JP2009292121A - Inkjet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce an ink consumption at the time of a recording head replacement as much as possible. <P>SOLUTION: This inkjet recording apparatus includes a recording head, a suction means, an ink tank, a pressure controlling means, and a valve driving means. In this case, the recording head is equipped with a first liquid chamber equipped with a discharging nozzle, a second liquid chamber to which an ink is fed through an ink feeding passage, and a valve. When the recording head is replaced, the valve is opened by the valve driving means regardless of the pressure in the second liquid chamber. At the same time, the inside of the ink tank is decompressed by the pressure controlling means, and the ink in the second liquid chamber is returned to the ink tank. Also, the ink in the first liquid chamber is collected by the suction means. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus that performs recording by discharging ink.

  An ink jet recording apparatus (hereinafter also referred to as “recording apparatus” for short) is an ink jet recording head (hereinafter “recording head”) mounted on a carriage that reciprocates in a direction crossing a recording medium (for example, paper). Are often referred to as “.”). In a recording apparatus having such a recording head, ink droplets are ejected from the ejection nozzles of the recording head that reciprocally move in the above direction, and an image or a character is formed on the recording medium. Further, when the amount of ink in the recording head decreases due to ejection of ink droplets, ink is supplied from an ink supply container (hereinafter also referred to as “ink tank”).

  Some recording apparatuses contain a replaceable ink tank in a part of the recording apparatus main body, and replenish ink to the recording head through a flexible and hollow fluid conduit connected to the ink tank. There is also a recording apparatus in which a recording head is disposed above the recording medium in the gravity direction and ink droplets are ejected downward from the recording head in the gravity direction. In this case, the inside of the recording head is maintained at a slight negative pressure, and the ink in the discharge nozzles should form a meniscus at the boundary with the atmosphere. Here, in order to form and maintain the meniscus, the pressure in the recording head needs to be maintained within a certain range. Specifically, when the negative pressure increases, the amount of ink ejected from the ejection nozzle decreases and the image density decreases, and when the negative pressure further increases, the meniscus is broken and the ink is sucked into the recording head, thus making it impossible to eject. . On the other hand, when the pressure inside the recording head becomes positive, it becomes difficult to maintain the meniscus, and ink flows out from the ejection nozzle, causing ejection failure.

  In view of this, as a method for maintaining the inside of the recording head at a slight negative pressure, a method using a water head difference has been proposed (see Patent Document 1). Specifically, one of the two hollow bottles pierced in the ink tank is communicated with the atmosphere, the other one is communicated with the recording head, and the head of the hollow bottle communicates with the atmosphere by the difference in water head between the recording head. A method for generating a slight negative pressure in a recording head has been proposed.

  However, in the above method, the position of the ink tank in the height direction is restricted, and thus the size of the printing apparatus is restricted. In addition, the pressure in the recording head is affected by pressure fluctuations due to pressure loss in the ink supply channel and acceleration / deceleration of the carriage. Therefore, the above method is not suitable for a large-format recording apparatus using a tube supply method in which the recording apparatus is downsized and speeded up and the ink supply flow path is large.

As another method for maintaining the inside of the recording head at a slight negative pressure, a method of providing a valve mechanism in the recording head has been proposed (see Patent Document 2). In this method, a valve mechanism that opens and closes according to the pressure in the recording head is provided, the ink in the ink tank is pressurized, and when the valve mechanism is opened, the ink is quickly supplied into the recording head. . When the ink is replenished and the pressure in the recording head returns to a slight negative pressure, the valve mechanism is closed and the pressurized ink does not flow into the recording head. With this method, the pressure loss in the ink supply channel can be compensated by pressurizing the ink. In addition, since the valve mechanism is normally closed, the pressure in the recording head is not easily affected by pressure fluctuations caused by acceleration / deceleration of the carriage. Furthermore, the degree of freedom of arrangement of the ink tank is high. For these reasons, this method has become the mainstream in large format recording apparatuses in recent years.
Japanese Patent Laid-Open No. 2002-248779 (Section 13, FIG. 3) JP-T-2001-514985 (paragraph 32, FIG. 1)

