JP2013059899A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute sufficient recover even if a negative pressure is increased in a head tank by a recovery operation by an suction and discharge.SOLUTION: An image forming apparatus, when executing suction and discharge operation, determines whether a first sensor 251 detects a first detection position 205a of a displacement member 205. When the first sensor 251 detects the first detection position 205a of the displacement member 205, the image forming apparatus drives a liquid feeding pump, feeds liquid from a main tank to the head tank 35 of a recording head executing the recovery operation and subsequently determines whether the first sensor 251 detects the second detection position 205b of the displacement member 205. When the first sensor 251 detects the second detection position 205b of the displacement member 205, the image forming apparatus stops driving the liquid feeding pump to stop feeding liquid.

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus including a recording head that discharges droplets and a sub tank that supplies liquid to the recording head.

  As an image forming apparatus such as a printer, a facsimile, a copying machine, a plotter, or a complex machine of these, for example, a liquid discharge recording type image forming using a recording head composed of a liquid discharge head (droplet discharge head) that discharges ink droplets. As an apparatus, an ink jet recording apparatus or the like is known.

  In such an image forming apparatus, a head tank (also referred to as a sub tank or a buffer tank) that supplies ink to the recording head is provided, and negative pressure is used to prevent ink from seeping out and sagging from the nozzles of the recording head. A head tank having a negative pressure forming function (mechanism) for generating the pressure is known.

  This head tank has a negative pressure forming means including a bendable film member that forms one surface of an ink containing portion that contains ink, and an elastic member that biases the film member outward, and is a liquid. A recording member having a displacement member (also referred to as a detection member or a detection filler) that is displaced according to the remaining amount and an openable and closable atmosphere opening mechanism that opens the inside of the ink container to the atmosphere. Ink is supplied to the printer.

  By the way, in the liquid discharge head, when bubbles flow into the head, the discharge direction of the discharged liquid droplet is bent, or the required amount of liquid droplets cannot be discharged, or the discharge itself becomes impossible. Defects occur.

  Therefore, in order to maintain and recover the performance of the head, for example, the nozzle surface of the head is sealed with a suction cap to which suction means is connected, and the liquid is sucked and discharged from the nozzle, or the head is pressurized. Air bubbles and other foreign matters in the head are discharged from the nozzle together with the liquid by a pressure supply method in which the liquid is supplied and discharged from the nozzle, a suction pressure method using these in combination, or the like.

  For example, pressurizing means for pressurizing ink liquid in the ink tank and sending ink to the ink liquid chamber, negative pressure generating means for generating negative pressure on the recording head via the cap member, and controlling the pressurizing means. And a suction recovery means for recovering the suction of the recording head by the negative pressure generating means. The suction recovery means uses the control means to close the flexible valve by using the negative pressure generating means to close the ink in the ink liquid chamber. It is known that after accumulating negative pressure in a liquid chamber, a flexible valve is opened by a pressurizing means to cause ink in an ink flow path to flow into the ink liquid chamber (Patent Document 1).

JP 2010-177876

  However, as described above, when a liquid discharge head unit having a head tank including a negative pressure generating means is used, if the recovery operation is performed by the suction / discharge method, the negative pressure becomes stronger together with the suction, and the suction becomes difficult at the same time. Air and foreign matter cannot be discharged. For this reason, when the recovery operation is performed again, there are problems that the maintenance time is wasted, the ink is wasted, and the life of the waste liquid tank for collecting the discharged waste liquid is shortened.

  On the other hand, in order to perform the recovery operation of the pressurized supply method, a strong negative pressure and a strong positive pressure are applied to the flow path, and pressure resistance is required for each component. Also, in the configuration where the ink in the ink tank is pressurized and the valve is opened to flow into the flow path, the pressure means is controlled while detecting with the pressure sensor in order to prevent the ink from returning to atmospheric pressure during pressurized liquid feeding. However, only the pressure in the ink tank and the flow path is detected, and the pressure in the head unit and the amount of ink are not directly grasped. There is a problem that the recovery performance varies.

  The present invention has been made in view of the above problems, and an object thereof is to improve the recovery performance of the recovery operation for the head having the head tank.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A recording head having nozzles for discharging droplets;
A head tank for storing liquid to be supplied to the recording head;
A carriage on which the recording head and the head tank are mounted;
A main tank for storing liquid to be supplied to the head tank;
Liquid feeding means for supplying liquid from the main tank to the head tank;
Recovery means for performing a recovery operation of sucking and discharging the liquid from the nozzles of the recording head to recover the discharge state of the nozzles,
The head tank has negative pressure generating means for generating a negative pressure according to the remaining amount of liquid, and a displacement member that is displaced according to the remaining amount of liquid.
The carriage is provided with detection means for detecting the displacement member,
When performing the recovery operation by the recovery means, controlling the liquid supply to the head tank by the liquid supply means from the detection of the displacement of the displacement member by the detection means,
During the recovery operation, the pressure in the head tank is maintained within a predetermined range.

  According to the image forming apparatus of the present invention, it is possible to improve the recovery performance of the recovery operation for the head having the head tank.

