JP2008176246A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which damage formed on the surface of a photoreceptor due to contact with a separation claw can be reduced. <P>SOLUTION: After appropriately setting pressuring force applied to the surface of the photosensitive drum 21 from a cleaning blade 26A, the modulus of impact resilience, rubber hardness and Young's modulus of the cleaning blade 26A are appropriately set by selecting the material of the cleaning blade 26A. The cleaning blade 26A is approximately always in sliding contact with the surface of the photosensitive drum 21; the cleaning blade 26A appropriately scraps the surface layer of the photosensitive drum 21, and the damage to the surface of the photosensitive drum 21 is smoothed thereby the surface of the photosensitive drum is restored. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly, to an image forming apparatus including a peeling claw for peeling a recording sheet from a photoreceptor surface and a cleaning blade for cleaning the photoreceptor surface.

  2. Description of the Related Art Conventionally, in an image forming apparatus, an electrostatic latent image on a surface of a photoconductor is developed with a developer to form a developer image (visible image) on the surface of the photoconductor. Transcript to.

  The transfer of the developer image is performed by superposing a recording sheet on the developer image on the surface of the photoreceptor in a transfer electric field. At this time, since the recording paper is charged and electrostatically attracted to the surface of the photosensitive member, it is necessary to peel off the recording paper from the surface of the photosensitive member after the transfer of the developer image.

  Various methods have already been proposed for peeling the recording paper from the surface of the photoconductor. However, the effect can be expected by reducing the diameter of the photoconductor and making the leading edge of the paper outside the photoconductor by the strength of the paper. There are a natural peeling method that makes it easy to move away from the curved surface of the circumference, and a peeling claw that abuts against the surface of the photoconductor, and a method that forcibly peels the front end of the paper from the surface of the photoconductor with this peeling claw.

In the natural peeling method, the stiffness of the leading edge of the paper varies depending on the type of paper (paper thickness, material, etc.), and the photoreceptor diameter is often determined according to the printing processing speed of the apparatus. It is rarely used because it does not necessarily have a curvature suitable for peeling. For example, the peel performance is good for thick paper (paper basis weight is 128 g / m ² or more), but the peel performance is poor for thin paper (paper basis weight is 80 to 100 g / m ² or less). This is due to the stiffness of the paper and the curvature of the photoreceptor.

  On the other hand, the method of forcibly peeling with the peeling claw can obtain a certain effect regardless of the type of paper and the printing processing speed of the apparatus.

  However, since the peeling claw abuts against the surface of the photosensitive member or collides with the leading edge of the paper, the peeling claw tip is chipped off while many papers are repeatedly peeled off, and a lot of the peeling claw tip comes off. A wound occurs. Then, when the scratches on the peeling claw come into contact with the surface of the photoconductor and are scratched, and the developer image on the surface of the photoconductor is transferred to the recording paper due to the scratch on the surface of the photoconductor, the recording paper Printing defects such as black lines and white lines occur on the top.

  For this reason, in Patent Document 1, the peeling claw is moved back and forth in a direction perpendicular to the rotation direction of the photoconductor and along the circumferential surface of the photoconductor to improve the paper peeling performance. It is intended to reduce the occurrence of scratches on the photoreceptor.

Various proposals relating to the selection of the material of the peeling claw have also been made.
Japanese Patent Laid-Open No. 05-249836

  However, in Patent Document 1, since the peeling claw is always in contact with the surface of the photoreceptor, the peeling claw is rapidly and greatly deteriorated, and it does not reduce or prevent scratches on the tip of the peeling claw. Further, even if the peeling claw is moved back and forth, it is unlikely that the paper peeling performance will be improved, and there is a possibility that the occurrence rate of paper jam will increase.

  Even if the material of the peeling nail is selected, the diameter of the photoconductor and the hardness of the surface layer are determined according to the sensitivity of the surface of the photoconductor suitable for the printing processing speed, and the peeling nail is determined by the diameter of the photoconductor and the hardness of the surface layer. Therefore, it is difficult to select the material of the peeling claw.

  Accordingly, the present invention has been made in view of the above-described conventional problems, and an object thereof is to provide an image forming apparatus capable of reducing scratches on the surface of a photoconductor caused by contact of a peeling claw.

  In order to solve the above problems, the present invention develops an electrostatic latent image on the surface of a photoconductor to form a visible image on the surface of the photoconductor, and transfers the visible image from the surface of the photoconductor to a recording sheet. In the image forming apparatus in which the recording paper is peeled off from the surface of the photoconductor with a peeling nail and the surface of the photoconductor is cleaned with a cleaning blade, the cleaning blade is brought into sliding contact with the surface of the photoconductor and the photosensitive nail is brought into contact with the peeling nail. The wound formed on the body surface is smoothed.

  Further, the scratches on the surface of the photoconductor are irregularities formed on the surface of the photoconductor, and the cleaning blade scrapes off the irregularities on the surface of the photoconductor.

  Further, the cleaning blade is a rubber member having a low rebound resilience, a high Young's modulus, and a high hardness.

  The sliding contact of the cleaning blade with the surface of the photoreceptor is continuously performed without interruption.

  Further, when the impact resilience of the cleaning blade is X, the impact resilience is set in a range of 25 <X <35.

If the Young's modulus of the cleaning blade is Y, the Young's modulus Y is set to 800 gf / mm ² or more.

  Furthermore, assuming that the hardness of the cleaning blade is Z, the hardness Z is set in a range of 70 ° <Z <80 °.

  The process speed of the image forming apparatus is 500 mm / sec or more.

  Further, the photoconductor is an organic photoconductor.

  Further, it is possible to change the contact position of the peeling claw with respect to the surface of the photoreceptor by moving the peeling claw with respect to the surface of the photoreceptor in a direction perpendicular to the moving direction of the surface of the photoreceptor. The contact position of the peeling claw with respect to the surface of the photoconductor is changed according to the number of prints processed by the forming apparatus.

  Further, the peeling claw is sequentially moved so as to come into contact with any one of a plurality of contact positions with respect to the surface of the photosensitive member, and the cleaning blade moves the peeling claw while the peeling claw goes around each contact position at least once. The scratches formed on the surface of the photoreceptor at the contact positions are smoothed by the nails.

