JP2010026122A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that is stable for a long period of time by accurately measuring surface unevenness of an image carrier surface in a main scanning direction, which causes shake of a cleaning blade or chipping of edges, and by performing additional control on the basis of the result of the measurement, thereby preventing the shake of the cleaning blade or chipping of edges. <P>SOLUTION: The image forming apparatus includes: a measuring means 102 for measuring changes in rotation load of the image carrier 5; and a comparison means 100 for comparing changes in rotation load before and after the time when the identical toner images formed at different times at different positions in the main scanning direction reach a cleaning section N. Based on the comparison of load changes of the image carrier when the toner images reach the cleaning section N, control is performed to make the surface of the image carrier uniform. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a transfer type and blade cleaning type image forming apparatus.

  An image forming apparatus such as a transfer type electrophotographic apparatus forms a latent image corresponding to image information on the surface of a rotatable image carrier such as a photoconductive photosensitive member, and the latent image is converted into a toner image (developer image). ), And after being transferred to a recording medium such as paper, it is fixed and output as an image formed product. The image carrier after the transfer is used for image formation repeatedly by removing residues such as transfer residual toner and paper powder adhering to the surface by a cleaning means.

  As a cleaning means for the image carrier, a blade cleaning system is widely used in which an elastic blade (cleaning blade) is used as a cleaning member and this blade is brought into contact with the rotation direction of the image carrier in the counter direction. The surface of the image carrier after the transfer of the toner image to the recording medium is wiped off at the edge of the blade by the subsequent rotation of the image carrier, and the drum surface residue is scraped off.

  Incidentally, in recent years, there is an increasing need for high image quality and high durability in electrophotographic image forming apparatuses such as printers and copiers. In order to achieve this, a spherical toner having a small particle diameter such as a polymerized toner and a photoreceptor having a protective layer with a small amount of surface scraping are often used as an image carrier.

  In such an image forming apparatus, for example, there is a tendency that the cleaning range of the residual toner after transfer, the set range of cleaning that is stable with respect to blade chattering, turning, and the like is small.

  The surface of an image carrier such as a photoreceptor is denatured due to durability, so that the dynamic torque generated between the blade and the image carrier changes.

  Factors that cause the dynamic torque to fluctuate include adhesion of ionized products (also referred to as discharge products) to the surface of the image carrier due to application of a high voltage in the charging process or the transfer process. In addition, when the amount of toner to be developed, polishing of the surface of the image carrier with external additives in the toner, unevenness of the surface of the image carrier, and a metal soap such as zinc stearate are applied, the film formation state Etc.

  In particular, when the amount of toner remaining after transfer varies depending on the position of the image carrier in the image pattern or the like of the print image, the surface property of the image carrier tends to vary.

  Here, a direction orthogonal to the rotation direction (plane movement direction) of the image carrier is defined as a main scanning direction. The cleaning blade is in contact with the image carrier along the main scanning direction. In the image forming apparatus as described above, when the dynamic torque varies greatly in the main scanning direction of the image carrier, the contact balance between the cleaning blade and the image carrier is lost, and the chatter of the cleaning blade or the worst case blade Some edges were missing.

  To solve such a problem, a belt-like toner image (toner belt) is formed on the surface of the image carrier along the main scanning direction, and is sent to the cleaning unit without transferring, thereby improving the slipping property of the cleaning blade. A method has been proposed.

  Patent Document 1 proposes an image forming apparatus that prevents the cleaning blade from turning over by changing the image forming frequency of the toner band according to the use history of the cleaning blade and the image carrier.

Patent Document 2 also proposes a method of inputting a toner band when the image area ratio is not more than a predetermined value.
JP-A-2005-250215 JP 2006-139111 A

  In these proposals, the slipperiness of the cleaning blade can be maintained, but the surface property variation in the main scanning direction of the image carrier cannot be measured. For this reason, in order to suppress chatter and edge chipping of the cleaning blade due to a difference in local slipperiness, it is necessary to frequently perform a control mode for that purpose over a long period of time.

  The present invention is a development of the above prior art. That is, an object of the present invention is to make it possible to accurately measure the surface unevenness in the main scanning direction of the surface of the image carrier that causes chattering and chipping of the cleaning blade with a small amount of toner. In addition, based on the measurement results, additional control is performed to eliminate surface irregularities in the main scanning direction on the surface of the image carrier, thereby reducing toner consumption and improving and maintaining the slipperiness of the cleaning blade. An object of the present invention is to provide an image forming apparatus that makes it possible.

