JP3037977B2 - Copy image density stabilization method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for stabilizing copy image density for a two-component developer.

[Conventional technology]

As a method of stabilizing a copy image density to obtain a stable copy image density in an electrophotographic apparatus or the like, for example, there is a method disclosed in JP-A-59-174862, "Method of stabilizing copy image density". This method uses two sensor patterns having a constant image density to specify development characteristics, and performs adjustment corresponding to the development characteristics to prevent the toner density from becoming abnormally high and to stabilize the image density. It is intended to be.

[Problems to be solved by the invention]

However, according to JP-A-59-174862, two constant image densities are used as sensor patterns. However, since there is an error in the constant image densities, development characteristics are not always properly specified. There was a problem.

Conventionally, the system was configured on the assumption that the error in the sensor pattern density was negligible,
For example, assume that two constant image densities are D ₁ and D _2, and the error of D ₁ is ± d
_1, an error of D ₂ as ± d _2, when obtaining the sensor pattern density and its gradient from the relationship of the toner pattern density corresponding thereto (development properties), as shown in FIG. 4, dashed lines 40
1, the inclination of the solid line 402 and the one-dot broken line 403 are obtained. The solid line 402 shows the inclination when there is no error in the constant image densities D ₁ and D ₂ , and as apparent from comparison with the broken line 401 and the dashed line 403,
The difference between the relationship between the sensor pattern density and the toner pattern density (that is, the error in the development characteristics) is not of a negligible level.

The present invention has been made in view of the above, and an object of the present invention is to reduce errors in development characteristics.

[Means for solving the problem]

The present invention achieves the above object by changing the exposure amount when exposing a sensor pattern having a constant density and exposing the sensor pattern to a potential distribution corresponding to the sensor pattern and the exposure amount other than the image area of the photoconductor. The potential of the formed toner pattern is optically detected, and based on the development potential and the detected density of the toner pattern, the inclination of the development characteristic is calculated. Based on the calculated inclination of the developing characteristics, the developing characteristics of the corresponding developer are specified from among the developing characteristics of the plurality of developers stored in advance, and the developing characteristics of the corresponding developer are transferred to the developer based on the developing characteristics of the specified developer. The present invention also provides a method for stabilizing a copied image by controlling toner replenishment and controlling at least one of control factors such as a photosensitive member charging current and an exposure amount in a predetermined control mode. It is.

[Action]

The copier stabilization method of the present invention is to change the exposure amount when exposing a sensor pattern having a constant density,
A potential distribution corresponding to the sensor pattern and the exposure amount is formed in an area other than the image area of the photoconductor, and the density of the toner pattern obtained by developing the potential distribution is optically detected. The development potential and the density of the detected toner pattern are detected. Based on the detected toner pattern density and the calculated inclination of the developing characteristic, the developing characteristic of the corresponding developer is specified from among the developing characteristics of a plurality of developers stored in advance. I do. Thereafter, the toner supply to the developer is controlled based on the specified developing characteristics, and at least one of control factors such as a photoconductor charging current and an exposure amount is controlled in a predetermined control mode.

〔Example〕

Hereinafter, the copy image density stabilizing method of the present invention will be described in detail with reference to the drawings.

First, some definitions are given for terms used prior to the description. The potential distribution for the sensor pattern is
An electrostatic latent image formed on the photoconductor in accordance with the sensor pattern. This is not called an electrostatic latent image, and in particular, a potential distribution is to distinguish it from an electrostatic latent image formed corresponding to an original to be copied. Therefore, in this specification, an electrostatic latent image refers to an electrostatic latent image corresponding to an original. Further, the image forming area refers to an electrostatic latent image forming area on the photoconductor. However, this image forming area is not always uniquely defined on the photoconductor.

In the present invention, a sensor pattern having a constant density is used, and when exposing the sensor pattern, the exposure amount is switched between the first half and the second half. For this reason, the sensor pattern has a uniform constant image density, but the toner pattern has two densities.

The density of the toner pattern is optically detected, and the development result is specified based on the detection result.

