JPH09236983A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always keep a specific toner density, and to always obtain a stable image thereby, by inhibiting detection of the toner stuck amount, when linear velocity of a photoreceptor is slow speed. SOLUTION: At the time of performing a high density recording, this device controls a rotation on and off of the toner replenishment roller 10, based on a detection result of the toner density detection signal only, outputted from a toner density detection sensor 19, by ignoring the toner density reference value changing signal ▵VREF outputted from the toner density reference value changing circuit 26. Then, at the time of performing the low density recording, the device controls the rotation on and off of the toner replenishment roller 10, by applying the toner density reference value changing signal ▵VREF outputted from the toner density reference value changing circuit 26, and the detection result of the toner density detection signal outputted from the toner density detection sensor 19.

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 used in a copying machine, a printer, or the like, and more particularly to an image forming apparatus which always performs optimum development even when a recording linear density is changed. .

[0002]

2. Description of the Related Art As an image forming apparatus used in a copying machine or a printer, an "image forming apparatus" disclosed in Japanese Patent Laid-Open No. 7-13413 has been known. This image forming apparatus, based on the developing conditions such as the rotation speed of the developing sleeve and the voltage of the developing bias applied to the developing sleeve among the developing conditions that define the operation of the developing unit, adheres the toner per unit area to the photoconductor. By adjusting the amount, the recording linear density and the like are switched, and even when the photosensitive member linear velocity is switched, the rotation speed of the developing sleeve is adjusted so that development can be performed with an appropriate toner amount. .

[0003]

By the way, the conventional image forming apparatus described above has the following problems. First, in an electrophotographic process that uses a two-component developer for the purpose of stabilizing image quality, a control circuit that controls the amount of toner attached to the photoconductor detects the amount of toner attached to the photoconductor, There is already a technique in which the detection result is fed back to the toner concentration detection unit to adjust the sensitivity when detecting the toner concentration in the developer. At this time, in the prior art, when the linear velocity of the photoconductor is changed by switching the recording linear density (pixel density), the developing time of the photoconductor increases, resulting in overdevelopment. In "Image forming apparatus" of Japanese Patent No. 13413, the developing condition is changed to correct it. However, in an image forming apparatus having a developing unit that uses a two-component developer, factors such as the number of rotations of the developing sleeve and the developing bias, which are mentioned in the related art, are factors that affect the amount of toner adhered to the photoconductor. In addition, there are toner concentrations and the like.

In order to stabilize the image quality, it is necessary to satisfy the condition that the toner adhesion amount on the photoconductor is constant, but the rotation speed of the developing sleeve provided in the developing unit is not changed. In the developing unit configured as described above, when the linear velocity of the photoconductor is slowed down due to the higher pixel density, the toner adhesion amount to the photoconductor increases, so that the toner adhesion amount control circuit decreases the toner density. The unit is controlled. For this reason, if image formation is continuously performed in this state, the pixel density will decrease, and switching will be performed to reduce the recording density in this state, and the linear velocity of the photoconductor will increase. However, there is a problem that the toner density is too low to obtain an image with a required density. Further, in the developing unit configured to adjust the rotation speed of the developing sleeve in proportion to the linear velocity of the photoconductor, the pixel density is increased because the ratio of the linear velocity of the photoconductor to the linear velocity of the developing sleeve does not change. To this end, when the photosensitive member linear velocity is slowed down, the toner adhesion amount control circuit controls the toner adhesion amount to be kept constant, and the rotation speed of the stirring member inside the developing unit decreases, so that the toner concentration detection unit In the vicinity of, the flow of the developer becomes slow, and the toner density is controlled to increase. Therefore, as in the case described above, if the pixel density is reduced after continuous image formation in this high pixel density mode, an abnormal image such as scumming may occur.

The present invention has been made in view of the above circumstances. In claim 1, the linear velocity of the photoconductor is changed according to the change.
An object of the present invention is to provide an image forming apparatus that can always obtain a stable image even if the linear velocity of the photoconductor changes by changing the toner density control method. Also,
According to a second aspect of the present invention, when the linear velocity of the photoconductor is low, the detection of the toner adhesion amount is prohibited so that the toner density can always be made constant, whereby a stable image can always be obtained. The purpose is to provide a device. Further, in claim 3, when the linear velocity of the photoconductor is low, the toner density control can be prohibited so that the toner adhesion amount can be made constant at all times, whereby a stable image can always be obtained. An object is to provide a forming device.

[0006]

In order to achieve the above object, the present invention provides, in claim 1, an electrostatic latent image after an optical image is exposed on a uniformly charged photoreceptor. In an image forming apparatus, which develops an electrostatic latent image on the photoconductor by a developing unit to form a toner image, transfers the toner image onto a transfer sheet, and ejects the sheet outside the machine, a developer contained in the developing unit. There are a plurality of toner density detection sensors for detecting the toner density of the toner, a toner adhesion amount detection sensor for detecting the toner adhesion amount of the toner image formed on the photoconductor, and a linear velocity of the photoconductor of the photoconductor. One of the toner density control methods is selected, and based on the toner density control method selected in this selection process, one of the detection result of the toner density detection sensor and the detection result of the toner adhesion amount detection sensor, or Use whichever is characterized in that a toner supply amount control unit for controlling the supply amount of the toner to the developing unit. Further, in claim 2,
The image forming apparatus according to claim 1, wherein the toner replenishment amount control unit ignores the detection result of the toner adhesion amount detection sensor when the photoconductor linear velocity of the photoconductor is low, and determines the toner density. It is characterized in that the toner replenishment amount to the developing unit is controlled by using a toner concentration control method that uses only the detection result of the detection sensor. According to a third aspect of the present invention, after the photosensitive member that has been uniformly charged is exposed with an optical image to form an electrostatic latent image, the rotating member provided inside the photosensitive member in accordance with the linear velocity of the photosensitive member is rotated. An electrostatic latent image on the photoconductor is developed by a developing unit that changes the number of rotations to form a toner image, which is transferred onto a transfer paper and discharged outside the machine. The toner adhesion amount detection sensor for detecting the toner adhesion amount of the formed toner image, and the detection result of the toner adhesion amount detection sensor when the photoconductor linear velocity of the photoconductor is low, is used for the developing unit. A toner replenishment amount control unit for controlling the toner replenishment amount is provided.

According to the above structure, in the first aspect, the electrostatic latent image on the photoconductor is formed by the developing unit after the optical image is exposed to the uniformly charged photoconductor to form the electrostatic latent image. In an image forming apparatus that develops a toner image, transfers the toner image onto a transfer sheet, and discharges the sheet outside the apparatus, a plurality of toner density control methods are used by a toner replenishment amount control unit according to the linear velocity of the photosensitive member. And one of the detection results of the toner concentration detection sensor, the detection result of the toner adhesion amount detection sensor, or both are used based on the toner concentration control method selected in this selection process. By controlling the replenishment amount of the developer to the developing unit, the toner density control method is changed according to the change in the linear velocity of the photoconductor to obtain a stable image even if the linear velocity of the photoconductor changes.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, when the photoconductor linear velocity of the photoconductor is low, the toner replenishment amount control unit controls the toner adhesion amount detection sensor. By ignoring the detection result and using the toner concentration control method that uses only the detection result of the toner concentration detection sensor to control the replenishment amount of the developer to the developing unit, the linear velocity of the photoconductor can be reduced. At certain times, detection of the toner adhesion amount is prohibited and the toner density is always kept constant, whereby a stable image is always obtained.

According to a third aspect of the present invention, an optical image is exposed on a uniformly charged photoconductor to form an electrostatic latent image, and then the photoconductor is provided inside according to the photoconductor linear velocity of the photoconductor. In an image forming apparatus that develops an electrostatic latent image on the photoconductor into a toner image by a developing unit that changes the number of rotations of a rotating member, transfers the toner image onto a transfer paper, and discharges the paper out of the machine,
When the photoconductor linear velocity of the photoconductor is low, the toner replenishment amount control unit uses the detection result of the toner adhesion amount detection sensor to control the replenishment amount of the developer to the developing unit. When the linear velocity of the body is low, the toner density control is prohibited so that the toner adhesion amount is always constant, whereby a stable image is always obtained.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a schematic configuration diagram showing a first embodiment of an image forming apparatus according to the present invention. The image forming apparatus 1 shown in this figure is rotationally driven by a drive unit,
A photoconductor drum 2 that serves as an image carrier, and a charging unit 3 that uniformly charges the photoconductor drum 2 and then forms an electrostatic latent image with an optical image emitted from an exposure unit (not shown).
The developing unit 4 that develops the electrostatic latent image formed on the photoconductor drum 2 into a toner image, and the transfer paper fed from the registration roller 5 of the paper feeding device onto the photoconductor drum 2
A transfer separation unit 6 for separating the toner image on the photosensitive drum 2 after transferring the toner image, a cleaning unit 7 for removing charges and residual toner remaining on the photosensitive drum 2, and a cleaning unit 7 in front of the cleaning unit 7. Adhesion of toner, which is composed of a light-reflective sensor or the like arranged on the side, detects the toner adhesion amount of the toner image (test toner image) formed on the photosensitive drum 2 and outputs a toner adhesion amount detection signal. And an amount detection sensor 8, and while the photoconductor drum 2 is rotated by the drive unit, an electrostatic latent image is formed on the photoconductor drum 2 by the optical image emitted from the exposure unit, and then the development unit 4 is used. This is developed into a toner image, and the toner image is transferred by the transfer separation unit 6 onto the transfer paper supplied from the registration roller 5 of the paper feeding device. Is supplied to the fixing device (not shown) to fix it, it is discharged to the outside.

In this case, the developing unit 4 is arranged in advance in a hollow unit casing 9 as shown in FIG. 2, and a rear upper side of the unit casing 9 (upper right side in FIG. 2). The toner replenishing roller 10 that rotates in the direction indicated by the arrow to take in the toner from the toner cartridge, and the toner replenishing roller 10 that is arranged at the rear side of the unit casing 9 and that rotates in the direction indicated by the arrow, , The developer 12, a stirring roller 11 for stirring, and a plurality of bucket-shaped blades arranged in the center of the unit casing 9, and rotates in the direction shown by the arrow to rotate the stirring roller 1
The paddle 13 that conveys the developer 12 agitated by 1 to the front, and the paddle 13 that is arranged at a position facing the photosensitive drum 2 on the uppermost front side of the unit casing 9 and rotate in the direction indicated by the arrow, The developer 12 carried by 13 is carried to the photosensitive drum 2 side, and an upper developing sleeve 14 to which the developer 12 is attached is provided.

Further, the developing unit 4 is arranged at a position facing the photosensitive drum 2 on the lower side of the foremost portion of the unit casing 9, rotates in the direction shown by the arrow, and is conveyed by the paddle 13 to the developing unit 4. The agent 12 is conveyed to the side of the photoconductor drum 2 to adhere the toner onto the photoconductor, and at the same time, the developer 12 transferred from the upper developing sleeve 14 is rubbed against the photoconductor drum 2 to adhere the toner to the development. A lower developing sleeve 15 for returning the developer 12 after the completion to the paddle 13 side, and a developer 12 which is arranged on the front side upper part of the unit case 9 and is conveyed forward by the paddle 13 for a necessary amount or more, So that it is not supplied to the sleeve 14,
A doctor blade 16 for restricting passage of the developer 12,
The doctor blade 16 is placed on top of the unit casing 9.
A separator 17 that guides the developer 12 not regulated by the above and not supplied to the upper developing sleeve 14 to the rear side of the paddle 13,
The developer 1 disposed on the upper rear side of the unit casing 9 and rotated in the direction indicated by the arrow and guided by the separator 17.
Transport screw 18 for dropping 2 to the rear side of paddle 13
And the stirring roller 1 on the lower rear side of the unit casing 9.
A toner concentration sensor 19 that is configured by a magnetic permeability change detection sensor or the like arranged below the first sensor 1 and that detects the toner concentration of the developer 12 stirred by the stirring roller 11 and outputs a toner concentration detection signal. I have it.

When developing the electrostatic latent image formed on the photosensitive drum 2, the agitating roller 11 agitates the developer 12 in the unit case 9, while the paddle 13 conveys the developer 12 forward. Then, toner is attached to the photosensitive drum 2 by the upper developing sleeve 14 and the lower developing sleeve 15 to develop the electrostatic latent image, and the electrostatic latent image is visualized. The doctor blade 16, the separator 17, and the transport screw 18 return the developer 12 not used in the development to the paddle 13 side. At this time, in the image forming apparatus 1, the surface moving speed (photosensitive member linear velocity) of the photosensitive drum 2 is 200 mm / s.
When the speed is changed from ec to 100 mm / sec, the paddle 13 is rotated at the same rate as the reduction rate of the rotation speed of the photosensitive drum 2.
When the rotation speed of the
2 is not conveyed to the upper developing sleeve 14 or the lower developing sleeve 15 side, the linear velocity of the photoconductor is 200 mm / s.
When ec, the rotation speed of the paddle 13 is set to 375 rpm,
When the linear velocity of the photoconductor reaches 100 mm / sec, the rotation speed of the paddle 13 is set to 300 rpm.

Next, the toner replenishment amount control circuit of the developing unit 4 will be described with reference to the block diagram shown in FIG. Toner supply amount control circuit 2 shown in this figure
Reference numeral 5 denotes a toner density reference value changing circuit 26 for processing a toner adhesion amount detection signal output from the toner adhesion amount detecting sensor (P sensor) 8, and the toner density reference value changing circuit 26.
The toner concentration reference value change signal ΔV _REF output from the toner concentration detection signal (T sensor) 19 is processed to control the rotation of the toner replenishing roller 10 to control the toner replenishment amount. Toner supply CL
An on-time determining circuit 27 is provided, and the toner adhesion amount detection signal output from the toner adhesion amount detection sensor 8 and the toner concentration detection signal output from the toner concentration detection sensor 19 are processed, and a toner replenishment roller is provided. Even if the recording linear density is switched and the photoconductor linear velocity of the photoconductor drum 2 is switched by controlling the rotation of 10 to control the toner replenishment amount, the optimum toner replenishment amount is always set to the photoconductor. The electrostatic latent image formed on the drum 2 is developed with the optimum toner density.

The toner density reference value changing circuit 26 processes the toner adhesion amount detection signal output from the toner adhesion amount detection sensor 8 and outputs a signal V _SG indicating the toner adhesion amount on the background portion.
And a signal V _SP indicating the toner adhesion amount of the pattern portion is generated, and then V _SP / V _SG = 0.4 V / by fuzzy calculation.
Toner concentration reference value V _REF required for setting to 4.0 V (This toner concentration reference value V _REF is such that when the developer 12 is put into the unit casing 9, the toner concentration in the developer 12 is 2.5 wt. %, The change amount is set to 2.5 V) and the toner density reference value change signal ΔV
_REF is generated and fed back to the toner replenishment CL on-time determination circuit 27.

The toner replenishment CL ON time determining circuit 27 is
When the photoconductor linear velocity of the photoconductor drum 2 is 200 mm / sec, the toner concentration reference value change signal ΔV _REF output from the toner concentration reference value change circuit 26 is fetched to change the toner concentration reference value V _REF. , The toner concentration detection signal value V _T output from the toner concentration detection sensor 19 and the toner concentration reference value V _REF are compared to obtain V
Fuzzy operation coefficient GAI required to satisfy _REF ≧ V _T
After N is determined, the fuzzy operation coefficient GAIN and the area of the pixel count writing vector portion, for example, if the image size is A4, the area corresponding to 6% of the total area, the replenishment ability of the toner replenishing roller 10, etc. Based on the above, the on-time of the toner replenishing roller 10 is determined by performing the calculation shown in the following formula, and the rotation of the toner replenishing roller 10 is controlled to be turned on / off based on the content of the determination, so that the optimum toner replenishing amount is
The electrostatic latent image formed on the photoconductor drum 2 is developed. ON time of toner replenishment CL = (GAIN × pixel × adhesion amount) / replenishment ability (1) Further, the linear velocity of the photosensitive drum 2 is 100 mm / s.
When it is ec, the toner concentration reference value change signal ΔV _REF output from the toner concentration reference value change circuit 26 is ignored and the toner concentration detection signal value V _T output from the toner concentration detection sensor 19 and The fuzzy calculation coefficient GAIN required to satisfy V _REF ≧ V _T is determined by comparing with the toner density reference value V _REF, and the fuzzy calculation coefficient GAIN and the area of the pixel count write vector portion, for example, the image If the size is A4, the on-time of the toner replenishing roller 10 is determined by performing the calculation shown in the equation (1) based on the area equivalent to 6% of the total area and the replenishing ability of the toner replenishing roller 10. Then, based on the content of this determination, the rotation of the toner supply roller 10 is turned on /
The off control is performed so that the electrostatic latent image formed on the photoconductor drum 2 is always developed with the optimum toner supply amount.

As a result, the pixel density is changed to 60
When the linear velocity of the photosensitive body of the photosensitive drum 2 is switched from 0 dpi to 400 dpi, the rotational speed of the upper developing sleeve 14 and the lower developing sleeve 15 is faster than the linear velocity of the photosensitive body of the photosensitive drum 2 increases. , The toner concentration adhesion amount increases, and the toner replenishment amount control circuit 25 outputs the toner concentration reference value change signal ΔV _REF for correcting the toner concentration decrease direction. With ΔV _REF ignored, only the toner concentration detection signal output from the toner concentration detection sensor 19
The rotation of the toner supply roller 10 can be controlled to be turned on / off, and even if the pixel density is switched, the toner density does not change at the time of switching and the image can be stabilized. As described above, in this embodiment, when performing high density recording, the toner density reference value change signal ΔV _REF output from the toner density reference value change circuit 26 is ignored, and the toner density detection sensor 19 outputs. When the low-density recording is performed by controlling the rotation of the toner replenishing roller 10 only by the toner concentration detection signal, the toner concentration reference value changing signal ΔV _REF output from the toner concentration reference value changing circuit 26 and the toner concentration Since the rotation of the toner supply roller 10 is controlled to be turned on / off by using the toner density detection signal output from the detection sensor 19, even if the recording density is switched,
It is possible to always obtain a stable image without changing the toner density.

FIG. 4 is a schematic block diagram showing an example of a developing unit used in the second embodiment of the image forming apparatus according to the present invention. The developing unit 30 shown in this drawing is arranged in a hollow unit casing 31 and a rear upper side (upper right side in FIG. 4) of the unit casing 31, and rotates in a preset direction. , A toner replenishing roller 33 that takes in toner from the toner cartridge, and a unit casing 31
A mixing roller 34 disposed on the rear side of the unit and rotating in a direction indicated by an arrow to mix the toner taken in by the toner supply roller 33 with the developer 32, and a unit casing 31.
Having a plurality of blades formed in a bucket shape arranged in the center of the mixing roller 34 and rotating in the direction indicated by the arrow.
While the developer 32 mixed by is agitated, it is arranged at a position facing the photoconductor drum 36 on the front side of the agitating roller 35 which conveys the developer 32 and the unit casing 31, and rotates in the direction shown by the arrow. And a developing sleeve 37 that conveys the developer 32 agitated by the agitating roller 35 to the photosensitive drum 36 side and attaches the toner.

Further, the developing unit 30 is disposed above the front side of the unit casing 31, and the developer 32 carried forward by the agitating roller 35 is supplied to the developing sleeve 37 in a necessary amount so as not to be supplied to the developing sleeve 37. The doctor blade 38 that restricts the passage of 32 and the developer 32 that is disposed on the upper front side of the unit casing 31 and that is conveyed forward by the stirring roller 35 is the developer 32 that has not been used in the developing sleeve 37. The separator 39 guided to the rear side of the stirring roller 35 and the rear upper side of the unit casing 31 are arranged and rotated in the direction indicated by the arrow so that the developer 32 guided by the separator 39 is transferred to the rear side of the stirring roller 35. The transport screw 40 to be dropped and the permeability change detection type disposed below the mixing roller 34 below the rear portion of the unit casing 31. It is constituted by such as capacitors, and a toner concentration detecting sensor 41 for outputting a toner density detection signal by detecting the toner density of the developer 32 is mixed by the mixing roller 34.

When the electrostatic latent image formed on the photosensitive drum 36 is developed, the unit roller 3 is moved by the mixing roller 34.
While mixing the developer 32 in the No. 1, the stirring roller 35
The developer 32 is conveyed forward by the developing sleeve 37.
The electrostatic latent image is developed by adhering it onto the photosensitive drum 36 by means of a toner image, and is not used for development by the doctor blade 38, the separator 39, and the transport screw 40. Developer 32
Is returned to the rear side of the stirring roller 35. In this case, as shown in FIG. 5, the toner replenishment amount control circuit 42 for controlling the toner replenishment amount of the developing unit 30 is used once for 200 copies when the photoconductor linear velocity of the photoconductor drum 36 is low. After processing the toner adhesion amount detection signal output from the toner adhesion amount detection sensor 43 at the detection timing to generate a signal V _SG indicating the toner adhesion amount on the background portion and a signal V _SP indicating the toner adhesion amount on the pattern portion. , Fuzzy calculation determines the on-time of the toner replenishing roller 33 required to set V _SP / V _SG = 0.4V / 4.0V. At this time, for example, if (V _SP / V _SG ) ≦ (1/12), the on time of the toner replenishing roller 33 is 1.0 sec, (1/1
2) ≦ (V _SP / V _SG ) ≦ (1/8), the on time of the toner supply roller 33 is 0.5 sec, (V _SP /
If V _SG )> (1/8), the toner replenishing roller 33
The on-time of is set to 0.0 sec. And
Based on the ON time of the toner replenishing roller 33 obtained by this determination operation, the rotation of the toner replenishing roller 33 is controlled to be ON / OFF to control the toner replenishment amount, the recording linear density is switched, and the photosensitive drum 36 is rotated. Even when the photoconductor linear velocity is switched, the optimum toner replenishment amount is always set and the electrostatic latent image formed on the photoconductor drum 36 is developed with the optimum toner density.

Even in this case, in this image forming apparatus, when recording is performed in high density recording (600 dpi), the linear velocity of the photosensitive drum 36 is reduced, and at this ratio, the mixing unit constituting the developing unit 30 is mixed. Even if the number of rotations of each driving component such as the roller 34 and the stirring roller 35 is reduced,
The developer 32 can be conveyed to the developing sleeve 37 without any problem, and the ratio of the rotation speed of the photosensitive drum 36 to the rotation speed of the developing sleeve 37 can be kept constant. Even if the linear velocity is switched, the amount of toner adhered onto the photosensitive drum 36 can be kept constant. That is, the developing unit 30
When the number of rotations of the driving parts constituting the above is reduced, the developer 3 flowing on the surface of the toner concentration detection sensor 41 as shown in FIG.
Since the output of the toner concentration detection sensor 41 tends to increase due to the change of the speed of No. 2, the toner concentration detection target of the toner adhesion amount is controlled by the linear velocity when the recording density is 600 dpi as in the conventional technique. Reference value V of sensor 41
When REF is set, when the recording density is set to 400 dpi, the reference value VREF of the toner density detection sensor 41 deviates from the optimum value, so it is impossible to suppress the toner density fluctuation at the time of switching, but in this embodiment, Since the on time of the toner replenishing roller 33 is determined based on the output of the toner adhesion amount detection sensor 43, it is possible to prevent the toner density from changing even during switching, thereby stabilizing the image. be able to. As described above, in this embodiment, when the linear velocity of the photosensitive drum 36 is low, the toner adhesion amount of the toner image developed by the developing unit 30 that develops with the one developing sleeve 37 is measured, and the measurement result is obtained. Since the on time of the toner replenishing roller 33 is determined based on the above, the toner adhesion amount can always be made constant, and thus a stable image can always be obtained.

[0022]

As described above, according to the present invention, in claim 1, even if the linear velocity of the photoconductor is changed by changing the toner density control method according to the change of the linear velocity of the photoconductor. , You can always get a stable image. Further, according to the second aspect, when the linear velocity of the photoconductor is low, detection of the toner adhesion amount can be prohibited so that the toner density can always be made constant, whereby a stable image can always be obtained. . Further, according to the third aspect, when the linear velocity of the photoconductor is low, the toner density control can be prohibited so that the toner adhesion amount can always be made constant, whereby a stable image can always be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a configuration diagram showing a detailed configuration example of the developing unit shown in FIG.

FIG. 3 is a block diagram showing a detailed circuit configuration example of a toner supply control circuit of the developing unit shown in FIG.

FIG. 4 is a schematic configuration diagram showing an example of a developing unit used in a second embodiment of the image forming apparatus according to the present invention.

5 is a block diagram showing a detailed circuit configuration example of a toner supply control circuit of the developing unit shown in FIG.

6 is a graph showing an output example of a toner density detection sensor used in the developing unit shown in FIG.

[Explanation of symbols]

1 ... Image forming device, 2 ... Photosensitive drum (photosensitive member), 3 ...
Charging unit, 4 ... Developing unit, 5 ... Registration roller, 6 ... Transfer separation unit, 7 ... Cleaning unit, 8 ... Toner adhesion amount detection sensor, 9 ... Unit casing,
10 ... Toner supply roller, 11 ... Agitation roller, 12 ... Developer, 13 ... Paddle, 14 ... Upper development sleeve, 15 ... Lower development sleeve, 16 ... Doctor blade, 17 ... Separator, 18 ... Conveying screw, 19 ... Toner concentration Sensor,
25 ... Toner supply amount control circuit (toner supply amount control unit),
26 ... Toner concentration reference value changing circuit, 27 ... Toner supply C
L on-time determination circuit, 30 ... Developing unit, 31 ... Unit casing, 32 ... Developer, 33 ... Toner supply roller, 3
4 ... Mixing roller, 35 ... Stirring roller (rotating member), 36
... Photosensitive drum (photosensitive member), 37 ... Developing sleeve (rotating member), 38 ... Doctor blade, 39 ... Separator,
40 ... Conveying screw, 41 ... Toner concentration detection sensor, 4
2 ... Toner supply amount control circuit (toner supply amount control unit), 4
3 ... Toner adhesion amount detection sensor

Claims (3)

[Claims] 1. An electrostatic latent image is formed by exposing a uniformly charged photoconductor to an optical image, and the electrostatic latent image on the photoconductor is developed into a toner image by a developing unit. In an image forming apparatus that transfers toner onto a transfer sheet and discharges the toner to the outside of the apparatus, a toner concentration detection sensor that detects the toner concentration of the developer housed in the developing unit, and a toner formed on the photoreceptor. A toner adhesion amount detection sensor for detecting the toner adhesion amount of the image and one of a plurality of toner density control methods are selected according to the linear velocity of the photoconductor of the photoconductor, and the toner concentration control selected in this selection process is performed. Based on the method, one or both of the detection result of the toner concentration detection sensor and the detection result of the toner adhesion amount detection sensor is used to control the toner supply amount to the developing unit. An image forming apparatus comprising: a toner replenishment amount control unit. 2. The image forming apparatus according to claim 1, wherein the toner replenishment amount control unit ignores the detection result of the toner adhesion amount detection sensor when the photoconductor linear velocity of the photoconductor is low. An image forming apparatus is characterized in that a toner replenishment amount to the developing unit is controlled by using a toner concentration control method using only the detection result of the toner concentration detection sensor. 3. The number of rotations of a rotating member provided inside the photosensitive member, which is uniformly charged, after the optical image is exposed to form an electrostatic latent image, and which is provided inside according to the linear velocity of the photosensitive member. In the image forming apparatus, the electrostatic latent image on the photoconductor is developed into a toner image by a developing unit that changes the value, and the toner image is transferred onto a transfer paper and ejected outside the machine. When the toner adhesion amount detection sensor for detecting the toner adhesion amount of the toner image and the photoconductor linear velocity of the photoconductor are low, the detection result of the toner adhesion amount detection sensor is used to detect the toner amount to the developing unit. An image forming apparatus comprising: a toner replenishment amount control unit that controls a replenishment amount.