JP2007101822A - Image forming apparatus and copying machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of reducing speed variation due to load variation of a photoreceptor depending upon on a pattern of a recorded image to reduce a position shift of recording, transfer, etc. <P>SOLUTION: It is decided whether the toner image area rate of an arbitrary image region of generated image data is larger than a specified rate and when there are one or more places where the toner image area rate is determined to exceed the specified rate per sheet of document, a specified pre-image as a dummy image for toner supply for forming a toner pool Tx on a cleaning blade 1-2 is formed not in a print region right before a latent image of document data is formed. The pre-image is preferably a solid image formed to the overall width of an image formable region along the axis of a photoreceptor 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a scanner apparatus, and a copying apparatus using the same, and more particularly to a full color image forming technique using an electrophotographic technique.

  Generally, a cleaning device for cleaning a toner residual image after transfer is provided around a photosensitive member provided in an image forming apparatus or the like. Since a cleaning device must be provided in contact with the photoreceptor in order to clean the photoreceptor, a load is generated there. Here, there may be a difference in the coefficient of friction between the bare photoconductor and the photoconductor on which the toner is placed, and as a result, a load fluctuation occurs. Speed fluctuations occur due to load fluctuations, and the recording position shifts to the photoconductor and slips with the transfer device, resulting in an abnormal image.

  In the image forming apparatus disclosed in Patent Document 1, a load resistance change occurs in an image forming unit, an erasing unit, a transfer roller, or the like that comes in contact with or leaves a photosensitive belt or transfer drum as an image forming member. The conveying speed of the forming member changes. Therefore, there is a problem in that a slight change in the length of the image occurs in the print page, and a high-quality image cannot be obtained. Therefore, a drum- or belt-shaped image forming member driven by a motor, an image forming unit that forms an image in contact with the image forming member, and an erasing unit that erases an image formed on the surface of the image forming member And a transfer unit that presses the recording medium against the image forming member in order to transfer the image on the surface of the image forming member to the recording medium, the load variation of the image forming unit, the erasing unit, and the transfer unit In response to this, the calculation means controls the speed of the motor.

  Further, in the drive control device disclosed in Patent Document 2 and the image forming apparatus using the drive control device, the rotation unevenness is caused by the rotational drive of the rotated body such as the photosensitive drum and the transfer material conveying belt driving roller in the image forming apparatus. In order to provide a drive control device capable of reducing and performing highly accurate control and an image forming apparatus using the drive control device, a powder brake for generating a load on the drive shaft of the photosensitive drum is provided, and the drive control unit However, the fluctuation of the rotational speed of the photosensitive drum is calculated from the output of the pulse encoder, and the load generated by the powder brake is controlled based on the calculated result.

Furthermore, in the multicolor electrophotographic apparatus disclosed in Patent Document 3, in the multicolor electrophotographic apparatus in which the residual toner on the photoconductor after transfer is removed using a rotating brush, the speed fluctuation pattern of the photoconductor is irregular. In order to prevent misalignment during writing, a plurality of developing units are provided for each color, and one of them is sequentially used to visualize the latent image written and written on the photosensitive member for each color. The visible image is sequentially transferred to an intermediate transfer member to form a multicolor image on the intermediate transfer member, and the multicolor image is collectively transferred and recorded on a sheet, while each color transfer is performed on the photosensitive member. The residual toner is removed using a rotating brush. Such a multicolor electrophotographic apparatus includes a clutch that is a transmission blocking unit that blocks rotation transmission to the rotating brush, and a control unit that operates the clutch during writing. Then, the rotation of the rotating brush is stopped at the time of writing so as to eliminate the influence of the load torque fluctuation applied to the photosensitive member.
Japanese Patent Laid-Open No. 2002-202706 JP 2000-224878 A Japanese Patent Application Laid-Open No. 8-21809

  That is, a photosensitive member on which a latent image is formed by light irradiation, an optical recording unit for forming a latent image on the photosensitive member, and a toner image is formed on the photosensitive member on which the latent image is formed. In an image forming apparatus and a copying apparatus provided with a developing device having a toner and a developer having both a carrier and a position for recording and transfer, etc. The above has been omitted to reduce the deviation.

  That is, in the technique of Patent Document 1, the speed of the drum drive motor is controlled by the calculation means according to the load fluctuation in response to the speed fluctuation caused by the load resistance change of the photosensitive drum. If it is large, the followability of speed control is questioned.

  In the technique of Patent Document 2, the fluctuation of the speed of the photosensitive drum is detected by an encoder and the powder brake is controlled in accordance with the detected change. In this method, the followability may be improved, but a powder brake is provided. This causes an increase in cost.

  In the technique of Patent Document 3, the cleaning rotary brush that causes the load fluctuation is stopped during writing, which is effective for the large-diameter drum, but the small-diameter drum intended for compactness is poorly cleaned. Causes an afterimage.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus and a copying apparatus that can reduce a speed fluctuation due to a load fluctuation of a photosensitive member due to a pattern of a recorded image and reduce a positional deviation such as recording or transfer.

  According to a first aspect of the present invention, there is provided an image forming apparatus including a photosensitive member on which a latent image is formed by light irradiation, an optical recording unit for forming the latent image on the photosensitive member, and the latent image formed thereon. A developing device having a developer having both a toner and a carrier for forming a toner image on the photosensitive member; a transfer device for transferring the toner image on the photosensitive member to paper or an intermediate transfer member; and In an image forming apparatus provided with a cleaning device for cleaning a residual toner image that has not been transferred, it is determined whether or not the toner image area ratio in an arbitrary image area of the formed image data is equal to or greater than a predetermined ratio. An image area ratio determining means, and when there are one or more positions per document determined by the image area ratio determining means to be a predetermined ratio or more, a latent image of the original data is formed. In the printing area outside just prior to, and forming a predetermined pre-image.

  According to a second aspect of the present invention, in the image forming apparatus of the first aspect, when the image data to be formed is only text, the pre-image is not formed.

  According to a third aspect of the present invention, in the image forming apparatus of the first aspect, the axial width of the photosensitive member in an arbitrary image region is the entire image-formable region.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, the length of the arbitrary image region in the rotation direction of the photosensitive member is 50 mm or less.

  According to the fifth aspect of the present invention, in the image forming apparatus of the first aspect, the length of the arbitrary image region in the rotation direction of the photosensitive member is 5 mm or more.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the first aspect, the predetermined ratio of the image area ratio determined by the image area ratio determination means is at least 10% or more.

  According to the seventh aspect of the present invention, in the image forming apparatus according to the first aspect, the width of the pre-image in the photosensitive member axial direction is the entire image formable region.

  According to an eighth aspect of the present invention, in the image forming apparatus of the first aspect, the length of the pre-image in the photoconductor rotation direction is shorter than the distance between sheets during continuous printing.

  According to a ninth aspect of the present invention, in the image forming apparatus of the first aspect, the pre-image is a solid image.

  According to a tenth aspect of the present invention, in the image forming apparatus of the first aspect, when the pre-image is created, the transfer bias between the photoconductor and the transfer device is turned off or a reverse bias is applied.

  The image forming apparatus according to claim 11 has a plurality of combinations of the photoconductor, the optical recording unit, the developing device, the transfer device, and the cleaning device. The developing devices in each group have toners of different colors, and the image area ratio determining means determines the image area ratios of individual toner colors.

  A copying apparatus according to a twelfth aspect of the present invention includes the image forming apparatus according to any one of the first to eleventh aspects.

  According to a thirteenth aspect of the present invention, the image forming apparatus according to any one of the first to eleventh aspects is used.

  The best mode for carrying out the present invention will be described below with reference to the embodiments shown in the drawings.

  FIG. 1 shows an outline of the overall configuration of an example of an image forming apparatus that is an object of the present invention. In the figure, an example of a full-color image forming apparatus is shown. An image forming apparatus for performing full-color printing has four color units of yellow (Y), magenta (M), cyan (C), and black (Bk). In the following, Y, C, M, and Bk indicating colors are attached to each code if necessary, but the addition of Y, C, M, and Bk is omitted in other cases.

  Each color unit has a photoreceptor 1 and a developing device 3 (in the drawing, Y, C, M, and Bk are sequentially from the left), and an individual latent image is formed on each photoreceptor 1. As described above, the optical recording means 2 emits at least four beams. In recent years, in order to increase the recording speed, a configuration in which a plurality of beams are used for one unit has increased, and in this case, the number of beams is appropriate for all units. The scanning method for the optical recording means 2 is not particularly limited. For example, there is a line head optical system in which the beam profile is in a straight line, but here, the description will proceed with the most general polygon scanning method.

  The polygon scanning method is a method in which the polygon mirror 2-1 is rotated at a high speed, the beam from the light source 2-2 is scanned in the axial direction of the photosensitive member 1, and recording is performed with the rotational direction of the photosensitive member 1 being sub-scanned. . Recording must be done for four colors. A configuration with only one polygon mirror is also possible. Of course, a method of using two or a method of using four for each color may be used.

  The developing device 3 includes a developing roller 3-1 for supplying toner to the photoconductor 1 so as to form a toner image on the photoconductor 1, a stirring roller 3-2 for stirring the developer and causing the toner to be charged, It is constituted by a doctor blade 3-3 or the like that makes the thickness of the developer layer on the developing roller 3-1 uniform. The developer is composed of two components, a carrier and a toner. In the case of the two-component type, the stirring roller 3-2 also has a role of mixing them uniformly as a whole. The developing roller 3-1 has magnetism, whereby the carrier is held by the developing roller 3-1. The carrier constitutes a magnetic brush, and the toner is conveyed therein at a constant density.

  The photoreceptor 1 is provided with a certain gap from the developing roller 3-1. On the periphery of the photoreceptor 1, a charging roller 1-1 and a toner cleaning blade 1-2 for charging the surface of the photoreceptor 1 are provided. If necessary, a neutralizing LED 1-3, a lubricant 1-4, a lubricant application roller 1-5, and the like are also provided.

  Each color toner image formed by each developing device 3 and the photoreceptor 1 is transferred to one transfer device 4. That is, since the images of the respective colors are superposed here, accurate color matching is necessary at this stage.

  The transfer device 4 includes a transfer belt 4-1 to which an image is transferred, a first transfer roller 4-2 provided at a position facing the photoconductor 1 of each color, and a first transfer roller 4-2 as necessary. Separating means 4-3 (mainly a cam 4-3-1 or the like is used. 4-3-2 is a fulcrum of rotation) and an image on the transfer belt 4-1. The second transfer roller 4-4 for transferring the toner onto the paper 7, the belt cleaning device 4-5, and the like. The second transfer roller 4-4 is provided to face the second transfer unit 5, and the image is transferred to the paper 7 by passing the paper 7 therethrough. Then, the image transferred to the paper 7 is fixed on the paper 7 by the fixing device 6.

  Note that the present invention is not limited to a full-color image forming apparatus but is also applied to a single-color image forming apparatus. In that case, there is only one combination of the developing device and the photosensitive member, and at the same time, the number of beams of the optical recording means and the number of first transfer rollers are also appropriate. Alternatively, a method of directly transferring from the photosensitive member to the paper 7 without using a transfer device may be used.

Below, the detail of the structure of the part in connection with the Example of this invention is demonstrated.
The toner image on the photoconductor 1 is transferred to the transfer belt 4-1, but 100% is not transferred, and some of the toner image remains on the photoconductor 1 without being transferred to the transfer belt 4-1. A toner cleaning blade 1-2 is provided so that the residual toner component does not become an afterimage. The toner cleaning blade 1-2 is made of an elastic material such as rubber or resin, and is attached in a counter direction with respect to the rotation direction of the photoconductor 1 in order to efficiently remove the toner on the photoconductor 1. Yes. For this reason, the load applied to the rotation of the photosensitive member 1 also increases. The load is friction between the photosensitive member 1 and the toner cleaning blade 1-2. In order to reduce this, the lubricant is usually applied to the surface of the photosensitive member 1 by the lubricant application roller 1-5. It is like that.

