JP2011170004A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inform a user of exchange time for a process cartridge even if an amount conveyed by a development roller of the process cartridge to be exchanged varies, the exchange time conforming to a corresponding amount which corresponds to the amount conveyed by the development roller. <P>SOLUTION: The exchange time for a process cartridge 7 is stored in a RAM 12b on the basis of the reflection density of a patch which is detected by a density-detection part 85 of a conveyed toner amount-detecting part 11b, the time conforming to the reflection density of a patch which is stored in a ROM 12a. A display part 13 displays the arrival of the exchange time stored in the RAM 12b, for the process cartridge 7 in use. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer, a FAX, or a copying machine that forms characters and images on a recording medium such as paper using toner or the like.

  In an electrophotographic image forming apparatus, an electrostatic latent image formed on a photosensitive drum is visualized as a toner image by a process cartridge that can be attached to and detached from the image forming apparatus.

  In this process cartridge, generally, a toner containing portion for containing toner, a developing roller for carrying toner supplied from the toner containing portion, and a layer thickness regulating blade for regulating the thickness of the toner layer on the developing roller And a photosensitive drum disposed opposite to the developing roller and on which an electrostatic latent image is formed.

  The toner supplied from the toner storage unit is conveyed onto the developing roller, charged by contact with the layer thickness regulating blade, and attached to the photosensitive drum on which the electrostatic latent image is formed. Further, the toner that has not adhered to the photosensitive drum is returned from the developing roller to the toner container. The toner is again used for development.

  When the case where the image forming ratio with respect to the sheet is small (the image ratio with respect to the sheet is low) continues, the toner that has not adhered to the photosensitive drum contacts the layer thickness regulating blade and the photosensitive drum many times. As a result, an external additive such as silica, which is externally added to the toner, is buried in the toner base particles, resulting in a problem that the chargeability of the toner is lowered. So-called toner deterioration occurs.

  In this way, when the amount of deteriorated toner increases in the process cartridge, toner with low chargeability may adhere to non-exposed areas on the photosensitive drum. This fogs the paper at the time of printing and leads to a decrease in print quality.

  On the other hand, the likelihood of toner deterioration varies depending on the amount of toner transported onto the developing roller of the process cartridge (hereinafter, the toner transport amount of the developing roller), as shown in FIG. FIG. 9 is a diagram illustrating the relationship between the number of printed sheets and the charge amount of toner.

  For example, when the toner conveyance amount of the developing roller is low, even if the number of printed sheets increases, the amount of toner that rubs against the layer thickness regulating blade is small, so that toner deterioration hardly occurs. That is, the inclination is small in FIG. On the other hand, when the amount of toner transported by the developing roller is high, if the number of printed sheets increases, the amount of toner that rubs against the layer thickness regulating blade increases, and therefore toner deterioration tends to occur. That is, the inclination is large in FIG. As described above, the likelihood of toner deterioration varies depending on the toner conveyance amount of the developing roller.

  As major factors that determine the toner conveyance amount of the developing roller, the surface roughness (glossiness) of the developing roller and the chargeability of the toner accommodated in the toner accommodating portion can be considered. For example, the toner transport amount of a developing roller having a high toner charging property and a rough developing roller surface is larger than the toner transport amount of a developing roller having a low toner charging property and a flat developing roller surface.

  In this way, since the toner conveyance amount of the developing roller of the process cartridge to be changed varies, the likelihood of toner deterioration changes. For example, in Patent Document 1, a predetermined number of prints that do not cause fogging is set, When the set number of sheets is reached regardless of the remaining amount, the user is prompted to replace the process cartridge.

  JP 2007-199514 A

  However, in the above image forming apparatus, as shown in FIG. 9, since the predetermined number of sheets is set as the number of printed sheets A, even when a process cartridge with a small amount of toner transported by the developing roller is mounted, the number of printed sheets A is increased. When this is reached, the user is prompted to replace the process cartridge. In other words, the process cartridge that has reached the number A of prints is urged to be replaced even though it can be printed up to the number B of prints that does not cause fogging. Therefore, the user is forced to replace the process cartridge being used with a new process cartridge even though the process cartridge is still usable in terms of print quality.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus in which a user can recognize an appropriate replacement time of a process cartridge.

  To achieve this object, the invention described in claim 1 is an image forming apparatus in which a process cartridge having a developing roller for developing an electrostatic latent image formed on a photosensitive drum with a developer is detachable. When the process cartridge is mounted on the image forming apparatus, the detection unit detects a corresponding amount corresponding to the transport amount by which the developer is transported by the developing roller, and the corresponding amount corresponding to the transport amount of the developing roller. A process corresponding to a corresponding amount corresponding to the transport amount of the developing roller stored in the first storage unit, based on the first storage unit that stores the replacement timing of the process cartridge and the corresponding amount detected by the detection unit A second storage unit for storing the replacement time of the cartridge and a notification for informing that the process cartridge being used has reached the replacement time stored in the second storage unit It is characterized by having a stage, a.

According to a second aspect of the present invention, in the first aspect of the present invention, the detecting means includes a developing bias applying means for applying a maximum developing bias value that saturates the amount of developer adhering to the photosensitive drum. A patch forming means for applying a maximum developing bias value by the developing bias applying means to form a density detection patch by a developer; a density detecting means for detecting the density of the patch formed by the patch forming means;
It is characterized by having.

  According to the first aspect of the present invention, the second storage unit responds to the equivalent amount corresponding to the transport amount of the developing roller stored in the first storage unit, based on the equivalent amount detected by the detection unit. The process cartridge replacement time is stored, and the notification means notifies the user that the process cartridge being used has reached the replacement time stored in the second storage unit. Even when the transport amount of the developing roller is different, it is possible to notify the user of the replacement timing of the process cartridge corresponding to a corresponding amount corresponding to the transport amount of the developing roller. Thereby, the user can recognize an appropriate replacement time of the process cartridge.

  According to the second aspect of the present invention, the detecting means includes a density detecting unit that forms a patch by applying a maximum developing bias value to the developing roller and detects the density of the patch. By detecting the density of the patch, the developer conveyance amount can be detected.

Side sectional view showing schematic configuration of laser printer Side sectional view showing the laser printer with the unit body removed Block diagram showing the configuration of the control device Explanatory drawing explaining the relationship between the reflection density of the patch and the developing bias value Explanatory drawing explaining the relationship between the reflection density of the patch and the development bias value in process cartridges with different toner conveyance amounts of the development roller A flowchart showing a processing procedure for determining the printable number of sheets of a mounted process cartridge when a new process cartridge is mounted. Flowchart showing the process until the laser printer displays the replacement timing of the process cartridge on the display unit during the image forming process Explanatory drawing explaining the relationship between the reflection density of the patch and the number of printable sheets Explanatory drawing explaining the relationship between the number of printed sheets and the charge amount of toner

[Overall structure of laser printer]
FIG. 1 is a side sectional view showing a schematic configuration of a laser printer 1 as an example of an image forming apparatus of the present embodiment.

  As shown in FIG. 1, the laser printer includes a main body housing 2, and in the main body housing 2, a paper feeding unit 3 that supplies paper to the image forming unit 4, and forms an image on the fed paper. An image forming unit 4 that performs the operation, a paper discharge unit 5 that discharges the paper on which the image is formed, and a control device 10 (see FIG. 3) that controls the operation of the laser printer.

  In the following description, unless otherwise specified, the vertical direction shown in FIG. 1 is up and down, the right side in FIG. 1 is front, the left side is rear, the back side of the paper is right, and the front side of the paper is left. Indicates. The direction here is defined based on the direction seen from the person standing in front of the laser printer 1.

  As shown in FIG. 1, the main body housing 2 is provided with a cover 21 that can open and close an opening.

