JP5353368B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which can reduce an air amount being fed into a waste liquid tank by reducing the driving load of a suction pump for discharging the waste liquid of ink, which has been preliminarily discharged in a cap, to the waste liquid tank. <P>SOLUTION: This image forming apparatus is equipped with: recording heads 34a and 34b which have nozzles for discharging liquid droplets of ink; a cap 82a which caps the nozzle surfaces of the recording heads; a suction tube which is connected with the cap and guides the waste liquid of ink to be discharged in the discharging direction; the suction pump which generates a suction force for sucking the waste liquid to be discharged into the tube; and the approximately sealed waste liquid tank 101 with which the tube is directly connected and holds the waste liquid. The liquid droplets which do not contribute to the recording is discharged from the recording heads to the caps before the recording motion is performed, and after temporarily storing the waste liquid in the cap in the tube after the recording motion completes, the waste liquid is discharged to the waste liquid tank. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus including a waste liquid tank that stores a waste liquid generated by a maintenance recovery operation of a recording head that discharges droplets.

  As an image forming apparatus such as a printer, a facsimile machine, a copying apparatus, a plotter, and a complex machine of these, for example, an ink jet recording apparatus is known as an image forming apparatus of a liquid discharge recording method using a recording head for discharging ink droplets. . This liquid discharge recording type image forming apparatus ejects ink droplets from a recording head onto a conveyed paper to form an image (recording, printing, printing, and printing are also used synonymously). Serial type image forming device that forms an image by ejecting droplets while the recording head moves in the main scanning direction, and a line type that forms images by ejecting droplets without the recording head moving There is a line type image forming apparatus using a head.

  In the present application, “image forming apparatus” means an apparatus for forming an image by landing ink on a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc. "Image formation" is not only the application of images with meanings such as characters and figures to the medium, but also the addition of images with no meaning such as patterns to the medium (simply applying droplets to the medium) Also means landing). The “ink” is not limited to the ink, but is used as a general term for all liquids that can perform image formation, such as a recording liquid, a fixing processing liquid, and a liquid. The term “paper” is not limited to paper, but includes the above-described OHP sheet, cloth, and the like, and means that ink droplets adhere to the recording medium, recording medium, recording paper, recording It is used as a general term for what includes what is called paper.

  In such an image forming apparatus (hereinafter, also simply referred to as “inkjet recording apparatus”), the recording head is caused by the evaporation of the solvent from the nozzle because of recording by discharging ink from the nozzle onto the paper. Maintenance and recovery to maintain and recover the performance of the print head due to problems such as increased ink viscosity, ink solidification, dust adhesion, and bubble failure due to air bubbles. It has a mechanism.

  For example, a cap (also referred to as a capping unit or a cap member) that seals the nozzles of the recording head is provided, and capping of the recording head is performed when the apparatus is not in operation, thereby suppressing drying and thickening of ink in the nozzles. To be able to. In addition, before and after the recording operation and during the recording operation, ink droplets that do not contribute to the recording operation are discharged, and the ink dried and thickened in the nozzles is discharged so that the discharge performance can be recovered and maintained. .

  The ejection of ink droplets that do not contribute to image formation for maintaining the ejection performance of the nozzle is called preliminary ejection or idle ejection, and is ejected to a dedicated idle ejection receptacle or ejected to a cap. .

  For example, as described in Japanese Patent Application Laid-Open No. H10-228688, the information processing apparatus includes a unit that manages information on the history of ink preliminarily ejected to the cap and the cumulative ejection amount, and the cap is used as the preliminary ejection based on the information. The inside of the cap is replenished with fresh ink to prevent troubles caused by thickening of the ink in the cap.

  In such a configuration, the ink preliminarily ejected to the cap tends to thicken when it comes into contact with the air, so holding it in the cap for a long time causes the cap to become clogged with ink, causing problems with the suction operation by the pump. Cause.

  Therefore, as described in Patent Document 2, there is a parameter for preliminary ejection history, and when the parameter reaches a predetermined value, ink retained in the cap is discharged by preliminary ejection and subsequent suction in the cap. The structure to make it known is known.

  Further, as described in Patent Document 3, when discharging ink discharged by preliminary discharge or the like to a waste liquid tank, storage means for temporarily storing ink is provided, and the temporary storage amount of ink is set to a constant amount. It is also known to discharge from the storage means to the waste liquid tank when it exceeds.

JP 2007-216499 A JP 2007-230204 A Japanese Patent Laid-Open No. 2004-009436

  However, in the configuration described in Patent Document 2, the ink preliminarily ejected into the cap needs to be driven to a pump connected to the cap that can be sucked and sent to a waste liquid tank located at the end of the discharge path. There is. In this case, since the preliminary discharge is performed for each recording operation for the purpose of flushing the ink in the nozzle before the recording operation and ensuring the discharge performance, when the liquid feeding operation to the waste liquid tank is performed every time, The frequency of liquid feeding in the long path from the cap to the waste liquid tank located at the end of the discharge path is increased, and the durability load applied to the pump is increased.

  In addition, since the pre-discharged ink is very small relative to the volume of the pump, a large amount of air is sent to the waste liquid tank together with the ink when the pump is driven, but the ink is stably held in the waste liquid tank. Therefore, a porous or fibrous waste liquid absorbing member is often used. When a large amount of air is sent together with the ink, the surface of the waste liquid absorbing member is dried, the absorption efficiency is lowered, and the waste liquid tank overflows. There is a problem of fear.

