JPH04120568A - Reversal developing controller - Google Patents

Abstract

PURPOSE:To prevent the scattering of toner and a carrier by gradually changing the voltage impression of an electrifying means up to a target voltage and the voltage impression of a bias giving means up to a prescribed voltage. CONSTITUTION:A photosensitive body 2 is electrified by the electrifying means 10, and when the photosensitive body 2 reaches a developing means 4, a prescribed bias voltage is impressed to the developing means 4 by the bias giving means 11, and the toner is soared up to the photosensitive body 2 to carry out development. At this time, the surface potential control means 9 of the electrifying means 1 and 10 controls the impression of the voltage so that the voltage is gradually changed up to the target voltage, and the bias control means 13 of the bias giving means 11 controls the impression of the voltage so that the voltage is gradually changed up to the prescribed voltage. Therefore, even if the timing of the impression to the developing means 4 is more or less deviated from normal timing, a difference between the surface potential and the voltage of the developing means 4 on a developing region is within tolerance. Thus, the unnecessary scattering of the toner and carrier is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reversal development control device used in an image forming apparatus such as a copying machine.

[Prior Art] In a positive development type copying machine that uses a two-component developer, the surface of a photosensitive drum that has been positively charged by a charging means is exposed to light to form an electrostatic latent image, and this positive image is then exposed to light. Toner of a developer consisting of positively charged carrier and negatively charged toner is attached to the non-exposed area on the charged electrostatic latent image portion for development. On the other hand, in a reversal development type copying machine that uses a two-component developer, the surface of the photosensitive drum is negatively charged, and the negatively charged toner of the developer is attached to the area (exposed area) where the voltage becomes zero due to exposure. It is being developed.

That is, in the reversal development method, as shown in FIG.
A negative voltage on the order of volts is applied, and the negatively charged portion rotates to a location on the exposure rod lens array 3, is exposed, and further rotates to reach the developing roller 41.

Then, when it reaches that point, the developing roller 41 has a -40
A negative bias voltage of approximately 0 volts is applied, and the negatively charged toner flies out due to the repulsive force and adheres to the exposed portion of the photosensitive drum 2 where the voltage is zero.

[Problems to be Solved by the Invention] Incidentally, it is desirable that the bias voltage to the developing roller 41 be applied at the same time as the charged and exposed portion of the photoreceptor drum 2 reaches a position facing the developing roller 41. However, controlling this timing is not easy. Therefore, for example, if the timing at which 1,400 volts is applied to the developing roller 41 is too early than the time when the portion of the photosensitive drum 2 charged to 1,800 volts reaches the developing roller 41, the photosensitive drum 41 The surface voltage becomes higher than the bias voltage of the developing roller 41, and the toner flies to the photosensitive drum 2. That is, as shown in FIG. 5(a), the photosensitive drum 2 and the developing roller 4 that have reached the developing area
If the voltage applied to 1 deviates, the voltage difference will exceed the allowable difference, as shown in FIG. 5(b) (relative difference assuming the bias voltage is O volts).

On the other hand, if the timing at which 1,400 volts is applied to the developing roller 41 is too late than the time when the portion of the photosensitive drum 2 charged at 1,800 volts reaches the developing roller 41, then -800 volts is applied to the developing roller 41. Even though the portion of the photosensitive drum to which is applied has reached the developing roller 41, no bias voltage is applied to the developing roller 41, so positively charged carriers are deposited on the surface of the photosensitive drum 2. Gravitate. That is, as shown in FIG. 6(a), the photosensitive drum 2 and the developing roller 4 that have reached the developing area
If the voltage applied to 1 deviates, the voltage difference will exceed the allowable difference, as shown in FIG. 6(b) (relative difference assuming the bias voltage is O volts).

On the other hand, some inventions have been made in which the bias voltage is not applied suddenly, but even so, if the timing of applying both types of pressure is wrong, the voltage difference will exceed the allowable range and the toner and carrier will be scattered. Put it away.

The present invention takes into consideration the problems of the conventional reversal development control device, and even if the timing of applying voltage to the photosensitive drum or the timing of applying bias voltage to the developing means deviates from the normal timing, toner and carrier It is an object of the present invention to provide a reversal development control device that does not cause scattering.

[Means for Solving the Problems] The present invention provides a photoreceptor on which a latent image is formed, a developing means for reversing and developing the latent image, and a charging means for charging the photoreceptor and applying a predetermined surface potential. In the reversal development control device for an image forming apparatus, the surface potential control means of the charging means gradually changes the voltage applied by the charging means to a target voltage. The bias control means of the bias applying means is a reversal development control device that controls the voltage application by the bias applying means to gradually change it to a predetermined voltage.

[Function] According to the present invention, a photoreceptor is charged by a charging means, and when the charged photoreceptor reaches a developing means, a predetermined bias voltage is applied to the developing means by a bias applying means to photosensitive the toner. When developing by spraying onto a body, the surface potential control means of the charging means controls the voltage applied by the charging means to gradually change to the target voltage, and the bias control means of the bias applying means controls the voltage applied by the charging means to gradually change the voltage applied by the charging means to the target voltage. The voltage application is controlled to be gradually changed up to a predetermined voltage. Therefore, the difference between the surface potential of the photoreceptor and the voltage of the developing means in the developing area is within an acceptable range even if the timing of application is slightly off from the regular timing, so unnecessary toner scattering and This prevents the carrier from scattering.

[Examples] Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view of main parts of a copying machine in which an embodiment of the reversal development control device according to the present invention is used.

In the figure, around the photosensitive drum 20, which is an example of a photosensitive member on which a latent image is formed, in the counterclockwise direction of the drawing,
In order, the charger 1, the surface potential sensor 6, the exposure rod lens array 3 provided at the exposure site, the developer 4 as an example of a developing means and its developing roller 41, the cleaning means 5 for cleaning residual toner, etc. is located. Note that 8 is a contact glass on which the original is placed;
is a lamp for exposure.

A high voltage power supply circuit IO for applying a high voltage of about -800 volts to the charger 1 is connected to the charger 1. The high voltage power supply circuit 10 also includes a control circuit 9 that controls the magnitude of the voltage generated by the high voltage power supply circuit 100.
is connected.

On the other hand, a high voltage power supply circuit 11 for applying high voltage to the developing device 4 is connected to the developing device 4 .

Further, the high voltage power supply circuit 11 includes the high voltage power supply circuit 1
A control circuit 12 for controlling the magnitude of the voltage generated by 1 is connected.

A central processing unit (CPtJ) 13 is provided for instructing the control contents of these control circuits 9 and 12, and an output signal from the surface potential sensor 60 is manually input thereto. This CP Ll 13 is
An instruction is given to gradually change the voltage application by the charger 1 to the target eA voltage, and an instruction is also given to gradually change the voltage application to the developing device 4 to the target voltage.

Next, the operation of the above embodiment will be explained.

The outline will be explained first. It is assumed that the photosensitive drum 2 is rotating counterclockwise as shown in FIG. The charger 1 charges the photosensitive drum 2 with a high voltage, and the surface potential sensor 6
The surface potential of the charged photosensitive drum 2 is measured, and when the charged part reaches the exposed area, it is exposed to light reflected by the lamp 7 from the document placed on the contact glass 8, and a latent image is formed there. is formed. When the toner rotates further and reaches the developing device 40, the high voltage power supply circuit 11 applies a high voltage to the developing device 4 to blow off the toner and perform development. After that, the developed part is transferred (not shown),
The remaining toner is cleaned by a cleaning device 5.

Next, the timing of voltage application in the above operation will be explained in detail.

It takes a certain amount of time until the photosensitive drum portion 1) to which a voltage is applied by the charger 1 rotates and reaches the developing location P2 of the developing roller 41 of the developing device 4. For example, suppose it takes 0.4 seconds.

First, the CPU 13 drives the control circuit 9 to apply voltage to the photosensitive tram 2 using the charger 1 using the high voltage power supply circuit 10.
The voltage is applied stepwise from 00 volts as shown in FIG. Then, 0.4 seconds after the start of the application,
By driving the control circuit 12 and using the high voltage power supply circuit 11,
A voltage is started to be applied to the developer 4 in steps from +100 volts as shown in FIG. That is, the portion of the photosensitive drum 2 to which 1100 volts is applied is exactly the part of the developing device 4.
When reaching the developing area, +100 is added to developer 4.
Volt voltage begins to be applied.

Thereafter, CPU ], 3 changes the surface potential of the photosensitive tram 2 in steps from -100 to -2 as shown in FIG.
00→-300→-400→-500→-600→-7
Change it to 00. Note that the timing (horizontal axis) of the graph of the surface potential of the photosensitive drum 2 in the drawing is drawn 0.4 seconds after the application time. On the other hand, similarly, the potential of the developing device 4 is increased by +10 in steps as shown in FIG.
Change as 0 → 0 → 100 → 200 → 300 → 400 → 400. These changes take place in about 0.5 seconds.

As a result, the difference between the surface potential of the photosensitive drum 2 at the development site and the potential of the developing device 4 becomes as shown in FIG.

The figure shows the relative difference in surface potential with respect to a bias voltage of zero.

That is, if the voltage is gradually changed at the timing shown in the figure, the relative difference in the potential of the photosensitive drum 2 with respect to the potential of the developing device 4 will fall within an allowable range.

Now, if the timing of voltage application to the charger 1 or the timing of voltage application to the developing device 4 is shifted back or forth, the difference between the surface potential of the photosensitive drum 20 and the potential of the developing device 4 will change, but even if there is a considerable shift, Since both potentials change gradually, they stay at about 400 volts. Therefore, inconveniences such as toner and carrier scattering do not occur.

In the present invention, the bias applying means for applying a predetermined bias voltage to the developing means is the high voltage power supply circuit 11 in the above embodiment, and the bias control means is the control circuit 1.
2, a CPU 13, etc., but the present invention is not limited to this embodiment, and in short, any structure that can reach a predetermined voltage by gradually changing the bias voltage may be used.

Further, in the above embodiment, the charging means in the present invention is composed of the charger 1 and the high-voltage power supply circuit 10, and the surface potential control means is composed of the control circuit 9, the CPU 13, etc.; The present invention is not limited to this, and in short, it is sufficient as long as the surface potential is gradually changed to reach a predetermined potential.

Furthermore, although the method of applying the voltage of the present invention is applied in steps in the above embodiment, the voltage is not limited to this, and of course may be applied continuously and gradually.

[Effects of the Invention] As is clear from the above explanation, the present invention provides a method in which the surface potential control means of the charging means gradually changes the voltage applied by the charging means to a target voltage, and the bias applying means The bias control means controls the voltage applied by the bias applying means to gradually change up to a predetermined voltage, so even if the timing of applying the bias voltage or the timing of applying the surface potential is slightly off,
It has the advantage that toner and carrier do not scatter.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram showing an embodiment of the reversal development control device according to the present invention, FIG. 2 is a graph showing temporal changes in surface potential and bias voltage of the same embodiment, and FIG. ,
FIG. 4 is a graph showing the difference between the surface potential and bias voltage of the same embodiment, and FIG. 4 is a schematic cross-sectional view showing the main parts of a conventional copying machine.
FIG. 5 is a graph showing the conventional relationship between surface potential and bias voltage, and FIG. 6 is a graph showing the conventional relationship between surface potential and bias voltage. l, 10...Charging means, 2...Photoreceptor, 4...Developer (developing means), 9.13...Surface potential control means,
11...Bias applying means, 12.13...Bias control means.

Claims (2)

[Claims] (1) A photoreceptor on which a latent image is formed, a developing means for reversing and developing the latent image, a charging means for charging the photoreceptor and applying a predetermined surface potential, and a predetermined bias voltage to the developing means. In the reversal development control device for an image forming apparatus, the surface potential control means of the charging means controls the voltage applied by the charging means to gradually change to a target voltage, and A reversal development control device characterized in that the bias control means of the bias application means controls the voltage application by the bias application means to gradually change up to a predetermined voltage. (2) The reversal development control device according to claim 1, wherein the surface potential control means and the bias control means apply a predetermined voltage in steps.