JP3127425B2 - Image forming device - Google Patents

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 an electrophotographic technique, such as a copying machine, a facsimile, and a laser printer, and more particularly to stabilization of image density.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus provided with a developing device using a two-component developer, a detection image is formed on an electrostatic latent image carrier, and the detection image is formed by an optical detection means or the like. There is generally known a method of measuring the amount of toner adhering to an image and using the detected value for controlling the toner replenishment amount. Usually, in this type of control method, a control point corresponding to one specific development potential is determined, and a detection value for a detection visual image formed by attaching toner on the latent image carrier at this specific development potential is used. The toner supply amount is controlled by judging the magnitude of the preset reference point at the control point.

According to this ordinary method, when the developer is stable, the amount of toner in the developing device can be appropriately controlled to obtain a stable image density, but the control point is set to one point. Therefore, the control may be unstable in a situation where the toner charge amount largely changes. That is, with respect to a change in the development characteristic such that the development γ curve rotates around the control point, it may not be possible to guarantee the density of the image portion corresponding to the development potential remote from the control point.

For example, FIG. 12 shows a development γ curve which is a relationship between the development potential and the optical density of a visible image on a latent image carrier, with the development potential on the horizontal axis and the optical density on the vertical axis.
, A point P corresponding to the development potential Vp is set as a control point. Here, a development γ curve in which the linear portion of the development γ curve rotates around this point P, as in the case of the curve A or B, due to the aging of the developer may occur. At this time, in the detection of only the detection visual image created at the development potential Vp corresponding to the point P, when the development characteristic changes as shown in the development γ curve A in the figure, the original image in which the image density is relatively important is considered. The optical density in the high development potential region corresponding to the high density portion becomes insufficient, and toner supply is not required even though toner supply is originally required. For this reason, the image in the high-density portion becomes lighter than the target density. On the other hand, when the development characteristics change as shown in the development γ curve B in the figure, the toner density increases because the toner replenishment request occurs even though the optical density in the high density area is sufficient. There is a possibility that an abnormal image such as soiling may occur.

A method is also known in which a change in toner charging ability due to a shape change of a carrier as a developer over time is predicted in advance by experiments or the like, and a control point is changed according to the number of image forming operations. However, it has been difficult to predict the change over time in the development characteristics only with the number of image forming operations.

Japanese Patent Application Laid-Open No. 1-222273 discloses that a developing γ characteristic is measured, and a developing γ characteristic is measured according to the shape of a developing γ curve.
A method for controlling toner replenishment is disclosed. The idea of this method itself is to capture the development characteristics as a whole, and so to say, a more effective control effect can be expected than the above-described control at one point.

However, the specific control method disclosed in the above-mentioned publication is basically the same as the above-described one point control method, and is not a fundamental solution.
That is, in the specific control method disclosed in the above publication, first, it is determined whether or not toner replenishment is necessary according to the amount of toner attached to the first detection visual image, and thereafter, the charging potential is determined in the second detection visual image. However, in the determination of the necessity of toner replenishment, it is the control itself at the above one point. In other words, this specific control method merely combines the charging potential control with the toner supply control at this one point. Further, in this method, since the surface potential is moved every time the determination routine is entered, there is a danger that the control becomes unstable and a runaway occurs.

The above is a problem of toner supply control in an image forming apparatus provided with a developing device using a two-component developer. However, in an image forming device provided with a developing device using a one-component developer, the problem is solved. In addition, it is necessary to appropriately control the amount of toner replenishment to stabilize the image density. That is, even in a developing device using a one-component developer, a developer carrier that supplies toner to a latent image formed on the latent image carrier is used from the viewpoint of replenishing operability of a toner that is a one-component developer. There is known a developing chamber provided with a toner storing chamber for storing toner to be supplied to the developing chamber, and a toner replenishing means for supplying toner in the toner storing chamber to the developing chamber. In such a developing device, the amount of toner charged in the developing chamber, particularly the amount of toner in the vicinity of the surface of the developer carrier, and the amount of toner attached to the surface of the developer carrier and supplied to the surface of the latent image carrier And the like, which may change the developing characteristics. Therefore, it is necessary to appropriately control the toner supply amount in order to stabilize the image density.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object the following:
An object of the present invention is to provide an image forming apparatus capable of obtaining a stable image density over a wide gradation range by controlling the amount of toner supply appropriately.

[0010]

According to another aspect of the present invention, there is provided an image forming apparatus, comprising: a latent image carrier; and a developer for supplying toner to the latent image formed on the latent image carrier. A developing device having a developing chamber provided with a carrier and a toner storage chamber for storing toner to be supplied to the developing chamber, and having a toner replenishing means for replenishing the toner in the toner storage chamber to the developing chamber; Detecting visual image forming means for creating at least two detecting visual images on the image carrier using a developing potential; detecting means for detecting the amount of toner adhering to the visual image on the latent image carrier; Calculating means for calculating a development γ curve based on a detection value of a visual image for detection by the toner, a toner replenishing control means for controlling a toner replenishing amount by the toner replenishing means in accordance with a calculation result of the calculating means, and a latent image Different development pots on the carrier Determining visual image forming means for creating a plurality of determining visual images using a char; calculating means for obtaining a developing γ curve based on a detection value of the determining visual image by the detecting means; and calculating by the calculating means based on the results have a developing potential setting means for setting a development potential to be used in the detection visualized forming means, said second arithmetic means
Is configured to determine the linear region of the development γ curve,
The developing potential setting means is determined by the second calculating means.
Of the development potential corresponding to both ends of
Development between 10% and 30% between lower and upper limits
Potential and development potential within 70-90%
And the developing potential used in the detection visual image forming means.
This is characterized in that it is configured to be set to the default . According to a second aspect of the present invention, in the image forming apparatus of the first aspect, a developing γ curve is calculated by a moving average method using a detected value of a visual image for detection by the detecting means. It is assumed that. According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, a potential detecting means for detecting a potential of the latent image formed by the determination visual image forming means and a detection value of the potential detecting means. Bias control means for controlling a developing bias value when developing the latent image. An image forming apparatus according to a fourth aspect of the present invention is the image forming apparatus according to the first aspect , wherein the detection visual image forming unit creates a detection visual image, the detection unit detects the detection visual image, and the first arithmetic unit uses A first control unit for executing the calculation and the control of the toner replenishment amount by the toner replenishment amount control unit at least at intervals of a predetermined number of image forming operations; and a calculation result of the first calculation unit. Development γ
Abnormality determining means for determining whether or not the curve is abnormal; and when the abnormality determining means determines that the curve is abnormal for a predetermined number of consecutive times,
Creating a visual image for determination by the visual image forming means for determination, detecting the visual image for determination by the detecting means, calculating by the second arithmetic means, and setting the developing potential by the developing potential setting means; And two control means. According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect , the toner remaining amount warning unit and the second control unit create a visual image for determination by the visual image forming unit for determination. After executing the detection of the visual image for determination by the above, the calculation by the second calculating means, and the setting of the developing potential by the developing potential setting means, the abnormality determining means continuously makes the developing γ curve abnormal for a predetermined number of times. And a drive control means for driving the toner remaining amount warning means when the determination is made.

[0011]

According to the first aspect of the present invention, at least two detection visual images are formed on the latent image carrier using the developing potential by the detection visual image forming means, and the at least two detection images are detected by the detection means. The first arithmetic means calculates the development γ curve based on the detection value of the detection visual image by the detection means, and the toner replenishment control means calculates the development γ curve.
The toner replenishing amount is controlled by the toner replenishing unit in accordance with the calculation result of the first calculating unit, whereby the toner replenishing amount is controlled by grasping the development characteristics based on the development γ curve. And
In the determination visual image forming means, a plurality of determination visual images are created using different developing potentials on the latent image carrier, and the detection means detects the toner adhesion amount of the plurality of determination visual images,
Based on the detected values for the determination visualized by the detection means Ru seeking linear region of the developing γ curve in the second computing means. This
Correspond to both ends of the straight line area obtained by the second calculating means.
Between the lower limit value and the upper limit value of the developing potential.
Development potential in the range of ~ 30% and 70-90%
The development potential within the range is defined as the above development potential.
The developing means used in the detection visual image forming means by the setting means
Set to potential. Thereby, even when the developing characteristics change over time, the developing characteristics are used in the detection visual image forming means.
It is ensured that the mutually different developing potentials are located in the linear region of the slope in the developing γ curve. Claim 2
The image forming apparatus calculates the development γ curve with the average value of the detection values for each of the detection visual images related to the preceding predetermined number of detections by the detection means. In the image forming apparatus according to the present invention, the potential detecting means detects the potential of the latent image formed by the determination visual image forming means, and the bias controlling means detects the latent image based on the detected value of the potential detecting means. The developing bias value at the time of development is controlled, so that even when the characteristics and the like of the latent image carrier change with time, the mutually different developing potentials used in the detection visual image forming means are inclined in the development γ curve. Ensure that it is located within the straight area of the part .
The image forming apparatus 請 Motomeko 4, the first control means, the creation of detecting visible by the detection toner images forming means, the detection of the detection visualized by the detection means, calculation by the first calculating means, Further, the control of the toner replenishment amount by the toner replenishment amount control means is executed at least at intervals of a predetermined number of image forming operations. Then, the first determination is performed by the abnormality determination means.
It is determined whether or not the development γ curve is abnormal based on the calculation result of the calculation means. When the abnormality determining means determines that the abnormality has occurred continuously for a predetermined number of times, the second control means creates a determination visual image by the determination visual image forming means, detects the determination visual image by the detection means, 2 The calculation by the calculating means and the setting of the developing potential by the developing potential setting means are executed. As a result, the development potential used by the detection visual image forming means is no longer located within the linear region of the inclined portion in the development γ curve due to a sudden environmental change or the like, so that the development γ curve calculated by the first calculation means becomes abnormal. In such a case, the developing potential setting means can promptly set the developing potential used in the detection visual image forming means to a value located within the linear region of the inclined portion in the developing γ curve. The image forming apparatus according to claim 5 , wherein the drive control means generates the determination visual image by the determination visual image formation means by the second control means.
After the detection of the visual image for determination by the detecting means, the calculation by the first calculating means, and the setting of the developing potential by the developing potential setting means are executed, the abnormality determining means continuously performs the developing γ for a predetermined number of times. When it is determined that the curve is abnormal, the toner remaining amount warning unit is driven,
Thus, the shortage of the remaining amount of toner in the toner storage chamber is accurately detected and notified to the operator.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter referred to as a copying machine) will be described. FIG. 1 is a front view showing a schematic configuration of a copying machine according to the present embodiment. In FIG. 1, a photosensitive drum 1 provided with a photoconductive photosensitive member serving as a latent image carrier is rotated clockwise by an arrow by a drive motor (not shown). The surface of the photosensitive drum 1 is given a predetermined potential from a charging charger 2 serving as a charging device, and is then image-exposed by light 3 from an exposure optical system (not shown). An image is formed. The electrostatic latent image is visualized as a toner image by supplying toner from the developing device 4. The toner image on the photosensitive drum 1 is transferred to a transfer sheet conveyed from a sheet feeding device 7 by a transfer charger 5 as a transfer device. The transfer paper onto which the toner image has been transferred is separated from the photosensitive drum 1 by a separation charger 6 as a separation device, and then heated by a fixing device 8 to fix the toner image thereon.
Emitted outside the machine. On the other hand, the photosensitive drum 1 after the transfer is
The toner remaining on the surface is removed by the cleaning device 9 so that the toner is initialized and the process proceeds to a new image forming process.

Next, the toner supply control will be described.
The developing device 4 includes a developing device 4a having an opening facing the surface of the photosensitive drum 1, and a toner container 4b for storing toner to be supplied into the developing device 4a.
In the developing device 4a, a developing roller 41, which is a developer carrying member, is rotatably provided at an opening, and contains a two-component developer composed of a carrier and a toner. The toner container 4b is provided with a replenishing roller 42 as a replenishing means for replenishing toner contained in the developing device 4a. The replenishing roller 42 is driven by a driving force from a drive motor (not shown) via a toner replenishing clutch 43. Is transmitted. The supply roller 4 depends on the ON time of the toner supply clutch 43.
By controlling the rotation time of No. 2, the amount of toner supplied into the developing device 4a is controlled.

The amount of toner replenishment by turning on the toner replenishment clutch 43 is determined by forming a reference latent image having a predetermined potential on the surface of the photosensitive drum 1 and developing the latent image with a developing device 4 to form a reference latent image. The toner adhesion amount per unit area of the toner image is determined to be a predetermined value. In order to detect the amount of toner attached per unit area of the detection visual image,
An optical detection unit 10 is provided so as to face the surface of the photosensitive drum 1. As shown in FIG. 2A, the optical detecting means 10 has a light emitting section 10a composed of an infrared light emitting LED and a light receiving section 10b composed of a phototransistor.
A detection circuit as shown in FIG. The light emitted from the light emitting unit 10a is partially absorbed by the toner on the photosensitive drum 1, and the remaining reflected light is received by the light receiving unit 10b, and the light is reflected by the intensity of the light received by the light receiving unit 10b. An electric signal is output to the output terminal Vout. This output terminal Vout
Are connected to the control unit 11.

FIG. 3 is a circuit diagram showing a schematic configuration for controlling the toner replenishment of the control section 11. The light emitting unit 10b
Output from the CPU 11 via the A / D converter 11a.
b. Also, this CPU 1
1b is configured to output a control signal to a driver 43a for the toner supply clutch 43.
The memory 11c attached to the CPU 11a stores a later-described toner supply control program. Further, a look-up table (LUT) 11d in which data used for toner supply control described later is stored is also a CP.
It is attached to U11b.