  Further, as described in Patent Document 3, a temporary storage unit is provided when ink is discharged, and the ink is discharged into a waste liquid tank when the temporary storage amount of ink exceeds a certain amount. The space for providing the storage means for temporarily storing the ink and the second liquid supply means for further supplying the temporarily stored ink to the waste liquid tank are required, which increases the size of the apparatus. Also, since the inside of the temporary storage means is supplied with ink from the cap and a large amount of air is also sent by the drive of the pump, the drying of the ink proceeds inside the temporary storage means, and the ink is absorbed and retained in the waste liquid tank. May reduce efficiency.

  Ink using a pigment tends to increase in viscosity when it comes into contact with air, and therefore, a considerable amount of waste ink is generated due to preliminary ejection or head maintenance in order to keep the ejection stability always good. In order to cope with this, there is a problem that both the storage means and the waste liquid tank need to have appropriate volumes, which tends to increase the size and complexity of the apparatus.

  The present invention has been made in view of the above problems, and has as its object to reduce the load on the durability of the pump and to reduce the amount of air fed into the waste liquid tank.

In order to solve the above problems, an image forming apparatus according to claim 1 of the present invention provides:
A recording head having nozzles for discharging ink droplets;
A cap for capping the nozzle surface of the recording head;
A tube member connected to the cap for guiding the waste liquid of the ink in the cap in the discharge direction;
A suction pump for generating a suction force for sucking the waste liquid into the tube member;
A substantially sealed waste liquid tank in which the tube member is directly connected and holds the waste liquid;
Before performing the recording operation, preliminary discharge of droplets that do not contribute to recording is performed from the recording head to the cap, and after completion of the recording operation, the suction pump is driven by a predetermined amount to be preliminary discharged into the cap. Control means for controlling the discharging operation of sucking the generated waste liquid in the cap into the tube member and temporarily storing the waste liquid in the tube member and then discharging the waste liquid to the waste liquid tank;
Temperature and humidity detection means for detecting environmental temperature and humidity,
The control means includes
Obtaining environmental temperature and humidity information by the temperature and humidity detection means, and setting a threshold for the temporary storage time to temporarily store based on the environmental temperature and humidity information,
Before the measured temporary storage time passes the threshold value, the waste liquid preliminarily discharged into the cap is sucked into the tube member from the cap and temporarily stored in the tube member,
When the measured temporary storage time exceeds the threshold value , the suction pump can be driven with a pump drive amount that can discharge the entire internal volume of the suction tube without performing a maintenance operation for performing a suction operation on the recording head. It is configured to drive and discharge all waste liquid temporarily stored in the suction tube to the waste liquid tank.

According to the image forming apparatus according to the present invention, to reduce the load on the durability of the pump, it is possible to reduce the amount of air fed into the waste tank.

1 is a configuration diagram showing an outline of a mechanism part of an image forming apparatus according to the present invention. It is principal part plane explanatory drawing of the mechanism part. It is a schematic model side surface explanatory view of a maintenance recovery mechanism. Similarly it is principal part plane explanatory drawing. It is a perspective explanatory view similarly. It is side explanatory drawing of FIG. It is a cross-sectional perspective explanatory view of the waste liquid tank. It is block explanatory drawing which shows the outline | summary of the control part of the apparatus. It is a flowchart with which it uses for description of a waste liquid temporary storage process. It is a flowchart with which it uses for description of the 1st example of all the discharge processes. It is a flowchart with which it uses for description of the 2nd example of all the discharge processes. It is a flowchart with which it uses for description of the 3rd example of all the discharge processes. It is a flowchart with which it uses for description of the 4th example of all the discharge processes. It is a flowchart with which it uses for description of the 5th example of all the discharge processes. It is a flowchart with which it uses for description of a 5th example similarly. It is a flowchart with which it uses for description of all discharge operation | movement. It is a disassembled perspective explanatory drawing explaining an example of the tube pump which comprises a suction pump. It is sectional explanatory drawing of the pump. It is a plane explanatory view at the time of suction operation of the pump. It is plane explanatory drawing at the time of cancellation | release of the suction operation of the pump. It is a plane explanatory view of the rotation press part pivot support member of the pump. It is a plane explanatory view of the press member regulation plate of the pump. It is plane explanatory drawing of the tube position control plate of the pump. It is a flowchart with which it uses for description of the head maintenance operation | movement using the pump. It is a plane explanatory view explaining an example of a tube pump of a comparative example.

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 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.

  The carriage 33 is equipped with sub tanks 35a and 35b (referred to as “sub tanks 35” when not distinguished) for supplying ink of each color corresponding to the nozzle rows of the recording head 34. The sub tank 35 is replenished and supplied with ink of each color from the ink cartridges 10 y, 10 m, 10 c, and 10 k of each color that is detachably attached to the cartridge loading unit 4 via the supply tube 36 of each color by the supply pump unit 5. Is done.

  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 non-replaceable waste liquid tank 100 for accommodating waste liquid generated by the maintenance recovery operation can be replaced on the lower side of the maintenance recovery mechanism 81 of the head, and can be replaced on the side of the maintenance recovery mechanism 81 from the front side of the apparatus main body. Each of the liquid waste tanks 101 is provided.

  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, the maintenance / recovery mechanism 81 in this image forming apparatus will be described with reference to FIGS. 3 is a schematic schematic configuration diagram of the maintenance and recovery mechanism, and FIG.
In the maintenance / recovery mechanism 81, caps 82 a and 82 b held by the cap holder 212, a wiper member 83 including an elastic body, and a wiper cleaner 86 as a first wiper cleaning unit can be moved up and down on the maintenance device frame 211. (Can move up and down).

  The cap 82 is a box-shaped member having an opening on the side facing the nozzle surface of the recording head 34. The cap 82 has an elastic portion on the upper surface portion of the opening, and the opening of the nozzle can be sealed (capped) by bringing the elastic portion into contact with and closely contacting the nozzle surface. In the cap 82, an absorbent member (not shown) that is a porous sponge-like member is disposed. Accordingly, the capillary force of the absorbing member holds the ink in the cap 82 in a uniform state, and at the same time, the negative pressure discharged when the ink in the cap 82a is discharged by the suction pump 220 described later is transmitted to the entire cap. Can be made.

  A cylindrical empty discharge receiver 84 is disposed between the wiper member 83 and the suction cap 82a. The upper end of the empty discharge receiver 84 on the wiper member 83 side scrapes ink adhering to the wiper member 83. A wiper cleaner portion 85 is formed as a second wiper cleaning means for dropping and removing. When cleaning the wiper member 83, the wiper member 83 is lowered while the wiper member 83 is pressed against the wiper cleaner portion 85 by the wiper cleaner 86, so that the ink adhering to the wiper member 83 is scraped off to the empty ejection receiver 84 side. .

  Further, a tubing pump (suction pump) 220 as suction means is connected to the cap 82a closest to the printing area via a flexible suction tube 219 made of an elastic member as a tube member, and only the cap 82a is suctioned. (Recovery) and moisturizing cap (hereinafter simply referred to as “suction cap”), and the cap 82b is merely a moisturizing cap. Therefore, when performing the recovery operation of the recording head 34, the recording head 34 that performs the recovery operation is selectively moved to a position where it can be capped by the suction cap 82a.

  The suction pump 220 generates suction force on the tube 210 by repeatedly pressing and moving the suction tube 219 with a plurality of pressure members.

  Although the suction tube 219 may be a silicon tube, in the present invention, since ink is temporarily stored in the suction tube 219, it is preferable to form the suction tube 219 from a material that hardly causes water vapor transmission from the tube wall surface. Therefore, here, a tube made of a thermoplastic elastomer is used. Examples of the thermoplastic elastomer used include polystyrene-based thermoplastic elastomer, polyolefin-based thermoplastic elastomer, polydiene-based thermoplastic elastomer, polyvinyl chloride-based thermoplastic elastomer, chlorinated polyethylene-based thermoplastic elastomer, polyurethane-based thermoplastic elastomer, polyester-based Examples include thermoplastic elastomers, polyamide thermoplastic elastomers, fluororesin thermoplastic elastomers, and the like.

  In addition, the hardness of the thermoplastic elastomer used for the suction tube 219 is approximately 50 degrees according to the JIS-A standard, so that an elastic force that enables liquid feeding by pumping can be obtained. The pump driving load given by can be reduced.

In addition, the water vapor permeability of the thermoplastic elastomer used for the suction tube 219 is set to 15 g / m ² · day or less, so that the rate at which the ink that is held evaporates in the tube 219 is reduced, and the ink is contained in the chew 219. Can be temporarily stored.

  On the other hand, below the caps 82a and 82b, the wiper member 83 and the like, a cam shaft 221 rotatably supported by the frame 211 is disposed, and on this cam shaft 221, a cap cam 222 for raising and lowering the cap holder 212, A wiper cam 224 for raising and lowering the wiper member 83, a roller 226 as a rotating body to which droplets discharged in the idle discharge receptacle 84 are applied, a cleaner cam 228 for swinging the wiper cleaner 86, and a carriage lock 87 are provided. A carriage lock cam 229 for raising and lowering is provided.

  Then, in order to rotationally drive the suction pump 220 and the cam shaft 221, the rotation of the maintenance and recovery motor 231 is meshed with the motor gear 232 provided on the motor shaft 231a and the pump gear 233 provided on the pump shaft 220a of the suction pump 220, Further, an intermediate gear 236 with a one-way clutch 237 is engaged with an intermediate gear 234 integrated with the pump gear 233 via an intermediate gear 235, and the cam shaft 221 is connected to an intermediate gear 238 coaxial with the intermediate gear 236 via an intermediate gear 239. The cam gear 240 fixed to the mesh is engaged. The intermediate shaft 241 that is the rotation shaft of the intermediate gears 236 and 238 with the clutch 237 is rotatably held by the frame 211.

  In this maintenance / recovery mechanism 81, when removing ink and impurities adhering to the surface (nozzle surface) where the nozzles of the recording head 34 are formed, the motor 231 is driven to raise the wiper member 83 via the wiper cam 224. In this state, by moving the carriage 33 in the main scanning direction, the wiper member 83 wipes the nozzle surface of the recording head 34 to wipe away impurities and the like.

  Further, if the nozzles of the recording head 34 are left exposed to the outside air, the ink in the inside dries and thickens and adheres, and the ink ejection performance is deteriorated. To prevent this, the recording head 34 is prevented. When the nozzle surface is covered with the cap 82, the motor 231 is rotated, the cap 82 is raised via the cap cam 213, and the nozzle surface of the recording head 34 is capped.