  According to the present invention as described above, the cleaning blade is in sliding contact with the surface of the photoconductor, and smoothes the scratches formed on the surface of the photoconductor by the contact of the peeling claw. That is, the surface of the photoreceptor is smoothed and repaired by sliding contact with the cleaning blade. Thereby, it is possible to prevent printing defects such as black stripes and white stripes on the recording paper due to scratches on the surface of the photoreceptor.

  Here, the conventional cleaning blade is given sufficient elasticity and its tip is pressed against the surface of the photoreceptor. In this state, when the surface of the photoconductor rotates, the tip of the cleaning blade is repeatedly elastically deformed or returned to its original shape, and vibrates repeatedly. Toner and paper dust are blown away. This vibration at the tip of the cleaning blade is called a stick-slip phenomenon.

  On the other hand, in the present invention, the residual toner and paper dust on the surface of the photoconductor are removed by merely sliding the cleaning blade on the surface of the photoconductor without using the stick-slip phenomenon. Is smoothed and repaired. Further, since the cleaning blade is merely brought into sliding contact with the surface of the photoreceptor, there is an advantage that the toner does not scatter and stains due to the toner scatter do not occur.

  In addition, the cleaning blade scrapes off the uneven protrusions that are scratches on the surface of the photoreceptor. When unevenness is formed on the surface of the photoreceptor, the electric field concentration at the top of the convex portion is remarkable, and black stripes, white stripes, etc. are likely to occur at this portion. By scraping off the convex portions, black stripes, white stripes and the like can be greatly reduced. In addition, the performance of the photoconductive layer can be maintained by minimizing the amount of photoconductive layer on the surface of the photoreceptor that is scraped off.

  Furthermore, the cleaning blade is a rubber member having a low rebound resilience, a high Young's modulus, and a high hardness. With such a cleaning blade, the photoconductive layer on the surface of the photoreceptor can be appropriately scraped off.

  The sliding contact of the cleaning blade with the surface of the photoconductor is continuously performed without interruption. This also makes it possible to scrape off the photoconductive layer on the surface of the photoreceptor as appropriate.

Furthermore, when the impact resilience of the cleaning blade is X, the impact resilience is set in the range of 25 <X <35. Alternatively, if the Young's modulus of the cleaning blade is Y, the Young's modulus Y is set to 800 gf / mm ² or more. When the hardness of the cleaning blade is Z, the hardness Z is set in the range of 70 ° <Z <80 °. By setting the rebound resilience X, Young's modulus Y, and hardness Z of such a cleaning blade, the photoconductive layer on the surface of the photoreceptor can be appropriately scraped off by the cleaning blade.

  Further, the process speed of the image forming apparatus is 500 mm / sec or more. At this time, the settings of the rebound resilience X, Young's modulus Y, and hardness Z are effective.

  Further, the photoreceptor is an organic photoreceptor. The surface layer of the organic photoreceptor is made of an organic photoconductor material and is easily scratched. For this reason, the present invention is extremely effective.

  In addition, since the contact position of the peeling claw with respect to the surface of the photoconductor is changed according to the number of prints processed by the image forming apparatus, it is possible to prevent deep scratches from being formed at specific locations on the surface of the photoconductor. And the performance of the photoconductive layer can be maintained by minimizing the amount of photoconductive layer that is scraped to smooth the photoreceptor surface.

  Further, since the peeling claw smoothes the scratches formed on the surface of the photoconductor at each contact position while the peeling claw makes at least one round of the plurality of contact positions, the surface of the photoconductor is in one cycle. Therefore, it is only necessary to smooth the shallow scratches formed in a wide range, and the performance of the photoconductive layer can be maintained while minimizing the amount of the photoconductive layer to be scraped off.

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

  FIG. 1 is a cross-sectional view showing a first embodiment of the image forming apparatus of the present invention. The image forming apparatus 100 acquires image data read from a document sheet, or acquires image data received from the outside, and forms a monochrome image indicated by the image data on a recording sheet. The configuration is roughly divided into an original paper transport unit (ADF) 101, an image reading unit 102, a printing unit 103, a recording paper transport unit 104, and a paper feed unit 105.

  When at least one document sheet is set on the document set tray 11 in the document sheet transport unit 101, the document sheet is pulled out from the document set tray 11 and transported one by one. The original paper is guided to the reading window 102a and passed, and the original paper is discharged to the paper discharge tray 12.

  A CIS (Contact Image Sensor) 13 is disposed above the document reading window 102a. The CIS 13 repeatedly reads an image on the back side of the original paper in the main scanning direction when the original paper passes through the original reading window 102a, and outputs image data indicating the image on the back side of the original paper.

  The image reading unit 102 exposes the surface of the original paper by the lamp of the first scanning unit 15 when the original paper passes through the original reading window 102a, and the original by the mirrors of the first and second scanning units 15 and 16. Reflected light from the paper surface is guided to the imaging lens 17, and an image on the surface of the original paper is formed on a CCD (Charge Coupled Device) 18 by the imaging lens 17. The CCD 18 repeatedly reads an image on the surface of the original paper in the main scanning direction, and outputs image data indicating the image on the surface of the original paper.

  Further, when the original paper is placed on the platen glass on the upper surface of the image reading unit 102, the first and second scanning units 15 and 16 are moved while maintaining a predetermined speed relationship with each other, so that the first scanning unit 15 The surface of the original paper on the platen glass is exposed by the first and second scanning units 15 and 16, and the reflected light from the original paper surface is guided to the imaging lens 17. An image is formed on the CCD 18.

  The image data output from the CIS 13 or the CCD 18 is subjected to various image processing by a control circuit such as a microcomputer and then output to the printing unit 103.

  The printing unit 103 records a document indicated by image data on a sheet, and includes a photosensitive drum 21, a charger 22, an optical writing unit 23, a developing unit 24, a transfer unit 25, a cleaning unit 26, and a fixing device. 27 etc.

  The photoconductor drum 21 is an organic photoconductor whose surface layer is made of an organic photoconductive material. The photoconductor drum 21 rotates in one direction, the surface is cleaned by the cleaning unit 26, and the surface is uniformly charged by the charger 22. Is done. The charger 22 may be of a charger type or of a roller type or a brush type that contacts the photosensitive drum 21.

  The optical writing unit 23 is a laser scanning unit (LSU) including two laser irradiation units 28a and 28b and two mirror groups 29a and 29b. In the optical writing unit 23, image data is input, laser light corresponding to the image data is emitted from the laser irradiation units 28a and 28b, and the laser light is transmitted through the mirror groups 29a and 29b. The drum 21 is irradiated to expose the uniformly charged surface of the photosensitive drum 21 to form an electrostatic latent image on the surface of the photosensitive drum 21.

  The optical writing unit 23 employs a two-beam method including two laser irradiation units 28a and 28b in order to cope with high-speed printing processing, thereby reducing the burden associated with increasing the irradiation timing.

  As the optical writing unit 23, an EL writing head or an LED writing head in which light emitting elements are arranged in an array can be used instead of the laser scanning unit.

  The developing device 24 supplies toner to the surface of the photosensitive drum 21 to develop the electrostatic latent image, and forms a toner image (also referred to as a visible image) on the surface of the photosensitive drum 21. The transfer unit 25 transfers the toner image on the surface of the photosensitive drum 21 onto the recording paper conveyed by the paper conveyance unit 104. The fixing device 27 heats and pressurizes the recording paper to fix the toner image on the recording paper. Thereafter, the recording sheet is further conveyed to the sheet discharge tray 47 by the sheet conveying unit 104 and discharged. The cleaning unit 26 removes and collects the toner remaining on the surface of the photosensitive drum 21 after development and transfer.

Here, the transfer unit 25 includes a transfer belt 31, a drive roller 32, a driven roller 33, an elastic conductive roller 34, and the like, and the transfer belt 31 is stretched between the rollers 32 to 34 and other rollers. Is rotating. The transfer belt 31 has a predetermined resistance value (for example, 1 × 10 ⁹ to 1 × 10 ¹³ Ω / cm), and conveys the recording paper placed on the surface thereof. The elastic conductive roller 34 is pressed against the surface of the photosensitive drum 21 via the transfer belt 31, and presses the recording paper on the transfer belt 31 against the surface of the photosensitive drum 21. A transfer electric field having a polarity opposite to the charge of the toner image on the surface of the photosensitive drum 21 is applied to the elastic conductive roller 34. The toner image on the surface of the photosensitive drum 21 is transferred to the transfer belt by the transfer electric field having the opposite polarity. The image is transferred to a recording paper on 31. For example, when the toner image has a (−) polarity charge, the polarity of the transfer electric field applied to the elastic conductive roller 34 is set to the (+) polarity.

  The cleaning unit 26 presses the cleaning blade 26 </ b> A against the surface of the photosensitive drum 21 to remove residual toner and paper dust on the surface of the photosensitive drum 21. The entire toner image on the surface of the photosensitive drum 21 is not transferred onto the recording paper. Generally, it is said that the transfer efficiency is approximately 85 to 95%, although it varies depending on the transfer mechanism. . On the other hand, when the recording paper is subjected to a transfer electric field, the floating matter (cellulose short fiber, extender, bleaching agent, etc.) on the surface of the recording paper is charged to the opposite polarity to the transfer electric field, and the charged floating matter is the photosensitive drum. 21 adsorbs on the surface and becomes a deposit called paper dust.

  If the residual toner and paper dust on the surface of the photosensitive drum 21 are not removed, the print quality is deteriorated. For this reason, it is necessary to clean the surface of the photosensitive drum 21 by the cleaning unit 26.

  The fixing device 27 includes a heating roller 35 and a pressure roller 36. Pressure members (not shown) are arranged at both ends of the pressure roller 36 so that the pressure roller 36 is pressed against the heating roller 35 with a predetermined pressure. When the recording paper is conveyed to a pressure contact area (referred to as a nip area) between the heating roller 35 and the pressure roller 36, the recording paper is conveyed by the rollers 35 and 36, and unfixed toner on the recording paper. The image is heated and melted and pressed to fix the toner image on the recording paper.

  The paper transport unit 104 includes a plurality of pairs of transport rollers 41, a pair of registration rollers 42, a transport path 43, reverse transport paths 44a and 44b, a plurality of branching claws 45, and a pair of paper discharge rollers 46 for transporting recording paper. Etc.

  In the conveyance path 43, the recording paper is received from the paper supply unit 105, and the recording paper is conveyed until the leading edge of the recording paper reaches the registration roller 42. At this time, since the registration roller 42 is temporarily stopped, the leading edge of the recording paper reaches and contacts the registration roller 42, and the recording paper is bent. The leading edge of the recording sheet is aligned parallel to the registration roller 42 by the elastic force of the bent recording sheet. Thereafter, the rotation of the registration roller 42 is started, the recording paper is conveyed to the transfer unit 25 of the printing unit 103 by the registration roller 42, and the recording paper is further conveyed to the paper discharge tray 47 by the paper discharge roller 46.

  The registration roller 42 is stopped and rotated by switching on and off the clutch between the registration roller 42 and the drive shaft, or by switching on and off the motor that is the drive source of the registration roller 42.

  Also, when recording an image on the back side of the recording paper, each branch claw 45 is selectively switched, the recording paper is guided from the transport path 43 to the reverse transport path 44b, and the transport of the recording paper is temporarily stopped. Further, each of the branch claws 45 is selectively switched again, the recording sheet is guided from the reverse conveying path 44b to the reverse conveying path 44a, the recording sheet is reversed, and the recording sheet is conveyed through the reverse conveying path 44a. Return to the registration roller 42 in the path 43.

  Such conveyance of the recording paper is referred to as switchback conveyance. By this switchback conveyance, the front and back of the recording paper can be reversed, and at the same time, the leading edge and the trailing edge of the recording paper are also switched. Accordingly, when the recording paper is reversed and returned, the trailing edge of the recording paper comes into contact with the registration roller 42 and the trailing edge of the recording paper is aligned in parallel with the registration roller 42. Is transferred to the transfer unit 25 of the printing unit 103 to perform printing on the back surface of the recording paper, and the unfixed toner image on the back surface of the recording paper is heated and melted by the nip area between the rollers 35 and 36 of the fixing device 27. The toner image is fixed on the back surface of the recording sheet by the pressure, and then the recording sheet is conveyed to the discharge tray 47 by the discharge roller 46.

