JP2006126603A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To securely prevent abnormal sound emitted from a cleaning blade even in case where a low printing rate continues in an image forming apparatus. <P>SOLUTION: Color developing units form toner images by developing electrostatic latent images on respective photoreceptor drums 11a to 11d. The toner images on the photoreceptor drums are transferred to an intermediate transfer belt 13 in order. The toner images on the intermediate transfer belt are transferred to recording paper and thus an image is formed. Cleaning blades 18a to 18d come into contact with the corresponding photoreceptor drums to clean off residual toners on the photoreceptor drum. An amount of toner consumption is detected for each developing unit. While image formation is not carried out, a toner image is formed, according to an amount of toner consumption of each developing unit, onto at least the photoreceptor drum corresponding to the developing unit whose toner consumption is the largest in amount. Part of the toner image is transferred to the intermediate transfer belt as a transfer toner image, and the toner image transferred is reversely transferred to the remaining image carriers from the intermediate transfer member. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus using an electrophotographic process such as a copying machine, a printer, or a facsimile machine, and more particularly from a cleaning member used when residual toner remaining on an image carrier such as a photosensitive drum is removed. The present invention relates to an image forming apparatus capable of reducing abnormal vibration sound that occurs.

  In general, in an image forming apparatus such as a copying machine, a cleaning member such as a cleaning blade is brought into contact with an image carrier such as a photosensitive drum, and residual toner remaining on the photosensitive drum after the transfer process is cleaned by the cleaning blade. ing.

  Although the cleaning blade is in contact with the photosensitive drum, the toner interposed between the cleaning blade and the photosensitive drum acts as a lubricant to reduce friction between the cleaning blade and the photosensitive drum. When the printing rate is low, the amount of toner interposed between the cleaning blade and the photosensitive drum becomes extremely small, and the lubricating action by the toner becomes extremely low, and the friction between the cleaning blade and the photosensitive drum increases. As a result, the amplitude of the minute vibration (stick slip motion) of the cleaning blade increases and abnormal noise is generated.

  In order to prevent such abnormal noise, a predetermined pattern of toner is adhered to the photosensitive drum in advance, and the photosensitive drum is cleaned with a cleaning blade, and toner interposed between the photosensitive drum and the cleaning blade is removed. In many cases, the vibration of the cleaning blade is suppressed.

  For example, the vibration of the cleaning blade is detected, the amplitude of the detected vibration is compared with a predetermined amplitude, and when the amplitude of the detected vibration exceeds a predetermined amplitude, a specific pattern is exposed on the photosensitive drum. In some cases, a toner pattern corresponding to a specific pattern is formed on a photosensitive drum to increase the toner interposed between the photosensitive drum and a cleaning blade (see Patent Document 1).

Japanese Patent No. 3126609

  By the way, most of the lubricating action by the toner is due to the external additive adhering to the toner surface. However, if the printing with a low printing rate is continuous, that is, if the toner consumption is extremely small, the toner is not contained in the developing device. When the mixture is stirred for a long time and stirred for a long time, the external additive is embedded in the toner and the lubricating action is lowered. Even if such a toner with reduced lubrication is supplied onto the photosensitive drum, it is difficult to reduce the friction between the photosensitive drum and the cleaning blade, resulting in increased vibration of the cleaning blade. An abnormal noise occurs.

  In the conventional image forming apparatus, the vibration of the cleaning blade is detected and the toner is supplied onto the photosensitive drum according to the detection result. However, when the low printing rate is continuous, the toner lubrication action is performed. Therefore, there is a problem that it is difficult to reduce the friction between the photosensitive drum and the cleaning blade, and abnormal noise is generated due to an increase in the amplitude of vibration of the cleaning blade.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of reliably preventing abnormal noise generated from a cleaning blade even in a state where a low printing rate is continuous.