  The cover 21 is rotatably supported by a cover shaft (not shown) provided at the lower end thereof. When the cover 21 is closed (closed state), the opening 22 is closed by the cover 21 as shown in FIG. When the cover 21 is opened (open state), the opening 22 is opened as shown in FIG. The user can attach and detach the unit main body 61 in which the process cartridges 7 described later are mounted from the opening 22.

(1) Paper Feed Unit The paper feed unit 3 includes a paper feed tray 31 that stores paper, a paper feed roller 32, a paper feed pad 33, and a registration roller 34 below the inside of the main body housing 2.

  In the sheet feeding unit 3 configured as described above, the sheets are separated one by one from the sheet feeding tray 31 and sent to the image forming unit 4.

(2) Image Forming Unit The image forming unit 4 includes an exposure unit 41, a process unit 6, a transfer unit 8, and a fixing unit 9.

(2-1) Exposure Unit The exposure unit 41 is provided in the upper part of the main body housing 2 and includes a laser light emitting unit, a polygon mirror, a lens, and a reflecting mirror (not shown).

  In the exposure unit 41 configured in this way, laser light emitted from a laser light source based on predetermined image data is scanned at high speed in the left-right direction by a polygon mirror, and passes or reflects through a lens and a reflecting mirror. The photosensitive drum 62 is irradiated.

(2-2) Process Unit The process unit 6 is disposed below the exposure unit 41 and above the paper feed unit 3. The process unit 6 includes a unit main body 61 and a process cartridge 7 containing toner of each color attached to the unit main body 61.

  The unit main body 61 is arranged side by side from the front side to the rear side, and has four drum subunits corresponding to the process cartridges 7 of the respective colors.

  Each drum subunit includes a photosensitive drum 62, a scorotron charger 63, a detection member (not shown) of a new article detection unit described later, and the like.

  The process cartridge 7 includes a cartridge frame 71, a developing roller 72 rotatably supported by the cartridge frame 71, a supply roller 73 that supplies toner to the developing roller 72, and the thickness of the toner on the developing roller 72 is regulated. A layer thickness regulating blade 74, and a toner accommodating portion 75 that accommodates toner as an example of a developer.

  The developing roller 72 has a metal roller shaft and a covering portion that covers the roller shaft with a conductive rubber material. In the covering portion, a surface made of conductive urethane rubber or silicone rubber containing carbon fine particles or the like is coated with a coating layer of urethane rubber or silicone rubber containing fluorine.

  The supply roller 73 has a metallic roller shaft and a covering portion that covers the roller shaft with a conductive foam material.

  The layer thickness regulating blade 74 is disposed in the vicinity of the developing roller 72. The layer thickness regulating blade 74 is provided on a metal leaf spring member whose upper end is fixed to the cartridge frame 71 and a lower end portion of the leaf spring member, and presses the surface of the developing roller 72 by the elastic force of the leaf spring member. Department.

  The toner container 75 is filled with a positively charged nonmagnetic one-component toner having electrical insulation as a developer. The toner container 75 is provided with an agitator 76 for stirring the toner in the toner container 75.

  In the process unit 6 configured as described above, the surface of the photosensitive drum 62 is uniformly charged by the charger 63, and the charged surface of the photosensitive drum 62 is exposed by scanning with laser light. As a result, the electrostatic latent image is formed on the surface of the photosensitive drum 62.

  On the other hand, the toner in the toner container 75 is supplied onto the developing roller 72 by the supply roller 73 and is frictionally charged between the supply roller 73 and the developing roller 72. Then, as the developing roller 72 rotates, the toner supplied onto the developing roller 72 enters between the layer thickness regulating blade 74 and the developing roller 72, and is further frictionally charged while being thin with a certain thickness. It is carried on the developing roller 72 as a layer.

  The toner supplied from the process cartridge 7 is held on the exposed portion of the photosensitive drum 62, so that a toner image is formed on the surface of the photosensitive drum 62.

(2-3) Transfer Unit The transfer unit 8 is disposed above the paper feed unit 3 and below the process unit 6. The transfer unit 8 includes a driving roller 81, a driven roller 82, a conveyance belt 83 that conveys a sheet to the fixing unit 9, and a transfer roller 84.

  The driving roller 81 and the driven roller 82 are spaced apart and arranged in parallel, and an endless conveyance belt 83 is stretched between them. The outer surface of the conveyor belt 83 is in contact with each photosensitive drum 62. In addition, four transfer rollers 84 that sandwich the conveyance belt 83 between the photosensitive drums 62 are disposed inside the conveyance belt 83. A transfer bias is applied to the transfer roller 84 in order to transfer the toner image on each photoconductive drum 62 onto a sheet.

  In the transfer unit 8 configured as described above, the sheet transported by the transport belt 83 during image formation is transported between the photosensitive drum 62 and the transfer roller 84 disposed inside the transport belt 83. Then, the toner image held on the photosensitive drum 62 is transferred to a sheet.

(2-4) Fixing Unit The fixing unit 9 includes a heating roller 91 that is disposed on the rear side of the process cartridge 7 and is heated by a heat source, and a pressure roller 92 that is in pressure contact with the heating roller 91.

  In the fixing unit 9 configured as described above, the toner image on the paper is heat-fixed on the paper as the paper passes between the heating roller 91 and the pressure roller 92.

(3) Paper Discharge Unit The paper discharge unit 5 includes a paper discharge roller 51 for conveying the paper that has passed through the fixing unit 9, and a paper discharge tray 52 that accumulates the paper conveyed by the paper discharge roller 51. Yes.

  In the paper discharge unit 5 configured as described above, the paper on which the toner image is fixed by the fixing unit 9 is conveyed by the paper discharge roller 51 and discharged onto the paper discharge tray 52.

[Electrical configuration]
Next, the configuration of the control device 10 will be described with reference to FIG.

  The control device 10 includes a control unit 11 and a storage unit 12.

  The control unit 11 includes an image forming unit 4, a display unit 13 as an example of a notification unit that displays to the user that it is time to replace the process cartridge 7, an attachment / detachment detection unit 14 that detects attachment / detachment of the unit main body 61, A new product detector 15 for detecting whether the process cartridge 7 mounted on the unit main body 61 is new (unused) is electrically connected. The control unit 11 includes a CUP 11a, a toner conveyance amount detection unit 11b as an example of a detection unit, a development bias control unit 11c as an example of a development bias application unit that controls a development bias applied to the development roller 72, and a conveyance. A patch forming unit 11d as an example of a patch forming unit that forms a patch on the belt, and a density detecting unit 85 as an example of a density detecting unit for detecting the density of the patch.

  The attachment / detachment detection unit 14 includes an optical sensor (not shown) including a light emitting unit and a light receiving unit. The light emitting unit and the light receiving unit are provided in the main body housing 2 and are disposed so as to face each other via the unit main body 61. The attachment / detachment detection unit 14 detects whether the unit main body 61 is attached to or detached from the main body housing 2 by turning on / off the optical sensor.

  The new article detection unit 15 detects whether or not the process cartridge 7 attached to the unit main body 61 is new in order to determine whether or not to reset the cumulative number of printed sheets stored in the storage unit described later.

  A new product detection sensor (not shown) constituting a part of the new product detection unit 15 is provided on the side wall of the main body housing 2. This new article detection sensor has an optical sensor.

  Specifically, before the unit main body 61 is attached to the main body housing 2, the new article detection sensor is in an ON state. When a unit main body 61 having a new process cartridge 7 is attached to the main body housing 2, a drive gear (not shown) provided in the process cartridge 7 is a drum subunit corresponding to the new process cartridge 7. The detection member provided on the side wall of the sensor is rotated, and the detection member blocks the light of the optical sensor. Further, since the drive gear provided in the non-new process cartridge 7 does not rotate the detection member, the optical sensor is in an ON state. In this way, the new article detection unit 15 determines whether or not the process cartridge 7 attached to the unit main body 61 is new by turning on / off the optical sensor.

  The development bias controller 11c controls to apply a development bias value lower than a maximum development bias value, which will be described later, when forming an image on a sheet, and to apply the maximum development bias value when detecting the toner conveyance amount. .

  The patch forming unit 11d detects the density of the toner image, and corrects the image forming conditions for printing an appropriate density on the paper, or detects a color shift and detects a patch used for correcting the color shift. In addition to forming, a patch used for detecting the toner conveyance amount is also formed.

  As shown in FIG. 1, the density detector 85 is disposed at a position facing the driven roller 82 with the conveyance belt 83 interposed therebetween (a position obliquely below the driven roller). The density detection unit 85 includes a density sensor for detecting the reflection density of the patch formed by the patch forming unit 11d. The density sensor includes a light emitting element such as a semiconductor laser, and a light receiving element that receives laser light emitted from the light emitting element and reflected from the surface of the patch or the surface of the conveyance belt. When the patch is conveyed to a position facing the density sensor, the density detection unit 85 obtains the amount of light reflected by the patch from the density sensor. Then, the density detector 85 obtains the reflection density of the patch based on the reflected light amount.

  The toner transport amount detection unit 11b forms a patch by the patch forming unit 11d and applies the reflection density (equivalent amount) of the patch when the development bias control unit 11c applies a maximum development bias value (described later) to the development roller 72. By detecting with the density sensor of the density detector 85, the toner conveyance amount of the developing roller 72 provided in the process cartridge 7 is detected.

  The storage unit 12 includes a ROM 12a as an example of a first storage unit and a RAM 12b as an example of a second storage unit.

  The ROM 12a stores various control programs for controlling the laser printer 1, various settings, initial values, and the like. For example, the ROM 12a is sensitive to a table (see FIG. 8) indicating the number of printable sheets (replacement timing) of the process cartridge 7 according to the reflection density of the patch, which will be described later, and the developing roller 72 by changing the developing bias value. A maximum developing bias value at which the amount of toner adhering to the body drum 62 is saturated is stored.

  The RAM 12b is used as a work area for temporarily storing various read control programs or as a storage area for temporarily storing image data. For example, in the RAM 12b, the number of printable sheets corresponding to the reflection density of the patch detected by the toner conveyance amount detection unit 11b of the mounted process cartridge 7 or the cumulative value of the number of printed sheets after mounting a new process cartridge 7 is displayed. A certain cumulative number of printed sheets is stored. The accumulated number of printed sheets is reset when a new process cartridge 7 is mounted.

  The CUP 11a controls each component of the laser printer 1 via the control unit 11 while storing the processing result in the RAM 12b according to the control program read from the ROM 12a.

[How to determine the toner transport amount]
Next, how to determine the toner conveyance amount will be described with reference to FIG.

  FIG. 4 is a diagram for explaining the relationship between the reflection density of the patch and the development bias value.

  The reflection density of the patch depends on the developing bias value.

  However, when the developing bias value becomes V1 or more, the reflection density of the patch does not depend on the developing bias value. This is because when the developing bias value is V1 or more, all the toner on the developing roller 72 corresponding to the electrostatic latent image on the photosensitive drum 62 has adhered to the photosensitive drum 62, so the developing bias value is increased by V1 or more. This is because the amount of toner on the developing roller 72 adhering to the electrostatic latent image on the photosensitive drum 62 does not change even if it is set.

  That is, by forming a patch with a developing bias value V1 at which the amount of toner adhering to the photosensitive drum 62 is saturated, and detecting the reflection density of the patch, the toner conveyance amount of the developing roller 72 of the mounted process cartridge can be known. .

  In this embodiment, when a new process cartridge 7 is mounted in the main body housing 2, the image forming unit 4 forms an electrostatic latent image of a patch on the photosensitive drum 62 corresponding to each color. Then, the development bias controller 11c applies a development bias value at which the amount of toner adhering to the photosensitive drum 62 is saturated to the development roller 72 of each color. Then, the patch forming unit 11d forms a toner image of the patch on the transport belt 83 with each color toner. The density detector 85 detects the density of each color patch. The controller 11 obtains the toner conveyance amount of the developing roller 72 of the new process cartridge 7 based on the detection result of the patch density.

[How to find the maximum development bias value]
Next, a method for obtaining the maximum developing bias value of the present embodiment will be described with reference to FIG.

  When the process cartridge 7 is manufactured, the process cartridge 7 is manufactured using a toner whose chargeability and the surface roughness of the developing roller 72 are within predetermined standard values. The relationship between the patch reflection density and the developing bias value at this time is as shown in FIG. A1 is the case where the charging property of the toner is maximum and the surface roughness of the developing roller 72 is minimum, A2 is the case where the charging property of the toner is minimum and the surface roughness of the developing roller 72 is minimum, and A3 is the toner Is the maximum and the surface roughness of the developing roller 72 is the maximum, A4 is the case where the toner charging property is minimum and the surface roughness of the developing roller 72 is maximum.

  As described above, the developing bias value when the reflection density of the patch is saturated differs depending on the chargeability of the toner of the process cartridge 7 and the surface roughness of the developing roller 72.

  However, when a bias equal to or greater than the developing bias value V4 is applied to the developing roller 72, the reflection density of the patch becomes constant regardless of which process cartridge 7 is mounted. In other words, when a bias equal to or higher than the developing bias value V4 is applied to the developing roller 72, any process cartridge 7 in which the chargeability of the toner and the surface roughness of the developing roller 72 are different within the standard values on the photosensitive drum 62 is used. All of the toner on the developing roller 72 corresponding to the electrostatic latent image adheres to the photosensitive drum 62.

  In the present embodiment, this development bias value V4 is determined as the maximum development bias value, and the value is stored in advance in the ROM 12a of the storage unit 12.

  As described above, the toner transport amount of the developing roller 72 of the process cartridge 7 to be replaced can be obtained by looking at the reflection density of the patch when a bias value equal to or higher than the developing bias value V4 is applied.

[Operation of control unit]
FIG. 6 is a flowchart showing a processing procedure for determining the printable sheet number of the mounted process cartridge 7 when a new process cartridge 7 is mounted.

  When a new process cartridge 7 is mounted, in step S101 (hereinafter simply referred to as S101. The same applies to other steps), the developing bias controller 11c applies a maximum developing bias to the developing roller 72 in the new process cartridge 7. Apply the value V4.

  Next, in S <b> 102, the patch forming unit 11 d performs an image forming operation for forming a patch made of toner at a predetermined position of the transport belt 83.

  In step S103, when the patch reaches the detection position of the density detection unit 85, the density detection unit 85 detects the reflection density of the patch.

  Next, in S104, the control unit 11 determines whether the density detection unit 85 has detected a reflection density of 1.45 or more. In S104, for example, as shown by A1 in FIG. 5, when the density detection unit 85 detects a value of reflection density of 1.45 or more (Yes in S104), in S105, the RAM 12b of the storage unit 12 stores in the ROM 12a. Based on the explanatory diagram of FIG. 8, 3500 printable sheets of the process cartridge 7 corresponding to the reflection density of 1.45 or more are stored.