  Further, since the toner itself is in the form of a powder having a small particle size, friction between the toner cleaning blade 1-2 and the photosensitive member 1 is reduced. This is a problem here. As described above, since the toner image on the photosensitive member 1 is not 100% transferred, there is a load depending on whether the portion passing through the cleaning blade 1-2 is a non-image portion or an image portion. It will change (see Figure 2). In the case of an image pattern in which this load fluctuation is abruptly generated, the torque of the drive motor (not shown) of the photosensitive member 1 does not follow and rotation unevenness of the photosensitive member 1 occurs. For example, the tendency becomes remarkable in a pattern in which there is a solid image immediately after the non-image portion.

  As a method for preventing such a phenomenon, means for constantly reducing the load or means for increasing the load is required. As means for increasing the load, means for forcibly generating friction on the photosensitive member 1 is required. This eliminates sudden load fluctuations, but increases the cost of the drive motor and increases the cost of the friction generating means due to the increased load. Therefore, in this embodiment, a means for reducing the load is examined.

  In order to prevent the load from being increased even when the non-image portion passes the cleaning blade 1-2, supplying toner onto the cleaning blade 1-2 is a quick means. As shown in FIG. 3, if there is a toner reservoir Tx on the cleaning blade 1-2, the load is low until all the toner in the toner reservoir Tx falls into the waste toner area or passes through the cleaning blade. Therefore, in this state, even if a portion having a high image density passes through the cleaning blade, the load does not fluctuate so much. Also, even if the non-image area continues for a long time and the toner in the toner pool runs out and the load becomes high, there is no problem unless a portion with a high image density comes abruptly.

  As described above, in this embodiment, the image area ratio determining unit that determines whether the toner image area ratio in an arbitrary image region of the formed image data is equal to or higher than a predetermined ratio is provided. When a predetermined ratio is determined to be equal to or greater than a predetermined ratio, there is at least one place per original so that a predetermined pre-image is formed outside the print area immediately before forming the latent image of the original data. Yes.

  The pre-image is a dummy image for supplying toner for forming a toner reservoir Tx on the cleaning blade 1-2. Therefore, in order to perform efficiently, the pre-image is desirably a solid image of the entire width of the image formable area in the axial direction of the photoreceptor 1. Further, it is desirable that the length of the pre-image in the rotation direction of the photosensitive member 1 is shorter than the distance between sheets during continuous printing so as not to reduce the printing speed for the pre-image.

  Further, when creating a pre-image, it is desirable to turn off the transfer bias between the photoconductor 1 and the transfer device 4 or apply a reverse bias. By doing so, the pre-image toner can be supplied to the cleaning blade 1-2 as much as possible without being taken up by the transfer belt 4-1. In addition, since almost no toner is transferred to the transfer belt 4-1, it is possible to prevent the rollers of the second transfer portion 5 from being soiled between sheets. If the roller transfer of the second transfer unit 5 still becomes a problem, the second transfer unit 5 may be separated between the sheets.

An arbitrary image area will be described below.
The width of the arbitrary image area in the axial direction of the photosensitive member 1 is not limited, but is desirably the entire width of the image formable area. This is because the cleaning blade 1-2 scrapes the remaining toner of the entire width in the axial direction of the photosensitive member 1 at a time, which can make an accurate determination.

  The length of the arbitrary image area in the rotation direction of the photosensitive member 1 is set to, for example, 5 to 50 mm. This is based on the graph of the load fluctuation rate shown in FIG. For example, when there is an image of a horizontal line over the entire width of the sheet, it is determined that the image is a solid image that extends locally in the entire axial direction of the photosensitive member 1 by the line width. In this case, it is determined that the load fluctuation occurs although the load fluctuation does not substantially occur. In order to prevent this, the lower limit is set to 5 mm.

