JP5053068B2 - Ink supply device, inkjet recording device - Google Patents

Description

The present invention relates to an inkjet recording apparatus that performs recording on a recording medium using a plurality of recording heads that eject ink, and an ink supply apparatus that supplies ink to the plurality of recording heads.

  Currently, an ink jet recording apparatus that performs recording by discharging ink from a recording head onto a recording medium is known. In such an ink jet recording apparatus, high-definition recording is generally performed using a recording head in which a plurality of nozzles from which ink is ejected are formed at a high density. Further, by arranging a plurality of the recording heads and supplying different color inks to the respective recording heads, color recording can be performed on the recording medium with a relatively inexpensive and small configuration. For this reason, ink jet recording apparatuses are used in various recording apparatuses such as printers, facsimiles, and copying machines regardless of whether they are for business use or home use.

  In such an ink jet recording apparatus, in order to stabilize the ink ejection operation from the recording head, the ink in the recording head is maintained at a predetermined negative pressure (the pressure acting on the ink in the recording head is set to a predetermined negative pressure). Is important). For this reason, a negative pressure generating means is generally provided in an ink supply system for supplying ink to the recording head, and ink to which negative pressure is applied by the negative pressure generating means is supplied to the recording head.

  As a negative pressure generating means, Patent Document 1 discloses a configuration in which a negative pressure is generated using the capillary action of a sponge-like ink absorber housed in an ink tank. As another negative pressure generating means, Patent Document 2 discloses a configuration including a flexible ink bag and a bow spring. As another negative pressure generating means, Patent Document 3 discloses that an ink tank communicating with a recording head is disposed below the recording head, and a negative pressure is generated in the recording head by utilizing a water head difference between the recording head and the ink tank. A configuration to be given is disclosed.

  Further, in the ink supply system including the negative pressure generating means as in Patent Document 1 to Patent Document 3, the negative pressure in the recording head increases as ink is ejected from the recording head. Using this increasing negative pressure, ink is supplied from the ink tank to the recording head. For this reason, when the amount of ink ejected from the recording head per unit time is large, the ink supply from the ink tank to the recording head cannot catch up, and the negative pressure in the recording head may become larger than a predetermined negative pressure. . Conversely, when the amount of ink ejected from the recording head per unit time is small, the negative pressure in the recording head may become smaller than a predetermined negative pressure due to the inertia of the ink. Such fluctuations in the negative pressure are factors that hinder the stabilization of ink ejection.

  In Japanese Patent Application Laid-Open No. 2004-228867, for this problem, ink is supplied to the recording head by a pump, and the negative pressure to be generated in the recording head is applied to the recording head or an ink supply system such as a sub tank that supplies ink to the recording head. This is disclosed by controlling the provided fan. That is, Patent Document 4 discloses a configuration in which ink supply and negative pressure control are performed separately.

  As proposed in Patent Document 4, the technique of keeping the negative pressure in the recording head within a predetermined range by a fan is a technique for stabilizing the negative pressure in the recording head in high-speed and variable printing such as an industrial inkjet recording apparatus. This is a very effective technology.

  However, in the recording apparatus described in Patent Document 4, when the recording operation is not performed, the fan is stopped and the recording head and the sub tank are sealed to maintain the negative pressure applied to the nozzles of the recording head. It has a configuration. For this reason, there is no problem when the environmental temperature is maintained at a constant temperature assumed in advance, but there is a problem that it cannot sufficiently cope with a change in the environmental temperature. In other words, when the ambient temperature changes and the air in the closed system such as the sub tank and the print head expands and contracts, the ink oozes out from the print head and the air is taken into the nozzle. May occur.

  Therefore, the liquid level of the ink tank that communicates with the print head and has a communication portion with the atmosphere is disposed below the formation surface of the discharge port of the print head to apply water head pressure to the nozzle, It has also been proposed and implemented to generate negative pressure. According to this, it becomes possible to generate a negative pressure due to a water head difference in the recording head even during standby, and it is possible to eliminate the bleeding of ink from the nozzles and the intake of air into the nozzles.

Japanese Patent Laid-Open No. 2002-1988 Japanese Patent Application Laid-Open No. 06-198904 JP 2003-11380 A JP 2006-326855 A

  In the recording apparatus having the negative pressure applied to the recording head as described above, providing these means in each of the plurality of recording heads causes an increase in size and cost of the apparatus. For this reason, in a recording apparatus using a plurality of recording heads, a plurality of ink tanks corresponding to the plurality of recording heads are communicated with each other, and a fan is provided at the communicating portion, so that the negative pressure is reduced with a fan smaller than the number of recording heads It has been proposed to grant

  However, when communicating a plurality of recording heads with each other, if the liquid levels of a plurality of ink tanks connected to each of the plurality of recording heads communicated with each other are different during standby of the recording operation, There arises a problem that a difference also occurs in the height of the liquid level.

  Hereinafter, this phenomenon will be described using the recording apparatus shown in FIG. In the figure, reference numeral 22K denotes a head unit as a recording head for discharging black ink, and reference numeral 22C denotes a head unit as a recording head for discharging cyan ink. Each head unit includes nozzles 22Kn and 22Cn that discharge ink, a storage unit 22Kr that stores ink to be supplied to the nozzles, and the like. The upper portions of the head units 22K and 22C communicate with each other through a communication path 64. The communication path 64 is connected to a negative pressure generation source (for example, a fan) outside the figure via a pressure reducing channel 65 and an atmospheric valve 84. Has been. The head units 22K and 22C are connected to ink tanks 70K and 70C (second storage portions) in which ink to be supplied to the storage portions 22Kr and 22Cr is stored. Each ink tank is arranged so that its liquid level is always located below the discharge port surface of the corresponding head unit (so that a water head difference occurs).

