JP2008246860A - Inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording device having a feeding system not leaving air in an ink feeding path when filling with ink. <P>SOLUTION: In the inkjet recording device 1, a valve drive control section 53 can fill the inside of a head 2 with the ink and discharge air in a second tube 5 having a solenoid valve 51 into an ink tank 3 by opening and closing the solenoid valve 51 when not printing and when driving a pump 41 arranged in a first tube 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inkjet recording apparatus that performs printing by ejecting ink droplets.

  Conventionally, in an ink jet recording apparatus, various mechanisms for supplying ink to a head for ejecting ink droplets have been proposed.

  For example, Patent Document 1 discloses an ink jet recording apparatus having a head including a plurality of ink discharge ports and a common liquid chamber, and supplies ink from an ink supply tank that stores ink to the common liquid chamber through a supply pipe. A first ink jet recording apparatus is described. The supply pipe is provided with a closed circuit portion, and a recovery pump whose discharge port communicates with the head side is provided in the closed circuit portion. The first ink jet recording apparatus is provided with a circulation pipe, and this circulation pipe is provided with an electromagnetic valve.

  The first ink jet recording apparatus closes the electromagnetic valve at the time of printing, and replenishes the common liquid chamber with ink by its own weight from the ink supply tank through the branch pipe of the supply pipe not provided with the recovery pump.

  On the other hand, during the recovery operation that is performed to cool the head along with the removal of bubbles remaining in the common liquid chamber and supply system, the first inkjet recording device opens the solenoid valve and starts the recovery pump to supply Ink is fed into the common liquid chamber through the pipe, and the ink is returned from the common liquid chamber to the ink supply tank through the circulation pipe and circulated.

  Also, at the time of initial filling in which ink is filled in the head and the supply pipe that are not filled with ink, the first inkjet recording apparatus sends ink to the common liquid chamber through the supply pipe by the recovery pump, and discharges the bubbles. Ink is ejected from the ejection port.

  Further, Patent Document 1 further includes that the supply pipe does not have a closed circuit portion, the discharge port of the recovery pump provided in the supply pipe communicates with the ink supply tank side, and an air valve is provided above the ink supply tank. Describes a second inkjet recording apparatus having the same configuration as the first inkjet recording apparatus.

In the second ink jet recording apparatus, the air valve is opened during printing, and the ink is supplied from the ink supply tank to the common liquid chamber by its own weight. On the other hand, in the second ink jet recording apparatus, during the recovery operation, the air valve is closed and the recovery pump is started, ink is supplied to the supply liquid chamber through the supply pipe, and ink is returned from the supply liquid chamber to the supply tank through the circulation pipe. Circulate.
Japanese Patent Laid-Open No. 3-234652 (released on October 18, 1991)

  However, in the conventional technique, it cannot be said that the removal of bubbles in the ink supply path is sufficient, and there is room for improvement.

  For example, in the first inkjet recording apparatus of Patent Document 1, even if the pump is driven during initial filling, air remains in the branch pipe where no recovery pump is provided. This air enters the head during printing and causes ejection failure.

  Further, in the second ink jet recording apparatus of Patent Document 1, negative pressure is applied to the head during the recovery operation. As a result, air may be taken in from the ink discharge port.

  Accordingly, an object of the present invention is to provide an ink jet recording apparatus capable of performing printing in a state where there is no bubble in the head in view of the problems of the conventional technology.

  In order to solve the above-described problems, an ink jet recording apparatus according to the present invention communicates at least two nozzles for ejecting ink droplets, a pair of ink supply ports, and a pair of ink supply ports. A head including an ink flow path that communicates each of the supply ports with the nozzles, an ink tank that stores ink, at least one of the pair of ink supply ports, and the ink tank communicate with each other. A first tube to be communicated, a second tube that communicates with the other ink supply port of the pair of ink supply ports, and the ink tank, and the ink tank to the head via the first tube. A pump for sending ink; a valve provided in the second tube, which can be opened and closed; a pump controller for controlling the pump; and opening and closing the valve A valve control unit for controlling, and the head and the ink tank are arranged so that ink is supplied from the ink tank to the head via the second tube by the surface tension of the ink meniscus in the nozzle. The pump control unit can stop the pump during printing and can operate the pump during non-printing. The valve control unit can open the valve during printing. Ink is supplied from the ink tank to the head by the surface tension of the ink meniscus, and the valve can be opened and closed while the pump is operating during non-printing.

