JP6135990B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus having a cleaning member that scrapes off transfer residual toner adhering to the surface of a latent image carrier to clean the surface.

  Conventionally, as this type of image forming apparatus, the one described in Patent Document 1 is known. In this image forming apparatus, a toner image formed on the surface of a photoreceptor by an electrophotographic process is transferred to an intermediate transfer belt, and then transferred to a recording sheet. Further, the surface of the photoconductor is cleaned by scraping off the transfer residual toner which is not transferred to the intermediate transfer belt but remains on the surface of the photoconductor with a cleaning blade. In such a configuration, when a large number of images with a high image area ratio are output, a large amount of untransferred toner is carried to the contact portion between the photoconductor and the cleaning blade, and the contact portion easily passes through. The untransferred toner may adhere to the surface of the photoreceptor due to pressure contact when passing through the contact portion. On the surface of the photoconductor, it is difficult to form an image at a fixing portion where the transfer residual toner is fixed, and thus white spots are generated in the image.

  Therefore, in the image forming apparatus described in Patent Document 1, in the process of continuously outputting an image having a relatively high image area ratio, the image formation of the toner image on the photoconductor is periodically paused to empty the photoconductor. Let it turn. By this idling, the transfer residual toner staying immediately before the contact portion between the photosensitive member and the cleaning blade is reduced, so that the transfer residual toner can be prevented from slipping through.

  Note that the inter-paper distance may be increased as in the image forming apparatus described in Patent Document 2 instead of temporarily rotating the photosensitive member during continuous output of images. The inter-paper distance is a distance between a recording sheet conveyed in advance in the apparatus during continuous output of an image and a subsequent recording sheet. As the inter-paper distance is increased, the amount of toner transported to the abutting portion per sheet is reduced and the amount of toner staying immediately before the abutting portion is reduced. be able to.

  The contact portion between the photoconductor and the cleaning blade until the image of all pages is output by continuous output of the image in either the configuration in which the photoconductor is periodically idled or the configuration in which the distance between the papers is increased. The length of the blank passage that is the length of the blank area of the photoconductor passed through is increased. More specifically, in the configuration in which the photoconductor is periodically idled, the empty area of the photoconductor is positively passed through the contact portion between the photoconductor and the cleaning blade by idle rotation, compared with the case where the photoconductor is not idled. , The blank passage length until all pages are output is increased. Also, in the configuration in which the inter-paper distance is increased, all pages are output by increasing the length of the blank area of the photosensitive member that enters the abutting portion for each sheet passing by the increased inter-paper distance. The length of blank passage is increased. That is, by increasing the blank passage length until the image of all pages is output, it is possible to suppress slipping of the transfer residual toner. However, if the blank passage length is increased, the time required to output images of all pages is lengthened. For this reason, in the image forming apparatuses described in Patent Documents 1 and 2, when the image area ratio of the output image is relatively low and the generation amount of the transfer residual toner is small, the frequency of performing idling is reduced, The printing time is not lengthened by making the distance between them relatively small. With such a configuration, it is possible to avoid an increase in print time due to a relatively large blank passage length despite a small amount of generated transfer residual toner.

  However, in the image forming apparatuses described in Patent Documents 1 and 2, depending on the environment, there is a possibility that the transfer residual toner may not be sufficiently suppressed. Specifically, the present inventors have found through experiments that the transfer residual toner easily slips through as the humidity increases. This is presumably because the higher the humidity is, the easier the fine vibration (chatter) of the tip edge portion of the cleaning blade occurs. In addition, in the configuration in which the lubricant powder is applied to the surface of the photosensitive member by the brush roller, the higher the humidity, the less the amount of powder scraped from the solid lubricant by the brush roller and the less the amount of lubricant applied. This is considered to be one of the causes that are likely to occur.

  In the image forming apparatus described in Patent Documents 1 and 2, the blank passage length is adjusted according to the difference in the image area ratio. White spots in the image due to high humidity may occur. For example, in a configuration in which the blank passage length is not adjusted, when an image with an image area ratio of 50% is continuously output, white spots do not occur in a low humidity environment, but white spots occur in a high humidity environment. It can happen.

  The present invention has been made in view of the above background, and the object of the present invention is to prevent the occurrence of white spots in an image due to high humidity in the environment without unnecessarily extending the printing time. An object of the present invention is to provide an image forming apparatus that can be suppressed.

In order to achieve the above object, the present invention provides a transfer means for transferring a toner image on a latent image carrier onto a recording sheet directly or via an intermediate transfer body, and the latent image carrier and latent image writing means. A developing means, an image forming means having a cleaning member for cleaning the surface by scraping off transfer residual toner adhering to the surface of the latent image carrier, and an image information acquiring means for acquiring image information. In the image forming apparatus, humidity detecting means for detecting humidity, temperature detecting means for detecting temperature, and lubricant applying means for applying a lubricant to the surface of the latent image carrier that has passed through a position facing the cleaning member As the average image area ratio of the image output in the most recent predetermined period increases, the blank of the latent image carrier that passes through the position facing the cleaning member until the image of all pages is output. The first algorithm for increasing the blank passage length that is the length of the area, the second algorithm for increasing the blank passage length as the humidity detection result increases, and the amount of use of the cleaning member increases. The third algorithm for increasing the blank passage length as the temperature detection result increases, the fourth algorithm for increasing the blank passage length as the temperature detection result increases, and the usage amount of the lubricant application means increases. It said fifth algorithm for increasing a space passage length, to determine the blank passage length is used to implement the blanks pass length greatly to that adjustment process as humidity detection result is higher A blank adjustment means is provided.

  In the present invention, the blank passage length is increased as the internal humidity increases, so that the blank passage length is set to an appropriate size according to the humidity. Accordingly, it is possible to suppress the occurrence of white spots in the image due to high humidity in the environment without unnecessarily extending the printing time regardless of the humidity inside the apparatus.

1 is a schematic configuration diagram showing a printer according to a reference form. FIG. 3 is a schematic diagram illustrating a configuration of an image forming unit for forming a Y toner image. FIG. 2 is a block diagram showing a part of an electric circuit of the printer. 6 is a flowchart showing a processing flow of an inter-paper distance adjustment process performed by the control unit of the printer. The schematic diagram which shows the algorithm for environmental division identification. The graph which shows the relationship between the lifetime of a cleaning blade, and the specification of a printer. The schematic diagram for demonstrating how to obtain | require the image area rate for every time interval. The graph which shows the relationship between CPM down rate D and the specification of a printer. 9 is a graph showing the relationship between the number of image formations during inter-sheet enlargement and PPJ in a printer according to a first modification . The graph which shows the relationship between PPJ and brush movement distance ratio (vs. 5PPJ). The graph which shows the relationship between the image formation frequency | count at the time of sheet | seat expansion at the printer which concerns on a 2nd modification, and PPJ.

Before describing an embodiment in which the present invention is applied to an electrophotographic printer (hereinafter simply referred to as a “printer”) as an image forming apparatus , a reference embodiment that is helpful in understanding the present invention will be described below. Will be described .
First, the basic configuration of the printer according to the reference embodiment will be described. FIG. 1 is a schematic configuration diagram illustrating a printer according to a reference embodiment. This printer includes four image forming units 1Y, 1C, 1M, and 1K for yellow, cyan, magenta, and black (hereinafter referred to as Y, C, M, and K). These use different colors of Y, C, M, and K toners as image forming substances for forming an image, but the other configurations are the same.

  FIG. 2 is a schematic diagram showing a configuration of an image forming unit 1Y for forming a Y toner image. Further, the image forming unit 1Y includes a photoreceptor unit 2Y and a developing unit 7Y. The photoconductor unit 2Y and the developing unit 7Y are configured to be detachable from the printer main body integrally as the image forming unit 1Y. However, in a state where it is detached from the printer main body, the developing unit 7Y can be attached to and detached from a photosensitive unit (not shown).

  The photoreceptor unit 2Y includes a drum-shaped photoreceptor 3Y as a latent image carrier, a drum cleaning device 4Y, a static eliminator (not shown), a charging device 5Y, and a lubricant applying device 18Y. The charging device 5Y as a charging unit uniformly charges the surface of the photoreceptor 3Y, which is driven to rotate clockwise in FIG. 2 by a driving unit (not shown), by the charging roller 6Y. Specifically, in FIG. 2, a charging bias is applied from a power source (not shown) to the charging roller 6Y that is driven to rotate counterclockwise, and the charging roller 6Y is brought close to or in contact with the photosensitive member 3Y. 3Y is uniformly charged.

  Instead of the charging roller 6Y, another charging member such as a charging brush may be used in proximity or contact. Further, a charger that uniformly charges the photosensitive member 3Y by a charger method, such as a scorotron charger, may be used. The surface of the photoreceptor 3Y uniformly charged by the charging device 5Y is exposed and scanned by a laser beam emitted from an optical writing unit 20 serving as a latent image forming unit, which will be described later, and carries an electrostatic latent image for Y.

  The developing device 7Y includes a first agent storage chamber 9Y in which a first conveying screw 8Y as a developer conveying unit is disposed, a toner concentration sensor 10Y including a magnetic permeability sensor as a toner concentration detecting unit, and the like. Further, it also has a second conveying screw 11Y as a developer conveying means, a developing roll 12Y as a developer carrying member, a second agent containing chamber 14Y in which a doctor blade 13Y as a developer regulating member and the like are arranged. Yes.

  In these two agent storage chambers forming the circulation path, a Y developer (not shown) which is a two-component developer composed of a magnetic carrier and a negatively chargeable Y toner is contained. The first transport screw 8Y is rotationally driven by a drive unit (not shown) to transport the Y developer in the first agent storage chamber 9Y from the back side to the front side in the direction orthogonal to the paper surface of FIG. The toner density of the Y developer in the middle of conveyance is detected by a toner density sensor 10Y fixed below the first conveyance screw 8Y. Then, the Y developer transported to the front end of the first agent storage chamber 9Y by the first transport screw 8Y enters the second agent storage chamber 14Y through a communication port (not shown).

  The second transport screw 11Y in the second agent storage chamber 14Y is rotationally driven by a driving unit (not shown) to transport the Y developer from the near side to the far side in the direction orthogonal to the paper surface of FIG. In this manner, the developing roll 12Y is arranged in a posture parallel to the second transport screw 11Y above the second transport screw 11Y that transports the Y developer. The developing roll 12Y includes a magnet roller 16Y fixedly disposed in a developing sleeve 15Y made of a nonmagnetic sleeve that is driven to rotate counterclockwise in the drawing.

  A part of the Y developer conveyed by the second conveying screw 11Y is pumped up to the surface of the developing sleeve 15Y by the magnetic force generated by the magnet roller 16Y. Then, after the layer thickness is regulated by a doctor blade 13Y disposed so as to maintain a predetermined gap from the surface of the developing sleeve 15Y, the layer is conveyed to a developing region facing the photosensitive member 3Y, and is transferred onto the photosensitive member 3Y. Y toner is adhered to the electrostatic latent image for Y. This adhesion forms a Y toner image on the photoreceptor 3Y. The Y developer that has consumed Y toner by the development is returned to the second transport screw 11Y as the developing sleeve 15Y rotates. Then, the Y developer transported to the end of the second agent storage chamber 14Y in the drawing by the second transport screw 11Y returns to the first agent storage chamber 9Y through a communication port (not shown). In this way, the Y developer is circulated and conveyed in the developing unit.

  The detection result of the toner concentration of the Y developer by the toner concentration sensor 10Y is sent as an electric signal to a control device (not shown). This control device converts the output voltage from the toner density sensor 10Y into the toner density of the Y developer in the RAM. Further, the output voltages from the toner density sensors (10C, 10M, 10K) mounted on the C, M, K developing units (7C, 7M, 7K) are used as the respective developers (C, M, K developers). ) Toner density. Note that the output voltage from the toner density sensor formed of a magnetic permeability sensor correlates with the toner density. As the toner concentration of the developer increases, the magnetic permeability of the developer decreases and the output value from the toner concentration sensor decreases.

  For the Y developing unit 7Y, the toner density detection result calculated based on the output voltage from the toner density sensor 10Y is compared with the Y toner density control target value stored in the RAM. Then, the Y replenishing motor of the toner replenishing device is driven for a time corresponding to the amount so that an amount of Y toner according to the comparison result is supplied from the toner replenishing port 17Y. As a result, an appropriate amount of Y toner is supplied to the first developer storage chamber 9Y for the Y developer whose Y toner density has decreased due to consumption of Y toner during development. For this reason, the toner concentration of the Y developer in the second agent storage chamber 14Y is maintained near the target value of the toner concentration. The same applies to the developers in the developing units 7C, 7M, and 7K for other colors.

  In FIG. 1, the Y toner image formed on the photoreceptor 3Y is intermediately transferred to an intermediate transfer belt 41 which is an intermediate transfer body. In FIG. 2, the drum cleaning device 4Y of the photoreceptor unit 2Y has the free end of the cleaning blade 4aY supported in a cantilever manner in contact with the surface of the photoreceptor 3Y in the counter direction. The cleaning blade 4aY cleans the surface of the photoreceptor 3Y by scraping off transfer residual toner adhering to the surface of the photoreceptor 3Y after the intermediate transfer process. The transfer residual toner scraped off is discharged toward the outside of the drum cleaning device 4Y by the rotational drive of the recovery screw 4bY of the drum cleaning device 4Y. Then, it falls into a waste toner bottle (not shown). Hereinafter, a contact portion between the cleaning blade and the photosensitive member is referred to as a “blade contact portion”.

  Thus, the surface of the photoreceptor 3Y cleaned by the drum cleaning device 4Y enters a position facing the lubricant applying device 18Y. The lubricant applying device 18Y includes a rotating application brush roller 18aY, a solid lubricant 18bY, a biasing spring 18cY, and the like. The biasing spring 18c presses the solid lubricant 18bY made of zinc stearate or the like against the application brush roller 1aY by the biasing force. The application brush roller 1aY is rotationally driven by a driving unit (not shown) in a state where it is in contact with both the photoreceptor 3Y and the solid lubricant 18bY. Then, the lubricant powder obtained by scraping from the solid lubricant 18bY is applied to the surface of the photoreceptor 3Y. As a result, the surface friction coefficient of the photoreceptor 3Y is reduced, thereby improving the toner releasability from the surface of the photoreceptor 3Y and improving the primary transfer rate of the toner or suppressing the surface wear of the photoreceptor 3Y. .

  The surface of the photoreceptor 3Y coated with the lubricant powder in this manner is neutralized by a neutralization device (not shown). By this charge removal, the surface of the photoreceptor 3Y is initialized and prepared for the next image formation. In the image forming units 1C, 1M, and 1K for other colors, C toner images, M toner images, and K toner images are formed on the photoreceptors 3C, 3M, and 3K in the same manner, and the intermediate transfer belt 41 has intermediate portions. Transcribed.

  An optical writing unit 20 is disposed below the image forming units 1Y, 1C, 1M, and 1K. The optical writing unit 20 irradiates the photoconductors 3Y, 3C, 3M, and 3K of the image forming units 1Y, 1C, 1M, and 1K with the laser light L emitted based on the image information. As a result, electrostatic latent images for Y, C, M, and K are formed on the photoreceptors 3Y, 3C, 3M, and 3K, respectively.

  The optical writing unit 20 deflects the laser light L emitted from the light source by the polygon mirror 21 that is rotationally driven by a motor, and passes through the photoreceptors 3Y, 3C, 3M, and 3K via a plurality of optical lenses and mirrors. Is irradiated. Instead of such a configuration, an LED array may be used.

