLUTION: A pump means is prepared which can suck and eject the ink in the ink tank from the same ink passage. Moreover, the air is mixed in the ink tank. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus, and more particularly, to an ink jet recording apparatus capable of always performing good recording from the start of use of ink stored in an ink tank to the end of use.

  The inks used in the ink jet recording apparatus can be roughly classified into two types, one is a dye-based ink, and the other is a pigment-based ink. Among these, pigment-based inks, in particular, have higher water resistance and light resistance than dye-based inks, so the amount used is increasing year by year. On the other hand, the ink tank for storing the ink can be roughly divided into three types.

  The first ink tank is a full sponge type ink that stores an absorber in an ink tank and generates a negative pressure for forming an ink meniscus at an ink discharge port by holding the ink in the container. The second ink tank is a semi-raw ink tank provided with an ink chamber containing an absorber for generating negative pressure and an ink liquid chamber for improving ink containing efficiency. The tank is a raw ink tank that contains only ink without providing an absorber.

  Here, among the above-described conventional examples, particularly when pigment-based ink is accommodated and held in a liquid chamber that does not have an absorber or the like, such as a semi-life or raw ink tank, the pigment or the like dispersed in the ink over time There are cases where the ink constituents settle vertically downward in the ink tank and the balance of the ink constituents to be uniformly dispersed in the ink liquid is lost. When such a problem occurs, for example, the density is lowered to about 75% or less or the fixing property is deteriorated.

  On the other hand, when the viscosity of the ink is increased, adverse effects such as an adverse effect on the ejection recovery property and the fixing property are brought about. In order to solve this problem, there is an invention having a pump unit capable of sucking and discharging ink in an ink tank from the same ink flow path (see, for example, Patent Document 1).

  The conventional pump means will be described below with reference to FIG.

  In FIG. 5, the flow path of the ink supply system will be described. 52A passes through the rubber plug 513 of the ink tank 501 and is hollow to send the ink in the ink tank 501 out of the ink tank 501. The ink supply hollow needle is composed of a needle and forms a part of the ink flow path, and 76 is connected to the ink supply hollow needle 52A to form an ink flow path to the recording head 401. The ink supply tube 222A passes through a rubber plug 416A provided on the recording head 401 mounted on the carriage 200 and supplies ink from the ink tank 501 to the ink liquid chamber in the recording head 401. This is a hollow needle for supplying ink.

  On the other hand, by applying a negative pressure to the ink chamber formed in the recording head 401, ink is supplied from the ink tank 501 to the recording head 401 via the ink supply tube 76 that is a flow path of the ink supply system. In the suction system, 222B is a suction hollow needle that penetrates the other rubber plug 416B provided in the recording head 401 and forms an ink flow path inside. Reference numeral 300 denotes the above-described recovery system unit, which selectively closes one of the supply valve 311 and the recovery valve 312 to generate a negative pressure in the recording head 401 to cause ink from the ink tank 501 to the recording head 401. And a pump capable of performing a recovery process of the recording head 401 by generating a negative pressure in the cap 321.

Further, it is necessary to apply a predetermined negative pressure to the nozzles provided in the recording head 401 so that the orifice on the nozzle surface of the recording head 401 is not destroyed by pressurization. Therefore, in this embodiment, the tip position of the air supply hollow needle 52B pierced in the ink tank 501 is configured to be lower than the nozzle of the recording head 401 by the optimum water head difference for the recording head 401. This is because the air pressure in the ink tank 501 becomes negative as the recording head 401 uses ink, and air is taken into the ink tank 501 through the air supply tube 323 and the air supply hollow needle 52B. This is because the tip position of the needle 52B in the ink tank 501 is atmospheric pressure. Reference numerals 325 and 52C denote a stirring tube and a hollow needle that form a flow path from the stirring pump 400 to the ink tank 501.
Japanese Patent Laid-Open No. 2002-19137 (5th page, FIG. 6)

  However, in the above-described conventional example, with the recent increase in capacity of the ink tank, there is a possibility that not all the ink in the ink tank can be stirred with the pump means alone. Accordingly, the present invention has been made in view of the above-described problems in the prior art, and an object thereof is to stir the ink stored in the ink tank by a simple mechanism to disperse the ink constituents. Another object of the present invention is to provide an ink jet recording apparatus that can always perform good recording from the beginning of use of ink until it is used up.

  As a specific configuration in the present invention, the ink in the ink tank is agitated by pump means, and air is mixed into the ink tank.

  In order to achieve the above object, an ink jet recording apparatus of the present invention is an ink jet recording apparatus having a recording head for recording by discharging ink, and sucking and discharging ink in an ink tank from the same ink flow path. It has a pump means that can do this, and air is mixed in the ink tank.

  Further, the pump means is provided in a recording apparatus.

  Further, the pump means is a diaphragm pump.

  The ink may be pigment-based.

  The recording head may include an electrothermal transducer that generates thermal energy that causes film boiling in the ink as an element that generates energy used to eject the ink.

  The ink jet recording apparatus of the present invention is an ink jet recording apparatus having a recording head for performing recording by discharging ink, and has a pump means capable of sucking and discharging ink in an ink tank from the same ink flow path. In addition, since air is mixed into the ink tank, the ink can be effectively stirred with a simple configuration.

  Further, since the pump means is provided in the recording apparatus, the ink can be satisfactorily stirred with a compact structure.

  Further, since the pump means is a diaphragm pump, the ink is efficiently stirred.

  Further, since the ink is pigment-based, the ink is excellent in water resistance and light resistance and can be recorded clearly.

  In addition, the recording head has an electrothermal transducer that generates thermal energy that causes film boiling in the ink as an element that generates energy used to eject the ink. Can be recorded.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 2 is a diagram showing a schematic configuration of the ink jet recording apparatus according to the position embodiment of the present invention. The inkjet recording apparatus of the present embodiment repeats the reciprocating movement (main scanning) of the recording head 201 and the conveyance (sub-scanning) of the recording sheet S such as general recording paper, special paper, and OHP film at a predetermined pitch. This is a serial type recording apparatus that forms characters, symbols, images, and the like by selectively ejecting ink from the recording head 201 and making it adhere to the recording sheet S in synchronization with these movements.

  In FIG. 2, a recording head 201 is detachably mounted on a carriage 202 that is slidably supported by two guide rails and is reciprocated along the guide rails by driving means such as a motor (not shown). The recording sheet S is opposed to the ink ejection surface of the recording head 201 by the conveying roller 203 and intersects the moving direction of the carriage 202 so as to maintain a constant distance from the ink ejection surface (for example, It is conveyed in the direction of arrow A, which is a direction orthogonal to each other.

  The recording head 201 has a plurality of nozzle rows that eject inks of different colors (for example, four colors of black, cyan, magenta, and yellow). This nozzle row is substantially orthogonal to the main scanning direction. A plurality of independent main tanks (ink tanks) 204 are detachably attached to the ink supply unit 205 corresponding to the color of ink ejected from the recording head 201. The ink supply unit 205 and the recording head 201 are connected to each other by a plurality of ink supply tubes 206 corresponding to the colors of the ink, and the main tank 204 is mounted on the ink supply unit 205 so that the ink is stored in the main tank 204. Each color ink can be independently supplied to each nozzle row of the recording head 201.

  A recovery unit 207 is disposed so as to face the ink ejection surface of the recording head 201 in a non-recording area that is within the reciprocal movement range of the recording head 201 and outside the passing range of the recording sheet S. Yes. The recovery unit 207 is a mechanism that forcibly sucks out ink, bubbles, and the like from the ejection nozzles of the recording head 201 and cleans the nozzles.

  Next, the basic principle of ink supply in this ink jet recording apparatus will be briefly described with reference to FIG.

  The recording head 201 and the main tank 204 are connected by an ink supply tube 206 to form an ink path. This ink path is filled with the ink 209, and the recording head 201 is arranged such that the position of the nozzle 201g is higher than the liquid level of the main tank 204 by the height H, and the inside of the recording head 201 is the water head difference of the height H. The negative pressure is maintained. Due to this negative pressure, the state where the ink meniscus is formed at the tip of the nozzle 201g of the recording head 201 is maintained. This prevents ink leakage from the nozzle 201g and entry of air. When ink is ejected from the nozzle 201g, the amount of ink in the recording head 201 decreases, the negative pressure temporarily increases and the meniscus moves backward, but the nozzle 201g fills the nozzle 201g again by the capillary force of the nozzle 201g, The ink 209 is sucked up from the main tank 204 via the ink supply tube 206, whereby the pressure in the recording head 201 returns to the original state, and the meniscus is stabilized at the tip of the nozzle 201g. Such ejection and ink supply (refilling) are repeated. The ink jet recording apparatus according to this embodiment conforms to this basic principle.

  Next, the detailed configuration of the ink supply system of the ink jet recording apparatus will be described with reference to FIG. FIG. 4 is a diagram for explaining the ink supply path of the ink jet recording apparatus shown in FIG. 2, and only the path for one color is shown for ease of explanation.

  First, the recording head 201 will be described. Ink is supplied to the recording head 201 from a connector insertion opening 201a to which a liquid connector provided at the tip of the ink supply tube 206 is airtightly connected. The connector insertion port 201a communicates with a sub tank portion (first liquid chamber) 201b formed at the top of the recording head 201. A liquid chamber (second liquid chamber) 201f that directly supplies ink to a nozzle portion having a plurality of nozzles 201g arranged in parallel is formed on the lower side in the gravity direction of the sub tank portion 201b. The sub-tank portion 201b and the liquid chamber 201f are partitioned by the filter 201c. The boundary between the sub-tank portion 201b and the liquid chamber 201f has a partition portion 201e in which an opening 201d is formed. It is installed on 201e.

  With the above-described configuration, the ink supplied from the connector insertion port 201a to the recording head 201 is supplied to the nozzle 201g through the sub tank 201b, the filter 201c, and the liquid chamber 201f. The space from the connector insertion port 201a to the nozzle 201g is kept airtight with respect to the atmosphere.

  An opening is formed on the upper surface of the sub tank 201b, and this opening is covered with a dome-shaped elastic member 201h. A space surrounded by the elastic member 201h is a pressure adjusting chamber 201i, and its volume changes according to the pressure in the sub tank 201b, and has a function of adjusting the pressure in the sub tank 201b as described later.

  The nozzle 201g has a cylindrical structure with a cross-sectional width of about 20 μm, and discharges ink from the nozzle 201g by applying discharge energy to the ink in the nozzle 201g. After the ink is discharged, the nozzle 201g is driven by the capillary force of the nozzle 201g. The ink is filled inside. Usually, this discharge is repeated at a cycle of 20 kHz or more, and fine and high-speed image formation is performed. In order to give ejection energy to the ink in the nozzle 201g, the recording head 201 has energy generating means for each nozzle 201g. In this embodiment, a heating resistor element that heats the ink in the nozzle 201g is used as the energy generating means, and the heating resistor element is selected by a command from a head control unit (not shown) that controls the driving of the recording head 201. The ink in the desired nozzle 201g is boiled, and ink is ejected from the nozzle 201g using the pressure of the bubbles generated thereby.

  The nozzle 201g is arranged with the tip for discharging ink facing downward, but no valve mechanism for closing the tip is provided, and the ink fills the nozzle 201g in a state where a meniscus is formed. For this reason, the inside of the recording head 201, particularly the inside of the nozzle 201g, is kept in a negative pressure state. However, if the negative pressure is too small, if foreign matter or ink adheres to the tip of the nozzle 201g, the ink meniscus may collapse and the ink may leak out of the nozzle 201g. On the other hand, if the negative pressure is too large, the force that pulls the ink back into the nozzle 201g becomes stronger than the energy applied to the ink during ejection, resulting in ejection failure. Therefore, the negative pressure in the nozzle 201g is kept in a certain range slightly lower than the atmospheric pressure. The negative pressure range varies depending on the number of nozzles 201g, the cross-sectional area, the performance of the heating resistance element, and the like, but according to the results of experiments by the present inventors, −40 mmAq (about −0.0040 atm = −4.053 kPa) The range of ˜−200 mmAq (about −0.0200 atm = −2.0265 kPa) (however, the specific gravity of ink≈the specific gravity of water) is preferable.

  In this embodiment, the ink supply unit 205 and the recording head 201 are connected by the ink supply tube 206, and the position of the recording head 201 with respect to the ink supply unit 205 can be set relatively freely. In order to obtain a negative pressure, the recording head 201 is arranged at a position higher than the ink supply unit 205.

  The filter 201c prevents foreign matter that clogs the nozzle 201g from flowing out from the sub tank 201b to the liquid chamber 201f. The area of the filter 201c is set so that the pressure loss due to the ink is less than the allowable value. The pressure loss increases as the mesh of the filter 201c becomes finer and the flow rate of ink increases, and is inversely proportional to the area of the filter 201c. In recent high-speed, multi-nozzle and small dot recording devices, pressure loss tends to increase, and a large filter 201c having a size of about 10 × 20 mm is used, and accordingly, upstream of the filter 201c. A large space is also required in the liquid chamber 201f downstream of the sub tank 201b and the filter 201c. The ink in the sub tank 201b is in contact with the upper surface of the filter 201c. The area in contact with this ink is the effective area of the filter 201c. The pressure loss due to the filter 201c depends on the effective area of the filter 201c. In this embodiment, the filter 201c is disposed so as to be horizontal in the usage state of the recording head 201, and ink is brought into contact with the entire upper surface of the filter 201c to maximize the effective area of the filter and reduce the pressure loss. .

  When the filter 201c comes into contact with the ink, the ink soaks into each hole (mesh) by capillary force to form a fine meniscus, which allows easy ink permeation, but makes air circulation difficult. Have. The finer the mesh, the greater the meniscus strength, making it more difficult for air to pass through.

  In the filter 201c of the present embodiment, the pressure required to transmit air is about 0.1 atm (10.1325 kPa) (experimental value). Therefore, if air is present in the liquid chamber 201f located downstream of the filter 201c with respect to the ink moving direction in the recording head 201, the air cannot pass through the filter 201c with the buoyancy of the air itself. The air inside remains in the liquid chamber 201f. In this embodiment, this phenomenon is utilized, the liquid chamber 201f is not filled with ink, and an air layer exists between the ink in the liquid chamber 201f and the filter 201c. A predetermined amount of ink is stored in the liquid chamber 201f so that the ink and the filter 201c are separated from each other.

  Further, when air from the liquid chamber 201f enters the nozzle 201g, ink is not replenished to the nozzle 201g after ink discharge, and discharge failure occurs. Therefore, the nozzle 201g needs to be always filled with ink.

  The pressure adjustment chamber 201i is a chamber whose volume decreases as the internal negative pressure increases. When the pressure adjustment chamber 201i is configured by the elastic member 201h as in the present embodiment, the elastic member 201h is a rubber material. Etc. are preferably used.

  When the pressure adjusting chamber 201i is not provided, the pressure in the sub tank 201b directly receives resistance due to pressure loss when ink passes through the main tank 204, the ink supply unit 205, and the ink supply tube 206. For this reason, in the case of a so-called high duty that ejects ink at a high rate, such as ejecting ink from all the nozzles 201g, the ink supplied to the recording head 201 becomes insufficient with respect to the ejected ink, resulting in a negative pressure. Will rise rapidly. If the negative pressure of the nozzle 201g exceeds -200 mmAq (about -2.0265 kPa), which is the above-mentioned limit value, the ejection becomes unstable, resulting in an inconvenient state in image formation.

  In the serial type recording apparatus as in this embodiment, there is a state in which the ejection of ink is interrupted when the carriage 202 (see FIG. 2) is reversed even in the case of image formation with a high duty. The pressure adjustment chamber 201i plays a role like a capacitor by reducing the volume during ink ejection to relieve the increase in the negative pressure in the sub-tank portion 201b and restore at the time of inversion.

  Next, the ink supply unit 205 and the main tank 204 will be described.

  The main tank 204 is detachable from the ink supply unit 205, and has an ink supply port sealed with a rubber plug 204b and an air introduction port sealed with a rubber plug 204c at the bottom of a rigid tank body. And have. The main tank 204 is an airtight container by itself, and the ink 209 is stored in the main tank 204 as a liquid.

  On the other hand, the ink supply unit 205 includes an ink supply needle 205 a for taking out the ink 209 from the main tank 204 and an air introduction needle 205 b for introducing the atmosphere into the main tank 204. The ink supply needle 205a and the air introduction needle 205b are both hollow needles, and are arranged with the needle points upward corresponding to the positions of the ink supply port and the air introduction port of the main tank 204. By being mounted on the ink supply unit 205, the ink supply needle 205a and the air introduction needle 205b penetrate the rubber plugs 204b and 204c, respectively, and enter the main tank 204.

  The ink supply needle 205a is connected to the ink supply tube 206 through a path of a liquid path 205c, a shutoff valve 210, and a liquid path 205d. The atmosphere introduction needle 205b communicates with the atmosphere via the liquid path 205e, the buffer chamber 205f, and the atmosphere communication port 205g.

  The shut-off valve 210 has a diaphragm 210a made of a rubber material, and opens and closes the two liquid paths 205c and 205d by displacing the diaphragm 210a. A cylindrical spring holder 210b for holding a pressing spring 210c is attached to the upper surface of the diaphragm 210a. By crushing the diaphragm 210a via the spring holder 210b by the pressing spring 210c, the liquid paths 205c, Between 205d is interrupted. The spring holder 210b has a flange with which a lever 210d operated by the link 207e is engaged. By operating the lever 210d and lifting the spring holder 210b against the spring force of the pressing spring 210c, the liquid paths 205c and 205d communicate with each other.

  The configuration of the ink supply unit 205 described above is provided for each main tank 204, that is, for each ink color (four colors of black, cyan, magenta, and yellow in this embodiment), except for the lever 210d. The lever 210d is common to all colors, and simultaneously opens and closes the shut-off valves 210 for all colors.

  With the above configuration, when ink in the recording head 201 is consumed, the negative pressure causes ink to be supplied from the main tank 204 to the recording head 201 via the ink supply unit 205 and the ink supply tube 206 as needed. At that time, the same amount of air as the ink supplied from the main tank 204 is introduced into the main tank 204 from the atmosphere communication port 205g through the buffer chamber 205f and the atmosphere introduction needle 205b.

  The buffer chamber 205f is a target space for temporarily holding ink that has flowed out of the main tank 204 due to the expansion of air in the main tank 204, and the lower end of the air introduction needle 205b is located at the bottom of the buffer chamber 205f. .

  FIG. 1 is a diagram showing the configuration of the stirring pump means 211.

  In the illustrated agitation pump means 211, a drive transmission mechanism 213 including gears and cams (not shown) is connected to a pump drive motor, and this pump drive motor 212 is a drive source for the agitation pump means 211. . Now, the pump drive motor 212 is driven, and the pump drive mechanism 213 is driven up and down by the cam drive of the drive transmission mechanism 213. The stirring pump 214 connected to the pump driving mechanism and pulling and pushing in synchronization with the vertical movement of the driving mechanism is located in the middle of the shutoff valve 210 and the main tank 204 in the ink supply tube 206 path, A member capable of inflow and outflow of ink by changing the internal volume. In this embodiment, a diaphragm is employed for the stirring pump 214. When stirring the ink in the main tank 204, it is desirable to block the shutoff valve 210. Thus, the ink in the stirring pump 214 flows in and out in one direction toward the main tank, and the ink in the main tank 204 can be stirred more efficiently.

  However, since this stirring means can only stir only around the bottom of the main tank 204, when the main tank has a large capacity, the entire region cannot be stirred. Therefore, the pump motor 207 d is driven with the suction cap 207 a capped, and ink is sucked from the recording head 201. The sucked ink is consumed from the main tank 204 through the supply tube, and the same amount of air as the consumed ink is mixed into the main tank through the atmosphere communication channel 216. When air is mixed into the ink, the air moves upward while lifting the dark ink at the bottom.Therefore, of the ink in the main tank, convection occurs where the light ink at the top moves downward and the dark ink at the bottom moves upward. The entire ink tank can be stirred.

Configuration diagram of pump mechanism for stirring A perspective view showing a schematic configuration of an ink jet recording apparatus of an embodiment Basic principle of ink supply in an ink jet recording apparatus Detailed configuration diagram of ink supply system of inkjet recording apparatus Schematic configuration diagram of an ink supply system of a conventional ink jet recording apparatus

Explanation of symbols

201 Recording Head 201a Connector Insertion Port 201b Subtank Portion (First Ink Chamber)
201c filter 201d opening 201e partitioning part 201f liquid chamber (second ink chamber)
201 g Discharging nozzle 201 h Elastic member 201 i Pressure adjusting chamber 202 Carriage 203 Conveying roller 204 Main tank (ink tank)
204b Rubber stopper 204c Rubber stopper 205 Ink supply unit 205a Ink supply needle 205b Atmospheric introduction needle 205c Channel 205d Channel 205e Channel 205f Buffer chamber 205g Atmospheric communication port 205h Circuit 206 Ink supply tube 207 Recovery unit 207a Suction cap 207b Cam 207c Suction Pump 207d Pump motor 207e Link 207f Cam 207g Cam control motor 209 Ink 210 Shut-off valve 210a Diaphragm 210b Spring holder 211 Stirring pump mechanism 212 Pump drive motor 213 Drive transmission mechanism 214 Stirring pump 215 Pump drive mechanism 216 Atmospheric communication channel 52A Hollow Needle 52B Hollow needle 52C Hollow needle 76 Supply tube 78 Suction tube 90 Power supply unit 91 Cable 93 -200 carriage 222A hollow needle 222B hollow needle 300 recovery unit 311 supply valve 312 recovery valve 321 cap 323 air communication tube 325 stirred tube 401 recording head 416A rubber stopper 416B rubber stopper 501 ink tank 513 rubber stopper

Claims (5)

In an inkjet recording apparatus having a recording head for recording by discharging ink,
An ink jet recording apparatus comprising: pump means capable of sucking and discharging ink in an ink tank from the same ink flow path; and air mixed in the ink tank.   2. An ink jet recording apparatus according to claim 1, wherein said pump means is provided in the recording apparatus.   3. An ink jet recording apparatus according to claim 1, wherein said pump means is a diaphragm pump.   4. The ink jet recording apparatus according to claim 1, wherein the ink is a pigment system.   2. The ink jet recording according to claim 1, wherein the recording head includes an electrothermal transducer that generates thermal energy that causes film boiling in the ink as an element that generates energy used to eject the ink. apparatus.

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