A typical configuration of the image forming apparatus according to the present invention for achieving the above object is as follows:
A rotatable image carrier on which a toner image is formed, an image forming unit that forms a toner image on the image carrier, a transfer unit that transfers the toner image to a recording medium, and a rotation direction of the image carrier A cleaning blade that is disposed in a counter direction and abuts the image carrier in a predetermined area to form a nip portion and removes residues from the transferred image carrier.
A toner image for measuring the rotational load of the image carrier is formed by the image forming means at different positions in the main scanning direction orthogonal to the rotation direction of the image carrier, and this is recorded by the transfer means. It has a rotational load change measurement mode in which the rotational load of the image carrier before and after the toner image arrives at the nip portion without being transferred to the medium and the toner image reaches the nip portion is measured.

Another typical configuration of the image forming apparatus according to the present invention for achieving the above object is as follows:
A rotatable image carrier on which a toner image is formed, an image forming unit that forms a toner image on the image carrier, a transfer unit that transfers the toner image to a recording medium, and a rotation direction of the image carrier A cleaning blade that is disposed in a counter direction and forms a nip portion that contacts the image carrier in a predetermined area, and removes residues from the image carrier after transfer.
A toner image for measuring the rotational load of the image carrier is formed by the image forming means at different positions in the main scanning direction orthogonal to the rotation direction of the image carrier, and this is recorded by the transfer means. Rotational load change measurement mode in which the rotation load of the image carrier before and after the toner image arrives at the nip portion is measured by the measuring means without transferring to the medium, and the fluctuation width of the rotational load is compared. When,
In the rotational load change measurement mode, when the fluctuation width of the rotational load in the main scanning direction of the image carrier has a difference of a predetermined threshold value or more, the image forming means is located at a position where the fluctuation width of the image carrier is large. A rotational load fluctuation width difference elimination mode in which a toner image for eliminating the difference in fluctuation width is formed and sent to the nip portion without being transferred to a recording medium by the transfer unit;
It is characterized by having.

  According to the present invention, surface unevenness in the main scanning direction of an image carrier can be accurately measured with a small amount of toner.

  In addition, by forming a toner image for eliminating the non-slip portion only when the surface irregularity is detected, the chatter of the cleaning blade due to the difference in local slip property with a small amount of toner can be reduced. Edge chipping can be prevented.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[Example 1]
(1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an image forming apparatus of this embodiment. This image forming apparatus is a transfer type / blade cleaning type electrophotographic digital copying machine.

  Reference numeral 1 denotes an original platen glass. An original O is placed on the glass with the image surface facing downward according to a predetermined placement reference, and an original holding plate 2 is placed thereon. When a copy start key of an operation unit (not shown) is pressed, the moving optical system 3 operates to optically scan (scan) the document surface. As a result, image information on the document surface is photoelectrically read as an electrical image signal by the image sensor (CCD) 4 and input to the image processing function unit 100a of the controller 100 (control circuit unit: CPU). The controller 100 is a control unit that comprehensively controls the image forming operation of the image forming apparatus in accordance with a predetermined control program and a reference table. An original document feeder (ADF, RDF) may be installed on the document table glass 1 to automatically feed the document O onto the document table glass 1.

  Reference numeral 5 denotes a drum-type electrophotographic photosensitive member (hereinafter referred to as a drum) as a rotatable image bearing member for forming a toner image, and an arrow through a power transmission means (not shown) by a motor M1 as a driving means. Are rotated at a predetermined process speed (rotational speed) in the clockwise direction.

  The surface of the rotating drum 5 is uniformly charged to a predetermined polarity and potential by a primary charger 6 as a charging means. In this embodiment, the primary charger 6 is a contact type charging roller that rotates following the rotation of the drum 5. A predetermined primary charging bias is applied to the charging roller 6 from a charging bias application power source S1. In this embodiment, the charging bias is a superimposed bias of an AC bias and a DC bias.

