JPH07253693A - Method for potential control in image forming device - Google Patents

Abstract

PURPOSE:To provide a method for potential control in an image forming device capable of minimizing toner consumption at the time of starting rotation of a photreceptor and the time of stopping the photoreceptor rotating. CONSTITUTION:The image forming device adopting the two component developer composed of the toner T and carrier E, and making the toner T stuck to the photreceptor 12 by applying the developing bias voltage VBias to a developing sleeve 15, is constituted so that the relative potential difference DELTAV between the surface potential VS.P of photoreceptor and the developing bias voltage VBias is controlled in step within the range of the carrier flying occurrence limit maximum potential difference Vmax and the toner stick quantity minimum potential difference Vmin at the time of the photoreceptor rotation starting and stopping.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a potential control method in an image forming apparatus, and more specifically, in a reversal developing method applied to an image forming apparatus such as an electrophotographic copying machine, the surface potential of a photosensitive member and a developing sleeve. The present invention relates to a reversal development control method for controlling both the development bias voltage applied to the.

[0002]

2. Description of the Related Art Generally, in a reversal development type image forming apparatus using a two-component developer, as shown in FIG.
The surface of the photoconductor 2 is positively charged by the charger 1, for example, and then exposed, and then the photoconductor 2 reaches the developing position G facing the developing sleeve 3 in the developing device, and the charging region 4 is charged with the two components. Of the developer, positively charged toner T is attached from the developing device to the exposed area 4a on the surface of the photoconductor to perform development.

[0003]

By the way, the positive developing bias voltage to the developing sleeve 3 is preferably applied at the same time when the charging region 4 reaches the developing position G where the charging region 4 faces the developing sleeve 3, but This timing control is not easy, and the application timing of the developing bias voltage may shift.

Then, at the start of rotation of the photosensitive member, in FIG. 4, the timing of applying a positive developing bias voltage V _Bias of, for example, +560 V to the developing sleeve 3 is the electrostatic charge portion of the photosensitive member 2 charged to, for example, +740 V. If S is later than the time when the developing position G is reached, the electrostatic charge portion S reaches the developing position G during that time,
Since the developing bias voltage V _Bias is not applied to the developing sleeve 3, as shown in FIG. 5, the negatively charged carrier E is attracted to the surface of the photoconductor 2 by the presence of the electrostatic charge portion S. That is, when the rotation of the photoconductor is started, the developing bias voltage V applied to the developing sleeve 3 is applied to the photoconductor 2 which has already reached the developing position G and whose surface potential has already been applied.
Carrier jump occurs if the _Bias timing is shifted.

This is because the relative difference ΔV between the surface potential V _SP and the development bias voltage V _Bias (= surface potential V _{SP −development} bias voltage V _Bias ) is the maximum potential difference in the state where carrier jump does not occur ( This is because the carrier jump occurrence limit maximum potential difference) V _max is exceeded (see FIG. 6).

In order to prevent the carrier jump from occurring, in the prior art, the timing of applying a positive developing bias voltage V _Bias of, for example, +560 V to the developing sleeve 3 in FIG. 7 and FIG. Although the electrostatic charge portion S of the photoconductor 2 charged to +740 V is set to be earlier than the time when it reaches the developing position G, a large amount of toner T adheres to the surface of the photoconductor 2 (solid black state). (See FIG. 9).

This is because the relative difference ΔV between the surface potential V _SP and the developing bias voltage V _Bias is the minimum toner adhesion amount potential difference V _min at which the toner adhesion amount is minimum (fog state shown by K in FIG. 3). This is because it will exceed (see FIG. 10). The above situation is the same when the rotation of the photoconductor is stopped.

In short, in the conventional control method, waste toner is consumed each time the rotation of the photoconductor is started or stopped in order to avoid carrier jump when the photoconductor starts or stops rotating. Also, since all toner is collected,
The toner recovery amount increases as the toner consumption amount increases.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of minimizing the toner consumption amount at the start of rotation of a photosensitive member and the stop of rotation of the photosensitive member. It is to provide a potential control method.

[0010]

According to a potential control method in an image forming apparatus of the present invention, a two-component developer composed of toner and carrier is used, and a developing bias voltage is applied to a developing sleeve to apply the toner to a photoreceptor. In the image forming apparatus to be attached, both the surface potential of the photoconductor and the developing bias voltage are controlled stepwise when the photoconductor starts and stops rotating.

Further, according to another aspect of the present invention, there is provided an image forming apparatus in which a two-component developer composed of a toner and a carrier is used, and a developing bias voltage is applied to a developing sleeve to attach the toner to a photoconductor. The relative potential difference between the surface potential of the photoreceptor and the developing bias voltage at the time of starting and stopping the rotation of the photoreceptor is controlled stepwise within the range of the carrier jump occurrence limit maximum potential difference and the toner adhesion amount minimum potential difference. A potential control method in an image forming apparatus is provided.

According to the present invention, at the time of starting and stopping the rotation of the photosensitive member, the surface potential V _SP satisfying V _min ≤ΔV ≤V _max is set in order to prevent the carrier jump and to suppress the toner adhesion amount to the fog level. The relative difference ΔV from the developing bias voltage V _Bias is held.

The minimum potential difference V _min of the toner adhesion amount, which is about the amount of fog, and the maximum potential difference V _max in the potential difference at which carrier jump does not occur are set appropriately according to the image forming apparatus used. It

[0014]

When the rotation of the photoconductor is started, the charge amount on the photoconductor surface is gradually changed from zero to a predetermined value, and the developing bias voltage is gradually changed to a predetermined voltage value to control the charge amount and the developing bias voltage. Thus, the relative potential difference ΔV between the surface potential V _SP of the photoconductor and the developing bias voltage V _Bias at the developing position is kept within the range of V _min and V _max in any ascending step until the copying operation. .

In short, the developing bias voltage V _Bias and the surface potential V _SP are controlled at each stage, and the relative potential difference Δ
By preventing V from _exceeding V _max , carrier jump can be prevented from occurring, and the relative potential difference ΔV is V
A large amount of toner can be avoided so as not to exceed _min .

Further, even when the rotation of the photoconductor is stopped, it is possible to avoid carrier jump and a large amount of toner adhesion in the same manner as when the rotation of the photoconductor is started.

[0017]

Embodiments of the present invention will be described below.
However, the present invention is not limited thereby. FIG. 1 is a diagram for explaining an embodiment of the present invention in which the surface potential of the photoconductor is controlled stepwise by changing the grid voltage of the charger when the photoconductor starts and stops. 9 is a timing chart of control of the surface potential and the developing bias voltage when starting and stopping the rotation of the photoconductor.

The potential control method shown in FIG. 1 uses a two-component developer comprising a toner T and a carrier E, and a developing sleeve 1
By applying the developing bias voltage V _Bias to 5,
In the image forming apparatus for adhering the toner T to the photoconductor 12, the surface potential V of the photoconductor at the start and stop of the rotation of the photoconductor.
Relative potential difference ΔV between _SP and developing bias voltage V _Bias
Is controlled stepwise within the range of the carrier jump occurrence limit maximum potential difference V _max and the toner adhesion amount minimum potential difference V _min .

FIG. 2 shows a reversal development type copying machine. First, its outline will be described. In FIG. 2, the photoconductor 12 rotates counterclockwise. By changing the grid voltage of the charger 11 (grid is indicated by symbol R), the charging of the photoconductor 12 is controlled stepwise at a high voltage, and the surface potential sensor 16 measures the surface potential of the photoconductor 12, When the charged electrostatic charge reaches the exposure position, L
It is exposed by the ED array 13 to form a latent image.
When the toner further rotates and reaches the developing device 14, the toner T is blown off to develop the toner. Then, the developed portion is transferred, and the residual toner is removed by the cleaning device L. The charger 11 is connected to a high-voltage power supply circuit 20 for charging the photoconductor 12 to about +850 volts (grid voltage is controlled to about +920 volts). The high-voltage power supply circuit 20 also includes a control circuit 1 for controlling the magnitude of the voltage generated by the high-voltage power supply circuit 20.
9 is connected. On the other hand, the developing device 14 is provided with the high-voltage power supply circuit 21, to which a control circuit 22 for controlling the magnitude of the voltage generated by the high-voltage power supply circuit 21 is connected. Further, the LED array 13 is connected to a control circuit 24 that controls the amount of exposure light. A CPU 23 for instructing the control contents of these control circuits 19, 22, 24 is provided, and the surface potential sensor 16 is provided therein.
The output signal of is input. This CPU
Reference numeral 23 instructs the charger 11 to gradually change the charge amount due to the grid voltage from 0 to a predetermined value, and also instructs the developing device 14 to gradually change the developing bias voltage to the predetermined voltage value. Has become.