In accordance with the specified developing characteristics, replenishment of the toner into the developer is controlled, and the charging current, exposure amount,
At least one of the control factors such as the developing bias voltage is controlled by a predetermined control mode, so that the copy image density is stabilized.

Originally, in the conventional stabilizing method, the toner supply is controlled according to the density of the toner pattern, and the toner density should be controlled within a certain fluctuation range. However, the appearance of an abnormally high toner density state that far exceeds the upper limit of the above-mentioned fluctuation area occurs when it should not be replenished.
This is probably because toner has been replenished. Now, using a gray scale of uniform density as the sensor pattern, developing the potential distribution corresponding to the gray scale where the exposure amount was switched between the first half and the second half, and optically detecting the density of the obtained toner pattern , The detected concentration,
The relationship between the developing potential (photoconductor potential-developing bias voltage) when developing the potential distribution formed by the combination of the sensor pattern and the exposure amount is, for example, the line 1--1 in FIG.
It looks like 1,1-2,1-3,1-4. Each of such correspondences is called a developing property of the developer. Here, as the light amount increases, the photoconductor potential decreases (in absolute value),
The development potential decreases (in absolute value).

For example, the toner concentration TS in the developer is a standard concentration TS ₁
If the development characteristic at the time of is the development characteristic 1-1,
As the toner concentration TS gradually increases, the development characteristics become
It fluctuates continuously to the side approaching the development characteristics 1-2, and
TS accordance becomes lower than the TS _1, the developing characteristics is continuously varied to the side of the developing properties 1-3.

Now, let TS ₂ be the toner concentration that gives the development characteristics 1-2,
Considering a higher density, generally, the developing characteristic for this density should be positioned higher than the developing characteristic 1-2, but in some cases, the developing characteristic at this time may be higher than the developing characteristic. There is an abnormal case such as the characteristic 1-4.

Such abnormalities are caused, for example, by an increase in environmental temperature, a decrease in the charging potential of the photoconductor, or a reduction in the charging current.

In the copy image density stabilizing method of the present invention, when exposing a sensor pattern having a uniform density, the amount of light is switched between the first half and the second half, so that when detecting a toner pattern corresponding to the sensor pattern, its output, that is, the detected density is , in the case of developing characteristics 1-4, since so that P _1, P ₂ points is detected, in such a detection method, the developing characteristics 1-
4 itself will be specified.

FIG. 2 shows an example of a copying apparatus to which the present invention is applied,
Only the parts necessary for the description are schematically shown.

In the figure, 101 is a document placing glass, 102 is a frame, 103 is a lamp, 104 is a sensor pattern, 105 is a photoreceptor, 106 is a charger, 108 is a developing device, 109 is a lamp, 110 is a light receiving element, and 111 is A / D converter, 112 is a developing bias power supply, 113
Is a control unit, 114 is a toner supply device, 115 is a development slave,
Reference numeral 116 denotes a charging high-voltage power supply, and reference numeral 117 denotes a lamp regulator. Here, T indicates the toner stored in the toner supply device 114.

The photoconductor 105 is drum-shaped, rotates in the direction of the arrow,
The charged image is uniformly charged by the charger 106, slit-exposed at the exposure position 107, developed by the developing device 108, and the obtained visible image is transferred and fixed on a recording medium such as paper.

The original document 100 is placed on a document placing glass 101. The lamp 103 is turned on during copying, moves in the direction of the arrow, that is, from left to right in the drawing, and performs illumination scanning of the original. The reflected light from the document illuminated portion is guided to an exposure position 107 by an exposure optical system (not shown), and is formed and projected on a photoconductor 105 at the exposure position 107.

 The operation of the above configuration will be described.

The back surface of the frame 102 reflects white light well, and the center pattern 104 is fixedly provided on the back surface. Here, the sensor pattern 104 has a constant density.

When the original 100 is placed as shown in FIG. 2 and the copying process is started, first, the photoconductor 105 rotates in the direction of the arrow, and the charger 106 discharges to uniformly charge the periphery of the photoconductor 105. .