  Therefore, in order to solve the problem, the present invention provides a plurality of image carriers, and a developer provided for each image carrier to develop an electrostatic latent image on the image carrier into a toner image, An intermediate transfer member to which toner images on the image carrier are sequentially transferred; and a cleaning blade for cleaning residual toner remaining on the image carrier in contact with the image carrier. In an image forming apparatus for forming an image by transferring the upper toner image onto a recording sheet, a toner consumption amount detecting means for detecting a toner consumption amount for each of the developing devices, and the developing device in a state where no image is formed. A toner image is formed on an image carrier corresponding to a developing unit having the largest amount of toner consumption according to the amount of toner consumed for each toner, and a part of the toner image is transferred to the intermediate transfer member as a transfer toner image. The intermediate toner image is transferred to the intermediate It is characterized in that a control means for performing control mode for reverse transcription to the rest of the image bearing member from Utsushitai.

  In the present invention, the toner consumption detecting means detects the toner consumption according to the printing rate of each developing device, and the control means, for example, from the image carrier to the intermediate transfer member. A first bias power source for transferring a toner image, a second bias power source for reversely transferring a toner image from the intermediate transfer member to the image carrier, and a switching control for switching the first and second bias power sources. Means.

  In the present invention, the control unit includes an intermediate transfer member cleaning member that is detachably disposed on the intermediate transfer member and cleans residual toner remaining on the intermediate transfer member when the intermediate transfer member contacts the intermediate transfer member. The intermediate transfer member cleaning member is moved to the intermediate transfer member during the control mode, except when the toner consumption of the developing unit corresponding to the image carrier located on the most upstream side in the rotation direction of the intermediate transfer member is the largest. Separated from the transfer body. The control unit enters the control mode when a predetermined time elapses after the start of image formation.

  As described above, the image forming apparatus according to the present invention forms a toner image on an image carrier corresponding to at least the developing device with the largest toner consumption according to the toner consumption for each developing device, and this toner image. Part of the toner was transferred to the intermediate transfer member as a transfer toner image, and the transferred toner image was reversely transferred from the intermediate transfer member to the remaining image carrier, so that the external additive was embedded in the toner. As a result, the toner is not supplied to each image carrier, so that the lubricating action of the toner does not decrease. As a result, the friction between the cleaning member and the image carrier does not increase, and the toner is caused by the vibration of the cleaning member. There is an effect that no abnormal sound is generated.

  In the present invention, the intermediate transfer member cleaning member is separated from the intermediate transfer member except when the toner consumption of the developing device corresponding to the image carrier positioned on the most upstream side in the rotation direction of the intermediate transfer member is the largest. Therefore, there is an effect that the transferred toner image can be reliably reversely transferred to the remaining image carrier.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

  First, referring to FIG. 1, FIG. 1 is a diagram schematically illustrating an example of a color image forming apparatus. The illustrated image forming apparatus includes a plurality of image forming units 10 a to 10 d and forms an image. The units 10a to 10d are provided with photosensitive drums 11a to 11d of respective colors (for example, yellow (Y), magenta (M), cyan (C), and black (BK)). Each color developing device is arranged in association with each of the photosensitive drums 11a to 11d (only the developing device 12b is shown in FIG. 1).

  The photosensitive drums 11a to 11d are arranged along an intermediate transfer belt 13 as an intermediate transfer member, and primary transfer rollers 14a to 14d are in contact with the photosensitive drums 11a to 11d with the intermediate transfer belt 13 interposed therebetween. . The intermediate transfer belt 13 is stretched around a belt driving roller 13a and a driven roller 13b, and the intermediate transfer belt 13 is rotationally driven in the direction indicated by the thick line arrow in the drawing by the rotational driving of the belt driving roller 13a.

  First bias power supplies (forward bias power supplies) 16a to 16d and second bias power supplies (reverse bias power supplies) 17a to 17d are connected to the primary transfer rollers 14a to 14b via switches 15a to 15d, respectively. Further, cleaning blades 18a to 18d as cleaning members are disposed in contact with the photosensitive drums 11a to 11d, and residual toners remaining on the photosensitive drums 11a to 11d are removed by the cleaning blades 18a to 18d, respectively. .

  Further, a belt cleaning blade 19 is disposed at the position of the driven roller 13b so as to be detachable from the intermediate transfer belt 13, and residual toner remaining on the intermediate transfer belt 13 is removed by the belt cleaning blade 19. Although not illustrated, the image forming units 10a to 10d are provided with a charger, an exposure device, and the like, and a secondary transfer roller is in contact with the belt driving roller 13a with the intermediate transfer belt 13 interposed therebetween.

  When image formation is performed, the photosensitive drums 11a to 11d are charged by a charger, and then the photosensitive drums 11a to 11d are exposed with image data (dot data) corresponding to each color, so that the photosensitive drums 11a to 11d are exposed. An electrostatic latent image is formed on 11d. Then, the electrostatic latent images on the photosensitive drums 11a to 11d are developed by a developing device to form respective color toner images on the photosensitive drums 11a to 11d. A control device (not shown) controls the switches 15a to 15d, connects the first bias power supplies 16a to 16d to the primary transfer rollers 14a to 14d, respectively, and applies the positive transfer bias to the primary transfer rollers 14a to 14d. . As a result, the color toner images on the photosensitive drums 11 a to 11 d are sequentially transferred (primary transfer) onto the intermediate transfer belt 13, and a color toner image is formed on the intermediate transfer belt 13.

  The recording paper is conveyed from a paper feeding device (not shown) to the nip portion between the secondary transfer roller and the intermediate transfer belt 13, and the color toner image on the intermediate transfer belt 13 is transferred to the recording paper (secondary transfer). It is conveyed to a fixing device (not shown), where the color toner image is fixed on the recording paper, and then discharged onto a paper discharge tray (not shown). On the other hand, residual toner remaining on the photosensitive drums 11a to 11d is removed by the cleaning blades 18a to 18d, and residual toner remaining on the intermediate transfer belt 13 is removed by the belt cleaning blade 19.

  By the way, when the state where the printing rate is low continues, the toner interposed between the cleaning blades 18a to 18d and the photosensitive drums 11a to 11d becomes extremely small, and the lubricating action by the toner becomes extremely low, and the cleaning blades 18a to 18d. 18d and the photosensitive drums 11a to 11d increase in friction, and the vibration amplitude of the cleaning blades 18a to 18d increases to generate abnormal noise. Therefore, here, the following processing was performed to prevent abnormal vibration of the cleaning blades 18a to 18d. It has been confirmed that even if the printing rate continues to be low and the lubricating action by the toner becomes extremely low, the image quality of the formed image is hardly affected.

  Referring to FIGS. 1 and 2, here, the resolution is 600 dpi, the number of printed sheets is 10 sheets / minute with A4 size paper, and the total number of dots that can be printed on one sheet is, for example, 35 million dots / A4. did. When a predetermined printing time (image forming time: development time, for example, a sufficient time) elapses after the start of image formation (step S1), the control device investigates whether or not the image is being formed (step S2). If it is in the middle, the process returns to step S1. If the image formation is completed, the control mode is set and the toner consumption amount in each color developing device is checked by the toner consumption amount detecting means (step S3). For example, the control device calculates the number of print dots after driving for a predetermined time for each color developer based on the image data for each color, and for each color developer according to the number of print dots for each color developer. Calculate the printing rate.

  Since it is 35 million dots / A4 and the number of printed sheets is 10 sheets / minute, 100 sheets are printed in a development time of 10 minutes, and the total number of printable dots is 3.5 billion dots. Since the printing rate (%) = printed dot number ÷ 3.5 billion dots × 100, if the number of print dots of each color developer is 26 million dots, 82 million dots, 15 million dots, and 50 million dots, printing The rates are 0.7%, 2.3%, 0.4%, and 1.4%, respectively, and the total printing rate is 1.2%. The developing device having a higher printing rate has a larger amount of toner consumption, and the control device determines the toner consumption amount from the printing rate of each color developing device.

  Subsequently, the control device determines the photosensitive member for the image forming unit 10b corresponding to the developing device having the highest printing rate (that is, the toner consuming the largest amount) (here, the developing device is the developing device 12b). After exposing the drum 11b, the photosensitive drum 11b is exposed with solid image data, and the electrostatic latent image is developed by the developing device 12b to form a solid toner image A on the photosensitive drum 11b (for example, by the developing device 12b). Development is performed for 4 seconds: Step S4).

  The control device controls the switch 15b to connect the second bias power source 17b and the primary transfer roller 14b, and applies a reverse transfer bias to the primary transfer roller 14b at the timing when the solid toner image reaches the transfer position. (The reverse transfer bias is applied for a time shorter than the development time, for example, 1 second), and the toner image B is supplied to the cleaning blade 18b without transferring the intermediate transfer belt 13 (step S5). Thereafter, the control device controls the switch 15b to connect the first bias power supply 16b and the primary transfer roller 14b, apply a positive transfer bias (for example, for 3 seconds), and transfer the solid toner image to the transfer toner image C. Is transferred to the intermediate transfer belt 13 (step S6).

  Subsequently, the control device controls the switch 15c to connect the second bias power source 17c and the primary transfer roller 14c, and applies the reverse transfer bias to the primary transfer roller at the timing when the transfer toner image C reaches the transfer position. 14c (for example, a reverse transfer bias is applied for 1 second), a part of the transfer toner image C is transferred onto the photosensitive drum 11c as a reverse transfer toner image D, and the reverse transfer toner image D is cleaned with a cleaning blade. 18c side (first reverse transfer: step S7).

  Similarly, the control device controls the switch 15d to connect the second bias power source 17d and the primary transfer roller 14d, and applies the reverse transfer bias to the primary at the timing when the transfer toner image C reaches the transfer position. The reverse transfer toner image E is applied to the transfer roller 14d (for example, reverse transfer bias is applied for 1 second), and a part of the transfer toner image C is transferred onto the photosensitive drum 11d as the reverse transfer toner image E. Supply to the cleaning blade 18d side (second reverse transfer: step S8).

  In the above example, since the photosensitive drum 11a is positioned upstream of the photosensitive drum 11b in the rotation direction of the intermediate transfer belt 13, the control device separates the belt cleaning blade 19 from the intermediate transfer belt 13 and transfers it. After preventing the toner image C from being removed by the belt cleaning blade 19, the switch 15a is controlled so that the second bias power source 17a and the primary transfer roller 14a are connected, and the transfer toner image C reaches the transfer position. At this time, a reverse transfer bias is applied to the primary transfer roller 14a (for example, a reverse transfer bias is applied for 1 second), and the transfer toner image C is transferred onto the photosensitive drum 11a as a reverse transfer toner image F to be reversed. The transferred toner image F is supplied to the cleaning blade 18a (third reverse transfer: step S9).

  Then, the control device ends the control mode. In this case, without immediately shifting to image formation, the belt cleaning blade 19 is brought into contact with the intermediate transfer belt 13, and then the intermediate transfer belt 13 is further rotated to remove residual toner remaining on the intermediate transfer belt 13. The cleaning blade 19 is used for removal.

  The peripheral length of the intermediate transfer belt 13 is set in advance in the control device, and the rotation speed of the intermediate transfer belt 13 (that is, the driving speed of the belt driving roller 13a) is given to the control device, and the photosensitive drums 11a to 11d. Is set in the control device. Accordingly, the control device can determine the timing at which the transfer toner image C on the intermediate transfer belt 13 reaches the positions of the photosensitive drums 11a to 11d, and based on this determination, the reverse transfer bias is applied to the primary as described above. It is applied to the transfer roller.

  In the above example, the case where the toner consumption amount of the developing device corresponding to the photosensitive drum 11b is the largest has been described, but the same applies to the case where the toner consumption amount of the developing device corresponding to the photosensitive drum 11c or 11d is the largest. Thus, the toner is supplied to the cleaning blades 18a to 18d with reference to the developing device that consumes the largest amount of toner.

  Similarly, when the toner consumption of the developing unit corresponding to the photosensitive drum 11a is the largest, the toner is supplied to the cleaning blades 18a to 18d. Since the belt cleaning blade 19 is positioned on the most upstream side of the transfer belt 13, it is not necessary to separate the belt cleaning blade 19 from the intermediate transfer belt 13, and the toner remaining on the intermediate transfer belt 13 is removed by the belt cleaning blade 19 and immediately proceeds to image formation. can do.

  In this manner, in the tandem type color image forming apparatus having a plurality of photosensitive drums and the intermediate transfer belt, the solid electrostatic latent image on the photosensitive drum corresponding to the developing device consuming the largest amount of toner is developed. Since the toner is supplied to each photosensitive drum, in the developing device that consumes the largest amount of toner, the time during which the toner is stirred is short, so that the external additive is less likely to be embedded in the toner. The lubricating action is hardly reduced, friction between the cleaning blade and the photosensitive drum can be reduced, and abnormal noise from the cleaning blade can be prevented. Therefore, even when the low printing rate is continuous, it is possible to reliably prevent abnormal noise generated from the cleaning blade.

