JP2008299199A - Color image-forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an intermediate transfer-type color image-forming apparatus which has a belt-control method which easily corrects a deviation of a transfer position of an intermediate transfer belt. <P>SOLUTION: After a belt is moved when color printing is made from a monochrome printing state or from a halt state, or when a power source is changed from turning off to turning on, when the number of paper sheets to which printing is made reaches at least a prescribed number N, or when printing period reaches a prescribed period of time M, at first, a transfer belt is subjected to empty rotation for two seconds for resist adjustment, and then the belt is stopped for two seconds. Then, the transfer belt thus stopped is subjected to empty rotation for about five seconds to reduce the distortion of the belt and is then subjected to full-scale rotation for color printing. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a color image forming apparatus having a color image forming position adjusting function.

  In recent years, color printer apparatuses (color image forming apparatuses) have been widely used in conjunction with the increase in the number of personal computers sold. In particular, tandem color image forming apparatuses have excellent printing speed and are attracting attention today. Yes.

  In this type of color image forming apparatus, images of three colors including yellow (Y), magenta (M), cyan (C), or four colors including black (K) are sequentially transferred and superimposed and fixed. Processing is performed to form an image.

  In addition, since an image is formed on a transfer medium (paper) that moves in the sub-scanning direction, each color needs to be accurately aligned. In the color image forming apparatus, the hue is also important, and even if the toner density of one color is deviated from the reference, the hue of the composite color becomes different.

  For this reason, in the color image forming apparatus, various methods have been proposed in order to achieve image matching and color matching.

For example, a tandem color printer that transfers a four-color toner image onto a paper while the paper is being transported by a transport belt. Is printed on a belt, and this resist patch is read by a density sensor to detect and correct misregistration of other colors with respect to black (K). (For example, see Patent Document 1)
The above is for adjusting the position of the paper transport belt. However, in the same four-color printer with an intermediate transfer method, the intermediate transfer belt is moved up and down to switch between color printing and monochrome printing. In order to detect misregistration, the position of the intermediate transfer belt that conveys the toner image with a simple configuration of the worm wheel and worm gear is calculated by automatically detecting the test printed image with a sensor. A method of adjusting is proposed. (For example, see Patent Document 2)
JP 2002-040746 A JP-A-2005-249853

  However, particularly in the case of an intermediate transfer belt, a toner image is transferred to the belt. Therefore, if the surface of the belt is slightly distorted, the transfer position of the pixel at the same position of the toner image for each color differs depending on the location of the belt. As a result, a location where the transfer position shift occurs for each color occurs.

  For this reason, it is difficult to correct the position of each color and all the places on the entire circumference of the belt, and it is difficult to correct the position.

  An object of the present invention is to provide a color image forming apparatus having a belt control method that can easily correct a transfer position shift of an intermediate transfer belt in an intermediate transfer type color image forming apparatus in view of the above-described conventional situation.

  The color image forming apparatus of the present invention includes a plurality of image carriers arranged side by side, a plurality of toner image forming units that individually form predetermined color toner images on the plurality of image carriers, and the plurality of images. A belt member that rotates to be in direct contact with at least one image carrier of the carrier, a position that separates the belt member from all of the plurality of image carriers, and an outermost end of the plurality of image carriers arranged side by side; Belt moving means for moving to a position in contact with only one of the plurality of image carriers and a position in contact with all of the plurality of image carriers, and inclining the belt body in accordance with the rotation of the belt body. In a color image forming apparatus comprising at least a skew correcting means for correcting, a position where the belt moving means comes into contact with only one of the plurality of image carriers arranged at the end of the plurality of image carriers, or Separate from all of the plurality of image carriers When the belt body is moved to a position in contact with all of the plurality of image carriers, the belt body is first rotated idle for about 2 seconds, then the belt body is stopped, and then the belt body is moved to 5 A belt rotation control unit is provided that rotates in the idle direction for about a second and then rotates in order to form a color image.

  The belt rotation control means, for example, when a predetermined number of prints is reached when participating in the formation of a color image while rotating at a position where the belt body contacts all of the plurality of image carriers, First, the belt body is idled for about 2 seconds, then the belt body is stopped, and then the belt body is idled for about 5 seconds, and then fully rotated for color image formation. Control belt rotation.

  In addition, the belt rotation control unit, for example, when a predetermined printing time has elapsed when the belt member is participating in the formation of a color image while rotating at a position where the belt member contacts all of the plurality of image carriers. At first, the belt body is idled for about 2 seconds, then the belt body is stopped, and then the belt body is idled for about 5 seconds, and then fully rotated for color image formation. Control the belt rotation.

  In addition, the belt rotation control means may be configured such that, for example, when the belt body is in a position in contact with all of the plurality of image carriers when the power of the image forming apparatus main body is turned on, the belt body Is rotated for about 5 seconds, and then the belt rotation is controlled so that it is fully rotated for color image formation.

  The belt body in the color image forming apparatus may be, for example, an intermediate transfer belt, or may be, for example, a paper transport belt.

  According to the present invention, before the start of printing or periodically when the belt body is in the color printing position, the belt body is idled for a minimum amount of time and stopped, and is further idled for about 5 seconds before full-scale rotation of color image formation. The belt body position can be adjusted simply by idling, stopping, and idling, so there is no need to add a special mechanism for position adjustment. The toner and time are not wasted for forming and adjusting the position with the density sensor, and it is possible to contribute to the improvement of economical and actual operation efficiency.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a cross-sectional view illustrating an internal configuration of a color image forming apparatus (hereinafter simply referred to as a printer) provided with a belt-type fixing device according to Embodiment 1 of the present invention.

  The printer 10 shown in FIG. 1 is an electrophotographic secondary transfer tandem color image forming apparatus, and includes an image forming unit 12, an intermediate transfer belt unit 13, a paper feeding unit 14, and a duplex printing transport unit 15. It consists of

  The image forming unit 12 has a configuration in which four image forming units 16 (16M, 16C, 16Y, and 16K) are arranged in a multistage manner from right to left in FIG.

  The three image forming units 16M, 16C, and 16Y on the upstream side (right side in the figure) of the four image forming units 16 are magenta (M), cyan (C), yellow (subtractive three primary colors), respectively. A monocolor image is formed with the color toner of Y), and the image forming unit 16K forms a monochrome image with the black (K) toner mainly used for characters and dark portions of the image.

  Each of the image forming units 16 has the same configuration except for the color of toner stored in a toner container (toner cartridge). Accordingly, the configuration of the black (K) image forming unit 16K will be described below as an example.

  The image forming unit 16 includes a photosensitive drum 17 at the bottom. The photosensitive drum 17 has a peripheral surface made of, for example, an organic photoconductive material. A cleaner 18, a charging roller 19, an optical writing head 21, and a developing roller 23 of the developing device 22 are arranged around the periphery of the photosensitive drum 17.

  The developing unit 22 applies magenta (M), cyan (C), yellow (Y), or black (K) toner to the upper toner container as indicated by M, C, Y, and K in FIG. An intermediate portion is provided with a toner replenishing mechanism for the lower portion.

  The developing unit 22 is provided with the developing roller 23 in the side opening at the lower portion thereof, a toner stirring member, a toner supply roller for supplying toner to the developing roller 23, and a toner layer on the developing roller 23 as a fixed layer. It has a doctor blade that regulates the thickness.

  The intermediate transfer belt unit 13 has an endless transfer belt 24 extending in a flat loop shape from substantially the left and right sides of the figure at the center of the main body, and the transfer belt 24 is stretched over the transfer belt 24. A driving roller 25 and a driven roller 26 are provided to circulate and move the belt 24 counterclockwise in the figure.

  The transfer belt 24 transfers the toner image directly to the belt surface (primary transfer) and conveys the toner image to the transfer position to the paper for further transfer (secondary transfer). The whole is called an intermediate transfer belt unit.

  The intermediate transfer belt unit 13 includes a belt position control mechanism 27 in the loop of the flat loop-shaped transfer belt 24. The belt position control mechanism 27 includes a primary transfer roller 28 made of a conductive foam sponge that presses against the lower peripheral surface of the photosensitive drum 17 via the transfer belt 24.

  The belt position control mechanism 27 includes three primary transfer rollers 28 corresponding to the three image forming units 16M, 16C, and 16Y of magenta (M), cyan (C), and yellow (Y) as vertical support shafts. Rotate to the center with the same period.

  Then, the belt position control mechanism 27 performs transfer by rotating one primary transfer roller 28 corresponding to the black (K) image forming unit 16K at a rotational movement period different from the period of the three primary transfer rollers 28. The belt 24 is separated from the photosensitive drum 17.

  That is, the belt position control mechanism 27 sets the position of the transfer belt 24 of the intermediate transfer belt unit 13 in the full color mode (all four primary transfer rollers 28 are in contact with the transfer belt 24) and the monochrome mode (in the image forming unit 16K). Only the corresponding primary transfer roller 28 is in contact with the transfer belt 24) and all non-transfer modes (all four primary transfer rollers 28 are separated from the transfer belt 24).

  In the intermediate transfer belt unit 13, a belt cleaner unit is disposed further upstream of the image forming unit 16M on the uppermost stream side in the belt movement direction on the upper surface, and is flat and thin so as to be almost along the entire lower surface. The waste toner collecting container 29 is detachably disposed.

  The paper feed unit 14 includes two paper feed cassettes 31 arranged in two upper and lower stages, and in the vicinity of the paper feed opening (right side in the drawing) of the two paper feed cassettes 31, respectively, A feeding roller 33, a separating roller 34, and a standby conveyance roller pair 35 are disposed.

  In the paper conveyance direction (vertical upward direction in the figure) of the standby conveyance roller pair 35, a secondary transfer roller 36 that is in pressure contact with the driven roller 26 via the transfer belt 24 is disposed, and a secondary transfer portion to the paper is arranged. Forming.

  A belt-type fixing device 37 is disposed downstream (upward in the drawing) of the secondary transfer portion, and the fixed sheet is carried out of the belt-type fixing device 37 further downstream of the belt-type fixing device 37. A pair of carry-out rollers 38 and a pair of paper discharge rollers 41 that discharge the discharged paper to a paper discharge tray 39 formed on the upper surface of the apparatus are provided.

  The duplex printing conveyance unit 15 includes a start return path 42a branched from the intermediate conveyance path between the carry-out roller pair 38 and the paper discharge roller pair 41 in the right lateral direction in the figure, and then an intermediate return path 42b bent downward. A terminal return path 42c that bends in the left lateral direction opposite to the above and eventually reverses the return sheet, and four return roller pairs 43a, 43b, 43c, 43d arranged in the middle of these return paths. ing.

  The exit of the end return path 42 c communicates with a conveyance path to the pair of standby conveyance rollers 35 corresponding to the sheet feeding cassette 31 below the sheet feeding section 14.

  In this example, a cleaning unit 45 and a take-in roller 46 are disposed on the upper surface of the intermediate transfer belt unit 13.

  The cleaning unit 45 abuts on the upper surface of the transfer belt 24 to scrape and remove the waste toner, and the take-in roller 46 takes over the waste toner removed by the cleaning unit 45 and is not shown in the figure, and is temporarily stored in the belt cleaner unit. The waste toner thus collected is conveyed to the upper part in the dropping cylinder by a conveying screw and sent to the waste toner collecting container 29 via the dropping cylinder.

  Further, in order to bring the cleaning unit 45 into pressure contact with the transfer belt 24 with an appropriate pressure, a pressure roller 47 is provided on the intermediate transfer belt unit 13 side to press the transfer belt 24 toward the cleaning unit 45 from below. ing.

  As shown in FIG. 1, the printer 10 does not directly transfer a toner image onto a conventional sheet, but passes a transfer belt 24 to a sheet that is vertically conveyed to a secondary transfer unit by a standby conveyance roller pair 35. Thus, the toner image is transferred.

  Therefore, it is possible to cope with a maintenance process for recovering from a problem such as a paper jam occurring in the paper transport path by simply opening the right side of FIG.

  In addition, since troubles such as paper jam do not occur in the arrangement section of the kits, the operation for attaching and detaching consumables such as kits concentrated on the left side of FIG. It is configured as follows.

  Thereby, the dimension between kits is reduced as much as possible, and size reduction of the whole apparatus main body is achieved. Further, the optical writing head itself is also miniaturized and is configured closer to the photosensitive drum.

  FIG. 2 is a circuit block diagram including the control device of the printer 10 described above. As shown in FIG. 2, the circuit block is centered on a central processing unit (CPU) 50, and an interface controller (I / F_CONT) 51 and a printer controller (PR_CONT) 52 are connected to the CPU 50 via a data bus. ing. A printer printing unit 53 is connected to the PR_CONT 52.

  Also connected to the CPU 50 are a ROM (read only memory) 54, an EEPROM (electrically erasable programmable ROM) 55, an operation panel 56 of the main body operation unit, and a sensor unit 57 to which outputs from sensors arranged in each unit are input. Has been.

  A system program is stored in the ROM 54, and the CPU 50 performs processing by controlling each unit in accordance with the system program.

  That is, in each unit, first, the I / F_CONT 51 converts print data supplied from a host device such as a personal computer into bitmap data and develops it in the frame memory 58. In the frame memory 58, a storage area is set for each of black (K), magenta (M), cyan (C), and yellow (Y), and data of each color is developed in a corresponding area.

  The data developed in the frame memory 58 is output to the PR_CONT 52 and is output from the PR_CONT 52 to the printer printing unit 53.

  The printer printing unit 53 is an engine unit, and under the control of the PR_CONT 52, the rotational drive system including the photosensitive drum 17, the primary transfer roller 28, etc. shown in FIG. 1, the charging roller 19, the optical writing head 21, etc. An image forming unit having a driven unit, a belt driving unit 59 that moves the intermediate transfer unit 13 up and down and rotationally drives the transfer belt 24, and a rotationally driven unit such as a paper take-out roller 32 to a paper discharge roller pair 41. A drive output to a process load such as a conveyance mechanism, a heat generating drive, and a belt type fixing device 37 driven to rotate is controlled.

  The black (K), magenta (M), cyan (C), and yellow (Y) data output from the PR_CONT 52 are respectively sent from the printer printing unit 53 to the corresponding optical writing head 21 shown in FIG. To be supplied.

  3A, 3B, and 3C are diagrams showing three types of vertical movement states of the transfer belt 24 of the intermediate transfer belt unit 13 in the printer 10 configured as described above. The three vertical movements are performed by the belt driving unit 59 under the control of the printer printing unit 53.

  First, FIG. 3A shows a photosensitive drum 17 (17K, 17C, 17M, 17Y) as a plurality of (four in this example) transfer belts 24 as a belt body of the intermediate transfer belt unit 13. The state which moved to the position which leaves | separates from all of and rests is shown.

  Next, FIG. 3B shows that the primary transfer roller 28 directly below the image forming unit 16K at the leftmost end arranged side by side moves upward, so that the transfer belt 24 has a plurality (four) of photosensitive drums. 17 shows a state in which only one (photosensitive drum 17K) disposed at the endmost portion of 17 arranged in contact is moved to a position for monochrome printing.

  3 (c) shows that the primary transfer roller 28 directly below all the image forming units 16 (16K, 16C, 16M, 16Y) moves upward, and the transfer belt 24 has a plurality of (four) photoconductors. A state is shown in which the drum 17 (17K, 17C, 17M, 17Y) is in contact with all of the drums 17 and moved to a position for color printing.

  Next, the basic operation of the printer 10 having the above configuration will be described. In the following description of the basic operation, the operation in the color printing state shown in FIG.

  First, printing (printing) is started when the power is turned on and the number of sheets to be used, the print mode, and other designations are input as keys or as signals from the connected host device.

  That is, the drive roller 25 rotates in the counterclockwise direction in the figure, and the rotation of the transfer belt 24 is started. The image forming units 16 are sequentially driven, and the photosensitive drum 17 rotates in the clockwise direction in the figure.

  The charging roller 19 initializes the peripheral surface of the photosensitive drum 17 by applying a uniform high negative charge, and the optical writing head 21 performs exposure according to the image signal on the peripheral surface of the photosensitive drum 17 by initialization. An electrostatic latent image including a high negative potential portion and a low negative potential portion by the exposure is formed.

  The developing roller 23 transfers the toner in the developing unit 22 to the low potential portion of the electrostatic latent image to form a toner image (reverse development) on the circumferential surface of the photosensitive drum 17.

  A magenta toner image formed on the peripheral surface of the photosensitive drum 17 of the image forming unit 16M in the uppermost stream in the sheet conveying direction is rotated and conveyed to the surface facing the transfer belt 24.

  The primary transfer roller 28 applies a transfer current output from a transfer bias power source (not shown) to the transfer belt 24. As a result, the magenta toner image on the photosensitive drum 17 is primarily transferred to the transfer belt 24.

  A cyan toner image formed on the peripheral surface of the photosensitive drum 17 of the image forming unit 16C is superimposed on the toner image primarily transferred to the transfer belt 24, and then is transferred by a primary transfer roller 28 directly below the image forming unit 16C. Transcribed.

  Further, the yellow toner image formed on the peripheral surface of the photoconductive drum 17 of the image forming unit 16Y is overlaid and transferred by the primary transfer roller 28 directly below the image forming unit 16Y, and finally, the photoconductive body of the image forming unit 16K. The black toner image formed on the peripheral surface of the drum 17 is transferred onto the primary transfer roller 28 directly below the image forming unit 16K.

  As described above, the toner images of four colors of magenta (M), cyan (C), yellow (Y), and black (K) are sequentially superimposed and primarily transferred to complete a full-color image on the transfer belt 24.

  The transfer belt 24 on which the four color toner images are primarily transferred is continuously rotated to convey the four color toner images to the secondary transfer position where the driven roller 26 and the secondary transfer roller 36 face each other. .

  On the other hand, the paper take-out roller 32 rotates to take out the paper stored in the paper feed cassette 31 slightly earlier than the printing timing on the paper. The roll roller 34 rotates in the reverse direction in order to inhibit the lower sheet from being fed in order to feed out only the uppermost sheet of the sheet taken out from the sheet cassette 31.

  The feeding roller 33 rotates in the forward direction and feeds the uppermost sheet to the standby conveyance roller pair 35.

  The standby conveyance roller pair 35 temporarily stops the rotation to stop the paper advance, corrects the conveyance posture such as the skew of the paper, waits for the conveyance timing, and sets the print start position of the paper by the transfer belt 24. In accordance with the timing coincident with the leading end of the four-color toner image conveyed to the secondary transfer position, the conveyance of the sheet is resumed and the sheet is fed to the secondary transfer position.

  At the secondary transfer position, the secondary transfer roller 36 applies a bias voltage supplied from a bias power source (not shown) to the sheet. As a result, the four color toner images on the transfer belt 24 are secondarily transferred to the paper.

  The sheet on which the four color toner images have been transferred is carried into the belt type fixing device 37 as it is. The belt-type fixing device 37 presses and holds the paper with an appropriate pressure contact force by the heat generation roller and the pressure contact roller, and applies heat and pressure to the paper and discharges it upward while fixing the four color toner images on the paper surface.

  The sheet discharged from the belt-type fixing device 37 is nipped by the pair of carry-out rollers 38 and taken over, and the pair of paper discharge rollers 41 places the image forming surface of the four color toner images on the paper discharge tray 39 downward. Discharged.

  The above has described color printing. However, for monochrome printing, except that the transfer belt 24 moves to the position shown in FIG. 3B and only the image forming unit 16K is operated. The operation is almost the same as in the case of color printing described above.

  In the intermediate transfer type tandem printer 1 that operates in this way, when switching from monochrome printing to color printing, the transfer belt 24 moves in the vertical direction, so that the surface of the transfer belt 24 is distorted.

  Regarding the deviation of the transfer position consistency (hereinafter simply referred to as “registration”) for each color on the transfer belt 24, a belt meandering control mechanism (not shown) is used. The meandering control mechanism corrects meandering of the belt body, and is generally provided as an accessory to belts.

  However, the registration deviation after the start of continuous printing cannot be easily corrected by only the meandering control mechanism of the belt body.

  However, the present inventor reduces the surface distortion of the transfer belt by performing idle rotation of the belt body for a short time, for example, around 5 seconds (simple rotation without performing the printing process) before full-scale operation of continuous printing is performed. And found that a good image of the resist was formed.

  Performing the above idle rotation for 5 seconds means that the belt body is temporarily stopped before that, and then the time is measured for 5 seconds.

  FIG. 4 is a chart showing the quality of the resist obtained as a result of various experiments and its determination in the above-mentioned belt body stop, short-time idling, and full-scale rotation for color image formation.

  The chart of FIG. 4 shows “printing experiment number”, “experiment contents”, “number of sheets whose registration deviation is 0.2 mm or more”, “number of printed sheets”, and “registration determination” from right to left. In addition, experiment contents A, B,..., I in the same table respectively indicate the following experiment contents.

  A is belt-down (state shown in Fig. 3 (a)), belt-up (state shown in Fig. 3 (c)), pre-rotation for 5 seconds (idle rotation before full-scale rotation), and continuous operation ( This shows a case where printing is performed in a full-scale rotation for color image formation). That is, here, the short-time driving and the temporary stop before the pre-rotation are not performed.

  B shows a case where the belt is moved up from the belt down, driven and stopped only for an instant, and then printed for continuous operation after the pre-rotation for 5 seconds.

  C shows a case where the belt is raised from the belt down, driven for 3 seconds and stopped, and then pre-rotated for 5 seconds and then printed in a continuous operation.

  D shows a case in which printing is performed in a continuous operation after leaving for 2 hours in the belt-up state after the previous printing and then performing a pre-rotation for 5 seconds.

  E shows a case where printing is performed by continuous operation after belt-up from belt-down, driving for 2 seconds and stopping, and then rotating 5 seconds before.

  F shows a case where printing is performed in a continuous operation after belt-up from belt-down and pre-rotating for 10 seconds. That is, the pre-rotation time is 5 seconds longer than the case of E, and the short-time driving and the temporary stop before the pre-rotation are not performed as in the case of E.

  G shows a case where printing is performed in a continuous operation after belt-up from belt-down and pre-rotating for 20 seconds. That is, the pre-rotation time is 10 seconds longer than that in the case of F, and here, the short-time drive and the temporary stop before the pre-rotation are not performed.

  H indicates a case where printing is performed in a continuous operation after belt-up from belt-down and pre-rotation for 30 seconds. In other words, the pre-rotation time is 10 seconds longer than in the case of G, and here, the short-time driving and the temporary stop before the pre-rotation are not performed.

  I shows a case where printing is performed in a continuous operation after leaving the belt up for several seconds after the previous printing, and after 5 seconds of pre-rotation. In this example, the standing time in the belt-up state is shorter than a few seconds than in the case of D.

  In any of the above cases, the number of printed sheets when printing is performed in a continuous operation is five. In addition to the experiment contents D, the five-sheet continuous printing experiment including the temporary stop and idling is performed five times each.

  In addition, since the user is likely to feel a sense of discomfort when the belt body is temporarily stopped, the suspension is set to 2 seconds regardless of the evaluation of the registration determination described later.

  After this experiment, the resist misalignment is measured, and when the resist misalignment of 0.2 mm or more is 0 or 1 out of 5 continuous prints, the evaluation of resist judgment is “◯”. It was.

  On the other hand, when there are two or more consecutive five-sheet prints in which a resist deviation of 0.2 mm or more has occurred, the evaluation of the resist determination is “x”.

  As can be seen from the chart of FIG. 4, in the determination of the above experimental results, the evaluation of the resist determination is “◯” in the experiment contents B, C, D, E, and I, and the resist is consistent. I understand.

  On the other hand, in the test contents A, F, G, and H, the evaluation of the resist determination is “x”, and it is understood that the resist is not matched.

  From the above results, it has been found that when printing is performed with the belt up from the belt down state, the resist deteriorates if printing is performed in a continuous operation following the pre-rotation.

  When printing with the belt up from the belt-down state, the resist can be improved if continuous printing is performed after the pre-rotation operation after a slight idling and then temporarily stopping. found.

  Also, the registration error is likely to occur when the number of printed sheets increases by a certain number or more, or when the printing time becomes longer by a certain time. Even in such a case, as a result of experiments, it was found that the resist is improved by continuing the printing after the idle rotation for 2 seconds, the temporary stop for 2 seconds, and the idle rotation for 5 seconds as described above.

  FIGS. 5A and 5B are flowcharts of belt drive control performed for registration correction by reducing distortion of the transfer belt based on the above experimental results.

  This process is performed via the printer controller 52, the printer printing unit 53, and the belt driving unit 59 under the control of the CPU 50 shown in FIG.

  5 (a) and 5 (b), it is used for the experiment contents B, C, D, E, or I in which the evaluation of the resist judgment of the experiment result shown in FIG. The control method is assembled in consideration of the stop period that does not impair the hearing of the person.

  FIG. 5A is a flowchart of the control to the belt drive unit 59 when performing monochrome printing or color printing from a pause state.

  In this case, control corresponding to the content of the experiment in which the evaluation of the registration determination is “◯” when the belt is moved from the belt-down state to the belt-up state in FIG.

  That is, as shown in FIG. 5A, the process is started when monochrome printing or color printing is designated from the pause state by an instruction input from the user.

  First, the CPU 50 moves the position of the transfer belt 24 (step S01). In this case, the transfer belt 24 moves from the monochrome printing position shown in FIG. 3B or the pause position shown in FIG. 3A to the color printing position shown in FIG.

  Next, the CPU 50 rotates (idly rotates) the transfer belt 24 for about 2 seconds (step S02), and then stops the transfer belt 24 for about 2 seconds (step S03).

  Subsequently, the CPU 50 causes the transfer belt 24 to rotate forward (idle rotation) for about 5 seconds, and then fully rotates for color printing (step S04).

  Generally, when switching from monochrome printing to color printing, the surface of the transfer belt is distorted due to the movement of the transfer belt. As described above, the intermediate transfer belt unit is provided by first rotating it for a short time. The distortion is slightly recovered by the meandering control. However, it will not disappear completely.

  Therefore, by next stopping the transfer belt and then restarting the rotation, the distortion of the belt surface is greatly reduced. This is considered to be common to the phenomenon in which wrinkles and folds of fabric products such as belts are reduced by repeating “tension” that stretches strongly and “relaxation” that relaxes the tension.

  Thus, when switching from monochrome printing to color printing, it is possible to reduce the surface distortion of the transfer belt by merely controlling the rotation operation of the transfer belt as temporary rotation, temporary stop, and short time pre-rotation. The resists can be matched anywhere.

  By the way, as described above, the registration error is likely to occur when the number of printed sheets increases by a certain number or more or when the printing time becomes longer by a certain time. Even in such a case, for example, it has been found that the resist is improved by continuing printing after performing idle rotation for 2 seconds, temporary suspension for 2 seconds, and idle rotation for 5 seconds. That was also mentioned above.

  In addition, as described above in Experiments D and I, there is no registration deviation when the pre-rotation is performed for 5 seconds even after the power is turned off in the belt-up state. It is clear from experimental results that a better result will be obtained if an idle rotation of 2 seconds and a pause of 2 seconds are added to this.

  FIG. 5 (b) shows the registration when the number of printed sheets increases from a certain number (N sheets) or more when the power is turned on, or when the printing time becomes longer than a certain time (M hours). It is a flowchart of control for deviation correction.

  This process is a process performed as an interrupt process at predetermined intervals during the normal process of the print process. As shown in FIG. 5B, first, the CPU 50 determines whether or not it is immediately after the power is turned on (step S101).

  If it is not immediately after the power is turned on (No in S101), it is next determined whether or not the number of printed sheets has reached a certain number (N) or more (step S102).

  This determination is made by detecting the paper feed by the paper sensor, counting it, accumulating the number of input prints specified, or accumulating the number of rotations of the paper take-out roller, and a predetermined number N stored in the EEPROM 55 in advance. Is determined by comparing with.

  If it is not equal to or greater than the predetermined number N (S102: No), it is then determined whether or not the printing time has reached a predetermined time (M time) or longer (step S103).

  This determination is made by comparing the value obtained by accumulating the printing operation time with a predetermined time M stored in the EEPROM 55 in advance.

  If it is not longer than the predetermined time M (S103: No), printing and other normal processing are performed (step S104).

  On the other hand, if it is determined immediately after the power is turned on in step 101 (S101: Yes), in this case, the transfer belt is first rotated for about 2 seconds (idle) for registration adjustment. (Step S105).

  Next, the transfer belt is stopped for about 2 seconds (step S106). Subsequently, the stopped transfer belt is pre-rotated (idly rotated) for about 5 seconds and then fully rotated for color printing (step S107), and the process proceeds to printing and other normal processing in step S104. .

  Further, when the number of printed sheets is determined to be greater than or equal to the predetermined number N in the determination of the number of printed sheets in step 102 (Yes in S102), in this case as well, the processes in steps S105 to S107 are performed, and then the printing in step S104 and the like. Move on to normal processing.

  If the printing time is determined to be equal to or longer than the predetermined time M in step 103 (S103: Yes), the processing in steps S105 to S107 is performed in this case, and the printing in step S104 is performed. Move on to normal processing.

  As described above, when the power is turned on from off, when the number of printed sheets reaches a certain number N or more, or when the printing time becomes a certain time M or more, the rotation operation of the transfer belt is temporarily performed. By simply controlling rotation, temporary stop, and short-time pre-rotation, it is possible to reduce the surface distortion of the transfer belt and correct registration deviation so that the four color resists match each other. .

  In the above description, the secondary transfer type intermediate transfer belt has been described as an example, but it is needless to say that the present invention can also be applied to registration adjustment of a sheet conveyance belt of a type in which a toner image is directly transferred to a sheet.

1 is a cross-sectional view illustrating an internal configuration of a color image forming apparatus (printer) including a belt-type fixing device according to Embodiment 1 of the present invention. FIG. 2 is a circuit block diagram including a printer control device according to the first embodiment. (a), (b), (c) is a figure which shows the state of three types of vertical movement of the transfer belt of the intermediate transfer belt unit in the printer of Embodiment 1. FIG. 6 is a chart showing the quality of resists and the judgments obtained as a result of various experiments in the first stop of the printer belt in Embodiment 1, a short idle rotation, and a full rotation for color image formation. (a), (b) is a flowchart of the belt drive control performed in order to reduce the distortion of the transfer belt of the printer and maintain the registration alignment in the first embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Printer 12 Image formation part 13 Intermediate transfer belt unit 14 Paper feed part 15 Duplex printing conveyance unit 16 (16M, 16C, 16Y, 16K) Image formation unit 17 (17m, 17c, 17y, 17k) Photosensitive drum 18 Cleaner 19 Charging roller 21 Optical writing head 22 Developer 23 Developing roller 24 Transfer belt 25 Drive roller 26 Drive roller 27 Belt position control mechanism 28 Primary transfer roller 29 Waste toner collection container 31 Paper feed cassette 32 Paper take-out roller 33 Feeding roller 34 Rolling Roller 35 Standby transport roller pair 36 Secondary transfer roller 37 Belt type fixing device 38 Unloading roller pair 39 Paper discharge tray 41 Paper discharge roller pair 42a Start return path 42b Intermediate return path 42c End return path 43a, 43b, 43c, 43d Return roller 45 Ningu 46 uptake roller 47 pressing roller 50 CPU (central processing unit)
51 Interface Controller (I / F_CONT)
52 Printer Controller (PR_CONT)
53 Printer printing section 54 ROM (read only memory)
55 EEPROM (electrically erasable programable ROM)
56 Operation panel 57 Sensor section 58 Frame memory

Claims (6)

A plurality of image carriers arranged side by side, a plurality of toner image forming means for individually forming predetermined color toner images on the plurality of image carriers, and at least one image carrier of the plurality of image carriers A belt member that rotates to directly contact the belt member, a position that separates the belt member from all of the plurality of image carriers, and only one disposed at the end of the plurality of image carriers arranged in parallel. A belt moving means for moving the belt body to a position in contact with the plurality of image carriers, and a skew correction means for correcting the skew of the belt body according to the rotation of the belt body. In a color image forming apparatus comprising at least
From the position where the belt body is brought into contact with only one of the plurality of image carriers, or the position separated from all of the plurality of image carriers, by the belt moving means. When moving to a position where it touches all of the image carrier,
First, the belt body is idled for about 2 seconds, then the belt body is stopped, and then the belt body is idled for about 5 seconds, followed by full rotation for color image formation. A color image forming apparatus comprising a control means. The belt rotation control means includes
When a predetermined number of prints is reached when participating in the formation of a color image while rotating at a position where the belt body contacts all of the plurality of image carriers,
First, the belt body is idled for about 2 seconds, then the belt body is stopped, and then the belt body is idled for about 5 seconds, followed by full rotation for color image formation.
The color image forming apparatus according to claim 1. The belt rotation control means includes
When a predetermined printing time has elapsed when the belt member participates in the formation of a color image while rotating at a position in contact with all of the plurality of image carriers,
First, the belt body is idled for about 2 seconds, then the belt body is stopped, and then the belt body is idled for about 5 seconds, followed by full rotation for color image formation.
The color image forming apparatus according to claim 1. When the belt body is in a position where the belt body contacts all of the plurality of image carriers when the power of the image forming apparatus main body is turned on,
The belt body is idled for about 5 seconds and then fully rotated for color image formation.
The color image forming apparatus according to claim 1.   The color image forming apparatus according to claim 1, wherein the belt body is an intermediate transfer belt.   The color image forming apparatus according to claim 1, wherein the belt body is a paper conveyance belt.