  Image exposure L is performed on the charging surface of the drum 5 by a laser scanner 7 as image exposure means. The laser scanner 7 scans and exposes the drum surface by outputting laser light modulated in accordance with the image forming signal generated by the image processing function unit 100a of the controller 100. A direction (drum bus direction, drum longitudinal direction) orthogonal to the rotation direction of the drum 5 (drum surface movement direction) is the main scanning direction X, and the rotation direction of the drum 5 is the sub-scanning direction Y. By this scanning exposure, an electrostatic latent image (latent image pattern) corresponding to the document image photoelectrically read as described above is formed on the drum surface. There are a background exposure method and an image exposure method as an electrostatic latent image forming method. The background exposure method is a method in which an electrostatic latent image is formed by exposing a charged drum surface corresponding to a background portion (background portion) of image information. The image exposure method is a method of forming an electrostatic latent image by exposing a charged drum surface corresponding to an image portion (image information portion) of image information.

  The electrostatic latent image is developed as a toner image by a developing device 8 as developing means. Reference numeral 8a denotes a developing roller (developing sleeve) as a developer carrying member which carries toner (developer) and is applied to the drum 5, and is driven at a predetermined speed in a counterclockwise direction indicated by an arrow by a driving means (motor: not shown). Driven by rotation. A predetermined developing bias is applied from the developing bias applying power source S2. When the electrostatic latent image forming method is a background exposure method, a normal development method that develops a portion other than the background portion is used, and when the image exposure method is used, a reversal development method that develops an unexposed portion is used. .

  The charging roller 6 (charging means), laser scanner 7 (image exposure means), and developing device 8 (developing means) are image forming means for forming a toner image on the drum 5 as an image carrier.

  A toner image formed on the drum 5 is used as a recording medium fed from the paper feeding unit to the transfer unit T in the transfer unit T which is a facing part between the drum 5 and the transfer charger 9 as a transfer unit. The recording material (transfer material) P is transferred. In this embodiment, the transfer charger 9 is a contact type transfer roller brought into contact with the drum 5, and a nip portion between the drum 5 and the transfer roller 9 is a transfer portion T. A charging bias having a predetermined potential opposite to the charging polarity of the toner is applied to the transfer roller 9 from a transfer bias applying power source S3. As a result, the toner image on the drum surface is sequentially electrostatically transferred onto the surface of the recording material P that is nipped and conveyed by the transfer portion T.

  The recording material P is stacked and stored in a paper feeding cassette 10 as a paper feeding unit, and is separated and fed by a paper feeding roller 11 driven at a predetermined control timing, and passes through a recording material conveyance path 12. It reaches the registration roller 13. Then, the recording material P is synchronized with the toner image on the drum 5 by the registration roller 13, and is sent to the transfer unit T through the recording material conveyance path 14.

  The recording material P that has passed through the transfer portion T is introduced into an image heating fixing device 17 as an image fixing means through a recording material conveyance path 16, and is a fixing nip portion that is a pressure contact portion between the fixing roller 17a and the pressure roller 17b. It is nipped and conveyed. As a result, the unfixed toner image on the recording material is fixed on the recording material surface as a fixed image by heat and pressure. Then, the recording material exits the fixing device 17 and is discharged to a discharge tray 19 by a discharge roller 18.

  The drum surface after separation of the recording material is cleaned by removing the drum surface residue such as transfer residual toner and paper dust by a cleaning device 20 as a residue removing unit, and is repeatedly used for image formation. In this embodiment, the cleaning device 20 is a blade cleaning device using a cleaning blade 21 as a cleaning member for cleaning the surface of the drum 5 as a member to be cleaned.

  The cleaning blade 21 is an elastic blade made of an elastic material such as urethane rubber. 2A, the edge portion of the blade end surface is disposed in the counter direction with respect to the rotation direction of the drum 5 along the main scanning direction X with respect to the drum 5 so as to be predetermined with the drum 5. A nip portion (cleaning portion) N that is in contact with the region is formed. The drum surface after separation of the recording material is wiped off at the edge portion of the blade 21 by the subsequent rotation, and residues such as transfer residual toner are scraped off from the drum surface. The drum surface residue scraped off falls to the bottom of the cleaning container 22 and is discharged from the cleaning container 22 to an external recovery toner container (not shown) by the discharge screw shaft 23.

  Reference numeral 101 denotes a driver of a motor M 1 that is a driving unit of the drum 5 and is controlled by the controller 100. Reference numeral 102 denotes, for example, a torque converter type torque measuring instrument or a torque measuring instrument based on the driving current value of the motor M1 as measuring means for measuring the rotational load (dynamic torque) of the drum 5.

(2) Operation Sequence of Image Forming Apparatus FIG. 3 shows a timing chart for executing the normal printing operation of the image forming apparatus and the rotational load change measurement mode of the drum 5. FIG. 4 shows a timing chart in the case of executing the rotational load fluctuation range difference elimination mode following the rotational load change measurement mode.

