JP2019095645A - Image formation device - Google Patents

Abstract

To elongate a product life of a photoreceptor more than a conventional photoreceptor.SOLUTION: An image formation device which has a photoreceptor carrying a latent image and forms an image corresponding to the latent image has: a print head that has a wavelength variable light source emitting a light beam, and irradiates the photoreceptor with the light beam so as to partially neutralize a surface of the photoreceptor in accordance with the latent image; and a control unit that controls a wavelength λ and amount of light U of the light beam in accordance with progress states A, B and C of wear-out of the photoreceptor. The control unit is configured to: conduct control in accordance with the progress state of the wear-out of the photoreceptor indicated by, for example, film thickness information; change the wavelength of the light beam so that sensitivity of the photoreceptor increases as the wear-out of the photoreceptor progresses; and adjust the amount of light of the light beam so that a neutralized region corresponding to a spot of the light beam in the photoreceptor becomes a prescribed size.SELECTED DRAWING: Figure 11

Description

  The present invention relates to an image forming apparatus.

  The electrophotographic image forming apparatus uniformly charges the circumferential surface of a cylindrical photosensitive member, performs light irradiation (pattern exposure) according to image data while the photosensitive member is rotating stably. To partially erase the charge on the peripheral surface to form a latent image (electrostatic latent image). Then, toner is attached to the circumferential surface of the photosensitive member to visualize the latent image as a toner image, and the toner image is transferred to the sheet to form an image on the sheet.

  The use of the image forming device causes the photoreceptor to wear gradually. As an effect thereof, there is a phenomenon that the charge removal region for one dot where the charge in the pattern exposure disappears becomes narrower as the film thickness of the surface layer portion of the photosensitive member decreases. If the charge removal area is narrowed, the quality of the image is degraded. For example, in image formation by reversal development in which toner is attached to the static elimination area, the entire image becomes pale, characters or thin lines are blurred, and color reproducibility is deteriorated.

  As a prior art for suppressing that a static elimination area | region becomes narrow, there exists a technique of patent document 1, two.

  Patent Document 1 discloses that the light quantity of exposure by laser light is controlled based on information such as the number of image formations related to the film thickness of the photosensitive member.

  In Patent Document 2, an exposure unit is configured to be capable of overlappingly irradiating the first laser beam and the second laser beam having different wavelengths and spot sizes, and both of them are formed depending on the number of image formations or the cumulative exposure time. It is disclosed to change the ratio of the light amount of the laser light.

  Further, as a prior art for reducing an image defect caused by a change with time of a photosensitive member, there is a technique described in Patent Document 3. In Patent Document 3, in an image forming apparatus in which light is discharged to a photosensitive member after transferring a toner image, the wavelength of light to be irradiated for discharging after transfer is changed according to the ambient temperature of the photosensitive member. It is disclosed that.

  As other prior art related to light irradiation for forming a latent image, there are techniques described in Patent Documents 4 and 5.

  According to Patent Document 4, in an image forming apparatus which performs light irradiation of a method of deflecting a laser beam using a polygon mirror, a wavelength is different from that of a laser beam for forming a latent image in order to determine a writing start position of the latent image. It is disclosed to provide a laser emitting means for emitting laser light.

  Patent Document 5 has a plurality of laser light sources having different oscillation wavelengths, forms a multi-gradation image using a laser light source having a long oscillation wavelength, and forms a character image using a laser light source having a short oscillation wavelength. An image forming apparatus is disclosed.

Unexamined-Japanese-Patent No. 2002-296853 Unexamined-Japanese-Patent No. 2008-281964 JP, 2005-208223, A Unexamined-Japanese-Patent No. 2004-122442 Unexamined-Japanese-Patent No. 08-164634 gazette

  There is a demand for reduction of CPP (Cost Per Page) for an image forming apparatus, and for the photosensitive member which is one of the consumable parts, the extension of the life is required. Here, the life of the photosensitive member is a period in which an image of appropriate image quality can be formed.

  Wear of the photoreceptor is inevitable. In particular, in the case of adopting a method in which the charging roller is in contact, the surface of the photosensitive member is charged while being scraped due to the deterioration of the photosensitive member due to the discharge.

  It is conceivable to form a thick photosensitive member for prolonging the life. However, the control of the irradiation light is related to the life of the photosensitive member, and the life can not be extended only by thickening the photosensitive member.

  For example, when controlling the amount of laser light as in the technique of Patent Document 1 described above, the amount of light is set just before the lower limit value at which laser light emission switches to LED light emission at the initial stage of new photoreceptor. As the film thickness decreases, the light quantity is increased. In this case, assuming that the initial film thickness is made thicker than in the prior art, at the initial stage, the charge removal region where the charge is lost due to the irradiation of the laser light becomes too large to obtain a desired resolution. And even if this static elimination area is narrowed, the light quantity is already the lower limit value and can not be further reduced. That is, the desired image quality can not be obtained until the film thickness decreases to the conventional initial film thickness. Therefore, a photosensitive member thicker than the conventional one is not suitable for practical use.

  In the method of overlapping and irradiating the first laser beam and the second laser beam as in the technique of Patent Document 2, it is difficult to overlap a plurality of light beams with a desired accuracy, and one photosensitive There is a problem that the optical system becomes complicated by providing a plurality of laser light sources to the body.

  The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to make the life of a photosensitive member longer than before.

  An image forming apparatus according to an embodiment of the present invention is an image forming apparatus having a photosensitive member carrying a latent image and forming an image corresponding to the latent image, wherein a wavelength variable light source emitting a light beam is used. Print head that emits the light beam to partially discharge the surface of the photosensitive member according to the latent image, and the progress of wear of the photosensitive member indicated by film thickness information and the like. And a control unit configured to control the wavelength and the light amount of the light beam.

  According to the present invention, the allowable range of reduction in the film thickness of the photosensitive member can be expanded as compared with the conventional case, and the initial film thickness can be made larger than in the conventional case to extend the life of the photosensitive member.

FIG. 1 is a diagram showing an outline of a configuration of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the structure of the imaging unit which has a photoreceptor. It is a figure showing composition of a print head. It is a figure which shows the example of a laser light source. FIG. 2 is a diagram showing a configuration of main parts related to control of the image forming apparatus. FIG. 6 is a diagram showing an example of spectral sensitivity characteristics of a photosensitive member. It is a figure which shows typically the example of a layer structure of a photoreceptor, and the change of the state of the photoreceptor by irradiation of a laser beam. FIG. 4 is a view schematically showing the relationship between the sensitivity of the photosensitive member and the size of the exposure area, and the relationship between the laser light amount and the size X of the exposure area. It is a figure which shows typically the relationship between the film thickness of a photoreceptor, the wavelength of a laser beam, and the magnitude | size of static elimination area | region. It is a figure which shows the example of the setting table of the 1st example of a wavelength shift, and the temperature correction table of a diffraction grating position. It is a figure which shows the 1st example of wavelength shift, and the example of light quantity control corresponding to it. It is a figure which shows the setting table of the 2nd example of a wavelength shift. It is a figure which shows the 2nd example of wavelength shift, and the example of light quantity control corresponding to it. It is a figure which shows the setting table of the 3rd example of a wavelength shift. It is a figure which shows the example of a stage change table, and the example of a simultaneous shift limit table. FIG. 2 is a diagram showing a flow of processing in the image forming apparatus 1; It is a figure which shows the flow of an image stabilization process. It is a figure which shows the 1st example of the flow of the wavelength shift necessity determination process in an image stabilization process. It is a figure which shows the 2nd example of the flow of wavelength shift necessity determination processing. It is a figure which shows the 1st example of the flow of the wavelength shift process in an image stabilization process. It is a figure which shows the 2nd example of the flow of a wavelength shift process. It is a figure which shows the 1st example of the flow of shift direction determination processing in wavelength shift processing. It is a figure which shows the 2nd example of the flow of shift direction determination processing.

  FIG. 1 shows an outline of the configuration of an image forming apparatus according to an embodiment of the present invention, and FIG. 2 shows the configuration of an imaging unit 3 having a photosensitive member 4.

  An image forming apparatus 1 illustrated in FIG. 1 is an MFP (Multi-functional Peripheral: multi-function device or multifunction device) in which functions such as a copier, a printer, a facsimile machine, and an image reader are integrated. The image forming apparatus 1 includes an automatic document feeder (ADF: Auto Document Feeder) 1A, a flatbed scanner 1B, a printer unit 1C, and a paper feeding unit 1D.

  The automatic document feeder 1A conveys a document (sheet) set in a document tray to a reading position of the scanner 1B. The scanner 1B reads an image from a sheet-like document conveyed from the automatic document feeder 1A or various documents set on a platen glass to generate image data.

  The printer unit 1C forms a color or monochrome image on one side or both sides of a sheet (recording sheet) P in print jobs such as copying, network printing (PC printing), facsimile reception, and box printing. For example, in a copy job, an image is formed based on the image data generated by the scanner 1B.

  The printer unit 1 </ b> C includes an electrophotographic tandem printer engine 2. The printer engine 2 has four imaging units 3y, 3m, 3c, 3k, a print head 6, an intermediate transfer belt 10, and the like.

  The imaging units 3y to 3k each have devices such as cylindrical photosensitive body 4, charging roller 5, developing device 7, cleaner 8 and cleaning roller 9, and memory (not shown) for storing individual information of photosensitive body 4 and the like. . Since the basic configurations of the imaging units 3y to 3k are the same, they may be hereinafter referred to as "imaging unit 3" without distinction.

  The print head 6 emits a laser beam LB as light for performing pattern exposure to each of the imaging units 3 y to 3 k. The laser beam LB is a so-called Gaussian beam whose radiation intensity exhibits a Gaussian distribution approximately.

  The intermediate transfer belt 10 is a transfer member in primary transfer of a toner image. The intermediate transfer belt 10 is wound and rotated between a pair of rollers. Inside the intermediate transfer belt 10, primary transfer rollers 11 are disposed for each of the imaging units 3y, 3m, 3c and 3k.

  The sheet feeding unit 1D has a plurality of sheet feeding cassettes 12a, 12b, and 12c, takes out the sheet P from any of the selected sheet feeding cassettes, and supplies the sheet P to the upper printer unit 1C.

  In the color printing mode, the imaging units 3y to 3k form four color toner images of Y (yellow), M (magenta), C (cyan), and K (black) in parallel. The four color toner images are sequentially primarily transferred to the rotating intermediate transfer belt 10. First, the toner image of Y is transferred, and the toner image of M, the toner image of C, and the toner image of K are sequentially transferred so as to be superimposed thereon.

  When the primary transfer toner image faces the secondary transfer roller 16, the secondary transfer is performed on the sheet P conveyed from the sheet feeding unit 1D via the timing roller 15. Thereafter, the sheet P is discharged by the separating member 18 and is fed to the sheet discharge tray 19 through the inside of the fixing unit 17. When passing through the fixing device 17, the toner image is fixed to the sheet P by heating and pressing. In the case where the finisher is connected to the image forming apparatus 1, the sheet P is carried into a communication path provided instead of the sheet discharge tray 19 and sent to the finisher.

  In FIG. 2, the photosensitive member 4 rotates in one direction integrally with a drum as a support. The charging roller 5 is a contact type charging member, and charges the circumferential surface of the photosensitive member 4 while contacting and rotating the photosensitive member 4. By performing pattern exposure on the uniformly charged portion of the peripheral surface of the photosensitive member 4 based on the image data, it is possible to form a latent image of the image to be printed. At the time of pattern exposure, that is, formation of a latent image, in the print head 6, main scanning for deflecting the laser beam LB in the rotational axis direction of the photosensitive member 4 is performed. Further, sub-scanning is performed to rotate the photosensitive member 4 at a constant speed.

  The developing unit 7 causes toner to adhere to the circumferential surface of the photosensitive member and visualizes the latent image as a toner image. The developing device 7 is charged, for example, by mixing and stirring the toner with the carrier. Then, the charged toner is supplied to a developing position in proximity to the photosensitive member 4.

  The cleaner 8 removes residual toner and charge from the circumferential surface of the photosensitive roller 4 after the primary transfer of the toner image. The method is, for example, a blade cleaning method.

  The cleaning roller 9 is a cleaning member that cleans the charging roller 5. The cleaning roller 9 removes toner and other foreign matter from the circumferential surface of the charging roller 5 while contacting and rotating the charging roller 5.

  In the vicinity of the intermediate transfer belt 10, a density sensor 21 is provided which outputs a signal according to the brightness of the transfer surface having passed through the primary transfer position. As a result, based on the output of the density sensor 21 when the toner image passes, it is possible to measure the density of the image, the amount of toner adhesion on the base portion, and the like.

  When forming an image, the charging roller 5 is biased to a negative potential by a high voltage power supply circuit, and a negative charge is applied to the surface of the photosensitive member 4 in contact with the charging roller 5. At the same time, the developing device 7 is also biased to a negative potential, and the toner in the developing device 7 is negatively charged. The output of the high voltage power supply circuit is adjusted so that the surface of the photosensitive member 4 and the toner have the same potential.

  Now, the image forming apparatus 1 has a function of enabling the mounting of the photosensitive member 4 thicker than the conventional one. Hereinafter, the configuration and operation of the image forming apparatus 1 will be described focusing on this function.

  The configuration of the print head 6 is shown in FIG. Specifically, FIG. 3 (A) shows the configuration seen from the front side, FIG. 3 (B) shows the configuration seen from above, and FIG. 3 (C) shows the configuration of the light source unit 60. There is. Further, FIG. 4 shows an example of the laser light source 61.

  As shown in FIGS. 3A and 3B, the print head 6 includes a light source unit 60, a polygon mirror 65, a polygon motor 66, an fθ lens 67, reflection mirrors 68 to 76, and an optical sensor 77.

  The light source unit 60 is means for emitting a single laser beam LB for exposure according to the latent image to each of the four photosensitive members 4 provided one by one in the imaging units 3y to 3k. . In color printing, a total of four laser beams LBy, LBm, LBc, LBk corresponding to the respective colors Y, M, C, K are emitted from the light source unit 60.

  The reflection mirror 68 guides the laser beam LB emitted from the light source unit 60 to the polygon mirror 65. The polygon mirror 65 is rotated at high speed by the polygon motor 66 to deflect the laser beam LB in the main scanning direction. The fθ lens 67 corrects the traveling direction of the angularly deflected laser beam LB so that the main scanning at an equal speed is performed on the photosensitive member 4.

  The laser beam LB that has passed through the fθ lens 67 is guided to the photosensitive members 4 of the imaging units 3 y to 3 k by the reflection mirrors 69 to 75, and illuminates the surface of the photosensitive members 4.

  Further, the laser beam LB is guided to the light sensor 77 by the reflection mirror 76 disposed outside the optical path corresponding to the formation area of the latent image. The detection signal of the laser beam LB by the optical sensor 77 is used as a SOS (Start of Scan) signal for synchronization of the main scan.

  As shown in FIG. 3C, the light source unit 60 includes laser light sources 61y, 61m, 61c and 61k, collimator lens units 63y, 63m, 63c and 63k, and reflection mirror units 64y, 64m, 64c and 64k. That is, four laser light sources, four collimator lens units, and four reflection mirrors are provided to correspond to the imaging units 3y to 3k.

  Hereinafter, the laser light sources 61 y to 61 k may be referred to as “laser light sources 61” without distinction. Similarly, the collimator lens units 63y to 63k may be described as "collimator lens units 63", and the reflection mirrors 64y to 64k may be described as "reflection mirror 64".

  The laser light source 61 is a light emitting device capable of changing the wavelength of the laser light to be emitted. The configuration will be described later.

  The collimator lens unit 63 includes a collimator lens 631 and a lens moving mechanism 632. The lens moving mechanism 632 can finely move the collimator lens 631 back and forth in the optical axis direction.

  The reflection mirror unit 64 includes a reflection mirror 641 and a mirror moving mechanism 642. The mirror moving mechanism 642 can minutely rotate the reflecting mirror 641 in two directions so that the in / out angle of the laser beam LB changes.

  In the light source unit 60 of the present embodiment, an optical path correction mechanism 62 is configured by the lens moving mechanism 632 and the mirror moving mechanism 642. The optical path correction mechanism 62 is provided to correct a subtle deviation of the irradiation position on the photosensitive member 4 due to the change of the wavelength or the change of the environmental temperature. The optical path correction mechanism 62 is controlled to move the collimator lens 631 with respect to the reference position, for example, in ± 5 steps, and to change the angular position of the reflection mirror 641 in, for example, ± 5 steps with respect to the reference position.

  The laser beam (non-collimated beam) Lb emitted by the laser light source 61 is collimated (collimated) by the collimator lens 631 to become a laser beam LB. The laser beam LB is reflected at the reflection mirror 641 toward the reflection mirror 68. The four reflection mirrors 641 are arranged with a step between them so that each of them is out of the optical path of the other reflection mirror 641. However, a half mirror may be used as the reflection mirror 641 and the four reflection mirrors 641 may be disposed without providing a step.

  In FIG. 4A, a laser light source 61 a has a semiconductor laser 611 and a diffraction grating (grating) 612 disposed outside the semiconductor laser 611. The semiconductor laser 611 emits a laser beam Lb having a light quantity (light intensity energy) according to the magnitude of the light emission drive current supplied from the drive circuit.

  The diffraction grating 612 is variably supported at an angle with respect to the optical waveguide of the semiconductor laser 611. The laser light source 61 a is configured to change the wavelength λ of the laser light Lb emitted from the semiconductor laser 611 by displacing the diffraction grating 612 using a MEMS (Micro Electro Mechanical System) technology. Assuming that the angular position of the diffraction grating 612 at which the wavelength λ is a predetermined reference wavelength λs is 0, the right rotation is +, and the left rotation is-, for example, displacement of about ± 10 steps is possible.

  In FIG. 4B, the laser light source 61 b includes a semiconductor laser 613 that emits laser light of a wavelength according to the refractive index control current. The semiconductor laser 613 has an optical waveguide 614 for light emission, and an optical waveguide 615 in which a diffraction grating for wavelength change is built. Laser light Lb having a light quantity corresponding to the magnitude of the drive current for light emission is emitted from the optical waveguide 614. The wavelength of the laser light Lb is changed by increasing or decreasing the refractive index control current flowing through the optical waveguide 615. With regard to the refractive index control current, it is possible to perform control of, for example, about ± 10 steps by setting the value of the wavelength λ to be the reference wavelength λs to 0, increasing + and decreasing −.

  FIG. 5 shows the configuration of the main parts related to the control of the image forming apparatus 1.

  The image forming apparatus 1 includes a main control unit 100 that controls the overall operation of the image forming apparatus 1, an engine control unit 120 that is responsible for control of the printer engine 2, and a PH control unit 160 that is responsible for control of the print head 6. The control units 100, 120, and 160 each include a processor that executes a control program and its peripheral devices (ROM, RAM, etc.).

  Main control unit 100 receives a job input by a user operation using operation panel 1E or by network communication, and controls the execution of the job. For example, in a copy job, the engine control unit 130 and the PH control unit 160 are instructed to prepare for image formation, and the scanner 1 B and the image processing unit 150 are controlled to give a print data signal S 6 to the PH control unit 160. The print data signal S6 is a signal that is the basis of laser emission control for pattern exposure when forming a latent image.

  The engine control unit 120 controls the drive circuit 32 of the motor group 30 that rotates various rotating bodies including the photosensitive member 4 and the intermediate transfer belt 10, and the high voltage power supply circuit 35 that outputs high voltage power necessary for the electrophotographic process. Output a control signal. Further, the detection signal S21 from the density sensor 21 is quantized and input to the main control unit 100 as density detection data D21.

  The PH control unit 160 outputs control signals to drive circuits of the laser light source 61, the diffraction grating drive source 610, the lens motor 630, and the mirror motor 640, and to the drive circuit 660 of the polygon motor 66. For example, the drive circuit of the laser light source 31 corresponding to each of the four colors (Y, M, C, K) is supplied with a light emission control signal S61 for interrupting laser light emission according to the print data signal S6 of each color.

  The diffraction grating drive source 610 is a diffraction grating motor for displacing the diffraction grating 612 when using the laser light source 61a of FIG. 4A, and when using the laser light source 61b of FIG. 4B. Is a power supply circuit for supplying a refractive index control current to the optical waveguide 615.

  The lens motor 630 is a motor provided in the collimator lens unit 63 to move the collimator lens 631. The mirror motor 640 is a motor provided in the reflection mirror unit 64 to rotate the reflection mirror 641.

  In addition, a temperature detection signal S78 is input to the PH control unit 160 from a temperature sensor 78 which is provided in the vicinity of or inside the light source unit 60 and detects the temperature around the laser light source 61.

  The PH control unit 160 acquires the machine state information D1 from the main control unit 100. The machine state information D1 is information indicating the operation mode, status, and condition of each part of the image forming apparatus 1, and includes film thickness information D4 indicating the progress of wear of the photosensitive member 4. The PH control unit 160 controls the light source unit 60 to emit the laser beam LB of the wavelength λ corresponding to the film thickness information D4 or the temperature detection signal S78. A storage unit 165 for storing a setting table and the like used for this control is provided in the PH control unit 160.

  An example of the spectral sensitivity characteristic of the photosensitive member 4 is shown in FIG. In FIG. 6, spectral sensitivity characteristics are shown in the initial stage when the photosensitive member 4 is new, when the photosensitive member 4 is worn to the standard film thickness Hs, and when the photosensitive member 4 is worn to a film thickness of 80%. It is shown collectively.

  The standard film thickness Hs corresponds to the spot of the laser beam LB on the surface of the photosensitive member 4 when the laser beam LB is irradiated with the wavelength λ of 780 nm determined to be the reference wavelength λs and the light amount U being the lower limit. Then, the film thickness is such that the charge removal area where the charge is lost becomes an appropriate size in image quality.

  Further, the film thickness having a life of 80% means the wear amount up to the present (initial value and the film thickness at that time with respect to the maximum allowable wear amount of the photosensitive member 4 (the difference between the film thickness initial value and film thickness lower limit). Film thickness is 80%, that is, the film thickness when the remaining life is 20%.

  In the example of FIG. 6, the sensitivity of the photosensitive member 4 to the laser beam LB monotonously increases as the wavelength λ increases in the wavelength range of 700 to 880 nm. Although the sensitivity decreases as the film thickness of the photosensitive member 4 decreases, the spectral sensitivity characteristics are substantially the same regardless of the decrease in the film thickness.

  That is, when the wavelength λ of the laser beam LB is changed from the reference wavelength λs (780 nm) to a shorter wavelength, the sensitivity becomes lower, and conversely, when the wavelength λ is changed to a longer wavelength, the sensitivity becomes higher. In the following, changing the wavelength λ may be referred to as “wavelength shift”. The wavelength shift at which the sensitivity decreases may be described as "wavelength shift to the low sensitivity side", and the wavelength shift at which the sensitivity increases may be described as "wavelength shift to the high sensitivity side".

  FIG. 7 shows an example of the layer structure of the photosensitive member 4 and changes in the state of the photosensitive member 4 due to the irradiation of the laser beam LB. FIG. 8 shows the relationship between the sensitivity of the photosensitive member and the size X of the exposure area 82 and the laser light quantity The relationship between U and the size X of the exposure area 82 is schematically shown.

  As shown in FIG. 7B, the photosensitive member 4 is composed of a conductive substrate 41, an undercoat layer 42, and a photosensitive layer 43. Among these, the photosensitive layer 43 has a two-layer structure of the charge generation layer 44 and the charge transport layer 45. The material of these layers may be known.

  The conductive substrate 41 is made of aluminum or another metal and supports the undercoat layer 42 and the photosensitive layer 43. The conductive substrate 41 is biased to a positive potential in charging by the charging roller 5.

  The undercoat layer 42 is provided to enhance the bonding between the conductive substrate 41 and the photosensitive layer 43, and is made of a resin binder in which conductive particles are dispersed.

  The charge generation layer 44 is made of a resin binder in which a charge generation material such as an azo raw material or a quinone pigment is dispersed.

  The charge transport layer 45 is made of a resin binder in which a charge transport material is dispersed. An example of a charge transport material is 4,4'-dimethyl-4 "-(. Beta.-phenylstyryl) triphenylamine. Examples of resin binders are polycarbonate resins, polystyrenes, acrylic resins, methacrylic resins and the like.

  Such a life of the photosensitive member 4 is a period until the charge transport layer 45 is worn and the film thickness H becomes the lower limit value. That is, the film thickness of the charge transport layer 45 is closely related to the life of the photosensitive member 4, and the dimensions of the charge generation layer 44, the undercoat layer 42 and the conductive substrate 41 are not directly related to the life of the photosensitive member 4. . That is, in the present embodiment, the film thickness H of the photosensitive member 4 is substantially the film thickness of the charge transport layer 45. The specific value of the film thickness H of the photosensitive member 4 illustrated below is the value of the film thickness H of the charge transport layer 45.

  When the surface of the photosensitive layer 43 is uniformly negatively charged and irradiated with the laser beam LB, positive and negative charges are generated on the exposed area (photosensitive area) 82 of the charge generation layer 44. Occur.

  As shown in FIG. 7A, the exposure region 82 is a region to which the irradiation energy of a size sensitive to the charge transport layer 45 is given by the laser beam LB, and the irradiation energy is within a spot 81 of a predetermined value or more. It occurs.

  The size (outside diameter) X of the exposure region 82 depends on the sensitivity of the charge transport layer 45, as shown in FIG. That is, the exposure area 82b in the middle sensitivity is larger than the exposure area 82a in the low sensitivity, and the exposure area 82c in the high sensitivity is larger (Xa <Xb <Xc).

  The size X of the exposure area 82 depends on the light amount (laser light amount) U of the laser beam LB, as shown in FIG. 8B. That is, the exposure region 82e in the case where the laser light amount U is larger than the exposure region 82d in the case where the laser light amount U is small is larger (Xd <Xe).

  Referring back to FIG. 7B, of the charges generated in the charge generation layer 44, negative charges move to the conductive substrate 41 through the undercoat layer 42. On the other hand, the positive charge moves from the charge generation layer 44 to the surface portion of the charge transport layer 45 as shown in FIG. 7C. At this time, the charge spreads in the surface direction as it approaches the surface layer. The charge transferred to the surface portion cancels the negative charge on the surface of the photosensitive layer 43. As a result, as shown in FIG. 7D, on the surface of the photosensitive layer 43, the charge elimination region 83 in which the charge has disappeared is formed.

  FIG. 9 schematically shows the relationship between the film thickness H of the photosensitive member 4, the wavelength λ of the laser beam LB, and the size Z of the static elimination area 83.

  In FIG. 9A, the film thickness H1 of the photosensitive member 4 is relatively large. The laser beam LB of the wavelength λa is irradiated to generate charges in the exposure area 82 of size X1, and the negative charge of the depression cancels out the negative charge on the surface to form the static elimination area 83. The size Z1 of the static elimination area 83 is a standard size Zs at which a good quality image having an appropriate resolution and density of the image can be obtained.

  In FIG. 9 (B), the charge transport layer 45 is worn out and thinner than the state of FIG. 9 (A). That is, the film thickness H2 is smaller than the film thickness H1 in the state of FIG. In the state of FIG. 9B, when the laser beam LB of the wavelength λa is irradiated in the same manner as in the case of FIG. 9A, charges are exposed in the exposure region 82 of size X1 as in the case of FIG. As a result, the negative charge on the surface is canceled by the positive charge to form the static elimination region 83. However, since the charge transport layer 45 is thin, the spread of the positive charge in the surface direction is small, and the size Z2 of the static elimination area 83 is smaller than the reference size Zs. Therefore, the quality of the image formed by causing the toner to adhere to the static elimination area 83 is degraded.

  Therefore, the image forming apparatus 1 changes the wavelength λ of the laser beam LB to a wavelength λc whose sensitivity in the charge transport layer 45 is higher than the wavelength λa. That is, wavelength shift to the high sensitivity side is performed. By performing this wavelength shift, as shown in FIG. 9C, the size X3 of the exposed region 82 is increased (X3> X1), and the surface direction of the positive charge due to the charge transport layer 45 becoming thinner. In addition, the size Z3 of the static elimination area 83 is the standard size Zs.

  The laser light amount U may be adjusted together with the wavelength shift. For example, with reference to the individual information stored in the memory in the imaging unit 3, individual differences in the characteristics of the photosensitive member 4 can be compensated by the light amount control, and the dimensional accuracy of the static elimination region 83 can be enhanced.

  The timing at which the wavelength shift is performed can be the timing at which the image forming apparatus 1 performs the image stabilization process. The image stabilization process is a process of adjusting the electrophotographic process conditions in order to keep the color reproduction constant, and the temperature in the image forming apparatus 1 is large when printing is performed on a large number of sheets when the power is turned on. It is performed when a predetermined execution condition is met, such as when changed.

  FIG. 10 shows an example of the setting table T1 of the first example of the wavelength shift and an example of the temperature correction table T4 of the diffraction grating position, and FIG. 11 shows the first example of the wavelength shift and an example of the light amount control corresponding thereto. It is done.

  In FIG. 10, the initial value of the film thickness H of the photosensitive member 4 is 40 μm, and the lower limit is 12.5 μm. That is, when the charge transport layer 45 is worn by about 27.5 μm, the life of the photosensitive member 4 is considered to be exhausted.

  In the setting table T1 of FIG. 10, the progress of wear until the end of the life of the photosensitive member 4 is divided into three stages of A, B and C, and a diffraction grating 612 corresponding to the laser wavelength λ and the laser wavelength λ for each stage. And the correction value by the light path correction mechanism 62 are set.

  Stage A is an initial stage in which the film thickness H decreases from an initial value of 40 μm to a reference film thickness (34 μm). Stage B is a middle stage in which the film thickness H decreases from the standard film thickness to a film thickness of 80% of life. Stage C is the final stage in which the film thickness H decreases from the film thickness with a life of 80% to the lower limit value.

  The PH control unit 160 determines which of A, B, and C the current stage is based on the film thickness information D4 acquired from the main control unit 100, and the setting content of the determined stage is set from the setting table T1. The print head 6 is controlled by reading out and applying the setting contents.

  At this time, the position of the diffraction grating 612 is corrected according to the temperature of the print head 6 with reference to the temperature correction table T4. For example, in step A, the setting value of the diffraction grating position indicated by the setting table T1 is “−6”. At this time, when the temperature of the print head 6 is, for example, 20 ° C., the correction setting value indicated by the temperature correction table T4 is “−1”. In this case, by setting “−7” obtained by adding “−1” to “−6” as a setting value of the diffraction grating position, the laser light source 61 a is controlled to emit a laser beam having a wavelength of 720 nm.

  The film thickness information D4 may be any as long as it indicates an approximate film thickness H, and may not exactly indicate the film thickness H. For example, information having a correlation with the film thickness H such as the cumulative number of printed sheets, the cumulative number of rotations of the photosensitive member, and the cumulative on time of the charging roller 5 can be used as the film thickness information D4. However, when the function of measuring the film thickness H is mounted, the measured value of the film thickness H may be the film thickness information D4.

  In the control according to the setting table T1, the laser wavelength λ is changed according to the film thickness H as shown in FIG. Since the setting of the laser wavelength λ is constant at each of the stages A, B, and C, the static elimination area 83 becomes narrower as the film thickness H decreases as described in FIG. Therefore, as shown in FIG. 11B, the laser light amount U is adjusted so that the static elimination area 83 has a reference size Zs.

  FIG. 12 shows a setting table T2 of the second example of wavelength shift, and FIG. 13 shows a second example of wavelength shift and an example of light amount control corresponding thereto.

  Also in FIG. 12, as in FIG. 10, the initial value of the film thickness of the photosensitive member 4 (the film thickness H of the charge transport layer 45) is 40 μm, and the lower limit is 12.5 μm.

  In the setting table T2 of FIG. 12, the progress of the wear of the photosensitive member 4 is divided into eight stages of A1, A2, A3, B1, B2, C1, and C2. This division further divides each stage of A, B, and C in the setting table T1 of FIG. 20 into a plurality of stages. In FIG. 12, the maximum value of the film thickness H corresponding to each step is shown. For example, the range of the film thickness H corresponding to the step A1 is from 40 μm to the maximum value (38 μm) of the next step A2.

  Also in the setting table T2, the laser wavelength λ, the position of the diffraction grating 612 corresponding to the laser wavelength λ, and the correction value by the optical path correction mechanism 62 are set every eight steps.

  The PH control unit 160 determines the current stage based on the film thickness information D4, reads the setting content of the determined stage from the setting table T2, and controls the print head 6 by applying the setting content. Further, as described above, the position of the diffraction grating 612 is corrected according to the temperature of the print head 6 with reference to the temperature correction table T4.

  In the control according to the setting table T2, the laser wavelength λ is changed according to the film thickness H as shown in FIG.

  In the example of FIG. 13, as shown in FIG. 13B, the laser light quantity U is made constant in the stages A1 to A3 in which the variation width of the film thickness H is relatively small and the stages B2, C1, and C2. Then, in step B1 in which the change width of the film thickness H is relatively large, the laser light amount U is adjusted so that the range in which the charge disappears becomes the reference size Zs. That is, in the example of FIG. 13, by finely dividing the steps and finely changing the laser wavelength λ, a period for keeping the static elimination area 83 at a size close to the reference size Zs is provided without adjusting the laser light amount U. It is an example.

  FIG. 14 shows a setting table T3 of the third example of the wavelength shift, and FIG. 15 shows an example of the stage change tables T5 and T7 and an example of the simultaneous shift limit table T, respectively.

  Also in FIG. 14, as in FIGS. 10 and 12, the initial value of the film thickness of the photosensitive member 4 (film thickness H of the charge transport layer 45) is 40 μm, and the lower limit is 12.5 μm.

  In the setting table T3 of FIG. 14, the progress of the wear of the photosensitive member 4 is divided into nine stages 1 to 9, and the position of the diffraction grating 612 corresponding to the laser wavelength λ and the laser wavelength λ and the optical path for each stage. A correction value by the correction mechanism 62 is set.

  A stage change table T5 shown in FIG. 15A is provided to change the laser wavelength λ in accordance with the degree of deterioration of the laser light source 61 and, for example, the image quality measured in the image stabilization process. The target stage from which the setting value of the nine stages in the setting table T3 is read out in accordance with the stage change table T5 is changed from the stage (original stage) indicated by the film thickness information D4 to another stage. The details are as follows.

  In the stage change table T5, the degree of deterioration of the laser light source 61 is represented by a ratio R of the accumulated light emission time to the life (durability time) of the laser light source 61. This ratio R is divided into five ranges of a range of less than 80% and four ranges of 80% or more divided by 5%, and the target stage change destination is determined for each of these ranges .

  For example, if the ratio R is less than 80%, the change destination is “no change”, so the original stage is the target stage. If the ratio R is 80% to 85%, the target phase is the next phase of the original phase, since the change destination is “the stage after one”. For example, if the original stage is stage 4, the target stage is stage 5. Also, if the ratio R is 95% or more, the stage after the original stage is the target stage.

  The light amount of the laser light source 61 decreases as it approaches the life of the laser light source 61. Therefore, the change destination of the target stage is determined so as to shift the wavelength λ to the higher sensitivity side as the ratio R is larger.

  Further, in the step change table T5, indices of image quality are a line width W and a toner adhesion amount Q measured by printing a test pattern.

  The line width W is divided into three, "thin", "within the reference range", and "thicker" than the reference range. The change destination of the target step is determined to shift the wavelength λ by one step to the high sensitivity side when the line width W is thin, and to shift by one step to the low sensitivity side when the line width W is large. There is.

  The toner adhesion amount Q is divided into three, "less than", "within the reference range", and "more than" the reference range. The change destination of the target step is determined so that the wavelength λ is shifted to the high sensitivity side by one step when the toner adhesion amount Q is small, and shifted to the low sensitivity side when the toner adhesion amount Q is large. It is done.

  The PH control unit 160 determines the current stage based on the film thickness information D4, tentatively determines the determined stage as the target stage, reads the change destination from the stage change table T5, and determines the target stage. Then, the setting content of the target stage is read out from the setting table T3, and the setting content is applied to control the print head 6. At that time, as described above, the temperature correction table T4 is referred to, and the position of the diffraction grating 612 is corrected according to the temperature of the print head 6.

  The change of the target stage may be performed according to only one of the ratio R, the line width W, and the toner adhesion amount Q, or may be performed according to a plurality of them.

  By the way, the implementation of wavelength shift includes an embodiment implemented individually for each color of Y, M, C, K, and an embodiment implemented simultaneously for three colors Y, M, C for four colors or color printing. The latter mode of simultaneously performing for a plurality of colors is hereinafter referred to as "simultaneous shift".

  In the simultaneous shift, when abrasion of the photosensitive member 4 progresses and the target stage in the setting table T3 changes from before with respect to any of a plurality of target colors, the latest target stage is set as the target stage also with other colors. Wavelength shift.

  The simultaneous shift limit table T6 shown in FIG. 15B indicates the range of the film thickness H at which simultaneous shift is performed and the range of the film thickness H at which simultaneous shift is not performed.

  According to the simultaneous shift limitation table T6 of the example of FIG. 15B, simultaneous shift is not performed when the film thickness H exceeds 30 μm and when the film thickness H is less than 22 μm. The simultaneous shift is performed when the film thickness H is in the range of 30 to 22 μm. That is, simultaneous shifts are not performed when the target stages determined for one color are stages 1 to 4 or 7 to 9, and simultaneous shifts are performed when the determined target stages are stages 5 and 6.

  As described above, the wavelength shift based on the setting tables T1, T2 and T3 is performed as needed when the image stabilization process is performed. Then, the wavelength λ after the shift is held as one of setting values in the control of printing until at least the next image stabilization processing is performed.

  The image forming apparatus 1 can perform wavelength shift (which is referred to as “temporary wavelength shift”) for temporarily changing the wavelength λ in accordance with the print mode, in addition to such wavelength shift. A stage change table T7 shown in FIG. 15C shows settings relating to temporary wavelength shift.

  In the stage change table T7, the change destination of the target stage in the setting tables T2 and T3 is defined for the four print modes classified according to the resolution M and the type of paper P (paper type J).

  In the normal resolution mode in which the resolution M is 600 dpi, "no change" is defined as the change destination. On the other hand, in the high resolution mode in which the resolution X is 1200 dpi, "the previous stage" is defined as the change destination. Thus, when the original target stage is, for example, stage 4 in the setting table T3, the target stage is changed to stage 3. Then, when printing in the high resolution mode is finished, the process is returned to the original stage 4. By performing the temporary wavelength shift to the low sensitivity side, it is possible to achieve high resolution of the dots.

  In the normal paper mode in which the paper type J is plain paper, “no change” is defined as the change destination. On the other hand, in the thick paper mode in which the paper type J is thick paper, “the second previous stage” is defined as the change destination. Thus, when the original target stage is, for example, stage 4 in the setting table T3, the target stage is changed to stage 2. Then, when printing in the high resolution mode is finished, the process is returned to the original stage 4.

  In the heavy paper mode, the system speed defining the operation of each part involved in the electrophotographic process is made slower than that of the normal paper mode, for example, because the paper P is sufficiently heated at the time of fixing. As a result, the peripheral speed of the photosensitive member 4 becomes slow, so that the irradiation energy per unit time in the irradiation of the laser beam LB becomes large, and the exposure area 82 and the corresponding charge removal area 83 expand. Therefore, temporary wavelength shift to the low sensitivity side is performed. As a result, the size Z of the static elimination area 83 can be optimized and an image of a desired image quality can be formed without reducing the light amount U of the laser beam LB.

  A flow of processing in the image forming apparatus 1 is shown in FIG.

