JPH08211722A - Image forming device - Google Patents

Abstract

(57) [Summary] [Object] To provide an image forming apparatus capable of detecting a toner adhesion amount characteristic with respect to a developing bias and always maintaining a stable image density. In an image forming apparatus using an electrophotographic process, a charging unit capable of continuously changing a charging potential of a photosensitive member,
The above-mentioned check is provided with a developing bias control means capable of continuously changing the developing bias, a toner adhesion amount detecting means for detecting a toner adhesion amount of a developed image, and a check mode for determining printing conditions in a normal image forming mode. In the mode, an area in which the photosensitive member charging potential is continuously changed is formed, and the toner adhesion amount of the toner image developed while continuously changing the developing bias of the test pattern formed by exposure in that area is set as the toner adhesion amount. An image forming apparatus having control means for setting and controlling the photoconductor charging potential and the developing bias in the normal image forming mode based on the signal detected by the amount detecting means.

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 for forming an image by using toner which is a minute colored powder, and more particularly, to detect and control a toner adhesion amount in order to maintain an image density at an appropriate value. The present invention relates to an image forming apparatus provided with a means for performing.

[0002]

2. Description of the Related Art The image density of an image forming apparatus depends on the amount of toner at the time of development. The amount of toner at the time of development depends on the difference in developing potential determined by the photoconductor charging potential, the exposure amount, the developing bias, and the like. Determined by quantity.

Generally, in the two-component developing system, a toner density control means is provided for controlling the mixing ratio of the toner and the carrier so that the toner charge amount becomes a specified value.
However, it is difficult to make the toner charge amount constant, and it is difficult to always maintain a stable image density only by such control.

Therefore, in order to keep the image density at an appropriate value,
Various methods for controlling the charging potential of the photoconductor, the amount of exposure, the developing bias, etc. have been proposed. Of these, the developing bias is relatively easy to greatly change the toner adhesion amount during development. In Japanese Patent Laid-Open No. 1-222273, the developing bias is changed stepwise, and the amount of developed toner at that time is detected to detect the toner concentration, the toner charge amount,
A method of controlling the developing bias, the developing speed, the exposure amount, etc. has been proposed. Further, Japanese Patent Application Laid-Open No. 60-217376 proposes a method in which a uniform surface potential is provided and development is performed while switching the development bias to form two or more toner adhesion amount detection regions.

[0005]

In the above-mentioned prior art, in the method of changing the developing bias in steps, if the developing bias is changed in steps, the toner density in the developed area around the changed position becomes unstable. In addition, there is a possibility that the carrier may be scattered from the developing machine when the developing bias is changed. Further, in the area where the toner density becomes unstable, it is necessary to perform the development with a sufficient width until the toner density becomes stable, because the accurate toner adhesion amount under the developing bias condition cannot be detected. Therefore, in order to measure the toner adhesion amount by changing a plurality of developing biases, a detection time and a wide area corresponding thereto are required, and the toner consumption amount is large accordingly.

In the system in which the developing bias is continuously changed, the region where the density is unstable does not occur unlike the stepwise changing of the developing bias. However, JP-A-60-217
In No. 376, a uniform surface potential region is formed by an erase lamp or the like, and the developing bias is changed in that region. In this case, the toner adhesion area for detection covers not only the position of the detection sensor but the entire development width, and therefore a large amount of toner is consumed.

As a countermeasure for this, a method is conceivable in which only the post-charge detection region is exposed by an exposure device so that the surface potential is uniform. However, the potential difference between the photoconductor charging potential and the developing bias changes as the developing bias changes.
When the potential difference between the developing bias and the photoconductor charging potential becomes small, so-called fog occurs in which toner adheres to the charging portion, resulting in unnecessary toner consumption. Further, when the potential difference between the developing bias and the photoconductor charging potential becomes large, so-called carrier pulling occurs in which carriers adhere to the charging portion.

An object of the present invention is to provide an image forming device capable of always maintaining a stable image density by providing means for detecting the toner adhesion amount characteristic with respect to a developing bias without wasteful toner consumption without causing the above-mentioned problems. To provide a device.

[0009]

The summary of the present invention for achieving the above object is as follows.

[1] In an image forming apparatus using an electrophotographic process, a charging unit capable of continuously changing a charging potential of a photosensitive member, a developing bias control unit capable of continuously changing a developing bias, and a developing image The toner adhesion amount detecting means for detecting the toner adhesion amount and the check mode for determining the printing condition in the normal image forming mode are provided, and in the check mode, an area in which the photoconductor charging potential continuously changes is formed. The photosensitive member in the normal image forming mode is based on a signal detected by the toner adhesion amount detecting means for the toner adhesion amount of the toner image developed while continuously changing the developing bias of the test pattern exposed and formed in the area. An image forming apparatus having control means for setting and controlling the charging potential and the developing bias.

[2] In the check mode, an area in which at least one of the photoconductor potential and the developing bias of the non-image area and the photoconductor potential and the developing bias of the image area continuously changes is formed, and the toner in the area is changed. The image forming apparatus described above, further comprising control means for setting and controlling the photoconductor charging potential and the developing bias in the normal image forming mode based on the signal detected by the toner adhesion amount detecting means.

[3] The shift to the check mode is
When the image forming apparatus is turned on and reset, when a preset time has elapsed, when the toner replenishment amount or the number of replenishment reaches a specified amount or the specified number of times, the temperature and humidity inside the device are out of the specified values. The image forming apparatus described above, which is provided with a means for detecting at least one of the number of recorded sheets when the number of recorded sheets reaches a prescribed number when the number of sheets has changed, and a control means for shifting to a check mode based on the detection signal.

Further, the control means for controlling the shift to the check mode is constituted so that the scanner can arbitrarily select.

[4] The charging means of the image forming apparatus is a scorotron charger, and is provided with a control means for controlling the grid voltage thereof.

[5] The toner adhesion amount detection means of the image forming apparatus includes an optical sensor including a light emitting element and a light receiving element.

[6] The toner adhesion amount detecting means of the image forming apparatus includes a high frequency removing means for removing a signal having a frequency higher than a preset frequency from the detection signal.

[7] In the image forming apparatus, when at least one of the toner concentration, the developing bias, and the photoconductor charging potential is out of a preset allowable variation range, a display unit is provided to display it. There is.

[8] In a color image forming apparatus using an electrophotographic process, a charging unit capable of continuously changing a charging potential of a photosensitive member, a developing bias control unit capable of continuously changing a developing bias, and a developing unit. Toner adhesion amount detection means for detecting the toner adhesion amount of the image, and a check mode for determining printing conditions in the normal image forming mode,
In the check mode, an area in which the photoconductor charging potential is continuously changed is formed, and at least one color image of the color image developed by continuously changing the developing bias of the test pattern exposed and formed in the area is formed. An image having a control means for setting and controlling the photoconductor charging potential and the developing bias at the time of developing each color in the normal image forming mode based on the detection signal detected by the toner adhesion amount detecting means Forming equipment.

[0019]

[9] An intermediate transfer member is provided which transfers and superimposes toner images of respective colors sequentially formed on the photosensitive member, and the toner adhesion amount of the color image formed on the intermediate transfer member is detected by the toner adhesion amount detection means. The color image forming apparatus configured to detect.

[0020]

[Function] By continuously changing the developing bias,
An unstable region of the toner adhesion amount that occurs when the developing bias is changed stepwise does not occur. Further, since the developing bias is continuously changed within one test pattern area, the test pattern area is small and the measuring time can be reduced as compared with a plurality of developing bias methods in which the developing bias is changed stepwise.

Further, only the toner adhesion amount detection area is exposed,
Since development can be performed, toner consumption can be reduced.

In the present invention, the charging means is provided only in the region where the photoconductor charging potential is continuously changed, and the photoconductor charging potential is changed corresponding to the region where the developing bias is continuously changed. By exposing the test pattern to that position, the potential difference between the photoconductor charging potential and the developing bias in the area where the toner adhesion amount is not measured can be controlled within an appropriate value, so the potential difference between the two is small. In this case, fogging and carrier pulling when the potential difference is large do not occur.

This makes it possible to provide an image forming apparatus which is always stable and has an appropriate image density.

[0024]

Embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1] FIG. 1 is a schematic configuration diagram of an image forming apparatus equipped with an image density control system according to an embodiment of the present invention. Around the photoconductor drum 31, there are a scorotron charger 1, a laser exposure device 2, a two-component developing device 3, a corotron type transfer device 4, an AC corona type static eliminator for peeling paper 5, an erase lamp 6, a photoconductor cleaner 7, and the like. Printing means necessary for image recording and toner adhesion amount measuring means 11
Is arranged.

The grid of the scorotron charger 1 is connected to the photoconductor charging potential control means 9 for controlling the applied voltage to control the photoconductor charging potential. Further, the laser exposure apparatus 2 is controlled by the exposure control circuit 10, and a prescribed test pattern can be exposed by an external signal.

The two-component developing machine 3 is equipped with a toner concentration measuring means 11 for measuring the mixing ratio of the carrier and the toner, and the amount of toner to be supplied to the two-component developing machine 3 based on the output value of the measuring means. A toner density control means 12 for adjusting and controlling the toner is provided. In this embodiment, replenishment and control are performed so that the toner density is always constant.

However, the charge amount may vary depending on the environmental conditions such as temperature and humidity even if the toner concentration is the same. In such a case, by adjusting the target value of the toner density to be controlled based on the detection values of the temperature and humidity detection sensor 13, it is possible to control the toner charge amount with higher accuracy. Further, the developing machine of this embodiment is provided with a developing bias control means 14 in addition to the toner density control means 12.

The toner adhesion amount measuring means 16 is provided with a toner adhesion amount detection sensor 15, which comprises a light emitting portion and a light receiving portion for receiving the reflected light of the toner. It is desirable that the light emitting portion emit infrared light that does not depend on the color of the toner. This is to detect the toner adhesion amount from the reflected light amount according to the toner adhesion amount.

The photoconductor charging potential control means 9, the exposure control means 10, the toner concentration control means 12, the developing bias control means 14 and the toner adhesion amount measuring means 16 are controlled by the printing process control means 17. The printing process control means 17 is configured to control all of the corotron type transfer device 4, the AC corona type static eliminator 5, the photoconductor cleaner 7, the sheet resist 18, etc. necessary for printing.

In this embodiment, the case of using the two-component developing machine has been described, but a system using a one-component developing machine can be similarly constructed. When the one-component developing machine is applied, the toner density control means 12 is not necessary. However, when other charge amount control means is used, a means for controlling it is necessary.

Normally, in the image forming mode, the printing process control means 17 controls the printing process such as charging, exposure, development, transfer and cleaner based on a recording signal from an external control means such as a computer. Image recording is performed in the photo process.

In the check mode, appropriate values such as the photoconductor charging potential and the developing bias are determined. FIG. 2 schematically shows the relationship between the photoconductor charging potential, the exposure position, and the developing bias value when creating a test pattern for measuring the toner adhesion amount on the photoconductor in the check mode.

First, the charging potential control means 9 for the photosensitive member forms a charging region in which the surface potential of the photosensitive member changes continuously.

Next, the controlled test pattern is exposed by the exposure device in synchronism with the charging potential change region of the photoconductor. Then, the developing bias is continuously changed in synchronization with the charge change region and the exposure region.

By controlling as described above, the potential difference between the developing bias and the exposed portion continuously changes in each area in the test pattern as shown in FIG. The potential difference does not change. Therefore, toner adhesion or carrier pulling due to fogging on the non-exposed portion does not occur, and a toner adhesion amount change test pattern due to the developing bias can be created.

The above-mentioned test pattern has a width in the axial direction of the photosensitive member which is sufficient for measurement by the toner adhesion amount measuring sensor, and the length in the rotating direction of the photosensitive member is the changed length of the photosensitive member charging potential and the developing bias. A rectangular pattern of corresponding length is obtained.

FIG. 3 is a diagram schematically showing a test pattern for measuring the toner adhesion amount created in the check mode. However, when developing is performed by continuously changing the developing bias, the toner density is light To a darker color.

The toner adhesion amount detection sensor 15 measures the toner adhesion amount of the test pattern. FIG. 4 shows an example of the measurement result. The appropriate values of the developing bias and the photoconductor charging potential are determined from the position where the toner adhesion amount of the test pattern is the appropriate value. The test pattern after the measurement of the toner adhesion amount is collected by the photoconductor cleaner 7 without being transferred to the paper.

If the photosensitive member surface potential of the exposed portion is set to a sufficient exposure amount, even if the exposure amount is the same, a substantially constant residual potential does not depend on the photosensitive member charging potential at the exposure position. Therefore, in this embodiment, the exposure light amount is not controlled during the test pattern exposure. However, when the exposure amount is low or when an exposure device having a high resolution is used, the residual potential may change depending on the charging potential of the photoconductor at the exposure position with the same exposure amount. In such a case, the residual potential is made constant by performing exposure amount control in consideration of the characteristics of the photoconductor, or the residual potential at each photoconductor charging potential at the same exposure amount is measured in advance. Then, it is necessary to perform arithmetic processing on the measurement result of the toner adhesion amount detection sensor 15 in consideration of the value. In such a case, it is preferable to control the exposure amount by linking it with the value of the charging potential of the photoconductor.

Next, the difference between the test pattern in which the density is continuously changed according to the present invention and the conventional test pattern in which the developing bias is changed stepwise will be described.

FIG. 5 shows the result of measuring the test pattern developed by changing the developing bias in steps, by the toner adhesion amount detecting sensor 15. At the position where the developing bias is changed stepwise (in the vicinity of A in the figure), the toner adhesion amount is unstable. In addition, B in the figure is
The figure shows a local variation in density due to scratches on the surface of the photoconductor. These areas cause an error in the measurement result of the toner adhesion amount. In order to reduce the measurement error, it is necessary to widen the measurement area (C in the figure) of the toner adhesion amount at each developing bias value.

FIG. 6 shows the measurement result of the toner adhesion amount detection sensor 15 of the test pattern of the present invention. In FIG. 6, since there is no rapid change in the developing bias, there is no unstable fluctuation portion of the toner adhesion amount as in FIG. Further, even if there is a local density fluctuation (B in the figure) due to a scratch on the surface of the photoconductor, the developing bias is continuously changed, and the toner adhesion amount also continuously changes. Such toner toner adhesion amount characteristic data can be predicted. Therefore, FIG.
The length of the test pattern can be made shorter than that of the conventional test pattern shown in (1), and more accurate toner adhesion amount characteristic data can be obtained.

The noise component of the measurement data indicated by B in the figure can be easily removed from the output signal of the toner adhesion amount detection sensor 15 by using a generally known high-frequency cut filter including a capacitor and a resistor. . Also,
The output of the toner adhesion amount detection sensor 15 is stored in the memory of the toner concentration control means, and the quadratic curve or EX
By performing processing such as P curve approximation, it is possible to perform noise removal processing with higher accuracy.

[Embodiment 2] An example of a method of determining the printing parameter in the present invention will be described.

According to the present invention, the toner adhesion amount measurement result as shown in FIG. 4 can be obtained. As described above, the proper values of the developing bias and the photoconductor charging potential can be determined from the position where the toner adhesion amount is the proper value within the test pattern range. By controlling both the developing bias and the photoconductor charging potential thus determined to shift to the normal image recording mode, an image having an appropriate density can be obtained.

However, the variable range of the developing bias and the charging potential of the photoconductor is limited, and if the control of the image density in the check mode as described above is repeated, there is a possibility that the density fluctuation beyond the above variable range will occur. is there. The cause of such changes in the developing bias and the charging potential of the photoconductor is a change in the toner charge amount.

Since the developing device of this embodiment is a two-component developing device, the charge amount of the toner is made constant by the control system which makes the toner concentration a prescribed constant value. However, the charge amount of the toner changes due to changes in the surrounding environment, changes over time, and the like. The developing bias and photoconductor charging potential control system of this embodiment is a system whose main purpose is to keep the image density constant in response to such changes.

Therefore, when the preset developing bias and the photoconductor charging potential are higher than the specified values, the toner density is increased in order to reduce the toner charge amount, and when they are lower than the specified values, the toner concentration is decreased. The toner density is controlled to be low in order to increase the charge amount. by this,
The toner charge amount becomes an appropriate value, and the image density can be held at an appropriate value without changing the developing bias or the photoconductor charging potential so much. The amount of change in the target value for toner density control at this time depends on the amount of change in the developing bias and the photoconductor charging potential from the specified values. It is desirable to determine the amount of change in the target value of the toner concentration control by fuzzy control using the amount of change from the specified value of the developing bias or the photosensitive member charging potential as a parameter. When one or more of the bias and the charging potential exceed a predetermined specified range, the control becomes impossible, and therefore an error signal or the like is issued so that the control can be recognized.

The image forming apparatus of this embodiment normally operates in the image forming mode. At a specific timing, it automatically switches to the check mode, and after determining printing parameters such as development bias, photoconductor charging potential, toner concentration target value, and exposure amount so that the image density during recording becomes an appropriate value, normal image formation is performed. The mode automatically switches.

The switching to the check mode is performed at the time of turning on the power of the apparatus and at the time of resetting, as well as after the specified time has elapsed or when the fluctuation of the temperature or the humidity exceeds the specified value, the specified number of copies are printed. Can be performed by the control means stored in the memory so as to be automatically switched when, for example, is completed.

The frequency of switching to this check mode is
Since it depends on the charge amount of the toner used, the environmental stability of the image forming apparatus, and the like, it is desirable to experimentally determine with an actual machine.

In addition to this, when the toner density is controlled in accordance with the developing bias and the changed value of the charging potential of the photoconductor,
Since it is expected that the toner charge amount changes and the image density changes abruptly as the toner density changes, it is preferable to increase the frequency of switching to the check mode. To determine the switching frequency to such a check mode, it is desirable to use fuzzy control or the like.

As described above, the switching to the check mode is performed by changing the elapsed time in the normal image forming mode, the amount of change in temperature and humidity, the number of recorded sheets, the number of toner replenishments, the target value of the toner density, and the developing bias value at that time. It is desirable to comprehensively evaluate and determine from parameters such as photoconductor charging potential. The application of a control method using a neuro is most effective for comprehensively judging these and switching to the check mode.

It is desirable that the check mode can be switched by the will of the person who operates the apparatus, and the check mode operation command can be issued by an external switch or a connected computer to switch the check mode. . Further, it is more desirable that the operator can arbitrarily change the target image density in the check mode.

[Embodiment 3] In a color image forming apparatus, it is very important to keep the image density of each color at an appropriate value, because two or more color toners are superposed to synthesize various colors. In this embodiment, an embodiment of the present invention in a color image forming apparatus will be described.

FIG. 7 is a schematic diagram showing an example of a color image forming apparatus equipped with the image density control means of the present invention.
This apparatus is characterized in that the toner images of the respective colors formed on the belt-shaped photosensitive belt 19 are superposed on the intermediate transfer drum 20.

Photoconductor belt 1 with scorotron charger 21
9 is uniformly charged, a yellow image pattern is exposed by the laser exposure device 22, and an electrostatic latent image (Y) of a yellow image is formed. Next, the electrostatic latent image (Y) on the photoconductor is developed by the yellow developing machine 23Y, and the intermediate transfer drum 20
Transfer the yellow image on top. The toner remaining on the photoconductor belt 19 is collected by the photoconductor cleaner 24.

Subsequently, charging and exposure are carried out in the same manner as above,
An electrostatic latent image (M) of magenta is formed on the photoconductor belt 19, and after being developed by the magenta developing machine 23M, the intermediate transfer drum 2
0 is transferred over the yellow image.

Further, the cyan image and the black image are also processed in the same manner as described above, and the transfer images of four colors are formed on the intermediate transfer drum 20 in an overlapping manner.

This is collectively transferred onto the sheet conveyed from the sheet cassette 25 by the transfer roller 26, and after the charge is removed by the AC corona charge eliminator 27, it is heated and fixed by the fixing device 28 to complete the image recording.

The transfer roller 26 and the transfer drum cleaner 29 on the intermediate transfer drum 20 are retracted from the surface of the intermediate transfer drum 20 during image transfer, and come into contact with each other during image transfer onto a sheet and during cleaning of the intermediate transfer drum after transfer. Controlled.

In this embodiment, the toner adhesion amount detecting sensor 3
0 is arranged at the toner adhesion amount measurement position on the intermediate transfer drum 20. By disposing the toner adhesion amount detection sensor 30 on the intermediate transfer drum 20, the photoconductor belt 19
This is because there is an advantage that the toner adhesion amount at a position close to the final image can be measured as compared with the case where the toner adhesion amount detection sensor is arranged above. However, the distance from the developing machine 23 increases the time required for the measurement in the check mode.

Further, since the use of the intermediate transfer drum 20 has a high degree of selectivity of the color and reflection state of the surface, it is possible to measure the adhesion amount with higher accuracy by selecting an appropriate surface. The surface of the photoconductor is close to regular reflection, but the diffused reflection of the intermediate transfer drum makes it easier to obtain stable measured values.

From the measurement of the toner adhesion amount, it is desirable that the intermediate transfer drum be a diffuse reflector and have a color whose reflection density is sufficiently low or high as compared with the reflection density of the toner to be measured. In addition, since the reflection density of general color toner is low and the reflection density of black toner is high, when measuring the toner adhesion amount using an optical sensor that detects reflected light, the measurement position of the intermediate transfer drum is the color toner. Then, one with a high reflection density (dark color) surface,
It is desirable to use black toner having a low reflection density (bright color). If the color toner and the black toner can be measured by using the intermediate transfer drums having different colors, the adhered amount of each toner can be measured more accurately. Further, when the color of the surface of the intermediate transfer drum is a single color, it is desirable to select a color having an intermediate density of the reflection intensities of the color toner and the black toner.

In this embodiment, since the density variation of the black toner is small, the adhesion amount of the three color toners of yellow (Y), magenta (M) and cyan (C) on the intermediate transfer drum having a high reflection density. Then, the black toner (K) was predicted and controlled from the set value of the developing bias and the like due to the variation in the density of the color toner.

Next, the operation in the check mode for controlling the printing process in this embodiment will be described.

In the check mode, a charging area in which the surface potential of the photoconductor belt is continuously changed is formed by the charge potential control means of the photoconductor. Next, a test pattern is formed by the exposure device in synchronization with the charging potential change region. Then, the yellow developing machine 23Y performs development while continuously changing the developing bias in synchronization with the charge change area and the exposure area. The yellow test pattern thus formed is transferred to the intermediate transfer drum 20.
The toner is transferred onto the surface and measured by the toner adhesion amount detection sensor 30.

The test pattern on the intermediate transfer drum 20 after the measurement is cleaned by the intermediate transfer drum cleaner to collect the toner. In the check mode, the transfer roller 26 is in a retracted state from the intermediate transfer drum 20, and the intermediate transfer drum cleaner 29 is controlled so as to always contact the intermediate transfer drum for cleaning.

Subsequent to the yellow adhesion amount measurement, a magenta and cyan test pattern is formed by the same method, and the toner adhesion amount is similarly measured by the toner adhesion amount detection sensor 30.

The method for determining the developing bias and the charging potential of the photoconductor is the same as that for the single color of the first embodiment, but in this embodiment, the black toner is not used, and the development of each color of yellow, magenta and cyan is performed. Predicted from bias and photoreceptor charging potential. Specifically, black is set based on the average value of the developing biases of yellow, magenta, and cyan and the charging potential of the photoconductor. This is because the four-color toners made of the same base material have substantially the same environmental characteristics and aging characteristics, and even if the setting accuracy of the black toner is lower than that of the color toners, the image density is low. Has a relatively small effect on the concentration and a wide tolerance range of the required concentration variation.

Depending on the target image density setting accuracy, the developing bias and the photoconductor charging potential of other colors are set for yellow, magenta, and cyan based on the measurement result of the toner adhesion amount of any one color. May be.

In the above description, black is set based on the average value of the developing bias and the photoconductor charging potential of each color of yellow, magenta, and cyan. However, the above-mentioned average value is multiplied by a predetermined coefficient, and the adhesion of each toner is determined. A method of comprehensively determining from various parameters such as the amount measurement result and the target value of the toner density may be used as in the case of a single color. Also in setting these parameters, it is extremely effective to perform control using fuzzy or neuro.

Also in the color image forming apparatus of this embodiment, the timing of switching from the normal image forming mode to the check mode can be set in the same manner as in the above embodiment. However, in the color image forming apparatus, since it is necessary to set a plurality of toners, the time required for the check mode becomes longer accordingly, and the recording speed decreases. In the color image recording apparatus of the present embodiment, when the power is turned on and at the time of resetting, the adhesion amount is measured for three colors of yellow, magenta and cyan.
Cyan control can be performed independently, and the number of checks of three colors can be reduced at the same time, or the method of checking one color and predicting the setting conditions of other colors from this result can be used together.

Since these should be determined according to the control target range of the image density, the environment and characteristics in the image forming apparatus, the toner characteristics, etc., it is preferable to experimentally determine the control conditions with an actual machine.

In any case, the time required for the check mode should be short. Also in this sense, the method of the present invention that forms the test pattern by continuously changing the developing bias has higher accuracy than the conventional method of switching the developing bias in steps.

[0077]

According to the present invention, since the toner adhesion amount at a plurality of developing biases can be measured with a short test pattern, the printing parameter control for obtaining an appropriate image density can be performed in a short time.

Further, it is possible to provide a monochromatic and color image forming apparatus capable of highly accurately and stably recording the image density, with the influence of noise or the like caused by scratches on the surface of the photoconductor being extremely small. .

Further, since the toner is attached only to the measurement area of the test pattern, the toner consumption is small.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image recording apparatus according to a first embodiment.

FIG. 2 is a graph illustrating a relationship among a photosensitive member charging potential, an exposure position, and a developing bias value when a test pattern is created.

FIG. 3 is a schematic diagram showing an example of a test pattern of the present invention.

FIG. 4 is a graph of a measurement result of a toner adhesion amount detection sensor of a test pattern of the present invention.

FIG. 5 is a graph of measurement results of a test pattern with a toner adhesion amount measuring sensor when the developing bias is changed stepwise.

FIG. 6 is a graph of measurement results of a tester pattern with a toner adhesion amount measuring sensor when the developing bias is continuously changed.

FIG. 7 is a schematic configuration diagram of a color image recording apparatus of Example 3.

[Explanation of symbols]

1, 21 ... Scorotron charger, 2, 22 ... Laser exposure device, 3 ... Two-component developing device, 4 ... Corotron type transfer device,
5 ... AC corona type static eliminator, 6 ... Erase lamp, 7,
24 ... Photoconductor cleaner, 8, 28 ... Fixing device, 9 ... Charging potential control means, 10 ... Exposure control means, 11 ... Toner density measuring means, 12 ... Toner density control means, 13 ... Temperature / humidity sensor, 14 ... Development bias Control means, 1530 ... Toner adhesion amount detecting sensor, 16 ... Toner adhesion amount measuring means, 17 ...
Printing process control means, 18 ... Paper resist, 19 ... Photosensitive belt, 20 ... Intermediate transfer drum, 23Y ... Yellow developing device, 23M ... Magenta developing device, 23C ... Cyan developing device, 23K ... Black developing device, 25 ... Paper cassette,
26 ... Transfer roller, 27 ... Static eliminator, 29 ... Intermediate transfer drum cleaner.

Claims (10)

[Claims] 1. An image forming apparatus using an electrophotographic process, a charging unit capable of continuously changing a charging potential of a photosensitive member, a developing bias control unit capable of continuously changing a developing bias, and a toner for a developed image. Toner adhesion amount detection means for detecting the adhesion amount, and a check mode for determining the printing conditions in the normal image forming mode, in the check mode, forming a region in which the photoconductor charging potential is continuously changed, The photoconductor charging in the normal image forming mode is performed based on the signal detected by the toner adhesion amount detecting means for the toner adhesion amount of the toner image developed while continuously changing the developing bias of the test pattern formed by exposure in that area. An image forming apparatus having a control means for setting and controlling an electric potential and a developing bias. 2. An image forming apparatus using an electrophotographic process, a charging unit capable of continuously changing a charging potential of a photosensitive member, a developing bias control unit capable of continuously changing a developing bias, and a toner of a developed image. A toner adhesion amount detecting means for detecting an adhesion amount and a check mode for determining printing conditions in a normal image forming mode are provided. In the check mode, the photoconductor potential and the developing bias of the non-image portion and the photoconductor of the image portion are provided. An area in which at least one of the potential and the developing bias is continuously changed is formed, and the photoconductor charging potential in the normal image forming mode is set based on the signal detected by the toner adhesion amount detection means in the area. An image forming apparatus having a control means for setting and controlling a developing bias. 3. When the image forming apparatus is powered on and reset, or when a preset time has elapsed, the toner replenishment amount or the number of replenishment reaches a prescribed amount or prescribed number of times when shifting to the check mode. When the temperature and humidity inside the device fluctuate outside the specified value, a means for detecting at least one when the number of recorded sheets reaches the specified number is provided, and a control means for shifting to the check mode based on the detection signal is provided. The image forming apparatus according to claim 1, which is provided. 4. The image forming apparatus according to claim 3, wherein the control means for controlling the shift to the check mode is configured so that a scanner can arbitrarily select and scan. 5. The image forming apparatus according to claim 1, wherein the charging means of the image forming apparatus is a scorotron charger, and a control means for controlling a grid voltage of the scorotron charger is provided. 6. The image forming apparatus according to claim 1, wherein the toner adhesion amount detecting means of the image forming apparatus includes an optical sensor including a light emitting element and a light receiving element. 7. The toner adhesion amount detecting means of the image forming apparatus comprises high frequency removing means for removing a signal having a frequency higher than a preset frequency from the detection signal.
The image forming apparatus according to item 1. 8. The image forming apparatus is provided with a display unit for displaying, when at least one of the toner density, the developing bias, and the photoconductor charging potential is out of a preset allowable fluctuation range. The image forming apparatus according to claim 1. 9. A color image forming apparatus using an electrophotographic process, a charging unit capable of continuously changing a charging potential of a photosensitive member, a developing bias control unit capable of continuously changing a developing bias, and a developed image. And a check mode for determining the printing conditions in the normal image forming mode. In the check mode, a region in which the photoconductor charging potential continuously changes is formed. Then, based on the detection signal detected by the toner adhesion amount detection means, the toner adhesion amount of at least one color in the color image developed while continuously changing the development bias of the test pattern formed by exposure in that area,
An image forming apparatus comprising: a control unit for setting and controlling a photoconductor charging potential and a developing bias during development of each color in the normal image forming mode. 10. An intermediate transfer member that transfers and superimposes toner images of respective colors sequentially formed on the photoconductor, and detects the toner adhesion amount of the color image formed on the intermediate transfer member by the toner adhesion amount detection. The image forming apparatus according to claim 9, wherein the image forming apparatus is configured to detect by means.