JP2009274325A - Image forming apparatus and negative pressure reforming method in image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that ink is uselessly consumed since a negative pressure recovery operation is performed even when negative pressure is normal, when air is mixed into a sub-tank. <P>SOLUTION: The amount of gas in the sub-tank 35 supplying the ink to a recording head 34 is detected by detecting electrode pins 208a and 208b, to be detected as the displacement amount of a displacement member 205 detecting the displacement amount of the elastic member 204 of the sub-tank 35. When the gas amount is a predetermined gas amount VGa or more and the displacement amount is below a predetermined displacement amount La, on the basis of the detected gas amount and displacement amount, the ink is supplied into the sub-tank 35 and then, a negative pressure forming operation is performed, in such a state that opening to the air through the air opening mechanism 207 of the sub-tank 35 is performed. When the gas amount is the predetermined gap amount VGa or more and the displacement amount is the predetermined displacement amount La or more, control not to perform the negative pressure forming operation is performed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus and a negative pressure re-forming method in the image forming apparatus, and more particularly to an image forming apparatus including a recording head that discharges droplets and a sub tank that supplies ink to the recording head, and a negative pressure re-forming in the image forming apparatus. Regarding the method.

  In general, a printer, a fax machine, a copier, a plotter, or an image forming apparatus that combines a plurality of these functions includes, for example, a recording head composed of a liquid ejection head that ejects ink droplets, It is also referred to as “paper”, but the material is not limited, and a recording medium, recording medium, transfer material, recording paper, etc. are also used synonymously.) Some perform formation (recording, printing, printing, and printing are also used synonymously).

  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 ejecting a droplet). means. The “ink” is not limited to so-called ink, and is not particularly limited as long as it becomes a liquid when ejected. For example, a liquid including a DNA sample, a resist, a pattern material, and the like. Used as a general term.

In such an image forming apparatus, a sub tank (also referred to as a head tank or a buffer tank) for supplying ink to the recording head is provided, and negative pressure is used to prevent the ink from seeping out and sagging from the nozzles of the recording head. The sub tank has a negative pressure forming function (mechanism) that generates a negative pressure, and when a negative pressure abnormality in the sub tank is detected, a negative pressure recovery operation (negative pressure regenerating operation) is performed to return the negative pressure to a normal state. What is made is known.
JP 2007-015153 A

  The sub-tank described in Patent Document 1 is composed of a case with an open side wall, a film that covers the opening of the case, and an elastic member that presses the film from the inside, and the negative pressure is generated by the restoring force of the elastic member. To keep generating.

Also, in Patent Documents 2 and 3, when a sub-tank having a similar configuration is used, when the amount of air in the sub-tank exceeds a predetermined amount, or when the amount of ink in the sub-tank becomes less than a predetermined amount It is described that negative pressure reforming is performed.
JP 2005-59274 A JP 2005-59491 A

  As described above, in order to prevent ink from seeping out and sagging from the nozzles of the recording head in the sub tank, it is necessary to always maintain a certain negative pressure state above a certain level, and if air flows into the sub tank, When the air flows in because the inside of the recording head becomes positive pressure, the image quality deteriorates due to the drop in droplet discharge performance, and the ink flows out of the recording head due to its own weight. The negative pressure recovery operation is performed.

  By the way, in order to regenerate the negative pressure of the sub-tank having the above-described configuration, by discharging the ink inside, the elastic member is displaced and a negative pressure is generated by the restoring force of the elastic member. In the case of negative pressure recovery), ink is consumed, and if the frequency of negative pressure regeneration increases, there is a problem in that the amount of ink consumed increases.

  As a result of intensive studies by the present inventors, as described above, even when the air amount in the sub-tank exceeds a predetermined amount, the negative pressure in the sub-tank may be appropriately maintained. We found that it was possible to grasp by other characteristics.

  The present invention has been made on the basis of the above problems and knowledge, and an object of the present invention is to reduce ink consumption due to negative pressure reformation when a sub-tank having a flexible member and an elastic member is provided.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A recording head for discharging droplets;
And a negative pressure forming unit including a flexible member that forms one surface of the ink storage unit that stores ink, and an elastic member that biases the flexible member outward, and the inside of the ink storage unit is exposed to the atmosphere. A sub-tank that has an openable openable air release mechanism and supplies ink from the ink container to the recording head;
Gas amount detection means for detecting the amount of gas in the ink storage portion of the sub tank;
A displacement amount detecting means for detecting a displacement amount of the elastic member of the sub tank;
Control means for performing a negative pressure forming operation after supplying ink into the sub tank in a state where the ink containing portion is opened to the atmosphere through the atmosphere release mechanism of the sub tank;
Based on the detected gas amount and displacement amount, the control means performs the negative pressure forming operation when the gas amount is equal to or greater than a predetermined gas amount and the displacement amount is less than the predetermined displacement amount, and the gas amount is When the displacement amount is greater than or equal to a predetermined gas amount and greater than or equal to the predetermined displacement amount, the negative pressure forming operation is not controlled.

  Here, when the gas amount is equal to or greater than the predetermined gas amount and the displacement amount is equal to or greater than the predetermined displacement amount, the control means is configured to have a predetermined second predetermined gas amount that is greater than the predetermined gas amount. In such a case, it is possible to control to perform the negative pressure forming operation.

  Further, the control means is configured such that when the gas amount is equal to or larger than the predetermined gas amount and the displacement amount is equal to or larger than the predetermined displacement amount, the ink usage amount after the gas amount becomes equal to or larger than the predetermined gas amount is set to a predetermined value. When the usage amount is greater than or equal to the usage amount, the negative pressure forming operation can be controlled.

  Further, the apparatus has means for storing an environmental temperature when the ink storage portion of the sub tank is opened to the atmosphere, and the control means has the gas amount equal to or greater than the predetermined gas amount and the displacement amount equal to or greater than the predetermined displacement amount. When the difference between the stored environmental temperature and the current temperature is greater than or equal to a predetermined temperature, the negative pressure forming operation is performed, and when the difference between the stored environmental temperature and the current temperature is less than the predetermined temperature, the negative pressure is performed. It can be set as the control which does not perform formation operation.

  Further, the apparatus has means for storing environmental humidity when the ink storage portion of the sub tank is opened to the atmosphere, and the control means has the gas amount equal to or larger than a predetermined gas amount and the displacement amount equal to or larger than a predetermined displacement amount. When the difference between the stored environmental humidity and the current humidity is greater than or equal to a predetermined humidity, the negative pressure forming operation is performed. When the difference between the stored environmental humidity and the current humidity is less than the predetermined humidity, the negative pressure is performed. It can be set as the control which does not perform formation operation.

The negative pressure re-forming method in the image forming apparatus according to the present invention is:
A recording head for discharging droplets;
And a negative pressure forming unit including a flexible member that forms one surface of the ink storage unit that stores ink and an elastic member that biases the flexible member outward, and the inside of the ink storage unit is exposed to the atmosphere. A sub-tank having an openable openable air opening mechanism for supplying ink from the ink containing portion to the recording head;
Gas amount detection means for detecting the amount of gas in the ink storage portion of the sub tank;
A displacement amount detecting means for detecting a displacement amount of the elastic member of the sub tank;
Negative pressure in an image forming apparatus, comprising: a control unit configured to perform a negative pressure forming operation after supplying ink into the sub tank in a state where the ink container is opened to the atmosphere through the atmosphere release mechanism of the sub tank. In the reforming method,
Based on the detected gas amount and displacement, when the gas amount is equal to or greater than a predetermined gas amount and the displacement amount is less than the predetermined displacement amount, the negative pressure forming operation is performed, and the gas amount is equal to or greater than the predetermined gas amount. The negative pressure forming operation is not performed when the displacement amount is equal to or greater than a predetermined displacement amount.

  According to the image forming apparatus and the negative pressure re-forming method according to the present invention, the gas amount is equal to or larger than the predetermined gas amount and the displacement amount is less than the predetermined displacement amount based on the detected gas amount in the sub tank and the displacement amount of the elastic member. The negative pressure forming operation is performed when the gas amount is equal to or greater than the predetermined amount and the negative pressure forming operation is not performed when the displacement amount is equal to or greater than the predetermined displacement amount. Even when the negative pressure is appropriate, negative pressure regeneration is not performed, and the number of negative pressure regeneration operations can be reduced to reduce wasteful consumption of ink.

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 the 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. 2 is moved and scanned in the direction indicated by the arrow (carriage main scanning direction) in FIG. 2 via a timing belt by a main scanning motor (not shown).

  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.

  As the recording head 34, as shown in FIG. 3, one having nozzle rows 34K, 34C, 34M, 34Y of each color in which nozzles 34n are arranged on one nozzle surface 34N can be used.

  Further, the sub tanks 35a and 35b, which are sub tanks as the second ink supply unit for supplying ink of each color corresponding to the nozzle row of the recording head 34, are referred to as the “sub tank 35” when they are not distinguished. ) Is installed. From the ink cartridges 10 y, 10 m, 10 c, and 10 k that are the first ink supply portions of the respective colors that are detachably attached to the cartridge loading portion 4, the sub-tank 35 is supplied through the supply tubes 36 of the respective colors by the supply pump unit 5. The recording liquid of each color is replenished and supplied.

  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 of FIG. 2 when the transport roller 52 is rotationally driven through timing by a sub-scanning motor (not shown).

  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, as shown in FIG. 2, a maintenance / recovery mechanism 81 for maintaining and recovering the state of the nozzles 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. Further, a waste liquid tank 100 for storing waste liquid generated by the maintenance recovery operation is mounted on the lower side of the head maintenance recovery mechanism 81 in a replaceable manner with respect to the apparatus main body.

  In addition, as shown in FIG. 2, in the non-printing area on the other side in the scanning direction of the carriage 33, idle discharge is performed to discharge liquid droplets that do not contribute to recording in order to discharge the recording liquid thickened during recording or the like. An empty discharge receiver 88 for receiving the liquid droplets at the time is disposed, and the empty discharge receiver 88 is provided with an opening 89 along the nozzle row direction of the recording head 34.

  In this 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 sheet 42 fed substantially vertically upward is guided by the guide 45, and includes the transport belt 51 and the counter. It is sandwiched between the rollers 46 and conveyed, and 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 sub tank 35 will be described with reference to FIGS. 3 is a schematic top view for explaining one head of the sub-tank, and FIG. 4 is a schematic front view for explaining one head of the sub-tank.
The sub-tank 35 has a tank case 201 that forms an ink containing portion opened on one side for holding ink. The opening of the tank case 201 is sealed with a flexible film 203, and the inside of the tank case 201 is The film 203 is constantly urged outward by a spring 204 as an elastic member disposed on the outside. As a result, an outward biasing force is applied to the film 203 of the tank case 201 by the spring 204, so that a negative pressure is generated when the remaining amount of ink in the tank case 201 decreases.

  Further, a displacement member 205 made of a filler whose one end is swingably supported is fixed to the film 203 on the outside of the tank case 201 by adhesion or the like, and the displacement member 205 is displaced in conjunction with the movement of the film 203. Therefore, the remaining amount of ink in the sub tank 35 can be detected by detecting the displacement amount of the displacement member 205 by the full tank detection sensor 301 including an optical sensor arranged on the apparatus main body side.

  A supply port 209 for supplying ink from the ink cartridge 10 is connected to the ink supply tube 36 at the upper portion of the tank case 201. An air release mechanism 207 that opens the inside of the sub tank 35 to the atmosphere is provided on the side of the tank case 201. The atmosphere release mechanism 207 includes a valve body 207b that opens and closes an atmosphere release path 207a communicating with the sub tank 35, a spring 207c that urges the valve body 207b to a closed state, and the like. Is opened by pushing the valve body 207b, and the sub tank 35 is opened to the atmosphere (a state communicating with the atmosphere).

  Electrode pins 208a and 208b for detecting the ink level in the sub 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 sub tank 35 has become a predetermined amount or more. The electrode pins 208a and 208b constitute gas amount detection means.

Here, the negative pressure formation in the sub tank 35 will be described with reference to FIG. 5 showing an outline of the ink supply / discharge system.
Ink is supplied from the ink cartridge 10 to the sub tank 35 via the supply tube 36 by the supply pump 241 of the supply unit 24. Further, by driving the suction pump 811 of the maintenance / recovery mechanism 81 with the nozzle surface of the recording head 34 capped by the suction cap 82a of the maintenance / recovery mechanism 81, the subtank 35 is sucked from the nozzles via the suction tube 812. The ink inside can be sucked, and the elastic member 204 pushes the flexible film 203 outward, whereby a negative pressure is formed in the sub tank 35. The sucked waste ink is discharged to a waste liquid tank 813.

Next, detection of the displacement amount of the elastic member 204 of the sub tank 35 will be described with reference to FIGS.
Here, the displacement amount of the elastic member 204 is detected as the opening amount of the displacement member 205. First, as shown in FIG. 6, for example, on the apparatus main body side, the transmission type optical sensor described above is located at a position where the tip of the displacement member 205 of each sub tank 35 passes when the carriage 33 moves in the main scanning direction. A full tank detection sensor 301 is installed. Here, the position of the carriage 33 in the main scanning direction is detected by reading the encoder scale 332 arranged along the carriage main scanning direction by the encoder sensor 331.

  Therefore, as shown in FIG. 7A, when the negative pressure of the sub tank 35 is normal, the carriage 33 is moved in the direction of the arrow from the predetermined position indicated by the solid line to move the sub tank 35 by the distance L1. The displacement member 205 can be detected by the full tank detection sensor 301.

  On the other hand, as shown in FIG. 7B, when the negative pressure of the sub tank 35 is abnormal, the displacement member 205 that should be moved to the sub tank 35 side is separated from the sub tank 35 (the elastic member 204). Similarly, when the carriage 33 is moved in the direction of the arrow from the predetermined position indicated by the solid line, the moving distance L1 when the negative pressure is normal is similarly determined. The full member detection sensor 301 detects the displacement member 205 when it has moved by a short distance L2.