Hereinafter, the toner supply control in this embodiment will be described in detail with reference to FIG. First, in step 1,
A reference latent image (hereinafter, referred to as a reference pattern) having a predetermined potential is formed on the photosensitive drum 1 and is developed into at least two development potentials which are located within a linear region of a slope in a development γ curve and are different from each other. A predetermined developing bias is applied to the developing device 4 so as to form a visible image for detection, and the image is developed and visualized.

This reference pattern can be formed by erasing the surface area of the photosensitive member charged to, for example, 900 V by the charging charger 2 by using an eraser (not shown) so that only a rectangular area of about 20 × 20 mm remains charged potential. it can. When the reference pattern composed of a rectangular region uniformly charged to 900 V faces the developing roller 41 of the developing device 4, the developing potential, which is the difference between the photoconductor potential and the developing roller 41 potential, becomes the developing γ curve. The developing bias applied to the developing roller 41 is switched between Vd ₁ and Vd _{2 so} that the developing bias is located within the linear region of the inclined portion and has a predetermined value different from each other. The image is developed, thereby forming first and second two detection visual images. Here, the developing bias Vd ₁
In the development potential of the first detection visualized obtained by developing V1, the development potential of the second detection visualized obtained by developing with a developing bias Vd ₂ and V2. In this example, such developing biases Vd ₁ and Vd ₂ are determined in advance by experiments and set.

Next, in a second step, the amount of toner adhered per unit area of the two detection visual images is detected by the above-mentioned optical detection means 10, and the detection output is read by the CPU 11b. Here, the detection output for the first detection visual image is Vp ₁ , and the detection output for the second detection visual image is Vp ₂ .

Next, in a third step, the detection output V
The optical densities D1 and D2 corresponding to p ₁ and Vp ₂ are looked up from the data table (LUT) 11d. Instead of using such a data table, the relationship between the detection output and the optical density may be stored in the form of an arithmetic expression, and the optical density may be obtained by an arithmetic operation using this arithmetic expression.

Next, in a fourth step, the optical densities D1,
The slope α of the development γ curve is calculated using D2. FIG. 5 shows a developing γ curve which is a relationship between the developing potential on the horizontal axis and the optical density on the vertical axis. Each development potential V1, V2 located in the linear region of the development γ curve
And the equation of a straight line passing through two points corresponding to the optical densities D1 and D2 can be written as y = αx + β (1). Here, the slope α is α = (D1−D2) / (V1−V2) (2) The intercept β is β = (V1 × D2−V2 × D1) / (V1−V2) (3) The value of the gradient α is calculated using the equation (2).

Then, in steps 5 to 9, the development γ
The toner supply amount is set using the slope α of the curve. Specifically, as shown in FIG. 5, the upper and lower limits of the gradient α of the development γ curve which can obtain a predetermined image density with a normal predetermined toner replenishment amount are obtained in advance through experiments and the like, and the upper limit gradient θ ₂ and θ ₁ are set. Then, the inclination α for detection is compared with these comparison values θ ₂ and θ ₁ to set the toner supply amount as described below. α <θ1 → maximum supply amount setting (step 6) θ1 ≦ α <θ2 → normal supply amount setting (step 8) θ2 ≦ α → supply stop (supply amount 0 setting) (step 9) In this example, supply stop is also performed. Although the supply amount is set in three stages including the supply amount, the comparison value may be increased to set the supply amount in four or more stages.

The above-described toner supply amount control subroutine is executed, for example, every ten copies. Then, the toner supply operation during the copying of the subsequent 10 sheets is executed with the set toner supply amount. When the next toner supply amount control execution timing is during continuous copying, it is desirable to set so that the toner supply amount control is executed after the continuous copy.

In the above embodiment, the toner replenishment amount is set based on the gradient α of the development γ curve obtained from the optical densities D1 and D2 for one generation of the detection visual image and the detection. In place of a plurality of optical densities D1 and D related to the generation of a plurality of detection visualizations executed in advance and the detection thereof.
2, the inclination α of the development γ curve may be calculated using the optical density obtained by the moving average method, and the toner replenishment amount may be set based on the calculation result.