  In the recording apparatus shown in FIG. 10, the atmospheric valve 84 is opened during the recording operation, and each of the head units 22K and 22C is suitable for discharging ink by a single negative pressure generating means (for example, a fan) not shown. Negative pressure is applied. On the other hand, when the recording operation is on standby, the atmospheric valve 84 is closed, and the head units 22K and 22C communicate with each other through the air flow path 64. Here, as shown in FIG. 10, it is assumed that there is a difference in liquid level between the ink tank 70K and the ink tank 70C. When the valves VA and VB are both opened in this state, the negative pressure generated in the head unit 22K due to the water head difference between the liquid level of the ink tank 70K and the discharge port surface 22Ks, the liquid level of the ink tank 70C, and the discharge port surface 22Cs. There is a difference between the negative pressure generated in the head unit 22C due to the water head difference. For this reason, in the recording apparatus, as shown by the arrows in FIG. 10, the ink flows so that the negative pressure difference in each head unit becomes zero. That is, the ink in the head unit 22C flows into the ink tank 70C with a low liquid level, and the ink flows into the head unit 22K from the ink tank 70K with a high liquid level. This flow continues until the liquid levels of both ink tanks are the same. As a result, a difference is generated between the liquid levels in the head unit 22K and the head unit 22C, so that control for eliminating the liquid level difference is required at the start of the recording operation, and the control becomes complicated. Further, when the ink flow as shown in FIG. 10 occurs, in the worst case, the ink may flow into the head unit 22 </ b> C through the communication path 64. In addition, when ink flows out from the head unit 22C, in the worst case, the ink in the head unit 22C may be lost and air bubbles may be drawn from the nozzles.

  According to the present invention, even when the negative pressure control or the bubble discharge control is simplified by using a plurality of recording heads communicating with each other, the height of the ink surface in the recording head can be appropriately maintained. An object is to provide an ink jet recording apparatus and an ink supply apparatus.

  In order to solve the above problems, the present invention comprises the following arrangement.

In other words, a first aspect of the present invention is an ink supply device that supplies ink to a plurality of ejection units capable of ejecting ink, and stores the ink supplied to the plurality of ejection units, and the upper part is air A plurality of first reservoirs having a filled space, and provided corresponding to each of the plurality of first reservoirs , store ink supplied to the corresponding first reservoirs, and communicate with the atmosphere connecting a plurality of second reservoir, of the space in which each of the plurality of first reservoir has a first air passage for communicating the at least two or more of said space, said first air flow path And a negative pressure generating means for generating a negative pressure in the first storage part, provided corresponding to each of the plurality of first storage parts, one end connected to the corresponding first storage part, and the other end a plurality but connected to said second reservoir unit corresponding to the first reservoir 1 and the ink supply channel, a plurality of ink supplying means provided wherein the second reservoir for supplying ink to the first reservoir, in response to each of the plurality of first ink supply passage, wherein The ink is provided in one of the plurality of first ink supply channels and not provided in the other first ink supply channels, and supplies ink from the second reservoir to the first reservoir. In the supply direction, one end of the first ink supply flow on the upstream side in the supply direction with respect to the ink supply means corresponding to one first ink supply flow channel of the plurality of first ink supply flow channels. A second ink supply channel that is connected to the channel and has the other end connected to the first ink supply channel on the downstream side in the supply direction with respect to the ink supply means, and opens and closes the second ink supply channel A first valve that can be connected to the first valve It is connected to the air passage, and a second air flow path and the other end is connected to the negative pressure generating means, and a second valve capable of opening and closing the second air passage,
And opening and closing operations of the first valve and the second valve, and a control unit for controlling driving operation and the of the negative pressure generating means, each of said plurality of ink supply means, when running Ink is supplied from the second reservoir to the first reservoir and the first ink supply flow path is blocked when the first reservoir is not in operation. Each of the plurality of second reservoirs is disposed in the reservoir. During the recording operation in which the liquid level of the stored ink is positioned below the ejection unit and the ink is ejected from the ejection unit to record an image on a recording medium, the control unit And the second valve is opened, and the negative pressure generating means is driven to bring the first reservoir into a negative pressure. During the standby time when the recording operation is not performed, the control unit Open 1 valve, Close the serial second valve, wherein the not driven negative pressure generating means.

  According to the present invention, even when the negative pressure control or bubble discharge control during the recording operation is simplified by using a plurality of communicating recording heads, the height of the ink level in the recording head can be reduced. It becomes possible to keep it appropriate. Therefore, not only the negative pressure control during the recording operation but also the negative pressure control in the standby state can be optimized, simplified, and optimized.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a front view schematically showing an ink jet recording apparatus (hereinafter also simply referred to as a recording apparatus) to which the present embodiment can be applied. The recording apparatus 10 is connected to the host PC 12, and based on the recording information transmitted from the host PC 12, ink is applied from four head units 22K, 22C, 22M, 22Y to a recording medium (hereinafter also referred to as roll paper) P. Recording is performed by discharging. The four head units 22K, 22C, 22M, and 22Y are arranged along the conveyance direction (arrow A direction) of the recording medium P. The head units are arranged in parallel with each other in the order of a black ink head unit 22K, a cyan ink head unit 22C, a magenta ink unit head 22M, and a yellow ink head unit 22Y. The head units 22K, 22C, 22M, and 22Y are so-called line heads, and nozzles are arranged at a predetermined density (dpi) along a direction that intersects the recording medium conveyance direction (a direction that is orthogonal in the figure). ing. The arrangement width of the nozzles (arrangement range in the conveyance direction of the recording medium) is equal to or larger than the maximum recording width of the recording medium to be used. When the recording apparatus performs recording, the recording is performed by ejecting ink from the nozzles by driving a heater provided in the head unit without moving each head unit.

  In the head unit, foreign matters such as dust and ink droplets adhere to the surfaces (hereinafter also referred to as discharge port surfaces) 22Ks, 22Cs, 22Ms, and 22Ys on which discharge ports that are openings at the ends of the nozzles are formed during recording. Doing so may change the discharge state and affect printing. Therefore, the recovery unit 40 is incorporated in the recording apparatus 10 so that ink can be stably ejected from the head units 22K, 22C, 22M, and 22Y. By periodically cleaning the discharge port surface by the recovery unit 40, the ink discharge state from the nozzles of the head units 22K, 22C, 22M, and 22Y can be recovered to the initial good ink discharge state. The recovery unit 40 includes a cap 50 that is used to remove ink from the ejection port surfaces 22Ks, 22Cs, 22Ms, and 22Ys of the four head units 22K, 22C, 22M, and 22Y during the cleaning operation. ing. The cap 50 is provided independently for each head unit 22K, 22C, 22M, 22Y, and includes a blade, an ink removing member, a blade holding member, a capping member, and the like.