  In addition, before and after the recording operation and during the recording operation, ink droplets that do not contribute to the recording operation are ejected (preliminary ejection) to the cap 82a to maintain the nozzle ejection performance.

Next, the waste liquid tank will be described with reference to FIGS. 5 is a perspective view of the maintenance and recovery mechanism and the waste liquid tank, FIG. 6 is a side view of the same, and FIG. 7 is a sectional perspective view of the waste tank.
In this image forming apparatus, as described above, the fixed waste liquid tank 100 that stores and holds the waste liquid (waste ink) from the idle discharge receptacle 84 of the maintenance recovery mechanism 81, and the maintenance recovery that stores and holds the waste liquid discharged from the cap 82a. A waste liquid tank 101 detachably attached to the mechanism 81 is provided.

  The waste liquid tank 101 is a substantially hermetically sealed container formed by a container body 111 and a lid member 112. The waste liquid tank 101 is a composite made of a fibrous nonwoven fabric or sponge-like absorber that absorbs and holds ink (waste liquid) inside. An absorption member 113 having a layer structure (here, a three-layer structure) is provided. A part of the absorbing member 113 is cut out to form an input space 114 for supplying the waste liquid. Further, the absorbing member 113 has a space 115 formed through three layers on the back side with respect to the charging space 114, and an air vent hole 116 is formed in the lid member 112 corresponding to the space 115.

  The suction tube 219 of the maintenance / recovery mechanism 81 is connected to the waste liquid tank 101 by inserting the joint portion 120 into the elastic member 118 provided in the introduction port portion 117 of the waste liquid tank 101. The joint portion 120 has a hollow needle shape, and discharges the waste liquid sent from the suction tube 219 through the opening 121 formed at the distal end portion into the input space 114.

  As described above, the waste liquid tank 101 is mounted so as to be detachable from the front surface of the main body of the image forming apparatus, and can be replaced by the user. When replacing the waste liquid tank 101, in order to prevent the waste liquid from overflowing or seeping out from the waste liquid tank 101, the waste liquid tank 101 has a small number of openings and is in a state that is almost as close as possible (substantially sealed). It is configured to hold waste liquid. Further, by holding the waste liquid in a substantially sealed state, it is possible to prevent water evaporation of the waste liquid.

Next, an outline of the control unit of the image forming apparatus will be described with reference to FIG. FIG. 8 is an overall block diagram of the control unit.
The control unit 500 temporarily stores a CPU 511 that also serves as a means for controlling the discharge operation according to the present invention, which controls the entire apparatus, a ROM 502 that stores programs executed by the CPU 511 and other fixed data, and image data and the like. RAM 503 for storing, rewritable nonvolatile memory 504 for holding data even while the power of the apparatus is shut 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 551 that moves and scans the carriage 33, a sub-scanning motor 552 that moves the conveyor belt 51 circulates, a motor drive unit 512 that drives the maintenance and recovery motor 231 of the maintenance and recovery mechanism 81. An AC bias supply unit 511 and the like 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, a print control unit 508, a motor drive unit 510, and an 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 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. In addition, a detection signal from a temperature / humidity sensor 516 that detects environmental conditions (temperature and humidity) and a detection signal from a full tank detection sensor that detects whether the waste liquid tank 101 is full are also input.

  The CPU 501 of the control unit 500 also serves as a means for determining a threshold for performing the full tank detection of the full tank detection sensor 110. Even when the apparatus power is shut off, the determined threshold value is updated and stored in rewritable storage means (memory) such as battery backup or VRAM.

Next, the waste liquid temporary storage process performed by the control unit will be described with reference to the flowchart of FIG.
First, if the recording operation is started, preliminary ejection is performed to eject ink from the recording head 34 to the cap 82a before the recording operation is started. When the recording operation is completed, the suction pump 220 is driven by a predetermined amount, and waste liquid (waste ink) generated by preliminary discharge into the cap 82a is sucked into the suction tube 219 and temporarily stored.

  Here, the driving amount of the suction pump 220 per recording operation is set according to the ink droplet amount to be preliminarily ejected. In this case, when the amount of ink droplets to be preliminarily ejected is a fixed amount, the driving amount of the suction pump 220 can also be a constant amount. In addition, the amount of droplets to be preliminarily ejected is a fluctuation amount determined by calculating from the minimum amount of droplets necessary to maintain recording quality, such as the temperature and humidity environment used and the elapsed time since the previous recording operation. In some cases, the driving amount of the suction pump 220 is set to an amount corresponding thereto.

  That is, since the preliminary discharge is performed for each recording operation, when the recording operation is performed a plurality of times, the amount of the waste liquid that is preliminarily discharged and held in the cap internal volume is saturated, and capping by the cap 82a is performed. Occasionally saturated waste liquid adheres to the nozzle surface of the recording head 34. Therefore, the waste liquid preliminarily discharged into the cap 82a is sucked into the suction tube 219 from the cap 82a and temporarily stored by driving the suction pump 220.

  In this case, as described above, the waste liquid tank 101 has a substantially sealed structure so as not to dry the waste liquid. However, the waste liquid is discharged from the cap 82a to the waste liquid tank 101 every time the recording operation is performed, and the contents of the suction tube 219 are stored. If the entire product is to be discharged, a large amount of air is sent into the waste liquid tank 101 in proportion to the drive amount of the suction pump 220, and the absorbability of the waste liquid in the absorbing member 113 in the waste liquid tank 101 may be reduced.