FIG. 2 is a schematic side view of a mechanism portion of the image forming apparatus for explaining the first embodiment of the present invention. It is principal part plane explanatory drawing of the mechanism part. It is a typical plane explanatory view showing an example of a sub tank. FIG. 4 is a schematic front sectional view of FIG. 3. FIG. 3 is a schematic explanatory diagram for explaining an ink supply / discharge system. It is block explanatory drawing explaining the outline | summary of a control part. It is typical explanatory drawing with which it uses for description of the negative pressure formation operation | movement of a sub tank. It is explanatory drawing with which it uses for description of the negative pressure management of a sub tank. It is explanatory drawing with which it uses for description of the detection position of the displacement member of the head tank with which it uses for description of 1st Embodiment of this invention. It is explanatory drawing with which it uses for description of the relationship between the detection position of a displacement member, a head tank internal pressure, and the amount of waste ink. It is a flowchart which similarly shows recovery operation control to a control part. It is a flowchart which shows recovery operation control in 2nd Embodiment of this invention. It is a flowchart which shows recovery operation control in 3rd Embodiment of this invention. It is a flowchart which shows recovery operation control in 4th Embodiment of this invention. It is a flowchart which shows recovery operation control in 5th Embodiment of this invention. It is a flowchart which shows recovery operation control in 6th Embodiment of this invention. It is a flow figure showing recovery operation control in a 7th embodiment of the present invention. It is explanatory drawing which shows an example of the relationship between environmental humidity and the opening amount of a displacement member (filler) with which it uses for description of 8th Embodiment of this invention. It is a flowchart with which it uses for description of the supply ink amount calculation process of the embodiment. It is a flow figure showing an example of recovery operation control in the embodiment.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an example of an image forming apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is an explanatory side view for explaining the overall configuration of the image forming apparatus, and FIG. 2 is an explanatory plan view of a main part of the apparatus.

  This image forming apparatus is a serial type ink jet recording apparatus, and a carriage 33 is slidable in a main scanning direction by main and sub guide rods 31 and 32 which are guide members horizontally mounted on the left and right side plates 21A and 21B of the apparatus main body 1. It is held and moved and scanned in the carriage main scanning direction via a timing belt by a main scanning motor described later.

  The carriage 33 is provided with recording heads 34a and 34b composed of liquid ejection heads for ejecting ink droplets of yellow (Y), cyan (C), magenta (M), and black (K). The “recording head 34” is arranged in a sub-scanning direction orthogonal to the main scanning direction, and the ink droplet ejection direction is directed downward.

  Each of the recording heads 34 has two nozzle rows. One nozzle row of the recording head 34a has black (K) droplets, the other nozzle row has cyan (C) droplets, and the recording head 34b has one nozzle row. One nozzle row ejects magenta (M) droplets, and the other nozzle row ejects yellow (Y) droplets.

  Further, the carriage 33 is equipped with head tanks 35a and 35b (referred to as “head tank 35” when not distinguished) for supplying ink of each color corresponding to the nozzle rows of the recording head 34. In the head tank 35, ink cartridges 10y, 10m, 10c, and 10k, which are main tanks of the respective colors that are detachably attached to the cartridge loading unit 4, are supplied from the ink pumps 24 through the supply tubes 36 of the respective colors. The recording liquid is replenished.

  An encoder scale 91 is provided along the main scanning direction of the carriage 33, and an encoder sensor 92 that reads the encoder scale 91 is provided on the carriage 33, and the linear encoder 90 is configured by the encoder scale 91 and the encoder sensor 92. The main scanning position (carriage position) and the movement amount of the carriage 33 are detected by the detection signal of the linear encoder 90.

  On the other hand, as a paper feeding unit for feeding the papers 42 stacked on the paper stacking unit (pressure plate) 41 of the paper feeding tray 2, a half-moon roller (feeding) that separates and feeds the papers 42 one by one from the paper stacking unit 41. A separation pad 44 made of a material having a large friction coefficient is provided facing the paper roller 43) and the paper feed roller 43, and the separation pad 44 is urged toward the paper feed roller 43 side.

  In order to feed the paper 42 fed from the paper feeding unit to the lower side of the recording head 34, a guide member 45 for guiding the paper 42, a counter roller 46, a transport guide member 47, and a tip pressure roller. And a holding belt 48 which is a conveying means for electrostatically attracting the fed paper 42 and conveying it at a position facing the recording head 34.

  The transport belt 51 is an endless belt, and is configured to wrap around the transport roller 52 and the tension roller 53 and circulate in the belt transport direction (sub-scanning direction). Further, a charging roller 56 that is a charging unit for charging the surface of the transport belt 51 is provided. The charging roller 56 is disposed so as to come into contact with the surface layer of the transport belt 51 and to rotate following the rotation of the transport belt 51. The transport belt 51 rotates in the belt transport direction when the transport roller 52 is rotationally driven through timing by a sub-scanning motor described later.

  Further, as a paper discharge unit for discharging the paper 42 recorded by the recording head 34, a separation claw 61 for separating the paper 42 from the conveying belt 51, a paper discharge roller 62, and a spur 63 that is a paper discharge roller. And a paper discharge tray 3 below the paper discharge roller 62.

  A duplex unit 71 is detachably mounted on the back surface of the apparatus body 1. The duplex unit 71 takes in the paper 42 returned by the reverse rotation of the conveyance belt 51, reverses it, and feeds it again between the counter roller 46 and the conveyance belt 51. The upper surface of the duplex unit 71 is a manual feed tray 72.

  Further, a maintenance / recovery mechanism 81 for maintaining and recovering the nozzle state of the recording head 34 is disposed in the non-printing area on one side of the carriage 33 in the scanning direction. The maintenance / recovery mechanism 81 includes cap members (hereinafter referred to as “caps”) 82a and 82b (hereinafter referred to as “caps 82” when not distinguished from each other) for capping the nozzle surfaces of the recording head 34, and nozzle surfaces. A wiper member (wiper blade) 83 for wiping the recording medium, an empty discharge receiver 84 for receiving liquid droplets when performing empty discharge for discharging liquid droplets that do not contribute to recording in order to discharge the thickened recording liquid, and a carriage And a carriage lock 87 for locking 33. A waste liquid tank 100 for storing waste liquid generated by the maintenance recovery operation is mounted on the lower side of the head recovery mechanism 81 in a replaceable manner with respect to the apparatus main body.

  Further, in the non-printing area on the other side of the carriage 33 in the scanning direction, there is an empty space for receiving liquid droplets when performing empty discharge for discharging liquid droplets that do not contribute to recording in order to discharge the recording liquid thickened during recording or the like. A discharge receiver 88 is disposed, and the idle discharge receiver 88 includes an opening 89 along the nozzle row direction of the recording head 34.