For example, in the above-described embodiment, the data of the optical densities D1 and D2 of the detection visual image obtained for every ten sheets is stored in the memory 11c for the preceding three detections, for example. Here, D1 is D1 (1), D1 (2), D1 (3), and D2 is D2 (1), D2 (2), and D2 (3) in chronological order. Assuming that the latest detected data is D1 (4) and D2 (4), the average values D1ave, D2a of the four points obtained by combining the three data stored in the memory 11c and the latest data.
ve is each Given by These D1ave and D2ave are set to the above-mentioned inclination α
Is used as D1 and D2 in Expression (2) to calculate the inclination α, and the toner replenishment amount is set by using this as in the above-described embodiment. At the time of the next detection, the suffix numbers are decremented by 1 as follows, and D1 (2) → D1 (1), D2 (2) → D2 (1) D1 (3) → D1 (2), D2 (3) ) → D2 (2) D1 (4) → D1 (3), D2 (4) → D2 (3) D1 (new) → D1 (4), D2 (new) → D2 (4) Discard oldest data, The newly read value D1 (ne
w) and D2 (new) are set as D1 (4) and D2 (4), and the same calculation is performed. That is, control is always performed using the latest four data. Here, the moving average method using the data of four times is shown, but the number may be set according to the apparatus. As the number of times increases, the stability against noise increases, but the responsiveness deteriorates. Therefore, it is desirable to set a value of about 4 to 8 times according to the actual machine. At the start of use of the copying machine, the preceding detected value initial values D1 (1), D1
Since (2), D1 (3), and the like do not exist, appropriate values predicted in advance are stored in the memory 11c as initial values.

FIG. 6 shows output fluctuations of the optical detection means 10 when the moving average method is used and when it is not used. The horizontal axis represents the number of generations of the detection visual image, and the vertical axis represents the inclination (tanα) of the straight line. As you can see from this figure,
When the moving average method is used, an extremely stable gradient α can be obtained as compared with the gradient α of the development γ curve obtained from the optical densities D1 and D2 for one generation of the detection visual image and the detection.

[0026] In the above example with previously stored data of the optical density D1, D2 in the memory 11c, but calculates the inclination α of the developing γ curve by the average value of the optical density, instead of this, the detection value Vd ₁ , Vd ₁ may be stored in the memory 11 c, the optical density is determined from the average value of the detected values Vd ₁ , Vd ₂ , and the slope α of the development γ curve may be calculated based on the optical density. .

Next, even when the developing characteristics change over time, the developing potentials V1 and V2 for developing the detected visual image for toner replenishment control are located within the linear region of the inclined portion in the developing γ curve. A description will be given of the development γ determination control for ensuring this. In the above embodiment, the developing biases Vd ₁ and Vd ₂ for developing the reference pattern are used.
Is set in advance by experiments, but as the development characteristics change over time, the development biases Vd ₁ and Vd ₁
At d ₂ , there is a possibility that a development potential corresponding to the linear region of the inclined portion in the development γ curve cannot be obtained. Therefore, in the present development γ determination control, the development γ curve obtained by detecting the linear region of the inclined portion of the development γ curve and detecting the development biases Vd ₁ and Vd ₂ when developing the visual image for detecting the toner supply amount is obtained. Is set so as to be located in the linear region of the inclined portion.

Hereinafter, the development γ determination control in this embodiment will be described in detail with reference to FIG. First, in step 1, for example, as shown in FIG.
A stepwise potential pattern (hereinafter referred to as a determination pattern) is formed, and is developed by applying a predetermined developing bias to the developing device 4, whereby the first to tenth potential patterns are formed.
Create a visual image for judgment. 8, the horizontal axis indicates the position of the surface of the photosensitive drum 1 in the rotation direction, and the vertical axis indicates the potential of the surface of the photosensitive drum 1. In this example, a judging pattern composed of 10 different potential portions from 100 V to 1000 V in 10 mm increments in the rotation direction of the photosensitive drum 1 is formed. For example, the surface may be formed by charging the surface of the photosensitive drum 1 to 1000 V with the charging charger 2 and then irradiating light by switching the output by 10 mm with an eraser lamp or the like, or by switching the output of the charging charger 2 by 10 mm. It may be formed by charging. Further, the surface of the photoconductor drum 1 is
After being charged to V, for example, it may be formed by exposing to light reflected from a reference plate having a ten-stage density pattern arranged in the vicinity of a contact glass for placing a document.

Next, in a second step, the amount of toner adhered per unit area of the ten judgment visual images is detected by the above-mentioned optical detection means 10, and the detection output is read by the CPU 11b. Here, the detection output of the determination visualized first to 10 and Vp ₁ to Vp _10.

Next, in a third step, the detection output Vp ₁
To an optical density D1 or D1 corresponding to each of the Vp ₁₀
0 is looked up from the data table (LUT) 11d. Instead of using such a data table, the relationship between the detection output and the optical density may be stored in the form of an arithmetic expression, and the optical density may be obtained by an arithmetic operation using this arithmetic expression.

Next, in a fourth step, using the optical densities D1 to D10, the developing potentials Vmin and Vmax corresponding to both ends of the linear region of the inclined portion of the developing γ curve are calculated by interpolation as shown in FIG. Ask for it. Here, the horizontal axis in FIG. 9 indicates the development potential and the vertical axis indicates the optical density. The development potential on the horizontal axis corresponds to the difference between the potential of each part of the determination pattern and the development bias at the time of development of the determination pattern as described above. I do.

Next, in a fifth step, the developing potential Vmi corresponding to both ends of the linear region of the inclined portion of the developing γ curve.
n and Vmax are set as developing potentials V1 and V2 at the time of forming a visible image in the toner supply control. Thus, the potential of the detection pattern at the time of forming a visible image in the toner supply control and the developing bias at the time of developing the detection pattern are determined.

In the development γ determination control of this embodiment, the linear region of the slope of the development γ curve is obtained by the interpolation method.
Calculate the rate of change between the detection outputs corresponding to the adjacent juxtaposed judgment images of p _{1 to} Vp ₁₀ , and determine that the judgment visual images in a range where the change rate is equal to or less than a predetermined value are in the linear region. The straight-line area may be determined assuming that.

The Vmax and Vmin obtained by the development γ determination control
Is directly used as the development potentials V1 and V2 at the time of forming a visible image in the toner supply control. When Vmax is set to 100% and Vmin is set to 0%, a value within 70 to 90% is used as the development potential V1. It is desirable to use a value of 10 to 30% as the development potential V2. The reason for this is that the development γ curve generally has a gradual change in its change point, so that when determining both ends of the linear region, the error at both ends is large when the number of sampling points is limited. . For example, in the example of FIG. 9, since Vmax = 800 V and Vmin = 200 V, V
It is preferable to use a value of 700 V as max and a value of 300 V as Vmin.

Further, when the characteristics of the photoreceptor deteriorate with time and the reliability of the potential stability decreases with the number of sheets used, the detection visual image for toner replenishment control is developed. In order to ensure that the development potentials V1 and V2 are located within the linear region of the inclined portion in the development γ curve, a surface voltmeter 20 is provided opposite to the surface of the photosensitive drum 1 as shown in FIG. Thereby, the surface potential V ₁ of the step-like determination pattern in the development γ determination control is obtained.
To measure the V _10, also set the developing bias Vd ₁ to Vd ₁₀ at the time of developing the determining pattern so that each developing potential of forming the first to tenth judgment developed image becomes a predetermined value good. FIG. 7B shows an example of the development γ determination control in this case.

The above-described development γ determination control may be executed each time the toner replenishment amount control is performed, but the control of the development potential at the time of forming the detection visual image is required as much as the conventional control at one point. Therefore, stable toner replenishment control can be performed even if the replenishment is not performed for each toner replenishment amount control but is performed as needed.

However, since the developing potential at the time of forming the detection visual image in the toner replenishment control is not located within the linear region of the inclined portion in the developing γ curve due to a sudden environmental change or the like, the accurate inclination α of the developing γ curve is obtained. It is desirable to immediately execute the development γ determination control when is no longer required. Hereinafter, an example of control for this will be described with reference to FIG. In FIG. 10, first, in steps 1 to 4, a reference pattern is formed and visualized, each visual image for detection is detected by the optical detection means 10, and the output of this detection is converted to the optical density, similarly to the toner supply control. Conversion,
Then, the inclination α in the linear region of the inclined portion of the development γ curve using the optical density is calculated.

Next, in step 5, step 7, and step A3, the toner replenishment amount is set by using the gradient α of the development γ curve, and the development at the time of forming the detection visual image is performed due to a sudden environmental change or the like. It is determined whether or not the detection output has become an abnormal value due to, for example, the potential no longer being located within the linear region of the inclined portion in the development γ curve. Specifically, in addition to the lower limit theta ₂ and theta ₁ over the slope α of the developing γ curve obtained predetermined image density in the normal predetermined toner supply amount, as shown in FIG. 11, determines the detection output abnormality Upper and lower limit comparison values θmax and θmin are set in advance. Then, by comparing each of these comparison values with the inclination α obtained by the calculation, the setting of the toner replenishment amount and the determination of whether there is an abnormality are performed as described below. α <θmin → Abnormal (Step A5) θmin ≦ α <θ1 → Maximum supply amount setting (Step 6) θ1 ≦ α <θ2 → Normal supply amount setting (Step 8) θ2 ≦ α <θmax → Supply stop (Replenishment amount setting 0) )
(Step 9) θmax ≦ α → Abnormal (Step A5)

When it is determined that there is no abnormality (Y in step 5, Y in step 7, or step A)
3) Y), after setting the toner supply amount as described above,
The continuous abnormality counter CNT for counting the number of times that it is determined that the toner is continuously abnormal in the toner supply control is reset (steps A1, A2, A4), and the process returns to the main flow of the copying machine control.