  The ink jet recording apparatus of the present invention can supply ink from the ink tank to the head via the second tube by utilizing the surface tension of the ink meniscus in the nozzle during printing. On the other hand, when the ink jet recording apparatus opens the valve while operating the pump during non-printing, the ink sent to the head through the first tube is further returned to the ink tank through the second tube. It is. As a result, the air in the first and second tubes is discharged into the ink tank. The ink jet recording apparatus can fill the ink in the head by closing the valve while the pump is operating so that the ink cannot pass through the second tube.

  In the ink jet recording apparatus of the present invention, it is preferable that the end of the second tube is disposed above the end of the first tube in the ink tank.

  In the ink jet recording apparatus of the present invention, when the valve is opened while the pump is operating during non-printing, the ink sent to the head through the first tube is further returned to the ink tank through the second tube. As a result, the air in the first and second tubes is discharged into the ink tank. The ink jet recording apparatus can fill the ink in the head by closing the valve while the pump is operating so that the ink cannot pass through the second tube.

  An embodiment of the present invention will be described below with reference to the drawings.

[1] Outline of Inkjet Recording Apparatus 1 FIG. 1 is a diagram showing a main configuration of an inkjet recording apparatus 1 according to the present embodiment.

  The ink jet recording apparatus 1 includes a head 2 that ejects ink and prints an image (including characters) on a sheet (not shown), and an ink tank 3 that stores the ink. The head 2 includes an ink discharge surface 23 that discharges ink and faces two sheets (not shown), and two supply ports 21 and 22 that are provided on the opposite side of the ink discharge surface 23 of the head 2. The ink tank 3 is formed with a vent hole 3h communicating from the inside to the outside.

  The ink jet recording apparatus 1 further has a first tube 4 extending from the ink tank 3 to the supply port 21, a second tube 5 extending from the ink tank 3 to the supply port 22, and the first tube 4 from the ink tank 3 toward the head 2. A pump 41 for feeding ink and an electromagnetic valve 51 for adjusting the flow of ink in the second tube 5 are provided. The first tube 4, the second tube 5, the pump 41, and the electromagnetic valve 51 constitute an ink supply path from the ink tank 3 to the head 2.

  Further, the inkjet recording apparatus 1 includes a cap 6 that covers the head 2 when not printing, and the cap 6 is provided with a discharge port 61 for discharging the ink accumulated in the cap 6. Although not shown, a pump or the like for discharging ink from the discharge port 61 may be provided.

  The first tube 4 and the second tube 5 are respectively provided with end portions 4T and 5T in the ink tank 3, and the end portion 4T is disposed below the end portion 5T. At this time, the height difference d between the end portion 4T and the end portion 5T is not particularly limited as long as the bubbles coming out from the end portion 5T do not enter the first tube 4 from the end portion 4T. Absent.

  As the pump 41, a device capable of moving the ink in the first tube 4 can be used as appropriate, and a tube pump is particularly preferably used.

  The inkjet recording apparatus 1 further includes a pump drive unit 42 that drives the pump 41, a pump drive control unit 43 that controls the operation of the pump drive unit 42, a valve drive unit 52 that drives the valve 51, and a valve drive unit 52. A valve drive control unit 53 that controls the operation is provided.

[2] Structure of Head 2 The structure of the head 2 will be described. 2 is a perspective view showing the external appearance of the head 2, FIG. 3 is a plan view of the lower body 20b constituting the head 2 as viewed from above (A direction in FIG. 1), and FIG. FIG. 5 is a cross-sectional view taken along the line XX ′ of FIG. 2, FIG. 6 is a cross-sectional view taken along the line YY ′ of FIGS. 2 and 3, and FIG. FIG. 8 is a cross-sectional view taken along the line ZZ ′ of FIG. For convenience of explanation, in FIG. 3, a common channel 27 described later is indicated by a dotted line, and members such as the flexible cable 33 are appropriately omitted.

  As shown in FIG. 2, the head 2 includes a head body 20, a flexible cable 33, and the like. The head main body 20 is divided into a main body upper portion 20a and a main body lower portion 20b.

  As shown in FIGS. 2 and 5, piezoelectric elements 32 are arranged on the main body lower portion 20 b, and the flexible cable 33 is connected to a circuit (not shown) for driving these piezoelectric elements 32 in a head driving unit (not shown). The drive signal from is transmitted.

  As shown in FIG. 4, a plurality of discharge ports 25 having a minute diameter are formed on the discharge surface 23 provided on the lower surface of the main body lower portion 20b. The head 2 prints on a sheet by ejecting ink from the ejection port 25 toward a sheet conveyed in the direction D by a sheet conveying unit (not shown). The size of the discharge surface 23 in the longitudinal direction (direction perpendicular to the direction D) is larger than the maximum width E of the print area of the paper, and the discharge port 25 covers at least the maximum width E in the longitudinal direction of the discharge surface 23. A plurality are provided.

  As shown in FIGS. 3 and 6, a plurality of ejection units 2 a that eject ink from one ejection port 25 are arranged in parallel to the ejection surface 23 in the main body lower portion 20 b. Further, a plurality of common flow paths 27 extending in parallel to the longitudinal direction of the head 2 and parallel to each other are provided in the main body lower portion 20b, and ink is supplied from one common flow path 27 to the plurality of ejection units 2a. It has become so. Further, each common flow path 27 and the following second ink reservoir 204 in the main body upper portion 20a are communicated with each other by an ink distribution port 201. In the present embodiment, one ink distribution port 201 is provided in the vicinity of the end in the longitudinal direction of the common flow path 27, that is, two for each common flow path 27.

  The main body upper portion 20 a includes ink supply ports 21 and 22. The main body upper portion 20 a has a first ink reservoir 202 communicating with the ink supply ports 21 and 22 and a bottom portion of the first ink reservoir 202. A filter 203, a second ink reservoir 204 that communicates with the first ink reservoir 202 via the filter 203, and an ink distribution port 201 that continues from the bottom of the second ink reservoir 204 to the common flow path 27 are provided. The ink distribution port 201 communicates with the common flow path 27.

  In this embodiment, two ink supply ports (ink supply ports 21 and 22) are provided for each head 2 in the present embodiment, but the present invention is not limited to this. In addition to this, two or more pairs of ink supply ports, or three or more pairs of ink supply ports are provided in each of the plurality of common flow paths, and two or more ink supply ports are provided for each head. It may be provided.

  The ink sent from the ink supply port 21 or 22 passes through the first ink reservoir 202, the filter 203, and the second ink reservoir 204 in this order, and is sent from the ink distribution port 201 to the common flow path 27 to be discharged from the ejection unit 2a. To be supplied. Further, the ink may be sent out from the ink supply port 21 through the reverse path.

  As shown in FIGS. 7 and 8, the discharge unit 2 a includes a pressurization chamber 26 provided for each discharge port 25, a nozzle 24 continuous from the pressurization chamber 26 to the discharge port 25, and pressurization. A piezoelectric element 32 and an individual electrode 31 provided above the chamber 26 are provided. The pressurizing chamber 26 and the common flow path 27 are communicated with each other through a supply hole 28 (see FIG. 6). The upper wall of the pressurizing chamber 26 is composed of a diaphragm 29 formed continuously over the plurality of pressurizing chambers 26. On the vibration plate 29, a common electrode 30 formed in a similar manner continuously over the plurality of pressurizing chambers 26 is laminated. A separate piezoelectric element 32 is provided for each pressurizing chamber 26 on the common electrode 30, and a separate individual electrode 31 is also provided for each pressurizing chamber 26 so as to sandwich the piezoelectric element 32 together with the common electrode 30. It is done. A region other than the discharge port 25 on the discharge surface 23 is covered with a water-repellent film 23a to prevent ink adhesion.

  Each piezoelectric element 32 is individually driven by applying a driving pulse to the individual electrode 31 from a head driving unit (not shown) via the flexible cable 33. The deformation of the piezoelectric element 32 due to this driving is transmitted to the vibration plate 29, and the pressurizing chamber 26 is compressed by the deformation of the vibration plate 29. As a result, pressure is applied to the ink in the pressurizing chamber 26, and the ink that has passed through the nozzles 24 is ejected from the ejection port 25 as ink droplets onto the paper. Thus, an image is recorded on the paper with ink.

[3] Control of drive of pump 41 and valve 51 (3-1) Ink filling operation The pump drive control unit 43 and the valve drive control unit 53 drive the pump drive unit 42 and the valve drive unit 52 so that they are not printing. The ink filling operation for filling the ink supply path including the head 2 and the first tube 4, the second tube 5, the pump 41, and the like is executed.

In particular,
1) The pump drive control unit 43 controls the pump drive unit 42 to operate the pump 41 for a predetermined time.

  2) While the pump 41 is operating according to the above 1), the valve drive control unit 53 controls the valve drive unit 52 to repeat opening and closing of the electromagnetic valve 51 one or more times.

  3) The valve drive control unit 53 controls the valve drive unit 52 to open the electromagnetic valve 51, thereby gradually reducing the pressure in the ink supply path and the head 2.

  4) The pump drive control unit 43 controls the pump drive unit 42 to stop the pump 41.

  During the operations 1) and 2), when the pump 41 is operated, ink is taken in from the end 4T and is sent from the ink tank 3 to the head 2 through the first tube 4. The fluid resistance (hardness of ink flow) in the first tube 4 and the second tube 5 is much smaller than that in the head 2. Therefore, when the electromagnetic valve 51 is “open”, most of the ink sent to the head 2 in the first tube 4 is returned to the ink tank 3 from the end portion 5T through the second tube 5. . The ink flow at this time is indicated by solid arrows in FIG.

  As the ink flows in this way, the ink supply paths such as the first tube 4, the second tube 5, and the pump 41 are filled with ink. Then, bubbles in the ink supply path are discharged into the ink tank 3 from the end portion 5T. At this time, bubbles are not taken in from the end 4T because the end 4T is arranged below the end 5T.

  Even when the electromagnetic valve 51 is “open”, a part of the ink sent to the head 2 through the first tube 4 is taken into the head 2 through the ink supply port 21 as described above. This ink may enter the first ink reservoir 202, the second ink reservoir 204, and even the common flow path 27. However, since the supply hole 28 is fine, it is difficult for the ink to reach the pressurizing chamber 26. That is, when the electromagnetic valve 51 is “open”, at least the pressurizing chamber 26 and the nozzle 24 are not easily filled with ink.

  When the electromagnetic valve 51 is “closed” by the operation 2), the ink cannot pass through the second tube 5 and the pressure by the ink in the second tube 5 increases. By this pressure, ink is also sent to the pressurizing chamber 26 and the nozzle 24, and the pressurizing chamber 26 and the nozzle 24 are filled with ink. At this time, excess ink is discharged from the discharge port 25, but this ink is received by the cap 6 and discharged from the discharge port 61 to the outside of the cap 6.

  According to the operation 2), during the operation of the pump 41, the solenoid valve 51 is “closed” and “opened” at least once. As described above, by opening the electromagnetic valve 51, bubbles are removed from the head 2 and the ink supply path, and ink is filled in the head 2 by closing. That is, the valve drive control unit 53 closes and opens the electromagnetic valve 51 via the valve drive unit 52 to fill the ink into the head 2 and the ink supply path, and to cause bubbles from the head 2 and the ink supply path. Can be removed. At this time, from the viewpoint of removing bubbles, “open” is preferably executed twice or more with “close” in between. While the valve is “closed”, the air bubbles gathered in the first ink reservoir 202 due to the buoyancy of the air bubbles are transferred to the supply port 22 from the supply port 21 when the valve is subsequently opened. The ink is discharged to the ink tank 3 through the second tube 5 by the flow.