  In this way, by detecting the position (movement distance) of the sub tank 35 when the displacement member 205 is detected, the displacement amount of the displacement member 205 (corresponding to the displacement amount of the elastic member 204 inside the sub tank 35) is obtained. Can be detected.

  The displacement amount of the elastic member 204 inside the sub tank 35 is detected as the displacement amount of the displacement member 205. However, the displacement amount can be directly detected by a laser displacement meter or the like from the main scanning direction. . In this case, the layout between the plurality of sub-tanks 35 is devised so that the displacement amount of the elastic member in the plurality of sub-tanks 35 can be measured with a single optical axis, or the laser displacement meter is attached to the sub-tank 35 to be measured. You may provide the mechanism which can change a position collectively. Further, a configuration in which a strain gauge is mounted on the surface of the flexible member of the sub tank 35 and the amount of displacement is measured is also possible. However, the configuration for detecting the amount of displacement of the displacement member 205 is simpler than the case where a pressure sensor or the like is used, and the cost can be reduced.

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 includes a CPU 511 that also serves as a control unit according to the present invention that controls the entire apparatus, a ROM 502 that stores programs executed by the CPU 511 and other fixed data, and a RAM 503 that temporarily stores image data and the like. And a rewritable nonvolatile memory 504 for holding data while the apparatus is powered off, image processing for performing various signal processing and rearrangement on image data, and other control of the entire apparatus And an ASIC 505 for processing input / output signals.

  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, An AC bias is applied to the charging roller 56, a main scanning motor 554 that moves and scans the carriage 33, a sub-scanning motor 555 that rotates the conveyance belt 51, a motor drive unit 510 that drives the maintenance / recovery motor 556 of the maintenance / recovery mechanism 81. An AC bias supply unit 511 to supply, a solenoid drive unit 512 to drive an atmosphere release solenoid 302 that opens and closes the atmosphere release mechanism 207 of the sub tank 35 are provided.

  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, and print control unit 508, motor control unit 510, AC bias supply unit Used to control 511. The sensor group 515 includes an optical sensor for detecting the position of the paper, a thermistor for monitoring the temperature and humidity in the machine, a sensor for monitoring the voltage of the charging belt, an interlock switch for detecting opening and closing of the cover, and the like. The I / O unit 513 can process various sensor information. The sensor group 515 input to the I / O unit 513 is also input with signals such as the full tank detection sensor 301 and the detection electrode pins 208a and 208b that detect the displacement member 205 of the sub tank 35 described above.

  As described above, the control unit 500 is configured to detect the amount of air in the sub tank 35 by a detection signal from the electrode pins 208a and 208b of the sub tank 35. Displacement amount detection means for detecting the displacement amount of the displacement member 205 (elastic member 204) based on the detection signal of the temperature sensor, the temperature sensor included in the sensor group 515, the temperature detected from the detection signal of the humidity sensor, the humidity, etc. As the storage means for storing the memory, a rewritable storage means (memory) such as a battery backup RAM or NVRAM 504 is used, which can hold the storage state even when the apparatus power is shut off.

Next, the negative pressure regenerating operation based on the gas amount detection of the sub tank 35 which is a premise of the present invention will be described with reference to the flowchart of FIG.
First, the amount of gas in the sub tank 35 is reduced to a predetermined amount by the ink liquid level being lowered to a predetermined height or less by a detection signal of the detection electrode pins 208a, 208b (hereinafter simply referred to as “detection electrode 208”) of the sub tank 35. When it is detected that the above has been reached, the sub-tank 35 is filled to the atmosphere and the negative pressure is restored to the normal state (negative pressure regenerating operation). This is because if the gas enters the sub tank 35 excessively beyond the originally permitted amount, the internal volume of the sub tank 35 increases by the intrusion amount, and the displacement amount of the internal elastic member 204 is reduced and restored. This is because it is determined that the subtank negative pressure generated from the force is also reduced.

  Here, in the negative pressure recovery (negative pressure reforming) operation, the atmosphere release solenoid 302 is operated to open the atmosphere release mechanism 207 of the sub tank 35, thereby opening the sub tank 35 to the atmosphere. In this state, the supply pump 241 is operated to replenish and supply the ink from the ink cartridge 10 into the sub tank 35 (filled to open to the atmosphere), and the electrical characteristics generated when the detection electrode 208 in the sub tank 35 contacts the ink. When the change is detected, the ink filling is finished. Thereafter, the air release mechanism 207 is closed, and the suction pump 812 is operated with the recording head 34 capped by the cap 82a to suck the required amount of ink from the nozzles, thereby restoring the restoring force of the elastic member 204. Thus, the inside of the sub tank 35 is brought into a required negative pressure state. Thereby, the negative pressure of the sub tank 35 in which the negative pressure abnormality has occurred can be recovered to a normal state. In this way, when the negative pressure value in the sub tank is abnormal, it is possible to regenerate the desired negative pressure value from the beginning by performing open air filling, so that the normal negative pressure value is maintained (recovered). Can do.