  The recording medium P is supplied from the roll paper supply unit 24 and is transported in the direction of arrow A by the transport mechanism 26 incorporated in the recording apparatus 10. The transport mechanism 26 includes a transport belt 26a for loading and transporting the roll paper P, a transport motor 26b for rotating the transport belt 26a, and a roller 26c for applying tension to the transport belt 26a.

  When recording, when the roll paper P being conveyed reaches below the black head unit 22K, black ink is ejected from the head unit 22K based on the recording information sent from the host PC 12. Similarly, ink of each color is ejected in the order of the head unit 22C, the head unit 22M, and the head unit 22Y, and color recording on the roll paper P is completed.

  Further, the recording apparatus 10 includes ink tanks 28K, 28C, 28M, and 28Y (second storage units) that store ink supplied to each head unit, a pump that can replenish ink to each head unit, and a cleaning that will be described later. A pump (see FIG. 3 etc.) for operation is provided.

  FIG. 2 is a block diagram showing a control system of the recording apparatus 10 of FIG. Recording information and commands transmitted from the host device 12 such as a host computer are received by the CPU 101 via the interface controller 102.

  The CPU 101 is an arithmetic processing unit that performs overall control such as reception of recording information of the recording apparatus 10, recording operation, handling of the roll paper P, and the like. After analyzing the received command, the CPU 101 develops a bitmap of the image data of each color component of the recording data in the image memory 106. In the operation process performed before recording, the capping motor 122 and the head up / down motor 118 are driven via the output port 114 and the motor driving unit 116, and the head units 22K, 22C, 22M, 22Y are separated from the cap 50 to the recording position. Move to. Further, as will be described later, the CPU 101 drives the fan motor that rotates the fan for applying an appropriate negative pressure to the head units 22K, 22C, 22M, and 22Y based on the pressure information obtained by the pressure sensor. Control to correct. Further, the CPU 101 drives the roll motor 126 that feeds out the roll paper P via the output port 114 and the motor drive unit 116, the transport motor 120 that transports the roll paper P, and the like to transport the roll paper P to the recording position. Control.

  When performing recording, the leading end detection sensor 109 detects the leading end position of the roll paper P in order to determine the timing (recording timing) at which ink is ejected onto the rolled paper P conveyed at a constant speed. Thereafter, in synchronism with the conveyance of the roll paper P, the CPU 101 sequentially reads the recording information from the image memory 106, and the read recording information is used to control the ejection of ink in each head unit 22K, 22C, 22M, 22Y. Transfer to the unit control circuit 112.

  Processing operations by the CPU 101 are executed based on a processing program stored in the program ROM 104. The program ROM 104 stores processing programs and tables corresponding to the control flow. The CPU 101 uses a work RAM 108 as a working memory. Further, the CPU 101 drives the pump motor 124 via the output port 114 and the motor drive unit 116 during the cleaning and recovery operations of the head units 22K, 22C, 22M, and 22Y, and controls the pressurization and suction of ink. .

  Next, the head unit and the ink supply device incorporated in the recording apparatus according to the present embodiment will be described with reference to FIGS.

  FIG. 3 is a schematic diagram showing an ink supply device in the recording apparatus of the present embodiment. Here, as an example, an ink supply device that supplies and recovers ink to the head units 22K and 22C is shown, but the other head units 22M and 22Y also have the same structure, and these head units The same ink supply device is also provided.

  The recording apparatus 10 illustrated in FIG. 10 includes an ink supply device 60 that supplies ink to the head units 22K and 22C. The head units 22K and 22C include the storage units 22Kr and 22Cr and an ejection unit that can eject ink. 22KSi. The ink supply device 60 includes ink tanks 28K and 28C that are detachable from the main body of the recording apparatus 10, and an ink supply that is disposed in the middle of an ink supply flow path 62 that connects the ink tanks 28K and 22C to the head units 22K and 22C. It consists of a pump 72 and the like. The supply pump 72 is responsible for supplying ink to the reservoirs 22Kr and 22Cr via the ink filter 90.

  Liquid level detection sensors 86 for detecting the levels of the liquid levels 22Krs and Crs of the stored ink (hereinafter also referred to as stored ink) are attached to the storage units 22Kr and 22Cr (first storage unit), respectively. Further, below the reservoirs 22Kr and 22Cr, nozzles 22Kn and 22Cn of the head units 22K and 22C and ejection units 22KSi and 22CSi in which ink supply ports to the nozzles 22Knk and 22Knk are formed are connected.

  A space (hereinafter referred to as an air chamber) 66 filled with air is formed above each of the reservoirs 22Kr and 22Cr, and each air chamber 66 of each of the reservoirs 22Kr and 22Cr is provided with an air filter 95. Connected to the air flow path 64. One connecting channel 65 is connected to the air channel 64, and a reduced pressure channel 65 is connected to the connecting channel 66 in a T shape. The connection channel 66 is provided with an atmospheric valve 84 that can switch between communication and blocking, and a pressure sensor 81 that detects the pressure in the channel. The decompression channel 65 has one end communicating with the atmosphere and the other end coupled to the fan 68.

  A detection sensor (not shown) for detecting the presence or absence of ink in the ink tank 28K is attached to the ink tank 28K. The ink tank 28K is provided with an air release valve 74 for setting the internal pressure of the ink tank 28K to atmospheric pressure.

  When it is determined that the ink liquid level 22Krs is below a certain level based on the detection result of the liquid level detection sensors 86 of the reservoirs 22Kr and 22Cr, the air release valve 74 of the ink tanks 28K and 22C is opened, and the supply pump 72 To operate. Accordingly, ink is sucked from the ink tanks 28K and 22C, and the sucked ink is supplied into the storage portion 22Kr. On the other hand, when the ink liquid levels 22Krs and 22Crs detected by the liquid level detection sensor 86 exceed a certain level, the supply pump 72 is stopped, the air release valve 74 of the ink tank 28K is sealed, and the ink supply is stopped. The

  By the way, in this embodiment, a known tube pump is used as the supply pump 72. Therefore, when the supply pump 72 is not in operation, the ink supply flow path 62 is blocked between the ink supply flow path ink tank 28K and the reservoir 22Kr.