  A first paper feed cassette 31 and a second paper feed cassette 32 are disposed below the optical writing unit 20 so as to overlap in the vertical direction. In each of these paper feed cassettes, a plurality of recording sheets P, which are recording materials, are accommodated in a state of a bundle of recording sheets, and the uppermost recording sheet P has a first paper feeding roller. 31a and the second paper feed roller 32a are in contact with each other. When the first paper feed roller 31a is driven to rotate counterclockwise in FIG. 1 by driving means (not shown), the uppermost recording sheet P in the first paper feed cassette 31 is vertical on the right side of the cassette in FIG. The paper is discharged toward a paper feed path 33 arranged to extend in the direction. Further, when the second paper feed roller 32 a is driven to rotate counterclockwise in FIG. 1 by a driving means (not shown), the uppermost recording sheet P in the second paper feed cassette 32 is discharged toward the paper feed path 33. Is done.

  A plurality of conveying roller pairs 34 are disposed in the sheet feeding path 33, and the recording sheet P sent to the sheet feeding path 33 is sandwiched between the rollers of the conveying roller pair 34 while being fed. 33 is conveyed from the lower side to the upper side in the vertical direction.

  A registration roller pair 35 is disposed at the end of the paper feed path 33. The registration roller pair 35 temporarily stops the rotation of both rollers as soon as the recording sheet P sent from the conveyance roller pair 34 is sandwiched between the rollers. Then, the recording sheet P is sent out toward a later-described secondary transfer nip at an appropriate timing.

  Above the image forming units 1Y, 1C, 1M, and 1K, a transfer unit 40 that moves the intermediate transfer belt 41 endlessly in a counterclockwise direction while being stretched is disposed. In addition to the intermediate transfer belt 41, the transfer unit 40 includes a belt cleaning unit 42, four primary transfer rollers 45Y, 45C, 45M, and 45K, a secondary transfer backup roller 46, a drive roller 47, an auxiliary roller 48, and a nip entrance roller. 49 and the like. The intermediate transfer belt 41 is endlessly moved counterclockwise in FIG. 1 by the rotational driving of the driving roller 47 while being stretched around these rollers.

The four primary transfer rollers 45Y, 45C, 45M, and 45K sandwich the endless intermediate transfer belt 41 between the photoreceptors 3Y, 3C, 3M, and 3K. As a result, primary transfer nips for Y, M, C, and K where the intermediate transfer belt 41 and the photoreceptors 3Y, 3C, 3M, and 3K abut are formed. Primary transfer rollers 45Y, 45C, 45M, the 45K, the primary transfer bias of reverse polarity (positive polarity in this preferred embodiment) of the toner is applied. The intermediate transfer belt 41 sequentially passes through the primary transfer nips for Y, C, M, and K along with its endless movement, and each color on the photoreceptors 3Y, 3C, 3M, and 3K is disposed on the outer peripheral surface thereof. The toner images are superimposed and primarily transferred. As a result, a four-color superimposed toner image (hereinafter referred to as “four-color toner image”) is formed on the intermediate transfer belt 41.

  The intermediate transfer belt 41 is sandwiched between the secondary transfer backup roller 46 and the secondary transfer roller 50 disposed outside the loop of the intermediate transfer belt 41. As a result, a secondary transfer nip where the intermediate transfer belt 41 and the secondary transfer roller 50 abut is formed. The registration roller pair 35 sends the recording sheet P sandwiched between the rollers toward the secondary transfer nip at a timing at which the recording sheet P can be synchronized with the four-color toner image on the intermediate transfer belt 41. The four-color toner image on the intermediate transfer belt 41 is affected by the secondary transfer electric field formed between the secondary transfer roller 50 to which the secondary transfer bias is applied and the secondary transfer backup roller 46, and the influence of the nip pressure. The secondary transfer is collectively performed on the recording sheet P in the secondary transfer nip. Then, combined with the white color of the recording sheet P, a full color toner image is obtained.

  Untransferred toner that has not been transferred to the recording sheet P adheres to the intermediate transfer belt 41 after passing through the secondary transfer nip. This is cleaned by the belt cleaning unit 42. The belt cleaning unit 42 scrapes and removes the transfer residual toner on the belt by a cleaning blade 42a that is in contact with the front surface of the intermediate transfer belt 41.

  When a monochrome image is formed, the printer moves the Y, C, and M primary transfer rollers 45Y, 45C, and 45M around the rotation axis of the auxiliary roller 48 by driving a solenoid (not shown). Revolve clockwise. Thus, the intermediate transfer belt 41 is separated from the Y, C, and M photoconductors 3Y, 3C, and 3M. Of the four image forming units 1Y, 1C, 1M, and 1K, only the K image forming unit 1K is driven to form a monochrome image. Accordingly, it is possible to avoid wear of the image forming units due to unnecessary driving of the Y, C, and M image forming units when forming a monochrome image.

  A fixing unit 60 as a fixing unit is disposed above the secondary transfer nip in the figure. The fixing unit 60 includes a pressure heating roller 61 that includes a heat source such as a halogen lamp, and a fixing belt unit 62. The fixing belt unit 62 includes a fixing belt 64, a heating roller 63 containing a heat source such as a halogen lamp, a tension roller 65, a driving roller 66, a temperature sensor (not shown), and the like. Then, the endless fixing belt 64 is endlessly moved in the counterclockwise direction in FIG. 2 while being stretched by the heating roller 63, the tension roller 65, and the driving roller 66. In the process of endless movement, the fixing belt 64 is heated from the back side by the heating roller 63.

  A pressure heating roller 61 that is driven to rotate in the clockwise direction in FIG. 1 is in contact with the heating belt 63 around the fixing belt 64 from the front surface side. Thereby, a fixing nip where the pressure heating roller 61 and the fixing belt 64 abut is formed.

  Outside the loop of the fixing belt 64, a temperature sensor (not shown) is disposed so as to face the front surface of the fixing belt 64 with a predetermined gap, and the fixing belt 64 just before entering the fixing nip. Detect surface temperature. This detection result is sent to a fixing power supply circuit (not shown). The fixing power supply circuit performs on / off control of power supply to the heat source included in the heating roller 63 and the heat source included in the pressure heating roller 61 based on the detection result by the temperature sensor. As a result, the surface temperature of the fixing belt 64 is maintained at about 140.degree.

  The recording sheet P that has passed through the secondary transfer nip is separated from the intermediate transfer belt 41 and then sent into the fixing unit 60. Then, in the process of being conveyed from the lower side to the upper side in the figure while being sandwiched by the fixing nip in the fixing unit 60, the full color toner image is applied to the recording sheet P by being heated or pressed by the fixing belt 64. To settle.

  The recording sheet P subjected to the fixing process in this manner is discharged outside the apparatus after passing between the rollers of the paper discharge roller pair 67. A stack unit 68 is formed on the upper surface of the housing of the printer main body, and the recording sheets P discharged to the outside by the discharge roller pair 67 are sequentially stacked on the stack unit 68.

  Above the transfer unit 40, toner bottles 72Y, 72C, 72M, and 72K, which are four toner containers that respectively store Y, C, M, and K toners, are disposed. The toners in the toner bottles 72Y, 72C, 72M, and 72K are appropriately supplied to the developing units 7Y, 7C, 7M, and 7K of the image forming units 1Y, 1C, 1M, and 1K, respectively, by the toner replenishing device. The toner bottles 72Y, 72C, 72M, and 72K are detachable from the printer main body independently of the image forming units 1Y, 1C, 1M, and 1K.