  Therefore, as described above, the waste liquid preliminarily discharged into the cap 82a is temporarily stored in the suction tube 219, and then discharged to the waste liquid tank 101 at a required timing to be sent to the waste liquid tank 101. The amount of air is reduced and the decrease in absorbability of the absorption member 113 is suppressed, and the drive amount of the suction pump 220 can be reduced, so that the drive load of the suction pump 220 can be reduced and the durability can be improved.

  As described above, the tube member (suction tube 219) that temporarily stores the waste liquid is made of a material that does not easily transmit water vapor, thereby suppressing the increase in the viscosity of the waste liquid temporarily stored in the tube member. Therefore, it is possible to prevent a decrease in discharge performance and a decrease in permeability to the waste liquid tank.

Next, a first example of a process of discharging all waste liquid temporarily stored in the suction tube to a waste liquid tank (referred to as a total discharge process) will be described with reference to the flowchart of FIG.
Here, when a maintenance operation including nozzle suction for sucking ink from the nozzles is started by capping the nozzle surface of the recording head 34 with the cap 82a by the maintenance / recovery mechanism 81 and setting the inside of the cap 82a to a negative pressure, maintenance is performed. Prior to the start of the operation, the suction pump 220 is driven with a pump driving amount capable of discharging the entire internal volume of the suction tube 219, and all waste liquid temporarily stored (held) in the suction tube 219 is stored in the waste liquid tank 101. Eject, then perform maintenance operation.

  That is, when performing the maintenance operation, if the suction operation is performed in a state where the waste liquid is held in the suction tube 219, the volume is reduced due to the waste liquid existing in the suction tube 219, so that a pressure loss occurs and the cap 82a enters the cap 82a. There is a possibility that the characteristics when forming the negative pressure become unstable. Therefore, before performing a maintenance operation for performing a suction operation on the recording head 34, a full discharge operation for discharging all the waste liquid in the suction tube 219 to the waste liquid tank 101 is performed in advance.

Next, a second example of the total discharge process will be described with reference to the flowchart of FIG.
Here, the time (temporary time elapsed since the previous full discharge operation) is temporarily stored in the suction tube 219 for temporarily storing the waste liquid generated by the preliminary discharge, and the predetermined time (threshold value) is set in advance. When the time elapses, the suction pump 220 is driven with a pump driving amount capable of discharging the entire internal volume of the suction tube 219, and all waste liquid temporarily stored (held) in the suction tube 219 is discharged to the waste liquid tank 101. .

  In other words, when the power of the image forming apparatus is on and the time for holding the waste liquid preliminarily discharged in the suction tube 219 exceeds a certain time, the waste liquid increases in the suction tube 219. Since there is a possibility that the pump driving load for viscous discharge is increased, all the waste liquid once retained is discharged to the waste liquid tank 101.

Next, a third example of the total discharge process will be described with reference to the flowchart of FIG.
Here, in the second example, the environmental temperature / humidity information of the image forming apparatus is acquired by the temperature / humidity sensor 516, and the threshold value of the temporary storage time is set based on the environmental temperature and the environmental humidity. When the set threshold value is compared with the temporary storage time measured as the predetermined time, and the temporary storage time has passed the predetermined time (threshold value), the suction pump 220 can similarly discharge the entire internal volume of the suction tube 219. Driven by the driving amount, all the waste liquid temporarily stored (held) in the suction tube 219 is discharged to the waste liquid tank 101.

  That is, since the evaporation rate of water vapor changes depending on the temperature and humidity of the environment in which it is used, if the predetermined time (threshold value) in the second example is fixed, the entire discharge process may not be performed at an appropriate timing. The output of the temperature and humidity sensor built in is referred to as needed, and an upper limit value (threshold value) for holding the waste liquid in the suction tube 219 is set according to the temperature and humidity.

Next, a fourth example of the total discharge process will be described with reference to the flowchart of FIG.
Here, when the power-off of the image forming apparatus is instructed, prior to power-off, the suction pump 220 is driven with a pump drive amount that can discharge the entire internal volume of the suction tube 219, and temporarily stored in the suction tube 219. All (holding) waste liquid is discharged into the waste liquid tank 101, and then the apparatus is turned off.

  That is, if the image forming apparatus is turned off, it may be left for a long time after that, and the waste liquid in the suction tube 219 cannot be discharged when the power is off. When the instruction is executed, all the waste liquid in the suction tube 219 is discharged as an operation when the power is turned off.

Next, a fifth example of the total discharge process will be described with reference to the flowcharts of FIGS.
Here, as shown in FIG. 14, in the fourth example, when the full discharge process is performed when the power is turned off, a history indicating that the full discharge process has been performed (all discharge history) is stored. Then, as shown in FIG. 15, when the power-on is instructed, referring to the history of total discharge, if there is no history of power-off, the suction pump 220 can discharge the entire internal volume of the suction tube 219. Driven by the driving amount, all the waste liquid temporarily stored (held) in the suction tube 219 is discharged to the waste liquid tank 101.

  That is, when the power supply is suddenly cut off without the power off operation being performed, for example, when the power outlet is disconnected or a power failure occurs, the waste liquid is completely discharged in the fourth example process. I can't. If a long time elapses in this state, the water content of the waste liquid held in the suction tube evaporates and thickens, and when the power is turned on again, the discharge property of the waste liquid in the suction tube may be reduced. Therefore, if the full discharge operation in the suction tube is normally executed during the power-off operation, the history is stored as normal completion, so that the presence or absence of the full discharge operation in the suction tube at the previous power-off is checked. If there is no history that the normal full discharge operation has been performed, the waste liquid in the suction tube is completely discharged during the power-on operation to try to discharge the waste liquid.