  A valve 100 capable of blocking and opening the flow path is provided in parallel with one of the two supply pumps 72 (here, the supply pump communicating with the ink tank 28K). Further, when the ink tank 28K connected to the ink supply channel 62 is in communication with the head unit 22K via the valve 100, a predetermined negative pressure due to a water head difference is applied to the head unit 22K. It is installed in a position where you can. Specifically, the ink tank 28K is installed at a position where the height difference (water head difference) between the ejection port surface 22Ks of the recording head 22K and the liquid level of the ink tank 28K falls within a predetermined range. Here, the height difference (water head difference) that falls within a predetermined range refers to a water head difference that can generate a negative pressure that can hold a meniscus in the nozzle 22Kn due to the water head difference.

  In the present embodiment, the air chambers 66 of the head units 22K and 22C are in communication with each other. For this reason, in the recording operation, when the atmospheric valve 84 is in the open state, by driving one decompression fan 68, while applying a uniform negative pressure to the liquid chambers 22Kr, 22Cr of the two recording heads 22K, 22C, A recording operation, an ink supply operation, and the like can be performed.

  In this embodiment, two head units, for example, 22K and 22C, 22Y and 22M, are connected in the recording operation, and negative pressure by a fan as one negative pressure generating unit is applied to the two heads communicating with each other. It was set as the structure to do. However, the present invention is not limited to this example. For example, the air chambers 66 of the head units 22K, 22C, 22M, and 22Y are communicated, and a negative pressure generated by one negative pressure generating means is applied to them. It is also possible. Further, in the above-described embodiment, the ink tank (for example, 28K) corresponding to one head unit (for example, 22K) of the two head units (for example, 22K, 22C) communicating with each other during standby is connected to both. The ink tanks 22K and 22C were communicated. However, the present invention is not limited to this example, and the plurality of head units communicated with each other may communicate with only the ink tank corresponding to one head unit among the plurality of head units during standby. It may be configured. For example, the air chambers of the head units 22K, 22C, 22M, and 22Y are sequentially communicated, and the four head units are communicated only to an ink tank corresponding to one of the head units, for example, 28K, during standby. You may make it let it.

  FIG. 4 is a flowchart showing a procedure for cleaning the discharge port surface 22Ks of the head unit. FIG. 5 is a schematic diagram showing a procedure for wiping ink from the ejection surface 22Ks with the wiper 52, (a) showing before the start of wiping, (b) showing immediately after wiping is completed, and (c) showing completion of wiping. It is a figure which shows the waiting state after. The term “cleaning” as used herein refers to an operation performed in order to continuously maintain the ink ejection of the head unit 22K in a good state. When conditions such as elapsed time and ejection conditions are satisfied, or there is an abnormality in recording quality. This is an operation that is performed automatically or arbitrarily when viewed. Hereinafter, the cleaning operation executed by the CPU 101 will be described in order.

  When the cleaning command is received in step S401, the atmospheric valve 74 is opened to communicate with the atmosphere in step S402. Thereafter, in step S403, the cleaning pump 92 is driven in a direction to depressurize the inside of the cap 50, and the ink in the reservoirs 22Kr and 22Cr is drawn into the cap 50 from the nozzles 22Kn and 22Cn and discharged. By discharging the ink, it is possible to discharge ink including fine bubbles accumulated in the nozzles 22Kn and 22Cn, a thickened ink, and foreign matters such as dust during the recording operation. Then, after a certain period of time has elapsed, the driving of the cleaning pump 92 is stopped at step 404 and the atmospheric valve 84 is closed at step 405.

  In this state, ink may still adhere to the ejection port surface 22Ks including the openings of the nozzles 22Kn of the head units 22K and 22C. Therefore, in order to remove the dirt, the discharge port surfaces 22Ks and 22Cs are wiped with a wiper 52 provided on the cap 50, as will be described later. At that time, first, in step S406, the head units 22K and 22C are moved to the upper position of the recovery cap 50 as shown in FIG. Thereafter, when the cap 50 is moved in the direction of arrow B in step S407, dirt such as ink adhering to the face surfaces 22Ks and 22Cs is wiped off by the wiper 52 as shown in FIG. Hereinafter, this operation is referred to as a wiping operation. After completion of the wiping operation, as shown in FIG. 5C, the head unit 22K is moved again above the cap 50 and then lowered (step S408), and the discharge port surface 22Ks is moved by the cap contact portion 54. , 22Cs is covered (capped), and a standby state is entered. Thereby, there is almost no air flow inside and outside the cap 50, and it is possible to prevent the ink in the nozzle 22Kn from drying and thickening. Thus, the cleaning operation is completed.

  The ink (waste ink) discharged from the nozzle 22Kn is received by the cap 50 and then sucked by the suction pump 92 (see FIG. 3). The absorbed waste ink is pumped to a waste ink tank 71 (see FIG. 3). The waste ink tank 71 is provided with a minute air opening 75, and with the inflow of waste ink (and bubbles), the air in the waste ink tank 71 escapes from the atmosphere opening 75 to the atmosphere, and the waste ink. An increase in pressure in the tank 71 is prevented. Note that the wiping operation may be performed in association with the ink suction recovery as described above, but only the wiping operation can be performed independently at an arbitrary timing.

Next, a negative pressure control operation applied to the head units 22K and 22C during the recording operation will be described.
As shown in FIG. 3, it is necessary to apply an appropriate negative pressure to the head units 22K and 22C in order to form meniscuses in the nozzles 22Kn and 22Cn of the head units 22K and 22C during the recording operation. Therefore, during the recording operation, the fan 68 is operated so as to create an air flow in the C direction, and then the atmospheric valve 84 is opened to communicate with the atmosphere. Thereby, the air in the connection channel 66 is sucked toward the fan 68, and the air chamber 66 in the head units 22K and 22C is decompressed. As a result, the pressure in the nozzles 22Kn and 22Cn is similarly reduced through the reservoirs 22Kr and 22Cr.

  In the present embodiment, the reservoirs 22Kr and 22Cr communicated with the atmosphere are arranged above the ejection units 22Ksi and 22Csi. At this time, when the atmospheric valve 84 is opened, the valve 100 is shut off, so that the negative pressure due to the water head difference of the ink tank 28K is reduced. As a result, a water head pressure (positive pressure) due to a water head difference H from the liquid surfaces 22Krs and 22Crs acts on the discharge ports formed at the tips of the nozzles 22Kn and 22Cn. Therefore, the amount of pressure reduction by the fan 68 into the air chamber 66 is set to be larger than the water head pressure due to the water head difference H. As a result, negative pressure is applied to the nozzles 22Kn and 22Cn of the head units 22K and 22C, and a meniscus suitable for ink ejection is formed in the openings of the nozzles 22Kn and 22Cn by the negative pressure.