  In the image forming apparatus configured as described above, the sheets 42 are separated and fed one by one from the sheet feed tray 2, and the sheets 42 fed substantially vertically upward are guided by the guide member 45, It is sandwiched between the counter roller 46 and conveyed, and further, the leading end is guided by the conveying guide 37 and pressed against the conveying belt 51 by the leading end pressing roller 49, and the conveying direction is changed by approximately 90 °.

  At this time, a positive output and a negative output are alternately repeated with respect to the charging roller 56, that is, an alternating voltage is applied, and a charging voltage pattern in which the conveying belt 51 alternates, that is, in a sub-scanning direction that is a circumferential direction. , Plus and minus are alternately charged in a band shape with a predetermined width. When the paper 42 is fed onto the conveyance belt 51 charged alternately with plus and minus, the paper 42 is attracted to the conveyance belt 51, and the paper 42 is conveyed in the sub-scanning direction by the circular movement of the conveyance belt 51.

  Therefore, by driving the recording head 34 according to the image signal while moving the carriage 33, ink droplets are ejected onto the stopped paper 42 to record one line, and after the paper 42 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 42 has reached the recording area, the recording operation is finished and the paper 42 is discharged onto the paper discharge tray 3.

  When performing the maintenance and recovery of the nozzles of the recording head 34, the nozzle 33 performs the suction from the nozzles by moving the carriage 33 to a position facing the maintenance and recovery mechanism 81 which is the home position and performing capping by the cap member 82. By performing a maintenance and recovery operation such as idle ejection for ejecting droplets that do not contribute to image formation, image formation by stable droplet ejection can be performed.

  Next, an example of the head tank 35 will be described with reference to FIGS. 3 is a schematic top view for explaining one nozzle row of the head tank 35, and FIG. 4 is a schematic front view for explaining the same.

  The head tank 35 has a tank main body 201 that is a tank case that forms an ink containing portion 202 that is open at one side for holding ink. The opening of the tank body 201 is sealed with a flexible film member 203 which is a flexible member to form an ink containing portion 202, and a flexible film member is formed by an elastic member disposed in the tank body 201 by a spring 204. 203 is always urged outward.

  As a result, an outward biasing force is applied to the film member 203 of the tank main body 201 by the spring 204, so that a negative pressure is generated by reducing the remaining amount of ink in the ink containing portion 202 of the tank main body 201. .

  In addition, a displacement member (hereinafter simply referred to as “a”), which is formed on the outer side of the tank main body 201, is supported by one end portion so as to be swingable by a support shaft 206 and is biased toward the tank main body 201 by a spring 210. ”205 is fixed to the film member 203 by adhesion or the like, and the displacement member 205 is displaced in conjunction with the movement of the flexible film member 203.

  The displacement member 205 is detected by a later-described second detecting means (second sensor) 301 provided on the carriage 33, a later-described first detecting means (first sensor, full sensor) 251 disposed on the apparatus body side, or the like. As a result, it is possible to detect the remaining amount of ink and negative pressure in the head tank 35.

  In addition, a supply port 209 for supplying ink from the ink cartridge 10 is connected to the ink supply tube 36 at the top of the tank body 201. In addition, an air release mechanism 207 that opens the inside of the head tank 35 to the atmosphere is provided on the side of the tank body 201. The atmosphere release mechanism 207 includes a valve body 207b that opens and closes an atmosphere release path 207a communicating with the inside of the head tank 35, a spring 207c that biases the valve body 207b to a closed state, and the like. When the valve body 207b is pushed by 302, the valve body 207b is opened, and the head tank 35 is opened to the atmosphere (connected to the atmosphere).

  Electrode pins 208a and 208b for detecting the ink liquid level in the head tank 35 are attached. Since the ink has electrical conductivity, when the ink reaches the electrode pins 208a and 208b, a current flows between the electrode pins 208a and 208b, and the resistance value of the two changes. It is possible to detect that the air amount in the head tank 35 has become a predetermined amount or more.

  Next, an example of the arrangement of detection means for detecting the ink supply / discharge system and the displacement member of the head tank in this image forming apparatus will be described with reference to FIG.

  First, ink is supplied from the ink cartridge (hereinafter also referred to as “main tank”) 10 to the head tank 35 through a supply tube 36 by a liquid feed pump 241 which is a liquid feed means of the supply pump unit 24.

  The liquid feed pump 241 is a reversible pump configured with a tube pump or the like, and a liquid feed operation for supplying ink from the main tank 10 to the head tank 35 and a reverse feed operation for returning ink from the head tank 35 to the main tank 10. Can be done.

  In addition, the maintenance / recovery mechanism 81 has the suction cap 82a for capping the nozzle surface of the nozzle plate 34N of the recording head 34 and the suction pump 812 connected to the suction cap 82a as described above, and is capped by the cap 82a. By driving the suction pump 812, the ink in the head tank 35 can be sucked by sucking ink from the nozzles via the suction tube 811. The sucked waste ink is discharged to the waste liquid tank 100.

  Further, the carriage 33 is provided with a first sensor 251 including an optical sensor which is a first detection unit for detecting the first detection unit 205A of the displacement member 205, and the second detection unit of the displacement member 205 is provided on the apparatus main body side. A second sensor 301 is provided as a second detection means including an optical sensor for detecting 205B. The ink supply operation to the head tank 35 can be controlled using the detection results of the first and second sensors 251 and 301.

  The control unit 500 controls the maintenance and recovery operations according to the present invention, such as the drive control of the liquid feed pump 241 and the suction pump 812 described above.

  Next, an outline of the control unit of the image forming apparatus will be described with reference to FIG. This figure is an overall block diagram of the control unit.

  The control unit 500 controls the entire apparatus, and includes a CPU 501 that also functions as a means for controlling the recovery operation (recovery control means) according to the present invention, a ROM 502 that stores programs executed by the CPU 501 and other fixed data. A RAM 503 for temporarily storing image data, a non-volatile memory 504 that also serves as a rewritable memory holding means for holding data even while the apparatus is powered off, and various signal processing and rearrangement for image data And an ASIC 505 for processing input / output signals for controlling the entire apparatus.

  Further, a print control unit 508 including a data transfer unit for driving and controlling the recording head 34 and a driving signal generating unit, a head driver (driver IC) 509 for driving the recording head 34 provided on the carriage 33 side, A main scanning motor 554 that moves and scans the carriage 33; a sub-scanning motor 555 that moves the conveyor belt 51 around; a motor drive unit 510 that drives the maintenance / recovery motor 556 of the maintenance / recovery mechanism 81 (including the suction pump 812); An AC bias supply unit 511 that supplies an AC bias to the charging roller 56, an air release solenoid (not shown) provided on the apparatus main body side that opens and closes the air release mechanism 207 of the head tank 35, and a supply system drive that drives the liquid feed pump 241. Part 512 and the like.

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

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

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

  The print control unit 508 transfers the above-described image data as serial data, and outputs a transfer clock, a latch signal, a control signal, and the like necessary for transferring the image data and confirming the transfer to the head driver 509. Including a D / A converter for D / A converting D / A conversion of drive pulse pattern data stored in the ROM, a voltage signal amplifier, a current amplifier, and the like, and a drive signal or a plurality of drive pulses Is output to the head driver 509.

  The head driver 509 selectively selects droplets of the recording head 7 as drive pulses constituting a drive signal given from the print control unit 508 based on image data corresponding to one line of the recording head 34 inputted serially. The recording head 7 is driven by applying it to a driving element (for example, a piezoelectric element) that generates energy to be discharged. At this time, by selecting a driving pulse constituting the driving signal, for example, dots having different sizes such as a large droplet, a medium droplet, and a small droplet can be sorted.

  The I / O unit 513 acquires information from various sensor groups 515 mounted on the apparatus, extracts information necessary for controlling the printer, a print control unit 508, a motor drive unit 510, and an AC bias supply unit. It is used for controlling 511, controlling ink supply to the head tank 35, and the like.

  In addition to the first sensor 251, the second sensor 301, and the detection electrode pins 208a and 208b, the sensor group 515 includes an optical sensor for detecting the position of the paper and a thermistor for monitoring the temperature and humidity in the machine ( Environmental temperature sensor, environmental humidity sensor), a sensor for monitoring the voltage of the charging belt, an interlock switch for detecting opening and closing of the cover, and the like, and the I / O unit 513 can process various sensor information.

  Next, the negative pressure forming operation of the head tank 35 in the image forming apparatus configured as described above will be described with reference to FIG.

  As shown in FIG. 7A, after supplying ink from the main tank 10 to the head tank 35, the ink is sucked from the head tank 35 as described above, or the recording head 34 is driven to eject droplets ( By ejecting droplets that do not contribute to image formation (empty ejection) and reducing the amount of ink in the head tank 35, as shown in FIG. The conductive film member 203 tends to be displaced inward, and a negative pressure is generated in the head tank 35 by the urging force of the spring 204.

  Further, by sucking the inside of the head tank 35 by the liquid feed pump 241, the flexible film member 203 is drawn inward of the head tank 35, and the spring 204 is further compressed to increase the negative pressure. Note that, as described above, the negative pressure can be similarly increased by ejection from the recording head 34 or suction by the suction pump 812.

  When ink is supplied into the head tank 35 from this state, the flexible film member 203 is pushed out of the head tank 35, so that the spring 204 extends and the negative pressure decreases.

  By repeating these operations, the negative pressure in the head tank 35 can be controlled to be kept constant.

  That is, as shown in FIG. 8, the negative pressure in the head tank 35 is correlated with the amount of ink in the head tank 35. When the amount of ink in the head tank 35 is large, the negative pressure in the head tank 35 is small. When the ink amount is small and the ink amount is small, the negative pressure in the head tank 35 is greatly increased. If the negative pressure in the head tank 35 is too weak, the ink leaks from the recording head 34. If the negative pressure is too strong, air and dust are mixed from the recording head 34, and ejection failure is likely to occur. Become.

  Therefore, the ink supply to the head tank 35 is performed so that the negative pressure in the head tank 35 falls within the range of the amount of ink discharged from the head tank 35 (the amount of discharged ink) B within the predetermined negative pressure control range A. I try to control it.

  Next, a first embodiment of the present invention will be described with reference to FIGS. FIG. 9 is an explanatory diagram for explaining the detection position of the displacement member of the head tank, FIG. 10 is an explanatory diagram for explaining the relationship between the detection position of the displacement member, the pressure in the head tank, and the amount of discharged ink, and FIG. It is a flowchart which shows an example of recovery operation control.

  First, in the present embodiment, the displacement member 205 (the first detection unit 205A detected by the first sensor 251) of the head tank 35 is a member having a certain thickness (width) in the displacement direction. Here, the outer end of the displacement member 205 opposite to the tank body 201 side is defined as a first detection position 205a, and the inner end of the tank body 201 side is defined as a second detection position 205b.

  When the first sensor 251 detects the first detection position 205a of the displacement member 205, the negative pressure in the head tank 35 is lower than the negative pressure corresponding to the ink supply upper limit position during printing (the negative pressure is small). It is assumed that the head tank 35 and the first sensor 251 are arranged so as to be positive pressure). Thereby, as shown in FIG. 10, the liquid feeding can be controlled so that the displacement member 205 is displaced between the first detection position 205a and the second detection position 205b of the displacement member 205.

  Therefore, referring to FIG. 11, when the recovery operation of the recording head 34 is performed, the nozzle surface of the recording head 34 is capped with the suction cap 82a. Then, it is confirmed that the position of the displacement member 205 (denoted as “filler” in the flowchart) is larger than the position where the first detection position 205a is detected. Thereafter, the suction pump 812 is driven to suck and discharge ink from the recording head 34.

  By this suction and discharge, the ink in the head tank 35 is consumed, and the displacement member 205 is displaced toward the tank body 201 side.

  Here, it is determined whether or not the first sensor 251 detects the first detection position 205a of the displacement member 205, and when the first sensor 251 detects the first detection position 205a of the displacement member 205, the liquid feed pump 241 is detected. Is fed from the main tank 10 to the head tank 35 of the recording head 34 performing the recovery operation.

  By this liquid feeding operation, the remaining amount of liquid in the head tank 35 increases and the displacement member 205 is displaced in a direction away from the tank body 201.

  Then, it is determined whether or not the first sensor 251 detects the second detection position 205b of the displacement member 205, and when the first sensor 251 detects the second detection position 205b of the displacement member 205, the liquid feed pump 241 is detected. Stop driving to stop feeding.

  After that, it is determined whether or not the recovery operation is finished. If the recovery operation is finished, the drive of the suction pump 812 is stopped, and then the recovery operation finish operation such as separation of the suction cap 82a, wiping, and idle discharge is performed.

  In this way, by performing liquid feeding into the head tank 35 during the recovery operation, the nozzle recovery operation can be performed while maintaining the pressure in the head tank 35 within a certain pressure range.

  Here, a comparative example in which the liquid feeding operation during the recovery operation as described above is not performed will be described.

  In this case, when the ink is sucked and discharged from the recording head 34 by the suction pump 812, the residual pressure of the liquid in the head tank 35 decreases, so that the negative pressure in the head tank 35 increases. When a certain amount of ink that can be sucked with a negative pressure that can be applied to the sealed space between the suction cap 82a and the nozzle surface is discharged from the head tank 35 or the head 34 by the suction pump 812, the head tank 35 side Since the negative pressure of the air becomes higher than the negative pressure in the sealed space, it becomes impossible to suck and discharge further, making it difficult to suck and remove fine foreign matters such as bubbles and dust.

  In addition, if the negative pressure in the head 34 is strong, the fluidity of the ink in the flow path in the head is lowered, ink and minute foreign matter in the head 34 are stagnated, and the recovery performance of the nozzle is remarkably lowered. .

  For this reason, if the nozzle clogging is not eliminated by a single recovery operation, it is necessary to perform a recovery operation repeatedly. As a result, wasteful ink consumption and a large maintenance time (time required for the recovery operation) are required. It will be wasted.

  On the other hand, by configuring as in the present embodiment, the negative pressure on the head tank 35 and the head 34 side is prevented from increasing, and the ink in the head is surely sucked and discharged by suction by the suction pump. Thus, bubbles and foreign matter can be discharged, and the recovery performance of the recovery operation is improved.

  In the process of FIG. 11, the position of the displacement member 205 is confirmed after capping, but this is based on an example in which ON / OFF control is performed only by the first sensor 251 and is not limited thereto. For example, the carriage can be operated, and the position of the displacement member 205 can be confirmed by the second sensor 301. In this case, naturally, a process for confirming the position is performed before capping (when the capping is performed, the carriage is moved). Because you can not). Since this point is the same for the second embodiment to be described later, re-explanation is omitted.

  Here, the relationship between the first detection position and the second detection position and the sub-tank pressure will be described.

  First, the relationship between the first detection position and the second detection position and the sub-tank pressure can be set by the installation position of the first sensor 251 and the thickness and shape of the displacement member 205 in the displacement direction.

  For example, in the present embodiment, when the first sensor 251 detects the second detection position 205 b of the displacement member 205, the pressure in the head tank 35 is set to 0 kPa, which is the atmospheric pressure, and the first sensor 251 performs the displacement. When the first detection position 205a of the member 205 is detected, it is set to be equal to or higher than a predetermined negative pressure lower limit value considering the recovery performance.

  In this case, for example, considering the pressure resistance of each component, when the first sensor 251 detects the second detection position 205b of the displacement member 205, the positive pressure upper limit value considering the pressure resistance is set. Even when the first detection position 205a is detected, the positive pressure value can be set to be smaller than when the second detection position 205b is detected.

  Next, a second embodiment of the present invention will be described with reference to a flowchart shown in FIG.

  As described above, since the nozzle recovery operation is performed while the first sensor 251 detects the first detection position 205a and the second detection position 205b of the displacement member 205, before the nozzle recovery operation is performed, the displacement member 205 is It is necessary to confirm that the sensor can be detected by the sensor 251. In other words, it is necessary to confirm that the pressure in the head tank 35 is within a predetermined pressure range (within a predetermined liquid remaining amount range).

  Therefore, in this embodiment, before starting the recovery operation (here, it is assumed that the capping is performed, but it is sufficient that the suction is started), the atmosphere release mechanism 207 of the head tank 35 is opened to open the head tank 35. After setting the inside to atmospheric pressure, the air release mechanism 207 is closed. Thereafter, the same processing as in the first embodiment is performed.

  By releasing the inside of the head tank 35 to the atmosphere, the displacement member 205 is always displaced to a position corresponding to the opening to the atmosphere. That is, in FIG. 9, the second detection position 205b of the displacement member 205 is located on the left side (the direction away from the tank body 201) from the first sensor 251, and the liquid consumption associated with the subsequent suction operation Since the displacement member 205 is displaced toward the tank body 201, the first detection position 205a can be detected.

  Next, a third embodiment of the present invention will be described with reference to the explanatory diagram of FIG.

  In the present embodiment, the second sensor 301 on the apparatus main body side is used in order to achieve the same object as in the second embodiment.

