JP2006251523A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that irregular rotation of a photoreceptor may be generated and color slippage or jitter may appear remarkably due to the periodical load variation of a photoreceptor peripheral member. <P>SOLUTION: The one-period operation time of the photoreceptor peripheral member is set to integer fraction of moving time between exposure and transfer of the photoreceptor. Further the one-period operation time of the photoreceptor peripheral member is changed at the time of input of a rotational variation pattern and at the time of printing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to rotation control and configuration of a photoreceptor and a photoreceptor peripheral member used in a color electrophotographic copying machine and a color printer.

  2. Description of the Related Art As an image forming apparatus to which electrophotography is applied, an apparatus having a configuration in which a plurality of photosensitive members are arranged in contact with an intermediate transfer member is known. The image forming apparatus includes a plurality of photosensitive members having a photosensitive layer formed on a surface thereof, an intermediate transfer member formed so as to be in contact with all of the plurality of photosensitive members in order, and a paper conveyance system including a fixing device. . Each photoconductor is configured to be surrounded by photoconductor peripheral members such as a charger, an exposure device, a developing device, a transfer device, and a cleaning device. By performing the electrophotographic process by the action of the peripheral member of the photoconductor, toner images are continuously formed on the photoconductor. The formed toner image is transferred and held on the intermediate transfer member by a transfer device. On the intermediate transfer member, toner images transferred from a plurality of photosensitive members are sequentially stacked. Here, a color toner image can be formed on the intermediate transfer member by setting the color of the toner image formed by the plurality of photosensitive members to yellow, magenta, cyan, and black. The color toner image formed on the intermediate transfer member is collectively transferred to the recording paper conveyed by the paper conveyance system, and further fixed by heating and fixing with a fixing device provided on the paper conveyance path. Print output.

  In the tandem type image forming apparatus as described above, in order to obtain a good image quality, it is necessary to realize superposition of toner images formed by a plurality of photoconductors with high accuracy. High-precision superposition of toner images is realized by high-precision rotation of the photosensitive member and the intermediate transfer member and an integer ratio design of each part size.

  High-precision rotation of the photosensitive member and the intermediate transfer member can be achieved by reducing rotational speed fluctuation and eccentricity of the drive motor and drive transmission system, and reducing rotational fluctuation by rotational control. Regarding rotation control, a method as in Patent Document 1 is known. In Patent Document 1, the rotation fluctuation of the photosensitive member is detected from the rotation information obtained from the rotation detecting means so that the photosensitive member is in a predetermined rotation state, and the drive correction value of the drive motor that cancels the rotation fluctuation is calculated. The method is shown. Thereby, the rotation fluctuation of the photosensitive member is canceled by the rotation control using the drive correction value, and the rotation is always kept constant.

  On the other hand, methods such as Patent Document 2 and Patent Document 3 are known for integer ratio design of dimensions of each part. Patent Document 2 discloses a method of designing a reduction ratio of a photosensitive member driving motor so as to move between exposure and transfer of the photosensitive member by integer rotation of the driving motor. If it does in this way, the period fluctuation of a drive motor will become the same phase by an exposure point and transfer transfer. As a result, the influence of the periodic image position variation of the electrostatic latent image generated at the exposure point cancels the transfer position variation generated at the transfer point, and an image having no positional deviation is formed on the intermediate transfer member. Japanese Patent Application Laid-Open No. H10-228561 describes that the amount of one rotation of the driving roller of the intermediate transfer member is designed to be an integral number of the photosensitive member interval. In this way, the phase of the periodic fluctuation that occurs in the intermediate transfer member drive system is the same phase at each photosensitive member contact portion. As a result, the toner image transfer position fluctuations that occur when transferring from the respective color photoconductors to the intermediate transfer body overlap each other, so that there is no overlay displacement.

JP-A-7-129034

JP 2004-117386 A JP 2003-270896 A

  As described above, in the image forming apparatus in which the toner image overlay accuracy is improved, the periodicity generated by the operation of the peripheral member of the photosensitive member such as the transfer roller, the developing roller, the cleaning blade, the cleaning brush, and the intermediate transfer member that contacts the photosensitive member. A large load fluctuation significantly affects the superposition of toner images. The superimposition accuracy of the toner image is reduced because the rotation of the photoconductor is induced by the periodic load fluctuation of the peripheral members of the photoconductor, so that the electrostatic latent image forming position at the exposure point and the transfer at the transfer point are transferred. This is because the position varies.