  In the conveyance path 43 and the reverse conveyance paths 44a and 44b, sensors for detecting the position of the recording paper and the like are arranged at various locations, and the conveyance roller and the registration roller are driven and controlled based on the position of the recording paper detected by each sensor. Thus, the recording paper is conveyed and positioned.

  The paper feed unit 105 includes a plurality of paper feed trays 51. Each paper feed tray 51 is a tray for accumulating recording paper, and is provided below the image forming apparatus 100. Each paper feed tray 51 is provided with a pick-up roller or the like for pulling out recording sheets one by one, and sends out the pulled recording sheets to the transport path 43 of the paper transport unit 104.

  Since the image forming apparatus 100 is intended for high-speed printing processing, each paper feed tray 51 has a capacity capable of storing 500 to 1500 standard size recording sheets.

  Further, on the side surface of the image forming apparatus 100, a large-capacity paper feed cassette (LCC) 52 capable of storing a large amount of a plurality of types of recording papers and a manual feed tray 53 for mainly supplying irregular-size recording papers are provided. ing.

  The paper discharge tray 47 is disposed on the side surface opposite to the manual feed tray 53. In place of the paper discharge tray 47, a post-processing device for paper discharge (such as stapling and punching) and a plurality of paper discharge trays can be arranged as options.

  In such an image forming apparatus 100, the printing process speed is increased to improve usability. For example, when A4 standard recording paper is used, the recording paper conveyance speed is set to 120 sheets / min (process speed 600 mm / sec).

  By the way, as shown in an enlarged view in FIG. 2, around the photosensitive drum 21, a charger 22, a developing device 24, a transfer unit 25, and a cleaning unit 26 are sequentially arranged in the rotation direction of the photosensitive drum 21. Further, a peeling claw 61 is disposed between the transfer unit 25 and the cleaning 26.

  The transfer unit 25 generates a transfer electric field, and the recording paper is superimposed on the toner image on the surface of the photosensitive drum 21 in the transfer electric field, and the toner image is transferred from the surface of the photosensitive drum 21 to the recording paper. The At this time, since the recording paper is charged and electrostatically attracted to the surface of the photosensitive drum 21, it is necessary to peel off the recording paper from the surface of the photosensitive drum 21 after the transfer. For this purpose, a peeling claw 61 is provided. ing.

  FIG. 3 is a plan view showing a peeling unit 62 having a plurality of peeling claws 61. As shown in FIG. 3, the peeling unit 62 rotatably supports a support shaft 63 parallel to the photosensitive drum 21, and a plurality of release claws 61 are fixedly supported on the support shaft 63 at intervals. A swing piece 64 is fixed to one end of 63, and the swing piece 64 is connected to a plunger of a solenoid 65.

  The tip of each peeling claw 61 is directed to the surface of the photosensitive drum 21 and contacts or slightly separates from the surface of the photosensitive drum 21 according to the position of the plunger of the solenoid 65.

  Normally, the tip of each peeling claw 61 is separated from the surface of the photosensitive drum 21, and the tip of each peeling claw 61 comes into contact with the surface of the photosensitive drum 21 at a timing when the leading edge of the recording paper passes the transfer unit 25. When the leading edge of the recording sheet is peeled off and the leading edge of the recording sheet is sufficiently peeled off, the leading edge of each peeling claw 61 is slightly separated from the surface of the photosensitive drum 21.

  Accordingly, each time the recording paper passes the transfer unit 25, each peeling claw 61 comes into contact with the surface of the photosensitive drum 21 and peels off the leading end portion of the recording paper.

  Since each peeling claw 61 generates heat by sliding contact with the surface of the photosensitive drum 21, a material excellent in heat resistance is preferable, and a material having conductivity is preferable in order to release the charged charge of the recording paper. For example, POM (polyacetal resin), polyimide, Duracon (registered trademark) and the like are preferable.

  However, every time the recording paper is peeled off from the surface of the photosensitive drum 21 by the peeling claw 61, the peeling claw 61 abuts on the surface of the photosensitive drum 21 or collides with the leading edge of the recording paper. In the meantime, the tip of the peeling claw 61 is chipped, and many scratches are generated at the tip of the peeling claw 61. Then, the scratches at the tip of the peeling claw 61 come into contact with the surface of the photosensitive drum 21, and the scratches on the surface of the photosensitive drum 21 cause the printing defects such as black stripes and white stripes on the recording paper. Will occur.

  When the photoconductor drum 21 is an organic photoconductor, scratches are easily generated on the surface layer, and scratches on the surface of the photoconductor drum 21 due to scratches at the tip of the peeling claw 61 are always generated.

  Further, the surface of the photosensitive drum 21 receives a history due to a temperature rise in the image forming apparatus and rubbing against each member arranged around the photosensitive drum 21 such as the developing unit 24, the cleaning blade 26A, and the charging unit 22. Then, the residual toner adhering to the surface of the photosensitive drum 21 is softened to cause a filming phenomenon in which a film-like state occurs, which leads to a decrease in print quality.

  Therefore, in this embodiment, attention is paid to the cleaning blade 26A of the cleaning unit 26 pressed against the surface of the photosensitive drum 21, and the scratch on the surface of the photosensitive drum 21 is smoothed using the cleaning blade 26A and the toner film is filled. Ming has been removed.

  The inventors set the rebound resilience, rubber hardness, and Young's modulus of the cleaning blade 26A appropriately to smooth the scratches on the surface of the photosensitive drum 21, and at the same time, the toner on the surface of the photosensitive drum 21 by the cleaning blade 26A. I found it possible to eliminate filming.

  Since the removal of the filming toner simultaneously removes the surface layer of the photosensitive drum 21, it is necessary to scrape the photosensitive drum 21 so as not to lower the sensitivity and shorten the life.

  The sensitivity reduction of the photosensitive drum 21 occurs when approximately 20 to 30% of the thickness (20 to 30 μm) of the surface layer of the photosensitive drum 21 is scraped. For this reason, if the maximum scraping amount of the surface layer of the photosensitive drum 21 is about 4 to 9 μm and the life of the photosensitive drum 21 is 1,000,000 prints (A4 lateral conveyance), the scraping amount per 100,000 sheets. 0.4 to 0.9 μm, and it is necessary to select the material of the cleaning blade 26 </ b> A that matches this amount of cutting and to set the pressure of the cleaning blade 26 </ b> A against the surface of the photosensitive drum 21.

  For example, if the hardness of the cleaning blade 26A is higher than the hardness of the conventional cleaning blade, the surface layer (including filming toner) of the photosensitive drum 21 can be appropriately scraped off by the cleaning blade 26A.

  The conventional cleaning blade is given sufficient elasticity and its tip is pressed against the surface of the photosensitive drum. For this reason, as shown in FIGS. 4A and 4B, with the rotational movement of the photosensitive drum 21, the tip of the conventional cleaning blade 201 is elastically deformed or returns to its original shape and vibrates repeatedly. However, the residual toner and paper dust on the surface of the photosensitive drum 21 are blown off by the tip of the vibrating cleaning blade 201. This vibration at the tip of the cleaning blade 201 is called a stick-slip phenomenon.

  In this embodiment, this phenomenon is eliminated without depending on such a stick-slip phenomenon. When the rebound resilience, rubber hardness, and Young's modulus of the cleaning blade 26A are appropriately set by selecting the material of the cleaning blade 26A, and the pressing force of the cleaning blade 26A against the surface of the photosensitive drum 21 is appropriately set, stick slip As shown in FIG. 5, the cleaning blade 26 </ b> A almost slidably contacts the surface of the photosensitive drum 21, and the cleaning blade 26 </ b> A appropriately scrapes the surface layer (including filming toner) of the photosensitive drum 21. The scratches on the surface of the photosensitive drum 21 are smoothed and repaired. At the same time, residual toner and paper dust on the surface of the photosensitive drum 21 can be removed by the cleaning blade 26A. Further, since the cleaning blade 26A is merely slidably brought into contact with the surface of the photosensitive drum 21, the toner does not scatter and contamination due to the toner scatter does not occur.

  Next, experiments on the rebound resilience, rubber hardness, and Young's modulus of the cleaning blade were performed, and the results of this experiment will be described.

  Prior to the experiment, it was confirmed beforehand by measurement that the depth of the scratch on the surface of the photosensitive drum 21 caused by a scratch at the tip of the peeling claw 61 (the height of the unevenness formed as a scratch) was 1 to 3 μm. Yes.

  Further, the cleaning blade is pressed against the surface of the photosensitive drum 21 with a predetermined pressure, and the surface layer is scraped off as appropriate, and the scratches on the surface of the photosensitive drum 21 are smoothed by the cleaning blade.

  Further, the photosensitive drum 21 is an organic photosensitive member. In addition, the conventional cleaning blade 201 and the cleaning blade 26A of this embodiment are of two types (one is represented by reference numeral 26A1 and the other is represented by reference numeral 26A2). The rebound resilience, rubber hardness, and Young's modulus of these cleaning blades are as shown in Table 1 below.

  The measuring instruments used for measuring the rubber properties of the cleaning blade are as follows. Moreover, the measuring method is based on JIS standard so that it may illustrate in FIG. 6 (a), (b).

Rebound resilience Rupke rebound resilience tester manufactured by Ueshima Seisakusho Hardness Tecock TYPE-A measuring instrument Young's modulus Autograph tester manufactured by Shimadzu Corp. Is set to 1.25N.

  The printing speed is set to 350 mm / sec (medium speed machine) and the conventional cleaning blade 201 is used for the printing process, and printing defects are detected every predetermined number of printed sheets (10,000 sheets). Determination, determination of contamination on the surface of the photosensitive drum 21, determination of the degree of abrasion of the surface of the photosensitive drum 21, and comprehensive determination were performed. Further, the same determination is performed under the three conditions that the process speed is set to 600 mm / sec (high speed machine) and the conventional cleaning blade 201 and the two types of cleaning blades 26A1 and 26A2 of the present embodiment are used. It was.

  The determination of printing failure is a visual determination of black stripes, white stripes, etc. on the recording paper caused by scratches at the tip of the peeling claw 61. The determination of the contamination on the surface of the photosensitive drum 21 is a visual determination of the degree of contamination. Determination of the degree of abrasion of the surface layer of the photosensitive drum 21 is based on the amount of abrasion by measurement, and it was determined that the smaller the amount of abrasion, the better. The results of such determination are as shown in Table 2 below.

  As apparent from Table 2 above, the process speed is low under the condition that the process speed is set to 350 mm / sec (medium speed machine) and the conventional cleaning blade 201 is used. However, the printing defect is not conspicuous, the degree of contamination on the surface of the photoconductive drum 21 is small, and the surface of the photoconductive drum 21 is well scraped.

  However, under the condition that the process speed was set to 600 mm / sec (high speed machine) and the conventional cleaning blade 201 was used, printing defects were conspicuous and the degree of contamination on the surface of the photosensitive drum 21 was large. Since the process speed is high, the rubber hardness of the conventional cleaning blade 201 is insufficient, and the tip of the blade is chipped due to reversal (twisting) of the blade tip and frictional heat between the blade tip and the surface of the photosensitive drum 21. This is probably because of this.

  Therefore, compared with the conventional cleaning blade 201, two types of cleaning blades 26A1 and 26A2 having a low rebound resilience, a high rubber hardness, and a high Young's modulus were applied.

  In the cleaning blade 26A1, there was almost no printing defect, the degree of contamination on the surface of the photoconductive drum 21 was generally small, and the degree of abrasion of the surface layer of the photoconductive drum 21 was generally good.

  In the cleaning blade 26A2, there was no printing defect, the degree of contamination on the surface of the photoconductive drum 21 was small, and the surface layer of the photoconductive drum 21 was also excellently scraped.

  Regarding printing defects such as black stripes or white stripes on the recording paper due to scratches at the tip of the peeling claw 61, the blade 26A2 is the best, the blade 26A1 is the next, and the conventional blade 201 is defective. Met.

  Regarding the contamination on the surface of the photosensitive drum 21, the blade 26A2 is the best, the blade 26A1 is the next, and the conventional blade 201 is the defective.

  Further, regarding the degree of abrasion of the surface layer of the photosensitive drum 21, the best blade (the smallest amount of abrasion) is the conventional blade 201, the next is the blade 26A2, and the next is the blade 26A1. More specifically, in the conventional blade 201 with the smallest amount of shaving, the amount of shaving is 0.4 μm (every 10,000 sheets), and in the blade 26A1 with the largest amount of shaving. The amount of scraping was 0.8 to 1.0 μm (every 10,000 sheets).

  However, since the amount of cutting for every 100,000 sheets must be 0.4 to 0.9 μm as described above, the amount of cutting by the conventional blade 201 is 0.4 μm, which is the lower limit.

  By comparing the result of such a degree of scraping with the characteristics of the blade in Table 1, it has been found that the degree of scraping of the surface layer of the photosensitive drum 21 depends greatly on the rubber hardness.

  Therefore, on the premise of a high-speed machine, the blade 26A2 is the best when comprehensively evaluated for defective printing (scratches at the tip of the peeling claw 61), contamination on the surface of the photosensitive drum 21, and the degree of abrasion of the surface layer of the photosensitive drum 21. The blade 26A1 is the next best, and the conventional blade 201 is the bad.

Further, in order to obtain a comprehensive result by comparing such comprehensive evaluation with the characteristics of the blade in Table 1, when the rebound resilience of the cleaning blade is X, the rebound resilience is 25 < If the Young's modulus of the cleaning blade is set to Y and the Young's modulus Y is set to 800 gf / mm ² or more and the hardness of the cleaning blade is Z, the hardness Z is set to 70 ° <Z <80. It was found that setting in the range of ° was preferable.

  On the other hand, FIG. 7A is a diagram showing a measurement of the depth of scratches on the surface of the photosensitive drum 21 when the conventional cleaning blade 201 is used.

  As shown in FIG. 7A, the scratches are deeper at the respective locations on the surface of the photosensitive drum 21 in contact with the peeling claws 61. FIG. 7B shows an enlarged scratch on the surface of the photosensitive drum 21 in contact with the peeling claw 61 in FIG. 7A, and FIG. 7C enlarges the scratch in FIG. 7B. This is shown schematically.

  When the conventional cleaning blade 201 is used, the amount of abrasion on the surface of the photosensitive drum 21 is too small, so that the scratches on the surface of the photosensitive drum 21 remain uneven as shown in FIG. 7C. . The electric field concentration at the concavo-convex convex portion is remarkable, the surface potential of the convex portion becomes abnormally high, and a discharge phenomenon occurs, resulting in a decrease in the surface potential at this portion, and excessive adhesion of toner to this portion. For this reason, black stripes, white stripes, etc. are likely to occur.

  FIG. 8A is a diagram showing a measurement of the depth of scratches on the surface of the photosensitive drum 21 when the cleaning blade 26A2 of this embodiment is used. As shown in FIG. 8A, the scratches are slightly deeper at the respective locations on the surface of the photosensitive drum 21 in contact with the peeling claws 61. 8B is an enlarged view of the scratch on the surface of the photosensitive drum 21 that contacts the peeling claw 61 in FIG. 8A, and FIG. 8C is an enlarged view of the scratch in FIG. 8B. This is shown schematically.

  As shown in FIG. 8C, the scratches on the surface of the photosensitive drum 21 are formed by scraping the concave and convex portions in FIG. 7C. This is because the concavo-convex convex portion was scraped off by the cleaning blade 26A2. Therefore, there are no convex portions that are likely to cause electric field concentration, and black streaks and white streaks do not occur.

  As apparent from these experiments, if the rebound resilience, Young's modulus, and hardness of the cleaning blade are set appropriately, the surface of the photosensitive drum 21 can be smoothed and substantially eliminated, and at the same time, The toner filming on the surface of the body drum 21 can be eliminated, and the cleaning performance of the high speed machine and the printing quality can be ensured.

  FIG. 9 is a plan view showing the peeling unit 62A in the second embodiment of the image forming apparatus of the present invention. Note that, in FIG. 9, the same reference numerals are given to portions that perform the same functions as those in FIG.

  The image forming apparatus according to the present embodiment has substantially the same configuration as that of the image forming apparatus 100 in FIG. 1 except that a peeling unit 62 </ b> A serving as a substitute for the peeling unit 62 is arranged around the photosensitive drum 21.

  Similar to the peeling unit 62 in FIG. 3, the peeling unit 62 </ b> A not only has a plurality of peeling claws 61, a support shaft 63, a swing piece 64, and a solenoid 65, but also includes a right end of the support shaft 63 (on FIG. The eccentric cam 66 that contacts the right end), the spring 67 that presses against the left end of the support shaft 63 (the left end in FIG. 9), and biases the support shaft 63 in the right direction, and the rotational drive that drives the eccentric cam 66 to rotate. A source 68 and a control unit 69 for driving and controlling the rotation drive source 68 are provided.

  The support shaft 63 is supported not only to be rotatable but also to be slidable in the longitudinal direction of the support shaft 63 (the axial direction of the photosensitive drum 21). The support shaft 63 is urged rightward by the spring 67, and the right end of the support shaft 63 is in contact with the circumferential surface of the eccentric cam 66. When the eccentric cam 66 is rotated by the rotational drive source 68 and the position of the circumferential surface of the eccentric cam 66 that contacts the right end of the support shaft 63 changes, the support shaft 63 moves in the longitudinal direction of the support shaft 63. Accordingly, the position of each peeling claw 61 fixed to the support shaft 63 also moves in the longitudinal direction, and the contact position of each peeling claw 61 with respect to the surface of the photosensitive drum 21 is changed.

  As shown in FIG. 10, the eccentric cam 66 is brought into contact with the right end of the support shaft 63 at any one of the three peripheral surface positions P1, P2, and P3. The circumferential surface position P1 is closest to the shaft 66a of the eccentric cam 66, the circumferential surface position P2 is slightly separated from the shaft 66a of the eccentric cam 66, and the circumferential surface position P3 is farthest from the shaft 66a of the eccentric cam 66. Therefore, in a state where the right end of the support shaft 63 is in contact with the circumferential surface position P 1 of the eccentric cam 66, the support shaft 63 is positioned at the rightmost position, and the right end of the support shaft 63 is positioned around the eccentric cam 66. In the state of contact with the surface position P 2, the support shaft 63 is moved and positioned slightly to the left, and when the right end of the support shaft 63 is in contact with the circumferential surface position P 3 of the eccentric cam 66, the support shaft 63 is It is positioned at the leftmost position. Along with the movement of the support shaft 63, each peeling claw 61 is also moved to the most right position P11, the slightly left position P12, and the most left position P13 as shown in FIG. The contact position of each peeling claw 61 with respect to the 21 surface is changed.

  As a result, it is possible to prevent deep scratches from being formed at specific locations on the surface of the photosensitive drum 21, and to minimize the amount of the photoconductive layer that is scraped off to smooth the surface of the photosensitive drum 21. The performance of the photoconductive layer can be maintained.

  In the present embodiment, the rotation drive source 68 is driven and controlled by the control unit 69, and the eccentric cam 66 is rotationally driven by the rotation drive source 68 to change the contact position of each peeling claw 61 with respect to the surface of the photosensitive drum 21. . The control unit 69 changes the contact position of each peeling claw 61 with respect to the surface of the photosensitive drum 21 in accordance with the number of sheets processed by the image forming apparatus. Further, the control unit 69 not only controls the rotation drive source 68 but also serves to control the entire image forming apparatus 100 as a whole.

  Next, a procedure for changing the contact position of each peeling claw 61 according to the number of print processing sheets will be described with reference to the flowchart of FIG.

  First, when a print request is made by operating an operation panel (not shown) of the image forming apparatus 100 (step S101), the print request is notified to the control unit 69. Upon receiving this print request, the control unit 69 waits until all the print conditions such as the print magnification, the number of print requests, and the print density are input (“No” in step S102), and all the print conditions are input. Then (“Yes” in step S102), which of the peripheral surface positions P1, P2, and P3 of the eccentric cam 66 is in contact with the right end of the support shaft 63, that is, each peeling from the surface of the photosensitive drum 21. The contact position of the nail 61 is confirmed, and the print processing sheet integrated value A is read from the memory 69a and confirmed (step S103).

  To confirm the position of the circumferential surface of the eccentric cam 66 that is in contact with the right end of the support shaft 63, the rotational angle of the eccentric cam 66 may be detected, and the rotational angle of the motor of the rotational drive source 68 is detected or controlled. Thus, the rotation angle of the eccentric cam 66 can be detected. Further, the print processing sheet number integrated value A is integrated until reaching a prescribed number B, which will be described later, and is reset to 0 when the prescribed number B is reached.

  Subsequently, the control unit 69 compares the print process number integrated value A read from the memory 69a with the specified number B (step S104), and determines whether the print process number integrated value A is less than the specified number B, that is, prints. It is determined whether or not the processed number integrated value A has reached the specified number B (step S105).

  For example, if the print processing number integrated value A is less than the specified number B (“Yes” in step S105), that is, if the print processing number integrated value A has not reached the specified number B, the control unit 69 performs step S101. , 102 is executed according to the print request and print conditions (step S106), and an image is printed on at least one recording sheet. Then, the control unit 69 confirms whether or not all of the requested printing processes have been completed (step S107). If not completed ("Yes" in step S107), the printing process of step S106 is continued. .

  Further, when all the requested printing processes are completed (“No” in step S107), the control unit 69 obtains the number of printed sheets processed in step S106, and this number of printed sheets is calculated as an integrated value A for the number of printed sheets. In addition, the print processing number integrated value A is updated, and the print processing number integrated value A in the memory 69a is also rewritten and updated (step S108).

  Thereafter, the control unit 69 determines whether or not the updated print processing number integrated value A is less than the specified number B, that is, whether or not the updated print processing number integrated value A has reached the specified number B ( Step S109).

  If the print processing number integrated value A is less than the specified number B (“Yes” in step S109), that is, if the print processing number integrated value A has not reached the specified number B, the control unit 69 performs image formation. When the apparatus 100 is placed in a standby state and there is a next new print request, the processing from step S101 is repeated.

  On the other hand, if the control unit 69 determines that the print processing sheet integrated value A has reached the specified number B before executing the printing process in step S106 ("No" in step S105), the surface of the photosensitive drum 21 is determined. (Step S110), the rotational drive source 68 is driven and controlled to rotate the eccentric cam 66, and each peeling claw 61 with respect to the surface of the photosensitive drum 21 is considered. The contact position is changed (step S111). At this time, if each peeling claw 61 is located at the most right position P11, it is moved to a slightly left position P12, and if each peeling claw 61 is located at a slightly left position P12, it is moved to the most left position P13. If each peeling claw 61 is at the leftmost position P13, it is moved to the rightmost position P11. Therefore, each peeling claw 61 is sequentially cyclically moved to each position P11, P12, P13.

  When the contact position of each peeling claw 61 is changed (“Yes” in step S112), the control unit 69 resets the print processing sheet integrated value A in the memory 69a to 0 and initializes it (step S113). Then, after step S106, the printing process is executed.

  Further, when it is determined that the print processing number integrated value A has reached the specified number B after the print processing in step S106 is executed and the print processing number integrated value A is updated (in step S109). “No”), it is considered that it is time to change the contact position of each peeling claw 61 (step S114), the rotation drive source 68 is driven and controlled, the eccentric cam 66 is rotated, and the contact of each peeling claw 61 is reached. The position is changed (step S115). Also at this time, each peeling claw 61 is moved in any of position P11 → position P12, position P12 → position P13, position P13 → position P11. When the contact position of each peeling claw 61 is changed (“Yes” in step S116), the print processing sheet integrated value A in the memory 69a is reset to 0 and initialized (step S117). And it will be in a standby state.

  Thus, before and after the printing process, it is confirmed whether or not the print processing sheet integrated value A has reached the prescribed number B. If the prescribed number B has been reached, the contact position of each peeling claw 61 is changed. Since the process is performed immediately, the contact position of each peeling claw 61 can be changed without significantly deviating from the timing when the print processing sheet integrated value A reaches the specified number B.