FIG. 3 is a block diagram showing a part of the electric circuit of the printer according to the reference embodiment. In the figure, a control device 100 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, and the like, and controls driving of various devices in the ROM. A control program is stored. Based on this control program, the drive of each device in the printer is controlled and information is exchanged with each device. The control device 100 includes Y, C, M, and K image forming units 1Y, 1C, 1M, and 1K, a writing control unit 101, a fixing device 60, a transfer unit 40, an image information input unit 102, and a humidity sensor 105. The temperature sensor 106 and the like are electrically connected.

  An image information input unit 102 serving as an image information acquisition unit receives image information sent from an external personal computer or scanner (not shown) and sends the image information to the control device 100 and the writing control unit 101. The writing control unit 101 controls the driving of the optical writing unit 20 based on the received image information, thereby performing an optical writing process on each color photoconductor. The humidity sensor 105 detects the humidity inside the printer using a known technique and transmits the detection signal to the control device 100. The temperature sensor 106 detects the temperature inside the printer of the printer by a known technique and transmits a detection signal to the control device 100.

The control device 100, each implementing one job for one sheet of the recording sheet which is an image forming operation for outputting an image, and counts up the count value of the cumulative job number (cumulative image forming operation times). The cumulative number of jobs is counted based on an A4 size recording sheet. When one job is executed for a recording sheet of A4 size or smaller, the count value of the accumulated job count is incremented by one. On the other hand, when one job is performed on a recording sheet larger than the A4 size, the count value of the cumulative job count is incremented by two.

  Further, every time one job is executed, the control device 100 first calculates the area of the toner image formed on the recording sheet that is the target of the one job, based on the image information. Then, the image area ratio on the recording sheet is calculated by dividing the calculation result by the plane area of the recording sheet and multiplying by 100. Then, the calculation result is stored in the flash memory in association with the count value of the cumulative number of jobs. In the case of a recording sheet larger than the A4 size, as described above, the cumulative job count is incremented by two. When counting up two, the calculation result of the image area ratio is stored in the flash memory in association with the count value obtained by counting up the cumulative job count by one and the count value obtained by counting up two.

  The control device 100 performs such image area ratio storage processing for each color of Y, C, M, and K every time one job is executed. One job includes a single image forming operation for outputting an image to only one recording sheet, and a continuous image forming operation for continuously outputting images to a plurality of recording sheets. There is something to be done in. In the single image forming operation, a start job for starting up the apparatus is executed before one job, and a stop job for stopping the apparatus is executed after one job. In the continuous image forming operation, a start job for starting up the apparatus is executed before the first one job, and a stop job for stopping the apparatus is executed after the last one job. Further, in one job other than the first and last jobs, so-called inter-sheet feeding is performed immediately after the job. This is a process for sending the surface of the photoreceptor 3 and the intermediate transfer belt 41, etc., with a blank corresponding to the inter-paper distance (the inter-sheet distance between the preceding recording sheet and the succeeding recording sheet). is there.

  The control device 100 counts up the count value of the number of cleaning blade operations every time one job is executed. The number of cleaning blade operations is also counted based on an A4 size recording sheet. When one job is performed on a recording sheet of A4 size or smaller, the count value of the number of cleaning blade operations is incremented by one. On the other hand, when one job is performed on a recording sheet larger than the A4 size, the count value of the cleaning blade operation count is incremented by two. Such blade operation count processing is performed for each color of Y, C, M, and K. When the service blade is replaced, the service man operates the control device 100 to reset the count value of the number of cleaning blade operations for the replaced color to zero.

In addition, when a user issues a continuous print job (continuous image forming operation) command, the control device 100 performs control for each job while performing the inter-paper distance adjustment processing. This inter-paper distance adjustment process is a process for adjusting the inter-paper distance. FIG. 4 is a flowchart showing a processing flow of the inter-paper distance adjustment processing executed by the control device 100. When starting the inter-paper distance adjustment process, the control device 100 first calculates the image area ratio of an image for one page to be imaged next (step 1: hereinafter, step is denoted as S). Next, after storing the image area ratio in association with the cumulative job count (S2), the image area ratio for the latest 500 jobs is read from the flash memory, and the average image area ratio for 500 jobs is calculated. (S3). Then, the image area ratio coefficient α is specified based on the calculation result and the first data table shown in the following Table 1 (S4). The first data table is stored in advance in the ROM of the control device 100.

  As shown in Table 1, when the average image area ratio for 500 times is 0 [%] or more and less than 50 [%], the image area ratio coefficient α is set to “0”. When the average image area ratio is 50% or more and less than 70%, the image area ratio coefficient α is set to “20”. When the average image area ratio is 70% or more, the image area ratio coefficient α is set to “30”.

  After specifying the image area ratio coefficient α in this way, the control device 100 next measures the temperature and humidity based on the outputs from the humidity sensor 105 and the temperature sensor 106 (S5). Then, based on these and the environment classification specifying algorithm shown in FIG. 5, the environment classification is specified (S6). This environment classification specifying algorithm is also stored in the ROM of the control device 100 in advance. As shown in the figure, when the temperature is 0 [° C.] or more and less than 15 [° C.] and the humidity is 0 [%] or more and less than 20 [%], the environmental classification is set to “A”. When the temperature is 0 [° C.] or more and less than 15 [° C.] and the humidity is 20 [%] or more and less than 60 [%], the environmental classification is set to “B”. In addition, when the temperature is 0 [° C.] or higher and lower than 15 [° C.] and the humidity is 60 [%] or higher, the environmental classification is set to “E”. [° C.] or more and less than 25 [° C.], and the humidity is 0 [%] or more and less than 20 [%], the environmental classification is set to “C”. ] If it is less than 25 [° C.] and the humidity is 20 [%] or more and less than 60 [%], the environmental classification is set to “D”. When the temperature is 15 [° C.] or higher and lower than 25 [° C.] and the humidity is 60 [%] or higher, the environmental classification is set to “H”. Also, the temperature is 25 [° C.] or higher. If the humidity is 0% or more and less than 20%, the environmental classification is set to “F”. The temperature is 25 ° C. or more and the humidity is 20%. If the temperature is 25 [° C.] or higher and the humidity is 60 [%] or higher, the environmental classification is set to “G”. , The environment classification is set to “I”.

After specifying the environmental classification in this way, the control device 100 next specifies the environmental coefficient β based on the environmental classification and the second data table shown in Table 2 below (see FIG. 4) (see FIG. 4). S7). This second data table is also stored in advance in the ROM of the control device 100.

  As shown in Table 2, the environmental coefficient β is set to a larger value as the environmental classification is the alphabet that comes later in the 26-character arrangement order of the alphabet.

Once the control device 100 has identified the environmental coefficient in this way (see FIG. 4), next, the member deterioration is based on the count value of the number of cleaning blade operations and the third data table shown in Table 3 below. The coefficient γ is specified (S8). This third data table is also stored in advance in the ROM of the control device 100.

  As shown in Table 3, as the cleaning blade operation frequency increases, the member deterioration coefficient γ is set to a larger value. After specifying the member deterioration coefficient γ in this way (see FIG. 4), the control device 100 next multiplies the image area rate coefficient α, the environmental coefficient β, and the member deterioration coefficient γ, and obtains the result as CPM. The down rate D (D = α × β × γ) is set (S9). CPM is the number of prints per minute. Further, the CPM down rate D is a rate of decreasing the CPM. As a method of reducing the CPM, there is a method of increasing the inter-paper distance without reducing the process line speed, in addition to a method of reducing the process line speed. In this printer, the CPM is lowered as necessary by the latter method.

The CPM in the default state differs depending on the recording sheet size in addition to the process linear velocity. In this printer, the inter-paper distance is increased so that the CPM is reduced by the calculated CPM down rate D with respect to the CPM of each size. An example is shown in Table 4 below.

  Table 4 shows the inter-paper distance for each size, the CPM after down, and the inter-paper distance after down when the CPM down rate D = 20%. When the CPM down rate D is 20 [%], the CPM after down becomes 80 [%] (100-20). The distance between the sheets after down is larger than that before down. As described above, when the inter-paper distance is increased, the amount of residual toner transferred to the “blade contact portion” per sheet is reduced in the photosensitive unit. As a result, it is possible to suppress the occurrence of toner slipping to the “blade contact portion” and to suppress the occurrence of whiteout images.

  When the calculated CPM down rate D exceeds 0 [%] (Y in S10 in FIG. 4), the control device 100 determines the current CPM, the CPM down rate D, the size of the recording sheet, and the process A new inter-paper distance is obtained based on the linear velocity (S11). This new inter-paper distance is larger than the previous inter-paper distance. Thereafter, the control device 100 updates the inter-paper distance to the newly obtained value (12), and sets the inter-paper distance in the subsequent inter-sheet feeding to the new value. Thereafter, if the continuous printing is not completed (N in S13), the control flow is looped to S1.

  On the other hand, if the calculated CPM down rate D does not exceed 0 [%] (N in S10), the control device 100 proceeds to the next process without changing the inter-paper distance. If the continuous printing is not completed (N in S13), the control flow is looped to S1. If the continuous printing has been completed (Y in S13), the distance between sheets is returned to the default value (S14), and then a series of processing flow is terminated.

The numerical values in Tables 1 to 3 shown above and the environment classification specifying algorithm shown in FIG. 5 are appropriate numerical values obtained by experiments conducted by the inventors. Specifically, the present inventors prepared a printer testing machine having the same basic configuration as the printer according to the reference embodiment. A4 size my paper (manufactured by NBS Ricoh Co., Ltd.) was set on the printer detector, and 200 sets (1000 sheets) of test prints were performed with 5 sheets of continuous printing as one set. In each set, the image area ratio of the output image, the cleaning blade (having different number of operations), the temperature and humidity, and the distance between sheets were varied. Then, it was observed whether or not streaky white spots due to toner fixation on the surface of the photoreceptor occurred on the output image. Based on this result, an appropriate relationship between the image area ratio coefficient α, the environmental coefficient β, the member deterioration coefficient γ, and the temperature and humidity, and an appropriate environment classification specifying algorithm were specified.

  The higher the CPM down rate D in the continuous print job, the more the inter-paper distance is increased, and the toner slippage at the “blade contact portion” can be more reliably suppressed. On the other hand, the higher the average image area ratio for the last 500 times, the more transfer residual toner is conveyed to the “blade contact portion” in the most recent 500 jobs. There is a high possibility that a larger amount of untransferred toner remains. That is, there is a high possibility that the toner slips more easily. As shown in Table 1, in this printer, the environmental coefficient α is set to a larger value as the average image area ratio increases. This means that the higher the image area ratio, the greater the inter-paper distance, making it more difficult for toner to slip through.

  Thus, in this printer, the higher the average image area ratio, the greater the inter-paper distance, thereby suppressing the occurrence of white spots due to toner slipping without unnecessarily prolonging the printing time. it can. However, the present inventors have found through experiments that it becomes easier for toner to slip through as the humidity increases. For this reason, if the inter-paper distance is simply determined based only on the average image area ratio, there is a possibility that toner may slip through in a high humidity environment.

  Therefore, in this printer, the inter-paper distance (CPM down rate D) is determined based not only on the image area rate coefficient α but also on the environmental coefficient β. As shown in Table 2, the environmental coefficient β is set to a larger value as the environmental classification is the alphabet that comes later in the 26-character arrangement order of the alphabet. Then, as shown in FIG. 5, at the same temperature, as the humidity increases, the alphabet that is later in the arrangement order is selected as the environmental classification. If the humidity is the same, the higher the temperature, the later the alphabet in the arrangement order is selected as the environmental classification. These mean that the higher the humidity is, the longer the distance between the papers and the longer the blank passage length. In addition, the higher the temperature is, the longer the distance between the sheets is and the longer the blank passage length is.

  In other words, in this printer, in addition to increasing the blank passage length as the average image area ratio increases, the blank passage length is increased by increasing the blank passage length as the internal humidity increases. Appropriate size according to. Accordingly, it is possible to suppress the occurrence of white spots due to slipping of the transfer residual toner without unnecessarily extending the printing time regardless of the humidity inside the apparatus. The reason why the environmental coefficient β is determined based not only on the humidity but also on the temperature is that the ease of slipping of the transfer residual toner shows a better correlation with the absolute humidity than with the relative humidity. is there. Based on the relative humidity detected by the humidity sensor 105 and the temperature, it becomes possible to specify the environmental coefficient β based on a numerical value close to absolute humidity. The passing length can be made closer to an appropriate value.

  The ease of slipping of the transfer residual toner is affected by the degree of deterioration of the cleaning blade in addition to the humidity and the average image area ratio. As the tip of the cleaning blade wears as it slides on the photoreceptor, transfer residual toner easily slips through. The deterioration degree of the cleaning blade is roughly proportional to the number of cleaning blade operations (usage amount).

  Therefore, in this printer, the inter-paper distance (CPM down rate D) is determined based not only on the image area rate coefficient α and the environmental coefficient β but also on the member deterioration coefficient γ. As shown in Table 3, the member deterioration coefficient γ is set to a larger value as the number of cleaning blade operations increases. This means that the greater the degree of deterioration of the cleaning blade, the greater the inter-paper distance and the longer the blank passage length. Thereby, regardless of the degree of deterioration of the cleaning blade, it is possible to suppress the occurrence of white spots due to slipping of the transfer residual toner without unnecessarily extending the printing time.

  The present inventors set the printer testing machine to a specification that adjusts the inter-paper distance based only on the average image area ratio as in the conventional machine. Then, an image having a high image area ratio was continuously printed in a high temperature and high humidity environment. As a result, when the number of cleaning blade operations exceeded 25000 [times], a streak-like white missing image was generated due to toner fixing to the photosensitive member.

  Next, the inventors set the printer testing machine to actually use the numerical values in Tables 1 and 2 and the algorithm for specifying the environmental classification in FIG. 5, and in a high-temperature and high-humidity environment, Images with a high image area ratio were continuously printed. As a result, when the number of cleaning blade operations exceeded 75,000 [times], a streak-like white missing image was generated due to toner fixing to the photoreceptor. This means that the cleaning blade replacement time can be extended to three times that of the conventional one, and the life of the cleaning blade can be extended to three times that of the conventional one as shown in FIG.

  Although the example of increasing the blank passage length by increasing the distance between papers has been described, the blank passage length can be increased by periodically stopping the toner image formation during a continuous print job. Also good.

Next, an embodiment in which a more characteristic configuration is added to the printer according to the reference embodiment and modifications thereof will be described. Unless otherwise specified below, the configuration of the printer according to the embodiment and each modification is the same as that of the reference embodiment.
[ Embodiment ]
In addition to the cleaning blade, there are application brush rollers (for example, 18aY) of a lubricant application device (for example, 18Y) as components that affect the ease of slipping of the transfer residual toner. When the application brush roller is deteriorated, the amount of lubricant applied to the photoconductor by the application brush roller is reduced and the surface friction coefficient of the photoconductor is increased. It is because it becomes easy to slip through.

Therefore, in the printer according to the embodiment , the value of the component deterioration coefficient γ is determined based on not only the number of cleaning blade operations but also the number of application brush operations.

  The control device 100 counts up the count value of the number of times of operation of the application brush roller every time one job is executed. The number of operations of the application brush roller is also counted based on the A4 size recording sheet. When one job is performed on a recording sheet of A4 size or smaller, the count value of the number of times of application brush roller operation is incremented by one. On the other hand, when one job is performed on a recording sheet larger than A4 size, the count value of the number of times of operation of the application brush roller is incremented by two. Such brush operation count processing is performed for each of the colors Y, C, M, and K. When the service brush is replaced, the service person operates the control device 100 to reset the count value of the operation frequency of the replaced application brush roller to zero.