  On the other hand, when the density detector 85 does not detect a value of the reflection density of 1.45 or higher in S104 (S104, No), the controller 11 in S106 determines that the density detector 85 has a reflection density of 1.3 or higher and 1.45. Determine whether a value less than is detected. In S106, for example, as shown by A2 and A3 in FIG. 5, when the density detection unit 85 detects a value of reflection density of 1.3 or more and less than 1.45 (S106, Yes), in S107, it is stored in the RAM 12b of the storage unit 12. Is stored based on the explanatory diagram of FIG. 8 stored in the ROM 12a, and 4000 printable sheets of the process cartridge 7 corresponding to a value of the reflection density of 1.3 or more and less than 1.45.

  In S106, for example, as in A4 shown in FIG. 5, when the density detection unit 85 does not detect a value of reflection density of 1.3 or more and less than 1.45 (S106, No), in S108, the storage unit 12 Based on the explanatory diagram of FIG. 8 stored in the ROM 12a, the RAM 12b stores 4500 printable sheets of the process cartridge 7 corresponding to a value of reflection density less than 1.3. As described above, when the new process cartridge 7 is mounted, the control unit 11 determines the number of printable sheets of the mounted process cartridge 7.

  FIG. 7 is a flowchart showing the process until the laser printer 1 displays the process cartridge replacement time on the display unit 13 in accordance with the image forming process.

  The RAM 12b stores the printable number X and the cumulative printable number A stored before the laser printer 1 is turned off.

  When the power of the laser printer 1 is turned on, in S201, the attachment / detachment detection unit 14 determines whether the unit body 61 has been attached / detached to / from the body housing 2.

  If the unit main body 61 is not attached or detached in S201 (S201, NO), the process proceeds to S203, and the image forming operation is started based on the image data sent to the laser printer 1.

  When an image is formed on the paper, in step S204, the control unit 11 causes the RAM 12b to store the cumulative number of printed sheets A, which is the number of sheets printed so far.

  In step S <b> 205, the control unit 11 determines whether the cumulative print number A is equal to or greater than the printable number X.

  In S205, when the cumulative number A of prints is equal to or greater than the printable number X (S205, Yes), the control unit 11 displays on the display unit 13 a message prompting the user to replace the process cartridge 7.

  In S205, when the cumulative number A of prints is less than the printable number X (S205, No), the process proceeds to S201.

  On the other hand, when the unit main body 61 is attached or detached in S201 (S201, Yes), in S202, the new article detection unit 15 determines whether the process cartridge 7 attached to the unit main body 61 is new.

  When a new process cartridge 7 is mounted (S202, Yes), in S207, the control unit 11 resets the cumulative number A of prints stored in the RAM 12b.

  Next, in S208, the control unit 11 performs a process of determining the printable sheet number X in the attached process cartridge 7 (the process shown in FIG. 6 described above). Then, the process proceeds to S203, and an image forming operation is started based on the image data sent to the laser printer 1. When an image is formed on the sheet, in S204, the control unit 11 stores the accumulated number A of printed sheets in the RAM 12b. When the cumulative number A of prints is equal to or greater than the printable number X, a display prompting replacement is displayed on the display unit 13.

  The effect of the laser printer configured as described above will be described.

  In the RAM 12b, based on the reflection density of the patch detected by the density detection unit 85 of the toner conveyance amount detection unit 11b, the replacement timing (number of printable sheets) of the process cartridge 7 according to the reflection density of the patch stored in the ROM 12a. Is displayed, and the display unit 13 displays that the process cartridge 7 being used has reached the replacement time stored in the RAM 12b, so that the toner transport of the developing roller 72 of the process cartridge 7 to be used is carried out. Even when the amounts are different, the user can be notified of the replacement timing of the process cartridge 7 according to the toner conveyance amount of the developing roller 72. Thereby, it is possible to inform the user of an appropriate replacement time of the process cartridge 7.

  In the toner conveyance amount detection unit 11b, the development bias control unit 11c applies the maximum development bias value V4 to the development roller 72, the patch forming unit 11d forms a patch with the maximum development bias value V4, and the density detection unit 85. Has a configuration for detecting the reflection density of the patch. As described above, the toner conveyance amount detection unit 11b can detect the toner conveyance amount of the developing roller 72 by detecting the reflection density of the patch.

  In addition, since the density detection unit 85 detects both the patch used for correcting the image forming condition and the patch used for detecting the toner conveyance amount, in the case of a laser printer having a plurality of developing rollers 72, each developing roller The toner conveyance amount can be detected without providing a toner conveyance amount detection unit 72. This can reduce the size and cost of the laser printer.

(Modification)
The embodiment of the present invention is not limited to the above-described embodiment, and can take various forms as long as it belongs to the technical scope of the present invention.

  In the present embodiment, the patch forming unit 11d is configured to form a patch on the conveyance belt 83, but the same effect can be obtained even if the transfer is performed on a photosensitive drum, paper, intermediate transfer belt, or the like. .

  In the present embodiment, the toner transport amount detection unit 11b detects the toner transport amount of the developing roller 72 based on the reflection density of the patch. However, a light emitting element such as a semiconductor laser and a light emitting device are disposed near the developing roller 72. A light receiving element that receives laser light emitted from the element and reflected by the surface of the developing roller 72 or the surface of the toner layer may be provided. With this configuration, the toner conveyance amount of the developing roller 72 can be detected more accurately.

  In the present embodiment, the maximum development bias value is stored in advance in the ROM 12a. However, the maximum development bias value may not be stored in advance. Specifically, when a new process cartridge 7 is mounted, a patch is formed by applying a developing bias value at the time of printing to the developing roller 72, and the reflection density of the patch is detected by the density detecting unit 85. Is stored in the RAM 12b. Then, a developing bias is applied at a predetermined interval to the developing roller 72, and the reflection density of each patch is detected. When the difference between the detected reflection density of the patch and the reflection density of the previous patch stored in the RAM is equal to or smaller than a predetermined value, the control unit 11 sets the development bias value that formed the patch last as the maximum development bias value. It is stored in the RAM 12b.

  In this embodiment, the replacement time of the process cartridge 7 is set by the number of printable sheets. However, the replacement time of the process cartridge 7 may be set by the remaining amount of toner.

  In this embodiment, the process cartridge 7 includes the developing roller 72 and the unit main body 61 includes the photosensitive drum 62. However, the process cartridge 7 may include the developing roller 72 and the photosensitive drum 62. Good.

DESCRIPTION OF SYMBOLS 1 ... Laser printer, 2 ... Main body housing | casing, 21 ... Cover, 3 ... Paper feed part, 4 ... Image formation part, 5 ... Paper discharge part, 6 ... Process 7, process cartridge 72, developing roller 74, layer thickness regulating blade 8, transfer unit 85, density detection unit 9, fixing unit 11, control , 11b... Toner transport amount detection unit, 11c... Development bias control unit, 11d... Patch formation unit, 12... Storage unit, 12a. ..Display section

Claims (2)

An image forming apparatus in which a process cartridge having a developing roller for developing an electrostatic latent image formed on a photosensitive drum with a developer is detachable,
Detecting means for detecting a corresponding amount corresponding to a transport amount by which the developer is transported by the developing roller when the process cartridge is mounted in the image forming apparatus;
A first storage unit that stores a replacement timing of the process cartridge according to a corresponding amount corresponding to the conveyance amount of the developing roller;
A second storage unit that stores a replacement timing of the process cartridge in accordance with a corresponding amount corresponding to the transport amount of the developing roller stored in the first storage unit based on the corresponding amount detected by the detection unit;
An informing means for informing that the process cartridge in use has reached the replacement time stored in the second storage unit;
An image forming apparatus comprising: The detection means includes
Developing bias applying means for applying a maximum developing bias value at which the amount of developer adhering to the photosensitive drum is saturated;
A patch forming means for applying a maximum developing bias value by the developing bias applying means to form a density detection patch by a developer;
Density detecting means for detecting the density of the patch formed by the patch forming means;
The image forming apparatus according to claim 1, further comprising: