JP4190001B2 - Image forming apparatus - Google Patents

Description

The present invention relates to an image forming apparatus including a sub tank .

  2. Description of the Related Art In an inkjet recording apparatus used as various image forming apparatuses such as a printer, a facsimile, a copying apparatus, and a plotter, a small-capacity subtank (liquid that supplies liquid ink to an inkjet head that is a droplet discharge head is provided on a carriage. There is a known device that is equipped with a large-capacity ink cartridge (main tank), which is a liquid storage tank, installed on the main body side of the apparatus, and supplies ink to the sub tank from the main tank on the main body side. Yes.

As such a subtank and a liquid supply device including a subtank, a negative pressure generating unit that expands and contracts by supplying and discharging a fluid is provided inside the subtank, and an atmosphere opening unit that opens the subtank to the atmosphere and an ink supply When supplying liquid from the main tank to the sub-tank, the sub-tank is opened to the atmosphere by the atmospheric release unit, and the negative pressure generating unit is expanded by supplying the fluid to supply the liquid to the sub-tank. In some cases, after the sub tank is replenished with liquid, the air release portion is shut off and the negative pressure generating portion is contracted to generate a negative pressure in the sub tank.
JP 2003-1846 A

In addition, an ink chamber that deforms in accordance with the ink capacity while maintaining a negative pressure of the ink, an ink introduction unit and an exhaust unit provided in the upper part of the ink chamber, and an ink supply unit provided in the lower part of the ink chamber are provided. And the ink introduction portion has a valve seat formed of an elastic body and having an ink introduction path, a valve body, and a replenishing valve made of an elastic member that presses the valve body against the valve seat and blocks the ink introduction path. The exhaust part is known to have a seal part formed of an elastic body and provided with a slit closed at the center.
JP 2002-86748 A

  In the sub-tank of Patent Document 1 described above, in order to provide a negative pressure generator that expands and contracts by supplying and discharging fluid inside the sub-tank, separately from the liquid supplied to the sub-tank to generate negative pressure. The structure is complicated because it is necessary to supply and discharge a fluid for expanding and contracting the negative pressure generating portion.

  Further, even in the sub-tank of Patent Document 2, a flexible container that stores ink is stored in the case, and the flexible container is inflated and contracted by suctioning / opening to the atmosphere. In addition, the configuration of the negative pressure generator is complicated.

The present invention has been made in view of the above problems, and an object of the present invention is to generate negative pressure with a simple configuration and to reduce variations in negative pressure associated with liquid filling of a sub tank .

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A subtank for supplying liquid to a droplet discharge head for discharging droplets, comprising a flexible film-like member constituting at least one surface, and an elastic member for biasing the flexible film-like member outward And a negative pressure generating part that generates a negative pressure by expanding and contracting by supplying and discharging the liquid, and abuts on the outer surface side of the film-like member, thereby deforming the film-like member A sub-tank having a lever that can be displaced according to the air and provided with an air release means for opening the inside to the atmosphere;
A main tank for supplying liquid to the sub tank;
A full tank detecting means for detecting the position of the lever of the sub tank;
After supplying the liquid from the main tank to the sub tank in a state where the sub tank is opened to the atmosphere by the atmosphere releasing means, the atmosphere releasing means is closed and a part of the liquid in the sub tank is discharged to discharge the negative. Store the position of the lever when the pressure generating part is contracted to generate a negative pressure in the sub tank,
Means for controlling to stop the supply of liquid when the position of the lever comes to the memorized position when supplying liquid from the main tank to the sub tank without opening the sub tank to the atmosphere; The configuration is provided.

The image forming apparatus according to the present invention includes a flexible film-like member that forms at least one surface, and an elastic member that urges the flexible film-like member outward, and supplies liquid. There is a negative pressure generating part that generates a negative pressure inside by expanding and contracting by discharging, further abutting on the outer surface side of the film-like member, and having a lever that can be displaced according to the deformation of the film-like member, A sub tank equipped with an air release means for opening the inside to the atmosphere, a main tank for supplying liquid to the sub tank, a full tank detection means for detecting the position of the sub tank lever, and a state where the sub tank is opened to the atmosphere by the air release means. After supplying the liquid from the main tank to the sub tank, close the air release means and discharge part of the liquid in the sub tank to contract the negative pressure generating part and generate negative pressure in the sub tank Controls the position of the lever when it is stored, and when the liquid is supplied from the main tank to the sub tank without opening the sub tank to the atmosphere, the supply of the liquid is stopped when the position of the lever reaches the stored position. Therefore, a negative pressure can be generated with a simple configuration, and variations in the negative pressure associated with the liquid filling of the sub tank can be reduced.

  An ink jet recording apparatus as an image forming apparatus according to the present invention including a liquid supply apparatus according to the present invention including a sub tank according to the present invention will be described. FIG. 1 is a perspective explanatory view of the ink jet recording apparatus as viewed from the front side.

  The ink jet recording apparatus includes an apparatus main body 1, a paper feed tray 2 loaded in the apparatus main body 1 for loading paper as a recording medium, and a paper loaded in the apparatus main body 1 on which an image is recorded (formed). A discharge tray 3 for stocking, and further, on one end portion side of the front surface 4 of the apparatus main body 1, a cartridge loading portion 6 that protrudes forward from the front surface 4 and is lower than the upper surface 5. An operation unit 7 such as operation keys and a display is arranged on the upper surface of the cartridge loading unit 6. The cartridge loading unit 6 has a front cover 8 that can be opened and closed for attaching and detaching an ink cartridge 10 that is a liquid storage tank (main tank).

  Next, the mechanism part of the ink jet recording apparatus will be described with reference to FIGS. FIG. 2 is a schematic configuration diagram for explaining the overall configuration of the mechanism unit, and FIG.

  A carriage 13 is slidably held in the main scanning direction by guide rods 11 and stays 12 which are horizontally mounted on left and right side plates (not shown), and moved and scanned in the direction of the arrow in FIG. 3 by a main scanning motor (not shown). To do.

  The carriage 13 has a recording head 14 composed of four ink jet heads for ejecting ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk). They are arranged in a direction crossing the main scanning direction, and are mounted with the ink droplet ejection direction facing downward.

  As the ink-jet head constituting the recording head 14, a piezoelectric actuator such as a piezoelectric element, a thermal actuator that utilizes a phase change caused by film boiling of a liquid using an electrothermal transducer such as a heating resistor, and a metal phase change caused by a temperature change. Although a shape memory alloy actuator to be used, an electrostatic actuator using an electrostatic force, or the like provided as energy generating means for ejecting ink can be used. Here, a head using a piezoelectric actuator (piezoelectric element) as energy generating means It is equipped with. Further, the recording head 14 can be constituted by a single inkjet head having a plurality of nozzle rows for ejecting droplets of each color.

  Further, the carriage 13 is equipped with a sub tank 15 which is a liquid container of each color for supplying ink of each color to the recording head 14. Ink is supplied to the sub tank 15 from the main tank (ink cartridge) 10 for each color through the ink supply tube 16. Here, the main tank 10 stores ink of each color of yellow (Y), cyan (C), magenta (M), and black (Bk) corresponding to each color, but the main tank 10 stores black ink. The tank 10 has a larger ink storage capacity than the main tank 10 that stores other color inks.

  On the other hand, as a paper feeding unit for feeding the paper 22 stacked on the paper stacking unit (pressure plate) 21 of the paper feed tray 3, a half-moon roller (feeding) that separates and feeds the paper 22 from the paper stacking unit 21 one by one. A separation pad 24 made of a material having a large friction coefficient is provided opposite to the sheet roller 23 and the sheet feeding roller 23, and the separation pad 24 is biased toward the sheet feeding roller 23 side.

  As a transport unit for transporting the paper 22 fed from the paper feed unit on the lower side of the recording head 14, a transport belt 31 for transporting the paper 22 by electrostatic adsorption, and a paper feed unit The counter roller 32 for transporting the paper 22 fed through the guide 25 while sandwiching it between the transport belt 31 and the paper 22 fed substantially vertically upward are turned approximately 90 ° and copied onto the transport belt 31. A conveying guide 33 for adjusting the pressure and a tip pressing roller 35 urged toward the conveying belt 31 by a pressing member 34. In addition, a charging roller 36 that is a charging unit for charging the surface of the transport belt 31 is provided.

  Here, the conveyance belt 31 is an endless belt, and is configured to be looped around the conveyance roller 37 and the tension roller 38 in the belt conveyance direction of FIG. The charging roller 36 is disposed so as to contact the surface layer of the conveyor belt 31 and rotate following the rotation of the conveyor belt 31, and applies 2.5 N to both ends of the shaft as a pressing force.

  In addition, a guide member 41 is disposed on the back side of the conveyance belt 31 so as to correspond to a printing area by the recording head 14. The upper surface of the guide member 41 protrudes toward the recording head 14 from the tangent line of the two rollers (the conveyance roller 37 and the tension roller 38) that support the conveyance belt 31. As a result, the conveyance belt 31 is pushed up and guided by the upper surface of the guide member 41 in the printing region, so that highly accurate flatness is maintained.

  Further, a plurality of grooves are formed in the main scanning direction, that is, in a direction orthogonal to the transport direction, on the surface side of the guide member 41 that contacts the back surface of the transport belt 31 to reduce the contact area with the transport belt 31. The conveying belt 31 can be moved along the surface of the guide member 41 smoothly.

  Further, as a paper discharge unit for discharging the paper 22 recorded by the recording head 14, a separation claw 51 for separating the paper 22 from the conveyance belt 31, a paper discharge roller 52, and a paper discharge roller 53 are provided. The paper discharge tray 3 is provided below the paper discharge roller 52. Here, the height from the sheet discharge roller 52 and the sheet discharge roller 53 to the sheet discharge tray 3 is increased to some extent in order to increase the amount that can be stored in the sheet discharge tray 3.

  A double-sided paper feeding unit 61 is detachably mounted on the back surface of the apparatus body 1. The double-sided paper feeding unit 61 takes in the paper 22 returned by the reverse rotation of the transport belt 31, reverses it, and feeds it again between the counter roller 32 and the transport belt 11. A manual paper feed unit 62 is provided on the upper surface of the double-sided paper feed unit 61.

  Further, as shown in FIG. 3, in a non-printing area on both sides in the scanning direction of the carriage 13, a maintenance / recovery mechanism (hereinafter referred to as “subsystem”) 71 for maintaining and recovering the nozzle state of the recording head 14. , 71 are arranged. The subsystems 71 and 72 include cap members 72a, 72b, 72c, and 72d for capping the nozzle surface of the recording head 14, a wiper blade 73 for wiping the nozzle surface, and the like. In the subsystems 71 and 72, the cap member 72a closest to the recording area side is a suction and moisture retention cap connected to a suction pump (not shown), and the other cap members 72b, 72c and 72d are simply moisture retention caps.

  In the ink jet recording apparatus configured as described above, the paper 22 is separated and fed from the paper feed tray 2 one by one, and the paper 22 fed substantially vertically upward is guided by the guide 25, and the conveyance belt 31 and the counter roller 32, and the tip is guided by the transport guide 33 and pressed against the transport belt 31 by the tip pressure roller 35, and the transport direction is changed by approximately 90 °.

  At this time, a positive output and a negative output are alternately repeated from the high voltage power source to the charging roller 36 by a control circuit (not shown), that is, an alternating voltage is applied, and a charging voltage pattern in which the conveying belt 31 is alternating, 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 sheet 22 is fed onto the conveyance belt 31 that is alternately charged with plus and minus, the sheet 22 is electrostatically attracted to the conveyance belt 31, and the sheet 22 is moved in the sub scanning direction by the circular movement of the conveyance belt 31. Be transported.

  Therefore, by driving the recording head 14 according to the image signal while moving the carriage 13, ink droplets are ejected onto the stopped paper 22 to record one line, and after the paper 22 is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal that the trailing edge of the paper 22 has reached the recording area, the recording operation is finished and the paper 22 is discharged onto the paper discharge tray 3.

  During printing (recording) standby, the carriage 13 is moved to the subsystem 37 side, the recording head 14 is capped by the caps 72a to 72d, and the nozzles are kept in a wet state to prevent ejection failure due to ink drying. In addition, a recovery operation for discharging ink not related to recording is performed before starting recording or in the middle of recording to maintain stable discharging performance. Since only the cap member 72a is a suction cap when performing this recovery operation, the target recording head 14 is moved to the position of the cap member 72a and capped.

  Next, details of the ink supply device, which is a liquid supply device in the recording apparatus, will be described with reference to FIGS. 4 is an exploded perspective view of a portion related to the ink supply device, FIG. 5 is an exploded perspective view of the sub tank, FIG. 6 is a schematic side view of the sub tank, and FIG. 7 is an AA line in FIG. FIG.

  As described above, the ink supply apparatus is a main tank for supplying and replenishing ink to the sub tank 15 via the supply tube 16 and the sub tank 15 which is mounted on the carriage 13 and supplies ink to the recording head 14. And a tank (ink cartridge) 10.

  The sub-tank 15 is a flexible film-like member (possible to seal an opening (one surface of the sub-tank 15) of the ink storage unit 100 to a container main body (case main body) 101 that forms the ink storage unit 100 that stores ink. (Flexible film-like member) 102 is adhered by adhesion or welding, and further, an elasticity for urging the film-like member 102 outwardly between the case main body 101 and the film-like member 102 inside the ink containing portion 100. A spring (spring) 103, which is a member, is provided, and a negative pressure generating unit that generates a negative pressure by supplying and discharging liquid is configured by these.

  Here, the film-like member 102 may have a single-layer structure, but as shown in FIG. 8A, a two-layer structure in which different types of first layer 102a and second layer 102b are laminated, for example, polyethylene and nylon. A configuration in which a film-like member is laminated, or a configuration in which a silica vapor deposition layer 102c is formed on the first layer 102a as shown in FIG. 5B, or a first configuration as shown in FIG. It is preferable that the silica vapor deposition layer 102c be sandwiched between the layer 102a and the second layer 102b.

  By forming the film-like member 102 with two or more different types of layers, it is possible to improve the liquid contact resistance and the mechanical strength with respect to the ink to be stored. For example, as shown in the example of FIG. 8A, when a film-like member made of polyethylene and nylon is laminated, the polyethylene comes into contact with the ink. In other words, polyethylene has excellent liquid resistance and moisture permeability, but it is slightly inferior in air permeability and weak in mechanical strength, stretchability, etc., so that the weak part of polyethylene is compensated by laminating nylon on it. be able to.

  In addition, when the film-like member 102 includes a silica vapor deposition layer, moisture permeability and air permeability of the film-like member 102 can be improved.

  The thickness of the film-like member 102 is preferably 10 to 100 μm. If the thickness is less than 10 μm, damage due to deterioration with time is likely to occur, and if it exceeds 100 μm, flexibility may be reduced and it may be difficult to efficiently generate negative pressure.

  Furthermore, a bulging portion 102a having a convex shape corresponding to the spring 103 is formed on the film-like member 102, and a reinforcing member 104 is attached to the outer surface thereof. Thus, by providing a convex portion on the flexible film-like member 102, it is possible to change the volume by recessing as the ink is consumed. In this case, the flexible film-like member 102 can be easily formed with a convex portion by forming a sheet-like film member into a convex shape.

  A negative pressure lever 106 that can be displaced according to deformation of the film-like member 102 is attached to support portions 107 and 107 provided on the side of the case 101 on the outer surface side of the film-like member 102 so as to be swingable. The negative pressure lever 106 is biased toward the side in contact with the film-like member 102 by a spring 108 provided between the negative pressure lever 106 and the case 101.

  As a result, the negative pressure lever 106 is displaced in accordance with the deformation of the film-like member 102, that is, in accordance with the volume change in the sub tank 15, so that the position of the detection end 106 of the negative pressure lever 106 will be described later. By detecting this, the ink capacity of the sub tank 15 can be detected.

  Further, the case 101 is provided with an ink introduction path portion 111 for replenishing ink in the ink containing portion 100, and a connecting means for connecting the ink introduction path portion 111 and the supply tube 16 connected to the ink cartridge 10. 112 can be detachably mounted. A liquid feed pump as described later is provided between the ink cartridge 10 and the sub tank 15 in order to pressure-feed ink from the ink cartridge 10 to the sub tank 15.

  Further, a connecting member 113 for supplying ink from the ink storage unit 100 to the recording head 14 is attached to the lower part of the case 101, and an ink supply path 114 of the recording head 14 is formed in the connecting member 113. A filter 115 is interposed between the two.

  An air flow path 121 is formed in the upper part of the case 101 for taking out air from the ink containing portion 100. The air flow path 121 includes an inlet flow path portion 122 having an opening facing the ink containing portion 100 and a flow path portion (referred to as an “orthogonal flow path portion”) 123 following the inlet flow path portion 122. An accumulation portion 126 is continuously formed in a portion that communicates with the atmosphere opening hole 131 provided in the case 101 on the downstream side, and that is further below the atmosphere opening hole 131 in use.