  Thus, when the bubble removal and the ink filling are completed, the discharge of the ink from the discharge port 25 is stopped by the operation 3), and the ink meniscus M is formed in the nozzle 24.

  Through the above operation, initial filling or recovery after printing is performed, and preparation for printing is completed.

(3-2) Printing Operation During printing, the pump 41 is stopped under the control of the pump drive control unit 43. When the valve drive control unit 53 controls the valve drive unit 52 to open the electromagnetic valve 51, ink is supplied into the head 2 through the second tube 5 by the surface tension of the ink meniscus M in the nozzle 24. The traveling direction of the ink at this time is indicated by a dotted arrow in FIG.

  The water head difference between the nozzle 24 and the ink tank 3 is caused by the balance between the gravity applied to the ink and the surface tension due to the ink meniscus M (the surface tension due to the capillary phenomenon in which the ink attempts to enter the thin nozzle 24). It is adjusted so that the ink is supplied without excess or deficiency. Gravity acts in the direction of flowing from the head 24 toward the ink tank 3, and the surface direct force of the meniscus M acts in the direction of moving ink from the ink tank 3 toward the head 2. When the meniscus M in the nozzle 24 moves backward due to the ejection of ink by the head 2, the surface tension increases, so that the ink moves from the ink tank 3 toward the nozzle 24.

  The present invention is not limited to the above embodiment. In addition, a technique obtained by adding various modifications such as adding a known technique within the scope of the claims is also included in the scope of the present invention.

FIG. 1 is a diagram showing a main configuration of an ink jet recording apparatus 1 according to the present embodiment. FIG. 2 is a perspective view showing the appearance of the head 2. FIG. 3 is a plan view of the head 2 as viewed from above (direction A in FIG. 1). FIG. 4 is an end view of the head 2 as viewed from below (direction B in FIG. 1). FIG. 5 is a cross-sectional view taken along arrow X-X ′ in FIG. 2. FIG. 6 is a cross-sectional view taken along arrows Y-Y ′ in FIGS. 2 and 3. FIG. 7 is a plan view showing a discharge unit 2a which is a part of FIG. FIG. 8 is a cross-sectional view taken along the line Z-Z ′ in FIG. 7.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet recording apparatus 2 Head 20 Head main body 20a Main body upper part 20b Main body lower part 21, 22 Supply port 23 Discharge surface 23a Water repellent film 24 Nozzle 25 Discharge port 26 Pressurization chamber 27 Common flow path 28 Supply hole 29 Diaphragm 30 Common electrode 31 Individual electrode 32 Piezoelectric element 3 Ink tank 31 Vent hole 4 First tube 4T End 41 Pump 42 Pump drive unit 43 Pump drive control unit 5 Second tube 51 Solenoid valve (an example of valve)
5T End 52 Valve control unit 53 Valve drive control unit M Meniscus surface

Claims (2)

A nozzle that ejects ink droplets; at least two ink supply ports that form a pair; and an ink flow path that connects the pair of ink supply ports to each other and each of the ink supply ports to the nozzle. Head,
An ink tank for storing ink;
A first tube for communicating at least one ink supply port of the pair of ink supply ports and the ink tank;
A second tube that communicates the other ink supply port of the pair of ink supply ports with the ink tank;
A pump for sending ink from the ink tank to the head via the first tube;
A valve provided on the second tube and capable of opening and closing;
A pump control unit for controlling the pump;
A valve control unit for controlling the opening and closing of the valve,
The head and the ink tank are arranged so that ink is supplied from the ink tank to the head via the second tube by the surface tension of the ink meniscus in the nozzle,
The pump control unit can stop the pump during printing, and can operate the pump during non-printing,
The valve control unit opens the valve at the time of printing to supply ink from the ink tank to the head by the surface tension of the ink meniscus. An ink jet recording apparatus that can be opened and closed.   The inkjet recording apparatus according to claim 1, wherein an end of the second tube is disposed above the end of the first tube in the ink tank.

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