Further, the control device 100 determines the member deterioration based on the count value of the cleaning blade operation count, the application brush roller operation count count, and the third data table shown in the following Table 5 during the continuous print job. Specify the coefficient γ.

  As shown in Table 5, when the number of cleaning blade operations is within the same numerical range, the member deterioration coefficient γ is set to a larger value as the number of operations of the application brush roller increases. This means that as the degree of deterioration of the application brush roller increases, the distance between sheets is increased to increase the blank passage length. Thereby, regardless of the degree of deterioration of the application brush roller, it is possible to suppress occurrence of white spots due to slipping of the transfer residual toner without unnecessarily extending the printing time.

  As shown in Table 5, if the deterioration of the application brush roller has not progressed much even though the cleaning blade has progressed, the component deterioration coefficient γ is set to “0”. This is because the latter deterioration has a greater effect on the ease of slipping of the transfer residual toner.

The inventors set the printer tester to actually use the numerical values of Table 1, Table 2 and Table 5 and the environment classification specifying algorithm shown in FIG. Thus, images with a high image area ratio were continuously printed. Then, when the number of application brush roller operations was in the range of 0 to 25000, the CPM down rate D could be reduced by about 30% compared to the printer according to the reference embodiment.

The following first modified configuration may be adopted for the printer according to the reference embodiment. That is, the method for obtaining the average image area ratio is different from the method described above . Specifically, in the above-described method , the image area ratio is obtained for each job, and the average image area ratio is obtained by averaging the image area ratios for the most recent 500 jobs. The aim of obtaining an average image area ratio, the residual amount of the transfer residual toner immediately before the "blade contact portion" (hereinafter, referred to as "toner residual amount") in order to grasp. However, even in the average image area ratio same, paper size, whether the process control, the presence or absence of activation job, by the presence or absence of stop job, "toner retention amount" is different. Specifically, although the "toner retention amount" becomes different depending on the blank passage length is as already mentioned, the method of obtaining the above-described average image area ratio is calculated first is a blank passage length Does not reflect. For example, when A4 size paper is used and 500 sheets are continuously printed at a distance of 2 cm, and when A4 size paper is used and 500 sheets of paper is printed at a distance of 4 cm, it is obtained. The obtained average image area ratio becomes the same value. However, since the blank passage length of the latter case is twice that of the former case, the “toner retention amount” should be significantly reduced. Nevertheless, since the average image area ratio is the same value, in the latter case, there is a possibility that the distance between sheets may be increased even though the “toner retention amount” is not so large. As shown in Table 4, when the paper size is different, the distance between the papers is different. Therefore, the prediction accuracy of the “toner retention amount” varies in each size.

Further, in the start job and the stop job, the photosensitive member is idled without forming a toner image at all, so that the blank passage length increases accordingly. For this reason, the blank passage length is greatly different between the case where the same 500 jobs are performed and the single print job is performed 500 times and the case where the job is performed 500 times in the continuous print job. Nevertheless, since the average image area ratio calculation result is the same in the above-described method for determining the average image area ratio, the “toner retention amount” cannot be accurately grasped.

The process control process is a process that is periodically performed to bring the image density close to the target value. In the continuous print job, the process is temporarily stopped. Then, for each color, a pattern image composed of a plurality of test toner images having different gradations is formed, and based on the result of detecting the image density of the pattern image by the reflection type photosensor, the image density of the target value is approximately Adjust the development potential etc. to obtain it. This process is a process control process. Since the pattern image formed by the process control process is not so large, it is close to the state where the photosensitive member is idle during that time. Therefore, when the process control process is performed, the “toner retention amount” is significantly reduced. Nevertheless, in the above-described method for obtaining the average image area ratio , the reduction is not reflected at all in the average image area ratio, so it is difficult to accurately grasp the “toner charge amount” based on the average image area ratio. become.

Therefore, in the first modified configuration , when the photosensitive member is driven to rotate, as shown in FIG. 7, the image of the toner image formed during every 1000 [msec] regardless of whether or not the image is formed. Calculate the area. Then, the calculation results are sequentially stored in the flash memory, and the average of the latest 500 calculation results is obtained as the average image area ratio. In such a configuration, since the average image area ratio is set closer to the “toner retention amount” than in the above-described method , the “toner retention amount” can be grasped more accurately. As a result, the inter-paper distance (blank passage length) can be set to a more appropriate value.

The inventors performed the following continuous print test. That is, the printer tester was set to calculate the image area ratio in the same manner as in the reference embodiment. Then, a process of outputting an image with an image area ratio of 72 [%] to A5 size recording paper by LEF paper feeding (horizontal conveyance) was continuously performed on 10,000 recording papers. During this time, for each sheet job, processing for adjusting the distance between sheets as necessary was performed. In addition, process control processing was performed every 50 sheets. Next, the printer tester was set to calculate the image area ratio in the same manner as in the first modified configuration, and then the image was output on 10,000 recording sheets in the same manner. Then, as shown in FIG. 8, in the first modified configuration , the CPM down rate D can be reduced by 30 [%] compared to the printer according to the reference embodiment.

In the first modified configuration , even if images having the same image area ratio are continuously output, if the CPM is lowered by increasing the inter-paper distance during a continuous print job, the average image area ratio is lowered accordingly. Calculated. For this reason, when the inter-paper distance is increased as the process control process is performed, the average image area ratio is lowered to some extent at a later desired timing without continuing the enlarged state without meaning. Can be shrunk back to the original. Therefore, the blank passage length (inter-paper distance) can be set to an appropriate value according to the “toner retention amount”.

[ First Modification ]
The printer according to the first modified example has the same configuration as the printer according to the embodiment except for the points described below. That is, for the application brush roller, the accumulated surface movement distance is obtained instead of the number of operations of the application brush roller. Specifically, during operation, the increase in brush surface travel distance is periodically calculated based on the process linear velocity and operation time, and the calculated result is added to the cumulative brush travel distance so far. To do. The timing for calculating and adding the increase in the surface movement distance is, for example, every 5 seconds. Such brush movement distance accumulation processing is performed for each color of Y, C, M, and K. When the service brush is replaced, the service man operates the control device 100 to reset the accumulated brush movement distance of the replaced color to zero.

In addition, the control device 100 specifies the member deterioration coefficient γ based on the count value of the number of cleaning blade operations, the accumulated brush movement distance, and the third data table shown in the following Table 6 during a continuous print job. To do.

The inventors set the printer tester to specify the member deterioration coefficient γ in the same manner as the printer according to the first modification , and used A4 size My Paper (manufactured by NBS Ricoh) as a recording sheet. I set it. Then, under the condition that the number of prints per set of continuous prints (hereinafter referred to as PPJ) was set to five, 1000 sets of continuous prints were performed and 50,000 test prints were performed. At this time, the number of image forming operations when changing from the default state to a state in which the distance between sheets is enlarged (hereinafter referred to as “number of times of image formation during sheet enlargement”) was examined. Next, 50 sets of continuous prints were performed under the condition that the PPJ was set to 1000 sheets, and 50000 test prints were generated to examine the “number of times of image formation during inter-paper enlargement”. As shown in FIG. 9, even when the same number of test prints is 50,000 sheets, the number of image forming operations during inter-sheet enlargement is greater when 1000 sets of 1000PPJ are performed than when 1000 sets of 5PPJ are performed. Was able to be extended to about 1.8 times. This is because, in the former case, compared to the latter case, the number of start jobs and stop jobs is significantly reduced, and the cumulative brush movement distance until the completion of printing 50000 sheets is reduced. By calculating the component deterioration coefficient γ using the accumulated brush movement distance instead of the number of times of operation of the application brush roller, it is possible to enlarge the sheet interval at a timing more suitable for the degree of brush deterioration. As a result, it is possible to suppress the occurrence of unnecessary lengthening of the printing time. For reference, FIG. 10 shows the relationship between PPJ and brush movement distance ratio (brush movement amount based on the brush movement distance of 5PPJ).

[ Second Modification ]
The printer according to the second modification has the same configuration as that of the printer according to the first modification , except for the points described below. That is, for the cleaning blade, the cleaning blade friction distance is obtained instead of the number of cleaning blade operations. Specifically, during operation, the increment of the surface movement distance (friction distance) of the photoreceptor that rubs against the cleaning blade is periodically calculated based on the process linear velocity and the operation time, The calculation result is added to the cumulative brush movement distance so far. The timing for calculating and adding the increase in the friction distance is, for example, every 5 seconds. Such a friction distance accumulation process is performed for each color of Y, C, M, and K. When the service blade is replaced, the service man operates the control device 100 to reset the cleaning blade friction distance of the replaced color to zero.

Further, the control device 100 specifies the member deterioration coefficient γ based on the cleaning blade friction distance, the accumulated brush movement distance, and the third data table shown in the following Table 7 during the continuous print job.

The inventors set the printer tester to specify the member deterioration coefficient γ in the same manner as the printer according to the second modification , and used A4 size My Paper (manufactured by NBS Ricoh) as a recording sheet. I set it. Then, under the condition that the number of prints per set of continuous prints (hereinafter referred to as PPJ) is set to five, 1000 sets of continuous prints are performed, and 50000 test prints are performed. I investigated. Next, 50 sets of continuous prints were performed under the condition that the PPJ was set to 1000 sheets, and 50000 test prints were generated to examine the “number of times of image formation during inter-paper enlargement”. Note that the cleaning blade was replaced every time the cleaning blade operated 10,000 times. As shown in FIG. 11, even when the same 50,000 test prints are performed, the number of image forming operations during inter-paper enlargement is greater when 50 sets of 1000 PPJ are performed than when 1000 sets of 5 PPJ are performed. Was able to be extended to about 1.8 times. This is because, in the former case, compared to the latter case, the number of start jobs and stop jobs is significantly reduced, so that the cumulative brush movement distance and cleaning blade friction distance until the completion of printing 50000 sheets are reduced. By obtaining the component deterioration coefficient γ using the cleaning blade friction distance instead of the number of cleaning blade operations, it is possible to expand the sheet interval at a timing more suitable for the degree of deterioration of the cleaning blade. As a result, it is possible to suppress the occurrence of unnecessary lengthening of the printing time.

Note that the following second modified configuration may be employed in the printer according to the reference embodiment.
That is, as the recording sheet, in addition to plain paper, glossy coated paper having a coated surface is known. Even when plain paper and coated paper are formed with the same toner adhesion amount per unit area, the image density and color are different. Coated paper has a higher image density than plain paper.

The control device 100 is connected to an operation display unit including a touch panel and a key button group (not shown). The user can input various information to the control device 100 by an input operation on the operation display unit. In the second modified configuration , the recording sheet type information (plain paper or coated paper) set in the paper feed cassette (31, 32) can be input to the control device 100 as one of the input information. That is, in the second modified configuration , the operation display unit functions as a sheet type information acquisition unit that acquires the type information of the recording sheet.

  The control device 100 as the adhesion amount adjusting means adjusts the toner adhesion amount per unit area with respect to the toner image by correcting the image forming condition of the image forming unit according to the input type information. More specifically, while the coated paper is input as the type information and the coated paper printing mode is set, the toner adhesion amount per unit area is reduced compared to the case where the plain paper printing mode is set. As a result, an image with a stable density can be obtained regardless of the type of recording sheet.

When adjusting the toner adhesion amount per unit area on the toner image according to the type of the recording sheet, the amount of residual toner transferred to the “blade contact portion” varies depending on the type of the recording sheet. The appropriate timing for expanding the gap between papers is different. Therefore, the control device 100 specifies the sheet type coefficient δ based on the recording sheet type information and the fourth data table shown in Table 8 below. The fourth data table is stored in advance in the ROM of the control device 100.

  As shown in Table 8, when plain paper is set, the sheet type coefficient δ is set to a larger value than when coated paper is set. This is because, when plain paper is set, the transfer amount of the transfer residual toner to the “blade contact portion” increases, and the transfer residual toner easily slips through.

  After specifying the sheet type coefficient δ, the control device 100 multiplies the image area rate coefficient α, the environmental coefficient β, the component deterioration coefficient γ, and the sheet type coefficient δ to obtain the CPM down rate D (D = α × β × γ × δ). Thereby, regardless of the type of the recording sheet, it is possible to suppress the occurrence of white spots in the image without unnecessarily prolonging the printing time by increasing the inter-paper distance at an appropriate timing and size.

The technique of obtaining the CPM down rate D by multiplication of the sheet type coefficient δ can be applied not only to the printer according to the embodiment but also to the printer according to the embodiment and each modification .

Further, the following third modified configuration may be adopted for the printer according to the reference embodiment . That is, the process for adjusting the inter-paper distance based on the image area ratio coefficient α, the environmental coefficient β, the component deterioration coefficient γ, etc. is performed as the first adjustment process. On the other hand, a process of adjusting the inter-paper distance based on the temperature of the fixing belt (fixing temperature) of the fixing device 60 is performed as the second adjustment process. The reason why the second adjustment process is performed is as follows. That is, cardboard and coated paper take more heat from the fixing belt than plain paper. For this reason, when continuous printing is performed using thick paper or coated paper, the frequency of turning on the heater of the fixing device 60 increases. As a result, the predetermined fixing temperature is maintained, but depending on the thickness of the thick paper, the material of the coated layer of the coated paper, the process linear velocity, etc., the heating cannot be made in time, and the temperature of the fixing belt is lowered as it is. There is. Therefore, when the surface temperature of the fixing belt detected by the temperature sensor falls below a predetermined threshold, the distance between sheets is further increased to reduce the sheet passing area per unit time (in the fixing device). Thus, the fixing temperature is raised to a predetermined temperature. At this time, the inter-paper distance is enlarged by the second adjustment process.

  Although the first adjustment process and the second adjustment process are performed separately, in some cases, the expansion timing of the inter-paper distance due to these processes may come almost simultaneously. In this case, if the inter-paper distance specified in each process is added up to increase the inter-paper distance to the total value, the inter-paper distance is unnecessarily increased. For example, it is determined that it is necessary to increase the distance between sheets by 10 [mm] in the second adjustment process, while it is determined that it is necessary to increase the distance between sheets by 8 [mm] in the first adjustment process. To do. In this case, if it is increased by 10 [mm], the blank passage length can be increased to a desired level to suppress the occurrence of white spots in the image, and the temperature of the fixing belt can be increased to a desired level. Nevertheless, if the total value of 18 [mm] is enlarged, 8 [mm] becomes a useless enlargement, and the print time is wasted.

  Therefore, when the difference between the execution timing of the first adjustment process and the execution timing of the second adjustment process is within a predetermined time lag, the control device 100 selects one of the inter-paper distances obtained by the adjustment process. Use the larger one to increase the distance between papers. As a result, it is possible to avoid an unnecessary increase in print time.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
[Aspect A]
Aspect A is a transfer means (for example, transfer unit 40) for transferring a toner image on a latent image carrier (for example, photoconductor 3) to a recording sheet directly or via an intermediate transfer body (for example, an intermediate transfer belt (41)). The latent image carrier, the latent image writing means (for example, the optical writing unit 20), the developing means (for example, the developing device 7), and the transfer residual toner adhering to the surface of the latent image carrier are scraped off to In an image forming apparatus including an image forming unit (for example, an image forming unit 1) having a cleaning member (for example, a cleaning blade 4a) for cleaning the surface, and an image information acquiring unit (for example, an image information input unit 102) for acquiring image information. The humidity detection means (for example, the humidity sensor 105) for detecting the humidity and the above-mentioned clear until the image of all pages is output as the humidity detection result increases. And a blank adjustment means for performing an adjustment process for increasing a blank passage length, which is a length of a blank area of the latent image carrier passing through a position facing the ning member. .

[Aspect B]
Aspect B is a first algorithm for increasing the blank passage length as the average image area ratio of the image output in the most recent predetermined period is increased in the adjustment process in Aspect A (for example, Table 1 and D = α × β × γ) and a second algorithm for increasing the blank passage length as the humidity detection result becomes higher (for example, Table 2, an environment classification specifying algorithm, and D = α × β × γ) ) And a third algorithm (for example, Table 3, and D = α × β × γ) that increases the blank passage length as the usage amount of the cleaning member increases, determines the blank passage length. The blank adjustment means is configured so as to perform the processing.

[Aspect C]
Aspect C is the same as aspect B in that the temperature detecting means (for example, temperature sensor 106) for detecting the temperature and the lubricant applying means (for example, applying the lubricant to the surface of the latent image carrier that has passed the position facing the cleaning member) In addition to the first algorithm, the second algorithm, and the third algorithm, in the adjustment process, the blank passage length increases as the temperature detection result increases. A fourth algorithm (for example, Table 2, an algorithm for specifying the environmental classification, and D = α × β × γ) and a method for increasing the blank passage length as the amount of the lubricant application unit increases. Using the fifth algorithm (for example, Table 5 and D = α × β × γ), the blank adjustment means performs the processing for determining the blank passage length. It is characterized in that the configuration was.

[Aspect D]
Aspect D is the aspect B or C, in which the sheet type information acquisition means (for example, an operation display unit) for acquiring the type information of the recording sheet sent to the transfer means, and the image forming means in accordance with the type information There is provided an adhesion amount adjusting means (for example, the control device 100) for performing processing for correcting the condition and adjusting the toner adhesion amount per unit area with respect to the toner image, and in the adjustment processing, at least the first algorithm, In addition to the second algorithm and the third algorithm, a sixth algorithm (for example, Table 8 and D = α × β × γ × δ) for changing the blank passage length according to the type information is used. And the blank adjustment means is configured to implement the process of determining the blank passage length.

[Aspect E]
Aspect E adopts a period in which a predetermined number of image forming operations are performed as the predetermined period in the adjustment process in any one of aspects B to D, and every time an image forming operation is performed, a recording sheet The blank adjustment means is configured to perform a process of changing the count value of the accumulated job count according to the size of the job.

[Aspect F]
Aspect F adopts a period required to move the surface of the latent image carrier by a predetermined distance as the predetermined period in the adjustment process in any one of aspects B to D, and the unit surface in the period The blank adjustment unit is configured to perform a process of adjusting the blank passage length based on an average image area ratio per moving distance.

[Aspect G]
Aspect G is characterized in that, in any of the aspects B to F, the rubbing distance between the cleaning member and the latent image carrier in the cleaning member is used as the usage amount of the cleaning member in the adjustment process. It is what.

[Aspect H]
Aspect H is that in the adjustment process according to aspect C, the amount of the lubricant application means used is a lubricant on the surface of the latent image carrier while bringing its endlessly moving surface into contact with the latent image carrier. The surface endless moving distance of the lubricant applying member for applying the coating is employed.

[Aspect I]
Aspect I is that in any one of aspects A to H, in addition to performing the adjustment process as a first adjustment process, the humidity detection result, the image area ratio, the usage amount of the cleaning member, the temperature, and the lubricant The second adjustment process for adjusting the blank passage length based on a predetermined control parameter different from any of the usage amount of the coating means is performed, and the blank passage length determined in the first adjustment process, When the blank passage length determined in the second adjustment process is different, the blank adjustment unit is configured to perform a process of selecting a larger one of the blank passage lengths. To do.

1Y, C, M, K: Image forming unit (image forming means)
7Y, C, M, K: Developing device (developing means)
3Y, C, M, K: photoconductor (latent image carrier)
4aY: Cleaning blade (cleaning member)
18aY: Application brush roller (lubricant application means)
20: Optical writing unit (latent image writing means)
40: Transfer unit (transfer means)
41: Intermediate transfer belt (intermediate transfer member)
100: Control device (blank adjustment means, adhesion amount adjustment means)
102: Image information input unit (image information acquisition means)
105: Humidity sensor (humidity detection means)
106: Temperature sensor (temperature detection means)

JP 2011-170320 A JP 2011-59320 A

Claims (7)

Transfer means for transferring the toner image on the latent image carrier to a recording sheet directly or via an intermediate transfer member;
An image forming means having a cleaning member for scraping off the transfer residual toner adhering to the surface of the latent image carrier, latent image writing means, developing means, and the surface of the latent image carrier;
In an image forming apparatus comprising image information acquisition means for acquiring image information,
Humidity detection means for detecting humidity;
Temperature detection means for detecting temperature;
A lubricant application means for applying a lubricant to the surface of the latent image carrier that has passed through a position facing the cleaning member;
This is the length of the blank area of the latent image carrier that passes through the position facing the cleaning member until the image of all pages is output as the average image area ratio of the image output in the most recent predetermined period increases. A first algorithm for increasing the blank passage length, a second algorithm for increasing the blank passage length as the humidity detection result increases, and the blank passage length as the amount of the cleaning member used increases. A third algorithm for increasing the blank passage length, a fourth algorithm for increasing the blank passage length as the temperature detection result increases, and the blank passage length as the amount of the lubricant application means increases. the fifth algorithm for increasing, by determining the blank passage length with, the blank passes length as the humidity of the detection result becomes higher An image forming apparatus characterized by providing a blank adjusting means for performing you greater adjustment process. The image forming apparatus according to claim 1 .
Sheet type information acquisition means for acquiring type information of the recording sheet sent to the transfer means;
An adhesion amount adjusting unit that performs a process of adjusting the toner adhesion amount per unit area with respect to the toner image by correcting the image forming condition of the image forming unit according to the type information;
In the adjustment process, in addition to at least the first algorithm, the second algorithm, and the third algorithm, using a sixth algorithm for changing the blank passage length according to the type information, An image forming apparatus, wherein the blank adjustment means is configured to perform processing for determining the blank passage length. The image forming apparatus according to claim 1 or 2 ,
In the adjustment process, a period during which a predetermined number of image forming operations are performed is adopted as the predetermined period, and the count value of the accumulated job count varies depending on the size of the recording sheet every time the image forming operation is performed. An image forming apparatus, characterized in that the blank adjustment means is configured to perform the processing. The image forming apparatus according to claim 1 or 2 ,
In the adjustment process, as the predetermined period, a period required to move the surface of the latent image carrier by a predetermined distance is adopted, and the blank is determined based on an average image area ratio per unit surface movement distance in the period. An image forming apparatus, wherein the blank adjustment means is configured to perform a process of adjusting a passage length. The image forming apparatus according to any one of claims 1 to 4 ,
The image forming apparatus according to claim 1, wherein a sliding distance between the cleaning member of the cleaning member and the latent image carrier is used as the usage amount of the cleaning member in the adjustment process. The image forming apparatus according to claim 1 .
In the adjustment process, as a usage amount of the lubricant application means, a lubricant application member that applies a lubricant to the surface of the latent image carrier while bringing its endlessly moving surface into contact with the latent image carrier. An image forming apparatus using a surface endless moving distance. The image forming apparatus according to claim 1 to 6,
In addition to performing the adjustment process as the first adjustment process, a predetermined difference that is different from any of the humidity detection result, the average image area ratio, the usage amount of the cleaning member, the temperature, and the usage amount of the lubricant application unit. A second adjustment process for adjusting the blank passage length based on a control parameter is performed, and the blank passage length determined in the first adjustment process and the blank passage length determined in the second adjustment process The image forming apparatus is characterized in that the blank adjustment means is configured to perform a process of selecting a larger one of the two blank passage lengths when the two are different.

Images