  In the example shown in the figure, the load fluctuation is almost constant at the maximum value at 50 mm or more, so the upper limit is set to 50 mm. This is because, if the upper limit is set too large, it may be determined that there is an actual load variation but it does not occur when there is an image as shown in FIG.

  Actually, since the state of load change changes depending on the conditions of the photosensitive member 1 and the cleaning blade 1-2, it is desirable to select an optimum value by an actual combination. In any case, it is considered that it falls within the range of 5 to 50 mm.

  FIG. 6 shows the relationship between the fluctuation of the load at the boundary between the background and the halftone image and the image area ratio of the halftone image. From the figure, the load fluctuation is conspicuous in the region of 10% or more. Therefore, it is determined that the load fluctuation has occurred when the image area ratio exceeds at least 10% for an arbitrary image, and a pre-image is formed. Needless to say, when the image area ratio is 10%, there is no problem of load fluctuation, and when there is a possibility that it will occur at 20%, the threshold value may be 20%.

  In the above description, the image disturbance caused by the speed fluctuation due to the load fluctuation of the photosensitive member 1 is conspicuous in an image using a lot of halftones and the like, and can hardly be recognized in a text-only image without any shading. Or something that does n’t matter. Since countermeasures against image disturbance involve toner consumption by a pre-image, it is not desirable to consume toner where it is not necessary. Therefore, it is desirable not to form a pre-image in the case of a text-only image.

  That is, the image forming apparatus of the present invention includes a photoreceptor on which a latent image is formed by irradiating light, an optical recording unit for forming the latent image on the photoreceptor, and a photoreceptor on which the latent image is formed. A developing device having a developer having both a toner and a carrier for forming a toner image thereon; a transfer device for transferring the toner image on the photosensitive member to paper or an intermediate transfer member; An image forming apparatus that includes a cleaning device for cleaning a residual toner image that has not been received, but for determining whether the toner image area ratio in an arbitrary image area of the formed image data is equal to or greater than a predetermined ratio An area ratio judging means, and when there are one or more places per document that are judged to be a predetermined ratio or more by the image area ratio judging means, In the printing area outside just before formed, to form a predetermined pre-image, to suppress abrupt load fluctuation of the photosensitive member by the recording image pattern, it is made possible to prevent disturbance of the image.

  In addition, when the image data to be formed is only text, a pre-image is not formed, so that extra toner consumption can be prevented for an image that does not require precise image quality.

  In addition, it is possible to reduce the determination error of the image area ratio determination unit by setting the width of the arbitrary image region in the photosensitive member axial direction as the entire image formable region.

  In addition, the length of the arbitrary image area in the rotation direction of the photosensitive member is set to 50 mm or less, so that the determination error of the image area ratio determination unit can be reduced.

  In addition, the length of the arbitrary image region in the rotation direction of the photosensitive member is set to 5 mm or more, so that a condition for causing a load fluctuation that causes a problem is given, and the determination accuracy of the image area ratio determination unit can be improved.

  Further, the predetermined ratio of the image area ratio determined by the image area ratio determination unit is set to at least 10% or more, and a condition for causing a problem load change is given to improve the determination accuracy of the image area ratio determination unit. Is possible.

  Still further, the photoconductor axial width of the pre-image can be suppressed for the entire image formable region to suppress a rapid load fluctuation of the photoconductor.

  Furthermore, the length of the pre-image in the photoconductor rotation direction is shorter than the distance between papers during continuous printing, so that rapid load fluctuations on the photoconductor can be suppressed without reducing the number of print outputs per hour. Is possible.

  Then, it is possible to suppress a rapid load fluctuation of the photoconductor using the pre-image as a solid image.

  Also, during pre-image creation, the transfer bias between the photoconductor and the transfer device is turned off or reverse biased to suppress sudden load fluctuations on the photoconductor as much as possible, and to prevent roller contamination of the second transfer section. Making it possible.