  That is, as shown in FIG. 13, the carriage 33 is moved until the second sensor 301 detects the displacement member 205 (second detection unit 205B), and the carriage position when the displacement sensor 205 is detected by the second sensor 301 is detected. Is detected by the carriage encoder 90. Then, in a state where the displacement member 205 is detected by the first sensor 251, the carriage position when the displacement member 205 is detected by the second sensor 301 is compared with the detected position, and the displacement is detected. It is confirmed whether or not the member 205 is in a position that falls within a predetermined pressure range.

  Next, a fourth embodiment of the present invention will be described with reference to the flowchart of FIG.

  In the present embodiment, before performing the nozzle recovery operation, it is determined whether or not the position of the displacement member 205 is at a position of an overnegative pressure that is outside a predetermined pressure range.

  When the position of the displacement member 205 is at a position of an overnegative pressure that is outside the predetermined pressure range, the liquid feed pump 241 is driven to rotate forward until the displacement member 205 is detected by the first sensor 251. The liquid is fed to the head tank 35 until the second detection position 295b is detected (until the pressure is within a predetermined pressure range).

  Further, if the position of the displacement member 205 is not at the position of the negative pressure that is outside the predetermined pressure range, it is determined whether or not the position of the displacement member 205 is at the position of the positive pressure that is outside the predetermined pressure range. .

  When the position of the displacement member 205 is at the position of the positive pressure that is outside the predetermined pressure range, the liquid feed pump 241 is driven in the reverse direction until the displacement member 205 is detected by the first sensor 251, for example. Until the 2 detection position 295b is detected (until it falls within a predetermined pressure range), the head tank 35 is fed back to the main tank 10.

  Thereafter, a recovery operation is started (a capping or suction operation is started).

  Thus, during the recovery operation, the first and second detection positions 205a and 205b of the displacement member 205 can be detected by the first sensor 251 and the liquid feeding operation can be performed correctly.

  Next, the relationship between the suction amount (suction flow rate) and the liquid supply amount (supply flow rate) during the recovery operation will be described.

  Next, a fifth embodiment of the present invention will be described with reference to the flowchart of FIG.

  As described above, the liquid supply pump 241 is driven to supply liquid while detecting and monitoring the displacement member 205 by the first sensor 251 during the recovery operation. Is larger than the ink suction flow rate by the suction pump 812 (supply flow rate> suction flow rate).

  Therefore, in the present embodiment, the first sensor 251 detects the first detection position 205a of the displacement member 205, drives the liquid feed pump 241, starts the liquid feed, and then sets the second detection position 205b of the displacement member 205. When a predetermined time elapses without detection, the liquid feeding pump 241 is stopped to stop the liquid feeding. In this case, although not shown, it is preferable to notify the ink supply operation failure.

  Here, the predetermined time is calculated by dividing the differential flow amount between the minimum flow rate of the liquid feed pump 241 and the maximum flow rate of the suction pump 812 with respect to the differential ink amount from the first detection position 205a to the second detection position 205b. Can do.

  That is, the predetermined time ≧ ((second detection position−first detection position) [mm] / ink amount conversion [cc / mm]) / (liquid pump minimum flow rate−suction pump maximum flow rate) [cc / sec] Can be obtained.

  Next, a sixth embodiment of the present invention will be described with reference to the flowchart of FIG.

  In the present embodiment, the displacement member 205 is located on the left side in FIG. 9 on the second detection position 205b side of the first sensor 251 in the atmosphere release operation in the initial recovery operation. Accordingly, since the displacement member 205 is displaced in the direction of arrow B in FIG. 9 in accordance with the suction operation, the detection output of the first sensor 251 detects the displacement member 205 when the second detection position 205b is detected. The state where the displacement member 205 is detected (for example, the ON state: non-detection) is changed from the state where the displacement member 205 is not (for example, OFF state: detection).

  Therefore, when the detection output of the first sensor 251 transits from a state where the displacement member 205 is not detected to a state where the displacement member 205 is detected, the liquid feeding pump 241 is driven.

  With this ink supply, the displacement member 205 is displaced in the direction in which the remaining amount of liquid increases (the direction of arrow A in FIG. 9).

  Therefore, when the detection output of the first sensor 251 transits from a state where the displacement member 205 is detected to a state where the displacement member 205 is not detected, the liquid feed pump 241 is stopped.

  In this way, the liquid feeding operation can be controlled only by detecting one end (second detection position 205b) of the displacement member.

  Next, a seventh embodiment of the present invention will be described with reference to the flowchart of FIG.

  In the present embodiment, the displacement member 205 is located on the left side in FIG. 9 on the second detection position 205b side of the first sensor 251 in the atmosphere release operation in the initial recovery operation. Accordingly, since the displacement member 205 is displaced in the direction of arrow B in FIG. 9 in accordance with the suction operation, the detection output of the first sensor 251 is the displacement member when the second detection position 205b of the displacement member 205 is detected. Transition from a state where 205 is not detected (for example, OFF state: detection) to a state where the displacement member 205 detects (for example, ON state: non-detection) and the suction operation continues, the first of the displacement member 205 again. On the detection position 205a side, a transition is made to a state where the displacement member 205 is not detected.

  Therefore, the detection output of the first sensor 251 transits from the state where the displacement member 205 is not detected (non-detection) to the state where the displacement member 205 is detected (detection), and further the state where the displacement member 205 is not detected (non-detection). When the transition is made to (detection), the liquid feed pump 241 is driven.

  With this ink supply, the displacement member 205 is displaced in the direction in which the remaining amount of liquid increases (the direction of arrow A in FIG. 9).

  Therefore, when the detection output of the first sensor 251 transits from a state where the displacement member 205 is not detected to a state where the displacement member 205 is detected, the liquid feed pump 241 is stopped.

  In this way, the liquid feeding operation can be controlled only by detecting one end portion (first detection position 205a) of the displacement member.