  Unlike the normal discharge operation of waste liquid in the normal suction tube, the total discharge operation of waste liquid when the power is turned on is maintained by reducing the speed of the motor 231 (for example, from 300 pps in the normal state to 200 pps). Make it possible to cope with increased load due to thickening of the waste liquid. In addition, by increasing the drive amount of the pump 220 as compared with the entire discharge operation of the waste liquid in the normal suction tube, it is possible to reliably discharge the waste liquid that may have a reduced discharge performance due to thickening.

Next, the full discharge operation in each of the above examples will be described with reference to the flowchart of FIG.
When the full discharge operation is performed, as described above, the suction pump 220 is started to drive the waste liquid in the suction tube 219 to the waste liquid tank 101. At this time, the means for detecting the presence or absence of the waste liquid tank 101 is detected. It is determined by referring to the result whether or not the waste liquid tank 101 is detected.

  If the absence of the waste liquid tank 101 is not detected, it is determined whether or not the suction pump 220 is driven by the drive amount for discharging all waste liquid (end of discharge). If the discharge is finished, the suction pump 220 is driven. finish.

  On the other hand, when the absence of the waste liquid tank 101 is detected before the end of the discharge, the driving of the suction pump 220 is immediately stopped.

  That is, when the user performs the detachment operation of the waste liquid tank 101 while the discharge operation of the waste liquid held in the suction tube 219 is being performed, the waste liquid is discharged without the waste liquid tank 101, and the inside of the apparatus If the separation of the waste liquid tank 101 is detected during the operation of discharging the waste liquid, the discharge operation is immediately stopped. Here, although the explanation is made during the entire discharge operation, when the waste liquid preliminarily discharged into the cap 82a is sucked into the suction tube 219, the amount of waste liquid that can be temporarily stored in the suction tube 219 is exceeded. In some cases, the discharge of the waste liquid from the suction tube 219 to the waste liquid tank 101 occurs. In this case as well, when the absence of the waste liquid tank 101 is detected, the drive of the suction pump 220 is immediately stopped.

Next, an example of a tube pump constituting the suction pump 220 will be described with reference to FIGS.
The tube pump 600 includes an accommodating housing (pump housing) 645 that accommodates the tube 644 along the arc-shaped inner wall surface, and presses the tube 644 so as to be crushed toward the inner wall surface side of the pump housing 645, and A rotating pressing member (pressure roller) 643 that repeatedly moves the pressing portion from one end side to the other end side of the tube 644 and a shaft portion 643a of the rotating pressing member 643 are movably fitted into the pressing member 643. And a rotation pressing portion pivot support member 631 which is a rotating body having a guide groove 635 for guiding the tube 644 from the suction position to the suction release position where the tube 644 is not crushed. The rotary pressing portion pivot support member 631 is rotatably mounted on the pump housing 645 via a sliding bearing portion 652.

  Then, by rotating the rotation pressing portion pivotal support member 631 and moving the rotation pressing member 643 along the guide groove 635, the pressing portion of the tube 644 by the rotation pressing member 643 moves, and the upstream side of the rotation pressing member 643. The internal pressure can be reduced to generate a negative pressure in the flow path of the tube 644, and the liquid in the flow path of the tube 644 can be sucked from one end side and sent out from the other end side.

  The material of the tube 644 is formed of an elastic body and uses a thermoplastic elastomer. Examples of the thermoplastic elastomer used in particular include, for example, a polystyrene-based thermoplastic elastomer, a polyolefin-based thermoplastic elastomer, a polydiene-based thermoplastic elastomer, a polyvinyl chloride-based thermoplastic elastomer, a chlorinated polyethylene-based thermoplastic elastomer, a polyurethane-based thermoplastic elastomer, Examples thereof include polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, and fluororesin-based thermoplastic elastomers. These have less water vapor permeation than silicone tubes and the like, and the ink remaining in the tube is difficult to solidify by drying, so that the reliability of the suction pump in the image forming apparatus can be improved.

  The tube pump 600 includes a pressing member restricting plate 636 that is a rotation range restricting member that restricts the movement of the rotating pressing member 643 in the circumferential direction and rotates coaxially with the rotating pressing portion pivot support member 631. The “circumferential regulation” means that the circumferential movement is regulated within a range in which the rotation of the shaft 643a of the rotation pressing member 643 and the shaft portion 632 of the rotation pressing portion support member 631 is prevented. is there. As a result, the rotation pressing member 643 rotates within a predetermined range in the circumferential direction and can be prevented from moving to a position other than the predetermined position, and the reliability can be improved during operation and release of the pump. It will be able to plan. Further, a tube position restricting plate 639 for restricting the movement of the tube 644 in the non-rotating direction is provided.

  Here, as shown in FIG. 21, the rotation pressing portion shaft supporting member 631 includes a locking end portion 633 provided at a suction operation position having a length c (c> d) from the center of the shaft portion 632, and a shaft A guide groove 635 having a locking end portion 634 provided at a suction release position having a length d from the center of the portion 632 is provided. In the guide groove 635, the shaft portion 643a of the rotary pressing member 643 is fitted.

  As shown in FIG. 22, the pressing member restricting plate 636 is provided with guide ends 637 and 639 and a movable region 650 of the rotating pressing member 643 to limit (restrict) the rotation range of the rotating pressing member 643. An opening portion 638 into which the shaft portion 632 of the rotation pressing portion shaft support member 631 is fitted is formed.

  As shown in FIG. 23, the tube position restricting plate 639 is provided with locking shapes 640 and 641 for restricting the rotation of the plate 639. Further, an asymmetrical shape 42 is provided so that the plate 639 can be assembled only in one direction in order to define the front and back of the plate 639 during assembly.

  In this tube pump 600, as shown in FIG. 19, when the pressing member regulating plate 636 that regulates the rotation range of the rotating pressing member 643 rotates in the direction of the arrow C, that is, during the suction operation, the rotating pressing member 643 When the tube 644 is repeatedly pressed and released, it rotates while the operation range is regulated within the movable region end portions 637 and 639 in the movable region 650 by the pressing member regulating plate 636.

  Further, as shown in FIG. 20, when the rotation pressing portion pivot support member 631 rotates in the direction of arrow D (the direction opposite to the direction of arrow C) in order to cancel the suction operation, the rotation pressing member 643 is rotated by the rotation pressing portion. The rotary pressing member 643 is held by moving to the locking end 634 along the guide groove 635 of the shaft support member 631.

  Therefore, according to this tube pump 600, at the time of the suction operation and when the suction operation is released, the rotary pressing member is held within the predetermined range in the circumferential direction by the control plate (pressing member control plate) and moves outside the predetermined range. Therefore, it is possible to improve the reliability during operation of the tube pump.

  Further, as shown in FIG. 18, the tube position regulating plate 639 has a non-rotating direction of the tube 644 in the pressing member regulating plate 636 that limits the movable range of the pressing member 643 and the movable region 651 in the non-rotating direction of the tube 644. Regulate movement to

  Since the movement of the tube 644 is restricted by the restriction plate 639 and does not come into contact with the flange portion 653 (the portion where the guide groove 635 is formed) of the rotation pressing portion pivot support member 631, wear of the tube 644 and an increase in load are prevented. Therefore, the reliability of the pump can be improved.

  In addition, when the regulation plate 639 is formed from a resin molded product that is inexpensive and has good mass productivity, irregularities such as ejector pin marks and parting lines are generated during molding, and the irregularities resulting from this molding come into contact with the tube 644. Therefore, by controlling the orientation of the front and back surfaces of the regulating plate 639 as an asymmetrical shape 642, the uneven portion can be managed so as not to contact the tube 644.

  This point will be described in relation to the comparative example shown in FIG. In the tube pump of this comparative example, when performing a suction operation, as shown in FIG. 5 (a), between the rear plate 712 and the front plate 713 held rotatably about the central shaft 711. A pair of pressure rollers 715 rotatably held by a pressure roller shaft 714 and a pressure roller shaft on the rear side (not shown) is connected to a front plate 713 and a rear plate 712 by a motor (not shown) as indicated by an arrow E in the figure. Is moved along the rear plate groove 716 provided in the rear plate 712 and the guide end 717 of the front plate 713. Then, the pressure roller 715 is locked to a locking end 718 provided at a position having a length a (a> b) from the center of the central shaft 711 at the guide end 717 of the front plate. When further rotated in this state, the pressure surface of the pressure roller 715 crushes the tube 720 fitted in a circular recess (not shown) on the housing 721 side. Therefore, when the tube 720 is compressed by being crushed by the pressure roller 715, a positive pressure is generated. Further, the pressure roller 715 is rotated and detached from the tube 720, and the tube 720 is released from the crushed state to be released. The ink suction operation (pumping operation) is performed by the negative pressure generated when the state is restored.

  When releasing the suction operation, the front plate 713 and the rear plate 712 are rotated in the direction of the arrow F in the figure (the direction opposite to the arrow E) as shown in FIG. The pressure roller 715 is moved along the rear plate groove 716 and the guide end 717, and a locking end 719 provided at a position that is a length b from the center of the central axis 711 at the guide end 717 of the front plate 713 Locked. The pressure surface of the pressure roller 715 in this state is not in contact with the tube 720, that is, a release state in which the pressure roller 715 is retracted. Therefore, the suction operation is released.

  However, in the tube pump of this comparative example, the pressure roller 715 moves freely unless the dimensional tolerance between the pressure roller 715 and the housing 721 is ± 0.1 or less. When the pressure roller 715 does not crush the tube 720 when it rotates in the direction of arrow E, that is, it escapes to the locking end 719 and becomes unable to suck, or the tube 720 is pressed by the pressure roller 715. If the position of the tube 720 changes within the pump housing 721 and interferes with the side surface of the shaft support member, the rotational load increases significantly due to wear of the tube or interference with the shaft support member.

  On the other hand, according to the tube pump described in the above embodiment, the rotation pressing member is held at a predetermined position in the circumferential direction by the pressing member restricting member, and is prevented from moving to a position other than the predetermined position. In addition to improving the reliability when the pump is operated and released, contact between the shaft support member and the tube is prevented by inserting a tube position regulating member (spacer) between the rotation pressing portion shaft support member and the tube. Further, durability can be improved by reducing load torque and preventing tube wear.

Next, an example of the head maintenance operation by the maintenance / recovery mechanism using the above-described tube pump as the suction pump 220 will be described with reference to FIG.
In this head maintenance operation, the target head 34 is moved to the suction position, the suction cap 82a is raised, the presence / absence of the waste liquid tank 101 is checked, and if there is the waste liquid tank 101, the head suction (pump 220 drive) is performed. When the separation of the waste liquid tank 101 is detected during the suction of the head and the separation of the waste liquid tank 101 is detected, the head suction is stopped and the process proceeds to the waste liquid tank separation detection sequence. If separation of the waste liquid tank 101 is not detected until the head suction is completed, the suction cap 82 a is lowered and the nozzle surface of the head 34 is wiped by the wiper member 83.

  Thereafter, the presence or absence of the waste liquid tank 101 is checked. If the waste liquid tank 101 exists, the suction pump 220 is driven to discharge the waste liquid in the suction cap 82a. While the waste liquid is being discharged, the separation detection operation of the waste liquid tank 101 is performed, and when the separation of the waste liquid tank 101 is detected, the driving of the suction pump 220 is stopped.

  If the removal of the waste liquid tank 101 is not detected until the waste liquid discharge is completed, empty discharge is performed into the suction cap 82a.

  Thereafter, the presence or absence of the waste liquid tank 101 is checked. If the waste liquid tank 101 exists, the suction pump 220 is driven to discharge the waste liquid in the suction cap 82a. While the waste liquid is being discharged, the separation detection operation of the waste liquid tank 101 is performed, and when the separation of the waste liquid tank 101 is detected, the driving of the suction pump 220 is stopped.

  Thus, by stopping the head suction from the recording head 34 in a state where the waste liquid tank 101 is detached, the possibility that the waste liquid flows out into the apparatus without the waste liquid tank 101 being mounted is reduced.

  Further, when transitioning to the waste liquid tank separation detection sequence, the operation of wiping the nozzle surface of the recording head is performed, thereby reliably removing the waste liquid adhering to the recording head and maintaining the reliability of the recording head.

  The image forming apparatus according to the present invention can be applied to a facsimile machine, a copying machine, a printer / fax / copier multifunction machine, etc., in addition to an inkjet printer. Furthermore, the present invention can also be applied to an image forming apparatus that discharges a liquid (recording liquid) other than ink, such as a resist or a DNA sample in the medical field.

33 ... Carriage 34, 34a, 34b ... Recording head (liquid ejection head)
35 ... Subtank 81 ... Maintenance recovery mechanism 82a ... Cap for suction and moisture retention 82b ... Cap for moisture retention 83 ... Wiper member 84 ... Empty discharge receptacle 101 ... Waste liquid tank 219 ... Suction tube 220 ... Suction pump

Claims (2)

A recording head having nozzles for discharging ink droplets;
A cap for capping the nozzle surface of the recording head;
A tube member connected to the cap for guiding the waste liquid of the ink in the cap in the discharge direction;
A suction pump for generating a suction force for sucking the waste liquid into the tube member;
A substantially sealed waste liquid tank in which the tube member is directly connected and holds the waste liquid;
Before performing the recording operation, preliminary discharge of droplets that do not contribute to recording is performed from the recording head to the cap, and after completion of the recording operation, the suction pump is driven by a predetermined amount to be preliminary discharged into the cap. Control means for controlling the discharging operation of sucking the generated waste liquid in the cap into the tube member and temporarily storing the waste liquid in the tube member and then discharging the waste liquid to the waste liquid tank;
Temperature and humidity detection means for detecting environmental temperature and humidity,
The control means includes
Obtaining environmental temperature and humidity information by the temperature and humidity detection means, and setting a threshold for the temporary storage time to temporarily store based on the environmental temperature and humidity information,
Before the measured temporary storage time passes the threshold value, the waste liquid preliminarily discharged into the cap is sucked into the tube member from the cap and temporarily stored in the tube member,
When the measured temporary storage time exceeds the threshold value , the suction pump can be driven with a pump drive amount that can discharge the entire internal volume of the suction tube without performing a maintenance operation for performing a suction operation on the recording head. An image forming apparatus that is driven to discharge all waste liquid temporarily stored in the suction tube to the waste liquid tank. A recording head having nozzles for discharging ink droplets;
A cap for capping the nozzle surface of the recording head;
A tube member connected to the cap for guiding the waste liquid of the ink in the cap in the discharge direction;
A suction pump for generating a suction force for sucking the waste liquid into the tube member;
A substantially sealed waste liquid tank in which the tube member is directly connected and holds the waste liquid;
Before performing the recording operation, preliminary discharge of droplets that do not contribute to recording is performed from the recording head to the cap, and after completion of the recording operation, the suction pump is driven by a predetermined amount to be preliminary discharged into the cap. A controller that controls the discharging operation of sucking the generated waste liquid in the cap into the tube member and temporarily storing the waste liquid in the tube member and then discharging the waste liquid to the waste liquid tank;
The control means includes
In the suction tube, calculate a temporary storage time for temporarily storing the waste liquid,
Before the measured temporary storage time passes a predetermined threshold, the waste liquid preliminarily discharged into the cap is sucked into the tube member from the cap and temporarily stored in the tube member,
When the temporary holding time has elapsed the threshold, the without performing maintenance operation for sucking operation for the recording head, and driving the suction pump with a pump drive amount can be discharged all the internal volume of said suction tube An image forming apparatus that discharges all waste liquid temporarily stored in the suction tube to the waste liquid tank.

Images