  The image forming apparatus includes a plurality of combinations of a photosensitive member, an optical recording unit, a developing device, a transfer device, and a cleaning device, each developing device having a different color toner, and an image area ratio determining unit. Is a multicolor (full color) printing that can prevent image distortion even in image forming apparatuses that determine the image area ratio of each individual toner color by suppressing rapid load fluctuations on the photoreceptor due to the recorded image pattern. It is possible to provide.

  Further, as a copying apparatus provided with the above-described image forming apparatus or as a copying apparatus using the image forming apparatus, it is possible to suppress image disturbance by suppressing a rapid load fluctuation of the photosensitive member due to a recorded image pattern. Yes.

1 is a schematic diagram illustrating an overall configuration of an example of an image forming apparatus that is an object of the present invention. FIG. 1 is an enlarged view around the thermal fixing device of the apparatus of FIG. FIG. 1 is an enlarged view around the thermal fixing device of the apparatus of FIG. The figure which shows the relationship between the photoconductor rotation direction length of an arbitrary image area | region, and a load fluctuation rate. Diagram showing the relationship of image areas on paper The figure which shows the relationship between the image area rate of a halftone image, and a load fluctuation rate

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 1-1 Charging roller 1-2 Toner cleaning blade 1-3 LED for static elimination
1-4 Lubricant 1-5 Lubricant application roller 2 Optical recording means 2-1 Polygon mirror 2-2 Light source 3 Developing device 3-1 Developing roller 3-2 Stirring roller 3-3 Doctor blade 4 Transfer device 4-1 Transfer belt 4 -2 First transfer roller 4-3 Separation means 4-3-1 Cam 4-3-2 Support point of separation means 4-4 Second transfer roller 4-5 Belt cleaning device 5 Second transfer section 6 Fixing device 7 Paper Tx Toner pool

Claims (13)

A photosensitive member on which a latent image is formed by light irradiation, an optical recording unit for forming a latent image on the photosensitive member, and a toner for forming a toner image on the photosensitive member on which the latent image is formed; In order to clean a developing device having a developer combined with a carrier, a transfer device for transferring a toner image on the photosensitive member to paper or an intermediate transfer member, and a residual toner image that has not been completely transferred on the photosensitive member. In an image forming apparatus provided with a cleaning device
Image area ratio determining means for determining whether or not the toner image area ratio in an arbitrary image region of the formed image data is equal to or greater than a predetermined ratio is determined by the image area ratio determination means to be equal to or greater than the predetermined ratio. An image forming apparatus for forming a predetermined pre-image outside a printing area immediately before forming a latent image of the original data when there are one or more places per original.   2. The image forming apparatus according to claim 1, wherein when the image data to be formed is only text, the pre-image is not formed.   2. The image forming apparatus according to claim 1, wherein an axial width of the photosensitive member in an arbitrary image area is the entire image formable area.   2. The image forming apparatus according to claim 1, wherein the length of the arbitrary image area in the rotation direction of the photosensitive member is 50 mm or less.   2. The image forming apparatus according to claim 1, wherein the length of the arbitrary image area in the rotation direction of the photosensitive member is 5 mm or more.   2. The image forming apparatus according to claim 1, wherein the predetermined ratio of the image area ratio determined by the image area ratio determining means is at least 10% or more.   2. The image forming apparatus according to claim 1, wherein the width of the pre-image in the photosensitive member axial direction is the entire image formable region.   2. The image forming apparatus according to claim 1, wherein the length of the pre-image in the direction of rotation of the photosensitive member is shorter than a distance between sheets during continuous printing.   2. The image forming apparatus according to claim 1, wherein the pre-image is a solid image.   2. The image forming apparatus according to claim 1, wherein when the pre-image is created, the transfer bias between the photoconductor and the transfer device is turned off or a reverse bias is applied.   2. The image forming apparatus according to claim 1, wherein a plurality of combinations of the photosensitive member, the optical recording unit, the developing device, the transfer device, and the cleaning device are provided, and the developing devices of each set are different. An image forming apparatus, wherein the image area ratio determining means determines the image area ratio of each individual toner color.   A copying apparatus comprising the image forming apparatus according to claim 1. A copying apparatus comprising the image forming apparatus according to claim 1.