JPH04329562A - Image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 using electrophotographic technology, such as an optical printer such as a laser printer, a copying machine, or a facsimile machine, which uses a two-component developer consisting of toner and carrier.

0002

2. Description of the Related Art An image forming apparatus as described above is equipped with a developing means having a developer carrying member that carries a developer and conveys it to a developing area facing the image carrying member, and the developer carrying member has two components. A developer is applied, and a magnetic field and a developing bias electric field are applied between the image carrier and the developer carrier to develop the latent image formed on the image carrier into a visible image. An image is obtained by transferring the image onto a transfer material or an intermediate transfer material.

[0003] The development characteristics of the developer in such an image forming apparatus generally change depending on the frequency of use of the developer or environmental conditions. Therefore, after forming an electrostatic latent image of a reference density pattern on an image carrier and developing this electrostatic latent image to form a visible image of the reference density pattern, the reflected or transmitted light of this visible image is There is an image forming apparatus that detects toner with a photodetecting element and controls toner replenishment according to the detected value.

[0004] According to this kind of control, the target development characteristics can be obtained using the development potential detected by the photodetector, but the image quality changes because the toner concentration varies depending on the environmental conditions. There was a problem where the For example, in the case of high humidity, the amount of charge on the toner decreases, which increases the developing ability, resulting in the toner density becoming too low, resulting in problems such as carrier adhesion and insufficient adhesion in high image density areas of the document. Problems may occur, or conversely, in the case of low humidity, the toner density may become too high, resulting in background stains and toner scattering, and it may not be possible to obtain a high-quality image density.

[0005] In order to eliminate such inconveniences, for example, as seen in Japanese Patent Laid-Open No. 177178/1982, environmental conditions such as temperature and humidity are detected by an environment detection means, and based on the detection results, It has been proposed that image forming conditions for determining image density are set based on the image density, and the previously set image forming conditions are changed based on the contents (development conditions) stored in a storage means.

[0006] Furthermore, as seen in, for example, Japanese Patent Application Laid-Open No. 2-97973, it is possible to maintain a constant mixing ratio of toner to carrier and to develop a reference latent image formed on the surface of an electrostatic latent image carrier. A method has also been proposed in which a reference pattern is formed, the image density of the reference pattern is read, and the deviation between the image density and the reference density is corrected by adjusting the developing bias voltage according to humidity.

[0007]

[Problems to be Solved by the Invention] However, in the former type of image forming apparatus, due to changes in the development characteristics of the developer over time, the development characteristics that are targeted for control and the actual development conditions vary depending on the stored development conditions. In some cases, the characteristics differ, and the desired image quality cannot be obtained.

In addition, in the latter type of image forming apparatus in which the developing conditions are controlled by detecting the developing density of the reference density pattern while the toner density is controlled constant, it is difficult to detect the developing ability. Although it can be said to be desirable,
Due to changes in the charging ability of the carrier over time, the condition that the toner concentration is constant may not necessarily be preferable for maintaining the charging ability of the toner appropriately.

[0009] This invention has been made in view of the above points, and aims to eliminate the above-mentioned problems and make it possible to obtain stable, high-quality images regardless of environmental conditions or changes in developer over time. The purpose is to

0010

[Means for Solving the Problems] In order to achieve the above object, the present invention is provided with a developing means having a developer carrying member for carrying a developer and conveying it to a developing area facing an image carrying member. A two-component developer is applied to the carrier, and a magnetic field and a developing bias electric field are applied between the image carrier and the developer carrier to develop and visualize the latent image formed on the image carrier. In an image forming apparatus that obtains an image by transferring the visible image onto a transfer material or an intermediate transfer material, an electrostatic latent image of a reference density pattern is formed on an image carrier,
After developing this electrostatic latent image to form a visible image of the reference density pattern, the reflected light or transmitted light of this visible image is detected by a light detection element, and based on the detected value, the a control means for controlling processing for forming a visible image; an environment detection means for detecting an environment such as temperature and humidity near the developing means;
A developing bias control means is provided for controlling the developing bias electric field of the reference density pattern based on the detection result of the means.

[0011] Note that the toner concentration in the developing means is detected,
a toner concentration detection means for comparing the detected value with a reference value and outputting a toner concentration control signal according to the comparison result; and a toner concentration control means for controlling the toner concentration based on the toner concentration control signal. It is desirable to provide means for controlling the reference value of the toner density detection means in conjunction with the development bias electric field of the reference density pattern being controlled by the development bias control means.

The control means, toner concentration detection means, toner concentration control means, environment detection means, and the reference value of the toner concentration detection means are changed based on the detection results of the environment detection means, and the reference value of the toner concentration detection means is changed to a predetermined toner concentration. means for detecting the developing characteristics when controlled by the photodetecting element using the photodetecting element, and controlling image forming conditions such as charging potential, developing bias electric field, or exposure amount based on the detected value of the photodetecting element. Also provided.

Further, the above-mentioned control means, toner concentration detection means, toner concentration control means, reference value control means for controlling the reference value of the toner concentration detection means based on the detection value of the above-mentioned photodetection element, and the above-mentioned photodetection means. When the difference between the current detection value and the previous detection value of the element is larger than a predetermined reference value, controlling the developing bias electric field of the reference density pattern,
A device provided with means for controlling image forming conditions such as a charging potential, a developing bias electric field, or an exposure amount is also provided.

Furthermore, the above-mentioned control means, toner concentration detection means, toner concentration control means, means for controlling a reference value of the toner concentration detection means based on the detected value of the photodetection element, and an upper limit value of the toner concentration are provided. , a lower limit value, or both values, and when the reference value reaches the upper limit value or the lower limit value of the toner density, means for changing either the developing bias electric field, the charging potential, or the exposure amount of the reference density pattern. We also offer those with

[0015]

According to the invention as claimed in claim 1, the environment such as temperature and humidity in the vicinity of the developing means is detected, and the developing bias electric field of the reference density pattern is controlled based on the detection result. It is not affected by changes in developer or developer over time.
You can always obtain stable, high-quality images.

Therefore, the present invention does not have a toner concentration detection means for detecting the toner concentration in the developing means, and toner replenishment control is performed based on the detection value of a photodetector that detects reflected light or transmitted light of a reference density pattern. The present invention can be applied to an image forming apparatus configured to perform That is, in the case of using such a photodetecting element, toner is consumed unnecessarily to develop the reference density pattern. Therefore, in order to suppress toner consumption, detection is often performed at intervals of about 10 copies, resulting in variations in toner density between detections. Therefore, the image forming apparatus employing the present invention is low-cost and useful for devices such as full-color copying machines where there is little need for accurate toner density control.

According to the second aspect of the invention, the developing bias electric field of the reference density pattern is controlled in the same manner as described above, and as the developing bias electric field is controlled, the reference value of the toner density detecting means is adjusted. Since the toner density is controlled based on the toner density control signal, the stability of image quality is further improved.

According to the third aspect of the invention, the reference value of the toner concentration detection means is changed based on the detection result of the environment detection means, and the development characteristics when the toner concentration is controlled to a predetermined value are detected by the photodetection element. Since the image forming conditions such as the charging potential, developing bias electric field, exposure amount, etc. are controlled based on the detected value of the photodetecting element, the same effects as described above can be obtained.

Therefore, the present invention according to claim 2 or 3 can be applied to a device that is equipped with a toner concentration detection means and a photodetection element in addition to the environment detection means, such as a full-color copying machine that requires accurate toner concentration control. Useful for things.

According to the fourth aspect of the invention, the reference value of the toner concentration detection means is controlled based on the detected value of the photodetecting element, and the current detected value and the previous detected value of the photodetecting element are When the difference is large compared to a predetermined reference value, the development bias electric field of the reference density pattern is controlled, as well as the image forming conditions such as the charging potential, development bias electric field, or exposure amount, so that it can be used for a relatively long period of time. It is possible to cope with changes in development characteristics due to changes in charging characteristics of the developer over time.

According to the fifth aspect of the invention, the reference value of the toner concentration detecting means is controlled based on the detected value of the photodetecting element, and the upper limit value, the lower limit value, or both of the toner concentration values are set. , when the above-mentioned reference value reaches the upper limit or lower limit of the toner density, either the developing bias electric field, charging potential, or exposure amount of the reference density pattern is changed, so that the same effect as described above can be obtained. Can be done.

Therefore, the present invention according to claim 4 or 5 can be applied to a relatively low-cost image forming apparatus that is not equipped with an environment detection means, that is, a developer whose development characteristics change relatively little depending on the environment, and which can be used in an accurate environment. It is preferable to apply this to an image forming apparatus that does not require much detection.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 2 is an overall configuration diagram of a copying machine showing a first embodiment of the present invention.

[0024] In this copying machine, an image carrier having a diameter of 120 (mm) is placed approximately at the center of the copying machine main body 1.
Around the organic photoconductor (OPC) drum 2, there is a charger 3 that charges the surface of the photoconductor drum 2, and a semiconductor laser beam is irradiated onto the uniformly charged surface of the photoconductor drum 2 to staticize it. A laser optical system 4 that forms an electrostatic latent image, a black developing device 5 that supplies toner of each color to the electrostatic latent image and develops it to obtain a toner image for each color, and three color developers of yellow Y, magenta M, and cyan C. Devices 6, 7, 8, an intermediate transfer belt 9 that sequentially transfers toner images of each color formed on the photoreceptor drum 2, a bias roller 10 that applies a transfer voltage to the intermediate transfer belt 9, and a photoreceptor after transfer. A cleaning device 11 that removes toner remaining on the surface of the drum 2, a charge eliminating section 12 that removes electric charge remaining on the surface of the photoreceptor drum 2 after transfer, and the like are sequentially arranged.

