JPH07168420A - Electrifying device - Google Patents

Abstract

PURPOSE:To always maintain fixed electrifying potential without causing toner blocking nor defective cohesion of toner by detecting temperature near a member for electrification and controlling impressed voltage based on the detected result. CONSTITUTION:The voltage is impressed on an electrifying roller 105 from a high voltage power source generation circuit 114, and a photoreceptive drum 102 is uniformly electrified. In the midst of copying process, the temperature near the electrifying roller is detected by a temperature detecting sensor 108, and the detected temperature is converted into an electrical signal by an electrical signal conversion circuit 112 and outputted to an impressed voltage control circuit 113. The control circuit 113 decides the impressed voltage on the generation circuit 114 based on the detected temperature and controls the circuit 114 so that the output voltage of the circuit 114 may be the decided impressed voltage. Thus, the fixed electrifying potential is maintained without heating the member for electrification.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device in which a charging member is brought into contact with the surface of a photoconductor to uniformly charge it, and more particularly to a charging device capable of performing charging at a stable charging potential. .

[0002]

2. Description of the Related Art A charging member is brought into contact with the surface of a photoconductor,
As a charging device for uniformly charging, there is, for example, a roller charging type charging device for bringing a charging roller into contact with a photoconductor. In the roller charging method, charging efficiency (= charging potential /
The applied voltage depends on the temperature of the charging roller, and the charging efficiency decreases in a low temperature environment. Therefore, in the constant voltage control, if the charging efficiency is lowered, the charging potential obtained with a constant applied voltage is lowered, and the image density is lowered and the process control controlled by using the other charging potential as a reference value is not normally performed. Inconvenience occurs.

Therefore, in order to solve this, for example, as shown in JP-A-4-6567, "Electrophotographic Method", the charging member itself is heated to increase the temperature of the charging member to 35 to 35 degrees. It has been proposed to maintain a constant charging potential by maintaining the temperature in the range of 55 ° C.

[0004]

However, according to the above conventional technique, the charging potential can be maintained by heating the charging member and keeping the temperature of the charging member constant, but Since the photoconductor and other units are heated together with the members for use, the residual toner on the photoconductor is collected and returned to the developing device.
There is a problem in that the toner remaining on the high-temperature photosensitive member is collected and reused, which causes toner blocking and deterioration of toner aggregation.

The present invention has been made in view of the above, and it is an object of the present invention to always maintain a constant charging potential without causing toner blocking or deterioration of toner aggregation degree.

[0006]

In order to achieve the above object, the present invention brings a charging member into contact with the surface of a photoreceptor,
In a charging device for uniformly charging, a voltage applying means for applying a voltage to the charging member, a temperature detecting means for detecting a temperature in the vicinity of the charging member and outputting a signal according to the temperature, and the temperature detecting means. And a control means for controlling the applied voltage of the voltage applying means based on the signal from the charging device.

The temperature detecting means is in contact with the surface of the charging member to detect the temperature of the charging member, and the material forming the contact portion of the temperature detecting means is the charging member. It shall have the same hardness as the surface.

Further, the temperature detecting means comes into contact with the surface of the charging member corresponding to the non-image forming portion of the photosensitive member.

[0009]

In the charging device of the present invention, the control means controls the applied voltage applied to the charging member based on the temperature in the vicinity of the charging member, so that the charging member can be charged at a constant level without heating. Keep the potential.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The charging device of the present invention will be described in detail below in the order of [First Embodiment], [Second Embodiment], and [Third Embodiment] with reference to the drawings.

[Embodiment 1] FIG. 1 shows a copying process of a copying machine equipped with a charging device of Embodiment 1, and
Reference numeral 101 denotes a precess cartridge in which a photosensitive drum, a charging device, and a cleaning device are integrally formed,
2 is a photosensitive drum, 103 is a cleaning blade, 1
Reference numeral 04 is a collected toner portion, 105 is a charging roller, 106 is a charging roller cleaner, 107 is an eraser, 108 is a temperature detection sensor, 109 is a developing device, 110 is a transfer unit,
Reference numeral 111 denotes a fixing device.

In addition to the charging roller 105, the charging roller cleaner 106 and the temperature detecting sensor 108, the charging device of the first embodiment includes an electric signal conversion circuit 112 for converting the temperature detected by the temperature detecting sensor 108 into an electric signal. , A high-voltage power supply generation circuit 11 for applying a voltage to the charging roller 105
4 and an applied voltage control circuit 113 for controlling the applied voltage of the high voltage power supply generation circuit 114 based on the electric signal from the electric signal conversion circuit 112.

The operation of the above configuration will be described. A voltage is applied from the high-voltage power supply generation circuit 114 to the charging roller 105 rotating together with the photoconductor drum 102 to uniformly charge the photoconductor drum 102. After that, an electrostatic latent image is formed on the photosensitive drum 102 by the laser light emitted from the optical writing unit (not shown), and after the exposure by the eraser 107, the electrostatic latent image is toner-developed by the developing device 109. Transcribing unit 110
Then, it is transferred to a recording sheet conveyed from a sheet feeding device (not shown). After that, the recording paper is subjected to toner fixing by the fixing device 111 and discharged. On the other hand, the toner remaining on the photosensitive drum 102 is scraped off by the cleaning blade 103 and collected by the toner collecting unit 104.

During the above copying process, the temperature detecting sensor 108 detects the temperature in the vicinity of the charging roller, the electric signal converting circuit 112 converts the detected temperature into an electric signal and outputs the electric signal to the applied voltage control circuit 113. It

The applied voltage control circuit 113 determines the applied voltage of the high voltage power supply generation circuit 114 based on the electric signal (that is, the detected temperature), and the output voltage of the high voltage power supply generation circuit 114 becomes the determined applied voltage. Thus, the high voltage power supply generation circuit 114 is controlled. Here, the applied voltage is determined according to the detected temperature by using the relationship between the applied voltage and the charging roller temperature when the charging potential is kept constant in the charging device of the first embodiment shown in FIG. The applied voltage to be applied is determined.

The high-voltage power supply generation circuit 114 applies the applied voltage determined by the applied voltage control circuit 113 to the charging roller 105 as an output voltage.

It is desirable that the temperature detection sensor 108 be as close as possible to the charging roller 105. However, if the temperature detection sensor 108 is brought into contact with the charging roller 105, the roller surface may be roughened by the contact and uneven charging may occur. In addition, the location where the roller temperature can be detected most accurately was selected and placed. Specifically, since the lamp in the optical unit (not shown) becomes high temperature by repeating the copying process, a ventilation fan is often installed in the rear part of the copying machine body. The ambient temperature near the charging roller 105 is different when the fan is operating and when it is not operating.

Therefore, regardless of the operation of the ventilation fan,
When the installation position of the temperature detection sensor 108 is always examined because it is more responsive to the surface temperature of the charging roller 105, the best responsiveness is obtained when the temperature detection sensor 108 is installed at the center of the eraser 107 on the charging roller side. Became clear.

It should be noted that the temperature change due to the operation of the ventilation fan is large on the inner side of the main body of the eraser 107 of the copying machine, which is not preferable. Further, the temperature detection sensor 108 is attached to the fixing device 11
Even if it is installed near 1 or on the fixing device side of the charging roller 105, it is not preferable because it is easily affected by the heat radiated from the fixing device 111.

As described above, in the first embodiment, the applied voltage applied to the charging roller 105 is controlled based on the temperature in the vicinity of the charging roller 105, so that a constant charging potential can always be maintained. In other words, since the temperature is always detected and the temperature-corrected applied voltage is applied to the charging roller 105, a constant charging potential can be maintained under any temperature environment, and a good image can always be obtained.

Further, since a constant charging potential is maintained without heating the charging roller 105, it is possible to avoid toner blocking and deterioration of toner cohesion.

[Second Embodiment] In the second embodiment, instead of the temperature detection sensor 108 of the first embodiment, a temperature detection sensor 301 for detecting the temperature in a state of being in contact with the charging roller 105 is used. The other configurations and operations are the same as those of the first embodiment.
In this case, only different parts will be explained here.

FIG. 3 shows a temperature detecting sensor 301 according to the second embodiment.
The arrangement is as shown in the figure, and as shown in the figure, the temperature is detected by contacting the charging roller 105. However, charging roller 1
05 In order to prevent the charging unevenness from occurring by roughening the surface, the material forming the contact portion of the temperature detection sensor 301 has the same hardness as the surface of the charging roller 105.

In the above-described structure, in the second embodiment, the temperature can be detected by contacting the charging roller 105, so that the temperature detection accuracy is improved, and compared with the first embodiment, the constant charging can be performed with higher accuracy. The potential can be maintained. Further, since the surface of the charging roller 105 is not roughened, uneven charging does not occur.

[Third Embodiment] In the third embodiment, instead of the temperature detection sensor 108 of the first embodiment, a temperature detection sensor 401 for detecting the temperature in a state of being in contact with the charging roller 105 is used. The other configurations and operations are the same as those of the first embodiment.
In this case, only different parts will be explained here.

FIG. 4 shows a temperature detection sensor 401 according to the third embodiment.
The arrangement is as shown in the figure, and as shown in the figure, the temperature is detected by contacting the charging roller 105. However, charging roller 1
05 In order to roughen the surface and prevent uneven charging, the temperature detection sensor 401 contacts the surface position of the charging roller 105 corresponding to the non-image forming area of the photosensitive drum 102.

In the above-mentioned configuration, in the third embodiment, the temperature can be detected by contacting the charging roller 105, so that the temperature detection accuracy is improved, and compared with the first embodiment, the constant charging can be performed with higher accuracy. The potential can be maintained. Further, even if the surface of the charging roller 105 is roughened, it does not affect the image forming area of the photoconductor drum 102, so that good images can be secured.

Also in the third embodiment, the temperature detecting sensor 40
It goes without saying that the material forming the contact portion 1 may have the same hardness as the surface of the charging roller 105.

[0029]

As described above, the charging device of the present invention is a charging device for bringing a charging member into contact with the surface of a photosensitive member to uniformly charge the surface of the photoreceptor, and a voltage applying means for applying a voltage to the charging member. A temperature detecting means for detecting a temperature in the vicinity of the charging member and outputting a signal according to the temperature; and a control means for controlling an applied voltage of the voltage applying means based on a signal from the temperature detecting means. Therefore, a constant charging potential can always be maintained without causing toner blocking or deterioration of toner cohesion.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating a copying process of a copying machine equipped with a charging device according to a first exemplary embodiment.

FIG. 2 is an explanatory diagram showing a relationship between an applied voltage and a charging roller temperature.

FIG. 3 is an explanatory diagram showing an arrangement of temperature detection sensors according to a second embodiment.

FIG. 4 is an explanatory diagram showing an arrangement of temperature detection sensors according to a third embodiment.

[Explanation of symbols]

 102 Photosensitive Drum 105 Charging Roller 106 Charging Roller Cleaner 108 Temperature Detection Sensor 112 Electric Signal Conversion Circuit 113 Applied Voltage Control Circuit 114 High Voltage Power Generation Circuit 301 Temperature Detection Sensor 401 Temperature Detection Sensor

Claims (3)

[Claims] 1. A charging member is brought into contact with the surface of the photoconductor,
In a charging device for uniformly charging, a voltage applying means for applying a voltage to the charging member, a temperature detecting means for detecting a temperature in the vicinity of the charging member and outputting a signal according to the temperature, and the temperature detecting means. And a control means for controlling the applied voltage of the voltage applying means based on a signal from the charging device. 2. The temperature detecting means is in contact with the surface of the charging member to detect the temperature of the charging member, and
The charging device according to claim 1, wherein the material forming the contact portion of the temperature detecting means has the same hardness as the surface of the charging member. 3. The charging device according to claim 1, wherein the temperature detecting means is in contact with a surface of the charging member corresponding to a non-image forming portion of the photoconductor.