  Therefore, according to the present invention, the one-cycle operation time of the peripheral member in contact with the photosensitive member is set to be an integral number of the moving time for the photosensitive member to rotate from exposure to transfer. By doing so, the periodic rotation fluctuation of the photoconductor caused by the load fluctuation of the peripheral member of the photoconductor cancels and overlaps the position fluctuation of the electrostatic latent image generated at the exposure point and the fluctuation of the transfer position generated at the transfer point. It will not affect the alignment.

  Further, according to the present invention, the one-cycle operation time of the peripheral member in contact with the photoconductor is set to be an integral number of the movement time for the photoconductor to rotate from exposure to transfer and to an integer of the rotation time of the photoconductor. Set to. This is because, in the rotation control of the photoconductor, the photoconductor is rotationally controlled with a reverse phase waveform of the fluctuation waveform of one rotation of the photoconductor, so that the cycle variation of the photoconductor due to the load variation is repeated in one rotation cycle of the photoconductor. If it is set in this way, the periodic fluctuation is also reduced by the rotation control of the photosensitive member.

  Furthermore, the present invention changes the one-cycle operation time of the peripheral member of the photoconductor to 1 / integer of the rotation time of the photoconductor when the rotation fluctuation waveform is taken in the rotation control. By doing so, the reproducibility of the load fluctuation pattern and the photosensitive member rotation fluctuation pattern of the peripheral member of the photosensitive member is improved, so that the effect of the rotation control of the photosensitive member can be maximized.

  The image forming apparatus of the present invention can reduce a toner image overlay shift due to a load change of a peripheral member in contact with a photosensitive member. In addition, high-precision rotation control of the photosensitive member can be achieved at the same time, so that good image quality with little color shift can be obtained.

  FIG. 1 is a diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention.

  The image forming apparatus includes a photosensitive member 21, peripheral members of the photosensitive member 21 (a charger 22, an exposure unit 23, a developing unit 24, a transfer unit 25, and a cleaning unit (either the cleaning blade 26 or the cleaning roller 27). Printing system 2a, 2b, 2c, 2d, intermediate transfer member 31, peripheral member of intermediate transfer member 31 (intermediate transfer member transport member composed of a plurality of transport rollers 35, and intermediate transfer member) The intermediate transfer system 3 is composed of a cleaning device 33 and a second transfer device 32), and the sheet transport system 4 is composed of a fixing device 42 and a paper transport mechanism (not shown).

  Image formation in each printing system 2a, 2b, 2c, 2d is performed by an electrophotographic process. In the electrophotographic process, each process proceeds in the order of charging, exposure, development, transfer, and cleaning by the peripheral members of the photoconductor 21 as the photoconductor 21 rotates. Then, a toner image is formed on the intermediate transfer member 31. The image forming process will be described below.

  First, in the charging process, a high voltage is applied to the charger 22, and charged particles generated by air discharge are moved electrically to charge the surface of the photoreceptor. In this embodiment, the charger 22 uses a charging roller that contacts and rotates on the surface of the photoreceptor. In this case, by applying a high voltage to the roller having the resistance layer, the charge is directly transferred to the surface of the photoreceptor to perform charging.

  In the exposure process, the surface of the photoconductor is exposed with a pattern corresponding to an image by a non-contact exposure unit 22 with respect to the photoconductor to form an electrostatic latent image. In the developing process, toner is supplied to the electrostatic latent image formed on the photosensitive member 21 by a developing device (developing roller) 24 and is electrostatically attached to form a visible image. In the intermediate transfer process, the visible image is transferred to the intermediate transfer member 31 by the transfer unit 25. In the cleaning process, the toner remaining on the photoreceptor after the toner image is transferred to the intermediate transfer member 31 is removed by the cleaners 27 and 28. In this embodiment, a plurality of printing systems 2a, 2b, 2c and 2d are provided. In each printing system, different color images are formed in parallel, and toner images are formed using yellow, magenta, cyan, and black toners, respectively.

  The intermediate transfer member 31 is a member that superimposes toner images formed in each printing system and transfers them to the recording paper 41. In the process of superimposing each color toner image, when the intermediate transfer body 31 passes through the contact point with each color photoconductor, the toner image is sequentially transferred onto the intermediate transfer body 31 by the transfer unit 25 to be superimposed. A color image is formed by this superposition process. In the transfer process to the recording paper 41, the second transfer device 32 performs batch transfer of color toner images onto the recording paper 41 conveyed by the paper conveying mechanism.

  The color toner image formed on the recording paper 41 by the above process is heated and melted by the fixing device 42, and after fixing the color image on the recording paper, it is discharged outside the apparatus.

  FIG. 2 is a diagram showing a configuration of the peripheral member of the photoreceptor according to the first embodiment of the present invention.

  The photosensitive member peripheral member includes a charger 22, an exposure device 23, a developing device 24, a transfer device 25, and cleaning devices 26 and 26.

  The charger 22 includes a non-contact type charging device such as a scorotron charger and a charging roller type contact. Since the scorotron charger does not cause a load on the photosensitive member unlike the charging roller, it is an effective means for improving the rotational accuracy of the photosensitive member, but the apparatus is larger than the charging roller method. However, when a charging roller is used to reduce the size of the apparatus as in this embodiment, rotational fluctuations of the charging roller are transmitted to the photoconductor, causing periodic fluctuations in the photoconductor.

  The exposure unit 23 irradiates the photoconductor with light emitted from a laser, LED, or the like, and therefore does not directly contact the photoconductor. For this reason, the exposure unit does not generate rotational fluctuations on the photosensitive member.

  The developing roller of the developing unit 24 supplies toner to the photosensitive member 21 with a very narrow gap to adhere to the electrostatic latent image. For this reason, the influence of the load is exerted on the photosensitive member 21 through the toner. In particular, when the developing roller is eccentric, the load resistance periodically varies due to a gap change.

  As the transfer device 25, a scorotron transfer device or a transfer roller can be used. The scorotron transfer device is convenient because it is non-contact and does not cause rotational fluctuation of the photoreceptor. On the other hand, the transfer roller is effective in reducing the size of the apparatus, but causes contact with the photosensitive member 21 via the intermediate transfer member 31 and causes load fluctuation.

  The cleaning device 27 uses a cleaning brush 26 or a cleaning blade 27 to directly contact the photoconductor and scrape off residual toner. The cleaning brush 27 is a member that rotates while bringing a brush-like roller into contact with the photosensitive member and collects residual toner. The eccentricity and rotation speed fluctuation of the cleaning brush 27 are generated in approximately one rotation cycle of the cleaning brush. Load fluctuations due to this cleaning are transmitted to the photoconductor 21, and periodic load fluctuations also occur in the photoconductor. Further, although the cleaning blade 27 is generally used in a fixed state, it is a swing mechanism that swings left and right to remove paper dust and developer clogged between the cleaning blade 27 and the photosensitive member 21. May be provided. The swing mechanism is realized by converting the rotational motion of the drive motor into a reciprocating motion using an eccentric cam or the like. The swinging of the cleaning blade 27 fluctuates the rotation because it fluctuates the friction load. If the swinging operation is obtained from the drive source of the drive motor of the photoconductor 21, a change in the transmission mechanism affects the rotation variation of the photoconductor, so that a configuration obtained from another drive source is desirable.

  In the present invention, in particular, the rotation cycle of the peripheral member that rotates or swings in contact with the photoconductor 21 is defined as a predetermined cycle, thereby suppressing the occurrence of rotation variation of the photoconductor and obtaining a highly accurate color image. There is.

  3, 4, 5, and 6 are diagrams for explaining the integer ratio design of the photosensitive member.

  FIG. 3 shows the relationship between the irradiation position on the photosensitive member from the exposure device related to the image forming position and the relationship between the photosensitive member and the contact position of the transfer device among the peripheral members of the photosensitive member. Assuming that the point at which the electrostatic latent image is formed by the exposure unit 23 is the exposure point A and the point at which the toner image is transferred by the transfer unit 25 is the transfer point B, both are installed with an angle θ.