  The atmosphere release hole 131 is provided with an atmosphere release valve mechanism 132 which is an atmosphere release means for switching between the sealed state and the atmosphere release state in the sub tank 15. The atmosphere release valve mechanism 132 is configured by accommodating a valve seat 134, a ball 135 as a valve body, and a spring 136 for urging the ball 135 toward the valve seat 134 in a holder 133.

  The operation of the storage unit 126 will be described. When the apparatus main body is tilted or shaken, there is a high possibility that ink will enter the air flow path 121. Therefore, the ink that has entered from the air flow path 121 can be stored in the storage unit 126, and even if the ink is dropped during transportation and the ink enters, the ink is placed in the atmosphere release port 131 and the atmosphere release valve mechanism 132 that opens and closes the ink. Prevents the atmosphere release valve mechanism 132 from malfunctioning due to intrusion and hardening.

  In addition, two detection electrodes 141 and 142 for detecting that the amount of gas in the sub tank 15 has reached a predetermined amount or more are mounted on the upper portion of the case 101. The amount of gas can be detected by changing the conduction state between the detection electrodes 141 and 142 in a state where both the detection electrodes 141 and 142 are immersed in ink and in a state where at least one of the detection electrodes 141 and 142 is not immersed in ink. it can.

  Further, as shown in FIG. 4, an air release pin 153 for releasing the air by pressing the ball 135 of the air release mechanism 132 of the sub tank 15 against the spring 136 is disposed so as to be able to advance and retreat. A drive unit 162 having a lever 161 for operating the atmosphere release pin 155 is disposed on the apparatus main body side.

Here, a liquid feeding mechanism for feeding ink from the ink cartridge 10 to the sub tank 15 will be described with reference to FIG.
This liquid feeding mechanism includes a piston pump 181. The piston pump 181 includes a cylinder 182 and a piston 183. The cylinder 182 is connected to the other end of the hollow needle 190 inserted into the ink discharge port of the ink cartridge (main tank) 10 described above. A connecting portion 184 to be connected is provided.

  The piston 183 of the piston pump 181 is driven by a cam 189 provided integrally with the worm wheel 188 (reciprocating motion) when the worm wheel 188 is rotationally driven by the rotation of the drive motor 186 via the worm gear 187. )

  In this liquid feeding mechanism, the ink in the ink cartridge 10 is guided into the cylinder 182 through the hollow needle 190 inserted by the negative pressure generated when the piston pump 181 operates, and the ink that has entered the cylinder 182 passes through the piston 181. By reciprocating operation 183, the liquid is fed from the connecting portion 184 to the sub tank 15 through the supply tube 16.

Next, an outline of the control unit of the image forming apparatus will be described with reference to the block diagram of FIG.
The control unit 280 includes a CPU 281 that controls the entire apparatus, a ROM 282 that stores programs executed by the CPU 281 and other fixed data, a RAM 283 that temporarily stores image data, and the like, while the apparatus is powered off. And a non-volatile memory (NVRAM) 284 for holding data, an image processing for performing various signal processing and rearrangement on image data, and an ASIC 285 for processing input / output signals for controlling the entire apparatus. Yes.

  The control unit 280 also includes an I / F 286 for transmitting and receiving data and signals to and from the host, a head drive control unit 287 and a head driver 288 for driving and controlling the recording head 14, and a main scanning motor 290. A main scanning motor driving unit 291 for driving the motor, a sub scanning motor driving unit 293 for driving the sub scanning motor 292, and a motor for operating a suction pump for performing suction from the suction cap 72a of the subsystem 71 A sub-system driving unit 294 for driving the 298; a sub-tank driving unit 295 for driving the driving unit 162 for releasing the sub tank 15 to the atmosphere; detection signals of the detection electrodes 141 and 142 of the sub tank 15; I / O for inputting detection signals from 298 and detection signals from various sensors (not shown) It has a such as 96.

  The full tank detection sensor 298 detects that the sub tank is full when ink is supplied to the sub tank 15 by detecting that the detection end 106a of the negative pressure lever 106 of the sub tank 15 is in a predetermined position. To do.

  The control unit 280 is connected to an operation panel 297 for inputting and displaying information necessary for the apparatus.

  The control unit 280 receives print data and the like from the host side such as an information processing apparatus such as a personal computer, an image reading apparatus such as an image scanner, and an imaging apparatus such as a digital camera, via the cable or the network by the I / F 286.

  The CPU 281 reads and analyzes the print data in the reception buffer included in the I / F 286, performs necessary image processing, data rearrangement processing, and the like in the ASIC 285, and transfers the image data to the head drive control unit 287. To do. The generation of dot pattern data for image output may be performed by storing font data in the ROM 282, for example, or image data is developed into bitmap data by a host-side printer driver and transferred to this apparatus. You may do it.

  When the head drive control unit 287 receives image data (dot pattern data) corresponding to one line of the recording head 14, the dot pattern data for one line is serialized to the head driver 288 in synchronization with the clock signal. Data is transmitted, and a latch signal is transmitted to the head driver 288 at a predetermined timing.

  The head drive control unit 287 includes a ROM (which can also be configured by a ROM 282) storing pattern data of a drive waveform (drive signal), and a D / A converter for D / A conversion of drive waveform data read from the ROM. A waveform generation circuit including an A converter and a drive waveform generation circuit including an amplifier and the like are included.

  The head driver 288 also receives a clock signal from the head drive controller 287 and serial data as image data, and a latch circuit that latches the register value of the shift register with a latch signal from the head drive controller 287. A level conversion circuit (level shifter) that changes the output value of the latch circuit, an analog switch array (switch means) that is controlled to be turned on / off by the level shifter, and the like, and controls on / off of the analog switch array. In this way, a required drive waveform included in the drive waveform is selectively applied to the actuator means of the recording head 14 to drive the head.

  Here, the CPU 281 measures the amount of liquid consumed by counting the number of droplets ejected from the recording head 14. In this case, when the droplet discharge amount corresponding to the discharge pattern is stored, the amount of liquid consumed (ink use amount) is measured by counting the number of discharges (number of droplets) for each pattern.

  That is, when the information regarding the liquid discharge amount and the suction amount is held in advance, the used ink amount (used amount V) can be calculated and detected by the following equation (1).

  That is, since the sub tank 15 is a plastic structure using a flexible film-like member and an elastic member, it is difficult to provide means for accurately detecting the liquid amount in the sub tank 15 itself. Therefore, it is possible to easily and accurately measure the consumed ink amount by adding the usage amount associated with the droplet ejection obtained from the droplet ejection amount and the number of ejections and the usage amount associated with the recovery operation (suction). it can. When there are a plurality of levels of discharge amounts and suction amounts, the sum of the products of the individual amounts and the number of times is obtained.

  In this case, in the actual head, the droplet discharge amount varies among the heads. Therefore, it is preferable to correct the calculated value of the droplet discharge amount by a coefficient set in advance according to a parameter reflecting the droplet discharge characteristic of the head. In other words, by reducing the number of drops in the head that produces large drops and conversely increasing the number of drops in the head that produces small drops, variations between devices and between heads of each color are reduced. So that a uniform image can be output.

  Further, when the information regarding the liquid discharge amount and the suction amount for each discharge pattern is held in advance, the used ink amount is calculated and detected by the following equation (2).

  For example, when performing gradation printing, since the discharge amount data corresponding to the gradation pattern is originally held, by multiplying the discharge amount data by the number of times of gradation generation, the droplet discharge amount and the discharge number It is possible to detect (calculate) the amount of liquid with higher accuracy than multiplying by. The difference between the expression (1) and the expression (2) described above tends to be different in the expression (1) due to the frequency characteristic of the discharge amount, but the difference is already incorporated into the data in the expression (2). Therefore, it is possible to perform detection with higher accuracy.

Next, the ink replenishment supply operation to the sub tank in this image forming apparatus will be described with reference to FIG.
In the ink supply device of this image forming apparatus, the operations for supplying and replenishing ink from the main tank 10 to the sub tank 15 include opening to the atmosphere with the sub tank 15 being opened to the atmosphere and supplying the ink to the sub tank 15 to the atmosphere. There is normal filling without supplying ink.

  Here, the operation of atmosphere release filling will be described with reference to FIG. 11. The atmosphere release pin mechanism 153 is actuated by the drive unit 162 to open the atmosphere release valve mechanism 132 of the sub tank 15, so that the inside of the sub tank 15. To open air. When the sub tank 15 is opened for standby, the film-like member 102 is pushed outward by the restoring force of the spring 103, so that the capacity of the sub tank 15 increases (the negative pressure generating portion expands).

  In this state, ink is supplied from the ink cartridge 10 to the sub-tank 15 by the liquid supply mechanism and supplied. Thereafter, the atmosphere release valve mechanism 132 is closed to shut off the sub tank 15 from the atmosphere release. Then, the nozzle surface of the corresponding head 14 is capped by the cap member 72a of the subsystem 71, and the suction pump (not shown) is operated by driving the motor 298, and the sub tank 15 to which ink is supplied is sucked from the nozzle side of the recording head 14. To discharge a predetermined amount of ink. As a result, the film-like member 102 of the sub tank 15 is deformed inwardly against the urging force of the spring 103 to reduce the volume of the sub tank 15 (the negative pressure generating portion contracts), and an initial negative pressure is generated.

  Thereafter, the position of the detection end 106a of the negative pressure lever 106 is detected and stored by the full tank detection sensor 298.

  In addition, as the method of open air filling, as another method, the following operation can also be performed. For example, after the sub tank 15 is opened to the atmosphere, the flexible film member 102 is pressed inward against the spring 103 by the negative pressure lever 106 to reduce the capacity of the sub tank 15, and then the ink cartridge 10. Then, the ink is supplied to the sub tank 15 by the liquid supply mechanism and replenished and supplied, and then the atmosphere release valve mechanism 132 is closed to shut off the inside of the sub tank 15 from the atmosphere release, and the pressure by the negative pressure lever 106 is released. By doing so, the flexible film-like member 102 is urged outward by the urging force of the spring 103, and a negative pressure is generated in the sub tank 15.

  Thus, since the negative pressure can be generated in the sub-tank by the flexible film-like member and the elastic member, the negative pressure generating mechanism is simplified.

  Next, normal filling will be described. In this case, as described above, the ink consumption V is detected (by counting the number of drops), and when the required consumption is reached, the sub tank 15 is opened to the atmosphere. Instead, the ink is supplied from the ink cartridge 10 to the sub-tank 15 by the liquid supply mechanism, and replenished and supplied by a required filling amount. The filling amount can be controlled by the driving time of the pump 181.

  Here, it is obvious that the replenishment amount of ink to be supplied is preferably the same as the consumption amount V. However, in practice, the calculation of the consumption amount V causes an error due to variations in the amount per droplet and the suction amount. Occurs. In addition, since the supply is a supply with pulsation due to the piston reciprocation, the supply amount varies depending on the timing. When ink consumption and normal filling are repeated, the actual ink amount in the sub tank 15 gradually shifts due to these errors. As a result, the negative pressure value in the sub tank 15 also shifts.

  Therefore, as described above, the position of the negative pressure lever 106 is stored when the initial negative pressure is formed by sucking a predetermined amount of liquid after filling in the atmosphere. As the ink in the sub tank 15 is consumed, the film-like member 102 is further recessed, so that the negative pressure lever 106 is moved (displaced) to the sub tank 15 side accordingly. During normal filling, the full tank detection sensor 298 reads that the position of the negative pressure lever 106 comes to the stored original position, and stops the filling operation there. As a result, errors due to variations as described above are reduced, and the original initial negative pressure can be maintained immediately after normal filling.

  As described above, the operation of releasing the atmosphere and supplying the ink to the sub tank 15 (filling with the atmosphere) need not be performed every time the ink in the sub tank 15 is consumed, and the ink consumption of the sub tank 15 is a certain amount. In other cases, it is preferable to perform an operation of replenishing and supplying ink to the sub tank 15 (normal filling) without releasing the atmosphere.

Details of such control will be described with reference to FIGS.
First, as shown in FIG. 12, when the printing of one sheet is completed during the printing process, the used amount V of each color ink measured as described above is read, and the used amount V is determined in advance. 3 Compared with the reference value V3, it is determined whether or not V ≧ V3. Here, “single-sheet printing” means one page, and in the case of double-sided printing, it means one page on one side (the same applies hereinafter).

  If the determination result for one or more colors of ink is V ≧ V3, the sub-tank 15 of the corresponding color (the color satisfying V ≧ V3) is filled from the main tank (ink cartridge) 10 to the atmosphere. For the sub-tanks 15 of other colors (colors not satisfying V ≧ V3), the printing process is continued after normal filling.

  On the other hand, for all color inks, if the determination result is not V ≧ V3, the usage amount V is compared with the second reference value (V2 <V3) to determine whether V ≧ V2. If there is an ink with a color satisfying V ≧ V2, the sub-tank 15 for all colors of ink is normally filled, and then the printing process is continued.

  Also, as shown in FIG. 13, when the printing process is completed, when a predetermined time has elapsed after printing, the ink usage amount V of each color is read, and the usage amount V is set to a predetermined first reference value V1. In comparison, it is determined whether or not V ≧ V1.

  If the determination result is V ≧ V1 for one or more colors of ink, the sub-tank 15 of the corresponding color (the color satisfying V ≧ V1) is normally filled during capping (nozzle recovery operation). .

  Specifically, it has a counter corresponding to the ink consumption (use amount) V (ml), the first reference value V1 is 0.2, the second reference value V2 is 0.9, and the third reference value. When V3 is set to 1.1 and V ≧ 0.2 when a predetermined time has elapsed after printing, only the corresponding color is normally filled in the capping state, and 1.1> V ≧ 0 when one sheet is printed. .9 if normal filling is performed for all colors and then printing is continued. If V ≧ 1.1, the atmosphere is filled for the atmosphere and the other colors are filled normally. Printing is continued.

  In the above embodiment, the present invention has been described with reference to an example in which the present invention is applied to an ink jet recording apparatus. However, the present invention can also be applied to a printer, a facsimile apparatus, a copying apparatus, a printer / fax / copier multifunction machine, etc. The present invention can also be applied to an image forming apparatus using a liquid other than the above, a liquid supply apparatus used therefor, and the like.

FIG. 3 is a perspective explanatory view seen from the front side of an ink jet recording apparatus as an embodiment of an image forming apparatus according to the present invention including a liquid supply apparatus according to the present invention including a sub tank according to the present invention. FIG. 2 is a configuration diagram illustrating an outline of a mechanism unit of the recording apparatus. It is principal part plane explanatory drawing of the mechanism part. It is a disassembled perspective explanatory drawing of the part concerning an ink supply apparatus. It is a disassembled perspective explanatory drawing of a sub tank. It is typical side surface explanatory drawing of the same sub tank. It is a schematic sectional explanatory drawing which follows the AA line of FIG. It is explanatory drawing of a flexible film-like member. It is explanatory drawing of the liquid feeding mechanism to a sub tank. FIG. 2 is a schematic block explanatory diagram of a control unit of the recording apparatus. It is a flowchart with which it uses for description of the open air filling operation | movement to the sub tank in the recording device. FIG. 6 is a flowchart for explaining a replenishment supply operation to a sub tank in the recording apparatus. It is a flowchart with which it uses for description of the replenishment supply operation | movement to a sub tank similarly.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Ink cartridge 13 ... Carriage 14 ... Recording head 15 ... Sub tank 100 ... Ink storage part 102 ... Flexible film-like member 103 ... Elastic member 132 ... Air release valve mechanism

Claims (1)

A sub-tank for supplying liquid to a droplet discharge head for discharging droplets, comprising a flexible film-shaped member constituting at least one surface, and an elastic member for biasing the flexible film-shaped member outward A negative pressure generating portion that generates a negative pressure by expanding and contracting by supplying and discharging the liquid, and abuts on the outer surface side of the film-like member, thereby deforming the film-like member A sub-tank having a lever that can be displaced according to the air and provided with an air release means for opening the inside to the atmosphere;
A main tank for supplying liquid to the sub tank;
A full tank detecting means for detecting the position of the lever of the sub tank;
After supplying the liquid from the main tank to the sub tank in a state where the sub tank is opened to the atmosphere by the atmosphere releasing means, the atmosphere releasing means is closed and a part of the liquid in the sub tank is discharged to discharge the negative. Store the position of the lever when the pressure generating part is contracted to generate a negative pressure in the sub tank,
Means for controlling the liquid supply to stop when the position of the lever reaches the memorized position when supplying the liquid from the main tank to the sub tank without opening the sub tank to the atmosphere; An image forming apparatus comprising the image forming apparatus.

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