JPS6146830B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a device for charging the surface of a photosensitive drum used in a copying machine or the like with a constant potential.

(b) Prior Art and Problems A voltage of several hundred volts is applied to the photosensitive drum of an electronic copying machine to make the potential distribution on the rotating drum uniform and to prevent uneven copying.

To charge the drum, the current generated by corona discharge from the charger is controlled so that the surface potential of the drum remains constant.

However, in such conventional devices, although the discharge current can be kept constant, there is no guarantee that the actual potential on the drum surface is constant, and there is a problem in that uneven copying occurs.

(c) Purpose of the Invention The purpose of this invention is to make the surface potential of a photosensitive drum constant, and to create a feedback loop between the charger and the drum surface so that the surface potential of the drum itself can be controlled. With the goal.

(d) Embodiment of the invention First, a configuration diagram of an embodiment of the invention is shown in the first diagram.
As shown in the figure.

In Figure 1, 1 is a drum, 2 is an inductive electrode, 3 is a capacitor, 4 is a conductor, 5 is a motor, 6 is a synchronous signal generator, 7 is a phase synchronized detector, 8 is a rectifier, 9 is a charger, 10 is a This is the reference power supply.

A surface potential Vx is applied to drum 1, and induction electrode 2
is electrostatically coupled to the drum 1 through the capacitor 3.

The conductor 4 is attached to the surface of the drum 1, and when the drum 1 is rotated, the charged surface of the drum 1 and the conductor 4
are alternately electrostatically coupled to the induction electrodes 2.

The conductor 4 in FIG. 1 has a "comb" tooth shape, and the rectangular tooth portion extends to the charging surface of the drum 1. In addition, the tooth portion may be shaped into a triangular wave, a sine wave, or the like.

The motor 5 rotates the drum 1.

Portions 1 to 5 in FIG. 1 are a conventional device for detecting the surface potential of a charged body, and a similar technique is also described in FIG. 1 of Japanese Unexamined Patent Publication No. 55-28059.

In this invention, parts 6 to 10 are added to 1 to 5 in FIG.

The synchronization signal generator 6 generates a synchronization signal when the boundary between the charged surface of the drum 1 and the conductor 4 faces the induction electrode 2.

In the embodiment shown in FIG. 1, a synchronization signal is generated when the side surfaces 41 to 43 of the teeth of the "comb" face the induction electrode 2.

Note that the width W1, which is composed of the side surfaces 41 to 43, etc.
W3 etc. do not necessarily have to be equal.

Next, a block diagram of an embodiment of the synchronizing signal generator 6 is shown in FIG.

In Figure 3, 11 is a disk, 12 is a hole, 13 is a light source,
14 is a photodetector, and 15 is an output terminal.

In FIG. 3, four holes 12 are made in the disk 11. The width of the hole 12 is made to correspond to the width W1 to W3 of the conductor 4, and the disk 11 is rotated together with the drum 1.

If the light source 13 and the disk 11 are arranged so that the light from the light source 13 passes through the hole 12 of the disk 11, and the light from the light source 13 that has passed through the rotating disk 11 is detected by the photodetector 14, the output will be A synchronizing signal can be taken out from the terminal 15.

The output of the induction electrode 2 and the synchronization signal of the synchronization signal generator 6 are applied to the phase synchronization detector 7 shown in FIG. Based on the synchronization signal, the phase synchronization detector 7 detects the surface potential Vx of the drum 1 and the surface potential Vs of the conductor 4 generated on the induction electrode 2, and determines the magnitude of both potentials.

A rectifier 8 rectifies the output of the phase locked detector 7.

The charger 9 is arranged along the charging surface of the drum 1 in the axial direction, and the output of the charger 8 is applied thereto.

The surface of the drum 1 is an insulating film, and the charger 9 is used to charge this insulating film.

The reference power source 10 is for keeping the surface potential Vx constant, and constantly applies a constant voltage Vs to the conductor 4 attached to the drum 1.

Next, the operation shown in FIG. 1 will be explained.

When the drum 1 is rotated by the motor 5, the conductor 4 attached to the drum 1 and the charged surface of the drum 1 have a capacity of 3.
They are alternately electrostatically coupled to the induction electrodes 2.

When the surface potential Vx and the surface potential Vs are different, the difference potential is taken out as the output of the phase synchronization detector 7, and the output of the rectifier 8 is applied to the charger 9.

Therefore, as the drum 1 rotates, the surface potential Vx approaches the surface potential Vs, and eventually both potentials become the same.

That is, the surface potential Vx is locked at the constant voltage Vs of the reference power supply 10.

Next, FIG. 2 shows a state in which the surface potential Vx approaches the surface potential Vs.

FIG. 2A shows the time course in which the surface potential Vx and the surface potential Vs face the induction electrode 2, and the horizontal axis represents time.

Synchronous signal generator 6 at the boundary of Vx and Vs in Figure 2 A
A synchronization signal is output from the phase synchronization detector 7 to control the phase synchronization detector 7.

FIG. 2A shows the potential of the induction electrode 2 in relative values.

Since the capacitor 3 conducts this potential, the potential of the inductive electrode 2 becomes an alternating current component. The first peak a is the potential due to the surface potential Vs when the drum 1 starts rotating.

The next peak b is a potential due to the surface potential Vx, and the larger the difference between the surface potentials Vs and Vx, the greater the difference between the peaks a and b.

The example in FIG. 2A shows a state where Vs>Vx.
When Vs<Vx, the directions of mountains a and b are opposite to each other.

FIG. 2C shows the output of the phase locked detector 7.

The polarity of the component indicated by the peak b in FIG. 2A is reversed in FIG.

FIG. 2(e) shows the output of the rectifier 8, and the output of FIG. 2(c) is rectified and integrated.

Therefore, as the drum 1 rotates, the output of the rectifier 8 approaches the constant voltage Vs of the reference power supply 10.

The reason why the third peak c in FIG. 2A is smaller than the first peak a is as follows.

That is, in FIG. 2E, the output of the rectifier 8 is applied to the charger 9, and the surface potential Vx increases, so that the difference between the surface potential Vx and the surface potential Vs becomes smaller.

(e) Effect of the invention According to this invention, the surface potential Vx is changed to the surface potential Vs
Since the feedback loop is configured to be the same as , the following effects are obtained.

(a) The surface potential Vx itself can be constantly brought close to the constant voltage Vs.

(a) The induction electrode 2 only needs to be able to detect the surface potential Vx, so it can be a simple metal plate.

(c) Since the feedback loop part can be built into the inside of the device together with the drum 1, it is less affected by external dust.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment according to the present invention, and FIG.
The figure is an explanatory diagram of a state in which the surface potential Vx approaches the surface potential Vs, and FIG. 3 is a configuration diagram of an embodiment of the synchronization signal generator 6. 1... drum, 2... induction electrode, 3... capacitance,
4... Conductor, 5... Motor, 6... Synchronous signal generator, 7... Phase synchronous detector, 8... Rectifier, 9...
...Charger, 10...Reference power supply, Vx...Drum 1
Surface potential of Vs...Surface potential of conductor 4.

Claims (1)

[Claims] 1. An inductive electrode 2 that is electrostatically coupled to the charged surface of a rotating drum 1 through a capacitance 3, and a
In the surface potential detector of a rotating drum, the surface potential detector is equipped with a conductor 4 attached to the charged surface of the drum 1 so as to be alternately electrostatically coupled to the charged surface of the drum 1. As the drum 1 rotates, the charged surface of the drum 1 and the conductor 4 a synchronizing signal generator 6 that generates a synchronizing signal when the boundary of the conductor 4 faces the inductive electrode 2;
a phase-locked detector 7 that determines the magnitude of the surface potential Vx of the drum 1, and a rectifier 8 that rectifies the output of the phase-locked detector 7.
A charger 9 is arranged along the charging surface in the axial direction of the drum 1, and a reference power supply 10 that gives a surface potential Vs to the conductor 4 is provided.The output of the rectifier 8 is added to the charger 9, and the reference power supply 1
A surface potential stabilizing device for a rotating drum, characterized in that the surface of the drum 1 is charged with the same potential as a constant voltage of 0.