On the other hand, if it is determined that there is an abnormality (N in step A3), the counter is incremented (step 5), and it is determined whether or not the content of the counter is, for example, "3". If the content is not "3" (N in step A6), the process returns to the main flow of the copying machine control. Conversely, if the content of the counter is "3", that is, if it is determined that the detection output of the optical detection means 10 is abnormal in all three consecutive toner supply controls, Assuming that the detection output has become an abnormal value due to, for example, the development potential at the time of forming the detection visual image no longer being located within the linear region of the inclined portion in the development γ curve due to a sudden environmental change, etc., the development γ determination control is immediately performed. (Step 7), thereby setting the developing bias at the time of developing the reference pattern at the time of forming the detection visual image in the toner supply control so as to obtain a predetermined developing potential, and then resetting the counter. To return to the main flow of copying machine control.

As described above, when the abnormal state continues continuously for a predetermined number of times, the development γ determination control is automatically executed, thereby preventing an unexpected abnormal state, for example, a sudden environmental change. , And can respond quickly. It should be noted that the development γ determination control can be executed every time an abnormality is determined. However, the development γ determination control requires extra time for processing as compared with a normal operation, and a temporary abnormal state (for a document having a high density). Since it cannot be distinguished from the case of continuous use, etc.), when a predetermined number of consecutive times (3 to 5) as in the above example,
Times).

In the toner replenishment amount control executed after the execution of the development γ determination control in step 7, the slope α of the development γ curve obtained by calculation for a predetermined number of consecutive times is the lower limit for abnormality determination. If it is determined that the remaining amount is smaller than the comparison value θmin, the remaining amount of toner in the toner container 4b or the like may be considered to be small, and a warning lamp or the like (not shown) may be turned on to perform a remaining toner warning display. This is also the case where the comparison value θ is continuously determined a predetermined number of times to distinguish it from the temporary abnormal state.
When it is determined that the value is smaller than min, a toner remaining amount warning display is performed, and the predetermined number is appropriately set in consideration of the capacity of the toner container 4b and the like.

The above is an explanation of the case where the developing device 4 uses a two-component developer. However, the present invention can be applied to a case where a one-component developer is used as the developing device 4. However, in this case, the setting of the toner supply amount in the toner supply amount control is set according to the characteristics of the one-component developing device to be used. For example, if the amount of toner in the developing device 4a is too large, the amount of toner adhering to the surface of the developing roller 41 and supplied to the surface of the photosensitive drum 1 decreases, whereby the toner per unit area of the detection visual image is reduced. In the case of such a characteristic that the amount of adhesion is reduced, the toner replenishment amount is set to be small when the gradient α of the development γ curve is small, and conversely, when the toner adhesion amount is excessive, the toner replenishment amount is increased. To set. The development γ determination control is also effective when a one-component developer is used as in the case of using the two-component developer.

[0044]

According to the image forming apparatus of the first aspect, the toner replenishment amount is controlled by grasping the development characteristics based on the development .gamma. Curve. The amount can be controlled, and the image density can be stabilized over a wide gradation range. Further, even when the development characteristics change over time, the development potential used in the detection visual image forming means is ensured to be located within the linear region of the inclined portion in the development γ curve, so that the development characteristics change over time. In this case, the toner supply amount can be accurately controlled, and the runaway of the toner supply amount control can be prevented. In particular, according to the image forming apparatus of the present invention, since the developing γ curve is calculated by the average value of the detection values for each of the detection visualizations related to the preceding predetermined number of detections by the detection means, the toner supply amount Immediately prior to the control, even when a noise such as a temporary decrease in the slope of the development γ curve due to the formation of an image that consumes a large amount of toner happens to occur, the toner replenishment amount is rapidly increased. As a result, a stable image density that does not cause a sudden change such as an excessive image density can be obtained. Further, according to the image forming apparatus of the third aspect, even when the characteristics of the latent image carrier change over time,
Since the developing potential used in the detecting visual image forming means is ensured to be located within the linear region of the inclined portion in the developing γ curve, even when the characteristics of the latent image carrier change over time, accurate toner Replenishment amount can be controlled . Also, the image forming apparatus according to claim 4, abrupt environmental change like in the first arithmetic by no longer positioned in the linear region of the inclined portion of the development potential development γ curve used in detecting visible forming unit When the developing γ curve calculated by the means becomes abnormal, the mutually different developing potentials used by the detecting visual image forming means are promptly set to those located within the linear region of the inclined portion in the developing γ curve. Therefore, runaway of toner supply amount control can be effectively prevented. Further, the image forming apparatus according to the fifth aspect can accurately detect the shortage of the remaining amount of toner in the toner storage chamber and notify the operator of the shortage.