The timing of applying the developing bias voltage and the surface potential of the photoconductor at the start of rotation of the photoconductor will be described below. In this embodiment, in FIG. 1, at the start of rotation, first, a developing bias voltage V _Bias (−200 V) having a reverse polarity is applied to the developing sleeve 15, and subsequently, before the polarity switching of the developing bias voltage V _Bias. At time A, the surface potential V _SP (+150 V) is applied to the photoconductor, and at time B, the bias voltage V _Bias is first controlled to the OFF state.

The relative potential difference ΔV at this time point B is ΔV (time point B) = 150 volt−0 volt = 150 volt. Therefore, even if the developing bias voltage V _Bias is 0 volt, the surface potential V _SP is It is as small as 150 V and the relative potential difference ΔV is V _max value (30 V in this embodiment).
Since it does not exceed 0 volt, carrier jump does not occur.

Subsequently, the surface potential V _SP is 150 at the time point C.
In the ascending phase of controlling from 300 to 300 volts,
The relative potential difference ΔV at the time point C is ΔV (time point C) = 300 V−0 V = 300 V, and the relative potential difference ΔV is the V _max value (in the present embodiment,
Since it does not exceed 300 volts, carrier jump does not occur.

Then, at the rising stage of controlling the developing bias voltage from 0 volt to +150 volt, the relative potential difference ΔV at the time point D is ΔV (time point D) = 300 volt−150 volt = 150.
Volts, and the relative potential difference Δ
Since V never exceeds the V _max value (300 V), carrier jump does not occur.

Further, as is apparent from FIG. 1, since the relative potential difference ΔV does not exceed the V _min value (150 V in this embodiment) at any time point, a large amount of toner can be prevented from adhering, and at most. It can be done with just a cover.

Thus, at the start of rotation of the photosensitive member, the charge amount on the surface of the photosensitive member is gradually changed from zero to a predetermined value (+850 V), and the developing bias voltage is gradually changed to a predetermined voltage value (+650 V). Then, the charge amount and the developing bias voltage are controlled to control the photoconductor 1 at the developing position G at any stage up to the copying operation.
The relative potential difference ΔV between the surface potential V _{SP of} 2 and the developing bias voltage V _Bias is set within the range of V _min and V _max .

That is, while maintaining the relative potential difference ΔV within the range of 300 V to 150 V, the developing bias voltage is maintained until the surface potential V _SP and the developing bias voltage V _bias become 850 V and 650 V, respectively. Both V _bias and surface potential V _SP are controlled stepwise.

The same control is performed when the rotation of the photoconductor is stopped after the copying operation.

As described above, in the present embodiment, the developing bias voltage V _Bias and the surface potential V _SP are mutually controlled at each stage,
Since the relative potential difference ΔV does not exceed V _max ,
It is possible to avoid the occurrence of carrier skipping and prevent the relative potential difference ΔV from exceeding V _min , so that a large amount of toner adhesion can be avoided.

In this embodiment, the surface potential V _SP is
Although the method of controlling stepwise by changing the grid voltage of the charger was shown, the surface potential can be controlled stepwise by changing the charger output, or the output of the laser or LED can be changed to expose the photoconductor. You may make it control stepwise by changing an amount.

Then, in setting the surface potential V _SP ,
When the method of changing the grid voltage or changing the charger output is adopted, the surface potential rises and falls only linearly, and therefore, the rise and fall of the surface potential is only gentle, but the laser and L
The use of the ED is advantageous in that the time width can be narrowed, time management can be performed, a sharp edge can be provided, and the setting of the surface potential V _SP can be further improved.

Furthermore, in this embodiment, the carrier jump occurrence limit maximum potential difference V _max as 300 volt potential difference [Delta] V, showed that set at 150 volts as toner adhesion amount minimum potential V _min, these maximum potential difference V _max And the value of the minimum potential difference V _min are set appropriately according to the device.

[0032]

As described above, according to the present invention, in the image forming apparatus in which the toner is attached to the photoreceptor by applying the developing bias voltage to the developing sleeve by using the two-component developer composed of the toner and the carrier. Since the relative potential difference between the surface potential of the photoreceptor and the developing bias voltage at the time of starting and stopping the rotation of the photoreceptor is controlled stepwise within the range of the carrier jump occurrence maximum potential difference and the toner adhesion amount minimum potential difference, It is possible to avoid the occurrence of carrier skipping, and to prevent a large amount of toner from adhering to minimize the consumption of toner not used for image formation. Further, since the amount of toner collected is reduced, there is an effect that the size of the collection container can be reduced.

[Brief description of drawings]

FIG. 1 is a timing chart for explaining an embodiment of the present invention.

FIG. 2 is an overall configuration explanatory diagram showing a reversal development type image forming apparatus applied to the above-described embodiment.

FIG. 3 is a diagram for explaining a reversal development method using a two-component developer.

FIG. 4 is a timing chart showing changes in the developing bias voltage V _Bias and the surface potential V _SP at the start of rotation of the photoconductor in the conventional example.

FIG. 5 is a diagram for explaining occurrence of carrier jump in a conventional example.

FIG. 6 is a diagram showing a relative difference ΔV between the surface potential V _SP and the developing bias voltage V _Bias used for explaining the occurrence of carrier jump in the conventional example.

FIG. 7 is a timing chart for explaining a conventional example.

FIG. 8 is a timing chart showing changes in the developing bias voltage V _Bias and the surface potential V _SP at the start of rotation of the photoconductor in the conventional example. .

FIG. 9 is a diagram for explaining a large amount of toner adhered in a conventional example.

FIG. 10 is a diagram showing a relative difference ΔV between the surface potential V _SP and the developing bias voltage V _Bias used for explaining the large amount of toner adhesion in the conventional example.

[Explanation of Codes] 12 ... Photosensitive Member, 15 ... Developing Sleeve, T ... Toner, E ...
Carrier, V _SP ... Surface potential, V _Bias ... Development bias voltage, ΔV ... Potential difference, V _max ... Carrier jumping limit maximum potential difference, V _min ... Toner adhesion amount minimum potential difference.

Claims (5)

[Claims] 1. An image forming apparatus in which a toner is attached to a photosensitive member by applying a developing bias voltage to a developing sleeve by using a two-component developer composed of toner and carrier, and the photosensitive member is started and stopped at the time of rotation of the photosensitive member. 2. A potential control method in an image forming apparatus, wherein both the surface potential of the device and the developing bias voltage are controlled stepwise. 2. An image forming apparatus in which a toner is attached to a photoconductor by applying a developing bias voltage to a developing sleeve by using a two-component developer composed of toner and carrier, and the photoconductor is started and stopped at the time of rotation. The potential control method in the image forming apparatus, wherein the relative potential difference between the surface potential of the above-mentioned and the developing bias voltage is controlled stepwise within the range of the maximum potential difference of carrier jump occurrence limit and the minimum potential difference of toner adhesion amount. 3. The image forming apparatus according to claim 1, wherein the surface potential of the photosensitive member is controlled stepwise by changing the grid voltage of the charger when starting and stopping the rotation of the photosensitive member. Potential control method. 4. The potential control in the image forming apparatus according to claim 1, wherein the surface potential of the photoconductor is controlled stepwise by changing the charger output when the photoconductor starts and stops. Method. 5. The image formation according to claim 1, wherein the surface potential of the photoconductor is controlled stepwise by starting and stopping the rotation of the photoconductor by changing the exposure amount to the photoconductor. Potential control method in device.