Then, the lamp 103 is turned on and moves rightward in FIG. If a result, the first half of the sensor pattern 104 is exposed with an exposure amount F ₁ prior to the illumination of the document 100, the second half is exposed with an exposure amount F _2, the optical image is irradiated to the photosensitive member 105, the sensor pattern 104 The potential distribution corresponding to
It is formed outside the image forming area of 05. As the lamp 103 moves further to the right, the document 100 is illuminated and scanned,
An original 100, that is, an electrostatic latent image corresponding to the original is formed in the image forming area.

Accordingly, with the rotation of the photoconductor 105, first, the potential distribution is developed, and then, the electrostatic latent image is developed. When the potential distribution is developed, a constant bias potential is applied to the developing unit, and immediately after the development of the potential distribution, a predetermined or operation-adjusted developing bias voltage is applied to the developing unit.

When the potential distribution is developed into a toner pattern, light from a lamp 109 is applied to the toner pattern, and light reflected by the toner pattern is detected by the light receiving element 110. In other words, the density of the toner pattern is optically detected.

The output of the light receiving element 110 is converted into a digital signal by the A / D converter 111, and is sampled by the control unit 113 in synchronization with the movement of the photoconductor 105. With this sampling, 3
Step signals TS ₀ , TS ₁ and TS ₂ are obtained. Where the signal TS
₀ is a signal obtained from a portion of the photoconductor 105 where no toner is attached (a sampling value corresponding to the portion of the photoconductor 105 where charging is not performed, not shown), and TS ₁ and TS ₂ are exposure amounts F ₁ ,
A signal corresponding to the toner pattern density corresponding to F _2.

In the control unit 113, a first said signal _{TS 0, TS 1, TS 2} , Is calculated, and ΔS = S ₂ −S ₁ is calculated from S ₁ and S ₂ .

Sensor pattern 104 and the exposure amount F _1, F ₂ photoreceptor potential V _P1 generated by, V _P2 and the developing bias voltage V developing potential V _P1 -V _B of the difference _B, and that V _P2 -V _B is constant If you think,
ΔS determines the inclination of the development characteristics (FIG. 1).

Therefore, one point of the development characteristic and its inclination are known from these signals S ₁ , S ₂ , and ΔS, and therefore, the development characteristic itself of the developer can be specified.

The control unit 113 stores various development characteristics to be specified by S ₁ , S ₂ , and ΔS including abnormal cases.
According to the input S ₁ , S ₂ , and ΔS, the stored characteristic that best corresponds to the signal value S ₁ , S ₂ , or ΔS is selected.

If the result is, for example, the developing characteristic 1-3, this indicates that the toner concentration in the developer at this time is low, and a predetermined command signal is issued to the toner replenishing device 114. Is operated to supply toner into the developer in the developing device 108. Also, even when developing with a developer having a lower toner density, a standard copy image density is obtained,
The charging current value of the photoconductor in the charger 106 is set to be relatively large.

Conversely, the specified developing characteristic is the developing characteristic 1- 1 in FIG.
In the case of 2, without supplying toner to the developer,
The charging current of the photoreceptor, which is a control factor, is set low to stabilize the density of the copied image.

Further, abnormal developing characteristics, for example, developing characteristics 1 shown in FIG.
If a characteristic such as -4 is specified, the charging current of the photosensitive member may be set higher without replenishing the toner.

How to set the photoconductor charging current as a control factor in accordance with the specified development characteristics may be experimentally determined in advance and stored in the control unit 113 together with the development characteristics. Although details are omitted, the control unit 113 includes a CPU, a RO
It can be composed of M, RAM, etc.

In the above example, were also used in addition to signal TS ₀ of the signal TS _1, TS _2.

The lamp 109 and the light receiving element 110 are easily stained with toner,
Since it is conceivable that the output of the light receiving element 110 changes with time due to contamination by the toner, the signal
By using TS ₀ as a reference, it is possible to reduce errors due to contamination of the lamp 109 and the light receiving element 110 by the toner.

When the lamp 109 and the light receiving element 110 are not likely to be contaminated by toner, for example, when the lamp 109 and the light receiving element 110 are to be cleaned each time the light and light receiving elements 110 are operated, a signal
It is not always necessary to use the TS _0.

In addition, the specification of the development characteristics by detecting the density of the toner pattern by optical detection may be performed for each copy process, or from a practical viewpoint, a plurality of processes, for example,
It suffices to carry out at a rate of about once for 5 to 10 processes.

In that case, i.e., once for multiple processes,
As the control factor of the photoconductor charging current, the previous result is held until a new developing characteristic is obtained.

FIG. 3 shows a flowchart of the operation described above. First, it is determined whether the number of copies is the tenth (step S
1) If it is the tenth sheet, the density TS ₀ of the portion where no toner adheres is detected (step S2), and the charger is turned on (step S2).
S3). Then, the lamp ON (step S4) at a light quantity F _1, followed by ON by switching the light amount of the lamp F ₂ (step S
Five). The potential distribution is developed, the toner patterns TS ₁ and TS ₂ are detected, and S ₁ , S ₂ and ΔS are obtained by calculation (step S
6, S7, S8, S9).

Thereafter, in step S10 to S16, a predetermined constant K _1, K
₂ , K ₃ (details are omitted), the toner supply stop, charger current decrease setting, toner supply, charger current increase setting, and the like are determined and executed.

〔The invention's effect〕

As described above, when exposing a sensor pattern having a constant density, exposure is performed by changing the exposure amount, and a potential distribution corresponding to the sensor pattern and the exposure amount is formed in an image area other than the image area of the photoconductor, and The density of the toner pattern obtained by developing the distribution is optically detected, and the slope of the developing characteristic is calculated based on the developing potential and the detected toner pattern density. Based on the detected toner pattern density and the calculated slope of the developing property, Specifying the development characteristics of the corresponding developer from among the development characteristics of the plurality of developers stored in advance, controlling the toner supply to the developer based on the development characteristics of the specified developer, In addition, since at least one of the control factors such as the photoconductor charging current and the exposure amount is controlled in a predetermined control mode, errors in the development characteristics can be reduced. In other words, since the density difference of the toner pattern is generated by switching the exposure amount for exposing the sensor pattern, it is possible to reduce the error (that is, the control error) of the development characteristic caused by the density error of the sensor pattern.

Further, as a secondary effect, only one density of the sensor pattern is required, so that the area of the sensor pattern can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing the principle of a method of stabilizing a copied image according to the present invention, FIG. 2 is a block diagram showing an embodiment of a copying apparatus to which the present invention is applied, and FIG. FIG. 4 is an explanatory view showing a conventional problem. EXPLANATION OF SYMBOLS 101: Document loading glass 102: Frame, 103: Lamp 104: Sensor pattern, 105: Photoconductor 106: Charger, 108: Developing device 109: Lamp, 110: Light receiving element 111 A / D converter 112 Development bias power supply 113 Control unit 114 Toner supply device 115 Development slave 116 High voltage power supply for charging 117 Lamp regulator

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI G03G 15/08 112 G03G 15/04 120 115 15/08 507L 507 (56) References JP-A-63-276070 (JP, A) JP-A-1-222273 (JP, A) JP-A-61-11762 (JP, A) JP-A-63-177178 (JP, A) JP-A-1-306874 (JP, A) JP-A-4-9074 (JP, A) Japanese Utility Model Showa 60-78049 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/00 303 G03G 13/08 G03G 15/08 G03G 21/00 370 -540

Claims (1)

(57) [Claims] 1. A method of exposing a sensor pattern having a constant density, wherein the exposure is performed by changing an exposure amount, and a potential distribution corresponding to the sensor pattern and the exposure amount is formed in an area other than an image area of a photoreceptor. Optically detects the density of the developed toner pattern, calculates the slope of the development characteristic based on the development potential and the detected density of the toner pattern, and calculates the density of the detected toner pattern and the calculated slope of the development characteristic. Based on the development characteristics of the plurality of developers stored in advance, the development characteristics of the corresponding developer are specified, and the toner supply to the developer is controlled based on the development characteristics of the specified developer. And a method for stabilizing a copy density, wherein at least one of control factors such as a photoconductor charging current and an exposure amount is controlled in a predetermined control mode.