[0045]

[0046]

[0047]

[0048]

[0049]

[0050]

[Brief description of the drawings]

FIG. 1 is a front view showing a schematic view of a copying machine according to an embodiment of the present invention.

2A is a configuration diagram of a detection element of an optical detection unit of the copying machine, and FIG. 2B is a detection circuit diagram of the optical detection unit.

FIG. 3 is a block diagram showing a schematic configuration of an electrical unit related to toner supply amount control of the copying machine.

FIG. 4 is a flowchart of toner supply amount control of the copying machine.

FIG. 5 is an explanatory diagram of a reference value used for the toner supply amount control.

FIG. 6 is a graph showing a tendency of a slope calculation value using an optical density by a moving average method.

FIG. 7A is a flowchart of a development γ determination control of the copying machine, and FIG. 7B is a flowchart of a development γ determination control according to a modification.

FIG. 8 is an explanatory diagram of a determination pattern in the development γ determination control.

FIG. 9 is an explanatory diagram of an example of a linear region calculation method in the development γ determination control.

FIG. 10 is a flowchart of toner supply amount control according to a modification.

FIG. 11 is an explanatory diagram of a reference value used for the toner supply amount control.

FIG. 12 is an explanatory diagram of a change in development characteristics due to a change with time of a developer.

DESCRIPTION OF SYMBOLS 1 photosensitive drum, 2 charging charger 3 exposure light, 4 developing device 4 a developing device, 4 b toner container 5 transfer charger, 6 separation charger 7 paper feeder, 8 fixing device 9 cleaning device, 10 optical Detecting means 10a Light emitting unit, 10b Light receiving unit 11 Control unit, 20 Surface potential meter 41 Developing roller, 42 Supply roller 43 Toner supply clutch

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/08 G03G 15/00 303

Claims (5)

(57) [Claims] A developing chamber having a latent image carrier, a developer carrier for supplying a toner to a latent image formed on the latent image carrier, and a toner accommodating chamber for accommodating toner supplied to the developing chamber; And a developing device having a toner replenishing means for replenishing the toner in the toner storage chamber with the toner in the developing chamber; and a developing device on the latent image carrier using a developing potential.
Detecting visual image forming means for creating three detecting visual images, detecting means for detecting the amount of toner adhering to the visual image on the latent image carrier, and a detecting value of the detecting visual image by the detecting means. A first calculating means for calculating a development γ curve; a toner replenishing control means for controlling a toner replenishing amount by the toner replenishing means in accordance with a calculation result of the calculating means; and a different developing potential on the latent image carrier. Determining image forming means for creating a plurality of determining images, a second calculating means for obtaining a development γ curve based on a detection value of the determining image by the detecting means, based on the calculation results have a developing potential setting means for setting a development potential to be used in the detection visualized forming unit, the second calculating means calculates a linear region of the developing γ curve
Configured to so that, the development potential setting means, determined by said second computing means
Of the development potential corresponding to both ends of
Development between 10% and 30% between lower and upper limits
Potential and development potential within 70-90%
And the developing potential used in the detection visual image forming means.
An image forming apparatus characterized in that the image forming apparatus is configured to set the image forming apparatus to the image forming apparatus. 2. The apparatus according to claim 1, wherein said first calculating means calculates a developing γ curve by a moving average method using a detected value of a visual image for detection by said detecting means. Image forming device. 3. A potential detecting means for detecting a potential of a latent image formed by said determining visual image forming means, and a developing bias value for developing said latent image based on a detection value of said potential detecting means. 2. The image forming apparatus according to claim 1, further comprising a bias control unit for controlling the image forming apparatus. 4. A visual image for detection by said visual image forming means for detection.
Of the detection, detection of the detection visual image by the detection means,
(1) calculation by the calculation means and the toner supply amount control
The control of the toner supply amount by the step
First control means for executing at intervals of image forming operation
And the developing γ curve based on the calculation result of the first calculating means.
Abnormality determining means for determining whether or not is abnormal, and the abnormality determining means has determined that the abnormality is a predetermined number of consecutive times
In some cases, a visual image for judgment by the above-mentioned visual image forming means for judgment is created.
Detection, detection of a visual image for judgment by the detection means, the second performance
Calculation means and developing potential setting means
Control for executing the setting of the developing potential according to
2. An image forming apparatus according to claim 1, further comprising:
Place. 5. A control device according to claim 1 , wherein said second control means controls said remaining amount of toner .
Create a visual image for determination, and determine the visual image for determination by the detection means.
Detection, calculation by the second calculation means, and development potential
The setting of the developing potential by the char setting means is executed.
After a predetermined number of times,
When it is determined that the development γ curve is abnormal,
Drive control means for driving the quantity warning means.
5. The image forming apparatus according to claim 4, wherein: