JP2011110870A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem of having difficulty in maintaining stable negative pressure with simple configuration and in preventing insufficiency of refilling with respect to attaining high speed, a long tube and high viscosity. <P>SOLUTION: This image forming apparatus includes a first passage 41 supplying ink to a head 10; a second passage 42 communicating with an ink cartridge 76; a passage resistance adjusting unit 83 serving for communication between the first passage 41 and the second passage 42 and changing passage resistance according to the flow direction and flow rate of liquid flowing inside; and a third passage 43 serving for communication between the second passage 42 and the passage resistance adjusting unit 83 and having a pump 78. When ejecting liquid drops, ink is fed from the ink cartridge 76 to the head 10 by the pump 78 in the communicating state of the head 10 and the ink cartridge 76 through the passage resistance adjusting unit 83. The passage resistance adjusting unit 83 is formed inside with a port 86c through which the inflow direction of ink fed from the pump 78 does not pass through a center axis of a horizontal section of a valve element 88. <P>COPYRIGHT: (C)2011,JPO&INPIT

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. And
The pressure regulating valve has a flow path member that forms a flow path, and a movable member that is movably accommodated in the flow path member, and the liquid feeding means passes the third flow path through the third flow path. A liquid inlet portion is provided in which the inflow direction of the liquid flowing into the flow path does not pass through the central axis in the horizontal section of the movable member.

  Here, the liquid inlet portion may be arranged at a position that is radially offset with respect to the central axis of the movable member.

  Further, the liquid inlet portion may be arranged at an angle with respect to the central axis of the movable member.

  The movable member may be provided with fins around the fin, and the fins may be arranged in a direction perpendicular to the liquid inflow direction.

  Further, the liquid inflow port portion can be configured to have a shape whose diameter decreases along the liquid inflow direction.

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. And
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
In the flow path member, the inflow direction of the liquid flowing into the flow path from the liquid feeding means through the third flow path is directed to the wall surface on the third flow path side of the valve body portion of the movable member. A liquid inflow port portion that is oriented is provided.

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. And
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
It was set as the structure which liquid-feeds with respect to the said pressure regulation valve, changing the liquid feeding amount per unit time from the said liquid feeding means.

  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 a shortage of refill due to an increase in the length of the tube member, an increase in the discharge flow rate, an increase in the viscosity of the discharge liquid, and the pressure adjustment valve includes a flow path member that forms a flow path. And a movable member movably accommodated in the flow path member, and the inflow direction of the liquid flowing into the flow path from the liquid feeding means via the third flow path is in the horizontal section of the movable member The direction does not pass through the central axis Since a configuration the body inlet port is provided, it is liquid within the pressure regulating valve easily flow times, it bubbles staying inside the flow path is likely to be discharged. 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 a shortage of refill due to an increase in the length of the tube member, an increase in the discharge flow rate, an increase in the viscosity of the discharge liquid, and the pressure adjustment valve includes a flow path member that forms a flow path. A movable member movably accommodated in the flow path member, the movable member having a valve body portion located on the first flow path side with respect to the communication section with the third flow path, In the body part, a through hole is formed in the direction of liquid flow, In the passage member, a liquid inflow port in which the inflow direction of the liquid flowing into the flow path from the liquid feeding means through the third flow path is directed to the wall surface on the third flow path side of the valve body portion of the movable member. Since the portion is provided, the bubbles are easily moved and discharged when the liquid sent to the bubbles remaining in the valve body in the pressure regulating valve hits. 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 a shortage of refill due to an increase in the length of the tube member, an increase in the discharge flow rate, an increase in the viscosity of the discharge liquid, and the pressure adjustment valve includes a flow path member that forms a flow path. A movable member movably accommodated in the flow path member, the movable member having a valve body portion located on the first flow path side with respect to the communication section with the third flow path, In the body part, a through hole is formed in the direction of liquid flow, Since the structure for feeding the pressure regulating valve while changing the feeding amount per unit time from the liquid means, movement bubbles turbulence in the pressure regulating valve is stationary occurs, it tends to be discharged. 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 a whole block explanatory drawing which shows the outline | summary of the control part of the apparatus. It is a flowchart with which it uses for description of the ink initial filling operation | movement by a control part. FIG. 6 is a flowchart for explaining the printing operation in the same manner. 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. It is a typical explanatory view of the flow resistance variable unit concerning a 1st embodiment of the present invention applied to the ink supply system. FIG. 18 is a cross-sectional explanatory diagram of a horizontal cross section taken along the line AA of FIG. It is sectional explanatory drawing similar to FIG. 18 which shows the road resistance variable unit of a comparative example. It is a typical explanatory view of a channel resistance variable unit concerning a 2nd embodiment of the present invention. FIG. 21 is a cross-sectional explanatory diagram of a horizontal cross section taken along line BB in FIG. It is a typical explanatory view of a channel resistance variable unit concerning a 3rd embodiment of the present invention. It is a typical explanatory view of a channel resistance variable unit concerning a 4th embodiment of the present invention. It is a typical explanatory view of a channel resistance variable unit concerning a 5th embodiment of the present invention. It is explanatory drawing with which it uses for description of the change of the liquid feeding amount of the assist pump with which it uses for description of 6th Embodiment of this invention.

