JP6031964B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to maintenance control of a recording head in an ink jet recording apparatus.

  As an image forming apparatus such as a printer, a facsimile, a copying machine, a plotter, or a multifunction device having these functions, for example, an ink jet recording apparatus (liquid discharge recording type image forming apparatus) using a recording head for discharging ink droplets is known. It has been.

  In such a liquid ejection type image forming apparatus, the recording head performs image recording by ejecting ink pressurized in a pressure generating chamber from a nozzle onto a sheet. For this reason, there is a problem that the ink viscosity rises due to the evaporation of the solvent from the nozzle, the ink solidifies, the dust adheres, and the air bubbles are mixed, resulting in a defective discharge, resulting in a recording failure. . Therefore, a maintenance / recovery mechanism that maintains and recovers the state of the recording head is provided. When the nozzle is clogged by this maintenance and recovery mechanism, the nozzle forming surface is sealed by the capping means, and ink is sucked and discharged (head suction) from the nozzle by the negative pressure from the suction pump. Relieve clogging. Furthermore, the maintenance / recovery mechanism has a function of wiping the ink adhering to the nozzle surface after the head suction with an elastic member (wiping), and re-strengthening the ink meniscus on the nozzle. The head cleaning is performed by a series of maintenance operations in which these are combined.

  In the maintenance and recovery mechanism, control for automatically performing head cleaning is already known in order to prevent the recording head from being clogged when the number of printed sheets of the ink jet recording apparatus exceeds a predetermined threshold. For example, Patent Document 1 discloses a configuration in which a nozzle surface contamination degree due to mist is calculated from the number of ejections of a recording head and the nozzle surface is cleaned when a threshold value is exceeded.

  However, the conventional automatic head cleaning control technology has a threshold value for each recording head. Therefore, in medium and high speed machines equipped with a plurality of recording heads, automatic head cleaning is activated at almost the same timing for a plurality of recording heads. Sometimes it is done. At this time, the respective recording heads are cleaned and maintained in order, but are cleaned using a common maintenance / recovery mechanism. Therefore, when the recording head is later maintained, the ink when the immediately preceding recording head is cleaned is used as the wiper. Sometimes left in the department. For this reason, there is a problem that the ink of the previous recording head is transferred to the next recording head, and maintenance failure such as nozzle omission or color mixing is likely to occur.

  Therefore, Patent Document 2 discloses a configuration in which a cleaning means for wiping the top surface of the wiper (blade) is provided and moved along the longitudinal direction of the top surface for the purpose of preventing maintenance failure due to ink remaining on the wiper. Has been. Further, in order to remove the ink to the details of the wiper, in Patent Document 3, after the recording head is wiped with a rotation-supported wiper, the ink attached to the wiper is dropped by rotating into a tank containing cleaning liquid and immersing the wiping surface. A configuration is disclosed. Further, Patent Document 4 discloses a configuration in which ink is removed by bringing an absorber into contact with a wiper. However, all of them have a problem that the cost is increased due to the increase in the size of the apparatus and the number of parts, or the durability is difficult.

  An object of the present invention is to prevent a maintenance failure caused by a cleaning operation being performed at the same time during printing for a plurality of recording heads.

In order to solve the above problems, according to the present invention, at least two droplet ejection heads that eject droplets from nozzles on the nozzle surface, a capping member that covers the nozzle surface of the droplet ejection head, and A suction pump that is connected to a capping member and sucks the nozzle surface, a wiping member that wipes the nozzle surface of the droplet discharge head, and the droplet discharge head and the wiping member along the nozzle surface When the amount of ink ejected from the droplet ejection head reaches a predetermined ink consumption threshold during a print job in which droplets are ejected from the droplet ejection head and drive means that moves relative to the direction, Automatic cleaning is performed by sucking with the suction pump while the nozzle surface of the droplet discharge head is covered with the capping member and wiping the nozzle surface with the wiping member. In the image forming apparatus comprising a control means, a to the weight of the ink remaining on top of the wiping member is the predetermined time the time taken until reduced to a predetermined value, a plurality of the liquid drop ejecting head within the predetermined time period When the threshold value is reached, the automatic cleaning execution timing of at least one of the droplet discharge heads is shifted with respect to the automatic cleaning execution timing of the other droplet discharge head. The control means executes the automatic cleaning so that the execution timing of the automatic cleaning of the head is set longer than the predetermined time .

  According to the present invention, when it is found that a cleaning operation that is maintenance is performed at a very close interval (within a predetermined time) with respect to a plurality of recording heads / droplet ejection heads during a print job, the cleaning interval between the recording heads is set. Since it is more than a certain amount than planned, the ink remaining on the wiping member when a certain recording head is wiped falls by its own weight or the volume is reduced by natural drying, and then the next recording head is cleaned. Therefore, the maintenance and recovery mechanism, and thus the image forming apparatus, can be saved without increasing the size, and therefore the cost can be avoided and the cleaning performance by the wiping member can be improved.

1 is a side view illustrating an overall configuration of an image forming apparatus. 1 is a plan view of a main part of an image forming apparatus. It is a perspective view of a maintenance recovery mechanism. It is a principal part top view of a maintenance recovery mechanism. It is a typical schematic block diagram of a maintenance recovery mechanism. It is a side view explaining the raising / lowering mechanism of a cap. It is a side view explaining the raising / lowering mechanism of a wiper member. It is a flowchart explaining a cleaning sequence. It is a figure explaining the wiping of a recording head, and shows the positional relationship of the head and wiper before wiping. It is a figure explaining the wiping of a recording head, and shows the positional relationship of the head and wiper which are being wiped off. It is a figure explaining the wiping of a recording head, and shows the positional relationship of a head and a wiper just before completion | finish of wiping. It is a figure explaining the wiping of a recording head, and shows the positional relationship of the head and wiper after completion | finish of wiping. It is a figure explaining the wiper cleaner operation | movement and the generation | occurrence | production process of the ink remaining of a wiper top | upper surface, and shows just before a wiper cleaner operation | movement. FIG. 6 is a diagram for explaining a wiper cleaner operation and a process of generating ink remaining on the top surface of the wiper, and showing a state during the wiper cleaner operation. It is a figure explaining the wiper cleaner operation | movement and the generation | occurrence | production process of the ink residue of a wiper top | upper surface, and shows the wiper cleaner operation | movement just before completion | finish. It is a figure explaining the wiper cleaner operation | movement and the generation | occurrence | production process of the ink remaining of a wiper top | upper surface, and shows immediately after completion | finish of a wiper cleaner operation | movement. FIG. 6 is a diagram for explaining the cause of unwiping of a recording head when another recording head is cleaned with a wiper member immediately after cleaning, and shows the positional relationship between the head and the wiper before wiping. FIG. 6 is a diagram for explaining the cause of unwiping of a recording head when another recording head is cleaned with a wiper member immediately after cleaning, and shows the positional relationship between the head being wiped and the wiper. It is a graph explaining the relationship between the time of the ink remaining on the top surface of the wiper member and the weight change. It is a flowchart which shows the control which opens a cleaning space | interval by automatic cleaning. It is a figure which shows the example of an actual operation | movement controlled by the flow of FIG. FIG. 10 is a flowchart showing control for separating the cleaning timing of a recording head that consumes less ink from the timing of other recording heads by automatic cleaning. It is a figure which shows the example of an actual operation | movement controlled by the flow of FIG. FIG. 10 is a flowchart showing a control for providing a cleaning interval between the print heads in inverse proportion to consumed ink by automatic cleaning. FIG. 25 is a diagram illustrating an actual operation example controlled by the flow of FIG. 24. It is a flowchart which shows the example including the step which does not shift, when the assumption ink consumption exceeds predetermined value in control which leaves an interval by automatic cleaning.

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 a side view showing the overall configuration of the image forming apparatus, and FIG. 2 is a plan view of the main part of the apparatus.