  In recent years, there has been a demand for improvement in durability of an ink jet recording apparatus, and in a large format recording apparatus used for business use, improvement in durability is particularly strongly demanded. However, the durability of the recording head is shorter than that of the recording apparatus main body, and the recording head is often replaced a plurality of times before the lifetime of the recording apparatus main body elapses. In a recording apparatus having a recording head with a built-in valve mechanism, the recording head is removed from the recording apparatus main body with ink in the recording head, a new recording head is mounted, and the new recording head is filled with ink. The exchange method is common. However, the above replacement method has a problem that the ink remaining in the old recording head is wasted every time the recording head is replaced. In particular, in a large format printing apparatus, the size of the recording head has been increased to cope with the higher speed, and the amount of ink in the recording head has also increased, so the amount of ink wasted when the recording head is replaced. Has also increased.

  The inkjet recording apparatus of the present invention includes a first liquid chamber provided with a discharge nozzle, a second liquid chamber to which ink is supplied via an ink supply path, and the pressure in the second liquid chamber is within a specified range. In this case, the ink supply path is closed so that ink does not flow into the second liquid chamber, and when the pressure drops beyond a predetermined range, ink flows from the ink supply path into the second liquid chamber. A recording head provided with a valve that opens, a suction means for collecting ink in the recording head via the ejection nozzle, and storing ink supplied to the second liquid chamber via the ink supply path An ink tank, and pressure control means for supplying or drawing ink back to the second liquid chamber by pressurizing and depressurizing ink in the ink tank. The valve drive means for opening and closing the valve regardless of the pressure in the second liquid chamber, and when replacing the recording head, the valve drive means allows the valve to be opened regardless of the pressure in the second liquid chamber. While the valve is opened, the pressure control means depressurizes the ink tank to return the ink in the second liquid chamber to the ink tank, and the suction means causes the ink in the first liquid chamber to be discharged. Collected.

  The amount of ink that is wasted when the recording head is replaced can be minimized.

  Hereinafter, an example of an embodiment of the ink jet recording apparatus of the present invention will be described. FIG. 1 is a schematic diagram of an ink jet recording apparatus 500 according to the present embodiment. The recording apparatus 500 includes a recording head 100 connected to a detachable (replaceable) ink tank 200 via a fluid conduit 250 that forms an ink supply path. The recording head 100 is supplied with ink through the fluid conduit 250 and selectively ejects ink droplets onto a recording medium (not shown) under the control of the control means.

  The ink tank 200 includes a bag body 202 that stores ink, a rubber plug 201 that seals the ink outlet port of the bag body 202, and a case 205 that seals the bag body 202. The bag body 202 has a flexibility that can be deformed according to a change in ambient pressure, and the bag body 202 of this embodiment is formed of a synthetic resin material.

  One end of the fluid conduit 250 is provided with an ink needle 203 which is a hollow tube having a sharp tip. The fluid conduit 250 communicates with the bag body 202 when the ink needle 203 is inserted into the rubber stopper 201, and ink can be led out. The tank pump 210 as pressure control means is connected to the case at the same time as the ink needle 203 is inserted into the rubber stopper. The tank pump 210 increases the pressure (atmospheric pressure) around the bag body 202 by sending air into the case 205, and supplies the ink stored in the bag body 202 to the recording head 100 via the fluid conduit 250. .

  The recording head 100 includes a first liquid chamber 101 and a second liquid chamber 110 located above the first liquid chamber 101 in the direction of gravity. The first liquid chamber 101 and the second liquid chamber 110 are connected to each other and are hermetically integrated. The first liquid chamber 101 is provided with a discharge nozzle 105 downward in the direction of gravity, and the second liquid chamber 110 is provided with negative pressure generating means.

  Further, the second liquid chamber 110 is provided with a supply port 113 for receiving ink supplied via the fluid conduit 250. In addition, a supply filter 102 is provided in a through hole (flow path) that connects the second liquid chamber 110 and the first liquid chamber 101 located below the second liquid chamber 110 in the gravity direction. .

  The negative pressure generating means provided in the second liquid chamber 110 is a diaphragm 111 that is a flexible member and a diaphragm spring 112 that deforms the diaphragm 111. One side of the diaphragm 111 faces the internal space of the second liquid chamber 110, and the other side is exposed to the atmosphere. The diaphragm spring 112 changes the pressure in the second liquid chamber to a pressure within a specified range (slight negative pressure) by deforming the diaphragm 111 to the atmosphere side so that the volume of the second liquid chamber 110 increases. When the second liquid chamber is in a slightly negative pressure state, the first liquid chamber, which is connected in an airtight manner, also has substantially the same slightly negative pressure state, and is applied to a recording medium (not shown) below the recording head 100. A good meniscus is formed in the discharge nozzle 105 that opens downward.

  Inside the second liquid chamber 110, a valve (supply control valve 160) is provided as supply control means that works in conjunction with the negative pressure generation means. The supply control valve 160 is formed of an elastic member, and opens and closes the supply port 113 intermittently. Specifically, an arm 161 connected to the supply control valve 160 is connected to the diaphragm 111. In short, the supply control valve 160 is connected to the diaphragm 111 via the arm 161. Accordingly, the supply control valve 160 receives the spring force applied by the diaphragm spring 112 and closes the supply port 113. On the other hand, when the internal pressure of the recording head decreases beyond the specified range due to ink ejection (lower than the slight negative pressure), the supply control valve 160 is opened and ink flows from the supply port 113. When the internal pressure of the recording head 100 increases with the inflow of ink and reaches a predetermined slight negative pressure again, the supply control valve 160 is closed and the inflow of ink is stopped. In the continuous recording operation, the supply control valve 160 is intermittently opened and closed as described above, and the amount of ink inside the recording head 100 is maintained at a predetermined amount.

  A pump chamber 120 is provided in the vicinity of the first liquid chamber 101 and the second liquid chamber 110, and these first liquid chamber 101, second liquid chamber 110, and pump chamber 120 form a circulation path. ing. This will be specifically described. As described above, the second liquid chamber 110 and the first liquid chamber 101 are connected to each other via a flow path provided with the supply filter 102. This flow path is provided in the first liquid chamber 101. It is provided on one end side (ink inlet side) of the row of ejected nozzles 105 (nozzle row). On the other end side (ink outlet side) of the nozzle row, a through hole (flow path) provided with a discharge filter 103 is provided, and the first liquid chamber 101 and the pump chamber 120 are connected via the flow path. The pump chamber 120 is connected to the second liquid chamber 110 through another through hole (flow path). In short, the pump chamber 120 is a small chamber that connects the first liquid chamber 101 and the second liquid chamber 110 to form a one-way circulation path.

  Here, the ceiling surface 104 of the first liquid chamber 101 is inclined. Specifically, the ceiling surface 104 is inclined so as to be separated from the bottom surface as it comes closer to the flow path provided with the discharge filter 103 that connects the first liquid chamber 101 and the pump chamber 120. In other words, the supply filter 102 is positioned below the inclined surface, and the discharge filter 103 is positioned above the inclined surface.

  The pump chamber 120 is provided with a diaphragm 121 formed of a flexible member that changes the volume of the pump chamber 120. An opening / closing valve 130 is provided in the flow path connecting the pump chamber 120 and the first liquid chamber 101, and an opening / closing valve 131 is provided in the flow path connecting the pump chamber 120 and the second liquid chamber 110. ing. The on-off valve 130 and the on-off valve 131 are one-way valves. Specifically, the on-off valve 130 opens only toward the inside of the pump chamber 120, and the on-off valve 131 opens only toward the inside of the second liquid chamber 110.

  The second liquid chamber 110 is provided with a discharge port 114 as a means for removing air. The discharge port 114 is connected to an air vent channel 181 in which an umbrella valve 180 is provided. The first liquid chamber 101 and the second liquid chamber 110 of the recording head 100 are isolated from the atmosphere by an umbrella valve 180. The discharge port 114 is intermittently opened and closed by the full tank control valve 150. The operation of the full tank control valve 150 is performed by the buoyancy of the float 140. Specifically, the float 140 and the full tank control valve 150 are respectively provided at the ends of the arms that rotate about the rotation shaft 145, and the second liquid chamber 110 is filled with ink and the float 140 is When it floats, the discharge port 114 is closed by the full tank control valve 150. On the other hand, when the ink in the second liquid chamber 110 is consumed by the recording operation and the float 140 is lowered, the full control valve 150 opens the discharge port 114. On the downstream side of the umbrella valve 180, an air vent 182 opens to the atmosphere.

  The ink jet recording apparatus 500 also includes a recovery system 300 that improves nozzle clogging of the recording head 100. The recovery system 300 includes a suction negative pressure generator 330, a nozzle cap 310, an air vent cap 320, flow paths 311 and 321 that connect the caps 310 and 320 and the suction negative pressure generator 330, and open / close valves 312 and 322, respectively. The The suction negative pressure generator 330 includes a tube pump (not shown), a drive motor, and a drive control board. Hereinafter, the flow of ink and the operation of each unit will be described.

(Initial filling operation)
There is no ink in the fluid conduit 250, the first liquid chamber 101, and the second liquid chamber 110 during the initial filling. When the ink needle 203 is connected to the bag body 202 and the tank pump 210 is connected to the ink tank 200, the bag body 202 is pressurized by the action of the tank pump 210 and enters an ink supply state.

  Next, the air vent cap 320 is engaged with the air vent port 182, and the nozzle cap 310 is engaged with the face surface of the recording head 100 having the ejection nozzle 105. At this time, the on-off valve 312 is closed and the on-off valve 322 is opened.

  After that, the suction negative pressure generating unit 330 operates the tube pump continuously, so that the negative pressure higher than the negative pressure generated by the diaphragm 111 and the diaphragm spring 112 that makes the inside of the second liquid chamber 110 a slight negative pressure. Is generated. The umbrella valve 180 is opened by this negative pressure. At this time, since the float 140 in the second liquid chamber without ink is in a lowered state, the discharge port 114 is opened. Therefore, the opening of the umbrella valve 180 causes the inside of the air vent channel 181 to be in a negative pressure state, and eventually the inside of the second liquid chamber 110 also becomes a negative pressure higher than the slightly negative pressure, and the supply control valve 160 is opened. Furthermore, the pressure in the fluid conduit 250 also becomes negative, whereby the ink in the ink tank 200 is guided to the second liquid chamber 110. The ink guided to the second liquid chamber 110 flows into the first liquid chamber 101 located below the gravitational direction. As the amount of ink in the second liquid chamber 110 increases, the float 140 rises and eventually the discharge port 114 is closed by the full tank control valve 150.

(Mixing of air)
When all the ink in the ink tank 200 is consumed, the ink tank 200 is replaced. However, when the ink tank 200 is replaced, the ink needle 203 that has been disconnected from the rubber plug 201 is exposed to the atmosphere. At this time, air enters the inside of the ink needle 203. The air in the ink needle is sent to the recording head 100 through the fluid conduit 250 when the ink supply from the new ink tank 200 that has been replaced is resumed. Moreover, although the fluid conduit | pipe 250 is formed with the flexible material (for example, polyethylene resin) with low gas permeability, there is no air mixing. The air mixed in the fluid conduit 250 during the non-use period of the recording apparatus 500 may be sent to the recording head 100 at the next use.

  When the air sent into the recording head 100 as described above is generated as bubbles in the first liquid chamber 101, the bubbles move along the inclined ceiling surface 104 of the first liquid chamber 101. Then, bubbles accumulate in the lower part of the discharge filter 103.

(Air venting operation)
First, the nozzle cap 310 is engaged with the face surface of the recording head 100 so that the meniscus of the discharge nozzle 105 is not destroyed. Next, the diaphragm 121 is vertically deformed by the reciprocating movement of the arm 400, and the volume and pressure of the pump chamber 120 are changed. Specifically, the diaphragm 121 is deformed downward by the lowering operation of the arm 400, whereby the pressure in the pump chamber 120 is increased, the on-off valve 130 is closed, and the on-off valve 131 is opened. On the other hand, the diaphragm 121 is deformed upward by the raising operation of the arm 400, whereby the pressure in the pump chamber 120 is reduced, the on-off valve 131 is closed, and the on-off valve 130 is opened.

  As the arm 400 moves up, the internal pressure of the pump chamber 120 becomes lower than the slight negative pressure inside the first liquid chamber 101, so that the ink below the discharge filter 103 moves to the pump chamber 120. At this time, if there is an air reservoir below the discharge filter 103, the air (bubbles) moves to the pump chamber 120 together with the ink. Next, when the internal pressure of the pump chamber 120 increases due to the lowering operation of the arm 400, the air that has moved from the first liquid chamber 101 moves to the second liquid chamber 110 by opening the on-off valve 131. As described above, the ink circulates in the order of the first liquid chamber 101 → the pump chamber 120 → the second liquid chamber 110 → the first liquid chamber 101, whereby the air inside the recording head 100 is changed to the second liquid chamber. Accumulated above 110.

  In the second liquid chamber 110, the liquid level of the ink is lowered by the inflow of air, and the full control valve 150 is opened as the float 140 is lowered. Here, if negative pressure is generated with the air vent port 182 closed by the air vent cap 320, it is obvious that the air in the second liquid chamber 110 is discharged through the umbrella valve 180.

  As described above, the air mixed in the fluid conduit 250 during the non-use period and the air mixed in the fluid conduit 250 by replacing the ink tank 200 are accumulated above the second liquid chamber 110 by resuming the recording operation. When the full tank control valve 150 is opened, it is discharged.

(Head replacement operation)
Next, the operation of each part during head replacement will be described with reference to FIGS. FIG. 2 shows a state where the control valve drive shaft 600 is lowered during head replacement. FIG. 3 shows the flow of head replacement control.

  When the user selects “head replacement” on an operation panel (not shown), the following operation is executed. First, the inside of the ink tank 200 is depressurized to a certain pressure (step 1). The tank pump 210 is provided with a pressure detector 211, and the pressure of the ink tank 200 (case 205) can be controlled to an arbitrary pressure. As the inside of the case 205 is depressurized, the inside of the fluid conduit 250 is also depressurized to a negative pressure.

  Next, a drive source (not shown) rotates the cam 601 to lower the control valve drive shaft 600 (step 2). The control valve drive shaft 600 is reciprocated in the axial direction by a drive source (not shown) and a cam 601. A position detection sensor 602 detects the position of the control valve drive shaft 600 (whether it is a lowered position or an elevated position).

  When the control valve drive shaft 600 is lowered, the diaphragm 111 is deformed downward. As a result, the supply control valve 160 is opened via the arm 161 regardless of the pressure inside the second liquid chamber 110, and the supply port 113 is opened. When the supply port 113 is opened, the ink in the second liquid chamber flows backward to the ink tank 200 side via the fluid conduit 250. Then, the ink in the second liquid chamber is reduced, the float 140 is lowered, and the full tank control valve 150 is opened. However, since the umbrella valve 180 is closed, air does not enter from the air vent 182 side. Therefore, the ink continues to flow back to the ink tank side until the meniscus of the discharge nozzle 105 is broken and air enters from the discharge nozzle 105.

  After the ink is sufficiently returned to the ink tank 200 side (after T1 time), the tank pump 210 is stopped and the negative pressure on the ink tank 200 side is released (steps 3 and 4). In addition, a drive source (not shown) raises the control valve drive shaft 600 (step 5). Thereafter, the nozzle cap 310 is engaged with the face surface of the recording head 100 having the discharge nozzle 105 (step 6), the on-off valve 312 is opened, and the on-off valve 322 is closed. Next, the suction negative pressure generator 330 is driven (step 7), and the ink remaining in the first liquid chamber is removed. After the ink is sufficiently removed from the first liquid chamber 101 (after T2 time), the suction negative pressure generating unit 330 stops and the engagement of the nozzle cap 310 with the face surface is released (steps 8, 9, 10). ). Thereafter, the head is replaced by the user (step 11).

  After the head is replaced, the above-described initial filling operation is executed, and ink is filled into the new head (step 12). Thus, the head replacement control is completed.

  By returning the ink in the recording head to the ink tank side, air is mixed into the fluid conduit or the ink tank. However, the mixed air is almost removed by the initial filling operation.

  Prior to head replacement, most of the ink remaining in the old recording head is collected in the ink tank. Accordingly, it is possible to replace the head while minimizing the waste of ink, and the running cost can be reduced.

  So far, the configuration in which the valve for controlling the ink supply to the recording head operates integrally with the negative pressure generating means in the recording head has been described, but the present invention is not limited to such a configuration. For example, the valve may be provided independently on the ink supply path, and detection means for detecting the pressure in the recording head may be provided to open and close the valve according to the detection result of the detection means.

  In addition, the method of supplying ink from the ink tank under pressure is not limited to a configuration that uses air pressure. For example, a configuration that mechanically pressurizes and depressurizes the container containing ink using a spring or a displacement plate is used. There may be.

1 is a schematic diagram illustrating an embodiment of an inkjet recording apparatus of the present invention. It is a schematic diagram which shows the state which the control valve drive shaft 600 of FIG. 1 fell. It is a figure which shows an example of the sequence of the recording head replacement | exchange in the inkjet recording device of this invention.

Explanation of symbols

100 Recording Head 101 First Liquid Chamber 105 Discharge Nozzle 110 Second Liquid Chamber 160 Supply Control Valve 330 Suction Negative Pressure Generating Unit 500 Inkjet Recording Device 600 Control Valve Drive Shaft 601 Cam

Claims (4)

A first liquid chamber having a discharge nozzle, a second liquid chamber to which ink is supplied via an ink supply path, and the pressure from the ink supply path when the pressure in the second liquid chamber is within a specified range. The recording is provided with a valve that is closed so that ink does not flow into the second liquid chamber, and that opens so that ink flows from the ink supply path into the second liquid chamber when the pressure drops beyond a predetermined range. Head,
A suction means for collecting the ink in the recording head through the ejection nozzle;
An ink tank for storing ink supplied to the second liquid chamber via the ink supply path;
In an ink jet recording apparatus comprising pressure control means for supplying or drawing ink back to the second liquid chamber by pressurizing or depressurizing ink in the ink tank,
Valve driving means for opening and closing the valve regardless of the pressure in the second liquid chamber;
When the recording head is replaced, the valve is opened by the valve driving means regardless of the pressure in the second liquid chamber, and the inside of the ink tank is depressurized by the pressure control means, so that the inside of the second liquid chamber is reduced. An ink jet recording apparatus, wherein ink is returned to the ink tank, and ink in the first liquid chamber is collected by the suction means.   The ink jet recording apparatus according to claim 1, wherein the valve is provided in the second liquid chamber.   2. The ink jet recording according to claim 1, wherein the valve is provided in the ink supply path, and has a detecting unit that detects a pressure in the recording head, and the valve is opened and closed based on a detection result of the detecting unit. apparatus.   The valve driving means has a shaft for operating an arm connected to the valve, and a cam for reciprocating the shaft in the axial direction. When the shaft is moved in one of the axial directions by the cam, The ink jet recording apparatus according to claim 1, wherein the arm is operated so that the valve is opened.

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