JPH09311541A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing surface staining on a formed image at the time of performing the development, fetching toner into a developer with its movement, by driving a developer carrier in a process other than the developing process in accordance with the detected value of an image area. SOLUTION: It is constituted so that as an image area detecting means, the image area of a copied original can be read in an image processing part. In such a case, when the total image area ratio of a fixed number of originals is larger than the reference ratio X% of the total image area, a developing sleeve driving mode is set and a developing sleeve 42 is rotated when the nonimage area of a photoreceptor drum 1 reaches a position facing the developing sleeve 42, so that the developer in a developer retaining part 45 is raised to an optimum electrostatic charge quantity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer.
A developer carrier for carrying the developer composed of toner and magnetic particles and conveying the developer to a region facing the latent image carrier of the image forming apparatus, and a magnetic field generated inside the developer carrier. Means, a developer regulating member for regulating the amount of the developer carried on the developer carrying member, and a surface of the cover member and the developer carrying member so that the developer blocked by the developer regulating member may stay. A developer accumulating portion that is formed so as to be surrounded, a developer that is adjacent to the developer accumulating portion from the upstream side in the developer conveying direction, and the toner that is accommodated is carried on the developer carrier or the developer. A toner accommodating portion having a toner replenishment opening in contact with the developer in the retention portion, and the toner in the toner accommodating portion is moved from the toner replenishment opening by the movement of the developer accompanying the developer conveyance of the developer carrier. Development device designed to be incorporated in the developer An image forming apparatus having.

[0002]

2. Description of the Related Art Conventionally, as a developing device used in this type of image forming apparatus, a magnetic particle layer is formed on a developer carrier in a container, and the magnetic particle layer is formed in the toner replenishing section in the container. The toner is accommodated so as to come into contact with the toner, and the toner is taken into the magnetic particle layer at the toner replenishing section by the movement of the magnetic particles in the magnetic particle layer in accordance with the rotation of the developer carrier having the magnet fixedly arranged inside. In a developing device in which a developer containing a mixture of toner and magnetic particles is regulated in layer thickness by a developer regulating member and conveyed to a developing area, the magnet does not have a magnetic pole facing the toner replenishing section, and the developer is carried. A magnetic pole is provided on the downstream side of the toner replenishing section and on the upstream side of the regulating member with respect to the rotating direction of the body, and within the range of the magnetic field of the magnetic pole on the downstream side of the toner replenishing section and on the upstream side of the regulating member. In the position A developing device having a cover member which is provided so as to face the image bearing member and forms a region (hereinafter referred to as a developer retaining portion) filled with the magnetic agent layer between the developing member bearing member and the developer bearing member (for example, Japanese Patent Publication No. (See Japanese Patent Publication No. 67233)
It has been known. In this developing device, when the developer stagnating in the developer stagnating portion has a high toner concentration and a large bulk of the developer, the developer filling rate increases and the developer hardly moves, and the developer passing through the regulating member is hardly moved. Except for the developer, there is almost no movement of the developer in the developer retaining section. vice versa,
When the toner density decreases due to toner consumption and the bulk of the developer becomes small, the filling rate of the developer in the developer retaining portion becomes low, the developer easily moves, and the toner is taken into the developer. Then, when the toner density of the developer increases and the bulk of the developer increases, the developer in the developer retaining portion hardly moves again as described above, and the toner intake stops. Further, the toner taken into the developer retaining portion is charged together with the magnetic particles due to the internal pressure of the developer retaining portion and the movement of the developer in the developer retaining portion.
According to this type of developing device, the toner concentration sensor and the toner replenishing device are not provided, the toner can be taken into the developer by the movement of the developer, and the stirring member for charging the developer is provided. Since the developer can be charged without the need, the device can be downsized.

[0003]

However, in the conventionally proposed image forming apparatus, when an original having a large image area is continuously developed, the background such as toner adhered to the white portion of the original on the formed image. It may have become dirty. On the other hand, when a document having a small image area is continuously developed, the image density may be reduced.

The inventors of the present invention conducted extensive research into the cause of this problem and found that it was related to the charge amount of the developer conveyed to the developing area. FIG. 5A is a graph showing the relationship between the number of passed sheets and the charge amount Q / m (MC / g) of the developer when a document having a large image area is continuously developed, FIG. b) shows the number of sheets passed and the charge amount Q / m of the developer when a document with a small image area is continuously developed.
It is a graph showing the relationship with (MC / g). FIG. 5 (a)
As shown in, when a document with a large image area is continuously developed, the charge amount Q / of the developer increases as the number of paper passing increases.
m (MC / g) gradually decreases. This is because the toner consumption is higher than usual, a large amount of new toner is taken into the developer, the magnetic particles and the toner are not sufficiently mixed in the developer retention portion, and as a result, the developer becomes insufficiently charged. It is thought to be because it ends up. Then, it is considered that when the insufficiently charged developer is conveyed to the developing area, the toner adheres to the white portion of the document to cause background stain. Also, FIG.
As shown in (b), when a document having a small image area is continuously developed, the charge amount Q / m (MC / g) of the developer gradually increases as the number of passed sheets increases. It is considered that this is because the amount of toner consumed in the developer retaining portion is reduced and the toner in the developer retaining portion is not excessively consumed and continues to be excessively mixed in the developer. Then, the magnetic particles and the toner are excessively charged, and the mutual connection due to the electric charge becomes strong,
It is considered that it becomes difficult for toner to be attracted to the image portion by the force of the potential on the latent image carrier, and the image density becomes low. For these reasons, in order to prevent the background stain and the decrease in the image density, it is desirable to control the charge amount of the developer conveyed to the developing area so as to be an appropriate value for the development.

Conventionally, a toner concentration sensor for detecting the toner concentration is provided in the developing device to control the toner concentration lower than the detection value detected by the toner concentration sensor in a state where the toner is stirred by the toner stirring means after the developer is set. It has been proposed to provide a reference value holding means for holding a reference value (see, for example, Japanese Utility Model Laid-Open No. 63-39249).

Immediately after replenishing the magnetic toner into the developer, the rotational speed of the rotary stirring member for agitating the developer is temporarily increased from the rotational speed immediately before replenishing the toner. A developing device has also been proposed (see, for example, Japanese Utility Model Laid-Open No. 61-79350).

Further, there has been proposed a device in which a clear image can be obtained by rotationally driving the developing sleeve and the toner supply roller even when the developing device does not contribute to the development (special feature). (See Kai 62-153974).

However, in these proposals, in the case where an original having a large image area is continuously developed in an image forming apparatus having a developing device that takes toner into the developer by moving the developer without providing a toner density sensor. There is no suggestion of background stains occurring in the background or reduction of image density when continuously developing a document having a small image area.

The present invention has been made in view of the above problems. A first object of the present invention is to form an image having a developing device that takes in toner into the developer by moving the developer without providing a toner density sensor. An object of the present invention is to provide an image forming apparatus capable of preventing a background stain on a formed image when continuously developing an original having a large image area. A second object of the invention is to continuously develop a document having a small image area in an image forming apparatus having a developing device that takes toner into the developer by moving the developer without providing a toner density sensor. An object of the present invention is to provide an image forming apparatus capable of preventing the image density of a formed image from becoming low.

[0010]

In order to achieve the first object, a developing device according to a first aspect of the present invention carries a developer composed of toner and magnetic particles and faces a latent image carrier of an image forming apparatus. A developer carrying member for transporting the developer to a region to be formed, and a magnetic field generating means arranged inside the developer carrying member,
A developer regulating member for regulating the amount of the developer carried on the developer carrying member, and a cover member and a surface of the developer carrying member so that the developer blocked by the developer regulating member is retained. The formed developer accumulating portion is adjacent to the developer accumulating portion from the upstream side in the developer conveying direction, and the stored toner is carried by the developer carrying member or the developer accumulating portion. A toner accommodating portion having a toner replenishment opening in contact with the developer, and the toner in the toner accommodating portion is moved from the toner replenishment opening to the developer by the movement of the developer accompanying the developer conveyance of the developer carrier. In the image forming apparatus having a developing device that mixes the developer in the developer accumulating portion by transporting the developer by the developer carrying member, an image area detecting unit for detecting the size of the image area of the copy original is provided. Provide the above image side In addition the step of performing development according to the detected values is characterized in the provision of the developer carrier driving mode for driving the developer carrying member.

According to another aspect of the image forming apparatus of the present invention, the image area detecting means detects the size of the image area of the copy document, and the developer in the developer accumulating portion may become insufficiently charged depending on the detected value. If there is such a presence, the developer carrying member is driven in a step other than the step of performing the development, thereby increasing the charge amount of the developer in the developer retaining portion without performing the development. For example, the detected value of the image area is larger than usual,
When it is determined that the developer in the developer retention area may be under-charged, the developer carrier is driven in a step other than the development process, which allows the developer retention without developing. The charge amount of the developer in the section is raised.

In order to achieve the above-mentioned second object, the image forming apparatus according to a second aspect of the invention carries a developer composed of toner and magnetic particles to a region facing the latent image carrier of the image forming apparatus. A developer carrying member for carrying the toner, a magnetic field generating means disposed inside the developer carrying member, a developer regulating member for regulating the amount of the developer carried on the developer carrying body, and the developer A developer accumulating portion formed by being surrounded by the surface of the cover member and the developer carrier so that the developer blocked by the regulating member may accumulate, and the developer accumulating portion is adjacent to the developer accumulating portion from upstream in the developer conveying direction. A toner storage section having a toner replenishment opening for allowing the stored toner to come into contact with the developer carried by the developer carrier or the developer in the developer retaining section, and the toner in the toner storage section Is developed along with the developer transport of the developer carrier. In an image forming apparatus having a developing device that takes in the developer from the toner replenishment opening by moving the image, image area detecting means for detecting the size of the image area of the copy original is provided, and development is performed according to the detected value of the image area. A toner removal mode for adhering the toner on the developer bearing member onto the latent image bearing member is provided in a step other than the step of performing.

According to another aspect of the image forming apparatus of the present invention, the size of the image area of the copy document is detected by the image area detecting means, and the developer in the developer accumulating portion is overcharged in accordance with the detected value. If there is a possibility that the toner is present, the toner on the developer carrier is attached to the latent image carrier to remove the excessively charged toner, except for the step of developing. As a result, new toner is supplied to the developer accumulating portion from the toner accommodating portion, the charge amount of the developer in the developer accumulating portion is reduced, and the excessively charged developer is not conveyed to the developing area. To do. For example, when the detected value of the image area is smaller than usual and it is determined that the developer in the developer retaining portion may be overcharged, it is developed on the latent image carrier other than the developing step. The toner on the agent carrier is adhered to remove the excessively charged toner in the developer retaining portion.

In order to achieve the first and second objects, an image forming apparatus according to a third aspect of the invention is an area in which a developer including toner and magnetic particles is carried to face a latent image carrier of the image forming apparatus. A developer carrier for transporting the developer to
A magnetic field generating means disposed inside the developer carrying member, a developer restricting member for restricting the amount of the developer carried on the developer carrying member, and a developer blocked by the developer restricting member are retained. As described above, the developer accumulating portion formed by being surrounded by the surface of the cover member and the developer carrying member is adjacent to the developer accumulating portion from the upstream side in the developer conveying direction, and the accommodated toner is carried by the developer carrying portion. A toner accommodating portion having a toner replenishment opening that comes into contact with the developer carried by the body and the developer in the developer accumulating portion, and conveys the toner in the toner accommodating portion to the developer in the developer carrying body. In the image forming apparatus having a developing device that takes in the developer from the toner replenishment opening by the movement of the developer accompanying the above, and mixes the developer in the developer retention portion by the transport of the developer by the developer carrying member, Large image area of original An image area detection unit for detecting the image area is provided, and a developer carrier driving mode in which the developer carrier is driven in a step other than the step of developing according to the detected value of the image area and the detected value of the image area A toner removal mode for adhering the toner on the developer bearing member onto the latent image bearing member is provided in a step other than the step of performing the development.