  Here, when the photosensitive member 21 undergoes rotational fluctuation, the electrostatic latent image formed at the exposure point A has an image extension position when the surface speed of the photosensitive member 21 is earlier than the exposure timing. Conversely, when the photosensitive member surface speed is low, the image forming position is clogged and image shrinkage occurs. In the toner image transferred at the transfer point B, image shrinkage occurs when the surface speed of the photoreceptor 21 is faster than that of the intermediate transfer body 31, and image extension occurs when the surface speed of the photoreceptor is slower than that of the intermediate transfer body. The change in the image length between the exposure point A and the transfer point B appears as a phenomenon in which the influence of the photoreceptor speed is reversed.

  When the photoconductor 21 periodically changes, the image length change amount at the exposure point A and the transfer point B is as shown in FIG. The vertical axis represents the amount of change in image length, with the image length increasing in the + direction and the image length shrinking in the-direction. As shown in FIG. 4, the change in image length between the exposure point A and the transfer point B is shown in reverse. Here, following the flow of image formation, the electrostatic latent image formed at the exposure point A moves between exposure and transfer, and is then transferred onto the intermediate transfer member at the transfer point B. Therefore, the exposure point A and the transfer point B have a time difference corresponding to the movement time between exposure and transfer.

  The plot in FIG. 4 shows a case where the electrostatic latent image is formed while the image is stretched at the exposure point A. This electrostatic latent image is transferred between exposure and transfer, and then transferred at a transfer point B indicated by another plot. FIG. 4 shows that the image length also increases at the transfer point B. The change in the length of the image formed on the intermediate transfer member is doubly affected by the rotational fluctuation of the photosensitive member.

  FIG. 5 is a graph in which the rotation fluctuation period of the photoreceptor is matched to the time between exposure and transfer. In this example, even if image expansion occurs in the electrostatic latent image formed at the exposure point A, image shrinkage occurs at the transfer point B. That is, it can be seen that the image length changes occurring at the exposure point A and the transfer point B cancel each other depending on the rotation fluctuation period of the photoconductor. According to this, it is understood that a good image can be obtained on the intermediate transfer member without completely removing the rotational fluctuation of the photosensitive member.

  FIG. 6 is a diagram showing the relationship between the rotational fluctuation frequency of the photosensitive member and the image length change amount on the intermediate transfer member. Here, the positional relationship between exposure and transfer is calculated as constant. The change in image length tends to be small at a frequency that is an integral multiple of the moving frequency corresponding to the moving time between exposure and transfer. From this, it can be seen that a good image can be obtained by setting the frequency of the periodic fluctuation acting on the photosensitive member to an integral multiple of the movement frequency between exposure and transfer.

  Of the peripheral members of the photosensitive member, the operating frequency of the member that rotates and swings in contact with it becomes a periodic load fluctuation frequency. For this reason, if the operating frequency of the peripheral member that rotates and swings in contact with the photosensitive member is set near an integral multiple of the movement frequency between exposure and transfer, the image quality deteriorates due to the influence of the load fluctuation of the peripheral member. There is no longer to do. For example, the oscillation frequency of the cleaning blade is set to the vicinity of the frequency a in FIG. 6 and the rotation frequency of the cleaning brush is set to the vicinity of the frequency b. In this case, periodic load fluctuations due to the contact between the cleaning blade and the cleaning brush are applied to the photosensitive member to cause rotational fluctuations of the photosensitive member, but changes in the length of the image formed on the intermediate transfer member are almost cancelled. Such an integer ratio design is applicable not only to the peripheral members but also to the frequency design of all members that can be a periodic variation component of the photoreceptor. For example, the change in the image length can be reduced by setting the rotation frequency of the drive motor for driving the photosensitive member to point c in FIG.

  7 and 8 are diagrams for explaining the rotation control of the photosensitive member.

  FIG. 7 shows a rotation control system of the photosensitive member. The rotation control system controls the drive motor 213 by using a rotation detector (encoder) 211 that detects the number of slits of the slit plate that is directly connected to the shaft of the photosensitive member 21 and rotates integrally, and an output signal of the rotation detector as an input. And a drive motor 213 that rotates the photosensitive member 21 via a gear according to a control signal. The controller 212 takes in the rotation variation pattern of the photoconductor, calculates the reverse waveform, and performs control as a drive motor command signal.

  In such a control method, as shown in FIG. 8, the rotation of the photosensitive member cancels out by adding a waveform driving pattern opposite to the rotational fluctuation pattern of the photosensitive member 21 to the driving motor 213, so that the rotation accuracy is high. Can be increased. In this type of rotation control, if the rotation fluctuation pattern of one rotation period of the photoconductor cannot be obtained with good reproducibility, the difference between the acquired rotation fluctuation pattern and the actual rotation fluctuation pattern becomes large. This deviation may induce rotational fluctuations. In this case, there may be a problem that the rotational fluctuation becomes rather large. Therefore, in order to perform the rotation control of the photosensitive member with high accuracy, it is necessary to set the periodic component of the fluctuation to a cycle repeated by one rotation of the photosensitive member.

  In the present embodiment, a method in which the one-cycle operation time of a member that rotates and swings in contact with the photosensitive member is reduced to an integer of the moving time between exposure and transfer, and to an integer of the rotating time of the photosensitive member. In the process from exposure to transfer, a peripheral member that contacts and rotates and swings in contact with the photosensitive member is proposed to be separated from the photosensitive member and stopped.

  In the former, the operation of the peripheral elements of the photosensitive member is determined at a frequency that is the least common multiple of the moving frequency between exposure and transfer of the photosensitive member and the rotational frequency of the photosensitive member. For example, when the movement time between exposure and transfer is 1 second and the rotation time of the photosensitive member is 1.2 seconds, the one-cycle operation time of the peripheral member that rotates or swings in contact with the photosensitive member is set to 0.2 seconds. Further, the same effect can be obtained even if the integral operating time is 1 / period.

  In the latter, during exposure, development, and transfer of the photosensitive member, a cleaning brush, a cleaning blade, or the like is separated from the photosensitive member and the operation is stopped. By doing so, there is no influence on the image because no load fluctuation occurs on the photoconductor.

  As described above, the one-cycle operation time of the peripheral member that contacts or rotates or swings in contact with the photosensitive member is set to 1 / integer of the movement time between the drum and the transfer of the photosensitive member, and is an integral number of the rotation time of the photosensitive member. In the case of 1, the operating frequency of the peripheral member of the photosensitive member tends to be high, and it is difficult to maintain the life and original performance. Therefore, in this embodiment, the operation speed of the photosensitive member peripheral member is properly used depending on the situation. For example, in the period when the rotation fluctuation pattern of the photoconductor is captured in the rotation control, the one-cycle operation time of the peripheral member that rotates or swings in contact with the photoconductor is set to 1 / integer of the rotation time of the photoconductor. Then, it is set to 1 / integer of the movement time between exposure and transfer of the photoreceptor. In this way, the rotational variation pattern reproducibility of the photoconductor can be obtained and the rotation accuracy can be improved, and a good image can be obtained that does not expand and contract by an integer ratio design between exposure and transfer during printing. .

  The operating frequency of the member that contacts or rotates or swings on the photosensitive member is changed to a frequency that is an integral multiple of the rotational frequency of the photosensitive member. As described above, by appropriately using the operating frequency of the peripheral member of the photosensitive member according to the situation, it is possible to achieve both improvement in the rotational accuracy of the photosensitive member and reduction in image positional deviation on the intermediate transfer member, and an image forming apparatus with good image quality. Will be able to provide.

  In the above, the rotation or swing frequency of the peripheral member that rotates in contact with the photosensitive member is made an integral multiple of the rotational frequency of the photosensitive member, and an integral multiple of the rotation period until the exposure position on the photosensitive member reaches the toner transfer position. Explained. On the other hand, the rotation of the photosensitive member may be controlled such that the rotational frequency of the photosensitive member is an integral fraction of the rotation or swing frequency of a peripheral member that rotates or swings in contact with the photosensitive member. If a plurality of peripheral members rotate or swing at different rotational frequencies, determine a reference peripheral member (for example, the rotational frequency of the developing device that rotates most in contact with the photoconductor and has the greatest effect on the image as a reference). And) the rotation frequency of the photosensitive member is adjusted to a rotation frequency of 1 / integer. Then, the rotational frequency of the other peripheral members is controlled to be an integral multiple of the reference rotational frequency or 1 / integer. Accordingly, it is possible to obtain the same effect as when the peripheral member that rotates and swings in contact with the photosensitive member is controlled.

  It can be seen that the frequency of periodic fluctuations acting on the photoconductor has less influence on image positional deviation as the frequency increases. That is, it is possible to maintain good image quality by designing the operating frequency of the photosensitive member peripheral member and the rotational frequency of the photosensitive member driving motor on the high frequency side.

1 is a diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. It is a figure which shows the structure of the photoreceptor surrounding member which concerns on Example 1 of this invention. FIG. 3 is a diagram illustrating a positional relationship between a photoconductor exposure device and a transfer device. It is a figure explaining the integer ratio design of a photoconductor. It is a figure explaining the integer ratio design of a photoconductor. It is a figure explaining the integer ratio design of the photoconductor peripheral member which concerns on Example 1 of this invention. FIG. 3 is a diagram illustrating a rotation control system for a photoconductor according to the first exemplary embodiment of the present invention. It is a figure explaining rotation control of a photoconductor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Printing system, 21 ... Photoconductor, 211 ... Rotation detector, 212 ... Controller, 213 ... Drive motor, 22 ... Charger, 23 ... Exposure device, 24 ... Developer, 25 ... Transfer device 26 ... Cleaning brush 27 ... Cleaning blade 3 ... Intermediate transfer system 31 ... Intermediate transfer member 32 ... Second transfer device 33 ... Intermediate transfer member cleaner 4 ... Paper transport system 41 ... Paper transport Mechanism, 42. Fixing device.

Claims (8)

A charger for charging the photosensitive member, an exposure unit for exposing the photosensitive member to form an electrostatic latent image, a developing unit for developing the electrostatic latent image with toner, and transferring the formed toner image. A printing system including a photoconductor including a photoconductor peripheral member including a transfer device and a cleaning device that cleans residual toner on the photoconductor after transfer, and a color formed by a plurality of the printing systems. An intermediate transfer member that forms a color image by superimposing different toner images, a second transfer unit that collectively transfers the color image on the intermediate transfer member to a recording medium, and residual toner on the intermediate transfer member after transfer are cleaned. An intermediate transfer system comprising an intermediate transfer body cleaning device, a fixing device that heats and fixes a color image transferred onto the recording medium, and a paper transport mechanism that transports the recording medium Conveying system and by electrophotographic process An image forming apparatus for forming a color image,
An operation time of one cycle of a member that rotates and swings in contact with the photoconductor among the peripheral members of the photoconductor is 1 / integer of a movement time from the exposure position to the transfer position of the photoconductor. An image forming apparatus.   2. The image forming apparatus according to claim 1, wherein an operation time of one cycle of a peripheral member that rotates and swings in contact with the photoconductor is set to 1 / integer of the rotation time of the photoconductor. Image forming apparatus.   3. The image forming apparatus according to claim 1, wherein one cycle operation time of a peripheral member that rotates and swings in contact with the photosensitive member is changed.   4. The image forming apparatus according to claim 3, wherein a one-cycle operation time of a peripheral member that rotates and swings in contact with the photosensitive member is changed to a time shorter than usual.   5. The image forming method according to claim 3, wherein an operation time of one cycle of a peripheral member that contacts and rotates and swings in contact with the photosensitive member is an integer of one rotation time of the photosensitive member. apparatus.   4. The image forming apparatus according to claim 3, wherein a peripheral member that rotates and swings in contact with the photosensitive member is separated and stopped from the photosensitive member.   3. The image forming apparatus according to claim 1, wherein one rotation time of the photosensitive member is changed. 8. The image forming apparatus according to claim 7, wherein one rotation time of the photosensitive member is controlled to be an integral multiple of one cycle operation time of any of the peripheral members rotating and swinging in contact with the photosensitive member. An image forming apparatus.

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