JP3610308B2 - Inkjet recording device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present inventionThe present invention relates to an ink jet recording apparatus.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, recording apparatuses that perform recording on a recording medium include various recording systems such as a wire dot system, a thermal system, a thermal transfer system, and an inkjet system. Among these, an ink jet recording apparatus that performs recording on a recording medium by discharging minute ink droplets from a minute nozzle is a recording apparatus of a so-called non-impact recording method, and can be used for high-density and high-speed recording and various recording media. Recording is possible, and there is an advantage that noise during recording hardly occurs, and it is widely used.
[0003]
A general ink jet recording apparatus includes a recording head, a conveying unit that conveys recording paper, and a control unit for controlling these. In order to generate energy for ejecting ink from the nozzles of the ink jet recording head, pressure is applied to the ink using an electromechanical transducer such as a piezo element, or heat is generated by irradiating an electromagnetic wave such as a laser. There are those that foam, and those that heat and foam a liquid with an electrothermal conversion element having a heating resistor. Among them, an ink jet recording apparatus of a system (bubble jet system) that ejects ink droplets using thermal energy can record high resolution because the nozzles can be arranged at high density. In particular, an ink jet recording head using an electrothermal transducer element as an energy generating element can be easily miniaturized, and has recently applied IC technology and micro processing technology that have made remarkable progress in technology and improved reliability in the field of semiconductor manufacturing. By fully utilizing the advantages, high-density mounting is easy and the manufacturing cost can be reduced.
[0004]
The conventional ink jet recording apparatus shown in FIG. 6 is a serial type in which a recording head is mounted on a carriage (not shown) and a recording operation is performed while moving the carriage. The recording head and the main tank are connected to a tube. It is a so-called tube supply type connected by the above. The ink jet recording apparatus includes a main tank (ink tank) 104 that stores ink, a recording head 101 that ejects ink droplets using thermal energy, and an ink for supplying ink from the main tank 104 to the recording head 101. An ink supply unit 105 and an ink supply tube 106; an exhaust tube 110a and a shut-off valve 110b and an exhaust pump 110c for opening the recording head 101 to the atmosphere; and a recovery unit 107 that performs recovery processing of the recording head 101. Yes.
[0005]
First, a schematic configuration of the recording head 101 will be described. The ejection nozzle 101g of the recording head 101 is a fine hole. There is no valve mechanism in the nozzle 101g, and the inside of the nozzle is kept at a negative pressure and an ink meniscus is formed at the tip, thereby preventing ink leakage from the nozzle 101g and entry of the atmosphere. This point will be described in detail. Since the nozzle 101g is open to the atmosphere, and the opening surface of the nozzle 101g is arranged facing downward, the recording is performed in order to prevent ink leakage from the nozzle 101g. The inside of the head 101 needs to be maintained at a negative pressure. On the other hand, if the negative pressure is too high, air will enter the nozzle 101g and ink cannot be ejected from the nozzle 101g. Therefore, in order to set the inside of the recording head 101 to an appropriate negative pressure state, the position of the opening surface of the nozzle 101g is set to a position higher by a height H than the liquid level of ink in the ink chamber 105f described later. The recording head 101 is disposed, and the inside of the recording head 101 is maintained at a negative pressure of a head differential of height H. As a result, the nozzle 101g is kept in a state of being filled with ink while a meniscus is formed on the opening surface.
[0006]
Ink is ejected by pushing out the ink in the nozzle 101g by the film boiling energy of a heater (heating resistor) (not shown) disposed in the vicinity of the nozzle 101g. After ejection, the nozzle is filled with ink again by the capillary force of the nozzle 101g, and the ink is sucked up from the main tank 104 through the ink supply tube 106 as needed. Such ejection and ink supply (refilling) are repeated.
[0007]
Inside the recording head 101, a filter 101c having a fine mesh structure that prevents clogging of fine holes in the nozzle 101g, a thinly branched channel 101f that connects the filter 101c and the nozzle 101g, and a filter 101c A sub-tank portion 101b that stores a certain amount of ink upstream is disposed, and the ink flowing from the ink supply tube 106 is supplied to the nozzle 101g.
[0008]
Next, schematic configurations of the main tank 104 and the ink supply unit 105 will be described. These have substantially the same configuration as that disclosed in, for example, Japanese Patent No. 2929804, and a hollow ink supply needle 105a and a hollow air introduction needle 105b fixed to the ink supply unit 105 are connected to the main tank. It penetrates through the connector 104 b on the bottom surface of 104 and enters the main tank 104. Inside the ink supply unit 105, there is an ink chamber 105f that is opened to the atmosphere by an atmosphere communication port 105g. In the ink chamber 105f, the two needles 105a, 105b are used for ink with the lower end height changed. Arranged to soak. The bottom of the ink chamber 105f communicates with the ink supply tube 106. As the ink is consumed, the ink in the ink chamber 105f decreases, and the lower end of the air introduction needle 105b is separated from the ink and exposed to the air. Therefore, air enters the main tank 104 from the lower end of the air introduction needle 105b, and ink in the main tank 104 flows out to the ink chamber 105f accordingly. When the ink flows and the liquid level in the ink chamber 105f rises, the lower end of the atmosphere introduction needle 105b is immersed again in the ink, and the introduction of the atmosphere into the main tank 104 and the inflow of the ink into the ink chamber 105f are completed. In this way, the ink in the main tank 104 is gradually taken out.
