JP7150502B2 - image forming device - Google Patents

Description

The present invention relates to image forming apparatuses such as copiers, printers, and facsimiles that form images by electrophotography, and more particularly to a cartridge type image forming apparatus that can be attached to and detached from an image forming apparatus main body.

2. Description of the Related Art Conventionally, an image forming apparatus adopts a process cartridge system in which an electrophotographic photosensitive member (called a photosensitive drum) and a process means acting on the photosensitive drum are integrated into a cartridge and detachable from the main body of the image forming apparatus. ing. According to this process cartridge system, the user can perform the maintenance of the apparatus by himself/herself without relying on service personnel, so that the operability can be improved.

In addition, a cartridge system is adopted in which a developing cartridge is a unit in which developing means is independent from a process cartridge, and a drum cartridge is an independent unit in which a photosensitive drum, charging means, and cleaning means are integrated. Since the developing cartridge and the drum cartridge can be independently attached to and detached from the main body of the image forming apparatus, the maintainability can be further improved. In addition, since the cartridges can be appropriately replaced according to the life of each cartridge, it is possible to set the replacement timing more appropriately.

Japanese Patent Application Laid-Open No. 2002-201002 discloses a method for detecting whether or not a cartridge is attached to an image forming apparatus. There is a way.

Patent No. 3000759

However, the method for detecting whether or not a cartridge is attached as disclosed in Patent Document 1 has the following problems. In the method disclosed in Japanese Patent Application Laid-Open No. 2002-200003, a current is supplied to a transfer member that is brought into contact with a photosensitive drum, and whether or not the cartridge is attached is determined from the obtained voltage value. Therefore, the detection result is determined by the presence or absence of the photosensitive drum. That is, the method of Japanese Patent Laid-Open No. 2002-200010 is suitable for determining whether a process cartridge or a drum cartridge having a photosensitive drum is used, but it cannot determine whether or not a developing cartridge is attached.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an image forming apparatus capable of determining whether or not a developing cartridge is attached.

In order to achieve this object, the image forming apparatus of the present invention includes an apparatus main body, a rotatable image carrier, and a charging section formed in contact with the image carrier together with the image carrier. A charging member that charges the image carrier, and a developing portion that is in contact with the image carrier and forms a developing portion together with the image carrier, and supplies toner onto the surface of the image carrier in the developing portion to form a toner image. wherein the developing cartridge is attachable to and detachable from the apparatus main body in a state in which the image carrier and the charging member are in the apparatus main body; charging voltage applying means for applying a charging voltage; detecting means for detecting a current value of a current flowing through the charging voltage applying means; and a control section for controlling the charging voltage applying means; In the case of an apparatus main body, while the image carrier is being rotated and the charging member is being applied with the charging voltage, the surface area of the image carrier which will form the developing portion is the above-mentioned area. According to the current value detected by the detecting means when the image bearing member reaches the charging portion due to the rotation of the image carrier, it is notified that the developing cartridge is not installed in the apparatus main body.

As described above, according to the present invention, it is possible to determine whether or not the developing cartridge is attached.

1 is a schematic configuration diagram of an image forming apparatus according to Embodiment 1; FIG. 2 is a schematic configuration diagram of the image forming apparatus according to Embodiment 1 when operation is stopped; FIG. 4 is a control block diagram according to the first embodiment; FIG. 8 is a diagram showing the relationship between the amount of surface potential reduction and the current value of the photosensitive drum according to Example 1. FIG. 2 is a schematic layout diagram of a current detection means according to Example 1. FIG. 8 is a diagram showing the relationship between the rotational speed ratio between the photosensitive drum and the developing roller and the surface potential reduction amount of the photosensitive drum according to the first embodiment; FIG. 5 is a diagram showing the relationship between the back contrast and the surface potential reduction amount of the photosensitive drum according to Example 1. FIG. 5 is a flowchart for explaining a cartridge detection method according to the first embodiment; 5 is a flowchart for explaining a cartridge detection method using development current according to the first embodiment; 4 is a timing chart of a cartridge detection operation and a detected development current according to Example 1; 9 is a flowchart for explaining a cartridge detection method according to the second embodiment; 8 is a flowchart for explaining a cartridge detection method using charging current according to the second embodiment; 9 is a timing chart of a cartridge detection operation and a detected charging current according to Example 2; FIG. 11 is a schematic configuration diagram of a full-color image forming apparatus according to Example 3; FIG. 11 is a control block diagram according to Example 3; 10 is a flowchart for explaining a cartridge detection method according to the third embodiment; 10 is a timing chart of drum cartridge detection operation and detected charging current according to the third embodiment; 10 is a timing chart of a developing cartridge detection operation and a detected charging current according to Example 3. FIG. 14 is a timing chart of a developing cartridge detection operation and a detected charging current according to Example 4. FIG.

Preferred embodiments of the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of components described in the following embodiments should be appropriately changed according to the configuration of the device to which the present invention is applied and various conditions. Accordingly, it is not intended to limit the scope of the present invention solely thereto unless specifically stated.

In this embodiment, a cartridge two-piece image forming apparatus in which a developing cartridge as developing means and a drum cartridge comprising an image carrier, a charging member, and a cleaning means are independently attachable to and detachable from the apparatus main body. will be explained.

1. 1. Image Forming Apparatus FIGS. 1 and 2 are diagrams showing a schematic configuration of an image forming apparatus 100 as a first embodiment according to the present invention. FIG. 1 is a schematic diagram of the configuration during image formation, and FIG. 2 is a schematic diagram of the configuration when the operation is stopped. When the operation is started, the photosensitive drum 1 as an image bearing member is rotationally driven in the direction of arrow Ra in FIGS. 1 and 2 by a photosensitive drum driving motor (not shown). The rotational driving speed of the photosensitive drum 1 was set to 200 mm/sec. The photosensitive drum 1 is a so-called organic photoreceptor in which a charge generation layer is formed on a conductive metal core made of aluminum or the like, and a charge transport layer is formed thereon. The thickness of the charge transport layer was 24 μm. A charging roller 2 serving as a charging member for charging the surface of the photosensitive drum 1 is applied with a negative voltage at a predetermined timing from a charging voltage power source 30 serving as a charging voltage applying means, so that the surface of the photosensitive drum 1 is uniformly charged. processed to form a dark potential Vd. The charging width of the charging roller 2 was set to 228 mm. After that, the charged photosensitive drum 1 is exposed by a laser exposure unit 3 as an exposure device. In accordance with image data, the photosensitive drum 1 is repeatedly exposed in the main scanning direction (rotational axis direction of the photosensitive drum 1) using a laser beam, and is also exposed in the sub-scanning direction (rotational direction of the photosensitive drum 1). This forms an electrostatic latent image. The image forming portion where the electrostatic latent image is formed has the bright portion potential Vl. A developing roller 41 as a developing member is rotatably supported by the developing cartridge 20 as developing means. As shown in FIG. 1, the developing roller 41 is brought into contact with the photosensitive drum 1 during image formation, and the image portion is exposed by the laser exposure unit 3 as exposure means. The toner in the developing container 4 is carried on the developing roller 41, and a developing voltage is applied to the developing roller 41 from a developing voltage power source 40, which is a developing voltage applying means. Development is performed on the latent image. The toner image visualized on the photosensitive drum 1 is further sent to the transfer roller 5 and the transfer portion (transfer nip portion) of the photosensitive drum 1, and transferred onto the conveyed recording material P at the correct timing. A transfer voltage is applied to the transfer roller 5 by a transfer voltage power supply 140, which is a transfer voltage applying means. After that, the recording material P onto which the toner image has been transferred is sent to the fixing device 7 . In the fixing device 7 , heat and pressure are applied to the recording material P, and the transferred toner image is fixed on the recording material P. FIG.

On the other hand, the toner remaining on the surface of the photosensitive drum 1 without being transferred after transfer is removed by a cleaning blade 6 as a cleaning device and stored in a waste toner container 61 . Thereafter, the surface of the photosensitive drum 1 is again charged by the charging roller 2 and the above steps are repeated.

Further, the developing cartridge 20 performs a contact/separation operation, which is a contact/separation operation with respect to the photosensitive drum 1, in accordance with the image forming operation. This contact/separation operation is performed by the action of the contact/separation cam 45, which is the developing contact/separation mechanism. FIG. 2 is a schematic configuration diagram in a non-image forming state when image formation is completed. The contact/separation cam 45 is controlled by the control unit 202 so as to move between a contact position where the developing cartridge 20 and the photosensitive drum 1 are brought into contact with each other and a separated position where the developing cartridge 20 and the photosensitive drum 1 are not contacted by rotation of the cam.

A control unit 202 is means for controlling the operation of the image forming apparatus 100, and transmits and receives various electrical information signals. It also processes electrical information signals input from various process equipment and sensors, processes command signals to various process equipment, and controls the contact/separation cam 45 to perform predetermined operations such as the operation of the developing cartridge 20 . Controls image sequence control, etc. FIG. 3 is a block diagram showing a schematic control mode of main parts of the image forming apparatus 100 in this embodiment. The controller 203 exchanges various electrical information with the host apparatus, and controls the image forming operation of the image forming apparatus 100 by the control unit 202 via the interface 201 according to a predetermined control program and reference table. control effectively. The control unit 202 includes a CPU 155 which is a central element for performing various arithmetic processing, a memory 156 such as a ROM and a RAM which are storage elements, and the like. The RAM stores sensor detection results, counter count results, calculation results, and the like, and the ROM stores control programs, data tables obtained in advance through experiments, and the like. Control objects, sensors, counters, and the like in the image forming apparatus 100 are connected to the control unit 202 . A control unit 202 controls the transmission and reception of various electrical information signals, the timing of driving each unit, and the like, thereby controlling a predetermined image forming sequence. For example, the control unit 202 controls the voltages applied by the charging voltage power supply 30, the development voltage power supply 40, the laser exposure unit 3, and the transfer voltage power supply 140, and the amount of exposure. In this embodiment, the control unit 202 also controls the determination means for determining whether or not the drum cartridge 10 or the developing cartridge 20 is installed. The image forming apparatus 100 forms an image on the recording material P based on an electrical image signal input from the host device to the controller 203 . Examples of host devices include image readers, personal computers, facsimiles, and smart phones.

2. Configuration of Developing Cartridge Next, the developing cartridge 20 of this embodiment will be described. In the developer cartridge 20 , the developer roller 41 and the toner supply roller 42 are rotatably supported by the developer container 4 . The toner supply roller 42 is arranged so as to be in contact with the outer peripheral surface of the developing roller 41 . Toner is supplied to the developing roller 41 by the toner supply roller 42 , and the toner is carried on the surface of the developing roller 41 . The directions of rotation of the developing roller 41 and the toner supply roller 42 are the same (opposite directions on the circumferential surface of the contact portion) as indicated by arrows Rb and Rc in FIGS. 1 and 2 . The developing roller 41 is formed by providing a conductive elastic rubber layer having a predetermined volume resistance around a metal core. The toner supply roller 42 has a urethane foam layer around a metal core. Foamed cells are opened in the surface layer of the foamed urethane layer, making it easy to hold and transport the toner.

The development blade 43 is made of a flexible elastic plate such as SUS, and one end of the development blade 43 is fixed to the development container 4 . The toner supplied from the toner supplying roller 42 forms a uniform toner coat on the developing roller 41 by the developing blade 43 . The uniformly formed toner coat is arranged so that the plate surface near the free end of the developing blade 43 rubs against the surface of the conductive elastic rubber layer of the developing roller 41, and the toner is triboelectrically charged.

The toner conveying member 44 is provided inside the developer container 4 and is configured to be rotatable around a rotation shaft. The rotation of the toner conveying member 44 agitates the toner in the developing container 4 and conveys the toner to the toner supply roller 42 . During the image forming operation, the developing roller 41 rotates in contact with the photosensitive drum 1 with a rotational speed difference. The rotational speed of the developing roller 41 and the rotational speed difference with respect to the photosensitive drum 1 are determined from the viewpoint of uniformity of the toner coat on the developing roller 41 by the developing blade 43 and the amount of toner required for developing on the photosensitive drum 1 . . In this embodiment, the developing roller 41 rotates in contact at a rotational speed 1.7 times greater than the rotational speed of the photosensitive drum 1 (ratio of rotational speed to the photosensitive drum: 170%).

3. Decrease in Surface Potential of Photosensitive Drum Due to Difference in Rotational Speed If there is a difference in rotational speed between the photosensitive drum 1 and the developing roller 41 as described above, an electric potential is formed on the surface of the photosensitive drum 1 at the development contact portion (developing portion). The accumulated charge may move to the developing roller 41 . The dark area potential Vd, which is the surface potential of the photosensitive drum 1 in the non-image forming portion in the configuration of the present embodiment, is set to be larger in absolute value than the developing voltage Vdc. , the dark potential Vd is lowered. This is because when the surface of the photosensitive drum 1 and the surface of the developing roller 41 are rubbed with each other with a difference in rotational speed, the charges formed on the photosensitive drum 1 due to electrification easily move electrically to the developing roller 41 . in order to move to As the potential difference between the dark portion potential Vd and the developing voltage Vdc increases, the amount of charge flowing from the surface of the photosensitive drum 1 to the developing roller 41 increases, and thus the movement of charges becomes more active. Also, as the difference in rotational speed between the developing roller 41 and the photosensitive drum 1 increases, the amount of movement of electric charge similarly increases, and thus the decrease in the dark potential Vd increases. In this embodiment, the dark potential Vd is set to -560V, and the development voltage Vdc is set to -360V. Here, the development voltage Vdc in this embodiment is expressed as a potential difference from the ground potential. Therefore, the development voltage Vdc=-360V is interpreted to have a potential difference of -360V with respect to the ground potential (0V) due to the development voltage applied to the core metal of the development roller 41 . This is the same for the charging voltage and the transfer voltage. The charging voltage is set to -1100 V, the transfer voltage is set to +600 V during image formation, and -1100 V during detection of whether or not the cartridge is installed. ing. When the development contact is performed in the above state, the surface of the photosensitive drum 1 passes through the developing portion, thereby lowering the dark portion potential Vd to -537V. That is, the surface potential of the photosensitive drum 1 is lowered by 23V. Due to the decrease in the surface potential of the photosensitive drum 1, electric charges are transferred in the developing section, and a current is generated. FIG. 4 shows the relationship between the amount of decrease in the surface potential of the photosensitive drum 1 and the current value detected at that time. The greater the amount of decrease in the surface potential of the photosensitive drum 1, the greater the current that flows. For example, when the surface potential of the photosensitive drum 1 drops by 23 V as in the configuration of this embodiment, the developing current detecting means 17, which is the detecting means shown in FIG. 5, detects 1.16 μA as the developing current. A decrease in the surface potential of the photosensitive drum 1 will be described later in detail. By detecting this current with the developing current detecting means 17, it can be determined that the developing roller 41 is in contact with the photosensitive drum 1 in the developing portion. FIG. 5 is a diagram showing the developing roller 41, the developing portion of the photosensitive drum 1, and the current detection circuit. Other members provided in the developing container 4 other than the developing roller 41 are not described. The current flowing from the photosensitive drum 1 to the developing roller 41 when the developing roller 41 is brought into contact with the photosensitive drum 1 and rotated can be detected by the developing current detecting means 17 arranged directly with respect to the developing roller 41 . I can. Accordingly, by detecting whether or not a current flows when the developing roller 41 is brought into contact with the developing roller 41, it is possible to determine whether or not a cartridge is mounted, which will be described later.

4. Relation Between Decrease in Surface Potential of Photosensitive Drum and Difference in Rotational Speed/Difference in Potential Next, the influence of the decrease in the surface potential of the photosensitive drum 1 due to contact with the developing roller 41 will be described. FIG. 6 shows the amount of decrease in the surface potential of the photosensitive drum 1 with respect to the rotational speed difference between the rotational speed of the photosensitive drum 1 and the rotational speed of the developing roller 41 . The horizontal axis of FIG. 6 represents the rotational speed ratio indicating the rotational speed difference between the photosensitive drum 1 and the developing roller 41. For example, when the rotational speed ratio is 200%, the rotational speed of the developing roller 41 is equal to the rotational speed of the photosensitive drum 1. It shows that it is rotating at a rotational speed twice as high as that of the . The vertical axis in FIG. 6 represents the amount of decrease in the surface potential of the photosensitive drum 1, which is the potential difference between the surface potentials measured before and after the surface of the photosensitive drum 1 passes through the developing section formed by the developing roller 41. ing. As can be seen from FIG. 6, when the rotational speed difference between the photosensitive drum 1 and the developing roller 41 is large, the amount of decrease in the surface potential of the photosensitive drum 1 is large. The reason why the surface potential of the photosensitive drum 1 is lowered is due to the charge transfer to the developing roller 41 . When the rotational speed difference is large, the actual contact area between the surface of the photosensitive drum 1 and the surface of the developing roller 41 becomes large, so the chances of charge transfer from the surface of the photosensitive drum 1 to the developing roller 41 increase. This result means that when the current is detected, increasing the difference in rotational speed between the photosensitive drum 1 and the developing roller 41 increases the current value, thereby increasing the detection accuracy. Therefore, it is desirable to increase the rotational speed difference between the photosensitive drum 1 and the developing roller 41 as much as possible when executing the cartridge detection method, which will be described later. Specifically, if the rotational speed difference between the photosensitive drum 1 and the developing roller 41 is larger during image formation than during image formation, the accuracy is further improved. In this embodiment, since the rotational speed ratio between the photosensitive drum 1 and the developing roller 41 during image formation is 170%, it is preferable that the rotational speed ratio when determining whether or not the cartridge is installed is greater than 170%. At this time, the rotation speed of the developing roller 41 may be increased or the rotation speed of the photosensitive drum 1 may be decreased when determining whether the cartridge is installed or not, compared to when forming an image. However, if the rotation speed difference is too large, the amount of decrease in the surface potential of the photosensitive drum 1 is too large, and the back contrast, which is the potential difference between the surface potential of the photosensitive drum 1 and the developing voltage applied to the developing roller 41, becomes small. As a result, the toner develops against the dark potential Vd of the surface of the photosensitive drum 1, which may cause fogging. Therefore, the rotation speed difference should be appropriately set in view of them.

FIG. 7 shows the amount of decrease in the surface potential of the photosensitive drum 1 with respect to the back contrast, which is the potential difference between the surface potential of the photosensitive drum 1 immediately before entering the developing section and the developing voltage applied to the developing roller 41 . Here, the term "immediately before entering the developing section" specifically refers to the area on the photosensitive drum 1 between the exposure reaching position on the photosensitive drum 1 and the developing section in the exposure by the laser exposure unit 3 shown in FIG. be. The horizontal axis of FIG. 7 indicates the value of the back contrast. The vertical axis in FIG. 7 indicates the amount of decrease in the surface potential of the photosensitive drum 1, as in FIG. A condition in which the rotation speed ratio between the photosensitive drum 1 and the developing roller 41 is 200% is used. As shown in FIG. 7, the amount of decrease in the surface potential of the photosensitive drum 1 increased as the back contrast increased. This is because when the back contrast is increased, the potential difference between the developing voltage applied to the developing roller 41 and the surface potential of the photosensitive drum 1 increases, so that the charge on the photosensitive drum 1 flows to the developing roller 41 more easily. . This result means that when detecting a current, increasing the back contrast increases the current value, thereby increasing the detection accuracy. Therefore, when executing the cartridge detection method, which will be described later, it is desirable to increase the back contrast as much as possible. Specifically, if the back contrast is made larger at the time of determining whether the cartridge is attached or not than at the time of image formation, the accuracy is further improved. In this embodiment, the dark area potential Vd during image formation is -560V, and the development voltage Vdc is -360V. Therefore, it is preferable that the back contrast at the time of judging whether or not the cartridge is attached is greater than 200V. At this time, even if the absolute value of the developing voltage applied to the developing roller 41 when judging whether or not the cartridge is installed is smaller than that during image formation, the absolute value of the surface potential of the photosensitive drum 1 immediately before entering the developing section is increased. You may That is, the absolute value of the charging voltage applied to the charging roller 2 may be increased. However, if the back contrast is increased too much, the reverse polarity toner charged to the opposite polarity of the normal polarity among the toner carried on the developing roller 41 develops on the photosensitive drum 1, causing fogging. There are things that can happen. Therefore, the back contrast should be appropriately set in consideration of these factors.

Based on the above results, set values for the rotational speed difference and the back contrast when executing the cartridge presence/absence detection are considered. Since the rotation speed ratio is 170% and the back contrast is 200 V during image formation, the surface potential drop amount of the photosensitive drum 1 is 23 V and the detected current amount is 1.16 μA from the relationships shown in FIGS. On the other hand, when detecting the presence or absence of a cartridge, both the rotation speed ratio and the back contrast are made larger than those during image formation. For example, when the rotation speed ratio is set to 200% and the back contrast is set to 300V, the surface potential drop amount of the photosensitive drum 1 is 42V and the detected current amount is 2.12 μA. This will increase the current sensing accuracy. In this embodiment, current detection is performed when cartridge presence/absence detection is performed.

5. Method for Detecting Attachment of Drum Cartridge and Developing Cartridge A process for detecting the current flowing through the developing roller 41 and determining the attachment state of the drum cartridge 10 and the developing cartridge 20 to the apparatus main body 100 will be described below. FIG. 8 is a flowchart for explaining a method for detecting whether or not a cartridge is attached to the image forming apparatus 100, which is executed by the control unit 202 provided in the image forming apparatus 100. As shown in FIG.

As a condition (S-1) for starting detection of whether or not the cartridge is mounted, there is a case where it is impossible to determine whether or not the cartridge is mounted, such as when the image forming apparatus main body 100 is powered on. In such a case, first, the open/closed state detection switch detects "closed" as the opening/closing door (not shown) for inserting each cartridge is opened/closed and the power supply of the apparatus main body 100 is turned on (S-2). When "closed" is detected, the photosensitive drum 1 of the image forming apparatus 100 starts rotating, and a charging voltage is applied to the charging roller 2 to uniformly charge the surface of the photosensitive drum 1 (S-3). Thereafter, a developing voltage is applied to the developing roller 41, and the developing roller 41 is exposed by the developing contact/separating cam 45 while the developing roller 41 is separated from the photosensitive drum 1 while the photosensitive drum 1 is driven to rotate. It is brought into contact with the drum (S-4). Then, the developing current flowing through the developing roller 41 is detected, and if a current of a predetermined amount or more flows, it is determined that both the drum cartridge 10 and the developing cartridge 20 are installed (S-5). After that, the development roller 41 is separated from the photosensitive drum 1 by using the development contact/separation cam 45, and the development voltage power source 40 applied to the development roller 41 is stopped (S-6). Then, the charging voltage power supply 30 applied to the charging roller 2 is stopped, and the rotational drive of the photosensitive drum 1 is stopped (S-7). With the above operation, the detection of whether or not the cartridge is installed is completed (S-8).

Next, a specific cartridge determination method will be described with reference to FIGS. 9 and 10. FIG. FIG. 9 is a flow chart showing in more detail the content of the flow chart of FIG. 8, and FIG. 10 is a timing chart showing sensing operations and sensed current signals.

Detecting whether or not the cartridge is installed is started (S-11), and in a state where the charging voltage is applied and the photosensitive drum 1 is driven (S-12), the developing roller 41 to which the developing voltage is applied is brought into contact with the photosensitive drum 1. (S-13). At this time, the developing current flowing through the developing roller 41 is detected (S-14). A method for determining whether or not a cartridge is mounted in current detection will be described in detail. In FIG. 10, when it is determined that the drum cartridge 10 and the developing cartridge 20 are installed, the detected current is not detected when the photosensitive drum 1 rotates in the main body operation, but the developing roller 41 contacts the photosensitive drum 1 . As soon as they come into contact with each other, current begins to flow. After that, the current continues to be detected as long as development contact is being performed. Therefore, in FIG. 9, if the absolute value of the developing current I1 is greater than 0, it is determined that the drum cartridge 10 and the developing cartridge 20 are attached to the apparatus main body. On the other hand, if it is equal to 0, it means that there is no change in the current, so it is determined that the developing roller 41 is not in contact with the photosensitive drum 1, that is, the drum cartridge 10 and the developing cartridge 20 are not attached to the main body of the apparatus. do. After that, the non-mounting notification of the drum cartridge 10 and the developing cartridge 20 is performed (S-18). At this time, the threshold value of the current value of the developing current I1 must be a threshold value indicating that the drum cartridge 10 and the developing cartridge 20 are not installed. In this embodiment, when the development current detection means 17 does not detect the detection current, it is determined that the drum cartridge 10 and the development cartridge 20 are not installed. However, the threshold value is not limited to 0, and a separate threshold value may be set in consideration of variations. When it is determined in (S-14) that the drum cartridge 10 and the developing cartridge 20 are installed (S-15), the developing roller 41 is separated from the photosensitive drum 1 by using the developing contact/separating cam 45. (S-16). Then, the developing voltage power supply 40 applied to the developing roller 41, the charging voltage power supply 30 applied to the charging roller 2, and the rotational driving of the photosensitive drum 1 are stopped (S-17). If it is determined that the drum cartridge 10 and the developing cartridge 20 are installed, the operation is completed (S-18) to prepare for the image forming operation.

As described above, detection of the presence of the drum cartridge 10 and detection of the presence of the development cartridge 20 can be performed simultaneously by detecting the development current I1. In this embodiment, detection can be performed by detecting a change in the development current I1 when the development cartridge 20 abuts. More specifically, when the developing cartridge 20 is installed or not, the photosensitive drum 1 is rotated and a voltage is applied to the charging roller 2 and the developing roller 41 . , the mounting state of the developing cartridge 20 is discriminated.

Further, in this embodiment, the image forming apparatus with two cartridges is described, but the presence or absence of the cartridge can also be detected by the same method in the image forming apparatus in which the drum cartridge 10 and the developing cartridge 20 are integrated. . The presence/absence detection of the integrated cartridge can be performed by determining the presence/absence of the cartridge by the current detection of (S-14) in FIG.

Further, in the configuration of this embodiment, it is effective to have a mechanism for detecting the drum cartridge 10 by another method, or to implement a configuration in which the drum cartridge 10 is tied to the main body. That is, in a configuration that determines whether or not only the developing cartridge 20 is attached after detecting that the photosensitive drum 1 is attached to the image forming apparatus main body 100, it is possible to determine whether or not the developing cartridge 20 is attached with a simple configuration. Suitable for

In Example 1, the current flowing through the developing roller 41 in the developing section is detected by the developing current detecting means 17 to determine whether or not the drum cartridge 10 and the developing cartridge 20 are attached at the same time. In the method of the first embodiment, whether or not the drum cartridge 10 is attached or not is detected separately, or whether or not the drum cartridge 10 and the developing cartridge 20 are attached is detected unless the image forming apparatus 100 is attached to the image forming apparatus 100 . cannot be determined individually. Specifically, when the development current is not detected by the development current detection means 17 in the first embodiment, it is known that the development roller 41 is not in contact with the photosensitive drum 1, but whether or not the drum cartridge 10 is attached is detected. cannot be determined. Therefore, in the second embodiment, when the developing roller 41 contacts the photosensitive drum 1, the absolute value of the surface potential of the photosensitive drum 1 decreases. A method that enables determination will be described. Although the current flowing through the developing roller 41 is detected in the first embodiment, the current flowing through the charging roller 2 and the transfer roller 5 is detected in this embodiment. Since the configurations of the image forming apparatus and the developing cartridge are the same as those described in the first embodiment, description thereof is omitted.

1. Utilization of Decrease in Surface Potential of Photoconductive Drum in Developing Section As described in Embodiment 1, when there is a difference in rotational speed between the photosensitive drum 1 and the developing roller 41 and there is a potential difference, the surface potential of the photosensitive drum 1 in the developing section is reduced. The charges formed in , move to the developing roller 41 . Therefore, the dark area potential Vd, which is the surface potential of the photosensitive drum 1, is lowered. Therefore, it means that the surface potential on the photosensitive drum 1 differs depending on whether or not the developing roller 41 is in contact. Here, if the surface potential of the photosensitive drum 1 is different, the current value of the current generated by charging will be different. This current is detected by charging current detection means connected to the charging roller 2 according to the layout shown in FIG. can be done. That is, by using this method, it is possible to individually determine whether or not a drum cartridge 10 and a developing cartridge 20, which will be described later, are attached.

2. Method for Detecting Attachment of Drum Cartridge and Developing Cartridge The process of detecting the current flowing through the charging roller 2 and separately determining the attachment state of the drum cartridge 10 and the developing cartridge 20 will be described below. FIG. 11 is a flowchart for explaining a method for detecting whether or not each cartridge is attached to the image forming apparatus 100, which is executed by the control unit 202 provided in the image forming apparatus 100. FIG.

When cartridge installation detection is started (S-21), first, the open/closed state detection switch is turned "closed" in accordance with the opening/closing operation of an opening/closing door (not shown) for inserting each cartridge and the power supply of the apparatus main body 100 being turned on. ” is detected (S-22). When "closed" is detected, the photosensitive drum 1 of the image forming apparatus 100 starts rotating, and a charging voltage is applied to the charging roller 2 to uniformly charge the surface of the photosensitive drum 1 (S-23). Then, the charging current flowing through the charging roller 2 is detected to determine whether or not the drum cartridge 10 is attached (S-24). After determining whether or not the drum cartridge 10 is attached, the process proceeds to detection of the developing cartridge 20 . The operation of the developing roller 41 starts when it is separated from the photosensitive drum 1. In the separated state, a developing voltage is applied to the developing roller 41, and while the photosensitive drum 1 is being driven to rotate, the developing roller 41 is brought into contact with the developing roller. The contact/separation cam 45 is brought into contact with the photosensitive drum 1 (S-25). Based on the relationship between the dark area potential Vd, which is the surface potential of the photosensitive drum 1 at this time, and the developing voltage Vdc, a change in the amount of charging current is detected to determine whether or not the developing cartridge 20 is attached (S-26). After determining whether or not the developing cartridge 20 is attached, the developer contact/separation cam 45 is returned to the separated position, and the voltage applied to the developing roller 41 is stopped (S-27). After that, the voltage applied to the charging roller 2 and the rotational driving of the photosensitive drum 1 are stopped (S-28). By the above operation, the detection of whether or not the drum cartridge 10 and the developing cartridge 20 are attached is completed (S-29).

Next, a specific cartridge determination method will be described with reference to FIGS. 12 and 13. FIG. FIG. 12 is a flow chart showing in more detail the contents of the flow chart of FIG. 11, and FIG. 13 is a timing chart showing the detection operation and the detection current signal.

Detecting whether or not the cartridge is attached is started (S-31), and in a state where the photosensitive drum 1 is driven by applying a charging voltage (S-32), the developing roller 41 is moved away from the photosensitive drum 1 by using the developing contact/separation cam 45. Separate them (S-33). In this state, the charging current I2 flowing through the charging roller 2 is detected (S-34). 20 (S-35). The detection of the charging current I2 and the determination of whether or not the drum cartridge 10 is installed in (S-34) will be described in detail. As shown in FIG. 13, when the drum cartridge 10 is present, the detection current I2 flows more in the initial stage of rotation as the photosensitive drum 1 rotates during the operation of the main body. Normally, when this sequence is executed, the surface potential of the photosensitive drum 1 is close to zero because a sufficient amount of time has passed since the previous driving. Therefore, the electric charge (current) required to set the dark potential Vd from this state flows into the photosensitive drum 1, so that a large amount of current flows at the beginning of rotation. Even after the potential formation is performed once, the current is detected, but this current is supplied because the surface potential of the photosensitive drum 1 decreases due to dark decay or the like, and is a very small current. In this embodiment, this minute current is set as the threshold value I0. Therefore, in FIG. 13, if the current value I2 of the charging current is larger in absolute value than the threshold value I0, it is determined that the drum cartridge 10 is mounted. If the current value I2 of the charging current is smaller in absolute value than the threshold value I0, it is determined that the drum cartridge 10 is not mounted. At that time, the charging voltage power supply 30 applied to the charging roller 2 is stopped, the rotational drive of the photosensitive drum 1 is stopped, and the drum cartridge 10 non-mounting notification is performed (S-41). The threshold I0 of the current value of the charging current I2 must be a threshold indicating that the drum cartridge 10 is not mounted. Instead of setting the threshold value I0 as in this embodiment, it may be determined that the drum cartridge 10 is not installed when the current is not detected by the detection means. The threshold value I0 is a current value detected by the detecting means when the developing roller 41 is separated from the photosensitive drum 1 and the photosensitive drum 1 is rotated with a voltage applied to the charging roller 2 by the charging voltage power supply 30. It is preferable to If the drum cartridge 10 is mounted, the surface potential of the photosensitive drum 1, which has been charged once by the charging roller 2, is rotated, and when the potential is formed again, the surface potential that has decreased by the amount of dark attenuation is returned to the original potential. A minute electric current flows due to the weak discharge that occurs at that time. On the other hand, even that does not occur when the drum cartridge 10 is not attached. Therefore, even if some noise is detected, it can be considered that the drum cartridge 10 is not mounted if the current value considering the dark decay, that is, is less than the threshold value. This threshold value I0 can also be applied to whether or not the developing cartridge 20 is mounted, which will be described later.

Next, detection of whether or not the developing cartridge 20 is attached will be described. While the charging voltage is applied and the photosensitive drum 1 is driven, the development contact/separation cam 45 is moved to the contact state (S-36). At this time, the current I3 flowing through the charging roller 2 is detected when the surface of the photosensitive drum 1 with which the developing roller 41 abuts reaches the position of the charging roller 2 by rotation (S-37). When I3 is compared with the threshold value I0 and the amount of charging current increases due to the contact operation, it means that the contact of the developing roller 41 with the photosensitive drum 1 has caused a decrease in the absolute value of the dark potential Vd. It is determined that the cartridge 20 is attached. That is, by calculating the difference between I3 and I0, it is possible to determine whether or not the developing cartridge 20 is attached. The charging current I3 is the voltage applied to the charging roller 2 and the surface potential of the photosensitive drum 1 when the surface potential of the photosensitive drum 1 decreases as described above, and the voltage applied to the charging roller 2 when the charging roller 2 is charged again. It is detected because the potential difference of the potential Vd increases. On the other hand, if there is no change in the amount of charging current even after the contacting operation is performed, it means that the developing roller 41 is not in contact with the photosensitive drum 1. Therefore, it is determined that the developing cartridge 20 is not attached, and the developing cartridge 20 is removed. A non-wearing notification is performed (S-42). When it is determined in (S-37) that the developing cartridge 20 is attached (S-38), the separating operation of the developing cartridge 20 is performed, and then the voltage applied to the developing roller 41 is stopped. (S-39). Then, the voltage applied to the charging roller 2 and the rotational driving of the photosensitive drum 1 are stopped (S-40), and detection of whether or not the developing cartridge 20 is installed is completed (S-43) to prepare for the image forming operation.

The flow chart shown in FIG. 13 can be summarized as follows. First, as a first step, the development contact/separation cam 45 performs a separating operation for separating the developing roller 41 from the photosensitive drum 1 , rotating the photosensitive drum 1 , and applying a voltage to the charging roller 2 and the developing roller 41 . to detect the current value. Next, as a second step, a contact operation is performed to bring the developing roller 41 into contact with the photosensitive drum 1, a current value is detected, and the detected current value and the current value detected in the first step are compared. Based on this, the mounting state of the developing cartridge is discriminated. Subsequently, as a third step, the development separation operation is performed, and the development voltage, the charging voltage, and the rotation operation of the photosensitive drum 1 are respectively stopped to prepare for image formation.

As described above, it is possible to determine whether or not the developing cartridge 20 is attached by detecting the charging current I3. A current value detected when the development contact/separation cam 45 is controlled by the control unit 202 to separate the development, and a time when the surface of the photosensitive drum 1 in development contact in the development unit reaches the charging unit of the charging roller 2. Whether or not the developing cartridge 20 is attached is determined from the detected current value. That is, the mounting state of the developing cartridge 20 is determined from the current value detected in the first step and the current value detected in the second step. At that time, it may be determined that the developing cartridge 20 is not installed when the current value does not change, or it may be determined that the developing cartridge 20 is not installed when the absolute value is smaller than the threshold value I0. . It is assumed that the set threshold value I0 is a current value detected when the photosensitive drum 1 is rotated and a voltage is applied to the charging roller 2 while the charging roller 2 is separated for development. Whether or not the developing cartridge 20 is attached is determined by comparing the current values in the two states of development contact and development separation. Further, as for the current value at the time of separation from development, a value stored in the memory 156 in advance may be used instead of the sequential measurement.

As described above, by detecting the charging currents I2 and I3, it is possible to separately detect whether or not the drum cartridge 10 is attached and whether or not the developing cartridge 20 is attached. In particular, in detecting whether or not the developing cartridge 20 is attached, determination can be made by detecting the charging current I3 when the developing cartridge 20 abuts. The current detected by the detection means when the photosensitive drum 1 in the apparatus main body 100 is rotated with the charging roller 2 applied with a charging voltage, and the area forming the developing portion on the surface of the photosensitive drum 1 reaches the charging portion. The mounting state of the developing cartridge 20 is determined according to the value.

(Modification 1)
In Example 1, whether or not the drum cartridge 10 and the developing cartridge 20 are attached is detected by detecting the charging current. However, the current detection based on the potential change of the photosensitive drum 1 can obtain the same result even if it is performed with a current other than the charging current. As Modified Example 1, a case in which the transfer current is detected instead of the charging current is detected will be described. By detecting the transfer current as well, the drum cartridge 10 and the developing cartridge 20 can be detected separately, similarly to the detection of the charging current. In detecting the transfer current, the detecting means is arranged so as to be directly connected to the transfer roller 5 according to the layout shown in FIG. A description of the method of detecting whether or not the cartridge is mounted using the transfer current is omitted because the part using the charging current described in the second embodiment is replaced with the transfer current. In the detection based on the transfer current as well as the detection based on the charging current, the presence/absence detection of the drum cartridge 10 and the presence/absence detection of the developing cartridge 20 can be performed separately. In particular, detection of the presence or absence of the developing cartridge 20 can be performed by detecting a change in the transfer current when the developing cartridge 20 abuts. Specifically, the photosensitive drum 1 is located in the main body 100 of the apparatus, and the transfer roller 5 is rotated with a transfer voltage applied. The mounting state of the developing cartridge 20 is determined according to the current value detected by . In the second embodiment, the charging voltage is applied to the charging roller 2. However, when detecting the presence or absence of the cartridge using the transfer roller 5, it is not necessary to apply the charging voltage as long as the transfer voltage is applied to the transfer roller 5. .

1. Image Forming Apparatus FIG. 14 is a diagram showing a schematic configuration of an image forming apparatus 200 as a third embodiment according to the present invention. The image forming apparatus 200 in this embodiment is a full-color image forming apparatus in which four unit cartridges are mounted. The four unit cartridges accommodate different colors of toner, namely, the three primary colors of yellow, magenta, and cyan, plus black. The unit cartridge is composed of a drum cartridge 110 and a developing cartridge 120, similar to the cartridge configuration of the first embodiment, and has a dual cartridge configuration in which the two cartridges can be separately attached to and detached from the apparatus main body 200. FIG.

The image forming apparatus 200 has a plurality of image forming stations, which are image forming units that accommodate cartridges corresponding to toner colors. The yellow station (Y), magenta station (M), cyan station (C), and black station (K) are arranged in this order from the left side of FIG. 14, and cartridges of colors corresponding to image forming stations are accommodated. In this embodiment, a uniform notation is used for multiple elements for each of the colors yellow, magenta, cyan, and black. Since the configuration of each image forming station is the same except for the color of the toner contained therein, one image forming station will be representatively described in the description of the image forming stations.

Embodiments 1 and 2 are referred to for the description of the developing cartridge 120 and the description of the decrease in the surface potential of the photosensitive drum 101 due to the difference in rotational speed. In this embodiment, an image forming operation and a method for detecting whether or not the drum cartridge 110 and the developing cartridge 120 are attached will be described.

The image forming operation will be described below. When the image forming operation is started, the photosensitive drum 101 is rotationally driven in the direction of the arrow in FIG. 14 by the driving motor of the photosensitive drum 101 . A charging roller 102 that charges the surface of the photosensitive drum 101 is applied with a negative voltage at a predetermined timing from a charging voltage power supply 130 shown in the block diagram of FIG. 15, and the surface of the photosensitive drum 101 is uniformly negatively charged. . In this embodiment, the voltage applied to the charging roller 102 is supplied from a single power supply regardless of the image forming station, so the same charging voltage is applied to the charging roller 102 .

In this embodiment, the laser exposure unit 103 that exposes the charged photosensitive drum 101 performs non-image area exposure by laser irradiation even on a so-called white background area, which is a non-image area with no image data. This operation is called background exposure. The white background portion referred to here is a portion of the dark portion potential Vd formed on the surface of the photosensitive drum 101 . The intensity of laser irradiation to the white background portion is sufficiently weak exposure compared to the image portion having the image data. The surface potential formed on the photosensitive drum 101 by this weak exposure is set to a large absolute value with respect to the development voltage Vdc. For this reason, toner development is not performed in the background exposure portion, which is the exposure area for the white background portion, and the white background, which is the non-image forming portion, can be maintained. By performing laser exposure on the white background portion as well, the surface potential of the photosensitive drum 101 at the developing portion where the photosensitive drum 101 and the developing roller 143 are in contact can be arbitrarily changed for each image forming station. Details of the background exposure will be described later.

Developing cartridge 120 applies developing voltage Vdc from developing voltage power source 141 shown in FIG. Develop with toner. As with the charging voltage, the developing voltage Vdc is also applied from the developing voltage power source 141 at a constant voltage regardless of the image forming station.

The toner image visualized on the photosensitive drum 101 is then sent to the transfer section. A toner image is primarily transferred onto an endless intermediate transfer belt 150, which is an intermediate transfer member, at the transfer portion. In the transfer section, a primary transfer roller 151 is arranged substantially opposite the photosensitive drum 101 with the intermediate transfer belt 150 interposed therebetween. The intermediate transfer belt 150 is arranged so as to be in contact with the photosensitive drums 101 respectively, and the surface resistivity of the outer peripheral surface thereof is 1×10 ¹¹ (Ω/□) when measured with 100 V applied. The intermediate transfer belt 150 has a thickness of 100 to 200 (μm), and is an endless resin film made of PVdf (polyvinylidene fluoride), nylon, PET (polyethylene terephthalate), PC (polycarbonate), or the like. A transfer voltage is applied to the primary transfer roller 151 by the primary transfer voltage power source 142 shown in FIG. The toner images formed on the photosensitive drums 101 at the respective image forming stations are sequentially superimposed on the intermediate transfer belt 150 at a predetermined timing, thereby forming a multiple toner image on the intermediate transfer belt 150 in which the toners of each color are layered. can do A driving portion 152 of the intermediate transfer belt 150 rotates to move the multiple toner image formed on the intermediate transfer belt 150 toward a contact portion with a secondary transfer roller 160 which is a secondary transfer portion. The recording material P starts to be supplied toward the contact portion with the secondary transfer roller 160 which is arranged in pressure contact with the intermediate transfer belt 150 so as to synchronize with the multiple toner image sent by the intermediate transfer belt 150 . be done. A secondary transfer voltage is applied to the secondary transfer roller 160 from the secondary transfer voltage power supply 161 shown in FIG. Secondarily transferred on top. After that, the recording material P is passed through the fixing device 170, where the toner image is fixed on the recording material P by heating and pressurization, and the recording material P is discharged.

After the toner image has been primarily transferred from the photosensitive drum 101 to the intermediate transfer belt 150, the residual toner or the like on the photosensitive drum 101 is removed by a cleaning blade 106 and collected and stored in a waste toner container. . Secondary transfer residual toner and the like on the intermediate transfer belt 150 are removed and cleaned by the intermediate transfer belt cleaning device 180 .

The toner or the like removed by the intermediate transfer belt cleaning device 180 is conveyed to a waste toner collecting container (not shown) attached to the image forming apparatus 200 by a rotary conveying member (not shown) arranged in the image forming apparatus 200 . , is recovered.

In this manner, the photosensitive drum 101 and the intermediate transfer belt 150 are cleaned by the cleaning blade 106 and the intermediate transfer belt cleaning device 180 to remove residual toner, etc., to prepare for the next image formation.

Further, the developing cartridge 120 performs a contact/separation operation, which is a contact/separation operation with respect to the photosensitive drum 101, in accordance with the image forming operation. This contact/separation operation is performed by the operation of the development contact/separation lever 145 which is the development contact/separation mechanism of the image forming apparatus 200 . 14, the developer contact/separation lever 145 moves left and right with respect to the protrusion of the developer cartridge 120, and is caught by the protrusion of the developer cartridge 120, causing the development roller 143 to contact the surface of the photosensitive drum 101. It is possible to make contact and separation.

FIG. 15 is a block diagram showing a schematic control mode of the main part of the image forming apparatus 200 in this embodiment. The controller 300 exchanges various electrical information with the host apparatus, and controls the image forming operation of the image forming apparatus 200 by the control unit 290 via the interface 301 according to a predetermined control program and reference table. control effectively. The control unit 290 includes a CPU 251 which is a central element for performing various arithmetic processing, a memory 252 such as a ROM and a RAM which are storage elements, and the like. The control unit 290 controls transmission and reception of various electrical information signals, timing of driving each unit, and the like, and controls a predetermined image forming sequence. For example, the voltage and exposure amount applied by the charging voltage power supply 130, the development voltage power supply 141, the laser exposure unit 103, the primary transfer voltage power supply 142, and the secondary transfer voltage power supply 161, the contact/separation operation by the development contact/separation lever 145, etc. image forming sequence. In this embodiment, the control section 290 also controls the determining means for determining whether the developing cartridge 120 or the drum cartridge 110 is installed.

Further, although the present embodiment adopts the configuration of the intermediate transfer member using the belt member, the recording material P is conveyed on the belt, and the recording material P is directly transferred at the transfer portion where the photosensitive drum 1 and the belt member are in contact with each other. You may adopt the form which transcribe|transfers to.

2. Background Exposure Background exposure will be described. Background exposure has the advantage that the surface potential of the photosensitive drum 101 in the developing section can be made uniform regardless of the image forming station, even if the charging potential differs for each image forming station. A specific mode of background exposure is non-image area exposure in which the laser exposure unit 103 exposes the photosensitive drum 101 charged by the charging roller 102 to form a surface potential that does not form a toner image. The amount of exposure is small, unlike the image area exposure that is larger than the exposure amount of the non-image area exposure in order to form a surface potential for forming a toner image. Even if the surface potential of the photosensitive drum 101 after charging varies, the surface potential of the photosensitive drum 101 can be appropriately set by performing background exposure. Therefore, by this background exposure, even if the charging voltage and the developing voltage Vdc are applied as constant voltages regardless of the image forming station in the color image forming apparatus 200, the same potential relationship can be maintained uniformly in the developing section. In other words, high-quality image formation can be output even in a cost-reduced main body in which the number of high-voltage elements is reduced.

3. Method for Detecting Attachment of Drum Cartridges and Developing Cartridges FIG. 16 is a timing chart showing a flow for individually detecting the attachment states of the drum cartridge 110 and the developing cartridge 120 for each image forming station in the image forming apparatus 200 having a plurality of cartridges. are shown in FIGS. 17 and 18 and will be described in detail below. Since the method for determining the mounting state of the cartridge is the same as the method shown in the second embodiment, the description is omitted.

FIG. 16 is a flow chart illustrating a method for detecting whether or not the drum cartridge 110 and the developing cartridge 120 are installed in each image forming station of the image forming apparatus 200, which is executed by the control unit 290 provided in the image forming apparatus 200. FIG. .

When cartridge installation detection is started (S-51), first, the open/closed state detection switch is turned "closed" in accordance with the opening/closing operation of an opening/closing door (not shown) for inserting each cartridge and the power supply of the apparatus main body 100 being turned on. ” is detected (S-52). When "closed" is detected, the photosensitive drum 1 of the image forming apparatus 100 starts rotating, and a charging voltage is applied to the charging roller 2 to uniformly charge the surface of the photosensitive drum 1 (S-53). Here, the applied charging voltage is a constant voltage regardless of the image forming station. However, the image forming station has different usage conditions and the thickness of the charge transport layer of the photosensitive drum 101. Therefore, the dark potential Vd formed on the photosensitive drum 101 differs from image forming station to image forming station.

Therefore, after the surface potential of the photosensitive drum 101 is sufficiently stabilized, background exposure is sequentially performed for each image forming station to match the surface potential of the photosensitive drum 101 (S-54). At this time, the developing roller 143 is separated from the photosensitive drum 101 . When the surface of the photosensitive drum 101 subjected to background exposure of each image forming station reaches the charging unit, charging current detection is performed to detect the current flowing through the charging voltage power source 130 of the charging roller 102 . The charging current detecting means (not shown) in this embodiment is connected to a common charging voltage power source 130, and detects the sum of the charging currents in all the image forming stations. Therefore, if the background exposure is performed at the same timing for all the image forming stations, it will be impossible to know which image forming station the signal is from. Therefore, it is possible to specify the position of the image forming station according to the timing by performing background exposure at different times for each image forming station. In the current detection when the background exposure is sequentially performed at each image forming station, the presence or absence of the drum cartridge 110 is detected by matching the exposure timing and charging current change timing of each image forming station (S -55).

In more detail, detection of whether or not the drum cartridge 110 is attached will be described with reference to the timing chart of FIG. FIG. 17 is a timing chart for explaining the above (S-51) to (S-55). FIG. 17 shows a timing chart when only the drum cartridge 110C of the cyan station C is not installed. At (S-53), a charging voltage is applied, and current flows as the photosensitive drum 101 is driven. This is because, as described in the second embodiment, the charge (current) required to bring the surface of the photosensitive drum 101 whose potential has been sufficiently lowered to the dark potential Vd flows into the photosensitive drum 1 . Although the current is still detected after that, it is a very small current that is supplied because the surface potential of the photosensitive drum 1 decreases due to dark decay or the like. Subsequently, in (S-54), background exposure is performed in order of yellow, magenta, cyan, and black. When the surface of the photosensitive drum 101 is exposed to light, the surface potential is lowered, and the photosensitive drum 101 is supplied with a current corresponding to the lowered potential. Therefore, a charging current corresponding to a decrease in the surface potential of the photosensitive drum 101 due to exposure is detected. Charging currents corresponding to background exposure performed at each image forming station are not always the same. This is because the amount of background exposure performed for each image forming station is different depending on the usage conditions and usage environment, and the layer thickness of the charge transport layer of the photosensitive drum 101 is different. In FIG. 17, since the drum cartridge 110C is not installed in the cyan station C, no potential change due to background exposure occurs and no current change is detected. In this embodiment, since the timing of background exposure is shifted for each image forming station, it is possible to determine whether or not the drum cartridge 110 is attached to each image forming station based on the timing at which the current flows. By detecting this charging current, it is possible to determine whether or not the individual drum cartridge 110 is attached in (S-55), as in the method of the second embodiment.

In (S-55), if it is determined that the drum cartridge 110 is not mounted, the rotational driving of the photosensitive drum 101 and the charging voltage are stopped. After that, it is notified that the drum cartridge 110 corresponding to the image forming station is not installed. If the drum cartridges 110 of all the image forming stations are installed, then it is determined whether or not the developing cartridges 120 are installed.

In detecting the developing cartridge 120 after it is determined that the drum cartridge 110 is installed in all the image forming stations, as shown in FIG. A contact operation is performed (S-56). When the developing roller 143 contacts the photosensitive drum 101, the surface potential of the photosensitive drum 101 decreases as described in the first and second embodiments. Due to the contact of the developing roller 143, the current supplied to the charging roller 102 increases. However, the presence or absence of the developing cartridge 120 for each image forming station cannot be determined only by measuring the change in this charging current. Therefore, background exposure is sequentially performed for each image forming station (S-57), and whether or not the developer cartridge 120 is attached is determined (S-58), as in the detection of the drum cartridge 110 after development contact. Whether or not the developing cartridge 120 is attached will be described in detail with reference to the timing chart of FIG. FIG. 18 is a timing chart from (S-56) to (S-56) in the flowchart of FIG. 62). FIG. 18 shows a timing chart when only the developing cartridge 120M of the magenta station M is not installed.

First, when the developing voltage Vdc is applied and the developing roller 143 comes into contact with the photosensitive drum 101 (S-56), the charging current amount increases accordingly. After the development roller 143 comes into contact, background exposure is performed in order from the yellow station Y to the black station K (S-57), in the same manner as the detection of whether or not the drum cartridge 110 is attached. The amount of charging current when the surface of the photosensitive drum 101 subjected to background exposure passes through the developing section and reaches the charging section is detected (S-58). When background exposure is performed, the amount of charging current increases by itself, as described in the attachment/non-attachment detection of the drum cartridge 110, but the surface potential drop caused by the contact of the developing roller 143 is also superimposed. Here, the charging current amount for each image forming station detected in (S-55) (corresponding to I0 in Example 2) and the charging current amount for each image forming station detected in (S-58) (Example 2 (equivalent to I3 in ). The amount of current detected at (S-58) is larger than the amount of current detected at (S-55) due to the increase due to contact with the developer. Therefore, it is determined that the developing cartridge 120 of the image forming station that detected a current larger than the amount of current detected in (S-55) is installed. In FIG. 18, since the developer cartridge 120M of the magenta station M is not mounted, the increase in the charging current when the background exposure of the magenta station M is performed is equivalent to the increased current amount detected in (S-55). becomes. On the other hand, the amount of charging current during background exposure at the yellow, cyan, and black image forming stations is greater than the amount of charging current detected in (S-55).

As described above, background exposure is sequentially performed at each image forming station (S-57), the charging current is detected (S-58), and attachment of the developing cartridge 120 is determined. At (S-58), after determining whether or not the developing cartridge 120 is attached, the developing roller 143 is separated, and the developing voltage Vdc is stopped (S-59). Then, the rotational driving of the photosensitive drum 101 and the charging voltage are stopped (S-60). After the completion of the operation, the detected image forming station is notified when the developing cartridge 120 is not installed. In this embodiment, since the timing of background exposure is shifted for each image forming station, it is possible to determine whether or not the developing cartridge 120 is attached to each image forming station based on the timing at which the current flows. By the above operations, the detection of whether or not the cartridge is installed is completed (S-61), and preparations are made for the image forming operation.

In this embodiment, the charging current is detected in order to detect whether or not the drum cartridge 110 and the developing cartridge 120 are attached. However, the same result can be obtained even if the change in the surface potential of the photosensitive drum 101 is detected by means other than the charging current. Therefore, the detection of the charging current may be performed by detecting the primary transfer current, similarly to the method described in the second embodiment and the first modification. In each cartridge detection based on the primary transfer current, it is possible to detect whether or not the cartridge is attached based on the detection result of the background exposure for each image forming station, similar to the detection of the charging current. By replacing the charging current detection with the transfer current detection, it is possible to separately detect whether or not the drum cartridge 110 is attached and whether or not the developing cartridge 120 is attached.

Further, in this embodiment, the amount of charging current detected when detecting whether or not the developing cartridge 120 is attached is compared with the amount of charging current detected when detecting the drum cartridge 110, and detection is performed. The detection of the presence or absence of the developing cartridge 120 is performed by comparing the detected charging current with the charge amount calculated from the usage history of the photosensitive drum 101 stored in the non-volatile memory (not shown) attached to the drum cartridge 110 . you can go Also, the amount of background exposure does not have to be weak exposure to form the dark potential Vd, and may be exposure to form the bright potential Vl. It may be used as a reference exposure for comparison. Since the developing roller 143 is separated when the presence or absence of the drum cartridge 110 is detected, toner development is not performed even if the photosensitive drum 101 is exposed. Therefore, it is possible to detect whether or not the drum cartridge 110 is attached by normal exposure.

In this embodiment, the charging voltage, the developing voltage Vdc, and the primary transfer voltage are applied uniformly from a single power supply regardless of the image forming station. A configuration in which individual settings can be made is also possible. An optimal cartridge detection method can be used in an image forming apparatus in which each voltage can be set individually for each image forming station. For example, consider an image forming apparatus 200 in which the charging voltage is a common output but background exposure is not performed and the developing voltage Vdc can be set for each image forming station. In detecting whether or not the developing cartridge 120 is attached, a method can be used in which the developing roller 143 is brought into contact with the photosensitive drum 101 and background exposure is not performed for each image forming station. Since the developing voltage Vdc can be changed for each image forming station, the developing voltage Vdc can be appropriately changed for each image forming station to detect the charging current or transfer current. From the current value at this time, the developer cartridge 120 can be detected for each image forming station.

Also in the full-color image forming apparatus 200 of this embodiment, as in the first embodiment, by detecting the development current, it is possible to simultaneously detect whether or not the drum cartridge 110 and the development cartridge 120 are attached.

An image forming apparatus as a fourth embodiment according to the present invention has the same configuration as the schematic diagram shown in FIG. The difference from the image forming apparatus of the third embodiment is that the contact/separation of the developing roller 143 is performed sequentially in the order of yellow, magenta, cyan, and black. As in this embodiment, when development contact and separation are sequentially performed, the contact state in the area not involved in image formation can be minimized, and damage due to contact between the photosensitive drum 101 and the developing roller 143 can be minimized. can be suppressed. In this embodiment, the method of detecting the drum cartridge 110 and the developing cartridge 120 will be explained, and the image forming operation, the developing cartridge 120, and the background exposure will be explained in the second and third embodiments. invoke.

1. Method for Detecting Attachment of Drum Cartridge and Developing Cartridge FIG. 19 shows a timing chart of main body operation and charging current detection in detecting the attachment of the developing cartridge 120, and will be described in detail below. In the fourth embodiment, the method for detecting whether or not the drum cartridge 110 is attached is the same as in the third embodiment, so the description is omitted.

After determining whether or not the drum cartridges 110 of all the image forming stations are installed, whether or not the developing cartridges 120 are installed is determined. In detecting the developing cartridge 120 after determining whether the drum cartridge 110 is attached or not, first, the developing voltage Vdc is applied, and the developing roller 143 is brought into contact with the photosensitive drum 101 . When the developing roller 143 contacts the photosensitive drum 101, the surface potential of the photosensitive drum 101 decreases as described in the first and second embodiments. In this embodiment, the contact of the developing roller 143 is performed sequentially for each image forming station. Therefore, it is possible to detect whether or not the developing cartridge 120 is attached to each image forming station by matching the contact timing with the charging current change. Detecting whether or not the developing cartridge 120 is attached will be described with reference to FIG. FIG. 19 is a timing chart from a state in which it is determined that the drum cartridges 110 of all the image forming stations have been installed after completion of detection of whether or not the drum cartridges 110 are installed. When the controller 290 sends a contact signal for the developing roller 143 , the developing roller 143 of each image forming station sequentially contacts the photosensitive drum 101 . The contact of the developing roller 143 in this embodiment advances in order of yellow, magenta, cyan, and black. This is because the image forming operation starts in this order. As the developing roller 143 sequentially contacts the photosensitive drum 101, the amount of charging current increases accordingly. Therefore, by detecting changes in contact timing and charging current for each image forming station, it is possible to detect whether or not the developing cartridge 120 is attached. When the developing cartridges 120 are attached to all the image forming stations, an increase in charging current is detected at the same timing as the contact timing. If, as shown in FIG. 19, the developing cartridge 120M of the magenta station M is not installed, the increase in the amount of current that should increase due to the contact of the developing roller 143 is not detected. Therefore, it can be detected that the magenta developing cartridge 120M is not mounted. As described above, in this embodiment, the presence or absence of the developing cartridge 120 is detected by associating the contact timing and the charging current for each image forming station. When it is determined that the developing cartridge 120 is not attached, the developing roller 143 is separated, and then the rotation of the photosensitive drum 101, the developing voltage Vdc, and the charging voltage are stopped. Then, it notifies that the developing cartridge 120 of the detected image forming station is not installed. When the attachment of the developing cartridge 120 is detected in all the image forming stations, the separating operation of the developing roller 143 is performed. Then, the rotational driving of the photosensitive drum 101, the developing voltage Vdc, and the charging voltage are stopped, the detection operation is completed, and preparations for image formation are made.

In this embodiment, as in the second and third embodiments, the same result can be obtained even if the change in the surface potential of the photosensitive drum 101 due to contact is detected by the transfer current.

Further, in this embodiment, the background exposure is performed and synchronized with the development contact/separation, but the background exposure may not be performed. By changing the development contact/separation timing for each image forming portion, it is possible to directly determine whether or not the development cartridge 120 is attached.

REFERENCE SIGNS LIST 1 photosensitive drum 2 charging roller 3 laser exposure unit 5 transfer roller 10 drum cartridge 20 developing cartridge 41 developing roller P recording material

Claims (20)

a device body;
a rotatable image carrier;
a charging member that forms a charging section together with the image carrier in contact with the image carrier and charges the image carrier in the charging section;
A developing cartridge comprising a developing member forming a developing portion together with the image carrier in contact with the image carrier, and developing a toner image by supplying toner onto the surface of the image carrier in the developing portion. a developing cartridge that can be attached to and detached from the apparatus main body in a state in which the image carrier and the charging member are in the apparatus main body;
a charging voltage applying means provided in the apparatus main body for applying a charging voltage to the charging member;
a detecting means for detecting a current value of the current flowing through the charging voltage applying means;
a control unit that controls the charging voltage applying means,
When the image carrier is in the apparatus main body, the image carrier that may form the developing section in a state in which the charging voltage is applied to the charging member while the image carrier is rotated. notifying that the developing cartridge is not installed in the apparatus main body according to the current value detected by the detecting means when the area of the surface of the image carrier reaches the charging section due to the rotation of the image carrier. An image forming apparatus characterized by: a contact/separation mechanism for moving between a contact position where the developing member contacts the image carrier in the developing unit and a separation position where the developing member is separated from the image carrier;
When the image carrier is in the apparatus main body, the image carrier is rotated, the charging voltage is applied to the charging member, and the contact/separation mechanism is moved to the contact position. In response to the current value detected by the detecting means when the area of the surface of the image carrier that may form a portion reaches the charging portion due to the rotation of the image carrier, the main body of the apparatus 2. The image forming apparatus according to claim 1, wherein the image forming apparatus notifies that the developing cartridge is not installed. The current value detected by the detection means when the contact/separation mechanism is moved to the separation position, and the current value detected by the detection means when the contact/separation mechanism is moved to the contact position. 3. The image forming apparatus according to claim 2, wherein, according to the difference between the current value and the current value, it is notified that the developing cartridge is not installed in the apparatus main body. When the absolute value of the current value detected by the detection means is less than a threshold value in a state where the contact/separation mechanism is moved to the contact position, the developing cartridge is not attached to the apparatus main body. 3. The image forming apparatus according to claim 2, wherein the notification is provided. a plurality of image forming units each including the image carrier, the charging member, and the developing cartridge;
exposing means for exposing the surface of the image carrier charged by the charging member to form an electrostatic latent image;
The exposing means exposes the image carrier charged by the charging member to non-image portion exposure to form a surface potential that does not form the toner image, and forms the surface potential that forms the toner image. and exposing the image area with an exposure amount larger than the exposure amount of the non-image area exposure,
The control section controls the amount of exposure for performing the non-image portion exposure when the detecting section detects the current value of the current flowing through the charging voltage applying section in order to determine the mounting state of the developing cartridge. 5. The image forming apparatus according to any one of claims 1 to 4, wherein said exposing means is controlled to perform the exposure. 6. The image forming apparatus according to claim 5, wherein said control section controls said exposing means so as to change the exposure timing of said non-image area exposure for exposing the surfaces of said plurality of image carriers. 7. The image forming apparatus according to claim 5, wherein the charging voltage applying means applies the common charging voltage to the charging members of the plurality of image forming units. 8. The apparatus according to any one of claims 1 to 7, further comprising a drum cartridge including said image bearing member and said charging member, wherein said drum cartridge is detachable from said apparatus main body independently of said developing cartridge. 1. The image forming apparatus according to claim 1. The control section detects the current value of the current flowing through the charging voltage applying means by the detecting means in order to discriminate the mounting state of the developing cartridge. 9. The method according to any one of claims 1 to 8, wherein control is performed so that the absolute value of the charging voltage applied to the charging member by the charging voltage applying means is larger than when an image is formed in which the charging voltage is applied to the charging member. Image forming device. a device body;
a rotatable image carrier;
A developing cartridge comprising a developing member forming a developing portion together with the image carrier in contact with the image carrier, and developing a toner image by supplying toner onto the surface of the image carrier in the developing portion. a developer cartridge that can be attached to and detached from the apparatus main body while the image carrier is in the apparatus main body;
The toner image is transferred to the intermediate transfer member or the recording material on which the toner image formed on the image carrier is transferred at a transfer portion where the image carrier and the intermediate transfer member or the recording material are in contact with each other. a transfer member for
a transfer voltage applying means provided in the main body of the apparatus for applying a transfer voltage to the transfer member;
a detecting means for detecting a current value of the current flowing through the transfer voltage applying means;
a control unit that controls the transfer voltage applying means,
When the image carrier is in the apparatus main body, the image carrier that may form the developing section in a state in which the transfer voltage is applied to the transfer member while the image carrier is rotated. notifies that the developing cartridge is not installed in the apparatus main body according to the current value detected by the detecting means when the area of the surface of the image carrier reaches the transfer portion due to the rotation of the image carrier. An image forming apparatus characterized by: a contact/separation mechanism for moving between a contact position where the developing member contacts the image carrier in the developing unit and a separation position where the developing member is separated from the image carrier;
When the image carrier is in the apparatus main body, the image carrier is rotated, the transfer voltage is applied to the transfer member, and the contact/separation mechanism is moved to the contact position. In response to the current value detected by the detecting means when the area of the surface of the image carrier that may form a portion reaches the transfer portion due to the rotation of the image carrier, the apparatus main body 11. The image forming apparatus according to claim 10, wherein the fact that the developing cartridge is not installed is notified. The current value detected by the detection means when the contact/separation mechanism is moved to the separation position, and the current value detected by the detection means when the contact/separation mechanism is moved to the contact position. 12. The image forming apparatus according to claim 11, wherein the fact that the developing cartridge is not installed in the apparatus main body is notified according to the difference between the current value and the current value. When the absolute value of the current value detected by the detection means is less than a threshold value in a state where the contact/separation mechanism is moved to the contact position, the developing cartridge is not attached to the apparatus main body. 12. The image forming apparatus according to claim 11, wherein the notification is provided. a plurality of image forming units each including the image carrier and the developing cartridge;
an exposure means for exposing the surface of the image carrier to form an electrostatic latent image;
The exposing means includes non-image portion exposure for forming a surface potential that does not form the toner image on the image carrier, and the non-image portion exposure for forming the surface potential for forming the toner image. and exposing the image area with an exposure amount greater than the exposure amount of
The control section controls the amount of exposure for performing the non-image area exposure when the detecting section detects the current value of the current flowing through the transfer voltage applying section in order to determine the mounting state of the developing cartridge. 14. The image forming apparatus according to any one of claims 10 to 13, wherein said exposing means is controlled to perform the exposure. 15. The image forming apparatus according to claim 14, wherein said control section controls said exposing means so as to change the exposure timing of said non-image area exposure for exposing the surfaces of said plurality of image carriers. 16. The apparatus according to any one of claims 10 to 15, further comprising a drum cartridge including the image bearing member, wherein the drum cartridge is detachable from the apparatus body independently of the developing cartridge. Image forming device. The control section controls the rotational speed of the developing member to be higher when determining the mounting state of the developing cartridge than when forming an image by developing the toner image from the developing member on the image carrier. The image forming apparatus according to any one of claims 1 to 16, characterized by: The control unit controls the rotational speed of the image carrier to be lower when determining the mounting state of the developing cartridge than when forming an image by developing the toner image from the developing member on the image carrier. The image forming apparatus according to any one of claims 1 to 17, characterized in that: a developing voltage applying means provided in the apparatus main body for applying a developing voltage to the developing member;
The controller applies the developing voltage to the developing member by the developing voltage applying means when determining the mounting state of the developing cartridge than when forming an image by developing the toner image from the developing member on the image carrier. 19. The image forming apparatus according to claim 1, wherein control is performed so as to reduce the absolute value of the developing voltage. When determining the mounting state of the developing cartridge, the control section controls the developing voltage applied to the developing member by the developing voltage applying means and the image bearing just before entering the developing section, rather than the image forming operation. 20. The image forming apparatus according to claim 19, wherein control is performed so as to increase the potential difference of the surface potential of the body.

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