  In the power-on state (# 101) where the power necessary for operation is supplied (# 101), the machine status information D1 is acquired by collecting the durability information and outputs of various sensors stored in various places (# 102), and the image is stable It is judged based on the machine state information D1 whether or not the conversion processing is to be performed (# 103).

  If it is determined that the image stabilization process is to be performed (YES in # 103), the image stabilization process is performed (# 104). If it is determined that the image stabilization process is not to be performed (NO in # 103) The print job is executed (# 105).

  During execution of the print job, for example, each time printing on one side of the sheet P is performed, it is determined whether printing is continued (# 106). That is, it is checked whether the printing for the number of print sheets designated by the print job is completed.

If it is determined that printing is not to be continued (NO in # 106), print end processing is performed (# 107). In the print end process, the printer engine 2 is put into a standby state, or the job execution history information is updated. If it is determined that printing is to be continued (YES in # 106), the process returns to step # 102 and The machine state information D1 is acquired. If the number of continuously printed sheets exceeds a predetermined value or the internal temperature is greatly increased by the execution of the print job, it is determined that the image stabilization processing is to be performed in the next step # 103. In this case, execution of the print job is interrupted to perform image stabilization processing (# 104).

  FIG. 17 shows the flow of the image stabilization process.

  First, a toner image of a test pattern is printed, and the image quality is detected based on the output of the density sensor 21 (# 201). At this time, the line width W, the toner adhesion amount Q, the color shift amount, and the like are measured.

  Next, wavelength shift necessity determination is performed (# 202), and if the result of the determination is "shift required" (YES in # 203), wavelength shift processing is performed (# 205). If the result of the determination is "shift not required" (NO in # 203), the current setting for the optical system including the laser wavelength λ and the optical path correction mechanism 62 is held (# 204).

  Then, the laser light amount U is adjusted with reference to the control table for setting the light amount based on the line width W and the toner adhesion amount Q measured in step # 201 and the set laser wavelength λ (# 206). Thereby, the size X of the exposure area 82 corresponding to the spot 81 is changed, and the size Z of the static elimination area 83 is optimized.

  Thereafter, other settings for adjusting conditions such as charging, development, and transfer are performed (# 207), and a toner image is formed again as necessary to confirm the image quality (# 208), and the image stabilization process is performed. Finish.

  FIG. 18 shows a first example of the flow of the wavelength shift necessity determination process in the image stabilization process, and FIG. 19 shows a second example of the flow of the wavelength shift necessity determination process.

  In the example of FIG. 18, when the film thickness H of the photosensitive member 4 decreases and the stage of progress of wear changes (YES in # 301), it is determined that a shift is necessary (# 306). Further, also in the case where the cumulative light emission time of the laser light source 61 is equal to or greater than the predetermined value (YES in # 302), the high resolution mode (YES in # 303), and the printing mode in which the system speed is slow (#) It is determined that the shift is necessary (YES in 304) (# 306). If none of these cases (NO in # 301 to # 304), it is determined that shifting is unnecessary (# 305).

  In the example of FIG. 19, when the film thickness H of the photosensitive member 4 decreases and the stage of progress of wear changes (YES in # 401), it is determined that a shift is necessary (# 405). Also, when the line width W is not within the reference range (NO in # 402) and when the toner adhesion amount Q is not within the reference range (NO in # 403), it is determined that the shift is necessary (# 405). If none of these cases (NO in # 404, YES in # 402 to # 403), it is determined that shifting is unnecessary (# 404).

  FIG. 20 shows a first example of the flow of wavelength shift processing in image stabilization processing, and FIG. 21 shows a second example of the flow of wavelength shift processing.

  In the example of FIG. 20, shift direction determination processing is performed to determine whether wavelength shift to the high sensitivity side or wavelength shift to the low sensitivity side is performed (# 501).

  If the result of determination by the shift direction determination process is "low sensitivity side", wavelength shift to the low sensitivity side is performed (# 502, # 503), and if the result of determination is "high sensitivity side", The wavelength is shifted to the high sensitivity side (# 502, # 504).

  In the example of FIG. 21, shift direction determination processing is performed as in the example of FIG. 20 (# 601), and subsequently, it is determined whether wavelength shift for four colors is to be performed (# 602). That is, it is checked whether the stage of progress of wear of the photosensitive member 4 is the stage of limiting the simultaneous shift.

  If it is determined that simultaneous shift is to be performed (YES in # 602) and the result of determination by the shift direction determination process is "low sensitivity", wavelength shift to low sensitivity is performed for four colors (# 603, # 604).

  If it is determined that simultaneous shift is to be performed (YES in # 602) and the result of determination by the shift direction determination process is "high sensitivity side", wavelength shift to the high sensitivity side is performed for four colors (# 603, # 605).

  On the other hand, if it is determined that simultaneous shift is not to be performed (NO in # 602) and the result of determination by the shift direction determination process is "low sensitivity side", the wavelength toward the low sensitivity side for only colors that need to be shifted. The shift is performed (# 606, # 607).

  If it is determined that simultaneous shift is not to be performed (NO in # 602), and if the result of determination by the shift direction determination process is “high sensitivity side”, wavelength shift to the high sensitivity side is performed only for colors that need to be shifted. Perform (# 606, # 608).

  FIG. 22 shows a first example of the flow of shift direction determination processing in wavelength shift processing, and FIG. 23 shows a second example of the flow of shift direction determination processing.

  In the example of FIG. 22, the factor which required the wavelength shift is checked (# 701). If the factor is a decrease in the film thickness H of the photosensitive member 4, the shift direction is determined to be the high sensitivity side (# 702). If the factor is the printing resolution or the system speed, it is determined that the shift direction is the low sensitivity side (# 703).

  If the factor is the accumulated light emission time of the laser light source 61, it is checked whether the wavelength shift to the higher sensitivity side is possible (# 704). That is, it is checked whether the setting value of the laser wavelength λ has already been set as the upper limit value of the variable range.

  If wavelength shift to the high sensitivity side is possible (YES in # 704), the shift direction is determined to be the high sensitivity side (# 705). If the wavelength shift to the high sensitivity side is not possible (NO in # 704), the current setting value of the laser wavelength λ is maintained (# 706). In this case, the wavelength shift processing is returned without performing any substantial processing.

  In the example of FIG. 23, when the factor that requires wavelength shift is a decrease in the film thickness H of the photosensitive member 4 (# 802), it is determined that the shift direction is the high sensitivity side (# 802).

  If the line width W is thicker than the width within the reference range (# 803), the shift direction is determined to be the low sensitivity side (# 804). Even when the line width W is thinner than the width within the reference range, but the toner adhesion amount Q is larger than the amount within the reference range (# 805), the shift direction is determined to be the low sensitivity side (# 804).

