JP5246599B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus provided with a recording head for discharging droplets.

  As an image forming apparatus such as a printer, a facsimile machine, a copying apparatus, a plotter, and a complex machine of these, for example, an ink jet recording apparatus is known as an image forming apparatus of a liquid discharge recording method using a recording head for discharging ink droplets. . This liquid discharge recording type image forming apparatus ejects ink droplets from a recording head onto a conveyed paper to form an image (recording, printing, printing, and printing are also used synonymously). Serial type image forming device that forms an image by ejecting droplets while the recording head moves in the main scanning direction, and a line type that forms images by ejecting droplets without the recording head moving There is a line type image forming apparatus using a head.

  In the present application, an “image forming apparatus” is an apparatus that forms an image by landing ink on a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics (simple liquid ejection apparatus) In addition, “image formation” not only gives an image having a meaning such as a character or a figure to a medium but also gives an image having no meaning such as a pattern to the medium. It also means (including what is simply referred to as a droplet discharge device or a liquid discharge device). In addition, the term “ink” is not limited to what is called ink, but is any liquid that can form an image, such as a recording liquid, a fixing liquid, a liquid, a DNA sample, or a patterning material. Used as a general term. The term “paper” is not limited to paper, but includes the above-described OHP sheet, cloth, and the like, and means that ink droplets adhere to the recording medium, recording medium, recording paper, recording It is used as a general term for what includes what is called paper.

  As a liquid discharge head (droplet discharge head) used as a recording head, a piezoelectric head or the like is used to displace a diaphragm and change the volume in the liquid chamber to increase the pressure to discharge the liquid droplet. There is known a thermal type head in which a heating element that generates heat is provided, the pressure in the liquid chamber is increased by bubbles generated by the heat generation of the heating element, and droplets are discharged.

  In such a liquid ejection type image forming apparatus, it is particularly desired to improve the image forming throughput, that is, to increase the image forming speed. From the large-capacity ink cartridge (main tank) installed on the main body through the tube. A system is used in which ink is supplied to sub-tanks (including head tanks and buffer tanks) above the recording head. By adopting a method for supplying ink using such a tube (tube supply method), the carriage portion can be reduced in weight and size, and the apparatus including the structure system and the drive system can be significantly reduced in size.

  By the way, in the tube supply method, ink consumed from the recording head in image formation is supplied from the ink cartridge to the recording head through the tube. For example, when a thin flexible tube is used, the tube is Since the fluid resistance when the ink flows is large, the ink supply is not in time for ink ejection, resulting in ejection failure. In particular, in a large machine that prints on a wide recording medium, the tube inevitably becomes long and the fluid resistance of the tube increases. Also, when printing at high speed or ejecting highly viscous ink, fluid resistance increases, and insufficient ink supply to the recording head becomes a problem.

  Therefore, as disclosed in Patent Document 1, conventionally, the ink in the ink cartridge is held in a pressurized state, and a differential pressure valve is provided on the upstream side of the ink supply of the head so that the negative pressure in the sub tank is a predetermined pressure. It is known to supply ink when it is larger.

  Also, as disclosed in Patent Document 2, the ink supply pressure is positively controlled by pumping ink to a negative pressure chamber that obtains a negative pressure by a spring upstream of the head, Patent Document 3 discloses As disclosed, there is also known a system that does not have a negative pressure chamber, but similarly positively controls the pressure by a pump.

  On the other hand, as a method of obtaining a negative pressure with a simple configuration, an ink cartridge communicated with the atmosphere and a recording head are connected by a tube, and the ink cartridge is simply disposed below the recording head, so that the negative pressure can be reduced by a water head difference. There are ways to get.

  In this method, a more stable negative pressure can be obtained while having an overwhelmingly simple configuration as compared to a method of constantly pressurizing using a negative pressure interlocking valve or a method of providing a negative pressure chamber and feeding liquid by a pump. However, this water head method has a problem of pressure loss due to the tube resistance described above.

  As a technique for solving this pressure loss with an ink supply system that obtains a negative pressure by the water head difference, for example, as disclosed in Patent Document 4, a pump is provided in a tube that connects a head and an ink cartridge, and further, It is known that a bypass path connecting the upstream side and the downstream side is provided, and a valve is provided in this bypass path, and the opening of the valve provided in the bypass path is appropriately controlled by printing to maintain a desired pressure. Yes.

  On the other hand, in the ink supply system, with respect to the discharge of mixed bubbles when a pressure adjustment valve is used, as disclosed in Patent Document 5, the pressure force adjustment valve is configured by a diaphragm, and the diaphragm is negatively deformed to form an ink. By releasing the diaphragm, releasing the diaphragm, and then releasing the diaphragm pressure, the amount of air bubbles in the pressure adjustment valve is reduced compared to the case of initial filling only by suction. It has been known.

Japanese Patent No. 3606282 JP 2005-342960 A Japanese Patent Publication No. 5-504308 JP 2004-351845 A JP 2006-082070 A

  However, although the technique disclosed in Patent Document 1 solves the above-mentioned problem of insufficient refill, the mechanism for controlling the negative pressure is complicated, and the sealing performance of the negative pressure interlocking valve is highly required. There is a problem. In addition, since the pressure is constantly applied, airtightness of all the connecting portions in the ink supply path is also highly required, and in the event of a failure, there is a risk that ink may be ejected.

  Further, in the techniques disclosed in Patent Documents 2 and 3, since the pressure is positively controlled by the pump, it is necessary to accurately control the pumped liquid amount according to the ink consumption amount. Feedback control using the pressure in the chamber is required. For example, when applied to an image forming apparatus using a plurality of types of inks having different colors, it is required to control the pump for each color type, and there is a problem in that the control is complicated and the apparatus becomes large.

  Further, even in the technique disclosed in Patent Document 4, when applied to an image forming apparatus using a plurality of types of inks having different colors, it is required to control a pump for each color type, which increases the size of the apparatus. is there.

  Further, the technique for reducing the mixed bubbles in the pressure regulating valve disclosed in Patent Document 5 is limited to the initial filling into the pressure regulating valve, and the mixed bubbles cannot be effectively discharged over a long period of time. .

  The present invention has been made in view of the above-mentioned problems, has a simple structure, maintains a stable negative pressure, and prevents refill shortage even when the speed is increased, the tube length is increased, and the viscosity is increased. An object of the present invention is to make it possible to reliably discharge bubbles remaining in the pressure adjusting means by using the pressure adjusting means.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A recording head having nozzles for discharging droplets;
A liquid tank for storing liquid to be supplied to the recording head;
A first flow path for supplying the liquid to the recording head;
A second flow path communicating with the liquid tank;
A pressure regulating valve that connects the first flow path and the second flow path, and an internal flow path resistance changes according to a flow rate of the liquid flowing through the first flow path;
A third flow path communicating the second flow path or the liquid tank and the pressure regulating valve;
Liquid feeding means provided in the third flow path,
When ejecting droplets from the nozzle, the liquid is fed from the liquid tank to the recording head by the liquid feeding means in a state where the recording head and the liquid tank are in communication with each other via the pressure adjusting valve. An image forming apparatus that
The pressure regulating valve includes a flow path member that forms a flow path, and a movable member that is movably accommodated in the flow path member.
The movable member has a valve body portion located on the first flow path side with respect to the communication section with the third flow path, and a through hole is formed in the valve body section in a liquid flow direction. And an inclined surface that is inclined toward the first flow path side is formed on the second flow path side,
The movable member is accommodated in the flow path member in a state in which the inclined surface of the valve body portion is in contact with the contact portion on the flow path member side as it moves. .

  Here, the inclined surface of the valve body portion of the movable member may be configured to be inclined from the valve body portion center side toward the valve body outer peripheral portion side toward the first flow path side.

  The inclined surface of the valve body portion of the movable member is inclined from the outer peripheral portion side of the valve body portion toward the central portion side of the valve body portion toward the first flow path side. The image forming apparatus described.

  Further, the through hole of the movable member can be configured to have a shape with an opening diameter that decreases toward the first flow path side.

  Further, a concave portion is formed in the opening on the second flow path side of the through hole of the movable member, and a convex portion that fits into the concave portion is provided in the contact portion on the flow path member side. it can.

  Moreover, it can be set as the structure by which the level | step-difference part was provided in the inclined surface of the valve body part of the said movable member.

  In addition, the contact portion on the flow path member side may have an inclined surface corresponding to the inclined surface of the valve body portion of the movable member.

An image forming apparatus according to the present invention includes:
A recording head having nozzles for discharging droplets;
A liquid tank for storing liquid to be supplied to the recording head;
A first flow path for supplying the liquid to the recording head;
A second flow path communicating with the liquid tank;
A pressure regulating valve that connects the first flow path and the second flow path, and an internal flow path resistance changes according to a flow rate of the liquid flowing through the first flow path;
A third flow path communicating the second flow path or the liquid tank and the pressure regulating valve;
Liquid feeding means provided in the third flow path,
When ejecting droplets from the nozzle, the liquid is fed from the liquid tank to the recording head by the liquid feeding means in a state where the recording head and the liquid tank are in communication with each other via the pressure adjusting valve. An image forming apparatus that
The pressure regulating valve includes a flow path member that forms a flow path, and a movable member that is movably accommodated in the flow path member.
The movable member has a valve body portion located on the first flow path side with respect to the communication section with the third flow path, and a through hole is formed in the valve body section in a liquid flow direction. And the opening on the second flow path side of the through hole is formed larger than the opening on the first flow path side,
The movable member is accommodated in the flow channel member in a state where the second flow channel side surface of the valve body part is in contact with the contact portion on the flow channel member side as it moves. did.

An image forming apparatus according to the present invention includes:
A recording head having nozzles for discharging droplets;
A liquid tank for storing liquid to be supplied to the recording head;
A first flow path for supplying the liquid to the recording head;
A second flow path communicating with the liquid tank;
A pressure regulating valve that connects the first flow path and the second flow path, and an internal flow path resistance changes according to a flow rate of the liquid flowing through the first flow path;
A third flow path communicating the second flow path or the liquid tank and the pressure regulating valve;
Liquid feeding means provided in the third flow path,
When ejecting droplets from the nozzle, the liquid is fed from the liquid tank to the recording head by the liquid feeding means in a state where the recording head and the liquid tank are in communication with each other via the pressure adjusting valve. An image forming apparatus that
The pressure regulating valve includes a flow path member that forms a flow path, and a movable member that is movably accommodated in the flow path member.
The movable member has a valve body portion located on the first flow path side with respect to the communication section with the third flow path, and a through hole is formed in the valve body section in a liquid flow direction. And an inclined surface that is inclined toward the first flow path side is formed on the first flow path side,
The movable member is configured to be accommodated in the flow path member in a state where the inclined surface of the valve body portion is in contact with the abutting portion on the flow path member side as it moves.

An image forming apparatus according to the present invention includes:
A recording head having nozzles for discharging droplets;
A liquid tank for storing liquid to be supplied to the recording head;
A first flow path for supplying the liquid to the recording head;
A second flow path communicating with the liquid tank;
A pressure regulating valve that connects the first flow path and the second flow path, and an internal flow path resistance changes according to a flow rate of the liquid flowing through the first flow path;
A third flow path communicating the second flow path or the liquid tank and the pressure regulating valve;
Liquid feeding means provided in the third flow path,
When ejecting droplets from the nozzle, the liquid is fed from the liquid tank to the recording head by the liquid feeding means in a state where the recording head and the liquid tank are in communication with each other via the pressure adjusting valve. An image forming apparatus that
The pressure regulating valve includes a flow path member that forms a flow path, and a movable member and a contact member that are movably accommodated in the flow path member.
The movable member has a valve body portion located on the first flow path side with respect to the communication section with the third flow path, and a through hole is formed in the valve body section in a liquid flow direction. And
The movable member and the contact member are accommodated in the flow path member in a state in which the contact member can come into contact with the surface on the second flow path side of the valve body portion of the movable member as the movement occurs. It was set as the structure.

  According to the image forming apparatus of the present invention, when droplets are ejected from the nozzles of the recording head, the recording head and the liquid tank are connected via the pressure adjustment valve whose internal flow path resistance changes according to the flow rate of the flowing liquid. Since the liquid is fed from the liquid tank to the recording head while in communication, the appropriate assist pressure is automatically adjusted according to the discharge amount of the recording head and applied to the recording head. In addition, it is possible to avoid shortage of refill due to the lengthening of the tube member, increase of the discharge flow rate, increase in viscosity of the discharge liquid, etc., and the pressure regulating valve is movably accommodated in the flow path member The movable member has a through hole formed in the valve body portion and an inclined surface formed on the second flow path side, and the inclined surface is brought into contact with the flow path member side as it moves. Housed in the channel member in contact with the part As a result, the bubbles inside the flow path are discharged through the through hole due to the contact between the inclined surface of the valve body portion of the movable member and the contact portion, and the retention of bubbles inside the pressure regulating valve can be reduced. it can. As a result, the negative pressure of the head can be maintained within an appropriate range with a simple configuration and control, and even a highly viscous liquid can be discharged at high speed without causing defective discharge.

  According to the image forming apparatus of the present invention, when droplets are ejected from the nozzles of the recording head, the recording head and the liquid tank are connected via the pressure adjustment valve whose internal flow path resistance changes according to the flow rate of the flowing liquid. Since the liquid is fed from the liquid tank to the recording head while in communication, the appropriate assist pressure is automatically adjusted according to the discharge amount of the recording head and applied to the recording head. In addition, it is possible to avoid shortage of refill due to the lengthening of the tube member, increase of the discharge flow rate, increase in viscosity of the discharge liquid, etc., and the pressure regulating valve is movably accommodated in the flow path member The movable member has a through hole formed in the valve body, and the through hole is formed such that the opening on the second flow path side is larger than the opening on the first flow path side. The inclined surface is the contact portion on the flow path member side. Since it is configured to be accommodated in the flow path member in a contact state, bubbles inside the flow path are discharged through the through hole due to the contact between the inclined surface of the valve body portion of the movable member and the contact portion, and the pressure adjustment valve It is possible to reduce the retention of bubbles in As a result, the negative pressure of the head can be maintained within an appropriate range with a simple configuration and control, and even a highly viscous liquid can be discharged at high speed without causing defective discharge.

  According to the image forming apparatus of the present invention, when droplets are ejected from the nozzles of the recording head, the recording head and the liquid tank are connected via the pressure adjustment valve whose internal flow path resistance changes according to the flow rate of the flowing liquid. Since the liquid is fed from the liquid tank to the recording head while in communication, the appropriate assist pressure is automatically adjusted according to the discharge amount of the recording head and applied to the recording head. In addition, it is possible to avoid shortage of refill due to the lengthening of the tube member, increase of the discharge flow rate, increase in viscosity of the discharge liquid, etc., and the pressure regulating valve is movably accommodated in the flow path member The movable member has a through hole formed in the valve body portion and an inclined surface formed on the first flow path side, and the inclined surface is brought into contact with the flow path member side as it moves. Housed in the channel member in contact with the part As a result, the bubbles inside the flow path are discharged through the through hole due to the contact between the inclined surface of the valve body portion of the movable member and the contact portion, and the retention of bubbles inside the pressure regulating valve can be reduced. it can. As a result, the negative pressure of the head can be maintained within an appropriate range with a simple configuration and control, and even a highly viscous liquid can be discharged at high speed without causing defective discharge.

  According to the image forming apparatus of the present invention, when droplets are ejected from the nozzles of the recording head, the recording head and the liquid tank are connected via the pressure adjustment valve whose internal flow path resistance changes according to the flow rate of the flowing liquid. Since the liquid is fed from the liquid tank to the recording head while in communication, the appropriate assist pressure is automatically adjusted according to the discharge amount of the recording head and applied to the recording head. In addition, it is possible to avoid shortage of refill due to the lengthening of the tube member, increase of the discharge flow rate, increase in viscosity of the discharge liquid, etc., and the pressure regulating valve is movably accommodated in the flow path member The movable member has a through-hole formed in the valve body portion, and the movable member and the contact member move with the movement of the second member of the valve body portion of the movable member. A state where the surface on the flow path side can contact the contact member Therefore, when the contact member and the valve body of the movable member are in contact with each other, the bubbles inside the channel are discharged through the through hole, and the bubbles inside the pressure regulating valve are discharged. Residence can be reduced. As a result, the negative pressure of the head can be maintained within an appropriate range with a simple configuration and control, and even a highly viscous liquid can be discharged at high speed without causing defective discharge.

1 is a schematic front explanatory view showing an ink jet recording apparatus as an image forming apparatus according to an embodiment of the present invention. It is a schematic plane explanatory drawing similarly. It is a schematic side surface explanatory drawing similarly. FIG. 2 is an enlarged explanatory view of a main part for explaining a recording head of the same apparatus. It is typical sectional explanatory drawing of the sub tank of the ink supply system (ink supply system) of the apparatus. It is explanatory drawing of a cartridge holder part similarly. It is explanatory drawing of a pump unit similarly. It is explanatory drawing of a pressure control unit similarly. It is the whole ink supply system explanatory drawing. It is explanatory drawing which similarly shows a flow-path resistance variable unit. It is plane explanatory drawing of the valve body of the flow path resistance variable unit. It is explanatory drawing which similarly shows an example of the relationship between head discharge flow volume, head pressure loss, and assist flow volume. FIG. 6 is a schematic explanatory diagram for explaining bubble retention inside the flow path resistance variable unit in the ink supply system. FIG. 3 is an explanatory cross-sectional view of the flow path variable resistance unit according to the first embodiment of the invention in the ink supply system. It is principal part expanded sectional explanatory drawing of the flow path variable resistance unit. It is principal part expanded sectional explanatory drawing with which it uses for description of the bubble discharge | emission operation | movement in the same flow path variable resistance unit. It is a sectional explanatory view for explaining bubble discharge operation similarly. It is a section explanatory view of a channel variable resistance unit concerning a 2nd embodiment of the present invention similarly. It is principal part expanded sectional explanatory drawing with which it uses for description of the bubble discharge | emission operation | movement in the same flow path variable resistance unit. It is a section explanatory view of the channel variable resistance unit concerning a 3rd embodiment of the present invention similarly. It is principal part expanded sectional explanatory drawing with which it uses for description of the bubble discharge | emission operation | movement in the same flow path variable resistance unit. It is a sectional explanatory view for explaining bubble discharge operation similarly. It is a section explanatory view of the channel variable resistance unit concerning a 4th embodiment of the present invention similarly. It is principal part expanded sectional explanatory drawing with which it uses for description of the bubble discharge | emission operation | movement in the same flow path variable resistance unit. It is a section explanatory view of a channel variable resistance unit concerning a 5th embodiment of the present invention similarly. It is principal part expanded sectional explanatory drawing with which it uses for description of the bubble discharge | emission operation | movement in the same flow path variable resistance unit. It is principal part expanded sectional explanatory drawing which similarly shows an example of the flow-path variable resistance unit which concerns on 6th Embodiment of this invention. It is principal part expanded sectional explanatory drawing which shows the other example of the flow-path variable resistance unit which similarly concerns on 6th Embodiment of this invention. It is a section explanatory view of a channel variable resistance unit concerning a 7th embodiment of the present invention similarly. It is a section explanatory view of the channel variable resistance unit concerning an 8th embodiment of the present invention similarly. It is sectional explanatory drawing with which it uses for description of bubble discharge | emission operation | movement in the same flow path variable resistance unit. It is a flowchart with which it uses for description of an example of the bubble discharge | emission sequence in the ink supply system. It is a flowchart with which it uses for description of the other example of the bubble discharge sequence in the ink supply system.

Embodiments of the present invention will be described below with reference to the accompanying drawings. An ink jet recording apparatus as an image forming apparatus according to an embodiment of the present invention will be described with reference to FIGS. 1 is a schematic front view of the recording apparatus, FIG. 2 is a schematic plan view, and FIG. 3 is a schematic side view.
The ink jet recording apparatus includes a guide rod 2 that is a guide member horizontally mounted on the left and right side plates 1L and 1R provided upright on the main body frame 1, and a guide rail attached to a rear frame 1B that is horizontally mounted on the main body frame 1. 3, the carriage 4 is slidably held in the main scanning direction (guide rod longitudinal direction), and the carriage 4 is moved and scanned in the longitudinal direction (main scanning direction) of the guide rod 2 by a main scanning motor and a timing belt (not shown). To do.

  For example, a recording head 10K that discharges black (K) ink droplets and a recording head 10C that discharges cyan (C), magenta (M), and yellow (Y) ink droplets are mounted on the carriage 4. The recording head 10 has a plurality of ink discharge ports (nozzles) arranged in a direction crossing the main scanning direction, and is mounted with the ink droplet discharge direction facing downward. The recording head 10C has at least three nozzle rows that eject at least independent CMY ink droplets. In the following description, each nozzle row corresponding to each color of C, M, and Y in the recording head 10K and the recording head 10 is referred to as a “recording head 10” unless otherwise noted.

  Here, the recording head 10 is composed of a heating element substrate 12 and a liquid chamber forming member 13 as shown in FIG. 4, and the common flow path 17 and the liquid chamber (individual flow paths) are formed from the flow path formed in the head base member 19. ) The ink sequentially supplied to 16 is ejected as droplets. This recording head 10 is of a thermal type that obtains a discharge pressure by boiling the ink film by driving the heat generating element 14, and the direction of ink flow to the discharge energy acting part (heat generating part) in the liquid chamber 16 and the nozzles. This is a side shooter type configuration in which the opening center axis of 15 is a right angle.

  As the recording head, there are various methods such as a method in which the diaphragm is deformed by using a piezoelectric element, and the diaphragm is deformed by an electrostatic force to obtain a discharge pressure. The present invention can be applied to such an image forming apparatus.

  In addition, among thermal heads, there is an edge shooter method in which the discharge direction is different. In this edge shooter method, the heating element 14 is gradually destroyed by an impact when bubbles disappear, so-called cavitation. There is a problem with the phenomenon. On the other hand, in the side shooter method described above, bubbles grow, and when the bubbles reach the nozzle 15, the bubbles communicate with the atmosphere, and the bubbles do not contract due to a temperature drop. Therefore, there is an advantage that the life of the recording head is long. Further, there is a structural advantage that the energy from the heating element 14 can be more efficiently converted into the formation of ink droplets and the kinetic energy of the flight, and the meniscus can be quickly returned by supplying ink. Therefore, the ink jet recording apparatus employs a side shooter type recording head.

  On the other hand, below the carriage 4, a sheet 20 on which an image is formed by the recording head 10 is conveyed in a direction perpendicular to the main scanning direction (sub-scanning direction). As shown in FIG. 3, the paper 20 is sandwiched between a transport roller 21 and a pressing roller 22, transported to an image forming area (printing unit) by the recording head 10, sent onto a printing guide member 23, and discharged. A pair of rollers 24 feeds in the paper discharge direction.

  At this time, the scanning of the carriage 4 in the main scanning direction and the ink ejection from the recording head 10 are synchronized at an appropriate timing based on the image data, and an image for one band is formed on the paper 20. After image formation for one band is completed, a predetermined amount of paper 20 is fed in the sub-scanning direction, and the same recording operation as described above is performed. These operations are repeated to form an image for one page.

  On the other hand, a sub tank (buffer tank, head tank) 30 in which an ink chamber for temporarily storing ink to be ejected is formed is integrally connected to the upper portion of the recording head 10. Here, “integral” includes that the recording head 10 and the sub-tank 30 are connected by a tube, a pipe, and the like, both of which are mounted on the carriage 4 together.

  The sub tank 30 is an ink cartridge (main tank) which is a liquid tank according to the present invention and contains ink of each color which is detachably attached to a cartridge holder 77 provided on one end side in the main scanning direction on the apparatus main body side. The ink of each color is supplied from a liquid supply tube 41 which is a tube member forming a part of the ink supply path from 76 and forming a first flow path.

  A maintenance / recovery mechanism 51 that performs maintenance / recovery of the recording head 10 is disposed on the other end side in the main scanning direction of the apparatus main body. The maintenance / recovery mechanism 51 includes a cap 52 for capping the nozzle surface of the recording head 10, a suction pump 53 for sucking the inside of the cap 52, a discharge path 54 for discharging the waste liquid of ink sucked by the suction pump 53, and the like. The waste liquid discharged from the discharge path 54 is discharged to a waste liquid tank 56 disposed on the main body frame 1 side. Further, as shown in FIG. 9 described later, the maintenance / recovery mechanism 51 is provided with a wiper member 57 for wiping the nozzle surface of the recording head 10 by a wiping unit 58 so as to be able to advance and retreat with respect to the nozzle surface. ing.

  Next, an ink supply system (ink supply system) applied to the ink jet recording apparatus will be described with reference to FIGS. 5 is a schematic cross-sectional explanatory view of the sub tank of the ink supply system, FIG. 6 is also an explanatory view of the cartridge holder portion, FIG. 7 is also an explanatory view of the pump unit, and FIG. 8 is an explanatory view of the pressure control unit. FIG. 9 is an explanatory view showing an example of the flow path resistance variable unit.

  First, the sub tank 30 is provided with a flexible rubber member 102 formed in a convex shape toward the outside at a part of the opening of the tank case 101 forming the ink chamber 103. A filter 109 is provided in the vicinity of the connection portion with the recording head 10, and is configured to supply the recording head 10 with ink that has been filtered to remove foreign matters.

  One end of an ink supply tube 41 is connected to the sub tank 30. The other end of the ink supply tube 41 is connected to a cartridge holder 77 that is stationary as shown in FIGS.

  The cartridge holder 77 is connected to an ink cartridge 76, a pump unit 80 that is a liquid feeding means, and a pressure control unit 81.

  As shown in FIG. 6, internal flow paths 70, 74, and 79 are formed in the cartridge holder 77 corresponding to each color ink, and pump connection ports 73 a and 73 b that communicate with the pump unit 80, and pressure control Pressure control ports 72a, 72b, 72c communicating with the unit 81 are provided. The pump connection port 73a and the pressure control port 72c communicate with each other through the internal flow path 70.

  As shown in FIG. 7, the pump unit 80 includes ports 85a and 85b that communicate with the pump connection ports 73a and 73b of the cartridge holder 77, respectively, and a pump (assist pump) 78 that communicates with these ports 85a and 85b. Yes. As the pump 78, various pumps such as a tubing pump, a diaphragm pump, and a gear pump can be applied. The pump unit 80 of FIG. 7 includes four pumps 78K, 78C, 78M, and 78Y corresponding to the four colors of ink. However, these four pumps are driven by one motor 82 in conjunction with each other. It is said.

  As shown in FIG. 8, the pressure control unit 81 includes ports 86a, 86b, 86c that communicate with the pressure control ports 72a, 72b, 72c of the cartridge holder 77, respectively, and pressure adjustments that communicate with these ports 86a, 86b, 86c. A variable flow path resistance unit 83 that is a valve is provided.

  As described above, the maintenance / recovery mechanism 51 is disposed on the recording head 10 side. The maintenance / recovery mechanism 51 prevents moisture drying of the ink during non-ejection, and at the same time removes bubbles in the recording head 10 and sucks ink in the recording head 10 when the nozzles are clogged. A cap 52 is provided. When the ink in the recording head 10 is sucked, the nozzle surface of the recording head 10 is capped with the cap 52, and the ink is discharged to the waste liquid tank 56 by the suction pump 53. Here, the cap 52 is used for both moisturizing and sucking, but a cap having independent roles may be formed. The sucked ink may be returned to the ink cartridge 76 instead of the waste liquid tank 56. Further, the waste liquid tank 56 may have a role as an empty discharge receiver that receives not only the suction operation but also empty discharge droplets that do not contribute to image formation from the recording head 10. Further, the wiper member 57 is attached to the wiping unit 58, and the wiper member 57 wipes the nozzle surface of the recording head 10 after maintenance, thereby adjusting the meniscus of the nozzle surface.

Next, the overall configuration and operation of the ink supply system will be described with reference to the schematic configuration diagram shown in FIG. FIG. 9 shows only main components connected to one liquid discharge head (recording head) 10 so that the operation and action of the ink supply system can be easily understood.
The ink supply system includes an ink cartridge 76 that stores ink to be supplied to the recording head 10, a liquid supply tube 41 that is a first flow path for supplying ink to the recording head 10, and a second that communicates with the ink cartridge 76. The pressure control unit 81 includes a flow path resistance variable unit 83 that is a pressure adjusting valve for communicating the flow path 42, the liquid supply tube (hereinafter also referred to as “first flow path”) 41 and the second flow path 42. A third flow path 43 that communicates the second flow path 42 with the variable flow path resistance unit 83 of the pressure control unit 81, and a pump (assist pump) that is a liquid feeding means provided in the third flow path 43. 78).

  Here, the variable flow path resistance unit 83 has a characteristic that the flow path resistance (fluid resistance) changes depending on the flow direction and flow rate of the liquid flowing inside. For example, as shown in FIG. 10, the flow path resistance variable unit 83 includes a pipe member 87 that is a flow path member (flow path forming member), and a movable member that is movably accommodated in the pipe member 87 in a free state. And a certain valve body 88.

  The pipe member 87 has a port 86 a that connects the first flow path 41, a port 86 b that connects the second flow path 42, and a port 86 c that connects the third flow path 43. The valve body 88 that is a movable member is a stepped shaft-shaped member having step portions having different diameters in the liquid flow direction, and is an upper portion (hereinafter referred to as a “first valve body portion”) that is a valve body portion in the present invention. ) 88t, a central portion 88m, and a lower portion (hereinafter referred to as a “second valve body portion”) 88b. The central portion 88m has a diameter smaller than that of the second valve body portion 88b. ing. The valve body 88 is movable inside the pipe member 87, and the position of FIG. 10 (a), the position of FIG. 10 (b), or the intermediate position thereof is determined according to the state of the internal flow. The position changes to each position.

  Here, as shown in FIG. 11, the first valve body 88 t of the valve body 88 is a communication path that connects the first flow path 41 and the third flow path 43 in the ink flow direction. A through hole 84 serving as a first throttle portion is provided. Further, a second throttle portion 182 is formed between the second valve body portion 88b of the valve body 88 and the flow path portion 87b of the pipe member 87, so that the valve body 88 is in an internal flow state or the like as described above. By moving accordingly, the amount of restriction of the second restricting portion 182 formed between the second valve body portion 88b and the wall surface of the flow passage portion 87b of the pipe member 87 that is the flow passage member changes.

  Here, as shown in FIG. 11, the through holes 84 are equally divided into four equal parts around the central axis of the valve body 88, but the size of the holes can be reduced to increase the number of holes, Conversely, it is also possible to enlarge the holes and reduce the number of holes as appropriate. However, the through holes 84 are evenly arranged in the circumferential direction in the first valve body portion 88t of the valve body 88 in that the valve body 88 is moved straight using the flow of ink discharge from the recording head 10. Is preferred.

  The pipe member 87 has a lateral hole (a part of the third flow path 43 between the position of the central portion 88m of the valve body 88, that is, between the first throttle portion 84 and the second throttle portion 182). Port) 86c is formed.

  The variable flow resistance unit 83 is arranged in the ink supply system with the state shown in FIG. 10, that is, the port 86a side up.

  Returning to FIG. 9, the ink cartridge 76 is provided with an air communication portion 90, and the liquid level in the ink cartridge 76 is disposed at a position lower than the nozzle surface of the recording head 10. As a result, in a state where ink is filled in the entire ink supply path, the recording head 10 is held at a negative pressure due to the water head difference h between the liquid levels of the recording head 10 and the ink cartridge 76, so that the recording head is stable. Ink droplet ejection can be performed from 10.

  As described above, when the viscosity of the ink to be ejected is large, the fluid resistance of the liquid supply tube 41 is large, for example, when the tube is thin or long, or when the ink ejection flow rate is large, the ink supply path There arises a situation where the ink supply cannot keep up with the fluid resistance. Specifically, the main elements that become the ink supply resistance in the ink supply system include the liquid supply tube 41, the filter 109, and the joint 89 (see FIG. 9).

For example, in a wide image forming apparatus including a long tube having a diameter of 2.8 mm and a length of 2500 mm, the liquid supply tube 41 has a fluid resistance of 2 when a high viscosity ink of 16 cP is ejected. 0.7e10 [Pa · s / m ³ ]. In this embodiment, the fluid resistance of the filter 109 and the joint 89 is 1e10 [Pa · s / m ³ ] and 2e9 [Pa · s / m ³ ], respectively.

  Here, when the limit value of the pressure loss that enables stable ejection from the recording head 10 is 2.5 kPa, and ink is ejected continuously from all the nozzles, the ejection flow rate is 0.1 cc / s. The pressure loss at that time is 6.9 kPa. Even in the absence of the pressure control unit 81, the pressure is 3.94 kPa, so that it cannot be naturally supplied by a simple water head difference ink supply system.

  In this way, when the pressure loss increases due to the resistance of the ink supply system and the refill is insufficient, the pump 78 is driven to draw ink from the third flow path 43 by the arrow Qa (Qa is the assist flow rate or the flow of the assist liquid). However, it is also used as an arrow sign for convenience.) The liquid supply of the pump 78 can compensate for the insufficient supply of ink (refill assist).

  FIG. 12 shows an example of the relationship between the discharge flow rate of the recording head 10, the liquid feed amount (assist flow rate) of the pump 78, and the pressure of the recording head 10. FIG. 12 shows a change in pressure loss of the ink supply system with respect to the head discharge flow rate when the assist flow rate is 0 to 2 cc / s. As described above, when the assist flow rate is “0”, the pressure loss of the head is about 7 kPa, and ink cannot be continuously ejected, resulting in ejection failure. However, by assisting with the pump 78, the pressure loss is 1 kPa. It becomes the following grade and can be continuously discharged.

Here, the assist principle of the ink supply system will be described with reference to FIG. 10 described above.
FIG. 10A shows a state where the droplet resistance is not discharged from the recording head 10 or the state of the variable flow path resistance unit 83 under a condition where the discharge flow rate is small. In this state, the valve body 88 is on the port 86b side. As shown in FIG. 10A, the total fluid resistance between the gap Gb between the pipe member 87 and the second valve body 88b of the valve body 88 and the through hole 84 serving as the first throttle part is the pipe member. A liquid supply tube (first flow path) having a larger fluid resistance than the gap Gt between the gap 87 and the first valve body 88t of the valve body 88 and the port 86a as shown in FIG. ) 41 and the filter 109, the ink fed by the pump 78 indicated by the arrow Qa flows toward the port 86b that is easy to flow (arrow C). Therefore, the ink flow generated by the pump 78 only circulates in the loop path formed by the pump unit 80 and the flow path resistance variable unit 83 in FIG. 9 and has almost no influence on the pressure of the liquid discharge head 10. Don't give.

  On the other hand, FIG. 10B shows the state of the variable flow path resistance unit 83 under the condition that the discharge flow rate of the recording head 10 is large. The gap Gt between the pipe member 87 and the first valve body portion 88t of the valve body 88 is narrow, and the ink flows by the droplet discharge from the recording head 10 indicated by the arrow Qh passing through the through hole 84 that is the first throttle portion, The valve body 88 is pulled toward the port 86a and the valve body 88 moves (moves upward in the figure). As a result, the second valve body portion 88b of the valve body 88 moves to the small diameter portion (flow path portion 87b: second throttle portion 182) of the pipe member 87, and the flow path portion 87b wall surface of the pipe member 87 and the valve body 88. The gap between the second valve body portions 88b is a small gap Gb1. As shown by the arrow Qa, the ink fed by the pump 78 tends to flow through this narrow gap Gb1 (arrow D), and pressure is generated. This pressure can reduce the pressure loss that occurs when the ink flows through the recording head 10, and can provide a large flow of ink.

  In this variable flow path resistance unit 83, the condition between the peripheral surface of the second valve body 88 b of the valve body 88 and the flow path portion 87 b of the pipe member 87 is increased as the discharge flow rate of the recording head 10 increases and the pressure loss increases. The opposing length in the ink flow direction (the length of the second throttle portion 182) becomes longer, and the length of the second valve body portion 88b of the valve body 88 and the narrow gap Gb1 of the tube member 87 becomes longer. The pressure increasing effect by the pump (assist pump) 78 is increased. Thereby, there is no trouble of controlling the flow rate adjustment valve with another actuator or the like as in the prior art, and stable ink supply can be realized automatically with a simple configuration.

  Since this image forming apparatus ejects four colors of ink, four ink supply systems having the configuration shown in FIG. 9 are provided for each color. In correspondence with each color pump 78, four actuators such as motors for driving the pump 78 can be individually provided, and the motor can be individually controlled according to the ink discharge amount of each recording head 10. As shown in FIG. 7 described above, only one motor (actuator) 82 may be provided in common for the number of pumps 78 (78K, 78C, 78M, 78Y) of the number of colors.

  When an image is formed by ejecting ink droplets of a plurality of colors, the amount of ink ejected from each recording head 10 varies. For example, a certain head ejects ink from all nozzles, The head may be in a non-ejection state. Even in such a case, in the ink supply system of the present invention, the fluid resistance of the flow path resistance variable unit 83 is automatically changed according to the discharge flow rate of the recording head 10, so that it corresponds to the discharge flow rate of each head. It is not necessary to control the pump.

  That is, control is performed automatically for a head that has a low discharge flow rate and does not require assistance, and that gives a large assist to a head that has a high discharge flow rate and requires assistance.

  Even in a system having a plurality of ink supply systems such as having a plurality of inks as described above, the pumps of all the ink supply systems can be driven together by a single actuator, which simplifies the configuration and control of the apparatus and reduces the cost. A small device can be realized.

  In general, since the viscosity of the liquid changes depending on the temperature of the liquid, the assist of the liquid to the recording head 10 is, for example, around the apparatus measured by a temperature sensor 27 provided in the carriage 4 as shown in FIG. It is preferable to control the driving of the pump 78 by feeding back the temperature, the temperature in the apparatus, the temperature of the ink, the predicted value thereof, and the like. Thereby, an easy-to-use image forming apparatus corresponding to any temperature can be realized.

  In addition, if a pressure sensor is provided in the ink supply path so that the pressure change when the head discharge is performed at a predetermined flow rate can be measured, the viscosity of the ink directly connected to the pressure loss can be detected thereby. Based on the detected viscosity, the control parameter of the pump 78 can be changed, and various inks having different viscosities can be used.

  Further, if the user inputs the control parameters of the pump 78 while confirming the discharge state, the liquid viscosity detecting means described above becomes unnecessary, and the apparatus can be simplified.

  As described above, a pressure adjusting valve is provided in the supply flow path for supplying the liquid from the liquid tank to the liquid discharge head (recording head), and a flow path communicating with the liquid tank is provided in the pressure adjusting valve through another path. The liquid supply means is provided, and the internal pressure resistance of the pressure adjustment valve changes according to the flow rate of the liquid flowing through the liquid discharge head. At least when liquid is discharged from the liquid discharge head, Since the liquid is sent to the liquid discharge head by the liquid supply means while the liquid tank is in communication, it is applied to the liquid discharge head while automatically adjusting the appropriate assist pressure according to the discharge amount of the liquid discharge head Thus, it is possible to easily avoid a shortage of refill due to an increase in the length of the liquid supply tube, an increase in the discharge flow rate, and an increase in the viscosity of the discharge liquid.

  In this case, the pressure regulating valve has a first throttle part on the liquid discharge side and a second throttle part on the liquid tank side, and a flow path from the liquid feeding means is provided between the first throttle part and the second throttle part. With the configuration in which the throttle amount of the second throttle unit changes according to the flow rate of the liquid that is communicated between them and flows to the liquid discharge head, the discharge of the liquid discharge head can be performed with a simple configuration using the throttle of the flow path. An appropriate assist pressure can be applied to the liquid discharge head while automatically adjusting the appropriate assist pressure according to the amount.

  In addition, the pressure adjustment valve has a movable member, and the movable member moves according to the discharge amount of the liquid discharge head, so that the throttle amount of the second throttle portion on the liquid tank side changes as the movable member moves. Thus, with a simple configuration using the movement of the movable member by the flow, an appropriate assist pressure can be applied to the liquid discharge head while automatically adjusting the appropriate assist pressure in accordance with the discharge amount of the liquid discharge head.

  The movable member is composed of a stepped shaft-like member having a plurality of step portions having different diameters in the liquid flow direction, and is configured to be accommodated in a free state in a flow path forming member that forms a flow path. Thus, high-precision parts can be easily formed, and a valve with high-precision characteristics can be easily obtained.

  In such an ink supply system, if bubbles remain in the flow path resistance variable unit 83 when the ink cartridge 76 is replaced or initially filled, a droplet ejection failure occurs.

  For example, as shown in FIG. 13, when the variable flow resistance unit 83 of the comparative example in which the first valve body portion 88t of the valve body 88 which is a movable member is formed in a flat plate shape (flat shape) is used, When 88 is drawn in the direction of the port 86a (first flow path direction), the bubbles 141 remain in the central region 140 sandwiched between the first valve body 88t and the second valve body 88b. When the bubbles 141 remain in the central region 140, the bubbles 141 accumulate on the port 86b side (the third flow path side or the second flow path side) of the first valve body 88t due to the buoyancy. In this state, even if the ejection operation is continued from the recording head 10, the bubbles 141 located away from the through hole 84 remain in the central region 140 without passing through the through hole 84. As a result, the pressure of the ink sent by the pump unit 80 is absorbed by the bubbles 141 in the central region 140, and the pressure required by the recording head 10 may be insufficient.

Therefore, the flow path resistance unit in the first embodiment of the present invention will be described with reference to FIGS. 14 is a schematic cross-sectional explanatory view of the variable flow path resistance unit, and FIG. 15 is an enlarged cross-sectional explanatory view of the main part of FIG. Further, although it is a cross-sectional explanatory view, the hatching showing the cross section is omitted for easy understanding.
As described above, in the variable flow path resistance unit 83 that is a pressure adjusting valve, a valve body 88 that is a movable member is movably accommodated in a pipe member 87 that is a flow path member that forms a flow path. Includes a first valve body portion 88t that is a valve body portion that is positioned closer to the first flow path 41 than the port 86c that is a communication portion with the third flow path 43 side, and the first valve body section 88t. A through hole 84 is formed in the direction of the liquid flow, and an inclined surface 188 inclined toward the first flow channel 41 side is formed on the second flow channel 42 side. 2 on the channel side (hereinafter referred to as “inlet side”) opens to the inclined surface 188, and the valve body 88 moves along with the movement of the pipe member 87 in which the inclined surface 188 of the first valve body part 88 t is a channel member. Is accommodated in the pipe member 87 in a state of contacting (contacting) the inclined surface 187 which is a contact portion formed in

  Here, the radial position of the through hole 84 is in a region where the inclined surface 187 of the pipe member 87 and the inclined surface 188 of the first valve body portion 88t of the valve body 88 are in contact with each other. In this case, it is preferable to be in the vicinity of the inclined end portion of the inclined surface 188 (the outer peripheral portion of the first valve body portion 88t). Further, the inclined surface 188 of the first valve body portion 88t is inclined from the valve body portion (first valve body portion 88t) central portion side toward the first flow passage 41 side from the valve body portion outer peripheral portion side. It is an inclined surface. Further, the inclined surface 187 of the pipe member 87 has an inclination corresponding to the inclined surface 188 of the first valve body portion 88t.

With such a configuration, a process of discharging the bubbles 141 remaining in the central region 140 of the flow path resistance variable unit 83 will be described with reference to FIGS. 16 and 17. Note that FIG. 16 is an enlarged cross-sectional explanatory view of a main part for explaining the operation of the unit, and FIG. 17 is a schematic cross-sectional explanatory view.
First, FIG. 16A shows the movement of the bubbles 141 remaining in the flow path resistance variable unit 83 when the recording head 10 is in the non-ejection state. When the air bubbles 141 generated by initial filling or cartridge replacement rise to the central region 141 of the flow path resistance variable unit 83 due to the buoyancy, the air bubbles 141 of the first valve body portion 88t are moved along the inclined surface 188 of the first valve body portion 88t. Naturally moves to the outer peripheral side. Here, since the through hole 84 is provided in the vicinity of the top of the inclined surface 188, that is, in the vicinity of the outer peripheral portion of the first valve body portion 88t, the bubbles 141 gather near the inlet of the through hole 84.

  When the valve body 88 changes position (moves) to the port 86b side (second flow path 42 side) by operating the pump unit 80, as shown in FIG. 16B, the volume of the central region 140 is increased. The air bubbles 141 accumulated on the outer peripheral side of the first valve body 88t of the variable flow resistance unit 83 are reduced by the contact between the inclined surface 188 of the first valve body 88t and the inclined surface 187 of the pipe member 87. Sandwiched. Since the through hole 84 is formed in this contact area, the bubble 141 is pressed toward the through hole 84.

  When a large amount of ink is ejected from the recording head 10 in this state, the position of the valve element 88 changes (moves) in the direction of the port 86a (the direction of the first flow path 41), as shown in FIG. Accordingly, the bubbles 141 collected near the entrance of the through hole 84 pass through the through hole 84 and move upward.

  As a result, as shown in FIG. 17, the bubbles 141 that have passed through the first valve body 88t move along the inclined surface 189 on the first flow path 41 side inside the pipe member 87, and the flow path resistance variable unit. 83 is discharged to the first external flow path 41.

  In this way, when the bubbles 141 are reliably collected in the vicinity of the inlet of the through-hole 84 and a large amount of ink is discharged from the recording head 10, the bubbles 141 remaining in the central region 140 of the flow path resistance variable unit 83. Can be removed effectively.

  Since the bubbles 141 flowing from the variable flow path resistance unit 83 move into the recording head 10, after this operation, the nozzle surface is always capped with the cap 52, and the suction operation is performed to remove the bubbles 141. It is preferable to eject from the recording head 10. Alternatively, a gas-liquid separator may be interposed between the variable flow resistance unit 83 and the recording head 10 so that the bubbles 141 do not enter the recording head 10.

  Thus, when ejecting droplets from the nozzles of the recording head, the recording head and the liquid tank are in communication with each other via a pressure adjustment valve whose internal flow path resistance changes according to the flow rate of the flowing liquid. Since the liquid is fed from the liquid tank to the recording head by the liquid feeding means, an appropriate assist pressure is automatically adjusted according to the discharge amount of the recording head and applied to the recording head to adjust the length of the tube member. In a liquid supply system that avoids shortage of refill due to scaling, increased discharge flow rate, increased viscosity of the discharged liquid, etc., the pressure regulating valve further has a movable member movably accommodated in the flow path member. The movable member has a through-hole formed in the valve body portion and an inclined surface formed on the second flow path side, and the inclined surface is in contact with the abutting portion on the flow path member side as it moves. Contained in the channel member Since a configuration, it is possible to air bubbles inside the flow path by contact with the inclined surface and the contact portion of the valve body portion of the movable member is discharged through the through holes, to reduce the retention of air bubbles inside the pressure regulating valve. As a result, the negative pressure of the head can be maintained within an appropriate range with a simple configuration and control, and even a highly viscous liquid can be discharged at high speed without causing defective discharge.

Next, the variable flow path resistance unit according to the second embodiment of the present invention will be described with reference to FIGS. 18 is a schematic cross-sectional explanatory view of the variable flow path resistance unit, and FIG. 19 is an enlarged cross-sectional explanatory view of a main part of FIG.
Here, the inclined surface 187 of the pipe member 87, which is a flow path member, is inclined at the same angle as the first valve body portion 88t, and the periphery of the opening of the through hole 84 of the first valve body portion 88t is in contact with the inclined surface 187. A bubble discharge member 144 that is a contact member that forms a contact portion is provided.

  As described above, the bubbles 141 generated by initial filling or cartridge replacement rise to the central region 140 and are collected near the inlet of the through hole 84 along the inclined surface 188 of the first valve body portion 88t. At this time, when the pump unit 80 is operated, the position of the valve body 88 changes to the port 86b side.

  In a state where the valve body 88 moves to the port 86b side, the bubbles 141 collected near the inlet of the through hole 84 are sandwiched between the bubble discharge member 144 and the first valve body portion 88t. The bubbles 141 are moved through the through holes 84 and discharged out of the variable flow path resistance unit 83 by discharging a large flow rate from the recording head 10.

  The shape of the bubble discharge member 144 forming the contact portion may be any shape as long as the bubble discharge effect is not impaired. The material of the bubble discharge member 144 may be any material as long as the bubble discharge effect is not impaired, but is preferably a member that is resistant to ink.

Next, the variable flow resistance unit according to the third embodiment of the present invention will be described with reference to FIGS. 20 is a schematic cross-sectional explanatory view of the variable flow path resistance unit, FIG. 21 is an enlarged cross-sectional explanatory view of a main part for explaining the operation of the unit, and FIG. 21 is a schematic cross-sectional explanatory view.
Here, the first valve body portion 88t of the valve body 88, which is a movable member, has a valve body portion outer peripheral portion from the valve body portion (first valve body portion 88t) central portion side toward the first flow path 41 side. An inclined surface 188a that is inclined to the side, and an inclined surface 188b that is inclined from the outer periphery side of the valve body part (first valve body part 88t) toward the first flow path 41 side toward the central part side of the valve body part. And a through hole 84 is provided near the top where the inclined surfaces 188a and 188b abut.

  The tube member 87 is provided with a bubble discharge member 144 that is a contact member that forms the contact portion with the same inclination as the inclined surface 188b of the first valve body portion 88t.

  In such a configuration, as shown in FIG. 21A, when the recording head 10 is in a non-ejection state, it occurs in the central region 140 of the flow path resistance variable unit 83 due to initial filling or cartridge replacement. When the remaining bubbles 141 rise to the central region 140 in the pipe member 87 due to their buoyancy, the inclined surfaces 188a and 188b of the first valve body 88t are naturally located at the highest position, that is, in the vicinity of the inlet of the through hole 84. It will be gathered. At this time, since the inclined surface 188b of the first valve body portion 88t is inclined toward the port 86b side (third flow path side) from the central portion toward the outer peripheral portion side, the bubbles 141 are formed in the first valve body portion 88t. It will not move to the outer peripheral side.

  Then, by operating the pump unit 80, as shown in FIG. 21B, when the valve body 88 changes (moves) to the port 86b side, the volume of the central region 141 decreases, and the inlet of the through hole 84 The bubble 141 accumulated in the vicinity is sandwiched between the inclined surface 188b of the first valve body portion 88t and the bubble discharge member 144. Here, the bubble 141 is pressed toward the through hole 84.

  When a large flow of ink is ejected from the recording head 10 in this state, the position of the valve element 88 changes in the direction of the port 86a as shown in FIG. The bubbles 141 collected in the passage pass through the through hole 84.

  As a result, as shown in FIG. 22, the bubbles 141 that have passed through the through hole 84 of the first valve body portion 88t are discharged from the flow path resistance variable unit 83 to the first flow path 41 side.

  In this way, the bubbles 141 can be reliably collected in the vicinity of the through hole 84, and a large amount of ink can be ejected from the recording head 10. As described above, the bubbles 141 discharged from the variable flow path resistance unit 83 may be removed by capping and sucking the recording head 10 with the cap 50, or between the recording head 10 and the variable flow resistance unit 83. It may be removed from the ink using a gas-liquid separator in between.

  Here, the bubble discharge member 144 is fixed to the pipe member 87 along the inclination of the first valve body portion 88t. However, instead of the bubble discharge member 144, the bubble discharge member 144 is directed toward the central portion of the first valve body portion 88t. Further, the inclined surface 187 of the tube member 87 is extended to be a contact portion, and the same effect as the bubble discharge member 144 can be obtained. Moreover, although the through hole 84 is provided only once in the outer peripheral portion of the first valve body portion 88t, the through hole 84 is not limited to one round as long as the pressure adjusting action by the pressure control unit 81 is not disturbed.

Next, the variable flow path resistance unit according to the fourth embodiment of the present invention will be described with reference to FIGS. FIG. 23 is a schematic cross-sectional explanatory view of the variable flow path resistance unit, and FIG. 24 is an enlarged cross-sectional explanatory view of a main part for explaining the operation of the unit.
Here, the first valve body 88t of the valve body 88 is provided with a stepped portion 188c on an inclined surface 188 inclined from the valve body central portion toward the outer peripheral portion toward the first flow path 41 side. Further, the inclined surface 187 of the pipe member 87 is also provided with a stepped portion 187c corresponding to the stepped portion 188c.

  Since it comprised in this way, as shown in FIG. 24, the bubble 141 which moved to the outer peripheral part side of the 1st valve body part 88t along the inclined surface 188 of the 1st valve body part 88t by own buoyancy is Once in the vicinity of the through hole 84, it is blocked by the step 188c provided in the first valve body portion 88t and the pipe member 87, and cannot move from the vicinity of the through hole 84 to the central portion side.

  As a result, when a large flow rate of ink is ejected from the recording head 10, the bubbles 141 that do not fully enter the through hole 84 are separated from the vicinity of the through hole 84 of the first valve body 88 t and remain in the central region 140. Can be prevented. Therefore, all the bubbles 141 remaining in the central region 140 can be discharged to the outside of the flow path resistance variable unit 83. The bubbles 141 can be discharged from the central region 140 with a simple configuration.

  Here, as in the first embodiment, the inclined surface 188 is inclined toward the port 86a from the central portion of the first valve body 88t toward the outer peripheral portion. However, as in the second embodiment described above. Alternatively, the first valve body 88t may have an inclined surface 188b that inclines toward the port 86a from the outer peripheral side toward the center. Further, the stepped portion in the inclined surface is preferably inside the through hole 84 on the outer peripheral portion side of the first valve body portion 88t, but is not particularly limited, and the entire stepped portion has a plurality of stepped portions on the inclined surface. It can also be provided.

  Moreover, although the step part 187c is provided in the pipe member 87, it can also be set as the structure which provides the bubble discharge member 144 like 2nd Embodiment mentioned above, and provides a level | step difference substantially.

Next, the variable flow path resistance unit according to the fifth embodiment of the present invention will be described with reference to FIGS. FIG. 25 is a schematic cross-sectional explanatory view of the variable flow path resistance unit, and FIG. 26 is an enlarged cross-sectional explanatory view of a main part for explaining the operation of the unit.
Here, the bubble accommodating hole 148 which is a recess larger than the opening of the through hole 84 is formed in a portion where the through hole 84 is opened on the inclined surface 188 of the first valve body portion 88t. On the other hand, the inclined surface 187 of the pipe member 87 is formed with a convex portion 149 that fits into the bubble accommodating hole 148.

  Since it comprised in this way, the bubble 141 which moved to the outer peripheral part side along the inclined surface 188 by own buoyancy enters into the bubble accommodation hole 148 in a position higher than the inclined surface 188 (port 86a side). . As a result, the bubbles 141 remaining in the central region 140 can be collected in the bubble accommodating hole 148.

  And since the convex part 149 which fits the bubble accommodation hole 148 is formed in the pipe member 87 which the 1st valve body part 88t contacts, the bubble 141 collected by the bubble accommodation hole 148 is the through-hole 84. Pushed into. In this state, by ejecting a large amount of ink from the recording head 10, the bubbles 141 accommodated in the bubble accommodation holes 148 are effectively discharged to the outside of the flow path resistance variable unit 83 through the through holes 84. be able to.

  As described above, the air bubbles 141 in the central region 140 can be effectively discharged with a simple configuration in which a recess is provided in the inlet portion of the through hole 84 of the inclined surface 188 of the first valve body portion 88t.

  Here, as in the first embodiment, the inclined surface 188 is inclined toward the port 86a from the central portion of the first valve body 88t toward the outer peripheral portion. However, as in the second embodiment described above. Alternatively, the first valve body 88t may have an inclined surface 188b that inclines toward the port 86a from the outer peripheral side toward the center. Even if the first valve body portion 88t is not inclined, the first valve body portion 88t may not be inclined because of the effect of collecting the bubbles 141. Further, the number, the inner diameter, the depth, and other shapes of the bubble accommodating hole portions 148 are not limited. Furthermore, the bubble discharge member 144 as in the second embodiment described above may be provided, and the bubble discharge member 144 may be provided with a convex portion that fits into the bubble receiving hole 148 of the first valve body portion 88t.

Next, different examples of the flow path resistance variable unit in the sixth embodiment of the present invention will be described with reference to FIGS. 27 and 28 are enlarged cross-sectional explanatory views of the main part of the variable flow path resistance unit.
In the example shown in FIG. 27, the opening diameter of the shape of the through hole 84 formed in the first valve body portion 88t becomes narrower from the third flow path side (the central region 140 side) toward the first flow path 41 side. It is a tapered hole. Thus, since the hole diameter of the through hole 84 on the central region 140 side is large, more bubbles 141 can be taken into the through hole 84. As a result, the bubbles 141 can be discharged through the through holes 84 when a large flow rate is discharged from the recording head 10.

  In the example shown in FIG. 28, the opening diameter of the through hole 84 formed in the first valve body 88t becomes narrower from the third flow path side (the central region 140 side) toward the first flow path 41 side. It is a horn-shaped (trumpet-shaped) hole. Thus, since the hole diameter of the through hole 84 on the central region 140 side is large, more bubbles 141 can be taken into the hole. As a result, the bubbles 141 can be discharged through the through holes 84 when a large flow rate is discharged from the recording head 10.

  Here, as in the first embodiment, the inclined surface 188 is inclined toward the port 86a from the central portion of the first valve body 88t toward the outer peripheral portion. However, as in the second embodiment described above. Alternatively, the first valve body 88t may have an inclined surface 188b that inclines toward the port 86a from the outer peripheral side toward the center. Even if the first valve body portion 88t is not inclined, the inlet side of the through hole 84 is a relatively larger opening than the outlet side, so that there is an effect of collecting the bubbles 141. There may be no inclination.

  As described above, the pressure regulating valve has a movable member movably accommodated in the flow path member, and the movable member has a through hole formed in the valve body, and the through hole is formed on the second flow path side. Since the opening is formed larger than the opening on the first flow channel side, and with the movement, the inclined surface is accommodated in the flow channel member in a state of contacting the contact portion on the flow channel member side. Due to the contact between the inclined surface of the valve body portion of the movable member and the abutting portion, bubbles inside the flow path are discharged through the through hole, and the retention of bubbles inside the pressure regulating valve can be reduced.

Next, the variable flow path resistance unit according to the seventh embodiment of the present invention will be described with reference to FIG. FIG. 29 is a schematic cross-sectional explanatory view of the flow path resistance variable unit.
Here, the same inclined surface 188d as the region 153 part of the pipe member 87 is provided on the port 86a side of the first valve body part 88t which is a movable member. Thereby, the bubble 141 which has passed through the through hole 84 can be pushed out.

  That is, the bubble 141 that has passed through the through hole 84 flows in the direction of the port 86a due to the pressure difference generated by the discharge of a large flow rate from the recording head 10, but at this time, the bubble 141 remains in the region 153 of the tube member 87. There is. Therefore, the air bubbles 141 remaining in the region 153 can be discharged to the port 86a side by setting the port 86a side of the first valve body 88t and the pipe member 87 to the same inclined surface.

  As described above, the pressure regulating valve has a movable member movably accommodated in the flow path member, and the movable member has a through hole formed in the valve body portion and an inclined surface on the first flow path side. As the structure is formed and accommodated in the flow path member in a state where the inclined surface is in contact with the contact portion on the flow path member side as it moves, it contacts the inclined surface of the valve body portion of the movable member. Bubbles inside the flow path are discharged through the through hole by the contact of the part, and the retention of the bubbles inside the pressure regulating valve can be reduced.

Next, the variable flow path resistance unit according to the eighth embodiment of the present invention will be described with reference to FIGS. 30 and 31 are schematic explanatory views of the flow path resistance variable unit.
In this variable flow path resistance unit 83, a valve body 88 that is a movable member and a bubble discharge member 244 that is a contact member are movably accommodated in a pipe member 87 that is a flow path member that forms a flow path. 88 has a first valve body portion 88t that is a valve body portion located on the first flow path 41 side from the port 86c that is a communication portion with the third flow path, and the first valve body portion 88t includes A through hole 84 is formed in the direction of liquid flow, and the valve body 88 and the bubble discharge member 244 are moved along the surface of the first valve body portion 88t on the second flow path 42 side and the bubble discharge member 244. Are accommodated in the pipe member 87 in a state where they can contact each other.

  That is, here, the first valve body portion 88t which is the valve body portion of the valve body 88 which is a movable member has a flat plate shape (a flat shape having a substantially constant thickness). A bubble discharge member 244, which is a contact member with which the first valve body portion 88t contacts the intermediate portion 88m of the valve body 88, is fitted in a free state so as to be movable, and the first valve body portion 88t and the second valve body portion 88t. The valve body 88b is in a shape that allows surface contact. The bubble discharging member 244 has a specific gravity or mass that sinks with respect to the ink as shown in FIG.

  With this configuration, when the recording head 10 is in the non-ejection state or the ejection amount is small, the position of the valve body 88 changes to the port 86b side due to the flow rate from the pump unit 80, but the bubble discharged in the free state is discharged. The member 244 also changes its position toward the port 86b. When a large flow rate of ink is ejected from the recording head 10, the valve element 88 changes its position toward the port 86a due to the pressure difference as shown in FIG. At this time, the position of the bubble discharge member 244 is also changed in the direction of the first valve body portion 88t due to the pressure difference. Then, the bubbles 141 remaining in the central region 140 are pushed out by the bubble discharge member 244 and the first valve body portion 88t coming into contact with each other, pass through the through hole 84, and outside the flow path resistance variable unit 83. To be discharged.

  When the bubble discharge member 244 moves to the first valve body 88t side in close contact with the first valve body 88t and closes the through hole 84 at the normal discharge rate of the recording head 10, it is normal. Cannot be discharged properly. For this reason, the bubble discharge member 244 can be brought into close contact with the first valve body portion 88t only when a sudden pressure difference occurs between the port 86a-side flow path and the valve body 88 using a sequence of discharging bubbles. The specific gravity or mass of the bubble discharge member 244 is preferably adjusted.

  In addition, here, the first valve body 88t and the bubble discharge member 244 have a flat configuration without an inclination, but an inclined surface may be provided on the contact surface as described in the above embodiment. That is, the inclined surfaces 188, 188a, 188b as described in the above-described embodiments may be provided on the first valve body portion 88t, and the inclined surface corresponding to the bubble discharge member 244 may be provided.

  As described above, the pressure adjusting valve has a movable member and a contact member movably accommodated in the flow path member, and the movable member has a through hole formed in the valve body portion, and the movable member and the contact member. Is configured to be accommodated in the flow channel member in a state where the contact member can come into contact with the surface on the second flow channel side of the valve body portion of the movable member with the movement. When the valve body portion of the movable member comes into contact, bubbles inside the flow path are discharged through the through hole, and the retention of bubbles inside the pressure regulating valve can be reduced.

  In the above description, in order to effectively realize the bubble discharge effect, the position change of the valve body 88 is important. The change in position is determined by a bubble discharge sequence mainly including the pump unit 80, the recording head 10, and the suction pump 53 for maintenance.

An example of the bubble discharge sequence will be described with reference to FIG.
In this example, the position of the valve body 88 is changed by the idle discharge of the recording head 10 (a large amount of ink is discharged from all nozzles) and the control of the assist pump 78 without using the suction pump 53.

  First, the valve body 88 is moved to the port 86b side by driving the assist pump 78 and feeding the liquid to the port 86c of the flow path resistance variable unit 83. Then, when a predetermined time T1 until the position change of the valve body 88 on the port 86b side is completed, the recording head 10 is moved to the idle discharge position, and the assist pump 78 is stopped. Thereafter, idle ejection is performed from the recording head 10. Thereby, an abrupt pressure difference is generated between the first flow path 41 and the valve body 88, and the valve body 88 moves to the port 86a side. Then, after a predetermined time T2 until the bubbles in the fluid resistance variable unit 83 are discharged from the recording head 10, the idle ejection operation is stopped, wiping is performed, and finally the nozzle surface is capped.

  The predetermined times T1 and T2 are values determined by the shape of the valve body 88 and the flow path resistance variable unit 83 to be used, the ink flow path length, the ink flow path diameter, and the ink used. In this sequence, the head capping is performed after wiping. However, when the ejection from the recording head 10 is continued, the print operation may be continued by moving to the print standby position.

Next, another example of the bubble discharge sequence will be described with reference to FIG.
In this example, the position of the valve body 88 is changed by the idle discharge of the recording head 10 and the control of the assist pump 78 and the suction pump 53.

  First, the valve body 88 is moved to the port 86b side by driving the assist pump 78 and feeding the liquid to the port 86c of the flow path resistance variable unit 83. After a predetermined time T1 until the position change of the valve body 88 on the port 86b side is completed, the recording head 10 is moved to the idle ejection position and the nozzle surface of the recording head 10 is capped with the cap 52. Then, the assist pump 78 is stopped.

  Then, an idle ejection operation is performed from the recording head 10 and suction is performed from the nozzle that drives the suction pump 53. As a result, an abrupt pressure difference occurs between the first flow path 41 and the valve body 88, and the valve body 88 moves to the port 86a side. At this time, the idle discharge operation and the suction operation by the suction pump are simultaneously performed. Therefore, as compared with the sequence of FIG. 31 described above, the negative pressure in the flow path connecting the port 86a side and the recording head 10 is increased, and the pressure difference acting between the valve body 88 and the port 86a side is increased. Also grows. Then, after the elapse of a predetermined time T2 until the bubbles in the fluid resistance variable unit 83 are discharged from the recording head 10, the idle ejection operation is stopped.

  Next, when a predetermined time T3 required for discharging the ink discharged into the cap 52 to the waste liquid tank 56 has elapsed, the suction pump is stopped, wiping is performed, and the nozzle surface is capped.

  The predetermined times T1 and T2 are values determined by the shape of the valve body 88 and the flow path resistance variable unit 83 to be used, the ink flow path length, the ink flow path diameter, and the ink used. In this sequence, the head capping is performed after wiping. However, when the ejection from the recording head 10 is continued, the print operation may be continued by moving to the print standby position.

  In the sequence of each example, the assist pump is stopped and then the head idle discharge operation is performed. However, if the bubbles 141 can generate a pressure difference that can be discharged from the flow path resistance variable unit 83, The assist pump 78 may not be stopped.

  In the above description, the operation and effect of the present invention have been described with an example in which different color inks are supplied to a plurality of heads. However, when the same color ink is supplied to a plurality of heads, it is not a color. The same applies to the case where inks having different prescriptions are supplied to a plurality of heads. Further, the present invention can also be applied to an ink supply system in a case where a liquid discharge head having a plurality of nozzle rows in one head discharges different types of liquid from one head. Further, the present invention is not limited to an image forming apparatus that discharges ink in a narrow sense, and can also be applied to a liquid discharging apparatus that discharges various liquids (included in the “image forming apparatus” in the present invention). .

4 Carriage 10 Recording head 30 Sub tank 41 Ink supply tube (first flow path)
42 Second flow path 43 Third flow path 76 Ink cartridge (main tank: liquid tank)
77 Cartridge holder 78 Pump (Assist pump)
80 Pump unit 81 Pressure control unit 83 Fluid resistance variable unit 84 Through hole 87 Pipe member (flow path member)
88 Valve body (movable member)
88t 1st valve body part (Valve body part: Upper part of valve body)
88b Second valve body (lower part of valve body)
144 Bubble discharge member (contact member: contact portion)
187 Inclined surface (contact part)
188 Inclined surface 189 Inclined surface 244 Bubble discharge member (contact member: contact portion)

Claims (10)

A recording head having nozzles for discharging droplets;
A liquid tank for storing liquid to be supplied to the recording head;
A first flow path for supplying the liquid to the recording head;
A second flow path communicating with the liquid tank;
A pressure regulating valve that connects the first flow path and the second flow path, and an internal flow path resistance changes according to a flow rate of the liquid flowing through the first flow path;
A third flow path communicating the second flow path or the liquid tank and the pressure regulating valve;
Liquid feeding means provided in the third flow path,
When ejecting droplets from the nozzle, the liquid is fed from the liquid tank to the recording head by the liquid feeding means in a state where the recording head and the liquid tank are in communication with each other via the pressure adjusting valve. An image forming apparatus that
The pressure regulating valve includes a flow path member that forms a flow path, and a movable member that is movably accommodated in the flow path member.
The movable member has a valve body portion located on the first flow path side with respect to the communication section with the third flow path, and a through hole is formed in the valve body section in a liquid flow direction. And an inclined surface that is inclined toward the first flow path side is formed on the second flow path side,
The movable member is accommodated in the flow path member in a state in which the inclined surface of the valve body portion is in contact with the contact portion on the flow path member side as it moves. .   The inclined surface of the valve body part of the movable member is inclined from the valve body part central part side to the valve body part outer peripheral part side toward the first flow path side. Image forming apparatus.   The inclined surface of the valve body part of the movable member is inclined from the valve body part outer peripheral part side to the valve body part central part side toward the first flow path side. Image forming apparatus.   4. The image forming apparatus according to claim 1, wherein the through hole of the movable member has a shape in which an opening diameter decreases toward the first flow path side.   A concave portion is formed in the opening on the second flow path side of the through hole of the movable member, and a convex portion that fits into the concave portion is provided in the contact portion on the flow path member side. The image forming apparatus according to claim 1.   6. The image forming apparatus according to claim 1, wherein a step portion is provided on an inclined surface of the valve body portion of the movable member.   The image forming apparatus according to claim 1, wherein the contact portion on the flow path member side has an inclined surface corresponding to the inclined surface of the valve body portion of the movable member. . A recording head having nozzles for discharging droplets;
A liquid tank for storing liquid to be supplied to the recording head;
A first flow path for supplying the liquid to the recording head;
A second flow path communicating with the liquid tank;
A pressure regulating valve that connects the first flow path and the second flow path, and an internal flow path resistance changes according to a flow rate of the liquid flowing through the first flow path;
A third flow path communicating the second flow path or the liquid tank and the pressure regulating valve;
Liquid feeding means provided in the third flow path,
When ejecting droplets from the nozzle, the liquid is fed from the liquid tank to the recording head by the liquid feeding means in a state where the recording head and the liquid tank are in communication with each other via the pressure adjusting valve. An image forming apparatus that
The pressure regulating valve includes a flow path member that forms a flow path, and a movable member that is movably accommodated in the flow path member.
The movable member has a valve body portion located on the first flow path side with respect to the communication section with the third flow path, and a through hole is formed in the valve body section in a liquid flow direction. And the opening on the second flow path side of the through hole is formed larger than the opening on the first flow path side,
The movable member is accommodated in the flow path member in a state where the second flow path side surface of the valve body portion is in contact with the abutting portion on the flow path member side as it moves. An image forming apparatus. A recording head having nozzles for discharging droplets;
A liquid tank for storing liquid to be supplied to the recording head;
A first flow path for supplying the liquid to the recording head;
A second flow path communicating with the liquid tank;
A pressure regulating valve that connects the first flow path and the second flow path, and an internal flow path resistance changes according to a flow rate of the liquid flowing through the first flow path;
A third flow path communicating the second flow path or the liquid tank and the pressure regulating valve;
Liquid feeding means provided in the third flow path,
When ejecting droplets from the nozzle, the liquid is fed from the liquid tank to the recording head by the liquid feeding means in a state where the recording head and the liquid tank are in communication with each other via the pressure adjusting valve. An image forming apparatus that
The pressure regulating valve includes a flow path member that forms a flow path, and a movable member that is movably accommodated in the flow path member.
The movable member has a valve body portion located on the first flow path side with respect to the communication section with the third flow path, and a through hole is formed in the valve body section in a liquid flow direction. And an inclined surface that is inclined toward the first flow path side is formed on the first flow path side,
The movable member is accommodated in the flow path member in a state in which the inclined surface of the valve body portion is in contact with the contact portion on the flow path member side as it moves. . A recording head having nozzles for discharging droplets;
A liquid tank for storing liquid to be supplied to the recording head;
A first flow path for supplying the liquid to the recording head;
A second flow path communicating with the liquid tank;
A pressure regulating valve that connects the first flow path and the second flow path, and an internal flow path resistance changes according to a flow rate of the liquid flowing through the first flow path;
A third flow path communicating the second flow path or the liquid tank and the pressure regulating valve;
Liquid feeding means provided in the third flow path,
When ejecting droplets from the nozzle, the liquid is fed from the liquid tank to the recording head by the liquid feeding means in a state where the recording head and the liquid tank are in communication with each other via the pressure adjusting valve. An image forming apparatus that
The pressure regulating valve includes a flow path member that forms a flow path, and a movable member and a contact member that are movably accommodated in the flow path member.
The movable member has a valve body portion located on the first flow path side with respect to the communication section with the third flow path, and a through hole is formed in the valve body section in a liquid flow direction. And
The movable member and the contact member are accommodated in the flow path member in a state in which the contact member can come into contact with the surface on the second flow path side of the valve body portion of the movable member as the movement occurs. An image forming apparatus.

Images