  This image forming apparatus is a serial type ink jet recording apparatus. The carriage 33 is slidably held 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. Then, the carriage 33 is moved and scanned in a direction indicated by an arrow in FIG. 2 (carriage main scanning direction) via a timing belt (also not shown) by a main scanning motor (not shown).

  The carriage 33 is provided with recording heads 34a and 34b composed of droplet discharge heads for discharging ink droplets of yellow (Y), cyan (C), magenta (M), and black (K) (when not distinguished, recording is performed). Head 34). In the recording head 34, nozzle rows composed of a plurality of nozzles are arranged in the sub-scanning direction orthogonal to the main scanning direction, and the ink droplet ejection direction is directed downward.

  Each recording head 34 has two nozzle rows, and one nozzle row of the recording head 34a discharges black (K) droplets, and the other nozzle row discharges cyan (C) droplets. Similarly, one nozzle row of the recording head 34b discharges magenta (M) droplets, and the other nozzle row discharges 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 with ink of each color from the ink cartridges 10y, 10m, 10c, and 10k of each color detachably attached to the cartridge loading unit 4 via a supply tube 36 of each color by a supply pump unit (not shown). Supplied.

  On the other hand, the paper feeding unit that feeds paper from the paper feeding tray 2 includes a half-moon roller (paper feeding roller) 43 that separates and feeds paper 42 one by one from the paper stacking unit (pressure plate) 41, and a paper feeding roller 43. A separation pad 44 made of a material having a large friction coefficient is provided. The separation pad 44 is urged toward the paper feed roller 43 side. A guide member 45 for guiding the paper 42 is provided in order to feed the paper 42 fed from the paper feeding unit to the lower side of the recording head 34. Further, a counter roller 46, a conveyance guide member 47, a pressing member 48 having a tip pressure roller 49, and a conveyance belt 51 that electrostatically attracts the sheet 42 and conveys the sheet 42 to a position facing the recording head 34. ing. The conveyor belt 51 is an endless belt, and is configured to wrap around the conveyor roller 52 and the tension roller 53 and circulate in the belt conveyance direction (sub-scanning direction). Further, a charging roller 56 for charging the surface of the conveyor belt 51 is attached. 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 conveyance belt 51 rotates in the belt conveyance direction of FIG. 2 when the conveyance 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 transport belt 51, a paper discharge roller 62, and a spur 63 serving as a paper discharge roller are provided. ing. A paper discharge tray 3 is provided on the paper conveyance downstream side of the paper discharge roller 62.

  Further, a duplex unit 71 is detachably mounted on the back side (as viewed from the user side) of the apparatus main 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 caps 82a and 82b (cap 82 when not distinguished) and a wiper member (wiper blade) 83 for wiping the nozzle surface. Further, there are also provided an empty discharge receiver 84 for receiving droplets for empty discharge for discharging droplets that do not contribute to recording in order to discharge the thickened recording liquid, a carriage lock 87 for locking the carriage 33, and the like. Yes.

  Also, below the maintenance / recovery mechanism 81, a non-replaceable waste liquid tank 100 (fixed waste liquid tank) for storing the waste liquid generated by the maintenance / recovery operation is disposed, and at the side of the maintenance / recovery mechanism 81, a replaceable waste liquid tank 101 is provided. However, each 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 droplet of the time is arranged. The idle discharge receiver 88 is provided with an opening 89 and the like along the nozzle row direction of the recording head 34.

  In the recording apparatus configured as described above, the sheets 42 are separated and fed one by one from the sheet feed tray 2, and the sheets 42 fed substantially vertically upward are guided by the guide member 45, and are conveyed to the conveyor belt 51 and the counter. It is sandwiched between the rollers 46 and conveyed. Then, the front end is guided by the transport guide 37 and pressed against the transport belt 51 by the front end pressure roller 49, and the transport direction is changed by approximately 90 °.

  At this time, an alternating voltage is applied to the charging roller 56 such that a positive output and a negative output are alternately repeated. As a result, a charging voltage pattern in which the conveyor belt 51 alternates, that is, a positive and a negative are alternately charged in a band shape with a predetermined width in the sub-scanning direction that is the circumferential direction. 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 recovery of the nozzles of the recording head 34, the carriage 33 is moved to a position facing the maintenance recovery mechanism 81 which is the home position. Thereafter, maintenance and recovery operations such as nozzle suction for performing capping by the cap 82 to perform suction from the nozzle, and idle ejection for discharging droplets that do not contribute to image formation are performed. By performing the maintenance and recovery operation, it is possible to realize image formation by stable droplet discharge.

  Next, the maintenance / recovery mechanism 81 will be described with reference to FIGS. 3 is a perspective view of the maintenance / recovery mechanism, FIG. 4 is a plan view of an essential part thereof, and FIG. 5 is a schematic schematic configuration diagram. In the maintenance / recovery mechanism 81, the caps 82a and 82b held by the cap holder 212, the wiper member 83 including an elastic body, and the wiper cleaner pressing portion piece 86 serving as the first wiper cleaning means can be moved up and down (up and down movement). Held by the maintenance device frame 211.

  A cylindrical idle discharge receiver 84 is disposed between the wiper member 83 and the cap 82a, and a second wiper that scrapes and removes ink adhering to the wiper member 83 at the upper end of the idle discharge receiver 84 on the wiper member side. A wiper cleaner piece 85 is formed as a cleaning means. When the wiper member 83 is cleaned, the wiper member 83 is lowered with the wiper cleaner pressing portion piece 86 pressed against the wiper cleaner piece 85 so that the ink adhering to the wiper member 83 is removed from the idle discharge receptacle 84 side. Scrap off.

  A tubing pump (suction pump) 220 is connected to the cap 82a on the side close to the printing area via a flexible tube 219. In this way, only the cap 82a is used as a suction (recovery) and moisture retention cap (hereinafter simply referred to as a suction cap), and the other cap 82b is merely a moisture retention 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.

  A cam shaft 221 that is rotatably supported by the maintenance device frame 211 is disposed below the caps 82a and 82b as capping members and the wiper member 83 as a wiping member. The cam shaft 221 is provided with a cap cam 222 that raises and lowers the cap holder 212, a wiper cam 224 that raises and lowers the wiper member 83, a roller 226, and a cleaner cam 228 that swings the wiper cleaner pressing portion piece 86. The roller 226 is in the idle discharge receptacle 84, and a droplet to be discharged is applied. Further, the camshaft 221 is also provided with a carriage lock cam 229 for raising and lowering the carriage lock 87.

  In order to drive the suction pump 220, the motor gear 232 provided on the motor shaft 231 a of the motor 231 is engaged with the pump gear 233 provided on the pump shaft 220 a of the suction pump 220. In order to drive the cam shaft 221, the third intermediate gear 236 is further meshed with the first intermediate gear 234 integrated with the pump gear 233 via the second intermediate gear 235. Further, the cam gear 240 fixed to the cam shaft 221 via the fifth intermediate gear 239 is meshed with the fourth intermediate gear 238 coaxial with the third intermediate gear 236. The third intermediate gear 236 is provided with a one-way clutch 237, and the intermediate shaft 241 that is the rotation shaft of the third intermediate gear 236 is rotatably held by the maintenance device 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 inside is dried and thickened / fixed, resulting in a decrease in ink ejection performance. In order to prevent this, when the nozzle surface of the recording head 34 is covered with the cap 82, the motor 231 is rotated, the cap 82 is raised via the cap cam 222, and the nozzle surface of the recording head 34 is capped.

  Next, the raising / lowering mechanism of the cap 82 is demonstrated with reference to FIG. The cap 82 is held by a cap holder 212 which is a cap holding member so as to be movable up and down (movable up and down). Between the cap 82 and the cap holder 212, a spring 301 that biases the cap 82 upward with respect to the cap holder 212 is interposed.

  The cap holder 212 is held by the slider 302 so as to be movable in the front-rear direction (nozzle alignment direction of the recording head 34). Guide pins 304 and 305 provided at the front and rear ends of the slider 302 are slidably fitted in guide grooves 306 formed in the maintenance device frame 211. Thereby, the slider 302, the cap holder 212, and the entire cap 82 can be moved up and down by the cap cam 222 connected to the slider 302.

  Guide pins 310 and 311 are provided at both longitudinal ends of the cap 82, and engagement holes 312 and 313 (which may be recesses or grooves) with which the guide pins 310 and 311 are engaged are provided in the cap holder 212. It has been.

  A guide shaft 315 is provided on the bottom surface of the cap 82 and is inserted into the flange portion of the cap holder 212 so as to be movable up and down. The cap 82 is attached to and held by the cap holder 212 so as to be movable up and down. A spring 301 interposed between the cap 82 and the cap holder 212 urges the cap 82 upward (in the direction of pressing toward the nozzle surface during capping).

  Further, the slider 302 and the cap holder 212 are inserted into the suction cap 82a, and the tube 219 from below is located at the center position of the cap with respect to the short direction of the cap 82a and at a position shifted from the center position in the longitudinal direction. Is connected by crawling.

  In order to move the cap 82 up and down, the slider 302 that holds the cap holder 212 is provided with a cam pin 321 engaged with the cap cam 222, and when the cap cam 222 rotates, the slider 302 is lifted and lowered. Is raised and lowered.

  Next, the lifting mechanism (vertical movement mechanism) of the wiper member 83 will be described with reference to FIG. The wiper member 83 is attached to the wiper holder 341. Guide pins 342 and 343 are provided at both ends of the wiper holder 341. These guide pins 342 and 343 are fitted into a guide groove 346 formed in a guide member 345 (or the maintenance device frame 211 itself), and can move up and down along the guide groove 346. A stopper 347 for restricting the end of upward movement of the guide pin 342 is provided at the upper end portion of the guide groove 346, thereby restricting the rising position of the wiper member 83. On the other hand, a flexible member (hereinafter referred to as a flexible member) 348 is attached between the leg portions 341 a and 341 a of the wiper holder 341. The flexible member 348 is formed with a tongue piece 348a having a cam pin 349 movably fitted in the cam groove of the wiper cam 224 (FIG. 5).

  Next, a cleaning sequence that is head maintenance using the above-described maintenance and recovery mechanism will be described. FIG. 8 is an overall flow of the cleaning sequence. When cleaning is performed, first, the recording apparatus is decaped from the capping state, which is a standby state. Subsequently, the carriage moves in the main scanning direction to move the cleaning target head to the maintenance position (suction cap position), and the head is capped. Subsequently, in order to remove foreign matter, thickened ink, bubbles, etc. in the nozzle, the pump of the maintenance / recovery mechanism is rotationally driven to suck ink (S1: head suction).

  After the head suction, unnecessary ink is still attached to the nozzle surface, and the meniscus of the nozzle is broken, so the carriage is moved in the main scanning direction, the nozzle surface is wiped with a wiper, the ink is wiped off, and the nozzle meniscus is removed. Form. Here, just before the end of wiping, the cam of the maintenance and recovery mechanism rotates to lower the wiper. At the same time, as described with reference to FIG. 5, the wiper cleaner pressurizes the wiper in conjunction with the cam, and the ink attached to the wiper is also removed (S2: wiping).

  Subsequently, after the head is retracted to the printing area side, the ink remaining in the cap when sucked by the head suction is again sucked by the pump of the maintenance recovery mechanism (S3: suction in cap). After suction in the cap, in the case of a head having a plurality of nozzle rows, the colors are mixed by wiping. Therefore, the head is driven and ink is ejected into the cap (S4: empty ejection). Finally, the ink ejected idle is processed by suction in the cap (S5: suction in cap) and capped. The above is a series of cleaning operations.

  Further, in order to prevent the mist and paper dust generated during printing from entering the nozzles and preventing the nozzles from being removed during printing, automatic cleaning that automatically activates the cleaning sequence during printing is set. In automatic cleaning, the amount of ink consumed from the nozzles after maintenance is added by a soft count and when a certain threshold is exceeded (to prevent omission due to mist), or when the total number of printed sheets exceeds a certain threshold ( To prevent paper powder from falling out).

  The wiping performed during cleaning will be described. As shown in FIG. 9, after the wiper member 83 is adjusted to the wiping position by the cam rotation of the maintenance and recovery mechanism as shown in FIG. 9, the wiper member 83 is moved relative to the wiper member 83 by the relative movement of the recording head 34 as shown in FIG. Is used to wipe the nozzle surface of the recording head 34. At this time, the edge portion of the wiper member 83 is brought into close contact with the nozzle surface, and ink remaining after the head suction is wiped downstream. Furthermore, as shown in FIGS. 11 and 12, when the wiping is finished, the amount of biting is gradually reduced by moving the wiper member 83 downward, and the ink is not splashed by not being wiped off.

  13 shows the positional relationship between the wiper member 83, the wiper cleaner piece 85, and the wiper cleaner pressing portion piece 86 immediately after the end of the wiping shown in FIG. 12, and the wiper surface of the wiper member 83 has nozzles of the recording head. The ink wiped from the surface is attached. FIG. 14 shows a state in which the wiper member 83 is further lowered from the positional relationship shown in FIG. 13, and the wiper cleaner pressing portion piece 86 presses the wiper member 83 against the wiper cleaner piece 85 at the reverse position in conjunction with the cam. The ink is removed in a stubborn manner. The free tip of the wiper cleaner pressing piece has a metal roller, and is in rotational contact with the wiper member 83 when it is lowered, thereby preventing damage to the wiper member 83 due to friction. FIG. 15 shows a state where the wiper member 83 is completely lowered and all the ink on the wiper wiping surface side is removed. Thereafter, as shown in FIG. 16, the wiper cleaner piece 85 and the wiper cleaner pressing portion piece 86 are separated from the wiper member 83, and the wiper cleaner operation is finished. However, in the configuration of the present embodiment, as can be seen from FIGS. 15 and 16, the ink that has moved to the upper part of the wiper member 83 rides on the top surface of the wiper member 83 and cannot be completely removed.

  Although the wiper cleaner operation has been described with reference to FIGS. 13 to 16, it has also been found that ink remains on the top surface of the wiper member. Here, when cleaning (wiping) is performed again immediately after cleaning (including wiper cleaner operation), as shown in FIGS. 17 and 18, wiping is performed from the state in which the ink on the top surface of the wiper member 83 is on the previous cleaning. Begins. Then, the ink is rubbed so as to extend to the nozzle surface of the recording head 34 just wiped. When the rubbed ink comes into contact with the nozzle surface, depending on the contact state, it may not be recovered by subsequent idle ejection, resulting in poor maintenance such as nozzle omission or color mixing due to meniscus destruction.

  On the other hand, as can be seen from FIG. 19, in general, when ink is dried in an external environment, its weight is reduced due to water evaporation, and at the same time its volume is reduced. Further, since the amount of ink on the top surface of the wiper member is also very small, the amount of ink on the top surface of the wiper member is reduced after a certain amount of time.

  Therefore, when it is time to clean (hereinafter abbreviated as CL) each of a plurality of recording heads at a short interval (within a predetermined time) at the same time, in order to avoid a maintenance failure due to remaining ink on the wiper member, An example of shifting the timing will be described with reference to FIG. When there is a CL execution flag in a certain recording head (a state in which the ink consumption or the number of prints reaches or exceeds the automatic CL threshold), it is determined whether the time from the previous automatic CL is less than T (S1). ). Here, “T” corresponding to a certain interval is the time taken for the ink adhering to the top surface of the wiper member to decrease to a level where there is no problem. Even if the threshold value of the automatic CL is used as a reference for the number of printed sheets, it depends on the assumed average value of the ink amount consumed per sheet, and therefore approximates the actual consumed ink amount. Then, if it is equal to or greater than T, the CL is executed as it is, and if it is less than T, the CL of the target head is postponed so that T or more passes (S2), and the execution timing of the automatic CL is shifted. As a result, as shown in FIG. 21, the automatic CL is not executed at intervals less than T, and the remaining ink in the wiper is reduced, so that nozzle missing and color mixing are unlikely to occur.

  Another example of shifting the execution timing of automatic CL when a plurality of recording heads are at the timing of CL at short intervals (within a predetermined time) at the same time will be described with reference to FIG. In this second example, when the contents of a print job are input to a processing apparatus that also controls automatic cleaning, the amount of ink consumed during the print job is calculated in advance for each recording head before starting the print job ( S1). Subsequently, the timing for entering the automatic CL is calculated from the amount of ink consumed and the number of sheets passed (S2). When there is a combination in which the CL interval is less than T among all the CLs, the ink consumption amount between jobs of each print head is compared (S3), and the one with the smaller ink consumption amount (H2 in FIG. 23) is recorded on the other side. The head is moved away from the CL so that there is an interval of T or more (S4). As a result, the execution timing of the automatic CL of the recording head that consumes a large amount of ink and has a high risk of missing due to mist adhesion during printing is not delayed, so that more stable printing performance can be maintained.

  In the third example, the shift amount in the second example is assigned to each print head as an inverse proportion of the ink consumption, and the execution timing of the automatic CL is shifted. That is, as shown in the flow of FIG. 24, after receiving a print job, the ink consumed during the job execution is first calculated for each recording head (S1), and automatic CL is entered from the consumed ink amount and the number of sheets passed. Timing is calculated in advance (S2). When there is a combination in which the CL interval is less than T among all CLs, the ink consumption amount between jobs of each print head is compared (S3). Then, the shift amount is assigned to each recording head as an inverse proportion of the ink consumption, and the automatic CL is shifted away from the other so that the interval of the automatic CL is more than T (S4, FIG. 25). As a result, even a recording head that consumes a large amount of ink and has a high possibility of coming off when it is shifted can equalize the risk of missing and maintain more stable printing performance.

  In the fourth example, as in the flow of FIG. 26, after determining the shift amount (S1 to S4) in the third example, the additional ink consumption amount when the recording head on the side shifted backward is shifted is calculated. (S5). In a job, if the ink consumption of the head is concentrated at a shifted position (shift time) or exceeds a certain threshold W (S6), the risk of missing by extending the automatic CL increases. Therefore, only in this case, it is determined that the risk of missing is higher than the risk of not opening the CL interval up to T, and the shifted time of both heads is restored (S7), that is, the shifting is stopped, Start the print job. This makes it possible to maintain more stable printing performance even if there is a deviation in the printing amount during the job.

  In the fifth example, an environment parameter is provided in the CL interval T in consideration of the fact that the decrease with time of ink remaining on the top surface of the wiper member during automatic CL varies depending on the environment as shown in FIG. is there. T is not an absolute value, but is a variable that becomes shorter on the high temperature and low humidity side where drying is quicker. As a result, the risk of missing can be avoided and the more stable printing performance can be maintained while preventing the postponement of the maintenance more than necessary due to the shift amount which becomes unnecessary depending on the environmental temperature and the environmental humidity.

1: apparatus main body, 2: paper feed tray, 3: paper discharge tray, 4: cartridge loading unit, 10: ink cartridge, 21: side plate, 31, 32: guide rod, 33: carriage, 34: recording head, 35: Sub tank, 36: supply tube, 37: transport guide, 41: pressure plate, 42: paper, 43: paper feed roller, 44: separation pad, 45: paper guide member, 46: counter roller, 47: transport guide member, 48: Pressing member, 49: tip pressure roller, 51: transport belt, 52: transport roller, 53: tension roller, 56: charging roller, 61: separation claw, 62: discharge roller, 63: spur (discharge roller), 71: Duplex unit, 72: Manual feed tray, 81: Maintenance / recovery mechanism, 82: Cap, 83: Wiper member, 84, 88: Empty discharge receptacle, 85: Wiper cleaner piece, 8 : Wiper cleaner pressing piece, 87: Carriage lock, 89: Opening, 100, 101: Waste liquid tank, 119: Tube, 211: Maintenance device frame, 212: Cap holder, 212a: Flange, 219: Flexible Tube, 220: Suction pump, 220a: Pump shaft, 221: Cam shaft, 222: Cap cam, 224: Wiper cam, 226: Roller, 228: Cleaner cam, 229: Carriage lock cam, 231: Motor, 231a: Motor shaft, 232 : Motor gear, 233: pump gear, 234, 235, 236, 238, 239: intermediate gear, 237: one-way clutch, 240: cam gear, 241: intermediate shaft, 301: spring, 302: slider, 304, 305, 310, 311 : Guide pin, 306: Guide groove, 312, 13: engagement hole, 315: guide shaft, 321: cam pin, 341: wiper holder, 342, 343: guide pin, 345: guide member, 346: guide groove, 347: stopper, 348: flexible member, 348a: tongue Piece, 349: Cam pin

Japanese Patent No. 4567716 Japanese Patent No. 4570865 JP 2010-184421 A JP-A-2005-313606

Claims (5)

At least two droplet discharge heads for discharging droplets from the nozzles on the nozzle surface,
A capping member that covers the nozzle surface of the droplet discharge head;
A suction pump that is connected to the capping member and sucks the nozzle surface;
A wiping member for wiping the nozzle surface of the droplet discharge head;
Driving means for relatively moving the droplet discharge head and the wiping member in a direction along the nozzle surface;
When the amount of ink ejected from the droplet ejection head reaches a predetermined ink consumption threshold during a print job ejecting droplets from the droplet ejection head, the nozzle surface of the corresponding droplet ejection head is changed. Control means for performing automatic cleaning for sucking with the suction pump in a state covered with the capping member and wiping the nozzle surface with the wiping member;
With
The time taken for the weight of the ink remaining on the top surface of the wiping member to decrease to a predetermined value is a predetermined time,
Wherein, when a plurality of the liquid drop ejecting head reaches each said threshold value within the predetermined time, the execution timing of the automatic cleaning of at least one of the droplet discharge head, wherein the other droplet ejection heads An image forming apparatus, wherein the automatic cleaning is executed such that the execution timing of the automatic cleaning of each droplet discharge head is set to be longer than the predetermined time by shifting from the execution timing of the automatic cleaning. It is determined from the contents of the print job input to the processing apparatus that also controls the automatic cleaning whether or not there is an interval for the automatic cleaning of the plurality of droplet discharge heads within the predetermined time. If it is determined that the ink is consumed, the amount of ink consumed during the print job of each droplet discharge head is compared, and the execution timing of the automatic cleaning of the droplet discharge head with the smaller amount of consumed ink is The image forming apparatus according to claim 1, wherein the image forming apparatus is shifted from the execution timing of the automatic cleaning of the droplet discharge head so as to be more than the predetermined time . It is determined from the contents of the print job input to the processing apparatus that also controls the automatic cleaning whether or not there is an interval for the automatic cleaning of the plurality of droplet discharge heads within the predetermined time. If it is determined that the ink is consumed, the amount of ink consumed during the print job of each droplet discharge head is compared, and the automatic cleaning of the droplet discharge head with the smaller amount of consumed ink is inversely proportional to the amount of consumed ink. Increase the execution timing, shift the execution timing of the automatic cleaning of the droplet discharge head with the larger amount of ink consumption to a small amount, and set the execution timing of the automatic cleaning of both droplet discharge heads more than the predetermined time. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 3, wherein the shifting is stopped when the amount of ink consumed in a shift time of the droplet discharge head that shifts so as to delay the execution of automatic cleaning exceeds a certain level. The image forming apparatus according to claim 1, wherein the predetermined time is changed according to environmental temperature or environmental humidity.

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