[0009]
Under the main tank 104, an electrode 104e is installed in contact with the ink and is electrically connected to a contact 105j installed in the ink supply unit 105. A detection circuit including a detector 105h that measures the electrical resistance of the ink is connected between the contact 105j and the air introduction needle 105b. The presence or absence of ink can be detected by measuring the electrical resistance of the ink with this detection circuit.
[0010]
Next, the exhaust tube 110a, the shutoff valve 110b, and the exhaust pump 110c will be described. In the sub-tank portion 101b of the recording head 101, there is a possibility that air that penetrates through a resin material such as the ink supply tube 106 or air dissolved in the ink accumulates. Therefore, the accumulated excess air is periodically sucked and discharged together with ink from the side portion of the sub tank portion 101b by the exhaust tube 110a and the exhaust pump 110c. When the discharge is completed, this path is sealed by the shutoff valve 110b.
[0011]
Next, the recovery unit 107 will be described. The recovery unit 107 has a suction cap 107a for removing the thickened material and bubbles when the ejected nozzle 101g is clogged with ink thickened material or when extra bubbles generated during ink ejection are clogged. Is in close contact with the recording head 101, and the ink is vigorously sucked from the nozzle 101g by a suction pump, and at the same time, the thickening material and bubbles are sucked to recover the recording head 101.
[0012]
[Problems to be solved by the invention]
In the conventional ink jet recording apparatus described above, when the heater corresponding to the nozzle 101g is heated for recording to foam the dissolved air in the ink and discharge the ink, the foamed bubbles break up and flow below the filter 101c. There is a phenomenon that bubbles are gradually accumulated in the flow path 101f due to accumulation in the path 101f or collection of fine bubbles dissolved in the ink due to temperature rise around the heater.
[0013]
In the conventional configuration described above, the flow path 101f has a narrowed shape, so that the ink flow tends to stagnate within the flow path 101f and bubbles do not easily move. If suction is performed vigorously by the recovery unit 107, the ink flow velocity is increased and the ink and bubbles in the channel 101f can be discharged. However, if the bubbles grow large enough to break the channel 101f, the nozzle 101g Therefore, it is necessary to perform suction frequently by the recovery unit 107 and discharge the bubbles before the bubbles grow so large. Accordingly, the amount of ink that is wasted in each case during suction increases.
[0014]
If the flow path 101f is formed thick so as not to be clogged with bubbles, that is, not clogged with bubbles, the bubbles rise above the flow path 101f, and no matter how much the recovery unit 107 sucks the ink from the nozzle 101g, The air bubbles cannot be sucked and discharged simply by sucking. On the other hand, since the filter 101c has a fine mesh structure, if ink soaks into each hole, a meniscus is formed in each hole and air cannot pass therethrough, so that bubbles can escape to the sub tank 101b. Instead, it accumulates in the upper part of the flow path 101f. By accumulating bubbles, the amount of ink decreases as the volume of air in the flow path 101f increases. When the amount of ink in the flow path 101f decreases, the portion that becomes the ink supply port on the upper surface of the nozzle 101g is eventually exposed to the air, which becomes a fatal problem that the ink supply to the nozzle 101g becomes impossible. There is a risk that.
[0015]
Particularly in recent years, in order to increase the recording speed, the number of nozzles of the recording head and the high-speed driving (high-frequency ejection) have progressed, and there is a tendency that bubbles are generated during printing. As a result, the amount of ink consumed per hour increases, and there is a problem that pressure loss increases in a conventional narrow flow path, resulting in ejection failure.
[0016]
Therefore, an object of the present invention is to prevent the ink amount in the recording head from being significantly reduced and the flow path in the recording head from being cut off by bubbles, thereby reducing the amount of wasted ink discharged that does not contribute to recording in the recovery process. ReduceInkjet recording deviceIt is to provide.
[0017]
[Means for Solving the Problems]
A feature of the present invention is an ink jet recording having a recording head that performs recording by discharging ink from nozzles, a suction unit that forcibly discharges ink from the nozzles from the nozzles, and an ink supply unit that supplies ink to the recording head In the apparatus, the recording head includes a first liquid chamber on the upstream side and a second liquid chamber on the downstream side with respect to the ink flow direction.The first liquid chamber and the second liquid chamber can store air, respectively, and have a filter that is located between the first liquid chamber and the second liquid chamber and separates them. The filter has a mesh structure having a large number of holes with meniscus strength,At least one of the first liquid chamber and the second liquid chamber has a volume determined based on the suction force of the suction means and a desired amount of ink that should exist after suction by the suction means. An ink supply means for containing ink, an ink supply tube for communicating the ink tank and the recording head, and a shutoff valve for opening and closing the ink supply tubeAnd withA suction cap that seals the recording head, and a suction pump that sucks through the suction capWhen filling ink from the ink supply means to the recording head using the suction means, the shut-off valve is closed and the second liquid chamber is reduced to a specific pressure by the suction means, Depending on the meniscus strength of the filter, the pressure in the first liquid chamber is set to a pressure different from the specific pressure, and then the pressure is released by opening the shut-off valve, and the ink in the ink tank is passed through the ink supply tube. Thus, the first liquid chamber and the second liquid chamber are filled with different amounts respectively in one cycle, and the ink can be filled in the one cycle..
