JPH03119377A - Developer control system in electrophotographic device - Google Patents

Abstract

PURPOSE:To prevent an abnormal image in terms of density drop and trouble from toner splashing by displaying abnormality if the comparison of a previously detected density with a currently detected density, both of which are detected by a sensor detecting density based on the density of the same reference image, indicates the difference between the two densities is against the correction of reference output and exceeds a prescribed one and inhibiting the action of an electrophotographic device. CONSTITUTION:The device is provided with an F sensor 9 which employs a two- component developer and detects the concentration of toner in a developer when the device starts up. The concentration of the toner is controlled so that an output detected by the sensor agrees with the reference output. When the device is inoperable, the reference image is formed on a photosensitive body 1, and the reference output is adjusted according to the reference image density detected by a P sensor 10, thereby adjusting the toner concentration. At this time, the previous density is compared with the current one, both of which are detected by the P sensor using the same reference image, and abnormality is displayed if the difference between the two densities is against the correction of the reference output and exceeds the prescribed one. Ultimately, the operation of the device is stopped. Thus, a drop in image density and troubles mainly from toner splashing can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developer control system for a developing device using a two-component developer in an electrophotographic apparatus.

[Conventional technology]

Conventionally, as a developer control method for a developing device using a two-component developer, in order to detect and control the toner concentration of the two-component developer, the developer is passed through a coil and the magnetic permeability is detected by capturing it as inductance. However, there is a method of comparing this detection output with a reference output to control the toner supply amount and controlling the toner concentration (hereinafter referred to as the F sensor control method). If the toner density deteriorates or the movement of the developer stops due to foreign matter getting mixed in, the toner concentration will be incorrectly detected, and as a result, toner will not be replenished and the image will become extremely pale, or the toner will not be replenished. As a result, the toner density of the developer increases extremely, causing toner scattering and contaminating other parts of the device, which is one of the causes of equipment failure.

There is also a toner density control method (hereinafter referred to as P sensor control method) in which a reference image is formed on a photoreceptor and toner supply is controlled on and off to keep the developed density constant.
Thereby, the developing ability of the developer can be easily compensated for due to environmental changes. Since this method requires creating a reference image between images, it is difficult to install it in a high-speed copying machine.

Therefore, a toner density control method that combines the above-mentioned P sensor control method and F sensor control method has been adopted. In this method, the reference output in the F sensor control method is adjusted to determine the toner density, and control is performed to obtain a predetermined toner density during image formation.

[Problem to be solved by the invention]

In the toner concentration control method that combines the P sensor control method and the F sensor control method as described above, it is possible to compensate for the developing ability of the developer due to environmental changes, but the developer coil clogging occurs in the F sensor. In such a case, there is no compensating means corresponding to this, resulting in drawbacks such as a decrease in image density and machine troubles due to toner scattering.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a toner concentration control method that eliminates the above-mentioned drawbacks and is equipped with a means for detecting device abnormalities such as developer coil clogging with respect to a bobbin in the F sensor control method. It is.

[Means to solve the problem]

In order to achieve the above object, the present invention uses a two-component developer as a developer, and is provided with a sensor that detects the toner concentration of the developer when the device is operated, so that the toner concentration detection output from the sensor matches the reference output. A reference latent image is created on the photoconductor when the device is not in operation, a reference latent image is developed to create a reference image, and a sensor is provided to detect the density of the reference image. In a developer control system in an electrophotographic device, the toner density is adjusted by lowering or increasing the reference output depending on whether the density is higher or lower than a predetermined range, the sensor detecting the density of the reference image. When the detected density is compared with the density detected by a sensor that detects the density of the same reference image last time, the amount of change is contrary to the correction of the reference output, and the amount of change is greater than a predetermined value, the developing device This is characterized by displaying an abnormality and stopping the operation of the electrophotographic device.

[For production]

With the configuration of the present invention, it is possible to detect an abnormality in the device such as developer coil clogging in the F sensor control method, and it is possible to prevent machine troubles due to a decrease in image density or toner scattering.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a schematic diagram of a developing device to which the toner density control system of the present invention is applied, in which the photoreceptor 1 is conveyed in the direction of the arrow after forming an electrostatic latent image, and the developing device uses a two-component developer. A
developing sleeves 2a, 2b.

Developed with developer pumped up by 2C.

The developing device A includes a toner cartridge 3 and an agitator 4a.
, 4b, and a paddle wheel 62.
．． Developing sleeves 2a and 2b with built-in 6b% magnets
, 2c, and the toner in the toner storage chamber 5 is fed into the developer storage chamber 7 by controlling a toner replenishment roller 8. lla, llb, l
lc is a developing backup roller, 12 is a conveyance auger, 1
3 is an F sensor control board.

In the present invention, in order to control the toner concentration, a first sensor that detects the toner concentration of the developer, the so-called F sensor 9, after the electrostatic latent image on the photoreceptor 1 is developed by the third developing sleeve 2c. A part of the developer passes through the bobbin of the F sensor 9, so that the F sensor 9 outputs a detection output V according to the toner concentration. This detection output vR is a reference output V that is set in advance to be an appropriate toner density. The detected output V is compared with the reference output V. If the value is lower than V, the toner replenishing roller 8 is driven to supply toner to the developer storage chamber 7, and the detected output V is the reference output V. If the value is higher than , the toner supply roller 8 stops and no toner is supplied to the developer storage chamber 7 .

In the developing device A, a P sensor 10, which is a second sensor, is arranged at a position facing the photoreceptor 1 on the downstream side of the developing sleeve 2. A P sensor pattern of a predetermined potential is formed on the surface of the photoconductor 1 by a charging device and an electrometer (not shown), and this is developed to form a toner image (pattern).
The second sensor 10, the so-called P sensor, detects the reflection density. Detection by the P sensor 10 is performed for the background and pattern of the photoreceptor 1, respectively. Let the detection output of the background of the photoreceptor 1 be VSC, and the detection output of the pattern of the photoreceptor 1 be V5p.

Based on the ratio of the detection output VSG of the background and the detection output VSP of the pattern by the P sensor 10, the density of the toner density is determined, and when it is determined that the toner density is high, the reference output V in the F sensor control method is determined. .

is lowered, and when it is determined that the toner concentration is low, the reference output Vo in the F sensor control method is raised. Therefore, when the two sensors 9 and 10 are operating normally, P
After the sensor 10 determines that the toner density is high, the reference output V of the F sensor control method is generated. As the toner density decreases, the toner concentration decreases, and in the next detection by the P sensor, an output lower than the concentration detected by the previous P sensor is obtained.

After the P sensor 10 determines that the toner concentration is low, a result opposite to that described above is obtained.

In the toner density control method of the present invention, as shown in the flowchart of FIG. 2, at the end of the copying operation or when the main switch is turned on, the P sensor IO generates a background detection output VSa and a pattern detection output V5p on the photoreceptor 1. The density of the toner is determined based on the ratio. In this case, the detection output of the background on the photoconductor 1 detected last time by the P sensor 10 is set as V S G + , and the detection output of the pattern is set as V5,1.

Then, the ratio of the background detection output VSC by the P sensor to the pattern detection output v s p is Vsa/Vsp<7.
If it is determined that the toner density is low, the previous background detection output Vsal and pattern detection output VSP+
The ratio of VSGI / Vspl < 7, it was determined that the toner density was low last time as well, and the difference TI (VSG / VSPVs) is calculated by subtracting the previous output ratio from this output ratio.
a+ /Vsp+) is T1<0, a message indicating that an abnormality has occurred in the toner density control device is displayed, and the device is stopped.

In addition, in the same case < Vsa/Vsp < 7, even if the previous detection output ratio Vsa+ /Vsp+ < 7, the difference T1 obtained by subtracting the previous output ratio from the current output ratio is T
,>0, or the previous detection output ratio Vsa+/
When VSPI>7, the reference output Vo of the F sensor
is the previous reference output V. 1 to Vo = Vo+ + 0
．． 12 and continues until the image forming sequence is completed.

Next, when the ratio of the background detection output V5 (,) by the P sensor and the pattern detection output VSP is ./vsp>9, and it is determined that the toner density is high, the previous background detection output V S G I and pattern detection output V3,1
The ratio of Vsa+ / Vspl > 9, and the toner density was determined to be high last time as well, and the difference T2 (VSGI / VS
When it is detected that T2<-2 (P-Vsa/Vsp), a message indicating that an abnormality has occurred in the toner density control device is displayed and the device is stopped.

In addition, in the case of the same <VSG/VSP>9, even if the previous detection output ratio Vsar / Vspl > 9, the difference T2 obtained by subtracting the current output ratio from the previous output ratio is T2>-2
or the previous detection output ratio V. 1/Vs
When pl < 9, the reference output V of the F sensor.

is the previous reference output V. 1 to V. =Vo+ 0゜12
and continues lowering until the image forming sequence is completed.

In the present invention, when the toner density does not show a normal value, the current detection output ratio and the previous detection output ratio by the P sensor are compared, and the toner density determination result is continuously in a dark or light state. In addition, even though the standard output of the F sensor has been changed, the difference in the detection output ratio between the two is in the opposite direction, so it is possible to know that the bobbin that is the F sensor is clogged with developer or that foreign matter has entered the bobbin. It is possible to stop the device and display any abnormalities in the device.

Therefore, it is possible to prevent failure of other subsystems due to toner scattering without creating an abnormal image with decreased density.

Note that the criteria for determining the toner concentration by the P sensor, the method of determining the difference between the two detection output ratios, etc. differ depending on the toner replenishment ability, developing ability, P sensor detection accuracy, etc. of each individual device. In the flow shown in FIG. 2, a little width is provided assuming that the toner density determination by the P sensor is continuously too dark or that a document with a low area ratio is used.

〔effect〕

With the configuration of the present invention, in a toner density control method using the P sensor control method and the F sensor control method, it is possible to detect an abnormality due to developer clogging in the F sensor, and to prevent the creation of an image with an abnormal density or the device caused by toner scattering. This has the effect of preventing breakdowns in advance.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a developing device to which the toner density control method of the present invention is applied, and FIG. 2 is a flowchart showing the toner density control method of the present invention. DESCRIPTION OF SYMBOLS 1... Photoreceptor, 2a, 2b, 2c... Developing sleeve, 5... Toner storage chamber, 7... Developer storage chamber, 8.
...Toner supply roller, 9...F sensor, 10...
P sensor.

Claims (1)

[Claims] A two-component developer is used as the developer, and a sensor is provided to detect the toner concentration of the developer when the device is in operation.The toner concentration is controlled so that the toner concentration detection output from the sensor matches the reference output, and the device is inactive. Sometimes, a reference latent image is formed on a photoreceptor, a sensor is provided to develop the reference latent image to create a reference image, and a sensor is provided to detect the density of the reference image, and a sensor is provided to detect whether the density detected by the sensor is higher or lower than a predetermined range. In a developer control method in an electrophotographic apparatus that adjusts the toner density by lowering or increasing the reference output according to the reference output, the density detected by the sensor that detects the density of the reference image is the same as the previous density of the same reference image. compared with the density detected by the sensor, if the amount of change conflicts with the correction of the reference output and the amount of change is greater than a predetermined value, an abnormality in the developing device is displayed and the operation of the electrophotographic device is stopped. A developer control method in an electrophotographic apparatus characterized by: