JP2003263009A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a shaving of a photoreceptor part of an image carrier caused by discharge between the photoreceptor part and the resistor layer of an electrifying means. <P>SOLUTION: A copying machine for forming image by transferring a toner image to a medium to be recorded P is equipped with an electrifying roller coming into contact with the surface of a photoreceptor drum 10, and an electrifying power source part 123 applying voltage obtained by superposing DC voltage on AC voltage to the electrifying roller and electrifying the surface of the drum 10. The power source part 123 is equipped with an adding part 111 for adding up the number of the media to be recorded P by the drum 10 and a CPU 101 and an amplification factor switching part 112 adjusting the AC voltage applied to the electrifying roller. By adjusting the AC voltage applied to the electrifying roller by the CPU 101 and the switching part 112 based on the result of detection by the adding part 111, discharge amount between the electrifying roller and the drum 10 is adjusted. <P>COPYRIGHT: (C)2003,JPO

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, and more particularly to adjusting a voltage applied to a charging means for charging an image carrier to discharge between the image carrier and the charging means. The present invention relates to an image forming apparatus capable of adjusting current.

[0002]

2. Description of the Related Art Conventionally, as an apparatus for forming an image on a recording medium with toner, there are image forming apparatuses such as a copying machine, a printer, a facsimile, and a composite machine of these.

FIG. 6 shows a copying machine 8 which is an example of an image forming apparatus.
Indicates 00. The copying machine 800 can be provided with either the first conventional charging power source 623 shown in FIG. 7 or the second conventional charging power source 724 shown in FIG. However, in the following description, the case where the charging power source unit 623 of the first conventional example is provided will be described.

The copying machine 800 is formed around a photoconductor drum 10 which is a rotatable image carrier having a photoconductor part 12 capable of carrying a toner image on its outer peripheral surface, and a conductor shaft 21 which is a conductor part. The charging roller 20, which is a charging unit, in which the resistor 22, which is the resistor layer, is in contact with the photoconductor portion 12 of the photoconductor drum 10, and the surface of the photoconductor portion 12 charged by the charging roller 20 is scanned to A laser scanner 91, which is an optical scanning unit that forms an electrostatic latent image on the surface, and a developing unit that causes charged toner T to fly toward the surface of the photosensitive drum 10 to form a toner image according to the electrostatic latent image. Developing device 3
0, a transfer device 40 that is a transfer unit that contacts the photosensitive drum 10 to transfer the toner image onto the recording medium P, and nips and conveys the recording medium at the contact portion with the photosensitive drum 10, and a charging roller. A charging power supply unit 623, which is a charging power supply device for applying a voltage obtained by superimposing a DC voltage and an AC voltage on the conductor shaft 21 of 20, is provided.

During the printing operation of the copying machine, the conductor shaft 21 of the charging roller 20 is applied with a voltage obtained by superimposing an AC voltage and a DC voltage of a charging power source section 623, which will be described later. At this time, in the vicinity of the contact portion between the photoconductor portion 12 of the photoconductor drum 10 and the resistor 22 of the charging roller 20, corona discharge occurs and the surface of the photoconductor portion 12 is charged. As a result, the surface potential of the photosensitive section 12 of the photosensitive drum 10 becomes substantially equal to the DC voltage applied by the charging power source section 623. The reason why the AC voltage is superposed on the charging power source section 623 is to promote corona discharge and to make the surface potential of the photoconductor section 12 uniform.

Next, the surface of the photosensitive portion 12 of the photosensitive drum 10 is irradiated with the laser scanning light 90 from the laser scanner 91, and the absolute value of the potential of the portion irradiated with the laser scanning light 90 decreases. . As a result, an electrostatic latent image is formed on the surface of the photoconductor portion 12 of the photoconductor drum 10. The developing device 30 is filled with the toner T charged to a negative potential, and is connected to the developing power source section 34. The developing power source unit 34 outputs a voltage in which an AC voltage and a DC voltage are superposed. Photoconductor part 12 of photoconductor drum 10
In the gap S between the developing device 30 and the conductor roller part 31 of the developing device 30, an electric field is generated by the application of the voltage of the developing power source part 34 to the developing device 30, and the toner T is transferred from the developing device 30 to the photosensitive drum 1.
Fly to zero.

Here, the portion of the surface of the photosensitive member 12 of the photosensitive drum 10 which is not irradiated with the laser scanning light 90 is charged to a negative potential. The surface potential of that portion is set to be lower than the DC voltage of the developing power source section 34,
The flying toner T charged with a negative voltage is the developing device 30.
Returned to.

On the other hand, in the portion of the surface of the photosensitive portion 12 of the photosensitive drum 10 irradiated with the laser scanning light 90, the negative charges on the surface are attenuated, and the potential of the portion is higher than the DC voltage of the developing power source portion 34. The flying toner T charged with a negative voltage adheres to the photoconductor portion 12. In this way, a toner image corresponding to the electrostatic latent image formed by the laser scanning light is formed on the surface of the photoconductor portion 12 of the photoconductor drum 10. The toner image formed on the surface of the photoconductor portion 12 is carried to the transfer device 40 by the rotation of the photoconductor drum itself.

The recording medium P is conveyed between the transfer device 40 and the photosensitive drum 10. Further, the transfer device 40 is connected to the transfer power supply unit 43. The transfer power supply unit 43 outputs a positive DC voltage when passing through the recording medium. At this time, the toner T on the photosensitive drum 10 is attracted toward the recording medium P, and the toner image formed on the photosensitive drum 10 is transferred to the recording medium P. The recording medium to which the toner image is transferred is then conveyed to a fixing device (not shown). The recording medium conveyed to the fixing device is heated and pressurized by the fixing device to fix the toner T, and the recording medium is discharged to the outside of the device.

In the above conventional example, the conductor shaft 21 of the charging roller 20 is applied with a voltage obtained by superposing an AC voltage and a DC voltage of the charging power source section 623, which will be described later. A constant current of the charging power source unit 724 may be applied.

7 and 8 are circuit diagrams of the charging power source section.

The charging power source unit 623 shown in FIG. 7 is a power source unit called constant voltage control because it outputs a constant voltage for both AC voltage and DC voltage.

The CPU 601 is adapted to output a pulse, stop the pulse, and control other operations of the entire copying machine which is an image forming apparatus. The amplifier 602 is a CP
The pulse waveform output from U601 is amplified. The filter unit 603 cuts off the high frequency component of the output waveform amplified by the amplification unit 602 and converts the square wave into a sine wave. Coupling capacitor 6
04 is designed to cut the DC component of the output of the filter unit 603.

The boosting unit 605 is configured to boost the voltage input via the coupling capacitor 604. The boosted AC voltage is output from the booster unit 605. The AC voltage output from the booster 605 is rectified and smoothed by the diode 606 and the capacitor 607. Capacitor 6
Resistors 608 and 609 and a current controller 610 are connected to both ends of 07.

The current controller 610 controls the capacitor 607 to the resistor 60 so that a constant voltage drop occurs in the resistor 608.
The control of the discharge current flowing through the switch 8,609 is performed. As a result, a voltage obtained by superimposing the AC voltage output from the boosting unit 605 and the DC voltage generated in the resistor 608 is output to the output terminal of the charging power supply unit 623.

The charging power source unit 724 shown in FIG. 8 is a power source unit called constant current control for controlling the output current to be constant.

The CPU 701 is adapted to output or stop a pulse and to control other operations of the entire copying machine which is an image forming apparatus. The amplifier 702 is a CP
The pulse waveform output from U701 is amplified. The filter unit 703 cuts off the high frequency component of the output waveform amplified by the amplification unit 702 and converts the square wave into a sine wave. Coupling capacitor 7
04 is designed to cut the DC component of the output of the filter unit 703.

The boosting unit 705 is configured to boost the voltage input via the coupling capacitor 704. The boosted AC voltage is output from the booster 705. In addition, the amplification unit 706 is
The pulse waveform output from U701 is amplified. The coupling capacitor 707 is the amplification unit 7
The DC component of the output of 06 is cut.

The boosting unit 708 is configured to boost the voltage input via the coupling capacitor 707. The AC voltage output from the booster 708 is rectified and smoothed by the diode 709, the capacitor 710, and the resistor 711 to generate a DC voltage. By connecting the DC voltage generation unit to the AC voltage generation unit, a voltage in which the AC voltage and the DC voltage are superimposed is output to the output terminal of the charging power supply unit 724. The current control unit 71
3 is connected to the output end of the charging power source unit 724, detects the output current, and controls the amplification factor of the amplification unit 702 so that the output current becomes constant.

[0020]

By the way, in the photoconductor portion 12 of the photoconductor drum 10, the resistor 2 of the charging roller 20 is provided.
The electric discharge between the two causes consumption. The constant voltage control in the charging power source unit 623 shown in FIG. 7 has an advantage that the circuit can be configured at low cost, but as the photoconductor unit 12 is consumed, the discharge amount increases and the photoconductor unit 12 is increased. There is a problem of promoting the exhaustion of
This control method is not suitable for increasing the speed and extending the life of the image forming apparatus.

On the other hand, in the constant current control in the charging power source section 724 shown in FIG. 8, since the output current is controlled to be constant, the discharge amount to the photoconductor drum 10 is also constant, and the photoconductor unit 12 is consumed. Can be significantly reduced as compared with the constant voltage control, and the control is suitable for increasing the speed and extending the life of the image forming apparatus. However, constant current control requires stable constant current control in DC voltage generation by diodes, capacitors, resistors, and current control units like constant voltage control, so a new power supply circuit for DC voltage generation is required. As a result, the control method is not suitable for downsizing and cost reduction of the image forming apparatus.

An object of the present invention is to provide an image forming apparatus in which abrasion of the photoconductor portion due to discharge between the photoconductor portion of the image carrier and the resistor layer of the charging means is reduced.

[0023]

In order to achieve the above object, an image forming apparatus of the present invention comprises a movable image carrier, the surface of which is charged and exposed to form an electrostatic latent image. Toner is attached to the latent image and developed as a toner image, and the toner image is transferred to another member to form an image, and a charging unit in contact with the surface of the image carrier and the charging unit. A charging power supply device for charging the surface of the image carrier by applying a voltage in which a DC voltage and an AC voltage are superimposed to the means, and the charging power supply device stores the usage history of the image carrier. A history detecting unit for detecting and an AC voltage adjusting unit for adjusting an AC voltage applied to the charging unit are provided,
Based on the detection result of the history detecting unit, the AC voltage adjusting unit adjusts the AC voltage applied to the charging unit to adjust the discharge amount between the charging unit and the image carrier. Has become.

In order to achieve the above object, the image forming apparatus of the present invention charges the surface of a movable image carrier and exposes it to form an electrostatic latent image, and adheres toner to the electrostatic latent image. Then, the toner image is developed as a toner image, and the toner image is transferred to another member to form an image. A charging unit in contact with the surface of the image carrier and a DC voltage and an AC voltage are applied to the charging unit. And a charging power supply device for charging the surface of the image carrier by applying a voltage with which the voltage is superimposed, the charging power supply device comprising history detection means for detecting a usage history of the image carrier. A temperature detecting means for detecting the temperature in the main body of the apparatus, and an AC voltage adjusting means for adjusting the AC voltage applied to the charging means, and based on the detection result of the history detecting means and the detection result of the temperature detecting means. By the AC voltage adjusting means, By adjusting the AC voltage applied to the serial charging means, thereby adjusting the amount of discharge between the charging means and the image bearing member.

The charging power supply device of the image forming apparatus of the present invention is adapted to adjust the amplitude of the AC voltage applied to the charging means.

The AC voltage adjusting means of the image forming apparatus of the present invention reduces the amplitude of the AC voltage of the charging power supply device when the detection value of the history detecting means reaches a predetermined value. .

In the AC voltage adjusting means of the image forming apparatus of the present invention, when the temperature detected by the temperature detecting means exceeds a predetermined temperature, the detected value of the history detecting means is smaller than the predetermined value. However, the amplitude of the AC voltage of the charging power supply device is reduced.

In the AC voltage adjusting means of the image forming apparatus of the present invention, when the temperature detected by the temperature detecting means becomes lower than a predetermined temperature, the detected value of the history detecting means becomes a value larger than the predetermined value. At this time, the amplitude of the AC voltage of the charging power supply device is reduced.

The AC voltage adjusting means of the image forming apparatus of the present invention is adapted to switch the AC voltage of the charging power supply apparatus in a plurality of stages in accordance with the detection value of the history detecting means.

The temperature detecting means of the image forming apparatus of the present invention is adapted to detect the temperature around the charging means.

The other member of the image forming apparatus of the present invention is a recording medium, and the history detecting means is recording medium counting means for counting the number of recording mediums to which the toner image is transferred.

The history detecting means of the image forming apparatus of the present invention is a rotation speed detecting means for detecting an integrated rotation speed of the image carrier.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION A copying machine which is an image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings. The image forming apparatus includes a copying machine, a printer, a facsimile, and a composite machine of these. Therefore, the present invention is applicable not only to the copying machine but also to other image forming apparatuses such as printers, and is not limited to the copying machine.

Further, although the image forming apparatus of the embodiment of the present invention is adapted to form a toner image on a photosensitive drum, an image forming a toner image on a photosensitive belt (image carrier) (not shown). Since the present invention can be applied to a forming apparatus, an image forming apparatus that forms a toner image on a photosensitive belt is also included in the present invention.

(Overall Description of Copier) FIG. 1 is a schematic configuration diagram of a copier 100 which is an image forming apparatus using an electrophotographic technique. In FIG. 1, the same parts as those of the conventional copying machine are designated by the same reference numerals. In the copying machine 100, the charging power supply unit (charging power supply device) 123 according to the first embodiment and the charging power supply unit (charging power supply device) 324 according to the second embodiment are provided.
However, in the following description, the charging power supply unit 1 of the first embodiment will be described.
The case where 23 is provided will be described.

The photoconductor drum (image bearing member) 10 has a photoconductor portion 12 provided on the outer periphery of a conductor portion 11. The conductor part 11 is grounded. Charging roller (charging means) 20
Is provided with an elastic resistor 22 on the outer periphery of the conductor shaft 21. The photoconductor portion 12 and the resistor 22 are in contact with each other. During the printing operation of the copying machine 100, the photosensitive drum 10 and the charging roller 20 are rotated in the arrow direction by a driving unit (not shown).

During the printing operation of the copying machine 100, the charging roller 2
A voltage obtained by superimposing an AC voltage and a DC voltage of the charging power supply unit 123 is applied to the conductor shaft 21 of 0. At this time, corona discharge is generated in the vicinity of the contact portion between the photoconductor portion 12 and the resistor 22, and the surface of the photoconductor portion 12 is charged. by this,
The surface potential of the photoconductor section 12 becomes substantially equal to the DC voltage applied by the charging power supply section 123. Note that the charging power supply unit 123 superimposes the AC voltage in order to promote corona discharge and uniformize the surface potential of the photoconductor unit 12.

Next, the surface of the charged photosensitive member 12 is irradiated with laser scanning light 90 from a laser scanner 91. At this time, the laser scanning light 90 is on / off controlled according to the image signal. When the surface of the photoconductor 12 is irradiated with the laser scanning light 90, the surface area of the photoconductor 12 that is irradiated is equivalently reduced in resistivity by the photoelectrons generated, and thus is charged by the charging power supply 123. Surface charge decays. Therefore, the laser scanning light 90
The absolute value of the electric potential of the portion irradiated with is decreased. As a result, an electrostatic latent image is formed on the surface of the photoconductor section 12.

The developing device 30 has a magnet 32 embedded in a hollow conductor roller portion 31. An elastic developing blade 33 is in contact with the surface of the conductor roller portion 31. Between the developing device 30 and the developing blade 33, the toner T charged to a negative potential by stirring is blocked.
The toner T itself is a magnetic substance and is attracted to the surface of the conductor roller portion 31 by the electrostatic force due to the electric mirror image effect generated by the surface of the conductor roller portion 31 and the magnet 32. Most of the toner T adhering to the surface of the conductor roller portion 31 is peeled off by the developing blade 33, and the toner T only near the surface is carried to the gap between the conductor roller portion 31 and the photoconductor portion 12. A minute gap S (about 200 microns or less) S is provided between the photoconductor portion 12 and the conductor roller portion 31.

A developing power source section 34 is connected to the conductor roller section 31. The developing power supply unit 34 outputs a voltage in which an AC voltage and a DC voltage are superposed. An electric field is generated in the gap between the photoconductor portion 12 and the conductor roller portion 31 by applying the voltage of the developing power source portion 34, and the toner T attached to the surface of the conductor roller portion 31 flies from the conductive roller portion 31. Here, a portion of the surface of the photoconductor portion 12 which is not irradiated with the laser scanning light 90 is negatively charged, and the surface potential thereof is set to be lower than the DC voltage of the developing power source portion 34. For this reason, a force acts on the toner T in the direction of pushing back the conductor roller portion 31 in terms of direct current, and the flying toner T is returned to the developing device 30.

On the other hand, in the portion of the surface of the photoconductor portion 12 where the laser scanning light 90 is irradiated, the negative charge on the surface is attenuated, so the potential of that portion becomes higher than the DC voltage of the developing power source portion 34. . For this reason, a force that attracts the toner T to the photoconductor portion 12 acts on the toner T in terms of direct current,
The flying toner T adheres to the photoconductor portion 12. In this way, a toner image corresponding to the electrostatic latent image formed by the laser scanning light 90 is formed on the surface of the photoconductor portion 12. The toner image formed on the surface of the photoconductor portion 12 is transferred to the transfer roller 40 by the rotation of the photoconductor drum itself.
Be carried to.

The transfer device 40 is formed in a roller shape by a conductor shaft 41 and an elastic resistor 42. The surface of the resistor 42 is in contact with the photoconductor portion 12, and the recording medium P is conveyed between the resistor 42 and the photoconductor portion 12.
Further, the conductor shaft 41 is connected to the transfer power source unit 43. The transfer power supply unit 43 outputs a positive DC voltage when passing through the recording medium. At this time, the toner T on the surface of the photoconductor portion 12 is attracted toward the recording medium, and
The toner image formed above is transferred to the recording medium. The recording medium to which the toner image is transferred is then conveyed to a fixing unit (not shown). The recording medium conveyed to the fixing unit is heated and pressurized in the fixing unit to fix the toner T, and is ejected to the outside of the apparatus.

The photosensitive member 1 is not transferred to the recording medium.
The toner T remaining on the toner 2 is removed by the cleaning blade 50. Then, the copying machine 100 prepares for the next printing operation.

(Charging Power Supply Unit of First Embodiment) FIG. 2 is a circuit diagram of the charging power supply unit 123 of the first embodiment.

The CPU 101 outputs a pulse, stops the pulse, and controls the operation of the entire copying machine which is an image forming apparatus. The amplification unit 102 is a CP
The pulse waveform output from U101 is amplified. The filter unit 103 cuts off high frequency components of the output waveform amplified by the amplification unit 102 and converts a square wave into a sine wave. Coupling capacitor 1
Reference numeral 04 is adapted to cut the DC component of the output voltage of the filter unit 103.

The boosting unit 105 boosts the voltage input via the coupling capacitor 104. The boosted AC voltage is output from the booster 105. The AC voltage output from the booster 105 is rectified and smoothed by the diode 106 and the capacitor 107. Capacitor 1
Resistors 108 and 109 and a current controller 110 are connected to both ends of 07.

The current control unit 110 controls the capacitor 107 to the resistor 10 so that a constant voltage drop occurs in the resistor 108.
The discharge currents flowing in 8 and 109 are controlled. As a result, the booster 105 is provided at the output end of the charging power source.
A voltage obtained by superimposing the AC voltage output from the DC voltage on the resistor 108 is output. The recording medium number counting unit (history detecting means, recording medium number counting means) 111 counts the total number of recording media printed by the copying machine 100, which is an image forming apparatus. There is. For this reason, the recording medium coefficient counting unit 111 uses the photosensitive drum 1
It is preferable to use, for example, a sensor that is provided in the vicinity of 0 and the transfer device 40 and detects passage of the recording medium.

The amplification factor switching unit 112 includes the CPU 101.
And the amplifier 102. The CPU 101 and the amplification factor switching unit 112 make up an AC voltage adjusting unit.

When the copying machine 100 prints and the number of recording media counted by the recording medium number counting unit 111 reaches a predetermined number, the CPU 101 causes the amplification factor switching unit 112 to output a pulse waveform from the CPU 101. Is the amplifier 10
2 reduces the amplification factor when amplifying. Amplifier 1
02 by reducing the amplification factor
3, the coupling capacitor 104, the booster 10
5, the amplitude of the AC voltage output from 5 decreases. As a result, the amount of discharge between the photoconductor drum 10 and the charging roller 20 is reduced.

As shown in FIG. 3, the charging power source unit 123 of this embodiment performs this control for every predetermined number of recording sheets (n1, n).
..) and gradually reduce the amplitude of the AC voltage, it is possible to suppress the increase in the discharge amount even if the number of recorded sheets increases.

As a result, the copying machine 100 of this embodiment is
By adding the recording medium number counting unit 111 and the amplification factor switching unit 112 to a low-cost circuit configuration equivalent to that of the conventional charging power source unit 623, it is possible to reduce the wear of the photoconductor unit 12 in the photoconductor drum 10. The life of the photoconductor drum 10 can be extended.

The charging power source 123 applies a voltage obtained by superposing an AC voltage and a DC voltage to the conductor shaft 21, but applies only the AC voltage and gradually changes the amplitude of the AC voltage. May be reduced to.

(Charging Power Supply Section of Second Embodiment) FIG. 4 is a circuit diagram of the charging power supply section 324 of the second embodiment.

The CPU 301 is adapted to output or stop a pulse and control the operation of the entire copying machine which is an image forming apparatus. The amplification unit 302 includes the CPU 30.
The pulse waveform output from 1 is amplified. The filter unit 303 cuts off the high frequency component of the output waveform amplified by the amplification unit 302 and converts the square wave into a sine wave. Coupling capacitor 304
Is designed to cut the DC component of the output voltage of the filter unit 303.

The boosting unit 305 boosts the voltage input via the coupling capacitor 304. The boosted AC voltage is output from the booster 305. The AC voltage output from the booster 305 is rectified and smoothed by the diode 306 and the capacitor 307. Capacitor 3
Resistors 308 and 309 and a voltage control unit 310 are connected to both ends of 07.

The CPU 301 is connected to a recording medium number counting section (history detecting means, recording medium number counting means) 311 and a temperature detecting section (temperature detecting means) 313. The recording medium number counting unit 311 is configured to count the number of recording mediums printed by the copying machine 100. For this reason,
The recording medium number counting unit 311 is preferably a sensor, which is provided in the vicinity of the photoconductor drum 10 and the transfer device 40 and detects passage of the recording medium.

The temperature detecting section 313 is adapted to detect the ambient temperature of the image forming apparatus. The temperature detector 313
It is preferable that the temperature sensor is provided near the photoconductor drum 10 and the charging roller 20 to detect the temperature.

The amplification factor switching unit 312 includes the CPU 301.
And the amplifier 302. The CPU 301 and the amplification factor switching unit 312 make up an AC voltage adjusting unit.

The copying machine prints and the recording medium number counting unit 3
When the number of recording media counted in 11 reaches a predetermined number, the CPU 301 causes the amplification factor switching unit 312 to perform C
The amplification factor when the pulse waveform output from the PU 301 is amplified by the amplification unit 302 is reduced. Amplifier 302
By reducing the amplification factor at
The amplitude of the AC voltage output from the booster 305 is reduced through the coupling capacitor 304. As a result, the amount of discharge between the photoconductor drum 10 (see FIG. 1) and the charging roller 20 is reduced. Further, the amount of discharge between the photoconductor portion 12 and the resistor 22 is easily affected by the ambient temperature and increases in a high temperature environment.

As shown in FIG. 5, the charging power source section 324 of this embodiment performs this control for every predetermined number of recording sheets (n1, n).
2, n3 ...) When the temperature detection unit 313 determines that the surrounding environment is a high temperature environment, the charging power supply unit 324 switches the amplification factor to a number smaller than the normal number of recording media (n.
1 ', n2', n3 ', ...). Conversely, in a low temperature environment, if the discharge amount is reduced too much, the photosensitive drum 1
There is a possibility that an image defect may occur due to a charging failure of 0. Therefore, when the temperature detection unit 313 determines that the surrounding environment is a low temperature environment, the charging power supply unit 324 switches the amplification factor with a number (n1 ″, ...), which is larger than the normal number of recording media. In addition, the charging power supply unit 324 can suppress the increase in the discharge amount even if the number of recorded sheets increases by gradually reducing the amplitude of the AC voltage.

The recording medium number counting units 111, 311
Instead of the above, a photoconductor drum tachometer for detecting the number of revolutions of the photoconductor drum 10 is provided, and when the photoconductor drum 10 reaches a predetermined number of revolutions, the AC voltage of the charging power supply devices 123 and 324 is adjusted. Alternatively, the amount of discharge between the charging unit and the image carrier may be adjusted.

Further, the charging power source section 324 is adapted to apply a voltage obtained by superposing an AC voltage and a DC voltage to the conductor shaft 21. However, by applying only the AC voltage, the amplitude of the AC voltage is changed stepwise. May be reduced.

[0063]

According to the image forming apparatus of the present invention, the charging power supply unit adjusts the AC voltage applied to the charging unit by the AC voltage adjusting unit based on the detection result of the history detecting unit, and the charging unit and the image forming apparatus. Since the amount of discharge between the image carrier and the carrier is adjusted, it is possible to reduce the consumption of the photoconductor part of the image carrier, which is low cost, space saving, speeding up image formation, and long life. Can be realized.

In the image forming apparatus of the present invention, the charging power supply device adjusts the AC voltage applied to the charging means by the AC voltage adjusting means based on the detection result of the history detecting means and the detection result of the temperature detecting means. Since the amount of discharge between the charging unit and the image carrier is adjusted, it is possible to reduce the consumption of the photoconductor portion of the image carrier, and to reduce the cost.
It is possible to save space and achieve high-speed image formation and long life.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a copying machine that is an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a charging power source unit of the first embodiment provided in the copying machine of FIG.

FIG. 3 is an output waveform of each part for explaining the operation of the charging power supply part of the first embodiment shown in FIG. (A) An output waveform of the amplifier. (B) An output waveform of the charging power source section. (C) A graph showing the discharge current between the photosensitive drum and the charging roller.

FIG. 4 is a circuit diagram of a charging power source unit of a second embodiment provided in the copying machine of FIG.

FIG. 5 is a graph showing a discharge current between a photosensitive drum and a charging roller, for explaining the operation of the charging power source unit of the second embodiment shown in FIG.

FIG. 6 is a schematic configuration diagram of a copying machine which is a conventional image forming apparatus.

7 is a circuit diagram of a charging power supply unit of a first conventional example provided in the copying machine of FIG.

8 is a circuit diagram of a charging power supply unit of a second conventional example provided in the copying machine of FIG.

[Explanation of symbols]

T toner S gap between photoconductor drum and developing device P recording medium 10 photoconductor drum (image bearing member) 11 photoconductor drum conductor 12 photoconductor unit 20 charging roller (charging means) 21 charge roller conductor shaft 22 Resistor 30 Developing device 34 Developing power source part 40 Transfer device 43 Transfer power source part 50 Cleaning blade 90 Laser scanning light 100 Copier (image forming apparatus) 101 CPU (AC voltage adjusting means) 102 Amplifying part 111 Recording medium number counting part ( Recording medium number counting unit) 112 Amplification factor switching unit (AC voltage adjusting unit) 123 Charging power source unit (charging power supply device) 301 CPU (AC voltage adjusting unit) 311 Recording medium number counting unit (history detecting unit, recording target) Medium number counting means) 312 Amplification factor switching section (AC voltage adjusting means) 313 Temperature detecting section (temperature detecting means) 324 Charging power source section (Charging power supply device)

Claims (10)

[Claims] 1. A surface of a movable image carrier is charged, exposed to form an electrostatic latent image, and toner is attached to the electrostatic latent image to develop as a toner image. In an image forming apparatus for transferring an image to a member to form an image, the charging means in contact with the surface of the image carrier, and the image carrying means for applying a voltage in which a DC voltage and an AC voltage are superimposed to the charging means. A charging power supply device for charging the surface of the body, wherein the charging power supply device, history detection means for detecting the use history of the image carrier, AC voltage for adjusting the AC voltage applied to the charging means Adjusting means, adjusting the alternating voltage applied to the charging means by the alternating voltage adjusting means based on the detection result of the history detecting means, and discharging between the charging means and the image carrier. Characterized by adjusting the amount Image forming apparatus. 2. A surface of a movable image carrier is electrically charged, exposed to form an electrostatic latent image, and toner is attached to the electrostatic latent image to develop it as a toner image. In an image forming apparatus for transferring an image to a member to form an image, the charging means in contact with the surface of the image carrier, and the image carrying means for applying a voltage in which a DC voltage and an AC voltage are superimposed to the charging means. A charging power supply device for charging the surface of the body, wherein the charging power supply device, history detection means for detecting the use history of the image carrier, temperature detection means for detecting the temperature in the apparatus main body, AC voltage adjusting means for adjusting the AC voltage applied to the charging means, and the AC voltage adjusting means applies the voltage to the charging means based on the detection result of the history detecting means and the detection result of the temperature detecting means. Adjust the AC voltage, An image forming apparatus, wherein an amount of discharge between the charging unit and the image carrier is adjusted. 3. The image forming apparatus according to claim 1, wherein the charging power supply device adjusts the amplitude of an AC voltage applied to the charging unit. 4. The AC voltage adjusting means reduces the amplitude of the AC voltage of the charging power supply device when the detection value of the history detecting means reaches a predetermined value. The image forming apparatus according to claim 1. 5. The AC voltage adjusting means, when the temperature detected by the temperature detecting means exceeds a predetermined temperature, even if the detected value of the history detecting means is smaller than the predetermined value, the charging The image forming apparatus according to claim 2, wherein the amplitude of the AC voltage of the power supply device is reduced. 6. The charging means for charging the AC voltage when the detected temperature of the temperature detecting means is lower than a predetermined temperature or when the detected value of the history detecting means is higher than a predetermined value. The image forming apparatus according to claim 2, wherein the amplitude of the AC voltage of the power supply device is reduced. 7. The AC voltage adjusting means adjusts the AC voltage of the charging power supply device by switching it in a plurality of stages in accordance with the detection value of the history detecting means. The image forming apparatus according to any one of items. 8. The temperature detecting means detects the temperature around the charging means.
5. The image forming apparatus according to any one of 5 and 6. 9. The other member is a recording medium, and the history detecting means is recording medium counting means for counting the number of recording mediums to which a toner image is transferred. 9. The image forming apparatus according to any one of items 8 to 8. 10. The image forming apparatus according to claim 1, wherein the history detection unit is a rotation speed detection unit that detects an integrated rotation speed of the image carrier.