Further, around the intermediate transfer belt 9, there is a transfer bias roller 13 that applies a voltage to transfer the transferred toner image to the transfer material, and a transfer bias roller 13 that cleans the toner image that remains after being transferred to the transfer material. A belt cleaning device 14 is provided for cleaning the belt. Note that the bias roller 10 can be moved toward and away from the direction of arrow A. A conveyor belt 1 that conveys the transfer material separated from the intermediate transfer belt 9
A fixing device 16 that heats and pressurizes the toner image to fix it is disposed at the exit side end of the fixing device 1.
A paper discharge tray 17 is attached to the exit portion of the paper sheet 6 .

Further, above the laser optical system 4, there is provided a contact glass 18 as a document mounting table disposed at the top of the copying machine main body 1, an exposure lamp 19 for irradiating the document on the contact glass 18 with scanning light, The reflected light from the original is guided to the imaging lens 22 by reflection mirrors 20 and 21,
CCD (Charge Couple) is a photoelectric conversion element.
The light enters the image sensor array 23 of the ED Device. The image signal converted into an electric signal by the CCD image sensor array 23 controls the laser oscillation of the semiconductor laser in the laser optical system 4 via an image processing device (not shown).

Inside the developing devices 5 to 8, non-magnetic cylindrical developing sleeves 5a, 6a, 7a, 8 as developer holding means are provided with a predetermined gap relative to the photosensitive drum 2.
a is arranged (the gap with the photoreceptor drum 2 is 0)
．． 60mm). These developing sleeves 5a, 6a, 7a, 8
Inside a, a developing magnet (not shown) in which a plurality of different magnetic poles are alternately arranged and a magnetic shield plate made of a magnetic material are provided, and these are held in a non-rotating state.

A developer containing black toner and carrier is stored in the black developing device 5, and this is stirred by the rotation of the developer stirring member 5b, and is transferred onto the developing sleeve 5a by the developer regulating member 5c. Adjust the amount of developer pumped up. The supplied developer is magnetically supported on the developing sleeve 5a and is rotated as a magnetic brush in the rotational direction of the developing sleeve 5a.

[0029] The carrier constituting the magnetic brush has a core material of ferrite having a true specific gravity of 5.0 to 5.5 (g/cm3) coated with a non-conductive resin having an average particle diameter of 40 to 60 μm. carrier is used. A negatively charged toner to which hydrophobic silica is attached is used as the toner, and is developed by a reversal development method. As a career,
In addition to ferrite carriers, amorphous iron powder carriers can also be used. Further, titanium oxide can also be used as an additive to the toner.

Next, the control system built into the copying machine will be explained in detail with reference to FIG. This copying machine includes a main control unit (CPU) 31, a predetermined ROM 32 and a RAM 33 are attached to the main control unit 31, and a laser optical system is connected to the main control unit 31 via an interface I/O 34. Control unit 35, power supply circuit 36, optical sensor 37, toner concentration sensor 38, environment sensor 39, surface potential sensor 40, toner replenishment circuit 41,
and an intermediate transfer belt drive unit 42 are connected to each other.

The laser optical system control section 35 controls the laser optical system 4.
The power supply circuit 36 applies a predetermined charging discharge voltage to the charging charger 3 and a predetermined developing bias voltage to the developing devices 5 to 8. A predetermined transfer voltage is applied to the transfer bias roller 13.

The optical sensor 37 is a photoelectric sensor (not shown) consisting of a light-emitting element such as a light-emitting diode and a light-receiving element such as a photosensor, which is placed close to the area of the photoreceptor drum 2 after the transfer. The toner adhesion amount in the toner image of the detection pattern latent image formed in the toner image and the toner adhesion amount in the background portion are detected for each color, and the so-called residual potential after the photoreceptor is neutralized is also detected.

The toner concentration sensor 38 detects the toner concentration based on the change in magnetic permeability of the developer present in the developing device 7. This toner concentration sensor 38 compares the detected toner concentration value with a reference value, and when the toner concentration falls below the reference value and a toner shortage condition occurs, a toner replenishment signal ( Toner density control signal)
The toner replenishing circuit 41 has a function of inputting the information to the toner replenishing circuit 41. Note that the developing devices 5, 6, and 8 are each provided with a toner concentration sensor equivalent to the toner concentration sensor 38, but their illustration is omitted here. The surface potential sensor 40 detects the surface potential of the photosensitive drum 2, which is an image carrier, and the intermediate transfer belt drive unit 42 controls the drive of the intermediate transfer belt 9.

Next, the image forming conditions under standard environmental conditions in this copying machine will be explained. First, while rotating the photosensitive drum 2 at a circumferential speed of 108 mm/sec, the surface thereof is charged to -600 V by the charger 3. Next, the laser optical system 4 irradiates the photosensitive drum 2 with laser light corresponding to a black (or yellow, magenta, cyan) image signal to form an electrostatic latent image. At this time, the potential of the background portion of the photoreceptor drum 2 becomes -30 [V].

Thereafter, the black developing device 5 (or cyan developing device 6, magenta developing device 7, yellow developing device 8) develops a developing sleeve placed with a gap of 0.6 mm with respect to the photosensitive drum 2. DC component -45 to 5a
0 [V], the peak-to-peak voltage (Vp
p=1.8 [V]) and frequency f=2 [KHz] (this is an example), a rectangular wave developing bias (this is an example) is applied, and the rotational circumferential speed ratio of the developing sleeve 5a to the photoreceptor drum 2 is set to about 1. 8
Develop as a double. The gap between the developing sleeve 5a and the developer regulating portion 5c is 0.6 mm.

The toner image formed on the photosensitive drum 2 is transferred onto the intermediate transfer belt 9 by a bias roller 10 to which a transfer bias is applied. In the case of a single color, the toner image on the intermediate transfer belt 9 is transferred onto a transfer material by a transfer bias roller 13 to which a transfer bias is applied. Then, the transfer material is transported by a transport belt 15, fixed by heat and pressure by a fixing device 16, and then discharged.

In the case of two or more colors, toner images of each color are sequentially transferred onto the intermediate transfer belt 9 and then transferred onto a transfer material by a transfer bias roller 13 to which a transfer bias is applied. Then, the transfer material is transported by a transport belt 15, fixed by heat and pressure by a fixing device 16, and then discharged. In this embodiment, an AC bias with a DC component superimposed was used as the developing electric field, but an electric field with a DC pulse component superimposed or a DC bias can also be used.

Next, the operation when an environmental change occurs will be explained. It has been known that there is a factor called development γ (gamma) as a factor for determining the quality of development characteristics. In general, the development potential ΔV (the value obtained by subtracting the DC component Vdc of the development bias electric field applied to the development sleeve from the photoreceptor surface potential Vs: ΔV = Vs - Vdc
) and the amount of toner adhesion on the photoreceptor corresponding to the development potential is expressed in a graph as straight lines A, B, C, etc. as shown in FIG.

The slope of these straight lines, ie, the slope of the toner adhesion amount with respect to the development potential, is called development γ. Generally, it is known that if the above-mentioned development γ is maintained constant, the development characteristics can be maintained in a desired state. In this example, the standard environment (temperature 23°C
, humidity 65%), the developing potential of the DC component is -250 (V), and the toner adhesion amount is 0.5 (mg/c).
The reference value of the toner concentration sensor is determined so that m2) is maintained. This varies depending on the color.

In the case of high temperature and high humidity (for example, the H state is defined as a temperature of 30° C. and a humidity of 90% or higher), the surface potential of the photosensitive drum 2 decreases as shown in FIG. 4, and the amount of charge on the toner decreases. Since the amount decreases, the developing ability increases, and the toner easily adheres to the photoreceptor drum 2. Therefore, even if the toner concentration is constant, the development γ is higher than that at normal temperature and humidity (in the N state).

Therefore, the main control unit 31 which receives the signal output from the optical sensor 37 as a photodetection element determines that the amount of toner adhering that constitutes the visible image of the reference density pattern is large, and accordingly, toner replenishment is performed. Since no toner replenishment instruction is given to the circuit 41, the toner concentration becomes low.

In this embodiment, the developing electric field of the reference density pattern is changed to lower the developing ability so that the amount of decrease in toner density is alleviated. Specifically, when the development bias is DC, the development potential of the reference density pattern is changed to a smaller value, and when the development electric field has a DC component superimposed on an AC component, the DC component is changed to a smaller development potential. The developing electric field of the reference density pattern can be made to have a lower developing ability by changing the direction of the developing voltage or by changing the peak-to-peak voltage value Vpp of the AC component. This is from Vp(A) in Figure 3 to V
This corresponds to changing the development potential of the reference density pattern to p(B). As a result, as shown in region H in FIG. 5, when the environmental correction is performed (straight line b), the decrease in toner density is alleviated compared to when the environmental correction is not performed (straight line a).

On the other hand, when the temperature is low and the humidity is low (for example, when the temperature is 10
℃, 15% or more is defined as the L state), as shown in FIG. 2 becomes difficult to adhere to. Therefore, even if the toner concentration is constant, the development γ becomes low. Therefore, the main control unit 31 that receives the signal from the optical sensor 37 determines that the amount of toner adhering that constitutes the visible image of the reference density pattern is small, and accordingly instructs the toner replenishment circuit 41 to replenish toner. Increase toner density.

In this case, the developing electric field of the reference density pattern is changed to lower the developing ability so that the amount of increase in toner density is moderated. Specifically, when the development bias is DC, the development potential of the reference density pattern is changed to be larger, and when the development electric field is superimposed with an AC component, the peak-to-peak voltage value Vpp of the AC component is changed. By increasing the developing electric field of the reference density pattern, it is possible to reduce the developing ability of the standard density pattern. This corresponds to changing the development potential of the reference density pattern from Vp(A) to Vp(C) in FIG. As a result, as shown in the L region of FIG. 5, when the correction is performed depending on the environment (straight line b), the increase in toner density is moderated compared to when no correction is performed (straight line a).

However, by changing the developing electric field of the reference density pattern, the phenomenon γ changes (see A in FIG. 3).
→B or A→C), therefore, the gradation reproducibility changes if the charging potential or exposure amount conditions remain unchanged. In order to correct this, it is necessary to change the charging potential and the exposure amount (in the case of laser writing, the laser light amount).

Under normal environmental conditions (N state), the development bias of the reference density pattern is -280 (V) as a DC component.
) is applied. Also, the amount of toner adhering on the photosensitive drum 2 (M/A) [mg/cm
0.9 [mg/cm] which gives the maximum image density as [2]
2], the development potential is 420V as shown in FIG. 3, so the exposed area potential Vl is -3
When the voltage is 0 [V], the charging potential Vd is -600 [V]
is given. The DC component Vdc of the developing bias is Vd
It is given by +150 [V].

In the H state, the development potential of the reference density pattern is controlled to be -200 [V], and the development potential that gives the maximum image density at that time is 34V.
0 [V], the charging potential Vd is Vd=V
The grid bias applied to the grid 3a of the charger 3 is adjusted so that the voltage is l+340+150 [V]. The exposed portion potential Vl is given as a detection value of the surface potential sensor 40.

As in this embodiment, when a toner density sensor is installed in the developing device, the target development γ can be obtained after changing the developing electric field of the reference density pattern according to the environmental conditions. The toner density is memorized, and toner replenishment is then executed to maintain the toner density.

The above control process will be explained with reference to the flowchart of FIG. 6. First, temperature and humidity are detected by the environment sensor 39, and absolute humidity (moisture content in the air) H is calculated based on the detection results. Then, it is compared with the absolute humidity H0 when the previous environmental correction was executed, and if the result is larger than the absolute humidity reference difference ΔH, the developing electric field of the reference density pattern is changed.

At this time, if H-H0 is positive, it is assumed that the state is heading towards a high humidity state, and the potential difference (development potential ΔVp) of the DC component of the developing electric field of the reference density pattern is set to be small, and H-H0 is set to be small. If H0 is negative, it is assumed that a low humidity state is being reached, and the potential difference of the DC component of the developing electric field of the reference density pattern is set to be large. This is done in units of Δv (Δv>0). ΔVp←ΔVp-(H-H0)
/|H−H0 |×Δv However, |A| represents the absolute value of A.

When the potential difference (development potential) of the DC component of the development electric field of the reference density pattern is set, the charging potential and the exposure amount are determined as described above, so the charging conditions are reset. Detection is performed by the optical sensor 37 under the obtained conditions, and the reference value of the toner concentration sensor is changed based on the detection. The reference value of the toner concentration sensor is changed as shown in the flowchart of FIG.

That is, the ratio Vsp/Vsg of the output value Vsg of the background portion of the photosensitive drum 2 detected by the optical sensor 37 to the output value Vsp of the reference density pattern portion is determined by the reference control ratio kn (n=black , yellow, cyan, magenta), and if it is larger, then
The reference value (control target value) of the toner concentration sensor is a predetermined amount ΔT
C (in this case, equivalent to 0.10 [wt%]) is increased, and in the opposite case, it is decreased (this may be made proportional to the difference between the detected value of the optical sensor 37 and the control reference value).

If the actual toner density falls outside the range determined by the upper and lower limits as a result of changing the reference value of the toner density sensor, it is corrected so that it falls within the range. At that time, the development potential of the reference density pattern is changed. The above processing is executed for four colors: black, yellow, cyan, and magenta.

Note that the detection by the optical sensor 37 is performed when the power is turned on (this is determined by the detection of the fixing temperature) and every 50 copies, and the detection by the environmental sensor 39 is performed when the power is turned on and at predetermined intervals. (Here, every 30 minutes)
This is executed simultaneously with the detection by the optical sensor 37. However, the detection after changing the development potential of the reference density pattern is changed at a detection frequency of once every five sheets, which speeds up the convergence of the toner density. This judgment is made by the toner density change FLAG, and when this FLAG is "1", the frequency is once every 5 sheets, and when it is "0", the frequency is once every 50 sheets. Detection is performed by This process is shown in FIG.

Next, a second embodiment of the present invention will be described. Since the hardware configuration and characteristics are the same as those of the first embodiment, reference will be made to FIGS. 1 to 4 again. First, a process for changing the reference value of the toner concentration sensor by a predetermined amount in accordance with the environment will be described.

When the environmental conditions change from the N state (normal environmental state) to the L state (low temperature, low humidity) in FIG. 3, the set value of the toner density in the N state is changed. Optical sensor 37
The detection characteristic for cyan toner is determined by the toner adhesion on the photoreceptor drum 2, as the output value Vsp of the amount of reflected light at the reference density pattern portion of the photoreceptor drum 2, and the output value Vsg of the background portion (portion to which no toner is attached). When the method disclosed in JP-A-1-306874 is used for the quantity (M/A), there is a relationship as shown in Equation 1.

[0057]

[Equation 1] (M/A)=-ln(Vsp/Vsg)/ββ
=-3.0 [cm2/mg]

Further, development γ:α(1) is approximately given by equation 2, where the development start voltage is Vk.

[Equation 2] α(1) = (M/A)/(ΔVp-Vk)

0
[059] From the values of Vsp and Vsg when the setting value of the toner density is changed from the N state to the L state, the toner adhesion amount (here, 0.5 [mg/
The development potential ΔVp(2) of the reference density pattern for making the density pattern ΔVp(2) cm2]) is determined by Equation 3 from the relationship between Equations 1 and 2.

[0060]

[Equation 3] ΔVp(2)=α(2)/0.5
[mg/cm2] + Vk [V] However, α (2)
=-ln(Vsp/Vsg)/{β・(ΔVp-Vk)
}

Here, although Vk generally changes depending on the characteristics (type) of the developer and the toner concentration (TC), it is treated as a constant value Vk=-10 [V] here. Vk may be stored in the RAM 33 of FIG. 1 as a toner concentration function Vk(TC), and the toner concentration TC may be detected by a toner density sensor to obtain Vk=Vk(TC). ΔVp(2) obtained from the above is used as the development potential of the reference density pattern after humidity correction for subsequent detection.

When the toner adhesion amount to obtain the maximum image density is (M/A)max, the development potential ΔVmax
is obtained from the relational expression of Equation 2 using Equation 4.

[Equation 4] ΔVmax = (M/A)max/α(2)+
Vk

From now on, as Vd, Vd=Vl+Δ
The grid bias applied to the grid 3a of the charger 3 is adjusted so that Vmax+150 [V]. Vl is given as a detection value of the potential sensor 40.

The above control process will be explained with reference to the flowchart of FIG. 9. Temperature and humidity are detected by the environment sensor 39, and absolute humidity (moisture content in the air) H is calculated based on the detection results. Then, compare it with the absolute humidity H0 when the previous environmental correction was performed,
When the result becomes larger than the absolute humidity reference difference ΔH, the reference value of the toner concentration sensor is changed.

At this time, if H−H0 is positive, it is assumed that the state is heading for a high humidity state, and the toner concentration is set to be slightly lower (0.
．． If H-H0 is negative, it is assumed that the humidity is heading towards a low humidity state, and the toner concentration is set to be slightly higher (about 0.2 [wt%]). do. The amount of change in the reference value of the toner concentration sensor is proportional to the magnitude of ΔH, and in this case, the upper limit value (here, 6 [wt%]) and lower limit value (here, 2 [wt%]) of the toner concentration.
is set so as not to exceed.

Toner concentration may be consumed or replenished before image formation so that the targeted development γ can be quickly achieved. When the toner density is consumed, a latent image for consumption is formed on the photosensitive drum 2, and the latent image is developed.

When the difference between the detected toner concentration TC1 and the set toner concentration TC0 is adjusted to within a predetermined range (for example, within ±0.05 [wt%]), detection by the optical sensor 37 is executed. be done. Based on the detected results, the potential difference (development potential) of the DC component of the development electric field of the reference density pattern is calculated, and the charging potential and exposure amount are determined based on the development characteristics determined therefrom.

[0068] If toner density adjustment is not performed, the difference between the detected toner density and the set toner density is
The calculated development potential is corrected. The above processing is executed for four colors: black, yellow, cyan, and magenta.

Next, a third embodiment of the present invention will be described, but it is assumed that a toner concentration sensor is not provided in this embodiment. Since the other hardware configuration and each characteristic are substantially the same as those of the first embodiment described above, FIGS. 1 to 4 will be described again.
See. In this embodiment, the development electric field of the reference density pattern is corrected according to the environmental conditions using the same method as in the first embodiment, but the toner density control method is different, and an optical sensor 37 is used to control toner replenishment. Execute.

That is, the photosensitive drum 2 is
After forming a reference density pattern on the top and detecting the density by the optical sensor 37, the density data is stored in the RAM 33.
The toner supply circuit 41 is controlled based on the comparison result. Note that toner supply is performed when Vsg<
This is done at kVsp (k is the proportionality coefficient). its coefficient k
differs depending on the type of toner.

This control process will be explained with reference to the flowchart in FIG. First, the environmental sensor 39 detects the temperature and humidity, and based on the detected results, the absolute humidity (
Calculate the moisture content (H) in the air. Then, it is compared with the absolute humidity H0 when the previous environmental correction was executed, and if the result is larger than the absolute humidity reference difference ΔH, the developing electric field of the reference density pattern is changed.

At this time, if H-H0 is positive, it is assumed that the state is heading towards a high humidity state, and the potential difference (development potential) of the DC component of the developing electric field of the reference density pattern is set to be low, and H-H0 is If is negative, it is assumed that the humidity is heading towards a low humidity state, and the potential difference (development potential) of the DC component of the development electric field of the reference density pattern is set to be high. When the potential difference of the DC component of the developing electric field of the reference density pattern is set, the charging potential and the exposure amount are determined as described above, so the charging conditions are reset.

Next, a fourth embodiment of the present invention will be described, but it is assumed that this embodiment does not include an environment detection sensor. Since the other hardware configuration and characteristics are substantially the same as those of the first embodiment, FIGS. 1 to 4 will be referred to again. This embodiment will be explained with reference to the flowchart of FIG. 11. At a predetermined detection interval (20 to 50 sheets), the optical sensor 37 detects the density of the reference density pattern, and the reference value of the toner density sensor is adjusted according to the amount of deviation from the reference value. Change only the specified amount.

The amount of change ΔT (=T1−
When the absolute value of T0) is larger than the reference change amount ΔT0, the development electric field (here, development potential ΔVp) of the reference density pattern is changed. Here, with ΔV [V] as a unit, it is changed as follows: ΔVp←ΔVp−ΔT/|ΔT|×ΔV. However, |ΔT| represents the absolute value of T.

When the potential difference (development potential) of the DC component of the development electric field of the reference density pattern is set, the charging potential and the exposure amount are determined as described above, so the charging conditions are reset. Incidentally, in each of the above-described embodiments, a reflective type photodetecting element is used, but if a belt-shaped photoreceptor is used as an image carrier, a transmissive type photodetecting element can also be used.

Furthermore, in each of the above embodiments, the photosensitive drum 2
A visible image of a reference density pattern is formed on the top of the image, and the reflected light of this visible image is detected by a reflective light detection element.
A visible image of the reference density pattern after transfer may be formed on the intermediate transfer belt 9, and reflected light or transmitted light of the visible image may be detected using a reflective or transmissive light detection element.

[0077] Above, an embodiment in which the present invention is applied to a copying machine has been described, but the present invention is not limited to this, and can be applied to toner and carrier for optical printers such as laser printers, LED printers, and liquid crystal shutter printers, and plain paper facsimile machines. It is applicable to an image forming apparatus using electrophotographic technology using a two-component developer consisting of:

[0078]

As described above, according to the present invention, stable, high-quality images can be obtained regardless of environmental conditions or changes in developer over time.

[Brief explanation of drawings]

FIG. 1 is a main part configuration diagram showing a control system of the copying machine shown in FIG. 2;

FIG. 2 is an overall configuration diagram of a copying machine showing a first embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between the development potential, the output of the optical sensor, and the amount of toner adhesion on the photoreceptor.

FIG. 4 is a diagram showing the relationship between environmental conditions and photoreceptor surface potential.

FIG. 5 is a diagram showing the relationship between environmental conditions and toner concentration.

FIG. 6 is a flow diagram showing environment correction processing according to this embodiment.

FIG. 7 is a flowchart showing a process for changing a reference value of a toner concentration sensor.

FIG. 8 is a flowchart showing a timing determination process for toner density control.

FIG. 9 is a flow diagram showing environment correction processing according to a second embodiment of the invention.

FIG. 10 is a flow diagram showing environment correction processing according to a third embodiment of the present invention.

FIG. 11 is a flow diagram showing environment correction processing according to a fourth embodiment of the present invention.

[Explanation of symbols]

1 Copy machine body 2
Photosensitive drum 3 Charger
4 Laser optical system 5 Black developing device
6 Yellow developing device 7
Magenta developing device 8 Cyan developing device 9 Intermediate transfer belt
10 Bias roller 31 Main control section
32 ROM33 RAM
34 Interface I/O 35 Laser optical system control section 36 Power supply circuit 37 Optical sensor
38 Toner concentration sensor 39 Environmental sensor 40
Surface potential sensor 41 Toner supply circuit
42 Intermediate transfer belt drive unit

Claims (5)

[Claims] 1. A developing means having a developer carrier that carries a developer and transports the developer to a development area facing the image carrier, the developer carrier is coated with a two-component developer, and the image carrier is coated with a two-component developer. A magnetic field and a developing bias electric field are applied between the image carrier and the developer carrier to develop the latent image formed on the image carrier into a visible image, and then transfer the developed image to a transfer material or an intermediate. In an image forming apparatus that obtains an image by transferring it onto a transfer material, an electrostatic latent image of a standard density pattern is formed on the image carrier, and this electrostatic latent image is developed to obtain a standard density pattern. After forming the visible image, a control means detects reflected light or transmitted light of the visible image with a photodetecting element, and controls processing for forming the visible image on the image carrier based on the detected value. and an environment detection means for detecting an environment such as temperature and humidity in the vicinity of the development means, and a development bias control means for controlling the development bias electric field of the reference density pattern based on the detection result of the means. An image forming apparatus characterized by: 2. The image forming apparatus according to claim 1, wherein the toner density within the developing means is detected, the detected value is compared with a reference value, and a toner density control signal is output in accordance with the comparison result. As the developing bias electric field of the reference density pattern is controlled by the toner density detecting means for controlling the toner density, the toner density controlling means for controlling the toner density based on the toner density control signal, and the developing bias controlling means, 1. An image forming apparatus comprising: means for controlling a reference value of a toner concentration detecting means. 3. A developing means having a developer carrier that carries a developer and transports the developer to a development area facing the image carrier, the developer carrier is coated with a two-component developer, and the image carrier is coated with a two-component developer. A magnetic field and a developing bias electric field are applied between the image carrier and the developer carrier to develop the latent image formed on the image carrier into a visible image, and then transfer the developed image to a transfer material or an intermediate. In an image forming apparatus that obtains an image by transferring it onto a transfer material, an electrostatic latent image of a standard density pattern is formed on the image carrier, and this electrostatic latent image is developed to obtain a standard density pattern. After forming the visible image, a control means detects reflected light or transmitted light of the visible image with a photodetecting element, and controls processing for forming the visible image on the image carrier based on the detected value. and a toner concentration detection means for detecting the toner concentration in the developing means, comparing the detected value with a reference value, and outputting a toner concentration control signal according to the comparison result, and the toner concentration control signal. a toner concentration control means for controlling the toner concentration based on the toner concentration, an environment detection means for detecting the environment such as temperature and humidity in the vicinity of the developing means, and a reference value of the toner concentration detection means based on the detection result of the means. At the same time, the development characteristics when the toner density is controlled to a predetermined level are detected by the photodetection element, and image forming conditions such as charging potential, development bias electric field, or exposure amount are determined based on the detected value of the photodetection element. An image forming apparatus comprising: means for controlling. 4. A developing means having a developer carrier that carries a developer and transports the developer to a development area facing the image carrier, the developer carrier is coated with a two-component developer, and the image carrier is coated with a two-component developer. A magnetic field and a developing bias electric field are applied between the image carrier and the developer carrier to develop the latent image formed on the image carrier into a visible image, and then transfer the developed image to a transfer material or an intermediate. In an image forming apparatus that obtains an image by transferring it onto a transfer material, an electrostatic latent image of a standard density pattern is formed on the image carrier, and this electrostatic latent image is developed to obtain a standard density pattern. After forming the visible image, a control means detects reflected light or transmitted light of the visible image with a photodetecting element, and controls processing for forming the visible image on the image carrier based on the detected value. and a toner concentration detection means for detecting the toner concentration in the developing means, comparing the detected value with a reference value, and outputting a toner concentration control signal according to the comparison result, and the toner concentration control signal. toner concentration control means for controlling the toner concentration based on the toner concentration, and means for controlling the reference value of the toner concentration detection means based on the detection value of the photodetection element;
When the difference between the current detection value and the previous detection value of the photodetection element is larger than a predetermined reference value, the developing bias electric field of the reference density pattern is controlled, and the charging potential,
1. An image forming apparatus comprising means for controlling image forming conditions such as a developing bias electric field or exposure amount. 5. A developing means having a developer carrier that carries a developer and transports the developer to a development area facing the image carrier, wherein a two-component developer is applied to the developer carrier, and the image carrier is coated with a two-component developer. A magnetic field and a developing bias electric field are applied between the image carrier and the developer carrier to develop the latent image formed on the image carrier into a visible image, and then transfer the developed image to a transfer material or an intermediate. In an image forming apparatus that obtains an image by transferring it onto a transfer material, an electrostatic latent image of a standard density pattern is formed on the image carrier, and this electrostatic latent image is developed to obtain a standard density pattern. After forming the visible image, a control means detects reflected light or transmitted light of the visible image with a photodetecting element, and controls processing for forming the visible image on the image carrier based on the detected value. and a toner concentration detection means for detecting the toner concentration in the developing means, comparing the detected value with a reference value, and outputting a toner concentration control signal according to the comparison result, and the toner concentration control signal. toner concentration control means for controlling the toner concentration based on the toner concentration, and means for controlling the reference value of the toner concentration detection means based on the detection value of the photodetection element;
An upper limit value, a lower limit value, or both values of the toner density are set, and when the reference value reaches the upper limit value or the lower limit value of the toner density, the development bias electric field, charging potential, or exposure amount of the reference density pattern is set. An image forming apparatus characterized by comprising means for changing any of the above.