JP6405773B2 - Head unit and image forming apparatus - Google Patents

Description

  The present invention relates to a head unit that discharges liquid and an image forming apparatus.

  As an image forming apparatus such as a printer, a facsimile, a copying apparatus, a plotter, and a complex machine thereof, for example, an ink jet recording apparatus or the like is used as a liquid discharge recording type image forming apparatus using a recording head (discharge head) that discharges ink droplets. Are known. This liquid discharge recording type image forming apparatus means that ink droplets are transported from a recording head (not limited to paper, including OHP, and can be attached to ink droplets and other liquids). The recording medium or recording medium (also referred to as recording medium, recording paper, recording paper, etc.) to form an image (recording, printing, printing, and printing are also used synonymously). .

  In the present application, “image forming apparatus” means an apparatus that forms an image by discharging liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc. "Image formation" is not only the application of images with meanings such as characters and figures to the medium, but also the addition of images with no meaning such as patterns to the medium (simply applying droplets to the medium) Also means landing). “Ink” is not limited to ink, but is used as a general term for all liquids capable of image formation, such as recording liquid, fixing processing liquid, and liquid. DNA samples, resists, pattern materials and the like are also included.

In an ink jet recording apparatus having a plurality of heads, it is already known that the minimum amount necessary for discharging thickened ink varies from head to head.
A wide-width printer will be described as an example. Among wide-width printers, those mainly for drawing output have a very large ratio of monochrome printing to color printing. For this reason, a monochrome head is provided for the purpose of high speed and high resolution in monochrome printing.

  On the other hand, since black (Bk) ink is easy to dry with respect to color (CMY) ink, a large amount of head suction for discharging thickened ink is required for color ink. For this reason, the minimum amount required for discharging the thickened ink differs between the monochrome head and the color head.

  Also, in the inkjet recording apparatus, as a negative pressure control method for maintaining a negative pressure in the sub tank that supplies liquid to the head, the side surface of the sub tank is sealed with a displacement member, and the displacement member is always outward (outside) by an elastic member. ), The displacement member is displaced according to the ink volume in the sub tank, and the negative pressure value of the sub tank changes.

However, in the conventional head suction method, there is a trade-off between shortening the head maintenance time and reducing the amount of thickened ink discharged (head suction amount). The reason is as follows.
(1) In order to shorten the head maintenance time, when a plurality of heads are sucked at the same time with one suction pump, the head suction amount needs to be matched to a necessary head. For this reason, a large amount of ink is sucked from a head having a small required amount, and ink is wasted.
(2) In order to reduce the discharge amount of thickened ink, if the required amount is sucked one head at a time, it cannot be sucked at the same time, and the head maintenance time increases.

  Japanese Patent Laying-Open No. 2008-012684 (Patent Document 1) discloses a configuration in which a plurality of capping positions are provided and a part of a plurality of heads can be selectively sucked for the purpose of reducing unnecessary ink discharge. However, even in this configuration, the problem that the head maintenance time becomes long cannot be solved.

  SUMMARY An advantage of some aspects of the invention is that it provides a head unit and an image forming apparatus that can perform head maintenance in a short time without wastefully consuming ink.

In order to solve this problem, the present invention provides a head unit that includes a plurality of ejection heads that eject droplets and a sub-tank that stores liquid to be supplied to the ejection heads, and simultaneously sucks liquid from the plurality of ejection heads. The sub tank is provided for each of the discharge heads, and is disposed in at least one of the plurality of sub tanks in a flow path between the discharge head and the sub tank. A valve mechanism for blocking the flow path when a predetermined amount of liquid in the sub tank is discharged is provided, and one of the plurality of sub tanks is not provided with the valve mechanism. To do.

  According to the present invention, it is possible to simultaneously perform head suction without wasting ink even when the required head suction amounts differ among a plurality of ejection heads. In addition, since head suction can be performed simultaneously on a plurality of heads, maintenance can be performed in a short time.

FIG. 2 is a diagram schematically illustrating a configuration example of an image forming unit that functions as a part of the ink jet recording apparatus according to the invention. It is a figure explaining the negative pressure generation mechanism in a sub tank. It is a graph which shows the relationship between the negative pressure in a sub tank, and the amount of ink. It is a figure explaining the method of setting the ink amount in a sub tank to a filling full tank position. It is a figure explaining an example of the composition which detects the amount of displacement of the flexible member of a sub tank. It is a schematic diagram which shows 1st Example of a head unit. It is sectional drawing which shows the 2nd Example of the sub tank with which the required small amount of head suction is mounted | worn with a head. It is a figure explaining the timing which the valve mechanism in a subtank closes. It is sectional drawing which shows the 3rd Example of the sub tank with which the required small amount of head suction is mounted | worn. It is a figure explaining 4th Example of the sub tank which gave the function of the choke valve to the valve mechanism. It is a figure which shows the structure which applied this invention to the inkjet recording device in which full color recording is possible.

First, the operation of the present invention will be briefly described with reference to an embodiment described later.
In FIG. 6, among the head set 100 including the head 101 and the sub tank 102, the sub tank 102A of the head set 100A of the head having a small head suction amount for discharging the thickened ink (ink having increased viscosity) has a valve mechanism. 130 is provided.

  Since the valve mechanism 130 opens and closes in conjunction with the displacement of the film (flexible member) 110 on the side surface of the sub tank, there is a large amount of ink in the sub tank 102A. A small amount of ink has been discharged (sucked by the suction pump 119). (B) In the state shown in FIG.

  When a plurality of heads are simultaneously sucked by a single suction pump 119, a valve mechanism 130 (for a headset that requires a small amount of head suction) is closed when a certain amount is sucked (closed) ( (b) State of the figure). Thereafter, by continuing the suction of the head, the ink can be discharged only from the head that is not provided with a valve mechanism (the required amount of head suction is large) (the thickened ink is discharged by + α). Accordingly, it is possible to perform appropriate suction for each head while simultaneously sucking a plurality of heads.

Hereinafter, the present invention will be described in more detail with reference to illustrated embodiments.
FIG. 1 is a front view schematically showing a configuration example of an image forming unit functioning as a part of an ink jet recording apparatus which is an example of an image forming apparatus according to the present invention, as viewed from a direction orthogonal to the main scanning direction. . The main scanning direction is the moving direction of the carriage 103, and is the left-right direction in FIG.

  As elements constituting the image forming unit of this embodiment, an ink is dropped to eject ink for recording on a recording medium, and temporarily before the ink is sent to the ejection head 101. There are sub-tanks 102 for storage, which are mounted on a carriage 103.

  In FIG. 1, only one headset 100 including the ejection head (recording head) 101 and the sub tank 102 is shown, but a plurality of headsets are mounted on the carriage 103 (other headsets are illustrated). (Omitted).

  The carriage 103 is capable of scanning in the horizontal direction in the figure, and includes an encoder 104 installed in a scanning range for measuring the position of the carriage 103 and a carriage position detection sensor 105 for detecting the position of the carriage 103. When 105 detects the number of slits of the encoder 104, the scanning position of the carriage 103 can be controlled. Further, there are a main tank 106 for storing ink to be supplied to the sub tank 102, and an ink supply path 107 for communicating the main tank 106 and the sub tank 102, and ink is supplied from the main tank 106 to the sub tank 102 in the path of the ink supply path 107. There is a liquid feed pump 108 for feeding the liquid. The liquid feed pump 108 is, for example, a tube pump, and can send and suck ink by forward and reverse operations.

FIG. 2 is a plan view for explaining a negative pressure generating mechanism in the sub tank 102.
In the sub tank 102, it is necessary to maintain a negative pressure state so that the stored ink does not leak from the ejection head 101. In order to create the negative pressure state, for example, the flexible member 110 is provided on one side surface of the sub tank 102, the negative pressure generating spring 109 that biases the flexible member 110 to the outside is provided, and ink is supplied into the sub tank 102. After the ink is supplied from the supply port 118 to which is supplied, negative pressure is generated in the sub tank 102 by sucking or discharging the ink from the sub tank 102. Further, the ink is sucked by the liquid feeding pump 108 (FIG. 1) capable of sucking ink, whereby the flexible member 110 is drawn in the sub tank 102, the negative pressure generating spring 109 is compressed, and the negative pressure is increased. When ink is supplied into the head tank from there, the flexible member 110 is pushed out of the sub tank 102 and the negative pressure generating spring 109 is extended, so that the negative pressure is weakened. By repeating these steps, the negative pressure in the sub tank 102 can be controlled to be kept constant.

  FIG. 3 is a graph showing the relationship between the negative pressure in the sub tank 102 and the ink amount. When the amount of ink in the sub tank 102 is large, the negative pressure in the sub tank 102 is small and weak. When the amount of ink is small, the negative pressure in the sub tank 102 is large and strong.

  If the negative pressure in the sub-tank 102 is too weak, there is a problem that ink leaks from the ejection head 101. If the negative pressure is too strong, air or dust is mixed from the ejection head 101. It becomes a problem. For this reason, it is necessary to control the sub tank 102 within the range of the negative pressure control range A which is from the full filling position considering negative pressure to the ink consumption lower limit position considering negative pressure, which is the ink in the sub tank 102. It is necessary to control the amount within the ink amount control range B.

  FIG. 4 is a side view of the sub tank 102 regarding a method of setting the ink amount in the sub tank 102 to a full filling position (hereinafter referred to as “fill full tank amount” in order to avoid confusion with the filer position and the carriage position). It will be explained from the direction.

  The sub tank 102 is provided with, for example, an electrode pin 111 as means for detecting the liquid level. In addition, the atmosphere communication path 112 for communicating with the atmosphere inside the sub tank 102 is provided, and the atmosphere communication path 112 has an atmosphere opening / closing valve 113 capable of communicating with and shielding the atmosphere.

  As an example of setting the full filling amount, first, the atmospheric on-off valve 113 is opened, so that the negative pressure in the sub tank 102 is released and the liquid level in the sub tank 102 is lowered. At this time, the supply port 118 is desirably below the liquid level. If the liquid level is present, air is mixed into the ink supply path 107 from the supply port 118, and when the ink is next supplied, bubbles may be discharged from the supply port 118 together with the ink. The bubbles may pass through the atmosphere communication path 112 and adhere to the atmosphere on / off valve 113, which may cause the valve to stick or to leak.

  Ink is supplied after the negative pressure is released and the liquid level drops. By supplying ink, the liquid level rises, and by detecting the electrode pin 111 that detects the liquid level, it is possible to supply ink to a predetermined position (amount). Thereafter, the atmospheric on-off valve 113 is closed again, and a predetermined negative pressure value is obtained by sucking a predetermined amount of ink therefrom, and the full filling amount in consideration of the negative pressure in the sub tank 102 can be set.

FIG. 5 is a plan view illustrating a configuration example for detecting the displacement amount of the flexible member 110 of the sub tank 102.
In this example, a filler 114 is provided to detect the amount of displacement of the flexible member 110 provided in the sub tank 102 mounted on the carriage 103 that can detect and control the scanning position. The filler 114 is provided in a swingable state with a support shaft 116 serving as a connection portion with the sub tank 102 as a rotation shaft. A biasing spring 115 is disposed between the end of the filler 114 and the sub tank 102. The urging spring 115 urges the end portion of the filler 114 in the upward direction in the drawing, so that the filler 114 is urged in a direction in which it presses and contacts the flexible member 110 with the support shaft portion 116 as a fulcrum. A detection sensor 117 (for example, a transmissive photosensor) that detects the filler 114 is not mounted on the carriage 103 but is installed at a predetermined position.

  In such a configuration, the position of the carriage 103 when the detection sensor 117 detects the filler 114 at a certain time is stored, and the stored position and the carriage 103 when the detection sensor 117 detects the filler 114 at the next time are stored. By detecting the displacement with respect to the position, the displacement amount of the flexible member 110 can be measured.

  That is, the carriage 103 on which the sub-tank 102 is mounted reciprocates in the left-right direction in the drawing for the recording operation, but in the figure (a), the detection sensor 117 inserts the filler 114 when the position of the carriage 103 is X1. Suppose that it is detected. If the position of the filler 114 has not changed (if the flexible member 110 is not displaced), even if the carriage 103 reciprocates, the position where the detection sensor 117 detects the filler 114 next is X1. When the detection sensor 117 detects the filler 114 at the same carriage position (X1), it can be seen that the position of the filler 114 is not changed (the flexible member 110 is not displaced).

  On the other hand, when the position of the filler 114 has changed as indicated by the solid line in FIG. 5B, the filler 114 is not detected at the carriage position X1, and the detection sensor 117 is placed at the carriage position X2 to the left of X1. Will be detected. Therefore, it can be seen that the filler 114, that is, the flexible member 110 is displaced by the difference between the positions X1 and X2. If X0 is the carriage home position, the displacement amount of the flexible member 110 is X2-X1. Considering the amount of displacement of the filler 114 as the amount of displacement of the flexible member 110 poses no problem in practice.

  As described with reference to FIG. 4, when setting the full filling amount in consideration of the negative pressure, the electrode pin 111 detects the ink after opening the atmospheric on-off valve 113 and setting the sub tank 102 to atmospheric pressure. Then, the ink is supplied to a predetermined amount, and the atmospheric on-off valve 113 is closed again. By scanning the carriage 103 in this state, the detection sensor 117 is detected by the filler 114, and the detected carriage position is stored as an atmospheric release position. Then, by sucking a predetermined amount of ink therefrom, the amount of ink in the head tank can be set to the full filling amount in consideration of the negative pressure.

  However, in this configuration example, every time it is necessary to detect the amount of displacement of the flexible member 110, it is necessary to move the filler 114 mounted on the carriage 103 to the position considered in accordance with the detectable position of the detection sensor 117. is there.

  Next, a first embodiment of the head unit will be described with reference to FIG. FIG. 6 shows an example of a head unit including two headsets 100 each composed of an ejection head (recording head) 101 and a sub tank 102. However, the number of headsets included in the head unit is limited to two. It is not something.

  FIG. 6 schematically shows a state in which each of the ejection heads 101 is capped by the cap 121 and undergoes maintenance when the headset 100A and the headset 100B are in a predetermined maintenance position. The cap 121 is connected to the waste liquid tank 120 via the suction pump 119. As described in FIG. 1, the ink supply path 107 (FIG. 1) is connected to the ink supply port 118 of the sub tank 102, and ink is supplied from the main tank 106.

  In the illustrated example, the headset 100A is a headset with a small amount of head suction for discharging thickened ink (ink with increased viscosity), and the headset 100B is a head suction for discharging thickened ink. Use a headset with a large amount.

  The headset 100 (100A, 100B) includes an ejection head (recording head) 101 and a sub tank 102. As described with reference to FIG. 2, the sub tank 102 includes the flexible member 110 on one side surface and the negative pressure generating spring 109 that biases the flexible member 110 outward.

  The configuration of each headset mounted on the head unit is basically the same, but in the illustrated example, the valve mechanism 130 is provided only in the sub tank 102A of the headset 100A.

  The valve mechanism 130 includes a pressing member 131 mounted inside the flexible member 110 of the sub tank, a seal member 132 attached to the tip of the pressing member 131, a valve seat 133 that is an inflow portion of the ink flow path, and the like. Has been. The valve mechanism 130 moves in conjunction with the displacement of the flexible member 110. (A) When the seal member 132 of the valve mechanism is separated from the valve seat 133 as shown in the figure, the valve is in the released state, and (b) the seal member 132 of the valve mechanism is pressed against the valve seat 133 as shown in the figure. As a result, the valve is closed.

  Now, when suction is performed by the suction pump 119 in the state shown in (a), ink is discharged from the sub-tanks 102A and 102B of both headsets. At this time, the flexible member 110 is displaced in the direction in which the valve is closed. When the suction is further continued, the valve of the sub tank 102A is closed when a predetermined amount of ink is discharged.

  If the suction is further continued with the valve closed (b), the ink cannot be discharged from the sub tank 102A, and the ink can be discharged only from the sub tank 102B of the other headset 100B. Therefore, even when the required head suction amount differs for each headset, head suction can be performed simultaneously without wasting ink. In the case of the illustrated example, if the valve of the sub tank 102A is closed, the ink is not discharged from the headset 100A even if the suction is continued, so that the ink is not discharged wastefully in the headset 100A.

An example of a wide-width printer is an example in which the required head suction amount is different for each head.
Among wide-width printers that mainly output drawings, the ratio of monochrome printing to color printing is very large. For this reason, a monochrome head is provided for the purpose of high speed and high resolution in monochrome printing.

  On the other hand, since black (Bk) ink is easy to dry with respect to color (C, M, Y) ink, a large amount of head suction for discharging thickened ink is required for color ink.

  For this reason, a monochrome head (black headset) and a color head (C, M, Y headset) have different minimum amounts for discharging thickened ink.

  In the configuration example of FIG. 6, the headset 100B is a black ink headset (a head that requires a large amount of suction), and the headset for each color of C, M, and Y is the headset 100A (necessary head). Head with a small amount of suction). That is, in the headset for color (C, M, Y) ink, the valve mechanism 130 is provided in the sub tank 102A.

  FIG. 7 is a cross-sectional view showing a second embodiment of a sub tank (head tank) mounted on a head that requires a small amount of head suction. In FIG. 7, the direction of the sub-tank is changed for easy explanation.

  The sub tank 202A shown in FIG. 7 constitutes a headset together with an unillustrated ejection head (recording head). The sub tank 202A is provided with a valve mechanism 230. The valve mechanism 230 includes a pressing member 231, a sealing member 232, a valve seat 233, a first lever 234, a second lever 236, and the like. Reference numeral 210 denotes a flexible member, and reference numeral 209 denotes a negative pressure generating spring that urges the flexible member 210 outward. Reference numeral 218 denotes an ink supply port, and 219 denotes an ink discharge port (head supply port).

  The pressing member 231 is mounted inside the flexible member 210. The first lever 234 and the second lever 236 are rotatably supported by the case member of the sub tank. The pressing member 231 is disposed so as to press the vicinity of one end of the first lever 234 when the flexible member 210 contracts. A weight 235 is fixed to the other end of the first lever 234. A seal member 232 is attached to one end of the second lever 236 (the end corresponding to the valve seat 233). A weight 237 is fixed to the other end of the second lever 236. The first lever 234 and the second lever 236 are arranged in a positional relationship such that when the first lever 234 rotates, the second lever 236 is pushed by the first lever 234 and the second lever 236 is rotated. .

  In the state shown in the figure where the sub tank 202A is sufficiently filled with ink, the first lever 234 is lowered on the weight 235 side, and the second lever 236 is also lowered on the weight 237 side. For this reason, the seal member 232 attached to the second lever 236 is separated from the valve seat 233, and the valve is released. At this time, ink can be supplied to an ejection head (not shown) connected to the ink discharge port 219.

  When the head is sucked by a suction pump (not shown) and ink is discharged from the sub tank 202A, the flexible member 110 contracts and the pressing member 231 moves downward in the drawing, and the pressing member 231 is moved to the first lever. One end of 234 is pressed. The pressed first lever 234 rotates in the direction indicated by an imaginary line arrow a in the figure, and presses one end of the second lever 236 at a certain point. The pushed second lever 236 rotates in the direction indicated by an imaginary line arrow b in the figure, and finally the seal member 232 attached to the other end of the lever is pressed against the valve seat 233 and crushed, and the flow path to the head The valve is closed.

  The rotation axis (rotation center) of the first lever 234 is provided closer to the weight 235 than the center of the lever. When the first lever 234 rotates in the direction of arrow a, the lever principle is used. And is provided to close the valve.

  Thus, in the second embodiment, since the valve mechanism 230 includes the lever member, the valve can be closed using the “leverage principle”, so that the force when the flexible member 110 contracts is reduced. Even if it is small, the sealing member 232 can be pressed against the valve seat with a large force, and the sealing performance can be improved.

  In the second embodiment, the two lever members (first lever 234 and second lever 236) of the valve mechanism 230 are each provided with a weight member (235, 237) at one end of the lever. Thus, each lever is biased in the valve release direction. Thereby, when the pressing member 231 is not pushing the 1st lever 234, a valve can be made into a released state and unintentional valve closing can be prevented.

  In the illustrated example, each lever is biased in the valve release direction by the weight members (235, 237), but each lever may be biased in the valve release direction by a biasing member such as a spring. In the configuration using the urging member, the lever can be urged in the valve release direction regardless of the direction of the sub tank, so that the degree of design freedom increases.

  The sub-tank 202A is a sub-tank provided with a valve mechanism, and is provided in a headset with a small amount of head suction for discharging thickened ink. For example, a head for color (C, M, Y) ink is used. It can be attached. A sub-tank that does not have a valve mechanism may be used for a headset (for example, for black ink) that has a large amount of head suction for discharging thickened ink.

  By the way, if the valve mechanism in the sub tank is closed (unintentionally) during printing, the amount of liquid (ink, etc.) supplied to the ejection head will be insufficient.

  Therefore, the timing for closing the valve mechanism in the sub-tank is set to the region C in FIG. 8, that is, the position where the amount of liquid in the sub-tank is the smallest (less than the lower limit value) during printing (during normal ink ejection operation). By doing so, it is possible to prevent a shortage of liquid supply to the ejection head. Such setting can be set according to the size of the pressing member 131 and the position of the valve seat 133 in the first embodiment of FIG. Further, in the second embodiment shown in FIG. 7, it can be set depending on the size of the pressing member 231, the position of the valve seat 233, the length of the lever member (first lever 234, second lever 236), or the like. .

  Further, it is preferable to set the suction start position so as to be the D region in FIG. 8 for each headset. Prior to the start of suction, the amount of liquid in the sub-tank is adjusted to a predetermined suction start position (D region) by liquid feeding or suction (pump reverse rotation) by the supply pump (liquid feed pump 108: FIG. 1). Since the suction end position at which the valve mechanism provided in the sub tank is closed is unchanged, it is possible to set the necessary minimum suction amount for each head by changing the suction start position.

Next, a third embodiment of a sub tank mounted on a head that requires a small amount of head suction will be described with reference to FIG.
A sub tank 302A shown in FIG. 9 is a sub tank attached to a head that requires a small amount of head suction, and includes a valve mechanism 330. Reference numeral 310 denotes a flexible member, and reference numeral 309 denotes a negative pressure generating spring that biases the flexible member 310 outward. Reference numeral 318 denotes an ink supply port, and 319 denotes an ink discharge port (head supply port).

  The valve mechanism 330 has a valve body 333 configured by a sub tank case, and an ink flow path 334 is formed in the valve body 333. A spherical sealing member 331 is positioned in the ink flow path 334. A predetermined range on the downstream side of the ink flow path 334 is a small-diameter portion 334a having a small flow path diameter. Further, a seal member 332 is disposed at a boundary portion between the upstream side portion (large diameter portion) of the ink flow path 334 in which the sealing member 331 is incorporated and the small diameter portion 334a.

  Although two seal members 332 are illustrated in the upper and lower directions in the drawing, they are provided in a ring shape along the inner surface of the ink flow path 334 having a circular cross section. When the spherical sealing member 331 abuts (fits) with the ring-shaped sealing member 332, the ink flow path 334 is sealed and the valve is closed. When the sealing member 331 is separated from the seal member 332, the valve is in an open state. The sealing member 331 has a specific gravity that floats on the liquid (ink or the like) in the sub tank 302A, and is normally at the position shown in FIG.

  When the head suction is started in the state shown in (a) with the valve opened, a suction force (liquid flow) for drawing the sealing member 331 in the direction of the arrow in (b) is generated. If the suction amount (flow rate) is constant, the flow velocity increases as the flow path width of the small diameter portion 334a decreases. That is, when the flow rate is large, the force for drawing the sealing member 331 becomes stronger.

  When the head suction is started, the sealing member 331 is drawn to the downstream side so that the vacuum cleaner sucks the dust, and finally, as shown in FIG. Is closed. When the head suction is stopped and ink is supplied into the head tank, the sealing member 331 returns to the position shown in FIG.

  With the configuration of this embodiment, a predetermined amount of head suction can be performed without worrying about the position of the flexible member (film) or the amount of liquid in the sub tank. Further, the suction amount for each head can be adjusted by adjusting (setting) the length of the F region (moving region of the sealing member) in FIG.

  The sub-tank 302A is a sub-tank having a valve mechanism, and is provided in a headset having a small amount of head suction for discharging thickened ink. For example, the sub-tank 302A is used in a head for color (C, M, Y) ink. It can be attached. A sub-tank that does not have a valve mechanism may be used for a headset (for example, for black ink) that has a large amount of head suction for discharging thickened ink.

  Next, a fourth embodiment of a sub-tank in which the valve mechanism has the function of a choke valve will be described with reference to FIG. The sub-tank configuration itself is the same as that of FIG.

  First, head suction is performed. If the suction is continued, the valve is closed as shown in FIG. 10, and if the suction is further continued, a strong negative pressure is generated on the downstream side of the valve (downstream side of the seal member 332 = the head side). The valve is kept closed by continuing the suction, and the liquid is fed into the sub tank 302A by the liquid feed pump 108 (FIG. 1), and the upstream side of the valve is brought into a pressurized state.

When there is a large pressure difference between the upstream and downstream of the valve, suction by a suction pump 119 (see FIG. 6) not shown in FIG. 10 is stopped and the valve is opened. Then, due to the large differential pressure, ink flows from the upstream to the downstream of the valve all at once, and the air (bubbles) in the supply path can be discharged. In this way, the valve mechanism 330 can have the function of a choke valve.

  Finally, a case where the present invention is applied to an ink jet recording apparatus capable of full color recording will be described with reference to FIG. Note that the same reference numerals are used for the same or equivalent parts as those of the image forming unit described with reference to FIG.

  The ink jet recording apparatus shown in FIG. 11 uses black (Bk), yellow (Y), magenta (M), and cyan (C) color inks, and four ink cartridges 106 (Bk, Y) containing the color inks. , M, C). The ink cartridge 106 corresponds to the main tank 106 in FIG.

  A total of four headsets 100 are mounted on the carriage 103 corresponding to each color ink. In this recording apparatus, four headsets are included in the head unit. In order to avoid complication of the drawing, reference numerals are omitted, but each head set 100 includes a discharge head (recording head) and a sub tank. For example, as described with reference to FIG. Is attached.

  Of the four headsets 100, the sub-tank of the headset with a small head suction amount for discharging the thickened ink is provided with the valve mechanism described above. As the sub tank provided with the valve mechanism, in addition to the sub tank 102A in FIG. 6, the sub tank 202A in FIG. 7, the sub tank 302A in FIG. 9, and the like can be used.

  In the apparatus configuration shown in FIG. 11, a headset with a small amount of head suction for discharging thickened ink corresponds to each color ink of yellow (Y), magenta (M), and cyan (C). A valve mechanism is provided in the sub-tank of the headset. Since black (Bk) ink is easy to dry with respect to color (C, M, Y) ink, a large amount of head suction for discharging thickened ink is required for color ink. Use a sub-tank for the corresponding headset that does not have a valve mechanism.

  A carriage 103 on which a head unit including a plurality of (four in this example) headsets is mounted is provided so as to be able to travel and move in the left-right direction in the figure. There is an encoder 104 installed in a scanning range for measuring the position of the carriage 103 and a carriage position detection sensor 105 for detecting the position of the carriage. The carriage position detection sensor 105 detects the number of slits of the encoder 104, thereby scanning the carriage 103. The position can be controlled.

  Each color ink cartridge 106 is disposed at a position away from the carriage 103, and ink is supplied to the sub-tank through the supply path 107 such as a tube by driving the liquid feeding pump 108. Then, according to the image information, while the recording paper S is intermittently sent, the recording head mounted on the carriage 103 reciprocates on the recording paper, and ejects ink droplets to obtain the required amount on the recording paper S. An image is formed.

  Further, a maintenance / recovery mechanism for maintaining and recovering the state of the nozzles of the recording head is disposed in the non-printing area in the carriage scanning direction. In the maintenance and recovery mechanism, each cap member 121 for capping each nozzle surface of each recording head, a suction pump 119 for suctioning after capping, a wiper blade 122 for wiping the nozzle surface, and a thickened A waste liquid tank 120 is provided for discharging the recording liquid.

  In such a configuration, as described above, even when the required head suction amount differs depending on the ejection head (recording head), it is possible to simultaneously perform head suction without wasting ink. In addition, since head suction can be performed simultaneously on a plurality of heads, maintenance can be performed in a short time.

  In addition, by providing a valve mechanism only in the sub-tank provided in the discharge head that discharges the liquid (ink) with increased viscosity and with a small head suction amount, the liquid (ink) ) Can be avoided.

  Further, by adopting a configuration in which the valve mechanism is closed by a force when the flexible member is displaced, parts for opening and closing the valve are not separately required, the cost can be suppressed, and the sub tank can be miniaturized.

  Moreover, since the valve mechanism is configured to close the valve using the lever principle, the valve can be closed with a small force, and the sealing performance can be improved.

  Further, the liquid amount in the sub tank when the valve mechanism is closed is set to be equal to or lower than the lower limit value of the liquid amount in the sub tank in the normal liquid discharge operation, so that the normal liquid discharge operation, for example, normal printing in the image forming apparatus is performed. Time trouble can be prevented.

In addition, the amount of suction for each head can be adjusted by adjusting the amount of liquid in the sub tank to a predetermined amount before the start of liquid suction by the suction means.
Further, the valve is closed by the sealing member coming into contact with the seal member by liquid suction by the suction means, so that the liquid amount in the sub tank can be changed from any state (regardless of the position of the flexible member). A fixed amount of head suction can be performed.

  In addition, by supplying liquid to the sub tank with the valve mechanism closed to pressurize the tank and opening the valve mechanism at a predetermined timing, the liquid can be discharged from the upstream to the downstream side of the valve at once. It becomes possible to discharge the air inside.

  In the image forming apparatus including the head unit according to the present invention, a plurality of heads can be sucked simultaneously without wasting ink. In addition, the head can be maintained in a short time.

  Further, the use of a maintenance / recovery mechanism for maintaining / recovering the state of the ejection head as the suction means can reduce costs. In addition, the image forming apparatus can be reduced in size.

  As mentioned above, although this invention was demonstrated by the example of illustration, this invention is not limited to this. The recording head (discharge head) can have an appropriate configuration. For example, any method such as a thermal method, a piezoelectric method, or an electrostatic method can be adopted as the pressure generating means. As the configuration of the valve mechanism provided in the sub tank, an appropriate configuration can be adopted as long as the present invention can be implemented. Further, the configuration and form of each part of the image forming apparatus can be appropriately changed within the scope of the present invention.

100 Headset 101 Discharge head (recording head)
102, 202, 302 Sub tank (head tank)
103 Carriage 105 Carriage position detection sensor 106 Main tank (ink cartridge)
107 Ink supply path 108 Liquid feed pump 109, 209, 309 Negative pressure generating spring 110, 210, 310 Flexible member 118, 218, 318 Ink supply port 119 Suction pump 120 Waste liquid tank 121 Cap 130, 230, 330 Valve mechanism 131 , 231 Press member 234, 236 Lever member 331 Seal member 332 Seal member

JP 2008-012684 A

Claims (11)

In a head unit that includes a plurality of ejection heads that eject droplets and a plurality of sub tanks that store liquid to be supplied to the ejection heads,
Having suction means for simultaneously sucking liquid from the plurality of ejection heads;
The sub tank is provided for each of the ejection heads,
At least one of the plurality of sub tanks is disposed in a flow path between the discharge head and the sub tank, and a valve mechanism that shuts off the flow path when a predetermined amount of liquid in the sub tank is discharged by the suction means. Provided ,
The head unit , wherein one of the plurality of sub tanks is not provided with the valve mechanism . In a head unit that includes a plurality of ejection heads that eject droplets and a plurality of sub tanks that store liquid to be supplied to the ejection heads,
Having suction means for simultaneously sucking liquid from the plurality of ejection heads;
The sub tank is provided for each of the ejection heads,
The first sub-tank of the plurality of sub-tanks is disposed in a flow path between the discharge head and the sub-tank, and when the liquid in the sub-tank is discharged by the suction means, a necessary amount for the sub-tank is A first valve mechanism for blocking the road is provided,
The second sub-tank of the plurality of sub-tanks is disposed in a flow path between the discharge head and the sub-tank, and the flow is discharged when a necessary amount of liquid in the sub-tank is discharged by the suction means. A second valve mechanism for blocking the path is provided,
The amount required for the first sub-tank is different from the amount required for the second sub-tank,
Further, the valve mechanism is not provided in one of the plurality of sub tanks.
A head unit characterized by that. The sub-tank provided with the valve mechanism is a sub-tank provided in a discharge head having a small head suction amount for discharging liquid having increased viscosity among the plurality of discharge heads. Or the head unit of 2 . The sub-tank has a flexible member that is displaced according to the amount of liquid in the tank,
The head unit according to claim 1 , wherein the valve mechanism is closed by a force when the flexible member is displaced. The valve mechanism is characterized by closing the valve by utilizing the principle of leverage, the head unit according to any one of claims 1-4. Liquid volume in the sub tank when the valve mechanism is closed, characterized in that it is set to less than the lower limit of the sub-tank liquid volume in conventional liquid discharging operation, in any one of claims 1 to 5 The head unit described. Wherein before starting the liquid suction by the suction means, and adjusting the amount of liquid within the sub tank to a predetermined amount, the head unit according to any one of claims 1-6. The valve mechanism includes a sealing member that floats on the liquid in the sub-tank, and a sealing member that is disposed in a flow path between the discharge head and the sub-tank. The head unit according to claim 1 , wherein the valve is closed by contacting the seal member. After the predetermined liquid suction is performed by the suction means, the liquid suction is further continued to close the valve mechanism, the liquid is supplied to the sub-tank in which the valve mechanism is closed, the tank is pressurized, and the predetermined timing is reached. The head unit according to claim 8 , wherein the valve mechanism is opened. An image forming apparatus comprising: a head unit according to any one of claims 1-9. The image forming apparatus according to claim 10 , wherein the suction unit is a maintenance / recovery mechanism for maintaining / recovering the state of the ejection head.

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