JP5354843B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of stabilizing an image without depending on the duration condition etc., such as duration initial period and end period, of a development device. <P>SOLUTION: The image forming apparatus 100A comprises an image carrier 10 in which the electrostatic image corresponding to image information is formed and a development device 2 which is the development device 2 for developing the electrostatic latent image formed by the image carrier 10 and includes a developer storage unit 20 for storing the developer, a developer carriage 17 for carrying and conveying the developer to a development section G for supplying the developer to the image carrier 10, and a developer supply member 19 for supplying the developer in the developer storage unit 20 into the developer carriage 17. The image forming apparatus 100A comprises a first bias application means 42 for applying a bias to the developer carriage 17 and a second bias application means 43 for applying a bias to the developer supply member 19. The bias impressed from the second bias application means 43 to the developer supply member 19 changes independently from the bias impressed from the first bias application means 42 to the developer carriage 17 according to the information indicating the durable condition of the development device 2. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a copying machine, a printer, a fax machine, or the like that forms an image by developing a latent image formed on an image carrier using an electrophotographic system or an electrostatic recording system with a developer using a developing device. The present invention relates to a forming apparatus.

  2. Description of the Related Art Conventionally, in an image forming apparatus using, for example, an electrophotographic system, a latent image (electrostatic image) formed on an image carrier by an exposure device is developed with a developer contained in a developing device, and the developer image Are transferred onto a recording material directly or via an intermediate transfer member or the like. The developer image transferred to the recording material is fixed by a fixing device, and then the recording material is discharged out of the device.

  Various configurations have been proposed and put into practical use as developing devices used in the electrophotographic system as described above. For example, as a typical developing device, there is a one-component developing device as shown in FIG.

  The developing device 202 shown in FIG. 23 is installed adjacent to an image carrier 210 as a latent image carrier on which a latent image is formed by an exposure device. The developing device 202 makes a non-magnetic one-component developer as a developer, that is, a developing roller 217 as a developer carrying member carrying and transporting toner, and a uniform developer thickness on the developing roller 217. A developing blade 218. The developing roller 217 is in contact with the image carrier 210 at a portion facing the image carrier 210 to form a developing unit G that supplies the developer to the image carrier 210. Further, the developing device 202 contacts the developing roller 217 to supply the developer to the developing roller 217, and at the same time collects the developer on the developing roller 217 after development, and a developer supplying roller 219 as a developer supplying member. Have The developing device 202 includes a developer storage unit 220 in which a developer is stored, and developer agitation paddles 221 and 222 that stir and convey the developer in the developer storage unit 220.

  Next, each bias related to image formation will be described. The bias (hereinafter referred to as “Vd”) of the image carrier 210 is determined by charging the image carrier 210, and the bias (hereinafter referred to as “Vl”) of the exposed portion on the image carrier 210 is charged. The determined image carrier 210 is determined by being exposed by an exposure apparatus. The bias (hereinafter referred to as “Vdc”) of the developing roller 217 is determined by a DC bias applied from an external power supply 228 provided in the image forming apparatus. The bias (hereinafter referred to as “Vk”) of the developer supply roller 219 is connected to the ground of the image forming apparatus.

  Next, the flow of the developer from the developer storage unit 220 in the developing device 202 shown in FIG. 23 will be described. The developer present in the developer storage unit 220 is mechanically conveyed to the developer supply roller 219 while being stirred by the developer stirring paddles 221 and 222. Next, the developer carried and conveyed on the developer supply roller 219 is supplied to the developing roller 217 by receiving an electrostatic force from a bias difference between Vdc and Vk (hereinafter referred to as “Vkcont”). Next, the developer supplied onto the developing roller 217 is adjusted to a certain thickness by the developing blade 218, and is then carried and conveyed by the developing roller 217, at the developing unit G that contacts the image carrier 210. , Vl and Vdc (hereinafter referred to as “Vcont”) are transferred onto the image carrier 210. As a result, the latent image on the image carrier 210 is developed. Thereafter, the developer (residual toner) remaining on the developing roller 217 is mechanically peeled off from the developing roller 217 by the developer supply roller 219 and returned to the developer storage unit 220. A similar configuration is described in Patent Document 1.

In addition, in the electrophotographic system, it is known that the amount of developer applied increases as the density increases when comparing the amount of developer applied at different locations on the recording material. Therefore, Patent Document 2 proposes changing the bias (equivalent to Vk) applied to the developer supply roller in accordance with image information. With such a configuration, an amount of developer necessary to output an image having a desired image density is supplied from the developer supply roller to the development roller. It is said that there is an effect that does not occur.
JP 61-42672 A JP-A-9-305014

  By the way, for example, in a one-component developing device, the proportion of fine particles having a particle size of 5 μm or less tends to increase as the durability progresses. The reason for this is considered to be that as the durability of the developing device progresses, the developer is pulverized by being stirred in the developing device, resulting in an increase in the developer amount of fine particles. Further, the fine particle developer has a characteristic that it is poor in fluidity and easily aggregates.

  On the other hand, in order to stabilize the development characteristics, it is preferable to keep the amount of developer on the developer carrying member constant. Therefore, in order to make the amount of developer on the developer carrying member the same at the end of durability of the developing device and at the end of the development, in view of the deterioration of the fluidity of the developer at the end of the end of the development, the developer is developed by increasing Vkcont at the end of the end of durability. It is desirable to transport the developer from the developer supply member to the developer carrier.

  However, the above-mentioned Patent Document 1 does not have a configuration for biasing the developer supply member, and Vk cannot be changed. Therefore, when Vkcont is changed according to the durability of the developing device, it is necessary to change Vdc. However, when Vdc is changed, Vcont is also changed, and the development characteristics change between the initial durability stage and the final stage of the developing device.

  On the other hand, in Patent Document 2, a bias is applied to a developer supply roller that is a developer supply member. However, in Patent Document 2, the bias applied to the developer supply roller is changed based on the printing rate for each printed matter. That is, since the bias applied to the developer supply roller is not changed according to the progress of the durability of the developing device, the Vkcont at the same image density is the same at the initial stage and the final stage. Therefore, since the amount of developer on the developing carrier changes between the durability initial stage and the end stage of the developing device, the development characteristics differ between the durability end stage and the end stage.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of stabilizing an image regardless of usage conditions such as the initial stage or the last stage of use of a developing device.

The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention is an image carrier on which an electrostatic image corresponding to image information is formed, and a developing device for developing the electrostatic image formed on the image carrier, which contains a developer. A developer container, a developer carrier that carries and transports the developer to the developing unit that supplies the developer to the image carrier, and the developer in the developer container is transferred to the developer carrier. An image forming apparatus comprising: a developer supply member that supplies a first bias applying unit that applies a bias to the developer carrying member; and a first bias that applies a bias to the developer supply member. Bias applied to the developer supply member from the second bias applying means is independent of the bias applied to the developer carrier from the first bias applying means. to initial use of the developing device An image forming apparatus characterized by changes in accordance with the usage information to correlate with the amount of the cumulative al.

According to another aspect of the present invention, there is provided an image carrier on which an electrostatic image corresponding to image information is formed, and a developing device for developing the electrostatic image formed on the image carrier, which contains a developer. A developer container, a developer carrier that carries and transports the developer to the developing part that supplies the developer to the image carrier, and the developer in the developer container to the developer carrier. A developer supply member that supplies the developer carrying member, a first bias applying unit that applies a bias Vdc to the developer carrier, and a second bias application that applies a bias Vk to the developer supply member. And the image density of the image density detection image formed on the image carrier using the developing device on the image carrier or on the transfer medium onto which the developer image is transferred from the image carrier. In an image forming apparatus having an image density detecting means The image density detecting image, by changing the bias difference Vkcont between the bias Vdc remains a bias difference Vcont was constant bias Vl and the bias Vdc of the exposure portion on the image bearing member and said bias Vk is formed, at the time of image formation, the bias Vk is the independent of the bias Vdc, the image forming apparatus is characterized in that it varies according to the image density detecting means and the image density information detected by Provided.

According to the present invention, it is possible to stabilize an image regardless of usage conditions such as an early stage and an end stage of use of the developing device.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Example 1
[Overall Configuration and Operation of Image Forming Apparatus]
FIG. 1 shows a schematic sectional configuration of an embodiment of an image forming apparatus according to the present invention. First, the overall configuration and operation of the image forming apparatus 100A of this embodiment will be described. The image forming apparatus 100A according to the present embodiment is a laser beam printer that can form and output an image on a recording material, for example, a recording sheet, an OHP sheet, or the like according to image information using an electrophotographic method. In this embodiment, a non-magnetic one-component developer, that is, a toner is used as the developer, and this toner is charged to a negative polarity having the same polarity as the charging polarity of the image carrier, and the reversal development is performed.

  The image forming apparatus 100A includes an image carrier 10 on which an electrostatic image (latent image) corresponding to image information is formed. The image forming apparatus 100A also includes an exposure apparatus 1 as an exposure unit that creates an electrostatic latent image on an image carrier 10 as a charged latent image carrier, and an image carrier by charging a developer to a predetermined negative charge. A developing device 2 that visualizes the electrostatic latent image on the body 10 with a developer is provided. In this embodiment, the image carrier 10 is a cylindrical electrophotographic photosensitive member, that is, a photosensitive drum. The detailed configuration of the developing device 2 and the periphery of the developing device 2 will be described later.

  The image forming apparatus 100 </ b> A also includes a recording material cassette 3 storing the recording material 40 before image formation, and a recording material supply roller 4 for conveying the recording material 40 from the recording material cassette 3. The image forming apparatus 100 </ b> A also includes a registration roller 5 for adjusting the leading edge registration (positioning accuracy) of the recording material 40 and transporting it to the transfer device.

  Further, the image forming apparatus 100A receives a developer image (toner image) visualized on the transfer belt 6 and the image carrier 10 for conveying the recording material 40 from the registration roller 5 through the transfer portion to the fixing portion. A transfer roller 7 is provided as transfer means for electrostatically transferring to the recording material 40. The image forming apparatus 100 </ b> A includes a transfer belt driving roller 8 connected to a drive motor (not shown) for driving the transfer belt 6. The transfer belt 6, the drive roller 8, the transfer roller 7, etc. constitute a transfer device.

  The image forming apparatus 100 </ b> A also includes a cleaning unit 9 as a cleaning unit for collecting the developer (residual toner) remaining on the surface of the image carrier 10 after the developer image is transferred to the recording material 40.

  The image forming apparatus 100A also includes a heat roller 11 that heats the developer to fix the developer image transferred onto the recording material 40 to the recording material 40, and the recording material 40 is applied to the heat roller 11 during fixing. It has the pressure roller 12 to press. The heat roller 11 is heated by a halogen heater (not shown) included therein.

  The image forming apparatus 100A is connected to a power source (not shown), and remains on the primary charger 13 and the transfer belt 6 as primary charging means for uniformly charging the image carrier 10 before development. A transfer belt cleaning unit 14 for collecting the developer (residual toner). Further, the image forming apparatus 100A includes a recording material discharge roller 15 for conveying the recording material 40 after fixing, and a recording material discharge tray 16 for storing the recording material 40 after completion of image formation.

  Various operations such as driving of each unit, application of a bias, and an image forming process in the image forming apparatus 100A are controlled by a controller 27 as a control unit provided in the main body of the image forming apparatus 100A.

  Next, an image output process to the recording material 40 when the user issues an image output command will be described.

  First, the recording material 40 is conveyed from the recording material cassette 3 to the registration roller 5. On the other hand, a latent image is formed by the exposure device 1 on the image carrier 10 that is uniformly charged by the primary charger 13, and the latent image is visualized by the developing device 2. A developer image of the output image is formed on 10.

  After that, the recording material 40 and the developer image visualized on the image carrier 10 are adjusted so that the timing is matched at the transfer position (where the transfer roller 7, the image carrier 10 and the transfer belt 6 overlap). Then, the recording material 40 is conveyed from the registration roller 5 by the transfer belt 6. Then, the developer image is transferred from the image carrier 10 onto the recording material 40 at the transfer position N. Thereafter, the recording material 40 is guided by the conveyance guide 41 and is conveyed to the nipping portion by the heat roller 11 and the pressure roller 12. When the recording material 40 is nipped and conveyed by the heat roller 11 and the pressure roller 12, the unfixed developer image on the recording material 40 is fixed on the recording material 40 by applying heat and pressure. The recording material 40 is finally output to the recording material discharge tray 16 by the recording material discharge roller 15.

[Configuration of developing device and its surroundings]
Next, the configuration of the developing device 2 and its periphery will be described in more detail.

  In the developing device 2, the developer is stored in a developer storage section (developer storage section) 20, and the developer storage section 20 has a developer as a stirring and conveying member for stirring and transporting the developer. Agitation paddles 21 and 22 are provided. The developer stirred by the developer stirring paddles 21 and 22 is conveyed to a developer supply roller 19 as a developer supply member. Thereafter, the developer is supplied to the developing roller 17 as a developer carrying member by electrostatic adhesion. The developer on the developing roller 17 is adjusted to a uniform coating amount by a developing blade 18 as a developer regulating member. The developer coated on the developing roller 17 is carried and conveyed by the developing roller 17 and conveyed to a contact location (developing part) G between the developing roller 17 and the image carrier 10. In the developing unit G, the latent image on the image carrier 10 is visualized by the developer. Thus, in this embodiment, the latent image on the image carrier 10 is contact-developed. On the other hand, the developer (residual toner) remaining on the developing roller 17 after the development is physically peeled off from the developing roller 17 by the developer supplying roller 19 and returned to the developer storing unit 20 again.

  Each driving member of the developing device 2 (developing roller 17, developer supplying roller 19, developer stirring paddles 21 and 22) is connected by a gear, and by a developing motor 25 as a driving means connected to the gear. Driven.

  The developing motor 25 includes an encoder that can measure the driving time and the driving speed. In addition, the image forming apparatus 100 </ b> A includes a memory 26 that can be written and read as a storage medium electrically connected to the controller 27. In this embodiment, the output value from the encoder is added to the developing roller 17 already stored in the memory 26, that is, the accumulated driving time of the developing device 2 via the controller 27, and stored as needed. It has become. Thus, in this embodiment, the controller 27 can calculate the cumulative driving time of the developing roller 17, that is, the developing device 2.

  The developing roller 17 and the developer supply roller 19 provided in the developing device 2 are electrically connected to a first DC power source 42 and a second DC power source 43 as independent bias applying units, respectively.

  A first transformer 23 is connected between the developing roller 17 and the first DC power source 42. The first transformer 23 is controlled by a controller 27 provided in the image forming apparatus 100A. Thereby, the bias (development bias) Vdc applied to the developing roller 17 can be arbitrarily determined.

  On the other hand, a second transformer 24 different from the first transformer 23 is also connected between the developer supply roller 19 and the second DC power source 43. Similarly, the second transformer 24 is controlled by the controller 27. Thereby, it is possible to arbitrarily determine the bias (developer supply bias) Vk applied to the developer supply roller 19.

  Therefore, since the image forming apparatus 100A of this embodiment can arbitrarily control Vdc and Vk, it can also arbitrarily control Vkcont.

  Typically, a large value of Vk is applied to the developer supply roller 19 on the same polarity side as Vdc, so that the developer is placed between the development roller 17 and the developer supply roller 19. An electric field in the direction of moving from the supply roller 19 toward the developing roller 17 is formed.

  In this embodiment, first, Vkcont is fixed as Vdc = −300 [V], Vk = −400 [V], that is, Vkcont = 100 [V], as each bias when the developing device 2 is new. Under the conditions, a paper passing durability test of a sample with a printing rate of 5% was performed. FIG. 2 shows a correlation between the cumulative driving time of the developing roller 17 at that time and the amount of developer applied on the developing roller 17.

  In particular, it can be seen that the amount of developer applied on the developing roller 17 decreases after the cumulative driving time is 8 hours or more. Therefore, when an accumulated drive time of 9 hours has passed and the amount of developer applied on the developing roller 17 is reduced, an all black image is output, and the reflection density is measured using a reflection densitometer manufactured by Macbeth. The reflection density decreased by about 0.4 compared to the time.

Therefore, another new developing device 2 having the same configuration is prepared, and Vkcont = 150 [V] is set when the cumulative driving time reaches 8 hours. As a result, the correlation between the cumulative driving time of the developing roller 17 and the developer loading amount on the developing roller 17 was the result shown in FIG. That is, the developer loading on the developing roller 17 did not become 0.37 mg / cm ² or less, and the decrease in reflection density could be suppressed to 0.2.

  That is, as described above, particularly in the one-component development system, in the latter half of the endurance of the developing device 2, the ratio of the fine-particle developer having a small particle diameter increases in the developing device 2, and the developer in the developing device 2 increases. The degree of aggregation increases and the fluidity tends to deteriorate. As a result, the amount of developer supplied to the developing roller 17 tends to decrease in the second half of the durability of the developing device 2. One of the objects of the present invention is to prevent a decrease in the amount of developer on the developing roller 17 in the second half of the durability of the developing device 2, and to keep the developer amount on the developing roller 17 substantially constant regardless of the durability of the developing device 2. Is to provide stable image quality. In this embodiment, therefore, the bias applied to the developer supply roller 19 can be arbitrarily set regardless of the bias applied to the developing roller 17 in accordance with the durability transition of the developing device 2. This makes it possible to always control the amount of developer on the developing roller 17 to be substantially constant and provide a stable image quality.

  FIG. 4 shows a control flow of the present embodiment based on the above results. Hereinafter, each step will be described.

  First, the controller 27 determines whether or not the image forming apparatus 100A has received an image formation request (S101). Next, the controller 27 reads the cumulative drive time from the memory 26 in which the cumulative drive time of the developing roller 17 is stored, and determines whether or not the cumulative drive time is 8 hours or more (S102). Next, the controller 27 sets the second transformer 24 so that Vkcont becomes 150 [V] when the cumulative driving time is 8 hours or more (S103). Next, the controller 27 starts image formation when the desired Vkcont is set (S104). The controller 27 counts the drive time of the developing roller 17 required for the image formation in S104, adds the drive time required for the current image formation to the accumulated drive time read in S102, and writes it in the memory 26 (S105). ). Next, the controller 27 determines whether or not the image formation is completed (S106). If the cumulative driving time of the developing roller 17 is less than 8 hours in the determination of S102, the controller 27 sets the second transformer 24 so that Vkcont becomes 100 [V] (S107).

  By performing control along the above flow, even when the durability of the developing device 2 has progressed, it has become possible to suppress a decrease in image density within 0.2.

  In this embodiment, since the amount of developer applied on the developing roller 17 decreased after the cumulative driving time of the developing roller 17 had elapsed for 8 hours, Vkcont was adjusted. However, the Vkcont adjustment timing can be changed according to the characteristics of the developing device 2 to be used. Also, a plurality of bias values may be adjusted in multiple stages.

  As described above, the developing device 2 according to the present exemplary embodiment includes the developer storing unit 20 in which the developer is stored, the developing roller 17 that carries and transports the developer, and that contacts the image carrier 10 for development, and the developing A developer supply roller 19 that conveys the developer from the agent storage unit 20 to the developing roller 17. Independent DC bias is applied to the developing roller 17 and the developer supply roller 19, and at least the value of the bias applied to the developer supply roller 19 changes according to the durability of the developing device 2. In this embodiment, the image forming apparatus 100 </ b> A has a control device that can grasp the accumulated driving time of the developing roller 17, that is, the developing device 2 as information indicating the durability status of the developing device 2. Then, the value of the DC bias applied independently to each of the developing roller 17 and the developer supply roller 19 changes according to the cumulative driving time.

  That is, according to the present embodiment, the applied bias Vk to the developer supply roller 19 and the applied bias Vdc to the developing roller 17 are variably controlled independently. Thereby, the bias difference Vkcont between the developer supply roller 19 and the developing roller 17 can be changed independently of Vdc. Therefore, even when the developer fluidity deteriorates at the end of the durability of the developing device 2, the developer amount on the developing roller 17 can be made substantially the same by increasing Vkcont without affecting Vcont. This makes it possible to maintain stable development characteristics regardless of the durability of the developing device 2.

  In particular, according to the present embodiment, as the information indicating the durability of the developing device 2, the cumulative driving time of the developing roller 17, that is, the developing device 2, is used, and Vkcont is changed according to the cumulative driving time. As a result, even when the durability of the developing device 2 progresses and the developer is pulverized to increase the proportion of fine particles and the fluidity of the developer is deteriorated, the development of approximately the same amount as the initial durability is achieved without affecting Vcont. It becomes possible to supply the developer from the developer supply roller 19 to the developing roller 17.

  As described above, according to the present exemplary embodiment, even when the developer fluidity changes depending on the durability state of the developing device 2 such as the initial durability and the final durability, the Vkcont is changed while maintaining substantially the same development characteristics. The developer amount on 17 can be made substantially the same. As a result, the output image can be stabilized regardless of the durability of the developing device 2 or the like.

Example 2
Next, another embodiment according to the present invention will be described. FIG. 5 shows a schematic cross-sectional configuration of the image forming apparatus 100B of the present embodiment. The basic configuration and operation of the image forming apparatus 100B of the present embodiment are the same as those of the image forming apparatus 100A of the first embodiment. Accordingly, elements having the same functions or configurations as those of the image forming apparatus 100A according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this embodiment, a light emitting unit 28 having a light emitting element that emits light and a light receiving unit 31 having a light receiving element that receives the light (detection light) are disposed in a predetermined portion around the developing device 2. Yes. Further, on the optical path of the detection light of the developing device 2, residual detection windows 29 and 30 that are light-transmitting windows are provided. As a result, a light detection circuit from the light emitting unit 28 to the light receiving unit 31 through the developing device 2 is configured as indicated by a broken line in the drawing. The light emitting section 28, the light receiving section 31, the remaining detection windows 29 and 30 and the like constitute a developer remaining amount detecting means 44.

  A cleaning member 32 made of Mylar (trade name of polyethylene glycol terephthalate film), which is an elastic member, is attached to the tip of the developer agitation paddle 22 for cleaning the residual detection windows 29 and 30. As a result, the container inner surface side of the residual detection windows 29 and 30 is wiped in synchronization with the rotation of the developer stirring paddle 22, and the remaining amount of the developer in the developer storage unit 20 is detected by the change in the detection light detected at that time. can do.

  However, when the remaining amount of developer is large, light is not transmitted because the cleaning member 32 is immediately covered with the developer even if the cleaning windows 32 and 30 are cleaned. On the other hand, the detection light can be detected by the light receiving unit 31 as the amount of the developer in the developer storage unit 20 decreases. Therefore, as shown in FIG. 6, the remaining amount of the developer in the developing device 2 can be detected as the output pulse width T based on the length of detection light detection time. As shown in FIG. 6, the width T of the output pulse is detected at the period t of the developer agitation paddle 22 and has a characteristic of increasing as the remaining amount of developer decreases.

  Therefore, when the correlation characteristic between the output pulse width T of the developer remaining amount detecting means 44 and the developer remaining amount in the developer storage unit 20 is measured, it is as shown in FIG. The controller 27 calculates the developer remaining amount in the developing device 2 from the output pulse width T of the developer remaining amount detecting means 44, and updates and stores information related to the developer remaining amount in the memory 26 as needed. It has become.

  Next, as in the first embodiment, first, as biases of the developing device 2 when they are new, Vdc = −300 [V], Vk = −400 [V], that is, Vkcont = 100 [V]. A paper passing durability test was performed on a sample with a printing rate of 5% under the condition that Vkcont is fixed. FIG. 8 shows the correlation between the developer remaining amount in the developing device 2 calculated from the output pulse width T of the developer remaining amount detecting means 44 at that time and the developer loading amount on the developing roller 17.

  In particular, it can be seen that when the developer remaining amount is 40% or less, the amount of developer applied on the developing roller 17 decreases. Further, when the developer remaining amount of the developing device 2 is 30% more advanced than the developer remaining amount of 40%, an all black image is output, and the reflection density is measured using a reflection densitometer manufactured by Macbeth. However, the reflection density was reduced by about 0.6 compared with the new product.

  Therefore, a new developing device 2 having the same configuration is prepared, and Vkcont = 150 [V] is set when the developer remaining amount becomes 40%. As a result, the correlation between the developer remaining amount calculated from the output pulse width T of the developer remaining amount detecting means 44 and the developer loading amount on the developing roller 17 is the result shown in FIG. That is, the developer loading on the developing roller 17 did not become 0.37 or less, and the decrease in reflection density could be suppressed to 0.2.

  FIG. 10 shows a control flow of the present embodiment based on the above results. Hereinafter, each step will be described.

  First, the controller 27 determines whether or not the image forming apparatus 100B has received an image formation request (S201). Next, the controller 27 detects the output pulse of the developer remaining amount detecting means 44, calculates the developer remaining amount in the developing device 2 from the width T of the output pulse, and the developer remaining amount is less than 40%. It is determined whether or not there is (S202). Next, when the developer remaining amount is less than 40%, the controller 27 sets the second transformer 24 so that Vkcont becomes 150 [V] (S203). Next, the controller 27 starts image formation when the desired Vkcont is set (S204). The controller 27 measures the developer remaining amount in the developing device 2 from the output pulse width T of the developer remaining amount detecting means 44 during image formation in S204, and writes it in the memory 26 (S205). Next, the controller 27 determines whether or not the image formation is completed (S206). Further, the controller 27 sets the second transformer 24 so that Vkcont becomes 100 [V] when the developer remaining amount is 40% or more in the determination of S202 (S207).

  By performing control along the above flow, even when the durability of the developing device 2 has progressed, it has become possible to suppress a decrease in image density within 0.2.

  In this embodiment, since the developer amount on the developing roller 17 was reduced when the developer remaining amount was 40%, Vkcont was adjusted. However, the Vkcont adjustment timing can be changed according to the characteristics of the developing device 2 to be used. Also, a plurality of bias values may be adjusted in multiple stages.

  As described above, in this embodiment, the image forming apparatus 100 </ b> B can detect the remaining amount of developer in the developer storage unit 20 as information indicating the durability status of the developing device 2. Then, the DC bias value applied independently to each of the developing roller 17 and the developer supply roller 19 is changed according to the detection result of the remaining amount of the developer.

  That is, according to the present embodiment, the remaining amount of developer in the developing device 2 is used as information indicating the durability status of the developing device 2, and Vkcont is changed according to the remaining amount of developer. That is, the load that the developer receives during the stirring process of the developing device 2 increases as the amount of the developer decreases, so the fine particles in the developing device 2 increase when the remaining amount of the developer is small, and depend on the remaining amount of the developer The nature is great. Therefore, in this embodiment, the remaining amount of the developer that makes it easier to grasp the increase in the proportion of the fine particles of the developer than the configuration of the first embodiment is used as the durability parameter of the developing device 2. As a result, the same effects as those of the first embodiment can be obtained, and control in accordance with the situation where the developer fine particles increase in the actual developing device 2 and the fluidity of the developer deteriorates becomes possible.

Example 3
Next, another embodiment according to the present invention will be described. FIG. 11 shows a schematic cross-sectional configuration of the image forming apparatus 100C of the present embodiment. The basic configuration and operation of the image forming apparatus 100C of the present embodiment are the same as those of the image forming apparatus 100A of the first embodiment. Accordingly, elements having the same functions or configurations as those of the image forming apparatus 100A according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this embodiment, as shown in FIG. 12, the developing device 2 can be detached from the main body of the image forming apparatus 100C by opening the side plate panel 39 provided in the image forming apparatus 100C. The developing device 2 is provided with a developing device-side memory 34 that can be written and read as a storage medium.

  In this embodiment, the developing device side memory 34 is a non-volatile readable / writable non-contact memory using an electromagnetic coupling method, and is provided on the side surface of the developing device 2. The developing device side memory 34 can transmit and receive data to and from the controller 27 via an antenna 37 provided in the main body of the image forming apparatus 100C. The antenna 37 is disposed opposite to the developing device side memory 34 in a state where the developing device 2 is mounted on the image forming apparatus 100C. The controller 27 can read / write information from / to the developing device side memory 34.

  The developing device-side memory 34 is not limited to a non-contact memory, and for example, a contact-type memory that transmits / receives data to / from the controller 27 via an electrical connector may be used.

  Information relating to individual identification is stored in advance in the developing device-side memory 34. Even if the developing device 2 is removed from the image forming apparatus 100C and remounted, the controller 27 has the same developing device 2. It is possible to identify whether or not.

  Next, a method for detecting the remaining amount of developer in the developer storage unit 20 using the pixel count method will be described as a method for obtaining the cumulative usage amount of the developer from the accumulated image information.

  As shown in FIG. 11, a controller 27 as a control unit for controlling the image forming apparatus 100C is provided in the image forming apparatus 100C, and reference data for controlling the image forming apparatus 100C is stored in the controller 27. A ROM for storage is provided. Further, in the image forming apparatus 100C, a signal processing circuit 35 that performs signal processing of image data, an addition circuit 36 that adds the number of laser ON signals (total light emission number L) among pixel signals described later, and the addition result Is stored through the controller 27.

  That is, the image data is input from the host computer 32 to the signal processing circuit 35 via the connector 33 and the controller 27 attached to the image forming apparatus 100C. This image data is developed into bitmap data by the signal processing circuit 35. The signal processing circuit 35 generates a laser ON / OFF signal based on the bitmap data. Based on this laser ON / OFF signal, laser light is irradiated from the exposure apparatus 1 to the image carrier 10, and a latent image is formed on the image carrier 10. Since this laser ON / OFF signal corresponds to a dot of an image, it is hereinafter referred to as a “pixel signal”.

  The adder circuit 36 calculates the light emission number by calling up the current light emission number from the memory 26 in which the result of adding the light emission numbers of the laser so far is stored and adding the new light emission number. .

  In addition to the total light emission number L, the following information can also be stored in the memory 26. That is, an application time for counting the time for applying the development bias, a unit application time for counting the time for applying the development bias for the image formation of a predetermined number of images, and a unit light emission number for counting the number of light emitted during the unit application time Etc.

  More specifically, since the reversal development system is used in this embodiment, the developer is consumed for the pixel corresponding to the laser ON signal portion of the pixel signal. Therefore, by adding the ON signal among the pixel signals processed based on the bitmap data by the signal processing circuit 35, the cumulative image information, that is, the total number of pixels of the image created on the recording material 40 is obtained. The consumption state of the developer can be grasped.

  In the present embodiment, the number of pixels (dots) of the laser ON signal is extracted from the pixel signals processed based on the bitmap data decomposed by the signal processing circuit 35. Further, the number of pixels already emitted is read from the memory 26, and the extraction result and the number of pixels stored in the memory 26 are added by the adding circuit 36.

  The added result is stored in the memory 26 via the controller 27. By repeating this, it is possible to grasp the number of laser emission (total emission number L) so far in the pixel signal. Then, it is possible to know the developer consumption so far by multiplying the total light emission number L so far by the developer consumption of one pixel.

  In this embodiment, at least information related to the total light emission number L is also stored in the developing device side memory 34 as needed.

The image forming apparatus 100C according to the present exemplary embodiment can form an image at 600 dpi using a non-magnetic one-component developer, that is, toner, and the developer consumption amount per pixel is 1.2 × 10 ^{−. 8} [g / dot]. Therefore, when an image of 8.3 × 10 ⁷ [dot] is formed, about 1 [g] of developer is consumed.

  As described above, it is utilized that the consumption amount of the developer is determined with respect to the number of emitted laser beams. The relationship between the developer consumption with respect to the total light emission number L or the remaining amount of developer with respect to the total light emission number L (= developer filling amount at new article-developer consumption) is stored in the ROM of the controller 27 in advance. I can leave. The controller 27 can detect the developer consumption or the developer remaining amount from the total light emission number L. Thereby, control similar to Example 2 can be implemented.

  FIG. 13 shows a control flow of the present embodiment based on the above results. Hereinafter, each step will be described.

  First, the controller 27 determines whether or not the image forming apparatus 100C has received an image formation request (S301). Next, the controller 27 reads the total light emission number L that is added by the addition circuit 36 and stored in the memory 26 (or the developing device side memory 34), and the total light emission number corresponds to the developer usage amount of 60%. It is determined whether or not it is equal to or greater than TL to be performed (S302). Next, the controller 27 sets the second transformer 24 so that Vkcont becomes 150 [V] when the total light emission number L is TL or more (S303). Next, the controller 27 starts image formation when the desired Vkcont is set (S304). The controller 27 measures the light emission number of the laser during image formation in S304, adds the light emission number measured this time to the total light emission number L read in S302 using the adder circuit 36, and the memory 26 (and the developing device). Side memory 34) (S305). Next, the controller 27 determines whether or not the image formation is completed (S306). Further, the controller 27 sets the second transformer 24 so that Vkcont becomes 100 [V] when the total light emission number L is less than TL corresponding to the developer usage amount of 60% in the determination of S302. (S307).

  By performing control along the above flow, even when the durability of the developing device 2 has progressed, it has become possible to suppress a decrease in image density within 0.2. Furthermore, in this embodiment, as compared with the second embodiment, it is possible to grasp the durability of the developing device 2 with a simple configuration that does not have a light emitting element, a light detection circuit, or the like around the developing device 2. In this embodiment, even if the developing device 2 is detached from the image forming apparatus 100C, the endurance state unique to the developing device can be grasped.

  In this embodiment, since the developer amount on the developing roller 17 was reduced when the developer remaining amount was 40%, Vkcont was adjusted. However, the Vkcont adjustment timing can be changed according to the characteristics of the developing device 2 to be used. Also, a plurality of bias values may be adjusted in multiple stages.

  Further, the developing device side memory 34 used in this embodiment can be used in the above-described first or second embodiment to store information indicating the durability status of the developing device 2 in each embodiment. As a result, similarly to the present embodiment, even when the developing device 2 is attached or detached, it is possible to provide a function capable of storing a durability state unique to the developing device 2 itself.

  As described above, in this embodiment, the image forming apparatus 100 </ b> C grasps the image information of the output image and the cumulative developer usage amount obtained based on the image information as information indicating the durability status of the developing device 2. It has a control device that can. Then, the DC bias value applied independently to each of the developing roller 17 and the developer supplying roller 19 is changed according to the amount of developer used since the developing device 2 is new.

  Further, in the present embodiment, the developing device 2 is provided with a developing device side memory 34 into which information indicating the durability status of the developing device 2 itself can be written, and indicates the durability status written in the developing device side memory 34. Information can be read out on the image forming apparatus 100C side. The DC bias value applied independently to each of the developing roller 17 and the developer supply roller 19 can be changed according to the information indicating the endurance status read from the developing device side memory 34. The developing device 2 is a cartridge that can be attached and detached from the main body of the image forming apparatus 100C.

  That is, according to the present embodiment, as information indicating the durability status of the developing device 2, cumulative image information of the image forming apparatus (here, image information is the total number of pixels of the image created on the recording material 40). Is used. Then, the amount of developer used for image formation on the recording material 40 is grasped from the accumulated image information, and Vkcont is changed. That is, when the same developer remaining amount is grasped, in the configuration of the second embodiment, it is necessary to provide a developer remaining amount detecting unit separately from the developing device 2. Therefore, in this embodiment, the developer usage amount is calculated from the information in the storage medium and the image information at the time of actual image formation to grasp the remaining amount of developer. As a result, the remaining amount of the developer can be grasped with a cheaper configuration as compared with the configuration of the second embodiment. In addition, a developing device side memory 34 that records the durability status of the developing device 2 is provided in the developing device 2. Accordingly, it is possible to easily grasp the endurance status of the developing device 2 by preparing only a device capable of reading the recorded contents of the developing device side memory 34 without turning on the main body of the image forming apparatus 100C. It becomes. Further, after the developing device side memory 34 in which the durability status of the developing device 2 is recorded is provided in the developing device, the developing device 2 can be attached to and detached from the main body of the image forming apparatus 100C. As a result, even when the developing device 2 that is not new but is being used is attached to the image forming apparatus 100C, the developer supply roller 19 supplies the same amount of developer as the initial durability of the developing device 2 without affecting Vcont. It becomes possible to supply to the developing roller 17.

Example 4
Next, another embodiment according to the present invention will be described. The basic configuration of the image forming apparatus of this embodiment is the same as that of the image forming apparatus 100B of Embodiment 2 shown in FIG. In the present embodiment, as in the first embodiment, the cumulative driving time of the developing device can be detected.

  That is, in this embodiment, as in the second embodiment, the remaining amount of developer is detected based on the output pulse width T from the developer remaining amount detecting means 44. In the memory 26 provided in the image forming apparatus 100B, information related to the developer remaining amount obtained from the output pulse width T of the developer remaining amount detecting means 44 is written.

  At the same time, in the present embodiment, as in the first embodiment, the cumulative driving time of the developing roller 17, that is, the developing device 2 is also obtained based on the output value from the encoder provided in the developing motor 25. 26 is written.

  In this embodiment, the remaining amount of developer is directly grasped by the optical sensor in the same manner as in the second embodiment. However, the present invention is not limited to this. For example, as in the third embodiment, cumulative developer usage is performed using information obtained by adding ON signals among pixel signals processed into bitmap data by the signal processing circuit 35. The remaining amount of developer may be grasped from the amount.

  As described in the third embodiment, when the developing device 2 is detachable from the main body of the image forming apparatus, the developing device 2 is provided with a developing device-side memory, and the developing device-side memory is provided with the above-described memory. Each information may be stored.

  Next, in the image forming apparatus 100B of the present example having the same configuration as that of Example 2, first, a sample paper passing durability test was performed using a new developing device 2 under the following conditions. In other words, Vdc = −300 [V], Vk = −400 [V], that is, Vkcont = 100 [V], and Vkcont is fixed. Further, a paper passing durability test of a sample having a printing rate of 1 [%] was performed. FIG. 14 shows the correlation between the cumulative driving time of the developing device 2 at that time and the amount of developer applied on the developing roller 17.

  When the cumulative driving time has passed for 10 hours or more despite the reduction in the printing rate, the amount of developer loaded on the developing roller 17 has decreased. %]Met. Thereafter, an accumulated drive time of 11 hours passed, an all black image was output in a state where the amount of developer applied on the developing roller 17 was reduced, and the reflection density was measured using a Macbeth reflection densitometer. The reflection density decreased by about 0.4 compared to the time.

  Therefore, a new developing device 2 having the same configuration is prepared, a paper passing durability test is performed using a sample with the same printing rate of 1 [%], and Vkcont = 150 [V] from the time when the cumulative driving time has elapsed 10 hours. It was. As a result, the correlation between the cumulative driving time of the developing device 2 and the amount of developer applied on the developing roller 17 is as shown in FIG. That is, the developer loading on the developing roller 17 did not become 0.37 or less, and the decrease in reflection density could be suppressed to 0.2.

  Next, another new developing device 2 is prepared, and Vdc = −300 [V], Vk = −400 [V], that is, Vkcont = 100 [V], and Vkcont is fixed as in the previous case. Then, the printing rate was increased to 8%, and the paper passing durability test was conducted. FIG. 16 shows the correlation between the cumulative driving time of the developing device 2 at that time and the amount of developer applied on the developing roller 17.

  In particular, after the cumulative driving time was 4 hours or more, the amount of developer applied on the developing roller 17 decreased, and the remaining amount of developer measured at this time was 40%. After that, when the cumulative driving time has elapsed 5 hours and the amount of developer applied on the developing roller 17 is reduced, an all black image is output, and the reflection density is measured using a Macbeth reflection densitometer. The reflection density was reduced by about 0.6 compared to the time.

  Therefore, a new developing device 2 having the same configuration is prepared, a paper passing durability test is performed using a sample with the same printing rate of 8%, and the remaining amount of developer is 40% after a cumulative driving time of 4 hours. Vkcont = 150 [V] was set from the time when it became below. As a result, the correlation between the cumulative driving time of the developing device 2 and the amount of developer applied on the developing roller 17 is as shown in FIG. That is, the developer loading on the developing roller 17 did not become 0.40 or less, and the decrease in reflection density could be suppressed to 0.1.

  FIG. 18 shows a control flow of the present embodiment based on the above results. Hereinafter, each step will be described.

  First, the controller 27 determines whether or not the image forming apparatus 100B has received an image formation request (S401). Next, the controller 27 reads the cumulative drive time from the memory 26 in which the cumulative drive time of the developing device 2 is stored, and determines whether or not the cumulative drive time is 10 hours or more (S402). Next, when the cumulative drive time is 10 hours or longer, the controller 27 sets the second transformer 24 so that Vkcont becomes 150 [V] (S403). Alternatively, if the developer remaining amount calculated from the output pulse of the developer remaining amount detecting means becomes less than 40% in the determination of S407 described later, the controller 27 sets Vkcont at S403 regardless of the cumulative driving time. The second transformer 24 is set so as to be 150 [V]. Next, the controller 27 starts image formation when the desired Vkcont is set (S404). The controller 27 counts the drive time of the developing roller 17 required for the image formation in S404, adds the drive time required for the current image formation to the accumulated drive time read in S402, and writes it in the memory 26 (S405). ). Next, the controller 27 determines whether or not the image formation is completed (S406). In addition, when the cumulative drive time is less than 10 hours in the determination of S402, the controller 27 determines that the remaining amount of developer in the developing device 2 obtained from the output pulse width T of the developer remaining amount detecting means 44 is 40%. It is determined whether or not it is less than (S407). Then, the controller 27 sets the second transformer 24 so that Vkcont becomes 100 [V] when the cumulative driving time is less than 10 hours and the developer remaining amount is 40% or more (S408). ).

  By performing control according to the above flow, even when the printing rate fluctuates and the durability of the developing device 2 progresses, the image density can be controlled by using two durability factors, that is, the cumulative driving time and the developer remaining amount. It was possible to suppress the decrease within 0.2.

  As described above, in this embodiment, the image forming apparatus 100 </ b> B uses the developing roller 17, that is, the driving time of the developing device 2, the developing remaining amount in the developing device 2, and the output as information indicating the durability status of the developing device 2. At least two pieces of image information of the image can be recognized. Then, based on the information indicating the at least two durability states, the DC bias value applied independently to each of the developing roller 17 and the developer supply roller 19 is changed. In the present embodiment, as information indicating the durability status of the developing device 2, the driving time of the developing device 2 and the developer remaining amount directly detected by the developer remaining amount detecting means including an optical sensor are included. Information was used. As described above, information on the remaining amount of developer obtained from the image information can be used instead of the information on the remaining amount of developer that is directly detected by an optical sensor or the like. Alternatively, for example, the former information is appropriately corrected with the latter information by using the developer remaining amount information obtained from the image information and the developer remaining amount information directly detected by an optical sensor or the like. It may be. Alternatively, three types of information, that is, information on the driving time of the developing device 2, information on the remaining amount of developer obtained from the image information, and developer remaining amount information directly detected by an optical sensor or the like may be used. Good.

  That is, according to this embodiment, as information indicating the durability status of the developing device 2, the developer is used by using at least two pieces of information of the cumulative driving time of the developing device 2, the remaining amount of developer, and the cumulative image information of the image forming device. Determining the deterioration status. By referring to such a plurality of pieces of information, it becomes possible to more accurately grasp the durability deterioration of the developer.

Example 5
Next, another embodiment according to the present invention will be described. FIG. 19 shows a schematic cross-sectional configuration of the image forming apparatus 100D of the present embodiment. The basic configuration and operation of the image forming apparatus 100D of this embodiment are the same as those of the second embodiment. Accordingly, elements having the same functions or configurations as those of the image forming apparatus 100A according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this embodiment, the image forming apparatus 100D is provided with a density sensor 38 as image density detecting means for measuring the image density in addition to the configuration of the image forming apparatus 100B of the second embodiment shown in FIG. Yes. The density sensor 38 is connected to the controller 27.

  As shown in FIG. 20, the density sensor 38 includes a light emitting element 381 such as an LED, a photodiode, a light receiving element 382 such as CdS, and a holder 383. The density sensor 38 irradiates light from the light emitting element 381 to a developer image (hereinafter referred to as “patch”) P for image density control formed on the image carrier 10 and reflects the light from the patch P. By receiving the light at the light receiving element 382, the density of the patch P is measured. In this embodiment, the density sensor 38 detects a developer image on the image carrier 10.

  Next, in the image forming apparatus 100 </ b> D of this example, first, using a new developing device 2, a sample paper passing durability test was performed under the following conditions. In other words, Vdc = −300 [V], Vk = −400 [V], that is, Vkcont = 100 [V], and a condition where Vkcont is fixed is set, and a sample with a printing rate of 5 [%] is passed. A paper durability test was conducted.

  As a result, the same correlation between the remaining amount of developer and the amount of developer applied on the developing roller 17 was observed as in Example 2. Then, with the developer remaining amount reduced to 30% and the developer loading on the developing roller 17 reduced to 0.35, an all black image is output and reflected using a reflection densitometer manufactured by Macbeth. When the density was measured, as in Example 2, the reflection density was reduced by about 0.6 compared to when it was new. Further, the output value of the image density converted by the controller 27 based on the sensor output characteristic of the image density at this time was 78% of the new product.

  Therefore, in this embodiment, in order to suppress a decrease in image density, a control for measuring the image density every predetermined driving time is incorporated. In particular, in this embodiment, the interval at which the control for measuring the image density is incorporated is set every driving time of the developing device 2 in consideration of development characteristics. Then, when the image density falls below 95% of the new product, the image density control is performed by obtaining Vkcont so that the development density becomes the same as the new product. As a result, even when the durability of the developing device 2 has advanced, the decrease in reflection density can be suppressed to less than 0.1.

  In this embodiment, the interval for measuring the image density is set as described above in consideration of the development characteristics. However, for example, the image density measurement timing determined based on the driving time of the developing device 2 is determined by the developing device 2 used. It can be set arbitrarily according to the characteristics. Further, when the environment changes in the conventional image forming apparatus, the image density control may be performed in synchronism with the image density adjustment timing every time a predetermined number of images are formed after replacing the developing device. That is, the reference information includes the cumulative driving time of the developer carrying member (developing device), the cumulative number of sheets passed, the developer remaining amount, and the like.

  Next, the image density control method used in this embodiment will be described.

  First, in the controller 27 provided in the image forming apparatus 100D, the continuous driving time of the developing device 2 is 1 hour from the time when the user starts using the image forming apparatus 100D for the first time or when the previous density control is performed. When it exceeds, control to measure the image density is performed. The continuous drive time of the developing device 2 is measured by the same method as in the first embodiment. Then, when the image density is reduced to less than 95% from the new time and the remaining amount of developer in the developing device 2 is 10% or more, the image density control is started. The remaining amount of developer is measured by the same method as in the second embodiment.

  Next, the controller 27 reads from the memory 26 the current Vkcont setting value (hereinafter referred to as “Vkcontold”) and the target image density Dm that was the image density at the time of a new article.

  Thereafter, the controller 27 uniformly charges the image carrier 10 using the primary charger 13. Next, the controller 27 reads an image density control pattern from the memory 26, causes the exposure apparatus 1 to emit light based on the image density control pattern, and P1 with the same image data along the rotation direction on the image carrier 10. A latent image of five patches P of .about.P5 is formed.

  The latent images of these patches P are developed by the developing device 2 while changing Vkcont while Vcont remains constant. That is, the latent image of the patch P1 is developed with Vkcont1, the latent image of the patch P2 is developed with Vkcont2, the latent image of the patch P3 is developed with Vkcont3, the latent image of the patch P4 is developed with Vkcont4, and the latent image of the patch P5 is developed with each Vkcont of Vkcont5. Here, these Vkconts have a relationship of Vkcont1 <Vkcont2 <Vkcont3 <Vkcont4 <Vkcont5. Thereby, as shown in FIG. 21, the latent images of the patch P are visualized as patches P1 to P5.

  Note that in this embodiment, each Vkcont is set as follows, considering that the target image density Dm at the time of image density control is always within the density range of the patches P1 to P5 developed by the Vkcont1 to Vkcont5. . That is, Vkcont1 was set to Vkcont-100-100 [V], and Vkcont5 was set to Vkcont + 200 [V]. Of course, this setting value is not particularly limited as long as the target image density Dm can be set within the range of the patch densities DP1 to DP5 in the characteristics of the developing device and the image forming apparatus to be used. A value may be used.

  Next, these visualized patches P1 to P5 are respectively measured by the density sensor 38, and the density measurement values DP1 to DP5 are written into the memory 26 via the controller 27.

  On the other hand, the patches P1 to P5 visualized on the image carrier 10 are cleaned by the cleaning unit 9 after being measured by the density sensor 38.

  When the writing of the density measurement values of the patches P1 to P5 to the memory 26 is completed, the controller 27 obtains a Vkcont (hereinafter ““ Vkcontnew ").

  As a calculation method, correlation characteristics between each Vkcont (Vkcont1 to Vkcont5) when the patches P1 to P5 are visualized and each density DP (DP1 to DP5) of the patches P1 to P5 generated by the Vkcont are shown in FIG. It is shown as 22. In the illustrated example, the target image density Dm is within the patch densities DP3 and DP4 formed by Vkcont3 and Vkcont4, respectively. Therefore, in this case, Vkcontnew for obtaining the target image density Dm can be obtained by the following linear interpolation calculation formula.

Vkcontnew = {(Vkcont4-Vkcont3) / (DP4-DP3)} * (Dm-DP3) + Vkcont3
The Vkcontnew value obtained in this way is written in the memory 26 as Vkcont until the subsequent image density control condition is satisfied, and is used for image formation.

  By directly feeding back to the development characteristics using the above control, it was possible to always suppress the decrease in image density to 0.1 or less.

  In this embodiment, the density of the patch on the image carrier 10 is fed back. However, it may be fed back based on the density of the patch on the transfer belt 6 transferred from the image carrier 10. Alternatively, depending on the configuration of the image forming apparatus, feedback is performed based on the density of the patch transferred onto the intermediate transfer body having a function similar to that of the transfer belt 6 or the density of the patch formed on the final recording material 40. It does n’t matter.

  As described above, in this embodiment, the image forming apparatus 100D applies the patch P based on the image data for adjusting the development density according to the command from the image forming apparatus 100D, separately from the developing process at the time of normal image formation. Development is performed on the image carrier 10. Further, the image forming apparatus 100D includes a density sensor 38 that can recognize density information of the patch. Based on the density information, the DC bias value applied independently to each of the developing roller 17 and the developer supply roller 19 is changed. In the present embodiment, the DC bias value applied independently to each of the developing roller 17 and the developer supply roller 19 is changed at a timing at which the development density adjustment is considered necessary from the durability information of the developing device 2. Only when image density detection is performed according to the above. The durability information of the developing device 2 includes, for example, the cumulative driving time of the developer carrier (that is, the developing device), the cumulative number of sheets passed, the remaining amount of developer, and the like.

  That is, according to the present embodiment, the change in the characteristics of the developing device 2 is determined based on image density information (here, the image density information is a density adjustment created on the image carrier 10 in accordance with a command from the image forming apparatus. Image density information) of the development patch for use. Then, Vkcont is changed based on the image density information. In this way, by directly feeding back the image density and adjusting Vkcont, the amount of developer on the developing roller 17 can be kept constant regardless of any variation factors, and a stable image can always be output. It becomes possible. Further, it is preferable to change the bias applied to the developer supply roller 19 only when the image density detection is performed in accordance with the timing at which the development density adjustment is considered necessary from the durability information of the developing device 2. The reference durability information is, for example, the cumulative driving time of the developer carrier (that is, the developing device), the cumulative number of sheets passed, the remaining amount of developer, and the like. As a result, the development density adjustment can be minimized, and the downtime of the image forming apparatus 100D (the time during which an image cannot be output due to an adjustment operation or the like) can be suppressed.

  As mentioned above, although this invention was demonstrated according to the specific Example, it should be understood that this invention is not limited to the above-mentioned embodiment.

  For example, in each of the above embodiments, the image forming apparatus transfers the developer image on the image carrier 10 directly to the recording material 40. However, the present invention can also be applied to an image forming apparatus that transfers a developer image to the recording material 40 via an intermediate transfer member, and can achieve the same effects as described above.

  In each of the above-described embodiments, an example in which the bias applied to the developer supply roller 19 is changed according to the durability of the developing device 2 has been described. However, the present invention is not limited to this. For example, a bias is applied to the developing blade 18 that functions as a developer supply member, and the bias is changed in accordance with the durability of the developing device 2. The developer loading amount may be changed.

  Further, in each of the above embodiments, the image forming apparatus having one developing device has been described. However, in an image forming apparatus using a plurality of developing devices represented by a color image forming apparatus, each of the developing devices is described above. The present invention can be applied as described in the embodiments. Also in this case, the same effects as described above can be obtained with respect to each developing device.

In the third embodiment, the developing device 2 is a cartridge (developing cartridge) that is detachable from the main body of the image forming apparatus as a cartridge that is detachable from the main body of the image forming apparatus. However, the developing device from the main body of the image forming apparatus may be a Removable ability as a process cartridge. In the process cartridge according to the present invention, at least an image carrier and a developing device including a developing unit and a developer storage unit as process units that act on the image carrier are integrally formed into a cartridge. In the process cartridge, at least one of charging means and cleaning means as process means may be integrally formed into a cartridge.

1 is a schematic cross-sectional configuration diagram of an image forming apparatus according to an embodiment of the present invention. It is a graph which shows an example of the correlation characteristic of the accumulation drive time of a developing roller, and the developer loading amount on a developing roller. It is a graph which shows the other example of the correlation characteristic of the cumulative driving time of a developing roller, and the developer loading amount on a developing roller. FIG. 5 is a flowchart showing a control flow of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is a schematic cross-sectional configuration diagram of an image forming apparatus according to another embodiment of the present invention. FIG. 6 is a graph showing an example of a remaining detection power characteristic of a developer remaining amount detection unit provided in the image forming apparatus shown in FIG. 6 is a graph showing an example of a correlation characteristic between an output pulse width of a developer remaining amount detecting unit and a developer remaining amount. FIG. FIG. 10 is a graph showing an example of a correlation characteristic between the remaining amount of developer in the developing device and the amount of developer applied on the developing roller. It is a graph which shows the other example of the correlation characteristic of the developing agent residual amount in a developing device, and the developer loading amount on a developing roller. It is a flowchart figure which shows the control flow of the image forming apparatus according to the other Example of this invention. FIG. 6 is a schematic cross-sectional configuration diagram of an image forming apparatus according to another embodiment of the present invention. It is a schematic diagram for demonstrating the developing device attachment or detachment aspect from the image forming apparatus shown in FIG. It is a flowchart figure which shows the control flow of the image forming apparatus according to the other Example of this invention. It is a graph which shows an example of the correlation characteristic of the accumulation drive time of a developing roller, and the developer loading amount on a developing roller. It is a graph which shows the other example of the correlation characteristic of the cumulative driving time of a developing roller, and the developer loading amount on a developing roller. It is a graph which shows the other example of the correlation characteristic of the cumulative driving time of a developing roller, and the developer loading amount on a developing roller. It is a figure which shows the other example of the correlation characteristic of the cumulative driving time of a developing roller, and the developer loading amount on a developing roller. It is a flowchart figure which shows the control flow of the image forming apparatus according to the other Example of this invention. FIG. 6 is a schematic cross-sectional configuration diagram of an image forming apparatus according to still another embodiment of the present invention. It is a schematic sectional block diagram of a density sensor. FIG. 5 is a schematic diagram for explaining a patch image created on an image carrier in development density control. It is a graph which shows the correlation characteristic of Vkcont and patch density DP for demonstrating the concept of development density control. It is a schematic cross-sectional block diagram which shows an example of the conventional developing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exposure apparatus 2 Developing apparatus 3 Recording material cassette 4 Recording material supply roller 5 Registration roller 6 Transfer belt 7 Transfer roller 8 Transfer belt drive roller 9 Cleaning unit 10 Image carrier 11 Heat roller 12 Pressure roller 13 Primary charger 14 Transfer belt Cleaning unit 15 Recording material discharge roller 16 Recording material discharge tray 17 Development roller 18 Development blade 19 Developer supply roller 20 Developer storage unit 21 Developer stirring paddle 22 Developer stirring paddle 23 Transformer 24 Transformer 25 Development motor 26 Memory 27 Controller 28 Light emitting section 29 Residual detection window 30 Residual detection window 31 Light receiving section 34 Development device side memory 35 Signal processing circuit 36 Addition circuit 38 Density sensor 40 Recording material 41 Transport guide 42 DC power supply 43 DC power supply 44 Developer Remaining amount detection means

Claims (10)

An image carrier on which an electrostatic image corresponding to image information is formed, a developing device for developing the electrostatic image formed on the image carrier, a developer containing portion for containing a developer, and the image A developer carrying member that carries and conveys the developer to a developing unit that supplies the developer to the carrying member; a developer supply member that supplies the developer in the developer containing unit to the developer carrying member; An image forming apparatus comprising:
A first bias applying means for applying a bias to the developer carrying member; and a second bias applying means for applying a bias to the developer supplying member. Usage amount information in which a bias applied to the developer supply member correlates with a cumulative usage amount from the initial use of the developing device, independently of a bias applied to the developer carrier from the first bias applying unit. An image forming apparatus that changes in accordance with the above.   The usage amount information is information on the cumulative driving time of the developing device, information on the remaining amount of developer in the developer accommodating portion, or cumulative image information integrated with image formation corresponding to the image information. The image forming apparatus according to claim 1, wherein:   When the usage amount information reaches a predetermined value, a difference between the bias applied to the developer carrier and the bias applied to the developer supply member is increased. The image forming apparatus according to claim 1, wherein the bias applied to the developer supply member changes independently of the bias applied to the carrier.   The usage amount information includes at least two of information on a cumulative driving time of the developing device, information on a remaining amount of developer in the developer accommodating portion, and cumulative image information accumulated with image formation corresponding to the image information. The image forming apparatus according to claim 1, wherein the information is one piece of information.   A bias to be applied to the developer carrier and a bias to be applied to the developer supply member when both of the at least two pieces of information reach predetermined values respectively determined corresponding to the two pieces of information. 5. The image forming apparatus according to claim 4, wherein the bias applied to the developer supply member changes independently of the bias applied to the developer carrier so that the difference between the image forming apparatus and the developer carrying member is increased. .   The image forming apparatus according to claim 1, further comprising a storage medium in which the usage amount information is stored.   The image forming apparatus according to claim 1, wherein the developing device is detachable and replaceable with respect to a main body of the image forming apparatus.   The image forming apparatus according to claim 7, further comprising a storage medium in which the usage amount information is stored. An image carrier on which an electrostatic image corresponding to image information is formed, a developing device for developing the electrostatic image formed on the image carrier, a developer containing portion for containing a developer, and the image A developer carrying member that carries and conveys the developer to a developing unit that supplies the developer to the carrying member; a developer supply member that supplies the developer in the developer containing unit to the developer carrying member; A first bias applying unit that applies a bias Vdc to the developer carrying member, a second bias applying unit that applies a bias Vk to the developer supply member, and the developing device. Image density detection means for detecting an image density of an image density detection image formed on the image carrier on the image carrier or a transfer medium onto which a developer image is transferred from the image carrier. In the image forming apparatus,
The image density detection image is formed by changing the bias difference Vkcont between the bias Vdc and the bias Vk while keeping the bias difference Vcont between the bias Vl and the bias Vdc of the exposure unit on the image carrier constant. And
During image formation, the bias Vk is the independent of the bias Vdc, the image forming apparatus characterized by changes in accordance with the image density the image density information detected by the detecting means. The image forming apparatus according to claim 9 , wherein the image density detection image is formed according to a usage state of the developing device, and the image density is detected by the image density detection unit.

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