According to another aspect of the image forming apparatus of the present invention, the developer carrying member is driven in a step other than the step of developing when it is judged from the detected value of the image area that there is a possibility that the charging state is insufficient. When the charge amount of the developer in the developer retaining portion is increased without performing development, and it is determined from the detection value of the image area that the developer in the developer retaining portion may be overcharged. , The amount of charge of the developer in the developer retaining portion by removing the toner that is excessively charged in the developer retaining portion by adhering the toner on the latent image bearing member on the latent image bearing member except in the developing process. Lower.
This prevents the developer from being supplied with insufficient charge or excessive charge in the developing area.

Further, in order to achieve the first object,
An image forming apparatus according to a fourth aspect is the image forming apparatus according to the first or third aspect, in which the drive amount of the developer carrier in the developer carrier drive mode is changed according to the detected value of the image area. It is characterized in that a rotation speed control mechanism is provided.

According to another aspect of the image forming apparatus of the present invention, in the developer carrier driving mode, the rotation speed control mechanism is used so that it is determined that the insufficient charge amount of the developer may be large based on the detected value of the image area. Increase the number of rotations of the agent carrier. As a result, the charging is started according to the insufficient charging amount of the developer in the developer retaining portion.

Further, in order to achieve the second object,
An image forming apparatus according to a fifth aspect is the image forming apparatus according to the second or third aspect, in which the toner adhesion amount on the latent image carrier in the toner removal mode is changed in accordance with the detected value of the image area. It is characterized in that a quantity control mechanism is provided.

According to another aspect of the image forming apparatus of the present invention, in the toner removing mode, the latent amount by the toner adhesion amount control mechanism is so large that it is determined by the detection value of the total image area that the excessive charge amount of the developer may be large. Increase the amount of toner attached to the image carrier. As a result, a large amount of toner is removed so that the excessive charge amount of the developer in the developer storage portion may be large, and new toner in the toner storage portion is taken into the developer storage portion.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter referred to as copying machine) which is an image forming apparatus will be described below. FIG. 1 is a schematic configuration diagram of a copying machine according to the present embodiment. This copying machine includes a scanner unit 20 for reading a document and an image processing unit 2 for electrically processing a digital signal output from the scanner unit 20.
1 and a printer unit 22 that forms an image on a transfer sheet based on a digital signal output from the image processing unit.

In the scanner section 20, the image of the document placed on the document table is read by an image reading device (not shown) via an irradiation lamp, a mirror and a lens (not shown), and the data is read. Image processing unit 21
Sent to In the image processing unit 21, this data is subjected to necessary processing, converted into an image signal, and sent to the printer unit 22.

In the printer section 22, the surface of the photosensitive drum 1 as a latent image carrier, which is rotationally driven in the direction of arrow A in the figure, is uniformly charged by the charger 2. Then, a latent image corresponding to the image of the original is formed on the surface of the photosensitive drum 1 by the exposure device 3 including a semiconductor laser, a polygon mirror, a reflection mirror, etc., based on the image signal from the image processing unit 21. . The latent image on the photoconductor drum 1 is developed with a developer supplied from a developing sleeve 41 as a developer carrying member of the developing device 4 at a portion facing the developing device 4 to form a visible image. Here, the developing device 4 will be described in detail later. Then, the visualized image is placed on the belt-shaped transport device 7 from the paper feed tray 5 at timing by the registration rollers 6 and is transported to a portion facing the photosensitive drum 1, for example, transfer paper (see FIG. (Not shown) is transferred by the transfer device 8. The transfer sheet onto which the visible image has been transferred is conveyed by the conveying device 7, and when passing through the fixing device 9, the visible image is fixed and discharged onto the paper discharge tray 10. Here, the untransferred toner remaining on the photoconductor drum 1 after the image transfer is cleaned from the photoconductor drum 1 by the cleaning device 11 and collected by the cleaning device 11. Then, the surface of the photosensitive drum 1 after cleaning is subjected to elimination of residual electric charges by an elimination lamp (not shown).

FIG. 2 is a partial sectional view showing a schematic structure of a developing device used in the copying machine of this embodiment. This developing device is disposed on the side of the photoconductor drum 1 and has a casing 41 having an opening formed toward the photoconductor drum 1. The toner 50a and magnetic particles (hereinafter, referred to as “a part of the casing 41” exposed from the opening). Carrier)), a developing sleeve 42 as a developer carrying member for carrying a developer 50 on its surface, a magnet roller 43 consisting of a fixed magnet group as a magnetic field generating means fixedly arranged inside the developing sleeve 42, and a developing sleeve. A developer retaining portion 45 of the developer is formed between the doctor 44 as a developer regulating member that regulates the amount of the developer carried and conveyed on the 42 and the surface of the sleeve above the developing sleeve 42. The doctor's front burr 46 serving as a cover member, the toner hopper 47 serving as a toner container, and the like are provided.

The above-mentioned front doctor blade 46 retains developer between the developing sleeve 42 and the developing sleeve 42. The portion 45 is formed. Further, the toner hopper has a toner replenishing port 48 as a toner replenishing opening that is adjacent to the upstream side of the developer retaining portion 45 in the developer conveying direction and faces the surface of the developing sleeve 42, and is adjacent to the toner replenishing port. In the space, a toner agitator 49 that sends the toner in the hopper toward the toner supply port while stirring is provided.

In the developing device having the above-described structure, the developer on the developing sleeve 42 is conveyed as the sleeve rotates, and is regulated by the doctor 44 to form a thin layer. The thinned developer is conveyed to a developing area facing the photoconductor drum 1 rotating in the arrow direction. Then, in the developing area, toner is supplied to the electrostatic latent image formed on the photosensitive drum 1, and the electrostatic latent image is visualized. The developer that has not been used for visualization is conveyed along with the rotation of the developing sleeve 42, and after taking in the new toner sent from the agitator 49 and supplied from the toner supply port, the developer accumulating portion 45. Return to. The internal pressure of the developer containing the new toner 50a increases due to the restriction by the doctor 44, and the toner of the developer is charged. In this way, the toner in the developer on the developing sleeve 42 can be charged by the internal pressure of the developer on the doctor side of the developer retaining portion 45, so that the developer such as the paddle and the screw is charged or stirred. No complicated stirring mechanism is required.

On the other hand, a part of the developer, which is not supplied to the developing area and is prevented from advancing by the doctor 44, moves to the vicinity of the toner replenishing port 48 in the developer retaining portion 45 due to the internal pressure and gravity of the developer itself. Then, with the movement of the developer moving layer due to the rotation of the developing sleeve 42, the developer sleeve 42 is rotated toward the doctor side so as to be circulated.

According to the developing device having the above structure, the toner density is self-controlled by the volume of the developer in the developer retaining portion 45 varying depending on the state of the toner taken into the developer retaining portion 45. Therefore, the toner concentration of the developer is always kept in a substantially constant concentration range. Therefore, a complicated toner concentration control mechanism such as a toner concentration sensor, a P sensor, a toner replenishing member, etc. is unnecessary.

By the way, in the copying machine of the present embodiment, a control for preventing a trouble in continuously developing a document having a large image area or continuously developing a document having a small image area is performed. It is configured to do so.
Therefore, in the copying machine of this embodiment, the image processing section 21 electrically converts the reflected light image from the original to read the image area as an image area detecting unit for reading the image area of the copy original. It is configured to be able to.

FIG. 3 is a control block diagram of this copying machine. In FIG. 3, an image processing unit 21, a drive unit 60 for forming a latent image, a drive unit 61 for development, a drive unit 62 for a photosensitive drum, etc. are connected to a main controller 66. The main controller 66 includes a central processing unit (CPU) 67, a read-only memory (ROM) 68,
It is composed of a readable / writable memory (RAM) 69 and the like. This read-only memory (ROM)
In 68, a control program is written to prevent a problem in the case where a document having a large image area or a document having a small image area is continuously developed, which will be described later. Then, in this main control device, various kinds of recognition / judgment are performed according to a control program read from the memory 68, in response to an input signal from the image processing unit 21, and while performing various kinds of recognition / judgment including operation timings of various driving units. An operation command is output to the drive unit to perform a predetermined operation.

FIG. 4 is a flow chart showing the control of this copying machine. Here, in the present embodiment, the detection by the image area detecting means is continuously performed for a predetermined number of predetermined images, and the control is performed based on the detection value of the total image area for the predetermined number of images. In FIG. 4, a predetermined number of total image areas are read (step 1). Next, the ratio of the total image area to the total area of the predetermined number of originals (hereinafter referred to as the total image area ratio) is the normal ratio to the total area of the predetermined number of originals (hereinafter referred to as the total image area ratio). The image area reference rate X%) is determined (step 2). If Y in step 2, the control is ended. When N in step 2, the total image area ratio is the total image area reference ratio X%.
It is determined whether or not it is larger (step 3). here,
When the total image area ratio is larger than the total image area reference ratio X% (Y in step 3), as the developing sleeve drive mode,
The developing sleeve 42 is rotated when the non-image area of the photosensitive drum 11 reaches a position where it faces the developing sleeve 42 (step 4). When the total image area ratio is smaller than the total image area reference ratio X% in step 2 (N in step 3), the photosensitive drum 1 is charged in the non-image area and the developing sleeve is in the non-image mode in the toner removal mode. The toner is attached to the surface of the photoconductor drum 1 by rotating in the area so that a so-called black solid image is developed (step 5). After performing the above step 4 or step 5, the control is ended.

According to the above construction, when a document having a large image area is continuously developed, a large amount of toner is taken in from the toner hopper 47 by the toner concentration self-control mechanism, and as shown in FIG. The developer in the developer retention portion 45, which has a shortage of Q / m (MC / g),
The developing sleeve 42 is rotated in the non-image area of the photosensitive drum 1 to positively charge it. As a result, the charge amount Q / m (MC / g) of the developer in the developer retaining portion can be raised, and it is possible to prevent the insufficiently charged developer from being conveyed to the developing area. It is possible to prevent the toner from adhering to the toner and causing the background stain.

Further, when a document having a small image area is continuously developed, the toner in the developer retaining portion 45 continues to be retained without being used for the development, so that the charge amount as shown in FIG. By optimally adhering the toner in the developer in the developer retaining portion 45 in which the Q / m (MC / g) is gradually increasing to the non-image area of the photosensitive drum 1, the optimum charge amount Q / m (MC / g) can be lowered. In this case, the toner adhering to the photoconductor drum 1 is sent to the portion facing the cleaning device 11 as it is without being transferred to the transfer paper, and the toner removal means including a blade of the cleaning device 11 causes the photoconductor drum 1 to move. 1 removed from above. As a result, it is possible to prevent the magnetic particles and the toner from being excessively charged and the mutual connection due to the electric charges to become strong, so that it becomes difficult to attract the toner to the image portion due to the force of the potential on the photosensitive drum 1, and the image density is low. Can be prevented.

When the image area is equal to the normal area, neither of the above two controls is performed and the development is continuously performed as it is.

In the present embodiment, when the charged state of the developer in the developer retaining portion 45 is determined by detecting the image area of the copy original, the image area of a predetermined number of originals is continuously determined. Although various controls are performed based on the detection result of the total image area, it is possible to obtain a better image by changing the predetermined number.

Next, a modified example of the above-described embodiment which can obtain a better image will be described. In this modified example, in step 3 described above, the number of rotations of the developing sleeve 42 corresponds to the difference of the total image area ratio from the total image area reference ratio X% (hereinafter referred to as the difference between the total image area ratio and the reference ratio). A developing sleeve rotation speed control mechanism that changes When Y in step 3 above, in the developing sleeve drive mode, the rotation speed of the developing sleeve 42 is changed in accordance with the magnitude of the difference between the total image area ratio and the reference ratio. As a result, the larger the difference between the total image area ratio and the reference ratio and the larger the insufficient charge amount of the developer, the greater the number of rotations of the developing sleeve 42. Therefore, depending on the insufficient charge state of the developer in the developer retention portion 45. Charge amount Q
/ m (MC / g) can be raised. This allows
There is no fear that the developer in the developer accumulating portion 45 will be excessively charged, and the background stain on the formed image can be better prevented by an easy configuration in which the rotation speed of the developing sleeve 42 is controlled. When N in step 3 above, in the toner removal mode, the rotation speed of the developing sleeve 42 is changed in accordance with the magnitude of the difference in the total image area ratio with respect to the reference ratio. Specifically, the rotational speed of the developing sleeve 42 is increased as the difference between the total image area ratio and the reference ratio is larger, and the rotational speed is decreased as the difference is smaller. As a result, the difference between the total image area ratio and the reference ratio is large, and the charge amount Q / m of the developer in the developer retaining portion 45 is large.
The larger the value of (MC / g), the more the amount of toner adhered to the photoconductor drum 1 can be increased. Therefore, the developing sleeve rotation speed control mechanism serves as the toner adhesion amount control mechanism. And
In the toner removal mode, it is possible to remove the toner according to the excessive charge amount of the developer in the developer retaining portion 45 and take in the new toner from the toner hopper 47.
It is possible to prevent the toner in the developer retaining portion 45 from being excessively removed, and it is possible to further stabilize the image density with an easy configuration of controlling the rotation speed of the developing sleeve 42.

[0036]

According to the image forming apparatus of the first aspect, when the developer in the developer accumulating portion may be in an insufficiently charged state, the developer is mixed in the developer accumulating portion except in the developing step. By increasing the charge amount, it is possible to prevent the developer from being insufficiently charged, so it is possible to prevent the toner conveyed to the image forming section from adhering to the white areas of the original, and to prevent background stains on the formed image. It has an excellent effect that it can be prevented.

According to the image forming apparatus of the second aspect, when it is determined that the developer in the developer retaining portion may be excessively charged, the excessively charged toner is removed to excessively charge the developer. Since the developed developer can be prevented from being transported to the development area, it is possible to prevent the image density of the formed image from being reduced due to the excessively charged developer used for development.

According to the image forming apparatus of the third aspect, the developer in the developer retaining portion is charged or the charge amount is reduced according to the detected value of the image area. It is possible to prevent the background image from being transported to the area and adhering to the white part of the original to cause background stain on the formed image, and it is possible to prevent the overcharged developer from being conveyed to the developing area to reduce the image density of the formed image. In addition, there is an excellent effect that it is possible to prevent problems such as background stains and a decrease in image density depending on the detected value of the image area of the copy document.

According to the image forming apparatus of claim 4,
Since the charge amount can be raised according to the insufficient charge amount of the developer in the developer retention portion, the developer in the developer storage portion is set to a charge amount more suitable for development in the developer carrier driving mode. There is an excellent effect that the formed image can be more stabilized.

According to the image forming apparatus of claim 5,
In the toner removal mode, excessively charged toner is removed according to the excessive charge amount of the developer in the developer storage area, and new toner can be taken in, so that the developer in the developer storage area can be adjusted to a charge amount more suitable for development. There is an excellent effect that it can be maintained and the image density of the formed image can be more stabilized.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a copying machine according to an embodiment.

FIG. 2 is a schematic configuration diagram of a developing device used in the copying machine according to the present embodiment.

FIG. 3 is a control block diagram of the copying machine according to the present embodiment.

FIG. 4 is a flowchart of the copying machine according to the present embodiment.

FIG. 5A is a graph showing the relationship between the number of passed sheets and the charge amount Q / m (MC / g) of the developer when the total image area is large. (B) is a graph showing the relationship between the number of sheets passed and the developer charge amount Q / m (MC / g) when the total image area is small.

[Explanation of symbols]

 1 Photoconductor Drum 2 Charging Device 3 Exposure Device 4 Developing Device 5 Paper Feed Tray 6 Registration Roller 7 Conveying Device 8 Transfer Device 9 Fixing Device 10 Paper Ejection Tray 11 Cleaning Device 20 Scanner Part 21 Image Processing Part 22 Printer Part 41 Casing 42 Development Sleeve 43 Magnet roller 44 Doctor 45 Developer retention area 46 Front of doctor 47 Toner hopper 48 Toner supply port 49 Toner agitator 50 Developer 50a Toner 66 Main controller 67 Central processing unit (CPU) 68 Read only memory (ROM) 69 Read And writable memory (RAM)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Akiba 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (5)

[Claims] 1. A developer carrier for carrying a developer composed of toner and magnetic particles to convey the developer to a region facing a latent image carrier of an image forming apparatus, and the inside of the developer carrier. Magnetic field generating means, a developer regulating member that regulates the amount of the developer carried on the developer carrying member, and a cover member and a developer for allowing the developer blocked by the developer regulating member to stay. A developer accumulating portion formed by being surrounded by the surface of the carrier, and a developing device in which toner contained in the developer accumulating member is adjoined to the developer accumulating portion from upstream in the developer conveying direction. And a toner accommodating portion having a toner replenishment opening that comes into contact with the developer in the developer accumulating portion, and the toner in the toner accommodating portion is moved by the movement of the developer accompanying the developer conveyance of the developer carrier. Take it into the developer through the toner supply opening and In an image forming apparatus having a developing device that mixes the developer in the developer retaining portion by conveying the developer by an image carrier, an image area detecting means for detecting the size of the image area of a copy original is provided, An image forming apparatus comprising a developer carrier driving mode for driving the developer carrier in a step other than the step of developing according to the detected value of the area. 2. A developer carrier for carrying a developer composed of toner and magnetic particles to convey the developer to a region facing the latent image carrier of the image forming apparatus, and the inside of the developer carrier. Magnetic field generating means, a developer regulating member that regulates the amount of the developer carried on the developer carrying member, and a cover member and a developer for allowing the developer blocked by the developer regulating member to stay. A developer accumulating portion formed by being surrounded by the surface of the carrier, and a developing device in which toner contained in the developer accumulating member is adjoined to the developer accumulating portion from upstream in the developer conveying direction. And a toner accommodating portion having a toner replenishment opening that comes into contact with the developer in the developer accumulating portion, and the toner in the toner accommodating portion is moved by the movement of the developer accompanying the developer conveyance of the developer carrier. A developing device that is taken into the developer from the toner supply opening In the image forming apparatus having the above, an image area detecting means for detecting the size of the image area of the copy document is provided, and the developer is carried on the latent image carrier except the step of developing according to the detected value of the image area. An image forming apparatus having a toner removal mode for adhering toner on the body. 3. A developer carrier for carrying a developer composed of toner and magnetic particles to convey the developer to a region facing a latent image carrier of an image forming apparatus, and the inside of the developer carrier. Magnetic field generating means, a developer regulating member that regulates the amount of the developer carried on the developer carrying member, and a cover member and a developer for allowing the developer blocked by the developer regulating member to stay. A developer accumulating portion formed by being surrounded by the surface of the carrier, and a developing device in which toner contained in the developer accumulating member is adjoined to the developer accumulating portion from upstream in the developer conveying direction. And a toner accommodating portion having a toner replenishment opening that comes into contact with the developer in the developer accumulating portion, and the toner in the toner accommodating portion is moved by the movement of the developer accompanying the developer conveyance of the developer carrier. Take it into the developer through the toner supply opening and In an image forming apparatus having a developing device that mixes the developer in the developer retaining portion by conveying the developer by an image carrier, an image area detecting means for detecting the size of the image area of a copy original is provided, The latent image carrier other than the developer carrier driving mode in which the developer carrier is driven in a step other than the step of developing according to the detected value of the area and the step of developing in accordance with the detected value of the image area. An image forming apparatus comprising: a toner removing mode for adhering toner on a developer carrying member thereon. 4. The image forming apparatus according to claim 1 or 3, wherein a rotational speed control for changing a driving amount of the developer carrying member in the developer carrying member driving mode in accordance with a detected value of the image area. An image forming apparatus having a mechanism. 5. The image forming apparatus according to claim 2 or 3,
An image forming apparatus provided with a toner adhesion amount control mechanism for changing the toner adhesion amount on the latent image carrier in the toner removal mode in accordance with the detected value of the image area.