  If the line width W is smaller than the width within the reference range (# 803) and the toner adhesion amount Q is smaller than the amount within the reference range (# 805), the shift direction is determined to be the high sensitivity side (# 806) ).

  According to the above embodiment, the wavelength λ of the light irradiated to the photosensitive member 4 is changed so as to increase the sensitivity in accordance with the progress of the wear of the photosensitive member 4, so the allowable range of the reduction of the film thickness H is expanded compared to the prior art. Thus, the life of the photosensitive member 4 can be extended by making the initial film thickness H larger than that of the prior art.

  In the embodiment described above, the variable range of the laser wavelength λ is a wavelength range in which the sensitivity monotonously changes in the spectral sensitivity characteristic of the photosensitive member 4, but the present invention is not limited thereto. In the case of using the photosensitive member 4 exhibiting a spectral sensitivity characteristic having one or more extreme values (peaks or valleys), the wavelength range including the extreme values can be a variable range of the laser wavelength λ. In that case, when there are a plurality of wavelengths (having the same sensitivity) selectable as the wavelength after change, the wavelength close to the wavelength before change is selected. By selecting a near wavelength, the amount of displacement of the optical components of the diffraction grating 612 and the optical path correction mechanism 62 is reduced, excess or deficiency of displacement is suppressed, and the accuracy of wavelength shift is enhanced.

  Although the positional deviation of the spot 81 caused by the change of the laser wavelength λ is mechanically corrected using the optical path correction mechanism 62, the light emission timing (main scanning start timing) of the laser light source 61 is controlled instead or in combination. The positional deviation of the spot 81 may be corrected.

  In the embodiment described above, when using a light emitting device without significant temperature dependence as a light source or providing means for keeping the temperature of the light source constant, temperature correction can be omitted in wavelength shift.

  In the embodiment described above, an example was given in which the progress of the wear of the photosensitive member 4 was divided into three or more stages, but may be divided into two stages.

  For example, in the initial stage (stage A in FIG. 11) in which the film thickness H decreases from the initial value to the first set value, the wavelength λ is set to the first wavelength (720 nm). Then, in the middle stage (step B in FIG. 11) in which the film thickness H decreases from the first set value to the second set value, and in the end stage thereafter (step C in FIG. 11) The second wavelength (780 nm) in which the sensitivity of the photosensitive member 4 is higher than that of

  Alternatively, in the non-end stage (steps A and B in FIG. 11) in which the film thickness H decreases from the initial value to the set value (18 μm), the reference wavelength λs is set as the wavelength λ of the laser beam LB. Then, in the final stage (step C in FIG. 11), a wavelength (860 nm) at which the sensitivity of the photosensitive member 4 is higher than the reference wavelength λs is set as the wavelength λ of the laser beam LB.

  However, the initial value of the film thickness H, the setting value, and the value of the wavelength λ to be set may be appropriately selected according to the spectral sensitivity characteristic of the photosensitive member 4 and the light emission characteristic of the light source, etc. It is not a thing.

  In addition, the configuration of the entire or each part of the image forming apparatus 1, the content of the process, the order, the timing, and the like can be appropriately changed in accordance with the spirit of the present invention.

1 image forming apparatus 4 photosensitive body 6 print head 61 laser light source (light source)
62 light path correction mechanism 81 spot 83 static elimination area D 4 film thickness information 160 PH control unit (control unit)
Lb laser beam (light beam)
LB laser beam (light beam)
U light intensity Zs standard size (predetermined size)
λ wavelength

Claims (12)

An image forming apparatus having a photosensitive member carrying a latent image and forming an image corresponding to the latent image,
A print head having a variable wavelength light source for emitting a light beam and irradiating the photosensitive body with the light beam so as to partially discharge the surface of the photosensitive member in accordance with the latent image;
And a controller configured to control the wavelength and the light amount of the light beam in accordance with the progress of the wear of the photosensitive member.
An image forming apparatus characterized by The control unit controls the wavelength and the light amount of the light beam according to the progress of the wear of the photosensitive member indicated by the film thickness information.
An image forming apparatus according to claim 1. The control unit changes the wavelength of the light beam so that the sensitivity of the photosensitive member becomes higher as wear of the photosensitive member progresses, and the charge removal region corresponding to the spot of the light beam on the photosensitive member is a predetermined one. Adjust the light quantity of the light beam to be of a size,
An image forming apparatus according to claim 1. The control unit changes the wavelength of the light beam at each of three or more stages where the progress of wear of the photosensitive member is classified.
An image forming apparatus according to claim 3. The control unit sets the wavelength of the light beam to a first wavelength at an initial stage in which the film thickness of the photoconductor decreases from an initial value to a first set value, and the film thickness of the photoconductor is In the middle stage where the first set value is decreased to the second set value, the wavelength of the light beam is set to a second wavelength at which the sensitivity of the photosensitive member is higher than the first wavelength.
The image forming apparatus according to claim 2. In the final stage where the film thickness of the photosensitive member decreases from the second set value to the lower limit value, the control unit controls the wavelength of the light beam to be higher than that of the second wavelength. Set to 3 wavelengths,
An image forming apparatus according to claim 5. In the non-end stage where the film thickness of the photosensitive member decreases from an initial value to a set value, the control unit controls the light at a reference wavelength capable of setting the discharge area to the predetermined size by controlling the light amount. In the final stage, which is set as the wavelength of the beam and the film thickness of the photosensitive member decreases from the set value to the lower limit value, the wavelength of the photosensitive member whose sensitivity is higher than the reference wavelength is set as the wavelength of the light beam. ,
An image forming apparatus according to claim 3. An electrophotographic image forming apparatus,
The control unit acquires the film thickness information and sets the wavelength of the light beam when an image stabilization process for correcting the conditions of the electrophotographic process is performed.
An image forming apparatus according to claim 2. A plurality of the photosensitive members are provided, and the light source is provided in the print head so as to correspond to each of the plurality of photosensitive members,
When changing the setting of the wavelength of the light emitted by any of the plurality of light sources, the control unit similarly changes the setting of the wavelength of the light emitted by another light source.
An image forming apparatus according to any one of claims 1 to 8. The control unit switches the wavelength of the light beam according to an image forming operation mode, a condition, or an image quality.
The image forming apparatus according to any one of claims 1 to 9. A plurality of modes with different resolutions or system speeds are defined as the operation mode, an accumulated emission time of the light source in the print head is defined as the condition, and toner adhesion per line area and unit area is defined as the image quality The amount is fixed,
The image forming apparatus according to claim 10. The print head includes an optical path correction mechanism that corrects the irradiation position of the light beam on the photosensitive member,
The control unit controls the light path correction mechanism so as to eliminate the deviation of the irradiation position according to the wavelength of the light beam and the internal temperature.
An image forming apparatus according to any one of claims 1 to 11.

Images