  However, according to the study by the present inventors, when the detection electrode 208 of the sub tank 35 detects that the gas amount exceeds the predetermined gas amount, the negative pressure inside the sub tank 35 is not necessarily broken. Was found.

  That is, when the apparatus is left in a state where the negative pressure shown in FIG. 10A is normal, the sub tank 35 is not used at all, and thus air leak (intrusion of the atmosphere) from the atmosphere release mechanism 207 occurs. As shown in FIG. 4B, the gas enters the sub tank 35 and the ink liquid level 251 is lowered, so that when the detection electrode 208 detects that the gas amount exceeds the predetermined gas amount, The elastic member 204 is extended and the negative pressure is destroyed. At this time, the gas intrusion into the sub tank 35 is nothing but a decrease in the deformation amount of the elastic member 204 inside the sub tank 35.

  On the other hand, when the negative pressure shown in FIG. 11 (a) is normal and an air leak from the atmosphere release mechanism 207 occurs, the gas amount is predetermined by the detection electrode 208 as shown in FIG. 11 (b). Since the remaining amount of ink in the sub tank 35 is reduced by printing before it is detected that the amount of gas has exceeded the amount of gas, it acts in a direction to cancel the increase in the volume of the sub tank 35 due to the inflow of gas. A decrease in the deformation amount of the elastic member 204 is reduced. Further, when ink supply (replenishment) is performed until full tank is detected by the displacement member 205 as shown in FIG. 4C, the elastic member 204 is displaced, and as shown in FIG. Although the displacement amount of the member 204 becomes a target displacement amount, the amount of gas inside can remain excessive. That is, there is a case where the negative pressure by the elastic member 204 is still maintained even when gas enters due to air leak and the ink liquid level becomes below the height of the detection electrode 208.

  Therefore, in the present invention, when the gas is detected by the detection electrode 208 of the sub tank 35 (when it is detected that the gas amount is equal to or greater than the predetermined gas amount), the opening amount of the displacement member 205 (the displacement of the elastic member 204). Amount) is detected by the full tank detection sensor 301, and it is determined whether or not there is an abnormality in the negative pressure in the sub tank 35 in accordance with the opening amount of the displacement member 205. That is, when the opening amount of the displacement member 205 is larger than a predetermined value (that is, when the displacement amount of the internal elastic member 295 is less than the predetermined displacement amount La), it is assumed that the negative pressure is excessively relaxed. Restore pressure to normal. Conversely, when the opening amount of the displacement member 205 is less than or equal to a predetermined value (that is, the displacement amount of the internal elastic member 204 is greater than or equal to the predetermined displacement amount La), it is assumed that the negative pressure is within the normal range and the negative pressure is recovered ( The operation of (reforming) is not performed.

Therefore, a first embodiment of the present invention will be described with reference to a flowchart shown in FIG.
Here, when it is detected by the detection signal of the detection electrode 208 of the sub-tank 35 that the ink liquid level has fallen below a predetermined height and the amount of gas in the sub-tank 35 becomes equal to or greater than the predetermined gas amount VGa, the elasticity The displacement amount of the member 204 is detected. As described above, the displacement amount is detected by the difference between the predetermined position and the carriage position when the full member detection sensor 301 detects the displacement member 205 by moving the carriage 33 from the predetermined position. This is detected as the opening amount of the displacement member 205.

  Then, it is determined whether or not the displacement amount of the elastic member 204 is less than a predetermined displacement amount La. When the displacement amount is less than the predetermined displacement amount La, the same open air filling as described in FIG. 9 is performed. When the negative pressure re-forming operation is performed to form a negative pressure, and the displacement amount is not less than the predetermined displacement amount La (predetermined displacement amount La or more), the gas amount is greater than or equal to the predetermined gas amount VGa. Do not perform negative pressure regeneration operation.

  Thus, based on the gas amount detected in the sub tank and the displacement amount of the elastic member, when the gas amount is equal to or larger than the predetermined gas amount and the displacement amount is less than the predetermined displacement amount, the negative pressure forming operation is performed, and the gas amount is By adopting a configuration in which the negative pressure forming operation is not performed when the displacement amount is equal to or greater than the predetermined displacement amount and the displacement amount is equal to or greater than the predetermined displacement amount, the negative pressure is appropriate when the negative pressure is appropriate even if the gas amount in the sub tank exceeds the predetermined amount. Without performing re-formation, the number of negative pressure re-formation operations can be reduced to reduce unnecessary ink consumption. At the same time, it is possible to prevent the printing speed from being lowered and the apparatus startup time from being unnecessarily prolonged due to the negative pressure re-forming operation.

