JP2007160618A - Image recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrict a hydraulic head difference in a main scanning range of a head to be within an allowable range. <P>SOLUTION: An ink tank (accurately, an atmospheric air opening section at the side of a tank) to be normally disposed to a light or left end is placed on a roughly central section in the main scanning range. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus using roll paper, roll film, or the like, for example, an image recording apparatus such as a printer, a facsimile machine, or a copying machine.

  Some image recording apparatuses have an ink tank for storing ink to be supplied to the recording head, and supply ink from the ink tank to the recording head through a tube.

For example, Patent Document 1, Patent Document 2, and Patent Document 3 can be cited as conventional examples.
JP 2003-326732 A JP 2001-38920 A Japanese Patent Laid-Open No. 2001-80088

  In the case of an ink jet printer, it is important to maintain a water head difference between a head and an ink tank (more precisely, an ink discharge nozzle surface and an air release surface on the tank side) within a specified range. However, when trying to increase the applicable paper size of the printer, even if the device tilts at the same angle, it will greatly affect the water head difference, and leveling work is required when installing the device, and the installation location is regulated. There is a possibility of becoming.

  It is an object of the present invention to provide an apparatus that reduces the effect on the head difference with respect to the inclination.

The configuration of the present invention for achieving the above object is as follows.
In an image recording apparatus that performs recording by discharging ink from a recording head that scans in the main scanning direction,
An image recording apparatus, wherein an ink tank for storing ink to be supplied to the recording head is disposed at a position corresponding to substantially the center in the main scanning direction.

  According to the present invention, since the air release part on the main tank side is arranged at about the center part of the head main scanning range, the influence on the water head difference due to the inclination of the apparatus can be halved. There are advantages such as an increase in the allowable inclination with respect to the horizontal, or the need for leveling the device during installation.

  FIG. 1 is a perspective view showing an outline of the apparatus.

The ink jet recording apparatus shown in FIG. 1 performs reciprocation (main scanning) of the recording head 201 and conveyance (sub scanning) of recording sheets S or rolls 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 repeatedly ejecting ink from the recording head 201 and attaching it to the recording sheet S while synchronizing with these movements.
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.

  The recording head 201 has a plurality of nozzle rows for ejecting inks of different colors. A plurality of independent main 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. What is important here is that the main tank is arranged at substantially the center of the head main scanning range. The reason will be described later.

  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.

  Next, the detailed configuration of the ink supply system of the ink jet recording apparatus will be described with reference to FIG. FIG. 2 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 for ease of explanation.

  First, the recording head 201 will be described.

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

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

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

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

The nozzle 201g is arranged with the tip for discharging ink facing downward, but no valve mechanism for closing the tip is provided, and the ink fills the nozzle 201g in a state where a meniscus is formed. For this reason, the inside of the recording head 201, particularly the inside of the nozzle 201g, is kept in a negative pressure state. However, if the negative pressure is too small, if foreign matter or ink adheres to the tip of the nozzle 201g, the ink meniscus may collapse and the ink may leak out of the nozzle 201g. On the other hand, if the negative pressure is too large, the force that pulls the ink back into the nozzle 201g becomes stronger than the energy given 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 range of the negative pressure 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 experimental results of the present inventors, the range is about −0.4 [kPa] to about −2 [kPa]. ] (However, the specific gravity of ink≈the specific gravity of water) is preferable.
In this embodiment, the ink supply unit 205 and the recording head 201 are connected by the ink supply tube 206, and the position of the recording head 201 with respect to the ink supply unit 205 can be set relatively freely. In order to obtain a negative pressure, the recording head 201 is arranged at a position higher than the ink supply unit 205. Details of this height will be described later.

  In the filter 201c as used in the present embodiment, the pressure required to transmit air is about 10.1 [kPa] (experimental value). Therefore, if air exists in the liquid chamber 201f located downstream of the filter 201c with respect to the ink moving direction in the recording head 1, 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 the present embodiment, this phenomenon is utilized, and the liquid chamber 201f is not filled with ink, and a fixed amount of ink is applied so that an air layer exists between the ink in the liquid chamber 201f and the filter 201c. It is stored in the chamber 201f.

  The amount of ink stored in the liquid chamber 201f is at least the amount necessary to fill the nozzle 201g with ink. If air from the liquid chamber 201f enters the nozzle 201g, the nozzle 201g after ink ejection is not replenished with ink, resulting in ejection failure. Therefore, the nozzle 201g must always be filled with ink.

  The pressure adjustment chamber 201i is a chamber whose volume decreases as the internal negative pressure increases. When the pressure adjustment chamber 201i is configured by the elastic member 201h as in the present embodiment, the elastic member 201h is a rubber material. Etc. are preferably used. Moreover, you may comprise by the combination of a plastic sheet | seat and a spring other than the elastic member 201h. The volume of the pressure adjusting chamber 201i is set according to the environmental temperature in which the recording head 201 is used, the volume of the sub tank 201b, and the like.

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

  The main tank 204 is detachable from the 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. The main tank 204 is an airtight container by itself, and the ink 209 is stored in the main tank 204 as it is.

  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 conductive hollow needles, and are arranged with the needle tips facing upward corresponding to the positions of the ink supply port and the air introduction port of the main tank 204. By attaching 204 to 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 inside of the main tank 204. That is, the flow path on the ink supply needle 205a side and the flow path on the air introduction needle 205b side communicate with each other as a single flow path when the main tank 204 is mounted on the ink supply unit 205, and are not mounted. The structure is divided.

  The ink supply needle 205a is connected to the ink supply tube 206 through a path of a liquid path 205c, a shutoff valve 210, and a liquid path 205d. The atmosphere introduction needle 205b communicates with the atmosphere via the liquid path 205e, the buffer chamber 205f, and the atmosphere communication port 205g. The liquid path 205c at the lowest position in the ink supply path from the ink supply needle 205a to the ink supply tube 206 and the lowest position in the path from the atmosphere introduction needle 205b to the atmosphere communication port 205g. Both of the liquid passages 205e have the same height. In this embodiment, the ink supply needle 205a and the air introduction needle 205b are thick ones having an inner diameter of 1.6 [mm] in order to suppress the flow resistance of the ink. 0.5 [mm].

  In order to prevent ink leakage from the atmosphere communication port 205g, the buffer chamber 205f communicates with the atmosphere communication port 205g via a liquid path 205j passing through a position higher than the upper opening 205i of the atmosphere introduction needle 205b. . For example, when the main tank 204 containing ink is attached by mistake without attaching the recording head 201 and the shutoff valve 210 is opened, air is introduced into the main tank 204 from the ink supply needle 205a. In this case, since the tip of the ink supply needle 205a is at atmospheric pressure, if the atmosphere communication port 205g is at a position lower than the upper opening 205i, ink flows and leaks to the lower side. In order to avoid such a problem, as described above, the buffer chamber 205f is communicated with the atmosphere communication port 205g through the liquid passage 205j passing through a position higher than the upper opening 205i. For example, as shown in FIG. 3 or FIG. 4, the same effect can be obtained with a configuration in which the atmosphere communication port 205g is provided at a position higher than the upper opening 205i.

  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. The diaphragms 210a are crushed by the pressing spring 210c, whereby the liquid paths 205c and 205d are blocked. . 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 resting, and is opened and closed in synchronization with the recovery unit 207 during an ink filling operation described later.

  The configuration of the ink supply unit 205 described above is provided for each main tank 204, that is, for each ink color, except for the lever 210d. The lever 210d is common to all colors, and simultaneously opens and closes the shut-off valves 210 for all colors.

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

  The buffer chamber 205f is a target space for temporarily holding ink that has flowed out of the main tank 204 due to the expansion of air in the main tank 204, and the lower end of the air introduction needle 205b is located at the bottom of the buffer chamber 205f. . When the air in the main tank 204 expands, such as when the environmental temperature rises while the inkjet recording apparatus is waiting or paused, the shutoff valve 210 is closed, so that the ink in the main tank 204 is transferred to the air introduction needle 205b. Then flows out 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 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.

  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.

  FIG. 3A shows a normal state in which ink can be supplied from the main tank 204 to the recording head 201 (see FIG. 2). In this state, the main tank 204 is airtight except for the buffer chamber 205f, so the ink tank 205 is kept at a negative pressure, and the ink front end 209a remains in the middle of the liquid path 205e. The pressure at the leading end 209a of the ink is atmospheric pressure (= 101.3 [kPa]) because it is in contact with the atmosphere. The liquid path 205e where the ink tip 209a is located and the liquid path 205c communicating with the ink supply tube 206 (see FIG. 2) have the same height, and the two liquid paths 205c and 205e communicate with each other 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.

  When the ink in the main tank 204 is consumed, as shown in FIG. 3B, the tip 209a of the ink gradually moves toward the air introduction needle 205b and reaches the position just below the air introduction needle 205b. As shown in FIG. 3 (c), the air bubbles become air bubbles and rise inside the air introduction needle 205 b and are introduced into 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.

  FIG. 3D shows a state where ink is accumulated in the buffer chamber 205f. In this case, the leading 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 −9.8 h1 [Pa]. It has become.

  As described above, in the present embodiment, the pressure due to the water head difference applied to the nozzle 201g (see FIG. 2) 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 In the normal state, the negative pressure Pn at Pn is Pn≈−9.8 (h2−h3−h4) [Pa], and in a state where ink is accumulated in the buffer chamber 205f, Pn≈−9.8 (h2− h1-h3-h4) [Pa]. The value of Pn is set so as to be within the above-described negative pressure range (−0.4 [kPa] to −2 [kPa]).

  Referring to FIG. 2 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 through the circuit 205h through the ink in the main tank 204 in a state where ink is present in the main tank 204, and no ink exists or the main tank 204 An electrical open is detected when 204 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.

  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 blocking surface 210.

  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 tube having a tube pump type suction pump 207c is connected to the suction cap 207a, and continuous suction is possible by driving the suction pump 207c by a pump motor 207d. Further, the suction amount can be changed according to the rotation amount of the pump motor 207d. In the present embodiment, the suction pump 207c capable of reducing pressure to 40.5 [kPa] is used.

  The cam 207b operates the suction cap 207a, and is rotated in synchronization with the cam 207f that operates the link 207e by the cam control motor 207g. The timings at which the positions a to c of the cam 207b come into contact with the suction cap 201g coincide 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 201g 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 201g 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.

  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 to prevent the nozzle 201g from drying and to prevent ink from flowing out of the recording head 201 (particularly when the apparatus itself is moving). In some cases, the device is tilted and ink flows out). The position of c of the cams 207b and 207f is used during the ink filling operation to the recording head 201 described below.

  The feature of the present invention resides in the arrangement of the main tank, and details thereof are as follows. FIG. 5 schematically shows the characteristics. In the case of a general apparatus (A), the tank is disposed at either the left or right end of the apparatus. However, in that case, for example, if the installation surface of the device is inclined, when the specified head difference is Ha, the amount of change is Hb and Hc due to the reciprocating movement of the carriage. In the end, the water head difference during printer operation falls within the range of Ha + Hc to Ha + Hb. On the other hand, if the main tank is arranged at the center of the main scanning range (B), the water head difference changes Hd and He due to the carriage reciprocation, but since He is almost equal to -Hd, Ha + Hd to Ha-Hd It becomes.

  When the device is tilted by the same amount, the change Hd of the head difference is about half that of Hb. As a result, the printer with the main tank placed in the center is tilted twice as much as the printer placed at the end. Will be allowed.

  This is particularly effective in large-format inkjet printers that target media sizes exceeding 1 m. As the width increases, the accuracy of long parts must be in a more severe direction, or the installation surface must require a wider range of flatness. What can be done is very advantageous in terms of technology and cost.

  Here, the main tank has been described so far. To be precise, the main tank itself may be disposed at a different position as long as the atmosphere-released portion on the tank side can be disposed at the center of the main scanning range. There is no loss of effect.

  As described above, the air release part on the main tank side is arranged at the center of the head main scanning range, so that the influence on the head difference due to the inclination of the device can be halved. There are merits such as an increase in the allowable value of inclination with respect to the angle or the need for leveling the device during installation.

  Moreover, it becomes possible to loosen part accuracy, leading to cost reduction.

It is a perspective view which shows an apparatus outline. FIG. 3 is a diagram illustrating a detailed configuration of an ink supply system of the ink jet recording apparatus. The figure which shows the example of arrangement | positioning of an air communication opening. The figure which shows the example of arrangement | positioning of an air communication opening. The figure which shows arrangement | positioning of the main tank.

Explanation of symbols

201 Recording Head 202 Carriage 203 Conveying Roller 204 Main Tank 205 Ink Supply Unit 205g Air Communication Port 206 Supply Tube 207 Recovery Unit

Claims (1)

In an image recording apparatus that performs recording by discharging ink from a recording head that scans in the main scanning direction,
An image recording apparatus, wherein an ink tank for storing ink to be supplied to the recording head is disposed at a position corresponding to substantially the center in the main scanning direction.

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