  In this embodiment, as disclosed in Patent Document 4, as a method of sucking air from a space where negative pressure is to be generated, negative pressure generated by a negative pressure source such as the fan 68 is directly applied as it is, and negative pressure is generated. It does not adopt a method of sucking air in the space where pressure should be generated. In the present embodiment, a negative pressure source (fan 68) is disposed at the other end of the decompression flow path 65 whose one end communicates with the atmosphere, and air flows from one end to the other end of the decompression flow path 65, A so-called indirect suction method is employed in which the air in the connection channel 66 connected to the decompression channel 65 is sucked. In other words, in the present embodiment, the negative pressure generated by operating the fan 68 is not directly applied to the air chamber 66 but is provided with the suction port 61 (air introduction portion) through which air can be introduced. The so-called ejector principle in which pressure is indirectly applied to the air chamber 66 is used.

  When the atmospheric valve 84 is released, it is necessary to always apply a constant negative pressure to the air chamber 66 in order to maintain the ink meniscus at the nozzle in an optimum state. When ink is ejected from the ejection units 22Ksi and 22Csi, the amount of ink in the storage unit 22Kr decreases, and accordingly, the negative pressure in the air chamber 66 increases. If the negative pressure of the air chamber 66 remains high, the meniscus cannot be formed at a predetermined position and ink cannot be ejected satisfactorily. For this reason, it is necessary to adjust the pressure in the air chamber 66 in order to return the negative pressure that has increased with ink ejection to a constant negative pressure.

  In the method of indirectly sucking air in the space of the air chamber 66 as in the present embodiment, since there is a portion communicating with the atmosphere between the air chamber 66 and the fan 68, The air flow is always generated by the rotation of the fan 68. Since the negative pressure in the air chamber 66 is generated by the flow of air in the decompression flow path 65, the air chamber increases as the rotational speed of the fan 68 increases and the flow rate (flow velocity) per unit area of air increases. The negative pressure in 66 increases. Conversely, the negative pressure in the air chamber 66 decreases as the rotational speed of the fan 68 decreases and the air flow rate decreases.

  In order to keep the negative pressure in the air chamber 66 constant, it is necessary to control the fan 68 according to the fluctuation of the negative pressure in the air chamber 66 and adjust the flow rate of the air in the decompression flow path 65. . In adjusting such a flow rate, air that constantly flows is advantageous. That is, when the pressure in the air chamber 66 fluctuates, the air flow rate in the decompression flow path 65 is automatically adjusted so that the pressure fluctuation in the air chamber 66 is absorbed to some extent even if the rotational speed of the fan 68 is constant. Change. Therefore, it is not necessary to control the fan 68 so finely as to follow the fine pressure fluctuation in the air chamber 66. In other words, the range in which pressure fluctuation can be followed under the constant rotation speed of the fan 68 (the extent that the pressure head can be absorbed) is wider than the configuration as in Patent Document 4, that is, the case where the air in the air chamber is directly sucked. Become. Therefore, the inside of the air chamber 66 can be stably maintained at a predetermined negative pressure by relatively simple control. By controlling the rotation of the fan 68, it is a matter of course that a constant negative pressure can be maintained even when a large amount of pressure fluctuation occurs in a short time. Moreover, in the method of indirectly sucking the air in the air chamber 66 as in this embodiment, the time until the pressure in the air chamber 66 converges to the target value by automatically taking in air from the atmosphere. It can be a short time.

  Further, by indirectly sucking the air in the air chamber 66 as in the present embodiment, the air in the air chamber 66 that comes into contact with the ink in the reservoir 22Kr is not greatly stirred. For this reason, the volatile components of the ink are less likely to evaporate and the ink is less likely to thicken. Further, in the present embodiment, since the air flow is always generated when the fan 68 is operated, the fan motor 82 can be cooled using the flow.

  Incidentally, when the air in the air chamber is directly sucked by the fan as in the configuration of Patent Document 4, it is necessary to control the fan so as to respond sensitively to pressure fluctuations in the air chamber. That is, since the negative pressure generated by the fan acts directly in the nozzle, it is necessary to finely control the rotational speed of the fan. However, in the case of pressure control by a fan, overshoot and undershoot are likely to occur, and it takes a relatively long time to converge to the target pressure. In addition, since the air in the air chamber is agitated by the fan, the evaporation of the volatile components of the ink in the reservoir may be promoted.

  FIG. 7 is a flowchart showing the operation from the reception of the recording signal to the end of recording.

  Normally, in a standby state in which no recording operation is performed, the atmospheric valve 84 is closed for the purpose of preventing ink leakage from the nozzle Kn. Here, when a recording command is received (S701), first, the valve 100 for blocking / opening the flow path arranged in parallel with the supply pump 72 is sealed (S702). Note that the standby state of the printer will be described later. Next, the air fan 68 is activated (S703). Subsequently, whether or not a predetermined negative pressure is obtained by the air fan is confirmed based on the output value of the pressure detection sensor 81 (S704). If the predetermined negative pressure is not obtained, the air fan is determined from the detected value. The number of revolutions 68 is corrected (S705). If a predetermined negative pressure is obtained by the air fan, the atmospheric valve 84 is opened (S706). As a result, the pressure in the air chamber 66 is reduced, and a negative pressure acts on the nozzles 22Kn and 22Cn, and a meniscus is formed in an optimal state at the opening (discharge port) of the nozzle Kn.

  Subsequently, the head units 22K and 22C are moved to the wiping position (S707), and the wiping operation is performed (S708). Thereafter, the head units 22K and 22C are lowered and moved to the recording position (S709).

