JP2007240607A - Image forming apparatus and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus equipped with a life decision sequence capable of surely deciding the life of a developing device 400, achieving the maintenance of image quality and the prevention of the trouble of a component or a device caused by the in-machine scattering of toner and reducing possibility of smearing user's hands when performing jamming disposal and the replacement of the developing device. <P>SOLUTION: The image forming apparatus has the developing device 400 in which developer is stored, an image carrier 100 and a density detection means 301 which detects the density of a developer image on an image carrier, and forms an image on a recording medium 900. The image forming apparatus has a judging sequence for the life of a developing device to detect the density of the developer image at a part where a latent image is not formed by the density detection means 301, and judge the life of the developing device according to a detected value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having a function of determining the life of a developing device including a developer.

  Further, the present invention relates to a developing cartridge, an image forming apparatus in which a process cartridge containing the developing device is detachably mounted, and a process cartridge.

  Here, the electrophotographic image forming apparatus forms an image on a recording medium using an electrophotographic image forming system. Examples of the electrophotographic image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (for example, a laser beam printer, an LED printer, etc.), a facsimile apparatus, a word processor, and the like.

  The developing cartridge means that the developing device is made into a cartridge and can be attached to and detached from the image forming apparatus main body. The process cartridge refers to a cartridge in which at least the latent image carrier (image carrier) and the developing device are integrally formed into a cartridge that can be attached to and detached from the image forming apparatus main body.

  2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, light corresponding to image information such as a laser, LED, or lamp is irradiated to a drum-shaped electrophotographic photosensitive member (hereinafter referred to as a drum) as a latent image carrier (image carrier). To do. As a result, an electrostatic latent image is formed on the drum. The electrostatic latent image is developed by a developing device containing a developer (hereinafter referred to as toner). Further, the developed image formed on the drum is transferred to a recording medium. Thereby, an image is formed on the recording medium.

  Then, a developer carrying member (developing member) for developing the electrostatic latent image formed on the drum and a toner containing portion for containing the toner are integrated into a cartridge by the cartridge frame. A developing cartridge system that allows the cartridge to be attached to and detached from the image forming apparatus main body is employed. Alternatively, a process cartridge system is adopted in which at least the drum and the developing device (process means) acting on the drum are integrally formed into a cartridge, and the cartridge can be attached to and detached from the main body of the electrophotographic image forming apparatus.

  According to such a developing cartridge system or process cartridge system, the maintenance of the apparatus can be performed by the user himself / herself without depending on the serviceman, so that the operability can be remarkably improved.

  Therefore, the developing cartridge system or the process cartridge system is widely used in electrophotographic image forming apparatuses.

  Such a developing cartridge or a process cartridge is used in an electrophotographic image forming apparatus in order to form an image on a recording medium using a developer. Therefore, the developer is consumed as the image is formed. When the developer is consumed to such an extent that an image having satisfactory quality cannot be formed for the user who purchased the developing cartridge or the process cartridge, the commercial value as the developing cartridge or the process cartridge is lost. That is, the developing cartridge or the process cartridge has a life span.

  Therefore, a toner remaining amount detection device is provided for measuring the remaining amount of toner stored in the toner container. There are various types of toner remaining amount detection devices, but there is a light transmission type toner remaining amount detection as disclosed in Patent Document 1 as a cheaper and simpler configuration.

  The light transmission type toner remaining amount detection is a method in which detection light is allowed to pass through a toner container and the remaining amount of toner stored in the toner container is detected based on the passing time of the detection light. That is, the detection light is blocked by the toner when there is a large amount of toner, and when the toner is consumed, the detection light begins to pass and the detection time becomes longer. The amount of toner remaining in the toner is detected.

  Then, a toner remaining amount detection sequence in which the passage time of the detection light passing through the toner container is associated with the remaining amount of toner in the toner container is created. Accordingly, it is possible to sequentially detect the remaining amount of toner that notifies the user of the remaining amount of toner in the toner container in real time corresponding to the passage time of the detection light in the toner container.

Patent Document 2 describes an image forming apparatus having a notifying unit for notifying the end of life of a developing device or notifying the end of life. This is because when the remaining amount of developer detected by the developer remaining amount detecting means becomes equal to or less than a predetermined value, the operation time counted by the counting means for the operation time of the developer carrier exceeds a predetermined threshold. In addition, a notice of the life of the developing device or the arrival of the life is notified. Alternatively, the process cartridge can prevent trouble in a state where the developer remaining amount in the cartridge is low.
JP 2003-241500 A JP 2003-114571 A

  A so-called “fogging” in which toner adheres to a non-image portion occurs as a phenomenon immediately before the end of the developing device life in which the remaining amount of toner in the developing device is low.

  In the case of the system that detects the remaining amount of toner in the developing device and notifies the end of life or the end of the life, the effect cannot be fully exerted when the detection accuracy of the remaining amount of toner is unstable due to various causes. there is a possibility. That is, there is a possibility that “fogging” may occur before the notice of the life of the developing device or the arrival of the life is notified by the above method. The occurrence of fogging means that the developing device cannot form an image with satisfactory quality for the user and is already in a state of reaching the end of its life.

  “Fog” is noticeably generated in an image forming apparatus used by a user who mainly prints an image with a small toner consumption and a low printing ratio. In particular, color printers for business use are mostly used for coloring only the part to be emphasized or for coloring some data on a graph. That is, it is often used such that the printing ratio of each color of yellow (Y), magenta (M), and cyan (C) is extremely low with respect to black (K) toner.

  In this way, when an image with a low printing ratio is continuously printed, the cause of a problem immediately before the end of use of the cartridge is that toner deterioration is easily promoted in a state where the remaining amount of toner is low. That is, when the amount of toner in the developing device is small and the toner coated on the developer carrying member is hardly consumed, coupled with the fact that the absolute amount of the toner to be replaced is small, the same toner is developed as a result. It will exist on the agent carrier for a long time. For this reason, the toner coated on the developer carrier is repeatedly rubbed against the regulating member and the like, and the deterioration is promoted. In particular, in the case of a contact development method using a one-component non-magnetic toner, sliding with a toner supply roller and a photosensitive member is also applied, and toner deterioration is rapidly accelerated.

  As a result, the toner is fused to the regulating member and the developer carrying member, and the coat on the developing roller becomes non-uniform, which causes fogging. In particular, in the case of a system using a non-magnetic toner, it is difficult to hold the toner on the developer carrying member because the charge imparting ability of the toner is lowered, and the fog is further deteriorated.

  As a typical example, FIG. 22 shows the transition of the number of images formed and the fog density on a transfer material as a recording medium when an image with a low printing ratio is continuously printed. It can be seen that the fog increases rapidly when the developer carrier is repeatedly used in a state where the remaining amount of toner is small.

  Therefore, the “fogging” is not limited to the phenomenon that the image quality is simply impaired, and may appear as the back stain of the output print sample. In addition, the toner is scattered in the apparatus and the toner adheres to the parts, which may cause a failure of the apparatus. In addition, the user's hand is soiled during jam processing or cartridge replacement.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and a process cartridge that can reliably detect the life of a developing device without causing the above-described problems.

  In order to achieve the above object, a typical configuration of an image forming apparatus according to the present invention includes a developing device that stores a developer, an image carrier, and a density detection that detects a developer image density on the image carrier. An image forming apparatus for forming an image on a recording medium, wherein the density detecting means detects a developer image density of a portion where a latent image is not formed, and determines a developing device life according to the detected value And a developing device life determination sequence.

  Further, a typical configuration of the process cartridge according to the present invention for achieving the above-described object has an image forming unit for forming an image on a recording medium, having density detecting means for detecting the developer image density on the image carrier. In a process cartridge that is detachable from the forming apparatus and includes at least a developing device that stores developer and a latent image and carrier, an image carrier in a portion where a latent image is not formed by the density detection unit The upper developer image density is detected, and the process cartridge life is determined by a life determination sequence provided in the image forming apparatus according to the detected value.

  It is possible to reliably determine the life of the developing device by detecting a developer image adhering to a portion where no latent image is formed, so-called “fogging”, and judging the life of the developing device according to the detected value. it can. Further, the maintenance of image quality and the failure of parts and devices due to the scattering of the developer in the machine are prevented, and further, the possibility of smearing the user's hand when jamming or replacing the developing device is reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the examples should be appropriately changed according to the configuration of the apparatus to which the present invention is applied and various conditions, and the scope of the present invention. It is not intended to limit.

(1) Image Forming Unit FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the first embodiment. This image forming apparatus is an electrophotographic laser printer. Reference numeral 100 denotes an electrophotographic photosensitive member as an image carrier (electrostatic latent image carrier). In the first embodiment, the photoconductor 100 is a rotary drum type (hereinafter referred to as a drum) having a diameter of Φ30, and is driven to rotate in a clockwise direction indicated by an arrow at a predetermined speed. The surface of the drum 100 is uniformly charged to a negative polarity by the charging device 200. Laser exposure is performed on the charged surface by the exposure apparatus 300. As a result, an electrostatic latent image corresponding to the image information is formed on the drum surface. To the electrostatic latent image, toner charged to negative polarity by the developing device 400 is applied. As a result, the electrostatic latent image is reversely developed and visualized as a toner image. The toner image is transferred by a transfer device 500 to a recording medium (recording medium / recording material: hereinafter referred to as a transfer material) 900 fed from a paper feed cassette 700. The transfer material 900 that has received the transfer of the toner image is separated from the drum surface and introduced into the fixing device 800, and the toner image is fixed on the surface of the transfer material as a permanently fixed image. The drum surface after separation of the transfer material is cleaned by removing residual deposits such as transfer residual toner by the cleaning device 600, and repeatedly used for image formation.

  The charging device 200 includes carbon black on a core metal of Φ6, a conductive elastic layer made of urethane rubber having a thickness of about 3 mm formed thereon, and urethane rubber having a thickness of several μm formed thereon. The charging roller 201 includes a dispersed high resistance layer or the like. Further, a conductive support member (not shown) that rotatably supports the charging roller 201 at both ends, and a spring member (not shown) that presses the support member and presses the charging roller 201 against the drum surface. There is. Further, there is a charging bias power source 202 that applies a voltage to the charging roller 201 via the spring member and the supporting member.

  The charging roller 201 is installed so as to come into contact with the drum surface and to rotate following the rotation of the drum. Then, a DC voltage of about −1000 V is applied between the drum 100 and the charging roller 201 by the charging bias power source 202. As a result, the drum surface is charged to a dark potential VD-500V.

  The surface of the drum 100 is charged by the charging device 200 to the dark potential VD, and then exposed to the image information by the exposure device 300. Accordingly, the potential (bright potential) VL of the exposed drum surface portion becomes −100 V, and an electrostatic latent image is formed on the drum surface by the electrostatic contrast between the dark potential VD and the light potential VL.

  The developing device 400 is partitioned by a partition 405 into a hopper 406 that stores toner as a developer and a developing chamber 407. A stirring device 404 is disposed in the hopper unit 406, and toner is sent from the hopper unit 406 to the developing chamber 407 by the operation of the stirring device 404. In Example 1, a one-component developer was used as the toner.

  In the developing chamber 407, a developing roller (developer carrier) 401 that develops toner on the electrostatic latent image on the drum surface, a supply roller 402 that supplies toner to the developing roller 401, and a toner layer thickness of the developing roller 401 are regulated. A metal developing blade 403 is disposed. In this embodiment, the developing roller 401 is a two-layer roller having a Φ16 urethane rubber as a base layer and an acrylic / urethane rubber coated on the surface. The supply roller 402 is a roller made of a Φ16 urethane sponge.

  The agitator 404, the developing roller 401, and the supply roller 402 are configured to be driven from the outside, and always rotate to supply toner to the drum surface during the development process.

  The developing roller 401 is installed so as to perform development with a predetermined gap on the drum surface. In the present embodiment, the developing roller 401 is arranged with a gap of 300 μm. A predetermined developing bias is applied to the developing roller 401 by a developing bias power source 408. As a result, the electrostatic latent image formed on the drum surface is reversely developed with the toner to be visualized. In the first embodiment, a voltage obtained by superimposing a DC voltage of about −300 V on an AC voltage of about 1700 Vpp and 2000 Hz is applied between the drum 100 and the developing roller 401.

  The transfer device 500 includes a transfer roller 501 made of a Φ12 EPDM sponge and a transfer bias power source 502 that applies a voltage to the transfer roller 501. The transfer roller 501 is in contact with the drum surface to form a transfer portion T. The transfer bias power source 502 is controlled at a constant voltage during image formation.

  The transfer material 900 stored in the paper feed cassette 700 is supplied to the registration roller 702 in synchronization with the formation of the toner image on the drum surface by the paper feed roller 701. Then, the transfer material 900 is fed to the transfer portion T between the transfer roller 501 and the drum 100 in synchronization with the leading edge of the toner image formed on the drum surface by the registration roller 702, and the transfer portion T is nipped and conveyed. It will be done. During this time, a DC voltage of about +2000 V is applied from the transfer bias power source 502 to the transfer roller 501. Thereby, the toner image on the drum surface is sequentially transferred onto the transfer material 900.

  The transfer material that has exited the transfer portion T is separated from the drum surface and conveyed to the fixing device 800. The toner image transferred to the transfer material 900 is fixed as a permanently fixed recording image on the transfer material surface by heat and pressure by the fixing device 800.

  On the other hand, the transfer residual toner on the drum surface after separation of the recording material is removed from the drum surface by a cleaning device 600 having a cleaning blade 601 made of polyurethane rubber, and stored in a waste toner container 602. Thereafter, the drum surface is charged again by the charging device 200 to prepare for the next image formation.

  FIG. 2 is a system block diagram of the image forming apparatus according to the present exemplary embodiment. Reference numeral 61 denotes an engine controller (hereinafter referred to as a controller) that performs system control of the entire image forming apparatus. The controller 61 executes an image forming operation based on a print signal input from a host device 60 such as a personal computer, an image reader, or a counterpart facsimile. A central processing unit (CPU: not shown) is provided inside the controller 61, and a series of system processing of the image forming apparatus is performed according to a program stored in advance in the central processing unit.

  The controller 61 controls the high voltage power supply 62, the sensor group 63, the display unit 64, the drive unit 66, and the like.

  The high voltage power supply 62 applies a DC voltage to the charging roller 201, a charging bias power supply 202 that applies a DC voltage to the charging roller 201, a developing bias power supply 408 that applies a DC voltage superimposed on the AC voltage to the developing roller 401, and a DC voltage to the transfer roller 501. It comprises a transfer bias power source 502 and the like.

  The sensor group 63 includes a toner image detection sensor 301 described later.

  The drive unit 66 includes a drive device for driving the exposure device 300, the drum 100, the developing device 400, and the like.

  FIG. 3 is an operation process diagram of the image forming apparatus executed by the controller 61.

a) Pre-multi-rotation operation The pre-multi-rotation operation is an apparatus start-up operation that is executed when the main power switch SW of the image forming apparatus is turned on. The main motor M is activated to rotate the drum 100 to execute a predetermined starting operation for a predetermined process device.

b) Standby (standby)
The standby is a state in which the main motor M is stopped when a predetermined pre-multi-rotation operation is finished, and a print signal (image signal: image formation execution request) is waiting to be input from the host device 60 to the controller 61.

c) Pre-rotation operation The pre-rotation operation is an operation before image formation that is executed when a print signal is input from the host device 60 to the controller 61. The main motor M is driven to rotate the drum 100 to execute a predetermined pre-image formation operation for a predetermined process device. This pre-rotation operation is executed following the pre-multi-rotation operation when a print signal is input during the pre-multi-rotation operation.

d) Image forming operation In this image forming operation, an image corresponding to image information input from the host device 60 to the controller 61 is formed on the transfer material 900. This is executed following the end of a predetermined pre-rotation operation. In the continuous image forming mode, the image forming operation for one transfer material is repeatedly executed for a predetermined set number of image forming sheets.

e) Between papers In the continuous image forming mode, after the rear end of one transfer material passes through the transfer portion T, the transfer portion T continues until the leading end of the next transfer material reaches the transfer portion T. The transfer material is in a non-sheet passing state.

f) Post-rotation operation This is a post-operation that is executed after the image forming operation for one or more set transfer materials is completed. After the image forming operation is completed, the main motor M is continuously driven for a predetermined time, and a predetermined process device is caused to execute a predetermined end operation.

g) Standby When the predetermined post-rotation operation is completed, the main motor M is stopped and the next print signal from the host device 60 to the controller 61 is waiting to be input. When the next print signal is input, the operation cycle of the pre-rotation operation, the image forming operation, and the post-rotation operation is executed again.

(2) Life Judgment Sequence of Developing Device 400 In the image forming apparatus according to the first exemplary embodiment, at least the developing device 400 is a developing cartridge that can be attached to and detached from the image forming apparatus main body.

  As described above, in such a developing cartridge, as the image forming operation of the image forming apparatus is repeated, the developer (toner) previously stored in the cartridge is consumed and decreased. When the developer is consumed to such an extent that an image with satisfactory quality cannot be formed for the user who purchased the developing cartridge, the commercial value of the developing cartridge is lost. That is, the developing cartridge (developing device) 400 has reached the end of its life.

  In the image forming apparatus according to the first exemplary embodiment, the life of the developing device 400 is determined by a life determination sequence described below. When it is determined that the life is near or has reached the end of life, the user is prompted to replace the developing device.

  The image forming apparatus according to the present exemplary embodiment includes a toner image detection sensor (density detection unit) 301 that detects a toner image density on a drum 100 that is an image carrier. The sensor 301 detects a fog toner density in a portion where a latent image is not formed on the drum 100, and has a lifetime determination sequence for determining the lifetime of the developing device 400 according to the detected value.

  The sensor 301 is disposed on the downstream side of the developing device 400 in the drum rotation direction and on the upstream side of the transfer device 500 in the drum rotation direction so as to face the drum surface. FIG. 4 shows a schematic diagram of the sensor 301 used in the first embodiment.

  The sensor 301 includes a light emitting element 301a and a light receiving element 301b, and is disposed to face the surface of the drum 100. The light emitting element 301a irradiates the toner image 310 on the drum surface with infrared light. In the sensor 301, the light receiving element 301b detects the irradiation angle α and the light reflected in the target direction with respect to the normal line of the drum surface. In the depth direction in FIG. 1, the sensor 301 is disposed opposite to the drum surface in a drum surface area where the developing roller 401 can reversely develop the electrostatic latent image on the drum surface to be visualized. It is.

  The correlation between the fog toner density on the drum 100 and the detection value of the sensor 301 is shown in FIG. As shown in the figure, the detection value of the sensor 301 has a substantially linear relationship with the fog toner density. Therefore, the fog toner density on the drum surface can be measured by the sensor 301.

  Electrical information related to the fog toner density on the drum surface detected by the sensor 301 is input to the controller 61. The controller 61 has a life determination sequence for determining the life of the developing device 400 according to the input detection value.

  By disposing the sensor 301 on the downstream side in the transfer material conveyance direction of the transfer device 500 or the fixing device 800, the fog toner density on the transfer material 900 can be measured. However, since the color and surface properties differ depending on the type of the transfer material 900, the detection accuracy of the fog toner density becomes unstable. Therefore, the sensor 301 is preferably arranged so as to measure the fog toner density on the drum 100 which is an image carrier without these unstable elements.

  When detecting the fog toner density on the drum 100 by the sensor 301, it is necessary to have the same conditions as in the actual image formation. For this purpose, the drum 100, the developing roller 401, the supply roller 402, the stirring device 404, and the like constituting the developing device 400 are driven under the same conditions as in the image formation. Further, the applied voltages from the charging bias power source 202 and the developing bias power source 408 are also set to the same conditions as in image formation.

  6, 8, and 9 are flowcharts of the life determination sequence of the developing device 400 that is executed by the controller 61.

  The sequence in FIG. 6 is executed during the pre-rotation operation of the image forming apparatus. The sequence shown in FIG. 8 is executed during the interval between sheets when image formation is continuously performed. The sequence in FIG. 9 is executed during the post-rotation operation.

(2-1) During Pre-Rotation Operation First, the life determination sequence executed during the pre-rotation operation in FIG. 6 will be described.

  When the controller 61 of the image forming apparatus in the standby state receives a print execution request from the host device 60 (step S1), the controller 61 executes a life determination sequence of the developing device 400 (S2).

  The drive unit 66 holds the exposure by the exposure apparatus 300 in the OFF state (S3), and then starts the driving operation of the drum 100 and the development apparatus 400 (S4).

  After the drum 100 and the developing device 400 are steadily driven in the same state as during image formation, the high-voltage power source 62 operates the charging bias power source 202, the developing bias power source 408, and the transfer bias power source 502 to perform image formation on each device. The same voltage is applied (S5).

  By doing so, it becomes possible to obtain a potential state equivalent to the non-image portion of the image forming area which is the latent image forming portion on the drum surface even in the portion where the latent image is not formed. The developing device 400 performs development.

  When the life of the developing device 400 is near or near the end of its life, the density of the fog toner generated on the drum surface increases. Therefore, the fogging toner density on the drum 100 that is in a potential state equivalent to the non-image portion of the image forming area in the portion where the latent image is not formed is detected by the sensor 301. That is, the light emitting element 301a of the sensor 301 is turned on (S6), and the reflected light received by the light receiving element 301b is processed by the controller 61 to obtain the sensor detection value A.

  The obtained sensor detection value A can be converted into fog toner density information from the correlation between the sensor detection value and the fog toner density as shown in FIG. The controller 61 has a correspondence relationship between the sensor detection value and the fog toner density in advance. Further, since the fog toner density on the drum correlates with the fog density on the transfer material as shown in the graph (b) of FIG. 7, when the fog density on the transfer material is the allowable value C0, The fog toner density corresponds to B0 in FIG. Accordingly, when the fog toner density reaches B0, that is, when the detected value of the sensor 301 in the graph (a) of FIG. 7 having the same contents as FIG. 5 reaches A0, the fog reaches an allowable value, and the developing device 400 Can be judged to have reached the end of their lives.

  Therefore, in step S7, if the detected value of the sensor 301 is equal to or greater than the predetermined value A0, the controller 61 determines that the fog density has reached an allowable value and the developing device 400 has reached the end of its life, and the sensor 301 emits light. The element 301a is turned off (S8). The high voltage power supply 62 stops voltage application from each high voltage power supply (S9), and the drive unit 66 stops driving the drum 100, the developing device 400, and the like (S10). Then, the controller 61 displays on the display section 64 that the developing device 400 has reached the end of life, such as “Developer life reached” (S11), and ends the life determination sequence of the developing device 400 (S12).

  The user removes the developing device 400 that has reached the end of its life from the image forming apparatus main body and replaces the developing device. The developing device to be replaced is a new one or a developing device that is not new but can be used because its life has not yet been reached.

  In step S7, when the detection value of the sensor 301 is less than the predetermined value A0, the controller 61 determines that the life of the developing device 400 has not reached. Then, after the controller 61 turns off the light emitting element 301a of the sensor 301 (S13), the drive unit 66 enables exposure by the exposure device 300 to prepare for latent image formation (S14), and starts an image forming operation (S15). .

(2-2) Between Papers Next, the life judgment sequence executed at the time between papers when continuously forming images in FIG. 8 will be described.

  During the image forming operation (S16), the controller 61 determines whether or not there is an image formation request continuously (S17). If there is a request, the controller 61 executes a life determination sequence for determining the life of the developing device 400 between the sheets. To do.

  First, the controller 61 controls the drive unit 66 to turn off the exposure of the exposure apparatus 300 (S18), and the drum surface portion corresponding to the inter-paper portion where the latent image is not formed is moved to the non-image portion of the image forming area. A potential state equivalent to is formed. The developing device 400 develops the drum surface portion. The light emitting element 301a of the sensor 301 is turned on (S19), and the fog toner density on the drum surface portion is detected (S20).

  The controller 61 drives the developing roller 401, the supply roller 402, the stirring device 404, and the like under the same conditions as in image formation. Further, the voltage applied from the charging bias power source 202 and the developing bias power source 408 is also controlled under the same conditions as in image formation.

Therefore, if the detected value of the sensor 301 is greater than or equal to the predetermined value A0 in step S20, the controller 61 determines that the fog density has reached an allowable value and the developing device 400 has reached the end of its life. Then, the controller 61 completes the subsequent image forming operation and the life determination sequence through steps S8 to S12 of FIG. 6 described above. The user removes the developing device 400 that has reached the end of its life from the image forming apparatus main body, and develops it. Replace the device.

  In step S20, if the detected value of the sensor 301 is less than the predetermined value A0, the controller 61 determines that the developing device 400 has not reached the end of its life. Then, after the light emitting element 301a of the sensor 301 is turned off (S21), the drive unit 66 enables exposure by the exposure apparatus 300 to prepare for latent image formation (S22), and subsequent image formation is executed (S23).

(2-3) During Post-Rotation Operation Next, the life determination sequence executed during the post-rotation operation in FIG. 9 will be described.

  In steps S16 and S17 in FIG. 8, the controller 61 determines whether or not there is a next image formation request during the image forming operation, and the life of the developing device 400 in the post-rotation operation following the end of the image forming operation when there is no request. A judgment sequence is executed.

  In Steps S16 and S17, the controller 61 that has determined that there is no continuous image formation request executes the sequence of FIG. That is, the drive unit 66 turns off the exposure of the exposure apparatus 300 (S24), and forms a potential state equivalent to the non-image portion of the image forming area on the drum surface where no latent image is formed. The developing device 400 develops the photosensitive drum surface portion. The light emitting element 301a of the sensor 301 is turned on (S25), and the fog toner density on the drum surface portion is detected.

  The developing roller 401, the supply roller 402, the stirring device 404, and the like are driven under the same conditions as in image formation. Further, the applied voltages from the charging bias power source 202 and the developing bias power source 408 are also set to the same conditions as in image formation.

  In step S26, if the detected value of the sensor 301 is equal to or greater than the predetermined value A0, the controller 61 determines that the developing device 400 has reached the end of its life because the toner fog density on the drum has reached an allowable value. And the controller 61 complete | finishes a lifetime judgment sequence through step S8-S12 of FIG. 6 mentioned above.

  The user removes the developing device 400 that has reached the end of its life from the image forming apparatus main body and replaces the developing device.

  In step S26, if the detected value of the sensor 301 is less than the predetermined value A0, the controller 61 determines that the developing device 400 has not reached the end of its life and turns off the light emitting element 301a of the sensor 301 (S27).

  Further, the controller 61 controls the high voltage power supply 62 to stop voltage application from each high voltage power supply (S28). In addition, the controller 61 controls the drive unit 66 to stop driving the drum 100, the developing device 400, and the like (S29), and ends the life determination sequence (S30).

  Then, the image forming apparatus shifts to a standby state until the next print execution request (print signal) is input from the host apparatus 60 to the controller 61.

  The toner image adhering to the surface portion of the drum 100 where the latent image is not formed, that is, the so-called “fogging density” is detected by the image forming apparatus provided with the life determination sequence of the first embodiment described above. The life of the developing device can be reliably determined by judging the life of the developing device 400 according to the detected value.

  Further, the maintenance of image quality and the failure of parts and devices due to the scattering of toner in the machine can be prevented, and further, the possibility of soiling the user's hand when jamming or replacing the developing device is reduced.

  In the first embodiment, the life determination sequence has been described with respect to the contents of the image forming apparatus that are executed during all operations of “pre-rotation operation”, “inter-paper rotation”, and “post-rotation operation”. However, it is not necessary to carry out the life judgment sequence in all the operations described above, and the execution timing is appropriately changed such that the life judgment sequence is carried out only in any one operation, for example, “at the time of paper”. May be. In addition, the execution timing may be changed as appropriate, such as executing the life determination sequence with a combination of any two operations.

  Further, in the first exemplary embodiment, the description has been made with respect to the content that the image forming operation is immediately terminated and the life determination sequence is completed after displaying that the developing device 400 has reached the end of life, such as “development device life reached”. However, a sequence for ending the image forming operation after enabling a predetermined number of image forming operations after the end of life of the developing device 400 is detected may be used.

  Furthermore, depending on the installation environment such as room temperature and humidity in which the developing device 400 is used, the correspondence between the usage state of the developing device 400 and the fog toner density may be slightly different. Therefore, considering such a case, the environment sensor ST (FIG. 2) is provided, and the installation environment information of the apparatus is input to the controller 61. Then, the controller 61 may be configured to appropriately correct the predetermined value A0 for determining the life of the developing device 400 according to the apparatus installation environment information input from the environment sensor ST.

  In the first embodiment, the method for detecting the fog toner density in the reversal development method has been described. However, the present invention is also applicable to the regular development method.

(1) Image Forming Unit FIG. 10 is a schematic diagram of an image forming apparatus according to the second embodiment. This image forming apparatus is a one-drum-intermediate transfer belt type full-color electrophotographic printer.

  The image forming apparatus includes a drum-type electrophotographic photosensitive member (drum) 18 as a first image carrier. The drum 18 is formed to have a diameter of 32 mm, and an arylate resin is contained in the surface layer material. The drum 18 is rotationally driven in the counterclockwise direction indicated by the arrow R3 at a predetermined speed, and the surface thereof is uniformly charged by the charging roller 19.

  An oscillating voltage in which an AC bias and a DC bias are superimposed is applied to the cored bar of the charging roller 19 through a sliding electrode brought into contact with the cored bar from a power source 203 provided in the image forming apparatus main body. Thereby, the peripheral surface of the drum 18 is contact-charged. In the second embodiment, an oscillation voltage in which 1500 Vpp, 1200 Hz as an AC bias and −500 V as a DC bias is superimposed is applied, and the surface potential on the drum 18 is charged to a dark potential (VD) of −500 V.

  Next, the charged surface of the drum 18 is subjected to scanning exposure with a laser beam emitted from the laser scanner 20 to form an electrostatic latent image of target image information. The potential of the exposed portion of the drum surface is bright potential (VL) -100V.

  The electrostatic latent image is reversely developed as a toner image using negative toner (one-component developer) by any one of the four developing devices 21a, 21b, 21c, and 21d of the rotary developing unit 21.

  The rotary developing unit 21 includes a rotary 21R that is rotatably supported and four developing devices (developing devices) 21a, 21b, 21c, and 21d that are detachably mounted on the rotary 21R. .

  The developing device 21a is a Y color developing device containing yellow toner (Y) as a developer. The developing device 21b is an M color developing device containing magenta toner (M). The developing device 21c is a C color developing device containing cyan toner (C). The developing device 21d is a K color developing device in which black toner (K) is accommodated.

  The rotary device 21R is rotationally controlled, and the developing devices 21 (a to d) containing toner of a color corresponding to the electrostatic latent image formed on the drum 18 are moved to the developing position facing the drum 18. The As a result, the electrostatic latent image on the drum surface is reversely developed as a toner image by the developing device.

  Each developing device 21 (a to d) has the same structure except that the color of the toner contained is different. FIG. 11 is an enlarged schematic cross-sectional view of the developing device 21 (a to d). Each developing device 21 (a to d) includes a hopper portion 5 for storing toner, a stirring device 7, a developing roller 3 as a developer carrier, a supply roller 4, a metal developing blade 6, and the like. The agitator 7 agitates the toner in the hopper 5 and sends the toner into the developing chamber where the developing roller 3 is located. The supply roller 4 is made of a urethane sponge having a diameter of 16 and supplies toner to the developing roller 3. The developing roller 3 is a roller in which, for example, a solid rubber is coated with a resin coating in consideration of the charge imparting property to the toner, and the electrostatic latent image on the drum 18 is developed. More specifically, the developing roller 3 is a two-layer roller having a Φ16 urethane rubber as a base layer and an acrylic / urethane rubber coated on the surface. The developing blade 6 regulates the toner layer thickness of the developing roller 3.

  The stirring device 7, the developing roller 3, and the supply roller 4 are configured to be driven from the outside, and always rotate to supply toner to the drum 18 during the development process of the developing device. The toner on the developing roller 3 is conveyed to the developing unit facing the rotating drum 18 by the rotation of the developing roller 3. In the developing unit, the developing roller 3 is in contact with the drum 18 through the toner layer, and a DC bias of about −300 V is applied from the power source 409, and the electrostatic latent image formed on the drum 18 is reversely developed. Thus, the toner image is visualized.

  Reference numeral 23 denotes a flexible intermediate transfer belt (intermediate transfer body: hereinafter abbreviated as a belt) as a second image carrier. The belt 23 is supported by three rollers, a driving roller 23a, a driven roller 23b, and a secondary transfer counter roller 23c, so that an appropriate tension is maintained. Further, the belt 23 is driven with the driving roller 23a, so that the surfaces of the belt 23 move with a speed difference with respect to the drum 18.

  The belt 23 is preferably made of, for example, polyvinylidene fluoride (PVDF), polyimide, polyetherimide, polyetheretherketone, polyethersulfone, polysulfone, polyarylate, or the like as a main material. Further, for example, a resin mainly composed of ethylene-vinyl alcohol copolymer resin, polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE) or the like is suitable. Moreover, what used as a main material any of polyvinyl fluoride (PVF) tetrafluoroethylene-hexafluoropropylene copolymer (PFEP) etc. is suitable. Further, a material mainly composed of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-ethylene copolymer (PETFE), or the like is preferable.

  A positive DC bias is applied from the primary transfer bias power source 503 to the primary transfer roller 22 disposed so as to face the drum 18 from the back surface of the belt 23. As a result, the toner image is primarily transferred from the surface of the drum 18 to the surface of the belt 23 in the primary transfer portion T1.

  The toner remaining on the drum 18 at the time of the primary transfer is scraped off by a cleaning device 24 provided with an elastic blade attached to a sheet metal, that is, a cleaning blade before being charged again, and is accumulated in the device.

  After that, the secondary transfer roller 25 is placed in contact with the secondary transfer counter roller 23c that is in contact with the back surface of the belt 23 and is in contact with the surface of the belt 23. Bias application is performed.

  A transfer material P fed from a paper feed cassette or a multi-feeder (not shown) in accordance with the electrostatic latent image formed by exposure is a secondary that is a contact portion between the belt 23 and the secondary transfer roller 25. Passes between the transfer portions T2. As a result, the toner image carried on the belt 23 is secondarily transferred to the surface of the transfer material P.

  The transfer material P is subsequently conveyed to the fixing device 26, and a fixed image is completed on the transfer material P.

  The color image forming procedure will be described. The drum 18 is rotated in the direction of the arrow R3, and the peripheral surface thereof is uniformly charged by the charging roller 19.

  Thereafter, an electrostatic latent image corresponding to the color separation image pattern of the color image is sequentially formed on the drum 18 by the laser scanner 20. These latent images are electrostatic latents corresponding to the respective color toners, yellow (Y), magenta (M), cyan (C), and black (K), which are filled in the developing devices 21 (a to d). It is a statue.

  First, the Y color developing device 23a for the first color is moved so as to face the drum 18, and the electrostatic latent image formed on the drum surface is developed in Y color.

  Subsequently, the yellow toner image formed on the drum 18 is primarily transferred onto the belt 23 at the primary transfer portion T1. The residual toner on the drum 18 is cleaned by the cleaning device 24.

