Patent Grant
8602537
1. Field of the Invention
The present invention generally relates to image forming apparatuses and, in particular, to an image forming apparatus having a recording head that ejects liquid droplets.
2. Description of the Related Art
As an image forming apparatus such as a printer, a facsimile machine, a copier, a plotter, and a multi-task machine having plural such functions, a known ink jet recording apparatus of a liquid ejection recording type uses a recording head that ejects, for example, ink liquid droplets. The image forming apparatus of this type ejects ink droplets onto a sheet during conveyance from the recording head to perform image formation (used synonymously with recording, printing, and imaging). Examples of an image forming apparatus include a serial-type image forming apparatus in which a recording head ejects liquid droplets to form an image while moving in a main scanning direction and a line-type image forming apparatus using a line-type head in which a recording head ejects liquid droplets to form an image without moving.
Note that in the present invention, an “image forming apparatus” refers to an apparatus that ejects ink droplets onto a medium such as paper, a thread, a fiber, a fabric, leather, metal, a plastic, glass, wood, and a ceramic so as to perform image formation. Further, “image formation” refers to forming not only relevant images such as characters and graphics but also irrelevant images such as patterns on a medium (the image forming apparatus also includes one referred to as a liquid droplet ejection apparatus or a liquid ejection apparatus that merely ejects liquid droplets onto a medium). Further, “ink” is not limited to one as generally called ink but is used as a generic name of various liquids available for image formation such as recording liquid, fixing treatment liquid, DNA samples, and patterning materials. Further, the material of a “sheet” is not limited to paper. That is, the sheet refers to those including an OHP sheet, a fabric, etc., onto which ink droplets are ejected and is used as a generic name of those including a medium to be recorded on, a recording medium, a recording sheet, a recording paper, etc. Further, an “image” is not limited to a two-dimensional image but also refers to an image added to a three-dimensional object and an image obtained by shaping an object into three dimensions.
A known liquid ejection head (a liquid droplet ejection head) used as a recording head includes a piezoelectric-type liquid ejection head and a thermal-type head. The piezoelectric-type liquid ejection head deforms a vibration plate with a piezoelectric actuator or the like and changes the volumes of liquid chambers. Thus, the piezoelectric-type liquid ejection head increases pressure inside the liquid chambers to eject liquid droplets. Further, the thermal-type head is provided with a heat generation body that generates heat when liquid chambers are energized. Thus, in ejecting liquid droplets, the thermal-type head increases pressure inside the liquid chambers with air bubbles produced when the heat generation body generates heat.
Such image forming apparatuses of the liquid ejection type are expected to in the future particularly increase image forming throughput, i.e., accelerate an image forming speed. Therefore, the image forming apparatus employs a method to for supplying ink from a high-capacity ink cartridge (main tank) installed in a main body a sub-tank (also including those referred to as a buffer tank) provided at the upper part of a recording head via a tube. According to the method (tube supply method) for supplying ink using the tube, a carriage part can be reduced in weight and downsized. In addition, the apparatus including a structure system and a driving system can be significantly downsized.
On the other hand, in order to stably perform liquid ejection with the recording head, it is necessary to apply appropriate negative pressure to nozzles. If the negative pressure is too low, liquid runs from the head. On the other hand, if the negative pressure is too high, the liquid ejection becomes unstable or is disabled.
A configuration for generating negative pressure in the ink supply system described above includes a method for connecting the ink cartridge to the recording head in communication with air by a tube and merely arranging the ink cartridge to be below the recording head. In this method, the negative pressure is obtained according to a water head difference between the ink cartridge and the recording head.
However, in this method, the water head difference fluctuates due to the lowering of the liquid surface of ink inside the ink cartridge when the ink is consumed in the ink cartridge. Therefore, the negative pressure inside the head may be gradually increased. With the increase in the negative pressure inside the head, problems such as unstable ink ejection and a difficulty in restoring the nozzles from their clogged state as described above are caused.
Accordingly, in order to maintain a head at constant pressure, Patent Document 1 (JP-A-2005-342961) discloses a configuration for communicating a head with a circulation path that circulates ink inside a sub-tank, detecting pressure inside the head that fluctuates according to the ejection status of the head with a pressure sensor, and controls the circulation pump provided in the circulation path based on a detection result.
However, the configuration disclosed in Patent Document 1 (JP-A-2005-342961) requires complicated control using the pressure sensor to compensate for the fluctuation of a water head difference.
The present invention has been made in view of the above problems and may have an object of maintaining the negative pressure inside a head at an appropriate range with a simple configuration.
According to a first aspect of the present invention, there is provided an image forming apparatus including a recording head having nozzles from which liquid droplets are ejected; a liquid tank that stores a liquid to be supplied to the recording head; a first flow path through which the liquid is supplied to the recording head; a second flow path in communication with the liquid tank; a pressure regulation unit having a flow path that connects the first flow path with the second flow path; a third flow path that bypasses the pressure regulation unit to connect the second flow path or the liquid tank with the first flow path; and a liquid supply unit provided in the third flow path. The pressure regulation unit varies a fluid resistance in accordance with a remaining amount of the liquid inside the liquid tank, decreases the fluid resistance if the remaining amount of the liquid is equal to or greater than a predetermined amount, increases the fluid resistance if the remaining amount of the liquid is less than the predetermined amount, and supplies the liquid with the liquid supply unit to eject the liquid droplets from the recording head, thereby generating a circulation flow that flows through the third flow path and the flow path of the pressure regulation unit.
According to a second aspect of the present invention, there is provided an image forming apparatus including a recording head having nozzles from which liquid droplets are ejected; a liquid tank that stores a liquid to be supplied to the recording head; a first flow path through which the liquid is supplied to the recording head; a second flow path in communication with the liquid tank; a fluid resistance part having a flow path that connects the first flow path with the second flow path; a third flow path that bypasses the pressure regulation unit to connect the second flow path or the liquid tank with the first flow path; a liquid supply unit provided in the third flow path; and a unit that supplies the liquid with the liquid supply unit to eject liquid droplets from the recording head, thereby generating a circulation flow that flows through the third flow path and the flow path of the fluid resistance part. The unit controls a flow rate to be supplied by the liquid supply unit to be decreased if the remaining amount of the liquid is equal to or greater than a predetermined amount and the flow rate to be increased if the remaining amount of the liquid is less than the predetermined amount in accordance with the remaining amount of the liquid inside the liquid tank.
According to a third aspect of the present invention, there is provided an image forming apparatus including a recording head having nozzles from which liquid droplets are ejected; a liquid tank that stores a liquid to be supplied to the recording head; a first flow path through which the liquid is supplied to the recording head; a second flow path in communication with the liquid tank; a pressure regulation unit having a flow path that connects the first flow path with the second flow path; a third flow path that bypasses the pressure regulation unit to connect the second flow path or the liquid tank with the first flow path; and a liquid supply unit provided in the third flow path. The pressure regulation unit varies a fluid resistance in accordance with a remaining amount of the liquid inside the liquid tank, decreases the fluid resistance if the remaining amount of the liquid is equal to or greater than a predetermined amount, increases the fluid resistance if the remaining amount of the liquid is less than the predetermined amount, and supplies the liquid with the liquid supply unit to perform a maintenance and restoration operation for the recording head, thereby generating a circulation flow that flows through the third flow path and the flow path of the pressure regulation unit.
According to fourth aspect of the present invention, there is provided an image forming apparatus including a recording head having nozzles from which liquid droplets are ejected; a liquid tank that stores a liquid to be supplied to the recording head; a first flow path through which the liquid is supplied to the recording head; a second flow path in communication with the liquid tank; a fluid resistance part having a flow path that connects the first flow path with the second flow path; a third flow path that bypasses the pressure regulation unit to connect the second flow path or the liquid tank with the first flow path; a liquid supply unit provided in the third flow path; and a unit that supplies the liquid with the liquid supply unit to perform a maintenance and restoration operation for the recording head, thereby generating a circulation flow that flows through the third flow path and the flow path of the fluid resistance part. The unit controls a flow rate to be supplied by the liquid supply unit to be decreased if the remaining amount of the liquid is equal to or greater than a predetermined amount and the flow rate to be increased if the remaining amount of the liquid is less than the predetermined amount in accordance with the remaining amount of the liquid inside the liquid tank.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.
Hereinafter, referring to the accompanying drawings, embodiments of the present invention are described. Referring to
In the ink jet recording apparatus, a carriage 4 is slidably held in a main scanning direction (in the longitudinal direction of a guide rod) by the guide rod 2 acting as a guide member bridged across right and left side plates 1L and 1R projectingly provided on a main body frame 1 and by a guide rail 3 attached to a rear frame 1B bridged across the main body frame 1. Thus, the carriage 4 is moved to scan in the longitudinal direction (main scanning direction) of the guide rod 2 by a main scanning motor 551 (see
In the carriage 4, one or more recording heads 10 that eject ink droplets of, for example, black (K), cyan (C), magenta (M), and yellow (Y) are mounted. Each of the recording heads 10 is mounted on the carriage 4 with its plural ink ejection ports (nozzles) arranged in a direction crossing the main scanning direction and its ink droplet ejection direction facing downward.
Here, as shown in
Note that although various types of recording heads such as one that deforms a vibration plate with piezoelectric elements or an electrostatic force to obtain ejection pressure are known, any type of the recording heads is applicable to the image forming apparatus according to the embodiments of the present invention.
Further, some of the thermal-type recording heads employ an edge-shooter method in which ejection directions are different from each other. However, the edge-shooter method causes so-called cavitation in which the heat generator 14 is gradually broken due to an impact when air bubbles collapse. Conversely, the side-shooter method grows air bubbles, and the air bubbles are in communication with air when they reach the nozzles 15. Therefore, the shrinkage of the air bubbles due to a decrease in temperature does not occur. For this reason, the side-shooter method is advantageous in that the service life of the recording head is increased. Further, the side-shooter method can more efficiently convert energy from the heat generator 14 into heat for forming ink droplets and kinetic energy for jetting the ink droplets, and also has a structural advantage in that the restoration of meniscuses by the supply of ink becomes fast. Accordingly, the ink jet recording apparatus according to the embodiments of the present invention has the recording head employing the side-shooter method.
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 (sub-scanning direction) perpendicular to the main scanning direction. As shown in
At this time, scanning by the carriage 4 in the main scanning direction and ink ejection by the recording head 10 are synchronized with each other at an appropriate timing based on image data, and an image corresponding to one band is formed on the sheet 20. After the formation of the image corresponding to the one band, the sheet 20 is fed in the sub-scanning direction by a predetermined amount to perform the recording operation as described above. These operations are repeatedly performed to form an image corresponding to one page.
On the other hand, a sub-tank (buffer tank or head tank) 30 in which an ink chamber for temporarily storing the ink to be ejected is integrally formed at the upper part of the recording head 10. Here, the expression “integrally formed” also includes connecting the recording head 10 to the sub-tank 30 via a tube, a pipe, or the like and refers to a state in which the recording head 10 and the sub-tank 30 are both mounted on the carriage 4.
The respective colors of ink are supplied from an ink cartridge (main tank) 76 acting as a liquid tank according to the embodiments of the present invention storing the respective colors of ink and detachably attached to a cartridge holder 77 provided on the side of the one end part of an apparatus main body in the main scanning direction to the sub-tank 30 via a liquid supply tube 71 acting as a tube member forming a part of the ink supply paths and forming a first flow path.
Further, on the side of the other end part of the apparatus main body in the main scanning direction, a maintenance and restoration mechanism 51 that maintains and restores the recording head 10 is arranged. The maintenance and restoration mechanism 51 has a cap 52 that caps the nozzle surface of the recording head 10, a suction pump 53 that suctions the ink inside the cap 52, a discharge path 54 through which the drainage of the ink suctioned by the suction pump 53 is discharged, and the like. The drainage discharged through the discharge path 54 is discharged into a drainage tank 56 arranged on the side of the main body frame 1. The maintenance and restoration mechanism 51 has a moving mechanism (cap moving mechanism 513 in
Next, referring also to
First, the sub-tank 30 is configured to have a rubber member 102 having flexibility and formed into a convex shape toward an outside at one opening of a tank case 101 forming an ink chamber 103, have a filter 109 near a connection part between the ink chamber 103 and the recording head 10 inside the ink chamber 103, and supply the ink from which foreign matter is removed by filtration to the recording head 10.
One end part of the ink supply tube 71 is connected to the sub-tank 30. Further, as shown in
The ink cartridge 76, a pump unit 80 acting as a liquid supply unit, and a pressure control unit 81 are connected to the cartridge holder 77.
As shown in
As shown in
As shown in
Next, referring to a schematic configuration view shown in
The ink supply system has the ink cartridge 76 acting as the liquid tank that stores ink to be supplied to the recording head 10; the liquid supply tube 71 (hereinafter also referred to as a “first flow path”) acting as the first flow path through which the ink is supplied to the recording head 10; a second flow path 60 having a branch part 63 along its way and in communication with the ink cartridge 76, the second flow path 60 including a section 60a between the pressure control unit 81 and the branch part 63 and a section 60b between the branch part 63 and the ink cartridge 76; the pressure control unit 81 including the fluid resistance variable unit 40 acting as the pressure regulation unit that connects the first flow path 71 with the second flow path 60; a third flow path 62 that bypasses the fluid resistance variable unit 40 to connect the branch part 63 with the first flow path 71; and the pump unit 80 acting as the liquid supply unit provided in the third flow path 62.
Here, the fluid resistance variable unit 40 varies fluid resistance with hydrostatic pressure applied to its inner flow path.
Next, referring to
In the fluid resistance variable unit 40, a pressure regulation chamber 43 that varies fluid resistance is provided in a part of a flow path 41a formed inside a flow path forming member 41. In the pressure regulation chamber 43, a rectangular opening part facing the flow path 41a is provided in the flow path forming member 41 and covered with a cover member 42 formed of an elastic member like rubber acting as a flexible member. When the cover member 42 is deformed by hydrostatic pressure, the squeezing amount (length) of the flow path is varied. As a result, the fluid resistance is varied.
Referring back to
Here, referring to
As described above, in the ink supply system of this embodiment, a vertical interval is provided between the head 10 and the ink cartridge 76 opened to air so as to maintain the head 10 at appropriate pressure. Accordingly, when the ink inside the ink cartridge 76 is reduced, the liquid surface of the ink is lowered. Therefore, the vertical interval (water head difference) between the head 10 and the liquid surface of the ink inside the ink cartridge 76 is increased, and the pressure inside the head 10 is increased in a negative pressure direction.
There is no problem with the increase in the negative pressure inside the head 10 as long as it is small. However, if the ink cartridge 76 is, for example, a high-capacity-type ink cartridge, the position of the liquid surface is greatly changed as the ink is consumed. Therefore, the negative pressure thus varied is not negligible. As the negative pressure is greatly varied, the size of ink droplets ejected from the head 10 is changed. As a result, problems such as unstable image formation and ejection abnormalities are caused. Further, since it is difficult for the meniscuses of the nozzles to be easily formed again in a nozzle restoration operation, restoring the nozzles becomes difficult.
Therefore, in the ink supply system of this embodiment, the increase in the negative pressure inside the ink cartridge 76 caused when the water head of the ink cartridge 76 is changed is suppressed by the change of fluid resistance of the fluid resistance variable unit 40 and the supply of the liquid by the (assist) pumps 78.
First, when the remaining amount of the ink inside the ink cartridge 76 is large, the fluid variable resistance unit 40 is deformed according to pressure inside the pressure regulation chamber 43 as shown in
In other words, the fluid resistance variable unit 40 is configured to reduce (G1→G2) the length of a gap forming the flow path of the pressure regulation chamber 43 when the remaining amount of the ink inside the ink cartridge 76 is decreased.
As described above, since the fluid resistance variable unit 40 is configured to automatically vary the fluid resistance according to a pressure difference between the fluid resistance variable unit 40 and the ink cartridge 76, the configuration of the pressure regulation unit is simplified. Further, since the flexible member is used in the part of the flow path, the configuration of the pressure regulation unit is further simplified. Moreover, since the elastic member is used as the flexible member, the squeezing amount (amount of fluid resistance) of the pressure regulation chamber 43 can be elastically varied. As a result, the characteristics of the pressure regulation chamber 43 are stabilized.
On the other hand, referring back to
When the ink is supplied by the assist pumps 78 in a direction as indicated by arrow Qa, some of the ink to be ejected from the head 10 flows in a direction as indicated by arrow C while the rest of the ink flows in a direction as indicated by arrow D. As a result, the ink circulates through the fluid resistance variable unit 40 and the assist pumps 78.
Accordingly, inside the fluid resistance variable unit 40, the ink flows in a direction as indicated by arrow D in
As described above, even if the negative pressure inside the head is increased due to the water head difference when the remaining amount of the ink inside the ink cartridge 76 is changed, the pressure regulation chamber 43 automatically generates the positive pressure to stably maintain the pressure inside the head 10. As a result, the ejection performance of the head 10 can be satisfactorily maintained. Further, even in performing the nozzle restoration operation when the nozzles of the head 10 are clogged, the negative pressure inside the head 10 can fall in a prescribed range regardless of the remaining amount of the ink inside the ink cartridge. As a result, the restoration performance of the head 10 can be satisfactorily obtained.
Next, referring to
The control unit 500 has a CPU 501, a ROM 502, a RAM 503, a rewritable non-volatile memory 504, and an ASIC 505. The CPU 501 controls the entirety of the image forming apparatus while acting also as a unit that performs various controls according to the embodiments of the present invention. The RAM 502 stores a program executed by the CPU 501 and other fixed data. The RAM 503 temporarily stores image data or the like. The rewritable non-volatile memory 504 maintains data even when the apparatus is powered off. The ASIC 505 performs image processing such as various signal processing and rearrangement with respect to image data and input/output signal processing for controlling the entirety of the apparatus.
Further, the control unit 500 has a print control part 508, a head driver (driver IC) 509, a motor drive part 510, a pump drive part 511, and the like. The print control part 508 drives and controls the recording head 10 in accordance with print data. The head driver 509 drives the recording head 10 on the side of the carriage 4. The motor drive part 510 drives the main scanning motor 551 that moves the carriage 4 to perform scanning, a sub-scanning motor 552 that rotates and drives the conveyance roller 21 for conveying the sheet 20, and a maintenance and restoration motor 512 that operates the cap moving mechanism 513 for moving the cap 52, the wiper member 57, or the like of the maintenance and restoration mechanism 51. The pump drive part 511 drives the suction pump 53 of the maintenance and restoration mechanism 51 and the assist pumps 78.
Further, the control unit 500 is connected to an operations panel 514 on which information items necessary for the apparatus are input and displayed.
The control unit 500 has an I/F 506 that sends and receives data and signals to and from a host. The I/F 506 receives the data and signals from the host 600 such as an information processing apparatus like a personal computer, an image reading apparatus like an image scanner, and an image pick-up apparatus like a digital camera via a cable or a network.
In the control unit 500, the CPU 501 reads and analyzes print data inside a receive buffer included in the I/F 506, the ASIC 505 performs necessary image processing, data rearrangement processing, or the like, and the print control part 508 transfers image data to the head driver 509. Note that dot pattern data for image output are generated by a printer driver 601 of the host 600.
The print control part 508 transfers the print data described above as serial data and outputs to the head driver 509 a transfer clock, a latch signal, a control signal, or the like necessary for the transfer of the print data and determining the transfer, or the like. The head driver 509 drives the heat generator 14 based on the serially-input print data corresponding to one line of the recording head 10.
An I/O part 515 acquires information items from a group of sensors 516, extracts information items necessary for controlling the printer from the extracted information items, and uses the extracted information items for controlling the print control part 508 and the motor drive part 510. The group of sensors 516 includes an optical sensor that detects the position of a sheet, a thermistor that monitors temperature inside the apparatus, a sensor that monitors the voltage of a charged belt, an interlock switch that detects the opening/closing status of a cover, and the like. The I/O part 515 can process information items from the various sensors. Further, a detection signal from a temperature and humidity detection sensor that detects environmental conditions (temperature and humidity) and a detection signal from a fill-up status detection sensor that detects the fill-up status of the drainage tank 56 are also input to the I/O part 515.
Next, referring to a flowchart shown in
After the confirmation of the attachment of the ink cartridge 76, the nozzle surface of the recording head 10 is capped by the cap 52 of the maintenance and restoration mechanism 51. With the nozzle surface capped by the cap 52, the suction pump 53 is driven to suction air inside the ink supply paths via the nozzles of the recording head 10. The suctioning of the air via the nozzles is continued until a predetermined time elapses. After the suctioning of the air for the predetermined time, the ink inside the ink cartridge 76 reaches the first flow path (liquid supply tube) 71.
Then, when a predetermined time elapses (a timer counts up) after starting the suctioning of the air via the nozzles, the motor 82 is driven to drive the pumps 78 of the pump unit 80. Since the ink supply paths are formed as shown in
The air pushed out to the liquid supply tube 71 is fed to the recording head 10 by the suctioning of the suction pump 53. When the suction pump 53 and the pumps 78 are both driven for a predetermined time, all the ink supply paths from the ink cartridge 76 to the recording head 10 can be filled with the ink.
Then, the wiper 57 of the maintenance and restoration mechanism 51 wipes off the nozzle surface of the recording head 10, and the recording head 10 is driven to eject a predetermined number of ink droplets from the nozzles. Thus, desired meniscuses can be formed in the nozzles.
In the manner described above, the initial ink filling operation is completed.
Next, referring to a flowchart shown in
After the reception of a print job signal, the remaining amount of the ink inside the ink cartridge 76 is confirmed. As a method (detection unit) for confirming the remaining amount of the ink, a method for providing an ink-remaining-amount detection sensor in the ink cartridge 76 to obtain information on the remaining amount of the ink, a method for estimating the remaining amount of the ink based on information on the histories of print and restoration operations, or the like may be employed. Although not shown in the figures, replacement or the like of the ink cartridge 76 is prompted when the remaining amount of the ink is small.
Then, the temperature sensor 27 detects an environmental temperature inside the apparatus to estimate the temperature of the ink. Note that although the temperature sensor 27 is installed in the carriage 4 (see
Next, the flow amount of the ink to be supplied by the assist pumps 78 is determined (conditions for driving the assist pumps 78 are set) based on the temperature of the ink, and the assist pumps 78 are driven. Subsequently, the cap 52 covering the nozzle surface of the recording head 10 is separated from the nozzle surface (capping of the nozzles is released), and the idle ejection of a predetermined number of droplets is performed. After that, the print operation is started.
After the completion of the print operation, the carriage 4 is stopped at the predetermined position (home position) of the apparatus, and the nozzle surface of the recording head 10 is capped by the cap 52. Then, the assist pumps 78 are stopped. Here, the assist pumps 78 may be stopped right after the completion of the print operation.
As described above, in order to perform the print operation, the assist pumps 78 are driven to supply the ink. Therefore, even if the negative pressure inside the recording head 10 is increased due to the water head difference when the remaining amount of the ink inside the ink cartridge 76 is decreased, the negative pressure inside the recording head 10 is reduced to be in a prescribed range by the operation of the pressure control unit 81. Therefore, the ink ejection can be stably performed.
As described above, the ink supply system is configured to have the pressure regulation unit 40 including the flow path that connects the first flow path 71 through which the liquid is supplied to the recording head 10 with the second flow path 60 in communication with the liquid tank 76; the third flow path 62 that bypasses the pressure regulation unit 81 to connect the second flow path 60 or the liquid tank 76 with the first flow path 71; and the liquid supply unit 80 provided in the third flow path 62. Further, the pressure regulation unit 40 is configured to vary the fluid resistance in accordance with the remaining amount of the liquid inside the liquid tank 76, decrease the fluid resistance if the remaining amount of the liquid is equal to or greater than a predetermined amount, increase the fluid resistance if the remaining amount of the liquid is less than the predetermined amount, and supply the liquid with the liquid supply unit 80 to eject liquid droplets from the recording head 10, thereby generating a circulation flow that flows through the third flow path 62 and the flow path of the pressure regulation unit 40. Thus, the increase in the negative pressure caused when the remaining amount of the liquid is decreased can be suppressed, and the negative pressure inside the head 10 can be maintained at an appropriate range with a simple configuration.
Further, since a circulation flow is also generated to perform a maintenance and restoration operation, the head 10 can be maintained at appropriate pressure when the nozzles of the head 10 are clogged. Therefore, the nozzles can be satisfactorily restored, and reliability of the apparatus can be enhanced.
Note that as described above, the image forming apparatus ejects the four colors of ink. Therefore, the four ink supply systems configured as shown in
In other words, the remaining amount of the ink inside the ink cartridge 76 is independently varied depending on the consumption amount of the ink corresponding to the color of ejected droplets. However, in the ink supply system of this embodiment, the cover member 42 of the fluid resistance variable unit 40 is deformed in accordance with the remaining amount of the ink inside the ink cartridge 76. Therefore, even if the pumps 78 supply the liquid of all the colors by the same amount, pressure necessary for each of the colors can be automatically generated.
Further, in the system having plural ink supply systems that use plural ink, the pumps (liquid supply units) of all the ink supply systems can be collectively driven by the single actuator. Therefore, the configuration of the apparatus and controlling the apparatus are simplified, whereby the cost reduction and downsizing of the apparatus can be achieved.
Further, the viscosity of the liquid is generally changed depending on the temperature of the liquid. Therefore, in order to assist the liquid to the recording head 10, temperature around the apparatus and temperature inside the apparatus measured by the temperature sensor 27, temperature of the ink and the prediction value of the temperature, or the like may be fed back to control the driving of the pumps 78. Thus, the apparatus, which is user-friendly and responding to any temperature, is obtained.
Next, referring to
First, the ink cartridge 76 has a bag member 93 formed of a flexible material and capable of being deformed (from a status shown in
With this configuration of the cartridge 76, the ink supply system is in a closed state. Therefore, it becomes easy to stably maintain the quality of the liquid to be supplied. Further, the head 10 is configured to be maintained at negative pressure by a vertical interval between the head 10 and the ink cartridge 76. Therefore, the negative pressure inside the head 10 is stabilized.
In the ink supply system of this embodiment, a vertical interval is provided between the head 10 and the ink cartridge 76 to maintain the head 10 at appropriate pressure. In the ink cartridge 76, pressure is gradually reduced when the ink inside the ink cartridge 76 is consumed. Particularly, when the remaining amount of the ink becomes small, the pressure is significantly reduced. As a result, the problems such as unstable ink ejection and a difficulty in restoring the nozzles from their clogged state as described above are caused. In order to address the problems, the ink supply system of this embodiment can prevent the pressure reduction by the supply of the liquid with the pumps 78 and by the operation of the pressure control unit 81.
Next, referring to
The fluid resistance variable unit 40 has a round opening at a part of the flow path 41a of the fluid forming member 41 and has the pressure regulation chamber 43 provided with the cover member 42 at the opening. Note that a resin film such as low-density polyethylene is used as the cover member 42 and fixed to the flow path forming member 41 with its periphery heat-sealed.
Further, the cover member 42 is biased by springs 45 provided in the flow path forming member 41 in a direction in which the volume of the pressure regulation chamber 43 increases (in a direction in which fluid resistance decreases). Thus, a unit is provided that presses a flexible member forming the wall surface of the pressure regulation chamber 43 in the direction in which the fluid resistance decreases. Therefore, even if a film member is used as the flexible member, the squeezing amount (fluid resistance) of the pressure regulation chamber 43 can be elastically varied. As a result, characteristics of the pressure regulation chamber 43 can be stabilized.
Moreover, the flow path forming member 41 has a groove 44 acting as a part of the flow path at the central part of its surface opposing the cover member 42.
Next, a description is made of the principle (pressure regulation principle) of preventing the pressure reduction by the supply of the liquid with the pumps 78 and by the operation of the pressure control unit 81 (fluid resistance variable unit 40).
Also, in this embodiment, as shown in
The pressure regulation chamber 43 of the fluid resistance variable unit 40 of the pressure control unit 81 is configured to cause the flow path to expand and contract in accordance with its inner pressure. The pressure inside the pressure regulation chamber 43 is relatively great if the remaining amount of the ink inside the ink cartridge 76 is large. In this case, the pressure regulation chamber 43 is largely opened as shown in
On the other hand, if the remaining amount of the ink inside the ink cartridge 76 gets small, negative pressure inside the pressure regulation chamber 43 becomes great. Therefore, as shown in
Accordingly, an increase in the negative pressure can be automatically cancelled as the remaining amount of the ink inside the ink cartridge 76 is decreased.
According to this embodiment of the present invention, since the increase in the negative pressure is automatically cancelled as the remaining amount of the ink is decreased, the ink inside the ink cartridge 76 can be completely consumed.
Further, the fluid resistance variable unit 40 of this embodiment has the groove 44 in the pressure regulation chamber 43. Therefore, as shown in
Further, in this embodiment, an opening/closing valve 69 is provided between the ink cartridge 76 and the fluid resistance variable unit 40 as shown in
Accordingly, even if the remaining amount of the ink gets small and the ink cartridge 76 is extracted when the negative pressure inside the pressure regulation chamber 43 is great, the cover member 42 is pressed by the operation of the springs 45 of the fluid resistance variable unit 40. As a result, air is prevented from entering in the ink cartridge 76 via a joint 89.
Next, referring to
In this embodiment, the ink cartridge 76 is a tank-type ink cartridge having the air communication part 90 as in the ink cartridge 76 of the first embodiment, and a liquid surface inside the ink cartridge 76 is positioned to be lower than the nozzle surface of the recording head 10.
Further, the ink cartridge 76 is provided with an ID chip 68 that stores information on the ink cartridge 76.
Next, referring to
Next, a description is made of pressure control using the fluid resistance variable unit 40.
When the remaining amount of the ink inside the ink cartridge 76 is decreased, a vertical difference (water head difference h) between the head 10 and the liquid surface of the ink inside the ink cartridge 76 becomes large. As a result, negative pressure applied to the head 10 is increased. Therefore, like the above embodiments, a circulation flow in the direction as indicated by the arrow D is produced in the fluid resistance variable unit 40 of the pressure control unit 81 by the assist pumps 78, and positive pressure is produced in the fluid resistance variable unit 40. Thus, the increase in the negative pressure described above is cancelled.
Here, where the flow rate of the liquid supplied by the assist pumps 78 is constant, the larger the fluid resistance of the fluid resistance variable unit 40 is, the greater the produced positive pressure becomes. Therefore, the fluid resistance of the fluid resistance variable unit 40 may be controlled to be increased as the remaining amount of the ink is decreased.
As described above, the fluid resistance variable unit 40 of this embodiment is composed of the tubes 47 having the different diameters and the opening/closing valves 48. Accordingly, for example, as shown in
Note that the fluid resistance variable unit 40 may be composed of tubes, each of which has the same diameter and the same length, and opening/closing valves. However, the fluid resistance variable unit 40 thus configured has lesser phases for varying fluid resistance compared with the fluid resistance variable unit 40 of this embodiment. For finer pressure control, it is preferable that the branch paths have different resistances.
Further, in this embodiment, the pressure control is performed with the selection of the plural flow paths having different fluid resistances. However, it is also possible to perform a similar control in such a manner that the fluid resistance variable unit 40 is configured to have a single flow path and vary the fluid resistance when the squeezed status of the flow path is varied.
Next, referring to a flowchart shown in
After the reception of a print job signal, the remaining amount of the ink inside the ink cartridge 76 is confirmed. In this embodiment, as described above, information on the remaining amount of the ink is stored in the ID chip 68 provided in the ink cartridge 76. When the ink is consumed by the print operation or the like, information on the amount of the consumed ink is written in the ID chip 68 and the information on the remaining amount of the ink is updated. The information on the remaining amount of the ink is read by a reading unit (not shown) to detect the remaining amount of the ink. Although not shown in the figures, replacement or the like of the ink cartridge 76 is prompted when the remaining amount of the ink is small.
Then, the temperature sensor 27 detects an environmental temperature inside the apparatus to estimate the temperature of the ink. Next, based on information on the temperature of the ink and the information on the remaining amount of the ink, the opening/closing valves 48 to be opened and closed in accordance with the remaining amount of the ink with the combination shown in
Then, any of the opening/closing valves 48 selected by the fluid resistance variable unit 40 is opened, and the pumps are driven to supply the liquid thus determined.
Subsequently, the cap 52 covering the nozzle surface of the recording head 10 is separated from the nozzle surface (capping of the nozzles is released), and the idle ejection of a predetermined number of droplets is performed. After that, the print operation is started.
After the completion of the print operation, the carriage 4 is stopped at the predetermined position (home position) of the apparatus, and the nozzle surface of the recording head 10 is capped by the cap 52. Then, the assist pumps 78 are stopped. Here, the assist pumps 78 may be stopped right after the completion of the print operation.
When the print operation described above is performed, the liquid supplying resistance (fluid resistance) of the fluid resistance variable unit 40 is set in accordance with the remaining amount of the ink inside the ink cartridge 76 and an appropriate amount of circulation flow is produced by the assist pumps 78. Therefore, the pressure inside the recording head 10 is lowered in a prescribed range by the operation of the pressure control unit 81 regardless of the remaining amount of the ink. Therefore, ink ejection can be stably performed.
Next, referring to
First, in this embodiment, the ink cartridge 76 is provided with a liquid surface sensor composed of plural electrodes. Further, the pressure control unit 81 is composed of a fluid resistance variable unit 83 and a squeeze member 66. Note that in this embodiment, the fluid resistance variable unit 83 and the squeeze member 66 are separately provided. However, the squeeze member 66 may be provided inside the fluid resistance variable unit 83.
The fluid resistance variable unit 83 has the characteristic of varying fluid resistance according to the flow direction and the flow rate of the liquid flowing inside the fluid resistance variable unit 83. For example, as shown in
The tube member 87 has a port 86a to which the first flow path 71 is connected, a port 86b to which the second flow path 60 is connected via the squeeze member 66, and a port (side hole) to which the third flow path 62 is connected. The valve body 88 acting as the movable member is a stepped shaft-shaped member having step parts with different diameters in the flow direction of the liquid. The step parts include at least three step part elements of an upper part (first valve body part) 88t, a central part 88m, and a lower part (second valve body part) 88b, and the diameter of the central part 88m is formed to be smaller than the diameter of the second valve body part 88b. The valve body 88 is capable of moving inside the tube member 87 and placed at various positions such as a position shown in
As shown in
Here, referring to
Accordingly, the ink supplied by the pumps 78 circulates inside a loop path formed by the pump unit 80 and the fluid resistance variable unit 83 in
At this time, since the ink flows in the squeeze member 66, positive pressure determined by the fluid resistance of the squeeze member 66 and the flow amount of the ink is produced.
At this time, since the ink supplied by the pumps 78 in the direction as indicated by the arrow Qa (where the amount of the ink supplied in the direction as indicated by the arrow Qa is generally greater than the amount of the ink supplied in the direction as indicated by the arrows Qh) naturally flows in the small gap Gb1, pressure (PA) is produced. This pressure reduces a pressure loss generated when the ink flows in the head 10. As a result, large amounts of the ink can be supplied.
Further, at the same time, since the ink flows in the squeeze member 66 in the direction as indicated by the arrow D, positive pressure (PB) determined by the fluid resistance of the squeeze member 66 and the flow amount of the ink is also produced.
Here, a description is made of the characteristics of the pressure (PA) and the pressure (PB). First, the pressure (PA) is determined by the squeezing amount of the gap Gb1 determined by the position (balanced position) of the valve body 88 and the flow amount (Qa−Qh) of the ink flowing in the gap Gb1. The position of the valve body 88 is determined by a balance between the upward force of the valve body 88 generated according to the ejection flow amount Qh of the head 10 and the downward force of the valve body 88 generated when the ink flows in the gap Gb1. Accordingly, since the balanced position of the valve body 88 is moved upward as shown in
On the other hand, when the flow amount (assist flow amount) Qa of the ink supplied by the pumps 78 is increased, a force for moving the valve body 88 downward is increased and the valve body 88 is moved downward. Therefore, the assist pressure (PA) remains the same. In other words, when the flow amount Qa is increased, the flow amount of the ink flowing in the gap Gb1 is increased. However, since fluid resistance of the fluid resistance variable unit 83 is decreased at the gap Gb1, the resulting assist pressure (PA) becomes constant.
Conversely, the pressure (PB) produced by the squeeze member 66 is increased in proportion to the assist flow amount Qa since the fluid resistance is constant.
As described above, in this embodiment, the pressure (PB) that is increased in proportion to the flow amount Qa of the ink supplied by the pumps 78 can be produced with the squeeze member 66. Therefore, with the control of the flow amount Qa of the ink supplied by the assist pumps 78, the increase in the negative pressure caused when the remaining amount of the ink inside the ink cartridge 76 is decreased can be lowered in a prescribed range.
Further, since the pressure inside the head 10 can be freely controlled in accordance with the flow amount Qa of the ink supplied by the assist pumps 78, it is also possible to arrange the ink cartridge 76 down below within the limitation of the water head pressure of the meniscus holding force of the head 10.
Further, since the head 10 can be regulated at appropriate pressure when the nozzles of the head 10 are clogged, the nozzles can be satisfactorily restored. As a result, the reliability of the apparatus can be enhanced.
As described above, the ink supply system is configured to have the first flow path 71 through which the liquid is supplied to the recording head 10; the second flow path 60 in communication with the liquid tank 76; the fluid resistance part 83 including the flow path that connects the first flow path 71 with the second flow path 60; the third flow path 62 that bypasses the fluid resistance part 83 to connect the second flow path 60 or the liquid tank 76 with the first flow path 71; the liquid supply unit 80 provided in the third flow path 62; and the unit 66 that supplies the liquid with the liquid supply unit 80 to eject liquid droplets from the recording head 10, thereby generating a circulation flow that flows through the third flow path 62 and the flow path of the fluid resistance part 83. The unit 66 controls the flow rate to be supplied by the liquid supply unit 78 to be decreased if the remaining amount of the liquid is equal to or greater than a predetermined amount and the fluid resistance to be increased if the remaining amount of the liquid is less than the predetermined amount in accordance with the remaining amount of the liquid inside the liquid tank 76. Thus, the increase in the negative pressure caused when the remaining amount of the liquid is decreased can be suppressed, and the negative pressure inside the head 10 can be maintained at an appropriate range with a simple configuration.
