JP2000356897A - Developing device and image forming device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device by which the toner concentration inside a developer can be uniformized and the irregularity of image density can be prevented with a simple constitution. SOLUTION: This developing device has a developing unit 1A developing a latent image on a photoreceptor drum 2, a toner storing part 1B which stores the toner for replenishment to the inside of the unit 1A, and whose toner replenishment port communicating with the inside of the unit 1A is covered by a leaf spring 23 with plural small holes formed, and a toner replenishment roller 22 disposed inside the part 1B and replenishing the inside of the unit 1A with the stored toner through the small holes by rotation. In this case, the rollers 22 whose both ends are supported are plurally disposed in the longitudinal direction of the toner replenishment port. Thus, contact pressure between the roller 22 and the spring 23 is nearly uniformized in the longitudinal direction, so that the dispersion of toner replenishment amount to the unit 1A is eliminated.

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, a printer, etc., and a developing device used in the image forming apparatus. More specifically, the present invention relates to developing a latent image on a latent image carrier. A toner container that contains toner to be replenished in the developing device, and a toner supply port that communicates with the developing device is closed by a partition plate having a toner passage opening formed therein. The present invention relates to a developing device having a toner replenishing member that is disposed in a storage portion and replenishes toner stored by rotation into the developing device through the toner passage opening, and an image forming apparatus using the developing device. is there.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus of this type includes a developing device for developing a latent image on a latent image carrier, and a toner passage opening for storing toner to be supplied into the developing device. A toner storage portion in which a toner supply port communicating with the inside of the developing device is closed by a partition plate; and a toner provided in the toner storing portion and housed by rotation inside the developing device through the toner passage opening. And a toner replenishing member for replenishing the toner. In this type of developing device,
At the time of development, when the toner concentration in the developing device becomes equal to or less than a certain value, the toner replenishing member is rotated to vibrate the partition plate, and the toner in the toner container is supplied to the developing device through the toner passage opening. The toner is carried by a developer carrying member provided in a developing device, and the latent image on the latent image carrying member is visualized.

However, if the development in which the image area is partially offset is repeated for a long time, the toner density in the area corresponding to the image area decreases, and the toner density tends to be different from that in the other areas where the development is not performed. Become. Therefore, if the entire image is developed immediately after that, a partial decrease in toner density will cause a partial defect in image density. Also,
When the toner concentration in this portion decreases due to continuous consumption of the toner, and the toner is uniformly replenished over the entire width by the signal of the toner concentration detector provided in the reduced portion, the toner and the carrier are removed in that portion. Is appropriate, but the toner becomes excessive in other portions, and a partial defect in image density occurs.

In order to prevent such a partial defect in image density, in a developing device using a two-component developer, the developer is agitated to make the toner density uniform in the developing width direction. In Japanese Patent Application Laid-Open No. H8-44182, the toner replenishing member is provided at the toner replenishing port by changing the rotational speed and the revolving speed of the toner replenishing member (the higher the revolving speed and the greater the number of revolving, the larger the toner replenishing amount). A developing device that controls the toner supply amount by changing the opening area of a toner passage opening of a partition plate is disclosed.

[0005]

However, in the above-described developing device, when a high-speed machine or the like is used, there is a time limit in uniforming the toner density, and a partial defect in the image density occurs. Further, in the above-described developing device, the amount of toner replenishment in the developing width direction cannot be controlled, so that if the developing width is increased, a partial defect in image density occurs.

In order to prevent such a partial defect of the image density, Japanese Patent Application Laid-Open No. 60-131573 discloses a method in which a toner supply port is covered with a plurality of plates and at least one plate is used in accordance with the copy size. There is disclosed a developing device that replenishes toner by changing the opening of a toner replenishing port by moving the toner supply port. In this developing device, the toner can be replenished in accordance with the place where the toner is consumed, so that a partial defect of the image density hardly occurs. However, in a developing device in which the toner supply port is covered with a plurality of plates to change the opening, a device for moving the plate is required, and there has been a problem that the device becomes large in configuration.

In each of the developing devices, the toner replenishing member is formed by one roller.
In a developing device such as a wide copying machine capable of copying the size, the toner supply width of the toner supply member naturally becomes long. In this case, at the central portion of the toner replenishing member, the toner enters between the toner replenishing member and the partition plate, and the toner replenishing member is lifted and deformed, so that the contact pressure between the toner replenishing member and the partition plate is reduced. On the other hand, since both ends of the toner supply member are supported, the contact pressure increases. Therefore, the amount of toner discharged from the toner storage unit to the developing device increases in a portion where the contact pressure is high, and decreases in a portion where the contact pressure is low. As described above, since the contact pressure between the toner replenishing member and the partition plate is different between the central portion and the both ends, the amount of toner supplied to the developing device varies. As a result, a difference occurs in the toner concentration in the developer in the developing device, resulting in image quality such as uneven image density.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to achieve a uniform toner concentration in a developer with a simple configuration and to reduce a partial defect in image density. An object of the present invention is to provide a developing device capable of preventing the occurrence of the developing device.

[0009]

According to a first aspect of the present invention, there is provided a developing device for developing a latent image on a latent image carrier, and containing a toner to be replenished in the developing device. A toner container in which a toner supply opening communicating with the inside of the developing device is closed by a partition plate having a toner passing opening formed therein;
A toner replenishing member disposed in the toner containing portion and replenishing the toner contained by rotation into the developing device through the toner passage opening, the toner replenishing member supported at both ends. Are provided in the longitudinal direction of the toner supply port.

[0010] In particular, the developing device according to claim 2 is the developing device according to claim 1, wherein the toner in the toner accommodating portion is:
The toner replenishing member having an uneven portion on the outer periphery is elastically pressed against the partition plate having a plurality of toner passage openings formed therein, and is rotated to be replenished into the developing device. It is assumed that.

In the developing device according to the first and second aspects of the present invention, since a plurality of toner supply members whose both ends are supported are arranged in the longitudinal direction of the toner supply port, both end portions and the center of each toner supply member are arranged. The difference in the contact pressure between the toner supply port and the partition plate is reduced, and the contact pressure is made substantially uniform in the longitudinal direction of the toner supply port, so that there is no variation in the amount of toner supply to the developing device.

According to a third aspect of the present invention, in the developing device of the first aspect, the toner supply members are driven independently of each other based on information about an image.

In the developing device according to the third aspect, each toner supply member is configured to be driven independently of each other by predicting the toner consumption based on the information regarding the image. Supplies new toner to the developing device when necessary.

According to a fourth aspect of the present invention, in the developing device of the first aspect, the toner replenishing members are connected to each other in accordance with an output of a toner density detecting means for directly or indirectly detecting the toner density in the developing device. It is characterized by being driven independently.

According to a fourth aspect of the present invention, the respective toner supply members are driven independently of each other in accordance with the output of the toner density detecting means for directly or indirectly detecting the toner density in the developing device. Therefore, only the toner replenishing member corresponding to the portion where the toner has been consumed replenishes the developing device with new toner in accordance with the toner consumption.

According to a fifth aspect of the present invention, there is provided an image forming apparatus comprising: a latent image carrier on which a latent image is formed; and a developing device for developing the latent image on the latent image carrier to form a toner image. The developing device according to claim 1, 2, 3, or 4 is used as the developing device.

In the image forming apparatus according to the fifth aspect, since a plurality of toner supply members, both ends of which are supported, are arranged in the longitudinal direction of the toner supply port, the both ends and the central portion of each toner supply member are provided. The difference in contact pressure with the partition plate is reduced, and the contact pressure is made substantially uniform in the longitudinal direction of the toner supply port, so that there is no variation in the amount of toner supplied to the developing device. Further, in the image forming apparatus according to the fifth aspect, each toner supply member is configured to be driven independently of each other by predicting the toner consumption based on the information regarding the image. When necessary, new toner is supplied to the developing device. Further, in the image forming apparatus according to the fifth aspect, the respective toner supply members are driven independently of each other in accordance with the output of the toner density detecting means for directly or indirectly detecting the toner density in the developing device. Thus, only the toner replenishing member corresponding to the portion where the toner has been consumed replenishes the developing device with new toner in accordance with the amount of toner consumed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a developing device of an electrophotographic copying machine (hereinafter, referred to as a printer) as an image forming apparatus will be described. FIG. 1 is a schematic configuration diagram showing the entire configuration of the developing device. The configuration of the developing device 1 and its functions in FIG. 1 will be described below. The developing device 1 includes a developing container 1A and a toner hopper 1B serving as a toner storage unit that stores toner to be supplied to the developing container 1A. The developing container 1A is shown in FIG.
It is arranged near a drum-shaped photoconductor (hereinafter, referred to as a photoconductor drum) 2 which is a latent image carrier movable in a direction indicated by an arrow X. The photosensitive drum 2 is scanned and exposed based on image information by a laser optical device (not shown) to form an electrostatic latent image on the surface.

A stirring roller 3 and a paddle wheel 4 are provided inside the developing container 1A. A magnetic or non-magnetic toner and a magnetic carrier, which are stirred and mixed by the stirring roller 3 and frictionally charged to opposite polarities, are provided. A two-component developer (hereinafter, referred to as a developer) composed of the following is drawn up by the paddle wheel 4. At the position where the developer is pumped up by the paddle wheel 4,
A developing roller 5 is provided near the photosensitive drum 2. A doctor blade 7 for regulating the layer thickness of the developer carried on the developing roller 5 is arranged at a position where an arbitrary point on the peripheral surface of the developing roller 5 reaches before facing the photosensitive drum 2. Have been. In the vicinity of the doctor blade 7, one end in the extension direction is
And a separator 8 whose other end in the extension direction is positioned above the stirring roller 3 is disposed. A rotatable transport screw 9 is disposed at the other end of the separator 8 in the extending direction. At the bottom of the developing container 1A, a toner concentration detector 10 for detecting the toner concentration in the developing container is provided.

In the developing container 1A having such a configuration, the developer is pumped up by the centrifugal force generated when the paddle wheel 4 rotates, and is discharged toward the developing roller 5. A part of the discharged developer is directly supplied to the developing roller 5 and carried on the surface of the developing roller 5 as shown by an arrow Y in the drawing. The developer carried on the developing roller 5 moves on the roller surface with the rotation of the developing roller 5, and after the layer thickness is regulated by the doctor blade 7, the developing roller 5 and the photosensitive drum 2 are separated. The electrostatic latent image on the photoreceptor drum 2 is developed by reaching the developing area opposed thereto. The developer not used for the development falls to the bottom after that, and is again stirred by the paddle wheel 4. Normally, this cycle is repeated.

The developer scraped off by the doctor blade 7 is received by the horizontal portion of the separator 8 and flows down on the falling slope while being deflected and guided in the depth direction by the developer deflecting guide member (fin). Paddle wheel 4,
It is returned to the stirring roller 3. In addition, a part of the developer is guided by the separator 8 toward the conveying screw 9 located at the other end in the extension direction, is conveyed to the near side by the conveying screw 9, and falls on the stirring roller 3. I have. For this reason, a slit for dropping the developer is formed at the other end of the separator 8 in the extending direction at a position facing the stirring roller 3. This is a so-called cross-mixing method in which developers are transported in opposite directions to each other.

A toner hopper 1B containing toner to be supplied to the developing container 1A is mounted on the developing container 1A. A side wall section that separates the inside of the developing container 1A and the inside of the toner hopper 1B is provided in the axial direction of the developing device 1 (hereinafter, referred to as “the inside”).
A toner supply port extending in the longitudinal direction is formed. Inside the toner hopper 1B, there are provided an agitator 21 for stirring the toner by rotation, and a toner replenishing roller 22 having irregularities on the outer periphery as a toner replenishing member, both ends of which are supported by bearings 24. A leaf spring 23 having a plurality of small holes is provided as a partition plate at a position that covers the entire mouth.

When the toner concentration detector 10 detects that the toner has been consumed over time and the toner concentration in the developing container 1A has become lower than a predetermined value, the toner hopper 1B
1 and the toner supply roller 22 is rotated. Then, the agitator 21 stirs the toner while the toner supply roller 22
, The toner supply roller 22 vibrates the leaf spring 23 by the uneven portion on the outer periphery. Toner supply roller 22
The toner sprinkled on the uneven portion is transported onto the leaf spring 23, falls from the small hole by the vibration of the leaf spring 23, and is supplied to the developing container 1A. When the toner amount detector 20 detects that the toner in the toner hopper 1B has decreased and has reached a certain amount or less, the toner in the toner bottle (not shown) is sent out by a driving force from a driving source (not shown). Then, the toner is supplied from the toner supply port into the toner hopper 1B. Then, the supplied toner is further agitator 2
In step 1, the toner is sent to the far side inside the toner hopper 1B so that the toner is kept at a constant amount.

Hereinafter, the inside of the toner hopper 1B will be described in more detail. FIG. 2 is a plan view showing a longitudinal direction of the developing device 1 described above. As shown in FIG. 2, the toner supply roller 22 (hereinafter, referred to as 22a and 22b) is divided into two in the longitudinal direction, and both ends are supported by bearings 24, respectively. The leaf spring 23 (not shown in FIG. 2) is also divided by the same length as the toner supply rollers 22a and 22b. At the bottom of the toner hopper 1B, toner concentration detectors 10a and 10b are provided at positions corresponding to the toner supply rollers 22a and 22b, respectively. Electromagnetic clutches 25a and 25b are locked to the ends of the toner supply rollers 22a and 22b, respectively.
The electromagnetic clutches 25a and 25b are independently driven by the output signals of the toner density detectors 10a and 10b.

Further, the toner supply rollers 22a, 22b
Are connected to an electromagnetic clutch driver 110 described later. The electromagnetic clutch driver 110 independently drives the electromagnetic clutches 25a and 25b based on image signals based on image information of the document 101.

Here, for example, in the case where the toner supply roller 22 is not divided but is one, it is compatible with A0 (effective image length 900 m
m) wide toner supply width of 700 mm
, And the toner discharge amount is different between the central portion and the both ends in the longitudinal direction. As described above, there is a problem that a difference occurs in the toner density in the developer and image density unevenness occurs. Further, as a result of the study by the present inventors, when the toner supply width exceeds 400 mm, a difference in the toner discharge amount starts to be seen, and the toner discharge amount difference increases in proportion to the increase in the toner supply width. I understood.

Further, for example, it is assumed that the transfer sheet is transported with reference to the position of the end face C, and the end face portion is 210 mm (length of A4).
If it is assumed that the toner is continuously consumed, the toner density in this portion decreases. At this time, if the toner concentration detector 10 is located at the center in the longitudinal direction, a decrease in the toner concentration cannot be detected. Conversely, if the toner density detector 10 is located near the reference position of the end surface C, toner is supplied from the toner hopper 1B, and the ratio of the toner to the carrier at the end (A4 vertical width) becomes appropriate, but the other parts are the toner. Becomes excessive. Regardless of the transfer paper size, even when a large number of originals in which the black image is partially offset are copied, a similar difference in toner density occurs in the longitudinal direction. There is a problem that unevenness of image density such as generation of unevenness occurs. In the developing container 1A, a separator 8 and a conveying screw 9 are provided as a horizontal stirring member for stirring the developer in the width direction, and the separator 8 and the conveying screw 9 uniformly distribute the developer in the width direction. It took some time to stir, and there was no way to eliminate the uneven density.

In this embodiment, the toner supply roller 22 is divided into two parts in the longitudinal direction.
a, 22b, the length is shortened (400 mm or less), and both ends are supported by bearings 24a, 24b.
The contact pressure between the toner supply rollers 22a and 22b and the leaf springs 21 and 21 is made substantially uniform so that toner can be supplied uniformly in the longitudinal direction.

Further, toner concentration detectors 10a and 10b are provided at positions corresponding to the toner supply rollers 22a and 22b at the bottom of the developing container 1A, respectively. Then, the respective electromagnetic clutches 25a and 25b connected to both ends of the toner replenishing rollers 22a and 22b are independently turned ON by the output of the detection signal of the toner concentration detectors 10a and 10b,
It is configured to be turned off. As a result, the toner replenishing rollers 22a corresponding to the portions where the toner is consumed,
22b is independently driven to supply new toner to the developing container 1A.
Even if a large-sized image is developed after a large amount of a small-sized image is developed, or an image is developed after a large amount of an image with a biased image area, A difference is hardly generated in the image density, and it is possible to prevent an image having an uneven image density from being formed.

The method of detecting the toner concentration in the developer in the developing container 1A is not limited to the method of directly detecting the toner concentration by the toner concentration detector 10. For example, a black portion is developed on the photosensitive drum 2 and the black portion is developed. The toner density may be indirectly detected by detecting the black density with an optical detection sensor such as a photosensor, and the same effect is obtained.

Further, the toner supply rollers 22a, 22b
Is connected to an electromagnetic clutch driver 110 that is driven based on image information of the document 101 placed on the printer. Hereinafter, based on the image information, the toner replenishing roller 2
A method of independently driving 2a and 22b will be described.
FIG. 3 is a block diagram showing a control system of the printer. As shown in FIG. 3, the document 101 is illuminated by a light source (not shown) while being
2, an image is formed on the CCD 103, photoelectric conversion and main scanning are performed, and the image of the document 101 is read. here,
The CCD 103 is driven by the clock driver 104 and outputs a change in density of the document 101 as a change in voltage.
An image signal output from the CCD 103 is input to a control unit (not shown) and is amplified by the amplifier circuit 105.
The digital signal is converted by the D conversion circuit 106. A / D
The digital signal from the conversion circuit 106 is transmitted to the image processing circuit 10
7 and is input to the first controller 108 and the second controller 109. The first controller 108 controls the electromagnetic clutch 2 via an electromagnetic clutch driver 110 according to an image signal from the image processing circuit 107.
ON and OFF of 5a and 25b are performed. The second controller 109 modulates and drives a semiconductor laser (not shown) via the laser driver 11 based on an image signal from the image image processing circuit 107, thereby causing the photosensitive drum 2 to perform image exposure from the semiconductor laser.

FIG. 4 is a processing flowchart of the first controller 108. The first controller 108 divides the two image data (image data composed of white and black) of 400 DPI from the image processing circuit 107 into two in the main scanning direction, and determines whether each is black data or white data (Step Ste).
p1). If it is black data, the count is incremented by +1 (Step 2). If it is white data, the count Ya, Y of the black data is not incremented.
b is calculated (Step 3). Then, the first controller 108 determines that the count number Ya or Yb is 5
If not more than 000, the electromagnetic clutch 25
a or 25b is not turned on, and when the count number Ya or Yb becomes 5000 or more, the electromagnetic clutch 2
Turn on 5a or 25b for 1.5 seconds (Step
4). As described above, the first controller 108 controls the electromagnetic clutches 25a and 25a through the electromagnetic clutch driver 110.
5b, the toner supply rollers 22a,
2b is driven.

The means for obtaining the information on the image is not limited to the control system shown in FIGS. 3 and 4. For example, as shown in FIG.
a, 30b. That is, the number of times of light emission or time of the laser diode (LD) when forming a latent image on the photosensitive drum 2 is divided into two parts by the exposure output detectors 30a and 30b. Thus, the ON time of the electromagnetic clutches 25a and 25b may be controlled. Further, the exposure output detector 3
Of course, the detection signals detected by Oa and 30b may be detection signals obtained from the first controller 108 or the second controller 109 (laser driver 111). Further, the information is not limited to such digital detection signals, but may be analog information obtained from an optical detection sensor or a potential difference detection sensor.

As described above, the above-described printer predicts where toner is to be consumed based on the information on the image divided into two right and left, and supplies the toner to the toner supply rollers 22a and 22b.
Can be driven independently of each other, so that even a large-sized image after a large amount of development of a small-sized image, or an image after a large amount of development of an image in which the image portion is biased, A difference in image density hardly occurs between the left and right portions. Further, a further effect can be obtained by combining both the means for estimating the toner consumption based on the information regarding the image and the means for detecting the toner density.

[0035]

According to the first to fourth aspects of the present invention, a plurality of toner supply members are arranged in the longitudinal direction of the toner supply port, and the contact pressure between the toner supply member and the partition plate is substantially reduced in the longitudinal direction. Since the toner is made uniform, it is possible to eliminate the variation in the amount of toner replenishment from the toner container to the developing device. Therefore, the toner concentration in the developer can be made uniform, and it is possible to prevent the occurrence of unevenness in image density and the occurrence of partial image density defects such as white spots on the image. Has an effect.

In particular, according to the developing device of the present invention, the respective toner replenishing members are driven independently of each other in accordance with the exposure output when forming the latent image on the latent image carrier. Therefore, even if a large-sized image is obtained by developing a large amount of a small-sized image, or an image obtained by developing a large amount of an image in which the image portion is biased, uneven image density or white There is an excellent effect that it is possible to prevent a defect that a partial defect of the image density such as omission occurs.

Further, according to the developing device of the present invention, the respective toner replenishing members are driven independently of each other in accordance with the output of the toner density detecting means for directly or indirectly detecting the toner density of the toner replenishing member. Due to this configuration, even if a large-sized image is developed after a large amount of small-sized images are developed, or an image is developed after a large amount of an image with a biased image portion, image density unevenness occurs. In addition, there is an excellent effect that a defect that a partial defect of image density such as an image becomes blank can be prevented.

According to the image forming apparatus of the present invention, a plurality of toner supply members are arranged in the longitudinal direction of the toner supply port,
Since the contact pressure between the toner replenishing member and the partition plate is substantially uniform in the longitudinal direction, it is possible to eliminate the variation in the amount of toner replenished from the toner container into the developing device. Therefore, the toner concentration in the developer can be made uniform, and it is possible to prevent the occurrence of unevenness in image density and the occurrence of partial image density defects such as white spots on the image. Has an effect.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a configuration of a developing device according to an embodiment.

FIG. 2 is a plan view showing a schematic configuration of the developing device.

FIG. 3 is a block diagram illustrating a control system of the printer according to the embodiment.

FIG. 4 is a flowchart showing processing of a first controller of the printer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Developing device 1A Developing container 1B Toner hopper 2 Photoreceptor drum 3 Stirring roller 4 Paddle wheel 5 Developing roller 7 Doctor blade 8 Separator 9 Conveyance screw 10 Toner density detector 20 Toner amount detector 21 Agitator 22 Toner supply roller 23 Plate spring 24 Bearing 25 Electromagnetic clutch 30 Exposure output detector

Claims (5)

[Claims] A developing device for developing a latent image on a latent image carrier;
A toner storage portion for storing toner to be supplied in the developing device and having a toner supply opening communicating with the developing device closed by a partition plate having a toner passage opening formed therein; And a toner replenishing member for replenishing the toner accommodated by rotation through the toner passage opening into the developing device. A developing device provided in a plurality of directions. 2. The developing device according to claim 1, wherein the toner in the toner containing portion is provided on the partition plate having a plurality of toner passing openings formed by the toner replenishing member having an uneven portion on the outer periphery. A developing device, wherein the developing device is replenished in the developing device by being elastically pressed and rotated. 3. The developing device according to claim 1, wherein said toner supply members are driven independently of each other based on information on an image. 4. The developing device according to claim 1, wherein said toner replenishing members are driven independently of each other in accordance with an output of a toner concentration detecting means for directly or indirectly detecting the toner concentration in said developing device. A developing device. 5. An image forming apparatus comprising: a latent image carrier on which a latent image is formed; and a developing device for developing the latent image on the latent image carrier to form a toner image. Item 6. An image forming apparatus using the developing device according to Item 1, 2, 3, or 4.