Another feature is that the amount of ink to be filled in one filling operation is necessary for the first liquid chamber and the second liquid chamber, which have been depressurized, to return to almost atmospheric pressure, respectively. It is in the volume.
[0018]
According to this, each of the liquid chambers divided into two is filled with ink so that an appropriate amount of ink is present. Even if the flow path in the recording head is wide, both the liquid chambers can be evacuated and filled with ink. In addition, the amount of ink does not become insufficient in both liquid chambers over a long period of time, so frequent recovery suction is not necessary, and the amount of wasteful consumption of ink is reduced. Further, when both the liquid chambers need to be filled with ink, the ink can be saved because only one filling step is required.
[0019]
Another feature of the present invention is that the volume V1 of the first liquid chamber, the reduced pressure value of the first liquid chamber at the time of suction is p1 [atm] (relative value from atmospheric pressure), and exist in the first liquid chamber. The amount of ink to be set is S1, and is set so as to substantially satisfy the relationship of V1 = S1 / | p1 |. Still another feature of the present invention is that the volume V2 of the second liquid chamber, the reduced pressure value of the second liquid chamber during suction is p2 [atm] (relative value from atmospheric pressure), and the second liquid chamber The amount of ink that should exist in the chamber is set to S2, and is set so as to substantially satisfy the relationship of V2 = S2 / | p2 |. Thus, ink can be filled so that the amount of ink in each liquid chamber becomes an appropriate amount by the filling operation using the law of PV = constant.
[0020]
It is preferable to have a filter that is located between the first liquid chamber and the second liquid chamber and separates them. The filter may have a mesh structure having a large number of holes. In that case, the ink meniscus strength pressure in each hole of the filter is pm, the reduced pressure value of the first liquid chamber at the time of suction is p1 [atm] (relative value from the atmospheric pressure), and the second liquid at the time of suction. If the reduced pressure value of the chamber is p2 [atm] (relative value from atmospheric pressure), the relationship of p1 = p2-pm is satisfied, and the volume V1 of the first liquid chamber is the ink that should exist in the first liquid chamber. The volume is set to be S1, so that the relationship of V1 = S1 / | p1 | is substantially satisfied, the volume V2 of the second liquid chamber is set to S2, and the amount of ink to be present in the second liquid chamber is set to S2. = S2 // p2 | is preferably set so as to substantially satisfy the relationship.
[0021]
Explaining this point, if the ink soaks into a filter having a fine mesh structure, a fine meniscus is formed in each hole, and the ink can easily pass through, but air circulation becomes difficult. The finer the mesh, the greater the meniscus strength and the more difficult it is to pass air, and pressure pm is required to permeate the air. This pressure pm can be specified by experiment. When suctioned from the nozzle by the recovery unit, the pressure p2 of the second liquid chamber is lower than the pressure p1 of the first liquid chamber by a pressure pm corresponding to the meniscus strength in order to allow the air in the sub tank portion to pass through the filter. Therefore, if this relationship is used when determining the volume of the liquid chamber, the conditions can be easily determined.
[0022]
The amount of ink that should be present in each of the first liquid chamber and the second liquid chamber is larger than the amount of air accumulated in each of the first liquid chamber and the second liquid chamber. More than the sum of the amount of air accumulated in each of the one liquid chamber and the second liquid chamber and the minimum amount of ink required to guarantee stable performance of the first liquid chamber and the second liquid chamber, respectively. It is preferable.
[0023]
The amount of ink accumulated in the first liquid chamber is larger than the minimum required amount of ink (the amount of ink in which the filter is surely immersed in the ink) in the first liquid chamber, and accumulates in the first liquid chamber for a predetermined time (for example, for a long period such as one month) Ink can be filled so that there is an ink amount S1 greater than the sum of the amounts, and similarly, the second liquid chamber is larger than the minimum required ink amount (the amount of ink that the nozzle is surely immersed in the ink). If the ink can be filled so that there is an ink amount S2 larger than the sum of the air amounts accumulated in the second liquid chamber in the same predetermined period as described above, the filling operation is performed once in the predetermined period. This can be done and can save ink to be discharged.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0025]
FIG. 1 is a perspective view showing a schematic configuration of an ink jet recording apparatus according to an 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.
[0026]
In FIG. 1, 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.
[0027]
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.
[0028]
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.
[0029]
Next, the basic principle of ink supply in this ink jet recording apparatus will be briefly described with reference to FIG.
[0030]
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.
[0031]
Next, the detailed configuration of the ink supply system of the ink jet recording apparatus will be described with reference to FIG. FIG. 3 is a diagram for explaining the ink supply path of the ink jet recording apparatus shown in FIG. 1, and only the path for one color is shown to simplify the explanation.
[0032]
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.
[0033]
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.
[0034]
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.
[0035]
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.
[0036]
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.
[0037]
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.
[0038]
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. .
[0039]
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.
[0040]
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.
[0041]
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.
[0042]
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.
[0043]
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.
[0044]
In the serial type recording apparatus as in the present embodiment, there is a state in which the ejection of ink is interrupted when the carriage 202 (see FIG. 1) is reversed even in the case of image formation at 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.
[0045]
Next, the ink supply unit 205 and the main tank 204 will be described.
[0046]
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.
[0047]
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.
[0048]
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. In this embodiment, the ink supply needle 205a and the air introduction needle 205b are thick with an inner diameter of 1.6 mm in order to suppress the flow resistance of the ink.
[0049]
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 that holds 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, a liquid path 205c, Between 205d is interrupted. The spring holder 210b has a flange with which a lever 210d operated by a link 207e of the recovery unit 207 described later 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 shut-off valve 210 is opened when the recording head 201 is ejecting ink, is closed during standby and during rest, and is opened and closed in synchronization with the recovery unit 207 during an ink filling operation described later.
[0050]
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.
[0051]
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.
[0052]
The buffer chamber 205f is a target space for temporarily holding ink that has flowed out of the main tank 204 due to 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. . When the air in the main tank 204 expands, such as when the environmental temperature rises or the external air pressure drops during standby or rest of the inkjet recording apparatus, the shut-off valve 210 is closed, so the inside of the main tank 204 The ink 209 flows out from the air introduction needle 205b through the liquid path 205e to the buffer chamber 205f. Conversely, when the air in the main tank 204 contracts, such as when the environmental temperature decreases, the ink that has flowed into the buffer chamber 205f returns to the main tank 204. Further, when ink is ejected from the recording head 201 in a state where the ink is present in the buffer chamber 205f, first, the ink in the buffer chamber 205f returns to the main tank 204, and after the ink in the buffer chamber 205f runs out, Air is introduced into the main tank 204.
[0053]
Volume V of buffer chamber 205f_bSet to satisfy the usage environment of the product. For example, if the product is assumed to be used within a temperature range of 5 ° C. (278 K) to 35 ° C. (308 K), if the capacity of the main tank 204 is 100 ml, V_b= 100 * (308-278) / 308 = Set as 9.7 ml or more.
[0054]
Here, the basic head of the main tank 204 and the behavior of air and ink in the liquid path of the ink supply unit 205 when air is introduced into the main tank 204 will be described with reference to FIG.
[0055]
FIG. 4A shows a normal state in which ink can be supplied from the main tank 204 to the recording head 201 (see FIG. 3). In this state, the inside of the main tank 204 is airtight except for the buffer chamber 205f, so the inside of the main tank 204 is kept at a negative pressure, and the leading end 209a of the ink remains in the middle of the liquid path 205e. The pressure at the leading end 209a of the ink is atmospheric pressure (= 0 mmAq) because it is in contact with the atmosphere. The liquid path 205c where the ink tip 209a is located and the liquid path 205e communicating with the ink supply tube 206 (see FIG. 3) have the same height, and the two liquid paths 205c and 205e are communicated only with ink. The pressure in the liquid path 205c is also atmospheric pressure. This is determined by the relationship between the height of the ink tip 209a and the liquid path 205c, and is not affected by the amount of ink 209 in the main tank 204.
[0056]
When the ink in the main tank 204 is consumed, as shown in FIG. 4B, the leading end 209a of the ink gradually moves toward the atmosphere introduction needle 205b and reaches the point immediately below the atmosphere introduction needle 205b. As shown in FIG. 4 (c), the air bubbles become air bubbles and rise inside the air introduction needle 205 b and enter the main tank 204. In exchange for this, the ink in the main tank 204 enters the atmosphere introduction needle 205b, and the leading end 209a of the ink returns to the original state shown in FIG.
[0057]
FIG. 4D shows a state where ink has accumulated in the buffer chamber 205f. In this case, the front end 209a of the ink is located at a position h1 (mm) higher than the liquid path 205c in the middle of the buffer chamber 205f in the height direction, and the pressure of the liquid path 205c is -h1 (mmAq). Yes.
[0058]
As described above, in the present embodiment, the pressure due to the water head difference applied to the nozzle 201g (see FIG. 3) indicates that the height from the flow path 205c to the ink upper surface 209b in the sub tank 201b is h2 (mm) as shown in FIG. If the height from the filter 201c to the ink upper surface 209b in the sub tank 201b is h3 (mm) and the height from the lower end of the nozzle 201g to the ink upper surface 209c in the liquid chamber 201f is h4 (mm), the lower end of the nozzle 201g Negative pressure P at_nIs normally P_n≈−9.8 × (h2−h3−h4) Pa, and in a state where ink is accumulated in the buffer chamber 205f, P_n≈−9.8 × (h 2 −h 1 −h 3 −h 4) Pa P_nIs set to fall within the above-described negative pressure range (−4.053 kPa to −2.0265 kPa).
[0059]
Referring to FIG. 3 again, the ink supply needle 205a and the atmosphere communication needle 205b are connected to a circuit 205h for measuring the electrical resistance of the ink, so that the presence or absence of ink in the main tank 204 can be detected. This circuit 205h detects an electrical close because an electric current flows to the circuit 205h via the ink in the main tank 204 when ink is present in the main tank 204, and no ink is present or the main tank 204 An electrical open is detected when is not attached. Since the detection current is weak, insulation between the ink supply needle 205a and the atmosphere introduction needle 205b is important. In this embodiment, the path from the ink supply needle 205a to the recording head 201 and the atmosphere communication needle 205b to the atmosphere communication are important. Consideration is made so that the electrical resistance of only the ink in the main tank 204 can be measured by making the path to the mouth 205g completely independent.
[0060]
Next, the recovery unit 207 will be described. The recovery unit 207 sucks ink and air from the nozzle 201g and opens and closes the shut-off valve 210, and a suction cap 207a for capping the ink discharge surface (the surface on which the nozzle 201g is opened) of the recording head 201; And a link 207e for operating the lever 210d of the shut-off valve 210.
[0061]
The suction cap 207a is formed of an elastic member such as rubber at least in contact with the ink ejection surface, and is provided so as to be movable between a position where the ink ejection surface is sealed and a position where the ink ejection surface is retracted. A suction pump 207c is connected to the suction cap 207a, and the suction pump 207c is driven by a pump motor 207d to perform suction through the suction cap 207a. The suction pump 207c is a tube pump system having a plurality of rollers, can perform continuous suction, and can change the suction amount according to the rotation amount of the pump motor 207d. In the present embodiment, the suction pump 207c capable of reducing pressure to 0.4 atm (40.53 kPa) is used.
[0062]
The link 207e is slid by the cam 207f and moves the lever 210d of the shut-off valve 210 to open and close the shut-off valve 210. The cam 207b and the cam 207f are arranged coaxially and can be rotated in the direction of the arrow in the figure by a cam control motor 207g. The timing at which the positions a to c of the cam 207b come into contact with the suction cap 207a coincides with the timing at which the positions a to c of the cam 207f come into contact with the link 207e, respectively. At the position a, the cam 207b moves the suction cap 207a away from the ink ejection surface of the recording head 201, and the cam 207f pushes the link 207e to push up the lever 210d to open the shut-off valve 210. At the position b, the cam 207b brings the suction cap 207a into close contact with the ink discharge surface, and the cam 207f pulls back the link 207e to close the shut-off valve. At the position c, the cam 207b brings the suction cap 207a into close contact with the ink discharge surface, and the cam 207f presses the link 207e to open the shut-off valve 210.
[0063]
During the recording operation, the cams 207b and 207f are set to the position a, so that ink can be ejected from the nozzle 201g and ink can be supplied from the main tank 204 to the recording head 201. During non-operation including standby and rest, the cams 207b and 207f are set to the position b, and the suction cap 207a covers the nozzle surface of the recording head 1 to prevent the nozzle 201g from drying and ink from the recording head 201. (Especially when the apparatus itself moves, the apparatus may be tilted to cause ink to flow out). The position c of the cams 207b and 207f is used during the ink filling operation to the recording head 201, which will be described below.
[0064]
The ink supply path from the main tank 204 to the recording head 201 has been described above. However, in the configuration shown in FIG. 3, air accumulates in the recording head 201 when viewed over a long period of time.
[0065]
In the sub-tank portion 201b, air that permeates through the ink supply tube 206 and the elastic member 201h and air dissolved in the ink accumulate. As the air that permeates the ink supply tube 206 and the elastic member 201h, it is sufficient to use a material having a high gas barrier property as a material constituting them. However, a material having a high gas barrier property is expensive and is used for mass-produced consumer products. In equipment, high-performance materials cannot be easily used due to cost considerations. In this embodiment, a low-cost, flexible and easy-to-use polyethylene tube is used for the ink supply tube 206, and butyl rubber is used for the elastic member 201h.
[0066]
On the other hand, in the liquid chamber 201f, when the ink is ejected from the nozzle 201g, the bubbles generated by the boiling of the ink film break up and return to the liquid chamber 201f, or the fine bubbles dissolved in the ink are in the nozzle 201g. As the temperature of the ink rises, the air bubbles gradually accumulate by forming large bubbles.
[0067]
According to the experiments conducted by the present inventors, in the configuration shown in the present embodiment, the accumulated amount of air in the sub-tank portion 201b is about 1 ml per month, and the accumulated amount of air in the liquid chamber 201f is 1. It was about 0.5 ml per month.
[0068]
If the accumulated amount of air in the sub tank 201b and the liquid chamber 201f is large, the amount of ink stored in each of the sub tank 201b and the liquid chamber 201f decreases. In the sub-tank portion 201b, when the ink is insufficient, the filter 201c is exposed to the air and the effective area of the filter 201c is reduced. As a result, the pressure loss of the filter 201c increases, and in the worst case, the ink enters the liquid chamber 201f. It becomes impossible to supply. On the other hand, in the liquid chamber 201f, when the upper end of the nozzle 201g is exposed to the air, ink supply to the nozzle 201g becomes impossible. As described above, both the sub tank 201b and the liquid chamber 201f have a fatal problem unless a certain amount or more of ink is stored.
[0069]
Therefore, by filling each sub tank 201b and liquid chamber 201f with an appropriate amount of ink every predetermined period, the ink ejection function can be stably maintained over a long period of time without using a material having a high gas barrier property. be able to. For example, in the case of this embodiment, the sub tank unit 201b and the liquid chamber 201f may be filled every month with an amount of air accumulated per month plus a variation during filling.
[0070]
The sub tank unit 201b and the liquid chamber 201f are filled with ink by using a suction operation by the recovery unit 207. That is, the suction pump 207c is driven with the suction cap 207a sealing the ink discharge surface of the recording head 201, and the ink in the recording head 201 is sucked from the nozzle 201g. However, if the ink is simply sucked from the nozzle 201g, almost the same amount of ink as the ink sucked from the nozzle 201g flows into the liquid chamber 201f from the sub tank 201b, and similarly, almost the same amount as the ink flowing out from the sub tank 201b. The ink just flows into the sub tank 201b from the main tank 204, and the situation is almost the same as before the suction, and an appropriate amount of ink cannot be filled.
[0071]
Therefore, in the present embodiment, in order to fill the sub-tank portion 201b and the liquid chamber 201f partitioned by the filter 201c with appropriate amounts of ink, respectively, the sub-tank portion 201b and the liquid chamber 201f are set to a predetermined pressure using the shutoff valve 210. The volume of the sub tank 201b and the liquid chamber 201f is set.
[0072]
Hereinafter, the ink filling operation and the volume setting to the sub tank 201b and the liquid chamber 201f will be described.
[0073]
In the ink filling operation, first, the carriage 202 (see FIG. 1) is moved to a position where the recording head 201 faces the suction cap 207a, and the cam control motor 207g of the recovery unit 207 is driven to set the cams 207b and 207e to b. Is rotated until the position comes into contact with the suction cap 107a and the link 207e. As a result, the ink ejection surface of the recording head 201 is sealed by the suction cap 207a, and the shutoff valve 210 is in a state where the ink path from the main tank 204 to the recording head 201 is closed.
[0074]
In this state, the pump motor 207d is driven, and suction is performed from the suction cap 207a by the suction pump 207c. By this suction, the ink and air remaining in the recording head 201 are sucked through the nozzle 201g, and the inside of the recording head 201 is decompressed. When the amount of suction by the suction pump 207c reaches a predetermined amount, the suction pump 207c is stopped and the cam control motor 207g is driven to bring the cams 207b and 207f into contact with the suction cap 207a and the link 207e, respectively. Rotate until As a result, the shutoff valve 210 is opened while the sealed state of the ink ejection surface by the suction cap 207a remains unchanged. The suction amount by the suction pump 207c is a suction amount at which the inside of the recording head 201 becomes a predetermined pressure, and can be obtained by calculation, experiment, or the like.
[0075]
When the pressure in the recording head 201 is reduced, ink flows into the recording head 201 via the ink supply tube 206, and the sub tank portion 201b and the liquid chamber 201f are filled with ink. The amount of ink to be filled is a volume necessary for the sub-tank part 201b and the liquid chamber 201f that have been decompressed to return to almost atmospheric pressure, and is determined by the volume and pressure of the sub-tank part 201b and the liquid chamber 201f.
[0076]
Filling the sub tank 201b and the liquid chamber 201f with ink is completed in about 1 second after the shutoff valve 210 is opened. When the ink filling is completed, the cam control motor 207g is driven to rotate the cams 207b and 207f to the positions where the positions of b come into contact with the suction cap 207a and the link 207e, respectively. As a result, the suction cap 207a is separated from the recording head 201, and the suction pump 207c is driven again to suck the ink remaining in the suction cap 207a. In this state, since the shutoff valve 210 is open, ink is ejected from the nozzle 201g so that characters, images, and the like can be formed on the recording sheet S (see FIG. 1). In the standby and inactive states, the cam control motor 207g is driven again to rotate the cams 207b and 207f to positions where the positions of b are in contact with the suction cap 207a and the link 207e, respectively. The surface is sealed with the suction cap 207a, and the shutoff valve 210 is closed.
[0077]
If the amount of ink in the sub-tank portion 201b and the liquid chamber 201f does not become insufficient for a long period of time, it is not necessary to frequently perform the suction operation by the recovery unit 207, and the opportunity for wasting ink is reduced. Furthermore, even when both the sub tank 201b and the liquid chamber 201f need to be filled with ink, the ink can be saved because only one filling operation is required.
[0078]
Here, the above-described filling operation and volume setting will be described.
[0079]
Assuming that the volume of the sub tank 201b is V1, the amount of ink that should exist in the sub tank 201b is S1, and the pressure in the sub tank 201b is P1 (relative value from atmospheric pressure), these are based on the principle of “PV = constant”. Is set so that V1 = S1 / | P1 | is satisfied, the ink can be filled so that an appropriate amount of ink exists in the sub-tank portion 201b by the filling operation. Similarly, when the volume of the liquid chamber 201f is V2, the amount of ink that should be present in the liquid chamber 201f is S1, and the pressure in the liquid chamber 201f is P2 (relative value from atmospheric pressure), these relationships are expressed as V2 = By setting so as to be S2 / | P2 |, ink can be filled so that an appropriate amount of ink exists in the liquid chamber 201f by the filling operation.
[0080]
Further, the filter 201c that divides the sub-tank portion 201b and the liquid chamber 201f has a fine mesh structure. As described above, the air flow is difficult in a state where the meniscus is formed. Here, let Pm be the pressure required to allow air to pass through the filter 201c on which the meniscus is formed. When suctioned from the nozzle 201g by the recovery unit 207, the pressure P2 in the liquid chamber 201f is lower than the pressure P1 in the sub tank 201b by the pressure Pm in order to allow the air in the sub tank 201b to pass through the filter 201c. Become. Therefore, when this relationship is used when determining the volumes of the sub-tank portion 201b and the liquid chamber 201f, the conditions for the filling operation can be easily determined.
[0081]
A specific example is shown below based on the above relationship. In the present embodiment, ink filling is performed once a month, and the amount of air accumulated in one month is 1 ml in the sub tank 201b and 0.5 ml in the liquid chamber 201f. In addition, the amount of ink necessary to prevent the filter 201c from being exposed to air in the sub-tank portion 201b is 0.5 ml, and the amount of ink necessary to prevent the nozzle 201g from being ejected to air in the liquid chamber 201f is The variation in the ink filling amount is 0.5 ml for both the sub tank 201b and the liquid chamber 201f, and is 0.2 ml. These numerical values are obtained by experiments. From the above, the amount of ink that should be present after one filling is the sum of these values, which is a relatively large value of 1.7 ml for the sub tank 201b and 1.2 ml for the liquid chamber 201f.
[0082]
The reduced pressure in the recording head 201 is set within a range not exceeding the capacity of the recovery unit 207. In this embodiment, since the capability limit of the suction pump 207c is −0.6 atm (−60.795 kPa), the pressure in the suction cap 207a becomes −0.5 atm (−50.6625 kPa) with a margin. As described above, the suction amount of the suction pump 207c is obtained by experiment and set, and is controlled as the rotation amount of the pump motor 207d.
[0083]
Here, since the pressure required to allow air to pass through the meniscus of the nozzle 201g is an experimental value of −0.05 atm (−5.06625 kPa), the pressure between the pressure in the suction cap 207a and the pressure in the liquid chamber 201f. A difference in resistance of the nozzle 201g occurs between them, and the pressure in the liquid chamber 201f becomes higher by 0.05 atm (5.06625 kPa) than the pressure in the cap 207a. Similarly, since the pressure necessary for permeating air by the meniscus of the filter 201c is an experimental value of −0.1 atm (−10.1325 kPa), the pressure between the pressure in the liquid chamber 201f and the pressure in the sub tank 201b is between A difference in resistance of the filter 201c occurs, and the pressure in the sub tank 201b becomes higher by 0.1 atm (10.1325 kPa) than the pressure in the liquid chamber 201f. Therefore, when the pressure in the suction cap 207a is set to −0.5 atm (−50.6625 kPa), the pressure in the liquid chamber 201f is −0.45 atm (−45.5963 kPa), and the pressure in the sub tank portion 201b is −0. .35 atm (−35.4638 kPa).
[0084]
In order for 1.7 ml of ink to be present in the sub-tank portion 201b, when the ink is sucked from the sub-tank portion 201b whose internal pressure is approximately 1 atm (101.325 kPa) by 1.7 ml, the internal pressure is -0.35 atm ( The volume V1 of the sub-tank portion 201b is set to be −35.4638 kPa). That is, V1 = 1.7 / 0.35 = 4.85 ml. Similarly, the volume V2 of the liquid chamber 201f is set to V2 = 1.2 / 0.45 = 2.67 ml.
[0085]
After depressurizing the inside of the recording head 201 under the above conditions, the ink flows into the recording head 201 having a negative pressure by opening the shutoff valve 210. More specifically, first, ink flows into the sub-tank portion 201b, and the air expanded to V1 by decompression is restored to almost atmospheric pressure. At this time, the volume of air in the sub tank 201b is V1._aThen, V1_a= V1 × (1−0.35) = 3.15 ml, and the sub-tank portion 201b has V1−V1._a= Calm down when ink is filled until 1.7 ml of ink is present. Similarly, also in the liquid chamber 201f, ink flows from the sub tank 201b, and the air that has been expanded to V2 by decompression is restored to almost atmospheric pressure. The volume of air in the liquid chamber 201f at that time is V2_aThen V2_a= V2 × (1−0.45) = 1.47 ml, and the liquid chamber 201f has V2−V2_a= Calm down when ink is filled until 1.2 ml of ink is present.
[0086]
As described above, by setting the volume of each of the sub-tank portion 201b and the liquid chamber 201f and the pressure to be reduced, each of the sub-tank portion 201b and the liquid chamber 201f partitioned by the filter 201c can be obtained in one filling operation. Ink can be filled so that an appropriate amount of ink is present, and even in a situation where air accumulates in the recording head 201, it can be operated normally for a long period of time without the suction operation.
[0087]
As for the problem that air bubbles block the flow path between the filter and the nozzle, in this embodiment, the cross-sectional area of the liquid chamber 201f is sufficiently larger than the diameter of the air bubbles that may exist in the liquid chamber 201f. In this configuration, the bubbles in the liquid chamber 201f do not hinder the flow of ink. Further, regarding the problem that bubbles in the liquid chamber enter the nozzle or block the communication portion between the liquid chamber and the nozzle, the liquid chamber 201f has a sufficiently large cross-sectional area as described above. The bubbles generated inside rise in the ink by the buoyancy and merge with the air layer, so that they do not enter the nozzle 201g. That is, by configuring the liquid chamber 201f separated from the sub tank portion 201b by the filter 201c as described above, bubbles are generated in the liquid chamber 201f or the bubbles are generated due to movement. The reliability with respect to ejection failure can be greatly improved.
[0088]
Even if only one of the sub-tank part and the liquid chamber is configured as in the present embodiment and the other is configured in the same manner as the conventional example, at least with respect to the former, the above-described functions can be achieved and air removal can be performed at the same time. Effective and effective.
[0089]
In the above description, it is assumed that even a small amount of ink remains in the sub tank 201b and the liquid chamber 201f after the suction operation, and the sum of the remaining ink amount and the ink filling amount is considered to be an appropriate amount, That is, the amount of ink to be present = the amount of ink remaining + the amount of ink filled. However, if the ink in the sub tank 201b or the liquid chamber 201f is once completely discharged by the suction operation, the amount of ink that should be present in the sub tank 201b or the liquid chamber 201f is equal to the amount of ink filled. Then, it is considered that the amount of ink to be present = the amount of ink to be filled.
[0090]
【The invention's effect】
According to the present invention, ink is filled so that an appropriate amount of ink exists in each of the two liquid chambers. Even if the flow path in the recording head is wide, both the liquid chambers can be evacuated and filled with ink. In addition, the amount of ink does not become insufficient in both liquid chambers over a long period of time, so frequent recovery suction is not necessary, and the amount of wasteful consumption of ink is reduced. Further, when both the liquid chambers need to be filled with ink, the ink can be saved because only one filling step is required. In addition, by using a constant law, PV can be filled with an appropriate amount of ink in each liquid chamber by a filling operation.
[0091]
The amount of ink accumulated in the first liquid chamber is larger than the minimum required amount of ink (the amount of ink in which the filter is surely immersed in the ink) in the first liquid chamber, and accumulates in the first liquid chamber for a predetermined time (for example, for a long period such as one month) Ink can be filled so that there is an ink amount S1 greater than the sum of the amounts, and similarly, the second liquid chamber is larger than the minimum required ink amount (the amount of ink that the nozzle is surely immersed in the ink). If the ink can be filled so that there is an ink amount S2 larger than the sum of the air amounts accumulated in the second liquid chamber in the same predetermined period as described above, the filling operation is performed once in the predetermined period. Since it is good, it can save ink to be discharged.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a schematic configuration of an ink jet recording apparatus according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram of an ink supply principle of the ink jet recording apparatus shown in FIG.
3 is a view for explaining an ink supply path for one color of the ink jet recording apparatus shown in FIG. 1; FIG.
4 is a diagram illustrating the behavior of air and ink in the liquid path of the ink supply unit when air is introduced into the main tank in the ink supply path shown in FIG. 3;
FIG. 5 is a diagram illustrating a pressure due to a water head difference applied to a nozzle in the ink supply path shown in FIG. 3;
FIG. 6 is a diagram of an ink supply system in a conventional tube supply type inkjet recording apparatus.
[Explanation of symbols]
201 Recording head
201a Connector insertion slot
201b Sub tank (first ink chamber)
201c filter
201d opening
201e partition
201f Liquid chamber (second ink chamber)
201g discharge nozzle
201h elastic member
201i Pressure adjustment chamber
202 Carriage
203 Conveying roller
204 Main tank (ink tank)
204b, 204c Rubber stopper
205 Ink supply unit
205a Ink supply needle
205b Air introduction needle
205c, 205d, 205e flow path
205f Buffer room
205g Air 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
210c Pressing spring
210d lever
S Recording sheet

Claims (2)

In an ink jet recording apparatus comprising: a recording head that performs recording by discharging ink from a nozzle; a suction unit that forcibly discharges ink in the recording head from the nozzle; and an ink supply unit that supplies ink to the recording head.
The recording head includes a first liquid chamber on the upstream side and a second liquid chamber on the downstream side with respect to the ink flow direction, and can store air in the first liquid chamber and the second liquid chamber, respectively. And
The filter is located between the first liquid chamber and the second liquid chamber and separates both, and the filter has a mesh structure having a large number of holes having meniscus strength,
At least one of the first liquid chamber and the second liquid chamber is determined based on the suction force of the suction means and a desired ink amount that should exist after the suction by the suction means. Has a volume,
The ink supply means includes an ink tank for storing ink, an ink supply tube for communicating the ink tank and the recording head, and a shut-off valve for opening and closing the ink supply tube .
The suction means includes a suction cap that seals the recording head, and a suction pump that sucks through the suction cap ;
In filling the recording head from the ink supply means with the suction means,
The pressure of the first liquid chamber is different from the specific pressure by the meniscus strength of the filter while closing the shutoff valve and reducing the second liquid chamber to a specific pressure by the suction means. After that, the decompression is eliminated by opening the shutoff valve, and the amount of ink in the ink tank is changed to the first liquid chamber and the second liquid chamber via the ink supply tube, respectively. The operation of filling only 1 cycle,
An ink jet recording apparatus, wherein ink can be filled in one cycle . 2. The ink jet recording apparatus according to claim 1, wherein the amount of ink to be filled in one filling operation is such that the first liquid chamber and the second liquid chamber, which are decompressed, return to substantially atmospheric pressure, respectively. An ink jet recording apparatus characterized by having a volume necessary for the above .

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