Next, referring to a flowchart shown in
First, a determination is made as to whether the ink cartridge 76 has been attached to the cartridge holder 77. If it is determined that the ink cartridge 76 has not been attached, a cartridge attachment request is displayed on the operations panel 514.
If it is determined that the ink cartridge 76 has been attached, the cap 52 of the maintenance and restoration unit 51 is moved upward to cap the nozzle surface of the head 10.
Then, the remaining amount of the ink inside the ink cartridge 76 is confirmed by the liquid surface sensor 67 of the ink cartridge 76, and an environmental temperature is detected by the temperature sensor 27. Thus, conditions for driving the pumps 78 are determined, and the pumps 78 are driven to supply the ink.
When the ink is supplied by the pumps 78, positive pressure is produced in the pressure control unit 81 and negative pressure inside the head 10 is reduced. As a result, the restoration of the nozzles can be enhanced.
Next, the suction pump 53 is driven to produce negative pressure inside the cap 52 so that the ink is suctioned and ejected from the nozzles.
Thus, air bubbles and foreign matter mixed with the ink are ejected from the nozzles 15 of the head 10.
Then, after a predetermined time elapses (count up), the driving of the suction pump 53 is stopped to stop the suctioning operation of the nozzles. Subsequently, the cap 52 is separated from the nozzle surface of the head 10 (capping of the nozzles is released), the nozzle surface is wiped off by the wiper member 57 of the maintenance and restoration unit 51, and the driving of the pumps 78 is stopped.
Thus, meniscuses are formed at the nozzle surface.
After that, liquid droplets (idle ejection) irrelevant to image formation are ejected from the head 10, the cap 52 is moved upward to cap the nozzle surface of the head 10, and the restoration operation is completed.
As described above, the ink supply system is configured to have the first flow path 71 through which the liquid is supplied to the recording head 10; the second flow path 60 in communication with the liquid tank 76; the fluid resistance part 83 including the flow path that connects the first flow path 71 with the second flow path 60; the third flow path 62 that bypasses the fluid resistance part 83 to connect the second flow path 60 or the liquid tank 76 with the first flow path 71; the liquid supply unit 80 provided in the third flow path 62; and the unit 66 that supplies the liquid with the liquid supply unit 80 to perform the maintenance and restoration operation for the recording head 10, thereby generating a circulation flow that flows through the third flow path 62 and the flow path of the fluid resistance part 83. The unit 66 controls the flow rate to be supplied by the liquid supply unit 78 to be decreased if the remaining amount of the liquid is equal to or greater than a predetermined amount and the fluid resistance to be increased if the remaining amount of the liquid is less than the predetermined amount in accordance with the remaining amount of the liquid inside the liquid tank 70. Thus, the increase in the negative pressure caused when the remaining amount of the liquid is decreased can be suppressed, and the negative pressure inside the head 10 can be maintained at an appropriate range with a simple configuration. As a result, the maintenance and restoration of the head can be enhanced.
Next, a description is made of the effects of the print operation of this embodiment. As described above, the ink supply system of this embodiment is configured to have the pressure control unit 81 in the supply flow path through which the liquid is supplied from the liquid tank 76 to the head 10; the flow path 62 in the pressure control unit 81 to be in communication with the ink cartridge 76 as another flow path; the pumps 78 in the flow path 62 as the liquid supply unit; and the fluid resistance variable unit 83 that varies the fluid resistance in accordance with the flow rate of the liquid flowing in the head 10 inside the pressure control unit 81.
In ejecting the liquid from the head 10, the liquid is supplied to the head 10 by the assist pumps 78 in a state in which the head 10 and the ink cartridge 76 are connected with each other. Therefore, it is possible to apply pressure to the head 10 while automatically regulating appropriate assist pressure in accordance with the amount of the ink ejected from the head 10. Thus, it is possible to easily prevent the elongation of the liquid supply tube 71, an increase in the flow rate of the liquid to be ejected, and the shortage of refill due to the high viscosity or the like of the liquid to be ejected.
Next, referring to
With this configuration, the ink supply system of this embodiment can also obtain the same effects as those of the above respective embodiments.
Note that the operations and effects of the embodiments of the present invention are described above using the example in which the different colors of ink is supplied to the plural heads. However, the embodiments of the present invention can also be applied to a case in which the same color of ink is supplied to the plural heads or a case in which ink different in prescription rather than color is supplied to the plural heads. Further, the embodiments of the present invention can also be applied to a liquid supply system in which a head has plural nozzle arrays and different types of liquid are ejected from the head. Further, the embodiments of the present invention are not limited to image forming apparatuses that eject ink in a narrow sense but can also be applied to liquid ejection apparatuses (included in the “image forming apparatus” in the present invention) that eject various liquids.
The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention.
The present application is based on Japanese Priority Application No. 2010-045258 filed on Mar. 2, 2010, the entire contents of which are hereby incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-045258 | Mar 2010 | JP | national |
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| Number | Date | Country | |
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| 20110216111 A1 | Sep 2011 | US |
