JP2010264594A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent image degradation or ink leakage caused by a difference between liquid levels by surely aligning the liquid levels of respective color inks when re-forming negative pressure in a sub tank for storing two or more color inks. <P>SOLUTION: When detecting an ink liquid level by an ink detection electrode 358 in any of ink storing parts 352a and 352b, the ink liquid level is detected and a liquid feed pump 23 corresponding to the ink storing part 352 is reversely rotated to return the ink in the ink storing part 352 to an ink cartridge 10 side, and then after both liquid feed pumps 23 are normally rotated to supply the ink from the respective ink cartridges 10 to the ink storing parts 352a and 352b, the ink storing parts 352a and 352b are set to a negative pressure state. When the ink storing parts 352a and 352b are set to the negative pressure state, the ink liquid levels in the ink storing parts 352a and 352b are set to a fixed level. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus in which a sub tank is mounted on a carriage separately from an ink cartridge.

  For example, when a large-capacity ink cartridge is used in an ink jet recording apparatus that records an image by discharging ink droplets from a recording head ink discharge port (nozzle) to a recording medium such as paper based on image information, the ink cartridge is mounted on the carriage. If an ink cartridge is directly mounted on the recording head and ink is supplied to the recording head, the carriage operation is hindered due to the weight of the ink cartridge, and the image quality is lowered. Therefore, a sub-tank, which is a small-capacity ink container that supplies ink to the recording head mounted on the carriage, is mounted, and a large-capacity ink cartridge is installed on the main body of the apparatus so that ink is supplied to the sub-tank from the ink cartridge. In other words, one that holds a large volume of ink is used.

  As shown in the front view of FIG. 10A, the side view of FIG. 10B, and the top view of FIG. 10C, the sub-tank of this image recording apparatus is flexible at the side opening of the ink containing portion 352 of the tank body. A spring 354 for energizing the film member 353 outward is provided inside the ink containing portion 352, and a negative pressure generating mechanism is configured by the film member 353 and the spring 354. An air release mechanism 356 for opening the ink storage portion 352 to the atmosphere and an ink supply port portion 377 for supplying ink from the ink cartridge to the ink storage portion 352 and detecting ink in the ink storage portion 352 are provided. Two ink detection electrodes 358 are provided. When ink is supplied from the ink cartridge to the sub tank 35, the atmosphere is released to the atmosphere by the atmosphere release mechanism 356 and the film member 353 is pressed against the spring 354 so that the ink is supplied to the ink storage portion 352. After that, the air release mechanism 356 is closed, a negative pressure is generated in the ink containing portion 352, and ink droplets are ejected from the nozzles of the recording head so that an image is recorded.

  In an ink jet recording apparatus equipped with a sub tank that temporarily stores ink supplied from a large-capacity ink cartridge, for example, an ink that has two nozzle rows in a recording head and stores two colors of ink in the sub tank 35 When the storage portions 352a and 352b are provided, the liquid level in both ink storage portions 352a and 352b when the negative pressure state in the sub tank 35 is released and the inks of both colors are supplied to the ink storage portions 352a and 352b. It is necessary to match the level. When supplying ink to the ink storage portions 352a and 352b of the sub tank 35, as shown in FIG. 10B, the ink storage is performed in a state where the liquid level does not match in the ink storage portions 352a and 352b. When the ink level is detected by the ink detection electrode 357b of one of the ink storage portions 352b when ink is supplied to the portions 352a and 352b, the liquid level does not match in both the ink storage portions 352a and 352b. If the supply of ink is stopped in the state and both ink storage portions 352a and 352b are set to a negative pressure, the negative pressure in both ink storage portions 352a and 352b is different, resulting in ejection failure and ink leakage. You cannot record the correct image. In addition, since the liquid level does not match, ink replenishment supply to the ink storage portions 352a and 352b and a negative pressure operation are performed more than in the normal use state, and troubles such as wasteful consumption of ink occur. End up. When adjusting the liquid level in order to prevent this problem, the ink is sucked from the nozzle and the inks are mixed with each other, and there is a high possibility that color mixing occurs. Further, the sucked ink becomes waste ink as it is, and wastes ink.

  In order to solve these problems, some proposals have been conventionally made. In the ink jet recording apparatus disclosed in Patent Document 1, an intermediate ink tank and a pressure sensor for detecting negative pressure of ink in the recording head are provided between the ink cartridge and the recording head, and the pressure sensor detects the ink in the recording head. The negative pressure is detected and the intermediate ink tank is moved up and down to maintain the ink in the recording head at a desired negative pressure.

  Further, in the ink supply device disclosed in Patent Document 2, the pressure in the main tank chamber decreases from the sub tank chamber having the meniscus forming member attached to the main tank chamber for storing ink as the ink is consumed. In this case, ink corresponding to the reduced pressure is automatically supplied from the sub tank chamber to maintain a desired negative pressure.

  The ink-jet pen disclosed in Patent Document 3 is filled with ink in a sealed ink tank, provided with a vent hole that is open to the atmosphere at one end, and when the ink in the ink tank is consumed, Air is supplied into the ink tank through the air holes so as to maintain the desired negative pressure in the ink tank.

  In the ink jet recording apparatus disclosed in Patent Document 1, since the recording head, the intermediate ink tank, and the back pressure sensor are disposed at separate locations, the configuration is complicated and the size is increased. Further, a mechanism for moving the intermediate ink tank up and down and its control are necessary, and the apparatus situation becomes complicated. Furthermore, it is difficult to accurately perform negative pressure control when bubbles enter the intermediate ink tank for some reason during the formation of back pressure.

  Further, in the ink supply device disclosed in Patent Document 2, it is difficult to maintain a desired negative pressure due to deterioration of the meniscus forming member. Further, when bubbles are introduced into the sub tank chamber for some reason during the formation of the negative pressure, the negative pressure control becomes difficult.

  Furthermore, in the ink-jet pen disclosed in Patent Document 3, since the ink tank is always open to the atmosphere through the vent hole, there is a high possibility that air bubbles will be mixed in, and air bubbles that have entered for some reason during negative pressure formation May enter the head flow path, which makes it difficult to control the negative pressure.

  The present invention solves such a problem, and when the negative pressure in the sub-tank capable of storing ink of two or more colors is reformed, the liquid level of each color is surely matched to make the difference in liquid level. It is an object of the present invention to provide an image forming apparatus capable of preventing wasteful consumption of ink by preventing image deterioration and ink leakage due to ink and preventing repeated unintended negative pressure re-forming operations. .

  The image forming apparatus according to the present invention is equipped with a recording head for ejecting recording liquid droplets from a nozzle, the recording head is supplied with the recording liquid, and the recording liquid is replenished from a main tank on the apparatus body side. In an image forming apparatus in which one or a plurality of head units each composed of a sub tank to be supplied are mounted on a carriage, a recording liquid supply mechanism that replenishes a recording liquid from a main tank on the apparatus body side to the sub tank and a control unit, The recording liquid supply mechanism includes a forward transfer liquid mechanism for supplying the recording liquid to the sub tank and a reverse transfer liquid mechanism for supplying the recording liquid from the sub tank to the main tank, and the control unit Is provided in the sub tank when the inside of the sub tank is opened to the atmosphere. When the recording liquid level is detected by the liquid level detection electrode that detects the recording liquid level, the recording liquid in the sub-tank is sent to the main tank by a predetermined amount by the reverse transfer liquid mechanism of the recording liquid supply mechanism. After that, the recording liquid is supplemented and supplied from the main tank to the sub tank by the positive transfer liquid mechanism of the recording liquid supply mechanism, and then the inside of the sub tank is set to a negative pressure.

  The sub-tank has an ink storage unit for storing recording liquids of a plurality of colors, and the control unit is a liquid level detection electrode for detecting the liquid level of the recording liquid provided in any one of the ink storage units. When the liquid level is detected, a predetermined amount of the recording liquid in the ink storage section in which the liquid level of the recording liquid is detected by the liquid level detection electrode is sent to the main tank by the reverse transfer liquid mechanism of the recording liquid supply mechanism. Features.

  In addition, the sub tank includes an ink storage unit that stores recording liquids of a plurality of colors, and the control unit detects a liquid level of the recording liquid provided in the ink storage unit for each color of the plurality of ink storage units. The liquid level detection electrode detects the liquid level of the recording liquid, and the liquid level detection electrode feeds the recording liquid in the ink container for each color to the main tank by a reverse transfer liquid mechanism of the recording liquid supply mechanism. The process is sequentially repeated for each color.

  In addition, the control unit starts feeding the recording liquid in the sub-tank to the main tank by the reverse transfer liquid mechanism of the recording liquid supply mechanism, and no longer detects the liquid level of the recording liquid by the liquid level detection electrode. The recording liquid in the sub-tank is fed to the main tank for a predetermined time.

  Further, the control unit may vary the predetermined time for feeding the recording liquid in the sub tank to the main tank by the reverse transfer liquid mechanism of the recording liquid supply mechanism according to the temperature in the apparatus main body, or It is variable according to the viscosity of the recording liquid.

  In addition, when the recording liquid is replenished and supplied from the main tank to the sub tank by the normal transfer liquid mechanism of the recording liquid supply mechanism, the control unit records when the liquid level of the recording liquid is detected by the liquid level detection electrode. The replenishment supply of the liquid is stopped to make the inside of the sub tank have a negative pressure.

  This invention detects the liquid level of the recording liquid provided in the sub tank when the sub tank is opened to the atmosphere when the sub tank is opened to the atmosphere after the sub tank is opened to the atmosphere and the recording liquid is replenished and supplied. When the liquid level of the recording liquid is detected by the liquid level detection electrode, the recording liquid in the sub-tank is fed to the main tank by a fixed amount by the reverse transfer liquid mechanism of the recording liquid supply mechanism, and then the forward transfer liquid of the recording liquid supply mechanism Since the recording tank is replenished and supplied from the main tank to the sub tank by the mechanism and the sub tank is set to a negative pressure, when the sub tank is set to a negative pressure, the liquid level of the recording liquid in the sub tank is always kept at a constant level. It is possible to prevent unintentional negative pressure regenerating operation from being performed and to prevent wasteful consumption of the recording liquid.

  In addition, when the sub tank has an ink container that stores recording liquids of a plurality of colors, the liquid level of the recording liquid is detected by a liquid level detection electrode that detects the liquid level of the recording liquid provided in any of the ink containers. In this case, the recording liquid in the ink container, which has detected the liquid level of the recording liquid with the liquid level detection electrode, is sent to the main tank by a fixed amount by the reverse transfer liquid mechanism of the recording liquid supply mechanism, thereby making the sub tank a negative pressure. When the recording liquid level in all the ink storage units can be kept constant, image deterioration and ink leakage due to the difference in liquid level are prevented, and unintended negative pressure regenerating operation is prevented from being recorded. It is possible to prevent wasteful consumption of the liquid.

  In addition, the recording liquid level detection process of the recording liquid in the ink storage unit for storing the recording liquids of a plurality of colors and the process of feeding the recording liquid in the ink storage unit to the main tank are sequentially repeated for each color, thereby recording for each color. When liquid is fed to the main tank, it is not necessary to drive the liquid feed pump at the same time, and liquid feeding to the main tank can be controlled with power saving. Furthermore, by sequentially performing the detection of the ink liquid level for each color without simultaneously performing the detection, the liquid level detection process for a plurality of colors can be performed by one liquid level detection circuit provided in the control unit. The configuration can be simplified and the cost can be reduced.

  Furthermore, the recording liquid supply mechanism reverse transfer liquid mechanism starts feeding the recording liquid in the ink storage section of the sub tank to the main tank, and the liquid level detection electrode stops detecting the liquid level of the recording liquid for a predetermined time. By sending the recording liquid in the ink storage section to the main tank, the liquid level of the recording liquid in the ink storage section can be made constant after the recording liquid in the ink storage section of the sub tank is sent to the main tank. It is possible to prevent image deterioration and ink leakage due to the difference in level, and to prevent unintended negative pressure re-forming operation from being performed, thereby preventing wasteful consumption of the recording liquid.

  Further, by changing the predetermined time for feeding the recording liquid in the ink storage portion of the sub tank to the main tank by the reverse transfer liquid mechanism of the recording liquid supply mechanism according to the temperature in the apparatus main body and the viscosity of the recording liquid, When the inside is set to negative pressure, the liquid level of the recording liquid in all ink storage units can be kept at a constant level, preventing image deterioration and ink leakage due to the difference in liquid level, and unintentional negative pressure regenerating operation It is possible to prevent wasteful consumption of the recording liquid by preventing the implementation.

  Further, when the recording liquid is replenished and supplied from the main tank into the ink storage portion of the sub tank by the normal transfer liquid mechanism of the recording liquid supply mechanism, if the liquid level of the recording liquid is detected by the liquid level detection electrode, the replenishing supply of the recording liquid is performed. By stopping and applying a negative pressure in the ink storage section of the sub tank, the liquid level of the recording liquid in all the ink storage sections can be kept at a constant level, preventing image deterioration and ink leakage due to the difference in liquid level. At the same time, it is possible to prevent unintended negative pressure regenerating operation from being performed and to prevent wasteful consumption of recording liquid.

It is the perspective view which looked at the image forming apparatus of this invention from the front side. 1 is a schematic configuration diagram illustrating an overall configuration of a mechanism unit of an image forming apparatus according to the present invention. It is a principal part top view of the mechanism part of the image forming apparatus of this invention. It is a perspective view which shows a sub tank. It is side surface sectional drawing which shows the structure of the ink accommodating part of a subtank. It is a figure which shows the state of a subtank which has an ink accommodating part of two colors, and a negative pressure formation. It is a block diagram of an ink supply mechanism part. It is a block diagram of a liquid feeding pump. It is a flowchart which shows the negative pressure formation process of an ink accommodating part. It is a block diagram of the sub tank which has a 2 color ink accommodating part.

  1 to 3 show a configuration of an image forming apparatus according to the present invention, FIG. 1 is a perspective view of the image forming apparatus as viewed from the front side, and FIG. 2 is a schematic configuration diagram showing an overall configuration of a mechanism portion of the image forming apparatus. FIG. 3 is a plan view of the main part of the mechanism.

  As shown in FIG. 1, an image forming apparatus includes an apparatus main body 1, a paper feed tray 2 for loading a recording sheet attached to the apparatus main body 1, and an image recorded (formed) attached to the apparatus main body 1. And a paper discharge tray 3 for discharging and stocking the recorded paper. One end side of the front surface 4 of the apparatus main body 1 has a cartridge loading portion 6 that protrudes forward from the front surface 4 and is lower than the upper surface 5. On the upper surface of the cartridge loading portion 6, operation keys, indicators, etc. The operation unit 7 is arranged.

  The cartridge loading unit 6 includes a plurality of main tanks each containing recording liquids (inks) of different colors, for example, black (K) ink, cyan (C) ink, magenta (M) ink, and yellow (Y) ink. A certain ink cartridge 10k, 10c, 10m, 10y can be inserted and loaded from the front side of the apparatus main body 1 toward the rear side. When the liquid cartridge 10 is attached to or detached from the front side of the cartridge loading unit 6, A front cover (cartridge cover) 8 to be opened is provided to be openable and closable.

  As shown in FIG. 3, the mechanism of this image forming apparatus is configured to move the carriage 33 in the main scanning direction by a guide rod 31 and a stay 32 which are guide members horizontally mounted on the left and right side plates 21A and 21B constituting the frame 21. It is slidably held and moved and scanned in the direction of the arrow (carriage main scanning direction) in FIG. 3 by a main scanning motor (not shown). The carriage 33 is provided with a recording head 34 having a plurality of nozzle rows that discharge droplets of black (K), cyan (C), magenta (M), and yellow (Y), and a plurality of nozzles (discharge ports). ) Are arranged in a direction crossing the main scanning direction, and the droplet discharge direction is directed downward. The recording head 34 includes a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses a phase change due to liquid film boiling using an electrothermal transducer such as a heating resistor, a shape memory alloy actuator that uses a metal phase change due to a temperature change, An electrostatic actuator using an electrostatic force or the like provided as energy generating means for ejecting ink droplets can be used.

  In addition, the carriage 33 is equipped with sub tanks 35k, 35c, 35m, and 35y for each color for supplying each color ink to each recording head 34, respectively. The sub tank 35 is supplied with ink from the ink cartridges 10 of each color mounted in the cartridge loading unit 6 via the ink supply tubes 36 of the respective colors. The cartridge loading unit 6 is provided with a unit of a liquid feeding pump 23 for feeding ink in the ink cartridge 10. Further, the ink supply tube 36 from the ink cartridge loading section 6 to the sub tank 35 is fixed and held by the main body side holder 25 on the rear plate 21C constituting the frame 21 in the middle of turning. Further, it is fixed on the carriage 33 by the fixing rib 26.

  As shown in the perspective view of FIG. 4, the sub tank 35 is provided above the recording head 34 via a filter unit 37. The sub tank 35 has an opening on the side surface of the ink containing portion 352 of the tank main body 351, and a flexible film member 353 is attached to the opening by adhesion or welding and sealed, and the inside of the ink containing portion 352 is sealed. 5, a spring 354 for biasing the film member 353 outward is provided between the tank body 251 and the film member 353, and a negative pressure generating mechanism is provided by the film member 353 and the spring 354. It is composed. Further, a negative pressure detection lever 355 that is displaced in accordance with the displacement of the film member 353 is attached to the tank body 351 so as to be swingable. In addition, an air release passage for opening the ink containing portion 352 to the atmosphere is formed in the upper portion of the tank body 351, and an air release mechanism 356 for opening and closing the air release passage is provided. Further, the upper surface of the tank main body 351 has an ink supply port 357 for supplying ink from the ink cartridge to the ink container 352 and two ink detection electrodes 358 for detecting ink in the ink container 352. An ink detection mechanism 359 is provided.

  When the recording head 34 has a plurality of rows, for example, two nozzle rows, as shown in the front view of FIG. 6A, the side view of FIG. 6B, and the top view of FIG. The ink storage units 352a and 352b for storing ink are provided, and the ink storage units 352a and 352b each include an air release mechanism 356, an ink supply port 357, and an ink detection mechanism unit 359.

  As shown in FIG. 2, one sheet of recording paper 42 is fed from the paper stacking unit 41 as a paper feeding unit for feeding the recording paper 42 stacked on the paper stacking unit (bottom plate) 41 of the paper feed tray 2. A half-moon roller (sheet feeding roller) 43 that separates and feeds the sheet and a separation pad 44 made of a material having a large friction coefficient are provided opposite to the sheet feeding roller 43. The separation pad 44 is urged toward the sheet feeding roller 43 side. Yes. A transport belt 51 for electrostatically attracting and transporting the recording paper 42 as a transport section for transporting the recording paper 42 fed from the paper feed section below the recording head 34, and a paper feed The counter roller 52 for transporting the recording paper 42 sent from the section via the guide 45 sandwiched between the transport belt 51 and the recording paper 42 sent substantially vertically upward is changed in direction by about 90 degrees to the transport belt. The conveyance guide 53 for making it follow on 51 and the front-end | tip pressurizing roller 55 urged | biased by the pressing member 54 at the conveyance belt 51 side are provided. In addition, a charging roller 56 that is a charging unit for charging the surface of the conveyance belt 51 is provided.

  The transport belt 51 is an endless belt, and is configured to be looped around the transport roller 57 and the tension roller 58 in the belt transport direction of FIG. The charging roller 56 is disposed so as to come into contact with the surface layer of the conveyor belt 51 and to be rotated by the rotation of the conveyor belt 51, and 2.5N is applied to both ends of the shaft as a pressing force. In addition, a guide member 61 is disposed on the back side of the conveyor belt 51 so as to correspond to a printing area by the recording head 54. The upper surface of the guide member 61 protrudes closer to the recording head 34 than the tangent line between the conveying roller 57 and the tension roller 58 that support the conveying belt 51. As a result, the conveyance belt 51 is pushed up and guided by the upper surface of the guide member 61 in the printing region, so that highly accurate flatness is maintained.

  Further, as a paper discharge unit for discharging the recording paper 42 recorded by the recording head 34, a separation claw 71 for separating the recording paper 42 from the conveying belt 51, a paper discharge roller 72, and a paper discharge roller 73, And a paper discharge tray 3 below the paper discharge roller 72. Here, the height from between the paper discharge roller 72 and the paper discharge roller 73 to the paper discharge tray 3 is increased to some extent in order to increase the amount that can be stored in the paper discharge tray 3.

  A double-sided paper feeding unit 81 is detachably attached to the back surface of the apparatus body 1. The double-sided paper feeding unit 81 takes in the recording paper 42 returned by the reverse rotation of the transport belt 51, reverses it, and feeds it again between the counter roller 52 and the transport belt 51. A manual paper feed unit 82 is provided on the upper surface of the duplex paper feed unit 81.

  Further, as shown in FIG. 3, a maintenance / recovery device 90 for maintaining and recovering the state of the nozzles of the recording head 34 is arranged in the non-printing area on one side of the carriage 33 in the scanning direction. The maintenance / recovery device 90 includes a recovery device 91 having four suction caps 92 for capping each nozzle surface of the recording head 34, a wiper blade 93 which is a blade member for wiping the nozzle surface, and an increaser. In order to discharge viscous ink, an empty discharge receiver 94 for receiving ink droplets when discharging ink droplets that do not contribute to recording is provided.

  Further, as shown in FIG. 3, when the non-printing area on the other side in the scanning direction of the carriage 33 is used to perform idle ejection for ejecting ink that does not contribute to recording in order to eject ink that has been thickened during recording or the like. An empty discharge receiver 98 for receiving the ink is disposed, and the empty discharge receiver 98 is provided with an opening 99 and the like along the nozzle row direction of the recording head 34.

  In the image forming apparatus configured as described above, the recording sheets 42 are separated and fed one by one from the sheet feeding tray 2, and the sheet 42 fed substantially vertically upward is guided by the guide 45, and the conveying belt 51 and the counter It is sandwiched between the rollers 52 and conveyed, and further, the leading end is guided by the conveying guide 53 and pressed against the conveying belt 51 by the tip pressing roller 55, and the conveying direction is changed by approximately 90 degrees. At this time, a positive output and a negative output are alternately repeated from the high-voltage power supply to the charging roller 56 by a control circuit (not shown), that is, an alternating voltage is applied, and a charging voltage pattern in which the conveying belt 51 alternates, that is, In the sub-scanning direction, which is the circumferential direction, plus and minus are alternately charged in a band shape with a predetermined width. When the recording paper 42 is fed onto the conveyance belt 51 that is alternately charged with plus and minus, the recording paper 42 is electrostatically attracted to the conveyance belt 51, and the recording paper 42 is moved by the circular movement of the conveyance belt 51. It is conveyed in the sub-scanning direction. Therefore, by driving the recording head 34 according to the image signal while moving the carriage 33, ink droplets are ejected onto the stopped recording paper 42 to record one line, and the recording paper 42 is conveyed by a predetermined amount. After that, the next line is recorded. Upon receiving a recording end signal or a signal that the trailing edge of the recording paper 42 has reached the recording area, the recording operation is terminated and the recording paper 42 is discharged onto the paper discharge tray 3.

  Further, while waiting for printing (recording), the carriage 33 is moved to the maintenance / recovery device 90 side, the recording head 34 is capped by each suction cap 92 of the recovery device 91, and the ink is dried by keeping the nozzle in a wet state. Prevents ejection failure due to Further, a recovery operation is performed in which ink is sucked from the nozzles while the recording head 34 is capped by the suction cap 92 and the thickened ink and bubbles are discharged. In addition, an idle ejection operation for ejecting ink not related to recording is performed before the start of recording or during recording. As a result, the stable ejection performance of the recording head 34 is maintained.

  During this standby, the ink supply mechanism that supplies the ink from the ink cartridge 10 to the sub tank 35 while the recording head 34 is capped by the suction cap 92 of the recovery device 91 by moving the carriage 33 to the maintenance recovery device 90 side. As shown in the block diagram of FIG. 7, the ink supply port portion 357 of the ink cartridge 10 and the sub tank 35 is connected by the ink supply tube 36 and the liquid feed pump 23. The suction pump 912 that sucks ink from the nozzle and sends it to the waste liquid tank 911 while the recording head 34 is capped by the suction cap 92 of the liquid feeding pump 23 and the maintenance and recovery device 90 is sent to the ink detection electrode 358 of the ink detection mechanism 356 of the sub tank 35. The drive is controlled by the control unit 100 according to the state.

  When the recording head 34 has two nozzle rows and the sub tank 35 has two ink storage portions 352a and 352b, an ink supply mechanism 38 is provided corresponding to each of the ink storage portions 352a and 352b.

  As shown in the block diagram of FIG. 8, the liquid feed pump 23 has a liquid feed tube 231 made of rubber, for example, which is elastic inside and is wound in an arc shape, and a plurality of, for example, four pump rotors 232 are pump-driven motors. Is a tube pump that locally crushes the liquid feeding tube 231 sequentially and moves the ink in the rotational direction of the pump rotor 232 to feed the liquid, and the pump rotor 232 is rotated forward as indicated by an arrow A. In this case, when the ink is sent from the carriage 33 to the sub tank 35 and the pump rotor 232 is reversed as indicated by the arrow B, it has a forward / reverse liquid feeding function for feeding ink from the sub tank 35 to the carriage 33.

  For example, when the recording head has two nozzle rows and the sub tank 35 has ink storage portions 352a and 352b for storing two colors of ink, the ink supply mechanism 38 uses the ink cartridge 10 to the ink storage portions 352a and 352b of the sub tank 35. When the ink is supplied to the ink container 352, the ink container 352 is opened to the atmosphere by the atmosphere release mechanism 356 and the film member 353 is pressed against the spring 354 by the negative pressure detection lever 355. After that, the air release mechanism 356 is closed and the negative pressure detection lever 355 is returned to generate a negative pressure in the ink containing portions 352a and 352b so that the recording head 34 can record an image.

  The operation when the ink is supplied to the ink storage portions 352a and 352b for storing the two colors of ink to form a negative pressure will be described with reference to the flowchart of FIG.

  When the negative pressure forming operation is started, the control unit 100 opens the ink storage units 352a and 352b to the atmosphere by the respective atmospheric release mechanisms 356 of the sub tanks 35 (step S1). In this state, the control unit 100 determines whether the ink level in the ink containing unit 352a is detected by the ink detection electrode 358 of the first color ink containing unit 352a (step S2). As a result of this determination, when the ink level is detected by the ink detection electrode 358 of the first color ink container 352a as shown in the side sectional view of the sub tank 35 in FIG. The liquid pump 23 is reversely operated to return the ink in the ink containing portion 352a to the ink cartridge 10 side, and the ink level in the ink containing portion 352a is lowered (step S3). The reverse operation of the liquid feed pump 23 is stopped when a predetermined time elapses after the ink liquid level in the ink containing portion 352a is lowered and the ink detection electrode 358 no longer detects the ink liquid level (step S4). S5, S6).

  In addition, the control unit 100 determines whether the ink detection electrode 358 of the first color ink storage unit 352a detects the ink level in the ink storage unit 352a, and uses the ink level in the ink storage unit 352a as the ink. When the detection electrode 358 is not detected (step S2) and when the ink liquid level in the ink containing portion 352a is not detected by the ink detection electrode 358 and the reverse operation of the liquid feed pump 23 is stopped (step S6), the second color It is determined whether the ink detection electrode 358 of the ink storage portion 352b detects the ink level in the ink storage portion 352b (step S7), and as shown in FIG. 6B, the ink in the ink storage portion 352b is detected. When the ink liquid level is not detected by the detection electrode 358, the liquid feeding pumps 23 for the first color and the second color are driven to rotate in the forward direction so that the ink containing portions 352a, Supplying ink from the ink cartridge 10 to 52 b (step S12). When the ink level is detected by the ink detection electrodes 358 of the ink storage portions 352a and 352b by the supply of the ink, the driving of the liquid feed pump 23 is stopped (steps S13 and S14). Thereafter, the ink containing portions 352a and 352b are set to a negative pressure (step S15).

  When the ink level is detected by the ink detection electrode 358 of the ink containing portion 352b, the liquid feeding pump 23 for the second color is reversely operated to return the ink in the ink containing portion 352b to the ink cartridge 10 side. The ink level in the ink containing portion 352b is lowered (step S8). The reverse operation of the liquid feed pump 23 is stopped when a predetermined time elapses after the ink liquid level in the ink containing portion 352a is lowered and the ink detection electrode 358 no longer detects the ink liquid level (step S9, S10, S11).

  Thereafter, the liquid pumps 23 for the first color and the second color are driven to rotate forward to supply ink from the ink cartridges 10 to the ink storage portions 352a and 352b (step S12). When the ink level is detected by the ink detection electrodes 358 of the ink storage portions 352a and 352b by the supply of the ink, the driving of the liquid feed pump 23 is stopped (steps S13 and S14). Thereafter, the ink containing portions 352a and 352b are set to a negative pressure (step S15).

  As described above, when the ink detection electrode 358 detects the ink level in any of the ink storage portions 352a and 352b, the ink detection level is detected by the ink detection electrode 358, and the ink supply portion 352 is supplied. The liquid pump 23 is reversely operated to return the ink in the ink containing portion 352 to the ink cartridge 10 side, and then both the liquid feed pumps 23 are forwardly operated to cause the ink containing portions 352a and 352b to receive ink from each ink cartridge 10. After the ink is supplied, the ink containing portions 352a and 352b are set to a negative pressure. Therefore, when the ink containing portions 352a and 352b are set to a negative pressure, the ink in the ink containing portions 352a and 352b is supplied as shown in FIG. The liquid level can be maintained at a constant level, and image deterioration and ink leakage can be caused by the difference in the ink liquid level in the ink containing portions 352a and 352b. Ink and prevent unintended negative 圧再 forming operation carried out it is possible to prevent possible to prevent the wasting.

Further, when it is detected that the ink level is detected by the ink detection electrode 358 of the ink container 352a for the first color, the liquid feeding pump 23 for the first color is operated in reverse to remove the ink in the ink container 352a. After returning to the cartridge 10 side and lowering the ink level in the ink container 352a, the second color is detected when the ink level is detected by the ink detection electrode 358 of the second color ink container 352b. The liquid feed pump 23 is rotated in the reverse direction to return the ink in the ink containing portion 352b to the ink cartridge 10 side and lower the ink level in the ink containing portion 352b. It is not necessary to reversely rotate the liquid feeding pump 23 at the same time. When the liquid feeding pump 23 reverses, it is not necessary to use a large amount of power at the same time. It is possible to reverse control of-flops 23. Furthermore, the first color is detected without simultaneously detecting the ink level by the ink detection electrode 358 provided in the first color ink storage portion 352a and the ink detection electrode 358 provided in the second color ink storage portion 352b. Since the ink level of the second color is detected after detecting the ink level of the first color, the ink level detection process for the first color and the second color can be performed by one liquid level detection circuit provided in the control unit 100, The circuit configuration of the control unit 100 can be simplified and the cost can be reduced.
Note that the first color liquid feeding pump 23 and the second color liquid feeding pump 23 may be simultaneously operated in reverse.

  In the above description, after the ink in the ink storage portions 352a and 352b is returned to the ink cartridge 10 side, the liquid feeding pump 23 for the first color and the second color is operated in the normal direction to move the ink storage portions 352a and 352b from the ink cartridges 10 to the ink storage portions 352a and 352b. Although the case where the ink is supplied has been described, the first color liquid feed pump 23 is rotated forward to supply ink from the ink cartridge 10 to the ink storage portion 352a, and then the second color liquid feed pump 23 is rotated forward. Ink may be supplied from the ink cartridge 10 to the ink storage portion 352b so that a large amount of power is not used at the same time.

  In the above description, the case where the sub tank 35 has the ink storage portions 352a and 352b of two colors is shown, but also when the sub tank 35 has the ink storage portion 352 of one color, the ink detection electrode 358 detects the ink level. When the ink detection electrode 358 detects the ink liquid level, the liquid feed pump 23 is operated in the reverse direction to return the ink in the ink containing portion 352 to the ink cartridge 10 side, and then the liquid feed pump 23 is operated in the normal direction. After the ink is supplied from the ink cartridge 10 to the ink containing portion 352, the ink containing portion 352 is set to a negative pressure so that when the ink containing portion 352 is set to a negative pressure, the ink liquid level in the ink containing portion 352 is always changed. Can be at a certain level.

  Further, in the above description, when the liquid feeding pump 23 is operated in reverse to return the ink in the ink containing portion 352 to the ink cartridge 10 side, the ink liquid level in the ink containing portion 352 is lowered and the ink detection electrode 358 causes ink liquid to fall. The case where the reverse operation of the liquid feed pump 23 is stopped when a predetermined time has elapsed from when the surface is no longer detected has been described. The predetermined time for stopping the reverse operation of the liquid feed pump 23 is set as the viscosity of the ink. It is good to change according to it. That is, when the ink viscosity is high, the ink flow rate per unit time sent from the liquid feed pump 23 decreases, and when the ink viscosity is low, the ink flow rate per unit time sent from the liquid feed pump 23 increases. The viscosity of this ink varies with temperature. Therefore, the temperature in the image forming apparatus is detected by a temperature sensor, and the control unit 100 shortens the predetermined time for reversely feeding ink when the temperature detected by the temperature sensor is high, and the predetermined value for reversely feeding ink when the temperature is low. What is necessary is just to lengthen time and to change predetermined time according to temperature. Alternatively, the viscosity of the ink may be directly detected by a viscosity sensor, and the predetermined time during which the ink is fed back may be varied according to the detected viscosity.

DESCRIPTION OF SYMBOLS 1; Apparatus main body, 2; Paper feed tray, 3; Paper discharge tray, 6: Cartridge loading part,
7; operation unit, 10; ink cartridge, 23; liquid feed pump, 34; recording head,
35; sub tank, 37; filter unit, 38; ink supply mechanism,
351; tank main body, 352; ink container, 353; film member,
354; Spring, 355; Negative pressure detection lever, 356; Air release mechanism,
357; ink supply port, 358; ink detection electrode, 359; ink detection mechanism.

Japanese Patent Laid-Open No. 2003-341028 Japanese Patent No. 3,269,268 Japanese Patent No. 2,898,746

Claims (7)

A head unit comprising a recording head for ejecting recording liquid droplets from a nozzle, and a sub-tank mounted on the recording head, supplying the recording liquid to the recording head, and supplemented with the recording liquid from the main tank on the apparatus body side In an image forming apparatus in which one or more are mounted on a carriage,
A recording liquid supply mechanism that replenishes the recording liquid from the main tank on the apparatus main body side to the sub tank and a control unit;
The recording liquid supply mechanism includes a normal transfer liquid mechanism for supplying the recording liquid to the sub tank, and a reverse transfer liquid mechanism for supplying the recording liquid from the sub tank to the main tank,
The controller is configured to release a recording liquid provided in the sub tank when the sub tank is opened to the atmosphere when the sub tank is opened to the atmosphere when the sub tank is opened to the atmosphere and the recording liquid is replenished and supplied. When the recording liquid level is detected by the liquid level detection electrode for detecting the surface, the recording liquid in the sub tank is supplied to the main tank by a predetermined amount by the reverse transfer liquid mechanism of the recording liquid supply mechanism, and then the recording liquid is detected. An image forming apparatus, wherein a recording liquid is supplementally supplied from the main tank into the sub tank by a positive transfer liquid mechanism of a liquid supply mechanism, and then the sub tank is set to a negative pressure.   The sub-tank has an ink storage unit for storing recording liquids of a plurality of colors, and the control unit is a liquid level detection electrode for detecting the liquid level of the recording liquid provided in any one of the ink storage units. When the liquid level is detected, a predetermined amount of the recording liquid in the ink storage section in which the liquid level of the recording liquid is detected by the liquid level detection electrode is sent to the main tank by the reverse transfer liquid mechanism of the recording liquid supply mechanism. The image forming apparatus according to claim 1, wherein:   The sub-tank has an ink storage section that stores recording liquids of a plurality of colors, and the control section detects a liquid level of the recording liquid provided in the ink storage section for each color of the plurality of ink storage sections. Processing for detecting the liquid level of the recording liquid with the detection electrode, and processing for feeding a predetermined amount of the recording liquid in the ink container for each color to the main tank by the reverse transfer liquid mechanism of the recording liquid supply mechanism with the liquid level detection electrode The image forming apparatus according to claim 1, wherein the process is sequentially repeated for each color.   The control unit starts supplying the recording liquid in the sub-tank to the main tank by the reverse transfer liquid mechanism of the recording liquid supply mechanism and does not detect the liquid level of the recording liquid by the liquid level detection electrode. 4. The image forming apparatus according to claim 1, wherein the recording liquid in the sub tank is fed to the main tank for a time.   The control unit varies the predetermined time for feeding the recording liquid in the sub tank to the main tank by a reverse transfer liquid mechanism of the recording liquid supply mechanism according to the temperature in the apparatus main body. The image forming apparatus according to claim 4.   The control unit varies the predetermined time for feeding the recording liquid in the sub tank to the main tank by a reverse transfer liquid mechanism of the recording liquid supply mechanism according to the viscosity of the recording liquid. Item 5. The image forming apparatus according to Item 4.   When the recording liquid is replenished and supplied from the main tank to the sub tank by the positive transfer liquid mechanism of the recording liquid supply mechanism, the control unit detects the recording liquid when the liquid level detection electrode detects the recording liquid level. The image forming apparatus according to claim 1, wherein the replenishment supply is stopped to make the inside of the sub tank have a negative pressure.

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