JP2006284671A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which is adaptable to various user's demands and is excellent in convenience and cost performance, and to provide an image forming method. <P>SOLUTION: Identification information for discriminating between a developing device which regards image quality as important and a developing device which regards economic efficiency as important is attached to the developing device. An apparatus body side selects and performs an operation mode based on the identification information read from the developing device. When performing the adjustment of developing bias being a density control factor, target density in accordance with the selected operation mode and the appropriate range of image density are set, and control based on the set values is performed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and an image forming method for forming an image using a process cartridge configured to be detachable from an apparatus main body.

  In image forming apparatuses such as copiers, printers, and facsimile machines that apply electrophotographic technology, the image density of the toner image varies due to individual differences, changes over time, and changes in the surrounding environment such as temperature and humidity. There is. In view of this, various density control techniques for stabilizing the image density have been proposed. For example, in the image forming apparatus described in Patent Document 1, in order to suppress fluctuations in image density due to changes in toner characteristics over time, a density target value is set according to the usage history of the developer (process cartridge), and The development bias and the exposure power that affect the image density are adjusted as density control factors so that the density of the toner image formed as the patch image becomes the density target value.

JP 2004-78062 A

  The mode of use of the image forming apparatus varies depending on the user. Also, the image quality level that each user wants from the apparatus varies greatly from user to user. For example, while there are users who always demand high image quality, more cost is emphasized, and there is no need for high quality image quality, and you want to use a cheaper process cartridge or install an installed process cartridge. Some users want to use it as long as possible. However, since conventional image forming apparatuses have been studied mainly to stabilize image quality, they have not been able to meet such diverse user requirements. In particular, for users who place importance on economics rather than image quality, no device has been provided that exhibits excellent cost performance in response to user requests.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus and an image forming method that can meet various user requirements and are excellent in convenience and cost performance.

  In order to achieve the above object, an image forming apparatus according to the present invention includes a process cartridge configured to be detachable from an apparatus main body, and an image forming unit that forms an image using the process cartridge mounted on the apparatus main body. A first operation mode for controlling the image forming means to form an image at a predetermined first image quality level; and an image at a second image quality level lower than the first image quality level. Control means for selectively executing the second operation mode, and for identifying whether the process cartridge is suitable for the first operation mode or the second operation mode. On the other hand, based on the identification information attached to the process cartridge attached to the apparatus main body, the control means It is characterized by selecting perform one of created mode and a second mode of operation.

  According to another aspect of the present invention, there is provided an image forming method for forming an image using a process cartridge mounted on a main body of an image forming apparatus. In order to achieve the above object, an identification attached to the process cartridge is provided. A step of reading information, a first operation mode in which an image is formed at a predetermined first image quality level, and a second operation mode in which an image is formed at a second image quality level lower than the first image quality level. And selecting and executing any one of them based on the identification information.

  In the invention configured as described above, identification information for identifying whether a high image quality level is required or not can be attached to the process cartridge in advance. Then, on the apparatus main body side, an operation mode corresponding to the required quality level is executed based on this identification information, and an image is formed. According to the configuration of the present invention, it is possible to configure an image forming apparatus excellent in convenience in response to various requests of users. That is, a user who desires high image quality can form an image at a desired image quality level by mounting the process cartridge with identification information corresponding to the first operation mode on the apparatus. On the other hand, the process cartridge to which the identification information corresponding to the second operation mode is attached can be used with an emphasis on cost performance because the required image quality level is low. Therefore, a user who attaches importance to economics may use a process cartridge with identification information corresponding to the second operation mode. In addition, by using these process cartridges interchangeably, both operation modes can be used properly.

  Since the quality standards required for the process cartridge are different in the two operation modes having different required image quality levels, in order to use the same process cartridge in both operation modes, Quality control becomes very complicated. On the other hand, according to the present invention, identification information is attached to a process cartridge that is detachable from the apparatus main body, and the apparatus main body executes an operation mode according to the identification information.

  The two operation modes can be distinguished as follows, for example. That is, in the first operation mode, an image is formed while controlling the image density to a predetermined first target density or within the first target density range. In the second operation mode, the image density is controlled while controlling the image density to a second target density lower than the first target density or within a second target density range wider than the first target density range. Is formed. As described above, by making the target density condition in the second operation mode gentler than that in the first operation mode, the required quality for the process cartridge in the second operation mode is higher than the required quality in the first operation mode. Be gentle. As a result, the manufacturing cost of the process cartridge can be reduced. For example, within the range of manufacturing variations of process cartridges, a product that satisfies a higher quality standard can be made to correspond to the first operation mode, while other products can be made to correspond to the second operation mode, thereby improving the yield. .

  Further, for example, when the density of the patch image formed by the image forming means is not within a predetermined appropriate density or an appropriate density range, it is determined that the apparatus is operating error, and the appropriate density in the first operation mode is determined as the first density. The concentration may be higher than the appropriate concentration in the second operation mode, or the appropriate concentration range corresponding to the first operation mode may be narrower than the appropriate concentration range corresponding to the second operation mode. . In this way, by making an error determination based on the density detection result of the image, it is possible to prevent a decrease in image quality due to an abnormal operation of the apparatus, and to change the determination criteria according to the process cartridge. Thus, the process cartridge can be used more effectively.

  In addition, for example, a density control operation for controlling the image density is performed by adjusting a density control factor that affects the image density based on the density detection result of the patch image formed by the image forming unit. In the apparatus, the density control operation may be executed in a manner corresponding to the attached process cartridge. Since the required image quality level is different in the two operation modes, the content of the necessary density control operation is also different. Therefore, the density control operation can be efficiently performed by performing the density control operation in a manner corresponding to each. In particular, in the density control operation corresponding to the second operation mode, toner density saving and processing time are shortened by executing a density control operation that is simplified compared to the density control operation corresponding to the first operation mode. Can be achieved.

  Further, for example, in an apparatus configured to manage the management information related to the total usage amount of the process cartridge and determine that the process cartridge has reached the end of its life when the management information reaches a predetermined threshold, The threshold value may be varied according to the identification information attached to the process cartridge. This makes it possible to manage the life of the process cartridge in a manner corresponding to the application of the process cartridge.

  Such a process cartridge may be, for example, a developing device that stores toner therein. In a developing device that stores toner that is a consumable item, there is a large variation in quality and state. Therefore, when the present invention is applied for the management of the developing device and its appropriate use, the effect becomes particularly remarkable.

  For example, in an apparatus configured such that a plurality of the developing devices can be mounted on the apparatus main body, when the plurality of developing devices are mounted on the apparatus main body, an image is formed while switching the plurality of developing devices, and When the identification information corresponding to the second operation mode is attached to at least one of the plurality of developing devices, the second operation mode can be executed regardless of which developing device is used. . The image quality may vary if the developing devices in different states are used while being switched. In such a case, by setting the requested image quality level to the second image quality level, it is possible to suppress variations in image quality for each developing device.

  Further, for example, in an apparatus configured such that a plurality of the developing devices can be mounted on the apparatus main body, when the plurality of developing devices are mounted on the apparatus main body, an image is formed while switching the plurality of developing devices, When using the developing device to which the identification information corresponding to the first operation mode is used among the plurality of developing devices, the first operation mode is executed, while the identification information corresponding to the second operation mode is When the attached developing device is used, the second operation mode may be executed. As a result, an operation mode corresponding to the state of each developing device is selected and executed. As a result, the two operation modes can be selectively used without replacing the developing device, for example, according to the user's request or according to the contents of the image to be formed.

  This is particularly useful in an image forming apparatus configured to be equipped with a plurality of developing devices that store toner of the same color. This is because, in such an apparatus, the color of the image formed is the same regardless of which developing device is used. Therefore, if the developing device can be selected and used according to the required image quality, each developing device can be used. This is because the vessel can be used effectively.

(First embodiment)
FIG. 1 is a diagram showing a first embodiment of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus of FIG. As will be described later, the apparatus 1 is an image forming apparatus in which four developing devices are mounted to form an image. In a state where developing devices storing different color toners are attached, a full color image using the developing devices and a monochrome image using one of the developing devices can be formed. Further, in a state where a developing device that stores toner of the same color is mounted, it functions as an image forming apparatus dedicated to monochrome images of the toner color. In the following, an embodiment in which the present invention is applied to an image forming apparatus dedicated to monochrome images and equipped with four developing units each storing black toner will be described.

  In this image forming apparatus 1, when an image forming command is given to the main controller 11 from an external device such as a host computer, the engine controller 10 controls each part of the engine unit EG in accordance with the command from the main controller 11. An image forming operation is executed, and a monochrome image corresponding to an image signal given from an external device is formed on the sheet S.

  In the engine unit EG, the photosensitive member 22 is provided to be rotatable in the arrow direction D1 in FIG. A charging unit 23, a rotary developing unit 4 and a cleaning unit 25 are arranged around the photosensitive member 22 along the rotation direction D1. The charging unit 23 is applied with a predetermined charging bias, and uniformly charges the outer peripheral surface of the photoconductor 22 to a predetermined surface potential. The cleaning unit 25 removes the toner remaining on the surface of the photosensitive member 22 after the primary transfer, and collects it in a waste toner tank provided inside. The photosensitive member 22, the charging unit 23, and the cleaning unit 25 integrally constitute the photosensitive member cartridge 2, and this photosensitive member cartridge 2 is detachably attached to the main body of the apparatus 1 as a whole.

  Then, the light beam L is irradiated from the exposure unit 6 toward the outer peripheral surface of the photosensitive member 22 charged by the charging unit 23. The exposure unit 6 exposes the light beam L onto the photoconductor 22 in accordance with an image signal given from an external device to form an electrostatic latent image corresponding to the image signal.

  The electrostatic latent image thus formed is developed with toner by the developing unit 4. The developing unit 4 is configured as a support frame 40 that is rotatably provided around a rotation axis that is orthogonal to the paper surface of FIG. 1, and is configured as a cartridge that is detachable with respect to the support frame 40, and includes four developing cartridges 4Ka that contain black toner. To 4Kd, and a rotary drive (not shown) for rotating them integrally. The developing unit 4 is controlled by the engine controller 10. Based on the control command from the engine controller 10, the developing unit 4 is rotationally driven in the direction D4 in FIG. 1, and the developing cartridges 4Ka to 4Kd are selectively brought into contact with the photosensitive member 22 or have a predetermined value. When positioned at a predetermined developing position facing each other with a gap, toner is applied to the surface of the photosensitive member 22 from the developing roller 44 provided in the developing cartridge. As a result, the electrostatic latent image on the photosensitive member 22 is developed with the toner in the developing cartridge positioned at the developing position.

  The toner image developed by the developing unit 4 as described above is primarily transferred onto the intermediate transfer belt 71 of the transfer unit 7 in the primary transfer region TR1. The transfer unit 7 includes an intermediate transfer belt 71 that is stretched over a plurality of rollers 72 to 75, and a drive unit that rotates the roller 73 to rotate the intermediate transfer belt 71 in a predetermined rotation direction D2. Yes. Then, the transfer unit 7 transfers the black toner image formed on the photosensitive member 22 onto the intermediate transfer belt 71 and is taken out one by one from the cassette 8 to the secondary transfer region TR2 along the transport path F. Secondary transfer is performed on the conveyed sheet S.

  At this time, in order to correctly transfer the image on the intermediate transfer belt 71 to a predetermined position on the sheet S, the timing of feeding the sheet S to the secondary transfer region TR2 is managed. Specifically, a gate roller 81 is provided on the transport path F on the front side of the secondary transfer region TR2, and the gate roller 81 rotates in accordance with the timing of the circumferential movement of the intermediate transfer belt 71. S is sent to the secondary transfer region TR2 at a predetermined timing.

  Further, the sheet S on which the monochrome image is thus formed is conveyed to the discharge tray portion 89 provided on the upper surface portion of the apparatus main body via the fixing unit 9, the pre-discharge roller 82 and the discharge roller 83. Further, when images are formed on both sides of the sheet S, when the rear end portion of the sheet S on which the image is formed on one side as described above is conveyed to the reversal position PR behind the pre-discharge roller 82. The rotation direction of the discharge roller 83 is reversed, whereby the sheet S is conveyed in the direction of the arrow D3 along the reverse conveyance path FR. Then, the sheet is again placed on the transport path F before the gate roller 81. At this time, the surface of the sheet S to which the image is transferred by contacting the intermediate transfer belt 71 in the secondary transfer region TR2 is first transferred. It is the opposite surface. In this way, images can be formed on both sides of the sheet S.

  A cleaner 76 is disposed in the vicinity of the roller 75. The cleaner 76 can be moved toward and away from the roller 75 by an electromagnetic clutch (not shown). Then, the blade of the cleaner 76 abuts on the surface of the intermediate transfer belt 71 that is stretched over the roller 75 while moving to the roller 75 side, and the toner that remains on the outer peripheral surface of the intermediate transfer belt 71 after the secondary transfer. Remove.

  A density sensor 60 is disposed in the vicinity of the roller 75. The density sensor 60 is provided to face the surface of the intermediate transfer belt 71 and measures the image density of the toner image formed on the outer peripheral surface of the intermediate transfer belt 71 as necessary. Based on the measurement result, this apparatus adjusts the operating conditions of each part of the apparatus that affects the image quality, for example, the developing bias applied to each developing cartridge, the intensity of the light beam L, and the like.

  The density sensor 60 is configured to output a signal corresponding to the image density of a region of a predetermined area on the intermediate transfer belt 71 using, for example, a reflection type photosensor. The CPU 101 can detect the image density of each part of the toner image on the intermediate transfer belt 71 by periodically sampling the output signal from the density sensor 60 while rotating the intermediate transfer belt 71.

  Further, as shown in FIG. 2, each of the developing cartridges 4Ka to 4Kd is provided with memories 91 to 94 for storing data relating to the manufacturing lot and usage history of the developing cartridge, the remaining amount of the built-in toner, and the like. Further, each of the developing cartridges 4Ka to 4Kd is provided with wireless communication devices 49Ka, 49Kb, 49Kc, and 49Kd. Then, if necessary, these selectively communicate with the wireless communication device 109 provided on the main body side in a non-contact manner, and data is transmitted between the CPU 101 and each of the memories 91 to 94 via the interface 105. Various information such as consumable management for the developing cartridge is managed by sending and receiving. In this embodiment, non-contact data transmission / reception is performed using electromagnetic means such as wireless communication. However, a connector is provided on the main body side and each developing cartridge side, and the connector is mechanically fitted. By doing so, you may make it mutually transmit / receive data.

  Further, as shown in FIG. 2, this apparatus includes a display unit 12 that is controlled by the CPU 111 of the main controller 11. The display unit 12 is constituted by, for example, a liquid crystal display, and in accordance with a control command from the CPU 111, the operation guidance to the user, the progress of the image forming operation, the occurrence of an abnormality in the apparatus, the replacement time of any unit, etc. A predetermined message for notification is displayed.

  In FIG. 2, reference numeral 113 denotes an image memory provided in the main controller 11 for storing an image given from an external device such as a host computer via the interface 112, and reference numeral 117 denotes a calculation result in the CPU 111 and other information. It is a RAM that temporarily stores data. Reference numeral 106 is a ROM for storing a calculation program executed by the CPU 101, control data for controlling the engine unit EG, and the like. Reference numeral 107 is a RAM for temporarily storing calculation results in the CPU 101 and other data. is there.

  In the image forming apparatus 1 configured as described above, the developing device mounted on the apparatus main body can be used in two types of operation modes. There are two types of operation modes: a high image quality mode (first mode) suitable for photographic images and graphic images, and a character image quality mode (second mode) suitable for images mainly composed of characters. In the first mode, a photographic image or a graphic image can be formed with high image quality, but toner consumption is also severe. That is, the first mode is an operation mode suitable for an application in which image quality is more important than the running cost of the apparatus. On the other hand, in the second mode, although it is slightly lower than the first mode in terms of maximum density and gradation reproducibility, a character image can be formed with a level of image quality that does not interfere with character interpretation. Further, since the maximum density is suppressed, the amount of toner consumed is small, and the frequency of replacement of the developing device can be reduced. That is, the second mode is an operation mode suitable for an application that requires a reduction in running cost instead of requiring a very high level of image quality.

  The quality level required for the developer is also different between the two operation modes. That is, the developing device used in the first mode is required to have a high component size and surface finishing accuracy, and the built-in toner must have a uniform particle size and charge amount. On the other hand, the quality level required for the developing device used in the second mode may be moderate. Therefore, in this image forming apparatus, identification information as to whether each developing device is compatible with the first mode or the second mode is attached to each individual developing device. The developing device conforming to the first mode is a developing device that satisfies the quality level for use in the first mode. On the other hand, the developing device conforming to the second mode is a developing device that does not meet or may not satisfy the quality level. Specifically, this identification information is stored in a memory provided in each of the developing devices 4Ka to 4Kd. On the apparatus main body side to which the developing device is attached, this identification information is read from the developing device to which the CPU 101 is attached, and an operation mode corresponding to the content is selected and executed.

  The main difference between the two operation modes is an operation condition (image formation condition) such as a bias potential and an operation parameter setting value given to each part of the apparatus when an image is formed in each operation mode. The image forming conditions are optimized according to the operation mode by executing a density control operation described below. In this density control operation, the development bias and exposure power as density control factors are adjusted based on the density detection result of the toner image formed as a patch image. There are many known examples of density control techniques for controlling image density by adjusting density control factors that affect image density, and these techniques can also be applied to this embodiment. The contents of the operation will be briefly described.

  FIG. 3 is a flowchart showing the density control operation in the first embodiment. In the density control operation (density control operation # 1) in the first embodiment, first, it is determined whether or not a developing unit conforming to the second mode is attached to the developing unit 4 (step S101). Here, when the developing device conforming to the second mode is not attached, that is, when all the developing devices conform to the first mode, the operation mode of the apparatus is set to the first mode (step S102). . If there is at least one developing device conforming to the second mode, the operation mode of the apparatus is set to the second mode (step S103). The fact that at least one developing device conforming to the second mode is mounted is an indication that the user is requesting the apparatus 1 to have a lower running cost than the image quality. Therefore, if at least one developing device conforming to the second mode is mounted, the entire apparatus is operated in the second mode. In other words, the developing device conforming to the first mode is also used in the second mode in the subsequent operations.

  Subsequently, pre-processing prior to density control is performed (step S104). This pre-processing is a process of calibrating the density sensor 60 and measuring the reflectance of the surface of the intermediate transfer belt 71 in order to accurately detect the density of the patch image formed on the intermediate transfer belt 71 as described later. It is. If the calibration of the density sensor 60 or the measurement of the reflectance of the intermediate transfer belt 71 cannot be properly performed in the preprocessing, it is determined as an error and the processing is interrupted. Otherwise, adjustment of the developing bias given to each developing device is performed next (step S105).

  FIG. 4 is a flowchart showing the developing bias adjustment process in the first embodiment. In the development bias adjustment process # 1 in the first embodiment, first, a toner image of a predetermined pattern is formed on the intermediate transfer belt 71 as a patch image with each bias value while changing and setting the development bias in multiple stages (step S201). . As the patch image here, for example, a high density image such as a solid image can be suitably used. Next, the density of these patch images is detected by the density sensor 60 (step S202). Then, the set operation mode of the apparatus is determined (step S203). If it is the first mode, the target density of the patch image is set to the value Dt1, and the appropriate density range is set to the range R1 (step S204). If the mode is two, the target density of the patch image is set to the value Dt2, and the appropriate density range is set to the range R2 (step S205).

  The target density is an image density that a patch image (here, a solid image) formed by a normally operating apparatus should have. Further, the appropriate density range is a density range that is acceptable in the specifications of the apparatus as the density of the formed patch image with the development bias set to the maximum value. If the setting value of the developing bias is determined, the image density at that time can be roughly predicted, and should be within a certain density range if the apparatus is operating normally. The concentration range in which this apparatus can be regarded as normal is the appropriate range described above. If the density of the formed patch image with the development bias set to the maximum value is out of this proper range, it is determined as an error. By doing so, it is possible to detect an abnormality of the device at an early stage.

  FIG. 5 is a diagram showing a target density and an appropriate range of density. When the operation mode of the apparatus is the first mode, it is determined that the operation of the apparatus is normal if the density of the patch image formed with the maximum developing bias is within the appropriate range R1 defined as the values Dmin1 to Dmax. . The lower limit value Dmin1 of the appropriate range R1 is set as the target density Dt1 in the first mode. In other words, the appropriate range R1 is determined with the target density Dt1 as the lower limit. Thus, if the target value Dt1 is set as the lower limit value of the appropriate range R1, the density of the patch image can always be controlled to the target density unless an error occurs. Further, if the density is too high, the density control may not function effectively.

  On the other hand, in the second mode, the target density Dt2 is set to a value lower than the target value Dt1 in the first mode. In the second mode, the main purpose of which is to form a character image, there is not much need to form a solid image at a high density, and as will be described later, the development bias is set so that the density of the solid image is low. This is because a necessary and sufficient image density can be obtained for an image mainly composed of thin lines such as a character image. The toner consumption can be reduced by lowering the target density.

  The appropriate range R2 has an upper limit value that is the same value Dmax as in the first mode, and a lower limit value Dmin2 that is lower than the target density Dt2. The reason for this is as follows. First, it is meaningless to set the upper limit value of the appropriate range R2 in the second mode to a value larger than that in the first mode. This is because it is not necessary to produce a higher concentration in the second mode than in the first mode. Further, even a developing device that conforms to the second mode can in principle produce a high density, so there is no need to lower the upper limit of the appropriate range. Therefore, the upper limit value of the appropriate range R2 is set to the same value Dmax as in the first mode. The lower limit value Dmin2 is considered as follows. In the second mode, the running cost is more important, but by expanding the allowable range of image density to the low density side, it is possible to form a larger number of images using one developing device.

  Note that, by setting the lower limit value Dmin2 of the appropriate range R2 to a value lower than the target density Dt2, there may be a case where the density of the patch image cannot be adjusted to the target density Dt2. That is, the image density may not reach the target density even when the development bias is set to the maximum value. However, since the developing device can be used for a long time by allowing image formation even in a state where the target density is not reached, this is done in the second mode in which running cost is emphasized. From a practical point of view, slight blurring is hardly noticeable in images composed of characters and fine lines.

  Returning to FIG. 4, the description of the developing bias adjustment processing will be continued. Following the setting of the target density and appropriate range, for each patch image formed with the development bias set to the maximum value, whether the density detection result is within the appropriate range determined as described above. Determination is made (step S206). Here, if the density of the patch image is outside the appropriate range, it is possible that some abnormality has occurred in the apparatus. Therefore, in this case, it is determined as an error, and a service call message is displayed on the display unit 12 to notify the user of the occurrence of an abnormality and to request an inspection by a service person, and the operation is stopped (step S208). On the other hand, if the patch image density is within the appropriate range, there exists an optimum development bias value that can match the density of the patch image with the target density within the variable range of the development bias. Therefore, the optimum developing bias is calculated based on the density detection result of each patch image, and the process is terminated (step S207).

  The description of the density control operation (FIG. 3) will be continued. When the adjustment of the developing bias is completed, the exposure power is subsequently adjusted (step S106). The exposure power greatly affects the image density of the fine line image.

  FIG. 6 is a flowchart showing the exposure power adjustment process. In this process, the intensity (exposure power) of the light beam L emitted from the exposure unit 6 is changed in multiple stages with the development bias fixed to the optimum value obtained previously, and each time a halftone is obtained as a patch image. An image is formed (step S301). As this halftone image, for example, a so-called 1 on 10 off image in which 10 off dots and 1 toner dot are alternately arranged can be used. The density of such a halftone image is easily influenced by the exposure power.

  The density of the patch image formed in this way is detected by the density sensor 60 (step S302). Then, the operation mode of the apparatus is determined (step S303). If it is the first mode, it is determined whether the patch image density is appropriate (step S304), and the optimum exposure power is calculated (step S305). . On the other hand, if the operation mode is the second mode, it is not determined whether or not the patch image density is appropriate. In the first mode where high image quality is required, the apparatus is required to meet strict quality standards, whereas in the second mode, the conditions can be relaxed. When the operation mode is the first mode and the density of the patch image is not within the proper range, an error is determined and a service call message is displayed as in the case of the development bias adjustment processing (step S306).

  The method of determining the target density value and appropriate range of the patch image in the exposure power adjustment process can be basically the same as in the case of the development bias adjustment process (FIG. 5). However, in this embodiment, the target density of the patch image in the exposure power adjustment process is the same between the first mode and the second mode. This is because if the target density of the halftone image is lowered in the second mode, the formed characters become thin and difficult to read.

  Thus, the target density and the appropriate range are individually determined in each of the first mode and the second mode, and the image density desired by the user is maintained by adjusting the developing bias and the exposure power based on the target density and the appropriate range. . That is, when the operation mode of the apparatus is set to the first mode, a predetermined target density is obtained for each of a high duty image (for example, a solid image) and a low duty image (for example, a 1 on 10 off image). Here, the duty of the image is the ratio of the area of the toner adhesion portion to the entire image. On the other hand, when the operation mode of the apparatus is set to the second mode, an image quality close to that of the first mode can be obtained in the low duty image, but the decrease in density compared to the first mode is large in the high duty image. .

  FIG. 7 is a diagram showing the relationship between the image duty and the image density. As described above, since the target densities (value Dt1 corresponding to the first mode and value Dt2 corresponding to the second mode) for the two solid images are different between the operation modes, as shown in FIG. In the duty image, the density difference ΔHigh between the two operation modes is large. On the other hand, in the low duty image, the density difference ΔLow between the operation modes is small. From this, it can be said as follows. That is, in the first mode, a low duty image can be expressed at a low density and a high duty image can be expressed at a high density, so that the dynamic range of the image is wide and a photographic image or graphic image can be formed with high definition. On the other hand, in the second mode, a high image density cannot be obtained in a high duty image, but an image quality equivalent to that in the first mode can be obtained in a low duty image. In other words, even if the target density on the high duty side is lowered, it can be used with no hindrance mainly for the purpose of forming a character image. By performing image formation while controlling the image density of a high duty image to a low target density in this way, it is possible to greatly reduce toner consumption and greatly reduce the running cost of the apparatus. it can.

  Incidentally, in order to obtain high image quality in the first mode, it is necessary to further improve the reproducibility of the halftone. Therefore, in the density control operation (FIG. 3) in this embodiment, only when the operation mode of the apparatus is set to the first mode, the gradation for adjusting the gradation correction characteristic of the apparatus following the adjustment of the exposure power. Correction control processing is executed (steps S107 and S108).

  FIG. 8 is a flowchart showing the gradation correction control process in the first embodiment. In the gradation correction control process, first, a predetermined gradation patch image is formed (step S401). This gradation patch image is an image including a plurality of image areas formed at different gradation levels. Subsequently, the density sensor 60 detects the density of each image area included in the gradation patch image (step S402). Here, it is determined whether or not the density detection result of the gradation patch image is appropriate (step S403). If it is not appropriate, an error is determined and a service call message is displayed on the display unit 12 (step S406). The determination of appropriateness is performed based on whether or not density reversal occurs, for example, an image area formed with a higher gradation level has a lower density than an image area formed with a lower gradation level. be able to.

  When the density detection result of the gradation patch image is appropriate, it is necessary to estimate the gamma characteristic of the device from the density detection result of each image area and correct it to reproduce the gradation characteristic faithfully. Correction characteristics are calculated (step S404). Then, the content of the gradation correction table referred to when performing signal processing on the image signal in the main controller 11 is updated to the one corresponding to the correction characteristic obtained above (step S405). As a result, in the subsequent image forming operation in the first mode, an image can be formed with excellent gradation.

As described above, by performing the density control operation in a mode corresponding to the operation mode of the apparatus, an image forming condition corresponding to the operation mode is obtained. By forming an image under the image forming conditions thus obtained, an image can be formed with an image quality desired by the user. The image forming operation process itself is the same in both operation modes. However, since the set image forming conditions are different, the quality level of the formed image is different, and the number of images that can be formed using one developing device also changes.

  FIG. 9 is a diagram showing the relationship between the remaining amount of toner and the number of images formed. Assuming that the duty of the image to be formed is constant, as shown in FIG. 9, the remaining amount of toner decreases linearly as the number of images formed increases. Due to the difference in the set value of the target density, the remaining amount of toner decreases in the first mode at a faster pace than in the second mode. In order to replace the developing device before the image quality deteriorates, if it is determined that the life of the developing device has expired when the remaining amount of toner is reduced to 10% of the initial amount, the developing device is used. The number of images that can be formed in this way is N1. On the other hand, in the second mode in which the inclination of the toner remaining amount decrease is small, the number of images that can be formed is larger than in the first mode if the remaining life of the developing device is set to the same remaining amount 10% as in the first mode. N0 sheets. However, in practice, in the second mode, since the allowable range of image quality is wider, the life of the developing device can be determined in an area where the remaining amount of toner is smaller. For example, assuming that the toner remaining amount is 1%, the number of images that can be formed using the developing device is further increased to N2. Thus, by forming an image in the second mode with a low target density, the number of images that can be formed using one developing device can be greatly increased.

  As described above, in the first embodiment of the image forming apparatus according to the present invention, depending on whether the developing device attached to the apparatus is compatible with the first mode or the second mode, The target density in the density control operation is varied. As a result, an image can be formed with high image quality in the first mode, while in the second mode, the toner consumption is reduced and the running cost of the apparatus is reduced while ensuring a certain quality for the character image. It becomes possible. In addition, since the determination criteria for determining normality / abnormality of the apparatus are different depending on the operation mode, a constant image quality is maintained in the first mode, while an error occurrence frequency is reduced in the second mode. Thus, the developing device can be used more effectively.

  In the second mode, quality requirements for the developing device and the toner are moderate. Therefore, it is possible to improve the production yield of the developing device and the toner and reduce the production cost. In addition, it is effective as a developing device that can be used only in the second mode, even if the developing device has a large variation in manufacturing, has not been used for a long time, or has been poorly stored and performance has deteriorated. Can be used. Further, for example, even a developing device whose lifetime as a developing device adapted to the first mode has expired can be continuously used as long as it is limited to use in the second mode. Therefore, if the identification information of the developing device is rewritten and changed for the second mode, the developing device can be used more effectively.

  Further, for example, a used developing device can be reused as follows. That is, the developer that has used up the toner is refilled with toner, and in which operating mode the developer is suitable for use is determined based on the degree of deterioration of each part of the developer, Identification information based on the determination result is given. However, a developing device that has deteriorated to a state unsuitable for use in the second mode is excluded from reuse. By doing so, the developing device is reused in a mode corresponding to the degree of deterioration, and the developing device can be effectively utilized.

  In addition, the user can switch the apparatus between the first mode with excellent image quality and the second mode with excellent economy by replacing the developing unit as necessary. As described above, according to the present invention, it is possible to provide an image forming apparatus that can meet various requests of users and is excellent in convenience and cost performance.

  In this embodiment, as long as there is at least one developing device conforming to the second mode, the entire apparatus is operated in the second mode, so that the image quality does not vary for each developing device to be used. . This is particularly important in a full-color image forming apparatus that is used with a developing device corresponding to different toner colors. This is because, in a full-color image forming apparatus, the color balance between toner colors is important, and it is meaningful to maintain high image quality for other toner colors in a state where a certain image quality is not guaranteed for one color. Because there is no. In such a case, by using all the developing devices in the second mode, it is possible to suppress wasteful toner consumption and achieve high cost performance.

(Second Embodiment)
Next, a second embodiment of the image forming apparatus according to the present invention will be described. The configuration of the image forming apparatus of the second embodiment is basically the same as that of the first embodiment. Therefore, here, the same components are denoted by the same reference numerals and description thereof is omitted. The apparatus according to the second embodiment is different from that according to the first embodiment in that the operation mode of the apparatus can be individually set for each developing device, and the adjustment of the developing bias is omitted in the density control operation in the second mode. It is different from the device. Below, it demonstrates centering around operation | movement of 2nd Embodiment different from 1st Embodiment.

  FIG. 10 is a flowchart showing the density control operation in the second embodiment. In the density control operation # 2 of the second embodiment, the preprocessing in step S501 is performed in step S104 in FIG. 3, the development bias adjustment in step S503 is performed in step S105 in FIG. 3, and the exposure power adjustment process in step S504 is performed in FIG. Step S106 and steps S505 and S506 correspond to steps S107 and S108 in FIG. 3, respectively. Then, the setting of the operation mode of the entire apparatus based on the identification information of each developing device (steps S101 to S103 in FIG. 3) is omitted. On the other hand, if the developing device corresponds to the second mode, the developing bias adjustment processing is performed. A determination process (step S502) for skipping is added.

  As described in the first embodiment, the developing bias adjustment process is performed for density adjustment in a high duty image. However, as described above, the image density of the high duty image is not so important in the image mainly composed of characters. Therefore, in this embodiment, only the adjustment of the exposure power that greatly affects the density of the fine line image is performed, and the adjustment of the developing bias is omitted. By doing this, it is possible to further reduce toner consumption and shorten the processing time required for the density control operation.

  Note that the density control operation in the second embodiment is changed in accordance with the identification information assigned to each developing device. That is, in this embodiment, the density control operation in a mode corresponding to the first mode is performed for the developing device to which the identification information indicating that the first mode is applied is applied, while the second mode is applied. The density control operation in a mode corresponding to the second mode is performed on the developing device to which the identification information indicating that this is to be performed. Therefore, when the developing devices corresponding to the two operation modes are mixed in one apparatus, the processing content of the density control operation differs for each developing device. The reason for this will be described later.

  FIG. 11 is a flowchart showing a developing bias adjustment process in the second embodiment. As described above, the developing bias adjustment process is executed only in the first mode. Therefore, in the development bias adjustment processing # 2 in this embodiment, the processing for setting the target value and appropriate density range according to the operation mode in the development bias adjustment processing # 1 (FIG. 4) in the first embodiment is omitted. It is. Except for this point, the processing content of the development bias adjustment processing # 2 in this embodiment is the same as the processing in the first embodiment. That is, steps S601, S602, S603, S604, and S605 of the developing bias adjustment process # 2 correspond to steps S201, S202, S206, S207, and S208 of FIG.

  Note that the processing contents of the exposure power adjustment process and the gradation correction control process in this embodiment are the same as those in the first embodiment.

  By performing the density control operation configured as described above, in this embodiment, the developing device to which the identification information indicating conformity to the first mode is applied is a mode corresponding to the first mode, and the second mode. The image forming conditions are set in a manner corresponding to the second mode for the developing device to which identification information indicating conformity to the mode is attached. In this way, the first and second modes can be used properly without particularly replacing the developing device.

  FIG. 12 is a flowchart showing an image forming operation in the second embodiment. In this image forming operation, processing is started when an image forming request command is given from an external device such as a host computer (step S701). Then, based on the content of the given image formation command, it is determined whether the image quality required for the image to be formed is a high-quality image such as a photographic image or a character image ( Step S702). The determination of the image quality may be made based on, for example, contents set and input by the user to the printer driver, or may be made based on the contents of the image to be formed.

  If high image quality is required, it is determined whether or not a developing device suitable for the first mode is attached to the apparatus (step S703). If the developing device conforming to the first mode is installed in the apparatus, an image is formed using the developing device (step S704). If not, the operation is stopped at that time (step S704). S707). This is to prevent a user who demands high image quality from outputting an image having a quality level that does not satisfy the requirement. On the other hand, when the character image quality is required, it is determined whether or not a developing device conforming to the second mode is attached to the apparatus (step S705). Is formed (step S706). Note that the operation is stopped when a developing device conforming to the second mode is not mounted (step S707). This is to prevent the developing device prepared for use in the first mode from being used against the user's will.

  As described above, in the second embodiment of the image forming apparatus according to the present invention, similarly to the apparatus of the first embodiment, an apparatus having excellent convenience and cost performance is configured according to a user request. be able to. In the density control operation # 2, only the exposure power adjustment process that greatly affects the character image quality is executed, so that the toner consumption can be suppressed and the processing time can be shortened.

  In addition, since the operation mode is set individually for each developing device, in the state where the developing devices corresponding to both operation modes are mixed, according to the user's request or according to the content of the image to be formed. Thus, it is possible to switch between the two operation modes as appropriate. Therefore, it is possible to make the device more convenient for the user.

(Other)
The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, the above-described image forming apparatus is an image forming apparatus dedicated to monochrome images equipped with four developing units that store black toner, but is a full color equipped with developing units that store toners of different colors. The present invention can also be applied to an image forming apparatus.

  In each of the above embodiments, the identification information of the developing device is stored in a memory provided in the developing device. However, the identification information of the present invention is limited to information in an electromagnetically stored manner as described above. Not. For example, a suitable operation mode may be identified depending on whether or not the claw-shaped protrusion provided on the housing of the developing device is folded, or identification information is set by a switch attached to the developing device. Also good. In this case, the user can freely switch the corresponding operation mode of the developing device according to the desire.

  In each of the above embodiments, the life management is performed based on the remaining amount of toner in each developing device. In other words, in these embodiments, the remaining amount of toner for each developing device corresponds to the “management information” of the present invention, but the management information includes, for example, rotation of the developing roller provided in each developing device. Time, the number of formed images, etc. can be used.

  In the development bias adjustment of the first embodiment, the development bias is adjusted so that the patch image has a predetermined target density Dt1 or Dt2. However, the present invention is not limited to this. For example, the development bias and other density control factors may be adjusted so that the patch image density falls within a predetermined target density range.

  In the first embodiment, when at least one of the four developing devices is adapted to the second mode, the entire apparatus operates in the second mode. You may make it operate | move by a 2nd mode only when it is a thing suitable for 2 modes.

  In each of the above embodiments, the presence / absence of abnormality of the apparatus is determined based on the density detection result of the patch image formed under a specific condition. More preferably, the density detection of the patch image formed under different conditions is performed. The presence or absence of an abnormality may be determined based on the result or based on the result of the comparison.

  In the above embodiments, the four developing cartridges 4Ka to 4Kd having the same shape are used. However, developing cartridges having different shapes may be used. In the above embodiment, the present invention is applied to a so-called rotary type image forming apparatus in which the rotary developing unit 4 is arranged for one photoconductor 22. The present invention can also be applied to an elevator type image forming apparatus in which a developing cartridge moves up and down and develops with each developing cartridge.

  Further, the present invention is not limited to the configuration of the above-described embodiment. For example, the present invention is also applied to an apparatus including a transfer medium (transfer drum, transfer sheet, etc.) other than the intermediate transfer belt, and also to other image forming apparatuses such as a copying machine and a facsimile machine. The invention can be applied.

  As described above, in each of the above embodiments, the developing devices 4Ka to 4Kd function as the “process cartridge” of the present invention, and the engine unit EG and the engine controller 10 of the present invention “image forming means”. And “control means”. Further, the first mode and the second mode in each of the above embodiments correspond to the “first operation mode” and the “second operation mode” of the present invention. The target concentrations Dt1 and Dt2 in the first embodiment correspond to the “first and second target concentrations” of the present invention, respectively, while the appropriate ranges R1 and R2 correspond to the “appropriate concentration range” of the present invention, respectively. ing.

1 is a diagram illustrating a first embodiment of an image forming apparatus according to the present invention. FIG. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus in FIG. 1. 6 is a flowchart showing a density control operation in the first embodiment. 6 is a flowchart showing development bias adjustment processing in the first embodiment. The figure which shows the target density | concentration and the appropriate range of a density | concentration. The flowchart which shows exposure power adjustment processing. The figure which shows the relationship between the duty of an image, and image density. 5 is a flowchart illustrating tone correction control processing according to the first embodiment. FIG. 4 is a diagram illustrating a relationship between a remaining amount of toner and the number of images formed. 9 is a flowchart showing a density control operation in the second embodiment. 9 is a flowchart showing development bias adjustment processing in the second embodiment. 9 is a flowchart showing an image forming operation in the second embodiment.

Explanation of symbols

  4Ka to 4Kd ... developer (process cartridge), 10 ... engine controller (control means), 22 ... photosensitive member, 91 ... memory, EG ... engine unit (image forming means)

Claims (13)

A process cartridge configured to be detachable from the apparatus body;
Image forming means for forming an image using the process cartridge mounted on the apparatus main body;
A first operation mode for controlling the image forming means to form an image at a predetermined first image quality level; and a second for forming an image at a second image quality level lower than the first image quality level. Control means for selectively executing the operation mode,
While the process cartridge is provided with identification information for identifying whether the process cartridge is compatible with the first operation mode or the second operation mode,
The image forming apparatus according to claim 1, wherein the control unit selectively executes either the first operation mode or the second operation mode based on the identification information attached to a process cartridge mounted on the apparatus main body.   In the first operation mode, an image is formed while controlling the image density to a predetermined first target density, while in the second operation mode, a second target whose image density is lower than the first target density. The image forming apparatus according to claim 1, wherein an image is formed while controlling the density.   The control unit determines that the apparatus has an operation error when the density of the patch image formed by the image forming unit is not a predetermined appropriate density, and the appropriate density in the first operation mode is determined in the second operation mode. The image forming apparatus according to claim 1, wherein the density is higher than the appropriate density.   In the first operation mode, an image is formed while controlling the image density within a predetermined first target density range. On the other hand, in the second operation mode, the second image density is larger than that in the first target density range. The image forming apparatus according to claim 1, wherein an image is formed while being controlled within a target density range.   The control means determines that the apparatus is operating error when the density of the patch image formed by the image forming means is not within a predetermined appropriate density range, and the appropriate density range corresponding to the first operation mode is The image forming apparatus according to claim 1, wherein the image forming apparatus is narrower than the appropriate density range corresponding to the second operation mode.   The control unit performs a density control operation for controlling the image density by adjusting a density control factor that affects the image density based on the density detection result of the patch image formed by the image forming unit in accordance with the operation mode. The image forming apparatus according to claim 1, wherein the operation algorithm of the density control operation corresponding to the first operation mode is different from the operation algorithm of the density control operation corresponding to the second operation mode. .   The image forming apparatus according to claim 6, wherein in the density control operation corresponding to the second operation mode, a density control operation obtained by simplifying the density control operation corresponding to the first operation mode is executed.   The control means is configured to manage management information related to the total usage amount of the process cartridge and to determine that the process cartridge has reached the end of its life when the management information reaches a predetermined threshold. The image forming apparatus according to claim 1, wherein the threshold value is varied according to the identification information attached to the cartridge.   The image forming apparatus according to claim 1, wherein the process cartridge is a developing unit that stores toner therein. When a plurality of the developing devices are configured to be attachable to the apparatus main body and a plurality of the developing devices are attached to the apparatus main body,
The image forming unit forms an image while switching the plurality of developing units,
When the identification information corresponding to the second operation mode is attached to at least one of the plurality of developing devices, the control means is configured to use the second operation mode regardless of which developing device is used. The image forming apparatus according to claim 9. When a plurality of the developing devices are configured to be attachable to the apparatus main body and a plurality of the developing devices are attached to the apparatus main body,
The image forming means forms an image while switching the plurality of developing devices,
The control means executes the first operation mode when using the developing device to which the identification information corresponding to the first operation mode is used among the plurality of developing devices, while corresponding to the second operation mode. The image forming apparatus according to claim 9, wherein the second operation mode is executed when the developing device to which the identification information is attached is used.   The image forming apparatus according to claim 11, wherein a plurality of developing units that store toner of the same color can be mounted. In an image forming method of forming an image using a process cartridge mounted on an image forming apparatus main body,
Reading the identification information attached to the process cartridge;
One of the first operation mode for forming an image at a predetermined first image quality level and the second operation mode for forming an image at a second image quality level lower than the first image quality level. And an image forming method comprising: selecting and executing based on the identification information.

Images