  Thereafter, the M color developing device 23b for the second color is moved so as to face the drum 18, and the electrostatic latent image formed on the drum surface is developed for M color. Then, the magenta toner image is transferred onto the belt 23 on which the yellow toner image of the first color has already been transferred in the primary transfer portion T2.

  By performing these operations four times corresponding to yellow (Y), magenta (M), cyan (C), and black (K), toner images of four colors are superimposed and formed on the belt 23. At this time, the bias voltage applied to the primary transfer roller 22 may be appropriately varied in order to obtain good transferability. In Example 2, primary transfer biases corresponding to yellow (Y), magenta (M), cyan (C), and black (K) were set to 1700 V, 1750 V, 1750 V, and 1800 V, respectively.

  Thereafter, the toner images stacked in four layers on the belt 23 are collectively transferred to the transfer material P in the secondary transfer portion T2, and then fused and fixed to the transfer material surface by the fixing device 26.

  The secondary transfer roller 25 is in contact with the belt 23 via the transfer material P when the transfer material P passes through the secondary transfer portion T2, and is otherwise separated from the belt 23. A voltage of 2000 V is applied from the secondary transfer bias power source 504 to the secondary transfer roller 25 when the toner images stacked on the belt 23 are collectively transferred onto the transfer material P.

  Further, the toner remaining on the belt 23 after the batch transfer in the secondary transfer section 25 is then transferred to the next by the intermediate transfer belt cleaning device 27 configured to contact and separate from the belt 23 at a predetermined timing. It is removed before the image is formed.

  FIG. 12 is a system block diagram of the image forming apparatus according to the second embodiment. A controller 71 performs system control of the entire image forming apparatus, and executes an image forming operation based on a print signal input from the host device 70. A central processing unit (CPU: not shown) is provided inside the controller 71, and a series of system processing of the image forming apparatus is performed according to a program stored in advance in the central processing unit.

  The controller 71 controls the high voltage power source 72, the sensor group 73, the display unit 74, the drive unit 76, and the like.

  The high-voltage power source 72 includes a charging bias power source 203 that applies a voltage in which a DC voltage is superimposed on an AC voltage to the charging roller 19, and a developing bias power source 409 that applies a DC voltage to the developing roller 3. The high-voltage power source 72 includes a primary transfer bias power source 503 that applies a DC voltage to the primary transfer roller 22 and a secondary transfer bias power source 504 that applies a DC voltage to the secondary transfer roller 25 that is a secondary transfer unit.

  A sensor group 73 including a toner image detection sensor 301 is disposed in the apparatus, and a display unit 74 that displays the state of the apparatus is provided.

  A driving unit 76 including a driving device for driving the exposure device 20, the drum 18, the rotary developing unit 21, the driving roller 23 a, the secondary transfer roller 25, the contact and separation mechanism of the intermediate transfer belt cleaning device 27, and the like. I have.

  In the image forming apparatus of the second embodiment, the operation process of the image forming apparatus executed by the controller 71 is the same as the operation process of FIG. 3 described in the image forming apparatus of the first embodiment. Is omitted.

(2) Life Determining Sequence of Developing Devices 21 (a to d) The image forming apparatus according to the second exemplary embodiment uses the life determining sequence described below to develop each of the developing devices 21 for Y, M, C, and K colors. The lifetime of (a to d) is determined.

  That is, the image forming apparatus according to the second exemplary embodiment includes a toner image detection sensor (density detection unit) 301 that detects the toner image density on the intermediate transfer belt 23 that is the second image carrier. The sensor 301 detects a fog toner density in a portion where a latent image on the belt 23 is not formed, and has a lifetime determination sequence for determining the lifetime of the developing device 21 (a to d) according to the detected value. is doing.

  As the toner image detection sensor 301, the sensor 301 described in FIG. 4 can be applied. In the second embodiment, a configuration is employed in which the toner image on the belt 23 is irradiated with infrared light and the fog toner density is detected. As shown in FIG. 10, the sensor 301 is disposed in the vicinity of the surface of the belt 23 and is disposed at a position facing the driving roller 23a. With this arrangement, the distance between the sensor 301 and the surface of the belt 23 is stabilized, and an improvement in detection accuracy is expected.

  FIGS. 13 and 15 are flowcharts of the life determination sequence of the developing devices 21 (a to d) executed by the controller 71, respectively.

  The sequence of FIG. 13 is executed during the pre-rotation operation of the image forming apparatus. The sequence shown in FIG. 15 is executed during the interval between sheets when image formation is continuously performed.

(2-1) During Pre-Rotation Operation First, the life determination sequence executed during the pre-rotation operation in FIG. 13 will be described.

  The controller 71 of the image forming apparatus in the standby state receives a print execution request from the host device 70 such as a computer connected to the image forming apparatus (step S1). Then, the controller 71 shifts to a life determination sequence for determining the life of the developing devices 21 (a to d) (S2).

  In order to detect the fog toner density on the intermediate transfer belt 23, the light emitting element 301a of the sensor 301 is turned on (S3).

  Next, the driving unit 76 holds the exposure by the exposure apparatus 20 in the OFF state (S4), and then starts the driving operation of the drum 18 and the driving roller 23a (S5). At this time, the drive unit 76 preferably keeps the intermediate transfer belt cleaning device 27 in contact with the belt 23.

  When the drum 18 and the driving roller 23a are driven steadily in the same state as during image formation, the driving unit 76 drives the rotary developing unit 21 to position the first color Y developing device 21a to the developing position. Move.

  Then, the driving of the Y color developing device 21a is started so as to perform the same operation as that during image formation. The high-voltage power supply 72 operates the charging bias power supply 203, the developing bias power supply 409, and the primary transfer bias power supply 503, and the same voltage as that during yellow image formation is applied (S6).

  After the Y color developing device 21a is driven for a predetermined time, the drive unit 76 moves the M color developing device 21b as the second color to the development position. The high voltage power source 62 applies the same voltage as during magenta image formation (S7).

  Such an operation is continued for the C color developing device 21c (S8) and for the K color developing device 21d (S9).

  As a result, for each color, the fog of each color in a potential state equivalent to the non-image portion of the image forming area can be transferred onto the belt 23 in a portion where no latent image is formed.

  In order to detect the fog toner density on the belt 23, the reflected light received by the light receiving element 301b of the sensor 301 is processed by the controller 71 to obtain a sensor detection value A (S10).

  The controller 71 has a correspondence relationship between the sensor detection value and the fog toner density in advance, and can convert the sensor detection value into the fog toner density on the belt 23. FIG. 14 shows an example of the detection result of the sensor 301.

  Through the operations in steps S6 to S9, the yellow, magenta, cyan, and black fog toners are sequentially transferred onto the belt 23. In the example of FIG. 14, the fog toner density on the belt 23 increases in the order of cyan (C), black (K), magenta (M), and yellow (Y). Since the fog toner has a property of increasing with the use of the developing device, it can be predicted that the lifetime of the developing device may be approaching a stage where the fog toner density slightly increases.

  Therefore, in FIG. 14, the sensor detection value corresponding to the fog toner density in the state where the life of the developing device is close to the detection result of the sensor 301 is set as the developing device life notice threshold A1. Further, the sensor detection value corresponding to the fog toner density in a state where the developing device has reached the end of its life and the fog may exceed the allowable value is set as the developing device life warning threshold A2. Then, by preparing the threshold value A1 and threshold value A2 in the controller 71, it is possible to give notice of the end of the life of the developing device. By displaying the result on the display unit 64 such as a display device, it is possible to provide the user with a preparation period for replacing the developing device.

  Therefore, when there is a developing device of a color whose detection value of the sensor 301 is equal to or greater than the threshold value A1 (S11), the display unit 64 displays an indication that the developing device is nearing the end of its life, such as a notice of the developing device life of the corresponding color. Perform (S12).

  Further, when there is a developing device of a color whose detection value of the sensor 301 is equal to or greater than the threshold value A2 (S13), it is determined that the fogging has reached an allowable value and the developing device life has been reached, and the light emitting element 301a of the sensor 301 is turned on. The light is turned off (S14). The high-voltage power supply 72 stops voltage application from each high-voltage power supply (S15), and the drive unit 76 stops driving the drum 18, the drive roller 23a, the developing device 21, and the like (S16). Then, the display unit 74 displays that the developing device has reached the end of its life, such as a developing device life warning for the corresponding color (S17), and the controller 71 ends the life determination sequence of the developing device (S18).

  The user removes the developing device 21 whose color has reached the end of its life from the rotary 21R and replaces the developing device.

  In the developing devices 21 (a to d) of all colors, when the detection value of the sensor 301 is less than the threshold value A2 (S13), the display of the developing device lifetime notice of the corresponding color is displayed on the display unit 74 (S12). The drive unit 76 enables exposure by the exposure device 20 to prepare for latent image formation (S18). Then, image formation is executed (S19).

  When the detection value of the sensor 301 is less than the threshold value A1 (S11), the developing device determines that the device life warning stage has not been reached, and the drive unit 76 can perform exposure by the exposure device 20 to prepare for latent image formation (S18). Then, image formation is executed (S19).

  After the drive unit 76 brings the intermediate transfer belt cleaning device 27 into contact with the belt 23 for at least one turn of the belt 23, the intermediate transfer belt cleaning device 27 may be set in the separated state and the process may proceed to step 19.

(2-2) Between Papers Next, the life determination sequence executed when the papers are spaced during continuous image formation shown in FIG. 15 will be described.

  In the image forming apparatus according to the second exemplary embodiment, each color toner image is stacked on the belt 23 to form a color image. Therefore, each color fog toner is stacked on the belt 23 corresponding to the space between the sheets.

  Therefore, the controller 71 obtains the Y-color fog toner density on the belt 23 corresponding to the gap between the sheets as the detection value A (y) from the toner image detection sensor 301 after performing the Y-color image forming operation (S20).

  Here, it is determined whether or not the detected value A (y) is equal to or greater than the threshold value A1 (S21). If the detected value A (y) is equal to or greater than the threshold value A1, the life notice of the Y color developing device 21a is displayed on the display unit 74. (S22).

  Subsequently, it is determined whether or not the detection value A (y) is equal to or greater than the threshold value A2 (S23). If the detection value A (y) is equal to or greater than the threshold value A2, a life warning of the Y color developing device 21a is displayed on the display unit 74 ( S24).

  Continuously, after the M color image forming operation is performed, the detected value A (y + m) is obtained from the sensor 301 as the Y and M fog toner density on the belt 23 corresponding to the space between the sheets. By calculating the difference between the detection value A (y + m) and the detection value A (y) by the controller 71, the detection value A (m) as the fog toner density of M color can be obtained (S25).

  Similarly to the Y color, the detection value A (m) is compared with the threshold value A1 (S26) and the threshold value A2 (S23), and the determination result is displayed on the display unit 74 according to the result.

  Similarly, following the C-color image forming operation, a detection value A (c) as a C-color fog toner density is obtained (S27), and the detection value A (c) is set to the threshold value A1 (S28) or the threshold value A2 (S23). Compare with

  Further, following the K-color image forming operation, a detection value A (k) as a K-color fog toner density is obtained (S29), and compared with the threshold value A1 (S30) and the threshold value A2 (S23). The detected value A (k) as the fog toner density of K color is compared with each threshold value.

  Then, the presence / absence of a life warning display is determined for each developing device (S31). If yes, the light emitting element 301a of the sensor 301 is turned off (S14), and the process proceeds to the subsequent steps. The life determination sequence is terminated (S18).

  At this time, since the life warning is already displayed on the display unit 74, step 17 may be omitted. If there is no life warning display for each developing device (S31), it is determined whether there is a continuous print execution request (S32), if there is, the process proceeds to a Y-color image forming operation (S20), and if not, the life is determined. The sequence is terminated (S33).

  Although the description is omitted, even in the post-rotation operation, for example, the life determination sequence according to the case of the pre-rotation operation can be executed.

  The above-described color image forming apparatus having the lifetime determination sequence of the second embodiment detects a toner image adhering to a portion where no latent image is formed, so-called “fogging”. Then, by determining the life of the developing device according to the detected value, it is possible to reliably determine the life of the developing device.

  In addition, the maintenance of image quality and the failure of parts and devices due to the scattering of toner in the machine can be prevented, and further, the possibility of soiling the user's hand during jam processing or replacement of the developing device is reduced.

  Further, the toner image density detection value of the portion where the latent image is not formed has at least two threshold values or more, and it is possible to notify the user of replacement of the developing device by judging the life of the developing device. It is possible to provide a preparation period for replacing the developing device.

  In particular, in a color image forming apparatus having a plurality of developing devices, it is effective to provide a preparation period in order to reduce the troublesomeness of replacing developing devices.

In this embodiment, the detected value of the toner image density has been described with the two threshold values A1 and A2. However, a threshold value higher than that may be set. When the print execution request (S1) is obtained, the display unit 74 has a lifetime. It may be determined whether a notice or the like is already displayed. In that case, the operation may be started from step 18 of FIG. 13, and the life determination may be performed during the image formation shown in FIG.

  The thresholds A1 and A2 may be set for each color.

  Further, depending on the installation environment such as the room temperature and humidity in which the developing device is used, the correspondence between the usage state of the developing device and the fog toner density may be slightly different. In this case, the thresholds A1 and A2 may be different depending on the installation environment of the device. May be set as appropriate.

  Further, the lifetime determination sequence of the developing device may be performed in all of “at the time of pre-rotation operation”, “at the time of paper”, and “at the time of post-rotation operation”, or may be performed in any one of them. , Any two combinations may be implemented.

  In the second embodiment, the method for detecting the fog toner density in the reversal development method has been described. However, the present invention can also be applied to the regular development method.

(1) Image Forming Unit FIG. 16 is a schematic diagram of an image forming apparatus according to the third embodiment. This image forming apparatus is a 4-drum type full-color electrophotographic printer.

  This image forming apparatus has four process cartridge mounting portions (not shown) arranged in parallel in the vertical direction. The process cartridges 7 (a to d) attached to the respective attachment portions are each provided with one electrophotographic photosensitive drum 1 (a to d) as a first image carrier. Each drum 1 (a to d) is driven to rotate counterclockwise in FIG.

  Around each drum 1 (a to d), charging means 2 (a to d) for uniformly charging the drum surface in order according to the drum rotation direction, a laser beam is irradiated based on image information, and the drum surface is A scanner unit 3 (ad) that forms an electrostatic latent image is arranged. Further, developing devices 4 (a to d) are provided for developing the electrostatic latent image on the drum surface with toner as a developer to form a visible image, that is, a toner image. Further, electrostatic transfer means 12 (ad) for transferring the toner image on the drum 1 to a transfer material (recording medium) S, and cleaning means 6 (ad) for removing the toner remaining on the drum surface after transfer. Is arranged.

  The drum 1 (a to d), the charging unit 2 (a to d), the developing device 4 (a to d), and the cleaning unit 6 (a to d) are integrally formed into a cartridge to form a process cartridge 7 (a to d). Is configured.

  The drum 1 is obtained by applying an organic photoconductor layer (OPC photoconductor) to an outer peripheral surface of an aluminum cylinder having a diameter of 30 mm, for example, and is driven to rotate at an outer peripheral surface of 94.2 mm / sec.

  Since the charging unit 2 is the same as that described in the first embodiment, the description thereof is omitted. In the third embodiment, a DC voltage of about −1000 V is applied between the drum 1 and the charging unit 2 to charge the surface potential on the drum 1 to a dark potential (VD) −500 V.

  The scanner unit 3 is arranged in a substantially horizontal direction of the drum 1. Then, image light corresponding to an image signal is irradiated to a polygon mirror 9 (ad) rotated by a scanner motor (not shown) by a laser diode (not shown). The image light reflected by the mirror 9 selectively exposes the charged drum surface via the imaging lenses 10 (a to d). Thereby, an electrostatic latent image corresponding to the image signal is formed.

  As in the first and second embodiments, each of the developing devices 4 (a to d) includes a hopper unit for storing toner, a stirring device, a developing roller 40 (a to d), a supply roller, a developing blade, and the like. Therefore, the description thereof is omitted. In the third embodiment, a DC bias of about −300 V is applied to the developing rollers 40 (a to d), and the latent image formed on each drum 1 is reversely developed for each color. Visualization is performed.

  The process cartridge 7a is a cartridge for forming a yellow toner image, and the developing device 4a stores yellow toner.

  The process cartridge 7b is a cartridge that forms a magenta toner image, and the developing device 4b contains magenta toner.

  The process cartridge 7c is a cartridge that forms a cyan toner image, and the developing device 4c contains cyan toner.

  The process cartridge 7d is a cartridge that forms a black toner image, and the developing device 4d contains black toner.

  In each process cartridge 7 (ad), the developing roller 40 (ad) is configured to be swung together with the developing device 4 (ad) by a swing mechanism (not shown). In the image information input standby state, the developing roller 40 is separated from the drum 1, and the developing device 4 is swung independently for each color to perform the developing process so that the developing roller 40 contacts the drum 1. It was.

  In the following description of the present embodiment, when the rotation driving of the developing roller 40 is started, the developing roller 40 is in contact with the drum 1 after the developing roller 40 rotates. When the rotation of the developing roller 40 is stopped, the drum 1 and the developing roller 40 are separated from each other after the developing roller 40 stops rotating.

Reference numeral 5 denotes a transfer material conveyance unit, which is provided with an electrostatic transfer belt 11 (transfer material conveyance member: second image carrier) that circulates and moves so as to face and contact all the drums 1 (a to d). ing. That is, the transfer belt 11 is stretched around four rollers, that is, a driving roller 13, driven rollers 14a and 14b, and a tension roller 15, and rotates in the clockwise direction indicated by an arrow. The transfer belt 11 is a film-like member having a volume resistivity of 10 ¹¹ to 10 ¹⁴ Ω · cm and a thickness of about 150 μm.

  Reference numeral 30 denotes a paper feed cassette, on which a transfer material S is stacked on a swingable inner bottom plate 31. The sheet feeding roller 32 is driven to separate and feed the transfer material S on the middle bottom plate tray 31. The fed transfer material S is fed from the lower side of the transfer material transport unit 5 to the transfer belt 11 at a predetermined control timing by the registration roller 33, and is charged by the electrode roller 22 to be statically applied to the transfer belt surface. It adheres electrically. The transfer material S is sequentially conveyed to the transfer position of each process cartridge 7 (ad) by the rotation of the transfer belt 11, and sequentially receives the transfer of the toner image on the drum 1 (ad). .

  As shown in FIGS. 16 and 17, a toner image detection sensor 302 is disposed above the drive roller 13 of the transfer material transport unit 5 while maintaining a predetermined gap from the transfer belt 11. The sensor 302 detects the density of the toner image directly transferred to the transfer belt 11 and used for measuring the image density control condition.

  Transfer rollers 12 (ad) are arranged side by side in contact with the inside of the transfer belt 11 and facing the four drums 1 (ad). Positive charges are applied from the transfer roller 12 to the transfer material S via the transfer belt 11. In Embodiment 3, a transfer bias of 1600V is applied to the transfer rollers 12a to 12c and 1700V is applied to 12d as the transfer bias. As a result, the toner image on the drum 1 is transferred to the transfer material S. On the transfer material S, the toner images on the drums 1 are sequentially superimposed and transferred by an electric field formed between the drums 1 (a to d) and the transfer rollers 12 (a to d).

  The transfer material S onto which the four color toner images are superimposed and transferred is separated from the transfer belt 11 by the curvature of the driving roller 13. Then, it is carried into the fixing unit 50. After the toner image is thermally fixed by the fixing unit 50, the transfer material S is discharged from the discharge unit 54 to the outside of the main body by the discharge roller pair 53.

  The fixing unit 50 fixes a plurality of color toner images transferred to the transfer material S. There is a heating roller 51a that rotates, and a pressure roller 51b that presses and applies heat and pressure to the transfer material S. That is, the transfer material S to which the toner image on the drum 1 is transferred is conveyed by the fixing roller pair 51 (51a, 51b) when passing through the fixing unit 50.

  FIG. 17 is a schematic diagram of the sensor 302. The sensor 302 has the same configuration as the sensor 301 described with reference to FIG. 4, includes a light emitting element 302 a and a light receiving element 302 b, and is disposed to face the transfer belt 11.

  As shown in FIG. 18, the toner image detection sensor 302 is arranged in a state of being maintained at a predetermined gap from the transfer belt 11 above the driving roller 13, and transfers the toner image 320 directly transferred onto the transfer belt 11. Detection is performed sequentially by 11 movements (arrow Y direction in the figure). The toner image detection sensor 302 may be in any position as long as an image can be formed in a direction (longitudinal direction) orthogonal to the moving direction of the transfer belt 11.

  Incidentally, the toner amount of the printed image varies depending on various conditions such as temperature and humidity conditions in which the color image forming apparatus is used, the degree of drum usage, and the number of printed sheets. The change in the toner amount becomes a change in the density of the printed image and is recognized as a color variation by the user. Therefore, many color image forming apparatuses are equipped with an image density control mechanism that automatically adjusts image forming conditions such as charging potential, exposure amount, and developing bias. A toner image for density detection, which is formed for controlling image forming conditions, is formed on a conventionally known image carrier or transfer material carrier, and the density is detected by a toner image detection sensor. Based on the detection result The image forming conditions are controlled. As a toner image detecting means prepared for controlling the image forming conditions of such a color image forming apparatus, the toner image detecting sensor 302 of this embodiment includes means for detecting the density of the toner image by an optical sensor. Using. As described in the first and second embodiments, the density of the fog toner can be measured by these toner image detection sensors 302.

  The system configuration of the image forming apparatus according to the third embodiment will be described with reference to the system block diagram of FIG. A central processing unit (CPU) (not shown) is provided in the controller 71 that performs system control of the entire image forming apparatus, and a series of system processing of the image forming apparatus is performed in the central processing unit (CPU). This is performed according to a program stored in advance. The high-voltage power source 72 generates a charging bias that is a DC voltage for the charging member 2, a developing bias that is a DC voltage for the developing roller 40, and a transfer bias that is a DC voltage for the transfer roller 12 for each color. A sensor group 73 including a toner image detection sensor 302 is disposed in the apparatus, and a display unit 74 that displays the state of the apparatus is provided. In addition, a driving unit 76 for driving the drum 1, the developing device 4, and the transfer belt 11 is provided.

(2) Life Judgment Sequence of Developing Devices 4 (a to d) The image forming apparatus according to the third exemplary embodiment uses the life judging sequence described below, and the developing devices 4 (a to d) in the process cartridges 7 (a to d). Let d) determine the lifetime.

  Here, in the third embodiment, the life of each developing device 4 (ad) is also the life of each process cartridge 7 (ad) including the developing device. That is, in Example 3, the life of the developing device and the life of the process cartridge are synonymous.

  The image forming apparatus according to the third exemplary embodiment includes a toner image detection sensor (density detection unit) 302 that detects the toner image density on the transfer belt 11 that is the second image carrier. The sensor 302 detects the fog toner density of the portion where the latent image is not formed on the transfer belt 11, and determines the lifetime of each developing device 4 (ad) according to the detected value. have.

  FIGS. 19 and 21 are flowcharts of the life determination sequence of the developing devices 4 (a to d), which are executed by the controller 71, respectively.

  The sequence in FIG. 19 is executed during the pre-rotation operation of the image forming apparatus. The sequence shown in FIG. 21 is executed during the interval between sheets when image formation is continuously performed.

(2-1) During Pre-Rotation Operation First, the life determination sequence executed during the pre-rotation operation in FIG. 19 will be described.

  When the controller 71 of the image forming apparatus in the standby state receives a print execution request from the host device 70 connected to the image forming apparatus (S1), the controller 71 shifts to a life determination sequence for determining the life of the developing device ( S2).

  In order to detect the fog toner density on the transfer belt 11, the light emitting element 302a of the toner image detection sensor 302 is turned on (S3).

  Next, the drive unit 76 holds the exposure by the scanner unit 3 (a to d) in the OFF state (S4), and subsequently starts the operation of driving all the drums 1 (a to d) and the drive roller 13 (S5). ).

  When the drum 1 (a to d) and the driving roller 13 are constantly driven in the same state as during image formation, the high voltage power source 72 applies the charging bias and transfer bias for all four colors (S6). At this time, the applied voltage is the same as the image forming condition automatically adjusted by the image density control mechanism.

  After driving all the four color developing devices 4 (a to d) (S7), the drive unit 76 has the same image forming conditions as those automatically adjusted by the image density control mechanism to the developing rollers 40 (a to d) of the respective colors. The high-voltage power supply 72 applies the development bias of the condition (S8).

  Subsequently, the drive unit 76 swings the developing devices 4 (a to d) for all colors, and brings the developing rollers 40 (a to d) for the respective colors into contact with the drum 1 (a to d) (S9). The fog of each color in a potential state equivalent to the non-image portion of the image forming area can be transferred onto the transfer belt 11 in a portion where a latent image is not formed for each color.

In order to detect the fog toner density on the transfer belt 11, the reflected light received by the light receiving element 302 b of the sensor 302 is processed by the controller 71 to obtain a detection value A of the sensor 302.
The controller 71 has a correspondence relationship between the detection value of the sensor 302 and the fog toner density in advance, and can convert the detection value A into the fog toner density on the transfer belt 11. FIG. 20 shows an example of the detection result of the sensor 302. By the above-described operation, each of the fog toners of black (K), cyan (C), magenta (M), and yellow (Y) is sequentially transferred on the transfer belt 11 in the reverse order of image formation. . In the example of FIG. 20, it can be seen that the fog toner density on the transfer belt 11 increases in the order of cyan (C), black (K), magenta (M), and yellow (Y).

  As described in the second embodiment, a sensor detection value corresponding to the fog toner density in a state where the life of the developing device is approaching is prepared in the controller 71 as the developing device life warning threshold value A1. This makes it possible to notify the end of the life of the developing device, that is, the process cartridge including the developing device. By displaying the result on the display unit 74 such as a display device, it is possible to provide the user with a preparation period for replacing the developing device, that is, the process cartridge.

  Therefore, when there is a color whose detection value of the sensor 302 is equal to or greater than the threshold value A1 (S10), the process cartridge is approaching the end of its life, such as a life warning for the process cartridge including the developing device of the corresponding color on the display unit 74. A message to that effect is displayed (S11).

  Further, when there is a developing device of a color whose detection value of the sensor 302 is equal to or greater than the threshold value A2 (S12), it is determined that the fogging has reached an allowable value and the life of the device has been reached, and the light emitting element 302a of the sensor 302 is turned off. (S13). The high-voltage power supply 72 stops voltage application from each high-voltage power supply (S14), and the drive unit 76 stops driving the drum 1, the drive roller 13, the developing unit 4 and the like (S15). Then, the display unit 74 displays that the process cartridge has reached the end of its life, such as a life warning for the process cartridge including the developing device of the corresponding color (S16), and the controller 71 ends the life determination sequence of the developing device. (S17).

  When the detection value of the sensor 302 is less than the threshold value A2 for all colors (S12), the display unit 74 displays a notice of the life of the process cartridge including the developing device of the corresponding color (S11), and the driving unit 76. Enables exposure by the exposure apparatus 3. Thereby, in preparation for latent image formation (S18), image formation is executed (S19).

  If the detection value of the sensor 302 is less than the threshold value A1 (S10), the developing device determines that the life warning stage has not been reached, and the drive unit 76 can perform exposure by the exposure device 20 to prepare for latent image formation (S18). Image formation is executed (S19).

(2-2) Between Papers Next, the life judgment sequence executed at the time between papers during continuous image formation in FIG. 21 will be described.

  In the image forming apparatus according to the third embodiment, the color toner images are stacked on the transfer material S held on the transfer belt 11 to form a color image. Each color fog toner is laminated on the belt 11.

  Therefore, after performing the image forming operation (S20), the controller 71 obtains the fog toner density of all four colors on the transfer belt 11 corresponding to the space between the toner image detection sensors 302 as the detection value A (y + m + c + k).

  The detection value A (y + m + c + k) is a value obtained as a result of stacking four color fogs, but the detection value A (y + m + c + k) is used as the threshold value A1 in order to reliably extract the possibility of being at least the threshold value A1 in at least one developing device. (S21).

  When the detected value A (y + m + c + k) is equal to or greater than the threshold value A1, the developing device is specified. Therefore, image formation is interrupted once at a predetermined timing, and the drive unit 76 swings the developing devices 4 (a to d) for all colors. Then, the developing rollers 40 (a to d) for the respective colors are separated from the drum 1 (a to d). Thereafter, the transfer belt 11 is cleaned (S22). In this embodiment, an electrostatic recovery method is used as a cleaning method. That is, the toner adhering on the transfer belt 11 is electrostatically attached to the drum 1 (ad) of the process cartridge 7 (ad), and is collected by the cleaning device 6 (ad).

  After cleaning the transfer belt 11, the driving unit 76 again swings the developing devices 4 (a to d) for all colors, and contacts the developing rollers 40 (a to d) of the respective colors against the drum 1 (a to d). Then, the process proceeds to step 10 in FIG. 19 to determine the life of each color developing device.

  The detected value A (y + m + c + k) is compared with the threshold value A1, and if it is less than the threshold value A1 (S21), it is determined whether there is a continuous print execution request (S23). If yes, the image forming operation (S20) is not performed. In this case, the developing device life determination sequence is terminated (S24).

  A latent image is not formed by using the color image forming apparatus provided with the life judgment sequence of the third embodiment described above, also using the toner image detecting means prepared for automatically adjusting the image forming conditions. A toner image adhering to the portion, so-called “fogging” is detected. Then, the detected value of the toner image density in a portion where no latent image is formed has at least two threshold values A1 and A2, and the life of the developing device is determined. As a result, the user can be notified of replacement of the process cartridge including the developing device, and can be provided with a preparation period for replacement of the process cartridge.

  In particular, in a color image forming apparatus having a plurality of process cartridges, it is effective to provide a preparation period in order to reduce the troublesome process cartridge replacement.

  In the third embodiment, the density of fog toner for all four colors is compared between the paper during image formation and the detected value A (y + m + c + k) of the toner image is compared with the developing device life warning threshold value A1. However, there is no problem even if a method for comparing the detected value A (y + m + c + k) with the threshold value A1 (y + m + c + k) is newly provided with a developing device lifetime notice threshold value A1 (y + m + c + k) taking into account the fog toner density of all four colors. No. Similarly, a developing device lifetime warning threshold A2 (y + m + c + k) may be prepared.

  In addition, the color image forming apparatus according to the third exemplary embodiment can swing the developing devices 4 (a to d) independently. Therefore, the toner images are detected independently for each color by swinging the developing devices so that the fog of the four developing devices 4 (a to d) can be individually transferred onto the transfer belt 11 between the sheets during image formation. It is also possible to obtain the detection value of the sensor.

  Although the description is omitted, even in the post-rotation operation, for example, it is possible to execute the developing device life determination sequence according to the case of the pre-rotation operation.

  The threshold values A1 and A2 may be set for each color.

  Depending on the installation environment such as room temperature and humidity in which the developing device is used, the correspondence between the usage state of the developing device and the fog toner density may be slightly different. In this case, the thresholds A1, A2, A1 ( y + m + c + k) and A2 (y + m + c + k) may be set as appropriate.

  The lifetime judgment sequence of the developing device may be performed in all of “at the time of pre-rotation operation”, “at the time of paper”, and “at the time of post-rotation operation”, or may be performed in any one of them, Or a combination of the two.

  In the third embodiment, the method for detecting the fog toner density in the reversal development method has been described. However, the present invention is also applicable to the regular development method.

1 is a schematic configuration diagram of an image forming apparatus in Embodiment 1. FIG. 1 is a system block diagram of an image forming apparatus. FIG. 3 is an operation process diagram of the image forming apparatus. It is a schematic diagram of a toner image detection sensor. It is a figure explaining fog toner image detection. It is a flowchart figure of the lifetime determination sequence at the time of pre-rotation operation | movement. It is a graph explaining the output value which detected the fog toner image. It is a flowchart figure of the lifetime determination sequence at the time of a paper interval. It is a flowchart figure of the lifetime determination sequence at the time of back rotation operation | movement. 6 is a schematic configuration diagram of an image forming apparatus in Embodiment 2. FIG. It is a schematic block diagram of a developing device. 1 is a system block diagram of an image forming apparatus. It is a flowchart figure of the lifetime determination sequence at the time of pre-rotation operation | movement. It is a graph explaining the output value which detected the fog toner image. It is a flowchart figure of the lifetime determination sequence at the time of a paper interval. 6 is a schematic configuration diagram of an image forming apparatus in Embodiment 3. FIG. It is a schematic diagram of a toner image detection sensor. FIG. 6 is a diagram illustrating a toner image density detection method. It is a flowchart figure of the lifetime determination sequence at the time of pre-rotation operation | movement. It is a graph explaining the output value which detected the fog toner image. It is a flowchart figure of the lifetime determination sequence at the time of a paper interval. It is a figure explaining transition of the fog to the number of printed sheets.

Explanation of symbols

  100 ... Electrophotographic photosensitive drum, 200 ... Charging means, 300 ... Scanner unit, 400 ... Developing device, 600 ... Cleaning means, 500 ... Transfer means, 301 ... Toner image detection sensor

Claims (8)

In an image forming apparatus that has a developing device for storing a developer, an image carrier, and a density detector that detects a developer image density on the image carrier, and forms an image on a recording medium.
An image forming apparatus comprising: a developing device life determination sequence for detecting a developer image density of a portion where a latent image is not formed by the density detection means and determining a developing device life according to a detected value.   The developing device life determination sequence determines the developing device life when the detected value of the developer image density of a portion where a latent image is not formed is at least the first and second predetermined density values, and the developer When the detected value of the image density is greater than or equal to the first predetermined value and less than the second predetermined value, it is determined that the developing device life is predicted, and the detected value of the developer image density exceeds the first predetermined value and the first 2. The image forming apparatus according to claim 1, wherein when the predetermined value of 2 is reached, it is determined as a developing device life warning.   The image forming apparatus according to claim 1, wherein the image bearing member is any one of an electrostatic latent image bearing member, an intermediate transfer member, and a transfer material conveying member.   4. The image forming apparatus according to claim 1, further comprising a display device configured to display a life of the developing device based on a result of the developing device life determination sequence. 5.   The image forming apparatus according to claim 1, wherein the developing device life determination sequence is performed under a developing condition set to the same condition as the image forming condition.   5. The developing device life determination sequence according to claim 1, wherein the image carrier is an intermediate transfer member, and the developing device life determination sequence is performed under development conditions and transfer conditions set to the same conditions as image forming conditions. The image forming apparatus described in 1.   The developing device is a developing cartridge that is detachable from the image forming apparatus main body, or at least the latent image carrier and the developing device are integrated as a process cartridge that is detachable from the image forming apparatus main body. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. It has density detecting means for detecting the developer image density on the image carrier and is detachable from an image forming apparatus for forming an image on a recording medium. In a process cartridge provided with a carrier,
The density detection means detects the density of the developer image on the image carrier in a portion where no latent image is formed, and the process cartridge life is determined by the life determination sequence provided in the image forming apparatus according to the detected value. Process cartridge characterized by.