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, which 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 also referred to as "first valve body portion") that is a valve body portion in the present invention. .) 88t, central portion 88m, lower portion (hereinafter also referred to as “second valve body portion”) 88b, and has a diameter of the central portion 88m smaller than that of the second valve body portion 88b. Is formed. 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 stably Ink droplet ejection can be performed from 10.

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. 87 and the first valve body 88t of the valve body 88 are larger than the fluid resistance of the gap Gt. Further, as shown in FIG. Therefore, the ink sent 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. 8, and has almost no influence on the pressure of the liquid ejection 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 88t of the valve body 88 is narrow, and the ink flow due to the droplet ejection from the recording head 10 indicated by the arrow Qh passing through the pipe through hole 84 which is the first throttle part, The valve body 88 is pulled to the port 86a side (first flow path side), 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 restricting portion 182) of the tube member 87, and the second valve body portion of the tube member 87 and the valve body 88. The gap between 88b becomes 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 direction of ink flow between the peripheral surface of the lower portion 88b of the valve body 88 and the flow path portion 87b of the tube member 87 under conditions where the discharge flow rate of the recording head 10 increases and the pressure loss increases. , The length of the narrow portion Gb1 between the lower portion 88b of the valve body 88 and the pipe member 87 is increased, and the length of the pump 88 is increased by the pump (assist pump) 78. Increase pressure effect. 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.

Next, an outline of the control unit of the image forming apparatus will be described with reference to FIG. FIG. 12 is an explanatory diagram of the entire block of the control unit.
The control unit 500 temporarily stores a CPU 501 also serving as a means for controlling the assist operation and the maintenance / recovery operation for controlling the entire apparatus, a ROM 502 for storing programs executed by the CPU 501 and other fixed data, and image data. RAM 503 for storing, rewritable nonvolatile memory 504 for holding data even while the power of the apparatus is shut off, image processing for performing various signal processing and rearrangement on image data, and other control of the entire apparatus And an ASIC 505 for processing input / output signals.

  In addition, a print control unit 508 for driving and controlling the recording head 10 according to print data, a head driver (driver IC) 509 for driving the recording head 10 provided on the carriage 4 side, and moving and scanning the carriage 4. A main scanning motor 551 for rotating, a sub-scanning motor 552 for rotating and driving the transport 21 for transporting the paper 20, a maintenance / recovery motor 512 for operating a cap lifting / lowering mechanism 513 for lifting / lowering the caps 52a and 52ab, the wiper member 57, etc. And a pump drive unit 511 for driving the suction pump 53 and the assisting pump 78 of the maintenance / recovery mechanism 51.

  The control unit 500 is connected to an operation panel 514 for inputting and displaying information necessary for the apparatus.

  The control unit 500 has an I / F 506 for transmitting and receiving data and signals to and from the host side, an information processing device such as a personal computer, an image reading device such as an image scanner, an imaging device such as a digital camera, and the like. From the host 600 side via the cable or network via the I / F 506.

  The CPU 501 of the control unit 500 reads and analyzes the print data in the reception buffer included in the I / F 506, performs necessary image processing, data rearrangement processing, and the like in the ASIC 505, and prints the image data. The data is transferred from the unit 508 to the head driver 509. Note that generation of dot pattern data for image output is performed by the printer driver 601 on the host 600 side.

  The print control unit 508 transfers the print data described above as serial data, and outputs a transfer clock, a latch signal, a control signal, and the like necessary for transfer of the print data and confirmation of the transfer to the head driver 509. The head driver 509 drives the heating element 14 based on print data corresponding to one line of the recording head 10 input serially.

  The I / O unit 515 acquires information from various sensor groups 516 mounted on the apparatus, extracts information necessary for controlling the printer, and uses it to control the print control unit 508 and the motor drive unit 510. . The sensor group 515 includes an optical sensor for detecting the position of the paper, a thermistor for monitoring the temperature in the machine, a sensor for monitoring the voltage of the charging belt, an interlock switch for detecting opening and closing of the cover, and the like. The I / O unit 515 can process various sensor information. Further, a detection signal from a temperature / humidity sensor that detects environmental conditions (temperature and humidity) and a detection signal from a full tank detection sensor that detects a full tank in the waste liquid tank 56 are also input.

Next, the ink initial filling operation by the control unit using the ink supply system will be described with reference to the flowchart of FIG.
After confirming that the ink cartridge 76 has been installed, the nozzle surface of the recording head 10 is capped with the cap 52 of the maintenance unit 51. In this capped state, the suction pump 53 is driven to suck air in the ink supply system path through the nozzles of the recording head 10 (nozzle suction start). The nozzle suction is performed until a predetermined time has elapsed from the start of nozzle suction. By performing suction for a predetermined time, the ink in the ink cartridge 76 reaches the first flow path (liquid supply tube) 71.

  Thereafter, when a predetermined time has elapsed from the start of nozzle suction (when the timer counts up), the motor 82 is driven to drive the pump (assist pump) 78. At this time, since the ink supply path is formed as shown in FIG. 9, the pump 78 is driven to send the liquid to the flow path resistance variable unit 83 toward the arrow Qa, and the third pump 78 is connected. Air in the flow paths 61 and 62 is pushed out to the flow resistance variable unit 83 side and is replaced with ink.

  Thereafter, when the predetermined time has elapsed (when the timer has counted up), both the suction pump 53 and the pump 78 are stopped. At this stage, the entire ink supply path can be filled with ink.

  Thereafter, the capping by the cap 52 of the maintenance unit 51 is released, the nozzle surface of the recording head 10 is wiped by the wiper member 57 provided in the maintenance unit 51, and the recording head 10 is driven so as not to contribute to image formation. A desired meniscus can be formed on the nozzle by ejecting the ink droplets from the nozzle (empty head ejection).

  In this way, the initial filling of ink is completed. In the flowchart shown in FIG. 13, the assist pump (pump 78) is continuously driven until the nozzle suction is stopped, but the ink replacement in the third flow paths 61 and 62 and the horizontal hole 86c described above is completed. Even if it stops as soon as possible, the initial filling can be performed. However, in the example shown in FIG. 13, since the pump 78 is driven also when the liquid supply tube 71 and the recording head 10 are filled, the initial filling can be completed in a shorter time.

Next, the printing operation will be described with reference to the flowchart shown in FIG.
After receiving the print job signal, first, the temperature sensor 27 detects the temperature inside the apparatus (inside the apparatus) to estimate the ink temperature. Although the temperature sensor 27 is mounted on the carriage 4 (see FIG. 2), it may be provided at another location such as an ink cartridge portion or a recording head portion. Alternatively, the ink temperature may be directly detected by providing the ink supply path.

  Then, based on the temperature of the ink, the flow rate of liquid fed by the assist pump 78 is determined, and the pump 78 is driven. Thereafter, the cap 52 covering the nozzle surface of the recording head 10 is separated from the nozzle surface (capping is released), and after a predetermined number of drops are ejected, printing is started.

  At this time, since the assist pump 78 is driven, even when a high-viscosity ink is used in a system with a long supply tube 71, the pressure loss accompanying the ink supply can be appropriately reduced, resulting in an insufficient supply of ink. And good printing can be performed.

  After printing, the carriage 4 is stopped at a predetermined position (home position) of the apparatus, and the nozzle surface of the recording head 10 is capped with a cap 52. Thereafter, the assist pump 78 is stopped.

  Here, the assist pump 78 may be stopped immediately after the end of printing. Further, although the liquid supply amount of the assist pump 78 is controlled based on the temperature, depending on the conditions such as the ink supply specification, all the temperatures can be obtained with the liquid supply amount that does not cause supply shortage in the ink supply in the lowest temperature environment. It is also possible to send liquids under conditions.

  When performing such a printing operation, 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, A situation occurs in which the ink supply cannot catch up due to the fluid resistance of the ink supply path. 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. 8).

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. 15 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. 15 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 0.20 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.

  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. 6 described above, only one motor (actuator) 82 can be used 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. 16, when the variable flow resistance unit 83 of the comparative example in which the first valve body 88t of the valve body 88 that 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. In addition, even if the bubbles remaining in this way drive the pump 78 in the pump unit 80 and send the liquid to the pressure regulating valve 81, the remaining bubbles are likely to remain in place and are not easily discharged from the through hole 84. Further, the valve body 88 in the variable flow path resistance unit 83 of the pressure regulating valve (pressure control unit) 81 according to the operation state of discharging the liquid from the recording head 10 and the state of liquid supply from the pump unit 80 performs the ascending and descending operations. However, it has been found that the bubbles remaining in the pressure regulating valve 81 are likely to stay in place and are not discharged unless a large amount of liquid is consumed in order to discharge from the through hole 84.

Accordingly, a first embodiment in which the present invention is applied to such an image forming apparatus will be described with reference to FIGS. FIG. 17 is a schematic explanatory view of the flow path resistance variable unit 83 according to the embodiment, and FIG. 18 is a cross-sectional explanatory view of a horizontal section along the line AA in FIG.
Here, the port 86 c serving as an inflow port through which liquid (ink) flows into the fluid resistance variable unit 83 from the pump 78 serving as the liquid feeding means through the third flow path 43 is in the horizontal cross section of the valve body 88. The liquid flow direction from the pump 78 to the variable flow resistance unit 83 is set so as not to pass through the central axis in the horizontal section of the valve body 88. Here, the tangential direction of the circular flow path portion 87b is the liquid inflow direction.

  Accordingly, the ink sent from the pump 78 can easily flow along the wall surface of the flow path portion 87b when flowing into the flow path portion 87b of the flow path resistance variable unit 83 through the port 86c. As shown, the bubbles 141 retained at the inlet portion of the through hole 84 are also likely to move due to the ink flow caused by the circulation, and are easily discharged from the through hole 84. On the other hand, for example, as shown in FIG. 19, when the port 86 c is arranged toward the central axis in the horizontal section of the valve body 88, it is difficult for the circulation to occur, and the bubble discharge performance is reduced.

A second embodiment to which the present invention is applied will be described with reference to FIGS. 20 is a schematic explanatory view of the flow path resistance variable unit 83 according to the embodiment, and FIG. 21 is a cross-sectional explanatory view of a horizontal section along the line BB in FIG.
Here, in the said 1st Embodiment, the fin 180 is provided in the side where the bubble of the valve body 88 of the fluid resistance variable unit 83 stops, ie, the lower surface of the 1st valve body part 88t. The fins 180 are preferably arranged as perpendicular (orthogonal to the direction) as possible with respect to the inflow direction of the ink to be fed. Further, the number of fins 180 is not limited to one, but is a plurality (four in this example).

  Thus, as described above, the ink fed from the pump 78 is easily circulated in the flow path portion 87b, and the valve body 88 is also easily rotated by receiving the fed ink by the fins 180. The bubbles are easily moved by the flow and are easily discharged from the through hole 84.

A third embodiment to which the present invention is applied will be described with reference to FIG. FIG. 22 is a schematic explanatory diagram of the flow path resistance variable unit 83 according to the embodiment.
Here, the port 86c serving as an inflow port into the flow path resistance variable unit 83 has a diameter that decreases along the ink flow direction, that is, has a tapered shape.

  As a result, the flow rate of the ink flowing into the flow path resistance variable unit 83 is higher than that in the above embodiment, the flow speed of the circulating current generated in the flow path resistance variable unit 83 is increased, and the bubbles that are retained more efficiently are moved. This makes it easier for bubbles to be discharged from the through hole 84.

A fourth embodiment to which the present invention is applied will be described with reference to FIG. FIG. 23 is a schematic explanatory diagram of the flow path resistance variable unit 83 according to the embodiment.
Here, a port 86 c serving as an inflow port into the flow path resistance variable unit 83 is provided to be inclined toward the lower surface of the first valve body 88 t of the valve body 88. That is, the liquid inflow direction is a direction toward the location where the bubbles of the flow path resistance variable unit 83 are retained.

  As a result, the ink sent by the pump 78 is likely to hit the air bubbles remaining in the variable flow resistance unit 83, and the air bubbles remaining in the variable flow resistance unit 83 are easily moved by the flow. 84 is easily discharged.

  As described above, the pressure regulating valve has the flow path member that forms the flow path and the movable member that is movably accommodated in the flow path member, and the movable member communicates with the third flow path. A valve body portion located on the first flow path side than the first flow path, the valve body section is formed with a through-hole in the direction of liquid flow, and the flow path member has a third flow path from the liquid feeding means. Pressure adjustment is achieved by providing a liquid inlet portion in which the inflow direction of the liquid flowing into the flow path through the first wall is directed to the wall surface on the third flow path side of the valve body portion of the movable member. When the liquid sent to the air bubbles staying in the valve body in the valve hits, the air bubbles move and are easily discharged.

A fifth embodiment to which the present invention is applied will be described with reference to FIG. FIG. 24 is a schematic explanatory diagram of the flow path resistance variable unit 83 according to the embodiment.
Here, the position of the penetration 84 of the valve body 88 is set to the outer peripheral portion side of the valve body 88 as compared with the respective embodiments. As a result, the bubbles 141 remaining in the flow path resistance variable unit 83 are moved to the outer peripheral side of the valve body 88 by the circulation of the ink, and the bubbles 141 are discharged by the through holes 84 arranged on the outer peripheral side of the valve body 88. It becomes easy.

A sixth embodiment to which the present invention is applied will be described with reference to FIG. In addition, FIG. 25 is explanatory drawing with which it uses for description of the change of the liquid feeding amount of the assist pump with which it uses for description of the embodiment.
Here, the liquid feed amount per unit time of the assist pump 78 is controlled to be switched between the liquid feed amounts Q1 and Q2 (Q1 <Q2), and the liquid feed amount per unit time is changed to the flow resistance unit 83. Liquid. In this way, the liquid supply operation by the liquid supply means is controlled to supply liquid while intermittently switching the liquid supply amount, thereby making the flow of ink flowing into the variable flow path resistance unit 83 turbulent. Therefore, it is possible to efficiently move the air bubbles staying in the variable flow path resistance unit 83 and to easily discharge the air bubbles from the through hole 84.

  As described above, the pressure regulating valve has the flow path member that forms the flow path and the movable member that is movably accommodated in the flow path member, and the movable member communicates with the third flow path. A valve body portion located on the first flow path side than the first flow path, the valve body section is formed with a through-hole in the direction of liquid flow, and the flow path member has a third flow path from the liquid feeding means. Pressure adjustment is achieved by providing a liquid inlet portion in which the inflow direction of the liquid flowing into the flow path through the first wall is directed to the wall surface on the third flow path side of the valve body portion of the movable member. When the liquid sent to the air bubbles staying in the valve body in the valve hits, the air bubbles move and are easily discharged.

  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 86c Port (liquid inlet)
87 Pipe member (channel 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)

Claims (7)

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. And
The pressure regulating valve has a flow path member that forms a flow path, and a movable member that is movably accommodated in the flow path member, and the liquid feeding means passes the third flow path through the third flow path. An image forming apparatus, comprising: a liquid inflow portion in which an inflow direction of liquid flowing into the flow path does not pass through a central axis in a horizontal section of the movable member.   The image forming apparatus according to claim 1, wherein the liquid inflow port portion is disposed at a position that is radially deviated with respect to a central axis of the movable member.   The image forming apparatus according to claim 1, wherein the liquid inflow port portion is disposed at an angle having an inclination with respect to a central axis of the movable member.   The image forming apparatus according to claim 1, wherein the movable member is provided with fins around the periphery, and the fins are arranged in a direction orthogonal to a liquid inflow direction.   5. The image forming apparatus according to claim 1, wherein the liquid inflow port has a shape with a diameter that decreases along a liquid inflow direction. 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. And
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
In the flow path member, the inflow direction of the liquid flowing into the flow path from the liquid feeding means through the third flow path is directed to the wall surface on the third flow path side of the valve body portion of the movable member. An image forming apparatus, characterized in that a liquid inflow port portion is provided. 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. And
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 image forming apparatus, wherein the liquid feeding unit feeds liquid to the pressure adjusting valve while changing a liquid feeding amount per unit time.

Images