  1) is a standby state in which the image forming apparatus is waiting for a print operation instruction. In this standby mode, the controller 100 turns off the motor M1 to stop (OFF) the rotation of the drum 5. In addition, the application of a bias to each of the charging roller 6 (charging), the developing roller 8a (developing), and the transfer roller 9 (transfer) is also turned off. The laser scanner 7 (exposure) is also turned off.

  2) is the time when the drum 5 is rotated forward. In response to the print operation instruction S in the standby state, the controller 100 starts the motor M1 and idles the drum 5 for a predetermined time. In addition, application of a charging bias to the charging roller 6 is started (ON).

  3) is when image formation is executed. When the controller 100 performs the pre-rotation for a predetermined time, the bias application to each of the developing roller 8a and the transfer roller 9 is turned on, and the laser scanner 7 is turned on to form a toner image on the drum 5 and to the recording material P. The toner image is transferred. The transfer bias for the transfer roller 9 at the time of image formation is a bias having a polarity opposite to the charging polarity of the toner image. In FIG. 3 and FIG. 4, it is represented by (+) for convenience. The recording material P that has received the transfer of the toner image is subjected to an image fixing process by the fixing device 17 and is discharged to the paper discharge tray 19.

  Image formation is executed for the set number of prints. K is the time when the last recording material in the set one recording material (in the case of mono print) or a plurality of continuous prints (in the case of multi print) is discharged out of the apparatus.

  4) is when the rotational load change measurement mode of the drum 5 is executed. The controller 100 continues to rotationally drive the drum 1 even after the set recording material or the last recording material in a plurality of continuous prints is discharged out of the apparatus, and executes the rotational load change measurement mode. This rotational load change measurement mode will be described in detail in section (3).

  5) is the time when the drum 5 is rotated backward. As a result of executing the rotational load change measurement mode, the controller 100 turns off the bias application to the charging roller 6 when it is determined that there is no more than a predetermined difference in the fluctuation range of the rotational load in the main scanning direction X of the drum 5. Then, the drum 5 is idled for a predetermined time and then stopped (OFF).

  Then, the image forming apparatus enters the standby state 6) until the next print operation instruction S is input.

  If the controller 100 determines that there is a difference greater than or equal to the fluctuation range of the rotational load in the main scanning direction X of the drum 5 as a result of executing the rotational load change measurement mode of 4), the controller 100 continues as shown in FIG. 7) The rotational load fluctuation range difference elimination mode is executed. This rotational load fluctuation range difference elimination mode will be described in detail in section (4).

  Then, after executing the rotation load fluctuation range difference elimination mode, the controller 100 executes 5) post-rotation, and maintains the image forming apparatus in the standby state of 6) until the next print operation instruction is input. .

(3) Rotation load change measurement mode In the rotation load change measurement mode 4), the rotation load of the drum 5 is measured by the image forming means 6, 7, 8 at different positions in the main scanning direction X of the drum 5. Forming a toner image having the same pattern. Further, the toner image is fed into the nip N between the drum 5 and the cleaning blade 21 without being transferred to the recording material P by the transfer means 9. The measuring means 102 measures the rotational load of the drum 5 before and after the toner image reaches the nip portion N, and compares the fluctuation width of the rotational load.

  In this embodiment, after the completion of the image formation in 3), after the drum idle rotation for several seconds in the time region a, the first toner image t1 for measuring the rotational load of the drum 5 is formed in the time region b. Exposure and development are performed. A bias having the same polarity as the charging polarity of the toner image t1 is applied to the transfer roller 9. In FIG. 3 and FIG. 4, it represents with (-) for convenience. As a result, most of the toner image t1 passes through the transfer portion T and is fed into the nip portion N between the drum 5 and the cleaning blade 21. In the time region c, the rotational load of the drum 5 before and after the toner image t1 reaches the nip portion N is measured by the measuring unit 102 and input to the controller 100. The controller 100 calculates a fluctuation width D1 of the rotational load of the drum 5 before and after the toner image t1 reaches the nip portion N based on the rotational load measurement information input from the measuring unit 102.

  Similarly, a second toner image t2 for measuring the rotational load of the drum 5 is formed in a portion different from the previous time in the main scanning direction X of the drum 5 in the time domain e after several seconds of drum idle rotation in the time domain d. Exposure / development is performed. A bias having the same polarity as the charging polarity of the toner image t2 is continuously applied to the transfer roller 9, and the toner image t2 passes through the transfer portion T without substantially adhering to the transfer roller 9, and the drum 5 And the cleaning blade 21 are fed into the nip portion N. Then, in the time region f, the rotational load of the drum 5 before and after the toner image t <b> 2 reaches the nip portion N is measured by the measuring unit 102 and input to the controller 100. The controller 100 calculates a fluctuation range D2 of the rotational load of the drum 5 before and after the toner image t2 reaches the nip portion N based on the rotational load measurement information input from the measuring unit 102.

  The controller 100 compares the fluctuation range D1 of the drum rotation load due to the first toner image t1 with the fluctuation range D2 of the drum rotation load due to the second toner image t2 by the comparison function unit 100b as a comparison unit. The difference of fluctuation range is calculated.

  Here, the difference between the fluctuation width D1 and the fluctuation width D2 is a division value (quotient: ratio of fluctuation width values) in which the smaller fluctuation width value is the denominator and the larger fluctuation width value is the numerator.

  Then, the controller 100 compares the difference in the fluctuation range with a predetermined threshold value, and if the difference in the fluctuation range is equal to or larger than the predetermined threshold value, the controller 5 causes the surface unevenness to be eliminated in the main scanning direction. Is determined to have occurred. When the difference in the fluctuation range is smaller than the predetermined threshold value, it is determined that the surface unevenness that should be eliminated in the main scanning direction X does not occur on the drum 5. The threshold value is preferably set to a value of 1.1 times or more. In this embodiment, the threshold value is set to 1.2 times. When the difference between the fluctuation ranges is equal to or greater than the threshold value, the controller 100 executes the rotational load fluctuation range difference elimination mode of 7) as shown in FIG. When the difference in fluctuation range is smaller than the above threshold, the rotational load fluctuation range difference elimination mode is not executed.

  In this embodiment, the first toner image t1 is the drum surface of the one side area A1 when the maximum development width A is divided into two in the main scanning direction X of the drum 5, as shown in FIG. Formed in part. The toner image is a toner band t1 having a predetermined main scanning direction width i and sub-scanning direction width j.

  Further, as shown in FIG. 5B, the second toner image t <b> 2 is formed on the drum surface of the other side region A <b> 2 when the maximum development width A is divided into two in the main scanning direction of the drum 5. The toner image has the same pattern as the first toner image t1, and is a toner band t2 having a predetermined main scanning direction width i and sub-scanning direction width j.

  The patterns of the first toner image t1 and the first toner image t2 are stored in the controller 100 in advance, and the controller 100 controls the image forming means 6, 7 and 8 to store the toner bands t1 and. t2 is formed.

  FIG. 6 shows the transition of the rotational load (dynamic torque) of the drum 5 during the period from 1) to 6) in the timing chart of FIG. The dynamic torque of the drum 5 may be measured by a torque converter type torque measuring device or a change in the drive current value of the motor.

  The toner image comes to the cleaning blade 21 at the time when the image formation is performed in 3) and at the portion b where the first toner image t1 is formed and e where the second toner image t2 is formed in the rotational load change measurement mode of 4). It can be seen that the torsional torque changes.

  Here, the difference (D1 / D2 or D2 / D1) between the dynamic torque fluctuation width D1 of the part a and the part b and the dynamic torque fluctuation width D2 of the part d and the part e is such that the toner reaches the cleaning blade 21. The difference between the front and the back is shown, and the slipperiness of the surface of the drum 5 is indirectly shown.

  The dynamic torque fluctuation range D1 is obtained by subtracting the dynamic torque value of the portion b from the dynamic torque value of the portion a. The dynamic torque fluctuation range D2 is obtained by subtracting the dynamic torque value of the portion e from the dynamic torque value of the portion d.

  Consider a case where there is a difference greater than or equal to a predetermined threshold value between the fluctuation range D1 and the fluctuation range D2, for example, the fluctuation range D1 is larger. In this case, the drum surface (area A1) on the side where the first toner band t1 is formed is more slippery than the drum surface (area A2) on the side where the second toner band t2 is formed. Is judged to be bad.

  According to the study by the present inventor, when the toner on the drum (on the image carrier) is blocked by the cleaning blade 21, the rotational load (dynamic torque) of the drum 5 changes instantaneously. The change in the dynamic torque is different depending on the surface property of the drum 5, the toner density, the image pattern, and the like.

  FIG. 2B shows a case where the slipperiness of the surface of the drum 5 is lowered due to durability. In this case, the change in the dynamic torque when the toner t is blocked by the nip portion (cleaning portion) N between the drum 5 and the cleaning blade 21 becomes large. That is, the fluctuation range D of the rotational load of the drum 5 before and after the toner image reaches the nip portion N increases. This is because the toner t improves the sliding property between the drum 5 and the cleaning blade 21 and reduces the amount of blade edge drawn.

  On the other hand, FIG. 2C shows the case where the surface of the drum 5 has a high slip property. In this case, the slipping property between the drum 5 and the cleaning blade 21 is ensured, and the amount of the cleaning blade 21 drawn is sufficiently small, so that the effect of the toner is small. That is, the fluctuation range D of the rotational load of the drum 5 before and after the toner image reaches the nip portion N is small.

FIG. 7 is a diagram showing the dynamic torque transition of the drum 5 before and after the toner image (toner band) t reaches the nip portion N. When the toner image t reaches the nip portion N in the contact state as shown in FIG. 2A, the dynamic torque changes from the time domain 1 to 2. In this case, the dynamic torque fluctuation range D1.
On the other hand, when the toner image t reaches the nip portion N in the contact state as shown in FIG. 2B, the dynamic torque changes from the time region 4 to 5. The dynamic torque fluctuation range D2 in this case is used. The fluctuation range D1 is larger than the fluctuation range D2.

  By utilizing such a phenomenon, the drum 5 having the state shown in FIGS. 2B and 2C mixed on the surface is created, and the same toner image is placed at different positions in the main scanning direction X of the drum 5. The change in dynamic torque before and after reaching the nip portion N was confirmed. As a result, the difference in dynamic torque change (dynamic torque fluctuation range) as shown in FIG. 6 was confirmed.

  The rotational load change measurement mode may be performed at the end of mono-printing or multi-printing (the end of printing each time) or may be performed as follows. That is, a print number counter may be provided, and the print number counter may be reset after the measurement mode is executed when the number of prints exceeds a predetermined count. The measurement interval (2 minutes) of Comparative Experiment 1 to be described later is executed about once every 60 sheets when converted by productivity in the copying machine main body.

(4) Rotation load fluctuation range difference elimination mode In the rotation load change measurement mode of 4), the controller 100 displays a difference when the fluctuation range of the rotation load in the main scanning direction of the drum 5 exceeds a predetermined threshold value. As in 4, following the rotational load change measurement mode, the rotational load fluctuation range difference elimination mode 7) is executed.

  In this rotational load fluctuation width difference elimination mode, a toner image ta for eliminating the difference in fluctuation width is formed by the image forming means 6, 7, 8 at the position where the fluctuation width is large on the drum 5, and this is applied to the transfer roller. 9 is sent to the nip N without being transferred to the recording material P.

  Specifically, in FIG. 4, after the completion of the mode 4), after the drum idle rotation for several seconds in the time domain g, the difference in the fluctuation width is eliminated at the position where the fluctuation width of the drum 5 is large in the time domain h. Exposure / development is performed to form a toner image ta. A bias having the same polarity as the charging polarity of the toner image ta is continuously applied to the transfer roller 9, and the toner image ta passes through the transfer portion T without substantially adhering to the transfer roller 9, and the drum 5 And the cleaning blade 21 are fed into the nip portion N.

  FIG. 5 (c) shows that when the rotational load change measurement mode determines that the slipperiness of the area A1 of the drum 5 is poor, the fluctuation width of the fluctuation range is displayed in the area A1 of the drum 5 by the rotational load fluctuation width difference elimination mode. A state in which a toner image ta for eliminating the difference is formed is shown. The pattern of the toner image ta is previously stored in the controller 100, and the controller 100 controls the image forming units 6, 7, and 8 to form the toner band ta according to the stored pattern in the area A 1 of the drum 5. The toner image is a toner band ta having a predetermined main scanning direction width i and sub-scanning direction width k. When it is determined in the rotational load change measurement mode that the slipperiness of the area A2 of the drum 5 is poor, a toner image ta for eliminating the difference in the fluctuation range is formed in the area A2.

  That is, the controller 100 compares the difference in dynamic torque fluctuation width with a predetermined threshold value in the rotational load change measurement mode, and only when the difference in fluctuation width is equal to or greater than the threshold value (when the difference in dynamic torque is confirmed). A control mode for eliminating the slippage is put in the low-slip area of the drum 5. Alternatively, the frequency of the control mode can be increased. As a result, it is possible to surely eliminate the unevenness of the surface property of the drum 5 in the scanning direction X, reduce the number of times that the control mode is required, and reduce the toner band used to maintain the slipperiness.

  This can be improved by further applying a toner band ta to the drum surface side that is determined to be poorly slidable. If the amount of toner in the toner band ta is small, a sufficient effect cannot be obtained, and if it is too large, a cleaning failure may occur. The improvement of the slipperiness due to the application of the toner band takes relatively longer than the measurement time because the polishing effect by the abrasive is proportional to the contact time between the external additive staying in the cleaning blade and the surface of the image carrier. The effect of improving the slip property can be confirmed by the next toner image for surface measurement.

Regarding the toner amount Wmg / cm ^{2 of} the toner image ta formed on the drum 5 in order to eliminate the difference in the fluctuation range, according to the study of the present inventors, 0.1 mg / cm ² ≦ W ≦ 0.7 mg / cm A range of ² is good.

(5) Comparative experiment with the conventional example The comparative experiment with the conventional example was performed under the following conditions.

・ Experimental machine: IRC 3380 drum empty rotating machine ・ Process speed: 140mm / sec
・ Primary charging AC bias: 1600Vpp
・ Primary charging DC bias: -500V
-Cleaning blade linear pressure: 35 gf / cm
・ Main scanning development width A: 320 mm
Toner image t1 and t2 for dynamic torque fluctuation measurement: W = 0.3 mg / cm ² , main scanning direction width i = 160 mm, sub-scanning direction width j = 5 mm
Cancel toner image ta: W = 0.3 mg / cm ² , main scanning direction width j =: 160 mm, sub-scanning direction width k = 15 mm
-Idle rotation time: 6 hours Table 1 shows the results of experiments conducted in this example.

  Experiment 1 is the result of putting in the measurement and toner band control (rotational load change measurement mode and rotational load fluctuation range difference elimination mode) in this embodiment. As shown in FIG. 5, the surface of the drum 5 was divided into two locations A1 and A2 in the main scanning direction and the measurement toners t1 and t2 were supplied once every two minutes as shown in FIG. The determination of the supply of the toner band for elimination ta is performed when the difference (D1 / D2 or D2 / D1) between the dynamic torque fluctuation ranges D1 and D2 between the drum areas A1 and A2 is 1.2 times or more as a threshold value. The drum area was increased once in one minute. As a result, no blade chattering or chipping of the edge was observed even during idling for about 6 hours.

  In Experiment 2, when a toner band for elimination was supplied every 5 minutes of idling, which was conventionally performed, blade edge chipping occurred after idling for 6 hours.

  In Experiment 3, the number of toner bands for elimination is supplied once every two minutes for idling. In this case as well, blade chipping occurred.

  In Experiment 4, the number of toner bands for elimination is supplied once per idle rotation for 1 minute. As a result, there was no chipping of the blade edge, but the toner consumption increased extremely.

  From the above results, in Experiment 1 according to the present invention, the difference in dynamic torque can be measured with a small amount of toner, and chattering and edge chipping of the cleaning blade 21 can be prevented. Further, it is possible to reduce the frequency while reducing the amount of toner consumed by supplying the toner to the cleaning unit N.

(6) Others 1) In the embodiment, in order to supply the toner bands t1, t2, and ta to the cleaning unit N at a high ratio in the rotational load change measurement mode and the rotational load fluctuation difference elimination mode, the toner is supplied to the transfer roller 9. A bias (-) having the same polarity as the charged polarity of the image is applied. However, the present invention is not limited to this, and in order to supply the toner to the cleaning unit N at a high ratio, the transfer high pressure may be turned off or may be temporarily floated. Further, the transfer roller 9 can be separated from the drum 5.

  2) In the rotational load change measurement mode, when forming toner images t1 and t2 for measuring the rotational load of the drum 5 by shifting the time to different positions in the main scanning direction of the drum 5, the time interval is one drum rotation. It is possible to measure with higher accuracy by making more space. That is, the time interval Δt for forming toner images t1 and t2 of the same pattern for measuring the rotational load of the drum 5 by the image forming means 6, 7 and 8 at different positions in the main scanning direction of the drum 5 is “Δt ≧ It is preferable that “the circumference of the image carrier / the travel distance per second of the image carrier”.

  3) The division of the drum 5 in the main scanning direction is two or more, preferably four or more. FIG. 8 shows a case where the toner images t1, t2, t3, and t4 are divided into four locations A1 to A4 and the time is shifted with respect to each of the regions A1 to A4 to measure the rotational load of the drum 5. ing. The calculation of the difference in the fluctuation range between the areas A1 to A4 is performed on the basis of the smallest fluctuation range value. Then, the rotational load fluctuation range difference elimination mode is executed for an area in which the difference in the dynamic torque fluctuation range is equal to or greater than a predetermined threshold in the areas A1 to A4.

  4) The image carrier is not limited to an electrophotographic photosensitive member. It may be an electrostatic recording dielectric or a magnetic recording magnetic material. Further, an intermediate transfer member may be used. The image carrier is not limited to the rotating drum type. It may be a rotating belt type.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. It is explanatory drawing of cleaning. FIG. 3 is an operation sequence diagram (No. 1) of the image forming apparatus. FIG. 6 is an operation sequence diagram (part 2) of the image forming apparatus. FIG. 6 is an explanatory diagram of toner image formation for measuring the rotational load of a drum and toner image formation for eliminating a difference in fluctuation range. FIG. 4 is a diagram showing a change in dynamic torque of the drum during the operation sequence of the image forming apparatus in FIG. 3. It is explanatory drawing of the slip property of a drum surface, and the change of dynamic torque. It is explanatory drawing of the other execution form of rotation load change measurement mode.

Explanation of symbols

  5 ·· Image carrier, 6 · 7 · 8 · · Image forming means, P · · Recording medium, 9 · · Transfer means, 21 · · Cleaning blade (21), t1 · t2 · · Rotational load of image carrier Toner image for measuring N, .. nip part (cleaning part), 102 .. rotational load measuring means, ta .. toner image for eliminating difference in fluctuation range

Claims (5)

A rotatable image carrier on which a toner image is formed, an image forming unit that forms a toner image on the image carrier, a transfer unit that transfers the toner image to a recording medium, and a rotation direction of the image carrier A cleaning blade that is disposed in a counter direction and abuts the image carrier in a predetermined area to form a nip portion and removes residues from the transferred image carrier.
A toner image for measuring the rotational load of the image carrier is formed by the image forming means at different positions in the main scanning direction orthogonal to the rotation direction of the image carrier, and this is recorded by the transfer means. An image forming method characterized by having a rotational load change measurement mode in which the measurement means measures the rotational load of the image carrier before and after the toner image arrives at the nip without being transferred to the medium. apparatus. A rotatable image carrier on which a toner image is formed, an image forming unit that forms a toner image on the image carrier, a transfer unit that transfers the toner image to a recording medium, and a rotation direction of the image carrier A cleaning blade that is disposed in a counter direction and forms a nip portion that contacts the image carrier in a predetermined area, and removes residues from the image carrier after transfer.
A toner image for measuring the rotational load of the image carrier is formed by the image forming means at different positions in the main scanning direction orthogonal to the rotation direction of the image carrier, and this is recorded by the transfer means. Rotational load change measurement mode in which the rotation load of the image carrier before and after the toner image arrives at the nip portion is measured by the measuring means without transferring to the medium, and the fluctuation width of the rotational load is compared. When,
In the rotational load change measurement mode, when the fluctuation width of the rotational load in the main scanning direction of the image carrier has a difference of a predetermined threshold value or more, the image forming means is located at a position where the fluctuation width of the image carrier is large. A rotational load fluctuation width difference elimination mode in which a toner image for eliminating the difference in fluctuation width is formed and sent to the nip portion without being transferred to a recording medium by the transfer unit;
An image forming apparatus comprising:   The image forming apparatus according to claim 2, wherein when the difference is 1.1 times or more, the rotational load fluctuation range difference elimination mode is executed. A time interval Δt for forming a toner image of the same pattern for measuring the rotational load of the image carrier by the image forming means at different positions in the main scanning direction of the image carrier,
The image forming apparatus according to claim 1, wherein Δt ≧ circumference of the image carrier / travel distance per unit second of the image carrier. In order to eliminate the difference in the fluctuation range, the toner amount W of the toner image formed on the image carrier is
0.1 mg / cm ² ≦ W ≦ 0.7 mg / cm ²
The image forming apparatus according to claim 2, wherein the image forming apparatus is an image forming apparatus.