  Next, an eighth embodiment of the present invention will be described with reference to FIG. FIG. 18 is an explanatory diagram showing an example of the relationship between the environmental humidity and the opening amount of the displacement member (filler). The filler opening amount means the amount of displacement when the displacement member is displaced in the direction away from the tank body (the direction of arrow A in FIG. 9).

  The flexible film member 203 of the head tank 35 changes in expansion / contraction characteristics depending on the ambient environment of the apparatus such as temperature, humidity, and atmospheric pressure. For example, when the film member 203 expands and contracts due to a change in humidity, when the atmosphere is released by the atmosphere release mechanism 207, the pressure in the head tank 35 becomes atmospheric pressure, and the position at which the displacement member 205 is displaced is the humidity environment. Depending on the position.

  Specifically, the film member 203 extends when the humidity is high, so that the displacement member 205 moves away from the tank main body 201 as compared with the low humidity (the position indicated by the solid line in FIG. 18). By contracting, the displacement member 205 is displaced to a position closer to the tank main body 201 side (a position indicated by a broken line in FIG. 18) than when the humidity is high.

  Therefore, the position of the displacement member 205 that is displaced when the inside of the head tank 35 is at atmospheric pressure is greater than the position of the displacement member 205 that is detected by the first sensor 251. An example of the recovery operation in the case where the first sensor 251 is installed on the side away from the center will be described.

  In this case, before performing the recovery operation, the position of the displacement member 205 when the pressure in the head tank 35 reaches atmospheric pressure is detected in advance by the second sensor 301 and stored as the carriage position.

  Thereafter, the liquid feeding pump 241 reversely feeds the ink, so that the displacement member 205 is detected by the first sensor 251, the carriage 33 is moved in this state, and the position detected by the second sensor 301 is stored. From the difference from the position of the displacement member 205 when the inside of the head tank 35 detected and stored previously becomes the atmospheric pressure, from the time when the displacement member 205 is detected by the first sensor 251 to the atmospheric pressure ( Alternatively, the ink supply amount during the nozzle recovery operation (until the predetermined nozzle recovery upper limit pressure is reached) is calculated.

  When performing the nozzle recovery operation, the liquid feed pump 241 is driven when the displacement member 205 is detected by the first sensor 251, and the liquid feed pump is supplied when the amount of ink supplied during the nozzle recovery operation is supplied. 241 is stopped.

  At this time, the position of the displacement member 205 detected by the first sensor 251 is set to one of the first detection position 205a and the second detection position 205b.

  Further, the amount of ink supplied during the recovery operation may be an amount obtained by adding a predetermined amount to the previously calculated amount of ink supplied during the recovery operation to further increase the positive pressure.

  In addition, the drive control of the liquid feed pump 241 during the recovery operation drives the liquid feed pump 241 for the liquid feed pump drive time calculated in consideration of the maximum flow rate of the liquid feed pump 241 from the amount of ink supplied during the recovery operation. It can also be controlled.

  In this case, it is obtained by [Supply pump driving time = Supply ink amount during recovery operation / Maximum flow rate of liquid feed pump].

  As another example of the recovery operation corresponding to the environmental change, as described above, a humidity sensor that detects humidity can be used to change the ink supply amount in accordance with the humidity change.

  For example, in a predetermined low humidity environment, when the first sensor 251 detects the second detection position 251b of the displacement member 205 at which the inside of the head tank 35 is at a predetermined pressure, the humidity has increased compared to the predetermined low humidity environment. When this is detected, when the recovery operation is performed, even if the second detection position 205b is detected, the driving of the liquid feeding pump 241 is not stopped, and a predetermined additional ink supply amount is fed according to the humidity difference. The driving of the liquid feed pump 241 is stopped.

  As a result, the recovery operation can be performed within the range of the proper pressure in the head tank for the recovery operation in accordance with environmental changes such as humidity changes.

  Next, an example of control reflecting this change in environmental humidity will be described with reference to the flowcharts of FIGS. 19 and 20.

  First, the supplied ink amount calculation process will be described with reference to FIG. In this process, the atmosphere release mechanism 207 is once opened to release the head tank 35 to the atmosphere, and then the atmosphere release mechanism 207 is closed.

  Thereafter, after the position of the displacement member 205 is detected by the second sensor 301, the liquid feed pump 241 is reversely driven (suction drive to the main tank 10 side = reverse feed), and the displacement sensor 205 is driven by the first sensor 251. Is detected.

  Thereby, the difference amount between the atmospheric release position and the position where the first sensor 251 detects the displacement member 205 is detected, and the supplied ink amount is calculated from this difference amount.

  Then, the ambient environment at this time is stored, and the supplied ink amount is stored.

  Next, with reference to FIG. 20, a case where the recovery operation including the process of changing the supply amount by a predetermined amount due to environmental change is controlled at the first detection position will be described as an example.

  First, after confirming the position of the displacement member 205, capping is performed. Then, it is determined whether or not the first sensor 251 has detected the first detection position 205a of the displacement member 205. Here, when the first detection position 205a is detected, it is determined whether or not there is an environmental change.

  If there is no environmental change, the liquid feeding pump 241 is driven to perform liquid feeding for the amount of ink supplied as described above, and the driving of the liquid feeding pump 241 is stopped. On the other hand, if there is an environmental change, the liquid feeding pump 241 is driven, and the liquid feeding pump 241 is driven by adding or subtracting the amount of correction of the environmental change from the amount of ink supplied as described above. To stop.

  Thereafter, if the recovery operation is completed, the suction pump 812 is stopped and the recovery end operation is performed.

  In the above embodiment, when performing the recovery operation, the ink suction operation by the suction pump 812 and the ink supply operation of the liquid feed pump 241 that is driven while detecting the displacement member 205 by the first sensor 251 are continuous. Not only the operation but also the intermittent drive that drives at intervals of a predetermined time, and the recovery operation can be performed by causing a pressure fluctuation with a undulating pressure in the head 34.

  As described above, the displacement member 205 of the head tank 35 is detected by the first sensor 251 mounted on the carriage 33, so that the liquid feed pump 241 directly monitors the amount of liquid in the head tank 35 and the head. Control to supply liquid to the tank 35 is performed.

  Thus, when performing the recovery operation, even if the liquid is sucked and discharged from the head tank by the suction pump, the first member detects the displacement member and supplies the liquid by the liquid feed pump. According to the discharge amount, the negative pressure in the head tank and the head does not increase, and it is possible to continuously suck and discharge the liquid at a constant predetermined pressure, and the liquid discharge fluidity from the nozzle of the head does not deteriorate High recovery performance can be obtained without stagnation of liquid or minute foreign matter in the head.

  Various controls (processes) for performing the above supply and discharge operations to the head tank are executed by a computer by a program stored in the ROM 502. This program can be downloaded to the information processing apparatus (host 600) and installed in the image forming apparatus. Further, the image forming apparatus and the information processing apparatus according to the present invention or the image forming apparatus and the information processing apparatus having a program for performing the processing according to the present invention can be combined to constitute an image forming system.

  In the present application, the “paper” is not limited to paper, but includes OHP, cloth, glass, a substrate, etc., and means a material to which ink droplets or other liquids can be attached. , Recording media, recording paper, recording paper, and the like. In addition, image formation, recording, printing, printing, and printing are all synonymous.

  The “image forming apparatus” means an apparatus that forms an image by discharging liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc. “Formation” means not only giving an image having a meaning such as a character or a figure to a medium but also giving an image having no meaning such as a pattern to the medium (simply causing a droplet to land on the medium). ) Also means.

  The “ink” is not limited to an ink unless otherwise specified, but includes any liquid that can form an image, such as a recording liquid, a fixing processing liquid, or a liquid. Used generically, for example, includes DNA samples, resists, pattern materials, resins, and the like.

  In addition, the “image” is not limited to a planar image, and includes an image given to a three-dimensionally formed image and an image formed by three-dimensionally modeling a solid itself.

  Further, the image forming apparatus includes both a serial type image forming apparatus and a line type image forming apparatus, unless otherwise limited.

10 Ink cartridge (main tank)
33 Carriage 34, 34a, 34b Recording head (liquid ejection head)
35 Sub tank 81 Maintenance and recovery mechanism 201 Tank case (liquid container)
203 flexible member (flexible film member)
205 Displacement member (filler)
205a
251 First sensor (detection means)
301 ... 2nd sensor 500 ... Control part

Claims (10)

A recording head having nozzles for discharging droplets;
A head tank for storing liquid to be supplied to the recording head;
A carriage on which the recording head and the head tank are mounted;
A main tank for storing liquid to be supplied to the head tank;
Liquid feeding means for supplying liquid from the main tank to the head tank;
Recovery means for performing a recovery operation of sucking and discharging the liquid from the nozzles of the recording head to recover the discharge state of the nozzles,
The head tank has negative pressure generating means for generating a negative pressure according to the remaining amount of liquid, and a displacement member that is displaced according to the remaining amount of liquid.
The carriage is provided with detection means for detecting the displacement member,
When performing the recovery operation by the recovery means, controlling the liquid supply to the head tank by the liquid supply means from the detection of the displacement of the displacement member by the detection means,
An image forming apparatus characterized in that the pressure in the head tank is maintained within a predetermined range during the recovery operation. The displacement member has a first detection position and a second detection position;
The first detection position is a position on the side where the liquid remaining amount of the head tank decreases, and the second detection position is a position on the side where the liquid remaining amount of the head tank increases.
When the detection means detects the first detection position of the displacement member, liquid feeding to the head tank is performed,
The image forming apparatus according to claim 1, wherein when the detecting unit detects the second detection position of the displacement member, liquid feeding to the head tank is stopped.   After the liquid feeding to the head tank is started, the liquid feeding to the head tank is stopped when the second detection position of the displacement member is not detected even after a predetermined time has elapsed. The image forming apparatus according to claim 2.   4. The image forming apparatus according to claim 2, wherein the pressure in the head tank when the detection unit detects the second detection position of the displacement member is equal to or higher than atmospheric pressure. 5.   When the position of the displacement member is a position where the remaining amount of liquid in the head tank is less than the position where the first detection position is detected by the detection means before starting the recovery operation, the detection means 5. The image forming apparatus according to claim 2, wherein the liquid is supplied to the head tank until the second position of the displacement member is detected. 6.   5. The image forming apparatus according to claim 1, wherein a liquid feeding amount by the liquid feeding unit during the recovery operation is larger than a suction discharge amount. Before starting the recovery operation, the position of the displacement member is a position where the remaining amount of liquid in the head tank is greater than the position where the detection unit detects the second detection position,
When performing the recovery operation,
When the detection output of the detection means transitions from a state where the displacement member is not detected to a detected state, liquid feeding to the head tank is performed,
2. The liquid feeding to the head tank is stopped when the detection output of the detection means transitions from a state in which the displacement member is detected to a state in which the displacement member is not detected. Image forming apparatus. Before starting the recovery operation, the position of the displacement member is a position where the remaining amount of liquid in the head tank is greater than the position where the detection unit detects the second detection position,
When performing the recovery operation,
When the detection output of the detection means transitions from a state where the displacement member is not detected to a detected state and further transitions to a state where the displacement member is not detected, liquid feeding to the head tank is performed. ,
3. The liquid feeding to the head tank is stopped when the detection output of the detection means transits from a state where the displacement member is not detected to a state where the displacement member is detected. The image forming apparatus according to claim 7.   8. The image forming apparatus according to claim 2, wherein when the liquid feeding to the head tank is stopped, the liquid feeding is stopped after a predetermined amount of liquid feeding is continued.   The image forming apparatus according to claim 9, wherein the predetermined amount is changed according to an environmental humidity of the apparatus.

Images