  In the above-described example, the solid toner image is formed on the photosensitive drum corresponding to the developing device with the largest toner consumption, and the toner is transferred to the remaining photosensitive drum by reverse transfer. In addition to the developing device with the largest amount of toner, a solid toner image is formed on the photosensitive drum corresponding to the developing device with the next largest toner consumption, and the toner is transferred to the remaining photosensitive drum by reverse transfer. In this case, it has been found that no abnormal noise is generated from the cleaning blade due to the lubricating action of the toner.

  In the above-described example, the control device, the switches 15a to 15d, the first bias power sources 16a to 16d, and the second bias power sources 17a to 17d function as control means, and the control device serves as toner consumption amount detection means. It also has a function.

  A toner image is formed on the photosensitive drum corresponding to the developing device that consumes the largest amount of toner according to the toner consumption for each developing device, and a part of the toner image is transferred to the intermediate transfer belt as a transfer toner image. In addition, since the transferred toner image is reversely transferred from the intermediate transfer belt to the remaining image carrier, the toner in which the external additive is not embedded in the toner is supplied to each photosensitive drum, and cleaning is performed. The friction between the blade and the photosensitive drum does not increase, and no abnormal noise due to the vibration of the cleaning blade is generated. As a result, an abnormality of the cleaning blade in an image forming apparatus such as a copying machine, a printer, or a facsimile machine Applicable for sound prevention.

It is a figure which shows an example of the image forming apparatus by Example 1 of this invention. 3 is a flowchart for explaining abnormal noise prevention control of a cleaning blade in the image forming apparatus shown in FIG. 1.

Explanation of symbols

10a to 10d Image forming units 11a to 11d Photosensitive drum 12b Developer 13 Intermediate transfer belts 14a to 14d Primary transfer rollers 15a to 15d Switches 16a to 16d First bias power source (positive bias power source)
17a to 17d Second bias power source (reverse bias power source)
18a to 18d Cleaning blade 19 Belt cleaning blade

Claims (5)

A plurality of image carriers, a developing device provided for each of the image carriers to develop an electrostatic latent image on the image carrier into a toner image, and the toner image on the image carrier are sequentially transferred. An intermediate transfer member, and a cleaning blade for cleaning residual toner remaining on the image carrier in contact with the image carrier, and transferring the toner image on the intermediate transfer member to a recording sheet to form an image In an image forming apparatus that performs
Toner consumption detecting means for detecting toner consumption for each of the developing devices;
A toner image is formed on an image carrier corresponding to at least the developing device that consumes the largest amount of toner according to the amount of toner consumed for each developing device in a state where no image is formed, and a part of the toner image is formed. An image forming apparatus comprising: a control unit configured to perform a control mode in which a transfer toner image is transferred to the intermediate transfer member as a transfer toner image, and the transfer toner image is reversely transferred from the intermediate transfer member to the remaining image carrier.   The image forming apparatus according to claim 1, wherein the toner consumption amount detecting unit detects the toner consumption amount according to a printing rate for each of the developing devices.   The control means includes: a first bias power source that transfers a toner image from the image carrier to the intermediate transfer member; a second bias power source that reversely transfers a toner image from the intermediate transfer member to the image carrier; 3. The image forming apparatus according to claim 1, further comprising a switching control unit configured to perform switching control of the first and second bias power sources. An intermediate transfer member cleaning member that is disposed so as to be detachable from the intermediate transfer member and cleans residual toner remaining on the intermediate transfer member when contacting the intermediate transfer member;
The control means is configured to remove the intermediate transfer member cleaning member during the control mode except when the toner consumption of the developing unit corresponding to the image carrier positioned on the most upstream side in the rotation direction of the intermediate transfer member is the highest. The image forming apparatus according to claim 1, wherein the image forming apparatus is separated from the intermediate transfer member.   The image forming apparatus according to claim 1, wherein the control unit enters the control mode when a predetermined time elapses after the start of image formation.

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