  The head units 22K and 22C are lowered and then moved to the recording position. Thereafter, based on the recording data, ink is ejected from the head unit 22K and a recording operation is executed (S710). While the recording operation (image formation) is being performed, the ink in the reservoirs 22Kr and 22Cr decreases due to the ink consumption due to the recording. Then, the air is guided into the air chamber 66 from the atmosphere. Further, when the ink liquid levels 22Krs / 22Crs are below a certain level, the liquid level detection sensor 86 detects the state. In this case, based on the detection result of the liquid level detection sensor 86, the ink supply pump 72 is operated, and ink is supplied into the reservoirs 22Kr and 22Cr until the liquid level detection sensor 86 detects the upper limit level of the ink liquid levels 22Krs and 22Crs. Supply. Also at this time, the air corresponding to the volume of the ink flowing into the reservoirs 22Kr and 22Cr is released to the atmosphere through the air flow path 64. Accordingly, pressure fluctuations acting on the nozzles 22Kn and 22Cn due to increase / decrease of ink in the head units 22K and 22C are suppressed.

  By the way, in the head units 22Kr and 22Cr, bubbles 69 may be mixed due to the deposition of dissolved gas in the ink or the ink supply operation. The dissolved gas in the ink refers to air dissolved in the ink, and generally dissolves more as the temperature is lower. In the conventional configuration, such bubbles accumulate and accumulate, and eventually cause a phenomenon that causes a problem in recording quality, such as blocking the ink supply flow path. For this reason, conventionally, the above-described cleaning operation is performed at a predetermined time interval to discharge bubbles accumulated in the storage portion together with the ink.

  The bubbles accumulated in the reservoirs 22Kr and 22Cr are generally difficult to remove, and there is a tendency for the waste liquid accompanying the cleaning operation to increase. In addition, a separate channel for removing bubbles has been provided. However, these measures cause an increase in running cost and apparatus cost, and when the cleaning operation is performed at the timing during the recording operation, the productivity is reduced due to the interruption of the recording operation.

  On the other hand, according to the present embodiment, the bubbles mixed in the reservoirs 22Kr and 22Cr move upward and disappear (hereinafter referred to as gas-liquid separation) after reaching the ink liquid levels 22Krs and 22Crs. In addition, since the ink amount in the reservoirs 22Kr and 22Cr is maintained within a certain range by the ink supply operation described above, the gas-liquid separated bubbles accumulate and accumulate in the air chamber 66 above the reservoirs 22Kr and 22Cr. There is no. Although the bubbles 69 may adhere to the wall surface or the like, these bubbles 69 are fine and do not cause any adverse effects such as blocking the flow path. If it becomes larger, it will be separated from the wall surface and separated from gas. Therefore, in this embodiment, in order to remove bubbles, it is unnecessary to perform a special sequence for removing bubbles.

  After the recording operation is finished, the recording heads 22K and 22C are raised and capped by the cap 50 again (S711). Thereafter, the atmospheric valve 84 is closed (S712), the operation of the air fan 68 is stopped (S713), the valve 100 is opened (S714), and the standby state is entered again, and this series of operations ends.

  Next, a standby state in which a recording operation (ink ejection operation) is not performed in the recording apparatus will be described. In the standby state, the atmospheric valve 84 is closed and the valve 100 is opened, and the ink tank 28K is open to the atmosphere. Further, since the ink supply pump 72 is in a stopped state, the flow paths before and after the ink supply pump 72 are in a blocked state. Further, a height difference (water head difference) is provided between the discharge port surface 22Ks of the head unit 22K and the liquid surface of the ink tank 28K.

  For this reason, pressure (negative pressure) due to a water head difference is generated in the nozzle 22Kn, and the meniscus is held in the nozzle 22Kn by this negative pressure. By forming the meniscus in this way, even if pressure fluctuation or the like occurs in the head unit 22K due to the expansion / contraction of the air in the head unit 22K during standby, adverse effects caused by this can be avoided. That is, it is possible to prevent ink leakage from the nozzle 22Kn due to a pressure increase in the head unit 22K, air intake into the nozzle 22Kn due to a pressure drop in the head unit 22K, and the like.

Further, other head units (22C in FIG. 3) communicated with the air flow path 64 are communicated with the ink tank 28K in the same manner as the head unit 22K. For this reason, even if the height difference (water head difference) between the discharge port surfaces 22Ks and 22Cs of the head units 22K and 22C and the liquid levels of the ink in the corresponding ink tanks 28K and 28C is different, the recording head. The liquid level inside does not change to a different height. For example, in the configuration of FIG. 3 in which the head unit 22K and 22C are in communication, and the head unit 22C and the ink tank 28C is in a state of being blocked by the pump 7 2, head unit 22C, the ink tank 28K and the only It is in a state of communication. Accordingly, a negative pressure is applied to the head unit 22C due to a water head difference between the liquid level of the ink tank 28K and the discharge port surface of the head unit 22C, as in the head unit 22K. That is, the same negative pressure is applied to the head unit 22C and the head unit 22K, whereby the ink level in both head units is made uniform. 3 shows only the state where the head units 22K and 22C communicate with each other, the other head units 22Y and 22M also communicate with each other. Since both the head units 22K and 22C communicate with only one ink tank corresponding to one of the head units, they are also maintained at a uniform liquid level as with the head units 22K and 22C.

  As described above, according to the present embodiment, even when each ink tank has a different liquid level during standby, it is possible to apply a uniform negative pressure to the head unit and communicate with each other. The liquid surface positions of the inks of the plurality of recording heads are all kept uniform. For this reason, even if complicated negative pressure control is not performed in the standby state, it is possible to reliably prevent problems such as ink leakage from the nozzle due to pressure increase in the head unit and air intake into the nozzle due to pressure drop in the head unit. It becomes possible to reduce.

  As described above, in the present embodiment, it is possible to simultaneously achieve the simplification of the negative pressure control during printing and the simplification of the negative pressure control by communicating the air chambers of a plurality of ink tanks.

  In addition, since the liquid level of the ink in the plurality of head units communicated with the air chambers is kept uniform during standby, adjustment of the liquid level position in each head unit may be performed at the start of the recording operation. It becomes unnecessary. For this reason, the recording operation can be started quickly after receiving the recording operation command, and the throughput can be improved.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to FIG.
FIG. 7 is a schematic diagram showing an ink supply device incorporated in the ink jet recording apparatus according to the second embodiment of the present invention.
The components of the ink supply device 60 according to the second embodiment are the same as those of the ink supply device 60 shown in FIG. 3 except for some components described below. Is omitted.

  In the second embodiment, head units 22C, 22M, and 22Y that discharge cyan (C), magenta (M), and yellow (Y) color inks are provided for each color. Further, one ink tank 28C, 28M, 28Y corresponds to each color head unit 22C, 22M, 22Y. In addition, two head units 22K and 22K 'are provided for ejecting black ink, and one ink tank 28K corresponds to the two head units 22K and 22K'.

An air chamber 66 formed in the upper part of each recording head is communicated via an air flow path 64 so that the ink storage portion in each recording head can be depressurized by one fan 68.
A valve 100 that can be opened and closed is provided in parallel with the supply pump 72 in the ink supply flow path 62 that connects the head unit 22K and the ink tank 28K. Further, the ink tank 28K is provided at a height position where a predetermined negative pressure can be applied to the nozzle surface of the recording head 22K when communicating with the recording head 22K in the standby state.

  Further, when the valve 100 is opened during standby, all the head units communicate with one ink tank 28Y. For this reason, it becomes possible to apply a fixed negative pressure to the discharge port surface of each head unit. Therefore, also in the second embodiment, it is possible to keep the liquid level in the storage portion of each head unit uniform, and the same effect as in the first embodiment can be expected.

(Third embodiment)
Hereinafter, a third embodiment of the present invention will be described with reference to FIG.
FIG. 8 is a schematic view showing an ink supply device incorporated in the ink jet recording apparatus according to the third embodiment.

The components of the ink supply device in the third embodiment are the same as those of the ink supply device 60 of FIG. 3 except for some components described below, and thus the description of the same components is omitted. .
The plurality of head units in the third embodiment are integrally provided in a single head cartridge. That is, the internal space of the head cartridge 22 is divided into four spaces 22Y, 22M, 22C, and 22K, and each of the divided spaces has a storage portion that stores K, C, M, and Y inks. is doing. In addition, an air chamber 66 is provided above the storage portion of each divided space, and each air chamber communicates with the air flow path 64, and the ink storage portion in each head unit is defined by one fan 68. The pressure can be reduced. Further, a discharge portion (not shown) in which nozzles for discharging ink are arranged is provided at the lower end portion of each head unit.

    In addition, the plurality of ink tanks in the third embodiment are integrally provided in a single ink cartridge. That is, the internal space of a single ink cartridge is divided into four spaces 28Y, 28M, 28C, and 28K, and each of the divided spaces stores inks of K, C, M, and Y. It is a tank. Each ink tank is connected to each head unit by an ink supply channel 62 so that the ink can be supplied to a storage portion that stores the corresponding color ink of the head unit 22. Each ink supply channel 62 is provided with a supply pump 72 for supplying ink from each ink tank to the head unit.

  In addition, among the plurality of head units, a valve 100 capable of blocking and opening the flow path is provided in parallel with the supply pump 72 in the ink supply flow path 62 that connects the head unit 22Y and the ink tank 28Y. It is connected.

  In the ink supply device configured as described above, when the ink cartridge 28 and the head cartridge 22 communicate with each other in the standby state, the head cartridge is at a height position at which a predetermined negative pressure can be applied to the ejection port surface of each head unit. Is provided. When the valve 100 is opened during standby, all the head units communicate with one ink tank 28Y, so that a constant negative pressure can be applied to the ejection port surface of each head unit. Become. For this reason, also in the third embodiment, it becomes possible to keep the level of the liquid level in the reservoir of each head unit uniform, and the same effect as in the first embodiment can be expected. In this embodiment, the valve 100 is provided in the ink tank 28Y. However, the valve 100 may be provided in any one of the ink tank 28K, the ink tank 28C, and the ink tank 28M.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described with reference to FIG.
FIG. 9 is a schematic view showing an ink supply apparatus incorporated in the fourth ink jet recording apparatus of the present invention. In the fourth embodiment, the same or corresponding parts as those in the ink supply apparatus shown in FIG. 3 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The ink supply device according to the fourth embodiment has one head unit 22Y, 22M, 22C, and 22K that discharges K, C, M, and Y inks, and an ink tank 28 that corresponds to each head unit. One is installed. Each head unit and the ink tanks 28Y, 28M, 28C, and 28K have the same configuration as the head unit in the second embodiment.

  However, in the third embodiment, each head unit 22Y, 22M, 22C, 22K and the four ink tanks 28Y, 28M, 28C, 28K corresponding thereto are connected by different ink supply channels 62, respectively. ing. A supply pump 72 is provided in the middle of each ink supply channel 62. Further, in the third embodiment, a valve 100 capable of blocking and opening the flow path for each ink supply flow path 62 is connected in parallel with each supply pump 72. However, this fourth embodiment is different from the second embodiment.

  Further, in the fourth embodiment, a negative pressure for removing bubbles accumulated in the head unit 22 is generated in the air flow path 64 communicating with the air chamber 66 formed in the upper part of each head unit 22. A defoaming pump 103 is connected as a negative pressure generating source. This point is also different between the fourth embodiment and each of the above embodiments. Here, the bubble removal pump 103 is constituted by a tube pump.

  In the present embodiment, each color ink tank 70 is provided at a height position at which a predetermined negative pressure can be applied to the discharge port surface of each head unit. During the recording operation, all the valves 100 are opened and the discharge of each head unit is performed. A predetermined negative pressure is applied to the outlet surface. During standby, only one arbitrary valve 100 among the four valves 100 is opened, and the other valves 100 are closed. Thereby, also in this 4th Embodiment, a uniform negative pressure can be given to each head unit at the time of standby, and the liquid level of the storage part in each head unit can be kept uniform. Therefore, also in the fourth embodiment, the same effect as in the first to third embodiments can be expected. Furthermore, according to the present embodiment, the air bubbles accumulated in the head unit can be sucked and discharged by the pump 103, and if the pump is kept in a stopped state, the air chamber of each head unit can be cut off from standby. It can also be made to function as the atmospheric valve 84 in each of the above embodiments, and the structure can be further simplified.

  As shown in the fourth embodiment, the present invention can be connected not only to the case where a fan is provided as a negative pressure means for connecting to the communicating portion for communicating the air chamber of each head unit, but also to a pump. is there. Moreover, what is connected to the communicating portion that communicates the air chamber of each head unit may be pressure adjusting means that generates not only negative pressure but also positive pressure. In a recording apparatus, a large amount of ink may be discharged from each head unit in a recovery operation or the like, and in that case, an excessive negative pressure may be generated inside. In such a case, if a positive pressure is applied by the pressure adjusting means described above, an excessive negative pressure can be reduced.

(Other embodiments)
In each of the above-described embodiments, the example in which the control unit that controls the negative pressure in the head unit is provided in the recording apparatus has been described. However, the present invention is not limited to this. It is also possible to provide as a component.

  In each of the above embodiments, a full-line type recording apparatus has been described as an example. However, the present invention is not limited to this, and recording is performed by alternately performing main scanning of the recording head and conveyance of the recording medium. The present invention can also be applied to a so-called serial type recording apparatus.

  In each of the above embodiments, a so-called non-volumetric pump that is a propeller type fan is used for the negative pressure generating mechanism, but a volumetric pump may be used.

  Note that “recording” (also referred to as image formation) in the present specification is not limited to forming significant information such as characters and graphics. In other words, recording means whether an image, a pattern, a pattern, etc. are widely formed on a recording medium regardless of whether it is significant or involuntary, or whether it is manifested so that humans can perceive it visually. In addition, the case where a medium is processed is included.

  The “recording medium” includes not only paper used in general recording apparatuses but also a wide range of cloth, plastic film, metal plate, glass, ceramics, wood, leather, and the like that can accept ink. Shall be.

  Further, the term “ink” should be broadly interpreted in the same way as the definition of “recording”. In other words, the ink is applied onto the recording medium to form an image, pattern, pattern, or the like, process the recording medium, or process the ink (for example, solidify or insolubilize the colorant in the ink applied to the recording medium). ) Shall be included.

  It goes without saying that liquids other than ink may be used in the apparatus of the present invention.

It is the front view which showed typically the inkjet recording device which can apply 1st Embodiment. FIG. 2 is a block diagram illustrating a control system of the recording apparatus in FIG. 1. FIG. 2 is a diagram schematically illustrating a path through which ink passes from an ink tank to a head unit in the recording apparatus according to the first embodiment. It is the flowchart which showed the procedure at the time of cleaning the discharge port surface of a head unit. It is a schematic diagram which shows the procedure of wiping off ink with a wiper from a discharge surface, (a) shows before wiping start, (b) shows immediately after completion | finish of wiping, (c) is a figure which shows the standby state after completion | finish of wiping. is there. It is a flowchart showing operation | movement from receiving a recording signal until recording is complete | finished. It is a schematic diagram which shows the ink supply apparatus integrated in the inkjet recording device in 2nd Embodiment. It is a schematic diagram which shows the ink supply apparatus integrated in the inkjet recording device in 3rd Embodiment. It is a schematic diagram which shows the ink supply apparatus integrated in the inkjet recording device in 4th Embodiment. It is a schematic diagram which shows the related technique of this invention.

Explanation of symbols

10 Inkjet recording device 12 Host PC
22K Head Unit 22C Head Unit 22M Head Unit 22Y Head Unit 22Kn Nozzle 22Kr Storage Unit 22Krs Liquid Level 22KSi Discharge Unit 22Kv Recording Head Unit 22Krb First Storage Unit 22Kra Second Storage Unit 24 Roll Paper Supply Unit 26 Conveying Mechanism 60 Ink Supply Device 62 Ink supply flow path 64 Air flow path 66 Air chamber 68 Fan 70 Ink tank 84 Atmospheric valve 100 Valve 101 Atmospheric communication port 102 Ink supply port 103 Foam removal pump

Claims (4)

An ink supply device that supplies ink to a plurality of ejection units capable of ejecting ink,
A plurality of first reservoirs for storing ink supplied to the plurality of ejection units and having a space filled with air at the top;
A plurality of second reservoirs provided corresponding to each of the plurality of first reservoirs , storing ink supplied to the corresponding first reservoirs, and communicating with the atmosphere;
A first air flow path communicating at least two or more of the spaces of the plurality of first storage portions;
A negative pressure generating means connected to the first air flow path for generating a negative pressure in the first reservoir;
Wherein the plurality of provided corresponding to each of the first reservoir, a plurality of end connected to the first reservoir which correspond, the other end connected to the second reservoir unit corresponding to the first reservoir A first ink supply flow path;
A plurality of ink supply means provided corresponding to each of the plurality of first ink supply flow paths for supplying ink from the second storage portion to the first storage portion;
The ink is provided in one of the plurality of first ink supply channels and not provided in another first ink supply channel, and ink is supplied from the second reservoir to the first reservoir. In the supply direction to be supplied, the first ink supply on the upstream side in the supply direction with respect to the ink supply means, one end of which corresponds to one of the first ink supply channels. A second ink supply flow path connected to the flow path and having the other end connected to the first ink supply flow path on the downstream side in the supply direction with respect to the ink supply means;
A first valve capable of opening and closing the second ink supply channel;
A second air flow path having one end connected to the first air flow path and the other end connected to the negative pressure generating means;
A second valve capable of opening and closing the second air flow path;
A controller that controls the opening and closing operations of the first valve and the second valve and the driving operation of the negative pressure generating means;
With
Each of the plurality of ink supply means supplies ink from the second storage section to the first storage section when operating , and blocks the first ink supply flow path when not operating .
Each of the plurality of second storage portions is arranged such that the liquid level of the ink stored in the storage portion is positioned below the discharge portion,
During a recording operation for recording an image on a recording medium by discharging ink from the discharge unit, the control unit closes the first valve and opens the second valve to drive the negative pressure generating unit. In this way, the control unit opens the first valve, closes the second valve, and sets the negative pressure generating means to a negative pressure in the first storage unit and when the recording operation is not performed. An ink supply device that is not driven . The ink supply apparatus according to claim 1, wherein the ink supply unit includes a tube pump. A pressure detection sensor provided in the second air flow path for detecting the pressure in the second air flow path,
  The second valve is provided in a portion of the second air flow path located between the pressure detection sensor and the air flow path,
  The control unit operates the negative pressure generating unit in a state where the second valve is shut off before the discharge unit starts an ink discharge operation, and then the pressure detection sensor detects a predetermined negative pressure. 3. The ink supply device according to claim 1, wherein the second valve is opened when the detection is detected. 4. An ink jet recording apparatus comprising: a discharge unit that discharges ink; and an ink supply device that supplies ink to the discharge unit,
The ink supply apparatus according to claim 1, wherein the ink supply apparatus is an ink supply apparatus according to claim 1.

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