Next, a second embodiment of the present invention will be described with reference to the flowchart shown in FIG.
Here, as will be described later, it is possible to detect whether or not the gas amount in the sub tank 35 is equal to or greater than a second predetermined gas amount VGb (VGb> VGa) greater than the first predetermined gas amount VGa. In the processing of the first embodiment, it is determined whether or not the displacement amount of the elastic member 204 is less than a predetermined displacement amount La, and when the displacement amount is not less than the predetermined displacement amount La (the predetermined displacement amount La or more). When the gas amount in the sub tank 35 is equal to or greater than a second predetermined gas amount VGb, the gas amount in the sub tank 35 is greater than or equal to a predetermined second predetermined gas amount VGb. In some cases, the negative pressure reforming operation is performed.

  This is because even if the displacement amount of the elastic member 204 in the sub tank 35 is approximately the same, if the gas amount is large, that is, if the ink liquid amount in the sub tank 35 is small, the negative pressure in the sub tank 35 is shifted in a strong direction. It is because it is doing.

  More specifically, the pressure corresponding to the height of the liquid level with respect to the nozzles of the recording head 34 acts in a direction of relaxing (decreasing) the negative pressure (upward pressure at the nozzles) in the sub tank 35, and the ink liquid. As the surface height decreases, the negative pressure relaxation width decreases, and as a result, even if the amount of displacement of the elastic member 204 is approximately the same, the greater the amount of gas, the more the negative pressure changes.

  For example, FIG. 14 shows an example of the relationship between the amount of ink used in the sub tank and the magnitude of the negative pressure in the sub tank for each gas amount in the sub tank. Here, when the gas amounts in the sub tank are the gas amounts VG1, VG2, and VG3 (VG3> VG2> VG1), the amount of change in the negative pressure accompanying the increase in the ink usage amount is substantially the same in the gas amounts VG1 and VG2. On the other hand, when the gas amount is VG3, the negative pressure shifts in a strong direction as the ink usage increases. It should be noted that the almost same negative pressure curve (negative pressure change) when the gas amount is less than the gas amount VG2 is not estimated, but the pressure of the flexible member constituting the sub tank 35 is slightly changed. This is considered to act as a damper.

  As described above, when the negative pressure is shifted in a strong direction, the reached negative pressure is increased with respect to the ink consumption amount of the same level for the ink in the sub tank 35. If the gas amount is in a normal state, the sub tank is in the normal negative pressure range. In some cases, an excessively negative pressure is generated with respect to the ink consumption amount in the ink 35, which may cause a discharge failure.

  Therefore, the gas amount that is not substantially affected by the negative pressure into the sub tank 35 is the second predetermined gas amount VGb (for example, the gas amount VG2 in the example of FIG. 14), and the gas amount entering the sub tank 35 is the second gas amount VGb. When the gas amount is less than the predetermined gas amount VGb, the negative pressure regenerating operation is not performed.

Here, a configuration for detecting that the gas amount in the sub tank 35 has become equal to or less than the second predetermined gas amount VGb will be described.
For example, in the case where two levels (references) of gas amount detection are performed using the detection electrode pins as in the above-described embodiment, two separate detection electrode pins 208a and 208b for grounding and signals are used. For example, there is a method of adding three length detection electrode pins for a signal to form a three-pin configuration. As another method, the two detection electrode pins can be detected as a difference in electrical characteristics according to the amount of gas (that is, the amount of ink immersed in the pins). In this case, since the wettability of the ink with respect to the electrode pins tends to affect, it is preferable to take measures to improve the liquid repellency in order to improve the detection accuracy.

  In addition, although it demonstrated by the structure which provides a new electrode pin in order to detect that the gas quantity of the sub tank 35 increased, for example, progress after negative pressure formation operation implementation without providing a new electrode pin Time can be used as a substitute for gas volume. That is, generally, the phenomenon in which air is mixed is considered to be due to a sealing failure of the structure including the sub tank 35, the supply pump 241, the supply tube 36, and their interface portions (connection portions).

  Here, the location where the sealability is most likely to be the lowest in this structure is the movable portion, that is, the portion of the air release valve 207 that is opened and closed by the negative pressure forming operation. Since the other sealing portions are not movable parts, they are considered to have a certain sealing property apart from good and bad as an individual. The atmospheric release valve 207, which is a movable part, is determined to have a sealing property when the valve is closed, and the gas inflow rate after the atmospheric release valve 207 is closed is considered to be substantially constant even if the sealing property of other non-movable parts is included. It is done. Therefore, instead of actually measuring the amount of gas, it is possible to roughly grasp the amount of gas flowing in by measuring the elapsed time from the time of sealing by the negative pressure forming operation.

Next, a third embodiment of the present invention will be described with reference to a flowchart shown in FIG.
Here, in the second embodiment, when the displacement amount of the elastic member 204 is not less than the predetermined displacement amount La (predetermined displacement amount La or more), instead of detecting the second predetermined gas amount VGb. The cumulative ink usage after the first predetermined gas amount VGa is detected, it is determined whether or not the cumulative ink usage is equal to or greater than a predetermined predetermined usage VL, and the cumulative ink usage is determined. When the amount is equal to or greater than a predetermined use amount VL, a negative pressure regenerating operation is performed.

  That is, as an alternative means for detecting the second predetermined gas amount VGb, a threshold is set for the ink usage amount in the sub tank 35. Starting from the time when the gas of the first predetermined gas amount VGa is detected in the sub-tank 35, the accumulated ink use amount consumed thereafter is measured, and the accumulated ink use amount exceeds a predetermined threshold value (use amount) VL. In this case, assuming that the second predetermined gas amount VGb is reached, the negative pressure regenerating operation is performed.

  The amount of ink used in the sub-tank 35 is the sum of consumption due to ejection and suction operations, and can be easily grasped theoretically and does not involve the addition of parts or parts processing, thereby reducing costs. The predetermined threshold value (predetermined usage amount) VL can be arbitrarily set according to the unit performance or the like. However, as an example, the case where the ink consumption is completely replaced with gas is considered the worst case as the gas intrusion amount. , VL can be set as a value corresponding to VGb-VGa. Actually, it is possible to set as a predetermined multiple of (VG2-VG1) in anticipation of an unintended gas intrusion speed.

A fourth embodiment of the present invention will be described with reference to a flowchart shown in FIG.
Here, in the third embodiment (which can also be applied to the first and second embodiments), when the displacement amount of the elastic member 204 is not less than a predetermined displacement amount La (a predetermined displacement amount La or more). If the cumulative ink usage amount after the first predetermined gas amount VGa is detected and the cumulative ink usage amount is not equal to or greater than the predetermined predetermined usage amount VL, the variation range of temperature or humidity is further increased. It is determined whether or not the amount is equal to or greater than a predetermined amount, and when the temperature or humidity change width is equal to or greater than a predetermined amount, a negative pressure regenerating operation is performed.

  That is, the internal pressure of the sub tank 35 changes with temperature. Here, FIG. 17 shows an example of a measurement result of the increase in the internal pressure of the subtank when the temperature is raised from room temperature to 50 degrees for each ink liquid amount (the amount obtained by subtracting the gas amount from the subtank capacity). In this case, as a matter of course, as the amount of gas increases, the range of pressure increase due to temperature rise increases. When the upper limit of the air amount (gas amount) in the sub-tank is relaxed as in the present invention (when the negative pressure is not regenerated when the displacement amount is not less than the predetermined amount even if the gas amount is not less than the predetermined amount), Since there is a risk of being affected by an increase in pressure due to temperature rise, the negative pressure is recreated if the temperature change width after allowing the gas equal to or greater than the first predetermined gas amount VGa is equal to or greater than the predetermined width. I have to.

  Therefore, the environmental temperature or humidity when the sub tank 35 is opened to the atmosphere is stored, and when the difference (change width) between the stored environmental temperature or humidity and the current temperature or humidity is equal to or greater than a predetermined value, a negative pressure forming operation is performed. By doing so, the effect of pressure increase due to temperature rise is suppressed.

  The control related to the sub-tank gas amount detection, displacement amount detection, and negative pressure regeneration operation (negative pressure regeneration process) can be executed 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. The negative pressure regeneration process may be performed by a printer driver on the information processing apparatus (host 600) side.

  The image forming apparatus according to the present invention is not limited to a printer having a single function configuration, and may be an image forming apparatus having a composite function such as printer / facsimile / copying.

1 is a schematic side view illustrating an overall configuration of a mechanism unit of an image forming apparatus according to 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 explanatory view of FIG. 3. FIG. 3 is a schematic explanatory diagram for explaining an ink supply / discharge system. It is a principal part explanatory drawing of the carriage used for description of the detection of the displacement amount of the elastic member of a sub tank, and a full tank detection sensor. FIG. 6 is a schematic explanatory view for explaining the detection of the displacement amount of the elastic member of the sub tank. It is a schematic block explanatory drawing explaining the control part of the apparatus. It is a flowchart with which it uses for description of the negative pressure regeneration process based on the detection of the subtank gas quantity which this invention presupposes. It is explanatory drawing with which it uses for description when the penetration | invasion of the air to a sub tank and destruction of a negative pressure correspond similarly. It is explanatory drawing with which it uses for description when the penetration | invasion of the air to a sub tank and destruction of a negative pressure do not correspond similarly. It is a flowchart with which it uses for description of 1st Embodiment of this invention. It is a flowchart with which it uses for description of 2nd Embodiment of this invention. It is explanatory drawing with which it uses for description of the change of the ink usage-amount in the sub tank used for description of the embodiment, gas amount, and negative pressure. It is a flowchart with which it uses for description of 3rd Embodiment of this invention. It is a flowchart with which it uses for description of 4th Embodiment of this invention. It is explanatory drawing with which it uses for description of the temperature change and sub tank internal pressure change which are provided for description of the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Ink cartridge 33 ... Carriage 34, 34a, 34b ... Recording head (liquid discharge head)
35 ... Sub tank 81 ... Maintenance / recovery mechanism 201 ... Tank case (ink storage unit)
203 ... Flexible member (flexible film)
204 ... Displacement member 208a, 208b ... Detection electrode pin 301 ... Full detection sensor 500 ... Control unit 600 ... Host (information processing apparatus)

Claims (6)

A recording head for discharging droplets;
And a negative pressure forming unit including a flexible member that forms one surface of the ink storage unit that stores ink, and an elastic member that biases the flexible member outward, and the inside of the ink storage unit is exposed to the atmosphere. A sub-tank having an openable openable air opening mechanism for supplying ink from the ink containing portion to the recording head;
Gas amount detection means for detecting the amount of gas in the ink storage portion of the sub tank;
A displacement amount detecting means for detecting a displacement amount of the elastic member of the sub tank;
Control means for performing a negative pressure forming operation after supplying ink into the sub tank in a state where the ink storage portion is opened to the atmosphere through the atmosphere release mechanism of the sub tank;
Based on the detected gas amount and displacement amount, the control means performs the negative pressure forming operation when the gas amount is equal to or greater than a predetermined gas amount and the displacement amount is less than the predetermined displacement amount, and the gas amount is An image forming apparatus that performs control so as not to perform the negative pressure forming operation when the amount of displacement is greater than or equal to a predetermined amount of gas and the amount of displacement is greater than or equal to a predetermined amount of displacement.   The image forming apparatus according to claim 1, wherein the control unit determines in advance that the gas amount is greater than the predetermined gas amount when the gas amount is equal to or larger than the predetermined gas amount and the displacement amount is equal to or larger than the predetermined displacement amount. An image forming apparatus that controls to perform the negative pressure forming operation when the amount is equal to or greater than a second predetermined gas amount.   2. The image forming apparatus according to claim 1, wherein when the gas amount is equal to or greater than a predetermined gas amount and the displacement amount is equal to or greater than a predetermined displacement amount, the control unit is configured to allow the gas amount to be equal to or greater than the predetermined gas amount. An image forming apparatus, wherein the negative pressure forming operation is controlled when the ink usage is equal to or greater than a predetermined usage.   4. The image forming apparatus according to claim 1, further comprising a unit that stores an environmental temperature when the ink storage portion of the sub tank is opened to the atmosphere, and the control unit has a predetermined amount of gas. When the amount of gas is equal to or greater than the amount of gas and the amount of displacement is equal to or greater than the predetermined amount of displacement, the negative pressure forming operation is performed when the difference between the stored ambient temperature and the current temperature is equal to or greater than the predetermined temperature. An image forming apparatus that performs control so as not to perform the negative pressure forming operation when a difference between the temperature and the temperature is less than the predetermined temperature.   5. The image forming apparatus according to claim 1, further comprising means for storing an environmental humidity when the ink storage portion of the sub tank is opened to the atmosphere, wherein the control means has a predetermined amount of gas. When the amount of gas is greater than or equal to the amount of gas and the amount of displacement is greater than or equal to a predetermined amount of displacement, the negative pressure forming operation is performed when the difference between the stored environmental humidity and the current humidity is greater than or equal to a predetermined humidity. An image forming apparatus that performs control so as not to perform the negative pressure forming operation when a difference from the predetermined humidity is less than the predetermined humidity. A recording head for discharging droplets;
And a negative pressure forming unit including a flexible member that forms one surface of the ink storage unit that stores ink, and an elastic member that biases the flexible member outward, and the inside of the ink storage unit is exposed to the atmosphere. A sub-tank having an openable openable air opening mechanism for supplying ink from the ink containing portion to the recording head;
Gas amount detection means for detecting the amount of gas in the ink storage portion of the sub tank;
A displacement amount detecting means for detecting a displacement amount of the elastic member of the sub tank;
Negative pressure in an image forming apparatus, comprising: a control unit configured to perform a negative pressure forming operation after supplying ink into the sub tank in a state where the ink container is opened to the atmosphere through the atmosphere release mechanism of the sub tank. In the reforming method,
Based on the detected gas amount and displacement amount, the negative pressure forming operation is performed when the gas amount is equal to or larger than a predetermined gas amount and the displacement amount is smaller than the predetermined displacement amount, and the gas amount is equal to or larger than the predetermined gas amount. The negative pressure re-forming method in the image forming apparatus, wherein the negative pressure forming operation is not performed when the displacement amount is equal to or greater than a predetermined displacement amount.

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