  Here, considering the depth of scratches on the surface of the photosensitive drum 21 due to the contact of each peeling claw 61, each peeling claw 61 makes a round of the positions P11, P12, and P13 every 5,000 to 10,000 sheets. It is preferable to do so. For this purpose, the prescribed number of sheets B may be set to 2,000 to 5,000 sheets, and each time the print processing sheet integrated value A reaches 2,000 to 5,000 sheets, Each time the contact position 61 is sequentially changed and the total number of sheets to be printed increases by about 5,000 to 10,000, each peeling claw 61 goes through the positions P11, P12, and P13. As a result, in each of the positions P11, P12, and P13 of the photosensitive drum 21, the period during which the peeling claw 61 contacts the surface of the photosensitive drum 21 is shortened, and the surface of the photosensitive drum 21 is damaged due to the contact of the peeling claw 61. The depth of the surface of the photoconductive drum 21 is reduced, and the amount of abrasion of the photoconductive layer of the photoconductive drum 21 by the cleaning blade 26A for uniformly smoothing the entire surface of the photoconductive drum 21 can be suppressed. Can be prevented, and the printing quality can be kept high.

  When the peeling claw keeps in contact with a specific portion of the photosensitive drum 21, a deep scratch is formed at the specific portion of the photosensitive drum 21. If the deep scratches are sharply removed, cracks or the like are likely to occur in the photoconductive layer of the photosensitive drum 21 and the print quality may be significantly impaired.

  In this embodiment, since each peeling claw 61 is cyclically moved sequentially to each position P11, P12, P13, the depth of scratches at each position is shallow, and each peeling claw 61 is located at each position P11, P12. The entire surface of the photoconductive drum 21 can be uniformly smoothed by slightly scraping the photoconductive layer of the photoconductive drum 21 with the cleaning blade 26A during one cycle of P13.

  In addition, this invention is not limited to the said embodiment, It can deform | transform variously. For example, the setting ranges of the rebound resilience X, Young's modulus Y, and hardness Z of the cleaning blade are obtained after defining the diameter of the photosensitive drum 21, the pressure contact pressure of the cleaning blade, the process speed, and the like. So, when these specified values change, they should be changed. In short, the rebound resilience X of the cleaning blade is made lower than before, the Young's modulus Y is made higher, the hardness Z is made higher, and the tip of the cleaning blade is always in sliding contact with the surface of the photosensitive drum. Thus, the scratches formed on the surface of the photoreceptor may be smoothed.

  The present invention can be applied not only to an organic photoreceptor but also to an amorphous silicon photoreceptor.

1 is a cross-sectional view showing an embodiment of an image forming apparatus of the present invention. FIG. 2 is an enlarged side view showing the periphery of a photosensitive drum in the image forming apparatus of FIG. 1. FIG. 2 is a plan view showing a peeling unit in the image forming apparatus of FIG. 1. (A), (b) is a figure which shows the stick slip phenomenon by the conventional cleaning blade. FIG. 2 is a diagram illustrating a sliding contact state of a cleaning blade in the image forming apparatus of FIG. 1. (A), (b) is a figure which illustrates the measuring method of the rubber characteristic of a cleaning blade. (A) is a figure which measures and shows the depth of the damage | wound on the surface of the conventional photoconductor drum, (b) is a figure which expands and shows a damage | wound, (c) is an enlarged figure of a damage | wound, and is shown typically. FIG. (A) is a figure which measures and shows the depth of the damage | wound of the photoreceptor drum surface in the image forming apparatus of FIG. 1, (b) is a figure which expands and shows a damage | wound, (c) is an enlarged view of a damage | wound. FIG. It is a top view which shows the peeling unit in 2nd Embodiment of the image forming apparatus of this invention. It is a side view which expands and shows the eccentric cam in the peeling unit of FIG. It is a flowchart which shows the change process procedure of the contact position of each peeling nail | claw in the peeling unit of FIG.

Explanation of symbols

21 Photosensitive drum 22 Charger 23 Optical writing unit 24 Developer 25 Transfer unit 26 Cleaning unit 26A Cleaning blade 27 Fixing unit 35 Heating roller 36 Pressure roller 41 Conveying roller 42 Registration roller 61 Peeling claw 100 Image forming apparatus 101 Document paper conveyance Unit 102 image reading unit 103 printing unit 104 recording paper transport unit 105 paper feeding unit

Claims (11)

The electrostatic latent image on the surface of the photoconductor is developed to form a visible image on the surface of the photoconductor, the visible image is transferred from the surface of the photoconductor to the recording paper, and the recording paper is peeled off from the surface of the photoconductor with a peeling claw. In an image forming apparatus that cleans the surface of the photoreceptor with a cleaning blade,
The image forming apparatus, wherein the cleaning blade is in sliding contact with the surface of the photosensitive member and smoothes a scratch formed on the surface of the photosensitive member by contact of the peeling claw. The scratches on the surface of the photoconductor are irregularities formed on the surface of the photoconductor,
The image forming apparatus according to claim 1, wherein the cleaning blade scrapes off the uneven portions on the surface of the photoreceptor.   The image forming apparatus according to claim 1, wherein the cleaning blade is a rubber member having a low rebound resilience, a high Young's modulus, and a high hardness.   The image forming apparatus according to claim 1, wherein the sliding contact of the cleaning blade with the surface of the photosensitive member is continuously performed without interruption.   2. The image forming apparatus according to claim 1, wherein the rebound resilience is set in a range of 25 <X <35, where X is the rebound resilience of the cleaning blade. ^2. The image forming apparatus according to claim 1, wherein the Young's modulus Y is set to 800 gf / mm ² or more, where Y is the Young's modulus of the cleaning blade.   2. The image forming apparatus according to claim 1, wherein the hardness Z of the cleaning blade is set in a range of 70 [deg.] <Z <80 [deg.].   The image forming apparatus according to claim 1, wherein a process speed of the image forming apparatus is 500 mm / sec or more.   The image forming apparatus according to claim 1, wherein the photoconductor is an organic photoconductor. It is possible to change the contact position of the peeling claw with respect to the photoconductor surface by moving the peeling claw in a direction perpendicular to the moving direction of the photoconductor surface with respect to the photoconductor surface,
2. The image forming apparatus according to claim 1, wherein the contact position of the peeling claw with respect to the surface of the photosensitive member is changed in accordance with the number of sheets processed by the image forming apparatus. The peeling claw is sequentially moved so as to contact at any of a plurality of contact positions with respect to the surface of the photoreceptor
11. The cleaning blade smoothes the scratches formed on the surface of the photosensitive member by the peeling claw while the peeling claw makes at least one round of the contact positions. The image forming apparatus described in 1.

Images